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- Creator:
- Ho, Thu Ngoc
- Description:
- The increasing awareness of human infections caused by the organisms in the Mycobacterium fortuitum complex, particularly in nosocomial infections, emphasizes the need to subdivide the species of this complex for epidemiological investigations. Biochemical characteristics were determined for 154 strains of these organisms in the arylsulphatase, nitrate reduction, iron uptake, and salt tolerance tests, and the utilization of sodium citrate, mannitol, and inositol as the sole source of carbon. The results for the various subspecies and biovars conformed to the expected results obtained with the respective reference strains. These biochemical test results were correlated to bacteriophage susceptibility patterns. A group of twelve mycobacteriophages, including three newly isolated for this study, were tested against the 154 strains. Susceptibility to lysis by at least one phage was found for 72.2% of the bacterial strains. M. fortuitum strains were more susceptible to the mycobacteriophages (79.5%) than were the M. chelonae strains (64.8%). Among the biotypes, 76.4% of the M. fortuitum biovar fortuitum strains, 88.0% of the M. fortuitum biovar peregrinum strains, 71.4% of the M. fortuitum 3rd biovar strains, 60.9% of the M. chelonae subsp. chelonae strains, and 70.0% of the M. chelonae subsp. abscessus strains were found to be phage susceptible. There was no consistent phage susceptibility pattern for a given biotype; each subgroup exhibited a sufficient diversity of lytic patterns to indicate that phage typing may be a practical tool to recognize strains for epidemiological studies. The results further indicate that within each particular biotype not all of the mycobacteriophages were appropriate and their number could be limited. The results strongly indicate that biochemical characterization and phage typing can provide evidence for a common source of contamination as the cause of mycobacterial infections. The findings in this study merit further investigations to establish a standardized phage typing system for the organisms of the M. fortuitum complex.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Buth, Jessie
- Description:
- The outermost portion of the brain, the cortex, is a six-layered structure of neurons that is responsible for higher cognitive functions such as thinking and speech. This region is the most evolutionarily new part of the brain and is disproportionately large in humans than predicted by body size. What has caused the cortex to expand across evolutionary time? Little is known about this process due to the inaccessibility to human tissue. Much of what is currently known stems from static images of human fetal tissue or extrapolation from model organisms. Mice, and other model organisms, fail to recapitulate hallmark features of human brain development. There is a need for a better system to study brain development and its disorders. One alternative is to use stem cells. Stem cells have the ability to form any cell type in the body, and in the lab can be directed to form any cell type, or tissue, of interest. Recently, Kadoshima et al. (2013) and Lancaster et al. (2013) published protocols to create organ-like structures, called organoids, that model some aspects of brain development in vitro using stem cells. Stem cells are exposed to factors normally present during development and spontaneously form cortical tissue. This system has not been well characterized and it remains to be determined how reproducible these studies are with other cell lines. This study determined cortical organoids derived from H9 human embryonic stem cells and MM13 mouse embryonic stem cells can model some aspects of in vivo cortex development with some modifications of previously published protocols. Cortical organoids derived from human cells efficiently and reproducibly formed cortical tissue that exhibited some established features of cortex development. Human cortical organoids produced a thick layer of FOXG1+ cortical progenitors, initially showed the correct apical-basal (inside-out) polarity, and formed cortical neurons with signs of laminar organization. Mouse cortical organoids also efficiently formed FOXG1+ progenitors and produced cortical neurons, but with less laminar organization than in the human organoids. This study is the first to thoroughly characterize how well cortical organoids model in vivo development and in which areas the methods could be improved.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sausner, Joshua
- Description:
- For closely related species, differences in morphology can provide insight as to the evolutionary history of a taxonomic group, as well as mechanisms for ecological segregation. Storm-petrels are among the smallest seabirds and their highest taxonomic diversity occurs in the eastern Pacific Ocean. Some storm-petrels exhibit a unique foraging behavior, known as pattering or sea-anchor soaring, in which they appear to walk on the surface of the ocean but this behavior is used to a varying degree among species. This study compares morphological traits related to this foraging behavior in storm-petrels that breed in the eastern Pacific. Measurements on the wing (wing loading, aspect ratio), beak (size), and leg (length and foot size) were analyzed using a discriminant function analysis (DFA). A thin-plate spline/relative warp analysis was also used to analyze subtle differences in wing shape. Those species that patter the most were found to have a low wing loading, low foot loading, and a long tarsus, and were fairly distinct from the species that were classified as intermediate and least pattering. The DFA and a cluster analysis also identified the behavior of some species as to their pattering abilities for which there was little known observational data. A molecular phylogeny was created from sequencing the mitochondrial ND1 gene. This was used to examine the relationship between the two sub-families of storm petrels as well as to gain insight to the evolutionary history of pattering within the family. There was some evidence for paraphyly between the subfamilies and the morphology associated with an intermediate use of pattering appears to be the ancestral form. A more comprehensive phylogeny using both mitochondrial and nuclear genes in combination with morphological data for more species would help resolve the results of this study
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Hemmati, Homa
- Description:
- Cellulase is widely used as an enzyme for saccharification of cellulosic materials. However, commercially available cellulase is an expensive enzyme. Recombinant ethanologenic bacteria have also become an important tool for production of bioethanol from lignocellulosic biomass. Heterogolous gene expression in transgenic microorganisms can be improved by utilization of an efficient promoter system to regulate genes encoding for cellulase or ethanol production pathway. Here, we evaluated the feasibility of bioengineering E. coli cells with an ethanol inducible promoter system driving a cellulase gene. We tested the strength of an ethanol inducible native alcA promoter from Aspergillus nidulans in E. coli and compared this promoter with T5, a strong promoter commonly used for gene expression in bacteria, and cauliflower mosaic virus 35S (CaMV 35S), a strong and widely used promoter in plants. The activity of alcA promoter was also compared to CaMV 35S promoter in tobacco by transiently expressing a GFP gene under the control of 35S and alcA promoters. E. coli cells were transformed with various plasmid constructs and quantitative PCR was performed to analyze promoter activities. The highest transcription level was observed for alcA promoter when it was expressed along with AlcR transcription factor in absence of ethanol in which alcA expression was 11 times higher than T5 promoter. The alcA promoter showed basal level expression in absence of AlcR, although, its expression level was higher in presence of AlcR. All cassettes harboring alcA promoter showed non-significant ethanol dose-dependent activity. Conducting SDS-PAGE and CMCase activity assay displayed no or low protein expression and no enzyme activity. Lack of protein expression might be due to the presence of 14 rare codons in cellulase DNA sequence inhibiting protein translation in E. coli. In contrast to E.coli, the inducible expression of alcA promoter system was tightly regulated in tobacco. We suggest further study for the utilization of ethanol inducible system in ethanol-tolerant ethanologenic E. coli strains which may lead to significant success in production of bioethanols and other biofuels. We hope, our work on inducible promoter system for in vivo cellulase production will open new avenues of research in the fields of developments of biofuel from prokaryotic and eukaryotic systems.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Jankay, Peter Thomas
- Description:
- Gibberellin-like activity from cotyledons, sead-coats and embryonic axis of Phaseolus vulgaris was measured by the barley reducing sugar assay and the dwarf pea stem assay during germination. In the first 48 hours of germination the amount of gibberellin-like substance decreases 1000 fold in the cotyledons and 10 fold in the axis when measured with the barley assay. This assay reveals significant activity from unimbibed seed coats. The activity increases in the initial stages of germination, and then decreases. When measured by the pea assay, no activity is detected from unimbibed.seed coats although small amounts of activity are obtained for a short period following the onset of germination. These decreases in levels of gibberellin- like material during germination could reflect its utilization and conversion to less active forms, the accumulation of inhibitors which mask activity of the hormone, or exudation into the medium. Comparison of results from the two assays suggests qualitative changes in gibberellin- like material, or the accumulation of inhibitors with different effects in the two assays.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kallenbach, Rein Jan
- Description:
- The freeze-fracture technique was used to analyze intercalations within the hydrophobic interior of the plasma membrane and the nuclear envelope of Sarcoma-180 ascites tumor cells. These membranes are extremely deformable and reflect basic, intrinsic alterations 1vi thin the membrane matrix. A quantitative analysis was made of membrane fracture faces in terms of particle densities, particle size frequency distributions, and mean density ratios for different membrane loci. These data were interpreted in terms of topological changes of these membranes, especially the extension and retraction of surface and nuclear lobation. The data suggest that a) particles are differentially bound to one leaflet versus the other, with a particle partition coefficient (kp) difference of 0. 66 between villous and non-villous membrane regions, and that b) membrane leaflets have different fluidity characteristics with respect to particle movements (displacement) and that c) these factors account for deformability modes within membranes which are reflected in topological changes of membranous structures as a whole. Other factors such as extrinsic proteins, microtubules and microfilaments may play a role in topological changes, depending upon cell type. In Sarcoma-180 cells, however, such extra-membranous components have not been observed in thin sections, suggesting that phase changes within the membrane per se may initiate cellular topological changes.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Palukuri, John Samuel Sukumar
- Description:
- The extracellular matrix is a tissue that is present around the cell which provides structural support to the cell. The extracellular matrix also plays an important role in growth and development; it consists of a set of components including proteoglycans, proteolipids, at fibers such as collagen, elastin, fibronectin etc., which play a primary role in the cell-cell adhesion process. Cell-cell adhesion is an important process for cell development and function. In several studies, glycans have been found to play an important role in cell- cell adhesion process (Kleene et al., 2004; Varki et al., 2009). Here, I evaluate the effect of commercially available glycosidase. Sea urchin embryos were used as a model organism and were treated with various concentration of thermostable xylanase. Sea urchin embryos were designated by NIH as model organism for biological studies, because of their availability, transparency and external fertilization. They share development and evolutionary relationships with humans, as reflected by homology of DNA sequences and similarities in several biochemical pathways. I am trying to understand the effects of xylanase on, archenteron organization/ elongation/ attachment to the blastocoel roof in the sea urchin embryos during embryogenesis. The hypothesis for this study was that Xylanase may inhibit the archenteron growth of sea urchin embryo. Enzyme activity was found with a known substrate. SDS PAGE analysis showed no contamination in the enzyme. The Azocoll test showed very minute protease contamination. I plated the Lytechinus pictus sea urchin embryos at the early gastrulation stage in a quantitative dose response manner of enzyme ranging from 0.12-31.81U/ml, xylanase to assess the morphological characteristics. One unit will liberate 1.0μmole of reducing sugar which is measured as xylose equivalents from xylan per minute at pH 4.5 at 30°C. Averages of 4000-7900 embryos were observed for each treatment/ concentration of xylanase. The different morphologies for each treatment were compared with the control, using MANOVA analysis. The p values, which are less than 0.05, indicate a significant difference compared to controls. There were significant differences between all of the concentrations in comparison to the controls. According to univariate F-tests and wilki’s lambda results, 0.99U/ml, 0.49U/ml, 0.24U/ml, and 0.12U/ml concentrations had much significant effect to the whole model. The results suggest that glycans are involved in cellular interactions, and was confirmed that xylan moieties are involved in archenteron development in the embryonic stages of sea urchin embryos. However, because the highest concentrations of xylanase had less effect on archenteron development than some lower concentrations, a dose-response effect was not established.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
208. Characterization of a TetR/AcrR family transcriptional repressor gene NpR3597 in Nostoc punctiforme
- Creator:
- Yazdani, Arash
- Description:
- Nostoc punctiforme is a filamentous cyanobacterium capable of differentiating its vegetative cells into spore-like akinetes that can withstand desiccation and cold. The NpR3597 gene was previously identified in a time-course DNA microarray experiment to be up-regulated during akinete formation, and up-regulated in dividing cells of the filament as indicated by GFP transcriptional reporter strains. Sequence similarity to characterized proteins indicates that this is a putative tetracycline repressor family protein similar to TetR/AcrR found in a vast array of bacteria species that represses divergently transcribed genes encoding for ABC transport proteins. The mechanism of AcrR repression typically involves binding to an inverted repeat in the promoter of the divergently transcribed gene, inhibiting attachment of RNA polymerase. Although no phenotype could be determined for a NpR3597 deletion mutant strain, an over-expression strain bearing multiple copies of this gene on a plasmid under control of its own promoter caused pigmentation changes. Desiccation-revival tests showed that over-expression of NpR3597 results in nonfunctional akinetes. Spectrophotometric examination of the over-expression strain indicated that the levels of phycocyanin, a light harvesting protein subunit of the photosynthetic phycobilisome apparatus, was significantly higher than normal. Through a second round of microarray analysis, it was found that over-expression of NpR3597 correlated to increased transcription of genes involved in phycocyanin synthesis as well as other photosynthetic genes, and down-regulation of upstream divergently transcribed multi-drug resistance efflux pump gene NpF3598. Strong down-regulation of a number of additional genes with inverted repeat sequences in their upstream intergenic region, particularly another multi-drug resistance efflux pump gene NpF1932, was also observed. To determine the binding site for NpR3597, a conserved inverted repeat sequence found upstream of both NpF3598 and NpF1932 was used in Electric Mobility Gel Shift Assays (EMSA). A plasmid encoding for a 6xHistidine tagged NpR3597 was constructed, and the His-tagged protein purified. DNA fragments containing or lacking the putative inverted repeat binding sites were generated by PCR, end-labeled with biotin and used for EMSA with the purified protein. Only fragments containing the following motif ANNNNACNN - N2 - CNGTNTAGT in their inverted repeat sequence exhibited a gel mobility shift, indicating NpR3597 likely acts as a dimer and represses transcription by binding to these inverted repeat (IR) sequences.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Cox, Destinney
- Description:
- Elevated carbon dioxide levels caused by greenhouse gasses result in rising temperatures that have a detrimental impact on crop production, which cost farmers billions of dollars and loss in crop productivity. In response to abiotic stress, plants emit terpenes as a response to protect themselves from harsh environmental conditions. Germacrene synthase is an enzyme involved in the production of sesquiterpenes specifically, germacrene. The sesquiterpene gene, germacrene synthase provides thermotolerance in plants and are differentially expressed in plants during heat stress. Helianthus annuus plants were placed in a chamber at 42°C for 24 hours. qPCR was utilized to visualize the expression of the gene, germacrene synthase after heat stress. GC-MS was also utilized to analyze the expression of terpenes under heat stress conditions. Arabidopsis thaliana plants were genetically modified with a germacrene synthase gene by the Agrobacterium tumefaciens mediated floral dip method with the GV101 strain of Agrobacterium tumefaciens containing the recombinant pBINmgfp5-er vector. Approximately three weeks after the floral dip was conducted, seeds were collected and plated on MSO media with the antibiotic, kanamycin to select for transformants. All transgenic plants had NPTII gene, which indicated kanamycin resistance. After 14 days, surviving plants on kanamycin plates were selected and planted on soil. Approximately 4 weeks after maturation, DNA from the transformed plants were extracted, and PCR was performed using NPTII primers to confirm transgenic plants. For heat tolerance assay, the three transgenic Arabidopsis thaliana plants and an untreated wild-type plant were placed in a chamber at 42°C for 72 hours. After 72 hours, no significant signs of thermotolerance were observed in the transgenic plants. Further studies need to be done to prove that the gene, germacrene synthase provides thermotolerance in plants.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Haley, Wyndee A.
- Description:
- Certain floral characteristics are associated with specific pollinators. Hummingbird-pollinated flowers are usually red, lack a landing platform, lack color patterns on the perianth, and contain a high amount of dilute sucrose-rich nectar compared to bee-pollinated flowers. The goal of this study was to test hypotheses concerning the reasons for these characters to the extent that they involve hummingbird behaviors. An array was set up that contained 16 artificial inflorescences, each with five artificial flowers. In Experiment 1, flowers were made that differed only in color, and birds showed very little preference, slightly preferring red over other colors. In Experiment 2, color was made to be associated with nectar offerings, and birds learned to visit flowers of the color that provided much more nectar (6 versus 2 μL but not 4 versus 2 μL), but generally 2 μL was above the threshold for inclusion in the diet. In Experiment 3, birds were offered bird-nectar (8 μL of 12% sucrose) versus bee-nectar (2 μL of 48% hexose), and birds did not prefer the nectars that were similar to natural bird-adapted flowers even though they could extract bird nectar with less handling time. In Experiment 4, birds were offered flowers with and without landing platforms, and birds preferred flowers that lacked landing platforms, which saved them time. In Experiment 5, birds were offered flowers that were patterned or not, associated with differing nectar volumes, and birds did not associate the higher nectar reward with either flower type. In general, the preferences of birds fall far short of explaining the natural phenomenon of bird- versus bee-pollination syndromes. Other factors, such as adaptation to discourage bees, are discussed as additional causes of the differences between the syndromes. Furthermore, I delve into the possibility that bird behaviors may be based on their drive to sample new and different flowers, i.e., flowers unlike those that are optimally rewarding.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Gutierrez Jr., Ricardo
- Description:
- Thyroid hormones have an overarching influence on cellular processes and directly affect gene expression. Thyroid hormones are involved in telomere maintenance, ribosomal pseudouridylation, and p53-mediated apoptosis. Males affected with X-linked Dyskeratosis Congenita (XDC), a deficiency in the dyskerin complex, experience problems with their hair, teeth, nails, and skin, and are susceptible to developing cancer. XDC fibroblasts from a seven-year-old boy were grown using conventional tissue culture methods to assess the effect of an elevated level of thyroxine (T4) on apoptosis and gene expression. Cells exposed to various levels of thyroxine over time periods up to 96 hours were examined by fluorescence microscopy for the detection of apoptosis. Purified RNA was assessed by quantitative PCR (qPCR) for expression of 11 genes and two reference (housekeeping) genes. These genes were c-myc, dkc1, thra, thra truncated isoform, thrb, dio3, 18S rRNA, 28S rRNA, rpl11, p53, and mdm2, genes purported to be involved in thyroxine's signaling cascade and apoptosis. The reference genes were ube2d2 and β-actin. Quantitative PCR showed that the vast majority of the genes studied were down-regulated by 96 hours in both low and high thyroxine. Exposure of cells to thyroxine generally resulted in reduced expression of the genes tested. In conclusion, the results of this investigation indicated that apoptosis is observed in response to high T4 exposure, as expected. However, it remains unclear if p53 mediates this response. This study offers insight into the specific effects of thyroid hormone in a rare disease and may contribute to a larger body of research investigating central cellular mechanisms. This study was limited by its focus on one particular pathway of the thyroid hormone and did not include a wild-type cell strain to compare results. A future study would consider more IRES-type transcripts, crosstalk into other pathways including Wnt/β-catenin and Sonic hedgehog. Future studies could also include an investigation into the significance of prenatal and postnatal gene regulation from thyroid response elements. This may offer new understanding of the effect of various interventions in premature neonate healthcare.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Moss, Martin.
- Description:
- The field of membrane investigation is over 80 years old. Yet that remarkably complex and diverse structure, the cell membrane, continues to elude precise definition of structure and function. Observers have found cell membranes to be involved in a variety of functions essential to cell survival, such as preservation of cell boundaries, regulation of passage of ions and other molecules into and out of the cell, modification of intercellular interaction, and regulation of release of cell products.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Mahoney, John.
- Description:
- The rate of growth of catfish farming in the United States during the past 16 years is. unequalled in the history of fish culture. Commercial production of channel catfish (Ictalurus punctatus) has increased from its beginnings in 1960 to an estimated 36,000,000 pounds in 1968, it now exceeds the total production of all other commercially reared fish species in the United States. (Fijan, et. al., 1970) .
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Lynch, Michael Wayne.
- Description:
- The presence or absence of intestinal parasites in a human population is one indication of the quality of life the people lead. Particularly, human intestinal helminths and protozoans have been used to indicate the sanitary standards of a population. Arnett, Wenrich, and Stabler (1933) reported on a survey for intestinal protozoans in 401 college freshmen in the eastern United States. They found 33.1% had one or more species of protozoans after analyzing one stool sample from each subject. McQuay found 20.1% protozoan and 20.2% helminth infections in 4,000 individuals drawn from furloughed missionary families from tropical and subtropical countries (McQuay, 1967). Gleason et al. reported on a stool survey of about half the permanent residents of Aspen, Colorado, done after an outbreak of giardiasis during the 1965-66 ski season (Gleason et al., 1970). Of the 419 people sampled, 5%. were positive for Giardia lamblla. All other protozoans were found in less than 2% of the subjects. The only helminth found was one case of Enterobius vermicularis. The outbreak was attributed to the contamination of water supplies with sewage. In 1971 Allen and Ridley reported on a survey for parasitic infections in patients of a British hospital who had once resided in tropical or subtropical areas (Allen and Ridley, 1971). In this study of 1,000 people, 33.3% were found to have pathogenic or potentially pathogenic helminths or protozoans. An additional 15.1% of the subjects were infected with commensals living in the digestive tract or elsewhere in the body. The present study was a survey for human intestinal parasites in Cantua Creek, a farm labor community 60 miles southwest of Fresno, California (Figure 1). It had a population of approximately 1,800 people, primarily Mexican Americans, Punjabis, and Caucasians. The only unifying force bringing the widely distributed labor camps into a community was the Cantua Creek Elementary School. There were several purposes for surveying Cantua Creek. The first was to determine what parasites the people had. The second was to determine if parasite transmission was occurring. The final purpose was to correlate demographic information on each subject with the presence of parasites.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Lam, Christine.
- Description:
- Shortly after the discovery of the role of bacteria as the etiological agents of human disease, the search for bacterial toxins began. Bacterial toxins were an important discovery, because they may enhance the pathogenicity of infection; the effect of toxins on pathogenicity depends upon the infecting microorganism, the dose, and the route of injection, as well as the interval between the administration of the toxin and the initiation of infection.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Lenchner, Stephan Charles
- Description:
- The social organization of the introduced fox squirrel (Sciurus niger) was studied in the Historical Orange Grove on the campus of California State University, Northridge, Los Angeles County, from 1 March 1973 to 16 July 1974. Twenty-one squirrels were color-marked for individual recognition and observed in the field. A dominance hierarchy was found to exist among the individuals of the population. Social rank was dependant primarily upon the age and sex of the squirrel. During the breeding period, females defended the immediate vicinity of their nests against other squirrels. A decrease in the number of agonistic interactions occurring during the non-breeding season was observed. Some visual, vocal, and tactile signals by fox squirrels in agonistic enounters are discussed. The organizational system of my population of fox squirrels differed slightly from that of an indigenous population of fox squirrels in Florida. The ultimate advantages of such a social system are: (1) conservation of energy; (2) increased reproductive success; and (3) maintainence of the more favorable genes in the gene pool of the population.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kline, Fereshteh Khosravi
- Description:
- Two pathways for serine biosynthesis in Neurospora crassa have been reported by Sojka and Garner. The phosphorylated pathway involves 3-phosphoglyceric acid, phosphohydroxypyruvic acid, and phosphoserine as intermediates, whereas the non-phosphorylated pathway involves glyceric acid and hydroxypyruvic acid as intermediates (1)The phosphorylated pathway was suggested to be the major pathway of serine biosynthesis in Neurospora by these authors. In this investigation a serine-requiring mutant of Neurospora crassa was mapped on linkage group V and was studied in order to determine the nature of its biochemical lesion. Each enzyme in the two postulated pathways was extracted from the mutant strain and compared with the extract of the corresponding enzyme from the nutritionally wild-type strain of Neurospora crassa from which the mutant was originally derived. All enzymes involved in the two pathways were comparable in activity in the mutant and in the wild-type, indicating that the serine requirement in the mutant does not arise from the loss or alteration of any of the enzymes in these two pathways.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sparr, Dustin
- Description:
- Numerous studies have shown that fish parasite communities change in response to pollution levels and could serve as effect bioindicators of ecosystem health. My study sought bioindicators of chemical pollution in parasitological data, i.e., species richness and overall abundance, and the prevalence and intensity of individual endohelminths in particular host fishes. The hosts I studied were Citharichthys stigmaeus (speckled sanddab), Citharichthys sordidus (Pacific sanddab), and Parophrys vetulus (English sole). Of these three species, 250 flatfish were collected from 13 trawl stations in the Santa Monica Bay and Los Angeles-Long Beach Harbor areas, both areas known to be affected by anthropogenic pollution. Flatfish were necropsied for macroparasites. Also recorded were host measures (sizes of fish and of livers, age, and gender). Sediment profiles of PCBs, DDT, and select heavy metals for spots near my sample locations were used from Hyperion's 2008 sediment pollutant data. I characterized pollutant risk at each station using Sediment Quality Values (SQVs), and I generated hazard quotients (HQ) scaled to Threshold Effects Levels (TEL) and Probable Effects Levels (PEL). My results indicate that endohelminth community parameters such as species richness and abundance may indicate sediment pollutant loads of DDT and of heavy metals. In addition, the endoparasites Lacistorynchus dollfusi, Scolex pleuronectis, Anisakis simplex, and Cucullanus annulatus may serve as effect bioindicators of pollution.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Conroy, Lauren P.
- Description:
- In the animal kingdom, males of many species possess striking weaponry used in intrasexual competition for access to females. Until recently, there were no known cases of male weaponry being used against females in sexual coercion. However, in the camel cricket Pristoceuthophilus marmoratus, males use modified hind legs (modifications consist of femoral spines and bent tibiae) not only to fight with each other, but also to trap females and force them to copulate. As male hind leg armaments are positively allometric, the largest males would be best equipped to force-copulate, although they should be the most attractive to females. In order to resolve this potential paradox and determine which males are most likely to force-copulate, I manipulated male body size with diet and performed mating trials. The use of forced copulation was conditional on male body size, with smaller males being more likely to attempt coercive mating. The finding is in accord with the literature on male predictors of forced copulation and suggests an evolutionary exaptation of hind leg armaments in this species, wherein an intrasexual fighting weapon took on a secondary function of sexual coercion. In addition to this study, I performed a comparative survey of armaments, examining fighting and mating behavior in four morphologically similar congeners (P.'Huachuca summer,' P. arizonae, P.'Madera,' and P.'Mt. Pinos') to determine whether hind leg armaments also serve intra- and intersexual functions in these species. Intrasexual leg fighting occurred in all species for which trials were performed, while hints of sexual coercion occurred in two species (P.'Huachuca summer' and P.'Mt. Pinos'), suggesting additional cases of a uniquely dual-purpose armament.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Schmidt, Jacqueline K.
- Description:
- Electron microscope histochemical and biochemical properties of S 180 lysosomes were studied in terms of intracellular disposition and stability. Using acid phosphatase and 5’ nucleotidase localization procedures, dense body lysosomes, secondary lysosomes, residual bodies and unusually large, lipoidal lysosomes were identified at the cell periphery. Electron micrographs reveal that these structures are continually passed from the cell to the exterior; a finding which possibly explains the general paucity of lysosomes in tumor cells. In spite of this small population of lysosomes, biochemical assays demonstrate high levels of lysosomal enzyme activity within these cells. Moreover, similar high levels of activity are found in the peritoneal fluid of the in vivo system as well as in the in vitro system where cells are grown in culture for up to 72 hours. Acid phosphatase with a high latency factor, is released into the extracellular environment at a low rate and remains unchanged over a period of three days. Cathepsin D has a high latency and is more active though more erratic extracellularly than acid phosphatase. Cathepsin B-1 has no latency, but when it is not inhibited by a serum factor, it shows a far greater level of extracellular activity than cathepsin D. Cathepsin B-1 is quite effective at ‘near’ neutral pH and attacks proteins quickly. Thus, this enzyme in particular is implicated in the many structural changes which occur at tumor cell surfaces. However, the possibility that other neutral lysosomal proteases contribute to cell surface protein degradation is not discounted.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
221. Comparative analysis of 16s ribosomal rna typing and physiological traits within sporosarcina ureae
- Creator:
- Kurbessoian, Tania
- Description:
- Sporosarcina ureae is a motile spore forming cocci that traditionally forms packets. The term sarcina is used to describe packets of cocci microorganisms that divide bilaterally, on two or three successive planes. Both physiological and partial 16S ribosomal RNA typing of the ATCC type strain places Sporosarcina ureae in the Bacillaceae family. A key characteristic of the family Bacillaceae is the rod shape and bacterial spore formation. Sporosarcina ureae nomenclature has changed as the result of morphological and biochemical observations. Thus a question arises as to which is a better predictor or tool for classification, physiology (Biolog®), 16S rRNA gene structure, DNA genome sequencing, or MALDI-TOF MS analysis. High throughput Pac Bio sequencing and Biolog® was completed on 6 of the 50+ strains from the California State University, Northridge (CSUN) collection based on extremes of urease activity. MALDI-TOF testing was completed on the entire collection while 16S rRNA sequencing was completed on 33 strains. Based on MALDI-TOF MS work, there are at least 9 different genera, 17 species and 6 strains of Sporosarcina present among the 59 while the 16S ribosomal sequencing found five clusters. Biolog® results created two clusters and reaffirmed nutritional work of Pregerson and Risen suggesting Sporosarcina utilizes the Hexose Monophosphate Pathway, Citric Acid Cycle, and Glyoxylate pathways. This study strongly supports the hypothesis that the 16S rRNA gene and physiological studies show a low degree of homology across geographically distributed isolates. The strongest agreement that we could find was between the PacBio 16S consensus sequence and MALDI-TOF MS for P33 and P37. This study also suggests a relatively ancient divergence between Sporosarcina (sarcina) and Bacillus (rod).
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Margaretten, Nadine Catherine
- Description:
- The effects upon the immune system of long-term exposure to cadmium, as 600 ppm CdCl2 in drinking water, was determined in CBA/H mice and compared to control mice given normal drinking water. Cadmium effects on the general health of the animals were evidenced by decreased weight and hematocrit and proteinuria indicative of kidney damage. The effects of cadmium on the immune system were measured by determining bone marrow cellularity, number and proportion of granulocyte-monocyte progenitor cells, effects on long-term bone marrow cultures, and effects on phagocytic capability of isolated Kupffer cells and resident and activated peritoneal macrophages. Cadmium treatment produced a decrease in cellularity and granulocyte-monocyte progenitor cell numbers in fresh bone marrow. Evidence for a cadmium-induced defect in the ability of bone marrow granulocyte-monocyte progenitor cells to proliferate and differentiate was provided by the results of weekly monitoring of long-term bone marrow cultures. (See more in text.)
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Cobos, Anthony
- Description:
- Convergent evolution is a widely studied evolutionary phenomenon that has been documented in taxonomically diverse groups representing numerous ecosystems and specialized habitats. Yet one traditionally understudied system is the cave environment. Cave life is often associated with novel adaptations for coping with the unique challenges of a subterranean existence. Accordingly, cave-adapted species are expected to converge on a common suite of adaptive differences-introduced here as Gollum's rule-relative to their surface-dwelling relatives. Here I tested for differences in morphology, performance, and physiology of cave-dwelling Malaysian bent-toed geckos (Cyrtodactylus pulchellus complex) relative to their close relatives living on granite boulders in the surrounding forests. I hypothesized that the measured traits would be adaptive as each lineage independently transitioned into its respective cave environment. I found strong evidence for convergence among cave-dwelling Cyrtodactylus. Conventional statistics and comparative analyses accounting for the phylogenetic relationships among the taxa generally agreed that, relative to non-cave-dwelling species (n = 4), twilight zone-dwelling cave species (n = 3) had shorter digits and small palmar and plantar surface areas, higher cling scores to cave substrata, and lower rates of resting metabolism. These data provide evidence that geckos occupying the twilight zone undergo a common suite of changes in traits that are likely adaptive for life in caves thus supporting Gollum's rule.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
224. Fawn production, habitat use, and growth in the North Kings deer herd, Fresno County, California.
- Creator:
- Holl, Stephen.
- Description:
- Previous work on the North Kings deer herd has shown that the reproductive potential of the does was high; however, there was a 50 percent neonatal loss of fawns. The neonatal loss was hypothesized to be the result of a nutritional stress experienced by the does during the spring migration, sufficient to retard fetal growth and development. A second loss of 50 percent of the remaining fawns was seen in 1971 and 1972, which appeared to coincide with the fall migration. Additional observations by Cal ifornia Department of Fish and Game personnel indicated that there were specific habitat requirements associated with the successful rearing of fawns. The present study was designed to refine the relationship between fetal growth and doe physical condition, quantitatively describe areas associated with successful fawning, and determine the physical condition, growth rates, and food habits of fawns prior to and following the fall migration
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Harp, Thomas Kring.
- Description:
- Ranch ponds are numerous in the foothills of the western Sierra Nevada. An article appearing in the California Cattleman (anon, 1975) estimated that there were more than 50,000 ponds of less than 0.0123 cubic hectometers (10 acre feet) in California. Nearly 40 ponds in Madera County were visited and fewer than one half were less than 0.0123 cubic hectometers. This small sample indicates that there are probably many more than 50,000 ponds in California. Most of these ponds were built to provide water for livestock or irrigation. Many ponds are stocked with fish and are a potentially valuable fishery. Currently, there is very little information available on the biology of fish in California ranch ponds.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- George, Nelda Lee.
- Description:
- Two hemipterans, Oncopeltus fasciatus Dallas (Lygaeidae) and Leptocoris trivittatus Say (Corizidae) (Feir, 1974; Woolley, 1949), have been used extensively in research and teaching due to availability and/or ease of rearing. The common squash bug, Anasa tristis De Geer, should be added to the list since it is easily reared in the laboratory, is larger in size than either of the above, and the internal organs are brightly and differently colored permitting color coding. Additional advantages are the plant and fruit feeding habit of this species as opposed to the strictly seed feeding O. fasciatus, and the fact that it belongs to another family (Coreidae). The first steps in establishing the squash bug as a laboratory animal are the development of rearing methods, the collation of current knowledge, and the preparation of an available anatomical study. This paper describes the gross anatomy of the majority of the internal non-skeletal organ systems of the squash bug A. tristis De G.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Ginther, Samuel
- Description:
- The susceptibility of ecosystems to the introduction of non-native species has increased drastically with the development of advanced transportation technologies. It is now quite common for organisms to be easily transported by humans across physiological, ecological, or behavioral barriers that once served as natural population constraints. Despite this increased rate of introductions to locations that were previously unreachable, most organisms that are introduced perish because they are not able to withstand the new environmental pressures of the introduced location, or there are simply not enough conspecifics to perpetuate the population. However, when introduced organisms are able to thrive and reproduce, they may have devastating economic or ecological consequences. A new opportunity to document and understand the effects of an invasive alga on native community members has presented itself in southern Californian waters. Native to northeastern Asia, Sargassum horneri is a macroalga that was presumably transported in ballast water and discovered in Long Beach Harbor in 2003. By 2006 it had spread to the western side of Santa Catalina Island, California, and within a year spread along the entire leeward coast, forming dense stands in numerous areas. Although not all exotic species are ecologically harmful, S. horneri has attributes (fast growing and occurs in high densities) that may allow it to readily establish and outcompete marine flora critical to the community structure of fishes. The purpose of this study aimed to document the effects of S. horneri on kelp forest fishes at Santa Catalina Island, California. I first employed observational, correlative methods to explore the role of S. horneri in shaping biotic and abiotic habitat characteristics of reefs and fish assemblages. I also explored habitat characteristics that predict fish assemblage structure, as well as species-specific responses of fish to habitat predictor variables during 4 distinct time periods. Fish assemblages changed over the course of my 4 sampling periods, and a number of habitat variables (including S. horneri) explained variation in fish assemblage during those times. However, there is more evidence that favors M. pyrifera as a driver of fish assemblage change, as indicated by species-level responses. Additionally, a field experiment testing whether the removal of S. horneri from reef areas affected the fish assemblage was used to evaluate whether patterns documented in the observational portion of my study that could be attributed to S. horneri do in fact appear to be caused by the invasive alga. Removing S. horneri from established areas of reef did not affect multivariate or univariate metrics of fish assemblage over the course of 7 sampling periods. Removal and control (unaltered) areas of reef contained strikingly similar fish assemblages, fish richness, and fish densities over time. Despite a drastic change in reef landscape, it appears that M. pyrifera, rather than S. horneri, was a more significant driver of differences in kelp forest fish assemblages observed in my study. Second, I compared the role of relatively low-lying S. horneri and vertically extensive M. pyrifera in shaping recruitment patterns of a popular sport fish (Paralabrax clathratus) by using an observational and experimental study. I first examined kelp bass recruit abundance on naturally standing S. horneri and M. pyrfera to better understand how fish recruitment rates differ between the introduced and native species. Additionally, I experimentally isolated 3 treatments (M. pyrifera only, S. horneri only, and M. pyrifera and S. horneri together) over a sandy bottom to understand whether the presence of S. horneri, and increased benthic complexity for young fish, enhances kelp bass recruitment. An overwhelming majority of kelp bass recruited to M. pyrifera, and larger recruits were located in the bottom two-thirds of the thalli. Kelp bass recruitment was were observed with S. horneri, regardless of whether the alga was alone or paired with M. pyrifera. Similar to my observational results, larger kelp bass recruits were observed in the bottom third of M. pyrifera treatments. Additionally, I found that that the presence of larger, predatory conspecifics explained a spatial pattern of declining recruitment rates across treatment plots. My study presents the first evidence that S. horneri negatively impacts the recruitment of an important southern California reef fish. Results from both of my studies offer contrasting outlooks on S. horneri's role in southern California kelp forests. When focusing on the entire fish assemblage, little evidence is in favor of S. horneri as a driver of kelp forest fish structure. However when focusing on a particular early life history characteristic of a common kelp forest fish, the effects of S. horneri are dramatically negative. The contrasting results of my studies are important reminders for the need of additional studies to generate a more comprehensive understanding of this invasive alga's impact on kelp forest organisms.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Hovanessian, Rebeka
- Description:
- Apoptosis is a form of cellular suicide activated by intracellular death programs, and is important for normal development and homeostasis. Glucocorticoids (GCs) are known inducers of human T-lymphoid cell apoptosis, and serve as therapeutic agents in leukemia. GCs primarily function by activating a nuclear glucocorticoid receptor (GR) within the cell, which in tum regulates the transcription of target genes. (See more in text.)
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Schram, Michael John
- Description:
- Overfishing has led to significant declines in worldwide fish stocks, particularly large bodied species. Contemporary management attempts to mitigate fishing effects to ensure the sustainability and accessibility of future fish stocks. A typical approach in fisheries management is to set size-limits, which focus fishing pressure on specific size-classes, a practice known as size-selective harvesting. Minimum size-limits are common, placing fishing pressure on the largest most fecund size-classes. In many sex-changing species, the largest size-classes are composed of a single sex. In the case of protogynous hermaphrodite species (those with female to male sex change), a few large males dominate harems of females. Size-selective harvesting therefore becomes sex-selective and has the potential for putting these types of species at risk for overfishing. Observational studies have noted life history changes in harvested protogynous species that correlated with fishing pressure, but controlled manipulative studies demonstrating causal effects of size-selective mortality have not been conducted. I used the blackeye goby (Rhinogobiops nicholsii) as a model species to test the effects of size-selective mortality. Because harvested species are not amenable to controlled manipulation of replicate populations in the field, use of similar model species may be the best approach to gain an in depth understanding of the effects of size-selective mortality on the ecology, reproductive characteristics, behavior, and life history of sex-changing species. Several aspects of the reproductive ecology of the blackeye goby, however, were unknown. My work aimed to (1) identify the factors influencing the reproductive patterns of the blackeye goby and (2) test the effects of simulated size-selective harvesting on their reproduction and growth using a field experiment. To conduct this work, twenty 2.25 m2 artificial reefs were built and stocked with natural densities of blackeye gobies. To determine the environmental characteristics influencing and behavioral changes associated with reproduction in blackeye gobies, I measured reproduction in artificial nests from weekly photographs. Photographs were taken for two months to test for the presence of a lunar cycle in blackeye goby reproduction. Temperature loggers were used to determine the effect of temperature on blackeye goby reproduction. Behavioral observations were made to explore whether behavior of three size-classes (male, female, and juvenile) changed when eggs were present on a reef versus when they were absent. Neither lunar phase nor water temperature were found to influence reproduction of the blackeye goby. The lengthy pelagic larval duration of the blackeye goby likely minimizes any potential fitness gains that could be obtained by timing reproduction with small-scale local variation in environmental factors. Rates of behavioral expression were unaffected by the presence of eggs on the reef. The persistent social dominance hierarchy exhibited by blackeye gobies may allow dominant, nest-guarding males to maximize their reproductive output without any behavioral changes. To test the effects of size-selective removals, populations of blackeye gobies were subjected to one of three size-selective removal treatments that reflected typical size-based management protocols (minimum, slot, and maximum size-limits) and these were compared to a control treatment with no removals. Reproductive output was measured on each reef, and individuals were tagged to track growth and sex change over the study period. Population densities were reduced by ~25%, which is a conservative reduction relative to known effects of fishing on population densities, but which ensured that not all individuals of a single sex were removed from any reef. The size-selective removals had no effect on reproductive output, growth, or incidence of sex change of blackeye gobies. The flexibility in social dynamics likely provides protogynous species the capacity to buffer modest losses of individuals from their populations. Future research incorporating additional species and a wider range of removal intensities and frequencies would provide additional insight into the impacts of size-selective harvesting on protogynous species.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kelly, Thomas Scott
- Description:
- The morphology of the glans penis of Dipodmys was examined for its taxonomics ignificance and its functional aspects.Individual variation occurs and is due to changes in the morphology of the glans during the breeding cycle whereas geographic variation is negligible.The three major glandular features which fluctuate are the size of the main body,the cyclic regenerati on of the spines, and the attachment of the inner membrane.The size of the glans varies according to the degree of engorgement of the blood sinuses.In all individuals which had a testis size of over eight millimeters the glans was engorged. The spines which cover the glans during the breeding season develop when the animal becomes sexually active and probably have the ability to regenerate themselves if they are torn off during copulation.The spines are well developed in breeding adults whereas absent in juveniles and non-breeding adults. Lastly,the glans is covered with an inner membrane which adheres tightly in juveniles and non-breeding adults but loosely covers the glans in sexually active males. See more in Text.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Williams, Robert Eugene
- Description:
- Transduction of streptomycin resistance at a frequency of 4.0 x l0-7 to 6.9 x l0-7 per cell was observed for the blue-green alga Synechococcus elongatus. This report provides the first direct evidence of gene transfer among the blue-green algae. Evidence is presented for the lysogenization of the unicellular blue-green alga, S.elongatus. The temperate phage has been designated S-lT and found to have a head capsid tip-to-tip distance of 840 angstroms. Induction experiments of lysogenic Synechococcus with the antibiotic, Mitomycin-C, resulted in the production of virus as confirmed by electron microscopy and plaque assay. The isolation of a new blue-green algal virus S-1, which infects S. elongatus is described. The new virus appears to be a hexagon with no obvious tail and having a head capsid tip-to-tip distance of 710 angstroms based upon comparisons with latex balls. Several characteristics indicate that the virus is distinct from SM-1 isolated by Safferman. S-1, unlike SM-1, is sensitive to chloroform and to filtration and is not neutralized by SM-1 antiserum.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
232. Reorienting gradient centrifugation: a new method for the quantitative isolation of cell components
- Creator:
- Wells, John Raymond
- Description:
- A reorienting gradient zonal rotor was designed and constructed to test the capabilities of this type of rotor for isolating cellular components. Problems associated with reorienting gradient centrifugation were investigated with this rotor. Density gradients were measured, accelerated in the rotor, decelerated, and measured again to determine the effect of reorientation on the gradient shape. Sample zones were sedimented and collected to test the effect of reorientation. Rate and isopycnic-zonal centrifugations of liver tissue carried out using the reorienting gradient rotor and the collected fractions were analyzed for content and purity. Native glycogen was isolated by combined rate-zonal centrifugation (in a reorienting gradient rotor) and isopycnic-zonal centrifugation. The isolated particles were examined with the electron microscope to record particle sizes and purity of fractions. A comparison of low--speed reciprocating-seal zonal rotors with reorienting gradient zonal rotors is presented. Similar experimental separations using both types of rotors re compared, and a discussion of the possible applications for reorienting gradient rotors based on these results is also presented.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Gharibi, Armen
- Description:
- Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy that affects nearly 50,000 patients each year. The overall 5-year survival rate for this malignancy remains the lowest of any cancer at around 7% due to limited diagnostic methods, disease aggressiveness and a lack of targeted therapeutic interventions. Therefore, there is a dire need for novel biomarkers and therapeutic targets for patients diagnosed with PDAC. Since most cancer-related deaths are a result of metastatic tumors, we reasoned that our previously published proteomic signature of the cell pseudopodium (PD) may be a good pool from which to identify novel protein biomarkers or therapeutic targets. Here, we cross-referenced PD proteins with Oncomine and identified 37 genes that are upregulated in PDAC. The function of integrin alpha 1 (ITGA1) - a cell surface receptor for collagen, had not been previously characterized in the context of PDAC. We discovered that collagen induces rapid ITGA1-dependent PDAC cell spreading. Epithelial-mesenchymal transition (EMT) is a well-characterized process by which pancreatic cancer cells become more invasive and gain metastatic potential. Analysis of EMT markers in comparison to ITGA1 in PDAC cell lines and patient samples suggests that ITGA1 may be a regulator of EMT. Since transforming growth factor beta (TGF) is a potent inducer of EMT, we tested the function of ITGA1 on TGF-induced EMT. Our results indicate that ITGA1 is upregulated by TGF during EMT, and required for complete EMT in the presence of collagen. In an effort to identify the mechanism by which ITGA1 is regulating TGF-induced EMT, we searched for the top ITGA1 co-expressors using RNA-Seq data from the Cancer Bio Portal. Interestingly, PEAK1 kinase (a protein that we've previously shown to be required for PDAC progression) co-expresses with ITGA1 (Pearson R-value = 0.70). Taken together, these results suggest that developing detection methods and/or therapies against ITGA1 may help diagnose PDAC earlier or improve patient responses to already existing chemotherapies.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Singh, Suprita
- Description:
- The enzymatic activities of commercially prepared glycosidases were verified by direct chemical assays using defined substrates and fixed and live sea urchin embryos to determine if a model cellular interaction (interaction of archenteron tip and roof of the blastocoel) was mediated by glycans. The sea urchin embryo has been used as a convenient system for studying cell to cell interaction and morphogenetic movements during gastrulation by developmental biologists for over a century. Understanding molecular mechanisms behind this interaction can improve the basic understanding of cell to cell adhesion and can help in understanding what goes wrong in diseases like cancer. In present study we are interested in understanding the role of cell surface sugars in adhesion by using three different beta-glycosidases b-amylase, b-glucosidase and b-galactosidase. These glycosidases were first independently characterized by performing enzyme assays on the known substrates to ensure that they are active. These were then tested for possible contaminations using SDS-PAGE and for cryptic protease activity using Azocoll. All glycosidases were found to be active and there was no or very little detectable protease contamination. To determine if sea urchin embryos have exposed glycans that can be degraded by glycosidases, disrupted live and fixed embryos were used as substrates for these enzymes and product release was detected by colorimetric assay. Active b-amylase released a substantial amount of product from both live and fixed embryos, indicating that glycans with terminal amylose-like structures must exist in the embryo and be accessible to the enzyme even after formaldehyde fixation. Some detectable amount of product was also obtained with active b-glucosidase and b-galactosidase. To confirm that the sea urchin embryos do not release inhibitors of glycosidases, mixed reactions were also conducted in which the defined substrates (e.g. starch, in the case of α- and β-amylase) were tested in the presence of long-term fixed sea urchin embryos. Under these conditions all the glycosidases displayed good activity with defined substrate alone, as well as with both the substrates together. We conclude that the amylase, glucosidases and galactosidase were functional in the experiments with long-term fixed sea urchin embryos and were not inhibited. The glycosidase preparations (both active and denatured) were incubated with microdissected archenterons and blastocoel roofs in a direct assay to learn if their action could prevent the normal adhesive interaction. Out of the three b-glycosidases only b-amylase (an exoglucosidase) showed immediate (1-2 minutes incubation) inhibition even with relatively low number of enzyme units. The other two enzymes (b-glucosidase and b-galactosidase) showed substantial inhibition after overnight (12 hours) incubation. Since proteases and other contaminants in enzyme preparations are known to often be effective after longer term incubations, only effects at very short incubations were deemed to be likely to be significant and biologically relevant. As expected, denatured enzyme didn't show any effect on adhesion. The results suggested a role for glycans in cell adhesion and action of glycosidases changed cell surface glycans that resulted in inhibition of the adhesive interactions.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Algiers, Joseph
- Description:
- Invasive species pose a large threat to native vegetation. Billions of dollars are spent annually on efforts to control invasive species in agricultural and natural settings. Studies have revealed multiple benefits from removing invasives. However, there have been no studies that have evaluated the outcomes of these strategies in fuels-reduction areas, at least not in southern California. I investigated efforts to control three invasive plant species (Carduus pycnocephalus Italian thistle, Centaurea solstitialis yellow star thistle, and Foeniculum vulgare sweet fennel) at three sites in the Santa Monica Mountains National Recreation Area. In all three cases, weed control efforts initially reduced the cover of invasive species targeted for eradication. Native cover was evaluated at one site, but it showed no differences in any year following treatment. Following eradication of Italian thistle in a fuels-reduction area, I planted disturbance-adapted native plants belonging to three life-history strategies (annuals, herbaceous perennials, and perennial grasses). I evaluated the ability of these natives to resist re-establishment of the invasive thistle. Unfortunately, this experiment was done during a drought. As replacement vegetation, perennial grass and herbaceous perennial cover was low and native annuals did not recruit. Italian thistle showed little difference in cover regardless of which native plant life-history strategy it occurred with. However, several months following planting, thistle grown with perennial grasses were smaller than thistle grown in plots that had been designated to receive annual plants (annuals that never grew). Although perennial grasses did not reduce the cover of thistle, they did reduce its size. Further research on the use of native species to prevent re-establishment of invasive species may help guide resource management strategies in fuels-reduction areas.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Simpson, Karen Renee
- Description:
- Aggregation promoting components from the sea urchin Stronglycentrotus purpuratus were obtained by dissociating blastula stage embryos in calcium-magnesium- free sea water (CMFSW). The CMFSW dissociation supernatant was termed DS as previously reported. Adhesion promoting components were isolated from DS using glutaraldehyde fixed S. purpuratus blastula cells as affinity adsorbants. The subset of molecules isolated in this manner was termed S-2 (as previously reported). DS and S-2 promoted cell aggregation in a species specific manner. An analysis of the proteins in DS and S-2 was accomplished using SDS polyacrylamide gel electrophoresis. Proteins ranged in molecular weights from 12 to 450 KD. Those found in S-2 were, with one exception, a subset of those in DS. Approximately 26 protein bands were identifiable in S-2. Further studies should reveal exactly which of these bands may be responsible for enhancing adhesion of sea urchin blastula cells. This study is one in a continuing series that is helping to provide insight into the nature of adhesion mechanisms in a model system.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Fstkchyan, Yesai Sevak
- Description:
- Apolipoprotein B mRNA editing enzyme catalytic polypeptide like-3 G (APOBEC3G) is a member of a family of cytidine deaminases that includes activation-induced deaminase (AID), the enzyme responsible for somatic hypermutation in B cells. While APOBEC3G (A3G) is best known for its activity in restricting both retroviral infection and the mobility of genomic retrotransposable elements, there is mounting evidence that A3G possesses a far more involved role in the cell. A3G has been localized to P-bodies, subcellular foci of mRNA editing and microRNA activity, and has been found to directly influence microRNA activity. The Broad Institute Differentiation Map (dMap) is a collection of microarray data that quantifies levels of gene expression in hematopoietic cells throughout their development. According to dMap, levels of A3G expression fluctuate tremendously throughout the process of hematopoiesis. This is inconsistent with a purely antiretroviral factor. We chose to determine whether A3G may be functionally important in hematopoietic development. Analysis by qRT-PCR of A3G expression at the mRNA level reveals that A3G is expressed in human embryonic stem cells (hESC). Moreover, there is a significant rise in A3G expression when hESCs are induced to differentiate into early hematopoietic progenitors. Together, these data suggest a role for A3G in the earliest stages of human hematopoiesis. While unpublished data from our lab provides evidence that suggests A3G has a role in intermediate hematopoietic lineage commitment, it is unclear how A3G might influence early hematopoietic development. We, therefore, asked whether A3G plays a role in the development of early hematopoietic progenitors derived from hESCs. To address our question, we applied a loss-of-function strategy to investigate whether the absence of A3G might impair or alter early hematopoietic development. To accomplish this, we used hESCs as a model system and knocked down A3G. We then characterized the ability of these genetically altered cells to give rise to early hematopoietic progenitors and their hematopoietic lineage commitment towards terminally differentiated cell types of the blood using flow cytometry and methylcellulose colony forming assays. Results from this study have identified a novel function for A3G in that it influences late progenitor fate decisions, but does not alter early development of hematopoietic progenitors demonstrated by impaired erythropoiesis and increased myelopoiesis. This study has uncovered a novel developmental factor previously not thought to be important in human hematopoietic development.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Wensel, Mary Susan
- Description:
- Suspensions of eight to ten day embryonic chick neural retina cells were exposed to four different concentrations of sugars or their derivatives. Evidence is presented, using a quantitative electronic particle counter assay to measure cell adhesion which indicates that N acetylneuraminic acid, D-galactose and D-mannose may be involved in the adhesion of embryonic chick retina. Plant lectins were used to study the agglutinability of suspensions of one to seven day old sea urchin embryo cells. Using the same quantitative assay for agglutination, evidence suggests that carbohydrate-containing lectin-binding sites change during sea urchin embryonic development. Sea urchin embryo cells are 26 ± 5% more agglutinable with Con A at early developmental stages (day one) than at later ones with a marked decline in agglutinability between day two and three. Agglutinability with Ricinus communis agglutinin (RCA) may also be more pronounced in young embryos. Normal embryonic sea urchin cells are not agglutinated with wheat germ agglutinin (WGA) unless the cells are trypsinized. The results suggest that changes in the amount, mobility, or distribution of Con A-binding receptor sites (containing α -D-mannose- like or α -D-glucose-like residues) occur with differentiation. In addition RCA-binding receptor sites (containing β- D- galactose or β -N-acety1-D-galactosamine- like residues) occur with differentiation in sea urchin embryos, while WGA-binding receptor sites (containing N-acetyl-D-glucosamine-like residues) are displayed in a state which precludes agglutination at all developmental stages studies. The results are discussed with respect to cell types present during sea urchin-embryo development and provide quantitative evidence for the contention that specific changes in carbohydrate-containing cell surface sites occur with differentiation and maturation.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Main, Kevan L.
- Description:
- The members of family Ovulidae are always found living on cnidarian hosts, usually alcyonarians. The colors of the shells tend to blend with the host on which they are found being purple on purple gorgonians or yellow on yellow gorgonians. Simnia aequalis lives on the gorgonian Lophogorgia rigida in the northern Gulf of California. S. barbarensis lives on the sea pens, Acanthoptilum gravile, Ptilosarcus gurneyi and the gorgonian, Lophogorgia chilensis in Southern California. External morphology, mantle cavity and radula of Simnia aequalis and of S. barbarensis are described and compared to those of other members of the family Ovulidae. Larval development of both species was studied through laboratory culture over a one-year period. Development of S. aequalis is compared to that of S. barbarensis. This work is related to other researcher’s descriptions of the larvae of S. spelta and S. patula. Planktotrophic larval culture in a closed seawater system was carried out and the problems are discussed. Feeding behavior of adult snails was observed and is described.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Szabo, Diana Joy
- Description:
- Three females and one male deermice (Peromyscus maniculatus) formed an experimental group in each of five experiments. Observations were conducted over a span of thirty-two months. Agonistic behaviors used to determine hierarchial relationships were scaled from a negative ten to zero (submissive) and from zero to positive ten (dominant). These quantitative data were then used to determine the hierarchial relationships in each experiment. The situation that seemed to most influence the hierarchies in each experiment was the birth of a litter to one of the females. The third ranked female in each experiment did not give birth to any offspring. Chi-square tests were used to determine levels of significance. Each experimental chi-square value (all individuals in that experiment) was found to have a p value of less than .001 and all were concluded to be highly significant. My research shows that female Peromyscus maniculatus form linear hierarchies based on agonistic behaviors such as those well-documented for male Peromyscus maniculatus.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Westall, Tory Lynn
- Description:
- The San Joaquin kit fox (Vulpes macrotis mutica) is an endangered species endemic to the San Joaquin Desert in the Central Valley of California. Much of the habitat in the San Joaquin Desert has been converted for agricultural, industrial, and urban development. The remaining San Joaquin kit foxes exist as a meta-population in several satellite populations and three core areas, the Panoche Valley, the Carrizo Plain, and western Kern County. Another substantial population that could be considered a core area is the urban population that is living in the City of Bakersfield. This population is fairly large and critical in contributing to the conservation of the species as a whole. The urban population of San Joaquin kit foxes has higher survival rates, lower dispersal potential, and higher reproductive success as well as increased incidence of philopatric young and larger family groups when compared to populations living in natural areas. The San Joaquin kit fox is a socially monogamous species, but philopatric young have been classified as Helpers because they assist in rearing future litters. Understanding how the altered ecosystem in the urban environment can affect reproductive traits of an endangered species is important for conservation. In this study I investigated the relative contributions of adult group members to pup rearing in urban San Joaquin kit foxes. My objectives were to quantify the relative time contributions of each individual, the different tasks performed by each individual, and the changes in time contributions and tasks performed by each individual as the pups aged. To quantify den attendance and behavior, I used proximity logging collars and base stations at each natal den, performed direct observations of behaviors, and set up remote camera stations at dens. I also compared these methods for efficiency in detecting behaviors. To determine role, I used behaviors and genetic analyses to classify each individual to one of three categories: Mother, Father, or Helper. To monitor changes in behavior as pups aged, I split the breeding season into three periods: Preparturition, Nursing, and Weaned. I monitored six groups at four locations in Bakersfield, California and had four groups that successfully reproduced and were consistently monitored. I found that proximity logging collars were unreliable in measuring den attendance of kit foxes. Cameras were an effective method for documenting behaviors, but they significantly underestimated the amount of time that foxes spent at the den. Direct observations were the most accurate method of gathering behavioral data and were used for analyses of parental care. I found that Mothers play a critical role in pup rearing. Mothers spend significantly more time at the den than either Fathers or Helpers. While Fathers spend most of their time away from the den, they provision the same amount of food as Mothers, whereas Helpers provisioned significantly less than either Mothers or Fathers. Mothers primarily groomed young, provisioned, guarded while young played, and performed den defense. Fathers primarily provisioned and provided den defense. Helpers mostly interacted with the pups through play, which may teach the pups the social hierarchy and establish dominance. While Helpers do not provide direct care to young, they may provide a form of insurance of parental care of young should something happen to either of the parents. Helpers are likely tolerated within their natal range because there is an increased abundance of food within the urban environment and their presence is not detrimental to the success of the current litter. I also documented two incidences of social polygyny and genetic polyandry over the course of my study. This is likely tied to the super abundance of resources because more plentiful resources result in a decreased need for paternal care and so one male can split his time between multiple litters. My results indicate that there is a decreased need for assistance in pup rearing in the urban environment due to the increased resources available. Helpers do not actually help in rearing pups and Fathers are not as necessary to successful pup rearing. Mothers play an essential role in pup rearing and are necessary for successful reproduction in the urban environment.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Clymore, Gary Lee.
- Description:
- Waters containing enteropathogenic microorganisms (i.e., Salmonella, Shigella) are considered unsafe for human consumption. Traditionally, indicator bacteria have been utilized for the assess- ment of bacteriologically unsafe waters. However, a demand for increased water quality assurance has created renewed interest in the natural relationships of enteric pathogens and indicator bacteria (14, 31, 32). The reliability of the coliform test, the utilization of Pseudomonas aeruginosa as an indicator organism, and the relationship of fecal streptococci to pollution have currently been under consideration. Furthermore, the criteria for determining these particular bacterial populations and the environmental factors capable of influencing them are becoming of utmost importance in water sanitation.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Adamian, Alina
- Description:
- MicroRNAs (miRs) are small, non-coding RNAs that regulate gene expression post-transcriptionally through mRNA degradation. MiRs are categorized as either oncomiRs, a microRNA associated with cancer, as functional tumor suppressors, or as both as in the case of miR-155. MiR-155 is encoded by the gene miR-155HG on chromosome 21 and lack of expression has been associated with Mantle Cell Lymphoma (MCL). In addition, miR-155 was found expressed in Small Lymphocytic Lymphoma (SLL), liposarcoma and breast cancer. MiR-155 has been found to be normally expressed in B-cells. We previously found miR-155HG associated with expression in indolent SLL but not aggressive MCL. MiR-155 promotes apoptosis by targeting anti-apoptotic mRNA as well as BCL2, which is involved in regulation of the apoptosis pathway, suggesting that perhaps low or dysregulated miR-155 expression in MCL contributes to the aggressive nature of this lymphoma. Here we have identified and characterized the proximal and core promoter regions of miR-155HG. Transient transfection analyses suggested the proximal promoter is located within the -117 base pairs from the TSS (Transcriptional Start Site). Several regulatory elements were predicted via transcription factor site databases within this region. One of these, AP1, is highly conserved throughout evolution. Mutagenesis analysis showed high transcriptional activity within the -117 bp region where the AP-1 TF binding site was predicted to be located at -38 bp from the TSS. Bioinformatics data suggested the AP-1 TF binding site was conserved through evolution in 11 species including 100% identity in the chicken (Gallus gallus miR-155GG). The AP-1 binding site sequence, TGA G/C TACAA, is located -40 bp from the TSS in G. gallus. Transient transfections showed equivalent transcriptional activity between miR-155HG and miR-155GG in this region. Mutagenesis of the AP1- site in both human miR-155HG and chicken miR-155GG showed decreased levels of expression, further suggesting that AP-1 is an essential TF driving transcription of these genes. MSA alignment revealed that the AP1 TF binding site is not conserved in Mus musculus, and as such, NIH 3T3 cells were also transfected for analysis of expression of miR-155 construct in these cells.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Quintero, David
- Description:
- Salmonella str. VNP20009 selectively colonizes solid tumors and has been shown to reduce their growth in mouse models. Studies have demonstrated that Salmonella can induce apoptosis through direct contact with cells. However, this property limits the potential of the bacterial therapy by requiring physical association with tumor cells. In order to overcome this limitation, these bacteria can be engineered to express and secrete cytotoxins that are tumor cell specific, which may enhance tumor destruction while sparing healthy adjacent tissues. Epidermal growth factor receptor (EGFR) is overexpressed in many cancer cell lines including breast, prostate, colon, brain and others, and is a validated target in the clinical setting. In this thesis, EGFR-targeting toxins were engineered and assessed for their ability to be secreted or released into the extracellular milieu by VNP20009. VNP20009 was able to secrete or release three forms of a truncated Pseudomonas aeruginosa Exotoxin A (ToxA) cytotoxin that was fused to the EGFR-binding ligand, tumor growth factor-alpha (TGFα), which resulted in bacterial culture supernatants that were selectively cytotoxic to cells overexpressing EGFR. Additionally, the native ToxA C-terminal endoplasmic reticulum (ER) retention signal was replaced with the mammalian consensus sequence KDEL to enhance toxicity, and were co-expressed with the pColE3 lysis protein to facilitate secretion. These genetic manipulations resulted in a supernatant that is more active against EGFR positive cells than the secreted wild type ToxA, and may translate into a potent, targeted bacterial therapy.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Merolla, Sarah
- Description:
- Coral reefs are currently facing multiple stressors that threaten their health and function, including ocean acidification (OA). OA has been shown to negatively affect many reef calcifiers, such as coralline algae that provide many critical contributions to reef systems. Past studies have focused on how OA independently influences coralline algae, but more research is necessary as it is expected that the effects of OA on coralline algae will vary depending on many other factors. To better understand how algal morphology, water flow, and algal acclimation interact with OA to affect coralline algae, three studies were conducted in Moorea, French Polynesia, from June 2015 to July 2016. In January 2016, I tested the hypothesis that algal individuals with higher morphological complexity would exhibit faster metabolic rates under ambient pCO2 conditions, but would also demonstrate higher sensitivity to OA conditions. For three species of crustose coralline algae, Lithophyllum kotschyanum, Neogoniolithon frutescens, and Hydrolithon reinboldii, algal individuals with more complex morphologies demonstrated faster rates of calcification, photosynthesis, and respiration in the ambient pCO2 treatment than individuals with simpler morphological forms. There also appeared to be a relationship between morphology and sensitivity to OA conditions, with calcification rates negatively correlated with higher morphological complexity. In the summers of 2015 and 2016, I conducted three experiments examining the effects of water flow and OA on different morphologies of coralline algae to test the hypotheses that increased flow would enhance metabolic rates and mitigate the effects of OA, and that algae with more complex morphologies would be more responsive to increased water flow and more sensitive to OA conditions. A field experiment investigating the effects of water flow on Amphiroa fragilissima, L. kotschyanum, N. frutescens, and H. reinboldii detected enhanced rates of calcification, photosynthesis, and respiration with increased flow, and this relationship appeared to be the strongest for the crustose algal species with the highest structural complexity. A flume manipulation examining the combined effects of water flow and OA on A. fragilissima, L. kotschyanum, N. frutescens, H. reinboldii, and Porolithon onkodes suggested that coralline algal species with high structural complexity were the most sensitive to OA conditions. Finally, A. fragilissima and L. kotschyanum were maintained in different pCO2 and water flow conditions in a long-term mesocosm experiment, which indicated that flow was unable to mitigate the effects of OA on coralline algae. In the summer of 2016, I investigated the acclimation potential of A. fragilissima and L. kotschyanum to OA, and predicted that the original treatment conditions would induce phenotypic modifications that would influence algal responses to the end treatment. There were negative effects of long-term exposure of coralline algae to elevated pCO2 conditions on calcification and photosynthesis, though partial acclimation in calcification to OA was observed. The instantaneous exposure of elevated pCO2 had negative impacts on algal calcification, but had a nominal effect on photosynthesis. No effects of long-term or instantaneous exposure to elevated pCO2 were observed for respiration. The results of these studies indicate that the coralline algal response to OA conditions will likely be complex and depend on numerous factors including water flow, morphology, and acclimation potential. Therefore, it is critical that future studies further investigate the effects of these factors; specifically examining the mechanisms that underlie these responses in order to better predict the future of coralline algae and thus coral reef ecosystems in a more acidic ocean.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Gupta, Dinesh
- Description:
- Non-renewable fossil fuels are responsible to meet more than 80% of global energy demand and its increasing price has ignited the interest in renewable biofuel production. 2-Methyl-3-buten-2-ol (MBO) is a natural volatile 5-carbon alcoholic compound produced by several pine species. MBO has the potential to be used as biofuel. Higher energy content and less solubility in water make MBO superior than bioethanol in terms of both energy output and cost effectiveness. In pine chloroplast, methyl-erythritol-4-phosphate (MEP) isoprenoid pathway produce dimethylallyl pyrophosphate (DMAPP) which is utilized by MBO synthase for production of MBO. MBO production from its natural host is challenging due to its volatile nature. However, the volatile nature of MBO makes its recovery easier when produced through bacterial cultures in closed system bioreactor. The aim of this study is to produce MBO from Escherichia coli and also from the photosynthetic microorganism Nostoc punctiforme. MBO production in E. coli was attained by metabolic engineering with mevalonate (MVA) dependent pathway to increase the intracellular supply of DMAPP substrate and co-transformation with codon optimized Pinus sabiniana MBO synthase gene. Production was characterized and quantified using gas chromatography (GC) analysis. Further, MBO production was optimized using different culture media and conditions. MBO toxicity to the host cells was also studied to estimate the maximum amount of MBO that can be produced from E. coli culture. N. punctiforme was used as another host to produce photosynthetically derived MBO by expressing the MBO synthase gene from a plasmid under control of an indigenous petE promoter. Reverse transcriptase (RT)-PCR and SDS PAGE were performed to analyze the MBO synthase gene expression at mRNA and protein level. Although, the transcription and translation of MBO synthase were confirmed, detectable level of MBO production was not detected through gas chromatograph-mass spectrometry (GC-MS). Instead, enhanced production of phytols in the transgenic strain was observed and confirmed through a GC-MS analysis of total extracted lipids. To explain the enhanced production of phytols in transgenic strains, two plausible hypothesis were proposed; first, presence of an indigenous broad range substrate specific prenyltrasferases and second, appropriation of a MBO synthase metabolic intermediate by a native geranyl diphosphate synthase. To study the location of phytol production and accumulation in N. punctiforme, cell fractionation was performed using French pressure cell press and ultracentrifugation. Phytols were found to be present in cytoplasmic fraction. This study demonstrates feasibility of MBO production through bioengineering of E. coli however further work is required to improve its production to an economically efficient level. At the same time, this work also highlights the challenges of bioengineering a non-native cyanobacterial host, N. punctiforme, for production of useful compounds.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Koleilat, Tasneem
- Description:
- Human embryonic stem cells (hESCs) have the unique ability to undergo self-renewal and are pluripotent, which enables them to differentiate into all three germ layers. Harnessing these properties could result in significant therapeutic outcomes for repair or cell replacement in many disease settings. However, many hurdles remain prior to use of these cells in cell-based therapies including lack of understanding of what signals regulate pluripotency and how to maintain stability of hESCs. OCT4, NANOG and SOX2 are transcription factors that regulate multi-gene networks involved in control of cell fate decisions important for maintaining self-renewal and stability of hESCs. RE1-Silencing Transcription Factor (REST) is one of the direct targets of this network which is a well known transcriptional repressor. REST acts by binding to RE1 sites in greater than 1900 genes in the genome. The main role of REST is to act as a transcriptional repressor in nonneuronal cell types to repress neuronal differentiation. This repression has been shown in some but not all mouse embryonic stem cell studies, however, its role in hESCs is not clear. To examine the role of REST in hESCs, we have performed lentiviral mediated knockdown of REST (REST KD) in three different cell lines and we have evaluated the effects of the loss of REST on hESC self-renewal, differentiation, genetic stability. REST KD hESCs seem to exhibit enhanced self-renewal and the ablation of REST does not have an effect on the pluripotency of hESCs. We also found that three out of four hESC lines with REST KD were genetically unstable, whereas control hESC lines were karyotypically normal. To determine the gene networks involved in this instability, we have examined several candidate genes differentially expressed upon REST KD by performing qPCR of individual REST targets. Some of the genes that are consistently and significantly up-regulated include ATM, RTEL1, CDK4 and E2F1. These genes have been instigated as direct REST targets and most are up-regulated upon DNA damage which is consistent with our previous result of chromosomal instability upon ablation of REST. We were also interested in changes to the expression of lineage markers in embryoid bodies (EBs) from REST KD and control cells in order to examine the effects of the loss of REST on differentiation. Upon REST KD, hESC EBs exhibited a bias towards endoderm and mesendoderm lineage. Contrary to our expectations, there was a reduction in ectodermal cells upon REST KD. Since our results confirmed a endoderm/mesoderm bias in vitro we next examined the signaling pathways that may be involved in producing the aforementioned lineage commitment. Using protein and RNA analysis we have shown a slight reduction in pMEK and pSMAD upon REST KD indicating that REST may be involved in the MAPK pathway as well as the TGF pathway. In summary, our work has shown that REST is a regulator of hESC genetic stability. Elucidating the targets mis-regulated upon REST KD could shed light on the gene networks regulating instability and differentiation in pluripotent stem cell cultures. This could improve our ability to stably expand and differentiate hESCs for use in regenerative medicine.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Evensen, Nicolas
- Description:
- As large amounts of information are becoming available describing the responses of corals to ocean acidification (OA), attention is turning to the effects of OA on ecological processes affecting community structure. One such process is competition for space among scleractinian corals, a process that could be affected by OA due to inter-specific differences in sensitivity of corals to increasing oceanic pCO2. Thus, experiments were carried out in Spring 2013 and 2014 in order to determine the effects of OA on species interactions among scleractinian corals. In 2013, experiments were designed to test the hypothesis that OA affects the ability of M. aequituberculata and massive Porites spp. to engage in spatial competition in Moorea, French Polynesia, and Okinawa, Japan. Using linear extension rates (μm d-1) as a proxy for competitive ability, the effects of OA were tested on intraspecific, interspecific, and control pairings. Linear growth of M. aequituberculata was affected by OA in Okinawa, with no OA effect on massive Porites spp. Much of the reduction in growth between the ambient and OA treatments was due to a decrease in the control pairings however, with corals in competitive pairings maintaining linear growth rates under OA. Subsequently in 2014, I tested the hypotheses that: (i) OA alters interactions among corals arising from conspecific and interspecific coral arrangements, and (ii) the effects of OA on coral growth are modulated by adjacent coral colonies. The hypotheses were tested by measuring the effects of OA on the growth of P. verrucosa in spatial arrangements with conspecific and interspecific colonies. In this experiment, the effects of OA on calcification of the focal P. verrucosa colonies was mediated by surrounding colonies, with calcification rates for the focal corals in conspecific aggregations increasing in the OA treatment. Furthermore, planar growth was reduced by OA, while apical growth was unaffected. Overall, the results of both studies demonstrate the potential for OA to affect the ability of corals, M. aequituberculata and P. verrucosa in this case, to engage in spatial competition, with linear and planar growth reduced by OA. The results also emphasize the importance of considering biotic interactions when assessing the effects of OA on corals, as M. aequituberculata was shielded from the detrimental effects of OA when engaged in competitive interactions, and the negative effects of OA alleviated for P. verrucosa colonies in conspecific aggregations.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Northcutt, Douglas H. C.
- Description:
- The development of alpha amylase and phosphatase in barley endosperm was studied in the presence and absence of an inhibitory fraction from an extract of carob fruit (Ceratonia). The amounts of the two enzymes were measured in both the medium and the seeds. The inhibitor reduced the amount of alpha-amylase in the medium at all time intervals measured over a period of 57 hours. There was no concurrent reduction in the seeds. Instead, ex-amylase from seeds incubated either with GA3 alone or with GA3 plus inhibitor increased to a relatively high level by 26 to 30 hours. Total enzyme content was approximately the same whether the inhibitor was added or not. Acid phosphatase in the medium was also reduced by the inhibitor. There was little difference in phosphatase content between the seeds incubated in media containing GA3 alone and those in GA3 plus inhibitor. High concentrations of inhibitor completely blocked the appearance of the enzyme in the medium. If the seeds were then washed with water and placed in fresh media with GA3 but no inhibitor, they would produce phosphatase. The presence of the inhibitor did not permanently affect the enzyme synthesizing ability of the seeds. Addition of inhibitor at various times during incubation resulted in a subsequent reduction of the amount of acid phosphatase produced. These data indicate that fraction C from carob has different effects on each of the two enzymes studied. In the case of alpha-amylase secretion seems to be blocked, and in acid phosphatase synthesis seems to be inhibited. The inhibition of phosphatase appears to be at the protein synthesis level rather than the RNA level.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Zung, Lisa L.
- Description:
- The reduction of suitable habitat due to urbanization is an increasing threat to many native plant populations. As a result, plant populations that were once continuous have become fragmented into smaller isolated populations. These resulting small populations face reduced gene flow and increased genetic drift, decreasing genetic variability. Populations with reduced genetic variability are more susceptible to disease and environmental change. Southern California is a region where the encroachment of urban development has taken a heavy toll on native plant populations. In particular, Pentachaeta lyonii, a native federally listed endangered plant that was once found in many parts of Los Angeles County and southeastern Ventura County now persists in a few locations in the Santa Monica Mountains and Simi Hills. The objective of this study was to determine the population structure and estimate gene flow between seven sites where P. lyonii occurred. To accomplish this, DNA was extracted from whole plants collected at each site, and the nuclear genetic markers internal transcribed spacer 1 and 2 (ITS1 and ITS2) were amplified and sequenced for each sample. The resulting sequences were then compared using an analysis of molecular variance (AMOVA), and used to estimate levels of gene flow. A high level of genetic variation was found among sites (90.82%) with very little variation found within them (9.18%). Gene flow was highly restricted (estimated Nem = 0.03) and there was a high level of genetic differentiation (FST = 0.91 and GST = 0.89) clustering sites into what seems to be larger northern and southern groups. Because only one set of nuclear molecular markers was assessed, and within these the sequence divergence was less than 1%, additional genetic analyses should be undertaken to verify this difference before developing restoration plans that would involve moving seeds and/or pollen from one area to another. Until more is known about the population genetics of P. lyonii, conservation of its habitat should be a priority.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Forster, Patricia
- Description:
- Murine monoclonal antibody preparations specific for Treponema pallidum subsp. pallidum were shown to bind to thin sections of T. pallidum, Nichols strain, by immunoelectron microscopy using colloidal gold-labeled antiglobulin, and the subcellular binding sites correlated with the proposed specificities of the various monoclonal antibodies. T. pallidum was fixed and embedded in epoxy resin by a modification of standard histological techniques and ultrathin sections were prepared. They were exposed to six different murine monoclonal antibody preparations with previously demonstrated antitreponemal specificity. Colloidal gold-conjugated goat antiglobulin specific for mouse IgG or IgM was applied to detect bound monoclonal antibodies by transmission electron microscopy. Non immune and polyclonal antitreponemal mouse serum, a heterologous murine anti-gonococcal monoclonal antibody, and appropriate combinations of antibody or gold conjugate alone and unconjugated colloidal gold were included as controls. The preparations were fixed and negatively stained after exposure to the various antibody reagents. The treponemal morphology was preserved, as evidenced by clear inner and outer membranes, well-defined endoflagella, and cytoplasmic tubules. Different monoclonal antibodies bound to the sections of intact treponemes on either the outer membrane or the endoflagella. These results confirm the specificity proposed by Lukehart (44) for each monoclonal antibody. The specificities of the various binding reactions were confirmed by the results of the controls. The results give the first visual evidence of the subcellular T. pallidum antigens which react specifically with antitreponemal monoclonal antibodies and provide a method for locating such immunogens.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Shah, Bansari
- Description:
- Gene therapy is a method with great potential for the treatment of heritable disorders. One difficulty with this approach is that the vectors used in early trials were derived from viruses. Viral genomes have several disadvantages as vectors for gene therapy, including the interruption of cancer-causing genes by random insertion into the genome and activation of the immune system. The purpose of this project was to compare vectors that could serve as a foundation for gene therapy that avoids these difficulties. I used as a model the treatment of Hunter syndrome, a lysosomal storage disease to compare efficiencies of non-viral vectors in delivering genes to cultured cells deficient in functional genes. Mucopolysaccharidosis type II (MPSII), also known as Hunter syndrome, is an x-linked recessive disorder that occurs when the IDS gene located on the X chromosome becomes mutated. The IDS gene is responsible for making the I2S enzyme. The lack of I2S or reduced function of this enzyme causes a buildup of glycosaminoglycans (GAGs) within cells everywhere in the body. Due to this accumulation, many cells of the body become swollen, which makes this disorder a progressive debilitating condition. Currently, enzyme replacement therapy (ERT) is the only FDA approved treatment option for affected individuals. Unfortunately, ERT does not treat or provide a cure for this disorder. For a permanent therapy in the future, gene therapy may be the solution. In this study, I examine the effect of a non-viral vector containing the IDS gene on MPSII fibroblasts. The IDS gene was cloned into a non-viral vector, pIRES-hrGFP-2a.. MPSII fibroblasts were transfected with the construct, which encodes the I2S enzyme. A 4-methylumbelliferyl sulfate (4-MUS) assay was performed to test for secreted sulfatases in the conditioned media (CM) after transcription of the IDS gene was allowed to proceed. Fluorescence indicated the release of a fluorophore when the sulfate group on the 4-MUS sulfate was cleaved by sulfatases. The highest sulfatase activity was present in the CM post transfection indicating that the I2S enzyme was successfully produced and secreted. The pIRES-hrGFP-IDS-2a construct yielded I2S enzyme up to 24 hours. MPSII fibroblasts survived with the construct for up to 48 hours. In this study, we show how a non-viral vector can be used to restore gene function and prolong the life of mutated cells. This non-viral construct. with modifications can be used to cross the blood-brain-barrier to treat this disease in the central nervous system (CNS), which is not currently available for treatment because of the blood-brain-barrier (BBB).
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Cammisa, Nickie
- Description:
- Invasive species can outcompete native species, decrease biodiversity, and negatively affect ecosystem processes and economies. Predictive power over how and where invasions occur is lacking, partially because invasions appear to be context-dependent. Both abiotic and biotic factors influence the probability of any given introduced organism becoming invasive. Abiotic factors such as drought complicate our understanding of how and why invasive plant species are successful. Biotic factors such as genotypic variation and mutualisms further complicate our ability to predict outcomes for introduced species. The work described here examined the importance of the genotype of plants, the origin of plants (meaning whether the plant came from the native or an invasive region), and mutualistic associations with soil bacteria on the success of a leguminous plant facing water stress in a greenhouse setting. I asked: 1) Is there genotypic variation in the response of a legume to watering level? and 2) Do bacterial mutualists alleviate the effects of soil drying on an invasive plant? Medicago polymorpha is an annual legume native to the Mediterranean region that has successfully invaded many areas around the world with different climates. I randomly assigned genotypes of Medicago polymorpha across factorial manipulations of water and mutualists using greenhouse experiments. The first study described here showed that genotypes of Medicago polymorpha responded differently, both in magnitude and direction, to four different watering levels. Genotypes varied significantly in all response variables measured: total biomass, aboveground-to-belowground biomass ratio, and fruit number. According to these results, genotype played a large role in the response of Medicago polymorpha to watering level. The literature suggests that genotypic variation is critical for invasion success, and drought can increase the invasibility of extensively managed ecosystems. Thus, invasion success may depend on the compatibility of genotypes in the pool of invasive plants and local environmental conditions. The second study described here found that bacterial mutualists determined the response of the plant to water stress, but that effect depended on whether the plant was grown from seed collected in a native or an invasive region. Together, these results suggest that it is important to examine the interaction of multiple factors-both abiotic and biotic-to determine the performance of an invasive plant experiencing water stress.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Lobnitz, Margaret Mary
- Description:
- The distribution and ecology of Claytonia nevadensis, an alpine endemic of the Sierra Nevada, Sweetwater Mountains, Trinity Alps, and Steen's Mountain, has been studied with respect to its congruence with certain aspects of the Nunatak Hypothesis. Ten study sites were visited along the species' range from Mineral King in the southern Sierra Nevada to Steen's Mountain in southeastern Oregon. Ecological, geological and glacial data were gathered for each location. Claytonia nevadensis specimens and soil samples were collected for growth chamber and laboratory experimentation. Chromosome counts resulted in N = 7 for all ten populations. Soil analysis shows the presence of necessary plant growth nutrients except for iron and manganese. A mean pH value of 5.5 was obtained for all soil samples. Cross-pollination experiments shows the populations to exhibit some interpopulation fertility, but no self-fertility. Computer analysis of leaf measurements revealed little morphological variation over C. nevadensis geographical range, except a minor amount in those populations most isolated geographically. From the field data, it was found that C.nevadensis occupies a stream and snowbank habitat situated on volcanic or metamorphic rock types. It is very cold tolerant and can begin its development under the snow, thus getting a head start on the growing season. It tolerates very little competition and its primary mode of reproduction is vegetative. From its disjunct distributional pattern, the extremely specialized habitat it occupies, the correlation of its locales with areas which were unglaciated during the Pleistocene, and its lack of interpopulational genetic exchange, it can be reasonably surmised that C.nevadensis existed in the Sierra Nevada in pre-Wisconsin times and survived each glacial advance by its persistence on ice-free refugia (called nunataks) situated above the Pleistocene ice cover. Claytonia nevadensis manages to survive this current interglacial climate by its ecological and edaphic restriction and vegetative propagation.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sorensen, Steven E.
- Description:
- Exogenously added saccharides were tested for their ability to inhibit intercellular adhesion of mouse teratoma cells in culture. Of the sixteen sugars assayed, acidic sugars consistently inhibited adhesion to the greatest extent, while the basic sugars inhibited adhesion the least. Inhibition of adhesion was shown to be dependent upon sugar concentration and cell density. Six sugars were tested for adhesion effects on cells synchronized in culture. These six sugars displayed the same order of inhibitory activity as shown in the unsynchronized cultures. An oscillatory pattern of cell adhesion was also observed in synchronized cultures. In preliminary experiments, synchronized cells treated with FITC-Con-A, showed a redistribution pattern of receptor sites from a homogeneous pattern evenly distributed over the cell surface to a concentrated pattern on the laminapodia of the cell. This suggests that the carbohydrate containing cell surface receptor sites can move from one part of the cell to another.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Bautista, Jeremiah
- Description:
- Years of intense fishing pressure has caused the fishery of the barred sand bass, (Paralabrax nebulifer) of southern California to decline precipitously in the first decade of the 21st century. The large aggregations that this marine species forms during their spawning season have left them vulnerable to fishermen who remove them by the tens of thousands each summer. Recently declared by the California Department of Fish and Wildlife as "severely depressed" this fishery is in a need of a change. Specifically this proposed study into the reproductive biology of barred sand bass aims to characterize macroscopic and microscopic reproductive stages of males and females, document for the first time a complete annual gonado-somatic index (GSI) and hepato-somatic index (HSI) for both male and females, determine batch fecundity for a wide size range of females, and distinguish spawning periodicity parameters. During 2011, the GSI first increased in June, peaked in July, and steadily declined after into the fall months across southern California. Batch fecundity showed a strong correlation with size, bigger fish can and do carry more eggs. Spawning frequency was estimated at 1.4 days and based on diel collection periods, occurs between mid-morning to the afternoon. Understanding the reproductive cycle and the duration of energy allocation towards reproduction is important for the proper management of this fishery and other aggregating species. Historically, barred sand bass have played a prominent role in the recreational fishing industry of Southern California. As one of the top three sport fish since the 1980's, it must be protected and properly manage to prevent any further decrease in the stocks and the ultimate collapse of the fishery.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Abravaya, Joseph Paul
- Description:
- A capture-mark-recapture grid was set up in southeastern Brazil to gather information on seasonal abundance, reproduction, movements, habitat and interspecific relationships of the poorly known rodent fauna. Two hundred seventy one individuals of twelve rodent species were captured 1293 times. The rodents on the grid changed seasonally in density and reproductive behavior. Reproduction as correlated with the rainy season when food resources were most abundant. Oryzomys moojeni was reproductively aseasonal, although breeding activity was most intense during the rainy season, whereas Thomasomys sublineatus and Oxymicterus hispidus bred seasonally. These differences may reflect different evolutionary histories or may be a result of competitive interactions. Declines in density during the latter part of the wet season may be due to the combined effects of flooding and reproductive stress. Most species tended to avoid hill areas, and preferred flat areas. It appeared, however, that flooding affected seasonal movements; o. moojeni, T. sublineatus and Thaptomys nigrita changed their habitat preference in favor of hill areas during the wet season. Habitat utilization was three dimensional: there were fossorial, aquatic, terrestrial, and arboreal species.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Molnar, Justin
- Description:
- HER2 (Epidermal Growth Factor Receptor Type 2) positive breast cancer accounts for 20-30 percent of cases and is associated with increased tumor cell proliferation, resistance to hormonal therapies and decreased patient survival. Trastuzumab (Herceptin®, Genentech-Roche) induces cytotoxicity in HER2+ breast cancer, significantly increases patient survival and is one of only a few targeted therapies approved for this aggressive malignancy. However, the majority of patients that qualify for this line of therapy exhibit innate or acquired resistance and must stop treatment. Herceptin resistance is associated with increased incidence of local invasion and systemic metastasis, and there is a need for in vivo methods to study the metastatic potential of Herceptin resistant and sensitive HER2+ breast cancer cells. Here, we have used the chicken (Gallus gallus) embryo chorioallantoic membrane (CAM) to establish an in vivo model of spontaneous metastasis for evaluating organotropism in Herceptin sensitive (SKBR3 and BT474) and resistant (AU565/innate and BT474-HR6/acquired) HER2+ breast cancer cells. Importantly, we demonstrate for the first time that Herceptin resistant cells are significantly more metastatic than their sensitive counterparts. We confirmed these results in vitro using 4D confocal microscopy and demonstrate that Herceptin resistant cells are also more invasive. Most notably, we report significant differences in the organotropisms for HER2+ breast cancer cells with innate versus acquired Herceptin resistance. Innately resistant cells exhibit significant increases in pulmotropic and hepatotropic metastases consistent with their increased expression of KRT81 and ID1. Alternatively, cells with acquired resistance exhibit significant increases in neurotropic metastasis consistent with their increased expression of HBEGF. Interestingly, cancer-associated fibroblasts (CAFs) derived from HER2+ breast cancer patients have been previously reported to also express elevated levels of HBEGF, suggesting that HER2+ CAFs may potentiate Herceptin resistance and neurotropic metastasis. To evaluate the role of stromal fibroblasts on HER2+ breast cancer cell organotropism, we first co-xenografted embryonic fibroblasts together with HER2+ breast cancer cells into the CAM model - we observed selective prometastatic effects of these stromal fibroblasts only on Herceptin resistant cells. We propose that this novel co-xenografting in vivo model can be used to evaluate the regulatory effects of patient-derived CAFs on organotropism of HER2+ breast cancer cells in relation to their Herceptin responsiveness. Findings from these studies will illuminate the cellular and molecular mechanisms that drive organotropism in aggressive and therapy-refractory breast cancers.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Denton, Timothy Lee
- Description:
- The effects of calcium deprivation and caffeine on the division, growth, respiration and macromolecular synthesis of Polytomella agilis were studied. Caffeine blocked cell division immediately and resulted in unbalanced growth. DNA, RNA. and protein synthesis were inhibited but the respiration rate was unchanged. The mean cell volume increased and the size distribution shifted from log-normal to normal. The transition point for cell division was shown to be late in the cell cycle. Removal of caffeine resulted in poor division synchrony. The ability of caffeine to inhibit the synthesis of DNA. RNA, and protein and to block cell division have been demonstrated for many organisms. The inhibition of protein synthesis may explain its effect on cell division in this organism. The inability of either theophylline or dbcAMP to inhibit cell division suggests that caffeine does not block division by increasing cellular concentrations of cAMP. External calcium is required for normal growth and division. The duration of inhibition of cell division by calcium -deprivation was a function of the age of the inoculated cells. Inocula from young cultures (0. 4 X 106 cells) spontaneously recovered after one hour. Older inocula (0. 6 X 106 cells} recovered after three hours. DNA and protein concentration, and mean cell volume all increased but RNA concentration and the respiratory rate decreased. The size distribution shifted from log-normal to normal. The transition point for calcium was also shown to be late in the cell cycle. The spontaneous recovery from division-inhibition may reflect some mobilization of internal calcium. Calcium may be required for regulation of microtubule assembly in mitosis.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Crowther, Susan D.
- Description:
- The dissociation supernatant (DS) isolated by disaggregating Strongylocentrotus purpuratus blastulae in calcium and magnesium-free seawater specifically promotes reaggreagtion of S. purpuratus blastula cells. The purpose of this study was to use scanning electron microscopy to examine the gross morphology of aggregates formed in the presence of DS to see if it resembles adhesion in partially dissociated blastulae. A new reaggregation procedure developed here, using large volumes of cell suspension and a large diameter of rotation, was utilized to obtain sufficient quantities of aggregates for scanning electron microscopy. The results indicate that aggregates formed in the presence of DS resemble partially dissociated intact embryos in terms of the direct cell-cell adhesion observed. DS did not cause aggregation to form as a result of the entrapment of cells in masses of extracellular material. These studies provide the groundwork for further studies using transmission electron microscopy to more precisely define the adhesive contacts made by cells in the presence of the putative adhesion molecules present in DS.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Csuti, Blair Alexander
- Description:
- Karyotypes were prepared for five species of kangaroo rats (genus Dipodomys) from Southern California. Slides were obtained using bone marrow preparations from animals previously injected with colchicine. A total of eight subspecies were examined: D. agilis agilis and D. a. perplexus (2n=62); D. panamintinus mohavensis (2n= 64); D. heermanni morroensis and D. h. arenae, and D. h. goldmani (2n=64); D. microps microps (2n=60); and D. merriami merriami (2n=52). The karyotype was used as a systematic tool to clarify the distribution and interrelations of these species. The karyotypic distinctness of the morphologically similar D. panamintinus and D. agilis enabled me to demonstrate the presence of D. pantamintinus associated with the Pinyon-Juniper Woodland within the supposed range of D. agilis agilis in the San Gabriel Mountains. D. microps was discovered in an Alkali Sink habitat near Lancaster. These localities represent -range extensions for D. pantamintinus and D. microps. Habitat is considered as a factor in determining distribution. That portion of the range of D. agilis perplexus which extends across the floor of the Antelope Valley as depicted in Hall and Kelson (1959) should be deleted. The similarity of the karyotypes of the broad-faced D. heermanni and D. panamintinus, and the difference of their karyotypes from that of the narrow-faced D. agilis, supports the current division of the heermanni group into broad-faced and narrow-faced subgroups.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sanchez, Barbara
- Description:
- Pollutants have the ability to be persistent, circulate worldwide, bioaccumulate, and biomagnify in the tissues of organisms. Pollutants can impact the local economy and human health by altering marine resources such as fisheries. These fisheries can be impacted by both lethal and sublethal effects on fish. Sublethal effects can result from physiological stress to individuals, especially in highly urbanized, polluted areas. Paralabrax nebulifer (barred sand bass) supports an important recreational fishery in southern California and the population has declined, possibly due to anthropogenic effects. This study had two main goals: (1) to characterize the levels of organic pollutants in the tissues of barred sand bass from sites across southern California; and (2) to determine if there are detectable sublethal effects of pollution on this species. To evaluate potential sublethal effects on barred sand bass, an array of commonly used physiological indices were used, including hepatosomatic index (HSI), gonadosomatic index (GSI), fecundity, reproductive potential, and growth. Fish were collected from four sites in southern California: Los Angeles/Long Beach Harbor, Huntington Flats, San Clemente Reefs, and San Diego Harbor. One hundred and seven organic pollutants were tested for and 77 of these were detected in the tissue of barred sand bass. There was a significant difference in tissue pollutant concentration among sites, with fish from LA/LB Harbor having the highest concentrations of pollutants, followed by Huntington Flats and San Diego Bay, while fish from the San Clemente Reefs had the lowest tissue concentrations. The pollutant with the highest tissue concentrations across all sites was 4,4'-DDE, but tissue burdens of it declined with distance from the Palos Verdes Shelf. Some metrics of individual performance showed evidence of sublethal effects of pollution, while others did not. Differences in condition (weight-at-length) and growth rate were unrelated to average pollutant concentrations in tissues of fish among sites. The site with the highest tissue concentrations of pollutants, LA/LB Harbor, had a higher proportion of inactive females than the other sites and had the lowest GSI. Fecundity did not differ among the four study sites, suggesting that this metric of reproductive success was not affected by differences in tissue concentrations of pollutants among sites, perhaps because the levels of pollutants were low enough not to impact fecundity in a multi-batch spawning species. Proportional liver size (HSI) was highest in fish from the LA/LB Harbor and Huntington Flats, which had the highest tissue concentrations of organic pollutants. Physiological parameters of individual barred sand bass were compared with the tissue concentrations of toxicants in those individuals. Condition and growth were both negatively related to a multivariate summary of tissue concentrations of pollutants. These results suggest that pollutants can negatively affect growth and body condition in the barred sand bass. This study provides some evidence that barred sand bass in polluted areas may be in poorer condition and grow at slower rates, which could be detrimental for this population that may already be on the verge of collapsing. This study measured concentration of organic pollutants in liver tissue, which is not typically consumed, but information about relative differences in pollutant tissue concentrations can be used to estimate and prevent exposure. For example, we now know that LA/LB Harbor and Huntington Flats are sites where barred sand bass have high tissue concentrations of organic pollutants. Huntington Flats is heavily targeted by anglers during the spawning season due to the presence of large aggregations of barred sand bass, making them easy to catch and increasing possible human exposure. It is important to continue to monitor populations in highly urbanized areas in order to understand accumulation rate, sublethal effects, and the persistence of legacy pollutants such as DDTs in southern California.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Neal, Paul Robert
- Description:
- The reproductive ecology of Oxalis frutescens was studied at Finca La Pacifica, in the gentle lowland foothills of the Pacific slope of the Cordillera de Guanacaste, Costa Rica. Several adaptations of this plant to the natural habitat of this area are correlated with the success of the species in areas of agricultural disturbance. The flower of 0. frutescens has floral characteristics belonging to blossoms designated as the bell/beaker syndrome. These characteristics determine the type and behavior of the pollen vectors. Accordingly, the principle pollen vectors are short-tongued bees. Primary attraction is accomplished by the corolla. Alighting by the insects is stereotypic for the bell/beaker syndrome; with the head oriented toward the center of the flower. Nectar guides are present. The secondary attractant, the pollen is halfhidden and centralized. Pollen deposition and reception takes place in the center of the blossom. This species is tristylous and self-incompatible. The ratio of the style length morphs is 0.9 long 1.1 medium: 1.0 short this is statistically different from equality. Anthesis is closely correlated with diurnal weather patterns.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Jordan, Timothy H.
- Description:
- L-glutamine is required for the synthesis of complex carbohydrates required for the intercellular adhesion of a variety of cancer cell types. It remained to be seen if these pathways were of general importance in the adhesion of other cell types. The present study shows that the same pathways involving L-glutamine for the synthesis of complex carbohydrates may be involved in the adhesion of a variety of chick embryonic cell types. Using an electronic particle counter to measure cell adhesion, results were obtained showing that L-glutamine would enhance the rate of aggregation of chick embryo liver, skin, brain, kidney, and limb bud cells after dissociation with trypsin. Inhibition of reaggregation of these various cell types and promotion of dissociation of these embryonic tissues were facilitated by preincubation of the cells with azaserine. Azaserine (0-diazoacetyl-serine) is a specific glutamine antagonist which decreased the action of L-glutamine in the metabolic pathways of the cells. Exogenous L-glutamine reduces the effect of azaserine on the various cell types. It is not known whether or not glutamine requiring pathways are important in all types of intercellular adhesion, but they seem to play a significant role in the initial adhesion and tissue cohesion of a variety of embryonic and tumor cell types.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Shayka, Bridget
- Description:
- As the global population increases, the occurrence of multiple anthropogenic impacts on valuable coastal ecosystems, such as coral reefs, also increases. These stressors can be global and long-term, like ocean acidification (OA), or local and short-term, like nutrient runoff in some areas. The combination of these stressors can potentially have additive or interactive effects on the organisms in coral reef communities. Among the most important groups of organisms on coral reefs are crustose coralline algae (CCA), calcifying algae that cement the reef together and contribute to the global carbon cycle. This thesis studied the effects of nutrient addition and OA on Lithophyllum kotschyanum, a common species of CCA on the fringing reefs of Mo'orea, French Polynesia. Two mesocosm experiments tested the individual and interactive effects of OA and short-term nitrate and phosphate addition on L. kotschyanum. These experiments showed that nitrate and phosphate addition together increased photosynthesis, OA had interactive effects with nutrient addition, and after nutrient addition ended, calcification and photosynthetic rates changed in unpredictable ways in different OA and nutrient treatments. Because the results of the first two experiments showed impacts of nutrients even after addition stopped, two more mesocosm experiments were conducted to study the changes in photosynthesis and calcification over hourly time scales more relevant to a single nutrient pulse event. These two experiments revealed the existence of diurnal variation in light-saturated photosynthetic rate, but not calcification rate, under ambient and elevated pCO2. This pattern of increased maximum photosynthesis in the middle of the day can have important implications for how the time of nutrient runoff events during the day impacts CCA physiology. Finally, a field experiment was conducted to determine the effects of short- and long-term nutrient addition on L. kotschyanum. The results showed that a series of short-term nutrient additions did not increase photosynthesis or calcification rates above those in ambient nutrient conditions, but continual nutrient enrichment for 6 weeks increased photosynthetic rates. This increase in photosynthesis under only long-term enrichment shows the need for consideration of specific nutrient addition scenarios on coral reefs when predicting how the community will be affected.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Smallwood, Jeffrey A.
- Description:
- Habitat utilization and foraging behavior of the avifauna at six different elevations (1770 to 2507 m) on Mount Pinos, Kern and Ventura counties, California, were studied. Bird species and their habitat utilization were sampled using a modified point sampling technique between 15 August and 22 November 1985. Species diversity among elevations was not statistically significant, although the species composition changed dramatically. Habitat structure was fairly homogeneous over the elevational gradient with Pinus jeffreyi predominant at all elevations. Guilds were distinguished and niche partitioning occurred primarily among foraging maneuver and substrate categories. Several species shifted in their utilization of certain habitat variables, but only two, the Mountain Chickadee and the Pygmy Nuthatch, shifted their foraging maneuvers significantly over the elevational gradient. Guild structural variations are indicated and possible causative factors, including competition and other biotic or abiotic influences, are discussed.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Krueger, Cheryl Christine
- Description:
- Polyclonal immunoglobulin G (IgG) from rabbits immune to Treponema pallidum subspecies pallidum, Nichols strain, was shown by immunoelectron microscopy (IEM) to bind specifically to recognizable subcellular structures in thin sections of T. pallidum. A method was developed for fixing and embedding T. pallidum to preserve treponemal morphology and antigenicity. Thin sections of treponemes extracted from 10- to 11-day old rabbit orchitides were prepared by a modification of standard histological techniques for electron microscopy. Sections of T. pallidum were incubated with IgG from either immune (IRS-IgG) or nonimmune (NRS-IgG) rabbit serum. Binding of antitreponemal IgG to T. pallidum sections was detected with colloidal gold-labeled Fe fragment-specific goat anti-rabbit IgG by IEM. Most treponemes appeared morphologically intact with the fine structure clearly defined; some cells exhibited disrupted outer membranes. Anti treponemal, but not non immune, IgG bound to outer membrane, endoflagella, and cytoplasmic components of T. pallidum as evidenced by the presence of gold-labeled antiglobulin on these structures. The specificity of the reaction between treponemal antigens and the immune rabbit serum IgG was emphasized by the virtual absence of bound gold label in control preparations; a small number of gold particles appeared in the background of the controls with NRS-IgG or no IgG. Colloidal gold alone did not bind to combinations of treponemes with any IgG preparation. The results demonstrate the effectiveness of the protocol for preserving the morphology and antigenicity of T. pallidum, show the location of antigens in situ in several different cell structures, and illustrate a technique to identify various immunogens which may elicit the immune response and thus be candidates for vaccines.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Long, Joseph
- Description:
- The use of engineered nucleases for targeted gene correction of the sickle mutation in hematopoietic stem and progenitor cells (HSPCs) combined with a homologous DNA donor template can result in targeted gene correction. However, due to a high sequence homology existing between the beta- and delta-globin genes, off-target cleavage events have been observed at delta-globin when using endonucleases targeted to the sickle mutation. Moreover, the introduction of multiple double stranded breaks by endonucleases has the potential to induce chromosomal alterations such as translocations, deletions, and inversions. We have developed a Droplet Digital PCR assay to characterize the frequency of deletions, inversions and translocations between the beta- and delta-globin paralogs when delivering these nucleases. Pooled CD34+ cells and colony forming units (CFUs) from SCD BM donors were treated with nuclease only or nuclease with a DNA donor template (as an integrase defective lentiviral vector or as a single stranded oligonucleotide); and then analyzed for each of the potential chromosomal rearrangements. We observed that in both pooled and CFU samples, the intergenic β-δ-globin deletion was the most frequent event, followed by the inversion of the intergenic fragment, and with the interchromosomal translocation as the least frequent. These findings demonstrate the need to develop site-specific endonucleases with high specificity to avoid unwanted chromosomal alteration.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Manohar, Subrajaa
- Description:
- Neural crest (NC) cells are a multipotent embryonic population of stem-like cells that form various tissues in vertebrates including pigment cells, craniofacial bone and cartilage, and the peripheral nervous system. NC cells are ectoderm-derived progenitor cells that begin as neuroepithelial cells in the neural tube but detach and migrate throughout the body after undergoing an epithelial to mesenchymal transition (EMT). These cells express a variety of cell-cell adhesion molecules, including cadherin proteins, which control their specification, EMT, and migration. Abnormal development of NC cells can lead to multiple congenital defects as well as NC-derived cancers such as neuroblastoma and melanoma. Here, we identify the role of Cadherin-11 (CDH11) in early chicken NC development. CDH11 is a type II cadherin protein that is crucial for NC cell migration in amphibian embryos, and also regulates cell survival, proliferation, and migration in cancer cells. Using immunohistochemistry, we determined that CDH11 protein has dynamic expression, which co-localizes with Sox2 in neural progenitor cells in early embryos. Then, as NC cells are specified in the dorsal neural tube and begin to undergo EMT, CDH11 becomes restricted to pre-migratory and migratory NC cells and is down regulated in the neural tube. Electroporation of a translation-blocking CDH11 morpholino at gastrula stages leads to a reduction of PAX7, SOX9, SNAI2 and SOX10-positive NC cells in the dorsal neural tube, but has no effect on more ventral neural tube cells marked by Sox2, suggesting that CDH11 is required specifically in NC cells. We determined that CDH11 is required for NC cell survival, as loss of CDH11 increases p53-mediated programmed-cell death, and blocking the p53 partially rescues the NC phenotype. Further, we have identified that CDH11 is expressed in multiple breast cancer cell lines, but that its intracellular localization differs. CDH11 is localized to the cytoplasm and nuclei of the cancer cells, changing with invasiveness, suggesting it has non-adhesion functions in those cells. Our findings demonstrate a requirement for CDH11 in early NC development, and may increase our understanding of early NC-related developmental defects.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kaufman, Stephen Arthur
- Description:
- Membrane topographic modulation accompaning cortical reaction in sea urchin egg fertilization was studied using freeze-fracture electron microscopy. Gross topographic changes and the behavior of intramembranous particles (IMP) were analyzed for the first two minutes of activation. Intramembranous particle counts and particle size class frequency distributions were recorded for both unfertilized plasma membrane, cortical vesicle membranes, and for the post-fusion composite plasma membrane. Results indicate that a single "disk of contact" between the plasma membrane and each cortical vesicle membrane initiates the fusion process. Increased intramembranous particle density of the post-fusion plasma membrane was attributed to the addition of particles from the cortical vesicle membranes. No distinctive particle arrays were identified, suggesting that intramembranous particles play no active role in the initiation or stabilization of cortical exocytosis in the sea urchin, Strongylocentrotus purpuratus.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Mastrangelo, Marta Beatriz
- Description:
- A study of feeding efficiency of olivaceous cormorants (Phalacrocorax olivaceous) was conducted at Laguna Nahuel Ruca, a coastal lagoon in the Argentine pampas. A population of thirty cormorants consisting of eighteen adults and twelve immatures was observed. Feeding observations were conducted between 0500 and 0700 from December 29, 1983, to February 15, 1984. Immature olivaceous cormorants exhibit deferred maturity demonstrated by their inferior foraging abilities. Adult cormorants made 3.5 successful dives for every unsuccessful dive whereas immature cormorants made 1.5 successful dives for every unsuccessful dive. In order to compensate for inefficient foraging technique, immatures made a greater number of dives by feeding for longer periods. As a result, immatures probably would not be physiologically able to obtain the additional energy required for reproduction and care of young until foraging techniques are fully developed. Delayed maturation of olivaceous cormorants is a device which has evolved through natural selection so that when the birds reproduce, they will be able to supply sufficient food for a maximum number of offspring.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Jensen, Robert Emery
- Description:
- Fifty-six young-of-the-year <YOY) California halibut (Paralichthys californicus), captured from Alamitos Bay, California, were aged using new method for grinding both faces of sagittal otoliths. The method was developed to produce a microscopic thin section that preserves growth rings at the margins while increasing the resolution of internal growth rings. The age-length relationship existing between six YOY halibut born in February and December can be described by the linear equation Y = 1.3x + 26.6 <r = 0.96, P < .01) where Y is the age (days) and x is the standard length <mm SL). The standard lengths of YOY halibut ranged from 34 to 81 mm in this data set. The rate of growth calculated from this model was 0.738 mm/day. The age-length relationship existing between 50 YOY halibut born in March, April. May, and June can be described by the linear equation Y = 0.9x- + 30.6 (r = 0.91, P < .01) where Y ls the age (days) and x ls the standard length (mm SL). The standard lengths of YOY halibut in this data set ranged from 11 to 142 mm. The rate of growth calculated from this growth model was 1.104 mm/day. The YOY halibut born in February and December (n = 6) were excluded from the following analysis because it was felt that these outliers would have a disproportionate influence on the growth model. The second degree polynomial equation: Y = 12.6 + 1.6x - .005x2; r = 0.94 was calculated for estimated age regressed on the standard length of YOY California halibut (n = 50) born in March, April, May, and June. The growth rate calculated from this curvilinear model was 0.86 mm/day for YOY California halibut whose range in standard length was 10 to 80 mm. The model predicted an overall growth rate of 1.25 mm/day for YOY with standard lengths ranging from 10 to 150 mm SL, The range in standard length and the associated back-calculated age of YOY halibut captured for this study was 11 to 142 mm SL and 38 and 154 days old, respectively. The age at settlement was 25 to 31 days. Three methods of validation involving the immersion of YOY halibut in various solutions of tetracycline were employed. The daily formation of growth rings was not validated by these methods. Recent work on laboratory reared California halibut has validated the production of growth increments as a dally phenomenon (Lavenberg, pers. comm. 1989).
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Underwood, Alexander
- Description:
- Splicing Factor 3b Subunit 3 (SF3B3) is a crucial splicing factor with a role in the gene regulation of several essential genes. While the role of SF3B3 alternative splicing has been well established, the mechanisms that regulate SF3B3 itself have not been identified. Using a 5' RACE, we determined a single transcription start site (TSS). Through analysis of transcriptional activity and sequence homology among species, we have identified the SF3B3 promoter region. We identified the SF3B3 proximal promoter region as within 189bp upstream from the TSS using a series of deletions and transfection. Within the proximal promoter region, we identified a TATA-box core transcription factor binding site and two proximal transcription factor binding sites, AP-2aA, and Elk-1. When we removed 2-3bp from the binding sites of AP-2aA, Elk-1, and the TATA-box, we revealed that the AP-2aA and Elk-1 binding sites are necessary for maximal levels of transfection and that the TATA-box binding site is required for transcription initiation. We showed that the SF3B3 promoter was an atypical Type III promoter containing both a TATA-box and a large CpG island. Furthermore, the TATA-box is atypical being outside of the normal range from the TSS. These data match data seen in a similar promoter sequence and may suggest a pattern for the highly unusual TATA-driven type III promoters.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kenny, James Joseph
- Description:
- Cultures of neurospora Crassa, strain SY4F8a, produce conidia on both the nitrate (c) and anm1onium (m) media designed by Turian(34). The number of conidia produced is consistently higher in nitrate grown cultures. The largest quantitative difference in conidiation(C 18 times greater than M)occurs in cultures grown at 20C for five days. The specific activity of isocitratase is three times greater in the C than in the M cultures, while the specific activity of nicotinamide adenine dinucleotidase(NADase)is 150 times greater in C cultures. Addition if ammonium chloride (0.005 M to 0.12M) to the nitrate medium causes a repression of condition, NADasa activity, and isocitratage activity. Conidiation and NADasa activity are repressed at all levels of ammonium tested, whereas repression of isocitatase activity occurs only at the highest concentration of ammonium tested. NADase activity and conidiation can be restored to half their maximum level by increasing the concentration of nitrate in the growth medium. Density gradient centrifugation in homogenates of nitrate grown cultures indicates that the NADase of N. crassa is localized in the soluble protein phase of the cell.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Nelson, Daniel Charles
- Description:
- Nos toe punctiforme is a member of the cyanobacteria that forms filaments of cells and is capable of cellular differentiation. Previous studies using differential display and GFP expression have shown that aet appears to be active during the process of vegetative cells differentiating into spore like cells called akinetes during periods of nutrient limitation. Bioinformatic analysis of the gene indicates that it is an ATP Binding Casette (ABC) type transporter based on conservation of conserved Walker A, Walker B, and signature sequence motifs. The domain organization of gene, which contains both a nucleotide binding domain and transmembrane domain within the same polypeptide, indicates it is of the exporter group of ABC transporters. GFP transcription studies using the full-length promoter region for the gene, as well as fragments of the promoter containing sequential deletions in their upstream regions, showed that as little as 43 base pairs upstream from the transcriptional start site was sufficient for expression. GFP transcriptional reporters containing the entire intergenic region or truncated versions lacking upstream sequences were all active at a constitutive low basal level in vegetative cells and pre-akinetes, but were not active in heterocysts. Phenotypic analysis demonstrated that the aet insetiional-mutant strain exhibited significantly slower than wild-type growth when exposed to chemicals and antibiotics that destabilize the outer membrane. Complementing the mutant with a wild-type copy of the aet gene in trans resulted in recovery of growth following treatment almost to near wild type levels. These findings indicate the aet gene encodes for an ABC transporter catalyzing cellular export, and that the mutation within this gene is responsible for the observed sensitivity to outer membrane stress. The data strongly indicate that the Aet transporter is responsible for transporting an as-yet undefined component of the bacterial envelope involved in the stabilization of the outer membrane. Transcriptional-reporter studies utilizing promoter-deletion clones indicates that upstream cis-acting transcriptional regulatory proteins are unlikely to be involved in transcriptional regulation of aet, supporting the hypothesis that regulation is achieved solely by developmentally regulated sigma factors associated with the RNA polymerase holoenzyme. Future studies identifying molecular components differing between the outer membrane of the wild type and aet mutant strain will be used to identify the allocrite actually transported by Aet.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Watkins, David Lavaun
- Description:
- Laboratory experiments demonstrated that lithium chloride is effective in inducing a conditioned taste aversion in the fox squirrel (Sciurus niger). Foods treated with lithium chloride produced illness in fox squirrels which resulted in avoidance behavior toward those specific foods. Squirrels ingesting between 0.12 and 0.17 grams of lithium chloride were shown to be conditioned in one lithium trial. In the field, incorporation of lithium chloride into a protective sheath placed around aerial cable is also effective. Three test sites, each consisting of five test sheaths (containing lithium chloride) ten feet in length and five control sheaths (without lithium chloride) ten feet in length, were compared to three control sites, each consisting of ten control lengths ten feet in length. The amount of cable damage to the control lengths compared to the amount of damage to the test and control sheaths showed a significant difference in damage sustained by the cable due to squirrel gnawing of cable insulation.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Koprowski, Carol Marie
- Description:
- A heterogeneous mixture of 129/J mouse teratocarcinoma cells were separated into two populations of cells on the basis of cell size and density using centrifugal force. The teratocarcinoma consistently separated into two populations, "large" cells and "small" cells. These two populations of cells were each studied in regards to their surface characteristics by the use of lectin assays and fluorescence microscopy. Lectins used included soybean agglutinin (SBA), Limulus polyphemus (LPA) , Ulex europus-I agglutinin (UEA-1), Lotus tetragonolobus agglutinin (LTA), and their fluorescein conjugates. The results of this study demonstrate that while both populations may have the ability to bind lectin, only the large cells were agglutinated to any appreciable degree. SBA was the only lectin that bound to both cell populations and induced agglutination in only the large cell population. LPA, LTA, and UEA-1 did not induce appreciable agglutination in either population. Fluorescence microscopy revealed that LPA bound only to the small cell population, while LTA and UEA-1 bound to neither cell population. The large cell population resembles malignant or transformed cells in regards to lectin-induced agglutinability characteristics, while the small cells have agglutinability characteristics typical of benign cells. The disparity observed in agglutination of the different populations may be due to the involvement of cytoskeletal rearrangements.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Tawa, Lawrence Shinzo
- Description:
- A new cell-to-cell adhesion assay has been devised. Using dissociated embryos of the sea urchin Strongylocentrotus purpuratus, this procedure involves rotating a 0.100 ml suspension of single cells (500,000/ml) with 0.100 ml of the solution to be tested in the bulb portion of a transfer pipet with the tip removed. After 1 hour of rotation at 60 rpm at 15 C, the contents of each bulb were transferred into individual wells of a 96-well flat-bottom plate. After the plate was incubated for 1 hour at 15 C, black and white photographs were taken with a 35 mm camera attached to an inverted photomicroscope. Examining a proof sheet i.e., of contact prints, or the negatives directly allowed rapid evaluation of suspected cell adhesion promoting factors. A ranking system was used to evaluate all samples. The assay was tested by examining the effect of specific solutions i.e., calcium-magnesium free-sea water with or without bovine serum albumin, Millipore-filtered sea water, or supernatant containing cell adhesion molecules colored with or without phenol red, on the aggregation of single cells obtained from dissociated 23-hour S. purpuratus embryos. Samples were scored as negative when single cells with no clumping were observed while clumping indicated a positive response; larger clumps were scored as increasingly positive. This serological assay differs from other adhesion assays in that it utilizes the rotation of small volumes of cell suspension, employs a scoring method based on the largest clumps observed, and requires only minimal laboratory experience and completely disposable supplies.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Barnes, Robert George
- Description:
- Activity patterns of twenty-seven adult (fourteen males and thirteen females) Mongolian gerbils (Meriones unguiculatus) were established for the 24-hour cycle in both activity wheels and "jiggle “cages. In addition, activity patterns for sixteen juveniles (seven males and nine females) were established in activity wheels and jiggle cages for the fifth through the fourteenth weeks of age. The activity patterns of juveniles were compared with those of adults. Patterns of juveniles were also studied to determine the effect of increased age on activity patterns. The type of apparatus and to a lesser extent the sex of the individual influenced the activity patterns. Gerbils are primarily nocturnal but are active at times throughout the 24-hour cycle. All gerbils displayed greater amounts of night activity in activity wheels than in jiggle cages even though the total activity was relatively the same in both types of apparatus. Adult and juvenile males showed greater amounts of night activity in activity wheels than did females, whereas adult and juvenile females showed slightly larger amounts of night activity in jiggle cages than did males. All juveniles displayed changes in activity patterns during the sixth, seventh, or eighth weeks of age which resulted in patterns similar to those of adults. The change in juvenile activity patterns was concomitant with the opening of the vagina or descent of the testis and with the initiation of aggressive behavior by parents toward juveniles. Spontaneous seizures occurred in some gerbils studied. Interactions (including agonistic) among gerbils were elicited by various conditions not fully understood.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Feucht, Laura
- Description:
- Cytokinins are plant hormones that regulate meristem activity in roots and shoots by initiating mitotic divisions. Such cytokinins are subject to environmental stresses such as light and nutrient availability and pH and temperature change. When temperature drops below optimum for metabolic processes a cytokinin, zeatin, levels decrease and Zeatin-O-glucoside (ZOG) increase, mitotic divisions arrest and growth ceases. Studies implicate that cold stress causes the enzyme zeatin-O-glycotransferase to glycosylate Zeatin and convert it into its storage form, ZOG. Return to 25oC causes β-glucosidase to hydrolyze the glycosidic linkage in ZOG N6 side chains and liberate the active form, zeatin. Zea mays β-glucosidase activity peaks within the first 24 hours of return to 25oC after cold stress. Zea mays β-glucosidase was localized to the plasma membrane in parenchyma cell wall regions of the cortex within 24 hours of recovery at 25oC after 4 days of cold stress. In addition, accumulation of the β-glucosidase protein was observed according to development, but not according to stress.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Johnson, Terrell Kent
- Description:
- Many cytologically normal and rearranged ct mutants have been reported, but no known deficiency involves both ct and its close neighbor, sn (Lindsley and Grell, 1968). This fact prompted an investigation of the mutational response of the ct-sn interval. Approximately 24,000 F1 female progeny of 7-day-old males given 2000 or 3000r X-ray' exposures were examined for the presence of newly induced mutations at the N, cm, ct, and sn loci. Altogether, 31 N, 2 cm-ct, 33 ct, and one sn mutants were found, indicating that the frequency of recovery of ct mutants was much greater than that of either cm or sn, exceeding even N. Among the F1female progeny were two deficiency mutants that expressed both cm and ct (separated by 21 bands) but none expressed both ct and sn (separated by only 14 bands). Of the 18 analyzed ct mutants, two proved to be deficiencies; neither extended further to the right than 7Cl. No reported ct deficiency extends with certainty further to the right than 7C4. This fact, together with the scarcity of deficiencies, suggests the presence of a haplo-insufficient locus between ct and that prevents the recovery of ct-sn deficiencies. The ana1ysis of Tpsns93, a short transposition which moves most of the ct-sn interval to Section 8D, proved the existence of a haploinviable locus just to the left of sn which prevents the development of females heterozygous for its deficiency. See more in text.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Roberson, Marie
- Description:
- It has been demonstrated that specific changes in carbohydrate-containing cell surface lectin receptor sites occur with differentiation and maturation of sea urchin embryo cells. In this study, evidence is presented using a quantitative electronic particle counter assay to measure agglutination, which indicates that concanavalin A (ConA) mediated agglutination of dissociated 32/64 cell sea urchin embryos differs dramatically with respect to Specific cell populations. The migratory cell type, the micromere, is significantly more agglutinable with ConA than the other cell types and colchicine treatment markedly increases sea urchin embryo cell agglutinability. The results like many malignant cells which display extensive migratory behavior, specific migratory populations of embryonic cells are agglutinable with ConA. The results are discussed with respect to the possible nature of lectin receptor sites on specific populations of embryonic cells and the possible role of colchicine- sensitive structures in controlling the display patterns of these sites.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Reidenbach, Leah
- Description:
- Ocean acidification is the increased absorption of atmospheric CO2 in seawater and the consequent decrease in pH. This phenomenon is occurring throughout the global oceans while land use changes and large human populations near coasts are linked to increased nutrient concentrations in seawater. Ulva spp. blooms caused by nutrient enrichment occur regularly in some parts of the world and are known as green tides. There is concern that ocean acidification may increase green tides and intensify ecological and economic damages. Ulva spp. can utilize bicarbonate (HCO3-) as an inorganic carbon source, but this comes at an energetic cost as HCO3- must be converted to CO2 before it can be used for carbon fixation. Therefore, increased utilization of pCO2 with ocean acidification may benefit Ulva spp. Ocean acidification and eutrophication will occur simultaneously in many coastal ecosystems. The goal of the following investigations was to determine the effects of ocean acidification and nutrient enrichment alone and their interaction on photosynthetic, nutrient, and growth physiology of Ulva spp. In Chapter 2, the response of Ulva australis to pHT and ammonium (NH4+) enrichment were investigated in a seven day growth experiment using a range of pHT (7.56 - 7.84) and ambient and enriched NH4+ concentrations. I measured relative growth rates (RGRs), NH4+ uptake rates and pools, photosynthetic characteristics, and tissue carbon and nitrogen content. There was no interaction of pHT and NH4+ enrichment on the physiological parameters. The RGR was not affected by pHT, but was an average of two times higher in the enriched NH4+ treatment. rETRmax, total chlorophyll, and tissue nitrogen increased with both NH4+ enrichment and decreased pHT. The C:N ratio decreased with decreasing pH and with NH4+ enrichment. Although rETRmax increased and the C:N ratio decreased under decreased pH, these metabolic changes did not translate to higher growth rates. The results show that U. australis growth and physiology is more sensitive to NH4+ than it is to pH and that there is no interactive effect of NH4+ enrichment and decreasing pH. In Chapter 3, Ulva lactuca was grown for 22 days under a range of pCO2 and NH4+ concentrations and a multiple linear regression was used to analyze RGRs, NH4+ and NO3- pools, in situ NH4+ and NO3- uptake rates, tissue carbon and nitrogen content, carbohydrate and protein concentrations, and photosynthesis irradiance curves (P-I curves). The results from model selection and model-averaging techniques allowed me to make predictive models across a range of relevant ocean acidification and eutrophication scenarios and measure the effect sizes of pCO2, NH4+ enrichment, and their interaction. Overall, there was no effect of pCO2 and NH4+ on RGRs after day 5. However, there was a synergistic effect of pCO2 and NH4+ enrichment on the growth rates during days 0 - 5. When pCO2 and NH4+ concentrations increased simultaneously, NO3- uptake rates increased, which may have contributed to increased growth as seen in days 0 - 5. Maximum photosynthetic rates (Pmax) decreased with increasing pCO2 and there was a positive interaction of pCO2 and NH4+ on indicating CCMs were altered under these conditions. This shows that under high light intensities, Pmax was negatively affected by pCO2 and CCMs are not altered when nutrients are limited. Ultimately, there was no longer-term effect of ocean acidification and eutrophication on Ulva lactuca growth. Nutrient enrichment is a major cause of green tide blooms around the world and Ulva australis had the ability to enhance nutrient, photosynthetic, and growth physiology with NH4+ enrichment. Conversely, Ulva lactuca collected from a eutrophic environment, did not respond to NH4+ in terms of growth. Both chapters provided evidence that ocean acidification is unlikely to affect the growth rates of Ulva spp. However, the exception was a positive interactive effect of pCO2 and NH4+ enrichment on the growth rate of U. lactuca during the first five days, suggesting ocean acidification could play a role in initiating Ulva spp. blooms in a eutrophic environment. This could be an important consideration for determining how green tides will be affected by ocean acidification in coastal areas where nutrient enrichment occurs in pulses, resulting in transiently increased nitrogen concentrations.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Block, Heidi Elise
- Description:
- In marine organisms with complex life histories it is possible for events occurring during earlier life stages to affect an individual's subsequent survival. In fishes, it has been proposed that settlement, the transition from a pelagic habitat to a benthic one, is a critical period in determining survivorship. Selection (i.e., non-random mortality) may occur on specific larval traits, which could influence an individual's probability of survival after settlement. Herein I examine the effects of larval traits on the survival of juveniles shortly after settlement in two temperate and two tropical reef fishes. This was achieved by comparing traits of individuals sampled just after settlement with those of individuals from the same cohort sampled one month later, which evaluated selective mortality occurring over a cohort's first month of life on the reef. The two temperate species studied were señorita, Oxyjulis californica, and blackeye goby, Rhinogobiops nicholsii. Collections were completed at four sites at Santa Catalina Island, California, and two times between June and August of 2009. For señorita, I examined four larval traits: planktonic larval duration (PLD), size at settlement, metamorphosis band width, and pre-settlement growth rates. For the blackeye goby I examined two traits: size at settlement and pre-settlement growth rates. This study revealed that selection was inconsistent in both species. There were differences in both the direction and intensity of selection between the different sites as well as times. Differences in selection intensity were not related to variation in habitat characteristics or conspecific densities. Unlike selection, I found some consistent differences in larval traits between cohorts in señorita. For the señorita I found that individuals settling earlier in the summer had longer PLDs and slower growth rates than those settling later in the summer. In Moorea, French Polynesia I studied the blue green chromis, Chromis viridis, and the Gnatholepis species complex, Gnatholepis scapulostigma/anjerensis. This study was conducted at two sites on the North side of the island. Unlike the temperate study, only one cohort was examined due to logistical constraints. I examined three larval traits for both "species": PLD, size at settlement, and pre-settlement growth rates. For the Gnatholepis species complex, I did not find any evidence of selection or any differences between the two study sites for any of the larval traits measured. For Chromis viridis, I found that there was selection for larger sizes at settlement at both sites. However, selection on the other two larval traits was inconsistent between the two sites, with one site showing selection for faster pre-settlement growth rates and the other showing selection for longer PLDs. For this study I also explored whether differences in habitat characteristics or predator densities between the two sites might be influencing these patterns. These two sites were not significantly different in terms of habitat or predator densities and therefore these factors could not explain differences in selection between sites. These two studies reveal that selection on larval traits can vary greatly on relatively small scales: with sites less than 3 km apart exhibiting differences in the direction or strength of selection on a larval trait. This small-scale variation in selection may be one reason why variability in larval traits is maintained in these species. Understanding the causes of variation in larval traits in these populations and how variation is being maintained, through processes such as selective mortality, will help to understand and predict recruitment dynamics and ultimately community structure.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kolettis, Nomiki
- Description:
- Apoptosis and Autophagy are two processes that play key roles in the death and survival of cells. Apoptosis is a cell death mechanism, where autophagy is a cell survival as well as a cell death mechanism. In this study we investigated whether and how these two processes interact with each other in human lymphoblastic leukemic cells. Two cell lines were used: the first being CEM C1-15, resistant to dexamethasone-induced apoptotic death. The second cell line being CEM C7-14, sensitive to dexamethasone-induced death. The drug reagent rapamycin, an mTOR inhibitor, was utilized to induce autophagy. Dexamethasone, a synthetic glucocorticoid, was used to induce Apoptosis. Additionally, 3-Methyl Adenine (3MA) was employed to rescue cells from an autophagic fate caused by rapamycin. We show that apoptosis and autophagy collaborate in CEM C1-15 and C7-14 cells, and are able to take place simultaneously in the same cell. We also show that there is a synergistic effect when both processes are induced, resulting in a stronger death response. Moreover, we have used cell growth assay data in conjunction with fluorescent microscopy images to show that when autophagy is inhibited, apoptosis takes over as the primary cell death mechanism. In summary, our results add to the knowledge of apoptotic-autophagic interaction in leukemic cells and show that epifluorescence microscopy is a useful tool in aiding researchers to take specific and detailed images of cellular processes.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Mortin, Mark Andrew
- Description:
- A sex-linked, EMS-induced homeotic mutant that mimics the third-chromosome dominant mutant, ultrabithorax-130 (Ubx130), has been discovered on the X chromosome of D. melanogaster. This Ultrabithorax-like (Ub1) mutant, when heterozygous, adds several hairs to and enlarges the apical segment (capitellum) of the haltere. Ubl is homozygous lethal, but males survive and are fertile when covered by Dp v74, Dp v65 or Dp Bs-y. Ubl fails to complement Ubln [previously l(1)L5), a recessive lethal that was placed in section 10C of Bridges’ (1938) map of the X chromosome (map position 35.7) by Lefevre (1971). Altogether, seven lethal alleles have been identified that fail to complement at this site (two have been lost). The double heterozygote, Unl/+;Ubx130/+, expresses an interaction that causes the capitellum to develop into a small wing-like structure with only three longitudinal wing veins, but with marginal wing hairs. No alula is present. None of the other alleles display this interaction with Ubx130. Ubl behaves as an antimorph. Deficiencies for section 100 display neither the same dominant phenotype as Ubl nor the interaction with Ubx130. Ubl shows dosage compensation. The maximum expression occurs in females with genotype, Ubl/Ubl;Dp v74, which have a capitellum about three times as large as that of Ubl/+, with two or more rows of hairs. These flies are poorly viable and sterile when mated to Ubl;Dp v74 males, but occasionally produce offspring when mated to Ubl+ males.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
287. Interspecies communication and alarm call eavesdropping on multiple birds by a sympatric mammal
- Creator:
- Shipp, Joshua
- Description:
- Just as communication within a species can have multiple functions, the same is true for communication between species; interspecies communication is possible, so long as two interacting species use the same general mode of communication, such as auditory, and overlap in the range of signals they can perceive. Functions for such communication includes evading predators, capturing prey, cooperating with or cheating off of competitors, forming partnerships with the enemy of an enemy (cross-trophic alliances), and receiving predator information from members of the same prey guild. Recent research has documented several examples of responses to heterospecific alarm signals in both aquatic and terrestrial realms; of particular interest are cases of alarm communication between very distantly related species, as between birds and mammals. I sought to investigate such bird-mammal communication between the California ground squirrel (Otospermophilus beecheyi) and four sympatric bird species, using field playback of bird calls to wild squirrel colonies. I hypothesized that bird alarm calls, indicating predation threat, would result in increased vigilance, causing both increased escape behavior and greater allocation to vigilance behavior, while bird songs, representing a lack of danger, would have the opposite result. I found that for three of the four sympatric bird species' calls, squirrels increased vigilance in response to alarms but did not change their vigilance in response to songs. This response is the broadest ever demonstrated for bird-mammal alarm communication. A single species of mammal responds to alarm calls from birds representing three different genera and two different biological orders.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Lopez, Jessie
- Description:
- Subcortical white matter stroke (WMS) constitutes up to 25% of all stroke subtypes. We recently developed a new subcortical WMS model with a large infarct area that simulates the larger white matter lesions seen in moderate to advanced human white matter ischemia. This model, which produces noticeable motor function deficits, has been adapted to immunodeficient mice as a platform for transplant study. While there is no medical intervention for white matter stroke, cell transplantation is emerging as a viable therapy to restore neurological function. Transplantation of Human embryonic stem cells (hESCs) is a promising approach to promote repair disrupted neuronal networks. Here, we examined a human stem cell line for its ability to produce white matter repair. The most critical readout of success is the long-term restoration of functional behavior; therefore we evaluated functional recovery in an extended behavioral study. To characterize how stem cell transplantation affected recovery from WMS we performed two types of behavioral assay: cylinder task, which evaluates lateralization of weight-bearing rearing behavior, and grid walking task, which evaluates gait deficit in spontaneously moving mice. We found that differences between stroked and non-stroked animals were difficult to detect using two standard behavioral assays. Further characterization of the WMS model in the immunodeficient strain and improved control of subtle confounding factors that can affect behavioral assays are needed to assess the ability of hESCs to facilitate behavioral recovery following WMS.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Leung, Edwin
- Description:
- During warm climate events, growth rates can increase in fish, suggesting that they benefit from the increase in sea surface temperature. Experienced around the world, climate events such as El Niño Southern Oscillation and Pacific Decadal Oscillation can greatly influence the growth of a species. Previous studies have shown that species of fish can either thrive or dramatically decline during these shifts between warm and cool phases. Proper management of fisheries requires information regarding the interaction between a species and its environment. White seabass (Atractoscion nobilis) is a prominent commercial and recreational fishery species in Southern California. Largely attributed to overfishing, by 1982 the population had dramatically declined and both fisheries collapsed. Recent studies have shown signs that the native population is in recovery and may benefit from an El Niño event through increased growth rates. I addressed the question, "do environmental conditions cause variation in year-class strength in white seabass?" This study determined the population structure of white seabass over a 12-year period (1997 - 2008) and revealed that year-class strength was the greatest in 1996 and 1997. Reports of commercial landings for the species have shown a steady increase following the strong 1997 El Niño event, suggesting a relationship between year-class strength and commercial landings on a ten-year lag. Although year-class strength was greatest around the El Niño event, it was not significantly correlated with sea surface temperature or any climate index. Year-class strength estimation is an informative tool in assessing population structure of a managed species over time. The information provided in my study can inform fisheries, update management approaches, and help ensure the persistence of white seabass as the marine environment continues to change.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
290. Dissecting the teratogenic effects of an insect host pheromone on Pristionchus pacificus embryos
- Creator:
- Renahan, Tess
- Description:
- Developmental toxicity can be caused by biotic and abiotic factors known as teratogens. Given the success of nematodes in inhabiting most of the Earth's known ecological niches, we know very little about the possible environmental teratogens that can adversely affect early nematode development inside their tough eggshells. Plant parasitic nematodes can suffer delayed hatching and irreversible arrested development when bathed in solutions of volatile fatty acids released during plant decomposition. Human-made environmental toxins, notably plasticizers in PVC, are known to cause embryonic and other developmental defects. Other elements, including barium and mercury, are also known to cause a reduced body size and abnormal vulvas in exposed C. elegans embryos. Quite unexpectedly, the volatile host pheromone of the nematode Pristionchus pacificus can irreversibly arrest early stage embryos but it is unclear how and what developmental stage embryos succumb to permanent arrest. To characterize the threshold of sensitivity to the oriental beetle pheromone ZTDO, we determined the minimum exposure duration and developmental window that would result in arrested embryos. While most unexposed embryos hatch as J2 larvae after 24 hours, we found that exposing embryos to ZTDO for as short as 3 hours during gastrulation can arrest embryonic development permanently. We referred to these active embryos that develop abnormally and do not hatch as "zombryos." To further determine whether the beetle pheromone arrests embryonic development indirectly by inhibiting gas exchange, or directly by entering the eggs' shells and disrupting normal developmental processes, we utilized the membrane-specific lipophilic dye FM®4-64 known to stain the membrane layers of pre-anaphase oocytes in C. elegans. We found that FM®4-64 stained the plasma membranes of embryonic tissues, suggesting that the ZTDO pheromone likely penetrates the eggshell and its permeability barrier. By contrast, in unexposed embryos only the outermost vitelline layer of the eggshell is stained by FM®4-64. As further support that ZTDO acts on embryonic development directly, we show that non-exposed P. pacificus embryos raised in an anaerobic chamber result in delayed hatching but otherwise normal phenotype, and thus limiting gas-exchange in the embryo does not phenocopy the effects of ZTDO exposure. These results support the hypothesis that ZTDO may disrupt the permeability barrier and interfere with cellular functions, rather than preventing gas exchange. To determine the genetic factors involved in ZTDO-induced arrest, we conducted an EMS mutagenesis for resistance to ZTDO. The strongest ZTDO-arrest resistant allele, zar-5, shows a delayed in hatching when exposed to ZTDO but has a superficially normal phenotype. The zar-5 eggshell also appears be more resistant to ZTDO since FM®4-64 stains only the eggshell of zar-5 embryos. This study challenges our stereotype about the impermeable nematode egg and shows that the nematode embryo is sensitive to a host pheromone that acts as a developmental teratogen.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Lemon, William Creed
- Description:
- Foraging American Kestrels (Falco sparverius) were observed in order to determine how they choose between the two primary hunting techniques; perch hunting and hover hunting. If kestrels forage optimally, the energetically more expensive hovering technique must result in a greater energy gain from captured prey than does the perch hunting technique. In addition to calculating the energy budgets that would answer this question, environmental factors which might influence choice of hunting method were identified. Variables measured include distance of the strike from the perch, percent ground cover, temperature, percent cloud cover, time of day, and wind speed. The study was conducted at two sites; one in Santa Barbara County and one in Los Angeles County, California. Five-hundred-sixty-one strikes were observed between 5 May and 28 September 1983. Environmental factors whose mean values were significantly different for perch strikes and hover strikes (p<0.05) were distance from the perch, wind speed, temperature, and time of day. Calculation of energy budgets showed that the capture rate was much greater for hover hunting than for perch hunting, and even though hovering was more expensive, it was between 7 and 14 times more profitable. American Kestrels hunt from a hover to fulfill the majority of their energy requirements when environmental conditions are appropriate for hovering, and at other times hunt opportunistically from a perch. Optimal foraging theory can not accurately predict American Kestrel foraging behavior since kestrels spend long periods of time hunting suboptimally.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Ochoa, April Elizabeth
- Description:
- Metabotropic glutamate receptors (mGluR) have been implicated as targets for the treatment of neurological diseases linked to glutamate excitotoxicity. Of the three major groups of mGluR, Group I (mGluRl and mGluR5) has been reported to play a role in excitotoxic neurodegeneration. Of particular interest to our lab, mGluR5 has been localized in the cerebellum, hippocampus, and basal ganglia, and has been linked to modulating the excitatory effects of glutamate in these regions. Recent studies have shown that the selective mGluR5 antagonist MPEP produced positive therapeutic effects in rat models suffering from neurodegenerative disorders, and the mGluR5 agonist CHPG caused epileptic seizures. This study was conducted to investigate the potential neuroprotective effects of mGluR5 receptors on the spastic Han-Wistar (sHW) rat, a genetic model of glutamate excitotoxicity. (See more in text.)
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Wetzel, John.
- Description:
- The primary emphasis in most studies of bacteria and the relationship they have with their host is directed at the study of pathogenic species and the diseases caused by them, However, in addition to the pathogenic bacteria, there are many bacteria which are essentially nonpathogenic and can often be found in very healthy animals. These bacteria, although differing from animal to animal, perform important biological functions and in doing so affect both directly and indirectly an animal's general health. In spite of the contribution of the normal bacteria, only a few studies have been performed which attempt to determine the normal populations of even some of our most common domestic and wild animals.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Dimov, Ivan Minchev
- Description:
- The Hawaiian Silversword Alliance (HSA) comprises more than 30 plant species endemic to Hawaii that descended from a single North American tarweed species that migrated to the islands about five million years ago. The Silverswords are exquisite example of adaptive radiation. They are known to have little genotypic variation, but large diversity in morphology, and the species existing today include shrubs, trees, rosette plants and vines with white, yellow or red flowers. These two facts suggest that one of the reasons for the morphological variation is the regulation of the expression of structural genes from different biochemical pathways. The Anthocyanin Biosynthetic Pathway (ABP) is one of the most well studied in the plant kingdom. It is exclusive to plants and its' products, anthocyanins, protoanthocyanidins and flavonols are secondary metabolites that have many functions in plants. They play a role in recruiting pollinators, in UV-protection and plant-pathogenic microbe interactions. It has been shown in the literature that bHLH transcription factors play an important role in the regulation of many processes in plants, including the transcriptional regulation of the genes from the ABP. In this study we report the isolation of gene sequences from two bHLH genes in Madia gracilis (a California Tarweed), four bHLH genes from Dubautia linearis and two bHLH genes from Wilkesia gymnoxiphium. Both Dubautia linearis and Wilkesia gymnoxiphium are Hawaiian Silverswords. For all the sequences obtained in this study it was confirmed that they are part of the bHLH gene families involved in the regulation of the ABP. This was shown by bioinformatics analysis comparing the sequences to the MYB interaction domain (MIR), which is a known domain for bHLH genes known to regulate the ABP process. The sequence of MIR is conserved among all higher plants including monocots and dicots, and the selection test done with all the sequences generated in this study confirmed a negative selection pressure. This is the first study to isolate bHLH genes involved in the regulation of the ABP for the tarweeds and silverswords. The phylogenetic analysis of the sequences isolated in this study show that they cluster together with other bHLH genes from plant members of the Asteraceae family known to participate in the regulation of the ABP. This is the first study to isolate bHLH genes involved in the regulation of the ABP for the tarweeds and silverswords. Since the regulation of structural genes appears to be more important for specific phenotypes than the presence or absence of the structural genes or mutations within them, the findings of this study will be helpful in understanding the mechanisms that created the large morphological variation seen in Hawaiian Silversword plants, many of which are threatened and endangered. A better understanding of the regulation of the ABP would be beneficial also for the public since it's well known that anthocyanins possess antioxidant capabilities and those substances have been used in medicine and pharmacy for many years.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sivalingam, Daniel
- Description:
- Idiopathic pulmonary fibrosis (IPF) is a debilitating disease characterized by fibrosis of the lung interstitium. IPF primarily affects the elderly and the only treatment option is lung transplantation when the decline in lung function necessitates it. The current animal model of IPF, the bleomycin mouse model, is less than ideal as the pulmonary fibrosis produced in in this mouse model is self-resolving, unlike in the permanent and progressive human IPF. Previously, iPSCs have been used to model various complex diseases; however, they have not yet been used to model IPF. We have reprogrammed fibroblasts from both IPF affected (Recipient) and healthy donor (Donor) lungs to iPSCs to create a better model of the disease. Previous work has shown that loss of lung epithelial cells is one hallmark of IPF. It is also hypothesized that the distal lung epithelium may play a role in the proliferation of α smooth muscle actin expressing myofibroblasts, another hallmark of the disease. This work focuses on developing a multi-step in vitro method for generating distal lung epithelial cell types from iPSCs. Building on developmental studies performed in mouse, our method recapitulates in vivo development. We first differentiated iPSCs into definitive endoderm expressing CXCR4, c-kit, and EPCAM. We then anteriorized those cells into foregut endoderm expressing FOXA2, SOX2, TBX1 and PAX9. Following foregut generation, we ventralized the cells generating anterior foregut endoderm expressing NKX2.1 and T1α as well as epithelial markers cytokeratin 5 and e-cadherin. Finally, we directed the cells to a distal lung fate and rapidly matured the cells to distal lung epithelial cells expressing SFPB, SFPC and AQP5. The cells also stained positive for intracellular lipid containing vacuoles, as would be expected in mature alveolar type II cells producing surfactants. The derivation of distal lung epithelium described here provides an appropriate tool for studying IPF and other lung diseases as well as for use in cell therapies.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Daniels, Jeffrey Irwin
- Description:
- It has teen reported in the literature that E. coli, a bacterium normally limited to the gut of warm-blooded animals, dies rather quickly under natural conditions in the external environment. For this reason, the occurrence of E. coli in surface waters is thought to indicate recent fecal contamination of the environment. It is also generally accepted that E.coli is an extremely hardy organism, and will live for indefinite periods under certain laboratory conditions. This study has attempted to define some of the factors that cause the death of the organism in the external environment. It has been confirmed in this study that populations of E. coli will survive indefinitely in laboratory cultures as long as toxic products are removed or neutralized. Acids which accumulate as a result of continued metabolism of substrate have been shown to be the cause of death frequently associated with densely populated laboratory cultures. When population density more closely approximates the natu~ally occurring conditions of contaminated waters, it was shown that starvation, nutritional imbalances, or metabolism in the absence of growth did not severely affect the viability of the cultures. Exposure of both growing and non growing cultures of E. coli to either artificial or natural sunlight did, however, kill the populations quickly. Contrary to our expectations, and to the generally accepted notions, bubbling of air seemed to impart some protection against the adverse effects of solar radiation. These results were interpreted to mean that nutritional or metabolic processes were not the primary factors involved in the death of E. coli populations in surface waters, but that sunlight probably plays a major role in the elimination of this organism from the external environment.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Margve, Gabriel S.
- Description:
- Skeletal variation within a lizard population of Sceloporus magister is described and analyzed. Thirty-four osteological measurements were recorded on three age groups. A decrease in skeletal variation was found with increasing age. Of the three skeletal regions studied in each age group, the skull was the least variable, followed by the pectoral girdle-limbs and pelvic girdle-limbs regions. Skeletal variation between the sexes for adult and sub-adult age groups was also examined. Statistically significant sexual dimorphism was found only in the adult age group, with the adult females being less variable than the adult males in all three skeletal regions. This sexual dimorphism is analyzed in terms of three hypothesis: 1) competition hypothesis – which accounts for sexual dimorphism as a result of a balance between interspecific and intraspecific competition; 2) optimal feeding hypothesis – which relates sexual dimorphism to feeding strategy; and 3) sexual selection hypothesis – which relates sexual dimorphism to energy budgets involving growth, maintenance, and reproduction. Statistically significant sets of discriminating characters -which allow for the separation of the sexes were found for the adult and sub-adult age groups as well as for a combined age group. The significance of the discriminating characters along with their value in paleontological studies are discussed.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Arias, Daisy
- Description:
- Nostoc punctiforme is a filamentous cyanobacterium capable of producing cytoplasmic lipid droplets (LDs) that contain triacylglycerides, alpha-tocopherol (vitamin E), and alkanes. Triacylglycerides are a feedstock for biodiesel, and alkanes found in N. punctiforme are of the length typically found in jet fuel. Synthesis of these compounds by photosynthetic microorganisms could potentially steer away from the use of fossil fuels. It is important to understand how the cell makes LDs or responds to LD production in order to alter metabolic pathways to improve and increase the efficiency of LD production. Previous work from our lab has shown that a N. punctiforme strain that overexpresses two N. punctiforme genes involved in alkane biosynthesis, aar and adc (2- gene expression strain), overproduces heptadecane and has an increased number of LDs in exponential phase compared to the wild-type strain. Proteomic analysis conducted on proteins associated with isolated LDs identified a putative lipase that when overexpressed alone increased alkane production. This putative lipase was confirmed to be associated with isolated LDs by Western blotting. Overexpression of this lipase in conjunction with aar and adc (3-gene expression strain) further increased LDs and heptadecanes compared to the 2-gene expression strain. Comparative transcriptomic analysis of wild-type and these LD/alkane overproducer strains were conducted to illuminate the function and formation of LDs and alkanes. Genes exhibiting a statistically significant >1.4 fold increase in the 2- and 3-gene overexpression strains relative to the plasmid-only control were hypothesized to enhance or cope with overproduction of LDs and alkanes. Thirteen genes showing up-regulation were cloned on a multi-copy plasmid and transformed into wild-type either alone and/or in an operon, or in conjunction with the 3-genes mentioned above to test the hypothesis that overexpression due to increased copy number enhanced, or mimicked, the increased LD or alkane production phenotype. A total of 17 overexpression strains were made. LDs from each of these strains were stained with BODIPY and viewed using fluorescence microscopy. Two overexpressor strains expressed structural alterations in LDs including one which did not express any visible neutral lipids. Alterations in alkane and lipid fatty acid composition were also analyzed using gas chromatography-mass spectrometry (GC-MS). Only one strain showed an enhanced heptadecane production relative to its control strain while three strains exhibited a decrease in heptadecane which could be indicative of a stress response mechanism. These data will ultimately help us develop strains capable of producing LDs enriched in biofuels or other high value compounds that can be utilized for biotechnological applications.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Cook, Maryn
- Description:
- Beetle-associated nematode Pristionchus pacificus (Diplogastridae) bears characteristics of both free-living and parasitic worms and is therefore a unique comparative system to study behavior and developmental regulation, including the regulation of molting. Molting is the regular and isochronous shedding of a cuticle or exoskeleton at the end of each juvenile or larval stage. Many nematodes, such as the widely-studied Caenorhabditis elegans (Rhabditidae), undergo four larval molts that divide five discreet developmental stages; however, in the nematode P. pacificus, only three larval molts are observed after hatching from eggs. Researchers hypothesize that rather than omitting a molt altogether, P. pacificus experience a molt prior to hatching known as the embryonic molt. Such an embryonic molt has been observed in other select Diplogastrids and is now a widely accepted developmental phenomenon defining the taxon. Another difference between P. pacificus and C. elegans is the presence of the insect ecdysone receptor homolog in its genome which suggests that the regulation of molting may differ within the phylum. In an effort to study the developmental process and evolution of molting and genetically characterize the embryonic molt in P. pacificus, we draw analogy from the well-studied model organism C. elegans. Using standard reciprocal basic local alignment search tools (TBlastN, BlastP, BlastX), we show that the P. pacificus genome encodes the putative ortholog of mlt-10, a nematode-specific protein necessary for the animal to successfully remove the larval cuticle during molting. We performed a reverse transcription polymerase chain reaction (RT-PCR) experiment using P. pacificus cDNA to amplify the most similar translated nucleotide sequence and obtain the full-length mRNA sequence. We compared the cDNA sequence to the genomic sequence to identify intron/exon length and boundaries and to determine the start and stop of translation. To identify regions of sequence conservation we conducted a multiple sequence alignment of the predicted P. pacificus MLT-10 with MLT-10 from three Caenorhabditis species and select nematode species and performed phylogenetic analysis. Using quantitative PCR (qPCR) on cDNA obtained from synchronized and staged worm populations we obtained a preliminary developmental profile of putative P. pacificus mlt-10 (Ppa-mlt-10). Using standard Blast queries of the conserved proline-rich-repeat C-terminal domain of MLT-10 followed by phylogenetic analysis, we show that the P. pacificus genome contains the mltn paralogous gene family and assign putative names to the newly identified genes. Using the BLAST/RT-PCR procedure described above and in order to find genes expressed only during embryogenesis, we identified, amplified and sequenced putative chs-1 and hch-1 orthologs in the P. pacificus transcriptome. Finally, we have generated a transcriptional reporter of the P. pacificus ecdysone receptor suitable for microinjection. An attempt was made to separate an egg population into four discrete developmental stages based on egg mass using a simple sucrose gradient assay. The goal of this experiment was to obtain staged egg populations and measure embryonic expression of Ppa-mlt-10 using qPCR. The assay failed to separate the eggs into the desired stages and instead produced a single heterogeneous population. We also pursued with unsuccessful outcome the RNA interference (feeding) of Ppa-pnhr-1 and Ppa-pnhr-2 and 5’RACE of Ppa-mlt-10 and Ppa-pnhr-1. Together these experiments provide our laboratory a starting point from which the differences in the molting pathway within the nematode phylum can be established particularly as they pertain to endocrine signaling and the embryonic molt.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Smith, Lareen M.
- Description:
- Marine benthic organisms are confronted with numerous physiological challenges in a variable environment. Sessile organisms are reliant upon the ability to sense and respond to vital environmental cues that allow them to tolerate environmental variation. Sessile, colonial invertebrates must have mechanisms to sense and integrate environmental signals to enable adaptive plasticity. Hydractiniid hydrozoans are ideal model organisms for studying phenotypic plasticity. Many hydrozoans grow continuously, lack determinate size and shape, and show a continuum of morphotypes. The arrangement of tissues of the gastrovascular system, into either highly interconnected networks (sheets) or disparate linear extensions of stolons (runners), determines the distribution of metabolites and signaling information amongst cells. Hydractiniid hydrozoan colonies that live on hermit crab shells experience variable environments due to host crab behavior. These hermit crabs often bury themselves in soft sediments, subjecting hydrozoan colonies to hypoxic conditions. In response to dissolved oxygen availability (pO2) and variable seawater viscosities, two variable abiotic factors, I found that hydrozoan colonies use both (pO2) and hydromechanical forces associated with gastrovascular transport as environmental cues to signal morphogenesis. By experimentally increasing the dynamic viscosity of seawater media, I was able to impose a proportional linear increase in gastrovascular shear stress to measure the effects of this physical force on the vascular wall independently of other signals generated by feeding. I also investigated mitotic rates of hydrozoan colonies whose pO2 and shear stress was manipulated in the gastrovascular system in factorial combination. I found a positive relationship between mitotic rate and shear stress. In a field experiment, I placed three genotypes in different environments in a factorial array, measured environmental parameters and followed the growth trajectories of hydrozoan colonies. Locations characterized by, saturating levels of pO2, persistent flow, and coarse sand showed a colony-wide increase in stolon branching, and sheet-like tissue across all genotypes. Environments characterized by reduced levels of pO2, low flow, and fine sand and silt showed genotype-specific morphological responses, suggesting a genotype x environment interaction. I used path analysis to infer the strength of morphological responses to these different environmental signals and found that colonies responded to hypoxic signals in a natural field setting, in the midst of many other conflicting environmental signals. This suggests hydrozoan colonies may be using as few as one or two environmental signals to coordinate colony morphogenesis across a range of habitats. These two experiments together demonstrate the importance of pO2 and gastrovascular shear stress as integrating signals that promote colony-wide morphological response to environmental conditions. That these signals reflect facets of both gastrovascular transport and habitat quality supports the argument that few important signals may be required for a wide range of plastic responses to a variety of stimuli in colonial organisms, suggesting that the complexity of hydrozoan growth and development is built from the simple recursive application of basic physiological rules.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology