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- Creator:
- Skorka, Christopher
- Description:
- Trypanosoma cruzi is the protozoan parasite that is the causative agent of Chagas disease. This disease is endemic to Latin America but has spread to other non-endemic areas due to globalization. the disease currently lacks an FDA approved treatment, and current treatments are non-specific and have severe side effects. More specific and novel pathways of T. cruzi must be identified to develop more effective treatments of Chagas. One potential target is ion channels, which play a wide array of important physiological roles throughout eukaryotic organisms. We have identified and characterized a calcium-activated potassium channel in Trypanosoma cruzi, TcCaKC, that is hypothesized to contribute to significant physiological function in T. cruzi. Using two-electrode voltage clamp method with Xenopus laevis oocytes heterologously expressing TcCaKC, the channel has been shown to be calcium-activated. This calcium activation causes an increase in current and a negative shift in reversal potential that is blocked by barium. These results suggest TcCaKC is a potassium conducting channel. Characterization of a selectivity filter mutant also supports this hypothesis. Fluorometric recording of parasites that were knockouts of TcCaKC showed that the channel plays a significant role in maintaining membrane potential, intracellular calcium, and pH of the parasite. Full biophysical characterization of this novel ion channel could potentially lead to the identification of a unique drug target for T. cruzi infection treatment.
- Resource Type:
- Masters Thesis
- Identifier:
- 9780438054202
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Huang, Harrison
- Description:
- The Southern California Bight receives approximately 1.5 million gallons of wastewater effluent per day. Although regional monitoring has occurred periodically since the implementation of wastewater treatment practices, few studies have attempted to investigate long-term fish population or environmental changes in response to changes in wastewater treatment. The present study compared Pacific sanddab, California lizardfish, and English sole populations and environmental parameters near a wastewater outfall site and far-field site located in Orange County, California, between 1990 and 2015. Biannual fish trawl data and environmental data (surface temperature, bottom temperature, salinity, dissolved oxygen) collected by Orange County Sanitation District’s Ocean Monitoring Program were analyzed using a two-way analysis of variance and regression analysis. Overall, there was no interaction between sample sites and treatment periods on the fish population (except English sole abundance) and environmental parameters analyzed. Fish abundance and relative condition factor did not differ significantly between sites, but all fish species were significantly larger at the outfall site. Wastewater effluent did not appear to adversely impact the three fish populations or the four environmental parameters investigated in this study. Further monitoring and investigation into other indicators of pollution are necessary to manage and further asses the effects of wastewater discharge.
- Resource Type:
- Masters Thesis
- Identifier:
- 9780438055247
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
3. Sex-specific Behavioral Strategies for Thermoregulation in the Common Chuckwalla (sauromalus Ater)
- Creator:
- Sanchez, Emily Rose
- Description:
- Intraspecific variability of behavioral thermoregulation in lizards due to habitat, temperature availability, and seasonality is well documented, but variability due to sex is not. Sex-specific thermoregulatory behaviors are important to understand because they can affect relative fitness in ways that result in different responses to environmental changes. the common chuckwalla (Sauromalus ater) is a great model for investigating sex differences in thermoregulation because males behave differently from females while they actively defend distinct territories while females may not. I recorded body temperatures of wild adult chuckwallas continuously from May to July 2016, as well as operative environmental temperatures in crevices and aboveground sites used by chuckwallas for basking. I compared the effect of sex on indices of thermoregulatory accuracy and effectiveness, aboveground activity, and the time chuckwallas selected body temperatures relative to their preferred temperature range (34–39 °C) for May-July. Males and females achieved the same thermoregulatory accuracy and effectiveness, and amount of time at preferred body temperatures, but males were more active aboveground than females, especially in June. These results indicate that different behavioral strategies can accomplish the same thermoregulatory outcomes. Further, chuckwallas might be able to cope with predicted changes in climate that result in a shorter amount of time they could be active at preferred body temperature because these lizards were only active aboveground for one to four hours per day, a fraction of the time available.
- Resource Type:
- Masters Thesis
- Identifier:
- 9780438054776
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Quinn, Brettni
- Description:
- Acinetobacter baumannii has emerged over the last few decades as a major nosocomial pathogen. Its ability to acquire genetic material and survive in extreme environments has positioned it as a paradigm of multidrug resistance. Horizontal genetic transfer, specifically natural transformation, has played a key role in its evolution. However, little is known about how competence for natural transformation is induced or regulated in A. baumannii and, therefore, our research focuses on identifying inducers of competence and characterizing genes involved in this process. to identify inducers of competence, A. baumannii cells were grown in the presence of host human products or antibiotics and transformation frequencies were assessed. Human serum albumin (HSA) was the only host human product that significantly increased transformation frequencies, suggesting that an albumin-specific mechanism exists in this species. in addition, all three antibiotics tested increased transformation frequencies, likely via different pathways. to better understand induction of competence, RNA sequencing was performed under HSA induction and 167 genes were identified as being significantly differentially expressed. Twenty-three genes were analyzed in depth, including putative transcriptional regulators and those associated with two component regulatory systems and type IV pili. This analysis led to the identification of a number of genes that were not explored before and whose roles in competence development are suitable for further analysis.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Carlin, Joseph A.
- Description:
- Extreme episodic events have the capacity to transport large amounts of terrestrial material to the coastal ocean. While estuaries and deltas are typically thought to trap most of this material, some escapes these coastal features and is transported to distal depocenters along the continental shelf. Distal shelf depocenters can act as the ultimate sink for event deposits, yet event sedimentation and the impact of terrestrial carbon burial within these shelf deposits remains understudied. Therefore, this study investigated event sedimentation within the Texas Mud Blanket (TMB), a distal shelf depocenter of the Brazos River located in the northwestern Gulf of Mexico. Using a core that was collected from the TMB during a months-long elevated discharge event in late 2015 to early 2016 we applied a multi-proxy approach to delineate the event deposit. We utilized physical sediment properties (fabric, texture, and bulk density), radioisotopes (7Be and 210Pb), and organic geochemical properties (ẟ13C, C/N, and lignin-phenols) to identify a 10 cm event layer at the surface of the core. Within this 10 cm layer, we also distinguished two sub-layers associated with separate extreme discharge periods in the winter and spring, respectively. Using these event layer characteristics, we identified three other earlier potential event deposits in the core that we have attributed to events in 2010, 2007, and 2000–2001. From these results, this study has demonstrated that the TMB may be an archive for event deposits over multi-decadal time periods, in particular the transition from periods of prolonged drought to extreme wetness associated with the Brazos River. This event-dominated sedimentation regime can enhance long-term carbon burial, potentially increasing current estimates of carbon burial significantly in the TMB and other similar distal shelf depocenters. Ultimately this study highlights the potential for distal shelf depocenters as organic carbon burial “hotspots,” and postulates that this role may expand in the future as climate change increases the intensity and frequency of extreme events.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Paig-Tran, E.W. Misty, Lowe, Andrew, Walker, Sean, and Walter, Ryan P.
- Description:
- The cory catfishes (Callichthyidae) are small, South American armored catfishes with a series of dermal scutes that run the length of the fish from posterior to the parieto-supraoccipital down to the caudal peduncle. In this study, we explore the anatomy and functional performance of the armored scutes in the three-striped cory catfish, Corydoras trilineatus . The lateral surface has a dorsal and a ventral row of scutes that interact at the horizontal septum. The scutes have little overlap with sequential posterior scutes (~33% overlap) and a deep ridge in the internal surface that connects to the underlying soft tissue. The internal surface of C. trilineatus scutes is stiffer than the external surface, contrary to the findings in a related species of cory catfish, C. aeneus , which documented a hypermineralized, enamel-like, non- collagenous, hyaloine layer along the external surface of the scute. Clearing and staining of C. trilineatus scutes revealed that the scutes have highly mineralized (~50% mineralization) regions embedded in be- tween areas of low mineralization along the posterior margin. Puncture tests showed that posterior scutes were weaker than both anterior and middle scutes, and scutes attached to the body required 50% more energy to puncture than isolated scutes. Corydoras trilineatus has the strongest armor in areas critical for protecting vital organs and the external armored scute receives synergistic benefits from interactions to the soft underlying tissue, which combine to provide a tough protective armor that still allows for flexible mobility.
- Resource Type:
- Article
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Oliverio, Ryan
- Description:
- Determining the reasons behind how and why evolutionary mechanisms that establish or remove genetic variations within a population is a fundamental question in evolutionary biology. by tying together, the origin, evolutionary patterns, molecular mechanisms, and functional outcomes of genotype to phenotype, we gain insight on how and why genes are conserved or changed. This methodology was followed to investigate the stress-inducible Hsp70 gene in humans (HSPA1A), a critical component of the cellular stress response, and whose modification has been associated with a variety of human diseases. My results indicate that the origin of the HSPA1A gene is in placental mammals. Additionally, a combination of purifying selection and genetic recombination with its closely-related paralog, HSPA1B, have conserved the amino acid sequence of this gene from possibly deleterious mutations in multiple mammalian species. This pattern can also be applied to human microevolution in how single-nucleotide polymorphisms are distributed for both HSPA1A and HSPA1B, in contrast to their closely-linked homolog HSPA1L. This finding is further supported by the fact that natural variants of HSPA1A, that were most likely to change function, only apply small changes to the primary function of HSPA1A and have very low allele frequencies within human populations. Altogether, my experimental observations show HSPA1A is subject to purifying selection and provide functional characterization of two positions, R36 and I480, that appear to have importance in the folding function of HSPA1A. Supplementary Tables 1 and 2 of extended mammalian evolutionary trends are provided.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Coombs, Kimberly Marie
- Description:
- Cryptic species can often cause problems for baseline and ecological studies as these species are not readily identified in the field. Lottia scabra and Lottia conus form a north/south cryptic species pair where they occupy the same habitat, but L. scabra is more abundant in northern California and L. conus is more abundant in at least the southern portions of southern California. Past El Niño events have resulted in prolonged anomalous warming of coastal seawater, which may be impacting the vertical and latitudinal distribution of these two species as has been documented for another north/south pair in California, L. austrodigitalis and L. digitalis. To monitor the current and potentially changing distribution of L. conus and L. scabra, quadrat sampling was performed at nine sites in California at various heights in the mid to high intertidal, collecting a subset of limpets to identify in the lab. A range refinement of L. conus has occurred with its previous documented northern limit being Point Conception to now its current northern limit being Jalama Beach, CA. A transition zone occurs from San Pedro to Jalama Beach where L. conus becomes less abundant and L. scabra becomes more abundant. With an established baseline, future studies may document whether this distribution changes in response to temperature variations from climate change or El Niño events. Susceptibility to temperature changes may make limpets good indicator species for detecting regional climate change effects in the intertidal as well as potential model species for future studies to use when observing rocky intertidal habitats.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
- Creator:
- Hue, Fong
- Description:
- Antibiotics are losing effectiveness as multidrug resistance among bacterial pathogens is spreading. Resistance enzymes, like AAC(6’)-Ib, allow bacteria to survive and proliferate in the presence of antibiotics. Conversely, discovery of new antibiotic compounds is decreasing; alternative strategies are needed to combat the rise and spread of antibiotic resistant bacteria. Studying the resistance enzymes can provide new insights into developing alternative strategies. This project set out to quantify the number of enzyme molecules within a cell and determine the relationship between the amount of enzyme molecules and the level of resistance granted by the number of molecules. E. coli strains carrying CRISPR-dCas9 genes and pFH3, a near-wild type plasmid expressing AAC(6’)-Ib, were created. Fluorescence assays were used to measure AAC(6’)-Ib tagged with an mMaple fluorophore. Resistance levels were determined using minimum inhibitory concentration (MIC) tests with amikacin Etest strips. It was found that the relationship between fluorescence and enzyme molecule number was linear. Additionally, resistance conferred by the enzyme was proportionally dependent on the number of enzyme molecules present within the measured range.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences
10. The Effects of Cryopreservation on the Mechanical Properties and Composition of Anosteocytic Bone
- Creator:
- Barrios, Andrew S.
- Description:
- Bone tissue is typically stored frozen (cryopreservation) for bone grafts or tissue investigation. Whole osteocytic bone, bone with osteocytes, is resistant to the damaging effects of cryopreservation. Anosteocytic bone, bone without osteocytes, is present in the most speciose group of vertebrate, teleost fishes, and has not been investigated for the effects of cryopreservation. Pacific chub mackerel, Scomber japonicus, were caught off the Newport pier in Newport Beach, California, USA, and separated into fresh and frozen (25 & 45 days) treatment groups. The opercles of S. japonicus were excised for mechanical testing, bone ash content, and histology to determine whether freezing affects anosteocytic bone. Bone beams were cut from opercles using a CO2 laser cutter and then subjected to 3-point bending. Whole opercles were ashed to determine mineral, collagen, and water content of the bone. Opercles were stained with picrosirius solution to measure collagen fibril width within the bone. Freezing did not affect the mechanical properties, composition, or collagen fibrils of the anosteocytic bone of S. japonicus. This will allow the storage and transportation of more fish species for expanded studies on the mechanical characteristics of their bone. Anosteocytic bone could also provide an easily accessible and abundant alternative to osteocytic bone for bone grafts. The lack of bone cells within the extracellular matrix of anosteocytic bone would likely reduce the chance of an immune response from the recipient while providing a framework for recipient cells to build new bone for a quick recovery.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fullerton
- Department:
- Department of Biological Sciences