Thesis

Inhibition of cell aggregation by specific carbohydrates

One approach to investigating the potential role of surface carbohydrates in mediating intercellular adhesion is to study cell reaggregation in the presence of defined concentrations of specific saccharides. Fifteen different exogenously added saccharides were tested for their-effect on the reaggregation of 24 hour sea urchin embryo cells (Stongylocentrotus purpuratus) dissociated by removal of divalent cations. Aliquots (0.2 ml) of cell suspension were rotated at 68 rpm, 17°C, pH 8.0 with varying concentrations (10-1 to 10-5 M) of the sugars. Relative percents of cell aggregation were determined using an electronic particle counter assay. In all experiments cell viability using trypan blue was over 95.8%. Among the sugars tested, in 15 separate experiments, D-galactose and N-acetyl-D-galactosamine consistently inhibited aggregation to the greatest extent at all-time points. D-galactose, at all concentrations tested, at 10, 20, 30, 40, and 60 minutes rotation, showed-mean decreases of aggregation over control values in the absence of sugar of 59.3%, 53.6%, 49.2%, 35.0% and 36.4% respectively. N-acetyl-D-galactosamine also caused mean decreases in aggregation of 73.5%, 54.5%, 40.8%, 42.2%, and 45.6% respectively. Each difference over the control is significant to the p value of less than 0.01. In three experiments, β- galactosidase substantially inhibited reaggregation of these cells. These results suggest that galactopyranosyl-like groups may be implicated in mediating adhesion of 24 hour sea urchin embryo cells to each other.

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