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The effects of Concanavalin-A derivatized beads on sea urchin gastrulation
Many studies have examined the effects of free lectins such as Concanavalin-A (Con-A) on sea urchin development and suggested that lectin binding ligands play a role in embryonic cellular interactions. In this study, the effects of immobilized Con-A on sea urchin cellular interactions were examined by incubating embryos 2 hours after fertilization, 24 hours after fertilization right before invagination, and 27 hours after fertilization when invagination has occurred, with no Con-A beads, low, medium, and high counts of Con-A derivatized agarose beads and the embryos were observed at various times after beads addition. The results showed that archenteron development and attachment were interrupted when high and medium counts of Con-A beads were added before invagination. Once invagination occuffed, the Con-A beads had no significant effect on further development. The results were statistically significant (P < 0.0001) when archenteron attachment was compared between controls and experimentals when beads were added before invagination. There were no significant differences in the controls and experimentals when the beads were added after invagination (P>0.061). Analysis of protein concentration in the supematants from Con-A beads alone, beads with embryos, and embryos alone, suggested that small quantities on order of ug/ml of Con-A might have been released from the beads by the embryos, although it is very possible that no Con-A was released and what was released was sea urchin proteins resulting from cell lysis in the presence of Con-A beads. Further study of this issue is required to determine if immobilized Con-A (and not free Con-A) can effect specific embryonic cellular interactions in this system, an issue that is of importance in identifying mechanisms of morphogenesis.