RESUMO
Blastula embryos of the sea urchin Paracentrotus lividus, when dissociated into single cells by exposure to Ca2+- and Mg2+-free sea water, reassociate spontaneously to form aggregates capable of development to the final larval form (pluteus). This aggregation is prevented by Fab fragments obtained by immunization with purified membranes from blastula embryos. The inhibition was reversed by soluble proteins extracted with butanol from purified membranes or from intact cells. These extracts also strongly stimulated the rate of reaggregation of dissociated cells in the absence of Fab fragments. Exposure of dissociated cells to 2.5% (vol/vol) butanol removed completely the protein(s) responsible for reaggregation of the cells without impairing their viability. Reaggregation and embryonic development were completely restored to the extracted cells by readdition of the proteins extracted from either membranes or cells. Extracted cells from Paracentrotus could be reconstituted with proteins from Arbacia.
