INHIBITION OF DIVISION AND DEVELOPMENT OF SEA-URCHIN EGGS BY ANTISERA AGAINST FERTILIZIN

Abstract

Rabbit antisera against fertilizin of sea urchins can block cell division in the early cleavage of the egg and can also inhibit the development of embryos introduced at later stages. The blocked eggs and the embryos later undergo cytolysis in the immune sera, the dilutions and times at which this effect is obtained being similar for all stages studied. Nuclear as well as cytoplasmic division is inhibited by the antiserum. Mitotic progress in strong antiserum is less than 1/4 of a division cycle, with no indication of a selective action on a particular mitotic phase. Swimming embryos in blastula to pluteus stages are almost immediately immobilized by strong antiserum. Absorption with sperm generally removes no detectable amount of cleavage-blocking antibodies but in some cases may reduce the titer by 25%. Absorption with gastrulae can remove about 90% of the cleavage-blocking antibodies. Precipitin tests show a reaction of the blocking antisera with extracts of the ectoplasmic layer of the fertilized eggs. Treatment with antiserum increases the tension at the surface of the egg. The rate of O2 uptake is temporarily increased by treatment of the fertilized eggs with blocking antiserum. Determination of the Na content of the eggs shows no significant increase upon treatment with antiserum. The cell division-blocking action of the fertilizin-antisera may be attributed to an initial reaction with surface constituents of the demembranated fertilized eggs that bear antigenic structures in common with fertilizin and that persist, for the most part, in the later embryos.