A cytoplasmic fraction acting on the surface layers of the Arbacia punctulata eggs

Abstract

A jelly precipitating factor was obtained from the eggs of Arbacia punctulata. The eggs were frozen and dried, extracted with 1 M KCl solution and thereafter submitted to ultracentrifugation. A fraction sedimenting following centrifugation for 45 minutes at 25000 × g presented no demonstrable activity. A second fraction, however, obtained following centrifugation for two hours at 155 000 × g gave a highly active fraction, whereas the supernatant proved to be inactive. The active fraction was shown by electrophoresis and ultracentrifugation to contain at least two components. The jelly precipitating factor inhibits the agglutination of the spermatozoa by the fertilizin and is thus identical with the egg antifertilizin. In eggs of Arbacia punctulata a factor was demonstrated which changes the membrane so as to render this tougher and more refractile. This factor is probably identical with antifertilizin or at least closely adhering to this. The factor was shown to escape from the pigment vacuoles of the egg. Supplementary observations indicate that also in eggs of Psammechinus miliaris substances given off from particulate components precipitate the jelly and toughen the membrane as well.