Action of periodate on the surface reactions attending the activation of the egg of the sea urchin, Psammechinus miliaris

Abstract

A solution of jelly coat substance inhibits a normal differentiation of the fertilization membrane in eggs of Psammechinus miliaris. The contraction of the egg surface does not occur, the coagulation of the vitelline membrane and the merging of the cortical material with this membrane are impeded. Furthermore the eggs present a varying degree of di- or plurispermy in presence of jelly coat solution. All the effects of the jelly coat solutions which have been mentioned in the preceding paragraph are removed by addition of 5 × 10 −5N sodium periodate. Periodate has also a certain activating effect on the ripe eggs. Particularly it sensitizes the egg to the activating effect of brief exposures to hypertonic medium. Pretreatment of underripe eggs with periodate has a most striking improving effect on membrane formation and further development. The jelly coats of periodate pretreated eggs are more weakly precipitated upon addition of clupein than are eggs not pretreated. Periodate treatment has a harmful effect on the oocytes. They elongate and a deep constriction separates the oocyte into one nucleated and one non nucleated part. Numerous bulges and appendages are formed from the latter (Fig. 11). It is inferred that underripeness is caused by the predominance of an inhibitor having a character similar to that of the jelly coat substance. The belief is expressed that the inhibitory agent is deeply engaged in the whole activation process.