Appearance of the oocyte activation ability of mouse round spermatids cultured in Vitro

This study was undertaken to determine the expression time of fertilization and oocytes activationabilities of spermatidsin the mouse. When elongatingor elongated spermatidsisolated from fresh testes of adult males (B6D2F1) were injected into mature mouse oocytes, both spermatidscould activate the mature oocytesand occur fertilization. On the one hand, the round spermatidscould not activate mature oocytes, when microinjected into oocytes. In some experiments, recovered round spermatidswere cultured under co- culture systemsusing Sertoli cellsas a feeder cell. Under the co- culture system, developed elongating spermatidscould stimulate and fertilized mature oocytes. These results indicate that the start of oocyte activationappearance is between the stage of round spermatidand elongating spermatidsand the activation ability increases with the advance of spermiogensis. On the other hand, round spermatidsisolated from males of ICR strain mouse already have the oocyte activationability and the fertilizing ability. The result obtained suggests that the expression time of the oocyte activatingability is difficult between the mouse strain.