Fertilization of Chinese Hamster Eggs in Vitro

Fertilization of eggs in vitro has been described in three mammalian species— the rabbit (Dauzier, Thibault & Wintenberger, 1954; Chang, 1959; Suzuki & Mastroianni, 1965; Brackett & Williams, 1965), Syrian hamster (Yanagimachi & Chang, 1964; Barros & Austin, 1967) and laboratory mouse (Whittingham, 1968). Penetration by spermatozoa and pronucleus formation have also been observed in rat eggs, following dissolution of the zona pellucida by chymotrypsin (Toyoda & Chang, 1968). In preliminary attempts to fertilize eggs of the Chinese hamster, Cricetulus griseus, in vitro, no success was achieved using fresh spermatozoa, but 10% of eggs (8 of 80) were penetrated by spermatozoa which had previously been incubated with Syrian hamster cumulus clot. This treatment was used in a larger study in August 1968, as described here. Immature and maturing Chinese hamsters, 5 to 8 weeks old, were injected