Department of Zoology, University of Rajasthan, Jaipur, Rajasthan, India
(Received 10th June 1974)
An injection of 5 i.u. PMSG to 21-day-old mice greatly increases the number of large follicles in the ovary but does not cause any morphological change in the oocyte (Merchant & Chang, 1971; Cross, 1973). If an injection of HCG is given 48 hr later, the oocytes pass rapidly through the remaining stages of meiosis and reach the second metaphase in 12 to 14 hr (Edwards & Gates, 1959). Oocytes which are mechanically released from the follicles and cultured in an appropriate medium without any hormonal stimulation reach second metaphase in 14 to 17 hr (Donahue, 1968; Cross & Brinster, 1970). The present report deals with the fate of oocytes left in the follicles and their developmental potential at various times after an injection of PMSG.
Mouse oocytes have been matured in vitro by many workers (Edwards,