A method for the in vivo experimental study of meiotic prophase in the golden hamster (Mesocricetus auratus).

Gonads of 15 day-old hamster fetuses were grafted under the kidney capsule of adult ovariectomized females. In 81.8% of the grafts, the germ cells developed and completed meiotic prophase; they reached the diplotene stage and gave rise to primordial follicles. These grafts could survive well in the host for at least 20 days. Meiotic prophase was not initiated within 24 h of grafting in contrast to the in vivo condition where it is observed 24 h after birth. In grafted ovaries, 69% of the germ cells were at the leptotene stage on day 3. By day 5, most of them were either at the zygotene (15%) or pachytene stages (60%). Oocytes at the diplotene stage were found from day 5 onwards and on day 7, 30% of the germ cells had already reached this stage. The highest numbers of atretic germ cells could be found on days 1, 9 and 10 post graft. It is noteworthy that the number of germinal cells remaining in the ovary 10 and 20 days after grafting were 11.4% and 12.9% of the total number of germinal cells present in normal animals of the same ages post-partum. This point is discussed in detail.