Initiation and control of meiosis in hamster gonads in vitro

Studies of fetal ovaries maintained in organ culture have shown that meiosis can proceed in vitro (Martinovitch, 1938; Borghese & Venini, 1956; Baker & Neal, 1973). However, if the ovaries are removed from the fetus before the onset of meiosis, the germ cells fail to undergo normal meiosis in culture and subsequently degenerate (mouse: Wolff, 1952; sheep: Mauléon, 1973; hamster: Challoner, 1975a). In the hamster, meiosis fails to occur if the ovaries are removed before the 15th day of gestation, even if gonadotrophic hormones or maternal serum are added to the cultures, suggesting that an 'inductor' is required to initiate meiosis (Challoner, 1975a). However, the meiosis inducing factor has not been investigated further. Byskov (1974) grafted fetal ovaries into nude mice and showed that the external rete ovarii was necessary to 'trigger' the induction of meiosis in the germ cells. In the present study, the effect of the external rete ovarii on the initiation of meiosis in the hamster was studied in organ culture.