The comparison of primordial germ cell populations in embryos of KE and CBA inbred strains of mice.

The changes in primordial germ cell (PGC) populations were compared in embryos of two inbred strains of mice-KE and CBA/Kw on 11, 12, 13 and 14 day of foetal life. The number of PGCs did not differ in 11-day embryos of both strains. In 12-day CBA/Kw embryos the proliferation rate of PGCs was higher and the number of PGC was significantly higher than in 12-day KE embryos. However, on subsequent days the PGC proliferation rate decreased in CBA/Kw but rapidly increased in KE embryos, leading to significantly higher number of PGCs in 14-day KE embryos. These differences in proliferation rate between KE and CBA/Kw PGCs can be regarded as the reason of strong selection against CBA/Kw derived gametes observed in KE<-->CBA aggregation chimaeras.