The culture of preimplantation rat embryos and the production of allophenic rats

Abstract

Rat embryos at all cleavage stages of development were cultured in vitro. The various cleavage stages were successfully cultured through at least 1 mitotic cycle with the exception of the 4 cell stage. No instance of development through the 4 cell stage was observed. The 8 cell stage was cultured to the blastocyst stage with about 80% success. There was no difference in viability of 8 cell embryos if they were cultured without the zona pellucida. Despite some difficulties with adhesion of embryos and cellular death, denuded embryo pairs aggregated into a single blastocyst during a 24 hr culture period. Of all such aggregation attempts, 45% proved successful. 25 aggregate blastocysts were transferred to 8 recipient females. Subsequently, 7 transferred embryos were born to 4 of the host females. 5 of these transferred embryos were externally female while the remaining 2 were normal males. 2 of these females were sibling aggregates (identical phenotypes) and no evidence of mosaicism should have been observed. Of the remaining 5 animals, 3 were of one parental phenotype or the other, while the remaining 2 (1 male and 1 female) expressed some degree of parental phenotype mosaicism.