Abstract
Superovulated eggs were obtained from mature females of three in-bred strains, Balb/c, C57BL/6J-at/at and C3H/He, and their F1 hybrids for the com-parison of their fertilizability and developmental potential. The eggs were fertilized in vitro by epididymal spermatozoa of JCL :ICR strain in a chemically defined medium under 5% CO2 in air at 37°C. At 6 hr after insemination, the eggs having second polar bodies were transferred to fresh medium and cultured for 90 hr. The percentages of eggs undergoing fertilization were 69 to 85% in all F1 and inbred strains and almost all of them developed to 2-cell stage 24 hr after insemination.
In contrast, marked difference was found in the percentages of eggs developing to 4-8-cell stages between F1 hybrids (69 to 93%) and inbred strains (3.6 to 28%). Further development to blastocyst was observed in 30 to 54% of the eggs from F1 hybrids in comparison with very low rates of development in those eggs from inbred strains of mice (0 to 3%). (Japan. J. Anim. Reprod. 24 (1922), 1978)
