Effects of the culture density of mouse zygotes on the development in vitro and in vivo.

Different numbers of CD-1 mouse zygotes(1, 5, 10, 20, 40 and 60) were cultured in 10 mul M16 medium, in M16 medium+EDTA, in M16 dedium+SOD+thioredoxin, and in CZB medium, respectively. When the zygotes, regardless of the number, were cultured with M16, no blastocysts could be obtained. The suitable ratio of embryos to 1 mul of M16 medium+EDTA or M16 medium+SOD+thioredoxin was 1:1 or 2:1. Medium volume from 1 to 10 mul did not affect blastocyst development when the embryo density was 1:1. However, blastocysts obtained from zygotes cultured singly had fewer cell numbers and showed inferior development to live fetuses after transfer to recipients. When CZB medium was used, suitable embryo density was not clear. The ratio of embryos to volume of culture medium was shown to be an important factor for in vitro culture of mouse zygotes.