Studies on the morphology of frozen-thawed mouse 8-cell embryos and on their development in vitro

SHIRAISHI Tetsuya, NIIMURA Sueo, ISHIDA Kazuo

doi:10.1262/jrd1977.27.133

After morphological observation of frozen-thawed mouse 8-cell embryos, their development was studied after 24 and 48 h of culture.<BR>The 698 frozen-thawed 8-cell embryos were divided into three groups according to the degen-erated blastomeres in each embryo. There were 405 healthy embryos having no degenerated blasto-meres to compose Group I. Those having both intact and degenerated blastomeres were 225, and parted into Group II. The rest, that is, the 68 embryos composed of degenerated blastomeres only, into Group III. The ratio was 58.0%, 32.2% and 9.7% respectively.<BR>Of 165 embryos in Group I, 141 (85.5%) and 4 (2.4%) developed into morulae and blastocysts in 24 h of culture. The rate of blastocysts reached 63.6% in 48 h, when 4.8% remained as morulae and the rest degenerated. In Group II, only 49 (37.4%) out of 131 embryos grew into morulae and 1 (0.8%) into a blastocyst in 24 h. The rate of blastocysts after 48 h of culture was 30.5%, while 3.1% remaining as morulae and the rest degenerated. None in Group III grew into morulae nor into blastocysts. The morulae and blastocysts in Group I occasionally possessed degenerated blastomeres, while all of those in Group II had one or more degenerated blastomeres.<BR>For most of the frozen-thawed mouse 8-cell embryos, the time needed to grow into blastocysts was 48 h, showing a delay of about 24 h compared to that needed by intact 8-cell embryos.

Studies on the morphology of frozen-thawed mouse 8-cell embryos and on their development in vitro

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