Abnormal development of blastocysts and blastomeres in the rhesus monkey.

Preimplantation stages were collected from normal rhesus monkeys by flushing of the uterine lumen. There was a high incidence of abnormal morulae and blastocysts (25%), as well as abnormal cells and cell death in otherwise normal blastocysts. In addition to cell and nuclear fragmentation, clustering of organelles in the center of the blastomeres was a common feature in early degeneration of ova and blastomeres. Large isolated cells that lagged in cytological development were found both in large numbers in an abnormal blastocyst and as individual cells in normal blastocysts. One apparently abnormal blastocyst was composed of normal trophoblast and inner cell mass cells, but lacked desmosomes and was collapsed. The cytological study of development of the blastocyst indicated that assessment of viability of primate blastocysts by light microscopic observation of morulae and blastocyst stages is probably more fraught with difficulty than might appear from studies of common laboratory animals.