Bongso A, Chye N S, Sathananthan H, Mui-Nee L, Mok H, Wong P C, Ratnam S
Department of Obstetrics and Gynaecology, National University of Singapore, National University Hospital.
Fertil Steril. 1988 May;49(5):908-12. doi: 10.1016/s0015-0282(16)59905-1.
Three freezing methods (slow-1,2 propanediol; ultrarapid-dimethyl sulphoxide; ultrarapid-1,2 propanediol) were used to assess the effects of low temperature storage on morphologic features and chromosome make-up of 2-cell mouse embryos. Weekly batches (15 weeks) of 2-cell mouse embryos were frozen for a period of 7 days using these three freezing methods, then thawed and subjected to chromosome analysis. After thawing, all three freezing regimens yielded 70.2% to 75.8% of healthy intact 2-cell embryos, and 5.5% to 8.1% of embryos with one healthy blastomere intact, respectively, out of 817 embryos examined. Chromosome analysis was possible in all 1- and 2-cell embryos. The incidence of aneuploidy and polyploidy in frozen-thawed embryos of all three methods (2.8% to 3.4%; 4.0% to 6.5%) was not significantly different from that of control unfrozen embryos (3.0%; 6.0%) (P greater than 0.01). Mitotic crossing over was observed in 3.5% of embryos frozen-thawed by the ultrarapid-dimethyl sulphoxide method only. It is not clear how the mitotic crossing over was induced by ultrarapid freezing in the presence of dimethyl sulphoxide.
