Effect of lipid polarization by centrifugation at different developmental stages on post-thaw survival, of bovine in vitro produced 16-cell embryos

The developmental rate to the blastocyst stage of frozen-thawed bovine in v itro produced embryos at stages earlier than Day 6 morula is not sufficient ly high for practical utilization. The present study was undertaken to dete rmine the effect of polarization of lipid droplets in the cytoplasm of bovi ne in vitro produced embryos from zygotes to the 8-cell stage, by centrifug ation without following micromanipulation, on the survival rate of Day 4 16 -cell embryos. After centrifugation at 15,500 x g in medium containing cyto chalasin D, embryos were cultured to the 16-cell stage, classified as eithe r mostly or partially delipidated by degree of lipid droplet removal, and t hen frozen. Embryos centrifuged at the 2-cell stage developed to the 16-cel l stage similarly to those centrifuged at the 8-cell stage. The development al rate to blastocysts after freezing of the mostly delipidated 16-cell emb ryos centrifuged at the 2-cell stage was higher than that of those centrifu ged at the zygote stage, those that were partially delipidated at the 2-cel l stage, and those that were not centrifuged. The results demonstrate that polarization of lipid droplets at the 2-cell stage by centrifugation withou t micromanipulation improved the survival rate of mostly delipidated 16-cel l embryos after freezing. (C) 2000 by Elsevier Science Inc.