Effects of various cryopreservations on chromosomes of oocytes of experimental and domestic animals

点击翻译按钮获取中文摘要

Newborns in several mammals can be obtained by successful transfer of embryos stored in liquid nitrogen into recipients synchronized estrously. The cryopreservation system for embryos and oocytes is one of the most important techniques for gamete use in mammalian genetic resources. However, the successful survival rate and fertilization rate of cryopreserved oocytes have been lower than those of the embryos divided. An increase in polyploidy was found in first-cleavage mouse embryos obtained from frozen-thawed oocytes fertilized in vitro, and the polyploids were derived from digyny in the oocytes. However, it was also reported that the incidence of parthenogenetic activation in frozen-thawed oocytes was not increased. Because more detailed cytogenetical information about frozen-thawed oocytes has been required, we analyzed chromosomes of 1st-cleavage mouse and bovine eggs derived from frozen-thawed oocytes.The present study showed that high incidence of chromosomes having structural aberrations was observed in the 1st-cleavage mouse eggs obtained from frozen-thawed oocytes fertilized in vitro. It appears that the causes of structural aberrations of chromosomes are cryoprotectant toxicity and the physical damage of cryopreservation to the chromosomes of oocytes. In bovine eggs, however, the incidence of chromosomes having structural aberrations was not significant.