SIMPLE AND EFFICIENT VITRIFICATION PROCEDURE FOR CRYOPRESERVATION OF MOUSE EMBRYOS

Mouse pronuclear oocytes and 2-cell embryos derived from in vitro fert ilization were cryopreserved by a novel simple vitrification procedure . Most cryopreserved oocytes/embryos were morphologically normal after warming, and 89-92% of them developed to the blastocyst stage during the culture. Moreover, the rate of morphologically normal pronuclear o ocytes after being repeatedly cooled and warmed three times was as hig h as that of oocytes cooled and warmed only once, and 85% of them deve loped to the blastocyst stage. In addition, 43-57% of the cryopreserve d oocytes/embryos transferred to recipients had developed normally to live fetuses observed on day 18.5 of pregnancy.