Survival of mouse morulae and blastocysts derived from in vitro fertilization after ultra rapid freezing.

Mouse morulae and blastocysts derived from in vitro fertilization were placed in a highly concentrated vitrification solution (DAP 213:2 M dimethyl sulfoxide, 1 M acetamide, 3 M propylene glycol in PB 1) in a sampling tube at room temperature, plunged into liquid nitrogen within ten seconds and cryopreserved. Thawing was carried out by directly pouring 37 degrees C 0.3 M sucrose solution into the sampling tube. The ratios of morphologically normal embryos at the morula and blastocyst stages after thawing were 92.0% (149/162) and 13.3% (13/98), respectively. The rate of development from morphologically normal morulae into blastocysts in vitro was 83.1% (74/89). Some of the morphologically normal morulae were transferred to pseudopregnant recipients immediately after thawing, and 45.0% (27/60) of the embryos developed into normal young.