Effects of low temperatures on survival of frozen-thawed mouse embryos.

Almost no damage to mouse morulae was observed between 0 and -40 degrees C, and freezing damage to embryos in DMSO, glycerol or ethylene glycol occurred after exposure to -60, -50 or -50 degrees C, respectively. Cooling embryos in DMSO or glycerol to temperatures below -50 to -60 degrees C increased freezing damage. To the contrary, in the presence of ethylene glycol, no more damage occurred after exposure to temperatures below -50 degrees C.