Abstract
For the establishment of successful cryopreservation of Caenorhabditis elegans, freezing survival of the nematode was investigated in the presence of cryoprotectant. Dimethylsulfoxide (DMSO) was found, as a result, to be more effective in the cryoprotective activity than glycerol. Highest activity of DMSO was obtained at the concentration of ca. 5 v/v % in the M9 buffer. In the presence of DMSO, survival rate of the nematode decreased with the life stage from L1 to L4. It also depended on the dipping time in the DMSO solution before freezing: it increased with the time until about 1 hour but decreased with further dipping time. Cooling rate, lowest temperature of cooling and initiation temperature of freezing also affected freezing survival. Slow cooling prevented complete freezing in a larger proportion of nematodes than fast cooling. When accompanied by the treatment of ice seeding, slow cooling caused higher survival rate.
