LETHAL AND CHROMOSOMAL EFFECTS OF FREEZING, THAWING, STORAGE TIME, AND X-IRRADIATION ON MAMMALIAN-CELLS PRESERVED AT -196-DEGREES IN DIMETHYL-SULFOXIDE

Tissue culture cells [Chinese Hamster Ovary] preserved at -196.degree. C in 10% glycerol or 10% PVP [polyvinylpyrrolidone] for up to 6 mo. showed no gross chromosomal aberrations as disclosed by the micronucleus test. In 1 experiment cells preserved in 10% DMSO [dimethyl sulfoxide], which offered the best protection (91% survival after freezing and thawing), showed a statistically (P = 0.05) greater number of micronuclei 20 h after thawing. This was a transient effect and 3 more separate experiments failed to demonstrate any chromosomal damage associated with freezing, thawing and storage at -196.degree. C for periods of up to 2 years in 10% DMSO. Both the lethal and chromosomal effects of X-irradiating cells in 10% DMSO at -196.degree. C were reduced by a factor of approximately 3.5 compared to irradiation at +22.degree. C. A period of approximately 30,000 yr of storage of cells in 10% DMSO at -196.degree. C evidently would pass before an accumulated X-ray dose from background radiation would reach a level, which upon cellular resurrection, would result in the equivalent lethal and chromosomal damage of an acute D10 dose. Cells cannot be kept at -196.degree. C ad infinitum as there is no escape from background radiation damage. Shielding would reduce the level but internal radiation from isotopic disintegration is inescapable.