Survival of unprotected, mammalian plateau-phase cells following freezing in liquid nitrogen.

Unprotected, mammalian cells in plateau phase are at least a factor of four times more sensitive to freeze-thaw damage than exponential-phase cells. The former suffer about 15-20% more sublethal damage after one freeze-thaw cycle than the latter and repair this damage more slowly. Exposure of plateau-phase cells to freeze-thaw damage lengthens the time required to traverse the cell cycle in the exposed generation. These cells may more closely represent the state in tissues than exponential-phase populations.