DSC MEASUREMENT OF CELL-SUSPENSIONS DURING SUCCESSIVE FREEZING RUNS -IMPLICATIONS FOR THE MECHANISMS OF INTRACELLULAR ICE FORMATION

The formation of intracellular ice in biological cells during freezing is considered almost universally lethal and is the major contributor to cell damage at high cooling rates. Despite its importance, our unde rstanding of the mechanisms of intracellular ice formation (IIF) is st ill incomplete. In this paper differential scanning calorimetry is use d to study IIF in human lymphocytes in the presence of dimethyl sulfox ide (Me(2)SO). Under conditions where damage due to IIF on the initial cooling run is 40-60%, the samples are studied as a function of multi ple successive cooling runs. This enables the study not only of the ce ll fraction which undergoes IIF, but also of the fraction which surviv es. The temperature at which IIF occurs and the fraction of cell volum e which undergoes IIF are analyzed as functions of successive cooling runs. Taking advantage of the large number of cells present in the sam ples (ca. 10(6)), the effect of successive cooling runs on susceptibil ity to IIF is examined. (C) 1995 Academic Press, Inc.