CELLULAR-RESPONSE OF MOUSE OOCYTES TO FREEZING STRESS - PREDICTION OFINTRACELLULAR ICE FORMATION

Successful protocols for cryopreservation of living cells can be desig ned if the physicochemical conditions to preclude intracellular ice fo rmation (IIF) can be defined. Unfortunately, all attempts to predict t he probability of IIF have met with very limited success. In this stud y, an analytical model is developed to predict ice formation inside mo use oocytes subjected to a freezing stress. According to the model, II F is catalyzed heterogeneously by the plasma membrane (i.e., surface c atalyzed nucleation, SCN). A local site on the plasma membrane is assu med to become an ice nucleator in the presence of the extracellular ic e via its effects on the membrane. This interaction is characterized b y the contact angle between the plasma membrane and the ice cluster. I n addition, IIF is assumed to be catalyzed at temperatures below -30-d egrees-C by intracellular particles distributed throughout the cell vo lume (i.e., volume catalyzed nucleation, VCN). In the present study, t hese two distinctly coupled modes of IIF, especially SCN, are applied to various experimental protocols from mouse oocytes. Excellent agreem ent between predictions and observations suggests that the proposed mo del of IIF is adequate.