Biochemical and functional aspects of recovery of mammalian systems from deep sub-zero temperatures.

The viability of isolated mammalian systems is, apart from possible morphological changes, essentially conditioned by the biochemical modifications from normal physiological conditions to an artificial environment where blood supply is interrupted leading to ischaemia and where the temperature is lowered. In order to survive freezing and thawing, mammalian systems have to be protected by cryoprotectants, which apart from some inherent toxicity, may also interact with vital metabolic mechanisms (Conover, 1969, 1975: Fahy, 1986: Fahy et al. 1984: Jacobs & Herschler, 1986: Karow, 1982: Penninckx et al. 198 3: Polge et al. 1949: Rowe et al. 1980: Schlafer, 1981: Taylor & Pignat, 1982). Cellular volume changes as a result of modifications in extra- a and intracellular osmolality occurring during freezing and thawing prove particularly detrimental to the normal functioning of the cellular membranes (Crowe et al. 1983: Farrant, 1980: Farrant et al. 1977b: Karow, 198 2: Mazur & Rigopoulos, 1983: Meryman, 1970: Meryman et al. 1977: Nei, 19 76: Santarius & Giersch, 1983). Furthermore intracellular ice formation enhances structural and metabolic injury to subcellular particles(Farrant et al. 1977a: Fink, 1986: Fishb ein & Griffin, 1976: Fujikawa, 1981: Fuller & De Loecker, 1985: Lazarus et al. 1982: Malinin, 1972: Mazur, 1984: Pavlock et al. 1984:Penninckx et al. 1984: Persidsky & Ellet, 1971: Rubinacci et al. 1986: Shikama, 1965: Steponkus & Wiest, 1979: Strauss & Ingenito, 1980: Takehara & Rowe, 1971: Tamiya et al. 1985). Even with the protection of structural integrity, the preservation of energy production and the maintenance of the specific intracellular medium are essential to secure viability (Pegg, 1981).