Structural changes and impairment of function associated with freezing and thawing in muscle, nerve, and leucocytes

In some tissues, especially of skeletal muscle, leucocytes, and peripheral nerves, the effects of freezing to low temperatures, e.g., −78 or −150 °C, and thawing have been a total loss of function and a severe cellular structural disturbance. In the case of muscle, the fibers are converted during thawing into a highly condensed form, called thaw-rigor, in which the individual sarcomeres are shortened beyond a supercontracted state. This effect must be avoided if muscle is to be frozen and stored successfully. Leucocytes and especially the neutrophils are seriously affected by exposure to low temperature. The result is a general swelling of the cell and of its nucleus which is suggestive of damage to the membranes of the cell. Rat cutaneous nerves frozen and exposed to temperature below −15 °C showed after thawing a general disturbance of the myelin involving rupture and separaration of the lamellae. In the axoplasm the neurofilaments and neurotuabules are converted into small aggregates and the mitochondria appear to be swollen. Nerves frozen at −5 and some at −10 °C showed little change in structure, the myelin and axoplasm exhibiting a normal appearance. A check on viability by excitation from an electric stimulus indicated survival after exposure to −5 and in a few cases to −10 °C. A study of freeze substituted preparations established the presence of intracellular ice when the tissues were frozen rapidly to temperatures below −15 °C. Preliminary investigation of the effect of cryoprotective agents, glycerol and dimethyl sulfoxide, on cutaneous nerves shows in electron micrographs that the axoplasm and the Schwann cell cytoplasm are shrunken during direct exposure to 15% solutions.