玉ねぎ表皮組織の凍結機構に関する実験的研究 : 細胞内凍結と細胞外溶液による脱水現象

抄録

Microscopic observations of the freezing process of onion skin cells have been made using a directional solidification stage, in order to study the freezing mechanism of living tissue. Experiments conducted under low cooling rates show that intracellular ice formation occurs due to surface-catalyzed nucleation (SCN) at the plasma membrane and proceeds cell by cell because the membrane blocks the growth of ice crystals. Since the probability of SCN increases with increase in the surface area in contact with the external ice, the tissue freezes at higher temperatures when the cell has a larger area in contact with the adjacent frozen cells. Dehydration and cell shrinkage were also observed in experiments with physiological saline simulating the effects of the vascular system in the organs. It is confirmed that a decrease of the cooling rate raises the dehydration rate and reduces the fraction of frozen cells but increases the amount of extracellular freezing.