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Biomedical subjects

T Nei

Publications and source records attributed to T Nei.

At least 19 recordsLinked to original sources
PubMed1986

Freezing injury in the yeast respiratory system.

The effect of freeze-thawing on the yeast respiratory system was studied at rapid rates of cooling. Freezing of whole cells with liquid nitrogen induced decrease of respiratory activity to under 20% of that of original cells. Mitochondria harvested from freeze-thawed cells have markedly decreased succinate oxidizing activity. Activity of succinate cytochrome c reductase was reduced significantly after freeze-thawing of whole cells while activities of succinate dehydrogenase and cytochrome c oxidase were reduced slightly. By spectrophotometric analysis it was found that about one-half the amount of cytochrome c + c1 was eluted from mitochondria to cytosol after freeze-thawing of cells. The activities of succinate oxidation in mitochondria from freeze-thawed cells were restored to normal levels by the addition of cytochrome c. Freeze-thawing of isolated mitochondria did not induce deactivation of succinate oxidizing activities and succinate cytochrome c reductase, and no elution of cytochrome c was observed. It was concluded that the decreased respiratory activities of yeast cells by freezing of cells with liquid nitrogen can be attributed primarily to the elution of cytochrome c from mitochondria.

Cell Fractionation↗
PubMed1978

Structure and function of frozen cells: freezing patterns and post-thaw survival.

Freezing patterns and post-thaw survival of cells varies with different cooling rates. The optimal cooling rates, indicating the highest percentage survival, were different in yeast and red blood cells. A difference of freezing patterns was also noticed in preparations frozen above and below the optimal cooling rate for each cell, namely, cell shrinkage at lower rates and intracellular ice formation at higher rates which showed similar trends in both the cells, even though there was some shifting of the optimum. Ultra-rapid freezing and addition of cryoprotectants are useful ways to minimize ice crystal formation and to cause such ice formations to approach the vitreous state. Ice crystals are hardly detectable in yeast cells as well as in erythrocytes, when these cells are frozen ultra-rapidly in the presence of cryoprotective agents in moderate concentration.

Cell Survival↗
PubMed1976

Observation of the freeze-drying process of biological materials with a scanning electron microscope.

Over the past few decades, numerous studies have been done on the freeze-drying of biological materials from a physical, chemical and biological point of view. Morphological observation of the freeze-drying process of specimens, however, has been tried by only a few investigators. In those studies, thin-layered aqueous specimens, which were sandwiched between two cover slips, were mostly observed with an optical microscope. For ultrastructural and stereoscopic observation, the scanning electron microscope has a great advantage, unlike that of the optical microscope. A specially designed cryo-scanning electron microscope, employed in the present study, made it possible to observe the freezing patterns of the specimens and also the sublimation process of ice in frozen specimens under vacuum. With this specially designed microscope, shrinkage of some specimens due to dehydration during the freeze-drying process was revealed and the extent of such shrinkage was quantitatively determined.

Animals↗