Abstract
The challenges to and involvement of cells in hibernation are as diverse as the phenomenon itself. Seasonal cycles of inanition, inactivity and hetero thermy that occur in many species of hibernators require adjustments in metabolic and perhaps neural pathways, in macromolecular synthetic activ ity, and in cellular work. While some features of such seasonal adjustments may be shared with species that do not hibernate, the short-term cycle of entry into, maintenance in, and arousal from a bout of hibernation presents in the more extreme cases of body cooling a thermal challenge not faced by the cells of the deep core of other mammals. This review focuses on the latter aspect-the problems of cells in the short cycle of hibernation. Many studies, however, have dealt, often unwit tingly, with seasonal differences in cells. The most extensive and explicit investigation of metabolic and cellular features of seasonal changes in a hibernator (hedgehog) compared with a nonhibernator (guinea pig) also provides the best review on this subject (28). Since the principal feature of the short cycle of hibernation is the large span of temperature in which cells must function, this discussion deals mainly with adaptation to cold. It neglects cellular requirements for re warming during arousal and for suppression of activity during entry. Spe cial adaptations for hibernation in these two categories have not been established, although suppression may be greater than what could be ac counted for by ordinary parasympathetic tone and by cooling (32). Recently suggested as factors responsible for such extraordinary metabolic suppres sion are an increase in relative acidity caused by the shift in the neutral point of water with cooling (32), and a specific hypothalamic neurohumor (47).
Published Version
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