9507437 Freeze tolerance is an adaptation that permits some organisms to tolerate ice formation within their bodies. Previous studies of freeze tolerance have been conducted in the laboratory, under conditions far removed from those experienced by animals in nature. This research combines both field and laboratory studies to elucidate the role of freeze tolerance in promoting over winter survival in two freeze-tolerant species. Freezing episodes naturally experienced during winter will be characterized using computer-assisted monitoring systems to record body temperature, environmental temperature, and water content and water potential of the microenvironments in which over- wintering occurs. Parallel measurement of protective responses including glucose mobilization and relocation of organ water will provide understanding of the physiological mechanisms that protect against freezing injury to cells, tissues, and organs, and of the ecological importance of these responses in the natural environment. Some studies will focus on the energetic costs of hibernation, particularly with regard to freezing and thawing. Nuclear magnetic resonance (NMR) imaging will be used to determine cell energy status and show whether survival duration in the frozen state is limited by the availability of finite energy reserves. These integrated field and laboratory studies will provide insights into the physiological mechanisms that promote survival at temperatures below the freezing point of tissue, and into their ecological significance. The research may also provide valuable clues for developing technology for the preservation of tissues and organs by freezing.
