Protein metabolism in hepatic tissue of hibernating and arousing ground squirrels

Whitten, Bertwell K.; Klain, GJ

doi:10.1152/ajplegacy.1968.214.6.1360

Cited by 41 publications

(12 citation statements)

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“…In regard to in vivo PS and RNAS during torpor, the results of the present study are in good agreement with previous in vivo PS [8][9][10] and in vivo RNAS studies [6,7]. The additional organs assayed in this study provide a more complete picture of PS and RNAS during torpor and the other phases of the hibernation cycle.…”

Section: Discussionsupporting

confidence: 91%

Section: (Cenothermia Is the Iups Term Replacing Euthermia [4])mentioning

confidence: 99%

“…Early investigations used radioactively labeled precursors to measure in vivo transcription in brains [6,7], translation in liver [8,9], and more recently translation in brain and heart [10], Abstract: This study measured in vivo synthesis of total RNA and protein from cortex, cerebellum and midbrain/brainstem and 6 major organs from Syrian hamsters (Mesocricetus auratus) during (a) 33 h of torpor (body temperature 5-6°C); (b) 90 min of the early arousal; (c) 90 min of the middle arousal; (d) 90 min in cold adapted cenothermic (CEN) hamsters of the same circannual period. Appropriate physiological parameters were used to confirm the phase of the hibernation cycle during infusion and incorporation of [ 14 C]-leucine.…”

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confidence: 99%

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Determination In Vivo of Newly Synthesized Gene Expression in Hamsters During Phases of the Hibernation Cycle

Osborne

Gao

Hashimoto

2004

JJP

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Hibernation is a circannual adaptation and within the hibernation season, the hibernation cycle of a 'classic' hibernator, such as the Syrian hamster, can be divided into six distinct physiological phases. An entrance phase, when metabolism is inhibited and body temperature decreases [1]. A long period of torpor when metabolic rate (MR) is approximately 2.5% of resting metabolic rate (RMR) [2, 3]. This is followed by an arousal period of three phases: an early arousal phase during which the animal warms anterior crucial organs by non-shivering thermogenesis; a middle arousal phase when shivering thermogenesis is recruited to heat the anterior body to cenothermia (CEN) and a late arousal phase when posterior organs attain CEN and the animal rests or sleeps. An inter-bout arousal phase, of hours to days, during which time the hibernator maintains CEN body temperature before the initiation of another hibernation cycle. At present the onset of the hibernation cycle cannot be predicted. (Cenothermia is the IUPS term replacing euthermia [4]).Molecularly orientated studies have searched for up-or-down regulation of gene expression in a small number of organs from torpid animals in an attempt to demonstrate molecular changes that are consistent with the enormous physiological changes occurring across the hibernation cycle [5]. Early investigations used radioactively labeled precursors to measure in vivo transcription in brains [6,7], translation in liver [8,9], and more recently translation in brain and heart 14 C]-leucine. In torpor, RNA synthesis was 5-25% of CEN levels depending upon tissue. In brain and heart mRNA was not preferentially synthesized. Protein was synthesized at low, tissue specific levels during torpor. Initiation of arousal and the warming of anterior organs via non-shivering thermogenesis during the early arousal occurred without measurable synthesis of RNA or proteins. Tissue specific levels of RNA and protein synthesis occurred later after shivering thermogenesis had been recruited and was strongly influenced by thermal gradients in the body. In the middle arousal phase, protein synthesis is most active in the brain despite modest synthesis of RNA and mRNA. The majority of molecular processing required for the induction and maintenance of torpor and the arousal from torpor up until the onset of shivering thermogenesis occurs during the cenothermic period before the hamster initiates the hibernation cycle. [The Japanese Journal of Physiology 54: [295][296][297][298][299][300][301][302][303][304][305] 2004]

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Section: Discussionsupporting

confidence: 91%

Section: (Cenothermia Is the Iups Term Replacing Euthermia [4])mentioning

confidence: 99%

mentioning

confidence: 99%

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Determination In Vivo of Newly Synthesized Gene Expression in Hamsters During Phases of the Hibernation Cycle

Osborne

Gao

Hashimoto

2004

JJP

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“…Protein translation slows dramatically during torpor but fully recovers during the interbout arousals (20,32,41,50,87,94,97). Protein synthesis is affected by hibernation at both the levels of initiation and elongation.…”

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confidence: 99%

Invited Review: Molecular adaptations in mammalian hibernators: unique adaptations or generalized responses?

Breukelen

Martin

2002

Journal of Applied Physiology

116

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are unique among mammals in their ability to attain, withstand, and reverse low body temperatures. Hibernators repeatedly cycle between body temperatures near zero during torpor and 37°C during euthermy. How do these mammals maintain cardiac function, cell integrity, blood fluidity, and energetic balance during their prolonged periods at low body temperature and avoid damage when they rewarm? Hibernation is often considered an example of a unique adaptation for low-temperature function in mammals. Although such adaptation is apparent at the level of whole animal physiology, it is surprisingly difficult to demonstrate clear examples of adaptations at the cellular and biochemical levels that improve function in the cold and are unique to hibernators. Instead of adaptation for improved function in the cold, the key molecular adaptations of hibernation may be to exploit the cold to depress most aspects of biochemical function and then rewarm without damage to restore optimal function of all systems. These capabilities are likely due to novel regulation of biochemical pathways shared by all mammals, including humans. torpor; hypothermia; differential gene expression WHEN A HUMAN IS EXPOSED TO low environmental temperatures and body temperature begins to fall, hypothermia ensues: the shivering response fails at a body temperature of 30-32°C, the heart fibrillates at 27-29°C, and ventilation ceases at 23-27°C, leading to death (reviewed in Refs. 47 and 48). However, a myriad of mammals avoid the damage associated with hypothermia by evoking controlled excursions to reduced body temperatures called torpor. In contrast to hypothermia, the reduction of body temperature in hibernators is not a patholological state (56). Deep hibernators are the masters of this adaptive hypothermia because they can maintain body temperatures below 0°C for up to 3 wk (2, 26, 34). Key characteristics of torpor include a profound reduction of metabolism (up to 1/100th of basal metabolic rate), reduced heart rate, and extremely low body temperature (reviewed in Ref. 90). The physiological consequences associated with hibernation provide a natural model for the study of ischemia, muscle and bone disuse atrophy, hypothermia, ketosis, organ transplant therapy, obesity, kidney failure, and cardiac arrhythmogenesis (e.g., Refs. 18,28,70,93,95).Ground-dwelling sciurid rodents have become the favorite model organisms for recent laboratory studies to explore the molecular bases of mammalian hibernation. In nature, these species exhibit a strict circannual rhythm of reproduction, fattening, and hibernation (for review, see Ref. 49). The cycle begins in the spring with mating, gestation, and birth. The seasons' young are

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“…In addition to the glucose sparing measures described above, it is reasonable to expect that gluconeogenic activities should be enhanced during the hibernation season. Significantly greater gluconeogenic capacities have been observed in liver (Whitten and Klain 1968;Petrovic et al 1985) and kidney cortex slices (Burlington and Klain 1967;Green et al 1985) of hibernating ground squirrels as compared to their summer active counterparts. In the arctic ground squirrel, an elevation in phosphoenolpyruvate carboxylase, a key enzyme involved in hepatic gluconeogenesis is observed during hibernation, presumably favoring gluconeogenesis during this state (Behrisch et al1981).…”

Section: Glucose Metabolismmentioning

confidence: 97%

Mammalian Hibernation: An Escape from the Cold

Wang

1988

Advances in Comparative and Environmental Physiology

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Protein metabolism in hepatic tissue of hibernating and arousing ground squirrels

Cited by 41 publications

References 0 publications

Determination In Vivo of Newly Synthesized Gene Expression in Hamsters During Phases of the Hibernation Cycle

Determination In Vivo of Newly Synthesized Gene Expression in Hamsters During Phases of the Hibernation Cycle

Invited Review: Molecular adaptations in mammalian hibernators: unique adaptations or generalized responses?

Mammalian Hibernation: An Escape from the Cold

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