Temperaturregulation und Tagesperiodik des Stoffwechsels bei Winterschl�fern

Pohl, H.

doi:10.1007/bf00297762

Cited by 57 publications

(14 citation statements)

References 40 publications

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“…Importantly, these contradictions may stem from species differences as well as from the variety of markers used to assess the functional state of the clock. Based on the recording of small circadian fluctuations in Tb, some reports have suggested the maintenance of circadian rhythms during hibernation (18)(19)(20). However, consistent with other reports (10, 14, 21), we did not detect such variations in the European hamster.…”

Section: Discussionsupporting

confidence: 84%

“…Finally, Oklejewicz et al (13) observed in Tau Syrian hamsters that mutation in the circadian system does not affect the torpor/arousal cycle (13). Curiously, it appears that the major difference between the studies that reported the persistence (12,(18)(19)(20)22) or the absence (10, 11, 13-17) of a circadian signal during hibernation might be related to the Ta at which the experiments were conducted. This difference correlates with electrophysiological studies indicating that the circadian clock of hibernators still functions at temperatures lower than 37°C (5, 9), but recordings below 16.6°C failed to detect action potentials (29).…”

Section: Discussionmentioning

confidence: 99%

“…We describe here the arrest of the master circadian clock over several days. The issue has been debated for many years (3,5,9), with various data either denying (10,11,(13)(14)(15)(16)(17) or supporting (12,(18)(19)(20)22) the existence of a functional pacemaker during deep torpor. Importantly, these contradictions may stem from species differences as well as from the variety of markers used to assess the functional state of the clock.…”

Section: Discussionmentioning

confidence: 99%

“…However, it has long been debated whether the circadian system remains functional during deep hibernation (3,5,9). Although several studies have addressed this question (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), uncertainty prevails because clock outputs rather than the core clockwork machinery were examined. In mammals, the master circadian clock is located in the suprachiasmatic nucleus of the hypothalamus (SCN) (6)(7)(8).…”

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confidence: 99%

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The circadian clock stops ticking during deep hibernation in the European hamster

Revel

Herwig

Garidou

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

128

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Hibernation is a fascinating, yet enigmatic, physiological phenomenon during which body temperature and metabolism are reduced to save energy. During the harsh season, this strategy allows substantial energy saving by reducing body temperature and metabolism. Accordingly, biological processes are considerably slowed down and reduced to a minimum. However, the persistence of a temperature-compensated, functional biological clock in hibernating mammals has long been debated. Here, we show that the master circadian clock no longer displays 24-h molecular oscillations in hibernating European hamsters. The clock genes Per1, Per2, and Bmal1 and the clock-controlled gene arginine vasopressin were constantly expressed in the suprachiasmatic nucleus during deep torpor, as assessed by radioactive in situ hybridization. Finally, the melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase, whose rhythmic expression in the pineal gland is controlled by the master circadian clock, no longer exhibits day/night changes of expression but constantly elevated mRNA levels over 24 h. Overall, these data provide strong evidence that in the European hamster the molecular circadian clock is arrested during hibernation and stops delivering rhythmic output signals.deep torpor ͉ suprachiasmatic ͉ euthermia

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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The circadian clock stops ticking during deep hibernation in the European hamster

Revel

Herwig

Garidou

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

128

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“…1). Both onset and oset of the arousal episode, as de®ned above, coincide with major changes in the metabolic rate of the hibernating animal (Pohl 1961;Snapp and Heller 1981;Heldmaier and Ruf 1992;Heldmaier et al1993;Boyer and Barnes 1999). We did not include the cooling phase in our de®nition of the arousal episode.…”

Section: De®nitions Of Dierent Phases In the Hibernation Cyclementioning

confidence: 90%

Body temperature patterns before, during, and after semi-natural hibernation in the European ground squirrel

Daan

2002

Journal of Comparative Physiology B: Biochemical, Systemic, and

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Body temperature patterns before, during, and after semi-natural hibernation in the European ground squirrel Hut, Roelof; Barnes, B.M.; Daan, S.; Heldmaier, G. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract Ground squirrels undergo extreme body temperature¯uctuations during hibernation. The eect of low body temperatures on the mammalian circadian system is still under debate. Using implanted temperature loggers, we recorded body temperature patterns in European ground squirrels kept in an enclosure under natural conditions. Although hibernation onset was delayed, hibernation end corresponded closely to that measured in a ®eld population. Circadian body temperature¯uctuations were not detected during deep torpor, but indications of circadian timing of arousal episodes at higher temperatures were found at the beginning and end of hibernation. One male exhibited synchronised arousals to a relatively constant phase of the day throughout hibernation. All animals ®rst entered torpor in the afternoon. Daily body temperature¯uc-tuations were decreased or distorted during the ®rst days after hibernation. We hypothesise that hibernation may aect the circadian system by either decreasing the expression of the circadian oscillator, or by decreasing the amplitude of the circadian oscillator itself, possibly due to gradual, temperature dependent, internal desynchronisation. The latter mechanism may be bene®cial because it might facilitate post-hibernation re-entrainment rates.Keywords Circadian rhythmicity á Torpor á Euthermia á Arrhythmicity á Implantable temperature loggers Abbreviations DD continuous darkness á LD light-dark cycle á SCN suprachiasmatic nuclei

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Hibernation in bats (Mammalia: Chiroptera) did not evolve through positive selection of leptin

Lazzeroni

Burbrink

Simmons

2018

Ecology and Evolution

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Temperature regulation is an indispensable physiological activity critical for animal survival. However, relatively little is known about the origin of thermoregulatory regimes in a phylogenetic context, or the genetic mechanisms driving the evolution of these regimes. Using bats as a study system, we examined the evolution of three thermoregulatory regimes (hibernation, daily heterothermy, and homeothermy) in relation to the evolution of leptin, a protein implicated in regulation of torpor bouts in mammals, including bats. A threshold model was used to test for a correlation between lineages with positively selected lep, the gene encoding leptin, and the thermoregulatory regimes of those lineages. Although evidence for episodic positive selection of lep was found, positive selection was not correlated with lineages of heterothermic bats, a finding that contradicts results from previous studies. Evidence from our ancestral state reconstructions suggests that the most recent common ancestor of bats used daily heterothermy and that the presence of hibernation is highly unlikely at this node. Hibernation likely evolved independently at least four times in bats—once in the common ancestor of Vespertilionidae and Molossidae, once in the clade containing Rhinolophidae and Rhinopomatidae, and again independently in the lineages leading to Taphozous melanopogon and Mystacina tuberculata. Our reconstructions revealed that thermoregulatory regimes never transitioned directly from hibernation to homeothermy, or the reverse, in the evolutionary history of bats. This, in addition to recent evidence that heterothermy is best described along a continuum, suggests that thermoregulatory regimes in mammals are best represented as an ordered continuous trait (homeothermy ← → daily torpor ← → hibernation) rather than as the three discrete regimes that evolve in an unordered fashion. These results have important implications for methodological approaches in future physiological and evolutionary research.

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Temperaturregulation und Tagesperiodik des Stoffwechsels bei Winterschl�fern

Cited by 57 publications

References 40 publications

The circadian clock stops ticking during deep hibernation in the European hamster

The circadian clock stops ticking during deep hibernation in the European hamster

Body temperature patterns before, during, and after semi-natural hibernation in the European ground squirrel

Hibernation in bats (Mammalia: Chiroptera) did not evolve through positive selection of leptin

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