Ultradian Episodes of Thermogenesis in Mammals: Implications for the Timing of Torpor Entry and Arousal

Meyer, Carola W.; Blessing, W.W.; Heldmaier, Gerhard

doi:10.1007/978-3-642-28678-0_20

Cited by 5 publications

(6 citation statements)

References 45 publications

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“…Lastly, the ultradian pattern of thermogenesis that accompanies URs in locomotor activity in Siberian hamsters may reflect UR rhythms of neural activity that maintain neuronal integrity and alertness and support cognitive function (Meyer et al, 2012). Many authors (e.g., Meyer et al, 2012) have speculated that the ultradian basic rest activity cycle (BRAC) positions animals to respond to both salient environmental events and internal physiological challenges.…”

Section: Discussionmentioning

confidence: 99%

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Pineal and gonadal influences on ultradian locomotor rhythms of male Siberian hamsters

Prendergast

Cable

Cissé

et al. 2013

Hormones and Behavior

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The extent to which changes in ultradian and circadian rhythms (URs and CRs) reflect seasonal variations in pineal melatonin secretion was assessed in male Siberian hamsters transferred from long to short day lengths. The period of the locomotor activity UR increased from 2.5 h in long days to 4.5 h in short day lengths, but this and most other features of the short-day ultradian phenotype were unaffected by pinealectomy; only the short-day increase in UR amplitude was counteracted by pineal extirpation. Virtually all UR components were unaffected by gonadectomy or replacement testosterone or estradiol treatment; changes in testicular hormone secretion appear insufficient to account for seasonal fluctuation in URs. Pinealectomy did not affect activity onsets and offsets or phase angles of CR entrainment in short and long day lengths; the duration of nocturnal activity was equivalently longer in short than long days in both pinealectomized and pineal-intact hamsters. CR robustness of pinealectomized hamsters in short days was intermediate between values of long-day and short-day sham-pinealectomized males. Hourly nocturnal locomotor activity was markedly reduced in SD, and this effect was completely reversed by PINx. We conclude that seasonal transitions in UR and CR waveforms controlled by day length are mediated primarily by melatonin-independent mechanisms, with lesser contributions from melatonin-dependent processes. Most seasonal changes in ultradian and circadian rhythms in males of this species are not influenced by gonadal hormones. URs may allow animals to respond appropriately to changing environmental contingencies. In winter reduced activity combined with temporal restructuring of activity to include longer intervals of rest may be adaptive in maintaining body temperature at lower values and down-regulating energy expenditure when above ground temperatures are extremely low.

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Section: Discussionmentioning

confidence: 99%

“…Many authors (e.g., Meyer et al, 2012) have speculated that the ultradian basic rest activity cycle (BRAC) positions animals to respond to both salient environmental events and internal physiological challenges.…”

Section: Discussionmentioning

confidence: 99%

Pineal and gonadal influences on ultradian locomotor rhythms of male Siberian hamsters

Prendergast

Cable

Cissé

et al. 2013

Hormones and Behavior

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“…There is some consensus in the literature on the adaptive value of EUEs, at least for the EUEs of activity and other behaviors [110]. Like other biological rhythms, the functional significance of EUEs might be in optimizing biological activities [111] by synchronizing compatible processes, and preventing the simultaneous activation of incompatible processes [10];preparing biological systems to respond to stimuli such as cell–cell communication [112], and the maintenance of neuronal integrity and alertness [113];interacting with circadian rhythms.…”

Section: The Role Of Euesmentioning

confidence: 99%

“…preparing biological systems to respond to stimuli such as cell–cell communication [112], and the maintenance of neuronal integrity and alertness [113];…”

Section: The Role Of Euesmentioning

confidence: 99%

Episodic Ultradian Events—Ultradian Rhythms

Goh

Maloney

Mark

et al. 2019

Biology

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In the fast lane of chronobiology, ultradian events are short-term rhythms that have been observed since the beginning of modern biology and were quantified about a century ago. They are ubiquitous in all biological systems and found in all organisms, from unicellular organisms to mammals, and from single cells to complex biological functions in multicellular animals. Since these events are aperiodic and last for a few minutes to a few hours, they are better classified as episodic ultradian events (EUEs). Their origin is unclear. However, they could have a molecular basis and could be controlled by hormonal inputs—in vertebrates, they originate from the activity of the central nervous system. EUEs are receiving increasing attention but their aperiodic nature requires specific sampling and analytic tools. While longer scale rhythms are adaptations to predictable changes in the environment, in theory, EUEs could contribute to adaptation by preparing organisms and biological functions for unpredictability.

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“…As would be expected following a sudden reversal of hypometabolism, mammalian hibernators must also find ways to protect tissues in the face of enormous increases in oxygen consumption and free-radical generation, as well as increased carbohydrate consumption following uncoupled cellular respiration in BAT and shivering thermogenesis in skeletal muscle (Carey et al, 2003;Kloner et al, 1998;Meyer et al, 2012). Increased levels of antioxidant defences are observed during arousal from hibernation including heme oxygenase 1, and associated effector proteins including nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and the transcription factor MafG, in the liver, kidney, brain and heart of aroused 13LGSs (Ni and Storey, 2010).…”

mentioning

confidence: 99%

Involvement of Reversible Protein Methylation in 13-Lined Ground Squirrel Hibernation.

Watts¹

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During winter hibernation, body temperature falls to near ambient levels, metabolism is shifted to favor lipid oxidation and transcriptional and translational activity is minimized in the face of limited resources and increased heat generation costs. In order to regulate such profound changes, mammals require control at least partly brought about by protein post-translational modifications. Protein lysine methylation provides a mechanism by which enzymes may alter the activity, stability and modification states of proteins relevant to hibernator physiology. Protein abundance of SMYD2, SUV39H1, SET8, SET7/9, G9a, ASH2L and RBBP5 in 13-lined ground squirrel (Ictidomys tridecemlineatus) skeletal muscle and liver was characterized. Tissue-specific regulation was seen and enzymes changed during either torpor, arousal, or transitory periods.Methylation of H3, HSP90, and p53 proteins were also quantified and typically followed patterns of modifying enzymes. Overall, these experiments show protein lysine methylation is differentially regulated during 13-lined ground squirrel hibernation.

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Ultradian Episodes of Thermogenesis in Mammals: Implications for the Timing of Torpor Entry and Arousal

Cited by 5 publications

References 45 publications

Pineal and gonadal influences on ultradian locomotor rhythms of male Siberian hamsters

Pineal and gonadal influences on ultradian locomotor rhythms of male Siberian hamsters

Episodic Ultradian Events—Ultradian Rhythms

Involvement of Reversible Protein Methylation in 13-Lined Ground Squirrel Hibernation.

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