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https://www.readbyqxmd.com/read/28432393/more-functions-of-torpor-and-their-roles-in-a-changing-world
#1
Julia Nowack, Clare Stawski, Fritz Geiser
Increased winter survival by reducing energy expenditure in adult animals is often viewed as the primary function of torpor. However, torpor has many other functions that ultimately increase the survival of heterothermic mammals and birds. In this review, we summarize new findings revealing that animals use torpor to cope with the conditions during and after natural disasters, including fires, storms, and heat waves. Furthermore, we suggest that torpor, which also prolongs longevity and was likely crucial for survival of mammals during the time of the dinosaur extinctions, will be advantageous in a changing world...
April 21, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28432150/specialist-generalist-model-of-body-temperature-regulation-can-be-applied-on-the-intraspecific-level
#2
Anna S Przybylska, Jan S Boratyński, Michał S Wojciechowski, Małgorzata Jefimow
According to theoretical predictions endothermic homeotherms can be classified as either thermal specialists and thermal generalists. In high cost environments thermal specialists are supposed to be more prone to use facultative heterothermy than generalists. We tested this hypothesis on the intraspecific level using laboratory male mice (C57BL/cmdb) fasted under different thermal conditions (20 and 10°C), and for different time periods (12-48 h). We predicted that variability of body temperature (Tb) and time spent with Tb below normothermy increase with the increase of environmental demands (duration of fasting and cold)...
April 21, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28417150/torpor-patterns-in-common-hamsters-with-and-without-access-to-food-stores
#3
Carina Siutz, Eva Millesi
Hibernating species significantly reduce energy expenditure during winter by entering torpor. Nevertheless, the various benefits of hibernation might be counteracted by negative effects of torpor such as immune depression, oxidative stress, or neuronal impairment. Considering these trade-offs, adequate energy reserves could allow animals to reduce the time spent in torpor or the extent of metabolic depression. Common hamsters use food stores during hibernation and previously documented high individual variations in body temperature patterns during winter could, therefore, be related to differences in external energy reserves...
April 17, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28404741/avian-blastoderm-dormancy-arrests-cells-in-g2-and-suppresses-apoptosis
#4
Mee Hyun Ko, Young Sun Hwang, Jong Seop Rim, Ho Jae Han, Jae Yong Han
In most avian species, the early embryo suspends development when the ambient temperature is too low; the resultant dormant state is called cold torpor. However, very little is known about dormant avian embryos at the cellular level. To investigate the molecular processes that occur in the chicken blastoderm during cold torpor, we performed transcriptome analysis and investigated cellular responses in dormant embryos. In embryos stored at low temperature, we observed up-regulation of genes and proteins related to endoplasmic reticulum stress and stress-activated protein kinase signaling...
April 12, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28402233/torpor-patterns-in-desert-hedgehogs-paraechinus-aethiopicus-represent-another-new-point-along-a-thermoregulatory-continuum
#5
Justin G Boyles, Nigel C Bennett, Osama B Mohammed, Abdulaziz N Alagaili
Documenting variation in thermoregulatory patterns across phylogenetically and geographically diverse taxa is key to understanding the evolution of endothermy and heterothermy in birds and mammals. We recorded body temperature (Tb) in free-ranging desert hedgehogs (Paraechinus aethiopicus) across three seasons in the deserts of Saudi Arabia. Modal Tb's (35°-36.5°C) were slightly below normal for mammals but still warmer than those of other hedgehogs. The single maximum Tb recorded was 39.2°C, which is cooler than maximum Tb's recorded in most desert mammals...
July 2017: Physiological and Biochemical Zoology: PBZ
https://www.readbyqxmd.com/read/28396263/stable-isotope-analysis-of-co2-in-breath-indicates-metabolic-fuel-shifts-in-torpid-arctic-ground-squirrels
#6
Trixie N Lee, Melanie M Richter, Cory T Williams, Øivind Tøien, Brian M Barnes, Diane M O'Brien, C Loren Buck
Stable carbon isotope ratios (δ(13)C) in breath show promise as an indicator of immediate metabolic fuel utilization in animals because tissue lipids have a lower δ(13)C value than carbohydrates and proteins. Metabolic fuel consumption is often estimated using the respiratory exchange ratio (RER), which has lipid and carbohydrate boundaries, but does not differentiate between protein and mixed fuel catabolism at intermediate values. Because lipids have relatively low δ(13)C values, measurements of stable carbon isotopes in breath may help distinguish between catabolism of protein and mixed fuel that includes lipid...
April 7, 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/28391591/syrian-hamster-neuroplasticity-mechanisms-fail-as-temperature-declines-to-15%C3%A2-%C3%A2-c-but-histaminergic-neuromodulation-persists
#7
Jock S Hamilton, Sat M Chau, Kevin J Malins, Giancarlo G Ibanez, John M Horowitz, Barbara A Horwitz
Previous research suggests that hippocampal neurons in mammalian hibernators shift their major function from memory formation at euthermic brain temperatures (T b = ~37 °C) to modulation of hibernation bout duration as T b decreases. This role of hippocampal neurons during torpor is based in part on in vivo studies showing that histamine (HA) infused into ground squirrel hippocampi lengthened torpor bouts by ~50%. However, it was unclear if HA acted directly on hippocampal neurons or on downstream brain regions via HA spillover into lateral ventricles...
April 9, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28378088/central-activation-of-the-a1-adenosine-receptor-in-fed-mice-recapitulates-only-some-of-the-attributes-of-daily-torpor
#8
Maria A Vicent, Ethan D Borre, Steven J Swoap
Mice enter bouts of daily torpor, drastically reducing metabolic rate, core body temperature (T b), and heart rate (HR), in response to reduced caloric intake. Because central adenosine activation has been shown to induce a torpor-like state in the arctic ground squirrel, and blocking the adenosine-1 (A1) receptor prevents daily torpor, we hypothesized that central activation of the A1 adenosine receptors would induce a bout of natural torpor in mice. To test the hypothesis, mice were subjected to four different hypothermia bouts: natural torpor, forced hypothermia (FH), isoflurane-anesthesia, and an intracerebroventricular injection of the selective A1 receptor agonist N(6-)cyclohexyladenosine (CHA)...
April 4, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28365894/gene-expression-analysis-and-microdialysis-suggest-hypothalamic-triiodothyronine-t3-gates-daily-torpor-in-djungarian-hamsters-phodopus-sungorus
#9
Jonathan H H Bank, Ceyda Cubuk, Dana Wilson, Eddy Rijntjes, Julia Kemmling, Hanna Markovsky, Perry Barrett, Annika Herwig
Thyroid hormones play an important role in regulating seasonal adaptations of mammals. Several studies suggested that reduced availability of 3,3',5-triiodothyronine (T3) in the hypothalamus is required for the physiological adaptation to winter in Djungarian hamsters. We have previously shown that T3 is involved in the regulation of daily torpor, but it remains unclear, whether T3 affects torpor by central or peripheral mechanisms. To determine the effect of T3 concentrations within the hypothalamus in regulating daily torpor, we tested the hypothesis that low hypothalamic T3 metabolism would favour torpor and high T3 concentrations would not...
April 1, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28356368/avian-torpor-or-alternative-thermoregulatory-strategies-for-overwintering
#10
Tegan K Douglas, Christine E Cooper, Philip C Withers
It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (Pomatostomus superciliosus), which has characteristics related to a high probability of torpor use; it is a sedentary, insectivorous, cooperative breeding species, which we studied during winter in a temperate habitat. Wild, free-living babblers maintained normothermy overnight, even at sub-zero ambient temperatures, with a mean minimum body temperature of 38...
April 1, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28356358/chilly-white-browed-babblers-huddle-to-avoid-torpor
#11
Kathryn Knight
No abstract text is available yet for this article.
April 1, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/28348515/transcriptome-analysis-of-hypothalamic-gene-expression-during-daily-torpor-in-djungarian-hamsters-phodopus-sungorus
#12
Ceyda Cubuk, Julia Kemmling, Andrej Fabrizius, Annika Herwig
Animals living at high or temperate latitudes are challenged by extensive changes in environmental conditions over seasons. Djungarian hamsters (Phodopus sungorus) are able to cope with extremely cold ambient temperatures and food scarcity in winter by expressing spontaneous daily torpor. Daily torpor is a circadian controlled voluntary reduction of metabolism that can reduce energy expenditure by up to 65% when used frequently. In the past decades it has become more and more apparent, that the hypothalamus is likely to play a key role in regulating induction and maintenance of daily torpor, but the molecular signals, which lead to the initiation of daily torpor, are still unknown...
2017: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/28344570/tanycytes-as-regulators-of-seasonal-cycles-in-neuroendocrine-function
#13
REVIEW
Jo E Lewis, Francis J P Ebling
Annual cycles of physiology and behavior are highly prevalent in organisms inhabiting temperate and polar regions. Examples in mammals include changes in appetite and body fat composition, hibernation and torpor, growth of antlers, pelage and horns, and seasonal reproduction. The timing of these seasonal cycles reflects an interaction of changing environmental signals, such as daylength, and intrinsic rhythmic processes: circannual clocks. As neuroendocrine signals underlie these rhythmic processes, the focus of most mechanistic studies has been on neuronal systems in the hypothalamus...
2017: Frontiers in Neurology
https://www.readbyqxmd.com/read/28332020/temperature-effects-on-the-activity-shape-and-storage-of-platelets-from-13-lined-ground-squirrels
#14
Scott Cooper, Sarah Lloyd, Anthony Koch, Xingxing Lin, Katie Dobbs, Thomas Theisen, Matt Zuberbuehler, Kaley Bernhardt, Michael Gyorfi, Tanner Tenpas, Skyler Hying, Sarah Mortimer, Christine Lamont, Marcus Lehmann, Keith Neeves
The objective of this study is to determine how a hibernating mammal avoids the formation of blood clots under periods of low blood flow. A microfluidic vascular injury model was performed to differentiate the effects of temperature and shear rate on platelet adhesion to collagen. Human and ground squirrel whole blood was incubated at 15 or 37 °C and then passed through a microfluidic chamber over a 250-µm strip of type I fibrillar collagen at that temperature and the shear rates of 50 or 300 s(-1) to simulate torpid and aroused conditions, respectively...
March 23, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28332019/comparative-tissue-transcriptomics-highlights-dynamic-differences-among-tissues-but-conserved-metabolic-transcript-prioritization-in-preparation-for-arousal-from-torpor
#15
Lori K Bogren, Katharine R Grabek, Gregory S Barsh, Sandra L Martin
During the hibernation season, 13-lined ground squirrels spend days to weeks in torpor with body temperatures near freezing then spontaneously rewarm. The molecular drivers of the drastic physiological changes that orchestrate and permit torpor are not well understood. Although transcription effectively ceases at the low body temperatures of torpor, previous work has demonstrated that some transcripts are protected from bulk degradation in brown adipose tissue (BAT), consistent with the importance of their protein products for metabolic heat generation during arousal from torpor...
March 23, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28332018/seasonal-loss-and-resumption-of-circadian-rhythms-in-hibernating-arctic-ground-squirrels
#16
Cory T Williams, Maya Radonich, Brian M Barnes, C Loren Buck
Circadian clocks are near universal among organisms and play a key role in coordinating physiological and metabolic functions to anticipate or coincide with predictable daily changes in the physical and social environment. However, whether circadian rhythms persist and are functionally important during hibernation in all mammals is currently unclear. We examined whether circadian rhythms of body temperature (T b) persist during multi-day, steady-state torpor and investigated the association between timing of animal emergence, exposure to light, and resumption of activity and T b rhythms in free-living and captive male arctic ground squirrels...
March 22, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28330964/thermoregulatory-inversion-a-novel-thermoregulatory-paradigm
#17
Domenico Tupone, Georgina Cano, Shaun F Morrison
To maintain core body temperature in mammals, the normal CNS thermoregulatory reflex networks produce an increase in brown adipose tissue (BAT) thermogenesis in response to skin cooling, and an inhibition of the sympathetic outflow to BAT during skin rewarming. In contrast, these normal thermoregulatory reflexes appear to be inverted in hibernation/torpor: thermogenesis is inhibited during exposure to a cold environment, allowing dramatic reductions in core temperature and metabolism, and thermogenesis is activated during skin rewarming, contributing to a return of normal body temperature...
March 22, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/28324159/hibernation-based-blood-loss-therapy-increases-survivability-of-lethal-hemorrhagic-shock-in-rats
#18
Cecilia E Perez de Lara Rodriguez, Lester R Drewes, Matthew T Andrews
A small-volume (1 ml/kg) resuscitation fluid based on metabolic adaptations in hibernating mammals was optimized using a rat model of hemorrhagic shock. A previous study of this therapy tested only one concentration of three specific components: 4 M D-stereoisomer of beta-hydroxybutyrate (BHB), 43 mM melatonin, and 20% DMSO. In this study, we considered the range of concentrations of BHB and melatonin seen during the physiological extremes of rapid arousal from hypothermic torpor in natural hibernators and applied these to the non-hibernating Sprague-Dawley rat model...
March 21, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28324158/the-influence-of-sex-and-diet-on-the-characteristics-of-hibernation-in-syrian-hamsters
#19
Marie Trefna, Maaike Goris, Cynthia M C Thissen, Vera A Reitsema, Jojanneke J Bruintjes, Edwin L de Vrij, Hjalmar R Bouma, Ate S Boerema, Robert H Henning
Research on deep hibernators almost exclusively uses species captured from the wild or from local breeding. An exception is Syrian hamster (Mesocricetus auratus), the only standard laboratory animal showing deep hibernation. In deep hibernators, several factors influence hibernation quality, including body mass, sex and diet. We examined hibernation quality in commercially obtained Syrian hamsters in relation to body mass, sex and a diet enriched in polyunsaturated fatty acids. Animals (M/F:30/30, 12 weeks of age) were obtained from Harlan (IN, USA) and individually housed at 21 °C and L:D 14:10 until 20 weeks of age, followed by L:D 8:16 until 27 weeks...
March 21, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/28322600/renal-mitochondrial-response-to-low-temperature-in-non-hibernating-and-hibernating-species
#20
George J Dugbartey, Maarten C Hardenberg, Wendelinde F Kok, Ate S Boerema, Hannah V Carey, James F Staples, Robert H Henning, Hjalmar R Bouma
SIGNIFICANCE: Therapeutic hypothermia is commonly applied to limit ischemic injury in organ transplantation, during cardiac and brain surgery and after cardiopulmonary resuscitation. In these procedures, the kidneys are particularly at risk for ischemia/reperfusion injury (IRI), likely due to their high rate of metabolism. Although hypothermia mitigates ischemic kidney injury, it is not a panacea. Residual mitochondrial failure is believed to be a key event triggering loss of cellular homeostasis, and potentially cell death...
April 26, 2017: Antioxidants & Redox Signaling
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