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Pablo A Cortes, Francisco Bozinovic, Pierre U Blier
Mammalian torpor is a phenotype characterized by a controlled decline of metabolic rate, generally followed by a reduction in body temperature. During arousal from torpor, both metabolic rate and body temperature rapidly returns to resting levels. Metabolic rate reduction experienced by torpid animals is triggered by active suppression of mitochondrial respiration, which is rapidly reversed during rewarming process. In this study, we analyzed the changes in the maximal activity of key enzymes related to electron transport system (complexes I, III and IV) in six tissues of torpid, arousing and euthermic Chilean mouse-opossums (Thylamys elegans)...
March 15, 2018: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
Mallory A Ballinger, Matthew T Andrews
Brown adipose tissue (BAT) is a unique thermogenic tissue in mammals that rapidly produces heat via nonshivering thermogenesis. Small mammalian hibernators have evolved the greatest capacity for BAT because they use it to rewarm from hypothermic torpor numerous times throughout the hibernation season. Although hibernator BAT physiology has been investigated for decades, recent efforts have been directed toward understanding the molecular underpinnings of BAT regulation and function using a variety of methods, from mitochondrial functional assays to 'omics' approaches...
March 7, 2018: Journal of Experimental Biology
Ana Stancic, Aleksandra Jankovic, Aleksandra Korac, Dusko Cirovic, Vesna Otasevic, Kenneth B Storey, Bato Korac
In the present study we hypothesized that myocardial adaptive phenotype in mammalian hibernation involves rearrangement of mitochondria bioenergetic pathways providing protective pattern in states of reduced metabolism and low temperature. European ground squirrels (Spermophilus citellus) were exposed to low temperature (4 ± 1 °C) and then divided into two groups: (1) animals that fell into torpor (hibernating group) and (2) animals that stayed active and euthermic for 1, 3, 7, 12, or 21 days (cold-exposed group)...
March 5, 2018: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Yuri Griko, Matthew D Regan
Animal research aboard the Space Shuttle and International Space Station has provided vital information on the physiological, cellular, and molecular effects of spaceflight. The relevance of this information to human spaceflight is enhanced when it is coupled with information gleaned from human-based research. As NASA and other space agencies initiate plans for human exploration missions beyond low Earth orbit (LEO), incorporating animal research into these missions is vitally important to understanding the biological impacts of deep space...
February 2018: Life Sciences in Space Research
Britta Mahlert, Hanno Gerritsmann, Gabrielle Stalder, Thomas Ruf, Alexandre Zahariev, Stéphane Blanc, Sylvain Giroud
For hibernators, being born late in the active season may have important effects on growth and fattening, hence on winter survival and reproduction. This study investigated differences in growth, fattening, energetic responses, winter survival and fecundity between early-born ('EB') and late-born ('LB') juvenile garden dormice ( Eliomys quercinus ). LB juveniles grew and gained mass twice as fast as EB individuals. Torpor use was low during intensive growth, that are, first weeks of body mass gain, but increased during pre-hibernation fattening...
February 20, 2018: ELife
Francis J P Ebling, Jo E Lewis
Studies from a number of areas of neuroendocrinology indicate that hypothalamic tanycytes play a key role in control of energy metabolism. First, profound annual changes in gene expression have been identified in these unusual glial cells in seasonal mammals, for example in genes relating to the transport and metabolism of thyroid hormone into the hypothalamus. The consequent changes in local thyroid hormone availability in the hypothalamus have been shown experimentally to regulate annual cycles in energy intake, storage and expenditure in seasonal species...
February 7, 2018: Glia
Amanda D V MacCannell, Ethan C Jackson, Katherine E Mathers, James F Staples
We used ECG telemeters to measure the heart rate of hibernating Ictidomys tridecemlineatus An increase in heart rate from 2.2 to 5 bpm accurately identified arousal from torpor before any change in body temperature was detected. Variability in raw heart rate data was significantly reduced by a forward-backward Butterworth low-pass filter, allowing for discrete differential analysis. A decrease in filtered heart rate to 70% of maximum values in interbout euthermia (from approximately 312 to 235 bpm) accurately detected entrance into torpor bouts...
January 18, 2018: Journal of Experimental Biology
Elisabeth Rosner, Christian C Voigt
Mammals fuel hibernation by oxidizing saturated and unsaturated fatty acids from triacylglycerols in adipocytes, yet the relative importance of these two categories as an oxidative fuel may change during hibernation. We studied the selective use of fatty acids as an oxidative fuel in noctule bats (Nyctalus noctula). Pre-hibernating noctule bats that were fed 13C-enriched linoleic acid (LA) showed 12 times higher tracer oxidation rates compared to conspecifics fed 13C-enriched palmitic acid (PA). After this experiment, we supplemented the diet of bats with the same fatty acids on 5 subsequent days to enrich their fat depots with the respective tracer...
December 21, 2017: Journal of Experimental Biology
Marion Soto, Lucie Orliaguet, Michelle L Reyzer, M Lisa Manier, Richard M Caprioli, C Ronald Kahn
Mice subjected to cold or caloric deprivation can reduce body temperature and metabolic rate and enter a state of torpor. Here we show that administration of pyruvate, an energy-rich metabolic intermediate, can induce torpor in mice with diet-induced or genetic obesity. This is associated with marked hypothermia, decreased activity, and decreased metabolic rate. The drop in body temperature correlates with the degree of obesity and is blunted by housing mice at thermoneutrality. Induction of torpor by pyruvate in obese mice relies on adenosine signaling and is accompanied by changes in brain levels of hexose bisphosphate and GABA as detected by mass spectroscopy-based imaging...
January 8, 2018: Proceedings of the National Academy of Sciences of the United States of America
Qing-Sheng Chi, Xiu-Juan Li, De-Hua Wang
The initiation of torpor is supposed to be related to the availability of metabolic fuels. Studies on metabolic fuel inhibition of glucose by using 2-deoxy-D-glucose (2DG) or fatty acid by mercaptoacetate (MA) in heterothermic mammals produced mixed outcomes. To examine the roles of availability of glucose and fatty acid in the initiation of torpor in desert hamsters (Phodopus roborovskii), we intraperitoneally administrated 2DG and MA to summer-acclimated male hamsters while body temperature (Tb), metabolic rate (MR) and respiratory quotient (RQ) were simultaneously recorded to monitor their thermoregulatory response...
January 2018: Journal of Thermal Biology
Franz Langer, Nadine Havenstein, Joanna Fietz
Hibernation is the most effective way to reduce thermoregulatory costs during periods of unfavourable environmental conditions. In preparation to hibernation, fat-storing hibernators accumulate large quantities of body fat, which increases their locomotor costs and also the risk of predation. As a consequence, there should be a strong selective pressure to restrict pre-hibernation fattening to a short-time period before the onset of hibernation. The edible dormouse (Glis glis) is characterized by having adapted its whole life history to the irregularly occurring mast-seeding pattern of the European beech (Fagus sylvaticus)...
January 3, 2018: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Gonzalo León-Espinosa, Mamen Regalado-Reyes, Javier DeFelipe, Alberto Muñoz
Mammalian hibernation proceeds alongside a wide range of complex brain adaptive changes that appear to protect the brain from extreme hypoxia and hypothermia. Using immunofluorescence, confocal microscopy, quantitative analysis methods and intracellular injections, we have characterized microglia morphological changes that occur in the neocortex and hippocampus of the Syrian hamster during hibernation. In euthermic hamsters, microglial cells showed the typical ramified/resting morphology with multiple long, thin and highly-branched processes homogeneously immunostained for Iba-1...
December 19, 2017: Brain Structure & Function
Bryan E Luu, Sanoji Wijenayake, Jing Zhang, Shannon N Tessier, Julian F Quintero-Galvis, Juan Diego Gaitán-Espitia, Roberto F Nespolo, Kenneth B Storey
The South American marsupial, monito del monte (Dromiciops gliroides) uses both daily torpor and multi-day hibernation to survive in its southern Chile native environment. The present study leverages multiplex technology to assess the contributions of key stress-inducible cell cycle regulators and heat shock proteins to hibernation in liver, heart, and brain of monito del monte in a comparison of control versus 4day hibernating conditions. The data indicate that MDM2, a stress-responsive ubiquitin ligase, plays a crucial role in marsupial hibernation since all three tissues showed statistically significant increases in MDM2 levels during torpor (1...
December 14, 2017: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Bryan E Luu, Sanoji Wijenayake, Jing Zhang, Shannon N Tessier, Julian F Quintero-Galvis, Juan Diego Gaitán-Espitia, Roberto F Nespolo, Kenneth B Storey
When faced with harsh environmental conditions, the South American marsupial, monito del monte (Dromiciops gliroides), reduces its body temperature and uses either daily torpor or multiday hibernation to survive. This study used ELISA and multiplex assays to characterize the responses to hibernation by three regulatory components of protein translation machinery [p-eIF2α(S51), p-eIF4E(S209), p-4EBP(Thr37/46)] and eight targets involved in upstream signaling control of translation [p-IGF-1R(Tyr1135/1136), PTEN(S380), p-Akt(S473), p-GSK-3α(S21), p-GSK-3β(S9), p-TSC2(S939), p-mTOR(S2448), and p70S6K(T412)]...
December 13, 2017: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Sanoji Wijenayake, Bryan E Luu, Jing Zhang, Shannon N Tessier, Julian F Quintero-Galvis, Juan Diego Gaitán-Espitia, Roberto F Nespolo, Kenneth B Storey
Hibernation is a period of torpor and heterothermy that is typically associated with a strong reduction in metabolic rate, global suppression of transcription and translation, and upregulation of various genes/proteins that are central to the cellular stress response such as protein kinases, antioxidants, and heat shock proteins. The current study examined cell signaling cascades in hibernating monito del monte, Dromiciops gliroides, a South American marsupial of the Order Microbiotheria. Responses to hibernation by members of the mitogen-activated protein kinase (MAPK) pathways, and their roles in coordinating hibernator metabolism were examined in liver, kidney, heart and brain of control and versus hibernating (4days continuous torpor) D...
December 13, 2017: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Sanoji Wijenayake, Bryan E Luu, Jing Zhang, Shannon N Tessier, Julian F Quintero-Galvis, Juan Diego Gaitán-Espitia, Roberto F Nespolo, Kenneth B Storey
Mammalian hibernation is characterized by extensive adjustments to metabolism that typically include suppression of carbohydrate catabolism and a switch to triglycerides as the primary fuel during torpor. A crucial locus of control in this process is the pyruvate dehydrogenase complex that gates carbohydrate entry into the tricarboxylic acid cycle. Within the complex, the E1 enzyme pyruvate dehydrogenase (PDH) is the main regulatory site and is subject to inhibitory phosphorylation at three serine residues (S232, S293, S300)...
December 13, 2017: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Cory T Williams, C Loren Buck, Michael J Sheriff, Melanie M Richter, Jesse S Krause, Brian M Barnes
Hibernation provides a means of escaping the metabolic challenges associated with seasonality, yet the ability of mammals to prolong or reenter seasonal dormancy in response to extreme weather events is unclear. Here, we show that Arctic ground squirrels in northern Alaska exhibited sex-dependent plasticity in the physiology and phenology of hibernation in response to a series of late spring snowstorms in 2013 that resulted in the latest snowmelt on record. Females and nonreproductive males responded to the >1-month delay in snowmelt by extending heterothermy or reentering hibernation after several days of euthermy, leading to a >2-week delay in reproduction compared to surrounding years...
December 2017: American Naturalist
Fritz Geiser, Clare Stawski, Chris B Wacker, Julia Nowack
No abstract text is available yet for this article.
2017: Frontiers in Physiology
Julia Nowack, Clare Stawski, Gerhard Körtner, Fritz Geiser
The recent observation that torpor plays a key role in post-fire survival has been mainly attributed to the reduced food resources after fires. However, some of these adjustments can be facilitated or amplified by environmental changes associated with fires, such as the presence of a charcoal-ash substrate. In a previous experiment on a small terrestrial mammal the presence of charcoal and ash linked to food restriction intensified torpor use. However, whether fire cues also act as a trigger of torpor use when food is available and whether they affect other species including arboreal mammals remains elusive...
February 1, 2018: Physiology & Behavior
Christine Elizabeth Cooper, Philip Carew Withers
'Insensible' evaporative water loss of mammals has been traditionally viewed as a passive process, but recent studies suggest that insensible water loss is under regulatory control, although the physiological role of this control is unclear. We test the hypothesis that regulation of insensible water loss has a thermoregulatory function by quantifying for the first time evaporative water loss control, along with metabolic rate and body temperature, of a heterothermic mammal during normothermia and torpor. Evaporative water loss was independent of ambient relative humidity at ambient temperatures of 20 and 30°C, but not at 25°C or during torpor at 20°C...
November 2017: Biology Letters
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