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1.
Curr Biol ; 34(4): 923-930.e5, 2024 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-38325375

RESUMO

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) hibernate for several months each winter without access to water,1 but the mechanisms that maintain fluid homeostasis during hibernation are poorly understood. In torpor, when body temperature (TB) reaches 4°C, squirrels decrease metabolism, slow heart rate, and reduce plasma levels of the antidiuretic hormones arginine vasopressin (AVP) and oxytocin (OXT).1 Squirrels spontaneously undergo interbout arousal (IBA) every 2 weeks, temporarily recovering an active-like metabolism and a TB of 37°C for up to 48 h.1,2 Despite the low levels of AVP and OXT during torpor, profound increases in blood pressure and heart rate during the torpor-IBA transition are not associated with massive fluid loss, suggesting the existence of a mechanism that protects against diuresis at a low TB. Here, we demonstrate that the antidiuretic hormone release pathway is activated by hypothalamic supraoptic nucleus (SON) neurons early in the torpor-arousal transition. SON neuron activity, dense-core vesicle release from the posterior pituitary, and plasma hormone levels all begin to increase before TB reaches 10°C. In vivo fiber photometry of SON neurons from hibernating squirrels, together with RNA sequencing and c-FOS immunohistochemistry, confirms that SON is electrically, transcriptionally, and translationally active to monitor blood osmolality throughout the dynamic torpor-arousal transition. Our work emphasizes the importance of the antidiuretic pathway during the torpor-arousal transition and reveals that the neurophysiological mechanism that coordinates the hormonal response to retain fluid is active at an extremely low TB, which is prohibitive for these processes in non-hibernators.


Assuntos
Hibernação , Torpor , Animais , Hibernação/fisiologia , Torpor/fisiologia , Sciuridae/fisiologia , Sequência de Bases
2.
J Therm Biol ; 120: 103811, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38382412

RESUMO

Each phenotype is a product of the interaction of the genes and the environment. Although winter phenotype in seasonal mammals is heritable, its development may be modified by external conditions. In today's world, global climate change and increasing frequency of unpredictable weather events may affect the dynamic equilibrium between phenotypes. We tested the effect of changes in ambient temperature during acclimation to short photoperiod on the development of winter phenotypes in three generations of Siberian hamsters (Phodopus sungorus). Based on seasonal changes in fur colour, body mass, and expression of daily torpor we distinguished three different winter phenotypes: responding, non-responding, and partially-responding to short photoperiod. We found that warm spells in winter can increase the proportion of non-responding individuals in the population, while stable winter conditions can increase photoresponsiveness among the offspring of non-responders. We conclude that the polymorphism of winter phenotype is an inherent characteristic of the Siberian hamster population but the development of winter phenotype is not fixed but rather a plastic response to the environmental conditions.


Assuntos
Phodopus , Torpor , Humanos , Cricetinae , Animais , Estações do Ano , Phodopus/fisiologia , Aclimatação/fisiologia , Fotoperíodo , Fenótipo
3.
J Therm Biol ; 120: 103792, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38403496

RESUMO

Small birds and mammals face similar energetic challenges, yet use of torpor to conserve energy while resting is considered less common among birds, especially within the most specious order Passeriformes. We conducted the first study to record the natural thermoregulatory physiology of any species from the family Hirundinidae, which we predicted would use torpor because of their specialised foraging by aerial pursuit of flying insects, that are less active during cold or windy weather. We used temperature telemetry on wild-living welcome swallows (Hirundo neoxena, 13 to 17 g) and found that skin temperature declined during nightly resting by an average by 5 °C, from daytime minima of 41.0 ± 0.8 °C to nightly minima of 36.3 ± 0.8 °C, and by a maximum of 8 °C to a minimum recorded skin temperature of 32.0 °C. The extent of reduction in skin temperature was greater on cold nights and following windy daytime (foraging) periods. Further, we found that transmitters glued directly to the skin between feather tracts (i.e., an apterium) provided a less variable and probably also more accurate reflection of body temperature than transmitters applied over closely trimmed feathers. A moderate decrease in skin temperature, equivalent to shallow torpor, would provide energy savings during rest. Yet, deeper torpor was not observed, despite a period of extreme rainfall that presumedly decreased foraging success. Further studies are needed to understand the resting thermoregulatory energetics of swallows under different environmental conditions. We advocate the importance of measuring thermal biology in wild-living birds to increase our knowledge of the physiology and ecological importance of torpor among passerine birds.


Assuntos
Passeriformes , Andorinhas , Torpor , Animais , Temperatura Corporal , Regulação da Temperatura Corporal/fisiologia , Torpor/fisiologia , Temperatura , Passeriformes/fisiologia , Metabolismo Energético/fisiologia , Mamíferos
4.
Commun Biol ; 7(1): 42, 2024 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-38182741

RESUMO

Torpor and arousal cycles, both daily and seasonal (e.g. hibernation), are crucial for small mammals, including bats, to maintain the energy and water balance. The alternation between torpor and arousal leads to metabolic changes, leaving traceable evidence of metabolic wastes in urine. In this study we investigated urinary creatinine and acetoacetate (a ketone body) in the Eastern bent-wing bat (Miniopterus fuliginosus) in Mungyeong, South Korea. We found an increase in urinary creatinine during torpor in summer, indicating changes in renal water reabsorption rates during the active season. Although we could not confirm ketonuria in hibernating bats due to a methodological limitation caused by the small amount of urine, we verified an increase in urinary creatinine concentration during hibernation. This finding suggests that managing water stress resulting from evaporative water loss is one of key reasons for arousal during hibernation in Eastern bent-wing bats.


Assuntos
Quirópteros , Hibernação , Torpor , Animais , Creatinina , República da Coreia
5.
Curr Biol ; 34(1): R33-R35, 2024 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-38194928

RESUMO

Torpor is a physiological state with substantial translational implications. In recent years, several brain regions responsible for controlling torpor have been pinpointed. The latest research, employing comprehensive whole-brain anatomical analysis, offers insights into a broader network responsible for regulating torpor.


Assuntos
Encéfalo , Torpor , Redes Neurais de Computação
6.
J Comp Physiol B ; 194(1): 95-104, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38170253

RESUMO

Mus musculus enters a torpid state in response to caloric restriction in sub-thermoneutral ambient temperatures. This torpid state is characterized by an adaptive and controlled decrease in metabolic rate, heart rate, body temperature, and activity. Previous research has identified the paraventricular nucleus (PVN) within the hypothalamus, a region containing oxytocin neurons, as a location that is active during torpor onset. We hypothesized that oxytocin neurons within the PVN are part of this neural circuit and that activation of oxytocin neurons would deepen and lengthen torpor bouts. We report that activation of oxytocin neurons alone is not sufficient to induce a torpor-like state in the fed mouse, with no significant difference in body temperature or heart rate upon activation of oxytocin neurons. However, we found that activation of oxytocin neurons prior to the onset of daily torpor both deepens and lengthens the subsequent bout, with a 1.7 ± 0.4 °C lower body temperature and a 135 ± 32 min increase in length. We therefore conclude that oxytocin neurons are involved in the neural circuitry controlling daily torpor in the mouse.


Assuntos
Hibernação , Torpor , Camundongos , Animais , Jejum , Ocitocina , Torpor/fisiologia , Temperatura Corporal/fisiologia , Neurônios/fisiologia , Hibernação/fisiologia
7.
FEBS Open Bio ; 14(2): 241-257, 2024 02.
Artigo em Inglês | MEDLINE | ID: mdl-37925593

RESUMO

Torpor or heterothermy is an energy-saving mechanism used by endotherms to overcome harsh environmental conditions. During winter, the garden dormouse (Eliomys quercinus) hibernates with multiday torpor bouts and body temperatures of a few degrees Celsius, interrupted by brief euthermic phases. This study investigates gene expression within the hypothalamus, the key brain area controlling energy balance, adding information on differential gene expression potentially relevant to orchestrate torpor. A de novo assembled transcriptome of the hypothalamus was generated from garden dormice hibernating under constant darkness without food and water at 5 °C. Samples were collected during early torpor, late torpor, and interbout arousal. During early torpor, 765 genes were differentially expressed as compared with interbout arousal. Twenty-seven pathways were over-represented, including pathways related to hemostasis, extracellular matrix organization, and signaling of small molecules. Only 82 genes were found to be differentially expressed between early and late torpor, and no pathways were over-represented. During late torpor, 924 genes were differentially expressed relative to interbout arousal. Despite the high number of differentially expressed genes, only 10 pathways were over-represented. Of these, eight were also observed to be over-represented when comparing early torpor and interbout arousal. Our results are largely consistent with previous findings in other heterotherms. The addition of a transcriptome of a novel species may help to identify species-specific and overarching torpor mechanisms through future species comparisons.


Assuntos
Hibernação , Myoxidae , Torpor , Animais , Hibernação/genética , Myoxidae/genética , Torpor/genética , Encéfalo , Perfilação da Expressão Gênica
8.
Curr Biol ; 33(24): 5381-5389.e4, 2023 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-37992720

RESUMO

Endotherms can survive low temperatures and food shortage by actively entering a hypometabolic state known as torpor. Although the decrease in metabolic rate and body temperature (Tb) during torpor is controlled by the brain, the specific neural circuits underlying these processes have not been comprehensively elucidated. In this study, we identify the neural circuits involved in torpor regulation by combining whole-brain mapping of torpor-activated neurons, cell-type-specific manipulation of neural activity, and viral tracing-based circuit mapping. We find that Trpm2-positive neurons in the preoptic area and Vgat-positive neurons in the dorsal medial hypothalamus are activated during torpor. Genetic silencing shows that the activity of either cell type is necessary to enter the torpor state. Finally, we show that these cells receive projections from the arcuate and suprachiasmatic nucleus and send projections to brain regions involved in thermoregulation. Our results demonstrate an essential role of hypothalamic neurons in the regulation of Tb and metabolic rate during torpor and identify critical nodes of the torpor regulatory network.


Assuntos
Hipotálamo , Torpor , Hipotálamo/fisiologia , Torpor/fisiologia , Área Pré-Óptica , Núcleo Supraquiasmático , Encéfalo
9.
PLoS One ; 18(11): e0293971, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37930992

RESUMO

Djungarian hamsters are small rodents that show pronounced physiological acclimations in response to changes in photoperiod, and unfavorable environmental conditions such as reduced food availability and low external temperature. These include substantial adjustments, such as severe body weight loss and the use of daily torpor. Torpor is a state of decreased physiological activity in eutherms, usually marked by low metabolic rate and a reduced body temperature. In this study, we investigated the effects of photoperiodic acclimation and food deprivation on systemic iron metabolism in Djungarian hamsters. Our study illustrates the association between liver iron levels and the incidence of torpor expression during the course of the experiment. Moreover, we show that both, acclimation to short photoperiods and long-term food restriction, associated with iron sequestration in the liver. This effect was accompanied with hypoferremia and mild reduction in the expression of principal iron-hormone, hepcidin. In addition to iron, the levels of manganese, selenium, and zinc were increased in the liver of hamsters under food restriction. These findings may be important factors for regulating physiological processes in hamsters, since iron and other trace elements are essential for many metabolic and physiological processes.


Assuntos
Hipotermia , Torpor , Cricetinae , Animais , Phodopus/fisiologia , Estações do Ano , Torpor/fisiologia , Fotoperíodo , Jejum
10.
J Exp Biol ; 226(21)2023 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-37815465

RESUMO

Insectivorous bats at northern latitudes need to cope with long periods of no food for large parts of the year. Hence, bats which are resident at northern latitudes throughout the year will need to undergo a long hibernation season and a short reproductive season where foraging time is limited by extended daylight periods. Eptesicus nilssonii is the northernmost occurring bat species worldwide and hibernates locally when ambient temperatures (Ta) limit prey availability. Therefore, we investigated the energy spent maintaining normothermy at different Ta, as well as how much bats limit energy expenditure while in torpor. We found that, despite being exposed to Ta as low as 1.1°C, bats did not increase torpid metabolic rate, thus indicating that E. nilssonii can survive and hibernate at low ambient temperatures. Furthermore, we found a lower critical temperature (Tlc) of 27.8°C, which is lower than in most other vespertilionid bats, and we found no indication of any metabolic response to Ta up to 37.1°C. Interestingly, carbon dioxide production increased with increasing Ta above the Tlc, presumably caused by a release of retained CO2 in bats that remained in torpor for longer and aroused at Ta above the Tlc. Our results indicate that E. nilssonii can thermoconform at near-freezing Ta, and hence maintain longer torpor bouts with limited energy expenditure, yet also cope with high Ta when sun exposed in roosts during long summer days. These physiological traits are likely to enable the species to cope with ongoing and predicted climate change.


Assuntos
Quirópteros , Hibernação , Torpor , Animais , Temperatura , Quirópteros/fisiologia , Regulação da Temperatura Corporal/fisiologia , Temperatura Baixa , Hibernação/fisiologia , Metabolismo Energético/fisiologia
11.
Pflugers Arch ; 475(10): 1149-1160, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37542567

RESUMO

Hibernation enables many species of the mammalian kingdom to overcome periods of harsh environmental conditions. During this physically inactive state metabolic rate and body temperature are drastically downregulated, thereby reducing energy requirements (torpor) also over shorter time periods. Since blood cells reflect the organism´s current condition, it was suggested that transcriptomic alterations in blood cells mirror the torpor-associated physiological state. Transcriptomics on blood cells of torpid and non-torpid Djungarian hamsters and QIAGEN Ingenuity Pathway Analysis (IPA) revealed key target molecules (TMIPA), which were subjected to a comparative literature analysis on transcriptomic alterations during torpor/hibernation in other mammals. Gene expression similarities were identified in 148 TMIPA during torpor nadir among various organs and phylogenetically different mammalian species. Based on TMIPA, IPA network analyses corresponded with described inhibitions of basic cellular mechanisms and immune system-associated processes in torpid mammals. Moreover, protection against damage to the heart, kidney, and liver was deduced from this gene expression pattern in blood cells. This study shows that blood cell transcriptomics can reflect the general physiological state during torpor nadir. Furthermore, the understanding of molecular processes for torpor initiation and organ preservation may have beneficial implications for humans in extremely challenging environments, such as in medical intensive care units and in space.


Assuntos
Hibernação , Torpor , Cricetinae , Humanos , Animais , Phodopus/fisiologia , Hibernação/genética , Transcriptoma , Torpor/fisiologia , Mamíferos/fisiologia
12.
Integr Comp Biol ; 63(5): 1039-1048, 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-37407285

RESUMO

Variability in body temperature is now recognized to be widespread among whole-body endotherms with homeothermy being the exception rather than the norm. A wide range of body temperature patterns exists in extant endotherms, spanning from strict homeothermy, to occasional use of torpor, to deep seasonal hibernation with many points in between. What is often lost in discussions of heterothermy in endotherms are the benefits of variations in body temperature outside of torpor. Endotherms that do not use torpor can still obtain extensive energy and water savings from varying levels of flexibility in normothermic body temperature regulation. Flexibility at higher temperatures (heat storage or facultative hyperthermia) can provide significant water savings, while decreases at cooler temperatures, even outside of torpor, can lower the energetic costs of thermoregulation during rest. We discuss the varying uses of the terms heterothermy, thermolability, and torpor to describe differences in the amplitude of body temperature cycles and advocate for a broader use of the term "heterothermy" to include non-torpid variations in body temperature.


Assuntos
Hibernação , Torpor , Animais , Hibernação/fisiologia , Regulação da Temperatura Corporal/fisiologia , Mamíferos/fisiologia , Temperatura Corporal , Água , Torpor/fisiologia , Metabolismo Energético/fisiologia
13.
Int J Mol Sci ; 24(13)2023 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-37446216

RESUMO

Hypothermia is a promising clinical therapy for acute injuries, including neural damage, but it also faces practical limitations due to the complexities of the equipment and procedures required. This study investigates the use of the A1 adenosine receptor (A1AR) agonist N6-cyclohexyladenosine (CHA) as a more accessible method to induce steady, torpor-like hypothermic states. Additionally, this study investigates the protective potential of CHA against LPS-induced sepsis and neuroinflammation. Our results reveal that CHA can successfully induce a hypothermic state by activating a neuronal circuit similar to the one that induces physiological torpor. This state is characterized by maintaining a steady core body temperature below 28 °C. We further found that this torpor-like state effectively mitigates neuroinflammation and preserves the integrity of the blood-brain barrier during sepsis, thereby limiting the infiltration of inflammatory factors into the central nervous system. Instead of being a direct effect of CHA, this protective effect is attributed to inhibiting pro-inflammatory responses in macrophages and reducing oxidative stress damage in endothelial cells under systemic hypothermia. These results suggest that A1AR agonists such as CHA could potentially be potent neuroprotective agents against neuroinflammation. They also shed light on possible future directions for the application of hypothermia-based therapies in the treatment of sepsis and other neuroinflammatory conditions.


Assuntos
Fármacos Cardiovasculares , Hipotermia , Torpor , Humanos , Hipotermia/induzido quimicamente , Células Endoteliais , Doenças Neuroinflamatórias , Agonistas do Receptor A1 de Adenosina/farmacologia , Agonistas do Receptor Purinérgico P1
14.
J Therm Biol ; 115: 103652, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37451039

RESUMO

Evolution of heterothermy in environments with variable temperatures has allowed bats to survive food scarcity during seasonal climatic extremes by using torpor as a hibernation strategy. The controlled reduction of body temperature and metabolism through complex behavioural and physiological adaptations at organismal, organ, cellular and molecular levels includes the ability of tissues and cells to adapt to temperature alterations. Based on the prediction that cells of different tissues cultured in vitro would differ in their ability to withstand freezing and thawing of the medium, we determined the survival rate of bat-derived cells following exposure to -20 °C for 24 h in media with no cryoprotective agents or medium supplemented by glucose in concentration range 0-3333 mM. Cell survival rates were determined in relation to availability of glucose in the medium, organ origin, cell concentration and bat species. In general, increased glucose helped cells survive at sub-zero temperatures, though concentrations up to 80-fold higher than those found in chiropterans were needed. However, cells in glucose-free phosphate buffered saline also survived, suggesting that other mechanisms may be contributing to cell survival at low temperatures. Highest in vitro viability was observed in nervus olfactorius-derived cell cultures, with high survival rates and rapid re-growth under optimal conditions after exposure to -20 °C. Kidney cells from different bat species showed comparable overall survival rate patterns, though smaller chiropteran species appeared to utilise lower glucose levels as a cryoprotectant than larger species. Our in vitro data provide evidence that cells of heterothermic bats can survive sub-zero temperatures and that higher glucose levels in important tissues significantly improve hibernation survival at extremely low temperatures.


Assuntos
Quirópteros , Hibernação , Torpor , Animais , Quirópteros/fisiologia , Glucose/metabolismo , Hibernação/fisiologia , Adaptação Fisiológica/fisiologia
15.
Am J Physiol Regul Integr Comp Physiol ; 325(4): R359-R379, 2023 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-37519255

RESUMO

Djungarian hamsters use daily torpor to save energy during winter. This metabolic downstate is part of their acclimatization strategy in response to short photoperiod and expressed spontaneously without energy challenges. During acute energy shortage, torpor incidence, depth, and duration can be modulated. Torpor induction might rely on glucose availability as acute metabolic energy source. To investigate this, the present study provides the first continuous in vivo blood glucose measurements of spontaneous daily torpor in short photoperiod-acclimated and fasting-induced torpor in long photoperiod-acclimated Djungarian hamsters. Glucose levels were almost identical in both photoperiods and showed a decrease during resting phase. Further decreases appeared during spontaneous daily torpor entrance, parallel with metabolic rate but before body temperature, while respiratory exchange rates were rising. During arousal, blood glucose tended to increase, and pretorpor values were reached at torpor termination. Although food-restricted hamsters underwent a considerable energetic challenge, blood glucose levels remained stable during the resting phase regardless of torpor expression. The activity phase preceding a torpor bout did not reveal changes in blood glucose that might be used as torpor predictor. Djungarian hamsters show a robust, circadian rhythm in blood glucose irrespective of season and maintain appropriate levels throughout complex acclimation processes including metabolic downstates. Although these measurements could not reveal blood glucose as proximate torpor induction factor, they provide new information about glucose availability during torpor. Technical innovations like in vivo microdialysis and in vitro transcriptome or proteome analyses may help to uncover the connection between torpor expression and glucose metabolism.


Assuntos
Phodopus , Torpor , Cricetinae , Animais , Phodopus/fisiologia , Glicemia , Glucose , Torpor/fisiologia , Temperatura Corporal/fisiologia , Fotoperíodo , Estações do Ano
16.
Cells ; 12(10)2023 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-37408188

RESUMO

Temperature changes and periods of detrimental cold occur frequently for many organisms in their natural habitats. Homeothermic animals have evolved metabolic adaptation strategies to increase mitochondrial-based energy expenditure and heat production, largely relying on fat as a fuel source. Alternatively, certain species are able to repress their metabolism during cold periods and enter a state of decreased physiological activity known as torpor. By contrast, poikilotherms, which are unable to maintain their internal temperature, predominantly increase membrane fluidity to diminish cold-related damage from low-temperature stress. However, alterations of molecular pathways and the regulation of lipid-metabolic reprogramming during cold exposure are poorly understood. Here, we review organismal responses that adjust fat metabolism during detrimental cold stress. Cold-related changes in membranes are detected by membrane-bound sensors, which signal to downstream transcriptional effectors, including nuclear hormone receptors of the PPAR (peroxisome proliferator-activated receptor) subfamily. PPARs control lipid metabolic processes, such as fatty acid desaturation, lipid catabolism and mitochondrial-based thermogenesis. Elucidating the underlying molecular mechanisms of cold adaptation may improve beneficial therapeutic cold treatments and could have important implications for medical applications of hypothermia in humans. This includes treatment strategies for hemorrhagic shock, stroke, obesity and cancer.


Assuntos
Adaptação Fisiológica , Temperatura Baixa , Resposta ao Choque Frio , Metabolismo dos Lipídeos , Receptores Ativados por Proliferador de Peroxissomo , Termogênese , Torpor , Torpor/fisiologia , Animais , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , Ácidos Graxos/metabolismo , Resposta ao Choque Frio/fisiologia , Fluidez de Membrana , Mitocôndrias/metabolismo
17.
Cells ; 12(10)2023 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-37408201

RESUMO

The utilisation of synthetic torpor for interplanetary travel once seemed farfetched. However, mounting evidence points to torpor-induced protective benefits from the main hazards of space travel, namely, exposure to radiation and microgravity. To determine the radio-protective effects of an induced torpor-like state we exploited the ectothermic nature of the Danio rerio (zebrafish) in reducing their body temperatures to replicate the hypothermic states seen during natural torpor. We also administered melatonin as a sedative to reduce physical activity. Zebrafish were then exposed to low-dose radiation (0.3 Gy) to simulate radiation exposure on long-term space missions. Transcriptomic analysis found that radiation exposure led to an upregulation of inflammatory and immune signatures and a differentiation and regeneration phenotype driven by STAT3 and MYOD1 transcription factors. In addition, DNA repair processes were downregulated in the muscle two days' post-irradiation. The effects of hypothermia led to an increase in mitochondrial translation including genes involved in oxidative phosphorylation and a downregulation of extracellular matrix and developmental genes. Upon radiation exposure, increases in endoplasmic reticulum stress genes were observed in a torpor+radiation group with downregulation of immune-related and ECM genes. Exposing hypothermic zebrafish to radiation also resulted in a downregulation of ECM and developmental genes however, immune/inflammatory related pathways were downregulated in contrast to that observed in the radiation only group. A cross-species comparison was performed with the muscle of hibernating Ursus arctos horribilis (brown bear) to define shared mechanisms of cold tolerance. Shared responses show an upregulation of protein translation and metabolism of amino acids, as well as a hypoxia response with the shared downregulation of glycolysis, ECM, and developmental genes.


Assuntos
Hipotermia , Torpor , Animais , Peixe-Zebra/genética , Torpor/fisiologia , Perfilação da Expressão Gênica , Músculos
18.
Integr Comp Biol ; 63(5): 1060-1074, 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-37279461

RESUMO

Migration is a widespread and highly variable trait among animals. Population-level patterns arise from individual-level decisions, including physiological and energetic constraints. Many aspects of migration are influenced by behaviors and strategies employed during periods of stopover, where migrants may encounter variable or unpredictable conditions. Thermoregulation can be a major cost for homeotherms which largely encounter ambient temperatures below the lower critical temperature during migration, especially during the rest phase of the daily cycle. In this review we describe the empirical evidence, theoretical models, and potential implications of bats and birds that use heterothermy to reduce thermoregulatory costs during migration. Torpor-assisted migration is a strategy described for migrating temperate insectivorous bats, whereby torpor can be used during periods of inactivity to drastically reduce thermoregulatory costs and increase net refueling rate, leading to shorter stopover duration, reduced fuel load requirement, and potential consequences for broad-scale movement patterns and survival. Hummingbirds can adopt a similar strategy, but most birds are not capable of torpor. However, there is an increasing recognition of the use of more shallow heterothermic strategies by diverse bird species during migration, with similarly important implications for migration energetics. A growing body of published literature and preliminary data from ongoing research indicate that heterothermic migration strategies in birds may be more common than traditionally appreciated. We further take a broad evolutionary perspective to consider heterothermy as an alternative to migration in some species, or as a conceptual link to consider alternatives to seasonal resource limitations. There is a growing body of evidence related to heterothermic migration strategies in bats and birds, but many important questions related to the broader implications of this strategy remain.


Assuntos
Quirópteros , Torpor , Animais , Quirópteros/fisiologia , Regulação da Temperatura Corporal , Torpor/fisiologia , Temperatura , Aves/fisiologia
19.
Lab Anim (NY) ; 52(7): 143, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37386169

Assuntos
Roedores , Torpor , Animais
20.
Integr Comp Biol ; 63(5): 1049-1059, 2023 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-37328423

RESUMO

Torpor was traditionally seen as a winter survival mechanism employed by animals living in cold and highly seasonal habitats. Although we now know that torpor is also used by tropical and subtropical species, and in response to a variety of triggers, torpor is still largely viewed as a highly controlled, seasonal mechanism shown by Northern hemisphere species. To scrutinize this view, we report data from a macroanalysis in which we characterized the type and seasonality of torpor use from mammal species currently known to use torpor. Our findings suggest that predictable, seasonal torpor patterns reported for Northern temperate and polar species are highly derived forms of torpor expression, whereas the more opportunistic and variable forms of torpor that we see in tropical and subtropical species are likely closer to the patterns expressed by ancestral mammals. Our data emphasize that the torpor patterns observed in the tropics and subtropics should be considered the norm and not the exception.


Assuntos
Torpor , Animais , Torpor/fisiologia , Mamíferos , Estações do Ano , Ecossistema , Regulação da Temperatura Corporal
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