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At least 19 recordsLinked to original sources
PubMed1978

Isolation of a hibernation inducing trigger(s) from the plasma of hibernating woodchucks.

Plasma from hibernating woodchucks was desalted utilizing a hollow fiber device having a M. W. cut-off of 5,000. This preparation was fractionated by isoelectric focusing (IEF) in a pH gradient extending from 3.5 to 10.0 resulting in protein components having isoelectric points (pIs) of 4.5, 5.2, 5.5, 6.3, and 7.0. Fraction I (comprised of proteins having pIs of 4.5 and 5.2) induced hibernation within 2 to 6 days in 8 out of 10 summer-active ground squirrels. Fraction II (pI 5.5) and Fraction III (pI 6.3 and 7.0) failed to induce any summer hibernation in 10 animal test groups at identical sample concentrations. Polyacrylamide gel electrophoresis of Fraction I indicated that albumin was a major constituent of this still heterogeneous preparation. Thus, in order to more clearly define the plasma locus of this hibernation inducing trigger(s) (HIT) molecule, whole plasma and/or Fraction I was fractionated by 3 distinct resolving techniques. These included sub-fractionation of Fraction I by isoelectric focusing utilizing a narrower pH gradient extending from 3.5 to 6.0, isotachophoresis of whole plasma and affinity chromatography of Fraction I and whole plasma. A total of 40 summer-active ground squirrels were injected and assayed for HIT activity with fractionated preparations derived by the three previously cited separation techniques. A total of 18 of these summer-active ground squirrels hibernated. However, a much more impressive figure is that 16 out of 21 animals hibernated when injected with resolved hibernating plasma fractions in which albumin was the predominant plasma protein. A total of 8 control animals were injected with vehicle and none of these hibernated.

Animals↗
PubMed1979

Comparative studies of blood coagulation in hibernating and non-hibernating frogs (Rana tigrina).

1. During hibernation in frogs (Rana tigrina) there occurs prolongation of several clotting tests, viz, whole blood clotting time, plasma recalcification time, cephalin time and prothrombin time. 2. The ambient body temperature of the frog during winter hibernation is low and the retarded blood clotting at lower temperature may play an important protective role against intravascular thrombosis. 3. Shorter plasma recalcification time in low-spun plasma as compared to high-spun plasma indicated the presence of procoagulant activity in platelets/leucocytes of frogs.

Animals↗
PubMed1977

A comparison of the effects of prior cold incubation on cerebral cortex function in a hibernator (Cricetus auratus) and a non-hibernator (Cavia porcellus)--II. High energy phosphate levels in cerebral cortex slices after in vitro cold incubation.

1. ATP and CP levels were measured in brain slices from golden hamster and guinea pig after varying periods of cold storage and subsequent incubation at 37 degrees C in the presence and absence of K+ salts. 2. ATP and CP levels were maintained at higher levels in hamster tissue. 3. The results are discussed in relation to the ability of a hibernator to transform and transport chemical energy at low temperatures.

Adenosine Triphosphate↗
PubMed1976

Protein metabolism in the black bear before and during hibernation.

During 3 to 5 months of hibernation, the American black bear does not defecate, urinate, or require food or water. Although the bear loses 15 to 25% of its body weight during this period, there is no significant change in its lean body mass. No net accumulation of the usual nitrogenous products of protein catabolism can be demonstrated in the dormant bear, and there is a decrease in urea production during hibernation. Because of these findings, it has been hypothesized that the black bear can alter its protein metabolism during hibernation by some unknown mechanism. During this study, the metabolis rate of protein turnover in four adult male black bears was measured before, during, and after hibernation, using 125I-labeled serum albumin from black bears as an indicator protein and 14C-labeled leucine as an indicator amino acid. For albumin during both phases, the disappearance rate of labeled albumin from serum was measured over 2 weeks and its turnover rate was calculated from these data. For [14C]leucine, the amino acid was injected during and after hibernation and its appearance in total proteins of plasma was measured. The results using labeled albumin revealed a threefold increase in turnover of protein during hibernation compared with protein turnover before hibernation. Leucine data supported these findings; more labeled leucine was incorporated in plasma proteins during hibernation than in the active state in spring. There were no significant changes in hematocrit, serum albumin concentration, thyroxin, or thyroxine-binding globulin between active and dormant periods, although triiodothyronine tended to decrease during hibernation. We speculate that increased protein turnover suggests a strongly acting protein-anabolic mechanism that would tend to compete with other catabolic pathways for amino acids. Another consequence of this increased protein turnover would be thermogenesis. This may have helped prevent any undue decrease in body temperature. It is notable that the body temperature of the dormant bear is appreciably higher than that of other hibernating animals.

Animals↗
PubMed1978

Seasonal variations in the renal cortical (Na+ + K+)-ATPase and Mg2+-ATPase of a hibernator, the ground squirrel (Spermophilus richardsonii).

1. The specific activity of renal cortical (Na+ + K+)-ATPase of the Richardson ground squirrel is markedly reduced during hibernation, in contrast to the specific activity of the accompanying Mg2+-ATPase which is markedly increased. 2. The sensitivity of (Na+ + K+)-ATPase to inhibition by ouabain is unchanged by hibernation. 3. Both the non-linear thermal dependence of (Na+ + K+)-ATPase and the linear thermal dependence of Mg2+-ATPase are also unchanged by hibernation. 4. The energy of activation of both enzymes is unchanged during hibernation, or by comparison with that determined in awake controls. 5. There is no evidence for inherent "cold resistance" in these enzyme preparations compared to similar preparations from the non-hibernating rabbit. This parameter does not change during hibernation. 6. Both the rate and amount of specific [3H]-ouabain binding to the renal cortical preparations of (Na+ + K+)-ATPase decrease during hibernation. This decrease matches the fall in enzyme activity so that the ratio of pumping sites/unit of enzyme activity shows no seasonal variations. 7. These findings suggest that the amount of renal cortical (Na+ + K+)-ATPase enzyme falls during hibernation, but that the enzyme which remains functions with the same thermodynamic efficiency and identical biochemical characteristics of that found in the awake summer controls.

Animals↗
PubMed1977

Carcinogenicity of N-nitrosodiethylamine in hibernating and nonhibernating European hamsters.

Hibernating European hamsters reacted differently to sc injections of N-nitrosodiethylamine (DEN) than did European hamsters that were not hibernating. Hibernating animals tolerated higher dose levels but developed fewer neoplasms. In contrast, hibernating males had more pulmonary tumors than did the respective nonhibernators. However, the hibernating females of the low dosage group developed fewer lung tumors. The survival times were longer for the male hibernators than for the male nonhibernators. The organ specificity of DEN, as well as the morphology and histogenesis of the neoplasms, showed no differences between the hibernating and nonhibernating groups.

Adenocarcinoma↗
PubMedDate not supplied

Hibernation: an opioid-dependent state?

Hibernation reduces substantially the heart rate of hamsters as well as the respiratory rate, the body temperature and the arousal level. The heart rate is reversed dramatically by the injection of low doses of Naloxone and in some cases the hamster arouses prematurely from hibernation. The effect is not due to the pain of the injection because saline injections do not produce such changes. The effect requires a pre-existing state of hibernation because Naloxone has no cardioacceleratory or arousal effect in non-hibernating hamsters that have had their heart rate and body temperature decreased substantially during hypothermia. These results suggest that endogenous opioids may contribute specifically to the state of hibernation. Moreover, a physiological role may exist for an anti-opioid system in the promotion of arousal from hibernation.

Animals↗
PubMed2026

Integrated transcriptomic analysis of mRNA and miRNA in Brown adipose tissue of the greater horseshoe bats during hibernation.

Hibernation enables animals survive harsh environments by conserving energy through reduced metabolism and body temperature. Brown adipose tissue (BAT) plays a critical role in non-shivering thermogenesis, crucial for warming up during arousal phase. The greater horseshoe bats (Rhinolophus nippon) are typical hibernators and non-shivering thermogenesis in BAT tissue may persist throughout the arousal process in bats. This study examines gene expression and regulatory changes in BAT of these bats across active, hibernation, and arousal phases using transcriptome and miRNA sequencing. A total of 2721 differentially expressed mRNAs and 268 differentially expressed miRNAs were identified. The results reveal that the BAT transcriptome undergoes state-dependent remodeling throughout the hibernation process. The most pronounced divergence occurs between the active phase and torpor, involving cell cycle arrest, immunosuppression, thermogenic signal desensitization, and upregulation of lipid metabolism and autophagy pathways, reflecting the coordinated adaptation of energy conservation and thermogenic reserve. In contrast, transcriptional alterations between torpor and arousal are extremely limited, indicating that torpid BAT is already pre-primed for thermogenesis and requires only modest transcriptional adjustments to activate heat production. Notably, although body temperature recovers to active-phase levels during arousal, the molecular signature of BAT remains highly similar to that of the torpid state. Furthermore, the core thermogenic gene UCP1 showed no significant expression differences across the three groups. In conclusion, this study systematically delineates the miRNA-mRNA regulatory landscape of bat BAT across the hibernation process, and deepens our understanding of the thermoregulatory mechanisms underlying mammalian hibernation.

BAT↗
PubMed1977

CNS regulation of body temperature in euthermic and hibernating marmots (Marmota flaviventris).

Hypothalamic thermosensitivity of marmots was characterized during euthermia and hibernation. Hypothalamic temperature (Thy) was manipulated with chronically implanted, water-perfused thermodes while the animal's rate of oxygen consumption was continuously measured. The threshold Thy for eliciting an increase in metabolic heat production (MHP) and the proportionality constant (alphaMHP) relating rate of MHP to Thy were determined. In four euthermic marmots alphaMHP averaged -1.1 W-kg-1-degrees C-1. During the entrance into hibernation, as body temperature (Tb) declined from 36 to 8 degrees C, the threshold Thy for the MHP response progressively declined and was demonstrable at all times. The Thy of marmots in deep hibernation at an ambient temperature (Ta) of 5 degrees C plateaued near 7.5 degrees C, but threshold Thy for MHP showed a continuous slow decline of 0.2-0.4 degrees C a day, until one day prior to arousal. Proportional regulation of Tb was demonstrable at all times during deep hibernation. The average proportionality constant for the MHP response to hypothalamic cooling during deep hibernation in three marmots was -0.08 W-kg-1-degrees C-1. These results demonstrate that the hypothalamic regulator of Tb is active throughout hibernation and that there are progressive changes in its thermosensitivity.

Animals↗
PubMed1977

Mechanisms responsible for decreased glomerular filtration in hibernation and hypothermia.

Mechanisms underlying the elimination or marked depression of renal function in hibernation and hypothermia were investigated through measurements of blood pressure, heart rate, red blood cell and plasma volumes, and relative distribution of cardiac output. Hamsters (Mesocricetus auratus) were made hypothermic (rectal temperature (Tre), 7 degrees C) by exposure to helox and cold, or permitted to hibernate with several weeks of cold exposure (Ta approximately 5 degrees C). Mean arterial pressure, 120 Torr in normothermic control animals, demonstrated a 55% and 60% decrease during hibernation and hypothermia, respectively. As the animals rewarmed from hypothermia or aroused from hibernation, blood pressure increased rapidly at 8-12 degrees C, more gradually at 12-17 degrees C, and plateaued thereafter. Blood pressure rapidly returned to near control levels whereas heart rate remained at less than one-half control value at the highest temperature examined. Red blood cell volume, 26.2 +/- 0.6 ml/kg body wt in the control animals appeared unaffected by hypothermia. Plasma volume, by contrast, decreased from control values of 33.0 +/- 0.8 to 21.3 +/- 0.6 ml/kg body wt in hypothermia, a decrease of approximately 35%. Distribution of cardiac output to various organs in hibernation and hypothermia followed a similar pattern. Relative flow to the heart, lung, diaphragm, and brown fat increased while the fraction distributed to the visceral organs appeared to decrease. The normothermic control kidney received approximately 16% of the cardiac output while the hibernating and hypothermic kidneys received approximately 10% and 6%, respectively. The data are discussed in terms of the determinants of glomarular filtration rate and explain, in part, the elimination or marked reduction in renal function observed in depressed metabolic states.

Animals↗
PubMed1976

Blood gas analyses of hibernating hamsters and dormice.

Blood gases were measured in hibernating and hypothermic animals as a biological model of clinical hypothermia. Blood gas analyses from hamsters and dormice were carried out with the aid of permanent arterial catheters during normothermia and hibernation. In golden hamster pH increased from 7.30 to 7.46 during hibernation and PaCO2 decreased from 59.7 to 40.5 mm Hg. In dormice pH increased from 7.24 to 7.44 and PaCO2 decreases from 38.5 to 27.4 mm Hg. The actual bicarbonate concentration increased from 29 to 52 mMol in golden hamsters and from 16 to 34 mMol in dormice during hibernation. In experiments with induced hypothermia in golden hamsters under ketamine-anaesthesia there was no correlation between temperature and PaCO2. Despite the slight decrease in PaCO2 during hibernation we conclude that PaCO2 rather than total carbon dioxide content is held constant when temperature is changed. During clinical hypothermia it will probably be safe to keep PaCO2 constant.

Acid-Base Equilibrium↗
PubMed1975

Spin label evidence for the role of lysoglycerophosphatides in cellular membranes of hibernating mammals.

The phospholipid composition of ground squirrel heart muscle changes during hibernation: more lysoglycerophosphatides are found in the hibernating state than in the active state. Phase transitions inferred from spin label motion occur in the usual manner typical of mammalian mitochondria for the mitochondria and mitochondrial lipids from active squirrels. However, a conspicuous absence of a spin label-detectable phase transition is observed in equivalent preparations from hibernating animals. The addition of lysolecithin to preparations from active squirrels removes the break and induces a straight line in the Arrhenius plot. The lack of a spin label-detectable phase transition in hibernating animals, therefore, is attributed to an increased content of lysoglycerophosphatides present in the phospholipids during hibernation.

Adaptation, Physiological↗
PubMed1978

Changes in the form of Arrhenius plots of the activity of glucagon-stimulated adenylate cyclase and other hamster liver plasma-membrane enzymes occurring on hibernation.

1. Arrhenius plots of the glucagon-stimulated adenylate cyclase, 5'-nucleotidase, (Na+ + K+)-stimulated adenosine triphosphatase and Mg2+-dependent adenosine triphosphatase activities of control hamster liver plasma membranes exhibited two break points at around 25 and 13 degrees C, whereas Arrhenius plots of their activities in hibernating hamster liver plasma membranes exhibited two break points at around 25 and 4 degrees C. 2. A single break occurring between 25 and 26 degrees C was observed in Arrhenius plots of the activities of fluoride-stimulated adenylate cyclase, basal adenylate cyclase and cyclic AMP phosphodiesterase of liver plasma membranes from both control and hibernating animals. 3. Arrhenius plots of phosphodiesterase I activity showed a single break at 13 degrees C for membranes from control animals, and a single break at around 4 degrees C for liver plasma membranes from hibernating animals. 4. The temperature at which break points occurred in Arrhenius plots of glucagon- and fluoride-stimulated adenylate cyclase activity were decreased by about 7--8 degrees C by addition of 40 mm-benzyl alcohol to the assays. 5. Discontinuities in the Arrhenius plots of 4-anilinonaphthalene-1-sulphonic acid fluorescence occurred at around 24 and 13 degrees C for liver plasma membranes from control animals, and at around 25 and 4 degrees C for membranes from hibernating animals. 6. We suggest that in hamster liver plasma membranes from control animals a lipid phase separation occurs at around 25 degrees C in the inner half of the bilayer and at around 13 degrees C in the outer half of the bilayer. On hibernation a change in bilayer asymmetry occurs, which is expressed by a decrease in the temperature at which the lipid phase separation occurs in the outer half of the bilayer to around 4 degrees C. The assumption made is that enzymes expressing both lipid phase separations penetrate both halves of the bilayer, whereas those experiencing a single break penetrate one half of the bilayer only.

Adenylyl Cyclases↗
PubMed1978

Ultrastruct of the hypothalamic neurosecretory nuclei of the dormouse (Eliomys quercinus L.) in the awakening and hibernating states.

The ultrastructure of the chief neurosecretory nuclei, supraoptic, (SON), parventricular, (PVN) and infundibular (IN), of the dormouse (Eliomys quercinus L.) has been studied during active and hibernating states. In the active state all three nuclei contained light, dark and intermediate type neurons. In hibernation the SON showed only a single light type which differed from the light neurons of the active state; the endoplasmic reticulum was vacuolized and sometimes grouped in 'honey-comb' structures; the cytoplasm contained accumulations of filamentous 'crystalline' material. None of these features occurred in the active state neurons. In the PVN and IN during hibernation both a light and a dark type neuron were present. 'Honey-comb' structures were seen in neurons of the PVN during hibernation, but never in those of the IN. Thus specific morphological features in the SON and PVN appear to be associated with the physiological changes of hibernation.

Animals↗