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PubMed1998

Isolation and partial characterization of an opioid-like 88 kDa hibernation-related protein.

Previous studies show that infusion of hibernating woodchuck albumin (HWA) induces hibernation in summer-active ground squirrels and results in profound behavioral and physiological depression in primates. These effects are reversed by the administration of opiate antagonists, suggesting that the putative hibernation induction trigger (HIT) may act through opioid receptors. We have demonstrated that both HIT-containing plasma and the synthetic alpha opioid D-Ala2-D-Leu5-enkephalin (DADLE), which mimics the activity of HIT in hibernators, extend tissue survival time of a multi-organ autoperfusion system by 3-fold. In this study we present the first data showing biological activity with a much more highly purified plasma fraction from hibernating woodchucks, identified as the hibernation-related factor (HRF). Both the HRF and DADLE show opiate-like contractile inhibition in the mouse vas deferens (Mvd) bioassay. We also have preliminary evidence in an isolated rabbit heart preparation indicating that the HRF and DADLE act similarly to restore left ventricular function following global myocardial ischemia. Furthermore, we have partially sequenced an alpha 1-glycoprotein-like 88 kDa hibernation-related protein (p88 HRP) present in this fraction, which may prove to be the blood-borne HIT molecule.

Amino Acid Sequence↗
PubMed2002

The timing of hibernation in Tasmanian echidnas: why do they do it when they do?

We investigated the patterns of hibernation and arousals in seven free-ranging echidnas Tachyglossus aculeatus setosus (two male, five female) in Tasmania using implanted temperature data loggers. All echidnas showed a 'classical' pattern of mammalian hibernation, with bouts of deep torpor interrupted by periodic arousals to euthermia (mean duration 1.04+/-0.05 (n=146). Torpor bout length increased as body temperature fell during the hibernation season, and became more variable as temperature rose again. Hibernation started in late summer (February 28+/-5 days, n=6) and males aroused just before the winter solstice (June 15+/-3 days, n=3), females that subsequently produced young aroused 40 days later (July 25+/-3, n=4) while females that did not produce young hibernated for a further two months (arousal Sept 27+/-5, n=7). We suggest that hibernation in Tasmanian echidnas can be divided into two phases, the first phase, marked by declining minimum body temperatures as ambient temperature falls, appears to be obligatory for all animals, while the second phase is 'optional' and is utilised to varying amounts by females. We suggest that early arousal and breeding is the favoured option for females in good condition, and that the ability to completely omit breeding in some years, and hibernate through to spring is an adaptation to an uncertain climate.

Animals↗
PubMed2001

Mechanisms for increased levels of phosphorylation of elongation factor-2 during hibernation in ground squirrels.

Previously, eEF-2 phosphorylation has been identified as a reversible mechanism involved in the inhibition of the elongation phase of translation. In this study, an increased level of phosphorylation of eukaryotic elongation factor-2 (eEF-2) was observed in the brains and livers of hibernating ground squirrels. In brain and liver from hibernators, eEF-2 kinase activity was increased relative to that of active animals. The activity of protein phosphatase 2A (PP2A), a phosphatase that dephosphorylates eEF-2, was also decreased in brain and liver from hibernators. This was associated with an increase in the level of inhibitor 2 of PP2A (I(2)(PP2A)), although there was an increase in the level of the catalytic subunit of PP2A (PP2A/C) in hibernating brains and livers. These results indicate that eEF-2 phosphorylation represents a specific and previously uncharacterized mechanism for inhibition of the elongation phase of protein synthesis during hibernation. Increased levels of eEF-2 phosphorylation in hibernators appear to be a component of the regulated shutdown of cellular functions that permits hibernating animals to tolerate severe reductions in cerebral blood flow and oxygen delivery capacity.

Animals↗
PubMedDate not supplied

The effects of afferent stimulation on neurons in slices of the medial septal area and their modulation by biologically active substances in hibernating and awake ground squirrels.

Evoked neuron activity in slices of the medial septal area and its modulation by neuropeptides and monoamines was studied in two groups of ground squirrels--hibernating and awake animals. Electrical stimulation of the medial forebrain bundle evoked predominantly inhibitory effects of different durations. In addition, responses were seen consisting of resetting of the phase of background volleys to the stimulus after initial inhibition: there were also small numbers of short-latency single-spike responses. All the neuropeptides tested. which had been identified from the brains of hibernating animals, induced differentiated reversible effects consisting of modulation of responses; changes in evoked activity were seen significantly more often than shifts in spontaneous activity. The effects depended on the state of the animal. Thus. peptide TSKYR increased the duration of inhibition in hibernating ground squirrels but shortened inhibition in awake animals. Peptide TSKY. which had little effect in hibernating animals, increased the duration of inhibition in awake animals. Dipeptide DY. which decreased the duration of inhibition and increased the amplitude of the activatory components of responses in hibernating ground squirrels. had little effect in awake animals. The effects of noradrenaline and serotonin correlated to a large extent with their effects on spontaneous activity. It is suggested that endogenous substances are involved in creating the conditions required for increasing the latent excitability and reactivity of septal neurons during hibernation. This allows the medial septal area to function as a "sentry post," allowing the receipt of signals and urgent arousal during hibernation.

Animals↗
PubMed2001

Characteristics of sarcoplasmic reticulum membrane preparations isolated from skeletal muscles of active and hibernating ground squirrel Spermophilus undulatus.

The total Ca-ATPase activity in the sarcoplasmic reticulum (SR) membrane fraction isolated from skeletal muscles of winter hibernating ground squirrel Spermophilus undulatus is approximately 2.2-fold lower than in preparations obtained from summer active animals. This is connected in part with approximately 10% decrease of the content of Ca-ATPase protein in SR membranes. However, the enzyme specific activity calculated with correction for its content in SR preparations is still approximately 2-fold lower in hibernating animals. Analysis of the protein composition of SR membranes has shown that in addition to the decrease in Ca-ATPase content in hibernating animals, the amount of SR Ca-release channel (ryanodine receptor) is decreased approximately 2-fold, content of Ca-binding proteins calsequestrin, sarcalumenin, and histidine-rich Ca-binding protein is decreased approximately 3-4-fold, and the amount of proteins with molecular masses 55, 30, and 22 kD is significantly increased. Using the cross-linking agent cupric-phenanthroline, it was shown that in SR membranes of hibernating ground squirrels Ca-ATPase is present in a more aggregated state. The affinity of SR membranes to the hydrophilic fluorescent probe ANS is higher and the degree of excimerization of the hydrophobic probe pyrene is lower (especially for annular lipids) in preparations from hibernating than from summer active animals. The latter indicates an increase in the microviscosity of the lipid environment of Ca-ATPase during hibernation. We suggest that protein aggregation as well as the changes in protein composition and/or in properties of lipid bilayer SR membranes can result in the decrease of enzyme activity during hibernation.

Anilino Naphthalenesulfonates↗
PubMed1998

Neurogenic and non-neurogenic responses in the urinary bladder of hibernating hamster.

1. Purinergic and cholinergic components of parasympathetic neurotransmission and contractile responses to exogenous alpha,beta-methylene ATP, acetylcholine, substance K, substance P, calcitonin gene-related peptide, vasoactive intestinal polypeptide and capsaicin have been investigated in the urinary bladder of hibernating hamsters (4 weeks), cold exposed (4 weeks) and age-matched controls. 2. Electrical field stimulation (EFS) evoked increased frequency-dependent contractions in the detrusor strips from hibernating hamsters compared with those obtained from cold-exposed and age-matched animals. Tetrodotoxin (10(-6) M) completely blocked the frequency-dependent contractions in all groups. 3. The purinergic component of the parasympathetic neurotransmission was not affected in hibernating and cold-exposed animals while the cholinergic component was increased with respect to age-matched animals. The neurogenic response to EFS, still present after incubation with atropine (10(-6) M) and suramin (10(-4) M), was attenuated by indomethacin (10(-6) M) and blocked by tetrodotoxin (10(-6) M). 4. Exogenous administration of alpha,beta-methylene ATP elicited a significantly reduced contraction in strips from hibernating and cold-exposed hamsters relative to age-matched animals. The contractile response to exogenous acetylcholine was greater in the detrusors from hibernating hamsters than in cold-exposed and age-matched animals. Substance K elicited reduced contractions in preparations from hibernating animals compared with cold-exposed and control animals. Calcitonin gene-related peptide, vasoactive intestinal polypeptide, substance P and capsaicin did not elicit any relaxant or contractile response either at resting tone or in carbachol (5 x 10(-7) M)-precontracted tissues. 5. In summary, our findings indicate that 4 weeks of hibernation can significantly increase neurogenic responses in the hamster urinary bladder. This appears to be due to an increase in postjunctional responses to acetylcholine. In contrast, there was a decrease of the postjunctional responses to the parasympathetic cotransmitter ATP and also to the sensory-motor neurotransmitter substance K.

Acetylcholine↗
PubMed1998

Low-temperature carbon utilization is regulated by novel gene activity in the heart of a hibernating mammal.

Hibernation is a physiological adaptation characterized by dramatic decreases in heart rate, body temperature, and metabolism, resulting in long-term dormancy. Hibernating mammals survive for periods up to 6 mo in the absence of food by minimizing carbohydrate catabolism and using triglyceride stores as their primary source of fuel. The cellular and molecular mechanisms underlying the changes from a state of activity to the hibernating state are poorly understood; however, the selective expression of genes offers one level of control. To address this problem, we used a differential gene expression screen to identify genes that are responsible for the physiological characteristics of hibernation in the heart of the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). Here, we report that genes for pancreatic lipase and pyruvate dehydrogenase kinase isozyme 4 are up-regulated in the heart during hibernation. Pancreatic lipase is normally expressed exclusively in the pancreas, but when expressed in the hibernating heart it liberates fatty acids from triglycerides at temperatures as low as 0 degreesC. Pyruvate dehydrogenase kinase isozyme 4 inhibits carbohydrate oxidation and depresses metabolism by preventing the conversion of pyruvate to Ac-CoA. The resulting anaerobic glycolysis and low-temperature lipid catabolism provide evidence that adaptive changes in cardiac physiology are controlled by the differential expression of genes during hibernation.

Animals↗
PubMed1988

The influence of hibernation on the interferon response in the spotted suslik (Spermophilus suslicus).

According to the season, the environmental temperature, and their physiological state (whether active or in hibernation), spotted susliks produce different amounts of interferon (IFN) in response to intraperitoneal induction with Newcastle disease virus (NDV). Even though injection of NDV aroused hibernating animals, susliks treated during deep winter hibernation or artificial summer hibernation, or when aroused from winter hibernation, had significantly less IFN in their serum and organs than animals active in summer. Minced tissues taken from such animals and infected with NDV in vitro produced similar relative amounts of IFN. The effects of other environmental factors were studied: IFN production in vivo was increased by a high concentration of CO2 (5%) in the air, but decreased by electric shock stress. A hyporeactive response to IFN induction in vivo was produced in active susliks but not in animals hibernating in summer. These changes in the IFN system associated with season and physiological state cannot be explained merely in terms of the effect of differences in body temperature; they involve also adaptive changes in the animal associated with the onset of hibernation.

Animals↗
PubMed1988

Interferon production in leukocytes of spotted sousliks--effect of hibernation on the interferon response in vitro.

A comparative study of interferon (IFN) production (types alpha and gamma) was carried out using leukocytes from blood, spleen, and peritoneal cavity of sousliks (ground squirrels) active in summer, hibernating in winter, awakened from hibernation in winter, and hibernating in summer. Newcastle disease virus, Radom velogenic strain (NDV-R), and lipopolysaccharide from Escherichia coli (LPS) were used as inducers for IFN-alpha and phytohemagglutinin M (PHA) and concanavalin A (ConA) for IFN-gamma production. There were significant differences between the titers of IFN-alpha and IFN-gamma produced by leukocytes from sousliks hibernating in winter and in summer in comparison with titers of IFNs produced by cells of sousliks active in summer. Cells of hibernating spotted sousliks exhibited diminished IFN production. The IFN production in blood and peritoneal leukocytes of sousliks awakened from winter hibernation was also lower than that observed in cultures of leukocytes of sousliks active in summer, and higher when spleen leukocytes of sousliks awakened from hibernation were examined.

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↗
PubMed1982

Hibernation in the female Turkish hamster (Mesocricetus brandti): an investigation of the role of the ovaries and of photoperiod.

The possible role of the ovaries in hibernation was examined by comparing patterns of hibernation in intact and ovariectomized Turkish hamsters (Mesocricetus brandti). Ovariectomy had little, if any, effect on hibernation in these studies. However, females which were anovulatory prior to cold exposure entered hibernation more rapidly as compared to cycling females. Most females (both intact and ovariectomized) maintained in short days returned to a second phase of hibernation several months after terminating the initial phase. In contrast, most females housed in long days failed to show a second phase of hibernation. Thus, it is possible that effects of day length may be more important than effects of ovarian hormones in regulating hibernation in the female Turkish hamster.

Animals↗
PubMed1988

Uterine steroid hormone receptors during the estrous cycle and during hibernation in the Turkish hamster (Mesocricetus brandti).

The Turkish hamster is a long-day breeder that hibernates for 4-5 mo if exposed to a short-day, cold environment. The objective of this study was to assess the uterine responsiveness of the hibernating animal to ovarian steroids. Our approach was 1) to characterize and determine uterine estrogen (E) and progesterone (P) receptors (R) during hibernation as compared to the levels observed in cycling females that had terminated hibernation, and 2) to assess the responsiveness of the uterus to E during hibernation by its ability to induce uterine P receptor. Females were exposed to short days (10L:14D) for 2 mo and then were placed in a cold-room (10L: 14D, 6 +/- 1 degrees C). After 2 or 4 mo in the cold, hibernating animals were killed and uterine steroid receptors were determined by 3H-steroid binding assay. Uterine receptors were also determined in cycling Turkish hamsters on each morning of the estrous cycle. Values for uterine receptors (pmol/g tissue, n = 4-6) during the estrous cycle (estrus, diestrus I, diestrus II, proestrus) were: 4.3 +/- 0.78, 3.9 +/- 0.19, 4.1 +/- 0.25, 3.7 +/- 0.5 for cytosolic ER; 36.6 +/- 5.8, 32.2 +/- 6.8, 36.3 +/- 1.5, 54.4 +/- 1.9 for cytosolic PR; 0.59 +/- 0.11, 0.54 +/- 0.07, 1.06 +/- 0.05, 1.42 +/- 0.17 for nuclear ER. Hibernating (torpid) animals sampled after 2 mo in the cold showed a significant (p less than 0.05) depression of cytosolic ER (2.6 +/- 0.12, n = 5) and cytosolic PR (19.0 +/- 2.6, n = 8) as compared to any day of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of induction versus prevention of hibernation on reproduction in captive male and female woodchucks (Marmota monax).

Reproductive performance and gonadal function were studied in two groups of woodchucks containing 16 females and 8-9 males each. The control group was maintained indoors under conditions that do not induce hibernation, including fluctuating temperature of 6-12 degrees C, ad libitum feed, and exposure to natural and incandescent light. The hibernaculum-housed group was, in addition, provided conditions that do induce hibernation, including temperature reduced to 5.6 +/- 1.7 degrees C, no food, and no light from 19 November to 21 February. Hibernaculum housing caused 67% of males and 94% of females to hibernate with reduced body temperature for significant periods of times. Compared to control conditions, hibernaculum housing caused (p less than 0.05) a delay in testis recrudescence, a reduction in mean peak testis size (1.8 vs. 3.0 cc) and its mean date of occurrence (14 March vs. 15 February), a reduction in mean testosterone concentrations in February, and a reduced incidence of fertile matings (22 vs. 88%). In females, hibernation resulted (p less than 0.05) in a greater loss in body weight and a reduced pregnancy rate (31 vs. 82%), which was related to post-hibernation body weights that, in turn, were related to prehibernation body weights. Among hibernaculum-housed females, the pregnancy rate was lower in smaller females (0%; 2.0 +/- 0.1 kg) than in the larger ones (63%; 2.9 +/- 0.1 kg). The results demonstrate that the experimental imposition of hibernation-inducing conditions for 3 mo prior to the expected breeding season can alter subsequent reproductive performance in laboratory-maintained woodchucks, whereas a reproductive rate of 88% can be obtained in animals prevented from hibernating during their first year in captivity.

Animals↗
PubMed1973

Maintenance of normal corneal thickness in the cold in vivo (hibernation) as opposed to in vitro.

1. Corneal thickness was measured in vivo in normothermic and hibernating (body temperature = 7-10 degrees C) woodchucks and the [Na(+)], [K(+)], [Mg(2+)] and water content of woodchuck and rabbit corneas were determined on freshly isolated tissues.2. Woodchuck eyes from both normothermic and hibernating animals were incubated in moist chambers at 5 or 11 degrees C and the corneal thickness was measured periodically.3. Woodchuck corneas undergo continuous swelling when kept in vitro in a moist chamber at either 5 or 11 degrees C. The rate of this swelling was the same for eyes from active and hibernating animals; it was almost completely reversible upon rewarming at 35 degrees C.4. In the hibernating woodchuck the corneal thickness did not increase measurably, even after several days of hibernation, although the mean corneal temperature was 9.4 degrees C.5. At 7 degrees C, the lactate production of corneas from both hibernating and normothermic woodchucks was reduced to about one fifth its levels measured at 37 degrees C. Oxygen consumption was also greatly reduced in the cold although the endothelial O(2) consumption of corneas from hibernating woodchucks appears to be relatively insensitive to cold.6. It is concluded that removal of the eye and/or the in vitro conditions per se render the cornea more vulnerable to the effects of cold, possibly as a result of the elimination of the influences of orbital tissues and/or secretions or as a result of changes in some intrinsic properties of the cornea due to the elimination of neurohumoural factors or the release of autocoids.7. The finding that normal corneal thickness can be maintained under conditions where the environment is maintained essentially constant for days strongly argues against the validity of the recently proposed nonsteady-state theory of corneal thickness control.

Animals↗
PubMed1975

Renal function in the hibernating, and hypothermic hamster Mesocricetus auratus.

Plasma and urine concentrations of Na+, K+, and urea were examined in hibernating, hypothermic, and normothermic hamsters. Plasma Na+ and K+ appear unaffected by 48 h of hypothermia (T-re 7 degrees C); however, plasma Na+ increased (P smaller than 0.05) from control values of 125.8 plus or minus 10.2 to 173 plus or minus 9.2 meg/liter in hibernators. Plasma K+ of the hibernator increased to 9.6 plus or minus 3.2 meq/liter from control values of 5.5 plus or minus 0.8 meq/liter (P smaller than 0.05). Plasma urea concentrations were increased (P smaller than 0.05) in both metabolically depressed groups from a control value of 0.5 plus or minus .05 to 0.8 plus or minus .16 and 7.2 plus or minus 2.8 mM in hypothermic and hibernating groups, respectively. Urine concentrations of solute for the hypothermic animals showed no detactable change from control values for Na+ and a decrease for both K+ and urea. Concentrations from hibernators showed a decrease from control values for both Na+ and K+ with no detectable change in urea. Renal tissue slice analysis demonstrated a marked corticomedullary solute gradient for Na+ and urea in normothermic control animals which is eliminated in hamsters hypothermic for 48 h and reduced in animals hypothermic for 15 min. Rewarming animals did not show a return of the solute gradient at T-re 18 degrees C. However, animals that had rewarmed to T-re 37 degrees C demonstrated a complete return with no difference (P greater than 0.05) from control values. Hibernators showed a slight (P smaller than 0.05) gradient for Na+ and no gradient for urea. Animals in all instances demonstrated a decrease in K+ concentration from cortex to papilla. A greater concentration of K+ was found in the renal cortex of animals hypothermic for 15 min and in hibernators (P smaller than 0.05).

Animals↗
PubMed2003

Tissue-specific depression of mitochondrial proton leak and substrate oxidation in hibernating arctic ground squirrels.

A significant proportion of standard metabolic rate is devoted to driving mitochondrial proton leak, and this futile cycle may be a site of metabolic control during hibernation. To determine if the proton leak pathway is decreased during metabolic depression related to hibernation, mitochondria were isolated from liver and skeletal muscle of nonhibernating (active) and hibernating arctic ground squirrels (Spermophilus parryii). At an assay temperature of 37 degrees C, state 3 and state 4 respiration rates and state 4 membrane potential were significantly depressed in liver mitochondria isolated from hibernators. In contrast, state 3 and state 4 respiration rates and membrane potentials were unchanged during hibernation in skeletal muscle mitochondria. The decrease in oxygen consumption of liver mitochondria was achieved by reduced activity of the set of reactions generating the proton gradient but not by a lowered proton permeability. These results suggest that mitochondrial proton conductance is unchanged during hibernation and that the reduced metabolism in hibernators is a partial consequence of tissue-specific depression of substrate oxidation.

Animals↗
PubMed1985

GDP binding to hamster brown fat mitochondria is reduced during hibernation.

Preparation for hibernation is accompanied by increased thermogenic capacity of brown fat (BAT), an important site of thermogenesis during arousal from hibernation. This study examined whether that thermogenic capacity is reduced in hibernation and reactivated during arousal. In one set of experiments, Syrian hamsters were exposed to short photoperiod (10:14 light-dark) and cold (7 degrees C). Those not hibernating at death (n = 10) served as controls for those that were (n = 9). A third group (n = 10) was killed 80-90 min after arousal was initiated by manual perturbation. Mitochondrial GDP binding (nmol/mg mitochondrial protein) was used to estimate thermogenic capacity. In a second experimental series, BAT citrate (si)-synthase and 3-hydroxyacyl-CoA dehydrogenase activities were measured in hibernating and nonhibernating hamsters. Although there were no differences in the maximum activities of these enzymes, GDP binding was markedly lower in the hibernators relative to the nonhibernators (0.214 +/- 0.031 vs. 0.535 +/- 0.039). However, in the partially aroused hamsters, GDP binding had doubled (0.438 +/- 0.04). Thus hibernation is accompanied by a substantial reduction of BAT thermogenic capacity (as manifested by GDP binding), which is reversed during arousal. The rapidity of this reversal indicates that it does not involve the synthesis of new GDP binding sites.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Cardiac mechanical restitution in active and hibernating Richardson's ground squirrel.

The cardiac mechanical restitution was compared in papillary muscles between the active and the hibernating Richardson's ground squirrels at 0.1, 2.8, and 5 mM external Ca2+ concentration [( Ca2+]o). The amplitude of the restitution was significantly higher in hibernating animals between 37 and 7 degrees C at all [Ca2+]o. The first postrest contraction (F1) was highest at 20 degrees C and lower at 37 and 7 degrees C in both groups. The pause duration for maximum F1 was 30 s in active but 10 s in hibernating animals at 37 degrees C and increased to 100 s in both groups at 7 degrees C. The postrest potentiation was eliminated by 10(-6) M ryanodine at 20 degrees C in both groups, and this inhibitory effect was more pronounced in the hibernating group. Together, our results suggest that the activator Ca2+ for excitation-contraction coupling is mainly derived from the sarcoplasmic reticulum (SR) pool in both active and hibernating ground squirrel, and the dependence on SR Ca2+ release via ryanodine-sensitive Ca2+ channels is more marked in the hibernating state. Furthermore, there is no significant difference in sensitivity of the cardiac mechanical restitution to [Ca2+]o between the active and the hibernating condition.

Activity Cycles↗