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At least 955 records · Page 53Linked to original sources
PubMed1978

Control of non-shivering thermogenesis in a hibernator.

Present experiments indicate that in hedgehogs two different control mechanisms of non-shivering thermogenesis (NST) exist. During arousal from hibernation catecholamines control heat production in the interscapular brown adipose tissue. In a non-hibernating state, cold-induced NST is controlled by a desoxycorticosterone-like acting compound. The effector system of this second mode of NST is obviously not the interscapular brown fat but a layer of brown adipose tissue which covers the whole back of the hedgehog.

Animals↗
PubMed1976

Miniature end-plate potentials and sensitivity to acetylcholine in the fast and slow limb muscles of hibernating golden hamsters.

During hibernation reduction of frequency of the miniature end-plate potential (m.e.p.p.) was observed. This parameter was reduced in the extensor digitorum longus (EDL) muscle to 16% and in the soleus muscle to 7% of values found in awake animals. The ACh-sensitive area of the individual muscle fibres in both types of muscle increased about three times during hibernation.

Acetylcholine↗
PubMed1990

Relationships between body temperature, thermal conductance, Q10 and energy metabolism during daily torpor and hibernation in rodents.

In the present paper we examine the ability of rodents to maintain body temperature (TB) following the marked reductions in metabolic heat production associated with torpor. Previously published values for metabolic rate (M), TB and ambient temperature (TA) were used to calculate thermal conductances (C') during normothermy and torpor in rodents capable of daily torpor (11 species) and hibernation (18 species). Values of C' for torpid animals are uniformly lower than C' in normothermic animals. In addition, C' of normothermic and torpid rodents decreases with increasing body mass (BM). However, the slope of the relationship between C' and BM is almost 4-fold greater for normothermic than for torpid animals. Thus, the ability of torpid rodents to conserve body heat by reducing C' decreases with increasing mass. Rodents that use daily torpor tend to be small and they tend to maintain TB well above TA during torpor. Hibernators tend to be larger and regulate TB relatively close to TA. Thus, the reductions in C' appear to be closely correlated with the level of TB regulation during torpor. We suggest that the changes in C' represent a suite of physiological adaptations that have played a central role in the evolution of torpor, enabling rodents to regulate TB above TA during periods of very low heat production. Based on the approach used here we address the controversy of whether reductions in M during torpor are due entirely to temperature effects or whether metabolic inhibition in addition to temperature effects may be important. We suggest that the controversy has been confused by using Q10 to evaluate the relationship of M and TB in endotherms.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1989

Auditory brainstem responses in ground squirrels arousing from hibernation.

Auditory brainstem responses (ABRs) were recorded in ground squirrels (Citellus lateralis) arousing from hibernation. Squirrels implanted with recording screws to record ABRs, and a thermistor to record brain temperature, were placed in a cold room at 9 degrees C on a 2L:22D light-dark cycle. Hibernating animals were moved from the cold room and ABRs recorded during arousal. The responses showed a gradual development of all brainstem peaks. At low temperatures there were very long latencies to the peaks. The amplitudes of the peaks increased (with fluctuations) as brain temperature increased. The data indicate that neural generators on the brainstem auditory pathway were all activated early in arousal. These results do not support the hypothesis that successive peaks appear and grow in amplitude only after previous peaks are fully developed.

Acoustic Stimulation↗
PubMed1992

Expression of myosin heavy and light chains and phosphorylation of the phosphorylatable myosin light chain in the heart ventricle of the European hamster during hibernation and in summer.

We investigated the expression of myosin subunits (myosin heavy chains) as well as light chains and the in vivo phosphorylation of the phosphorylatable myosin light chain in the heart ventricle of the adult male European hamster (Cricetus cricetus L.). Two myosin heavy chain isoenzymes could be detected under native and denaturing electrophoretic conditions having high (alpha-myosin heavy chain) and low (beta-myosin heavy chain) enzymatic activity. Enzymatic activity of alpha- and beta-myosin heavy chain revealed a different temperature dependency. When temperature increased ATPase activity of the alpha-myosin heavy chain isoenzyme increased relatively more than ATPase activity of the beta-myosin heavy chain isoenzyme. Summer animals expressed predominantly the beta-myosin heavy chain (79% of total myosin) while during hibernation the alpha-myosin heavy chain expression increased to 53% of total myosin. Winter-active hamsters kept at 22 degrees C and 12 h day/night rhythm showed the same myosin heavy chain isoenzyme pattern as summer-active animals. Two myosin light chain forms were expressed in the ventricle of all animal groups. The in vivo phosphorylation level of the phosphorylatable myosin light chain decreased from 45% in summer-active hamster to 23% during hibernation.

Animals↗
PubMed1986

Excitation-contraction coupling in the myocardium of hibernating chipmunks.

In the myocardium of nonhibernating chipmunks, replacing external Ca by Sr markedly prolongs the action potential plateau with an increase in contraction, while in preparations from hibernating animals this procedure inhibits both responses. Pretreatment with 4-aminopyridine causes a prolongation of the action potential plateau by Sr in hibernating animals.

Action Potentials↗
PubMed1980

Naltrexone influence on hibernation.

In the garden dormouse, opiate receptor blockade by naltrexone decreased the score for sleeping behaviour during hibernation at 24.00 h, indicative of a possible involvement of endorphins in the control of hibernation.

Acclimatization↗
PubMed1982

Early skin responses of hibernating and nonhibernating ground squirrels to topical applications of DMBA.

Skin patches on hibernating and nonhibernating ground squirrels were treated with multiple topical applications of the carcinogen 7,12-dimethylbenza(a)anthracene. Nonhibernators showed blistering, peeling, drying, hair loss, increased vascularization and hyperpigmentation in proportion to DMBA concentration. The latter was apparently due to a) an increased number of dermal and epidermal melanocytes and b) the appearance of melanocytes with large coarse cytoplasmic granules. Notably, hibernators remained free of gross skin changes and were histologically similar to untreated controls.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

The effect of hibernation on the positional distribution of ethanolamineglycerophospholipid fatty acids in hamster brain membranes.

Microsomal and myelin membrane fractions were prepared from the brains of warm-adapted (room temperature) and hibernating Syrian Hamsters (Mesocricetus auratus). Ethanolamineglycerophospholipids were isolated and subjected to a fractionation scheme to separate the fatty acids of the plasmenylethanolamine and the phosphatidylethanolamine 1 and 2 positions. The major changes in microsomal phosphatidylethanolamine with hibernation were relative increases in 18:1 at the 1 position and 20:4(n-6) in the 2 position. In myelin, 18:1 increased and 18:0 decreased at the 1 position while the 2 position showed an increase in 16:0 and a decrease in 22:6(n-3). Plasmenylethanolamine fatty acids also changed in microsomes and myelin although the magnitudes were not as great and confined to longer chain fatty acids. In both membranes, fatty acid alterations were position-specific, and no new types of fatty acids were introduced at any position.

Animals↗
PubMed2002

Ubiquitin conjugate dynamics in the gut and liver of hibernating ground squirrels.

Protein synthesis is severely depressed in hibernating mammals. In the absence of significant protein synthesis, the continued turnover of proteins as a function of normal cellular activity would result in the net depletion of protein pools. We measured levels of ubiquitylated proteins in the gut of thirteen-lined ground squirrels ( Spermophilus tridecemlineatus) and liver of golden-mantled ground squirrels ( Spermophilus lateralis). In both tissues, ubiquitin conjugate concentrations increased during entrance into torpor and were elevated 2-3 fold by late torpor compared with levels in active animals. The data are consistent with a depression of proteolysis with a resultant high level of ubiquitylated proteins during the natural hypothermia of torpor. The periodic returns to euthermy during the hibernation season allow for degradation of these conjugated proteins and may serve to restore protein pools.

Animals↗
PubMed2000

Glucose uptake increases relative to oxygen consumption during short-term hibernation.

BACKGROUND: Although glucose uptake is increased in chronically hypoperfused, viable myocardium, the dynamic changes in glucose uptake relative to oxygen consumption in "short-term" models of hibernation have not been fully explored. METHODS: 14 anesthetized swine were instrumented with an hydraulic occluder and flow probe on the proximal LAD artery. Blood flow was reduced approximately 30% for 1 hour. Myocardial blood flow and uptake of oxygen, free fatty acids, glucose and lactate were determined in the LAD region at baseline and at 10, 30, and 60 minutes of ischemia. Transmural biopsies for ATP and creatine phosphate (CP) were obtained in the LAD region prior to and at 15 and 45 minutes of ischemia. In 5 animals, glycogen was assayed at baseline and at the end of 60 minutes of ischemia. RESULTS: In the LAD region, myocardial oxygen consumption was reduced from 2.06 +/- 0.16 micromol/min/gram to 1.46 +/- 0.13 micromol/min/gram (P < 0.05). By 15 minutes of ischemia, transmural creatine phosphate fell from 7.48 +/- 0.76 micromol/g-wet weight at baseline to 6.19 +/- 0.32 micromol/g-wet weight (P < 0.05) but normalized by 45 minutes of ischemia (7.39 +/- 0.56 micromol/g-wet weight; NS). Between 10 and 60 minutes of constant flow reduction, glucose uptake as a percentage of MVO2 increased from 3 +/- 2% to 10 +/- 2% (P < 0.05) while lactate uptake increased from -9 +/- 9% to -1 +/- 2% (P < 0.05). Glycogen decreased from 27.8 +/- 3.7 at baseline to 16.9 +/- 1.2 micromol/g-wet weight at end-ischemia. CONCLUSIONS: In this model of short-term hibernation, glucose and lactate uptake increase relative to oxygen consumption during sustained ischemia, and temporally coincide with the recovery of bioenergetics. The findings are consistent with the notion that glycolytically derived ATP is important for the maintainance of energy supply during sustained ischemia.

Animals↗
PubMed2003

Molecular adaptation to hibernation: the hemoglobin of Dryomys nitedula.

The oxygen binding properties of Dryomys nitedula hemoglobin (Hb) were investigated as a function of pH both in the absence and in the presence of its physiological cofactors (i.e. chloride ions and 2,3-biphosphoglyceric acid) and at different temperatures. Moreover, the alpha- and beta-chains of the Dryomys Hb were partially sequenced. The results obtained show that the effects of Bohr protons, chloride ions, organic phosphates and temperature are significantly lower for Dryomys Hb than for human Hb. Thus, the increase in Hb oxygen affinity, resulting from the reduction of red cell organic phosphates and body temperature that occurs during hibernation, is advantageous for loading oxygen at the lung level without compromising oxygen release at the tissues, as could occur if Dryomys Hb had similar functional properties to those of other non-hibernating mammals. Furthermore, it is possible that the reduced Bohr effect may moderate the potential effects of increased CO(2) associated with prolonged apnea on the loading and unloading of oxygen. Moreover, the overall heat of oxygenation (Delta H) for Dryomys Hb is much less exothermic than that of the human Hb and it is completely independent of the 2,3-biphosphoglyceric acid concentration.

2,3-Diphosphoglycerate↗
PubMed2006

Effect of temperature on the development of Schistosoma japonicum within Oncomelania hupensis, and hibernation of O. hupensis.

The objectives of this investigation were to assess the effect of temperature on the development of Schistosoma japonicum harboured in Oncomelania hupensis and to determine the lowest temperature threshold at which the hibernation of O. hupensis occurs. In the first experiment, adult infection-free O. hupensis, collected from Jiangsu province in eastern China, were infected with S. japonicum miracidia and raised at different temperatures under laboratory conditions. The development of miracidia until the release of cercariae was monitored employing the cercarial shedding method. In the second experiment, batches of O. hupensis were kept at temperatures below 13 degrees C with the temperature gradually reduced. Snail activity was assessed by a pin puncture method. We found a positive relationship between the development of S. japonicum within O. hupensis and temperature. In snails kept at 15.3 degrees C, S. japonicum arrested their development, while the fastest development occurred at 30 degrees C. The temperature at which half of the snails were in hibernation (ET(50)) was 6.4 degrees C. Our results underscore the pivotal role temperature plays on the biological activity of O. hupensis and the development of S. japonicum within the intermediate host. These findings are likely to have implications for the transmission of schistosomiasis in a warmer future China.

Animals↗
PubMed2005

Seasonal effects of Selank on the behavior of hibernating animals.

We studied the seasonal effects of peptide preparation Selank on orientation and exploratory activity in 36 arctic ground squirrels Citellus undulatus in the open-field and hole-board tests. Selank most significantly increased behavioral activity of hibernating animals in the spring and fall. The test peptide had no effect on locomotor activity of animals. The selective stimulatory effect of Selank on exploratory behavior of hibernating animals was season-dependent. The maximum effect was observed under conditions of seasonal depression-like state.

Animals↗
PubMed1984

Metabolic consequences of limited substrate anion permeability in brown fat mitochondria from a hibernator, the golden hamster.

Brown fat mitochondria obtained from a hibernator, the golden hamster, were investigated in order to elucidate the significance of membrane permeability for metabolic functioning at different temperatures. The mitochondria were shown to have active permeases for phosphate and pyruvate, but very poorly developed permeases for di- and tricarboxylate substrate anions. This was shown with both osmotic swelling techniques and respiration-driven uptake studies. It was shown that the very limited malate permeation observed was compatible with it being a non-carrier-mediated diffusion process. The role of malate transport in supporting fatty-acid oxidation in vitro as a function of temperature was studied in detail. The results support our earlier suggestion that physiologically pyruvate carboxylase probably functions to generate oxaloacetate when high concentrations of condensing partner are needed during thermogenesis. They may also explain earlier observations that acetate was produced from palmitoyl-carnitine at low temperatures even when malate was present; this is here shown to be due to the limited malate permeability at these low temperatures. Thus, even at the body temperature of the hibernating hamster (4-5 degrees C), brown fat is probably able to combust fatty acids totally.

Adipose Tissue, Brown↗
PubMed1991

Altered properties of calsequestrin and the ryanodine receptor in the cardiac sarcoplasmic reticulum of hibernating mammals.

A novel isoform of calsequestrin was identified in sarcoplasmic reticulum vesicles from myocardial tissue of two species of hibernating ground squirrel. The protein was identified as calsequestrin by its cross-reactivity with antibodies raised against bovine cardiac calsequestrin, its pH-sensitive mobility in sodium dodecylsulphate-polyacrylamide gels, staining blue with the cationic carbocyanine dye 'Stains-All', binding peroxidase-conjugated concanavalin A, its endoglycosidase F sensitivity. Its NH2-terminal amino acid sequence is similar, but not identical, to that already determined for cardiac calsequestrin. Some of the biochemical properties of this protein distinguish it from the other mammalian isoforms. It has a unique electrophoretic mobility in both alkaline and neutral sodium dodecylsulphate-polyacrylamide gel electrophoresis, it appears to have a molecular weight approximately 7% greater than that of cardiac calsequestrin from other mammalian species, and its glycosylation pattern differs. This novel form of calsequestrin is expressed in cardiac SR vesicles which possess an abnormally high number of Ca2(+)-release channel/ryanodine receptor molecules. This ryanodine receptor also shows an altered Ca2(+)-sensitivity of ryanodine binding. The divergent biophysical properties of this novel form of cardiac calsequestrin, together with the apparently atypical ryanodine receptors in the cardiac sarcoplasmic reticulum membranes may have some functional significance in the adaptive mechanisms which allow the heart to function despite the severely reduced body temperatures (to approx. 0 degree C) encountered during hibernation.

Amino Acid Sequence↗
PubMed1988

VIP-like immunoreactivity in the anterior hypothalamic area of a hibernating bat varies with physiological state.

Vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the anterior hypothalamic area (AHA) was studied in 15 bats which are seasonal hibernators, using the unlabeled antibody enzyme method of Sternberger. Our results showed that the density of immunoreactive fibers and terminal plexuses in the AHA was greatest in euthermic animals and decreased dramatically when body temperature and cardiac rate were depressed and animals entered hibernation.

Animals↗