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At least 991 records · Page 55Linked to original sources
PubMed1991

Warming up for sleep? Ground squirrels sleep during arousals from hibernation.

Hypothermia during mammalian hibernation is periodically interrupted by arousals to euthermy, the function of which is unknown. We report that arctic ground squirrels (Spermophilus parryii) consistently sleep during these arousals, and that their EEG shows the decrease in slow wave activity (delta power) that is characteristic of a declining requirement for sleep. These results are consistent with the novel hypothesis that the need for sleep slowly accumulates during torpor, and that returning to euthermy is periodically required to allow sleep. Sleep thus seems to be energetically expensive for a hibernating mammal, and cannot be considered solely a strategy for saving energy.

Animals↗
PubMed1978

Phospholipid composition of hibernating ground squirrel (Citellus lateralis) kidney and low-temperature membrane function.

1. Phospholipid analysis of kidney lipids from active and hibernating ground squirrels (Citellus lateralis) indicate that molar quantities of phosphatidyl choline increase, while sphingomyelin decreases in hibernating animals. 2. Both of these changes are in such a direction as to enhance membrane fluidity and possibly contribute to low-temperature membrane function in these organisms.

Animals↗
PubMed1979

Changes in brain ganglioside composition of normothermic and hibernating golden hamsters (Mesocricetus auratus).

1. Brain ganglioside patterns of normothermic and hibernating golden hamsters (Mesocricetus auratus) and laboratory mice had been investigated. 2. The ganglioside pattern of normothermic golden hamsters in comparison to that of mice is characterized by an unusual high amount of the polar trisialoganglioside GT1. 3. In the hibernating golden hamster in contrast to normothermic counterparts the brain gangliosides are more polar (polysialization-effect). 4. The results are discussed with regard to the hypothesis that neuronal membranes provided with more polar gangliosides at lower environmental temperatures might be more efficient with respect to the high complexation ability of gangliosides with Ca2+-ions.

Animals↗
PubMed1982

Changes in lipid composition of the brain cellular membranes of an hibernating mammal during its circannual rhythm.

The lipid composition of whole brain hemispheres and subcellular fractions of European Hamsters (Cricetus cricetus) was investigated at four different periods of the year. 1. No difference was observed in winter between hibernating animals and active animals awake for 24 hr. 2. A slight increase of cholesterol/phospholipid molar ratio was observed in winter. 3. A slight increase of the ratio ethanolamine phosphoglycerides/choline phosphoglycerides was observed in summer and autumn. 4. Some changes in sugar moieties proportions of gangliosides were observed, with a tendency of increased polysialylation in winter. 5. An increase of docosahexaenoic acid was observed in summer, while a slight increase of linoleic acid and of the monounsaturated fatty acids was observed in winter. These changes were mainly exhibited in the synaptosomal fraction. All the changes observed were of very small magnitude and might not be sufficient for the maintenance of a fluid state of membranes during hibernation.

Animals↗
PubMed1991

Morphometric and metabolic indices of disuse in muscles of hibernating ground squirrels.

1. Morphological, biochemical and metabolic characteristics of hindlimb muscles from summer-active (SA), winter-active (WA) and hibernating (H) golden-mantled ground squirrels (Spermophilus lateralis) were examined to identify alterations resulting from seasonal periods of inactivity. 2. Cross-sectional areas of fibers from the soleus were reduced in both WA and H, although only significantly (P less than 0.05) in WA. Fibers in the EDL exhibited significant reductions in cross-sectional areas in both H and WA groups. Muscle fiber and capillary densities were altered in quantitative agreement with changes in cross-sectional areas. 3. Protein content was reduced 20% (P less than 0.05) in EDL from H and WA groups, but reductions (10%) in the soleus were not statistically significant. RNA content in WA and H groups was significantly decreased in soleus (20%) and EDL (35%) compared with SA, but DNA content was unchanged. 4. In the plantaris, triglyceride content was unchanged, but citrate synthase activity in H (210 +/- 13 mumol min-1 g-1) was significantly greater than in SA (177 +/- 10). In contrast, LDH activity in H was reduced by 25% (P less than 0.05) compared with SA. 5. These results demonstrate atrophic effects associated with seasonal inactivity in hibernating ground squirrels, but suggest the existence of natural mechanisms which limit the response.

Adaptation, Physiological↗
PubMed1992

Regulation of oxidative activity and delta psi of liver mitochondria of active and hibernating gophers. The role of phospholipase A2.

1. In the present work the initially lowered oxidase activity of liver mitochondria of hibernating gophers is shown to increase upon Ca(2+)-loading, after freezing-thawing repeated three times and after swelling in a medium containing potassium acetate as well as in a hypotonic sucrose medium. 2. In all cases the inhibition of phospholipase A2 hindered the increase of the oxidase activity of mitochondria. 3. Mitochondria of hibernating gophers have a lowered delta psi in comparison with active animals, which is restored in the hypotonic medium.

Animals↗
PubMed1988

A pharmacological study of hibernation in rodents.

1. Hamsters and ground squirrels in deep hibernation were infused intra-arterially with drugs. 2. Norepinephrine and epinephrine sometimes caused arousal, sometimes transitory effects. 3. Adrenalectomy did not affect arousal. L-DOPA and amphetamine produced a slow arousal. 4. Arousal was blocked with alpha-methyltyrosine and the block was released with L-DOPA, DL- and L-threo-DOPS resulted in arousal and bromocriptine did not cause arousal, indicating that dopamine was not necessary for arousal. 5. Isoproterenol caused a transient increase in heart rate which was blocked by propranolol. 6. Phenylephrine caused vasoconstriction, but did not result in arousal. 7. No drug increased the sensitivity to peripheral stimuli during hibernation.

Adrenalectomy↗
PubMed1989

Neuronal plasticity in the hedgehog supraoptic nucleus during hibernation.

The purpose of the present study was to identify processes of plasticity in the receptive field of neurosecretory neurons of the supraoptic nucleus during hibernation in the hedgehog, in order to correlate them with the increased neurosecretory activity observed in this nucleus during this annual period. Using the Rapid Golgi method, a quantitative study was conducted in the receptive field of bipolar and multipolar neurons (the main components of the nucleus). Results indicate a generalized increase in the following characteristics: (1) number of dendritic spines per millimeter along the dendritic shafts; (2) degree of branching in the dendritic field; and (3) dendritic density around the neuronal soma. These data demonstrate modification of the dendritic field in the supraoptic nucleus during hibernation, a change undoubtedly related to functional conditions. Since the observed changes affect structures such as dendritic spines which are directly related to the arrival of neural afferences, the discussion is centered on the types of stimuli which may be responsible for the observed processes.

Animals↗
PubMed1992

Hibernation-induced structural changes in synaptic contacts between mossy fibres and hippocampal pyramidal neurons.

Mossy fibre synapses on the CA3 hippocampal neurons in the brain of ground squirrels repeatedly undergo a striking structural transformation during hibernation. In the middle of hibernation bout the giant complex mossy fibre synapses have a reduced number of dendritic spine infoldings that are smaller and have a decreased number of postsynaptic densities in comparison with mossy fibre synapses of active animals. Two hours after arousal all these parameters of mossy fibre synapses increase and significantly exceed their levels not only in torpid but in active euthermic animals between bouts of torpor. The longer postsynaptic densities and the greater proportion of perforated postsynaptic densities were found soon after arousal. These rapid, reversible and repeated changes indicate a cyclic process of partial denervation/reinnervation of hippocampal neurons by mossy fibres in the course of the innate, stereotyped behaviour.

Animals↗
PubMed1990

Sudden infant death syndrome and hibernation: is there a link?

Two very large bodies of information seem to overlap, one being the epidemiological and pathological studies on sudden infant death syndrome (SIDS), the other being the research on hibernation. Until now, these two phenomena have been studied independently; however, it will be argued here that the role of the pineal gland, that of brown adipose tissue (BAT) and sleep patterns in both endothermic hibernating mammals and those babies presenting as SIDS provide clues and support for the hypothesis that SIDS is pathoplastic to the hibernatory response.

Adipose Tissue, Brown↗
PubMed1992

Seasonal and state-dependent changes in brain TRH receptors in hibernating ground squirrels.

Quantitative autoradiography was used to localize and quantify thyrotropin-releasing hormone (TRH) receptors in the brain of hibernating (H), winter euthermic (WE), and summer euthermic (SE) animals to further explore the state-dependent physiological and behavioral effects of TRH in ground squirrels. The pattern of [3H]MeTRH binding (Kd 6.7 +/- 0.1 nM) was heterogeneous and highly concentrated in structures primarily associated with the limbic forebrain. Statistically significant seasonal changes (SE vs. WE) were reflected by decreases in TRH receptor binding in the arcuate nucleus, dorsomedial nucleus, and ventral pallidum of WE animals. Increased binding in WE animals was evident in the suprachiasmatic nucleus and choroid plexus of the lateral ventricles. Significant state-dependent changes (WE vs. H) were characterized by decreases in TRH receptor binding in the hypothalamic paraventricular nucleus, medial preoptic area, ventral tegmental area, and choroid plexus of the lateral ventricles of H animals. Increased binding occurred in the anterior cortical nucleus of the amygdala in H animals. The results suggest that naturally occurring changes in central TRH systems may be important in the mediation of physiological and behavioral processes that undergo seasonal and state-dependent adjustments in hibernating mammals.

Animals↗
PubMed1993

NPY and galanin in a hibernator: hypothalamic gene expression and effects on feeding.

Neuropeptides such as neuropeptide Y (NPY) and galanin may play a role in regulating the pronounced seasonal changes in food intake shown by golden-mantled ground squirrels (Spermophilus saturatus). We used in situ hybridization histochemistry to localize the expression of NPY and galanin mRNA in the hypothalamus of normally feeding animals. NPY mRNA was abundantly expressed in the arcuate nucleus, while galanin mRNA was concentrated in both the arcuate nucleus and the dorsomedial nuclei. When NPY (0.1, 0.5, 2, and 8 micrograms) or galanin (0.1, 0.5, 2, and 8 micrograms) were injected into the third cerebral ventricle, food intake was significantly and dose-dependently increased over the subsequent 30 min. NPY stimulated significant increases in food intake for up to 2 h whereas galanin's effect did not extend beyond 30 min. Our results suggest that hibernating and nonhibernating rodents share common neural substrates for the regulation of food intake. Seasonal modulation of these neural pathways may contribute to annual cycles of food intake in hibernating mammals.

Analysis of Variance↗
PubMed1986

Persistence of weight gain and hibernation onset in juvenile thirteen-lined ground squirrels (Spermophilus tridecemlineatus) in spite of long-term administration of naloxone.

Sexual differences in body weight of juvenile thirteen-lined ground squirrels (Spermophilus tridecemlineatus) were significant (P less than 0.05) at all weeks of age except weeks 0-4, 6, 7, 9, 20 and 24. Hibernation onset between sexes did not differ significantly. Naloxone administration did not alter weight gain nor onset of hibernation when compared to saline controls.

Animals↗
PubMed1995

Anti-lymphoproliferative activity of brown adipose tissue of hibernating ground squirrels is mainly caused by AMP.

A fraction with mol wt < 1 kDa was obtained from the brown fat of hibernating ground squirrels (Citellus undulatus) by means of delipidization, acid extraction, ultracentrifugation and ultrafiltration. This fraction suppressed the proliferation of mouse lymph node cells under standard mitogenic stimuli for T lymphocytes. In contrast, the fraction with mol wt < 1 kDa obtained from the brown fat of active ground squirrels in spring did not display such activity. Further HPLC purification of the biologically active fraction and chemical and structural analysis of its most potent antilymphoproliferative component revealed that this is adenosine 5'-monophosphate (AMP). These data lend support to the notion that in hibernating mammals AMP originating, at least partly, from the brown fat down-regulates the seasonally-dependent proliferation of the thymus.

Adenosine Monophosphate↗
PubMed2006

Force development at elevated [Mg2+]o and [K+]o in myocardium from the freshwater turtle (Trachemys scripta) and influence of factors associated with hibernation.

The effects of high [Mg(2+)](o) on force development were examined for heart muscle of freshwater turtle. Plasma [Mg(2+)] during hibernation may increase drastically and like plasma [K(+)] approach values as high as 10 mM. Each experiment performed at either 20 or 5 degrees C involved four ventricular preparations of which one pair was exposed to 10, and one to 1 mMMg(2+). One preparation of each pair was furthermore exposed to 10 mM K(+), whereas the other was maintained at 2.5 mM K(+). During oxygenation, high relative to low [Mg(2+)](o) displayed a weak tendency to reduce twitch force; a tendency that was not reduced by elevations of [Ca(2+)](o). Severe hypoxia accentuated the negative effect of high [Mg(2+)](o). This effect disappeared, however, when hypoxia was combined with acidosis obtained by 24 mM lactic acid. In comparison to [Mg(2+)](o), high [K(+)](o) strongly depressed force development under both oxygenation and hypoxia, but no consistent interplay between the two ions was revealed. The negative inotropic effects of both high [Mg(2+)](o) and high [K(+)](o) were reduced or eliminated by 10 muM adrenaline. In conclusion the cardiac effects of elevations in [Mg(2+)](o) appear to be small during hibernation, in particular when considering the concomitant adrenergic stimulation and acidosis.

Acidosis↗
PubMed2006

Purification, identification, characterization, and cDNA cloning of a high molecular weight extracellular superoxide dismutase of hamster that transiently increases in plasma during arousal from hibernation.

We previously studied antioxidant profiles in the plasma of hibernating Syrian hamsters and found a transient increase of a superoxide radical-scavenging activity during the arousal phase. In this report, we purified and identified the high molecular weight superoxide dismutase (SOD)-like factor from the plasma of arousing hamsters. The cyanide-sensitive 240 kDa SOD-like factor showed a significant homology to mammalian extracellular SOD (EC-SOD) reported, although the molecular mass of EC-SOD was 135 kDa. The cDNA cloning revealed that the 240 kDa SOD-like factor was identical to the hamster ortholog of EC-SOD. It consisted of 245 amino acid residues including a signal sequence of 20 amino acid residues. Five cysteine residues that would participate in inner- and inter-subunit bonds were well conserved among species. Interestingly, there were four potential N-glycosylation sites in hamster EC-SOD, whereas there is only one site in other species. The amino acid sequence analysis indicated that three of the four sites were modified. These results suggest that the anomalistically high molecular weight of hamster EC-SOD is ascribed, at least in part, to the addition of extra sugar chains. Furthermore, results obtained here also propose the involvement of EC-SOD in the antioxidative defense of hibernating hamsters.

Amino Acid Sequence↗
PubMed2004

Effects of hibernation on mitochondrial regulation and metabolic capacities in myocardium of painted turtle (Chrysemys picta).

Painted turtles hibernating during winter may endure long-term exposure to low temperature and anoxia. These two conditions may affect the aerobic capacity of a tissue and might be of particular importance to the cardiac muscle normally highly reliant on aerobic energy production. The present study addressed how hibernation affects respiratory characteristics of mitochondria in situ and the metabolic pattern of turtle myocardium. Painted turtles were acclimated to control (25 degrees C), cold (5 degrees C) normoxic and cold anoxic conditions. In saponin-skinned myocardial fibres, cold acclimation increased mitochondrial respiratory capacity and decreased apparent ADP-affinity. Concomitant anoxia did not affect this. Creatine increased the apparent ADP-affinity to similar values in the three acclimation groups, suggesting a functional coupling of creatine kinase to mitochondrial respiration. As to the metabolic pattern, cold acclimation decreased glycolytic capacity in terms of pyruvate kinase activity and increased lactate dehydrogenase (LHD) activity. Concomitant anoxia counteracted the cold-induced decrease in pyruvate kinase activity and increased creatine kinase activity. In conclusion, cold acclimation seems to increase aerobic and decrease anaerobic energy production capacity in painted turtle myocardium. Importantly, anoxia does not affect the mitochondrial functional integrity but seems to increase the capacity for anaerobic energy production and energy buffering.

Adenosine Diphosphate↗
PubMed2006

Up-regulation of an extracellular superoxide dismutase-like activity in hibernating hamsters subjected to oxidative stress in mid- to late arousal from torpor.

Torpor-arousal cycles, one of the inherent features in hibernators, are associated with a rapid increase in body temperature and respiration, and it would lead to elevation of reactive oxygen species (ROS) generation. However, hibernators apparently tolerate this oxidative stress. We have observed in Syrian hamsters (Mesocricetus auratus) a maximal temperature shift and respiratory rate in mid- to late arousal (16-33 degrees C rectal temperature) from torpor. To examine plasma antioxidant status during arousal, we studied total superoxide radical-scavenging activity in plasma by electron spin resonance. The superoxide radical-scavenging activity reached a maximum at 32 degrees C, coincident with a peak in plasma uric acid levels, a ROS generation indicator. The up-regulated activity at 32 degrees C was attributable to the peak of the activity eluted at 260-kDa on gel-filtration chromatography, but was not to small antioxidant molecules such as ascorbate and alpha-tocopherol. The activity eluted at 260-kDa increased 3-fold at 32 degrees C compared with that of the torpid state, and was not detected either at 6 h after the onset of arousal or in the euthermic state. Moreover, the activity exhibited extracellular SOD-like properties: its induction in plasma by heparin injection and its affinity for heparin. Our results suggest that the 260-kDa extracellular SOD-like activity plays a role in the tolerance for the oxidative stress during arousal from torpor.

Animals↗