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PubMed1983

The concentrations of four neuropeptides in various brain areas of summer active and hibernating Spermophilus lateralis.

1. Twenty-six female golden-mantled ground squirrels were divided into four physiological stages; low weight summer, medium weight summer, high weight summer, and early hibernation period. 2. Sections of six brain regions from each animal were analyzed by radioimmunoassay for bombesin, cholecystokinin, neurotensin and somatostatin-like immunoreactivity. 3. Significant (P less than 0.05) between-stage differences were detected in thalamic bombesin, thalamic and hypothalamic neurotensin, and cerebellum somatostatin concentrations. 4. Significant (P less than 0.05) peptide concentration versus physiological stage correlations were found in cerebral cortex and hypothalamic cholecystokinin and hypothalamic somatostatin concentrations.

Animals↗
PubMed1993

Role of GABA in hypoxia tolerance, metabolic depression and hibernation--possible links to neurotransmitter evolution.

1. The roles of the inhibitory neurotransmitter GABA and the excitatory neurotransmitter glutamate in anoxic survival and anoxic death are discussed, with particular reference to the brain. 2. It is pointed out that the metabolic relationship between GABA and glutamate causes the neural levels of GABA to increase and glutamate to decrease during anoxia. 3. It is suggested that increased levels of GABA could mediate metabolic depression, and, thus, anoxic survival in ectothermic as well as endothermic vertebrates. Furthermore, evidence for a role of GABA in hibernation is discussed. 4. A hypothesis is presented suggesting that hypoxia has been a selective pressure in conserving GABA and glutamate as major inhibitory and excitatory neurotransmitters in vertebrates as well as invertebrates.

Animals↗
PubMed2006

Neuroprotective effects of hibernation-regulating substances against low-temperature-induced cell death in cultured hamster hippocampal neurons.

The neuroprotective effects of hibernation-regulating substances (HRS) such as adenosine (ADO), opioids, histamine and thyrotropin-releasing hormone (TRH) on low-temperature-induced cell death (LTCD) were examined using primary cultured hamster hippocampal neurons. LTCD was induced when cultures were maintained at <22 degrees C for 7 days. ADO (10-100 microM) protected cultured neurons from LTCD in a dose-dependent manner. The neuroprotective effects of ADO were reversed by both 8-cyclopenthyltheophilline (CPT; A(1) receptor antagonist) and 3,7-dimethyl-1-propargylxanthine (DMPX; A(2) receptor antagonist). Morphine (a non-selective opioid receptor agonist) was also effective in attenuating LTCD at an in vitro dose range of 10-100 muM. The neuroprotective effects of morphine were antagonized by naloxone (a non-selective opioid receptor antagonist). In addition, although [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]-enkephalin (DAMGO; mu-opioid receptor agonist), [D-Pen(2,5)]-enkephalin (DPDPE; delta-opioid receptor agonist) and U-69593 (kappa-opioid receptor agonist) were also effective, LTCD of cultured hippocampal neurons was not affected by TRH. Furthermore, histamine produced hypothermia in Syrian hamsters and protected hippocampal neurons in vitro at 100 microM. The neuroprotective effect of histamine was reversed by pyrilamine (H(1) receptor antagonist). Apoptosis was probably involved in LTCD. These results suggest that ADO protected hippocampal neurons in vitro via its agonistic actions on both A(1) and A(2) receptors, whereas morphine probably elicited its neuroprotective effects via agonistic effects on the mu-, delta- and kappa-opioid receptors. In addition, histamine also protected hippocampal neurons via its agonistic action on the H(1) receptor. Thus, HRS-like adenosine-, opioid- and histamine-like hypothermic actions would most likely induce neuroprotective effects against LTCD in vitro.

Adenosine↗
PubMed2004

Comparison of surface temperature in 13-lined ground squirrel (Spermophilus tridecimlineatus) and yellow-bellied marmot (Marmota flaviventris) during arousal from hibernation.

Surface temperatures (Ts) of eight 13-lined ground squirrels and seven yellow-bellied marmots were measured during arousal from hibernation using infrared thermography (IRT) and recorded on videotape. Animals aroused normally in 5 degrees C cold rooms. Body temperatures were recorded during arousal using both cheek pouch and interscapular temperature probes. Warming rate in arousal was exponential. Mean mass specific warming rates show the squirrels warm faster (69.76 degrees C/h/kg) than the marmots (4.49 degrees C/h/kg). Surface temperatures (Ts) for 11 regions were measured every few minutes during arousal. The smaller ground squirrel shows the ability to perfuse distal regions without compromising rise in deep body temperature (Tb). All squirrel Ts's remained low as Tb rose to 18 degrees C, at which point, eyes opened, squirrels became more active and all Ts's rose parallel to Tb. Marmot Ts remained low as Tb rose initially. Each marmot showed a plateau phase where Tb remained constant (mean Tb 20.3+/-1.0 degrees C, duration 9.4+/-4.1 min) during which time all Ts's rose, and then remained relatively constant as Tb again began to rise. An anterior to posterior Ts gradient was evident in the ground squirrel, both body and feet. This gradient was only evident in the feet of the marmots.

Animals↗
PubMed2006

Hibernation proteins: preparing for life in the freezer.

Hibernation is an extreme response to a seasonal environment, yet we know almost nothing about how it is timed or how vital cellular functions are sustained in the face of plummeting body temperature. In this issue of Cell, kondo et al. (2006) identify a liver-derived protein complex as an essential coordinator of this adaptation to the depredations of winter.

Animals↗
PubMed1997

The effect of some peptides from the hibernating brain on Ca2+ current in cardiac cells and on the activity of septal neurons.

The effects of the peptides TSKYR and DY isolated from the brain of hibernating ground squirrels on Ca2+ current were studied. TSKYR activated Ca2+ current in frog auricle fibers and in single cells from frog ventricle whereas DY blocked Ca2+ current in both preparations. In isolated rat and ground squirrel cardiocytes, TSKYR had no effect on Ca2+ current, and DY increased it. In brain slices of rat, DY blocked the activity of medial septal neurons. TSKYR increased activity of septal neurons at the initial phase, which was followed by decrease of neuronal activity.

Animals↗
PubMed2001

The physiology of hibernation among painted turtles: the midland painted turtle (Chrysemys picta marginata).

Midland painted turtles from Michigan were submerged at 3 degrees C in normoxic and anoxic water. In predive, and in turtles submerged for up to 150 days, plasma PO2, PCO2, pH, [Cl-], [Na+], [K+], total Mg, total Ca, lactate, glucose, and osmolality were measured; hematocrit and mass were determined, and plasma [HCO3-] was calculated. Anoxic turtles developed a severe metabolic acidosis, accumulating lactate from a predive value of 4.4 mmol/L to a 150-day value of 185 mmol/L, associated with a fall in pH from 7.983 to 7.189. To buffer lactate increase, total calcium and magnesium rose from 3.7 and 2.6 to 58.9 and 11.8 mmol/L, respectively. Plasma [HCO3-] was titrated from 39.2 to 4.8 mmol/L in anoxic turtles. Turtles in normoxic water had only minor disturbances of their acid-base and ionic statuses, associated with a much smaller increase of lactate to 23 mmol/L; there was a marked increase in hematocrit from 29.1% to 42.1%. We suggest that it is ecologic, rather than phylogenetic, relationships that determine the responses of painted turtles to prolonged submergence associated with hibernation.

Acid-Base Equilibrium↗
PubMed2003

Effect of ischaemic preconditioning on genomic response to cerebral ischaemia: similarity to neuroprotective strategies in hibernation and hypoxia-tolerant states.

BACKGROUND: Molecular mechanisms of neuroprotection that lead to ischaemic tolerance are incompletely understood. Identification of genes involved in the process would provide insight into cell survival and therapeutic approaches for stroke. We developed a mouse model of neuroprotection in stroke and did gene expression profiling to identify potential neuroprotective genes and their associated pathways. METHODS: Eight mice per condition were subjected to occlusion of the middle cerebral artery for 15 min (preconditioning), 60 min (injurious ischaemia), or preconditioning followed 72 h later by injurious ischaemia. RNA was extracted from the cortical regions of the ischaemic and non-ischaemic hemispheres. Three pools per condition were generated, and RNA was hybridised to oligonucleotide microarrays for comparison of ischaemic and non-ischaemic hemispheres. Real-time PCR and western blots were used to validate results. Follow-up experiments were done to address the biological relevance of findings. FINDINGS: Microarray analysis revealed changes in gene expression with little overlap among the conditions of injurious ischaemia, ischaemic preconditioning, or both. Injurious ischaemia induced upregulation of gene expression; 49 (86%) of 57 genes regulated showed increased expression in the ischaemic hemisphere. By contrast, preconditioning followed by injurious ischaemia resulted in pronounced downregulation; 47 (77%) of 61 regulated genes showed lower expression. Preconditioning resulted in transcriptional changes involved in suppression of metabolic pathways and immune responses, reduction of ion-channel activity, and decreased blood coagulation. INTERPRETATION: Preconditioning reprogrammes the response to ischaemic injury. Similar changes reported by others support an evolutionarily conserved endogenous response to decreased blood flow and oxygen limitation such as seen during hibernation.

Animals↗
PubMed1997

Ambient temperature during torpor affects NREM sleep EEG during arousal episodes in hibernating European ground squirrels.

Ambient temperature (Ta) systematically affects the frequency of arousal episodes in mammalian hibernation. This variation might hypothetically be attributed to temperature effects on the rate of sleep debt increase in torpor. We studied this rate by recording sleep electroencephalogram (EEG) in arousal episodes induced after 4 days of torpor at different Ta. Spontaneous torpor bout duration (TBD) varied with Ta: TBD was maximal at 5.5 degrees C (10.7 days), and was reduced at lower (-5 degrees C: 5.0 days, 0 degrees C: 9.3 days) and higher Ta (10 degrees C: 8.7 days, 15 degrees C: 5.0 days). Slow wave activity (SWA) during non-rapid-eye-movement (NREM) sleep, an indicator for sleep debt, showed initial high values after torpor at Ta ranging from -5 degrees C to 10 degrees C. When torpid at 15 degrees C, SWA was not increased in the subsequent arousal episode. The data are thus inconsistent with a rate of sleep debt explanation for the temperature dependence of TBD.

Animals↗
PubMed2001

The physiology of hibernation in common map turtles (Graptemys geographica).

Map turtles from Wisconsin were submerged at 3 degrees C in normoxic and anoxic water to simulate extremes of potential respiratory microenvironments while hibernating under ice. In predive turtles, and in turtles submerged for up to 150 days, plasma PO2, PCO2) pH, [Cl-], [Na+], [K+], total Mg, total Ca, lactate, glucose, and osmolality were measured; hematocrit and body mass were determined, and plasma [HCO3-] was calculated. Turtles in anoxic water developed a severe metabolic acidosis, accumulating lactate from a predive value of 1.7 to 116 mmol/l at 50 days, associated with a fall in pH from 8.010 to 7.128. To buffer lactate increase, total calcium and magnesium rose from 3.5 and 2.0 to 25.7 and 7.6 mmol/l, respectively. Plasma [HCO3-] was titrated from 44.7 to 4.3 mmol/l in turtles in anoxic water. Turtles in normoxic water had only minor disturbances of their acid-base status and ionic statuses; there was a marked increase in hematocrit from 31.1 to 51.9%. This study and field studies suggest that map turtles have an obligatory requirement for a hibernaculum that provides well-oxygenated water (e.g. rivers and large lakes rather than small ponds and swamps) and that this requirement is a major factor in determining their microdistribution.

Acid-Base Equilibrium↗
PubMed2006

Behaviour and chemical signature of pre-hibernating females of Polistes dominulus infected by the strepsipteran Xenos vesparum.

Polistes dominulus are social wasps which are the host of the strepsipteran endoparasite Xenos vesparum. In the hibernating phase, unparasitized and parasitized wasps leave natal nests and aggregate together in sheltered quarters. In aggregations, wasps are socially active, and some individuals perform helping behaviour. Here we investigated if castrated parasitized wasps perform worker tasks in mixed aggregations. Moreover, by gas chromatography and mass spectrometry, we examined the cuticular hydrocarbons of unparasitized and parasitized wasps to evaluate if the infection alters the composition of cuticular waxes that are recognition cues in social insects. In clusters, infected females do not perform helping behaviour and they are less active than unparasitized wasps. Cuticular hydrocarbons are slightly differentiated between unparasitized and parasitized wasps but, generally, unparasitized wasps are more similar to wasps infected by Xenos females compared to wasps infected by Xenos males. Wasps infected by Xenos males do not usually survive the winter. This chemical similarity is probably a consequence of the similar physiological condition of unparasitized and female-affected Polistes wasps. At this stage, it is difficult to affirm whether these modifications are a true parasite manipulation or a consequence of infection.

Animals↗
PubMed2003

Role of lipids in the assembly of endoplasmic reticulum and dictyosomes in neuronal cells from the cerebral cortex of Yakutian ground squirrel (Citellus undulatus) during hibernation.

Phospholipids and cholesterol were assayed in homogenates and microsomal fractions from the cerebral cortex of summer-active, winter-torpid, and winter-active Yakutian ground squirrels (Citellus undulatus). Ultrastructural analysis of both microsomal fraction and intact neurons was performed by serial ultramicrotomy. The levels of sphingomyelin (SM), phosphatidylserine (PS), and phosphatidylethanolamine (PEA) were decreased in homogenates from the cerebral cortex of winter ground squirrels compared with the summer-active animals, while the levels of phosphatidylcholine (PC) and cardiolipin (CL) were increased. The level of cholesterol was decreased in the cerebral cortex of winter-torpid animals compared with both winter-active and summer-active animals, and the level of total phospholipids was decreased in comparison to the summer-active animals. Three-dimensional reconstruction of serial membrane profiles displayed the microsomal fraction to be an interconnected system of cisterns and vesicles, which corresponds to endoplasmic reticulum and dictyosomes (Golgi stacks) of intact neurons. In winter the content of PC was increased in the microsomal fraction, while the contents of lysophosphatidylcholine (LPC), PS, phosphatidylinositol (PI), and SM were decreased. In winter-torpid animals compared with the winter-active ones the contents of total phospholipids, PEA, LPC, and cholesterol were decreased. As for the winter-active ground squirrels, their lipid contents did not differ from those in the summer-active animals, but LPC content was decreased. The changes in microsomal lipid contents in intact pyramidal neurons throughout the hibernation were accompanied by disassembly of dictyosomes and endoplasmic reticulum (ER), including the decomposition of polyribosomes to monosomes. The ultrastructural analysis of nucleoli, ER, and dictyosomes of both winter-active and torpid ground squirrels showed a direct correlation between the increasing contents of both cholesterol and total phospholipids (mainly PEA and LPC) in microsomes and the structural recovery of endoplasmic reticulum, Golgi stacks, and nucleoli in intact pyramidal neurons. A role of seasonal variations in lipid contents of brain cells in their adaptation to low temperature is discussed. We also propose an involvement of cholesterol in the activation of protein-synthesizing function of endoplasmic reticulum and Golgi stacks in intact neurons.

Animals↗
PubMed1997

Sleep during arousal episodes as a function of prior torpor duration in hibernating European ground squirrels.

EEG's were recorded in hibernating European ground squirrels during euthermic arousal episodes at an ambient temperature of 5.5 degrees C. Spontaneous torpor bouts ranged from 6 to 15 days, body temperature during torpor was 7.5 degrees C. The torpor duration prior to EEG measurements was experimentally manipulated: the animals were induced to arouse by gentle handling after torpor of less then 1 day (n = 3), 1-2 days (n = 6), 3-4 days (n = 9) and 5-12 days (n = 9). The animals slept 71.5% of euthermic time, of which 61.4% NREM and 10.2% REM sleep. NREM percentage was slightly positively and REM percentage negatively correlated with prior torpor duration (TD). Spectral analysis showed changes in EEG activity during the euthermic phase in the slow wave frequency range (1-4 Hz) and in higher frequencies. Prior TD specifically affected the slow waves. Slow wave activity decreased exponentially during the euthermic phase. The initial slow wave activity showed a systematic increase with prior TD, which could be described by an exponentially saturating function, albeit with a relatively small time constant compared with spontaneous torpor duration. It is concluded that sleep during arousal episodes following torpor at an ambient temperature of 5.5 degrees C is affected both in structure and intensity by prior TD. The results are consistent with the proposition that torpor inhibits the restorative function of sleep.

Animals↗
PubMed1999

Increase in liver pigmentation during natural hibernation in some amphibians.

The amount/distribution of liver melanin in 3 amphibian species (Rana esculenta, Triturus a. apuanus, Triturus carnifex) was studied during 2 periods of the annual cycle (summer activity-winter hibernation) by light and electron microscopy, image analysis and microspectrofluorometry. The increase in liver pigmentation (melanin content) during winter appeared to be correlated with morphological and functional modifications in the hepatocytes, which at this period were characterised by a decrease in metabolic activity. These findings were interpreted according to the functional role (e.g. phagocytosis, cytotoxic substance inactivation) played by the pigment cell component in the general physiology of the heterothermic vertebrate liver and, in particular, in relation to a compensatory engagement of these cells against hepatocellular hypoactivity during the winter period.

Amphibians↗
PubMed1988

Hatchling turtles survive freezing during winter hibernation.

Hatchlings of the painted turtle (Chrysemys picta marginata) are unique as the only reptile and highest vertebrate life form known to tolerate the natural freezing of extracellular body fluids during winter hibernation. Turtles survived frequent exposures to temperatures as low as -6 degrees C to -8 degrees C in their shallow terrestrial nests over the 1987-1988 winter. Hatchlings collected in April 1988 had a mean supercooling point of -3.28 +/- 0.24 degrees C and survived 24 hr of freezing at -4 degrees C with 53.4% +/- 1.98% of total body water as ice. Recovery appeared complete after 20 hr of thawing at 3 degrees C. However, freezing at -10.9 degrees C, resulting in 67% ice, was lethal. A survey of possible cryoprotectants revealed a 2- to 3-fold increase in glucose content of liver and blood and a 3-fold increase in blood glycerol in response to freezing. Although quantitatively low, these responses by spring turtles strongly indicate that these may be the winter-active cryoprotectants. The total amino acid pool of blood also increased 2.25-fold in freezing-exposed turtles, and taurine accounted for 52% of the increase. Most organs accumulated high concentrations of lactate during freezing, a response to the ischemic state imposed by extracellular freezing. Changes in glycogen phosphorylase activity and levels of glucose 6-phosphate and fructose 2,6-bisphosphate were also consistent with a dependence on anaerobic glycolysis during freezing. Studies of the molecular mechanisms of natural freeze tolerance in these turtles may identify protective strategies that can be used in mammalian organ cryopreservation technology.

Animals↗
PubMed1996

Season related ultrastructural features of the parotid, submandibular and von Ebner's glands in hibernating bats.

The parotid, submandibular and the von Ebner's salivary glands of hibernating insectivorous bats (Pipistrellus pipistrellus, Rhinolophus f. e. and Eptesicus serotinus) were studied by transmission electron microscopy and by histochemical methods during various seasons of the year. We report the seasonal ultrastructural changes that occur in the cytoplasmic organelles and the secretory granules of the serous and mucous cells and in the intercalated and striated ducts of the major glands. It previously has been hypothesized that the heterogeneity of the inclusions in the serous granules is closely related to the varying seasonal levels of proteinaceous and glycidic constituents. Lymphatic vessels are present only in the perivascular and periductal connective tissue. Morphofunctional and comparative studies seem to confirm a relationship between secretory activity and nutritional status as well as a likely involvement of the intercalated and striated ducts in determining the composition of the saliva.

Animals↗
PubMedDate not supplied

The physiology of hibernation among painted turtles: the Eastern painted turtle Chrysemys picta picta.

Eastern painted turtles (Chrysemys picta picta) from Connecticut were submerged at 3 degrees C in normoxic and anoxic water to simulate potential respiratory environments within their hibernacula. Those in normoxic water could survive submergence for at least 150 d, while those in anoxic water could survive for a maximum of about 125 d. Turtles in normoxic water developed a slight metabolic acidosis as plasma lactate accumulated to about 50 mM in 150 d, while anoxic turtles developed a severe lactic acidosis as plasma lactate reached about 200 mM in 125 d; there was no respiratory acidosis in either group. Plasma [Na+] changed little in either group, [Cl-] fell by about one-third in both, and [K+] increased by about fourfold in anoxic turtles but only slightly in those in normoxic water. Total plasma magnesium and calcium increased profoundly in anoxic turtles but moderately in those in normoxic water. Consideration of charge balance indicates that all major ions were measured in both groups. Plasma glucose remained unchanged in anoxic turtles until after about 75 d of submergence, when it increased and continued to increase with the duration of anoxia, with much variation among individuals; glucose remained unchanged throughout in turtles in normoxic water. Hematocrit doubled in 150 d in turtles in normoxic water; in anoxic turtles, an initial increase was no longer significant by day 100. Plasma osmolality increased markedly in anoxic turtles, largely because of accumulation of lactate, but anoxic turtles only gained about half the mass of turtles in normoxic water, who showed no increase in osmolality. The higher weight gain in the latter group is attributed to selective perfusion and ventilation of extrapulmonary gas exchange surfaces, resulting in a greater osmotic influx of water. The physiologic responses to simulated hibernation of C. picta picta are intermediate between those of Chrysemys picta bellii and Chrysemys picta dorsalis, which correlates with the severity of the winter each subspecies would be expected to encounter.

Acidosis, Lactic↗
PubMedDate not supplied

The physiology of hibernation in Canadian leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana).

Canadian northern leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana) were acclimated to 3 degrees C and submerged in anoxic (0-5 mmHg) and normoxic (Po(2) approximately 158 mmHg) water. Periodic measurements of blood Po(2), Pco(2), and pH were made on samples taken anaerobically from subsets of each species. Blood plasma was analyzed for [Na(+)], [K(+)], [Cl(-)], [lactate], [glucose], total calcium, total magnesium, and osmolality. Blood hematocrit was determined, and plasma bicarbonate concentration was calculated. Both species died within 4 d of anoxic submergence. Anoxia intolerance would rule out hibernation in mud, which is anoxic. Both species survived long periods of normoxic submergence (R. pipiens, 125 d; R. catesbeiana, 150 d) with minimal changes in acid-base and ionic status. We conclude that ranid frogs require a hibernaculum where the water has a high enough Po(2) to drive cutaneous diffusion, allowing the frogs to extract enough O(2) to maintain aerobic metabolism, but that an ability to tolerate anoxia for several days may still be ecologically meaningful.

Analysis of Variance↗