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At least 883 records · Page 49Linked to original sources
PubMed1985

Innervation of bat heart: cholinergic and adrenergic nerves innervate all chambers.

Adult Miniopterus schreibersii were anesthetized with chloroform, and in vitro preparations of cardiac chambers were prepared. Stimulation of intramural nerves in right ventricles paced at 6 Hz caused an inhibition (56.3 +/- 3.5% decrease on basal force) mediated by cholinergic nerves and an excitation (91.5 +/- 9.9% increase on basal force) mediated by adrenergic nerves. Mean pD2s (-log effective concentration, 50%) for ventricular beta-adrenoceptors and muscarinic cholinoceptors were 6.99 +/- 0.03 and 6.42 +/- 0.07, respectively. The inhibition of ventricular contractility, by nerve stimulation or exogenous acetylcholine, occurred even after blockade of beta-adrenoceptors. The results were comparable to those obtained on atria. In some experiments, the heart was perfused in situ and paced via electrodes on the ventricle: stimulation of the right vagus nerve decreased right ventricular contractility by up to 90%. The results show that, at least in this hibernating mammal, there is an adrenergic innervation of the ventricle. The presence of a cholinergic vagal innervation capable of inhibiting the basal force of ventricular contraction has not been shown in any other mammal.

Animals↗
PubMed1985

Ventricular repolarization and fibrillation threshold in hibernating species.

Hibernators are resistant to ventricular fibrillation (VF) induced by hypothermia. This is in contrast to non-hibernating mammals which develop circulatory arrest, usually VF, in the temperature region 15-20 degrees C. The hedgehog which is a hibernator showed resistance to VF also when VF-evoking procedures other than hypothermia were used, such as local application of aconitine on the epicardium, administration of 0.55 M CaCl2 to isolated hearts perfused with a potassium-free modified Tyrode solution, injection of procaine HCl into isolated hearts perfused with a modified Tyrode solution after previous adrenaline administration, and ligation of the left descending coronary artery. Electrical stimulation in the vulnerable period produced VF in some but not in all the hedgehogs but a greater current was necessary than in guinea-pigs, all of which developed VF. Factors of possible importance to explain this difference in VF resistance are the QT duration which is short in hibernators, adrenergic innervation (ventricular muscle fibres in hibernators lack sympathetic innervation), metabolic factors (different temperature activity curves in hibernators compared to nonhibernating mammals) and ultrastructure (less skeletin filament in the conduction system of the hedgehog heart).

Aconitine↗
PubMed2002

Maintaining muscle mass during extended disuse: aestivating frogs as a model species.

Prolonged muscle disuse in vertebrates can lead to a pathological change resulting in muscle wasting and a loss of muscle strength. In this paper, we review muscle disuse atrophy in the vertebrates and examine the factors that influence the magnitude of the atrophic response during extended periods of inactivity, both artificially imposed (e.g. limb immobilisation) and naturally occurring, such as the quiescence associated with dormancy (e.g. hibernation and aestivation). The severity of muscle atrophy is positively correlated with mass-specific metabolic rate, and the metabolic depression that occurs during dormancy would appear to have a protective role, reducing or preventing muscle atrophy despite periods of inactivity lasting 6-9 months. In the light of these findings, the role of reactive oxygen species and antioxidants during muscle disuse is emphasised.

Animals↗
PubMed1987

Prolongation of hibernation bout duration by continuous intracerebroventricular infusion of melatonin in hibernating ground squirrels.

Melatonin was infused intracerebroventricularly into hibernating golden-mantled ground squirrels (Citellus lateralis) maintained at 5 degrees C in darkness. Continuous infusion at a rate of 0.5 microliter/h was accomplished using an osmotic minipump. The effect of melatonin on hibernation bout duration was determined with reference to the natural trend in bout duration for each animal. At doses of 200 and 400 ng/h, melatonin produced a dose-related increase in bout duration. No effect was observed following control infusions of artificial cerebrospinal fluid or lower doses of melatonin.

Animals↗
PubMed1999

Cardiomyocyte remodelling during myocardial hibernation and atrial fibrillation: prelude to apoptosis.

OBJECTIVE: Similar structural changes in the myocardium can be observed in chronic hibernating myocardium and in myocardium taken from hearts suffering chronic atrial fibrillation. We investigated whether or not these changes are indicative of apoptosis. METHODS: Myocardial biopsies from 28 strictly selected patients with chronic hibernating myocardium and heart samples from 13 goats with pacing-induced chronic atrial fibrillation were used. Special attention was paid to processing the tissues immediately (fixation/freezing) in order to prevent artificial degenerative changes, thereby excluding false positive identification of apoptosis. Infarcted areas or infarcted border zones were excluded from our study. Apoptosis was detected with light and electron microscopy and terminal deoxynucleotidyl transferase nick end-labelling. Immunohistochemistry was used for detecting Bcl-2, P53 and PCNA-proteins associated with apoptosis/DNA damage. RESULTS: The results obtained for chronic hibernating left ventricular myocardium were similar to those for chronic fibrillating atrial myocardium. No apoptotic nuclei, as characterised by extensive chromatin clumping, could be observed in normal or dedifferentiated cardiomyocytes under the electron microscope. The end-labelling assay did not reveal any cardiomyocytes with damaged DNA. Nor could we find any evidence of substantial expression of Bcl-2, P53 or PCNA, a result indicative of the absence of apoptotic threat or DNA damage. CONCLUSION: Cardiomyocyte dedifferentiation, but not extensive degeneration through apoptosis, can be observed in chronic hibernating myocardium and chronic fibrillating atrium. Dedifferentiation may be the best way to survive prolonged exposure to the unfavourable conditions imposed by increased wall stress, a relative lowered oxygen environment, or both.

Animals↗
PubMedDate not supplied

[A comparative analysis of restoration of electroencephalographic and protein-synthesizing activities in neocortex and hippocampus in hibernating (ground squirrels) and nonhibernating (rats) animals during exit from hypothermia].

A similarity in the sequence of restoration of the EEG spectrum between ground squirrels arousing from torpor and rats passing out of artificial hypothermia (17-18 degrees C) was shown. First of all, the low-frequency part of the EEG spectrum was restored. As animals warmed up, their breathing became hurried, cold shivering appeared, and the theta- and alpha-rhythms increased. During the exit from hypothermia, the activity of the protein-synthesizing system in both rats and ground squirrels was almost entirely restored when the animal body temperature achieved 21-22 degrees C. In ground squirrel, the rate of protein synthesis in the neocortex was lower than in hippocampus CA1 and CA3 areas, whereas in rats, on the contrary, it was higher in the neocortex in comparison with the CA3 area.

Animals↗
PubMed1993

Effect of light entrainment and temperature on the reproductive cycle in the male hedgehog (Erinaceus europaeus).

The role of photoperiod in the entrainment and synchronization of the reproductive cycle of male hedgehogs, seasonal breeders and hibernating mammals, was investigated. Groups of adult hedgehogs were either maintained outdoors (controls, n = 6) or submitted to accelerated 6-month artificial light regimens under constant ambient temperatures (20 +/- 2 degrees C versus 5 +/- 1 degrees C) in light-proofed rooms. The daily duration of light was varied sinusoidally to produce an amplitude change from 8 h (winter solstice) to 16 h (summer solstice) during the 6-month light cycle. Animals were transferred from outdoors to a high ambient temperature (20 +/- 2 degrees C) and submitted to accelerated 6-month light regimens at two times of the year: from winter solstice (Group 1, n = 14) with increasing daylengths (from 8 to 16 h) and from summer solstice (Group 2, n = 8) with decreasing daylengths (from 16 to 8 h). The light regimens were then reversed for Groups 1 and 2. After the first 6-month cycle, the animals in Group 1 were allocated to two groups and maintained under the same initial light regimen but submitted to two ambient temperatures: Group 1 (n = 7) was maintained at 20 +/- 2 degrees C and Group 3 (n = 7) was transferred to a cold environment (5 +/- 1 degrees C). In control and experimental animals, testicular volume was estimated and blood samples were obtained twice a month to measure plasma testosterone and LH concentrations by radioimmunoassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed2000

Direct and correlated responses to individual selection for large adult weight in the edible snail Helix aspersa Muller.

A selection experiment for large adult weight based on individual performance was conducted for three generations in Helix aspersa aspersa. A second line was kept as an unselected control line. Direct response measured as deviation from the control line was 3.55 g after three generations of artificial selection, which averaged 13%. Realized heritability was 0.38 +/- 0.04. Correlated responses to selection showed a significant increase in weight after hibernation, mean egg weight and mean weight of newly-hatched snails with selection. For adult age, egg number, and hatching rate, no significant change correlated to selection was found, but this is to be confirmed.

Animals↗
PubMed1995

Modulation of synaptic transmission at low temperatures by hibernation-related changes in ionic microenvironment in hippocampal slices of golden hamsters.

In hamsters, the entrance into hibernation is associated with a respiratory acidosis and elevation of the blood plasma concentrations of potassium, calcium, and magnesium. To investigate the effects of presumed hibernation-related ionic changes in the brain interstitium on neuronal function, the transmission properties of hippocampal slices prepared from golden hamsters were studied at low temperatures in vitro. Slices were investigated at 15-20 degrees C in artificial cerebrospinal fluid (ACSF) of variable composition (K+, 3-5 mM; Ca2+, 2-4 mM; Mg2+, 2-4 mM; pH 7.0-7.7). Population action potentials (population spikes, PS) of CA1 pyramidal cells were continuously evoked with 100-microseconds stimulus pulses delivered to the Schaffer collaterals/commissural fibers in intervals of 30 s. The PS amplitude was measured as a function of extracellular ion concentrations at given temperatures or as a function of temperature at a given ACSF composition. Elevation of [K+]o, [Mg2+]o, or [H+]o all reduced the PS amplitude at low temperatures, whereas elevation of [Ca2+]o increased the PS amplitude. In conclusion, changes in the ionic microenvironment occurring during entrance into hibernation presumably result in depression of synaptic transmission at low temperatures in the hamster hippocampus. The modulatory effect of ionic changes may be an important factor supporting a general depression of the brain during entrance into hibernation.

Animals↗
PubMed1987

Plasma steroid hormone levels of female red-sided garter snakes, Thamnophis sirtalis parietalis: relationship to mating and gestation.

Plasma levels of progesterone (P), testosterone (T), estradiol (E2), and corticosterone (B) of female red-sided garter snakes were measured during the period of ovarian development. Differences in hormone levels were analyzed with respect to three factors: whether the female mated in the spring, ovarian condition, and time after emergence from hibernation. The influence of these three factors on steroid hormone levels of two groups of females were then compared. In experiment I, females were obtained in the fall, subjected to an artificial dormancy period, and placed on warm, summer-like conditions in the laboratory. In experiment II, females were collected in the spring and sampled in the field. They were held in the field on fluctuating conditions for several weeks and then returned to the laboratory for sampling during early vitellogenesis. Females in experiment I had a shortened but otherwise normal ovarian and gestational cycle, whereas females in experiment II had an ovarian and gestational cycle typical of females in the field. In spite of these differences, the steroid hormone levels in relation to the ovarian cycle were remarkably similar for the two groups of females. We confirmed that mating in the spring induces a surge in E2; E2 also was elevated in a single sample obtained from animals collected in the fall. This elevation in plasma levels of E2 in the fall occurs at a time when the majority of females have recently deposited sperm in their oviducts. Plasma levels of T, P, and B were not significantly influenced by mating. Unlike previous reports of other viviparous snakes, plasma levels of P were low and mostly nondetectable, even during late gestation. Plasma T was significantly elevated around the time of late vitellogenesis and ovulation, and there was a tendency for E2 levels to be elevated at this time. In the field, plasma B levels were initially high immediately after capture and declined with time. Plasma B was significantly elevated in all females several weeks after emergence, suggesting that levels of B may vary with other annual cycles.

Animals↗
PubMed1985

Behavioral and physiological control of yolk synthesis and deposition in the female red-sided garter snake (Thamnophis sirtalis parietalis).

Ovarian recrudescence in female garter snakes, Thamnophis sirtalis parietalis, follows spring emergence from hibernation and mating. In the laboratory, courtship and mating stimuli significantly increased the proportion of female garter snakes becoming pregnant, although some noncourted nonmated controls also became pregnant. Females given artificial mating stimuli under anesthetic, without courtship stimuli, were no more likely than either noncourted, nonmated or anesthetized controls to become pregnant. Hormonal changes and yolk synthesis rapidly followed mating in both laboratory and field females; serum estradiol increased more than 10-fold in 2 days and serum calcium, a measure of yolk precursor lipoprotein (vitellogenin) concentration, increased more than two times in 10 days. Administration of exogenous estradiol stimulated yolk synthesis, but did not result in yolk deposition into ovarian follicles. However, administration of ovine follicle-stimulating hormone induced both hepatic yolk synthesis and yolk deposition. Our results are consistent with the hypotheses that courtship and copulation are facilitatory to ovarian recrudescence but neither alone nor in combination is necessary nor sufficient, and in this species yolk synthesis and yolk deposition are separately regulated.

Animals↗