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At least 1,153 records · Page 64Linked to original sources
PubMed1997

[18Fluoro-FDG SPECT for the demonstration of hibernating myocardium: an interim account].

AIM: The present investigation demonstrates an intraindividual comparison of FDG-PET and FDG-SPECT. MATERIAL AND METHODS: Thirty patients with CHD and planed revascularisation underwent both modalities. Myocardial perfusion was evaluated by 99mTc-MIBI SPECT. The myocardium was divided into 25 segments and the results were compared by two experienced observers. RESULTS: Segmental concordance of FDG-PET and -SPECT was 94.1%. PET indicated a higher percentage of hibernating myocardium (8.9% vs. 5.7%) and a lower rate of matched defects (11.5% vs. 16.0%). In 22 cases the need for revascularisation was assessed identically. In the remaining 8 patients FDG-PET and FDG-SPECT required an intervention in 6 and 2 cases, respectively. CONCLUSION: The results of FDG-PET and FDG-SPECT showed a high segmental concordance, but the individual assessment of hibernation worthwhile for revascularisation demonstrated important differences in patient management.

Aged↗
PubMed1997

[Effect of a revascularization procedure on functioning of the hibernating myocardium].

Persistent abnormalities of left ventricular wall motion in patients with chronic coronary artery disease can be reversed by successful coronary artery bypass surgery or coronary angioplasty. The identification of hibernating myocardium has therefore important therapeutic and prognostic implications. Echocardiography with low dose dobutamine infusion can detect viable myocardium in patients with chronic left ventricular dysfunction. We have studied 32 patients with angiographically confirmed coronary artery disease and left ventricular dysfunction. The effect of dobutamine infusion (5 micrograms/kg/min. followed by 10 micrograms/kg/min) on left ventricular function was evaluated before coronary revascularization (PTCA, n = 20); CABGm b = 12) and compared with early period after revascularization (1-7 days) and 6-7 months later. Before revascularization 226 segments were hypokinetic, akinetic or dyskinetic, improvement was observed in 122 segments during dobutamine echocardiography. Mean (+/- SD) segment score indexes were 2.50 +/- 0.17 at baseline, 2.04 +/- 0.19 (p < 0.001) after dobutamine infusion, 2.24 +/- 0.25 (p < 0.001) early after and 1.87 +/- 0.25 (p < 0.001) late after revascularization. Sensitivity of dobutamine infusion to predict improvement early and late after revascularization was 84% and 85% respectively, specificity was 85% and 90% respectively. Echocardiography during low dose dobutamine infusion is save and accurate method for identifying of hibernating myocardium and predicts early and late reversibility of wall motion in selected patients with coronary artery disease and chronic left ventricular dysfunction.

Cardiotonic Agents↗
PubMed1963

Brown fat: thermogenic effector of arousal in hibernators.

Earlier indications that brown fat has a thermogenic role in rats exposed to cold suggested that certain comparable functions in hibernating marmots be investigated. From the results it appears that arousal of the animal by cold is induced by sympathetically activated thermogenesis in areas of brown fat so located, relative to the vasculature, that heat is transferred to the thoracic structures and cervical spinal regions.

Adipose Tissue↗
PubMed1993

Unique features of the cauda epididymidal epithelium of hibernating bats may promote sperm longevity.

Measurements of extremely high osmolalities in cauda epididymidal fluids of hibernating bat species led to an investigation of the junctional complex morphology of the epithelium of this sperm storage site. Freeze fracture replicas revealed the presence, at certain times of the year, of a tight junction architecture that resembled that traditionally thought to be exclusive to the blood-testis barrier, the strongest permeability barrier in the body. It is hypothesized that seasonal establishment of these specialized Sertoli cell-like tight junctions is necessary to the maintenance of the high osmotic state of the luminal environment, allowing for the prevention of dilution of its contents by paracellular routes and its protection from bursting under the osmotic pressure contained within.

Animals↗
PubMed1994

Microcalorimetric study on myocardial metabolism in a hibernator and two nonhibernators at 20 degrees C and 37 degrees C.

Metabolic activity in cardiac tissue slices from the guinea pig (GP), the rat (RT), the nonhibernating summer and winter hedgehog (SH and WH), respectively, was determined at 20 degrees and at 37 degrees C from their rates of heat production, P, (units, W/g tissue) by direct and indirect calorimetry. Energy-linked transport of Na+ and K+ in the tissues was determined from changes in metabolic rate induced by specific inhibition of the Na/K pump, the functional expression of Na/K-ATPase, the pacemaker enzyme in energy production assigned the role of transporting Na+ and K+ out of and into the cell. The results indicate a higher rate of energy production and utilization in the cardiac tissue of the hedgehog than in that of the nonhibernators, the rat and the guinea pig, at both temperatures. At 37 degrees C the rate at which the cardiac tissue from the hedgehog consumed oxygen was as much as six times that registered for the guinea pig. The temperature coefficients of P and of the Na/K pump in the tissues from the two groups of hedgehogs were significantly higher than in the tissues from the rat and the guinea-pig (P < 0.001). The determined metabolic indices, the basal rate of heat production P, the rate of oxygen consumption, P(O2) in thermal units (W/g tissue), and the Na/K-pump capacity (PC) indicate species-specific differences between the animals. Both PC and its variation with temperature, delta PC/delta T(o)C, were in the order WH > SH > RT > GP. These results indicate that the hedgehog's cardiac tissue, in comparison with that of the nonhibernators, has a greater capacity to generate energy in general and for active transport of Na+ and K+ at 37 degrees C after exposure to a lower temperature. A role is suggested for the Na/K-ATPase and some other unique rate-limiting enzymes in the metabolic pathway for the observed differences in temperature tolerance and cardiac performance between hibernators and nonhibernators.

Animals↗
PubMed1994

Dopaminergic inhibition of gonadotropic release in hibernating frogs, Rana temporaria.

The influence of a dopaminergic antagonist, metoclopramide (MET), and an agonist, bromocriptine (BROMO), on reproductive status was examined in female frogs, Rana temporaria. MET induced advanced ovulation during hibernation, suggesting dopaminergic inhibition of gonadotropin (LH) release during this period. BROMO did not decrease plasma LH in intact females in comparison with vehicle (VEH)-treated controls (VEH: 11 +/- 6 vs BROMO: 5 +/- 4 ng/ml) or in sham-lesioned (SL) females (SL; 12 +/- 5 vs SL + BROMO: 9 +/- 8 ng/ml). However, BROMO significantly depressed the rise in plasma LH following lesioning (L) which disconnected the hypothalamus from the medium eminence-pituitary complex (L + BROMO: 29 +/- 10 vs L: 74 +/- 30 ng/ml; P < 0.002). Taken together with previous results of lesion studies, these data point to an important role of dopaminergic inhibition in the regulation of seasonal reproduction in this frog.

Animals↗
PubMed1996

Effects of gonadal sex steroids on sexual behavior in the big brown bat, Eptesicus fuscus, upon arousal from hibernation.

Vespertilionid bats are thought to have a dissociated pattern of reproduction; mating occurs in autumn as well as during periodic arousals from hibernation when testes are regressed and ovaries are "in stasis." Sex steroid levels in both sexes are basal at this time. This pattern would indicate that sex steroids per se may not be activating sexual behavior. Gonadectomy of male and female big brown bats, Eptesicus fuscus, months before the mating season, did not significantly affect the probability of expressing sexual behavior in either sex when staged behavior tests were conducted. Ovariectomized females, in fact, mated significantly more and exhibited proceptive behavior. Males mated at the same frequency whether they were intact, orchidectomized, or given testosterone implants. These results argue that gonadal sex steroids are not the direct activators of sexual behavior in this species. However, when males were allowed to mate freely within a large flight cage, orchidectomized males were not seen to mate, while intact males mated at the same frequency as in the staged trials. Females are apparently either differentiating between the two groups of males or there is male-male competition for mates within a system that has multiple matings with different individuals in both sexes.

Animals↗
PubMed1978

Glucocorticoids and carbohydrate metabolism in hypothermic and hibernating hamsters.

In hibernating hamsters carbohydrate reserves are regulated and are in dynamic equilibrium. During "deep" hypothermia (Tb 7-8 degrees C) hamsters undergo a progressive hypoglycemia, depletion of liver glycogen, and death within 24 hours. Glucocorticoid treatment results in enhanced blood and liver carbohydrates, prolonged survival at Tb 7-8 degrees C, and enhanced thermogenic capacity leading to arousal.

Animals↗
PubMed1978

Comparison of induced and spontaneous arousals in hibernating hedgehogs.

Respiratory and circulatory differences between periodic spontaneous arousals and induced arousals in hibernating hedgehogs were studied in a constant ambient temperature of + 4.2 +/- 0.5 oC. The increase in O2 consumption, blood pressure and heart rate was faster during induced arousals than during periodic spontaneous arousals. Based on our present studies we suggest that even the smallest stimulus able to induce the awakening is sufficient to modify the process so that it differs markedly from a spontaneous arousal.

Animals↗
PubMed1979

The hypothalamo-hypophysial system in the ground squirrel, Citellus erythrogenys Brandt. II. Seasonal changes in the classical neurosecretory system of a hibernator.

Monthly observations of the "Gomori-positive" hypothalamo-hypophysial neurosecretory system (HHNS) of the ground squirrel, Citellus erythrogenys Brandt, were carried out light microscopically using several quantitative methods. From the beginning of hibernation, formation of neurosecretory material (NSM) in the neurosecretory cells (NSC) progressively decreases and release of neurohormones from the HHNS is almost fully inhibited. A maximal accumulation of NSM in the perikarya of the NSC and in the posterior pituitary (PP) is found in December. By this time the volume of the cell nuclei and nucleoli is at a minimum. Signs of activation of the HHNS appear and become more conspicuous as the time of arousal from torpor approaches. The amount of NSM in the NSC and the PP decreases simultaneously with the increase in volume of the NSC. Hyperemia and activation of glial elements is visible throughout the HHNS. The morphological signs of activation reach their peak in March. After reproduction is completed (April to beginning of May), the NSC and the PP are almost devoid of NSM. Beginning with June and during the summer and autumn months a progressive accumulation of NSM in the NSC and the PP parallels gradual diminution in the volume of the NSC structures and the glial cells. Mechanisms and effector pathways by which the HHNS influences seasonal adaptation of the organism and reproduction are discussed.

Animals↗
PubMed1994

An attempt to correlate brain areas containing melatonin-binding sites with rhythmic functions: a study in five hibernator species.

High affinity melatonin-binding sites have been described, by means of autoradiography with 2-125I-melatonin as the ligand, in more than 60 brain areas of about 20 mammalian species, with dramatic variations in the nature and number of labelled structures among the different species studied. As melatonin is involved in the synchronization of biological rhythms, we have tried to correlate the brain areas containing melatonin-binding sites with some rhythmic functions typical of given species. Therefore, we have studied the location of melatonin-binding sites in the complete brain of five long-day breeders with hibernation cycles, viz. one insectivore and four rodents. With the exception of the suprachiasmatic nuclei and the pars tuberalis of the pituitary, both of which contain binding sites in all five species, few reactive structures are common, even among species from the same family, e.g. the edible dormouse and the garden dormouse.

Animals↗
PubMed1994

The degree of dietary fatty acid unsaturation affects torpor patterns and lipid composition of a hibernator.

Diets rich in unsaturated and polyunsaturated fatty acids have a positive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of double bonds in dietary fatty acids are responsible for these alterations in torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a different number of double bonds (0, 1, or 2) on the pattern of hibernation of the yellow-pine chipmunk, Eutamias amoenus. The response of torpor bouts to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5 degree C (stearic acid C18:0, 4.5 +/- 0.8 days, oleic acid C18:1, 8.6 +/- 0.5 days; linoleic acid C18:2, 8.5 +/- 0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, +2.3 +/- 0.3 degrees C; C18:1, +0.3 +/- 0.2 degree C; C18:2, -0.2 +/- 0.2 degrees C), which torpid individuals defended by an increase in metabolic rate, and the metabolic rate of torpid animals also differed among diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phospholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 and for heart mitochondria 7 of 14 of the identified fatty acids differed significantly among the three diet groups. Significant differences among diet groups were also observed for the sum of saturated, unsaturated and polyunsaturated fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1996

Plasma triglyceride and beta-hydroxybutyric acid levels in red-sided garter snakes (Thamnophis sirtalis parietalis) at emergence from hibernation.

Measurement of plasma levels of triglycerides and beta-hydroxybutyric acid in females and males of the red-sided garter snake (Thamnophis sirtalis parietalis) suggest that the former may provide a useful physiological marker of condition. Levels of triglycerides at emergence from hibernation during a month of natural aphagia were significantly greater in females than in males and she-males, a subset of the male population that mimics females. Higher levels of triglycerides in the females may be attributed to their greater body mass per unit length, which was correlated with the level of triglycerides. Plasma triglyceride levels declined in females within one month of emergence, at the onset of feeding, and were unrelated to mating.

3-Hydroxybutyric Acid↗
PubMedDate not supplied

Effects of a number of short peptides isolated from the brain of the hibernating ground squirrel on the EEG and behavior in rats.

Intracerebroventricular administration of the peptides kyotorphin (Tyr-Arg), neokyotorphin (Thr-Ser-Lys-Tyr-Arg), and Asp-Tyr at doses of 4 and 8 micrograms altered the behavior of rats in a manner similar to that seen after similar administration of brain fractions from hibernating ground squirrels (Citellus undulatus), which contained these peptides; there were increases in orientational reactions, increases in the frequency of stereotypical scratching movements, grooming, yawning, hiccuping, and sneezing. Animals became drowsy after 15-20 min. Peptides and brain fractions also had similar effects on the EEG of rats. Brain fractions reduced theta and alpha rhythms and enhanced delta and beta frequencies. Increases in delta waves were seen with all peptides (a 4-microgram dose of kyotorphin produced alternating increases and reductions in the delta rhythm). Inhibition of theta and alpha rhythms after administration of Asp-Tyr and kyotorphin was more transient than after brain fractions. Increases in beta frequencies were seen only after administration of 8 micrograms of Asp-Tyr, the smaller dose not producing this effect.

Analgesics↗
PubMed2003

The effect of metabolic fuel availability on thermoregulation and torpor in a marsupial hibernator.

The physiological signal for torpor initiation appears to be related to fuel availability. Studies on metabolic fuel inhibition in placental heterotherms show that glucose deprivation via the inhibitor 2-deoxy-D-glucose (2DG) initiates a torpor-like state, whereas fatty acid deprivation via mercaptoacetate (MA) does not. As previous studies using inhibitors were limited to quantifying body temperature in placentals, we investigated whether inhibition of glucose or fatty acids for cellular oxidation induces torpor in the marsupial hibernator Cercartetus nanus, and how the response of metabolic rate is related to body temperature. Glucoprivation initiated a torpor-like state in C. nanus, but animals had much higher minimum body temperatures and metabolic rates than those of torpid food-deprived animals and arousal rates were slower. Moreover, 2DG-treated animals were thermoregulating at ambient temperatures of 20 and 12 degrees C, whereas food-deprived torpid animals were thermo-conforming. We suggest that glucoprivation reduces the hypothalamic body temperature set point, but only by about 8 degrees C rather than the approximately 28 degrees C during natural torpor. Reduced fatty acid availability via MA also induced a torpor-like state in some C. nanus, with physiological variables that did not differ from those of torpid food-deprived animals. We conclude that reduced glucose availability forms only part of the physiological trigger for torpor initiation in C. nanus. Reduced fatty acid availability, unlike for placental heterotherms, may be an important cue for torpor initiation in C. nanus, perhaps because marsupials lack functional brown adipose tissue.

Adaptation, Physiological↗