共查询到20条相似文献,搜索用时 0 毫秒
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A Riesenfeld 《American journal of physical anthropology》1976,44(1):111-112
Rats exposed to cold stress show a reduction of relative cortical thickness in their long bones. The reaction resembles reduction of cortical thickness observed in Asiatic humans of the Mongoloid race, in whom many morphological features have been postulated to be cold-adaptive. However, until it can be established that the physiological processes underlying the experimental and phylogenetic condition are similar, no extrapolation can be attempted from the one to the other. 相似文献
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C. Adán A. Ardévol X. Remesar M. Alemany J. A. Fernández-López 《Molecular and cellular biochemistry》1994,130(2):149-157
The changes in hind leg tissue (muscle and skin) amono acid pool size and arteriovenous balance were measured in rats subjected to 0–90 min of cold exposure (4°C). Tissue free amino acid pools presented a different composition pattern from protein amino acids. Muscle rapidly reacted to cold exposure by releasing small amounts of some amino acids (alanine, aspartate), with only small changes in pool size during the first 30 min. Amino acid oxidation was very limited during the whole period of cold exposure, since at all times tested there was either nil ammonia efflux or net absorption of ammonia and glutamine; i.e. the muscle was in positive nitrogen balance throughout the period studied. Thus most of the amino acid nitrogen taken up from the blood and not found in the free amino pools must have been incorporated into protein, since it was not oxidized, as shown by the glutamine and ammonia blance. The data on amino acid incorporation into proteins indicate that hind leg protein turnover is rapidly and widely modulated from a low initial setting upon cold exposure to a higher protein synthesis rate immediately afterwards, suggesting that protein turnover may have an important role in short-term events in cold-exposed muscle, in addition to its influence in long-term adaptation. 相似文献
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Uncoupling protein has been thought to be expressed only in the brown adipose tissue mitochondria of mammals. However, mRNA encoding mitochondrial uncoupling protein was detected in the liver of newborn rats and adult rats after cold exposure, although not in the liver of untreated adult rats. 相似文献
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Venditti P Napolitano G Di Stefano L Di Meo S 《Journal of bioenergetics and biomembranes》2011,43(4):387-397
In cold exposed rats, it is known that vitamin E induces an increase in the respiration of the whole mitochondrial population
isolated from liver. To obtain information on the effects of cold exposure and vitamin E treatment on the dynamics of mitochondrial
population, we determined characteristics of rat liver mitochondrial fractions, resolved at 1,000 (M1), 3,000 (M3), and 10,000 g (M10). We found that cold exposure increased the liver content of total mitochondrial proteins irrespective of vitamin E treatment.
Conversely, protein distribution among the mitochondrial subpopulations was differentially affected by cold and antioxidant
integration. In a cold environment, the M1 fraction, characterized by the highest O2 consumption and H2O2 production rates, underwent a remarkable protein content reduction, which was attenuated by vitamin E. These changes were
dependent on the opposite effects of the two treatments on mitochondrial oxidative damage and susceptibility to swelling.
The proteins of the other fractions, in which the above effects were lower, underwent smaller (M3) or no change (M10) in the treatment groups. The cold also led to an increase in O2 consumption of the M1 fraction which was accentuated by vitamin E treatment. This phenomenon and the vitamin-induced recovery of the M1 proteins supply an explanation of the previously reported increase in the respiration of the whole mitochondrial population
induced by vitamin E in the liver from cold exposed rats. 相似文献
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Nira Ben-Jonathan 《Life sciences》1978,23(1):39-43
During the last day of gestation, dopamine was higher in fetal than in maternal plasma whereas norepinephrine and epinephrine were similar. Immediately after birth, plasma norepinephrine and epinephrine fell to 10% of their levels in term fetuses, remained low in the second day of life and reached adult levels within one to two weeks. Plasma dopamine, however, did not reduce much after birth. The data are consistent with the predominance of the extra-adrenal chromaffin tissue in the fetus, its postnatal involution, and the delayed maturation of the adrenal medulla in the newborn. 相似文献
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Electroacupuncture (EA) stimulation mediated the release of [3H]norepinephrine (NE) from synaptosomes prelabeled with [3H]NE. The pulse release of [3H]NE by EA stimulation was dependent on the presence of Ca2+. Treatment of rats with EA for 30 min at 4 Hz did not significantly alter the dopamine (DA) content in hypothalamus, cerebellum, pons, midbrain, and cerebral cortex regions, but the DA level was decreased by 20% in caudate nucleus. The NE level was found to increase by 43% in caudate nucleus and 38% in hypothalamus. The results indicate that only certain neuronal pathways are affected by the EA treatment, and that NE and DA may respond differently to such stimulation. 相似文献
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Pulmonary vascular responsiveness in cold-exposed calves 总被引:1,自引:0,他引:1
K J Greenlees A Tucker D Robertshaw C R Vader 《Canadian journal of physiology and pharmacology》1985,63(2):131-135
The pulmonary vascular responses to acute hypoxia and to infusions of histamine and 5-hydroxytryptamine (5-HT) were recorded in unanesthetized standing bull calves under neutral (16-18 degrees C) and cold (3-5 degrees C) temperature conditions. Cold exposure alone resulted in a significant increase in pulmonary arterial wedge pressure from 10.2 +/- 3.5 to 15.9 +/- 4.9 Torr (1 Torr = 133.322 Pa). Resistance to blood flow between the pulmonary wedge and the left atrium significantly increased from 0.50 +/- 0.51 to 1.21 +/- 0.78 mmHg . L-1 . min-1 (1 mmHg = 133.322 Pa) with cold exposure. This apparent pulmonary venoconstrictor response to cold exposure was further evaluated to determine if hypoxia, histamine, or 5-HT responsiveness was altered by cold exposure. Twelve minutes of hypoxia increased pulmonary arterial and systemic arterial pressures, heart rate, and respiratory rate similarly in cold and neutral temperatures. Cold exposure did not alter the dose-related reductions of systemic arterial and pulmonary arterial pressures in response to histamine. Similarly, the decreases in systemic arterial pressure and heart rate and increases in pulmonary arterial and left atrial pressures in response to 5-HT were not significantly different in cold and neutral conditions. It was concluded that acute, mild cold exposure results in an increase in resistance to blood flow in the pulmonary venous circulation without a general increase in pulmonary vascular reactivity, as measured by responses to hypoxia, histamine, and 5-HT. 相似文献
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Loss of brown adipose tissue uncoupling protein mRNA on deacclimation of cold-exposed rats 总被引:1,自引:0,他引:1
S Reichling R G Ridley H V Patel C B Harley K B Freeman 《Biochemical and biophysical research communications》1987,142(3):696-701
The effect of environmental temperature on the level of uncoupling protein mRNA from rat brown adipose tissue was examined using a cDNA probe. A 4.4 fold increase in the mRNA level was observed after 1 day exposure of rats to 6 degrees C, which was followed by a slow loss with longer times of exposure. When rats were returned to a thermoneutral environment, there was a dramatic loss of uncoupling protein mRNA within 1 day. Comparison wih poly(A)+ RNA levels suggest that the response to temperature is specific for uncoupling protein mRNA. 相似文献
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Gabaldón AM Gavel DA Hamilton JS McDonald RB Horwitz BA 《American journal of physiology. Regulatory, integrative and comparative physiology》2003,285(1):R91-R98
Near the end of life, old F344 rats undergo a transition, marked by spontaneous and rapidly declining function. Food intake and body weight decrease, and these rats, which we call senescent, develop severe hypothermia in the cold due in part to blunted brown fat [brown adipose tissue (BAT)] thermogenesis. We tested the hypothesis that this attenuation may involve diminished sympathetic signaling by measuring cold-induced BAT norepinephrine release in freely moving rats using linear microdialysis probes surgically implanted into interscapular BAT 24 and 48 h previously. In response to 2 h at 15 degrees C, senescent rats increased BAT norepinephrine release 6- to 10-fold but did not maintain homeothermy. This increase was comparable to that of old presenescent (weight stable) rats that did maintain homeothermy during even greater cold exposure (2 h at 15 degrees C followed by 1.5 h at 8 degrees C). Tail temperatures, an index of vasoconstrictor responsiveness to cold, exhibited similar cooling curves in presenescent and senescent rats. Thus cold-induced sympathetic signaling to BAT and tail vasoconstrictor responsiveness remain robust in senescent rats and cannot explain their cold-induced hypothermia. 相似文献