Author Keywords: E. coli endotoxin; starvatipn; brown adipose tissue; direct calorimetry; indirect calorimetry; shivering thermogenesis 相似文献
1. 1. The calorigenic responses of 60-h fasted (F) and control (C) guinea pigs to E. coli endotoxin (5 μg·kg−1 i.v.) injection were compared at Ta = 25°C.
2. 2. In contrast to fed (C) guinea pigs, the F group showed significantly lower calorigenic response.
3. 3. The brown adipose tissue (BAT) thermogenesis judge by the BAT temperature did not change significantly. Shivering activity was not different from that in the C group.
4. 4. The results conclude that fasting attenuates endotoxin-induced fever and this attenuation is due to suppression of nonshivering thermogenesis (NST) in guinea pigs.
5. 5. The results from direct calorimetry indicate that endotoxin injection evoked a prominent increase in heat production, while the changes in heat loss do not have an important role.
1. 1.|The metabolic role of the thyroid gland was studied in intact snakes, Naja naja and Ptyas korros treated with tri-iodo-thyronine (T3) and thyroxine (T4) and in thyroidectomized (Tx) N. naja kept at 21°C by analyzing tissue composition and glycogen phosphorylase a activity.
2. 2.|Liver weight was unaffected by thyroid hormone injection in both species but decreases in liver glycogen followed T3 or T4 injection, and there was an increase in liver glycogen in N. naja. These changes in liver glycogen were accompanied by a decrease in glycogen phosphorylase a activity with T3 injection. T3 decreased muscle glycogen in Ptyas and Tx increased it in N. naja.
3. 3.|T3 increased % liver lipid in Ptyas but not in Naja.
4. 4.|Between species, there were differences in liver weight, blood glucose level, cholesterol level and % muscle lipid.
5. 5.|The results showed that thyroid hormones affected carbohydrate and lipid metabolism at a low temperature of 21°C, although the significance is not known.
Author Keywords: Snake, metabolism; liver glycogen and lipid; low temperature; Naja naja; Ptyas korros 相似文献
1. 1|Energy metabolism of 38 rats acclimated to 10, 20 and 30°C was measured at these ambient temperatures and the regression equations over body weight were calculated.
2. 2|Expressing metabolic rate as M = kWn, the results showed that the value of n is apparently variable according to the acclimation and measurement temperatures.
3. 3|It was also shown that the 2/3 power of body weight is a suitable parameter to express metabolic rate, regardless of acclimation or environmental temperatures.
Author Keywords: Acclimation; energy metabolism; O2 consumption 相似文献
1. 1. A new and simple device for measurements of thermal conductivity of fur and blubber is described.
2. 2. The device measures temperature differences across the sample and across a polyethylene plate with known conductivity which is placed in series with the sample.
3. 3. The conductivity of the polyethylene was determined from the steady state temperature difference and heat flux through the wall of a polyethylene pipe with a central heat source.
4. 4. The accuracy of the device is ±4.0%.
5. 5. The thermal conductivity of harp seal (Phoca groenlandica) and minke whale (Balaenoptera acutorostrata) blubber, as determined by use of this device, is very close to previously reported values.
Author Keywords: Seal; whale; thermoregulation; energetics; thermal conductivity; blubber; fur 相似文献
1. 1.|Hypothalamic and rectal temperatures were recorded in 8 warm-reared (wr) and in 12 warm-acclimated control rats during resting in the heat and during 30 min running under thermoneutral conditions.
2. 2.|Brain and body temperatures of wr rats were significantly higher (P < 0.001) than control rats, both in normothermia as well as in hyperthermia; at rest, and also during exercise.
3. 3.|Warm-reared rats were more tolerant to heat.
4. 4.|During normothermia a weak selective brain cooling was present in control but absent in wr rats. During hyperthermia, however, the cooling intensified in control and occurred in wr rats.
5. 5.|The main strategy of adaptation to heat in wr rats is an upward resetting of the temperature set-point and increased passivity.
Author Keywords: Warm rearing; temperature regulation; exercise; heat stress; selective brain cooling; rats 相似文献
1. 1.The changes in fatty acid composition of trout liver phosphatidyl-choline, when the environmental temperature was increased, resulted in modifications in the amounts of the different molecular species.
2. 2.In vivo, incorporation of 32P occurred more rapidly in the molecular species with high degree of unsaturation.Temperature acclimation did not modify the relative proportions of label shown in the five subfractions.
3. 3.In vitro incorporation of 14C-methyl-choline also occurred more rapidly in the most unsaturated molecular species. However, when the incubation temperature was raised, the proportion of label decreased in the unsaturated fractions.
Author Keywords: Acclimation; 14C-choline incorporation; environmental temperature; fatty acid; molecular species; 32P incorporation; phosphatidyl-choline; trout 相似文献
1. 1.|Circadian changes in heat production (M), heat loss (H), core temperature (Tc) and feeding activity (FA) of ad-lib fed rats were observed by direct and indirect calorimetry.
2. 2.|M, H and Tc showed a clear nocturnal increase associated with several discrete increases.
3. 3.|Whereas the slope of M vs Tc relation did not change appreciably within a day, the slope of H vs Tc or thermal conductance vs Tc relation tended to decrease at night, implying that the correlation between heat loss and body temperature is also a function of time of day in rats.
Author Keywords: Heat loss vs core temperature; thermal conductance; circadian rhythm; direct and indirect calorimetry 相似文献
1. 1.|Selected body temperatures (SBT) of adult male, female and subadult Lacerta vivipara from a Belgian population, were measured monthly in a laboratory thermogradient.
2. 2.|Monthly mean SBTs varied between 29.9 and 34.0°C and differed significantly among months in all three lizard groups, and among lizard groups in 4 out of 6 months.
3. 3.|Evidence for a positive relationship between monthly SBT and air temperature was found in the subadults, but not in the adult lizards.
4. 4.|Monthly mean SBTs measured in this study were consistently higher (mean difference = 2.0°C) than those obtained by Patterson and Davies (1978) in a similar study on Lacerta vivipara from southern England.
Author Keywords: Selected body temperature; behavioural thermoregulation; Lacerta vivipara; intraspecific variation in body temperature 相似文献
1. 1.|Newly-released larvae of both E. modestus and B. balanoides show similar tolerances to steady temperature levels.
2. 2.|Both species show an ability to withstand a wider range of temperatures when subjected to cyclic thermal shocks.
3. 3.|E. modestus shows a greater tolerance to short-term thermal shocks than B. balanoides.
Author Keywords: Tolerance; cyclic temperautres; barnacles; larvae 相似文献
1. 1.|Dinitrophenol (DNP) was administered to rats in two equal dosages (20 mg/kg, 30 min interval); the second injection was followed immediately by exercise (9.14 m/min) in the heat (30°C) or at room temperature (21°C).
2. 2.|At 21°C control (saline-treated) rats manifested a mean endurance of 94 min which was reduced to 32 min among DNP-treated animals.
3. 3.|At 30°C, control rats ran for 65 min (δTre/min = 0.05°C) while DNP-treated animals had a mean endurance of only 12 min (δTre/min = 0.22°C).
4. 4.|DNP-treated rats (30°C) manifested no decrements in tail-skin heat loss (δTsk/min = 0.17°C vs 0.10°C) or saliva secretion (0.78 g/min, DNP vs. 0.19 g/min, control) for their brief treadmill duration.
5. 5.|The increased metabolic heat production of DNP severely reduced performance.
Author Keywords: Dinitrophenol; exercise; heat stress; endurnace; temperature regulation 相似文献
1. 1.|Fourteen male volunteers were examined under passive heating.
2. 2.|Electrical skin resistance (ESR) and rectal temperature (Tre) were measured during the whole period of exposure.
3. 3.|It was found that:
• —|ESR decreases rapidly with increasing air temperature. Assuming an exponential curve yields a mean time constant of 14 min.
• —|There is a correlation between the individual ESR time constants and Tre increases (r = 0.695, P < 0.005).
• —|Additional changes of ESR were noted in 8 subjects at a constant air temperature of 42°C.
4. 4.|It is concluded that ESR may be a useful indicator of the sweating response of the human thermoregulatory system during exogenous heat load.
Author Keywords: Electrical skin resistance; rectal temperature; sweating; heating, man 相似文献
1. 1.|Mean supercooling points (SCP) of Anguispira alternata (Say) gradually declined in autumn and increased in spring. SCP also declined in autumn in Discus conrkhitei (Newcomb) and Gastrocopta armifera (Say).
2. 2.|Supercooling ability varied among the species, being the greatest in G. armifera.
3. 3.|Prolonged exposure of winter animals to high temperatures resulted in only a modest increase in SCP.
4. 4.|Low temperature survival of D. cronkhitei and G. armifera was slightly poorer than predicted by the mean SCP.
Author Keywords: Cold-hardiness; supercooling point; land snail; Pulmonata; Anguispira alternata; Discus cronkhitei; Gastrocopta armifera; Helicodiscus parallelus 相似文献
1. 1.|Larval development and metamorphosis of Achaea junta were prolonged at 22°C, compared to 27, 32 and 35°C.
2. 2.|Overall rates of consumption, assimilation, production and metabolism of the larvae increased with temperature.
3. 3.|Efficiencies of assimilation and conversion of the digested food were significantly altered by life stage and temperature.
4. 4.|About 60% of the pupal energy was transferred to the imago at the tested temperatures.
Author Keywords: Lepidoptera; Noctuidae; Achaea junta; insect; development; bioenergetics; temperature effect; moths 相似文献
1. 1.Rana perezi adult frogs were acclimated to cold (10 ± 2°C) and warm (29 ± 1°C) temperatures for 4 months.
2. 2.After acclimation, a partial compensation of the oxygen consumption of the animals was found because of a reduction of its thermal sensitivity.
3. 3.Activities of liver and lung catalase, selenium (Se)-dependent and Se-independent glutathione peroxidases were not changed by thermal acclimation.
4. 4.Tissue peroxidation (TBA-RS) increased in the liver of heat acclimated animals.
5. 5.Hydroperoxide detoxifying enzyme activities did not show inverse compensation of temperature during acclimation. It is proposed that the pattern of thermal compensation shown by these enzymes in different species depends on a variety of factors including: (a) the thermal sensitivities of hydroperoxide producing and scavenging systems; (b) the changes induced by acclimation in the rate of hydroperoxide generation.
Author Keywords: Temperature acclimation; thermal compensation; oxygen radicals; hydroperoxides; catalase; glutathione peroxidase; lipid peroxidation; oxygen consumption; hydrogen peroxide; oxidative stress; free radicals; frog; acclimation; compensation; detoxifying enzymes; Rana perezi 相似文献
1. 1. A method for assessing the set temperature regulating behavioural thermoregulation in the fish Chromus chromus is described.
2. 2. Cholinergic stimulation of the brain, both muscarinic and nicotinic, lowered the thermoregulatory set point.
3. 3. Histamine raised the set temperature by an action on H1-receptors.
4. 4. Increasing brain catecholamines, with -Dopa, also raised the set temperature but it was not possible to distinguish between dopaminergic or noradrenergic components of this response.
Author Keywords: Behavior; thermoregulation; fish (Chromus chromus); acetylcholine; histamine; dopamine; norepinephrine; neurotransmission 相似文献
1. 1. In a diel cycle Procambarus clarkii has two preferred temperatures: 24.0 ± 0.15 SEM °C during the day and 26.7 ± 0.13 SEM °C at night.
2. 2. The preferred temperatures are independent from the weight of the organisms.
3. 3. In the photophase the animals are dispersed, in the scotophase they congregate.
4. 4. The crawfish seem to feed during the thermal interphases.
5. 5. Animals in a constantly dark condition maintain a diel preferendum of temperature.
Author Keywords: Diel thermoregulation; Procambarus clarkii 相似文献
1. 1. Western Grey Kangaroos generally inhabit more arid and hotter regions than Eastern Greys.
2. 2. Ears from Western Greys are significantly thinner, less furred and have smaller, thinner hairs than those from Eastern Grays.
3. 3. Ears may act as better heat dissipators in the Western Greys than in the Eastern Greys.
Author Keywords: Grey kangaroos; Macropus giganteus; Macropus fuliginosus; ears; thermoregulation; heat loss 相似文献
1. 1.Three month-old seedlings of Taxodium distichum, Nyssa aquatica, Cephalanthus occidentalis and cuttings of Salix nigra were acclimated to simulated natural swamp conditions (ambient temperature, saturated soil) and then used to assess direct high temperature injury of root tissue.
2. 2.Electrolyte leakage from excised root tissue exposed for 30 min to temperatures ranging from 30 to 66°C was used to assess cellular injury.
3. 3.The relationship between leakage and temperature was sigmoidal for each species.
4. 4.Inflection point temperatures on the response curves, ranged from 45.4 to 51.0°C, were species-specific, and indicated differences in thermal tolerance of root membranes.
5. 5.Root of C. occidentalis and N. aquatica were more heat tolerant than roots of T. distichum and S. nigra.
Author Keywords: Bald cypress; waver tupelo; button bush; black willow; direct heat injury; membrane heat tolerance 相似文献
1. 1. A new type of simulator for clothing microclimate was designed and constructed.
2. 2. The simulator was designed to simulate the humidity fluctuation of clothing microclimate as observed under light working conditions and to measure the surface temperature of sample fabrics against the skin by means of a radiation thermometer.
3. 3. Knitted fabrics of cotton and polyester, and polyethylene films were used as specimens with different hygroscopicities.
4. 4. The quick rise and fall in the surface temperature of cotton fabric was observed under rapid fluctuations of the microclimate humidity.
5. 5. Under the same humidity fluctuations, the temperature of polyester fabric rose and fell more moderately than that of cotton fabrics, and the temperature of the polyethylene film did not change. When the rate of change in stimulus temperature is higher, the threshold temperature of warm sensation of the skin comes closer to a given adaption temperature.
6. 6. Therefore, the rapid and large changes in the fabric temperature against the skin, which were observed especially for hygroscopic cotton fabric, must affect the thermal comfort of clothing.
Author Keywords: Clothing microclimate; humidity changes; temperature change; simulator thermal sensation; cotton; polyester hygroscopic fiber 相似文献