Keywords: Core temperature; Face skin temperature; Cheek thermal resistance; Cold exposure; Exercise 相似文献
The data was obtained from 20 subjects (age: 19–36 years; BMI: 17–32 kg/m2). BC, MR, rectal and skin temperatures were measured for 1 h at 22 °C, followed by 3 h at 15 °C.
A mean bias of 1.8 °C, with a standard error of 0.7 °C, resulted for the mean skin temperature of an average person at 15 °C. When subjective BC and measured MR were incorporated the bias was −0.2±0.9 °C. For the hand-back skin temperature the bias ± standard error fell from 5.3±2.8 °C for an average person to 2.0±2.5 °C, when using individualized characteristics. Trunk skin temperatures were not significantly affected by the adjustments.
In conclusion, this study shows that on a group level predictions of skin temperatures can be improved when adopting individualized body characteristics and measured MR, but the predictions on an individual level were not improved. 相似文献
2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.
3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.
4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD). 相似文献
- 1. The present study examined the effect of the thermal state of the body (as reflected by rectal temperature) on cheek skin temperature and thermal resistance in active and inactive subjects.
2. Active subjects were exposed to a 30 min conditioning period (CP) (0 °C air with a 2 m/s wind), followed immediately by a 30 min experimental period (EP) (0 °C with a 5 m/s wind). Inactive subjects were exposed to a 30 min CP (22 °C air with no wind), followed immediately by a 45 min EP (0 °C air with a 4.5 m/s wind). The CP period was used to establish a core temperature difference between the active and inactive subjects prior to the start of EP. The 0 °C exposure was replaced with a −10 °C ambient air exposure and the experiment was repeated on a separate day. Subjects were comfortably dressed for each ambient condition.
3. Cheek skin temperature was not significantly higher in active subjects when compared to inactive subjects, but thermal resistance was higher in active subjects.
4. Cheek skin temperature and thermal resistance both decreased as ambient temperature decreased from 0 to −10 °C. The lower cheek thermal resistance at −10 °C may have been due to a greater cheek blood flow as a result of cold-induced vasodilation.
2. Skin temperatures, core temperature, thermal sensation, and comfort responses were collected for 19 local body parts and for the whole body.
3. Core temperature increased in response to skin cooling and decreased in response to skin heating.
4. Hand and finger temperatures fluctuated significantly when the body was near a neutral thermal state.
5. When using a computer mouse in a cool environment, the skin temperature of the hand using the mouse was observed to be 2–3 °C lower than the unencumbered hand. 相似文献
- 1. Each half rete from five Boer goats was perfused with water at 38 °C and flow rate of 2 ml min−1 while simultaneously perfusing the cavernous sinus with water at different temperatures and flow combinations and recording temperatures across the rete.
2. The minimum temperature difference across the rete was recorded at a cavernous sinus perfusion temperature of 37.8 °C and flow rate of 2 ml min−1.
3. Slopes of heat exchange increased threefold when the flow was increased four times.
4. These results support the idea that the rete is an obligate heat exchanger.
Keywords: Carotid rete; Selective brain cooling; Thermoregulation; Artiodactyls; Cavernous sinus 相似文献
2. At 37.5°C the relationship between HP and embryonic age follows a sigmoid curve. Between D18 (HP 7.25 J g−1 h; 2.01 W kg−1) and D19 (HP 7.21 J g−1 h−1; 2.00 W kg−1) this function had a plateau phase with a duration of about 24 h.
3. During the cooling process, HP decreased continuously and the relationship between Ta and HP could be described by an exponential function. From the results, it was possible to calculate the relationships between Taf, as a measure of body core temperature, and Q10; the lower the Taf the higher the Q10.
4. Because the actual measured HP is the result of the negative effect of Q10 on HP and the stimulating influence of the CNS-generated HP, a Q10 of more than 2.0 demonstrates the absence of endothermy. Chicken embryos aged between 14 and 21 d have a Q10 of less than 2.0 at body temperatures (Taf) between 34 and 30°C. It is postulated that in chicken embryos of this age endothermic reactions may occur.
5. The Q10-method is suitable for investigating the prenatal development of endothermic reactions in avian embryos. 相似文献
1. 1. The naked mole-rat (Heterocephalus glaber) is a poikilothermic mammal. During gestation metabolic shifts that differ from both mammalian and reptilian thermoregulatory patterns occurred.
2. 2. Body temperature was directly dependent on ambient temperature. At low ambient temperatures the temperature differential (Tb − Ta) was approximately 3°C, whereas at higher ambient temperatures the temperature differential diminished.
3. 3. In early pregnancy (prior to week 3) oxygen consumption at low ambient temperatures was greater than that of non-reproductive animals. A maximal metabolic rate (3.2 ± 1.0 ml O2 . g−1 . h−1) occurred at an ambient temperature of 27°C. Thereafter the endothermic pattern of metabolism with increasing ambient temperatures was evident. Oxygen consumption decreased with increasing ambient temperature to minimal rates of 1.2 ± 0.1 ml O2 . g−1 . h−1 over the ambient temperature range of 31–34°C.
4. 4. Oxygen consumption in late pregnancy (1.8 ± 0.1 ml O2 . g−1 . h−1) was not correlated with ambient temperature over the entire ambient temperature range measured (24–36°C).
5. 5. Differences in thermoregulation in early and late pregnancy may be attributed to different rates of heat loss as a consequence of (a) changes in surface area and body mass or (b) vascular changes. Furthermore the thermoregulatory changes in late pregnancy may indicate that maximal overall metabolic capacity had been reached, for peak resting metabolism (expressed per animal rather than per gram body mass) in early pregnancy was similar to observed metabolism in late pregnancy.
6. 6. The dissociation of metabolism from both ambient temperature and body temperature in late pregnancy could confer an energetic advantage to this arid dwelling underground inhabitant; for it may enable the breeding female to partition a greater portion of available energy into reproduction.
Author Keywords: Body temperature; endothermy; eusocial; gestation; Heterocephalus glaber; metabolic changes; naked mole-rat; oxygen consumption; poikilothermy; pregnancy; rectal temperature; thermoregulation 相似文献
1. 1.The forearm of 5 female subjects ws thermally stimulated by 2 sets of interposed servo-thermodes that respectively drove skin temperature at ±0.1°C.s−1 for 25 s and then held it constant. Mean skin temperature remained constant. The sequence was repeated at adapting temperatures between 22.5 and 37.5°C.
2. 2.Thermal sensations, continuously reported by the position of a dial, were warmer for heterogeneous thermal stimuli than for homogeneous stimuli when mean skin temperature was greater than 30°C and cooler when less than 27.5°C.
3. 3.This phenomenon is inconsistent with a single additive contribution of “warm” and “cold” information to thermal sensations.
Author Keywords: Man; thermal sensation; skin temperature 相似文献
- 1. Heat production (HP) and body core temperature (CT) where measured in 1- to 10-day old Muscovy ducklings and turkey chick, incubated during the last week before hatching at a lower (34.5 °C, LT-group) or at higher (38.5 °C, HT-group), than the normal temperature of 37.5 °C (control C-group).
2. In Muscovy ducklings, on the 1st day post-hatching HP was affected by exposure to low Ta of 10 °C Ta 28.2±3.9 W kg−1 in the LT-group vs. 18.1±2.4 W kg−1 in normal controls. On the same day, CT was higher (39.5±1.1 °C) in the HT- than in the CT-group (37.5±2.9 °C).
3. In turkeys, the relationships between Ta and HP could be described by parabola-like functions. Apart from the first day of life, the HP of the LT-group and the HT-group was higher than of the CT-group.
4. The low prenatal temperature of incubation resulted in a decrease of the preferred temperature in the LH-group and in an increase in the HT-group.
5. It is concluded that changes in incubation temperature at the end of embryonic development may induce an epigenetic temperature adaptation, which results in a long-lasting cold- and warm-adaptation in ducks but not in turkeys.
Keywords: Muscovy duck; Turkey; Epigenetic temperature adaptation; Imprinting; Determination; Heat production 相似文献
(2) The lower SCP in mummies reared at 25 °C may be partially explained by their smaller size, a negative relationship being observed between SCP and size.
(3) A bimodality was observed in SCP distributions, with two modes around −26 and −22 °C, likely because of presence/absence of gut content.
(4) The type of exposure had a striking impact, mortality being considerably lower under fluctuating regime.
(5) While energy storage is an important factor, vulnerability to chill-injury is supposed to be the primary factor regulating survival at low temperature. 相似文献
1. 1.|Neuronal activity in slices of the preoptic and anterior hypothalamic area of guinea-pigs during slow low-amplitude temperature changes analogous to temperature changes in the brain of endothermic animals, was extracellularly recorded.
2. 2.|42% of neurons showed threshold temperature responses. The threshold of response averaged 37.4°C for warm-sensitive neurons during warming and 37.0°C for cold-sensitive neurons during cooling.
3. 3.|The thresholds differed, on average, by 0.1°C in the same neuron at repeated temperature changes.
4. 4.|With temperatures 0.8°C above threshold on average (0.2°C in some units) neuronal activity reached a new high level that did not change either during a further exceeding of the threshold or prolonged maintenance of suprathreshold temperature.
5. 5.|The characteristics of the threshold temperature response of a hypothalamic neuron meet the criteria of thermoinduced structural rearrangements of cell membranes, caused by phase transitions of lipids, changes in protein conformation and cytoskeletal activity.
Author Keywords: Hypothalamic slice; thermosensitive neuron; threshold temperature response; guinea-pig 相似文献
2. Induction kinetics of delayed light varied depending on temperature. It was found to be composed of two phases; one was an initial rapid rise followed by a rather fast decline to a low steady state level (fast phase), and the other was a slow increase after the initial rapid rise to the maximum followed by an insignificant slow decrease to a high steady state level (slow phase). The fast phase existed between −175 and 40 °C with the maximum at −40 °C, while the slow phase, between 0 and 40 °C with the maximum at 25 °C.
3. The intensity of delayed light at −175 °C was found to be less than one fiftieth that at 0 °C, and no delayed light emission was observed at −196 °C within experimental accuracy. This is in contrast to the results reported by Tollin, G., Fujimori, E. and Calvin, M. ((1958) Proc. Natl. Acad. Sci. U.S. 44, 1035–1047) in which the intensity of delayed light measured at −170 °C was about a half that at 0 °C.
4. The induction of delayed light measured at −96 °C was found to be significantly suppressed by the preillumination at −196 °C. This finding suggests that the primary photochemical event still survives at −196 °C without emission of delayed light.
5. Decay kinetics of delayed light after the flash excitation revealed the presence of at least two decay components. A slow decay component with a half decay time of several tens of milliseconds was observed at temperatures higher than 0 °C. A fast decay component with a half decay time of about 0.2 ms was observed at temperatures between −120 and 25 °C. The decay rate of this component was slightly retarded on cooling.
6. The System II particles derived from spinach chloroplasts with digitonin treatment showed a temperature dependence of delayed light similar to that of the chloroplasts. System I particles, on the other hand, scarcely emitted the delayed light at any temperature between 40 and −196 °C. 相似文献
1. 1. Seven thermal conditions were imposed on male sitting subjects (slightly clothed: 0.6 clo).
2. 2. A thermal mannikin was also used to determine the exact operative temperature, T0.
3. 3. Conditions were: uniform (UN: all parameters at 24.5°C, air velocity at 0.15 ms−1), heated ceiling (HC at 45°C), heated floor (HF at 34°C), cold floor (CF at 14°C), two conditions of one cold wall at 6°C (CW1 and CW2 respectively with and without air temperature compensation) and increased air velocity (AV at 0.4 ms−1).
4. 4. Local skin temperatures and answers to questionnaires were obtained.
5. 5. Skin temperature variations were affected by conditions and slight T0 changes.
6. 6. Comfort judgments were fairly well related to T0, especially when expressed as differences between actual non-uniform environment and the uniform one.
7. 7. It is concluded that, in case of non-uniform environments close to thermoneutral zone, thermal comfort or discomfort reflects the climate alterations better than the thermal sensation does.
Author Keywords: Skin temperature; thermal sensation; comfort; climate heterogeneity 相似文献