Keywords: Carotid rete; Selective brain cooling; Thermoregulation; Artiodactyls; Cavernous sinus 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
(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
2. Mean thermal conductance of winter and summer pelage was 1.64 W/m2 °C and 1.79 W/m2 °C, respectively.
3. Mean heat loss in natural pelage, in free convection conditions was 1.74 W/m2 °C and 2.3 W/m2 °C in sheared pelts.
4. From our results, there is seasonal moult in guanacos. 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
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
(2) The response of the barnacle larvae (naupliar and cyprid stages) to elevated temperature was dependent on exposure time and their stage of development.
(3) Among the stages tested, N-6 larvae showed maximum tolerance. Exposure to 37°C did not affect larval survival, but delayed development of N-2 larva to cypris by one day.
(4) Exposure at 40°C delayed, hastened or did not affect the development time of N-2 and N-4 larvae through cypris, depending on exposure time.
(5) Ten mins exposure at 43°C proved lethal to all larval stages with mortality ranging from 20 to 86%.
(6) Development success of the surviving larvae, measured in terms of cypris yield, showed no significant difference from controls, at temperatures below 40°C.
(7) Settlement activity was significantly affected in only those cyprid larvae which were exposed to 43°C for 10 min.
(8) Results of the present study indicate that thermal stress experienced in the once-through cooling system does not have significant impact on survival and development of the barnacle larvae at temperatures of 37–40°C. 相似文献
4 groups of 10 pigs (Large White × Dutch Landrace) of approximately 10 weeks old were used. They were housed in 2 calorimeters with 2 pens each. In the reference chamber air temperature was kept constant at 25°C, in the other chamber air temperature could be lowered to 15°C, and a draught was also applied. Surface temperatures of the pigs were measured by means of Probey® Thermal Video System, with an accuracy of ±0.3°C.
Surface temperatures of growing pigs were obviously related to air temperature, draught and the duration of food withdrawal. Acclimation to air temperature or draught as measured by surface temperatures was not observed between days, but within and between night periods.
Also indications of huddling, vasocontriction and even cold-induced vasodilatation within the neck, chest and abdomen region of the pigs' body surface were observed. 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.
2. One approach to understanding human thermoregulatory capacity is to examine the upper limits of thermal balance between man and the air environment, i.e. the maximal environmental conditions under which humans can maintain a steady-state core temperature. Heat acclimation expands the zone of thermal balance.
3. Human beings can and do, often willingly, tolerate extreme heat stresses well above these thermal balance limits. Survival in all such cases is limited to abbreviated exposure times, which in turn are limited by the robustness of the thermoregulatory response.
4. Figures are provided that relate tolerance time and the rate of change in core temperature to environmental characteristics based on data compiled from the literature. 相似文献
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 Metabolic rates (Vo2), body temperature (Tb), and thermal conductance (C) were first determined in newly captured Maximowiczi's voles (Microtus maximowiczii) and Djungarian hamsters (Phodopus campbelli) from the Inner Mongolian grasslands at a temperature range from 5 to 35 °C.
2 The thermal neutral zone (TNZ) was between 25 and 32.5 °C for Maximowiczi's voles and between 25 and 30 °C for Djungarian hamsters. Mean Tb was 37.0±0.1 °C for voles and 36.2±0.1 °C for hamsters. Minimum thermal conductance was 0.172±0.004 ml O2/g h °C for voles and 0.148±0.003 ml O2/g h °C for hamsters.
3 The mean resting metabolic rate within TNZ was 2.21±0.05 ml O2/g h in voles and 2.01±0.07 ml O2/g h in hamsters. Nonshivering thermogenesis was 5.36±0.30 ml O2/g h for voles and 6.30±0.18 ml O2/g h for hamsters.
4 All these thermal physiological properties are adaptive for each species and are shaped by both macroenvironmental and microenvironmental conditions, food habits, phylogeny and other factors.
Keywords: Basal metabolic rate; Body temperature; Djungarian hamster (Phodopus campbelli); Maximowiczi's vole (Microtus maximowiczii); Nonshivering thermogenesis; Minimum thermal conductance 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.
Keywords: Core temperature; Face skin temperature; Cheek thermal resistance; Cold exposure; Exercise 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. Sceloporus at temperate latitudes had mean Tb’s of 35°C throughout their elevational range. This pattern is associated with “tropical” temperatures that extend into high north latitudes during the summer and the relatively low elevations occupied by the lizards.
3. At tropical latitudes, mean Tb declined from 35°C at low elevations to 31°C at high elevations. This pattern is associated with low seasonal variation in temperature at tropical latitudes and the relatively high elevations occupied by the lizards. 相似文献
1. Entomopathogenic nematodes penetrate and kill Galleria mellonella within 48 h at optimal temperatures.
2. Low temperature induces infection latency, preventing host death until optimal conditions resume.
3. Infected Galleria survived 25 days at 5°C. On transfer to 25°C, 100% and 12.5% of Steinernema carpocapsae and Steinernema riobravis infected larvae died within 72 h.
4. Infective juvenile penetration decreased with decreasing temperature; declining from 49.7 and 49.3 nematodes/host at 25°C to 6.3 and 0.25 nematodes/host at 5°C for S. carpocapsae and S. riobravis, respectively.
5. Latent infection occurs, albeit infrequently, due to low host penetration at low temperature.
Author Keywords: Nematode; Steinernema carpocapsae; Steinernema riobravis; Low temperature 相似文献
1. 1.|In the freshwater fish Chalcalburnus chalcoides, an increase in the body (standard) size caused decreases in the upper LT-50 from 36.6° to 36.0°C and lower LT-50 from 6.3° to 5.3°C
2. 2.|The fish acclimated to constant temperatures between 10°C and 30°C showed reasonable heat acclimation and also reasonable cold acclimation. Thus, an increase in the acclimation temperature from 10°C to 30°C caused increases in the upper LT-50 from 34° to 36.2°C and the lower LT-50 from 1.25 to 6.5°C.
3. 3|The mean survival time — temperature curves of 10°, 20° and 30°C acclimated fish at various constant temperatures showed decreased in the survival tim ewith increasing lethal temperatures. Furthermore, an increase in the acclimation temperature causes a shift in the survival duration-temperature curve to the right, i.e., the fish become more heat resistant. Thus, the mean survival duration of 10°, 20° and 30°C acclimated fish at 35°C were 7.5, 79.6 and 530 minutes, respectively.
4. 4.|The effect of the thermal experience to changing lethal temperatures depends on the first lethal temperature to which the fish were exposed as well as the sequence of temperature changes. In the experiments in which the first lethal temperatures were between 32° and 34°C and the temperature was varied in an ascending order, their thermal resistance was increased and the fish required 114 to 174% of the expected lethal doses to die while in the experiments in which the starting temperature were between 38° and 40°C and the temperature varied in descending order, the fish become more sensitive to the upper lethal temperature and they died after receiving only 62 to 81% of the expected lethal doses. Thus, with a gradual increase in the lethal temperature, the fish show additional acclimation in the zone of resistance which in turn causes an increase in the thermal resistance. This may have ecological significance in nature.
Author Keywords: acclimation; lethal temperatures; temperature change; survival 相似文献