Author Keywords: thermoregulation; BMR; gerbil 相似文献
1. 1. The response of oxygen consumption (VO2), thermal conductance (Cd and Cmin, body temperature (Tb), and evaporative water loss (EWL) of Tatera leucogaster and Desmodillus auricularis were measured over the range of ambient temperatures (Ta) from 5–35°C.
2. 2. Basal metabolic rate (BMR) of T. leucogaster was 0.841 ± 0.049 ml O2 g−1 h−1 and lower than predicted, while that of D. auricularis was similar to the expected value (1.220 ± 0.058 ml O2 g−1 h−1). D. auricularis had a high, narrow thermoneutral zone (TNZ) typical of nocturnal, xerophilic, burrowing rodents.
3. 3. D. auricularis and T. leucogaster regulated Tb over the range Ta = 5–35°C and kept EWL and dry thermal conductance at a minimum below the TNZ. However, the EWL of T. leucogaster increased rapidly above Ta = 30°C.
4. 4. After comparison with data from other species, it was concluded that there is an optimum size for xeric, nocturnal, burrowing rodents.
1. 1.|Oxygen consumption ( ) and body temperture (Tb) of Hawaiian brown noddies (Anous stolidus pileatus [Aves: Laridae]) during late incubation and in the first 24 h after hatching were measured at ambient temperatures (Ta) between 28 and 38°C and between 15 and 43°C, respectively. Evaporative cooling by hatchings at Ta of 36–43°C was also measured.
2. 2.|Throughout the late incubation stages studied, and Tb both varied directly with Ta in an ectothermic pattern.
3. 3.|The hatchlings successfully regulated Tb at Ta between ca. 29 and 43°C.
4. 4.|The functional basis of the abrupt increase in thermoregulatory capacity with hatching is discussed.
Author Keywords: Anous stolidus pileatus; bird; late incubation embryos; pipping; hatchlings; metabolic level; development of homeothermy; regulatory thermogenesis; evaporative cooling 相似文献
1. 1.|Heat production (HP) and body temperature (Tb) measurements were conducted at ambient temperatures (Ta) between 10 and 40°C. In addition preference temperatures (PT) were determined in a temperature channel and Tb was measured at preferred Ta
2. 2.|The influence of age on Tb at constant, as well as at PT, was proved. Increasing age was accompanied by an elevation of Tb whereas HP remained constant in the mid-range of Ta
3. 3.|The lower Tb in the first days of life is suggested to result from a lower thermoregulatory set point during the postnatal period.
4. 4.|The PT were different for the observed types of behaviour. The PT at rest was higher than the PT during locomotion, food intake and drinking.
Author Keywords: Bird; Meleagris gallopavo; heat production; body temperature; preference temperatures; thermoregulatory set point 相似文献
1. 1.|Preferred ambient temperature (Ta) and ventilatory frequency were measured in free-moving hamsters exposed to 2450 MHz microwaves. A waveguide exposure system which permits continuous monitoring of the absorbed heat load accrued from microwave exposure was imposed with a longitudinal temperature gradient which allowed hamsters to select their preferred Ta. Ventillatory frequency was monitored remotely by analysing the rhythmic shifts in unabsorbed microwave energy passing down the waveguide.
2. 2.|Without microwave exposure hamsters selected an average Ta of 30.2°C. This preferred Ta did not change until the rate of heat absorption (SAR) from microwave exposure exceeded approx. 2 W kg−1. In a separate experiment, a SAR of 2.0 W kg−1 at a Ta of 30°C was shown to promote an average 0.5°C increase in colonic temperature. Hamsters maintained their ventilatory frequency at baseline levels by selecting a cooler Ta during microwave exposure. In contrast, hamsters maintained at a Ta of 30°C (without a temperature gradient) underwent a sharp increase in ventilatory frequency compared to animals allowed to select their own Ta.
3. 3.|These data support previous studies suggesting that during thermal stress behavioural thermoregulation (i.e. preferred Ta) takes prescedence over autonomic thermoregulation (i.e. ventilatory frequency). It is apparent that selecting a cooler Ta is a more efficient and/or effective than autonomic thermoregulation for dissipating a heat load accrued from microwave exposure.
Author Keywords: 2450 MHz; breathing rate; preferred Ta; specific absorption rate; hamster; Mesocricetus auratus; thermoregulation 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
1. 1.|The turtle Mauremys caspica cools significantly faster than it heats in air. The heating/cooling ratio is 0.49.
2. 2.|The variation of body temperature in relation to time-course in response to a step-function change of environmental temperature, fitted to a second-order system improves that of a first-order system.
3. 3.|The gradient between ambient temperature (Ta) and equilibrium body temperature (Tb) increases significantly and progressively when ambient temperature rises over 25°C.
4. 4.|At 40°C thermoregulatory hyperventilation was detected, implying an increase in air convection requirement (ventilation relative to O2 consumption, ).
Author Keywords: Turtles; heating and cooling rates; thermoregulation; ventilation; Mauremys caspica; reptile 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. 1. Thermoregulatory respones to gradual rise and fall in the ambient temperature (Ta) were compared between 8 old (68–78 years) and 8 younger (20–25 years) male subjects.
2. 2. Starting at Ta of 31.5°C (r.h. 40%), Ta was raised to 39.5°C, then lowered to 21.5°C, and raised back to 31.5°C at a constant rate of 0.3°C/min.
3. 3. Noticeable differences in responses between the age groups were as follows: decline of sweating rate and reduction of acral blood flow during room cooling were retarded in the aged group, with wider variations among individuals, compared with those in the younger group; the tympanic and oesophageal temperatures fell considerably during cooling in the elderly group, failing to return to the level at start during the rewarming of the room, in contrast to the younger group.
4. 4. Such sluggish responses may be attributed largely to reduced cutaneous thermal perception with advancing age.
Author Keywords: Ageing; thermoregulation; sweating; skin blood flow; thermal perception 相似文献
1. 1.|Oil caused a substantial decrease in the insulative value of polar bear (Ursus maritimus) pelts measured in vitro.
2. 2.|Following oil contamination the calm air heat transfer coefficient increased by a factor of 2 to 5: the wind coefficient averaged 290% greater and the solar utilization increased by 55%.
3. 3.|Conductance through oil-covered furs remained high at winter temperatures (Ta = 0.6°C) but decreased with time at summer temperatures (Ta = 24.7°C).
4. 4.|The most viscous of the three oils tested had a more consistently negative effect on insulation.
Author Keywords: Conductance; fur; insulation; marine mammals; oil pollution; petroleum; polar bear; solar radiation; thermal; thermoregulation; Ursidae; Ursus maritimus; windchill 相似文献
1. 1.|Intraventricular injections of serotonergic agonists and receptor blockers were given to sheep to determine whether the central nervous pathway mediating the drive to heat production involves serotonergic synapses.
2. 2.|At 15°C ambient temperature (Ta), 5-hydroxytryptamine (5-HT) at all doses tested, and norfenfluramine (NF) in low doses increased heat loss and decreased rectal temperature (Tre); lysergic acid diethylamide (LSD-25) and methysergide prevented these effects.
3. 3.|AT 0°C Ta, 5-HT, even in high doses failed to increase heat production but NF increased heat production and Tre.
4. 4.|The results suggest the effects of NF and LSD-25 on heat production may be related to synapses activated by an indoleamine other than 5-HT.
Author Keywords: Heat loss; heat production; 5-hydroxytryptamine; hypothalamus; lysergic acid diethylamine; methysergide; norfenfluramine; sheep; thermoregulation 相似文献
1. 1.|Linearization techniques commonly used to solve energy budget equations of animals and plants can result in inaccurate estimates of body temperature(Tb).
2. 2.|Errors can be large when actual Tbs differ from the temperature used in linearization techniques; this is especially true for wet-skinned animals.
3. 3.|Iterative solutions of linearized equations can give accurate calculations of Tb.
Author Keywords: Energy balance; biophysical ecology; iterative numerical methods 相似文献
- 1. We investigated the association between field body temperatures (Tb), field air temperatures (Ta), and their differences (Δ) with measurements of foraging activity (percentage of time moving (PTM), number of movements per minute (MPM) and proportion of prey attacked while moving (PAM)) for 25 species of lacertid lizards.
2. Lizards active at relatively high field body temperatures tended to have higher PTM and PAM values. We found no association between temperatures and MPM. The difference Δ did not co-vary with PTM and MPM, but showed a positive trend with PAM.
3. Our results seem robust with regard to the assumptions of different models of evolution and to the phylogenetic trees used.
Keywords: Foraging; Thermal ecology; Lizard; Lacertidae; Evolution 相似文献
Ten volunteers, four females, six males, mean age 51.1±11.8 years, gave informed consent to wear the two systems for the duration of the passage of the temperature capsule through their digestive tracts. Minute-by-minute comparisons were made between the temperatures recorded by the two systems. Parameters reported include: average transit time of the capsule; temperature at each minute of the experiment; mean difference in temperature at each time point; correlation coefficient for the two temperature measurements; and number of missed data points for each system.
Mean capsule transit time was 48.6±35.5 h with a range of 12.4–136.2 h. The mean temperature for all subjects was 36.93 °C±0.15 °C and 36.96 °C±0.16 °C for the capsule and rectal probe respectively, with no significant difference between the means. The mean difference between readings (capsule–rectal probe) was 0.04 °C±0.03 °C. There was a significant correlation between the capsule and rectal probe temperatures, R2=0.80,p<0.05 and R2=0.90,p<0.05 for all data points and quiescent periods respectively. Of the average 2916±2132 data points per subject, there was a significant (p<0.05) difference in data points lost, 105±120 with VitalSense vs. 449±697 with the rectal probe. The percentage of missing data points was 3.1%±2.5% for the capsule (monitor out of the one-meter range of the capsule) and 11.4%±15.9% for the rectal probe (primarily due to probe slippage, but also due to removal for personal hygiene). The data support the finding that the VitalSense core body temperature monitoring system is at least as accurate as rectal probe monitors and the subjects found it to be much more acceptable. 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