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 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.
1. 1. At the preferred body temperature (35°C) resting metabolic rate was 0.155 ± 0.015 ml O2/g·h and heart rate was 54 ± 11 beats/min. Spontaneous activity at this body temperature caused a two-fold increase in heart rate and a six-fold increase in O2 consumption. Maximum values being 0.86 ml/g·h with an O2 pulse of 13.6 × 10−5 ml/g·beat.
2. 2. Pre-treatment for seven days with thyroxine caused a 27% increase in resting metabolic rate and a 63% increase in the thermal gradient between core and ambient temperature at the preferred body temperature.
3. 3. Noradrenaline reduced heart rate but had no effect at the dosage recommended on metabolic rate at body temperatures of either 35 or 15°C, suggesting that non-shivering thermogenesis is absent in lizards. The evolutionary implications of these results have been briefly discussed.
Author Keywords: Thermoregulation; preferred body temperature; oxygen consumption; metabolic rate; cardiac rate; non-shivering thermogenesis; thyroxine; noradrenaline; reptiles; Varanus species 相似文献
1. 1.|Resistance to cold through non-shivering thermogenesis (the absolute increase in O2 consumption caused by noradrenaline injection) was increased 3-fold in individuals of the broad-toothed mouse A. mystacinus, kept for 3 weeks under a short photoperiod (long scotophase 8L:16D) at an ambient temperature of 28°C, compared to control conditions (12L:12D; 28°C), and did not differ significantly from the winter-acclimatized group.
2. 2.|Acclimation of the same individuals to long scotophase and cold (8L:16d; 7°C) caused a significant (P < 0.01) increase in absolute O2 consumption and maximal body temperature, as a response to noradrenaline injectin, when compared to long-scotophase individuals (8L:16D; 28°C).
3. 3.|The results of this study support the idea that winter acclimatization of heat-production mechanisims may be induced by the extension of scotophase, which cycles very regulary in nature and in the Mediterranean region occurs before the beginning of the cold season.
Author Keywords: Non-shivering thermogenesis; long scotophase; winter acclimatization; photoperiod; resistance to cold; Apodemus mystacinus 相似文献
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. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.
- 2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.
- 3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.
- 4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.
- 5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.
1. 1.|Oxygen consumption and organ growth were measured in domestic-fowl embryos incubated at different temperatures (36, 38 and 40°C).
2. 2.|Embryonic oxygen consumption was highest at an incubation temperature of 40°C and lowest at 36°C. These differences were ascribed largely to variations in embryo size at different incubation temperatures.
3. 3.|At incubation temperatuers of 40 and 38°C, there was a plateau in oxygen consumption late in incubation, but this was not apparent at 36°C.
4. 4.|At 36°C, some tissues (e.g. eyeballs) were “spared” the repression of growth that characterized the embryo as a whole, while other tissues (e.g. stomach) incurred a much greater growth reduction. Similarly, at 40°C, stomach growth exceeded that of the embryo as a whole, while the eyeballs were largely spared the enhanced growth.
5. 5.|A simple index of tissue age revealed that, in general, there were consensual changes in tissue maturity and growth at different temperatures but that there were some disparities between growth and maturity in individual organs.
Author Keywords: Avian embryos; temperature; organ growth; oxygen consumption; Gallus domesticus 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. 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.
Author Keywords: thermoregulation; BMR; gerbil 相似文献
Variations in ambient oxygenation always induced large changes of ventilatory activity, hyperventilation in hypoxia, hypoventilation in hyperoxia. Conversely, PwCO2 changes either at constant PO2 or in combination with different PO2 values (hypoxic hypercapnia or hyperoxic hypocapnia) led only to small or even non-significant ventilatory responses. In the field, strong hyperventilation developed during tidal exposure at night, when the pool water became hypoxic and hypercapnic, whereas during the day the animals hypoventilated in progressively more hyperoxic and hypocapnic conditions.
Thus, in a typical intertidal animal such as C. maenas, the only ventilatory stimulus of ecological significance appears to be the ambient water oxygenation. 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. The effects of sudden changes by increasing or decreasing the measurement temperature on the oxygen consumption of the brains of Bufo arenarum and Leptodactylus ocellatus were determined.
2. 2. The experiments were carried at in vitro at temperatures which range from 4 to 37°C. The brain was oxygenated and stabilized for 20 min at each of the temperatures to which it was subjected before oxygen consumption measurements were made.
3. 3. A theoretical curve representing the variation of oxygen consumption with temperature was calculated according to the following exponential relationship; for Leptodactylus ocellatus y = 0.408 × 1.07x and for Bufo arenarum y = 0.389 × 1.065x.
4. 4. These results were compared with the brain oxygen consumption of animals acclimated to different temperatures, whose oxygen consumption was measured at a fixed temperature. Only Leptodactylus ocellatus had a significantly lower oxygen consumption in a high range of temperatures, indicating thermal compensation, probably to save metabolic reserves.
5. 5. No deterioration of the brain tissue was observed, as several passages from high to low temperatures in the range of 20°–30°C, showed a reversible oxygen consumption in acclimated and non-acclimated Bufo arenarum and Leptodactylus ocellatus.
Author Keywords: Anuran brain; brain metabolism; oxygen consumption; acclimation 相似文献