EXERCISE AND TEMPERATURE REGULATION IN LEMMINGS AND RABBITS

1955 ◽  
Vol 33 (1) ◽  
pp. 428-435 ◽  
Author(s):  
J. S. Hart ◽  
O. Heroux
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Heat Production ◽  
Temperature Regulation ◽  
Thermal Equilibrium ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Temperature Changes ◽  
Extreme Cold ◽  
Environmental Temperatures

Oxygen consumption and body temperatures were determined in lemmings at environmental temperatures from 20 °C. to −10 °C. and in rabbits from 20 °C. to −50 °C. Body insulation indices were estimated as the ratio [Formula: see text]. In both species, increase in activity and decrease in temperature led to increases in oxygen consumption that were additive over the temperature range. Oxygen increments of work were independent of environmental temperature in the absence of progressive hypothermia. Work led to increases in body temperature at the upper environmental temperatures and to decreases in body temperature at the lower temperatures. In extreme cold, rabbits became progressively hypothermic during work and there was a decline in oxygen consumption. Body temperatures started to fall at environmental temperatures 18 °C. higher in working than in resting rabbits. Insulation was lower in working than in resting animals. During exercise there appears to be a readjustment of body temperature, insulation, and heat loss until thermal equilibrium is established. The regulation of heat production, within limits, seems to be independent of body-temperature changes during exercise.

EXERCISE AND TEMPERATURE REGULATION IN LEMMINGS AND RABBITS

1955 ◽  
Vol 33 (3) ◽  
pp. 428-435 ◽  
Author(s):  
J. S. Hart ◽  
O. Heroux
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Heat Production ◽  
Temperature Regulation ◽  
Thermal Equilibrium ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Temperature Changes ◽  
Extreme Cold ◽  
Environmental Temperatures

Oxygen consumption and body temperatures were determined in lemmings at environmental temperatures from 20 °C. to −10 °C. and in rabbits from 20 °C. to −50 °C. Body insulation indices were estimated as the ratio [Formula: see text]. In both species, increase in activity and decrease in temperature led to increases in oxygen consumption that were additive over the temperature range. Oxygen increments of work were independent of environmental temperature in the absence of progressive hypothermia. Work led to increases in body temperature at the upper environmental temperatures and to decreases in body temperature at the lower temperatures. In extreme cold, rabbits became progressively hypothermic during work and there was a decline in oxygen consumption. Body temperatures started to fall at environmental temperatures 18 °C. higher in working than in resting rabbits. Insulation was lower in working than in resting animals. During exercise there appears to be a readjustment of body temperature, insulation, and heat loss until thermal equilibrium is established. The regulation of heat production, within limits, seems to be independent of body-temperature changes during exercise.

Temperature regulation in the new-born lamb. III. Effect of environmental temperature on metabolic rate body temperatures, and respiratory quotient

1961 ◽  
Vol 12 (6) ◽  
pp. 1152 ◽  
Author(s):  
G Alexander
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Temperature Regulation ◽  
Low Temperatures ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Normal Body Temperature ◽  
Ambient Temperatures ◽  
New Born

Studies were made on temperature regulation of lambs in a closed circuit indirect calorimeter. Dry new-born lambs were able to maintain normal body temperature in ambient temperatures as low as -5°C. This was accomplished by increasing heat production to 2–3 times "basal" levels, apparently by increased oxidation of fats, and by reducing heat loss through the extremities by vasoconstriction. The lower limit of the zone of thermal neutrality was about 29°C. In unsuckled lambs within 24 hr of birth, the heat produced in response to cold appeared to be independent of pre-natal nutrition and age. It was considerably lower in lambs with hairy coats than in lambs with fine coats. Milk intake increased heat production, and this increase was abolished after 12 hr of fasting in lambs up to 3 days old, but the increase persisted in older lambs. The increase was accompanied by, and was apparently due to, elevated heat loss from the extremities, which persisted even at low temperatures. The maximal thermal insulation of the tissues, calculated from these results, was about 1 Clo; that of the fleece plus air was only 1 to 2 Clo.

Learning in hypothermic rats

1963 ◽  
Vol 18 (5) ◽  
pp. 1016-1018 ◽  
Author(s):  
J. A. Panuska ◽  
Vojin Popovic
Keyword(s):  
Body Temperature ◽  
Temperature Regulation ◽  
Operant Behavior ◽  
Environmental Temperature ◽  
Experimental Situation ◽  
External Heat ◽  
Body Temperatures ◽  
White Rats ◽  
Survival Studies ◽  
Colonic Temperature

Inexperienced shaved adult white rats cooled to a colonic temperature of 18.5 C and then rewarmed to 26.0 C, were placed at an ambient temperature of 2.0 C with the possibility of using a lever-activated heat reinforcement apparatus. Their body temperatures leveled at 29 C; and during the next 40–80 min the rats either learned to press the lever systematically for external heat and thereby rewarmed themselves to euthermia, or they drifted into deeper hypothermia leading to death. Activity records and visual observations indicate that after an average of 48 min and at a body temperature of 29.6 C (28.5–30.2 C), out of a group of 14 rats 12 learned this technique necessary for their survival. All 12 rats reached euthermia and continued to use the lever as long as they remained in the experimental situation. It is concluded that learning is possible even at a low body temperature of 29.6 C. performance; heat reinforcement; temperature regulation; body temperature; environmental temperature; operant behavior; survival studies; motivation; physiology of learning; cold physiology Submitted on March 7, 1963

CALORIMETRIC DETERMINATION OF AVERAGE BODY TEMPERATURE OF SMALL MAMMALS AND ITS VARIATION WITH ENVIRONMENTAL CONDITIONS

1951 ◽  
Vol 29 (3) ◽  
pp. 224-233 ◽  
Author(s):  
J. S. Hart
Keyword(s):  
Body Temperature ◽  
Heat Production ◽  
Temperature Rise ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Dewar Flask ◽  
Air Temperatures ◽  
Calorimetric Determination ◽  
Average Body

A method is described for determining average body temperature of mice by placing them immediately after killing in a Dewar flask containing water and recording the temperature rise. Evidence is presented to show that postmortem heat production does not contribute appreciably to the results. Average body temperatures are usually about 2 °C. lower than colonic temperatures except during lethal chilling when average temperatures are frequently higher than colonic. The rise in average body temperature produced by activity increases with environmental temperature. Body temperatures may be lower during activity than during rest at cold air temperatures.

A study of newborn rats exposed to the cold

1968 ◽  
Vol 46 (6) ◽  
pp. 865-871 ◽  
Author(s):  
G. E. Thompson ◽  
R. E. Moore
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Heat Production ◽  
Environmental Temperature ◽  
Maximum Oxygen Consumption ◽  
Maximum Heat ◽  
Endogenous Noradrenaline ◽  
Old Rats ◽  
Environmental Temperatures ◽  
Oxygen Difference

The purpose of this investigation was to study heat production in the newborn rat, and the factors which may be limiting maximum heat production in the cold. Rats of varying ages between 1 and 30 days were exposed to various environmental temperatures. The minimum oxygen consumption in the warm, and maximum oxygen consumption in the cold, increased with age. The critical environmental temperature, and the environmental temperature at which oxygen consumption was maximal, fell with increase in age. Exogenous noradrenaline raised the oxygen consumption of 6-day-old but not of 12-day-old rats above the maximum oxygen consumption found with cold exposure. The cardiac output and arteriovenous oxygen difference of 12-day-old rats was increased in the cold. These results are consistent with the view that oxygen consumption in the cold is limited in 6-day-old rats by the release of endogenous noradrenaline and in 12-day-old rats by cardiac output and the supply of oxygen to the heat-producing tissues.

Body temperature regulation and oxygen consumption in young chicks fed thyroid hormone

1991 ◽  
Vol 69 (7) ◽  
pp. 1842-1847 ◽  
Author(s):  
Gregory K. Snyder ◽  
Joseph R. Coelho ◽  
Dalan R. Jensen
Keyword(s):  
Oxygen Consumption ◽  
Thyroid Hormone ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Exposure ◽  
Elevated Serum ◽  
Body Temperatures ◽  
Serum Thyroid Hormone ◽  
Regulate Body Temperature ◽  
Young Chicks

In chicks the ability to regulate body temperature to adult levels develops during the first 2 weeks of life. We examined whether the ability of young chicks to regulate body temperature is increased by elevated levels of the thyroid hormone 3,3′5-triiodothyronine. By 13 days following hatch, body temperatures of chicks were not significantly different from those expected for adult birds. Furthermore, at an ambient temperature of 10 °C, 13-day-old control chicks were able to maintain body temperature, and elevated serum thyroid hormone levels did not increase rates of oxygen consumption or body temperature above control values. Six-day-old chicks had body temperatures that were significantly lower than those of the 13-day-old chicks and were not able to regulate body temperature when exposed to an ambient temperature of 10 °C. On the other hand, 6-day-old chicks with elevated serum thyroid hormone had significantly higher rates of oxygen consumption than 6-day-old control chicks, and were able to maintain constant body temperatures during cold exposure. The increased oxygen consumption rates and improved ability to regulate body temperature during cold exposure were correlated with increased citrate synthase activity in skeletal muscle. Our results support the argument that thyroid hormones play an important role in the development of thermoregulatory ability in neonate birds by stimulating enzyme activities associated with aerobic metabolism.

Interaction of central and peripheral factors in physiological temperature regulation

1961 ◽  
Vol 200 (3) ◽  
pp. 572-580 ◽  
Author(s):  
M. M. Fusco ◽  
J. D. Hardy ◽  
H. T. Hammel
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Heat Production ◽  
Temperature Regulation ◽  
Physiological Temperature ◽  
Warm Environment ◽  
Quantitative Estimates ◽  
Cool Environment ◽  
Localized Heating ◽  
Environmental Temperatures

To evaluate the relative importance of central and peripheral factors in physiological temperature regulation, calorimetric measurements of thermal and metabolic responses in the unanesthetized dog to localized heating of the supraoptic and preoptic regions were made at various environmental temperatures. At all temperatures, heating the hypothalamus caused an imbalance in the over-all heat exchange, and lowered core temperature by 0.8°–1.0°C. In a neutral environment, this was effected by a 30–40% depression of the resting rate of heat production. In a cool environment, heating inhibited shivering so that heat production, relative to heat loss, was low. In a warm environment, vigorous panting and vasodilatation were elicited, thereby increasing heat loss. On cessation of heating, shivering occurred in response to the lowered core temperature, but differed in intensity depending upon the peripheral thermal drive. Reapplication of heating suppressed shivering in all cases. From these data some quantitative estimates were made of the sensitivity of the hypothalamic thermoregulatory ‘centers’, and of the interaction and relative contributions of central and peripheral control.

Shivering and nonshivering thermogenesis in the bat (Myotis myotis Borkh.) during arousal from hibernation

1970 ◽  
Vol 48 (2) ◽  
pp. 102-106 ◽  
Author(s):  
Jiří Mejsnar ◽  
Ladislav Janský
Keyword(s):  
Body Temperature ◽  
Great Increase ◽  
Late Period ◽  
Nonshivering Thermogenesis ◽  
Body Temperatures ◽  
Metabolic Capacity ◽  
Middle Range ◽  
Myotis Myotis ◽  
Speed Up ◽  
Environmental Temperatures

Nonshivering thermogenesis exists in the bat (Myotis myotis Borkh.) arousing from hibernation at environmental temperatures of 4–6 °C. Nonshivering thermogenesis is essential for the start of the arousal, and it is stimulated by noradrenaline since hexamethonium prevents the increase in metabolism and body temperature. Injection of noradrenaline abolishes this inhibition by hexamethonium by inducing nonshivering thermogenesis. After simultaneous administration of hexamethonium and alderlin no calorigenic effect of noradrenaline occurs. Shivering heat production during arousal appears at body temperatures between 10 and 17 °C predominantly. In normothermic bats the calorigenic effect of noradrenaline was observed, which indicates that nonshivering thermogenesis might also be present in awake animals. During arousal at 25 °C a great increase in intensity of shivering was observed. Elimination of nonshivering thermogenesis by hexamethonium does not prevent the attainment of the homoiothermic level of body temperature, and administration of noradrenaline does not speed up the process of arousal. As is evident from the metabolic capacity of the brown fat, the heat derived from this organ could maximally participate in total metabolism by 25% at the beginning and at the late period of arousal. In the middle range of body temperatures its significance for total metabolism is only about 10–13%.

Standard metabolic rate and preferred body temperatures in some Australian pythons

1998 ◽  
Vol 46 (4) ◽  
pp. 317 ◽  
Author(s):  
Gavin S. Bedford ◽  
Keith A. Christian
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Metabolic Rate ◽  
Thermal Sensitivity ◽  
Standard Metabolic Rate ◽  
Allometric Equations ◽  
Metabolic Rates ◽  
Body Temperatures ◽  
Daily Cycle ◽  
Preferred Body Temperature

Pythons have standard metabolic rates and preferred body temperatures that are lower than those of most other reptiles. This study investigated metabolic rates and preferred body temperatures of seven taxa of Australian pythons. We found that Australian pythons have particularly low metabolic rates when compared with other boid snakes, and that the metabolic rates of the pythons did not change either seasonally or on a daily cycle. Preferred body temperatures do vary seasonally in some species but not in others. Across all species and seasons, the preferred body temperature range was only 4.9˚C. The thermal sensitivity (Q10) of oxygen consumption by pythons conformed to the established range of between 2 and 3. Allometric equations for the pooled python data at each of the experimental temperatures gave an equation exponent of 0.72–0.76, which is similar to previously reported values. By having low preferred body temperatures and low metabolic rates, pythons appear to be able to conserve energy while still maintaining a vigilant ‘sit and wait’ predatory existence. These physiological attributes would allow pythons to maximise the time they can spend ‘sitting and waiting’ in the pursuit of prey.

scholarly journals Do endotherms have thermal performance curves?

2021 ◽  
Vol 224 (3) ◽  
pp. jeb141309
Author(s):  
Danielle L. Levesque ◽  
Katie E. Marshall
Keyword(s):  
Body Temperature ◽  
Thermal Performance ◽  
Environmental Temperature ◽  
Comparative Approach ◽  
Evaporative Heat Loss ◽  
External Temperature ◽  
Performance Curves ◽  
Interspecific Comparisons ◽  
Measure Of Performance ◽  
Environmental Temperatures

ABSTRACTTemperature is an important environmental factor governing the ability of organisms to grow, survive and reproduce. Thermal performance curves (TPCs), with some caveats, are useful for charting the relationship between body temperature and some measure of performance in ectotherms, and provide a standardized set of characteristics for interspecific comparisons. Endotherms, however, have a more complicated relationship with environmental temperature, as endothermy leads to a decoupling of body temperature from external temperature through use of metabolic heat production, large changes in insulation and variable rates of evaporative heat loss. This has impeded our ability to model endothermic performance in relation to environmental temperature as well as to readily compare performance between species. In this Commentary, we compare the strengths and weaknesses of potential TPC analogues (including other useful proxies for linking performance to temperature) in endotherms and suggest several ways forward in the comparative ecophysiology of endotherms. Our goal is to provide a common language with which ecologists and physiologists can evaluate the effects of temperature on performance. Key directions for improving our understanding of endotherm thermoregulatory physiology include a comparative approach to the study of the level and precision of body temperature, measuring performance directly over a range of body temperatures and building comprehensive mechanistic models of endotherm responses to environmental temperatures. We believe the answer to the question posed in the title could be ‘yes’, but only if ‘performance’ is well defined and understood in relation to body temperature variation, and the costs and benefits of endothermy are specifically modelled.

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