Metabolic Heat Production and Evaporative Heat Loss in Desert Phasianids: Chukar and Sand Partridge

1986 ◽  
Vol 59 (6) ◽  
pp. 592-605 ◽  
Author(s):  
Rafael Frumkin ◽  
Berry Pinshow ◽  
Yitzhak Weinstein
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Evaporative Heat Loss ◽  
Metabolic Heat

Mechanisms of thermal stability during flight in the honeybee apis mellifera

1999 ◽  
Vol 202 (11) ◽  
pp. 1523-1533 ◽  
Author(s):  
S.P. Roberts ◽  
J.F. Harrison
Keyword(s):  
Thermal Stability ◽  
Heat Loss ◽  
Heat Production ◽  
Radiative Heat ◽  
Carbon Dioxide Production ◽  
Metabolic Heat Production ◽  
Evaporative Heat Loss ◽  
Radiative Heat Loss ◽  
Convective Heat Loss ◽  
Metabolic Heat

Thermoregulation of the thorax allows honeybees (Apis mellifera) to maintain the flight muscle temperatures necessary to meet the power requirements for flight and to remain active outside the hive across a wide range of air temperatures (Ta). To determine the heat-exchange pathways through which flying honeybees achieve thermal stability, we measured body temperatures and rates of carbon dioxide production and water vapor loss between Ta values of 21 and 45 degrees C for honeybees flying in a respirometry chamber. Body temperatures were not significantly affected by continuous flight duration in the respirometer, indicating that flying bees were at thermal equilibrium. Thorax temperatures (Tth) during flight were relatively stable, with a slope of Tth on Ta of 0.39. Metabolic heat production, calculated from rates of carbon dioxide production, decreased linearly by 43 % as Ta rose from 21 to 45 degrees C. Evaporative heat loss increased nonlinearly by over sevenfold, with evaporation rising rapidly at Ta values above 33 degrees C. At Ta values above 43 degrees C, head temperature dropped below Ta by approximately 1–2 degrees C, indicating that substantial evaporation from the head was occurring at very high Ta values. The water flux of flying honeybees was positive at Ta values below 31 degrees C, but increasingly negative at higher Ta values. At all Ta values, flying honeybees experienced a net radiative heat loss. Since the honeybees were in thermal equilibrium, convective heat loss was calculated as the amount of heat necessary to balance metabolic heat gain against evaporative and radiative heat loss. Convective heat loss decreased strongly as Ta rose because of the decrease in the elevation of body temperature above Ta rather than the variation in the convection coefficient. In conclusion, variation in metabolic heat production is the dominant mechanism of maintaining thermal stability during flight between Ta values of 21 and 33 degrees C, but variations in metabolic heat production and evaporative heat loss are equally important to the prevention of overheating during flight at Ta values between 33 and 45 degrees C.

Effects of phentolamine on thermoregulatory functions of rats to different ambient temperatures

1979 ◽  
Vol 57 (12) ◽  
pp. 1401-1406 ◽  
Author(s):  
M. T. Lin ◽  
Andi Chandra ◽  
T. C. Fung
Keyword(s):  
Heat Loss ◽  
Rectal Temperature ◽  
Heat Production ◽  
Room Temperature ◽  
Metabolic Heat Production ◽  
Central Component ◽  
Evaporative Heat Loss ◽  
Central Administration ◽  
Ambient Temperatures ◽  
Metabolic Heat

The effects of both systemic and central administration of phentolamine on the thermoregulatory functions of conscious rats to various ambient temperatures were assessed. Injection of phentolamine intraperitoneally or into a lateral cerebral ventricle both produced a dose-dependent fall in rectal temperature at room temperature and below it. At a cold environmental temperature (8 °C) the hypothermia in response to phentolamine was due to a decrease in metabolic heat production, but at room temperature (22 °C) the hypothermia was due to cutaneous vasodilatation (as indicated by an increase in foot and tail skin temperatures) and decreased metabolic heat production. There were no changes in respiratory evaporative heat loss. However, in the hot environment (30 °C), phentolamine administration produced no changes in rectal temperature or other thermoregulatory responses. A central component of action is indicated by the fact that a much smaller intraventricular dose of phentolamine was required to exert the same effect as intraperitoneal injection. The data indicate that phentolamine decreases heat production and (or) increases heat loss which leads to hypothermia, probably via central nervous system actions.

Effects of intracerebroventricular injection of d-amphetamine on metabolic, respiratory, and vasomotor activities and body temperatures in the rat

1980 ◽  
Vol 58 (8) ◽  
pp. 903-908 ◽  
Author(s):  
M. T. Lin ◽  
A. Chandra ◽  
Y. F. Chern ◽  
B. L. Tsay
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Behavioral Responses ◽  
Nerve Fibers ◽  
Metabolic Heat Production ◽  
Evaporative Heat Loss ◽  
Central Administration ◽  
Metabolic Heat ◽  
Behavioral Excitation ◽  
Cutaneous Vasoconstriction

Systemic and central administration of d-amphetamine both produced dose-dependent hypothermia in the rat at ambient temperature (Ta) 8 °C. The hypothermia was brought about solely by a decrease in metabolic heat production. However, at both Ta 22 and 30 °C, d-amphetamine produced hyperthermia accompanied by behavioral excitation. The hyperthermia was due to cutaneous vasoconstriction and increased metabolic heat production (due to behavioral excitation) at Ta 22 °C, whereas at Ta 30 °C the hyperthermia was due to cutaneous vasoconstriction, decreased respiratory evaporative heat loss, and increased metabolism (due to behavioral excitation). Furthermore, both the thermal and the behavioral responses induced by d-amphetamine were antagonized by pretreatment with intracerebroventricular administration of 6-hydroxydopamine (a depletor of central catecholaminergic nerve fibers). The data indicate that, by eliminating the interference of behavioral responses induced, d-amphetamine leads to an alteration in body temperature of rats by decreasing both metabolic heat production and sensible heat loss, probably via the activation of central catecholaminergic receptors.

scholarly journals Sex-related differences in local and whole-body heat loss responses: Physical or physiological?

2014 ◽  
Vol 39 (7) ◽  
pp. 843-843
Author(s):  
Daniel Gagnon
Keyword(s):  
Sex Differences ◽  
Heat Loss ◽  
Heat Production ◽  
Experimental Studies ◽  
Metabolic Heat Production ◽  
Whole Body ◽  
Fixed Rate ◽  
The Third ◽  
Metabolic Heat ◽  
Body Heat

The current thesis examined whether sex differences in local and whole-body heat loss are evident after accounting for confounding differences in physical characteristics and rate of metabolic heat production. Three experimental studies were performed: the first examined whole-body heat loss in males and females matched for body mass and surface area during exercise at a fixed rate of metabolic heat production; the second examined local and whole-body heat loss responses between sexes during exercise at increasing requirements for heat loss; the third examined sex-differences in local sweating and cutaneous vasodilation to given doses of pharmacological agonists, as well as during passive heating. The first study demonstrated that females exhibit a lower whole-body sudomotor thermosensitivity (553 ± 77 vs. 795 ± 85 W·°C−1, p = 0.05) during exercise performed at a fixed rate of metabolic heat production. The second study showed that whole-body sudomotor thermosensitivity is similar between sexes at a requirement for heat loss of 250 W·m−2 (496 ± 139 vs. 483 ± 185 W·m−2·°C−1, p = 0.91) and 300 W·m−2 (283 ± 70 vs. 211 ± 66 W·m−2·°C−1, p = 0.17), only becoming greater in males at a requirement for heat loss of 350 W·m−2 (197 ± 61 vs. 82 ± 27 W·m−2·°C−1, p = 0.007). In the third study, a lower sweat rate to the highest concentration of acetylcholine (0.27 ± 0.08 vs. 0.48 ± 0.13 mg·min−1·cm−2, p = 0.02) and methacholine (0.41 ± 0.09 vs. 0.57 ± 0.11 mg·min−1·cm−2, p = 0.04) employed was evidenced in females, with no differences in cholinergic sensitivity. Taken together, the results of the current thesis show that sex itself can modulate sudomotor activity, specifically the thermosensitivity of the response, during both exercise and passive heat stress. Furthermore, the results of the third study point towards a peripheral modulation of the sweat gland as a mechanism responsible for the lower sudomotor thermosensitivity in females.

Effect of 5-hydroxytryptamine and acetylcholine on the energy budget of chickens

1980 ◽  
Vol 239 (1) ◽  
pp. R57-R61
Author(s):  
P. E. Hillman ◽  
N. R. Scott ◽  
A. van Tienhoven
Keyword(s):  
Physical Activity ◽  
Heart Rate ◽  
Body Temperature ◽  
Heat Loss ◽  
Energy Budget ◽  
Heat Production ◽  
Evaporative Heat Loss ◽  
Neural Pathways ◽  
Metabolic Heat ◽  
Intraventricular Injections

Intraventricular injections of 5-hydroxytryptamine-HCl (258 nmol) or acetylcholine-HCl (550 nmol) in the chicken caused body temperature to rise at 35 degrees C ambient, a result of decreased evaporative heat loss due to bradypnea. At 10 and 20 degrees C ambient, neither drug affected body temperature. Although these drugs decreased physical activity or shivering or both at 10 and 20 degrees C, metabolic heat production was not depressed enough to alter body temperature significantly. Heart rate decreased simultaneously with decreased activity at 20 degrees C. This study is the first to inject 5-hydroxytryptamine as a salt of HCl, instead of creatinine sulfate, as is commonly used. It is suggested that some of the differences reported herein, compared to other studies, are due to the type of salt used. It is postulated that either 5-hydroxytryptamine or acetylcholine, rather than norepinephrine, may be an important neurotransmitter in the neural pathways for thermoregulation in chickens, even though their action on thermoregulation is minor compared with norepinephrine.

SHORT-TERM THERMAL AND METABOLIC RESPONSES OF SHEEP TO RUMINAL COOLING: EFFECTS OF LEVEL OF COOLING AND PHYSIOLOGICAL STATE

1990 ◽  
Vol 70 (3) ◽  
pp. 833-843 ◽  
Author(s):  
A. M. NICOL ◽  
B. A. YOUNG
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Physiological State ◽  
Heat Content ◽  
Metabolic Heat Production ◽  
Mean Body Temperature ◽  
Metabolic Heat ◽  
Reduced Body ◽  
Cooling Effects ◽  
Body Heat

In a series of studies to simulate the ingestion of cold food, the rumen of adult sheep was cooled by 0–400 kJ over 1 h. Ruminal cooling reduced body heat content, increased rate of metabolic heat production and reduced apparent rate of heat loss to the environment. On average, each 100 kJ of cooling reduced heat content by 46 kJ, increased heat production by 20 kJ and reduced heat loss by 70 kJ. Precooling thermal status of the sheep affected the magnitude of the responses to cooling. A 0.1 °C higher precooling mean body temperature decreased the response in metabolic heat production by 6 kJ and increased the reduction in body heat content by 4.6 kJ. The heat production associated with eating reduced the heat loss response to ruminal cooling but did not affect the change in heat content. Well-insulated sheep were less affected by ruminal cooling. Key words: Sheep, rumen, cooling, heat production, temperature

Heat Balance and Distribution during the Core-Temperature Plateau in Anesthetized Humans

1995 ◽  
Vol 83 (3) ◽  
pp. 491-499. ◽  
Author(s):  
Andrea Kurz ◽  
Daniel I. Sessler ◽  
Richard Christensen ◽  
Martha Dechert
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Heat Production ◽  
Heat Balance ◽  
Thermal Flux ◽  
The Body ◽  
Metabolic Heat Production ◽  
The Core ◽  
Metabolic Heat ◽  
Temperature Plateau

Background Once triggered, intraoperative thermoregulatory vasoconstriction is remarkably effective in preventing further hypothermia. Protection results from both vasoconstriction-induced decrease in cutaneous heat loss and altered distribution of body heat. However, the independent contributions of each mechanism have not been quantified. Accordingly, we evaluated overall heat balance and distribution of heat within the body during the core-temperature plateau. Methods Nine minimally clothed male volunteers were anesthetized with propofol and isoflurane and maintained in an approximately 22 degrees C environment. They were monitored for approximately 2 h before vasoconstriction and for 3 h subsequently. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular temperatures, ten skin temperatures, and "deep" foot temperature. Heat constrained by vasoconstriction to the trunk and head was calculated by subtracting the expected change in that region (overall heat balance multiplied by the fractional weight of the trunk and head) from the actual change (change in distal esophageal temperature multiplied by the specific heat of human tissue and the weight of the trunk and head); the result represents the amount by which core heat exceeded that which would be expected based on overall heat balance, assuming that the change was evenly distributed throughout the body. Results Vasoconstriction and passive tissue cooling decreased heat loss but not to the level of heat production. Consequently, heat loss exceeded metabolic heat production throughout the study. Core temperature decreased approximately 1.3 C during the 2-h prevasoconstriction period; however, core temperature remained virtually constant during the subsequent 3 h. In the 3 h after vasoconstriction, arm and leg heat content decreased 57 +/- 9 kcal, and vasoconstriction constrained 22 +/- 8 kcal to the trunk and head. Conclusions These results confirm the efficacy of thermo-regulatory vasoconstriction in preventing additional core hypothermia. Decreased cutaneous heat loss and constraint of metabolic heat to the core thermal compartment contributed to the plateau.

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