Correction to: Phenotypic flexibility in heat production and heat loss in response to thermal and hydric acclimation in the zebra finch, a small arid-zone passerine

AbstractTo maintain constant body temperature (Tb) over a wide range of ambient temperatures (Ta) endothermic animals require large amounts of energy and water. In hot environments, the main threat to endothermic homeotherms is insufficient water to supply that necessary for thermoregulation. We investigated flexible adjustment of traits related to thermoregulation and water conservation during acclimation to hot conditions or restricted water availability, or both, in the zebra finch, Taeniopygia guttata a small arid-zone passerine. Using indirect calorimetry, we measured changes in whole animal metabolic rate (MR), evaporative heat loss (EHL) and Tb before and after acclimation to 23 or 40 °C, with different availability of water. Additionally, we quantified changes in partitioning of EHL into respiratory and cutaneous avenues in birds exposed to 25 and 40 °C. In response to heat and water restriction zebra finches decreased MR, which together with unchanged EHL resulted in increased efficiency of evaporative heat loss. This facilitated more precise Tb regulation in heat-acclimated birds. Acclimation temperature and water availability had no effect on the partitioning of EHL into cutaneous or respiratory avenues. At 25 °C, cutaneous EHL accounted for ~ 60% of total EHL, while at 40 °C, its contribution decreased to ~ 20%. Consistent among-individual differences in MR and EHL suggest that these traits, provided that they are heritable, may be a subject to natural selection. We conclude that phenotypic flexibility in metabolic heat production associated with acclimation to hot, water-scarce conditions is crucial in response to changing environmental conditions, especially in the face of current and predicted climate change.

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Accidental Hypothermia

PEDIATRICS ◽

10.1542/peds.63.6.926 ◽

1979 ◽

Vol 63 (6) ◽

pp. 926-928

Keyword(s):

Heat Loss ◽

Heat Production ◽

Weather Conditions ◽

Accidental Hypothermia ◽

Good Judgment ◽

Hand Coordination ◽

Body Heat ◽

Unfavorable Weather

Pediatricians may be able to bring the dangers of accidental hypothermia to the attention of their patients at the time of a sports, camp, or college "physical." People who spend time outdoors must learn to recognize hypothermia-producing weather and water; to know that shivering indicates heat loss exceeding available insulation and body heat production; and to understand that loss of good judgment and hand coordination soon follow uncontrollable shivering. They must not go into areas in which, without proper gear, unfavorable weather conditions or dangerous water may develop, and they must understand that most tragedies from cold result from failure to make camp or to return to safety when weather conditions become unfavorable.

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External work in level and grade walking on a motor-driven treadmill

Journal of Applied Physiology ◽

10.1152/jappl.1960.15.5.759 ◽

1960 ◽

Vol 15 (5) ◽

pp. 759-763 ◽

Cited By ~ 16

Author(s):

J. W. Snellen

Keyword(s):

Heat Loss ◽

Heat Production ◽

Total Energy Expenditure ◽

The Body ◽

External Work ◽

Thermal Exchange ◽

Level Walking ◽

The Subject ◽

Set Up ◽

Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

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Energy balance in ovariectomized rats with and without estrogen replacement

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1980.238.5.r400 ◽

1980 ◽

Vol 238 (5) ◽

pp. R400-R405 ◽

Cited By ~ 13

Author(s):

M. L. Laudenslager ◽

C. W. Wilkinson ◽

H. J. Carlisle ◽

H. T. Hammel

Keyword(s):

Energy Balance ◽

Heat Loss ◽

Body Mass ◽

Heat Production ◽

Hormone Treatment ◽

Ovariectomized Rats ◽

Dark Phase ◽

Evaporative Heat Loss ◽

Estrogen Replacement ◽

Dry Heat

The effect of estrogen replacement on several parameters of energy balance was investigated in ovariectomized rats tested during the dark phase of their diurnal cycle. Estrogen replacement, either as 17 beta-estradiol or beta-estradiol-3-benzoate via subcutaneous Silastic capsules, was associated with elevated rates of heat production and dry heat loss relative to untreated ovariectomized controls. Estrogen treatment reduced body mass and retarded fur growth. The effects of estrogen replacement on heat production and dry heat loss could not be attributed to these differences in body mass and fur growth or locomotor activity. Estrogen replacement had no effect on rate of evaporative heat loss. If estrogen replacement was delayed 75 days following ovariectomy, the increase in heat production and dry heat loss was not observed. There was no effect of the hormone treatment on rectal temperature. It was concluded that either heat production was elevated, with dry heat loss increased to compensate for the additional thermal load, or dry heat loss was accelerated with heat production elevated in compensation.

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Interaction of central and peripheral factors in physiological temperature regulation

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1961.200.3.572 ◽

1961 ◽

Vol 200 (3) ◽

pp. 572-580 ◽

Cited By ~ 55

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.

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Extinction Limits of Nonadiabatic, Catalyst-Assisted Flames in Stagnation-Point Flow

10.1115/imece2001/htd-24259 ◽

2001 ◽

Author(s):

Stephen B. Margolis ◽

Timothy J. Gardner

Keyword(s):

Stagnation Point ◽

Heat Loss ◽

Heat Production ◽

Fuel Efficiency ◽

Premixed Flames ◽

Stagnation Point Flow ◽

Pollutant Formation ◽

Flow Geometry ◽

Parameter Ranges

Abstract Because combustion is essentially an Arrhenius process, premixed flames generally can only exist within certain parameter ranges, or extinction limits, that correspond to a rate of heat production that is sufficient to sustain the reaction in a given flow geometry. Nonetheless, it is frequently desirable to extend these limits, often for the purpose of increasing fuel efficiency and/or reducing the rate of formation of pollutant species. Another emerging motivation is to allow combustion to be sustained in relatively small volumes, which are characterized by larger surface-to-volume ratios, that would otherwise lead to extinguishing levels of heat loss. Surface catalysts are widely used to achieve such enhancements with respect to efficiency and pollutant formation, and we wish to now consider the role catalysts might play with respect to nonadiabatic flames.

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Mechanisms of thermal stability during flight in the honeybee apis mellifera

Journal of Experimental Biology ◽

10.1242/jeb.202.11.1523 ◽

1999 ◽

Vol 202 (11) ◽

pp. 1523-1533 ◽

Cited By ~ 11

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.

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Effect of pressure on thermal insulation in humans wearing wet suits

Journal of Applied Physiology ◽

10.1152/jappl.1988.64.5.1916 ◽

1988 ◽

Vol 64 (5) ◽

pp. 1916-1922 ◽

Cited By ~ 1

Author(s):

Y. H. Park ◽

J. Iwamoto ◽

F. Tajima ◽

K. Miki ◽

Y. S. Park ◽

...

Keyword(s):

Temperature Gradient ◽

Water Temperature ◽

Heat Loss ◽

Thermal Insulation ◽

Heat Production ◽

Water Immersion ◽

The Other ◽

Body Parts ◽

Metabolic Heat ◽

Healthy Males

The present work was undertaken to determine the critical water temperature (Tcw), defined as the lowest water temperature a subject can tolerate at rest for 3 h without shivering, of wet-suited subjects during water immersion at different ambient pressures. Nine healthy males wearing neoprene wet suits (5 mm thick) were subjected to immersion to the neck in water at 1, 2, and 2.5 ATA while resting for 3 h. Continuous measurements of esophageal (T(es)) and skin (Tsk) temperatures and heat loss from the skin (Htissue) and wet suits (Hsuit) were recorded. Insulation of the tissue (Itissue), wet suits (Isuit), and overall total (Itotal) were calculated from the temperature gradient and the heat loss. The Tcw increased curvilinearly as the pressure increased, whereas the metabolic heat production during rest and immersion was identical over the range of pressure tested. During the 3rd h of immersion, Tes was identical under all atmospheric pressures; however, Tsk was significantly higher (P less than 0.05) at 2 and 2.5 ATA compared with 1 ATA. A 42 (P less than 0.001) and 50% (P less than 0.001), reduction in Isuit from the 1 ATA value was detected at 2 and 2.5 ATA, respectively. However, overall mean Itissue was maximal and independent of the pressure during immersion at Tcw. The Itotal was also significantly smaller in 2 and 2.5 ATA compared with 1 ATA. The Itissue provided most insulation in the extremities, such as the hand and foot, and the contribution of Isuit in these body parts was relatively small. On the other hand, Itissue of the trunk areas, such as the chest, back, and thigh, was not high compared with the extremities, and Isuit played a major role in the protection of heat drain from these body parts.

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Light masking of circadian rhythms of heat production, heat loss, and body temperature in squirrel monkeys

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1999.276.2.r298 ◽

1999 ◽

Vol 276 (2) ◽

pp. R298-R307 ◽

Cited By ~ 1

Author(s):

Edward L. Robinson ◽

Charles A. Fuller

Keyword(s):

Body Temperature ◽

Heat Loss ◽

Heat Production ◽

Whole Body ◽

Direct Calorimetry ◽

Set Point ◽

Subjective Night ◽

Timing System ◽

Circadian Timing System ◽

Body Heat

Whole body heat production (HP) and heat loss (HL) were examined to determine their relative contributions to light masking of the circadian rhythm in body temperature (Tb). Squirrel monkey metabolism ( n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of body temperature and activity. Feeding was also measured. Responses to an entraining light-dark (LD) cycle (LD 12:12) and a masking LD cycle (LD 2:2) were compared. HP and HL contributed to both the daily rhythm and the masking changes in Tb. All variables showed phase-dependent masking responses. Masking transients at L or D transitions were generally greater during subjective day; however, L masking resulted in sustained elevation of Tb, HP, and HL during subjective night. Parallel, apparently compensatory, changes of HL and HP suggest action by both the circadian timing system and light masking on Tb set point. Furthermore, transient HL increases during subjective night suggest that gain change may supplement set point regulation of Tb.

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

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2014-0020 ◽

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.

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