Interaction of peripheral and central temperatures in control of heat production and respiratory evaporative heat loss (REHL) in the conscious goat

1982 ◽  
Vol 394 (S1) ◽  
pp. R39-R39
Author(s):  
A. Nagel ◽  
G. Feistkorn ◽  
C. Jessen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Evaporative Heat Loss

Energy balance in ovariectomized rats with and without estrogen replacement

1980 ◽  
Vol 238 (5) ◽  
pp. R400-R405 ◽  
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.

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.

No dynamic effector responses to fast changes of core temperature at constant skin temperature

1987 ◽  
Vol 65 (6) ◽  
pp. 1339-1346 ◽  
Author(s):  
Ulrike Roos ◽  
Claus Jessen
Keyword(s):  
Skin Temperature ◽  
Heat Loss ◽  
Core Temperature ◽  
Heat Production ◽  
Control Level ◽  
Time Derivative ◽  
Rate Of Change ◽  
Dynamic Responses ◽  
Evaporative Heat Loss ◽  
Blood Temperature

Experiments in conscious goats were done to see whether heat production and respiratory evaporative heat loss show dynamic responses to changing core temperature at constant skin temperature. Core temperature was altered by external heat exchangers acting on blood temperature, while skin temperature was maintained constant by immersing the animals up to the neck in a rapidly circulating water bath. Core temperature was altered at various rates up to 0.9 °C/min. Step deviations of core temperature from control values were always followed by a positive time derivative of effector response, but never by a negative time derivative during sustained displacement of core temperature. Ramp experiments showed that the slopes at which heat production or heat loss rose with core temperature deviating from its control level grew smaller at higher rates of change of core temperature. It is concluded that neither heat production nor respiratory evaporative heat loss respond to the rate of change of core temperature. At constant skin temperature, thermoregulatory effector responses appear to be proportional to the degree to which core temperature deviates from its set level.

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.

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.

scholarly journals Metabolic effects of altering the 24 h energy intake in man, using direct and indirect calorimetry

1980 ◽  
Vol 43 (2) ◽  
pp. 257-269 ◽  
Author(s):  
M. J. Dauncey
Keyword(s):  
Energy Expenditure ◽  
Metabolic Rate ◽  
Heat Loss ◽  
Energy Intake ◽  
Heat Production ◽  
Resting Metabolic Rate ◽  
Metabolic Effects ◽  
Evaporative Heat Loss ◽  
High Intake ◽  
Total Heat Loss

1. The metabolic effects of increasing or decreasing the usual energy intake for only 1 d were assessed in eight adult volunteers. Each subject lived for 28 h in a whole-body calorimeter at 26° on three separate occasions of high, medium or low energy intake. Intakes (mean±SEM) of 13830 ± 475 (high), 8400 ± 510 (medium) and 3700 ± 359 (low) kJ/24 h were eaten in three meals of identical nutrient composition.2. Energy expenditure was measured continuously by two methods: direct calorimetry, as total heat loss partitioned into its evaporative and sensible components; and indirect calorimetry, as heat production calculated from oxygen consumption and carbon dioxide production. For the twenty-four sessions there was a mean difference of only 1.2 ± 0.14 (SEM)% between the two estimates of 24 h energy expenditure, with heat loss being less than heat production. Since experimental error was involved in both estimates it would be wrong to ascribe greater accuracy to either one of the measures of energy expenditure.3. Despite the wide variation in the metabolic responses of the subjects to over-eating and under-eating, in comparison with the medium intake the 24 h heat production increased significantly by 10% on the high intake and decreased by 6% on the low intake. Mean (± SEM) values for 24 h heat production were 8770 ± 288, 7896 ± 297 and 7495 ± 253 kJ on the high, medium and low intakes respectively. The effects of over-eating were greatest at night and the resting metabolic rate remained elevated by 12% 14 h after the last meal. By contrast, during under-eating the metabolic rate at night decreased by only 1%.4. Evaporative heat loss accounted for an average of 25% of the total heat loss at each level of intake. Changes in evaporative heat loss were +14% on the high intake and −10% on the low intake. Sensible heat loss altered by +9% and −5% on the high and low intakes respectively.5. It is concluded that (a) the effects on 24 h energy expenditure of over-feeding for only 1 d do not differ markedly from those estimated by some other workers after several weeks of increasing the energy intake; (b) the resting metabolic rate, measured at least 14 h after the last meal, can be affected by the previous day's energy intake; (c) the zone of ambient temperature within which metabolism is minimal is probably altered by the level of energy intake.

Influence of air humidity on the partition of heat exchanges of cattle

1972 ◽  
Vol 78 (2) ◽  
pp. 303-307 ◽  
Author(s):  
J. A. McLean ◽  
D. T. Calvert
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Air Temperature ◽  
Heat Production ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Air Humidity ◽  
Total Heat Loss ◽  
Air Temperatures ◽  
Heat Exchanges

SUMMARYThe balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

Hypothalamic and striatal dopamine receptor activation inhibits heat production in the rat

1982 ◽  
Vol 242 (5) ◽  
pp. R471-R481 ◽  
Author(s):  
M. T. Lin ◽  
A. Chandra ◽  
B. L. Tsay ◽  
Y. F. Chern
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Direct Injection ◽  
Receptor Activation ◽  
Anterior Hypothalamus ◽  
Evaporative Heat Loss ◽  
Dopaminergic Agonist ◽  
Striatal Dopamine Receptor ◽  
Cutaneous Vasoconstriction ◽  
Intrahypothalamic Injection

Direct injection of dopaminergic agonist apomorphine into the lateral cerebral ventricle, the preoptic anterior hypothalamus, the caudate-putamen complex, or the globus pallidus caused hypothermia, decreased metabolism and cutaneous vasoconstriction at ambient temperature (Ta) 8 and 22 degrees C, and hyperthermia and cutaneous vasoconstriction in the rat at Ta 30 degrees C. On the other hand, local injection of dopaminergic antagonists such as haloperidol and pimozide into the preoptic anterior hypothalamus and the striatal nuclei caused hyperthermia, increased metabolism and cutaneous vasoconstriction at Ta 8, 22, and 30 degrees C. However, there was no change in respiratory evaporative heat loss in response to administration of either dopaminergic agonist or antagonists in the rat at all Ta studied. The data indicate that hypothalamic and striatal dopaminergic receptor activation inhibits metabolic heat production in rats. In addition, intrahypothalamic injection of 5-hydroxytryptamine caused hypothermia, decreased metabolism and cutaneous vasodilatation in the rat at Ta 8 and 22 degrees C, whereas at Ta 30 degrees C caused an insignificant change in the thermoregulatory responses. Furthermore, the thermal responses induced by intrahypothalamic injection of apomorphine were not altered by depletion of hypothalamic 5-hydroxytryptamine. These observations do not support the contention that there is a dopamineserotonin link in the hypothalamic pathways that mediate heat loss mechanisms in the rat.

Two-dimensional determination of thermosensitive sites within the goat's hypothalamus

1976 ◽  
Vol 40 (4) ◽  
pp. 514-520 ◽  
Author(s):  
C. Jessen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Anterior Hypothalamus ◽  
Evaporative Heat Loss ◽  
Two Dimensional

In two conscious goats with chronically implanted multithermodes the distribution of thermosensitive sites within the anterior hypothalamus was determined. Changes in heat production at Ta=+5 degrees C and changes in respiratory evaporative heat loss at Ta=+33 degrees C in response to discrete temperature stimuli were measured and the magnitude of the responses was correlated with the histologically assessed position of the probes transmitting the stimuli. In both animals the array of probes was centered close to the center of the thermosensitive area. The density of thermosensitive structures increased toward the center of the area covered by the probes. The most sensitive points were situated close to either side of the midline in those frontal planes which contained the nuclei supraoptici and paraventriculares. No difference was found between cold- and warm-sensitive sites.

The role of the cholinergic systems in the central control of thermoregulation in rats

1979 ◽  
Vol 57 (11) ◽  
pp. 1205-1212 ◽  
Author(s):  
M. T. Lin ◽  
F. F. Chen ◽  
Y. F. Chern ◽  
T. C. Fung
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Nerve Fibers ◽  
Cholinergic Receptors ◽  
Evaporative Heat Loss ◽  
Central Administration ◽  
Ambient Temperatures ◽  
Dose Dependent ◽  
Selective Blocker

Systemic and central administration of methacholine (a synthetic choline derivative) both produced dose-dependent decreases in rectal temperature in rats at all the ambient temperatures studied. Both at room temperature (22 °C) and in the cold (8 °C), the hypothermia in response to methacholine application was brought about by both a decrease in metabolic heat production and an increase in cutaneous circulation. In the heat (29 °C), the hypothermia was due solely to an increase in respiratory evaporative heat loss. Furthermore, the methacholine-induced hypothermia was antagonized by central pretreatment of atropine (a selective blocker of cholinergic receptors), but not by the central administration of either 6-hydroxy-dopamine (a relative depletor of catecholaminergic nerve fibers) or 5,6-dihydroxytryptamine (predominately a serotonin depletor). The data indicate that activation of the cholinergic receptors within brain with methacholine decreases heat production and (or) increases heat loss which leads to hypothermia in rats.

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