Intraventricular administration of isoproterenol inhibits both heat production and heat loss mechanisms in rats

1980 ◽  
Vol 36 (7) ◽  
pp. 851-853 ◽  
Author(s):  
M. T. Lin ◽  
A. Chandra ◽  
Y. C. Fan ◽  
R. Sun
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Intraventricular Administration ◽  
Loss Mechanisms

The catecholamine precursor L-3,4-dihydroxyphenylalanine inhibits both heat production and heat loss mechanisms in the rabbit

1980 ◽  
Vol 58 (8) ◽  
pp. 956-964 ◽  
Author(s):  
M. T. Lin
Keyword(s):  
Heat Loss ◽  
Intravenous Administration ◽  
Heat Production ◽  
Nerve Fibers ◽  
Evaporative Heat Loss ◽  
Intraventricular Administration ◽  
Ambient Temperatures ◽  
Behavioral Excitation ◽  
6 Hydroxydopamine ◽  
Loss Mechanisms

The effects of the catecholamine precursor L-3,4-dihydroxyphenylalanine (L-DOPA) on the thermoregulatory responses of conscious rabbits to different ambient temperatures (Ta) (2, 22, and 32 °C) were assessed. Intravenous administration of L-DOPA alone, intravenous administration of L-DOPA plus R04-4602 (a peripheral decarboxylase inhibitor), and intraventricular administration of L-DOPA or norepinephrine all produced a hypothermia at Ta 2 °C. The hypothermia was due to a decrease in metabolic heat production (M). On the other hand, L-DOPA or norepinephrine produced both behavioral excitation and hyperthermia at both Ta 22 and 32 °C. At Ta 22 °C, the hyperthermia was due to decreased ear skin blood flow (EBF) and slightly increased M (due to behavioral excitation) whereas at Ta 32 °C the hyperthermia was due to decreased EBF, decreased respiratory evaporative heat loss, and slightly increased M (due to behavioral excitation). Further, the temperature effects induced by L-DOPA were antagonized by pretreatment with 6-hydroxydopamine (a relative depletor of catecholaminergic nerve fibers) but not with haloperidol (a relative blocker of dopaminergic receptors). The data indicate that activation of central adrenergic receptors via the endogenous release of norepinephrine with L-DOPA inhibits both heat production and heat loss mechanisms in the rabbit.

Intracerebroventricular injection of sympathomimetic drugs inhibits both heat production and heat loss mechanisms in the rat

1980 ◽  
Vol 58 (8) ◽  
pp. 896-902 ◽  
Author(s):  
M. T. Lin ◽  
A. Chandra ◽  
Y. F. Chern ◽  
B. L. Tsay
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Intracerebroventricular Injection ◽  
Ambient Temperatures ◽  
Adrenoceptor Antagonist ◽  
Sympathomimetic Drugs ◽  
Cutaneous Temperature ◽  
Behavioral Excitation ◽  
Cutaneous Vasoconstriction ◽  
Loss Mechanisms

The effects of intracerebroventricular (i.c.v.) injections of sympathomimetic drugs on thermoregulatory functions in conscious rats maintained at low (8 °C), moderate (22 °C), and high (30 °C) ambient temperatures were assessed. Norepinephrine, tyramine, and ephedrine each produced hypothermia at ambient temperature (Ta) 8 °C and hyperthermia at Ta 22 and 30 °C. At Ta 8 °C, the hypothermia in response to norepinephrine, tyramine, and ephedrine was due to decreased metabolic rate (M) whereas at Ta 22 °C the hyperthermia was due to cutaneous vasoconstriction. At Ta 22 °C, the hyperthermia in response to norepinephrine and tyramine was due to cutaneous vasoconstriction whereas the hyperthermia in response to ephedrine was brought about by increased M (due to behavioral excitation). Intracerebroventricular injection of epinephrine produced hypothermia followed by hyperthermia at Ta 8 and 22 °C. The hypothermia was due to decreased M whereas the hyperthermia was due to cutaneous vasoconstriction and increased M. At Ta 30 °C, epinephrine led to a reduction in cutaneous temperature and hyperthermia. Furthermore, i.c.v. administration of phenylephrine produced a decreased M and hypothermia at Ta, 8 °C and an increased M (due to behavioral excitation) and hyperthermia at Ta 30 °C. At Ta 22 °C, phenylephrine produced hyperthermia (due to cutaneous vasoconstriction and increased M) preceded by hypothermia (due to decreased M). Moreover, the temperature effects induced by norepinephrine were antagonized by pretreatment with the adrenoceptor antagonist phentolamine. In general, the data indicate that activation of central adrenoceptors with sympathomimetic drugs inhibits both heat production and heat loss mechanisms in the rat.

Angiotensin II inhibits both heat production and heat loss mechanisms in the rat

1980 ◽  
Vol 58 (8) ◽  
pp. 909-914 ◽  
Author(s):  
M. T. Lin ◽  
A. Chandra ◽  
J. J. Jou
Keyword(s):  
Angiotensin Ii ◽  
Heat Loss ◽  
Heat Production ◽  
Ambient Temperatures ◽  
Thermoregulatory Responses ◽  
Adrenergic Antagonist ◽  
Intracerebroventricular Injections ◽  
6 Hydroxydopamine ◽  
Dose Dependent ◽  
Loss Mechanisms

The effects of intracerebroventricular injections of angiotensin II on thermoregulatory responses of conscious rats to ambient temperatures (Ta) of 8, 22, and 30 °C were assessed. Administration of angiotensin II produced dose-dependent hypothermia in rats at both Ta 8 and 22 °C. The hypothermia in response to angiotensin II was due to decreased metabolic heat production. In addition, angiotensin II produced cutaneous vasoconstriction at Ta 8–22 °C. However, at Ta 30 °C angiotensin II produced no change in rectal temperature or other thermoregulatory responses. Furthermore, the hypothermia induced by angiotensin II was antagonized by pretreatment with 6-hydroxydopamine (a selective catecholamine neurotoxin) and propranolol (a selective β-adrenergic antagonist) but not by either 5,6-dihydroxytryptamine (a selective serotonin neurotoxin), atropine (a cholinergic antagonist), or phentolamine (a selective α-adrenergic antagonist). The data indicate that angiotensin II inhibits both heat production and heat loss mechanisms which lead to an alteration in body temperature, probably via the activation of central adrenergic receptors.

Evaporative Heat Loss Mechanisms of the Newborn Calf, Bos Taurus

1968 ◽  
Vol 124 (2) ◽  
pp. 83-88 ◽  
Author(s):  
J.R.S. Hales ◽  
J.D. Findlay ◽  
D. Robertshaw
Keyword(s):  
Heat Loss ◽  
Bos Taurus ◽  
Evaporative Heat Loss ◽  
Loss Mechanisms

Accidental Hypothermia

PEDIATRICS ◽  
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.

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

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
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

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.

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.

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

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.

Sign in / Sign up

Export Citation Format

Share Document