Temperature regulation in the new-born lamb. IV. The effect of wind and evaporation of water from the coat on metabolic rate and body temperature

1962 ◽  
Vol 13 (1) ◽  
pp. 82 ◽  
Author(s):  
G Alexander
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Heat Production ◽  
Temperature Regulation ◽  
Tap Water ◽  
High Heat ◽  
Cooling Efficiency ◽  
Experimental Conditions ◽  
Ambient Temperatures ◽  
New Born

The study of temperature regulation in new-born lambs has been extended from dry lambs in "still air" at various ambient temperatures to dry lambs in a wind of 550 cm sec-l, and to lambs whose coats are drying. Exposure to wind resulted in an increased slope of the line relating heat production to ambient temperature, but under the experimental conditions evaporation of water from the coat added approximately the same increment at all ambient temperatures. The effects of wind and evaporation at any one temperature appeared additive. The heat loss from naturally wet new-born lambs less than 1 hr old, in a wind, was greater than in slightly older lambs wetted with tap water. Lambs with hairy coats were able to conserve heat more readily than lambs with fine coats. The cooling efficiency of evaporation from the coat was about 25%. The elevation in temperature of the extremities which follows feeding and persists under conditions of moderate heat loss, appears to be almost abolished under conditions of high heat loss. During the studies on drying lambs, beat loss in many lambs exceeded heat production, and rectal temperature fell, which thus indicated the maximum possible heat production (summit metabolic rate) of which lambs are capable. Lambs from ewes on low or medium levels of feeding during pregnancy cooled more readily than lambs from well-fed ewes.

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.

Thermoregulatory and metabolic changes during fever in young and old rats

2003 ◽  
Vol 285 (5) ◽  
pp. R1165-R1169 ◽  
Author(s):  
Jessica B. Buchanan ◽  
Elizabeth Peloso ◽  
Evelyn Satinoff
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Heat Production ◽  
Metabolic Changes ◽  
Body Temperatures ◽  
Ambient Temperatures ◽  
Young Rats ◽  
Heat Conservation ◽  
Old Rats ◽  
S Peak

We injected old and young rats with lipopolysaccharide (LPS; 50 μg/kg ip) at two ambient temperatures ( Ta; 21 and 31°C). Young rats mounted equivalent fevers at both Tas [peak body temperatures ( Tb) of 38.3 and 38.7°C, respectively]. The Tbof old rats was not different from baseline (37.3°C) after LPS at Ta21°C, whereas, at 31°C, their Tbrose to a mean peak of 38.4°C. We also measured the associated thermoregulatory responses by use of calorimetry. At 21°C, young rats developed a fever by increasing both O2consumption and heat conservation. Old rats did not become febrile, and O2consumption fell by 15%. Heat loss was the same in old and young rats. At 31°C, young and old rats developed similar fevers with similar increases in heat production and conservation. Our results suggest that the lack of LPS fever in old rats at 21°C is due mainly to the lowered metabolic rate.

The Mechanisms and Energetics of Honeybee Swarm Temperature Regulation

1981 ◽  
Vol 91 (1) ◽  
pp. 25-55
Author(s):  
BERND HEINRICH
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Temperature Regulation ◽  
Resting Metabolic Rate ◽  
Primary Role ◽  
Set Point ◽  
Ambient Temperatures ◽  
Thermal Environments ◽  
Lower Temperature

1. Free (active) honeybee swarms regulated their core temperature (Tc) generally within 1 °C of 35 °C. They maintained the same temperature around freshly built honeycomb, and in the brood nest of the hive, from ambient temperatures of between at least 1 and 25 °C. Captive (inactive) swarms in the laboratory often allowed Tc to decline below 35 °C. 2. The temperature of the swarm mantle (Tm) varied with the general activity of the swarm as well as with ambient temperature (TA), but in captive swarms (and sometimes at night in free swarms), Tm was generally held above 17 °C, even at TA < 5 °C. 3. Within the swarm, temperatures varied between 36 °C, an upper temperature set-point, and 17 °C, a lower temperature set-point. 4. Before swarm take-off, all temperature gradients in the swarm were abolished and Tm equalled Tc. 5. The regulated Tc and Tm were unrelated to size and passive cooling rates in swarms ranging from 1000 to 30000 bees. 6. The weight-specific metabolic rate of swarms was correlated with TA and Tc, but relatively little affected by swarm size. 7. Bees on the mantle experiencing low temperatures pushed inward, thus contracting the mantle, diminishing the mantle porosity, and filling interior passageways. As a result, their own rate of heat loss, as well as that from the swarm core, decreased. 8. In large tightly clumped swarms, even at TA < 5 °C, the resting metabolic rate of the bees in the swarm core was more than sufficient to maintain Tc at 35 °C or above. The active thermoregulatory metabolism was due to the bees on the swarm mantle. 9. There was little physical exchange of bees between core and mantle at low (< 5 °C) TA. In addition, there was no apparent chemical or acoustic communication between the bees in the swarm mantle that are subjected to the changes of the thermal environments and the bees in the swarm interior that constantly experience 35 °C regardless of TA. 10. The data are summarized in a model of Tc control indicating a primary role of the mantle bees in controlling heat production and heat loss. 11. The possible ecological significance of swarm temperature regulation is discussed.

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.

Thermoregulation of African and European Honeybees during Foraging, Attack, and Hive Exits and Returns

1979 ◽  
Vol 80 (1) ◽  
pp. 217-229 ◽  
Author(s):  
HEINRICH BERND
Keyword(s):  
Metabolic Rate ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Warm Up ◽  
Ambient Temperatures ◽  
Thoracic Temperature

1. While foraging, attacking, or leaving or returning to their hives, both the African and European honeybees maintained their thoracic temperature at 30 °C or above, independent of ambient temperature from 7 to 23 °C (in shade). 2. Thoracic temperatures were not significantly different between African and European bees. 3. Thoracic temperatures were significantly different during different activities. Average thoracic temperatures (at ambient temperatures of 8–23 °C) were lowest (30 °C) in bees turning to the hive. They were 31–32 °C during foraging, and 36–38 °C in bees leaving the hive, and in those attacking. The bees thus warm up above their temperature in the hive (32 °C) before leaving the colony. 4. In the laboratory the bees (European) did not maintain the minimum thoracic temperature for continuous flight (27 °C) at 10 °C. When forced to remain in continuous flight for at least 2 min, thoracic temperature averaged 15 °C above ambient temperature from 15 to 25 °C, and was regulated only at high ambient temperatures (30–40 °C). 5. At ambient temperatures > 25 °C, the bees heated up during return to the hive, attack and foraging above the thoracic temperatures they regulated at low ambient temperatures to near the temperatures they regulated during continuous flight. 6. In both African and European bees, attack behaviour and high thoracic temperature are correlated. 7. The data suggest that the bees regulate thoracic temperature by both behavioural and physiological means. It can be inferred that the African bees have a higher metabolic rate than the European, but their smaller size, which facilitates more rapid heat loss, results in similar thoracic temperatures.

Effects of altered ambient temperature on metabolic rate during CO2 inhalation

1985 ◽  
Vol 58 (5) ◽  
pp. 1592-1596 ◽  
Author(s):  
R. P. Kaminski ◽  
H. V. Forster ◽  
G. E. Bisgard ◽  
L. G. Pan ◽  
S. M. Dorsey ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Heat Production ◽  
Pulmonary Ventilation ◽  
O2 Consumption ◽  
Breathing Frequency ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Respiratory Heat Loss ◽  
Unit Increase ◽  
Stimulation Of

The purpose of this study was to determine if the changes in O2 consumption (VO2) during CO2 inhalation could in part be due to stimulation of thermogenesis for homeothermy. Twelve ponies were exposed for 30-min periods to inspired CO2 (PIco2) levels of less than 0.7, 14, 28, and 42 Torr during the winter at 5 (neutral) and 23 degrees C ambient temperatures (TA) and during the summer at 21 (neutral TA), 30, and 12 degrees C. Elevating TA in both seasons resulted in an increased pulmonary ventilation (VE) and breathing frequency (f) (P less than 0.01) but no significant increase in VO2 (P greater than 0.05). Decreasing TA in the summer resulted in a decrease in VE and f (P less than 0.01) but no significant change in VO2 (P greater than 0.05). At neutral TA in both seasons, VO2 increased progressively (P less than 0.05) as PIco2 was increased from 14 to 28 and 42 Torr. The increases in VO2 during CO2 inhalation were attenuated (P less than 0.05) at elevated TA and accentuated at the relatively cold TA in the summer (P less than 0.05). Respiratory heat loss (RHL) during CO2 inhalation was inversely related to TA. Above a threshold RHL of 2 cal X min-1 X m-2, metabolic heat production (MHP) increased 0.3 cal X min-1 X m-2 for each unit increase in RHL during CO2 inhalation at the neutral and elevated TA. However, during cold stress in the summer, the slope of the MHP-RHL relationship was 1.6, indicating an increased MHP response to RHL.

Temperature regulation in the new-born lamb. V. Summit metabolism

1962 ◽  
Vol 13 (1) ◽  
pp. 100 ◽  
Author(s):  
G Alexander
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Rectal Temperature ◽  
Prolonged Exposure ◽  
High Heat ◽  
Practical Significance ◽  
Body Temperatures ◽  
Prolonged Fasting ◽  
Body Weights ◽  
Summit Metabolic Rate

"Summit metabolism" was estimated by measuring respiratory exchange during a 20 min period of falling rectal temperature. The rate of fall was controlled at about 1°C per 20 min, by varying the wind velocity while the lamb was exposed to conditions of high heat loss. At body temperatures near normal, summit metabolism was not predictable from rectal temperature. Below 36°C the metabolic rate was proportional to rectal temperature. When expressed as kilocalories per kilogram per hour, summit metabolism in young lambs was approximately constant at all body weights, and hence summit, metabolism per unit of surface area increased with increasing body weight. Heavy lambs are therefore able to maintain homeothermy under conditions of higher heat loss than light lambs. Summit metabolism was usually established at about 17 kcal kg-1 hr-1 within half an hour of birth, i.e. heat production increased rapidly to 15 times foetal levels or five times "basal" levels. There was no increase after ingestion of milk, and the summit metabolic rate appeared to decline slowly with advancing age. It also declined during prolonged exposure to cold and during prolonged fasting, particularly in very young lambs. Blood analyses indicated a great mobilization of fat and carbohydrate during exposure to conditions which evoked a summit response. The practical significance of these results is discussed.

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.

Development of thermoregulation in ducklings

1972 ◽  
Vol 50 (10) ◽  
pp. 1243-1250 ◽  
Author(s):  
G. Untergasser ◽  
J. S. Hayward
Keyword(s):  
Metabolic Rate ◽  
Heat Loss ◽  
Cold Resistance ◽  
Rapid Development ◽  
Metabolic Rates ◽  
Ambient Temperatures ◽  
Common Eiders

The embryos of mallards and scaups show no evidence of homeothermy before the point of hatching. The ability to thermoregulate develops quickly directly after hatching, so that day-old mallards remain homeothermic for at least 2.5 h at ambient temperatures down to +2 °C. The lowest ambient temperatures at which 1-day-old scaups and common eiders remain homeothermic for at least 2.5 h are −2 °C and −7 °C respectively. This rapid development of cold resistance is related to increases in peak metabolic rates and insulative capacities. In embryos of pipped eggs, metabolic rates do not exceed 1.1 ml O2/g h for mallards and 1.6 ml/g h for scaups, while the peak metabolic rates of the day-old young are 6.1 and 7.0 ml/g h respectively. One-day-old common eiders have a peak metabolic rate of about 5 ml/g h. After an age of 3 days, cold resistance increases with age while peak metabolic rates decrease, indicating that reduced heat loss contributes to increased cold resistance. At an age of 7 days, mallards can maintain homeothermy for at least 2.5 h at −4 °C, scaups at −14 °C, and common eiders at −16 °C. Insulation indices of eider ducklings are significantly higher than those of young mallards and scaups.

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.

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