Effect of cutaneous denervation of face and trunk on thermoregulatory responses to cold in rats

1985 ◽  
Vol 58 (2) ◽  
pp. 376-383 ◽  
Author(s):  
M. E. Heath
Keyword(s):  
Critical Temperature ◽  
Body Temperature ◽  
Heat Production ◽  
Afferent Input ◽  
Metabolic Rates ◽  
Cool Environment ◽  
Lower Critical Temperature ◽  
The Face ◽  
Regulate Body Temperature ◽  
Made In

The effect of eliminating afferent input from cutaneous thermoreceptors of the face and trunk on the ability of rats to regulate body temperature in cool environments was studied. Thermoregulatory ability in a cool environment was assessed first in a 25 degrees C environment and then during slow (20 min) and rapid (5 min) reductions of ambient temperature (Ta) to 15 degrees C by monitoring rate of heat production, rectal temperature, and skin temperature on the back, ear, and tail. These measurements were made in four rats while they were intact and during the 2 wk after cutaneous denervation. Rats were found to regulate body temperature well even after the cutaneous nerves of the trunk and face were sectioned. In eight rats the metabolic curve was determined before and 7–10 days after cutaneous denervation. Although the minimal resting metabolic rates did not differ in the two conditions, the lower critical temperature was significantly elevated from 26.8 to 28.9 degrees C and the rate of rise in metabolic rate per degrees celsius decrease in Ta was also significantly higher after cutaneous denervation. It appears that the higher rate of heat production is in compensation for an increase in the rate of heat loss in denervated rats.

scholarly journals Human thermoregulatory responses during serial cold-water immersions

1998 ◽  
Vol 85 (1) ◽  
pp. 204-209 ◽  
Author(s):  
John W. Castellani ◽  
Andrew J. Young ◽  
Michael N. Sawka ◽  
Kent B. Pandolf
Keyword(s):  
Body Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Alternative Explanation ◽  
Cold Water ◽  
Metabolic Heat Production ◽  
Normal Body Temperature ◽  
Repeat Trial ◽  
Metabolic Heat ◽  
Made In

This study examined whether serial cold-water immersions over a 10-h period would lead to fatigue of shivering and vasoconstriction. Eight men were immersed (2 h) in 20°C water three times (0700, 1100, and 1500) in 1 day (Repeat). This trial was compared with single immersions (Control) conducted at the same times of day. Before Repeat exposures at 1100 and 1500, rewarming was employed to standardize initial rectal temperature. The following observations were made in the Repeat relative to the Control trial: 1) rectal temperature was lower and heat debt was higher ( P < 0.05) at 1100; 2) metabolic heat production was lower ( P < 0.05) at 1100 and 1500; 3) subjects perceived the Repeat trial as warmer at 1100. These data suggest that repeated cold exposures may impair the ability to maintain normal body temperature because of a blunting of metabolic heat production, perhaps reflecting a fatigue mechanism. An alternative explanation is that shivering habituation develops rapidly during serially repeated cold exposures.

Effects of food deprivation on daily changes in body temperature and behavioral thermoregulation in rats

2000 ◽  
Vol 278 (1) ◽  
pp. R134-R139 ◽  
Author(s):  
Tamae Yoda ◽  
Larry I. Crawshaw ◽  
Kyoko Yoshida ◽  
Liu Su ◽  
Takayoshi Hosono ◽  
...  
Keyword(s):  
Body Temperature ◽  
Food Deprivation ◽  
Escape Behavior ◽  
The Body ◽  
Behavioral Thermoregulation ◽  
Cold Environments ◽  
The Face ◽  
Regulate Body Temperature ◽  
Behavioral Mechanisms ◽  
Escape Behaviors

Homeothermic animals regulate body temperature (Tb) by using both autonomic and behavioral mechanisms. In the latter process, animals seek out cooler or warmer places when they are exposed to excessively hot or cold environments. Thermoregulation is affected by the state of energy reserves in the body. In the present study, we examine the effects of 4-day food deprivation on circadian changes in Tb and on cold-escape and heat-escape behaviors in rats. Continuous measurement of Tb during food deprivation indicated that the peak Tb amplitude was not different from baseline values, but the trough amplitude continuously decreased after the onset of food deprivation. Cold-escape behavior was facilitated by food deprivation, whereas heat-escape behavior was unchanged. After the termination of food deprivation, the lowered Tb returned to normal on the first day. However, cold-escape behavior was still facilitated on the third day after food reintroduction. Autonomic and behavioral thermoregulatory effectors are modulated in the face of food shortage so as to maintain optimal performance during the active period, whereas increasing energy conservation occurs during the quiescent phase.

Defective thermoregulatory thermogenesis does not cause onset of obesity in Zucker rats

1990 ◽  
Vol 259 (1) ◽  
pp. E11-E18 ◽  
Author(s):  
R. Kaul ◽  
G. Heldmaier ◽  
I. Schmidt
Keyword(s):  
Oxygen Consumption ◽  
Critical Temperature ◽  
Body Temperature ◽  
Consumption Rate ◽  
Dry Mass ◽  
Excess Energy ◽  
Zucker Rats ◽  
The Third ◽  
Genetic Lesion ◽  
Lower Critical Temperature

To test whether or not the onset of obesity in fatty (fa/fa) Zucker rats is caused by decreased thermoregulatory thermogenesis, pups were artificially reared above their lower critical temperature from 3 or 4 days of age. Littermates were continuously fed identical amounts of synthetic rat milk while body temperature (Tc) and oxygen consumption rate (VO2) were continuously recorded. When the daily mean Tc of all pups was held greater than 37 degrees C, neither Tc nor VO2 differed between fa/fa and genetically lean (Fa/-) pups during the first 2 wk of life. Tc and VO2 were significantly elevated in Fa/- pups during the third postnatal week. At both 16 and 21 days of age, fa/fa pups were identified by their low Tc during a brief cold exposure. Body fat and fat-free dry mass of fa/fa and Fa/- littermates differed at 21 but not at 16 days of age. The excess energy deposited as fat was partly derived from decreased nonthermoregulatory energy expenditure and decreased synthesis of lean body mass. Calculations support the speculation that a greater extraction of energy from the synthetic diet additionally supports the excess fat deposition. Decreased thermoregulatory thermogenesis and excess fat storage appear to be secondary and independent consequences of the primary genetic lesion.

Further studies on the heat production and effective lower critical temperature of early-weaned pigs under commercial conditions of feeding and management

1984 ◽  
Vol 39 (2) ◽  
pp. 283-290 ◽  
Author(s):  
K. J. McCracken ◽  
R. Gray
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Thermal Conductance ◽  
Open Circuit ◽  
Weaned Pigs ◽  
Respiration Chamber ◽  
Lower Critical Temperature ◽  
The Mean ◽  
The Difference ◽  
Practical Implications

ABSTRACTIn two separate experiments pigs were weaned at 14 or 28 days and heat production was determined in an open-circuit respiration chamber at temperatures above and below the lower critical temperature (Tcl) at intervals during the post-weaning period.With 14-day weaned pigs the mean 24 h heat production above Tc1 averaged 267, 328, 474 and 554 kJ/h per m2 at 3, 9, 15 and 21 days post weaning respectively. The mean thermal conductance (H/AT, kJ/h per m2 per °ΔT, where H is total heat production, m2 is the surface area calculated as 0·097 M kg0·633 and °Δ is the difference between rectal temperature, taken at 39°, and air temperature) below TC1 was calculated as 20·5, 20·1, 23·1 and 24·2 at 17, 23, 29 and 35 days of age respectively and the corresponding values for Tc1 were 25·9, 23·0, 18·4 and 16·0°C.With 28-day weaned pigs the mean 24 h heat production above Tc1 averaged 280, 361 and 445 kJ/h per m2 at 3, 9 and 15 days post weaning. The calculated values for H/ΔT were 19·7, 20·8 and 21·6 and the corresponding values of Tcl were 24·8, 21·7, and 18·8°C at 31, 37 and 43 days of age respectively.The results are discussed in relation to previous studies on 10-day and 28-day weaned pigs and in relation to the practical implications for pigs weaned into controlled-environment accommodation.

EFFECT OF FEED TEMPERATURE ON COLD SUSCEPTIBILITY OF CATTLE AND SHEEP

1990 ◽  
Vol 70 (1) ◽  
pp. 191-197 ◽  
Author(s):  
A. M. NICOL ◽  
B. A. YOUNG
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Metabolic Heat Production ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Lower Critical Temperature ◽  
Temperature Heat ◽  
Feed Temperature ◽  
Key Words Cold ◽  
Cattle And Sheep

The metabolic heat production of steers was measured at ambient temperatures of +10, −8 and −20 °C following their consumption of 15-kg turnip bulbs (Brassica napus) with a temperature of 27, 2 or −8 °C, or 10-kg turnips with a temperature of 2 °C followed by 1 kg hay. Metabolic heat production was elevated 13–80% after eating the cold and frozen turnips when steers were exposed to −8 °C and 35–80% when exposed to −20 °C. Sheep fed 20, 35, 55, 80 and 110 g pelleted ration per kg−0.75 d−1, accompanied by a ruminal infusion of water at 38 or 2 °C at a volume required to simulate a 10% dry matter feed had their metabolic heat production measured at +10 and −20 °C. Heat production was significantly increased at −20 °C for only the 2 °C infusion although with the 38 °C infusion at the lower feed intake levels, metabolic heat production was higher by up to 37% at an ambient temperature of −20 °C than at +10 °C. The lower critical temperature of the steers after ingestion of the turnips was estimated to be −4.5, −2.4, +3.2 and +13.9 °C forthe27, 2 + hay, 2 and −8 °C turnips, respectively. The lower critical temperature of sheep was raised by 1, 11, 31, 25 and > 22 °C by the ruminal infusion of water at 2 °C compared to water at 38 °C in sheep fed 20, 35, 55, 80 and 110 g feed kg−0.75 d−1, respectively. Key words: Cold, temperature, heat production, cattle, sheep

Energy metabolism and thermoregulation of beaver (Castor canadensis)

1989 ◽  
Vol 67 (3) ◽  
pp. 651-657 ◽  
Author(s):  
Robert A. MacArthur
Keyword(s):  
Critical Temperature ◽  
Castor Canadensis ◽  
Resting Metabolic Rate ◽  
Whole Body ◽  
Metabolic Rates ◽  
Body Temperatures ◽  
Thermoneutral Zone ◽  
Air Temperatures ◽  
Lower Critical Temperature ◽  
Predicted Values

Metabolic rates and body temperatures (Tb) of adult and immature beavers were recorded at air temperatures from −20 to 28 °C. The thermoneutral zone of beavers > 1 year of age extended from 0–2 °C to at least 28 °C. Lower critical temperature, whole-body conductance, and resting metabolic rate were similar for yearlings and beavers ≥ 2 years old, and conformed closely to weight-predicted values for terrestrial eutherians. The estimated lower critical temperature of a growing beaver kit declined from 24–25 °C at 2–3 weeks of age when the animal weighed 0.59–0.62 kg to 0–2 °C at 11–13 weeks when the kit weighed 2.92–3.50 kg. Rectal Tb of the kit was generally lower and less stable than abdominal Tb recorded telemetrically from older animals. In beavers > 1 year old, abdominal Tb was independent of air temprature (−20 to 28 °C), with no evidence of hypothermia or metabolic depression at subfreezing temperatures. Neither the level nor the daily rhythm of Tb was substantially altered by 24–48 h fasting in this species.

Cold-induced inhibition of thermal panting in shorn sheep. 2. Effect of previous acclimatization to cold

1973 ◽  
Vol 17 (1) ◽  
pp. 9-19 ◽  
Author(s):  
J. Slee
Keyword(s):  
Heart Rate ◽  
Heat Stress ◽  
Body Temperature ◽  
Heat Production ◽  
Cold Exposure ◽  
Heat Dissipation ◽  
Heat Storage ◽  
Metabolic Rates ◽  
Respiratory Centre ◽  
Reduction Effect

SUMMARY1. Short cold exposures (2 hr at 18° or 8°C) were used to delay or block panting during subsequent heat stress in shorn Merino and Scottish Blackface sheep. The effect of previous acclimatization to cold upon the block to thermal panting was studied.2. After acclimatization the block was reduced, but less in Merinos than in Blackfaces. In Blackfaces, the reduction effect was inconsistent after short periods of acclimatization, but became significant after prolonged (3 weeks) acclimatization.3. Acclimatization produced elevations in heart rate and body temperature implying increased heat production. Variation in block reduction between breeds and between individuals was related to these presumed changes in heat production. Sheep with highly elevated metabolic rates showed complete block prevention. 4. After cold exposure ceased, elevated heat production disappeared within 8 days and the block returned.5. It was concluded that elevated heat production resulting from acclimatization caused block prevention partly because increased heat storage cancelled the heat debt otherwise incurred during blocking treatment and partly because the increased requirement for heat dissipation overruled the respiratory centre block.

scholarly journals Studies on diurnal variations of heat production and the effective lower critical temperature of early-weaned pigs under commercial conditions of feeding and management

1980 ◽  
Vol 43 (2) ◽  
pp. 321-328 ◽  
Author(s):  
K. J. McCracken ◽  
B. J. Caldwell
Keyword(s):  
Critical Temperature ◽  
Heat Production ◽  
Thermal Conductance ◽  
Open Circuit ◽  
Respiration Chamber ◽  
Mean Values ◽  
Maximum Value ◽  
Lower Critical Temperature ◽  
The Mean ◽  
The Difference

1. The heat production of groups of pigs, weaned at 10 d of age, was determined in an open-circuit respiration chamber at various ages between 10 and 33 d at temperatures above and below the lower critical temperature (Tcl).2. The heat production was lowest on the second or third day post weaning when pigs were given feed increasing by 25 g/pig per d from day 2. There was a marked diurnal pattern in heat production, the lowest values being recorded between 24.00 and 08.00 h.3. The mean thermal conductance (H/ΔT, kJ/h per m2 per °ΔT, where His total heat production, m2 is the surface area calculated as 0.097 W kg0.633 (Brody, 1945) and °ΔTis the difference between rectal temperature, taken as 39°, and air temperature) below Tcl was calculated as 18.0, 16.9, 18.5 and 21.2 respectively at 10, 17, 24 and 31 d of age. Maximum values of H/ΔT obtained during feeding periods were. on average, 4.5 kJ/h per me per °ΔT higher than the mean values.4. The maximum value for Tcl during the immediate post-weaning period was 25.9°. The mean Tcl at 17, 24 and 31 d were respectively 21.7, 18.4 and 18.6° for pigs fed almost to appetite.

Shivering and nonshivering thermogenic responses of rats subjected to different patterns of heat acclimation

1993 ◽  
Vol 71 (8) ◽  
pp. 576-581 ◽  
Author(s):  
Sohtaro Sakurada ◽  
Osamu Shido
Keyword(s):  
Adipose Tissue ◽  
Critical Temperature ◽  
Ambient Temperature ◽  
Brown Adipose Tissue ◽  
Heat Production ◽  
Heat Exposure ◽  
Control Group ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose ◽  
Lower Critical Temperature

Male Wistar rats were divided into five groups: a control group kept at an ambient temperature of 24 °C for 14 days, and four heat-acclimated groups (two groups subjected to a constant ambient temperature of 33 °C for 4 days or 14 days (HC-14) immediately preceding the measurement; and another two groups subjected to an ambient temperature of 33 °C for about 5 h once a day for 4 days, or 14 days (HI-14) just prior to the measurement). After the completion of the schedule, the rats were placed in a temperature-controlled chamber. Hypothalamic (Thy) and interscapular brown adipose tissue (TBAT) temperatures, oxygen consumption [Formula: see text], and shivering activity were measured during a gradual fall in temperature of a water jacket surrounding the chamber (Tw) from 30 to 10 °C at a constant rate of 0.18 °C/min. During the fall in Tw, [Formula: see text] and TBAT increased significantly and shivering was induced without associate changes in Thy in all groups. Tw at the onset of a rise in metabolic heat production (onset of cold-induced thermogenesis) coincided with that at the onset of a rise in TBAT (onset of BAT thermogenesis), but was significantly higher than that at the onset of shivering. In HC-14 and HI-14 rats, Tws at the onset of cold-induced thermogenesis and BAT thermogenesis were significantly higher than those in control rats, whereas Tws at the onset of shivering were not different from those in control rats. The onset of cold-induced thermogenesis did not change after the 4-day heat exposure. These results suggest that heat exposure for 14 days, regardless of the pattern, shifts the lower critical temperature to a high level, and the changes are attributed to an upward shift in the ambient temperature at which nonshivering thermogenesis occurs.Key words: heat exposure, heat production, brown adipose tissue, lower critical temperature.

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