SEASONAL ADJUSTMENTS IN CAPTURED WILD NORWAY RATS: II. SURVIVAL TIME, PELT INSULATION, SHIVERING, AND METABOLIC AND PRESSOR RESPONSES TO NORADRENALINE

1962 ◽  
Vol 40 (1) ◽  
pp. 537-545 ◽  
Author(s):  
O. Héroux ◽  
Donna Wright
Keyword(s):  
Survival Time ◽  
Metabolic Response ◽  
Cold Temperature ◽  
White Rats ◽  
Winter Conditions ◽  
Pressor Responses ◽  
Wild Rats ◽  
Norway Rats ◽  
Shivering Thermogenesis

During the winter, wild rats (Rattus norwegicus) develop metabolic adjustments similar to those found in the white rats acclimated to cold in the laboratory. The rate of shivering found in the winter-captured wild rats is lower than that found in the summer-captured rats, indicating the presence of non-shivering thermogenesis. The metabolic response to noradrenaline is enhanced suggesting that non-shivering metabolism in these wild rats, as in the case of white rats, is mediated by noradrenaline. Unlike white rats acclimated to a constant cold temperature in the laboratory, but like white rats acclimatized to cold by group exposure to outdoor winter conditions, wild rats develop a greater pelt insulation in winter.

SEASONAL ADJUSTMENTS IN CAPTURED WILD NORWAY RATS: II. SURVIVAL TIME, PELT INSULATION, SHIVERING, AND METABOLIC AND PRESSOR RESPONSES TO NORADRENALINE

1962 ◽  
Vol 40 (4) ◽  
pp. 537-545 ◽  
Author(s):  
O. Héroux ◽  
Donna Wright
Keyword(s):  
Survival Time ◽  
Metabolic Response ◽  
Cold Temperature ◽  
White Rats ◽  
Winter Conditions ◽  
Pressor Responses ◽  
Wild Rats ◽  
Norway Rats ◽  
Shivering Thermogenesis

During the winter, wild rats (Rattus norwegicus) develop metabolic adjustments similar to those found in the white rats acclimated to cold in the laboratory. The rate of shivering found in the winter-captured wild rats is lower than that found in the summer-captured rats, indicating the presence of non-shivering thermogenesis. The metabolic response to noradrenaline is enhanced suggesting that non-shivering metabolism in these wild rats, as in the case of white rats, is mediated by noradrenaline. Unlike white rats acclimated to a constant cold temperature in the laboratory, but like white rats acclimatized to cold by group exposure to outdoor winter conditions, wild rats develop a greater pelt insulation in winter.

THE EFFECT OF INTERMITTENT INDOOR COLD EXPOSURE ON WHITE RATS

1960 ◽  
Vol 38 (6) ◽  
pp. 517-521 ◽  
Author(s):  
O. Héroux
Keyword(s):  
Constant Temperature ◽  
Cold Exposure ◽  
Cold Resistance ◽  
Muscle Growth ◽  
Cold Temperature ◽  
Continuous Exposure ◽  
White Rats ◽  
Winter Conditions ◽  
The One ◽  
Cellular Alterations

Recently it has been shown that when white rats are kept in individual cages and exposed indoors to constant cold temperature or when they are exposed in groups to the outdoor winter conditions, they develop similar degrees of cold resistance and similar metabolic adjustments but they differ in endocrine, insulative, and peripheral adjustments.In an attempt to determine whether variations in temperature alone could be responsible for the type of adjustments developed outdoors, white rats were kept at 30 °C for 4 weeks but exposed to 6 °C for a few hours every day. Through these intermittent cold exposures, the animals developed the same type of acclimation as the one produced indoors by continuous exposure to a constant temperature, but to a lesser degree. Adrenals tended to hypertrophy, body and muscle growth tended to decrease, and over-all insulation appeared to decrease. In contrast to continuously exposed rats, however, they showed no cold injury, no change in ear vascularization, and no thickening of the ear epidermis, probably because the skin was never cooled long enough at any given time for the cold temperature to produce cellular alterations that could not be corrected during the warm periods.

THE CALORIGENIC RESPONSE OF COLD-ACCLIMATED WHITE RATS TO INFUSED NORADRENALINE

1960 ◽  
Vol 38 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Florent Depocas
Keyword(s):  
Oxygen Consumption ◽  
Time Course ◽  
Cold Resistance ◽  
Striated Muscle ◽  
Metabolic Response ◽  
Maximal Increase ◽  
Resistance Increase ◽  
White Rats ◽  
Major Alteration ◽  
Shivering Thermogenesis

The increase in oxygen consumption during continuous intravenous injection of various doses of L-noradrenaline was measured in anesthetized rats fully acclimated to 6 °C. The metabolic response was found to be linearly related to the logarithm of the amount of noradrenaline infused per minute. The calorigenic response to infusion of noradrenaline at a level of 1 μg per minute was then measured in rats undergoing acclimation to cold. The calorigenic response was found to increase with time of exposure to the cold environment, thus paralleling previous observations in the time course of gain in cold resistance, increase in food consumption, and loss of dependence on shivering during acclimation of white rats to cold. Also, the same maximal increase in oxygen consumption was obtained on infusion of noradrenaline into functionally eviscerated and sham-operated cold-acclimated rats, thus indicating that the liver and other abdominal viscera (kidneys excluded) are not involved in the calorigenic response to noradrenaline. It is proposed, as a working hypothesis, that striated muscle is the site of the major alteration in sensitivity to noradrenaline induced by acclimation to cold. Difficulties associated with consideration of striated muscle as the source of non-shivering thermogenesis in the cold-acclimated rat are discussed.

THE EFFECT OF INTERMITTENT INDOOR COLD EXPOSURE ON WHITE RATS

1960 ◽  
Vol 38 (1) ◽  
pp. 517-521 ◽  
Author(s):  
O. Héroux
Keyword(s):  
Constant Temperature ◽  
Cold Exposure ◽  
Cold Resistance ◽  
Muscle Growth ◽  
Cold Temperature ◽  
Continuous Exposure ◽  
White Rats ◽  
Winter Conditions ◽  
The One ◽  
Cellular Alterations

Recently it has been shown that when white rats are kept in individual cages and exposed indoors to constant cold temperature or when they are exposed in groups to the outdoor winter conditions, they develop similar degrees of cold resistance and similar metabolic adjustments but they differ in endocrine, insulative, and peripheral adjustments.In an attempt to determine whether variations in temperature alone could be responsible for the type of adjustments developed outdoors, white rats were kept at 30 °C for 4 weeks but exposed to 6 °C for a few hours every day. Through these intermittent cold exposures, the animals developed the same type of acclimation as the one produced indoors by continuous exposure to a constant temperature, but to a lesser degree. Adrenals tended to hypertrophy, body and muscle growth tended to decrease, and over-all insulation appeared to decrease. In contrast to continuously exposed rats, however, they showed no cold injury, no change in ear vascularization, and no thickening of the ear epidermis, probably because the skin was never cooled long enough at any given time for the cold temperature to produce cellular alterations that could not be corrected during the warm periods.

THE CALORIGENIC RESPONSE OF COLD-ACCLIMATED WHITE RATS TO INFUSED NORADRENALINE

1960 ◽  
Vol 38 (2) ◽  
pp. 107-114 ◽  
Author(s):  
Florent Depocas
Keyword(s):  
Oxygen Consumption ◽  
Time Course ◽  
Cold Resistance ◽  
Striated Muscle ◽  
Metabolic Response ◽  
Maximal Increase ◽  
Resistance Increase ◽  
White Rats ◽  
Major Alteration ◽  
Shivering Thermogenesis

The increase in oxygen consumption during continuous intravenous injection of various doses of L-noradrenaline was measured in anesthetized rats fully acclimated to 6 °C. The metabolic response was found to be linearly related to the logarithm of the amount of noradrenaline infused per minute. The calorigenic response to infusion of noradrenaline at a level of 1 μg per minute was then measured in rats undergoing acclimation to cold. The calorigenic response was found to increase with time of exposure to the cold environment, thus paralleling previous observations in the time course of gain in cold resistance, increase in food consumption, and loss of dependence on shivering during acclimation of white rats to cold. Also, the same maximal increase in oxygen consumption was obtained on infusion of noradrenaline into functionally eviscerated and sham-operated cold-acclimated rats, thus indicating that the liver and other abdominal viscera (kidneys excluded) are not involved in the calorigenic response to noradrenaline. It is proposed, as a working hypothesis, that striated muscle is the site of the major alteration in sensitivity to noradrenaline induced by acclimation to cold. Difficulties associated with consideration of striated muscle as the source of non-shivering thermogenesis in the cold-acclimated rat are discussed.

SEASONAL ADJUSTMENTS IN CAPTURED WILD NORWAY RATS: I. ORGAN WEIGHTS, EAR VASCULARIZATION, AND HISTOLOGY OF EPIDERMIS

1961 ◽  
Vol 39 (12) ◽  
pp. 1865-1870 ◽  
Author(s):  
O. Héroux
Keyword(s):  
Morphological Changes ◽  
Abdominal Fat ◽  
Organ Weights ◽  
White Rats ◽  
Cold Room ◽  
Liver And Kidney ◽  
Hypertrophy Of The Heart ◽  
Wild Rats ◽  
Norway Rats ◽  
Indoor And Outdoor

Male wild rats (Rattus Norwegicus) captured during the winter had different organ weights from similar animals captured during the summer. These seasonal changes in organ weights were different from those observed in white rats acclimated to cold in a cold room (indoor) or acclimatized to winter outdoors in groups of 10 to a cage.Unlike both the indoor and outdoor cold-conditioned white rats, the wild rats, in winter, did not have a reduced muscle mass as compared to the summer-captured rats, or a reduced abdominal fat reserve, or an enlargement of the liver and kidney. The abdominal fat reserve actually increased during the winter.Like the outdoor white rats, the wild rats, during the winter, did not show the enlargement of the thyroids, adrenals, pituitary, and digestive tract or the reduction in pelt and the ear cold injury that were invariable outcomes of continuous individual exposure to a constant low-temperature indoors. Like the indoor and unlike the outdoor white rats, however, they showed an hypertrophy of the heart and an increased vascularization of the ear.Because the wild rats trapped during the winter showed very few of the morphological changes usually found in cold-exposed white rats, it is suggested that winter conditions encountered were not stressful to the wild rats.

SEASONAL ADJUSTMENTS IN CAPTURED WILD NORWAY RATS: III. PRODUCTION OF ADRENAL STEROIDS IN VITRO

1963 ◽  
Vol 41 (1) ◽  
pp. 1147-1153
Author(s):  
J. S. Willmer ◽  
O. Héroux
Keyword(s):  
Environmental Conditions ◽  
Rattus Norvegicus ◽  
Seasonal Effect ◽  
Seasonal Adjustment ◽  
Adrenal Steroids ◽  
Steroid Secretion ◽  
Adrenal Steroid ◽  
White Rats ◽  
Norway Rats

The in vitro adrenal steroid secretion of wild Norway rats (Rattus norvegicus) captured during the winter differed in quantity, but not in quality, from that of similar rats captured during the summer. Whereas there was no evident seasonal effect on adrenal weight either in males or in females, adrenals of both sexes secreted at a faster rate during the winter than during the summer, this increase involving the four groups of steroids characterized chromatographically during both seasons and in both sexes; the predominant steroid secreted was corticosterone. This seasonal adjustment in adrenal activity is similar to that observed in white rats kept in group cages exposed outdoors to the natural summer and winter environmental conditions, but it differs from that found in white rats cold-acclimated in the laboratory, in which adrenal activity is lower than normal after cold acclimation.

COMPARISON BETWEEN SEASONAL AND THERMAL ACCLIMATION IN WHITE RATS: II. SURFACE TEMPERATURE, VASCULARIZATION, AND IN VITRO RESPIRATION OF THE SKIN

1959 ◽  
Vol 37 (1) ◽  
pp. 1247-1253 ◽  
Author(s):  
O. Héroux
Keyword(s):  
Oxygen Uptake ◽  
Surface Temperature ◽  
Respiratory Rate ◽  
Environmental Conditions ◽  
Cold Temperature ◽  
Dorsal Skin ◽  
Adult Rats ◽  
White Rats ◽  
Different Types

The effect of cold temperature on the skin was studied on white rats exposed to two different types of environmental conditions. Two groups of adult rats kept in individual cages were continuously exposed for 3 months to constant cold temperature (18° and 6 °C) in the laboratory (indoor rats) while other groups of the same colony kept in groups of 10 were exposed for the same length of time to the fluctuating environmental conditions prevailing outside (outdoor rats).Indoor rats acclimated to 18 °C and 6 °C showed the same increase in the number of opened capillaries in the ears over the number observed in controls acclimated to 30 °C. "Summer and winter" outdoor rats showed the same number of capillaries as the "18 °C or 6 °C" indoor rats. Signs of injury healing such as thicker epidermis and larger nuclei were found in the ears of all the "6 °C" rats but in none of the "winter" rats. While the skin temperature measured at + 6 °C was slightly higher (0.4 to 1.0 °C) in rats acclimated at 6 °C than in those at 30 °C, it was lower (1.3 to 2.9 °C) in "winter" than in "summer" rats. After 28 days of acclimation, the rate of oxygen uptake of the dorsal skin of the foot was lower in "6 °C" than in "30 °C" rats but after 84 days it was significantly higher in the cold-acclimated rats. Similarly, after 3 months, the respiratory rate of the dorsal skin of the foot was higher in "winter" rats than in "summer" rats.

ADJUSTMENTS TO CONSTANT LOW TEMPERATURES IN WHITE RATS LIVING IN GROUPS

1963 ◽  
Vol 41 (3) ◽  
pp. 587-595 ◽  
Author(s):  
O. Héroux
Keyword(s):  
Low Temperatures ◽  
Metabolic Adaptation ◽  
Experimental Conditions ◽  
Cold Stimulus ◽  
White Rats ◽  
Essential Components ◽  
Resting Metabolism ◽  
Increased Sensitivity ◽  
Shivering Thermogenesis ◽  
Fundamental Mechanism

White rats, in groups of 10, were exposed for 3 months in the laboratory to constant temperatures of 19 °C or −10 °C. Grouping the animals did not alter the pattern of metabolic adaptation usually observed in individually cold-acclimated rats and recently observed in group-caged white rats exposed outdoors during the winter. This pattern of adaptation is characterized by an increased capacity for heat production, as shown by a longer survival time at −35 °C, a reduction of shivering, an increased sensitivity to noradrenaline, an increased ear vascularization, a reduction in protein and fat deposition, and an enlargement of heart, liver, and kidneys. Group-caging at constant low temperature (a) prevented the development of cold injuries and the enlargement of pituitary, thyroid, adrenals, which are usually observed in individually cold-exposed rats indoors, (b) resulted in an increased resting metabolism, normal adrenal cortex activity, and no increase in pelt insulation in contrast to that previously found in white rats grouped outdoors during the winter. These different adjustments to cold in white rats exposed to different sets of environmental conditions are compared with similar adjustments found in wild Norway rats.From these comparisons, one must conclude that many of the structural and endocrine adjustments observed in individually cold-acclimated rats in the laboratory are reactions peculiar to continuous cold stimulus, i.e. reactions to a specific set of experimental conditions rather than essential components of the fundamental mechanism for non-shivering thermogenesis.

The effect of environmental temperature during pregnancy on thermoregulation in the newborn lamb

1985 ◽  
Vol 41 (3) ◽  
pp. 341-347 ◽  
Author(s):  
A. W. Stott ◽  
J. Slee
Keyword(s):  
Blood Glucose ◽  
Metabolic Rate ◽  
Metabolic Response ◽  
Water Immersion ◽  
Cold Treatment ◽  
Rate Capability ◽  
Late Pregnancy ◽  
Cold Test ◽  
Brown Adipose ◽  
Shivering Thermogenesis

AbstractTwenty-four pregnant Scottish Blackface ewes were divided into three temperature-treatment groups 14 days before expected lambing: closely shorn and kept at 6°C (cold treatment, CD); in full fleece at 26°C (warm treatment, WM); and in full fleece at 6°C (controls, CL). Food allocation and intakes were similar for each group. Their lambs were tested for cold-induced summit metabolic rate capability (SMR) on the day of birth at a mean age of 12 h using water immersion to provide cooling. On the following day, the calorigenic response to subcutaneous injections of noradrenaline (NA) was measured to assess non-shivering thermogenesis capability. The ewes were blood-sampled during pregnancy and the lambs before and after the SMR test.In the ewes, blood glucose and free fatty acid levels were higher during cold treatment, but not significantly so. Blood glucose was lower in lambs from CD ewes (CD lambs) before SMR tests; other differences were not significant.During the cold test, SMR was highest in CD lambs, but not significantly so. Rectal temperature declined least during test in the CD lambs (P < 0·05).The peak metabolic response (PMR) following NA injection was about 1·5 times greater in CD lambs than in the CL and WM lambs (P < 0·05). The mean elevation of PMR over thermoneutral metabolic rate was respectively: 2·8, 1·8 and 1·7 times in the CD, CL and WM lambs (P < 0·05), and this elevation was sustained for longer in the CD lambs (P < 0·01). Thus, the total metabolic response to NA was markedly greater in CD lambs.It was concluded that cold exposure during late pregnancy favoured the deposition of (or checked the normal decline in) foetal brown adipose tissue, so raising the neonatal capacity for non-shivering thermogenesis.

Sign in / Sign up

Export Citation Format

Share Document