Thermoregulation during pentobarbital and ketamine anesthesia in rats

1.) Core temperature, tail temperature, metabolic heat production, and evaporative heat loss were measured in rats exposed to various ambient temperature conditions. 2.) Control rats increased heat production in the cold and heat loss in a warm environment, thus maintaining a relatively constant core temperature. 3.) Pentobarbital anesthesia reduced the thermoregulatory responses and caused core temperature to vary considerably with ambient temperature. Ketamine anesthesia resulted in minor thermoregulatory deficits. 4.) It is concluded that ketamine can be used in thermal physiological studies that require an anesthetised preparation, although it is not completely devoid of inhibitory effects on thermoregulatory responses.     

Thermoregulation in Tunas

Because tunas possess countercurrent vascular pathways servingthe trunk musculature, metabolic heat is retained, and muscletemperatures can considerably exceed that of the surroundingwater (+1° to +21°C). And because tunas have this excess,it is reasonable to suppose they have some means of controllingits magnitude. Tunas must contend with two exigencies whichcan perturb body temperature: changes in water temperature and,in contrast to non-thermoconserving fish, changes in activity.Both can be met by adaptive change in excess muscle temperature.If this could be accomplished in the absence of changes in environmentaltemperature or activity level, this would constitute physiologicalthermoregulation. If excess muscle temperature cannot be alteredsufficiently to acceptable levels, more favorable environmentaltemperatures must be sought or activity levels changed. We wouldconsider this behavioral thermoregulation. High sustained swimspeeds, characteristic of the continuously swimming tunas, requirespecial consideration. Heat production is proportional to approximatelythe cube of swim speed. In order to maintain a slight temperatureexcess at basal swim speeds (1–2 lengths/sec), and yetnot overheat during sustained high speed swimming (>4 lengths/sec),mechanisms are required to conserve heat under the former conditionsand to dissipate it effectively under the latter. In this report,we review published observations other investigators have interpretedas physiological thermoregulation in tunas, describe recentfindings in our laboratory, and suggest some possible thermoregulatorymechanisms.     

Thermoregulation characteristics of rats exposed to cold in the early postnatal period

Cold adaptation of adult rats (at 4-5 degrees C for 7 weeks) increased their ability to respond to noradrenaline by the rise of body temperature and heat radiation, led to an almost 2-fold increase in the relative brown fat mass (BFM). Adult rats which experienced "cold imprinting" (from the first to the seventh day after birth, 15 min at 4-5 degrees C) showed a far less increment of the BFM on cold adaptation, no additional rise of body temperature and heat radiation in response to noradrenaline. In cold-imprinted rats, the relative surface of the tail and the body surface heat radiation transfer conefficient were found to be reduced. This attests to stable adaptive changes in physical thermoregulation, directed toward increase in animals' heat insulation.     

Thermoregulation in rats during early postnatal maturation: importance of nitric oxide

Experiments were carried out to determine the role of nitric oxide in mediating autonomic and behavioral thermoregulatory control in rat pups on postnatal days 1-2, 5-6, and 10-11. For an experiment, each pup received a subcutaneous injection of vehicle, NG-nitro-D-arginine methyl ester (D-NAME; 100 mg/kg), or NG-nitro-L-arginine methyl ester (L-NAME; 100 mg/kg) before being placed in a metabolic chamber or in a thermocline with a linear temperature gradient of 23 to 43 degrees C. In the metabolic chamber, oxygen consumption and core temperature were measured as ambient temperature was decreased from 40 to 15 degrees C over a 60-min period. Decreasing ambient temperature elicited an increase in oxygen consumption in all age groups that received vehicle or d-NAME. The lower critical temperature and peak oxygen consumption upon exposure to cold after vehicle were 41 +/- 10 ml x kg(-1) x min(-1) at 30 degrees C, 43 +/- 12 ml x kg(-1) x min(-1) at 28 degrees C, and 55 +/- 11 ml x kg(-1) x min(-1) at 25 degrees C in the 1- to 2-, 5- to 6-, and 10- to 11-day-old pups, respectively. Administration of L-NAME abolished the oxygen consumption response to cold in the 1- to 2- and 5- to 6-day-old pups and significantly attenuated the oxygen consumption response to cold in the 10- to 11-day-old pups. Selected ambient temperature in the thermocline was not significantly affected by prior administration of D-NAME or L-NAME compared with vehicle. Thus our data provide evidence that the nitric oxide system plays a role in mediating autonomic but not behavioral thermoregulatory control in rat pups during early postnatal maturation.     

Thermoregulation in the hippopotamus

Measurements of the sub-lingual temperature and of the skin temperature of the nose, ears, neck, dewlap, sides and back of two hippopotami (HIPPOPOTAMUS AMPHIBIUS L.) in the Zoological Park at Wroclaw have been made. The mean sub-lingual temperature was 36.1C but a diurnal rhythm of sub-lingual temperature was evident, which was not related to changes in the environmental temperature. The skin temperatures varied with the environmental temperature. When the animals were immersed in water at 9C the sub-lingual temperature dropped to 24.5C but it had returned to its pre-immersion value within one hour of leaving the water.

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Zusammenfassung Es wurden Messungen der Sublingualtemperatur und der Temperatur der Haut an Nase, Ohren, Nacken, Wamme, Seiten und Rücken von 2 Hippopotamus (HIPPOPOTAMUS AMPHIBUUS L.) im Zoologischen Garten in Warschau vorgenommen. Die mittl. Sublingualtemperatur war 36.1C. Ein diurnaler Rhythmus ohne Beziehung zu den Änderungen der Umwelttemperatur konnte nachgewiesen werden. Die Hauttemperatur Änderte sichmit der Umwelttemperatur. Wenn die Tiere im Wasserbecken (9C) standen,fiel die Sublingualtemperatur auf 24,5C. Sie stieg nach Verlassen des Wassers innerhalb einer Stunde auf den Ausgangswert.

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Resume La température sublinguale ainsi que les températures cutanées du nez,de l'oreille, de la nuque, du ventre, des flancs et du dos ont été relevées chez deux hippopotamus (HIPPOPOTAMUS AMPHIBIUS L.) du Jardin Zoologique de Varsovie. La température sublinguale moyenne a été de 36,1C. L'existence d'un rythme nycthéméral indépendant des variations de la température ambiante a été observée.La température cutanée varie en fonction de la température ambiante.Quand les animaux se tenaient debout dans leur bassin d'eau froide à 9C, la température sublinguale tombait à 24,5C.Lorsque les animaux quittaient ce bassin, cette température remontait au bout d'environ b heure à sa valeur de départ.

     

Thermoregulation im Hornissennest

Zusammenfassung Im Nest von Vespa crabro wird im Bereich der Puppen von den weiblichen Imagines (Arbeiterinnen und Königinnen) eine sehr konstante Temperatur von 30,0° C aufrecht erhalten. Zwischen Larvenzellen sind die Tagesschwankungen größer, die Durchschnittstemperatur um 0,4° C niedriger. Die Larven werden von den Imagines nicht gewärmt.In Nestern ohne Imagines läßt sich eine autonome Temperaturregulation durch die Larven nachweisen. Die thermoregulatorischen Bewegungen der Larven werden beschrieben und von den als Hungersignale zu wertenden Bettelbewegungen abgegrenzt.Weibliche Imagines wärmen ältere, pigmentierte Puppen auch außerhalb des Nestes. Dieses Verhalten wird vermutlich durch ein Pheromon ausgelöst. Es werden die Unterschiede in der Thermoregulation gegenüber den Honigbienen und V. orientalis diskutiert.

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Thermoregulation in the nests of hornets

Summary In the nest of Vespa crabro, a very constant temperature of 30° C is maintained by female adults (workers and queens) in the vicinity of pupae. Daily temperature variation between larval cells on the other hand is larger and the average temperature about 0,4° C lower. Larvae are not warmed by the adults.Larvae in nests without adults exhibit an autonomous temperature regulation. In this paper the thermoregulatory movements of larvae are described and distinguished from those normally described as hunger signals and begging movements.Female adults warm older pigmented pupa, even when outside the nest. This behavior is probably stimulated by a pheromone.Differences in thermoregulation are discussed and are contrasted with those of the honey bee and V. orientalis.

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Der Stiftung Volkswagenwerk sind wir für die Förderung dieser Arbeit zu Dank verpflichtet.     

Thermoregulation in army ant bivouacs

ABSTRACT. The temporary nests (bivouacs), of Eciton burchelli (Westwood) thermoregulate with considerable precision. Temperatures at the core of the bivouac are maintained at 28.5±1C even though ambient temperatures in their tropical rainforest home change during the day over a range of 7C. Temperatures just under the mantle of the bivouac vary much more than at the core. Calculations suggest that the basal metabolic rate of the army ants in bivouac will generate all the heat that they need to keep warm when ambient temperatures drop. The army ants probably regulate heat loss by opening up ventilation channels within the nest.     

Energetics and Thermoregulation in Chiroptera

This review deals with analysis of current experimental data obtained predominantly by foreign authors on energetics and thermoregulation in many species of the Chiroptera order in connection with their circadian and seasonal hypometabolism due to the habitation temperature conditions, type of nutrition, reproduction, and flying activity.