Electroencephalographic studies in toad (Bufo melanostictus) following prolonged exposure to heat during hibernation and non-hibernation

Résumé L'électroencephalogramme des grenouilles qui ont été exposées à 48°C pendant 8 jours durant la nonhibernation révéla une extrême «low voltage fast activity» avec une absence complète de la «high voltage slow activity» (HVSA). L'hibernation (à 58°C pendant 8 jours) montra un HVSA irrégulier à régulier avec 100% d'augmentation en longuer et quelques méchanismes corticaut et subcorticaux restent actifs même lors d'une prolongation de la chaleur.     

Acute cold exposure increases the glucagon sensitivity of thermogenic metabolism in the rat

Administration of glucagon to rats at 25 degrees C had no effect upon their VO2, while administration of noradrenaline or noradrenaline plus glucagon raised the VO2. At 5 degrees C, noradrenaline had no effect upon the cold-enhanced VO2, while glucagon caused a rise of 13.7%, implying increased glucagon sensitivity at 5 degrees C. The glucagon-induced enhancement of VO2 was abolished by concurrent administration of noradrenaline.     

Acute cold exposure increases the glucagon sensitivity of thermogenic metabolism in the rat

Summary Administration of glucagon to rats at 25°C had no effect upon their VO₂ while administration of noradrenaline or noradrenaline plus glucagon raised the VO₂-At 5°C, noradrenaline had no effect upon the cold-enhanced VO₂, while glucagon caused a rise of 13.7% implying increased glucagon sensitivity at 5°C. The glucagon-induced enhancement of VO₂ was abolished by concurrent administration of noradrenaline.     

Ascorbic acid in brown adipose tissue: effect of cold acclimation and high intake of the vitamin

Summary The ascorbic acid content of brown adipose tissue increased 62% when rats underwent cold acclimation; however, the increase was 126% when rats living in the cold were fed a basal diet supplemented with 2% ascorbic acid. These findings suggest a role for ascorbic acid in this tissue during nonshivering thermogenesis.Bureau of Nutritional Sciences, publication No. 113.     

Thermoregulatory heat production by periaortic brown adipose tissue in the non-cold-acclima. tized rat

Zusammenfassung Mit Thermoelementen im Aortenbogen und 35 mm distal davon gemessener Temperatur zeigt sich in thermoneutraler Umgebung entweder keine oder nur eine geringere Temperaturerhöhung des distalen Punktes. In kalter Umgebung hingegen ist die Differenz signifikant vergrössert.     

Influence of brown adipose tissue on deep cervical temperature during sleep in the young rabbit

Summary In young rabbits the slope of the temperature in the deep cervical region close to brown adipose tissue increased during desynchronized sleep at low ambient temperature. No increase occurred at neutral ambient temperature. In control rabbits (after disappearance of brown adipose tissue), the slope of deep cervical temperature did not increase during desynchronized sleep at low or neutral ambient temperatures.Preliminary data were reported at the Association des Physiologistes, Réunion de Poitiers, 20–23 June 1983.Acknowledgments. We wish to thank Giuseppe Mancinelli and Leonida Sabattini for technical assistance. This work was supported by a grant from the Consiglio Nazionale delle Ricerche, Rome. J.P.L. wishes to thank NATO for partial financial support during his stay at the Physiology Department in Bologna.     

Influence of brown adipose tissue on deep cervical temperature during sleep in the young rabbit

In young rabbits the slope of the temperature in the deep cervical region close to brown adipose tissue increased during desynchronized sleep at low ambient temperature. No increase occurred at neutral ambient temperature. In control rabbits (after disappearance of brown adipose tissue), the slope of deep cervical temperature did not increase during desynchronized sleep at low or neutral ambient temperatures.     

Increased cardiac noradrenaline turnover in the rat after acute exposure to environmental heat

Summary In male rats, the cardiac turnover of noradrenaline is significantly increased on acute exposure to an environmental temperature of 32°C, when compared to control experiments performed at 23°C.Supported by a grant from the Deutsche Forschungsgemeinschaft.     

Alpha-adrenergic subsensitivity of isolated femoral arteria following short-term cold acclimatisation in rats

Summary Cold acclimatisation lasting 2 and 4 days lowered the response of isolated femoral arteria to noradrenaline and phenylephrine in rat.This study was supported by the Academy of Finland.     

Opposing temperature responses to intrahypothalamic injections of 5-hydroxytryptamine in the pigeon exposed to cold

Summary 5-Hydroxytryptamine injected into posterior and anterior parts of the pigeon hypothalamus evoked a short lasting hyperthermia or hypothermia, respectively. Variable responses obtained within the same brain region suggest the existence of different 5-HT systems, even in rather limited hypothalamic areas.     

A muscular dystrophy induced by cold following restriction of the arterial blood supply

Zusammenfassung Nach vollkommener Ligatur der Aorta knapp unterhalb der Nierenarterien gelingt es bei der Ratte, durch Abkühlung der Hinterbeine regelmässig eine streng auf die kaudale Körperhälfte beschränkte Dystrophie der Skelettmuskulatur hervorzurufen.

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This work was supported by the Medical Research Council of Canada and the Canadian Arthritis and Rheumatism Society.     

Dopamine-beta-hydroxylase activity in adrenal gland and spleen of rats after fasting and cold exposure

Fasting (48 h) results in dopamine-beta-hydroxylase (DBH) release both in adrenal gland and spleen, suggestive of an increase in the activity of these organs. Cold exposure (48 h) produces a dissociation of the sympathoadrenal response. When both stimuli are simultaneously employed, the DBH response suggests the preponderance of the response to fasting. Plasma DBH is decreased in all groups studied, this could be due to its half-life and the splenic DBH depletion.     

Dopamine-beta-hydroxylase activity in adrenal gland and spleen of rats after fasting and cold exposure

Summary Fasting (48 h) results in dopamine-beta-hydroxylase (DBH) release both in adrenal gland and spleen, suggestive of an increase in the activity of these organs. Cold exposure (48 h) produces a dissociation of the, sympathoadrenal response. When both stimuli are simultaneously employed, the DBH response suggests the preponderance of the response to fasting. Plasma DBH is decreased in all groups studied, this could be due to its half-life and the splenic DBH depletion.This work was supported by a grant of Fondo de Investigaciones Sanitarias de la Seguridad Social, No. 83/0905.     

Morphological and enzymehistochemical changes in the interscapular adipose tissue of adult guinea-pigs during prolonged exposure to cold

Zusammenfassung Dauereinwirkung von Kälte (2 Monate +4°C) führte beim Meerschweinchen zum Auftreten multilokularer Fettzellen, welche intensive histochemische Reaktion für mehrere oxydative Enzyme zeigten. Die Zahl der Mitochondrien und LDH-1 war im Kälteversuch vermehrt.

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Acknowledgment. This study was initiated when Dr.J. Hirvonen worked as a post-doctoral fellow of NIH, U.S. Public Health Service (No. F05 TW 1546) at Arctic Health Research Center, Fairbanks (Alaska).