Effects of thyrotrophic-releasing hormone (TRH) on thermoregulation in the rat

At ambient temperatures (Ta) of both 8 and 22 degrees C, intraventricular administration of TRH (10-80 microgram) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30 degrees C Ta, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia.     

Haloperidol produces hypothermic effects in rats

Summary Intraperitoneal administration of either haloperidol or chlorpromazine produced hypothermia both in the cold (8° C) and at room temperature (22°C). The hypothermia was brought about both by a decrease in metabolic heat production and an increase in the cutaneous temperature of tail and foot skin. However, at a higher temperature (29°C), there were no changes in rectal temperature and other thermoregulatory responses.The work reported here was supported by grants from the National Science Council of Republic of China and J. Aron Charitable Foundation (New York, N.Y.). The authors are grateful to Dr C.Y. Chai for his advice during the experimentation. The generous support of Dr C.J. Shih was much appreciated by the authors. Also, we thank Dr C.D. Bloomer (Smith, Kline and French Co.) for the supply of chlorpromazine.     

Hypothermia induced in mice by enzyme-mediated depletion of serotonin

Injection of a purified serotonin (and tryptophan)-degrading enzyme into mice produced a pronounced hypothermia when the mice were maintained at 22 degrees C, but not at 30 degrees C. Brain levels of serotonin and tryptophan were strikingly depleted, but concentrations of norepinephrine and dopamine remained unchanged.     

Mastoparan induces hypothermia in mice

The polypeptide mastoparan, isolated from the venom of the Oriental Hornet, Vespa orientalis, induces hypothermia in white mice 15 minutes after its intraperitoneal injection. The hypothermic effect is induced by mastoparan obtained from different hornet and wasp venoms. The normal murine core temperature is lowered by mastoparan from 38 degrees C to as far as 33 degrees C. This lowering lasts for one hour and is reversible.     

Influences of temperature change on the relaxation and amplitude inhibition by noradrenaline in the rabbit jejunum.

In the rabbit jejunum, the elevation of temperature within the range of 25-37 degrees C diminished the sensitivity to noradrenaline (NA) for both the relaxation and amplitude inhibition. The relaxation by NA was mainly mediated via adrenergic beta-receptors at 25, 30 or 37 degrees C. The amplitude inhibition was mediated via alpha-receptors at 37 degrees C, and both alpha- and beta-receptors at 30 or 25 degrees C.     

Hypothalamic histamine modulates adaptive behavior of rats at high environmental temperature

Histamine content in the rat hypothalamus was lower at 4 degrees C and higher at 31 degrees C compared to that at 21 degrees C. Pretreatment with alpha-fluoromethylhistidine, a 'suicide' inhibitor of histamine decarboxylase, attenuated both the increased level of hypothalamic histamine and rat adaptive behavior at 31 degrees C. Increase of histamine content in the hypothalamus appears to be an important factor contributing to rat adaptive behavior to high environmental temperature.     

Profound hypothermia in golden hamsters (Mesocricetus auratus) induced by serotonergic potentiating and noradrenergic inhibiting drugs

Profound hypothermia (6 degrees C) was induced in cold exposed golden hamsters (Mesocricetus auratus) by a combination of drugs that potentiate brain serotonergic activity (fluoxetine and pargyline) and inhibit noradrenergic activity (alpha-methyl-p-tyrosine). Individual drugs and combinations of 2 were ineffective.     

Intraventricular administration of isoproterenol inhibits both heat production and heat loss mechanisms in rats

Summary At an ambient temperature (T_a) of 8°C, intraventricular administration of isoproterenol inhibited metabolic heat production and led to hypothermia in rats. In contrast, at a T_a of 22°C and of 30°C, isoproterenol decreased cutaneous circulation and led to hyperthermia. The data indicate that isoproterenol inhibits both heat production and heat loss mechanisms in rats.This work was supported by a grant from the National Science Council of the Republic of China. The authors are grateful to Dr C.Y. Chai for pertinent advice.     

Effects of storage and processing on the nutritive value of certain Nigerian foods

The effects of storage and processing on the nutritive value of two Nigerian foods--raw cowpea (Vigna unguiculata) flour and palm oil, have been investigated. Increased retention of both thiamine and riboflavin as a result of increased water activity (Aw) were recorded for cowpea flour stored for 6 months. A storage temperature of 5 degrees C led to minimal losses of both vitamins in the stored flour. Differences in physico-chemical characteristics were observed between palm oil produced by the traditional method and that produced by a modern commercial method. Increasing Aw led to decreasing loss of unsaturation in the traditionally-produced palm oil during 4-week storage at ambient temperature (25 degrees C).     

Isonicotinic acid hydrazide: early effects on peripheral nerve conduction velocity

This report describes the effects of short treatments with isonicotinic acid hydrazide (isoniazid), 300 mg/kg/day, on conduction velocity in the rat tail dorsal nerve trunk. After 6 days of continuous treatment, conduction velocity falls significantly for measurements made at 35 degrees C. After 10 days it falls significantly at both 25 degrees C and 35 degrees C. This appears to be the first electrophysiological corroboration of the early neuropathological changes recently observed in isoniazid treated rats and seems to provide evidence that the temperature at which the experiments are made is important in determining conduction velocity changes.     

Effects of photoperiod, temperature and testosterone-treatment on plasma T3 and T4 levels in the Djungarian hamster, Phodopus sungorus

The effects of photoperiod, temperature and testosterone treatment on plasma T3 and T4 levels were investigated in the Djungarian hamster. Plasma T3 level was affected by temperature (25 degrees C less than 7 degrees C) but not by photoperiod. Plasma T4 level was affected by photoperiod (short day less than long day) at 25 degrees C. Administration of testosterone increased plasma T4 level under short photoperiod at 25 degrees C. Thus, higher plasma T4 level under long photoperiod at 25 degrees C might be induced by testosterone.     

Temperature dependence of neurotransmitter release in the antarctic fish Pagothenia borchgrevinki

The quantal contents of endplate potentials from extraocular muscles of an antarctic fish Pagothenia borchgrevinki were measured over a range of temperatures. Quantal release was maximal at about 5 degrees C but showed little dependence on temperature between -2 degrees C and 10 degrees C. Above 10 degrees C quantal content declined until release ceased about 18 degrees C. In view of the fact that the ambient temperature at which these fish live is constant at -1.9 degrees C, the results suggest that Pagothenia borchgrevinki is only partially adapted to its environment despite 25 million years acclimatization.     

Effects of thyrotrophic-releasing hormone (TRH) on thermoregulation in the rat

Summary At ambient temperatures (T_a) of both 8 and 22°C, intraventricular administration of TRH (10–80 g) produced a dose-dependent hypothermia in rats. The hypothermia was due to both decreased metabolic heat production and cutaneous vasodilatation. In contrast, at 30°C T_a, TRH increased metabolic heat production (due to behavioral excitation) and led to hyperthermia.This work was supported by the grants from the National Science Council of Republic of China and the Pjing-Ling Neurological Foundation (VGH, Taipei, Taiwan).     

Cholecystokinin-octapeptide-induced hyperthermia in guinea-pigs

Intracerebroventricular administration of cholecystokinin-octapeptide (CCK-8) at room temperature (21 degrees C) induced dose-related hyperthermia in guinea-pigs and also produced hyperthermia at low (10 degrees C) and high (30 degrees C) ambient temperatures. CCK-8-induced hyperthermia was direct and not mediated by prostaglandins, norepinephrine, cyclic AMP or naloxone-sensitive receptors.     

Effects of hypothalamic injections of 5,6-dihydroxytryptamine on thermoregulation in rats.

5,6-Dihydroxytryptamine, a serotonin depletor, infused directly into the anterior hypothalamus of rat's brain, produced an increase in both heat production and heat loss (as indicated by changes in peripheral circulation) at temperatures of 8, 15 and 22 degrees C. The rectal temperature of these treated rats remained constant.     

A thermosensitive inhibitor of the replication of polyomavirus, an extract from BHK2I cells transformed by the Tsa mutant of this virus

BHK21 cells transformed by wild type or Ts3 mutant polyoma virus contain an inhibitor of polyoma virus replication when grown at permissive (36 degrees C) as well as non-permissive temperature (39 +/- 0.5 degrees C). Cells transformed by the Tsa mutant contain the inhibitor at the permissive but not at the non-permissive temperature. The inhibitor reappears in the latter cells however, upon shift from the non-permissive to the permissive temperature. If a reversible protein inhibitor (methionyl-adenylate, reversible inhibitor of the aminoacyl-t-RNA synthetase) is applied during the temperature shift experiments, the inhibitor does not reappear indicating that new protein synthesis is required for the recovery of its activity.     

Improved separation at low temperature of glycoproteins by Con A-Sepharose affinity chromatography in the presence of sodium dodecyl sulfate (SDS)

The Con A-Sepharose affinity chromatography of glycoproteins was even more effective at 4 degrees C than that at room temperature (26-28 degrees C) in the presence of sodium dodecyl sulfate (SDS). Application of this methodology to the separation of several glycoproteins from SDS-solubilized membrane proteins in rat cerebellum, including a glycoprotein characteristic of the Purkinje cells, was successful.     

The Na/K pump,resting potential and selective permeability in canine Purkinje fibres at physiologic and room temperatures

All mammalian cells maintain a resting potential generated by ions moving down concentration gradients. In excitable cells, the inside potential is negative relative to outside. In order to maintain this electrochemical gradient, the sodium potassium (Na/K) pump actively transports out three sodium ions for every two potassium ions it brings in. This process generates a net outward current and thus hyperpolaizes the resting potential. I employed dihydroouabain (DHO) to inhibit the Na/K pump and thus measure its contribution to the resting potential. It contributed 9.0 mV at 34°C and 3.8 mV at 25°C. The P_K/P_Na ratios were calculated at both temperatures before and after subtracting the Na/K pump contribution. These ratios also suggested a decreased contribution of the Na/K pump under hypothermia. Taken together, these results suggest that the pump contribution to the resting potential is more significant at physiologic temperatures (34°C) than at room temperature (25°C), and that estimates of selective permeability can only be accurately obtained after assessing and eliminating the Na/K pump contribution to the resting potential.     

Changes in Plasmodium berghei berghei in mice maintained at high temperatures]

The study of the evolution of Plasmodium berghei berghei is made in mice kept in a high temperature (35 degrees C) throughout the experiment. Some of these mouse parasites (less than 30%) show a gigantic atypical morphology. In the parasite growing in animals kept at 35 degrees C, the amount of DNA is higher than DNA rate of the parasites growing in control mice (20-22 degrees C). There is no evidence of any relation between the increase of DNA amount and the morphological modification of these parasites.     

Lesions in the substantia nigra of rats induce thermoregulatory deficit in the cold

Summary Rats with either electrolytic or chemical (6-hydroxydopamine) lesions in the substantia nigra displayed decreased metabolism and hypothermia when they were exposed to cold (8 °C T_a), although they showed no deficiency in thermoregulation at both moderate (22 °C) and hot (30 °C) environmental temperatures.This work was supported by grants from the Pjing-Ling Neurological Foundation (Veterans General Hospital, Taipei, Taiwan, China) and the National Science Council (Republic of China). The authors are grateful to Mr C.C. Wei for his generous support.