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At least 739 records · Page 41Linked to original sources
PubMed1981

The effect of whole body heat exposure and of cooling the hypothalamus on antibody titre in the rat.

In rats implanted with chronic hypothalamic thermodes and immunized with sheep erythrocytes, body temperature was increased, 4 h per day for 2 weeks, either by exposing the animals to external heat or by cooling the preoptic area. The titre of antibodies against sheep erythrocytes was nearly tripled by preoptic cooling but was drastically decreased by heat exposure. These opposing effects of active and passive increases in body temperature indicate that factors other than the change in body temperature must also have played a significant role in modifying the humoral immune response.

Animals↗
PubMed1991

Hormone response of diabetic patients to exercise at cool and warm temperatures.

Both exercise and high ambient temperatures stimulate the secretion of counterregulatory hormones which can change glucose homeostasis. We studied whether in diabetic patients there are any differences in the hormonal response to exercise performed at cool or warm ambient temperatures. A study was performed on eight male insulin-dependent patients at rest and during exercise at +10 degrees C and +30 degrees C. Exercise consisted of three consecutive 15-min periods at 60% of maximal aerobic capacity. The concentrations of plasma lactate and counterregulatory hormones at rest were similar at warm and cool temperature, whereas prolactin concentration was higher (P less than 0.01) at +30 degrees C. Exercise resulted in an increase in noradrenaline, growth hormone and prolactin (P less than 0.01), prevented the diurnal decrease in cortisol, but had no effect on glucagon. Hormone responses to exercise were similar at +10 degrees C and at +30 degrees C, except for cortisol and noradrenaline which showed greater responses at warm than at cool temperatures. This may have been due to the higher relative work load at warm compared to cool temperatures as suggested by the higher heart rate and greater increase of lactate at +30 degrees C. These data indicate that within a range of ambient temperatures commonly occurring in sports, the response of counterregulatory hormones is largely independent of ambient temperature in insulin-dependent diabetic patients.

Adult↗
PubMed1986

Whither brown fat?

Explore the source record for details and available documents.

Adipose Tissue, Brown↗
PubMed1980

Influence of method of feeding on stress ulcer development in the rat.

Maintenance of rats on total parenteral nutrition for 10 days increased the susceptibility of these animals to gastric ulceration and death due to cold-temperature restraint stress. Animals fed the identical diet orally were much less susceptible. Serum gastrin concentrations were increased by stress in both groups of animals despite initially low serum levels. Glucosamine synthetase specific activity was not altered by the method of feeding but tended to be decreased by restraint. These results suggest that orally administered food protects the animal from stress-induced damage by a mechanism(s) involving neither dietary composition nor gastrin.

Animals↗
PubMed1990

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.

Adaptation, Physiological↗
PubMed2003

Pharmacological characterization of the effects of 3,4-methylenedioxymethamphetamine ("ecstasy") and its enantiomers on lethality, core temperature, and locomotor activity in singly housed and crowded mice.

RATIONALE: Few studies have directly compared the effects of methylenedioxymethamphetamine (MDMA, "ecstasy") and its enantiomers across measures. OBJECTIVES: To investigate the capacity of MDMA and its stereoisomers to produce aggregate toxicity in mice, the influence of 5-HT(2) receptors, 5-HT transporters, and ambient temperature on this effect, and to directly compare the racemate and its enantiomers in terms of their effects on core temperature and locomotor activity with and without various serotonergic pretreatments. METHODS: Mice were injected with various doses of MDMA and its stereoisomers in various housing conditions, with and without pretreatments of serotonergic drugs, and at two distinct ambient temperatures; lethality was quantified 2 h after MDMA administration. For temperature/activity studies, mice were injected with various doses of MDMA and its enantiomers, with and without ketanserin, MDL100907, or fluoxetine pretreatments, and core temperature and locomotor activity data were collected for 24 h. RESULTS: Racemic MDMA and its isomers produced aggregate toxicity in mice. The lethal effects of racemic MDMA and its enantiomers were differentially attenuated by the various serotonergic pretreatments and manipulation of the ambient temperature across housing conditions. Racemic and S(+)-MDMA produced hyperthermic effects in mice, while R(-)-MDMA did not. The pretreatment drugs attenuated the hyperthermic effects of racemic MDMA, but were less effective in blocking S(+)-MDMA-induced hyperthermia. Racemic MDMA and both enantiomers stimulated locomotor activity, although R(-)-MDMA was least effective. The pretreatments all reduced the locomotor stimulant effects of racemic MDMA but potentiated S(+)-MDMA-induced hyperlocomotion. CONCLUSIONS: The MDMA isomers have heterogeneous effects that can be demonstrated across a wide range of endpoints.

Animals↗
PubMed1997

Mutations in the M4 domain of the Torpedo californica nicotinic acetylcholine receptor alter channel opening and closing.

We studied the functional effects of single amino acid substitutions in the postulated M4 transmembrane domains of Torpedo californica nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes at the single-channel level. At low ACh concentrations and cold temperatures, the replacement of wild-type alpha418Cys residues with the large, hydrophobic amino acids tryptophan or phenylalanine increased mean open times 26-fold and 3-fold, respectively. The mutation of a homologous cysteine in the beta subunit (beta447Trp) had similar but smaller effects on mean open time. Coexpression of alpha418Trp and beta447Trp had the largest effect on channel open time, increasing mean open time 58-fold. No changes in conductance or ion selectivity were detected for any of the single subunit amino acid substitutions tested. However, the coexpression of the alpha418Trp and beta447Trp mutated subunits also produced channels with at least two additional conductance levels. Block by acetylcholine was apparent in the current records from alpha418Trp mutants. Burst analysis of the alpha418Trp mutations showed an increase in the channel open probability, due to a decrease in the apparent channel closing rate and a probable increase in the effective opening rate. Our results show that modifications in the primary structure of the alpha- and beta subunit M4 domain, which are postulated to be at the lipid-protein interface, can significantly alter channel gating, and that mutations in multiple subunits act additively to increase channel open time.

Amino Acid Sequence↗
PubMed2004

Molecular adaptation in the ice worm, Mesenchytraeus solifugus: divergence of energetic-associated genes.

The ice worm, Mesenchytraeus solifugus, is the largest glacially obligate metazoan and among only a few metazoan species that complete their life cycle at 0 degrees C. We conducted a large-scale sequencing analysis of cDNAs isolated from ice worm anterior segments. Sequence comparisons among an available group of ice worm, arthropod, chordate, and nematode homologues suggest that ice worms encode proteins that are less bulky, are less polar, and contain fewer charged residues. Also, subunits of the catalytic F1 ATP synthase complex appear to have diverged more rapidly than other ice worm genes examined, suggesting a role in cold-temperature adaptation. Modeling of F1 ATP synthase beta and gamma subunits identified nonconservative, ice worm-specific amino acid substitutions at subunit contact sites and at sites proximal to the catalytic site.

Amino Acid Sequence↗