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At least 19 recordsLinked to original sources
PubMed1976

[Variability of the ova of mulberry silkworm (Bombyx mori L.) with regard to capacity for thermal parthenogenesis and heat resistance. 4. Relationship between the capacity of oocytes from different females for thermal parthenogenesis and heat resistance of ova at the early stage of development and heat resistance of the muscles of these females].

The reliable positive correlation was established between the variability of unfertilized eggs by their ability of thermal parthenogenesis and the heat resistance of fertilized eggs at the early stages of development. At the same time the ability of oocytes of parthenogenesis correlates negatively with the heat resistance of muscles. The data obtained suggest that the variability of oocytes by their ability of thermal parthenogenesis is partially due to the variability of heat resistance of their proteins.

Animals↗
PubMed1978

Heat stress upon undressed man due to different combinations of elevated environmental temperature, air humidity, and metabolic heat production: a critical comparison of heat stress indices.

In several 100 climatic chamber experiments young healthy acclimatized men were exposed successively to combinations of ambient temperature and air humidity that were varied systematically from day to day within the range of 15 to 57 degrees C and 8 to 97% relative humidity, with air speed kept constant at 0.3 m/s. The subjects who were nearly nude were exposed at rest and at different treadmill work levels (metabolic rates up to about 1350 kJ/h). Each exposure lasted between two and six h. It was found that body temperatures and heart rate, but not loss of sweat, were suitable criteria for indicating equal stress conditions. Equations were derived describing those climatic combinations which were equivalent at the various activity levels of each subject. The slope of the respective equivalence curves plotted in psychrometric charts varied systematically with work level. The curves obtained for various subjects at any given activity level showed similarities, so that the calculation of an equivalence system common to all subjects seemed to be justified. A detailed comparison of these results with previous indices is presented. The combinations of ambient temperatures and humidities that were found to be equivalent under the given conditions of physical activity corresponded particularly well with the Index of Physiological Effect (ROBINSON et al.). There was also good agreement with the P4SR Index (MCARDLE et al.). The combinations corresponded with other indices (Heat Stress Index of BELDING and HATCH, Index of Thermal Stress of GIVONI) and with Basic Effective Temperature and Wet-bulb Globe Temperature only within limited ranges of climate depending upon work level. A procedure is presented which allows one to evaluate in terms of physiological responses how far various indices describe equivalent stress conditions correctly.

Adult↗
PubMed1977

Comparison of indirect calorimetry and direct heat flow discs results in measuring R+C heat loss in burned patients.

This study was carried out on 17 burned patients. Metabolic heat production, rectal and skin temperatures, and heat exchanges by R+C were measured. It was found that R+C heat loss takes into account 60 to 80% of the increased metabolic heat production. Two methods were used to measure R+C heat loss: calculation by indirect calorimetry and direct measurements by using heat flow discs. The direct relationship which exists between the results of these two methods showed the reliability of the use of heat flow discs for measuring R+C heat loss. This fast-responding techniques may allow the elaboration of a thermal setting system which could modulate ambient air temperature, thus limiting exagerated heat loss due to the skin lesions.

Body Temperature Regulation↗
PubMed1976

Cutaneous heat flow during heating and cooling in Alligator mississipiensis.

Direct in vivo measurement of heat flow across the skin of the American alligator (Alligator mississipiensis) showed increased heat flow during warming. Mean values at 25 degrees C during warming (15-35 degrees C) in air (airspeed 300 cm/s) were 17.9 +/- 92 SE cal/cm2 per h (mean alligator wt 3.27 kg). Cooling heat flow at the same temperature was 13.6 +/- 0.57 cal/cm2 per h. Subdermal heat flow was reduced during warming and was not significantly different from cutaneous heat flow during cooling. This indicated that the alligator was able to control its rate of heat exchange with the environment by altering cutaneous perfusion. Atropine, phenoxybenzamine, nitroglycerin, and Xylocaine did not affect cutaneous heat flow or heating and cooling rates. Atropine blocked bradycardia during cooling.

Alligators and Crocodiles↗
PubMed1978

The effect of cholera toxin and heat labile and heat stable Escherichia coli enterotoxin on cyclic AMP concentrations in small intestinal mucosa of pig and rabbit.

The effect of cholera toxin, heat labile and heat stable Escherichia coli enterotoxin on mucosal cyclic AMP concentrations was determined on the proximal jejunum of weanling pigs and young rabbits. Ligated loops were injected with solutions containing no enterotoxin for control and either cholera toxin, heat labile or heat stable E. coli enterotoxin. The loops were drained after either two, four or six hours incubation at which time accumulated fluid was recorded and mucosal samples removed for determination of cyclic AMP concentration. In the rabbit, cholera toxin and heat labile, but not heat stable E. coli enterotoxin stimulated intestinal secretion while in the pig all three enterotoxins induced net fluid accumulation. Cholera toxin and heat labile, but not heat stable E. coli enterotoxin elevated rabbit mucosal cyclic AMP concentrations. In the pig these enterotoxins had no significant effect on mucosal cyclic AMP concentrations. The results are inconsistent with the hypothesis that the adenyl cyclase system is an essential step for enterotoxin induced intestinal secretion. The activation of intestinal adenyl cyclase by bacterial enterotoxins may only be an associated and not a necessary event for the stimulation of intestinal secretion.

Animals↗
PubMed1978

Effects of intraluminal glucose on intestinal secretion induced by heat stable and heat labile Escherichia coli enterotoxin, cholera toxin and theophylline.

Glucose, l-alanine, l-aspartate, l-methionine and glycine enhanced net fluid and electrolyte absorption in acute isolated loops of the proximal jejunum of weanling swine. The effect of glucose on intestinal secretion induced by heat stable and heat labile Escherichia coli entero-toxin, cholera toxin and theophylline was examined in both the proximal and distal jejunum of weanling swine. In the proximal jejunum glucose enhanced the rate of net fluid and electrolyte absorption. This increase was accompanied by an increase in unidirectional dosium absorption. In loops exposed to either heat stable or heat labile enterotoxins, glucose significantly decreased the rate of net fluid and electrolyte secretion. The magnitude of glucose enhancement in loops exposed to heat stable and heat labile enterotoxins was similar to adjacent control loops. However, glucose enhancement did not occur in loops exposed previously to cholera toxin or concurrently to theophylline. Therefore, cholera toxin and theophylline may inhibit substrate dependent sodium absorption in the proximal jejunum. In the distal jejunum glucose enhancement did occur but the rate of enhancement was less than in the proximal jejunum. In this region glucose enhancement was not evident in loops exposed to either theophylline, heat stable, heat labile or cholera toxin.

Amino Acids↗
PubMed2026

Heat-responsive ONSEN long terminal repeats integrate heat shock factor motifs, DNA methylation and natural sequence variation in Arabidopsis.

ONSEN is a heat-activated Ty1/copia retrotransposon in Arabidopsis thaliana controlled by heat shock factors (HSFs) and epigenetic silencing. Heat shock element (HSE)-like sequences in ONSEN long terminal repeats (LTRs) contribute to heat responsiveness, but relationships among sequence architecture, basal DNA methylation and natural variation remain unclear. We combined transcription-factor motif prediction, transposable-element comparisons, methylome and RNA sequencing (RNA-seq) data, and Arabidopsis genome assemblies. In silico disruption of five HSE cores eliminated HSF-family motif compatibility in the selected design and all 5119 exact-guanine-cytosine (GC) alternatives. Across 16 curated Columbia-0 terminal windows, ONSEN contained 33-49 non-redundant HSF motif-coordinate placements per 800 bp window and was strongly enriched relative to 1930 non-ONSEN transposable elements across score thresholds and continuous metrics. Direct comparison with 779 non-ONSEN LTR retrotransposons showed selectively elevated basal CHH methylation (where H = A, C or T) at ONSEN termini. Genome-wide RNA-seq analysis revealed broad heat-responsive gene and transposable-element changes, including strong ONSEN induction, whereas candidate-window analysis distinguished ONSEN from most HSF-rich non-ONSEN outliers. ONSEN-like variants across eight accessions generally retained HSF-compatible motifs while altering predicted DNA binding with one finger-family motif composition. Together, these findings define ONSEN terminal regions as HSF-rich regulatory sequences that retain heat-responsive potential within a methylated chromatin context and identify candidates for functional analysis.

DNA Methylation↗
PubMed1976

Mechanisms of heat damage in proteins. 7. The significance lysine-containing isopeptides and of lanthionine in heated proteins.

1. Studies have been made with solvent-extracted chicken muscle, bovine plasma albumin (BPA) and other proteins, all severely heated in the absence of carbohydrates so as to cause a large decrease in their fluorodinitrobenzene (FDNB)-reactive lysine contents. 2. epsilon-N-(beta-L-aspartyl)-L-lysine and epsilon-N-(gamma-L-glutamyl)-L-lysine isopeptides were determined after enzymic digestion of heated chicken muscle, and their content was found to increase as the material was subjected to more heat treatment. Heated chicken muscle was not found to contain lanthionine. Heated BPA, on the other hand, was found to contain lanthionine but not the isopeptides. Both lanthionine and isopeptide cross-linkages were detected in most of the other heated proteins. There was some difficulty in quantifying the amounts of isopeptides formed on heat treatment, because the enzymic digestion procedure used in their isolation appeared to be incomplete. Neither lysinoalanine nor ornithinoalanine was detected in any of the test materials.

Alanine↗
PubMed1977

Effect of heat stable and heat labile Escherichia coli enterotoxins, cholera toxin and theophylline on unidirectional sodium and chloride fluxes in the proximal and distal jejunum of weanling swine.

Acute, isolated loops of proximal and distal jejunum of weanling swine were exposed to either heat stable porcine Escherichia coli enterotoxin, heat labile porcine Escherichia coli enterotoxin, cholera toxin or theophylline. Unidirectional sodium fluxes in response to heat stable in the proximal jejunum were dependent on the length of time that the intestinal mucosae was exposed to the enterotoxin. Net water, sodium and chloride and unidirectional sodium and chloride flux measurements in the proximal jejunum in response to each agent uniformly indicated that net secretion of fluid and electrolytes was the result of increased unidirectional sodium secretion or blood-to-lumen flux and decreased unidirectional chloride absorption or lumen-to-blood flux. In addition heat stable cholera toxin and theophylline but not heat labile decreased unidirectional chloride secretion a small but significant amount in the proximal jejunum. Sodium and chloride flux measurements in the distal jejunum demonstrated that all four secretory agents could stimulate net secretion of water, sodium and chloride in that region. The response to these secretory agents as measured by sodium and chloride unidirectional flux rates was not similar to changes observed in the proximal jejunum. In the distal small intestine, whereas heat labile cholera toxin and theophylline induced similar qualitative changes in unidirectional sodium and chloride fluxes, that induced by heat stable differed.

Animals↗
PubMed1979

Cardiovascular and metabolic manifestations of heat stroke and severe heat exhaustion.

We prospectively studied the clinical, biochemical (including creatine phosphokinase (CPK) isoenzymes) and electrocardiographic features of exertional heat stroke in 13 patients (group 1) and severe heat exhaustion in 14 patients (group 2). Despite initial presentations with severe hyperthermia, tachycardia and hypotension, only one patient with heat stroke had myocardial ischemia. The CPK isoenzymes were not indicative of myocardial damage in any patient. The patients with heat stroke were somewhat more dehydrated than those with heat exhaustion as measured by differences in serum creatinine, sodium and osmolality, and the former (group 1) had a significantly lower initial glucose level (P less than 0.05). Although significant differences in potassium were not observed in the pretreatment samples, at 12 hours the serum potassium was significantly lower in group 1 (P less than 0.05). This suggests that this group may have been more potassium-depleted at the time of heat stroke. Prompt recognition and vigorous therapy were successful in rapidly lowering high temperatures and in preventing serious complications.

Alanine Transaminase↗
PubMed1976

Effect of heat acclimatization on intravascular responses to acute heat stress in man.

The effects of a 185-min exposure to 48 degrees C db/33 degrees C wb, on intravascular volume and osmolarity and on intravascular electrolyte, aldosterone, and cortisol concentrations have been studied in five male subjects before and after acclimatization to heat. Changes in the hematocrit and plasma protein concentration indicated that a hemodilution occurred during the first 35 min of the heat exposures, and that this was followed by a hemoconcentration. Although these changes in intravascular volume were not affected by acclimatization, the plasma volume after heat acclimatization was 6.7% greater than before. This increase in plasma volume was associated with an elevation in the ratio [Na]/[K]. However, since plasma osmolarity decreased the intravascular expansion could not be explained in terms of elevated electrolyte levels. Plasma aldosterone and cortisol levels were not affected by heat acclimatization, although both were elevated following exercise in the heat. It is concluded that the adrenal cortex is not an important factor in maintaining a state of heat acclimatization once a salt balance has been achieved.

Acclimatization↗
PubMed1978

Heat-induced changes of chlorophyll fluorescence in isolated chloroplasts and related heat-damage at the pigment level.

The heat-induced changes of chlorophyll fluorescence excitation and emission properties were studied in isolated chloroplasts of Larrea divaricata Cav. An analysis of the temperature dependency of fluorescence, under Fo and Fmax conditions, of temperature-jump fluorescence induction kinetics, and of 77 degrees K emission spectra of preheated chloroplasts revealed two major components in the heat-induced fluorescence changes: (1) a fluorescence rise, reflecting the block of Photosystem II reaction centers; and (2) a fluorescence decrease, caused by the functional separation of light-harvesting pigment protein complex from the rest of the pigment system. Preferential excitation of chlorophyll a around 420 nm, produced a predominant fluorescence rise. Preferential excitation of chlorophyll b, at 480 nm, gives a predominant fluorescence decrease. It is proposed that the overlapping of the fluorescence decrease on the somewhat faster fluorescence rise, results in the biphasic fluorescence rise kinetics observed in isolated chloroplasts. Both the rise component and the decay component are affected by the thermal stability of the chloroplasts, acquired during growth of the plants in different thermal environments. Mg2+ enhances the stability against heat-damage expressed in the decrease component, but has no effect on the rise component. Heat pretreatment leads to a decrease of the variable fluorescence in the light-induced 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) rise curve, but no change in half-rise time is observed. It is concluded that the block of Photosystem II reaction centers precedes the loss of the light-harvesting pigment protein complex. However, the approximately antiparallel heat-induced Fmax decrease and Fo increase suggest a common cause for the two events. A heat-induced perturbation of the thylakoid membrane is discussed.

Chlorophyll↗
PubMed1977

Exercise and heat orthostatism and the effect of heat acclimation and physical fitness.

Twelve trained and 16 untrained young men were administered five orthostatic tests while leaning upright against a wall, for 20 min--before exercise; after 60 min of exercise at a load of 40 W; after 15 min of exercise at a load of 80 W; after a Vo2 max test, and after 3 h of exercise at a load of 40 W in heat (39.4 degrees C DB, 30.3 degrees C WB). Eight of the untrained subjects were retested in the five orthostatic tests after 8 d of heat acclimation. The number of fainters in the orthostatic tests administered before exercise, after exercise at 40 W and 80 W, and after exercise in heat, were 3, 4, 6, and 13, respectively. There were no fainting episodes after the Vo2 max tests. Orthostatic responses in the different conditions were partially related. The trained subjects showed substantially better responses than the untrained ones (10% vs. 25% of fainting episodes), and heat acclimation resulted in marked improvement in orthostatism (decrease to 5% faintings). The results show that Vo2 max and heat tolerance account for most of the variability which determines orthostatic tolerance.

Acclimatization↗
PubMed1977

Deletions of two heat-activated loci in Drosophila melanogaster and their effects on heat-induced protein synthesis.

Deficiencies that delete two heat-induced puffs in Drosophila melanogaster have been isolated. Two deficiencies delete the puff arising from 87C1, and one deletes the two puffs at 87A and 87C1. Homozygotes for these deletions can be recognized by their abnormal, transparent malpighian tubules. The influence on heat-induced protein synthesis of deleting one or both of these puffs has been examined. Unexpectedly, deleting only the 87C1 puff has no apparent effect. Deleting both the 87A and 87C1 puffs eliminates synthesis of a 71,000 dalton protein. We map a coding locus for the 71,000 dalton heat-induced protein to 87A7-B3, a seven band region which also contains a heat-induced puff. The roles of the 87A and 87C1 puffs in coding for heat-induced proteins are discussed in the light of these results.

Animals↗
PubMed1975

Heat stabilization produced by protein-protein association. A differential scanning calorimetric study of the heat denaturation of the trypsin-soybean trypsin inhibitor and trypsin-ovomucoid complexes.

The irreversible thermal denaturation of the association complexes of bovine beta-trypsin with soybean trypsin inhibitor or ovomucoid was observed with a differential scanning calorimeter. Association of trypsin with either inhibitor results in increased heat stability. The largest effect is observed with beta-trypsin and soybean trypsin inhibitor. At pH 6.7, first order rate constants (s-1) for denaturation at 72 degrees, determined at a heating rate of 10 degrees per min, are: beta-trypsin, 30 times 10-3; soybean trypsin inhibitor, 9 times 10-3; trypsin-soybean trypsin inhibitor complex, 0.4 times 10-3. Under equivalent conditions, rate constants for ovomucoid and trypsin-ovomucoid complex are 4 times 10-3 and 1 times 10-3 s-1, respectively. These changes in rate correspond to heat stabilization of trypsin equivalent to an increase of 16 and 9 degrees, respectively, in its observed denaturation temperature. Rate constants determined for beta-trypsin and trypsin-soybean trypsin inhibitor complex are independent of heating rate; those for soybean trypsin inhibitor and ovomucoid are a function of heating rate. This suggests that predenaturational conformational alterations may be important steps in the denaturation of the inhibitors. Activation energies for denaturation of the complexes and their components are all similar, averaging 70 kcal per mol. The large activation energies observed suggest that denaturation of the complexes is not rate-limited by their dissociation.

Animals↗
PubMed1979

Relationships among training, heat acclimation, and heat tolerance in men and women: the controversy revisited.

For more than a decade there has been a controversy over the beneficial effects of physical training in a cool environment on exercise-heat tolerance. The issues include (a) inadequate controls regarding the physical characteristics of subjects, (b) marked variability in the conditions of the standard heat tolerance tests and (c) differences in the intensity and duration of the training programs employed. Intense training in a cool environment cannot serve as a substitute for exercise in the heat if acclimation is desired within a 2 week period. However, a substantial improvement (50%) in heat tolerance can be derived from 8-11 weeks of training under temperate conditions (21 degrees C) and thermal equilibrium can be maintained for at least 4 hours during mild work (200 W/m2) in dry or wet heat by endurance runners. These adjustments occur in both men and women and appear to be independent of aerobic capacity. The key to improved thermal tolerance with training in a cool environment is maintenance of an elevated core temperature for a sufficient duration of time to produce an adaptive response.

Acclimatization↗