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PubMed1990

Evidence for a heat shock transcription factor-independent mechanism for heat shock induction of transcription in Saccharomyces cerevisiae.

Transcription of the DNA damage-responsive gene, DDRA2, of Saccharomyces cerevisiae is activated by heat shock treatment as well as by mutagen/carcinogen exposure. Deletion analysis of upstream noncoding sequence indicated that sequences between approximately -190 and -140 base pairs were necessary for heat shock and DNA damage regulation of transcription. Fusion of this region to a CYC1-lacZ reporter gene demonstrated that the sequence between -202 and -165 base pairs was sufficient for basal level and heat shock-induced expression. This DNA sequence was unable to bind heat shock transcription factor as judged by binding competition experiments in vitro. These results indicate that yeast possesses a second, heat shock transcription factor-independent mechanism for activating transcription in response to thermal stress.

Amino Acid Sequence↗
PubMed1987

[Effects of factors of nutrition and husbandry on the heat production of rats and broilers. 1. Heat production of growing broiler chicks kept in groups depending on the environmental temperature].

In 2 experiments with young broiler chickens, origin Tetra B, heat production was measured in dependence on ambient temperature indirectly and with the gas exchange both over 24 h and in 20-minute periods beginning on their 5th day of live. The chickens, divided into 2 X 2 groups according to sex, were constantly kept in a climatic chamber changed in to a respiration chamber during the 8- or 11-week-long experiments. The maximum variation of the temperature was between 5 and 35 degrees C. In the periods of 24-h measurements over 4 days each, the ambient temperature was changed from day to day in steps of 5 degrees C. Heat production was influenced by the age of the chickens, energy intake and ambient temperature. The results of the measurements at the same age and the same energy intake and a temperature variation between 5 and 35 degrees C can well be described by polynomes of the 3rd degree up to the 8th week of live. The thermoregulatory conditioned heat production per 1 degree C below the critical temperature decreased with the age of the chickens. In the first few weeks of life it was 20 kJ, in the 6th and 7th weeks of life 10-15 kJ and then decreased to 4-5 kJ/kg life weight 0.75.d. degrees C. Based on the temperature of minimal heat production, the heat production of 16- to 30-day-old chickens increased to 60-80% at an ambient temperature of 5 degrees C; the metabolism of chickens older than 7 weeks was only increased by about 20%. For the first 2 weeks 35 degrees C were ascertained as critical temperature, for the 3rd to 6th weeks 30 degrees C and for the 7th and 8th weeks 25 degrees C.

Animals↗
PubMed2001

Heat-related death and mental illness during the 1999 Cincinnati heat wave.

During a 1999 heat wave in Cincinnati, Ohio, the Hamilton County Coroner reported 18 heat-related deaths. The Centers for Disease Control and Prevention and the Cincinnati Department of Health conducted a case-control study using surrogate case information and first-person control information to identify risk factors for mortality during the heat wave. Surrogate data were supplemented by systematic death scene investigation reports and comprehensive toxicologic screens, important sources of data that are routinely collected by the Hamilton County Coroner's Office. The study included 17 case subjects and 34 controls from the decedents' neighborhood. Among 17 case subjects, 8 (47.1%) had mental illness (odds ratio [OR], 14.0; 95% confidence interval [CI], 1.8-633). There was a suggestion of an interaction between age and mental health. A working air-conditioner was the strongest protective factor (OR, 0.03; 95% CI, 0-0.2). Toxicologic screening indicated that case subjects with reported mental illness and a prescription for psychotropic drugs may not have been medication compliant. Three decedents lived in group homes for people with mental illness, indicating that opportunities for prevention may have been missed. Systematic death investigations, including toxicologic screening, provide valuable information about the circumstances of heat-related death, particularly the role of medication compliance as a risk factor. Prevention programs during heat waves should target people with mental illness, especially those who take psychotropic medication.

Adult↗
PubMed1987

Establishment of thermotolerance in maize by exposure to stresses other than a heat shock does not require heat shock protein synthesis.

Maize (Zea mays) seedlings were pretreated prior to heat shock with either a progressive water stress of -0.25 megapascal PEG/hour from 0 to -1.25 megapascal over a 6-hour time period, or various concentrations of copper, cadmium, or zinc for 4 days. When the subsequent heat shock of 40 or 45 degrees C was administered for 3 hours, the seedlings showed an induced thermotolerance to these temperatures, which were otherwise lethal to control (water grown) seedlings. Thermotolerance was exhibited by both the root and the shoot of pretreated seedlings, even though the water and heavy metal stresses were applied only to the roots. Neither of these pretreatments had induced the synthesis of detectable levels of heat shock proteins (Hsps) at the time of heat shock. Pretreatment of seedlings with a progressive heat shock of 2 degrees C/hour from 26 to 36 degrees C, which did induce Hsps 18, 70, and 84, resulted in tolerance of a severe water stress of -1.5, -1.75, or -2.0 megapascal for 24 hours. But these seedlings producing Hsps were no better protected against water stress than those pretreated with a progressive water stress which did not produce Hsps. Hsps appear not to act as general stress proteins and their presence is not always required for the establishment of thermotolerance.

Journal Article↗
PubMed1990

Maintenance of body temperature in elderly patients who have joint replacement surgery. A comparison between the heat and moisture exchanger and heated humidifier.

The effect of a heat and moisture exchanger on intra-operative aural canal (core) and mean skin temperatures was investigated in elderly patients who had elective total hip arthroplasty under general anaesthesia with artificial ventilation of the lungs. Group 1 (n = 20) did not receive any form of artificial humidification while in group 2 (n = 20) a heat and moisture exchanger was inserted in the breathing system and in group 3 (n = 20) the inspired gases were humidified and warmed at 40 degrees C by means of a heated humidifier. Time of surgery, intravenous fluid administration and operating theatre temperature were standardised. Mean (SD) aural canal (core) temperature decreased significantly in groups 1 and 2 (p less than 0.001), while there was a fall of 0.3 degrees C (0.6) in group 3, which was not significant. Mean skin temperature decreased during anaesthesia and surgery in both groups 1 and 2 (p less than 0.05), while it increased in group 3. There was a significantly greater loss of body heat in groups 1 and 2 compared with group 3 intra-operatively (p less than 0.001). We conclude tha a heat and moisture exchanger did not prevent the decrease in intra-operative body temperature in elderly patients.

Aged↗
PubMed1990

Heat resistance in Salmonella enteritidis phage type 4: the influence of storage temperatures before heating.

Storage of cultures of Salmonella enteritidis PT4 at either 4 degrees or 8 degrees C before heating significantly increased heat sensitivity. The differences between fresh and stored cultures, which became apparent after 4-7 h, were more pronounced with cultures stored at the lower temperature and in those heated at 60 degrees rather than 55 degrees C. Incubation of the stored cultures in either egg or Lemco broth for 30 min at 37 degrees C prior to heating enabled the organisms to recover heat resistance.

Bacteriophage Typing↗
PubMed1987

In vitro and in vivo evaluation of a factor VIII concentrate heat-treated to inactivate HTLV-III/LAV viruses. Favourable effects of heating on the von Willebrand factor.

We report here the results of our evaluation of the effects of a dry heat treatment (96 h at 68 degrees C) to eliminate LAV/HTLV-III virus on factor VIII (FVIII) and von Willebrand factor (vWf) present in an intermediate-purity concentrate. This thermal inactivation appears to have little effect on FVIII. There is an acceptable loss (12.3 +/- 3.6%; n = 25) in FVIII coagulant activity (FVIII: C) and a good in vivo performance in haemophilia A patients. A precise analysis of vWf indicates that whereas the vWf antigen and its ristocetin cofactor activity decrease during heating, there is an increase in potentially functional forms of vWf. Heat treatment induces an increase in high molecular weight forms of vWf and an enhancement in platelet adhesion to collagen. These changes probably explain the correcting effect on the bleeding time of the heated FVIII concentrate in patients with von Willebrand's disease. Thus, this heat-treated concentrate appears to be equivalent to the untreated product in haemophilia A, with the additional benefit of being efficient for the treatment of von Willebrand's disease.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Theoretical evaluation of contributions of heat conduction and countercurrent heat exchange in selective brain cooling in humans.

The purpose of this work is to evaluate the capacity of the heat loss from the carotid artery in the human neck and thus, to provide indirect evidence of the existence of selective brain cooling in humans during hyperthermia. A theoretical model is developed to describe the effects of blood flow rate and vascular geometry on the thermal equilibration in the carotid artery based on the blood flow and the anatomical vascular geometry in the human neck. The potential for cooling of blood in the carotid artery on its way to the brain by heat exchange with the jugular vein and by radial heat conduction loss to the cool neck surface is evaluated. It is shown that the cooling of the arterial blood can be as much as 1.1 degrees C lower than the body core temperature, which is in agreement with previous experimental measurements of the difference between the tympanic and body core temperatures. The model also evaluates the relative contributions of countercurrent heat exchange and radial heat conduction to selective brain cooling. It is found that these mechanisms are comparable with each other. Results of the present study will help provide a better understanding of the thermoregulation during hyperthermia.

Blood Flow Velocity↗
PubMed2006

Heat resistance and mechanism of heat inactivation in thermophilic campylobacters.

The heat resistance of Campylobacter jejuni strains AR6 and L51 and the heat resistance of Campylobacter coli strains DR4 and L6 were measured over the temperature range from 50 to 60 degrees C by two methods. Isothermal measurements yielded D55 values in the range from 4.6 to 6.6 min and z values in the range from 5.5 to 6.3 degrees C. Dynamic measurements using differential scanning calorimetry (DSC) during heating at a rate of 10 degrees C/min yielded D55 values of 2.5 min and 3.4 min and z values of 6.3 degrees C and 6.5 degrees C for AR6 and DR4, respectively. Both dynamic and isothermal methods yielded mean D55 values that were substantially greater than those reported previously (0.75 to 0.95 min). DSC analysis of each strain during heating at a rate of 10 degrees C/min yielded a complex series of overlapping endothermic peaks, which were assigned to cell wall lipids, ribosomes, and DNA. Measurement of the decline in the numbers of CFU in calorimetric samples as they were heated showed that the maximum rate of cell death occurred at 56 to 57 degrees C, which is close to the value predicted mathematically from the isothermal measurements of D and z (61 degrees C). Both estimates were very close to the peak m1 values, 60 to 62 degrees C, which were tentatively identified with unfolding of the 30S ribosome subunit, showing that cell death in C. jejuni and C. coli coincided with unfolding of the most thermally labile regions of the ribosome. Other measurements indicated that several essential proteins, including the alpha and beta subunits of RNA polymerase, might also unfold at the same time and contribute to cell death.

Animals↗
PubMed1983

Protection in rabbits immunized with a vaccine of Escherichia coli heat-stable toxin cross-linked to the heat-labile toxin B subunit.

Rabbits and rats were immunized with a vaccine consisting of synthetically produced Escherichia coli heat-stable toxin cross-linked by the carbodiimide reaction to the B subunit of biologically produced porcine heat-labile toxin. The vaccine contained 50% of each toxin component by weight and antigenicity; the toxicity of the heat-stable enterotoxin component was reduced by greater than 600-fold. Two or three peroral immunizations with vaccine containing 1,000 antigen units of each component raised greater-than-threefold increases in specific mucosal immunoglobulin A antitoxin titers to each component in all animal groups. Protection index values for challenge with either heat-labile or heat-stable toxins in ligated ileal loops were 3.4 to 4.0 in rats immunized by a parenteral primary immunization followed by two peroral booster immunizations, greater than 9 in rabbits immunized by these routes, and greater than 8 in rabbits given just three peroral immunizations. The antigenicity of the B-subunit component of the peroral vaccine was protected equally well against gastric acidity either by pretreatment with cimetidine or by delivery of the vaccine encapsulated in pH-dependent microspheres. The vaccine did not cause diarrhea when given perorally to any of the experimental animals or evoke fluid secretion when instilled into rabbit ligated ileal loops. These observations (i) confirm the effectiveness of this vaccine as an immunogen in a second animal model, (ii) establish that it is effective when given exclusively by the peroral route, and (iii) provide further evidence regarding its lack of toxicity.

Administration, Oral↗
PubMed2005

Effects of heat removal through the hand on metabolism and performance during cycling exercise in the heat.

OBJECTIVE: This two-part study tested the hypotheses that the use of a new cooling device, purported to extract heat from the body core through the palm of the hand, would (a) attenuate core temperature rise during submaximal exercise in the heat, thereby suppressing exercise-associated metabolic changes, and (b) facilitate a higher sustained workload, thus shortening the completion time of a time-trial performance test. METHODS: In Study 1, 8 male triathletes (age 27.9 +/- 2.0 yrs, mass 77.2 +/- 3.1 kg, VO2peak 59.0 +/- 4.1 ml x min(-1) x kg(-1)) cycled for 1 hr at the same absolute workload (approximately 60% VO2peak) in a heated room (31.9 +/- 0.1 degrees C, 24 +/- 1% humidity) on two occasions counterbalanced for cooling (C) or noncooling (NC). In Study 2, 8 similar subjects (age 26.9 +/- 2.0 yrs, mass 75.2 +/- 3.7 kg, VO2peak 54.1 +/- 3.1 ml x min(-1) x kg(-1)) performed two 30-km cycling time-trial performance tests under the same conditions (C(T), NC(T)). RESULTS: In Study 1, cooling attenuated the rise in tympanic temperature (T(TY)) (1.2 +/- 0.2 vs. 1.8 +/- 0.2 degrees C; p < 0.01) and lowered mean oxygen consumption (VO2, 2.4 +/- 0.1 vs. 2.7 +/- 0.1 L x min(-1); p < 0.05) and blood lactate (1.7 +/- 0.2 vs. 2.2 +/- 0.2 mmol x L(-1); p < 0.01) during exercise. There were no significant differences in respiratory exchange ratio (RER), blood glucose, heart rate (HR), face temperature (T(F)), or back temperature (T(B)) between NC and C. In Study 2, time to complete 30 km was 6 +/- 1% less with cooling than without cooling (60.9 +/- 2.0 vs. 64.9 +/- 2.6 min; p < 0.01). During the last 20% of C(T), subjects sustained a workload that was 14 +/- 5% (p = 0.06) higher than NC(T) at the same T(TY) and HR. CONCLUSIONS: Heat extraction through the hand during cycle ergometer exercise in the heat can (a) lower T(TY), lactate concentration, and VO2 during a submaximal set-workload test and (b) reduce the time it takes to complete a 30-km time-trial test.

Adolescent↗
PubMed1982

Open-loop gain of evaporative heat loss during radiant heat exposure in the mouse.

Whole-body evaporative water loss of the mouse during radiant heating was determined at ambient temperatures of 20-35 degrees C. The ratio of evaporated to absorbed heat per gram body weight, which is equal to open-loop gain (OLGEHL), increased over sixfold with each 1 degrees C increase in ambient temperature. At 35 degrees C, OLGEHL was equal to 0.8, which implies that the mouse evaporates 80% of the absorbed radiant heat. At 20 degrees C, less than 1% of the absorbed heat is evaporated and the remainder of the heat load is dissipated passively. A previous estimate of OLG for the mouse is similar to the data from this study at an ambient temperature of 35 degrees C. Determining OLG with natural ambient stimulation may make future studies in thermoregulation comparable.

Animals↗
PubMed1990

Thermoregulatory responses to acute body heating in rats acclimated to continuous heat exposure.

Thermoregulatory responses to an acute heat load with intraperitoneal heating (IH) or indirect external warming (EW) by increasing ambient temperature (Ta) were investigated with direct and indirect calorimetry in rats acclimated to environments of 24.0 degrees C (Cn), 29.4 degrees C (H1), and 32.8 degrees C (H2) for greater than 15 days. The rats were placed in a direct calorimeter where the air temperature was maintained at 24 degrees C for the initial 3 h. IH was then made for 30 min through an electric heater implanted chronically (6.5 W.kg-1) in the peritoneal cavity, and EW was performed by raising the jacket water temperature surrounding the calorimeter from 24 to 39 degrees C (0.19 degrees C.min-1). Hypothalamic (Thy) and colonic temperature immediately before the start of the heat load tended to be higher as the acclimation temperature increased. During IH, the threshold Thy for the tail skin vasodilation (Tth) was significantly higher in H2 than in Cn rats. During EW, however, there was no difference in Tth between the groups. Metabolic heat production (M) was slightly suppressed during IH and significantly depressed only in H2 rats. During EW, M was suppressed in all the groups. The magnitude and duration of suppression were greater in H2 rats than in the other two groups. The responses in nonevaporative heat loss and thermal conductance (C) to the rise in Thy did not differ among the three groups during IH. According to the rise in Thy, however, there was a greater C increase in H2 than in Cn and H1 rats during EW.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1996

Heat acclimation: cardiovascular response to hot/dry and hot/wet heat loads in rats.

Body temperature, blood pressure (BP) and heart rate (HR) of rats before and after acclimation to heat were studied in chronically cannulated sedentary conscious rats in different hot environmental conditions [hot/dry: 40 degrees C, 20% relative humidity (RH) and hot/wet: 35 degrees C, 70% RH]. During exposure to heat stress, acclimated rats showed an attenuated increase in colonic temperature (Tc) compared to non-acclimated rats. Concomitantly, an abrupt decrease in HR, delayed and attenuated elevation in mean arterial BP and improved cardiac efficiency were recorded. Differences were observed upon exposure to the hot/wet and hot/dry climates: the hot/dry climate imposed a greater physiological burden than the hot/wet climate. The data suggest that for sedentary rats dry heat produces a greater load than humid heat. Thus, the conventional heat load indices do not apply universally but have a thermoregulatory pattern specificity.

Acclimatization↗
PubMed1992

Psychophysical features of the transition from pure heat perception to heat pain perception.

The psychophysical features of the transition from the pure heat to the heat pain range were studied in 25 healthy subjects (mean age 28.8 years). Thirty short heat stimuli from -1.6 degrees C to +1.6 degrees C relative to the pain threshold were applied to the thenar of the left hand with an apparatus containing a Peltier thermode (nine different temperatures at 0.4 degrees C intervals). The subjects rated the sensation intensity on a visual analogue scale. The resulting stimulus/sensation intensity relations could be explained equally well (same goodness of fit) by a model with a power function (PF) and by a model with two linear regression lines (TLR), one for stimulus intensities below and one for those above the pain threshold and intersecting at the pain threshold. The slopes of the TLR model were significantly larger above the pain threshold than below it. The PF model produced exponents between 1.8 and 1.9. We conclude that to describe the transition area, it is sufficient to use simple linear models for both the pure heat and the heat pain ranges.

Adult↗
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↗
PubMed2005

[Evaluating influence of individual protective means on heat state of individuals working in heating microclimate].

The authors evaluate working clothes protecting against electromagnetic waves and chemical pollution to exemplify that the clothes use in heating surroundings deteriorates human heat state due to disordered heat-mass exchange with environment and higher physical exertion caused by the clothes weight. The article demonstrates necessity to correct requirements to microclimate parameters, if using working clothes deteriorating heat-mass exchange with environment in heating microclimate. For adequate evaluation of work conditions, the materials include temperature modification values in accordance with some working clothes types.

Adult↗
PubMed1986

Survival of heated or irradiated Chinese hamster ovary microcolonies that develop after an initial dose of heat.

Asynchronous or synchronous G1 cells were heated initially and then heated or irradiated a second time when the multiplicity of viable cells in microcolonies that developed from cells surviving the first heat dose had increased to 6-30. The survival of these microcolonies was compared with the survival of single cells that were heated or irradiated after the microcolonies had been trypsinized and dispersed into single cells. The survival of the single cells was similar to the survival of the microcolonies and much higher than single cell survival calculated by correcting microcolony survival for multiplicity. However, when microcolonies developed from control unheated cells, the observed single cell survival corresponded to single cell survival calculated by correcting microcolony survival for multiplicity. Therefore, multiplicity corrections, which assume that cells within a microcolony survive independently from one another, are not valid when the microcolony has developed from a cell surviving an initial heat treatment.

Animals↗