Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Heating”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1990

Heat loss responses in rats acclimated to heat loaded intermittently.

The present study examined the heat loss response of heat-acclimated rats to direct body heating with an intraperitoneal heater or to indirect warming by elevating the ambient temperature (Ta). The heat acclimation of the rats was attained through exposure to Ta of 33 or 36 degrees C for 5 h daily during 15 consecutive days. Control rats were kept at Ta of 24 degrees C for the same acclimation period. Heat acclimation lowered the body core temperature at Ta of 24 degrees C, and the core temperature level was lowered as acclimation temperature increased. When heat was applied by direct body heating, the threshold hypothalamic temperature (Thy) for the tail skin vasodilation was also lower in heat-acclimated rats than in the control rats. However, the amount of increase in Thy from the resting level to the threshold was the same in all three groups. When heat was applied by indirect warming, threshold Thy was slightly higher in heat-acclimated than in control rats. The amount of increase in Thy from the resting level to the threshold was significantly greater in heat-acclimated rats. In addition, Ta and the skin temperature at the onset of skin vasodilation were significantly higher in heat-acclimated rats. The results indicate that heat-acclimated rats were less sensitive to the increase in skin temperature in terms of threshold Thy. The gain constant of nonevaporative heat loss response was assessed by plotting total thermal conductance against Thy.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed2006

Heat stress-induced H(2)O (2) is required for effective expression of heat shock genes in Arabidopsis.

The mechanisms of sensing and signalling of heat and oxidative stresses are not well understood. The central question of this paper is whether in plant cells oxidative stress, in particular H(2)O(2), is required for heat stress- and heat shock factor (HSF)-dependent expression of genes. Heat stress increases intracellular accumulation of H(2)O(2) in Arabidopsis cell culture. The accumulation was greatly diminished using ascorbate as a scavenger or respectively diphenyleneiodonium chloride (DPI) as an inhibitor of reactive oxygen species production. The mRNA of heat shock protein (HSP) genes, exemplified by Hsp17.6, Hsp18.2, and the two cytosolic ascorbate peroxidase genes Apx1, Apx2, reached similar levels by moderate heat stress (37 degrees C) or by treatment with H(2)O(2), butylperoxide and diamide at room temperature. The heat-induced expression levels were significantly reduced in the presence of ascorbate or DPI indicating that H(2)O(2) is an essential component in the heat stress signalling pathway. Rapid (15 min) formation of heat shock promoter element (HSE) protein-binding complex of high molecular weight in extracts of heat-stressed or H(2)O(2)-treated cells and the inability to form this complex after ascorbate treatment suggests that oxidative stress affects gene expression via HSF activation and conversely, that H(2)O(2) is involved in HSF activation during the early phase of heat stress. The heat stress induction of a high mobility HSE-binding complex, characteristic for later phase of heat shock response, was blocked by ascorbate and DPI. H(2)O(2 )was unable to induce this complex suggesting that H(2)O(2) is involved only in the early stages of HSF activation. Significant induction of the genes tested after diamid treatment and moderate expression of the sHSP genes in the presence of 50 mM ascorbate at 37 degrees C occurred without activation of HSF, indicating that other mechanisms may be involved in stress signalling.

Arabidopsis↗
PubMed1995

Heat-shock proteins Hsp104 and Hsp70 reactivate mRNA splicing after heat inactivation.

BACKGROUND: The heat-shock protein Hsp104 plays a crucial role in the survival of cells exposed to high temperatures and other severe stresses, but its specific functions and the biological pathways on which it operates have been unclear. Indeed, very little is known about the specific cellular processes in which any of the heat-shock proteins acts to affect thermotolerance. One essential process that is particularly sensitive to heat in many organisms is the splicing of intervening sequences from mRNA precursors. RESULTS: We have examined the role of Hsp104 in the repair of splicing after disruption by heat shock. When splicing in the budding yeast Saccharomyces cerevisiae was disrupted by a brief heat shock, it recovered much more rapidly in wild-type strains than in strains containing hsp104 mutations. Constitutive expression of Hsp104 promoted the recovery of heat-damaged splicing in the absence of other protein synthesis, but did not protect splicing from the initial disruption, suggesting that Hsp104 functions to repair splicing after heat damage rather than to prevent the initial damage. A modest reduction in the recovery of splicing after heat shock in an hsp70 mutant suggested that Hsp70 may also function in the repair of splicing. The roles of Hsp104 and Hsp70 were confirmed by the ability of the purified proteins to restore splicing in extracts that had been heat-inactivated in vitro. Together, these two proteins were able to restore splicing to a greater degree than could be accomplished by an optimal concentration of either protein alone. CONCLUSIONS: Our findings provide the first demonstration of the roles of heat-shock proteins in a biological process that is known to be particularly sensitive to heat in vivo. The results support previous genetic arguments that the Hsp104 and Hsp70 proteins have different, but related, functions in protecting cells from the toxic effects of high temperatures. Because Hsp104 and Hsp70 are able to function in vitro, after the heat-damaged substrate or substrates have been generated, neither protein is required to bind to its target(s) during heating in order to effect repair.

Fungal Proteins↗
PubMed1987

Heating efficacy of external heat supply during and after open-heart surgery with hypothermia.

Heat balance after cardiac surgery with hypothermic cardiopulmonary bypass (CPB) was studied in 156 patients. In spite of rewarming during CPB there was residual hypothermia at the end of operation. This heat deficit could not be prevented by intraoperative use of a heating mattress at 38 degrees C and/or heated (39 degrees C) humidified inspired gases. Postoperatively, in four groups of patients, the core and finger skin temperatures were recorded and the mean skin and mean body temperatures and heat balance were calculated. Heating of humidified inspired gases (n = 22) gave little improvement in the time course of the temperatures and heat balance as compared with that in a control group with no external warming postoperatively (n = 49). A thermal ceiling (a low-temperature radiator suspended above the bed and providing radiant heat (n = 35] significantly increased the measured temperatures, which were restored to normal earlier than those in the controls. Also, with this radiant heat postoperative shivering was almost abolished. With a combination of radiant heat and heated, humidified gases (n = 50), the postoperative heat balance was improved somewhat further. For patients treated with radiant heat, postoperative rewarming was accomplished in a shorter time and almost without active endogenous muscular thermogenesis, as was evident by the great reduction in postoperative shivering.

Anesthesiology↗
PubMed1986

Heat shock protein levels are not elevated in heat-resistant B16 melanoma cells.

Heat-resistant variants have been selected from B16 melanoma cells and from surface mutants previously derived from them. The aim of the present study was to explore the possible role of heat shock proteins in the manifestation of this heat resistance. The major heat shock proteins evident after heating have subunit molecular weights of 68, 70, 89, and 110K on sodium dodecyl sulfate-polyacrylamide gels. The 68-kDa protein is not evident in any of the unheated B16 cell lines while the levels of the other heat shock proteins are elevated after heating. The constitutive levels of the 70, 89, and 110-kDa heat shock proteins were assessed after gel electrophoretic separation of proteins in several of the heat-resistant variants. No major differences were found in the levels of these proteins between the heat-sensitive parent lines and the heat-resistant variants. We therefore conclude that heat shock proteins are not a determining factor in the heat-resistant phenotype of B16 melanoma cells.

Acclimatization↗
PubMed1999

Proteasome inhibitors lactacystin and MG132 inhibit the dephosphorylation of HSF1 after heat shock and suppress thermal induction of heat shock gene expression.

Recently, we have shown that two proteasome inhibitors, MG132 and lactacystin, induce hyperphosphorylation and trimerization of HSF1, and transactivate heat shock genes at 37 degrees C. Here, we examined the effects of these proteasome inhibitors and, in addition, a phosphatase inhibitor calyculin A (CCA) on the activation of HSF1 upon heat shock and during post-heat-shock recovery, with emphasis on HSF1 hyperphosphorylation and the ability of HSF1 to transactivate heat shock genes. When lactacystin, MG132, or CCA was present after heat shock, HSF1 remained hyperphosphorylated during post-heat-shock recovery at 37 degrees C. Failure of HSF1 to recover to its preheated dephosphorylated state correlated well with the suppression of the heat-induced hsp70 expression. In vitro, HSF1 from heat-shocked cells, when dephosphorylated, showed an increase in HSE-binding affinity. Taken together, these data suggest that phosphorylation of HSF1 plays an important role in the negative regulation of heat-shock response. Specifically, during post-heat-shock recovery phase, prolonged hyperphosphorylation of HSF1 suppresses heat-induced expression of heat shock genes.

Acetylcysteine↗
PubMed2004

[Expressions of JWA protein and heat stress protein 70 induced by cell differentiation inducers combined with heat stress in K562 cells].

OBJECTIVE: To study how the combined effects of various differentiation inducers and heat stress on the expression of JWA protein in K562 cell, the relationship between JWA and Hsp70 expression, and the signal regulation mechanism possibly involved. METHODS: The experimental model was established in K562 cells. Various directional differentiation inducers (TPA, Ara-C, hemin, adriamycin, ATRA and As(2)O(3)) were used alone or combined with heat shock treatment (42 degrees C, 2 h). Western blot was used for detecting expressions of JWA, Hsp70, heat stress factor 1 (HSF1) and HSF2. RESULTS: (1) The expressions of both JWA protein and Hsp70 were significantly up-regulated after K562 cells treated by TPA (100, 200 ng/ml) or adriamycin (4 x 10(-8) mol/L) 48 h, and followed by heat shock (42 degrees C, 2 h). However, the opposite effects were observed when the cells treated by hemin (3 x 10(-5) mol/L, 48 h), Ara-C (80 ng/ml, 48 h) and As(2)O(3) (1 x 10(-6) mol/L, 48 h) followed by 2 h heat shock. No obvious changes were found when the cells treated by ATRA (1 x 10(-6) mol/L, 48 h) alone or followed by heat shock. (2) Both the heat shock transcriptional factors HSF1 and HSF2 did not show any significant changes when K562 cells were treated with various differentiation inducers and followed by heat stress. CONCLUSION: JWA not only takes part in the regulation of K562 cellular differentiation, but also of heat stress, it might be the co-target gene of several differentiation inducers and heat stress. The expression of Hsp70 seems not mediated by both HSF1 and HSF2 in K562 cells undergoing directional differentiation or heat stress treatment. JWA is likely to be a new signal molecule similar to Hsp70 signal pathways. The results show that JWA takes part in the mechanism of K562 cell response to heat stress.

Blotting, Western↗
PubMed1998

Heat shock protein 72 restores cyclic AMP accumulation after heat shock in N18TG2 cells.

Although there are several reports on the alteration of intracellular signal transduction during heat shock in somatic cells, the long term effects of heat shock on neuronal cells remain unknown. In this report, we investigated cyclic AMP (cAMP) accumulation and the expression of heat shock proteins following heat shock in mouse neuroblastoma N18TG2 cells. Basal cAMP accumulation, or that stimulated by serotonin (10 microM), cholera toxin (1 microg/ml), and forskolin (1 microM) was suppressed at 0, 3, and 6 h following heat shock (45 degrees C for 30 min). The cAMP levels were restored at 15 and 24 h after heat shock, corresponding with the expression of stress-induced heat shock protein 72 (HSP72). Quercetin, an inhibitor of HSP expression, decreased the expression of HSP72 and inhibited the recovery of cAMP levels 24 h after heat shock. Quercetin also decreased the basal expression of the constitutive heat shock cognate protein 70 (HSC70) and suppressed cAMP accumulation in non-heat shocked cells. These results suggest that stress-induced HSP72 restores cAMP accumulation to control levels following heat shock and that constitutive HSC70 is related to cAMP levels in non-stress conditions.

Animals↗
PubMed1987

Differential antigen presentation by heat-treated peripheral blood mononuclear cells and Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL): heated EBV-LCL present alloantigen and soluble antigen but are deficient in the stimulation of autologous EBV-LCL primed T cells.

Heat-treated PBM (1 hr at 45 degrees C) cannot present soluble Candida albicans antigens (CAN) or stimulate in the mixed lymphocyte culture (MLC) reaction. This is despite their continued expression of serologically defined class II MHC antigens. In contrast, heat-treated EBV-LCL present soluble CAN and stimulate allogeneic T cells in the MLC. Heated EBV-LCL stimulate strong secondary responses from allogeneic alloprimed T-cell lines in the primed lymphocyte test (PLT), while heated PBM stimulate only weak secondary allogeneic responses. To test whether this difference was due to a subtle difference in the thermal stability of the functional expression of class II MHC antigens on PBM and EBV-LCL cells, the EBV-LCL cells were heated for 1 hr at temperatures from 45 degrees C to 60 degrees C. Even after treatment at 60 degrees C, the heated EBV-LCL strongly stimulated alloreactive T cells in MLC and PLT reactions. Heated EBV-LCL are not nonspecifically mitogenic, as they do not stimulate autologous T-cell lines primed to alloantigens. However, the weak response of alloprimed T-cell lines to heated allogeneic PBM can be augmented by coculturing with autologous heated EBV-LCL, suggesting heated EBV-LCL maintain a metabolic activity necessary for allogeneic stimulation that is deficient in heated PBM. While heated EBV-LCL stimulate allogeneic alloprimed T-cell lines, they no longer stimulate autologous EBV-LCL primed T-cell lines; irradiated EBV-LCL stimulate both strongly. This suggests the involvement of a heat labile antigenic or metabolic factor in the T-cell recognition of autologous but not allogenic EBV-LCL.

Antigen-Presenting Cells↗
PubMed1997

Heat resistance of Talaromyces flavus ascospores as determined by a two phase slug flow heat exchanger.

Heat resistance of Talaromyces flavus was determined using two methods. Standard thermal death time vials were used to determine the heat resistance of T. flavus ascospores, from 80 to 90 degrees C with a decimal reduction time D90 of 6.2 min. A continuous two-phase slug flow heat exchanger system with heating, holding and cooling sections was used to determine the heat resistance from 90 to 100 degrees C. Inoculated heating medium was pumped through 1.85 mm ID tubing in 'slugs' separated by air bubbles to interrupt laminar flow. Varying pump speed, length of tubing in the heating bath and temperature allowed collection of data under varied heating conditions. D90 with the slug flow heat exchanger system was 6.4 min, indicating the two methods were comparable, z values were 6.7 and 6.4 degrees C, respectively. The slug flow heat exchanger system permits rapid determination of heat resistance over a range of temperatures. Because of minimum come-up time the slug flow heat exchanger can be used at temperatures near the upper limit of heat resistance for the microorganism being tested.

Hot Temperature↗
PubMed1997

Effects of near-lethal heat stress on bud break, heat-shock proteins and ubiquitin in dormant poplar (Populus nigra Charkowiensis x P. nigra incrassata).

We assessed the effects of near-lethal heat stress on bud break, heat-shock proteins (HSPs) and ubiquitin in hybrid poplar (Populus nigra (L.) Charkowiensis x P. nigra (L.) incrassata). Shoots, with 10-15 buds each, were collected from September to March and exposed to temperatures between 20 and 60 degrees C for 2 h. Shoots were then placed in a greenhouse at 18-22 degrees C with supplemental light and cumulative bud break was recorded over a 4-week period. Samples of bud tissues were collected during and up to 96 h after heat treatment for protein analysis. De novo synthesis of proteins was monitored by exposing excised buds to [(35)S]-methionine for 3 h before, during, or after heat treatment. Heat treatments of 40-45 degrees C resulted in both a release from endodormancy and a decrease in thermal units needed for bud break during ecodormancy. The response to near-lethal heat stress was complex and was affected by intrinsic thermal sensitivity. Heat treatments were least effective during August and became progressively more effective as endodormancy progressed. In the later stages of ecodormancy, a heat treatment of 45 degrees C either inhibited bud break or killed the buds. Although temperatures of 42.5 to 45 degrees C inhibited incorporation of [(35)S]-methionine into proteins for at least 48 h, several HSPs were synthesized in response to temperatures of 40-45 degrees C. Immunoblots indicated that one of the heat-induced proteins was immunologically related to HSP70. Increases in free and conjugated forms of ubiquitin were also observed in response to heat treatment. Production of HSPs and ubiquitin, however, was not consistently associated with the heat treatments that induced the highest percentage of bud break. The roles of heat-induced protein degradation, HSPs, and ubiquitin in overcoming dormancy by near-lethal heat stress are discussed.

Journal Article↗
PubMed2003

Heat acclimation increases skin vasodilation and sweating but not cardiac baroreflex responses in heat-stressed humans.

In the present study, to test the hypothesis that exercise-heat acclimation increases orthostatic tolerance via the improvement of cardiac baroreflex control in heated humans, we examined cardiac baroreflex and thermoregulatory responses, including cutaneous vasomotor and sudomotor responses, during whole body heating before and after a 6-day exercise-heat acclimation program [4 bouts of 20-min exercise at 50% peak rate of oxygen uptake separated by 10-min rest in the heat (36 degrees C; 50% relative humidity)]. Ten healthy young volunteers participated in the study. On the test days before and after the heat acclimation program, subjects underwent whole body heat stress produced by a hot water-perfused suit during supine rest for 45 min and 75 degrees head-up tilt (HUT) for 6 min. The sensitivity of the arterial baroreflex control of heart rate (HR) was calculated from the spontaneous changes in beat-to-beat arterial pressure and HR. The HUT induced a presyncopal sign in seven subjects in the preacclimation test and in six subjects in the postacclimation test, and the tilting time did not differ significantly between the pre- (241 +/- 33 s) and postacclimation (283 +/- 24 s) tests. Heat acclimation did not change the slope in the HR-esophageal temperature (Tes) relation and the cardiac baroreflex sensitivity during heating. Heat acclimation decreased (P < 0.05) the Tes thresholds for cutaneous vasodilation in the forearm and dorsal hand and for sweating in the forearm and chest. These findings suggest that short-term heat acclimation does not alter the spontaneous baroreflex control of HR during heat stress, although it induces adaptive change of the heat dissipation response in nonglabrous skin.

Acclimatization↗
PubMed2000

Implication of a small GTPase Rac1 in the activation of c-Jun N-terminal kinase and heat shock factor in response to heat shock.

Heat shock induces c-Jun N-terminal kinase (JNK) activation as well as heat shock protein (HSP) expression through activation of the heat shock factor (HSF), but its signal pathway is not clearly understood. Since a small GTPase Rac1 has been suggested to participate in the cellular response to stresses, we examined whether Rac1 is involved in the heat shock response. Here we show that moderate heat shock (39-41 degrees C) induces membrane translocation of Rac1 and membrane ruffling in a Rac1-dependent manner. In addition, Rac1N17, a dominant negative mutant of Rac1, significantly inhibited JNK activation by heat shock. Since Rac1V12 was able to activate JNK, it is suggested that heat shock may activate JNK via Rac1. Similar inhibition by Rac1N17 of HSF activation in response to heat shock was observed. However, inhibitory effects of Rac1N17 on heat shock-induced JNK and HSF activation were reduced as the heat shock temperature increased. Rac1N17 also inhibited HSF activation by l-azetidine-2-carboxylic acid, a proline analog, and heavy metals (CdCl)), suggesting that Rac1 may be linked to HSF activation by denaturation of polypeptides in response to various proteotoxic stresses. However, Rac1N17 did not prevent phosphorylation of HSF1 in response to these proteotoxic stresses. Interestingly, a constitutively active mutant Rac1V12 did not activate the HSF. Therefore, Rac1 activation may be necessary, but not sufficient, for heat shock-inducible HSF activation and HSP expression, or otherwise a signal pathway(s) involving Rac1 may be indirectly involved in the HSF activation. In sum, we suggest that Rac1 may play a critical role(s) in several aspects of the heat shock response.

Animals↗
PubMedDate not supplied

The augmentative effect of repeated heat shock preconditioning on the production of heat shock protein 72 and on ischemic tolerance in rat liver tissue.

OBJECTIVE: Heat shock pretreatment induces heat shock protein (HSP)72 strongly in rat livers and provides the tolerance against subsequent ischemia-reperfusion injury. In this study, the effects of repeated heat shock pretreatment on the production of HSP72 in rat livers and on subsequent ischemic tolerance were investigated. METHODS: Rats pretreated with repeated heat shock were compared with those that received a single heat shock pretreatment. The production of HSP72 was analysed using Western-blotting and densitometer. At 48 h after heat shock pretreatment, all rats were subjected to warm liver ischemia for 30 or 45 min and then reperfused. Survival rate of the animals and liver functions during reperfusion were analysed. RESULTS: The production of HSP72 increased in the repeated heat shock group more than in the single heat shock group. Although there were no significant differences in animal survival or in liver functions after a 30-min ischemia between the single heat shock group and the repeated heat shock group, animal survival and liver functions after a 45-min ischemia were significantly better in the repeated heat shock group. CONCLUSION: In rats, repetition of heat shock pretreatment augmented the production of HSP72 in liver tissue and protected the liver from ischemia-reperfusion injury.

Animals↗
PubMed2002

Heat stress- and heat shock transcription factor-dependent expression and activity of ascorbate peroxidase in Arabidopsis.

To find evidence for a connection between heat stress response, oxidative stress, and common stress tolerance, we studied the effects of elevated growth temperatures and heat stress on the activity and expression of ascorbate peroxidase (APX). We compared wild-type Arabidopsis with transgenic plants overexpressing heat shock transcription factor 3 (HSF3), which synthesize heat shock proteins and are improved in basal thermotolerance. Following heat stress, APX activity was positively affected in transgenic plants and correlated with a new thermostable isoform, APX(S). This enzyme was present in addition to thermolabile cytosolic APX1, the prevalent isoform in unstressed cells. In HSF3-transgenic plants, APX(S) activity was detectable at normal temperature and persisted after severe heat stress at 44 degrees C. In nontransgenic plants, APX(S) was undetectable at normal temperature, but could be induced by moderate heat stress. The mRNA expression profiles of known and three new Apx genes were determined using real-time PCR. Apx1 and Apx2 genes encoding cytosolic APX were heat stress and HSF dependently expressed, but only the representations of Apx2 mRNA met the criteria that suggest identity between APX(S) and APX2: not expressed at normal temperature in wild type, strong induction by heat stress, and HSF3-dependent expression in transgenic plants. Our data suggest that Apx2 is a novel heat shock gene and that the enzymatic activity of APX2/APX(S) is required to compensate heat stress-dependent decline of APX1 activity in the cytosol. The functional roles of modulations of APX expression and the interdependence of heat stress and oxidative stress response and signaling mechanisms are discussed.

Arabidopsis↗
PubMed1999

Heat acclimation increases the basal HSP72 level and alters its production dynamics during heat stress.

It has been previously shown that heat acclimation leads to an elevated basal level of 72-kDa heat shock protein (HSP72). Augmented expression of HSP72 is considered as a cytoprotective response. This led us to hypothesize that alterations in the heat shock protein (HSP) defense pathway are an integral part of the heat acclimation repertoire. To investigate this, we studied the temporal profile of basal HSP expression upon acclimation and the dynamics of their accumulation subsequent to acute heat stress (HS). In parallel, HSP72 mRNA level before and after HS was measured. For comparison, HSC mRNA [the constitutive member of 70-kDa HSP (HSP70) family] was measured in similar conditions. Heat acclimation was attained by continuous exposure of rats to 34 degrees C for 0, 1, 2, and 30 days. HS was attained by exposure to 41 or 43 degrees C for 2 h. Thermoregulatory capacity of the rats was defined by rectal temperature, heating rate, and the cumulative heat strain invoked during HS. HSP72 and HSP70 gene transcripts were measured in the left ventricle of the heart by means of Western immunoblotting and semiquantitative RT-PCR, respectively. The resultant acclimatory change comprised a higher resting level of the encoded 72-kDa protein (Delta175%, P < 0.0001). After HS, peak HSP72 mRNA level was attained, 40 and 20 min post-HS at 41 and 43 degrees C, respectively, vs. 60 and 40 min in the nonacclimated group. The subsequent HSP synthesis, however, was dependent on the severity of the cumulative heat strain. At the initial phase of heat acclimation, augmented HSP72 transcription unaccompanied by HSP synthesis was observed. It is concluded that upon heat acclimation, the HSP defense pathway is predisposed to a faster response. At the initial phases of heat acclimation, inability to elevate the HSP cytosolic level rules out their direct cytoprotective role.

Acclimatization↗