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 1,693 records · Page 94Linked to original sources
PubMed1991

Heat shock and thermotolerance in plant and animal embryogenesis.

Although the strategies of early embryogenesis differ greatly among multicellular eukaryotes, there are certain parallels in structure, form, and function that cross even kingdom lines: the extreme heat sensitivity of zygotes and very early embryos, followed by the acquisition of thermotolerance during subsequent development, is one such parallel. The heat sensitivity may be so extreme that even moderate increases in temperature result in lethality (generally associated with the earliest phases of embryogenesis), or the effects may be less severe, resulting in defects in development but not in lethality. Mechanistically, and molecularly, these two forms of thermosensitivity appear to have different origins. On the one hand, outright lethality appears to result from an inability to induce heat shock genes and proteins; on the other hand, heat-induced developmental defects appear to result from an alteration in expression of non-heat shock genes and from a delay in the overall developmental program that generally accompanies the cell's response to heat shock. This review is focused on the developmental regulation of the heat shock response during early embryogenesis and on the impact of this regulation on the development of both animal and plant embryos. The two basic issues that we address here are (i) the expression of heat shock genes in the absence of heat shock during embryogenesis and (ii) the expression (or lack of expression) of heat shock genes after deliberate exposure of the embryos to heat shock and the consequences of this expression on its subsequent survival and development.

Animals↗
PubMedDate not supplied

Heat shock-induced loss of the glucocorticoid receptor protein in cultured cells.

Effects of heat shock on the glucocorticoid receptor (GR) hormone binding activity and its degradation have been studied in mouse AtT-20 pituitary tumor cells in culture. Heat shock of cultured cells rapidly (30 min at 42 degrees C) enhanced the incorporation of [35S]methionine into heat shock protein 70 (hsp70), hsp90, and other unidentified hsp's. Maximum induction of newly synthesized hsp's occurred after 2-4 h at 42 degrees C. The initiation of the heat shock response rapidly and progressively decreased the total cellular GR hormone binding activity, and 4 h of heat shock resulted in the loss of about 80% of the initial hormone binding. This loss of GR hormone binding occurred at times when the general protein synthesis pattern or cellular viability was not significantly affected. In addition, cycloheximide prevented subsequent heat shock-induced loss of cellular hormone binding, suggesting that protein synthesis is required for this effect. By labeling of cellular GR with [3H]dexamethasone 21-mesylate at 37 degrees C and then transferring the cells to 42 degrees C, it was shown that heat shock caused an actual degradation (loss) of the 94 kDa GR protein. In addition, heat shock also caused loss of immunoreactive 94 kDa GR as detected by anti-GR (BuGR2) in a Western blot assay. A comparison of the loss of hormone binding and the disappearance of 94 kDa GR band during heat shock of AtT-20 cells followed similar kinetics (t1/2 = 1 h). Finally, the residual GR remaining in the cells after heat shock did not associate normally with the cell nucleus, perhaps indicating that a substantial alteration in GR structure had occurred. These studies suggest that the initiation of the shock response, and possibly the elevated levels of hsp's themselves, may be involved in the specific degradation of cellular GR. Therefore, heat shocked cells are likely to be refractile to the glucocorticoids.

Affinity Labels↗
PubMed1990

Age-dependent decrease in the heat-inducible DNA sequence-specific binding activity in human diploid fibroblasts.

In order to gain a better understanding of the molecular mechanism of the attenuated heat shock response in aging diploid fibroblasts (Liu, A. Y.-C., Lin, Z., Choi, H.-S., Sorhage, F., and Li, B. (1989) J. Biol. Chem. 264, 12037-12045), we examined the regulation of a heat-inducible, heat shock element (HSE) sequence-specific binding protein in IMR-90 diploid fibroblasts. Using gel retardation assay, we showed that the HSE binding activity in extracts of IMR-90 cells was very dependent on heat shock of the cells; that the induction was transient with a maximal increase observed at 1 h of heat shock. Significantly, the level of this heat-inducible HSE-binding activity was age-dependent, being high in young cells and low in old cells. By Scatchard analysis, we determined that this difference in HSE binding in young and old cells was not due to a change in the affinity of the binding, rather the level of the heat-inducible HSE-binding activity was different. The equilibrium dissociation constants (Kd) were estimated to be 30, 25, and 31 pM for cells with population-doubling levels of 22, 35, and 45, respectively; the corresponding Bmax values were 0.087, 0.042, and 0.0059 pmol of 32P-HSE bound per mg of whole cell extract protein. The decreased 32P-HSE-binding activity in the old cells was not a reflection of global alteration of many transcription factors; assay of the DNA binding activity of activating transcription factor showed little difference as a function of age. Experiments of mixing extracts from young and old cells provided evidence of a dominant inhibitor of the HSE-binding activity in old cells. Probing of protein blots with 32P-HSE showed that the subunit molecular weight of the HSE-binding protein was 83,000 in both young and old cells. The pattern of regulation of this HSE-binding protein upon heat shock and cell aging as well as the identity, in DNA sequence specificity and subunit molecular weight, of this protein with that of the human heat shock gene transcription factor suggest that the HSE-binding protein is involved in the transcriptional activation of hsp genes in IMR-90 cells. We concluded that there was an age-associated decrease in the heat shock gene transcription factor DNA-binding activity and that this could account for the attenuated heat shock gene expression in aging diploid cells.

Base Sequence↗
PubMed1990

Hsp56: a novel heat shock protein associated with untransformed steroid receptor complexes.

The recently-described p59 protein has been shown to be associated with untransformed steroid receptors present in rabbit uterus and rat liver cytosols (Tai, P. K., Maeda, Y., Nakao, K., Wakim, N. G., Duhring, J. L., and Faber, L. E. (1986) Biochemistry 25, 5269-5275; Renoir, J.-M., Radanyi, C., Faber, L. E., and Baulieu, E.-E. (1990) J. Biol. Chem. 265, 10740-10745), while a smaller version of this protein (p56) interacts with glucocorticoid receptors in human IM-9 cell cytosols (Sanchez, E. R., Faber, L. E., Henzel, W. J., and Pratt, W. B. (1990) Biochemistry 29, 5145-5152). In addition to interacting with glucocorticoid receptors, the p56 protein of IM-9 cell cytosol is also found as part of a large heteromeric complex that contains both the 70-kDa and 90-kDa heat shock proteins (hsp70 and hsp90, respectively). Given this association of p56 with the two major stress proteins, I have speculated that p56 may itself be a heat shock protein. In this paper, the effect of heat stress on the rate of synthesis of p56 is determined. Intact IM-9 cells were exposed to 37 or 43 degrees C for 4 h, followed by pulse-labeling with [35S]methionine. Analysis of whole cytosolic extracts by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography reveal an increased rate of radiolabeling for hsp70, hsp90, hsp100, ad hsp110, but no heat-inducible protein of smaller relative molecular mass is detected. However, immune-purification of p56 from normal and heat-stressed cytosols with the EC1 monoclonal antibody results in the presence of a 56-kDa protein that exhibits an increased rate of synthesis in response to heat stress. The results of two-dimensional gel Western blots employing the EC1 antibody demonstrate that this heat-inducible protein is indeed the EC1-reactive p56 protein and that the induction effect is not due to unequal yields of p56 during immune-purification. Heat stress has no effect on the composition of the p56.hsp.70.hsp90 complex, except that the complex derived from heat shocked-cells contains both the constitutive and heat-inducible forms of hsp70. Induction of p56 also occurs in IM-9 cells subjected to chemical stress (sodium arsenite). It is proposed that p56 is a steroid receptor-associated heat shock protein which can now be termed hsp56. Like hsp90, hsp56 likely serves in some vital cellular role apart from any specific function it provides in steroid receptor action.

Autoradiography↗
PubMed1987

Protection of Chinese hamster ovary cells from heat killing by treatment with cycloheximide or puromycin: involvement of HSPs?

Cycloheximide (CHM) or puromycin (PUR) added for 2 h before heating at 43 degrees C followed by either PUR or CHM during heat greatly protected cells from heat killing. This protection increased with inhibition of protein synthesis. Since treatment with a drug both before and during heating was required for heat protection, and since one drug could be exchanged for the other after the 2-h pretreatment without affecting the heat protection, a common mode of action involving inhibition of protein synthesis is suggested for the two drugs. Drug treatment reduced the synthesis of heat-shock proteins (HSPs) as studied by one-dimensional gel electrophoresis by 80-98% relative to 37 degrees C untreated controls. Synthesis of large molecules (greater than 30 kDa) was preferentially inhibited by PUR but not by CHM. Also for CHM, but not for PUR treatment, a 42 kDa band appeared along with a great reduction in the 43 kDa actin band during CHM treatment at both 37 and 43 degrees C. Furthermore, during CHM or PUR treatment, incorporation of [35S]methionine into HSP families 70, 87, or 110 was not increased relative to incorporation into total protein. However, synthesis of the 70 kDa HSP family was selectively suppressed when cells were incubated at 37 degrees C after CHM treatment, but when cells were incubated at 37 degrees C after treatment at 43 degrees C with CHM, synthesis of the 70 kDa HSP family resumed. When cells were labeled for 3 days, there was no preferential accumulation or turnover of HSP families during heating with or without CHM. Therefore, heat protection caused by treatment with CHM or PUR apparently involves a common mode of action not associated with changes in either total levels or synthesis of HSP families during drug treatment before and during heating. The significance of the changes observed in the synthesis of the HSP 70 family after heat is unknown. As thermotolerance developed during 5 h at 42 degrees C without drugs, synthesis of HSP families 70, 87, and 110, as studied with one-dimensional gels, increased 1.4-fold relative to synthesis of total protein, but compared to HSP families in cells labeled for 5 h at 37 degrees C incorporation was reduced by 40%. The increase of unique HSPs, if studied with two-dimensional gels, would probably be much greater.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Biological↗
PubMed1985

Partitioning of heat losses and gains in premature newborn infants under radiant warmers.

The partition of heat loss into convective and evaporative components, and heat gain into metabolic rate of production and radiant heat needed to maintain thermal equilibrium was determined in ten premature neonates (weight 1.39 +/- .08 [SEM] kg, gestation 31 +/- 1 weeks) who were nursed naked and supine on open radiant warmer beds. Warmer beds were servocontrolled to maintain each infant's abdominal skin temperature at three different levels: 35.5, 36.5, and 37.5 degrees C. The quantity of radiant heat delivered by the warmer in vivo was measured directly and compared with the heat need calculated from the partition. Convective heat loss comprised the major component of net heat loss and increased significantly with servocontrol temperature from 2.86 +/- .24 to 3.27 +/- .23 kcal/kg/h (P less than .01), and to 3.72 +/- .26 kcal/kg/h (P less than .001). Evaporative heat loss increased with servocontrol temperature from .96 +/- .13 to 1.41 +/- .33 kcal/kg/h, and to 1.35 +/- .32 kcal/kg/h, but this increase was not significant. Metabolic rate decreased from 2.08 +/- .17 to 1.90 +/- .14 kcal/kg/h, and to 1.78 +/- .16 kcal/kg/h with increased servocontrol temperature, but this decrease was not significant. Radiant heat needed to maintain infants at higher temperatures increased from 1.73 to 2.80 kcal/kg/h, and to 3.32 kcal/kg/h. The radiant heat delivered by the warmer to infants was directly proportional to the heat need calculated from the partition (r = .68, P less than .001).

Apnea↗
PubMed1985

Mechanism of inhibition of polypeptide chain initiation in heat-shocked Ehrlich cells involves reduction of eukaryotic initiation factor 4F activity.

Almost all living organisms studied respond to elevated temperature with a marked inhibition of overall protein synthesis but increased synthesis of a specific set of proteins, the so-called heat-shock proteins. We have prepared a cell-free protein synthesizing system (lysate) from heat-shocked Ehrlich ascites tumor cells that reflects the inhibition of protein synthesis in intact cells at elevated temperatures. We have isolated and partially purified a stimulator of the heat-shocked cell lysate from Ehrlich cells. Through four purification steps, the stimulator is chromatographically identical to eukaryotic initiation factor 4F (eIF-4F), an initiation factor which specifically binds mRNA cap structure. Therefore, we have tested the effects of highly purified reticulocyte eIF-4F on the heat-shocked cell lysate. Protein synthesis is strongly stimulated by addition of highly purified eIF-4F. Synthesis in the heat-shocked lysate is more inhibited at high (70 mM) KCl concentrations, than at lower concentrations, and stimulation by eIF-4F is correspondingly greater at higher KCl concentrations, so that the rate of protein synthesis is returned to control (non-heat-shocked lysate) levels at all KCl concentrations. Furthermore, at 70 mM KCl, in heat-shocked lysates, synthesis of the 68-kDa heat-shock protein is much less inhibited than synthesis of the bulk of non-heat-shock proteins, and eIF-4F stimulates synthesis of 68-kDa protein to a much lesser extent than non-heat-shock proteins. Thus, addition of purified eIF-4F reverses the effects of elevated temperatures on Ehrlich cells that are reflected in lysates. Therefore, we propose that the inhibition of translation in heat-shocked Ehrlich cells is the result of inactivation of eIF-4F function.

Acetates↗
PubMed1994

Impaired wound healing in Cushing's syndrome: the role of heat shock proteins.

BACKGROUND: Glucocorticoids impair wound healing and cause surgical morbidity. Heat shock proteins are essential to cellular stress tolerance and are associated with glucocorticoids. The adrenal heat shock protein response is under hypothalmic-pituitary-adrenal-axis control, whereas the vascular response is associated with alpha-1 receptors. Because heat shock proteins affect cellular stress responses and are under hypothalmic-pituitary-adrenal-axis control in other tissues, we postulated an association between heat shock proteins and glucocorticoids in healing wounds. METHODS: Modified Hunt-Schilling wound chambers were implanted subcutaneously in rats. They received subcutaneous time-release dexamethasone (25 mg) or placebo pellets. Wound chamber heat shock protein 25 and heat shock protein 72/73 were serially assayed for 21 days with western analysis and immunocytochemistry. RESULTS: Dexamethasone caused Cushing's syndrome with approximately 10% weekly weight-loss and adrenal atrophy. Total wound tissue decreased 90% with profound differences in molecular wound responses manifested by decreased heat shock protein 25, 72, and 73 in animals treated with dexamethasone despite equal protein loads. Furthermore, dexamethasone caused heat shock protein 72 redistribution by immunocytochemistry. CONCLUSIONS: This study represents the first description of heat shock proteins in a wound healing model and demonstrates tissue-specific decrease of heat shock proteins with glucocorticoid therapy. Thus the heat shock protein response is intimately associated with normal wound healing and is profoundly altered in subjects with Cushing's syndrome. Manipulation of this response may have clinical importance in wound healing.

Adrenal Glands↗
PubMed1994

Induction of the heat shock response reduces mortality rate and organ damage in a sepsis-induced acute lung injury model.

OBJECTIVE: To test the hypothesis that induction of heat shock proteins before the onset of sepsis could prevent or reduce organ injury and death in a rat model of intra-abdominal sepsis and sepsis-induced acute lung injury produced by cecal ligation and perforation. DESIGN: Prospective, blind, randomized, controlled trial. SETTING: University research laboratory. SUBJECTS: One-hundred forty-two adult Sprague-Dawley rats (weight range 200 to 300 g). INTERVENTIONS: Production of intra-abdominal sepsis and exposure to heat stress. Animals were randomly divided into four groups: heated and septic, heated and sham-septic, unheated and septic, and unheated and sham-septic. MEASUREMENTS AND MAIN RESULTS: We evaluated the mortality rate and pathologic changes in lung, heart, and liver at 18 hrs after cecal perforation, at 24 hrs after removal of the cecum, and at 7 days after perforation. Heated animals exhibited a maximum increase in heat shock protein of 72 kilodalton molecular weight protein concentrations in the lungs and heart 6 to 24 hrs after the hyperthermic stress. By 18 hrs after perforation, 25% of the septic, unheated animals had died whereas none of the septic heated animals had died (p < .005). Septic, heated animals showed a marked decrease in 7-day mortality rate (21%) compared with septic unheated animals (69%) (p < .01). Furthermore, septic heated animals showed less histologic evidence of lung and liver damage than septic unheated animals. CONCLUSIONS: These data suggest that thermal pretreatment, associated with the synthesis of heat shock proteins, reduces organ damage and enhances animal survival in experimental sepsis-induced acute lung injury. Although the mechanisms by which heat shock proteins exert a protective effect are not well understood, these data raise interesting questions regarding the importance of fever in the protection of the whole organism during bacterial infection.

Animals↗
PubMed1998

Forensic pathology of heat-and cold-related injuries.

The human body must maintain a relatively constant temperature to function. The thermoregulatory system plus human behavior control the balance of heat loss and heat gain. Heat is produced at a relatively constant rate by the body's basal metabolism. Heat production can be increased by increasing skeletal muscular activity. Heat is lost from the body to the environment by conduction, convection, radiation, and evaporation. Illness due to heat stress develops when the body gains more heat than it loses. Illness due to cold stress develops when the body loses more heat than it can produce or gain from external sources. During periods of extreme heat, mortality may rise sharply, sometimes to epidemic proportions. Because nearly all heat-related deaths are preventable, early detection of these deaths will allow appropriate preventive measures to be implemented. The autopsy findings in both heat-related and cold-related deaths are nonspecific. Information about environmental conditions, scene investigation, and the available medical history are very important in formulating the diagnosis.

Body Temperature Regulation↗
PubMed1995

Both ambient temperature and the DnaK chaperone machine modulate the heat shock response in Escherichia coli by regulating the switch between sigma 70 and sigma 32 factors assembled with RNA polymerase.

In Escherichia coli individual sigma factors direct RNA polymerase (RNAP) to specific promoters. Upon heat shock induction there is a transient increase in the rate of transcription of approximately 20 heat shock genes, whose promoters are recognized by the RNAP-sigma 32 rather than the RNAP-sigma 70 holoenzyme. At least three heat shock proteins, DnaK, DnaJ and GrpE, are involved in negative modulation of the sigma 32-dependent heat shock response. Here we show, using purified enzymes, that upon heat treatment of RNAP holoenzyme the sigma 70 factor is preferentially inactivated, whereas the resulting heat-treated RNAP core is still able to initiate transcription once supplemented with sigma 32 (or fresh sigma 70). Heat-aggregated sigma 70 becomes a target for the joint action of DnaK, DnaJ and GrpE proteins, which reactivate it in an ATP-dependent reaction. The RNAP-sigma 32 holoenzyme is relatively stable at temperatures at which the RNAP-sigma 70 holoenzyme is inactivated. Furthermore, we show that formation of the RNAP-sigma 32 holoenzyme is favored over that of RNAP-sigma 70 at elevated temperatures. We propose a model of negative autoregulation of the heat shock response in which cooperative action of DnaK, DnaJ and GrpE heat shock proteins switches transcription back to constitutively expressed genes through the simultaneous reactivation of heat-aggregated sigma 70, as well as sequestration of sigma 32 away from RNAP.

DNA-Directed RNA Polymerases↗
PubMed1997

Distinct stress-inducible and developmentally regulated heat shock transcription factors in Xenopus oocytes.

The presence of a maternal pool of heat shock factor (HSF) in Xenopus oocytes has been suggested by two lines of evidence from previous studies. First, heat shock response element (HSE)-binding activity is induced in heat-shocked eggs and embryos prior to expression of zygotic HSF. Second, expression from microinjected heat shock protein promoters in oocytes is induced upon heat shock. To date, however, endogenous oocyte HSF molecules have not been detected, nor has induction of HSE-binding activity been directly demonstrated. Here we report the detection of distinct stress-inducible and developmentally regulated HSE-binding activities of endogenous oocyte factors. Exposure of defolliculated oocytes to heat, cadmium, and arsenite resulted in the formation of an HSE-specific complex detectable by gel mobility shift assay. Induction of HSE-binding activity by each of these stressors corresponded to increased expression from a microinjected hsp70 promoter. The stress-inducible HSE-binding complex was recognized by antiserum against mammalian HSF1, but not by HSF2 antiserum, suggesting that a Xenopus homologue of HSF1 is the major component of this activity. The HSE-binding activity of HSF1 was induced by stress treatments of stage I through VI oocytes, an indication that it is responsive to stress throughout oogenesis. During recovery from heat shock, the HSF1-HSE complex rapidly declined to control levels, but was induced for prolonged periods in oocytes exposed to continuous stress, a pattern unlike the transient activation previously observed in fertilized eggs or embryos. The kinetics of HSF1 activation in oocytes suggests that a key protein(s) regulating attenuation of the stress response is present at exceedingly low levels or is somehow modified during preembryonic development. We also detected an unusual constitutive HSE-binding complex in unstressed stage I and II oocytes, but not in later stage oocytes, eggs, developing embryos, or A6 cells. This constitutive complex was unaffected by heat or chemical treatments and was not recognized by either HSF1 or HSF2 antiserum. Appearance of the constitutive HSE-binding activity during oogenesis corresponded closely with peak levels of hsp70 mRNA detected by Northern blot analysis of RNA from staged oocytes. We suggest that the constitutive HSE-binding activity in early oocytes is formed by a unique developmentally regulated heat shock factor that may play a role in the expression of heat shock proteins during early stages of oogenesis.

Animals↗
PubMed2001

Effects of heat pretreatment on histopathology, cytokine production, and surfactant in endotoxin-induced acute lung injury.

To determine the effect of heat stress on histopathology of acute lung injury (ALI) caused by administration of lipopolysaccharide (LPS), and to determine the roles of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, interferon (IFN)-gamma, IL-10 and surfactants in heat-induced tolerance to ALI, we administered either saline or LPS (3 mg/kg of body weight) intravenously to male Sprague-Dawley rats without and with heat pretreatment. Five hours after LPS or saline treatment (23 h after heat-pretreatment), samples were obtained. We found that the histopathologic features of LPS-induced ALI were attenuated by heat-pretreatment. Heat-pretreatment did not decrease the elevated plasma or BAL fluid levels of TNF-alpha, IL-1beta, and IFN-gamma by LPS. The plasma level of IL-10 in LPS-treated rats with heat-pretreatment, however, was increased compared to that of LPS-treated rats without heat-pretreatment (P = 0.001). There were no differences in the BAL fluid concentrations of light or heavy density pulmonary surfactant phospholipids depending on heat-pretreatment in LPS-treated rats. These observations suggest that IL-10 might play a role in decreasing LPS-induced acute lung injury after heat-pretreatment.

Acute Disease↗
PubMed1998

Treatment of suspected heat illness.

1. Despite advances in the art and science of fluid balance, exertional heat illness -- even life-threatening heat stroke -- remains a threat for some athletes today. 2. Risk factors for heat illness include: being unacclimatized, unfit, or hypohydrated; certain illnesses or drugs; not drinking in long events; and a fast finishing pace. 3. Heat cramps typically occur in conditioned athletes who compete for hours in the sun. They can be prevented by increasing dietary salt and staying hydrated. 4. Early diagnosis of heat exhaustion can be vital. Early warning signs include: flushed face, hyperventilation, headache, dizziness, nausea, tingling arms, piloerection, chilliness, incoordination, and confusion. 5. Pitfalls in the diagnosis of heat illness include: confusion preventing self-diagnosis; the lack of trained spotters; rectal temperature not taken promptly; the problem of "seek not, find not;" and the mimicry of heat illness. 6. Heat stroke is a medical emergency. Mainstays of therapy include: emergency on-site cooling; intravenous fluids; treating hypoglycemia as needed; intravenous diazepam for seizures or severe cramping or shivering; and hospitalizing if response is slow or atypical. 7. The best treatment is prevention. Tips to avoiding heat illness include: rely not on thirst; drink on schedule; favor sports drinks; monitor weight; watch urine; shun caffeine and alcohol; key on meals for fluids and salt; stay cool when you can; and know the early warning signs of heat illness.

Acclimatization↗
PubMed2004

Reduction of skeletal muscle injury in composite tissue allotransplantation by heat stress preconditioning.

Ischemia-reperfusion injury is a dominant factor limiting tissue survival in any microsurgical tissue transplantation, a fact that also applies to allogeneic hand transplantation. The clinical experience of the 12 human hand transplantations indicates that shorter ischemia times result in reduced tissue damage and, ultimately, in better hand function. Heat stress preconditioning and the accompanying up-regulation of the heat shock protein 72 have been shown to reduce the ischemia-reperfusion injury following ischemia of various organs, including organ transplantation. The aim of this study was to reduce the ischemia-reperfusion injury in a model of composite tissue allotransplantation. Allogeneic hind limb transplantations were performed from Lewis (donor) to Brown-Norway rats. Donor rats in group A (n = 10) received a prior heat shock whereas rats in group B (n = 10) did not receive any prior heat shock. Group C served as a control group without transplantation. The transplantations were performed 24 hours after the heat shock, at which time the heat shock protein 72 was shown to be up-regulated. The outcome was evaluated 24 hours after transplantation by nitroblue tetrazolium staining and wet-to-dry weight ratio of muscle slices (anterior tibial muscle). The nitroblue tetrazolium staining showed a significant reduction of necrotic muscle in group A (prior heat shock) (p = 0.005). The wet-to-dry ratio was significantly reduced in group A (prior heat shock), indicating less muscle edema and less tissue damage (p = 0.05). Heat shock preconditioning 24 hours before an ischemic event leads to an up-regulation of heat shock protein 72 in muscle and to a tissue protection reducing ischemia-reperfusion injury in composite tissue transplantation.

Animals↗
PubMed2005

Hypoxia abolishes transience of the heat-shock response in the methylotrophic yeast Hansenula polymorpha.

The heat-shock response is conserved amongst practically all organisms. Almost invariably, the massive heat-shock protein (Hsp) synthesis that it induces is subsequently down-regulated, making this a transient, not a sustained, stress response. This study investigated whether the heat-shock response displays any unusual features in the methylotrophic yeast Hansenula polymorpha, since this organism exhibits the highest growth temperature (49-50 degrees C) identified to date for any yeast and grows at 47 degrees C without either thermal death or detriment to final biomass yield. Maximal levels of Hsp induction were observed with a temperature upshift of H. polymorpha from 30 degrees C to 47-49 degrees C. This heat shock induces a prolonged growth arrest, heat-shock protein synthesis being down-regulated long before growth resumes at such high temperatures. A 30 degrees C to 49 degrees C heat shock also induced thermotolerance, although H. polymorpha cells in balanced growth at 49 degrees C were intrinsically thermotolerant. Unexpectedly, the normal transience of the H. polymorpha heat-shock response was suppressed completely by imposing the additional stress of hypoxia at the time of the 30 degrees C to 49 degrees C temperature upshift. Hypoxia abolishing the transience of the heat-shock response appears to operate at the level of Hsp gene transcription, since the heat-induced Hsp70 mRNA was transiently induced in a heat-shocked normoxic culture but displayed sustained induction in a culture deprived of oxygen at the time of temperature upshift.

Cell Cycle↗
PubMed1996

Amplification and altered expression of the hsc70/U14 snoRNA gene in a heat resistant Chinese hamster cell line.

We have recently demonstrated that the heat resistant phenotype of the HR-1 variant isolated from HA-1 Chinese hamster fibroblasts after a series of heat shocks is associated with the increased expression of Hsc70, the constitutive form of Hsp70 (Laszlo and Li 1985). Here, we report the cloning and characterization of the Chinese hamster hsc70 gene and its organization and expression in wild type HA-1 and permanently heat resistant HR-1 cells. DNA sequencing revealed that the structure and nucleotide sequence of the hamster hsc70 gene is highly homologous to the human and rat genes coding for Hsc70. Three of the eight introns of the hamster hsc70 gene encode U14 small nucleolar RNAs, as has been demonstrated in other species. Although putative transcriptional elements, including a TATA box, two inverted CAT boxes, and two sets of heat shock elements (HSEs) are completely conserved in the human and hamster hsc70 genes, the regulation of expression of the hamster hsc70 gene is different from that reported for its human counterpart in that the mRNA coding for Hsc70 increases at least 10-fold after a mild heat shock in Chinese hamster cells while no induction of Hsc70 by heat shock has been reported in human cell lines. In situ hybridization revealed a complex chromosomal rearrangement in HR-1 cells which results in the 4- to 5-fold amplification of the hsc70 gene as indicated by genomic Southern blots. In association with this amplification of the hsc70 gene, the levels of Hsc70 mRNA and U14 snoRNA are increased in the HR-1 cells under both normal growing conditions and after heat shock. Thus, the elevated expression of both Hsc70 and U14 snoRNA might play a role in the heat resistant phenotype of the HR-1 cells. This is the first report of the amplification of a heat shock gene and the possible induction of gene amplification by heat shock.

Amino Acid Sequence↗
PubMed2001

Heat shock factor 1-mediated thermotolerance prevents cell death and results in G2/M cell cycle arrest.

Mammalian cells respond to environmental stress by activating heat shock transcription factors (eg, Hsf1) that regulate increased synthesis of heat shock proteins (Hsps). Hsps prevent the disruption of normal cellular mitosis, meiosis, or differentiation by environmental stressors. To further characterize this stress response, transformed wild-type Hsf1+/+ and mutant Hsf1-/- mouse embryonic fibroblasts (MEFs) were exposed to (1) lethal heat (45 degrees C, 60 minutes), (2) conditioning heat (43 degrees C, 30 minutes), or (3) conditioning followed by lethal heat. Western blot analysis demonstrated that only Hsf1+/+ MEFs expressed inducible Hsp70s and Hsp25 following conditioning or conditioning and lethal heat. Exposure of either Hsf1+/+ or Hsf1-/- MEFs to lethal heat resulted in cell death. However, if conditioning heat was applied 6 hours before lethal heat, more than 85% of Hsf1+/+ MEFs survived, and cells in G2/M transiently increased 3-fold. In contrast, conditioned Hsf1-/- MEFs neither survived lethal heat nor exhibited this G2/M accumulation. Coinfection with adenoviral Hsp70 and Hsp25 constructs did not fully recreate thermotolerance in either Hsf1+/+ or Hsf1-/- MEFs, indicating other Hsf1-mediated gene expression is required for complete thermotolerance. These results demonstrate the necessity of Hsf1-mediated gene expression for thermotolerance and the involvement of cell cycle regulation, particularly the G2/M transition, in this thermotolerant response.

Animals↗