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PubMed2003

Role of BRCA1 in heat shock response.

The heat shock response is an evolutionarily conserved response to heat and other stresses that promotes the maintenance of key metabolic functions and cell survival. We report that exposure of human prostate (DU-145) and breast (MCF-7) cancer cells to heat (42 degrees C) caused a rapid disappearance of the breast cancer susceptibility gene-1 (BRCA1) protein, starting at approximately 1 h after the onset of heating and slightly lagging behind the increase in heat shock protein 70 (HSP70) levels. The heat-induced loss of BRCA1 occurred at the protein level, since: (1) BRCA1 mRNA expression was unaffected; and (2) the BRCA1 protein loss was also observed in DU-145 cells that expressed exogenous wild-type BRCA1 (wtBRCA1). In addition to heat regulation of BRCA1 protein levels, we also found that BRCA1 could modulate the heat shock response. Thus, wtBRCA1 overexpressing DU-145 cell clones showed significantly decreased sensitivity to heat-induced cytotoxicity; and Brca1 mutant mouse embryo fibroblasts showed increased sensitivity to heat. The DU-145 wtBRCA1 clones also showed increased expression of the small heat shock protein HSP27; and reporter assays revealed that wtBRCA1 stimulated a two to four-fold increase in HSP27 promoter activity, consistent with its ability to upregulate HSP27 mRNA and protein levels. In studies using epitope-tagged truncated BRCA1 proteins, the ability to stimulate the HSP27 promoter and to mediate heat-induced degradation required the amino-terminus but not the carboxyl-terminus of BRCA1. Although the heat-induced loss of BRCA1 appeared to be due to protein degradation, various protein metabolic agents (or combinations) failed to block this event, including: MG132 (a 26S proteasomal inhibitor), N-acetyl-leucyl-leucyl-norleucinal (a calpain inhibitor), z-VAD-fmk (a pan-caspase inhibitor), and ammonium chloride and chloroquine (which stabilize lysosomes). These findings suggest that in addition to its other functions, BRCA1 may participate in mammalian heat shock response pathways.

BRCA1 Protein↗
PubMed1997

Intracellular distribution of stress glycoproteins in a heat-resistant cell model expressing human HSP70.

Heat stress results in the cellular accumulation of heat-shock proteins (HSP) and increased protein glycosylation. Among known stress glycoproteins, GP50 and GP62 are associated with the expression of thermotolerance. In the present study, we characterized subcellular localization and redistribution of GP62 and GP50 in a rodent cell line, M21, before and after cellular heat-stress. M21 cells are heat-resistant cells that overexpress human HSP70 and also have concomitantly high GP62 levels. Cellular fractionation by differential centrifugation showed that GP62 and GP50 was present in each subcellular fraction. However, each stress glycoprotein exhibited a characteristic kinetic pattern of redistribution during cellular recovery after heat stress. For example, glycosylated GP62 was seen predominantly in the mitochondria before heat-stress. Immediately after heat-stress, its presence in the mitochondrial fraction was dramatically reduced, while it increased in lysosomes, microsomes and cytosol. By 1 h after heat stress, it had largely disappeared from microsomal and cytosolic fractions. After 24 h, all subcellular fractions showed only trace amounts of residual GP62. By comparison, GP50 was also highest in the mitochondrial fraction before heat-stress, redistributed like GP62 immediately after heat stress, but remained relatively unchanged thereafter. In contrast to GP62, GP50 showed little redistribution during 24 h after heat-stress and remained at high concentrations in all cell fractions, including microsomes. Distribution of GP50 and GP62 before and after heat stress, based on differential centrifugation, was consistent with immunolocalization data. Following heat stress, both GP50 and GP62 showed a partial overlap in distribution with HSP70. The above results indicate that each stress glycoprotein has a specific subcellular location, both before and after heat stress. The presence of GP62 in virtually all cell fractions is consistent with a multifunctional role for GP62 in the cellular stress response.

Cell Line↗
PubMed1998

Biphasic effect of heat stress pretreatment on ischemic tolerance of isolated rat hearts.

Improvement of post-ischemic cardiac function 24 h after heat stress has been attributed to the increased cardiac tissue content of the inducible heat stress protein hsp70. Previous studies indicated that hsp70 is already significantly upregulated a few hours after heat stress. To delineate the relationship between hsp70 tissue content and heat stress-induced cardioprotection in the early time frame after heat stress, if any, post-ischemic functional recovery of isolated, ejecting rat hearts and the actual cardiac hsp70 content were investigated 0.5, 3, 6 and 24 h after heat stress (42 degrees C for 15 min). Recovery (% of pre-ischemic value) of cardiac output, left ventricular developed pressure, and positive and negative left ventricular dP/dtmax was studied during reperfusion after 45 min of global ischemia. Anesthetized non heat-stressed rats served as controls. The recovery of all hemodynamic variables was significantly worse in hearts isolated 30 min after heat stress than in control hearts. When the time interval between heat treatment and the ischemic episode was prolonged, a gradual improvement of post-ischemic functional recovery was observed. Only 24 h after heat treatment functional recovery was significantly better in the heat-stressed than in the control group. Compared to control hearts (0.27+/-0.10 mg/g total protein) cardiac hsp70 content was already significantly increased 0.5 h after heat stress (0.51+/-0.03 mg/g total protein). The cardiac hsp70 content further increased to 0. 70+/-0.11, 0.89+/-0.35 and 1.01+/-0.25 mg/g total protein, at 3, 6 and 24 h after heat stress, respectively. The present findings clearly show that heat stress is associated with a fast rise in the myocardial hsp70 content which, however, is not uniquely correlated with improved ischemia tolerance of the treated hearts, which only occurs 24 h later.

Animals↗
PubMed2006

Mechanism and function of heat shock-dependent IkappaBalpha expression.

OBJECTIVE: Heat shock is known to inhibit activation of the NF-kappa B pathway. One potential mechanism of this effect is de novo expression of the intracellular NF-kappaB inhibitor, Ikappa Balpha. Herein we sought to elucidate the mechanisms by which heat shock induces Ikappa Balpha gene expression and the functional consequences of heat shock-mediated Ikappa Balpha gene expression in A549 cells. METHODS: Nuclear run-on assays demonstrated that heat shock had a small effect on transcription of the Ikappa Balpha gene relative to the level of steady state Ikappa Balpha mRNA that is seen following heat shock. Accordingly, we determined the effect of heat shock on Ikappa Balpha mRNA stability by treating cells with actinomycin D to induce transcriptional arrest. RESULTS: The half-life of IkappaBalpha mRNA was 36 +/- 7.2 min in control cells and 101 +/- 3.7 min in cells subjected to heat shock. These data were consistent with heat shock-mediated increased stability of Ikappa Balpha mRNA. Heat shock induced activation of p38 MAP kinase and inhibition of p38 MAP kinase substantially reduced heat shock-dependent expression of Ikappa Balpha mRNA. After a 4 h recovery period from heat shock, there was inhibition of tumor necrosis factor-alpha-mediated NF-kappaB activation. The introduction of an Ikappa Balpha anti-sense oligonucleotide reversed this inhibitory effect of heat shock. CONCLUSIONS: We conclude that heat shock increases IkappaBalpha gene expression primarily by increasing Ikappa Balpha mRNA stability and this effect is partially dependent on p38 MAP kinase. The functional consequence of heat shock-mediated Ikappa Balpha gene expression is inhibition of NF-kappaB activation.

Cell Line↗
PubMed2002

Temporal and mechanistic effects of heat shock on LPS-mediated degradation of IkappaBalpha in macrophages.

Previous studies demonstrated important interactions between the heat shock response and the IkappaBalpha/NF-kappaB pathway when these two pathways are induced sequentially. One such interaction involves the ability of heat shock to inhibit subsequent degradation of IkappaBalpha in response to a proinflammatory signal. Herein we investigated the temporal relationship between recovery from heat shock and inhibition of IkappaBalpha degradation, and the proximal mechanisms by which heat shock inhibits degradation of IkappaBalpha in macrophages. In RAW 264.7 murine macrophages, prior heat shock inhibited LPS-mediated IkappaBalpha degradation up to 4 h after recovery from heat shock, and this effect correlated with inhibition of LPS-mediated activation of NF-kappaB. Beyond these recovery periods, heat shock did not inhibit IkappaBalpha degradation. IkappaB kinase (IKK) assays demonstrated that heat shock inhibited LPS-mediated activation of IKK up to 1 h after recovery from heat shock. Heat shock also increased intracellular phosphatase activity, and inhibition of intracellular phosphatase activity partially reversed the ability of heat shock to inhibit both LPS-mediated degradation of IkappaBalpha and LPS-mediated activation of IKK. These data demonstrate that the ability of heat shock to inhibit degradation of IkappaBalpha is dependent on the recovery period between the heat shock stimulus and the proinflammatory stimulus. The mechanism by which heat shock inhibits degradation of IkappaBalpha involves dual modulation of IKK and intracellular phosphatase activity.

Animals↗
PubMed1989

Novel regulation of heat shock genes during carrot somatic embryo development.

We have determined that somatic embryos of carrot exhibit a number of interesting and unusual properties when exposed to heat shock at different times in their development. Specifically, we have seen that mid-globular embryos can be arrested irreversibly in their development when heat-shocked, whereas all other stages of embryogenesis, both before and after this stage, are fully capable of normal development after the stress. In investigating the molecular basis of this developmental sensitivity to heat shock, using a cloned heat shock gene encoding a small heat shock protein, we have determined that globular embryos both synthesize and accumulate significantly less heat shock mRNA when compared with embryos of any other stage or to callus suspension cells. In fact, there appears to be no transcriptional induction of heat shock gene expression in response to heat shock during this time period; the gene is expressed at the same relatively low level both before and after heat shock. However, in spite of the low level of heat shock mRNA available, globular embryos synthesize the full complement of heat shock proteins in response to heat treatment. The globular embryos appear to accomplish this by translating the existing heat shock mRNAs at an elevated rate, which compensates for the low level of available mRNA. Once the embryos have progressed beyond the globular stage of development, regulation at the transcriptional level resumes, and the embryos again exhibit normal development after heat shock.

Animals↗
PubMed1984

Synthesis, modification and structural binding of heat-shock proteins in tomato cell cultures.

Synthesis of about 30 acidic and 18 basic heat-shock proteins (hsps) is induced in suspension cultures of tomato (Lycopersicon peruvianum) if subjected to supraoptimal temperature conditions (35-40 degrees C). A characteristic aspect of the plant heat-shock response is the formation of cytoplasmic granular aggregates, heat-shock granules, containing distinct heat-shock proteins as major structural components and, in addition, several hitherto undetected minor acidic and basic heat-shock proteins. Structural binding of heat-shock proteins, i.e. assembly of heat-shock granules, is dependent on the persistance of supraoptimal temperature conditions. Despite the ongoing synthesis also at 25 degrees C, e.g. in pulse heat-shocked cultures, these proteins are accumulated exclusively in soluble form. Individual heat-shock proteins are characterized by their kinetics of synthesis and are classified by their compartmentation behaviour into class A proteins (exclusively found in soluble form, e.g. hsps 95 and 80), class B proteins (5-10% bound to heat-shock granules, e.g. hsps 70, 68), class C proteins (30-80% bound to heat-shock granules, e.g. hsps 21, 17, 15) and class D proteins, which are minor heat-shock proteins only detected in structure-bound form. Major representatives are modified proteins, i.e. hsps 95, 80, 70 and 68 are phosphorylated and hsps 80, 74, 70 and 17 are methylated proteins (numbers 70, 80 etc. refer to 10(-3) Mr). Under heat-shock conditions synthesis of the proteins detected in control cells (25 degrees C proteins) exhibits two patterns. There are proteins with continued and proteins with discontinued synthesis. Synthesis of most of the latter proteins is resumed very rapidly after shift-down to 25 degrees C, even in the presence of actinomycin D. We conclude that reversible segregation of distinct mRNA species from the translation apparatus contributes to the heat-shock-specific pattern of protein synthesis in plants also.

Autoradiography↗
PubMed2006

Cerebrovascular dysfunction is an attractive target for therapy in heat stroke.

1. The aim of the present review is to summarize clinical observations and results of animal models that advance the knowledge of the attenuation of cerebrovascular dysfunction in the setting of heat stroke. It is a narrative review of selected published literature from Medline over the period 1959-2005. 2. All heat-stressed rodents, even under general anaesthesia, have hyperthermia, systemic inflammation, hypercoagulable state, arterial hypotension and tissue ischaemia and injury in multiple organs. These findings demonstrate that rodent heat stroke models can nearly mirror the full spectrum of human heat stroke. Experimental heat stroke fulfills the empirical triad used for the diagnosis of classical human heat stroke, namely hyperthermia, central nervous system alterations and a history of heat stress. 3. These physiological dysfunctions and survival during heat stroke can be improved by whole-body or brain cooling therapy adopted immediately after the onset of heat stroke. 4. However, in the absence of body or brain cooling, these heat stroke reactions can still be reduced by the following measures: (i) fluid replacement with 3% NaCl solution, 10% human albumin or hydroxyethyl starch; (ii) intravenous delivery of anti-inflammatory drugs, free radical scavengers or interleukin-1 receptor antagonists; (iii) hyperbaric oxygen therapy; or (iv) transplantation of human umbilical cord blood cells. 5. In addition, before initiation of heat stress, prior manipulations with one of the following measures was found to be able to protect against heat stroke reactions: (i) systemic delivery of alpha-tocopherol, mannitol, inducible nitric oxide synthase inhibitors, mu-opioid receptor antagonists, endothelin ETA receptor antagonists, serotoninergic nerve depletors or receptor antagonists, or glutamate receptor antagonists; or (ii) heat shock protein 72 preconditioning. 6. There is compelling evidence that cerebrovascular dysfunction is an attractive target for therapy in heat stroke.

Animals↗
PubMed1993

Glucocorticoids modulate the synthesis and expression of a 72 kDa heat shock protein in cultured Graves' retroocular fibroblasts.

Glucocorticoids modulate numerous proliferative, metabolic and immunological functions in human fibroblasts, some of which appear to be mediated via glucocorticoid receptors. We studied the influence of glucocorticosteroids on the synthesis and expression of a 72 kDa heat shock protein that is thought to play a role in thyroid autoimmunity. Experiments were performed using orbital fibroblasts derived from patients with Graves' ophthalmopathy and normal individuals. Cell monolayers were exposed to various concentrations of dexamethasone, the specific glucocorticoid agonist RU 28362, the glucocorticoid antagonist RU 38486, or combinations thereof, prior to heat stress or exposure to hydrogen peroxide. Heat shock protein 72 expression was assessed using sodium dodecylsulfate polyacrylamide-gel electrophoresis of cellular extracts, followed by autoradiography or immunoblotting with a mouse monoclonal antibody against the 72 kDa heat shock protein and quantitative scanning densitometry. In addition, cellular distribution of the immunoreactivity for the 72 kDa heat shock protein was studied using indirect immunofluorescence on parallel cultures. In other experiments, aimed at studying heat shock protein synthesis, cell cultures were pulse-labeled with [35S]-methionine prior to harvesting. Treatment with dexamethasone or RU 28362 markedly attenuated the heat stress-enhanced synthesis and expression of the 72 kDa heat shock protein and several other heat shock proteins both in normal and in Graves' retroocular fibroblasts (p < 0.001). In addition, either treatment reduced baseline expression of the 72 kDa heat shock protein in Graves' retroocular fibroblasts (p < 0.01). These effects were dose-dependent and appeared to be mediated via the glucocorticoid receptor, because combined exposure to dexamethasone or RU 28362 plus RU 38486 completely restored synthesis and expression of the 72 kDa heat shock protein. Baseline or stress-enhanced expression of the 72 kDa heat shock protein was not altered by treatment of monolayers with RU 38486 alone. As demonstrated by immunofluorescence, the characteristic intracellular shifting of the 72 kDa heat shock protein in response to cellular stress was partially inhibited by glucocorticoid agonists and restored by simultaneous exposure to glucocorticoid agonists and RU 38486. These results demonstrate that dexamethasone and the specific glucocorticoid agonist RU 28362 can modulate baseline- and stress-induced synthesis and expression of the 72 kDa heat shock protein, as well as its subcellular distribution, in cultured retroocular fibroblasts. Our studies suggest that these compounds exert these effects via the glucocorticoid receptor.

Androstanols↗
PubMed1984

Experimental study on the pathogenesis of heat stroke.

A heat-balance study was carried out on conscious rabbits exposed to ambient temperatures (Ta) from 8 degrees to 40 degrees C. At Ta = 40 degrees C, heat gain exceeded heat loss and led to hyperthermia and heat stroke, and the latency for the onset of heat stroke was found to be around 87 minutes. At the onset of heat stroke, the comatose animals showed higher levels of rectal temperature, ear skin blood flow, respiratory evaporative heat loss, metabolic rate, intracranial pressure (ICP), and cerebral water content as compared to those of control animals (kept at an ambient temperature of 24 degrees C). Before the start of heat stress, the animals had an average mean arterial blood pressure (MABP) of 94 mm Hg and cerebral perfusion pressure (CPP) of 80 mm Hg. However, at the onset of heat stroke, the average MABP and CPP decreased to 67 and 19 mm Hg, respectively. The reduction in CPP at the onset of heat stroke was due to both a decrease in MABP and an increase in ICP. In addition, the comatose animals which received an intravenous infusion of 10% glycerol (3 ml/min) had a survival time (interval between onset of heat stroke and death) longer than that of the comatose animals which received the control-vehicle solution. The prolongation of survival time in the glycerol-treated animals may be due to lower rectal temperature, lower cerebral water content, or lower ICP during the development of heat stroke. The present data indicate that not only hyperthermia but also cerebral edema, intracranial hypertension, decreased MABP, and decreased CPP are the main causes of heat stroke. The therapeutic values of glycerol on heat stroke may be related to the depressant action on cerebral edema, intracranial hypertension, and body temperature.

Animals↗
PubMed2000

[In vitro induction of autologous T cell killing by heat treated human chronic myelogenous leukemia cells].

OBJECTIVE: To investigate the potential of autologous T cell killing of heat treated chronic myelogenous leukemia (CML) cells (autologous tumor killing, ATK). METHODS: (51)Cr release assay was used to measure the ATK activity of autologous T cells against CML cells treated with 42 degrees C for 30 minutes (heat) or 37 degrees C for 30 minutes (non-heat). The phenotypes of T cells and heat shock protein 70 (HSP70) expression of CML cells were measured by flow cytometry (FCM). T cells from the CML patients were stimulated and expanded by autologous mixed lymphocyte/tumor cell cultures (MLTC). RESULTS: ATK activity of autologous T cells to the non-heated and heated CML cells were found in 4 (19.05%) and 10 (47.62%) of the 21 cases, respectively. The ATK activity of interleukin-2 (IL-2) stimulated autologous T cells against heated CML cells was markedly higher than that of unstimulated autologous T cells against non-heated CML cells (P < 0.001). FCM analysis showed that no HSP70 was expressed on the CML cell membranes whether heated or non-heated, but intracellular HSP70 expressions were (83.42 +/- 5.65)% and (78.34 +/- 6.32)% pre- and post-heated, respectively. The phenotypes of T cells stimulated and expanded in MLTC were TCRgammadelta - CD(3)(+), mostly CD(8)(+), with some activation markers (CD(25) and HLA-DR) expression. The ATK activities of these T cells against the heated and non-heated CML cells and K562 cells were (51.25 +/- 4.26)%, (36.52 +/- 3.83)% and (2.92 +/- 1.19)%, respectively. CONCLUSIONS: ATK activity of autologous T cells against CML cells could be induced or enhanced by heat treatment of the CML cells particularly of T cells stimulated with IL-2. This ATK activity was not associated with gammadelta T cells or HSP70 expression of CML cells.

Adolescent↗
PubMed2002

[Tumor necrosis factor and nitric oxide in the protective heat stress model].

OBJECTIVE: To investigate the variation and the effect of TNF and NO in the process of the creation of protective heat stress model and provide more thoretical basis. METHODS: The rats were properly treated with heat and then the serum was separated. Radioimmunoassay and nitrate reductase assay were employed to measure the concentration of TNF and NO at different time between 0 h and 24 h after heat stress respectively. RESULTS: Compared with the control, the concentration of TNF increased significantly 2 h, 4 h, 8 h, 12 h after heat stress, of which 2 h, 12 h(P < 0.05), 4 h, 8 h(P < 0.01), but no significant changes 0 h, 24 h after heat stress. The concentration reached the peak 4 h after heat stress[(3.35 +/- 0.20) ng/ml] and increased significantly than 0 h, 2 h, 8 h, 12 h, 24 h after heat stress(P < 0.01, P < 0.05). 24 h after heat stress it recovered to normal standard. Compared with the control, the concentration of NO was higher 2 h, 4 h, 8 h, 12 h, 24 h after heat stress(P < 0.05), but no significance at 0 h. The concentration amounted to peak 8 h after heat stress[(108.21 +/- 27.89) mumol/L] and increased than 0 h, 2 h, 4 h after heat stress(P < 0.01). After 8 h it began to decrease continuously in heat stress group, however it was higher 24 h after heat stress than control. CONCLUSION: TNF and NO played an important role in the process of the creation of protective heat stress model.

Animals↗
PubMed1978

Index for the assessment of heat tolerance.

Heat tolerance was assessed by magnitude of strain induced in the body as a whole by heat load. The strain was represented by a combination of relative water loss, relative rise in rectal temperature and relative salt loss, using those critical values of the three factors which cause heat stroke (40.6 degrees C), water depletion heat exhaustion (7% of body weight) and salt depletion heat exhaustion (0.75 g per kg of body weight). As this numerical heat tolerance index is defined as the degree of disturbance induced by heat exposure concerning thermal regulation, water and electrolyte metabolism, the magnitude of the index is inversely proportional to that of heat tolerance. Our studies showed that adaptive changes in heat tolerance of unacclimatized subjects during short-term heat acclimatization could be followed up by this heat tolerance index and that superior heat tolerance of residents in subtropical zone and athletes could by reasonably evaluated by the index. Thus, it might be said that this numerical heat tolerance index is a reliable index for the assessment of heat tolerance.

Acclimatization↗
PubMed1999

Biochemical requirements for the expression of heat shock protein 72 kda in human breast cancer MCF-7 cells.

Heat shock alters the susceptibility of tumor cells to chemotherapeutic agents. Cultured breast cancer MCF-7 and MDA-MB-231 cells that express high levels of heat shock protein 70 and 27 kDa are resistant to treatment with certain anticancer drugs. These findings indicate that expression of HSPs can negatively regulate the effectiveness of cytotoxic drugs. We conducted experiments to study the regulation of expression of heat shock proteins (HSPs) in human breast cancer MCF-7 cells exposed to heat shock by intracellular free Ca2+ and protein kinase C. Cells exposed to 44 degrees C for 20 min displayed increased expression of HSP-72 and GRP-94, that reached a maximum 4-5 h later and returned to baseline levels within 24 h. Levels of HSP-72 mRNA in cells exposed to heat shock increased, suggesting that the heat-induced increase in HSP-72 occurs at the transcriptional level. The synthesis of HSP-72 but not GRP-94 was inhibited when cells were exposed to heat shock in medium devoid of Ca2+ and attenuated by more than 50% when cells were pretreated with the calcium chelator BAPTA for 30 min prior to heat shock. HSP-72 synthesis was enhanced when cells were treated with the protein kinase C inhibitor, GF-109203X. These data indicate that Ca2+ and PKC are involved in regulation of HSP-72 synthesis. However, removal of external Ca2+ and treatment with BAPTA, GF-109203X, or exposure to sublethal heat shock protected cells from subsequent thermal injury. The intracellular free calcium concentration ([Ca2+]i) in resting fura-2-loaded MCF-7 cells was 156 +/- 16 nM (n = 29). Heat shock increased [Ca2+]i in a time- and temperature-dependent manner. Exposure of cells to 44 degrees C for 20 min increased [Ca2+]i by 234 +/- 13%, which subsequently returned to baseline levels within 120 min. Removal of external Ca2+ eliminated the increase, indicating that the increase in [Ca2+]i was due to Ca2+ influx. Pretreatment of the cells with BAPTA or GF-109203X for 30 min or a sublethal heat shock to allow HSP-72 overexpression led to an attenuation of the increase in [Ca2+]i by a subsequent heat shock. The results suggest that HSP-72 but not GRP-94 is regulated by [Ca2+]i and PKC activity. The cytoprotection produced by chelation of Ca2+, GF-109203X, or HSP-72 overexpression is probably due to their ability to attenuate the [Ca2+]i response to heating.

Breast Neoplasms↗
PubMed1988

Thermotolerance induced by heat, sodium arsenite, or puromycin: its inhibition and differences between 43 degrees C and 45 degrees C.

When CHO cells were treated either for 10 min at 45-45.5 degrees C or for 1 hr with 100 microM sodium arsenite (ARS) or for 2 hr with 20 micrograms/ml puromycin (PUR-20), they became thermotolerant to a heat treatment at 45-45.5 degrees C administered 4-14 hr later, with thermotolerance ratios at 10(-3) isosurvival of 4-6, 2-3.2, and 1.7, respectively. These treatments caused an increase in synthesis of HSP families (70, 87, and 110 kDa) relative to total protein synthesis. However, for a given amount of thermotolerance, the ARS and PUR-20 treatments induced 4 times more synthesis than the heat treatment. This decreased effectiveness of the ARS treatment may occur because ARS has been reported to stimulate minimal redistribution of HSP-70 to the nucleus and nucleolus. Inhibiting protein synthesis with cycloheximide (CHM, 10 micrograms/ml) or PUR (100 micrograms/ml) after the initial treatments greatly inhibited thermotolerance to 45-45.5 degrees C in all cases. However, for a challenge at 43 degrees C, thermotolerance was inhibited only for the ARS and PUR-20 treatments. CHM did not suppress heat-induced thermotolerance to 43 degrees C, which was the same as heat protection observed when CHM was added before and during heating at 43 degrees C without the initial heat treatment. These differences between the initial treatments and between 43 and 45 degrees C may possibly be explained by reports that show that heat causes more redistribution of HSP-70 to the nucleus and nucleolus than ARS and that redistribution of HSP-70 can occur during heating at 42 degrees C with or without the presence of CHM. Heating cells at 43 degrees C for 5 hr after thermotolerance had developed induced additional thermotolerance, as measured with a challenge at 45 degrees C immediately after heating at 43 degrees C. Compared to the nonthermotolerant cells, thermotolerance ratios were 10 for the ARS treatment and 8.5 for the initial heat treatment. Adding CHM (10 micrograms/ml) or PUR (100 micrograms/ml) to inhibit protein synthesis during heating at 43 degrees C did not greatly reduce this additional thermotolerance. If, however, protein synthesis was inhibited between the initial heat treatment and heating at 43 degrees C, protein synthesis was required during 43 degrees C for the development of additional thermotolerance to 45 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Survival of Vibrio spp. including inoculated V. cholerae 0139 during heat-treatment of cockles (Anadara granosa).

The effect of heat-treatment on the internal temperature of raw cockles (Anadara granosa) and survival of their intrinsic flora of Vibrio spp. as well as of inoculated V. cholerae 0139 was examined. The cockles were purchased from markets in Malaysia and had an average weight including shells of 8.90+/-2.45 g. In one experiment heatpenetration of individual cockles was examined. Cockles weighing < 8 g (including shell) exhibited maximum internal temperatures of between 50 and 75 degrees C when heated in water at 99 degrees C for 10 s and 71-93 degrees C when heated for 30 s. Cockles weighing > 12 g exhibited maximum internal temperatures between 42 and 58 degrees C when heated in water at 99 degrees C for 10 s and 56-69 degrees C when heated for 30 s. In another experiment, heat-treatment of 10 cockles treated as a group at 99 degrees C for 10 or 30 s resulted in reduction of levels of intrinsic Vibrio spp. (enumerated directly on thiosulphate-citrate-bile salt sucrose agar; TCBS) from 5.73 to 3.15 log cfu g(-1) or below 1 log cfu g(-1), respectively. The levels of Vibrio spp. after heat-treatment decreased with an increase in numbers of cockles grouped together during treatment. In a third experiment V. cholerae 0139 was inoculated into cockles and subjected to heat-treatment at 99 degrees C for 0, 10, 15, 20, 25 or 30 s. The levels of Vibrio spp. in uninoculated, non-heat-treated cockles was 4.89 log cfu g(-1) on TCBS, and the predominant species were V. parahaemolyticus and V. alginolyticus. V. cholerae 0139 inoculated into cockles with an average weight of 13.5+/-1.90 g (including shell) decreased for samples examined immediately after heat-treatment from 6 log cfu g(-1) initially to 3.5 log cfu g(-1) after 25 s and < 1 log cfu g(-1) (TCBS) after 30 s of heat-treatment. The most probable number method by enrichment in alkaline peptone water gave in general within 1 log unit higher counts than TCBS direct enumeration. TCBS direct enumeration and MPN counts were up to 2.38 or 1.30 log units higher, respectively, for samples heat-treated for 20 s or longer and stored for 6 h at 30 degrees C before examination, than for samples heat-treated for same periods of time and examined immediately. This study shows that a mild heat-treatment of cockles for up to 25 s is inadequate to ensure a large reduction in numbers of Vibrio spp., including V. cholerae 0139.

Animals↗
PubMed2001

Heat, but not mechanical hyperalgesia, following adrenergic injections in normal human skin.

The development of adrenergic sensitivity in nociceptors has been suggested as a mechanism of neuropathic pain. We sought to determine if nociceptors in the skin of normal subjects exhibit adrenergic sensitivity. We investigated the effects of intradermal administration of norepinephrine, phenylephrine, and brimonidine on heat pain sensitivity. Norepinephrine and phenylephrine (in concentrations ranging from 0.1 to 10 microM by factors of 10), brimonidine (at 0.01-1 microM), and saline were injected (30 microl volume) in a random, double-blind manner to different sites on the volar surface of the forearm in ten subjects. Before and after the injections, heat testing was performed with a non-contact laser thermal stimulator. Heat pain threshold was measured by means of a 'Marstock' technique in which subjects pressed a reaction time key when they perceived that a slowly increasing heat stimulus (1 degrees C/s ramp from a 36 degrees C base) was painful. In addition, the subjects used magnitude estimation techniques to rate the intensity of pain to a suprathreshold heat stimulus (47 degrees C, 2 s). Mechanical testing was done using 200-microm diameter probes attached to calibrated weights that provided forces over the range of 16-512 mN. The intradermal injections of norepinephrine, phenylephrine and brimonidine produced little evoked pain. However, a dose-dependant decrease in heat pain threshold, but not mechanical pain threshold, was observed. At the highest drug dose injected, all three adrenergic compounds produced a significant decrease in heat pain threshold compared to the saline injection. A significant increase in response to the suprathreshold heat stimulus was also found. One possible explanation for this apparent heat hyperalgesia is that the decrease in perfusion due to the localized vasoconstriction may alter the heat response. However, in control studies we found that the non-adrenergic vasoconstrictors, angiotensin II and vasopressin did not produce heat hyperalgesia at doses that produced comparable decreases in blood flow. In addition, occlusion of blood flow with a blood pressure cuff did not lead to heat hyperalgesia. Thus, the heat hyperalgesia observed with the adrenergic agonists is not due to a decrease in perfusion associated with the injection. These results indicate that alpha(1)- and alpha(2)-adrenoceptor-mediated mechanisms may play a role in sensitization of nociceptors to heat stimuli in normal skin.

Adolescent↗
PubMed2000

Secondary heat, but not mechanical, hyperalgesia induced by subcutaneous injection of bee venom in the conscious rat: effect of systemic MK-801, a non-competitive NMDA receptor antagonist.

Subcutaneous (s.c.) administration of bee venom into the plantar surface of one hind paw in rats has been found to produce an immediate single phase of persistent spontaneous nociceptive responses (continuously flinching, licking or lifting the injected paw) for 1-2 h accompanied by a 72-96 hour period of primary heat and mechanical hyperalgesia in the injection site and a spread of heat, but not mechanical, hyperalgesia in the non-injected hind paw (Chen et al., 1999b). To gain insight into the underlying mechanisms of the bee venom-induced hyperalgesia in particular, we further identified a heat, but not mechanical, hyperalgesia in an area (paw pad) distant from the injection site induced by s.c. injection of bee venom into the posterior leg 0.8-1.2 cm proximal to the heel measured by paw withdrawal reflex to radiant heat or von Frey monofilament stimuli in conscious rats. In the bee venom-treated hind limb, however, significant reduction in both thermal latency and mechanical threshold of withdrawal reflex was identified for a period of more than 96 h in the heel with a similar characteristic to the primary heat and mechanical hyperalgesia identified in the injection site previously. The time course of the heat hyperalgesia identified in the paw pad of the bee venom-treated side was shorter and lasted for less than 48 h, which was in parallel with the reduction in thermal latency of the withdrawal reflex identified in the non-injected hind paw. Moreover, pre- or post-treatment with a single dose of MK-801 (0.01 mg/kg, i.p.), a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, completely blocked the occurrence, and reversed the established process of the heat hyperalgesia identified in either the bee venom-treated or non-treated paw pads, while the same treatments with the drug did not produce any influence upon the development and maintaining of the heat and mechanical hyperalgesia identified in the heel of the injected hind limb. Taken together with our previous results following s.c. intraplantar bee venom injection, we conclude that: (1) in addition to the well-identified primary heat and mechanical hyperalgesia in the injection site and its adjacent area, s.c. bee venom is also able to produce a secondary heat hyperalgesia in a region distant from the injection site which has a similar characteristic to the contralateral heat hyperalgesia; (2) NMDA receptors are involved in either development or maintenance of the secondary and the contralateral heat hyperalgesia, but without any role in those processes of the primary heat and mechanical hyperalgesia; (3) the secondary heat hyperalgesia seen in the injected hind limb is likely to share the same neural mechanisms with that identified in the non-injected side via co-activation of NMDA receptors.

Animals↗