The relationship between hsp 70 localization and heat resistance

Ultrasonic Deep-Plane Neck Lift

Ultrasonic deep-plane neck lift is a new approach for addressing both the subsuperficial musculoaponeurotic system and subplatysmal soft tissues during facial rejuvenation procedures. This innovative surgical approach utilizes 2.2, 2.9, and 3.7 stainless steel probes that are powered by high-frequency ultrasound. Using high-frequency ultrasound in the subcutaneous spaces has been accomplished for the past 20 years with a very suitable safety profile. In this technique, emulsification of the fat layer in both the superficial and deep planes is accomplished with tumescence of the soft tissues in the same fashion as subcutaneous liposuction. In ultrasonic deep-plane neck lift, the superficial and deep layers of fat are targeted for emulsification, and this creates a loosening of these spaces for lifting and repositioning. The procedure facilitates more accurate surgery, because the tissue effects include hemostasis and scalpel- and scissor-free undermining due to the emulsification of the fat layers of the face and neck. The other advantages of ultrasound-assisted facial contouring and rejuvenation include treatment of hard-to-treat areas like the perioral region and distal neck, which can be rapidly and safely undermined utilizing this technology. The third component of ultrasound- and energy-based facial rejuvenation surgery is the long-term remodeling and tightening that occurs beginning approximately 8 weeks after the procedure. When many conventional facelifts are beginning to fall at 3 to 4 months postoperatively, the energy-based facelifts are still tightening and this remodeling continues for up to a year after the procedure. Combining technology with conventional facelift procedures is a new approach to facial rejuvenation and is the result of 15 years of research and cooperation with the aesthetic device industry. The result of this merger of technology with conventional surgery is TESLA Facelifting, the facelift of the future.

Tesla Facelifting Using Energy Devices during Rhytidectomy

Tesla facelifting is the process of utilizing energy devices as surgical tools during rhytidectomy and neck lifting. Devices used for Tesla face and neck lifting include fiber lasers, radio frequency devices, high-frequency ultrasound, and plasma energy devices. Advantage of Tesla face and neck lifting include better visualization for surgical intervention due to reduced bleeding, better access to hard to access facial and neck locations, and long-term skin tightening from the subdermal energy treatment.

Ultrasound-Assisted Rhytidectomy Including Sub-SMAS and Subplatysmal Dissection

Energy-based facelifting techniques are a relatively new genre of surgery. In this approach, the energy-based device-whether laser, radiofrequency plasma, or ultrasound-can be used in the superficial plane to elevate skin flaps before performing more traditional facelift techniques involving the superficial musculoaponeurotic system (SMAS) or platysma. The initial reports of utilizing fiber lasers as surgical tools date back to approximately 2007 and initial lipolasers were used to elevate facial skin flaps. The other energy-based devices were also tested. The author has probably the largest series of energy-based facial rejuvenation procedures, having performed over 3,000 of these procedures. The advantages of laser-assisted rhytidectomy include hemostasis, facilitated dissection in areas hard to elevate conventionally such as nasolabial folds or distal neck and the remodeling and tightening of tissue that results from the activation of the wound healing cascade of neocollagenesis and wound contraction. The author currently has a preference for energy device used during rhytidectomy and it is a high frequency ultrasound energy delivered by a five-ring 2.9- and 3.7-mm probe. The use of the ultrasound dissector in both superficial and deep procedures is highlighted in this article with emphasis on its use for deep cervicoplasty and subplatysmal procedures as well as sub-SMAS elevations of the facial deep plane.

Laser-Assisted Facelifting and Energy-Based Rejuvenation Techniques During Rhytidectomy

The use of energy-based devices as surgical tools during rhytidectomy was introduced in early 2007 to 2008 and occurred when the first fiber laser was approved for laser lipolysis. It became evident that the fiber laser-assisted rhytidectomy could offer several advantages compared with conventional rhytidectomy. The use of energy devices now includes temperature-controlled radiofrequency and helium plasma devices. Energy devices continue to offer advantages compared with knife and scissor approaches: improved hemostasis; an ability to dissect into areas without full flap elevation; and the shrink-wrap late effects of collagen remodeling after energy-based treatment, which improves the results of rhytidectomy.

Hyperthermia effects on Hsp27 and Hsp72 associations with mismatch repair (MMR) proteins and cisplatin toxicity in MMR-deficient/proficient colon cancer cell lines

PURPOSE

Hyperthermia is used in combination with conventional anticancer agents to potentiate their cytotoxicity. One of its key events is the synthesis of heat shock proteins (HSPs), which are able to associate with components from DNA repair mechanisms. However, little is known about their relationship with the mismatch repair system (MMR). Our aim was to study the effects of hyperthermia on cisplatin (cPt) sensitivity and to determine whether MLH1 and MSH2 associate with Hsp27 and Hsp72 in MMR-deficient(-)/-proficient(+) cells.

MATERIALS AND METHODS

HCT116+ch2 (MMR-) and HCT116+ch3 (MMR+) cell lines were exposed to cPt with or without previous hyperthermia (42 °C, 1 h). Clonogenic survival assays, MTT, confocal immunofluorescence, immunoprecipitation, immunoblotting and flow cytometry were performed.

RESULTS

Hyperthermia increased the cPt resistance in MMR- cells 1.42-fold. Immunofluorescence revealed that after cPt, Hsp27 and Hsp72 translocated to the nucleus and colocalisation coefficients between these proteins with MLH1 and MSH2 increased in MMR+ cells. Immunoprecipitation confirmed the interactions between HSPs and MMR proteins in control and treated cells. Hyperthermia pretreatment induced cell cycle arrest, increased p73 expression and potentiated cPt sensitivity in MMR+ cells.

CONCLUSIONS

This is the first report showing in a MMR-/+ cellular model that MLH1 and MSH2 are client proteins of Hsp27 and Hsp72. Our study suggests that p73 might participate in the cellular response to hyperthermia and cPt in a MMR-dependent manner. Further functional studies will confirm whether HSPs cooperate with the MMR system in cPt-induced DNA damage response or whether these protein interactions are only the result of their chaperone functions.

Immunohistochemical expression of heat shock protein 70 in vitiligo

Heat shock proteins (HSPs) are proteins that are expressed under variety of stresses including pathologic conditions. How stresses affect vitiligo is not fully understood and little is known about the role of HSPs generally and Hsp70 specifically in vitiligo. The current study investigated the expression of Hsp70 in vitiliginous (32) and normal skin (10) by immunohistochemistry together with correlating this expression with the clinicopathologic parameters in the studied vitiligo group. Hsp70 was expressed in the cytoplasm of epidermis in all normal skin compared with its localization to the cytoplasm in 35.5% and to the nuclei in 64.5% of epidermis in vitiligo lesions. Intense (P < .001) and diffuse (P < .001) expression of Hsp70 was in favor of vitiligo skin compared with normal skin. Nuclear form of Hsp70 tended to be expressed in progressive forms of the disease. The percentage of Hsp70 expression tended to be decreased with the duration of the disease. From the present study, up-regulation of HSP 70, in the form of its intense and diffuse expression, may be blamed in pathogenesis of vitiligo. Nuclear localization of HSP 70 may be more important than its presence or absence, beside it may be related to progression of the disease.

Protein refolding in peroxisomes is dependent upon an HSF1-regulated function

Post-heat shock refolding of luciferase requires chaperones. Expression of a dominant negative HSF1 mutant (dnHSF1), which among other effects depletes cells of HSF1-regulated chaperones, blocked post-heat shock refolding of luciferase targeted to the cytoplasm, nucleus, or peroxisomes, while refolding of endoplasmic reticulum (ER)-targeted luciferase was inhibited by about 50 %. Luciferase refolding in the cytoplasm could be partially restored by expression of HSPA1A and fully by both HSPA1A and DNAJB1. For full refolding of ER luciferase, HSPA1A expression sufficed. Neither nuclear nor peroxisomal refolding was rescued by HSPA1A. A stimulatory effect of DNAJB1 on post-heat shock peroxisomal luciferase refolding was seen in control cells, while refolding in the cytoplasm or nucleus in control cells was inhibited by DNAJB1 expression in the absence of added HSPA1A. HSPB1 also improved refolding of peroxisomal luciferase in control cells, but not in dnHSF1 expressing cells. HSP90, HSPA5, HSPA6, and phosphomevalonate kinase (of which the synthesis is also downregulated by dnHSF1) had no effect on peroxisomal refolding in either control or chaperone-depleted cells. The chaperone requirement for post-heat shock refolding of peroxisomal luciferase in control cells is thus unusual in that it can be augmented by DNAJB1 or HSPB1 but not by HSPA1A; in dnHSF1 expressing cells, expression of none of the (co)-chaperones tested was effective, and an as yet to be identified, HSF1-regulated function is required.

Heat shocks enhance procollagen type I and III expression in fibroblasts in ex vivo human skin

BACKGROUND

The well-known characteristics of aging skin are the development of fine lines and wrinkles, but changes in skin tone, skin texture, thickness and moisture content are also aspects of aging. Rejuvenation of the skin aims at reversing the signs of aging and can be established in the epidermis as well as in the dermis. Aged dermis, in fact, has a degenerated collagen matrix. To regenerate this matrix, fibroblasts need to be stimulated into synthesizing new collagen.

AIMS

In this study, the effects of heat shocks of different temperatures on human dermal fibroblasts in ex vivo skin on the expression of procollagen 1, procollagen 3, heat shock protein (hsp)27, hsp47, and hsp70 are investigated.

MATERIALS AND METHODS

The heat shocks were applied on ex vivo skin samples by immersing the samples in heated phosphate-buffered saline of 45 °C or 60 °C. Metabolic activity was measured and at similar time points propidium-iodide-calceine staining was performed to establish cell viability. Quantitative polymerase chain reaction (qPCR) was performed after the heat shock to determine gene expression levels relative to the reference temperature. Furthermore, PicroSirius Red and hematoxylin stainings were performed to visualize the collagen network and the cells.

RESULTS

The skin samples were shown to be viable and metabolically active. Histology indicated that the heat shocks did not influence the structure of the collagen network or cell appearance. qPCR results showed that in contrast to the 45 °C heat shock the 60 °C heat shock resulted in significant upregulations of procollagen type I and III, hsp70 and hsp47.

CONCLUSION

A 60 °C, heat shock stimulates the human dermal fibroblasts in ex vivo skin to upregulate their procollagen type I and type III expression.

Pulsed heat shocks enhance procollagen type I and procollagen type III expression in human dermal fibroblasts

BACKGROUND

The formation of wrinkles is associated with degeneration of the collagen matrix. For regeneration of the matrix, fibroblasts need to be stimulated in producing new collagen.

AIMS

In this study, the effect of short-pulsed heat shocks on gene expression of procollagen type I, procollagen type III, heat shock protein (hsp)27, hsp47 and hsp70 and on the expression of remodeling markers, procollagen type I carboxy-terminal peptide (P1P) and carboxy-terminal telopeptide of type I (ICTP), of human dermal fibroblasts in vitro, is investigated.

MATERIALS AND METHODS

Temperatures of 45 degrees C and 60 degrees C were used for the heat shocks. The proliferation rates, viability and metabolic activity were measured directly after the pulsed heat shocks and quantitative PCR was performed at five different time points after the heat shocks. Enzyme Immuno Assays were performed to determine the concentrations of P1P and ICTP.

RESULTS

A decreased proliferation rate of the 60 degrees C heat shocked cells was shown, whereas the viability and metabolic activity did not differ. Furthermore, gene expressions were upregulated in both 45 degrees C and 60 degrees C heat-shocked cells. However, remodeling marker analyses showed a larger amount of collagen produced by 60 degrees C heat-shocked cells.

CONCLUSION

It can be concluded that these findings, together with upregulation in gene expression, show that it is possible to stimulate the cells to produce more collagen with short-pulsed heat shocks.

The heat-induced gamma-H2AX response does not play a role in hyperthermic cell killing

PURPOSE

The goal of this study was to determine whether the heat-induced formation of gamma-H2AX foci is involved in hyperthermic cell killing.

MATERIALS AND METHODS

The heat-induced gamma-H2AX response was determined in cells exhibiting various degrees of heat sensitivity. The panel of cells tested included cells that are transiently thermotolerant, permanently heat resistant, permanently heat sensitive, and permanently resistant to oxidative stress. Cells exposed to non-thermal environmental conditions that lead to protection from, or sensitization to, heat were also tested. The heat sensitivity of cells in which H2AX was knocked out was also ascertained.

RESULTS

The protein synthesis independent state of thermotolerance, but not the protein synthesis dependent state of thermotolerance, was found to be involved in the attenuation of the gamma-H2AX response in thermotolerant cells. The initial magnitude of the gamma-H2AX response was found to be the same in all cell lines with altered heat sensitivity. Furthermore, no differences in the resolution of gamma-H2AX foci were found among the cell lines tested. We also found that H2AX knock-out cells were not more heat sensitive.

CONCLUSIONS

We conclude that the heat-induced gamma-H2AX response does not play a role in heat-induced cell killing, thereby adding further evidence that the heat-induced gamma-H2AX foci are not due to DNA double strand breaks.

Heat-induced perturbations of DNA damage signaling pathways are modulated by molecular chaperones

Heat is one of the most potent radiosensitizers known. Several randomized trials have shown that hyperthermia is a good adjuvant for radiotherapy at several different cancer sites. However, the mechanism(s) involved in the interaction of heat and radiation that lead to radiosensitization remain to be elucidated. In this report, we have determined that heat induces perturbations in some of the earliest events in the cellular response to DNA damage induced by ionizing radiation. We studied the effect of heat on the formation of complexes containing gamma-H2AX/MDC1/53BP1 in heated-irradiated cells. We found that the formation of this complex was delayed in heated-irradiated cells, in a heat but not radiation dose-dependent manner. The length of the heat-induced delay of complex formation was attenuated in thermotolerant and heat radiosensitization-resistant cells. The length of the delay of gamma-H2AX/MDC1/53BP1 complex formation correlated with the magnitude of heat radiosensitization and was modulated by the molecular chaperone Hsc70. Heat radiosensitization was attenuated in 53BP1-null cells, implying that the delay of the formation of the gamma-H2AX/MDC1/53BP1 complex plays a role in heat radiosensitization. Heat also induced a delay of events in the DNA damage response that are downstream from 53BP1. Our results support the notion that heat-induced perturbations in the earliest events of the cellular response to ionizing radiation-induced DNA damage play a role in heat radiosensitization.

Poly(ADP-ribose) polymerase-1 inhibition increases expression of heat shock proteins and attenuates heat stroke-induced liver injury

OBJECTIVE

Heat stroke is a life-threatening illness characterized by an increased core body temperature as a result of exposure to high ambient temperature. Despite advances in supportive care, heat stroke is often fatal, and no specific and effective therapies exist. The pathophysiological responses to heat stroke involve a systemic inflammatory response and a disseminated intravascular coagulation in the host, which lead to a multiorgan dysfunction syndrome. Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear DNA-binding protein that has been shown to play a relevant role in cell necrosis and organ failure in various diseases associated with inflammation. Therefore, we set out to investigate whether inhibition of PARP activity might affect the heat stroke-induced injury.

DESIGN

Controlled animal study.

SETTING

Research laboratory of an academic institution.

SUBJECTS

PARP-1-deficient mice (Parp-1(-/-)) and wild-type mice (C57BL/6J).

INTERVENTIONS

Wild-type mice untreated or treated with either PJ34 or 3-AB, two generic PARP inhibitors, and Parp-1(-/-) mice were subjected to heat exposure as a model to study heat stroke.

MEASUREMENTS AND MAIN RESULTS

We measured rectal temperature, serum interleukin-1beta and interleukin-6, liver histology, and heat shock proteins expression. We found that the heat stroke-induced injury was attenuated in mice lacking PARP-1 and was markedly reduced in wild-type mice treated with PARP inhibitors. Interestingly, heat-induced expression of heat shock proteins 27 and 70 was boosted after PARP inhibition. Indeed, PARP inhibition increased expression of heat shock proteins 27 and 70 even in the absence of heat exposure. Accordingly, PARP inhibition increased thermal tolerance that may contribute to attenuate the clinical effects of heat stroke, resulting in increased survival.

CONCLUSIONS

Our results find a new protective function of PARP inhibitors and support their potential therapeutic application in the treatment of heat stroke.

HSP70 kinetics study by continuous observation of HSP-GFP fusion protein expression on a perfusion heating stage

The direct correlation between levels of heat shock protein expression and efficiency of its tissue protection function motivates this study of how thermal doses can be used for an optimal stress protocol design. Heat shock protein 70 (HSP70) expression kinetics were visualized continuously in cultured bovine aortic endothelial cells (BAECs) on a microscope heating stage using green fluorescent protein (GFP) as a reporter. BAECs were transfected with a DNA vector, HSP(p)-HSP70-GFP which expresses an HSP70-GFP fusion protein under control of the HSP70 promoter. Expression levels were validated by western blot analysis. Transfected cells were heated on a controlled temperature microscope stage at 42 degrees C for a defined period, then shifted to 37 degrees C for varied post-heating times. The expression of HSP70-GFP and its sub-cellular localization were visualized via fluorescence microscopy. The progressive expression kinetics were measured by quantitative analysis of serial fluorescence images captured during heating protocols from 1 to 2 h and post-heating times from 0 to 20 h. The results show two sequential peaks in HSP70 expression at approximately 3 and 12 h post-heat shock. A progressive translocation of HSP70 from the cytoplasm to the nucleus was observed from 6 to 16 h. We conclude that we have successfully combined molecular cloning and optical imaging to study HSP70 expression kinetics. The kinetic profile for HSP70-GFP fusion protein is consistent with the endogenous HSP70. Furthermore, information on dynamic intracellular translocation of HSP70 was extracted from the same experimental data.

Comparison of Intra-organellar Chaperone Capacity for Dealing with Stress-induced Protein Unfolding

Molecular chaperones are essential for cells to prevent that partially unfolded proteins form non-functional, toxic aggregates. This requirement is increased when cells experience protein unfolding stresses and such could affect all compartments in the eukaryotic cell. Whether all organelles are equipped with comparable chaperone capacities is largely unknown, mainly due to the lack of suitable reporters that allow such a comparison. Here we describe the development of fluorescent luciferase reporters that are sorted to various cellular locations (nucleus, cytoplasm, endoplasmic reticulum, and peroxisomes) and that differ minimally in their intrinsic thermal stability properties. When heating living cells, the rate of inactivation was most rapid for the nuclear-targeted luciferase, indicating that the nucleus is the most sensitive organelle toward heat-induced denaturing stress. Post-heat re-activation, however, occurred at equal kinetics irrespective of luciferase localization. Also, induction of thermotolerance by a priming heat treatment, that coordinately up-regulates all heat-inducible chaperones, resulted in a transient heat resistance of the luciferase in all organelles in a comparable manner. Overexpression of the main heat-inducible Hsp70 family member, HspA1A, protected only the cytosolic and nuclear, but not the other luciferases. Together, our data suggest that in each compartment investigated, including the peroxisome in which so far no chaperones could be detected, chaperone machines are present and can be induced with activities similar to those present in the cytosolic/nuclear compartment.

Is hypothermia a stress condition in HepG2 cells?

To understand hypothermia as a stress condition we determined the expression and localization of Hsp70 under hyperthermic and hypothermic stress in human hepatoma HepG2 cells. Western blot analysis indicates that there was a statistically significant increase of Hsp70 expression under thermal stresses. Immunohistochemically, the distribution of inducible Hsp70 in stressed cells showed a granular pattern mostly in the cytoplasm. At subcellular level, Hsp70 was localized in the nucleus, vacuoles, cytoskeletal components and dispersed throughout the cytoplasm. Accumulation of Hsp70 in cells under hypothermia could be related to restitution of cell equilibrium modified by this thermal stress condition. The protective effect of hypothermia could be associated with promotion of Hsp expression. We suggest that hypothermia is a stress capable of inducing Hsp70 expression in human HepG2 cells.

Stored of Hsp72/Hsp73 in Germinal Vesicle-stage Mouse Oocytes

Heat-shock proteins (hsps) Hsp72 and Hsp73 are the stored maternal proteins found in mouse oocytes. Both hsps appear in mouse oocytes at germinal vesicle (GV) and metaphase II (M-II)-stages as previously demonstrated by immunoblotting analysis. In this report, we further determined the presences of Hsp72/Hsp73 proteins in mouse embryos at stages of 2-pronucleus, arrested 1-cell, 2-cell, arrested 2-cell, 4-cell, arrested 4-cell, 8-cell to morula and blastocyst. Except for the blastocyst stage, the Hsp72/Hsp73 proteins were detectable in most embryo stages. The concentration of Hsp72/Hsp73 in GV-stage oocytes was higher than that in M-II-stage oocytes, and in any stages of embryos before implantation. A dramatical increase in Hsp72/Hsp73 expression was found at the 2-cell stage. Together with these findings, we speculated that hsps accumulated or stored earlier in the GV-stage mouse oocytes to protect the oocytes against environmental influences acting on ovary, and hsps may be required for zygotic gene activation and provided a protective effect against apoptosis.

Hsp70 attenuates hypoxia/reoxygenation-induced activation of poly(ADP-ribose) synthetase in the nucleus of adult rat cardiomyocytes

Effects of heat shock protein 70 (Hsp70) translocated to nuclear fraction on hypoxia/reoxygenation injury was examined by using adult cardiomyocytes isolated from rats. Cardiomyocytes were exposed to heat shock at 42 degrees C for 15 min (HS group), and then incubated at 37 degrees C for 6-24 h. Hsp70 production increased and the protein translocated from cytosol to nucleus. The maximum level of Hsp70 in the nuclear fraction was observed 12 h after HS. When cardiomyocytes without exposure to HS (nHS group) were subjected to 120 min hypoxia/15 min reoxygenation (Hypo/Reoxy), post-hypoxic cell viability was approximately 25% of the pre-hypoxic value. A rise in poly(ADP-ribose) synthetase (PARS) activity in the nuclear fraction was observed in nHS group, associated with an increase in polyADP-ribosylated protein. In contrast, post-hypoxic cell viability of HS group was approximately 60% of the pre-hypoxic value. Hypo/reoxy-induced rise in PARS activity and increase in polyADP-ribosylated protein were attenuated in HS group. To confirm the relationship between an increase in cell viability after Hypo/Reoxy and attenuation of PARS activation, cardiomyocytes without exposure to HS were subjected to Hypo/Reoxy in the presence of 1 mM 3-aminobenzamide, an inhibitor of PARS. Treatment of cells with 3-aminobenzamide attenuated Hypo/ Reoxy-induced decrease in cell viability. These results suggest that Hsp70 translocated into nucleus after HS may attenuate PARS activation during Hypo/Reoxy, leading to the cytoprotection of cardiomyocytes against Hypo/Reoxy injury.

beta-Adrenergic signaling and thyroid hormones affect HSP72 expression during heat acclimation

Heat acclimation upregulates 72-kDa heat shock protein (HSP72) and predisposes to faster activation of the heat shock response (HSR). This study investigates the role played by beta-adrenergic signaling and/or plasma thyroxine level in eliciting these features by using rats undergoing 1) heat acclimation (AC; 34 degrees C, 2 and 30 days); 2) AC with beta-adrenergic blockade; 3) AC-maintained euthyroid; 4) hypothyroid; 5) hyperthyroid; and 6) controls. The hsp72 mRNA (RT-PCR) and HSP72 levels (Western blot) were measured before and after heat stress (2 h, 41 degrees C, rectal temperature monitored). beta-Adrenergic blockade during AC abolished HSP72 accumulation, without disrupting HSR. Low thyroxine blunted the HSR at posttranscriptional level, whereas thyroxine administration in hyperthyroid and AC-maintained euthyroid rats arrested heat stress-evoked hsp72 transcription. We conclude that beta-adrenergic signaling contributes to the high HSP72 level characterizing the AC state. Thyroxine has two opposing effects: 1) direct repressive on rapid hsp72 transcription after heat stress; and 2) indirect stimulatory via beta-adrenergic signaling. Low thyroxine could account for diminished HSP72 synthesis via lower heat production and thermoregulatory set point.

Differential accumulation of U14 snoRNA and hsc70 mRNA in Chinese hamster cells after exposure to various stress conditions

We have previously characterized the unique organization of the U14 small nucleolar ribonucleic acid (snoRNA) gene in Chinese hamster HA-1 cells. The single copy of the hsc70/U14 gene is the only source for the production of both U14 snoRNA species and hsc70 messenger ribonucleic acid (mRNA) in these cells. Here we report that the accumulations of U14 snoRNA and hsc70 mRNA are different in response to various stress conditions, although both of them are transcribed in a single primary transcript. Heat shock induced an increased accumulation of both U14 snoRNA and hsc70 mRNA. On the other hand, exposure to sodium arsenite or azetidine induced an increased accumulation of hsc70 mRNA, but did not lead to a concomitant increase in the level of U14 snoRNA. Under normal growth conditions, the variations in the levels of U14 snoRNA and hsc70 mRNA, in the different phases of the cell cycle, are correlated. The increased expression of U14 snoRNA and hsc70 mRNA, and the hsc70 protein induced specifically by heat shock suggest that they participate in the repair process of heat-induced damage to macromolecular complexes involved in the synthesis and processing of ribosomal RNA.

Heat shock proteins and cardiovascular pathophysiology

In the eukaryotic cell an intrinsic mechanism is present providing the ability to defend itself against external stressors from various sources. This defense mechanism probably evolved from the presence of a group of chaperones, playing a crucial role in governing proper protein assembly, folding, and transport. Upregulation of the synthesis of a number of these proteins upon environmental stress establishes a unique defense system to maintain cellular protein homeostasis and to ensure survival of the cell. In the cardiovascular system this enhanced protein synthesis leads to a transient but powerful increase in tolerance to such endangering situations as ischemia, hypoxia, oxidative injury, and endotoxemia. These so-called heat shock proteins interfere with several physiological processes within several cell organelles and, for proper functioning, are translocated to different compartments following stress-induced synthesis. In this review we describe the physiological role of heat shock proteins and discuss their protective potential against various stress agents in the cardiovascular system.

Characterization of the differential protein expression associated with thermoresistance in human gastric carcinoma cell lines

Resistance to chemotherapeutic agents is one of the major problems faced during palliative therapy of tumor cells. Thus, chemotherapy is frequently combined with other modes of therapy such as radiation therapy and/or hyperthermia. Tumor cells respond to heat stress with development of thermotolerance and the interactions between chemo- and thermoresistance phenomena are not clearly understood. In this paper, we analyze the differential protein expression in vitro in human stomach cancer cells, their chemoresistant and thermoresistant counterparts using proteomics. The immediate aim was to identify sets of proteins that may lead to the development of thermoresistance. Based on these results, we aim to develop functional tests and methods for the modulation of thermoresistance and chemoresistance phenomena that may assist the therapy of inoperable cancers.

Cytoprotective mechanism of heat shock protein 70 against hypoxia/reoxygenation injury

The role of heat shock protein 70 (HSP70) in the cytoprotection against hypoxia/reoxygenation injury was examined. Adult rat cardiomyocytes were isolated, subjected to hyperthermia at 42 degrees C for 15 min (heat shock treatment), and then incubated at 37 degrees C for 3 to 24 h (HSP production process). Heat shock treatment increased HSP70 production (80-260% increase); the peak increase was seen after 9 h of HSP production process. Thereafter, the cells were subjected to 120-min hypoxia and 15-min reoxygenation. Heat shock treatment increased the survival of the cells subjected to hypoxia/reoxygenation (1.5-2.5-fold); the maximal cytoprotection was observed after 12 h of HSP production process. Heat shock treatment increased HSP70 content in the nucleus when cells were subjected to 12 h of HSP production process. To examine the role of HSP70 accumulation in the nuclear fraction, the activity of poly(ADP-ribose) synthetase (PARS), which functions in the nucleus and consumes high-energy phosphates excessively in the reoxygenated state, were measured in the cells with heat shock and 12 h of HSP production process. Heat shock treatment attenuated the hypoxia/reoxygenation-induced increase in the PARS activity (50% decrease). Treatment of the cells with 3-aminobenzamide, an inhibitor of PARS, exerted the effects similar to those of heat shock treatment. These results suggest that attenuation of the PARS activity in the nucleus may play an important role in the cytoprotective effect of HSP70 on hypoxia/reoxygenation injury.

Histopathological features of liver damage induced by laser ablation in rabbits

BACKGROUND AND OBJECTIVE

Possible mechanisms that promote or interfere with the effects of laser ablation of the liver have not been clarified. The aim of this study was to define the chronological alterations in the normal rabbit liver at early stages after laser ablation.

STUDY DESIGN/MATERIALS AND METHODS

Rabbit livers were ablated with a laser via an optical fiber and then analyzed histopathologically by immunostaining for heat shock protein 70 (HSP70) and by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) method.

RESULTS

The lesions increased in size progressively over the 24 h that followed ablation and the area of the lesion coincided with the area that had been heated above 43 degrees C. TUNEL-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes were surrounded, at some distance, by HSP70-positive hepatocytes at 6 h, and such cells were in contact with each other at 24 h.

CONCLUSIONS

Injury to hepatocytes induced by laser ablation increases for 24 h and dying cells express nuclear HSP70, with subsequent fragmentation of DNA.

Heat-induced alterations in the localization of HSP72 and HSP73 as measured by indirect immunohistochemistry and immunogold electron microscopy

The heat shock proteins are a family of stress-inducible proteins that act as molecular chaperones for nascent proteins and assist in protection and repair of proteins whose conformation is altered by stress. HSP72 and HSP73 are two major cytosolic/nuclear stress proteins of mammalian cells, with extensive sequence homology. HSP73 is constitutively expressed, whereas HSP72 is highly stress-inducible. However, it is unclear why two isoforms are expressed and whether these two proteins have different functions in the cell. To assist in the delineation of function, we have completed a detailed study of the localization of HSP72 and HSP73 in the cell before and after heat stress, using two different methods of detection. By indirect immunohistochemistry, the localization of these two proteins is similar, cytoplasmic and nuclear in nonstressed cells with a translocation to nucleoli immediately after heat. By the more sensitive immunogold electron microscopy technique, differences in localization were noted. In nonstressed cells, HSP72 was primarily nuclear, localized in heterochromatic regions and in nucleoli. HSP73 was distributed throughout the cell, with most cytoplasmic label associated with mitochondria. Mitotic chromosomes were also heavily labeled. After stress, HSP72 concentrated in nuclei and nucleoli and HSP73 localized to nuclei, nucleoli, and cytoplasm, with increased label over mitochondria. These differences in localization suggest that the HSP72 and HSP73 may associate with different proteins or complexes and hence have different but overlapping functions in the cell.

Licania michauxii Prance root extract induces hsp 70 mRNA and necrotic cell death in cultured human hepatoma and colon carcinoma cell lines

An extract of Licania michauxii Prance root was found to be cytotoxic to cultured human hepatoma (HepG2) and colon carcinoma (Caco-2) cells. Morphological and nuclear characteristics of treated cells were consistent with necrotic death. Increases in the chaperone protein hsp 70 and hsp 70 mRNA were dose dependent reaching peak mRNA levels (40-fold above control) at 6 h. Increases in nuclear localization of hsp 70 was also observed with treatment. Heat treatment of cells for 45 min to induce hsp 70 prior to treatment with the extract provided transient protection from the necrotic response.

Differential expression of stress proteins in nonhuman primate lung and conducting airway after ozone exposure

The presence of seven stress proteins including various heat shock proteins [27-kDa (HSP27), 60-kDa (HSP60), 70-kDa (HSP70) and its constitutive form HSC70, and 90-kDa (HSP90) HSPs] and two glucose-regulated proteins [75-kDa (GRP75) and 78-kDa (GRP78) GRPs] in ozone-exposed lungs of nonhuman primates and in cultured tracheobronchial epithelial cells was examined immunohistochemically by various monoclonal antibodies. Heat treatment (42 degrees C) resulted in increased HSP70, HSP60, and HSP27 and slightly increased HSC70 and GRP75 but no increase in GRP78 in primary cultures of monkey tracheobronchial epithelial cells. Ozone exposure did not elevate the expression of these HSPs and GRPs. All of these HSPs including HSP90, which was undetectable in vitro, were suppressed in vivo in monkey respiratory epithelial cells after ozone exposure. Both GRP75 and GRP78 were very low in control cells, and ozone exposure in vivo significantly elevated these proteins. These results suggest that the stress mechanism exerted on pulmonary epithelial cells by ozone is quite different from that induced by heat. Furthermore, differences between in vitro and in vivo with regard to activation of HSPs and GRPs suggest a secondary mechanism in vivo, perhaps related to inflammatory response after ozone exposure.

Heat shock-induced acquisition of thermotolerance at the levels of cell survival and translation in Xenopus A6 kidney epithelial cells

In this study we have investigated the acquisition of thermotolerance in a Xenopus laevis kidney A6 epithelial cell line at both the level of cell survival and translation. In cell survival studies, A6 cells were incubated at temperatures ranging from 22 to 35°C for 2 h followed by a thermal challenge at 39°C for 2 h and a recovery period at 22°C for 24 h. Optimal acquisition of thermotolerance occurred at 33°C. For example, exposure of A6 cells to 39°C for 2 h resulted in only 3.4% survival of the cells whereas prior exposure to 33°C for 2 h enhanced the survival rate to 69%. This state of thermotolerance in A6 cells was detectable after 1 h at 33°C and was maintained even after 18 h of incubation. Cycloheximide inhibited the acquisition of thermotolerance at 33°C suggesting the requirement for ongoing protein synthesis. The optimal temperature for the acquisition of translational thermotolerance also occurred at 33°C. Treatment of A6 cells at 39°C for 2 h resulted in an inhibition of labeled amino acid incorporation into protein which recovered to approximately 14% of control after 19 h at 22°C whereas cells treated at 33°C for 2 h prior to the thermal challenge recovered to 58% of control levels. These translationally thermotolerant cells displayed relatively high levels of the heat shock proteins hsp30, hsp70, and hsp90 compared to pretreatment at 22, 28, 30, or 35°C. These studies demonstrate that Xenopus A6 cells can acquire a state of thermotolerance and that it is correlated with the synthesis of heat shock proteins.Key words: Xenopus laevis, heat shock protein, hsps, A6 cells, chaperone, thermotolerance.

Intracellular distribution of hsp70 during long duration moderate hyperthermia

Hyperthermia causes cell killing and is also an effective radiosensitizer. In recent years, the protocol of long duration moderate hyperthermia (LDMH) has been used to treat cancer patients in the clinic. However, the results of many studies indicate that some tumour cells may reveal the capability to express chronic thermotolerance, a factor of potentially critical impact in the efficacy of clinical hyperthermia. Previously it has been reported that two out of five human cell lines studied were able to proliferate at 41.1 degrees C. In the present study, the intracellular distribution of hsp70 during LDMH was measured as a potential marker for chronic thermotolerance with continued cell proliferation. In all cell lines studied, hsp70 became localized in the nucleus immediately after the cells were shifted from 37 degrees C to 41.1 degrees C. However, in the two cell lines which recovered and continued to proliferate, NSY42129 and HT29, hsp70 was delocalized from the nucleus within 4 h. Conversely, in the cell lines for which 41.1 degrees C was lethal, hsp70 did not delocalize from the nucleus but rather became localized in the nucleolar regions. Neither the NSY42129 cells nor the HT29 cells showed any preferential nucleolar punctate staining. Thus, it appears that the pattern of hsp70 nuclear localization and delocalization is related to the cells' ability to survive moderate heat shocks.

Heat shock and proinflammatory stressors induce differential localization of heat shock proteins in human monocytes

Heat shock (HS) proteins (HSP) are a family of molecular chaperones induced by environmental stresses such as oxidative injury, and contribute to protection from and adaptation to cellular stress. We investigated in human monocytes the expression and subcellular distribution of hsp70 and hsc70 after HS and inflammation-related stresses leading to generation of reactive oxygen species by these cells, such as the phorbol ester PMA and erythrophagocytosis (E phi). By combining immunofluorescent staining and Western blot on subcellular fractions, we found that all three stress factors resulted in an increased hsp70 expression, however the subcellular distribution pattern was different depending on the type of stress. While HS induced a rapid translocation of hsp70 into the nucleus, no nuclear translocation of hsp70 was observed after PMA or E phi. Neither of the examined stresses induced membrane expression of hsp70. The observed differences in subcellular distribution pattern might relate to distinct regulation and specific functions of hsp70 in inflammation.

Effects of an inhibitor of protein kinases on the response to heat treatment in cultured mammalian cells

Effects of H7, a protein kinase C inhibitor, on responses to hyperthermic treatment were investigated in relatively heat sensitive Chinese hamster V79 cells and resistant human glioma A7 cells. In V79 H7 (2-50 microM) enhanced cell killing of heat treatment of 42 or 44 degrees C. The magnitude of the heat sensitization was dependent on concentration and timing of H7 addition; addition of the inhibitor between 0 and 2 h before heat treatment was most effective. In A7 the inhibitor did not show such synergistic effect with heat treatment, but showed mere added toxicity. In split-heat experiments using V79 with addition of H7 (20 microM) before the initial heat treatment and thereon, the development of thermotolerance was partially inhibited. However, already thermotolerant cells were not sensitized when H7 was added before the test heat. In V79 there was a tendency for H7 to accelerate cell death and DNA ladder formation by heat. No significant change was detectable in HSP70 induction determined by Western analyses although H7 seemed to accelerate shifting of HSP70 out of nuclei back into cytoplasm. These results indicate that heat sensitizing effect of H7 may depend on cell type and that the effectiveness of H7 depends on timing of addition.

Induction of Hsp72 and transient nuclear localization of Hsp73 and Hsp72 correlate with the acquisition and loss of thermotolerance in postimplantation rat embryos

A number of cell culture studies have indicated that there is a positive correlation between the induction and decay of thermotolerance and the kinetics of Hsp72 expression. In this study, we have demonstrated that, in gestational day 10 embryos, induction and decay of thermotolerance occur over an 8 hr period. To test the hypothesis that there is a correlation between loss of thermotolerance and the decline of Hsp72 or Hsp73 gene products over time, expression levels of both Hsp72 and constitutively expressed Hsp73 mRNAs and proteins were examined at several time points following exposure to a thermotolerance-inducing exposure of 42 degrees C. Our results indicated that Hsp72 mRNA was strongly induced 1 hr after exposure but no longer detectable by 8 hr. Although our Western blot results indicated that Hsp72 protein was present beyond 8 hr after exposure, Northern blot analysis showed that Hsp72 mRNA was no longer present 5 hr after exposure to 42 degrees C. The latter finding indicates that no new Hsp72 can be synthesized at this time point and beyond. Although there was very little or no induction of Hsp73, immunohistochemical analysis revealed a dramatic, transient shift in intracellular localization of Hsp73 protein, as well as Hsp72. Under non-stress conditions, Hsp73 was cytoplasmically localized but localization was largely nuclear 1 hr after exposure, when thermotolerance was demonstrable. Hsp73 and Hsp72 proteins were no longer localized in the nucleus by 8 hr, when thermotolerance was no longer detectable. Thus, the induction of Hsp72 and the transient nuclear localization of both Hsp72 and Hsp73 correlate with the kinetics of thermotolerance in the postimplantation rat embryo.

Differential expression of heat shock 70 proteins in primary cultures from rat cerebellum

While a number of studies have described the heat shock response in established cell lines and in primary cultures of cells derived from the nervous system, there has been no systematic analysis comparing expression and localization of the inducible heat shock 70 (hsp70) proteins and the constitutively synthesized members of the family (hsc70) in neurons and glia. In the present communication, we utilized specific probes to compare the expression of hsp70 and hsc70 mRNAs and proteins in two types of primary cultures, astroglial and neuro-astroglial, from postnatal rat cerebellum. Conditions were adjusted to maintain physiological numbers of microglia in both types of culture, and cultures were analyzed at a number of different time points following a precisely defined heat shock. The northern, in situ hybridization and immunohistochemical analyses resulted in a number of novel observations concerning the nature of the heat shock response in these neuronal and glial cells. In postnatal day 4-5 cultures, hsp70 mRNA levels were elevated for at least 10 h in both types of culture, but in situ hybridization analysis showed no evidence for hsp70 mRNAs in neurons. Microglia were the only cell type in which hsp70 was detected in non-stressed cultures and this cell type contained the highest concentrations of hsp70 proteins in stressed cultures. Hsc70 mRNA levels were also increased after heat shock, but the increase was more transient. Hsc70 mRNAs and proteins were present in all cell types, again with the highest concentrations being present in microglia. Hsc70 mRNAs and proteins were localized in the cytoplasm at all time points examined, with hsc70 protein also being localized in nucleoli. Hsp70 mRNAs and proteins were diffusely localized over nuclei of astrocytes, as well as of most microglia. Hsp70, but not hsc70, was localized on chromosomes in glia once they had resumed cell division after heat shock, suggesting a role for hsp70 either in targeting damaged chromosomal proteins or in cell division. Some cytoplasmic hsp70 was observed in astrocytes of the mixed neuro-astroglial cultures and a delayed hsp70 immunoreactivity was observed in granule neurons in these cultures, suggesting either that translation of low levels of hsp70 mRNAs was more efficient in neurons, or that glial-neuronal translocation of hsp70 proteins had taken place. These results suggest that metabolism and functions of different heat shock protein family members may not always be identical and that care must be taken in extrapolation of results from one cell type to another.

High constitutive levels of heat-shock proteins in human-pathogenic parasites of the genus Leishmania

We have analysed the transcription of three heat-shock genes, HSP70, HSP83 and ClpB, in the protozoan parasite Leishmania. All three heat-shock genes are transcribed constitutively and not heat-inducibly. However, we find that two major heat-shock proteins, HSP70 and HSP83, are synthesized at elevated rates during heat stress. We conclude that the cellular stress response in Leishmaniae is regulated exclusively on a post-transcriptional level much in contrast with all other eukaryotes examined so far. The induced synthesis of HSP70 and HSP83, however, does not increase the steady-state level of either protein significantly. This is compensated by high constitutive levels of both proteins: HSP70 and HSP83 make up 2.1% and 2.8%, respectively, of the total protein in unstressed Leishmania promastigotes. Also, HSP70 is a strictly cytoplasmic protein in Leishmania and does not relocate into the nucleus during heat stress, as it does in other eukaryotes examined in the past.

Cloning and characterization of cDNAs for 70-kDa heat-shock proteins (Hsp70) from two fish species of the genus Oryzias

cDNA corresponding to two hsp70-related genes (OLHSC70 and CEHSC70) were isolated from two lines of cultured fish cells derived from the genus Oryzias. OLHSC70 was 2,261 bp in length and encoded a protein of 686 amino acids with a predicted molecular mass of 76,120 daltons. CEHSC70 was 2,114 bp in length and it lacked the 5' region found in OLHSC70. Two-dimensional electrophoresis revealed that Oryzias latipes has at least three heat-inducible proteins with molecular masses of about 70,000 daltons. One of these proteins (Hsp70.1) was barely expressed under normal conditions but its high-level expression was induced by hyperthermia. The other two proteins (Hsc70.1, and Hsc70.2) were constitutively expressed under normal conditions and only slightly enhanced levels were induced by hyperthermia. Transfection with the cloned sequence, RNA dot-blot analysis and the two-dimensional electrophoresis of proteins showed that OLHSC70 encoded Hsc70.1.

70-kDa heat shock protein expression in cultured rat astrocytes after hypoxia: regulatory effect of almitrine

Induction of heat shock proteins (Hsps), especially the 70-kDa family, is well observed in nervous tissues in response to various stressful conditions. By using rat astrocytes in primary culture, the expression of the inducible (Hsp70) and the constitutive (Hsc70) 70-kDa Hsps immunoreactivity of cells exposed to hypoxic conditions has been investigated. We observed that exposure of astroglial cells to an hypoxic-normoxic sequence induces a significant decrease of Hsc70 immunoreactivity. The presence of the heat inducible stress protein Hsp70 is never observed in hypoxic cells nor in control. Hsc 70 lowering is associated with ultrastructural alterations characterized by mitochondria swelling, formation of vacuoles and accumulation of dense material in the cell cytoplasm. The effects of addition of almitrine to the culture medium before and during hypoxia on Hsps immunoreactivity have been examined. The presence of the drug prevents the decrease of Hsc70 immunoreactivity induced by hypoxia. Furthermore, some ultrastructural improvement is observed in astroglial cells treated with almitrine suggesting some protecting role of Hsc70 on cell damage induced by hypoxia.

DNA damage and stress protein synthesis induced by oxidative stress proceed independently in the human premonocytic line U937

Heat shock proteins (HSPs) function as stress-inducible molecular chaperones and exert protective effects against cellular injury. The induction of the HSPs is considered to be mediated by the presence of abnormal proteins within the cell and/or by classical second messengers. Several lines of evidence have however suggested a relationship between DNA damage, HSP induction and thermotolerance. We investigated whether DNA alterations could represent a common signal for the induction of stress protein synthesis during heat shock or exposure to reactive oxygen species in the human premonocytic line U937. We measured, in parallel, DNA damage (both strand breaks and fragmentation) and HSP synthesis (by biometabolic labeling and Western blotting) after exposure to heat shock, hydrogen peroxide, bleomycin, cadmium or erythrophagocytosis. Heat shock induced DNA alterations along with HSP synthesis. In contrast, exposure to hydrogen peroxide or bleomycin induced DNA damage, but no HSP synthesis, suggesting that oxidation-induced DNA damage and HSP synthesis proceed independently in U937 cells. Erythrophagocytosis and cadmium induced the classical HSPs but no detectable DNA damage. Since these latter stresses also induced the oxidation-specific stress protein heme oxygenase, we suggest a protective role for heme oxygenase against oxidative DNA damage.

Putative determinants of the cellular response to hyperthermia

Recently, it has been demonstrated that two different thermal resistant states found in Chinese hamster cells, one transient, associated with thermotolerance, and the other permanent, associated with the increased expression of the cognate member of the hsp 70 family, are characterized by faster recovery from heat-induced perturbations in several cellular processes (Laszlo 1992b). These processes include total cellular protein and RNA synthesis, the localization of hsp70, the organization of vimentin, and the protein composition of the nucleus. In the present study, the recovery from heat-induced perturbations in cellular physiology was extended further to two more types of Chinese hamster cells: permanently heat resistant cells in which thermoresistance is associated with the overexpression of hsp27 and heat-sensitive cell lines. When the heat-resistant hsp27 transfected cell lines were compared with the control wild-type cell line, the recovery of protein synthesis from heat-induced inhibition was similar in the normal and hsp27 transfected cells, while the recovery from heat-induced inhibition of total RNA synthesis and the recovery from heat-induced increased association of hsp70 with nuclei were both more rapid in the hsp27 transfected cell lines. In the permanently heat-sensitive cell lines, the kinetics of recovery from heat-induced inhibition of protein synthesis did not correlate with the heat sensitive state. However, delays in the recovery from heat-induced alterations in total cellular RNA synthesis and from heat-induced excess nuclear association of hsp70 were associated with the heat-sensitive state. Overall, these results suggest that the kinetics of recovery from heat-induced alterations in total cellular RNA synthesis and the localization of hsp 70 are putative candidates for being determinants of the cellular response to hyperthermia, and thus have the potential to form the basis of predictive assays for use in conjunction with clinical hyperthermia.

Effect of amino acid analogs on the development of thermotolerance and on thermotolerant cells

Exposure of HA-1 Chinese hamster fibroblasts to amino acid analogs has been shown to have a heat-sensitizing effect as well as inducing the heat shock response (Li and Laszlo, 1985a). In this study, we have examined the effect of amino acid analogs on the development of thermotolerance after a brief heat shock or exposure to sodium arsenite and the effect of amino acid analogs on cells that are already thermotolerant. Exposure of HA-1 cells to amino acid analogs inhibited the development of thermotolerance following a mild heat shock or treatment with sodium arsenite. However, cells that were already thermotolerant were resistant to the sensitizing action of amino acid analogs. The refractoriness of thermotolerant cells to amino acid analog treatment developed in parallel with thermotolerance. The uptake of the arginine analog, canavanine, and its incorporation into proteins was not altered in the thermotolerant cells. Furthermore, another biological consequence of exposure to amino acid analogs, sensitization to ionizing radiation, also was not altered in the thermotolerant cells. The inhibition of the development of thermotolerance by amino acid analogs and the refractoriness of thermotolerant cells to the heat-sensitizing action of amino acid analogs lend further support the role of heat-shock proteins in the phenomenon of thermotolerance.

Stress proteins in aquatic organisms: an environmental perspective

The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors, including elevated temperatures, ultraviolet (UV) light, trace metals, and xenobiotics. The stress response entails the rapid synthesis of a suite of proteins referred to as stress proteins, or heat-shock proteins, upon exposure to adverse environmental conditions. These proteins are highly conserved and have been found in organisms as diverse as bacteria, molluscs, and humans. In this review, we discuss the stress response in aquatic organisms from an environmental perspective. Our current understanding of the cellular functions of stress proteins is examined within the context of their role in repair and protection from environmentally induced damage, acquired tolerance, and environmental adaptation. The tissue specificity of the response and its significance relative to target organ toxicity also are addressed. In addition, the usefulness of using the stress response as a diagnostic in environmental toxicology is evaluated. From the studies discussed in this review, it is apparent that stress proteins are involved in organismal adaptation to both natural and anthropogenic environmental stress, and that further research using this focus will make important contributions to both environmental physiology and ecotoxicology.

The thermoresistant state: protection from initial damage or better repair?

The induction of and recovery from heat-induced perturbations in several cellular parameters were examined in normal, transiently thermotolerant, and permanently heat-resistant HA-1 Chinese hamster fibroblasts. The initial heat-induced perturbations in total cellular protein synthesis, RNA synthesis, vimentin-containing intermediate filaments, and nuclear protein mass were similar in the three different cell types which display various levels of thermal resistance as determined by clonogenic survival. The posthyperthermia recovery from the heat-induced perturbations in all of the cellular parameters was more rapid in both the permanently heat-resistant cells and in the transiently thermotolerant cells. This response was observed in cells in which transient thermotolerance was induced by either a mild heat shock or exposure to sodium arsenite. The development and decay of the capacity for more rapid recovery from the initial heat-induced perturbations in total cellular protein and RNA synthesis paralleled the development and decay of clonogenic thermotolerance. Overall, these results support the notion that more rapid recovery from similar levels of heat-induced perturbations in various cellular parameters are a salient feature of both the transiently and permanently heat-resistant state.