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PubMed1996

Effect of acute heat stress on heat shock protein 70 messenger RNA and on heat shock protein expression in the liver of broilers.

1. The synthesis of heat shock protein 70 (Hsp70) mRNA and the expression of Hsp70 in the liver of broiler chickens submitted to acute heat stress (35 degrees C for 5 h) was investigated. 2. Hsp70 expression was detected by SDS-PAGE and Western blot analysis using a polyclonal antiserum against Hsp70 of Blastocladiella emersonii. The specific signal of Hsp70 mRNA was analysed by Northern blot using as probe a Hsp70 cDNA of B. emersonii. 3. An increase in the amount of Hsp70 was detected from the first up to the fifth hour of acute heat exposure. This increase in the amount of Hsp70 was accompanied by an increase in Hsp70 mRNA which peaked at 3 h. 4. This study shows that the heat induced increase in Hsp70 mRNA and protein in broiler liver, in vivo, are time dependent, similar to that in mammals.

Animals↗
PubMed2002

Induction of heat shock protein 47 synthesis by TGF-beta and IL-1 beta via enhancement of the heat shock element binding activity of heat shock transcription factor 1.

With most immunological reactions, tissue fibrosis, collagen overproduction caused by immune cytokines, is inevitably associated. Among the various immune cytokines, heat shock protein 47 (HSP47) is a procollagen-specific molecular chaperon and is essential for secretion of procollagen from cells. Induction of HSP47 by TGF-beta has been previously reported in rat skeletal myoblasts and mouse osteoblasts, but not in human diploid fibroblasts. As for IL-1beta, its effect on HSP47 has not been elucidated. In the present study, using human embryonic lung fibroblast cells, we first disclosed that both TGF-beta and IL-1beta induced HSP47 synthesis. We then revealed that the binding of the heat shock element (HSE) by heat shock transcription factor 1 (HSF1) was enhanced by both cytokines. We further demonstrated that trimer formation of HSF1, which is essential for its binding to HSE, was induced by these cytokines. The enhancement of HSP47 synthesis and their trimer formation of HSF1 were augmented by using a combination of both cytokines. Collectively, TGF- beta and IL-1beta were found to induce trimer formation of HSF1 which in turn bound to HSE of HSP47, resulting in the enhancement of HSP47 expression. Thus, HSP47 could well be a good candidate for molecular targeting in controlling tissue fibrosis, given that both principal fibrinogenetic cytokines (TGF-beta, IL-1beta) are commonly involved in its induction through HSF1 trimerization.

Cell Line↗
PubMed2006

Heat shock protein 25 or inducible heat shock protein 70 activates heat shock factor 1: dephosphorylation on serine 307 through inhibition of ERK1/2 phosphorylation.

The expression of heat shock proteins (HSPs) is known to be increased via activation of heat shock factor 1 (HSF1), and excess expression of HSPs exerts feedback inhibition of HSF1. However, the molecular mechanism to modulate such relationships between HSPs and HSF1 is not clear. In the present study, we show that stable transfection of either Hsp25 or inducible Hsp70 (Hsp70i) increased expression of endogenous HSPs such as HSP25 and HSP70i through HSF1 activation. However, these phenomena were abolished when the dominant negative Hsf1 mutant was transfected to HSP25 or HSP70i overexpressed cells. Moreover, the increased HSF1 activity by either HSP25 or HSP70i was found to result from dephosphorylation of HSF1 on serine 307 that increased the stability of HSF1. Either HSP25 or HSP70i inhibited ERK1/2 phosphorylation because of increased MKP1 phosphorylation by direct interaction of these HSPs with MKP1. Treatment of HOS and NCI-H358 cells, which showed high expressions of endogenous HSF1, with small interfering RNA (siRNA) of either HSP27 (siHSP27)or HSP70i (siHSP70i) inhibited both HSP27 and HSP70i proteins; this was because of increased ERK1/2 phosphorylation and serine phosphorylation of HSF1. The results, therefore, suggested that when the HSF1 protein level was high in cancer cells, excess expression of HSP27 or HSP70i strongly facilitates the expression of HSP proteins through HSF1 activation, resulting in severe radio- or chemoresistance.

Animals↗
PubMed1992

Accumulation of heat shock protein 72 (hsp 72) in postimplantation rat embryos after exposure to various periods of hyperthermia (40 degrees -43 degrees C) in vitro: evidence that heat shock protein 72 is a biomarker of heat-induced embryotoxicity.

A monoclonal antibody to the 72 kDa heat shock protein and Western blot analysis were used to determine the induction, accumulation and turnover of hsp 72 after day 10 rat embryos were exposed to elevated temperatures (40 degrees-43 degrees C) for various lengths of time (2.5 minutes to 18 hours). Embryos exposed to temperatures that exceed the normal culture temperature (37 degrees C) by 4 degrees C or more for as little as 2.5 minutes (43 degrees C) or 15 minutes (41, 42 degrees C) synthesized and accumulated detectable amounts of heat-inducible hsp 72. Hsp 72 could not be detected by Western blot analysis of proteins from embryos cultured at 40 degrees C or below. Once induced, hsp 72 can be detected in embryos for 24-48 hours after they are removed from the hyperthermic conditions and returned to normothermic conditions. Our results also indicate that hsp 72 is induced by all hyperthermic exposures that induce alterations in rat embryo growth and development; therefore, hsp 72 is a potential biomarker for heat-induced embryotoxicity.

Animals↗
PubMed1991

Expression of heat shock protein 70 and heat shock cognate 70 messenger RNAs in rat cortex and cerebellum after heat shock or amphetamine treatment.

The expression of strictly inducible hsp70 mRNAs and constitutively expressed hsc70 mRNAs was compared in cerebellum and cerebral cortex of control rats, heat-shocked rats, and rats made hyperthermic with amphetamine. An hsc70-specific oligonucleotide probe identified a 2.55-kb mRNA in cerebellum and cerebral cortex of all rats. An hsp70-specific oligonucleotide probe identified a 3.05-kb mRNA and a 3.53-kb mRNA in cerebellum and cerebral cortex of heat-shocked and amphetamine-treated rats, but not in control rats. Quantitation demonstrated that both hsp70 and hsc70 mRNA levels, relative to 18S rRNA levels, were increased following each treatment. The relative levels of both mRNAs were higher in cerebellum than in cerebral cortex. In amphetamine-treated rats, hsc70 mRNA relative levels increased at body temperatures greater than 39 degrees C, whereas hsp70 mRNA synthesis was induced at temperatures greater than 40 degrees C. Total thermal response values and relative levels of both mRNAs were compared. The results suggested that both the transcription and turnover of hsp70 mRNAs differed between cerebellum and cerebral cortex. At equivalent total thermal response values, amphetamine-treated rats had higher relative levels of hsp70 mRNAs than heat-shocked rats, suggesting that amphetamine enhanced the induction of hsp70 mRNAs.

Amphetamine↗
PubMed2004

A Trypanosoma cruzi heat shock protein 40 is able to stimulate the adenosine triphosphate hydrolysis activity of heat shock protein 70 and can substitute for a yeast heat shock protein 40.

The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated alpha-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.

Adenosine Triphosphatases↗
PubMed1976

[Variability of the ova of mulberry silkworm (Bombyx mori L.) with regard to capacity for thermal parthenogenesis and heat resistance. 4. Relationship between the capacity of oocytes from different females for thermal parthenogenesis and heat resistance of ova at the early stage of development and heat resistance of the muscles of these females].

The reliable positive correlation was established between the variability of unfertilized eggs by their ability of thermal parthenogenesis and the heat resistance of fertilized eggs at the early stages of development. At the same time the ability of oocytes of parthenogenesis correlates negatively with the heat resistance of muscles. The data obtained suggest that the variability of oocytes by their ability of thermal parthenogenesis is partially due to the variability of heat resistance of their proteins.

Animals↗
PubMed1987

Heat shock phenomena in Aspergillus nidulans. II. Combined effect of heat and bleomycin to heat shock protein synthesis, survival rate and induction of mutations.

The combined action of hyperthermia and Bleomycin on Aspergillus nidulans was studied at three different levels: mycelial protein synthesis, spore viability and induction of mutations. It was found that Bleomycin treatment of preincubated mycelia during the heat shock enhances the incorporation of 35S-methionine into heat shock bands. Furthermore, simultaneous treatment with hyperthermia (43 degrees C) and Bleomycin results in greater cytotoxic activity in spores and in a higher induction rate of point mutations.

Aspergillus nidulans↗
PubMed1981

Effect of heat shielding on convective and evaporative heat losses and on radiant heat transfer in the premature infant.

Ten premature infants nursed on servocontrolled radiant warmer beds were studied in three environments designed to alter one or more factors affecting heat transfer (convection, evaporation, and radiation). In the control environment, infants were nursed supine on an open warmer bed. The second environment (walled chamber) was designed to reduce convection and evaporation by placing plastic walls circumferentially around the bed. In the third environment convection and evaporation were minimized by covering infants with a plastic blanket. Air turbulence, insensible water loss, and radiant warmer power were measured in each environment. There was a significant reduction in mean air velocity in the walled chamber and under the plastic blanket when compared to the control environment. A parallel decrease in insensible water loss occurred. In contrast, radiant power demand was the same for control and walled environments, but decreased significantly when infants were covered by the plastic blanket. This study suggests that convection is an important factor influencing evaporation in neonates nursed under radiant warmers. The thin plastic blanket was the most effective shield, significantly reducing radiant power demand.

Bedding and Linens↗
PubMed2004

Effect of heat preconditioning on the uptake and permeability of R123 in brain microvessel endothelial cells during mild heat treatment.

The purpose of this study was to assess the effect of mild heat and heat preconditioning on the uptake and permeability of a P-glycoprotein (P-gp) substrate, rhodamine 123 (R123), in a cell culture model of the blood-brain barrier (BBB). An immediate goal was to determine whether prior mild heat treatment could render brain microvessel endothelial cells more resistant to future heat stress and affect BBB drug permeation by future ultrasound-induced mild heat (USMH) treatment. To address this issue, the expression level of two proteins, P-gp and heat shock protein 70 (Hsp70), and their effects on uptake of R123 and permeability of R123 and [14C]-sucrose in combination with mild heat and P-gp modulator PSC833 during and after mild heat treatment in heat-preconditioned and heat-unconditioned bovine brain microvessel endothelial cell (BBMEC) monolayers were studied. Mild heat caused a significant increase in BBB permeability of R123 and [14C]-sucrose when compared with control and PSC833. Exposure of BBMECs to heat preconditioning caused a slight but insignificant decrease in cellular uptake of R123 both during and immediately after mild heat treatment. Heat preconditioning also caused a slight but insignificant decrease in permeability of R123 and [14C]-sucrose in BBMEC monolayers during mild heat treatment. Because exposure of BBMEC monolayers to mild heat did not affect P-gp expression but slightly affected Hsp70 expression, a heat preconditioning that results in a reinforcement of the BBB other than increased expression of P-gp is suggested. However, heat preconditioning is not sufficient to override the permeation-enhancing effects of mild heat because mild heat caused a significant increase in R123 uptake and permeability of R123 and [14C]-sucrose in both heat-preconditioned and heat-unconditioned cells. Because Hsp70 is known to play a major role in cellular repair and protective mechanisms, our results would imply a relative benign nature of mild heat treatment. Because heating produced by ultrasonic waves can be controlled and localized to a small volume within the tissue, the present results also suggest that USMH could play a pivotal role in the treatment of brain tumors and other brain-related diseases.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2006

The roles of exercise-induced immune system disturbances in the pathology of heat stroke : the dual pathway model of heat stroke.

Heat stroke is a life-threatening condition that can be fatal if not appropriately managed. Although heat stroke has been recognised as a medical condition for centuries, a universally accepted definition of heat stroke is lacking and the pathology of heat stroke is not fully understood. Information derived from autopsy reports and the clinical presentation of patients with heat stroke indicates that hyperthermia, septicaemia, central nervous system impairment and cardiovascular failure play important roles in the pathology of heat stroke. The current models of heat stroke advocate that heat stroke is triggered by hyperthermia but is driven by endotoxaemia. Endotoxaemia triggers the systemic inflammatory response, which can lead to systemic coagulation and haemorrhage, necrosis, cell death and multi-organ failure. However, the current heat stroke models cannot fully explain the discrepancies in high core temperature (Tc) as a trigger of heat stroke within and between individuals. Research on the concept of critical Tc as a limitation to endurance exercise implies that a high Tc may function as a signal to trigger the protective mechanisms against heat stroke. Athletes undergoing a period of intense training are subjected to a variety of immune and gastrointestinal (GI) disturbances. The immune disturbances include the suppression of immune cells and their functions, suppression of cell-mediated immunity, translocation of lipopolysaccharide (LPS), suppression of anti-LPS antibodies, increased macrophage activity due to muscle tissue damage, and increased concentration of circulating inflammatory and pyrogenic cytokines. Common symptoms of exercise-induced GI disturbances include diarrhoea, vomiting, gastrointestinal bleeding, and cramps, which may increase gut-related LPS translocation. This article discusses the current evidence that supports the argument that these exercise-induced immune and GI disturbances may contribute to the development of endotoxaemia and heat stroke. When endotoxaemia can be tolerated or prevented, continuing exercise and heat exposure will elevate Tc to a higher level (>42 degrees C), where heat stroke may occur through the direct thermal effects of heat on organ tissues and cells. We also discuss the evidence suggesting that heat stroke may occur through endotoxaemia (heat sepsis), the primary pathway of heat stroke, or hyperthermia, the secondary pathway of heat stroke. The existence of these two pathways of heat stroke and the contribution of exercise-induced immune and GI disturbances in the primary pathway of heat stroke are illustrated in the dual pathway model of heat stroke. This model of heat stroke suggests that prolonged intense exercise suppresses anti-LPS mechanisms, and promotes inflammatory and pyrogenic activities in the pathway of heat stroke.

Adult↗
PubMed2003

The effect of heat transfer mode on heart rate responses and hysteresis during heating and cooling in the estuarine crocodile Crocodylus porosus.

The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions; (2) heated via radiant energy while half-submerged in flowing water at 23 degrees C and (3) heated via convective transfer by increasing water temperature from 23 degrees C to 35 degrees C. Cooling was achieved in all treatments by removing the heat source and with C. porosus half-submerged in flowing water at 23 degrees C. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate ('rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (<0.5 degrees C) resulted in Q(10) values greater than 4000, calling into question the usefulness of this measure on heart rate during the initial stages of heating and cooling. In the later phases of heating and cooling, heart rate changed with body temperature, with Q(10) values of 2-3. The magnitude of the heart rate response differed between treatments, with radiant heating during submergence eliciting the smallest response. The heart rate of C. porosus outside of the 'rapid response' periods was found to be a function of the heat load experienced at the animal surface, as well as on the mode of heat transfer. Heart rate increased or decreased rapidly when C. porosus experienced large positive (above 25 W) or negative (below -15 W) heat loads, respectively, in all treatments. For heat loads between -15 W and 20 W, the increase in heart rate was smaller for the 'unnatural' heating by convection in water compared with either treatment using radiant heating. Our data indicate that changes in heart rate constitute a thermoregulatory mechanism that is modulated in response to the thermal environment occupied by the animal, but that heart rate during heating and cooling is, in part, controlled independently of body temperature.

Alligators and Crocodiles↗
PubMed1998

Increased expression of HDJ-2 (heat shock protein 40) and heat shock protein 70 in biopsy specimens of transplanted human lungs.

BACKGROUND: Heat shock proteins are expressed during several forms of stress and inflammation. This study was done to determine whether the expression of heat shock protein HDJ-2 (heat shock protein 40), heat shock protein 60, and heat shock protein 70 are increased during rejection in human pulmonary allografts. METHODS: Thirty-five transbronchial biopsy specimens were obtained from adult lung transplant recipients. Histologic analysis and assessment of heat shock protein HDJ-2, heat shock protein 60, and heat shock protein 70 mRNA expression was performed. Total RNA was extracted, reverse transcribed, and amplified by polymerase chain reaction with oligonucleotide primers specific for the heat shock proteins. The identity of the amplified message was verified by Southern blot and slot blot analysis. RESULTS: The expression of heat shock protein HDJ-2 was significantly higher in samples from lung transplant recipients undergoing rejection when compared with recipients without rejection or infection. Heat shock protein 70 expression was also increased in rejection. Expression of heat shock protein 60 did not show any increase in recipients with no evidence of rejection and infection or transplant recipients with rejection or infection. Serial analysis of heat shock protein HDJ-2 and heat shock protein 70 obtained in biopsy specimens during and after rejection showed a decrease of heat shock protein HDJ-2 and heat shock protein 70 expression after resolution of lung rejection. CONCLUSION: Our data demonstrate that the expression of heat shock protein HDJ-2 and heat shock protein 70 increases during lung rejection. However, only heat shock protein HDJ-2 was able to differentiate between rejection and infection. Measurement of heat shock protein HDJ-2 in transbronchial biopsy specimens may assist in the differential diagnosis between rejection and infection in lung transplant recipients.

Carrier Proteins↗
PubMed1994

Abscisic acid-induced heat tolerance in Bromus inermis Leyss cell-suspension cultures. Heat-stable, abscisic acid-responsive polypeptides in combination with sucrose confer enhanced thermostability.

Increased heat tolerance is most often associated with the synthesis of heat-shock proteins following pre-exposure to a nonlethal heat treatment. In this study, a bromegrass (Bromus inermis Leyss cv Manchar) cell suspension cultured in a medium containing 75 microM abscisic acid (ABA) without prior heat treatment had a 87% survival rate, as determined by regrowth analysis, following exposure to 42.5 degrees C for 120 min. In contrast, less than 1% of the control cells survived this heat treatment. The heat tolerance provided by treatment with 75 microM ABA was first evidenced after 4 d of culture and reached a maximum tolerance after 11 d of culture. Preincubation with sucrose partially increased the heat tolerance of control cells and rendered ABA-treated cells tolerant to 45 degrees C for 120 min (a completely lethal heat treatment for control cells). Comparative two-dimensional polyacrylamide gel electrophoresis of cellular protein isolated from heat-tolerant cells identified 43 ABA-responsive proteins of which 26 were heat stable (did not coagulate and remained soluble after 30 min at 90 degrees C). Eight heat-stable, ABA-responsive proteins ranging from 23 to 45 kD had similar N-terminal sequences. The ABA-responsive (43-20 kD), but none of the control heat-stable, proteins cross-reacted to varying degrees with a polyclonal antibody directed against a conserved, lysine-rich dehydrin sequence. A group of 20- to 30-kD heat-stable, ABA-responsive proteins cross-reacted with both the anti-dehydrin antibody and an antibody directed against a cold-responsive winter wheat protein (Wcs 120). In ABA-treated cells, there was a positive correlation between heat- and pH-induced coagulation of a cell-free homogenate and the heat tolerance of these cells. At 50 degrees C, control homogenates coagulated after 8 min, whereas cellular fractions from ABA-treated cells showed only marginal coagulation after 15 min. In protection assays, addition of heat-stable, ABA-responsive polypeptides to control fractions reduced the heat-induced coagulation of cell-free homogenates. Sucrose (8%) alone and control, heat-stable fractions enhanced the thermostability of control fractions, but the most protection was conferred by ABA-responsive, heat-stable proteins in combination with sucrose. These data suggest that stress-tolerance mechanisms may develop as a result of cooperative interactions between stress proteins and cell osmolytes, e.g. sucrose. Hypotheses are discussed implicating the role of these proteins and osmolytes in preventing coagulation and denaturation of cellular proteins and membranes.

Abscisic Acid↗
PubMed1994

Altered regulation of heat shock gene expression in heat resistant mouse cells.

PURPOSE: The differences in the heat shock gene regulation between the RIF-1 cell line and its heat resistant derivative TR4 are further characterized. METHODS AND MATERIALS: In vitro gel retardation assays were used to assess the presence of activated heat shock transcription factor in the two cell lines. The levels of the heat-inducible HSP 70.1, the constitutive HSC 70, the germ line-specific HSP 70.2, and the HSP 28 mRNAs in both untreated and iso-heated RIF-1 and TR4 cells were determined using the polymerase chain reaction coupled with the reverse transcriptase reaction. Induction and decay of induced heat shock protein synthesis was measured by 35S-methionine labeling of proteins. RESULTS: Unheated TR4 cells display characteristics of heat shocked RIF-1 cells. TR4 cells have a constitutively activated heat shock transcription factor and elevated levels of the HSP 70.1, HSC 70, and the HSP 28 mRNAs. Upon an equal heat dose of 45 degrees C, 15 min, the TR4 cells exhibited a more rapid onset in heat shock mRNA and protein induction than did the RIF-1 cells. During the recovery from heat shock, the activated heat shock transcription factor and the induced HSP70 mRNAs decayed more slowly in the TR4 cells, although the protein synthesis pattern of the TR4 cells returned to control levels more rapidly following heat shock than did protein synthesis of the RIF-1 cells. CONCLUSION: Unheated TR4 cells are similar to heat shocked RIF-1 cells at the transcriptional level. Induced HSP70 expression is modulated by the severity of the heat treatment (or the degree of heat damage) perceived by the cells rather than by the absolute heat dose given. We propose that the unheated TR4 cells are locked into the "ON" state of the heat shock response.

Animals↗
PubMed1984

Alpha-hydroxylation and oxidation of lignoceric acid in brain: the role of heat-stable and heat-labile factors.

Our previous investigations disclosed that the heat-stable and heat-labile factors obtained from brain cytosol are required for alpha-hydroxylation and oxidation of lignoceric acid by rat brain particulate fraction. The heat-stable factor was recently found to contain glucose-6-phosphate, N- acetylaspartate , glutamate, aspartate, glutamine, inorganic phosphate and low levels of adenosine nucleotide as active components. A combination of these compounds was as effective as the crude heat-stable factor for enzymic activity. Using these compounds, we reinvestigated the requirement for the heat-labile factor. With crude heat-stable factor there was an absolute requirement for the heat-labile factor; however, with various combinations of the individual components of the heat-stable factor, some degree of activity was obtained without the heat-labile factor. When aspartate or one of its derivatives, N- acetylaspartate or oxaloacetate, was used in place of the heat-stable factor, the activity was relatively low but highly stimulated by the addition of heat-labile factor. On the other hand, higher activity was obtained when glutamate or one of its derivatives, glutamine or alpha-ketoglutarate, was used without heat-labile factor. The addition of heat-labile factor to this system did not stimulate the activity. When studying the aspartate family, we discovered that the requirement for the heat-labile factor varied in a descending order: N- acetylaspartate greater than aspartate greater than oxaloacetate. Lignoceric acid oxidation was further characterized with rat brain particulate fraction, NADPH, Mg2+, glutamate, inorganic phosphate, and AMP without heat-stable and heat-labile factors. It was found that the requirement for NADPH was also partially eliminated with glutamate but not aspartate. The effects of various inhibitors, such as inhibitors of the electron transfer system, oxidative phosphorylation, the enzymes involved in citric acid cycle, and glycolysis, suggest that the heat-stable factor is involved in producing ATP or other high energy compounds to be used for the activation of lignoceric acid. ATP added to the system in place of heat-stable factor resulted in less than one-half of the lignoceric acid oxidation.

Adenine Nucleotides↗
PubMed1994

Weak acid preservatives block the heat shock response and heat-shock-element-directed lacZ expression of low pH Saccharomyces cerevisiae cultures, an inhibitory action partially relieved by respiratory deficiency.

Inhibition of microbial growth by weak acid preservatives increases with medium acidification, since these agents enter cells in the undissociated state. Many of the effects of these acids are due to the cytoplasmic acidification they cause as they dissociate in the higher pH environment of the cytosol. Sorbic and benzoic acids, two widely used preservatives, were found to exert pronounced effects on the heat shock response and thermotolerance of Saccharomyces cerevisiae. These effects were strongly influenced by the pH of the culture medium. In low pH cultures sorbate inhibited the induction of thermotolerance by sublethal heat shock, causing strong induction of respiratory-deficient petites among the survivors of heat treatment. However, when the culture pH was above 5.5 sorbate acted as a powerful chemical inducer of thermotolerance in the absence of any sublethal heat treatment. Sorbate and benzoate also inhibited heat induction of the major heat shock proteins in low pH yeast cultures. This appears to result from lack of induction of the heat shock element (HSE) promoter sequence since sorbate prevented heat induction of a HSE-lacZ fusion at low pH. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and the plasma-membrane-ATPase inhibitor diethylstilboestrol were identified as additional inhibitors of heat induction of heat shock proteins. Numerous chemicals induce the heat shock response in the absence of heat stress, but sorbate, benzoate, CCCP and diethylstilboestrol are the first compounds shown to act as selective inhibitors of heat-induced protein expression in yeast. In the presence of sorbate concentrations which, at low pH, totally inhibit both the heat shock response and growth of cells competent in respiration, respiratory-deficient petites still retain a limited capacity for growth and for heat induction of heat shock proteins. This restoration of a response to heat shock in acidified sorbate-treated cultures of petites might contribute to their higher capacity for growth in the presence of sorbate.

Adaptation, Physiological↗