Transient Heat Stress Research Articles

Thermal Fatigue Analysis of HSK Shrink Toolholder

The principle which the tool is embedded into the HSK shrink toolholder is expanding with heat and contracting with cold. The thermal cycle that the tool is embedded into or taken out the toolholder is heating toolholder and cooling it quickly. After a few thermal cycles, the HSK shrink toolholder is damaged with the way of thermal fatigue. The analysis of thermal fatigue is transient heat transfer and stress coupling and the temperature distributionstress and strain of every time are gained in thermal cycle. The fatigue of shrink tool holder is strain fatigue by analyzing the stress. The fatigue life is gained with Coffin-Manson formula.

Transient Heat Stress Compromises the Resistance of Wheat (Poales: Poaceae) Seedlings to Hessian Fly (Diptera: Cecidomyiidae) Infestation

Heat stress exerts a profound impact on the resistance of plants to parasites. In this research, we investigated the impact of an acute transient heat stress on the resistance of the wheat line 'Molly,' which contains the R gene H13, to an avirulent Hessian fly (Mayetiola destructor (Say)) population. We found that a significant portion of Molly seedlings stressed at 40 degrees C for 6 h during or after the initial Hessian fly larval attack became susceptible to otherwise avirulent insects, whereas unstressed control plants remained 100% resistant. Specifically, 77.8, 73.3, 83.3, and 46.7% of plants heat stressed at 0, 6,12, and 24 h, respectively, after the initial larval attack became susceptible. Biochemical analysis revealed that heat stress caused a transient decrease in 12-oxo-phytodienoic acid, but an increase in salicylic acid accumulation in Molly plants. The change in phytohormones after heat stress and Hessian fly infestation was not observed in 'Newton,' a near-isogenic but Hessian fly susceptible wheat line. Instead, heat stress caused a relatively prolonged reduction in palmitoleic acid. The role of phytohormones in heat-induced loss of wheat resistance was discussed.

Individual and combined effects of transient drought and heat stress on carbon assimilation and seed filling in chickpea.

High temperatures and decreased rainfall are detrimental to yield in chickpea (Cicer arietinum L.), particularly during grain filling. This study aimed to (i) assess the individual and combined effects of drought and heat stress on biochemical seed-filling processes, (ii) determine genotypic differences in heat and drought tolerance, and (iii) determine any cross-tolerance. Plants were grown outdoors in the normal growing season when temperatures during seed filling were <32-20°C or were planted late (temperatures >32-20°C; heat stress). Half of the pots were kept adequately watered throughout, but water was withheld from the others from the initiation of seed filling until the relative leaf water content reached 50% of the irrigated plants (drought stress); all plants were rewatered thereafter until seed maturit. Water was withheld for 13 days (normal sowing) and 7 days (late sowing), so soil moisture decreased by 54-57%. Tests on leaves and seeds were performed after the stress. Individual and combined stress damaged membranes, and decreased cellular oxidising ability, stomatal conductance, PSII function and leaf chlorophyll content; damage was greater under combined stress. Leaf Rubisco activity increased with heat stress, decreased with drought stress and decreased severely with combined stress. Sucrose and starch concentrations decreased in all seeds through reductions in biosynthetic enzymes; reductions were greater under combined stress. These effects were more severe in heat- and drought-sensitive genotypes compared with drought-tolerant genotypes. Drought stress had a greater effect than heat stress on yield and the biochemical seed-filling mechanisms. Drought- and heat-tolerant genotypes showed partial cross-tolerance.

YES1 Activation Elicited by Heat Stress Is Anti-Apoptotic in Mouse Pachytene Spermatocytes1

Deregulated expression of protein tyrosine phosphorylation has been implicated in testicular response to different stimuli. Herein, YES1, a nonreceptor protein tyrosine kinase, was found to be significantly up-regulated in pachytene spermatocytes (PS) during early recovery from a transient testicular heat stress. Coculture of PS with Sertoli cells (SCs) could enhance the hyperthermia-induced YES1 activation, indicative of a positive regulation of the paracrine signaling. Moreover, SU6656, a selective YES1 inhibitor, was shown to effectively block YES1 activity, thereafter resulting in a dramatic increase of heat stress-induced apoptosis in primary cultured PS. Mechanistically, the antiapoptotic effect of YES1 activation in response to testicular heat insult may mediate via the regulation of extracellular signal-regulated kinase (ERK)/metastasis-associated 1 (MTA1) cascade. From a clinical standpoint, a notably higher level of YES1 expression was observed in the pathological testis from varicocele patients as compared to a negligible staining in the control group. Taken together, our present results provide the first evidence that the YES1/ERK/MTA1/p53 cascade may serve as a naturally occurring, indispensable self-defensive mechanism maintaining apoptotic balance during meiotic heat stress. Our study may have also partially answered the question of how activation of signal pathways at the cell membrane surface interacts with the key regulatory events occurring in the nucleus during testicular heat shock.

Reexamining Transcriptional Regulation of the Bacillus subtilis htpX Gene and the ykrK Gene, Encoding a Novel Type of Transcriptional Regulator, and Redefining the YkrK Operator

HtpX is an integral cytoplasmic membrane metalloprotease well conserved in numerous bacteria. A recent study showed that expression of the Bacillus subtilis htpX gene is under dual negative control by Rok and a novel type of transcriptional regulator, YkrK. Here we report that expression of the B. subtilis htpX gene is strongly heat inducible. Contrary to the previous prediction, ykrK expression has been found to be not subject to autoregulation. We have identified the htpX promoter and the authentic ykrK promoter, which is also distinct from the previously predicted one. We have redefined a conserved inverted repeat sequence to be the YkrK operator, which is somewhat different from the previously proposed one. We provide evidence that YkrK is not a substrate of HtpX and that heat induction of htpX is not YkrK mediated. We have also found that the absence of FtsH or HtpX alone did not impair B. subtilis cell viability on LB agar plates at high temperature, whereas the absence of both FtsH and HtpX caused a severe growth defect under heat stress. This finding supports the notion that FtsH and HtpX may have partially overlapping functions in heat resistance. Finally, we show that htpX expression is subject to transient negative control by sigB under heat stress in a Rok- and YkrK-independent manner. Triple negative control of htpX expression at high temperature by rok, sigB, and ykrK may help cells to prevent uncontrolled and detrimental oversynthesis of the HtpX protease.

Enhanced isoprene-related tolerance of heat- and light-stressed photosynthesis at low, but not high, CO2 concentrations

The principal function of isoprene biosynthesis in plants remains unclear, but emission rates are positively correlated with temperature and light, supporting a role for isoprene in maintaining photosynthesis under transient heat and light stress from sunflecks. Isoprene production is also inversely correlated with CO(2) concentrations, implying that rising CO(2) may reduce the functional importance of isoprene. To understand the importance of isoprene in maintaining photosynthesis during sunflecks, we used RNAi technology to suppress isoprene production in poplar seedlings and compared the responses of these transgenic plants to wild-type and empty-vector control plants. We grew isoprene-emitting and non-emitting trees at low (190 ppm) and high (590 ppm) CO(2) concentrations and compared their photosynthetic responses to short, transient periods of high light and temperature, as well as their photosynthetic thermal response at constant light. While there was little difference between emitting and non-emitting plants in their photosynthetic responses to simulated sunflecks at high CO(2), isoprene-emitting trees grown at low CO(2) had significantly greater photosynthetic sunfleck tolerance than non-emitting plants. Net photosynthesis at 42°C was 50% lower in non-emitters than in isoprene-emitting trees at low CO(2), but only 22% lower at high CO(2). Dark respiration rates were significantly higher in non-emitting poplar from low CO(2), but there was no difference between isoprene-emitting and non-emitting lines at high CO(2). We propose that isoprene biosynthesis may have evolved at low CO(2) concentrations, where its physiological effect is greatest, and that rising CO(2) will reduce the functional benefit of isoprene in the near future.

Cooperativity of α- and β-Subunits of Group II Chaperonin from the Hyperthermophilic Archaeum Aeropyrum pernix K1

alpha- and beta-subunits (ApCpnA and ApCpnB) are group II chaperonins from the hyperthermophilic archaeum Aeropyrum pernix K1, specialized in preventing the aggregation and inactivation of substrate proteins under conditions of transient heat stress. In the present study, the cooperativity of alpha- and beta-subunits from the A. pernix K1 was investigated. The ApCpnA and ApCpnB chaperonin genes were overexpressed in E. coli Rosetta and Codonplus (DE3), respectively. Each of the recombinant alpha- and beta- subunits was purified to 92% and 94% by using anionexchange chromatography. The cooperative activity between purified alpha- and beta-subunits was examined using citrate synthase (CS), alcohol dehydrogenase (ADH), and malate dehydrogenase (MDH) as substrate proteins. The addition of both alpha- and beta-subunits could effectively protect CS and ADH from thermal aggregation and inactivation at 43 degreesC and 50 degreesC, respectively, and MDH from thermal inactivation at 80 degreesC and 85 degreesC. Moreover, in the presence of ATP, the protective effects of alpha- and beta-subunits on CS from thermal aggregation and inactivation, and ADH from thermal aggregation, were more enhanced, whereas cooperation between chaperonins and ATP in protection activity on ADH and MDH (at 85 degreesC) from thermal inactivation was not observed. Specifically, the presence of both alpha- and beta- subunits could effectively protect MDH from thermal inactivation at 80 degreesC in an ATP-dependent manner.

Epidermolysis bullosa simplex due toKRT5mutations: mutation-related differences in cellular fragility and the protective effects of trimethylamineN-oxide in cultured primary keratinocytes

Epidermolysis bullosa simplex (EBS) is a mechanobullous skin fragility disease characterized by cytolysis of basal keratinocytes and intraepidermal blistering often caused by mutations in keratin genes (KRT5 or KRT14). No remedies exist for these disorders presenting a need for development of novel therapies. To identify new genotype-phenotype relationships in vivo and in cultured primary EBS keratinocytes in vitro, and to study the cytoskeletal stabilizing effects of trimethylamine N-oxide (TMAO) in heat-stressed EBS cells. Genomic DNA and cDNA samples from three Swedish patients with EBS were analysed for keratin mutations. Primary EBS keratinocyte cultures were established, heat stressed with and without added TMAO, followed by evaluation of cellular fragility. In addition to the previously reported KRT5 mutation (V186L) in one patient, two patients were found to have a novel I183M and recurrent E475G replacements in KRT5. Cultured EBS keratinocytes did not exhibit keratin aggregates or cell loss, except in the patient with the p.I183M mutation who showed 3% aggregates and 2% cell loss. Upon transient heat stress the number of aggregate-containing cells increased to 21%, 27% and 13%, respectively, in the p.I183M, p.E475G and p.V186L mutant cells. Interestingly, pretreatment with TMAO prior to heat stress, dose dependently reduced the number of aggregate-containing cells and cell loss. These results revealed a genotype-phenotype correlation in EBS keratinocytes upon heat stress and suggest protein stabilization as a new therapeutic strategy.

The effect of long-term soil management on the physical and biological resilience of a range of arable and grassland soils in England

In agricultural systems, soils are subjected to a range of stresses which may affect soil physical and biological properties and compromise the ability of the soil to function. How the soil responds to stress both initially and over time defines resistance and resilience respectively and is key to sustainable soil management. As soil organic matter (OM) is a fundamental soil property, we hypothesised that resilience would be controlled, in part, by this. As soil OM is itself affected by long-term soil management, we therefore sought to establish a direct link between this and resilience to physical and biological stresses. Fifteen soils were taken from a range of arable and grassland sites in England, including the Broadbalk and Highfield long-term experiments at Rothamsted. The soils were subjected to physical (uniaxial compaction stress) or biological (transient heat stress or persistent Cu stress) stresses in the laboratory and the effects on general physical (void ratio) and biological (substrate-induced respiration) functions were monitored over a recovery period of up to 28 days. Wet–dry and freeze–thaw cycles were also imposed on the soils following the initial recovery after compression. The initial recovery of void ratio following compression was greater in grassland soils (0.28–0.80) than arable soils (0.16–0.58) which was probably related to the elastic effect of particulate OM and the redistribution of the greater water content in the former soils. Wet–dry and freeze–thaw cycles had an additional effect in soils with clay contents greater than 26%. The transient heat stress reduced respiration rates in the grassland soils by up to 45%. Grassland soils are less likely to have been subjected to heat stress in the field since they carry a greater vegetation covering than arable soils. The more persistent Cu stress reduced respiration rates in arable soils by up to 85% but only up to 30% in grassland soils. The difference was ascribed to the greater microbial biomass and diversity in grassland soils and buffering by the OM. We defined resistance and resilience indices as the absolute value of the measured soil functions at maximum stress and after the recovery period respectively. Reasonable linear regressions (adjusted R 2 up to 0.68) were established for resistance or resilience as a function of soil OM content, used as a proxy index of soil management. Expressed in this way, grassland soils were more resistant and resilient to the physical and biological stresses than the arable soils. Linear relationships were also found to link physical and biological resistance and resilience (adjusted R 2 up to 0.96). An arable soil with 65% clay was found to be highly resilient also. We found large differences in physical and biological resilience to stress between arable and grassland soils. We attributed this primarily to the effect of soil management on the OM content, although we recognised the importance of clay content.

A single, mild, transient scrotal heat stress causes hypoxia and oxidative stress in mouse testes, which induces germ cell death.

Spermatogenesis is a temperature-dependent process, and increases in scrotal temperature can disrupt its progression. We previously showed that heat stress causes DNA damage in germ cells, an increase in germ cell death (as seen on TUNEL staining), and subfertility. The present study evaluated the stress response in mouse testes following a single mild transient scrotal heat exposure (40 degrees C or 42 degrees C for 30 min). We investigated markers of three types of stress response, namely, hypoxia, oxidative stress, and apoptosis. Heat stress caused an increase in expression of hypoxia-inducible factor 1 alpha (Hif1a) mRNA expression and translocation of HIF1A protein to the germ cell nucleus, consistent with hypoxic stress. Increased expression of heme oxygenase 1 (Hmox1) and the antioxidant enzymes glutathione peroxidase 1 (GPX1) and glutathione S-transferase alpha (GSTA) was consistent with a robust oxidative stress response. Germ cell death was associated with an increase in expression of the effector caspase cleaved caspase 3 and a decrease in expression of the protein inhibitor of caspase-activated DNase (ICAD). Reduced expression of ICAD contributes to increased activity of caspase-activated DNase and is consistent with the increased rates of DNA fragmentation that have been detected previously using TUNEL staining. These studies confirmed that transient mild testicular hyperthermia results in temperature-dependent germ cell death and demonstrated that elevated temperature results in a complex stress response, including induction of genes associated with oxidative stress and hypoxia.

A strategy for meta-analysis of short time series microarray datasets

Many time series microarray experiments have relatively short (less than ten) time points and lack in repeats, weakening the confidence of results. Combining the microarray data from different groups may improve the statistical power of detecting differentially expressed genes. However, few efforts have been taken to combine or compare the time-course array datasets generated by independent groups. Here we demonstrated a suitable strategy for meta-analysis of short time series microarray datasets and implemented this strategy on four published heat shock microarray datasets of Saccharomyces Cerevisiae. We first assessed the significance of each gene in each datasets based on area calculation and the null distribution of the areas. Then the similarity of significance values across datasets was assessed with meta-analysis methods, yielding a set of transient heat shock stress sensitive genes. Following correlation calculation helped us to combine the transformed data at the same time points of each gene. Further bioinformatic investigation showed the significance of our strategy, and also indicated some interesting features of regulatory systems in S. cerevisiae during transient heat stress.

A single, mild, transient scrotal heat stress causes DNA damage, subfertility and impairs formation of blastocysts in mice

Infertility represents a major clinical problem and 50% of cases are attributable to the male partner. Testicular function is temperature dependent, and in both man and mouse the position of the testes in the scrotum ensures that they are kept at between 2 and 8 degrees C below core body temperature. We used a mouse model to investigate the impact of a single, transient, mild, scrotal heat stress (38, 40 or 42 degrees C for 30 min) on testicular function, sperm DNA integrity and embryo survival. We detected temperature-dependent changes in testicular architecture, number of apoptotic cells and a significant reduction in testis weight 7 and 14 days after heat stress at 42 degrees C. We report for the first time that DNA strand breaks (gamma-H2AX-positive foci) were present in spermatocytes recovered from testes subjected to 40 or 42 degrees C. Fertility of heat-stressed males was tested 23-28 d after treatment (sperm at this time would have been spermatocytes at time of heating). Paternal heat stress at 42 degrees C resulted in reduced pregnancy rate, placental weight and litter size; pregnancies from the 40 degrees C group had increased resorptions at e14.5. Abnormalities in embryonic development were detected at e3.5 and in vitro fertilisation with sperm recovered 16 h or 23 d after scrotal stress at 42 degrees C revealed a block in development between the 4-cell and blastocyst stages. This study has provided evidence of temperature-dependent effects on germ cell DNA integrity and highlighted the importance of an intact paternal genome for normal embryo development.

Heat stress induces Cdc2 protein decrease prior to mouse spermatogenic cell apoptosis

Both mitosis and meiosis are driven by M-phase promoting factor (MPF), a complex with Cdc2 and Cyclin B. The concentration of Cdc2 remains relatively constant during the cell cycle, while the concentration of Cyclin B fluctuates periodically. Many studies have demonstrated high expression levels of Cdc2 and Cyclin B in the testis. In some gene knock-out mice insufficient amounts of MPF blocked the spermatocytes at the G2/M transition and this was followed by spermatocyte apoptosis. In this study, we examined the expression and the alteration of Cdc2 in testis during the spermatocyte apoptosis process induced by transient heat stress. The results showed that the spermatogenic cell apoptosis was detectable by the TUNEL assay at 4h post-treatment. At 10h, almost all spermatocytes began apoptosis. In situ hybridization and immunohistochemistry indicated that cdc2 was primarily expressed in spermatocytes. Neither the distribution nor the amount of cdc2 mRNA was significantly influenced by the heat stress. In contrast, the amount of Cdc2 protein decreased significantly at 3h post-treatment, which was detectable before apoptosis. This indicated that Cdc2 was susceptible to heat stress in the testis. Cdc2 levels remained low until 8h post-treatment. It was possible that the swift decline in Cdc2 and the resulting lack of MPF blocked the spermatocytes at G2/M transition. Meiosis in the spermatocytes was disrupted leading to the initiation of apoptosis. The results provide evidence that the lack of Cdc2 might induce spermatocyte apoptosis after transient heat stress.

Lentivirus Mediated HO-1 Gene Transfer Enhances Myogenic Precursor Cell Survival After Autologous Transplantation in Pig

Cell therapy for Duchenne muscular dystrophy and other muscle diseases is limited by a massive early cell death following injections. In this study, we explored the potential benefit of heme oxygenase-1 (HO-1) expression in the survival of porcine myogenic precursor cells (MPCs) transplanted in pig skeletal muscle. Increased HO-1 expression was assessed either by transient hyperthermia or by HO-1 lentiviral infection. One day after the thermic shock, we observed a fourfold and a threefold increase in HSP70/72 and HO-1 levels, respectively. This treatment protected 30% of cells from staurosporine-induced apoptosis in vitro. When porcine MPC were heat-shocked prior to grafting, we improved cell survival by threefold at 5 days after autologous transplantation (26.3 +/- 5.5% surviving cells). After HO-1 lentiviral transduction, almost 60% of cells expressed the transgene and kept their myogenic properties to proliferate and fuse in vitro. Apoptosis of HO-1 transduced cells was reduced by 50% in vitro after staurosporine induction. Finally, a fivefold enhancement in cell survival was observed after transplantation of HO-1-group (47.5 +/- 9.1% surviving cells) as compared to the nls-LacZ-group or control group. These results identify HO-1 as a protective gene against early MPC death post-transplantation.

Expression of rice heat stress transcription factor OsHsfA2e enhances tolerance to environmental stresses in transgenic Arabidopsis

Plant growth and crop yields are limited by high-temperature stresses. In this study, we attempted to isolate the rice genes responsible for high-temperature stress tolerance using a transformed Arabidopsis population expressing a full-length cDNA library of rice. From approximately 20,000 lines of transgenic Arabidopsis, we isolated a thermotolerant line, R04333, that could survive transient heat stress at the cotyledon stage. The rice cDNA inserted in R04333 encodes OsHsfA2e, a member of the heat stress transcription factors. The thermotolerant phenotype was observed in newly constructed transgenic Arabidopsis plants expressing OsHsfA2e. Among 5 A2-type HSF genes encoded in the rice genome, four genes, including OsHsfA2e, are induced by high temperatures in rice seedlings. The OsHsfA2e protein was localized to the nuclear region and exhibited transcription activation activity in the C-terminal region. Microarray analysis demonstrated that under unstressed conditions transgenic Arabidopsis overexpressing OsHsfA2e highly expressed certain stress-associated genes, including several classes of heat-shock proteins. The thermotolerant phenotype was observed not only in the cotyledons but also in rosette leaves, inflorescence stems and seeds. In addition, transgenic Arabidopsis exhibited tolerance to high-salinity stress. These observations suggest that the OsHsfA2e may be useful in molecular breeding designed to improve the environmental stress tolerance of crops.

Small heat shock proteins prevent aggregation of citrate synthase and bind to the N-terminal region which is absent in thermostable forms of citrate synthase

Citrate synthase (CS) is often used in chaperone assays since this thermosensitive enzyme aggregates at moderately increased temperatures. Small heat shock proteins (sHsps) are molecular chaperones specialized in preventing the aggregation of other proteins, termed substrate proteins, under conditions of transient heat stress. To investigate the mechanism whereby sHsps bind to and stabilize a substrate protein, we here used peptide array screening covering the sequence of porcine CS (P00889). Strong binding of sHsps was detected to a peptide corresponding to the most N-terminal alpha-helix in CS (amino acids Leu(13) to Gln(27)). The N-terminal alpha-helices in the CS dimer intertwine with the C-terminus in the other subunit and together form a stem-like structure which is protruding from the CS dimer. This stem-like structure is absent in thermostable forms of CS from thermophilic archaebacteria like Pyrococcus furiosus and Sulfolobus solfatacarium. These data therefore suggest that thermostabilization of thermosensitive CS by sHsps is achieved by stabilization of the C- and N-terminae in the protruding thermosensitive softspot, which is absent in thermostable forms of the CS dimer.

Trimethylamine oxide suppresses stress-induced alteration of organic anion transport in choroid plexus

The effect of physicochemical stress on organic anion transport across the vertebrate blood-cerebrospinal fluid (CSF) barrier in the presence and absence of an endogenous cytoprotectant, trimethylamine oxide (TMAO), was investigated in isolated IVth choroid plexus (CP) of spiny dogfish shark (Squalus acanthias), an animal with naturally high levels of TMAO ( approximately 70 mmol l(-1)). Active transepithelial absorption of the organic anion, 2,4-dichlorophenoxyacetic acid (2,4-D), by IVth CP mounted in Ussing chambers was measured after in vitro stress, and a marker for the cellular stress response, inducible heat shock protein 70 (Hsp70), was assayed by immunoblot analysis. Transient heat stress (a shift from the normal 13.5 degrees C to 23.5 degrees C for 1 h) decreased 2,4-D transport by approximately 66%; however, the same stress minus TMAO (isosmotic replacement with urea) had no effect on transport rate. In the absence of TMAO, stress-induced Hsp70 accumulation was more than double that seen in the presence of TMAO. Likewise, exposure to 50 micromol l(-1) Zn for 6 h induced a twofold greater Hsp70 accumulation in the absence of TMAO than in its presence, and the higher Hsp70 level was associated with a higher 2,4-D transport rate. Heat stress and 50 micromol l(-1) Zn also induced more pronounced increases in Hsp70 mRNA in the absence of TMAO. Thus, the cellular stress response can significantly alter CP organic anion transport capacity, and an endogenous osmolyte can suppress that response.

Regulatory role of RsgI in sigI expression in Bacillus subtilis

The sigma gene, sigI, of Bacillus subtilis belongs to the group IV heat-shock response genes and has many orthologues in the bacterial phylum Firmicutes. The B. subtilis sigI gene is considered to constitute an operon with rsgI (regulation of sigI, formerly ykrI). As little is known about either the structure and function of the sigI-rsgI operon or the SigI regulons, the role of RsgI in heat-inducible transcription of the sigI-rsgI operon was investigated, using Northern analysis and a heat-stable beta-galactosidase reporter assay. Heat-inducible, SigI-dependent transcription of the sigI-rsgI operon was stimulated greatly by disrupting rsgI. Yeast two-hybrid analysis showed direct interaction between the N-terminal portion of the presumed RsgI protein and SigI. Without RsgI function, induction of transcription of the sigI-rsgI operon upon transient heat stress depended on dnaK activity. However, transcription of the operon was induced during growth at prolonged higher temperature even without DnaK function. Without RsgI function, sigI-rsgI operon transcription was induced after the end of growth independent of any temperature shift in a sporulation medium and toward the end of growth in a rich complex medium. Furthermore, glucose addition resulted in a strong suppression of sigI-rsgI transcription. Therefore it is hypothesized that transcription of the sigI-rsgI operon of B. subtilis is negatively regulated by the putative transmembrane protein RsgI, which moderates SigI's sensitivity to heat shock or nutritional stress.

Evaluation of Effect of Process Conditions on Microstructures in Plasma Sprayed Coating by In Situ Laser AE

In recent years, a thermal barrier coating technology becomes more important because it is required to develop materials which avoid high-temperature oxidation and corrosion. In order to ensure reliability of coating, it is necessary to understand microfracture criterion in terms of stress distribution and fracture morphology. The objective of this study is to clarify the damage generation process by comparing Acoustic Emission AE) generation behavior and thermal stress simulation result based on heat history measurement. Al2O3 as the top coat (TC) and NiCrAlY as the bond coat (BC) were sprayed to SUS304 disc or plate as a base material. AE in cooling process were detected by laser heterodyne interferometer after spraying finished. Two-dimensional axisymmetric mesh for samples was made and transient heat conductivity was analyzed for various boundary conditions. Then, using the obtained heat history, transient heat stress was analyzed and the distribution of stress elements was calculated. The fracture process of ceramic coating was evaluated from these experiments and analyses.

Constitutive Nuclear Import and Stress‐Regulated Nucleocytoplasmic Shuttling of Mammalian Heat‐Shock Factor 1

Inducible expression of major cytosolic and nuclear chaperone proteins is mediated by the heat-shock transcription factor HSF1 that is activated by derepressive mechanisms triggered by transient heat stress and sustained proteotoxicity. Despite progress in defining essential aspects of HSF1 regulation, little is known about the cellular dynamics enabling this factor to mediate gene responses to cytosolic stress signals. We report that the inactive, stress-responsive form of HSF1 accumulates in the nucleus due to a relatively potent import signal, which can be recognized by importin-alpha/beta, and simultaneously undergoes continuous nucleocytoplasmic shuttling due to a comparatively weak, nonetheless efficient, export activity not involving the classical exportin-1 pathway. Strikingly, experimental stresses at physiological or elevated temperature reversibly inactivate the export competence of HSF1. Likewise, mutations mimicking stress-induced derepression impair export but not import. These findings are consistent with a dynamic process whereby exported molecules that are derepressed in an inductive cytosolic environment are recollected and pause in the nucleoplasm, replacing progressively the inactive pool. While steady-state nuclear distribution of the bulk of HSF1 ensures a rapid gene response to acute heat stress, our results suggest that the capture in the nucleus of molecules primed for activation in the cytosol may underlie responses to sustained proteotoxicity.