Influence Of Heat Shock Research Articles

The influence of heat shock on the rate of reserves allocated by wheat seeds for germination and growth

We studied the accumulation and consumption of biomass by five-day-old seedlings of various wheat varieties (Triticum aestivum L.) grown from control and exposed to heat shock (HS) seeds. The suppression shoot and roots growth intensified with the temperature, which caused HS. With increasing the temperature (+50°С, +51°С, +52°С și +53°С) of HS, the biomass of the endosperm of the seeds transferred to the seedling, and spent on respiration during seed germination, and seedling growth decreased. Moreover, the effect of HS was more pronounced on the biomass of endosperm substances transferred to the seedling. To increase the resolution of separating wheat varieties according to their resistance to HS, we applied the optimal value (+52°С) of the HS temperature (HSo). The rate of dry matter transferred from the endosperm to the shoot, roots, and spent on respiration, made it possible to rank various wheat varieties following their resistance to high temperatures. The higher the resistance of a wheat cultivar to high temperatures, the higher the proportion of endosperm substances consumed by exposed to HSo seeds for seedling growth and respiration. With increasing the wheat varieties to high temperatures, the rate of endosperm biomass transferred to the seedling also increased, at the same time that spent on respiration on the contrary, decreased. After exposure to HSo, the seeds of the resistant to high temperatures varieties also showed higher metabolic efficiency than those of less resistant varieties. All parameters characterizing the resistance of leaves and roots to HS suggested that the high-temperature resistance of roots is lower than that of leaves. The method for determining the resistance of wheat varieties to high temperatures, based on the ability of seeds exposed to HSo, to mobilize reserve substances for germination and growth is fast, characterized by increased resolution, and ensures the distribution of wheat varieties according to their resistance to high temperatures.

Effect of high pressure processing combined with temperature on the inactivation and germination of Alicyclobacillus acidoterrestris spores: Influence of heat-shock on the counting of survivors

This study evaluated the effect of high pressure processing (HPP) and high pressure processing combined with temperature (HPP + T) on the inactivation and germination of Alicyclobacillus acidoterrestris spores, with and without heat-shock prior to enumeration. Results showed that process up to 300 and 600 MPa/5 min failed to inactivate spores at room temperature, while 2.56 log (300 MPa) and 2.40 log (600 MPa) was reached when HPP was carried out at 70 °C. Moreover, spores enumeration was up to 1.70 times lower if the heat-shock for spores activation (80 °C/10min) was applied, suggesting that part of the spores were germinated due to HPP process and becoming sensitive to heat-shock used prior to plate counting. These results highlighted the importance of evaluating the efficacy of the HPP with and without the use of heat-shock, avoiding sub-dimensioning of the process.

Influence of heat shock and osmotic stresses on the growth and viability of Saccharomyces cerevisiae SUBSC01.

BackgroundWith a preceding scrutiny of bacterial cellular responses against heat shock and oxidative stresses, current research further investigated such impact on yeast cell. Present study attempted to observe the influence of high temperature (44–46 °C) on the growth and budding pattern of Saccharomyces cerevisiae SUBSC01. Effect of elevated sugar concentrations as another stress stimulant was also observed. Cell growth was measured through the estimation of the optical density at 600 nm (OD600) and by the enumeration of colony forming units on the agar plates up to 450 min.ResultsSubsequent transformation in the yeast morphology and the cellular arrangement were noticed. A delayed and lengthy lag phase was observed when yeast strain was grown at 30, 37, and 40 °C, while at 32.5 °C, optimal growth pattern was noticed. Cells were found to lose culturability completely at 46 °C whereby cells without the cytoplasmic contents were also observed under the light microscope. Thus the critical growth temperature was recorded as 45 °C which was the highest temperature at which S. cerevisiae SUBSC01 could grow. However, a complete growth retardation was observed at 45 °C with the high concentrations of dextrose (0.36 g/l) and sucrose (0.18 g/l). Notably, yeast budding was found at 44 and 45 °C up to 270 min of incubation, which was further noticed to be suppressed at 46 °C.ConclusionsPresent study revealed that the optimal and the critical growth temperatures of S. cerevisiae SUBSC01 were 32.5 and 45 °C, respectively; and also projected on the inhibitory concentrations of sugars on yeast growth at that temperature.

Abstract 2261: Heat-shock and autophagy in cancer: Novel role for DGK iota

Abstract Autophagy is a cellular process by which damaged proteins, protein aggregates, and organelles are sequestered by lysosome-like compartments and degraded. Autophagy contributes to quality control, cell death, and senescence. Defects in autophagy cause the accumulation of cellular damage, inhibit cell death processes, and promote an inflammatory state that facilitates tumor development. In contrast, the heat shock response, which is mediated primarily by the transcription factor, HSF1 is frequently enhanced in cancer. Despite this inverse relationship between autophagy and heat-shock in cancer, the direct influence of heat-shock and HSF1-mediated gene expression on autophagy has not been investigated. Our study suggests that heat-shock mediated gene expression suppresses autophagy in a human colorectal cancer cell line. Our data show that diacylglycerol kinase iota (DGK iota) expression is regulated by HSF1. DGK iota phosphorylates diacylglycerol, generating phosphatidic acid (PA), which is a potent suppressor of autophagy through its activation of the serine/threonine kinase mTOR (mammalian target of rapamycin). The aim of our study was to evaluate the influence of HSF-1-mediated gene expression on autophagy, and to examine the specific contribution of DGK iota in this effect. We utilized RKO colorectal cancer cells for this investigation and assayed autophagy using complimentary techniques, including: conversion of LC3-I to LC3-II, which was monitored by Western blot; and the formation of autophagic vesicles (autophagosomes), which were visualized by high-content screening confocal microscopy of cells harboring an LC3-GFP expression construct. The influence of basal and heat-shock (42°C)-simulated HSF1 activity on autophagy was analyzed using siRNA. Silencing of HSF1 led to a profound increase in autophagic markers, suggesting a role for HSF1-driven gene expression in the suppression of autophagy. In HSF1-deficient cells we also observed increased phosphorylation of p70S6K, which is a surrogate marker for mTOR activation. We confirmed that DGK iota mRNA and protein expression is mediated by HSF1. Using biochemical inhibitors of DGK activity, we observed a significant increase in autophagy, supporting our hypothesis that DGK iota participates in suppressing autophagy. Additional siRNA experiments of DGK iota are being performed to confirm this effect, along with measurements of cellular PA levels. Taken together, these results indicate an important role for HSF1 in the suppression of autophagy, and provides mechanistic insight into a potential, tumor-promoting role for DGK iota. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2261. doi:1538-7445.AM2012-2261

Influence of heat shock on glycerol production in alcohol fermentation

The influence of single and double heat shocks induced during the exponential growth phase of the Saccharomyces cerevisiae fermentation of cultivar Sauvignon Blanc grape must was examined. Rapid temperature changes from 18 degrees C to 34 degrees C have been applied. The effect of the duration of exposure to a high temperature has been analyzed. By the applications of a single heat shock and a double heat shock, up to 8.2 g l(-1) and 11.0 g l(-1) glycerol have been produced, respectively. To prevent the evaporation of fine wine bouquet compounds during the temperature changes, reflux coolers on the top of bioreactors have been employed. By using this method, glycerol production was increased by up to 65%.

Heat shock proteins in the skin

Heat shock proteins (hsp) are expressed in all cells and organisms. Their expression is induced by heat shock (temperatures above 42 degrees C) and other forms of pathophysiological stress. Elevated levels of hsp protect cells from further stress exposure. Hsp are expressed intracellularly. They are highly conserved throughout evolution indicating hsp being necessary for survival under potentially harmful environmental conditions. Hsp are divided into families according to their molecular weight. The majority of hsp function as molecular chaperones. Chaperone function is characterized by binding to other proteins and mediating their folding, transport and interaction with other molecules. In human epidermis hsp are abundantly expressed and have been linked with functions in cell differentiation and photobiology. Recent research has mainly focused on the 27 and 72 kD hsp that are constitutively expressed in human keratinocytes. ultraviolet radiation (UV)-induced cell death and sunburn cell formation can be inhibited by previous heat shock exposure and UV itself can induce hsp expression. The expression of the 27 kD hsp (hsp27) in epidermal keratinocytes in situ and in culture correlates with differentiation. Expression of hsp27 increases simultaneously with keratinocyte differentiation. For that reason, hsp27 is described as a marker of epidermal differentiation. Changes in the expression and inducibility of hsp have been linked with ageing. In the skin, recent data indicate that hsp72 expression remains remarkably stable with intrinsic ageing. In contrast, levels of hsp27 have been found to be elevated in sun-protected aged skin indicating a link between hsp27 expression and age-dependent epidermal alterations. Regulation of hsp can be modified by pharmacological intervention and the development of safe topical and systemic treatments for the prevention of skin damage and disorders of keratinocyte differentiation can be expected for the future.

Influence of heat shock on seed germination of plants from regularly burnt savanna woodlands and grasslands in Ethiopia

The effect of heat shock on the germination of seeds of 21 plant speciesfrom fire-prone wooded savanna ecosystems in western Ethiopia was analysed inorder to examine the possible implications of fire upon plant regenerationafterthis disturbance. Seeds were subjected to 6 different heat intensities (20, 60,90, 120, 150 and 200 °C) for 1 or 5 minutes, in ordertosimulate the situation in the upper soil layers or on the soil surface duringfires. Germination tests were carried out in pots in a greenhouse over 20weeks.After 9 weeks no more seedlings emerged. There was wide interspecific variationin the responses of seeds to the different treatments. In all species,germination was significantly affected by the temperature treatment level.Shortexposure of seeds to high temperatures generally stimulated germination whereasprolonged exposure reduced seed germination. However, some species eventolerated 5 min treatment at 200 °C. Seedheat resistance was positively correlated with seed length and mass among thespecies. Hence, production of large seeds with protective tissues promotessurvival in fire-prone savanna areas. Also, the seeds of some species showedboth a low and a high temperature optimum which ensures that at least someseedsgerminate in the absence of fire, but also that viable seeds still remain ifsubsequent late fires kill emerging seedlings. Frequent and light burning inwooded savanna grasslands seems to stimulate and enhance germination of most ofthe studied plant species.

Influence of heat shock on cell volume regulation: protection from hypertonic challenge in a human monocyte cell line.

Heat shock response provides cells with higher tolerance against a variety of insults such as heavy metals, reperfusion injury, and endotoxin. In addition, heat treatment is known to affect ion transport mechanisms associated with vital cellular processes, including cell volume regulation. However, there has been no reports to date of a heat shock effect on cellular volume regulation itself. The aim of our study was to investigate whether the heat shock response influences volume regulation of cells. Human promonocytic U937 cells display an increase in volume in response to osmotic shrinkage. This regulatory volume increase (RVI) is mediated mainly by ion antiporters. U937 cells exposed to a temperature of 45 degrees C for 10 min (heat shock) show an enhancement of RVI after hypertonic challenge compared with untreated cells. Also, heat-treated cells display a lower intracellular pH (pHi) than untreated cells; similar control mechanisms are believed to be involved in regulating both pHi and RVI. In agreement with this, heat-shocked cells demonstrated increased activity of an HCO3(-)-independent/DIDS-sensitive pHi down-regulator, postulated to be a Cl-/HCO3- exchange. We suggest that heat shock-mediated RVI enhancement is at least partially mediated by an increased Cl-/HCO3- exchange. Our results indicate that heat shock of U937 cells activates a hitherto unknown cytoprotective effect that may help cells to overcome hypertonic challenge.

Heat shock response enhances acid tolerance of Escherichia coli O157:H7.

Escherichia coli O157:H7 (O157) has unusual acid tolerance. The influence of heat shock on acid tolerance of O157 was studied. Seven strains of O157 and E. coli K-12 were tested for their ability to survive in minimum glucose medium (pH 2.5) at 37 degrees C. The survival of heat-shocked (10 min at 48 degrees C) cells was about 10-100 times greater compared with untreated cells depending on the strain. No significant difference (P > 0.05) for O157 strain 932 was observed between heat shock-induced and acid adaptation-induced (pH 5.0) acid tolerance. Chloramphenicol prevented heat shock-induced acid tolerance, indicating the requirement of newly synthesized protein(s). Two outer membrane proteins (OMP) (22 and 15 kDa) were synthesized within 10 min of heat shock and were expressed for at least 6 h by cells held at 37 degrees C. N-terminal amino acid sequence analysis suggested that the 22 kDa OMP is a component of an alkyl hydroperoxide reductase. This protein contains a redox active disulphide, which is probably involved in H+ transport. Results indicate that sublethal heat treatment of O157 cells substantially increases their tolerance to acidic conditions. This could have practical implications for foods that receive a mild heat treatment and rely on acid as a preservative.

Influence of heat shock, drugs, and radiation on karyotype of Leishmania major.

Leishmaniasis is one of the important tropical diseases in the world. Although it is not prevalent in Korea, imported cases have been recorded. The karyotype of Leishmania sp. has been observed to be variable by localities or by strains, but the karyotype of a strain is known to be stable. This study was performed to observe if the karyotype of a Leishmania sp. would be changed under some stressful conditions. The karyotype, analyzed by pulsed field gradient gel electrophoresis, was not grossly changed by heat shock, chemotherapeutics, UV illumination, and gamma irradiation. Radiation destroyed the chromosomes mechanically, but subcultured organisms after irradiation showed unaffected karyotype. The present findings suggest that the karyotype of a Leishmania strain is so stable that it is not altered by temporary stimulation with heat, drugs, and radiation.

Heat shock factor-independent heat control of transcription of the CTT1 gene encoding the cytosolic catalase T of Saccharomyces cerevisiae

Transcription of the Saccharomyces cerevisiae CTT1 gene encoding the cytosolic catalase T has been previously shown to be derepressed by nutrient stress. To investigate whether expression of this gene is also affected by other types of stress, the influence of heat shock on CTT1 expression was studied. The results obtained show that expression of the gene is low at 23 degrees C and is induced rapidly at 37 degrees C. By deletion analysis, a promoter element necessary for high level induction by heat shock was located between base pairs -340 and -364 upstream of the translation start codon. This region was demonstrated to be sufficient for heat shock control by placing it upstream of a S. cerevisiae LEU2-lacZ fusion gene. Mutagenesis of the region showed that the response to heat shock is not mediated by a sequence similar to canonical heat shock elements, but by DNA elements also involved in nutrient control of transcription. Catalase T appears to have a function in protecting yeast cells against oxidative damage under stress conditions. Catalase T-containing strains are less sensitive to exposure to 50 degrees C ("lethal heat shock") than isogenic catalase T-deficient mutants, and catalase T-containing strains pretreated by incubation at 37 degrees C are less sensitive to H2O2 than pretreated catalase-deficient mutants.

Immunochemical study of M-HeLa cells as producers of human placental alkaline phosphatase

While analyzing M-HeLa cells by IFA technique secretory and membrane-bound forms of human placental alkaline phosphatase (HPAP) were detected. Activity of secretory HPAP increased if cell density and incubation time were increased too. After short influence of heat shock (15 min at 42 degrees C) activity of secretory HPAP increased for 45% and intracellular HPAP 3 for 37%. It is proposed that HPAP take part in organization of first response to heat shock and support cellular thermotolerance.

The influence of heat shock on the puffing pattern of Drosophila auraria polytene chromosomes

The influence of heat shock on the puffing pattern of salivary gland polytene chromosomes of D. auraria from five developmental stages was investigated. Under heat shock conditions, seven puffs appear to be transcriptionally active, five of which are active during normal development as well. Two sublines of D. auraria, differing in the activity of one of the Balbiani rings known to exist in this species, also differ clearly in the size and the transcriptional activity of a puff (64B) which is induced by heat shock in one of the sublines, but not in the other; the polytene chromosomes of the hybrids between the sublines do not exhibit this puff under heat shock conditions.

RNA synthesis in the drosophila melanogaster puffs

Autoradiographical analysis of [ 3H]-uridine incorporation into three large puffs of Drosophila melanogaster has revealed that after 1 min pulse with isotope the label is observed above the whole puff area. When puffs were induced by high temperature, RNA synthesis was sharply increased (or started) in many sites of the developing puff. No significant delay in the transport of newly-synthesized RNA in large puffs, in comparison with small ones, has been found. In regions without temperature-induced puffs RNA synthesis and its transport are apparently delayed under influence of heat shock.