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At least 433 records · Page 24Linked to original sources
PubMed1984

Microbiological aspects of heat sterilization of medicines. II. A method for the determination of the effectiveness of a sterilization process using the bioburden and the bioburdens heat resistance.

In order to verify whether the sterilization process of 60 min at 100 degrees C for invert sugar 20% is sufficiently effective to attain the generally accepted probability of survival of maximum 1 X 10(-6), we determined the bioburden and the bioburdens heat resistance for this product. We examined 98 bottles by the membrane filtration method and found 84 bottles with 0 colony forming units (CFU's) and 14 bottles with 1-9 CFU's. Because none of the isolated CFU's was heat resistant (Bacillus species), we isolated heat resistant CFU's from the environment and determined the heat resistance in invert sugar, water and NaCl solution 0.9% of four different Bacillus species. The results in invert sugar for the most heat resistant Bacillus species were a D-value of 0.92 min at 100 degrees C. For the determination of the D-value the end-point method is the most practical one, and the D-value calculation with the most probable number method is sufficiently accurate. Because of unavoidable inaccuracies in the experimentally determined D-value, safety margins of 100% have to be taken into account in the sterilization process calculations in which these D-values are used. Hence, in our case, we have to use a D-value of 2 X 0.92 min in the sterilization process calculation for invert sugar 20%. The maximum bioburden in the examined 98 test bottles was 9 CFU's. The maximum heat resistant bioburden which must be used in sterilization process calculations may be safely fixed at 10% of the total bioburden, therefore we have to use 0.9 micro-organisms in our calculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacillus↗
PubMed2001

IbpA/B small heat-shock protein of marine bacterium Vibrio harveyi binds to proteins aggregated in a cell during heat shock.

The IbpA and IbpB are 16-kDa Escherichia coli proteins belonging to a family of small heat-shock proteins (sHsps). According to the present model, based on the in vitro experiments, sHsps are molecular chaperones that bind and prevent aggregation of nonnative proteins during heat shock. Previously, we have shown that IbpA and IbpB bind to endogenous E. coli proteins aggregated intracellularly by heat shock, which can be separated from soluble proteins and membranes in sucrose density gradients (fraction S). In this work we have found that marine bacterium Vibrio harveyi contains a single sHsp which is strongly induced by heat shock and reacts with the anti-IbpA/B serum. The 26 amino-terminal amino acids of this sHsp bear high homology to E. coli IbpA and IbpB proteins (73% and 54% identity, respectively). Fraction S was prepared from heat-shocked cells of V. harveyi, it contained high amounts of the IbpA/B protein. This result indicates that the IbpA/B protein of V. harveyi binds to the proteins that aggregate in V. harveyi cells during heat shock.

Journal Article↗
PubMed1978

Heat-induced changes of chlorophyll fluorescence in isolated chloroplasts and related heat-damage at the pigment level.

The heat-induced changes of chlorophyll fluorescence excitation and emission properties were studied in isolated chloroplasts of Larrea divaricata Cav. An analysis of the temperature dependency of fluorescence, under Fo and Fmax conditions, of temperature-jump fluorescence induction kinetics, and of 77 degrees K emission spectra of preheated chloroplasts revealed two major components in the heat-induced fluorescence changes: (1) a fluorescence rise, reflecting the block of Photosystem II reaction centers; and (2) a fluorescence decrease, caused by the functional separation of light-harvesting pigment protein complex from the rest of the pigment system. Preferential excitation of chlorophyll a around 420 nm, produced a predominant fluorescence rise. Preferential excitation of chlorophyll b, at 480 nm, gives a predominant fluorescence decrease. It is proposed that the overlapping of the fluorescence decrease on the somewhat faster fluorescence rise, results in the biphasic fluorescence rise kinetics observed in isolated chloroplasts. Both the rise component and the decay component are affected by the thermal stability of the chloroplasts, acquired during growth of the plants in different thermal environments. Mg2+ enhances the stability against heat-damage expressed in the decrease component, but has no effect on the rise component. Heat pretreatment leads to a decrease of the variable fluorescence in the light-induced 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) rise curve, but no change in half-rise time is observed. It is concluded that the block of Photosystem II reaction centers precedes the loss of the light-harvesting pigment protein complex. However, the approximately antiparallel heat-induced Fmax decrease and Fo increase suggest a common cause for the two events. A heat-induced perturbation of the thylakoid membrane is discussed.

Chlorophyll↗
PubMed1985

Role of heat loss and heat production in generation of the circadian temperature rhythm of the squirrel monkey.

To study heat production and heat loss in determination of the daily body temperature rhythm, we examined colonic temperature, skin (tail, foot and abdomen) temperatures and oxygen consumption in chair-restrained squirrel monkeys maintained in isolation in an environmental chamber with a 24-hr light-dark cycle (LD 12:12), maintained at a constant thermoneutral temperature (26 degrees C). In all experiments repeated high amplitude (2 degrees C) diurnal rhythms in colonic temperature were observed. Heat loss, estimated from changes in skin temperature, also displayed a circadian rhythm, although there was considerable variation in waveform. On average, a rhythm in heat production, indicated by changes in the rate of oxygen consumption, was also present. However, a large degree of variability was seen in oxygen consumption, and in several cycles from various animals there were no observable 24-hr rhythms. The circadian body temperature rhythm is thus not simply a consequence of daily changes in metabolism, but rather a regulated response that involves both heat production and heat loss.

Animals↗
PubMed1990

Suppressed peripheral blood lymphocyte blastogenesis in pre- and postpartal sheep by chronic heat-stress, and suppressive property of heat-stressed sheep serum on lymphocytes.

Phytohemagglutinin (PHA) and concanavalin A (Con A)-induced blastogenesis of peripheral blood lymphocytes was examined in heat-stressed pre- and postpartal sheep. The peak responses of lymphocytes to PHA and Con A in heat-stressed sheep revealed significant reduction before and after parturition compared with those in the corresponding control animals kept under thermoneutral conditions. Furthermore, the effect of serum from control or heat-stressed sheep on PHA-induced lymphocyte blastogenesis was examined. Supplementation of serum from heat-stressed sheep significantly suppressed the blastogenesis of lymphocytes obtained from healthy sheep, bovine, and human donors. Unlike dexamethasone, heat-stressed sheep serum did not inhibit IL-2 production by PHA-stimulated human peripheral blood lymphocytes. These results indicate that the immunosuppression of heat-stressed sheep is in part mediated by serum factor(s) that can modulate T-cell function in a species nonspecific manner.

Animals↗
PubMed1985

Variability of heating and cooling rates during radiant heating in a scincid lizard, Egernia cunninghami.

Heating rates were significantly greater than cooling rates in Egernia cunninghami. Male lizards had significantly slower cooling rates than females, while heating rates of both sexes were similar. Faster heating and cooling rates were recorded in the earlier months of the 32-week experiment than during the winter season. The effect of infra-red heat intensity on heating and cooling rates was apparent only in the winter months. Painting the animals black retarded the radiant heating rates, rather than enhancing them.

Animals↗
PubMed1995

A unified model for cell-killing by heat: interpretation of continuous, step-down, step-up and split heating.

We have already proposed a model for the lethal effects of heat on cells. In the model, a three-step process for cellular inactivation was hypothesized: 1) heating produces sublethal damage; 2) the damage is repaired in a certain time period; 3) the cell is inactivated when it undergoes cumulative sublethal damage to the extent that it cannot be repaired. Using the previous model, we investigated the modifications of the survival curve in 1) continuous heating, 2) step-down heating, 3) step-up heating, and 4) recovery from the thermal injury by split heating. These four phenomena were explained well with the mathematical model.

Animals↗
PubMed2005

Pronounced enhancement of glucocorticoid-induced gene expression following severe heat shock of heat-conditioned cells hints to intricate cell survival tactics.

We have previously reported that severe heat shock of HeLa cells stably transfected with a chloramphenicol acetyltransferase (CAT) gene, transcription of which is controlled by two glucocorticoid-responsive elements and a minimal promoter, pronouncedly enhanced glucocorticoid-induced CAT expression compared to that of non-heated cells, in spite of the glucocorticoid-receptor-mediated transcription of the gene being temporarily compromised by the shock. We now report that prolonged severe heat shock of properly heat-conditioned cells resulted in far more pronounced enhancement of glucocorticoid-induced CAT mRNA and protein expressions, in spite of a similar heat-induced loss of receptor-mediated CAT gene transcription. During recovery from the shock the hormonal activation of transcription exceeded that of non-heated cells. While CAT mRNA translation was restored appreciably later than CAT gene transcription, mRNA and protein expressions were thermally enhanced to a comparable extent, consistent with the integrity of CAT mRNA being preserved during recovery. CAT mRNA turnover was fully impaired during early recovery, suggesting that stabilisation of CAT mRNA as well as stimulation of the hormonal activation of CAT gene transcription account for the thermal enhancement of glucocorticoid-induced CAT expression. This data hint to cell survival tactics designed to safeguard high expression of genes of stress-enduring function.

Cell Survival↗
PubMed2000

Thermal behavior of proteins: heat-resistant proteins and their heat-induced secondary structural changes.

Most proteins are denatured by heat treatment, and the process is usually irreversible. However, some proteins, such as hyperthermophilic proteins are known to be stable even at the boiling temperature of water. We here describe a systematic investigation of thermal behavior of proteins by purifying and characterizing some heat-resistant proteins (HRPs) that are not aggregated upon heat treatment. Although most proteins were precipitated by boiling in a water bath, about 20 and 70 wt % of total proteins appeared to be heat-resistant in Jurkat T-cell lysates and human serum, respectively. We identified major HRPs from Jurkat T-cells and human serum by N-terminal amino acid sequencing and Western blot analysis. HRPs of 20 and 45 kDa (HRP20 and HRP45) were identified as alpha-synuclein and calreticulin, respectively, and HRPs of 60, 27, and 16 kDa (HRP60, HRP27, and HRP16) were identified as human serum fetuin, apolipoprotein A-I, and transthyretin, respectively. By a systematic investigation of the effect of heat on the secondary structure of the purified HRPs by circular dichroic spectroscopy, we observed four major types of thermal behavior, suggesting that the proteins could protect themselves through these pathways. Although our analysis is restricted to protein secondary structural changes, our data indicate that heat resistance of protein can be achieved in several different ways depending on the thermodynamic stability of native (N), unfolded (U), denatured (D), and intermediate (I) states.

Amino Acid Sequence↗
PubMed2002

Localized heat urticaria in a patient is associated with a wealing response to heated autologous serum.

We report a case of localized heat urticaria in a 71-year-old woman who developed weals and loss of consciousness after taking a bath. Exposing her skin to heat at 40 degrees C or immersing her hands in water at 40 degrees C produced urticarial lesions and increased her plasma histamine level. Desensitization with hot water improved her symptoms and normalized her plasma histamine level after heat challenge. An intracutaneous injection of her serum produced no reaction, while an injection of her serum that had been heated at 40 degrees C for 15 min induced a weal flare response. Further examination revealed that the weal-inducing activity of her heated serum remained for at least for 6 h and that treatment of her serum at 60 degrees C for 2 h did not abrogate its weal-inducing activity. These findings indicate that certain materials in her serum that are activated by heat are responsible for the development of her anaphylactic and urticarial reactions and that these reactions may be mediated by histamine.

Aged↗
PubMed1990

Heterogeneous radiation and heat sensitivity in vitro of human melanoma xenograft lines established from different lesions in the same patient. Comparisons with the radiation and heat sensitivity of cells isolated from the donor patient's surgical specimens.

Human melanoma xenograft lines were established in athymic nude mice (BALB/c-nu/nu/BOM) from the primary tumour (OKL-PRI), a s.c. metastasis (OKL-SCM) and a lymph node metastasis (OKL-LNM) in the same patient. The three lines differed in growth rate, melanin content, and radiation and heat sensitivity in vitro. The OKL-PRI line grew more slowly than the OKL-SCM and OKL-LNM lines and was the only line that synthesized significant amounts of melanin. The D0 values were 0.96 +/- 0.07 Gy, 0.87 +/- 0.07 Gy and 1.52 +/- 0.09 Gy (X-rays); 143 +/- 21 min, 109 +/- 12 min and 195 +/- 40 min (heat, 42.5 degrees C); and 21.3 +/- 2.7 min, 15.3 +/- 1.7 min and 26.7 +/- 3.0 min (heat, 44.5 degrees C) for the OKL-PRI, OKL-SCM and OKL-LNM line, respectively. The ranking of the lines in treatment sensitivity was equal for radiation and heat. The radiation and heat sensitivities were similar to those for cells isolated directly from the surgical specimens of the donor patient. The lines were thus established from a single neoplastic disease without artificial cloning in vitro or in vivo, and the cellular radiation and heat sensitivity did not change during the establishment procedure, suggesting that they constitute a relevant experimental model system for studies of clonal tumour heterogeneity in response to radiation and hyperthermia treatments.

Acclimatization↗
PubMed1955

The specific heat and the heat of compression of human red cells, sickled red cells, and paracrystalline rat red cells.

The investigation of two thermal properties of red cells throws some light on whether sickling is a process involving the crystallization of a relatively insoluble hemoglobin. These properties are the specific heat and the heat of compression, both of which would be expected to become numerically less if the hemoglobin of the red cell were to crystallize. In the case of paracrystalline rat red cells, which give spacings at 45 A and 58 A by x-ray diffraction, the specific heat is reduced to 85 per cent of that of the normal red cells, and the heat of compression is only about 75 per cent of that found for the normal red cell. In the case of the red cell sickled by a reduction of the O(2) tension, the specific heat and the heat of compression are substantially the same as found for the normal red cell. This is an argument against sickling being the result of a crystallization process, and supports the observation that sickled cells do not give x-ray spacings. The result is compatible, on the other hand, with sickling being the result of the formation of an oriented and birefringent gel.

Anemia, Sickle Cell↗
PubMed1988

The effect of staged burn wound closure on the rates of heat production and heat loss of burned children and young adults.

The sequential metabolic studies of nine severely burned patients were examined retrospectively. Information analyzed included heat production (M), partitioned heat loss (HL), the percentage of the body surface area open wound (% open wound) and skin (TS) and rectal (TR) temperatures. The reduction in the hypermetabolic response correlated with the number of days postburn (DPB), % open wound, average body temperature (TB = 0.8TR + 0.2TS) and evaporative heat loss (EV) (r = 0.62, 0.55, 0.56, 0.63, respectively). However, decrements in metabolic rate between sequential studies correlated only with the change in % open wound and the change in EV (r = 0.41 and 0.49, respectively). While changes in heat loss are not capable of predicting all of the variation in metabolic rate, burned patients demonstrate an increase in heat production largely secondary to the inability to conserve heat effectively in the periphery. This response is compounded by an altered central thermoregulation.

Adolescent↗
PubMed1989

Interaction of the fluorescent dye 1-N-phenylnaphthylamine with Escherichia coli cells during heat stress and recovery from heat stress.

The fluorescent dye 1-N-phenylnaphthylamine permeated Escherichia coli cells after exposure to a heat stress at 55 degrees C in Tris/Mg2+ buffer, pH 8.0. The rate of dye permeation increased with time during heat treatment and decreased gradually during subsequent incubation at 37 degrees C in a minimal medium. The initial level of rapid adsorption of the dye also increased with heating time, although it remained roughly constant during post-heating incubation. The results obtained suggest that the permeability barrier to the dye in the outer membrane was damaged by heat stress and was repaired after sublethal heating. RNA, protein and lipid syntheses, as well as an energy-yielding process, appeared to be necessary for the repair of impermeability to the dye.

1-Naphthylamine↗
PubMed1996

Heat-Shock Response in Heat-Tolerant and Nontolerant Variants of Agrostis palustris Huds.

The heat-shock response in heat-tolerant variants (SB) and non-tolerant variants (NSB) of creeping bentgrass (Agrostis palustris Huds.) was investigated. Both variants were derived from callus initiated from a single seed of the cultivar Penncross. SB and NSB synthesized heat-shock proteins (HSPs) of 97, 83, 70, 40, 25, and 18 kD. There were no major differences between SB and NSB in the time or temperature required to induce the heat-shock response. When the HSPs synthesized by SB and NSB were analyzed by two-dimensional gel electrophoresis, it was apparent that SB synthesized two to three additional members of the HSP27 family, which were smaller (25 kD) and more basic than those synthesized by NSB. Analysis of F1 progeny of NSB x SB indicated that 7 of the 20 progeny did not synthesize the additional HSP25 polypeptides. These progeny were significantly less heat tolerant than progeny that did synthesize the additional HSP25 polypeptides. The X2 test of independence (X2 = 22.45, P < 0.001) indicated that heat tolerance and the presence of the additional HSP25 polypeptides are linked traits.

Journal Article↗
PubMed1997

Tissue-Type-Specific Heat-Shock Response and Immunolocalization of Class I Low-Molecular-Weight Heat-Shock Proteins in Soybean.

A monospecific polyclonal antibody was used to study the tissue-type specificity and intracellular localization of class I low-molecular-weight (LMW) heat-shock proteins (HSPs) in soybean (Glycine max) under different heat-shock regimes. In etiolated soybean seedlings, the root meristematic regions contained the highest levels of LMW HSP. No tissue-type-specific expression of class I LMW HSP was detected using the tissue-printing method. In immunolocalization studies of seedlings treated with HS (40[deg]C for 2 h) the class I LMW HSPs were found in the aggregated granular structures, which were distributed randomly in the cytoplasm and in the nucleus. When the heat shock was released, the granular structures disappeared and the class I LMW HSPs became distributed homogeneously in the cytoplasm. When the seedlings were then given a more severe heat shock following the initial 40[deg]C -> 28[deg]C treatment, a large proportion of the class I LMW HSPs that originally localized in the cytoplasm were translocated into the nucleus and nucleolus. Class I LMW HSPs may assist in the resolubilization of proteins denatured or aggregated by heat and may also participate in the restoration of organellar function after heat shock.

Journal Article↗
PubMed1997

Recovery from Heat Shock in Heat-Tolerant and Nontolerant Variants of Creeping Bentgrass.

Recovery from the heat-shock response was tested in heat-tolerant (selected bentgrass [SB]) and nontolerant (nonselected bentgrass [NSB]) variants of creeping bentgrass (Agrostis palustris Huds.) SB increased incorporation of radioactive amino acids into protein 2 h earlier than NSB when leaf blades were incubated at the recovery temperature following heat shock. Electrophoresis indicated that heat-shock protein (HSP) synthesis decreased and normal protein synthesis increased at 4 h in SB and at 6 to 8 h in NSB. Increased synthesis of normal proteins was not due to increased abundance of normal mRNAs, which were equivalent in SB and NSB at 4 h. But at 4 h, more of the normal mRNA population was associated with polysomes in SB than in NSB. Synthesis of HSP70 and HSP18 decreased earlier in SB than in NSB. The decreased synthesis of these HSPs appeared to be correlated with decreased mRNA abundance. But at 4 h, some of the HSP18 mRNA may have been associated with heat-shock granules in SB. Synthesis of HSP25 continued through the 8-h recovery in both variants. Although the abundance of HSP25 was equivalent in SB and NSB during heat shock and recovery, more HSP25 mRNA was associated with polysomes in SB than in NSB.

Journal Article↗
PubMed2003

Heat transfer from protein crystals: implications for flash-cooling and X-ray beam heating.

Three problems involving heat transfer from a protein crystal to a cooling agent are analyzed: flash-cooling in a cold nitrogen- or helium-gas stream, plunge-cooling into liquid nitrogen, propane or ethane and crystal heating in a cold gas stream owing to X-ray absorption. Heat transfer occurs by conduction inside the crystal and by convection from the crystal's outer surface to the cooling fluid. For flash-cooling in cold gas streams, heat transfer is limited by the rate of external convection; internal temperature gradients and crystal strains during cooling are very small. Helium gas provides only a threefold improvement in cooling rates relative to nitrogen because its much larger thermal conductivity is offset by its larger kinematic viscosity. Characteristic cooling times vary with crystal size L as L(3/2) and theoretical estimates of these times are consistent with experiments. Plunge-cooling into liquid cryogens, which can give much smaller convective thermal resistances provided that surface boiling is eliminated, can increase cooling rates by more than an order of magnitude. However, the internal conduction resistance is no longer negligible, producing much larger internal temperature gradients and strains that may damage larger crystals. Based on this analysis, factors affecting the success of flash-cooling experiments can be ordered from most to least important as follows: (1) crystal solvent content and solvent composition, (2) crystal size and shape, (3) amount of residual liquid around the crystal, (4) cooling method (liquid plunge versus gas stream), (5) choice of gas/liquid and (6) relative speed between cooling fluid and crystal. Crystal heating by X-ray absorption on present high-flux beamlines should be small. For a fixed flux and illuminated area, heating can be reduced by using crystals with areas normal to the beam that are much larger than the beam area.

Algorithms↗