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At least 793 records · Page 44Linked to original sources
PubMed1986

Ecdysterone and heat shock induction of transfecting and endogenous heat shock genes in cultured Drosophila cells.

Various combinations of the heat shock genes of Drosophila melanogaster are transcribed in response to elevated temperature and also during normal development and in certain ecdysterone-treated Drosophila cell lines. Here I describe an homologous transient expression system using Schneider 3 cells, a Drosophila line responsive to ecdysterone. I compare the constitutive, ecdysterone and heat shock-induced accumulation of transcripts of five transfecting heat shock genes (hsp82, hsp70, hsp28, hsp26 and hsp23) to the accumulation of transcripts of their endogenous counterparts. The pattern of expression of the transfecting genes under these various conditions is generally similar to that of the endogenous genes.

Animals↗
PubMed1987

High molecular weight heat-stable alkaline proteinase from white croaker and chum salmon muscle: comparison of the activating effects by heating and urea.

Effects of heating and urea on the heat-stable alkaline proteinase from white croaker and chum salmon muscle were compared in order to know the regulating mechanism of the proteinase. Chum salmon proteinase required a higher temperature for activity and was more heat-stable than white croaker proteinase. In the presence of 5M urea, the activity was observed to some degree at 37 degrees C only in white croaker proteinase, while both proteinases lost their activities at usual assay temperature around 60 degrees C. These results suggest that the stability of the regulatory and catalytic subunits of the proteinases is somewhat different among fish species.

Animals↗
PubMed2006

Calibration in isothermal titration calorimetry: heat and cell volume from heat of dilution of NaCl(aq).

An isothermal titration calorimeter of the perfusion type (MicroCal model VP-ITC) is calibrated using the heat of dilution of NaCl in water. The relative apparent molar enthalpy function (L(phi)) for NaCl(aq) varies strongly and nonlinearly with concentration in the low-concentration region (<0.2M) that is sampled easily and extensively in a single program of injections of NaCl solution into water. This nonlinearity makes it possible to calibrate with respect to two quantities: the measured heat and the active cell volume. The heat factor is determined with typical standard error 0.003; its value in the current case is 0.987. The cell volume factor is 0.93 but is quite sensitive to possible systematic errors in the temperature and in the literature values for L(phi). Both correction factors are closely tied to the delivered volume from the injection syringe, which required a correction factor of 0.973, attributed to an instrumental gear ratio error. Temperature calibration of the instrument showed a small offset of 0.12K at the temperature 25 degrees C of the experiments, but the error increased to more than 1K at 46 degrees C. The experiments were not able to distinguish clearly between mixing algorithms that assume instantaneous mixing on injection and those that assume instantaneous injection followed by mixing; however, examination of these algorithms has revealed an error in a program widely used to analyze isothermal titration calorimetry data.

Algorithms↗
PubMed2001

Heat does not come in different colours: entropy-enthalpy compensation, free energy windows, quantum confinement, pressure perturbation calorimetry, solvation and the multiple causes of heat capacity effects in biomolecular interactions.

Modern techniques in microcalorimetry allow us to measure directly the heat changes and associated thermodynamics for biomolecular processes in aqueous solution at reasonable concentrations. All these processes involve changes in solvation/hydration, and it is natural to assume that the heats for these processes should reflect, in some way, such changes in solvation. However, the interpretation of data is still somewhat ambiguous, since different non-covalent interactions may have similar thermodynamic signatures, and analysis is frustrated by large entropy-enthalpy compensation effects. Changes in heat capacity (Delta C(p)) have been related to changes in hydrophobic hydration and non-polar accessible surface areas, but more recent empirical and theoretical work has shown how this need not always be the case. Entropy-enthalpy compensation is a natural consequence of finite Delta C(p) values and, more generally, can arise as a result of quantum confinement effects, multiple weak interactions, and limited free energy windows, giving rise to thermodynamic homeostasis that may be of evolutionary and functional advantage. The new technique of pressure perturbation calorimetry (PPC) has enormous potential here as a means of probing solvation-related volumetric changes in biomolecules at modest pressures, as illustrated with preliminary data for a simple protein-inhibitor complex.

Calorimetry↗
PubMed2000

Expression of heat shock protein 60 in human proximal tubule cells exposed to heat, sodium arsenite and CdCl(2).

The expression of hsp 60 mRNA and protein were determined in human proximal tubule cells (HPT) exposed to lethal and sub-lethal concentrations of Cd(2+) under both acute and extended conditions of exposure. It was demonstrated that HPT cells exhibited the classic heat shock response when subjected to a physical (heat) or chemical stress (sodium arsenite). Heat stress, elevated temperature at 42.5 degrees C for 1 h, caused an increase in both hsp 60 mRNA and protein following removal of the stress. Similar results were obtained when the cells were subjected to a classic chemical stress of exposure to 100 microM sodium arsenite for 4 h. Acute exposure of HPT cells to 53.4 microM CdCl(2) for 4 h also resulted in an increase in hsp 60 mRNA and protein following removal of the metal. An extended exposure to Cd(2+) was modeled by treating the cells continuously with Cd(2+) at both lethal and sub-lethal levels over a 16-day time course. It was demonstrated that chronic exposure to Cd(2+) failed to increase either hsp 60 mRNA or protein expression in HPT cells, even at concentrations of Cd(2+) that were lethal to the cells during the time course. In fact, hsp 60 protein levels were decreased compared to controls at lethal levels of Cd(2+) exposure. These findings suggest that hsp 60 expression may have two distinct roles when the human proximal tubule cell is exposed to Cd(2+). A protective role through hsp 60 induction when the proximal tubule cell is acutely exposed to Cd(2+) and a deleterious role when hsp 60 protein is down-regulated during extended exposure to Cd(2+).

Arsenites↗
PubMed1999

Capillary gas chromatographic detection of invert sugar in heated, adulterated, and adulterated and heated apple juice concentrates employing the equilibrium method.

The equilibrium method is introduced for the detection of invert sugar addition to apple juice. The method consists of a pre-equilibration of the sample with dry pyridine at 50 degrees C for 20 min followed by the addition of trimethylsilylimidazole and heating at 75 degrees C for 40 min. The resulting derivatized carbohydrates are then analyzed by capillary gas chromatography. This method was successfully used by independent laboratories to distinguish heated pure, intentionally adulterated (with invert sugar), and intentionally adulterated and then heated apple juice concentrates. The equilibrium method was shown to give significantly lower coefficients of variation for this sample set when compared to the original capillary gas chromatographic method. In addition, these results indicate that it may also be an effective method for the detection of medium invert sugar, depending on the level of the fingerprint oligosaccharides in this sweetener.

Beverages↗
PubMed2001

The ability of heat-killed Mycobacterium vaccae to stimulate a cytotoxic T-cell response to an unrelated protein is associated with a 65 kilodalton heat-shock protein.

Exogenous antigens are generally presented by Class II major histocompatibility (MHC) molecules. When administered with an adjuvant, however, they are capable of inducing a CD8+ T-cell response where antigen recognition is associated with Class I MHC. Accordingly, immunization with soluble ovalbumin (OVA) alone does not activate CD8+ cytotoxic T cells (CTL) but when given in complete Freund's adjuvant (CFA), or in formulations of a number of novel adjuvants, an OVA-specific CD8+ CTL response can be detected. We show in this report that immunization with soluble OVA mixed with heat-killed Mycobacterium vaccae, but not with other common pathogenic and saprophytic mycobacteria, can activate OVA-specific CD8+ CTL. An OVA-specific CTL response is detected when mice are immunized by either the intraperitoneal or intranasal route and their spleen cells are re-stimulated in vitro. Adjuvant activity of heat-killed M. vaccae is present in M. vaccae culture filtrate, in soluble protein components of whole M. vaccae and in the 65 kDa heat-shock protein (hsp) of M. vaccae. Mycobacterium vaccae has previously been shown to have no adverse side-effects in humans. The current results suggest that M. vaccae may be useful as an adjuvant for vaccines and other immunotherapies where CD8+ CTL responses to exogenous proteins are crucial.

Adjuvants, Immunologic↗
PubMed2006

Thermal performance assessment of heat resistant fabrics based on a new thermal wave model of skin heat transfer.

A thermal wave skin model incorporating surface heat flux from a skin simulant sensor is developed to characterize the thermal performance of heat resistant fabrics covering the skin simulant sensor. Comparisons of time to 2nd-degree skin burn and temperature elevation of skin beneath a layer of fabric between the Pennes' equation and the newly developed thermal wave skin model are performed in this research. Results of tolerance time from the Stoll criterion method are also compared with those from 2 skin models in a thermal protective performance calorimeter. It is concluded that the thermal properties of heat resistant fabrics can be characterized more precisely than previously.

Alberta↗
PubMed1975

Analytical calculation of the skin temperature distribution due to subcutaneous heat production in a spherical heat source.

An analytical solution of the thermal conductivity equation describing the surface temperature distribution over a buried heat source is given in tabular form. The solution is applicable to experimental models for studies of the surface temperature over an implanted artificial heat source. The results can also be used for the analysis of the skin temperature over biological heat sources such as breat tumours.

Body Temperature Regulation↗
PubMed2004

Influence of angle between the nozzle and skin surface on the heat flux and overall heat extraction during cryogen spray cooling.

High speed video imaging and an inverse heat conduction problem algorithm were used to observe and measure the effect of the angle between the nozzle and surface of a skin phantom on: (a) surface temperature; (b) heat flux q; and (c) overall heat extraction Q during cryogen spray cooling (CSC). A skin phantom containing a fast-response temperature sensor was sprayed with 50 ms cryogen spurts from a commercial nozzle placed 30 mm from the surface. The nozzle was systematically positioned at angles ranging from 5 to 90 degrees (perpendicular) with respect to the phantom surface. It is shown that angles as low as 15 have an insignificant impact on the surface temperature, q and Q. Only exaggerated angles of 5 show up to 10% lower q and 30% lower Q with respect to the maximal values measured when nozzles are aimed perpendicularly. This study proves that the slight angle that many commercial nozzles have does not affect significantly the CSC efficiency.

Algorithms↗
PubMed2001

Performance of heated humidifiers with a heated wire according to ventilatory settings.

Delivering warm, humidified gas to patients is important during mechanical ventilation. Heated humidifiers are effective and popular. The humidifying efficiency is influenced not only by performance and settings of the devices but the settings of ventilator. We compared the efficiency of humidifying devices with a heated wire and servo-controlled function under a variety of ventilator settings. A bench study was done with a TTL model lung. The study took place in the laboratory of the University Hospital, Osaka, Japan. Four devices (MR290 with MR730, MR310 with MR730; both Fisher & Paykel, ConchaTherm IV; Hudson RCI, and HummaxII; METRAN) were tested. Hummax II has been developed recently, and it consists of a heated wire and polyethylene microporous hollow fiber. Both wire and fiber were put inside of an inspiratory circuit, and water vapor is delivered throughout the circuit. The Servo 300 was connected to the TTL with a standard ventilator circuit. The ventilator settings were as follows; minute ventilation (V(E)) 5, 10, and 15 L/min, a respiratory rate of 10 breaths/min, I:E ratio 1:1, 1:2, and 1:4, and no applied PEEP. Humidifying devices were set to maintain the temperature of airway opening at 32 degrees C and 37 degrees C. The greater V(E) the lower the humidity with all devices except Hummax II. Hummax II delivered 100% relative humidity at all ventilator and humidifier settings. When airway temperature control of the devices was set at 32 degrees C, the ConchaTherm IV did not deliver 30 mg/L of vapor, which is the value recommended by American National Standards at all V(E) settings. At 10 and 15 L/min of V(E) settings MR310 with MR730 did not deliver recommended vapor, either. In conclusion, airway temperature setting of the humidifying devices influenced the humidity of inspiratory gas greatly. Ventilatory settings also influenced the humidity of inspiratory gas. The Hummax II delivered sufficient water vapor under a variety of minute ventilation.

Equipment Design↗
PubMed1994

Heat shock-induced repression of proteolysis: poly(A)-binding protein degradation patterns can illusorily suggest its specific loss during heat shock.

Poly(A)-binding protein (PABP) is highly susceptible to proteolysis during cell lysis of Drosophila tissue culture cells unless substantial amounts of proteolysis inhibitors are included in the extraction buffer. This intrinsic proteolytic activity is substantially reduced during heat shock. An artifactual appearance that poly(A)-binding protein is specifically degraded by heat shock can result. Several contradictory descriptions of PABP may also be related to its proteolysis. Repression of proteolysis is likely to reflect a physiologically significant regulatory event, based on recent examinations of HSP70 stability during and after heat shock.

Animals↗
PubMed2000

Effects of changes in packed cell volume on the specific heat capacity of blood: implications for studies measuring heat exchange in extracorporeal circuits.

Extracorporeal circuits such as cardiopulmonary bypass (CPB) and renal dialysis machines cause active and/or passive loss of body heat. Attempts to quantify this heat loss are generally based on the Fick principle which requires knowledge of the specific heat capacity (SHC) of blood. As changes in packed cell volume are common, we investigated the effect of these changes on the SHC of blood over a range of packed cell volumes (PCV) from whole blood at 43.1% (3594 J kg-1 degrees C-1) to pure Hartmann's solution (4153 J kg-1 degrees C-1). The SHC of other fluids used during CPB was also measured and found to be 4139 J kg-1 degrees C-1 and 4082 J kg-1 degrees C-1 for normal saline and Gelofusine, respectively. The maximum variability in SHC over the range of PCV values encountered during CPB was calculated to be small (5.5%). We conclude that use of a constant value of SHC for calculation of thermal energy transfer is currently justified.

Blood Physiological Phenomena↗
PubMed2000

Performance of discrete heat engines and heat pumps in finite time

The performance in finite time of a discrete heat engine with internal friction is analyzed. The working fluid of the engine is composed of an ensemble of noninteracting two level systems. External work is applied by changing the external field and thus the internal energy levels. The friction induces a minimal cycle time. The power output of the engine is optimized with respect to time allocation between the contact time with the hot and cold baths as well as the adiabats. The engine's performance is also optimized with respect to the external fields. By reversing the cycle of operation a heat pump is constructed. The performance of the engine as a heat pump is also optimized. By varying the time allocation between the adiabats and the contact time with the reservoir a universal behavior can be identified. The optimal performance of the engine when the cold bath is approaching absolute zero is studied. It is found that the optimal cooling rate converges linearly to zero when the temperature approaches absolute zero.

Journal Article↗
PubMed2003

Adiabatic heating and convection caused by a fixed-heat-flux source in a near-critical fluid.

Dynamics and heat transfer in a near-critical fluid in a square cavity with a finite heat source located at the bottom are studied numerically. A thermally insulated enclosure and a fixed-heat-flux source are considered. The two-dimensional simulation is based on the full Navier-Stokes equations with two-scale splitting of the pressure and the van der Waals equation of state. It is shown that the piston effect is independent of convection. Near the critical point, this effect becomes independent of criticality and convective motions are damped.

Journal Article↗
PubMed1993

Biliverdin reductase is heat resistant and coexpressed with constitutive and heat shock forms of heme oxygenase in brain.

Two heme oxygenase (HO) isozymes--HO-1, which is a heat shock protein (HSP32), and HO-2--catalyze the isomer-specific production of biliverdin IX alpha and carbon monoxide. The latter has the potential of functioning as a neurotransmitter, whereas the reduced form of biliverdin, bilirubin, has potent antioxidant activity. Formation of bilirubin is catalyzed by biliverdin reductase (BVR). The reductase is a unique enzyme in being dual pyridine nucleotide and dual pH dependent. Here, we show that the reductase is resistant to thermal stress at both the protein and message level. We further demonstrate that the reductase is coexpressed in cells that display HO-1 and/or HO-2 under normal conditions, as well as in regions and cell types that have the potential to express heat shock-inducible HO-1 protein. Exposure of male rats to 42 degrees C for 20 min did not decrease brain BVR activity, but caused a slight increase in NADPH- and NADH-dependent activities at 1 and 6 h following hyperthermia. High levels of the approximately 1.5-kb BVR mRNA were detected in control brain; it too displayed thermal tolerance. Similarly, the pattern of multiplicity of net charge variants of the enzyme purified from brain of heat-shocked rats did not differ from the control pattern. Immunochemical localization of BVR protein in normal brain correlated well with the presence of HO-1 and/or HO-2 throughout the forebrain, diencephalon, cerebellum, and brainstem regions. There were select neuronal and nonneuronal cells in the substantia nigra and cerebellum that did express the reductase under normal conditions, wherein no HO isozymes could be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Modelling the influence of the incubation temperature upon the estimated heat resistance of heated bacillus spores.

AIMS: In this study, the influence of the incubation temperature on the D-values was described according to a simple Bigelow-like model. METHODS: Model parameters were estimated from different sets of data from the literature and from our own data. For different Bacillus species and heat-treatment conditions, the influence of the recovery temperature was quantified and the optimal recovery temperature was determined. RESULTS: The impacts of species, bacterial strains belonging to the same species, heat-treatment temperature and composition of recovery media on the model parameters were analysed. The optimum recovery temperatures differ greatly from one species to another; however, no difference appears clearly between strains belonging to the same species. D values were significantly affected by recovery temperature. This influence of recovery temperature was dependent on the species, and affected by the composition of recovery media but not by the heating temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: The developed model could be useful for determining the optimal incubation temperature and quantifying the weight of the recovery temperature influence for safe security control in the canning industry.

Bacillus↗