Errors in heat flux measurements due to the thermal resistance of heat flux disks

Questions have been raised regarding the effect of the thermal resistance of heat flux transducers (HFTs) on the thermal flux from the skin. A model capable of simulating a large range of "tissue" insulation (variable-R model) was used to study the effect of the underlying tissue insulation on the relative error in heat flux due to the thermal resistance of the HFTs. The data show that the deviation from the true value of heat flux increases as the insulation of the underlying tissue decreases (r = 0.99, P less than 0.001). The underestimation of the heat flux through the skin measured by an HFT is minimal when the device is used on vasoconstricted skin in cool subjects (3-13% error) but becomes important when used during vasodilation in warm subjects (29-35% error) and even more important on metallic-skin mannequins (greater than 60% error).     

Nutritional needs for exercise in the heat

Although hot conditions are not typically conducive to optimal sports performance, nutritional strategies play an important role in assisting an athlete to perform as well as possible in a hot environment. A key issue is the prevention of hypohydration during an exercise session. Fluid intake strategies should be undertaken in a cyclical sequence: hydrate well prior to the workout, drink as much as is comfortable and practical during the session, and rehydrate aggressively afterwards in preparation for future exercise bouts. There is some interest in hyperhydration strategies, such as hyperhydration with glycerol, to prepare the athlete for a situation where there is little opportunity for fluid intake to match large sweat losses. Recovery of significant fluid losses after exercise is assisted by the simultaneous replacement of electrolyte losses. Carbohydrate (CHO) requirements for exercise are increased in the heat, due to a shift in substrate utilization towards CHO oxidation. Daily food patterns should focus on replacing glycogen stores after exercise, and competition strategies should include activities to enhance CHO availability, such as CHO loading for endurance events, pre-event CHO intake, and intake of sports drinks in events lasting longer than 60 min. Although CHO ingestion may not enhance the performance of all events undertaken in hot weather, there are no disadvantages to the consumption of beverages containing 4-8% CHO and electrolytes. In fact, the palatability of these drinks may enhance the voluntary intake of fluid. Although there is some evidence of increased protein catabolism and cellular damage due to production of oxygen radicals during exercise in the heat, there is insufficient evidence to make specific dietary recommendations to account for these issues.     

Convective heat transfer coefficients in the circulation

Convective heat transfer in the vessels of the circulatory system is investigated numerically. In the modeling, account is taken of the non-Newtonian rheological properties of blood and the presence of a cell-depleted plasma layer at the vessel wall. The latter is found to produce a remarkable enhancement of the heat transfer rate in the small vessels, while the effects due to the rheological behavior of blood are comparatively low. A comparison with experimental data available in the open literature is finally attempted.     

MK801 impairs thermoregulation in the heat

The effects of MK801 (dizocilpine), a glutamate NMDA receptor antagonist, on thermoregulation in the heat were studied in awake rats exposed to 40 degrees C ambient temperature until their body core temperature reached 43 degrees C. Under these conditions, MK801-treated rats exhibited enhanced locomotor activity and a steady rise in body core temperature, which reduced the heat exposure duration required to reach 43 degrees C. Since MK801-treated rats also showed increased striatal dopaminergic metabolism at thermoneutrality, the role of dopamine in the MK801-induced impairment of thermoregulation in the heat was determined using co-treatment with SCH23390, a dopamine D1 receptor antagonist. SCH23390 normalized the locomotor activity in the heat without any effect on the heat exposure duration. These results suggest that the MK801-induced impairment of thermoregulation in the heat is related to neither a dopamine metabolism alteration nor a locomotor activity enhancement.     

Local heat in the treatment of sporotrichosis

Summary After making some considerations concerning the therapeutic methods used in the treatment of sporotrichosis, the case of a 45 years old woman with numerous tumor-like dermoepidermic lesions with lymphangitic dissemination of sporotrichosis of the left leg is presented. Treatment by immersing the affected limb in a waterbath at 45° C for 30 minutes 4 times daily was performed. After the third day of treatment the lesions began to improve, and the number of colonies in the cultures decreased. After the 21th day of treatment cultures from the lesions were consistently negative. After 8 weeks of treatment the patient was discharged and a year later there have been no recurrences. The effect of temperature on this organism and the distribution of lesions in patients in the tropics are discussed.

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Resumen Después de hacer algunas consideraciones sobre los procedimientos terapéuticos utilizados en la esporotricosis, se presenta un caso de esporotricosis, con gran número de lesiones tumorales dermoepidérmicas y diseminación linfática, localizada en la pierna izquierda de una mujer de 45 años de edad.El tratamiento de esta paciente por medio de inmersión del miembro afectado en un baño de agua a 45° C durante 30 minutos 4 veces al día, determinó que desde el tercer día comenzaron a mejorar las lesiones y a disminuir el número de colonias en los cultivos tomados de las mismas. A partir del 21° día de tratamiento los cultivos sembrados con material de las lesiones fueron siempre negativos. Se consideró terminado el tratamiento al cabo de 8 semanas. Un año más tarde no se había presentado recidiva.Se hacen algunas consideraciones sobre los mecanismos de acción de los yoduros y el calor en la esporotricosis y del calor en otras enfermedades cutáneas producidas por protozoarios o por virus. Se señala el hecho de que en zonas tropicales como Centro América no se conocen casos de esporotricosis visceral u ósea.

     

Changes in the heat shock 70 kDa protein level in human neutrophils induced by heat shock

Changes in the content of constitutive and inducible proteins of the family of heat shock 70 kDa proteins (HSP70) caused by heat shock in human neutrophils, white blood cells with an atypically short lifespan, which provide a nonspecific defense of the organism against bacterial pathogens, have been studied. An analysis of the intracellular content of the constitutive and inducible HSP70 proteins by flow cytometry revealed a biphasic dynamics of changes in the protein level, which was characterized by an increase in the protein level immediately after heat shock followed by a decrease within 15–30 min after the termination of heat treatment. Because the inhibitor of protein synthesis cycloheximide did not change the dynamics profile, it was assumed that the increase in the HSP70 level is related not to the de novo synthesis of these proteins but to conformational changes of HSP70 molecules and an increased accessibility of some epitopes for antibody binding. Using a panel of antibodies specific to the N-terminal ATP-binding or the C-terminal substrate-binding domains of the protein, it was shown by cell immunofluorescence and flow cytometry that the heat shock-associated increase in the intracellular HSP70 level results from an increased efficiency of the binding of antibodies recognizing the substrate-binding domain. It was also demonstrated that the decrease in the intracellular HSP70 level after the heat shock, may be partially due to a release into the extracellular space of both the constitutive and inducible HSP70 proteins, which is regulated with the involvement of ABC-transporters.     

Characterization of the heat shock response in cultured sugarcane cells : I. Physiology of the heat shock response and heat shock protein synthesis

Effect of heat shock on the growth of cultured sugarcane cells (Saccharum officinarum L.) was measured. Heat shock (HS) treatment at 36 to 38°C (2 hours) induced the development of maximum thermotolerance to otherwise nonpermissive heat stress at 54°C (7 minutes). Optimum thermotolerance was observed 8 hours after heat shock. Development of thermotolerance was initiated by treatments as short as 30 minutes at 36°C. Temperatures below 36°C or above 40°C failed to induce maximum thermotolerance. In vivo labeling revealed that HS at 32 to 34°C induced several high molecular mass heat shock proteins (HSPs). A complex of 18 kilodalton HSPs required at least 36°C treatment for induction. The majority of the HSPs began to accumulate within 10 minutes, whereas the synthesis of low molecular mass peptides in the 18 kilodalton range became evident 30 minutes after initiation of HS. HS above 38°C resulted in progressively decreased HSP synthesis with inhibition first observed for HSPs larger than 50 kilodaltons. Analysis of two-dimensional gels revealed a complex pattern of label incorporation including the synthesis of four major HSPs in the 18 kilodalton range and continued synthesis of constitutive proteins during HS.     

Thermoregulation and thermal perception in the cold and heat before and after intermittent heat adaptation

Students wearing swim suits were exposed for 30 min to neutral room temperature (T_R=28C). During the following 60 min they were subjected to gradual decreases or increases of room temperature reaching 12C or 45C, respectively. Static thermal stimuli were applied to the palms of the right (38C) and left (25C) hands. Hands and feet of all subjects were thermally isolated at 22C ambient temperature. General thermal comfort (GTC), local thermal comfort (LTC), skin blood flow (which is proportional to heat transport index ) several body temperatures, oxygen-consumption , and sweat rate (S), were measured. After moderate intermittent heat exposures (7 times for 1h at T_R=42.5C) the experiments started again. From GTC, LTC, or as functions of T_R, no new knowledge about thermoregulatory or adaptive mechanisms was available. The high in the cold stimulated left hand, however, and the oscillatory thresholds (_OSC) for rhythmic vasomotion indicated the peripheral influence of skin temperature, as well as local, mean skin temperature (¯T_s) and core temperature. When exposed to moderate temperature decreases or increases the body seems to react only with increasing thermal resistance by vasoconstriction or an increase of sweat rate, respectively. Moderate heat adaptation is only able to raise sweat rate, but not the thresholds and gain of the S-function. We assume that functional studies of adaptive modifications in humans must be conducted at temperatures greatly beyond those used in these experiments.     

Regulation of heat shock protein 70 synthesis by heat shock in the preimplantation murine embryo

Induced thermotolerance in murine embryos occurs at the 8-cell stage when embryos are maintained in vitro but not until the blastocyst stage if development proceeds in vivo. Present results indicate that ability of embryos to undergo induced thermotolerance is not limited by heat shock protein 70 (HSP70) synthesis. Exposure of 8-cell embryos to 40 degrees C enhanced synthesis of 2 constitutive HSP70 proteins (HSC70 and HSC72) and induced another protein, HSP68; exposure of 43 degrees C was required to induce similar responses in expanded blastocysts. Unlike induced thermotolerance, increased synthesis of HSP70 molecules did not depend on whether embryos were cultured or developed in vivo. Thus, other biochemical mechanisms in addition to HSP70 confer thermotolerance in the preimplantation-stage murine embryo. The observation that the temperature threshold for induction of HSP70 synthesis increased from the 8-cell to the blastocyst stage is indicative of these other biochemical processes.