Control of local heat gain by vasomotor response of the hand

Finger blood flow (BF) was measured by venous occlusion plethysmography using mercury-in-Silastic strain gauges during immersion of one hand in hot water (raised by steps of 2 degrees C every 10 min from 35 to 43 degrees C), the other being a control (kept immersed in water at 35 degrees C). The measurements were made in three different thermal states on separate days: 1) cool-25 degrees C, 40% rh, esophageal temperature (Tes) = 36.64 +/- 0.10 degrees C; 2) warm-35 degrees C, 40% rh, Tes = 36.71 +/- 0.11 degrees C; and 3) hot-35 degrees C, 80% rh with the legs immersed in water at 42 degrees C, Tes = 37.26 +/- 0.11 degrees C. When water temperature was raised at 42 degrees C, Tes = 37.26 +/- 0.11 When water temperature was raised to 39-41 degrees C in the warm state, finger BF in the hand heated locally (BFw) decreased. When water temperature was raised to 43 degrees C, however, BFw returned to the control value. In the hot state, Tes rose steadily, reaching 37.90 +/- 0.12 degrees C at the end of the 50-min sessions. BF in the control finger also increased gradually during the session. BFw showed a tendency to decrease when water temperature was raised to 39 degrees C, but the change was not greater than that observed in the warm state. In the cool state, no such reduction in BFw was observed when water temperature was raised to 39-41 degrees C. On the contrary, BFw increased at water temperatures of 41-43 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Temperature influence on stimulated PMN respiratory burst.

Body temperature can modulate the pathogenesis of infectious, metabolic and autoimmune diseases. This effect has been attributed to several hypothesized mechanisms. Body temperature could play an important role in influencing some cellular functions of human white blood cells. In this work we examined the temperature effect on the respiratory burst in human neutrophils. Human polymorphonuclear leucocytes (PMN) were obtained from heparinized venous blood by dextran sedimentation and erythrocyte lysis with NH4Cl (0.87%). Granulocytes were stimulated with opsonized zymosan (OZ), formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate (PMA), and monosodium urate (MSU) crystals at different temperatures (26, 37, 39, 40, 42 degrees C). The technique of luminol dependent chemiluminescence (CL) was used as indicator of oxygen free radicals (OFR) release by stimulated cells. OFR production from PMN stimulated with OZ, PMA, FMLP was higher at 37 degrees C than at 26, 39, 40, 42 degrees C (p < 0.001 OZ stimulated PMN at 40-42 degrees C; p < 0.05 PMA stimulated PMN at 42 degrees C. Significantly different from 37 degrees C value). OFR release from PMN stimulated with MSU crystals was significantly increased at 39 degrees C compared to 37 degrees C value (p < 0.001). This effect could not only be attributed to temperature influence on neutrophil activity. The specific polymorphonuclear leukocyte response to the microcrystals and the temperature influence on chemical and physical characteristics of the crystals may play an important role. We are now studying the temperature effect on activity of PMN exposed to others crystals.     

Human whole-blood oxygen affinity: effect of temperature

phe effect of temperature changes on human whole-blood O2 affinity was measured in the blood of six healthy donors over almost the entire O2 saturation (SO2) range (1-99%). The results showed that temperature has no influence on the shape of the O2 dissociation curve, implying that the temperature coefficient (delta log PO2/delta T) is independent of SO2. Simultaneous measurements of the total (proton) Haldane factor (delta[HbH]/[delta HbO2]) at the five temperatures under study (22, 27, 32, 37, and 42 degrees C) revealed that this factor depends on temperature. The liberation of protons from hemoglobin appeared to be linear with respect to changes in SO2. We therefore conclude that the (proton) Bohr factor (H+ factor) is dependent on temperature over the entire SO2 range in the same way as previously described for SO2 = 50%. The exothermic oxygenation reaction in whole blood was accompanied by a heat evolution (delta HO2) of 42.7 kJ/mol (monomeric) hemoglobin.     

Decrease in heart rates by artificial CO2 hot spring bathing is inhibited by beta1-adrenoceptor blockade in anesthetized rats.

To investigate the effects of carbon dioxide (CO2) hot spring baths on physiological functions, head-out immersion of urethane-anesthetized, fursheared male Wistar rats was performed. Animals were immersed in water (30 or 35 degrees C) with high-CO2 content ( approximately 1,000 parts/million; CO2-water). CO2-water for bathing was made by using an artificial spa maker with normal tap water and high-pressure CO2 from a gas cylinder. When a human foot was immersed for 10 min in the CO2-water at 35 degrees C, the immersed skin reddened, whereas skin color did not change in normal tap water at the same temperature. Arterial blood pressure, heart rate (HR), underwater skin tissue blood flow, and temperatures of the colon and immersed skin were continuously measured while animals were immersed in a bathtub of water for approximately 30 min at room temperature (26 degrees C). Immersed skin vascular resistance, computed from blood pressure and tissue blood flow, was significantly lower in the CO2-water bath than in tap water at 30 degrees C, but no differences were apparent at 35 degrees C. HR of rats in CO2-water was significantly slower than in tap water at 35 degrees C. Decreased HR in CO2-water was inhibited by infusion of atenolol (beta1-adrenoceptor blocker), but it was unaffected by atropine (muscarinic cholinoceptor blocker). Theses results suggest that bradycardia in CO2 hot spring bathing is caused by inhibition of the cardiac sympathetic innervation. This CO2-water maker should prove a useful device for acquiring physiological evidence of balneotherapy.     

Does the direct effect of atmospheric CO2 concentration on leaf respiration vary with temperature? Responses in two species of Plantago that differ in relative growth rate

The objective of this study was to investigate the direct effect of elevated atmospheric CO2 concentrations on leaf respiration in darkness (R) over a broad range of measurement temperatures. Our aim was to further elucidate the underlying mechanism(s) of the often-reported inhibition of leaf R by a doubling of the atmospheric CO2 concentration. Experiments were conducted using two species of Plantago that differed in maximum relative growth rate (fast-growing Plantago lanceolata L. and the slow-growing P. euryphylla Briggs, Carolin & Pulley). Rates of leaf respiration (R) were measured at atmospheric CO2 concentrations ranging from 75 to 2000 &mgr;mol mol-1 at temperatures from 12 to 42 degrees C. R was measured as CO2 release with a portable gas exchange system with infrared gas analysers. Our hypothesis was that the changes in temperature alter the flux coefficient (i.e. the extent to which changes in potential enzyme activity has an effect on the rate of a reaction) of enzymes potentially affected by CO2. Initial analysis of our results suggested that R was inhibited by elevated CO2 in both species, with the apparent degree of inhibition being greatest at low temperature. Moreover, the apparent degree of inhibition following a doubling of atmospheric CO2 concentration from 350 to 700 &mgr;mol mol-1 was similar to that reported by several previous studies (approximately 14% and 26% for P. lanceolata and P. euryphylla, respectively) at a temperature equal to the mean of the previous studies. However, subsequent correction for diffusion leaks of CO2 across the gas exchange's cuvette gaskets revealed that no significant inhibition had occurred in either species, at any temperature. The inhibitory effect of elevated CO2 on leaf respiratory CO2 release reported by previous studies may therefore have been overestimated.     

Cryopreservation of isolated hepatocytes: intracellular ice formation under various chemical and physical conditions.

Kinetics of intracellular ice formation (IIF) for isolated rat hepatocytes was studied using a cryomicroscopy system. The effect of the cooling rate on IIF was investigated between 20 and 400 degrees C/min in isotonic solution. At 50 degrees C/min and below, none of the hepatocytes underwent IIF; whereas at 150 degrees C/min and above, IIF was observed throughout the entire hepatocyte population. The temperature at which 50% of hepatocytes showed IIF (50TIIF) was almost constant with an average value of -7.7 degrees C. Different behavior was seen in isothermal subzero holding temperatures in the presence of extracellular ice. 50TIIF from isothermal temperature experiments was approximately -5 degrees C as opposed to -7.7 degrees C for constant cooling rate experiments. These experiments clearly demonstrated both the time and temperature dependence of IIF. On the other hand, in cooling experiments in the absence of extracellular ice, IIF was not observed until approximately -20 degrees C (at which temperature the whole suspension was frozen spontaneously) suggesting the involvement of the external ice in the initiation of IIF. The effect of dimethyl sulfoxide (Me2SO) on IIF was also quantified. 50TIIF decreased from -7.7 degrees C in the absence of Me2SO to -16.8 degrees C in 2.0 M Me2SO for a cooling rate of 400 degrees C/min. However, the cooling rate (between 75 and 400 degrees C/min) did not significantly affect 50TIIF (-8.7 degrees C) in 0.5 M Me2SO. These results suggest that multistep protocols will be required for the cryopreservation of hepatocytes.     

Human whole-blood O2 affinity: effect of CO2

The proton Bohr factor (phi H = alpha log PO2/alpha pH), the carbamate Bohr factor (phi C = alpha log PO2/alpha log PCO2), the total Bohr factor (phi HC = d log PO2/dpH[base excess) and the CO2 buffer factor (d log PCO2/dpH) were determined in the blood of 12 healthy donors over the whole O2 saturation (SO2) range. All three Bohr factors proved to be dependent on SO2, although to a lesser extent than reported in some of the recent literature. At SO2 = 50% and 37 degrees C, we found phi H = -0.428 +/- 0.010 (SE), phi C = 0.054 +/- 0.006, and phi HC = -0.488 +/- 0.007. The values obtained for phi H, phi C, and d log PCO2/dpH were used to calculate phi HC. Calculated and measured values of phi HC proved to be in good agreement. In an additional series of 12 specimens of human blood we determined the influence of PCO2 on phi H and the influence of pH on phi C. At SO2 = 50%, phi H varied from -0.49 +/- 0.009 at PCO2 = 15 Torr to -0.31 +/- 0.010 at PCO2 = 105 Torr and phi C from 0.157 +/- 0.015 at pH = 7.80 to 0.006 +/- 0.009 at pH = 7.00. When on the basis of these data a second-order term is taken into account, a still slightly better agreement between measured and calculated values of phi HC can be attained.     

Cryopreservation of umbilical cord blood: 2. Tolerance of CD34(+) cells to multimolar dimethyl sulphoxide and the effect of cooling rate on recovery after freezing and thawing

Cryopreservation protocols for umbilical cord blood have been based on methods established for bone marrow (BM) and peripheral blood stem cells (PBSC). The a priori assumption that these methods are optimal for progenitor cells from UCB has not been investigated systematically. Optimal cryopreservation protocols utilising penetrating cryoprotectants require that a number of major factors are controlled: osmotic damage during the addition and removal of the cryoprotectant; chemical toxicity of the cryoprotectant to the target cell and the interrelationship between cryoprotectant concentration and cooling rate. We have established addition and elution protocols that prevent osmotic damage and have used these to investigate the effect of multimolar concentrations of Me(2)SO on membrane integrity and functional recovery. We have investigated the effect of freezing and thawing over a range of cooling rates and cryoprotectant concentrations. CD34(+) cells tolerate up to 60 min exposure to 25% w/w (3.2M) Me(2)SO at +2 degrees C with no significant loss in clonogenic capacity. Exposure at +20 degrees C for a similar period of time induced significant damage. CD34(+) cells showed an optimal cooling range between 1 degrees C and 2.5 degrees C/min. At or above 1 degrees C/min, increasing the Me(2)SO concentration above 10% w/w provided little extra protection. At the lowest cooling rate tested (0.1 degrees C/min), increasing the Me(2)SO concentration had a statistically significant beneficial effect on functional recovery of progenitor cells. Our findings support the conclusion that optimal recovery of CD34(+) cells requires serial addition of Me(2)SO, slow cooling at rates between 1 degrees C and 2.5 degrees C/min and serial elution of the cryoprotectant after thawing. A concentration of 10% w/w Me(2)SO is optimal. At this concentration, equilibration temperature is unlikely to be of practical importance with regard to chemical toxicity.     

Effect of temperature dependent changes in mechanical stability of red cell aggregates on relative apparent whole blood viscosity

As the temperature dependence of relative apparent whole blood viscosity eta rel is still controversial, the relation between the temperature dependence of red cell aggregation (RCA) and that of eta rel was examined in normal donors and in patients with venous ulcers of the leg. Apparent whole blood viscosity was measured in the DEER-rheometer (0.01 Pa less than tau less than 2.9 Pa) at 10 degrees C, 20 degrees C, 30 degrees C and 37 degrees C. The instrument was calibrated for each temperature to correct for changes in viscometer geometry. Simultaneously the minimal shear stress tau Tmin to keep RCA dispersed was determined by photometric aggregometry. eta rel was found to increase with decreasing temperature. By basing the relative cold induced increase in eta rel on the state of RCA as defined by the ratio of tau/tau Tmin the relation between both features is verified: With increasing RCA the cold induced increase in eta rel is progressively enhanced.     

The response of the high altitude C(4) grass Muhlenbergia montana (Nutt.) A.S. Hitchc. to long- and short-term chilling.

The acclimation of C(4) photosynthesis to low temperature was studied in the montane grass Muhlenbergia montana in order to evaluate inherent limitations in the C(4) photosynthetic pathway following chilling. Plants were grown in growth cabinets at 26 degrees C days, but at night temperatures of either 16 degrees C (the control treatment), 4 degrees C for at least 28 nights (the cold-acclimated treatment), or 1 night (the cold-stress treatment). Below a measurement temperature of 25 degrees C, little difference in the thermal response of the net CO(2) assimilation rate (A) was observed between the control and cold-acclimated treatment. By contrast, above 30 degrees C, A in the cold-acclimated treatment was 10% greater than in the control treatment. The temperature responses of Rubisco activity and net CO(2) assimilation rate were similar below 22 degrees C, indicating high metabolic control of Rubisco over the rate of photosynthesis at cool temperatures. Analysis of the response of A to intercellular CO(2) level further supported a major limiting role for Rubisco below 20 degrees C. As temperature declined, the CO(2) saturated plateau of A exhibited large reductions, while the initial slope of the CO(2) response was little affected. This type of response is consistent with a Rubisco limitation, rather than limitations in PEP carboxylase capacity. Stomatal limitations at low temperature were not apparent because photosynthesis was CO(2) saturated below 23 degrees C at air levels of CO(2). In contrast to the response of photosynthesis to temperature and CO(2) in plants acclimated for 4 weeks to low night temperature, plants exposed to 4 degrees C for one night showed substantial reduction in photosynthetic capacity at temperatures above 20 degrees C. Because these reductions were at both high and low CO(2), enzymes associated with the C(4) carbon cycle were implicated as the major mechanisms for the chilling inhibition. These results demonstrate that C(4) plants from climates with low temperature during the growing season can fully acclimate to cold stress given sufficient time. This acclimation appears to involve reversal of injury to the C(4) cycle following initial exposure to low temperature. By contrast, carbon gain at low temperatures generally appears to be constrained by the carboxylation capacity of Rubisco, regardless of acclimation time. The inability to overcome the Rubisco limitation at low temperature may be an inherent limitation restricting C(4) photosynthetic performance in cooler climates.     

Blood osmolality during in vivo changes of CO2 pressure

In 16 experiments male subjects, age 22.4 +/- 0.5 (SE) yr, inspired CO2 for 15 min (8% end-tidal CO2) or hyperventilated for 30 min (2.5% end-tidal CO2). Osmolality (Osm) and acid-base status of arterialized venous blood were determined at short intervals until 30 min after hypo- and hypercapnia, respectively. During hypocapnia [CO2 partial pressure (PCO2) -2.31 +/- 0.32 kPa (-17.4 Torr), pH + 0.19 units], Osm decreased by 3.9 +/- 0.3 mosmol/kg H2O; during hypercapnia [PCO2 + 2.10 +/- 0.28 kPa (+15.8 Torr), pH -0.12 units], Osm increased by 5.8 +/- 0.7 mosmol/kg H2O. Presentation of the data in Osm-PCO2 or Osm-pH diagrams yields hysteresis loops probably caused by exchange between blood and tissues. The dependence of Osm on PCO2 must result mainly from CO2 buffering and therefore from the formation of bicarbonate. In spite of the different buffer capacities in various body compartments, water exchange allows rapid restoration of osmotic equilibrium throughout the organism. Thus delta Osm/delta pH during a PCO2 jump largely depends on the mean buffer capacity of the whole body. The high estimated buffer value during hypercapnia (38 mmol/kg H2O) compared with hypocapnia (19 mmol/kg H2O) seems to result from very strong muscle buffering during moderate acidosis.     

Temperature-dependence of rapid axonal transport in sympathetic nerves of the rabbit.

Stop-flow techniques were used to determine how temperature affected the axonal transport of dopamine-beta-hydroxylase (DBH) activity in rabbit sciatic nerves in vitro. These nerves were cooled locally to 2 degrees C for 1.5 hr, which caused a sharp peak of DBH activity to accumulate above the cooled region. Accumulated DBH was then allowed to resume migration at various temperatures. From direct measurements of the rate of migration, we found that the axonal transport velocity of DBH was a simple exponential function of temperature between 13 degrees C and 42 degrees C. Over this range of temperatures, the results were well described by the equation: V=0.546(1.09)T, where V is velocity in mm/hr, and T is temperature in degrees centigrade. The Q10 between 13 degrees and 42 degrees C was 2.33, and an Arrhenius plot of the natural logarithm of velocity versus the reciprocal of absolute temperature yielded an apparent activation energy of 14.8 kcal. Transport virtually halted when temperature was raised to 47 degrees C, although only about half of the DBH activity disappeared during incubation at this temperature. Another transition occurred at 13 degrees C; below this temperature, velocity fell precipitously. This was not an artifact peculiar to the stop-flow system since the rate of accumulation of DBH activity proximal to a cold-block also decreased abruptly when the temperature above the block was reduced below 13 degrees C.     

The secondary structure of human plasma fibronectin: conformational changes induced by acidic pH and elevated temperatures; a circular dichroic study

The secondary structure of native human plasma fibronectin, based on circular dichroic spectra, has been estimated to contain 79% beta sheet and 21% beta turn structures (Osterlund, E., Eronen, I., Osterlund, K. and Vuento, M. (1985) Biochemistry 24, 2661-2667). In this work changes in the secondary structure of the protein molecule are followed as a function of different temperatures and pH values by using circular dichroic spectroscopy in far- and near-ultraviolet regions. Conformational changes are reversible when raising the temperature quickly to 55 degrees C, and then cooling slowly to 20 degrees C. A few percent of alpha-helix is apparent, when the temperature is raised to 58.5 degrees C, but only about 9% random coil is formed, when the temperature is raised up to 70 degrees C. The largest conformational change is taking place, when fibronectin samples are heated from 57 to 58.5 degrees C. According to this study more than 90% of the secondary structure of the fibronectin molecule is preserved throughout the whole temperature range studied from 20 to 70 degrees C, and this is a fact even at pH as low as 3.0, when samples are fresh and not denatured by preparative procedures.     

Development of optimal techniques for cryopreservation of human platelets. I. Platelet activation during cold storage (at 22 and 8 degrees C) and cryopreservation.

Using the current blood bank storage conditions at 22 degrees C, the viability and function of human platelets can be maintained for only 5 days. This does not allow for the necessary and extensive banking of platelets needed to treat patients afflicted with thrombocytopenia, a side effect of many invasive surgeries such as cardiopulmonary bypass or bone marrow transplantation. The development of optimal techniques for long-term cryopreservation and banking of human platelets would provide the ability to greatly extend the viable life of the platelet and would fulfill an increasing and urgent need in many clinical applications. To determine the optimal techniques for platelet preservation, the expression of an activation marker, phosphatidylserine, on the platelet membrane during storage at 22 and 8 degrees C as well as during the different freezing preservation processes was examined using flow cytometry and annexin V binding assay. Human platelets were identified by both CD41 and light scatter in flow cytometry. In cryopreservation experiments, effects of the following factors on platelet activation were evaluated: (a) cryoprotective agents (CPAs) type: dimethyl sulfoxide (Me2SO), ethylene glycol (EG), and propylene glycol (PG), (b) CPA concentration ranging from 0 to 3 M, and (c) ending temperatures of a slow cooling process at -1 degrees C/min. Our results demonstrated that (a) approximately 50% of platelets were activated on days 7 and 16 at 22 and 8 degrees C, respectively; (b) platelets were not significantly activated after 30-min exposure to 1 M Me2SO, EG, and PG at 22 degrees C, respectively, and (c) there was a significant difference in cryoprotective efficacy among these three CPAs in preventing platelets from cryoinjury. After being cooled to -10 degrees C, 74% of the cryopreserved platelets survived (nonactivated) in 1 M Me2SO solution, while in 1 M EG and 1 M PG solutions, 62 and 42% of the platelets survived, respectively. Using the information that Me2SO consistently yields higher percentages of nonactivated platelets and does not seem to be cytotoxic to platelets for 30-min exposure time, this was found to be the optimal cryoprotective agent for platelets. In addition, significant Me2SO toxicity to platelets was not noted until Me2SO concentrations exceeded 2 M. Finally, a concentration of 1 M Me2SO proved to be the most effective at all cryopreservation ending temperatures tested (-10, -30, -60, and -196 degrees C). In conclusion, under the present experimental conditions, a storage temperature of 8 degrees C appeared to be much better than 22 degrees C. Although the potential chemical toxicity of 1 M Me2SO, EG, or PG is negligible, 1 M Me2SO was found to be optimum for cryopreservation of human platelets. PG has the least cryoprotective function for low-temperature platelet survival.     

Effects of temperature, pH, water activity and CO2 concentration on growth of Rhizopus oligosporus NRRL 2710

AIMS: To investigate the effects of temperature, pH, water activity (aw) and CO2 concentration on the growth of Rhizopus oligosporus NRRL 2710. METHODS AND RESULTS: Hyphal extension rates from mycelial and spore inocula were measured on media with different aw (approximately 1.0, 0.98 and 0.96) and pH (3.5, 5.5 and 7.5) incubated at 30, 37 or 42 degrees C in atmospheres containing 0.03, 12.5 or 25% (v/v) CO2. The effects of environmental conditions on hyphal extension rate were modelled using surface response methodology. The rate of hyphal extension was very sensitive to pH, exhibiting a pronounced optimum at pH 5.5-5.8. The hyphal extension rate was less sensitive to temperature, aw or CO2, exhibiting maximum rates at 42 degrees C, a(w) approximately 1.0 and 0.03% (v/v) CO2. CONCLUSIONS: The fastest hyphal extension rate (1.7 mm h(-1)) was predicted to occur at 42 degrees C, pH 5.85, a(w) approximately 1.0 and 0.03% CO2. SIGNIFICANCE AND IMPACT OF THE STUDY: The present work is the first to model the simultaneous effects of temperature, pH, aw and CO2 concentration on mould growth. The information relates to tempe fermentation and to possible control of the microflora in Tanzanian cassava heap fermentations.     

The oxygen uptake of Sarotherodon niloticus L. and the oxygen binding properties of its blood and hemolysate (Pisces: Cichlidae)

The oxygen consumption of Sarotherodon niloticus L. was found to decline below a critical oxygen concentration of about 2 mg O2/l. An important influence of CO2 on the oxygen affinity of whole blood was observed at all temperatures between 20 and 35 degrees C for gas mixtures containing 5.6% CO2. Purified hemolysate showed extremely high oxygen affinities (p50 = 1.08 mmHg at pH 8.2 and 20 degrees C). Low cooperativity was observed at all temperatures from 20 to 35 degrees C, and pH values between 6.5 and 8.2. The Bohr effect proved to be important at pH values lower than pH 7.5 (phi = delta log P50/delta pH = -0.58 between pH 6.5 and 7.0 at 35 degrees C). The oxygen affinities show high thermal sensitivity without a marked pH influence (delta H value for overall oxygenation at pH was -71.7 kJ/mol). The obtained results are interpreted as adaptations to diurnal variations in ambient temperature and oxygen availability.     

Partitional measurement of capillary and arteriovenous anastomotic blood flow in the human finger by laser-Doppler-flowmeter

This study was made to see whether changes in blood flow through the capillaries and arteriovenous anastomoses (AVA's) of the human finger can be measured by noninvasive flowmetry. Total finger blood flow (FBF) was measured by venous occlusion plethysmography; blood flow was measured by a laser-Doppler flowmeter (ADVANCE, ALF-2100, Tokyo, Japan) using probes with optic fiber separations of 0.3 mm (LDF-0.3) and 0.7 mm (LDF-0.7). The maximum sensitivities for LDF-0.3 and LDF-0.7 were at depths of 0.8 and 1.2 mm from the tissue surface respectively. Two series of experiments were performed on separate days. In the first series the test hand was immersed in a water bath whose temperature (Tw) was 25 degrees C at an ambient temperature (Ta) of 25 degrees C. Tw was raised to 35 degrees C (local hand warming), which was then followed by an increase in Ta to 35 degrees C (whole body warming). FBF, LDF-0.3, and LDF-0.7 increased during these thermal stimulations. However, the relationship of FBF to LDF-0.3 showed two different regression lines. In contrast, the relationship of FBF to LDF-0.7 showed a single regression line. In the second series, with Ta at 35 degrees C, the test hand was immersed in a water bath at Tw 35 degrees C. Tw was then raised every 10 min by 2 degrees C steps from 35 to 41 degrees C. At Tw 39-41 degrees C, FBF and LDF-0.7 in the test hand were significantly decreased compared with those at Tw 35 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of local heating on blood flow in the finger and the forearm skin

Blood flow of the finger and the forearm were measured in five male subjects by venous occlusion plethysmography using mercury-in-Silastic strain gauges in either a cool-dry (COOL: 25 degrees C, 40% relative humidity), a hot-dry (WARM: 35 degrees C, 40% relative humidity), or a hot-wet (HOT: 35 degrees C, 80% relative humidity) environment. One hand or forearm was immersed in a water bath, the temperature (Tw) of which was raised every 10 min by steps of 2 degrees C until it reached 41 degrees or 43 degrees C. While the other hand or forearm was kept immersed in a water bath (Tw, 35 degrees C), blood flow in the heated side (BFw) was compared with the corresponding blood flow in the control side (BFc). Under WARM or HOT conditions, finger BFw was significantly lower than finger BFc at a Tw of 39-41 degrees C in the majority of subjects. When Tw was raised to 43 degrees C, however, finger BFw became higher than BFc in nearly half of the subjects. In the COOL state, finger BFw did not decrease but increased steadily when Tw increased from 37 degrees to 43 degrees C. In the forearm, BFw increased steadily with increasing Tw even in WARM-HOT environments. No such heat-induced vasoconstriction was observed in the forearm. From these results we conclude that in hyperthermic subjects, the rise in local temperature to above core temperature produces vasoconstriction in the fingers, an area where no thermal sweating takes place.