Apart from in cystic fibrosis, where sweat analysis provides valuable diagnostic information, sweat yields remain an overlooked biological fluid. Technical problems (dilution, condensation, contamination, evaporation, etc.) linked to currently available collection procedures are of concern and thwart their use. To overcome some of these technical difficulties, an original sweat-collection technique is described. A collection capsule is created inside a flexible, adhesive and disposable anchoring membrane pasted onto the skin. A fluid-tight window is positioned in the upper part of the pocket and gives access to its content. Through the collection window, complete emptying of the sweat collector can be achieved repeatedly by suction using a vacutainer tube inserted in a tube holder equipped with a long dull needle. With prior addition of a suitable marker, fractional samplings can also be performed using a precision micropipette. This collecting method allows for kinetic studies on sweat rate and sweat content. The limited bias-inducing manipulations linked to the described technique, coupled with the ease of performing kinetic studies on sweat volume and content, make this original tool a reliable and accurate sweat-collection technique.
Factors associated with heat-induced increase in blood prolactin (PRL) were investigated. Ten male volunteers (23.7 +/- 2.2 yr) were exposed to exogenous heating (head-out immersion) in 41 degrees C water (control 37 degrees C) for 30 min with and without face fanning and cooling. In seven of the subjects, endogenous heating was produced by a 45-min exercise in a warm environment (41 degrees C; control 10 degrees C) with and without selective face fanning. Venous blood was collected before and after each trial; blood hormones were analyzed by radioimmunologic techniques. Heat loading, whether exogenous or endogenous in origin, induced significant increases in blood PRL, beta-endorphin, and vasoactive intestinal peptide (VIP) levels. Blood thyrotropin (TSH) level decreased significantly during water immersion and more significantly with face cooling. From measurement in peripheral blood, the differential beta-endorphin, VIP, and TSH responses to selective face ventilation during exogenous and endogenous heat exposures suggest that blood PRL released in heat derives from secretory stimuli that are independent of these prolactinotropic factors.
This study was designed to verify if the decrease in blood prolactin (PRL) induced by selective face cooling during exercise could be part of a response to specific body thermal stress. Five healthy trained male cyclists presenting a significant plasma PRL elevation to exercise were, on three occasions and at weekly interval, submitted to a submaximal exercise (approx. 65% VO2max) on ergocycle with and without selective face cooling. In absence of face cooling a first trial served to establish reference values for workload, heart rate and plasma PRL levels, the latter increasing markedly (450% of resting values) in these conditions. On a second trial but with workload maintained at reference values (222 +/- 9 W), a significant bradycardia was observed with face cooling; furthermore, plasma PRL response to exercise was significantly reduced (to 31% of original response). On a third trial with face cooling, workload had to be significantly augmented (242 +/- 10 W) to maintain heart rate at reference level (78% HRmax); in addition, plasma PRL response to exercise was almost unchanged compared to the reference-value level. The absence of a significant face cooling-induced decrease in sympathetic tonus, as evaluated through peripheral plasma catecholamines response, does not indicate a role for the autonomic nervous system in the face cooling-induced reduction of both heart rate and PRL responses during exercise. Assay of circulating peripheral beta-endorphins could indicate that the face cooling-induced PRL blunted response does not necessarily involve an opioid mediation.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this study was to compare the "NaCl equivalent" values determined by the Wescor's sweat conductivity analyzer (Sweat-Chek) with the sweat Na+ and Cl- concentration values measured by conventional methods. The sweat was induced by 60-min exercise and collected by a closed-pouch collector. The "NaCl equivalent" values determined by the sweat conductivity analyzer (mean: 75 mmol.L-1, range: 38 - 122, n = 72) were significantly (P < 0.05) greater than Na+ concentration values (mean: 71 mmol.L-1, range: 24 - 123, n = 72) measured by flame photometry and Cl-concentration values (mean: 61 mmol.L-1, range: 18 - 100, n = 48) measured by coulometric titration. The difference were most accentuated for low concentration values. The 95% confidence-agreement intervals around the mean differences between methods were 11 mmol.L-1 (14%) for both Na+ and Cl-. The Sweat-Chek conductivity analyzer is a portable instrument which approximates the actual Na+ and Cl- concentrations in sweat but with a positive bias probably due to the other unmeasured anions present in sweat.
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