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PubMed1979

Human skin wettedness and evaporative efficiency of sweating.

Rates of evaporation and sweating were recorded for three acclimatized male subjects in hot humid conditions, the ambient parameters of which were set so that the various imposed evaporative rates required the same skin wettedness at different levels of sweating. Rectal and skin temperatures were measured. Results showed that during steady state occurring during the 2nd h of exposure each subject reached the required evaporative rate by means of increases in skin wettedness regardless of the level of sweating; the sweat evaporative efficiency, defined as the ratio between evaporative rate and sweat rate, decreased as skin wettedness increased, in a range between 0.74 and 1.0 Sweat efficiency fell to 0.67 for fully wet skin. The body temperatures did not increase with time if skin wettedness was less than unity. Evaporative heat transfer coefficient (he), maximum evaporative capacity, and wettedness were estimated on the basis of the observed decrease of sweat efficiency. The relationship between skin wettedness and sweat efficiency was interpreted as a combined effect of differences in local he as well as in local sweat rates.

Adult↗

PubMed1992

Plasma ammonia is the principal source of ammonia in sweat.

Sweat contains ammonia. However, neither its source nor factors affecting its concentration in the sweat are known. The aim of this study was to examine the effect of plasma concentrations of ammonia and urea on the concentration of ammonia in the sweat. Four groups of male volunteers were examined: one control, two after ingestion of ammonium chloride, three cirrhotic, hyperammonaemic, four uraemic. Sweat was collected from each subject from the palmar side of the forearm using gauze pads, after previous iontophoresis of pilocarpine. Ammonia and urea concentrations were determined in the sweat and in the plasma. It was found that elevated plasma ammonia concentration in healthy subjects after ingestion of ammonium chloride as well in the cirrhotic patients resulted in an increase of ammonia concentration in the sweat. High plasma and sweat urea concentration in the uraemic subjects did not affect the concentration of ammonia in the sweat. It was concluded that plasma ammonia was the principal source of ammonia in the sweat.

Administration, Oral↗

PubMed1979

Effects of baroreceptor activation on spontaneous activity in the sweat glands and nictitating membrane of the cat.

(1) In chloralose-anesthetized cats, elevation of carotid sinus pressure caused blood pressure, sweat gland potentials and nictitating membrane tension to decrease. (2) The onset and recovery of the sweat gland and nictitating membrane responses usually preceded the respective phases of the blood pressure (depressor) response; the latencies of the sweat gland and nictitating membrane responses agreed with the latencies predicted for neural reflex pathways. (3) The sweat gland and nictitating membrane responses were evoked less consistently than the depressor response. (4) In experiments where only the sweat gland potentials and blood pressure were studied: (a) the sinus pressure threshold for inhibition of sweat gland activity was similar to the threshold for the depressor response; (b) cutting the sinus nerves, or blocking the efferent neural activity to the sweat glands, eliminated the effects of sinus pressure elevation on the sweat gland potentials; (c) with carotid sinus pressure held constant, decreases in blood pressure, produced by stimulating the peripheral end of the vagus nerve, did not affect the sweat gland potentials. (5) These results indicate that baroreceptors can reflexly modulate activity in sympathetic neurons whose target organs are not fundamentally involved in blood pressure regulation.

Adrenergic Fibers↗

PubMed1976

The effects of sweat nitrogen losses in evaluating protein utilization by preadolescent children.

A nitrogen balance study was conducted to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess further the impact of sweat nitrogen on protein needs of preadolescent children. Values were determined through the collection of 24-hr, total body sweat samples from twelve healthy boys having a mean age of 8 years, 8 months. Mean height and weight of the subjects were 131.4 cm and 31.0 kg, respectively. Environmental conditions were relatively constant during the study. Mean sweat nitrogen losses were 208, 287, and 368 mg/day on daily protein intakes of 29, 54, and 84 g, respectively. Mean nitrogen balances per day were 0.39, 0.09, and 1.95 g when sweat nitrogen losses were included in the calculations. At the lower and moderate levels of protein intake, nine and six subjects were in negative nitrogen balance when sweat losses were considered. Sweat nitrogen losses in the boys were similar to a previous study with preadolescent girls. Based upon published basal metabolic rates and mean sweat nitrogen losses of 261 and 288 mg/day for girls and boys, the nitrogen lost through sweat was 0.25 mg/basal kcal for both sexes. An estimation of 0.5 mg/basal kcal for integumental nitrogen loss appears realistic for this age group.

Body Surface Area↗

PubMed1977

Limitations of diagnostic value of the sweat test.

The sweat test, even if carried out by an experienced technician, sometimes lacks reproducibility owing presumably to physiological variations (patient's diet, temperature, and other factors at present unrecognized). Some patients are particularly prone to exhibit this variability and in them a single sweat test is almost valueless. The aldosterone status is believed to be responsible for a reciprocal relationship between sweat sodium and potassium concentrations: tests done on 8 patients show that a high sweat potassium is associated with a correspondingly lower sodium--a circumstance which must be borne in mind when interpreting a patient's sweat sodium. Of 30 patients presenting with a variety of symptoms compatible with a diagnosis of cystic fibrosis and with sweat sodium ranging from 50 to 75 mEq/1 (50-75 mmol/1), only 4 have proved to have cystic fibrosis after several years of observations; 13 have later been diagnosed as having asthma. The problem of the 'grey area' of uncertainty is aggravated by the heterozygous state which is also associated with a sweat sodium in this range. Repeated sweat tests are indicated if the sweat sodium lies within the 'grey area', and the diagnostic importance accorded the test should diminish as the sodium value approaches this area. The diagnosis of cystic fibrosis must remain in doubt unless there is strong supportive clinical evidence.

Adolescent↗

PubMed1975

Sweating on paws and palms: what is its function?

Man sweats on his palms and the soles of his feet in response to stress and exercise, but not in response to heat. Several functions have been proposed for this type of sweating: increasing friction between skin and substrate; increasing the toughness of the skin; and increasing tactile sensitivity. This study uses a comparative approach to evaluate the role of footpad sweating on increasing friction, utilizing a variety of mammals which possess sweat glands on their footpads (rat, tenrec, hyrax, and dog). We found that all of these animals sweat on their paws while running. Blocking this sweating with atropine sulfate dramatically decreased the coefficient of static friction between the paw and the tread of an inclined treadmill. A similar dose of atropine sulfate had no effect on the coefficient of static friction in a rabbit, and animal that possesses no sweat glands on its paws. We conclude that an important function of this type of sweating is to help prevent slipping between the paw and sthe substrate during running or climbing, and we postulate that the sweating observed in response to stress may play an important role in preparing an animal for fleeing from stressful situations.

Animals↗

PubMed1976

[Influence of hydrothermal ambient conditions on sweat evaporation efficiency].

Sweat efficiency is defined as the ratio between evaporative and sweat rates. The work was carried out on two resting subjects acclimatised to humid heat. Body sweat rate and rate of sweat loss by dripping were recorded separately by continuous weighing. Evaporation from the skin was obtained by the difference between the two weight loss curves. The subjects were exposed for 75 minutes to increases in humidity levels as constant air temperatures (42, 44, 46, or 48 degrees C). The amplitude of the increases was successively equal to 7.5, 15.0, 22.5 or 50.0 mb of water vapor pressure. During the 75 minutes preceding each increase the water vapor pressure of the air was maintained at 20.0 mb. 1. Sweat efficiency decreases prior to complete wetting of the skin surface. The inter-individual mean value of the wetted skin area threshold over which sweat efficiency is less than 1 is around 60%. 2. Sweat efficiency is linearly related to the reciprocal of the required wetted skin area (see article). These results are compared with those of other authors. The differences observed are explained in terms of physiological or physical variables involved in the sweat rate control or in the evaporative sweat loss. These include wetness of skin, posture, activity of subjects and the velocity of air over the skin surface.

Adult↗

PubMed1992

[Effect of thermal dehydration on blood levels of volume- regulating hormones and sweat electrolytes in patients with essential hypertension treated with propranolol].

The present study aims to answer the following questions: 1. do secretion of volume related hormones in patients with EH pre- and post treatment with propranolol differ from normotensive subjects if examined in thermal dehydration conditions; 2. is the electrolyte composition of thermal sweat related to the plasma profile of volume related hormones? and 3. does treatment by propranolol influence sweat electrolytes in EH patients. In 15 patients with EH and in 20 healthy subjects a thermal dehydration test was performed. In patients with EH this test was done twice: before treatment and after 6 weeks of propranolol therapy. In all subjects the plasma renin activity (PRA), aldosterone (Ald), AVP and ANP were measured before and after thermal dehydration. In sweat samples collected after 15' and 45' of thermal dehydration (the concentration of Na, K and Cl was assessed). In hypertensive patients before propranolol treatment significantly higher values of PRA, Ald and ANP were found, while sweat concentrations of Na and Cl were significantly lower than in controls. After propranolol treatment sweat electrolytes concentrations showed a tendency to normalize. No significant correlation was found between the plasma hormonal profile and sweat Na, K and Cl concentrations respectively both in controls and patients with EH pretreatment. A significant positive correlation was noticed only in hypertensive patients posttreatment between ANP and sweat potassium concentration respectively, and significant negative correlation between PRA and sweat sodium and chloride concentration. From results obtained in this paper it seemed, that volume related hormones (Ald, AVP, ANP) do not seem to influence markedly the electrolyte composition of thermal sweat both in healthy subjects and in hypertensive patients.

Adult↗

PubMed1992

Sweat electrolyte loss during exercise in the heat: effects of gender and maturation.

Humans may lose large amounts of water and electrolytes from sweat during prolonged exercise in a hot climate. Gender and maturational differences for the total sweat electrolyte losses have not been reported. The purpose of this study was to compare sweat electrolyte losses of prepubescent (PP), pubescent (P) and young adult (YA) males and females, under the same environmental conditions and relative exercise intensities. Twenty-five females (8 PP, 9 P, 8 YA) and 26 males (10 PP, 8 P, 8 YA) cycled for two 20-min bouts at 50% of their peak VO2 in a climatic chamber (42 degrees C, 18% relative humidity). Sweat was collected from a plastic bag attached to the lower back. Total body sweat loss was calculated from the differences in nude body weight corrected for fluid intake, urine, and respiratory water loss. Sweat [Na+] and [Cl-] tended to increase with maturation while sweat [K+] was lower in YA compared with that of PP. Children had a lower sweating rate than YA, even when corrected for body surface area. As a result, total Na+ and Cl- losses per kg body weight from sweat (mEq.kg-1.h-1) were higher in YA compared with those of PP and P; however, no maturational difference was found in K+ losses. Within the same maturational group, there were no gender differences in any of the electrolyte losses. These results may be useful in recommending "optimal" fluid-electrolyte drinks for children exercising in the heat.

Adolescent↗

PubMed1991

A simple and disposable sweat collector.

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.

Adolescent↗

PubMed1976

Sweat studies in hyperhidrosis palmaris and plantaris. A survey of 60 patients before and after cervical sympathectomy.

60 patients suffering from excessive sweating in the hands underwent cervical sympathectomy. At follow-up 1-7 years after operation the hands were dry in 55. No differences in electrolyte concentrations were found in the sweat from palms, arms, or body prior to and after the surgical intervention. Similarly no differences were found in electrolyte concentrations between healthy subjects and hyperhidrotics. Palmar sweat was hypertonic in comparison to arm or body sweat. The Na and K sweat concentrations were: palmar 50 +/- 20 and 16 +/- 7 mEq/1; arm 30 +/- 11 and 8 +/- 2 mEq/1; and body 21 +/- 20 and 4 +/- 3 mEq/1, respectively. Na/K ratio was: palmar 3.2; arms 3.6 and body 5.8. Total sweat loss prior to the operation was 5.7 +/- 4.2 g/kg BW/h; afterwards it was 5.9 +/- 4 g/kg BW/h. These equal sweat rates were associated with compensatory sweating in areas of the body not affected prior to the operation.

Adolescent↗

PubMed1992

Sweating response to moderate thermal stress in atopic dermatitis.

The local sweating response to thermal stress (mean ambient temperature 33 degrees C) was assessed under resting conditions on the non-eczematous back skin of 26 young men with atopic dermatitis (AD) and in 22 non-atopic controls with other dermatoses. The baseline (transepidermal) water loss was separately determined at room temperature (mean 23.6 degrees C) to calculate the pure sweat loss. A gravimetric collecting method was used for the measurements at 40, 60 and 80 min. In the heated room the sweat loss in AD patients was significantly lower at all time intervals. The cumulative sweat loss was 50-60% lower in AD patients than in the controls (P less than 0.02). Subjects with dry AD skin had a lower sweat loss than subjects with normal-looking skin. Compared with controls the sweat loss in AD patients was lowest at 40 min, suggesting a retarded sweating response. Half of the patients with AD and half of the controls had active participation in sports, and showed a greater sweat loss compared to the non-sporting subjects in the same group.

Adult↗

PubMed1991

Regional differences in the sweating responses of older and younger men.

Ten older (60-71 yr) and nine younger (20-25 yr) active healthy men were exposed to passive heating [by placing the lower legs and feet in a 43 degrees C water bath for 60 min while sitting in a warm (35 degrees C, 45% relative humidity) chamber] in summer and winter. The increase in rectal temperature (Tre) was significantly (P less than 0.05) greater, and mean skin temperature and forearm blood flow were lower, for the older men in both seasons. Total sweating rate was lower in the older men, but significantly (P less than 0.05) so only in the summer. The Tre threshold for sweating was unaffected by either age or site (back vs. thigh). The local sweating rate (msw) on the thigh was significantly lower (P less than 0.05) for the older men throughout the exposure, whereas there were no significant age-related differences for the average or peak values of back msw, although lesser sweating on the back occurred during the first 30 min of exposure. The decreased msw on the thigh was due to a lower sweat output per heat-activated sweat gland rather than from recruitment of fewer glands. It was concluded that regional differences exist in the age-related decrement in sweat gland function. Furthermore, these findings suggest that aging leads to a decreased ability to maintain body temperature with passive heating of the extremities, which may be attributed in part to decreased regional sweat gland function.

Adult↗

PubMed1992

Variation of sweat sodium and chloride with age in cystic fibrosis and normal populations: further investigations in equivocal cases.

Patients attending cystic fibrosis clinics had sweat sodium and chloride concentrations measured, were reassessed clinically and had DNA studies performed. Sweat test results were compared with a matched control population. In both populations sweat sodium increased with age up to 12 years, and did not change significantly thereafter. The age-related increase was significantly less in the cystic fibrosis group. Sweat chloride increased with age in normal, but not in cystic fibrosis children. After age 12 years there was no age-related change in the normal group, and a fall with age in the cystic fibrosis group. Sweat chloride provided the best discrimination between normal and cystic fibrosis populations and this was particularly important in older subjects. Combining sweat sodium and chloride results did not improve discrimination. Nine patients were identified with equivocal sweat chloride results. DNA studies showed six of these subjects were heterozygous for the delta F508 mutation in the cystic fibrosis gene. Clinical assessment did not always resolve cases with borderline sweat chloride results.

Adolescent↗

PubMed1978

The significance of the sweat test in chronic pancreatitis.

In order to study the disposition which is thought to be latent in chronic pancreatitis, we investigated the sweat chloride concentration of 95 normal subjects, 43 cases of chronic pancreatitis, 12 cases of cholelithiasis, 15 cases of peptic ulcers, 16 cases of hepatic diseases and 23 cases of diabetes mellitus with the sweat test, using the method of pilocarpine iontophoresis. We obtained the following results. (1) In normal subjects, the sweat chloride concentration was inclined to rise gradually with age from childhood to adulthood; the mean value of sweat chloride concentration was 30.0 mEq/liter in adults from 20 years old, and the upper limit was about 60 mEq/liter. (2) The mean value of sweat chloride concentration was 60.0 mEq/liter in chronic calcifying pancreatitis; this value was markedly higher than that of control subjects of the same age (p is less than 0.001). (3) The mean value of sweat chloride concentration in cholelithiasis, peptic ulcer and hepatic diseases did not differ significantly from control subjects. The mean value of sweat chloride concentration in diabetes mellitus was significantly higher than that of control subjects (p is less than 0.01), but was significantly lower than that in chronic pancreatitis (p is less than 0.01). (4) It was supposed that some cases of chronic pancreatitis have a congenital disposition toward abnormal secretion of sweat glands and epithelium in the pancreatic duct, resembling cystic fibrosis, and this disposition leads easily to pancreatic disorders when the individual is exposed to various external factors.

Adolescent↗

PubMed1991

[The effect of ageing on the active sweat gland density in the dorsum of foot].

Focal sweating in the dorsum of foot induced by iontophoresis of 1% pilocarpine was quantitatively evaluated using silastic impression mold technique in 111 control subjects (71 men & 40 women), aged 14 to 89 years, to reveal the effect of aging on the density of active sweat glands. The subjects were divided into four groups (group I: aged 14 to 29 years, group II: aged 30 to 49 years, group III: aged 50 to 69 years, group IV: aged 70 to 89 years), and the difference of the density of active sweat glands was evaluated among the groups with Wilcoxon's rank sum test. It was statistically significant (p less than 0.001) between group II and III, and between group III and IV, but not significant between group I and II. Therefore, it was concluded that the density of active sweat glands decreases prominently after 50 years of age. The density of active sweat glands was not significantly different between man and woman in each group. In the regression analysis of the density of active sweat glands on age, the relationship (Density = -0.0178.Age2 + 232.6 (R2 = 0.54), p less than 0.0001) was obtained. Based on such relationship, the predicted density and the upper and lower limits of 95% confidence interval of the predicted density for each age were obtained. These results indicate that decrease of the density of active sweat glands due to ageing should be taken into consideration in the evaluation of the density of active sweat glands in the dorsum of foot among the patients with various neurological diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMedDate not supplied

[Excretion of nitrogen compounds in sweat during a sauna].

The aim of the study was to determine a loss of nitrogen compounds with sweat in sauna and to estimate their plasma concentration. Sweat was collided during 30 min stay in sauna. Blood was taken before and immediately after the sauna. Concentrations of ammonia, urea, creatinine and uric acid were determined in the both fluids. It has been found, that the concentration of ammonia in sweat exceeds, that in plasma by 77 times. Ammonia plasma concentration following sauna increased by about 60%. Sweat urea concentration exceeded that in plasma by 3.5 times. Plasma urea concentration was significantly reduced after sauna. Sweat creatinine concentration was about two times higher than that in plasma. No uric acid was detected in sweat. Sweating did not affect plasma creatinine and uric acid concentrations. Results indicate that considerable amount of nitrogen is lost with sweat during sauna.

Adult↗

PubMed1991

Sweat lactate in exercising children and adolescents of varying physical maturity.

This study attempts to explain some of the individual variability in sweating pattern by comparing prepubescents and pubescents. Sweating rate and muscular anaerobic capacity are higher in adults than in children; thus we hypothesized that sweat gland anaerobic metabolism, as reflected by lactate excretion, might be higher with advanced physical maturity (PM). Lactate concentration in sweat ([LAC]sw) was measured at various stages of PM in boys who exercised in the heat. The subjects were divided into three groups on the basis of Tanner staging: prepubertal (PP, n = 16), midpubertal (MP, n = 15), and late pubertal (LP, n = 5). Subjects cycled at 50% of maximal O2 uptake for three 20-min bouts, with 10-min rest periods, in 42 degrees C and 18% relative humidity. Sweat samples were harvested, and population density of activated sweat glands was determined after each exercise bout. [LAC]sw during bout 1 was higher in PP than in LP [PP = 22.2 +/- 2.2, MP = 19.5 +/- 1.4, LP = 14.3 +/- 1.3 (SE) mmol/l]. In all groups, [LAC]sw decreased during subsequent bouts, and there were no intergroup differences in [LAC]sw during bout 3 (PP = 11.2 +/- 0.4, MP = 10.6 +/- 0.5, LP = 9.7 +/- 0.2 mmol/l). [LAC]sw was inversely related to sweating rate. Lactate excretion rate per gland was greater with the increase in PM (PP = 61.0 +/- 8.2, MP = 79.1 +/- 11.3, LP = 99.9 +/- 11.0 pmol/min; P = 0.08).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗