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PubMed1981

Effect of physical training on exercise-induced sweating in women.

The effect of physical training on the time course of sweat rate in women has been examined. Physically untrained and trained young female subjects pedaled a bicycle ergometer at work rates of 483 and 981 kgm.min-1, for 2 h in summer and winter in an ambient environment of 30 degrees C db and 60% rh. The trained women also worked at 1,070 kgm.min-1 and the untrained at 391 kgm.min-1. Rectal temperature was measured, and capsule sweat samples were collected from the back every 5 min. Sweating was initiated more rapidly in the trained group than in the untrained group. The trained group working at a load of 981 kgm.min-1 exhibited a progressive decrease in sweat rate. This was not observed at a work load of 483 kgm.min-1. Hidromeiosis was rarely seen in the untrained group. However, in the untrained women who underwent 60 days of physical training, initiation of sweating occurred more quickly and hidromeiosis was observed. It was concluded that previous physical training improved women's capacity for useful sweating during exercise in a hot environment.

Adult↗

PubMed1990

Functional and morphological changes in the eccrine sweat gland with heat acclimation.

Three adult male patas monkeys (11-15 kg) were heat acclimated by continuous exposure to an ambient temperature of 33 +/- 1 degree C at 13% relative humidity for 9 mo. During the last month, they were also exposed to 45 degrees C at 10% relative humidity for 4 h/day and 5 days/wk. Before and after 3 wk of acclimation, the animals were given a heat-tolerance test in which rectal (Tre) and mean skin (Tsk) temperatures, heart rate, and sweat rate (msw) were monitored during a 90-min exposure to 45 degrees C heat with 24% relative humidity under lenperone (1.0-1.4 mg/kg im) tranquilization. Maximal in vivo msw was also determined in response to subcutaneous injections (1 and 10% solutions) of methacholine (MCh). Before and after 9 wk and 9 mo of acclimation, sweat glands were dissected from biopsy specimens of the lateral calf, cannulated, and stimulated in vitro with MCh. Morphological measurements of isolated tubules were compared with maximal secretory rates produced by MCh stimulation. Three weeks of acclimation 1) reduced Tre and Tsk and increased msw during the heat tolerance test and 2) significantly increased maximal msw in response to MCh stimulation. Acclimation also increased (P less than 0.05) sweat gland size, as measured by tubular length and tubular volume. Maximal in vitro msw produced by MCh stimulation and msw per unit length of secretory coil also increased significantly. We conclude that heat acclimation increases the size of eccrine sweat glands and that these larger glands produce more sweat. They are also more efficient because they produce more sweat per unit length of secretory coil.

Acclimatization↗

PubMed1997

Rate and composition of sweat fluid losses are unaltered by hypohydration during prolonged exercise in horses.

Rate and ionic composition of sweat fluid losses and partitioning of evaporative heat loss into respiratory and cutaneous components were determined in six horses during three 15-km phases of exercise at approximately 40% of maximal O2 uptake. Pattern of change in sweat rate (SR) and composition was similar during each phase. SR increased rapidly for the first 20 min of exercise but remained at approximately 24-28 ml . m-2 . min-1 during the remainder of each phase. Similarly, the concentrations of Na and Cl in sweat increased until 30 min of exercise but were unchanged thereafter. Sweat osmolality and concentrations of Na and Cl were positively correlated with SR. Sweat K concentration decreased during exercise but was not correlated with SR. Fluid losses were 33.8 +/- 1.5 liters, resulting in decreases of approximately 21% in plasma volume and approximately 11% in total body water. The approximately 6% hypohydration was not associated with an alteration in SR, sweat composition, or heat storage. Respiratory and cutaneous evaporative heat loss represented approximately 23 and 70%, respectively, of the total heat dissipated, and the partitioning of heat loss was similar in each exercise phase. We conclude that SR and the relative proportions of respiratory and cutaneous evaporative heat loss are unchanged in horses during prolonged low-intensity exercise despite moderate hypohydration.

Animals↗

PubMed1985

Characteristics of central sudomotor mechanism estimated by frequency of sweat expulsions.

Each of six male subjects was exposed during rest to at least ten different thermal environments (Ta, 22-44 degrees C; rh, 40%). Local sweat rates from both forearms were continuously recorded in a steady state of each exposure, using capacitance hygrometry. In the absence of spontaneous sweating, localized sweating was induced by intradermal administration of pilocarpine. Sweat expulsions synchronous at the two test areas were counted and their frequency (Fsw) was calculated. For each of additive and multiplicative combinations of Tcore (Tre, Tty) and Ts, the best combination for estimation of thermal input to the sudomotor center was determined using multiple regression analysis. Approximately 0.75Tre + 0.25Ts or 0.85Tty + 0.15Ts, and (Tre-36.33) (Ts-33.13) or (Tty-36.42) (Ts-32.24) were obtained for the additive and multiplicative combinations, respectively. The correlation coefficient (r) for the relationship of Fsw to the obtained best combination, either additive or multiplicative, and that of Fsw to Tb were almost comparable to each other. It is considered that Tb can be used as an approximation of thermal input and that the characteristics of frequency of sweat expulsion is a useful index for determining whether and how much the central sudomotor mechanism is involved in the change of sweat rate in response to various thermal and non-thermal stresses.

Adult↗

PubMed1991

Local cholinergic sweat stimulation in atopic dermatitis. An evaporimetric study.

In atopic dermatitis the nature of potential sweating disturbances is still obscure. Using an evaporimeter, local sweating response to a supra-threshold concentration of methacholine and baseline water loss were measured from non-eczematous back skin of 167 young males in five main groups (pure atopic dermatitis, atopic dermatitis with rhinitis/asthma, rhinitis/asthma, non-atopic dermatosis, and non-atopic healthy). Subjects with atopic dermatitis were further divided into two subgroups: dry-looking and normal-looking back skin. Compared with non-atopic healthy individuals, the sweat loss was significantly depressed (p less than 0.01) and the baseline water loss significantly increased (p less than 0.001) in the main groups with atopic dermatitis. Both these trends were most distinct in atopic dry-looking skin, whereas in normal-looking atopic skin only the sweat loss was depressed (p less than 0.05). Respiratory atopy had no effect on the sweating response. No significant correlation was found between the individual baseline water loss and the sweating response.

Adolescent↗

PubMed1989

Acetylcholine-induced activation of the eccrine sweat glands in a case of hypohidrotic congenital ectodermal dysplasia.

In a male patient suffering from congenital ectodermal dysplasia with sweating only on the plantar and palmar surface, we found that the anhidrotic eccrine sweat glands became able to produce sweat after repeated local application of acetylcholine. We ultrastructurally examined the sweat glands in skin biopsies before and after acetylcholine treatment. The secretory portion of the sweat glands of the right plantar region was characterized by well-developed basal infoldings and intercellular interdigitations, and also by dilated intercellular spaces and canaliculi. In the flexor region of the right brachium (anhidrotic area), the secretory portion showed hypoplastic features, especially denoted by the presence of few locally distributed basal infoldings and intercellular canaliculi. The secretory cells seemed to be hypofunctional with the nuclei containing much heterochromatin. After treatment, in the flexor region of the left brachium and the right infraclavicular region, where sweating was induced, the secretory portion appeared to be considerably activated, though hypoplastic structures were unchanged: the secretory cell nuclei contained dispersed chromatin, the Golgi apparatus in the dark cells was well developed, and both in the clear cells and the myoepithelial cells micropinocytotic vesicle-like structures increased in number. In ductular cells, mitochondria also increased in number.

Acetylcholine↗

PubMed1984

Local sweat stimulation with the skin prick technique.

Intracutaneous injections of cholinergic agonists are usually employed for induction of local sweating. The possibility to apply a less painful skin prick technique as a sweat test was examined. Pricks were made on the forearm skin of 25 young men by puncturing the skin through drops of methacholine (MCH) and control saline solutions with lancets having a point length of 1 mm. The drops were kept on skin for 10 min and were then wiped off. Using an evaporimeter the measurements of water loss (WL) were started 5 min later and continued at 5 min intervals. Sweat loss (SL) was calculated from the difference of rates of evaporative WL recorded at the MCH and saline pricks. Ten, 1, 0.1, and 0.01% solutions of MCH elicited the following average peak evaporative sweat losses: 107.1, 77.5, 32.4 and 5.4 g m-2h-1. Both the degree and duration of the sweat responses were dependent on concentration. The prick technique is well tolerated and may serve for comparative studies of local sweating.

Adolescent↗

PubMed1997

Norepinephrine facilitates the development of the murine sweat response but is not essential.

During development, the sympathetic neurons innervating sweat glands undergo a neurotransmitter switch from noradrenergic to cholinergic between postnatal day (P) 4, when the sympathetic neurons first contact the sweat glands, and P21. Several in vitro experiments suggest that norepinephrine (NE), produced by sympathetic neurons, stimulates sweat glands to produce a factor that then induces the phenotypic switch. We tested this hypothesis in vivo using dopamine beta-hydroxylase-deficient mice (DBH -/-), which are unable to synthesize NE and epinephrine, and tyrosine hydroxylase-deficient mice (TH -/-), which are unable to synthesize any catecholamines. The cholinergic agonist pilocarpine and electrostimulation of the sciatic nerve both elicited a sweat response in adult DBH -/- mice that was indistinguishable from the response of controls, and the cholinergic antagonist atropine effectively blocked these responses. We did note, however, a 1- to 2-week delay in the acquisition of the sweat response in DBH -/- mice. Although diminished in magnitude, a sweat response to pilocarpine was also noted in TH -/- mice at P21. Immunohistochemistry demonstrated that TH and vasoactive intestinal peptide were detectable at P14 and increased to adult levels by P21 in DBH +/- and DBH -/- mice. These observations indicate that NE is not essential for the acquisition of the cholinergic phenotype, but it may facilitate its postnatal development.

Acetylcholine↗

PubMed1983

Sweating and its disorders.

Eccrine sweat is produced by millions of miniscule glands buried in the skin. Eccrine sweating from the general body surface is an extremely important function in human thermoregulation; disturbances either in the control of sweating activity or in the glands themselves can result in problems ranging from minor social embarrassment to fatal hyperpyrexia. A general review of the function and control of normal sweating precedes an overview of sweating abnormalities.

Absorption↗

PubMed2000

Proposal of sampling process for collecting human sweat and determination of caffeine concentration in it by using GC/MS.

Caffeine concentration in human sweat was estimated by measuring separately the amounts of water and caffeine. After washing a finger with tap water for 15 s and waiting 2 min for drying, 70 microL aqueous ethanol solution in a small vial (0.6 mL) was used to sample for several minutes. Then 3 microL of the aliquot was used for GC/MS analysis of caffeine. As a first-order relationship between the sweat amount secreted on the left and right hands was obtained (correlation factor 0.848), the amount of sweat secretion during sampling on one hand was estimated by the value obtained on the other hand. This new indirect evaluation was used for the estimation of the amount of sweat secreted during sampling. Typical variations of caffeine concentration in sweat were demonstrated. Thirty minutes after the intake of caffeine, it was secreted in sweat, and the secretion had continued for more than 4 h.

Caffeine↗

PubMed1997

Treatment of gustatory sweating with botulinum toxin.

Gustatory sweating is an autonomic disorder that frequently occurs after parotid gland surgery. We investigated the action of intracutaneous injections of botulinum toxin (BTX) (1.0-2.0 mouse units/2.25-cm2 skin area) in 45 patients (mean age, 52 years) with gustatory sweating. The area of hyperhidrosis was determined by Minor's iodine test before and up to 24 weeks after the injection. The effect of BTX was assessed by measuring the hyperhidrotic area. The maximum BTX-induced reduction of gustatory sweating was seen at 7.4 +/- 4.5 days after injection. The area of sweating decreased from 17.6 +/- 8.6 cm2 before BTX to 1.3 +/- 1.6 cm2 after BTX (p < 0.0001). Half the patients rated gustatory sweating subjectively as completely abolished, and the remainder felt pronounced improvement. No toxic effects were observed. In none of the patients did hyperhidrosis recur over a 6-month follow-up. We conclude that BTX is a safe and effective treatment that can be recommended as the therapy of choice in gustatory sweating.

Adult↗

PubMed1984

Ultrastructure of the secretory epithelium, nerve fibers, and capillaries in the mouse sweat gland.

The ultrastructure of the mouse sweat gland was examined, in support of neurological studies of sweat glands and their relationships to the autonomic nervous system. It was found that the mouse sweat gland is similar to that of the rat and has only one type of secretory cell. Many nerve fibers are entwined with the secretory tubule and contain accumulations of round, clear vesicles, some microtubules, but apparently no neurofilaments. Cholinesterase is found in the clefts between nerve fibers and their ensheathing Schwann cells. The nerve fibers tend to run parallel with capillaries, but have no close association with either the capillaries or the secretory epithelium. Capillaries provide an abundant blood supply to the sweat gland and are fenestrated. The relationships between cellular elements of the sweat gland provide no direct evidence of the mechanisms involved in neurogenic sweating, although it seems likely that effector substances are diffusely distributed.

Animals↗

PubMed2002

Use of nasal potential difference and sweat chloride as outcome measures in multicenter clinical trials in subjects with cystic fibrosis.

One of the goals of current research in cystic fibrosis (CF) is to develop treatments that correct or compensate for defects in function of the cystic fibrosis transmembrane regulator (CFTR) gene. The use of outcome measures that assess CFTR function such as nasal potential difference (NPD) measurements and sweat chloride determinations will be required to evaluate the efficacy of such treatments in multicenter clinical trials. The purpose of this work was to identify the sources and magnitude of variability in NPD and sweat chloride measurements when performed at multiple centers. For the variance component analysis presented here, we used NPD and sweat chloride measurements from 37 subjects with CF participating in a phase I, four-center clinical trial of CPX (8-cyclopentyl-1,3-dipropylxanthine), a drug intended to enhance trafficking of Delta F508 CFTR to the cell membrane. The specific techniques used to measure these outcomes were not standardized, and varied between the four sites. Variability of both NPD measurements (baseline potential difference during infusion with Ringer's solution; change in response to addition of 0.1 mM amiloride; and subsequent change in response to perfusion with low chloride solution containing 0.1 mM amiloride and 0.01 mM isoproterenol) and sweat chloride measurements differed significantly between study sites. For change in NPD, one study site had significantly greater variability (lower reproducibility) of measurement than the other three sites. For sweat chloride measurements, reproducibility was lower at two of the sites relative to the other two sites. Sample size calculations showed that lower reproducibility at one or more sites can substantially reduce the power of studies using NPD or sweat chloride determinations as outcome measures. Standardization of measurement protocols, careful operator training and certification, and ongoing monitoring of individual operator performance may help to improve reliability in multicenter trials.

Adolescent↗

PubMed1991

Predicted sweat rate in fluctuating thermal conditions.

The ISO 7933 Required Sweat Rate Index is inappropriate under conditions of fluctuating exposure. Time weighted average values can introduce large underestimations as, for hot conditions, the relationship between physical stress and physiological strain is not linear. Mean skin temperature and sweat rate vary as a first order system, that is, according to an exponential averaging system, in response to a step function of the primary parameters. A very simple algorithm has been derived to take into account this exponential averaging and to predict the sweat rate at any time, taking into account the past exposure of the subject. It is based on time constants of 3 min for the mean skin temperature and of 25 min (up to a sweat rate of 50 W.m-2) and 10 min for the sweat rate. The correlation coefficient is 0.780 between observed and predicted sweat rates in independent experiments used for the validation of the model. This emphasises the necessity for exponential averaging as differences between individuals are very important and the precision of the observed data in these experiments was lower than for laboratory experimental data.

Algorithms↗

PubMed1992

Thermal and sweating responses in normal and atopic subjects under internal and moderate external heat stress.

To compare the thermoregulatory responses of normal subjects and patients with atopic dermatitis, the effect of exercise under moderate heat stress was examined in two groups of subjects. Each group of eight subjects (controls or clinical atopics) underwent a 90-min experiment after being equipped with probes for measurement of core and skin temperatures, heart rate and overall and local sweating rates. Sweat surface tension was determined from sweat collection made at the end of the session. The experimental procedure was as follows: 30 min rest at thermoneutrality, 30 min cycling at 90 W at 36 degrees C, followed by 30 min recovery sitting at rest at 36 degrees C on the cycloergometer. None of the registered variables differed significantly between the normal and atopic subjects except for variations in mean skin temperature, core-to-skin temperature difference and sweat surface tension. Since local sweating on non-affected skin under a controlled thermal clamp was not altered by atopy, it can be concluded that the thermoregulatory modifications under heat stress is of vasomotor origin, the benefit of which, in terms of heat dissipation capacity, remains uncertain. There may be alterations in the constituents of sweat, but not in its excretion rate. Local, rather than central, factors are probably involved in this qualitative change, which remains to be investigated.

Adult↗

PubMed1983

Isolation of a viable eccrine sweat gland by dispase.

Dispase was used to obtain viable eccrine sweat glands from human skin in an intact shape. The full thickness of human skin was soaked in a solution of dispase in Eagle's minimum essential medium at a concentration of 500 units/ml and kept in a refrigerator at 4 degrees C for 24 h. The epidermal sheet with its appendages could then be easily separated from the dermis by lifting the epidermis with fine forceps. Electron-microscopic observation revealed that the eccrine sweat gland was completely separated froM the dermis at the basement membrane zone. The isolated epidermal sheet was scarcely dissociated by mechanical agitation in the presence of Ca2+ and Mg2+ ions. The eccrine sweat gland was cut away from the epidermis by using microscissors under a stereomicroscope. A cell suspension of the isolated eccrine sweat glands was obtained after trypsinization. The cells remained more than 90% viable up to 48 h in the culture medium. The obtained viable eccrine sweat glands will be useful for the study of the biology of sweating.

Eccrine Glands↗

PubMed1979

ADH and thermal sweating.

Sweating responses to heat exposure were compared in healthy subjects pretreated with pitressin or alcohol and in the control group. Between the three groups, there were no consistent differences in the rate of sweating expressed both as a total body weight loss during 2-h heat exposure and in mg of sweat per skin area covered by a paper disc. Likewise, there were no differences in the sweat osmolality or electrolyte concentration. There was also no evidence of inverse correlation between plasma ADH level and rate of sweat secretion or its concentration when pooled data of all subjects were analyzed. It was concluded that ADH did not substantially affect thermal sweating in men.

Adult↗

PubMed1979

Quantitative study of free amino acids in human eccrine sweat excreted from the forearms of healthy trained and untrained men during exercise.

The free amino acids in eccrine sweat collected from the forearms of 20 healthy trained and 20 healthy untrained men during controlled exercise were determined quantitatively using ion exchange column chromatography. Sweat was deproteinized by adding an equal volume of 5% sulphosalicylic acid. The amino acid concentrations showed a constant qualitative pattern in sweat and large individual differences. Essential amino acids, such as isoleucine, leucine, lysine, methionine, phenylalanine, and valine were excreted in relatively small amounts. As compared to the trained men, untrained men showed statistically significantly higher concentrations in sweat for the following amino acids: Alanine, arginine, glycine, histidine, isoleucine, leucine, lysine, ornithine, phenylalanine, serine, taurine, threonine, tyrosine, and valine. No significant differences were found for citrulline, cystine, ethanolamine, and methionine. The comparison of the amino acid excretions in sweat obtained under controlled exercise and in urine showed that the amounts of amino acids excreted in sweat under controlled exercise were comparable to the losses of amino acids in urine.

Adult↗