Eccrine sweat in humans is normally a hypotonic solution, the solutes of which consist mainly of sodium, chloride, potassium, lactate, and urea (1). The sodium and chloride concentrations increase with increasing sweat rate (2), and at moderate to high sweat rates, the sodium concentration is an adequate measure of tonicity (3).It is generally presumed that sweat is elaborated by the secretory coil of the gland and altered during its passage down the duct (4). However, analysis of the physiology of the duct depends upon relatively precise knowledge of the nature of the fluid elaborated at the secretory coil (secretory fluid). Previous studies give values for the sodium concentration of the secretory fluid that are distinctly hypotonic (2, 5) or suggest that it is isotonic (6). Our studies in which we analyzed the relationship of rate of sodium excretion to sweat rate from the forehead give approximately isotonic values for the sodium concentration of the secretory fluid. MethodsSix healthy men, ages 21 to 29, were used as subjects. For 1 week before the experiment, the only exercise allowed was that necessary for the usual duties of a dermatology resident or laboratory assistant. The The skin of the forehead was gently cleansed with soap and water, rinsed with ion-free distilled water, and air dried. Aluminum chambers with internal diameter of 3.8 cm as described by Schwartz and Thaysen (2) were secured to the skin with Weldwood contact cement. Two Whatman 540 filter papers, 3.7 cm in diameter, were removed from weighed plastic bottles and introduced into the chamber and sealed at time zero. The filter papers were collected and replaced in their weighing bottles, and fresh preweighed filter papers were inserted every 3 to 10 minutes depending upon an estimate of the volume of sweat being produced. The time required for changing the filter papers was usually less than 5 seconds. Eight to twelve collections were obtained from each subject.The subjects, wearing swimming trunks, entered a room with temperatures ranging from about 950 to 1100 F and humidity around 40%. By altering the temperature and humidity in conjunction with mild, moderate, and vigorous exercise in the form of calisthenics, varying sweat rates were produced. At some time during the experiments the subjects were encouraged to maximal tolerated exercise. Sweat rates were increased and decreased so as to preclude sweat rate being a function of time. The subjects were weighed before and after the experiment, but were allowed water ad libitum during the experiment. The maximal duration of the experiment was 75 minutes for one subject and 60 minutes for the other five.Sweat volumes were determined by weight differences of the filter papers. The filter papers were then eluted with ion-free distilled water and the sodium concentrations determined on appropriate dilutions with a Perkin Elmer atomic absorption spectrophotometer. Suitable blanks were used for each subject. Recovery experiments in which 0.1 ml of a 100 mEq per L sodium chloride solution wa...

ABSTRA CT This paper describes a method for isolating and studying the metabolism of human eccrine sweat glands. (a) Electron microscopy of glands which had been isolated and then incubated for an hour revealed no apparent alteration in morphology. (b) Known variation in gland size (male > female > children) was reflected in the relative rates of lactate production. (c) Lactate production was approximately 1.5 nmoles/ gland per hr in the absence of glucose and rose to 2.7 at physiological concentrations of glucose (5.6 mmoles/ liter). This amount of lactate production agrees well with the amounts found in sweat. (d) Both adrenergic (epinephrine) and cholinergic (methacholine) stimuli increased lactate production. (e) Glycogen depletion was demonstrated during incubation. (f) 02 consumption was measured and aerobic metabolism was found to account for less than 1% of the energy derived from anaerobic pathways.These studies demonstrate that the large amounts of lactate appearing in human eccrine sweat can be accounted for by glandular metabolism and that both glycogen and glucose can be used as substrates.

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The hypothesis advanced independently in 1960 by Nastuk et. al. ' and Simpson' that myasthenia gravis is a disorder with a possible autoimmune etiology, together with studies dealing with presumed immune associations of myasthenia gravis:'-12 have recently been reviewed in detai1,l3-I5 and need not be considered here.A t the New York Academy of Sciences Conference on Autoimmunity, held in February, 1964, Strauss et al.," reported findings which essentially confirmed and extended to a larger series the various observations of several previous investigations by Strauss et al.,3 Beutner et al.,5 Feltkamp et a1.' and van der Geld et al. ' with respect to a striated muscle (A-Band) binding serum globulin factor in myasthenia gravis, as well as to the more recent finding reported by van der Geld et a1." of associated serological reactivity with thymic epithelial cells. Serum 7-globulins of 99 (30 per cent) of 336 patients with myasthenia gravis were shown to react concurrently against alternate skeletal muscle striations and thymic epithelial cell cytoplasm. This was an in vitro demonstration, using the indirect fluorescent antibody technique, within specific test limits. Serums of 19 (95 per cent) of 20 patients with myasthenia gravis and associated thymomas were reactive against both skeletal muscle and thymus. In the same coded and random survey,I4 serological reactivity against both skeletal muscle and thymus was not seen in serums of 128 of 129 healthy individuals, nor in serums of 673 of 674 disease control individuals, including those with other so-called "auto-immune diseases," myopathies, dystrophies, heredo-familial neuromuscular diseases, lymphomas, tuberculosis, granulomatoses, dysproteinemias, thymomas unassociated with myasthenia gravis, etc., nor in individuals with histories of anticholinesterase consumption in the absence of myasthenia gravis. Reactivity, in the control 557 558 Annals New York Academy of Sciences FIGURE la. Pattern observed with serums of 930 individuals in earlier series:" 223 with myasthenia gravis, 128 normal controls, and 579 "disease controls." The same pattern was observed, in the present study, with serums of 32 patients with thymomas uraassociated with myasthenia gravis. No fluorescent striations nor thymic epithelial cells were seen. FIGURES l a through e. Patterns of immunofluorescence in skeletal muscle and thymus encountered in the coded, random study of serums from 1,139 individuals, previously reported.!' Patterns similar to those illustrated in FIGURES 1 a through d were observed, as detailed in text and below, with serums from 51 additional patients with thymomas unussociated with myasthenia gravis in the present study and with serums from thirteen additional patients with myasthenia gravis and thymomas not previously reported. Composite sections were (1) fixed with 95 per cent ethanol for 5 minutes, (2) washed in repeated changes of pH 7.2, 0.01M phosphate buffered 0.15M saline for 15 minutes, (3) incubated with serums, diluted 1:60, for 30 minutes, (4) washed with s...

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