Opioid-like adverse effects of tianeptine in male rats and mice.

RATIONALE: Tianeptine is a mu-opioid receptor (MOR) agonist with increasing reports of abuse in human populations. Preclinical data regarding the abuse potential and other opioid-like adverse effects of tianeptine at supratherapeutic doses are sparse. OBJECTIVES: The present study evaluated tianeptine in a rat model of abuse potential assessment and in mouse models of motor, gastrointestinal, and respiratory adverse effects. METHODS: Abuse potential was assessed in adult male Sprague-Dawley rats using an intracranial self-stimulation (ICSS) procedure to determine effects of acute and repeated tianeptine on responding for electrical brain stimulation. Male ICR mice were used to determine the effects of tianeptine in assays of locomotor behavior and gastrointestinal motility. Male Swiss-Webster mice were monitored for respiratory changes using whole-body plethysmography. RESULTS: In rats, acute tianeptine produced weak and delayed evidence for abuse-related ICSS facilitation at an intermediate dose (10 mg/kg, IP) and pronounced, naltrexone-preventable ICSS depression at a higher dose (32 mg/kg, IP). Repeated 7-day tianeptine (10 and 32 mg/kg/day, IP) produced no increase in abuse-related ICSS facilitation, only modest tolerance to ICSS depression, and no evidence of physical dependence. In mice, tianeptine produced dose-dependent, naltrexone-preventable locomotor activation. Tianeptine (100 mg/kg, SC) also significantly inhibited gastrointestinal motility and produced naloxone-reversible respiratory depression. CONCLUSIONS: Tianeptine presents as a MOR agonist with resistance to tolerance and dependence in our ICSS assay in rats, and it has lower abuse potential by this metric than many commonly abused opioids. Nonetheless, tianeptine produces MOR agonist-like acute adverse effects that include motor impairment, constipation, and respiratory depression.

Effectiveness of reporting on latent tuberculous infection in Massachusetts, 2006-2008.

Massachusetts is one of five states that mandate the reporting of latent tuberculous infection (LTBI). We assessed 2006-2008 Massachusetts surveillance data for LTBI to describe the system and examine the characteristics of persons with LTBI. Over 3 years, 15 301 LTBI cases were reported (4742-5398/year). Among those with known country of birth (n = 11 655), 9983 (85.7%) were foreign-born. Substantial under-ascertainment and/or under-reporting appear likely; mandatory reporting does not appear sufficient for LTBI detection. Enhanced targeted testing, active LTBI surveillance, or laboratory-based surveillance may be needed to eliminate tuberculosis disease in the United States.

Le Massachusetts est l'un des cinq états qui exige la déclaration de l'infection tuberculeuse latente (LTBI). Nous avons évalué les données de surveillance de la LTBI au Massachusetts de 2006 à 2008 afin de décrire le système et d'étudier les caractéristiques des patients. En trois ans, 15 301 cas ont été rapportés (4742 à 5398 par an). Parmi les 11 655 patients dont le pays d'origine était connu, 9983 (85,7%) étaient nés à l'étranger. Il est probable que ce système de déclaration et de surveillance est déficient, car la déclaration obligatoire ne parait pas suffire à la détection de la LTBI. L'élimination de la tuberculose aux Etats-Unis pourrait nécessiter de mettre l'accent sur le dépistage ciblé, la surveillance active de la LTBI ou une surveillance basée sur les examens de laboratoire.

Massachusetts es uno de los cinco estados en los cuales la notificación de la infección tuberculosa latente (LTBI) es obligatoria. En el presente estudio se evaluaron los datos de la vigilancia de esta afección entre el 2006 y el 2008, con el objeto de describir el sistema de vigilancia y examinar las características de las personas con diagnóstico de LTBI en Massachusetts. Durante el período de 3 años del estudio se notificaron 15 301 casos (de 474 a 5398 por año). De los casos en los cuales se conocía el país de origen (n = 11 655), 9983 personas habían nacido en el extranjero (85,7%). Es muy probable que exista una considerable deficiencia en la verificación y la notificación; la declaración obligatoria no parece una medida suficiente para detectar la LTBI. Se precisa una intensificación de las pruebas diagnósticas dirigidas, una vigilancia activa o una vigilancia de laboratorio de esta afección, con el propósito de eliminar la enfermedad tuberculosa en los Estados Unidos de América.

Mapping giant salvinia with satellite imagery and image analysis.

QuickBird multispectral satellite imagery was evaluated for distinguishing giant salvinia (Salvinia molesta Mitchell) in a large reservoir in east Texas. The imagery had four bands (blue, green, red, and near-infrared) and contained 11-bit data. Color-infrared (green, red, and near-infrared bands), normal color (blue, green and red bands), and four-band composite (blue, green, red, and near-infrared bands) images were studied. Unsupervised image analysis was used to classify the imagery. Accuracy assessments performed on the classification maps of the three composite images had producer's and user's accuracies for giant salvinia ranging from 87.8 to 93.5%. Color-infrared, normal color, and four-band satellite imagery were excellent for distinguishing giant salvinia in a complex field habitat.

Ultrastructure of the hyperhidrotic eccrine sweat gland.

BACKGROUND: Hyperhidrosis is the secretion of inappropriately large amounts of sweat by eccrine glands; it can be very debilitating. Little is known of the causes of primary hyperhidrosis. OBJECTIVES: To determine whether the glands exhibit any structural abnormality in primary hyperhidrosis. METHODS: Skin biopsies were obtained from the axilla (n = 6) or neck (n = 2) of individuals aged 26-62 years with primary hyperhidrosis and from five age- and sex-matched normal individuals, with informed consent and ethical committee approval. Samples were prepared by standard methods for light and electron microscopic examination. RESULTS: All characteristics observed in the hyperhidrotic specimens were consistent with the changes seen in normal glands following strong activation: degranulation of the granular (dark) cells, dilatation of the basolateral infoldings and the canaliculi of the non-granular (clear) cells, contraction of the myoepithelial cells and thickening of the basal lamina, and presence of cellular debris including lipid droplets in the gland lumen. Pathological changes were not observed. CONCLUSIONS: The present finding of the absence of structural defects in the glands indicates that future studies should concentrate on the investigation of neurohumoral or secretory cell metabolic abnormalities.

Vacuolar-type H+ -ATPase distribution in unstimulated and acetylcholine-activated isolated human eccrine sweat glands.

The presence and cellular distribution of subunits of the V1 sector of the vacuolar-type H+ -ATPase (V-ATPase) was investigated in isolated human eccrine sweat glands. In every instance, V-ATPase was located in the cytoplasm and apical membranes of the luminal cells of the reabsorptive duct segment. In the secretory coil, both diffuse and perinuclear staining was demonstrated in the secretory cells, with additional expression at the apical and basolateral membranes and on the intercellular canaliculi. There was no detectable difference in V-ATPase expression as a result of prior application of 100 microM acetylcholine.

Nucleotide-evoked ion transport and [Ca(2+)](i) changes in normal and hyperhidrotic human sweat gland cells.

Apical and basolateral application of ATP and UTP evoked [Ca(2+)](i) and short circuit current (Isc) increases in normal and hyperhidrotic human eccrine sweat gland cells grown into functionally polarised epithelia on permeable supports. Basolateral application to hyperhidrotic cells exhibited a markedly greater increase in Isc than in normal cells. Hyperhidrotic cells also demonstrated differences from the normal in [Ca(2+)](i) and Isc responses to ATP when pre-treated with thapsigargin. The data demonstrate the presence of apical and basolateral receptors that allow nucleotides to increase [Ca(2+)](i) and Isc. The results suggest that changes from the normal in transepithelial ion transport contribute to the characteristic excessive fluid production of hyperhidrotic sweat glands.

Psychological influences on the perception of immune function.

BACKGROUND: Perception of deficiencies in immunity are common in a number of patient complaints. However, little is known about the way in which individuals form perceptions about the competence of their immune system. In two studies we examined the relationship between subjects' perceptions of their immune functioning, physical symptoms, mood and measures of immunity. METHODS: In Study 1, 20 healthy volunteers completed global ratings of their immune system functioning, as well as mood and symptom reports, twice a week for 5 weeks. At the same time, blood samples were taken to assess serum IgA, IgG, and IgM antibodies. In Study 2, another sample of 58 subjects completed the same measures weekly for 5 weeks and their blood was tested for concentrations of CD3, CD4, CD8, and CD16 lymphocytes. RESULTS: We found perceptions of immune functioning to be unrelated to the concentrations of serum antibodies or blood lymphocytes. Immune perceptions were strongly related to mood and in particular, feelings of fatigue and vigour. The experience of recent physical symptoms, while not as strong as mood variables, was also important in perceptions of immune functioning. CONCLUSIONS: Mood seems to be an important determinant in the perception of immune function, and complaints about immune dysfunction in clinical situation should be investigated with this possibility in mind.

Spinal bone density in women using depot medroxyprogesterone contraception.

OBJECTIVE: To determine factors possibly associated with reduced bone density in women using the injectable contraceptive depot medroxyprogesterone acetate. METHODS: In a cross-sectional study, bone mineral density of the lumbar spine was measured by dual energy x-ray absorptiometry in 200 current users of depot medroxyprogesterone acetate who had used this method of contraception for 2-26 years and compared with 350 control subjects. Bone density results are expressed as standard deviation scores (z score). RESULTS: The bone density was significantly lower in depot medroxyprogesterone acetate users (mean z score: -0.65, 95% confidence intervals [CI] -0.80, -0.49, P < .001). Bone density was significantly reduced in nonsmokers and smokers, and there was no significant difference in mean z score between smokers and nonsmokers (mean -0.75 versus -0.58, P=.30). Women who had started depot medroxyprogesterone acetate after the age of 20 years and who had used it for 15 or fewer years had a significantly higher bone density than the remainder of the cohort (mean -0.45 [95% CI -0.62, -0.27] versus -1.02 [95% CI -1.32, -0.73], P < .005). Bone density in depot medroxyprogesterone acetate users was not related to current age, parity, body mass index, calcium intake, or exercise. CONCLUSION: Depot medroxyprogesterone acetate use is associated with a significant reduction in bone density, and although a high proportion of depot medroxyprogesterone users do smoke, the reduction in bone density cannot be explained by smoking. Women who use it for a long time and those who start it before peak bone mass is attained may be at highest risk.

Nosocomial infections in HIV-infected patients: preliminary results from a multicenter surveillance system (1989-1995).

OBJECTIVE: To describe the characteristics of and trends in nosocomial infection among human immunodeficiency virus (HIV)-infected patients. DESIGN: Multicenter prospective cohort study. SETTING/PATIENTS: HIV-infected patients were enrolled at time of first inpatient admission at five Veterans' Administration Medical Centers (VAMCs). RESULTS: As of March 1995, 2,541 patients with 6,625 inpatient admissions had been monitored in the five VAMCs. A total of 530 nosocomial infections were detected using standard Centers for Disease Control and Prevention definitions. Overall distribution by infection site was 31% for primary bloodstream infections (BSIs), 28% for urinary tract infections, 15% for pneumonia, and 26% for all other sites. Of BSIs, 63% were central line-associated bloodstream infections (CLABs). The rate of CLABs per 1,000 central line days was 6.5 (range, 2.3-8.3) for all patients from participating hospitals, similar to the median CLAB rate of 6.0 for patients in medical intensive-care units (ICUs) of National Nosocomial Infections Surveillance (NNIS) System hospitals from January 1990 through September 1994. For ICU-specific CLABs, the rate from hospitals reporting at least one ICU CLAB was 12.7 (range, 12.1-13.1), comparable to the 90th percentile of NNIS hospital medical ICUs (13.1). Staphylococcus aureus, associated with 35% of BSIs, was the most common nosocomial BSI pathogen. Our data demonstrated the following: 13 (10%) of 134 patients with CD4 counts > or = 200 cells/mm3 had a CLAB, compared with 61 (6%) of 1,011 patients with CD4 counts < 200 cells/mm3, P = .08; the per-day risk of CLABs did not change with increased duration of catheterization (P = .4); and the per-day risk of a temporary (ie, short-term) CLAB was greater than that of a permanent CLAB (P < .001). CONCLUSIONS: The data suggest that HIV-infected patients were at higher risk of acquiring a BSI than were patients in the NNIS population; patients with CD4 counts > or = 200 cell/mm3 and temporary central lines were at increased risk for BSI, perhaps reflecting widespread prophylaxis with trimethoprim-sulfamethoxazole among patients with CD4 counts < 200 cells/mm3, and, in contrast to most studies, S aureus, not coagulase-negative Staphylococcus, was the most common BSI pathogen.

Activation of apical P2U purine receptors permits inhibition of adrenaline-evoked cyclic AMP accumulation in cultured equine sweat gland epithelial cells.

Experiments were undertaken using cultured equine sweat gland epithelial cells that express purine receptors belonging to the P2U subclass which allow the selective agonist uridine triphosphate (UTP) to increase the concentration of intracellular free Ca2+ ([Ca2+]i). Experiments using pertussis toxin (Ptx), which inactivates certain guanine-nucleotide-binding proteins (G-proteins), showed that this response consisted of Ptx-sensitive and Ptx-resistant components, and immunochemical analyses of the G-protein alpha subunits present in the cells showed that both Ptx-sensitive (alpha i1-3) and Ptx-resistant (alpha q/11) G-proteins were expressed. P2U receptors may, therefore, normally activate both of these G-protein families. Ptx-sensitive, alpha i2/3 subunits permit inhibitory control of adenylate cyclase, and UTP was shown to cause Ptx-sensitive inhibition of adrenaline-evoked cyclic AMP accumulation, suggesting that the receptors activate Gi2/3. Experiments using cells grown on permeable supports suggested that P2U receptors became essentially confined to the apical membrane in post-confluent cultures. Polarised epithelia may, therefore, express apical P2U receptors which influence two centrally important signal transduction pathways. It is highly improbable that these receptors could be activated by nucleotides released from purinergic nerves, but they may be involved in the autocrine regulation of epithelial function.

The regulation of membrane 125I- and 86Rb+ permeability in a virally transformed cell line (NCL-SG3) derived from the human sweat gland epithelium.

We have explored the factors that may regulate membrane permeability in a cell line (NCL-SG3) derived from the human sweat gland epithelium. Ionomycin increased the rate of 125I-efflux from preloaded cells and this action appeared to be due to an increase in intracellular free calcium ([Ca2+]i). The ionomycin-evoked increase in 125I- efflux was reduced in cells that were exposed either to barium or to valinomycin in the presence of a high concentration of external potassium. It thus appears that a fraction of the ionomycin-evoked increase in 125I- efflux is due to the activation of potassium channels and experiments using 86Rb+ also suggested that ionomycin increased the rate of potassium efflux, an effect which was totally abolished by barium. Blockade of Na(+)-K(+)-2Cl- cotransport and of Cl- -HCO3- exchange reduced the basal rate of 125I- efflux and the ionomycin-evoked increase in 125I-efflux from control cells and from cells depolarized by valinomycin. These transport systems thus contribute to anion efflux, although [Ca2+]i-dependent chloride channels also appear to be present. Acetylcholine increases [Ca2+]i in the secretory cells of human sweat glands, but this neurotransmitter did not increase [Ca2+]i in NCL-SG3 cells and so membrane permeability was not under cholinergic control. Adrenaline did not increase [Ca2+]i, but this hormone did evoke cyclic-3',5'-adenosine monophosphate (cyclic AMP) production. However, membrane permeability was not under adrenergic control, as the cells did not appear to express functional, cyclic AMP-dependent anion channels. This may be because they were not fully differentiated under the culture conditions. ATP consistently evoked a dose-dependent increase in anion efflux that appeared to be mediated by [Ca2+]i. The increase in [Ca2+]i was initiated by the release of calcium from a limited internal store and was subsequently sustained by calcium influx. UTP and ADP also increased [Ca2+]i, whereas adenosine, AMP and alpha,beta-methylene ATP were without effect. These data thus suggest that a subclass of type 2 purine receptor, which is functionally coupled to phosphoinositidase C, is present in these cells.

Extracellular ATP can activate autonomic signal transduction pathways in cultured equine sweat gland epithelial cells.

Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP > or = ATP > ADP >> AMP = adenosine = alpha,beta-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this response developed during repeated stimulation with ATP and this was blocked by staurosporine, an inhibitor of protein kinase C, and augmented by a phorbol ester which acts as an exogenous activator of this enzyme. A protein-kinase-C-dependent inhibitory pathway thus seems to become active during repeated stimulation with ATP. ATP and related compounds could also raise cellular cyclic AMP content. The order of potency was ATP > ADP = AMP = adenosine >> UTP, suggesting that this response is mediated via a separate subclass of P2 receptor. The present results demonstrate that ATP can activate autonomic signal-transduction pathways in cultured equine sweat gland cells and suggest that there may be a purinergic component to the control of secretory activity in the equine sweat gland.

The effect of removing external sodium upon the cholinergic regulation of potassium permeability in the rat submandibular gland in vitro.

Fragments of rat submandibular gland were loaded with 86Rb+ and superfused so that the rate of 86Rb(+)-efflux could be quantified as an indicator of potassium permeability. Acetylcholine evoked an increase in permeability consisting of a transient, calcium-independent response and a sustained, calcium-dependent. Total removal of external sodium significantly inhibited both phases of this response. The results thus confirm that the cholinergic regulation of potassium permeability is compromised by removal of external sodium but do not support the view that this is due, exclusively, to an effect on calcium influx.

Investigation of stimulus-secretion coupling in equine sweat gland epithelia using cell culture techniques.

When sweat glands isolated from samples of horse skin were explanted and cultured under favourable conditions, they could exhibit cellular outgrowth. This growth could be maintained for 2-4 weeks and these primary cultures were then disaggregated and the resultant cell suspensions used to initiate epithelial cell lines. Secretion from intact equine sweat glands is regulated by beta 2-adrenoceptors and appears to be mediated by cyclic AMP, but there is evidence that calcium may also play a role. Adrenaline could increase the cyclic AMP content of the cultured cells and this response was mediated by beta 2-adrenoceptors. Adrenaline was also able to evoke a small increase in intracellular free calcium ([Ca2+]i) but the pharmacology of this response remains obscure. Adrenaline thus activates at least two potentially important second-messenger signalling pathways which have the capacity to interact, because adrenaline-evoked cyclic AMP formation was inhibited if [Ca2+]i was raised with ionomycin. The chloride permeability of mammalian epithelial cells characteristically rises during secretion, and adrenaline could increase chloride permeability in the cultured epithelia but the cells did not contain cyclic-AMP-dependent chloride channels and so this response was mediated by [Ca2+]i.

Temporal changes in the granulocytic responses to experimental infection of the skin of mice and sheep with Dermatophilus congolensis.

The patterns of dermal inflammatory cell response to infection with Dermatophilosis congolensis were determined in mice and sheep from histological samples taken before and at intervals after topical application of infective zoospores to ether-swabbed skin. Neutrophils, eosinophils, basophils and mast cells were identified by histochemical staining. Temporal changes in the B cell, T cell, and MHC Class II+ dendritic cell populations form part of a separate report. The filamentous stages of the bacterium were observed in the stratum corneum of both species; in the sheep they were also found in the outer layers of the living epidermis. In both species, large numbers of neutrophils and some lymphocytes penetrated the epidermis and entered the infected surface region. Within the underlying dermis there was an accumulation of dendritic cells immediately below the infected epidermis and evidence of mast cell degranulation; the basophils and eosinophils did not appear to be actively involved. The striking difference between the two species was the duration of the infection and the associated response which, in the mouse, lasted about five days in comparison with over 21 days in the sheep. Neutrophil numbers in the mouse for example were elevated by 12 h and had peaked at 60 h after infection, while in the sheep they did not peak until about 120 h.

Human studies to measure the effect of antibiotic residues.

This epidemiological study compares the frequency of resistant bacteria in stool microflora among vegetarians and nonvegetarians over a 12 month period. Two well characterized vegetarian populations (one in Boston, MA and the other in Loma Linda, CA) as well as appropriate controls were studied. No apparent differences in the prevalence of antibiotic resistance in the microflora were noted; however, vegetarians had a significantly greater incidence of multi-antibiotic resistance. E. coli of the same API biotype had the same frequency of antibiotic resistance in both vegetarians and nonvegetarians. Quantitative studies showed similar percents of tetracycline resistant facultative isolates and of "bacteroides." Klebsiella were more common in the stool of the nonvegetarians. As shown in previous studies, exposure to animal products either as meat eaters or production workers in a poultry abattoir was not associated with an increased incidence of resistant bacterial flora or infections caused by resistant strains.

Amiloride impairs the cholinergic regulation of potassium permeability in the human sweat gland but not in the rat submandibular gland.

Potassium permeability was monitored in human sweat glands and rat submandibular glands. Acetylcholine increased permeability in both tissues and the responses consisted of transient, calcium-independent and sustained, calcium-dependent components. Amiloride, a drug which inhibits Na(+)-H+ countertransport, impaired the regulation of potassium permeability in sweat glands but not in the submandibular gland. It is suggested that the stimulus-permeability coupling process in the sweat gland may be sensitive to the lowering of internal pH.

Histological and electron microprobe studies of mineralisation in aluminium-related osteomalacia.

AIMS: To determine a possible mechanism to explain the presence of aluminium lines within fully calcified bone in aluminium-related osteomalacia. METHODS: Fifty five bone cases shown by bone biopsy to be aluminium-related osteomalacia were studied. In 38 specimens aluminium lines were identified within calcified bone by means of the Aluminon stain and a characteristic form of patchy mineralisation was seen within thickened osteoid seams. Five representative examples were analysed quantitatively by histomorphometry and electronprobe X-ray microanalysis and compared with five cases of vitamin D deficiency-related osteomalacia which also had patchy mineralisation. RESULTS: The patchy calcification occupied 40 +/- 8% (mean +/- SEM) of the osteoid and consisted of small focal deposits (less than 40 microns diameter), often (52%) around osteoid osteocytes (probably an underestimate of the association), and larger areas that extended to the aluminium lines at the underlying mineralisation front. Small and large mineralisation nuclei were seen ultrastructurally in the patchy calcification. Quantitative electronprobe X-ray microanalysis showed that calcium concentrations and calcium:phosphorus ratios in the mineralisation nuclei and in the superficial layer of the fully calcified bone of the aluminium-related osteomalacia cases were significantly less than values measured at similar sites in the vitamin D deficiency-related osteomalacia cases. Furthermore, aluminium could not be detected by means of this technique at the mineralisation front or along cement lines in these specimens. CONCLUSIONS: Calcification can occur in thickened osteoid seams in osteomalacia. It can begin around osteoid osteocytes as small deposits that enlarge within the osteoid and extend to the underlying mineralisation front or cement line where aluminium lines may become trapped. Complete calcification of osteoid could account for the presence of aluminium lines within fully calcified bone. The Aluminon stain appears to be a more sensitive method for the detection of aluminium in bone than electronprobe X-ray microanalysis.

The role of potassium and other ions in the control of aldosterone synthesis.

Fast and slow K+ efflux components, independently regulated by angiotensin II (AII), have been identified in bovine adrenocortical cells. We have further investigated the role of potassium in the control of aldosterone synthesis in two ways. Firstly, isotopic tracers, in conjunction with channel modulators, have been used to study the interrelationship of K+ and Ca2+ in the control of AII-stimulated aldosterone synthesis. Secondly, electron probe X-ray microanalysis (EPXMA) was used to quantify potassium, sodium, chlorine and phosphorous in control and AII-stimulated cells. The effects of verapamil on 43K efflux were measured at two stages during AII stimulation. During the first ten minutes of treatment, when efflux via the fast component predominates, AII and verapamil both slowed efflux and their effects were additive. If verapamil was added later, at the time when efflux by the fast component appeared exhausted and the stimulatory effect of AII on the slow efflux component was apparent, it again slowed efflux. These data suggest that verapamil prevents calcium-gated K+ channels from opening by blocking Ca2+ channels. However, verapamil had no effect on AII-stimulated calcium efflux. In addition to blocking Ca2+ channels, verapamil may directly inhibit potassium efflux. EPXMA showed a bimodal distribution of potassium concentrations in control cells. However, in cells stimulated with AII for five minutes, the mean potassium content was less than in controls and was not bimodally distributed. Sodium content was increased by AII-treatment, chlorine was lowered and phosphorus remained unchanged. The data confirm previous observations that AII inhibits Na+/K+ ATPase activity.

The effects of removing external sodium upon the control of potassium (86Rb+) permeability in the isolated human sweat gland.

The changes in cytoplasmic free calcium ([Ca2+]i) which occur in isolated human sweat glands during cholinergic stimulation have been studied indirectly by monitoring potassium permeability. The acetylcholine-evoked permeability increase normally consists of transient and sustained phases which are attributed to the mobilization of intracellular calcium stores and to calcium influx respectively. Such consistent responses to acetylcholine could not be obtained during superfusion with bicarbonate-free, HEPES-buffered solutions. The human sweat gland in vitro therefore appears to have a strict requirement for bicarbonate. The sustained component of the response was not affected by total removal of external sodium, suggesting that calcium influx does not occur via a sodium-dependent system. The transient component, however, was abolished when external sodium was replaced by N-methyl-D-glucammonium (NMDG+). It therefore appears that secretagogue-evoked mobilization of cytoplasmic calcium is dependent, in some way, upon external sodium. This dependence is not, however, absolute as the response was essentially normal when sodium was replaced by lithium.