Occupational electric and magnetic field exposure and brain cancer: a meta-analysis

We conducted a meta-analysis to acquire an understanding of the association between central nervous system cancer and occupational exposure to electric and magnetic fields. To explore sources of heterogeneity, study characteristics were scored and examined using regression analysis. An inverse-variance weighted pooling leads to a small overall increase in relative risk (10 to 20%) for the broad group of electrical occupations. One of the largest differences was lower relative risk for Scandinavian studies. Lower relative risks were also reported in cohort- and incidence-based studies. Findings were not sensitive to assumptions, including unpublished data, influence of individual studies, weighting schemes, and modeling. Whereas most studies present a small elevation in risk, there is considerable heterogeneity among the results.

Dose-dependent suppression of toluene metabolism by isopropyl alcohol and methyl ethyl ketone after experimental exposure of rats

In order to examine possible suppression of toluene metabolism due to coexposure to other solvents, female Wistar rats were exposed for 8 h to toluene alone (at 50 or 100 ppm), or in combination with either methyl ethyl ketone (at 50, 100, 200 or 400 ppm) or isopropyl alcohol (at 50, 100, 200, 400, 800 or 1600 ppm). Urine samples were collected for 24 h after initiation of each exposure, and subjected to analysis for two toluene metabolites, hippuric acid and o-cresol, both by HPLC. The excretion of hippuric acid, a major metabolite, was not modified when the concentrations of methyl ethyl ketone or isopropyl alcohol were low, i.e. 100 ppm or below, whereas it was reduced when methyl ethyl ketone or isopropyl alcohol concentrations were twice or more times higher than that of toluene. There were no changes in any cases in excretion of o-cresol, a minor metabolite. The observation after coexposure to methyl ethyl ketone or isopropyl alcohol at low concentration is in line with the negative interaction between toluene and methyl ethyl ketone as well as between toluene and isopropyl alcohol after occupational exposures at low concentrations. Metabolic interaction may take place when the exposure intensity is high, as observed in the present study and also after experimental exposure of volunteers to toluene and m-xylene, or occupational exposure to benzene and toluene.

Dietary intake of cadmium and lead among the general population in Korea

This survey was conducted in Seoul, Pusan, Chunan, and Haman in Korea to clarify cadmium and lead burden in the general Korean populations in terms of dietary intake of cadmium and lead and the concentrations of the two metals in blood. People who participated in the study were 141 healthy nonsmoking women aged 21-56 years. Determination of cadmium and lead in 24-hr food duplicates and blood samples was carried out by graphite furnace atomic absorption spectrophotometry. The geometric means for the four sites in combination were 21.2 micrograms/day for dietary cadmium, 20.5 micrograms/day for dietary lead, 1.27 ng/ml for blood cadmium, and 44.3 ng/ml for blood lead. Cadmium intake from boiled rice accounted for 23% of total daily cadmium intake. The counterpart value for lead intake from boiled rice was 12%. Blood cadmium levels and dietary cadmium intake were lower and blood lead level and dietary lead intake were higher in Korean women than in Japanese women. The values for dietary cadmium are similar to, and the values for dietary lead are somewhat lower than, the levels reported from Europe and the United States. Dietary intake was the main source of cadmium exposure, whereas lead exposure was from both ambient air and foods in the Korean population.

Patch-clamp analysis of glycine-induced currents in chick ciliary ganglion neurons

1. The whole-cell configuration of the patch-clamp technique was used to analyse currents induced by glycine in chick ciliary ganglion neurons freshly dissociated from 14- to 15-day-old embryos. 2. Application of glycine to cells voltage-clamped at -60 mV induced inward currents in all neurons tested. Dose-response curves yielded an EC50 of about 50 microM. Similar responses were elicited by beta-alanine and taurine though higher concentrations were required. 3. Strychnine reversibly inhibited the glycine-induced responses. The effect was dose dependent with a half-maximal effect being obtained with 20 nM strychnine. 4. Glycine-induced currents were inhibited by 100 microM Zn2+. The inhibition had slow rates of onset and recovery, in contrast to Zn2+ inhibition of GABA responses. Both bicuculline and d-tubocurarine inhibited glycine responses in a dose-dependent manner. 5. The steady-state I-V curve for glycine-induced currents was linear over the range -60 to +60 mV, but showed an outward rectification at very hyperpolarized membrane potentials. The reversal potential of glycine-induced currents shifted with changes in intracellular chloride concentration in a manner expected for chloride-selective channels. 6. Expression of functional glycine receptors during development was examined at embryonic day 8 (E8), 11, 14, and 18. The mean peak current was about 60-fold larger at E14 than at E8 and vastly exceeded changes in cell size. During the same period, responses to GABA increased only 2-fold in amplitude and correlated with changes in cell size.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary alpha1-microglobulin, beta2-microglobulin, and retinol-binding protein levels in general populations in Japan with references to cadmium in urine, blood, and 24-hour food duplicates

Possible cadmium (Cd) exposure-associated changes in urinary levels of low-molecular-weight proteins were studied in nonsmoking and non-drinking female members of the general Japanese population (378 subjects with no known occupational heavy metal exposure) who lived at 19 study sites (all without any known environmental heavy metal pollution) in 13 prefectures throughout Japan. The external Cd dose was evaluated in terms of daily Cd intake via food (Cd-F), whereas Cd levels in blood (Cd-B) and urine (Cd-U) were taken as internal dose indicators. When the subjects were classified according to Cd-F into three groups with "low" (20.4 micrograms/day as a geometric mean of 97 women), "middle" (35.0 micrograms/day, 120 women) and "high" (67.0 micrograms/day, 66 women) exposure, both Cd-B and Cd-U increased in parallel with the changes in Cd-F. However, there were no dose-dependent changes in beta2-microglobulin or retinol-binding protein levels in urine, alpha1-microglobulin levels appeared to increase, but the distribution of the cases above the two cutoff levels of 9.6 and 15.8 micrograms/mg creatinine among the three Cd-F groups did not show any bias. Overall, it was concluded that there was no apparent Cd exposure-associated elevation in urinary low-molecular-weight protein levels in the study population.

Effects of methanol on styrene metabolism among workers occupationally exposed at low concentrations

A survey was conducted in the second half of a work week on 39 male workers who were occupationally exposed to styrene in combination with methanol and methyl acetate during the production of plastic buttons. Time-weighted average exposure during an 8-h shift to styrene (Sty-A) and methyl acetate was monitored by carbon cloth-equipped personal samplers and to methanol by water-equipped ones. Urine samples were collected near the end of the shift and analyzed for mandelic (MA-U) and phenylglyoxylic acids (PhGA-U) by HPLC. Geometric mean styrene concentration was 12.4 ppm (micrograms/g) with the maximum of 46 ppm, whereas the values for methanol and methyl acetate in combination were 23.5 ppm and 229 ppm, respectively. The relationship of MA-U and PhGA-U with Sty-A was examined by linear regression analysis. The equations for the regression lines were compared with the results from a previous survey (Ikeda et al. 1983) in which workers were exposed only to styrene, and the methods employed were identical with that in the present study. The comparison showed no evidence to suggest that styrene metabolism is suppressed by coexposure to methanol and methyl acetate at low concentrations below the current occupational exposure limit of 200 ppm.

A randomized prospective comparison of clarithromycin versus amoxycillin in combination with omeprazole for eradication of Helicobacter pylori

AIM

To compare H. pylori eradication rates using omeprazole in conjunction with either amoxycillin or clarithromycin.

BACKGROUND

Omeprazole with amoxycillin is the most widely used dual therapy regimen for eradication of H. pylori. A recent open study suggested a high eradication rate combining omeprazole with the newer macrolide, clarithromycin.

METHODS

A randomized prospective trial in 54 patients was conducted to compare 2 weeks of treatment with omeprazole 40 mg once daily and either amoxycillin 500 mg three times daily or clarithromycin 500 mg three times daily. H. pylori eradication was assessed using the 13C urea breath test.

RESULTS

Eradication was achieved in 18/26 (69.2%) of subjects treated with omeprazole and amoxycillin and 18/25 (72.0%) of those treated with omeprazole and clarithromycin (P = N.S.). Minor side effects, most commonly altered taste, were reported by 16% of patients and were more frequent in those randomized to clarithromycin (P = 0.01).

CONCLUSIONS

These regimens are similarly effective. However, clarithromycin is more expensive, associated with a greater frequency of side effects and, unlike amoxycillin, resistance by H. pylori has been reported. This suggests that clarithromycin may be a useful alternative when there is penicillin allergy or previous treatment failure, but it should not replace amoxycillin as first choice in omeprazole-based dual therapy.

[Changes in and significance of atrial natriuretic peptide, angiotensin II after experimental brain injury]

We used the method of RIA determined the contents of atrial natriuretic peptide (ANP), angiotensin II (ANG II) in plasma and brain tissues after brain injury in 70 rats. The results showed that the ANP was significantly decreased in brain tissues on 6, 72 hours after brain injury. At the same time, the plasma and brain tissues ANG II, brain water contents were significantly increased. The results suggested that the unbalance of ANP and ANG II may be related to the pathophysiological process of brain edema.

Regulation of human chorionic gonadotropin secretion and messenger ribonucleic acid levels by follistatin in the NUCC-3 choriocarcinoma cell line

In this study, the NUCC-3 choriocarcinoma cell line was used as an in vitro placental cell model to investigate the effects of follistatin on basal and GnRH-stimulated hCG secretion and/or its subunit mRNA levels. Follistatin (1.5-100 ng/ml; 48 h) alone did not affect basal hCG secretion or its subunit mRNA levels. GnRH increased hCG secretion and hCG beta-subunit mRNA levels in a dose-dependent manner, with maximal effects (2.37- and 2.4-fold increases, respectively) at a dose of 10(-8) M after 24 h of culture (P < 0.001). The time-course study showed that the increase in hCG secretion induced by GnRH occurred between 6-48 h after treatment. Follistatin (6-100 ng/ml; 48 h) significantly suppressed GnRH-stimulated hCG secretion and hCG alpha- and beta-subunit mRNA levels, with maximal suppression of 73.1%, 106.9%, and 129.1%, respectively (P < 0.001). In addition, follistatin (25 ng/ml) inhibited hCG secretion in response to phorbol 12-myristate 13-acetate (100 nM) by 90.3%. However, follistatin had no effect on hCG secretion evoked by forskolin (10 microM), and no change in hCG secretion was observed after treatment with a calcium ionophore (A23187; 10 microM) alone or in combination with follistatin. Furthermore, there was no significant difference in the half-lives of hCG alpha and -beta mRNA induced by GnRH alone compared with those induced by GnRH plus follistatin (P > 0.1), indicating that follistatin did not affect the stability of hCG alpha and -beta mRNA. Our data suggest that follistatin inhibits GnRH-stimulated hCG secretion as well as hCG alpha- and beta-subunit mRNA levels in the NUCC-3 choriocarcinoma cell line by decreasing the rate of transcription through the second messenger transduction system-protein kinase-C, rather than by affecting the stability of mRNA. These findings indicate that follistatin may play an important role in the regulation of hCG production in the placenta during pregnancy.

Neuronal acetylcholine receptors that bind alpha-bungarotoxin with high affinity function as ligand-gated ion channels

Neuronal membrane components that bind alpha-bungarotoxin with high affinity can increase intracellular levels of free calcium, demonstrating the components function as nicotinic receptors. Though such receptors often contain the alpha 7 gene product, which by itself can produce ionotropic receptors in Xenopus oocytes, numerous attempts have failed to demonstrate an ion channel function for the native receptors on neurons. Using rapid application of agonist, we show here that the native receptors are ligand-gated ion channels which are cation selective, prefer nicotine over acetylcholine, and rapidly desensitize. Much of the calcium increase caused in neurons by the receptors under physiological conditions appears to result from their depolarizing the membrane sufficiently to trigger calcium influx through voltage-gated channels.

Induction of c-fos expression in the rostral medulla of rats following electroacupuncture stimulation

The present study was designed to examine the induction of c-fos mRNA and Fos-like protein in the rostral medulla of awake rats following electroacupuncture (EA) stimulation, using in situ hybridization and immunohistochemical method. Rats were subjected to EA stimulation (100 Hz, 1-2-3 mA) for 30 min by inserting two needles into acupoints Zusanli (S36) and Sanyingjiao (Sp6) of each hind leg. Animals were sacrificed 1h and 2h after EA for in situ hybridization and immunohistochemical study, respectively. c-fos mRNA or Fos-like-immunoreactivity (FLI) neurons were densely distributed in the rostral ventromedial medulla (RVM), including raphe magnus nucleus, gigantocellular reticular nucleus, gigantocellular reticular nucleus alpha, as well as intermediate reticular nucleus. Neurons in the solitary tract nucleus also showed c-fos expression. The results suggest that the RVM may be an important region for mediating EA effect.

Preliminary study on aluminum content of foods and aluminum intake of residents in Tianjin

Aluminum contents of 64 kinds mof foods in Tianjin were determined. The results showed that the aluminum levels in different kinds of foods varied greatly, and most foodstuffs from natural sources (including contamination from food processing) contained less than 10 mg/kg. Aluminum contents were higher in foodstuffs of plant origin, especially dry beans containing large amounts of aluminum naturally. Lower concentration of aluminum seemed to be present in foodstuffs of animal origin. It was estimated that the potential daily intake of aluminum per person from natural dietary sources in Tianjin was about 3.79 mg. This estimated figure of dietary aluminum intake was very close to the measured data from 24 daily diets of college students, which was 4.86 +/- 1.72 mg. Considering all the potential sources of natural aluminum in foods, water and the individual habitual food, it would appear that most residents in Tianjin would consume 3-10 mg aluminum daily from natural dietary sources.

Increased release of immunoreactive cholecystokinin octapeptide by morphine and potentiation of mu-opioid analgesia by CCKB receptor antagonist L-365,260 in rat spinal cord

This is the first report showing, in an in vivo study, that systemic morphine produced a marked (89%, P < 0.01) increase of the cholecystokinin octapeptide (CCK-8) immunoreactivity in the perfusate of the rat spinal cord, an effect completely reversed by naloxone. Since CCK-8 has been shown to possess potent anti-opioid activity at a spinal level, a blockade of the spinal cholecystokinin effect would be expected to potentiate opiate analgesia. With tail flick latency as a nociceptive index, it was found that intrathecal (i.t.) injection of a novel CCKB antagonist L-365,260 produced a marked potentiation of the analgesic effect induced by the mu-opioid agonists morphine (4 mg/kg s.c.) or ohmefentanyl (32 ng i.t.). Similar effects were obtained with the CCKA antagonist devazepide at a dose 40-50 times higher than that of L-365,260. Both devazepide and L-365,260 showed a bell-shaped dose-response curve. The results confirm the notion that an increased release of CCK-8 may constitute a self-limiting process for opioid effects at the spinal level, and that it is the CCKB receptor which mediates the anti-opioid effect of CCK-8 in the rat spinal cord.

Accelerated expression of cholecystokinin gene in the brain of rats rendered tolerant to morphine

Results from behavioural studies have shown that central cholecystokinin octapeptide (CCK-8) is a powerful antagonist against opioid effects and that an increased release of central CCK-8 plays an important role in the mechanisms of tolerance to morphine analgesia. No information is available concerning the rate of biosynthesis of CCK-8 in response to chronic morphine administration. Blot hybridization experiments made in the present study revealed a marked increase in preproCCK mRNA in the brain of rats receiving chronic morphine treatment for 1, 3 and 6 days, showing an increment of 52% (p < 0.05), 62% (p < 0.05) and 97% (p < 0.01) respectively. The results suggest that an acceleration of the expression of the CCK gene during long-term morphine treatment might constitute one of the mechanisms for morphine tolerance.

Expression of mRNA for follicle-stimulating hormone suppressing protein in ovarian tissues of cows

The expression of bovine follicle-stimulating hormone (FSH)-suppressing protein (FSP) mRNA was investigated in different ovarian tissues of cows. Northern blot analysis, using a cDNA probe to bovine FSP, demonstrated that the FSP gene in the bovine ovary is highly expressed in a pool of isolated granulosa cells. Two bands (2.8 and 1.8 kb) were observed in all tissues expressing the mRNA. FSP mRNA was low in small antral follicles and increased in growing follicles to reach a maximum in preovulatory follicles. Low amounts of mRNA of steady state FSP were observed in all stages of the corpus luteum as well as in the corpus luteum of pregnant cows, in the corpus albicans and theca tissue, whereas this mRNA could not be detected in the liver. These results are consistent with the hypothesis that, in cows, FSP functions as an autocrine regulator in developing follicles to facilitate luteinization of granulosa cells.

Nicotinic receptors that bind alpha-bungarotoxin on neurons raise intracellular free Ca2+

Many populations of vertebrate neurons have a membrane component that binds alpha-bungarotoxin and cholinergic ligands. Despite the abundance of this component and its similarities to nicotinic receptors, its function has remained controversial. Using a fluorescence assay, we show here that activation of the component elevates the intracellular concentration of free Ca2+, demonstrating a receptor function for the toxin-binding component. Whole-cell voltage-clamp and intracellular recordings did not detect a significant current resulting from receptor activation, possibly because the currents were small or the receptors rapidly desensitized. The rise in intracellular free Ca2+ caused by the receptor was prevented by Ca2+ channel blockers. This suggests a signaling cascade likely to have important regulatory consequences for the neuron.

Transferrin inhibits aromatase activity of rat granulosa cells in vitro

The effect of transferrin on basal and FSH-stimulated aromatase activity of granulosa cells from immature female rats treated with diethylstilboestrol (DES) was examined in vitro by a radiometric method. The basal activity of the enzyme was very low after 3 days of incubation. Treatment with FSH (20 ng/ml) resulted in a 9.6-fold increase in activity, whereas coincubation with increasing doses of transferrin (3-300 micrograms/ml) produced a dose-dependent inhibition of FSH-stimulated aromatase activity with a projected minimal effective dose of less than 2 micrograms/ml. A time-course study showed that the inhibitory effect of transferrin on aromatase activity has become significant at 48 h of incubation. The inhibitory action of transferrin on the enzyme complex was further confirmed by showing that the FSH dose-response curve was significantly suppressed by concomitant treatment with 100 micrograms transferrin/ml with a maximum suppression of 54.1% at a dose of 30 ng FSH/ml. The possibility that transferrin may act through a non-specific inhibitory effect seems unlikely, as no changes in cell number and DNA content per well were observed. In fact, protein synthesis was enhanced after treatment with transferrin. Aromatase activity, stimulated by several promoters of cyclic AMP (cAMP), such as prostaglandin E2 (PGE2), forskolin and 8-bromo-cAMP, was significantly suppressed by 100 micrograms transferrin/ml (36.6, 47.4 and 23.4% inhibition respectively), suggesting that the effect of transferrin on FSH action may involve a site(s) distal to cAMP generation. These findings indicated that transferrin, present in follicular fluid, may play an important role in the regulation of granulosa cell differentiation.

Acetylcholine synthesis in a primary culture of porcine intermediate lobe cells

Abstract Previous pharmacological studies with the pituitary gland have suggested that acetylcholine (ACh) might be involved in the regulation of intermediate lobe (IL) function. Whether ACh is endogenous to the IL cells or provided from an extrinsic source is unclear. The present experiments tested the possibility that the endocrine cells of the IL may be a source of ACh by measuring certain cholinergic markers in a primary culture of dissociated porcine cells. The endogenous ACh content was readily measurable in both the freshly dissociated IL cells and in 2- or 4-day primary cultures. Choline acetyltransferase activity was also measurable in the freshly dissociated and cultured IL cells and was reduced by 53% in the presence of a specific inhibitor, napthylvinylpyridine (50 muM). IL cells incubated in the presence of [(14)C]choline (1 muM) were able to synthesize [(14)C]ACh and the accumulation of the new ACh was inhibited by hemicholinium-3 (30 muM), a competitive inhibitor of high affinity choline uptake at cholinergic nerve terminals. In conclusion, these results demonstrate that the endocrine cells of the IL are capable of synthesizing and storing ACh.

Changes of nerve excitability and urinary deltamethrin in sprayers

The nerve excitability of median nerve as well as the urinary deltamethrin and its metabolite dibromovinyl-dimethyl-cyclopropane carboxylic acid (Br2A) were detected in 24 deltamethrin sprayers in an assessment of the exposure and effect of deltamethrin. Twenty-nine male, unexposed referents of the same age range were also selected. The urinary deltamethrin and its metabolite Br2A were detectable by GC and HPLC in the sprayers after exposure. The nerve excitability detected with an electromyograph and pairs of stimuli at variable intervals showed that there was a prolongation of supernormal period in median nerve of the exposed group after a 3-d spraying compared with that before spraying which became more significant 2 d after cessation of exposure. In the mean time, no change of supernormal period in the median nerve of reference group was found at the 3-d interval. Nearly half of the sprayers had a supernormal period prolonged by more than 4 ms after spraying, whereas nearly none of the reference group showed similar changes after repeated examinations. Although there was neither correlation between the nerve excitability changes and the urinary deltamethrin or Br2A excretion, nor was a case of acute deltamethrin poisoning diagnosed, the non invasive technique used for nerve excitability detection in this study seems to be valuable in studying deltamethrin toxicity on human.

[Exposure levels and biological monitoring of pyrethroids in spraymen]

In order to assess the exposure levels of pyrethroids in spraymen, 50 adult male cotton growers were selected as monitoring subjects. The exposure levels were evaluated by measuring the air concentration, dermal exposure and urinary content of pyrethroids. The results showed that the air concentrations of deltamethrin at breathing zone were 0.02-0.32 micrograms/m3 in deltamethrin exposed group, and of fenvalerate at 0.69-1.09 micrograms/m3 in exposed spraymen. The dermal exposure was more prominent and indicated the most significant route of absorption. In one-day spraying, the urinary deltamethrin was not detected at 12 hours after the beginning of exposure while the fenvalerate was still detected 24 hours after starting exposure. However, both can be consecutively detected even two days after cessation of a three-day spraying. Health effects were investigated by interviews and physical examination. 32 out of 50 spraymen at the above exposure levels complained of abnormal facial sensations. No acute pyrethroid poisoning cases were found.

The effects of sonication on alpha-crystallin

Sonication of bovine alpha-crystallin increases its molecular mass from around 770 kDa to in excess of 2,300 kDa. Exposure to 2M urea or 0.1 M glycine pH 7, did not affect the size of the sonicated protein, indicating that it did not consist of dimers and higher polymers of the original molecule. Sonication of a mixture of alpha-crystallins labelled on the A chain sulphydryl group with either an aminonaphthalene or a fluorescein chromophore, generated a product exhibiting substantial energy transfer. The average distance between the probes was calculated to be 5 nm. These observations suggest that sonication has generated a new quaternary structure, incorporating subunits from two or more different alpha-crystallin molecules. No significant differences were observed in the microenvironments of tryptophan residues although those in the sonicated protein could be more easily exposed by controlled denaturation with urea. A small decrease was observed in the quenchability of a fluorescent probe attached to the sulphydryl group and a small increase in the uptake of an hydrophobic probe. These data suggest that sonication may have altered the conformation of the subunits at, or near the surface of the protein.

Levels of exposure and biological monitoring of pyrethroids in spraymen

To assess the exposure response relation of pyrethroids in spraymen, 50 adult male cotton growers were selected and divided into three groups, one group to spray pyrethroids for one day, two groups to spray for three days. Deltamethrin, fenvalerate, and a deltamethrin methamidophos mixture were sprayed by appropriate subgroups for five hours a day. Exposure levels were evaluated by measuring the air concentration, dermal exposure concentration, and urinary content of pyrethroids by gas chromatography. Air concentrations of deltamethrin at the breathing zone were 0.01-0.89 microgram/m3 in the deltamethrin exposed group. For fenvalerate, air concentrations were 0.06-1.98 micrograms/m3. Dermal exposure, particularly on the legs, feet, and hands was appreciable and indicated that this was the main route of absorption. In those spraying for one day, urinary deltamethrin was not detectable by 12 hours after the beginning of exposure whereas fenvalerate was still detectable up to 24 hours after first exposure. Both pyrethroids could be detected two days after the end of three day spraying. Health effects were investigated by interview and physical examination. Twenty nine spraymen complained of abnormal facial sensations that developed mostly two to three hours from the start of pyrethroid spraying and that disappeared by 24 hours after exposure ceased. Some had dizziness, headache, and nausea, but no subject was diagnosed as having acute pyrethroid poisoning. The symptoms showed no significant correlation with urinary pyrethroid excretion. Blood cholinesterase activity of spraymen using the pyrethroid methamidophos mixture did not change.

An epidemiological study on occupational acute pyrethroid poisoning in cotton farmers

A cross sectional survey on the prevalence of acute pyrethroid poisoning in cotton farmers was conducted in 1987 and 1988. A total of 3113 pyrethroid spraymen (2230 men (71.6%) and 883 women (28.4%] were interviewed after spraying and followed up for 72 hours. Adverse effects of pyrethroid exposure were found in 834 of them (26.8%) manifested as abnormal facial sensations, dizziness, headache, fatigue, nausea, or loss of appetite. Only 10 subjects, who developed significant systemic symptoms and had signs of listlessness or muscular fasciculation, were diagnosed as having mild occupational acute pyrethroid poisoning with a prevalence of 0.31% in subjects exposed to pure pyrethroids and 0.38% in subjects exposed to pyrethroid organophosphate mixtures. Measurements of pyrethroid concentrations in the air of the breathing zone, in skin pads, and in urine samples showed that dermal contamination is the main route of exposure to pyrethroids in cotton growers. Preventive measures are recommended.

Bicuculline blocks nicotinic acetylcholine response in isolated intermediate lobe cells of the pig

1. The effect of bicuculline on nicotinic acetylcholine (ACh) responses in isolated intermediate lobe (IL) cells of the pig was investigated by use of patch-clamp techniques. Bicuculline was found to reduce ACh-evoked whole-cell currents (IACh) in all cells tested (n = 40). 2. The blocking effect of bicuculline on IACh was dose-dependent, the concentration producing half-maximal blockade being 43.8 microM. 3. The blockade of IACh by bicuculline was not voltage-dependent at membrane potentials above -60 mV, but a slight voltage-dependence was observed at holding potentials (HP) of -80 and -100 mV. 4. The inhibitory effect of bicuculline on IACh was partially competitive at a HP of -60 mV. 5. Neither SR 95531, a pyridazinyl gamma-aminobutyric acid derivative, nor t-butylbicyclophosphorothionate (TBPS) blocked IACh in IL cells. 6. It is concluded that bicuculline interacts directly with the ACh receptor-ionophore complex on porcine IL cells.

Nicotinic acetylcholine receptors in porcine hypophyseal intermediate lobe cells

1. Acetylcholine (ACh) was found to depolarize isolated porcine intermediate lobe cells maintained in primary cells culture. We investigated the ACh-induced responses in both whole-cell and cell-attached configurations of the patch-clamp technique. 2. From noise analysis of ACh-evoked whole-cell currents, we estimated an elementary conductance of 20 pS and a channel open duration of about 1.7 ms at -60 mV. From single-channel recordings, we obtained a slope conductance of 26 pS and a mean open time of 1.8 ms at membrane potentials between -60 and -80 mV. 3. ACh-evoked responses were blocked by d-tubocurarine (d-TC), hexamethonium and mecamylamine, but were insensitive to alpha-bungarotoxin. These characteristics define a neuronal type of nicotinic receptors. 4. The whole-cell current induced by ACh showed a strong inward rectification with no outward current being obtained. This phenomenon was observed when the intracellular ion is either sodium or caesium, and even when Ca2+ and Mg2+ were totally removed from the intracellular medium. 5. ACh-gated channels in intermediate lobe cells were cation selective and were permeable to Na+ and Cs+. In Ca2(+)-free extracellular solution, single-channel conductances were much larger (46 pS) than in the presence of 2 mM-Ca2+ (26 pS). 6. The possibility of an excitatory cholinergic control of intermediate lobe cells is discussed.

Transforming growth factor beta enhances basal and FSH-stimulated inhibin production by rat granulosa cells in vitro

Transforming growth factor beta (TGF beta) caused a dose-dependent increase in both basal and follicle-stimulating hormone (FSH)-stimulated inhibin production by rat granulosa cells in culture. The TGF beta dose-response curve in the absence of FSH was approximately parallel to that in the presence of either a minimally effective dose (1 ng/ml) or a maximally effective dose (30 ng/ml) of FSH, suggesting an additive effect of these two agents on inhibin production. There was also a suggestion of an increased sensitivity of granulosa cell inhibin production to FSH when the cells were coincubated with TGF beta. The time course study showed that similar to FSH, the stimulatory effect of TGF beta on basal and FSH-stimulated inhibin production was evident on day 1 and was maximal by day 4. In addition, epidermal growth factor (EGF) reduced FSH-stimulated inhibin production with an ID50 value of 1.3 ng/ml. Coincubation of cells with EGF and 1 ng TGF beta/ml enhanced greatly the inhibitory action of EGF on FSH-induced inhibin production (ID50 less than 0.1 ng/ml). It is concluded that: (1) TGF beta directly stimulates inhibin production by rat granulosa cells and the combined effect with FSH was largely additive, (2) the inhibitory effect of EGF on FSH-induced inhibin production was enhanced by TGF beta, (3) individual members of the TGF beta/inhibin gene family regulate ovarian function, not only by direct action on follicle cells but also indirectly by influencing the production rate of other members of that family.

Direct inhibition of rat granulosa cell inhibin production by epidermal growth factor in vitro

The effect of epidermal growth factor (EGF) on inhibin production by rat granulosa cells has been investigated using a recently developed inhibin radioimmunoassay (RIA). Granulosa cells from intact immature diethylstilbestrol (DES)-treated rats were exposed to EGF (1-100 ng/ml) in the presence or absence of FSH for varying periods in vitro. An inhibitory effect of EGF on basal inhibin secretion was evident at day 2 of culture and was sustained over the subsequent 2 days. This action on basal inhibin secretion was dose-dependent, and maximal inhibition to 50% of control was observed at a dose of 100 ng EGF/ml at day 4. EGF also inhibited basal progesterone secretion in a similar manner. EGF caused a dose-dependent inhibition of FSH-stimulated inhibin secretion, with an ID50 (0.5 ng/ml, 0.08 nM) about one-eighth that in the absence of FSH. In addition, EGF also inhibited the stimulation of inhibin production by 8-Br-cAMP and prostaglandin E2. To exclude the possibility that EGF was toxic to the granulosa cells, several biochemical parameters related to cell growth were measured. EGF treatment did not alter cell number but slightly increased [3H]thymidine incorporation into cellular DNA. The effect of EGF on [35S]methionine incorporation into cellular protein was biphasic, being stimulatory at doses less than 10 ng/ml but inhibitory at 100 ng/ml. The present data have demonstrated a direct inhibitory effect of EGF on basal and FSH-stimulated inhibin production by granulosa cells suggesting an important regulatory role of this growth factor in the differentiation of ovarian function.

Follicle-stimulating hormone and somatomedin-C stimulate inhibin production by rat granulosa cells in vitro

The direct effect of somatomedin-C (Sm-C) and FSH on inhibin production by rat granulosa cells in vitro has been examined. FSH stimulated accumulation of inhibin in culture media in a dose-dependent manner with maximal stimulation (6-fold) being observed at a dose of 300 ng FSH/ml. Addition of Sm-C (30 ng/ml) either alone or in the presence of FSH (3-300 ng/ml) increased inhibin production (up to 5-fold). Sm-C alone was effective over the physiological dose range of 3-100 ng/ml. Concomitant addition of FSH (100 ng/ml) and Sm-C (3-100 ng/ml) resulted in a significant increase in inhibin production at all doses of Sm-C. The dose-dependent effects of FSH and Sm-C were also time dependent with a synergistic effect apparent after 48 h of culture. The Sm-C induced FSH inhibitory activity of granulosa cell culture media was confirmed as authentic inhibin by the demonstration of a dose-dependent neutralization of this activity by a monoclonal antibody raised against purified bovine inhibin. The data indicate a direct role for both FSH and Sm-C in ovarian inhibin production and provide additional evidence for an autocrine-paracrine role for Sm-C in granulosa cell differentiation.