Involvement of Bcl-2 family genes and Fas signaling system in primary and secondary male germ cell apoptosis induced by 2-bromopropane in rat.

Epidemiological surveys and animal experimental studies suggest that exposure to 2-bromopropane (2-BP) could result in reproductive and hematopoietic disorders. The objectives of this study were to investigate the role of apoptosis in 2-BP-induced testicular toxicity and whether this process involves Bcl-2 family genes and the Fas signaling system. Rats were injected percutaneously with 1350 mg/kg 2-BP for 1 to 5 days and then were euthanized at 6 or 12 h after one dose, 6 h after two, three, or five doses, and 2 or 9 days after the final treatment. Light and electron microscopic analyses, TUNEL staining of DNA fragments, agarose gel electrophoresis of low-molecular-weight DNA, and Western blotting analysis of Bcl-2 family proteins and Fas receptor and ligand were conducted. Two-day treatment resulted in selective degeneration of spermatogonia with marked nuclear chromatin condensation. DNA ladder formation on the agarose gel further validated the findings of TUNEL-stained apoptotic cells. The percentage of apoptotic-positive tubules and apoptotic cell index increased time dependently. 2-BP treatment resulted in two distinct morphological changes: an immediate effect on spermatogonia and secondary apoptosis of spermatocytes 9 days after treatment. Downregulation of Bcl-2 after the first or second injection of 2-BP and upregulation of Bax after the first treatment contributed to the initiation of primary apoptosis of spermatogonia. Expression of FasL was inhibited while expression of Fas increased after the 2-BP treatment and remained at levels about two times of the control. However, it increased about sixfold of the control by day 9 after final injection, which contributed to the induction of secondary apoptosis of spermatocytes. Our results indicate that 2-BP resulted in apoptotic death of testicular germ cells and that this process involves the Bcl-2 family genes and the Fas signaling system.

Neurotoxicity of 2-bromopropane and 1-bromopropane, alternative solvents for chlorofluorocarbons.

To clarify the neurotoxicity of 2-bromopropane (2-BP) in comparison with 1-bromopropane (1-BP), 36 Wistar strain male rats were divided into 4 groups of 9 and exposed daily to 100-ppm 2-BP, 1000-ppm 2-BP, 1000-ppm 1-BP, or fresh air for 8 h a day. Exposure to 1000 ppm of 1-BP was discontinued after 5 or 7 weeks' exposure because of the unexpected appearance of incomplete hindlimb paralysis followed by serious emaciation. The other groups were sacrificed at the end of 12 weeks' exposure. Exposure to 1000 ppm of 2-BP resulted in significant decreases in body weight and motor nerve conduction velocity (MCV) and elongation in distal latency (DL). A ball-like enlargement of myelin sheaths was observed. Significant reductions in the number of erythrocytes, platelets, and leukocytes, testicular germ cell loss, and seminiferous atrophy were also observed in this group, but not in 100-ppm 2-BP group. Exposure to 1000 ppm of 1-BP for 5 or 7 weeks caused a significant decrease in body weight and MCV and elongation in DL. Linearly arranged ovoid- or bubble-like debris of the axons and myelin sheaths in the teased tibial nerves and axonal swelling in gracilis nucleus were found in this group. No significant changes in hematological indices or histopathological findings of the testis were found in this group. In conclusion, 2-BP is neurotoxic to the peripheral nerves in addition to its toxic effects on the reproductive and hematopoietic systems at 1000 ppm. No noticeable changes were found in the rats exposed to 100 ppm of 2-BP. 1-BP is a potent neurotoxicant at 1000 ppm for 5 or 7 weeks, while testicular and hematopoietic toxicity was not found.

Experimental study on skin sensitization potencies and cross-reactivities of hair-dye-related chemicals in guinea pigs.

In screening patch testing of hairdressers with occupational contact dermatitis, multiple positive reactions to hair dye-related chemicals, such as p-phenylenediamine (PPD), p-toluenediamine x 2HCl (PTD) and p-aminophenol (PAP), a fabric dye p-aminoazobenzene (PAB), and a tar dye Sudan III, were frequently encountered. To investigate individual skin sensitization potency and the cross-reactivities among above chemicals, a guinea pig maximization test with the above 5 chemicals was performed. In each group, 6 animals were induced with one of the chemicals at 0.1% concentration by intradermal injection and at 1.0% by topical application. The animals were challenged with all 5 chemicals in concentrations of dilution by 10 from 0.1% to 0.001%. Under the conditions of 0.1% challenges, similar sensitization potencies were observed in PPD (6/6), PTD (6/6), PAP (5/6) and PAB (6/6) groups, but no positive reactions were elicited in the Sudan III group. The cross-reactivities to PPD were confirmed in the animals challenged with PTD (6/6), PAP (6/6), PAB (6/6) and Sudan III (3/6). In the PTD-induced group, positive responses to cross-challenges were elicited by PPD (5/6), PAP (3/6), PAB (5/6) and Sudan III (1/6). The cross-reactivities to PAP were observed only with PPD (2/5) and PAB (5/5). PAB-induced animals responded only to PPD (1/6). The results indicate that all these chemicals except Sudan III are strong sensitizers. Their cross-reactivities are different in sensitized conditions, respectively. The cross-reactivities to PPD were higher than those to PTD, PAP and PAB.

1-Bromopropane, an alternative to ozone layer depleting solvents, is dose-dependently neurotoxic to rats in long-term inhalation exposure.

1-Bromopropane has been newly introduced as an alternative to ozone layer-depleting solvents. We aimed to clarify the dose-dependent effects of 1-bromopropane on the nervous system. Forty-four Wistar male rats were randomly divided into 4 groups of 11 each. The groups were exposed to 200, 400, or 800 ppm of 1-bromopropane or only fresh air 8 h per day for 12 weeks. Grip strength of forelimbs and hind limbs, maximum motor nerve conduction velocity (MCV), and distal latency (DL) of the tail nerve were measured in 9 rats of each group every 4 weeks. The other 2 rats of each group were perfused at the end of the experiment for morphological examinations. The rats of the 800-ppm group showed poor kicking and were not able to stand still on the slope. After a 12-week exposure, forelimb grip strength decreased significantly at 800 ppm and hind limb grip strength decreased significantly at both 400 and 800 ppm or after a 12-week exposure. MCV and DL of the tail nerve deteriorated significantly at 800 ppm. Ovoid or bubble-like debris of myelin sheaths was prominent in the unraveled muscular branch of the posterior tibial nerve in the 800-ppm group. Swelling of preterminal axons in the gracile nucleus increased in a dose-dependent manner. Plasma creatine phosphokinase (CPK) decreased dose-dependently with significant changes at 400 and 800 ppm. 1-Bromopropane induced weakness in the muscle strength of rat limbs and deterioration of MCV and DL in a dose-dependent manner, with morphological changes in peripheral nerve and preterminal axon in the gracile nucleus. 1-Bromopropane may be seriously neurotoxic to humans and should thus be used carefully in the workplace.

Reproductive toxicity of 1-bromopropane, a newly introduced alternative to ozone layer depleting solvents, in male rats.

1-Bromopropane has been newly introduced as an alternative to ozone-depleting solvents. We aimed to clarify its dose-dependent reproductive toxicity in male rats. Thirty-six Wistar male rats were randomly divided into 4 groups of 9. The groups were exposed to 200, 400, or 800 ppm 1-bromopropane or only fresh air, 8 h per day for 12 weeks. Epididymal sperm indices were evaluated after a 12-week exposure. The testes, epididymides, seminal vesicle, prostate, and other organs were weighed and examined histopathologically. Spermatogenic cells, in stage VII seminiferous tubules, and retained spermatids, at the basal region of stages IX-XI seminiferous epithelium, were counted. Plasma testosterone levels were measured by radioimmunoassay. The testicular weight did not significantly change, but the weight of epididymides, seminal vesicle, and prostate dose-dependently decreased. The weight of seminal vesicle decreased significantly at the lowest concentration of 200-ppm and over. 1-Bromopropane induced a dose-dependent decrease in the epididymal sperm count and in motility, as well as an increase in tailless sperm and sperm with an immature head shape. The spermatogonia, preleptotene spermatocytes, pachytene spermatocytes, and round spermatids did not decrease significantly at stage VII. Retained, elongated spermatids near the basement membrane at the postspermiation stages IX-XI increased dose-dependently. Plasma testosterone levels significantly decreased at the 800-ppm dosage. 1-Bromopropane caused failure of spermiation. Its reproductive toxicity is different from that of 2-bromopropane, which specifically impairs spermatogonia. Thus, this solvent may have serious reproductive toxic effects in men, and should be used very cautiously in the workplace.

2-Bromopropane causes ovarian dysfunction by damaging primordial follicles and their oocytes in female rats.

Ovarian dysfunction induced by 2-bromopropane (2-BP) has been described in female factory workers and experimental animals. However, the underlying mechanism is still unclear. To establish the reproductive target site and define mechanisms of 2-BP toxicity in adult female rats, we examined the effects of different doses and duration of exposure to 2-BP in female rats. In the dose-dependent experiments, female rats were exposed to 2-BP at 100, 300, or 1000 ppm or fresh air (n = 9 each) in exposure chambers for 8 h/day for 9 weeks. In the time-course experiments, female rats were exposed to 2-BP at 3000 ppm for 8 h (n = 7 each). The rats were then euthanized 1, 3, 5, and 17 days after exposure. Differential follicle counts and in situ terminal deoxynucleotidyl transferase assay were used to evaluate 2-BP effect on primordial, growing, and antral follicles. Exposure to 2-BP at 300 and 1000 ppm produced a significant reduction in the percentage of primordial, growing, and antral follicles in a dose-dependent manner. Significant reduction in the percentage of primordial follicles at 17 days after exposure was observed in time-course experiments. Exposure to 2-BP at 3000 ppm for 8 h resulted in histological changes in primordial follicles complex at 5 and 17 days after exposure. These changes consisted of distortion of the symmetry of oocytes and their nuclei at Day 5 after exposure and appearance of eccentric pyknotic cells and shrinkage of oocyte nuclei at Day 17 after exposure. In situ end labeling showed increased numbers of apoptotic oocytes and granulosa cells in primordial follicles at Days 5 and 17 after exposure. Our results suggested that ovarian dysfunction induced by 2-BP was caused by the destruction of primordial follicle and its oocyte due to the induction of apoptosis. Our studies also show that the follicle differential count is a more sensitive method than the vaginal smear in monitoring the female reproductive disorders induced by 2-BP.

Effect of inhalation exposure to 2-bromopropane on the nervous system in rats.

Exposure to 2-bromopropane (2-BP) is suspected to have adverse effects on the nervous system. The aim of this study was to investigate whether the exposure of rats to 2-BP had neurotoxic effects using histological and electrophysiological studies. Wistar strain male rats were exposed daily to either 100 or 1000 ppm 2-BP or to fresh air for 8 h a day for 12 weeks. Body weight was measured before exposure and every 2 weeks. Motor nerve conduction velocity (MCV) and distal latency (DL) were measured before exposure and every 4 weeks during exposure. Histological examination of the nervous system was also performed. Exposure of rats (n = 9) to 1000 ppm resulted in suppression of body weight gain and a significant decrease in brain weight compared to the control (n = 9). Electrophysiological measurements showed a significant decrease in MCV in 1000 ppm exposed rats at 8 weeks and significant prolongation of DL at 8 and 12 weeks. Abnormalities of the myelin sheath were detected in the common peroneal nerves. In 100-ppm exposed rats (n = 9), no significant changes were noted in body weight and the peripheral nerve. In conclusions, long-term exposure to 1000 ppm of 2-BP may result in peripheral neuropathy in rats.

Occupational health survey on workers exposed to 2-bromopropane at low concentrations.

BACKGROUND: Recent case studies in Korea and animal studies revealed the reproductive and hematopoietic toxicity of 2-bromopropane introduced into workplaces as an alternative to ozone-layer depleting chlorofluorocarbons. We aimed to clarify the dose-effect relationship of 2-bromopropane in workers. METHOD: The exposure concentration of 2-bromopropane and hematological indices, hormonal levels, menstruation status, and sperm indices were examined in 25 workers (11 males, 14 females) at a 2-bromopropane factory. Regression analyses of the examined indices against time-weighted average (TWA) of exposure concentration were conducted. RESULTS: Amenorrhea or polymenorrhea was observed only in older females. Hematological indices had a significant relation with TWA of exposure concentration in females with normal menstruation. However, no other indices showed any significant relation with TWA of 2-bromopropane. CONCLUSIONS: No severe cases of reproductive or hematopoietic disorders were found at less than 10 ppm (TWA), but a possible adverse effect of 2-bromopropane on hematopoiesis could not be disproved.

Epicondylitis among cooks in nursery schools.

OBJECTIVES: To investigate the prevalence and risk factors of epicondylitis among cooks in nursery schools in a cross sectional study because they are suspected to have strenuous workloads on the hands and arms. METHODS: Prevalence of epicondylitis among 209 nursery school cooks and 366 control workers aged 40-59 were studied. Both groups consisted of women workers chosen from 1299 subjects who agreed to participate from 1329 social welfare employees in a city. All workers were interviewed with a questionnaire and had a clinical examination of the tenderness to palpation of epicondyles and epicondylar pain provoked by resisted extension and flexion of the wrist. RESULTS: Nursery school cooks had a significantly higher prevalence of epicondylitis (11.5%) than the controls (2.5%). In a logistic regression model, job title of the cook was also found to have a strong association with epicondylitis (odds ratio (OR) 5.4, 95% confidence interval (95% CI) 2.4 to 11.9) after adjustment for age, body length, and body mass index. Weaker associations were also found between epicondylitis and suspected job stress or workload scores for mechanical workload and psychosocial stressors based on factor analysis. CONCLUSIONS: This study supported the hypothesis that nursery school cooks had a higher prevalence of epicondylitis than other workers with less strenuous hand and arm tasks. It was suggested that risk factors of epicondylitis would be multifactorial, including mechanical workload and psychosocial factors.

Urinary 2,5-hexanedione increases with potentiation of neurotoxicity in chronic coexposure to n-hexane and methyl ethyl ketone.

OBJECTIVE: MEK (methyl ethyl ketone) is widely and frequently used as an ingredient of mixed solvents together with n-hexane. MEK is known to decrease urinary levels of 2,5-hexanedione dose-dependently in an acute or chronic coexposure with a constant level of n-hexane. This change in urinary 2,5-hexanedione appears to contradict the potentiation effect of MEK on n-hexane-induced neurotoxicity because it is believed that the toxicity of n-hexane is activated through n-hexane metabolism. We aimed to clarify how the urinary level of 2,5-hexanedione changes when MEK modifies the degree of n-hexane-induced neurotoxicity. METHOD: A total of 32 male Wistar rats were divided into 4 groups of 8 each and were then exposed to fresh air only, 2000 ppm n-hexane only, 2000 ppm n-hexane plus 200 ppm MEK, and 2000 ppm n-hexane plus 2000 ppm MEK, respectively. Inhalation exposures were performed 12 h/day, 6 days/week, for 20 weeks. Motornerve conduction velocity (MCV), distal latency (DL), and urinary 2,5-hexanedione were measured every 4 weeks. RESULTS: The MCV decreased, the DL increased, and urinary levels of 2,5-hexanedione increased in the 2000-ppm n-hexane plus 200 ppm MEK group in comparison with the 2000-ppm n-hexane only group following 4 weeks' exposure. On the 1st day of exposure, however, coexposure to MEK decreased urinary levels of 2,5-hexanedione dose-dependently. CONCLUSIONS: The present study showed that urinary concentrations of 2,5-hexanedione increased with potentiation of n-hexane neurotoxicity. Urinary 2,5-hexanedione concentration does not necessarily reflect the exposure concentration of n-hexane in coexposure to n-hexane along with MEK or other solvents, but it may be useful as a marker in the assessment of neurotoxicity in coexposure to n-hexane and other solvents.

A cohort mortality study of construction workers.

This report presents a mortality study among the 17,344 members of the Construction Workers' Health Insurance Society of Mie Prefecture in Japan. The study period was between 1973 and 1993. During this period, 480 members died. Age-specific mortality rates of Mie Prefecture were used as comparison standards. Significantly elevated standardized mortality ratio (SMR) and proportionate mortality ratio (PMR) were observed for "accidents and adverse effects." In addition, the PMRs of all cancers and "cancers of trachea, bronchus and lung" were also significantly elevated. The job classifications were reorganized into three groups, according to the frequency of asbestos exposure the workers experienced on the construction sites. The asbestos exposure was based on job classifications among 7,411 workers who had completed a self-administered survey questionnaire. In the frequent-exposure group, the PMR was significantly elevated for all cancers. In the medium-exposure group, the SMRs were significantly elevated for all cancers and "cancer of trachea, bronchus and lung." The PMR was significantly elevated for "cancer of trachea, bronchus and lung." In the less-exposure, group, the PMR was significantly elevated for "accidents and adverse effects." This study provided support for the hypothesis that working in the construction industry might be associated with high risks for asbestos-associated cancers and accidental deaths.

Effects of asymmetric dynamic and isometric liftings on strength/force and rating of perceived exertion.

A laboratory study was undertaken to determine the postural and physical characteristics and subjective stress during dynamic lifting of a usual load (10 kg) compared with during isometric lifting. The authors also aimed to clarify the effects of asymmetric lifting on these parameters. The subjects were thirteen male college students. They were asked to lift a box weighing 10 kg. They performed sixteen different lifting tasks from the floor to a height of 71 cm, involving a combination of three independent factors: two lifting modes (isometric lifting and dynamic lifting), four lifting angles in relation to the sagittal plane (sagittal plane, right 45 degree, right 90 degree and left 90 degree planes) and two lifting postures (squat and stoop). For each lifting task, strengths or forces and ground reaction forces were measured. At the end of each task, the authors asked the subjects to rate their perceived exertion (RPE) during lifting at ten sites of the body. Angle factor had a significant effect on isometric strengths and dynamic peak forces. Isometric strengths during the maximum 3 s were highest in lifting in the right 45 degree plane, followed by that in the sagittal plane, while those in the right 90 degree and left 90 degree planes were the lowest. However, peak forces in dynamic lifting were the highest in the lifting in the sagittal plane, followed by that in the right 45 degree plane, while those in the right 90 degree and left 90 degree planes were the lowest. Postural factor had a significant effect on height at peak force, which is higher in squat lifting than in stoop lifting. RPEs for the left arm, the backs and the right whole body in isometric lifting were significantly higher than in dynamic lifting of 10 kg. There were remarkably high RPEs for the ipsilateral thigh to the box in right 90 degree and left 90 degree planes during both isometric and dynamic liftings. Locations of the resultant force consisting of three component forces on the force plate were closer to the foot on the same side as the box in asymmetric lifting. Thus, some similarities and differences were found between isometric lifting and dynamic liftings regarding the indexes of strength used in this experiment. The authors consider that the subjects used the foot nearer to the box as a fulcrum during asymmetric lifting. Dynamic measurement using the 10 kg weight is less stressful than the conventional isometric measurement. It was possible to obtain the height data at peak force and time-based changes in the force and the box location during lifting only through dynamic lifting measurement. The results provide new knowledge about the biomechanical features of dynamic lifting tasks.

Toxic effects of hexane derivatives on cultured rat Schwann cells.

The cytotoxic effects of the following five hexane-related compounds were examined on Schwann cell DNA synthesis: 2,5-hexanedione (2,5-HD), 2-hexanol (2-OH), 2-hexanone (MnBK), 2,5-dimethylfuran (DF) and gamma-valerolactone (VL). Schwann cells were isolated from the sciatic nerves of neonatal Sprague-Dawley rats and cultured. [(3)H]-thymidine incorporation into Schwann cell nuclei was measured by scintillation spectrometry and autoradiography when hexane derivatives were added to the culture medium. All of the hexane-related compounds suppressed [(3)H]-thymidine incorporation in a concentration-dependent manner. DF was the most cytotoxic for the inhibition of Schwann cell DNA synthesis among the compounds. The finding suggests that DF-mediated cytotoxicity should be taken into account as a possible additional mechanism of hexane intoxication, especially in the impairment of mitotic cells.

Toluene induces behavioral activation without affecting striatal dopamine metabolism in the rat: behavioral and microdialysis studies.

We examined the effects of toluene on the release of dopamine (DA) and its metabolites in rat striatum using microdialysis. Intraperitoneal injection of 800 mg/kg toluene significantly increased motor activity in rats, as did methamphetamine (MAP) (1 mg/kg). However, 800 mg/kg toluene did not affect the extracellular levels of DA, 3,4-dihydroxyphenylacetic acid, homovanillic acid, or 5-hydroxyindoleacetic acid. This is in contrast to MAP, which significantly increased extracellular DA and decreased the extracellular levels of its metabolites. These results suggest that toluene-induced behavioral augmentation may not be associated with alterations in DA or serotonin neurochemistry such as are associated with MAP-induced behavioral augmentation.