Carbon disulfide removal from gasoline fraction using zinc-carbon composite synthesized using microwave-assisted homogenous precipitation

Carbon disulfide (CS2) is one of the sulfur components that are naturally present in petroleum fractions. Its presence causes corrosion issues in the fuel facilities and deactivates the catalysts in the petrochemical processes. It is a hazardous component that negatively impacts the environment and public health due to its toxicity. This study used zinc-carbon (ZC) composite as a CS2 adsorbent from the gasoline fraction model component. The carbon is derived from date stone biomass. The ZC composite was prepared via a homogenous precipitation process by urea hydrolysis. The physicochemical properties of the prepared adsorbent are characterized using different techniques. The results confirm the loading of zinc oxide/hydroxide carbonate and urea-derived species on the carbon surface. The results were compared by the parent samples, raw carbon, and zinc hydroxide prepared by conventional and homogeneous precipitation. The CS2 adsorption process was performed using a batch system at atmospheric pressure. The effects of adsorbent dosage and adsorption temperatures have been examined. The results indicate that ZC has the highest CS2 adsorption capacity (124.3 mg.g-1 at 30 °C) compared to the parent adsorbents and the previously reported data. The kinetics and thermodynamic calculation results indicate the spontaneity and feasibility of the CS2 adsorption process.

Carbon disulfide induced decidualization disorder in the mice uterus at the window of implantation

Carbon disulfide (CS₂) is regarded as a common occupational poison that is widely used in the textile industry in China. Our previous research suggests that CS₂ can induce significant implantation disorders in pregnant mice; however, the specific mechanism remains unclear. Uterine conception in mice must undergo decidualization, which is the prerequisite for propitious blastocyst implantation into the endometrium. Therefore, in this study, we established models of pregnant mice to explore the toxic effects of CS₂ on decidualization to elucidate the basic mechanism of implantation disorder after CS₂ exposure. The uterine tissues were immediately collected according to the predetermined endpoints to measure the expression levels of IGFBP1 and PRL (markers of decidualization differentiation), IL-11 (representing the secretory function of decidual cells), AKT and pAKT by western blotting, RT-PCR, immunohistochemical staining, H&E staining and ELISA. N-carbamoyl glutamic acid (NCG) acted as an agonist of AKT to verify the upstream regulatory mechanism of decidualization disorder by CS₂. The results showed that the normal reaction of decidual transformation was obviously disrupted by CS₂ upon 3.5 dpc and 4.5 dpc exposure. The blastocyst did not adhere to the epithelium after 3.5 dpc-exposure and did not invade the endometrium after 4.5 dpc-exposure, resulting in its suspension in the uterine cavity, stagnation and eventual loss. The proteins expression levels were decreased by 95.2% for IGFBP1 and 76.2% for PRL at the 4.5 dpc endpoint after 3.5 dpc CS₂ exposure compared with the control. Simultaneously, the mRNA and protein expression levels of IL-11 in uterine tissues were significantly reduced by CS₂, and consistent decreasing trends over time were observed for IGFBP1 and PRL, compared with the control. Additionally, the ratio of pAKT/AKT protein expression was decreased by 72.2% and 94.8% at 12 h and 18 h after 3.5 dpc exposure and by 53.3% and 74.3% at 6 h and 12 h after 4.5 dpc exposure, respectively, compared with the corresponding controls. Furthermore, NCG could recover the IGFBP1 and PRL protein expression, which was increased by 27.5% and 52.3% at 4.5 dpc and 6.5 dpc, respectively, after 3.5 dpc exposure for IGFBP1 and by 30.3% at 6.5 dpc after 4.5 dpc exposure for PRL, compared with CS₂ exposure alone. Collectively, this study suggested that the decidualization disorder caused by CS₂ at the window of implantation in pregnant mice, which is triggered by pAKT, contributed to the implantation disorder and eventually led to embryo loss. It is worth noting that our study may provide a new perspective and reference for exploring the toxic mechanism of implantation disorder and even infertility in harmful circumstances.

[Effect of carbon disulfide exposure on fatty acid metabolism in ApoE knockout and C57BL/6J mice]

OBJECTIVE

To study the influences of carbon disulfide (CS2) exposure on fatty acid metabolism in apolipoprotein E (ApoE) knockout mice and C57BL/6J mice.

METHODS

Twenty-four male ApoE knockout mice were randomly and equally divided into four groups: a CS2-exposed normal diet group, a CS2-unexposed normal diet group, a CS2-exposed high-fat diet group, and a CS2-unexposed high-fat diet group. Twenty-four C57BL/6J male mice were divided into four groups in the same way. The CS2-exposed groups were exposed to CS2 (1 g/m(3)) by static inhalation for 5 hours a day, 5 days a week. After two weeks, the whole blood of mice was collected. Methyl ester derivatization of fatty acids was performed using an acid-catalyzed method. Fatty acid contents before and after exposure were compared by gas chromatography-mass spectroscopy.

RESULTS

There were significant differences in fatty acid contents of mice between the four groups. For the C57BL/6J mice, the arachidic acid contents in the CS2-exposed high-fat diet group were significantly lower than those in the CS2-unexposed high-fat diet group (P = 0.045 0). For the ApoE knockout mice, the arachidonic acid contents in the CS2-exposed normal diet group were significantly lower than those in the CS2-unexposed control diet group (P = 0.045 2). For the ApoE knockout mice, the γ-linolenic acid contents in the CS2-exposed high-fat diet group were significantly higher than those in the unexposed high-fat diet group (P = 0.044 7).

CONCLUSION

Exposure to CS2 can induce fatty acid metabolism disorder in mice, indicating that CS2 may increase the risk of atherosclerosis and other cardiovascular diseases.

[Rapid determination of 28 pesticides and tetramine in whole blood by online gel permeation chromatography coupled with gas chromatography-mass spectrometry]

OBJECTIVE

To study the influences of carbon disulfide (CS2) exposureon fatty acid metabolism in apolipoprotein E (ApoE) knockout mice and C57BL/6J mice.

METHODS

Twenty-four male ApoE knockout mice were randomly and equally divided into four groups: a CS2-exposed normal diet group, a CS2-unexposed normal diet group, a CS2-exposed high-fat diet group, and a CS2-unexposed high-fat diet group. Twenty-four C57BL/6J male mice were divided into four groups in the same way. The CS2-exposed groups were exposed to CS2 (1 g/m³) by static inhalation for 5 hours a day, 5 days a week. After two weeks, the whole blood of mice was collected. Methyl ester derivatization of fatty acids was performed using an acid-catalyzed method. Fatty acid contents before and after exposure were compared by gas chromatography-mass spectroscopy.

RESULTS

There were significant differences in fatty acid contents of mice between the four groups. For the C57BL/6J mice, the arachidic acid contents in the CS2-exposed high-fat diet group were significantly lower than those in the CS2-unexposed high-fat diet group (P = 0.0450). For the ApoE knockout mice, the arachidonic acid contents in the CS2-exposed normal diet group were significantly lower than those in the CS2-unexposed control diet group (P = 0.0452). For the ApoE knockout mice, the γ-linolenic acid contents in the CS2-exposed high-fat diet group were significantly higher than those in the unexposed high-fat diet group (P = 0.0447).

CONCLUSION

Exposure to CS2 can induce fatty acid metabolism disorder in mice, indicating that CS2 may increase the risk of atherosclerosis and other cardiovascular diseases.

Animal models of peripheral neuropathy due to environmental toxicants

Despite the progress in our understanding of pathogeneses and the identification of etiologies of peripheral neuropathy, idiopathic neuropathy remains common. Typically, attention to peripheral neuropathies resulting from exposure to environmental agents is limited relative to more commonly diagnosed causes of peripheral neuropathy (diabetes and chemotherapeutic agents). Given that there are more than 80,000 chemicals in commerce registered with the Environmental Protection Agency and that at least 1000 chemicals are known to have neurotoxic potential, very few chemicals have been established to affect the peripheral nervous system (mainly after occupational exposures). A wide spectrum of exposures, including pesticides, metals, solvents, nutritional sources, and pharmaceutical agents, has been related, both historically and recently, to environmental toxicant-induced peripheral neuropathy. A review of the literature shows that the toxicity and pathogeneses of chemicals adversely affecting the peripheral nervous system have been studied using animal models. This article includes an overview of five prototypical environmental agents known to cause peripheral neuropathy--namely, organophosphates, carbon disulfide, pyridoxine (Vitamin B6), acrylamide, and hexacarbons (mainly n-hexane, 2,5-hexanedione, methyl n-butyl ketone). Also included is a brief introduction to the structural components of the peripheral nervous system and pointers on common methodologies for histopathologic evaluation of the peripheral nerves.

[Effects of carbon disulfide inhalation on lipid levels of ApoE gene knockout mice and C57BL/6J mice]

OBJECTIVE

To investigate the effects of carbon disulfide (CS(2)) inhalation on the lipid levels of ApoE knockout gene mice and C57BL/6J mice.

METHODS

Fifty-one male ApoE gene knockout mice were randomly divided into four groups: CS(2)-exposed normal diet group, CS(2)-unexposed normal diet group, CS(2)-exposed high-fat diet group, and CS(2)-unexposed high-fat diet group. Fifty male C57BL/6J mice were divided into four groups in the same way. The exposed groups received 1000 mg/m3 CS(2) by static inhalation (5h/d, 5d/w) for four weeks. The weight of each mouse was determined and recorded once a week. On the 14th day of exposure, six mice in each group were randomly selected to measure serum total cholesterol (TC) levels. On the 28th day of exposure, the serum levels of TC and low-density lipoprotein (LDL) in the remaining mice were measured.

RESULTS

The mean weight gain of exposed groups was less than that of the unexposed groups. On the 14th and 28th days of experiment, the TC levels of the CS2-exposed high-fat diet group were significantly higher than those of the CS(2)-unexposed high-fat diet group among ApoE knockout gene mice (P < 0.01 for both). On the 14th day of experiment, the TC levels of the CS(2)-unexposed high-fat diet group were significantly higher than those of the CS(2)-unexposed normal-diet group among C57BL/6J mice group (P < 0.05). On the 28th day of experiment, the LDL levels of the CS(2)-exposed high-fat diet group were significantly higher than those of the CS(2)-unexposed high-fat diet group among ApoE knockout gene mice (P = 0.003).

CONCLUSION

CS(2) exposure, high-fat diet, and ApoE gene knockout can elevate blood lipids in mice, thus increasing the risk of atherosclerosis.

Serum miRNA profiling identifies miR-150/30a as potential biomarker for workers with damaged nerve fibers from carbon disulfide

As crucial small regulatory molecules, serum microRNAs (miRNAs) have been widely identified as potential noninvasive biomarkers. To survey and identify serum miRNAs associated with workers who had experienced injury to their nerve system from carbon disulfide (CS2), we profiled abnormally expressed miRNAs using the microarray technique and further performed qRT-PCR validation in case and control samples (n=20). Microarray profiling in pooled RNA samples showed that many miRNAs in workers exposed to CS2 were aberrantly expressed. Based on control samples exposed to CS2, a great amount of abnormal miRNAs, including some miRNA gene clusters and families, were obtained from microarray datasets. Most of deregulated miRNAs were up-regulated, and almost all miRNAs showed consistent expression patterns between workers with different numbers of damaged nerve fibers. Functional enrichment analysis suggested that these abnormal miRNAs showed versatile roles by contributing to multiple biological processes. Some aberrantly expressed miRNAs were characterized as miRNA gene clusters or families, and they always showed consistent expression patterns. miR-150 and miR-30a were selected to be further validated by qRT-PCR as up-regulated species, and they could discern case samples from control samples. miR-150 and miR-30a may be potential noninvasive biomarkers for a damaged nervous system.

[Changes in expression of motor protein for axonal transport in nerve tissues of carbon disulfide-intoxicated rats]

OBJECTIVE

To study the changes in microtubule motor protein expression in the spinal cord and sciatic nerve of rats exposed to carbon disulfide, and to investigate the possible molecular mechanism of changes in axonal transport in carbon disulfide-induced peripheral neuropathy.

METHODS

Healthy adult male Wistar rats were randomly divided into one control group and three experimental groups (10 rats per group). The rats in experimental groups were intoxicated by gavage of carbon disulfide at a dose of 200, 400, or 600 mg/kg 6 times a week for 6 consecutive weeks, while the rats in control group were given the same volume of corn oil by gavage. Animals were sacrificed after exposure, with nerve tissue separated. The levels of dynein, dynactin, and kinesin in the spinal cord and sciatic nerve were determined by Western blot.

RESULTS

The content of dynein, dynactin, and kinesin in the sciatic nerve decreased significantly under exposure to carbon disulfide. The levels of dynein in the sciatic nerve were reduced by 23.47% and 33.34% at exposure doses of 400 and 600 mg/kg, respectively. The levels of dynactin in the sciatic nerve of the three experimental groups were reduced by 19.91%, 24.23%, and 41.30%, respectively. The level of kinesin was reduced by 25.98%under exposure to 600 mg/kg carbon disulfide. All the differences were statistically significant (P < 0.01). As compared with the control group, the 600 mg/kg group experienced a 28.24% decrease in level of dynactin in the spinal cord (P < 0.01), but no significant change was observed in the level of dynein or kinesin.

CONCLUSION

Carbon disulfide has an impact on microtubule motor protein expression in nerve tissues, which might be involved in the development of carbon disulfide-induced peripheral neuropathy.

Activation of lysosomal degradative pathway in spinal cord tissues of carbon disulfide-treated rats

Chronic exposure to carbon disulfide (CS₂) can induce polyneuropathy in occupational worker and experimental animals, but underlying mechanism for CS₂ neuropathy is currently unknown. In the present study, male Wistar rats were randomly divided into three experimental groups and one control group. The rats in experimental groups were treated with CS₂ by gavage at dosages of 200, 400 and 600 mg/kg/day respectively, six times per week for 6 weeks. The formation of autophagosomes and lysosomes in motor neurons of rat spinal cord was observed by transmission electron microscopy, the level of autophagy-related proteins, lysosome-associated membrane protein 1 (LAMP-1), and cathepsin B in spinal cord tissues was determined by Western blot analysis, and the activity of cathepsin B was measured by fluorescence assay. The results demonstrated that the number of lysosomes in motor neurons was markedly increased in CS₂-treated rats. In the meantime, the administration of CS₂ significantly increased the level of microtubule-associated protein light chain 3-II (LC3-II), Atg1, UVRAG and LAMP-1 in rat spinal cord. Furthermore, the content and activity of cathepsin B in rat spinal cord also showed a significant elevation. Taken together, this study suggested that CS₂ intoxication was associated with the activation of lysosomal degradative machinery, which might play a protective role against CS₂-induced neuronal damage.

Carbon disulfide induces rat testicular injury via mitochondrial apoptotic pathway

Carbon disulfide (CS2), one of the most important volatile organic chemicals, was shown to have serious impairment to male reproductive system. But the underline mechanism is still unclear. In the present study, we aim to investigate the male germ cell apoptosis induced by CS2 exposure alone and by co-administration with cyclosporin A (CsA), which is the inhibitor of membrane permeability transition pore (MPTP). It was shown that CS2 exposure impaired ultrastructure of germ cells, increased the numbers of apoptotic germ cells, accumulated intracellular level of calcium, elevated ROS level, and increased activities of complexes of respiratory chain. Meanwhile, exposure to CS2 dramatically decreased the mitochondrial transmembrane potential (ΔΨm) and levels of ATP and MPTP opening. Exposure to CS2 can also cause a significantly dose-dependent increase in the expression levels of Bax, Cytc, Caspase-9, and Caspase-3, but decreased the expression level of Bcl-2. Moreover, co-administration of CsA with CS2 can reverse or alleviate the above apoptotic damage effects of CS2 on testicular germ cells. Taken together, our findings suggested that CS2 can cause damage to testicular germ cells via mitochondrial apoptotic pathway, and MPTP play a crucial role in this process.

[Effect of carbon disulfide on mitochondrial respiratory chain in spermatogenic cells in male rats]

OBJECTIVE

To investigate the effect of carbon disulfide (CS(2)) on the mitochondrial respiratory chain in testicular spermatogenic cells in male rats and to explore the possible mechanism of reproductive system damage caused by CS(2) in male rats.

METHODS

Twenty-four male Sprague-Dawley rats (clean grade) were randomly divided into four groups: three CS(2) exposure groups (CS(2) concentrations: 50, 250, and 1250 mg/m(3)) and a control group. The rats in CS(2) exposure groups were exposed to CS(2) by static inhalation for 10 weeks (2 h/d, 5 d/w), while the rats in control group were exposed to air. Then, all rats were sacrificed by decapitation; testicular tissues were collected, and mitochondrial protein in spermatogenic cells were extracted; the levels of mitochondrial respiratory chain enzyme complex I∼V were measured by enzyme-linked immunosorbent assay.

RESULTS

Compared with the control group, all CS(2) exposure groups had significantly increased levels of mitochondrial respiratory chain enzyme complex I∼V in spermatogenic cells (P < 0.05). There were no significant differences in the levels of respiratory chain enzyme complex I∼IV between the CS(2) exposure groups (P < 0.05), but the level of respiratory chain enzyme complex V rose significantly as the concentration of CS(2) increased (P<0.05).

CONCLUSION

Various levels of CS(2) exposure may increase the levels of mitochondrial respiratory chain enzyme complex in testicular spermatogenic cells among male rats, thus affecting the normal oxidative phosphorylation in mitochondria.

[Effect of carbon disulfide on mitochondrial apoptosis-related proteins in cytoplasm of testicular tissue among male rats]

OBJECTIVE

To investigate the role of mitochondrial pathway in the apoptosis of spermatogenic cells induced by inhalation of carbon disulfide in male rats.

METHODS

Twenty-four male Sprague-Dawley rats (clean grade) were divided into four groups according to their body weights: three CS(2) exposure groups (CS(2) concentrations: 50, 250, and 1250 mg/m(3)) and a control group. The rats in CS(2) exposure groups were exposed to CS(2) by static inhalation for 10 weeks (2 h/d, 5 d/w), while the rats in control group were exposed to air. Then, all rats were sacrificed by decapitation; testicular tissues were collected, and cytoplasmic proteins were extracted; the levels of apoptosis-inducing factor (AIF), cytochrome c (cyto c), Bcl-2, Bax, procaspase-9, and procaspase-3 were measured by Western blot, and the activities of caspase-9 and caspase-3 were measured using a test kit.

RESULTS

Compared with the control group, all CS(2) exposure groups had significantly increased levels of cyto c in the cytoplasm of testicular tissue (P<0.05); in the 250 mg/m(3) CS(2) exposure group, the Bax/Bcl-2 ratio and activities of caspase-9 and caspase-3 increased significantly (P<0.05), and the content of procaspase-9 and procaspase-3 decreased significantly (P<0.05); in the 1250 mg/m(3) CS(2) exposure group, the relative expression levels of Bax and AIF in cytoplasm increased significantly (P<0.05), and the expression level of Bcl-2 decreased significantly (P<0.05).

CONCLUSION

Mitochondrial pathway plays an important role in the CS(2)-induced apoptosis of spermatogenic cells in testicular tissue among male rats.

[DNA damage of splenic lymphocytes in pregnant mice exposed to carbon disulfide in implantation phase]

OBJECTIVE

To investigate the DNA damage of splenic lymphocytes in pregnant mice exposed to carbon disulfide (CS2) in the implantation phase and to explore the mechanism of abnormal implantation induced by CS2 from the perspective of immune injury.

METHODS

Mice were exposed to CS2 at different doses or at different time points in the implantation phase to establish model 1 and model 2. For model 1, mice were assigned to four groups to receive a single intraperitoneal injection of low-dose CS2 (0.1 LD50, 157.8 mg/kg), middle-dose CS2 (0.2 LD50, 315.7 mg/kg), and high-dose CS2 (0.4 LD50, 631.4 mg/kg) as well as an equal volume of olive oil (control) on gestational day (GD) 4. For model 2, mice were assigned to four groups to receive a single intraperitoneal injection of CS2 (0.4 LD50, 631.4 mg/kg) or an equal volume of olive oil (control) on GD3, GD4, GD5, and GD6. At the end, single cell suspension of splenic lymphocytes was prepared. Cell viability was measured by trypan blue staining, and the DNA damage of splenic lymphocytes was evaluated by alkaline single cell gel electrophoresis assay.

RESULTS

The middle-dose and high-dose exposure groups showed significantly more DNA damage of splenic lymphocytes than the control group (P < 0.01); there was significant regression relationship between indicators of DNA damage and exposure doses (P < 0.01). The GD3, GD4, GD5, and GD 6 exposure groups showed significantly more DNA damage of splenic lymphocytes than the control group (P < 0.01), and the GD 4 exposure group had the most DNA damage.

CONCLUSION

Exposure to CS2 in the implantation phase can induce DNA damage of splenic lymphocytes in pregnant mice, and the DNA damage was aggravated with the increase in CS2 concentration. GD4 may be the sensitive time point for DNA damage of splenic lymphocytes induced by CS2 in pregnant mice.

[Effects of carbon disulfide exposure during peri-implantation on estrogen receptor-α expression in uterus and serum level of estrogen in pregnant mice]

OBJECTIVE

To evaluate the effects of carbon disulfide (CS(2)) exposure during peri-implantation on the estrogen receptor-α (ER-α) expression in the uterus and serum level of estradiol (E(2)) in pregnant mice, and to explore the mechanism of embryotoxicity of CS(2).

METHODS

Healthy female mice were exposed to a single dose of CS(2) (631.4 mg/kg) or olive oil (solvent control) on gestational day (GD)3, GD4, GD5, or GD6. At different time points after exposure, the serum E(2) levels of the pregnant mice were measured by enzyme-linked immunosorbent assay, and the expression levels of ER-α in the uterus were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot.

RESULTS

Compared with the control group, the GD3, GD4, GD5, and GD6 exposure groups showed significantly decreased serum E(2) levels on day 7 of gestation (P < 0.05); the GD3 and GD5 exposure groups showed significantly decreased serum E(2) levels on day 6 of gestation (P < 0.05). The expression level of ER-α in the GD 4 exposure group was 23.6% lower than that in the control group on day 5 of gestation, and the expression level of ER-α in the GD 5 exposure group was 72.9% lower than that in the control group on day 6 of gestation (P < 0.05); the GD 3 and GD 6 exposure groups showed lower expression levels of ER-α than the control group at any time point, but no significant difference was found (P > 0.05).

CONCLUSION

CS(2) exposure during peri-implantation can reduce the ER-α expression in the uterus and the serum level of E(2) in pregnant mice, which may be one of the mechanisms of embryotoxicity of CS(2).

Nitric oxide mediated effects on reproductive toxicity caused by carbon disulfide in male rats

This study investigated nitric oxide (NO) mediation of carbon disulfide (CS(2)) toxicity that compromised male rat spermatogenesis and endocrine function. Rats were exposed to multiple levels of CS(2) concentration (0, 50, 250, 1250 mg/m(3)). A 1250 mg/m(3) CS(2)+sodium nitroprusside (SNP) group and a 1250 mg/m(3) CS(2)+NG-monomethyl-L-arginine (L-NMMA) group were established to explore the role of NO in mediating CS(2) toxicity. NO concentrations, NO synthase (NOS) activity, and sex hormone levels were measured, and sperm characteristics were observed and analyzed. Our data show that CS(2) exposure decreased: NOS activity; tissue NO concentrations; serum levels of gonadotropin-releasing hormones, luteinizing hormones, and testosterone; and sperm count and activity. In contrast, increased serum follicle-stimulating hormone concentrations and teratospermia were observed with CS(2) exposure. SNP reduced some of the toxic effects of CS(2), while L-NMMA treatment showed no effect. The results suggests that NO mediates compromised reproductive system function caused by CS(2) exposure.

Blood oxidative stress in Taiwan workers exposed to carbon disulfide

BACKGROUND

Overexposure to carbon disulfide (CS(2) ) has been associated with an increase in coronary heart disease, but the mechanisms mediating this effect remain unclear. We aimed to examine the relationship between CS(2) exposure and oxidative stress markers, in order to clarify the oxidative mechanisms involved in CS(2) -induced atherosclerosis.

METHODS

A total of 89 workers from a viscose rayon plant were recruited for this study, and 111 workers not exposed to CS(2) served as controls. Cholesterol, triglyceride, malondialdehyde (MDA), superoxide dismutase (SOD), catalase, GSH peroxidase, as well as total antioxidants were analyzed.

RESULTS

The workers exposed to CS(2) had significantly higher MDA levels and lower SOD levels than the controls. The average MDA levels were 776 ± 268.2 (240-1,220) in the high exposure (≥10 ppm; n = 38), 751.6 ± 274 (170-1,320) in the low exposure (<10 ppm; n = 51), and 550.4 ± 199 (115-1,050) mM in the control group (n = 111). The average SOD levels were 36.5 ± 38.8 (0-223.5), 39.3 ± 38.8 (0-160), and 58.8 ± 60.8 (5.25, 400) U/ml in the high exposure-, low exposure-, and control group, respectively. MDA level increased significantly at a cumulative CS(2) exposure of over 60 ppm-years. Dyslipoproteinemia was borderline significantly associated with CS(2) exposure and MDA level.

CONCLUSIONS

These results indicate that CS(2) exposure can induce oxidative stress as well as reduce the levels of antioxidative enzymes, and that a cumulative exposure level of 60 ppm-years may be a threshold value for the oxidative and the antioxidant response. Am. J. Ind. Med. 54:637-645, 2011. © 2011 Wiley-Liss, Inc.

[Effect of carbon disulfide on expression of matrix metalloproteinase-2 and metalloproteinase-9 in embryo and uterus of pregnant mice]

OBJECTIVE

To observe the effect of carbon disulfide (CS(2)) on the expression of matrix metalloproteinase (MMP)-2, MMP-9 in mouse embryo and uterus tissues and to explore the mechanism of embryo toxicity induced by CS(2).

METHODS

At the phases of follicular development and embryonic implantation which was subdivided into early-implantation phase and late-implantation phase, mice were intraperitoneally exposed to CS(2) (the dosage was 631.4 mg/kg, and the volume was 0.1ml/10 g body weight) for 2 consecutive days. All indicators were got at the ninth day in gestation, and the expression of MMP-2 and MMP-9 in embryo and uterus tissues was analyzed by gelatin zymography.

RESULTS

The number of implanted embryos significantly decreased after exposure at late-implantation phase (16.000 ± 12.166) compared with those of the control (30.700 ± 5.599, P < 0.05). Expression of MMP-2 and MMP-9 in embryos declined obviously at the three reproductive phases (P < 0.01), and the levels of MMP-2 and MMP-9 expression in embryos at the phases of late-implantation phase (0.6837 ± 0.0929, 0.7309 ± 0.0822) and follicular development (0.6222 ± 0.0997, 0.7520 ± 0.1068) were much lower than those of the control (1.0000 ± 0.0710, 1.0000 ± 0.0413, P < 0.01). Expression of MMP-2 and MMP-9 in uterus significantly increased at the phase of late-implantation (1.3153 ± 0.3032, 5.0210 ± 4.0307) compared with those of the control (1.0000 ± 0.1771, 1.0000 ± 0.0996, P < 0.01).

CONCLUSION

Embryo toxicity of CS(2) is more obvious at the phase of late-implantation. Exposure to CS(2) disturbs expression of MMP-2 and MMP-9 in embryo and uterus tissues, which might be one of the important factors contributed to embryo toxicity induced by CS(2).

[DNA damage of mice endometrial cells at implantation phase exposed to carbon disulfide]

OBJECTIVE

To detect the DNA damage of mice endometrial cells induced by carbon disulfide with single cell gel electrophoresis (SCGE) and explore the mechanism of embryo implantation disorder.

METHODS

Endometrial cells, obtained by mechanical scrape, were used to test cell viability by trypan blue. Single cell suspension was exposed to the different concentrations of carbon disulfide (CS(2)) at four dose groups (0, 500, 1000, 2500 micromol/L). DNA damage was detected by SCGE. The SCGE results were analyzed by CASP software.

RESULTS

Different dosages of CS(2) concentration induced different varying degrees of damage, forming typical normal cell and comet cell images. Compared with the control group, HDNA% decreased by 7.49%, 12.19% and 24.36% respectively, and TDNA%, TL, OTM increased by 7.13, 11.60, 23.18, 3.68, 5.98, 9.62, and 9.16, 16.84, 39.32 times respectively, in the groups of 500, 1000, 2500 micromol/L CS(2) (P < 0.01). Compared with the group of 500, 1000 micromol/L CS(2), TDNA%, TL, CL, TM, OTM in the group of 2500 micromol/L CS(2) increased by 1.98, 0.92, 1.27, 0.52, 0.37 and 0.17, 5.31, 1.90, 2.97, 1.26 times respectively(P < 0.01). Compared with the group of 500 micromol/L CS(2), TDNA%, TL, CL, TM, OTM in the group of 1000 micromol/L CS(2) increased by 0.55, 0.49, 0.16, 1.18, 0.76 times respectively (P < 0.01). The result of regression analysis showed that regression coefficients between HDNA%, TDNA%, TL, TM, OTM and the doses were -13.78, 13.78, 0.05, 4.38 and 3.23 respectively.

CONCLUSIONS

CS(2) exposure could induce DNA damage in the endometrial cells of mice at the phase of implantation. The degree of DNA damage increases with the increasing CS(2) concentration. CS(2) might affect the implantation of embryo by doing harm to the endometrial cells.

Transfer of occupational health problems from a developed to a developing country: lessons from the Japan-South Korea experience

Many corporations move their manufacturing facilities or technologies from developed to developing countries. Stringent regulations have made it costly for industries to operate in developed, industrialized countries. In addition, labor costs are high in these countries, and there is increasing awareness among the general public of the health risks associated with industry. The relocation of hazardous industries to developing countries is driven by economic considerations: high unemployment, a cheaper labor force, lack of regulation, and poor enforcement of any existing regulations make certain countries attractive to business. The transfer of certain industries from Japan to Korea has also brought both documented occupational diseases and a new occupational disease caused by chemicals without established toxicities. Typical examples of documented occupational diseases are carbon disulfide poisoning in the rayon manufacturing industry, bladder cancer in the benzidine industry, and mesothelioma in the asbestos industry. A new occupational disease due to a chemical without established toxicities is 2-bromopropane poisoning. These examples suggest that counter-measures are needed to prevent the transfer of occupational health problems from a developed to a developing country. Corporate social responsibility should be emphasized, close inter-governmental collaboration is necessary and cooperation among non-governmental organizations is helpful.

Synergistic neurotoxicity of carbon tetrachloride/carbon disulfide (80/20 fumigants) and other pesticides in grain storage workers

Neurophysiologic, neurobehavioral, and neuropsychologic profiles in 17 grain storage workers, 1 grain inspector, and 4 malting laboratory workers are described. The effects of CS2 toxicity as seen in viscose rayon workers as well as in experimental animals is remarkably similar to the clinical profile of our grain storage workers. CS2 use explains the dysfunction of peripheral axons, auditory nerve, the optic nerve, and the extrapyramidal system, as well as altered behavior and cognition changes. The signs and symptoms in these workers seem to be dose-related and we note that workers separated out from the areas where fumigation took place reported improvement not seen by fellow workers who continued the fumigant treatment routine. Likewise, malting laboratory workers exposed only to the grain dust from 3 to 7 years showed only minimal symptoms. Though a number of mechanism have been suggested for the alteration of neuropsychological function, the chelating ability of DDC derived from CS2 and its ability to markedly increase copper and zinc within the central nervous system suggests a mechanism of toxicity analogous to copper intoxication as in Wilson's Disease and may explain the production of extrapyramidal symptoms in these patients. Chelation of copper might prove therapeutic in CS2 poisoning. It is obvious that both basic and clinical research will be necessary to sort out the questions raised. We applaud the EPA's decision to ban the use of 80/20 fumigants and also methyl bromide, and trust that similar toxic substances be carefully studied before their selection for replacing these previous toxic agents. We further decry the technique of re-introducing grain dust into the food chain rather than destroying it, since the dust contains very high residues of fumigant material. We speculate on the possible role of CS2 and other pesticides in the food chain and the incidence of Parkinsonian symptoms in these patients and the general public.

[Study of the possible mechanism of effects of carbon disulfide on c-myc expression in rat testicles]

OBJECTIVE

To survey the expression of c-myc of teticles in rats exposed to carbon disulfide (CS2) and the possible mechanism of effects on it.

METHODS

36 wistar male rats were randomly divided into six groups. Four groups were exposed to CS2 at the dose of 0, 50, 250 and 1250mg/m3. The other two groups were treated at the dose of 1250 mg/ m3 CS2 plus VitE (250mg/kg diet) and VitE (250mg/kg diet) respectively. After 10-week esposures, rats were sacrificed and the SOD activity and MDA content and the c-myc expressions in testicles were determined.

RESULTS

When compared with the control group, SOD activities of testicles in the exposure group were decreased significantly (P < 0.01), MDA contents of testicles were increased significantly at the concentration of 1250mg/m3 CS2 (P < 0.01). The expression of c-myc of testicles present biphasic, and decreased at the concentraton of 50mg/m3 CS2 and increased at the other concentrations and higher than these of controls at the concentration of 1250mg/m3 CS2 significantly (P < 0.05). After treatment of CS2 combined with antioxidant VitE, SOD activity of testicles increased (P < 0.05), MDA content of testicles decreased (P < 0.01) and c-myc expression of testicles decreased consequently (P < 0.05).

CONCLUSION

the modulation of c-myc expression in testicles of rats treated with CS2 could be associated with lipid peroxidation induced by CS2.

[Effect of carbon disulfide on inducible nitric oxide synthase and apoptosis in retina of rats]

OBJECTIVE

To investigate the effect of carbon disulfide (CS2) on inducible nitric oxide synthase (iNOS) and apoptosis in in the retina of rats.

METHODS

Twenty-four male SD rats were randomly divided into 3 groups the control group, the group receiving high-dose CS2 and the group receiving low-dose CS2. After treatment, retina were harvested and made into slice. The thickness of inner retina including outer plexiform layer, inner nuclear layer, ganglion cell layer, optic nerve fiber and inner limiting membrane was measured. Expression of iNOS in retina was measured by NADPH-NDP histochemical assay. Apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL).

RESULTS

(1) The thickness of inner retina decreased in groups receiving CS2. There was significant difference between control group and groups receiving CS2 (P < 0.05). There was also significant difference between group receiving high-dose CS2 and group receiving low-dose CS2 (P < 0.05). (2) The expression of iNOS increased in groups receiving CS2. There was significant difference between control group and groups receiving CS2 (P < 0.05 or P < 0.01). There was also significant difference between the group receiving high-dose CS2 and the group receiving low-dose CS2 (P < 0.05). (3) Apoptosis was observed in groups receiving CS2. There were significant differences in apoptosis index between the control group and groups receiving CS2 (P < 0.05 or P < 0.01). There was also significant difference between the group receiving high-dose CS2 and the group receiving low-dose CS2 (P < 0.05).

CONCLUSIONS

CS2 can evoke the expression of iNOS, and the nitric oxide thus produced can be one of the causes of retina destruction. And apoptosis is also one of the causes of retina destruction.

[Apoptosis and gene FasL expression induced by carbon disulfide in rat sertoli cells]

OBJECTIVE

To study apoptosis and gene FasL expression induced by carbon disulfide in sertoli cells of male rats.

METHODS

Sertoli cells were exposed to different concentrations of CS(2) (0, 0.36, 0.72, 1.44 micromol/ml) for 24 hours. Survival rate, apoptosis rate, expression level of gene FasL were measured using MTT, FCM, and RT-PCR methods respectively.

RESULTS

Sertoli cell survival rate decreased as the concentration of CS(2) increased. The survival rate (73.34% +/- 1.39%) was significantly lower than the control group (99.98% +/- 5.48%) when the concentration of CS(2) > or = 1.44 micromol/ml (P < 0.05). Apoptosis rate increased as the CS(2) concentration increased. Apoptosis rate (7.93% +/- 0.43%) was significantly higher when the concentration of CS(2) > or = 1.44 micromol/ml (P < 0.05). Expression level of the FasL significantly increased as the concentrations of CS(2) (P < 0.05).

CONCLUSION

CS(2) is cytotoxic to sertoli cells. It could cause apoptosis of sertoli cells.

Carbon Disulfide-Induced Alterations of Neurofilaments and Calpains Content in Rat Spinal Cord

To investigate the mechanism of carbon disulfide-induced neuropathy, male Wistar rats were randomly divided into two experimental groups and one control group. The rats in two experimental groups were treated with carbon disulfide by gavage at dosages of 300 and 500 mg/kg/day, respectively, five times per week for 12 weeks. Spinal cords of carbon disulfide-intoxicated rats and their age-matched controls were Triton-extracted and ultracentrifuged to yield a pellet fraction of neurofilament (NF) polymer and a corresponding supernatant fraction. Then, the contents of NF triplet proteins (NF-H, NF-M, NF-L) and two calpain isoforms (m-calpain and mu-calpain) in both fractions were determined by immunoblotting. In the meantime, the mRNA levels of NF-H, NF-M, and NF-L in spinal cords were quantified using reverse transcriptase-polymerase chain reaction. Results showed that in the pellet fraction, the contents of three NF subunits in both treated groups decreased significantly except NF-L in low dose group. In the supernatant fraction, the pattern of NFs alteration varied according to dose-levels. Compared to controls, three neurofilmant subunits in the high dose group displayed significant reduction consistently. However, in the low dose group, they remained unaffected. As for calpains, the contents of mu-calpain in both fractions increased significantly regardless of carbon disulfide dose-levels. Meanwhile, m-calpain demonstrated a significant decline in the supernatant fraction, and remained unchangeable in the pellet fraction compared to the control group. Furthermore, the levels of mRNA expression of NF-H, NF-M, and NF-L genes were elevated consistently in CS(2)-treated groups. These findings suggested that carbon disulfide intoxication was associated with obvious alterations of NFs content in rat spinal cord, which might be involved in the development of carbon disulfide neurotoxicity.

Use of genotypic selection to detect P53 codon 273 CGT>CTT transversion: application to an occupationally exposed population

CGT>CTT transversion in codon 273 of the P53 tumor-suppressor gene is one of the major mutations detected in human tumors. Within an epidemiological framework, we investigated the use of a genotypic selection method to measure this point mutation. The allele-specific polymerase chain reaction (AS-PCR) that was developed was able to detect 10 mutant copies of the gene among a total of 5 x 10(5) wild-type copies. We used this assay to detect CGT>CTT transversions in buccal cell DNA of production workers (n=76) from a viscose factory exposed to carbon disulfide (amongst other pollutants) and in the DNA of non-exposed office workers (n=67). The mutation appeared more frequently in the exposed than in the non-exposed worker who were smokers. The results of the study indicate that occupational exposure results in a significant increase in P53 CGT>CTT transversions and more especially identified occupational exposure in combination with smoking as a significant risk factor for the mutation. We conclude that AS-PCR of the P53 273rd codon transversions is a suitable technique for studying the effects of occupational exposure.

Dithiocarbamates have a common toxic effect on zebrafish body axis formation

We previously determined that the dithiocarbamate pesticide sodium metam (NaM) and its active ingredient methylisothiocyanate (MITC) were developmentally toxic causing notochord distortions in the zebrafish. In this study, developing zebrafish were exposed to isothiocyanates (ITCs), dithiocarbamates (DTCs) and several degradation products to determine the teratogenic relationship of these chemical classes at the molecular level. All dithiocarbamates tested elicited notochord distortions with notochord NOELs from <4 to 40 ppb, while none of the ITCs caused notochord distortions with the exception of MITC. Carbon disulfide (CS(2)), a common DTC degradate, also caused distortions at concentrations >200 times the DTCs. Whole mount in situ hybridization of developmental markers for collagen (collagen2a1), muscle (myoD), and body axis formation (no tail) was perturbed well after cessation of treatment with pyrolidine-DTC (PDTC), dimethyl-DTC (DMDTC), NaM, MITC, and CS(2). Therefore, distinct albeit related chemical classes share a common toxic effect on zebrafish notochord development. To test the responsiveness of the distortion to metal perturbation, five metal chelators and 2 metals were studied. The membrane permeable copper chelator neocuproine (NCu) was found to cause notochord distortions similar to DTC-related molecules. DMDTC and NCu treated animals were protected with copper, and collagen 2a1 and no tail gene expression patterns were identical to controls in these animals. PDTC, NaM, MITC, and CS(2) were not responsive to copper indicating that the chelation of metals is not the primary means by which these molecules elicit their developmental toxicity. Embryos treated with DMDTC, NaM, and NCu were rescued by adding triciaine (MS-222) which abolishes the spontaneous muscle contractions that begin at 18 hpf. In these animals, only collagen 2a1 expression showed a similar pattern to the other notochord distorting molecules. This indicates that the perturbation of no tail expression is in response to the muscle contractions distorting the notochord, while collagen 2a1 is associated with the impact of these molecules on much earlier developmental processes.

Neurobehavioral and clinical effects in workers exposed to CS2

OBJECTIVES

Diffuse vascular encephalopathy, parkinsonism and peripheral polyneuropathy (PNP) due to CS(2) exposure are known since long. Data concerning low exposure are sparse. The current study aimed to evaluate whether the decrease of exposure below the threshold limit value (TLV) of 31 mg/m(3) results in an absence of neurological health effects using the same health outcomes as in the first study.

METHODS

The study was conducted in a group of workers of a viscose rayon plant and a control group (CG, n=66). The exposed group was divided into two groups, according to the average CS(2) exposure being below (EG1; n=60) or above 31 mg/m(3) (EG2; n=25). If the current TLV seemed insufficient to prevent effects, the analysis was repeated with three subgroups (10, >10 to 30, >30 mg/m(3)) to estimate the NOEL. Every participant filled in the neurotoxicity symptom checklist (NSC-60) and the Q16. Clinical neurological examination, computer-assisted neurobehavioral tests (NES) and neurophysiological examinations (nerve conduction velocities and electromyography (EMG)) were performed.

RESULTS

Sensorimotor complaints (NSC-60) were significantly worse in both EG1 and EG2 compared to CG (p=0.032) and both exposure groups had a higher proportion of positional tremor compared with CG (p=0.046). Finger tapping in the dominant and non-dominant hand (NES) was worse in EG1 and EG2 compared with CG (both p<0.001). A significant increase in sural nerve SCV, a significant decrease in sural nerve SNAP amplitude and duration and sympathetic skin response (SSR) amplitude, and higher prevalence of EMG abnormalities and PNP was also found in both EG1 and EG2 (p<0.003). All effects remained significant after controlling for possible confounding factors. Further analysis suggested that even average CS(2) exposures of 10 mg/m(3) could still cause effects on positional tremor, finger tapping dominant and non-dominant hand, sural nerve amplitude, SSR amplitude and EMG abnormalities.

CONCLUSIONS

An excess of psychomotor slowing, tremor and PNP was found in workers on average exposed to CS(2) concentrations below 31 mg/m(3). Data suggest that even average exposures as low as 10 mg/m(3) can cause the deleterious effects. This indicates that the current TLV insufficiently protects against neurological effects and, as a consequence, should be lowered.

[Antagonism of vitamin E on lipid peroxidation in testis of male rats with carbon disulfide]

OBJECTIVE

To study the antagonistic joint action of vitamin E (VE) lipid peroxidation of testis in the male rats with carbon disulfide (CS2).

METHODS

36 wistar male rats were randomly dicided into six groups. It took 10-week for the rats to breath CS2 in different concentrations (0, 50, 250 and 1250 mg/m3), respectively, CS2 (1250 mg/m3) with VE (250 mg/kg diet) and VE (250 mg/kg diet) group. After 10-week treatment, rats were killed and the following parameters of lipid peroxidation in testis were determined:SOD, MDA, GST, GSH, GSH-px, NO, NOS and iNOS.

RESULTS

Compare with the control group, SOD, GST, GSH-px, NOS and iNOS activity were decreased (P < 0.05 or P < 0.01), GSH, NO content decreased also, MDA content was increased (P < 0.01). After the antioxidant VE treatmented, the parameters were significantly increased (the amount of MDA was decreased).

CONCLUSION

The antioxidant VE significantly protects against on lipid peroxidation in testes of male rats with CS2.

Carbon Disulfide-Induced Changes in Cytoskeleton Protein Content of Rat Cerebral Cortex

To investigate the mechanism of carbon disulfide-induced neuropathy, male wistar rats were administrated by gavage at dosage of 300 or 500 mg/kg carbon disulfide, five times per week for 12 weeks. By the end of the exposure, the animals produced a slight or moderate level of neurological deficits, respectively. Cerebrums of carbon disulfide-intoxicated rats and their age-matched controls were Triton-extracted and centrifuged at a high speed (100,000 x g) to yield a pellet fraction of NF polymer and a corresponding supernatant fraction, which presumably contained mobile monomer. Then, the contents of six cytoskeletal protein (NF-L, NF-M, NF-H, alpha-tubulin, beta-tubulin, and beta-actin) in both fractions were determined by immunoblotting. Results showed that the contents of the three neurofilament subunits in the pellet and the supernatant fraction decreased significantly regardless of dose levels (P<0.01). As for microtubule proteins, in the pellet fraction of cerebrum, the levels of alpha-tubulin and beta-tubulin demonstrated some inconsistent changes. However, in the supernatant fractions, the content of alpha-tubulin and beta-tubulin increased significantly in both two dose groups (P<0.01). In comparison to neurofilament and tubulin proteins, the content of beta-actin changed less markedly, only the supernatant fraction of the high dose group displayed significant increase (P<0.01), but the others remained unaffected. These findings suggested that the changes of cytoskeleton protein contents in rat cerebrum were associated with the intoxication of carbon disulfide, which might be involved in the development of carbon disulfide neurotoxicity.

Effects of industrial solvents on hearing and balance: A review

Industrial hearing loss has generally been associated with noise exposure, but there is a growing awareness that industrial solvents can have an adverse effect on the auditory and vestibular systems in man. Both animal experiments and human studies point to an ototoxic effect of industrial solvents, as well as some central auditory and vestibular disturbances. This review examines the research from the last four decades in an attempt to get an overview of the available evidence. Research shows that industrial solvents are ototoxic in rats. The majority of the solvents studied cause a loss of auditory sensitivity in the mid-frequencies in rats, affecting outer hair cells in the order OHC 3 > OHC 2 > OHC 1 . Inner hair cells are generally unaffected. Spiral ganglion cells are most vulnerable to trichloroethylene. Simultaneous exposure to solvents and noise results in a synergistic effect; the pattern of trauma mirrors that due to solvent exposure rather than noise, but is more enhanced. There is a critical level when synergy occurs. The effects of solvents on the vestibular system are neurotoxic and influence the vestibulo-oculomotor system in both animals and humans; humans also present with problems in postural sway. There is a strong suggestion from human studies that solvents are ototoxic in man, but findings show that both the peripheral and central auditory pathways can be affected. Hearing losses can be in the high frequency region or can affect a wider range of frequencies. Hearing loss and balance disturbances can occur at levels below permitted levels of exposure. The synergistic effect of combined exposure to solvents and noise has also been noted in humans, resulting in greater hearing losses than would be expected from exposure to noise and solvents alone. The findings from both human and animal studies indicate that exposure to industrial solvents or to industrial solvents and noise can have an adverse effect on hearing and balance. The implications for industry and hearing conservation are far reaching.

[Study on the reproductive effects of carbon disulfide in male rats and their subgeneration]

OBJECTIVE

To study reproductive toxicity of carbon disulfide and the effects of their subgeneration.

METHODS

40 male rats were randomly divided into four groups. It took ten weeks for the rats to breath CS2 in different densities (0, 50, 250, 1250 mg/m3). Five rats were randomly chosen from the controlling group, high and low dosage group, put them together with female rats for copulation in the ninth week. We observed the pregnant rates, miscarry counts, resorption counts, the numbers and body weight of their subgeneration, weight of the placenta, length of the body, length of the tail, length of the belly, the distance from the rectum to the genital, the effects of the sketetion and the purtenunce. In the eleventh weeks, we measured testide coefficient and testide horizontal of male rats, epididymal weight, sperm count, sperm motility and its classification, the ratio of sperm deformity, etc.

RESULTS

The pregnant rats of the dosage groups were all lower than the control group, but the differences were not statistically significant. The data of the high dosage group was obviously lower than the control group (P < 0.05 or P < 0.01). The body weight and the organ coefficient were all lower than the control group, but only brain coefficient of the high group between the control group were statistically significant (P < 0.05). Teside coefficient of the high dosage group obvioulsly decreased than the control group (P < 0.05). Epididymal weight, sperm count, sperm molitity and incidence rate of ospermia of middle and high dosage group obviously decreased than control group.

CONCLUSION

The effects of CS2 in distortion rate and abnormal data of growth are possibly related to the decrease in sperm quality and quantity.

Topical exposure to carbon disulfide induces epidermal permeability alterations in physiological and pathological changes

Carbon disulfide (CS2) has been suggested its possible skin toxicity. Neither a dose-response relationship nor any mechanism of CS2-exposure regarding epidermal permeability alterations has been postulated. The objectives of this study were to evaluate the dose-dependent association and the pathological changes with CS2 topically applied to mouse epidermis. Four concentrations of CS2 (0% (controls), 10%, 15%, and 20% in ethanol) were topically applied to a 1.8 cm2 area of the lateral abdomen of female nude mice for 10 min. Time-series transepidermal water loss (TEWL) profile, morphological examinations by both light microscopy (hematoxylin/eosin stain and Nile Red stain) and electronic microscopy, and lipid analysis by high performance thin-layer chromatography (HPTLC) were used to evaluate the epidermal impairment. We found no recovery occurred within 72 h exposure to 20% CS2 in contrast to substantial recovery found in 10% and 15% CS2-exposure. Clear dose-dependent fashions were shown in TEWL elevations, recovery retardation, and lipid extraction across the ethanol (control), 10%, 15%, and 20% CS2 exposures. Two mechanistic pathways were raised to account for CS2-induced epidermal alterations: intercellular lipid depletion and keratinocyte damage. A study with different test animal species is warranted owing to the discrepancies in epidermis between nude mice and other species.

Interdisciplinary neurotoxicity inhalation studies: Carbon disulfide and carbonyl sulfide research in F344 rats

Inhalation studies were conducted on the hazardous air pollutants, carbon disulfide, which targets the central nervous system (spinal cord) and peripheral nervous system (distal portions of long myelinated axons), and carbonyl sulfide, which targets the central nervous system (brain). The objectives were to investigate the neurotoxicity of these compounds by a comprehensive evaluation of function, structure, and mechanisms of disease. Through interdisciplinary research, the major finding in the carbon disulfide inhalation studies was that carbon disulfide produced intra- and intermolecular protein cross-linking in vivo. The observation of dose-dependent covalent cross-linking in neurofilament proteins prior to the onset of lesions is consistent with this process contributing to the development of the neurofilamentous axonal swellings characteristic of carbon disulfide neurotoxicity. Of significance is that valine-lysine thiourea cross-linking on rat globin and lysine-lysine thiourea cross-linking on erythrocyte spectrin reflect cross-linking events occurring within the axon and could potentially serve as biomarkers of carbon disulfide exposure and effect. In the carbonyl sulfide studies, using magnetic resonance microscopy (MRM), we determined that carbonyl sulfide targets the auditory pathway in the brain. MRM allowed the examination of 200 brain slices and made it possible to identify the most vulnerable sites of neurotoxicity, which would have been missed in our traditional neuropathology evaluations. Electrophysiological studies were focused on the auditory system and demonstrated decreases in auditory brain stem evoked responses. Similarly, mechanistic studies focused on evaluating cytochrome oxidase activity in the posterior colliculus and parietal cortex. A decrease in cytochrome oxidase activity was considered to be a contributing factor to the pathogenesis of carbonyl sulfide neurotoxicity.

Biological monitoring of carbon disulphide and phthalate exposure in the contemporary rubber industry

OBJECTIVES

We studied the range in urinary levels of 2-thiothiazolidine-4-carboxyl acid (TTCA), a metabolite of CS2 and phthalic acid (PA), a common metabolite of phthalates, across factories and departments in the contemporary rubber manufacturing industry.

METHODS

Spot urine samples from 101 rubber workers employed in nine different factories were collected on Sunday and during the workweek on Tuesday, Wednesday and Thursday at approximately 4 pm. In total, 386 urine samples were successfully analyzed.

RESULTS

Levels of both biomarkers increased significantly by a factor 2 (paired t-test P-value <0.05) during the working week as compared to the Sunday biomarker levels with absolute increases of approximately 70 microg/l and 5 micromol/mol creatinine for PA and TTCA, respectively. Levels in both biomarkers did not differ markedly between working days. Increases seemed to be restricted to specific factories and/or departments (e.g. molding and curing).

CONCLUSIONS

The results of this study demonstrate that rubber workers in the contemporary rubber industry are exposed to phthalates and low levels of CS2 ( approximately 0.05 ppm) as measured by PA and TTCA, respectively. Exposures to both compounds are largely driven by specific circumstances in factories. Therefore, when estimating exposures to phthalates and CS2 detailed information should be collected on the type and amount of phthalate containing ester plasticizers, dithiocarbamates and thiurams used. Preferably, personal exposure data should be collected. In this case, biological monitoring seems a reasonable approach. However, in the case of PA attention should be given to individual background levels as this could lead to a substantial overestimation of the occupational contribution to total phthalate exposure.

The effects of carbon disulfide and ethanol on the circulatory system of rats

Carbon disulfide exerted adverse effects on the structure or hemodynamics of the cardiovascular system, and whether ethanol exposure modifies the cardiovascular effect of carbon disulfide, was examined. Male Sprague-Dawley rats were used in the study. Animals in the control and ethanol groups drank water containing 5% sugar, or 10% ethanol in addition to 5% sugar, respectively, for 14 wk. Sepatare animals inhaled 700 mg/m3 of carbon disulfide for 6 h daily. Carbon disulfide treatment did not affect the food and fluid consumption of the animals, while this gas decreased body mass gain. CS2 increased arterial blood pressure and cardiac index, decreased their cardiac output, the fraction of the cardiac output, and blood flow for the kidneys and the lungs, and increased the relative heart, liver, and kidneys mass and the vascular resistance of the brain, lungs, and kidneys. Ethanol decreased the food and fluid consumption and body mass gain of the animals, the fraction of the cardiac output for the kidneys, and the vascular resistance of the liver, while it increased the blood flow of the brain and liver. Simultaneous administration of carbon disulfide and ethanol decreased the heart rate and increased the QRS duration. Significant interaction was found between the effect in case of heart rate, PQ distance, and QRS duration; carbon disulfide significantly increased the minimal-moderate effect of ethanol on all three parameters. With histological examinations no pathologic alterations were found in the organs studied. It was concluded that the early hemodynamic changes produced by carbon disulfide may play a significant role in the pathomechanism of the effects of the substance (hypertension, damage to the myocardium and kidneys). On the other hand, a potentiating interaction of carbon disulfide was expected with the effects of ethanol, at the administered concentration and dose in the study.

[Effect of carbon disulfide exposure at different phases on the embryonic development in mid-pregnancy of female mice]

OBJECTIVE

To explore the sensitive point of embryotoxicity of carbon disulphide on female mice.

METHODS

At the phases of follicle developing, implanting and post-implantation of blastocyst, female mice were injected intraperitoneally with carbon disulphide 631.4 mg/kg per day for three days while controls with plant oil. All indexes were detected at the fourteenth day of pregnancy.

RESULTS

(1) In follicle developing CS(2) exposed group, the weight of embryos fossa [(1.23 +/- 0.36) g was 41% less than that in controls [(2.08 +/- 0.48) g, P = 0.000], and in implanting CS(2) exposed group the weight of embryo fossa, and embryos [(1.27 +/- 0.97) g, and (0.12 +/- 0.09) g respectively] were 39% and 37% less than those in controls [(2.08 +/- 0.48), (0.19 +/- 0.06) g, P = 0.068, P = 0.045]; (2) In both follicle developing and implanting CS(2) exposed group, the weights of uterus and placenta were also less than those in controls (P < 0.01). (3) In post-implantation CS(2) exposed group, the above parameters were not significantly different from those in controls.

CONCLUSION

Follicle developing phase as well as implanting of blastocyst may be sensitive point for embryotoxicity induced by carbon disulphide.

Carbonic anhydrase metabolism is a key factor in the toxicity of CO2 and COS but not CS2 toward the flour beetle Tribolium castaneum [Coleoptera: Tenebrionidae]

The analogues carbon dioxide (CO(2)), carbonyl sulfide (COS) and carbon disulfide (CS(2)) have been useful as substrate probes for enzyme activities. Here we explored the affinity of the enzyme carbonic anhydrase for its natural substrate CO(2), as well as COS and CS(2) (1) by in vitro kinetic metabolism studies using pure enzyme and (2) through mortality bioassay of insects exposed to toxic levels of each of the gases during carbonic anhydrase inhibition. Hydrolysis of COS to form hydrogen sulfide was catalysed rapidly showing parameters K(m) 1.86 mM and K(cat) 41 s(-1) at 25 degrees C; however, the specificity constant (K(cat)/K(m)) was 4000-fold lower than the reported value for carbonic anhydrase-catalysed hydration of CO(2). Carbonic anhydrase-mediated CS(2) metabolism was a further 65,000-fold lower than COS. Both results demonstrate the deactivating effect toward the enzyme of sulfur substitution for oxygen in the molecule. We also investigated the role of carbonic anhydrases in CO(2), COS and CS(2) toxicity using a specific inhibitor, acetazolamide, administered to Tribolium castaneum (Herbst) larvae via the diet. CO(2) toxicity was greatly enhanced by up to seven-fold in acetazolamide-treated larvae indicating that carbonic anhydrases are a key protective enzyme in elevated CO(2) concentrations. Conversely, mortality was reduced by up to 12-fold in acetazolamide-treated larvae exposed to COS due to reduced formation of toxic hydrogen sulfide. CS(2) toxicity was unaffected by acetazolamide. These results show that carbonic anhydrase has a key role in toxicity of the substrates CO(2) and COS but not CS(2), despite minor differences in chemical formulae.

Male exposure mediated adverse reproductive outcomes in carbon disulphide exposed rayon workers

The authors examined 100 carbon disulphide (CS2) exposed male workers who had been employed ten years prior to study were selected for the study. They were virtually obliged to participate in the study by the Medical Labor Inspector and all of them participated voluntary. The aim was to assess the effects of occupational exposure to carbon disulphide concentrations below the threshold limit value (31 mg/m3) on the reproductive functions with special emphasis on miscarriages. Specially, workers history records were build up on number of children, miscarriages and general weakness, mental fatigue etc. It was found that the incidences of number of miscarriages against number of living children correlated well with environmental concentration of CS2. Where the average CS2 levels were 1.695 ppm, the incidences of miscarriages was 5.71% (group 1). Where as in group 2 environmental concentrations were 12.28 ppm and the incidences of miscarriages were 18.91%. It was also found that in the spinning department the exposure exceeds many times the Threshold Limit Values (TL V).

Six year observational cohort study of the effect of carbon disulphide on brain MRI in rayon manufacturing workers

AIMS

To clarify whether the current occupational exposure limit (OEL) for carbon disulphide (CS2) is low enough to prevent the occurrence of adverse effects on the cerebrovascular system.

METHODS

A total of 432 male workers exposed to CS2 and 402 male referent workers in 11 Japanese viscose rayon factories were studied at baseline; 750 of these were followed up. Brain MRI was performed at both baseline and follow up surveys. Changes in the number of hyperintense spots in T2 weighted images (HIS), which point to so-called "silent cerebral infarctions", were evaluated over six years. A total of 666 subjects (217 exposed, 125 ex-exposed, and 324 referent subjects) who twice received brain MRI were subjected to analysis. Mean duration of exposure to the end of the study was 19.6 years for the exposed workers. The geometric mean CS2 (ppm) and TTCA (mg/g creatinine) concentrations for the past six years were 4.9 and 1.6 for all exposed workers, 5.8 and 1.9 for spinning/refining workers, and 2.7 and 0.9 for other exposed workers, respectively.

RESULTS

Exposed subjects showed a significantly higher risk for an increase in the number of HIS over six years. Odds ratios adjusted for possible confounders in the exposed and ex-exposed workers were 2.27 (95% CI 1.37 to 3.76) and 1.33 (95% CI 0.70 to 2.54), respectively. No exposure-response relations were observed in a number of analyses among the exposed workers.

CONCLUSIONS

Exposure to CS2 under the current Japanese OEL, 10 ppm, might increase the number of HIS in brain MRI. However, results should be interpreted with caution.

Dopamine Transporter Binding Study in Differentiating Carbon Disulfide Induced Parkinsonism from Idiopathic Parkinsonism

Long-term exposure to carbon disulfide (CS(2)) may induce parkinsonian features. There may be confusion in distinguishing between CS(2) parkinsonism and idiopathic parkinsonism, especially for workers who developed parkinsonian features in viscose rayon plants. We performed clinical examinations, and laboratory studies including magnetic resonance imaging (MRI) and dopamine transporter (DAT) studies with (99m)Tc-TRODAT-1 brain single photon emission computed tomography (SPECT) in three workers who had long-term exposure to CS(2). Patient 1 had polyneuropathy, and encephalopathy with tremor; patient 2 had polyneuropathy, and encephalopathy with parkinsonian features; and patient 3 had pure parkinsonian features without polyneuropathy or cerebellar signs. The treatment with l-dopa was effective in patient 3, but non-effective in patient 2. Brain MRI revealed multiple high signal intensities over the subcortical white matter, basal ganglia, and/or even the brainstem in patients 1 and 2, but normal in patient 3. In DAT studies, the bindings were normal in patients 1 and 2 and was decreased in patient 3. We conclude that CS(2) exposure may induce polyneuropathy, and cerebellar dysfunction in addition to parkinsonian features and that brain MRI may show multiple lesions in the cerebral white matter and basal ganglia. In addition, DAT with (99m)Tc-TRODAT-1 brain SPECT may provide a useful information in differential diagnosis between CS(2) parkinsonism and idiopathic parkinsonism.

A six year follow up study of the subclinical effects of carbon disulphide exposure on the cardiovascular system

AIMS

A six year prospective cohort study was conducted to clarify whether the current carbon disulphide (CS2) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate health effects due to previous high exposure. This paper describes the effects on the cardiovascular systems.

METHODS

The study subjects were 432 male workers exposed to CS2 and 402 non-exposed workers in Japan, all of whom were examined in 1992-93. A total of 251 CS2 exposed, 140 formerly exposed, and 359 non-exposed workers participated in the follow up survey (follow up rate 89.9%) in 1998-99. Mean duration of exposure was 19.3 years at the end the study. Mean CS2 and 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations were 5.0 ppm and 1.6 mg/g creatinine. Health items examined were serum biochemical indices including lipids and coagulation-fibrinolysis factors, blood pressure, aortic stiffness, ophthalmography, and electrocardiography at rest and after Master's double 2 step test. Potential confounding factors were adjusted for.

RESULTS

Incidence of ischaemic findings, defined as Minnesota codes I, IV(1-3), V(1-3) (at rest and after the load), or receiving treatment for ischaemia, was significantly higher in the exposed workers, especially for the spinning/refining workers (adjusted OR 2.1; 95% CI 1.1 to 4.0) or the highest quartile of six year mean TTCA (adjusted OR 3.9; 95% CI 1.8 to 8.7), although the observed increase in risk was diminished when rigorous ECG criteria were applied. Incidence of retinal microaneurysm was increased with marginal significance. Among cardiovascular risk factors we examined, only blood pressure values were significantly increased in the exposed workers.

CONCLUSIONS

Increased risk of ischaemic electrocardiogram findings among Japanese viscose rayon workers was observed. Although its clinical significance is to be discussed, the current Japanese occupational exposure limit for CS2, 10 ppm, would be high to prevent subclinical cardiovascular effects in this study population.

[Detection of DNA damage induced by carbon disulfide in mice sperm with single-cell gel electrophoresis assay]

OBJECTIVE

To study the genotoxicity of carbon disulfide by detecting DNA damage in mice sperm with single-cell gel electrophoresis assay (SCGE).

METHODS

SCGE was used to detect sperm DNA damage. The index of DNA damage, tail length and tail moment were used to evaluate the extent of DNA damage.

RESULTS

In three dosage groups, the rate of DNA damage (67.14%, 84.29% and 91.00%, respectively), index of DNA damage intensity (507, 656 and 745, respectively), tail length (5.87, 8.81 and 13.49 microm, respectively) and tail moment (1.30, 1.63, 2.66 microm, respectively) were significantly increased, while the percentage of head of the comet was significantly decreased (84.55%, 73.84% and 55.71%, respectively). A significant changes were clearly observed in all dosage groups compared to those of the control group (P<0.05).

CONCLUSION

SCGE which is a quick and sensitive method to detect DNA damage induced by CS2 may be used to monitor carcinogen and mutagen.

Hearing loss in workers exposed to carbon disulfide and noise

Simultaneous exposure to carbon disulfide and noise may have a combined effect on hearing impairment. In this study we investigated hearing loss in 131 men with exposure to noise [80-91 A-weighted decibels; dB(A)] and CS(2) (1.6-20.1 ppm) in a viscose rayon plant. These men were compared with 105 men in the adhesive tape and electronic industries who were exposed to noise only and with 110 men employed in the administrative office of the rayon plant who were exposed to low noise and no CS(2). We conducted interviews to obtain sociodemographic information and exposure assessments, and we performed physical examinations, including hearing tests. Results showed that the prevalence of hearing loss of > 25 dB hearing loss (dBHL) in rayon workers (67.9%) was much higher than that in administrative workers (23.6%) and in the adhesive tape and electronic industrial workers (32.4%). Hearing loss occurred mainly for speech frequencies of 0.5, 1, and 2 kHz. When the CS(2) exposure was measured by the product of CS(2 )exposure level and employment years, the adjusted odds ratios of hearing loss of > 25 dBHL in rayon workers, compared with administrative workers, were 3.8 [95% confidence interval (CI), 1.5-9.4] for those with the exposure of 37-214 year-ppm, 14.2 (95% CI, 4.4-45.9) with 215-453 year-ppm exposure, and 70.3 (95% CI, 8.7-569.7) with exposure of > 453 year-ppm. The study suggests that CS(2) exposure enhances human hearing loss in a noisy environment and mainly affects hearing in lower frequencies.

[Exposure to low doses of CS2 and cardiovascular risk factors]

The effects were studied on cardiovascular risk factors of occupational exposure to carbon disulfide (CS2) concentrations ranging from 0.05 to 1.60 mg/m3, 74 workers exposed (E) to CS2 and 79 non-exposed (NE) workers were examined. Information was obtained on age, working age and life habits (alcohol, smoke, etc.) through a questionnaire and height and weight were measured to assess body mass index (BMI). All the workers underwent blood collection for the assessment of total cholesterol, HDL cholesterol and triglyceride levels and electrocardiogram. No clinically evident heart disease were detected in the workers examined and the prevalences of obesity and hypertension resulted to be similar among workers of the two groups. Mean triglyceride levels and frequencies of hypertriglyceridemia and of HDL cholesterol values < 40 mg/dl were significantly higher in exposed workers than non-exposed. The triglyceride levels resulted to be significantly and directly influenced by BMI and exposure to CS2. Occupational exposure to low environmental CS2 concentrations seems to interacts with other factors to determine alterations of lipid metabolism.

Disassociation of carbon disulfide-induced depression of flash-evoked potential peak N166 amplitude and norepinephrine levels

Exposure to organic solvents frequently causes functional impairment of the central nervous system (CNS). One method to examine the effects of solvent exposure on visual function is flash-evoked potentials (FEPs). Greater knowledge of the role of various neurotransmitters in generating FEP peaks would be beneficial for understanding the basis of neurotoxicant-induced changes. FEP peak N166 is influenced by the psychological construct of arousal, which in turn is believed to be influenced by the function of neurons containing norepinephrine (NE). Because of its known effects on both NE and FEPs, we utilized carbon disulfide (CS2) as a means to examine the possible role of NE in modulating the amplitude of FEP peaks N36 and N166. Our hypothesis was that CS2-induced alterations in cortical NE levels would be correlated with changes in FEP peak N36 and N166 amplitudes. Adult male Long-Evans rats were implanted with electrodes over their visual cortex and allowed to recover. To develop peak N166, FEPs were recorded for two days prior to dosing. On the third day, FEPs were recorded prior to dosing, and one group of animals was sacrificed to serve as pretreatment controls. The remaining animals were dosed ip with 0 (corn oil vehicle; 2 ml/kg), 100, 200, or 400 mg/kg CS2. The treated animals were retested at 1, 4, 8, or 24 h after dosing, immediately sacrificed, and samples of the cortex, cerebellum, striatum, and brain stem were frozen for high performance liquid chromatography (HPLC) analysis of monoamine levels. Treatment with CS2 decreased peak N166 amplitude at 1 h, and peak N36 amplitude was depressed at 4 h, relative to the subject's pretreatment values. Peak latencies were increased, and colonic temperature was decreased by treatment with CS2. Exposure to CS2 depressed NE levels in the cortex, brain stem, and cerebellum 4 h after treatment. Conversely, at 4 h, levels of dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid were increased in the brain stem and cerebellum, and levels of the DA metabolite homovanillic acid were increased in the brain stem. Levels of serotonin were unaffected by CS2 treatment. There was a slight increase in striatal levels of the serotonin metabolite 5-hydroxyindole acetic acid at all times after treatment with CS2. There was no apparent association between the decreases in NE levels and the reductions in amplitudes for peaks N36 and N166. The neurochemical mechanism for CS2-induced reductions in FEP peak amplitudes remains to be determined.

Carbon disulfide cytotoxicity on cultured cardiac myocyte cell of rats

Although mostly epidemiological studies suggested that carbon disulfide produces cardiovascular effects in occupationally exposed workers, little is known about its cellular mechanism. The purpose of the present study was to evaluate the functional and histological effects on cardiac myocytes cultured under the condition of carbon disulfide exposure. Cardiac myocytes were isolated from neonatal rat ventricles by trypsin dispersion and cultured for 3 days in a full (Dulbecco's modified eagle medium) medium containing 2% calf serum. Thereafter the myocytes (10(6) myocytes/culture flask) were incubated with carbon disulfide at (CS(2)) the concentrations of 0, 20, 40, and 80 micromol/mL) for 24h. The beating arrest rate of myocytes for each group was examined and succinodehydrogenase (SDH) activity in the myocardial cells was also assessed by cytochemical method, and morphological examination was also performed. We found that the beating arrest rate of cardiac myocytes increased with increasing exposure levels. Vacuolization and pseudopodia may be seen in the cytoplasm of exposure group. SDH activity decreased with increasing exposure levels. The results suggested that CS(2) has a direct cytotoxic effect which is dose dependent. The biochemical mechanism may be a reduction of the availability of energy of the cardiac cytocyte in the form of ATP, resulting in a decrease of contractility by lacking of energy.

Lack of Relationship between Occupational Exposure to Carbon Disulfide and Endocrine Dysfunction: A Six‐year Cohort Study of the Japanese Rayon Workers

OBJECTIVES

A six-year prospective cohort study was conducted to clarify whether the current carbon disulfide (CS2) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate health effects due to previous high exposure. This paper describes the follow-up results, exposure assessment, and effects on the endocrine system.

METHODS

The study subjects were 432 male workers exposed to CS2 at one of the 11 rayon factories in Japan and 402 referent workers from the same factories, all of whom were examined in 1992-93. 251 CS2-exposed, 140 former-exposed and 359 referent workers participated in the follow-up survey (follow-up rate 89.9%) in 1998-99. Urinary 2-thiothiazolidine-4-carboxylic acid (TTCA) at the end of a shift as internal exposure index and the time-weighted average CS2 concentration as external exposure index were measured twice a year from 1992-1993. By using various blood indices, we evaluated effects on thyroid, hypophysis, and gonad function, as well as effects on glucose metabolism. Information on potential confounding factors, such as age, smoking and alcohol drinking, were collected and adjusted for.

RESULTS

When the individual exposure level was represented by arithmetic mean for TTCA and CS2 concentration, geometric means (SD) of CS2 workers were 1.61 (1.91) mg/g.crea and 5.02 (1.84) ppm, respectively. There were no exposure-related differences in glucose metabolism or any of the endocrinological indices.

CONCLUSIONS

No biologically significant effects of CS2 were found on endocrine function in Japanese rayon manufacturing workers when the average internal and external exposure levels were maintained below the current occupational exposure limit.

Neuropsychiatric Effects in Workers with Occupational Exposure to Carbon Disulfide

In a cross-sectional study, prevalence of dysfunctions of the central nervous system was assessed in 134 male workers exposed to different levels of carbon disulfide (CS2) in a rayon viscose plant and compared to 38 non-exposed workers. In three groups of workers from the same plant with different levels of CS2 (heavy, intermediate, none) estimated by personal samplers, disorders in the central nervous system were examined by means of psychiatric examination and questionnaire 16 (Q16). Unconditional logistic regression was calculated adjusted for age, alcohol consumption and education. Psychoorganic syndrome was diagnosed significantly more often in workers with heavy CS2 exposure, with adjusted OR of 17.9 (95% CI 2.18-146.73), and insignificantly in workers with intermediate exposure. Prevalence of workers with more than 6 positive answers on the Q16 was higher in the heavily exposed workers (OR=4.76; 95% CI 1.80-12.60). A similar result was found for almost all the questions in the Q16, and the most pronounced psychological symptom was of less interest in sex (adjusted OR=8.14; 95% CI 2.19-30.22). High correlation was found between symptoms recorded on neuropsychiatric examination and on Q16. Both neuropsychiatric exams and Q16 indicated disturbances in the central nervous system due to the long-term heavy exposure to CS2. Disorders of the central nervous system were found more often in workers with heavy exposure to CS2. Questionnaire Q16 is a valuable means for selecting workers for further neuropsychiatric testing.

Effects of the dithiocarbamate fungicide propineb in primary neuronal cell cultures and skeletal muscle cells of the rat

After repeated-dose toxicity studies with the fungicide propineb, reversible effects on muscle functions were found. Therefore, mechanistic investigations should contribute to clarification of its mode of action in relation to disulfiram and diethyldithiocarbamate neurotoxicity or direct effects on muscle cells. In principle, besides the dithiocarbamate effects, two different mechanisms have been discussed for this fungicide. One mechanism is the degradation to carbon disulfide (CS(2)) and propylenthiourea (PTU) and the other are direct effects of zinc. Primary neuronal cell cultures of the rat are a well established model to identify neurotoxic compounds like n-hexane or acrylamide. In this cell culture model, endpoints such as viability, energy supply, glucose consumption and cytoskeleton elements were determined. Additionally, skeletal muscle cells were used for comparison. Propineb and its metabolite PTU were investigated in comparison to CS(2), disulfiram and diethyldithiocarbamate. The toxicity of zinc was tested using zinc chloride (ZnCl(2)). It was clearly shown that propineb exerted strong effects on the cytoskeleton of neuronal and non-neuronal cell cultures (astrocytes, muscle cells). This was similar to ZnCl(2,) but not to CS(2). With CS(2) and disulfiram effects on the energy supply were more prominent. In conclusion, the toxicity of propineb is not comparable to disulfiram, diethyldithiocarbamate or CS(2) neurotoxicity. In regard to these findings, a direct reversible effect of propineb on skeletal muscle cells seems to be more likely.

Carbon disulfide cytotoxicity on cultured cardiac myocytes of rats

Although epidemiological studies have suggested that carbon disulfide produces cardiovascular effects in occupationally exposed workers, little is known about its cellular mechanism. The purpose of the present study was to evaluate the functional and histological effects on cardiac myocytes cultured under a condition of carbon disulfide exposure. Cardiac myocytes were isolated from neonatal rat ventricles by trypsin, dispersed and cultured for 3 days in a full Dulbecco's Modified Eagle Medium containing 2% calf serum. Then the myocytes (10(6) myocytes/mL) were incubated with carbon disulfide at concentrations of 0, 20, 40, and 80 micromol/mL for 24 h. The beating arrest rate of myocytes for each group was examined, succinodehydrogenase (SDH) activity in the myocardial cells was assessed using a cytochemical method, and a morphological examination was performed. We found that the beating arrest rate of cardiac myocytes increased with increasing exposure levels. Vacuolization and pseudopodia could be seen in the cytoplasm of the exposed group. SDH activity decreased with increasing exposure levels. The results suggest that CS2 has a direct and dose-dependent cytotoxic effect. The biochemical mechanism may be a reduction of the availability of energy (adenosine triphosphate) to cardiac myocytes, resulting in a decrease of contractility by lack of energy.