[The intervention effect of N-carbamoyl glutamic acid on embryo implantation disorder induced by carbon disulfide and its possible molecular mechanism].

Objective: To explore the preventive effect and possible molecular mechanism of dietary supplementation of N-carbamylglutamate (NCG) in the implantation of carbon disulfide (CS(2)) into embryo implantation disorders. Methods: embryo implantation disorder model was established by single intraperitoneal exposure to CS(2) on the 3rd, 4th, and 5th days after pregnancy. Endometrial tissues were collected for 24h after exposure to CS(2) for western-blot and immunohistochemical staining. Results: The number of embryo implantation was increased in NCG+CS(2) group, compared with CS(2) alone group. Day 4 of pregnancy when CS(2)-exposed after 24 h, the expression of pAKT protein in NCG+CS(2) group was significantly increased (P<0.05), the expression level of pAMPK protein in NCG+CS(2) group was significantly decreased, compared with CS(2) alone group, respectively. Immunohistochemical results showed that pAKT, pAMPK, AKT and AMPK proteins were expressed in luminal epithelial cells, glandular epithelial cells and stromal cells of endometrium; Day 4 of pregnancy when CS(2)-exposed after 24 h, deep staining of ATK and pAKT protein in NCG+CS(2) group, the AMPK and pAMPK protein staining became lighter. Conclusion: Dietary supplementation of NCG can interfere with the embryo loss induced by CS(2) by altering the total amount of AKT/AMPK molecules.

Combined exposure to carbon disulfide and low-frequency noise reversibly affects vestibular function.

Chronic occupational exposure to carbon disulfide (CS2) has debilitating motor and sensory effects in humans, which can increase the risk of falls. Although no mention of vestibulotoxic effects is contained in the literature, epidemiological and experimental data suggest that CS2 could cause low-frequency hearing loss when associated with noise exposure. Low-frequency noise might also perturb the peripheral balance receptor through an as-yet unclear mechanism. Here, we studied how exposure to a low-frequency noise combined with 250-ppm CS2 affected balance in rats. Vestibular function was tested based on post-rotary nystagmus recorded by a video-oculography system. These measurements were completed by behavioral tests and analysis of the cerebellum to measure expression levels for gene expression associated with neurotoxicity. Assays were performed prior to and following a 4-week exposure, and again after a 4-week recovery period. Functional measurements were completed by histological analyses of the peripheral organs.Nystagmus was unaltered by exposure to noise alone, while CS2 alone caused a moderate 19% decrease of the saccade number. In contrast, coexposure to 250-ppm CS2 and low-frequency noise decreased both saccade number and duration by 33% and 34%, respectively. After four weeks, recovery was only partial but measures were not significantly different from pre-exposure values. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis of cerebellar tissue revealed a slight but significant modification in expression levels for two genes linked to neurotoxicity in CS2-exposed animals. However, neither histopathological changes to the peripheral receptor nor behavioral differences were observed. Based on all these results, we propose that the effects of CS2 were due to reversible neurochemical disturbance of the efferent pathways managing post-rotatory nystagmus. Because the nervous structures involving the vestibular function appear particularly sensitive to CS2, post-rotary nystagmus could be used as an early, non-invasive measurement to diagnose CS2 intoxication as part of an occupational conservation program.

Continuous exposure to low-frequency noise and carbon disulfide: Combined effects on hearing.

Carbon disulfide (CS2) is used in industry; it has been shown to have neurotoxic effects, causing central and distal axonopathies.However, it is not considered cochleotoxic as it does not affect hair cells in the organ of Corti, and the only auditory effects reported in the literature were confined to the low-frequency region. No reports on the effects of combined exposure to low-frequency noise and CS2 have been published to date. This article focuses on the effects on rat hearing of combined exposure to noise with increasing concentrations of CS2 (0, 63,250, and 500ppm, 6h per day, 5 days per week, for 4 weeks). The noise used was a low-frequency noise ranging from 0.5 to 2kHz at an intensity of 106dB SPL. Auditory function was tested using distortion product oto-acoustic emissions, which mainly reflects the cochlear performances. Exposure to noise alone caused an auditory deficit in a frequency area ranging from 3.6 to 6 kHz. The damaged area was approximately one octave (6kHz) above the highest frequency of the exposure noise (2.8kHz); it was a little wider than expected based on the noise spectrum.Consequently, since maximum hearing sensitivity is located around 8kHz in rats, low-frequency noise exposure can affect the cochlear regions detecting mid-range frequencies. Co-exposure to CS2 (250-ppm and over) and noise increased the extent of the damaged frequency window since a significant auditory deficit was measured at 9.6kHz in these conditions.Moreover, the significance at 9.6kHz increased with the solvent concentrations. Histological data showed that neither hair cells nor ganglion cells were damaged by CS2. This discrepancy between functional and histological data is discussed. Like most aromatic solvents, carbon disulfide should be considered as a key parameter in hearing conservation régulations.

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.

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.

[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.

Effects of chronic carbon disulfide inhalation on sensory and motor function in the rat.

Chronic carbon disulfide (CS2) exposure produces debilitating motor, sensory and neuropsychiatric consequences in humans. Sensory, especially auditory, tests have been considered for indexing early intoxication. This study examines effects of chronic CS2 exposure in rat upon auditory and neuromuscular function using reflex modulation audiometry to test the feasibility of using pure tone detection thresholds as such an index. This method is sensitive to the differential effects of toxicants upon acoustic and neuromuscular functioning. Rats were tested before, during and after five or 12 weeks of 500 ppm CS2 inhalation, six h/day, five days/week. Neuromuscular integrity, reflected by baseline startle amplitude, decreased 50% after five weeks and 67% following 12 weeks of CS2 exposure; recovery to 70% of preexposure values occurred on the fourth postexposure week. Twelve weeks of CS2 inhalation had no significant effect upon acoustic thresholds. Pure tone detection thresholds, therefore, do not appear adequate to index early CS2 exposure levels in the rat, as severe neuromuscular compromise occurred at a time when acoustic thresholds remained stable.

The potentiation of the non-behavioural effects of amphetamine by carbon disulphide.

In agreement with the inhibition of dopamine-beta-hydroxylase by exposure to CS2, the extension of exposure time from 4 to 16 h increased dopamine concentrations in the hypothalmus and adrenals, and decreased noradrenaline concentration in the hypothalmus. The extension of exposure time also increased the toxicity of amphetamine. In conscious animals the stereotypic activity produced by 6.0 mg/kg and even that of 3.0 mg/kg amphetamine sulphate was suppressed by severe hyperthermia resulting in exhaustion, prostration and eventually death. A 16 h exposure to CS2 did not increase the lethal or hyperthermic effects of amphetamine in rats anaesthetized with 60 mg/kg sodium pentobarbitone. In fact the CS2 exposed rats became more hypothermic than non-exposed rats.