Physiological concentrations of zinc reduce taurine-activated GlyR responses to drugs of abuse

Taurine is an endogenous ligand acting on glycine receptors in many brain regions, including the hippocampus, prefrontal cortex, and nucleus accumbens (nAcc). These areas also contain low concentrations of zinc, which is known to potentiate glycine receptor responses. Despite an increasing awareness of the role of the glycine receptor in the rewarding properties of drugs of abuse, the possible interactions of these compounds with zinc has not been thoroughly addressed. Two-electrode voltage-clamp electrophysiological experiments were performed on α1, α2 α1β and α2β glycine receptors expressed in Xenopus laevis oocytes. The effects of zinc alone, and zinc in combination with other positive modulators on the glycine receptor, were investigated when activated by the full agonist glycine versus the partial agonist taurine. Low concentrations of zinc enhanced responses of maximally-effective concentrations of taurine but not glycine. Likewise, chelation of zinc from buffers decreased responses of taurine- but not glycine-mediated currents. Potentiating concentrations of zinc decreased ethanol, isoflurane, and toluene enhancement of maximal taurine currents with no effects on maximal glycine currents. Our findings suggest that the concurrence of high concentrations of taurine and low concentrations of zinc attenuate the effects of additional modulators on the glycine receptor, and that these conditions are more representative of in vivo functioning than effects seen when these modulators are applied in isolation.

Binge toluene exposure in pregnancy and pre-weaning developmental consequences in rats

Binge Toluene Exposure in Pregnancy and Pre-weaning Developmental Consequences in Rats. Bowen, S.E. and Hannigan, J.H. The persistent rate of abuse of inhaled organic solvents, especially among women of child-bearing age, raises the risk for teratogenic effects of maternal toluene abuse. In this study, timed-pregnant Sprague Dawley rats were exposed from Gestation Day (GD) 8 to GD20 to 12,000 or 8000 parts per million (ppm) toluene, or 0ppm (controls) for 30min twice daily, 60min total daily exposure. Pups were assessed from postnatal day (PN) 4 to PN21 using a developmental battery measuring growth (i.e., body weight), maturational milestones (e.g., eye opening & incisor eruption), and biobehavioral development (e.g., negative geotaxis & surface righting). Pups exposed in utero to 12,000ppm or 8000ppm toluene weighed significantly less than the non-exposed control pups beginning at PN4 and PN12 (respectively) until PN21. Toluene resulted in significant increases in an index of poor perinatal outcome, specifically a composite of malformations, defined "runting" and neonatal death. No significant delays were observed in reaching maturational milestones. The results reveal that brief, repeated, prenatal exposure to high concentrations of toluene can cause growth retardation and malformations in rats. A comparison of the present, conservative results with findings in previous studies implies that binge patterns of toluene exposure in pregnant rats modeling human solvent abuse can result in developmental and morphological deficits in offspring. These results do not exclude the possibility that maternal toxicity as well as teratogenic effects of toluene may contribute to outcomes. The results suggest that abuse of inhaled organic solvents like toluene may result in similar early developmental outcomes in humans.

Low temperature oxidation of benzene and toluene in mixture with n-decane

The oxidation of two blends, benzene/n-decane and toluene/n-decane, was studied in a jet-stirred reactor with gas chromatography analysis (temperatures from 500 to 1100 K, atmospheric pressure, stoichiometric mixtures). The studied hydrocarbon mixtures contained 75% of aromatics in order to highlight the chemistry of the low-temperature oxidation of these two aromatic compounds which have a very low reactivity compared to large alkanes. The difference of behavior between the two aromatic reactants is highly pronounced concerning the formation of derived aromatic products below 800 K. In the case of benzene, only phenol could be quantified. In the case of toluene, significant amounts of benzaldehyde, benzene, and cresols were also formed, as well as several heavy aromatic products such as bibenzyl, phenylbenzylether, methylphenylbenzylether, and ethylphenylphenol. A comparison with results obtained with neat n-decane showed that the reactivity of the alkane is inhibited by the presence of benzene and, to a larger extent, toluene. An improved model for the oxidation of toluene was developed based on recent theoretical studies of the elementary steps involved in the low-temperature chemistry of this molecule. Simulations using this model were successfully compared with the obtained experimental results.

The characteristics of the appearance and health risks of volatile organic compounds in industrial (pohang, ulsan) and non-industrial (gyeongju) areas

OBJECTIVES

The aim of this study was to identify the health and environmental risk factors of air contaminants that influence environmental and respiratory diseases in Gyeongju, Pohang and Ulsan in South Korea, with a focus on volatile organic compounds (VOCs).

METHODS

Samples were collected by instantaneous negative pressure by opening the injection valve in the canister at a fixed height of 1 to 1.5 m. The sample that was condensed in -150℃ was heated to 180℃ in sample pre-concentration trap using a 6-port switching valve and it was injected to a gas chromatography column. The injection quantity of samples was precisely controlled using an electronic flow controller equipped in the gas chromatography-mass spectrometer.

RESULTS

The quantity of the VOC emissions in the industrial area was 1.5 to 2 times higher than that in the non-industrial area. With regards to the aromatic hydrocarbons, toluene was detected at the highest level of 22.01 ppb in Ulsan, and chloroform was the halogenated hydrocarbons with the highest level of 10.19 ppb in Pohang. The emission of toluene was shown to be very important, as it accounted for more than 30% of the total aromatic hydrocarbon concentration.

CONCLUSIONS

It was considered that benzene in terms of the cancer-causing grade standard, toluene in terms of the emission quantity, and chloroform and styrene in terms of their grades and emission quantities should be selected for priority measurement substances.

Protective effects of quercetine on the neuronal injury in frontal cortex after chronic toluene exposure

The aim of this study was designed to evaluate the possible protective effects of quercetine (QE) on the neuronal injury in the frontal cortex after chronic toluene exposure in rats. The rats were randomly allotted into one of the three experimental groups, namely, groups A (control), B (toluene treated) and C (toluene-treated with QE), where each group contains 10 animals. Control group received 1 ml of normal saline solution, and toluene treatment was performed by the inhalation of 3000 ppm toluene in an 8-h/day and 6-day/week order for 12 weeks. The rats in QE-treated group was given QE (15 mg/kg body weight) once a day intraperitoneally for 12 weeks, starting just after toluene exposure. Tissue samples were obtained for histopathological investigation. To date, no histopathological changes of neurodegeneration in the frontal cortex after chronic toluene exposure in rats by QE treatment have been reported. In this study, the morphology of neurons in the QE treatment group was well protected. Chronic toluene exposure caused severe degenerative changes, shrunken cytoplasm and extensively dark picnotic nuclei in neurons of the frontal cortex. We conclude that QE therapy causes morphologic improvement in neurodegeneration of frontal cortex after chronic toluene exposure in rats. We believe that further preclinical research into the utility of QE may indicate its usefulness as a potential treatment on neurodegeneration after chronic toluene exposure in rats.

Evaluation of occupational exposure of shoe makers to benzene and toluene compounds in shoe manufacturing workshops in East tehran

BACKGROUND

Shoe making is among the oldest traditional occupations. Hazardous chemical substances such as adhesives containing benzene and toluene are used in the manufacturing process. Due to the lack of studies on exposure of shoemakers to benzene and toluene in Iran, this study was organized aiming at evaluating occupational exposure and risk assessment in shoemakers.

MATERIALS AND METHODS

Overall, 48 shoemakers (12 workshops) in East Tehran were selected randomly for this study. Personal exposure of shoemakers in four different task groups of cutting, modeling, fitting and finishing was examined during three consecutive months (October, November and December) with different climatic conditions. Sampling and analysis of samples were based on an OSHA method (Method No.12).

RESULTS

The results of personal monitoring of subjects' exposure to benzene and toluene in each of the three consecutive months (Mean ± standard error) were 1.10± 0.11, 1.37 ± 0.14 and 1.52 ± 0.18ppm, 11.78 ± 1.77, 14.87 ± 1.71 and 16.08 ± 2.31ppm respectively. Due to climatic temperature changes from October to December and restriction of air flow due to closure of windows and shut down of general ventilation systems, a general trend of increased exposure was noticed. However, the difference among these three examinations was not statistically significant. Shoemakers in four task groups did not have statistically significant differences in exposure to benzene and toluene. The severity of shoemaker's exposure to toluene was significantly correlated with the number of manufactured shoes and the amount of glue used for the process.

CONCLUSION

Considering the magnitude of personal exposure of task groups to benzene and toluene which was higher than TLV-TWA and unacceptably high risk of cancer and non-cancerous diseases in these subjects, improvement of work conditions for shoemakers seems imperative.

Transformation of pWWO in Rhizobium leguminosarum DPT to Engineer Toluene Degrading Ability for Rhizoremediation

Rhizoremediation of organic xenobiotics is based on interactions between plants and their associated micro-organisms. The present work was designed to engineer a bacterial system having toluene degradation ability along with plant growth promoting characteristics for effective rhizoremediation. pWWO harboring the genes responsible for toluene breakdown was isolated from Pseudomonas putida MTCC 979 and successfully transformed in Rhizobium DPT. This resulted in a bacterial strain (DPT(T)) which had the ability to degrade toluene as well as enhance growth of host plant. The frequency of transformation was recorded 5.7 × 10(-6). DPT produced IAA, siderophore, chitinase, HCN, ACC deaminase, solubilized inorganic phosphate, fixed atmospheric nitrogen and inhibited the growth of Fusarium oxysporum and Macrophomina phaseolina in vitro. During pot assay, 50 ppm toluene in soil was found to inhibit the germination of Cajanus cajan seeds. However when the seeds bacterized with toluene degrading P. putida or R. leguminosarum DPT were sown in pots, again no germination was observed. Non-bacterized as well as bacterized seeds germinated successfully in toluene free soil as control. The results forced for an alternative mode of application of bacteria for rhizoremediation purpose. Hence bacterial suspension was mixed with soil having 50 ppm of toluene. Germination index in DPT treated soil was 100% while in P. putida it was 50%. Untreated soil with toluene restricted the seeds to germinate.

A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame

An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C4 + C2 species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C6H4CH3 radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a methyl C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C6H4CH3 radicals have promoting effect for the consumption of toluene. Moreover, flow rate analysis is performed to illustrate the formation pathways of mono- and polycyclic aromatics.

Rapidly progressive toxic leukoencephalomyelopathy with myelodysplastic syndrome: a clinicopathological correlation

Neurological disorders induced by long-term exposure to organic solvents typically have a slowly progressive clinical course, which may be arrested or even reversed following discontinuation of exposure. We report an unusual case of rapidly progressive toxic leukoencephalomyelopathy in a 29-year-old man who had worked at a chemical factory that used toluene for the manufacture of nylon 66 for 5 years. He presented with progressive weakness of legs, recurrent seizures, and cognitive decline. Widespread white-matter changes in the brain and spinal cord, and myelodysplastic syndrome were noted. He died 6 months after the onset of his symptoms, and autopsy showed discrete multifocal demyelination and necrosis in the central nervous system, and dysplastic cells of erythroid, myeloid, and megakaryotic lineages in blood vessels. The co-occurrence of leukoencephalomyelopathy and myelodysplastic syndrome highlights the vulnerability of the white matter and bone marrow to injury from organic solvents. Intravascular congestion of dysplastic hematopoietic cells might have led to his unusually rapid progression of leukoencephalomyelopathy.

Changes in the amounts of neurotransmitters released from the striatum and spontaneous motor activity in rats exposed to high doses of toluene

We studied the neurotoxicological effects of high-dose toluene exposure by measuring neurotransmitter release from the striatum and spontaneous motor activity in freemoving Tokai High Avoider (THA) male rats. The rats were exposed to 1,000, 2,000, and 4,000ppm toluene for 4 hours. During the 4-hour exposure period and each one hour pre- and post-exposure periods, acetylcholine (ACh), 3, 4-dihydroxyphenylacetic acid (DOPAC), homovanilic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the microdialysate from kthe striatum of each rat were measured continuously using microdialysis. Simultaneously, spontaneous motor activity of each rat was monitored using an Aimex device. The amounts of neurotransmitters released and spontaneous motor activity showed similar changes for every concentration of toluene exposure during those periods. Although minimal changes in neurotransmitters and motor activity were observed in the 1,000 ppm group, increases in neurotransmitter release and motor activity were observed in the 2,000 ppm group during the entire exposure period and also in the 4,000 ppm group during the early period of exposure. On the other hand, decreases in neurotransmitter release and motor activity were observed in the 4,000 ppm group during the late period of exposure. These findings indicate that the striatum influences motor activity via changes in the amounts of neurotransmitters released during the period of high-dose toluene exposure.