Determination of selected herbicides and phenols in water and soils by solid-phase extraction and high-performance liquid chromatography. (57/1376)

A high-performance liquid chromatography procedure or the determination of the herbicides simazine, propazine, bromacil, metoxuron, and hexazinone is elaborated. Stationary phases RP8 and RP18 and mixtures of methanol-water (2:1 and 1:1, v/v) as a mobile phase are applied for this purpose. The conditions for solid-phase extraction are established, allowing the separation of phenols and herbicides in their mixtures and the extraction of phenols (from river and coke plant water) and herbicides (from the soil samples).  (+info)

Metabolism of fluroxypyr, fluroxypyr methyl ester, and the herbicide fluroxypyr methylheptyl ester. I: during percutaneous absorption through fresh rat and human skin in vitro. (58/1376)

Percutaneous absorption of pesticides is a major determinant for risk assessment. Furthermore, cutaneous metabolism plays a role in penetration of certain chemicals. Therefore, the aim of these studies was to determine the transdermal metabolism of three related compounds [the herbicide, fluroxypyr methylheptyl ester (FPMH), fluroxypyr methyl ester (FPM), and fluroxypyr (FP)] during penetration through human and rat skin in vitro. The data presented in this article show that both FPM and FPMH were completely metabolized during their passage through human and rat skin in vitro. The only metabolite produced was that of the hydrolysis product, FP, with no parent ester penetrating through the skin. The extent of FP formation within the skin was directly correlated to the degree of stratum corneum reservoir formation. The larger the stratum corneum reservoir, the lower the levels of FP recovered from within the skin. This suggests that as the ester partitioned out of the SC it was immediately hydrolyzed to FP, which could then pass freely through the remainder of the epidermis and dermis. Similar metabolic profiles were observed for the transdermal metabolism of FPM and FPMH in previously frozen rat skin, indicating the robust nature of the esterase enzymes involved. In conclusion, systemic exposure after skin contact with FPM or FPMH is likely to be to the acid metabolite, FP, only and not to the parent ester. In addition, the rate and extent of percutaneous absorption will be a major determinant of cutaneous metabolism.  (+info)

Metabolism of fluroxypyr, fluroxypyr methyl ester, and the herbicide fluroxypyr methylheptyl ester. II: in rat skin homogenates. (59/1376)

Fluroxypyr methyl ester (FPM) and the herbicide fluroxypyr methylheptyl ester (FPMH) are completely hydrolyzed during penetration through human and rat skin in vitro to the acid metabolite, fluroxypyr (FP) (). This article presents additional studies to determine the enzyme kinetics (K(m) and V(max)) of this ester hydrolysis, using crude rat whole-skin homogenate. Both FPM and FPMH were extensively metabolized in rat skin homogenates to the acid metabolite, FP. In no instance were any other metabolites detected. FPM was essentially hydrolyzed completely within 1 h. In FPMH incubations, there was still parent ester present after 24 h at all concentrations tested. The kinetics of hydrolysis of the two esters were different: V(max) was approximately 3-fold greater for FPM than FPMH (1400 and 490 micromol FP/min/g of tissue, respectively); however, K(m) values were very similar, 251 and 256 microM, respectively. Preliminary inhibitory studies suggest that FPM and FPMH are hydrolyzed by a carboxylesterase, because this reaction was inhibited by bis-p-nitrophenyl phosphate. Mercuric chloride (an inhibitor of A-esterase and arylesterase) and eserine (a cholinesterase inhibitor) had no inhibitory effect on the hydrolysis of FPM or FPMH. Taken together with the data presented by, it can be concluded that no parent ester will pass through the skin in vivo, only the metabolite, FP. Therefore, first pass metabolism will be complete before these compounds reach the systemic circulation.  (+info)

Increased urinary excretion of thioethers as a marker for detecting exposure to herbicide containing 2,4-dichlorophenoxyacetic acid dimethylamine - experimental study on mice. (60/1376)

The possibility that urinary thioethers concentration might be a marker for detecting exposure to herbicide containing 2,4-dichlorophenoxyacetic acid dimethylamine (2,4-DMA) was investigated in animals. Mice were treated with the herbicide containing 2,4-DMA consecutively for 4 days. Urinary concentrations of thioethers related either to body weight or creatinine concentration in urine in the group of animals treated with herbicide were significantly higher compared to control group. Results suggest that thioethers determination in urine might be a noninvasive and simple method for detecting exposure to herbicide containing 2,4-DMA.  (+info)

2,4-Dichlorophenoxyacetic acid disrupts the cytoskeleton and disorganizes the Golgi apparatus of cultured neurons. (61/1376)

2,4-Dichlorophenoxyacetic acid (2,4-D) is a potent neurotoxic herbicide widely used in agriculture. The basic mechanisms by which 2,4-D produces cell damage have not yet been determined. In this study we have examined the effects of 2,4-D in primary cultures of cerebellar granule cells in order to obtain insights into the possible mechanisms underlying the toxic effects of this herbicide. The results obtained indicate that a 24-hour exposure to 2,4-D produces a striking and dose-dependent inhibition of neurite extension. This phenomenon is paralleled by a significant reduction in the cellular content of both dynamic and stable microtubules, a disorganization of the Golgi apparatus, and an inhibition in the synthesis of complex gangliosides. Interestingly, 2,4-D inhibits the in vitro polymerization of purified tubulin. Taken together, the present observations raise the possibility that at least one basic mechanism underlying 2,4-D neurotoxicity involves an inhibition of microtubule assembly. That event may cause a decreased neurite outgrowth response, and could also explain the observed differences in the pattern of ganglioside biosynthesis and/or the disorganization of the Golgi apparatus.  (+info)

Characterization of an atrazine-degrading Pseudaminobacter sp. isolated from Canadian and French agricultural soils. (62/1376)

Atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. Fourteen bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from soils obtained from two farms in Canada and two farms in France. These strains were indistinguishable from each other based on repetitive extragenic palindromic PCR genomic fingerprinting performed with primers ERIC1R, ERIC2, and BOXA1R. Based on 16S rRNA sequence analysis of one representative isolate, strain C147, the isolates belong to the genus Pseudaminobacter in the family Rhizobiaceae. Strain C147 did not form nodules on the legumes alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), chickpea (Cicer arietinum L.), and soybean (Glycine max L.). A number of chloro-substituted s-triazine herbicides were degraded, but methylthio-substituted s-triazine herbicides were not degraded. Based on metabolite identification data, the fact that oxygen was not required, and hybridization of genomic DNA to the atzABC genes, atrazine degradation occurred via a series of hydrolytic reactions initiated by dechlorination and followed by dealkylation. Most strains could mineralize [ring-U-(14)C]atrazine, and those that could not mineralize atrazine lacked atzB or atzBC. The atzABC genes, which were plasmid borne in every atrazine-degrading isolate examined, were unstable and were not always clustered together on the same plasmid. Loss of atzB was accompanied by loss of a copy of IS1071. Our results indicate that an atrazine-degrading Pseudaminobacter sp. with remarkably little diversity is widely distributed in agricultural soils and that genes of the atrazine degradation pathway carried by independent isolates of this organism are not clustered, can be independently lost, and may be associated with a catabolic transposon. We propose that the widespread distribution of the atrazine-degrading Pseudaminobacter sp. in agricultural soils exposed to atrazine is due to the characteristic ability of this organism to utilize alkylamines, and therefore atrazine, as sole sources of carbon when the atzABC genes are acquired.  (+info)

The selective toxicity of 1-methyl-4-phenylpyridinium to dopaminergic neurons: the role of mitochondrial complex I and reactive oxygen species revisited. (63/1376)

1-Methyl-4-phenylpyridinium (MPP(+)) is selectively toxic to dopaminergic neurons and has been studied extensively as an etiologic model of Parkinson's disease (PD) because mitochondrial dysfunction is implicated in both MPP(+) toxicity and the pathogenesis of PD. MPP(+) can inhibit mitochondrial complex I activity, and its toxicity has been attributed to the subsequent mitochondrial depolarization and generation of reactive oxygen species. However, MPP(+) toxicity has also been noted to be greater than predicted by its effect on complex I inhibition or reactive oxygen species generation. Therefore, we examined the effects of MPP(+) on survival, mitochondrial membrane potential (DeltaPsim), and superoxide and reduced glutathione levels in individual dopaminergic and nondopaminergic mesencephalic neurons. MPP(+) (5 microM) selectively induced death in fetal rat dopaminergic neurons and caused a small decrease in their DeltaPsim. In contrast, the specific complex I inhibitor rotenone, at a dose (20 nM) that was less toxic than MPP(+) to dopaminergic neurons, depolarized DeltaPsim to a greater extent than MPP(+). In addition, neither rotenone nor MPP(+) increased superoxide in dopaminergic neurons, and MPP(+) failed to alter levels of reduced glutathione. Therefore, we conclude that increased superoxide and loss of DeltaPsim may not represent primary events in MPP(+) toxicity, and complex I inhibition alone is not sufficient to explain the selective toxicity of MPP(+) to dopaminergic neurons. Clarifying the effects of MPP(+) on energy metabolism may provide insight into the mechanism of dopaminergic neuronal degeneration in PD.  (+info)

Differential modulation of catecholamines by chlorotriazine herbicides in pheochromocytoma (PC12) cells in vitro. (64/1376)

Epidemiological, wildlife, and laboratory studies have pointed to the possible adverse health effects of chlorotriazine herbicide (i.e. , atrazine, simazine, and cyanazine) exposure. However, the cellular mechanism(s) of action of these compounds remains unknown. Recently, it was reported by Cooper et al. (2000, Toxicol. Sci. 53, 297-307) that atrazine disrupts ovarian function by altering hypothalamic catecholamine concentrations and subsequently the regulation of luteinizing hormone (LH) and prolactin (PRL) secretion by the pituitary. In this study, we examined the effect of three chlorotriazines on catecholamine metabolism in vitro using PC12 cells. Intracellular norepinephrine (NE) and dopamine (DA) concentrations and spontaneous NE release were measured following treatment with different concentrations of atrazine, simazine (0, 12. 5, 25, 50, 100, and 200 microM) and cyanazine (0, 25, 50, 100, and 400 microM) for 6, 12, 18, 24, and 48 h. Atrazine and simazine significantly decreased intracellular DA concentration in a concentration-dependent manner. Intracellular NE concentration was also significantly decreased by 100 and 200 microM atrazine and 200 microM simazine. Similarly, there was a dose-dependent inhibition of NE release with 100 and 200 microM concentrations of both compounds. Although 100 and 400 microM cyanazine increased intracellular NE concentration, 50, 100, and 400 microM cyanazine significantly increased NE release at 24 and 36 h. In contrast, intracellular DA concentration was decreased by cyanazine, but only at 400 microM. The GABA(A)-receptor agonist, muscimol (0, 0.01, 0.1, and 1.0 microM) had no effect on either the release or on intracellular catecholamine concentrations from 6 through 24 h of treatment. Cell viability was somewhat lower in the groups exposed to 100 and 200 microM atrazine and simazine. However, the reduction in viability was significant only in the highest dose of atrazine used (200 microM) at 24 h. Cyanazine did not have an effect on the viability at any of the doses tested, and the cells were functional, even up to 48 h of exposure. These data indicate that both atrazine and simazine inhibit the cellular synthesis of DA mediated by the tyrosine hydroxylase (TH), and NE mediated by dopamine beta-hydroxylase (DbetaH), and, as a result, there is a partial or significant inhibition of NE release. Cyanazine, on the other hand, stimulated the synthesis of intracellular NE, and not DA. Thus, chlorotriazine compounds presumably act at the enzymatic steps or sites of CA biosynthesis to modulate monoaminergic activity in PC12 cells.  (+info)