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At least 865 records · Page 48Linked to original sources
PubMed1985

New amphibian models for the study of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

We report the development of two animal models in amphibians (frogs and salamanders) in whom 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces the behavioral (neurological) and biochemical equivalents of the human disease and, in addition, a measurable modification in at least one form of pigment-bearing cell from the neural crest, the skin melanocyte. We propose that this new approach can become an inexpensive, easily quantifiable model for the study of the effect of MPTP on the central and peripheral nervous systems. We also demonstrate that the toxic effect of MPTP can be completely abolished in vivo by treatment with a monoamine oxidase inhibitor and potentiated by an inhibitor of catechol-O-methyltransferase. MPTP is catabolised by oxidation into toxic metabolites, but 1-methyl-4-phenylpyridinium ion (MPP+), the proposed end-metabolite, is even more toxic than MPTP in this model, possibly through a different mechanism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Genotoxicity of the alkenylbenzenes alpha- and beta-asarone, myristicin and elimicin as determined by the UDS assay in cultured rat hepatocytes.

While the alkenylbenzenes alpha- and beta-asarone are hepatocarcinogenic in rodents, myristicin and elimicin, two other alkenylbenzenes, are not. The present study investigated the mechanism of genotoxicity of the asarones to elucidate the role of cytochrome P-450 and obtain further information about the relationships between the structure, metabolism and genotoxicity of the alkenylbenzenes. The data on the ability of these compounds to induce unscheduled DNA synthesis (UDS) in hepatocytes derived from male Fischer 344 rats are presented in this paper. Cytotoxicity was assessed by lactate dehydrogenase leakage. Elimicin and alpha- and beta-asarone are genotoxic in the UDS assay but myristicin is not. The genotoxicity of the asarones is inhibited by the cytochrome P-450 inhibitor cimetidine but the sulfotransferase inhibitor pentachlorophenol (PCP) is without effect. The major metabolite of the asarones in hepatocytes was identified by liquid chromatography-mass spectrometry as 2,4,5-trimethoxycinnamic acid but this was not genotoxic when tested separately. Simple allylbenzenes such as safrole, estragole and methyleugenol are activated by sequential 1-hydroxylation and sulfation, and this is the likely mechanism of the genotoxicity of elimicin. The propenyl analogues isosafrole, anethole and methylisoeugenol, which cannot undergo 1-hydroxylation, are not genotoxic. The positive results obtained with the asarones suggest the occurrence of a novel activation 'option' for alkenylbenzenes which features a 2-methoxy group in the aromatic ring.

Alkylation↗
PubMed2006

Removal of added nitrate in cotton burr compost, mulch compost, and peat: mechanisms and potential use for groundwater nitrate remediation.

We conducted batch tests on the nature of removal of added nitrate in cotton burr compost, mulch compost, and sphagnum peat that may be potentially used in a permeable reactive barrier (PRB) for groundwater nitrate remediation. A rigorous steam autoclaving protocol (121 degrees C for 2h each day for three consecutive days) for the cotton burr compost and autoclaving of all labware and the nitrate working solutions resulted in drastically different results compared to the non-autoclaved treatment. In the non-autoclaved cotton burr compost, added nitrate at 20 mg N l(-1) decreased rapidly and was not detected after 3d; whereas, the autoclaved cotton burr compost showed persistent nitrate above 15.5 mg N l(-1) even after 10d, which is comparable with nitrate concentrations above 17.6 mg N l(-1) in a treatment using NaN(3) at 1000 mg l(-1). Dewaxed cotton burr compost showed decreased nitrate reduction compared to the pristine cotton burr compost. No nitrate reduction was detected in the dewaxed sphagnum peat. It is concluded that nitrate removal in the organic media is controlled by microbiologically mediated processes. The use of readily available cotton burr and mulch composts may offer a cost-effective method of nitrate removal from contaminated groundwater.

Gossypium↗