Abstract  A shower decontamination bench model has been used to assess quantitatively the importance of several variables (water pressure and temperature, surfactant concentration in the decontamination fluid, nozzle type, and shower time) on decontamination of nontoxic chemical warfare-agent simulants diethyl malonate and thickened diethyl malonate from pig skin in vitro. Diethyl malonate was validated as a simulant for 1,2,2-trimethylpropyl methylphosphonofluoridate (soman) by comparison of the skin penetration and decontamination of radiolabeled diethyl malonate to the radiolabeled phosphonofluoridate in shower decontamination trials of pig skin in vitro. Percutaneous penetration of diethyl malonate was significantly greater than that of the phosphonofluoridate during the 15-min period after application. However, both were less than 0.1% of the applied dose. Showering or thickener had no significant effect on the percutaneous penetration of diethyl malonate or the phosphonofluoridate. Most of the phosphonofluoridate removed by showering or scrubbing the skin was inactivated. The quantity of intact 1,2,2-trimethylpropyl methylphosphonofluoridate that penetrated through the skin was below the detection limit of the enzymatic analysis. There was no statistically significant difference between the phosphonofluoridate and diethyl malonate in efficacy of shower decontamination. The presence of thickener did not have a significant effect on decontamination efficacy.

Abstract  During research on nematocidal toxins produced by microorganisms, a metabolite has been found active and identified as a volatile fatty acid (monocarboxylic), namely acetic acid. That volatile fatty acid showed selective nematotoxic activity against some plant-parasitic nematodes, but linked to pH and with recovery effect. To improve its efficacy, a structure/activity study on some derivatives has been performed with biological tests on different nematode species. Adding a second carboxylic function and a double bond in the volatile fatty acid hydrocarbonic chain provided unsaturated dicarboxylic acids; these compounds exhibited a significant selective nematocidal activity in considerably shorter periods of time than the monocarboxylic acids, at lower concentrations, in a broad range of pH and without reversible effect of juvenile paralysis. The methyl esters of those dicarboxylic acids and cyclic derivatives exhibited toxicological activity without pH dependency. The importance of the spatial configuration of those molecules which triggered the appearance of significant nematocidal properties is discussed.

Abstract  Oxidative stress plays a significant role in the neurotoxicity of a variety of agents that interact with the N-methyl-D-aspartate (NMDA) receptors. Here we investigated in a comparative way the pro-oxidative effects of quinolinic acid (QA) and malonate, two neurotoxic substances that act through distinct primary molecular mechanisms on the production of thiobarbituric acid reactive species (TBARS) by brain homogenates. In fact, QA is thought to activate directly the NMDA receptor, whereas malonate seems to act primarily by inhibiting oxidative metabolism. The malonate-induced TBARS formation was not modified by cyanide (CN-) or 2,4-dinitrophenol. MK-801 did not reduce basal or malonate induced-TBARS production in fresh tissues preparations. However, in heat-treated preparations a significant effect of MK-801 against basal TBARS production was observed, but not on the malonate induced-TBARS production. QA induced-TBARS production was significantly prevented by MK-801 either in fresh or heat-treated preparations. The antioxidant effect of MK-801 on basal and QA-induced TBARS production increased as the temperatures used to treat S1 were increased. Succinate dehydrogenase (SDH) was inhibited by malonate but not by QA. Malonate was able to chelate iron(II) and the malonate-iron complex(es) is(are) active as measured by its(their) activity on deoxyribose degradation assay. These findings indicate that direct interactions of malonate with NMDA receptors are not involved in malonate pro-oxidative activity in vitro. QA pro-oxidative activity in vitro was related, at least in part, to its capability in stimulate NMDA receptors. Taken together, these findings indicated that malonate pro-oxidative activity in vitro could be attributed to its capability of changing the ratio Fe2+/Fe3+, which is essential to TBARS production.

Abstract  Altered energy metabolism, including reductions in activities of the key mitochondrial enzymes alpha-ketoglutarate dehydrogenase complex (KGDHC) and pyruvate dehydrogenase complex (PDHC), are characteristic of many neurodegenerative disorders including Alzheimer's Disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). Dihydrolipoamide dehydrogenase is a critical subunit of KGDHC and PDHC. We tested whether mice that are deficient in dihydrolipoamide dehydrogenase (Dld+/-) show increased vulnerability to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), malonate and 3-nitropropionic acid (3-NP), which have been proposed for use in models of PD and HD. Administration of MPTP resulted in significantly greater depletion of tyrosine hydroxylase-positive neurons in the substantia nigra of Dld+/- mice than that seen in wild-type littermate controls. Striatal lesion volumes produced by malonate and 3-NP were significantly increased in Dld+/- mice. Studies of isolated brain mitochondria treated with 3-NP showed that both succinate-supported respiration and membrane potential were suppressed to a greater extent in Dld+/- mice. KGDHC activity was also found to be reduced in putamen from patients with HD. These findings provide further evidence that mitochondrial defects may contribute to the pathogenesis of neurodegenerative diseases.

Abstract  Propionic and methylmalonic acidemic patients have severe neurologic symptoms whose etiopathogeny is still obscure. Since increase of lactic acid is detected in the urine of these patients, especially during metabolic decompensation when high concentrations of methylmalonate (MMA) and propionate (PA) are produced, it is possible that cellular respiration may be impaired in these individuals. Therefore, we investigated the effects of MMA and PA (1, 2.5 and 5mM), the principal metabolites which accumulate in these conditions, on the mitochondrial respiratory chain complex activities succinate: 2,6-dichloroindophenol (DCIP) oxireductase (complex II); succinate: cytochrome c oxireductase (complexII+CoQ+III); NADH: cytochrome c oxireductase (complex I+CoQ+complex III); and cytochrome c oxidase (COX) (complex IV) from cerebral cortex homogenates of young rats. The effect of MMA on ubiquinol: cytochrome c oxireductase (complex III) and NADH: ubiquinone oxireductase (complex I) activities was also tested. Control groups did not contain MMA and PA in the incubation medium. MMA significantly inhibited complex I+III (32-46%), complex I (61-72%), and complex II+III (15-26%), without affecting significantly the activities of complexes II, III and IV. However, by using 1mM succinate in the assay instead of the usual 16mM concentration, MMA was able to significantly inhibit complex II activity in the brain homogenates. In contrast, PA did not affect any of these mitochondrial enzyme activities. The effect of MMA and PA on succinate: phenazine oxireductase (soluble succinate dehydrogenase (SDH)) was also measured in mitochondrial preparations. The results showed significant inhibition of the soluble SDH activity by MMA (11-27%) in purified mitochondrial fractions. Thus, if the in vitro inhibition of the oxidative phosphorylation system is also expressed under in vivo conditions, a deficit of brain energy production might explain some of the neurological abnormalities found in patients with methylmalonic acidemia (MMAemia) and be responsible for the lactic acidemia/aciduria identified in some of them.

Abstract  JETOC has been carrying out classification of the chemical substances, for which SIDS Initial Assessment Report (SIAR) were published, under the Globally Harmonized System (GHS) since autumn of 2004 and published the results in the Information Sheet (Issue No.53-56). Meanwhile, MHLW, METI and MOE launched a project to classify ca.1500 chemical substances based on the GHS in 2005 and published the results on the website: http://www.safe.nite.go.jp/english/ghs_index.html. As the Project released the GHS Classification Manual (Manual) on October 2005, we have reviewed our former results so that they are consistent with the Manual. We will continue the work for substances not classified by the Project based on the information in SIAR. Followings are proposed allocation of the hazard categories. Proposed toxicological classification for 40 chemicals: methacrylamide, linalool, DL-pantolactone, 2-hydroxyethyl m?thacrylate, 2,4-dichlorotoluene, diphenyl carbonate, isobutanal,1,3-dimethyl-urea, 2-methylpropyl-2-methyl-2 propanoate, tetrahydro-2-furanmethanol, 4-methyl-benzenesulfonyl chloride, nicotinamide, m-toluic acid, 1,2-dichloro-4-nitrobenzene, 2-propoxy-ethanol, 2-butoxyethyl acetate, 2-(hexyloxy) ethanol, 2,2'-thiodiethanol, dimethyl malonate, 1,2,3,4-tetrahydronaphthalene, ethyleneglycolmonophenylether, sodium methoxide, potassium methoxide, tetramethylenesulfone, diallyl phthalate, 4-(1,1,3,3-tetramethylbutyl)phenol, 6,10-dimethyl 3,5,9-undecatrien-2 one, butanedioic acid disodium salt, 1H-imidazole, triethylene glycol monobutylether, pentafluoroethane, cyanoguanidine, 2-(1,3-dihydro-3oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one, triacetin, p-chlorotoluene, @eg-caprolactone, isophytol, trimethyl phosphate, 2-methyl-2-butene.

Abstract  The in vitro distribution and fate of [14C]diethyl malonate and [14C]diisopropyl fluorophosphate were evaluated on normal and heat-treated pig skin. The extent of hydrolysis from the skin surface, skin, and receptor fluid was determined. A significant skin-mediated hydrolysis (15-35% of applied dose) was observed for diethyl malonate in normal skin, but not in heat-treated skin. These results indicated that a heat labile process (e.g., enzymatic hydrolysis) was in part responsible for the degradation of diethyl malonate after topical application to normal skin. Heat treatment tripled the skin penetration of diisopropyl fluorophosphate and reduced the amount of recovered hydrolysis product, diisopropyl phosphoric acid. Enzymatic and spontaneous hydrolysis, as well as impurity, accounted for the presence of degradation product.

Abstract  The CA1 region of hippocampus is selectively vulnerable to a variety of insults, including hypoxia-ischemia and Alzheimer's disease, but the basis of this regional susceptibility is poorly understood. We examined the regional hippocampal sensitivity to mitochondrial metabolic disruption induced by malonate, an inhibitor of succinate dehydrogenase. The CA1 region was exquisitely sensitive to malonate and the dentate gyrus was extremely resistant; the CA3 region had intermediate sensitivity. This pattern of vulnerability is reminiscent of hypoxic-ischemic damage. Malonate damage was blocked by the N-methyl-D-aspartic acid (NMDA) antagonist, MK-801, but regional susceptibility to malonate did not correlate with the density of NMDA receptors. Instead, malonate toxicity was inversely correlated with activity of succinate dehydrogenase. Our results suggest that regional metabolic capacity may help to determine sensitivity to metabolic/excitotoxic insults such as hypoxia-ischemia.

Abstract  Past studies have shown that inhibiting energy metabolism with malonate in mesencephalic cultures damages neurons by mechanisms involving N-methyl-D-aspartate receptors and free radicals. Overstimulation of N-methyl-D-aspartate receptors is known to produce free radicals. This study was, therefore, carried out to determine if N-methyl-D-aspartate receptor activation triggered by energy impairment was a significant contributor to the oxidative stress generated during energy inhibition. Exposure of mesencephalic cultures to malonate for the minimal time required to produce toxicity, i.e. 6h, resulted in an increase in the efflux of both oxidized and reduced glutathione, and a decrease in tissue levels of reduced glutathione. In contrast, exposure to 1mM glutamate for 1h caused an increased efflux of reduced glutathione, but no changes in intra- or extracellular oxidized glutathione or intracellular reduced glutathione. Blocking N-methyl-D-aspartate receptors with MK-801 (0.5 microM) during malonate exposure did not modify malonate-induced alterations in glutathione status or free radical generation as monitored by dihydrochlorofluorescein diacetate and dihydrorhodamine 123 fluorescence. In contrast, the increase in dihydrorhodamine fluorescence caused by glutamate was completely blocked by MK-801. Reduction of tissue glutathione with a 24h pretreatment with 10 microM buthionine sulfoxamine, as shown previously, greatly potentiated malonate-induced toxicity to dopamine and GABA neurons, but had no potentiating effect on toxicity due to glutamate. The findings indicate that although oxidative stress mediates damage due either to energy deprivation or excitotoxicity, N-methyl-D-aspartate receptor over-stimulation does not contribute significantly to the oxidative stress that is incurred during malonate exposure.

Abstract  Biosis copyright: biol abs. rrm human personnel skin diethylmalonate toxic chemicals model

Abstract  The maximization test for detecting contact allergens has proved to possess both sensitivity and specificity. However, modifications have become necessary because of excessive irritancy reactions to sodium lauryl sulfate. Fewer exposures are now recommended during induction and lower concentrations for challenge patch testing. Pre-testing of each subject in the panel is now standard procedure. The problem of interpreting challenge patch tests is discussed in detail.

Abstract  The pharmacological study of heterocyclic N-ethylacetic and N-ethylmalonic esters indicate a stimulating effect on central nervous system. Some derivatives show antidepressive and psychostimulant activities.