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PubMed1994

Temporal epileptic seizures and occupational exposure to solvents.

Long term exposure to organic solvents is usually not considered as a possible cause of chronic epileptic seizures. A case that shows a remarkable coincidence between exposure to organic solvents and occurrence of epileptic seizures is reported. The man was a 58 year old sign writer with lifelong exposure to a mixture of organic solvents (mainly cyclohexanone, white spirit, and isopropanol). Epileptic seizures of temporal type were occurring in relation to solvent exposure. The seizures disappeared shortly after stopping exposure but returned just after a short term re-exposure to cyclohexanone. The case history suggests that exposure to organic solvents may elicit or maintain epileptic seizures despite medical treatment.

Chronic Disease↗
PubMed1993

Studies on the metabolism of a monoterpene ketone, R-(+)-pulegone--a hepatotoxin in rat: isolation and characterization of new metabolites.

1. The metabolic disposition of R-(+)-pulegone (I) was examined in rats following four daily oral doses (250 mg/kg). 2. Six metabolites, namely pulegol (II), 2-hydroxy-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (IV), menthofuran (V), 5-methyl-2-(1-methyl-1-carboxyethylidene)cyclohexanone (VI), and 5-methyl-5-hydroxy-2-(1-hydroxy-1-carboxyethyl)cyclohexanone (VII) have previously been isolated from rat urine, and identified (Moorthy et al. (1989a). Eight new metabolites have now been isolated from rat urine, namely, 5-hydroxy-pulegone (VIII), piperitone (IX), piperitenone (X), 7-hydroxy-piperitone (XI), 8-hydroxy piperitone (XII), p-cresol (XIII), geranic acid (XIV) and neronic acid (XV). These were identified by n.m.r., i.r. and mass spectrometry. 3. Based on these results, metabolic pathways for the biotransformation of R-(+)-pulegone in rat have been proposed.

Animals↗
PubMed1994

Methodological approach to the evaluation of neurotoxicity data and the classification of neurotoxic chemicals.

This text is the result of the authors' involvement in a working group on criteria for the identification and classification of neurotoxic chemicals. (The work of the group does not necessarily represent the official stand of the affiliated institutes.) A definition of neurotoxicity and criteria for evaluating studies dealing with neurotoxicology are presented. The evaluation is a stepwise process that ends with assigning the chemicals to groups depending on the available evidence for neurotoxicity (ie, neurotoxic, probably neurotoxic, possibly neurotoxic, probably not neurotoxic, or not classifiable). Finally, the description of the potency of neurotoxic chemicals is briefly discussed. The model has been tested by evaluating selected research papers on the following 10 chemicals: manganese, aluminum, tetrahydrofuran, cyclohexanone, dichlorvos, trichloroethylene, formaldehyde, tri-ortho-cresyl phosphate, n-hexane, and vinyl chloride. There was sufficient evidence for classifying five of the ten chemicals (aluminum, manganese, n-hexane, trichloroethylene, tri-ortho-cresyl phosphate) as definitely neurotoxic to humans, and three were considered to be possibly neurotoxic to humans (dichlorvos, tetrahydrofuran, vinyl chloride). Cyclohexanone and formaldehyde were not classifiable according to the model.

Animals↗
PubMed1976

[Effects of aromatic bisamidines on blood coagulation and fibrinolysis].

The effect of the aromatic diamidine derivative 2,6-bis (4-amidinobenzyl)-cyclohexanon-(1) on blood coagulation and fibrinolysis in vitro and in vivo was compared with that of the benzamidine derivative 4-amidinophenyl pyruvic acid and the aromatic diamidine derivative 4,4'-diamidinophenoxypentane. 2,6-Bis(4-amidinobenzyl)-cyclohexanon-(1) was found to be a strong inhibitor of the clotting enzyme thrombin. Because of the toxic side effects and pharmacokinetic properties of both diamidine derivatives their in vivo use as anticoagulants is limited.

Amidines↗
PubMed1981

Absorption and alveolar excretion of cyclohexane in workers in a shoe factory.

The lung uptake and excretion of cyclohexane were studied in five workers and three volunteers in a shoe factory. Air samples were collected from the breathing zones with personal samplers, and simultaneous samples of inhaled and alveolar air were collected with the aid of a Rhan-Otis valve. Cyclohexane was absorbed on activated NIOSH approved charcoal tubes. The uptake was calculated from the pulmonary ventilation, the retention coefficient and environmental concentration. Alveolar excretion was monitored during a 6 h post-exposure period. The amount of exhaled cyclohexane was calculated from the decay curve. According to experimental data, the alveolar retention of cyclohexane is about 34% of the inhaled dose. This corresponds to a lung uptake of 23%. The post-exposure alveolar excretion does not exceed 10% of the total uptake. The difference between respiratory uptake and excretion indicates that the amount metabolized may be very large. Nevertheless, the urinary excretion of the main metabolites, cyclohexanol and cyclohexanone, was only about 1% of the absorbed dose.

Absorption↗
PubMed1976

Microenvironmental kinetic effects within a lyotropic smectic biophase model: conformational restrictions in Fischer indole cyclization.

The microenvironmental orientation effects, arising from an orderer solvent structure, were studied in a model liquid crystalline biophase for the cyclization of a series of 2-substituted cyclohexanone phenylhydrazones. The magnitude of such solvent-induced intramolecular conformational constraints were determined from a comparison of the kinetics of the Fischer indole rearrangement in a lyotropic smectic liquid crystal versus those in an isotropic liquid of similar chemical composition but lacking the structured nature of the mesophase. Solutions consisting of 50% (w/w) polyoxyethylene 6 tridecyl ether or 44% (w/v) polyethylene glycol in aqueous buffers comprised the smectic or isotropic media, respectively. The apparent dissociation constants of the conjugate acids of the phenylhydrazones were determined kinetically, as were their partition coefficients between lipid and polar isotropic phases approximating the compositions of the smectic lamellae. Intrinsic first-order rate constants, corrected for partitioning within the lamellar mesophase, were used to compute the enthalpies and entropies of activation. The somewhat slower intrinsic rates of cyclization and the accompanying less negative entropies of activation generally observed in the liquid crystalline medium, as opposed to the isotropic system, are attributed to the orienting effects of the lamellar lyotropic mesophase.

Chemical Phenomena↗
PubMed1993

Novel magnesium ion-selective microelectrodes based on a neutral carrier.

Two types of Mg(2+)-selective microelectrodes based on a synthetic neutral carrier and containing poly-(vinyl chloride) (PVC) are described. The first is applicable to intracellular Mg2+ assays and suffers no interference from alkali and all other alkaline-earth metal cations. The second can be used for determining intra- as well as extracellular Mg2+ activities, but Ca2+ and especially lipophilic cations (e.g. acetylcholine) may interfere. Cyclohexanone is used for dissolving the PVC-containing membrane phases thus avoiding problems encountered with the much more volatile tetrahydrofuran. The procedure gives a higher output of working microelectrodes and can also be applied with other membrane phases.

Calcium↗
PubMed1987

Diacylglycerol breakdown in plasma membranes of bovine chromaffin cells is a two-step mechanism mediated by a diacylglycerol lipase and a monoacylglycerol lipase.

The recently identified diacylglycerol lipase activity in membranes of chromaffin cells from bovine adrenal medulla [24] is now shown to consist of two enzymes working in series. First the predominantly saturated fatty acid in the sn-1-position is split by a diacylglycerol lipase (glycerol ester hydrolase, EC 3.1.1.34). Subsequently the resulting sn-2-monoacylglycerol is split by a monoacylglycerol lipase (glycerol-monoester acylhydrolase, EC 3.1.1.23) which prefers sn-2-arachidonoyl-monoacylglycerol to sn-2-palmitoyl-monoacylglycerol. At pH 4.0 only the diacylglycerol lipase is active, whereas the monoacylglycerol lipase is irreversibly inactivated. At pH 6.0 both enzymes are active. Pretreatment of the membranes at pH 10 leads to the selective inactivation of the diacylglycerol lipase. Both enzymes are Ca2+- and calmodulin-independent and both are partially inhibited by p-bromophenacyl bromide, however, only at relatively high concentrations of the inhibitor. Chlorpromazine inhibits the diacylglycerol lipase to about the same extent as p-bromophenacyl bromide but the monoacylglycerol lipase is less sensitive. The specific diacylglycerol lipase inhibitor RHC 80267 (1,6-di(O-(carbamoyl)cyclohexanone oxime)hexane) only interacts with the first step, i.e. the diacylglycerol lipase.

Acetophenones↗
PubMed1984

The inhibition of arachidonic acid metabolism in human platelets by RHC 80267, a diacylglycerol lipase inhibitor.

The diacylglycerol lipase inhibitor, RHC 80267, 1,6-di(O-(carbamoyl)cyclohexanone oxime)hexane, was tested for its ability to block the release of arachidonic acid from human platelets. At a concentration (10 microM) reported to completely inhibit diacylglycerol lipase in fractions of broken platelets, RHC 80267 had no effect on diacylglycerol lipase activity or the release of arachidonic acid from washed human platelets stimulated with collagen. At a high concentration (250 microM), the compound inhibited the formation of arachidonyl-monoacylglycerol by 70% and the release of arachidonate by 60%. However, at this concentration RHC 80267 was found to inhibit cyclooxygenase activity, phospholipase C activity and the hydrolysis of phosphatidylcholine (PC) (presumably by inhibiting phospholipase A2). The phospholipase C inhibition was attributed to the inhibition of prostaglandin H2 formation, as it was alleviated by the addition of the endoperoxide analog, U-46619. PC hydrolysis was only partially restored with U-46619, suggesting that RHC 80267 directly alters phospholipase A2 activity. The inhibition of arachidonate release observed was accounted for by the inhibition of PC hydrolysis. We conclude that RHC 80267, because of its lack of specificity at concentrations needed to inhibit diacylglycerol lipase, is an unsuitable inhibitor for studying the release of arachidonic acid in intact human platelets.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1986

Inhibition of the effects of thrombin on guinea pig platelets by the diacylglycerol lipase inhibitor RHC 80267.

Phospholipase C (PLC) and diacylglycerol lipase (DGL) activities were found in guinea pig platelet microsome preparations. No phospholipase A2 (PLA2) activity was detected. RHC 80267 (1,6-di (0-(carbamoyl) cyclohexanone oxime)hexane) inhibited DGL activity (IC50 = 4 uM) from guinea pig platelet microsomes but had no effect on PLC. RHC 80267 inhibited platelet aggregation (IC50 = 11 uM), release of arachidonic acid (AA), its metabolites, and ATP (IC50 = 4.5 uM) when guinea pig platelets were challenged with a low concentration of thrombin. We propose that PLC-DGL is an important enzymatic pathway for the release of AA in guinea pig platelets.

Adenosine Triphosphate↗
PubMed1983

NAD+-dependent ethanol oxidation: redox effects and rate limitation.

Effects of ethanol on interconversion of cyclohexanol and cyclohexanone was studied in isolated hepatocytes. Oxidation and reduction catalyzed by alcohol dehydrogenase were markedly inhibited and stimulated, respectively. The changed ratio between the rates indicated that the ratio of NAD+ to NADH bound to alcohol dehydrogenase decreased several hundred times. This is much more than for the NAD+ system used by, e.g., lactate dehydrogenase, and deuterium from [1,1-2H2] ethanol was incorporated in cyclohexanol much more than in, e.g., lactate. These results indicate that the coenzyme bound to alcohol dehydrogenase is not equilibrated with free coenzyme. Thus, the dissociation of NADH might be rate-limiting for ethanol oxidation. Deuterium transfer from chiral [1-2H] ethanols and [2-2H] glycerol in hepatocytes indicated that cytosolic malate dehydrogenase and lactate dehydrogenase were not completely equilibrated, whereas there was no difference in the utilization of NADH formed at alcohol dehydrogenase and at glycerol-3-phosphate dehydrogenase. Fluxes in redox reactions during ethanol oxidation may be too high for equilibration of cytosolic dehydrogenases.

Animals↗
PubMed1987

The size of mitral cells is altered when rats are exposed to an odor from their day of birth.

Rats were exposed to a moderate concentration of ethyl acetoacetate, amyl acetate, cyclohexanone or heptanol, for 69 days from postnatal day 1, whilst other rats were exposed to deodorized air, or the normal range of rat colony odors (Controls). The size of approximately 3% of all mitral cells in the olfactory bulb were measured using a computer-assisted method. As in previous studies in which stimulation began at day 14 or later, some regions of the olfactory bulb had cells that were significantly smaller than those of controls, and rats exposed to deodorized air generally had the smallest cells. Unlike in earlier studies, however, some regions of the olfactory bulb had cells that were significantly larger than similar regions of controls. The distribution of these changes appears to be odor-specific and consists of coronal patterns that extend throughout the rostro-caudal extent of the bulb. The different patterns obtained for the 4 odors used in this study provide evidence for a topographic coding of odor quality at the level of the mitral cells.

Acetoacetates↗
PubMed1989

Acetone compared to other ketones in modifying the hepatotoxicity of inhaled 1,2-dichlorobenzene in rats and mice.

The ability of acetone and 3 other ketone vapours to influence the hepatotoxicity of inhaled 1,2-dichlorobenzene (DCB) was examined in rats and mice. Methylethylketone, methylisobutylketone or cyclohexanone increased liver cytochrome P-450 content and glutathione-S-transferase (GST) activity, but did not affect serum glutamate dehydrogenase (GLDH) activity in rats. Pre-exposure to these ketones enhanced DCB-induced increase in serum GLDH activity (8-63-fold), while the increases in cytochrome P-450 content (33-86%) and GST activity (42-64%) were identical to those resulting from exposure to ketones alone. Each of the 3 levels of exposure to acetone elicited cytochrome P-450 and GST responses comparable with those caused by the other ketones. In spite of that, acetone pre-exposure potentiated (4785 ppm), reduced (10670 ppm) or suppressed (14790 ppm) DCB-induced liver toxicity. In mice, the 3 ketones mentioned above interacted with DCB on centrolobular liver glucose-6-phosphatase (G-6-Pase) while acetone pre-exposure elicited an interactive G-6-Pase response in the mediolobular area alone, suggesting topographic change.

Acetone↗
PubMed1975

Gas chromatographic-mass spectrometric study of volatile organic metabolites in urines of patients with diabetes mellitus.

Abnormally increased concentrations of the aliphatic alcohols ethanol, n-propanol, isobutanol, n-butanol and isopentanol and the ketones 4-heptanone and cyclohexanone in human urine reflect metabolic disorders related to diabetes mellitus. For the determination of these low-molecular-weight metabolites, the components are trapped on an absorbent, separated by gas chromatography and identified by mass spectrometry. After standardization of the adsorption and desorption techniques, the procedure is applicable for comparative studies and for screening.

1-Propanol↗
PubMed1981

Mechanistic deductions from isotope effects in multireactant enzyme mechanisms.

In the enzymatic mechanism with two or more substrates, comparison of the isotope effects on the maximum velocity and on the apparent V/K values when each substrate concentration is varied allows one to deduce the kinetic mechanism and obtain quantitative information on the relative rates at which substrates dissociate from the enzyme, as opposed to undergoing reaction to give products. Theory is also presented for using the effects of other reactants on the apparent isotope effects determined by the equilibrium perturbation method to determine the same information. With liver alochol dehydrogenase, DPN is not released at an appreciable rate from the E-DPN-cyclohexanol complex, while cyclohexanol is released much more rapidly than it reacts to give products, so that the mechanism appears ordered. With DPNH and cyclohexanone, however, the reaction is random since DPNH can be released from the ternary complex at a finite rate. With yeast alcohol dehydrogenase, acetone, when present, prevents DPNH release from the enzyme so that the mechanism at equal rates from E-DPN-2-propanol so tht the reaction is random in this direction.

Alcohol Oxidoreductases↗
PubMed1987

Effect of ethanol on the redox state of the coenzyme bound to alcohol dehydrogenase studied in isolated hepatocytes.

Hepatocytes were isolated from fed female rats and incubated with a redox indicator system consisting of cyclohexanone and unlabelled or perdeuterated cyclohexanol. The concentrations and deuterium contents of these were measured by g.l.c. and g.l.c.-m.s. of oxime t-butyldimethylsilyl derivatives. The equilibrium composition represented the redox state of the coenzyme bound to alcohol dehydrogenase, since 4-methylpyrazole inhibited the interconversion. Reduction appeared to be catalysed to a small extent also by an NADPH-dependent aldehyde reductase. The NADH/NAD+ ratio on alcohol dehydrogenase was 3 orders of magnitude higher in the presence of ethanol than in its absence. This redox shift has the degree expected from reported kinetic constants. The shift was due both to a decreased rate of oxidation and to an increased rate of reduction in the indicator system. The results indicate that the redox effect of ethanol on the free NAD system is due to efficient removal of acetaldehyde from a near-equilibrium system consisting of ethanol, acetaldehyde and bound coenzymes, together with dissociation of NADH from the enzyme. The effect on the redox state of the bound coenzyme was less marked when the ethanol was deuterated at C-1, indicating an isotope effect. The 2H excess in the cyclohexanol formed was about 70% of that in the [1,1-2H2]ethanol. This dilution, which is caused by binding of free NADH to the enzyme, indicates that reoxidation of cytosolic NADH partly limits the rate of ethanol oxidation.

Alcohol Dehydrogenase↗
PubMed1982

Exposure to isophorone and other organic solvents in a screen printing plant.

A study was conducted in a screen printing plant to determine the exposure of workers to isophorone and other organic solvents. One hundred twenty-four charcoal tube samples were collected from both workers breathing zones and various workplace areas. Sampling times were 50-90 minutes. Maximum mean TWACs of isophorone and cyclohexanone were 23 +/- 5.4 ppm and 28 +/- 5 ppm, respectively, at the breathing zones of printing press workers. Exposure levels for other organic vapors such as cellosolve acetate, butyl acetate, xylenes, diacetone alchohol, and petroleum distillate are also presented. Mean TWACs of personal samples were generally higher than area samples due to proximity of the solvent evaporating surfaces to the workers breathing zones. Mean TWACs for the individual organic vapors did not exceed OSHA Limits. However, the sum of (TWAC/TLV) ratios of organic vapors with additive health effects exceeded unity at the breathing zones of workers handling inks and solvents. Actual 8-hour worker exposures were assumed to be lower because workers were exposed to lower concentrations (about 9/10 of the additive TLVs) in the plant's general atmosphere during non-active periods of the work shift. Recommendations for improvement of working conditions and reduction of exposure levels are made.

Air Pollutants↗
PubMed1977

Sensitivity to 2-chlorocyclohexanone and its derivatives.

Three workers developed dermatitis when synthesizing lysine from cyclohexanone; they showed positive patch tests to 2-chlorocyclohexanone and some of its derivatives. Two of them became sensitive to at least two differen compounds.

Adult↗