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PubMed1988

A comparison of the discriminatory ability and sensitivity of the trigeminal and olfactory systems to chemical stimuli in the tiger salamander.

Trigeminal receptors can respond to a wide variety of chemical stimuli, but it is unknown whether these receptors mediate discrimination between chemical stimuli matched for equal perceptual intensity. The present electrophysiological and behavioral experiments address this issue using tiger salamanders, Ambystoma tigrinum, and four compounds (amyl acetate, cyclohexanone, butanol, and d-limonene). In addition, the relative sensitivities of the trigeminal and olfactory systems to these compounds are compared. In electrophysiological cross-adaptation experiments (amyl acetate vs cyclohexanone; butanol vs d-limonene), there was complete cross adaptation such that only concentrations above the background (cross-adapting) stimulus concentration elicited responses, suggesting that chemical stimuli may stimulate trigeminal receptors nonspecifically. In behavioral experiments (amyl acetate vs cyclohexanone; butanol vs d-limonene), only animals with intact olfactory nerves could discriminate between perceptually equivalent concentrations, that is concentrations that elicited the same level of responding. Both electrophysiologically and behaviorally, the trigeminal system exhibited higher thresholds than the olfactory system. We conclude that trigeminal chemoreceptors, at least in salamanders, are unable to discriminate between these two pairs of compounds when matched for equal perceptual intensity, and that trigeminal chemoreceptors are less sensitive than olfactory receptors.

Action Potentials↗
PubMed1975

The metabolism of cyclohexanol by Acinetobacter NCIB 9871.

Acinetobacter NCIB 9871 was isolated by elective culture on cyclohexanol and grows with this compound as sole source of carbon. It displays a restricted growth spectrum, being unable to grow on a wide range of alternative alicyclic alcohols and ketones. Cyclohexanol-grown cells oxidize the growth substrate at a rate of 230 mul of O2/h per mg dry wt with the consumption of 5.65 mumol of O2/mumol substrate. Cyclohexanone is oxidized at a similar rate with the consumption of 4.85 mumol of O2/mumol. 1-Oxa-2-oxocycloheptane and 6-hydroxyhexanoate are both oxidized at the same slow rate of 44 mul of O2/h per mg dry wt and adipate is not oxidized. Studies with cell extracts reveal the presence of inducible dehydrogenases for cyclohexanol, 6-hydroxyhexanoate and 6-oxohexanoate and a monooxygenase, that in conjunction with a lactonase converts cyclohexanone to 6-hydroxyhexanoate. The monooxygenase is therefore presumed to be of the lactone-forming type and the pathway for conversion of cyclohexanol to adipate; cyclohexanol leads to cyclohexanone leads to 1-oxa-2-oxocycloheptane leads to 6-hydroxyhexanoate leads to 6-oxohexanoate leads to adipate; for which key intermediates have been identified chromatographically, is identical with the route for the oxidation of cyclohexanol by Nocardia globerula CL1.

Acinetobacter↗
PubMed1992

Nuclear type II sites and malignant cell proliferation: inhibition by 2,6-bis-benzylidenecyclohexanones.

Methyl-p-hydroxyphenyllactate (MeHPLA) is a bioflavonoid and/or tyrosine metabolite which may regulate cellular growth and proliferation through interactions with nuclear type II sites. Our current studies suggest that type II sites may function as MeHPLA receptors which are localized on the nuclear matrix, and occupancy of this binding site by MeHPLA directly correlates with the inhibition of normal and malignant cell proliferation. This ligand is inactivated by MeHPLA esterase in mammary tumors, resulting in a deficiency in MeHPLA, high quantities of unoccupied type II sites, and uncontrolled cellular proliferation. For these reasons we synthesized 2,6-bis((3,4-dihydroxyphenyl)methylene)-cyclohexanone (BDHPC) and 2,6-bis((3-methoxy-4-hydroxyphenyl)-methylene)cyclohexanone (BMHPC) for assessment as nuclear type II site and cell growth antagonists. These two esterase stable cyclohexanone derivatives, which bind to nuclear type II sites with high affinity (Kd 1-7 nM), mimic MeHPLA as cell growth-regulating agents. Dose-dependent occupancy of type II sites in MCF-7 human cells by BDHPC and BMHPC directly correlated with the inhibition of cell proliferation, and administration of BDHPC by silastic implant inhibited mouse mammary tumor growth in vivo. These findings demonstrate that esterase-stable type II antagonists such as BDHPC and BMHPC inhibit mammary cancer cell proliferation in vitro and in vivo and support earlier studies demonstrating that MeHPLA and functionally related compounds may regulate malignant cell proliferation at the level of this binding site.

Animals↗
PubMed1989

Enzyme reactions involved in anaerobic cyclohexanol metabolism by a denitrifying Pseudomonas species.

The enzymes involved in the anaerobic degradation of cyclohexanol were searched for in a denitrifying Pseudomonas species which metabolizes this alicyclic compound to CO2 anaerobically. All postulated enzyme activities were demonstrated in vitro with sufficient specific activities. Cyclohexanol dehydrogenase catalyzes the oxidation of the substrate to cyclohexanone. Cyclohexanone dehydrogenase oxidizes cyclohexanone to 2-cyclohexenone. 2-Cyclohexenone hydratase and 3-hydroxycyclohexanone dehydrogenase convert 2-cyclohexenone via 3-hydroxycyclohexanone into 1,3-cyclohexanedione. Finally, the dione is cleaved by 1,3-cyclohexanedione hydrolase into 5-oxocaproic acid. Some kinetic and regulatory properties of these enzymes were studied.

Aerobiosis↗
PubMed1987

Assessment of the safety of chemicals administered intravenously in the neonatal rat.

A 3-day-old neonatal rat model for the safety assessment of various drugs, chemicals, and nutrients administered intravenously is described. This model was used to assess the safety of di(2-ethylhexyl) phthalate (DEHP), cyclohexanone, and a 3:1 mixture of medium and long-chain triglyceride emulsions following subchronic administration using the intravenous route. The administration of DEHP at dosage of 164.8 mg/kg for 18 consecutive days resulted in a small but statistically significant increase in liver weight and SGOT activity. However, no conclusive histopathological alternations could be discerned between livers from DEHP and normal saline (control) animals. No effects were observed among neonates treated with cyclohexanone at dosages up to 25 mg/kg for 18 consecutive days. Because of technical difficulties emanating from high dosage volumes, the administration of lipid emulsion mixture lasted 9 consecutive days only. Except for transient ataxia and sedation, no adverse effects were observed among neonates that received 3:1 medium- and long-chain triglyceride emulsion for 9 consecutive days beginning on day 3 postpartum. No adverse effects were observed among neonates receiving the lipid emulsions for 7 consecutive days beginning on day 12 postpartum.

Animals↗
PubMed1988

Spine density on olfactory granule cell dendrites is reduced in rats reared in a restricted olfactory environment.

The Golgi technique was used to study the development of spines on the external dendrites of granule cells in the olfactory bulbs of young rats that had been continuously exposed to cyclohexanone vapor, deodorized air, or rat odors. Exposure to deodorized air for 3 weeks from postnatal day 1 reduced spine density on the medial and lateral sides of the bulb, whilst exposure to cyclohexanone reduced spine density on the lateral side only. These reductions were evident in other animals exposed for 7 weeks. With all treatments, spine density reached a maximum at postnatal day 21 and decreased markedly during the next month.

Age Factors↗
PubMed1989

Analysis of the inactivation of liver alcohol dehydrogenase during storage in Aerosol-OT/isooctane microemulsions.

Changes in the enzymatic properties of horse liver alcohol dehydrogenase (HLADH; EC 1.1.1.1) were studied as a function of incubation time in Aerosol-OT/isooctane microemulsions. The enzyme was characterized by fluorimetric binding studies of the inhibitor isobutyramide to the binary complex, HLADH-NADH and by determination of Km,app and Vmax,app values for cyclohexanone. The Km,app values for cyclohexanone and the Kd,app for isobutyramide stay constant throughout a 48-h incubation, whereas the Vmax,app and the total number of inhibitor binding sites decrease. Thus the inactivation process previously described corresponds to progressive loss of functional sites, while the properties of the remaining functional sites are unchanged. If no co-enzyme is added to the system, the enzyme loses catalytic activity within less than an hour, but if co-enzyme is added, a fraction of the HLADH enzyme population retains enzyme activity over a long period of time. Hence the presence of bound co-enzyme significantly inhibits the process(es) leading to inactivation of the enzyme in the microemulsions.

Aerosols↗
PubMed1982

Metabolism of cyclohexaneacetic acid and cyclohexanebutyric acid by Arthrobacter sp. strain CA1.

A strain of Arthrobacter was isolated by enrichment culture with cyclohexaneacetate as the sole source of carbon and grew with a doubling time of 4.2 h. In addition to growing with cyclohexaneacetate, the organism also grew with cyclohexanebutyrate at concentrations not above 0.05%, and with a variety of alicyclic ketones and alcohols. Oxidation of cyclohexaneacetate proceeded through formation of the coenzyme A (CoA) ester followed by initiation of a beta-oxidation cycle. beta-Oxidation was blocked before the second dehydrogenation step due to the formation of a tertiary alcohol, and the side chain was eliminated as acetyl-CoA by the action of (1-hydroxycyclohexan-1-yl)acetyl-CoA lyase. The cyclohexanone thus formed was degraded by a well-described route that involves ring-oxygen insertion by a biological Baeyer-Villiger oxygenase. All enzymes of the proposed metabolic sequence were demonstrated in cell-free extracts. Arthrobacter sp. strain CA1 synthesized constitutive beta-oxidative enzymes, but further induction of enzymes active toward cyclohexaneacetate and its metabolites could occur during growth with the alicyclic acid. Other enzymes of the sequence, (1-hydroxycyclohexan-1-yl)acetyl-CoA lyase and enzymes of cyclohexanone oxidation, were present at negligible levels in succinate-grown cells but induced by growth with cyclohexaneacetate. The oxidation of cyclohexanebutyrate was integrated into the pathway for cyclohexaneacetate oxidation by a single beta-oxidation cycle. Oxidation of the compound could be divided into two phases. Initial oxidation to (1-hydroxycyclohexan-1-yl)acetate could be catalyzed by constitutive enzymes, whereas the further degradation of (1-hydroxycyclohexan-1-yl)acetate was dependent on induced enzyme synthesis which could be inhibited by chloramphenicol with the consequent accumulation of cyclohexaneacetate and (1-hydroxycyclohexan-1-yl)acetate.

Acetates↗
PubMed1989

Metabolism of a monoterpene ketone, R-(+)-pulegone--a hepatotoxin in rat.

1. R-(+)-Pulegone was administered orally to rats and the urinary metabolites were investigated. Six metabolites were isolated and purified using column and thin layer chromatographic techniques. Metabolites were identified by i.r., n.m.r. and mass spectral analyses. 2. The neutral metabolites isolated from urine of rats treated with pulegone (I) were: pulegone (II), 2-hydroxy-2(1'-hydroxy-1'-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (V) and menthofuran (VII). Metabolites II and III were also excreted in conjugated form. 3. Acidic metabolites isolated from urine of rats treated with pulegone (I) were: 5-methyl-2(1'-methyl-1'-carboxyethylidene)cyclohexanone (IV) and 5-methyl-5-hydroxy-2(1'hydroxy-1'-carboxyethyl)cyclohexanone (VI).

Administration, Oral↗
PubMedDate not supplied

Evaluation of the role of free hydroxyl radicals in the cytochrome P-450-catalyzed oxidation of benzene and cyclohexanol.

The possible role of free hydroxyl radicals in the oxidation of cyclohexanol to cyclohexanone and of benzene to phenol was examined in a reconstituted system containing rabbit phenobarbital-inducible P-450LM2. From steady state kinetic studies, a KM for cyclohexanol of 8.7 mM and a Vmax of 5.7 nmol of cyclohexanone formed/min/nmol of P-450 were determined. Similarly, a KM for benzene of 105 mM and a Vmax of 22 nmol of phenol formed/min/nmol of P-450 were obtained. With intact microsomes from phenobarbital-treated rabbits, a KM for benzene of 18 mM and a Vmax of 1.7 nmol of phenol formed/min/nmol of P-450 were determined. With the use of substrate concentrations in the range of the respective KM values, superoxide dismutase, desferrioxamine, and dimethyl sulfoxide were found to have no significant effect on the P-450-catalyzed reactions. When the oxidation of benzene or cyclohexanol was examined in a model hydroxyl radical-generating system containing xanthine, xanthine oxidase, and Fe-EDTA, no dependence of the rate of oxidation on the substrate concentrations used was observed. Since the rate of hydroxyl radical generation by the model system was adjusted to be greater than the rate of product formation in the P-450 system, the lack of dependence on substrate concentration suggests that free hydroxyl radicals are not involved in the P-450-catalyzed reactions studied. Taken together, these findings indicate that the free hydroxyl radical-mediated pathway observed by other investigators does not contribute significantly to product formation when these substrates are present at concentrations within the range of their respective KM values.

Animals↗
PubMed1985

Prolonged exposure to an odor or deodorized air alters the size of mitral cells in the olfactory bulb.

The size and distribution of mitral cells in the olfactory bulbs of rats were determined using a computer-assisted morphometric technique. Rats were reared from 2 weeks of age for 10 weeks in an animal colony, or in cages through which a stream of deodorized air or cyclohexanone vapor passed. Statistical analyses indicated that each treatment produced a different distribution of cell sizes in the coronal but not along the rostrocaudal plane of the bulb. The mean size of mitral cells in rats reared in deodorized air was substantially smaller than that of normal rats, and the mean length of their mitral cell layer in the coronal plane was less than in the other groups. Overall, these findings indicate that mitral cells which were of normal size in rats exposed to cyclohexanone had been stimulated by this odor. Cells which had not been stimulated by an odor in either of the experimental groups were smaller than normal and were degenerating or underdeveloped. The results also suggest that there are bands of mitral cells aligned along the rostrocaudal axis of the olfactory bulb which are responsive to specific odors and other evidence is presented which supports this view. The functional significance of exposure effects and their implications for the spatial coding of odor quality are discussed.

Animals↗
PubMed1966

Substrate activation and inhibition in coenzyme-substrate reactions cyclohexanol oxidation catalysed by liver alcohol dehydrogenase.

1. The activity of liver alcohol dehydrogenase with cyclohexanol and cyclohexanone as substrates was studied, and the initial-rate parameters were determined from measurements at low substrate concentrations. In contrast with aliphatic ketones, cyclohexanone is a fairly good substrate, although less active than aliphatic aldehydes. The Michaelis constant for cyclohexanol is of the same order as that for ethanol, and the maximum rate and Michaelis constant for NAD(+) obtained with cyclohexanol are very similar to those obtained with primary aliphatic alcohols. The data for this substrate at low concentrations are therefore consistent with a compulsory-order mechanism in which ternary complexes are not rate-limiting. 2. With large concentrations of NAD(+), substrate activation is observed with increasing concentrations of cyclohexanol, whereas with small NAD(+) concentrations substrate inhibition is observed. This complex behaviour is explained by a mechanism previously proposed for this enzyme, which also satisfactorily described the kinetics of oxidation of primary and secondary aliphatic alcohols and aldehydes, including the substrate inhibition exhibited by primary alcohols, and the reduction of aldehydes. The activation with large concentrations of both NAD(+) and cyclohexanol is attributed to the formation of an abortive complex, E.NADH.ROH, from which NADH dissociates more rapidly than from the normal product complex E.NADH. Substrate inhibition in the presence of small NAD(+) concentrations is attributed to the formation of an active complex E.ROH, with which NAD(+) reacts more slowly than with the free enzyme. 3. Some support for these mechanisms of substrate activation and inhibition is obtained by approximate theoretical calculations, and their applicability to other two-substrate reactions that exhibit complex initial-rate behaviour, as a more likely alternative to the postulate of a second binding site for the substrate, is suggested.

Alcohol Oxidoreductases↗
PubMed1978

Effects of age and sex on ketamine anaesthesia in the rat.

Intraperitoneal injections of ketamine 75 mg kg-1 in rats of both sexes (age 1--16 weeks) revealed a significant relationship between increased age and decreased duration of sleeping time for both sexes during the first 3 weeks of age. This decrease in sleeping time seemed to be associated with the increased production of the cyclohexanone oxidation metabolite of ketamine. After 3 weeks of age there was a greater sleeping time in the female rat than the male and this seemed to be associated with a greater ability of the male to produce the cyclohexanone oxidation metabolite.

Age Factors↗
PubMed1987

Activity and stability of horse-liver alcohol dehydrogenase in sodium dioctylsulfosuccinate/cyclohexane reverse micelles.

Horse liver alcohol dehydrogenase (EC 1.1.1.1) solubilized in sodium dioctylsulfosuccinate (AOT)/cyclohexane reverse micelles was used for the oxidation of ethanol and reduction of cyclohexanone in a coupled substrate/coenzyme recycling system. The activity of the enzyme was studied as a function of pH and water content. The enzyme was optimally active in microemulsions prepared with buffer of pH around 8. An increase in enzymatic activity was observed as a function of increasing water content. The Km values for the substrates were calculated based on the total reaction volume. The apparent Km for ethanol in reverse micelles was about eight times lower as compared to that in buffer solution, whereas the Km for cyclohexanone was almost unaltered. Storage and operational stability were investigated. It was found that the specific activity of the alcohol dehydrogenase operating in reverse micellar solution was good for at least two weeks. The steroid eticholan-3 beta-ol-17-one was also used as a substrate. In this case the reaction rate was approximately five times higher in a reverse micellar solution than in buffer.

Alcohol Dehydrogenase↗
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↗
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↗