Observations on the neuromuscular blocking action of 2-(4-phenylpiperidino)-cyclohexanol (AH 5183).
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A new colourimetric method is described for the quantification of diquat using a yellow-coloured derivative produced by heating diquat in alkaline solution at 80 degrees C. The absorption maximum of the yellow derivative is 420 nm and the molar absorption coefficient is 2.76 x 10(4) (0.15 in 1 microgram diquat/ml with 1 cm light path). The absorption at 420 nm shows a linear concentration dependence in the range 0.1-10 micrograms/ml and fading of the colour is about 5% after 1 h. Under the same conditions, paraquat does not produce any coloured products. The concentration of diquat in the solution containing both diquat and paraquat can be determined by the absorption of diquat derivative at 420 nm without interference from paraquat. By adding sodium dithionite to the solution the concentration of paraquat can be determined by the absorption of paraquat radicals at 600 nm without interference from diquat, because the yellow derivative does not react with dithionite. This yellow diquat derivative can be extracted completely with cyclohexanol by saturating the solution with Na2SO4. The absorption maximum in cyclohexanol shifts to 440 nm with the same molar absorbance and the same half-band width as in water. Fading of the colour is less than 5% after 24 h in cyclohexanol. Perchloric acid (3%) and trichloroacetic acid (4.5%) which are often used for deproteinization of tissue homogenates, do not inhibit production of the coloured derivative at pH 13.5 or extraction of the derivative with cyclohexanol. This method is suitable for a quick determination of small amounts of diquat in tissues, since the extraction with cyclohexanol not only concentrates the derivative rapidly but also quite efficiently eliminates the coloured substances in tissue homogenates. The detection limit of diquat is 0.02 microgram/ml for blood and 0.05 microgram/g for liver when 1 ml or 1 g is used for analysis. In three human cases of fatal intoxication, both paraquat and diquat were quantified using 50 microliters of serum. In non-toxic dosing of diquat to rats for 14 days, the diquat level was highest in the spleen followed by the kidneys.
Comparative thermodynamic studies on the interactions of aqueous dispersions of dipalmitoyl phosphatidylcholine (DPPC) bilayer vesicles with hydrophobic and amphipathic species were conducted to elucidate the nature of the solute-induced interdigitated lipid phase. Cyclohexanol, a strong hydrophobic species, lowers the temperature (tm) of the lipid main phase transition from the gel to the liquid-crystalline phase. Unlike ethanol (an amphipathic species), as reported previously, cyclohexanol does not exert a biphasic effect on tm (lowering tm at lower concentrations and raising tm at higher concentrations). At cyclohexanol greater than or equal to 15.4 mg/ml or 0.154 M, the thermogram of DPPC vesicles exhibits a small transition adjacent to the main phase transition but at a lower temperature. In contrast, ethanol does not promote such a small transition. Furthermore, the enthalpy (delta H) of the transition is increased in the presence of cyclohexanol. The sign of the enthalpy change (delta H-delta Ho) is positive and that of the free energy change (delta G-delta Go) is negative, a characteristic of solute-solute hydrophobic interaction. In contrast, DPPC bilayer vesicles exhibit both (delta H-delta Ho) and (delta G-delta Go) greater than 0 in the presence of ethanol in a concentration range where lipid vesicles exist in an interdigitated phase. To support the above distinct thermodynamic observations, fluorescence steady-state polarization (P) measurements were also performed. At the temperature below tm, the value of P decreases as cyclohexanol concentration increases, while a biphasic effect on P was found in the presence of ethanol. These findings support the postulation that the solute-induced interdigitated lipid phase requires the solute molecule to be amphipathic in nature.
Previous studies showed that natural human liver alcohol dehydrogenase gamma exhibits negative cooperativity (substrate activation) with ethanol. Studies with the recombinant gamma(2) isoenzyme now confirm that observation and show that the saturation kinetics with other alcohols are also nonhyperbolic, whereas the kinetics for reactions with NAD(+), NADH, and acetaldehyde are hyperbolic. The substrate activation with ethanol and 1-butanol are explained by an ordered mechanism with an abortive enzyme-NADH-alcohol complex that releases NADH more rapidly than does the enzyme-NADH complex. In contrast, high concentrations of cyclohexanol produce noncompetitive substrate inhibition against varied concentrations of NAD(+) and decrease the maximum velocity to 25% of the value that is observed at optimal concentrations of cyclohexanol. Transient kinetics experiments show that cyclohexanol inhibition is due to a slower rate of dissociation of NADH from the abortive enzyme-NADH-cyclohexanol complex than from the enzyme-NADH complex. Fluorescence quenching experiments confirm that the alcohols bind to the enzyme-NADH complex. The nonhyperbolic saturation kinetics for oxidation of ethanol, cyclohexanol, and 1-butanol are quantitatively explained with the abortive complex mechanism. Physiologically relevant concentrations of ethanol would be oxidized predominantly by the abortive complex pathway.
Occupational exposure to cyclohexanone was studied for 59 workers through the analysis of environmental air, alveolar air, and urinary cyclohexanol. Environmental cyclohexanone exposure was measured by personal sampling with a carbon-felt passive dosimeter. Cyclohexanone in alveolar air and cyclohexanol in urine were determined with gas chromatography with a flame ionization detector. The end-of-shift urinary cyclohexanol levels correlated well with the time-weighted average environmental cyclohexanone values (r = 0.66). Urinary cyclohexanol corrected for creatinine correlated best with cyclohexanone in air (r = 0.77); when corrected for specific gravity, it gave a similar correlation coefficient (r = 0.73). When the time-weighted average of the exposure was 25 ppm, the corresponding calculated concentration for urinary cyclohexanol was 54.5 mg/1, 23.3 mg/g of creatinine, or 43.5 mg/l at a specific gravity of 1.018. The relationship between cyclohexanone exposure and its concentration in exhaled breath was found to be poorer than that for cyclohexanone exposure and the urinary metabolite (r = 0.51).
To further investigate factors contributing to the action of alcohol in the solute-induced lipid interdigitation phase, thermodynamic and fluorescence polarization measurements were carried out to study the interaction of benzyl alcohol with dipalmitoyl phosphatidylcholine bilayer vesicles. The obtained results were compared with those previously reported for ethanol and cyclohexanol (L. G. Roth and C-H. Chen, Arch. Biochem. Biophys. 296, 207, 1992). Similar to ethanol, benzyl alcohol was found to exhibit a biphasic effect on the enthalpy (delta Hm) and the temperature (tm) of the lipid-phase transition and the steady-state fluorescence polarization (P) monitored by 1,6-diphenyl-1,3,5-hexatriene. At a total concentration of benzyl alcohol < 30 mg/ml (the alcohol concentration in lipid phase < 21 mg/ml), benzyl alcohol was found to exhibit large increases in delta Hm and P, which were correlated with the formation of a lipid interdigitated phase, as evidenced by reported X-ray diffraction data. Combining the results with benzyl alcohol and ethanol suggested that simultaneously large changes in delta Hm and P can be used as an indication of the occurrence of a solute-induced lipid interdigitated phase. The overall interacting force in the formation of this lipid phase, as derived from the interactions of the hydroxyl portion of an alcohol with the lipid phosphate head group and the hydrophobic portion of an alcohol with the lipid hydrocarbon chains, may or may not be dominated by hydrophobic interaction. Although lipid/water partition coefficients and the contribution of hydrophobic interaction to the overall interacting force were comparable between benzyl alcohol and cyclohexanol, benzyl alcohol induced lipid interdigitated phase, but not for cyclohexanol. This was due to the ability of benzyl alcohol to be more effective than cyclohexanol in simultaneously interacting with the phosphate head group and the hydrocarbon chains of lipid.
1. [1-(14)C]Cyclohexylamine hydrochloride was synthesized and given orally or intraperitoneally to rats, rabbits and guinea pigs (dose 50-500mg/kg) and orally to humans (dose 25 or 200mg/person). The (14)C is excreted mainly in the urine, most of the excretion occurring in the first day after dosing. Only small amounts (1-7%) are found in the faeces. 2. In the rat, guinea pig and man, the amine is largely excreted unchanged, only 4-5% of the dose being metabolized in 24h in the rat and guinea pig and 1-2% in man. In the rabbit about two-thirds of the dose is excreted unchanged and about 30% is metabolized. 3. In the rat, five minor metabolites were found, namely cyclohexanol (0.05%), trans-3- (2.2%), cis-4- (1.7%), trans-4- (0.5%) and cis-3-aminocyclohexanol (0.1% of the dose in 24h). 4. In the rabbit, eight metabolites were identified, namely cyclohexanol (9.3%), trans-cyclohexane-1,2-diol (4.7%), cyclohexanone (0.2%), cyclohexylhydroxylamine (0.2%) and trans-3- (11.3%), cis-3- (0.6%), trans-4- (0.4%) and cis-4-aminocyclohexanol (0.2%). 5. In the guinea pig, six minor metabolites were found, namely cyclohexanol (0.5%), trans-cyclohexane-1,2-diol (2.5%) and trans-3- (1.2%), cis-3- (0.2%), trans-4- (0.2%) and cis-4-aminocyclohexanol (0.2%). 6. In man only two metabolites were definitely identified, namely cyclohexanol (0.2%) and trans-cyclohexane-1,2-diol (1.4% of the dose), but man had been given a smaller dose (3mg/kg) than the other species (50mg/kg). 7. The hydroxylated metabolites of cyclohexylamine were excreted in the urine in both free and conjugated forms. 8. Although cyclohexylamine is metabolized to only a minor extent, in rats the metabolism was mainly through hydroxylation of the cyclohexane ring, in man by deamination and in guinea pigs and rabbits by ring hydroxylation and deamination.
1. Acinetobacter TD63 was one of some thirty organisms isolated by elective culture with trans-cyclohexan-1,2-diol as sole source of carbon. The great majority of these isolates displayed the same growth spectrum as Nocardia globerula CL1 and Acinetobacter NCIB 9871 being capable of utilizing trans-cyclohexan-1,2-diol, 2-hydroxycyclohexan-1-one, cyclohexanol, cyclohexanone,1-oxa-2oxocycloheptane and adipate and were assumed to use well described metabolic pathways. 2. Acinetobacter TD63 was distinctive in being incapable of growth with cyclohexanol, cyclohexanone or 1-oxa-2-oxocycloheptane and because of this it was hoped that it would display an alternative pathway for the oxidation of trans-cyclohexan-1,2-diol. 3. Studies with cell extracts have shown the presence of inducible dehydrogenase for the conversion of trans-cyclohexan-1,2-diol to 2-hydroxycyclohexan-1-one and cyclohexan-1,2-dione and of 6-oxohexanoate to adipate. These enzymes are linked into a metabolic sequence by the action of a monooxygenase of broad specificity but efficiently capable of converting 2-hydroxy-cyclohexan-1-one into the lactone 1-oxa-2-oxo-7-hydroxycycloheptane that spontaneously rearranges to yield 6-oxohexanoate. 4. An enzyme capable of attacking cyclohexan-1,2-dione (mono-enol) in the absence of an electron donor or oxygen has also been detected. Evidence has been presented indicating that this enzyme catalyses a keto-enol tautomerization between cyclohexan-1,2-dione (mono-enol) and cyclohexan-1,2-dione (mono-hydrate) and is not involved in the pathway of ring cleavage. 5. The failure of Acinetobacter TD63 to grow with cyclohexanol, cyclohexanone or 1-oxa-2-oxocycloheptane is due not to this organism possessing a distinctive metabolic sequence but to a narrow inducer specificity coupled with an inability to form a lactone hydrolase enabling it to cleave the stable 1-oxa-2-oxocycloheptane which is an intermediate in the established pathway of cyclohexanol and cyclohexanone oxidation.
The initial rates of hydrolysis of Bz-Gly-Lys and Bz-Gly-Phe by carboxypeptidase B (CPB) are increased in the presence of the modifiers beta-phenylpropionic acid, cyclohexanol, Bz-Gly, and Bz-Gly-Gly. The hydrolysis of the tripeptide Bz-Gly-Gly-Phe is also activated by Bz-Gly and Bz-Gly-Gly, but none of these modifiers activate the hydrolysis of Bz-Gly-Gly-Lys, Z-Leu-Ala-Phe, or Bz-Gly-phenyllactic acid by CPB. All modifiers except cyclohexanol display inhibitory modes of binding when present in high concentration. Examination of Lineweaver-Burk plots in the presence of fixed concentrations of Bz-Gly has shown that activation of the hydrolysis of neutral and basic peptides by CPB, as reflected in the values of the extrapolated parameters, Km(app) and kcat, occurs by different mechanisms. For Bz-Gly-Gly-Phe, activation occurs because the enzyme-modifier complex has a higher affinity than the free enzyme for the substrate, whereas activation of the hydrolysis of Bz-Gly-Lys derives from an increase in the rate of breakdown of the enzyme-substrate complex to give products. Cyclohexanol differs from Bz-Gly and Bz-Gly-Gly in that it displays no inhibitory mode of binding with any of the substrates examined, activates only the hydrolysis of dipeptides by CPB, and has a greater effect on the hydrolysis of the basic dipeptide than on the neurtal dipeptide. Moreover, when Bz-Gly-Lys is the substrate, cyclohexanol activates its hydrolysis by CPB by increasing both the enzyme-substrate binding affinity and the rate of the catalytic step, an effect different from that observed when Bz-Gly is the modifier. The anomalous kinetic behavior of CPB is remarkably similar to that of carboxypeptidase A, and is a good indication that both enzymes have very similar structures in and around their respective active sites. A binding site for activator molecules down the cleft of the active site is proposed for CPB to explain the observed kinetic behavior.
Cytochrome P-450 is present in the endoplasmic reticulum at varying concentrations in almost all tissues. However, the existence and role of cytochrome P-450 in normal and neoplastic reproductive tissues has not been clearly demonstrated. Our interest lies in the possibility that variations in cytochrome P-450 levels may influence the responsiveness of breast and endometrial carcinomas to endocrine therapy. This may be of particular importance with agents such as tamoxifen where hydroxylation reactions are known to alter therapeutic activities. Therefore, a simple, sensitive spectrophotometric assay for determining levels of cytochrome P-450-dependent cyclohexane hydroxylase activity in breast and uterine microsomes has been developed. Cyclohexane was chosen as a substrate because of the relatively high levels of cyclohexane hydroxylase activity in tumor microsomes and because cyclohexane serves as a substrate for several forms of cytochrome P-450. In order to confirm the results of the spectrophotometric assay, a direct method utilizing isotope dilution gas chromatography/mass spectrometry (GC/MS) has been developed for detecting low levels of the hydroxylated product, cyclohexanol. By employing a stable isotopically labeled analog of cyclohexanol (cyclohexanol-d12), good agreement was demonstrated between the simple, indirect method (measuring NADPH oxidation at 340 nm) and the more complex, direct method (measuring cyclohexanol formation) utilizing GC/MS. The agreement of results obtained using these two techniques indicates that they are equally valid measures of NADPH-dependent cyclohexane hydroxylase activity. The use of the spectrophotometric method is proposed for rapid, multiple assays such as in the clinical setting, reserving GC/MS analysis for use as a research tool.
A conformational change, termed the T --> R transition, which can be detected by visible, circular dichoric, and fluorescence spectroscopy, occurs in native insulin and tryptophan substituted insulin analogs ([TrpB25]-, [TrpB26]-, [GlyB24,TrpB25]-, and [GlyB24,TrpB26]insulin) upon binding specific alcohol ligands, including phenol and cyclohexanol. In these studies we have demonstrated that changes in the visible absorbance spectrum of an insulin6(Co2+)2 solution are not a definitive means of determining the occurrence of T --> R transitions in the presence of alcohol ligands. We also have presented evidence that fast protein liquid chromatography (FPLC) can be used to determine the aggregation state of insulin and that des-octapeptide(B23-30)insulin (DOI) forms Zn(2+)-coordinated hexamers that appear to be stabilized by the T --> R transformation. Using fluorescence spectroscopy, we have shown that in the presence of specific alcohol ligands the B-chain COOH-terminal residues, particularly position B25, of hexameric, as well as monomeric insulin undergo a conformational change which appears to be related to the T --> R transformation. Circular dichroic studies indicate that a conformation similar to the R-state of metal-coordinated hexameric insulin can be induced by binding cyclohexanol; however, this new conformational state (RI-state) exists independent of divalent metal ion coordination, and therefore of hexamer formation. We further show that monomeric insulin can be induced to assume the RI-state upon alcohol binding, therefore illustrating the first defined conformational change described for monomeric insulin. We suggest that this new conformation may be an intermediate state in the T --> R transformation in metal-coordinated hexameric insulin, such that T --> RI --> R. The model presented here of the structural adjustments undergone by insulin upon binding cyclohexanol provides further insight into the conformational flexibility of insulin in solution.
The specificity of horse liver alcohol dehydrogenase for cyclohexanol and its 3-methyl derivatives was investigated by stopped-flow and initial velocity kinetic studies. The (1S,3S)-3-methylcyclohexanol was 7 times more reactive (V/Km) than cyclohexanol, whereas the (1R,3R)-3-methylcyclohexanol was at least 1000 times less reactive than its enantiomer. Computer simulation of the transient reaction of NAD+ and the cyclohexanols catalyzed by the enzyme suggests that the rate of transfer of hydrogen from the alcohol to NAD+ is increased with the 1S,3S isomer. Modeling of the three-dimensional structure of the ternary complex of the enzyme suggests that the 1S,3S isomer should only bind in a productive, reactive mode, whereas the 1R,3R isomer would bind predominantly in a nonproductive, inhibitory mode.
OBJECTIVES: To examine the effect of occupational exposure to cyclohexane on the peripheral nervous system. METHODS: A nerve conduction study was performed on 18 workers exposed to cyclohexane in a luggage factory and on age and sex matched occupationally unexposed controls. 12 workers had been exposed to n-hexane (median 2.8 years) before the start of exposure to cyclohexane. To confirm the effect of exposure, a follow up study was performed on nine workers one year after the first study. The mean exposure to cyclohexane was 1.2 years in the first study. A symptom survey was performed. The exposure was measured by air sampling of the breathing zone of each worker. The urinary metabolite cyclohexanol was also monitored. RESULTS: The concentration of airborne cyclohexane ranged from 5 to 211 ppm. The urinary concentration of cyclohexanol ranged from 0.12 to 1.51 mg/l. There was a strong correlation between the cyclohexane exposure in personal air and urinary cyclohexanol. No differences were found in nerve conduction velocities (NCV) between workers exposed to cyclohexane and age and sex matched controls. The results of the follow up study showed significant improvements in peroneal motor NCV (P < 0.01) and sural sensory NCV (P < 0.05) and in ulnar motor distal latency (MDL, P < 0.05) and peroneal MDL (P < 0.05) compared with the first study. Although the past n-hexane exposure affected the first neurophysiological study, the effect had disappeared in the second study, one year later. CONCLUSION: Occupational exposure to the concentrations of cyclohexane experienced in this study had no adverse effects on the peripheral nervous system.
A survey was conducted in the second half of a working week on 33 women who either applied glue (with cyclohexane as an almost exclusive solvent component) or worked in the vicinity of glue application. Carbon cloth-equipped diffusive samplers were used for personal measurement of time-weighted average intensity of exposure to the solvent. The geometric mean and the highest cyclohexane concentration observed in air were 27 ppm and 274 ppm, respectively. Concentrations of cyclohexanol in urine samples and cyclohexane in whole blood and serum collected at the end of a shift showed significant correlations with the solvent exposure levels. Urinary cyclohexanone also correlated, but with a smaller correlation coefficient. The observation suggests that cyclohexanol in urine and cyclohexane in blood or serum collected at the end of a shift are useful indicators of occupational exposure to cyclohexane vapor. Quantitative estimation of balance at the end of the shift suggested that only a minute portion (< 1%) of cyclohexane absorbed is excreted in the urine as cyclohexanol, almost exclusively as a glucuronide. A survey of subjective symptoms revealed an increase in the prevalence of "dimmed vision " and "unusual smell", but hematology and serum biochemistry testing did not indicate any specific signs.
An assay was developed for the simultaneous measurement of cyclohexene oxide and its metabolites (cyclohexanol, trans-cyclohexane-1,2-diol, cyclohexane-1,2-diol-O-glucuronide, and N-acetyl-S-(2-hydroxycyclohexyl)-L-cysteine) in rat urine and plasma using gas chromatography. A mixture of ethyl acetate-acetonitrile (70:30) was used as the extracting solvent for both matrices. This liquid-liquid extraction procedure was followed by the separation of cyclohexene oxide and its metabolites on an HP-FFAP fused-silica capillary column. In order to determine the amount of cyclohexane-1,2-diol-O-glucuronide, samples were incubated at 37 degrees C with beta-glucuronidase and the amount of cyclohexane-1,2-diol formed from the reaction determined. The extraction efficiencies of cyclohexene oxide and cyclohexanol were greater than 90% both in urine and plasma. However, recovery from the plasma and urine for trans-cyclohexane-1,2-diol (60-68%) and N-acetyl-S-(2-hydroxycyclohexyl)-L-cysteine (approximately 76%) were considerably less. Long term stability studies showed that urine samples spiked with cyclohexene oxide and trans-cyclohexane-1,2-diol are stable at -20 degrees C for up to 9 weeks. However, plasma samples are only stable for up to 2 weeks under the same conditions. The calibration curves for all analytes were linear over the range of 12.5 to 400 micrograms/ml and correlation coefficients (r2) were greater than 0.990. The limit of detection for cyclohexene oxide, cyclohexanol, and N-acetyl-S-(2-hydroxycyclohexyl)-L-cysteine is 1.56 micrograms/ml, while the limit of detection for trans-cyclohexane-1,2-diol is 3.12 micrograms/ml. This method has been used for the determination of the disposition and metabolism of cyclohexene oxide, and may be applied in environmental monitoring, as well as in microbiological studies for other epoxide materials.