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At least 631 records · Page 35Linked to original sources
PubMed1990

Microbial metabolism of monoterpenes--recent developments.

Monoterpenes are important renewable resources for the perfume and flavour industry but the pathways and enzymology of their degradation by microorganisms are not well documented. Until recently the acyclic monoterpene alcohols, (+)-camphor and the isomers of limonene were the only compounds for which significant sections of catabolic pathways and associated enzymology had been reported. In this paper recent developments in our understanding of the enzymology of ring cleavage by microorganisms capable of growth with 1,8-cineole and alpha-pinene are described. 1,8-Cineole has the carbocyclic skeleton of a monocyclic monoterpene with the added complication of an internal ether linkage. Ring hydroxylation strategy and biological Baeyer-Villiger oxygenation lead to an efficient method for cleaving the ether linkage. alpha-Pinene is an unsaturated bicyclic monoterpene hydrocarbon. At least two catabolic pathways exist. Information concerning one of them, in which alpha-pinene may be initially converted into limonene, is rudimentary. The other involves attack at the double bond resulting in formation of alpha-pinene epoxide. Ring cleavage is then catalysed by a novel lyase that requires no additional components and breaks both carbocyclic rings in a concerted manner.

Bicyclic Monoterpenes↗
PubMed1996

Cannabinoid receptor-mediated inhibition of dopamine release in the retina.

The possible occurrence of cannabinoid (CB) receptors was studied on superfused guinea-pig retinal discs preincubated with [3H]dopamine or [3H]noradrenaline. Tritium overflow was evoked either electrically (3 Hz) or by re-introduction of Ca2+ 1.3 mM after superfusion with Ca(2+)-free medium containing K+ 30 mM. The accumulation of [3H]dopamine ([3H]DA) and [3H]noradrenaline ([3H]NA) was inhibited by the selective inhibitor of the neuronal dopamine transporter GBR-12909 (pIC50% 7.29 and 7.41, respectively) but not by the selective inhibitor of the neuronal noradrenaline transporter desipramine (1 microM). The electrically or Ca(2+)-evoked tritium overflow in retinal discs preincubated with [3H]DA or [3H]NA was reduced by the CB receptor agonists CP-55,940 and WIN 55,212-2 (pIC50% in discs preincubated with [3H]NA, electrical stimulation: 7.03 and 6.70, respectively) but not affected by the inactive S(-)enantiomer of the latter, WIN 55,212-3 (up to 10 microM). The concentration-response curve of WIN 55,212-2 was shifted to the right by the CB1 receptor antagonist SR 141716 (apparent pA2: 8.29) which, by itself, increased the evoked overflow. The facilitatory effect of SR 141716 was not affected by GBR-12909 and the dopamine receptor antagonist haloperidol. In conclusion, the dopaminergic neurones of the guinea-pig retina can be labelled by both [3H]DA and [3H]NA. Transmitter release from the dopaminergic neurones is inhibited by activation of cannabinoid receptors of the CB1 type, which appear to be tonically activated by an endogenous CB receptor ligand.

Animals↗
PubMed1993

Discriminating parts from the whole: determinants of odor mixture perception in squirrel monkeys, Saimiri sciureus.

In a task designed to simulate olfactory-guided foraging, the ability of squirrel monkeys to discriminate an artificial 12-component odorant from 3-, 6-, 9- or 11-component submixtures was investigated. A combination of factors was found to contribute to the animals' performance: 1. Discriminability generally decreased as the number of components in the submixture increased. 2. Submixtures did not contribute equally to mixture perception, and one component in particular (cineole) disproportionately influenced stimulus discriminability. 3. Interactive effects between submixtures resulted in marked deviations from the general pattern of discriminability. 4. Changes in the relative concentration of submixtures could also influence discriminability. 5. Finally, individual differences in responsiveness to particular stimuli were apparent. These findings demonstrate that the interaction between components in odor mixtures can be complex and that seemingly small changes in composition can strongly affect perception and thus potential signal function. It is therefore suggested that in future investigations of squirrel monkey semiochemistry, the method of systematically varying submixtures may be particularly useful in defining the contribution of components to a signal.

Adult↗
PubMed1985

Cross-modal identification: effects of contingent changes in the stimulus series.

Two computer controlled experiments in an olfactory cross-modal matching task, using two-component odour mixtures matched against bar diagrams, were designed so that stimulus presentation was contingent upon the recent performance of the subject; stimuli that were relatively poorly (in experiment 1) or well (in experiment 2) matched were more frequently presented. Analysis shows that the autoregressive structure of the performance is modified by such contingent presentation and that there is a weak relationship between transmitted information in matching and the time series structure of the matching errors. It is suggested that the process is nonlinear.

Adolescent↗
PubMed1981

Double-blind comparison of the analgesic response to oral ciramadol (WY-15.705) and pentazocine in post-operative pain.

The efficacy and safety of oral ciramadol, a synthetic partial agonist-antagonist analgesic, in rapid control of postoperative pain was compared with oral pentazocine in a double blind study in 46 patients. Ciramadol 20 mg and 60 mg and pentazocine 50 mg had a rapid analgesic effect, peaking within one hour. Although a similar pattern of activity was observed for ciramadol 20 mg and pentazocine 50 mg, ciramadol 60 mg provided significantly better and longer lasting pain relief (P less than 0.02). Side effects included sedation and sweating, which occurred with a similar frequency in the various treatment groups. Oral ciramadol appears to be a safe and highly effective analgesic.

Administration, Oral↗
PubMed1993

Roles of sulfhydryl and disulfide groups in the binding of CP-55,940 to rat brain cannabinoid receptor.

The roles of sulfhydryl and disulfide groups in the specific binding of synthetic cannabinoid CP-55,940 to the cannabinoid receptor in membrane preparations from the rat cerebral cortex have been examined. Various sulfhydryl blocking reagents including p-chloromercuribenzoic acid (p-CMB), N-ethylmaleimide (NEM), o-iodosobenzoic acid (o-ISB), and methyl methanethiosulfonate (MMTS) inhibited the specific binding of [3H]CP-55,940 to the cannabinoid receptor in a dose-dependent manner. About 80-95% inhibition was obtained at a 0.1 mM concentration of these reagents. Scatchard analysis of saturation experiments indicates that most of these sulfhydryl modifying reagents reduce both the binding affinity (Kd) and capacity (Bmax). On the other hand, DL-dithiothreitol (DTT), a disulfide reducing agent, also irreversibly inhibited the specific binding of [3H]CP-55,940 to the receptor and about 50% inhibition was obtained at a 5 mM concentration. Furthermore, 5 mM DTT was abelt to dissociate 50% of the bound ligand from the ligand-receptor complex. The marked inhibition of [3H]CP-55,940 binding by sulfhydryl reagents suggests that at least one free sulfhydryl group is essential to the binding of the ligand to the receptor. In addition, the inhibition of the binding by DTT implies that besides free sulfhydryl group(s), the integrity of a disulfide bridge is also important for [3H]CP-55,940 binding to the cannabinoid receptor.

Animals↗
PubMed1988

Spatial variation in response to odorants on the rat olfactory epithelium.

We have measured the electro-olfactogram produced by four odorants, nicotine, i-pentyl acetate, i-pentanoic acid and cineole from twelve positions on an in vitro preparation of rat olfactory tissue. Each odorant shows a different pattern of response over the twelve positions which can be explained by differences in olfactory receptor populations between regions of the rat olfactory epithelium. The result for nicotine is further evidence that there are olfactory receptors which are stimulated by nicotine when it is presented as a vapour.

Action Potentials↗
PubMed1987

Anaphylactoid reactions and histamine release do not occur after application of the opioid tramadol.

After an i.v. application of 100 mg tramadol in 13 healthy volunteers no change in plasma histamine concentration could be detected,( systemic anaphylactoid reactions did not occur, cutaneous reactions were not rated as anaphylactoid since itching and erythema were seen only once after tramadol whereas erythema was also observed twice after saline, blood pressure and heart rate were only very slightly and transiently elevated without any abnormalities in ECG-readings and only side effects typical for opioid therapy were observed.

Anaphylaxis↗