Mass spectrometric analysis of fluorescent products originating from the molybdenum cofactor.

Mass spectra of 4 fluorescent HPLC fractions originating from the molybdenum cofactor in xanthine oxidase extracts have been obtained with the method of field desorption (FD). The most polar fraction contains compounds which show peaks in the M/Z = 110-230 and M/Z = 580-750 range. Two other fractions exhibit in the FD spectra peaks at M/Z = 1,113 and M/Z = 886, respectively. Both corresponding compounds contain at most 24 C atoms and lack S, Mo, Cl and Br, as judged from the isotopic pattern. The most apolar fluorescent compound, which could be isolated only from xanthine oxidase extracts prepared in the absence of phosphate, has been identified as a species with a molecular weight around 482.

Review of the animal pharmacology and pharmacokinetics of fluvoxamine.

1 Fluvoxamine maleate is a compound from the series of 2-aminoethyloximethers of aralkylketones which possesses marked inhibition effects on 5-hydroxytryptamine (5-HT) uptake by blood platelets and brain synaptosomes. In contrast, it has no effect on noradrenaline uptake processes. 2 Fluvoxamine is completely absorbed in rats and dogs; the main metabolic path was similar in rat, dog, hamster, mouse and rabbit. The metabolites of fluvoxamine are inactive with regard to aminergic uptake processes. 3 Fluvoxamine is neither sedative nor stimulating, shows a very low cardiotoxic effect and no affinity for the cholinergic receptor. On the basis of the pharmacological profile, a highly favourable therapeutic ratio of antidepressant effects vs disturbing side-effects is predicted.

Molybdenum cofactor from the cytoplasmic membrane of Proteus mirabilis.

Molybdenum cofactor was extracted from membranes of Proteus mirabilis by three methods: acidification, heat treatment and heat treatment in the presence of sodium-dodecylsulphate (SDS). Extracts prepared by the latter method contained the highest concentration of molybdenum cofactor. In these extracts molybdenum cofactor was present in a low molecular weight form. It could not penetrate an YM-2 membrane during ultrafiltration suggesting a molecular weight above 1000. During aerobic incubation of cofactor extracts from membranes at least four fluorescent species were formed as observed in a reversed-phase high performance liquid chromatography (HPLC) system. The species in the first peak was inhomogeneous while the species in the others seem to be homogeneous. In water, all fluorescent products had an excitation maximum at 380 nm and an emission maximum at 455 nm. Their absorption spectra showed maxima at around 270 nm and 400 nm. Fluorescent compounds present in the first peak could penetrate an YM-2 membrane during ultrafiltration, whereas the compounds in the other peaks hardly did. Using xanthine oxidase from milk as source of molybdenum cofactor apparently identical cofactor species were found. Cytoplasmic nor membrane extracts of the chlorate resistant mutant chl S 556 of P. mirabilis could complement nitrate reductase of Neurospora crassa nit-1 in the presence of 20 mM molybdate. However, fluorescent species with identical properties as found for the wild-type were formed during aerobic incubation of extracts from membranes of this mutant.

The influence of growth conditions on the synthesis of molybdenum cofactor in Proteins mirabilis.

Cell-free extracts of Proteus mirabilis were able to reconstitute NADPH-dependent assimilatory nitrate reductase in crude extracts of the Neurospora crassa mutant strain nit-1, lacking molybdenum cofactor. Molybdenum cofactor was formed in the cytoplasm of the bacterium even in the presence of oxygen during growth though under these conditions no molybdo enzymes are formed. As a consequence no cofactor could be released by acid treatment from membranes of cells growth aerobically. The amount of cofactor released from membranes of cells grown anaerobically under various conditions was proportional to the amount of molybdo enzymes formed. During growth in the presence of tungstate a cofactor, which lacks molybdenum, was found in the cytoplasm. For detection of this so-called demolybdo cofactor the presence of molybdate during reconstitution was essential. Moreover, the cytoplasmic cofactor pool in cells grown in the presence of tungstate appeared to be two to three times higher than in cells grown under similar conditions without tungstate. After anaerobic growth in the presence of tungstate, the inactive demolybdo reductases were shown to contain partly no cofactor and partly a demolybdo cofactor. The P. mirabilis chlorate resistant mutant S 556 did not contain molybdenum cofactor. In two other chl-mutants the cofactor activity was the same as in the wild type.

Secoverine selectively antagonizes muscarinic effects in various in vivo preparations.

Time-activity studies of secoverine and atropine were made with respect to mydriasis and oxotremorine-induced salivation, lacrimation and tremors. Marked differences were found in the anticholinergic activity relation between secoverine and atropine for various tissues. These differences remained present at all time intervals, which excludes a pharmacokinetic explanation. It may be concluded that secoverine possesses a different affinity for various muscarinic receptors.

Pharmacology of secoverine, a new spasmolytic agent with specific antimuscarinic properties. Part 1: Antimuscarinic and spasmolytic effects.

1-Cyclohexyl-4-[ethyl(p-methoxy-alpha-methylphenethyl)amino]-1-butanone hydrochloride (secoverine hydrochloride) is a neurotropic spasmolytic agent with specific antimuscarinic properties. On the basis of the results obtained, the possibility exists that secoverine acts only a sub-group of muscarinic receptors. 1. In in vitro experiments the competitive antagonism of secoverine against muscarinomimetics was demonstrated on guinea pig ileum, rat jejunum and calif trachea smooth muscle. On the basis of the mean difference of the pA2 values and in accordance with the relative activity as determined by 4-point assays, it may be concluded that secoverine is about 0.6 times as active as atropine. 2. In in vivo experiments the antimuscarinic activity of secoverine on ileum of guinea pig, rat and dog proved to be 0.6 times of atropine, by both parenteral and intraduodenal routes of administration. It was shown that the action of secoverine was reversible, of quick onset and of long duration. 3. By contrast, secoverine had only marginal effects on the sphincter and ciliary muscle of the eye, almost no effect on cholinergically-induced salivation and lacrimation, gastric acid production, urinary bladder function, gastric emptying or normal peristalsis. 4. The central anticholinergic activity was more in accordance with the activity found in the spasmolytic tests. 5. Apart from the neurotropic action, secoverine has also a good musculotropic activity as was found in in vivo and in vitro experiments. The activity varied from 3.3--13.3 times that of papaverine in the different organs investigated. The musculotropic activity is not caused by a specific, verapamil-like, calcium antagonism. 6. Secoverine has no nicotinolytic or antihistaminic activity, a moderate antisterotonic activity, an inhibiting effect on the noradrenaline uptake mechanism of the vas deferens and a marked local anaesthetic activity.

Pharmacology of secoverine, a new spasmolytic agent with specific antimuscarinic properties. Part 2: General pharmacological properties.

The general pharmacological properties of 1-cyclohexyl-4-[ethyl(p-methoxy-alpha-methylphenethyl)amino]-1-butanone hydrochloride (secoverine hydrochloride), a neurotropic spasmolytic agent with specific antimuscarinic properties, are described. 1. No effects on blood pressure were seen in dogs with doses up to 3 mg/kg .i.v. In hypertensive rats no blood pressure lowering effect was seen after oral doses of 25 and 100 mg/kg. In cats a marginal increase of the blood pressure was observed with i.v. doses up to 3 mg/kg, in pentobarbital-anaesthetized animals. This effect was not present in the chloralose-anaesthetized animal. The sinus carotis occlusion pressor reflex was increased at doses of 0.1 and 0.3 mg/kg but was decreased after an i.v. dose of 3 mg/kg. At a dose of 1 mg/kg i.v. a small decrease in heart contractility was seen. At relative high concentrations, secoverine showed in vitro a non-specific negative inotropic effect on the isolated atrium and rat ventricle strip. 2. No serious effects on the ECG were found in dogs with i.v. doses up to 10 mg/kg. In rabbits at 1 mg/kg i.v. atrioventricular dissociation was seen. In cats irregularly, anaesthetic dependent ventricular ectopics were observed. 3. With 10 mg/kg i.v. doses in rabbits some increase in respiration volume occurred, due to an increase in respiratory frequency and tidal volume. 4. Secoverine had no central depressant effects. In high doses central stimulating effects probably related to the antimuscarinic activity were found. 5. Secoverine did not cause ulceration of the stomach wall of the rat during acute or prolonged oral administration of high doses. A potentiation of ulceration was observed in Shay rats; however, the ulceration in rats caused by acetyl salicylic acid and by reserpine was antagonized by the compound. 6. No effects were seen on blood glucose levels, blood coagulation, platelet aggregation, detoxification mechanisms and diuresis, neither were analgetic or antiinflammatory effects observed.

Fluvoxamine, a specific 5-hydroxytryptamine uptake inhibitor.

1. On the basis of both in vitro and in vivo experiments fluvoxamine has been characterized as a potential anti-depressant drug with almost exclusively 5-hydroxytryptamine (5-HT) uptake inhibiting properties. 2. Fluvoxamine is effective in inhibiting 5-ht uptake by blood platelets and brain synaptosomes. Due to inhibition of the membrane pump the compound prevents 5-HT depletion by the tyramine-derivatives H 75/12 and H 77/77. As a result of the interference with the neuronal re-uptake mechanism for 5-HT, fluvoxamine produces a decreased 5-HT turnover in the brain. Effects of 5-hydroxytryptophan (5-HTP) are potentiated in mice and in combination with pargyline, fluvoxamine induces 5-HT-like behavioural effects. 3. In contrast to tricyclic antidepressants, noradrenaline uptake processes are either unaffected or only slightly inhibited by fluvoxamine. The noradrenaline depleting effects of tyramine derivates are not influenced by fluvoxamine. Reserpine effects, such as ptosis are affected only at very high doses of the test compound. The antagonism by fluvoxamine of the reserpine-induced lowering of the pentamethylenetetrazole convulsive threshold can be regarded as due to an effect upon 5-HT uptake. In contrast to the effects of desmethylimipramine and imipramine, no stimulatory effects are found in rats when rapidly acting reserpine-like compounds are given following a dose of fluvoxamine.