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Biomedical subjects

M Claeys

Publications and source records attributed to M Claeys.

At least 91 records · Page 5Linked to original sources
PubMed1986

Determination of dopamine-beta-hydroxylase in cerebrospinal fluid by high-performance liquid chromatography with electrochemical detection.

An improved method is described for the measurement of dopamine-beta-hydroxylase (D beta H) activity in cerebrospinal fluid, which is based on an incubation with dopamine at a saturated substrate concentration and quantitation of the reaction product noradrenaline, by high-performance liquid chromatography with electrochemical detection using 3,4-dihydroxynorephedrine as internal standard. Sample workup consists in an ion pair extraction to isolate the catecholamines from the rather complex incubation medium, a cation ion exchange to eliminate the bulk amount of dopamine, and alumina adsorption to concentrate the sample prior to high-performance liquid chromatography. The methodology was used to evaluate some of the characteristics of D beta H in cerebrospinal fluid and the stability of the enzyme. The procedure was also employed to determine the change in the D beta H following drug administration. Intravenously administered yohimbine caused an increase in D beta H activity in cerebrospinal fluid of rabbits as expected from its known alpha 2-antagonist properties.

Adrenal Glands↗
PubMed1986

Antibacterial activity of enoxacin: comparison with aminoglycosides, beta-lactams and other antimicrobial agents.

The activity of enoxacin, a new quinolone carboxylic acid, was evaluated against 3014 clinical isolates of Enterobacteriaceae, Pseudomonas and other non-fermenters and Staphylococcus aureus. Comparison was made with gentamicin, tobramycin, amikacin, netilmicin, ampicillin, piperacillin, carbenicillin, ticarcillin, ticarcillin plus clavulanic acid, trimethoprim, cotrimoxazole and erythromycin. In general enoxacin was the most active compound and resistance was only rarely encountered.

Aminoglycosides↗
PubMed1985

Metabolic profile of linoleic acid in porcine leukocytes through the lipoxygenase pathway.

Porcine neutrophilic leukocytes were found to contain a lipoxygenase which converted linoleic acid into 13-hydroxy-9,11-octadecadienoic acid (n-6 specificity), arachidonic acid into 12-hydroxy-5,8,10,14-eicosatetraenoic acid (n - 9 specificity) and 5-hydroxy-6,8,11,14-eicosatetraenoic acid into 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid. This lipoxygenase was partially purified and it appeared that its substrate specificity and other properties were quite different from the 12-lipoxygenase of blood platelets. Incubations of intact or broken porcine leukocytes with added linoleic acid revealed the formation of not only 13-hydroxy-9,11-octadecadienoic acid but also of substantial amounts of epoxyhydroxy and trihydroxy isomers. These products from linoleate, collectively described by the name 'octadecanoids' were characterized in detail by a combination of chemical, chromatographic and mass spectrometric techniques. The phospholipids of porcine leukocytes contain more than twice as much linoleate than arachidonate (22 vs. 8%). In accordance with this fatty acid composition we found that in the stimulated neutrophil the endogenous production of octadecanoids often surpassed that of the eicosanoids. Lipoxygenation of endogenously liberated linoleic acid was especially pronounced when a suspension of leukocytes in citrated plasma was recalcified and allowed to clot.

Animals↗
PubMed1985

No evidence for a physiological role of 5-hydroxykynuramine in chicken hemostasis.

Pharmacological effects of 5-hydroxykynuramine (5-HK) were investigated in chicken whole blood. It was shown that 5-HK had a time-depending inhibiting activity on platelet aggregation induced by 5-hydroxytryptamine (5-HT). Experiments were carried out in order to determine whether the inhibitory effect of chicken aorta upon 5-HT-induced aggregation of chicken whole blood could be explained by the formation of 5-HK, a metabolite of 5-HT. Using high performance liquid chromatography (HPLC) in combination with sensitive electrochemical detection, the presence of 5-HK could not be confirmed in chicken blood or aortic tissue, despite the fact that 5-HT levels of chicken blood (6.78 +/- 0.54 micrograms/ml) and aorta (0.69 +/- 0.11 micrograms/g of tissue wet weight) could be determined. These results do not point to a physiological role of 5-HK in chicken whole blood aggregation.

Animals↗
PubMed1985

Isolation and identification of two isomeric trihydroxy octadecenoic acids with prostaglandin E-like activity from onion bulbs (Allium cepa).

Two fractions with prostaglandin E-like activity were isolated from onion (Allium cepa) by using XAD-2 adsorption, silicic acid column chromatography and thin layer chromatography. The fractions were analyzed by gas chromatography/mass spectrometry and were characterized as isomeric mixtures of 9,10,13-trihydroxy-11-octadecenoic and 9,12,13-trihydroxy-10-octadecenoic acid, which are lipoxygenase metabolites of linoleic acid. Bio-assay, for which cascade superfusion was used and the rabbit coeliac and mesenteric arteries and the rat fundus strip were employed as assay organs, was utilized to monitor the bio-active profile throughout the isolation procedures. The activity of 1 microgram of the pharmacologically active fractions T1 and T2 was found to be equivalent to that of respectively 1.33 and 0.63 ng of prostaglandin E2.

Chromatography, Gel↗
PubMed1984

Influence of prostaglandins on bovine abomasum: biosynthesis and in vitro motility experiments.

Pieces of the fundus, antrum pyloricum and pyloric sphincter of abomasa from freshly killed cows were studied for their capacity to biotransform arachidonic acid (AA) and for the effects of PG's on their in vitro motility. Biotransformation experiments revealed an AA-conversion (3.8 to 11.5%) into cyclooxygenase and lipoxygenase metabolites. The mucosa mainly synthetized hydroxy-eicosatetraenoic acids (HETE's) and PGE2 + TXB2. For the muscularis PGI2 was the major AA-metabolite. Incubation in the presence of indomethacin resulted in a reduction of the AA-conversion into cyclooxygenase metabolites. In the fundic strips the three PG's induced an increase in tension. In the antral strips PGF2 alpha and PGE2 resulted in an activation of spontaneous motility whereas PGI2 provoked a dose-dependent inhibition. The three PG's induced an inhibitory response in the tissue strips from the pyloric sphincter. The results suggest a possible function for PG's in the control of tone and motility of the bovine abomasum.

Abomasum↗
PubMed1984

Antihypertensive activity of tibalosine (CP 804 S) in the rat. Possible involvement of a central alpha 1-adrenergic receptor blockade.

The effect of tibalosine (CP 804 S) on systolic blood pressure and heart rate of unanaesthetized normotensive, spontaneously hypertensive (SHR) and DOCA-salt and Goldblatt hypertensive rats has been examined. After a single oral dose, tibalosine (1.9 to 15 mg/kg) elicited dose-dependent reductions in blood pressure in the four models tested. These reductions are accompanied by a tachycardia except in the SHR where no variation in heart rate is observed. The same result is obtained in SHR after oral, i.v. or i.c.v. administration. After repeated treatment (9 to 14 weeks), the blood pressure lowering effect of tibalosine (10 mg/kg, p.o.) is observed only in hypertensive rats. No variation in heart rate is observed in normotensive, DOCA-salt and Goldblatt rats. A significant bradycardia is observed in the SHR. The antihypertensive effect of tibalosine in SHR is suppressed by naloxone, like that of clonidine and unlike that of prazosin. The present study suggests that the antihypertensive activity of tibalosine is at least partly centrally mediated.

Administration, Oral↗
PubMed1984

The metabolism of arachidonic and linoleic acid in rabbit peritoneal tissue: a short review.

The results obtained in the biotransformation studies demonstrate that lipoxygenase and PG-cyclo-oxygenase reactions represent major pathways in the metabolism of both arachidonic and linoleic acid in rabbit peritoneal tissue. Although the physiological significance of the hydroxy derivatives of arachidonic acid and linoleic acid is still unclear, it is tempting to assume that in tissues containing lipoxygenase activity, some of the effects ascribed to hydroxy arachidonates and their hydroperoxy precursors, e.g. inhibition of leukotriene and of PGI2 biosynthesis (16, 17) could for a great part be invoked by linoleic acid derivatives, as these products can be formed in larger quantities than the corresponding arachidonate derivatives.

Animals↗
PubMed1983

Simultaneous determination of the three major monoamine metabolites in cerebrospinal fluid by high-performance liquid chromatography with electrochemical detection.

A simple method is described for the simultaneous determination of the three monoamine metabolites, 4-hydroxy-3-methoxyphenylacetic acid, 4-hydroxy-3-methoxyphenylethyleneglycol and 5-hydroxyindole-3-acetic acid, in cerebrospinal fluid by high-performance liquid chromatography with electrochemical detection. Quantitation is accomplished by the standard addition technique. Chromatographic peak heights are corrected for volume effects by comparison with the signal obtained for an added auxiliary reference substance. Sample preparation is kept to a minimum, involving precipitation of proteins by means of perchloric acid and subsequent neutralization. The reproducibility was estimated to be 10%. For one of the metabolites, 4-hydroxy-3-methoxyphenylethyleneglycol, a correlation between the results obtained by this method and a mass fragmentographic method was made, and a satisfactory correlation (r = 0.904, slope = 0.914, intercept 3.26 ng/ml) found. The sensitivity of the method is in the picogram range. The methodology has been applied to measure biogenic amine metabolites in both rabbit and human cerebrospinal fluid. The levels found are in agreement with previously reported values.

Animals↗
PubMed1983

Mechanism of complement-induced stimulation of prostacyclin production by isolated rabbit peritoneum.

The interaction between the complement system and prostaglandin synthesis has not thoroughly been explored, although both mediators are known to be involved in inflammatory reactions and endotoxic shock. When rabbit peritoneum, a rich source of prostacyclin forming activity was incubated in serum in which the complement system was activated (CVF, LPS, zymosan), the tissue produced significantly more PGI2, when compared with appropriate controls, indicating that by activation of the complement, factors were generated that stimulated PGI2 biosynthesis. Further results indicated that tryptic cleavage products of complement factor C3 and C5 also led to the appearance of PGI2 releasing principles with a molecular weight of about 7000-11000. The stimulation of PGI2 biosynthesis was explained by enhanced release of AA, and not due to increased activity of cyclo-oxygenase or PGI2 synthetase. Our results suggest that complement-derived products may promote the supply of prostaglandins at the site of inflammation.

6-Ketoprostaglandin F1 alpha↗
PubMed1982

Characterization of monohydroxylated lipoxygenase metabolites of arachidonic and linoleic acid in rabbit peritoneal tissue.

Rabbit peritoneal tissue contains a lipoxygenase which converts arachidonic acid preferentially into 15-hydroxy-5,8,11,13-eicosatetraenoic acid. Stereochemical analysis of the menthyloxycarbonyl derivative of this metabolite by means of a high-pressure liquid chromatography method, involving the use of a Ag+ -loaded cation-exchange column, indicated that it has mainly the 15-Ls-hydroxy configuration. The biosynthesis of 15-hydroxy-5,8,11,13-eicosatetraenoic acid could be confirmed during examination of the monohydroxy acids obtained without addition of fatty acids, thus formed from endogenously released substrate. However, the 9-and 13-hydroxy derivatives of linoleic acid were also formed and in quantities exceeding those of 15-hydroxy-5,8,11,13-eicosatetraenoic acid.

Animals↗
PubMed1982

Arachidonic acid metabolism by cultured mesothelial cells. Different transformations of exogenously added and endogenously.

The capacity of cultured mesothelial cells to produce prostaglandins from both exogenous an endogenous arachidonic acid has been investigated. Incubations with labelled [1-14C]arachidonic acid and [1-14C]prostaglandin endoperoxide H2 indicated the formation of prostacyclin and prostaglandin E2. Evaluation of the transformation of endogenously released arachidonic acid, however, could only confirm the production of prostacyclin.

Animals↗
PubMed1982

Rat cardiac muscarinic receptors. II. Influence of thyroid status and cardiac hypertrophy.

The effects of the thyroid state and of aortic stenosis on muscarinic cholinergic binding sites in heart membranes were compared (with proper controls) by simultaneously determining total and high-affinity binding sites and estimating low-affinity binding sites by difference. Hyper- and hypothyroidism induced decreased and increased concentration of high-affinity agonist binding sites, respectively, supporting the hypothesis that these sites were directly regulated by thyroid hormones. This was not the case for low-affinity binding sites, as they decreased in number in both hyper- and hypothyroidism. In hyperthyroid rats, this decreased number of low-affinity binding sites could be due to the rapidly developing cardiac hypertrophy. Indeed, cardiac hypertrophy provoked by aortic stenosis led also to a decreased concentration of low-affinity binding sites without affecting the concentration of high-affinity binding sites.

Animals↗
PubMed1982

Endothelium-dependent inhibitory effects of acetylcholine, adenosine triphosphate, thrombin and arachidonic acid in the canine femoral artery.

Experiments were designed to investigate the importance of endothelial metabolism of arachidonic acid in the relaxation of isolated arteries caused by acetylcholine, ATP, arachidonic acid itself and thrombin. Rings of canine femoral arteries were mounted for isometric tension recording in organ chambers filled with Krebs-Ringer-bicarbonate solution. Acetylcholine, arachidonic acid, ATP, 15-hydroperoxy-5,8,11,13 eicosatetraenoic acid, thrombin and prostacyclin caused relaxations of control rings made to contract with norepinephrine. Removal of the endothelium abolished the relaxations caused by acetylcholine, ATP, thrombin and 15-hydroperoxy-5,8,11,13 eicosatetraenoic acid, reduced those caused by arachidonic acid, but did not affect the inhibitory effect of prostacyclin. The inhibitory response to arachidonic acid was abolished by indomethacin and 5,8,11,14-eicosatetraynoic acid (ETYA); that to acetylcholine was abolished by mepacrine and reduced by ETYA. The relaxations induced by thrombin and ATP were not affected by these inhibitors. Canine femoral arteries with endothelium, but not de-endothelialized preparations, transformed part of exogenously added [14C] arachidonic acid to prostaglandins (6-oxo-prostaglandin (F1 alpha) and a hydroxy derivative. The formation of prostanoids was inhibited by indomethacin, ETYA and 15-hydroperoxy-5, 8,11,13 eicosatetraenoic acid and that of hydroxy derivative by ETYA. These results suggest that the endothelial cells of canine femoral arteries initiate relaxation of the vascular smooth muscle cells of the media by: 1) producing prostacyclin, when exposed to arachidonic acid; 2) producing a lipoxygenase product, when exposed to acetylcholine; and 3) producing a signal of unknown nature, when exposed to thrombin or ATP.

Acetylcholine↗