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M Claeys

Publications and source records attributed to M Claeys.

At least 73 records · Page 4Linked to original sources
PubMed1991

Clinical evaluation of a new in-vitro assay for specific IgE, the immuno CAP system.

The Pharmacia CAP system is a new assay for specific IgE characterized by a new solid phase (hydrophilic polymer encased in a capsule). The CAP results were compared to those of the Phadebas IgE RAST and skin-prick tests (SPT) performed in 145 subjects suffering from rhinitis and/or asthma with eight common inhalant allergens (total number of tests = 1160). Concording CAP/RAST results were found in 91% of the tests. The CAP was positive in 78% and the RAST in 65% of the positive SPT. Conversely, the CAP was negative in 90.6% and the RAST in 96.4% of the negative SPT. A pattern negative SPT, negative RAST and positive CAP' was found in 56 tests (40 subjects): in four such subjects, the CAP positivity was confirmed by a positive IgE crossed radioimmunoelectrophoresis. Three borderline positive results were found among 240 negative controls (serum from cord blood or non-atopics). These data indicate that compared with SPT the CAP system is (a) more sensitive than the Pharmacia RAST and (b) does not seem less specific.

Adolescent↗
PubMed1990

Adduct formation identification between phenyl glycidyl ether and 2'-deoxyadenosine and thymidine by chromatography, mass spectrometry and nuclear magnetic resonance spectroscopy.

Thymidine and 2'-deoxyadenosine were reacted with phenyl glycidyl ether in order to study the formation of the corresponding 2'-deoxynucleoside adducts. Separation methods were elaborated using either reversed-phase high-performance liquid chromatography with photodiode-array detection, or centrifugal circular thin-layer chromatography. The adducts were isolated on a preparative scale and were fully characterized by UV spectroscopy, desorption chemical ionization and fast atom bombardment mass spectrometry and 270- and 360-MHz 1H NMR spectrometry. For thymidine the main adduct was characterized as N-3-(2-hydroxy-3-phenoxypropyl)thymidine. With 2'-deoxyadenosine, predominantly N-1-(2-hydroxy-3-phenoxypropyl)-2'-deoxyadenosine was formed. With longer reaction times, the formation of a minor amount of dialkylated 2'-deoxyadenosine was observed. These nucleoside adducts will be used as marker compounds for studies of DNA adduct formation.

Chromatography, High Pressure Liquid↗
PubMed1989

Structural characterization of cisplatin analogues by fast atom bombardment (FAB) and laser microprobe mass spectrometry (LAMMA).

The present study is concerned with the investigation of the potentials and limitations of fast atom bombardment (FAB) and laser microprobe mass spectrometry (LAMMA) for the structural characterization of a series of cisplatin analogues. The limiting factors for obtaining good quality FAB spectra are the solubility and the stability of the organometallic platinum complexes in the FAB matrix. In the case of a suitable matrix being found, molecular weight information is derived from the (M + H)+ and/or (M - H)- ions. Drawbacks of the application of FAB are (i) the low signal intensities of the molecular ion-like species as compared to the matrix signals and (ii) the scarcity of fragmentation necessary for structure determination. Combination of FAB with tandem mass spectrometry was used to overcome these problems. LAMMA provides a valuable alternative for the direct mass spectral analysis of cisplatin analogues. For some compounds, LAMMA results in useful mass spectra, whereas FAB fails. The abundant fragmentation yields structural information which is complementary for positive and negative ions. The laser power density applied to the sample is of critical importance for the quality of the spectra.

Cisplatin↗
PubMed1989

Relaxations to endothelium-derived relaxing factor and the metabolite of molsidomine, SIN-1, in the aorta and the hindquarters of the rat.

The effects of SIN-1 were studied on isolated aortic rings and perfused hindquarters of the rat and were compared with the effects of nitroglycerin and endothelium-derived relaxing factor (EDRF) released by acetylcholine or histamine (aorta) and carbachol (hindquarters). SIN-1 relaxes rat aortic rings in a dose-dependent and endothelium-independent way. Aortic rings made tolerant to nitroglycerin in vitro show cross-tolerance to isosorbide dinitrate but no cross-tolerance to EDRF, sodium nitroprusside, or SIN-1. Aortic rings made tolerant to nitroglycerin by in vivo treatment show an important cross-tolerance to isosorbide dinitrate, a small degree of tolerance to sodium nitroprusside, but no significant tolerance to SIN-1 or EDRF. Also, in the nitroglycerin-tolerant hindquarter vasculature, no cross-tolerance is found to EDRF or SIN-1. In the aorta of renal hypertensive rats, in which the relaxation to EDRF-dependent dilators is impaired, no depression of the maximal response to SIN-1 occurs.

Animals↗
PubMed1988

[Hyperphosphatemia and transient renal insufficiency following chemotherapy of acute lymphoblastic leukemia].

Acute renal failure during treatment of lymphoblastic malignancies is usually due to drug toxicity or acute uric nephropathy. Observations were recently reported where extreme hyperphosphatemia may represent another pathophysiological mechanism. We describe 2 cases, in 36- and 77-year-old women, with acute lymphoblastic leukemia. Acute renal failure was observed 2 days after cytotoxic treatment. Maximal blood creatinine values were 860 and 550 mumol/l respectively, and for phosphate 6.3 and 7.5 mmol/l. With oral phosphate binders, and after four peritoneal exchanges for the second patient, renal function gradually returned to normal values within 4 weeks. Tumor lysis syndrome with associated hyperphosphatemia is described exclusively in lymphoblastic malignancies and renal failure is probably a consequence of intratubular calcium phosphate precipitation. In this situation prophylactic administration of phosphate binders and attentive monitoring of phosphatemia are necessary.

Acute Kidney Injury↗
PubMed1988

[The treatment of acute cardiac insufficiency: toward a physiopathological approach].

The development of new inotropic or vasodilator agents, with different spectra of action makes possible a physiological approach to the treatment of acute cardiac failure. The choice depends on the functional disturbances measured and is then adapted to the response obtained. In the most serious cases, where pharmacological treatment proves insufficient, there need be no hesitation in using invasive methods which were formerly reserved for the treatment of cardiogenic shock. Systematic application of therapeutic formulae gives way to rational selection of the agent best adapted to the particular conditions brought about by a specified cardiopathy in a given patient.

Acute Disease↗
PubMed1988

Evaluation of sample work-up methods and internal standards for the determination of catecholamines in urine by HPLC with electrochemical detection.

Two sample work-up methods: (I) one consisting of adsorption of the catecholamines onto alumina followed by ion pair extraction and (II) another consisting of isolation by cation exchange and subsequent adsorption onto alumina, have been evaluated for the assay of urinary catecholamines by means of HPLC with electrochemical detection. With the aim of achieving high precision, two internal standards, i.e. dihydroxybenzylamine and epinine, have been compared. The results indicate that clean HPLC chromatograms are obtained with both work-up methods and that the highest precision (RSD < 4%) is achieved with method II and with epinine as internal standard, whereas the lowest precision is obtained with method I and with dihydroxybenzylamine.

Journal Article↗
PubMed1988

Evaluation of sample work-up methods and internal standards for the determination of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in brain by HPLC with electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection is described for the determination of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in brain. Results of studies on sample work-up methods and on the use of various internal standards are reported. The reproducibility of determination of 5-HT and 5-HIAA in two regions of rabbit brain has been evaluated.

Journal Article↗
PubMed1987

Effects of the alpha 2-antagonist idazoxan on monoaminergic parameters measured in the cerebrospinal fluid of rabbits.

The alpha 2-antagonist idazoxan was administered intravenously to rabbits. The increase in central noradrenergic, dopaminergic and serotonergic activity was followed as a function of time by determining neuronal parameters in the cerebrospinal fluid (CSF) and was compared with changes previously determined after yohimbine. These parameters include the enzyme dopamine-beta-hydroxylase (D beta H), the noradrenergic metabolites 3-methoxy-4-hydroxyphenylmandelic acid (VMA) and 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), the dopaminergic metabolite 3-methoxy-4-hydroxyphenylacetic acid (HVA) and the serotonergic metabolite 5-hydroxyindole acetic acid (5-HIAA). Control experiments with physiological saline were also performed. D beta H activity increased to 211% in control experiments, and to 570 and 530%, respectively after yohimbine and idazoxan. Compared to the control experiments yohimbine was able to elevate VMA, MHPG and HVA concentrations, but 5-HIAA levels were reduced. Idazoxan caused increased MHPG concentrations, slight increases in VMA, little effect on HVA and no effect on 5-HIAA levels. We conclude that idazoxan was as potent as yohimbine as an alpha 2-antagonist in our in vivo experiments and that idazoxan shows a much greater selectivity with regard to the noradrenergic system.

Adrenergic alpha-Antagonists↗
PubMed1987

Selected ion monitoring analysis of monoamine metabolites in cerebrospinal fluid. Application to the study of in vivo effects of alpha 2-antagonists.

The technique of isotope dilution mass spectrometry has been used for the measurement of biogenic amine metabolites in cerebrospinal fluid (CSF). CSF samples were collected from rabbits treated with alpha 2-antagonists. The aim of our study was to determine the specificity of these drugs on the central nervous noradrenergic, dopaminergic and serotonergic activity as measured by the release of corresponding monoamine metabolites. 3-Methoxy-4-hydroxyphenylethylene glycol (MHPG) and vanilmandelic acid (VMA) were used as parameters for the noradrenergic activity, whereas homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) were employed to follow the dopaminergic and serotonergic activity, respectively. For the measurement of the biogenic amine metabolites a published GCMS method has been adapted. Samples of 200 microliters CSF were processed. Following addition of deuterated internal standards and acidification, extraction was carried out with ethyl acetate. Preliminary experiments with the analysis of MHPG using diethyl ether for extraction gave rise to emulsion formation and resulted in poor recoveries for MHPG and in irreproducibility problems due to a preferential extraction of non-labelled MHPG, effects which were not observed with ethyl acetate extraction. Derivatization was done with a mixture of pentafluoropropionic anhydride/pentafluoropropanol (or hexafluoroisopropanol) in order to derivatize both hydroxyl and carboxylic acid groups. The derivatization procedure was optimized for the analysis of 5-HIAA by carrying out a second reaction step with pentafluoropropionic anhydride alone in order to complete the derivatization for the indolic NH moiety. The molecular ions of the derivatized products were selected for detection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1987

Formation of leukotriene B4, 20-hydroxy leukotriene B4 and other arachidonic acid metabolites by macrophages during peritonitis in patients with continuous ambulatory peritoneal dialysis.

Macrophages, isolated from dialysis fluid of three patients with continuous ambulatory peritoneal dialysis (CAPD) at different times during peritonitis were labelled with 14C-arachidonic acid and stimulated with the calcium ionophore A23187. The main metabolites formed by 5-lipoxygenase activity were leukotriene B4 (LTB4) and 5-hydroxy-6, 9, 11, 14-eicosatetraenoic acid (5-HETE). Smaller amounts of cyclooxygenase metabolites were present and also a major compound with an elution time between 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2). This substance was isolated, analyzed by GC-MS and identified as 20-hydroxy-leukotriene B4 (20-OH-LTB4). This indicates that human peritoneal macrophages obtained from CAPD not only produce leukotrienes and prostaglandins, but also the omega-hydroxylase product of LTB4, which has been demonstrated to be present in polymorphonuclear leucocytes. The activity of this enzyme was not correlated with the severity of the peritonitis.

Aged↗
PubMed1986

Evaluation of parameters for central neuronal activity in cerebrospinal fluid of rabbits following yohimbine.

Rabbits were treated intravenously with yohimbine at a dose of 5 mg/kg. The concomitant increase in noradrenergic activity was followed in function of time by measuring dopamine-beta-hydroxylase activity and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) and 3-methoxy-4-hydroxymandelic acid (VMA) levels in cerebrospinal fluid. In addition, the effect of yohimbine on the dopaminergic, serotonergic and enkephalinergic neurotransmission was also determined. For this purpose, the dopamine metabolite, 3-methoxy-4-hydroxyphenylacetic acid (HVA), the serotonin metabolite, 5-hydroxy-indole acetic acid (5-HIAA) and methionine-enkephalin (Met-Enk) were quantified. The D beta H activity in control experiments, in which physiological saline was administered, increased up to 200% whereas in the yohimbine experiments a rise to 500-600% was observed. VMA and MHPG levels increased to 290%, and 209% respectively. HVA levels reached a value of 233% versus the concentration before drug injection, whereas 5-HIAA concentrations initially slightly increased and thereafter decreased. In the corresponding control experiments metabolite concentrations were virtually stable. Following yohimbine injection, methionine-enkephalin concentrations did not show significant variations compared with the control experiments. We conclude that noradrenergic and dopaminergic neurotransmission are increased following administration of the alpha 2-antagonist yohimbine whereas serotonergic neurotransmission is slightly decreased and enkephalinergic neurotransmission is unaltered. The value of the different parameters for measuring neuronal activity in cerebrospinal fluid is discussed.

Animals↗
PubMed1986

Characterization of serotonin receptors and lack of effect of antidepressant therapy on monoamine functions in various regions of the rabbit brain.

The effects of single and long-term administration of the antidepressants imipramine, desimipramine, amitriptyline, zimelidine and maprotiline were studied in the rabbit brain. Special attention was given to the brain serotonin (5-HT) receptors. Our results show that in different areas of the rabbit brain, the binding sites for 5-HT display pharmacological characteristics very similar to those of the 5-HT1 and 5-HT2 receptors described for the rat brain. No significant correlation could be shown between the distribution of either of the receptors and the distribution of serotonergic nerve terminals (as measured by the 5-HT content and the [3H]5-HT accumulation). Addition of antidepressants to rabbit brain slices, in vitro, caused an inhibition of the [3H]5-HT accumulation. The compounds only weakly inhibited the binding of [3H]5-HT and [3H]ketanserin as compared to the inhibition caused by serotonergic agonists and antagonists. The [3H]5-HT accumulation in brain slices was markedly reduced 2 h after a single i.p. injection of imipramine. After a two-week administration of the antidepressants, the specific binding of neither [3H]5-HT nor [3H]ketanserin was significantly altered. The simultaneous determination of monoamine metabolites and of dopamine-beta-hydroxylase in the cerebrospinal fluid of these treated rabbits did not reveal any significant difference from the control animals.

Animals↗
PubMed1986

Inhibition of rabbit platelet activation by lipoxygenase products of arachidonic and linoleic acid.

The hydroperoxy fatty acids, 15-hydroperoxyeicosatetraenoic acid (15-HPETE), 13-hydroperoxy and 9-hydroperoxyoctadecadienoic acid (13- and 9-HPODE) and the corresponding hydroxy compounds (15-HETE and 13-HODE) were synthesized and purified. Washed rabbit platelets were incubated with these fatty acid derivatives before aggregation was induced. Arachidonic acid-induced aggregation, as well as the secretion of ATP and the formation of thromboxane B2 (TXB2) were dose-dependently inhibited by these compounds. Low thrombin-, collagen- and ADP-induced aggregations were also suppressed by 15-HPETE. Platelet activation induced by the calcium ionophore A23187 and by high thrombin concentrations were not affected by 15-HPETE. In addition, doses of 15-HPETE which were inactive by themselves, potentiated the anti-aggregating activity of prostacyclin (PGI2). It is suggested that the hydroperoxy and hydroxy compounds suppress platelet activation by interference with the rise in cytoplasmic calcium in addition to the inhibition of cyclo-oxygenase.

Adenosine Triphosphate↗
PubMed1986

Diacylglycerols interfere in normal phase HPLC analysis of lipoxygenase products of docosahexaenoic or arachidonic acids.

A methodological problem with the normal phase high performance liquid chromatography (HPLC) of hydroxylated products of docosahexaenoic and arachidonic acids is described. Diacylglycerols present in lipid extracts of rat retina co-elute with monohydroxy derivatives of docosahexaenoic or arachidonic acid, when samples are applied to uPorosil columns and eluted with hexane/isopropanol/acetic acid. Analysis of fatty acid composition of diacylglycerols which were acetone-extracted from the incubation medium showed a profile similar to diacylglycerols extracted from the tissue by hexane/isopropanol, although acetone extraction resulted in extremely variable recovery of diacylglycerols. This co-elution of diacylglycerols with monohydroxy polyunsaturated fatty acids can lead to a significant error in estimation of lipoxygenation activity by conversion of radiolabeled precursors, because the incorporation of fatty acids into diacylglycerols is very active in many tissues. An alternative extraction method and reverse phase HPLC procedures that result in the complete separation of hydroxy fatty acids and diacylglycerols are described.

Animals↗