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Biomedical subjects

M Luyckx

Publications and source records attributed to M Luyckx.

At least 19 recordsLinked to original sources
PubMed2002

Effects of Rosa canina fruit extract on neutrophil respiratory burst.

Respiratory burst leads polymorphonuclear neutrophils (PMN) to produce reactive oxygen species (ROS) such as superoxide anions (O(2)(o-)), hypochlorous acid (HOCl) and hydrogen peroxide (H(2)O(2)) which may possess deleterious effects for the organism. Rosa canina fruits are well known to contain a large amount of vitamin C which is antioxidant. This study was focused on the polyphenolics contained in rose hips to evaluate their antioxidative properties. We prepared a rose hip extract deprived of vitamin C. The extract contained mainly phenolics such as proanthocyanidins and flavonoids. We investigated its effects directly against (O(2)(o-)), HOCl and H(2)O(2) and investigated its effects on isolated PMN. For that, in vitro inflammatory conditions were reproduced by stimulating PMN with stimuli having different transductional pathways, in order to determine a possible mechanism of action. The results showed that the extract can inhibit ROS tested in acellular and cellular systems. The IC(50) obtained were 5.73 mg/L, 1.33 mg/L and 2.34 mg/L respectively for (O(2)(o-)), HOCl and H(2)O(2) in acellular experiments. For cellular experiments, the IC(50) were quite similar. Thus, the extract did not present an effect on PMN metabolism. Therefore, the antioxidative effects of Rosa canina are due not only to vitamin C but also to polyphenolics.

Anthocyanins↗
PubMed2001

Comparative study of the leachability of di(2-ethylhexyl) phthalate and tri(2-ethylhexyl) trimellitate from haemodialysis tubing.

The leachability of both Di(2-ethylhexyl) phthalate (DEHP) and Tri(2-ethylhexyl) trimellitate (TEHTM) or Trioctyl trimellitate (TOTM) from haemodialysis tubing was investigated in 20 patients with chronic renal failure undergoing maintenance haemodialysis. The blood tubing made of common polyvinyl chloride (PVC) plasticized with DEHP (group 1 patients) were replaced with tubing plasticized with TOTM-DEHP (group 2 patients). The patient blood obtained from the inlet and the outlet of the dialyzer was analyzed during a 4 h-dialysis session. Thus, the circulating concentrations of both DEHP and TOTM resulting from the release from dialyzer tubes were estimated using High-performance Liquid chromatograph (HPLC). With the common PVC-DEHP blood tubing, a DEHP quantity of 122.95+/-33.94 mg was extracted from tubing during a single dialysis session (ranging from 55 to 166.21 mg). During the same period, the total amounts of DEHP retained by the patients were 27.30+/-9.22 mg (ranging from 12.50 to 42.72 mg). As for blood tubing plasticized with TOTM-DEHP, 41.80+/-4.47 mg of DEHP and 75.11+/-25.72 mg of TOTM were extracted. During the same period, the amounts of DEHP and TOTM retained by the patients were 3.42+/-1.37 mg and 4.87+/-2.60 mg, respectively. The extraction rate both plasticizers was correlated with serum lipid content (cholesterol+triglyceride) (r(2)=0.75 for DEHP and r(2)=0.64 for TOTM). In the present investigation, less TOTM and DEHP were apparently released from haemodialysis tubing plasticized with TOTM-DEHP than DEHP released from haemodialysis tubing plasticized with DEHP only. TOTM seems to be a superior alternative to DEHP for use in medical devices because of its potential lower leachability. To recommend it as an alternative plasticizer, its possible toxicity towards human body should be investigated before it can be used routinely. However, patients undergoing haemodialysis using tubing plasticized with DEHP only are regularly exposed to non negligible amounts of DEHP. In view of several biological effects previously reported, it is time to reconsider the use of DEHP only as a plasticizer.

Adult↗
PubMed2001

High-performance liquid chromatographic method for the determination of di(2-ethylhexyl) phthalate in total parenteral nutrition and in plasma.

A simple, rapid and sensitive reversed-phase high-performance liquid chromatographic method with UV detection was developed for the quantification of di(2-ethylhexyl) phthalate (DEHP) in parenteral nutrition admixtures containing fat emulsion and in plasma samples of children daily treated by total parenteral nutrition. The analyte and the internal standard, di-n-heptyl phthalate, were extracted twice using hexane and the organic layer separated and dried under nitrogen. The residues were reconstituted with acetonitrile and 20 microl was injected into a Waters Spherisorb C18 column, the UV detector was set at 202 nm. The mobile phase was acetonitrile-aqueous buffer (triethylamine 0.08% adjusted to pH 2.8 with 1 M phosphoric acid) mixture (88:12, v/v) and it was pumped at 1 ml/min. Average recoveries were 97% or greater. This method was successfully used to investigate the amounts of DEHP which can leach from bags and tubing into fat emulsion and which could contaminate children under long-term parenteral nutrition. On the other hand, the circulating DEHP concentrations were estimated in four children under regular long-term parenteral nutrition.

Child↗
PubMed2001

Investigation of the inhibitory effects of chelerythrine chloride on the translocation of the protein kinase C betaI, betaII, zeta in human neutrophils.

The protein kinase C (PKC) is a serine/threonine kinase, consisting of different isoforms, implicated in numerous processes of signal transduction. To understand this enzyme well, different pharmacological tools were developed. To activate PKC specifically, phorbol esters were previously used but recent research has shown that these compounds are able to stimulate other proteins. Our model is the respiratory burst in the polymorphonuclear neutrophils. A decrease in the inflammatory process was measured using chelerythrine chloride. Action on PKC was proved by a binding study and by showing the absence of translocation of this enzyme from the cytoplasm to the plasmic membrane during stimulation.

Alkaloids↗
PubMed2001

Investigation of the inhibitory effects of HA-1077 and Y-32885 on the translocation of PKCbetaI, PKCbetaII and PKCzeta in human neutrophils.

To transmit the information inside the cell, one possibility is the action of an enzyme called kinase that phosphorylates other proteins. To study these enzymes, chemical compound synthesis was needed to know the function and the mechanism of activation. The major difficulty is creating a specific molecule for one kinase. In this study, we test the action of Rho-kinase inhibitors (HA-1077 and Y-32885) on protein kinase C (PKC) in the respiratory burst in the human polymorphonuclear neutrophils. We have shown that these compounds could inhibit the anion superoxide production. To prove their action on PKC, we have shown a decrease of binding of a specific ligand (phorbol-12,13-dibutyrate) with each inhibitor. During its activation, PKC was translocated from the cytoplasm to the plasmic membrane. We have also shown an inhibition of this translocation, proving an inhibition of PKC by HA-1077 and Y-32885.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

High-performance liquid chromatographic determination of naltrexone in plasma of hemodialysis patients.

A simple, sensitive, selective and reliable reversed-phase high-performance liquid chromatographic (HPLC) method with UV detection is described for the determination of naltrexone in plasma samples. Naltrexone and the internal standard, naloxone, were isolated from plasma either with a liquid-liquid extraction method using ethyl acetate or with a solid-phase extraction method using Sep-Pack C18 cartridge before chromatography. The extracts were dried under a stream of nitrogen and the samples were reconstituted in the mobile phase, then 20 microL were injected on a Waters Symmetry C18 column (5 microm particle size, 4.6 x 150 mm). The mobile phase consisted of 0.06% triethylamine (pH 2.8)-acetonitrile (92:8, v/v) pumped at 1 mL/min. The peak-area ratio versus plasma concentration was linear over the range of 10-500 ng/mL and the detection limit was less than 8 ng/mL. Quantification was by ultra-violet detection at 204 nm. The present method was applied to the determination of the plasma concentration of naltrexone in dialyzed patients. Patients (n = 8) with severe generalized pruritus received 50 mg of naltrexone orally per day for 2 weeks. The variability in the therapeutic response in treated patients required plasma concentration investigations of this opioid antagonist.

Chromatography, High Pressure Liquid↗
PubMed2000

Phenolic compounds and antioxidant activities of buckwheat (Fagopyrum esculentum Moench) hulls and flour.

The interest of polyphenolics as therapeutic agents against diseases involving radical damage is growing. The phenolic contents of the hulls and flour from the seeds of Fagopyrum esculentum (French variety 'La Harpe') (total phenols, flavonoids, total flavanols, oligomeric proanthocyanidins) are compared with the antioxidative effects of the extracts against reactive oxygen species: hydrogen peroxide, hypochlorous acid, superoxide anion. The higher efficiency of the flour extract can be related to its higher flavanolic content rather than to flavonoids which are predominant in the hull extract.

Anthocyanins↗
PubMed2000

A pharmacokinetic interpretation of increasing concentrations of DEHP in haemodialysed patients.

The degree of exposure to DEHP was assessed in 11 patients with chronic renal failure undergoing maintenance haemodialysis. The amount of DEHP leached from the dialyser during a 4-h dialysis session was estimated by monitoring the DEHP blood concentration using a HPLC method. When a patient undergoes a dialysis treatment, the concentration of di-2-ethylhexyl phthalate (DEHP) in venous blood is increased when the blood crosses through the dialysis apparatus. This increase may be explained either because DEHP is not extracted by the dialyser or because DEHP comes from the dialysis bath due to contact of blood against plasticized pipes. To explain the increasing concentration of DEHP during treatment of renal failure using plasticized tubing, we propose a pharmacokinetic compartmental model in order to fit raw data obtained from dialysed patients and to get the amount of DEHP which enters the body by AUC calculations. Results obtained after HPLC analysis show a high degree of interpatient variability in DEHP retained. This amount can reach a toxicity level because of repetitive dialysis treatments over prolonged periods of time. In the coming years, it seems necessary to reconsider the use of DEHP as a plasticizer in medical devices. Highly unacceptable amounts of DEHP leached during the dialysis session could be easily avoided by careful selection of haemodialysis tubing.

Adult↗
PubMed2000

Reduced ammonium chloride haemolysis time enhances the number of isolated functional rabbit polymorphonuclear neutrophils.

In the present study we compared seven different methods for isolating rabbit polymorphonuclear neutrophils (PMNs) with a view to assessing viability, lymphocyte contamination and isolation yield. The two methods offering the best isolation yield and functional PMNs were retained. Leukocyte-containing plasma fraction was obtained after erythrocyte sedimentation with dextran. First, PMNs were isolated from this fraction, using hypotonic ammonium chloride haemolysis followed by Histopaque density gradient centrifugation (Method-A). Second, PMNs were obtained from leukocyte-containing plasma after centrifugation on two Percoll layers (Method-B). These processes resulted in a high cellular yield: 2.66x10(6)+/-0.22 PMNs per ml of blood (Method-A) and 1.87x10(6)+/-0.37 PMNs per ml of blood (Method-B). In both cases the PMNs isolated were of high purity and viability. In comparison, when using the standard techniques for rabbit - consisting of ammonium chloride haemolysis taking at least four times as long--fewer PMNs were isolated. The PMNs isolated by Method-A and -B were able to generate a high amount of reactive oxygen species (ROS) after stimulation with phorbol 12-myristate 13-acetate (PMA). These methods to separate PMNs are recommended for in vitro studies.

Ammonium Chloride↗
PubMed2000

Neurosedative and antioxidant activities of phenylpropanoids from ballota nigra.

Ballota nigra is a European plant known for its neurosedative properties. In this study, the ability of five phenylpropanoids (verbascoside, forsythoside B, arenarioside, ballotetroside, and caffeoyl malic acid) isolated from a hydroalcoholic extract, to bind to benzodiazepine, dopaminergic, and morphinic receptors was investigated. To carry out these studies, affinity tests with rat striata, entire brains and receptor rich preparations were employed. In addition, the phenolic aspect of these five phenylpropanoid esters led to investigate antioxidant activities using cell-free experiments and cellular experiments including isolated polymorphonuclear neutrophils (PMN). Effects of phenylpropanoid esters against reactive oxygen species as superoxide anion, peroxide hydrogen, hypochlorous acid and hydroxyl radical were tested. These molecules are liberated by PMN during inflammatory disorders, so that reproduction of this process in vitro stimulating PMN by chemical stimulants was undertaken. Results show that four of the five compounds are able to bind to the studied receptors. Inhibitory concentrations at 50% were determined and vary from 0.4 to 4.7 mg/ml. This may be in relation with the Ballota nigra known neurosedative activities. Results concerning antioxidant investigations evidence an ability to scavenge reactive oxygen species. Inhibitory concentrations at 50% obtained are comparable to those of known antioxidant drugs (mesna or N-acetyl cysteine). Moreover, the use of different stimuli having various pathways of action on PMN oxidative metabolism permits to establish that each phenylpropanoid ester has its own particular way of action by using proteine kinase C or phospholipase C pathways.

Animals↗
PubMed2000

A simple method for isolating human and rabbit polymorphonuclear neutrophils (PMNs).

We report the successful application to human venous blood of a novel method developed to purify rabbit polymorphonuclear neutrophils (PMNs) from whole blood. Human PMNs were separated from whole blood after sedimentation with dextran and histopaque density gradient centrifugation. 3.92 +/- 0.26 x 10(6) PMNs per ml of blood was harvested. The purity of the preparation was 92.00 +/- 1.10%. The PMNs isolated were capable of generating a high amount of reactive oxygen species (ROS) and elastase after stimulation with phorbol 12-myristate 13-acetate (PMA): 13.43 +/- 0.3 microM of O2-, 9.62 +/- 0.15 microM of H2O2 and 5.48 +/- 0.01 microM of elastase. This method gives equivalent yield and viability when applied to isolating human or rabbit PMNs, in comparison with standard methods used to isolate human PMNs. Our method could be usefully exploited for comparative studies of rabbit and human PMNs with a cellular model of inflammatory oxidative stress in which the monitoring parameters are ROS and elastase. Thus, the results of animal (rabbit) studies can be extended to human diseases.

Animals↗
PubMed1999

Antioxidant properties of albumin: effect on oxidative metabolism of human neutrophil granulocytes.

The present study aims at investigating the effect of bovine serum albumin (BSA) on the trial of oxidative-stress. The antioxidant effects of BSA were determined by human neutrophil granulocytes oxygen free radicals and their by-products (O2-, H2O2, HOCl) productions. BSA interacts with those reactive oxygen species (ROS) in a dose-dependent manner. The 50% inhibitory concentration (IC50) of BSA estimated, after phorbol-12-myristate-13-acetate (PMA) stimulation were: 33.5 mg/ml for O2-, 6.5 mg/ml for H2O2, and 6.85 mg/ml for HOCl. When neutrophils were washed after pre-incubation with BSA, there was no significant decrease of ROS after stimulation of PMA (maximal: 15 +/- 1.2%). In the free cell experiments, IC50 for H2O2 and HOCl were 7.86 mg/ml and 0.67 mg/ml, respectively. The mechanism at which BSA acts may result from a simple chemical interaction with ROS rather than an intracellular mechanism by intervention in PMA oxidative metabolism. These antioxidant activities confer to BSA properties, which might be used to prevent damage inflicted by these ROS during inflammatory disorders.

Animals↗
PubMed1999

Exposure of hemodialysis patients to di-2-ethylhexyl phthalate.

The migration of di-2-ethylhexyl phthalate (DEHP) from dialyzers was studied in 21 patients with chronic renal failure undergoing maintenance hemodialysis. The circulating concentrations of DEHP were measured by high performance liquid chromatography in blood of patients obtained from the inlet and the outlet of the dialyzer during a 4-h dialysis session. During treatment of renal failure using plasticized tubing, the plasma level of DEHP increased. On average, an estimated 75.2 mg of DEHP was extracted from the dialyzer during a single dialysis session, with a range of 44.3-197. 1 mg. On the other hand, the total amount of DEHP retained by the patient during the dialysis session was evaluated by the difference between the AUCout and the AUCin and ranged from 3.6 to 59.6 mg. The rate of extraction of DEHP from the dialyzer was correlated (r=0.705, P<0.05) with serum lipid content (cholesterol and triglyceride).So, we confirmed that patients on hemodialysis are always regularly exposed to considerable amounts of DEHP. However, several metabolic effects have been reported in various animal species following treatment with DEHP, such as changes in lipid metabolism and in hepatic microsomal drug-metabolizing enzyme activities. DEHP is now a well-known hepatic peroxisomal proliferator in rodents and an inducer of many peroxisomal and non-peroxisomal enzymes. So, lipid metabolism modifications and hepatic changes observed in hemodialysis patients could be explained from chronic exposition to DEHP. In the coming years, it seems necessary to reconsider the use of DEHP as a plasticizer in medical devices. Highly unacceptable amounts of DEHP leached during the dialysis session could be easily avoided by careful selection of hemodialysis tubing.

Adult↗
PubMed1999

Effects of PVC bags sterilization process on the 5-fluorouracil stability.

The stability and compatibility of 5-fluorouracil (5-FU) in undiluted or diluted admixtures stored in beta-radiation sterilized portable poly(vinyl chloride) (PVC) infusion bags were investigated. Admixtures containing 5-FU 50 mg ml(-1) not diluted or 25 mg ml(-1) diluted in 0.9% sodium chloride injection were placed in 100 or 250 ml empty PVC reservoirs sterilized initially by beta-irradiation. They were protected from light and placed at 37 degrees C. Two ml quantities were withdrawn immediately after preparation and after storage for 1, 2, 3, 4, 5, 6, 7 and 14 days. For each condition, samples from each admixture were tested for drug concentration by stability-indicating high-performance liquid chromatography. The admixtures were also monitored for precipitation, color change and pH. Evaporative water loss from the containers was also measured. 5-FU was compatible with PVC containers in all tested conditions for 14 days. No loss of drug and no color change were detected throughout the storage period. pH values were stable and neither precipitation nor loss of water through the reservoirs was observed when drug 50 or 25 mg ml(-1) (diluted using 0.9% sodium chloride) was stored in 100 ml capacity polyvinyl PVC bags. However, when stored in 250 ml capacity PVC bags, the 5-FU solution showed precipitation after 13 and 14 days of storage, but no drug loss was detected due to a substantial loss of water. The precipitation of the drug was due to the decrease of pH induced by the dehydrochlorination of PVC during beta-irradiation leading to the formation of hydrochloric acid in solution. Differences observed between 100 and 250 ml capacity bags can be explained by the greater area of PVC present in 250 ml reservoirs, and consequently more HCl formed. Finally, more plasticizer, di-(2-ethylhexyl) phthalate (DEHP), was then detected in drug solutions stored in 250 ml PVC bags. So, we recommend the use of 100 ml bags to store 5-FU at longer storage times and higher temperatures.

Antimetabolites, Antineoplastic↗
PubMed1999

Stability, compatibility and plasticizer extraction of quinine injection added to infusion solutions and stored in polyvinyl chloride (PVC) containers.

The stability of quinine was determined in various diluents and in polyvinyl chloride (PVC) containers. The release of diethyhexyl phthalate (DEHP) from PVC bags into intravenous infusions of quinine was also measured. We used an injection of two doses of quinine; quiniforme at 500 mg and quinimax at 400 mg in either 250- or 500-ml PVC infusion bags containing 5% dextrose, to give initial nominal concentrations of 2 or 1 mg ml(-1) quiniforme and 1.6 or 0.8 mg ml(-1) quinimax, the mean concentrations commonly used in clinical practice. Samples were assayed by stability-indicating high-performance liquid chromatography (HPLC) and the clarity was determined visually. Experiments were conducted to determine whether the stability and compatibility of quinine would be compromised, and whether DEHP would be leached from PVC bags and PVC administration sets during storage and simulated infusion. There was no substantial loss of quiniforme and quinimax over 1- or 2-h simulated infusion irrespective of the diluent, and storage during 8 h at 22 degrees C, 48 or 72 h at 4 degrees C and 96 h at 45 degrees C. Leaching of DEHP was also detected during simulated infusion delivery using PVC bags and PVC administration sets. The quantity was less than 2 microg ml(-1). During storage at 4 degrees C and room temperature the leaching of DEHP was low, but when the temperature was 45 degrees C the quantity was high, 21 microg ml(-1). To minimise patient exposure to DEHP, quinine solutions with all drugs should be infused immediately or stored for a maximum of 48 h at 4 degrees C.

Antimalarials↗
PubMed1999

Evaluation of the effects of Gd complexes used as magnetic resonance imaging contrast agents, on superoxide dismutase: comparison of two methods.

Investigations are currently being made into the safety of gadolinium complex contrast agents used in Magnetic Resonance Imaging. Their hyperosmolality or potential Gd3+ release is evoked as a cause of various anaphylactoid reactions to be observed in humans after intravenous injection. An estimation has already been made of their effects on the liberation of reactive oxygen intermediates by neutrophils. The purpose of this study was to find a suitable method to measure SOD activity in the presence of these hyperosmolar solutions, and to evaluate their action on this activity. Two techniques were compared to measure this activity. Results and statistical analysis showed that pyrogallol autoxidation was greatly affected by solution osmolalities, whereas ferricytochrome C reduction was not. Gadopentetate dimeglumine and gadoterate meglumine seemed to activate Cu, Zn SOD in vitro, but did not exhibit any SOD-like activity. Gadodiamide did not interfere with this system of detoxication.

Contrast Media↗
PubMed1999

Comparative oxidation of loxapine and clozapine by human neutrophils.

The clozapine-induced agranulocytosis could be due to the formation of a reactive intermediate formed in polymorphonuclear neutrophils and granulocyte precursors with the myeloperoxidase-hydrogen peroxide system. On the contrary, no case of agranulocytosis has been described for loxapine, an other neuroleptic drug with a very close structural analogy. We have compared the clozapine and loxapine interaction with the oxidative burst and particularly with this enzymatic complex. On the one hand, the assay of the oxidative species demonstrated a different impact for the two neuroleptics. The 50% inhibitory concentration was 92 microM for hydrogen peroxide and 40 microM for hypochlorous acid for loxapine. The loxapine target is located before the myeloperoxidase-hydrogen peroxide system in the oxidative stream, whereas clozapine diverts the chlorination pathway of the enzyme. On the other hand, the in vitro metabolism of drugs by the myeloperoxidase-hydrogen peroxide system has been investigated by mass spectrometry. Loxapine remains inert but clozapine undergoes the oxidation. The glutathione or ascorbate addition in the medium leads to a removal of the oxidation. Glutathione is able to trap the toxic intermediate and could avoid its formation.

Antioxidants↗