Biomedical subjects
Publications and source records attributed to M Luyckx.
Ethacrynic acid is a well known diuretic drug. We present here evidence that this compound is also an antimicrotubular agent which inhibits the brain tubulin polymerization and can displace 3H colchicine from its binding site. Since 2-mercaptoethanol reversibly inhibits the anti-microtubular properties, we conclude that ethacrynic acid binds covalently to brain tubulin through a cysteine near the colchicine site.
We have evaluated the effects that methodology (incubation time, concentration of beef brain tubulin) have on the measurement of the interaction of tubulin with colchicine. The results show that, with DEAE filter paper assay, binding is maximal for 3 hr of incubation at 37 degrees C, and for low concentrations of tubulin (0.05 mg/ml). In these conditions binding constants determined with SCATCHARD plot are: constant of dissociation (KD) of complex tubulin-colchicine equal to 9.8 X 10(-7) M and stechiometry equal to 0.57 mole of colchicine bound for 1 mole of tubulin dimer. Competition of drugs with colchicine binding site may be evaluated with this methodology. IC50 and affinity constants (Ki) of podophyllotoxin, a competitive inhibitor of colchicine-binding determined with these experimental conditions were 1.3 X 10(-6) M and 1.1 X 10(-6) M, respectively.
Levamisole, an anthelmintic drug with immunopotentiating activity, is shown to have variable effects on cell-mediated immunity. We have studied the effect of a single oral dose (2.5 mg/kg or 5 mg/kg) on early and spontaneous E rosettes percentages in healthy and cancer patients. Pharmacokinetic study of this compound was conducted in parallel. The results indicated that single administration of levamisole (2.5 mg/kg) in healthy men can promote an increase of early E rosettes with mean peak plasma level of 0.8 micrograms. ml-1. On the other hand, there was no change in the proportion of early E rosettes in cancer patients and in the proportion of spontaneous E rosettes in healthy and cancer subjects.
Radioactive arsenic trioxide is given to pregnant mice in order to complete a recent pharmacokinetics study in the same species and to investigate an eventual transplacental passage, whole body autoradiographic study is performed in the mouse after a single administration of that compound considering its fast elimination process. Both in mice and foetus a fixation has particularly kept our attention: the radioactivity is well fixed in the bone marrow and it might be related to some malformations which occur in the newborns.
Chemical and pharmacological properties of potent anorectic compounds with phenylpiperazinyl structure were studied. Among them, the three derivatives having the most interesting anorectic activity are product VI obtained by pharmacomodulation from amfepramone and the compounds IV and V, analogs of GABA. The derivative VI possesses an anorectic activity very similar to that of fenfluramine, namely: modification of feeding behaviour in treated rats, wasting away and decrease of adipose tissue. The two other compounds and more particularly compound V seem to be effective even when treatment is over. Perhaps this is in relation with metabolic effects modifying the regulation of feeding behaviour in the central nervous system. In fact, these compounds have substituents able to interfere with GABA systems.
Considering the diversity of previous observations given by literature about the metabolic fate or arsenic, the authors using a radioactive tracer, study the pharmacokinetics of that arsenical derivative after giving the mouse a non toxic dose. By the oral route, this compound is quickly absorbed and resorbed. The elimination process mainly occurs by renal route then by the faecal route. The blood results or the concentrations in the tissues do not reveal any retention process though the latter always rise above blood levels. During the first two hours the concentrations in the thymus seem to be particularly interesting.
A routine high-performance liquid chromatographic method for measuring midazolam in human serum has been developed. The sample preparation procedure consisted of simple liquid-liquid extraction with dichloromethane, followed by evaporation under nitrogen. The mobile phase used was a mixture of acetonitrile at 0.02 M and sodium acetate at pH 3.0 (80:20, v/v) and a flow-rate of 1.2 mL/min. The separation was performed on two cyanopropyl columns (150 x 4.6 mm). The detection was by UV absorption at 240 nm. A linear range from 10 to 1,000 ng/mL and a quantification limit of 7.4 ng/mL of serum was reached. The mean intra-assay and inter-assay reproducibility from serum sample spiked with 100 ng/mL were 4.1 and 4.7%, respectively. The recoveries from serum sample spiked with 50, 100, 500 ng/mL were 85.46, 85.38 and 85.57%, respectively. This method was developed to allow pharmacokinetics study of midazolam in young patients in short surgical interventions.
A high performance liquid chromatographic procedure is described for the determination of cyclohexanone leached in intravenous solutions from the poly(vinyl chloride) bags. After derivatization with 2,4-dinitrophenylhydrazine and extraction with pentane, the cyclohexanone derivative was analysed on a C18 BDS Hypersil column using mobile phase mixture of acetonitrile:water (55:45). Ultra-violet detection was performed at 368 nm. The limit of quantification was 30 ng/mL and the assay was linear from 0.05 to 50 micrograms/mL. The recovery was better than 95%. The proposed method is satisfactory in its accuracy and precision with particularly relative standard deviations (RSD) for intra-assay and inter-assay of below 10%. This method has been successfully used for the determination of cyclohexanone in aqueous solutions such as sodium chloride (0.9%) and glucose (5%) stored in PVC containers. The values obtained varied between 2.04 and 44.9 micrograms/mL according to solutions and volume.
An isocratic reversed-phase high performance liquid chromatographic method has been developed for th e determination of dobutamine in the plasma of dialysed patients. A solid phase extraction method with a Sep-Pak C18 cartridge was used to isolate the drug and isoxsuprine (internal standard) from plasma. The separation was carried out on an ODS-Hypersil column with 0.1 M phosphate buffer:acetonitrile:methanol (72:20:8 v/v/v) as the mobile phase. The recovery of dobutamine added to plasma by the extraction procedure was 87 +/- 2.3% (mean +/- SD). The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-1000 ng/mL. Quantification was by fluorescence detection at 275 nm excitation and 310 nm emission wavelengths with a detection limit of 5 ng/mL for dobutamine. This procedure was applied to ascertain the pharmacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.
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In France, the legal routes used to administer midazolam to a patient are intravenously and intramuscularly. For anaesthetists, these routes are not well adapted to paediatric use; they lead to pain at injection site and stress on children. The sublingual route should be a good compromise between stress and quick efficiency. We have developed a sublingual tablet of midazolam. The aim of the present investigation is to compare the pharmacokinetic parameters of midazolam tablets administered by the sublingual and intravenous routes in 6 rabbits to determine the bioequivalence between these routes. We have estimated the 1-hydroxy-midazolam serum level by difference between RRA and HPLC values. By the sublingual route, midazolam absorption is substantial and fast. The statistical analysis, on data obtained with HPLC dosage, shows no significant difference between pharmacokinetic parameter values calculated after intravenous and sublingual administration (0.5 mg). The absolute bioavailability was close to 100%. With RRA dosage, however, AUCs were greater than those obtained by HPLC dosage (174%). 1-hydroxy-midazolam seems to have a great importance in BZD activity. To estimate the bioequivalence between intravenous and sublingual midazolam administration, it is necessary to take into account the active metabolites.
The aim of the present study was to monitor plasma levels of progabide and its metabolites in the rabbit following single oral administration of 20 mg.kg-1. The plasma levels were determined selectively using high performance liquid chromatography (HPLC) and then correlated with a global estimation by a (3H) muscimol radioreceptor assay (RRA). In our "in vitro" binding conditions progabide itself was virtually ineffective (IC50 greater than 100 microM) so only RRA active materiel plasma concentrations were studied. A good enough correlation (r = 0.71) has been established between HPLC and RRA plasma concentrations from 0 to 3 hours following oral administration specially considering the absorption phase. But with closed regards to the elimination pharmacokinetic parameters specially the elimination half-life values (t1/2el (RRA) = 1.67 h and t1/2el (HPLC) = 0.70 h) that correlation should be weaker than the former instead metabolites including GABAmide and GABA itself are probably present in amounts likely to affect the displacement of specific binding in the (3H) muscimol radioreceptor assay.
Blood lines of polyvinyl chloride (PVC) for hemodialysis usually contain di(2-ethylhexyl) phthalate (DEHP) as a plasticizer. Previous studies show that 1 mg/kg of this plasticizer can leach into the blood during one dialysis session. It is rapidly metabolized in the liver. Mono(2-ehtylhexyl) phthalate (MEHP), its main metabolite can be detected as well. After oral administration to rodents, both compounds caused a variety of adverse biological effects such as testicular atrophy, peroxisome proliferation and hepatic peroxisomal enzyme induction. Male wistar rats were treated intraperitoneally by DEHP and MEHP using twice the dose of that involved in human exposure during a dialysis session. Propranolol metabolism by hepatocytes was investigated after fresh isolation from treated and untreated rats by means of reverse phase HPLC. The choice of propranolol as a substrate was made because of its rather quick liver metabolisation. Phenobarbital was chosen in the study as a reference of enzymatic inducer to evaluate the inducing effect of DEHP and MEHP. Propranolol was metabolized by the hepatocytes of both treated and untreated rats. Hepatocytes isolated from rats treated by phenobarbital, MEHP and DEHP were shown to have a higher speed constant of metabolism indicating a rapid metabolism of propranolol. Under these conditions, in fact, propranolol metabolisation was found to be respectively 6, 2.7, 2 times faster than the propranolol metabolisation of untreated rats. The hypothesis that DEHP and MEHP are enzymatic inducers, particularly cytochrome P450 (CYP) inducers of the xenobiotics metabolism on the intact liver after IP administration has become been found to be valid. The results obtained in this study confirm the value of isolated hepatocytes as an in vivo drug metabolism predictive model.
Polymorphonuclear neutrophils are the predominant cells in acute inflammatory lesions and their functions and recruitment are regulated by cytokines, including IL1, TNF and IL8. Antibiotic modulation of inflammatory effects has stimulated investigations of antibiotics for their potential activity as immunomodulators over their primary bactericidal or bacteriostatic activities. This study reports the influence of macrolides, spiramycin and dirithromycin on IL1 beta production. Mononuclear cells, isolated from healthy human volunteers, were preincubated with macrolides (0.1 to 500 micrograms/ml) and stimulated by Escherichia coli lipopolysaccharide. Then, IL1 beta production was detected by western blotting analysis. At therapeutic concentrations, dirithromycin and spiramycin seemed to enhance IL1 beta production by LPS-stimulated cells, with +37 per cent and +28 per cent at 1 microgram/ml respectively. At supratherapeutic concentrations, these drugs seemed to inhibit IL1 beta production through protein kinase C inhibition, with inhibitory concentrations 50 per cent of 378 micrograms/ml for dirithromycin and 234 micrograms/ml for spiramycin. So, macrolides may modulate the host defence system through their influence on cytokine production.
The stability and compatibility of 5-fluorouracil (5-FU) in admixtures for continuous intravenous infusion using PVC bags and administration sets were studied. 5-fluorouracil was reconstituted and diluted to 1.8 mg/ml for infusion in polyvinyl chloride and glass containers, and to 1 mg/ml to 16 mg/ml for storage in polyvinyl chloride bags containing 5 per cent dextrose or 0.9 per cent sodium chloride injections. Admixtures were stored at +4 degrees C and with protection from light, for 7 days. Analyses were performed by HPLC. No significant drug loss was observed during simulated infusions using PVC infusion bags and administration sets vs glass bottles and administration sets, over an infusion period used in hospitals (24 h). The solution stored at +4 degrees C with protection from light in PVC bags showed that at 1 mg/ml to 16 mg/ml, 5-fluorouracil was stable at least for 7 days in 0.9 per cent sodium chloride and 5 per cent dextrose.
Glutamate, aspartate and possibly other excitatory acidic amino acids are thought to be, neurotransmitters at the majority of excitatory synapses in the vertebrate CSN. The synaptic response elicited by excitatory amino acids is mediated by at least four (probably five) different receptor subtypes. These were known as the N-methyl-D-aspartate, quisqualate, kainate and L-AP4 receptor subtypes. More recently a fifth receptor subtype has been discovered that is linked to phosphoinositol metabolism. The most well characterized excitatory amino acid receptor subtype is the NMDA receptor. This receptor consists of a recognition site for NMDA, a cation-selective ion channel and binding site for glycine, Zn2+ and phencyclidine-like compounds. In addition the channel can be blocked by Mg2+. New and selective ligands and radioligands have facilitated mapping the distribution of the major excitatory receptor subtypes in normal and diseased brain, examines allosteric interactions within the NMDA receptor, searching for novel therapeutic agents and determining drugs mechanisms.
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A radioreceptor assay (RRA) was developed to determine plasma levels of amisulpride. In in vitro binding conditions, the RRA technique was sensitive (11.6 nmol/l) and reliable, with a high degree of precision. The reproducibility of the method through statistical coefficients was < 7%. This method was applied to a pilot pharmacokinetic study in rabbits following single i.v. administration of amisulpride at 10 mg/kg. The results obtained were compared with those obtained by high performance liquid chromatography method (HPLC) in order to assess the validity of this new RRA technique.