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J Chopineau

Publications and source records attributed to J Chopineau.

13 recordsLinked to original sources
PubMed1995

Solid-phase extraction of isosorbide dinitrate and two of its metabolites from plasma for gas chromatographic analysis.

A rapid, accurate and selective method for the determination of isosorbide dinitrate and its 2- and 5-isosorbide mononitrate metabolites in 1.0 ml of human plasma has been developed. Before chromatographic quantitation by gas-liquid chromatography with electron-capture detection, the compounds are subjected to solid-phase extraction, using ENVI 18 cartridges (Supelco). The intra-day and inter-day coefficients of variation are less than 10%, except the inter-day coefficient of variation for the assay of 5-isosorbide dinitrate which is less than 15%. Limits of quantitation are 10, 10 and 20 ng/ml for isosorbide dinitrate, 2-isosorbide mononitrate and 5-isosorbide mononitrate, respectively. Recoveries are in excess of 90% for isosorbide dinitrate and 70% for its two metabolites.

Chromatography, Gas↗
PubMed1995

Stability and compatibility of a mixture of the anti-cancer drugs etoposide, cytarabine and daunorubicine for infusion.

We evaluated (i) the stability of a mixture of the three anti-cancer agents used for the treatment of leukemia, namely etoposide, cytarabine and daunorubicine, in 5% glucose, and (ii) its compatibility towards various materials during an infusion protocol as performed for therapeutic purposes in hospital practice. Etoposide and cytarabine were assayed by high-performance liquid chromatography with a C18 type column and UV detection. Daunorubicine was assayed by visible spectrophotometry. The stability study showed all three anti-cancer drugs to be stable in 5% glucose solution, both alone and mixed. Best conservation was obtained by keeping bottles containing the mixture in the dark at room temperature. During the infusion protocol used in clinical practice, etoposide, cytarabine and daunorubicine were stable and compatible with the various materials present in the infusion sets and extension tubing (polyvinyl chloride, polyethylene) and catheters (silicone). Observed variations in concentration did not exceed 10% of initial concentrations of each drug, though we would advocate changing infusion sets and extension tubing daily.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Synthesis of new serotonergic 2-substituted 4,6-diaryl pyridazin-3-ones.

A series of 4,6-diaryl pyridazin-3-ones substituted in the 2-position by [4-(4-aryl piperazin-1-yl]-but-2-ynyl moieties was synthesized and evaluated for antidepressant activity. The structures of these new pyridazine derivatives were confirmed by IR, 1H-NMR spectra and by elementary analysis. At 150 mg/kg i.p., they induced little or no reduction of the duration of immobility of mice in the forced swimming test. Head twitches produced by L-5-hydroxytryptophan in mice pretreated with pargyline were significantly potentiated by most of the tested compounds. In addition, pyridazine derivatives did not antagonize reserpine-induced palpebral ptosis or enhance the toxic effects of yohimbine and were almost devoid of anticholinergic properties in mice.

5-Hydroxytryptophan↗
PubMed1994

Evaluation of free radical production in an ischaemia-reperfusion model in the rabbit using a tourniquet.

Use of a tourniquet on a limb to stem blood flow is frequent in surgery. However, this results in an ischaemia-reperfusion effect that causes damage through the production of free radicals. The aim of this work was to evaluate this production of free radicals in an ischaemia-reperfusion model in the rabbit after placement of a tourniquet. Plasma lipoperoxides were measured by high-performance liquid chromatography using the malondialdehyde assay method. We found significant (P < 0.01) production of free radicals 1 min after release of the tourniquet compared with controls; no variation in levels of free radicals was observed during the ischaemia phase.

Animals↗
PubMed1993

Fatty acid acylation of RNase A using reversed micelles as microreactors.

A water soluble protein, RNAse A, was fatty-acylated using AOT reversed micelles in 2,2,4-trimethyl pentane as microreactors and myristoyl chloride as reagent. Artificial attachment of lipid molecules to this protein was performed for different hydration degrees by changing Wo = [water]/ [AOT], the parameter which controls the microreactor size. The chemically modified protein was monitored using reverse phase HPLC and characterized by HPLC, free amino groups titration, and electrophoresis. An RNase A/myristoyl chloride ratio of 1:4 (mol/mol) at Wo = 7 was found to give 60% of modified protein.

Acylation↗
PubMed1991

Solid-phase extraction of midazolam and two of its metabolites from plasma for high-performance liquid chromatographic analysis.

A rapid, sensitive and selective assay of midazolam and two of its metabolites in plasma, based on high-performance liquid chromatography, has been developed. The compounds are subjected to solid-phase extraction, using C18 cartridges (Bond-Elut). Recoveries are in excess of 90% for midazolam and its metabolites. The limit of quantitation of the assay is 50 ng/ml of plasma for each compound.

Chromatography, High Pressure Liquid↗
PubMed1989

Dynamic interactions between enzyme activity and the microstructured environment.

A new approach for the study of an enzyme's relationship with its own reaction medium has been developed. One technique of micellar enzymology is the use of pseudohomogeneous systems composed of surfactant/water/organic solvent. In such systems, the physicochemical properties and textures of the medium depend on the relative ratios of the different components. Enzymes are catalytically active in such systems and up to the present have been studied in different microenvironments, such as micelles, microemulsions and lyotropic liquid crystals. Our purpose was to develop a system in which the enzyme could, by its activity, modify one of the components in such a way that the relative ratios among them changed sufficiently to produce a transition from one phase domain to another. The three components, water (or glucose in water), octanol and octyl-beta-D-glucoside, form a classical ternary water/oil/surfactant system. The relevant phase diagram shows different macroheterogeneous phases and microstructured domains. The enzyme beta-D-glucosidase hydrolyses octyl-beta-D-glucoside to form glucose and octanol. The enzyme was found to change the relative ratios of water (or glucose in water), octanol and octyl-beta-D-glucoside in such a manner that the physicochemical structure of the medium was modified. At the beginning of the reaction beta-D-glucosidase was present in a micellar solution of octyl-beta-D-glucoside in water. As the enzymatic reaction proceeded, the medium became biphasic. One of the two phases was the micellar solution of octyl beta-D-glucoside in water, while the other phase was either a microemulsion or a liquid crystalline phase. In addition the enzyme, through its catalytic activity, was able to modify the physiocochemical properties of the reaction medium.

Chemical Phenomena↗
PubMedDate not supplied

[Effects of optotoxic substances on several glycolytic enzyme activities in the retina of the pig (author's transl)].

1. The authors report the results obtained after the action of certain optotoxic substances on several enzyme activities in the retina of the pig. 2. This in vitro study involved enzyme interferences of the following optotoxic agents : ethionamide, d-penicillamine, ethylene diaminotetra-acetic acid (EDTA), disodium and dicobalt salts. The enzyme activities studied involved glycolysis, the enzymes selected being as follows: glucose phosphate isomerase (GPI, E.C. 5.3.1.9), fructose-1,6-diphosphate aldolase (F1-6diPA, E.C. 4.1.2.13), lactate dehydrogenase (LDH, E.C. 1.1.1.27). 3. Following the action of the effectors studied, a marked decrease in the enzyme activities examined was found in the retina. This decrease, of varying rapidity and regularity, went as far in some cases as total inhibition; there was disturbance of glycolysis. 4. These results indicate the existence of interactions with a complex mechanism. It may be noted that all of the effectors studied were chelating agents of divalent metals and the changes which they induced in the enzyme activities examined may be explained by interference of the chelates formed with metal cations, such as Zn++, co-factors or effectors of these glycolysis enzymes (with the exception of GPI). These stable chelates are formed by virtue of the primary amine--NH2, thiol--SH, thionyl-[Formula: see text] groups, i.e. groups belonging to molecules essential to cell metabolism.

Animals↗
PubMedDate not supplied

[Analysis of opiates in the urine of children with gas chromatography coupled to mass spectrometry].

Acute intoxication by opiates is quite frequent and very serious, especially in children whence the need to assay these compounds in biological fluids. The authors have developed an assay for opiates (codeine, codethyline, morphine and pholcodine) by gas chromatography/mass spectrometry (GC/MS) on a capillary column. This assay can identify different opiates due to its high specificity. Before chromatography, urine from children undergoes acid hydrolysis and solid phase extraction. The compounds are derivatized by acetylation before being chromatographied. This assay is carried out after a first search for opiates in urine by immunoenzymology. Each sample containing opiates is then analysed by GC/MS in order to determine specifically the opiates responsible for intoxication.

Child↗
PubMedDate not supplied

[Use of a dynamometer in hospital pharmacy. Its use to study the mechanical properties of plastic materials].

The stretching test is in current use in Pharmaceutical Industry to characterize the mechanical properties of materials or to control medical devices such as catheters. Given the lack of official standards in the French Pharmacopée, we present here the results of an experiment carried out in Hospital Pharmacy. The value of the results will be depending on the manual gesture of the operator and on the experimental conditions for a given material. The factors which appear to be essential are the following: numerous samples, necessary to assess a good repeatability, the stretching speed and the place of the rupture that have to be defined, so as the manual fixation of the samples. This test is interesting in Hospital Pharmacy but the methodology remains a problem so that it cannot be recommended for an occasional use, in spite of an apparent simplicity.

Catheterization↗