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Biomedical subjects

J Chopineau

Publications and source records attributed to J Chopineau.

At least 19 recordsLinked to original sources
PubMed1999

Compatibility of paclitaxel in 5% glucose solution with ECOFLAC low-density polyethylene containers-stability under different storage conditions.

The compatibility of paclitaxel with low-density polyethylene containers (ECOFLAC) was studied under different temperature and light conditions. Solutions of 0.4 and 1.2 mg/ml of paclitaxel in 5% glucose solution were prepared, put into ECOFLAC containers and stored: (i) at ambient temperature (20-25 degrees C) and in ambient light; (ii) at ambient temperature in the dark; and (iii) at +4 degrees C in the dark. Paclitaxel was assayed by high-performance liquid chromatography after visual inspection of the solutions. The results show that solutions of TAXOL in 5% glucose should not be stored for more than 5 days in glass or ECOFLAC containers because a whitish precipitate tends to form, lowering the paclitaxel concentration. The decrease in the paclitaxel concentration observed after chromatographic analysis ranged very widely (from 12 to 83% of the initial concentration). However solutions of TAXOL diluted in 5% glucose was stable for 5 days in ECOFLAC containers under all the storage conditions tested. These additive-free low-density polyethylene containers offer the advantage of not releasing DEHP into the paclitaxel solutions.

Chemical Precipitation↗
PubMed1999

Kinetic impairment of nitrogen and muscle glutamine metabolisms in old glucocorticoid-treated rats.

Aged rats are more sensitive to injury, possibly through an impairment of nitrogen and glutamine (Gln) metabolisms mediated by glucocorticoids. We studied the metabolic kinetic response of adult and old rats during glucocorticoid treatment. The male Sprague-Dawley rats were 24 or 3 mo old. Both adult and old rats were divided into 7 groups. Groups labeled G3, G5, and G7 received, by intraperitoneal injection, 1.50 mg/kg of dexamethasone (Dex) for 3, 5, and 7 days, respectively. Groups labeled G3PF, G5PF, and G7PF were pair fed to the G3, G5, or G7 groups and were injected with an isovolumic solution of NaCl. One control group comprised healthy rats fed ad libitum. The response to aggression induced specifically by Dex (i.e., allowing for variations in pair-fed controls) appeared later in the aged rats (decrease in nitrogen balance from day 1 in adults but only from day 4 in old rats). The adult rats rapidly adapted to Dex treatment, whereas the catabolic state worsened until the end of treatment in the old rats. Gln homeostasis was not maintained in the aged rats; despite an early increase in muscular Gln synthetase activity, the Gln pool was depleted. These results suggest a kinetic impairment of both nitrogen and muscle Gln metabolisms in response to Dex with aging.

Aging↗
PubMed1998

Monoacylation of ribonuclease A enables its transport across an in vitro model of the blood-brain barrier.

A major challenge in correcting disorders affecting the central nervous system is to induce blood-brain barrier (BBB) crossing of exogenous biological compounds such as proteins or specific nucleic acid sequences. Fatty acids, due to their high membrane affinity and low toxicity, are good potential candidates to promote this barrier crossing when covalently bound to proteins. In this paper, we report that regiospecific monoacylation of ribonuclease A (RNase A) enables its transport across an in vitro model of the BBB. Myristoylated, palmitoylated and stearoylated RNases A were prepared using reversed micelles as microreactors. All the purified acylated RNases A kept their original enzymatic activity. A single fatty acid moiety was linked to RNase A through the alpha-amino group of its N-terminal lysine as shown by powerful analytical techniques. The ability of monoacylated RNases A to cross an in vitro model of the BBB is strictly dependent on the acyl chain length, which must be at least 16 carbon atoms long.

Acetylation↗
PubMed1998

Antioxidant activity of some ascorbic and cinnamic acids derivatives.

Some 4-benzoyl 3-hydroxy furan-2 (5H) ones (3a-d) and 2-amino 3-hydroxymethyl 4-aryl 4-oxo 2-butenoic acids (4a-h) have been synthesized. Compound 3c with an isobutyl substituent in the 5-position of the furan ring was the most effective (IC50 = 8.69 x 10(-4) M) in scavenging the superoxide anion. In vivo, 3c was also protective against reperfusion injury.

Animals↗
PubMed1998

Compatibility of tropisetron with glass and plastics. Stability under different storage conditions.

The compatibility of tropisetron (pure undiluted 1 mg mL(-1) and diluted with 5% glucose or 0.9% NaCl (saline)) with glass, poly(vinyl chloride), polypropylene or polyethylene containers has been studied over a period of two weeks. The drug solutions were exposed to different light and temperature conditions. Tropisetron was assayed by high-performance liquid chromatography. The results show that undiluted tropisetron is stable in polypropylene syringes for two weeks under all the storage conditions tested (daylight at room temperature, dark at room temperature, refrigerator at 4 degrees C). Some variations in concentration were observed after dilution of tropisetron but these remained within 10% of the initial concentration. Tropisetron can be stored undiluted at 1 mg mL(-1) in polypropylene syringes, although it is preferable to perform dilutions extemporaneously. Tropisetron diluted with 5% glucose or saline can be kept equally well in glass, poly(vinyl chloride) (Travenol bags) or polyethylene (ecoflac) containers.

Antiemetics↗
PubMed1997

Crystallization of monoacylated proteins: influence of acyl chain length.

The crystallization of monoacylated proteins has been investigated using a model system. Acylated derivatives of bovine pancreatic ribonuclease A, differing in their acyl chain lengths (10 to 16 carbon atoms), have been prepared using reverse micelles as microreactors. With one fatty acid moiety per polypeptide chain, covalently attached to the NH2 terminus of the protein, all the modified proteins have similar enzymatic activity and hydrodynamic radius as the native protein. Only the caprylated derivative can give crystals which diffract to high resolution. The resolved structure indicates that: (i) the protein folding is not modified by the chemical modification, (ii) the capryl moiety is not buried within the molecule but available for external interactions. Dynamic light scattering experiments on concentrated solutions show that the protein-protein interactions are dependent on acyl chain length. Proteins with the longest attached chains (14 and 16 carbon atoms) tend to self-associate through acyl group interactions.

Acylation↗
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

Self-evolving microstructured systems upon enzymatic catalysis.

The consequences of cell microstructuration on enzyme functions is discussed in the framework of self-evolving microstructured systems. Molecular assemblies of amphiphiles or lipids are spontaneously formed by self-organisation. Among these different structures, reversed micelles, liquid crystalline mesophases and vesicles are hosts for enzymatic reaction studies. Inside a living cell, phospholipid metabolism is responsible for membrane structural modifications; the catalytic behaviour of lipolytic enzymes, mainly phospholipase (PL) A2, is described in relation with structural aspects of biological membranes. The implication in cellular regulation events of PLC and PLD is discussed in relation with the role of their reaction products as second messengers in membrane fusion processes. The in vitro synthesis of dialkyl phosphatidylcholines, via the enzymatic 'salvage pathway' which leads to the formation of vesicles upon phospholipid formation, is considered in relation with autopoiesis. More recent studies on self-evolving systems based on enzyme-surfactants reactions are detailed. The interactions between amphiphilic aggregates and enzymes allow to explore the OG/octanol/water phase diagram. Enzymatic formation of dipalmitoylphosphatidylcholine (DPPC) liposomes and non-ionic surfactant vesicles (NSV), starting from mixed micelles or open structures, finally sets an example of a biomimetic self-evolving system.

Cholesterol↗