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Biomedical subjects

F Couderc

Publications and source records attributed to F Couderc.

At least 91 records · Page 5Linked to original sources
PubMed2001

Catecholamines in murine bone marrow derived mast cells.

Cultured murine bone marrow derived mast cells (BMMC) were found to store high levels of dopamine (3753+/-844 pg/10(7) cells) and occasionally produce norepinephrine and epinephrine. The catecholamine synthesis inhibitor, alpha-methyl-para-tyrosine, decreased intracellular catecholamine concentrations, and activation with ionomycin stimulated dopamine release. Neither dopaminergic receptor antagonists nor exogenous dopamine < or =10 microM affected IL-3-induced cell proliferation. High exogenous dopamine (20-100 microM) decreased proliferation and increased apoptosis, and the anti-oxidant ascorbic acid prevented these effects. Increased expression of the anti-apoptotic factor Bcl-2 or loss of pro-apoptotic Bax expression attenuated dopamine-induced apoptosis, suggesting the apoptosis proceeds through a mitochondrial pathway.

Animals↗
PubMed2001

Capillary electrochromatography-laser-induced fluorescence method for separation and detection of dansylated dialkylamine tags in encoded combinatorial libraries.

LC-fluorescence and LC-MS methods have been previously reported for use in decoding bead-based combinatorial libraries. We present the use of capillary electrochromatography (CEC) for highly selective decoding in combination with laser-induced fluorescence (LIF) detection for high sensitivity. The results are compared to prior data obtained using HPLC with fluorescence detection. The use of CEC shows promise for miniaturization and multiplexing for future applications, and the use of LIF detection can allow for detection at sub-pmol amounts.

Amines↗
PubMed2001

Some applications of near-ultraviolet laser-induced fluorescence detection in nanomolar- and subnanomolar-range high-performance liquid chromatography or micro-high-performance liquid chromatography.

In this work we present some applications of near-UV laser-induced fluorescence (LIF) with micro-HPLC (microHPLC) and HPLC. To test the sensitivity of the detection, we used pyrene and aflatoxins, because both of these molecules exhibit native fluorescence. Then we studied catecholamines derivatized with 1,2-diphenylethylenediamine. The results show that we were able to reach better sensitivity levels than previously described in LIF studies. For catecholamines, a 50-fold increase in sensitivity compared to conventional fluorescence was obtained. These results indicate that LIF detection associated with HPLC or microHPLC can be used to detect very low concentrations of substances that can be excited in the near-UV range after labeling at nanomolar concentrations.

Aflatoxins↗
PubMed2001

Recent advances in amino acid analysis by capillary electrophoresis.

Amino acids are studied extensively using capillary electrophoresis. In this review we will report the different researchs which have been done in the literature since 1998. We will describe the developments of, detection methods, separations of enantiomers, the new medical applications, and amino acids in food and plants.

Amino Acids↗
PubMed2000

Assays for total homocysteine and other thiols by capillary electrophoresis-laser-induced fluorescence detection. I. Preanalytical condition studies.

In recent papers, we presented a new analytical method for thiol quantification in serum. It is based on the use of capillary electrophoresis and laser-induced fluorescence to analyze thiol 6-iodoacetamidofluoresceine (IAF) derivatives. Quantitative results of homocysteine, glutathione, cysteine-glycin, and cysteine were shown (Clin. Chem. 45 (1999) 412). A comprehensive comparison of the quantitation of homocysteine in serum, using high-performance liquid chromatography/conventional fluorescence detection and fluorescence polarization immunoassay was also used (E. Caussé et al., Electrophoresis 21 (2000) 2074). Sample preparation prior to derivatization with IAF had never been investigated. In this work we present the results of quantitation of thiols in serum and plasma with three different anticoagulants widely used: ethylenediaminetetraacetic acid (EDTA), heparin, and sodium citrate. We show that serum and EDTA plasma gave the same results. Then serum protein precipitations by acetonitrile, acetone, sulfosalicylic acid, perchloric acid and trichloracetic acid, prior to derivatization by IAF, were also investigated. Their influence on the concentrations of the thiols were determined. Sulfosalicylic acid and acetonitrile precipitations are well adapted, whereas acetone cannot be used.

Adult↗
PubMed2000

Chiral determination of amino acids by capillary electrophoresis and laser-induced fluorescence at picomolar concentrations.

In this publication we present results on the determination of enantiomers of amino acids at very low concentrations. A fluoresceine-based chiral dye was synthesized to allow the separation of diastereoisomers of D- and L-amino acids. We used capillary electrophoresis with different non-ionic surfactants (Brij). The separation parameters were optimized and separations of D- and L-isovaline, an unusual terrestrial amino acid, were obtained. The sensitivity limits were also determined using a commercial laser-induced fluorescence detector. The quantitation of these amino acids is very important to understand the process of chiral selection on Earth.

Amino Acids↗
PubMed2000

Determination of asymmetrical dimethylarginine by capillary electrophoresis-laser-induced fluorescence.

Asymmetric dimethyl-L-arginine (ADMA) is a naturally occurring analogue of L-arginine (L-Arg), the substrate of nitric oxide synthase (NOS). ADMA is a potent endogenous inhibitor of NOS and accumulates in the plasma of patients with renal failure, with peripheral arterial occlusive disease or with clinically asymptomatic hypercholesterolemia. We measured circulating concentrations of L-arginine, symmetric and asymmetric dimethylarginine (SDMA and ADMA, respectively) in human serum. We developed a new method for the rapid determination of these molecules using capillary electrophoresis and laser-induced fluorescence (CE-LIF). All methylated arginines were labeled with fluorescein isothiocyanate (FITC) prior to analysis. Under the capillary electrophoresis (CE) conditions used, methylated arginine derivatives were well separated, with a migration time of around 10 min. These migration times were smaller than the ones of other amino acids which do not have the same charge at pH 10. Consequently, such basic amino acids were well separated from most of the other amines or amino acids. Moreover, CE allowed one to separate all the analogues of fluorescein thiocarbamyl-arginine. The results indicated that CE-LIF is useful as a selective, rapid, cheap and sensitive tool for the determination of methylated arginine products. This new technology might appreciate the endogenous substrate for NO synthase and facilitate the knowledge of the physiological and pathophysiological regulation of NO synthesis.

Arginine↗
PubMed2000

Routine analysis of short-chain fatty acids for anaerobic bacteria identification using capillary electrophoresis and indirect ultraviolet detection.

The diagnosis of anaerobes can be difficult to perform, using classical biochemical tests. Characterization of metabolic end-products such as short-chain fatty acids (SCFA) was often used because of their reproducible biosynthesis. Despite this, SCFA are difficult to study using gas chromatography, due to their high volatility. Furthermore, the treatment of the samples are long and fastidious. Capillary electrophoresis and indirect UV detection (CE-indirect UV) is a well-known analytical method to study inorganic or organic anions. In this work, we validate the analysis of SCFA using CE-indirect UV detection. To do this, we studied the culture media of 98 anaerobic strains for the detection and quantitation of the following acids: succinic, pyruvic, acetic, lactic, propionic, 2-hydroxybutyric, butyric, 2-hydroxyvaleric, isovaleric, isocaproic, and 3-phenylpropionic. We verified that the CE-indirect UV detection analysis of SCFA for taxonomical data can be used as a mean for rapid identification for the study of anaerobes.

Bacteria, Anaerobic↗
PubMed2000

Plasma total homocysteine and other thiols analyzed by capillary electrophoresis/laser-induced fluorescence detection: comparison with two other methods.

We present a new analytical method for thiol quantification in plasma, based on the use of capillary electrophoresis (CE) and laser-induced fluorescence (LIF) to analyze 6-iodoacetamidofluorescein derivatives. Quantitative results of homocysteine, glutathione, cysteinylglycine, and cystationine are presented. A comparison of the quantitation of homocysteine in plasma, using high performance liquid chromatography/fluorescence detection and fluorescence polarization immunoassay is proposed. The results indicate that these techniques for plasma total homocysteine (tHcy) determination can be used interchangeably. The major advantage of CE-LIF is that it can quantitate the thiols in one run while keeping the price of consumables reasonable.

Chromatography, High Pressure Liquid↗
PubMed1999

Anthracycline analysis by capillary electrophoresis. Application to the analysis of daunorubicine in Kaposi sarcoma tumor.

Laser-induced fluorescence (LIF) detection is now a well-known sensitive and selective detection mode for capillary electrophoresis (CE) analysis. It has been shown to be 100- to 100,000-times more sensitive than UV detection and little work has been done using LIF in conjunction with high-performance liquid chromatography (HPLC). The need for greater resolution and higher sensitivity for the analysis of anthracyclines (fluorescent chemotherapic drugs), prompted us to compare CE-LIF and HPLC-LIF, for the detection of these substances. CE-LIF sensitivity based on quantity of anthracycline injected is 50-times greater than that obtained with HPLC-LIF, because of the injected sample volume. Analysis of daunorubicin in Kaposy sarcoma tumors and in plasma are presented. The decrease of the concentration of daunorubicin in the tumor and in the plasma following time show the same behavior, indicating identical concentrations of the anthracycline in both samples.

Antibiotics, Antineoplastic↗
PubMed1999

Determination of tartaric acid in solid wine residues by capillary electrophoresis and indirect UV detection.

Tartaric acid, used in pharmaceuticals and industrial food preparation, is an important by-product of wine preparation. It is produced by wine factories in large quantities and cannot be rejected into the environment. Wineries precipitate tartaric acid using calcium hydroxide and then evaporate the mixture. The raw compact powder obtained, which contains calcium tartarate and a lot of other constituents (sugars, tannins, etc.) is sold to factories which purify tartaric acid. The different analytical methodologies which are used to determine the tartaric acid concentration in the solid wine residues are long and tedious (Goldenberg method, 14 samples per day). They also suffer from poor reproducibility. Some other methods use ion chromatography or solid Fourier transform IR, which are not currently used for such topics. We propose a capillary electrophoresis method, which not only is very quick (2 min of analysis) but also highly reproducible. Finally it provides very simple electropherograms. The intra-day and inter-day repeatability, the inter-person reproducibility and recovery were estimated. They demonstrate the ruggedness of this new method.

Benzoates↗
PubMed1998

Quantitation of homocysteine in human plasma by capillary electrophoresis and laser-induced fluorescence detection.

Homocysteine (Hcy) represents a branching point between the transsulfuration and transmethylation pathway of methionine. A large increase of plasma concentration of Hcy is observed in patients with inherited hyperhomocysteinemia. A moderated increase (above 10 microM) is also observed in various pathological conditions, such as arterial occlusion, hypertension, hyperlipidemia and chronic renal failure. While amino acids were largely studied using capillary electrophoresis with UV or laser-induced fluorescence detection (LIF), thiol-amino acids were not. In this work we present a new approach for testing homocysteine in human plasma using CE-LIF and fluorescein isothiocyanate. The low fluorescence yield of the fluorescein thiocarbamyl (FTC) thiol-amino acids limits, probably, the sensitivity of the detection to 8 x 10(-10) M (instead of 10(-12) M for FTC-arginine).

Electrophoresis, Capillary↗
PubMed1998

Drug analysis by capillary electrophoresis and laser-induced fluorescence.

This review briefly presents the different laser-induced fluorescence detectors, outlines the different dyes used to derivatize molecules which are used with capillary electrophoresis/laser-induced fluorescence (CE-LIF), and provides an overview and current status of CE-LIF in drug analysis.

Electrophoresis, Capillary↗
PubMed1995

Child cerebrospinal fluid analysis by capillary electrophoresis and laser-induced fluorescence detection.

Capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was used to analyze a 50-microliters sample of cerebrospinal fluid from leukaemic children treated with high doses of methotrexate. Free amino acids and primary amines are labelled with fluorescein isothiocyanate prior to analysis. Electropherograms containing more than 50 peaks were obtained in less than 22 min. Twenty-one peaks were identified, and 19 were quantitated. Observed differences in individual amino acid levels are compared with healthy reference values. The results indicate that CE-LIF is useful as a selective, rapid and sensitive tool for the determination of free amino acids and amines in clinical biology studies.

Adolescent↗
PubMed1995

Gas chromatography/tandem mass spectrometry as an analytical tool for the identification of fatty acids.

Structures of fatty acids present at very low quantities in mycobacteria are difficult to determine. A commonly used strategy is to introduce heteroatoms into functional groups by chemical means before subjecting them to gas chromatography/tandem mass spectrometry (GC/MS/MS) analysis. Routinely used methods give very low abundance diagnostic ions leading to ambiguities in structural conclusions. GC/MS/MS associated with electron capture ionization of pentafluorobenzyl esters was used to study very complex mixtures of fatty acids from Mycobacterium fallax and M. aurum. The charge-remote fragmentation of fatty acid carboxylate anions was used for structure determination at the nanogram level of a large number of unsaturated, branched, and cyclopropane-containing fatty acids. Some of them have not been observed previously in these Mycobacteria. On the basis of these studies, biosynthetic pathways of unsaturated, branched, and cyclopropane-containing fatty acid are proposed.

Electrochemistry↗
PubMed1992

Contribution of high-performance liquid chromatography to the identification of some Corynebacterium species by comparison of their corynomycolic acid patterns.

Reverse-phase high-performance liquid chromatography of corynomycolic acids provided a specific pattern for each Corynebacterium species studied. These data suggest that a fast and reproducible procedure is now available for bacteriological identification at the genus and at the species level of corynomycolic-acid-containing bacteria. Mass spectrometry analysis of post-column collected fractions provided the order of elution of some corynomycolic acids and isomers and showed the high specificity of the chromatographic assay which could be used for the routine bacteriological identification of some species belonging to the genus Corynebacterium.

Chromatography, High Pressure Liquid↗
PubMed1992

High-performance liquid chromatography of corynomycolic acids as a tool in identification of Corynebacterium species and related organisms.

A high-performance liquid chromatography (HPLC) study of 307 strains of Corynebacterium species and related taxa revealed that strains classified as "Corynebacterium aquaticum"; "Corynebacterium asperum"; and Centers for Disease Control (CDC) groups 1, 2, A-3, A-4, A-5, B-1, B-3, E, F-2, and I-2 as well as some unidentified coryneforms do not contain any corynomycolic acids; therefore, they should not be included in the genus Corynebacterium. Such an HPLC method of identification permitted the correct assignment to the genus Rhodococcus of two unpigmented strains of coryneform bacteria whose mycolic acid profiles were comparable to those of Rhodococcus equi. Bacteria belonging to CDC groups ANF-1, ANF-3, F-1, G-1, G-2, and I-1, as well as some other Corynebacterium sp. strains, yielded corynomycolic acid HPLC patterns related to those of Corynebacterium species. Either similarities or differences were observed in the corynomycolic acid profiles of Corynebacterium species tested after culture on sheep blood agar and/or sheep blood agar supplemented with Tween 80, which demonstrated that identification at the species or group level is possible. However, Corynebacterium striatum and CDC group I-1 bacteria as well as CDC group G-1 and group G-2 bacteria had indistinguishable HPLC patterns. Conversely, some variations were observed within some species as Corynebacterium xerosis, C. striatum, and Corynebacterium minutissimum. The evaluation procedure of this HPLC method by mass spectrometry analysis of isolated eluted peaks revealed that analytical reverse-phase HPLC alone does not provide any structural information, since isomers with identical polarities coeluted as a single peak. Nevertheless, HPLC is a rapid and reliable method for identification of corynomycolic acid-containing bacteria in the clinical microbiological laboratory.

Chromatography, High Pressure Liquid↗