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Biomedical subjects

D Fraisse

Publications and source records attributed to D Fraisse.

30 records · Page 2Linked to original sources
PubMed1996

[Standardization of the birch leaf].

Dried leaves of Betula pendula Roth (14 batches) and B. pubescens Ehrh. (3 batches) present a similar flavonoid pattern. The mean levels of the principal flavonoid compounds were respectively: total flavonoids 3.29 and 2.77%, hyperoside 0.80 and 0.77%, avicularin (two forms) 0.57 and 0.26%, galactosyl-3 myricetol 0.37 and 0.18%, glucuronyl-3 quercetol 0.25 and 0.36%, quercitrin 0.14 and 0.12%. The flavonoid levels were higher in young leaves and lower in old leaves of B. pendula. 14 batches of commercial origin were also examined for a comparative study. Pharmacopoeial specifications are proposed for a revision of the monograph "Betulae folium".

Chromatography, High Pressure Liquid↗
PubMed1996

[Polyphenolic composition of the leaf of bilberry].

Dried leaves of 14 harvested batches and one batch from commercial origine of Vaccinium myrtillus L present a similar polyphenolic pattern. The mean levels of the harvested batches and the levels of the commercial batch were respectively: total polyphenol compounds 12.98 and 10.62%, tannins 7.84 and 7.43%, total flavonoid compounds 2.98 and 2.20% (spectrophotometry), 1.41 and 1.16% (HPLC), quercetin 3-glucuronide 1.02 and 0.83%, hyperoside 0.22 and 0.16%, chlorogenic acid 3.66 and 1.58%. The levels were higher in young leaves and lower in old leaves. A specific chromatographic profile of the flavonoid compounds and a determination method of the tannin or the total polyphenol content were proposed in a standardization purpose.

Chromatography, High Pressure Liquid↗
PubMed1994

Microbiological conversions of solamargine.

A strain of Aspergillus ochraceus, a microorganism classically used for bioconversions of the steroid nucleus, was tested on solasodine glucosides. It induced specific modifications to the oside chain of the solamargine molecule, without modifying the genin nucleus. These modifications depended on the composition of the culture medium and the aeration, and led under certain conditions to a single isomer of the secondary glucoside beta 2-solamargine or Khasianine: o-alpha-L-rhamnopyranosyl-(1-->4 glu)-O-(3)-beta-D-glucopyranosyl solasodine.

Aspergillus ochraceus↗
PubMed1992

Comparison of gas chromatographic-mass spectrometric methods for screening of chlorotriazine pesticides in soil.

The performance of a coupled technique resulting from the combination of gas chromatography with a selective mass spectrometric technique (tandem mass spectrometry) (GC-MS-MS) with collisionally activated dissociation (CAD) and multi-reaction monitoring (MRM) was compared with that of GC-low resolution MS (GC-LRMS) at a resolving power of 1000 and GC-high-resolution MS (GC-HRMS) at resolving powers of 5000 and 10,000 for the determination of atrazine, simazine, cyanazine, deethylatrazine and deisopropylatrazine in polluted soil samples. GC-MS-MS daughter ion spectra for the parent ions [M]+. and [M - CH3]+ were generated using collisionally activated dissociation and studied. Also, by optimizing the collision energy for maximum sensitivity a method for screening chlorotriazines by MRM was developed. Analyses of soil sample extracts showed that GC-MS-MS overcomes interferences from other chlorotriazines and interfering compounds that could not be removed by GC-HRMS or GC-LRMS at resolving powers of 10,000 and 1000, respectively. The limits of detection for GC-MS-MS and GC-HRMS at a signal-to-noise ratio of 10 ranged between 1 and 24 pg, with a mean relative standard deviation of 25-30%. Soil samples known to contain chlorotriazines and their degradation products were analysed by GC-MS-MS and the results obtained were compared with those given by GC-HRMS at resolving powers of 5000 and 10,000, with quantification differences of 25-30%.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

Approach to the analysis of diuretics and masking agents by high-performance liquid chromatography-mass spectrometry in doping control.

The application of thermospray and plasmaspray high-performance liquid chromatography-mass spectrometry to the analysis of diuretics and probenecid has been investigated. The latter method gave better ionization efficiency than the former, and its response was optimized by altering the solvent composition: best results were obtained with water-methanol-acetonitrile-trifluoroacetic acid. Using different proportions of these solvents, three isocratic systems were developed to separate the compounds under study. The principal characteristic of plasmaspray positive-ion mass spectra was a protonated molecular ion and very little fragmentation was evident. In the negative ionization mode, the plasmaspray method gave mass spectra showing more fragmentation, which resulted in additional structural information. The ability of trifluoroacetic acid to form negative cluster ions precluded its use as a mobile phase component. The minimum detectable amounts determined by the analysis in the positive-ion mode was compound-dependent, but generally ca. 10-150 ng. In many cases the compounds could be detected in urine extracts.

Chromatography, High Pressure Liquid↗
PubMed1989

Mass spectrometry analyses of recombinant hirudins (7 kDa).

The use of liquid secondary ion mass spectrometry (LSIMS) in the characterization of related recombinant 7-kDa peptides illustrates the adequacy of average mass measurement by scanning at low resolution. The difficulty in using the high-resolution technique in the case of poor LSIMS sensitive peptides is discussed, as well as the fact that it does not give, for these molecular weights, any real advantage. The average (or chemical) molecular weights of three recombinant hirudin molecules, hirudin variant 2 (rHV2, 6892.4 Da), hirudin variant 2-Lys47 (rHV2-Lys47, 6906.5 Da), and hirudin variant 2-Arg47 (rHV2-Arg47, 6934.5 Da), less than or equal to 10 micrograms each, have been measured with an accuracy less than or equal to 0.3 Da in the narrow-scan mode and less than or equal to 0.5 Da (from the protonated molecular ion) in the wide-scan mode within 10-15 min; this allows easy distinction of the three 65 amino acid proteins, which differ by a single amino acid. These three molecules could also be distinguished from one another in a mixture. Mass spectrometry and limited sequence characterization of several minor, similarly isolated peptides identified them to be N-terminal additions and/or C-terminal deletions of rHV2-Lys47. LSIMS analysis is consistent with there being no covalent dimer of rHV2-Lys47 as a narrow scan of the 7-kDa molecular ion cluster at high resolution shows it not to be a doubly charged ion.

Amino Acid Sequence↗
PubMed1989

[Feasibility of calcium inhibitors in the treatment of brain disease following cardiac arrest].

One of the crucial factors affecting mortality and morbidity after circulatory arrest the ischemic neuronal damage following complete cessation of cerebral blood-flow. To date, no accepted pharmacologic neuroprotective therapy has emerged. Cerebral ischemia causes a rapid shift of Ca++ from the extracellular spaces into cells and it is assumed that this excessive entry of Ca++ is the final pathway of cell death. In addition, Ca++ is involved in the diffuse vasospasm which occurs after global cerebral ischemia. Therefore, calcium entry blockers such as dihydropyridines derivatives have sparked considerable interest especially because of their preferential cerebrovasodilating effects. In vivo studies have demonstrated protection from brain ischemia with calcium entry blockers. However no direct protective effect of these drugs has been shown on neurons. More recent results have underscored the importance of excitatory amino acid neurotransmitters and receptors (particularly N-Methyl-D-Aspartate receptors) in causing intracellular calcium overload and neuronal death after ischemia. Blockade of these receptors or their associated channels may be an interesting way to protect the brain against ischemic damage.

Calcium Channel Blockers↗
PubMed1988

Application of fast atom bombardment and tandem mass spectrometry to the identification of organic micropollutants in water.

Organic compounds in raw and drinking water, not amenable to gas chromatography/mass spectrometry, were characterized by fast atom bombardment (FAB) and collision-induced decomposition/mass-analysed ion kinetic energy (CID/MIKE) spectrometry. Anionic, cationic and non-ionic surfactants were successfully identified by comparison of their FAB spectrum and CID/MIKE of prominent ions with commercial standards. Organic dyes were spiked to water extracts and the detection limit for some of them reported.

Chromatography, High Pressure Liquid↗
PubMed1986

[Use of thiopental in man. Determination of this drug and its metabolites in plasma and urine by liquid phase chromatography and mass spectrometry].

Thiopental is an anaesthetic drug which is currently used for cerebral resuscitation. In this last indication the drug is administrated at high doses over a period of several days. Under clinical trials thiopental and two metabolites namely 5 ethyl-5 (1' methyl-3' hydroxy-butyl) 2 thiobarbituric acid and 5 ethyl-5 (1' methyl-3' carboxy-propyl) 2 thiobarbituric acid have been determined by high performance liquid chromatography and mass spectrometry. In human plasma high concentrations of thiopental and 5 ethyl-5 (1' methyl-3' hydroxy-butyl) 2 thiobarbituric acid and a lower concentration of 5 ethyl-5 (1' methyl-3' carboxy-propyl) 2 thiobarbituric acid have been found. In urine samples these metabolites are excreted in large and approximately equal quantities, whereas small amounts of thiopental were recovered.

Adult↗
PubMed1984

An enzymatic method for the determination of enantiomeric composition and absolute configuration of deuterated or tritiated succinic acid.

The distribution of hydrogen isotope between pro-R and pro-S positions of succinic acid has been determined by comparison of its isotopic content before and after incubation with isocitrate lyase. This enzyme, in the presence of glyoxylate, exchanges exclusively the pro-S protons of succinate with water (M. Sprecher, R. Berger, and D. B. Sprinson (1964) J. Biol. Chem. 239, 4268-4271). With [1-14C,2(R,S)-3H]succinate as substrate, the exchange was easily followed by the decrease of 3H/14C ratio (dried aliquots), which accounted for the high isotopic effect of this reaction. The final ratio was within +/- 5% of the theoretical one. The evolution of the exchange of deuterated succinate added with [1-14C,2(R,S)-3H]succinate acid was again followed by 3H/14C ratio. The deuterium content of [2,3-2H2]succinic acid, [2-2H2]succinic acid (derived from L-[4-2H2]glutamic acid by oxidation) and of the corresponding succinates isolated after incubation with isocitrate lyase was determined by gas chromatography-mass spectroscopy of their dimethylester under NH4+ chemical ionization. This method provides the basis for a quantitative measurement of the distribution of hydrogen isotopes in unsymmetrically 2-labeled succinate or 4-labeled glutamate.

Deuterium↗