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C Besson

Publications and source records attributed to C Besson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Plasma metabolites of quercetin and their antioxidant properties.

Quercetin is one of the most widely distributed flavonoids present in fruits and vegetables. The present experiments were performed on rats adapted for 3 wk to a semipurified diet supplemented with 0.2% quercetin. The major part of the circulating metabolites of quercetin (91.5%) are glucurono-sulfo conjugates of isorhamnetin (3'-O-methyl quercetin; 89.1 +/- 2.1 microM) and of quercetin (14.7 +/- 1.7 microM); the minor part (8.5%) is constituted by glucuronides of quercetin and its methoxylated forms (9.6 +/- 2.3 microM). Conjugated dienes formation, resulting from Cu2+-catalyzed oxidation of rat very low density lipoproteins + low density lipoproteins (LDL), was effectively inhibited in vitro by conjugated metabolites of quercetin. These metabolites appeared to be four times more potent than trolox in inhibiting LDL oxidation. Moreover, the plasma from rats adapted to a diet containing 0.2% quercetin exhibited a total antioxidant status markedly higher than that of control rats (+60%). This study shows that ubiquitous quercetin is conjugated in vivo, yielding metabolites that exhibit antioxidant properties. Thus the health benefits of flavonoids in foods can be due to the antioxidant properties of their metabolites.

Animals↗
PubMed1997

Striatal dopaminergic changes depend on the attractive or aversive value of stimulus.

Using a conditioned aversion paradigm we reported previously that dopaminergic (DA) responses were opposite in the core part of the nucleus accumbens depending on the affective value of the stimulus. The opposite responses were more marked in the left hemisphere. Anatomo-functional similarities between the core part of the nucleus accumbens and the dorsal striatum have been described. In the present study we tested the hypothesis that DA responses in the left ventromedial part of dorsal striatum (VMS) depend on the affective value of the stimulus. Responses of DA neurons were studied using in vivo voltammetry coupled with computer-assisted numerical analysis. A rapid and marked DA increase and a delayed DA decrease were observed in rats presented to the appetitive and the aversive olfactory stimulus, respectively.

Animals↗
PubMed1997

[Gender control and Olympics events from Albertville to Atlanta or good practices in gene biochemistry].

Gender verification in sport was introduced in 1967 based on the insufficient Barr test. For Albertville's Olympic Games we proposed the Medical Commission of IOC to carry out the control for the first time thanks to molecular biochemistry. PCR/SRY amplification is described giving more than 99.9% of good results. After Albertville, Barcelona and Lillehammer the method will be used in Atlanta and Nagano. Results and ethics are discussed. Easy and respectful of athletes, this reliable gender verification is indispensable for their protection. According to the good practices of CM/IOC, samples have to be discarded after the analysis is done.

Ethics, Medical↗
PubMed1996

Synthetic peptide substrates for a conductimetric assay of Pseudomonas aeruginosa elastase.

Pseudomonas aeruginosa is a zinc metalloprotease which may be involved in many infection processes, especially in the lung. In order to evaluate the production of the enzyme in culture supernatants, we developed an assay using peptide derivatives; the conductimetric method was used for monitoring the enzymatic activities. Tetrapeptide derivatives were enzymatically synthesized by coupling Z-Ala2 and X-AlaR using either thermolysin or P. aeruginosa elastase itself. In these substrates, X could be phenylalanine, tyrosine, or leucine and C-protection was performed by either an amide (NH2) or a methyl (OMe) group. Z-Ala2-Phe-AlaNH2 was found to be the best substrate, giving a catalytic ratio kcat/KM of 8600 mM-1.s-1. The evaluation of the alkaline protease activity with this substrate showed that the catalytic ratio is 1000-fold lower. The sensitivity of the conductimetric method was also demonstrated with as little as 1 nM elastase (0.13 microgram), being easily and accurately detected (SD, 3.8% for 10 measurements). Furthermore, the enzymatic activity was measured in a culture supernatant from a clinical strain.

Amino Acid Sequence↗
PubMed1996

Transmission of Plasmodium falciparum by allogeneic bone marrow transplantation.

We describe a case of Plasmodium falciparum infection in a Comorian patient undergoing BMT. The patient's last visit to an endemic area was 1 year prior to BMT. The donor left the Comoro Islands 2 months before marrow harvesting. They had both had previous episodes of malaria and were seropositive for Plasmodium falciparum. At the time of BMT, blood smears were negative in both the donor and recipient. On day 12 post-BMT the patient was asymptomatic but a blood smear revealed 12.5% parasitemia. We consider that donors and recipients at risk pre-BMT should routinely be given specific treatment before marrow harvesting and conditioning, independent of the appearance of blood smears.

Adult↗
PubMed1995

Asymmetrical involvement of mesolimbic dopaminergic neurons in affective perception.

Pharmacological studies suggest that increases and decreases in dopamine levels in the nucleus accumbens contribute to positive and negative affective states, respectively. In vivo neurochemical investigations have led to contradictory conclusions, since increases and decreases in dopamine release have been observed in aversive situations. Clinical and experimental observations argue for a hemispheric asymmetry in the processing of appetitive and aversive stimuli. Mesolimbic dopaminergic neurons are part of integrative networks which appear specifically organized in the right and left hemispheres. Dopaminergic neurons may thus be involved in affective processes but in a different manner in the two hemispheres. We tested this hypothesis in the nucleus accumbens of male rats using in vivo voltammetry and a conditioned aversion paradigm to an olfactory stimulus. We found that dopaminergic responses were similar in the two hemispheres following the initial encounter with the stimulus. After conditioning, however, dopaminergic responses to a naturally attractive olfactory stimulus were more elevated in the right nucleus accumbens and responses to an aversive stimulus more marked in the left nucleus. In addition, dopaminergic responses displayed an intraaccumbal regionalization, in particular opposite variations were obtained in the core and shell subterritories in response to the aversive situation. These results may provide new insights in the understanding of the relative contribution of the two hemispheres in affective perception in normal and psychopathological conditions.

Affect↗
PubMed1995

Effect of propionate on fatty acid and cholesterol synthesis and on acetate metabolism in isolated rat hepatocytes.

In the present study the actual role of propionic acid in the control of fatty acid and cholesterol synthesis was investigated in isolated liver cells from fed rats maintained in the presence of near-physiological concentrations of glucose, glutamine and acetate. Using 3H2O for lipid labelling, propionate appears as an effective inhibitor of fatty acid synthesis and to a lesser extent of cholesterol synthesis, even at the lowest concentration used (0.6 mmol/l). Butyrate is a potent activator of both synthetic pathways, and the activating effect was not counteracted by propionate. Using 1-[14C]acetate, it was observed that propionate at a moderate concentration, or 1 mmol oleate/l, are both very effective inhibitors of 14C incorporation into fatty acid and cholesterol. This incorporation was drastically inhibited when propionate and oleate were present together in the incubation medium. The net utilization of acetate by rat hepatocytes was impaired by propionate, in contrast to oleate. 1-[14C]butyrate was utilized at a high rate for fatty acid synthesis, but to a lesser extent for cholesterol synthesis; both processes were unaffected by propionate. Intracellular citrate concentration was not markedly depressed by propionate, whereas it was strongly elevated by butyrate. In conclusion, propionate may represent an effective inhibitor of lipid synthesis when acetate is a major source of acetyl-CoA, a situation which is encountered with diets rich in readily-fermentable fibres. The present findings also suggest that propionate may be effective at concentrations close to values measured in vivo in the portal vein.

Acetates↗
PubMed1994

Quercetin exerts a preferential cytotoxic effect on active dividing colon carcinoma HT29 and Caco-2 cells.

The effect of the naturally occurring flavonol, quercetin, was investigated on cell growth and metabolism of two human carcinoma cell lines, HT29 and Caco-2 cells, both during the exponentially growing phase and after confluence. Our results show clearly that, after a 48-h period of treatment, quercetin (in the range of concentration from 15 microM to 120 microM) exerted a preferential cytotoxic effect on active proliferating cells. This effect was dose dependent and was accompanied by a simultaneous inhibition of lactate release and a dramatic decrease of total cellular ATP content. In contrast, in confluent cells, quercetin failed to affect cell viability or lactate release, but led nevertheless to a depletion of cellular ATP level. In conclusion, the cytotoxicity of quercetin is markedly higher in actively growing cells in comparison with confluent cells.

Adenosine Triphosphate↗
PubMed1994

Importance of the modulation of glycolysis in the control of lactate metabolism by fatty acids in isolated hepatocytes from fed rats.

In liver cells from fed rats, lactate utilization depends on its extracellular concentration and the threshold concentration at which lactate uptake equilibrates release is about 3 mM. Even-chain fatty acids (butyrate, octanoate, or oleate) played a crucial role (i) to depress the lactate release, from 40% (butyrate or oleate) to 72% (octanoate), and (ii) to lower the threshold concentration for lactate utilization (down to 1 mM with octanoate). The effects of fatty acids were connected to their inhibition of hepatic glycolysis, estimated by the detritiation of [6-3H]glucose (about -30% with butyrate or oleate and -45% with octanoate). Fatty acids depressed the cellular concentration of pyruvate which, at physiological concentration of lactate, favors its utilization. The rise in ketone bodies concentration in response to fatty acids reflected an enhanced acetyl CoA production, resulting in an accumulation of citrate. In parallel there was a drop of the cellular concentration of fructose 2,6-biphosphate. As a result, there was an inhibition of the flux through 6-phosphofructo-1 kinase (50, 75, or 40% inhibition with butyrate, octanoate, or oleate, respectively). The other regulatory glycolysis steps, catalyzed by glucokinase and pyruvate kinase, were not affected by fatty acids. Inhibition of hepatic glycolysis by fatty acids seems connected to acetyl-CoA generation since octanoate, readily metabolized to acetyl-CoA and ketone bodies by hepatocytes, had a more potent stimulatory effect on the hepatic uptake of lactate than butyrate or oleate. Propionate, which yields practically no acetyl CoA, slightly stimulated lactate release and elevated the threshold of lactate utilization. The present data suggest thus that, in hepatocytes from fed rats, fatty acids effectively inhibit glycolysis and switch liver cell metabolism toward gluconeogenic conditions, which promotes lactate utilization.

Acetyl Coenzyme A↗
PubMed1994

The gender-marking effect in spoken word recognition.

In this paper we examine whether the recognition of a spoken noun is affected by the gender marking--masculine or feminine--that is carried by a preceding word. In the first of two experiments, the gating paradigm was used to study the access of French nouns that were preceded by an appropriate gender marking, carried by an article, or preceded by no gender marking. In the second experiment, subjects were asked to make a lexical decision on the same material. A very strong facilitatory effect was found in both cases. The origin of the gender-marking effect is discussed, as well as the level of processing involved--lexical or syntactic.

Adult↗
PubMed1994

[Evaluation of the diagnostic contribution of a test. Main information indices].

Evaluating a new diagnostic test is an essential step required before using a new examination technique. The information concerning the disease provided by the test must be examined in terms of diagnostic value and cost. A test can be evaluated using several indexes. For tests giving binary results, the main information indexes were defined and the calculation of the index was illustrated by an example. The sensitivity, specificity, the Youden index, and the positive and negative predictive values were presented together with the likelihood and odds-ratio. For tests giving quantitative results, the analysis of the ROC curves was discussed. Indexes were interpreted in terms of disease prevalence, the modalities (diagnosis, screening) for applying the test, the sampling technique for the tested population, the gain in diagnosis, and cost of the examination.

Diagnosis↗
PubMed1993

Work disability among adults with asthma.

OBJECTIVE: To estimate the incidence of work disability among adults with asthma and to evaluate a clinically based illness severity score as a predictor of such disability. DESIGN: Baseline and follow-up telephone interviews and medical record review. SETTING: University-based outpatient pulmonary specialty practice. PATIENTS: Fifty-six patients interviewed at baseline; 42 reinterviewed 2 years later. MEASUREMENTS: Work disability ascertained by interview report and defined as change in job duties, reduction in pay, or change in job or employment status attributed to asthma. Severity of asthma score derived from medical records and based on respiratory symptom frequency, asthma history, and prescribed medications. Pulmonary function by routine testing. Logistic regression analysis of the 5-year incidence of work disability on severity score and forced expiratory volume in 1 s (FEV1). RESULTS: The 5-year work disability cumulative incidence was 19 percent for change in duties, 17 percent for reduction in pay, 20 percent for change in job or work status, and 36 percent for any of these measures. The median asthma score was 10 (range, 2 to 26). The mean FEV1 as a percent predicted (FEV1 percent) was 88 +/- 25 percent. Score and FEV1 percent were statistically correlated (r = -0.6, p < 0.0001). Severity of asthma score statistically predicted each measure of work disability (p < 0.01). Addition of FEV1 percent added little additional explanatory power to the logistic regression model (maximum chi 2 = 1.3, p > 0.2). CONCLUSIONS: Work disability is common among adults with asthma. A severity of asthma score based on clinical variables is statistically correlated with lung function but appears to be a stronger predictor of disability than airflow measured at one point in time.

Adolescent↗
PubMed1993

Peptide synthesis catalysed by Pseudomonas aeruginosa elastase.

Pseudomonas aeruginosa elastase was used for peptide-bond synthesis with benzyloxycarbonylalanine and amino acid amides as nucleophilic substrates. Dipeptide-bond synthesis was observed only for hydrophobic amino acid amides. The rate of peptide synthesis, measured by h.p.l.c., was in the decreasing order: Phe > Leu > Tyr > Val, Ile > Ala, which is consistent with the decreasing order of hydrolysis rates of the corresponding tetrapeptides Ala-Ala-Xaa-Ala. In contrast with thermolysin, Ps. aeruginosa elastase permits the synthesis of tyrosine-containing peptides with tyrosine in the P'1 position. Furthermore, the rates of synthesis for other hydrophobic amino acid amides are higher with elastase than with thermolysin.

Amino Acid Sequence↗
PubMed1992

Purification and characterization of recombinant pyrrolidone carboxyl peptidase of Bacillus subtilis.

Bacillus subtilis pyrrolidone carboxyl peptidase (Pcp) overexpressed in Escherichia coli was purified to homogeneity in less than 12 h using ammonium sulphate precipitation and hydrophobic interaction chromatography. The enzyme, which removes amino-terminal L-pyroglutamic acid from peptides, appears to be a tetramer of 25,200 molecular mass subunits. The protein cross-reacted with polyclonal antibodies raised against Pcp from Streptococcus pyogenes. The overexpressed enzyme exhibits an absolute substrate specificity towards N-terminal pyroglutamyl residues with a Michaelis constant of 1.04 mM for L-pyroglutamyl-beta-naphthylamide. The enzyme could be used for the removal of pyroglutamyl residues that block amino termini of proteins and peptides before performing Edman sequential degradation.

Amino Acid Sequence↗
PubMed1992

Control of glycogen metabolism by gluconeogenic and ketogenic substrates in isolated hepatocytes from fed rats.

1. This study was conducted to examine the effects of gluconeogenic and ketogenic substrates on the activities of the glycogen-metabolizing enzymes and on glycogenolysis in isolated hepatocytes from fed rats. 2. Gluconeogenic substrates like fructose, dihydroxyacetone or lactate turned out to stimulate the glucose-induced activation of glycogen synthase and this effect may be linked, to some extent, to the increase of the cellular glucose 6-phosphate concentration. 3. The effect of fructose was accompanied by the onset of glycogen synthesis. 4. Energetic substrates like fatty acids were also potent activators of glycogen synthase, especially in the presence of glucose. 5. When fatty acids were added alone or together with a physiological concentration of glucose, they induced or potentiated the inhibition of glycogen phosphorylase-a. 6. This inhibitory effect was mediated by a decrease of lactate release. 7. The stimulatory effect of amino acids on glycogen synthase seemed to be direct, non mediated by an inhibition of the phosphorylase-a activity although hepatic glycogenolysis markedly decreased. 8. Moreover, the amino acid action could be linked to their capacities to induce cell swelling and/or to limit proteolysis.

Amino Acids↗
PubMed1991

Hydrolysis of alanine oligomers and of elastin by P. aeruginosa proteinases and thermolysin.

The hydrolysis of alanine oligomers by P. aeruginosa proteinases, thermolysin and porcine pancreatic elastase was studied. The concentrations of substrates and cleavage products were determined using reverse phase high pressure liquid chromatography. Tetraalanine was the shortest oligomer for which we could demonstrate hydrolysis by all the proteinases, except for porcine pancreatic elastase which only significantly hydrolyzed peptides longer than hexaalanine. Porcine pancreatic elastase hydrolyzes hexaalanine at a single site, whereas the other enzymes may split it either into two trialanine molecules, or into di- and tetraalanine, the latter being further cleavable to dialanine. A kinetic model based on first-order kinetic rate constants is proposed and the individual constants determined. Although P. aeruginosa elastase and thermolysin are closely similar in structure, they have shown a marked difference in their hydrolysis of either elastin or tetraalanine. Elastolytic activity of thermolysin was higher than that of elastase but tetraalanine was hydrolyzed more slowly by thermolysin.

Alanine↗
PubMed1990

[Transient reduction of ventricular tachycardia with adenosine-5'-triphosphate. A possible action of ATP on purinergic receptors].

The authors report the case of a 46 year old man in whom a regular, wide complex tachycardia was terminated temporarily by the injection of adenosine-5'-triphosphate (ATP:Striadyne); endocavitary electrophysiological studies showed the tachycardia to be of ventricular origin. After aminophylline, an inhibitor of certain purinergic receptors, the tachycardia could be reproduced at will and was sustained whereas only short runs of tachycardia could be induced under basal conditions. The mode of action of the ATP on this type of tachycardia could be a direct effect of the molecule on the purinergic receptors specifically inhibited by aminophylline.

Adenosine Triphosphate↗