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Biomedical subjects

A Favier

Publications and source records attributed to A Favier.

At least 163 records · Page 9Linked to original sources
PubMed1992

[Effect of folic acid and folinic acid on zinc absorption].

We have investigated the effect of folic and folinic acids on intestinal zinc absorption in humans, using zinc tolerance tests. Zinc (30 mg) as the gluconate was given by mouth to 10 healthy subjects, alone (1), with 200 mg of folic acid (2) or with 200 mg of folinic acid (3). The zinc/folate molar ratio was 1:1. These three oral loading doses were given after overnight fasting to each of the 10 subjects, at weekly intervals. Serum zinc was measured at 0, 1, 2, 3, 6, 12 and 24 h. Zinc was also determined in urine collected for a 6-hour period following the ingestion of oral loading dose. The results do not indicated any inhibition of zinc absorption and urinary zinc excretion by folates. The areas under the curves varied from 48.2 +/- 20.0 mumol/6 h (1) to 57.0 +/- 10.3 mumol/6 h (3), peak zinc concentration from 28.8 +/- 7.3 mumol/l (1) to 32.1 +/- 4.1 mumol/l (3), half-life from 3.12 +/- 1.12 h (3) to 3.42 +/- 1.48 h (1), elimination rate constant from 0.22 +/- 0.08 (1) to 0.24 +/- 0.07 (3), mean urinary zinc excretion from 58.1 mumol/6 h (2) to 98.7 mumol/6 h (1) and mean zinc clearance from 1.15 l/h (3) to 3.26 l/h (1). All these indices were not statistically significantly different among the three different loading doses.

Absorption↗
PubMed1992

Development of a simple antioxidant screening assay using human skin fibroblasts.

The purpose of this study was to develop a simple antioxidant screening assay for quantifying the protective effects of antioxidant enzymes, inhibitors and scavengers against extracellularly generated oxygen species on human skin fibroblast cytotoxicity. Different in vitro oxidative stresses have been studied: xanthine oxidase-hypoxanthine, flavin mononucleotide-NADH, and hydrogen peroxide. Cytotoxicity and protection were evaluated by two procedures: evaluation of the living cells using a colorimetric method (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT), and ability of the viable cells to adherate and proliferate. Hypoxanthine-xanthine oxidase and H2O2 induced a dose dependent cytotoxicity only when we considered the delayed toxicity. The influence of the cell density was also investigated. The delayed toxicity was higher when cell density increased. One hundred percent protection against free radical cytotoxicity induced by the three systems were obtained with catalase (500 U/ml). When the oxidative stress used was H2O2 90-96% protection was obtained with deferoxamine an iron chelating agent that prevents iron catalysed radical reactions. Using the colorimetric method no significant protection was obtained when SOD was added before and during the stresses. Using the fibroblasts ability to proliferate SOD (10-150 micrograms/ml) reduced xanthine oxidase (20 U/l)-hypoxanthine (0.10-0.30 mM) or H2O2 (1-6 mM) cytotoxicity by 15-20%. SOD did not act as antioxidant when the applied stress was mediated by flavin. In this study we showed a paradoxical effect and the cytotoxicity of flavin-NADH system increased when we added SOD to the cell medium. This simple and reliable antioxidant screening assay required no costly or radioactive equipment.

Catalase↗
PubMed1992

Problems associated with the use of exclusion-diffusion chromatography for identification of zinc ligands in human milk.

The effect of operating conditions used in gel filtration, i.e. the type of gel and elution buffer, on the qualitative and quantitative distribution of zinc in human milk was studied. The gels used were Sephadex G10 and G15, Biogel P2 and Trisacryl GF05. The three elution buffers used were 0.05 M Tris-HCl, pH = 7.4, 0.05 M Tris-acetate, pH = 7.4 and 0.1 M ammonium acetate, pH = 6.5. Ultrafiltration was used as an additional technique for the verification of a number of the results obtained. Zinc ligands in human milk are, possibly, serum albumin and citric acid. The results showed a gel effect, which was greater on the identification and quantitation of the low molecular-weight ligand (the percentage of zinc associated with citric acid was lower with Biogel P2). The elution buffer had a considerable effect, particularly when quantifying the protein-bound fraction. The percentage of zinc coeluted with proteins decreased when the elution buffer contained acetate ions. The combination of Sephadex G15 and 0.05 M Tris-HCl, pH = 7.4 was found to be the best compromise. Zinc distribution with this system was 35-44% of zinc coeluted with proteins and 18-22% with citric acid.

Chromatography, Gel↗
PubMed1992

[Comparison of different methods for serum folate assay].

Folates were determined in 148 patient sera, using four different methods: a microbiological assay (Reference Method), two radioassays (Magic B12 FOL [NB] and SimulTRAC SNB no boil kits) and a non isotopic competition method (Magic Lite kit). Folate mean varied according to the methods 10.0 nmol.l-1 (reference method), 12.2 nmol.l-1 (Magic Lite), 8.7 nmol.l-1 (Magic B12 FOL [NB]) and 10.8 nmol.l-1 (SimulTRAC SNB NO boil). Poor correlations were also noted (0.83 < r < 0.95, figures 1 and 2). Differences between methods were explained according to the literature.

Bacteriological Techniques↗
PubMed1992

Malondialdehyde kit evaluated for determining plasma and lipoprotein fractions that react with thiobarbituric acid.

The determination of thiobarbituric acid reactants (TBARs) is a widely used method for investigating overall lipid peroxidation. An assay kit that could be used with plasma and lipid fractions would facilitate standardization of the method. The results reported here indicate that the malondialdehyde (MDA) kit manufactured by Sobioda (Grenoble, France) complies with criteria of good analytical practices. The detection limit was 0.11 mumol of MDA per liter of plasma. The within-run (CV = 1.8-3.3%) and between-run (CV = 3.3-4.4%) precisions were acceptable. The analytical recovery of MDA after supplementing human plasma samples with tetraethoxypropane standards varied from 88% to 100%. The mean (SD) lipoperoxide concentration determined in 32 healthy adults, ages 20-40 years, was 2.51 (0.25) mumol/L. No significant sex-related difference was noted: 2.57 (0.28) in men vs 2.44 (0.20) mumol/L in women. Applying the method to lipid fractions showed that lipoprotein fractions contain relatively little MDA: 0.07 (0.03) mumol/L of plasma for very-low-density lipoproteins and 0.19 (0.10) mumol/L for low-density lipoproteins.

Adolescent↗
PubMed1991

Simultaneous determination of retinol, alpha-tocopherol and beta-carotene in serum by isocratic high-performance liquid chromatography.

A simultaneous determination of retinol, alpha-tocopherol and beta-carotene in serum by high-performance liquid chromatography is described. Total analysis time is 13 min. A reversed-phase (Ultrasphere ODS, 5 microns) column is used with a mobile phase of acetonitrile-methanol-dichloromethane (70:10:20, v/v/v) and a flow-rate of 1.2 ml/min. Retinol is monitored at 325 nm, alpha-tocopherol at 292 nm and beta-carotene at 450 nm. Serum is deproteinized with ethanol containing the internal standard (alpha-tocopherol acetate), then extracted with hexane. The evaporated organic layer is reconstituted with the mobile phase and injected. The choice of the eluent is discussed, as well as the choice of an internal standard and the need for an antioxidant during the extraction step. Sixteen different eluents are compared in terms of analysis time and selectivity. The linear concentration ranges (retinol 0.016-13.7 microM, alpha-tocopherol 0.18-91.8 microM, beta-carotene 0.05-5.75 microM), within-run coefficients of variation (retinol less than 7%; alpha-tocopherol less than 8%, beta-carotene less than 7%), between-run coefficients of variation (retinol less than 13%, alpha-tocopherol less than 9%, beta-carotene less than 8%) and recoveries (retinol greater than 95%, alpha-tocopherol greater than 91%, beta-carotene greater than 80%) are suitable for clinical investigations. Serum reference values were found to be 2.47 +/- 0.61 microM (retinol), 30.5 +/- 6.8 microM (alpha-tocopherol) and 0.91 +/- 0.55 microM (beta-carotene). A significant difference (p less than 0.001) between males and females was found for retinol.

Carotenoids↗
PubMed1991

Effect of an acute zinc depletion on rat lipoprotein distribution and peroxidation.

The aim of this study was to determine the extent to which zinc depletion leads to lipoprotein modifications by measuring both lipoprotein-fraction distribution and peroxidation in zinc-depleted rats. The animals were divided into three groups and fed for 8 wk a zinc-adequate diet (100 ppm) ad libitum (AL), a zinc-deficient diet (0.2 ppm) ad libitum (ZD), or a zinc-adequate diet according to the pair feeding method (PF). Trace-element status, tissular lipids, and lipoprotein-fraction study were performed. The MDA production by the lipoprotein fraction was measured before and after induced peroxidation. Cholesterol and phospholipids were increased in ZD rats. An important increase of VLDL and IDL was observed and a significant enhanced production of MDA by the LDL was related to zinc deficiency. From this observation, we may conclude that LDL fractions of ZD rats are more susceptible to induced oxidative damage. These results suggest that in zinc deficiency, the lipoprotein fragility is an aggravating factor of peroxidation and the dyslipoproteinemia may lead to an atherogenic risk.

Animals↗
PubMed1991

Parenteral supplementation with zinc in surgical patients corrects postoperative serum-zinc drop.

Zinc has been known for a long time to facilitate wound healing. But, so far, supplementation trials in patients treated by major severity surgery gave either partial or controversial results. In a double-blind, randomized study including 30 patients, we show that zinc supplements (30 mg/d for 3 d) administered by a drip correct postoperative drop of serum zinc, that this correction concerns the available part of serum zinc (i.e., zinc that is bound to compounds other than alpha-2 macroglobulin in serum), and that this supplementation can improve clinical wound healing. Possible influence of increased urinary output after the intervention is discussed, and we found that serum cortisol remains stable when zinc/albumin ratio is stable, and increases sharply when the same ratio drops. Cortisol, therefore, seems to play a major role in zinc redistribution after surgery.

Aorta, Abdominal↗
PubMed1991

Zinc deficiency, ethanol, and myocardial ischemia affect lipoperoxidation in rats.

The production of oxygen free radicals can be stimulated by excess iron, cadmium, nickel, and the like. Inversely, copper, zinc, and selenium inhibit production, either via their own action or via antiradical metalloenzymes. The study involved determining the effect of zinc deficiency combined with chronic ethanol administration on the status of blood and tissue free radicals, as well as on cardiac function in isolated, perfused rats' hearts. Animals were fed a basic diet containing residual zinc at 0.2-0.3 ppm. Following a zinc deficiency lasting 5 wk, which during the last 4 wk was accompanied by chronic ethanol administration, hearts were submitted to ischemia for 30 min in vitro, followed by reperfusion. Biochemical analyses (zinc, superoxide dismutase, malondialdehyde, conjugated dienes, and so on) were performed in the blood and in the homogenates of different organs. The experimental zinc deficiency caused a slight decrease of superoxide dismutase activity, accompanied by increased production of peroxidated lipids. Ethanol administration appeared to increase the levels of peroxidated lipids in the heart. Finally, the combination of zinc deficiency and ethanol administration had very harmful effects, especially on lipid peroxidation and contractile function of the isolated, perfused heart in preischemic conditions.

Alkaline Phosphatase↗
PubMed1991

Acute infusions of bile salts increase biliary excretion of iron in iron-loaded rats.

The mechanisms of biliary excretion of iron are not well known. The aim of this study was to examine the effect of choleresis induced by several agents on biliary iron excretion in iron-loaded rats. Iron overload was obtained with a diet supplemented by 3% iron carbonyl during a 6-week period. Bile was collected with an external bile fistula. Biliary iron concentration was measured by atomic absorption spectrophotometry, and hepatic iron concentration was measured by a chemical method. Compared with controls, iron overload resulted in a 14-fold increase in hepatic iron concentration but only a 3.9-fold increase in biliary iron output. In iron-loaded rats, taurocholate infusion caused a 1.8-fold significant increase in biliary iron output. Dehydrocholate, given at the same dose, induced a significant but less pronounced (1.3-fold) increase in biliary iron output in spite of a higher bile flow. Taurochenodeoxycholate, tauroursodeoxycholate, and tauro-7-ketolithocholate induced an increase in biliary iron output similar to that observed with taurocholate. The canalicular bile salt-independent choleretic dihydroxydibutyl ether caused a significant but less pronounced increase in biliary iron output (1.4-fold). These results confirm that in iron-loaded rats biliary iron excretion is increased much less than hepatic iron concentration. They show that in iron loaded rats (a) bile salts can increase biliary iron secretion, and (b) this increase is related in part to choleresis and in part to bile salts themselves. This increase may be related to an interaction of iron with bile salt monomers and/or micelles.

Animals↗
PubMed1991

Trace elements and lipid peroxidation abnormalities in patients with chronic renal failure.

Plasma selenium (Se), zinc (Zn) and copper (Cu) levels and antioxidant metalloenzymes, glutathione peroxidase (GPX) and superoxide dismutase (SOD), were studied in 17 patients on maintenance hemodialysis (HD) (group I), 14 uremic patients (group II) and 14 healthy subjects (group III). Plasma Se levels and erythrocyte GPX were significantly lower in the HD group (for Se: 0.69 +/- 0.12 vs. 1.05 +/- 0.13 mumol/l in controls; for erythrocyte GPX: 34.4 +/- 6.4 vs. 49.2 +/- 9 IU/g hemoglobin in controls) and a significant correlation was found between the two parameters (r = 0.66, p less than 0.005). There was also a correlation between decreased plasma Zn and erythrocyte SOD activity (r = 0.58, p less than 0.02) and between decreased plasma Cu and erythrocyte SOD (r = 0.60, p less than 0.02). Plasma malondialdehyde levels were augmented in HD patients (5.08 +/- 0.26 vs. 2.55 +/- 0.15 mumol/l in controls and 2.79 +/- 0.40 mumol/l in the uremic group). The catalase activity was increased in HD patients (202 +/- 24 vs. 140 +/- 40 IU/mg hemoglobin in group III). A defective antioxidant activity may thus contribute to increased peroxidative damage to cells in the course of dialysis.

Adult↗
PubMed1991

Selenium bioavailability as selenite (74Se) and as a selenium drug (76Se) by stable isotope methodology.

Many forms of selenium supplement are commercialized. The purpose of this work was to study the bioavailability of one selenium drug, "Granions de Sélénium", as compared with sodium selenite. Each product was labelled with enriched stable isotopes, and by means of gas chromatography/mass spectrometry (GC/MS), the metabolism of the two forms was followed simultaneously. In a first study, the absorption of a single dose of 480 micrograms Se (Na-Selenite) containing 100 micrograms of 74Se was compared with that of 480 micrograms Se (Granions) containing 100 micrograms of 76Se. Measurement precision was mediocre and only apparent absorption, urinary excretion and body retention could be measured. In a second experiment, kinetic studies were performed after a single oral dose of 100 micrograms of 74Se (Na-selenite) and 100 micrograms of 76Se (Granions). Blood, urine and feces samples were collected for a week to determine the true absorption, plasma half-life, and turnover of these two compounds. No significant difference in the metabolism of selenium was observed between "Granions de Sélénium" and selenite. Both present two maximal absorption peaks at 6 h and 12 h and a bioavailability of 76%.

Adult↗
PubMed1990

Kawasaki disease and oxidative metabolism.

The plasmid lipid peroxidation products: malonyldialdehyde (MDA), organic hydroperoxides (OHP) and zinc peripheral values were analysed in seven children with Kawasaki disease, in the acute phase, before and after treatment with intravenous immunoglobulins. In the acute phase, plasma levels of MDA (2.95 +/- 0.30 mumol/l, control group: 2.52 +/- 0.08 mumol/l) and OHP (235 +/- 65 mumol/l, control group: 120 +/- 10) were increased (p less than 0.05 and p less than 0.01). Moreover, plasma zinc levels were significantly decreased (10 +/- 2.15 mumol/l versus 15.6 +/- 2.5 mumol/l in control group, p less than 0.05). After treatment with immunoglobulins, MDA, OHP and plasma zinc levels returned to normal. The parallel normalisation of clinical injury draws attention to the possible role of oxygen intermediates in connective tissue degradation and in the pathogenesis of vascular abnormalities in Kawasaki disease.

Acute-Phase Reaction↗
PubMed1990

Determination of the major zinc fractions in human serum by ultrafiltration.

In this paper we report a method for measuring ultrafiltrable zinc in human serum by electrothermal atomic absorption spectrophotometry. We show also that ultrafiltration permits to determine alpha-2-macroglobulin bound zinc and loosely bound zinc if a strong zinc ligand (EDTA) is added to serum before ultrafiltration. This last fraction, after deduction of ultrafiltrable zinc, represents roughly all albumin bound zinc. In 20 controls we found that ultrafiltrable zinc amounted 0.311 mumol/L (S.D. = 0.117 mumol/L), alpha-2 macroglobulin bound zinc 3.08 mumol/L (S.D. = 0.221 mumol/L), and albumin bound zinc 12.11 mumol/L (S.D. = 1.95 mumol/L). Our method needs only a small volume of serum, it is simple and rapid but also very accurate and reliable. The loosely bound fraction is very dynamic and, representing the physiologically active part of serum zinc, it could be a good marker of zinc deficiency.

Biomarkers↗