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Biomedical subjects

A Nouvelot

Publications and source records attributed to A Nouvelot.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of preterm infant formula supplementation with alpha-linolenic acid with a linoleate/alpha-linolenate ratio of 6: a multicentric study.

OBJECTIVE: To investigate the effects of a milk formula supplemented with a alpha-linolenic acid (ALA) (18:2 n-6/18:3 n-3 ratio near 6/1) on plasma and red blood cell (RBC) fatty acids (FAs) in premature infants and compare with a non supplemented formula (18:2 n-6/18:3 n-3 = 22/1). DESIGN AND SUBJECTS: Infants of mothers who elected not to breast-feed were randomly assigned to either a high alpha linolenic formula (HLF: n = 31) group or a low alpha-linolenic formula (LLF: n = 32) control group. Infants fed human milk (HM: n = 25) were enrolled concurrently as a reference group. Anthropometric and biological measurements were made after two days (D2) and 15 d (D15) of enteral feeding and at the 37th week (W37) of postconceptual age. In HLF, the 18:3 n-3 content was 1.95% of total FAs (0.77% of total energy) and the 18:2 n-6/18:3 n-3 ratio was near 6/1. In LLF, the 18:3 n-3 content was 0.55% of total FAs (0.22% of total energy) and the 18:2 n-6/18:3 n-3 ratio was 22/1. RESULTS: ALA supplementation had minimal effect on the n-6 series, did not alter the anthropometric data and confirmed the conversion of ALA into docosahexaenoic acid (DHA). Throughout the study, it maintained, the RBC membrane DHA values within the confidence interval of those obtained in the HM group. Such was not the case with LLF CONCLUSION: alpha-linolenic acid supplementation (from Rapeseed oil and in a 18:2 n-6/18:3 n-3 ratio = 6) in premature infant formula can contribute efficiently to the maintenance of the n-3 status in the premature newborns.

Chromatography, Gas↗
PubMed1996

Cytotoxic effects of an oxidative stress on neuronal-like pheochromocytoma cells (PC12).

Although the generation of oxygen derivatives during ischemia and reperfusion is generally held as a major event in the process leading to neuronal death, the biochemical mechanisms responsible for cell degeneration remain poorly understood. To better understand the toxicity induced by oxidative stress in neural tissue, we have tested the effect of an exogenous hydroperoxide, cumene hydroperoxide (CHP), on the metabolism and viability of PC12 cells. Addition of CHP in the culture medium leads to significant cell death that becomes perceptible at concentrations above 1 microM and reaches a maximum (80-90% toxicity) at 100 microM. A time-course study shows that Trypan blue uptake is preceded by a rapid phase of cell rounding and detachment from the substratum (within 30 min) followed by a progressive uptake of the dye (60-120 min). During this 2-hr period, we failed to observe any major signs of membrane lipoperoxidation (such as MDA production or fatty acid release). On the other hand, we observed that cell death is preceded by a striking decrease in cellular ATP content and in the retention of rhodamine 123 (within 15-30 min of treatment); thus, suggesting that the mitochondria may be the primary target of hydroperoxide action.

Animals↗
PubMed1996

Relationships between red blood cell vitamin E and polyunsaturated fatty acid in the premature infant.

Low-birth-weight infants were fed breast milk (BM, n = 25) for 1 of 2 formulas containing 0.5 (PG, n = 32) or 1.7% fatty acids as alpha-linolenic acid (ALA)(ALA-PG, n = 31). Polyunsaturated fatty acids (PUFA) and alpha-tocopherol (alpha T) of RBC membrane phospholipids were measured at days 2 (D2) and 15 (D15) of enteral feeding, and at term. PUFA concentrations did not differ significantly between the 3 groups from D2 to term. The membrane integrity assessed by the alpha T/phospholipids ratio neither changed with time nor differed between formula groups. A metabolic relationship between alpha T and long-chain PUFA in RBC membranes was suggested by multiple regression analysis: alpha T showed a significant positive correlation with docosahexaenoic acid at D15 and term and with arachidonic acid at D15; the correlation with arachidonic acid tended toward significantly (p = 0.06) at term.

Arachidonic Acid↗
PubMed1995

Modulation of mouse cerebral Na+,K(+)-ATPase activity by oxygen free radicals.

There is increasing evidence that oxygen free radicals (OFR) are involved in cerebral ischaemia-reperfusion injury, possibly via a modulation of Na+,K(+)-ATPase activity, one of the major membrane pumps responsible for ionic homeostasis. We measured OFR-mediated modulation of this enzymatic activity and examined the roles of lipid and/or protein alterations. Using mouse brain microsomes exposed to UV-C irradiation, our results show a good correlation between activity inhibition and lipoperoxidation estimated by PUFA loss as well as malondialdehyde production. The protective effect of thiourea (OH scavenger) and the lack of effect noted with DTT (thiol protector) suggest that the functionality of the Na+,K(+)-ATPase is altered by perturbation of membrane integrity rather than by a structural alteration of the protein itself.

Adenosine Triphosphate↗
PubMed1995

Polyclonal antibodies against malondialdehyde-modified proteins: characterization and application in study of in vitro lipid peroxidation of cellular membranes.

In order to develop an immunofluorescent technique able to detect the cellular damage induced by lipid peroxidation, we produced rabbit polyclonal antibodies (AbAIP) against malondialdehyde (MDA)-modified lysozyme. These antibodies specifically recognized all the MDA-treated proteins tested, but not native proteins or proteins treated by other aldehydes. Moreover, we showed by an enzyme-linked immunosorbent assay (ELISA) that the amount of immunoreactive protein in MDA-treated erythrocytes was proportional to the concentration of MDA added, suggesting that this ELISA measurement may represent a quantitative determination of peroxidative protein alterations. In addition, when coupled to an indirect fluorochrome antibody conjugate [fluorescein isothiocyanate (FITC)], these antibodies permitted precise localization of the modified proteins within the membranes of peroxidized cells.

Animals↗
PubMed1995

Protection of polyunsaturated fatty acids against iron-dependent lipid peroxidation by a Ginkgo biloba extract (EGb 761).

Iron can induce a peroxidative degradation of the membrane polyunsaturated fatty acids by the well-known Fenton reaction. Chelated iron can also form a complex with oxygen, called perferryl ion, which is able to induce lipoperoxidation without a detectable production of hydroxyl radicals. The antioxidant properties of a titrated and standardized extract of Ginkgo biloba leaves (EGb 761) against iron-dependent peroxidative degradation of the membrane polyunsaturated fatty acids were studied. Rat liver microsomes were exposed to a mixture of NADPH, ADP and FeCl3 hypothesized to produce iron-oxygen complexes. The results of the analysis of the microsomal polyunsaturated fatty acids by gas chromatography show that the susceptibility to peroxidation of the different polyunsaturated fatty acids increases with their unsaturation level, and that EGb 761 protects these membrane polyunsaturated fatty acids regardless of their susceptibility to peroxidation. This protective effect is correlated with the decrease in the thiobarbituric acid-reactive substances concentration, but the calculation of the antioxidant potency of EGb 761 as an IC50 value using results of the thiobarbituric acid reaction leads to an underestimated evaluation when the reaction is carried out in the presence of iron ions.

Animals↗
PubMed1992

The biosynthesis of polyunsaturated fatty acids by rat sertoli cells.

1. The biosynthesis of polyunsaturated fatty acids (PUFA) of the n-6 and n-3 series was investigated in cultured Sertoli cells. 18:2n-6, 18:3n-6, 20:2n-6, 18:3n-3 and 20:3n-3 were added individually at a concentration of 20 mumol to culture media. 2. Maximum incorporation of 20- and 22-carbon PUFA into membrane lipids was observed after 72 hr of incubation with all the exogenous substrates used. 3. As reported in other cell systems, the delta 6 desaturation was the first rate-limiting step; the major factor regulating this activity was the concentration of linoleic acid or alpha-linolenic acid in the medium. 4. Our data show that the delta 5-desaturation represents a second regulatory step in PUFA biosynthesis. 5. The sum of n-6 and n-3 PUFA of the 22 carbon chain length constantly represented between 11 and 12% of total fatty acids, regardless of the exogenous substrate used. 6. Our kinetic studies of the incorporation of PUFA of the n-6 and n-3 series did not permit detection of a delta 8 desaturase activity.

Animals↗
PubMed1992

UV-C irradiation-induced peroxidative degradation of microsomal fatty acids and proteins: protection by an extract of Ginkgo biloba (EGb 761).

After exposure of rat liver microsomes to UV-C irradiation, analysis of membrane fatty acids by gas chromatography confirmed that EGb 761, a drug containing a dosed and standardized extract of Ginkgo biloba, provides effective protection against free radical attack in vitro. This analysis, coupled with thiobarbituric acid (TBA) reaction, permitted qualitative and overall quantitative evaluation of radical-induced damage to polyunsaturated fatty acids (PUFA), as well as evidence of the antioxidant properties of the Ginkgo biloba extract. Assay of thiobarbituric acid reactive substances (TBARS) showed a correlation between TBARS concentration and the state of degradation of the polyunsaturated fatty acids. Mannitol (5.5 mM) did not prevent degradation of microsomal PUFA or malondialdehyde (MDA) production, nor did it prevent polymerization of membrane proteins. Low doses of EGb 761 were found to provide efficient protection of membrane PUFA regardless of individual susceptibility to peroxidation. This protection was accompanied by a decrease in the production of TBARS. EGb 761 also protected membrane proteins from the irreversible polymerization induced by these degradation products, but did not appear to prevent thiols oxidation into disulfide bonds.

Animals↗
PubMed1991

Metabolic utilization of linoleate and alpha-linolenate in cultured Sertoli cells.

1. The capacity of cultured Sertoli cells to synthesize long-chain polyunsatured fatty acids (PUFA) from the essential fatty acid (EFA) precursors 18:2 n-6 and 18:3 n-3 was tested, and the concentrations of each EFA required to obtain maximal incorporation into membrane lipids were determined. 2. The two EFA were added to the culture medium as free fatty acids complexed to albumin in a molar ratio of 12:1. 3. When the substrates were added individually, the maximal levels of biosynthesis were obtained with 0.7 micrograms/ml of 18:2 n-6 and 2 micrograms/ml of 18:3 n-3. 4. When the two EFA were added together, clear alterations in the behavior of the desaturases with regard to the n-6 and n-3 fatty acids were observed. 5. It was found that a concentration of 0.35 micrograms/ml of each EFA represented the "ideal" required level in order to ensure optimal incorporation of 22-carbon PUFA into the membrane lipids. 6. These results provide the first data on the definition of EFA requirements for Sertoli cells in culture.

Animals↗
PubMed1990

Partial purification of androgen binding protein from bull epididymis.

An androgen binding protein (ABP), with an equilibrium dissociation constant of 4.2 nM and a molecular weight of about 100 kDa, has been purified from bull epididymal extracts using a four-step procedure. These preliminary results underline the main difficulties encountered in the purification of this protein present at a very low concentration (i.e. 50-fold less than in rat or rabbit epididymides). Ammonium sulfate precipitation is not a suitable step due to the formation, in presence of salt, of insoluble material leading to a loss of ABP. Lipids, particularly phospholipids, might be implicated in this phenomenon. Several steps, including anion exchange in batch followed by concentration, affinity chromatography and HPLC gel filtration allowed us to obtain a 7667-fold purified protein with a 9% yield.

Androgen-Binding Protein↗
PubMed1990

Determination of size and molecular weight distributions of lipoproteins using automatic image analysis and density gradient ultracentrifugation.

A Leitz-Tas automatic image analysis system has been used to investigate the size distributions of human lipoprotein particles isolated by density gradient ultracentrifugation. Computerized image analysis enabled us to obtain more precise determinations of modal diameter and overall range in diameter for each lipoprotein subspecies than those determined by classical methods. In addition, lipoprotein molecular weight distributions were calculated from measurements of flotation density and particle size distributions. This method offers certain advantages over other procedures used to characterize mean molecular weight with regard to the ability to define lipoprotein polydispersity. The method and its limitations are discussed and illustrated with results obtained with human lipoproteins.

Adult↗
PubMed1989

Lipid and apolipoprotein distribution as a function of density in equine plasma lipoprotein.

1. Equine lipoproteins were isolated from plasma by density gradient ultracentrifugation and apolipoprotein composition determined by SDS-polyacrylamide gel electrophoresis. 2. VLDL and IDL were present at low concentration (0.2 mg/ml). Two apoB components of Mr corresponding to human apoB-100 and one apoB-48-like component were represented in VLDL fraction. 3. LDL-1 and LDL-2 subfractions have displayed an almost equal concentration (0.4 mg/ml). Two apoB-100-like components were the major apolipoproteins in each fraction. Small amounts of apoB-48-like component were detectable in LDL-1 and LDL-2. 4. HDL-2 represented a major class of equine lipoproteins (1.8 mg/ml). ApoA-1-like component was the dominant protein in HDL-1, HDL-2 and HDL-3. Dimeric apoA-II-like components were slightly represented in HDL subfractions. 5. HDL-3 displayed the same apolipoprotein pattern as HDL-1 and HDL-2, but two further minor proteins of Mr 20,000 and 14,000 were detected. 6. VHDL represented a minor class of lipoprotein (0.2 mg/ml). ApoA-I-like component was the major apolipoprotein of VHDL. Small amounts of apoA-IV-like, apoE-like, and Mr 55,000 protein were detectable. 7. ApoC-like of Mr lower than 10,000 was represented in all equine lipoprotein classes.

Animals↗
PubMed1987

Analysis of phospholipid transfer during HDL binding to platelets using a fluorescent analog of phosphatidylcholine.

Electron microscopic examination of the interaction of gold labelled HDL with platelets indicates that the internalized lipoprotein becomes closely associated with surface connected canaliculae and endocytic vacuoles. At the same time granule centralization occurs. Using fluorescent derivatives of naturally occurring lipids we have further investigated lipid exchange between HDL and platelets. Analogs of phosphatidylcholine containing fluorescent fatty acids are rapidly transferred from the lipoproteins to the cells and remain at the plasma membrane as long as they are kept at 4 degrees C. However when the platelets are warmed to 37 degrees C, a rapid degradation of the fluorescent lipids occurs, generating fluorescent diacylglycerol as a consequence of the activation of platelet enzymes.

Blood Platelets↗
PubMed1987

Characterization of equine plasma lipoproteins after separation by density gradient.

1. Plasma lipoproteins from six thoroughbred horses were separated by density gradient ultracentrifugation. For each sample, lipoprotein bands were visualized by means of a prestained plasma control and characterized by electrophoretic, chemical and morphological analysis. 2. Very low density lipoproteins (VLDL) were isolated at d less than 1.018 g/ml. 3. Two clearly resolved bands were detected in the low density lipoprotein fraction (LDL). The density limits were evaluated as follows: LDL1(1.028 less than d less than 1.045 g/ml) and LDL2(1.045 less than d less than 1.070 g/ml). Marked differences were observed in the chemical composition and particle size of LDL1 and LDL2 fractions. 4. High density lipoprotein fraction (HDL) was usually isolated as a single band, distributed over the range 1.075 less than d less than 1.180 g/ml. However, chemical composition and particle size revealed heterogeneity in HDL subfractions. 5. The density limit of LDL and HDL bands varied in each animal, indicating differences in equine lipoprotein distribution.

Animals↗
PubMed1987

Qualitative and quantitative alterations of bovine serum lipoproteins with ageing.

1. Plasma lipoproteins from six calves at 8, 43 and 118 days old, six heifers and six cows were separated by density gradient ultracentrifugation. For each sample lipoproteins bands were visualized by prestained control and characterized by electrophoretic, chemical and morphological analysis. 2. Two resolved bands were detected in the low density lipoprotein fraction (LDL). At an early stage of development, LDLI and LDLII were present with almost equal concentration. With ageing, LDLII became the major fraction of LDL lipoproteins. 3. HDL were isolated as a single band distributed over the range 1.064-1.166 mg/ml in young calf and 1.050-1.152 mg/ml in adult. This progressive decrease of density limits with ageing, associated with a decrease of protein content and an increase of phospholipids and cholesteryl esters content, was consistent with higher HDL particle diameters in adult. 4. With ageing, free cholesterol/esterified cholesterol ratio decreased in LDL fractions and increased in HDL fractions.

Aging↗
PubMed1986

Hepatic metabolism of dietary alpha-linolenic acid in suckling rats, and its possible importance in polyunsaturated fatty acid uptake by the brain.

The presence of large amounts of long chain-polyunsaturated fatty acids (PUFA) in the brain implies an exogenous intake of unsaturated fatty acids, either as essential fatty acids, or in the form of higher homologues resulting from hepatic metabolism. To determine the influence of the diet upon the potential availability of polyunsaturated fatty acids to the brain, four different diets were used with comparable amounts of 18:2 n-6, but variable amounts of 18:3 n-3 (0.2, 1, 2 and 9%). These diets were administered to female rats from the day of mating and during the periods of gestation and lactation. Fifteen days after birth suckling animals were killed and the fatty acid distribution was studied in the serum in two lipoprotein classes (VLDL-LDL and HDL). On the whole, an increase in dietary 18:3 n-3 resulted in an increase of polyunsaturated fatty acids of the n-3 series and a decrease in fatty acids of the n-6 series. The modification chiefly concerned the terminal fatty acids in each series (22:5 n-6 and 22:6 n-3). It is noteworthy that the influence of exogenous 18:3 n-3 upon the 20:4 n-6 content of lipoproteins was not significant below 2% of 18:3 n-3 intake, a level that we have previously shown to be both necessary and sufficient to satisfy the requirements of the brain for fatty acids of the n-3 series. In the liver, the intermediary metabolism ensures an important release of long-chain polyunsaturated fatty acids, which may help to satisfy the lipid requirements of the brain.

Animals↗
PubMed1985

[Specific contribution of dietary polyunsaturated fatty acids of the n-3 series to the development of nervous system membranes].

Polyunsaturated fatty acids, especially omega 3 fatty acids, made a specific contribution to the nervous tissue. Retarded intrauterine growth caused a twofold reduction in the oligodendrocyte ratio of omega 3/omega 6 while the same ratio increased by more than twofold in the neurons. A fatty acid-poor diet composed of arachid or sunflower oil dramatically altered the composition of cells and subcellular particles when compared with a soya or rapeseed oil diet containing omega 3 fatty acids; phosphatidylethanolamine was particularly affected. Nerve cell culture showed that brain essential fatty acids are probably docosahexaenoic acid and arachidonic acid.

Animals↗