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Biomedical subjects

M Lefevre

Publications and source records attributed to M Lefevre.

At least 55 records · Page 3Linked to original sources
PubMed1989

Acetylaminofluorene-labelled ribosomal RNA for use in molecular epidemiology and taxonomy.

The use of acetylaminofluorene-labelled 16 + 23S rRNA (from Escherichia coli) is described for determining rRNA-gene-restriction patterns. The labelled probe allowed molecular fingerprinting of bacteria belonging to diverse phylogenetic branches (Enterobacteriaceae, Haemophilus, Pseudomonas, Acinetobacter, Brucella, Leptospira, Cytophaga, Campylobacter, Methylophaga). The labelled probe can be stored frozen (-20 degrees C) for at least a year and can endure vacuum dessication, ethanol precipitation or lyophilization.

2-Acetylaminofluorene↗
PubMed1989

[Frequency of germ isolation from urinary infections in community practice; their sensitivity to 7 antibiotics including a combination of amoxicillin and clavulanic acid. Evaluation on 1611 samples].

A multicenter study including 10 outpatient private laboratories (hospital laboratories excluded) was carried out in France. 1,611 urines samples from patients with UTI were collected during the forth trimester of 1987. The most frequently recovered pathogens were: E. coli (71%), Proteus mirabilis (9%), Staphylococcus coagulase (6%), Klebsiella (6%), Enterobacter (2%). Other sorts (Streptococcus D, Proteus sp, Pseudomonas aeruginosa, Enterobacter sp) were infrequent (less than 1%). The sensitivity of the aerobic Gram-negative bacteria to ampicillin, clavulanic acid-amoxicillin, cephalothin, gentamicin, pipemidic acid, norfloxacin and co-trimoxazole was tested.

Adult↗
PubMed1988

Localization of lipoprotein unesterified cholesterol in nondenaturing gradient gels with filipin.

A method is described for the staining of lipoprotein unesterified cholesterol in nondenaturing polyacrylamide gradient gels with the fluorescent polyene antibiotic, filipin. The sensitivity of the filipin stain was comparable to that of oil red O and Coomassie R250 in terms of the amount of lipoprotein applied. Filipin successfully stained discoidal complexes of apoA-I-phosphatidylcholine-cholesterol, which in turn were stained poorly with oil red O. The potential for the identification of unesterified cholesterol-enriched lipoprotein subclasses was demonstrated.

Cholesterol↗
PubMed1988

[The frequency of isolating urinary infection germs at a community practice and their sensitivity to various antibiotics].

Nine hundred and thirty one urine's specimens of patients affected by urinary infection have been studied by pathology practising in different towns in France. The most frequently germs retrieved are: Escherichia coli 76%, Proteus mirabilis 12%, Klebsiella 5%, Staphylococcus epidermidis 2%. Were studied Gram negative rods sensibility to ampicillin (A), cephalosporin 1st generation (C), nalidixic acid (Nal), gentamicin (G), norfloxacin (Norf); Gram positive cocci resistance to oxacillin (Oxa), erythromycin (E), pristinamycin (P), gentamicin (G), norfloxacin (Norf). For E. coli: the resistance was 24% A, 2% C1, 0.1% G, 4% Nal, 0.1% Norf. For Klebsiella: the resistance was respectively 96% A, 12% C1, 10% Nal, 18% G., 4% Norf. For P. mirabilis: 11% A, 3% C1, 0% Nal, 9% G, 0% Norf. E. coli strains cephalo R; Gram negative rods Genta R or quinolone R; staphylocoque oxa R or pristina R have been checked by HIA Begin microbiology laboratory. Discrepancies in results have been analysed. This study enabled the participants to improve their bacteriological technic, antibiogramm's reading, results' interpretation.

Adult↗
PubMed1988

Characterization of dog prenodal peripheral lymph lipoproteins. Evidence for the peripheral formation of lipoprotein-unassociated apoA-I with slow pre-beta electrophoretic mobility.

Dog plasma and prenodal peripheral lymph apoA-I distribution was examined by nondenaturing gradient gel electrophoresis-immunoblot analysis. In control dogs, plasma apoA-I could be localized to two distinct populations of particles with modal diameters of 8.4 nm and 10.4 nm. The smaller sized population accounted for over 50% of plasma apoA-I. Peripheral lymph apoA-I distribution was significantly different. The percentage of apoA-I localized to the 10.4 nm population was reduced by 40% and the modal diameter of the smaller HDL apoA-I population was significantly decreased by 0.1 nm. Additionally, peripheral lymph apoA-I could be localized to particles smaller than albumin (lipoprotein-unassociated apoA-I). The presence of lipoprotein-unassociated apoA-I particles was confirmed by gel filtration chromatography. Immunoblots of column fractions subjected to agarose electrophoresis revealed that these particles had slow pre-beta electrophoretic mobility. In dogs fed an atherogenic diet, lipoprotein-unassociated apoA-I particles with slow pre-beta electrophoretic mobility could be found in both plasma and peripheral lymph. With increasing degree of hypercholesterolemia, the relative amount of plasma lipoprotein-unassociated apoA-I tended to increase. In peripheral lymph, an increasing degree of hypercholesterolemia was associated with a decrease in the relative amount of lipoprotein-unassociated apoA-I. Instead, a population of large apoA-I particles (11-25 nm) became increasingly prominent.

Animals↗
PubMed1987

Gradient acrylamide/agarose gels for electrophoretic separation of intact human very low density lipoproteins, intermediate density lipoproteins, lipoprotein a, and low density lipoproteins.

An exponential gradient gel with 0-10% acrylamide and 0.5% agarose was developed for electrophoresis of intact high molecular weight lipoproteins. This system resolves very low density lipoproteins, intermediate density lipoproteins, lipoprotein a, and low density lipoproteins in a size-dependent fashion. The characteristic relative mobility of these species can be determined in relation to protein and colloidal gold reference materials. Electron microscopy of selected lipoprotein fractions confirmed that relative mobility was related to apparent lipoprotein diameter. The composite gel medium can be used with prestained lipoproteins and permits immunoelectroblotting for qualitative analysis of apolipoprotein constituents.

Electrochemistry↗
PubMed1987

Gradient gel electrophoresis-immunoblot analysis (GGEI): a sensitive method for apolipoprotein profile determinations.

A method is described which will determine the distribution of individual apolipoproteins within the HDL subclasses. This method requires 1-2 microliters of plasma per determination and involves six steps: 1) electrophoresis of samples on non-denaturing 2-30% concave acrylamide gradient gels; 2) electrophoretic transfer of the lipoproteins to charge-modified nylon membranes; 3) fixation of the transferred lipoproteins with glutaraldehyde; 4) immunolocalization of the apolipoproteins with iodinated monospecific antibodies; 5) autoradiography followed by densitometry; and 6) reduction of the data to provide a plot of percent distribution versus particle size. When this method was applied to the analysis of rat apolipoproteins, differences were noted in the distribution of apoA-I, apoA-IV, and apoE. The majority of apoA-I was localized to HDL particles between 9 and 12 nm in diameter, with a median diameter of 10.0 nm, while apoE resided on substantially larger particles with a median diameter of 12.5 nm. ApoA-IV could be localized to three distinct areas: an HDL particle with a median diameter approximately 0.4 nm larger than apoA-I HDL, a particle smaller than albumin (lipoprotein-free apoA-IV), and a particle of 7.6 nm that does not appear to contain apoA-I or apoE.

Adult↗
PubMed1986

The role of apolipoprotein A-IV in reverse cholesterol transport studied with cultured cells and liposomes derived from an ether analog of phosphatidylcholine.

Cholesterol efflux was studied in a model system in culture using apolipoproteins and phospholipids added in the form of liposomes at concentrations expected to be present in the extracellular fluid. Fibroblasts were seeded in medium containing [3H]cholesterol-labeled serum, grown till confluent, and the [3H]cholesterol efflux was studied in serum-free medium. Addition of delipidated HDL apolipoprotein resulted in a very low release of [3H]cholesterol, which did not increase with time of exposure or concentration of apolipoproteins. Addition of increasing amounts of HDL apolipoprotein to liposomes prepared from either dioleoylphosphatidylcholine (PC) or its nonhydrolysable ether analog, dioleylphosphatidylcholine (DOEPC) resulted in a 3-5-fold increase of [3H]cholesterol efflux, over that achieved with liposomes alone. This model system permitted the test of the putative role of apolipoprotein A-IV in cholesterol removal from cells. The ability of apolipoprotein A-IV to enhance [3H]cholesterol efflux from cells by DOEPC liposomes was compared to that of apolipoproteins A-I, E and C, which were added at equimolar concentrations. At nM concentrations, apolipoproteins A-IV, A-I and E were equally able to enhance cholesterol efflux, while C apolipoproteins were less effective at these low concentrations. Mixtures prepared from apolipoprotein A-IV, A-I and E and PC or DOEPC liposomes were equally effective in cholesterol removal, while phosphatidylethanolamine liposome apolipoprotein mixtures had a much lower capacity. The present study provides the first evidence that apolipoprotein A-IV can play a role in reverse cholesterol transport as was suggested on the basis of high concentrations of this apolipoprotein in nonlipoprotein form in plasma and extracellular fluid. The efficacy of DOEPC liposomes to serve as cholesterol acceptors might be of potential value for enhancement of reverse cholesterol transport in vivo.

Apolipoprotein A-I↗
PubMed1986

Alteration in lipoprotein composition with intravenous compared to intragastric fat-free feeding in the rat.

Rats were fed continuously for 7 d with fat-free total parenteral nutrition solutions delivered intravenously (IV) or intragastrically (IG) to determine changes in plasma lipoprotein composition due to elimination of intestinal nutrient absorption. IV feeding resulted in significantly lower plasma levels of apoA-I and A-IV, which are synthesized by the intestine, and in a 40% reduction in the weight of intestinal mucosa. Higher apoE levels in plasma, a greater proportion of apoE-enriched HDL1 particles and proportionately more HDL cholesterol were observed in IV- than in IG-fed animals. IV feeding also resulted in lower apoC-II levels in the HDL fraction. These differences in plasma apolipoprotein and HDL composition suggest alterations in lipoprotein metabolism with IV compared to IG feeding in the rat.

Animals↗
PubMed1986

Copper deficiency-induced hypercholesterolemia: effects on HDL subfractions and hepatic lipoprotein receptor activity in the rat.

Male Sprague-Dawley rats (10 per group) were fed diets adequate (control) or deficient (CuDef) in copper for 6 wk. In the CuDef group, plasma total cholesterol, high density lipoprotein (HDL) cholesterol and apoA-I levels were significantly higher than in controls. Apolipoprotein analysis of the HDL fractions revealed a relative enrichment of apoE in the CuDef group. Size analysis of 1.21 density lipoproteins by nondenaturing gradient gel electrophoresis demonstrated the presence of more material migrating in the size range of HDL1 in the CuDef group. Separation of HDL into apoE-rich and apoA-I-rich fractions by heparin-affinity chromatography confirmed the presence of increased apoE-rich HDL in the CuDef group. To determine the mechanism responsible for higher apoE-rich HDL in the CuDef group, the lipoprotein receptor binding activity in hepatic membranes from the control and CuDef group was assayed. Kinetic analysis of the binding data revealed that the lipoprotein binding assay was primarily measuring the activity of the HDL receptor, which is not apoE mediated. When corrected for differential enrichment of plasma membrane, hepatic membranes from the CuDef group bound significantly fewer lipoproteins than did controls. Furthermore, the hepatic receptor binding activity was negatively correlated with the proportion of HDL enriched with apoE.

Animals↗
PubMed1986

ApoA-IV metabolism in the rat: role of lipoprotein lipase and apolipoprotein transfer.

Factors influencing the association of apoA-IV with high density lipoproteins (HDL) were investigated by employing a crossed immunoelectrophoresis assay to estimate the distribution of rat plasma apoA-IV between the lipoprotein-free and HDL fractions. Incubation of rat plasma at 37 degrees C resulted in the complete transfer of lipoprotein-free apoA-IV to HDL within 45 min. When plasma obtained from fat-fed rats was incubated at 37 degrees C in the presence of postheparin plasma as a source of lipolytic activity, there was a complete transfer of HDL apoA-IV to the lipoprotein-free fraction within 30 min. With extended incubation (120 min), lipoprotein-free apoA-IV began to transfer back to HDL. Similar patterns of apoA-IV redistribution were seen when plasma from fat-fed rats was incubated with postheparin heart perfusate or was perfused through a beating heart. Incubations conducted with plasma obtained from fasted rats showed similar but markedly attenuated apoA-IV responses. Similar observations were found in vivo following intravenous heparin administration. To determine whether the transfer of apolipoproteins from triglyceride-rich lipoproteins to HDL was partially responsible for the lipolysis-induced redistribution of apoA-IV, purified apoA-I, apoE, and C apolipoproteins were added to plasma from fasted rats. When added to plasma, all of the apolipoproteins tested displaced apoA-IV from HDL in a dose-dependent manner. Conversely, apolipoproteins were removed from HDL by adding Intralipid to plasma from fasted rats. With increasing concentrations of Intralipid, there was a progressive loss of HDL apoC-III and a progressive increase in HDL apoA-IV. Intravenous injection of a bolus of Intralipid to fasted rats resulted in a transient decrease of HDL apoC-III and concomitant increase in HDL apoA-IV. From these studies, we conclude that the binding of apoA-IV to HDL is favored under conditions that result in a relative deficit of HDL surface components, such as following cholesterol esterification by LCAT or transfer of apolipoproteins to nascent triglyceride-rich lipoproteins.

Animals↗
PubMed1985

Different effects of zinc and copper deficiency on composition of plasma high density lipoproteins in rats.

Male Sprague-Dawley rats (six per group) were fed an egg white-based diet containing 0 or 5 micrograms/g Cu with 1, 10, 100 or 1000 micrograms/g Zn. After 6 wk of feeding, the rats were killed, and the tissues were processed for trace element, lipid and lipoprotein analysis. Copper deficiency was associated with a higher concentration of plasma free cholesterol, high density lipoprotein (HDL) cholesterol and HDL apolipoproteins. Plasma total cholesterol was not significantly affected. No significant differences were noted in HDL lipid composition. However, HDL apo E and apo A-I concentrations were higher with copper deficiency. Lecithin:cholesterol acyltransferase (LCAT) was not affected in a consistent manner by copper status. Varying the amount of zinc in the diet did not produce significant changes in plasma total cholesterol, plasma free cholesterol, HDL cholesterol, or HDL apolipoprotein concentrations. However, HDL from zinc-deficient rats were enriched in free cholesterol and depleted in triglycerides. Furthermore, the concentration of HDL apo C increased as the level of dietary zinc increased.

Animals↗
PubMed1984

High density lipoprotein composition in rats fed casein or soy protein isolate.

We investigated the effects of dietary plant and animal proteins on high density lipoprotein (HDL) composition of rats fed diets containing either casein or soy protein isolate for 5 weeks. Rats fed casein had increased plasma total cholesterol, triglycerides, very low density and low density lipoprotein (VLDL + LDL) and HDL while HDL cholesterol was unchanged. HDL from casein-fed rats had an increase in percent protein and a decrease in percent cholesterol leading to a decreased cholesterol to protein ratio. Of the individual HDL apoproteins, only the C apoproteins were significantly elevated by casein. In addition, casein-fed rats had an increased proportion of the less sialylated forms of apo C-III. Liver cholesterol was not significantly affected by protein source but was negatively correlated with both HDL cholesterol and HDL protein levels. Addition of cholesterol to the diets largely eliminated any effect of protein source on HDL composition. These data demonstrate that dietary protein source can significantly influence HDL composition despite a lack of effect on HDL cholesterol levels.

Animals↗
PubMed1984

Composition of high density lipoproteins in rats fed various dietary fibers.

Several studies have suggested that dietary fibers, especially water-soluble sources, are effective agents for lowering plasma cholesterol. This study was undertaken to determine the effect of various fibers on the composition of apoproteins in high density lipoproteins. Rats were fed experimental diets that contained either 20% wheat bran, oat bran or cellulose or 5% pectin or guar gum for 4 weeks. Final body weight was similar among groups. HDL cholesterol and total apoprotein concentrations were not significantly altered by diet. The percentage of apo A-I was significantly elevated and apo E and the apo C's were significantly lower in the guar gum group relative to the wheat bran group. Lecithin cholesterol acyl transferase activity and the C-II-to-C-III ratio were highest in the guar gum group. Differences in the absorption and subsequent metabolism of lipid could account for differences in HDL composition.

Animals↗
PubMed1983

Modification of arterial elastin in vivo. Effects of age and diet on changes in the N-terminal amino acid content of aorta elastin.

We have previously demonstrated that aorta elastin, a highly crosslinked protein, does not undergo turnover that is easily measured in vivo. Therefore, it was hypothesized that when proteolysis of elastin occurs, a positive increase in N-terminal amino acids should result. Such an increase would represent elastin-derived fragments held covalently in situ. A cyanate carbamylation procedure was used to estimate the changes in N-terminal amino acids in aorta elastin. To provide tissue for the studies, Japanese quail (3 weeks old) were fed diets with or without the addition of 1% cholesterol. It was found that, in normal birds, the number of N-terminal amino acid residues increased from two to approximately three residues per 800 total residues (or mole of tropoelastin) throughout sexual development (3 to 8 weeks, post-hatching), with little increase thereafter. In hypercholesterolemic birds, the rate of appearance of new N-terminal residues, particularly glutamine or glutamic acid, appeared enhanced throughout early development, but by sexual maturity the number of N-terminal amino acid residues in aorta elastin from cholesterol-fed birds was similar to that for the control birds. For each of the elastin samples analyzed, approximately one residue of glycine was recovered per 800 total residues. Other amino acids that predominated as N-terminal residues were serine, aspartic and glutamic acids.

Aging↗