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R Couderc

Publications and source records attributed to R Couderc.

At least 37 records · Page 2Linked to original sources
PubMed1999

International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Standardization Project for the Measurement of Lipoprotein(a). Phase 2: selection and properties of a proposed secondary reference material for lipoprotein(a).

The International Federation of Clinical Chemistry and Laboratory Medicine Working Group for the Standardization of Lipoprotein(a) Assays has initiated a project to select a secondary reference material for lipoprotein(a) that can standardize the measurement of this lipoprotein. Most of the analytical problems with lipoprotein(a) assays are due to apolipoprotein(a) kringle 4 type 2 reactive antibodies and values being expressed in mg/l mass units rather than as nmol/l of apolipoprotein(a) particles. In Phase 2, four manufactured materials were compared for analytical performance, commutability properties and method harmonization in 27 lipoprotein(a) test systems. Results of precision and linearity testing were comparable for all materials whereas testing for the harmonization effect resulted in an among-assay coefficient of variation for corrected lipoprotein(a) values of between 11% and 22%. The material that gave maximum harmonization achieved a variation of < 8% for 18 immunonephelometric and immunoturbidimetric assay systems. It can be hypothesized that this residual variation in part takes into account the inaccuracy of lipoprotein(a) measurement due to apolipoprotein(a) size polymorphism. On the basis of acceptable analytical performance, maximal harmonization effect and documented stability, a lyophilized material has been selected as the common calibrator for lipoprotein(a) to be used in a value transfer procedure by diagnostic companies.

Evaluation Studies as Topic↗
PubMed1999

[Evaluation of the quality of blood glucose meters using the HemoCue B glucose system].

Analytical evaluation three models of blood glucose meters (Glucometer IV (Bayer), Glucotrend (Roche Diagnostics) and One touch (Life Scan, Johnson & Johnson)) were compared within a central laboratory to an analyzer (Hitachi 747, Boehringer-Mannheim, Grenoble, France) and to a photometric device (HemoCue B-glucose). Each glucose meters met the criteria of within-run precision defined by the Association Française d'Etudes du Diabète et des Maladies Métaboliques (ALFEDIAM). Furthermore, HemoCue B-glucose met criteria defined by the French Society of Biological Chemistry (SFBC). In the study realized within laboratory, 28 to 66% of glucose tests realized with meters differed by more than 10% from plasma values and 43% of glucose assays realized with different meters differed by more than 10% from HemoCue B-glucose value. Within clinical departments, 46 glucose meters from 5 different models were evaluated. Answers to a questionnaire stored in HemoCue B-glucose underlined the weak development of glucose meters quality assurance. Within clinical departments, 65% of glucose values realized with meters differed by more than 10% from reference values. Development in clinical departments of glucose meters quality assurance programs can be monitored by HemoCue B-glucose, and must allowed improvement of glucose meter quality.

Blood Chemical Analysis↗
PubMed1999

A novel kringle-4 number-based recombinant apo[a] standard for human apo[a] phenotyping.

Apolipoprotein[a] phenotyping is a critically important method to explore the role of kringle-4 repeat number as a modulator of lipoprotein[a]-associated cardiovascular risk. The availability of a kringle-4 number-based reference standard is therefore necessary for a reliable and generally accepted classification of apo[a] phenotypes. We propose here a battery of recombinant apo[a] isoforms that may be used as the reference standard in various gel systems. Five plasmids encoding for r-apo[a] containing a known number (n = 9, 13, 17, 25, 33) of plasminogen-like kringle-4 copies were constructed, and transfected into the human embryonic kidney cell line 293. The electrophoretic mobility of the recombinant apo[a] isoforms expressed by these cells in a hollow-fiber bioreactor was determined after reduction by SDS-gel (agarose, acrylamide or a mixture of both) electrophoresis and immunoblotting using an antibody specific for human apo[a]. The equation of the linear relationship between log r-apo[a] kringle number and relative migration was used to determine the isoform size of apo[a] in normal human plasma. A very good correlation (r = 0.97) was found with the genotype (pulsed-field gel eletrophoresis of kpnI-digested restriction fragments of genomic DNA) and among electrophoretic methods. The proposed recombinant standard offers the possibility to identify apo[a] isoforms within a large range of molecular sizes, 9 to 33 kringle-4 copies, using simple electrophoretic techniques and a nomenclature based on its molecular structure, i.e., the number of kringle-4 repeats.-Anglés-Cano, E., S. Loyau, G. Cardoso-Saldaña, R. Couderc, and P. Gillery. A novel kringle-4 number-based recombinant apo[a] standard for human apo[a] phenotyping.

Apolipoproteins A↗
PubMed1998

Effects of postprandial hyperlipemia on the vitamin E content of lipoproteins. GERBAP section Lipoprotéines. Groupe d'Evaluation et de Recherche de l'Assistance Publique des Hôpitaux de Paris.

Delayed postprandial clearance of triglyceride-rich lipoproteins (TGRL) could induce a decrease of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) vitamin E content through its transfer into TGRL. We thus studied lipoprotein vitamin E content during postprandial hypertriglyceridemia induced by a high fat meal without vitamin E supplement. Venous blood was drawn from five healthy male volunteers following a 12 h fast at (t0) then 2 h (t2), 4 h (t4), 6 h (t6) and 8 h (t8) after a 80 g fat meal. In plasma, only TG significantly varied during the postprandial period with a large interindividual variability. Mean composition of lipoproteins in terms of mass was not significantly modified. The amount of vitamin E significantly increased in TGRL and decreased in LDL plus HDL at t4 and t6 relative to t0. Vitamin E content of TGRL and LDL but not of HDL decreased significantly at t4. The mean decrease was 20% (range 5%-54%) for the LDL. LDL- and HDL vitamin E content correlated inversely with plasma TGRL levels. Our data suggest that LDL from subjects with delayed chylomicron clearance could be less protected against oxidation.

Dietary Fats↗
PubMed1998

[Lipoprotein (a), a cardiovascular risk factor: importance of its determination in current clinical practice].

Lipoprotein (a) [Lp(a)] is a LDL-like particle linked to an apo-lipoprotein (a) which has high sequence homology with plasminogen that gives Lp(a) thrombogenic properties in addition to atherogenic capacity. Many epidemiological studies have shown that a high plasma level of Lp(a) is a risk factor for coronary, cerebral and peripheral atherosclerosis. Out of thirteen prospective studies, ten have confirmed this result. The negative results from the three remaining studies were probably due to either inadequate storage of the samples or preventive drug treatment given to the patients during the studies. This review of the literature clearly demonstrates the relationship between Lp(a) and atherosclerosis and the need to measure Lp(a) in order to better evaluate the risk of atherosclerotic vascular disease especially in patients with a hyper LDLemia, an early cardio- or cerebrovascular disease or a family history of atherosclerosis.

Arteriosclerosis↗
PubMed1998

International Federation of Clinical Chemistry standardization project for the measurement of lipoprotein(a). Phase I. Evaluation of the analytical performance of lipoprotein(a) assay systems and commercial calibrators.

A secondary reference material for lipoprotein(a) is required to standardize the measurement of lipoprotein(a) in clinical laboratories worldwide. Towards this aim, the International Federation of Clinical Chemistry Working Group for the Standardization of Lipoprotein(a) Assays has initiated a standardization project involving a total of 33 diagnostic company and clinical chemistry laboratories from 12 countries. In Phase 1, the analytical performance of 40 lipoprotein(a) assay systems was evaluated by testing sera and manufactured lipoprotein(a) calibrator materials for precision, linearity, and parallelism. Twenty test systems were nonoptimized according to the results for a pooled serum, which tested nonlinear in 16 systems and imprecise in 4. Acceptable analytical properties and harmonization of lipoprotein(a) values were shown by some commercial calibrators, suggesting their possible use as reference materials. This study highlights the problems that currently occur for lipoprotein(a) measurement in existing assay systems.

Calibration↗
PubMed1997

Effects of plasma lipoproteins on the production of superoxide anion by human polymorphonuclear leukocytes in vitro.

Polymorphonuclear leukocytes (PMN) generate highly reactive oxygen derived free radicals that may cause lipoprotein lipid oxidation and so contribute to the pathogenesis of atherosclerosis. On the other hand it has been shown that lipoproteins can alter cell functions in vitro. We therefore studied the effects of atherogenic lipoproteins, VLDL and LDL, on the production of superoxide anion by human PMN in the presence or absence of formyl-methionyl-leucyl-phenylalanine (fMLP). VLDL and LDL stimulate PMN superoxide production and potentialize PMN stimulation by fMLP. The lipid moiety of the lipoproteins might be mainly involved in these effects. The binding of radio-labelled fMLP to its specific membrane receptor was significantly enhanced in the presence of VLDL and only slightly in the presence of LDL. The study of the signal transduction suggests that modulation of phospholipase D and A2 activities could be involved in the modification by LDL of PMN response to fMLP.

Arteriosclerosis↗
PubMed1997

Effects of human low-density lipoproteins on superoxide production by formyl-methionyl-leucyl-phenylalanine activated polymorphonuclear leukocytes.

Neutrophils play a major role in the host defence by producing reactive oxygen species. These products are liberated by activated cells and are known to cause endothelial cell injury and damage. The present study shows that low-density lipoproteins increase superoxide anion production by twofold in polymorphonuclear leukocytes stimulated by formyl-Met-Leu-Phe in vitro. Moreover, LDL induced a large increase in phosphoinositides and cytosolic-free calcium. Data from experiments performed on neutrophils treated with pertussis toxin, staurosporine, propranolol or niflumic acid suggest that modulation of phospholipase D and A2 activities could be involved in the modification by LDL of leukocyte response to formyl-Met-Leu-Phe. LDL lipid moiety could play a key role in their action on polymorphonuclear functions because cholesterol was exchanged between lipoproteins and cells that can modify membrane fluidity and interact with the formyl-Met-Leu-Phe receptor.

Adrenergic beta-Antagonists↗
PubMed1996

Characterization of lipoproteins during human cholestasis.

We have characterized changes in lipoproteins from cholestatic individuals and reproduced them by incubating lipoproteins from healthy individuals with cholic acid. The cholestatic patients showed an increase in low density lipoprotein (LDL) (>85%), with a smaller proportion of esterified cholesterol, and a fall in high density lipoprotein (HDL) (<10%), with a larger proportion of phospholipids. The protein composition of cholestatic HDL1 was characterized by a smaller proportion of apo A (I, II) and a prominent apo E fraction (39% vs. 9%). These changes involved an increase in degree of molecular packing (order) of HDL1. The addition of cholic acid to serum from healthy individuals altered the lipoprotein distribution, with an increase in LDL, the disappearance of HDL2 and HDL3 and the appearance of HDL1. These HDL1 were characterized by increased phospholipid and reduced apo AI fractions. They also showed a lower density and appeared as spherical particles in contrast to cholestatic HDL. Incubation of healthy HDL with cholic acid in vitro reproduces some of the alteration observed in cholestatic HDL.

Chemical Phenomena↗
PubMed1996

Determination of plasma protein-bound malondialdehyde by derivative spectrophotometry.

We describe a method for the measurement of protein-bound malondialdehyde with the thiobarbituric acid reaction in human plasma using second-derivative spectrophotometry. Calibration was done by spectrum height measurement from the baseline at 532 nm. The data were compared with those obtained by using conventional absorbance and fluorimetric measurements. The results were linear from 0.2 to 80 mumol/l and the detection limit was 0.19 mumol/l. Within-run and between-run precision, evaluated by analysing pooled normal plasma, were 8 and 14% respectively. The method was tested for the influence of bilirubin, haemoglobin, glucose, urea, uric acid, sucrose and N-acetyl-neuraminic acid which interfered in the colorimetric method but not in the technique proposed here. The mean (+/-SD) malondialdehyde concentration determined in 59 healthy blood donors with the new assay was 0.34 (+/-0.14) mumol/l. This assay procedure could represent an alternative to high-performance liquid chromatography for the measurement of malondialdehyde in biological media.

Blood Proteins↗
PubMed1995

[Isoform 4 of apolipoprotein E and Alzheimer disease. Specificity and clinical study].

We studied apolipoprotein E (apoE) phenotype in 113 patients with possible and probable Alzheimer's disease (AD), 49 patients with Parkinson's disease (including 11 patients with dementia) and 23 patients with mixed and vascular dementia. Normal controls were 498 young, healthy blood donors previously recorded. All patients were assayed for blood lipid parameters. All AD patients underwent a neuropsychological evaluation (including a mini-mental status and 5 subtests of Cole and Dastoor hierarchic dementia scale) and a detailed interrogation of them and their caregivers about their familial and personal medical history. The recorded data included age at onset, clinical subtype (i.e. amnesic or aphaso-apraxic), occurrence of fits, cases of probable dementia in relatives, and ages of their parents at death. There was a significant association between the fourth isoform of apoE and AD, as in previous works. We did not found such an association for PD patients (even with dementia) nor mixed and vascular demented patients. We failed to find any association between any clinical characteristic of the patients and the biological subgroups defined by the number of epsilon 4 alleles, except with regard for the age of onset. Surprisingly, the mothers of epsilon 4 bearers had a significantly longer life than mothers of other patients. We failed to found any significant difference of apoE2 isoform frequency between AD patients and controls. AD patients had higher levels of cholesterol and apoAl than did MP and mixed and vascular demented patients. ApoAl level is known to constitute a protective factor against coronary heart disease, which is usually increased by the presence of apoE-epsilon 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Alzheimer Disease↗
PubMed1995

Acquired circulating anticoagulant with anti-factor V activity in AIDS: first case report.

An acquired circulating anticoagulant with anti-factor V activity appeared in a 29 year old AIDS patient with widespread Kaposi's sarcoma following 21 days of fresh frozen plasma therapy for haemolytic and uraemic syndrome. Residual factor V activity was very low (< 5% of normal). However, the inhibitor was of low titre (0.5 Bethesda Units/ml), while antigenic factor V levels remained at 100%. Dot blotting with human factor V and polyvalent and specific immunoglobulin antisera showed the antibody to belong to the IgG class. Haemostatic tests in vitro were only partly corrected by addition of washed human platelets and despite transfusion of large amounts of platelets the patient died from massive pulmonary haemorrhage. This would appear to be the first documented case of an anti-factor V inhibitor occurring in an AIDS patient.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Lipoprotein(a) in childhood: relation with other atherosclerosis risk factors and family history of atherosclerosis.

The relation between lipoprotein(a) [Lp(a)], apolipoprotein (apo) E phenotypes, cholesterol, triglycerides, apo A-I, apo B, and a family history of atherosclerosis or risk factors was studied in 2- and 4-year-old French Caucasian children (n = 499). Lp(a) concentrations were distributed in a typical skewed manner and were found to be an independent lipid variable. The distribution of apo E phenotypes did not differ by gender. Cholesterol and apo B were under apo E phenotype control; Lp(a) was not. A significant positive relation was found between Lp(a) concentrations and the number of parental risk factors. Children whose grandparents had a history of cardiovascular disease had Lp(a) concentrations shifted towards higher values. Measurement of Lp(a) in children may help to identify those at an increased risk of atherosclerotic disease, especially when their parents have at least two relevant risk factors.

Apolipoprotein A-I↗
PubMed1994

Effects of alpha-1 acid glycoprotein on human polymorphonuclear neutrophils: influence of glycan microheterogeneity.

The biological functions of alpha-1 acid glycoprotein (AGP) are poorly understood but appear to depend on glycan microheterogeneity. Variations of AGP glycan structure (in terms of concanavalin A (ConA) reactivity) have been observed during the inflammatory process. We studied these modifications in AGP from patients with chronic renal impairment and investigated the effects of AGP microheterogeneity on healthy polymorphonuclear leukocyte (PMN) chemotaxis and oxidative metabolism. AGP was extracted by a two-step procedure from sera from ten patients with various degrees of renal impairment, selected according to AGP glycan heterogeneity determined by crossed immunoaffinity electrophoresis with ConA. AGP (0.5 g/l) significantly inhibited the chemotactic response of PMN to formyl-methionyl-leucyl-phenylalanine (10(-7) mol/l) and complement fraction C5a, regardless of ConA reactivity. AGP also inhibited superoxide anion generation in response to phorbol myristate acetate (10(-7) mol/l). After stimulation by opsonized zymosan (1 g/l), the effect of AGP appeared to depend on its glycan structure (r = 0.70, P < 0.05), decreasing with ConA non-reactivity. These data suggest that AGP can down-regulate neutrophil responsiveness, an effect that depends in part on its glycan microheterogeneity. Alterations of AGP microheterogeneity in various pathological states, particularly renal failure, may be related to the inflammatory process.

Adult↗