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Biomedical subjects

M Rosseneu

Publications and source records attributed to M Rosseneu.

At least 127 records · Page 7Linked to original sources
PubMed1988

Immunochemical characterization of two antigenic sites on human apolipoprotein A-I; localization and lipid modulation of these epitopes.

Two monoclonal antibodies, A17 and A30, were raised against human apolipoprotein A-I (apo A-I). They were studied by competitive inhibition of 125I-labeled HDL3 with HDL subfractions, delipidated apo A-I, and complexes of dimyristoylphosphatidylcholine (DMPC) containing apo A-I and apo A-II. Immunoblotting located the A17 antibody on CNBr fragment 4 of apo A-I and the A30 antibody on CNBr fragment 1. The A17 antigenic determinant was expressed identically in all HDL subclasses, on delipidated apo A-I as well as all on the DMPC-apo A-I and DMPC-apo A-I/apo A-II complexes. In contrast, the apparent affinity constant of the A30 antibody for delipidated apo A-I was about 30-times less than for HDL3 or for apo A-I/apo A-II-phospholipid complexes. These data suggest that the association of apo A-I with phospholipids improves the reactivity of the A30 monoclonal antibody towards apo A-I, and that this antigenic determinant has a different conformation in delipidated apo A-I compared to apo A-I complexed with phospholipids. Turbidimetric and fluorescence experiments monitoring the phospholipid-apo A-I association in the presence and in the absence of the A17 and A30 antibodies were consistent with the competition experiments carried out by solid phase radioimmunoassay (RIA). After reaction of apo A-I with the A30 antibody, we observed an enhancement of the degradation kinetics of large multilamellar vesicles (LMV), while the A17 antibody did not have a significant effect. Calcein leakage experiments carried out below the transition temperature of DPPC showed an enhancement of the degradation kinetics with both monoclonal antibodies, while the phase-transition release was independent of the reaction of apo A-I with the monoclonal antibodies. These data therefore suggest the existence of at least two different types of epitope on apo A-I, which might account for the differences in immunological reactivity of apo A-I that is either delipidated or present on HDL.

Antibodies, Monoclonal↗
PubMed1988

Apolipoprotein E polymorphism in The Netherlands and its effect on plasma lipid and apolipoprotein levels.

By isoelectric focusing of delipidated sera followed by immunoblotting we studied the apolipoprotein (apo) E polymorphism in 2018 randomly selected 35-years-old males from three different areas in the Netherlands. Comparison of the APOE allele (E*2, E*3, and E*4) frequencies estimated in this study with those reported for several other population samples showed that there are marked differences between the Dutch population and the populations of Japan, New Zealand, Finland, and the United States. These differences in APOE allele frequencies appeared to be mainly due to differences in frequencies of the E*2 allele (decreased in Japan and Finland; increased in New Zealand) and the E*4 allele (increased in Finland; decreased in Japan and the United States). No difference in APOE allele frequencies was found between the Dutch population and the populations of West Germany and Scotland. Measurements of plasma cholesterol and apo B and E concentrations showed that the E*4 allele is associated with elevated plasma cholesterol and apo B levels and with decreased apo E concentrations, whereas the opposite is true for the E*2 allele. In the Dutch population, the sum of average allelic effects of the common APOE alleles on plasma cholesterol and apo B levels is 6.8% and 14.2%, respectively, of the total population mean. The total average allelic effect on plasma apo E concentrations was more pronounced (50.1%), suggesting that the APOE alleles primarily affect apo E concentrations rather than plasma cholesterol and apo B levels. This hypothesis is sustained by the observation that for plasma apo E levels the genetic variance associated with the APOE gene locus contributed about 18% to the total phenotypic variance. For plasma cholesterol and apo B this contribution was only 1.4% and 2.3% and is relatively low as compared with that reported for other population samples.

Adult↗
PubMed1988

Changes in plasma lipids and apoproteins associated with physical training in middle-aged sedentary men.

The effect of endurance training on plasma lipoproteins was investigated in 27 healthy sedentary men between the ages of 20 and 55 years. During the first 4 months of the study, 13 of them (group A) participated in a training program (3 hours/wk), whereas the others served as control subjects (group B). At the end of this period the control subjects also underwent a 4-month training program. In both groups the training significantly increased physical working capacity at a heart rate of 130 bpm (PWC130), whereas it decreased the resting heart rate (p less than 0.05). Concomitantly with this improvement in cardiorespiratory fitness, a significant increase in the high-density lipoprotein (HDL) cholesterol concentration was observed (p less than 0.01); this was due to an increase in both HDL2 beta and HDL2 alpha + 3 cholesterol concentrations. The plasma total and HDL-apoprotein AI and apoprotein AII concentrations were not significantly affected by the training. Significant decreases in plasma triglyceride (p less than 0.05), very-low-density lipoprotein cholesterol (p less than 0.05), and low-density lipoprotein (LDL) cholesterol (p less than 0.001) concentrations were also observed, but only in group B, which showed a much greater increase in PWC130 at the end of the training period than group A; the decrease in the LDL cholesterol concentration in this group was accompanied by a slight decrease in the LDL-apoprotein B concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Plasma and erythrocyte lipids in two families with heterozygous hypobetalipoproteinemia.

Erythrocyte morphology, kinematic viscosity, and membrane lipid composition have not been well documented in heterozygous hypobetalipoproteinemia (HBL). In our study of nine subjects with HBL from two kindreds, three presented with schistocytes (3-6%) while two of them also showed acanthocytosis (25-35%) on their peripheral blood films. The other affected family members had a normal RBC morphology despite a decreased kinematic viscosity of RBC suspension at 37 degrees C (log eta = 0.20 +/- 0.02 vs. log eta = 0.26 +/- 0.02) in all nine subjects; erythrocyte osmotic fragility however was normal. Although some subjects showed acanthocytosis total cholesterol (0.63 +/- 0.05 mol x 10(-6)/mg membrane protein) and sphingomyelin/lecithin ratio (0.905 +/- 0.042) of RBC membranes were normal while plasma from the subject with schistocytosis had a significantly decreased sphingomyelin/lecithin ratio in plasma (17.2 +/- 2.4 vs. 29.1 +/- 3.3) suggesting that sphingomyelin and lecithin are not freely exchangeable between plasma and the outer surface of RBC membranes.

Adult↗
PubMed1988

Immunoturbidimetric assays for serum apolipoproteins A1 and B using Cobas Bio centrifugal analyser.

Immunoturbidimetric assays for measuring the apolipoproteins A1 and B using the Cobas Bio centrifugal analyser are described. The methods were specific, offered good sensitivity (less than 0.05 g/l) and intrabatch variability, with coefficients of variation between 2.4% and 3.5%, and were cost effective. Reference ranges were calculated for a group of civil servants, aged 35 to 55 years.

Adult↗
PubMed1988

Changes in erythrocyte sodium and plasma lipids associated with physical training.

The intracellular concentrations and transmembrane fluxes of Na+ and K+ in erythrocytes, and plasma lipids were investigated in 30 middle-aged volunteers, before and after physical training. During the first 4 months of the study, half of the subjects (group A) were subjected to a training programme (3 h/week), while the others (group B) served as controls. At the end of the control period the group B subjects also underwent a period of training. At the end of the training, in both experimental groups, the intra-erythrocyte Na+ concentration was decreased (P less than 0.001); the magnitude of this decrease was related to the increase achieved in physical working capacity (r = -0.44; P less than 0.05). After training the activity of the erythrocyte Na+-Li+ counter-transport system was decreased (P less than 0.001) in both groups, whereas Na+,K+ cotransport activity was increased (P less than 0.001). The training intervention did not affect erythrocyte ouabain-sensitive 86Rb uptake, or the calculated rate constant for ouabain-sensitive Na+ efflux. Furthermore, the plasma concentrations of high density lipoproteins (HDL)2- and HDL3-cholesterol (P less than 0.001) markedly increased in both groups during the training period. However, these changes were not significantly correlated with the observed training-induced changes in erythrocyte transmembrane cationic fluxes. It is concluded that physical training decreases intra-erythrocyte Na+ concentration. No significant associations between training-induced changes in plasma lipids and erythrocyte sodium balance could be demonstrated.

Adult↗
PubMed1988

Immunoturbidimetric method for routine determinations of apolipoproteins A-I, A-II, and B in normo- and hyperlipemic sera compared with immunonephelometry.

We describe a method for routine immunoturbidimetry of apolipoproteins (apo) A-I, A-II, and B in both normo- and hyperlipemic sera. A special antiserum reagent, consisting of a highly concentrated mixture of nonionic and anionic detergents (final concentration in the assay, 36 g/L), rapidly removes intrinsic turbidities of even strongly lipemic sera without interfering with the antigen-antibody precipitation reaction. The method has good precision, and obviates the need for special sample pretreatment, extended incubation periods, and measurment of sample blanks. A comparison with established immunoephelometric assays generally showed close agreement for analytical recoveries of the three apolipoproteins. However, in samples containing greater than or equal to 18 g of triglycerides per liter, the nephelometric assays yielded about two- to threefold higher values for apo A-II and B than did the turbidimetric procedure. To elucidate this discrepancy, we used the turbidimetric methods to assay sera with and without enzymatic lipolytic pretreatment. Even for samples with triglyceride concentrations up to 60 g/L, complete enzymatic lipolysis (as evidenced by thin-layer chromatography) did not significantly alter the recoveries of apo A-II and B from those obtained with the untreated specimens. Thus the immunoturbidimetric methods yield reliable results for apo A-I, A-II, and B, not only in normo- but also in hyperlipemic sera.

Apolipoprotein A-I↗
PubMed1988

Apolipoprotein A-IV polymorphism and its effect on plasma lipid and apolipoprotein concentrations.

Recently, we determined the apolipoprotein E (apoE) phenotype distribution in 2,000 randomly selected 35-year-old male individuals by slab gel isoelectric focusing of delipidated plasma samples, followed by immunoblotting using anti-apoE antiserum. These blots have been successfully re-used for immunovisualization of apoA-IV isoelectric focusing patterns. In a population sample of 1,393 individuals, four distinct apoA-IV isoforms were detected, encoded by the alleles A-IV*0, A-IV*1, A-IV*2, and A-IV*3 with gene frequencies of 0.002, 0.901, 0.079, and 0.018, respectively. The mean of plasma cholesterol, triglyceride, apoB and E levels did not differ significantly among the different apoA-IV phenotype groups. For these lipoprotein parameters, less than 0.1% of the total phenotypic variance could be accounted for by the APOA-IV gene locus. Our results did not show any effect of apoA-IV polymorphism on plasma apoA-I levels nor could we find any correlation between plasma levels of apoA-I and apoA-IV within the different apoA-IV phenotype groups. The plasma level of apoA-IV in subjects bearing the A-IV*3 allele is significantly lower than in subjects without the A-IV*3 allele (5 mg/dl versus 14 mg/dl). We therefore conclude that, in contrast to the apoE polymorphism, the polymorphism at the APOA-IV locus does not influence any of the levels of the lipoprotein parameters considered except apoA-IV.

Adult↗
PubMed1988

Quantification of human apolipoprotein A-IV by "sandwich"-type enzyme-linked immunosorbent assay.

A specific and sensitive "sandwich"-type enzyme-linked immunosorbent assay (ELISA) has been developed for quantifying human apo A-IV. Using apo A-IV immunosorbent columns, we isolated monospecific anti-apo A-IV antibodies for coating the ELISA plates and for preparing peroxidase-antibody conjugate. The assay can detect as little as 0.20 ng of apo A-IV, with mean intra- and interassay CVs of 3.6% and 8.2%, respectively. The apoA-IV concentrations in normolipemic and hyperlipemic plasma were unaffected by either delipidation or treatment with detergents or urea. To validate the ELISA assay we compared it with an immunoelectrophoretic technique. ApoA-IV concentrations in plasma from normo- and dyslipemic subjects compared well by the two assays (r = 0.89). The mean apo A-IV concentration, measured by ELISA in plasma from 50 normolipemic subjects, was 143 (SD 52) mg/L; values for dyslipemic subjects were not significantly different. We also used this new assay to monitor apo A-IV profiles of normolipemic and hypertriglyceridemic plasma after chromatographic fractionation.

Apolipoproteins A↗
PubMed1987

Apolipoprotein B-48 is the product of a messenger RNA with an organ-specific in-frame stop codon.

The primary structure of human apolipoprotein (apo) B-48 has been deduced and shown by a combination of DNA excess hybridization, sequencing of tryptic peptides, cloned complementary DNAs, and intestinal messenger RNAs (mRNAs) to be the product of an intestinal mRNA with an in-frame UAA stop codon resulting from a C to U change in the codon CAA encoding Gln2153 in apoB-100 mRNA. The carboxyl-terminal Ile2152 of apoB-48 purified from chylous ascites fluid has apparently been cleaved from the initial translation product, leaving Met2151 as the new carboxyl-terminus. These data indicate that approximately 85% of the intestinal mRNAs terminate within approximately 0.1 to 1.0 kilobase downstream from the stop codon. The other approximately 15% have lengths similar to hepatic apoB-100 mRNA even though they have the same in-frame stop codon. The organ-specific introduction of a stop codon to a mRNA appears unprecedented and might have implications for cryptic polyadenylation signal recognition and RNA processing.

Amino Acid Sequence↗
PubMed1987

Functional differentiation of amphiphilic helices of the apolipoproteins by hydrophobic moment analysis.

The amphiphilic character of different plasma apolipoproteins was investigated by a combination of established hydrophobicity analysis methods. These methods proved to be powerful in the detection of amphiphilic phospholipid-binding domains. Within this class of lipid-binding domains, lecithin-cholesterol acyltransferase activating and non-activating helices could be differentiated by calculating hydrophobic moments at different angles. We conclude that the hydrophobic characteristics of the different helices determined the mode of lipid binding and the substrate properties of these phospholipid-protein complexes for the lecithin-cholesterol acyltransferase reaction.

Apolipoprotein A-II↗
PubMed1987

Distribution and composition of HDL subclasses in students whose parents suffered prematurely from a myocardial infarction in comparison with controls.

The purpose of this study was to analyze the distribution and composition of the HDL subclasses in students whose parents suffered from a premature coronary heart disease (CHD), in comparison with a control group without any familial history of CHD. In the first part of this study, we observed significantly lower apo A-I concentrations in the cases than in the controls. Since there was a significant difference in smoking habits between cases and controls, and since we wanted to study the effect of a parental history of premature CHD on the composition of the HDL subclasses independently of smoking, the present study was conducted on the 17 pairs of non-smokers male cases and controls. In agreement with the results on total serum, we observed lower apo A-I concentrations in the HDL2b and HDL2a + 3a fractions in the cases compared to the controls. The apo A-II and cholesterol levels in these fractions were not significantly different between the 2 groups. The selective decrease of apo A-I in the HDL subclasses with the lowest density might be due to a decreased number of particles containing only apo A-I, with which a protective effect against atherosclerosis might be associated.

Adult↗
PubMed1987

Human apolipoprotein B: analysis of internal repeats and homology with other apolipoproteins.

Apolipoprotein B (apoB) is the major protein component of plasma low density lipoproteins (LDL) and, through its binding to the LDL receptor, it plays a prominent role in lipoprotein metabolism and in the development of atherosclerosis. Specially developed computer programs were applied to detect potential internal repeats in the human apoB sequence and homology of some of these repeats with other apolipoproteins. The simultaneous computer alignment of several (repeated) sequences, carried out in an iterative way to generate consensus sequences, showed the presence of repeated amphipathic helical regions and of repeated hydrophobic proline-rich domains. Extensive Monte-Carlo statistics were used to demonstrate the statistical significance of the internal repeats. Both classes of repeats may contribute to the specific lipid-binding characteristics of apoB. Additional homology, detected between apoB and apoE, the other apolipoprotein-ligand of the LDL receptor, further defined the structural requirements for this receptor-ligand interaction. The computer programs developed in this study should also be useful for detecting internal repeats in other proteins.

Amino Acid Sequence↗
PubMed1986

Influence of dietary factors on the plasma lipoprotein composition and content in neonates.

Previous studies have shown that the cholesterol and apoprotein concentrations in newborn plasma are dependent on the degree of saturation (polyunsaturated/saturated fatty acids ratio) of the dietary fats. In the present study we compare the influence on the lipoprotein patterns of breast-feeding and of two adapted formulae with a similar P/S ratio in 30 infants. The lipoprotein distribution and composition were investigated by density-gradient ultracentrifugation at days 0, 7 and 30. The lipoprotein patterns were quite comparable at 0 and 7 days in the three groups. We found low VLDL and LDL and relatively elevated HDL concentrations with a high percentage of HDL2. A significant increase of both VLDL and LDL was observed between 0 and 7 days. The VLDL concentration in the breast-fed infants subsequently decreased between 7 and 30 days to a value close to that measured at birth. The infants receiving an adapted formula had significantly higher VLDL and lower LDL at 30 days compared to breast-fed children. HDL concentrations were not significantly different whereas the HDL2 percentage was significantly lower in the infants receiving the adapted formulae. These data further support the hypothesis that the lipoprotein patterns in infants are sensitive to the type of nutrition and that breast-feeding induces specific lipoprotein patterns compared to adapted milk formulae.

Apolipoproteins↗
PubMed1986

Serum lipids and apoproteins in students whose parents suffered prematurely from a myocardial infarction.

Lipids and apoproteins as well as other coronary risk factors were measured in offspring of patients who suffered from a myocardial infarction before the age of 50 years; the results are compared with the results of a control group matched for age and sex. Significant differences were observed in the apoprotein A1 level, in the protein/fat ratios of high- and low-density lipoproteins, and in smoking habits. In a multivariate analysis, the offspring group was found to be different from the control group in nonhigh-density lipoprotein cholesterol/apoprotein B ratio, high-density lipoprotein cholesterol/apoprotein A1 ratio, smoking habits, apoprotein A1, and apoprotein A2. By means of these variables a total of 85% of all subjects could be correctly classified. We conclude that as early as age 21 years the offspring of patients with premature coronary heart disease differ from matched control subjects in lipoprotein measurements and in smoking habits.

Adult↗
PubMed1986

Use of hydrophobicity profiles to predict receptor binding domains on apolipoprotein E and the low density lipoprotein apolipoprotein B-E receptor.

We have used mean hydrophobicity and hydrophobic moment calculations to predict the receptor binding domains in apolipoprotein E and in the low density lipoprotein apolipoprotein B-E receptor. In apolipoprotein E, two receptor binding domains, residues 136-160 and 214-236, having a high hydrophilicity and a high mean helical hydrophobic moment, were identified. The first domain has been located experimentally and mutations influencing the hydrophobicity parameters of the binding site have been shown to affect the receptor binding. The second domain is probably, either separately or in combination with the first domain, involved in receptor binding or in heparin binding. In the low density lipoprotein apolipoprotein B-E receptor, six protein domains were identified. In the first domain (residues 1-371), eight hydrophilic maxima, organized in pairs through disulfide bonds, form the four experimentally observed receptor binding sites. These sites consist of repeats of 26 amino acids but differ from those reported by others [Yamamoto, T., Davis, C. G., Brown, M. S., Schneider, W. J., Casey, M. L., Goldstein, J. W. & Russell, D. W. (1984) Cell 39, 27-38]. The second, more hydrophobic, domain (residues 372-640) forms the core of the receptor, explaining its homology with the precursor of mouse epidermal growth factor, while the cysteine residues in the third domain (residues 641-699), interacting with those of the first domain, further stabilize the molecule. Beyond the fourth hydrophilic domain (residues 700-767), to which carbohydrates are linked, a very hydrophobic membrane spanning region (residues 768-789) could be detected easily. The last domain (residues 790-839), situated in the cytoplasma, contains hydrophilic maxima, as this region might interact with clathrin-related proteins. These data suggest that hydrophobicity analysis can detect and predict protein domains: hydrophilic receptor sites as well as hydrophobic core-forming and membrane-spanning regions.

Amino Acid Sequence↗