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Biomedical subjects

G M Kostner

Publications and source records attributed to G M Kostner.

At least 235 records · Page 13Linked to original sources
PubMed1980

Turnover of lipoprotein (a) in man.

An elevated concentration of lipoprotein (a) [Lp(a)] in the serum has been considered a risk factor for coronary heart disease by various investigators. In the present study, the turnover of Lp(a) was investigated in nine individuals with serum Lp(a) levels ranging from 1 to 68 mg/100 ml. After intravenous injection of radioiodinated Lp(a), the radioactivity time-curve of the serum and the specific activitity time-curves of the isolated Lp(a) and Lp(a) apolipoproteins were measured for 14 d. More than 97% of the label was found in the protein moiety of Lp(a). During the entire study period, the serum radioactivity remained with Lp(a), only insignificant amounts of radioactivity were detectable in other lipoprotein fractions. The serum radioactivity time-curves and the specific activity time-curves of the isolated Lp(a) and Lp(a) apolipoproteins were identical. The kinetic parameters of Lp(a) turnover were calculated in terms of a two-compartment model. 76.5+/-5.1% (mean+/-1 SD) of total Lp(a) was contained in the intravascular space. The biological half-life of Lp(a) was 3.32+/-0.52 d, the fractional catabolic rate (FCR) was 0.306+/-0.054/d, and the rate of synthesis was 5.00+/-3.37 mg/kg/d. A positive correlation was found between serum concentration and synthetic rate of Lp(a) apoprotein. No relationship could be demonstrated between serum level and FCR of Lp(a). The results of this study indicate that Lp(a) is not converted to other serum lipoproteins. From the correlations between serum concentration and kinetic parameters of Lp(a) it is concluded that an elevated Lp(a) level is the consequence of an increased Lp(a) apoprotein synthesis.

Adult↗
PubMed1979

Structural organization of free and esterified cholesterol in human high density lipoproteins. A 100.6 MHz 13C NMR study.

The structural organization of free and esterified cholesterol in human high density lipoproteins has been studied by high-field 1H and 13C NMR. The measurements are consistent with free cholesterol being present in at least two different environments. Part of the free cholesterol is oriented in the outer surface layer of the high density lipoprotein particle in contact with phospholipid or apoprotein, or both. The rest is probably present in the liquid, hydrophobic core of the HDL particle.

Cholesterol↗
PubMed1979

Studies on the protein composition of human serum very low density lipoproteins: demonstration of the beta 2-glycoprotein-I.

Human serum VLDL isolated by polyanion precipitation and ultracentrifugation have been delipidated with ethanal/diethyl ether. By electrophoresis in 10% polyacrylamide gels containing 8M urea, we found a protein which comigrated with apolipoprotein E. This protein was purified by column chromatography and turned out to be identical with beta 2-glycoprotein-I, the serum factor which is necessary for the precipitation of triglyceride-rich lipoproteins with sodium decyl sulfate or sodium dodecyl sulfate. Upon analytical isoelectric focusing, beta 2-glycoprotein-I gave four major bands in the pH region 5.7--6.6. All four bands gave an immunochemical reaction of identity with a monospecific antiserum. From its unique amino acid composition we conclude that beta 2-glycoprotein-I is distinct from all apolipoproteins described previously in the literature.

Amino Acids↗
PubMed1979

Determination of high-density lipoproteins: screening methods compared.

Factors reflecting the concentration of high-density lipoproteins in serum were assessed for 108 men and 106 women participating in a Venetian screening program for hyperlipoproteinemia. The methods applied, optimized in our laboratory, were: (a) cholesterol in high-density lipoproteins, determined in the supernate after sedimentation of the very-low-density lipoproteins + low-density lipoproteins with dextran sulfate or sodium phosphotungstate; and (b) immunochemical quantitation of apolipoprotein A-I and apolipoprotein A-II by Laurell's "rocket" technique. The latter determinations were performed with total serum before and after delipidation with diispropyl ether/n-butanol (6/4 by vol). The dextran sulfate method gave about 5% higher values than did the phosphotungstate method, but the correlation between the two was excellent (r = 0.95). Results of the immunochemical quantitation indicate that delipidation of lipoproteins before Laurell electrophoresis may not be necessary if only freshly drawn sera are used.

Adult↗
PubMed1978

Isolation of subfractions of human very low density lipoproteins by zonal ultracentrifugation.

Very low density lipoproteins (VLDL) have been isolated and subfractionated on the basis of their differing flotation rates. The procedure consists of a single 45-min zonal ultracentrifugation step using a linear density gradient of d = 1.00 to 1.15 g/ml. Appropriate fractions of the zonal rotor effluent containing the entire VLDL spectrum were characterized by analytical ultracentrifugation, gel filtration chromatography, and complete chemical analysis. Flotation rates of VLDL subspecies from hypertriglyceridemic and normolipemic plasmas correlated directly with their Stokes radii and triglyceride content and inversely with their proportion of cholesterol, cholesteryl esters, phospholipids, and total protein. There was also an inverse correlation of flotation rate with the fraction of tetramethylurea-insoluble protein. This procedure provides a reliable methodology for a rapid isolation of VLDL subfractions and the accurate determination of their flotation rates.

Centrifugation, Zonal↗
PubMed1977

The separation of human serum high density lipoproteins by hydroxy apatite column chromatography. Evidence for the presence of discrete subfractions.

Human serum high density lipoprotein subfractions 2 and 3, isolated by preparative ultracentrifugation after blocking the enzyme phosphatidylcholine: cholesterol acyl transferase, have been subfractionated further by hydroxyapatite column chromatography. From subfraction 2 we reproducibly obtained 5 and from subfraction 3, 6 fractions differing in chemical composition and apolipoprotein content. The fractions eluting at low salt concentrations were composed primarily of apolipoprotein-A polypeptides while those eluting at high salt concentrations consisted primarily of apolipoprotein-C. From all the 11 subfractions only one contained the "arginine-rich" polypeptide. The apolipoprotein-C-containing fractions were richer in triacylglycerol, phospholipids and free cholesterol as compared to the apolipoprotein-A-containing ones. Although small differences of their partial specific volumes existed, the obtained values indicate that all subfractions belonged to the parent density class. The implications of these results to the current view of lipoprotein metabolism are discussed.

Apolipoproteins↗
PubMed1977

Separation of subclasses of human serum high density lipoproteins by zonal ultracentrifugation.

An improved one-step method for the preparative separation of three subfractions of high-density lipoproteins from normal human serum has been developed. It employs the method of rate zonal ultracentrifugation in a z-60 rotor using a discontinuous NaBr gradient in the density range of 1.0-1.4. The density gradients were monitored directly by a flow-through density meter allowing the direct read-out of the actual densities in the process of filling and emptying the rotor. The separation of the three density fractions from 5 to 15 ml serum was achieved during a single 12 hours run at 59.000 rpm. The three fractions showed characteristically different patterns on polyacrylamide gel electrophoresis and differences in their lipid and protein composition.

Centrifugation, Zonal↗
PubMed1977

[A rheological study on plasma lipoproteins (author's transl)].

Lipoproteins of the types LpB and LP-X are studied in a microviscometer to measure intrinsic viscosity. Up to a shear rate of 1700s-1 no shear dependence of viscosity is observed. Intrinsic viscosities are 3.5 and 4.0 for LpB, and 8.5 ml/g for LP-X. Density measurements are used to calculate apparent specific volumes. The results are compatible with a spherical model. An upper limit of 0.45 is estimated for the hydration.

Blood Viscosity↗
PubMed1976

Investigation of the abnormal low-density lipoproteins occurring in patients with obstructive jaundice.

The abnormal lipoproteins of the density range 1.019-1.063g/cm3 occurring in the plasma of patients with obstructive jaundice were studied. Subfractionation of this density class by combined sodium phosphotungstate precipitation, ultracentrifugation, and column chromatography on hydroxyapatite and agarose gel yielded essentially three fractions: (1) lipoprotein-X, (2) A triglyceride-rich lipoprotein for which we propose the term lipoprotein-Y and (3) an abnormal lipoprotein, lipoprotein-B. Marked differences between these fractions with respect to electron-microscopic appearance, hydrated densities, chemical composition and immunochemical characteristics were observed. The protein moiety of lipoprotein-X consisted primarily of apolipoprotein-C and albumin. Lipoprotein-Y showed, in addition to apolipoprotein-C, the presence of apolipoprotein-B. The 'lipoprotein-B' fraction isolated from sera of these patients had higher triglyceride and free cholesterol contents than that of normal individuals and an unusually high content of apolipoprotein-C. The relative distribution of lipoprotein-X, lipoprotein-Y and 'lipoprotein-B' varied from patient to patient. The importance of considering the existence of lipoprotein-Y in screening patients for cholestasis by the lipoprotein-X test is discussed.

Cholestasis↗