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Biomedical subjects

G M Kostner

Publications and source records attributed to G M Kostner.

At least 199 records · Page 11Linked to original sources
PubMed1986

Isolation of pure LpB from human serum.

Low density lipoproteins (LDL), even after isolation from a narrow density cut and after several washes by preparative ultracentrifugation, are contaminated by 3-5% non-apoB proteins. Incubation of these LDL with artificial triglyceride-rich lipid emulsions (TGRP) removed all contaminating apoC and also, under certain conditions, apoA proteins. TGRP treatment did not, however, change the lipid composition and the flotation behavior of LDL. Residual apoE and albumin, amounting up to 0.5% of the apoB mass, were resistant to removal by TGRP treatment as well as by heparin-Sepharose column chromatography. ApoE and albumin could only be removed by immunoabsorption.

Apolipoproteins↗
PubMed1986

Improved estimation of cholesteryl ester transfer/exchange activity in serum or plasma.

This simple, routine assay for measuring cholesteryl ester transfer/exchange activity in human plasma is based on the removal of interfering lipoproteins--very-low-density (VLDL) and low-density lipoproteins (LDL)--by precipitation with polyethylene glycol. High-density lipoproteins (HDL) in the samples do not affect the results. The supernate after precipitation is mixed with [14C]cholesteryl ester-labeled LDL as donor and with HDL as the acceptor for the cholesteryl ester. After incubation for 16 h at 37 degrees C, LDL is separated from HDL by precipitation with dextran sulfate and the radioactivity measured in the supernate, which contains the HDL. The assay is applicable to samples containing as much as 10 mmol of triglycerides per liter. The within-assay CV was 2.7%, the day-to-day CV 6.8%. Results compared well with those by conventional procedures.

Chemical Precipitation↗
PubMed1985

Influence of beta 2-glycoprotein-I upon the content of cAMP and cGMP in human blood platelets.

The influence of beta 2-glycoprotein-I on the cyclic nucleotide content in human gel filtered platelets (GFP) was studied: beta 2-G-I up to a concentration of 5 mg/ml does not alter the basal cAMP level in resting GFP and also does not influence the action of PGE1 which strongly inhibits platelet aggregation by elevation of cAMP. Collagen induced aggregation of GFP leads to an increase of the platelet cGMP content. Preincubation of GFP with 0.2 mg/ml of beta 2-G-I enhances significantly the cGMP increase by collagen. In a similar manner beta 2-G-I also amplifies the increase in cGMP concentration induced by ADP. In this case, a concomitant alteration of the aggregation pattern is observed. Thrombin produces a much higher cGMP elevation in GFP than ADP or collagen. The admixture of 0.2 mg/ml of beta 2-G-I is not able to enhance further the thrombin effect on cGMP. The results are discussed in view of the possible significance of these observations for platelet aggregation in vivo.

Adenosine Diphosphate↗
PubMed1985

Interaction of beta 2-glycoprotein-I with human blood platelets: influence upon the ADP-induced aggregation.

The interaction of beta 2-glycoprotein-I (beta 2-G-I), a plasma constituent of unknown function, with blood platelets was studied. The following results were obtained: 1) beta 2-G-I binds to washed human platelets isolated by centrifugation (WP) at one kind of specific, saturable binding sites. The dissociation constant was found to be approx. 1 X 10(-6) M. In the presence of physiological concentrations of Ca++ (2.5 mM), this specific binding is markedly reduced. Unspecific binding of beta 2-G-I to platelets, however, is not influenced by Ca++. Platelets prepared by gel filtration (GFP), differing in their in vitro aggregability from WP, exhibit no specific binding of beta 2-G-I. Binding to GFP is also not induced by activation with thrombin, collagen or ADP. beta 2-G-I causes significant alteration of the ADP-induced aggregation of GFP. Aggregation induced by thrombin, collagen, arachidonic acid or PAF-acether, however is not altered by beta 2-G-I. It is suggested, that pelleting during centrifugation causes irreversible rearrangements in the membrane of platelets.

Adenosine Diphosphate↗
PubMed1985

Factors affecting the conversion of high-density lipoproteins: experiments with pig and human plasma.

The conversion of pig high-density lipoproteins (HDL) (mainly HDL3) to fractions of lower densities was studied by incubating pig plasma for 24 h at 37 degrees C in the presence and absence of lipoprotein lipase from bovine milk, lecithin:cholesterol acyltransferase, cholesteryl ester transfer protein and triacylglycerol-rich particles (very-low-density lipoproteins (VLDL) or Intralipid). The results can be summarized as follows. In the presence of lipoprotein lipase and at a VLDL/HDL mass ratio of 2, the F-1.210 of pig HDL was shifted from 3.3 to 4.2, which is characteristic for human HDL2. This shift was caused by the excessive increase in the free fatty acid content in HDL. If 50 g/l of bovine serum albumin were added prior to incubation, the flotation rate of HDL remained in the HDL2a region. If lecithin:cholesterol acyltransferase was active in fasting pig plasma during incubation, we observed only a negligible increase of F-1.210 in HDL. If pig lipoproteins were incubated with human lipoprotein-free serum as a source of cholesteryl ester transfer activity, a slight increase in the flotation rate of HDL was observed, which was amplified in the presence of active lecithin:cholesterol acyltransferase. Pig HDL was converted to a fraction with F-1.210 of 4.2, which is typical for human HDL2, only if active lecithin:cholesterol acyltransferase, cholesteryl ester transfer protein and triacylglycerol-rich particles were present in the incubation mixture. From our results we also concluded that apolipoprotein A-II plays no role in the HDL2 formation.

Animals↗
PubMed1985

Serum lipids and lipoproteins in patients with primary gout.

Serum lipid and lipoprotein values of 32 male patients suffering from gout were quantitated and compared with corresponding values of a random control group which did not differ significantly with regard to age, body weight index and socio-economic status. All patients were on therapy with allopurinol which lasted on average for 6 years. The most striking differences between patients and controls were the increased triglyceride and apo B values and the decreased HDL-cholesterol (HDL-C) and HDL-phospholipid (HDL-PL) values in the patient group. The values of total cholesterol, LDL-cholesterol, apo A-I and Lp (a) were not significantly different between patients and controls. The great differences in the ratios of apo B/LDL-C, apo A-I/HDL-C and apo A-I/HDL-PL values suggest that gout is connected with changes in the chemical composition of the major lipoprotein classes. In three normolipemic individuals who were treated for 3 weeks with allopurinol no changes in lipoproteins and apolipoproteins were apparent. The results are discussed in view of the atherosclerosis risk of patients suffering from gout.

Apolipoproteins A↗
PubMed1985

Plasma lipids and lipoproteins of a patient with cholesteryl ester storage disease.

The plasma lipids, lipoproteins and lipolytic enzymes of a patient suffering from cholesterol ester storage disease were investigated and followed over a time period of 3 years. The patient was hypertriglyceridaemic and cholesterolaemic and exhibited very low levels of high density lipoproteins. These lipoproteins consisted almost exclusively of the HDL-subfraction-3. Apolipoprotein-B was elevated and apoAI and AII were grossly reduced. The activity of lipoprotein lipase was normal, but hepatic lipase values were increased. Lecithin: cholesterol acyltransferase was in the upper normal range. The corresponding lipoprotein and enzyme values of one brother were within normal limits but some components measured in the plasma of the father were abnormal. It is speculated that the low plasma HDL levels in this disease may be a consequence of increased hepatic lipase activity in addition to a derangement in the reverse cholesterol flow.

Adolescent↗
PubMed1985

The interaction of human plasma low density lipoproteins with glycosamino-glycans: influence of the chemical composition.

Human plasma of 5 normolipemic individuals was incubated for 24 hr at 37 C in the presence or in the absence of lecithin:cholesterol acyltransferase (LCAT)-inhibitors. Plasma stored at 4 C served as a control. The low density lipoprotein (LDL) fractions of the samples were isolated and investigated with respect to changes in chemical composition and complexing activity with glycosamino glycans (GAG). Incubation of plasma in the presence of LCAT inhibitors caused a significant increase of LDL triglycerides at the expense of cholesteryl esters. Incubation with active LCAT not only changed the core but also the surface constituents (decrease in phospholipids and in free cholesterol). The amount of GAG bound per mg of LDL was not uniformly changed in samples incubated after LCAT inhibition. LDL isolated from plasma incubated in the presence of LCAT, on the other hand, showed a significant reduction in GAG binding. The ratio of free cholesterol:GAG in the complex was most significantly reduced in LCAT-modified LDL. There was in addition a highly significant correlation between the LDL:GAG ratio in the complex and the free cholesterol and phospholipid content of the LDL samples. It is concluded that alterations in surface lipid constituents of LDL strongly affect their interaction with sulfated polysaccharides, an effect which may be relevant also in vivo for the interaction of LDL with cell surfaces and intercellular matrices.

Female↗
PubMed1985

Altered metabolism of low density lipoprotein in humans after prolonged incubation in plasma.

Lecithin: cholesterol acyltransferase (LCAT) in combination with exchange and transfer proteins is known to alter the composition of all plasma lipoprotein fractions. Human plasma from healthy donors was incubated for 24 h at 37 degrees C in the absence and at 4 degrees C and at 37 degrees C in the presence of the LCAT inhibitors sodium iodoacetate (5 mmol/l), and the low density lipoprotein fractions (LDL) were isolated. LDL isolated from LCAT-active plasma (LDL-a) exhibited pronounced alterations in their surface material: the relative content of phospholipids and of free cholesterol was reduced and the content of tetramethylurea-soluble apolipoproteins was increased. LDL isolated from plasma incubated at 37 degrees C with or without sodium iodoacetate showed significantly increased triglyceride concentrations. The LDL fractions from LCAT-active and LCAT-inactive (LDL-i) incubates were iodinated with 125I and 131I respectively, and their metabolic behaviour was studied in humans. LDL-a was cleared from circulation at a slower rate as compared with LDL-i (t 1/2 = 3.17 +/- 0.47 vs 2.88 +/- 0.45 days). The apparent fractional catabolic rate of LDL-a, calculated according to a two-pool model, was reduced by 22.2 +/- 3.1%. Comparing LDL-a with LDL isolated from LCAT-inactive plasma which had been incubated at 37 degrees C, the changes in the metabolic variables were less pronounced. It is concluded that physiological alterations of the chemical compositions, caused by LCAT and exchange/transfer proteins, influence the metabolism of LDL.

Adult↗
PubMed1985

Demonstration of receptor binding of two apo-B containing lipoproteins by differential labelling with colloidal gold.

The interaction of two types of apo-B containing lipoproteins, human low density lipoprotein (LDL) and lipoprotein-a (Lp(a], with cultured human skin fibroblasts was studied by differential colloidal gold labelling in conjunction with thin sectioning and surface replication techniques. After separate exposure of the fibroblasts to either gold labelled LDL or Lp(a) for 15 to 30 min at 37 degrees C, labelled lipoproteins were predominantly found in coated pit areas. Excess of unlabelled LDL or Lp(a) completely displaced the gold labelled lipoproteins, indicating specific binding by the LDL-receptor. Simultaneous exposure of fibroblasts to LDL-16 nm gold and Lp(a)-40 nm gold conjugates revealed that both LDL and Lp(a) are bound in the same coated pit and internalized into the same endosome. In contrast to native lipoproteins, gold labelled acetylated lipoproteins were found diffusely distributed on membrane surface areas predominantly representing fibronectin-containing fibrils.

Apolipoproteins B↗
PubMed1985

The in vitro formation of HDL2 during the action of LCAT: the role of triglyceride-rich lipoproteins.

We examined the effects of lecithin:cholesterol acyl transferase (LCAT) and of lipoprotein lipase (LPL) on the conversion of high density lipoproteins (HDL) towards fractions of lower densities using the analytical ultracentrifuge. Freshly isolated whole plasma was incubated for 24 h at 37 degrees C in the presence or absence of active enzyme systems. In some cases, lipoproteins were removed by selective precipitations; alternatively, we added triglyceride-rich lipoproteins (TGRLP) or Intralipid to the incubations. The results are as follows. 1) The incubation of whole plasma containing active LCAT leads to a conversion of HDL3 to a fraction of lower density, notably HDL2a. If LCAT is inhibited, the conversion is far less pronounced. 2) If very low and low density lipoproteins are removed by phosphotungstate precipitation and the supernatant is incubated with LCAT, HDL3 shifts towards higher densities. 3) The presence of phosphatidylcholine/cholesterol liposomes or the presence of blood cells as a source of additional LCAT substrate had only little influence on the HDL conversion in our system. 4) The addition of TGRLP or of Intralipid at minimal ratios of 2.5:1 caused an almost complete conversion of HDL3 to HDL2b. This conversion was dependent on active LCAT. 5) LPL also caused a shift of HDL3 to HDL2a if TGRLP was present. HDL2b, however, was not formed by LPL unless LCAT was active.

Cholesterol↗
PubMed1984

The low-density-lipoprotein pathway of native and chemically modified low-density lipoproteins isolated from plasma incubated in vitro.

Normal fasting human plasma was incubated for 24 h at 37 degrees C in the presence or absence of lecithin:cholesterol acyltransferase (LCAT) inhibitors. The low-density lipoprotein (LDL) fractions of incubated plasma (control LDL and LCAT-modified LDL) were studied with respect to their chemical and functional properties. LCAT-modified LDL differed from control LDL by a decreased phospholipid and free-cholesterol content, but increased cholesteryl esters. Furthermore, an increase of the relative protein content in LDL by 16-20% was found. Apolipoproteins of LCAT-modified LDL exhibited a 10-fold increase of apo AI, a 4-5-fold increase of apo E, and a 2-fold increase of apo C. All these apolipoproteins resided together with apo B on the same particles. LCAT-modified LDL displayed a higher electrophoretic mobility, a higher hydrated density, a decreased flotation constant and a smaller diameter. Cultured human fibroblasts bound and internalized LCAT-modified LDL to a lower extent than control LDL. The degradation, however, was faster. Modified LDL suppressed 3-hydroxy-3-methylglutaryl-CoA reductase activity to a lower extent than did control LDL. Our results demonstrate that LCAT action, together with lipid transfer and exchange processes, markedly alters the chemical and physiochemical properties of LDL. This in turn significantly influences LDL catabolism in vitro.

Cells, Cultured↗
PubMed1984

[Lipoprotein Lp(a) as a risk factor for heart infarct--a family study].

Lp(a) concentrations, apolipoprotein A-I and B, and various lipid parameters were measured from members of 3 families in which myocardial infarction frequently occurred. No correlation could be found between Lp(a) concentration and other lipoprotein parameters. It has been demonstrated that myocardial infarction and atherosclerotic diseases occur only in patients with Lp(a) concentrations higher than 70 mg/dl. An unfavourable Apo B/Apo A-I relation or LDL/HDL relation, associated with high Lp(a) concentration seems to play a decisive role in the development of atherosclerosis or myocardial infarction. The study suggests that subjects with Lp(a) values higher than 100 mg/dl could suffer from a special form of hyperlipoproteinemia ("Hyper-Lp(a)").

Adolescent↗