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Biomedical subjects

G M Kostner

Publications and source records attributed to G M Kostner.

244 records · Page 14Linked to original sources
PubMed1975

Studies on the composition of pig serum lipoproteins. Isolation and characterization of different apoproteins.

1. Different lipoprotein density fractions from pig serum were isolated by phosphotungstate precipitation followed by purification in the preparative ultra-centrifuge. 2. The protein part of very low density lipoproteins was composed of approximately 52 percent lipoprotein B apoprotein and the rest of lipoprotein C II apoprotein and other as yet unidentified peptides. 3. The protein moiety of low density lipoproteins consisted primarily of lipoprotein B apoprotein (over 95 percent); the amino acid compositions of lipoprotein B apoprotein of very low and low density lipoproteins were practically identical. 4. The predominant polypeptide of pig serum high density lipoproteins exhibited an amino acid composition and a molecular weight very similar to human liprotein A I apoprotein. In contrast to human lipoprotein A I apoprotein, the apoprotein from pigs was found to release leucine first followed by alanine, threonine, and lysine upon incubation with carboxypeptidase A. 5. In pig serum the major lipoprotein C apoprotein was found to be a polypeptide similar in amino acid composition to lipoprotein C II apoprotein from human serum. The molecular weight of this polypeptide is approximately 8000. Incubation experiments with carboxypeptidase A indicate serine to be the most likely C-terminal amino acid.

Amino Acid Sequence↗
PubMedDate not supplied

Platelet activation in normo- and hyperlipoproteinemias.

In the last few years it became obvious that platelets are involved in the development of atherosclerotic diseases. This involvement of platelets has been taken into account in the "response to injury" hypothesis of atherosclerosis. The hypothesis is based on the assumption that atherosclerotic lesions result from endothelial injury, followed by the interaction of vessel wall constituents with lipoproteins, macrophages, and platelets. In the first part of this review, general aspects of platelet activation are summarized and the pathways of platelet aggregation as well as their involvement in blood coagulation are discussed. The second part of this paper describes the influence of cholesterol, lipoproteins, and apolipoproteins upon the activation and metabolic behavior of platelets. Physiological and pathophysiological processes particularly occurring in different types of hyperlipoproteinemias and atherosclerotic disorders are discussed in this context.

Adenosine Diphosphate↗
PubMedDate not supplied

Distribution and concentration of apolipoprotein E in high and low density lipoproteins.

An electroimmunoassay of apolipoprotein E (Apo E) in total human plasma and in the supernatant following precipitation with sodium phosphotungstate in the presence of MgCl2 of the apolipoprotein B (Apo B)-containing lipoproteins is described. The assay is specific and sensitive enough to record also low levels of Apo E found in isolated lipoprotein fractions. In 30 normal male subjects, the method gave a total plasma Apo E concentration of 6.67 +/- 1.92 mg/dl and a HDL Apo E concentration of 2.58 +/- 0.91 mg/dl. Total Apo E is positively correlated with total plasma triglycerides. The values of Apo E in the lipoproteins obtained by ultracentrifugation were lower than the corresponding values obtained by a precipitation procedure, with a mean Apo E loss of 12.1% in the low density lipoproteins (VLDL + LDL) and of 34.3% in HDL. After ultracentrifugation, a substantial amount of Apo E was detected in the d greater than 1.210 g/ml fraction. The proposed method allows to study the Apo E concentration and distribution between low and high density lipoproteins in large samples, avoiding the problems connected with high salt concentrations and centrifugal forces.

Apolipoproteins↗
PubMedDate not supplied

Lipoprotein Lp(a). A risk factor for myocardial infarction.

The aim of this study was to test plasma lipoprotein Lp(a) and other lipid and lipoprotein levels for association with the incidence of myocardial infarction. Total plasma cholesterol, triglycerides, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, and Lp(a) were measured in 1486 men at the age of 18 years. In addition, the Broca Index (a measure of relative body weight) and other data were recorded. The sample was divided into probands whose mothers or fathers suffered a myocardial infarction (case group, n = 52) and into probands whose parents had no myocardial infarction (control group, n = 1434). In the case group, 32% had Lp(a) plasma concentrations greater than 25 mg/dl, but only 13.4% of the control group had this level of concentration, a highly significant difference (p less than 0.01). In addition, there was a statistically significant difference in the ratio of LDL cholesterol/HDL cholesterol (p less than 0.05) and the Broca Index (p less than 0.01) between cases and controls. The parents of the case group were significantly older than the parents of the control group; however, when a control group was matched for parents' age, the results were similar. These data suggest that parents of male children with Lp(a) plasma concentrations greater than 25 mg/dl have a 2.5-fold higher incidence of myocardial infarction. Considering the familial aggregation of elevated Lp(a) levels, we conclude that increased levels of this lipoprotein may be a significant risk factor for myocardial infarction.

Adolescent↗
PubMedDate not supplied

Interaction of lipoprotein Lp(a) and low density lipoprotein with glycosaminoglycans from human aorta.

The lipoprotein complexing activity of glycosaminoglycans (GAG) prepared from human aortas with lipoprotein Lp(a) in comparison to low density lipoproteins (LDL) was determined tubidimetrically in the presence of Ca++. In control experiments, purified chondroitin-6 sulfate and proteoglycans (PG) were used. Lp(a) exhibited approximately a threefold higher reactivity. Analyzing the chemical composition of the complexes, we found that Lp(a) had greater than fourfold higher binding capacity for GAG. The binding capacity of Lp(a) to PG was 3.4-fold higher as compared to LDL. The binding capacity of both lipoproteins for chondroitin-6 sulfate was only 50% in comparison to GAG, but again Lp(a) was four times more reactive. Neuraminidase treatment of LDL or Lp(a) did not interfere with GAG or chondroitin-6 sulfate binding. If, on the other hand, Lp(a) was treated with dithiothreitol and the Lp(a)-specific protein (apoprotein [apo] a) was removed, the GAG binding was reduced by about 45%. Apo a by itself gave no insoluble complexes with GAG. LDL and Lp(a)-s GAG and -LP(a)-PG complexes were incubated with mouse peritoneal macrophages (MPM), and the stimulation of cholesteryl ester formation was studied. At identical lipoprotein cholesterol concentrations, Lp(a)-GAG complexes exhibited a 1.3-fold higher stimulation of cholesterol esterification as compared to LDL-GAG. This difference was even more striking if lipoproteins were compared at a molar basis. PG-lipoprotein complexes were much more active with respect to interactions with MPM. The highest amount of cholesterol ester formation upon incubation with MPM was found with PG-Lp(a) complexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗