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Biomedical subjects

G Assmann

Publications and source records attributed to G Assmann.

At least 433 records · Page 24Linked to original sources
PubMed1980

Lipoprotein and apoprotein values in coronary angiography patients.

In this study the lipoprotein and apoprotein patterns of patients with coronary artery disease were evaluated. The patient population consisted of 179 men who underwent coronary arteriography. On the basis of the results of coronary arteriography these patients were subdivided into a control group (score 0) with normal arteriograms and three groups each having coronary artery disease (CAD) of increasing severity (scores 1 to 3). The patients with coronary artery disease had significantly higher plasma concentrations of total cholesterol, LDL cholesterol, triglycerides and apolipoprotein B (apo B) than the controls. HDL cholesterol as well as apolipoprotein A-I (apo A-I) were significantly lower in patients with coronary artery disease. However, no difference was found in apolipoprotein A-II (apo A-II) values. Apo B and LDL cholesterol increased with the degree of coronary atherosclerosis. In the discriminant function analysis, apo B was the best separating parameter between control patients and CAD patients (scores 1-3).

Apoproteins↗
PubMed1979

[Tangier-disease (author's transl)].

Tangier disease is a rare autosomal recessive lipid transport disease characterized by the absence of the usual high density lipoproteins from plasma and cholesteryl ester storage in many organs. 25 cases of Tangier disease have been described so long. The predominant clinical symptoms include tonsilar hypertrophy, splenomegaly and peripheral neuropathy. The cholesteryl ester storage is limited to macrophages, Schwann's cells and intestinal smooth muscle cells. Hypocholest erolemia (less than 80mg/dl), hypertriglyceridemia (greater than 200 mg/dl), and the absence of high density lipoproteins in agarose electrophoresis are the major plasma abnormalities. The protein moiety of normal high density lipoprotein consists of apoprotein A-I and apoprotein A-II. In Tangier disease, serum concentrations of these apoproteins are reduced to less than 1% and 5-10%, respectively. Theories concerning the pathogenesis of Tangier disease are only incomplete and unproved up to now; however, a structural abnormality of apoprotein A-I causing an inability to bind to lipid or other proteins (apoprotein A-II) is consistent with several of the recent biochemical findings. The imbalance of cellular cholesterol metabolism caused by the absence of high density lipoproteins as well as the presumed role of these lipoproteins in cholesterol removal from cells are discussed in this article.

Cholesterol↗
PubMed1979

Demonstration of human apolipoprotien A in isolated mucosal cells from small intestine and isolated hepatocytes.

Isolated mucosal cells from the human jejunum and stomach, cryostat sections from the jejunum, isolated parenchymal liver cells and lymphocytes were investigated for the presence of apolipoprotien A (apoA). Antisera against purified human apoA-I and apoA-II were raised in rabbits and conjugated with fluorescein-isothiocyanate (FITC). Mucosal cells from jejunum and stomach were isolated with pronase from tissue obtained from operated patients. ApoA-I and apoA-II could be demonstrated in isolated mucosal cells as well as in cryostat sections from the jejunum. The fluorescence pattern in isolated jejunal cells was coarse granular. In the radial gel diffusion test the homogenate from mucosal cells of jejunum showed a single precipitation line with anti-apoA-I and with anti-apoA-II, respectively. The reaction was more intensive with anti-apoA-I than with anti-apoA-II. Isolated gastric cells were negative for apoA. Hepatocytes incubated with FITC anti-apoA-I showed a fine granular fluorescence pattern in the cytoplasm. Anti-apoA-II did not react with hepatocytes. There was no evidence for an in vivo fixation of serum-apoA at the surface of isolated mucosal cells from jejunum or isolated hepatocytes. The results support the hypotheses that in man apoA is synthesised in the epithelial cells of the small intestine and in parenchymal liver cells.

Apolipoproteins↗
PubMed1978

Characterization of the oligosaccharide side chain of apolipoprotein C-III from human plasma very low density lipoproteins.

Apolipoprotein C-III1 and apolipoprotein C-III2 each contain one oligosaccharide side chain, bound O-glycosidically to threonine in position 74 of the amino acid sequence. The studies reported in this paper characterize these alkali labile oligosaccharides, thereby demonstrating the complete structure of apolipoprotein C-III. Monosaccharide analysis revealed the following sugar composition: D-galactose/N-acetyl-D-galactosamine/sialic acid 1 : 1 : 1 and 1 : 1 : 2 for apolipoprotein C-III1 and apolipoprotein C-III2, respectively. Treatment of desialylated apolipoproteins with alkaline borohydride released the reduced disaccharide beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol, which was detected by gas-liquid chromatography. Further studies employing periodate oxidation and Smith degradation indicated that the structure of the trisaccharide from apolipoprotein C-III1 was alpha-N-acetylneuraminyl-(2 leads to 3)-beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol. The tetrasaccharide structure from apolipoprotein C-III2 is made up of this trisaccharide plus one sialic acid residue linked to C6 of N-acetyl-D-galactosaminitol, as was shown by the assessment of chromogens formed upon alkaline degradation.

Alkalies↗
PubMed1978

High density lipoprotein infusion and partial plasma exchange in Tangier disease.

High density lipoprotein (HDL) infusion and partial plasma exchange were undertaken in two patients homozygous for Tangier disease. Serum samples and ultracentrifugally isolated serum fractions were analysed over a period of 7 days post infusion by agarose electrophoresis, two-dimensional immunoelectrophoresis (employing antibodies to HDL, HDL3, Apoprotein A-I, and Apoprotein A-II), Apoprotein A radioimmunoassay, and analytical polyacrylamide electrophoresis. The following observations were made: (a) immediately after HDL substitution the broad-beta band, normally visible upon agarose electrophoresis of Tangier plasma, resolved into a distinct beta and pre-beta band; (b)as HDL was catabolized, an abnormal alpha-migrating lipoprotein was generated which contained Apoprotein A-II as protein constituent; and (c) there was a proferential loss of Apoprotein A-I from HDL and the plasma compartment in the course of HDL catabolism. The results suggest that the defect in Tangier disease resides with enhanced catabolism or defective synthesis of Apoprotein A-I.

Apolipoproteins↗
PubMed1978

The role of high density lipoproteins in lecithin:cholesterol acyltransferase activity: perspectives from Tangier disease.

Lecithin:cholesterol acyltransferase activity and the lipid composition of VLDL and LDL were examined in five patients homozygous for Tangier disease. The following results were obtained: I. The percentage of cholesterol that was esterified was similar in Taniger and control lipoproteins. II. Linoleic acid was the predominant fatty acid constituent of cholesteryl esters in Tangier plasma. III. Molar cholesterol esterification rates in Tangier plasma were reduced; however, fractional rates of cholesterol esterification were equal to or exceeded those of control plasma. IV. In vitro addition of apoprotein A-I and isolated lipoproteins led to a concentration-dependent increase in the initial rates of cholesterol esterification in Tangier plasma. It is concluded that HDL is not an exclusive substrate for the LCAT reaction, and that cholesterol esterification is not impaired in Tangier plasma.

Apolipoproteins↗
PubMed1978

Phosphatidylcholine substrate specificity of lecithin:cholesterol acyltransferase.

Lecithin:cholesterol acyltransferase (LCAT) has been partially purified by the combined method of ultracentrifugation and dextranblue-2000 4 B affinity chromatography. The enzyme was incubated with liposomes consisting of phosphatidylcholine-cholesterol in a molar ratio of 10/1. Chemically synthesized phosphatidylcholine substrates with labeled fatty acids in 1-and 2-position were chosen to evaluate the degree of transesterification. It was found that the fatty acid in the 1-position of phosphatidylcholine significantly influences cholesteryl ester formation, both by its direct involvement in the LCAT reaction and its contribution to the physico-chemical properties of phosphatidylcholine.

Chemical Phenomena↗
PubMed1977

The lipoprotein abnormality in Tangier disease: quantitation of A apoproteins.

In this study we have determined by radioimmunoassay and double immunoelectrophoresis the total quantities and distributions of A apoproteins in three adult patients affected with Tangier disease (hereditary alpha-lipoprotein deficiency). Compared with normal plasma, the total quantities of apoproteins A-I and A-II in Tangier plasma were determined to be less than 1% and 5-7%, respectively. In Tangier patients, approximately 90% of the apoprotein A-I sedimented when ultracentrifugations of plasma were carried out at density 1.21 g/ml KBr. By contrast, more than 95% of the apoprotein A-II floated under those conditions. In normal plasma, approximately 90% of both apoproteins A-I and A-II is found in the 1.063-1.21-g/ml KBr density fraction. These findings suggest that complete dissociation of A apoproteins occurs in Tangier plasma. This dissociation of apoproteins was confirmed by double immunoelectrophoresis with monospecific antisera. Immunochemical and electrophoretic experiments did not provide evidence for a structural abnormality of apoprotein A-I in these patients, The results taken together strongly suggest that normal high-density lipoproteins are absent from Tangier plasma.

Adult↗
PubMed1977

Isolation and characterization of an abnormal high density lipoprotein in Tangier Diesase.

The nature of the high density lipoproteins has been investigated in five patients homozygous for Tangier disease (familial high density lipoprotein deficiency). It has been established that Tangier high density lipoproteins, as isolated by ultracentrifugation, are morphologically heterogenous and contain several proteins (Apo B, albumin, and Apo A-II). An abnormal lipoprotein has been isolated from the d = 1.063-1.21 g/ml ultracentrifugal fraction by agarose-column chromatography which contains apoprotein A-II as the sole protein constituent. In negative-stain electron microscopy, these lipoproteins appeared as spherical particles 55-75 A in diameter. By a variety of criteria (immunochemical, polyacrylamide electrophoresis, amino acid composition, and fluorescence measurements), apoprotein A-I the major apoprotein of normal high density lipoproteins and the C apoproteins were absent from this lipoprotein. As demonstrated by (125)I very low density lipoprotein incubation experiments with Tangier plasma, C apoproteins did not associate with lipoproteins of d = 1.063-1.21 g/ml. Tangier apoprotein A-II, isolated to homogeneity by delipidation of the apoprotein A-II-containing lipoprotein or Sephadex G-200 guanidine-HCl chromatography of the d = 1.063-1.21 g/ml fraction, was indistinguishable from control apoprotein A-II with respect to amino acid composition and migration of tryptic peptides in urea-polyacrylamide electrophoresis. The ability of Tangier apoprotein A-II to bind phospholipid was demonstrated by in vitro reconstitution experiments and morphological and chemical analysis of lipid-protein complexes. It is concluded that normal high density lipoproteins, as defined by polypeptide composition and morphological appearance, are absent from Tangier plasma and that as a consequence, the impairment of C apoprotein metabolism contributes to the hypertriglyceridemia and fasting chylomicronemia observed in these patients.

Amino Acids↗
PubMed1977

Characterization of high density lipoproteins in patients heterozygous for Tangier disease.

In this study a large family group affectd with Tangier disease has been investigated. Besides two homozygous propositi, several heterozygous patients have been identified on the basis of quantitative measurements of high density lipoproteins and their constitutive polypeptides. By a variety of quantitative immunological methods, such as one-dimensional Laurell eletrophoresis, two-dimensional immunoelectrophoresis, and double-antibody radioimmunoassay, the total amount of apoprotein A-I and apoprotein A-I contained in the serum of heterozygous patients and the distribution of these A apoproteins among serum lipoproteins have been determined. The molar ration of apoprotein A-I and apoprotein A-II contained in high density lipoproteins of heterozygous patients did not significantly differ from that of control preparations, although the total mass of high density lipoproteins was reduced by approximately 50%. The elution profile of high density lipoproteins from agarose columns and their morphological appearance, as ascertained by electron microscopy, were similar to control preparations. In addition to the quantitative alterations of serum lipoproteins, lipid storage in histiocytes of the rectal mucosa obtained from heterozygous patients has been documented. It is concluded that patients heterozygous for Tangier disease have normal high density lipoproteins in circulation, the total mass of which is reduced by approximately 50%.

Apolipoproteins↗
PubMed1976

Swine aortic smooth muscle in tissue culture. Some effects of purified swine lipoproteins on cell growth and morphology.

Smooth muscle cells (SMC) were grown from inner media explants of swine aorta and used as a model for studying the role of lipoproteins in atherogenesis. These cultured cells retain the characteristics of SMC through multiple passages. Cell growth curves, in time, were obtained by using standard counting techniques, SMC grew slowly (0.019 cycle/day) in modified Dulbecco-Vogt medium supplemented with 1.5% swine serum. Purified lipoproteins were prepared from three normolipidemic and two hyperlipidemic (cholesterol-fed) swine. When the medium of 84 growth experiments was supplemented with these lipoproteins, SMC growth rate increased linearly with lipoprotein cholesterol concentration up to 10 mg/dl. At 10 mg/dl of lipoprotein cholesterol, very low density lipoproteins (VLDL) increased growth rate 7.2-fold (P less than 0.01); low density lipoproteins (LDL) 5.7-fold (P less than 0.01); high density lipoproteins (HDL2) 3,4-fold (P less than 0.02); and HDLc, and lipoprotein appearing in the hyperlipidemic swine, 3.0-fold (P less than 0.01). Addition of 10% lipoprotein-free serum stimulated growth rate 6.0-fold (P less than 0.01). There was no difference between normo- and hyperlipidemic lipoproteins with respect to cell growth rate. Factors present in the ultracentrifugal bottom, and factors appearing during the platelet release reaction, were shown to contribute to the SMC growth response. Morphological alterations characteristic of intimal foam cells occurred in SMC grown in VLDL at triglyceride levels in excess of 15 mg per 100 ml. Thus there are distinct parallels between SMC response in this model in vitro and atherogenesis in vivo.

Animals↗