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Biomedical subjects

A M Scanu

Publications and source records attributed to A M Scanu.

At least 163 records · Page 9Linked to original sources
PubMed1981

Rapid fractionation of human high density apolipoproteins by high performance liquid chromatography.

A simple and rapid fractionation procedure (30 min) has been developed for the isolation of the major apoproteins from human serum high density lipoproteins by molecular sieving in a high performance liquid chromatographic column. Apo A-I, apoA-II and the C peptides are quantitatively resolved up to a protein load of 3 mg. The technique has also been successfully applied to the final purification of A apoproteins which had been isolated by conventional chromatographic procedures and as a sensitive analytical tool for assessing apoprotein purity.

Apolipoprotein A-I↗
PubMed1981

Effect of oxygenated sterol compounds on human bone marrow granulocytic progenitor cells.

Oxygenated sterol compounds are potent inhibitors of sterol and DNA synthesis in mammalian cells. We studied the effects of oxygenated sterols on human marrow granulocytic progenitor cells in vitro (CFU-C). 25-Hydroxycholesterol was found to be a potent inhibitor of sterol synthesis in marrow mononuclear cells, with 50% inhibition occurring at approximately 10(-7) M. This compound, as well as 6-ketocholestanol, 7-ketocholesterol, and 20 alpha-hydroxycholesterol, also demonstrated marked inhibition of CFU-C proliferation. The latter effect, which was not a result of direct cytoxicity of the compounds, was reversible by cholesterol, but not by mevalonic acid. We conclude that inhibition of sterol synthesis by oxygenated sterol compounds may be insufficient to explain their suppression of CFU-C proliferation.

Bone Marrow↗
PubMed1980

The structure of plasma low density lipoproteins: experimental facts and interpretations--a minireview.

From data on size and chemical composition, low density lipoprotein (LDL) can be described as a spherical particle having cholesteryl esters and triglycerides contained in a spherical core covered by the closely packed hydrophobic ends of phospholipids and unesterified cholesterol, while the head groups of the phospholipids, together with protein, occupy the surface. Such a model is compatible with early small angle X-ray and neutron scattering studies which, by prostulating spherical symmetry, assigned the LDL constituents to locations predicted from the radial electron density distribution. However, the concept of spherical symmetry, as applied to LDL structure, was recently challenged by results obtained from freeze-etching electron microscopy and small angle X-ray scattering experiments. Novel interpretations of these data suggest that the surface of LDL contains 4 electron-dense globules, located at tetrahedral positions, which have a capacity for structural remodeling at least as a function of the 2 temperatures studied (21C and 41C). It is reasonable to presume that the LDL protein (apo LDL) plays a role in the organization of the surface and overall LDL structure. However, until the chemical properties of apoLDL, and its behavior in solution and at the water-lipid interface are better understood, the validity of the proposed models cannot be assessed.

Animals↗
PubMed1980

Characterization and measurement of human apolipoprotein A-II by radioimmunoassay.

The development of a radioimmunoassay for apolipoprotein A-II (apo A-II) is described. Initial studies revealed a lack of immunological identity between purified apo A-II used as the standard and serum or HDL. Extensive testing of different buffers, standards, antisera, tracers, utilization of a detergent, and heating of sera failed to resolve the problem. Gel filtration of iodinated and non-iodinated apo A-II on Sephadex G-100 columns showed that apo A-II, in dilute solution, elutes in a higher molecular zone than expected with a broad, assymetrical profile. The use of a subfraction of the tracer in the assay resulted in parallelism in the serum and standard dilution curves. The apo A-II assay was sensitive, specific, and reproducible. Apo A-II added to sera was fully recovered and delipidation did not affect the immunoreactivity of either serum or HDL. Apo A-II contributed approximately 20% to the protein mass of HDL. Comparison of these results with those obtained by radial immunodiffusion, and with previously reported data, indicates that the reactivity of apo A-II in its native and delipidated forms may be markedly influenced by different immunologic methodologies and their specific reagents. Caution should thus be shown at present in assigning absolute concentrations to apo A-II in serum or HDL.

Adult↗
PubMed1979

Atherogenic diets and neutral-lipid organization in plasma low density lipoproteins.

The plasma low density lipoproteins (LDL) of rhesus monkeys fed 3 atherogenic diets exhibited thermal transitions at temperatures much higher (37--43 degrees C) than those observed in control animals or in normal humans (20--33 degrees C). The same differences were noted in the neutral lipids (cholesteryl esters and triglycerides) which were isolated from the respective lipoproteins. In particular, the difference in thermal properties between the normal and abnormal LDLs was attributable to subtle differences in their cholesteryl ester compositions (mainly an increase in the saturated and monounsaturated fatty acid moieties), with altered triglyceride contents playing only a minor role. Thus, at body temperature, the hyperlipidemia that follows the administration of atherogenic diets is associated with a high degree of order of the neutral lipids in the core of the LDL particle. This, in turn, may be related to the atherogenicity of the abnormal lipoprotein species.

Animals↗
PubMed1979

Inhibition of human lymphocyte E-rosette formation by oxygenated sterols.

25-Hydroxycholesterol, 20 alpha-hydroxycholesterol, 7 alpha-hydroxycholesterol, and 5 alpha-hydroxy-6-ketocholestanol, when added to cultures of human lymphocytes in lipoprotein-depleted medium (LPDM) at a concentration of 2.5 x 10(-6) M, inhibit E-rosette formation with sheep red blood cells. 20 alpha-Hydroxycholesterol, 7 alpha-hydroxycholesterol, and 5 alpha-hydroxy-6-ketocholestanol are more potent inhibitors than 25-hydroxycholesterol. The inhibitory effect of 5 alpha-hydroxy-6-ketocholestanol on E-rosette formation appears after 15 min of exposure; with the other three compounds, an exposure time of 18 hr is necessary. The inhibitory effect of E-rosette formation can be abolished by addition of free cholesterol, low-density lipoprotein, or high-density lipoprotein to the LPDM or by incubation of the cells in normal AB serum, but not by the addition of mevalonic acid to the LPDM. These observations suggest that the capacity of oxygenated sterol compounds (OSC) to inhibit E-rosette formation is independent of their inhibitory effect on sterol synthesis. It is possible that OSC inhibit E-rosette formation as a consequence of their insertion into the lymphocyte membrane as cholesterol analogues.

Cell Survival↗
PubMed1978

Studies of the cyanogen bromide fragments of the apoprotein of human serum low density lipoproteins.

The apoprotein of human serum low density lipoproteins was reduced and carboxymethylated and then cleaved by cyanogen bromide (CNBr). The peptides which were produced from this cleavage (90% yield, based upon loss of methionine) were resolved by SDS polyacrylamide gel electrophoresis into 10 major bands, each having an amino acid composition very similar to that of intact reduced and carboxymethylated LDL apoprotein. The fractionation of the CNBr fragments by preparative gel filtration was dependent upon the nature of the eluting solvent. NH4OH and SDS solvents eluted all of the material in the void volume. In 6 M guanidinium chloride solvents several peaks were, however, resolved, each having an amino acid composition similar to that of the unfractionated products. Whereas no NH2-terminal was detected in reduced and carboxylmethylated LDL apoprotein, automated Edman degradation of the protein following treatment with CNBr revealed the presence of several NH2-termini. The results suggest that LDL apoprotein may be made of segments of, at least, very similar amino acid composition and that both the protein itself and derivative fragments have a great tendency to aggregate even in denaturing solvents.

Amino Acids↗