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Biomedical subjects

E Koren

Publications and source records attributed to E Koren.

At least 55 records · Page 3Linked to original sources
PubMed1992

Apolipoprotein A-I and apolipoprotein B containing lipoprotein particles in coronary patients treated with extracorporal low density lipoprotein precipitation (HELP).

Evidence for chemical and biological heterogeneity of human plasma lipoprotein density classes has been steadily accumulating over the last 15 years. Furthermore, several recent reports have indicated potential clinical significance of certain lipoprotein subspecies as either atherogenic or antiatherogenic. It is generally accepted that lipid lowering treatments can retard or even reverse development of atherosclerotic lesions. However, very little is known about effects of various lipid lowering treatments on specific lipoprotein particles. The purpose of this study was to explore the effects of heparin induced extracorporal low density lipoprotein precipitation (HELP) on various subspecies of plasma lipoprotein particles defined primarily by their apolipoprotein composition. Using particle specific enzyme immunoassays, the immediate changes in lipoprotein particle profiles were analyzed after a single HELP treatment in 12 patients with angiographically documented coronary artery disease. In a separate group of 6 patients, particles were repeatedly measured over a period of 96 h following a HELP treatment. Single HELP treatment caused an immediate and highly significant decrease (67%) in the concentration of simple lipoprotein particles containing apolipoprotein B (apo B) as a sole apolipoprotein (LP-B). Various subspecies of complex particles containing apo B and other apolipoproteins (Lp-B-complex) were also decreased although to a lesser degree (44-53%). HELP treatment caused an insignificant, 3% decrease of lipoprotein particles containing apo A-I but no apo A-II (Lp-A-I) and a 6% decrease in the concentration of particles containing both apo A-I and apo A-II (Lp-A-I:A-II). During the 96-h period following HELP treatment various apo B containing particles recovered at different rates in different patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Apolipoprotein A-I↗
PubMed1992

Effect of mast cell chymase on the morphology of thyroid cells in vitro.

We studied the effect of mast cell chymase on the thyroid cells in culture. Rat serosal mast cells, similar functionally to connective tissue mast cells, were obtained after lavage of the peritoneal cavity and lyzed by freezing. The resulting lysate was used as crude enzyme preparation. Mast cell chymase was purified from the crude preparation by anion exchange chromatography. Crude and purified chymase incubated with thyroid cells induced cellular retraction, the appearance of long processes and gradual cell detachment from the substratum. The effect of the enzyme was not cytotoxic. The immunofluorescence studies of thyroid cells showed a decreased amount of polymerized actin and tubulin after incubation with chymase. Neutral protease inhibitor abolished the effect of crude and purified chymase on thyroid cell morphology. The above findings suggest that mast cell chymase may have a function in the control of cell morphology and cell-matrix interaction.

Actins↗
PubMed1992

Autoantibodies to the ribosomal P proteins react with a plasma membrane-related target on human cells.

Autoantibodies to ribosomal P-proteins are present in 12-16% of patients with systemic lupus erythematosus and are associated with neuropsychiatric disease. As the ribosomal P proteins are located in the cytoplasm, the pathogenic effects of their cognate autoantibodies are unclear. In this study affinity-purified anti-P autoantibodies were used to explore the cell surface of several types of human and animal cells. Immunofluorescence as well as EM immunogold analysis demonstrated, on the surface of human hepatoma cells, the presence of an epitope that is antigenically related to the immunodominant carboxy terminus of P-proteins. The presence of this epitope was also demonstrated on the surface of human neuroblastoma cells and, to a lesser extent, on human fibroblasts. Furthermore, the Western blot technique revealed in purified human and animal plasma membranes a 38-kD protein that is closely related or identical with ribosomal P0 protein. The availability of reactive P peptide on the surface of cells makes possible the direct effect of autoantibodies on the function and viability of cells that express this antigenic target. This delineates one of the possible impacts of anti-P antibodies in disease expression.

Amino Acid Sequence↗
PubMed1991

Isolation and characterization of an apoA-II-containing lipoprotein (LP-A-II:B complex) from plasma very low density lipoproteins of patients with Tangier disease and type V hyperlipoproteinemia.

Previous studies have shown that very low density lipoproteins (VLDL) from patients with Tangier disease are less effective as a substrate for human milk lipoprotein lipase (LPL) than VLDL from normal controls as assessed by measuring the first order rate constant (k1) of triglyceride hydrolysis. Tangier VLDL also has a higher content of apolipoprotein (apo) A-II than normal VLDL. To explore the possible relationship between the relatively high concentration of apoA-II in VLDL and low k1 values, Tangier VLDL were fractionated on an anti-apoA-II immunosorber. The retained fraction contained a newly identified triglyceride-rich lipoprotein characterized by the presence of apolipoproteins A-II, B, C-I, C-II, C-III, D, and E (LP-A-II:B:C:D:E or LP-A-II:B complex), whereas the unretained fraction consisted of previously identified triglyceride-rich apoB-containing lipoproteins free of apoA-II. In VLDL from patients with Tangier disease or type V hyperlipoproteinemia, the LP-A-II:B complex accounted for 70-90% and 25-70% of the total apoB content, respectively. The LP-A-II:B complexes had similar lipid and apolipoprotein composition; they were poor substrates for LPL as indicated by their low k1 values (0.014-0.016 min-1). In contrast, the apoA-II-free lipoproteins present in unretained fractions were effective substrates for LPL with k1 values equal to or greater than 0.0313 min-1. These results indicate that triglyceride-rich lipoproteins consist of several apoB-containing lipoproteins, including the LP-A-II:B complex, and that lipoprotein particles of similar size and density but distinct apolipoprotein composition also possess distinct metabolic properties.

Adult↗
PubMed1990

Adipogenesis in a murine bone marrow stromal cell line capable of supporting B lineage lymphocyte growth and proliferation: biochemical and molecular characterization.

Recent advances in long-term bone marrow (BM) culture techniques have allowed investigators to dissect cellular components responsible for lympho hematopoiesis. Consequently, a number of "stromal" cell clones have been developed which are capable of supporting B lineage lymphocyte growth and proliferation in vitro by direct cell-cell interactions and the release of cytokines. While much work has focused on the support function of these cells, questions remain regarding their own differentiation potential. We have examined adipogenesis in the cloned BM stromal cell, BMS2. The presence of hydrocortisone, methylisobutylxanthine, or 30% fetal calf serum each accelerated adipocyte differentiation. This process was accompanied by the accumulation of triglycerides and cholesterol esters along with the induction of adipocyte-specific enzymes. Likewise, the steady-state level of mRNA transcripts increased for genes related to lipid metabolism. However, the pattern of mRNA expression in BMS2 adipocytes differed from that of a well-established, pre-adipocyte cell line, 3T3-L1, with respect to the following genes: glycerol phosphate dehydrogenase, CAAT/enhancer binding protein and angiotensinogen. Adipocyte BMS2 cells retailed the ability to support stromal cell-dependent B lineage lymphocytes in methylcellulose assays. The adipocytes continued to express macrophage-colony-stimulating factor mRNA constitutively and interleukin 6 mRNA in an inducible manner, similar to the BMS2 pre-adipocytes. Together, these data document a close developmental relationship between a specialized fibroblasts and adipocytes in the BM and suggest that adipocyte stromal cells may play an active role in lympho-hematopoiesis.

Adipose Tissue↗
PubMed1990

Analysis of cholesterol ester accumulation in macrophages by the use of digital imaging fluorescence microscopy.

Low density lipoprotein (LDL) induced accumulation of cholesterol esters was analyzed by the digital imaging fluorescence microscopy (DIFM) in murine tumor macrophages. To analyze cholesterol ester accumulation, P388D1 macrophages were incubated with increasing quantities of unmodified or acetylated human LDL, washed, and live stained with a lipophylic fluorescent dye Nile Red. The increase in fluorescence intensity was quantitatively determined by the interactive laser cytometer (ACAS 470) and compared with the accumulation of cellular cholesterol esters determined by the gas liquid chromatography. Correlation between the two methods was highly significant (r greater than 0.9, P less than 0.001). A good agreement between the two methods was also found in terms of sensitivity and reproducibility. With the use of 589 nm narrowband interference filter in the light path of emitted light the intensity of fluorescence correlated well with cellular cholesterol ester content even in the presence of relatively high concentrations of triglycerides. Therefore, digital imaging fluorescence microscopy appears to be a reliable method for quantification of cholesterol ester accumulation at the single cell level offering new possibilities of studying interactions between cells and cholesterol ester rich lipoproteins.

Animals↗
PubMed1989

Identification and partial characterization of discrete apolipoprotein A-containing lipoprotein particles secreted by human hepatoma cell line HepG2.

The purpose of this study was to identify the apolipoprotein A-containing lipoprotein particles produced by HepG2 cells. The apolipoprotein A-containing lipoproteins separated from apolipoprotein B-containing lipoproteins by affinity chromatography of culture medium on concanavalin A were fractionated on an immunosorber with monoclonal antibodies to apolipoprotein A-II. The retained fraction contained apolipoproteins A-I, A-II and E, while the unretained fraction contained apolipoproteins A-I and E. Both fractions were characterized by free cholesterol as the major and triglycerides and cholesterol esters as the minor neutral lipids. Further chromatography of both fractions on an immunosorber with monoclonal antibodies to apolipoprotein A-I showed that 1) apolipoprotein A-II only occurs in association with apolipoprotein A-I, 2) apolipoprotein A-IV is only present as part of a separate lipoprotein family (lipoprotein A-IV), and 3) apolipoprotein E-enriched lipoprotein A-I:A-II and lipoprotein A-I are the main apolipoprotein A-containing lipoproteins secreted by HepG2 cells.

Apolipoproteins A↗
PubMed1989

Cholesterol crystal uptake and metabolism by P388D1 macrophages.

Cholesterol monohydrate crystals are frequently detected in intermediate and advanced atherosclerotic lesions. Little is known regarding mobilization of this molecular form of cholesterol into metabolically active pools. To study a potential mechanism for mobilization of crystalline cholesterol, we examined its uptake by a mouse macrophage cell line (P388D1). Crystals were overlayered on a P388D1 cell monolayer maintained in a serum-free medium. Following incubation, the monolayer was washed, and the cells were harvested and analyzed for crystal internalization. By transmission electron microscopy, crystals were found intracellularly surrounded by a bilayer membrane. Analyses of the cellular cholesterol ester content by gas-liquid chromatography and esterification of [14C]cholesterol indicated the conversion of crystalline cholesterol to cholesterol esters. This pathway for solubilization of cholesterol crystals by macrophages could play an important role in the regression of atherosclerotic lesions.

Animals↗
PubMed1988

Anti-Ro (SS-A) antibodies from Ro (SS-A)-immunized mice.

Immunization of BALB/c mice with immunoaffinity-purified bovine or human Ro (SS-A) induces the production of antibodies reactive with Ro (SS-A). Fusion of spleen cells from the hyperimmunized mice to SP2/0 cells resulted in hybridoma cell lines that produced anti-Ro (SS-A) antibodies. Anti-Ro (SS-A) binding was established by solid-phase immunosorbent assay, immunoblotting, or RNA immunoprecipitation. Most of the anti-Ro (SS-A) antibodies bound to both human and bovine Ro (SS-A) in the solid phase, but only one of the monoclonal antibodies selectively bound to human Ro (SS-A); this suggests that there are species differences between the bovine and human Ro (SS-A) antigens. Indirect immunofluorescence studies demonstrated that most anti-Ro (SS-A) antibodies bound to cytoplasmic or nuclear HEp-2 cellular antigens, whereas others did not bind to fixed HEp-2 tissue culture cells. Nuclear staining of mouse substrates by one of the sera containing anti-Ro (SS-A) demonstrated that autoantibodies were induced by immunization with human Ro (SS-A).

Animals↗
PubMed1987

Identification and partial characterization of discrete apolipoprotein B containing lipoprotein particles produced by human hepatoma cell line HepG2.

The purpose of this study was to test the use of human hepatocarcinoma HepG2 cells as a model for studying the formation and secretion of human hepatic lipoproteins. To this end, we determined the rate of accumulation and percent composition of neutral lipids and apolipoproteins in the culture medium of HepG2 cells and isolated and partially characterized the apolipoprotein B (ApoB) containing lipoprotein particles. The rates of accumulation in the medium of HepG2 cells, grown in minimum essential medium during a 24-h incubation, of triglycerides, cholesterol, and cholesterol esters expressed as microgram/(g of cell protein X h) were 373 +/- 55, 167 +/- 14, and 79 +/- 10, respectively; the secretion rates for apolipoproteins B, A-I, E, A-II, and C-III were 372 +/- 36, 149 +/- 14, 104 +/- 13, 48 +/- 4, and 13 +/- 1 microgram/(g of cell protein X h), respectively. The major portion of ApoB was present in very low density lipoproteins (VLDL) and low-density lipoproteins (LDL) (84%), with the remainder occurring in high-density lipoproteins (HDL) (16%). Approximately 10-13% of ApoA-I and ApoA-II were present in VLDL and LDL, while 60% of ApoE occurred in HDL and 40% in VLDL and LDL. To separate ApoB-containing lipoproteins, secreted lipoproteins were fractionated by either sequential immunoprecipitation or immunoaffinity chromatography with antibodies to ApoB and ApoE. Results showed that 60-70% of ApoB occurred in the culture medium as lipoprotein B (LP-B) and 30-40% as lipoprotein B:E (LP-B:E). Both ApoB-containing lipoproteins represent polydisperse systems of spherical particles ranging in size from 100 to 350 A for LP-B and from 200 to 500 A for LP-B:E. LP-B particles were identified in VLDL, LDL, and HDL, while LP-B:E particles were only present in VLDL and LDL. The major neutral lipid of both ApoB-containing lipoproteins was triglyceride (50-70% of the total neutral lipid content); cholesterol and cholesterol esters were present in equal amounts. The LP-B:E particles contained 70-90% ApoB and 10-30% ApoE. The ApoB was identified in both types of particles as B-100. A time study on the accumulation of ApoB-containing lipoproteins showed that LP-B particles were secreted independently of LP-B:E particles.

Apolipoproteins B↗
PubMed1987

Selective isolation of human plasma low-density lipoprotein particles containing apolipoproteins B and E by use of a monoclonal antibody to apolipoprotein B.

A monoclonal antibody to human plasma apolipoprotein B was used in a single-step immunoaffinity chromatography procedure to isolate a subpopulation of low-density lipoprotein particles from normolipidemic human plasma. The isolated particles were homogeneous in terms of size (20 nm), flotation coefficient (Sf = 9.5), and electrophoretic mobility (beta band). Their protein moiety consisted of apolipoproteins B and E in a molar ratio close to 2. The lipid moiety consisted of 47.3% cholesterol, 4.7% triglycerides, and 48.0% phospholipids. To indicate its characteristic apolipoprotein composition and hydrated density properties, this family of particles was named LP-B:EL2. In most normolipidemic subjects, LP-B:EL2 particles accounted for less than 10% of the total plasma apolipoprotein B content. The LP-B:EL2 particles bound to the membranes of the human hepatoma HepG2 cells in a specific and saturable manner indicative of receptor-mediated binding. Their binding was significantly higher than that of low-density lipoprotein particles containing only apolipoprotein B.

Antibodies, Monoclonal↗
PubMed1987

Apolipoprotein A-I containing lipoproteins in coronary artery disease.

At least 2 main types of lipoprotein particles are identified within HDL. Those which contain apo A-I and apo A-II (LpA-I:A-II) and those which contain apo A-I but not apo A-II (LpA-I). This study was designed to elucidate to what degree the HDL cholesterol decrease observed in coronary artery disease affects these 2 types of lipoprotein particles. Concentrations of LpA-I:A-II and LpA-I were measured in plasma from 100 normolipidemic male subjects with angiographically defined coronary artery disease (CAD(+)) or without CAD (CAD(-)) and from 50 control subjects, matched for age. CAD(+) subjects had significantly lower levels of HDL cholesterol, total apo A-I, and LpA-I than controls. When compared to CAD(-) subjects, only their levels of HDL cholesterol and LpA-I were found lower. In both cases (CAD(+) vs CAD(-) and CAD(+) vs controls), LpA-I levels were decreased while LpA-I:A-II levels were unchanged. Even, when the levels of their total plasma lipids and lipoproteins are normal, atherosclerotic patients are characterized by a different distribution of apo A-I between LpA-I and LpA-I:A-II. These data support the view that LpA-I might represent the "antiatherogenic" fraction of HDL.

Angiocardiography↗
PubMed1987

Quantification of two different types of apolipoprotein A-I containing lipoprotein particles in plasma by enzyme-linked differential-antibody immunosorbent assay.

We describe a method for measuring apolipoprotein A-I (ApoA-I) associated and unassociated with apolipoprotein A-II (ApoA-II) in plasma. To directly determine associated ApoA-I, we coated microtiter plates with antibody to ApoA-II, blocked the nonspecific binding sites, and incubated the plate with plasma, immobilizing the lipoprotein particles containing both ApoA-II and ApoA-I. The unbound constituents of plasma were washed away, peroxidase-labeled antibody to ApoA-I was added, the plate rewashed, peroxidase substrate added, and the resulting color measured. ApoA-I unassociated with ApoA-II was evaluated by subtracting the concentration of associated ApoA-I from the total ApoA-I concentration. The method is specific, rapid, and precise. Within- and between-assay CVs were 5.6 and 9.8%, respectively. Analytical recovery of ApoA-I was 94%. The average normolipidemic concentration of ApoA-I associated with ApoA-II in 50 women was 790 mg/L; in 50 men, it was 788 mg/L. The corresponding values for unassociated ApoA-I were 644, 577 mg/L. Both lipoprotein forms of ApoA-I were detected in all major density classes, but were most abundant in high-density lipoproteins. The technique is applicable to measurement of any two apolipoproteins that occur in both associated and unassociated forms in plasma.

Apolipoprotein A-I↗