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E A Podrez

Publications and source records attributed to E A Podrez.

28 records · Page 2Linked to original sources
PubMed1990

[The effect of khellin and timefurone on secretion and catabolism of lipoproteins by cultured human and rabbit hepatocytes].

Using human and rabbit hepatocyte cultures, the effects of khellin and timefurone on lipoprotein metabolism were studied with special reference to the following parameters: i) binding and degradation of 125I-labeled low density lipoproteins (LDL); ii) apoprotein B (apo-B) secretion measured by immunoenzymatic assay, iii) [35S]methionine labeled apo-B and apo-E within the composition of very low density lipoproteins (VLDL); iiii) total cholesterol synthesis and cholesterol secretion within the composition of VLDL. The therapeutic concentrations (0.1-10 micrograms/ml) of the above drugs had no appreciable effect on the binding and degradation of 125I-LDL but inhibited the secretion of apo-B VLDL, leaving the apo-E VLDL unaffected. This was paralleled with inhibition of cholesterol synthesis (by 30-50%) and VLDL secretion. These results suggest that khellin and timefurone mediate the hypolipidemic effect via the reduction of the intracellular synthesis of cholesterol and secretion of apo-B containing VLDL by hepatocytes.

Animals↗
PubMed1989

Composition and structure of lipopolysaccharide-human plasma low density lipoprotein complex. Analytical ultracentrifugation, 31P-NMR, ESR and fluorescence spectroscopy studies.

Complexes of Salmonella typhimurium lipopolysaccharide toxin (LPS) with low density lipoproteins (LDL) prepared in vitro have been analyzed. LPS-LDL complexes were found to comprise approx. 0.24 mg LPS/mg LDL protein. The major protein of complexes was apolipoprotein apoB-100 (greater than or equal to 90-95%). Incorporation of LPS molecules into LDL was accompanied by small changes in lipid composition, i.e. the phosphatidylcholine content was diminished by approx. 11% and the free fatty acid concentration was raised 2-fold. Analytical ultracentrifugation showed that insertion of LPS into LDL results in the increase of a portion of particles with higher density (lower flotation coefficient) compared to initial LDL. As was evidenced by ESR, in LPS-LDL complexes, the phospholipid hydrocarbon chains are more ordered than in LDL. 31P-NMR spectra indicated that in LPS-LDL complexes the mobility of phospholipid polar headgroups is restricted in comparison with LDL. Application of the shift reagent (Pr3+) revealed that phospholipid molecules form a monolayer structure on the surface of complexes. Upon binding of LPS to LDL, a maximum of the apoB intrinsic fluorescence was slightly red-shifted (1-2 nm) which may testify that the localization of apoB remains nearly unchanged. For LPS-LDL complexes, the accessibility of apoB fluorophores to quenchers (I-, Cs+, acrylamide) did not dramatically differ from that of LDL. It is concluded that rather large amounts of LPS (about 9-10 molecules) can accommodate in one LDL particle without severely perturbing its original composition and structure. Moreover, in the LPS-LDL complexes, oligosaccharide chains of LPS screen notably neither phospholipid polar headgroups nor, what is very important, apoB. LPS-LDL complexes are suggested to be able in vivo to bind to cellular apoB/E receptors, possible LPS receptors and scavenger-receptors of macrophages (monocytes).

Electron Spin Resonance Spectroscopy↗
PubMed1989

Very low density lipoprotein secretion by cultured hepatocytes of rabbits fed purified or autoxidized cholesterol.

The main objectives of this study were to compare the effects of dietary commercial cholesterol (containing 5% of oxidized cholesterol derivatives) and purified cholesterol on the secretion rate of very low density lipoprotein apolipoproteins and lipids by cultured rabbit hepatocytes and to verify the hypothesis that products of cholesterol autoxidation stimulate the rapid development of hypercholesterolemia. Rabbits fed dietary (old) commercial cholesterol for six weeks showed a fivefold increase in the serum concentration of cholesterol compared with that in purified cholesterol-fed rabbits. The secretion rates of very low density lipoprotein total protein and very low density lipoprotein [3H]apolipoproteins were similar for the hepatocytes of these two cholesterol-fed groups of animals and were two- and threefold greater, respectively, than for cells from control rabbits. Cholesteryl ester content of the hepatocytes from dietary (old) commercial cholesterol-fed rabbits was dramatically increased in comparison with hepatocytes from control and purified cholesterol-fed rabbits. The elevated intracellular cholesteryl ester content is assumed to account for such an increase of very low density lipoprotein-cholesteryl ester secretion by cells prepared from dietary (old) commercial cholesterol-fed rabbits. These effects appear to be caused by activation of cholesterol esterification by oxidized cholesterol derivatives. The rapid development of hypercholesterolemia induced by dietary (old) commercial cholesterol is associated, at least in part, with the stimulated production of hepatic very low density lipoprotein apolipoproteins and cholesteryl esters.

Animals↗
PubMed1989

[Secretion of very low density lipoproteins by cultured rabbit hepatocytes with hypercholesteremia, induced by purified cholesterol and containing autooxidation products].

To evaluate the impact of oxidized derivatives of cholesterol on the development of hypercholesterolemia in rabbits, the secretion of very low density lipoprotein (VLDL) apoproteins and lipids was studied in cultures of hepatocytes obtained from: i) control rabbits, ii) rabbits fed on purified cholesterol (PCH), and, iii) rabbits fed on old commercial cholesterol (OCH) containing 5% of oxidized cholesterol derivatives. The rabbits fed on OCH for 6 weeks revealed a 5-fold increase in the serum cholesterol level compared with that in PCH-fed rabbits. The secretion of VLDL apoproteins and lipids by hepatocytes of two cholesterol-fed groups was similar, but was 2-3 times as high as that of cells from control rabbits. The cholesterol ester content in hepatocytes and the secretion of VLDL cholesterol esters by hepatocytes from OCH-fed rabbits was dramatically increased in comparison with hepatocytes from control and PCH-fed rabbits. These effects appear to be caused by the activation of cholesterol esterification by oxidized cholesterol derivatives. The rapid development of hypercholesterolemia in OCH-fed rabbits is at least partly associated with the stimulation of hepatic VLDL production.

Animals↗
PubMed1988

[Immunochemical properties of immunoglobulin G conjugated with dextran].

Antigen-binding activity and effector functions of immunoglobulin G from horse and rabbit sera have been investigated, using hemagglutination, kinetic immune lysis, immune lysis in microplates and rosette-forming test with peritoneal mononuclear cells of mice, after their conjugation with dextran, MW 35-50 kD. The formation of conjugates of two types has been demonstrated: protein-dextran and protein-dextran-protein. It has been revealed that protein-dextran-protein conjugates have high specific antigen-binding activity, as compared to native IgG from rabbit sera specific for SRBC, while interactions with the complement system and Fc receptors is depressed.

Animals↗
PubMed1987

Effect of bezafibrate on lipoprotein secretion by cultured human hepatocytes.

The secretion of newly synthesized very low density lipoprotein and low density lipoprotein (VLDL + LDL) and high density lipoprotein (HDL) in cultured human hepatocytes in the presence or absence of bezafibrate added to the culture medium has been evaluated. The content of triacylglycerol, apolipoprotein B, 3H-labeled proteins and 14C-labeled lipids accumulated in a culture medium increased linearly for periods up to 18 h. During incubation, cellular triacylglycerol content was unchanged. This hypolipidemic agent, at a concentration of 10 microM, inhibited secretion of the several VLDL + LDL [3H]apolipoproteins and the VLDL + LDL [14C]lipids, suggesting it can affect the processes of biosynthesis and secretion. The secretion of total [3H]apolipoproteins in the HDL fraction and [3H]protein (d greater than 1.21 g/ml) was unchanged after an exposure to bezafibrate (10 microM). Incubation in the presence of 10 microM bezafibrate resulted also in decreases in both total VLDL neutral lipids and apolipoprotein B secreted into the medium. These results indicate that bezafibrate might exert its plasma lipid-lowering effect by suppressing the VLDL production in liver and reducing the secretion of VLDL into the circulation.

Bezafibrate↗
PubMed1986

Apolipoprotein B release from activated human platelets.

Apolipoprotein B (apoB) release from activated washed human platelets was measured by enzyme-linked immunosorbent assay (ELISA) using monospecific rabbit antibodies to human low density lipoprotein (LDL). Activation of platelets with thrombin, Ca2+-ionophore A23187 or stable analogue of prostaglandin endoperoxides U46619 stimulated release of approximately 20 ng apoB/10(8) platelets. Thrombin-induced apoB release was inhibited by the prostacyclin analogue carbacyclin. Dose-response curves of thrombin stimulation and carbacyclin inhibition of apoB and beta-thromboglobulin (beta-TG) release were very similar. Treatment of platelets with heparin did not remove significant amounts of apoB or affect the subsequent release of apoB induced by thrombin. The results of density gradient ultracentrifugation indicated that most of the apoB was released in the LDL density range. These data suggest that human platelets contain immunoreactive apoB, which can be released during platelet activation.

Apolipoproteins B↗
PubMed1986

[Effect of bezafibrate on lipoprotein secretion by cultured human hepatocytes].

The rate of synthesis and secretion of lipid and apoprotein components of lipoprotein fractions and of proteins of the nonlipoprotein fraction d greater than 1.21 g/ml by human hepatocytes in culture was determined. The cells were incubated for 18 hours in the media containing [14C] acetate or [3H]-marked leucine in the presence of bezafibrate or without it. VLDL, HDL and d greater than 1.21 g/ml fractions were separated by differential ultracentrifugation. The lipids were divided using thin-layer chromatography, and the apoprotein-using SDS-electrophoresis in polyacrylamide gel. Bezafibrate in the therapeutic concentration of 10 microM specifically inhibits apoprotein and VLDL lipid secretion. Lowered secretion of all VLDL apoproteins was revealed, which points to a decrease in the number of secreted particles. The effect of bezafibrate was found to be associated with the inhibition of the intracellular synthesis of lipids. The secretion of HDL proteins and of d greater than 1.21 g/ml fraction proteins was unchanged with 10 microM of bezafibrate.

Adult↗
PubMed1984

Step-by-step analysis of adhesion of human platelets to a collagen-coated surface defect in initial attachment and spreading of platelets in von Willebrand's disease.

Adhesion of platelets from the platelet-rich plasma (PRP) of patients with von Willebrand's disease (vWD) and healthy donors has been studied in a simple model system - wells of multiwell tissue culture plates coated with fibrillar calf skin collagen (CSC). This model is characterized by: (i) the presence of only one constituent of the vessel wall connective tissue matrix (collagen), (ii) the absence of surface-bound aggregates and thrombi, (iii) absence of overlapping of neighbouring spread platelets. A morphometric quantitation of adhesion by scanning electron microscopy (SEM) has been carried out. It allows to subdivide this process into three stages: 1) initial attachment of unspread platelets to the substrate, 2) platelet spreading on the substrate, and 3) attachment of unspread platelets to the upper surface of spread platelets. It was established that the PRP of vWD patients, compared to that of healthy donors, is characterized by a decreased total adhesion of platelets to a CSC-coated surface, which is manifested in the impairment of both the initial attachment and subsequent spreading of platelets. Addition of platelet-free plasma from healthy donors to the vWD PRP completely restores platelet spreading on collagen but little affects the initial attachment. These experiments performed on isolated collagen preparations provide further evidence for the initial attachment and spreading of platelets on collagenous constituents of the subendothelium being factor VIII/von Willebrand factor (FVIII/vWF)-dependent. In contrast to the adhesion on the collagen substrate, the adhesion of platelets from vWD PRP to a foreign surface, polystyrene plastic of uncoated wells, is the same as that of the normal PRP and, thus, FVIII/vWF-independent.

Collagen↗