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V S Repin

Publications and source records attributed to V S Repin.

At least 19 recordsLinked to original sources
PubMed1992

Studies on the proteins involved in the interaction of high-density lipoprotein with isolated human small intestine epithelial cells.

Treatment of 125I-labelled high-density lipoprotein ([125I]HDL3) with monospecific polyclonal antibodies against apolipoproteins A-I and A-II resulted in a dose-dependent inhibition of the [125I]HDL3 binding to isolated human small intestine epithelial cells by 25% and 50%, respectively. Both antibodies also inhibited intracellular degradation of [125I]HDL3 by 80%. Treatment of enterocytes with polyclonal antibody against apolipoprotein A-I binding protein, a putative HDL receptor, inhibited both binding and degradation of [125I]HDL3 by these cells by 50%. Antibodies to apolipoprotein A-I, A-II and apo A-I-binding protein also inhibited [125I]HDL3 binding to cholesterol-loaded cells.

Antibodies↗
PubMed1992

[The effect of natural and synthetic antioxidant polyhydroxynaphthoquinones on cholesterol metabolism in cultured rabbit hepatocytes].

Primary cultures of rabbit hepatocytes were used to examine the effect of natural and synthetic antioxidants--polyhydroxynaphthoquinones (PHNQ) and alpha-tocopherol on cholesterol and bile acid synthesis. Histochrome, one of the PHNQ, slightly decreased cholesterol synthesis at concentrations 10-100 microM, whereas alpha-tocopherol stimulated cholesterol synthesis. After administration of histochrome or alpha-tocopherol into culture medium a significant stimulation of bile acid synthesis in dose-dependent manner was observed. The increase of bile acid secretion by histochrome in the presence of physiological concentration of HDL2 was found as well. Since histochrome in contrast to alpha-tocopherol enhanced accumulation of [14C] cholesterol of HDL2 in the hepatocytes, it was concluded that histochrome stimulated bile acid synthesis as a result of increased input of HDL2 cholesterol into hepatocytes. These data suggest that histochrome may exhibit a hypocholesterolemic effect by stimulation of bile acid synthesis and inhibition of cholesterol synthesis.

Animals↗
PubMed1992

[Effect of mevinolin and glycyrrhizinic acid on cholesterol and bile acid metabolism in cultured rabbit hepatocytes].

A comparison of effects of two hypocholesterolemic drugs--mevinolin and glycyrrhizinic acid, on cholesterol and bile acid metabolism in cultured rabbit hepatocytes has been carried out. The following parameters have been determined: i) cholesterol synthesis from [2-14C]acetate; ii) bile acid production from newly synthesized and [4-14C]-labeled HDL2 cholesterol, and, iii) total cholesterol efflux into the incubation medium Mevinolin (0.5 microgram/ml) inhibited [2-14C] acetate incorporation into cholesterol by more than 90%. Conversely, glycyrrhizinic acid did not influence cholesterol synthesis even when used at high (100 micrograms/ml) concentrations but stimulated the conversion of endogenous (by 37%) and exogenous (by 18%) cholesterol into bile acids and increased, in addition, the proportion of bile acids in the total sterol pool released from hepatocytes into the incubation medium. At the same time, mevinolin used at 0.5 microgram/ml decreased the bile acid production by endogenous (by 27%) and exogenous (by 40%) cholesterol. The data obtained suggest that glycyrrhizinic acid exerts hypocholesterolemic action by stimulation of cholesterol conversion into bile acids without any effect on cholesterol synthesis. As for mevinolin, it has a cholesterol-suppressing effect via a mechanism of cholesterol synthesis inhibition only.

Animals↗
PubMed1992

[Means of improving and characteristics of the use of beta spectrometry of 90Sr after the Chernobyl accident].

The paper is concerned with a theoretical possibility of the use of 90Sr beta-spectrometry in a mixture of radionuclides including 137Cs, 134Cs, 144Ce and 106Ru after the Chernobyl accident. Special attention is paid to the choosing of a detector and spectrum treatment techniques as factors determining the minimum detectable activity of the method. A brief description of the spectrometric system as well as of the software used is given. The comparison of the method with traditional radiochemical and gamma-spectrometric methods has shown that it is applicable to a wide range of activities and to different objects including those of biological origin. The sources of errors are considered in detail. Approaches to the development of the method are given.

Accidents↗
PubMed1991

Interaction of apolipoprotein B-containing lipoprotein secreted by Hep G2 cells with receptors for low-density lipoprotein.

Radioligand and immunoenzymatic techniques were used to characterize the receptor binding properties of apolipoprotein B-containing lipoprotein produced by HepG2 cell line (H-LpB). It was found that compared to plasma low-density lipoprotein (LDL), the interaction of H-LpB nonseparated from conditioned medium with normal fibroblasts was 6-8-times lower and only slightly exceeded the nonspecific binding of LDL modified by malondialdehyde, while the uptake of the indicated lipoproteins by LDL receptor-negative strain of fibroblasts were identical. The uptake of H-LpB by normal fibroblasts increased 1.5-2-times after isolation from the culture medium by immunoaffinity chromatography. The effect of isolation could be explained by the finding that apolipoprotein E-containing lipoprotein secreted by HepG2 cells effectively competed for the binding with LDL-receptors. The obtained results suggest that H-LpB produced by HepG2 cells is poorly recognized by the LDL-receptors.

Apolipoproteins B↗
PubMed1991

Characterization of an antiglycoprotein Ib monoclonal antibody that specifically inhibits platelet-thrombin interaction.

Platelet glycoprotein Ib (GPIb) acts as a high-affinity thrombin binding site and as a receptor for von Willebrand Factor (vWF). A new anti-GPIb monoclonal antibody (mAB) VM16d was produced that specifically inhibited platelet-thrombin but not platelet-vWF interaction. The epitope for VM16d was located within the 45 kDa N-terminal region of the alpha-chain of GPIb. VM16d inhibited platelet aggregation induced by low dose thrombin (0.05 U/ml) but did not affect platelet aggregation induced by ristocetin, bovine vWF, ADP or collagen. The same inhibitory effects on thrombin-induced platelet aggregation were observed with the whole IgG molecule of VM16d and its F(ab')2 and F(ab') fragments. VM16d also inhibited 14C-serotonin secretion induced by low dose thrombin and binding of 125I-thrombin but not ristocetin-dependent binding of 125I-vWF to platelets. These data indicate that the high-affinity thrombin binding site is located on the N-terminal 45 kDa domain of GPIb and that it is topographically separated from the vWF binding site.

Adenosine Diphosphate↗
PubMed1991

Effect of chylomicron remnants on cholesterol metabolism in cultured rabbit hepatocytes: very low density lipoprotein and bile acid production.

The interrelationship between very low density lipoprotein (VLDL) secretion and bile acid production was studied in primary culture of rabbit hepatocytes. Chylomicron remnants (CR) were added to the cultures to study their effect on VLDL secretion and bile acid production. After 24 hr preincubation of cells with CR (10-50 micrograms protein/mL), intercellular neutral lipid content was increased 1.5-4-fold in a dose-dependent manner. Neutral lipid accumulation was accompanied by a 70-90% reduction of [14C]acetate incorporation into cholesterol, while no stimulation of [14C]oleate incorporation into cholesteryl esters was observed. Incubation of cells with CR increased secretion of free cholesterol, triacylglycerol and apoproteins B and E in VLDL. Stimulation of VLDL cholesterol secretion was accompanied by a reduction of taurocholic acid synthesis. These data demonstrate the existence of an inverse relationship between secretion of VLDL cholesterol and bile acid production under conditions of effective uptake of triacylglycerol-rich CR by hepatocytes.

Acetates↗
PubMed1991

[Adhesive activity of blood platelets in patients with stable or unstable angina pectoris and acute myocardial infarct].

Platelet adhesive activity was assayed in patients with stable angina (SA) or unstable angina (UA) and acute myocardial infarction (AMI). With scanning electron microscopy, platelet adhesions to Type IV collagen (C-IV) and plastic material, which had been stimulated by low-dose ADP, epinephrine and U-46 619, a stable thromboxane A2 analogue (agonist-induced adhesion) were determined. As compared with the control group, patients with SA or UA, showed significantly higher adhesion of platelets to the collagen substrate, whereas UA patients alone displayed a significantly increased agonist-induced adhesion when epinephrine was employed as an agonist. A sharp enhancement of platelet adhesion was characteristic of patients with AMI on days 1-3 of the onset. On days 4-5, the adhesive activity slightly dropped, and on day 7-10, it returned to the control level of healthy volunteers. The time course of adhesive activity decrease correlated with lower blood levels of creatine phosphokinase in patients with AMI. A high correlation was established between the alterations found in all the types of platelet adhesion during the course of AMI, which suggests there is an unspecific nature of increase and subsequent decrease platelet responses to all the inductors used. A comparison of patients taking and not taking aspirin (250 mg/day) revealed no differences both in the magnitude of an increase in platelet adhesion in the first 3 days and in that of its decrease on days 7-10 of AMI.

Adult↗
PubMed1991

[The effect of pure and long-stored commercial cholesterol on the binding of very low density and low density lipoproteins by rabbit hepatocytes (in vitro research)].

Effects of pure and long-stored commercial cholesterol feeding on rabbit plasma cholesterol level, on rabbit hepatocyte cholesterol esters levels, and on receptor activity of rabbit hepatocytes were investigated in three experimental groups. In comparison with control, the cholesterol levels in plasma of rabbits, fed with pure and long-stored cholesterol, were 3 and 15 times higher accordingly. Free cholesterol and cholesterol esters concentrations were enhanced in hepatocytes of rabbits fed with pure cholesterol (1.4 and 2.3 times, accordingly, p 0.05) and much more enhanced in hepatocytes of rabbits fed with long-stored cholesterol (4.5 and 24 times, accordingly, p less than 0.05). Specific binding of 125-1-labeled VLDL and LDL to rabbit hepatocytes was decreased in experimental groups by 20% and 32%, accordingly in the first group and by 40% and 77%, accordingly in the second group.

Animals↗
PubMed1990

Comparison of the effect of six compactin-related compounds on cholesterol synthesis in five human cell types.

We have investigated the effect of six compactin-related compounds--mevinolin, compactin, ML-236A, monacolin X, monacolin L and dihydromonacolin L--on cholesterol synthesis in human umbilical vein endothelial cells, human small intestine epithelial cells, human hepatoma cell line HEP G2, normal human skin fibroblasts and in skin fibroblasts from a patient with familial homozygous hypercholesterolemia. The inhibition of cholesterol synthesis was found to depend on both the cell type and the type of compound used. The most effective compounds were mevinolin and compactin. Monacolin X, monacolin L and ML-236A were less effective, and dihydromonacolin L was the least efficacious. Endothelial and epithelial cells were sensitive to very low concentrations of inhibitors (IC50 = 1.0-30 pg/mL), HEP G2 cells required higher concentrations (IC50 = 0.01-66 ng/mL) and fibroblasts needed even higher concentrations (IC50 = 0.1-200 ng/mL). Lactone and acid forms of the inhibitors were equally active. None of the inhibitors had any effect on either protein or fatty acid synthesis in any of the cell types studied. It can be concluded that different compactin-related compounds show a range of potencies as cholesterol synthesis inhibitors and a dose-dependent tissue-selectivity.

Anticholesteremic Agents↗
PubMed1990

Inhibition of cholesterol synthesis by lovastatin tested on six human cell types in vitro.

Lovastatin (mevinolin) caused a strong and dose-dependent inhibition of cholesterol synthesis in six types of cultured human cells. Fifty percent inhibition of cholesterol synthesis in human enterocytes was observed at a lovastatin concentration of about 0.004 ng/ml and in other cells at a lovastatin concentration of about 0.03 ng/ml. At lovastatin concentrations between 1.0 and 100.0 ng/ml, a moderate tissue selectivity of lovastatin action was noted. At optimal concentrations, lovastatin inhibited cholesterol synthesis in hepatocytes by 98%, in normal and LDL-receptor negative fibroblasts, arterial smooth muscle cells and hepatoma G-2 cells by about 90%, and in enterocytes by 75%. In rat enterocytes lovastatin inhibited cholesterol synthesis by only 60%.

Anticholesteremic Agents↗
PubMed1990

[Effect of chylomicron remnants on cholesterol metabolism in cultured rabbit hepatocytes: production of very low density lipoproteins and bile acids].

Primary cultures of rabbit hepatocytes were used to investigate the effect of purified (B-100 free) chylomicron remnants (CR) on lipid and bile acid metabolism. ApoB-100-containing lipoproteins were removed from the CR-enriched plasma fraction by affinity column chromatography on Sepharose 4B conjugated with anti-apoB-100 monoclonal antibodies. CR were shown to stimulate the accumulation of neutral lipids in hepatocytes in a dose-response manner. After 24-hour preincubation of rabbit hepatocytes with 50 micrograms protein/ml CR the cellular neutral lipid content increased: 1.9-4-fold for triglycerides, 1.5-3.7-fold for free cholesterol and 1.5-2.5-fold for esterified cholesterol. This accumulation was accompanied by a decreasing incorporation of [14C] acetate into cholesterol (80-90%) and triglycerides (70-80%). At the same time the incorporation of [14]oleate into triglycerides increased by 50-65%. The inhibited biosynthesis of fatty acids might account for this effect. No effect of CR on cholesterol esterification by [14C]oleate was observed. CR increased the amount of triglycerides and free cholesterol secreted in very low density lipoproteins (VLDL). The secretion of taurocholic acid was decreased. These data confirm our hypothesis that dietary cholesterol is preferentially secreted by hepatocytes within VLDL but is not accumulated as cholesterol esters or oxidized to bile acids.

Animals↗
PubMed1990

Both apolipoproteins B-48 and B-100 are synthesized and secreted by the human intestine.

Apolipoprotein B (apoB), an apolipoprotein associated with very low density lipoproteins and the atherogenic low density lipoproteins (LDL), directs the metabolism of lipoprotein particles in plasma by interacting with the LDL receptor. Utilizing human intestinal biopsy organ cultures, we have studied the synthesis of intestinal apoB in man. Intestinal organ cultures from normal adults (n = 6) were incubated in the presence of protease inhibitors in media supplemented with [35S]methionine. Media from these cultures were evaluated by sequential NaDodSO4 polyacrylamide gel electrophoresis, radioautography, and Western blot analyses, and intestinal biopsies were studied using immunohistochemistry. The relative abundance of apoB-100 and apoB-48 mRNA was assessed using reverse transcriptase-polymerase chain reaction followed by primer extension. Although apoB-48 was the principal isoprotein that was newly synthesized by intestinal organ cultures, apoB-100 was also synthesized and secreted by human intestinal organ cultures with 16 +/- 3% of the intestinal apoB mRNA coding for apoB-100. These results establish that apoB-100 is produced by the human intestine. The synthesis of the atherogenic apoB-100 by the intestine has pathophysiologic implications for the development of diet-induced atherosclerosis.

Adult↗