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Biomedical subjects

A D Morozkin

Publications and source records attributed to A D Morozkin.

At least 19 recordsLinked to original sources
PubMed1999

Distribution of exogenous 25-hydroxycholesterol in Hep G2 cells between two different pools.

Binding of [26,27-(3)H]25-hydroxycholesterol (25HC) to human hepatoma Hep G2 cells was saturated within 120 min. Two intracellular pools of 25HC were identified in a pulse-chase experiment: (i) an exchangeable pool which was in dynamic equilibrium with 25HC in the medium (t(1/2) of reversible exchange 15 min) and (ii) an unexchangeable pool which remained in cells during incubation in medium containing LPDS. 25HC from the exchangeable pool inhibits cholesterol biosynthesis, decreases the HMG CoA reductase mRNA level and stimulates cholesterol acylation. 25HC from the unexchangeable pool was partially bound to cytosolic proteins and apparently utilized for metabolic transformation. Incubation of Hep G2 cells with [26,27-(3)H]25HC in the presence of a 30-fold molar excess of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one was found to cause (i) 2-fold decrease in the binding of [26,27-(3)H]25HC to cytosolic proteins (sedimentation constant of radioactive complex was 4-5 S) and (ii) the 35% inhibition of 25HC transformation to polar metabolites.

Acylation↗
PubMed1998

Immunoreactivity of apolipoprotein B-100 and binding to LDL-receptor of phospholipase A2-treated low density lipoproteins.

Lipid--protein particles were obtained by treatment of low density lipoproteins (LDL) with phospholipase A2 from bee venom. Under these conditions, half of the phosphatidylcholine (PC) of LDL was changed to lysophosphatidylcholine (LPC). At the same time, the composition of other lipids and the apoprotein structure were unaffected. Three monoclonal antibodies (MAbs) against various apo B epitopes were used to test immunoreactivity of phospholipase A2-treated LDL (pl-LDL). The apo B epitope interacting with MAb 4C11 (amino acid residues 2377-2658) showed significantly decreased immunoreactivity. Increase in MAb 4C11 binding was demonstrated to depend on oxidation degree of LDL. Thus, changing of half of PC to LPC modified apo B translocation in the lipoprotein globule in an opposite manner as compared with changes induced by oxidative modification. A minor increase in immunoreactivity of pl-LDL with 1D1 MAb against a large middle part of apo B (residues 1297-3249) may be due to the effect of the change of surface lipid composition on the extent of immersion of apo B into the hydrophobic phase. No changes in the interaction of pl-LDL with MAb 2G8 (residues 3748-4306) were observed in comparison with native LDL. This fact demonstrates that 50% phospholipolysis of LDL does not affect the expression of apo B C-terminal residues in pl-LDL. Twofold increase in pl-LDL affinity to immobilized LDL-receptor was shown in contrast to LDL. The data indicate that LPC accumulation in LDL results in better elimination of LDL from the blood stream than in case of accumulation of oxidative products.

Antibodies, Monoclonal↗
PubMed1997

[Affinity of 3-beta-(2-hydroxyethoxy)-5-alpha-cholest-8(14)-ene-15-one to oxysterol binding protein and its metabolism in HepG2 hepatoma cells].

beta-(2-Hydroxyethoxy)-5 alpha-cholest-8(14)-en-15-one, a synthetic inhibitor of cholesterol biosynthesis, was shown to exhibit a high affinity to oxysterol binding protein. This was proved by ultracentrifugation of the protein fraction from rabbit liver in the presence of the 3H-labeled inhibitor, 3 beta-(2-hydroxy-2-[3H]ethoxy)-5 alpha-cholest-8(14)-en-15-one, or by the substitution of the [3H]-25-hydroxycholesterol in its complex with the oxysterol binding protein. In human hepatoma Hep G2 cells, the inhibitor decreased activity of 3-hydroxy-3-methylglutaryl CoA reductase [ID50 (2.7 +/- 0.7) x 10(-5) M] and was transformed into 3 beta-[2-(9-Z-octadecenoyloxy)ethoxy]-5 alpha-cholest-8(14)-en-15-one.

Animals↗
PubMed1997

Effect of lysophosphatidylcholine on the structure and function of low density lipoproteins.

The treatment of LDL with bee-venom phospholipase A2 resulted in the formation of lipid-protein particles (phl-LDL) with an increased content of lysophosphatidylcholine (LPC). At the same time, the composition of other lipids and the protein structure remained unaffected. phl-LDL, as well as LPC, abolished the hormone-induced [Ca2+] increase in platelets and platelet aggregation induced by PAF, AMP and thrombin, whereas LDL produced no effect on the hormone-stimulated increase in the intracellular [Ca2+]. The effect persisted in a Ca(2+)-free medium, indicating that phl-LDL and LPC did not abolish the mobilization of intracellular stores with the above-mentioned inducers. Neither LPC no phl-LDL affected the [Ca2+]i level in platelets and suppressed the platelet aggregation evoked by tapsigargine, a specific inhibitor of endoplasmic reticulum Ca(2+)-ATPase, or by phorbol myristate acetate. The inhibitory effect depended on the LPC concentration and the time of platelet incubation with phl-LDL or LPC. The half-maximum efficient LPC concentrations were identical for LPC and phl-LDL (2-4 microM). The inhibitory effect was dependent on the LPC structure: lysophosphatidylethanolamine and phosphatidylcholine displayed no inhibitory effect. The results suggest that when added to washed platelets, free LPC and phl-LDL inhibit only the receptor-dependent increase of [Ca2+]i.

Adenosine Diphosphate↗
PubMed1993

Nanomolar concentrations of prostaglandin E1 induce changes in the surface organization of high-density lipoproteins.

Incubation of high-density lipoproteins (HDL) with small amounts of the prostaglandin E1 (PGE1) results in mobilization of the spin-label 5-doxylstearic acid incorporated into the HDL surface monolayer as well as in decreased binding of apoprotein A1 antibodies to the HDL surface. These effects are manifested at strikingly low PGE1 concentrations, corresponding to one prostaglandin molecule per 10(2)-10(3) lipoprotein particles. At the same time, the flotation properties of HDL are not changed in the presence of PGE1. The data are interpreted on the basis of a nonequilibrium model proposed earlier for prostaglandin-lipoprotein interactions (Bergelson, L. D., et al. (1987) Biochim. Biophys. Acta 921, 182-190).

Alprostadil↗
PubMed1991

Interaction of low-density lipoproteins with gangliosides.

The ganglioside uptake capacity of human serum low-density lipoproteins (LDL), the mode of ganglioside-LDL binding, and the influence of gangliosides on the floatation properties, size distribution, stability and fluorescence of LDL were investigated. The data obtained suggest that both hydrophobic and electrostatic forces are involved in formation of ganglioside-LDL complexes, but the former appear to be more important. Although association of gangliosides with LDL is predominantly unspecific, nonsaturable, and weak, a small saturable component due to specific ganglioside-apolipoprotein binding, also appears to be involved. In the presence of gangliosides the lipoprotein particles aggregate, the intrinsic fluorescence of LDL and their interaction with antibodies against apo-B change indicating that the state of apo-B [corrected] is modified by gangliosides.

Antigen-Antibody Reactions↗
PubMed1991

[Assessment of the composition and structure of covalent complexes of superoxide dismutase with aldehyde dextran by analytical ultracentrifugation].

Superoxide dismutase was covalently coupled wih aldehyde dextran, a polymeric carrier of molecular mass of 70 kDa. Modification produced an increase in the enzyme thermostability. Modified preparations retained a high specific activity. The composition of the thus obtained conjugates was analyzed by the ultracentrifugation and diffusion methods. The protein induced the destruction of aldehyde dextran, the enzyme being modified by its fragments. The presence of aldehyde dextran excess in the incubation medium promoted superoxide dismutase dissociation into individual subunits. At the enzyme/carrier ratio of 1:02 modification occurred as covalent coupling of the biocatalyst subunits and its one-point modification.

Dextrans↗
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↗
PubMed1988

[Physico-chemical and functional characteristics of a subfraction of low-density lipoproteins isolated by ion-exchange column chromatography].

Fractionation of human blood plasma low density lipoproteins (LDL) was performed by ion-exchange chromatography, using a linear NaCl gradient. It was shown that the binding of LDL subfractions eluted with a low ionic strength buffer (i.e., containing the particles with a lower negative charge) to B, E-receptors of fibroblasts was more effective than that of subfractions eluted with a high ionic strength buffer (i.e., containing the particles with a higher negative charge). The LDL particles with a lower negative charge had lower values of flotation coefficients (according to analytical ultracentrifugation data), smaller dimensions (according to gradient gel electrophoresis data) and a lower phospholipid/protein ratio (w/w). The experimental results suggest that LDL subfractions having different electrical parameters of the particle surface also differ in other physicochemical properties and seem to play a different role in atherogenesis.

Cells, Cultured↗
PubMed1986

[Salt ion interaction with the protein molecule: the facts and the concept].

The effect of salt concentration and its nature on some properties of alpha-chymotrypsin (the catalytic activity, the solution optical density, the sedimentation coefficient) has been considered. The limiting stage of enzyme-salt interaction has been shown to change with the variation of experimental conditions. As salt concentration increases the surface electrostatic interaction of salt ions with the enzyme molecule changes by ions penetration via certain channels within the protein globule and their subsequent binding to regulatory centers. The difference in ions nature and binding centers provides the variety of modifications observed. At high salt concentrations the solvent structure becomes predominant.

Catalysis↗
PubMed1985

A comparative study of structural properties of fibronectin and its 180 kDa fragment.

Fibronectin from human plasma and its 180 kDa fragment which retained collagen-binding, cell-attachment and heparin-binding activities, were studied by velocity centrifugation and 1H-NMR methods. The fibronectin hydrodynamic radius strongly increased at pH 11 while the hydrodynamic properties of the fragment did not change noticeably. 1H-NMR spectroscopy also showed differences in the molecular properties of fibronectin and its 180 kDa fragment. Under physiological conditions the structure of fibronectin differs from that of its 180 kDa fragment. At pH 11 and in 4 M urea no differences in their structures are observed. It is suggested that interdomain and intersubunit interactions play an important role in maintaining the native conformation of intact fibronectin.

Cell Adhesion↗
PubMed1985

Recombinant models of lipoproteins. Apolipoprotein A-I/phosphatidylcholine/cholesterol complexes formed in a 2-chloroethanol-water mixture.

Apolipoprotein A-I can spontaneously associate with phosphatidylcholine and cholesterol in 2-chloroethanol-water mixture. It was demonstrated, using a spin label technique, that dissolved molecules participate in complex formation. The apolipoprotein A-I/phosphatidylcholine/cholesterol complexes were isolated by gel chromatography. Complexes of three types were prepared and characterized: type A, large heterogeneous aggregates with molecular weight 600 000, sedimentation coefficient 10 S and the following molar composition - protein/phosphatidylcholine/cholesterol, 1:(70-100):(10-12); types B and C, with weight average molecular weights 140 000 and 110 000, average sedimentation coefficients 3.6 S and 1.7 S, respectively. Both types have the same molar composition - protein/phosphatidylcholine/cholesterol, 1:25:8. The dissimilar sedimentation coefficients between complexes B and C may be explained by the difference in the monomer/tetramer ratio (monomer molecular weight 50 000). The spin label sn-1-O-stearoyl-2-O-9'-spiro(4'',4''-dimethyloxazolidine-3''-oxyl) heptadecanoylglycero-3-phosphocholine introduced into the complexes A and B showed different thermal properties of these complexes, which may be due to differences in the lipid-protein interactions.

Apolipoprotein A-I↗
PubMedDate not supplied

[Inhibition of oxidation of human blood low density lipoproteins by carotenoids from paprika].

beta-Carotene (C1), acyl derivatives of capsanthin (C2), and acyl derivatives of capsorubin (C3) were isolated from red paprika (Capsicum annuum) oleoresin. Incorporation of carotenoids C1, C2, and C3 into human plasma LDLs changed the LDL flotation coefficient distribution for LDL fraction 1.019 < d < 1.050 g/ml. The comparative studies of Cu(2+)-catalyzed oxidation for LDL, LDL-C1, LDL-C2, and LDL-C3 revealed that carotenoids C1, C2, and C3 efficiently suppressed the oxidation of LDL, inhibited the formation of conjugated dienes from polyunsaturated fatty acid residues, lowered the content of small dense LDL subfraction, and inhibited the transformation of cholesterol to auto oxidized products (in particular to 5,6-epoxycholesterol, 7-ketocholesterol and 7 beta-hydroxycholesterol). This suggests that the main carotenoids may effectively inhibit LDL oxidation in vitro with probable lowering the "atherogenic" LDL subfraction production in vivo.

Capsicum↗
PubMedDate not supplied

[Flotation mass-spectra and surface potential of low density lipoprotein particles of hyperlipidemic patients after forced abolishment of lavostatin treatment].

The lipid status of lovastatin-treated hyperlipidemic patients with documented atherosclerosis of coronary arteries and carotid artery atheroma without signs of calcinosis significantly changed 4 weeks after termination of lovastatin therapy. LDL flotation mass-spectra were shown to be a sensitive indicator of variations of the lipid status. All LDL mass-spectra can be subdivided into four subfractions (from 12 to 32 S at solvent density of 1.170 g/ml and a step of 5 S). Taking into consideration previous data on total electronegative charge of LDL subfractions flotation mass-spectra indicate that lovastatin caused reduction of total negative surface charge of LDL by 1.8-fold mainly due to reduction of (17-22) and (22-27) S. However, in patients with high level of triglycerols reduction of LDL electronegative charge was due to decrease of cholesterol in (12-17) S subfraction. The latter consists of the smallest particles of the highest density. Combined analysis of similarity in lipid parameters and flotation mass-spectra of LDL allows recognizing rather homogenous groups of patients demonstrating similar responsiveness to lovastatin therapy.

Adult↗