PubMed Health⌕ Search

Biomedical subjects

A V Viktorov

Publications and source records attributed to A V Viktorov.

At least 19 recordsLinked to original sources
PubMed2006

[A new HPLC method for determination of main constituents of the streptothricin complex. Analysis of nourseothricin, grisin and kormogrisin].

A simple and reliable HPLC method for quantitative analysis of complex antibiotics consisting of a mixture of streptothricins F, E, D and C in a biological matrix was developed. The method is based on ion-pair separation of streptothricins on the reversed-phase C18 analytical column with UV detector (210 nm). Aqueous solution of acetonitrile containing trifluoroacetic acid and octane-1-sulfonic acid sodium salt was used as eluent. Retention times of streptothricins became longer as the molecular weight increased, i.e. the component F was eluted first, then followed components E, D and C. The total time of the analysis was ca. 22 min. Composition of the standard samples of nourseothricin and grisin, as well as the streptothricin content of the commercial grisin-based kormogrisin were determined. Components F and D were found to be dominant in the streptothricin complex comprising totally 70-90%, with streptothricin F prevailing in nourseothricin (56%) and streptothricin D being the major constituent in grisin (51%), while in the kormogrisin the concentrations of components D and F were approximately the same. The portion of E varied from 5 to 20% and the concentration of streptothricin C changed within the range of 3-11%. The peaks of the admixtures present in kormogrisin did not interfere with determination of the streptothricin components. It is suggested that the method described can be applied to determination of the streptothricins in biological objects without a complex preliminary sample preparation.

Chromatography, High Pressure Liquid↗
PubMed2005

Binding of LPS and LPS--LDL complexes to rat hepatocytes.

We studied binding of 3H-LPS toxin and LPS complexes with serum 125I-LDL to primary culture of rat hepatocytes. Receptor binding of LPS and LDL--LPS complex was 50 and 77% of the total, respectively. Scatchard plot was linear in both cases. LDL and LDL--LPS complexes were inessential for LPS binding, while LDL--LPS binding was appreciably suppressed by LPS (-30%) and LDL (-65%).

Animals↗
PubMed2003

Effect of ivermectin on function of liver macrophages.

Ivermectin had no effect on phagocytic function of liver macrophages, but blocked LPS-induced secretion of tumor necrosis factor, NO, prostaglandin E2, and increase of intracellular concentration of Ca2+. These inhibitory effects were observed only in the presence of chlorine ions in the extracellular medium, which attested to involvement of glycine-dependent chlorine channels.

Animals↗
PubMed2003

[Ivermectin inhibits activation of Kupffer cells induced by lipopolysaccharide toxin].

Lipopolysaccharide-stimulated liver macrophages (Kupffer cells) secrete many physiologically active substances responsible for inflammatory reaction of the organism. The mechanism by which ivermectin, a macrocyclic lactone possessing a broad antiparasitic activity, modulates basic effects elicited by lipopolysaccharide in the primary culture of rat Kupffer cells was studied. It was found that ivermectin in the absence of endotoxin did not affect a functional state of the Kupffer cells. Preincubation of Kupffer cells with ivermectin (1 mM), however, significantly blocked response to the subsequent administration of lipopolysaccharide (1 mg/ml). In particular, secretion of tumor necrosis factor TNF alpha, nitric oxide NO and prostaglandin E2 was suppressed. Also, an LPS-triggered rise in the intracellular concentration of calcium ions was less pronounced. Removal of chloride anions from the extracellular medium completely abolished inhibitory effects of ivermectin. It is suggested that invermectin exerts its action via binding to the glycine-gated chloride receptors/channels of the Kupffer cells, which may reduce toxic reactions manifestations observed under infections caused by Gram-negative bacteria.

Animals↗
PubMed2002

[Comparative analysis of degradation of native avermectins and spinosyns by UV-HPLC].

Degradation rates and compositional changes in active ingredients of the two crop protection insecticides, Fitoverm and Spinosad, have been compared by using a reverse-phase HPLC with UV detection (250 nm). Decay of the major components of active ingredients: spinosyns A and D (Spinosad) and avermectins A1a, A2a, B1a and B2a (Fitoverm) was studied in the thin dry layer on the glass at sunlight at regular day/night changes of temperature. The following results were obtained: 1) 50% degradation time for spinosyns was about two times shorter than that for avermectins: at 40 degrees C day-time temperature it was 6 hours and 10 hours, respectively, while at 23 degrees C these times increased approx. ten-fold; 2) the initial composition of spinosyns was changed during degradation: ratio of spinosyns A/D was increased (i.e. D component degraded faster than the A one) and additionally 4-5 new spinosyns and/or their derivatives were formed; 3) rate of degradation of each avermectin was practically the same, i.e. percent composition of avermectins did not significantly alter; 4) retention times of avermectins B2a, A2a and A1a were similar to those of either initial spinosyns (A) or products of their decay. It is concluded that determination of spinosysn residues with the aid of UV-HPLC is a complex task since both initial spinosyns (A and D) and their conversion/decay products must be measured. The latter can be dominant residues and not always easy to identify. Analysis consider to be complicated when a sample contains residues of both spinosyns and avermectins.

Anti-Bacterial Agents↗
PubMed2001

[Selective cytostatic and cytotoxic effects of avermectins].

A natural avermectin complex, aversectin C, was shown to be capable of exerting selective cytostatic effect. It killed proliferating neuroblastoma B 103 cells but was non-toxic for differentiated cells of this culture. The activity of aversectin C was related neither to activation of the GABA alpha-receptors nor to their blocking and was at a large extent due to the action of avermectin A1, a component of aversectin C.

Animals↗
PubMed2001

[Effect of avermectns on Ca(2+)-dependent chloride currents in plasmalemma of Chara corallina cells].

A natural complex of avermectins, aversectin C, and a component of this complex, avermectin A1, were shown to change the conductivity of Ca(2+)-dependent chloride channels of plasmalemma of Chara corallina cells by acting only from the outer side of the cellular membrane. Low concentrations of aversectin C and avermectin A1 increased the chloride current: K1/2 = 3.5 x 10(-5) mg/ml for the whole complex and K1/2 = 2.1 x 10(-3) mg/ml for A1. Relatively high concentrations of the compounds suppressed the chloride current: K1/2 = 2.2 x 10(-3) mg/ml for aversectin C and K1/2 = 4.2 x 10(-6) mg/ml for A1. The Hill coefficients for the interaction of avermectin A1 with the corresponding targets for stimulation and suppression of the chloride current were 2.8 and 2.5 respectively. Bicuculine, a non-specific inhibitor of the GABA alpha-receptors, did not influence stimulation of chloride currents caused by action of low concentrations of avermectins, but at the same time blocked suppression of the chloride currents associated with the action of high doses of avermectins. Avermectins A2, B1 (abamectin), B2 and 22,23-dihydroavermectin B1 (vermectin) in the concentration range studied, did not affect the chloride currents of Chara corallina cells.

Calcium↗
PubMed2000

[Cytotoxic and cytostatic effect of avermectines on tumor cells in vitro].

Effect of natural avermectin complex (aversectin C) and separate avermectins A1, A2, B1 and B2 in the cell culture of murine myeloma Ns/o, Erlich carcinoma ascites and human larynx carcinoma Hep-2 was investigated. It was shown that aversectin C within the concentrations of 0.1 to 1.0 mcg/ml inhibited proliferation of tumor cells and induced their death. Proliferation inhibition was due to the delay of the cells cycle start (lag-phase prolongation) and blocking of mitotic cycle. Ns/o cells death had apoptosis signs: chromatin condensation and fragmentation, DNA fragmentation. It was demonstrated that only avermectin A1 has cytotoxic activity within the concentrations used, avermectins A2 and B2 had cytostatic activity, avermectin B1 showed no activity under the experimental conditions.

Animals↗
PubMed1999

[Action of avermectins on lymphoid leukemia P-388 cells in vitro].

Avermectins are final products in the fermentation process with Streptomyces avermitilis. They have parasitocidic activity and are used as the main substances of insectoacaronematocides. The study of the activity of the natural avermectin complex (aversectin C) and separate avermectins A1, A2, B1 and B2 in the cell culture of lymphoid leukemia P-388 showed that within the concentrations of 0.1 to 1.0 microgram/ml aversectin C inhibited the growth of the tumor cells and induced their death. The inhibition was due to blocking the cell mitosis. The cell death was accompanied by internucleosomal degradation of the DNA nuclei i.e. the death was of the apoptosis type. The sensitivity of the cells to aversectin C was directly proportional to their initial proliferative activity. As for the separate avermectins only avermectin A1 had the cytotoxic activity within the concentrations used, avermectin A2 had the cytostatic activity and avermectins B1 showed no activity under the experimental conditions.

Animals↗
PubMed1989

[Effect of lipopolysaccharide toxin on lipid and protein composition of human serum low density lipoproteins].

Complexes of lipopolysaccharide (LPS) B of Salmonella typhimurium with human low density lipoproteins (LDL) formed during in vitro coincubation via spontaneous incorporation of LPS (complex LDL-LPS) or through the incorporation stimulated by the serum protein fraction (LPS/LDL complex) were studied. The LPS/LDL complex was shown to maximally bind 0.24 mg of LPS per 1 mg of LDL protein, whereas the LDL-LPS complex contained only 0.07 mg of LPS per 1 mg of LDL protein. The observed incorporation of LPS into LDL particles was not possibly associated with a transfer of lipids or proteins from high density lipoproteins to LDL. The insertion of LPS was probably accompanied by the expulsion of a small portion of phosphatidylcholine molecules from the outer monolayer of LDL into the aqueous medium and by an increase in the phosphatidylethanolamine concentration in LDL. Simultaneously, the level of esterified cholesterol in the LPS/LDL complex decreased, and the concentrations of free cholesterol and triacylglycerols showed a rise. The level of free fatty acids in the LPS/LDL complex increased more than twofold compared with intact LDL. The enhancement of LPS incorporation did not result in the insertion of any serum proteins into LDL, in which apoB-100 remained the major apolipoprotein (ca. 90%); apoB-100 fragments made up to 5-7%, whereas apoE and apoC contained altogether ca. 3-5%. It is suggested that the LPS/LDL complex obtained can bind to three types of cell receptors, i.e., apoB/E receptors, LPS receptors and scavenger receptors of macrophages (monocytes); the increased level of free fatty acids in the LPS/LDL complex may accelerate its subsequent catabolism.

Blood Proteins↗
PubMed1989

[Structure of the lipopolysaccharide/human plasma low density lipoprotein complex. 31P-NMR and fluorescence spectroscopy studies].

Complexes of Salmonella typhimurium lipopolysaccharide toxin (LPS) with low density lipoproteins (LDL) containing various amounts of LPS were prepared in vitro. The 31P-NMR spectra showed that in the LDL-LPS complexes as well as in native LDL all phosphate groups of phospholipids are accessible to the paramagnetic shift reagent, Pr3+. Besides, the low frequency mobility of phospholipid phosphates in the complex is diminished. It was supposed that the phospholipid molecules in the LDL/LPS complex as in native LDL form a monolayer structure on the surface of LDL. The intrinsic fluorescence spectra of tryptophan residues of the apoprotein (apo B-100) revealed that the incorporation of LPS molecules into LDL particles is accompanied by minor changes in the conformation and orientation of the apo B molecule. As a result of these changes, certain fragments become exposed to a more hydrophilic environment and become more accessible to fluorescence quenchers. The use of charged (I-, Cs+) and uncharged (acrylamide) quenchers permitted to identify in the apo B molecule different tryptophan residues, some of which are localized in the vicinity of negatively charged groups, whereas others are neighbouring positively charged groups. It is suggested that the LPS molecules incorporated into LDL particle do not screen the apo B molecule to such an extent that it would hinder the LDL/LPS complex binding to apo B/E cellular receptors.

Humans↗
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

[Ability of a lipopolysaccharide toxin to intensify the functional response of human thrombocytes to thrombin stimulation].

The preincubation of isolated washed human platelets with lipopolysaccharide toxin (LPS) from Salmonella typhimurium (10 min, 37 degrees) speeds up the thrombin-induced aggregation. Besides, LPS-pretreatment was shown to alter the turnover of polyphosphoinositides stimulated by thrombin and significantly elevated concentrations of diacylglycerol and thromboxane B2 in comparison with control platelets. However, LPS does not influence on the lipid fluidizing effect of thrombin action as testifies by ESR spectroscopy with doxyl-stearic acids as spin-probes. An LPS pretreatment of platelets that induces no aggregation by itself is proposed might transform cells into a state of hidden activation" associated with the accumulation of such products as diacylglycerol and precursors of thromboxane B2. Addition of thrombin to such "preactivated" platelets could cause a more effective aggregation.

Bacterial Toxins↗
PubMed1988

[Phosphoinositide breakdown and diacyl glycerin formation in human thrombocytes as affected by a lipopolysaccharide toxin].

The interaction of lipopolysaccharide toxin (LPS) with isolated washed human blood platelets has been studied. LPS was found to induce the rapid (1-2 min) and marked (15-20%) breakdown of mono- and polyphosphoinositides and formation of significant amounts of diacylglycerols (ca. 20%). However TxB2 biosynthesis from endogenous 14C-arachidonic acid was stimulated by LPS incubation only by ca. 20%. Phosphatidylcholine and phosphatidylethanolamine were also hydrolysed by ca. 8 and 12%, respectively, presumably via the activation of endogenous phospholipase A2. Besides, LPS caused the decreasing of the lipid fluidity of a platelet plasma membrane as was shown by ESR spectroscopy using doxylstearic acid probes. All these changes by LPS induce no aggregation of platelets. It is concluded that an enhancement of a phosphoinositide cycle is not a possibly necessary and sufficient condition for a platelet aggregation.

Bacterial Toxins↗
PubMed1988

[Lipopolysaccharide-induced hydrolysis of plasmalogenic phosphatidylethanolamine in human platelets].

The composition of human platelet major phospholipids-phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidic acid (PA), sphingomyelin (SM), plasmalogenic and diacyl species of phosphatidylethanolamine (PPE and APE, respectively) was quantitatively analyzed by high performance liquid chromatography. Incubation (10 min, 37 degrees C) of washed platelets with lipopolysaccharide B (LPS) of Salmonella typhimurium was found to produce (in the absence of aggregation) marked hydrolysis of PI (ca. 15%) and PPE (ca. 19%) containing the bulk of polyenic fatty acids. PC and APE were less degraded (8-9%), while the amounts of PS and SM were practically unchanged and the level of PA rose by 20%. Addition of thrombin to LPS-pretreated platelets resulted in their more rapid aggregation which was accompanied by a decreased and nearly equal hydrolysis of APE and PPE (7-8%) as compared with control platelets (10 and 12%, respectively). The extent to which PI was degraded (ca. 34%), by the action of thrombin was not affected by preliminary incubation with LPS. It is suggested that thrombin (as well as LPS) activating endogenous phospholipase(s) A2 can liberate from PPE not only arachidonic acid but also other essential polyenic fatty acids present in PPE in relatively high amounts. Besides, the agents studied may activate the intrinsic platelet system of rapid arachidonoyl transfer from diacyl PC and PE to PPE.

Blood Platelets↗
PubMed1988

[Lipid metabolic indices in patients with the gastrointestinal form of food poisoning].

The serum concentration of some substances of lipid nature was studied in 103 patients with food toxinfections with relation to the severity of a course and period of the disease. The levels of cholesterol, triglycerides, diglycerides, nonesterified fatty acids (NEFA), and phospholipids were determined using thin-layer chromatography. A mild course of the disease was characterized by a slight rise of lipid concentration. Moderately severe courses were characterized by hyperlipidemia with an increase in the level of NEFA, lysophosphatidylcholine (LPC), phosphatidylcholine. Patients with a severe course demonstrated a decrease in the concentration of most lipid fractions with an increase in the amount of LPC and NEFA. All disorders were observed on the 1st-2nd day of the disease and disappeared against a background of routine rehydration therapy by the 5th-7th day of disease, in patients with a severe course of the disease by the 10th day.

Acute Disease↗