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Biomedical subjects

G E Dobretsov

Publications and source records attributed to G E Dobretsov.

At least 19 recordsLinked to original sources
PubMed1991

Depolarizing action of allergens on passive sensitized lymphocytes.

An ability of rat thymus lymphocytes to respond to pollen allergens has been found. The lymphocytes were exposed with plasma of pollinosis patients. The subsequent addition of allergens specific for the patient caused the decrease of lymphocyte plasma membrane potential. The decrease was detected by use of potential-sensitive fluorescent probe 4-(p-dimethylaminostyryl)-1-methylpyridinium. This newly found effect can be employed for diagnostics of atopic states.

Allergens↗
PubMed1979

[Fluorescent probe-indicator of differences between T- and B-lymphocytes in the blood].

A new physico-chemical marker for the human peripheral blood lymphocytes was worked out. The lymphocytes were vitally stained with the fluorescent probe 3-methoxybenzanthrone and measured by microfluorometry. The blood lymphocytes population was found to be heterogeneous; this population consists of the two main groups of cells differing by the intensity of their fluorescence. By means of immunological lymphocyte fractionation it was shown that one of these cell groups was represented by T-lymphocytes, and the other one--by B-lymphocytes.

Adult↗
PubMed1977

[Correlation between the antiarrhythmic activity of acyl derivatives of phenothiazine and their affinity for phospholipid membranes].

The interaction of thirteen antiarrhythmic active phenothiazine 10-acylaminopropionil derivatives with artificial phospholipid membranes was studied. Blinding constant (K) of this interaction was determined by means of a fluorescent probe. There was found a valid correlation between K and antiarrhythmic activity (A) for 10 substances; the greater the K--the greater the A. Three substances characterized by the greatest K had, however, a low A. It can be assumed that the interaction of antiarrhythmic drugs with phospholipids of target membranes in vivo is an important element of the molecular mechanism of action. At the same time a very high affinity to lipids can possibly cause a delocalization of the drug in the organism and a decrease of its antiarrhythmic activity.

Animals↗
PubMed1976

[Interaction of nonachlazine and noradrenaline on a model phospholipid membrane].

The binding of nonachlazine (NCL), imipramine (IMP), and noradrenaline (NA) with the model phospholipid membrane vesicles--liposomes--was studied. The binding was determined by the qunching effect of these substances on the fluorescence of 3-methoxybenzantrone (MBA) present in the membrane of the fluorescent probe. A method rendering possible calculation of the binding of the preparations under study with the membrane of the basis of the fluorescence changes was developed. The binding constant of the NCL, IMP, and NA interaction with the membrane was equal to (4.3 +/- 0.3)-10(3)M-1, (2.7 +/- 0.2)-10(3)M-1, and (0.7 +/- 0.15)-10(3)M-1, respectively. It was shown that NCL and IMP could compete with NA for the membrane binding centers. Such competitive interactions could be regarded as a probable mechanism of the block of the reverse NA transport through the synaptic and the vesicular membranes characteristic of NCL and IMP.

Binding, Competitive↗
PubMedDate not supplied

[Partial fractionation and physico-chemical properties of non-histone chromatin proteins].

The non-histone chromatin proteins (NHP) were isolated by a modified Wang technique. NHP were easily dissoluble in solutions of a physiological ionic strength within a wide pH range. NHP were subdivided into 18 zones by analytical polyacrylamide gel electrophoresis. NHP have molecular weights within the range 15,000 greater than 200,000. A part of NHP showed similar molecular weight but different values of molecular charge. NHP were separated by a gel filtration into 6 fractions. Two fractions were individual proteins. The great bulk of NHP has a molecular weight less than 40,000, and 6-6.5% of NHP-more than 100,000. The fractions different from each other in a specific UV-absorbtion, fluorescence and circular dichroism. The nhp fraction of a smaller molecular weight has a smaller content of alpha-helix (8%) and the greatest polarity of the environment of tryptophan residues; the molecules of this fraction may have a loose tertial structure. Other NHP have 15-24% of alpha-helix and possibly have compact globular sites.

Chromatin↗
PubMedDate not supplied

[Distribution of small hydrophobic molecules in membranes. I. Artificial lipid membranes].

A hydrophobic uncharged fluorescent probe of 4-dimethylaminochalcone (DMC) interacted with synthetic phospholipid membranes. Comparison of absorption spectra and fluorescence of DMC in the membranes and organic solvents shows that in the membranes the DMC molecules are located not in the hydrocarbon layer but in the polar regions near the surface. The probe is distributed regularly along the surface forming no dimers and clusters. Polar groups which surround the probe in the membrane are less mobile than the molecules of organic solvents at the same temperature. The evaluation shows that the relaxation time of polar groups in the probe environment is longer than 0.15-10(-9) sec. The DMC molecules may be located in different sites of the membrane surface, which seem to differ from one another in the mobility of polar groups.

Chalcone↗
PubMedDate not supplied

[Application of x-ray analysis for the study of the orientation in DNP films].

A planar texture in dried film samples of DNP was found by X-ray study. Axes of DNA macromolecules are located in the film plane and the 77 A reflection is directed along this axis. Periodic structures corresponding to 55 and 34 A are packed parallel to the film plane. The results obtained do not contradict with a supercoil DNP model, however they all allow other possible packing models of DNP molecules, in particular, histone layers alternating with DNA layers in oriented films.

Binding Sites↗
PubMedDate not supplied

[Anion-binding centers of human serum albumin during an N-F conformation transition and in isolated albumin and blood serum].

Fluorescent probe N-phenyl-1-amino-8-sulfonaphthalene (ANS) was used for studying pH-dependent structural N-F-transition in human serum albumin of two kinds: in commercial albumin and in natural blood serum. The kinetics of ANS fluorescence decay in albumin solutions was measured. There were found two types of the sites occupied by ANS in albumin under physiological conditions (pH 7.4). In the first binding site ANS fluorescence decay time was 16.6 +/- 0.3 nsec and it was not significantly changed at N-F transition (pH 4.0). In the second binding site the decay time was dependent on pH in commercial albumin and was not significantly changed in serum. In the second binding site there were individual differences of ANS decay time (4.3 +/- 0.6 nsec). The observed ANS fluorescence intensity enhancing (about 40-50%) in N-F transition may be explained by an increase of albumin binding sites capacity for ANS.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

[Study of phenothiazine binding to membranes by the fluorescent probe method].

Binding of chlorpromazine, etaperazine and triftazine with model phospholipid membranes was investigated by using a 3-methoxybenzanthrone (MBA) fluorescent probe. All these preparations interacted with the membranes, this being registered by the MBA fluorescence extinction. The phenothiazine molecules bound with the membrane are localized in its superficial layer and extinguish the MBA fluorescence in different ways. The chlorpromazine binding was heterogenous and there are, apparently, 2 different ways of its molecules combination with the membranes. The effective extinction of MBA by phenothiazine increased in the following order: chlorpromazine, etaperazine, triftazine.

Antipsychotic Agents↗
PubMedDate not supplied

[Isolation of rat liver chromatin non-histone protein].

A chromatin with the protein/DNA ratio of 3.0 was obtained from rat liver cells nuclei. The chromatin was dissolved in 2 M NaCl, pH 7, and reprecipitated by decreasing the ionic strength to 0.4 and increasing pH to 9.0. A fraction of non-histone proteins (NH-1) remained in a supernatant solution, the NH-1/DNA ratio being equal to 1.3 and the ratio of acidic to basic aminoacid residues equal to 1.31. After chromatography on Bio-Rex 70 cation-exchang resin, a fraction (NH-2) with the NH-2/DNA ratio of 1.0 +/- 0.15 and the ratio of acidic to basic aminoacid residues of 1.57 was obtained. According to the data of polyacrylamide gel electrophoresis, the NH-2 fraction contained 2.7% of histone f2 + f3 as an admixture whereas histone f1 was not revealed.

Amino Acids↗
PubMedDate not supplied

[Effect of low temperatures on the functional state of the membranes of the hepatic endoplasmic reticulum].

Oxidation of fluorescent substrates--NADPH and 4-dimethylamine chalcone (DMC) by microsomes from liver endoplasmic reticulum was studied after freezing and thawing of these cells organelles. Slow freezing to -25 degrees or quick freezing to -196 degrees did not affect distinctly the rate of NADPH oxidation after thawing, but oxidation of DMC by microsomes was decreased in both cases. Freezing and subsequent thawing of microsomes impaired apparently the terminal sites of electron transfer and/or the systems of hydroxylation, including cytochrome P-450. Slow freezing to -25 degrees impaired microsomes more markedly than quick freezing to -196 degrees.

Animals↗
PubMedDate not supplied

[Relationship between the structure, affinity for phospholipid membranes and anti-arrhythmic activity of 10-acylaminopropionyl derivatives of phenothiazines].

The interaction of thirteen 10-acylaminopropionyl derivatives of phenothiazine with phospholipid membranes was investigated. A correlation between the affinity of these substances to membranes and their antiarrhythmic activity was found. A molecular model of a complex of the substance-membrane is proposed. It shows how the molecular structure of the study substances affects their affinity to phospholipids and thus influences the activity of the former. The affinity chiefly depends on the accordance between the structure and the disposition of the lateral substitute, on the one hand, and the structure of the phospholipid bis-layer, and also of the hydrophobic nature of the 10-acylaminopropionyl group, on the other.

Aconitine↗
PubMedDate not supplied

[Effect of peroxidation on the physical structure of phospholipid membranes].

Peroxidation of lipids caused rearrangements in physical structure of biomembranes as it was shown by a method of fluorescent probes. These structural rearrangements were accompanied by an increase in the viscosity on the surface and in the depth of the phospholipid bilayer. The increase in the viscosity was apparently due to oxidation and to elimination from the phospholipid bilayer of the unsaturated fatty acid residues. Presence of the unsaturated fatty acids in biomembranes decreases their viscosity. The fraction of saturated fatty acids after peroxidation was respectively increased in the bilayer.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

[Water molecule mobility in the surface layer of a membrane recorded with the fluorescent probe 4-dimethylaminochalcone].

A scheme of the location of a fluorescent probe 4-dimethylaminochalcone (DCM) in a phospholipid membrane has been proposed. According to the scheme the DMC dimethylamino group is located near phosphate groups and the oxygen atom--in the carbonyl groups region of phosphatidylcholine molecules. It is shown that DMC fluorescence is dynamically quenched by water molecules in the membrane. Therefore the quantum yield and, partly the position of DMC fluorescence maximum are determined by the water concentration near the probe, by the ability of water molecules to penetrate into the membrane as far as the carbonyl groups of fatty acid residues and by the water mobility in the membrane layer.

Chalcone↗
PubMedDate not supplied

[Influence of the physical structure of phospholipid membranes on peroxidation induced by Fe2+ ions].

Kinetics of free radical lipid peroxidation, induced by Fe2+ in presence of ascorbic acid, was studied in phospholipid membranes. The maximal rate of peroxidative oxidation was observed at 2.5 muM concentration of Fe2+, in this case a half of the maximal amount of peroxidative oxidation products was formed within 20-30 min at 20 degrees and at 200 muM concentration of ascorbic acid. The rate of peroxidative oxidation depended on addition of substances modifying the membrane structure (linoleic acid, cetyl trimethylammonium, Tween-60, derivatives of phenothiazol). Charge of the membrane surface was shown to have a distinct effect on the peroxidative oxidation. Loosening of membranes by non-ion detergent (Tween-60) increased the rate of the process, whereas the increase of the membranes rigidity by cholesterol did not cause any effect. Uneffectiveness of cholesterol is discussed with relation to diffusion of radicals, participating in peroxidative oxidation, from depth of the membrane to its surface and in the opposite direction.

Ascorbic Acid↗