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Biomedical subjects

G E Dobretsov

Publications and source records attributed to G E Dobretsov.

At least 55 records · Page 3Linked to original sources
PubMed1980

[Evaluation of the degree of tryptophan residue immersion into the lipid phase of low density serum lipoproteins].

Based on the theory of inductive resonance energy transfer, it was demonstrated that in a two-phase waterlipid system the efficiency of the transfer from the donor to the acceptor, which is evenly distributed in the lipid phase, depends on the donor localization with respect to the interface. The inductive resonance energy transfer from the tryptophane residues of protein of low density serum lipoproteins (LDL) to the pyrene fluorescent probe distributed in the lipid phase of LDL was studied. The degree of immersion of the tryptophane residues with respect to the LDL surface is 11,6 +/- 2,6 A. Among the existing models of LDL where the proteins are localized at 20--80 A above the particle surface or are arranged in a monolayer on the particle surface, the first one does not coincide with the experimental data, whereas the second one agrees well with them.

Humans↗
PubMed1980

[Use of fluorescent probes for detecting structural reorganizations in the membranes of the hepatic endoplasmic network during the maintenance of rats on an atherogenic diet].

Prolonged feeding of rats with a full-value semi-synthetic diet or diet enriched with cholesterol provoked material changes in the lipid content (the molar ratio of cholesterol/phospholipids) in the liver endoplastic reticulum, in the functional activity (the activity of the membrane-bound glucoso-6-phosphatase) and in the physical structure of the membranes. The changes were detected by means of the fluorescent probes (pyrene, 4-dimethylaminochalcone, 1-anilinonaphthalene-8-sulfonate). All the changes were more pronounced in liver microsomes of rats fed with the atherogenic diet. Fluorescence of the probes in microsomes and in model lipid membranes (liposomes) containing varying amount of cholesterol was compared to find that in vivo changes in the physical properties of microsomal membranes do not completely reduce to the effects consequent on membrane enriching with cholesterol.

Adaptation, Physiological↗
PubMed1980

[Membrane permeability to aminazine and nonachlazine].

Model phospholipid vesicles (liposomes) and the fluorescent probe p-terphenyl were used to study membrane permeability by phenothiazine anesthetics. The anesthetics quenched the fluorescence of the probe bound to the membrane. The extent of the quenching depended on the quenching ability to penetrate the lipid bilayer. Aminazin was able to penetrate the lipid bilayer, while nonachlazin was not. This may be accounted for by the presence of two nitrogen atoms capable of binding to H+ in the nonachlazin molecule in contrast to one nitrogen atom in the aminazin molecule.

Chlorpromazine↗
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

[Concentration and properties of albumin in the serum and peritoneal exudate in patients with peritonitis].

A new fluorescent method was used to study albumin concentration and properties in blood serum and peritoneal exudate of patients with peritonitis of different origin excluding pancreatogenic one. Total albumin concentration (TA), effective albumin concentration (EA) dependent on both TA and properties of binding sites in albumin molecules, and their ratio EA/TA dependent only on the site properties were measured. Peritonitis led to significant decrease of TA, EA and their ratio EA/TA. Thus, leak of blood albumin was accompanied by some change of albumin binding site structure. As a rule, albumin of peritoneal exudate was changed in the same extent of blood albumin, i.e. the albumin transfer from blood to exudate keeps it's changed structure because the ratio EA/TA correlated well in serum and exudate (r = 0.75) while the ratio was very mach variable both in serum and exudate. The gradient TA exudate/TA serum was found as a linear function of the serum TA with personal correlation coefficients from 0.8 up to 1.0 in 12 of 16 patients studied. The linear equation coefficients reflected character of the peritonitis development in these patients.

Ascitic Fluid↗
PubMedDate not supplied

[Size of a human serum albumin molecule in solution].

The size of a human serum albumin molecule in aqueous solution containing 150 mM NaCl was studied using small-angle neutron scattering. The molecular radius of gyration was estimated to be 27.4 +/- 0.35 A. The compact sphere should have a smaller radius of gyration, whereas the popular human serum albumin model, a "cigar" 136 A long, should correspond to a greater radius of gyration. Possible shapes of the human serum albumin molecule which are in accordance with the results obtained, are the following: an extended ellipsoid less than 110 A of length or a nonsymmetrical oblate ellipsoid with a diameter of 85 A. The oblate ellipsoid might be close to the heart"-shaped structure of the crystalline human serum albumin molecule. The size of the albumin molecule does not change significantly as pH increases to 8.9. The possibility of the dynamic coexistence of various human serum albumin conformers in solution is discussed.

Humans↗
PubMedDate not supplied

[Blood fatty acid transporters in acute pancreatitis].

A relationship between of acute pancreatitis severity and concentrations of blood transporters of nonesterified fatty acids (albumin) and esterified fatty acids (lipoproteins) was studied. In necrotizing pancreatitis, there was a positive correlation between decrease of albumin and lipoprotein concentrations in serum, but no correlation was in edematous pancreatitis. High levels of serum albumin (> 32 g/L) and lipoproteins (cholesterol + triglycerides, CH + TG, > 260 mg/dL) had good prognostic value in terms of favourable development of this disease, whereas lower concentrations indicated unfavourable prognosis. Both albumin and lipoproteins appeared in the peritoneal exsudate where they represented 73 and 53% of the serum concentrations, respectively. Albumin efflux from blood to the exsudate correlated with lipoprotein efflux (r = 0.7) in necrotizing pancreatitis. The latter suggests that proteins penetrated together the tissue barrier blood/peritoneal space. The less albumin and lipoprotein concentrations in serum, the more they are in the exsudate (r = -0.57 and -0.47, respectively); probably, their concentration decrease in blood is due to to their efflux into the exsudate.

Acute Disease↗
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↗