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Biomedical subjects

G E Dobretsov

Publications and source records attributed to G E Dobretsov.

At least 73 records · Page 4Linked to original sources
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

[Fluorescent probe 4-dimethylaminochalcone: mechanism of fluorescence quenching in nonpolar media].

The reasons for the high sensitivity of the fluorescent probe 4-dimethylaminochalcone (DMC) to nonpolar environment were explored. It was shown that, at room temperature, the fluorescence quantum yield in nonpolar media at 20 degrees C is lower than 0.01 (0.001 in methylcyclohexane). However, as temperature was lowered to -196 degrees C, the yield in methylcyclohexane increased more than 200 times. At the same time, the oscillator strength of absorption transition increased, and the absorption spectrum was shifted to red. These results, together with quantum chemistry calculations suggest that, for fluorescence quenching to occur, some barrier in the DMC molecule, probably the barrier of rotation about C-C bonds, should be overcome. In other words, the quenching is associated with the transition of DMC molecules from a flat conformation (energy minimum) to other, nonflat conformations through rotations about C-C bonds. The phosphorescence of DMC at low temperatures was detected. This suggests that fluorescence quenching is caused by radiationless transitions from the excited singlet level to the ground and triplet levels, and rotation about bonds facilitates these transitions.

Chalcone↗
PubMedDate not supplied

[Informative value of the parameter "effective concentration of albumin" in diffuse peritonitis: data from a multi-center study].

The paper represents data on new potentialities in evaluating a severity of patients with total peritonitis (TP). They are based on the fluorescence analysis of the physical-and-chemical properties of blood albumin. The findings are a result of a multi-center research undertaken by clinics of Moscow and Moscow Region. The properties of albumin-molecule binding sites were investigated by the fluorescence test. The parameter, measured in the test, was named "effective albumin concentration". The study protocol comprised the data of clinical examinations, scales SAPS and MPI as well as laboratory findings and EAC. The subsequent analysis denoted that a combination of 2 parameters, i.e. EAC and serum urea concentration routinely measured, is highly informative in evaluating the TP severity and correlates well with the survival rate in the discussed pathology. The study results could be a basis for an early individual prognostication of TP course made on the 1st postoperative day.

Fluorescent Dyes↗
PubMedDate not supplied

[Low-density lipoproteins with different capacity for aggregation].

Preparations of low-density lipoproteins from healthy donor blood contain lipoprotein particles with different capacity for aggregation: upon stirring, some particles form aggregates significantly more quick than others. After stirring, lipoprotein particles are separated by ultracentrifugation into two fractions: a fraction of large aggregates and a fraction of small particles without intermediate forms. It is known that lipoprotein aggregates can accelerate intracellular accumulation of lipids. Therefore, it is supposed that particles of high aggregation ability are more atherogenic.

Centrifugation, Density Gradient↗
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[Albumin redistribution between blood and peritoneal exudate in abdominal diseases].

Albumin concentrations were measured in blood serum (As) and in peritoneal exudate (Ae) of patients with peritonitis and acute pancreatitis. As and Ae registration during several days revealed strong negative correlation between an index, Ae/As, and serum albumin As in 51% of the patients. The absolute value of the linear correlation coefficient, r, exceeds 0.7 in each of these patients. Moreover, pooled data in this group of patients showed that integral correlation coefficient was very high, r approximately equal to 0.94 at p < 0.01. In other words, the higher ratio Albumin in exudate/Albumin in serum, the lower albumin concentration is in serum. Other patients had either lesser coefficient of the negative correlation, between -0.3 and -0.7 (14% of all patients) or very low negative or even positive correlation of the index, Ae/As, and serum concentration As (35% of all patients). Probable albumin redistribution between blood, peritoneal exudate and tissue pool in relation to ratio exudate Albumin/serum Albumin is discussed.

Acute Disease↗
PubMedDate not supplied

[The lipophilic fluorescent probe 4-dimethylaminochalcone: factors responsible for the fluorescence yield].

Factors responsible for fluorescence quenching of the lipophylic fluorescent probe 4-dimethylaminochalcone in nonpolar and polar media were studied. The femtosecond dynamics of 4-dimethylaminochalcone excited state was measured using the absorption method of "excitation probing". In nonpolar hexane where the fluorescence quantum yield is very low (0.001), all excited 4-dimethylaminochalcone molecules go to the triplet state with a rate constant of 2.10(11) s(-1). At the same time, the radiation rate constant is 1000 times lower; therefore, such a fast transition to triplet is the major cause of the very small fluorescence yield. In polar acetone, the fluorescence yield is 220 times higher than in hexane. In acetone, no transitions to triplet state were detected. At the same time, a radiationless conversion to the ground state took place with a rate constant of 10(9) s(-1), which decreased the fluorescence yield to 0.22. The activation energy of the quenching processes is polarity dependent and decreases from 6 in nonpolar to 3 kcal/mol in polar media. The yield of 4-dimethylaminochalcone fluorescence varies hundreds times in media of different polarity but is a linear function of the Lippert's polarity parameter f(epsilon,n) where epsilon is the dielectric constant at low frequencies. It is supposed that polar media stabilize the "flat" conformation of the 4-dimethylaminochalcone molecule prior to its excitation, and this conformation is optimal for fluorescence. In this case, stabilization is determined only by medium polarity.

Chalcone↗
PubMedDate not supplied

[Serum albumin in systemic inflammatory reaction syndrome].

A group of patients with pyoinflammatory surgical disease, which showed a strong correlation between the serum concentration of albumin and the number of signs of a systemic inflammatory reaction (SIR), was examined. It was found that the more number of such signs the patient had, the less blood concentration of albumin was: the linear correlation coefficient averaged -0.78 (p < 0.01) in the group. In the natural development of the disease, the larger number of signs of SIR (negative changes) is followed by decreased albumin concentrations and their reduction (positive changes) leads to an increase and even complete restoration of albumin concentrations. With a fatal outcome, there is a much greater drop in the serum concentration of albumin, which is inconsistent with the magnitude of criteria of SIR. The possible reasons for a reduction in blood albumin concentration and for ineffective correction of hypoalbuminemia in sepsis are discussed.

Adult↗
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

[Interaction of N-phenyl-1-amino-8-sulfonaphthalene (ANS) with albumin in blood in hyperbilirubinemia].

The fluorescent intensity of the N-phenyl-1-amino-8-sulfonaphthalene (ANS) probe significantly decreases in hyperbilirubinemic serum. A decrease of the albumin concentration and absorption of ANS fluorescence by bilirubin cannot explain such a considerable reduction of the probe fluorescence intensity. Measurements of the fluorescence decay kinetics has shown two types of sites occupied by ANS in albumin. ANS quantum yields in hyperbilirubinemic and normal serum are practically identical. The coupling parameters for ANS decrease, but the coupling constant increases under hyperbilirubinemia. As a result the coupling of organic anions with serum albumin significantly decreases if there is high anion concentration, and it does not decrease at low anion concentration. Bilirubin is not a main cause of a decrease of the albumin binding capacity.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

[Fluorescent method of determination of serum albumin in hyperbilirubinemia].

A procedure is developed for estimation of human blood serum albumin in hyperbilirubinemia using a fluorescent probe 9,10-dianiline-2-sulfoanthracene (K-33). Use of the probe N-phenyl-I-amino-8-sulfonaphthalene (ANS) led to underestimation of albumin in hyperbilirubinemia as bilirubin and other inhibitors prevented the ANS binding with blood serum albumin. Substitution of ANS for K-33 enabled to estimate the albumin concentration under conditions of the pathology accompanied by an increase of endogenous ligands content in blood serum. The rate of K-33 (15 mM) fluorescence in blood serum (diluted 400-fold, at pH 4.0) correlated with albumin concentration (r-0.955).

Fluorescent Dyes↗
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

[Size distribution of plasma lipoproteins].

Particle diameters of very low density lipoprotein (VLDL)--29.5, 36.3, 22.0; low density lipoprotein (LDL)--18.4, 19.0, 22.0; high density lipoprotein subclass 2 (HDL2)--8.5, 9.7, 15.0; and high density lipoprotein subclass 3 (HDL3)--7.2, 7.6, 14.4 nm were evaluated by means of flotation velocity (FV), optical mixing (OM), and fluorescent probe (FP) respectively. On the basis of the calculated frictional ratio f/f0 from FV and OM data for VLDL, LDL, HDL2, and HDL3--1.51, 1.07, 1.31, and 1.10, assuming the sphericity lipoprotein particles as an index for structural peculiarity a conclusion is made that in contrast to LDL and HDL3 HDL2 have asymmetrical weight distribution per particle volume. A model is suggested suitable for the structural peculiarity of VLDL established on the data of three independent methods which outlines VLDL as particles consisting of several associated subunits with the mean diameter of about 20 nm.

Fluorescent Dyes↗
PubMedDate not supplied

[Free energy of the accumulation of a fluorescent cation probe within lymphocyte mitochondria].

Fluorescent probe-cation 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM) can be accumulated in mitochondria of rat thymus lymphocytes. A method is proposed for microfluorometric measuring of DSM concentrations ratio inside the thymocyte mitochondria and in the external medium. This method requires no knowledge about the cell and mitochondria volume, the number of accumulated probe and formation of ionic gradients in the cell by carriers. DSM concentration in energisized mitochondria of the thymocyte exceeds its concentration in the external medium by 10(4) times. This corresponds to the free energy accumulated by DSM equaling 5.2 +/- 0.2 kcal/mole. If such work on the probe accumulation is performed by the electrostatic fields on the plasma and mitochondrial cell membranes, the sum of the potentials of these two fields is 230 +/- 10 mV.

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↗