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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
PubMed2006

Dipolar relaxation in a lipid bilayer detected by a fluorescent probe, 4''-dimethylaminochalcone.

The dynamic behavior of polar molecules in egg phosphatidylcholine (PC) bilayers has been studied using a membrane fluorescent probe, 4''-dimethylaminochalcone (DMAC). Time and spectrally resolved fluorescence spectroscopy of DMAC incorporated in PC liposomes, as compared to studies of the probe in organic solvents, shows the existence of two independent populations, associated with different extent and speed of dipolar solvent relaxation. The first DMAC population represents approximately 69% of the fluorescence-emitting molecules, has a short fluorescence decay time (0.32 ns) and undergoes Stokes shift of 80 nm. The remaining 31% fraction of DMAC molecules has a decay time of 0.74 ns and undergoes a high (106 nm) Stokes shift. A fraction of the shift, ca. 24 nm for the first and 46 nm for the second population, is attributed to the fast (<0.1 ns) rotational relaxation of nearby dipolar molecules, which might be water. This two-state model accounts well for the detailed fluorescence properties of DMAC in egg PC, i.e. its broadened steady-state spectrum, its average fluorescence quantum yield and its complex wavelength-dependent fluorescence decays.

Animals↗
PubMed2006

Conformational properties of serum albumin binding sites in rats with different behaviour in the open field test.

In this study, the hypothesis was tested that behaviour of rats under the open field test condition and effects of subsequent acute stress relate to conformational properties of the main plasma carrier protein, albumin.To evaluate albumin properties, fluorescence intensity of a molecular probe CAPIDAN (N-carboxyphenylimide of dimethylaminonaphthalic acid) at N (at pH 7.4) and F (at pH 4.2) albumin conformations was measured and the N-F signal ratio was calculated. The data obtained showed that CAPIDAN fluoresces selectively from albumin in rat serum and its fluorescence is sensitive to binding of fatty acids and some other ligands to albumin. Behaviour of 78 Wistar male rats was characterized from the fraction of time taken for exploratory and ambulatory activity during the open field test. In rats not subjected to stress (n = 40), a negative correlation was revealed between open field activity and CAPIDAN N-to-F ratio for albumin (r = - 0.55, p < 0.0005). In the group of rats subjected to acute stress (immobilization plus stochastic electrocutaneous stimulation) the correlation between behavioural activity and the albumin conformational properties was significantly positive (r = 0.59, p < 0.0001): the CAPIDAN albumin fluorescence ratio increased in the highly active rats and decreased in the low-activity rats. The mechanisms of the observed effects may involve differences in nonesterified fatty acid production during stress.

Animals↗
PubMed2003

Blood albumin in the mechanisms of individual resistance of rats to emotional stress.

This report describes studies of the characteristics of serum albumin in rats with different predicted levels of resistance to emotional stress in control conditions and in conditions of experimental emotional stress. The effects of peptides increasing the resistance of animals to emotional stress (delta sleep-inducing peptide and Semax) on serum albumin were analyzed in rats predicted to be resistant and susceptible to emotional stress.

Adrenocorticotropic Hormone↗
PubMed2002

[Diagnostic significance of albumin transporting characteristics and blood level of troponin T in myocardial infarction].

Serum albumin binding capacity (ABC) was studied using K-35 hydrophobic fluorescent probe in order evaluate the passive transfer and absorption of saturated fatty acids (s-FA) by the cells. ABC decreases on day 3 of myocardial infarction and remains low till discharge and is paralleled by hyperTG. We believe that ABC decrease reflects activation of passive transfer and absorption of s-FA by the cells during simultaneous blocking (presumably by acute phase proteins) of active apoE/B-100 receptor endocytosis of s-FA in the form of TG as VLDL remnants. Decrease of ABC reflects a later than erythrocyte sedimentation rate and acute phase proteins normalization of metabolic consequences of inflammation. ABC helps indirectly evaluate the blocking of active (receptor) absorption of s-FA in the form of TG and activation of passive absorption of s-FA from associations with albumin by the cells.

Aged↗
PubMed2002

[Blood albumin in mechanisms of individual resistance of rats to emotional stress].

Serum albumin parametres in the rats with various prognostic resistance against emotional stress in the control and in conditions of experimental emotional stress were investigated. Analysis of action of peptides raising the animals' resistance against emotional stress (DSIP and SEMAX) in rats with different prognostic resistance against emotional stress, on the serum albumin characteristics, was carried out.

Adrenocorticotropic Hormone↗
PubMed2001

Protein-lipid interactions in reconstituted high density lipoproteins: apolipoprotein and cholesterol influence.

Two fluorescent probes-cis- and trans-parinaric acids were used to study the dimensions, lipid dynamics and apolipoprotein location in the reconstituted discoidal high density lipoproteins (rHDL). The rHDL particles made from apolipoprotein A-I (apoA-I), dipalmitoylphosphatidylcholine (DPPC), with or without cholesterol (Chol) were compared with the analogous particles with two other apolipoproteins-apoE and apoA-II. The data obtained for apoA-I-containing rHDL were as follows: (1) the inclusion of 8 mol.% of cholesterol did not significantly change the particle dimensions (13+/-1 nm) or the mean distance between apoA-I and the disc axis; (2) the phospholipid domains-boundary lipid region in the close vicinity to apoA-I molecule and the remaining part of the bilayer-existed at temperatures both lower and above DPPC transition temperature T(t); (3) at T<T(t) Chol molecules preferentially accumulated in the central area with a radius of 2.8 nm that conserved partially after DPPC phase transition; (4) inhomogeneous cholesterol distribution was assumed to exist within these domains. A hydrophobic matching concept was used to compare protein-lipid interactions in rHDL particles. For complexes with all three apolipoproteins studied, at T<T(t) the probe mobility in the lipid phase of rHDL was significantly higher compared to pure DPPC bilayer. After temperature-induced transition, mobility increased significantly still being lower in rHDL. The comparative study of lipid dynamics in apoA-I-, apoE- and apoA-II-containing complexes revealed the presence of boundary lipid in all three complexes without cholesterol. The degree of cholesterol exclusion from the boundary lipid region seems to increase in the order A-I<E<A-II for Chol-containing complexes, the exclusion being an inherent property of the particular apolipoprotein molecule.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

Albumin fluorescent test in surgical stress.

Albumin fluorescent test showed that serum albumin concentration was normal in patients with uncomplicated inguinal hernia before surgery, but albumin binding centers were considerably changed. Surgery also modified binding centers, but these changes were less pronounced than before the operation. It was assumed that long-term psychic distress before surgery is responsible for preoperative changes in albumin molecule.

Adolescent↗
PubMed2000

Conformational changes in albumin molecule: a new response to pathological process.

A new fluorescent test developed at the Institute of Physicochemical Medicine (Ministry of Health of the Russian Federation) allows to determine not only blood concentration of albumin, but also to evaluate the state of its molecule. The test is feasible and enables express-analysis of the plasma and serum without fractionation and other preliminary procedures. This test reveals abnormalities in albumin molecule caused by toxic metabolites or conformational changes. Many diseases are accompanied by conformational changes in albumin, while its concentration often remains unchanged. Changes in albumin conformation can serve a diagnostic and prognostic criterion in some pathologies.

Blood↗
PubMed2000

Apolipoprotein A-I localization and dipalmitoylphosphatidylcholine dynamics in reconstituted high density lipoproteins.

The structure and molecular dynamics of recombinant high density lipoproteins (rHDL) were studied by non-radiative energy transfer (NRET), fluorescence anisotropy and intensity measurements. The rHDL particles contained human plasma apolipoprotein (apo) A-I and dipalmitoylphosphatidylcholine (DPPC). Fluorescent cis- and trans-parinaric acids were used both as probes of molecular motion in the particle lipid phase and as acceptors in the Forster's energy transfer from apo A-I tryptophan residues to determine particle dimensions, apolipoprotein localization and lipid dynamics. The probes are sensitive to thermal wobbling (macromobility) and conformational deformations (micromobility) of phospholipid acyl chains. The experimental data fitted to various models of the particle structure are compatible with the following: (a) at T < Tt the particles appeared as lens-like discs with a radius of the lipid phase of 5 nm and a mean thickness of 4 nm, the value being more by 20% in the particle centre, the alpha-helices of about 1 nm thickness were located around the edge of the lipid core. Compared to liposomes, both macro- and micromobility of DPPC molecules in rHDL were more rapid due to a significant disorder of the boundary lipid molecules close to the apo A-I molecule. This disorder led to the increase of the specific surface area per one lipid molecule, S(o). The lipid phase can be divided into three regions: (i) zone I of the most tightly packed lipid (0-1.7 nm from the disc axis) with a S(o) value small as 0.5 nm2; (ii) intermediate zone II (from 1.7 to 4.0 nm); and (iii) boundary lipid zone III (4-5 nm) of significantly disordered lipid with a S(o) value large as 0.65 nm2. (b) at T> Tt the S(o) heterogeneity disappeared, the radius of the lipid phase did not increase significantly, not exceeding 5.2-5.4 nm, but protein-induced immobilization of lipid molecules which affected about half or more of the total lipid, became remarkable. The overall effect was the suppression of the transition amplitude in rHDL compared to liposomes. The structural inhomogeneity might underlie the function of the native plasma HDL as the key component of the transport and metabolism of plasma lipids.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Estimation of surface area in very low density human serum lipoproteins.

The surface area of very low density lipoproteins (VLDL) from the serum of 15 healthy donors and the surface area of artificial lipid particles have been estimated. The artificial particles were prepared as a mixture of egg phosphatidylcholine and triolein. Two fluorescent probes - energy donor and acceptor - were placed on the surface, and Forster's nonradiative energy transfer was measured; the transfer efficiency is a function of surface area. The fluorescent probe K-68 (4-[5-(phenyloxazolyl-2)-1-pentadecyl)pyridinium) was used as a donor, and DSP-12 (dimethylamino)styryl-N-dodecylpyridinium) was used as an acceptor. The specific surface area of the artificial lipid particles was estimated to be 0.585 +/- 0.015 nm2 per phosphatidylcholine molecule, which is 15% less than in lipid bilayers. The specific area of VLDL particles was 259 +/- 65 m2 per g of total VLDL. This value is close to the specific area of low density lipoproteins (LDL), and corresponds to the area of a spherical particle 10-12 nm in radius. However, VLDL are assumed to be much larger particles as compared with LDL. Therefore, the new data of the VLDL surface area raise a problem of revision of the existing VLDL models.

Energy Transfer↗
PubMed1999

[Prognosis of the course of suppurative-inflammatory surgical diseases of the abdominal cavity when using a fluorescent test for albumin].

Fluorescent parameters named total and effective albumin concentrations (TA and EA, respectively) were used for prognosis of development of inflammatory surgical abdominal diseases: peritonitis, acute pancreatitis and some related states. Normal range of EA values is 35-55 g/L. At EA less than 8 g/L the mortality was 92%, and at EA more than 20 g/L the mortality was 5%. Very high mortality risk (up to 100% for patients above 50 years of age) was expected at narrow range of the parameter IT = TA/EA-1 values (from 0.7 to 0.8). Thus EA and IT could be taken as new parameters to estimate mortality and survival chances in acute inflammatory surgical diseases.

Acute Disease↗
PubMed1997

The spatial structure of lipids in human leukocytes: studies by nonradiative energy transfer.

The spatial structure of lipids in living human lymphocytes and granulocytes has been studied using the energy transfer between lipophilic fluorescent probes. One of the probes, an energy donor (DMC), was localized in the lipid interior, whereas another donor (K-68) and an energy acceptor (DSP-12) were near the lipid/water interface. The energy transfer in lymphocytes was the same as in artificial lipid membranes (liposomes). Obviously, in lymphocytes as in liposomes, both donors are localized near the lipid surface (the distance from the donors to the lipid surface is less than Forster's radius R0, i.e., 3.4-5 nm). On the contrary, in granulocytes, the energy transfer from K-68 was 2.2 times more efficient than from the lipid-immersed DMC. It was suggested that a fraction of DMC molecules was immersed into some lipid particles, and the distance from the molecules to the surface of the particles was greater than R0. The positions of the DMC fluorescence spectrum maxima in lymphocytes and in liposomes were the same, but in granulocytes the spectrum was blue-shifted (as in the case of lipoproteins). After subcellular fractionation the DMC fluorescence intensity correlated only with phospholipid concentration in different fractions but not with protein or nucleic acid concentrations. It was suggested that lipid organelles are the main source of the DMC fluorescence. The studies of cell-lipoprotein model mixtures support the suggestion that lipids in lymphocytes are mainly present as lamellar structures (membranes); the presence of lipoprotein-like particles of rather small radius can not be excluded either. On the other hand, in addition to membrane lipids, granulocytes have lipid-containing particles similar to large serum very low density lipoproteins.

Chalcone↗
PubMed1997

Difference between blood cells as measured by flow cytofluorometry with a lipophilic fluorescent probe 4-dimethylaminochalcone.

Human peripheral blood was stained with a vital membrane fluorescent probe 4-dimethylaminochalcone (DMC) and studied by flow cytofluorometry. The cell fluorescence histogram contained three parts. A fraction of highly fluorescing cells was attributed to granulocytes, the medium fluorescence intensity was attributed to mononuclears (lymphocytes and monocytes), and weakly fluorescing cells were thrombocytes and erythrocytes. The origin of the fraction completely correlated with the results of the histological count of blood smears. Quantitative analysis of the difference between DMC fluorescence intensities in granulocytes and mononuclear cells suggests that granulocytes may contain intracellular lipoprotein-like particles while in mononuclear cells the lipid forms mainly membrane structures.

Blood Cells↗
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↗
PubMed1990

[The effect of the plasma of patients with asthma of physical effort on the energy state of the lymphocytes].

The effect of the plasma obtained before and after graded submaximal exercise was examined in 10 bronchial asthma patients with the syndrome of asthma of physical effort (APE) by means of fluorescent exploration using the cation probe 4-(p-demethylaminostyryl)-1-methylpyridinum and rat thymocytes as a test system. Four normal donors and five bronchial asthma patients without the APE syndrome were used as control. The plasma of patients with the APE syndrome, obtained after physical exercise, brought about a decrease of the number of fluorescent cells. In APE patients, the coefficient of the drop of thymocyte fluorescence amounted to 0.65 +/- 0.04, that in the control group to 1.1 +/- 0.08 (p less than 0.01). It is assumed that after physical exercise in the plasma of APE patients, there may occur factor depolarizing the membrane of thymocytes, which is likely to play a substantial role in the pathogenesis of the afterload bronchospasm.

Adult↗
PubMed1989

Determination of fluorescent probes localization in membranes by nonradiative energy transfer.

One of the new methods of studying the structure and dimensions of biological membranes is based on the Förster's nonradiative energy transfer between special molecules, the so-called 'membrane fluorescent probes'. Further development of the approach is presented in this article. It consists of the combined use of the time-resolved and steady-state fluorescence data with subsequent computer simulation of the energy transfer in membranes. Anthracene as an energy donor, and 4-p-(dimethylamino)styryl-N-dodecylpyridinium (DSP-12) or 4-dimethylaminochalcone (DMC) as energy acceptors were bound with artificial phospholipid membrane vesicles ('liposomes'). The synchrotron radiation was used as an impulse source for the excitation light. The steady-state fluorescence data permit the area of possible probe localization in membranes to be distinguished, while the kinetic data allow them to be narrowed significantly. There is a good agreement between the obtained localization and our present-day knowledge of lipid bilayer structure. The accuracy of the method is ca. several Angströms.

Anthracenes↗
PubMed1989

[Ryodipine--a new fluorescent probe in the determination of differences between lymphocytes].

Ryodipine (foridon ), a fluorescent compound possessing hypotensive activity, can be useful as fluorescence probe to distinguish between lymphocyte populations. The heterogeneity of cells revealed by the intensity of ryodipine fluorescence is mainly due to differences in the amount of membranous material in the cells. The use of ryodipine for lymphocyte identification has certain advantages over MBA, a known fluorescence probe generally employed for this purpose. Ryodipine is less prone to photodegradation and its fluorescence intensity shows no dependence on cell concentration over a much wider dye/cell ratio range.

Animals↗