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Biomedical subjects

M A Kisel'

Publications and source records attributed to M A Kisel'.

30 records · Page 2Linked to original sources
PubMedDate not supplied

[Effect of products of radiation-induced free radical fragmentation of phospholipids and temperature on lipid membranes].

Thermotropic behavior of liposomes exposed to gamma-radiation was studied by differential scanning microcalorimetry. It was found that the peak corresponding to the gel-liquid crystal transition for liposomes composed of bovine brain sphingomyelin and dipalmitoyl phosphatidylglycerol broadened and shifted toward the high-temperature region. No effect of irradiation on dipalmitoyl phosphatidylcholine liposomes was observed. Previously it was shown that, on exposure to gamma-rays, sphingomyelin and phosphatidylglycerol, as opposed to phosphatidylcholine, broke down into fragments of lower molecular weight. It is concluded that the accumulation of products of phospholipid fragmentation in the membrane results in the changes of phase transition parameters.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

[Effect of lysophosphatidylcholine on the radiation-induced lipid peroxidation in liposomes].

The effect of lysophosphatidylcholine (LPC) on the lipid peroxidation process (LPO) in liposomes of rat liver phosphatidylcholine initiated by irradiation of 137Cs source was studied. The formation of diene conjugates (DC) is shown to increase dramatically on incorporation of more than 10% LPC into liposomes. The dependence of DC proportion on the irradiation dose is practically linear in the range of 0 to 5 kGy. The DC concentration in the liposomes without LPC grows at least to dose of 3.3 kGy and is unchanged on further irradiation. The malonic dialdehide accumulation follows the similar dependence. The LPC effect is neutralized by the incorporation of cholesterol into liposomes. The product of free radical fragmentation of LPC, palmitoxyacetone, practically has no influence on the DC concentration. The reasons of LPC effect on the irradiation initiated LPO in liposomes is discussed.

Animals↗
PubMedDate not supplied

[Effects of complexes of alpha-fetoprotein and amphiphilic docosaenoic acid derivatives on the humoral immune response in C57BL/6 mice].

The immunotropic activity of three derivatives of docosahexaenic acid (N-docosahexaenoyl-L-serine phosphate, N-docosahexaenoyl-L-threonine phosphate, and N-docosahexaenoyl-L-tyrosine phosphate) in complexes with high-purity human alpha-fetoprotein was evaluated. The polyene compounds stimulate the humoral immunity in mice immunized with T-dependent antigen (ram red blood cells). The immunotropic activity of the alpha-fetoprotein-ligand complexes studied depends on the structure and the content of polyene ligands.

Animals↗
PubMedDate not supplied

[Effect of phosphatidic acid on the radiation-initiated peroxidation of phosphatidylcholine in liposomes].

It was found that the incorporation of anionic dipalmitoyl phosphatidic acid (DPPA) into phosphatidylcholine (PC) liposomes up to 15 mol % was accompanied by the intensification of accumulation of diene conjugates (DC), which are primary products of lipid peroxidation (LPO), if the LPO was initiated by gamma-irradiation of a 137Cs source. Monoethyl ester of DPPA, phosphatidylethanol (DPPEt), exerted a lesser influence at the same concentrations. Ca2+ ions inhibited the DC production not only in liposomes consisting of lipid mixture but in lipid membranes of PC alone as well. It was assumed that the electrostatic repulsion of negatively charged DPPA and DPPEt resulted in the loosening of polarside region of membrane hydrophobic layer and in consequence the access of hydroxyl radicals to hydrocarbon chains of PC. This assumption is in good agreement with the results of osmotic behavior of liposomes in hypertonic urea solution.

Gamma Rays↗
PubMedDate not supplied

[Transformation of phospholipids by cabbage phospholipase D in mixed micelles containing 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate].

We compared the activities of cabbage phospholipase D during hydrolysis and transesterification of phosphatidylcholine in mixed micelles of surface-active compounds with various physicochemical properties. Mixed micelles of phospholipids and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (ratio, 1:2) were among the best substrates. Hydrolysis and transphosphatidylation were studied in micelles containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. Mixed micelles of phosphatidylcholine and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate may serve as a new substrate for measurements of phospholipase D activity and preparative isolation of phospholipids using this enzyme.

Brassica↗
PubMedDate not supplied

[Bromoacyl analogues of phosphatidylcholine with intramolecular fluorescence quenching and their use as substrates for continuous monitoring of phospholipase A2 activity].

Two new derivatives of phosphatidylcholine with intramolecular fluorescence quenching were obtained by substituting residues of pyrene butyric and bromine-containing fatty acids for acyl chains. The two compounds can be used for quantitative evaluation of catalytic activity of pancreatic phospholipase A2 in kinetic mode.

Bromouracil↗
PubMedDate not supplied

[Spin label study of the surface of lipid bilayers].

The surface of liposomes and natural membranes has been studied by the method of "spin label--spin probe". Various nitroxyl radicals have been attached to membranes either dueto covalent binding with NH2-groups of phosphatidylethanolamine or due to hydrophobic interactions. Addition of paramagnetics of different charge signs (potassium ferricyanide and dibenzenechromium iodide) to spin labeled membranes results in a decrease of the EPR line intensity without marked broadening. Since the paramagnetic is attached to the membrane surface near the label it broadens the label's EPR spectrum so that it can not be observed. In this case one can observe only the spectrum of labels which have no paramagnetics in the vicinity, the nitroxyl part of radicals being inaccessible to direct paramagnetic impacts. The constants of binding of paramagnetics to the membrane surface have been determined from these experiments. All results (including the assymetry of label rotation) can be explained most simply by assuming that the polar lipid groups are oriented parallel to the membranes surface.

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

[The use of hemoglobin for determination of phospholipase A2 activity].

A spectrophotometric method is proposed for determining phospholipase A2 activity, which is based on the conversion of hemoglobin into hemichrome under the fatty acid action. The spectral difference between hemoglobin and hemichrome was registered by the difference spectrum with a minimum at 405 nm and a maximum at 423 nm. The absorption value determined as the difference between the spectrum maximum and minimum was proportional to the amount of the fatty acid derived from hydrolysis of phospholipids. The method enables the enzyme activity to be determined directly in the spectrophotometric cell.

Hemoglobins↗
PubMedDate not supplied

[Temperature quenching of cytochrome P-450 fluorescence in proteoliposomes with different physical states of the lipid bilayer].

Studies were carried out of temperature quenching of self-fluorescence of cytochrome P-450 in solution and liposomes from natural phosphatidylcholine, dimiristoylphosphatidylcholine, dipalmitoylphosphatidylcholine. The fluorescence spectrum of cytochrome P-450 is a superposition of triptophane and tyrosine components. During protein incorporation into liposomes a significant short-wave shift of the emission spectrum takes place. Temperature dependence of the intensity of cytochrome P-450 self-fluorescence in solution has bends at 30, 45 and 50 degrees C. When protein is incorporated into liposomes the location of bends depends on individual properties of lipids forming the bilayer. Effect of lipid surrounding on temperature conformational rearrangements of cytochrome P-450 molecule is discussed.

Cytochrome P-450 Enzyme System↗
PubMedDate not supplied

[Effect of phospholipids on the activity of highly-purified liver microsome cytochrome P-450 in a reaction of aniline and naphthalene hydroxylation by hydroperoxides].

The effect of different phospholipids on the functional activity of highly purified cytochrome P-450 used as a co-substrate of cumene hydroperoxide was examined. At the molar ratio of phospholipids to cytochrome P-450 that was equal to 30, phosphatidyl serine, phosphatidyl inositol, the total fraction of microsomal phospholipids, and lysophosphatidyl choline increased the hydroxylation rate of aniline and naphthalene. The effect of the above phospholipids on the rate of naphthalene oxidation was much more pronounced. Phosphatidyl choline and sphingomyelin in similar large quantities did not exert a stimulating effect on the reactions studied. The kinetic parameters of aniline oxidation in the systems containing phospholipids that produced an activating effect were investigated.

Aniline Compounds↗
PubMedDate not supplied

[The phospholipase A2 hydrolysis of irradiated lipid membranes].

Phospholipase A2 hydrolysis of dioleoylphosphatidylcholine, dimyristoylphosphatidylcholine or their equimolar mixture with sphingomyelin in liposomes exposed to gamma-radiation has been investigated. Stabilization of the gamma-irradiated lipid bilayer to hydrolysis by sphingomyelin has been shown.

Free Radicals↗