Biomedical subjects
Publications and source records attributed to E M Popova.
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The kinetics of oxidation of 15 alpha-methyl-8-aza-16-oxagona-1,3,5(10),13-tetraen-17-on with rat liver microsomal cytochrome P-450 was investigated. The kinetic parameters, Km and Vmax, of the oxidation reaction were found to be equal to 1,3 X 10(-4) M and 4.0 X 10(-7) M X s-1, respectively. Using thin-layer chromatography, mass-spectrometry, PMR-spectroscopy and reciprocal synthesis, it was shown that 3-hydroxy-15 alpha-methyl-8-aza-16-oxagona-1,3,5(10), 13-tetraen-17-on is the main reaction product.
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The interaction of the 8-aza-16-oxasteroid series (8-AS) with cytochrome P-450 from liver microsomes of intact and phenobarbital-induced rats has been studied. It has been shown that 8-AS are the substrates for the cytochrome P-450-dependent enzyme system, and that their affinity for cytochrome P-450 is determined by the structure of the compounds tested. Using inhibitory analysis, the site in the active center of hemoprotein responsible for 8-AS binding was examined. The possibility of direct participation of the 8-AS ketogroup in their binding with cytochrome P-450 is discussed.
The comparative study of 16 Leptospira cultures, serogroup Canicola, isolated from humans and animals in different years in the North-West of the RSFSR and 2 reference strains of the Canicola serovar, Hond Utrecht IV and Kashirsky, was carried out in the agglutinin cross-adsorption tests. The absence of the antigenic homogeneity of the cultures under test was established: 9 of them proved to be identical to strain Kashirsky and 7, to strain Hond Utrecht IV.
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The results obtained in the study of the intensity and character of immunity in persons immunized with commercial leptospirosis vaccine are presented. These results indicate that antibody formation occurs only in 12.5% of the vaccinees; antibodies are not formed to all Leptospira strains contained in the vaccine, and in 6 months all antibodies completely disappear. In persons immunized with a single vaccine dose the agglutinating activity of blood sera was linked only with IgM. In persons subjected to multiple immunizations for a number of years IgG could also be detected. Cases of leptospirosis among vaccinees have been registered.
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The kinetics of 1-naphthol oxidation by rat liver microsomes in a phosphate buffer (pH 7.6) with participation of NADPH and O2 were studied at 9.5-27 degrees C. The activation energy of 1-naphthol oxidation (12.6 +/- 1.0 kcal/mol) was determined from the temperature dependence of initial oxidation rates. The kinetics of 1-naphthol oxidation by oxyhemoglobin in a phosphate buffer (pH 8.0) were studied at 13-25.5 degrees C. The activation energy equal to 17.7 +/- 1.0 kcal/mol for 1-naphthol oxidation by oxyhemoglobin was determined. The differences in oxidation mechanisms in the reactions with participation of cytochrome P-450 and oxyhemoglobin are discussed. Oxyhemoglobin Fe3+O2- interacts via one-electron way, whereas the microsomal cytochrome P-450 complex Fe3+O22- interacts with 1-naphthol via a two-electron way.
The main pathways of aliphatic alcohols oxidation in human and mammalian liver, i.e. dehydration of alcohols by cytosolic alcohol dehydrogenases and oxidation in the presence of microsomal enzymatic system, catalase and hydrogen peroxide are described. A special emphasis is laid upon the interaction of alcohols with terminal oxidase of the microsomal hydroxylating system, i.e. cytochrome P-450. The relative role of these three oxidative pathways in alcohol conversions is evaluated.
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The interaction of alyphatic alcohols and cyclohexanol with cytochrome P-450 in microsomes has been investigated. All alchohols induced the modified 11 type spectral changes by mixing with microsomes. These changes are characterized by lambdamax = 412 and lambdamin = 380-382 nm in difference spectra. The dissociation constants of the alcohol cytochrome P-450 complexes are determined. On this dissociation constants influence pH and Triton X-100 presence. The interaction of the alcohols with cytochrome P-450 in phosphate buffer pH = 6,0 in the detergents absence is characterized by one dissociation constant for MeOH, EtOH, n-BuOH and cyclohexanol and by two dissociation constants for i-PrOH, i-BuOH and tert.-BuOH. The interaction of the alcohols with cytochrome P-450 in Tris-HCL-buffer (pH 7.5) in the Triton X-100 presence is characterized for all above alcohols by the dissociations constants, which are described by Taft equation with coefficient rho =-1.55. This fact confirms the interaction of alcohols HO-groups with heme iron of cytochrome P-450. The scheme of interaction of alcohols with cytochrome P-450 is discussed.
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The membrane fraction isolated from cattle brain and vagal nerve was treated by ultrasonic irradiation in the presence of 22Na. It was shown that 22Na was trapped in vesicles formed from sonicated membranes in an osmotically active forms and slowly released into a nonradioactive solution. The efflux of 22Na from vesicles was studied in the presence and in the absence of substances which change the sodium conductance of excitable membranes. The local anesthetics (procaine, dibucaine) and tetrodotoxin at concentrations blocking electrical excitation in vivo decreased the sodium efflux from the vesicles. Veratrine, an activator of sodium channels, increased this efflux. The results are interpretated as an indication of the presence of functionally active sodium channels in the isolated membrane fragments.