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Biomedical subjects

Iu A Vladimirov

Publications and source records attributed to Iu A Vladimirov.

At least 19 recordsLinked to original sources
PubMed2000

[Nitric oxide, hemoglobin and laser irradiation].

The paper deals with the present views of some chemical properties and biological effects of nitric oxide (NO) and chiefly its formation and primary conversions. The interaction of NO with superoxide radical is shown to one of the most important reactions of the former, which gives rise to peroxynitrite whose breakdown yields a hydroxy radical. Emphasis is laid on the substances that are a temporary depot or a possible transport form of NO, such as nitrosothiols and nitrosyl complexes of non-hemic iron. NO is well-known to release when these compounds are degraded. It is suggested that hemoglobin is another NO depot, which forms stable complexes with the latter. These hemoglobin complexes may be degraded on exposure to laser radiation to form free NO that ha a vasodilatory effect. Photolysis of nitrosyl complexes of hemoglobin may be responsible for the therapeutical effect of laser radiation.

Animals↗
PubMed1999

[Serum antioxidative activity].

Model systems used in the determination of serum antioxidative activity (AOA), which differ both in the way of generating free radicals and in the mode of their detection, are clinically analyzed. The specific features and potentialities of the model systems developed at the authors' laboratory are characterized. These included yolk lipoprotein suspensions, liposomal suspensions formed from total phospholipid fraction, the hemoglobin-hydrogen peroxide-luminol system. The investigations show that most model systems for determining serum AOA contribute to the water soluble interceptors of free radicals (ascorbate, urate, plasma proteins, etc.), chelating and oxidative agents of catalytically active Fe2+ (ceruloplasmin, transferrin, albumin, etc.). The serum AOA levels measured with different model systems vary with the body's status. To determine serum AOA and the contribution of major endogenous antioxidants and inhibitors of free radical reactions may be a basis for the goal-oriented use of exogenous antioxidants in the therapy of a great variety of diseases.

Animals↗
PubMed1999

[Physicochemical aspects of cataract genesis].

Based on their own studies and the data available in the literature, the authors consider the physicochemical aspects of cataract genesis. Emphasis is laid on the role of oxidative stress in this diseases. It is suggested that one of the key mechanisms of cataract genesis is the exhausted lenticular potential and oxidative stress, resulting in the formation of products that enhance lenticular photo lesion and imbalance of cyclonucleotide- and Ca(2+)-dependent cascade systems of regulation, which leas to impaired cAMP-dependent protein phosphorylation. Decreased phosphorylation of lenticular fiber proteins reduces their solubility and results in their sorption on the cell membranes, resulting in progressive impairment of the regulatory membrane placement. Light scattering on the folded membrane surfaces in the lenticular fibers is considered to be a main cause of lenticular opacity in cataract.

Animals↗
PubMed1998

[Free radicals and antioxidants].

The data obtained from the author's laboratory were used to make this review. The author's classification of free radicals, approaches, the origin and metabolism of primary radicals, the contribution of iron ions to the production of secondary radicals and the mechanisms of antioxidative protection of cells and tissues from damage are considered. According to the classification proposed, the radicals may be divided into primary (superoxide, semiquinones and nitric oxide), secondary (hydroxyl and lipid radicals) and tertiary (radicals of antioxidants). The primary radicals are formed by enzymatic systems and perform biologically important functions. The secondary radicals are formed from hydroperoxides in the reactions of divalent iron ions and damage to cell structures. In the cells and blood plasma, there is a complicated system of antioxidants that prevent the production of secondary radicals. All antioxidants may be arbitrarily divided into water-soluble and hydrophobic. The first group involves the enzymes catalase and glutathione peroxidase, iron ion chelators (such as ceruloplasmin and transferrin in the blood and carnosine in other tissues), and, probably, hydroxyl radical traps, such as uric acid and ascorbate. The hydrophobic antioxidants include primarily the free radical traps alpha-tocopherol, flavonoids, and carotenes. Studies of lipid peroxidation kinetics in the membranous structures, carried out by chemiluminescence and mathematical modeling of the reactions have shown that the radicals of antioxidants (such as alpha-tocopherol) enter the further reactions in the lipid phase, including those with lipid hydroperoxides.

Antioxidants↗
PubMed1995

[Generation of active forms of oxygen by antibiotics of the tetracycline series during tetracycline catalysis of oxidation of ferrous iron].

During oxidation of Fe(2+) catalyzed by tetracyclines there was recorded lucigenin, activated chemiluminescence evident of generation of the oxygen radicals. It was also observed that during the Fe(2+) oxidation by the molecular oxygen catalyzed by tetracyclines there generated hydrogen peroxide which accelerated the Fe(2+) oxidation recorded photometrically by the formation of strongly absorbing tetracycline complexes with Fe(2+). In the presence of ascorbate reducing Fe(2+) in the complexes with tetracyclines and their subsequent oxidation there generated radicals modifying the antibiotic molecules evident from a change in their absorption spectra after the respective incubation. The results offered a pattern describing the mechanism of the tetracycline toxic effect on biological objects.

Acridines↗
PubMed1995

[Interaction of hypochlorite with hydroperoxides and other oxidation products of phosphatidylcholine liposomes].

The chemiluminescence in the presence of luminol has been used to measure the amount of hypochlorite and its reduction during the interaction with oxidized and non-oxidized liposomes from egg yolk phosphatidylcholine as well as with organic peroxides (tert-butylhydroperoxide, cumene hydroperoxide, di-tert-butylperoxide, tert-butylperbenzoate, di-benzoylperoxide), and epoxides (cis- and trans-2,3-epoxy-butane, cholesterol-5 alpha,6 alpha-epoxide, and cis-9,10-epoxystearic acid). Since hypochlorite did not react with the saturated phospholipid, dimyristoylphosphatidylcholine (DMPC), and the reduction of double bonds in egg yolk phosphatidylcholine liposomes occurred at the same rate in both oxidized and non-oxidized liposomes, it may be suggested that hypochlorite interacted precisely with LPO products. None of the epoxides tested in this study, similar to di-tert-butylperoxide, tert-butylperbenzoate, di-benzoylperoxide, incorporated into liposomes reacted with hypochlorite. In contrast, tert-butylhydroperoxide and cumene hydroperoxide effectively reacted with it. The data obtained suggest that epoxides, dialkyl-, diacyl-, and alkyl-acyl-peroxides are not involved in hypochlorite-induced LPO. At the same time, organic hydroperoxides commonly present in certain amounts in the biomembrane lipid phase in vivo may play a role lf an intermediate; its interaction with HOCl/OCl- gives rise to free radical formation followed by accumulation of LPO products.

Free Radicals↗
PubMed1995

[The property of tetracyclines to induce methemoglobin formation in erythrocytes and to inactivate catalase when exposed to radiation in the visible range].

When tetracycline and chlortetracycline were incubated an a dark room in the presence of erythrocytes with erythrocytic catalase completely inactivated by sodium azide, the antibiotics induced methemoglobin formation in them. If the catalase was not inactivated, no such phenomenon was observed. This meant that after the penetration into the erythrocytes the tetracyclines induced in them the generation of hydrogen peroxide which was the immediate cause of the methemoglobin formation. The effect of the methemoglobin formation on the erythrocytes was also induced by tetracycline without the catalase blocking when the erythrocytes were exposed to the antibiotic and visible light. The effect was not mediated by the hydrogen peroxide action on hemoglobin in the erythrocytes as it was in the previous case, since even when catalase was added exogenously to the suspension medium it induced no suppression of the methemoglobin formation in the erythrocytes. Additional introduction of exogenous catalase to the erythrocyte hemolysates prior to the exposure did not either influence the methemoglobin formation photoinduced in them by tetracycline. The effect manifestation was not practically influenced by L-histidine, mannitol or ethanol used as traps for the radicals which could form during the antibiotic exposure to visible light in the suspension medium. The calorimetric estimation of the catalase functional properties showed that when exposed to visible light in the presence of the enzyme (a commercial product) tetracycline induced its inactivation. It was indicated that the catalase photoinactivation by tetracycline was due not to a steady decrease of the activity of every molecule of the enzyme but to a dislodge of separate molecules among the active ones, i.e. a one-fold change of the enzyme molecule from the initial active state to the completely inactive one. The catalase photoinactivation by tetracycline was not eliminated by L-histidine or comparatively high concentrations of mannitol but was entirely eliminated by ethanol used in relatively low concentrations. When the erythrocytes were exposed to visible light in the presence of tetracycline, the effect of the catalase photoinactivation by the antibiotic was also observed. In this case the same as in the experiments with isolated catalase, ethanol as well protected the enzyme from the photoinactivation by tetracycline. The tetracycline photoeffects on hemoglobin, catalase and possibly other heme-containing proteins were likely realized in the immediate closeness of their hemes. The photoeffects of the tetracyclines associated with the heme-containing proteins possibly play a certain role in the phototoxicity of the antibiotics.

Animals↗
PubMed1995

[Metabolites of tetracycline obtained during its irradiation with visible light or peroxidase oxidation. Their toxic properties in relation to hemoglobin].

It was indicated in the literature that when exposed to visible light tetracycline induced phototoxic effects with respect to heme-containing proteins. The present study showed that when tetracycline was exposed to visible light it formed metabolites due to the photochemical transformations, the metabolites formation being slightly affected by the anti-radical drugs such as L-histidine, mannitol, ethanol and catalase. The investigation of the conditions of the metabolites formation as a result of the photochemical transformations revealed a specific role of ascorbate in the process. The comparative analysis of the physico-chemical properties of the metabolites resulting from the tetracycline exposure to visible light or peroxidase oxidation provided a conclusion that the nature of the metabolites was the same. It was shown that the metabolites were equal in their phototoxic capacity for the damage of hemoglobin by inducing its oxidative degradation.

Animals↗
PubMed1995

[Chelating and oxidizing properties of tetracycline metabolites forming during its peroxidase or photoinduced oxidation].

Tetracycline metabolites forming on the antibiotic exposure to visible light or peroxidase as well as tetracycline as such showed the ability to bind iron cations. When the metabolites bound the cations of iron protoxide, they catalyzed its oxidation. Chelating agents such as o-phenanthroline and EDTA arrested the ions of iron protoxide and iron oxide in the respective iron/tetracycline complexes at a much lower rate than that with the use of the native tetracycline. This means that the affinity of the metabolites with the above mentioned iron ions was much higher than that of the native tetracycline. When the metabolites and tetracycline bound iron protoxide, they catalyzed its oxidation to the oxide. Tetracycline and its metabolites were shown as well to have the property of reversible regeneration of iron oxide to the protoxide.

Anti-Bacterial Agents↗
PubMed1994

[Metabolic transformation of antibiotics of the tetracycline series in peroxidase reactions].

In was shown calorimetrically that in the presence of horse radish peroxidase tetracyclines induced degradation of hydrogen peroxide. Under such conditions changes in the tetracycline optical properties were detected photometrically. It was concluded that tetracyclines were metabolized in the peroxidase reactions catalyzed by horse radish peroxidase as their substrates. The tetracycline peroxidase oxidation was catalyzed not only by horse radish peroxidase but also by methemoglobin possessing the peroxidase activity. In the experiments with ascorbate there were detected characteristic peculiarities of the tetracycline peroxidase oxidation catalyzed by both horse radish peroxidase and methemoglobin. These peculiarities made it possible to classify the tetracyclines as the substrates of the peroxidase reaction belonging to the oxidogenic group. The fact that tetracyclines can be metabolized in peroxidase reactions is discussed in regard to its possible influence on their mechanism of antibacterial action and the development of tetracycline resistance.

Biotransformation↗
PubMed1992

[Antiradical activity of complex copper compounds (II) on coumarin ligand base].

The antioxidant capacity of copper chelates with coumarins has been studied by the method of iron-induced chemiluminescence. All substrates studied were potent antioxidants, comparable to butylated hydroxytoluene. The mechanism of the antioxidant action of these copper-coumarin chelates was similar to that of Cu-Mn-superoxide dismutase, with a coumarin part of the complex being involved as a free radicals trap.

Antioxidants↗
PubMed1991

[Mechanism of oxyhemoglobin oxidation induced by hydrogen peroxide].

The process of oxyhemoglobin oxidation initiated by hydrogen peroxide in low (10(-7) M) concentrations was investigated. It was found, that H2O2 in this concentration is able to induce the process of chain oxidation of oxyhemoglobin to methemoglobin. The following observations indicate that the process is essentially the chain reaction: 1) The amount of the methemoglobin in haem groups, produced in the reaction, exceed by 20 times the quantity of hydrogen, added initially, to induce the oxidation. 2) Catalase stopped this process at any stage of the reaction. This fact implies that the chain process involves generation of new molecules of H2O2 in the course of oxidation of oxyhemoglobin. The chain reaction proceeded only in the presence of oxygen. But if oxygen was introduced into hemoglobin solution, preincubated with H2O2 in vacuum, than again the oxidation of hemoglobin developed. Apparently, H2O2 in low concentrations appears, mainly, as an inductor of the oxyhemoglobin autooxidation.

Animals↗
PubMed1991

[Antiradical activity of 3-substituted coumarins and their effect on iron-dependent chemiluminescence].

The antioxidant capacity of 3-aminocoumarin, 3-oxycoumarin, 3-acetylaminocoumarin, and 3-coumarin carbonic acid has been investigated with chemiluminescence measurement and by the accumulation of TBA-active products. All coumarins were found to be antioxidants, with 3-oxy-, 3-amino- and 3-acetylamino coumarins being capable of amplifying chemiluminescence at early stages of the process.

Antioxidants↗