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Biomedical subjects

O A Azizova

Publications and source records attributed to O A Azizova.

At least 19 recordsLinked to original sources
PubMed1992

Surface potential changes of mitoplasts in the presence of pyridoxal phosphate modified cytochromes c.

1. The addition of native cytochrome c to mitoplasts leads to a decrease of surface potential of the mitoplast membrane. However the surface potential is slightly decreased (approximately 3 mV) when PLP(Lys 86)-cytochrome c and PLP(Lys 79)-cytochrome c were added. 2. The native and PLP-modified cytochromes c do not influence the order parameters S and isotropic constant a when both spin probe I and probe II were used. It is shown that cytochrome c binding to the membrane does not affect the hydrophobic intermembrane area as well as the lipid arrangements of the mitoplast membrane. 3. At low ionic strength there was observed a significant difference in the membrane potential when PLP-cytochromes c were added to the mitoplasts. 4. At high ionic strength the addition of native or PLP-modified cytochromes c does not change the membrane potential.

Cytochrome c Group↗
PubMed1992

Intracellular free iron in liver tissue and liver homogenate: studies with electron paramagnetic resonance on the formation of paramagnetic complexes with desferal and nitric oxide.

Treatment of intact liver and liver homogenate with sodium nitrite, or desferal, brings about the appearance of g = 2.03 and g = 4.3 electron paramagnetic resonance spectroscopy (EPR) signals, respectively. The g = 2.03 signal is conditioned by the formation of dinitrosyl complexes of Fe(II); the g = 4.3 signal is related to the appearance of paramagnetic desferal-Fe(III) complexes. Desferal and sodium nitrite were administered successively into liver homogenate, resulting in only a g = 4.3 EPR signal. And, vice versa, if desferal was administered after sodium nitrite, there appeared only the signal with g = 2.03. These data testify to the fact that one and the same endogenous free iron is included in both paramagnetic centers. The concentration of iron ions was measured in intact tissue according to the formation of dinitrosyl-iron complexes and desferal-iron complexes. It was 33.2 +/- 4.6 and 20.3 +/- 4.0 nmol/g of tissue weight, respectively. The data obtained testify to the fact that free endogenous iron is present in intact tissue. Possibilities of the EPR method for estimation of the content of intracellular free iron are discussed.

Animals↗
PubMed1991

Free radical modification of lipoproteins and cholesterol accumulation in cells upon atherosclerosis.

An electron spin probe study was made of the effect of lipid peroxidation (LPO) on the structure of surface proteolipid layer of human serum low-density lipoproteins (LDL). The results obtained with a positively charged spin label and stearic acid spin probes with doxyl labels at positions 5, 12, and 16 revealed that LPO caused a decrease in phospholipid molecule mobility both in the region of polar heads and in the region of acyl chains till the depth of at least 1.7 mm from water-lipid interface. Under relatively high levels of oxidation (more than 6 mumol MDA/g LDL phospholipid) the polarity of lipid phase increased. The decrease in efficiency of tryptophan fluorescence quenching by nitroxide fragments incorporated in hydrophobic regions at the depth of approximately 2 nm from water-lipid interface indicated that lipid-protein interaction was disturbed as a result of oxidation of LDL lipids. In addition, the LPO-induced modification of apo-B, the main protein of LDL, was examined with maleimide spin label. LPO led to increase in mobility of strongly immobilized maleimide labels and in the number of weakly immobilized ones. Oxidized LDL revealed decreased ability to incorporate spin-labeled steroid (androstane) as compared to native ones. LPO-induced structural changes of LDL surface are supposed to be a reason of enhanced accumulation of cholesterol in human monocytes during their incubation with oxidized LDL. The cholesterol content in red cells was shown to be directly correlated to MDA content in apo-B containing lipoproteins but not in whole serum. Our findings suggest that free radical modification of serum lipoproteins but not solely an increased level of LPO products in blood is one important cause for cholesterol accumulation in cells and, apparently, for their transformation into foam cells during atherosclerosis.

Arteriosclerosis↗
PubMed1991

Antioxidant properties of albumin during the oxidation of linolenic acid and low density lipoproteins in the presence of ferrous ions.

A spin-labelled fatty acid with an epr spectrum that is sensitive to the localization of the probe was used to show that albumin binds free fatty acids present in solution and also free fatty acids present in low density lipoproteins (LDL). Furthermore, albumin binds the thiobarbituric acid-reactive (TBA-reactive) products formed during the oxidation of linolenic acid, whereas the TBA-reactive substances formed during the oxidation of LDL are not bound by albumin. Linolenic acid bound to albumin essentially does not undergo peroxidation in the presence of ferrous ions, in contrast to a suspension of linolenic acid and LDL in which peroxidation occurs quite readily in the presence of ferrous ions. The highest rate of oxidation was found for linolenic acid alone. Albumin-bound spin-labelled fatty acid was essentially not reduced by ferrous ions, whereas free fatty acid or fatty acid incorporated into LDL was reduced quite rapidly, the highest rate of reduction being for free fatty acids. Thus the ability of fatty acids to undergo oxidation correlates with their accessibility to ferrous ions. The data obtained indicate that serum albumin is a relatively effective antioxidant in the blood and its mode of action is based on the immobilization of free fatty acids.

Animals↗
PubMed1991

Free-radical generation by monocytes and neutrophils: a possible cause of plasma lipoprotein modification.

The activation of freshly isolated human blood monocytes and neutrophils monitored by oxidized human plasma lipoproteins (LP) was measured by detecting luminol-amplified chemiluminescence. The activation was accompanied by production of superoxide radicals. This finding was confirmed by measuring superoxide dismutase-sensitive reduction of cytochrome c. Incubation of monocytes or neutrophils with low-density lipoproteins (LDL) resulted in the accumulation of lipid peroxidation (LPO) products which were assayed by the 2-thiobarbituric acid test. Data from inhibitory analysis suggest that the hydroxyl radical scavenger, mannitol, had no appreciable effect on the accumulation of LPO products during the incubation of LDL with either cell type. However, catalase, superoxide dismutase, the metal ion chelators desferrioxamine and EDTA, as well as the free radical scavenger, butylated hydroxytoluene, markedly decreased the accumulation of LPO products in the medium--by 88%, 67%, 38%, 52%, and 47%, respectively, after incubation of LDL with monocytes, and by 65%, 47%, 41%, 65%, and 100% after incubation of LDL with neutrophils. These results indicate that activation of monocytes and neutrophils by oxidized LP intensifies LPO which proceeds via a free-radical mechanism that is superoxide-dependent and is catalyzed by transition metals.

Adult↗
PubMed1991

[Structural and functional aspects of erythrocyte membrane in children, delivered with asphyxia].

Serum and red blood cell membrane lipid peroxidation (LPO), antioxidative activity (AOA) of the ceruloplasmin/transferrin (CP/TF) system, and biophysical parameters of the structure of a red blood cell membrane lipid bilayer were examined in fetuses experienced acute hypoxia at birth and in babies born to healthy mothers with uncomplicated pregnancy. The intensity of LPO product accumulation in mild asphyxia was ascertained to be proportional to the duration of hypoxic exposure of a fetus. In severe asphyxia accompanied by lower formation of primary LPO products, the levels of secondary LPO products showed a rise. A slight increase of AOA in the CP/TF system was unable to adequately compensate a high intensity of LPO processes, which provides strong evidence for altered structural parameters in the lipid bilayer. It was concluded that it was essential to correct hypoxic states in children with antioxidants immediately after birth.

Antioxidants↗
PubMed1990

[Measurement of superoxide radicals produced by human activated neutrophils by accumulation of stable nitroxide radicals detected by MR spectroscopy].

An important index of neutrophil function is the production of superoxide radicals (O2-) upon activation. Thus a development of a new adequate assay of O2- generation measurement is of great interest for phagocyte researchers. The present article considers the quantitative determination of O2- generation based on the interaction of O2- with 1-oxy-2,2,6,6-tetramethyl-4-oxypiperidine producing 4-oxo-2,2,6,6-piperidine-1-oxyl, detected by ESR. The kinetic curve of nitroxyl radical (NR) formation has a linear character. The NR formation rate after a short induction period (appr. 2 min.) approaches 3.3 X 10(-3) M/s, where cell concentration was 4 X 10(5) per ml. Hydroxylamine (3.8 mM) auto-oxidation rate is negligible as compared with activated neutrophils and is equal to 2 X 10(-9) M/s. Sensitivity NR to the presence of superoxide dismutase (SOD) came as evidence that NR formation is due O2- radicals. SOD (10(-7) M) inhibits NR formation by 90%. Hydroxylamine oxidation by O2- is an irreversible reaction--20-min incubation of activated neutrophils with NR do not influence NR concentration. The NR generation rate dependence upon the neutrophil concentration is linear in the cell concentration range from 4 X 10(5 up to 6 X 10(6) per ml. In this range a quantitative measurement of O2- production is suitable. The sensitivity of hydroxylamine assay is close to the sensitivity of chemiluminescent method, but specificity is higher, as SOD inhibits chemiluminescence only by 50%.

Free Radicals↗
PubMed1990

[Caused of intensified lipid peroxidation in the blood of patients with viral hepatitis B].

The tissue oxygen concentration, the serum antioxidant system state and the serum malondialdehyde (MDA) concentration were studied in patients with hepatitis B. The good correlations were studied in patients with hepatitis B. The good correlations between MDA concentration in patients serum and the oxygen concentration in tissues (R-0.79), and the cytoplasmic enzymes activity (R-0.75 for lactate dehydrogenase; R-0.75 for alanine transferase) were found. On the other hand, it was shown an antioxidant activity decrease of ceruloplasmin-transferrin system in patients serum. It is proposed, that the tissue hypoxia and the decrease of the serum antioxidant activity are the general factors leading to the MDA accumulation in the serum of patients with hepatitis B.

Adolescent↗
PubMed1990

[Ceruloplasmin-transferrin antioxidant system in in experimental and clinical atherosclerosis].

The antioxidative system (AOS) ceruloplasmin-transferrin (Cp-Tr) was studied by means of electron paramagnetic resonance in 14 rabbits with experimental atherosclerosis and in 33 patients with ischemic heart disease (IHD). A correlation was found between the AOS Cp-Tr activity and the pathological process severity: mild disease was associated with high AOS activity, while in severe disease course, this activity was threefold lower. This regularity was detectable both in experimental animals and in human IHD patients. It was found that hemosorption (HS) exerted a positive effect only in the presence of low AOS Cp-Tr activity which increased after HS in these cases. In high AOS activity HS caused deterioration of the patients' condition and accumulation of lipid peroxidation products in the blood plasma; this was attended with lowering of the AOS Cp-Tr activity.

Adult↗
PubMed1989

Blockade of ADP-induced Ca2+-signal and platelet aggregation by lipoxygenase inhibitors.

Stimulation of platelets results in the liberation of arachidonic acid (AA) which is further metabolized via the cyclooxygenase or lipoxygenase (LPG) pathway. We have examined the effect of inhibition of LPG on (i) the ADP-induced increase of cytoplasmic Ca2+ concentration and (ii) platelet aggregation. Lipoxygenase inhibitors, nordigidroguaiaretic acid (NDGA) and BW-755C, both suppressed ADP-induced Ca2+-signals and aggregation in a dose-dependent manner, with an IC50 value of 1 2 microM for NDGA. Qualitatively the same effect was obtained with 4-bromophenylacyl bromide, the inhibitor of phospholipases A2 and C. By contrast, cyclooxygenase inhibitor indomethacin had only a negligible effect on Ca2+-signals and suppressed only the second phase of ADP-induced aggregation. It is concluded that the LPG pathway of AA metabolism in platelets might play a crucial role in ADP-induced Ca2+-signal generation and platelet aggregation.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1989

Neutrophil superoxide production measurement by means of stable nitroxide radical accumulation detected by ESR.

A new assay for superoxide radicals is based on the interaction of hydroxylamine (1-oxy-2,2,6,6-tetramethyl-4-oxopiperidine) with superoxide, giving rise to a stable nitroxide radical. Working concentration ranges of hydroxylamine and cells are determined. It was shown that the amount of superoxide generated was proportional to the concentration of nitroxide radicals. The sensitivity and specificity of the proposed assay were compared to chemiluminescence and cytochrome-c reduction.

Electron Spin Resonance Spectroscopy↗
PubMed1989

Free radical lipid oxidation affects cholesterol transfer between lipoproteins and erythrocytes.

Human erythrocytes were incubated for 5 h at 37 degrees C with lipoproteins (LP), preliminary oxidized to different extent, as assessed by thiobarbituric acid (TBA) test. Cholesterol content in the cells was increased by 12-14% after incubation with low-density lipoproteins (LDL) along with augmentation of order parameter and rotational correlation time of spin-labeled stearic acids incorporated into membranes. If erythrocytes were incubated with oxidized LDL, containing 2.5-4 times more TBA-reactive material than native ones, cellular content of cholesterol was increased by 24-28%. In contrast, high-density lipoproteins (HDL2 and HDL3) removed cholesterol from cell membranes, when incubated with erythrocytes. This was followed by increased fluidity of membrane lipid phase as detected by the spin probe method. Oxidation of HDL2 and HDL3 decreased their ability to accept cholesterol from cell membranes. No detectable accumulation of TBA-reactive material was observed in the samples during the incubation. The antioxidant, butylated hydroxytoluene (BHT), in the concentration of 10(-5) M did not influence the cholesterol transfer between LP and erythrocytes. Hence, the effects of lipid peroxidation (LPO) on the cholesterol transfer seem to result from LP alterations by oxidation rather than from free radical reactions occurring during the incubation. By increasing cholesterol-donating ability of LDL and inhibition of cholesterol-accepting capacity of HDL lipid peroxidation in LP may activate cholesterol accumulation in blood vessel cells and thus contribute to atherosclerosis.

Butylated Hydroxytoluene↗
PubMed1989

[Indices of lipid peroxidation and the ceruloplasmin-transferrin antioxidant system in donors].

The blood serum ceruloplasmin, transferrin, malonic dialdehyde, iron and copper levels have been measured in donors. These parameters varied in groups of subjects aged 20-29 and 30-45, no age-associated differences being recorded within both the groups. Certain differences have been revealed between the donors who furnished their blood more or less than 3 times a year. The results of this investigation may be useful in clinical screenings of donors.

Adult↗
PubMed1989

[Na+/H+ metabolic activity in the thrombocytes of spontaneously hypertensive rats].

The sodium-proton exchange was determined in platelets of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). The platelets were suspended in sodium propionate; the cytoplasmic acidification activated the exchanger and intracellular pH (the increasing) and volume of the platelets (the swelling) were registered. The activity of Na+/H+ exchange was inhibited by isopropyl amiloride. The platelets' volume and the exchange rate constant of SHR were increased on 30-40% as compared with those of WKY.

Animals↗
PubMed1989

[The red light of the helium-neon laser reactivates superoxide dismutase].

The effect of low-energy helium-neon laser (HNL) on enzymatic activity, absorbtion spectra and electron paramagnetic resonance (EPR) signals of superoxide dismutase (SOD) from bovine erythrocytes in acid medium were investigated. It was found that incubation during 2 hours at pH 5.9 led to eventually complete inactivation of the enzyme. The subsequent illumination of inactivated SOD by HNL brought about the enzyme reactivation. Both absorption and EPR-spectra were changed after incubation at pH 5.9. These changes may be attributed to protonation of histidine residue in the enzyme active site. After laser irradiation both absorption and EPR spectra were restored to those typical of native enzyme at pH 8.2. In a model system, copper-histidine complex, absorption maximum was shifted from 632-633 nm at pH 5.8 to 639-640 nm at pH 8.5-9.0. The similar long-wave length shift of the maximum was observed after illumination by HNL at pH 5.8. It may be postulated that the photoreactivation of SOD consists essentially in deprotonation of His-61 residue in the enzyme active site and subsequent recovery of imidazole bridge between copper and zinc which had been destroyed at low pH. Since many other enzymes possess similar copper-histidine structures in their active sites, one may expect diverse effects of red (laser) light on the enzyme activity.

Animals↗
PubMed1989

[Physicochemical and functional properties of the peripheral blood lymphocytes in ischemic heart disease].

Electron spin resonance techniques was used for the investigation of the structural organization of lymphocyte plasma membranes of healthy donors and IHD patients. We found the increased fluidity of peripheral blood lymphocyte membranes of patients with IHD using 5 doxyl stearic acid spin label. The ordering of the membrane lipids increased proportionally to the increase of cholesterol cell content. This is the important reason for the inhibition of mitogenic cell activity during IHD. Measured by the chlortetracycline-fluorescence alterations in the processes of mitogen-induced Ca+2 redistribution might be one of the mechanisms which mediates the influence of membrane structure changes on the lymphocyte functions.

Calcium↗
PubMed1989

[The measurement of the amount of iron (III) complexes with desferal in the perfused rat liver by an EPR method].

Rat liver was perfused by Hank's solution, containing desferal (deferoxamine). It was shown that in perfusion of the liver spectrum EPR a signal (g = 4.3; H = 63 G) appears. This signal belongs to desferal complexes, containing intracellular Fe/3/. Desferal transfer to the liver tissue and further formation of desferal complexes there takes place within first 5-10 min of liver perfusion by solution, containing 0.5 mM of desferal.

Animals↗