11 research outputs found

    Thymocyte Proliferation and Apoptosis Induced by Ionizing Radiation

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    Proliferation and apoptosis of rat and mouse thymocytes caused by ionizing radiation were studied. The percentage of proliferating cells was determined by the method of colchicine metaphases and the apoptosis was estimated as DNA fragmentation. In vitro irradiation with 0.05-0.2 Gy was found to stimulate thymocyte proliferation, the maximum was observed at 0.05 Gy for mouse thymocytes and at 0.1 Gy for rat thymocytes. These doses caused a slight decrease in DNA fragmentation, as compared to control. By raising the radiation dose, proliferation was reduced and DNA fragmentation was increased. The results obtained indicate that low radiation doses stimulate cell proliferation while higher doses trigger apoptosis of thymocytes

    On the role of intracellular concentration of Ca2+ and H+ in thymocyte death after irradiation

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    AbstractThe role of intracellular Ca2+ and H+ concentrations in radiation-induced interphase death of rat thymocytes has been studied. In response to concanavalin A treatment in the Ca2+-containing medium, or to the CaCl2 treatment in the Ca2+-free medium, the [Ca2+]i rise in irradiated cells was as in the non-treated cells. No changes in the level of [Ca2+]i and pHi were found within l h after irradiation of thymocytes with a dose of 6 Gy. 15 ÎŒM 5-(N-ethyl-N-isopropyl)-amiloride. an inhibitor of Na+/H+ exchange, did not affect the DNA fragmentation. The fragmentation was prevented by 2–4 ÎŒM (1 -[bis(4-chlorophenyl)methyl]-3-[2-(2,4-dichlorophenyl)]-2-[(2,4-dichlorophenyl)-methoxy]-ethyl)-1 -H-imidazoliumchloride, an inhibitor of calmodulin. The above data indicate that triggering of interphase death in irradiated thymocytes is not mediated by changes in either [Ca2+]i or pHi. Such changes seem to be involved in intermediate steps of the interphase death process

    Low doses of ethanol decrease the activity of the angiotensin-converting enzyme in the aorta of aging rats and rats treated with a nitric oxide synthase inhibitor and dexamethasone

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    A B S T R A C T In the present study, the activity of ACE (angiotensin-converting enzyme) in the aorta of senescent rats and rats treated with the NOS (NO synthase) inhibitor L-NAME (N G -nitro-L-arginine methyl ester) or dexamethasone and the effect of low doses of ethanol (0.2-1.2 g/kg of body weight, daily for 8-12 days) on this activity were studied. We found that ACE activity increased with age and in response to L-NAME and dexamethasone treatment. Ethanol at a dose of 0.4 g/kg of body weight per day decreased ACE activity in the aorta of aged rats and of rats treated with L-NAME or dexamethasone to the level of activity in young control rats. The optimal ethanol dose (the dose inducing a maximum decrease in ACE activity) increased with increasing doses of dexamethasone: 0.4 g/kg of body weight per day at 30 ÎŒg of dexamethasone/kg of body weight and 0.8 g/kg of body weight per day at 100 ÎŒg of dexamethasone/kg of body weight. It was also found that optimal doses of ethanol increased the number of cells in the thymus of rats treated with dexamethasone. The optimal dose of ethanol of 0.4 g/kg of body weight per day, which induced a maximum decrease in ACE activity in rat aorta, corresponded to a dose of 30 g of ethanol/day, which, according to epidemiological data, produces a maximum decrease in the incidence of cardiovascular disease in humans. In conclusion, the decrease in ACE activity in vessels may be one of the main mechanisms of the beneficial effects of low doses of ethanol on human health

    (+)-Catechin Stereoisomer and Gallate Induce Oxidative Stress in Rat Aorta

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    The goal of the work was to study changes in the activity of the angiotensin-converting enzyme (ACE) and production of reactive oxygen species (ROS) in the aorta of rats after the intraperitoneal injection of stereoisomers of catechin and gallate. The activity of ACE in the aorta sections was determined by measuring the hydrolysis of hippuryl-l-histidyl-l-leucine. The production of ROS in the aorta sections was estimated from the oxidation of dichlorodihydrofluorescein. The time and dose dependences of the effect of catechin stereoisomers and gallate on ACE activity and ROS production in the aorta were studied. It was shown that (+)-catechin and gallate increased the ACE activity and ROS production, and (−)-catechin and (−)-epicatechin did not influence these parameters. The doses of (+)-catechin and gallate that increased the ACE activity to a half-maximal value (AD50) were 0.04 and 0.03 µg/kg, respectively. Fucoidin, a blocker of leukocyte adhesion to the endothelium, reduced the ACE activity to the control level in the aortas of (+)-catechin-treated rats

    Non-Conjugated Copoly(Arylene Ether Ketone) for the Current-Collecting System of a Solar Cell with Indium Tin Oxide Electrode

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    The mechanism of charge carrier transport in the indium tin oxide (ITO)/polymer/Cu structure is studied, where thin films of copoly(arylene ether ketone) with cardo fluorene moieties are used. This copoly(arylene ether ketone) is non-conjugated polymer which has the properties of electronic switching from the insulating to the highly conductive state. The dependence on the polymer film thickness of such parameters as the potential barrier at the ITO/polymer interface, the concentration of charge carriers, and their mobility in the polymer is studied for the first time. The study of this system is of interest due to the proven potential of using the synthesized polymer in the contact system of a silicon solar cell with an ITO top layer. The parameters of charge carriers and ITO/polymer barrier are evaluated based on the analysis of current–voltage characteristics of ITO/polymer/Cu structure within the injection current models and the Schottky model. The thickness of the polymer layer varies from 50 nm to 2.1 ”m. The concentration of intrinsic charge carriers increases when decreasing the polymer film thickness. The charge carrier mobility depends irregularly on the thickness, showing a maximum of 9.3 × 10−4 cm2/V s at 210 nm and a minimum of 4.7 × 10−11 cm2/V s at 50 nm. The conductivity of polymer films first increases with a decrease in thickness from 2.1 ”m to 210 nm, but then begins to decrease upon transition to the globular structure of the films at smaller thicknesses. The dependence of the barrier height on polymer thickness has a minimum of 0.28 eV for films 100–210 nm thick. The influence of the supramolecular structure and surface charge field of thin polymer films on the transport of charge carriers is discussed
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