The hypothesis that decreases in brain blood flow during respiration of hyperbaric oxygen result from inactivation of nitric oxide (NO) by superoxide anions (O2(-)) is proposed. Changes in brain blood flow were assessed in conscious rats during respiration of atmospheric air or oxygen at a pressure of 4 atm after dismutation of O2(-) with superoxide dismutase or suppression of NO synthesis with the NO synthase inhibitor L-NAME. I.v. administration of superoxide dismutase increased brain blood flow in rats breathing air but was ineffective after previous inhibition of NO synthase. Hyperbaric oxygenation at 4 atm induced decreases in brain blood flow, though prior superoxide dismutase prevented hyperoxic vasoconstriction and increased brain blood flow in rats breathing hyperbaric oxygen. The vasodilatory effect of superoxide dismutase in hyperbaric oxygenation was not seen in animals given prior doses of the NO synthase inhibitor. These results provide evidence that one mechanism for hyperoxic vasoconstriction in the brain consists of inactivation of NO by superoxide anions, decreasing its basal vasorelaxing action.
When choosing metal packaging for canned vegetables, it is advisable to take into account their corrosivity, because the inner surface corrosion is one of the factors affecting product quality during storage. To rationalize the corrosion tests of metal packaging materials, it is advisable to replace food with model media – organic acids solutions. The aim of this work was to study the corrosion kinetics of electrolytic tinplate in model media–aqueous solutions of oxalic (mass fraction 0.25–1.00%) and citric (mass fraction 0.25–1.50%) acids, as well as their compositions. The uniform corrosion rate was measured by the linear polarization resistance method, pitting corrosion–zero resistance amperometry method. The tests were carried out using the “Expert-004” corrosion-meter, according to a two-electrode scheme. For oxalic acid solutions with a mass fraction of 0.25% and 0.50% and for all citric acid solutions, the process is characterized as uniform corrosion – the pitting corrosion rates average steady values are 7–11 times less than the corresponding uniform corrosion rates values (1.52–3.93 µm/year and 17.42–26.56 µm/year, respectively). The most aggressive with respect to tinplate are oxalic acid solutions with a mass fraction of 0.25 and 0.50% and citric acid solutions with a mass fraction of 0.25 and 0.50%. On this basis, two-component solutions of the following composition were chosen: 0.25% citric acid + 0.25% oxalic acid; 0.25% citric acid + 0.50% oxalic acid; 0.50% citric acid + 0.25% oxalic acid; 0.50% citric acid + 0.50% oxalic acid. For these solutions, the process is characterized as uniform corrosion — the pitting corrosion rates average steady values are 7–10 times less than the corresponding the uniform corrosion rates values (2.04–3.85 ?m/year and 19.56–26.93 ?m/year, respectively). For two-component solutions, an additive effect is observed–the uniform and pitting corrosion rates average experimental steady values correspond to the calculated additive values. By mathematical processing of experimental data, it was found that the uniform corrosion steady rate maximum value the corresponds to a two-component solution containing 0.40% citric acid and 0.30% oxalic acid. This is confirmed by experimental data–the uniform corrosion rate average steady value for this solution is 28.18 ?m/year. According to the research results it was found that as a model corrosive medium that simulates canned vegetables, it is advisable to use a solution containing 0.40% citric acid and 0.30% oxalic acid, because it is the most aggressive.
Because of the metal packaging corrosion, during storage of canned food the quality deteriorates.One of the ways to reduction of quality loss and increase the shelf life of canned products is the use of food additives - corrosion inhibitors. From the literary data it is known that pectin and gelatin are corrosion inhibitors whose action is based on adsorption to the metal surface.Besides the usual gelatin, in the work we used hydrolyzed gelatin, which does not increase in the viscosity of the liquid phase.The aim of the present work was to study the effect of pectin, gelatin and hydrolysed gelatin on the tinplate corrosion rate in the liquid phase of stone fruit compotes (cherries, merries, peaches and plums). The corrosion rate was measured by the method of linear polarization resistance, based on the creating a potential difference between two identical samples of metal and measuring the amperage.The measurements were carried out using the universal automatic corrosion-meter "Expert-004".For all corrosive media, the corrosion rate kinetics is as follows: at the beginning of the test, the maximum corrosion rate of tinplate is observed, which decreases to a stationary value within 24-36 hours. The presence of inhibitors has not effect the kinetics of the process, but the steady-state corrosion rate for the liquid phase of compote from cherries decreased 1.6 - 3 times, for the liquid phase of compote from peaches - by 1.9 times.For the liquid phase of compotes from merries and plums, the application of pectin and hydrolysed gelatin does not has an inhibitory effect.The greatest inhibitory effect for the liquid phase of compotes from cherries is observed when applying 0.5% hydrolyzed gelatin - without an inhibitor, the steady-state corrosion rate of tinplate was 8.3 ?m / year, with the inhibitor - 2.8 ?m / year. According to the results of the study, it was found that in order to reduce quality losses during the storage of stone fruit compotes in a metal package, it is advisable to apply hydrolyzed gelatin in an amount of 0.5% to the mass of the liquid phase.
Studies on conscious rats with inhibition of NO synthase were used to assess the dynamics of brain blood flow and EEG traces during hyperbaric oxygenation at 4 or 5 atm. Oxygen at a pressure of 4 atm induced cerebral vasoconstriction in intact animals and decreased blood flow by 11-18% (p < 0.05) during 60-min exposure to hyperbaric oxygenation. Paroxysmal EEG activity and oxygen convulsions did not occur in rats at 4 atm of O2. At 5 atm, convulsive activity appeared on the EEG at 41 +/- 1.9 min, and blood flow decreased significantly during the first 20 min; blood flow increased by 23 +/- 9%, as compared with controls, (p < 0.01) before the appearance of convulsions on the EEG. Prior inhibition of NO synthase I (NOS I) and NO synthase III (NOS III) with N(omega)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg) or inhibition only of NOS I with 7-nitroindazole (7-NI, 50 mg/kg) prevented the development of hyperoxic hyperemia and paroxysmal spikes on the EEG during hyperbaric oxygenation at 5 atm. These results show that hyperbaric oxygen induces changes in cerebral blood flow which modulate its neurotoxic action via nitric oxide synthesized both in neurons and in cerebral vessels.
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