The ascorbic acid (AA) concentration in anterior pituitary and blood plasma was measured by the Roe-Kuether method in control rats and rats treated with oestradiol benzoate alone, methylene blue alone and with both oestradiol and methylene blue. We have found that methylene blue alone caused a significant drop in hypophyseal both AA and plasma AA concentrations. Methylene blue treatment prevented the increase in plasma AA concentration in oestradiol benzoate-treated rats.
Maghemite (γ-Fe2O3) nanoparticles, 12 nm in size, were prepared by co-precipitation of Fe(II) and Fe(III) chlorides with ammonium hydroxide and oxidation with hydrogen peroxide. To achieve stability and biocompatibility, obtained particles were coated with silica, to which glucose and ascorbic acid were bound by different mechanisms. The composite particles were thoroughly characterized by transmission electron microscopy, dynamic light scattering, elemental analysis, and FT-Raman and fluorescence spectroscopy to determine composition, morphology, size and its distribution, ζ-potential, and scavenging of peroxyl and hydroxyl radicals. As the particles showed promising antioxidative properties, they may have a possible application as a stable magnetically controlled scavenger of reactive oxygen species., M. Moskvin, D. Horák., and Obsahuje bibliografii
Ascorbic acid (Asc) is a major plant antioxidant. L-galactono-1,4-lactone dehydrogenase (GLDH) is an enzyme that catalyzes the last step of Asc biosynthesis in higher plants. Effects of endogenous Asc on resistance to high-temperature stress were studied by using GLDH-overexpressed (GO-2) and GLDH-suppressed transgenic rice (GI-2) as experimental materials. After high-temperature treatment, the maximal quantum yield of PSII was significantly lower in GI-2, and higher in GO-2 compared to wild type rice. The content of reactive oxygen species (ROS) was the highest in GI-2. The higher Asc content resulted in lower lipid peroxidation in GO-2. The contents of chlorophyll, soluble proteins, and Rubisco large and small subunit were positively correlated to the Asc content. These results show that the higher Asc content reduced the accumulation of ROS and maintained the function of rice leaves. We suggest that the higher Asc content could improve the rice resistance to high-temperature stress., Q. L. Zhang, Y. X. Wei, C. L. Peng., and Obsahuje bibliografii
Application of the electrostatic precipitator (ESP) dust to soil and leaves of Cajanus cajan, Vigna mungo, Vigna radiata, Vigna catjung and Glycina max increased biomass, chloroplast pigments, Chemical constituents and enzyme activities of leaves, besides crop productivity evidently indicating that the dust acted as a fertilizer. The net photosynthetic rate, photosystem 2 activity and rate of transpiration were not altered in špite of the dust forming a thin uniform coating ověř the leaf surface. The contents of intermediary N-compounds like allantoin, allantoic acid and total ureides of the leaves, which might serve as an indirect evidence of symbiotic N2-fixation, were higher in the treated plants. There were increments in free proline, soluble proteins, total nitrogen, nitrates, nitrites, soluble sugars and phenols in the treated plants. The concentrations of ffee amino acids, soluble starch, total sucrose and water soluble SH compounds of the leaves of the control and treated plants did not show any significant difference. The activity of superoxide dismutase was significantly higher which possibly indicated its role in alleviation of H2O2 and Oj toxicity. Enzymes like nitráte reductase, nitrite reductase, glutamine S3mthetase, acid and alkaline phosphatases, carbonic anhydrase, catalase, glutathione reductase and ascorbate peroxidase also functioned normally. In the treated plants, the concentration of ascorbic acid was significantly higher in the roots and nodules indicating the possible role of ascorbic acid in stress alleviation.
To understand the interactive effects of O3 and CO2 on rice leaves; gas exchange, chlorophyll (Chl) fluorescence, ascorbic acid and glutathione were examined under acute (5 h), combined exposures of O3 (0, 0.1, or 0.3 cm3 m-3, expressed as O0, O0.1, or O0.3, respectively), and CO2 (400 or 800 cm3 m-3, expressed as C400 or C800, respectively) in natural-light gas-exposure chambers. The net photosynthetic rate (PN), maximum (Fv/Fm) and operating (Fq'/Fm') quantum efficiencies of photosystem II (PSII) in young (8th) leaves decreased during O3 exposure. However, these were ameliorated by C800 and fully recovered within 3 d in clean air (O0 + C400) except for the O0.3 + C400 plants. The maximum PSII efficiency at 1,500 μmol m-2 s-1 PPFD (Fv'/Fm') for the O0.3 + C400 plants decreased for all measurement times, likely because leaves with severely inhibited PN also had a severely damaged PSII. The
PN of the flag (16th) leaves at heading decreased under O3 exposure, but the decline was smaller and the recovery was faster than that of the 8th leaves. The Fq'/Fm' of the flag leaves in the O0.3 + C400 and O0.3 + C800 plants decreased just after gas exposure, but the Fv/Fm was not affected. These effects indicate that elevated CO2 interactively ameliorated the inhibition of photosynthesis induced by O3 exposure. However, changes in antioxidant levels did not explain the above interaction. and H. Kobayakawa, K. Imai.
An increase in brain superoxide dismutase activity was found in rats exposed to high altitude hypoxia (7000 m, 30 min daily for five days) and ascorbic acid treatment (1 mg.g'1 daily s.c.) while no significant change was observed after high altitude hypoxia or ascorbic acid alone.
Changes in serum and liver lipids, hepatic ascorbic acid (AA) and cytochrome P-450 were investigated in female guinea pigs divided into three groups with different AA intake in drinking water (10, 100 and 1000 mg AA per liter) for 10 weeks. Serum and liver total cholesterol significantly decreased in guinea pigs receiving 100 and 1000 mg AA per liter of drinking water when compared with guinea pigs with suboptimal AA intake (10 mg/1). Similarly, serum triglycerides were decreased in the groups with higher AA intake. Liver AA concentration increased significantly in accordance with rising AA doses. High AA intake (1000 mg/I) for 10 weeks resulted in significant increase of both cytochromes P-450 and cytochrome b5 and total haeme content in liver microsomes when compared to guinea pigs with suboptimal AA intake. A significant positive correlation between hepatic AA concentration and cytochrome P-450 content was observed. A close negative correlation between liver total cholesterol and cytochrome P-450 content in hepatic microsomes was also seen. Long-term suboptimal AA intake may unfavourably alter the blood and liver lipid profile as well as the capacity of hepatic drug metabolizing enzymes in both male and female guinea pigs.
Control (physiological saline treated) and ascorbic acid (AA) treated (1 mg . g'1 b.w. one hour before exposure) 18-day-old rats were exposed for 1 hour to high altitude in a hypobaric chamber and the mean lethal altitudes were calculated. AA displayed a protective effect, so that in two identical experiments the mean lethal altitude was 10 900 and 10 150 m in controls, while it was 11 500 and 11 450 m in AA treated animals.
Ascorbate is an important antioxidant involved in both enzymatic and nonenzymatic reactions in plant cells. To reveal the function of ascorbate associated with defense against photo-oxidative damage, responses of the ascorbate-deficient mutant vtc2-1 of Arabidopsis thaliana to high-light stress were investigated. After high-light treatment at 1,600 μmol(photon) m-2 s-1 for 8 h, the vtc2-1 mutant exhibited visible photo-oxidative damage. The total ascorbate content was lower, whereas accumulation of H2O2 was higher in the vtc2-1 mutant than that in the wild type. The chlorophyll (Chl) content and PSII Chl fluorescence parameters, such as maximal quantum yield of PSII photochemistry, yield, and electron transport rate, in vtc2-1 mutant decreased more than that in the wild type, whereas the nonphotochemical quenching coefficient increased more in the wild type than that in vtc2-1 mutant. Therefore, the vtc2-1 mutant was more sensitive to high-light stress than the wild type. Accumulation of reactive oxygen species was mainly responsible for the damage of PSII in the vtc2-1 mutant under high light. The results indicate that ascorbate plays a critical role in maintaining normal photosynthetic function in plants under high-light stress., L.-D. Zeng, M. Li, W. S. Chow, C.-L. Peng., and Obsahuje bibliografické odkazy
The goldfish (Carassius auratus gibelio Bloch.) were exposed to cadmium in the concentration of 20 mg Cd/1 water under aquarium conditions for 1, 4, 7 and 15 days. After exposure to cadmium, the activities of superoxide dismutase (SOD) and catalase (CAT) were significantly decreased. At the same time, the liver ascorbic acid (AsA) content was increased.