Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:EXPT00568 (ascorbate)
 23,072 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Experiments were conducted on rats with alloxan diarbetes. It appeared that the use of metabolic regulators (inssulin, vitamin C, vitamins of group B and nerobolyl) increased the assimilation of caseine hydrolysate; this was indicated by a positive nitrogen balance, retention of body weight and an increase in the tissue dry residue. The data obtained served as a further experimental foundation of-combination of hydrolysates with vitamins and hormones for the purpose of increasing the efficacy of parenteral nutrition.
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PMID:[Role of metabolic regulators in casein hydrolysate assimilation in alloxan diabetes]. 82 Mar 85

The differentiation of filaments of a continuous culture of Anabaena cylindrica after removal of fixed nitrogen has been examined. Rapid development of proheterocysts (4-5 h) and mature heterocysts (14 h) in an ordered sequence was observed; the development of the latter was concomitant with the onset of nitrogenase activity. Commitment times of 2-3 h (proheterocyst) and 5-0 (heterocyst) were measured. Evidence is presented that shows that heterocyst development, rather than any product of heterocyst function in nitrogen fixation, is responsible for the imposition of the pattern of heterocysts in a filament of vegative cells. Both phycocyanin content and carbon dioxide fixation declined markedly throughout the filament during the early stages of heterocyst development, indicating that all the cells of the filament are involved in the initial stages of the differentiation process. Heterocysts do not evolve oxygen in the light, but do respire. Nitrogenase activity in isolated heterocysts and in intact filaments was stimulated by phosphoenolpyruvate, ATP and dichlorophenolindophenol-ascorbate.
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PMID:Heterocyst and nitrogenase development in Anabaena cylindrica. 82 2

The light-induced changes in the yield of chlorophyll alpha fluorescence and photooxidation of P-700 in the P-700-enriched particles isolated from spinach chloroplasts were studied. 1. Fluorescence emitted from the particles was found to show light-induced transient changes in the yield. In the presence of ascorbate, illumination induced quenching of fluorescence in parallel to the photooxidation of P-700. The time course of dark reduction of photooxidized P-700 agreed well with that of dark recovery of variable fluorescence yield in the presence of ascorbate. When illuminated in the presence of dithionite, the emission yield increased, whereas no photooxidation of P-700 was observed. 2. The yield of variable fluorescence and redox state of P-700 depended similarly upon the redox potential. 3. At liquid nitrogen temperature, illumination induced a rise of the fluorescence yield and a complete photooxidation of P-700 in the ascorbate-treated sample. When the particles had been preincubated with dithionite in the light before cooling, light-induced rise in the fluorescence yield was accompanied by only a small extent of P-700 photooxidation. It is suggested that both the oxidized form of P-700 and the primary electron acceptor act as quenchers for the variable fluorescence. 4. The emission spectrum for the constant part of fluorescence (F679) has a peak at 679 nm, and that for the variable part of fluorescence (F694) has a peak at 694 nm at room temperature. The emission maxima were slightly shifted and the yield of variable fluorescence was markedly enhanced at liquid nitrogen temperature. 5. Excitation spectra determined show a peak at 672 nm for F679, and a peak at 672 nm and a shoulder at 685 nm for F694. Action spectrum for P-700 photooxidation was similar to the excitation spectrum for F694.
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PMID:Fluorescence changes related in the primary photochemical reaction in the P-700-enriched particles isolated from spinach chloroplasts. 99 Feb 93

Denitrification by Thiobacillus denitrificans "RT" strain was investigated using manometry and gas chromatography. 1. From nitrate, resting cells produced only nitrogen anaerobically with thiosulfate as the electron donor. The data suggest that nitrate was assimilated and dissimilated by the same nitrate reductase, assayed with benzyl-viologen as the electron donor. 2. From nitrite, whole cells produced nitric oxide, nitrous oxide and nitrogen, using thiosulfate as the electron donor; nitrogen was the final product of the reduction. Crude extract reduced nitrite to nitrogen with p-phenylene-diamine and dimethyl-p-phenylene diamine as the electron donors, and produced nitric oxide, nitrous oxide and nitrogen with tetramethyl-p-phenylene-diamine as the electron donor. Nitrite was reduced to nitric oxide and nitrous oxide by crude extract using ascorbate-phenazine methosulfate as the electron donor. 3. From nitric oxide, whole cells produced nitrous oxide and nitrogen using thiosulfate as the electron donor, nitrogen was the final reduction product. Nitric oxide was reduced to nitrous oxide by crude extract with the ascorbate-phenazine methosulfate system. 4. Whole cells reduced nitrous oxide to nitrogen with thiosulfate as the electron donor. It was not possible to detect any nitrous oxide reductase activity in crude extract. 5. A scheme was of denitrification by Thiobacillus denitrificans "RT" strain.
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PMID:Reduction of oxidized inorganic nitrogen compounds by a new strain of Thiobacillus denitrificans. 116 40

Rats fed a control casein diet, when exposed to immobilization, loose more nitrogen, urea and vitamin C in urine. Animals receiving a protein deficient diet excrete less nitrogen, urea and ascorbic acid in urine than their controls. When protein deficiency and immobilization are associated, there is not an increase on the urinary excretion of those substance compared to the deficient animals.
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PMID:[Stress due to immobilization and low protein intake in rats. Biochemical changes]. 122 Jun 15

Irradiated and chemically treated potatoes were then stored at 10 degrees C and 80-85% relative humidity. Radiations caused complete inhibition of sprouting and for up to 10 months after harvest the physical and chemical condition of the potatoes remained satisfactory. On the other hand chemical treatment controlled sprouting for up to 7-8 months only. Irradiation and chemical condition of the potatoes rotting. Weight loss was higher in the chemically treated samples. Treatment by radiation did not effect vitamin C and niacin content as compared with chemically treated samples. Irradiation did not cause any change in the sucrose and the total sugar content, as compared with chemical treatment. Total and soluble nitrogen contents were not affected by either treatment. The response to both irradiation and chemical treamtments was only slightly affected by varietal factors provided that the potatoes were healthy and mature at harvest time.
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PMID:[Sprout inhibition by radiation and chemical treatment in four potato cultivars (author's transl)]. 124 71

The N-nitrosoproline (NPRO) test for in vivo nitrosation was applied in a study of 44 rural Nebraska men drinking high- or low-nitrate water from private wells. The subjects followed diets low in NPRO and nitrate for 5 days. On days 4 and 5 they avoided ascorbate-rich foods. Urine was collected for 24 h on day 4 while the subjects followed normal activities and on day 5 after an overnight fast and taking 500 mg L-proline. We determined NPRO, nitrate, creatinine, and specific gravity in the urines, and nitrite and nitrate in single saliva specimens collected on days 4 and 5. Results for all variables were separated into those above and below the median values and were analyzed by univariate and multivariate consideration of the contingency tables. Nitrate concentration in drinking water (> or = or < 10 ppm nitrate-nitrogen) was significantly associated with both day 4 and day 5 NPRO (> or = or < 1.5 micrograms/day; P < 0.04); and with urine nitrate (> or = or < 1.5 mmol/day), saliva nitrite (> or = or < 5 mg/liter), and saliva nitrate (> or = or < 25 mg/liter) (P < or = 0.002). Urine nitrate was significantly (P < or = 0.03) associated with both day 4 and day 5 NPRO, with odds ratios of 4.2 and 5.4, respectively. Creatinine was positively associated with NPRO on day 4 (P = 0.04). These findings, like those of a recent study in Denmark, showed an association between nitrate intake in water and NPRO formation. Their significance for people drinking high-nitrate water remains to be determined.
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PMID:N-nitrosoproline excretion by rural Nebraskans drinking water of varied nitrate content. 130 57

A study was made of the interaction of plasma ascorbate and ascorbate free radical (AFR) with exogenously added iron. The quantitative determination of AFR has the advantage that transient increases in ascorbate oxidation can be directly monitored by e.p.r. spectroscopy. An AFR signal was found in the plasma of all donors and was unaffected by superoxide dismutase, catalase and the strong iron chelator deferoxamine. These findings and the rapid decrease in AFR under a nitrogen atmosphere suggest that plasma AFR is probably a result of air auto-oxidation. Iron loading of plasma did not affect the intensity of the AFR signal until the iron concentration approached or exceeded the plasma latent iron-binding capacity. In iron-overloaded plasma, the intensity of the AFR signal increased to about 10 times the normal level before decreasing rapidly to undetectable levels after 15-20 min. Determination of plasma ascorbate showed that the disappearance of AFR was due to a complete loss of the vitamin. When 50 microM-ascorbate was loaded with iron in iso-osmotic phosphate buffer there was an increase in the AFR signal, independent of the iron concentration, which was stable at least for 15 min. Thus the rate of ascorbate loss in the iso-osmotic phosphate buffer was considerably lower than in iron-overloaded plasma. The addition of different iron chelators produced comparable effects on the intensity of the AFR signal in both iron-overloaded plasma and ascorbate solution. These results suggest that the characteristic behaviour of plasma AFR after iron loading is due to its specific iron-binding capacity and to plasma ferroxidase activity. The ferroxidase activity of plasma is important to promote the transfer of Fe2+ into transferrin without a transient ascorbate oxidation. Spin-trapping studies with 5,5-dimethyl-1-pyrroline N-oxide and N-t-butyl-alpha-phenylnitrone revealed that iron-overloaded plasma was unable to produce spin-trap adducts even in the presence of 50-300 microM-hydrogen peroxide or 100 microM-azide. Evidence of OH. radical formation was obtained only after the addition of EDTA. Therefore, iron-overloaded plasma itself does not produce a Fenton reaction and, if ascorbate does indeed have a free-radical-mediated pro-oxidant role, it is not detectable in plasma by spin-trapping experiments.
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PMID:Iron-induced ascorbate oxidation in plasma as monitored by ascorbate free radical formation. No spin-trapping evidence for the hydroxyl radical in iron-overloaded plasma. 131 30

Nitric oxide (NO) is produced both by macrophages in vivo as a physiological response to infection and by a variety of cell types as an intercellular messenger. In addition, NO and nitrogen dioxide (NO2) are significant components of many combustion processes. The ubiquitous exposure of humans to nitrogen oxides (NOx), both endogenously and exogenously, may play a significant role in the carcinogenic process due to nitrosation of amines by NOx. We report here that exposure to low concentrations of NO, alone or in combination with NO2, results in significantly enhanced mutation in Salmonella typhimurium TA1535 using a modified Ames Salmonella reversion assay. The observed mutagenicity requires that the bacteria be actively dividing at the time of exposure to NO or NO2, suggesting that the nitrogen oxides, or their reaction products, function as direct-acting mutagens and that the induced lesion is easily repairable by non-dividing cells. Exposure to NO resulted in a time- and dose-dependent increase in the number of revertants approximately proportional to the square of the NO concentration from 0 to 20 ppm. NO was a more effective mutagen relative to NO2, however, the observed requirement for O2 suggests limited oxidation of NO (presumably to NO2) is necessary. Numerous lipid- and aqueous-phase inhibitors of nitrosation, as well as a number of other general antioxidants and free-radical trapping agents, were examined for their effectiveness in blocking the mutagenic effects of NO. The mutagenic activity of NO was most effectively inhibited by beta-carotene and tocopherols. BHT, dimethyl sulfoxide and mannitol also blocked the mutagenic effects of NOx but appeared less effective than beta-carotene or vitamin E, while ascorbate was ineffective as an inhibitor of mutation resulting from NO exposure.
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PMID:Mutagenicity of nitric oxide and its inhibition by antioxidants. 137 42

Ascorbate treatment 30 min prior to sodium dichromate (20 or 30 mg/kg, s.c.) shows higher potency than that of glutathione (GSH) in protecting against both the metabolic disturbance and nephrotoxicity induced by dichromate. However, ascorbate treatment after 2 h of dichromate intoxication had no effect on dichromate-induced blood urea nitrogen (BUN) elevation 3 days after intoxication. In contrast, dichromate-induced glucosuria, which reached maximum levels at 3 days after treatment, was significantly decreased by GSH or N-acetyl cysteine (NAC) treatment, even if its administration was after 24 h of dichromate intoxication. Pretreatment with GSH depletors such as diethyl maleate (DEM) and buthionine sulfoximine (BSO) had no effect on dichromate-induced nephrotoxicity. GSH levels in the liver and kidney were not affected at 3 h after dichromate treatment. However, dichromate significantly increased tissue GSH levels with a marked increase in liver per kidney GSH ratio at 24 h after treatment, if food was withheld subsequent to dichromate treatment, indicating that GSH biosynthesis resulted from the accelerated protein breakdown. These results suggest that GSH-mediated dichromate reduction is not a kinetically favorable pathway in vivo; however, GSH plays an important role in protection against dichromate-induced nephrotoxicity. In addition, the cellular metabolism of dichromate in the early period after treatment is important in the pathogenesis of its nephrotoxicity.
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PMID:The role of glutathione in the acute nephrotoxicity of sodium dichromate. 148 88


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