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)

Indoleamine 2,3-dioxygenase (IDO) and nitric oxide synthase are part of the anti-tumor and antimicrobial activities of mononuclear phagocytes induced by interferon-gamma (IFN gamma). As IDO is a heme-containing enzyme and NO, the product of nitric oxide synthase-initiated arginine degradation, is a regulator of heme enzymes, we investigated whether NO is capable of modulating IDO activity in IFN gamma-primed mononuclear phagocytes. Authentic NO gas or the NO-generating compound, diethylamine dinitric oxide adduct, dose-dependently inhibited IDO activity in cell lysates prepared from IFN gamma-primed human peripheral blood mononuclear cells, as assessed by the ascorbate/methylene blue assay for IDO. In contrast, neither nitrite nor nitrate affected IDO activity. Exposure of intact IFN gamma-primed human peripheral blood mononuclear cells or monocyte-derived macrophages to any of the NO-generating compounds, sodium nitroprusside, glyceryl trinitrate, S-nitroso-N-acetylpenicillamine, or diethylamine dinitric oxide adduct, resulted in inhibition of both the consumption of tryptophan from and formation of its metabolite, kynurenine, in the culture medium. The observed inhibition of IDO activity was not due to toxicity of the NO generators and was abrogated by the co-addition of oxyhemoglobin, an antagonist of NO function. Comparable concentrations of nitrite or nitrate did not inhibit IDO activity in intact cells. In contrast to human cells, addition of IFN gamma to murine macrophages, cultured in complete RPMI 1640 medium, readily induced nitric oxide synthase. Others have reported that such treatment does not induce IDO activity in these cells. However, induction of IDO activity was observed in murine macrophages when the synthesis of reactive nitrogen species was inhibited, by using arginine-free medium and/or the nitric oxide synthesis inhibitor, NG-monomethyl-L-arginine. Together, these results demonstrate that both exogenous and endogenous NO inhibit IDO activity and that oxidative arginine and tryptophan metabolism in IFN gamma-primed mononuclear phagocytes are functionally related. Our study thereby provides an insight into how these cells may regulate some of their antimicrobial and anti-tumor activities.
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PMID:Nitric oxide inhibits indoleamine 2,3-dioxygenase activity in interferon-gamma primed mononuclear phagocytes. 751 70

Azotobacter vinelandii is a free-living, nitrogen-fixing bacterium with a branched electron transport chain terminating with two terminal oxidases, cytochromes d and o. Cytochrome o is thought to receive its electrons from cytochromes c. The gene encoding cytochrome c4 has been cloned and sequenced (termed the cycA locus). The deduced amino acid sequence contains a 20 residue signaling peptide sequence on the N-terminal end. Mutagenesis was performed by inserting a Kmr cassette into the structural gene. The subsequent mutant strains showed reduced amounts of cytochromes c (approximately 60% of wild-type levels) based on difference absorption spectra measurements. Heme staining confirmed the complete loss of cytochrome c4 protein in the mutant strains. These mutants could grow and respire normally, like the wild type, under both diazotrophic or non-diazotrophic conditions. Surprisingly, the cytochrome o terminal oxidase was still turning over in membranes from the cycA mutants as evidenced by substrate-reduced CO difference spectra and inhibition experiments with the use of the cytochrome o inhibitor, chlorpromazine. Still, the levels of oxidation by ascorbate-TMPD were greatly reduced in the cycA mutants. Therefore, it is proposed that cytochrome c4 does not exist in complex with cytochrome o as a multi-component terminal oxidase complex, yet still passes electrons to it in parallel like cytochrome c5, as opposed to in an obligate sequential manner with cytochrome c5. In this pathway the proposed new branch is at the ubiquinone to cytochromes c level.
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PMID:Cloning, sequencing, and mutagenesis of the cytochrome c4 gene from Azotobacter vinelandii: characterization of the mutant strain and a proposed new branch in the respiratory chain. 761 30

Since Vitamin C (ascorbate, AH2) is an important airway antioxidant and is an essential component of tissue repair, and since acute (4 hr) O3 toxicity is enhanced by AH2 deficiency, we hypothesized that longer-term O3 effects might also be increased. Female Hartley guinea pigs (260-330 g) were fed either an AH2-sufficient or an AH2-deficient diet 1 week prior to exposure, and were maintained on their respective diets during 1 week of continuous exposure to O3 (0, 0.2, 0.4, and 0.8 ppm, 23 hr/day), and during 1 week postexposure recovery in clean air. The AH2-deficient diet caused lung AH2 to drop to about 30% of control in 1 week, and to below 10% by the end of exposure and recovery. Body weight gains during exposure were decreased in the 0.8 ppm O3 group, while the AH2 deficiency began to affect body weights only during recovery. O3 caused a concentration-dependent decrease in total lung capacity, vital capacity, carbon monoxide diffusing capacity, nitrogen washout, and static compliance, while increasing forced expiratory flow rates and residual or end-expiratory volume (suggestive of pulmonary gas-trapping). The lung/body weight ratio and fixed lung displacement volume were also increased in O3-exposed animals. Lung pathology consisted of mononuclear cell and neutrophil infiltration, airway as well as alveolar epithelial cell hyperplasia, and general decrease in epithelial cell cytoplasm. Thickening of the interstitium and an apparent increase in collagen staining were seen at the terminal bronchiolar regions. Some of these effects were marginally exacerbated in AH2-deficient guinea pigs. One week postexposure to air reversed all O3-induced abnormalities, irrespective of AH2 deficiency. Whole lung hydroxyproline and desmosine were not changed at any time by either O3 or AH2 deficiency. Measurement of lung prolyl hydroxylase activity suggested that AH2 deficiency as well as O3 exposure may have increased the tissue levels of this enzyme. The lack of a significant increase in toxicity with the longer-term exposure scenario suggests that AH2 has minimal influence on other compensatory mechanisms developed over time.
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PMID:Ozone-induced pulmonary functional, pathological, and biochemical changes in normal and vitamin C-deficient guinea pigs. 773 27

Transport of acidic amino acids in Bacillus subtilis is an electrogenic process in which L-glutamate or L-aspartate is symported with at least two protons. This is shown by studies of transport in membrane vesicles in which a proton motive force is generated by oxidation of ascorbate-phenazine methosulfate or by artificial ion gradients. An inwards-directed sodium gradient had no (stimulatory) effect on proton motive force-driven L-glutamate uptake. The transporter is specific for L-glutamate and L-aspartate. L-Glutamate transport is inhibited by beta-hydroxyaspartate and cysteic acid but not by alpha-methyl-glutamate. The gene encoding the L-glutamate transport protein of B. subtilis (gltPBsu) was cloned by complementation of Escherichia coli JC5412 for growth on glutamate as the sole source of carbon, energy, and nitrogen, and its nucleotide sequence was determined. Putative promoter, terminator, and ribosome binding site sequences were found in the flanking regions. UUG is most likely the start codon. gltPBsu encodes a polypeptide of 414 amino acid residues and is homologous to several proteins that transport glutamate and/or structurally related compounds such as aspartate, fumarate, malate, and succinate. Both sodium- and proton-coupled transporters belong to this family of dicarboxylate transporters. Hydropathy profiling and multiple alignment of the family of carboxylate transporters suggest that each of the proteins spans the cytoplasmic membrane 12 times with both the amino and carboxy termini on the inside.
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PMID:Characterization of the proton/glutamate symport protein of Bacillus subtilis and its functional expression in Escherichia coli. 775 Dec 98

Aging is associated with a decline in energy expenditure (EE), glucose intolerance, and a reduction in body nitrogen content. In addition, a reduction in the thermic response to glucose but not to fructose or protein has been reported in the elderly. The present study was conducted to further examine nutrient-induced thermogenesis and the effects of specific sugars on amino acid metabolism in relation to age. After 3 days on a weight-maintaining, 250-g carbohydrate diet, 16 healthy non-obese men and women in two age groups (18 to 29 and 66 to 80 years) consumed on 4 different days 500 mL of either a 75-g fructose or 75-g glucose solution, with or without 300 mg caffeine or vitamin C as a placebo. Blood substrate and hormone levels and EE, using indirect calorimetry, were measured at timed intervals for 3 hours after consumption of the drinks. There was no difference in the carbohydrate-induced increase in EE in either young or old even after adjustments for body weight and fat-free mass (FFM). An approximately 20-fold increase in serum caffeine levels increased EE in both groups (P < .003), but had minimal effects on substrate and hormone responses. In contrast to glucose, fructose induced a marked elevation in plasma alanine from combined basal levels of 301 +/- 24 to approximately 500 +/- 18 mumol/L (mean +/- SEM) in both groups (P < .001). However, both fructose and glucose ingestion resulted in a similar decline in branched-chain and aromatic amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acute effects of fructose and glucose ingestion with and without caffeine in young and old humans. 775 12

The effect of congeners of nitrogen monoxide (NO) on iron (Fe) uptake from 59Fe-125I-transferrin (Tf) and release of 59Fe from prelabelled cells have been investigated in SK-MEL-28 human melanoma cells, human K562 cells and mouse MDW-4 cells. These studies have been initiated as it has been suggested that the tumoricidal effects of NO may be mediated by its acting to release Fe from cells (Hibbs et al., 1984 Biochem. Biophys. Res. Commun. 123, 716-723; Hibbs et al., 1988 Biochem. Biophys. Res. Commun. 157, 87-94). The nitrosonium ion (NO+) generator, sodium nitroprusside (SNP), decreased 59Fe uptake by melanoma cells to 57% of the control without decreasing 125I-Tf uptake after a 4-h incubation with 59Fe-125-Tf (1.25 microM). Longer incubations up to 24 h decreased 59Fe uptake and also 125I-Tf uptake. Two breakdown products of SNP, ferricyanide and cyanide, had no effect on 59Fe uptake. In addition, photolysis of the SNP solution prevented the inhibition of 59Fe uptake, suggesting that NO was the active agent. Two nitric oxide (NO.) producing agents, 3-morpholinosydnonimine (SIN), and S-nitroso-N-acetylpenicillamine (SNAP), also decreased 59Fe uptake from 59Fe-125I-Tf. Superoxide dismutase increased the efficacy of SIN, and the NO-scavenger, oxyhaemoglobin, prevented the inhibition of 59Fe uptake mediated by SNAP, again suggesting that NO was the active agent. Furthermore, dialysis studies demonstrated that none of the NO-generating agents could remove 59Fe from 59Fe-125I-Tf, suggesting that the decrease in cellular Fe uptake observed was not due to NO releasing Fe from the Fe-binding sites of Tf. Despite the ability of NO-producing agents at inhibiting 59Fe uptake by cells, they could not remove significant amounts of 59Fe from melanoma cells prelabelled with either 59Fe-citrate or 59Fe-125I-Tf. Similar data were obtained using K562 and MDW-4 cells. Interestingly, the NO+ generating agent, SNP, had no effect on [3H]thymidine uptake. However, when SNP was converted to an NO. generator by the addition of 1 mM ascorbate, its effect was similar to the NO. generator, SNAP, markedly reducing [3H]thymidine incorporation to 33% of the control value. The addition of unlabelled diferric Tf (0.625 microM) to SNAP ameliorated its inhibitory effect on cellular [3H]thymidine uptake, suggesting that the interaction of NO. with Fe was of importance in the inhibition observed. The results are discussed in the context of the cytostatic potential of NO via its binding to Fe.
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PMID:Nitrogen monoxide decreases iron uptake from transferrin but does not mobilise iron from prelabelled neoplastic cells. 776 11

Iron-exposed murine macrophages have a modified bactericidal activity as shown by previous observations. In order to assess the role of iron in macrophage activation, as measured by free radical production and by intracellular bacterial killing, murine peritoneal macrophages were cultivated in the presence of various sources of iron, human iron-saturated transferrin and ammonium ferric citrate, or iron chelators, Desferal, and human Apo-transferrin, and were infected with an enteropathogenic strain of E. coli. The release of nitrite (NO2-), and the production of superoxide anion (O2-) and hydrogen peroxide (H2O2) by the phagocytes were measured and compared to the production by uninfected macrophages. The synergistic action with murine r.IFN-gamma was also studied in the radical production reaction and for the bactericidal activity of macrophages. Our results show that in vitro phagocytosis of E. coli induced elevated production of NO2- and H2O2 by macrophages, and that oxygen derivatives were released independently of the presence of added iron or chelator. Despite a phagocytosis-related enhancement of NO2- release, reactive nitrogen intermediates (RNI) are not directly involved in the bactericidal mechanism, as revealed by increased intracellular killing owing to RNI inhibitors. Moreover, bacterial killing may depend on oxygen derivatives, as suggested by the effect of the antioxidant sodium ascorbate leading to both a diminished H2O2 production and a decreased bactericidal activity of macrophages.
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PMID:Effect of iron and phagocytosis on murine macrophage activation in vitro. 777 72

Crisphead lettuce (Lactuca sativa L. var capitata cvs. Marius and Saladin) were grown with a nitrogen supply from 50 to 200 kg N/hectare. Heads were stored for one or two weeks at 1 degree C in cold storage or ice bank cooling. Samples were taken for measurement of dry matter, sugars, vitamin C and nitrate. The content of dry matter, sugars (glucose, fructose) and vitamin C decreased with increasing level of nitrogen, and the content of nitrate increased. Except for nitrate the contents of the other quality attributes decreased at all nitrogen supply levels during storage. No differences were found between the storage systems, and beside fructose no significant differences were found between the two cultivars. The content of dry matter, vitamin C, and nitrate decreased from the outer to the inner head fraction, while the content of sugars increased. Trimming decreased the content of dry matter, vitamin C and nitrate and increased the content of sugars. To obtain heads from storage with a relatively high content of dry matter, sugars and vitamin C, and a relatively low content of nitrate the nitrogen supply must be as low as possible. Except for nitrate where no distinct results were found in this experiment it must also be recommended to store the heads as short time as possible. Possibly the cv. Saladin has some advantage quality attributes after storage compared with the cv. Marius.
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PMID:Influence of growth conditions on the value of crisphead lettuce. 4. Quality changes during storage. 779 64

The recommendations for protein consumption depend on the essential amino acid and total nitrogen content of a diet, and food digestibility. International recommendations are based on egg or milk proteins. However, populations eat different food mixtures. Brazilians use rice and beans as their main protein food source. This study presents different Brazilian diets, with variable amount of rice and beans. The results show that for each diet there is a different amount of protein recommended. Pre-school children, for example, must receive from 1.15 to 1.77 g/protein/day, depending on the mixture of their dietary protein intake. Besides the diet protein's quality and quantity, the total food intake and presence of other essential nutrients, such as iron, calcium and vitamin C has also to be considered. The correct protein recommendation with respect to a diet or a mixture of food, should take into consideration: digestibility, total nitrogen, essential amino acids, presence of others nutrients and weight of food consumed.
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PMID:[Calculation of recommendations regarding protein intake: their application to preschool, school students and adults taking Brazilian foods]. 782 48

Bacterial phosphotriesterase catalyzes the hydrolysis of organophosphate triesters. To be active, the enzyme requires that two divalent cations are bound. These metal ions are bound in close proximity to one another as a binuclear center. To characterize the structure and function of the binuclear metal binding sites, we have prepared the copper-substituted enzyme. The kinetic data indicate that this enzyme is essentially inactive toward the hydrolysis of phosphotriesters. The EPR signal arising from the copper-substituted enzyme is nearly axial, with g parallel = 2.24 and g perpendicular = 2.05 and shows at least seven superhyperfine transitions in the g perpendicular region with A perpendicular = 1.45 x 10(-3) cm-1. These splittings are consistent with the direct ligation of more than one nitrogen to the metal center. The average spin quantitation of copper-substituted enzymes are 0.6 spin/Cu, approximately half of that observed for noninteracting Cu2+ ions. The spin intensity increases to ca. 1 spin/Cu when samples are denatured with acid. The binding of metal ions to the designated alpha and beta sites is highly synergistic (i.e., the metal ions bind in pairs). Mixed metal complexes of the type Cu/X and X/Cu were prepared. When X is a diamagnetic ion (Zn2+ or Cd2+), the spin quantitation increases, but when X is the paramagnetic Co2+ ion, the spin quantitation decreases. This behavior indicates that the low spin intensities observed for copper-substituted phosphotriesterase arise from spin-coupling of the two adjacent Cu2+ ions. The addition of dithiothreitol, ascorbate, or dithionite to the copper-substituted phosphotriesterase results in nearly the complete loss of spin intensity. This indicates that the bound coppers can be reduced to the cuprous state.
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PMID:Utilization of copper as a paramagnetic probe for the binuclear metal center of phosphotriesterase. 786 32


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