Carcinogenicity of triethanolamine in mice and its mutagenicity after reaction with sodium nitrite in bacteria.
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Mice fed a diet containing 0.3 or 0.03% triethanolamine developed malignant tumors. Females showed a high incidence of tumors in lymphoid tissues, while this type was absent in males. Tumors in other tissues were produced at a considerable rate in both sexes, but no hepatoma was found. Triethanolamine was not mutagenic to Bacillus subtilis by itself, but it became mutagenic after reacting with sodium nitrite under acidic conditions or when the mixture was heated. Although N-nitrosodiethanolamine, a known carcinogen and mutagen, was detected in the reaction mixture by thin-layer chromatography, it may not be the main mutagenic product, because the product was a stable and direct mutagen and its mutagenic activity was destroyed by liver enzymes, unlike N-nitrosodiethanolamine. The lethal and mutagenic DNA damages produced by this unidentified product were susceptible to some extent to the repair functions of the bacteria. (+info)
Inhibitory effects of nitric oxide on the expression and activity of aromatase in human granulosa cells.
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The aim of the present study was to explore the mechanisms by which nitric oxide (NO) may inhibit aromatase activity of human granulosa cells. Ovarian granulosa-luteal cells, obtained from patients undergoing in-vitro fertilization (IVF) were cultured in the presence of NO-related substances. After 24 h of culture, aromatase activity of the cells was significantly inhibited by treatment with the NO donors, SNAP or NOC12 at > or =10(-4) M in a dose-dependent manner. Treatment with NO catabolites or a peroxynitrite-releasing compound, SIN1, had no significant influence. Treatment with SNAP at 10(-3) M decreased relative aromatase mRNA values by 72% (P<0.05) and intracellular cyclic AMP concentrations by 53% (P<0.01). However, treatment with H89, an inhibitor of protein kinase A, did not inhibit aromatase activity. Since there were no significant effects of NO catabolites or peroxinitrite, the inhibitory action of NO donors on aromatase must be related to NO release. The action of NO is, in part, attributable to the down-regulation of aromatase gene transcription. Although NO decreased intracellular cAMP values, down-regulation of aromatase gene transcription may not be mediated by protein kinase A-dependent mechanisms. (+info)
In vitro survival and germination of Candida albicans in the presence of nitrogen compounds.
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The in vitro effect of nitric oxide (NO) and nitrite on blastoconidia and hyphae of Candida albicans was studied. Sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) were used as NO donors. Both minimal and complex media at two pH values, 7.0 and 4.5, were used for the assays. Blastoconidia were more susceptible than hyphae to NO. The NO effect on blastoconidia was greater at acidic pH. Nitrite affected the viability of blastoconidia in complex medium. The percentage germination and the relative rate of elongation of hyphae were both enhanced when NO was present in acidic conditions. (+info)
Membrane effects of nitrite-induced oxidation of human red blood cells.
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The aim of our investigation was to study the red blood cell (RBC) membrane effects of NaNO(2)-induced oxidative stress. Hyperpolarization of erythrocyte membranes and an increase in membrane rigidity have been shown as a result of RBC oxidation by sodium nitrite. These membrane changes preceded reduced glutathione depletion and were observed simultaneously with methemoglobin (metHb) formation. Changes of the glutathione pool (total and reduced glutathione, and mixed protein-glutathione disulfides) during nitrite-induced erythrocyte oxidation have been demonstrated. The rates of intracellular oxyhemoglobin and GSH oxidation highly increased as pH decreased in the range of 7.5-6.5. The activation energy of intracellular metHb formation obtained from the temperature dependence of the rate of HbO(2) oxidation in RBC was equal to 16.7+/-1.6 kJ/mol in comparison with 12.8+/-1.5 kJ/mol calculated for metHb formation in hemolysates. It was found that anion exchange protein (band 3 protein) of the erythrocyte membrane does not participate significantly in the transport of nitrite ions into the erythrocytes as band 3 inhibitors (DIDS, SITS) did not decrease the intracellular HbO(2) oxidation by extracellular nitrite. (+info)
The presence of salt and a curing agent reduces bacteriocin production by Lactobacillus sakei CTC 494, a potential starter culture for sausage fermentation.
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The specific conditions in the batter of raw fermented sausages may reduce the efficiency of bacteriocin-producing starter cultures. In this work, using in vitro fermentation, we found that sodium chloride and sodium nitrite interfere with the growth of Lactobacillus sakei CTC 494, an organism which produces the antilisterial bacteriocin sakacin K. Because sakacin K production follows primary metabolite kinetics, a decrease in cell formation resulted in a decrease in sakacin K production as well. Sodium chloride dramatically influenced bacteriocin production by decreasing both biomass production and specific bacteriocin production. Sodium nitrite, however, had no effect on specific bacteriocin production and decreased bacteriocin production only because of its effect on cell growth. Moreover, sodium nitrite enhanced the toxic effect of lactic acid on bacterial growth. (+info)
Site-directed mutagenesis of restriction endonuclease HindIII.
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Site-directed mutagenesis by inverse PCR was done on the HindIII gene. Target residues to be mutated were chosen according to (i) the fact that a mutant obtained by sodium nitrite treatment showed almost no HindIII activity, where Asp-123 was replaced with Asn, and (ii) the model proposed by Stahl et al. (Stahl, F., Wende, W., Jeltsch, A. and Pingoud, A. Biol. Chem. 379, 467-473 (1998)). Seven kinds of mutants were obtained by the PCR, and their enzymatic and biochemical properties were examined. Three mutants, P50S, D108L, and D123N, showed fairly low HindIII activity. On the other hand, the other four, P84Q, E86K, V106E, and K125N, retained the activity. In particular, E86K showed higher activity than the wild enzyme. This fact was confirmed when activities of the purified wild and E86K enzymes were assayed. These results coincided fairly well with data using E. coli strains that carry the respective mutant plasmids, on their resistance to phage T7 and on growth rate. We conclude that the PE motif at residues 50 and 51, and DXK motif at residues 108-110, are responsible for the enzymic reaction of HindIII. (+info)
Iron and the antibotulinal efficacy of nitrite.
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Combination of nitrite, isoascorbate, and ethylenediaminetetraacetic acid were compared for their antibotulinal efficacy in perishable canned cured meat. A dose response relationship of available iron to the antibotulinal efficacy of nitrite was demonstrated. (+info)
Visualization of myoglobin-facilitated mitochondrial O(2) delivery in a single isolated cardiomyocyte.
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The purpose of the present study was to visualize myoglobin-facilitated oxygen delivery to mitochondria at a critical mitochondrial oxygen supply in single isolated cardiomyocytes of rats. Using the autofluorescence of mitochondrial reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H), the mitochondrial oxygen supply was imaged from approximately 1.4 microm inside the cell surface at a subcellular spatial resolution. Significant radial gradients of intracellular oxygenation were produced by superfusing the cell suspension with a mixed gas containing 2-4% oxygen while stimulating mitochondrial respiration with an uncoupler of oxidative phosphorylation. Augmentation of the NAD(P)H fluorescence started from the core of the cell (anoxic core) and progressively expanded toward the plasma membrane, as the extracellular Po(2) was lowered. Inactivation of cytosolic myoglobin by 5 mM NaNO(2) significantly enlarged such anoxic regions. Nitrite affected neither mitochondrial respiration in uncoupled cells nor the relationship between Po(2) and the NAD(P)H fluorescence in coupled cells. Thus we conclude that myoglobin significantly facilitates intracellular oxygen transport at a critical level of mitochondrial oxygen supply in single cardiomyocytes. (+info)