SEARCH · PubMed Health

Results for “Nitrites”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed1981

Reevaluation of anaerobic nitrite production as an index for the measurement of metabolic pool of nitrate.

The use of anaerobic nitrite production as an index for the measurement of metabolic pool of nitrate was reevaluated using primary leaves of 7-day-old barley and 10-day-old soybean seedlings. The seedlings were grown in nutrient solutions containing 5 to 15 millimolar nitrate. The nitrate-free in vivo assay system of nitrate reductase was used for measuring the production of nitrite. Both the duration and extent of nitrite production were dependent on the level of endogenous nitrate in the tissue. At cessation of nitrite production, 30 to 50% of the endogenous nitrate was reduced to nitrite. Nitrate from the tissue leaked continuously into the surrounding medium so that, at cessation of nitrite production, nitrate supply from the tissue was exhausted. The cessation of nitrite production, therefore, may have been caused by the depletion of endogenous nitrate from the tissue. It is concluded that anaerobic nitrite production is not a valid index for the measurement of the size of the metabolic pool of nitrate.

Journal Article↗

PubMed1984

Synthesis and degradation of nitrite reductase in pea leaves.

We have shown in a previous publication (Gupta, Beevers 1983 J Exp Bot 34: 1455-1462) that the level of extractable nitrite reductase activity in pea (Pisum sativum cv Burpeeana) leaves is subject to environmental perturbations. In the current study, we have used rocket immunoelectrophoresis to quantitate the level of nitrite reductase protein in extracts from pea plants subjected to various environmental treatments. The level of nitrite reductase cross-reacting material closely followed the level of assayable nitrite reductase activity. The environmental conditions which enhanced the level of extractable nitrite reductase activity resulted in an increased level of nitrite reductase cross-reacting material in the extracts. In contrast, environmental conditions which resulted in a decrease in the level of extractable nitrite reductase activity produced a decline in cross-reacting material. These results indicate that the environmentally induced modulation of extractable nitrite reductase activity involves alteration of enzyme level and is not mediated by a reversible activation-inactivation of the existing enzyme.

Journal Article↗

PubMed1988

Nitrite Uptake into Intact Pea Chloroplasts : II. Influence of Electron Transport Regulators, Uncouplers, ATPase and Anion Uptake Inhibitors and Protein Binding Reagents.

The relationship between net nitrite uptake and its reduction in intact pea chloroplasts was investigated employing electron transport regulators, uncouplers, and photophosphorylation inhibitors. Observations confirmed the dependence of nitrite uptake on stromal pH and nitrite reduction but also suggested a partial dependance upon PSI phosphorylation. It was also suggested that ammonia stimulates nitrogen assimilation in the dark by association with stromal protons. Inhibition of nitrite uptake by N-ethylmaleimide and dinitrofluorobenzene could not be completely attributed to their inhibition of carbon dioxide fixation. Other protein binding reagents which inhibited photosynthesis showed no effect on nitrite uptake, except for p-chlormercuribenzoate which stimulated nitrite uptake. The results with N-ethylmaleimide and dinitrofluorobenzene tended to support the proposed presence of a protein permeation channel for nitrite uptake in addition to HNO(2) penetration. On the basis of a lack of effect by known anion uptake inhibitors, it was concluded that the nitrite uptake mechanism was distinct from that of phosphate and chloride/sulfate transport.

Journal Article↗

PubMed1998

Nitrospira-like bacteria associated with nitrite oxidation in freshwater aquaria.

Oxidation of nitrite to nitrate in aquaria is typically attributed to bacteria belonging to the genus Nitrobacter which are members of the alpha subdivision of the class Proteobacteria. In order to identify bacteria responsible for nitrite oxidation in aquaria, clone libraries of rRNA genes were developed from biofilms of several freshwater aquaria. Analysis of the rDNA libraries, along with results from denaturing gradient gel electrophoresis (DGGE) on frequently sampled biofilms, indicated the presence of putative nitrite-oxidizing bacteria closely related to other members of the genus Nitrospira. Nucleic acid hybridization experiments with rRNA from biofilms of freshwater aquaria demonstrated that Nitrospira-like rRNA comprised nearly 5% of the rRNA extracted from the biofilms during the establishment of nitrification. Nitrite-oxidizing bacteria belonging to the alpha subdivision of the class Proteobacteria (e.g., Nitrobacter spp.) were not detected in these samples. Aquaria which received a commercial preparation containing Nitrobacter species did not show evidence of Nitrobacter growth and development but did develop substantial populations of Nitrospira-like species. Time series analysis of rDNA phylotypes on aquaria biofilms by DGGE, combined with nitrite and nitrate analysis, showed a correspondence between the appearance of Nitrospira-like bacterial ribosomal DNA and the initiation of nitrite oxidation. In total, the data suggest that Nitrobacter winogradskyi and close relatives were not the dominant nitrite-oxidizing bacteria in freshwater aquaria. Instead, nitrite oxidation in freshwater aquaria appeared to be mediated by bacteria closely related to Nitrospira moscoviensis and Nitrospira marina.

Journal Article↗

PubMed2001

A kinetic method for the determination of nitrite by its catalytic effect on the oxidation of chlorpromazine with nitric acid.

A catalytic spectrophotometric method for the determination of trace amounts of nitrite is proposed. In acidic solution, chlorpromazine (CP) is oxidized by nitric acid to form a red compound, which is further oxidized to a colorless compound. The reaction is accelerated by trace amounts of nitrite and can be followed by measuring the absorbance at 525 nm: nitrite ion is regenerated and multiplied by nitric acid. The absorbance of the reaction increased with an increase in the reaction time, reached a maximum and decreased rapidly. Since the time required for the absorbance to reach the maximum decreased with increasing nitrite concentration, this value was used as the measured parameter for the nitrite determination. Under the optimum experimental conditions (2.3 M nitric acid, 1.2 x 10(-5) M CP, 40 degrees C), nitrite can be determined in the range 0-100 microg l(-1). The relative standard deviations (n = 6) are 4.7 and 1.8% for 40 and 100 microg l(-1) nitrite, respectively. The detection limit of this method (3sigma) is 1.2 microg l(-1). This method was successfully applied to a determination of nitrite in natural water samples.

Antipsychotic Agents↗

PubMed1983

Estimation of the daily intake of nitrates and nitrites which children one to six years old, who attend State Nurseries in the City of Havanna, may consume.

The knowledge of the amounts of nitrates and nitrites consumed by the child population is of great importance due to three fundamental aspects: Reduction of nitrates to nitrites. Relation of these to methemoglobinemia. Carcinogenicity of the N-nitroso compounds, of which nitrites are the precursors. In the present article information is given as to the estimated amounts of nitrates and nitrites, which about 10 000 children between one and six years of age, who attend State Nurseries in the City of Havanna, may consume through the daily intake of food, milk and water offered by the Centralized Kitchen "Cuba-Finland Friendship". The method of analysis used to determine nitrates and nitrites is that reported by the Mixed Committee FAO/OMS in 1976, using a reducing column containing cadmium described by FOLLET et al. in 1963. The statistical method employed is the t-Test of the comparison of media. Estimated quantities of nitrates and nitrites, which these children may consume according to the offer of food, milk and water they receive, are: 25.6 mg of NaNO3 and 1.04 mg of NaNO2 for children one to three years of age, and 36.1 mg of NaNO3 and 1.48 mg of NaNO2 for children four to six. These values lie under those recommended as admissible daily intake reported by the Mixed Committee FAO/OMS. Therefore, there does not seem to exist a risk to health through consumption of nitrates and nitrites by the population under investigation.

Animals↗

PubMed1993

nir1, a conditional-lethal mutation in barley causing a defect in nitrite reduction.

Eleven green individuals were isolated when 95000 M2 plants of barley (Hordeum vulgare L.), mutagenised with azide in the M1, were screened for nitrite accumulation in their leaves after nitrate treatment in the light. The selected plants were maintained in aerated liquid culture solution containing glutamine as sole nitrogen source. Not all plants survived to flowering and some others that did were not fertile. One of the selected plants, STA3999, from the cultivar Tweed could be crossed to the wild-type cultivar and analysis of the F2 progeny showed that leaf nitrite accumulation was due to a recessive mutation in a single nuclear gene, which has been designated Nir1. The homozygous nir1 mutant could be maintained to flowering in liquid culture with either glutamine or ammonium as sole nitrogen source, but died within 14 days after transfer to compost. The nitrite reductase cross-reacting material seen in nitrate-treated wild-type plants could not be detected in either the leaf or the root of the homozygous nir1 mutant. Nitrite reductase activity, measured with dithionite-reduced methyl viologen as electron donor, of the nitrate-treated homozygous nir1 mutant was much reduced but NADH-nitrate reductase activity was elevated compared to wild-type plants. We conclude that the Nir1 locus determines the formation of nitrite reductase apoprotein in both the leaf and root of barley and speculate that it represents either the nitrite reductase apoprotein gene locus or, less likely, a regulatory locus whose product is required for the synthesis of nitrite reductase, but not nitrate reductase.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoproteins↗

PubMed1988

Formation of a mutagenic diazoquinone by interaction of phenol with nitrite.

Reaction of phenol with nitrite under mildly acidic conditions produced p-nitrosophenol, p-diazoquinone and o-diazoquinone. p-Diazoquinone showed mutagenicity in Salmonella typhimurium strains TA98 and TA100 without metabolic activation; the number of his+ revertant colonies in strain TA98 was 85 with a dose of 20 nmol (after deduction of the background (control) number of about 20). Higher doses of the compound were bactericidal. While the reaction of phenol with an equivalent amount of nitrite at pH 3 produced p-nitrosophenol in high yield, reaction with excess nitrite produced a high yield of p-diazoquinone. p-Nitrosophenol was converted to p-diazoquinone by reaction with nitrite. Formation of o-diazoquinone also increased with increasing amounts of nitrite. The formation of these compounds was not greatly affected by the presence of dimethylamine. Nitrosation of dimethylamine with nitrite was stimulated by phenol because of the formation of p-nitrosophenol and its stimulatory effect. Thus, the reaction of phenol with nitrite can produce mutagenic p-diazoquinone, and can also stimulate nitrosation of secondary amines by production of p-nitrosophenol.

Chromatography↗

PubMed2026

ScRNA-seq analysis reveals the effects of nitrite stress on the endocrine system of the eyestalk in Litopenaeus vannamei.

Nitrite is a harmful substance generated in Litopenaeus vannamei farming systems, largely originating from the inadequate breakdown of surplus feed and shrimp feces. Its accumulation in the water can affect the growth and physiological functions of shrimp, damage the immune system, and even cause mass mortality, thus becoming a key environmental factor restricting the green development of the industry. Under nitrite stress, the eyestalk, as an important neuroendocrine regulatory center in crustaceans, participates in the stress adaptation of the organism and exerts a protective effect by regulating energy metabolism and immune function. However, the molecular regulatory mechanism of the eyestalk in response to nitrite stress remains unclear. In this study, single-cell RNA sequencing (scRNA-seq) technology was used to analyze the heterogeneity of eyestalk cells in L. vannamei under nitrite stress. A total of 18, 394 high-quality cells were obtained, and six major cell subpopulations, including Neurosecretory cell, Motor neuron, Sensory neuron, Interneuron, Neurogliocyte, and Support cell, were identified. Differential expression analysis identified 839 differentially expressed genes, and different cell types showed distinct specific responses to nitrite stress. Functional enrichment analysis indicated that pathways such as glycolysis, oxidative phosphorylation, ribosome function, and endoplasmic reticulum protein processing were significantly activated, while signal transduction and DNA repair-related pathways were inhibited. Further analysis revealed that nitrite stress could induce mitochondrial function changes and trigger oxidative stress, thereby affecting the neuroendocrine system function of the eyestalk. This study provided insights into transcriptomic responses of the eyestalk to nitrite stress at the single-cell level, laying a theoretical foundation for the management of aquaculture environments.

Animals↗

PubMed2004

Bidirectional catalysis by copper-containing nitrite reductase.

The copper-containing nitrite reductase from Alcaligenes faecalis S-6 was found to catalyze the oxidation of nitric oxide to nitrite, the reverse of its physiological reaction. Thermodynamic and kinetic constants with the physiological electron donor pseudoazurin were determined for both directions of the catalyzed reaction in the pH range of 6-8. For this, nitric oxide was monitored by a Clark-type electrode, and the redox state of pseudoazurin was measured by optical spectroscopy. The equilibrium constant (K(eq)) depends on the reduction potentials of pseudoazurin and nitrite/nitric oxide, both of which vary with pH. Above pH 6.2 the formation of NiR substrates (nitrite and reduced pseudoazurin) is favored over the products (NO and oxidized pseudoazurin). At pH 8 the K(eq) amounts to 10(3). The results show that dissimilatory nitrite reductases catalyze an unfavorable reaction at physiological pH (pH = 7-8). Consequently, nitrous oxide production by copper-containing nitrite reductases is unlikely to occur in vivo with a native electron donor. With increasing pH, the rate and specificity constant of the forward reaction decrease and become lower than the rate of the reverse reaction. The opposite occurs for the rate of the reverse reaction; thus the catalytic bias for nitrite reduction decreases. At pH 6.0 the k(cat) for nitrite reduction was determined to be 1.5 x 10(3) s(-1), and at pH 8 the rate of the reverse reaction is 125 s(-1).

Alcaligenes faecalis↗

PubMed2002

A novel, kinetically stable, catalytically active, all-ferric, nitrite-bound complex of Paracoccus pantotrophus cytochrome cd1.

The oxidized form of Paracoccus pantotrophus cytochrome cd(1) nitrite reductase, as isolated, has bis-histidinyl co-ordination of the c haem and His/Tyr co-ordination of the d(1) haem. On reduction, the haem co-ordinations change to His/Met and His/vacant respectively. If the latter form of the enzyme is reoxidized, a conformer is generated in which the ferric c haem is His/Met co-ordinated; this can revert to the 'as isolated' state of the enzyme over approx. 20 min at room temperature. However, addition of nitrite to the enzyme after a cycle of reduction and reoxidation produces a kinetically stable, all-ferric complex with nitrite bound to the d(1) haem and His/Met co-ordination of the c haem. This complex is catalytically active with the physiological electron donor protein pseudoazurin. The effective dissociation constant for nitrite is 2 mM. Evidence is presented that d(1) haem is optimized to bind nitrite, as opposed to other anions that are commonly good ligands to ferric haem. The all-ferric nitrite bound state of the enzyme could not be generated stoichiometrically by mixing nitrite with the 'as isolated' conformer of cytochrome cd(1) without redox cycling.

Catalysis↗

PubMedDate not supplied

Mechanisms of vasodilatation induced by nitrite instillation in intestinal lumen: possible role of hemoglobin.

It has been shown that nitrite can be reduced to nitric oxide (NO) in intestine and a number of other tissues and released into the blood to form nitrosylhemoglobin (NO-Hb), existing in an equilibrium with S-nitrosohemoglobin. The latter has been suggested to be an NO transporter to distant organs. The aim of this study was to define the pathway of nitrite reduction to form NO in intestinal wall and to estimate whether this pathway has an effect on peripheral circulation. We have shown that in rat intestine at pH 7.0 70% of nitrite is converted to NO in mitochondria. At pH 6.0, nonenzymatic nitrite reduction becomes as efficient as the mitochondrial pathway. To prove whether the NO formed from nitrite in intestine can induce vasodilatation, sodium nitrite was instilled into intestinal lumen and the concentration of NO formed and diffused into the blood was followed by measuring of NO-Hb complex formation. We found that the concentration of NO-Hb gradually increases with the increase of nitrite concentration in intestinal lumen. However, it was not always accompanied by a decrease in systemic blood pressure. Blood pressure dropped down only after NO-Hb reached a threshold concentration of approximately 10 microM. These data show that NO-Hb cannot provide enough NO for vasodilatation if the concentration of NO bound to Hb is < 10 microM. The exact mechanism underlying vasodilatation observed when the concentration of NO-bound Hb was > 10 microM is, however, not clear yet and requires further studies.

Animals↗

PubMed2007

The effect of Glc6P uptake and its subsequent oxidation within pea root plastids on nitrite reduction and glutamate synthesis.

In roots, nitrate assimilation is dependent upon a supply of reductant that is initially generated by oxidative metabolism including the pentose phosphate pathway (OPPP). The uptake of nitrite into the plastids and its subsequent reduction by nitrite reductase (NiR) and glutamate synthase (GOGAT) are potentially important control points that may affect nitrate assimilation. To support the operation of the OPPP there is a need for glucose 6-phosphate (Glc6P) to be imported into the plastids by the glucose phosphate translocator (GPT). Competitive inhibitors of Glc6P uptake had little impact on the rate of Glc6P-dependent nitrite reduction. Nitrite uptake into plastids, using (13)N labelled nitrite, was shown to be by passive diffusion. Flux through the OPPP during nitrite reduction and glutamate synthesis in purified plastids was followed by monitoring the release of (14)CO(2) from [1-(14)C]-Glc6P. The results suggest that the flux through the OPPP is maximal when NiR operates at maximal capacity and could not respond further to the increased demand for reductant caused by the concurrent operation of NiR and GOGAT. Simultaneous nitrite reduction and glutamate synthesis resulted in decreased rates of both enzymatic reactions. The enzyme activity of glucose 6-phosphate dehydrogenase (G6PDH), the enzyme supporting the first step of the OPPP, was induced by external nitrate supply. The maximum catalytic activity of G6PDH was determined to be more than sufficient to support the reductant requirements of both NiR and GOGAT. These data are discussed in terms of competition between NiR and GOGAT for the provision of reductant generated by the OPPP.

Electrons↗

PubMed1987

Type 1, blue copper proteins constitute a respiratory nitrite-reducing system in Pseudomonas aureofaciens.

Pseudomonas aureofaciens truncates the respiratory reduction of nitrate (denitrification) at the level of N2O. The nitrite reductase from this organism was purified to apparent electrophoretic homogeneity and found to be a blue copper protein. The enzyme contained 2 atoms of copper/85 kDa, both detectable by electron paramagnetic resonance (EPR) spectroscopy. The protein was dimeric, with subunits of identical size (40 +/- 3 kDa). Its pI was 6.05. The EPR spectrum showed an axial signal g at 2.21(8) and g at 2.04(5). The magnitude of the hyperfine splitting (A parallel = 6.36 mT) indicated the presence of type 1 copper only. The electronic spectrum had maxima at 280 nm, 474 nm and 595 nm (epsilon = 7.0 mM-1 cm-1), and a broad shoulder around 780 nm. A copper protein of low molecular mass (15 kDa), with properties similar to azurin, was also isolated from P. aureofaciens. The electronic spectrum of this protein showed a maximum at 624 nm in the visible range (epsilon = 2.5 mM-1 cm-1) and pronounced structures in the ultraviolet region. The EPR parameters were g parallel = 2.26(6) and g perpendicular = 2.05(6), with A parallel = 5.8 mT. The reduced azurin transferred electrons efficiently to nitrite reductase; the product of nitrite reduction was nitric oxide. The specific nitrite-reducing activity with ascorbate-reduced phenazine methosulfate as electron donor was 1 mumol substrate min-1 mg protein-1. The reaction product again was nitric oxide. Nitrous oxide was the reaction product from hydroxylamine and nitrite and from dithionite-reduced methyl viologen and nitrite. No 'oxidase' activity could be demonstrated for the enzyme. Our data disprove the presumed exclusiveness of cytochrome cd1 as nitrite reductase within the genus Pseudomonas.

Azurin↗

PubMed1979

Sodium nitrite and sorbic acid effects on Clostridium botulinum spore germination and total microbial growth in chicken frankfurter emulsions during temperature abuse.

Samples of (i) a control or of (ii) sodium nitrite-containing or (iii) sorbic acid-containing, mechanically deboned chicken meat frankfurter-type emulsions inoculated with Clostridium botulinum spores, or a combination of ii and iii, were temperature abuse at 27 degrees C. Spore germination and total microbial growth were followed and examined at specified times and until toxic samples were detected. The spores germinated within 3 days in both control and nitrite (20, 40 and 156 micrograms/g) treatments. Sorbic acid (0.2%) alone or in combination with nitrite (20, 40, and 156 micrograms/g) significantly (P less than 0.05) inhibited spore germinations. No significant germination was recorded until toxic samples were detected. A much longer incubation period was necessary for toxin to be formed in nitrite-sorbic acid combination treatments as contrasted with controls or nitrite and sorbic acid used individually. Total growth was not affected by the presence of nitrite, whereas sorbic acid appeared to depress it. Possible mechanisms explaining the effects of nitrite and sorbic acid on spore germination and growth are postulated.

Animals↗

PubMed1987

Inactivation of clostridial ferredoxin and pyruvate-ferredoxin oxidoreductase by sodium nitrite.

Clostridial ferredoxin and pyruvate-ferredoxin oxidoreductase activity was investigated after in vitro or in vivo treatment with sodium nitrite. In vitro treatment of commercially available Clostridium pasteurianum ferredoxin with sodium nitrite inhibited ferredoxin activity. Inhibition of ferredoxin activity increased with increasing levels of sodium nitrite. Ferredoxin was isolated from normal C. pasteurianum and Clostridium botulinum cultures and from cultures incubated with 1,000 micrograms of sodium nitrite per ml for 45 min. The activity of in vivo nitrite-treated ferredoxin was decreased compared with that of control ferredoxin. Pyruvate-ferredoxin oxidoreductase isolated from C. botulinum cultures incubated with 1,000 micrograms of sodium nitrite per ml showed less activity than did control oxidoreductase. It is concluded that the antibotulinal activity of nitrite is due at least in part to inactivation of ferredoxin and pyruvate-ferredoxin oxidoreductase.

Clostridium↗

PubMed1974

Uptake of nitrite by Neurospora crassa.

Like the nitrate transport system, the nitrite uptake system in Neurospora crassa is induced by either nitrate or nitrite. This induction is prevented by cycloheximide, puromycin, or 6-methyl purine. The K(m) for nitrite of the induced nitrite uptake system is 86 muM, and the V(max) is 100 mumol of nitrite per g (wet weight) per h. Nitrite uptake is inhibited by metabolic poisons such as arsenate, dinitrophenol, cyanide, and antimycin A. No repression or inhibition of the nitrite transport system by ammonia, nitrate, or Casamino Acids was observed.

Amino Acids↗

PubMed1979

Nitrite reduction in Veillonella alcalescens.

Nitrite reduction was examined in Veillonella alcalescens C-1, and obligate anaerobe with an ATP-yielding nitrate-reducing system. Hydrogen donors for nitrite reduction included hydrosulfite, hydrogen gas, and pyruvate, but not pyridine nucleotides, in the presnece or absence of flavins. Pyruvate-linked nitrite reduction was not inhibited by 4,4,4-trifluoro-1-(2-thienyl) 1,3-butanedione, dicoumarol, or 2-heptyl-4-hydroxy-quinoline-N-oxide. The noninvolvement of membrane-bound factors was supported by the fact that 100% of pyruvate-linked activity remained in the soluble fraction after fractionation of crude extracts by ultracentrifugation. Using DEAE-cellulose column chromatography, however, the participation of ferredoxin in nitrite reduction was demonstrated. The product of nitrite reduction appeared to be ammonia, as determined from H2-to-NO2- ratios. Nitrite reductase was induced by nitrate or nitrite and was repressed by increased levels of reduced nitrogenous compounds.

Anaerobiosis↗