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At least 19 recordsLinked to original sources
PubMed2004

Nitrite toxicity to crayfish, Astacus leptodactylus, the effects of sublethal nitrite exposure on hemolymph nitrite, total hemocyte counts, and hemolymph glucose.

The 48-h acute toxicity range of nitrite to narrow-clawed crayfish, Astacus leptodactylus was within 22 and 70 mg L(-1) (mean 29.43 mg L(-1)). Environmental chloride (100 mg L(-1) chloride) increased the 48-h toxicity of nitrite to a range of 31 and 80 mg L(-1) (mean 49.20 mg L(-1)). Hemolymph nitrite, total hemocyte counts (THCs), and hemolymph glucose were examined in A. leptodactylus exposed to different sublethal nitrite concentrations. The same parameters were also determined for A. leptodactylus exposed to different sublethal nitrite concentrations with additional environmental chloride. Additionally, hemolymph nitrite and THCs were analyzed for crayfish exposed to nitrite-free water after 24 h following a 48-h exposure to nitrite. In the nitrite-exposed tests, hemolymph nitrite increased directly with water nitrite; however, after recovery, nitrite in hemolymph decreased. In the nitrite plus chloride-exposed tests, the accumulation of nitrite in hemolymph was relatively low compared to the nitrite-exposed tests. Thus, hemolymph to environment ratios of nitrite in the nitrite-exposed tests were higher than those of nitrite plus chloride-exposed tests. THCs decreased following nitrite exposure and, in general, increased after recovery. In the nitrite with chloride exposed and recovery from nitrite tests, THCs increased. Hemolymph glucose levels elevated following nitrite exposure, independent of water nitrite concentrations. However, with environmental chloride nitrite exposure did not cause elevation of hemolymph glucose. Hemolymph nitrite accumulation was found to be closely related to the decrease in THCs and increase in hemolymph glucose.

Animals↗
PubMed1977

Nitrate reduction to nitrite, a possible source of nitrite for growth of nitrite-oxidizing bacteria.

Growth yields and other parameters characterizing the kinetics of growth of nitrite-oxidizing bacteria are presented. These parameters were measured during laboratory enrichments of soil samples with added nitrite. They were then used to reanalyze data for nitrite oxidizer growth in a previously reported field study (M. G. Volz, L. W. Belser, M. S. Ardakani, and A. D. McLaren, J. Environ. Qual. 4:179-182, 1975), where nitrate, but not nitrite or ammonium, was added. In that report, analysis of the field data indicated that in unsaturated soils, the reduction of nitrate to nitrite may be a significant source of nitrite for the growth of nitrite oxidizers. A yield of 1.23 x 10(4) cells per mug of N was determined to be most appropriate for application to the field. It was determined that if nitrite came only from mineralized organic nitrogen via ammonium oxidation, 35 to 90% of the organic nitrogen would have had to have been mineralized to produce the growth observed. However, it is estimated that only about 2% of the organic nitrogen could have been mineralized during the growth period. Thus, it appears that another source of nitrite is required, the most likely being the reduction of nitrate to nitrite coupled to the oxidation of organic matter.

Nitrates↗
PubMed1979

[Analytical methods for nitrate and nitrite determination in foods. 3. Spectrophotometric determination of nitrate and nitrite using sulphanilic acid/1-naphylamine, and of nitrite using resorcinol/zirconium (IV) oxychloride].

The Nitrate content of foods may be determined by means of azo-dye coupling after reduction of the nitrate with the aid of active cadmium produced in the sample solution. An easy method for determining nitrite consists in the colorimetric estimation of a coloured chelate formed from nitrite, resorcinol and zirconium(IV) oxychloride.

1-Naphthylamine↗
PubMed1988

Nitrite uptake into intact pea chloroplasts : I. Kinetics and relationship with nitrite assimilation.

The uptake of nitrite into intact pea chloroplasts was observed and its relationship with internal nitrite reduction was assessed. Net nitrite uptake exhibited saturation kinetics and an alkaline pH preference. This evidence questioned the accepted major role for neutral HNO(2) permeation and its reported influence on photosynthesis. The possible involvement of a nitrite permeation channel or transport protein is discussed. Net nitrite uptake curves were closely comparable with those for nitrite reduction within the chloroplast. Net nitrite uptake into chloroplasts was profoundly influenced by darkness, incubation temperature, and plant nitrate nutrition. Of several inorganic salts tested, sulfite was the only anion to exhibit a distinct inhibition of nitrite uptake. In contrast, nitrite uptake could be stimulated by the presence of certain cations, particularly at acidic pH values. It was concluded that nitrite uptake was closely related to stromal pH, internal nitrite accumulation, and nitrite reduction. The possible dependence of nitrite reduction on nitrite uptake rather than electron transport is discussed. External ATP and NAD(P)H did not significantly affect net nitrite uptake. This suggested that cytoplasmic ATP or reductant could not directly support nitrite uptake and, possibly, nitrite assimilation.

Journal Article↗
PubMedDate not supplied

Nitrite adulteration of workplace urine drug-testing specimens. I. Sources and associated concentrations of nitrite in urine and distinction between natural sources and adulteration.

The active ingredient in the commercial workplace urine drug-testing adulterant, Klear, was previously determined to be nitrite ion. Nitrite adulteration compromises the confirmation of some drugs, notably the marijuana metabolite. A previously reported bisulfite step overcomes some nitrite adulteration, but it cannot do so in every case, which leaves the laboratory to report the specimen as not suitable for testing. Unlike many other adulterants, nitrite is found in normal urine at low concentrations. In order to defend a report of nitrite adulteration, it is necessary to provide evidence that the amount of nitrite in a workplace urine specimen could not arise by normal means. The objectives of this study were to identify all sources of nitrite in urine and the range of concentrations associated with these sources and to determine if nitrite adulteration can be supported based upon a quantitative result. The scientific literature was reviewed for internal and external sources of nitrite and their concentration ranges and are reported. The following specimens were obtained and nitrite concentrations measured by a spectrophotometric method: clinical specimens nitrite positive by test strip (< 15 micrograms/mL); specimens culture positive for nitrate-reducing microorganisms (< 36 micrograms/mL); specimens from patients on medications that may metabolize to nitrite (< 6 micrograms/mL); and drug-test specimens, both negative (< 130 micrograms/mL) and others that appeared to be adulterated with nitrite (range 1910-12,200 micrograms/mL, mean 5910). The literature and the nitrite measurements of this study indicate a substantial difference between concentrations from natural sources compared with adulteration. A quantitative measurement of nitrite by a well-structured assay can provide scientifically valid and forensically defensible proof of adulteration with a nitrite-containing substance.

Drug Contamination↗
PubMed2001

Blood plasma response and urinary excretion of nitrite and nitrate in milk-fed calves after oral nitrite and nitrate administration.

There is marked endogenous production of nitrate in young calves. Here we have studied the contribution of exogenous nitrate and nitrite to plasma concentrations and urinary excretion of nitrite and nitrate in milk-fed calves. In experiment 1, calves were fed 0 or 200 &mgr;mol nitrate or nitrite/kg(0.75) or 100 &mgr;mol nitrite plus 100 &mgr;mol nitrate/kg(0.75) with milk for 3 d. In experiment 2, calves were fed 400 &mgr;mol nitrate or nitrite/kg(0.75) with milk for 1 d. Plasma nitrate rapidly and comparably increased after feeding nitrite, nitrate or nitrite plus nitrate. The rise of plasma nitrate was greater if 400 than 200 &mgr;mol nitrate or nitrite/kg(0.75) were fed. Plasma nitrate decreased slowly after the 3-d administration of 200 &mgr;mol nitrate or nitrite/kg(0.75) and reached pre-experimental concentrations 4 d later. Urinary nitrate excretions nearly identically increased if nitrate, nitrite or nitrite plus nitrate were administered and excreted amounts were greater if 400 than 200 &mgr;mol nitrate or nitrite/kg(0.75) were fed. After nitrite ingestion plasma nitrite only transiently increased after 2 and 4 h and urinary excretion rates remained unchanged. Plasma nitrate concentration remained unchanged if milk was not supplemented with nitrite or nitrate. Nitrate concentrations were stable for 24 h after addition of nitrite to full blood in vitro, whereas nitrite concentrations decreased within 2 h. In conclusion, plasma nitrate concentrations and urinary nitrate excretions are enhanced dose-dependently by feeding low amounts of nitrate and nitrite, whereas after ingested nitrite only a transient and small rise of plasma nitrite is observed because of rapid conversion to nitrate.

Journal Article↗
PubMed1992

Characterization of Tn5 mutants deficient in dissimilatory nitrite reduction in Pseudomonas sp. strain G-179, which contains a copper nitrite reductase.

Tn5 was used to generate mutants that were deficient in the dissimilatory reduction of nitrite for Pseudomonas sp. strain G-179, which contains a copper nitrite reductase. Three types of mutants were isolated. The first type showed a lack of growth on nitrate, nitrite, and nitrous oxide. The second type grew on nitrate and nitrous oxide but not on nitrite (Nir-). The two mutants of this type accumulated nitrite, showed no nitrite reductase activity, and had no detectable nitrite reductase protein bands in a Western blot (immunoblot). Tn5 insertions in these two mutants were clustered in the same region and were within the structural gene for nitrite reductase. The third type of mutant grew on nitrate but not on nitrite or nitrous oxide (N2O). The mutant of this type accumulated significant amounts of nitrite, NO, and N2O during anaerobic growth on nitrate and showed a slower growth rate than the wild type. Diethyldithiocarbamic acid, which inhibited nitrite reductase activity in the wild type, did not affect NO reductase activity, indicating that nitrite reductase did not participate in NO reduction. NO reductase activity in Nir- mutants was lower than that in the wild type when the strains were grown on nitrate but was the same as that in the wild type when the strains were grown on nitrous oxide. These results suggest that the reduction of NO and N2O was carried out by two distinct processes and that mutations affecting nitrite reduction resulted in reduced NO reductase activity following anaerobic growth with nitrate.

Blotting, Southern↗
PubMed2002

Accumulations of nitrite and nitrate in the tissues of Penaeus monodon exposed to a combined environment of elevated nitrite and nitrate.

Penaeus monodon (11.86 +/- 0.63 g) exposed individually to six different nitrite and nitrate regimes [nitrite at 0.002 (control), 0.360, and 1.455 mM combined with nitrate at 0.005 (control) and 7.275 mM] in 25 ppt sea water were examined for the nitrite and nitrate concentrations in tissues and nitrite uptake and nitrate uptake after 24 h in 25.3 degrees C. In P. monodon following exposure to 1.455 mM nitrite only, nitrite levels increased by factors of 0.33, 1.05, 1.36, 1.79, 2.10, 2.16, 2.21, and 3.58 in muscle, hepatopancreas, gill, foregut, hemolymph, heart, eyestalk, and midgut, respectively, over the ambient nitrite level. In P. monodon, following exposure to combined solutions of 1.455 mM nitrite and 7.275 mM nitrate, nitrite levels were factors of 0.34, 1.05, 1.44, 1.86, 2.21, 2.30, 2.67, and 3.83 in muscle, hepatopancreas, gill, foregut, heart, hemolymph, eyestalk, and midgut, respectively, over the ambient nitrite levels, whereas nitrate levels were factors of 0.06, 0.11, 0.27, 0.29, 0.45, 0.51, 0.57, and 0.61 in muscle, hepatopancreas, foregut, heart, hemolymph, gill, midgut, and eyestalk, respectively, over the ambient nitrate levels. It is concluded that incorporation of nitrite is converted to nitrate in midgut, heart, hemolymph, foregut, and eyestalk, whereas incorporation of nitrate in tissues is converted to nitrite and accumulated in eyestalk when P. monodon are exposed to combined nitrite and nitrate environments.

Animals↗
PubMed1992

Nitrate Reductase Regulates Expression of Nitrite Uptake and Nitrite Reductase Activities in Chlamydomonas reinhardtii.

In Chlamydomonas reinhardtii mutants defective at the structural locus for nitrate reductase (nit-1) or at loci for biosynthesis of the molybdopterin cofactor (nit-3, nit-4, or nit-5 and nit-6), both nitrite uptake and nitrite reductase activities were repressed in ammonium-grown cells and expressed at high amounts in nitrogen-free media or in media containing nitrate or nitrite. In contrast, wild-type cells required nitrate induction for expression of high levels of both activities. In mutants defective at the regulatory locus for nitrate reductase (nit-2), very low levels of nitrite uptake and nitrite reductase activities were expressed even in the presence of nitrate or nitrite. Both restoration of nitrate reductase activity in mutants defective at nit-1, nit-3, and nit-4 by isolating diploid strains among them and transformation of a structural mutant upon integration of the wild-type nit-1 gene gave rise to the wild-type expression pattern for nitrite uptake and nitrite reductase activities. Conversely, inactivation of nitrate reductase by tungstate treatment in nitrate, nitrite, or nitrogen-free media made wild-type cells respond like nitrate reductase-deficient mutants with respect to the expression of nitrite uptake and nitrite reductase activities. Our results indicate that nit-2 is a regulatory locus for both the nitrite uptake system and nitrite reductase, and that the nitrate reductase enzyme plays an important role in the regulation of the expression of both enzyme activities.

Journal Article↗
PubMed1991

Regulation of nitrite uptake and nitrite reductase expression in Chlamydomonas reinhardtii.

Expression of nitrite uptake and nitrite reductase activities has been studied in Chlamydomonas reinhardtii under different nutritional conditions. Both activities were expressed at a low level in derepressed cells (with no nitrogen source) and at a high level in induced cells (with nitrate or nitrite). Nitrate was required for both activities to be maximally expressed. Ammonium-grown cells did not show nitrite uptake capability and had a basal nitrite reductase activity. Nitrite uptake but not nitrite reductase levels decreased very significantly in nitrate-induced cells subject to cycloheximide treatment, which suggests that protein(s) involved in the uptake are under a rapid turnover. Nitrite uptake expression was strongly inhibited by the presence of the glutamine synthetase inhibitor L-methionine-D,L-sulfoximine under either derepression or induction conditions, whereas that of nitrite reductase was not affected under the same conditions. Our results indicate that nitrite uptake expression is regulated primarily by ammonium, and that of nitrite reductase by both ammonium and ammonium derivative(s).

Ammonia↗
PubMed2006

Effect of nitrite concentration on the distribution and competition of nitrite-oxidizing bacteria in nitratation reactor systems and their kinetic characteristics.

Genus Nitrospira and Nitrobacter species are the key nitrite-oxidizing bacteria (NOB) in nitrifying wastewater treatment plants. It has been hypothesized that genus Nitrospira are K-strategists and can exploit low amounts of nitrite more efficiently than Nitrobacter. In contrast, Nitrobacter species are r-strategists that can grow faster than Nitrospira. To elucidate the K/r hypothesis and to analyze the effect of substrate (nitrite) concentration on the competition and distribution of the two NOB, two different reactor types were employed for nitrite oxidation (nitratation) and NOB growth. The continuous biofilm airlift reactor (CBAR) maintained low nitrite concentration due to the complete oxidation of nitrite in continuous operation while the sequencing batch reactor (SBR) was kept in a relatively high nitrite concentration environment due to a cyclic substrate concentration profile. Fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) showed that both Nitrobacter species and genus Nitrospira were present in the CBAR and the SBR. Quantitative FISH analyses of the CBAR showed that Nitrospira occupied 59% of the total bacteria while Nitrobacter occupied only 5%. On the other hand, Nitrobacter, occupying 64%, was the dominant NOB in the SBR, and only 3% of total bacteria belonged to genus Nitrospira. Nitrite oxidation kinetics and quantitative FISH analyses revealed that the specific nitrite oxidation activities of Nitrobacter and Nitrospira are 93.8 and 10.5 mg/g NOB h, respectively, and the specific activity of Nitrobacter is about 9 times higher than that of Nitrospira. In conclusion, the results confirm the K/r hypothesis and the distribution of Nitrobacter and Nitrospira is likely to depend mainly on nitrite concentration. It seems that nitrite load and starvation conditions do not give a direct effect on the distribution of NOB.

Bacteria↗
PubMed2004

Linkage isomerism in nitrite reduction by cytochrome cd1 nitrite reductase.

Nitrite reduction by cytochrome cd(1) nitrite reductase (cd(1)NIR) is currently accepted to involve coordination of the nitrite nitrogen atom to the ferrous d(1) heme. Here, density functional theory results are reported on the previously unexplored O-binding of nitrite to ferrous and ferric cd(1)NIR. Although the N-isomer (nitro) is energetically favored over the O-nitrite (nitrito), even one single strong hydrogen bond may provide the energy required to put the two isomers on level terms. When hydrogen bonding existent at the cd(1)NIR active site is accounted for in the computational model, the O-nitrite isomer is found to spontaneously protonate and thus yield a ferric-hydroxo species, liberating nitric oxide. An O-nitrite ferrous cd(1)NIR complex appears to be an energetically feasible intermediate for nitrite reduction. O-Coordination would offer an advantage since the end product of nitrite reduction would be a ferric-hydroxo/water complex, rather than the more kinetically inert iron-nitrosyl complex implied by the N-nitrite mechanism.

Cytochromes↗
PubMed2000

Optical biosensing of nitrite ions using cytochrome cd1 nitrite reductase encapsulated in a sol-gel matrix.

Nitrite is an important human health and environmental analyte. As such, the European Union (EU) has imposed a limit for nitrite in potable water of 0.1 mg l-1 (2.18 microM). In order to develop an optical biosensing system for the determination of nitrite ions in environmental waters, cytochrome cd1 nitrite reductase has been extracted and purified from the bacterium Paracoccus pantotrophus. The protein has been spectroscopically characterised in solution and important kinetic parameters of nitrite reduction of the cytochrome cd1 enzyme, i.e., Km, Vmax and kcat have been determined. The influence of pH on the activity of the cytochrome cd1 has been investigated and the results suggest that this enzyme can be used for the determination of nitrite in the pH range 6-9. Biosensing experiments with the cytochrome cd1 in solution suggested that the decrease in intensity of the absorption band associated with the d1 haem (which is the nitrite binding site), at 460 nm, with increasing nitrite concentrations would enable the measurement of this analyte with the optimum limit of detection. The cytochrome cd1 has been encapsulated in a bulk sol-gel monolith with no structural changes observed and retention of enzymatic activity. The detection of nitrite ions in the range 0.075-1.250 microM was achieved, with a limit of detection of 0.075 microM. In order to increase the speed of response, a sol-gel sandwich thin film structure was formulated with the cytochrome cd1. This structure enabled the determination of nitrite concentrations within ca. 5 min. The sol-gel sandwich entrapped cytochrome cd1 enzyme was found to be stable for several months when the films were stored at 4 degrees C.

Biosensing Techniques↗
PubMed1981

Methylene blue inhibits coronary arterial relaxation and guanylate cyclase activation by nitroglycerin, sodium nitrite, and amyl nitrite.

Relaxation by nitroglycerin, sodium nitrite, and amyl nitrite of bovine coronary arterial smooth muscle was inhibited by the oxidant methylene blue. Methylene blue also inhibited activation of bovine coronary arterial soluble guanylate cyclase by nitroglycerin, which required addition of cysteine. At concentrations less than 10 mM, sodium nitrite required the addition of one of several thiols or ascorbate to activate guanylate cyclase from bovine coronary artery. Guanylate cyclase activation by large amounts (50 microL) of saturated amyl nitrite gas did not require, but was enhanced by, the addition of thiols or ascorbate. However, similar to sodium nitrite, guanylate cyclase activation by smaller amounts (5 microL) of saturated amyl nitrite gas did require the addition of one of various thiols or ascorbate. Methylene blue markedly inhibited guanylate cyclase activation by sodium nitrite in the presence of cysteine or ascorbate and similarly inhibited enzyme activation by amyl nitrite either in the absence or presence of cysteine or ascorbate. These data support the hypothesis that nitrates and nitrites relax vascular smooth muscle by stimulating cyclic GMP formation. The results further suggest that, similar to relaxation and guanylate cyclase activation by nitroso-containing compounds, relaxation and enzyme activation by nitrates and and nitrites may involve the formation of nitric oxide or complexes of nitric oxide as active intermediates.

Amyl Nitrite↗
PubMed2000

Accumulation of nitrite in the tissues of Penaeus monodon exposed to elevated ambient nitrite after different time periods.

Penaeus monodon (29.42 +/- 0.39 g) that had been exposed individually to 0.001 (control), 0.07, 0.36, 0.72, and 1.44 mM nitrite in 25 ppt sea water were examined for the nitrite accumulation in hemolymph, gill, eyestalk, heart, foregut, midgut, hepatopancreas, and muscle and nitrite uptake after 1, 3, 6, 12, 24, and 48 h, respectively. Concentration of nitrite in the tissues increased directly with ambient nitrite and exposure time except for muscle. P. monodon following 48-h exposure to 0.36 mM nitrite, nitrite concentration progressively increased from the muscle (0.40 micromol/g), hepatopancreas (1.24 micromol/g), gill (1.82 micromol/g), foregut (2.03 micromol/g), hemolymph (0.39 micromol/mL), heart (2.43 micromol/g), eyestalk (3.07 micromol/g), and to the midgut (4.14 micromol/g), which is 1.1, 3.4, 5.0, 5.6, 6.6, 6.8, 8.5, and 11.4 times the ambient nitrite concentration, respectively. It is concluded that when P. monodon is exposed to ambient nitrite, nitrite is immediately incorporated in the hemolymph and midgut via branchial chloride uptake of NO(2)(-), and accumulated in the tissues.

Animals↗
PubMed1986

The kinetic differences between sodium nitrite, amyl nitrite and nitroglycerin oxidation of hemoglobin.

The effect of sodium nitrite, amyl nitrite and nitroglycerin (glyceryl trinitrate) on the hemoglobin of adult erythrocytes was examined in vitro. Both amyl nitrite and nitroglycerin reacted immediately with oxyhemoglobin to effect oxidation into methemoglobin while sodium nitrite required an inductionary period (lag phase) prior to the reaction. Kinetic studies of the biomolecular rate law for each of the preceding reaction's reactionary periods (log phases) allowed rate constant calculations to be made. The values are 1.14 x 10(4) M-1 min-1, 7.45 x 10(4) M-1 min-1, and 3.50 x 10(1) M-1 min-1 for sodium nitrite, amyl nitrite and nitroglycerin, respectively. A comparison of the amyl nitrite and nitroglycerin rate constants reveals that amyl nitrite is approximately 2000-fold more toxic to oxyhemoglobin than nitroglycerin. These oxidant's effect on in vitro hemoglobin solutions are comparable since both reactions approximate to rectangular hyperbolae. Sodium nitrite reacts about 300-fold faster with oxyhemoglobin than does nitroglycerin. However, the sodium nitrite reaction proceeds in a sigmoidal fashion which makes a strict comparison between these compounds relative toxicities less clear cut.

Erythrocytes↗
PubMed1997

Structure of nitrite bound to copper-containing nitrite reductase from Alcaligenes faecalis. Mechanistic implications.

The structures of oxidized, reduced, nitrite-soaked oxidized and nitrite-soaked reduced nitrite reductase from Alcaligenes faecalis have been determined at 1.8-2.0 A resolution using data collected at -160 degrees C. The active site at cryogenic temperature, as at room temperature, contains a tetrahedral type II copper site liganded by three histidines and a water molecule. The solvent site is empty when crystals are reduced with ascorbate. A fully occupied oxygen-coordinate nitrite occupies the solvent site in crystals soaked in nitrite. Ascorbate-reduced crystals soaked in a glycerol-methanol solution and nitrite at -40 degrees C remain colorless at -160 degrees C but turn amber-brown when warmed, suggesting that NO is released. Nitrite is found at one-half occupancy. Five new solvent sites in the oxidized nitrite bound form exhibit defined but different occupancies in the other three forms. These results support a previously proposed mechanism by which nitrite is bound primarily by a single oxygen atom that is protonable, and after reduction and cleavage of that N-O bond, NO is released leaving the oxygen atom bound to the Cu site as hydroxide or water.

Alcaligenes↗