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 937 records · Page 52Linked to original sources

PubMed1976

A mechanism for the conversion of oxyhemoglobin to methemoglobin by nitrite.

Each mole of oxyhemoglobin iron converted to methemoglobin causes the oxidation of 1.5 mol of nitrite to nitrate and consumes 1 mol of protons. No oxygen is liberated. The overall reaction has two simultaneously occurring parts. In the beginning the rate-limiting reaction converting O2Hb to metHb is directly proportional to H+ and NO2- concentrations and is independent of metHb. The second portion accounts in major part for the stoichiometry and rate of the overall reaction. In this portion O2Hb tetramers and metHbNO2- are the reactants. Essentially no reaction takes place in the presence of CN-, which displaces nitrite from the metHbNO2-, nor in the presence of 0.5 mol/liter Nal, which converts the O2Hb to alphabeta-dimers. The autocatalytic nature of the overall reaction in the presence of excess nitrite is the result of metHb, which is formed in both parts of the reaction, associating with nitrite to increase the concentration of one reactant of the cyanide-sensitive part. The reaction rates at constant pH in excess nitrite are porportional to the product of the O2Hb concentration and the square of the metHb concentration. The rate increases up to about 66% conversion of O2Hb followed by a decrease as the O2Hb becomes limiting. The dissociation constant of metHbNO2- at 25 degrees C and pH = 6.4 was found to be 1.11+/-0.11 mmol/liter.

Chemical Phenomena↗

PubMedDate not supplied

[The role of xanthine oxidase in the cytotoxic action of nitrates and nitrites].

It is established, that in rat organism nitrites and nitrates can be restored in nitrogen oxide due to nitrate and nitrite reductase activity of xanthine oxidase system. The rat thymocytes were shown in the experiment in vitro to have nitrate reductase activity, which was activated by hypoxanthine and inhibited by allopurinol. As a result of thymocytes apoptosis, provoked by papaverine, there is an essential increase of nitrate reductase activity of xanthine oxidase. The comparative research of thymocytes destruction character under the action of sodium nitroprusside (NP), N-nitrosodimethylamine (NDMA), NaNO2 and NaNO3 has been revealed, that their cytotoxicity, is dose-dependent and it decreases in order of these compounds mentioning. Synergism is revealed at the action on thymocytes of NP combined with sodium nitrite. These data as the results of investigation of EPR-spectrometry as well as use of thymocytes, containing a trap--complex of diethyldithiocarbamate-iron (DETK-Fe), allow to assume, that cytotoxic effect of NP is caused by the action of liberated from it. Cytotoxic action of nitrate is connected with reducibility to nitrite which influences on the cells independently, and nitrite action doesn't depend on its transformation to NO. The death of thymocytes caused by N-nitrosodimethylamine is not a result of its denitrozation.

Animals↗

PubMed2002

Exhaled hydrogen peroxide, nitrite and nitric oxide in healthy children: decrease of hydrogen peroxide by atmospheric nitric oxide.

Hydrogen peroxide (H2O2) and nitrite (NO2-) in exhaled breath condensate have recently been suggested as non-invasive markers of airway inflammation. The goal of this study was to clarify the role of factors that may potentially influence the measurement of H2O2 and nitrite and to look for possible correlations among these inflammatory markers. H2O2 and nitrite values were assessed fluorometrically in breath condensate of 102 healthy children (age 4-18 years) and a detailed status of atopy (including history, lung function and skin prick test) was taken in all children. To find out the role of atmospheric nitric oxide, eNO and envNO were measured via chemiluminescence in association with the sampling of the breath condensate. Median (interquartile range) H2O2 was 0.51 (0.26 - 0.74) microM and nitrite was 3.3 (2.7 4.1) microM. A significant negative correlation between H2O2 and envNO was observed (r = -0.50; p < 0.0001). ENO was independent of envNO at our envNO range up to 56 ppb. No further correlation was found. The inflammatory markers in exhaled breath condensate H2O2, nitrite and eNO are not interrelated to each other in healthy children. Whereas eNO was not dependent on envNO values, high envNO values must be taken into account when measuring H2O2 in exhaled breath condensate.

Adolescent↗

PubMed1999

[Determination of nitrite in serum and tissue by oscillopolarography].

A method for determining nitrite in serum and placenta tissue by oscillopolaropgraphy is reported in this paper. Nitrite in 0.10 ml of serum or placenta homogenate reacts with sulfanilmide and N-1 (1-Naphthyl)-ethylendiamindihydrochloride in diluted hydrochloric acid medium to form an azo compound which can produce a sensitive reductive polarographic wave in ammonium alkaline medium. The wave height is directly proportional to the nitrite content, the method has a detection limit of 0.56 microgram/L (corresponding to the nitrite content of 0.61 mumol/L in serum or 0.22 microgram/g), RSD, of 6.1%-7.8% and recoveries of 92.0%-108.0% (mean value 100.6%). The method is sensitive, simple and can determine the nitrite directly without removal of the proteins in the samples.

Humans↗

PubMed2000

[Determination of trace amounts of nitrite and reaction mechanism by triple-wavelength spectrophotometry].

A new method was proposed for the determination of nitrite ion by triple-wavelength spectrophotometry. This limits ranges of determination are 0-0.560 mg.L-1 nitrite ion at 599.1 nm, 420.6 nm and 283.4 nm. It has been applied to analysis trace amounts of nitrite ion of standard sample and environmental water with satisfactory result, the relative error was less 1.7% and recovery of the real samples was between 96.5 and 100.0%. This method is based on the diazotization-coupling react of thionine with nitrite ion in acidic medium, the mole ratio of thionine:nitrite is 2:1 by the continuous variation and mole ratio method.

Nitrites↗

PubMed1992

[Effect of the fermentation process on levels of nitrates and nitrites in selected vegetables].

The aim of this study was to follow the changes in the levels of nitrates and nitrites throughout the process of fermentation of sauerkraut from white and red cabbage and red beets. The nitrate and nitrite levels were determined in raw and fermentation as well as in red beets and "beet acid" after a week of souring. Nitrate were determined by the brucine method, while nitrates by the Griess colorimetric method. Mean reduction of nitrates in sauerkraut (in relation to raw cabbage) was ca. 55.5% and that of nitrites ca. 76.7%. In the red sour cabbage a decrease in the level of nitrates in relation to the product by ca. 84.1% and in that of nitrites by ca. 67.4% was found. The stabilization of both nitrate levels in both kinds of cabbages followed as after the second month of storage, as confirmed by statistical analysis of the results. In the red beets after the process of fermentation a decrease in the level of nitrates by ca. 91.6% was noted. An undefined portion of the studied compounds passed into the liquid. The "beet acid" contained 595.9 mg/dm1 of nitrates and 3.26 mg/dm3 of nitrites.

Brassica↗

PubMed2003

Dietary nitrate and nitrite levels in an endemic upper gastrointestinal (esophageal and gastric) cancer region of Turkey.

BACKGROUND/AIMS: The aim of this study was investigate nitrate and nitrite levels in some traditional foods and drinking water in Van, an endemic upper gastrointestinal (esophageal and gastric) cancer region of Eastern Turkey. METHODS: Cheese with added herbs, drinking water, bread baked by wood fire and bread baked by burning animal manure specimens collected in the Van region were analyzed by Stahr's modification method. Nitrite was reduced to nitrate by the following three reagents: hydrazine sulphate ((NH2) 2SO4), CuSO4 and NaOH. Nitrate was then determined by coupling reagent containing sulphanlyamide, phosphoric acid and N-1-naphtyl ethylendiamine dihydrochloride. RESULTS: Nitrate and nitrite levels of all traditional foods and nitrite levels of drinking water were very significantly elevated compared to standard values (p<0.001- 0.01). CONCLUSIONS: These findings suggest that the influence of a traditional diet rich in nitrate and nitrite is significant in the development of endemic upper gastrointestinal (esophageal and gastric) cancers in the Van region of Turkey.

Age Distribution↗

PubMed1992

Effect of nitrite ingestion on the bioavailability of folate in the rat.

The effect of nitrite ingestion on the intestinal deconjugation and absorption of folic acid (PGA) and brewers yeast folate was investigated using a rat bioassay and liver folate uptake as the response parameter. Male weanling Sprague Dawley rats were depleted on a low folate AIN-76A formulated basal diet for 21 days. During a 14 day repletion period, folic acid (PGA) and brewers yeast were added to provide 0.25, 0.5 and 1.0 mg of folate per kg of diet. Potassium nitrite was administered as part of the diet at 0.5%. All diets were made isonitrogenous and isocaloric. Based on a parallel line assay, the relative bioavailability of folate in the brewers yeast diet (109) was significantly higher than in the standard diet (PGA = 100). When combined with nitrite, the relative bioavailability of the PGA diet was not significantly different (101), while that of the brewers yeast diet was significantly lower than the standard diet. Concomitant ingestion of nitrite significantly reduced the bioavailability of brewers yeast folate but not that of PGA in rats. This appeared to be a direct effect of oxidation by nitrite on the more susceptible substituted folates in brewers yeast.

Animals↗

PubMedDate not supplied

[Assay validation for determining nitrites and nitrates in biological fluids].

INTRODUCTION: Nitric oxide is an important modulator of numerous physiological and pathophysiological processes. An indirect form to detect NO production has been the quantification of its stable end products, nitrites and nitrates (NO2- + NO3-). These metabolites can be detected with a commercial kit, but it is somewhat expensive and not accessible to some laboratories in our country. OBJECTIVE: To validate an easy, accessible and less expensive assay for detecting nitrates and nitrites in biological fluids. MATERIAL AND METHODS: In this study we determined nitrates and nitrites by reducing nitrates enzymatically with nitrate reductase, followed by nitrites quantification using the Griess reagent. To validate the assay, NO3- concentration was evaluated in aliquots with known amounts of sodium nitrate, also NO2- + NO3- concentrations were detected in plasma containing known amounts of sodium nitrate, finally NO2- + NO3- levels were evaluated in plasma (n = 17) and ascites (n = 11) samples of cirrhotic patients. In samples of patients, NO2- + NO3- levels were also detected by using a commercial kit. RESULTS: The assay that we describe here detects nitrates in the range between 25 to 400 microM/L and nitrites between 25 to 100 microM/L. When specific concentrations of nitrates were added to plasma samples, the recovery percentage in most cases was greater than 95%. In plasma samples of cirrhotic patients, average concentrations of NO2- + NO3- was 44.6 +/- 22.4 microM (mean +/- SD), similar to that found using the commercial kit, 40.9 +/- 18.3 microM/L (p = 0.107). In ascitis samples, similar results using both methods were seen, 64.5 +/- 42.0 vs. 58.2 +/- 39.3 microM/L (p = 0.172) respectively. CONCLUSIONS: Our results suggest that the method described here could be considered as an alternative instead of commercial kits to determine NO2- + NO3- in plasma and ascites samples. In addition, this assay results more attractive because, it does not, require special equipment, it is very accessible to most laboratories, it may be use to assay one or more samples at any given time, but the most important advantage, is its cost effectiveness; thus each sample determination is about one fifth of the cost using the commercial kit.

Body Fluids↗

PubMed2004

On the effect of pharmaceuticals on bacterial nitrite oxidation.

Pharmaceuticals or their metabolites are partially excreted with urine or faeces ending up in raw sewage. Many of these substances are not biodegradable and their presence in influents of municipal wastewater treatment plants may cause adverse effects to sensitive biological processes such as nitrification, while on the other hand, they may go through the activated sludge process unreacted. The second step of nitrification, i.e. oxidation of nitrite to nitrate is particularly sensitive. Inhibition of this step under uncontrolled conditions may lead to accumulation of nitrite nitrogen in the plant effluent, a form of nitrogen which is particularly toxic. The effects caused by the presence of seven different pharmaceuticals to a culture of nitrite-oxidizing bacteria isolated from activated sludge are presented. These pharmaceuticals were ofloxacin, propranolol, clofibrate, triclosan, carbamazepine, diclofenac and sulfamethoxazole. Different effects were observed for each of the pharmaceuticals tested in this study. In the cases of ofloxacin and sulfamethoxazole significant inhibition was observed. Triclosan presented a substantial inhibitory effect on the substrate (nitrite) reduction rate. The long-term effect of triclosan on nitrite oxidizers was also examined in a CSTR reactor and conclusions were drawn regarding the reversibility of the inhibition caused by this compound.

Bacteria, Anaerobic↗

PubMed2005

Effect of sublethal levels of nitrite on some blood parameters of juvenile Labeo rohita (Hamilton-buchanan).

Juveniles of L. rohita were exposed to sublethal levels of nitrite (0.02, 0.1 and 0.4 mg/l) for 2, 24, 48 and 96 hr. The time of exposure at individual concentrations of nitrite did not show any significant difference in haemoglobin, cortisol, chloride and lactic acid. Haematocrit showed significant reduction with increasing concentration of nitrite irrespective of duration of exposure. Fishes exposed to 0.4 mg/l nitrite showed significantly high levels of glucose beyond 2 hr. The mean erythrocytic fragility of fishes exposed to the 3 concentrations of nitrite for 3 exposure periods showed significant higher sensitivity to osmotic stress. The results suggest decrease in haematocrit and cell wall strength of erythrocytes creating stress to fish.

Analysis of Variance↗

PubMed2005

Achieving and maintaining biological nitrogen removal via nitrite under normal conditions.

The principal aim of this paper is to develop an approach to realize stable biological nitrogen removal via nitrite under normal conditions. Validation of the new method was established on laboratory-scale experiments applying the sequencing batch reactor (SBR) activated sludge process to domestic wastewater with low C/N ratio. The addition of sodium chloride (NaCl) to influent was established to achieve nitrite build-up. The high nitrite accumulation, depending on the salinity in influent and the application duration of salt, was obtained in SBRs treating saline wastewater. The maintenance results indicated that the real-time SBRs can maintain stable nitrite accumulation, but conversion from shorter nitrification-denitrification to full nitrification-denitrification was observed after some operation cycles in the other SBR with fixed-time control. The presented method is valuable to offer a solution to realize and to maintain nitrogen removal via nitrite under normal conditions.

Bioreactors↗

PubMed1992

Nitrite and nitrosamine synthesis by hepatocytes isolated from normal woodchucks (Marmota monax) and woodchucks chronically infected with woodchuck hepatitis virus.

Hepatocytes isolated from woodchucks (Marmota monax) were shown to produce nitrite in vitro from L-arginine after stimulation with lipopolysaccharide (LPS). Hepatocytes isolated from woodchucks that were chronic carriers of woodchuck hepatitis virus formed twice as much nitrite as hepatocytes from noninfected animals. Nitrite synthesis by hepatocytes was directly related to L-arginine and LPS concentrations in the tissue culture medium and reached a plateau at 0.5 mM L-arginine and 1.0 micrograms/ml LPS. LPS-stimulated hepatocytes nitrosated morpholine to form N-nitrosomorpholine in the presence of L-arginine at a physiological pH of 7.4. There was a 10-fold increase in N-nitrosomorpholine production when hepatocytes were stimulated with LPS compared to unstimulated hepatocytes under similar conditions when both nitrite and morpholine were directly added to the medium. NG-monomethyl-L-arginine, a selective inhibitor of nitric oxide synthase, inhibited formation of both nitrite and N-nitrosomorpholine. These results demonstrate that nitrosating agents are formed in hepatocytes via the L-arginine-nitric oxide pathway. This suggests that endogenous formation of carcinogenic N-nitroso compounds could influence the process of hepatocarcinogenesis in woodchucks with chronic woodchuck hepatitis virus infection.

Animals↗

PubMedDate not supplied

Lipoprotein (a) and nitrites in Behcet's disease: relationship with disease activity and vascular complications.

Our objective was the assessment of serum lipoprotein(a) {Lp(a)} and nitrites in Behcet's disease (BD) patients and their relation to vascular events and disease activity. Thirty cases of BD and 14 healthy volunteers were included. Serum levels of Lp(a) were estimated using enzyme-linked immunosorbent assays. Serum nitrites were measured according to the method of Benjamin and Vallence. Compared to controls, BD patients had significantly lower concentrations of serum nitrites, and significantly higher concentrations of Serum Lp(a). Significantly higher levels of serum Lp(a) were observed in patients with vascular complications, while significantly lower levels of serum nitrites were found during disease activity and in patients with erythema nodosum like lesions. Increased serum lipoprotein (a) may contribute to the increased incidence of vascular complications in Behcet's disease. Decreased nitrites can be considered as a marker of disease activity that may be related to endothelial dysfunction.

Adult↗

PubMed2005

Near-fatal methemoglobinemia after recreational inhalation of amyl nitrite aerosolized with a compressed gas blower.

Adverse effects associated with recreational inhalation of nitrites are usually mild and rarely life-threatening. We report a rare case of near-fatal methemoglobinemia after inhalation of amyl nitrite after aerosolizing the liquid using a compressed gas blower designed to clean photographic equipment that employed hydrofluoroalkane-134a as a propellant. A 31-year-old previously healthy male became dyspneic and fainted soon after the recreational inhalation of amyl nitrite aerosolized using a compressed gas blower. He was brought to the emergency department with severe cyanotic appearance and profound shock. Oxygen saturation was 82%, unresponsive to oxygen supply. His methemoglobin blood level was 52.2%. After 100 mg of methylene blue (2 mg/kg body weight) was administered intravenously, he recovered consciousness, and dyspnea and cyanosis subsided gradually. This case illustrates the extraordinary hazard of the use of a compressed gas blower in the recreational inhalation of nitrites. Prompt recognition and rapid antidotal treatment may adequately correct near-fatal overdose associated with recreational use of amyl nitrite.

Adult↗

PubMed2006

[Nitrate and nitrite contents of drinking water in some areas of Shanxi Province].

OBJECTIVE: To understand the nitrate and nitrite contents of drinking water in Shanxi Province, China. METHODS: Water samples were collected from Pingding and Taigu counties and Taiyuan City. The nitrate and nitrite contents were determined following the 'Drinking water hygienic standard-2001'. RESULTS: The median nitrate content of drinking water was 3.5 mg/L, and the proportion of samples above national hygienic standard for drinking water was 4.0% in study areas. The median nitrite content of well water samples(5.l mg/L) was higher than that of tape water (2.7 mg/L). The median content of nitrite was 0.004 mg/L for all samples, and the median content of spring water was highest (0.017 mg/L) than that of other sources. Conclusion The contents of nitrate and nitrite in drinking water were similar to that reported form other regions. Maternal nitrate exposure from drinking water may not be among the important risk factors of high prevalence of birth defects in Shanxi Province.

China↗

PubMed2006

[Effects of nitrite on phosphorus uptake in anaerobic/oxic process].

Abstract:Intermediate products of biological nitrogen removal process, nitrate and nitrite, could be used as electron acceptors for phosphorus removal. This study investigated the effects of nitrite on phosphorus uptake in anaerobic/oxic (A/O) biological phosphorus removal process. The results indicated that in addition to oxygen and nitrate (DPB(Na), Denitrifying Phosphorus removal Bacteria with nitrate as electron acceptor), to some extent, nitrite can also serve as electron acceptor to achieve the nitrite denitrifying phosphorus removal (DPB(Ni)). The quantity and rate of phosphorus uptake of DPBNi, however, were evidently lower than that of DPBN,. The nitrite existed in anoxic reactor made no difference to the quantity and rate of denitrifying phosphorus removal. But it would reduce the consumption of nitrate. Moreover, the data showed that the aerobic phosphate uptake of DPBNi was lower than that of anaerobic phosphorus-released sludge in traditional A/O process. However, there was no much difference between these two kinds of sludge in terms of the total phosphorus uptake quantity and the effluent quality.

Bacteria, Anaerobic↗

PubMed1976

[Metabolism of nitrates-nitrites].

Once the pair nitrate-nitrite--in quantity respectively set by the ingestion level or transformation level by intestinal bacteria--has entered through the intestinal mucosa, it may react with active biochemical groups. Nitrite, owing to its high oxido-reduction potential, may induce the oxidation of a large number of compounds, as for example the Fe++ heme-Fe+++ hemine system, reduced cytochromes-oxidized cytochromes system, etc. If the presence of nitrite in blood is not clearly established, this is due to the nitrite high chemical reactivity. Moreover, a transformation by the tissues of nitrates into nitrites after a nitro-reduction is quite possible.

Amines↗