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 667 records · Page 37Linked to original sources

PubMed2006

Changes in the mutagenic and estrogenic activities of 17beta-estradiol after treatment with nitrite.

We determined the changes in the mutagenic and estrogenic activities of 17beta-estradiol after a nitrite treatment. Nitrite-treated 17beta-estradiol showed mutagenic activities toward Salmonella typhimurium strains TA 100 and TA 98. We confirmed that nitrite-treated 17beta-estradiol generated radicals from the results of an analysis of electron spin resonance. By applying an instrumental analysis, we identified 2-nitro-17beta-estradiol to have been formed in the reaction mixture. 2-Nitro-17beta-estradiol did not exhibit mutagenic activities toward Salmonella typhimurium strains, suggesting that other mutagens might have been formed in the reaction mixture. The clastogenic properties of nitrite-treated 17beta-estradiol and 2-nitro-17beta-estradiol were analyzed by a micronucleus test with male ICR mice. Nitrite-treated 17beta-estradiol and 2-nitro-17beta-estradiol induced a significantly higher frequency of micronucleated reticulocytes in mice. The estrogenic activity of 2-nitro-17beta-estradiol was found to be lower than that of 17beta-estradiol. These data suggest that a daily oral intake of 17beta-estradiol and nitrite might induce the formation of mutagenic compounds in our body.

Animals↗

PubMed2005

Ontogenic delays in effects of nitrite exposure on tiger salamanders (Ambystoma tigrinum tigrinum) and wood frogs (Rana sylvatica).

Under certain conditions, nitrite can be present in freshwater systems in quantities that are toxic to the fauna. I exposed wood frog (Rana sylvatica) and eastern tiger salamander (Ambystoma tigrinum tigrinum) embryos and young tadpoles and larvae to elevated concentrations of nitrite in chronic toxicity tests: 0, 0.3, 0.6, 1.2, 2.1, 4.6, and 6.1 mg/L NO2-N, exposing individuals as both embryos and larvae. Nitrite caused significant declines in wood frog hatching success (3.4 mg/L NO2-N, wood frog), and lower concentrations caused significant mortality during the early larval stages (4.6 mg/L NO2-N, salamander; 0.5 mg/L NO2-N, wood frog). Later tests exposing individuals to nitrite only after hatching showed that both wood frog and tiger salamander vulnerability to nitrite declined shortly after hatching. Hence, examining a single life-history stage, especially later in development, may miss critical toxic effects on organisms, causing the researcher potentially to underestimate seriously the ecological consequences of nitrite exposure.

Ambystoma↗

PubMed1978

Effect of nitrite on microsomal cytochrome P-450.

1. Addition of nitrite to anaerobic rat liver microsomes leads to the appearance of a difference spectrum similar to the spectrum of the ferrous cytochrome P-450-NO complex. A Soret band is found at 444 nm in phenobarbital-stimulated microsomes but at 442 nm in 3-methylcholanthrene-stimulated microsomes. An alpha-band is located at 583 nm in both types of microsome. 2. The initial nitrite-induced difference spectrum is converted into a spectrum lacking a Soret band but with a prominent absorbance minimum at 417 nm. This is more rapid in microsomes from phenobarbital-treated animals where it is completed in 8 min than in microsomes from 3-methylcholanthrene-treated animals. A similar spectrum can be obtained by addition of nitrite to urea-treated microsomes in which cytochrome P-450 has been converted to cytochrome P-420. 3. Azo cleavage of neoprontosil in anaerobic microsomes is markedly inhibited by 1 mM nitrite. In contrast, oxidative drug metabolism is affected only by very high nitrite concentrations around 100 mM. It is concluded that in anaerobic microsomes, NO formed from nitrite complexes with ferrous cytochrome P-450 and thereby inhibits reductive drug metabolism.

Animals↗

PubMed1988

Nitrite inhalants: patterns of abuse in Baltimore and Washington, D.C.

Nitrite inhalants, as drugs of abuse, have received a new prominence in the literature since their use has been associated with Kaposi's Sarcoma and possibly other manifestations of acquired immunodeficiency syndrome (AIDS). Changes in patterns and prevalence of use have not been investigated since the onset of the AIDS epidemic. We have examined the abuse patterns of nitrite inhalants (poppers) in several different groups. The use of poppers among drug abusers in the Baltimore-Washington, D.C. metropolitan area has remained constant over the past 5 years, with the prevalence of use being approximately 11% for recreational drug users and 22% for heavy abusers. Self-reported use by a homosexual group had decreased over the same time period. Sixty-nine percent of the homosexual sample had experience with nitrities, but only 21% had used them in the 6 months prior to being surveyed. The mean interval since last use was 25 months, and since peak use, 4.1 years. Among substance abusers, nitrites appear to be a drug whose use starts late, with the mean age of first use being 25.6 years compared to 14.6 years for glue, 17.6 years for marijuana, and 18.5 years for heroin. We found both heterosexual and homosexual groups utilize nitrites primarily to "get high," but homosexuals more often use them during overt sexual activity. Experience with amyl nitrite was much more prevalent than that with the butyl derivative in both populations. We conclude that the prevalence of nitrite abuse among drug users has not changed as a result of the AIDS epidemic, but such use appears to have decreased within the homosexual community.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Production of nitric oxide (NO) during the oxidation of human oxyhemoglobin by nitrite: application of a NO-selective electrode for the measurement of NO.

By using a nitric oxide (NO) selective electrode system. NO produced during the oxidation of human hemoglobin by nitrite was monitored. When 160 microM oxyhemoglobin (in heme) was reacted with 500 microM nitrite. NO was generated quickly at the initial lag phase of the oxidation of oxyhemoglobin by nitrite and decreased gradually during the second burst phase of the reaction. While the oxidation of oxyhemoglobin by nitrite proceeded in a sigmoidal manner including the initial lag phase and second burst phase. The maximal amount of NO produced under this condition was estimated to be 48 microM. According to the increase of nitrite concentrations added, the amounts of NO produced at the initial phase increased, being in good accordance with the increased rate of the oxidation of oxyhemoglobin. These results strongly suggest the critical role of NO in the oxidation mechanism of oxyhemoglobin by nitrite.

Electrodes↗

PubMed1995

[Effect of sodium nitrite on Trichomonas vaginalis].

We have investigated the action of sodium nitrite on the growth and morphologic changes of T. vaginalis and on the treatment of subcutaneous abscess by trichomonad in mice. Sodium nitrite inhibited the growth of metronidazole-sensitive KT9 isolate and metronidazole-resistant CDC85 strain of T. vaginalis as concentration of 6 mM and 10 mM, respectively. Intraperitoneal injection of sodium nitrite (70 micrograms, 100 micrograms, 130 micrograms/g body weight) did not reduce the size of abscess produced by subcutaneous inoculation of T. vaginalis in mice. T. vaginalis, treated with sodium nitrite at concentration giving about 50% inhibition of growth, showed fissures, many vacuoles and electron-translucent zone in the cytoplasm by transmission electron microscopy. In the case of CDC85 treated with 9 mM sodium nitrite, hydrogenosomal matrical change, destruction of hydrogenosomal membrane, autophagic vacuoles, disappearance of Golgi complex and polysome were notably observed. With above results, it is assumed that sodium nitrite inhibits the growth of metronidazole-sensitive and--resistant strains of T. vaginalis and induces the morphological changes of T. vaginalis although it does not affect in reducing of abscess size by T. vaginalis in mice.

Abscess↗

PubMed1999

[The evaluation of nitrates and nitrites food intake among Polish households in 1991-1995].

The studies on nitrates and nitrites food intakes in year 1991-1995 were carried out in four types of households i.e. works, worker-farmers, farmers, pensioners and retired persons and from 1993 in self-employed households and families maintaining themselves on non-income sources; altogether and with regard to the number of persons in family. Using household budget data and literature concerning nitrates and nitrites contents in food products, mean and maximum food intakes of these compounds were calculated and compared to acceptable daily intake (ADI) taking into consideration main sources of them. The obtained results indicated that the mean nitrate and nitrite food intakes did not exceed ADI but maximum intakes of one were several times higher than ADI. Nitrate and nitrite food intakes depended on type of household being highest at farmers, pensioners and the number of persons in family. Six persons families took nearly half less than did one-person one. There were no differences in main food sources of nitrates and nitrites for all types of households and number of person in families. Vegetables and their products supplied 94-98% of nitrates whereas meat products supplied 98% of nitrites.

Adult↗

PubMedDate not supplied

[Damage to erythrocytes caused by the interaction of nitrite-ions with hemoglobin].

The formation of two hemoglobin forms (methemoglobin and nitrite methemoglobin) in native human erythrocytes in the presence of sodium nitrite in suspension was shown. In normal erythrocytes, the interaction of intracellular oxyhemoglobin with nitrite ions results in the formation of methemoglobin, whereas in metabolically exhausted erythrocytes, this leads predominantly to the formation of nitrite methemoglobin. The nitrite methemoglobin reacts with hydrogen peroxide to form reactive intermediates (e.g. peroxynitrous acid) and the products of hemoglobin destruction. During the storage of erythrocyte suspensions containing methemoglobin and modified nitrite methemoglobin, differences in the forms of erythrocytes and the degree of their hemolysis were revealed. It is assumed that the formation of methemoglobin leads to the destruction of erythrocytes.

Erythrocytes↗

PubMed1999

Kinetic studies on the oxidation of nitrite by horseradish peroxidase and lactoperoxidase.

The reaction of nitrite (NO2-) with horseradish peroxidase and lactoperoxidase was studied. Sequential mixing stopped-flow measurements gave the following values for the rate constants of the reaction of nitrite with compounds II (oxoferryl heme intermediates) of horseradish peroxidase and lactoperoxidase at pH 7.0, 13.3 +/- 0.07 mol(-1) dm3 s(-1) and 3.5 +/- 0.05 x 10(4) mol(-1) dm3 s(-1), respectively. Nitrite, at neutral pH, influenced measurements of activity of lactoperoxidase with typical substrates like 2,2'-azino-bis[ethyl-benzothiazoline-(6)-sulphonic acid] (ABTS), guaiacol or thiocyanate (SCN-). The rate of ABTS and guaiacol oxidation increased linearly with nitrite concentration up to 2.5-5 mmol dm(-3). On the other hand, two-electron SCN- oxidation was inhibited in the presence of nitrite. Thus, nitrite competed with the investigated substrates of lactoperoxidase. The intermediate, most probably nitrogen dioxide (*NO2), reacted more rapidly with ABTS or guaiacol than did lactoperoxidase compound II. It did not, however, effectively oxidize SCN- to OSCN-. NO2- did not influence the activity measurements of horseradish peroxidase by ABTS or guaiacol method.

Benzothiazoles↗

PubMed2000

[Nitrates and nitrites in homemade and industrial cheeses commercialized in the Southern region of Minas Gerais, Brazil].

The evaluation of nitrate and nitrite in homemade and industrialized cheeses commercialized in the southern region of Minas Gerais State, was the aim of this work. In Brazil, the use of these additives is permitted at maximum levels of 50 mg/kg. The basis of the previously validated method is the quantitative reduction of nitrate to nitrite through cadmium column and spectrophotometric determination after nitrite diazotation with sulphanilic acid/alpha-naphtol reagent. From all samples analyzed, 38 (88.37%) showed neither a nitrate nor nitrite detectable content; 5 samples (11.63%) presented nitrate, 4 of them being above the tolerated level and only one (2.33%) showed detectable nitrite, however below the permissible limit. The majority of samples did not show nitrate or nitrite at detectable levels. However, though probably safe from a toxicological point of view, the results can implicate an increased risk of bacteriological contamination.

Brazil↗

PubMed2001

[Nitrate and nitrite content in potatoes from ecological and conventional farms].

The aim of this investigation was to determine nitrate and nitrite content in potatoes from ecological and conventional farms. The influence of variety on nitrate and nitrite content was also evaluated. Vegetables and potatoes from ecological cultures are supposed to contain less nitrates and nitrites and on this basis could have been advised for children, sick and people in special physiological stages. Nitrite content was determined colorimetrically, with sulfanilic acid, nitrate content was determined following reduction of nitrites by means of metallic cadmium. The results showed significantly lower nitrate content in potatoes from ecological farms, and almost twice higher in those from conventional farms. The nitrite content showed no differentiation in conventional and ecological farms. Within three varieties of potatoes (sokół, bryza, ania) significantly highest content of nitrate was determined in bryza. Considering low nitrate level potatoes from ecological farms could be advised for children and sick people, but for the complete safety evaluation also content of other contaminants (i.e. heavy metals) have to be assessed.

Colorimetry↗

PubMed2004

Operation of a nitrite-type airlift reactor at low DO concentration.

Laboratory scale experiments were performed to evaluate the feasibility and potential of nitrite-type nitrification process with an airlift reactor having aerobic granular biomass. Oxygen limitation was selected as the main control parameter for inhibiting the growth of nitrite oxidizer and thus achieving only nitritation. To enhance granule formation, seeding of methanogenic anaerobic granules was used to serve as an initial carrier material. After 90 days of operation at low DO concentration of less than 1.0 mg/l, the maximum nitrite conversion rate of 2.6 g NO2-N/L/d could be achieved. During the continuing year-long stable operation, the granular mass of nitritation granules increased to about 15 g VSS/L with an average granule size of 0.7 mm. Nitrate-N concentration was observed to be below 10 mg/L during the whole operational period. From the results of the experiments, it is concluded that a granule-type airlift reactor with DO control is feasible for achieving stable nitritation.

Bacteria, Aerobic↗

PubMed2004

Difficulties in maintaining long-term partial nitritation of ammonium-rich sludge digester liquids in a moving-bed biofilm reactor (MBBR).

Nitrogen can be eliminated effectively from sludge digester effluents by anaerobic ammonium oxidation (anammox), but 55-60% of the ammonium must first be oxidized to nitrite. Although a continuous flow stirred tank reactor (CSTR) with suspended biomass could be used, its hydraulic dilution rate is limited to 0.8-1 d(-1) (30 degrees C). Higher specific nitrite production rates can be achieved by sludge retention, as shown here for a moving-bed biofilm reactor (MBBR) with Kaldnes carriers on laboratory and pilot scales. The maximum nitrite production rate amounted to 2.7 gNO2-Nm(-2)d(-1) (3 gO2m(-3)d(-1), 30.5 degrees C), thus doubling the dilution rate compared to CSTR operation with suspended biomass for a supernatant with 700 gNH4-Nm(-3). Whenever the available alkalinity was fully consumed, an optimal amount of nitrite was produced. However, a significant amount of nitrate was produced after 11 months of operation, making the effluent unsuitable for anaerobic ammonium oxidation. Because the sludge retention time (SRT) is relatively long in biofilm systems, slow growth of nitrite oxidizers occurs. None of the selection criteria applied - a high ammonium loading rate, high free ammonia or low oxygen concentration - led to selective suppression of nitrite oxidation. A CSTR or SBR with suspended biomass is consequently recommended for full-scale operation.

Bacteria, Anaerobic↗

PubMed2004

Nitrite accumulation by aeration controlled in sequencing batch reactors treating domestic wastewater.

The feasibility of obtaining and keeping stable nitrite accumulation in Sequencing Batch Reactors (SBRs) treating domestic wastewater is studied. The final product of ammonium oxidation is either reproducible nitrate or nitrite depending on the aeration strategy. With the aerobic-anoxic sequence, two SBRs fed with domestic wastewater are operated in parallel. One SBR (SBR1) is controlled by the aeration control strategy, and the other SBR (SBR2) by alternate aeration control strategy. Based on the on-line indirect measurements of DO and pH, the relationship between pH (or DO) and nitrogen concentration (NH4+-N, NO(3-)-N and NO(2-)-N) is investigated. The result indicates that pH and DO can be used as control parameters for the real-time aeration control strategy to obtain nitritation in SBR treating domestic wastewater. The result of SBR1 indicates that long-term stable nitritation is possible at 32+/-1 degrees C. The result of SBR2 indicates that the aeration control strategy is necessary for nitritation during the acclimation period, because the nitrite accumulation disappears when the aeration is extended.

Bacteria, Anaerobic↗

PubMed2005

[Nitrite and nitrate content in selected herbal medicaments used in obesity and diabetes mellitus type 2 treatment].

In this study we assessed the content of nitrites III and V in selected herbal medicaments used in obesity and diabetes mellitus type 2 treatment. The spectrophotometry Griess and Ilosvay method with cadmium column was used. Nitrites III content in all investigated herbal medicaments did not make any health menace for patients but content of nitrites V is very high and impacts on ADI. The percentage of extraction nitrites III was higher than theoretical counting value of 100% extraction, it could be due to nitrites V reduction to nitrites III during boiling.

Diabetes Mellitus, Type 2↗

PubMedDate not supplied

Ion chromatographic determination of nitrate and nitrite in vegetable and fruit baby foods.

An ion chromatographic method was developed for the determination of nitrate and nitrite in vegetable and fruit baby foods. The introduction of nitrate or nitrite to food may be natural or artificial as a preservative. Because of the higher pH found in babies' stomachs, nitrate can act as a reservoir for the production of nitrite by nitrate-reducing bacteria that can be harbored in the intestinal tract. This problem does not exist in adults because of the lower pH of the adult stomach. Exposure to nitrite by infants can result in methemoglobinemia (blue baby syndrome). There are also indications that carcinogenic nitrosamines can be formed from nitrates at the higher pH. These gastric conditions disappear at approximately 6 months of age. In this method, nitrate and nitrite were separated on a hydroxide-selective anion exchange column using online electrolytically generated high-purity hydroxide eluant and detected using suppressed conductivity detection. Average recoveries of spiked nitrite residue ranged from 91 to 104% and spiked nitrate residue ranged from 87 to 104%. This method and the AOAC Official Method yield comparable results for samples containing incurred nitrate residue. In addition, this method eliminates the hazardous waste associated with the use of cadmium found in the AOAC Official Method.

Cadmium↗

PubMed1991

Nitrite-trapping capacity of thioproline in the human body.

Human nitrosating capacity has been monitored using proline; however, N-nitrosothiazolidine 4-carboxylic acid (NTCA; N-nitrosothioproline), one of the predominant N-nitroso compounds in human urine, is also nonmutagenic and, presumably, noncarcinogenic. Thioproline is nitrosated about 1000 times faster than proline in vitro, and NTCA is excreted into the urine without being metabolized. We have therefore proposed thioproline as an effective nitrite-trapping agent in the human body. Recently, we found thioproline in various cooked foods, including cod and dried shiitake mushrooms. In the study reported here, we evaluate the nitrite trapping capacity of thioproline in a male nonsmoking volunteer ingesting NO3- and eating a controlled diet. The highest level of NTCA excreted, 5.89 mumol, was measured after the subject ingested 6 mmol NO3- followed by 0.45 mmol (60 mg) thioproline. We estimated the effective amount of nitrite, defined as the actual amount of nitrite participating in nitrosation in the stomach, to be 0.3% of the NO3- ingested. Thus, the effective amount of NO2- for 6 mmol NO3- ingested was calculated to be 18 mumol, and 33% of this nitrite was trapped by ingestion of 0.45 mmol thioproline. We conclude that thioproline is a most sensitive probe for evaluating human nitrosating capacity and an effective nitrite-trapping agent.

Ascorbic Acid↗

PubMed1990

[Presence of nitrates and nitrites in baker's products and in certain other flour products].

The results of the study demonstrated that the content of nitrates and nitrites in various baker's products varied from 0.96 (in wheat rolls and baguettes) to 44.07 mg KO3/kg in pumpernickel bread. In wholemeal bread, village bread, tourist bread, rye brown bread and Graham bread the content of these compounds was from 1.46 to 27.10 mg KNO3/kg. The mean content of nitrites in these bread sorts was 1.76 mg NaNo2/kg, range 0.10-4.40 mg NaNo2/kg. In white wheat flours (Wrocław flour, cake flour and Poznań flour) the content of nitrates ranged from 1.10 to 19.08 mg KNO3/kg, and in the dishes produced from them in household was from 0.50 to 16.33 mg KNO3/kg. The content of nitrites in these flours was in the range from 0.00 to 4.16 mg NaNo2/kg, and in the products prepared from them it was from 0.00 to 1.60 mg NaNO2/kg. Eleven types were tested also of popular biscuits, wafers, gingerbread and hard cakes in which the content of nitrates was from 3.66 to 17.72 mg/kg, and that of nitrites was from 0.00 to 8.80 mg NaNo2/kg. Considering the average consumption of these products per one person in the seashore region and the mean values of nitrates and nitrites it was calculated that they provided daily about 3.9 mg KNO3 and 0.4 NaNo2, that is about 1.8% of nitrates and 7.7% of nitrites consumed by adults in daily food ration.

Bread↗