Showing papers on "Nitrite published in 1978"

Nitrite and nitrate are formed by endogenous synthesis in the human intestine

Abstract: Studies of nitrate balance in humans and analyses of fecal and ileostomy samples indicate that nitrite and nitrate are formed de novo in the intestine, possibly by heterotrophic nitrification. These findings significantly alter our previous conceptions of human exposure to nitrite and suggest an even wider role for nitrite in the etiology of human cancer.

Loss of fixed nitrogen from soils by nitric oxide exhalation

Abstract: LABORATORY studies1–8 have indicated that chemical de-nitrification processes in nitrogen rich soils and nitrite solutions can produce NO or NO2 and perhaps methyl nitrite9. It has been suggested1–6 that self decomposition of nitrite produces various gaseous nitrogen compounds including nitric oxide (NO) and it was thought that NO was unlikely to escape from the soil because in aerobic soils NO is readily oxidised by molecular oxygen to NO2 and this in turn is rapidly adsorbed by soil materials and by soil water1,2. However the half life of oxidation is dependent on the NO concentration because it is a termolecular reaction10,11. At concentrations of 100 p.p.m. or greater (as in some studies) the half life for oxidation of NO to NO2 by atmospheric oxygen is one hour or less respectively, whereas at low concentrations (∼0.01 p.p.m.) the half life for this oxidation is of the order of 104 h. This variation in the oxidation rate by molecular oxygen explains why NO at low concentrations in the field can pass unoxidised from the soil to the atmosphere and perhaps explains why in some of the laboratory studies (at high concentrations) NO2 and not NO is detected. This NO exhalation in the field could not be detected previously due to the lack of a sufficiently sensitive measurement technique. We report here the first measurements indicating that NO is continuously exhaled from soils including ungrazed, unfertilised grassland. The measured rates of exhalation from the soil to the atmosphere are 0.06 to 0.73 × 10−11 kg nitrogen m−2 s−1 (equivalent to 0.2 to 2.3 kg N ha−1 yr−1). We show that this exhalation of NO is a significant source of nitrogen oxides (NOx) in the lower atmosphere as has been previously suggested12,13. These nitrogen oxides exert a direct influence on the ambient ozone and hydroxyl radical concentrations14 which in turn predominantly determine the oxidation rate of almost all substances in the troposphere.

Prevention and Treatment of Nitrite Toxicity in Juvenile Steelhead Trout (Salmo gairdneri)

Abstract: The efficacy of mineral salts, pH, and tetramethylthianine (methylene blue) treatment in reducing the acute toxicity of nitrite to fingerling steelhead trout (Salmo gairdneri) was determined using ...

Acute Toxicity of Ammonia and Nitrite to Cutthroat Trout Fry

Abstract: The toxicity of ammonia and of nitrite was tested on cutthroat trout (Salmo clarki) fry (1-3 g) for periods up to a month in eight laboratory flow-through bioassays. Median lethal concentration (LC50) values for ammonia (mg/liter un-ionized NH3) were 0.5-0.8 for 96 hours, and 0.3-0.6 for 36 days. Nitrite LC50 values (mg/liter NO2-N) were 0.5-0.6 for 96 hours, and 0.4 for 36 days. Tissues of fish exposed for 29 days to 0.34 mg/liter un-ionized ammonia evidenced degenerative changes in gills, kidneys, and livers. Cutthroat trout fry are comparable to rainbow trout (Salmo gairdneri) fry in their susceptibility to acute toxicity from aqueous ammonia and nitrite.

Determination of a non-volatile N-nitrosamine on a food matrix

Abstract: A method devised for the determination of N-nitrososarcosine, in which the N-nitrosamine in solution is denitrosated with hydrogen bromide to form volatile products that are rapidly removed and determined in a chemiluminescence analyser, has been applied successfully to the same compound on powdered corn flakes. Differentiation of N-nitrososarcosine and a number of other N-nitrosamines and N-nitrosamides from inorganic nitrite was achieved by decomposing the nitrite with acetic acid prior to the denitrosation of the N-nitroso compounds. In the presence of a secondary-amine receptor limited nitrosation can occur during the process of differentiation but this can be prevented through the use of ascorbyl palmitate. In differentiating between large amounts of nitrite and much lower levels of N-nitrososarcosine on corn flakes, using a chemiluminescence analyser, the duration of the response from the nitrite can be shortened by freeze-drying the food matrix in the presence of ascorbic acid. The spectrophotometric determination of N-nitrososarcosine as nitrosyl bromide released into solution by the action of hydrogen bromide was hindered by the presence of powdered corn flakes.

Regulation of nitrate reduction by light, ATP and mitochondrial respiration in wheat leaves

Abstract: ASSIMILATION of nitrate in leaves is closely linked with photosynthesis1,2 because ammonia, the end product of the former process, is incorporated into amino acids by means of carbon skeletons derived from the assimilation of CO2. Canvin and Atkins3,4 have shown that the reduction of nitrate to nitrite in leaves of barley is dependent on light and ceases when the light is extinguished. On the other hand, in the in vivo5 method for assay of nitrate reductase, nitrate is reduced to nitrite by leaf disks even in the dark. As Canvin and Atkins3,4 pointed out, the in vivo method is not a true reflection of what happens in plants in physiological conditions. A regulatory mechanism must exist in leaves, which shuts off nitrate reduction immediately when light is extinguished, so that the accumulation of toxic amounts of nitrite, which can only be reduced by photosynthetic reactions6, is avoided. We now propose that this regulation functions through mitochondrial respiration, which operates in the dark, but is inhibited in light, because of the increased cytoplasmic adenylate charge due to photosynthesis.

A mutation leading to the total lack of nitrite reductase activity in Escherichia coli K 12

Abstract: Mutants of E. coli, completely devoid of nitrite reductase activity with glucose or formate as donor were studied. Biochemical analysis indicates that they are simultaneously affected in nitrate reductase, nitrite reductase, fumarate reductase and hydrogenase activities as well as in cytochrome c552 biosynthesis. The use of an antiserum specific for nitrate reductase shows that the nitrate reductase protein is probably missing. A single mutation is responsible for this phenotype: the gene affected, nir R, is located close to tyr R i.e. at 29 min on the chromosomal map.

Nitrate Utilization by the Diatom Skeletonema costatum: I. Kinetics of Nitrate Uptake

Abstract: Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased.

Denitrifying Pseudomonas aeruginosa: some parameters of growth and active transport.

Abstract: Optimal cell yield of Pseudomonas aeruginosa grown under denitrifying conditions was obtained with 100 mM nitrate as the terminal electron acceptor, irrespective of the medium used. Nitrite as the terminal electron acceptor supported poor denitrifying growth when concentrations of less than 15 mM, but not higher, were used, apparently owing to toxicity exerted by nitrite. Nitrite accumulated in the medium during early exponential phase when nitrate was the terminal electron acceptor and then decreased to extinction before midexponential phase. The maximal rate of glucose and gluconate transport was supported by 1 mM nitrate or nitrite as the terminal electron acceptor under anaerobic conditions. The transport rate was greater with nitrate than with nitrite as the terminal electron acceptor, but the greatest transport rate was observed under aerobic conditions with oxygen as the terminal electron acceptor. When P. aeruginosa was inoculated into a denitrifying environment, nitrate reductase was detected after 3 h of incubation, nitrite reductase was detected after another 4 h of incubation, and maximal nitrate and nitrite reductase activities peaked together during midexponential phase. The latter coincided with maximal glucose transport activity.

Estimate of the volatile nitrosamine content of UK food

Abstract: MANY nitrosamines are carcinogenic1 and can be formed by the interaction of nitrite with primary2, secondary3 or tertiary amines4, or even quaternary ammonium salts5. Foods contain many amines, and in cured meats sodium nitrite provides the other precursor for the potential formation of nitrosamines. Some strains of bacteria reduce nitrate to nitrite, so that nitrate in conjunction with the appropriate amine could also lead to nitrosamine formation6. There have been several studies in which cured meats and a few other foods have been examined for nitrosamines, although most of these have been restricted to the detection of the volatile dialkyl and simple heterocyclic compounds7. Combined gas chromatography and mass spectrometry is the most reliable method, and has a typical detection limit of 1 µg per kg of food for volatile nitrosamines. More recently, the chemiluminescent detection of nitrosamines has enabled much lower concentrations to be measured8. We have carried out a survey of foods commonly encountered in the UK, using mass spectrometry9 and chemiluminescence, and we now summarise our data to assess the intake of volatile nitrosamines from these foods.

Improved colorimetric method for determining nitrate and nitrate in foods.

Abstract: A method is described for determining nitrate and nitrite in cured meat products, cheeses, and vegetables. The nitrite is determined colorimetrically by diazotization of sulfanilic acid and subsequent coupling with N-(1-naphthyl)-ethylenediamine. The concentration of nitrate plus nitrite is determined similarly but after reduction of the nitrate to nitrite on a cadmium column. The difference of the 2 values is a measure of the nitrate concentration. The main improvements are replacing the Griess reagent, which contains a carcinogen, with a mixture of sulfanile acid and N-(1-naphthyl)-ethylenediamine, providing for adjustment of pH of the sample suspension during extraction and digestion by heating, and maintaining constant pH by controlled addition of buffers and acids during color development. The method was successfully applied to the analysis of 15 samples of meat products, 23 cheeses, and 6 different vegetables. The average recovery of sodium nitrite added at levels ranging from 10 to 30 ppm was 95% and recovery of sodium nitrate added at levels from 30 to 400 ppm was 94% (corrected for cadmium column efficiency).

EFFECT OF SORBIC ACID AND SODIUM NITRITE ON Clostridium botulinum OUTGROWTH AND TOXIN PRODUCTION IN CANNED COMMINUTED PORK

Abstract: Experiments to determine the effect of sorbic acid alone and in combination with low nitrite and phosphate on botulinal toxin production in inoculated perishable, canned, comminuted, cured pork were conducted. Forty-eight test lots of product were inoculated with approximately 100 spores per gram of five strains each of type A and B Clostridium botulinum. Twenty-five cans of each test lot were incubated at 27° C for up to 110 days. The time of swelling was recorded for each can and the first 10 swells per test lot were tested for toxin. Multiple regression analysis of the time to first swell showed nitrite concentration had a significant linear effect on delaying outgrowth and toxin production of C. botulinum. Sorbic acid concentration was also significantly related to inhibition but through the fourth power of sorbic acid concentration. The use of either sodium acid pyrophosphate or sodium hexametaphosphate was synergistic with sorbic acid as indicated by their statistically significant positive interactions. Several test lots containing 0.2% sorbic acid and either phosphate had no toxic swells after 110 days of incubation with or without 50 ppm NaNO2. These data indicate that sorbic acid may be a potential alternative preservative to high levels of nitrite in canned, comminuted pork products.

Nitrate Utilization by the Diatom Skeletonema costatum: II. Regulation of Nitrate Uptake.

Abstract: Nitrate utilization has been characterized in nitrogen-deficient cells of the marine diatom Skeletonema costatum. In order to separate nitrate uptake from nitrate reduction, nitrate reductase activity was suppressed with tungstate. Neither nitrite nor the presence of amino acids in the external medium or darkness affects nitrate uptake kinetics. Ammonium strongly inhibits carrier-mediated nitrate uptake, without affecting diffusion transfer. A model is proposed for the uptake and assimilation of nitrate in S. costatum and their regulation by ammonium ions.

Effects of low concentrations of bisulfite-sulfite and nitrite on microorganisms.

Abstract: A wide range of microorganisms was tested to determine their sensitivity to low concentrations of bisulfite-sulfite and nitrite, solubility products of SO2 and NO2, respectively. Photosynthesis by blue-green algae (cyanobacteria) was more strongly inhibited by 0.1 mM bisulfite-sulfite and 1 mM nitrite at pH 6.0 than photosynthesis by eucaryotic algae and respiration of bacteria, fungi, and protozoa. At pH 7.7, blue-green algae were still more sensitive to bisulfite-sulfite and nitrite than eucaryotic algae, but the toxicity of bisulfite-sulfite and nitrite decreased as the pH increased. Photosynthesis by Anabaena flos-aquae at pH 6.0 was inhibited 25% by a bisulfite-sulfite concentration of 10 micrometer and 15% by a nitrite concentration of 50 micrometer. Photosynthesis by the blue-green alga, Lyngbya sp., was not exceptionally sensitive to chlorate and thiosulfate. Acetylene-reducing activity of Beijerinckia indica was completely inhibited by 0.1 mM bisulfite-sulfite at pH 4.0, the suppression being decreased with increasing pH.

Metal corrosion inhibitor

Abstract: Metal corrosion inhibitor comprising (a) benzoic acid and/or a benzoate, (b) nitrous acid and/or a nitrite, (c) phosphoric acid and/or a phosphate, and (d) at least one selected from mercaptobenzothiazole, its salts, benzotriazole and tolyltriazole, which can exhibit excellent anti-corrosive property to various metals for a long term and can be diluted with an aqueous liquor and can be employed in combination with usual anti-freezing agents.

Aerobic and anaerobic growth of Paracoccus denitrificans on methanol.

Abstract: 1. The dye-linked methanol dehydrogenase from Paracoccus denitrificans grown aerobically on methanol has been purified and its properties compared with similar enzymes from other bacteria. It was shown to be specific and to have high affinity for primary alcohols and formaldehyde as substrate, ammonia was the best activator and the enzyme could be linked to reduction of phenazine methosulphate. 2. Paracoccus denitrificans could be grown anaerobically on methanol, using nitrate or nitrite as electron acceptor. The methanol dehydrogenase synthesized under these conditions could not be differentiated from the aerobically-synthesized enzyme. 3. Activities of methanol dehydrogenase, formaldehyde dehydrogenase, formate dehydrogenase, nitrate reductase and nitrite reductase were measured under aerobic and anaerobic growth conditions. 4. Difference spectra of reduced and oxidized cytochromes in membrane and supernatant fractions of methanol-grown P. denitrificans were measured. 5. From the results of the spectral and enzymatic analyses it has been suggested that anaerobic growth on methanol/nitrate is made possible by reduction of nitrate to nitrite using electrons derived from the pyridine nucleotide-linked dehydrogenations of formaldehyde and formate, the nitrite so produced then functioning as electron acceptor for methanol dehydrogenase via cytochrome c and nitrite reductase.

The Use of Nitrite in Meat

Abstract: The continued use of nitrite as a meatcuring agent is currently being questioned by the United States Department of Agriculture. In one way, the problem with nitrite is no different from the other numerous current problems regarding additives, residues, and contaminants; in another way, the problem with nitrite has certain unique features, which make it a classic case for study. Nitrite added to meat for the purpose of curing may react with amines to produce nitrosamines, which are carcinogens. The confirmed analytical detections of nitrosamines in cured meats

Electron-paramagnetic-resonance studies of the mechanism of leaf nitrite reductase. Signals from the iron–sulphur centre and haem under turnover conditions

Abstract: Low-temperature e.p.r. spectra are presented of nitrite reductase purified from leaves of vegetable marrow (Cucurbita pepo). The oxidized enzyme showed a spectrum at g=6.86, 4.98 and 1.95 corresponding to high-spin Fe(3+) in sirohaem, which disappeared slowly on treatment with nitrite. The midpoint potential of the sirohaem was estimated to be -120mV. On reduction with Na(2)S(2)O(4) or Na(2)S(2)O(4)+Methyl Viologen a spectrum at g=2.038, 1.944 and 1.922 was observed, due to a reduced iron-sulphur centre. The midpoint potential of this centre was very low, about -570mV at pH8.1, decreasing with increasing pH. On addition of cyanide, which binds to haem, and Na(2)S(2)O(4), the iron-sulphur centre became further reduced. We think that this is due to an increased midpoint potential of the iron-sulphur centre. Other ligands to haem, such as CO and the reaction product NH(3), had similar but less pronounced effects, and also changed the lineshape of the iron-sulphur signal. Samples were prepared of the enzyme frozen during the reaction with nitrite, Methyl Viologen and Na(2)S(2)O(4) in various proportions. Signals were interpreted as due to the reduced iron-sulphur centre (with slightly different g values), a haem-NO complex and reduced Methyl Viologen. In the presence of an excess of nitrite, the haem-NO spectrum was more intense, whereas in the presence of an excess of Na(2)S(2)O(4) it was weaker, and disappeared at the end of the reaction. A reaction sequence is proposed for the enzyme, in which the haem-NO complex is an intermediate, followed by other e.p.r.-silent states, leading to the production of NH(4) (+).

Effects of nitrite toxicity on soil bacteria under aerobic and anaerobic conditions

Abstract: Isolates of a soil Pseudoimonas , as well as other soil bacteria, showed a different sensitivity towards NO − 2 when grown under aerobic or anaerobic conditions. The tolerance to NO − 2 was increased in the presence of O 2 : for instance, a concentration of 200parts 10 6 of NO − 2 -N proved to be toxic to a Pseudomonas sp. under anaerobic conditions, whereas over 400 parts 10 6 were needed aerobically to suppress its growth completely. The addition of NO − 3 as an electron acceptor for anaerobic respiration did not overcome the inhibitive effect of NO − 3 . The pH range, at which NO − 2 was utilized anaerobically, was narrowed with increasing NO − 2 concentration (pH 6.8–8.8 at 70 parts 10 6 of NO − 2 -N and 7.4–8.5 and 140 parts 10 6 of NO − 2 -N). Tolerance to nitrite varied considerably among the bacteria tested. Each species was able to overcome the inhibitory effect of NO − 2 up to a certain concentration, while the length of the lag phase was related to NO − 2 concentration.

Urinary nitrite and urinary-tract infection.

Abstract: Two dipstick procedures and an automated quantitative urinary nitrite assay were used to study nitrite in 786 samples of urine submitted to the bacteriology laboratory for routine culture and sensitivity testing. Many samples that had more than 100,000 nitrite-reducing organisms/ml and no detectable nitrite were studied. Limited nitrate concentration in urine was not a significant cause of false-negative nitrite results. However, in some urine samples nitrite added in vitro was lost during a four-hour incubation in vitro at 37 C in the presence of more than 100,000 nitrite-reducing organisms/ml. Ascorbic acid, abnormal amounts of urobilinogen, and urinary p H below 6.0 are all possible causes of false-negative nitrite determinations.

Influence of tumbling and sodium tripolyphosphate on salt and nitrite distribution in porcine muscle

Abstract: The effect of tumbling and sodium tripolyphosphate on the migration of salt and nitrite in pork muscle tissue was studied using the semi-membranosus muscles from 20 matched hams. Uniform sections of these muscles were injected with a column of cure placed in the geometric center of the muscle section perpendicular to the muscle fibers. Portions of these muscle samples were subsequently analyzed after tumbling or holding for extent of cooked cured color development. Uncooked portions were analyzed for salt and nitrite concentration at specific distances from the injection site. Both sodium tripolyphosphate and tumbling independently significantly increased the migration of salt and nitrite and resulted in a significant increase in color development. Although percent cured color area was significantly increased, both tumbling and sodium tripolyphosphate increased the residual nitrite content. Sodium tripolyphosphate added to the effect of tumbling on the percent of cured area.