Showing papers on "Nitrite published in 1975"

Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid

Abstract: An analysis is described for the rapid determination of nitrate‐N in plant extracts. The complex formed by nitration of salicylic acid under highly acidic conditions absorbs maximally at 410 nm in basic (pH>12) solutions. Absorbance of the chromophore is directly proportional to the amount of nitrate‐N present. Ammonium, nitrite, and chloride ions do not interfere.

The toxicology of nitrate, nitrite and n-nitroso compounds†

Abstract: Nitrate is essentially non-toxic to mammals but it can be reduced to nitrite either in improperly stored food, in the rumen of cattle, in the gastrointestinal tract of the human infant, and by the microflora of the human mouth The nitrite from these and other sources, including that purposely added to food, presents a toxic hazard both because of the direct toxicity of nitrite, and by the formation of carcinogenic N-nitroso compound by reaction with amino compounds Administration of toxic amounts of nitrite induces methaemoglobinaemia The nature of this disease, its importance in human medicine and the reason for the particular sensitivity of the infant, are briefly discussed The carcinogenic properties of N-nitroso compounds are described These compounds have been found in the environment and may be formed in the stomach from amines and nitrite Our knowledge of the amount of N-nitroso compounds to which man is exposed, is continually increasing but with the lack of epidemiologic evidence, the assessment of the significance to man of these traces of N-nitroso compounds depends upon the interpretation of animal experiments and their extrapolation to man This extrapolation would be more certain if there were a more clear understanding of the factors determining tissue selectivity by carcinogens and tissue sensitivity, and of the mechanism of cumulation of carcinogenic doses and of synergism between carcinogens Recent experiments suggest that there may soon be a significant breakthrough in the understanding of this These experiments are briefly discussed

Energy Yield of Denitrification: An Estimate from Growth Yield in Continuous Cultures of Pseudomonas denitrificans under Nitrate-, Nitrite- and Nitrous Oxide-limited Conditions

Abstract: The molar growth yields of Pseudomonas denitrificans, for nitrate, nitrite and nitrous oxide, were determined in chemostat culture under electron acceptor-limited conditions. Glutamate was used as the source of energy, carbon and nitrogen. The catabolic pattern was identical, irrespective of the terminal electron acceptors. The molar growth yields, corrected for maintenance energy, were 28-6 g/mol nitrate, 16-9 g/mol nitrite and 8-8 g/mol nitrous oxide. The energy yield, expressed on an electron basis, was proportional to the oxidation number of the nitrogen: nitrate (plus 5), nitrite (plus 3) and nitrous oxide (plus 1). It was concluded that oxidative phosphorylation occurs to a similar extent in each of the electron transport chains associated with the reduction of nitrate to nitrite, nitrite to nitrous oxide and nitrous oxide to nitrogen.

Reaction of Nitrite With Ascorbate and Its Relation to Nitrosamine Formation

Abstract: In this study of the nitrosation of morpholine in the presence of ascorbic acid, the amount of ascorbate required to inhibit completely the formation of nitrosomorpholine depended on whether oxygen was present in the system. The nitric oxide (produced during the oxidation of ascorbate by nitrous acid) might have reacted with oxygen to yield additional oxidizing equivalents, or oxygen might have directly oxidized the ascorbate semiquinone intermediate produced in the initial step of oxidation reaction. A pH- dependent induction period observed during the nitrosation of morpholine in the presence of ascorbate and excess nitrite was accounted for by the kinetics of the reactions.

Contribution of nitrite and nitrate to the colour and flavour of cured meats

Abstract: The formation of nitric oxide myoglobin from nitrite and myoglobin involves a complex series of reactions not all of which are completely understood even now, and the stability of the cured colour, so important from the marketing point of view, continues to be investigated. The amount of nitrite necessary for complete formation of nitric oxide myoglobin is very small and the presence of no more than 25 mg/kg of nitrite in the cured meat is enough to ensure an adequately stable colour. At least four times this level is essential to produce a full development of the typical cured flavour. Very little is known of the mechanism of the reactions leading to the formation of cured flavours in cooked products or of the identity of the volatile substances responsible for it.

Analysis of nitrate and nitrite in foodstuffs: A critical review

Abstract: A general review is presented of published methods for the determination of nitrate and nitrite levels in foodstuffs especially meat. Published methods show wide variations in techniques for extraction, clean-up (clearing) of extracts and final determinative steps and these are critically compared. The effect of interferences due to the presence of ascorbate, sulphite and phosphate together with the formation of a “meat blank” when nitrate is reduced to nitrite with spongy cadmium are discussed. Newer techniques based on the use of ion selective electrodes and automated techniques are outlined and the application of techniques such as amperometry, liquid chromatography, ion exchange and spectrophotometry are listed.

Effect of Nitrite on Methemoglobin and Total Hemoglobin of Juvenile Rainbow Trout

Abstract: (1975). Effect of Nitrite on Methemoglobin and Total Hemoglobin of Juvenile Rainbow Trout. The Progressive Fish-Culturist: Vol. 37, No. 1, pp. 36-38.

Achromobacter cycloclastes nitrite reductase. The function of copper, amino acid composition, and ESR spectra.

Abstract: 1. Dialysis against cyanide at pH 7 of Achromobacter cycloclastes nitrite reductase [EC 1.7.99.3] of a dissimilatory type led to the removal of about 50% of the copper from the enzyme molecule, with a concomitant decrease of the enzymatic activities. It was inferred that enzyme-bound copper atoms play an essential role in the catalytic activities of the enzyme. 2. The amino acid composition of the enzyme was determined after acid hydrolysis. 3. ESR spectra of the frozen solution and lyophilized powder of the nitrite reductase predominantly showed the presence of two kinds of copper: Type 1 Cu2+, which had narrow and sharp hyperfine splitting, and Type 2 Cu2+, which had broader hyperfine splitting. The bond between the oxidized enzyme and nitrite seems to be ionic.

Reduction of gastrtc carcinogens with ascorbic acid

Abstract: The formation of nitrite from nitrate was studied in potatoes incubated at room temperature. After 24 hours of incubation at 25 degrees, 112 ppm and 373 ppm of nitrite formed in homogenized cooked potatoes containing 284 ppm and 584 ppm of nitrate, respectively. In homogenized fresh potatoes incubated at 21 degrees and containing 284 ppm of nitrate, 103 ppm of nitrate formed within 24 hours. During the period of nitrite formation, nitrate levels decreased sharply, indicating that reduction of nitrate to nitrite occurred. Incubation at 2 degrees completely prevented nitrite formation in all cases. The formation of methylnitrosourea from added methylurea and nitrite was observed in potato incubated under simulated gastric conditions (37 degrees, pH 1.5). An ascorbate-nitrite mole ratio of 4 gave a 93% inhibition of methylnitrosourea formation. Ascorbate reacted directly with nitrite in potato incubated under identical conditions, yielding a 43% decrease in nitrite concentration. Ascorbate did not react with methylurea or the product, methylnitrosourea.

Cell comprising an alkali metal and aqueous electrolyte

Abstract: In a reactive metal-water electrochemical cell, an alkaline electrolyte containing soluble inorganic ions which are reduced preferentially to water at the cathode. More particularly, the additives substantially reduce or eliminate reduction of water and evolution of hydrogen at the cathode resulting in significant improvement in current efficiency, gravimetric energy density and cell potential at a given current. Additionally, suppression of hydrogen evolution makes possible a sealed system with venting of gases from the cell no longer necessary. The inorganic ions of the invention are nitrite, hypochlorite, chlorate, bromate, dinitrogen trioxide and sulfite ions which are formed when soluble salts of nitrite, sulfite, hypochlorate, bromate, chlorate, soluble gases such as dinitrogen trioxide and sulfur dioxide and other soluble inorganic compounds are dissolved in the alkaline electrolyte.

Inhibition of Nitrite Reduction by Photosynthetic Inhibitors

Abstract: Using a modified in vivo nitrate reductase assay, all photosynthetic inhibitors tested were shown to effectively block light-dependent nitrite reduction in green leaf tissue. Nitrate reduction continued so that nitrite accumulated. Ni- trite, vacuum infiltrated into leaf tissue, disappeared linearly with time when incubated in the light. Nitrite, vacuum in- filtrated with a photosynthetic inhibitor, did not disappear but accumulated to even higher levels. The degree of inhibition of nitrite reduction was a function of herbicide concentration Reaction solution. The aqueous reaction solution contained 0.05 M KNO3, 0.05 M KH2PO4, 0.3% Tergitol 15-S-7 sur- factant (a non-ionic linear alcohol ethoxylate3) and 4% eth- anol (v/v). Final pH was adjusted to 7.5 with 3 N KOH. When herbicides were included in the reaction solution, they were first dissolved in absolute ethanol and brought to proper vol- ume with the reaction solution minus ethanol. Final concen- tration of ethanol in all solutions was 4%.

Influence of nitrate on fermentation pattern, molar growth yields and synthesis of cytochrome b in Propionibacterium pentosaceum.

Abstract: Under anaerobic conditions, Propionibacterium pentosaceum reduces nitrate to nitrite until nitrate is exhausted from the medium when nitrite is converted into N2 or N2O. In the presence of nitrate, fermentation patterns for lactate, glycerol and pyruvate were different from those obtained during anaerobic growth without an inorganic electron acceptor. In the presence of these substrates, a drastic decrease in propionate formation was observed, some pyruvate accumulated during growth with lactate, and acetate was produced from glycerol. Acetate production from lactate and pyruvate was not influenced by the presence of nitrate. Furthermore, CO2 was produced by citric acid cycle activity. The fermentation pattern during nitrite reduction resembled that of P. pentosaceum grown anaerobically without an inorganic electron acceptor. Nitrits has a toxic effect, since bacteria inoculated into a medium with 9 mM-nitrite failed to grow. The cytochrome spectrum of anaerobically grown P. pentosaceum was similar with and without nitrate. In membrane fractions of bacteria grown anaerobically with nitrate, cytochrome b functioned in the transfer of electrons from lactate, glycerol I-phosphate and NADH to nitrate. Molar growth yeilds were increased in the presence of nitrate, indicating an increased production of ATP. This could be explained by citric acid cycle activity, and by ocidative phosphorylation coupled to nitrate reduction. Assuming that I mol ATP is formed in the electron transfer from lactate or glycerol I-phosphate to nitrate, and that 2 mol ATP are formed in the electron transfer from NADH to nitrate, YATP values (g dry wt bacteria/mol ATP) were obtained of between 5-0 and 12-6. The higher YATP values were similar to those obtained during anaerobic growth without an inorganic electron acceptor. This supports the assumptions about the efficiency of oxidative phosphorylation for electron transport to nitrate. Low YAPT values were found when high concentrations of nitrite (15 to 50 mM) accumulated, and were probably due to the toxic effect of nitrite.

The microbiological role of nitrite and nitrate

Abstract: In unheated products nitrite, together with sodium chloride and the pH value, contributes to the selection of the bacteria which grow during storage. Nitrate per se is generally believed to serve only as a reservoir for nitrite, but the commercial use of nitrate-free cover brines in the Wiltshire bacon industry shows that such a reservoir is not always essential. Nitrate sometimes reduced the growth rate of bacteria in experimental Wiltshire collar bacon, but was of no benefit in back bacon. The clostridia occurring naturally in the bacon grew to higher numbers in collar cured without nitrate than that cured with nitrate. Clostridium botlinum (types A and B) was detected in these bacons, but did not grow in the bacon. In heated products the growth of surviving bacteria is controlled by the interaction of several factors including pH, sodium chloride, storage temperature and sodium nitrite or a substance derived from it upon heating. Further experiments are warranted to investigate the effects of dextrose, nitrate, ascorbate and polyphosphate.

Stoichiometry between photosynthetic nitrate reduction and alkalinisation by Ankistrodesmus braunii in vivo.

Abstract: The uptake of nitrate or nitrite in the light, the release of nitrite and ammonia, and the corresponding alkalinisation of the medium were measured in synchronous Ankistrodesmus braunii (Naeg.) Brunnth. The increase in the OH− concentration in the medium reflects a stoichiometric ratio between OH− and NO3 − of 1.3–1.8 in air, reaching almost 2.0 in CO2−free air or nitrogen. At low CO2 concentrations a large proportion of the nitrogen taken up as nitrate is released as ammonia, much less as nitrite. The stoichiometry of alkalinisation and NO3 − or NO2 − uptake can be quantitatively explained by assuming: 1) a counter-transport, at a ratio of 1:1, of OH− against NO3 − at the plasmalemma and of OH− against NO2 − at the chloroplast envelope, and 2) a co-transport of 1:1 of OH− and NH4 + to the medium through both membranes. The first OH− required is formed by proton consumption in nitrite reduction, the second OH− by proton consumption in the formation of NH4 + ions. Transport of K+, Na+ and Ca2+ is not or only scarcely involved. This proposed transport system could provide charge equilibrium between inside and outside the cells and could enable the cells to avoid nternal pH changes in nitrate and nitrite reduction.

Tumor induction in rats by feeding aminopyrine or oxytetracycline with nitrite

Abstract: Sprague-Dawley rats were given combinations of aminopyrine or oxytetracycline and sodium nitrite in drinking water. Of 30 animals receiving 0.1% (1,000 ppm) of aminopyrine and sodium nitrite for 30 weeks, 29 died with hemangioendothelial sarcomas of the liver. The same tumor caused death in 26 of 30 animals that received 0.025% (250 ppm) of both aminopyrine and sodium nitrite for 50 weeks. No animals in a control group of the same size that received 0.1% aminopyrine for 30 weeks developed this tumor, although one-half of them were still alive 2 years after the experiment was begun. After feeding a comparable dose (0.1%) of oxytetracycline and sodium nitrite for 60 weeks, liver tumors were present in 4 of 30 rats (3 hepatocellular tumors and 1 cholangioma). Since aminopyrine has been widely used for medicinal purposes in the human population, it is possible that many people have been exposed to a potent carcinogen (dimethylnitrosamine) by its formation in vivo. It is not certain whether the result of feeding oxytetracycline and sodium nitrite indicates significant carcinogenicity of this combination.

Effect of ascorbic acid on amine-nitrite toxicity.

Abstract: Sodium nitrite can react with a variety of secondary and tertiary amines, at the pH of the mammalian stomach, to form nitrosamines. In many instances these nitrosamines are highly toxic and/or carcinogenic.'Amines susceptible to nitrosation are ubiquitous in man's environment. They are present as normal constituents of our food supply and are ingested as a variety of therapeutic agents. Nitrite enters the human food chain in several ways. Nitrate, which is converted to nitrite by a varicty of microorganisms\" is an important component of crop fertilizers. Sodium nitrite is used in meat processing to suppress the outgrowth of botulinum bacteria and to impart characteristic flavor and color to cured meat products.s Thus, it is of considerable importance to eliminate or significantly reduce the potential threat to human health imposed by man's ingestion of nitrite and amines or preformed nitrosamines. Work in our laboratory has been concerned with a role for ascorbic acid in preventing nitrosamine formation from amine-nitrite reactions in vivo. Our investigations have concentrated on the acute hepatotoxicity that results from feeding relatively large amounts of amine and nitrite to rats.

The very‐low‐pressure pyrolysis (VLPP) of n‐propyl nitrate, tert‐butyl nitrite, and methyl nitrite. Rate constants for some alkoxy radical reactions

Abstract: The pyrolysis of n-propyl nitrate and tert-butyl nitrite at very low pressures (VLPP technique) is reported. For the reaction the high-pressure rate expression at 300°K, log k1 (sec−1) = 16.5 − 40.0 kcal/mole/2.3 RT, is derived. The reaction was studied and the high-pressure parameters at 300°K are log k2(sec−1) = 15.8 − 39.3 kcal/mole/2.3 RT. From ΔS1,−10 and ΔS2,−20 and the assumption E−1 and E−2 ⋍ 0, we derive log k−1(M−1·sec−1) (300°K) = 9.5 and log k−2 (M−1·sec−1) (300°K) = 9.8. In contrast, the pyrolysis of methyl nitrite and methyl d3 nitrite afford NO and HNO and DNO, respectively, in what appears to be a heterogeneous process. The values of k−1 and k−2 in conjunction with independent measurements imply a value at 300°K for of 3.5 × 105M−1·sec−1, which is two orders of magnitude greater than currently accepted values. In the high-pressure static pyrolysis of dimethyl peroxide in the presence of NO2, the yield of methyl nitrate indicates that the combination of methoxy radicals with NO2 is in the high-pressure limit at atmospheric pressure.

Studies on In Vivo Formation of Nitroso Compounds (VI)

Abstract: The relationship between dietary nitrate intake and nitrite detected in human saliva was studied with a basal diet and high nitrate diet. Nitrite contents in foodstuff and in saliva were determined colorimetrically by a diazo-coupling reaction with sulfanilamide and naphthylethylenediamine, and nitrate contents were determined as nitrite after conversion to nitrite by passing a cadmium column. Determinations of nitrite and nitrate in saliva were carried out at intervals of 1-2hr except at night.When 200g of salted Chinese cabbage was taken, the average concentrations of nitrite and nitrate in saliva increased to large quantities of 71.9 and 544.5ppm, however, in the case of basal diet, decreased to 12.2 and 76.5ppm, respectively.From these results, it should be concluded that the changes of nitrite and nitrate concentrations in human saliva depended upon those contents in the diets. Furthermore, when daily secretion volume of saliva was presumed as 1, 000ml, the total amount of nitrite in saliva were 7-28 times that of the diet ingested, and it was assumed that nitrite in saliva was formed in vivo by the reduction of nitrate. We can not give a clear explanation for this reduction mechanism yet, but nitrite in saliva might be produced by the action of micro-organisms in alimentary tract, perhaps in mouth.