Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

Nitrite and Red Cell Function in Carp: Control Factors for Nitrite Entry, Membrane Potassium Ion Permeation, Oxygen Affinity and Methaemoglobin Formation

Abstract: Red cell function was studied in carp by a combination of in vivo and in vitro experiments with nitrite as the perturbing agent. In vivo accumulation of nitrite caused a marked increase in the red cell methaemoglobin content, and reduced the mean cellular volume. The oxygen affinity of unoxidized haemoglobin was strongly decreased, partly as result of the elevated concentration of cellular nucleoside triphosphates and haemoglobin associated with red cell shrinkage. Red cell pH was unchanged compared to controls, but reduced when referred to constant extracellular pH and O 2 saturation. The mean cellular K + content decreased, reflecting a K + loss from the red cells during their shrinkage. This K + loss contributed significantly to the large plasma hyperkalaemia during nitrite exposure. In vitro experiments revealed that nitrite influx into deoxygenated red cells was much larger than into oxygenated red cells. Nitrite permeation of the red cell membrane was not inhibited by DIDS and did not change extracellular pH. Methaemoglobin (MetHb) formation was more pronounced in deoxygenated blood than in oxygenated blood, but quasi-steady states were reached, reflecting a balance between nitrite-induced MetHb formation and the action of MetHb reductase. Red cells incubated in the oxygenated state released K + , whereas a net K + uptake occurred in deoxygenated cells. Nitrite did not change the K + loss from oxygenated cells, but shifted the K + uptake in deoxygenated cells to a pronounced K + release by the time high MetHb levels were reached. Both types of red cell K + release were inhibited by DIDS and appeared to occur via a route involving Band 3. The data are consistent with the hypothesis that a significant DIDS-sensitive K + efflux from the red cells occurs whenever a large fraction of the haemoglobin molecules assumes an R-like quaternary structure.

Enhancement of dye sonochemical degradation by some inorganic anions present in natural waters

Abstract: The sonochemical degradation rate of the charged substrates Acid Blue 40 (AB40) and methylene blue (MB) is enhanced by scavengers of hydroxyl radicals such as bicarbonate, carbonate, bromide, iodide and (only in the case of AB40) nitrite. No rate variation was observed with chloride, nitrate or sulphate, excluding a mere ionic strength effect. Oxidation of bicarbonate, carbonate, bromide, iodide and nitrite yields the corresponding radicals CO3 −, Br2 −, I2 − and NO2, reactive but less than OH. Degradation enhancement can occur if these radicals are sonochemically formed on the surface of the collapsing cavitation bubbles and undergo there radical–radical recombination at a lesser extent than OH. In this way the radicals would be more available than OH for substrate degradation, both at the bubble surface and in the solution bulk, which could more than compensate for their lower intrinsic reactivity. The varied reactivity toward different substrates of the sonochemically formed radical species could then explain why nitrite inhibits MB degradation while enhancing that of AB40. The sonochemical formation of Br2 −, I2 − and NO2 can give rise to halogenation and nitration in addition to oxidation processes. In fact bromo-, iodo- and nitrophenols were detected upon sonication of phenol in the presence of the corresponding anions, but only at quite elevated concentration values of nitrite, bromide or iodide (above 10 mM). Formation of harmful halogeno- and nitroderivatives could therefore take place on sonication of some wastewater rather than of typical natural waters.

Inhibition of tobacco nitrite reductase activity by expression of antisense RNA

Abstract: Summary A tobacco nitrite reductase (NiR) cDNA and its corresponding gene were isolated from cDNA and genomic libraries. An NiR antisense mRNA was expressed in transgenic tobacco under the control of a double 35S promoter. Transformants were obtained on a medium containing ammonium as the sole source of nitrogen. One plant growing normally on ammonium but displaying drastically reduced development and chlorotic leaves when grown on nitrate as the sole source of nitrogen was studied further. This plant accumulated nitrite fivefold over wild-type level and showed reduced amounts of ammonium (11% wild-type level), glutamine (19%), and total protein (8%). NiR mRNA and activity were below detectable levels. Under these conditions, nitrate reductase (NR) activity and mRNA were overexpressed, suggesting that N-metabolites resulting from nitrate reduction are responsible for the repression of the expression of the NR gene, independently from the presence or absence of a functional NR protein.

Nitrite Curing of Meat: The N-Nitrosamine Problem and Nitrite Alternatives

Abstract: Meat has been treated for centuries with rock salt as a means of preservation. However, only one century has passed since the German researchers, Polenske in 1891, Kisshalt in 1899, and Lehmann in 1899, discovered that the active component in the curing process was nitrite. Soon after the role of nitrite as a meat curing agent was revealed, government regulators placed guidelines on the level of nitrite and nitrate permitted for use in cured meat formulations. In the late 1960s and early 1970s, the development of the so-called "nitrite problem" surfaced because of the detection of N-nitrosamines in processed meats. The industry was in an uproar and the issue was of paramount interest to scientists and the public. A major technical advance in the analytical technique for Nnitrosamine detection was achieved when Thermo Electron of Waltham, Massachusetts introduced the thermal energy analyzer (TEA). This unit allowed the screening of a large number of samples for nitrosamine with only a minimum preparation. The role of nitrite in revealing the desired and unique flavor of cured products, perhaps by suppressing the formation of lipid oxidation products was another development in revealing other properties of nitrite. Above all, the antimicrobial role of nitrite, together with salt, had a major influence on the popularity of nitrite/nitrate in food preservation.