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At least 37 records · Page 2Linked to original sources

PubMed1979

Effect of processing variables on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted meat cured with sorbic acid and sodium nitrite.

The effects of the initial pH and a "short pump" on the outgrowth of Clostridium sporogenes PA 3679 spores in comminuted cured pork were studied. Fresh ground pork was cured with salt, sugar, phosphate, ascorbate, and varying amounts of sodium nitrite and sorbic acid. The product was comminuted and inoculated with 1,000 spores of C. sporogenes per g. The meat was stuffed into 1-ounce (ca. 28.4-g) aluminum tubes, cooked to 58.5 degrees C, cooled, and incubated at 27 degrees C to observe for swells. Product cured with 0.2% sorbic acid in combination with 40 ppm sodium nitrite (40 microgram/g) had better clostridium inhibition than did product cured with 120 ppm nitrite within a pH range of 5.0 to 6.7. The sorbic acid-40 ppm nitrite combination also gave better clostridial protection than did the 120 ppm nitrite alone when reduced amounts of curing ingredients were present.

Animals↗

PubMed1975

Enzymatic and non-enzymatic reduction of nitrite by extracts of Neurospora crassa.

Two activites causing nitrite disappearance are found in extracts of Neurospora; one, inducible by nitrate or nitrite and present only in nitrite-utilizing strains, catalyze the stoichiometric reduction of nitrite to ammonia; the other, present in all strains under all conditions, causes the disappearance of nitrite to something other than ammonia. The latter activity has a molecular weight of about 600 and may contain an oligopeptide, a metal, and an SH group(s). It has no known physiological function.

Ammonia↗

PubMed1975

Tumor induction in rats by feeding aminopyrine or oxytetracycline with nitrite.

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.

Adenoma, Bile Duct↗

PubMed1978

The mechanism of the control of carbon fixation by the pH in the chloroplast stroma. Studies with nitrite-mediated proton transfer across the envelope.

1. CO2 fixation of intact spinach chloroplasts is inhibited by nitrite in a pH-dependent mode. At pH 7.3 in the medium 1 mM NaNO2 and at pH 7.9 5 mM NaNO2 were required for 50% inhibition. 2. The addition of nitrite leads to an acidificiation in the stroma. It appears that nitrite renders the envelope permeable for protons resulting in a breakdown of the pH gradient between the external space and the stroma. 3. In view of earlier results on the pH sensitivity of C02 fixation it is concluded that this pH shift in the stroma is responsible for the observed inhibition of CO2 fixation by nitrite. 4. Octanoate and to some extent also high concentrations of bicarbonate and acetate have a similar effect as nitrite in inhibiting CO2 fixation through an acidification in the stroma. 5. The levels of the intermediates of the CO2 fixation cycle were measured. A strong rise of the levels of fructose- and sedoheptulose biphosphates and a concomitant decrease of the corresponding monophosphates was observed during inhibition of CO2 fixation. It appears that the enzymatic steps of the CO2 fixation cycle responsible for the overall inhibition of CO2 fixation caused by lowering of the H+ concentration in the stroma are fructose- and sedopheptulose bisphosphatase. These two enzymes have an important function in the light regulation of CO2 fixation.

Ammonium Chloride↗

PubMed1975

Growth of Staphylococcus and Salmonella on frankfurters with and without sodium nitrite.

Conventional and nitrite-free frankfurters in loosely wrapped packages were compared as to their ability to support growth of Salmonella, Staphylococcus, and their naturally occurring spoilage flora at 7 C (simulating refrigerated storage) and 20 C (simulating possible temperature abuse). At 7 C Salmonella did not grow in either type of frankfurter; Staphylococcus and the natural spoilage flora sometimes grew more rapidly in the absence of nitrite, but the difference was not significant. At 20 C growth of Salmonella, Staphylococcus, and of the spoilage flora was, at most, only slightly faster on nitrite-free frankfurters. Salmonella was not suppressed in broth culture experiments the pH and nitrite content found in frankfurters. Although either type of frankfurter can become hazardous due to growth of Salmonella or Staphylococcus, no unusual or additional hazard resulted from the omission of nitrite from frankfurters.

Cell Count↗

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↗

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↗

PubMed1976

[Effect of nitrites and nitrates on various aspects of vitamin nutritional status].

Nitrites--and sometimes nitrates--decrease the biological availability of dietary vitamins in several animal species. 1. Numerous studies show that ingested nitrites decrease the stock of liver vitamin A in nonruminants (Rat, Pig, Chicken); the effect of nitrates is less pronounced even lacking. In vitro, experiments allow to think that vitamin A and beta-carotene can be destroyed by nitrites in the diet and/or in the gastrointestinal tract. 2. Some recent works--those of Lhuissier particularly--show that nitrites can affect some vitamins of B group and their metabolism. Thiamine and vitamin B6 contents of several tissues decrease when nitrites are fed to the Rat. In the case of thiamine, the result could be partially explained by destruction of the vitamin in the diet and may be in the gastrointestinal tract. No such explanation seems to be possible in the case of vitamin B6.

Animals↗

PubMed1979

Identification of the iron-sulfur center of spinach ferredoxin-nitrite reductase as a tetranuclear center, and preliminary EPR studies of mechanism.

EPR spectroscopic and chemical analyses of spinach nitrite reductase show that the enzyme contains one reducible iron-sulfur center, and one site for binding either cyanide or nitrite, per siroheme. The heme is nearly all in the high spin ferric state in the enzyme as isolated. The extinction coefficient of the enzyme has been revised to E386 = 7.6 X 10(4) cm-1 (M heme)-1. The iron-sulfur center is reduced with difficulty by agents such as reduced methyl viologen (equilibrated with 1 atm of H2 at pH 7.7 in the presence of hydrogenase) or dithionite. Complexation of the enzyme with CO (a known ligand for nitrite reductase heme) markedly increases the reducibility of the iron-sulfur center. New chemical analyses and reinterpretation of previous data show that the enzyme contains 6 mol of iron and 4 mol of acid-labile S2-/mol of siroheme. The EPR spectrum of reduced nitrite reductase in 80% dimethyl sulfoxide establishes clearly that the enzyme contains a tetranuclear iron-sulfur (Fe4S4) center. The ferriheme and Fe4S4 centers are reduced at similar rates (k = 3 to 4 s-1) by dithionite. The dithionite-reduced Fe4S4 center is rapidly (k = 100 s-1) reoxidized by nitrite. These results indicate a role for the Fe4S4 center in catalysis.

Dithionite↗

PubMed1979

Gastric cancer in Colombia. IV. Nitrite and other ions in gastric contents of residents from a high-risk region.

Samples of gastric contents from 2 groups of patients from a region of high risk for gastric cancer were analyzed for pH, nitrite, nitrate, thiocyanate, and chloride. In each group, the patients could be divided into 2 subgroups: those with a gastric pH of less than 5 and those with a gastric pH of greater than 5. Above pH 5, nitrite was correlated with nitrate. The pH greater than 5 subgroups had significantly higher (P less than 0.01) nitrite content (20- to 100-fold). Some high- and low-nitrite samples were also analyzed for macro and trace metal ions, but differences were not significant. This is the first report in which patients with diagnosed gastric pathology related to a precancerous state were shown to have high levels of a putative carcinogen precursor. The results were compatible with our original hypothesis of intragastric nitrite formation by bacterial reduction of nitrate and concomitant synthesis of carcinogenic N-nitroso compounds.

Aged↗

PubMed1977

Action of Nitroglycerin and amyl nitrite in labile and essential hypertension: hemodynamic differences.

Seventeen patients with labile hypertension received nitroglycerin and 18 received amyl nitrite. Twelve patients with established essential hypertension received nitroglycerin and 12 received amyl nitrite. Nitroglycerin reduced the systolic and mean arterial pressures and cardiac output in both groups, but had no effect on diastolic pressure and total peripheral resistance. Amyl nitrite decreased systolic, diastolic, and mean arterial pressures and peripheral vascular resistance and increased heart rate and cardiac output in labile hypertensives. In established hypertensive patients, amyl nitrite decreased systolic, diastolic, and mean arterial pressures and cardiac output, and had little effect on peripheral vascular resistance. Nitroglycerin reduced arterial pressure in labile and established hypertensives through venodilation and peripheral venous pooling. Amyl nitrite and effects similar to nitroglycerin in established hypertensives; in labile hypertensives it reduced arterial pressure through arterial dilation and a decrease in peripheral vascular resistance.

Adult↗

PubMed1976

Ferredoxin-dependent photosynthetic reduction of nitrate and nitrite by particles of Anacystis nidulans.

The dark and light reduction of nitrate and nitrite by cell-free preparations of the blue-green alga Anacystis nidulans has been investigated. The three following methods have been successfully applied to the preparation of active particulate fractions from the alga cells: (a) shaking with glass beads, (b) lysozyme treatment and lysis of the resulting protoplasts, and (c) sonication. The two enzymes of the nitrate-reducing system-namely, nitrate reductase and nitrite reductase-are firmly bound to the isolated pigment-containing particles, and can be easily solubilized by prolonging the vibration or sonication time. Both enzymes-whether solubilized or bound to the particles-depend on reduced ferredoxin as the immediate electron donor. In its presence, the alga particles catalyze the gradual photoreduction of nitrate to nitrite and ammonia, a process that can thus be considered as one of the most simple and relevant examples of Photosynthesis. Some of the properties of nitrate reductase have been studied. Nitrate reductase as well as nitrite reductase are adaptive enzymes repressed by ammonia.

Cyanobacteria↗

PubMed1979

Model experiments on nitrite and nitrate in simulated primeval conditions.

In experiments on the prebiotic formation of nitric oxides, anoxic mixtures of N2 and water vapour were sparked in contact with phosphate buffer solutions at various pH values. Nitrite was found in the aqueous phase, and nitrate grew from it, presumably by reaction with H2O2. In acid solutions, these anions were reduced and destroyed by Fe2+, and the same was true of nitrite in solutions kept at a pH value similar to that of the contemporary ocean (8.2) with HEPES buffer. Nitrate was not destroyed in short-term experiments, but as in sparking nitrate is formed only vianitrite, neither anion could accumulate. In further sparking experiments with alkaline sulphide, both nitrite and nitrate were reduced entirely. It is concluded that it is unlikely that the primeval ocean contained appreciable concentrations of nitrite or nitrate either at the reducing or at the redox-neutral stage.

Anaerobiosis↗

PubMed1977

Nitrite reductase system involved in the terminal oxidation of the Streptomyces griseus respiratory particle.

A nitrite reductase system which was associated with the electron transfer system of the respiratory particle in Streptomyces griseus was studied. The electron transfer pathway consisted of the cytochrome oxidase and the nitrite reductase systems under aerobic and anaerobic conditions respectively, and these systems showed the exact opposite response to 2-n-heptyl-4-hydroxyquinoline-N-oxide and azide. Azide inhibited specifically the nitrite reductase system. It seems that cytochrome d works as the nitrite reductase and the reduced cytochrome b works as an intermediate electron donor for cytochrome d respectively. The respiratory particle also had a hydroxylamine reductase activity and ammonia was identified as the product of hydroxylamine reduction by the respiratory particle. A terminal electron transfer pathway in Streptomyces griseus was proposed.

Anaerobiosis↗

PubMed1979

Stoichiometry of the reaction of oxyhemoglobin with nitrite.

During the reaction of oxyhemoglobin (HbO2) with nitrite, the concentration of residual nitrite, nitrate, oxygen, and methemoglobin (Hb+) was determined successively. The results obtained at various pH values indicate the following stoichiometry for the overall reaction: 4HbO2 + 4NO2- 4H+ leads to 4Hb+ + 4NO3- + O2 + 2H2 O (Hb denotes hemoglobin monomer). NO2- binds with methemoglobin noncooperatively with a binding constant of 340 M-1 at pH 7.4 and 25 degrees C. Thus, the major part of Hb+ produced is aquomethemoglobin, not methemoglobin nitrite, when less than 2 equivalents of nitrite is used for the oxidation.

Hemoglobin A↗

PubMed2026

Deciphering the effects of sulfonamide antibiotics on denitrification from a metagenomic perspective: Inhibition of nitrite reduction and succession patterns of functional microorganisms.

Limited research has thoroughly elucidated the impact mechanisms of antibiotics on the denitrification process at the genomic and gene levels, which has hindered the optimization and development of nitrogen removal technology for antibiotic-containing swine wastewater. Lab-scale sequencing batch reactors were constructed in this study to treat synthetic wastewater containing different sulfonamides and nitrate. Investigations were carried out on denitrification performance, microbial community diversity, denitrifier succession patterns, and functional gene distribution. The stress of sulfonamides inhibited the nitrite reduction process, transforming complete denitrification into partial denitrification and causing significant nitrite accumulation. The average nitrogen removal efficiency in the treatment groups decreased from 81.0% ± 2.2-40.1% ± 6.1%. Alicycliphilus and Thauera were identified as the key taxa, accounting for 32.2% and 16.9% of all potential denitrifying bacteria, respectively. Although metagenome-assembled genomes (MAGs) from Thauera were enriched with genes encoding nitrate reductases (nap, nar) and nitrite reductases (nir), this genus preferentially utilized nitrate as an electron acceptor, resulting in the preferential nitrate reduction and subsequent nitrite accumulation. In contrast, Alicycliphilus MAGs developed tolerance to the sulfonamides stress during later stages, with concomitant enrichment of associated functional genes. They replaced Thauera to reemerge as the dominant group, thereby restoring complete denitrification. This study provides new insights into the regulatory mechanisms governing complete versus partial denitrification in nitrogen removal from antibiotic-containing wastewater.

Denitrifier succession↗

PubMed1977

Effects of amyl nitrite on phasic aortocoronary bypass graft blood velocity in man.

With the use of a Doppler flowmeter catheter, phasic instantaneous aortocoronary saphenous vein bypass graft blood velocity was continuously measured during the inhalation of amyl nitrite in 20 closed-chest conscious subjects. Administration of amyl nitrite augmented peak diastolic and systolic graft blood velocity within 10 seconds and maximal blood velocities were recorded between 8 and 60 seconds after inhalation. Control mean (+/- 1 S.D.) bypass graft blood velocity was 25 +/- 10 cm. per second and after amyl nitrite 46 +/- 14 cm. per second, resulting in an average 84 per cent rise of blood velocity. It is concluded that amyl nitrite increases aortocoronary bypass graft blood velocity, suggesting a possible enhancement of blood flow to the distal native circulation in patients so operated upon.

Adult↗

PubMed1976

Gastric-juice nitrite. A risk factor for cancer in the hypochlorhydric stomach?

Nitrite and hydrogen ion concentrations have been measured in the fasting gastric juice of 69 patients undergoing routine gastrointestinal investigations. There was an inverse relationship between nitrite concentration and hydrogen ion concentration, with a highly significant increase in gastric-juice nitrite in hypochlorhydric subjects. Thiocyanate was also found in all specimens in concentrations likely to increase nitrosamine formation, if nitrosation of amines occurs in the fasting stomach. Neutral gastric juice contains metabolically active bacteria capable both of generating nitrite from nitrate and of catalysing nitrosation. In this way an intragastric environment suitable for the formation of carcinogenic nitrosamines exists in the hypochlorhydric and achlorhydric stomach, providing a possible mechanism for the high incidence of gastric cancer in these subjects.

Achlorhydria↗