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PubMed2005

Comparison of influence of free ammonia and dissolved oxygen on nitrite accumulation between suspended and attached cells.

The shortcut biological nitrogen removal (SBNR) hybrid (suspended cells combined with attached cells) process is an innovative technology that nitrosofies ammonium to nitrite and then denitrifies nitrite to nitrogen gas. Theoretically, this results in a 25% savings of the oxygen needed for nitrification and a 40% of savings in carbon source needed for denitrification. In this study, the influences of free ammonia (FA) and dissolved oxygen (DO) concentrations on nitrite accumulation were investigated to find the optimal operational factors for stable nitrite accumulation over a long period. The maximum specific utilization rates for ammonium (qa) and nitrite (qn) were determined for suspended and attached cells taken from a bench-scale SBNR reactor and a pilot-scale livestock wastewater treatment plant reactor. For the ammonium and nitrite oxidations in both reactors, the attached cells were more resistant to the FA concentration, but were more significantly influenced by the DO concentration than the suspended cells. In addition, the effect of the DO concentration was more significant than that of the FA concentration for both types of cells from both reactors. In this SBNR hybrid system, a simultaneous manipulation of DO concentration (<1.5 mg l(-1)) and FA concentration (10-20 mg l(-1)) was required for maintaining high levels of nitrite accumulation.

Ammonia↗

PubMed2003

Activity of three disinfectants and acidified nitrite against Clostridium difficile spores.

OBJECTIVE: To identify environmentally safe, rapidly acting agents for killing spores of Clostridium difficile in the hospital environment. DESIGN: Three classic disinfectants (2% glutaraldehyde, 1.6% peracetyl ions, and 70% isopropanol) and acidified nitrite were compared for activity against C. difficile spores. Four strains of C. difficile belonging to different serogroups were tested using a dilution-neutralization method according to preliminary European Standard prEN 14347. For peracetyl ions and acidified nitrite, the subjective cleaning effect and the sporicidal activity was also tested in the presence of organic load. RESULTS: Peracetyl ions were highly sporicidal and yielded a minimum 4 log10 reduction of germinating spores already at short exposure times, independent of organic load conditions. Isopropanol 70% showed low or no inactivation at all exposure times, whereas glutaraldehyde and acidified nitrite each resulted in an increasing inactivation factor (IF) over time, from an IF greater than 1.4 at 5 minutes of exposure time to greater than 4.1 at 30 minutes. Soiling conditions did not influence the effect of acidified nitrite. There was no difference in the IF among the 4 strains tested for any of the investigated agents. Acidified nitrite demonstrated a good subjective cleaning effect and peracetyl ions demonstrated a satisfactory effect. CONCLUSIONS: Cidal activity was shown against C. difficile spores by glutaraldehyde, peracetyl ions, and acidified nitrite. As acidified nitrite and peracetyl ions are considered to be environmentally safe chemicals, these agents seem well suited for the disinfection of C. difficile spores in the hospital environment.

Clostridioides difficile↗

PubMed2004

The depletion of sodium nitrite by lactic acid bacteria isolated from kimchi.

Nitrites, whether added or naturally occurring in foods, are potential carcinogens, and controlling their concentrations is important for maintaining a safe food supply. In this study we investigated the depletion of sodium nitrite (150 microg/mL) during the fermentation in Lactobacilli MRS broth at 5, 10, 15, 20, 25, 30, and 36 degrees C by lactic acid bacteria (LAB-A, -B, -C, and -D) isolated from kimchi and Leuconostoc mesenteroides strain KCTC3100. The four species of lactic acid bacteria isolated from kimchi were identified as L. mesenteroides, and all produced depletion of less than 20% of sodium nitrite after 10 days of incubation at 5 degrees C. There was less than 40% depletion after 9 days at 10 degrees C, 86.4-92.8% after 7 days at 15 degrees C, 81.4-87.8% after 4 days and more than 90.0% after 5 days at 20 degrees C, 76.3-85.7% after 3 days and more than 90.0% after 5 days at 25 degrees C, and more than 90.0% after 2 days at 30 and 36 degrees C. The depletion by LAB isolates was similar or higher than that by L. mesenteroides strain KCTC3100, and in particular, the LAB-D strain showed the highest depletion effect of all the strains tested, up to 15 degrees C. From these results, the strains isolated from kimchi were very effective for the depletion of sodium nitrite at high temperature, and all sodium nitrite was depleted at the initial period of incubation (1-2 days) at 30 and 36 degrees C. But as the temperature was lowered, the depletion effect of sodium nitrite was decreased in all the strains tested from kimchi. This illustrates that the depletion of nitrite by each strain is subject to the influence of temperatures.

Brassica↗

PubMed1990

Gastric nitrite processing in the surgically altered maximal and minimal bile reflux ferret model.

Ingested nitrate and nitrite have been shown to contribute to endogenous, N-nitroso compound formation in man and experimental animals. N-nitroso compounds have long been suspected of contributing to higher levels of gastric cancer in various populations. Reconstructive gastric surgery to treat ulcers is accompanied by a change in bile reflux, gastritis and an increased incidence of gastric cancer in humans. To evaluate possible connections between gastric nitrite processing, reconstructive surgery and gastric cancer, the surgically altered domestic ferret, Mustela putorius furo, was used as an experimental model. The aim of the study was to determine if surgery would alter the stomach in a way which would increase gastric nitrite concentration, and thereby enhance the likelihood of gastric N-nitroso compound formation. Three groups of ferrets, one control group (n = 6) and two groups of surgically altered ferrets, one to simulate maximal bile reflux (MABR, n = 6), and the other to model minimal bile reflux (MIBR, n = 7), were studied. Each group's response to an exogenously administered dose of sodium nitrite did not differ significantly with respect to rate of gastric nitrite absorption, with half-lives in the 13-min range. Permeability of gastric mucosa to nitrite did not differ between controls and MIBR ferrets. Mean doubling time of gastric nitrate appeared slowed in surgically altered ferrets. Mean rate of gastric emptying was the same in the three groups, but appeared delayed initially in MIBR ferrets. Thiocyanate concentrations, pH and HCl secretion, all parameters which have been shown to affect gastric nitrite processing, did not differ significantly between groups. Gastric mucosal endoscopic biopsies obtained at 6-month intervals showed no clear difference in degree of mucosal inflammation and/or dysplasia in the three groups. These findings indicate that gastric mucosal neoplasia has not occurred in this model and that changes in parameters favoring gastric N-nitrosation, even if relevant to the disease process, are not apparent at this time.

Animals↗

PubMed1991

Sodium nitrite-stimulated metabolic activation of benzo[a]pyrene 7,8-dihydrodiol in human polymorphonuclear leukocytes.

Sodium nitrite was shown to enhance the metabolism of trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) to 7/8,9,10- and 7,10/8,9-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (tetraols) in phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMNs). The production of these tetraols implicates the intermediate formation of the corresponding trans-7,8-dihydroxy-9,10-epoxy-7,8-9,10-tetrahydrobenzo[a]pyrene (anti-BPDE). A 2- to 3-fold increase in the tetraol yield was observed in the presence of nitrite in excess of 1 mM. Sodium azide, an inhibitor of myeloperoxidase and catalase, reduced the nitrite-stimulated metabolism of BP-7,8-diol in PMA-activated leukocytes. Diphenylene iodonium sulphate, a NADPH-oxidase inhibitor, lowered the production of tetraols in PMA-stimulated leukocytes both in the absence and presence of nitrite. Additionally, nitrite markedly enhanced the covalent binding of metabolites derived from [3H](-)-BP-7,8-diol to leukocyte proteins as well as to DNA present extracellularly. The nitrite-stimulated covalent binding to both proteins and DNA was inhibited by the presence of sodium azide. The mechanism underlying the effect of nitrite on the metabolism of BP-7,8-diol to reactive intermediates in PMA-activated human polymorphonuclear leukocytes is not known. However, the results are compatible with a peroxidase-dependent mechanism although other possible pathways may contribute to the enhanced rate of metabolism.

Biotransformation↗

PubMed1993

N-nitroso compounds in fresh gastric juice and their relation to intragastric pH and nitrite employing an improved analytical method.

In order to examine further the relationship between intragastric N-nitrosation, gastric pH and nitrite, 457 fresh, fasting gastric juice samples were analysed for total N-nitroso compounds (NOC) and nitrite concentrations using a recently described improved assay method. Nitrite in log values was linearly related to intragastric pH (r = 0.887, P < 0.01) with a regression equation log[nitrite] (mumol/l) = 0.489 x pH - 2.209. Significantly higher NOC concentrations were found at intragastric pH ranges of 1.13-2.99 (mean +/- SE: 1.45 +/- 0.17 mumol/l, P < 0.05) and 6.00-8.42 (3.57 +/- 0.33 mumol/l, P < 0.01) compared with that at pH 3.00-5.99 (1.02 +/- 0.12 mumol/l). NOC concentration was significantly related to log nitrite concentration at both the low pH range 1.13-4.99 (r = 0.169, P < 0.01) and the high pH range 5.00-8.42 (r = 0.450, P < 0.01). The results in the present study confirm that both acid-catalysed N-nitrosation and biologically-catalysed N-nitrosation occur in the human stomach. However, great variations in nitrite and NOC concentrations were observed in both low and high pH samples, indicating that, as expected, both the acid-catalysed N-nitrosation and biologically-catalysed N-nitrosation processes are markedly affected by factors other than intragastric pH and nitrite.

Gastric Juice↗

PubMed2005

In higher plants, only root mitochondria, but not leaf mitochondria reduce nitrite to NO, in vitro and in situ.

At oxygen concentrations of < or =1%, even completely nitrate reductase (NR)-free root tissues reduced added nitrite to NO, indicating that, in roots, NR was not the only source for nitrite-dependent NO formation. By contrast, NR-free leaf slices were not able to reduce nitrite to NO. Root NO formation was blocked by inhibitors of mitochondrial electron transport (Myxothiazol and SHAM), whereas NO formation by NR-containing leaf slices was insensitive to the inhibitors. Consistent with that, mitochondria purified from roots, but not those from leaves, reduced nitrite to NO at the expense of NADH. The inhibitor studies suggest that, in root mitochondria, both terminal oxidases participate in NO formation, and they also suggest that even in NR-containing roots, a large part of the reduction of nitrite to NO was catalysed by mitochondria, and less by NR. The differential capacity of root and leaf mitochondria to reduce nitrite to NO appears to be common among higher plants, since it has been observed with Arabidopsis, barley, pea, and tobacco. A specific role for nitrite to NO reduction in roots under anoxia is discussed.

Methacrylates↗

PubMed1992

The relation between nitrite inhalants, unprotected receptive anal intercourse, and the risk of human immunodeficiency virus infection.

The role of nitrite was evaluated between 1985 and 1988 in a study of sexual transmission of the human immunodeficiency virus (HIV) among homosexual male couples in Boston, Massachusetts. Initial enrollment data suggested that a history of unprotected receptive anal intercourse (odds ratio (OR) = 2.3, 95% confidence interval (CI) 1.4-3.6) and a history of nitrite use (OR = 1.7, 95% CI 1.1-2.5) were independent risk factors for HIV infection. In addition, interaction between nitrite use and unprotected receptive anal intercourse was observed (OR = 5.5, 95% CI 2.8-11.1) after controlling for number of unprotected receptive anal sex partners and history of sexually transmitted diseases. Since it was felt that nitrite use might be a marker for unprotected receptive anal sexual activity, a supplemental questionnaire was administered to obtain information on simultaneous nitrite use and unprotected receptive anal intercourse. The supplemental data suggested a strong interaction between nitrite use and unprotected receptive anal intercourse in increasing the risk of HIV infection. In the adjusted analyses, the odds ratio for HIV infection was considerably greater among men who always used nitrites during unprotected receptive anal intercourse (OR = 31.8, 95% CI 12.9-76.7) compared with men who sometimes (OR = 7.1, 95% CI 2.1-23.6) or never (OR = 9.0, 95% CI 2.5-32.1) used them. These findings have preventive public health implications and may add insight into our understanding of the mechanism by which HIV infection spread rapidly among homosexual men in the early 1980s.

Adult↗

PubMed1999

The pH-dependent changes of intramolecular electron transfer on copper-containing nitrite reductase.

Electron transfer over 12.6 A from the type 1 copper (T1Cu) to the type 2 copper (T2Cu) was investigated in the copper-containing nitrite reductases from two denitrifying bacteria (Alcaligenes xylosoxidans GIFU 1051 and Achromobacter cycloclastes IAN 1013), following pulse radiolytical reduction of T1Cu. In the presence of nitrite, the rate constant for the intramolecular electron transfer of the enzyme from A. xylosoxidans decreased 1/2 fold to 9 x 10(2) s-1 (20 degrees C, pH 7.0) as compared to that for the same process in the absence of nitrite. However, the rate constant increased with decreasing pH to become the same (2 x 10(3) s-1) as that in the absence of nitrite at pH 6.0. A similar result was obtained for the enzyme from A. cycloclastes. The pH profiles of the two enzymes in the presence of nitrite are almost the same as that of the enzyme activity of nitrite reduction. This suggests that the intramolecular electron transfer process is closely linked to the following process of catalytic reduction of nitrite. The difference in redox potential (DeltaE) of T2Cu minus T1Cu was calculated from equilibrium data for the electron transfer. The pH-dependence of DeltaE was in accord with the equation: DeltaE = DeltaE(0)+0.058 log (Kr[H+]+[H+]2)/(K(0)+[H+]), where K(r) and K(0) are the proton dissociation constants for the oxidized and reduced states of T2Cu, respectively. These results raise the possibility that amino acid residues linked by the redox of T2Cu play important roles in the enzyme reaction, being located near T2Cu.

Alcaligenes↗

PubMed1994

Interleukin-1 beta stimulates nitrite production in the rat ovary: evidence for heterologous cell-cell interaction and for insulin-mediated regulation of the inducible isoform of nitric oxide synthase.

Recent studies suggest that endogenously generated nitric oxide (NO) may mediate the effects of cytokines in a variety of tissues. In an effort to determine whether NO generation mediates any of the intraovarian actions of interleukin-1 beta (IL-1 beta), we have looked for and characterized the accumulation of nitrite by IL-1 beta-treated, cultured whole ovarian dispersates. Application of IL-1 beta significantly enhanced basal nitrite release in a dose-, cell density- and time-dependent manner, the latter characterized by a lag time of about 20 h, suggestive of induction of NO synthase (NOS). Cellular NOS activity was also elevated by IL-1 beta. Sustained nitrite accumulation required continuous application of IL-1 beta. The maximally stimulating dose of IL-1 beta (50 ng/ml) produced a 10-fold increase in nitrite accumulation by 96 h of culture, an effect reduced 23% when cells were cultured in substrate (i.e., arginine)-free media. IL-1 beta-stimulated nitrite accumulation was reduced to control levels by the simultaneous application of an IL-1 beta receptor antagonist, thereby suggesting a specific receptor-mediated effect. Both the control and IL-1 beta-stimulated levels of nitrite accumulation were attenuated in a dose-dependent manner by inhibitors that favor the inducible form of NOS. In contrast, selective inhibitors of the constitutive form of NOS were significantly less potent. No inhibition was noted after application of an inactive stereoisomeric analogue. IL-1 beta-induced nitrite accumulation was shown to require cell-cell interaction between granulosa and theca-interstitial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗

PubMed1995

Increased serum nitrite and nitrate concentrations in children with the sepsis syndrome.

OBJECTIVES: To measure total serum nitrite and nitrate concentrations in children with the sepsis syndrome as an indicator of endogenous nitric oxide production. To determine if there is an association between total serum nitrite and nitrate concentrations and vascular responsiveness to norepinephrine. DESIGN: A prospective, clinical study. SETTING: Tertiary, multidisciplinary, pediatric intensive care unit. PATIENTS: Thirty-one children with the sepsis syndrome, 18 of whom were also hypotensive. Sixteen critically ill children without signs of the sepsis syndrome served as controls. INTERVENTIONS: Blood samples were obtained from indwelling catheters. The norepinephrine dose to reach the age appropriate, 50th percentile mean arterial blood pressure was determined in patients receiving norepinephrine. MEASUREMENTS AND MAIN RESULTS: Total serum nitrite and nitrate concentrations were measured on the first three days after the recognition of the sepsis syndrome. Patients with the sepsis syndrome had increased mean total serum nitrite and nitrate concentrations (day 1, 118 +/- 93 microM; day 2, 112 +/- 94 microM; day 3, 112 +/- 93 microM) vs. controls (43 +/- 24 microM, p < .05) on all 3 days. When sepsis syndrome patients were separated into nonhypotensive and hypotensive groups, only the patients with hypotension had increased concentrations vs. controls on all three days (p < .05). Sepsis syndrome patients with hypotension also had higher total serum nitrite and nitrate concentrations (145 +/- 97 microM) than sepsis syndrome patients without hypotension (82 +/- 76 microM, p < .05) on day 1. In five patients receiving norepinephrine infusions, increased total serum nitrite and nitrate concentrations were associated with higher norepinephrine requirements to maintain an age-appropriate, 50th percentile mean arterial blood pressure on each of the three study days (day 1, rs = 0.821, p < .05; day 2, rs = 0.900, p < .05; day 3, rs = 0.872, p < .05). CONCLUSIONS: Children with the sepsis syndrome, particularly those patients with hypotension, have increased total serum nitrite and nitrate concentrations that likely reflect increased endogenous production of nitric oxide. Vascular hyporesponsiveness to norepinephrine during the sepsis syndrome may be, in part, a nitric oxide-mediated process.

Adolescent↗

PubMed1998

Plasma nitrite and nitrate concentrations and multiple organ failure in pediatric sepsis.

OBJECTIVE: To determine whether plasma nitrite and nitrate concentrations are associated with the development of sepsis-induced multiple organ failure. DESIGN: Prospective study. SETTING: University children's hospital. PATIENTS: Fifty-three consecutive children meeting criteria for sepsis and not receiving exogenous sources of nitric oxide. INTERVENTIONS: Plasma nitrite and nitrate concentrations were measured, and the number of organs failing was scored using an organ failure index on the first 3 days of sepsis. MEASUREMENTS AND MAIN RESULTS: Children with three or more organs failing on day 3 of sepsis had higher plasma nitrite and nitrate concentrations than children who had resolution of failure of three or more organs by day 3 of sepsis (days 2 and 3) and children who never had three organs failing in the first 3 days of sepsis (days 1, 2, and 3). Children who developed sequential pulmonary/hepatic/renal organ failure had significantly higher plasma nitrite and nitrate concentrations (days 1, 2, and 3). Nonsurvivors had significantly higher plasma nitrite and nitrate concentrations (days 2 and 3) than survivors. Plasma nitrite and nitrate concentrations on day 1 predicted the development of persistent failure of three of more organs and sequential multiple organ failure but not mortality. CONCLUSION: Increased plasma nitrite and nitrate concentrations are associated with the development of multiple organ failure in pediatric sepsis.

Adolescent↗

PubMed1988

Augmenting effect of a nonmutagenic fraction in soy sauce on mutagenicity of 3-diazotyramine produced in the nitrite-treated sauce.

When 25 kinds of Japanese soy sauce at a concentration of 5% were incubated with 50mM sodium nitrite (pH 2) at 37 degrees for 1 hr, the reaction mixtures induced 34-834 (average 368 +/- 228) revertants per microliter of soy sauce equivalent in Salmonella typhimurium strain TA100 in the absence of S9 mix. The mutagen(s) formed was very unstable under natural daylight and a fluorescent lamp but quite stable under a yellow lamp as well as in the dark. In addition to the known precursors, i.e., tyramine and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, 1-methyl-1,2,3,4-tetrahydro-beta-carboline, which caused weak mutagenesis, was found in the soy sauce. However, the sum of the activities of the three mutagen-precursors after nitrite treatment accounted for only a part of the mutagenicity of nitrite-treated soy sauce. There was in the soy sauce a factor which increased ninefold the mutagenicity of nitrite-treated tyramine, 3-diazotyramine. Therefore, tyramine was considered the principal precursor of the mutagen produced in the nitrite-treated soy sauce. These three precursors together with the mutagenicity augmentation accounted for all the mutagenicity of nitrite-treated sauce. The mutagenicity-augmenting factor in the soy sauce was nonmutagenic before and after nitrite treatment and was stable to heat and light irradiation.

Carbolines↗

PubMed2000

Renal carcinogenicity of concurrently administered fish meal and sodium nitrite in F344 rats.

The effects of long-term concurrent administration of powdered fish meal and sodium nitrite were examined in F344 rats. A total of 600, 6-week-old rats were divided into 6 male and 6 female groups, each consisting of 50 animals. Rats in groups 1-3 and 7-9 were respectively fed diets supplemented with 64%, 32% and 8% (basal diet) fish meal, and simultaneously given 0.12% sodium nitrite in their drinking water. Groups 4-6 and 10-12 were respectively given 64%, 32% and 8% fish meal and tap water. At the 104th week, all surviving animals were killed and examined histopathologically. Treatment with fish meal dose-dependently increased the incidences and multiplicities of atypical tubules, adenomas and renal cell carcinomas in sodium nitrite-treated males. Females were less susceptible than males for renal tumor induction. In males given the 64% fish meal diet alone, the incidence and multiplicity of atypical tubules were also significantly increased as compared with the 8% fish meal alone case. Nephropathy was apparent in fish meal-treated groups in a clear dose-dependent manner, irrespective of the sodium nitrite treatment, and was more prominent in males than in females. Dimethylnitrosamine was found in the stomach contents after 4-week treatment with 64% fish meal plus 0.12% sodium nitrite, at a level twice that in the 8% fish meal plus 0.12% sodium nitrite group. The results clearly indicate that concurrent administration of fish meal and sodium nitrite induces renal epithelial tumors. Further studies are required to elucidate how nephropathy and nitrosamines produced in stomach contents may contribute to the observed renal tumor induction.

Animals↗

PubMed2005

Comparative effects of glyceryl trinitrate and amyl nitrite on pulse wave reflection and augmentation index.

AIMS: The influence of vasodilators on augmentation index (AIx) offers a simple, rapid and noninvasive method of evaluating vascular function. Glyceryl trinitrate (GTN) is widely used as an endothelium-independent vasodilator, although other nitrates that are shorter acting may have advantages in clinical studies. The aim of this study was to compare the effects of two short-acting nitrates, GTN and amyl nitrite, which have differing pharmacodynamic profiles. METHODS: Twenty-one healthy volunteers (15 male; mean age 35 years, range 21-56 years) attended on three occasions and received sublingual GTN (0.5 mg for 3 min), inhaled amyl nitrite (0.2 ml inhaled for 30 s), or no treatment in a randomized cross-over design. Haemodynamic responses of AIx, blood pressure and thoracic bioimpedance (heart rate, cardiac index) were assessed by measurement at baseline, every 60 s for the first 5 min, and then every 5 min for a further 55 min. RESULTS: AIx was reduced by amyl nitrite (peak effect -9 +/- 2% at 1 min, P < 0.002) and GTN (peak effect -12 +/- 3% at 4 min, P < 0.05). Compared with amyl nitrite, the onset and offset of action of GTN was slower. Amyl nitrite initially increased heart rate by 27 +/- 4% (P < 0.001) and cardiac index by 13 +/- 3% (P < 0.001) whereas GTN had no significant effect (P > 0.05). Neither agent affected blood pressure. CONCLUSIONS: GTN causes a slower and more sustained reduction in AIx than amyl nitrite. Although amyl nitrite causes a more rapid fall and recovery in AIx, it induces a reflex tachycardia that may limit interpretation of the initial (1 min) but not later (2 min) changes in AIx. The prolonged offset of GTN suggests that a sufficient washout period must be included when making repeated measures or when assessing the subsequent effects of other agents.

Adult↗

PubMed1983

Nitrite loss and spoilage microflora development in chub-packed luncheon meat.

Residual nitrite was lost from chub-packed luncheon meat during storage through both chemical breakdown and microbial consumption. The relative importance of these mechanisms in this pasteurized product was determined by the speed of development of the spoilage microflora, which is influenced by storage conditions. The nitrite half-life due to chemical loss was 13 d at 25 degrees C and 36 d at 10 degrees C. When microbial growth occurred these half-lives were reduced to 2.6 d and 21 d, respectively. Qualitative differences in the microflora that developed at these two temperatures (denitrifying Bacillus spp. at 25 degrees C and non-denitrifying Streptococcus spp. at 10 degrees C) account for the large temperature effect. Growth of Streptococcus spp. increased the rate of chemical nitrite loss in chubs by reducing the pH value. Nitrite did not inhibit the aerobic growth of either Bacillus or Streptococcus species associated with spoilage but did inhibit the anaerobic growth of Bacillus spp. This bacteriostatic effect of residual nitrite in anaerobic conditions will decrease during storage as nitrite level falls and oxygen penetrates the chub pack. Nitrite-mediated bacteriostasis does not obviate the need for refrigerated storage but does afford a real, if ephemeral, safeguard against spoilage occurring during short periods of temperature abuse.

Animals↗

PubMed2006

Broad-band ultraviolet B phototherapy is associated with elevated serum thiobarbituric acid reactive substance and nitrite-nitrate levels in psoriatic patients.

BACKGROUND: Although the local anti-inflammatory, immunosuppressive and oxidative activity of UVB is known, the systemic effect of UVB phototherapy in dermatological patients has not been investigated. OBJECTIVE: We aimed to investigate the lipid peroxidation status (as represented by thiobarbituric acid reactive substance, TBARS) and nitrite-nitrate levels in psoriatic patients under broad-band ultraviolet B (BB-UVB) phototherapy in order to determine the systemic effects of UVB. SUBJECTS AND METHODS: Thirty-two psoriatic patients and 20 healthy controls were included. Blood samples were obtained at the beginning, after 6-10 exposures to BB UVB phototherapy (mean 5 weeks) and at the end of the therapy period (mean 21 weeks). Serum TBARS and nitrite-nitrate levels were evaluated. RESULTS: There was no statistically significant difference in serum TBARS and nitrite-nitrate levels between psoriatic patients (basal) and healthy volunteers. There was no statistically significant correlation between disease duration, disease severity, or the total cumulative dose of UVB and serum levels of TBARS and nitrite-nitrate in psoriatic patients. Total nitrite levels in samples obtained during and at the end of therapy were significantly higher than basal levels (P=0.033 and P=0.005, respectively). TBARS levels in samples obtained during and at the end of therapy were significantly higher than basal levels (P=0 and P=0.026, respectively). There was a negative correlation (r=-0.576, P=0.039) between the total nitrite and TBARS levels in psoriatic patients at the end of therapy. CONCLUSION: Our study showed that chronic exposure to UV irradiation may lead to a systemic effect on lipid peroxidation and NO levels, which are shown by a significant elevation in TBARS and nitrite-nitrate levels in serum.

Adult↗

PubMed2002

Enzymology and bioenergetics of respiratory nitrite ammonification.

Nitrite is widely used by bacteria as an electron acceptor under anaerobic conditions. In respiratory nitrite ammonification an electrochemical proton potential across the membrane is generated by electron transport from a non-fermentable substrate like formate or H(2) to nitrite. The corresponding electron transport chain minimally comprises formate dehydrogenase or hydrogenase, a respiratory quinone and cytochrome c nitrite reductase. The catalytic subunit of the latter enzyme (NrfA) catalyzes nitrite reduction to ammonia without liberating intermediate products. This review focuses on recent progress that has been made in understanding the enzymology and bioenergetics of respiratory nitrite ammonification. High-resolution structures of NrfA proteins from different bacteria have been determined, and many nrf operons sequenced, leading to the prediction of electron transfer pathways from the quinone pool to NrfA. Furthermore, the coupled electron transport chain from formate to nitrite of Wolinella succinogenes has been reconstituted by incorporating the purified enzymes into liposomes. The NrfH protein of W. succinogenes, a tetraheme c-type cytochrome of the NapC/NirT family, forms a stable complex with NrfA in the membrane and serves in passing electrons from menaquinol to NrfA. Proteins similar to NrfH are predicted by open reading frames of several bacterial nrf gene clusters. In gamma-proteobacteria, however, NrfH is thought to be replaced by the nrfBCD gene products. The active site heme c group of NrfA proteins from different bacteria is covalently bound via the cysteine residues of a unique CXXCK motif. The lysine residue of this motif serves as an axial ligand to the heme iron thus replacing the conventional histidine residue. The attachment of the lysine-ligated heme group requires specialized proteins in W. succinogenes and Escherichia coli that are encoded by accessory nrf genes. The proteins predicted by these genes are unrelated in the two bacteria but similar to proteins of the respective conventional cytochrome c biogenesis systems.

Bacteria↗