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PubMed2006

Osmotic stress on nitrification in an airlift bioreactor.

The effect of osmotic pressure on nitrification was studied in a lab-scale internal-loop airlift-nitrifying reactor. The reactor slowly adapted to the escalating osmotic pressure during 270 days operation. The conditions were reversed to the initial stage upon full inhibition of the process. Keeping influent ammonium concentration constant at 420 mg N L(-1) and hydraulic retention time at 20.7h, with gradual increase in osmotic pressure from 4.3 to 18.8x10(5) Pa by adding sodium sulphate, the ammonium removal efficiencies of the nitrifying bioreactor were maintained at 93-100%. Further increase in osmotic pressure up to 19.2x10(5) Pa resulted in drop of the ammonium conversion to 69.2%. The osmotic pressure caused abrupt inhibition of nitrification without any alarm and the critical osmotic pressure value causing inhibition remained between 18.8 and 19.2x10(5) Pa. Nitrite oxidizers were found more sensitive to osmotic stress as compared with ammonia oxidizers, leading to nitrite accumulation up to 61.7% in the reactor. The performance of bioreactor recovered gradually upon lowering the osmotic pressure. Scanning and transmission electron microscopy indicated that osmotic stress resulted in simplification of the nitrifying bacterial populations in the activated sludge as the cellular size reduced; the inner membrane became thinner and some unknown inclusions appeared within the cells. The microbial morphology and cellular structure restored upon relieving the osmotic pressure. Addition of potassium relieved the effect of osmotic pressure upon nitrification. Results demonstrate that the nitrifying reactor possesses the potential to treat ammonium-rich brines after acclimatization.

Bioreactors↗
PubMed1999

Incorporation of ammonium into intracellular UDP-activated N-acetylhexosamines and into carbohydrate structures in glycoproteins.

The negative effects of ammonia on animal cells, especially in vitro cultures, are well known, but the mechanism of how ammonia inhibits cell growth and influences the glycosylation of proteins is not completely understood. We investigated the ammonium action on the synthesis of the intracellular UDP-N-acetylhexos- amines (UDPGNAc), which are precursors of glycosylation as well as on N-linked oligosaccharides of a recombinant human IL-2 mutant variant model glycoprotein expressed in BHK-21 cells under defined and controlled culture conditions in a continuously perfused bioreactor. The examinations were based on our previous observations that increased ammonia concentrations in the medium lead to the intracellular formation and accumulation of UDPGNAc (Ryll et al., 1994). The kinetics of formation of the UDPGNAc pool after adding ammonia and its reconstitution to normal conditions are shown. To study the pathway leading to the intracellular increase of UDPGNAc, the uptake and incorporation of 15NH4+ was confirmed by the detection of 15N in UDP-N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc was purified using high pH anion-exchange chromatography with pulsed amperometric detection and analyzed by GC/MS. The proportion of UDP-GlcNAc containing 15N was approximately 60% and corresponds quantitatively to the increased intracellular concentration of UDP-GlcNAc. In order to confirm the direct influence of ammonia on protein glycosylation, the human IL-2 mutant glycoprotein variant IL-Mu6, bearing a novel N-glycosylation site, has been produced under defined protein-free medium conditions in the presence of 15NH4Cl. IL-Mu6 glycoprotein was purified and N-glycans released were analyzed by matrix-assisted laser desorption ionization time of flight mass spectroscopy. Maximally 60-80% of N-acetylated sugars in N-glycan structures contained 15N indicating that ammonium is used as a building block during synthesis of the carbohydrate structures expressed from in vitro cultivated mammalian cells.

Animals↗
PubMed2006

Citric-acid-coated magnetite nanoparticles for biological applications.

Water-based magnetic fluids, generally intended for biomedical applications, often have various coating molecules that make them stable and compatible with biological liquids. Magnetic fluids containing iron oxide particles have been prepared by a co-precipitation method, using citric acid as stabilizer. The magnetic particles of the magnetic fluids were obtained by chemical precipitation from ferric (FeCl(3)) and ferrous salts (FeSO(4) or FeCl(2)) in alkali medium (ammonia hydroxide). Citric acid was used to stabilize the magnetic-particle suspension. Physical tests were performed in order to determine various microstructural and rheological features. Transmission electron microscopy was the main investigation method for assessing the magnetic-particle size. The dimensional distribution of the magnetic-particle physical diameter was analyzed using the box-plot statistical method while infrared absorption spectra were used to study the colloidal particle structure. The magnetic-fluid density (picnometric method), viscosity (capillary method) and surface tension (stalagmometric method) were measured using standard methods.

Ammonium Hydroxide↗
PubMed2006

[Inhibitory effect of pyrazole compound DL-1 on soil nitrification: a preliminary study].

The study with soil incubation test under constant temperature and humidity showed that compared with DCD, DL-1 could significantly inhibit the oxidation of soil ammonium. In the first 3 weeks of incubation, DL-1 had an inhibitory effect of >70% on soil nitrification, with the best effect during 14-28 d of incubation. On the 14, 21, and 28 d of incubation, DL-1 with its dosage being 1.0 % of (NH4)2SO4-N decreased the soil NO3- -N content by 26.23%, 33.27% and 23.31%, respectively, compared with the same dosage of DCD, and by 71.12%, 69.10% and 55.14%, respectively, compared with no inhibitors applied. When the dosage of DL-1 accounted for 2.0% of applied N, soil nitrification was strongly inhibited, and soil NO3- -N content remained at a lower level till to the end (90 d) of incubation.

Ammonia↗
PubMed2006

Ammonium exchange in aqueous solution using Chinese natural clinoptilolite and modified zeolite.

In this study, the Chinese natural clinoptilolite (sample 1) was fused with sodium hydroxide prior to hydrothermal reaction, and it was transformed to modified zeolite Na-Y (sample 2). The uptake of ammonium ion from aqueous solutions in the concentration range 50-250 mg NH(4)(+)/l on to the two samples was compared and the equilibrium isotherms have been got. The influence of other cations present in water upon the ammonia uptake was also determined. The cations studied were potassium, calcium and magnesium. In all cases the anionic counterion present was chloride. The results showed that sample 2 exhibited much higher uptake capacity compared with sample 1. At the initial concentration of 250 mg NH(4)(+)/l, the ammonium ion uptake value of sample 2 was 19.29 mg NH(4)(+)g(-1) adsorbent, while sample 1 was only 10.49 mg NH(4)(+)g(-1) adsorbent. For the natural clinoptilolite, the effect of the metal ions suggested an order of preference K(+)>Ca(2+)>Mg(2+). These contrasted with the modified zeolite, where the order appeared to be Mg(2+)>Ca(2+)>K(+).

Quaternary Ammonium Compounds↗
PubMed1997

Anti-aflatoxin mutagenic factors in corn.

Extracts, isolated through sequential fractionation and partition procedures described previously (Martinez et al. 1994) from aflatoxin-free corn and aflatoxin-contaminated corn with and without ammonia treatment, were investigated for mutagenic potential using the Ames test (TA 100 tester strain). 2-Aminofluorene (2-AF) and pure aflatoxin B1 (AFB1) were used as positive controls. Although TA100 showed mutagenic response to pure AFB1 at a dose of ca 10 ng/plate, all isolates tested from ammonia-treated aflatoxin-contaminated corn containing 7500 ng AFB1/g did not exhibit positive results in the Ames test. Additionally, isolates from non-ammonia-treated aflatoxin-contaminated corn failed to give positive mutagenic potentials. These results indicate that differences between the mutagenic potentials of pure aflatoxins and of aflatoxins in naturally-contaminated corn exist. CH2Cl2 extracts (the fractions containing aflatoxins) obtained from aflatoxin-contaminated corn with and without ammonia treatment were applied to preparative thin layer chromatography (TLC) in an effort to separate aflatoxins and/or ammonia/aflatoxin reaction products from the "unknown interfering materials' existing in the corn matrix. Each of the fractions separated by TLC was tested by the Ames test with S9 activation and none of them gave a mutagenic response to TA100. CH2Cl2 extracts in dimethylsulphoxide (DMSO) obtained from non-ammonia-treated aflatoxin-free corn were spiked with pure AFB1 and tested by TA100 with S9 activation. Again, no positive responses were observed. These findings provide further evidence of "unknown interfering materials' in corn which may bind with aflatoxin and/or can be extracted by CH2Cl2 together with aflatoxin, and, therefore, block the mutagenic activity of aflatoxin in the Ames test. Those materials were not separated from the aflatoxins by the TLC technique used in the present study. Possible reasons and further studies required to evaluate this phenomenon are discussed.

Aflatoxins↗
PubMed2005

[Operation performance of membrane nitrification bioreactor for ammonia-containing wastewater].

The operation performance of membrane nitrification bioreactor to treat ammonia-containing wastewater as well as the capabilities of separation and filtration of polypropylene membrane modules were tested. The removal efficiency of ammonia was kept higher than 95% when the hydraulic retention time was set at 1 day, the influent concentration was increased up to 80 mmol (NH4+ -N) x L(-1) and the volume loading rate was increased up to 1.12 kg (NH4+ -N) x m(-3) x d(-1). The biomass in the reactor was accumulated from 5 g x L(-1) to 10 g x L(-1) within 50 days, which indicated that polypropylene membrane modules were efficient in retaining biomass. The biomass attached to the membrane also contributed to the conversion of ammonia and nitrite. When the hydraulic pressure was lower than 80cm, the increase of hydraulic pressure improved the permeation of membrane. However, when the hydraulic pressure was beyond 80cm, the increase of hydraulic pressure did not significantly improve the permeation of membrane. The permeate flux was the highest 2.51 (L x m (-2) x h(-1)) but the resistance was the lowest (2.63 x 10(-5)) m(-1) when the hydraulic pressure was about 20 cm. The results showed that the membrane nitrification bioreactor could be run normally without extra energy input.

Biodegradation, Environmental↗
PubMed1987

Effects of feeding or infusing ammonium salts of volatile fatty acids on ruminal fermentation, plasma characteristics, and milk production of cows.

Eight rumen-fistulated Holstein cows, averaging 77 d postpartum, were used in a replicated 4 X 4 Latin square design with 28-d periods to investigate the effect of ammonium salts of isobutyrate, 2-methylbutyrate, isovalerate, and n-valerate on animal performance and their possible mechanism(s) and site(s) of action. Each cow was fed ad libitum a complete mixed diet of 55% corn silage and 45% concentrate on a dry basis that was supplemented with 1.8 kg of premix daily. Treatments were 1) control, 2) ammonium salts of volatile fatty acids in premix, 3) ammonium salts of volatile fatty acids ruminally infused, or 4) ammonium salts of volatile fatty acids abomasally infused. Mean ruminal fluid pH and concentrations of ammonia and volatile fatty acids for treatment comparisons were not different. Plasma concentrations of isobutyrate, 2-methylbutyrate, and valerate differed among treatments, but there was no significant effect on dry matter intake, milk production, milk composition, or efficiency of feed utilization. Apparent nutrient digestibility; disappearance of dry matter, cellulose, and nitrogen from polyester bags suspended in the rumen; and plasma concentrations of glucose, free fatty acids, and growth hormone also were not significantly affected by treatment.

Abomasum↗
PubMed1990

Renal excretion of zinc in patients with chronic uremia.

Though uremic patients have been reported to have subnormal zinc levels in plasma and an abnormal zinc metabolism, data on their renal excretion of zinc are still unavailable. In our study, 55 nondialyzed uremic patients had a markedly lower concentration of zinc in plasma and a lower urinary zinc excretion. They had a higher excretory fraction of zinc in the renal tubules and a higher ratio of zinc to creatinine excretion than normal subjects. We found that the total daily excretion of zinc, calcium, phosphate and ammonia was reduced, and that the ratio of calcium or ammonia to creatinine excretion decreased in uremic patients. Urinary zinc excretion was correlated with renal creatinine clearance (r = 0.50, p less than 0.001) in both normal subjects and uremic patients, but ammonia excretion was correlated with zinc excretion in normal subjects only. In uremia, urinary zinc excretion was correlated with urinary calcium (r = 0.55, p less than 0.001) and urinary phosphate excretion (r = 0.30, p less than 0.05). We conclude that the increased ratio of zinc to creatinine excretion and the excretory fraction of zinc in the renal tubules of uremic patients may increase the urinary zinc excretion, but a severe diminution of the glomerular filtered load of zinc may be the major factor in decreasing the urinary zinc excretion in uremia.

Adult↗
PubMed2000

Nitrate reductase and nitrous oxide production by Fusarium oxysporum 11dn1 under aerobic and anaerobic conditions.

The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produce nitrous oxide on nitrate-containing medium in anaerobic conditions. The rate of nitrous oxide formation was three to six orders of magnitude lower than the rates of molecular nitrogen production by common denitrifying bacteria. Acetylene and ammonia did not affect the release of nitrous oxide release. It was shown that under anaerobic conditions fast increase of nitrate reductase activity occurred, caused by the synthesis of enzyme de novo and protein dephosphorylation. Reverse transfer of the mycelium to aerobic conditions led to a decline in nitrate reductase activity and stopped nitrous oxide production. The presence of two nitrate reductases was shown, which differed in molecular mass, location, temperature optima, and activity in nitrate- and ammonium-containing media. Two enzymes represent assimilatory and dissimilatory nitrate reductases, which are active in aerobic and anaerobic conditions, respectively.

Aerobiosis↗
PubMed2003

Differences between weekday and weekend air pollutant levels in southern California.

Ambient air quality data were analyzed to empirically evaluate the effects of reductions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) emissions on weekday and weekend levels of ozone (O3; 1991-1998) and particulate NO3- (1980-1999) in southern California. Despite significantly lower O3 precursor levels on weekends, 20 of 28 South Coast Air Basin (SoCAB) sites (28 of all 78 southern California sites) showed statistically significant higher mean O3 levels on Sundays than on weekdays (p < 0.01); 49 of the remaining 50 sites showed no significant differences between mean weekday and Sunday peak O3 levels. We also observed no statistically significant differences between mean weekday and weekend concentrations of particulate NO3- or nitric acid (HNO3, the precursor of particulate NO3-). Averaged over sites, the mean Sunday NOx and nonmethane hydrocarbon concentrations were 25-41% and 16-30% lower, respectively, than on weekdays. Site-to-site differences between weekend and weekday mean peak hourly O3 levels were related to whether O3 formation was limited by the availability of NOx. A thermodynamic equilibrium model predicts that particulate NO3- levels would decrease in response to a reduction of HNO3, and that particulate ammonium NO3- formation was not limited by the availability of ammonia. The similarity of mean weekday and weekend levels of NO3- therefore did not result from limitations on the formation of particulate NO3- from its precursor, HNO3.

Air Pollutants↗
PubMed1995

Potassium/proton antiport system of growing Enterococcus hirae at high pH.

The cytoplasmic pH (pHin) of Enterococcus hirae growing at pH 9.2 was maintained at about 8.1. Membrane-permeating amines such as ammonia alkalinized the pHin from 8.1 to 9.0 at a high concentration and induced K+ extrusion. The pHin alkalinization was transient; the pHin fell from 9.0 to the original value of pH 8.1, at which point K+ extrusion ceased, and remained constant. Cells accumulated ammonium ion to an extent stoichiometrically equivalent to the K+ loss. This bacterium continued to grow well under this condition. These results suggest that the pHin-responsive primary K+/H+ antiport system (Y. Kakinuma, and K. Igarashi, J. Biol. Chem. 263:14166-14170, 1988) works for the pHin regulation of this organism growing at a high pH.

Amines↗
PubMed2002

Effect of carbon dioxide and ammonium removal on pH changes in polishing ponds.

If nutrient removal is to be obtained in ponds treating sewage, the pH must be raised so that ammonia can desorb and phosphates can precipitate. In this paper it is shown that the pH increase in ponds can be predicted quantitatively from simple stoichiometry, taking into consideration physical and biological carbon dioxide removal, ammonia stripping and calcium carbonate precipitation. Biological CO2 removal by photosynthesis is identified as the main process to effect pH increase in ponds. The rate of pH increase and consequently the required retention time depend on the net rate of CO2 consumption, the extent of ammonium stripping, the characteristics of the influent (alkalinity and pH) as well as factors concerning the environment (temperature) and dimensions (depth) of the pond. A high pH (range 9 to 10) can be obtained in about 5 days if digested sewage is used (low organic material concentration), climate conditions are favourable and the pond is shallow (< 0.5 m deep).

Adsorption↗
PubMed1997

Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women.

Previously we demonstrated that low grade chronic metabolic acidosis exists normally in humans eating ordinary diets that yield normal net rates of endogenous acid production (EAP), and that the degree of acidosis increases with age. We hypothesize that such diet-dependent and age-amplifying low grade metabolic acidosis contributes to the decline in skeletal muscle mass that occurs normally with aging. This hypothesis is based on the reported finding that chronic metabolic acidosis induces muscle protein breakdown, and that correction of acidosis reverses the effect. Accordingly, in 14 healthy postmenopausal women residing in a General Clinical Research Center and eating a constant diet yielding a normal EAP rate, we tested whether correcting their "physiological" acidosis with orally administered potassium bicarbonate (KHCO3; 60-120 mmol/day for 18 days) reduces their urinary nitrogen loss. KHCO3 reduced EAP to nearly zero, significantly reduced the blood hydrogen ion concentration (P < 0.001), and increased the plasma bicarbonate concentration (P < 0.001), indicating that pre-KHCO3, diet-dependent EAP was significantly perturbing systemic acid-base equilibrium, causing a low grade metabolic acidosis. Urinary ammonia nitrogen, urea nitrogen, and total nitrogen levels significantly decreased. The cumulative reduction in nitrogen excretion was 14.1 +/- 12.3 g (P < 0.001). Renal creatinine clearance and urine volume remained unchanged. We conclude that in postmenopausal women, neutralization of diet-induced EAP with KHCO3 corrects their preexisting diet-dependent low grade metabolic acidosis and significantly reduces their urinary nitrogen wasting. The magnitude of the KHCO3-induced nitrogen-sparing effect is potentially sufficient to both prevent continuing age-related loss of muscle mass and restore previously accrued deficits.

Acidosis↗
PubMed1983

Degradation of microinjected proteins: effects of lysosomotropic agents and inhibitors of autophagy.

HeLa cells, injected with radioiodinated proteins by fusion with RBC ghosts, were exposed to inhibitors of lysosomal proteolysis and autophagy. The degradation of injected [125I]bovine serum albumin (BSA) was unaffected by chloroquine, NH4Cl, nocodazole, colcemid, puromycin, cycloheximide, or enucleation. Although degradation of [125I]lactate dehydrogenase (LDH) and [125I]pyruvate kinase (PK) was inhibited one-third by chloroquine or ammonia, their degradation was unaffected by the other compounds. In contrast, enhanced degradation of 125I-PK resulting from depriving injected HeLa cells of amino acids and serum was inhibited 70% by colcemid and abolished by chloroquine or ammonia. Similarly, degradation of [14C]sucrose-labeled BSA-polylysine conjugates that entered HeLa cells by endocytosis was inhibited as much as 80% by chloroquine and ammonia. Sensitivity of both enhanced proteolysis and degradation of exogenous proteins to ammonia or chloroquine indicates they are effective inhibitors of lysosomal proteolysis in HeLa cells. Failure of ammonia or chloroquine to inhibit degradation of injected 125I-BSA and the modest inhibition of degradation of injected 125I-LDH or 125I-PK indicates that virtually all BSA molecules and most PK or LDH molecules are degraded by a nonlysosomal proteolytic system. Components of this degradative system are present in vast excess or are long lived, since inhibition of protein synthesis for 20 hr had no effect on the degradation of injected proteins.

Ammonium Chloride↗
PubMed1995

Effects of ammonia on the de novo synthesis of polypeptides in cells of Nitrosomonas europaea denied ammonia as an energy source.

The effects of ammonium on the de novo synthesis of polypeptides in the soil-nitrifying bacterium Nitrosomonas europaea have been investigated. Cells were incubated in the presence of both acetylene and NH4+. Under these conditions, the cells were unable to utilize NH4+ as an energy source. Energy to support protein synthesis was supplied by the oxidation of hydroxylamine or other alternative substrates for hydroxylamine oxidoreductase. De novo protein synthesis was detected by 14C incorporation from 14CO2 into polypeptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. In the presence of NH4+, acetylene-treated cells synthesized the 27-kDa polypeptide of ammonia monoxygenase (AMO) and two other major polypeptides (with sizes of 55 and 65 kDa). The synthesis of these polypeptides was completely inhibited by chloramphenicol and attenuated by rifampin. The optimal concentration of hydroxylamine for the in vivo 14C-labeling reaction was found to be 2 mM. The effect of NH4+ concentration was also examined. It was shown to cause a saturable response with a Ks of approximately 2.0 mM NH4+. Labeling studies conducted at different pH values suggest cells respond to NH3 rather than NH4+. No other compounds tested were able to influence the synthesis of the 27-kDa component of AMO, although we have also demonstrated that this polypeptide can be synthesized under anaerobic conditions in cells utilizing pyruvate- or hydrazine-dependent nitrite reduction as an energy source. We conclude that ammonia has a regulatory effect on the synthesis of a subunit of AMO in addition to providing nitrogen for protein synthesis.

Acetylene↗
PubMed1978

ATP, trehalose, glucose and ammonium ion localization in the two cell types of Dictyostelium discoideum.

Ultra-microfluorometric techniques were adapted to follow several compounds related to energy metabolism through the developmental cycle of Dictyostelium discoideum. Each compound (ATP, trehalose, glucose, and ammonium ion) was found to be present in stalk and/or spore cells. The accumulation of NH4+ was interpreted as an indication of protein degradation, a source of energy in this organism. During the early stages of differentiation NH4+ was localized only in prestalk cells. However, it accumulated in spore cells during culmination such that levels were comparable in the two cell types by the end of development. Trehalose, an energy source for germinating spores, was found in both cell types but was preferentially degraded in stalk cells late in development. Glucose, the degradation product of trehalose, was localized in prestalk cells and varied inversely with trehalose levels. ATP was not localized in a specific cell type during development. However, ATP declined in stalk cells at an earlier stage of development.

Adenosine Triphosphate↗
PubMed2004

Nitrite oxidation inhibition by hydroxylamine: experimental and model evaluation.

A proposed approach for biological nitrogen removal significantly reduces cost by reducing biomass production and carbon requirements via inhibition of nitrite oxidation (NO2- to NO3-). Batch experiments were conducted to examine the effect of hydroxylamine (HM) on nitrite oxidizers, ammonia oxidizers, and nitrite reducers. Hydroxylamine effect experiments were done at initial pH values of 7.4-8.4, nitrogen concentrations of 100 mg N/L, biomass concentrations of 100-400 mg VSS/L and HM dosages up to 43 mg/L. Nitrite oxidizer activity was completely inhibited by HM at dosages of 7.0 and 8.9 mg/L for pH values of 8.4 and 7.6, respectively. Relatively low HM concentrations (0.35-5.5 mg/L) can be used to completely inhibit nitrite oxidation, but do not significantly affect ammonia oxidizers and nitrite reducers. A model developed to describe the effect of pH on nitrite oxidation rate fits the data well (R2 = 0.89) with values for Vmax of 0.372 (mg N/mg VSS-hr), pH* of 7.72, and the inhibition constant Kh of 0.154. Incorporation of HM inhibition into the model provided a good fit to relative nitrite oxidation rate as a function of undissociated HM concentration (R2 = 0.80, Vmax = 0.028 mg N/mg VSS-hr, pH = 7.89, Kh = 0.302, a = 0.195, and Ki= 0.277 mg/L).

Biomass↗