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PubMed2004

Tacrolimus ameliorates cerebral vasodilatation and intracranial hypertension in the rat with portacaval anastomosis and hyperammonemia.

Arterial hyperammonemia and cerebral vasodilatation correlate with cerebral herniation in patients with fulminant hepatic failure (FHF). Tacrolimus is a calcineurin inhibitor that passes the blood-brain barrier and may increase cerebrovascular tone and restrict cerebral ammonia influx. In this study, we determined if tacrolimus prevents cerebral vasodilatation and high intracranial pressure (ICP) in the rat with portacaval anastomosis (PCA) challenged to high arterial ammonia (NH4+) concentration. Seven groups of mechanically ventilated rats, with 6-9 rats in each group, were investigated within 48 hours after construction of a PCA (4 groups) or after sham operation (3 groups). Three groups of the rats received infusion of NH4+ and 4 groups received saline for approximately 180 minutes. Two groups of the PCA rats receiving either NH4+ or saline had an i.v. injection of tacrolimus (0.4 mg/kg) or vehicle before start of NH4+ or saline infusion. Cerebral blood flow (CBF) was monitored by a laser Doppler probe in brain cortex. ICP was monitored by placement of a catheter in the cerebrospinal fluid. CBF and ICP increased in PCA rats receiving NH4+ infusion compared to PCA controls and to all groups of sham-operated animals (P <.05). In the group of PCA rats pre-treated with tacrolimus before receiving ammonia infusion, the increase in ICP was ameliorated compared to the ammonia infused group receiving vehicle (P <.03). Tacrolimus also prevented an increase in CBF in the PCA group receiving NH4+ (P <.05) compared to the control groups. In conclusion, Tacrolimus prevents cerebral vasodilatation and ameliorates intracranial hypertension in PCA rats receiving NH4+ infusion. These findings indicate that tacrolimus could be of clinical value in the prevention of cerebral hyperemia, high ICP, and serious brain damage in patients with FHF.

Anastomosis, Surgical↗
PubMed2005

Modelling the human rhesus proteins: implications for structure and function.

The mammalian rhesus (Rh) proteins that carry the Rh blood group antigens of red blood cells are related to the ammonium channel (Amt) proteins found in both pro- and eukaryotes. However, despite their clinical importance the structure of the Rh antigens is presently unknown. We have constructed homology models of the human Rh proteins, RhD and RhAG using the structure of the Escherichia coli ammonia channel AmtB as a template, together with secondary structure predictions and the extensive available biochemical data for the Rh proteins. These models suggest that RhAG and the homologous non-erythrocyte Rhesus glycoproteins, RhBG and RhCG, have a very similar channel architecture to AmtB. By comparison, RhD and RhCE have a different arrangement of residues, indicating that if they function as ammonia channels at all, they must do so by a different mechanism. The E. coli AmtB protein is a homotrimer and our models provoke a reassessment of the widely accepted tetrameric model of the organisation of the erythrocyte Rh complex. A critical analysis of previously published data, together with sequencing yield data, lead us to suggest that the erythrocyte Rh complex could indeed also be trimeric.

Amino Acid Sequence↗
PubMed2001

Role of glutamine synthetase in nitrogen metabolite repression in Aspergillus nidulans.

Glutamine synthetase (GS), EC 6.3.1.2, is a central enzyme in the assimilation of nitrogen and the biosynthesis of glutamine. We have isolated the Aspergillus nidulans glnA gene encoding GS and have shown that glnA encodes a highly expressed but not highly regulated mRNA. Inactivation of glnA results in an absolute glutamine requirement, indicating that GS is responsible for the synthesis of this essential amino acid. Even when supplemented with high levels of glutamine, strains lacking a functional glnA gene have an inhibited morphology, and a wide range of compounds have been shown to interfere with repair of the glutamine auxotrophy. Heterologous expression of the prokaryotic Anabaena glnA gene from the A. nidulans alcA promoter allowed full complementation of the A. nidulans glnADelta mutation. However, the A. nidulans fluG gene, which encodes a protein with similarity to prokaryotic GS, did not replace A. nidulans glnA function when similarly expressed. Our studies with the glnADelta mutant confirm that glutamine, and not GS, is the key effector of nitrogen metabolite repression. Additionally, ammonium and its immediate product glutamate may also act directly to signal nitrogen sufficiency.

Amino Acid Sequence↗
PubMed2003

Effect of high salinity on anaerobic treatment of low strength effluents.

In anaerobic treatment, it is obligatory to know the effect of potentially inhibitory compounds due to the fact that methane formation may retard severely and may proceed slower than organic acid production. One of the most important inhibitory substances in anaerobic treatment is high salinity. In many cases, the main collectors of a municipal sewer system should have been built in the coastal zone and below the ground water level due to the available topography of wastewater catchments area, which is carrying the risk of seawater infiltration. Besides, one of the most convenient methods for leachate control is to treat landfill leachates with domestic wastewaters in the central municipal wastewater treatment plants such as in Istanbul. Thus, the nitrogen load of the treatment plants increase significantly. In this study, the effects of high salinity and ammonium nitrogen levels on mesophilic anaerobic tretament processes were investigated. In the first part of the study, high salinity effect on anaerobic treatment was investigated by feeding synthetic wastewater containing high salinity between 0.15%-1.5% ratios. In the second part of the study, the simultaneous effect of high salinity and ammonia (1.5% salinity+1,000 mg NH3/l) was examined by a lab-scale Upflow Anaerobic Sludge Bed Reactor (UASBR). Results indicated no significant inhibition in both cases and effective COD removals (89%) and total biogas productions having methane content of 84% could be achieved.

Ammonia↗
PubMed1989

Regulation of nitrogen catabolic enzymes in Streptomyces clavuligerus.

The levels of several enzymes involved in assimilation of different nitrogen compounds were investigated in Streptomyces clavuligerus in relation to the nitrogen source supplied to the cultures. Threonine dehydratase, serine dehydratase, proline dehydrogenase, histidase and urocanase were not decreased in the presence of ammonium. The latter two enzymes were induced by histidine in the culture medium, while proline dehydrogenase was induced by proline. Glutamine synthetase, urease and ornithine aminotransferase levels were higher with poor nitrogen sources and were repressed by ammonium. Arginase was induced by arginine and repressed by ammonium. Glutamine synthetase was rapidly inactivated upon addition of ammonium to the culture, and could be reactivated in vitro by treatment with snake venom phosphodiesterase, which suggested that adenylylation is involved in the inactivation. Three previously isolated mutants with abnormal glutamine synthetase activities showed pleiotropic effects on urease formation. All these data point to a mechanism controlling preferential utilization of some nitrogen sources in this species.

Ammonia↗
PubMed2001

A new method for conservation of nitrogen in aerobic composting processes.

Several factors, such as pH, C/N ratio, temperature, mixing and turning, and aeration rate, could affect the loss of ammonia in composting reactions. Substantial loss of ammonia can reduce the nutrient value of the compost product and may lead to a severe odor problem in the composting facility. A new method for conservation of ammonia in composting was proposed and tested in this study. The ammonia being produced during the composting was precipitated into struvite crystals by addition of Mg and P salts. Ammonia volatilization was greatly reduced by this method and it also contributed to a remarkable increase in total ammoniacal-N (TAN) content in the compost, reaching up to 1.4% of dry mass. This value of TAN content was 3-5 times higher than that in normal compost. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses confirmed the formation of struvite crystals in the aerobic composting process.

Air↗
PubMed1985

Protein supplementation of ammoniated roughages. III. Corncobs supplemented with a blood meal-corn gluten meal mixture--steer studies.

Two factorial experiments were conducted to investigate site and extent of organic matter (OM) digestion, nitrogenous fractions flowing at the abomasum and rates-of-passage in steers fed 0, 2 or 4 g NH3/100 g dry matter of treated corncobs supplemented with either a corn or a blood meal-corn gluten meal (BM-CGM) supplement. Rumen and total tract OM digestion coefficients were quadratically increased (P less than .05) and dietary N was quadratically increased (P less than .07) due to the main effect of ammonia. The main effect of protein supplement increased (P less than .05) postruminal OM digestibility, nonammonia N and dietary-N flow. Quadratic protein X ammonia interactions were noted for fluid flow, total-N flow, total amino acid flow and ammonia-N flow. Linear protein X ammonia interactions were noted for bacterial-N flow, which appeared to indicate that N utilization of the ammoniated corn-cob was improved by the inclusion of BM-CGM in the diet. Diet dry matter intake, fluid volume, rate of fluid passage, particulate mass and rate of particulate passage in rumen-fistulated steers were unaffected by either main effect. However, rumen fluid pH of steers fed BM-CGM was lower than that from steers fed the corn supplement.

Animal Feed↗
PubMed2002

Influence of straw types and nitrogen sources on mushroom composting emissions and compost productivity.

The effects of different straw types and organic and inorganic nitrogen (N) sources on the chemical composition and odor concentration (OC) of mushroom composting emissions, compost parameters, and mushroom yield were examined using bench-scale and large-scale (windrows and aerated tunnels) composting systems. There were close correlations between the butanol or combined H(2)S+dimethyl sulfide (DMS) concentration and OC of air samples taken from different composting ingredients (r=0.83 and 0.76-0.87, P<0.01, for log(e)-transformed data). Differences in N availability, in terms of NH(3) and N losses during composting, were found between different N sources. Materials in which the N was less available (chipboard and digester wastes, cocoa shells, ammonium sulfate) produced lower mushroom yields than materials in which the N was more readily available (poultry manure, urea, brewers' grains, hop and molasses wastes, cocoa meal). Replacement of poultry manure with the other N sources at 50-100% or wheat straw with rape, bean, or linseed straw in aerated tunnel or windrow composts reduced the OC and emissions of odorous sulfur-containing compounds, but also reduced yield. Urea and cocoa meal may be suitable for "low odor" prewetting of straw, with addition of poultry manure immediately before aerated tunnel composting. Rape straw in compost reduces the formation of anaerobic zones and resulting odorous emissions, since it maintains its structure and porosity better than wheat straw.

Agaricales↗
PubMed2002

The application of membrane filtration for the removal of ammonium ions from potable water.

It is well recognized that soluble ammonia and nitrite in drinking water has chronic effects on humans. Ammonia has potential environmental health hazards, particularly to young children. European Union Standards limit the concentration of ammonia to 0.5 mg/l in drinking water. In Eskisehir (Turkey) drinking and tap water are supplied from a water treatment plant, consisting mainly of screening, sedimentation, filtration and sterilization units and having a capacity of 80.000 m3/d. Depend on the industrial and climatic effects the observed high ammonium concentration in treated water causes undesirable effects of water quality. Therefore, people in Eskisehir do not want to use tap water for drinking. The aim of the study was to evaluate the performance of membrane processes, i.e. Nanofiltration and reverse osmosis to the removal of ammonium and Ca ions from plant effluent and recommend one of them for a subsequent pilot plant application.

Climate↗
PubMed1994

Comparative biological potency of acidic sulfate aerosols: implications for the interpretation of laboratory and field studies.

Biological responses to inhaled acid sulfates result from the deposition of hydrogen ion (H+) on airway surfaces. Thus, effects from sulfuric acid and ammonium bisulfate, the two major ambient species, have been assumed to be the same for a given H+ concentration within the exposure atmosphere, assuming similar respiratory tract deposition patterns. However, recent inhalation studies have indicated that sulfuric acid is disproportionately potent compared to ammonium bisulfate when the H+ content of the exposure atmosphere is considered, suggesting that some factors following inhalation affect the amount of H+ contacting airway surfaces. This study assessed a mechanism potentially underlying this phenomenon, namely, the extent of neutralization by respiratory tract ammonia. This was evaluated using a physical model system designed to mimic transit of these aerosols in the upper respiratory tract of the animal model used in this laboratory, the rabbit. The results suggest that for equal exposure quantities of H+, more acid would be deposited when sulfuric acid is inhaled than when ammonium bisulfate is inhaled. Furthermore, results from a series of in vitro exposures of tracheal epithelial cells to sulfuric acid and ammonium bisulfate aerosols indicated that the biological response is a function of the total mass (ionic) concentration of H+ deliverable to the cells or the total extractable H+ per particle. The results of this study have possible implications for ambient monitoring of particulate-associated strong acidity, suggesting that it may be necessary to specilate such measures into the relative amounts of H+ as sulfuric acid or ammonium bisulfate in order to most accurately relate atmospheric acid levels to observed health effects. In addition, since much of the ambient particulate-associated H+ exists as sulfuric acid/ammonium bisulfate mixtures rather than pure compounds, H(+)-associated health effects from controlled exposure studies of sulfuric acid may not be transferable to ambient population situations on a 1:1 basis. Since any such errors in exposure assessment will necessarily bias downward the strength of H(+)-related health effects associations found via epidemiological studies, failure to address the specification of H+ may cause such studies to underestimate the human health effects of strong acids.

Aerosols↗
PubMed1984

Nitrogen Assimilation in Mycorrhizas : Ammonium Assimilation in the N-Starved Ectomycorrhizal Fungus Cenococcum graniforme.

Ammonium assimilation was followed in N-starved mycelia from the ectomycorrhizal Ascomycete Cenococcum graniforme. The evaluation of free amino acid pool levels after the addition of 5 millimolar NH(4) (+) indicated that the absorbed ammonium was assimilated rapidly. Post-feeding nitrogen content of amino acids was very different from the initial values. After 8 hours of NH(4) (+) feeding, glutamine accounted for the largest percentage of free amino acid nitrogen (43%). The addition of 5 millimolar methionine sulfoximine (MSX) to NH(4) (+)-fed mycelia caused an inhibition of glutamine accumulation with a corresponding increase in glutamate and alanine levels.Using (15)N as a tracer, it was found that the greatest initial labeling was into glutamine and glutamate followed by aspartate, alanine, and ornithine. On inhibiting glutamine synthetase using MSX, (15)N enrichment of glutamate, alanine, aspartate, and ornithine continued although labeling of glutamine was quite low. Moreover, the incorporation of (15)N label in insoluble nitrogenous compounds was lower in the presence of MSX. From the composition of free amino acid pools, the (15)N labeling pattern and effects of MSX, NH(4) (+) assimilation in C. graniforme mycelia appears to proceed via glutamate dehydrogenase pathway. This study also demonstrates that glutamine synthesis is an important reaction of ammonia utilization.

Journal Article↗
PubMed1987

Detection of polyols and sugars by cuprammonium ion in the presence of strong base.

A new and more sensitive cuprammonium reagent containing strong base has been developed for the colorimetric detection of polyols and sugars. A reagent blank with an absorbance at 280 nm, less than half that of previous methods, was achieved by reducing the cupric ion and ammonia concentrations to 1 mM (from 5 mM) and 0.4 M (from 2.25 M), respectively, and adding 0.2 M sodium hydroxide. Polyols are particularly well suited to the new method, showing up to an eightfold increase in sensitivity. The new reagent is readily applicable to the postcolumn detection of polyols and sugars after high-performance liquid chromatography and is linear over the range 40-180 nmol for D-glucitol (sorbitol) and 10-300 nmol for glucose, using standard HPLC equipment.

Carbohydrates↗
PubMed2001

Metabolism of the phosphonate herbicide glyphosate by a non-nitrate-utilizing strain of Penicillium chrysogenum.

A Penicillium chrysogenum strain was isolated for its ability to grow in minimal medium containing the herbicide glyphosate as the only nitrogen source. The presence of concentrations up to 25 mM progressively stimulated the fungal growth rate, which was negligible in media lacking reduced nitrogen. However, glyphosate utilization never exceeded 1 mmol g-1 mycelial dry mass, and below a threshold concentration both herbicide uptake and fungal growth were subject to a lag phase, suggesting that the herbicide may enter the cell by either simple passive diffusion or inducible carriers. Amino acids, possible products of glyphosate breakdown, as well as ammonia, were found to replace the herbicide in restoring mycelial growth. Cells were devoid of detectable nitrate reductase activity, thus the isolate seems to be impaired in its ability to convert nitrate to ammonium. In vitro activity of 5-enol-pyruvyl-shikimate-3-phosphate synthase, the target site of glyphosate action, was highly sensitive to the herbicide. Fungal growth rate was considerably lower when the herbicide was also the only phosphorus source, whereas glyphosate utilization was substantially unaffected, suggesting an unusual route for its degradation. Herbicide metabolism was strongly reduced when other sources of organic nitrogen were made available.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed2004

Investigation of the effect of free ammonia concentration upon leachate treatment by shortcut biological nitrogen removal process.

A shortcut biological nitrogen removal (SBNR) process was operated to treat an ammonium rich landfill leachate using a pilot-scale reactor. The SBNR process was intended to oxidize ammonia to nitrite and, then, to reduce it to nitrogen gas. When the hydraulic retention time was 4-3 days, a half of the ammonium oxidized was accumulated as nitrite in the oxidation tank. The nitrite was denitrified completely in the anoxic tank when recycled. The average free ammonia (FA) concentration in the ammonium oxidation tank was 3.7 mg/L. The specific substrate utilization rates of ammonium oxidizers and nitrite oxidizers were investigated at varying FA concentrations through batch experiments. The highest specific ammonium oxidation rate was observed when the FA concentration was 10 mg/L. The rate decreased slightly when the FA concentration was increased to 20 or 50 mg/L, or decreased significantly when it was 5 mg/L. In case of nitrite oxidation, the specific nitrite utilization rate decreased significantly with increasing FA concentration up to 10 mg/L. Consequently, the optimal FA concentration in leachate treatment was 10 mg/L for maximum nitrite accumulation and maximum ammonium removal, or 5 mg/L for lower ammonium concentration and reasonable nitrite accumulation.

Bioreactors↗
PubMed2002

Cyclitol-based metal-complexing agents. Effect of the relative orientation of oxygen atoms in the ionophoric ring on the cation-binding ability of myo-inositol-based crown ethers.

myo-Inositol-derived crown ethers having varying relative orientations (1,3-diaxial, 1,2-diequatorial, and 1,2-axial-equatorial) of the oxygen atoms in the ionophoric ring were synthesized and the extent of their binding with picrates of alkali metals, ammonia, and silver were estimated. These crown ethers bind very well with potassium and silver picrates and show good to moderate binding toward lithium, sodium, cesium, and ammonium picrates. These myo-inositol-derived crown ethers exhibit very strong binding for silver, even though they do not have sulfur or nitrogen coordinating sites in them, which are known to have high affinity for silver. The ratio of binding constants for silver to other ions tested varies from 10(2) to 10(5). The ion selectivity and the strength of binding are dependent on the relative orientation of the oxygen atoms in the ionophoric ring as well as on the size of the macrocyclic ring.

Ammonia↗
PubMed2005

Influence of the order of reagent addition on NDMA formation during chloramination.

The formation of the potent carcinogen, N-nitrosodimethylamine (NDMA), during chlorine disinfection has caused significant concern among drinking water and wastewater recycling utilities practicing intentional or unintentional chloramination. Previous research modeled NDMA formation as arising from a reaction between monochloramine and organic nitrogen precursors, such as dimethylamine, via an unsymmetrical dimethylhydrazine (UDMH) intermediate. Contrary to the importance of monochloramine indicated by previous studies, hypochlorite formed an order of magnitude more NDMA than monochloramine when applied to a secondary municipal wastewater effluent containing excess ammonia. Experiments involving variation of the order that each reagent (i.e., hypochlorite, ammonium chloride, and dimethylamine) was added to solution suggest two factors that may be more important for NDMA formation than the presence of monochloramine: (i) the chlorination state of organic nitrogen precursors and (ii) the partial formation of dichloramine. Although dichloramine formation was most influenced by the pH conditions under which inorganic chloramine formation was performed, mixing effects related to the order of reagent addition may be important at full-scale plants. Chloramination strategies are suggested that may reduce NDMA formation by nearly an order of magnitude.

Ammonium Chloride↗
PubMed1999

Water quality management for low temperature marine fishes in space.

Vestibular Function Experiment Unit (VFEU), one of the Spacelab facility flown in Neurolab mission (STS-90) in April, 1998, was to support neurophysiological research using a marine fish, Opsanus tau (oyster toadfish). The functions of the VFEU were primarily a quality management of environmental water during the mission at 14 degrees C and for acquiring physiological signals from implanted micro-electrodes in the otolith nerves as well as the spatial acceleration of the fish. A key element of the life support system was a balanced biological filter containing two types of nitrifying bacteria, Nitrosomonas for ammonia oxidization and Nitrobacter for nitrite oxidization. Although the 16 days mission was successful, two toadfishes died in late phase of the mission. Ammonium concentration in those two life support systems elevated to remarkably high level at the end of the mission whereas the other two indicated very low. This report summarizes the results of the water quality management of the VFEU during the Neurolab mission based on analysis of water samples taken during the flight and those taken prior and just after the flight.

Animals↗
PubMed1986

Induction of contact dermatitis in guinea pigs by quaternary ammonium compounds: the mechanism of antigen formation.

Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of the eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites at the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable "ion-pairs" are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface.

Allergens↗