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PubMed1993

H1- and H2-receptor influences of histamine and ammonia on rapidly adapting pulmonary stretch receptor activities.

Studies were designed to establish the difference of the excitatory mechanisms between histamine and ammonia on rapidly adapting pulmonary stretch receptors (RARs). We therefore examined the responses of RARs to histamine administered as an aerosol and ammonia inhaled as a vapor before and after aerosol administration of mequitazine or cimetidine in spontaneously breathing rabbits. The excitatory responses of RARs to aerosols of histamine at different concentrations were completely blocked by administration of aerosol mequitazine but potentiated by aerosol cimetidine. However, the increases of RAR activity produced by inhalation of ammonia vapor at different concentrations were not significantly affected by aerosol administration of either a H1-receptor blocker or a H2-receptor antagonist. These results suggest that the stimulation of RARs by aerosol histamine occurs as a result of the interaction between H1 (excitatory)- and H2 (inhibitory)-receptor effects, whereas these two receptor effects do not contribute to the ammonia-induced RAR stimulation.

Administration, Inhalation↗
PubMed1987

Ammonia effects on microinvertebrates and fish in outdoor experimental streams.

Laboratory data on ammonia effects, the US EPA national water quality criteria for ammonia, and ammonia site-specific criteria were evaluated in four outdoor experimental streams (one control and three treatment streams) over a 76-week period. Calculated un-ionised ammonia concentrations varied daily and seasonally according to pH and temperature changes. Populations of four major microinvertebrate taxonomic groups (cladocerans, copepods, rotifers and protozoans) were monitored during a 4-week period early in the study, and six fish species (fathead minnows, bluegills, channel catfish, white suckers, walleyes, and rainbow trout) were tested for various time intervals, from 4 to 26 weeks, throughout the 76-week study period. Copepods and rotifers were unaffected in all three treatment streams, based on comparisons with the control stream. Cladoceran and protozoan populations were reduced in at least two treatment streams, but because of large variability, effects were considered to be inconclusive. However, complete mortality of cladocerans did occur in the high and medium treatments when placed in in situ biomonitor chambers. All six fish species were affected in one or more treatments. Generally, the fish effect values agreed with most laboratory effect values. Of 12 fish groups tested, one channel catfish group and one white sucker group were affected below the recommended protection levels of the national and site-specific criteria. The lowest effect concentrations tested for the other ten groups occurred above the criteria levels.

Journal Article↗
PubMed1994

Uncertainties in current estimates of emissions of ammonia in the United Kingdom.

Estimates of the emissions of ammonia have previously concentrated on animal husbandry sources from agricultural systems. Animal husbandry sources still constitute the major fraction of emissions of ammonia, but we have also considered the potential magnitude of other 'minor' sources, which may include coal combustion, waste incineration, road vehicles, sewage treatment plants, fertiliser manufacture and application, vegetation senescence and crop emissions, domestic pets, and human sources. Where possible, a provisional estimate of UK emissions from each of these sources is given. It is concluded that the potential magnitude of emissions from these 'minor' sources may make a significant contribution to the total emissions of ammonia to the atmosphere. On the basis of the available data, and the application of a range of emission factors to the UK situation, an additional annual emission potential lying in the range of approximately 80-140 ktonne year(-1) over and above that from animal husbandry has been calculated. The uncertainties in the emission estimates and instances in which a better resolution of sources is required are discussed. The emission factors used for animals in various inventories are reviewed and applied to the main UK agricultural animal populations. By using this approach, estimates of emissions from these sources range between 113 and 647 ktonne year(-1), which illustrates the uncertainties involved. It is suggested that our knowledge of the sources of ammonia, and their distribution, is far from complete.

Journal Article↗
PubMed1994

Ammonia-induced upregulation of peripheral-type benzodiazepine receptors in cultured astrocytes labeled with [3H]PK 11195.

Evidence suggests that peripheral-type benzodiazepine receptors (PBRs) may play a role in hepatic encephalopathy (HE), a condition associated with increased levels of ammonia in brain. In the present study, the regulation of [3H]PK 11195-binding to PBRs in cultured rat astrocytes that had been previously exposed to NH4Cl was investigated. 24 h treatment of 21-28-day-old cultures with 2, 5 or 10 mM NH4Cl resulted in 25 +/- 3, 48 +/- 3 and 42 +/- 4% increase in the number of [3H]PK 11195-binding sites, respectively. No further change in [3H]PK 11195-binding was observed after exposure of astrocytes to 5 mM NH4Cl for 48 or 72 h. Ammonia treatment did not cause any significant alteration in the affinity of [3H]PK 11195 for PBRs. The present study demonstrates the susceptibility of the PK 11195-binding site of PBRs in cultured astrocytes to ammonia and suggests that increase in brain ammonia concentration causes a supersensitivity of PBRs.

Ammonium Chloride↗
PubMed1981

Regulation of urea synthesis. The effect of ammonia on the N-acetylglutamate content of isolated rat liver cells.

(1) Incubation of isolated rat liver cells in the presence of lactate and ammonia increases the AcGlu content. The increase is very fast in the first minutes and a steady-state concentration is reached in approx. 10 min after the addition of ammonia. (2) The amount of increase depends on the diet rats were fed before isolation of liver cells. AcGlu is increased 4-fold in hepatocytes from rats fed a carbohydrate-rich diet. If ornithine is simultaneously present with ammonia a further increase is found. (3) Urea synthesis in hepatocytes from rats fed a carbohydrate-rich diet has a marked lag period. The reason for this lag phase is the low initial AcGlu concentration. (4) Increase in AcGlu is closely associated with increase in mitochondrial glutamate content. Thus, it is concluded that the glutamate concentration is the mediator of the ammonia effect.

Ammonium Chloride↗
PubMed1991

Stimulation of alanine metabolism by ammonia in the perfused rat liver. Quantitative analysis by means of a mathematical model.

The effect of ammonia on the catabolism of alanine was studied in the perfused rat liver. Addition of 0.5 mM NH4Cl to the perfusion medium containing 5 mM alanine plus 0.1 mM octanoate produced drastic changes in the metabolite concentrations in the efflux medium. Not only the rate of ureogenesis was activated, but also the formation of glucose, lactate and pyruvate. Additionally, respiration was stimulated, the output of ketone bodies decreased, and the redox ratios lactate/pyruvate as well as 3-hydroxybutyrate/acetoacetate became more oxidized. To interpret the causes of these metabolic changes, a mathematical model was developed. It contains kinetic equations by which fluxes through essential pathways of alanine catabolism, gluconeogenesis and energy metabolism were related to the intracellular concentrations of pyruvate, oxaloacetate and ammonia, as well as to the redox ratios lactate/pyruvate and 3-hydroxybutyrate/acetoacetate. Using a nonlinear regression procedure, the model was suitable to be fitted to the data found in the experiments. The consistency of the model and experiment allowed the changes caused by ammonia to be explained. Primarily, ammonia stimulated ureogenesis hence accelerating the deamination of alanine which led to the increased formation of pyruvate, lactate and glucose. The enhanced energetic load resulting from ureogenesis and gluconeogenesis shifted the mitochondrial and cytosolic NAD systems towards more oxidized states which additionally modified the flux rates. The results demonstrate that there is a high degree of cooperativity between the metabolic pathways.

3-Hydroxybutyric Acid↗
PubMed1995

Evidence that particulate methane monooxygenase and ammonia monooxygenase may be evolutionarily related.

Genes encoding particulate methane monooxygenase and ammonia monooxygenase share high sequence identity. Degenerate oligonucleotide primers were designed, based on regions of shared amino acid sequence between the 27-kDa polypeptides, which are believed to contain the active sites, of particulate methane monooxygenase and ammonia monooxygenase. A 525-bp internal DNA fragment of the genes encoding these polypeptides (pmoA and amoA) from a variety of methanotrophic and nitrifying bacteria was amplified by PCR, cloned and sequenced. Representatives of each of the phylogenetic groups of both methanotrophs (alpha- and gamma-Proteobacteria) and ammonia-oxidizing nitrifying bacteria (beta- and gamma-Proteobacteria) were included. Analysis of the predicted amino acid sequences of these genes revealed strong conservation of both primary and secondary structure. Nitrosococcus oceanus AmoA showed higher identity to PmoA sequences from other members of the gamma-Proteobacteria than to AmoA sequences. These results suggest that the particulate methane monooxygenase and ammonia monooxygenase are evolutionarily related enzymes despite their different physiological roles in these bacteria.

Amino Acid Sequence↗
PubMed2004

Effect of ammonia on the methanogenic activity of methylaminotrophic methane producing Archaea enriched biofilm.

Ammonia is a metabolic product in the decomposition of protein wastes, and has a recognized inhibitory effect on methanogenesis; this effect has been slightly quantified on methanogenic biofilms and particularly those populated by methanogenic Archaea which produce ammonia as a catabolic product from methylated amines. This paper presents studies on the effect of ammonia on maximum methanogenic activity of anaerobic biofilms enriched by methylaminotrophic methane producing Archaea (mMPA). The effect of unionized free ammonia on the specific maximum methanogenic activity of a mMPA enriched biofilm was studied, using 250 mL flasks containing ceramic rings colonized by 30 day-old experimental biofilm and adding 48.8 (control system), 73.8, 98.8, 148.8, 248.8, 448.8 and 848.8 mg NH(3)-N/L. The systems were maintained for ten days at a pH of 7.5 and temperature of 37 degrees C. The results showed that at 848.8 mg NH(3)-N/L, biofilm methane production required 36 h adaptation period, prior to entering into maximum production phase. The highest maximum methanogenic activity reached a value of 2.337+/-0.213 g COD methane/g VSS *day when 48.8 mg NH(3)-N/L was added, and inhibition was clearly observed in those systems above 148.8 mg NH(3)-N/L, producing under 1.658+/-0.185 g COD methane/g VSS *day. The lowest methanogenic activity reached was 0.639+/-0.162 g COD methane/g VSS *day at the system added with 848.8 mg NH(3)-N/L. When applying the Luong and non-competitive inhibition models, the best fit was obtained with the non-competitive model, which predicted 50% inhibition of methanogenic activity at 365.288 mg NH(3)-N/L.

Journal Article↗
PubMed2004

Ammonia metabolism and hepatic encephalopathy.

Hepatic encephalopathy is a complex neuropsychiatric syndrome, which derives from liver failure associated with severe liver damage such as fulminant hepatitis and liver cirrhosis, and vascular abnormalities associated with liver cirrhosis. Although the cause is explained by a multifactorial theory, the accumulation of ammonia has traditionally been considered to have an important role in the pathogenesis of hepatic encephalopathy. In addition, a number of other possible mechanisms have recently proposed, including production of false neurotransmitter, activation of central gamma-aminobutyric acid-benzodiazepine receptors by ligands of endogenous origin, altered cerebral metabolism. These pathogenetic mechanisms are not necessarily exclusive. The principle of treatment is to remove or correct aggravating factors and inhibit the transfer of toxic substances such as ammonia into the bloodstream by minimizing the interaction of intestinal bacteria and nitrogen substances. Most treatments of proved value are based on the ammonia hypothesis. Ammonia metabolism is regulated by numerous factors, among which zinc has long been indicated to be involved, and its clinical application has drawn attention recently.

Journal Article↗
PubMed2003

Taurine reduces ammonia- and N-methyl-D-aspartate-induced accumulation of cyclic GMP and hydroxyl radicals in microdialysates of the rat striatum.

Acute ammonia neurotoxicity caused by intraperitoneal administration of ammonium salts is mediated by overactivation of N-methyl-D-aspartate (NMDA) receptors, with ensuing generation of free radicals and extracellular accumulation of cyclic GMP (cGMP) arising from stimulation of nitric oxide (NO) synthesis. In this study, infusion of ammonium chloride or NMDA into the striata of rats via microdialysis probes increased the contents of cyclic GMP and hydroxyl radicals in the microdialysates. Co-infusion of taurine virtually abolished both the ammonia- and NMDA-induced accumulation of cGMP. Taurine also attenuated accumulation of hydroxyl radicals evoked by either treatment. This result is the first evidence of a potential of taurine to attenuate the effects of NMDA receptor overactivation by ammonia in vivo and points to the inhibition of the NMDA receptor-mediated NO synthesis as a possible mechanism of its neuroprotective action. Taurine or its blood-brain barrier penetrating analogues may be applicable in treatment of ammonia-induced neurological deficits.

Ammonium Chloride↗
PubMed1998

The acute toxicity of phenol and unionized ammonia, separately and together, to the ephemeropteran Baetis rhodani (Pictet).

The acute toxicity of phenol and ammonia, singly and in combination, to larvae of the ephemeropteran, Baetis rhodani, was examined using a computerized continuous flow system in the laboratory. The 24 h LC50 values (with 95% confidence intervals) were calculated to be 29.9 (17.3-51.5) mg phenol litre(-1) and 8.2 (2.0-33.0) mg un-ionized ammonia litre(-1). When phenol and ammonia were together in low concentration (< 20 mg litre(-1) and < 3 mg litre(-1) [un-ionized], respectively), they expressed their toxicity additively, but at higher concentrations they behaved in a greater-than-additive manner. When the 24 h LC50 values were used to predict the toxicity of a coking plant effluent, containing principally ammonia and phenol, it was found that the B. rhodani larvae died quicker than expected indicating the presence of other toxic chemicals. This exemplifies the value of using direct toxicity assessments to detect the presence of unknown toxicants.

Journal Article↗
PubMed2004

Enhanced production of L-lactic acid by ammonia-tolerant mutant strain Rhizopus sp. MK-96-1196.

By a monospore isolation technique, Rhizopus sp. MK-96-1 was selected from colonies of Rhizopus sp. MK-96, which was isolated from the soil sample collected in Fujieda, Japan, and used as a parent strain. By the ammonia-concentration-gradient agar plate technique after mutation using N-methyl-N'-nitro-N-nitrosoguanidine (NTG) method, a mutant strain designated Rhizopus sp. MK-96-1196 producing more than 90 g/l L-lactic acid under pH control using liquid ammonia in an airlift bioreactor was successfully isolated. Compared with the parent strain, this mutant strain produced about twofold the amount of L-lactic acid in half fermentation time under the same culture conditions. Ammonium L-lactate was recovered and purified as free L-lactic acid via n-butyl L-lactate. The ammonia used for pH control in the fermentation broth was recovered as liquid ammonia during the recovery and purification process and subsequently reused for the next fermentation. Thus, we have developed a new highly purified L-lactic acid production process without producing recalcitrant wastes, e.g., CaSO4 (gypsum).

Journal Article↗
PubMed2005

Development of an analytical method for distinguishing ammonium bicarbonate from the products of an aqueous ammonia CO2 scrubber.

The link between anthropogenic emissions of carbon dioxide, increasing atmospheric CO2 levels, and concomitantly increasing global temperatures is established and accepted. The use of aqueous ammonia, to capture CO2 and produce an inexpensive nitrogen fertilizer, ammonium bicarbonate (ABC), is believed to be a feasible approach to CO2 sequestration. Due to the varying concentrations of reactants and varying reaction conditions, different ammonia-carbon compounds may be produced. ABC is the ideal product for maximizing NH3 utilization in CO2 capture; therefore, identification and quantification of ABC in the reaction products is mandatory. Various analytical techniques were used to distinguish and quantify the ABC. Fourier transform infrared spectroscopy can only be used to distinguish ammonium carbamate, and. X-ray diffraction can be used to qualitatively distinguish ABC from the other possible products of the CO2 capture reaction. Carbon-hydrogen-nitrogen elemental analysis and near-infrared (NIR) spectroscopy were used to quantify ABC, with both techniques giving +/-5% agreement for ABC concentrations for 8 of 13 samples from a bench-scale aqueous ammonia CO2 scrubbing system. An additional 3 of the 13 samples were within +/-12%. Results indicate that NIR will be an ideal tool for real-time, on-line measurements of ABC in a full-scale aqueous ammonia CO2 scrubber. The ABC in 11 samples from the bench-scale scrubber at Western Kentucky University was determined by these techniques and assessed to have very good quality as a fertilizer in accordance with GB-3559-92, the Agricultural Ammonium Bicarbonate National Standard of China.

Journal Article↗
PubMed2006

Predicting catalysis: understanding ammonia synthesis from first-principles calculations.

Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state theory with or without tunneling corrections, and quantum dynamics) to a range of relevant elementary reaction steps, such as N(2) dissociation, H(2) dissociation, and hydrogenation of the intermediate reactants. A complete kinetic model based on the most relevant elementary steps can be established for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations. Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully integrated tool in the search for the next generation of catalysts.

Journal Article↗
PubMed2006

Effect of high-pressure ammonia treatment on the activity of Ge3N4 photocatalyst for overall water splitting.

The photocatalytic activity of beta-Ge(3)N(4) powder for overall water splitting is successfully enhanced by ammonia treatment at 823 K for 5-24 h at ammonia pressures of 20 MPa or greater. The surface and bulk nitrogen content in the treated samples varies according to the treatment temperature and treatment time, related to the stability of beta-Ge(3)N(4) powder under pressurized ammonia. The change in nitrogen content resulted in a change in the photocatalytic activity for overall water splitting. A beta-Ge(3)N(4) powder treated at 823 K for 5 h under ammonia at 20 MPa exhibited a photocatalytic activity 4 times higher than that of the as-synthesized powder, attributable to a decrease in the density of anion defects in the bulk and surface.

Journal Article↗
PubMed2004

Sampling small volumes of ambient ammonia using a miniaturized gas sampler.

The development of a gas sampler for a miniaturized ambient ammonia detector is described. A micromachined channel system is realized in glass and silicon using powder blasting and anodic bonding. The analyte gas is directly mixed with purified water, dissolving the ammonia that will dissociate into ammonium ions. Carrier gas bubbles are subsequently removed from the liquid stream through a venting hole sealed with a microporous water repellent PTFE membrane. A flow restrictor is placed at the outlet of the sampler to create a small overpressure underneath the membrane, enabling the gas to leave through the membrane. Experiments with a gas flow of 1 ml min(-1), containing ammonia concentrations ranging from 9.4 ppm to 0.6 ppm in a nitrogen carrier flow have been carried out, at a water flow of 20 microl min(-1). The ammonium concentration in the sample solution is measured with an electrolyte conductivity detector. The measured values correspond with the concentration calculated from the initial ammonia concentration in the analyte gas, the fifty times concentration enhancement due to the gas-liquid volume difference and the theoretical dissociation equilibrium as a function of the resulting pH.

Journal Article↗
PubMed2004

Reactions of cationic iron clusters with ammonia, models of nitrogen hydrogenation and dehydrogenation.

The gas phase reactivities of small cationic iron clusters, Fen+ (n = 1-20), towards ammonia were investigated using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Sequential addition of ammonia molecules to the clusters was observed to be the dominating process for n > 4. In the case of n = 4 we observed addition of ammonia accompanied by dehydrogenation. This reaction was modelled using hybrid density functional theory. Clusters with n < 4 do not react with ammonia. Clusters Fen+ (n = 1-20) react with neither N2 nor H2 at around 10(-8) mbar. When dinitrogen was seeded into the expanding helium, mixed clusters of the type FenNm+ were observed. These ions react with H2, either by addition, or by substitution of N2. The clusters with m = 1 were isolated in separate experiments and reacted with H2, which showed that mixed clusters with n = 5-13 add up to 5 molecules of dihydrogen in successive slow reactions.

Journal Article↗
PubMed2001

Genetics of larval urea and ammonia tolerance and cross-tolerance in Drosophila melanogaster.

Five laboratory populations of Drosophila melanogaster previously selected for over 60 generations for larval resistance to ammonium chloride (NH4Cl), and five populations selected for over 60 generations for larval resistance to urea, were investigated to determine the genetic mechanisms through which such tolerance had evolved. To examine the genetics of tolerance to urea and ammonia, egg-to-adult survivorship and developmental time were measured at two different NH4Cl levels and two different urea levels for each selection regime relative to the control lines, and among reciprocal crosses between each selection regime and the control lines. To examine tolerance to novel nitrogenous compounds (cross-tolerance), egg-to-adult survivorship and developmental time were measured at two different NH4Cl levels and two different urea levels for reciprocal crosses between the selection lines. Dominance is a major genetic factor in egg-to-adult survivorship in the presence of either urea or ammonia, while cross-tolerance to novel nitrogenous compounds also shows dominance as a major genetic mechanism controlling egg-to-adult survivorship. Dominance and X-linkage appear to be factors affecting developmental time in the presence of either urea or ammonia, although we could not exclude cytoplasmic inheritance as influencing our results. Cross-tolerance to novel nitrogenous compounds shows dominance and X-linkage as the main genetic factors controlling developmental time. We develop a simple hypothesis, in accordance with the results, that there may be two X-linked loci: one controlling urea tolerance and one controlling ammonia tolerance, and one autosomal locus exerting a pleiotropic control of tolerance. However, many other possibilities exist.

Ammonium Chloride↗