Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AMMONIA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,351 records · Page 75Linked to original sources
PubMed2000

Metabolic responses of the white shrimp, Penaeus vannamei, to ambient ammonia.

Juvenile shrimp were individually exposed during 24 h to 0.007 (control), 0.36, 1.07, and 2.14 mmol/l total ammonia-N at 28 degrees C and 39 ppt salinity. After 22 h of ammonia-N exposure, oxygen consumption was measured for 2 h, and then hemolymph, hepatopancreas, and muscle tissues were sampled. Oxygen consumption, and levels of lactate and glycogen in the hepatopancreas increased significantly at the highest ammonia-N concentration. Concentration of oxyhemocyanin, acylglycerol, and cholesterol in hemolymph, and lactate in muscle decreased significantly in the group exposed to the highest ammonia levels. The changes observed in hemolymph and tissue metabolic fuels suggest a reduced use of carbohydrate through anaerobic metabolism and an increase in the use of lipids to satisfy the metabolic demand.

Ammonia↗
PubMed2003

Simultaneous measurements of oxygen consumption and ammonia-N excretion in embryos and larvae of marine invertebrates.

The quantification of oxygen consumption and ammonia-N excretion rates is essential in determining energy requirements for development of larval invertebrates. In larval energetics, there is a need for accurate and uncomplicated techniques to quantify metabolic rates. A method for simultaneous measurements of oxygen and ammonia-N concentrations is presented. It employs sealed respirometric chambers (ca. 30 ml) in which embryos and larvae are incubated. Analysis is carried out in end-point samples by Winkler's titration and indophenol-blue for oxygen and ammonia-N, respectively. Water is sampled into volume-calibrated glass syringes and oxygen consumption and ammonia-N excretion rates were determined by the difference between experimental and control (no animals) units. The method was successfully used to measure metabolic rates in embryo and larval stages of the shrimp Farfantepenaeus paulensis and in veliger of the mussel Perna perna. The accuracy denoted by the coefficient of variation is comparable to previous results on larval metabolic rates. A biomass: volume (microg ml(-1)) is proposed to extend its application to further species of marine invertebrates. The method is simple to operate, involves non-expensive material and is portable enough for field work. A substantial number of replicates can be analyzed at the same time and O:N ratio, an indicator of the catabolized substrate, can be calculated.

Ammonia↗
PubMed1998

Short-term physiological changes in turbot and seabream juveniles exposed to exogenous ammonia.

Seabream and turbot juveniles (40-520 g) were exposed to constant exogenous NH5-N concentrations (1.27-4.27 mmol/l; pH, 8.15). In 96 hr acclimated fish, plasma TA-N (total ammonia nitrogen) contents were positively correlated to ambient ammonia concentrations. The LD50 were 2.2-2.5 mmol/l TA-N in both species. There were no marked osmoregulatory disturbances and plasma urea-N, thyroid hormones levels and gill (Na-K)-ATPase activities were only affected at the highest concentrations. Liver GOT, GPT and GIDH activity dose-response were low and species dependent. In cannulated and non-cannulated turbot exposed to half 96 hr LC50 (lethal ambient concentration for 50% of the population), there was a rapid, pronounced and prolonged increase in plasma TA-N, followed by an immediate decline when exogenous ammonia supply was stopped. Maximum loading and unloading were observed within 1-3 hr. Plasma cortisol levels indicated a stressful situation in exposed fish (150 ng/ml) and a quick recovery capacity. In dose and time response experiments, the most relevant physiological indicator of ammonia stress was blood TA-N content. Other parameters tested led either to transient or low amplitude responses except when fish approached death.

Acclimatization↗
PubMed1986

Free and total serum valproate concentrations: their relationship to seizure control, liver enzymes and plasma ammonia in children.

The relationships between total and free serum valproate (VPA) concentrations and seizure control, serum liver enzyme activity and plasma ammonia concentration were studied in 61 epileptic children. Enzyme-immunoassay (EMIT)R methods gave higher values of total VPA concentration than gas-liquid chromatography (GLC) methods. In over 80% of children with complete seizure control the ranges of total VPA concentration were 140-420 mumol/L with GLC methods and 210-560 mumol/L with EMIT methods. The range of free VPA concentrations in 78% of children with complete seizure control was 8.8-26.4 mumol/L. Increased liver enzyme activity was observed in 6 of the 61 children and raised plasma ammonia concentration in 11 of 50 children. Plasma ammonia concentration was related to total serum VPA but was not related to free serum VPA. Increased serum liver enzyme activity was related to VPA dose per kg but not to free or total serum VPA concentration. Thus free VPA concentrations do not appear to be more useful than total VPA concentrations in predicting seizure control and do not correlate with liver enzyme activity or plasma ammonia concentration.

Adolescent↗
PubMed1992

Evaluation of transient responses of ammonia-selective potentiometric electrodes for quantitative applications.

An error-compensating, predictive kinetic method is adapted and evaluated for quantitative applications based on transient responses from an ammonia-selective electrode. Transient data collected during the early part of the electrode response are used with a curve-fitting method and appropriate mathematical models to predict the signal that would be measured if the response were monitored to equilibrium. Several different theoretical and empirical models were evaluated, and all but one of the models tested permitted reliable prediction of equilibrium potentials for most responses. Predicted values of equilibrium signal were close to measured values and exhibited the expected logarithmic dependence on ammonia concentration in the range from 0.1 to 100 mmol/L. Slopes of calibration plots E infinity vs log C, varied from about 50.5 to 65.0 mV per decade with an average value of 56.9 +/- 4.2 mV per decade. Quantitative data are used to rank the different models in terms of their utility for kinetic-based determinations of ammonia by using the ammonia-selective electrode.

Ammonia↗
PubMed2006

Measurement of ammonia in human breath with a liquid-film conductivity sensor.

Measurement of breath NH3 is of interest in clinical applications as it can be used as a measure of kidney/liver functions as well as halitosis. We have developed a liquid-film conductivity sensor to measure NH3 in human breath. A film of dilute H2SO4 is formed on the top of two metal capillary tubes placed in a concentric annular arrangement. The tube exterior has been specially treated to render it hydrophilic. As breath passes over the sensor tip, the film collects NH3 and the solution conductivity (measured by the concentric capillaries functioning as electrodes) decreases accordingly. This initial rate of conductivity decrease was determined to be the best metric (most rapid and least dependent on breath pCO2) for ammonia, relative to time to attain complete neutralization (conductivity minimum) or the final rate of conductivity increase as more ammonia dissolves after neutralization. The absorbing solution composition was optimized so that CO2 does not interfere. Both dynamic measurement using mask sampling and offline balloon sampling were performed. Ammonia readily absorbs on surfaces when significant concentrations of water vapor are present. As such, memory effects are common when analyzing human breath for ammonia. This problem was successfully eliminated. The results from this sensor agreed well with data obtained by a solution-phase fluorometric technique using a porous membrane diffusion scrubber and o-phthalaldehyde derivatization chemistry. For breath CO2 measurement, the applicability of a similar sensor that relies on a NaOH film was also demonstrated.

Ammonia↗
PubMed1976

Histidine ammonia-lyase from rat liver. Purification, properties, and inhibition by substrate analogues.

Histidine ammonia-lyase (EC 4.3.1.3) from rat liver was purified more than 250-fold to near homogeneity. Electrophoretic determinations indicated a native molecular weight of approximately 200,000. The enzyme has a pH optimum of approximately pH 8.5. The minimum Km for L-histidine was 0.5 mM at pH 9.0. The Michaelis constant in the physiological pH range was, however, more than 2.0 mM. D-alpha-hydrazinoimidazolylpropionic acid was found to be a potent competitive inhibitor of liver histidine ammonia-lyase (Kis=75 muM); the L enantiomer of this compound was less effective in this regard. The enzyme was also inhibited competitively by L-histidine hydroxamate (Kis=0.4 mM), and to a lesser extent by L-histidinol, D-histidine, and glycine. Failure of a wide variety of other histidine analogues to inhibit the enzyme substantially indicates high specificity of the active site for L-histidine. No alternate substrates were identified for the enzyme. DL-alpha-Hydrazinophenylpropionic acid, the alpha-hydrzino analogue of phenylalanine, was similarly shown to be a very potent competitive inhibitor of a mechanistically similar L-phenylalanine ammonia-lyase purified from Rhodotorula glutinis. The properties of histidine ammonia-lyase from rat liver differ significantly from those of the enzyme from Pseudomonas fluorescens which has been studied most extensively to date.

Ammonia-Lyases↗
PubMed2003

Substrate-induced changes in the ammonia channel for imidazole glycerol phosphate synthase.

IGP synthase is a glutamine amidotransferase that incorporates ammonia derived from glutamine into the unusual nucleotide, N(1)-[(5'-phosphoribulosyl)-formimino]-5-aminoimidazole-4-carboxamide ribonucleotide (PRFAR) to form 5'-(5-aminoimidazole-4-carboxamide) ribonucleotide (AICAR) and imidazole glycerol phosphate (IGP). A common feature of all glutamine amidotransferases is the upregulation of glutamine hydrolysis in the presence of an acceptor substrate. A refined assay system was developed to establish that Saccharomyces cerevisae IGP synthase shows a 4900-fold stimulation of glutaminase in the presence of the substrate acceptor PRFAR. The structure and function of IGP synthase acceptor substrate binding site were probed with competitive inhibitors that are nucleotide substrate and product analogues. In addition, these analogues were also used to establish that the normal steady-state turnover cycle involves a random sequential mechanism. Upregulation of the glutaminase active site occurs when these competitive inhibitors bind in the nucleotide site over 30 A away. One of the key structural features of IGP synthase is that the transfer of ammonia from the glutaminase site occurs through the (beta/alpha)(8) core of the protein. Upon the basis of the recent substrate-occupied structure for yeast IGP synthase (1), kinetic investigations of site-directed mutants revealed that a conserved K258 residue is key to productive binding and the overall stoichiometry of the reaction. The binding of the ribulosyl phosphate portion of the substrate PRFAR appears to be transduced through reorientation of K258 resulting in a conformational switch at the base of the (beta/alpha)(8) core that enables the passage of ammonia through the core of the protein. The overall analysis also leads to further discussion of how the residues that cover the opening of the (beta/alpha)(8) in the closed state may assist the channeling of ammonia at the interface of the two functional domains in the open state.

Amino Acid Substitution↗
PubMedDate not supplied

Substitution of glutamine by pyruvate to reduce ammonia formation and growth inhibition of mammalian cells.

In mammalian cell culture technology glutamine is required for biomass synthesis and as a major energy source together with glucose. Different pathways for glutamine metabolism are possible, resulting in different energy output and ammonia release. The accumulation of ammonia in the medium can limit cell growth and product formation. Therefore, numerous ideas to reduce ammonia concentration in cultivation broths have been developed. Here we present new aspects on the energy metabolism of mammalian cells. The replacement of glutamine (2 mM) by pyruvate (10 mM) supported cell growth without adaptation for at least 19 passages without reduction in growth rate of different adherent commercial cell lines (MDCK, BHK21, CHO-K1) in serum-containing and serum-free media. The changes in metabolism of MDCK cells due to pyruvate uptake instead of glutamine were investigated in detail (on the amino acid level) for an influenza vaccine production process in large-scale microcarrier culture. In addition, metabolite profiles from variations of this new medium formulation (1-10 mM pyruvate) were compared for MDCK cell growth in roller bottles. Even at very low levels of pyruvate (1 mM) MDCK cells grew to confluency without glutamine and accumulation of ammonia. Also glucose uptake was reduced, which resulted in lower lactate production. However, pyruvate and glutamine were both metabolized when present together. Amino acid profiles from the cell growth phase for pyruvate medium showed a reduced uptake of serine, cysteine, and methionine, an increased uptake of leucine and isoleucine and a higher release of glycine compared to glutamine medium. After virus infection completely different profiles were found for essential and nonessential amino acids.

Ammonia↗
PubMedDate not supplied

Role of nucleotide sugar pools in the inhibition of NCAM polysialylation by ammonia.

Ammonia in animal cell cultures has been shown to specifically inhibit terminal sialylation of N- and O-linked oligosaccharides of glycoproteins. For example, we have previously shown that as little as 2.5 mM NH4Cl can decrease neural cell adhesion molecule (NCAM) polysialylation in both small cell lung cancer (SCLC) and Chinese hamster ovary (CHO) cells. Besides its potential involvement in SCLC metastasis, polysialic acid (PolySia) is a sensitive marker for measuring changes in sialylation. The role of UDP-N-acetylglucosamine (UDP-GlcNAc) in ammonia's inhibition of NCAM polysialylation was examined by adding glucosamine (GlcN) and uridine (Urd) to the cultures. This bypassed feedback inhibition of GlcN-6-P synthase and increased UDP-GlcNAc content by 25-fold in SCLC cells. After 3 days, PolySia levels were reduced to 10% of control with little effect on NCAM protein content. The extensive decrease in PolySia was confirmed in CHO cells. The effects of GlcN or Urd alone were less extensive, lending support to a specific role for UDP-GlcNAc in inhibition by ammonia. By comparison, 20 mM NH4Cl decreased PolySia content by 45% and increased UDP-GlcNAc in SCLC cells by 2-fold. The discrepancy between the ¿GlcN+Urd¿ and NH4Cl effects on UDP-GlcNAc and PolySia suggests that accumulation of UDP-GlcNAc is only partially responsible for decreased polysialylation in response to NH4Cl. In an attempt to increase NCAM polysialylation, N-acetylmannosamine and cytidine were added to cultures in order to circumvent the feedback inhibition of CMP-sialic acid synthesis. However, this only slightly increased PolySia levels and failed to counter ammonia's inhibition of NCAM polysialylation.

Ammonia↗
PubMed2002

Livestock ammonia management and particulate-related health benefits.

Agricultural operations are the largest source of ammonia emissions in the United States and contribute to the formation of ammonium nitrate and ammonium sulfate, two prevalent forms of fine particulate matter. Researchers have found an association between fine particulate matter and a variety of adverse healths effects, including premature mortality, chronic bronchitis, hospital admissions, and asthma attacks. Management practices that reduce ammonia emissions may decrease adverse health effects, resulting in significant economic benefits. We estimated the impact of a variety of emission controls, including diet optimization, alum, and incorporation of manure into the land. The results suggest that relatively modest management policies can have a significant impact on fine particulate formation in the atmosphere. Because of the heterogeneous nature of particulate matter, a key question is the importance of particulate matter size and composition. To the extent that ammonium nitrate and ammonium sulfate contribute to adverse health effects, ammonia management may have significant health implications. Our results suggestthat a 10% reduction in livestock ammonia emissions can lead to over $4 billion annually in particulate-related health benefits.

Agriculture↗
PubMed2003

Automated measurements of ammonia and nitric acid in indoor and outdoor air.

Simultaneous temporally resolved indoor and outdoor measurements of ammonia and nitric acid are valuable for determining the gas-particle equilibrium conditions governing concentrations of ammonium nitrate aerosol. We report the results of simultaneous automated indoor and outdoor measurements of ammonia and nitric acid concentrations made at an unoccupied, single-story residence in Clovis, CA during three periods from October 2000 to January 2001. The measurements were conducted as part of a controlled study to explore mechanisms governing indoor concentrations of fine aerosols of outdoor origin. The gas-phase measurements were performed using diffusion denuders and ion chromatography with 30 min temporal resolution and detection limits below 1 ppb. The conditions of the field experiment span a wide range of outdoor climate as well as natural and forced indoor conditions. During all periods ammonia concentrations were generally slightly higher indoors than out, with both outdoor and indoor concentrations varying in a range from approximately 5 to 30 ppb. Nitric acid was only detected in outdoor air in October 2000, at concentrations up to 3 ppb. During the October period, the product of outdoor nitric acid and ammonia concentrations sometimes deviated from that expected for equilibrium between gas and ammonium nitrate particulate phases and the degree and direction of disequilibrium were correlated with trends in air temperature. The consistently low indoor concentrations of nitric acid were not consistent with equilibrium between gas and particle phases and suggest that a combination of low penetration into the building and a high loss rate for nitric acid reduce indoor concentrations significantly below those outdoors.

Aerosols↗
PubMed2004

Characterization of atmospheric ammonia emissions from a commercial chicken house on the Delmarva Peninsula.

A three-dimensional sampling grid using passive collectors was used to characterize the downwind gas-phase ammonia plumes originating from a commercial chicken house on the Delmarva Peninsula in the Chesapeake Bay watershed. Inverse Gaussian plume modeling was used to determine the source strength of the chicken house and the corresponding chicken emission factors. A total of seven field deployments were performed during two different flocks with a sampling duration ranging from 6 to 12.6 h. The deployments occurred during weeks 3, 4, and 5 of the 6-week chicken grow-out period in the months of May-July 2002. The ammonia emission factors ranged from 0.27 to 2.17 g of NH3-N bird(-1) day(-1) with a mean of 1.18 g of NH3-N bird(-1) day(-1). Weighted emissions factors that accounted for the nonlinear increase in ammonia emissions over the 6-week grow-out period were also calculated and ranged from 0.14 to 1.65 g of NH3-N bird(-1) day(-1) with a mean of 0.74 g of NH3-N bird(-1) day(-1). These weighted emission values would correspond to an annual release of approximately 18 x 10(6) kg of NH3-N to the atmosphere from broiler production on the Delmarva Peninsula. This assumes that the emission factors in this study are representative for the entire year with varying meteorological conditions and are representative of all chicken husbandry practices. The Delmarva Peninsula could represent a significant source of nutrient nitrogen to the Chesapeake Bay and Delaware Bay watersheds through atmospheric deposition when considering the size of this annual release rate, the relative short atmospheric lifetime of ammonia due to deposition, and the proximity of the Delmarva Peninsula to the Chesapeake and Delaware Bays.

Agriculture↗
PubMed2006

Measurement of un-ionized ammonia in complex mixtures.

The toxicity of un-ionized ammonia, NH3 (aq), in anaerobic digestion of high-nitrogen wastes has been researched extensively. Previous estimates of NH3 (aq) concentration have relied on a simple speciation approach, based only on the acid dissociation constant and the sample pH and total ammonia concentration. The distinction between concentration and chemical activity has generally not been made, despite the potential for resulting errors in the calculation of NH3 (aq) concentration, and the greater applicability of activity to toxicity work. The currently accepted approach for estimating NH3 (aq) concentration is based on assumptions that are not valid in digested animal manure or other concentrated wastes. This work presents an approach for directly measuring NH3 (aq) activity in complex mixtures using gaseous/aqueous equilibrium across microporous tubing. Application of this approach to anaerobic digester samples confirms that the currently accepted approach is not accurate; it overestimated NH3 (aq) activity in unaltered samples by 45-200%. Previous work on the toxicity of ammonia to methanogenesis has probably overestimated the tolerance of consortia to NH3 (aq), due to overestimation of concentrations. The method introduced here is expected to be useful in a range of research on ammonia toxicity and volatilization.

Ammonia↗
PubMed1999

Effects of ammonia on pentylenetetrazole-induced seizure threshold.

The effect of chronic perfusion of ammonia on the seizure threshold against pentylenetetrazol was studied. Ammonia plus sodium bicarbonate and saline (0.9%) was continuously administered to two groups of rats respectively. All animals were tested three times for seizure threshold, and were then decapitated and the brains removed for analysis of the amino acids. The results showed that the infusion of ammonia increased the seizure threshold, and this protective effect was accompanied by selective changes in brain glutamate and glutamine. Thus, continuous infusion of ammonia may cause an imbalance between excitatory and inhibitory systems in favor of inhibitory systems. These findings may provide insights into the basic mechanisms of seizures observed in hepatic failure, in other hyperammonemic states, and in epilepsy.

Ammonia↗
PubMed2003

Electrogenic ion transport in mammalian colon involves an ammonia-sensitive apical membrane K+ conductance.

It is remarkable that high ammonia concentrations can be present within the colonic lumen without compromising normal epithelial function. We investigated the impact of luminal ammonia on Cl- secretion in native tissue. Stripped human colonic mucosa and unstripped rat distal colon were used. Paired samples were mounted in modified Ussing chambers for electrophysiological studies. In rat distal colon, apical ammonia dose-dependently blocked forskolin-activated short-circuit current with an IC50 to approximately 5 mM. Basolateral NH4Cl was less effective. Luminal methylamine (50 mM), chromanol 293B (10-50 microM), and Ba2+ (5 mM) blocked cAMP-activated short-circuit current but apical clotrimazole (100 microM) was without effect. In stripped human colonic mucosa, luminal but not basolateral NH4Cl (10 mM) and luminal Ba2+ (5 mM) suppressed forskolin-activated short-circuit current. Ammonia may be an endogenous regulator of colonic water and salt secretion. Apical K+ channels may be involved in the regulation of cAMP-stimulated Cl- secretion in mammalian colon.

Ammonia↗
PubMed2003

Effect of blood ammonia elevation following oral glutamine load on the psychometric performance of cirrhotic patients.

Oral glutamine challenge is a method to increase blood ammonia and may be used to study the ammonia lowering effect of drugs potentially useful in hepatic encephalopathy (HE). We tested its influence on the psychometric performance of 18 cirrhotic patients without HE. Twelve nonencephalopatic cirrhotic patients were studied before and after glutamine load (20 g in 100 mL tap water) and six patients before and after placebo (100 mL tap water) by using the Number Connection Test (NCT), the Covert Visual Attention Orienting Test (CVAOT), and the Scan Test (SCT). Blood ammonia increased significantly after glutamine (from 79 +/- 34 to 211 +/- 66 microg/dL) but not after placebo (from 94 +/- 41 to 88 +/- 26). No difference in the NCT was found before and after glutamine load or placebo. The CVAOT was similar after glutamine challenge and placebo, nor any interaction between Loads (glutamine or placebo) x Cue position was found, suggesting that glutamine load did not influence attention-orienting. SCT results were also similar after glutamine and placebo, suggesting a lack of influence on the working memory. Glutamine challenge is a safe method to induce hyperammonemia in nonencephalopatic cirrhotic patients and, therefore, to study the efficacy of ammonia lowering treatments.

Administration, Oral↗
PubMed2003

Ammonia neurotoxicity: role of the mitochondrial permeability transition.

Hepatic encephalopathy (HE) is an important cause of morbidity and mortality in patients with severe liver disease. Although the mechanisms responsible for HE remain elusive, ammonia is generally considered to be involved in its pathogenesis, and astrocytes are thought to be the principal target of ammonia neurotoxicity. Altered bioenergetics and oxidative stress are also thought to play a major role in this disorder. In this paper, we present data invoking the mitochondrial permeability transition (MPT) as a factor in the pathogenesis of HE/hyperammonemia. The MPT is a Ca2+-dependent, cyclosporin A (CsA) sensitive process due to the opening of a pore in the inner mitochondrial membrane that leads to a collapse of ionic gradients and ultimately to mitochondrial dysfunction. Many of the factors that facilitate the induction of the MPT are also known to be implicated in the mechanism of HE, including free radicals, Ca2+, nitric oxide, alkaline pH, and glutamine. We have recently shown that treatment of cultured astrocytes with 5 mM NH4Cl resulted in a dissipation of the mitochondrial membrane potential (delta(psi)m), which was sensitive to CsA. Similarly treated cultured neurons failed to show a loss of the delta(psi)m. Further support for the ammonia induction of the MPT was obtained by observing an increase in mitochondrial permeability to 2-deoxyglucose-6-phosphate, and a decrease in calcein fluorescence in astrocytes after ammonia treatment, both of which were also blocked by CsA. CsA was likewise capable of exerting a protective effect against hyperammonemia in mice. Taken together, our data suggest that the MPT represents an important component of the pathogenesis of HE and other hyperammonemic states.

Ammonia↗