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 487 records · Page 27Linked to original sources
PubMed1997

Gender differences in blood ammonia response during exercise.

In order to test for possible gender differences in blood ammonia accumulation during exercise, groups of young, physically active women (n = 8) and men (n = 8) performed an incremental load (until exhaustion) and a constant load (30 min at 75% VO2 peak) treadmill exercise test. The groups were matched for physical activity habits. VO2 peak was significantly higher in males (55.8 +/- 2.6 ml/kg/min) than in females (44.5 +/- 2.8 ml/kg/min). During the incremental exercise test to exhaustion blood ammonia concentration progressively increased with increasing workload in both groups. Blood ammonia concentration was significantly higher in males at 70, 80 and 90% of VO2 peak. Peak blood ammonia concentration was higher in males than in females (155 +/- 35 vs 136 +/- 67 mumol/l, respectively), but the difference did not reach the level of statistical significance. During the constant load exercise test blood ammonia concentration increased in both groups. At the end of the exercise test blood ammonia concentration was significantly higher in males than in females (137 +/- 42 vs 91 +/- 24 mumol/l, respectively). In conclusion, the blood ammonia concentration during submaximal exercise is dependent on gender, the males showing higher ammonia concentrations compared to females at the same relative workload (percent of VO2 peak).

Adult↗
PubMed1998

Implications of gastric topical bioactive peptides in ammonia-induced acute gastric mucosal lesions in rats.

BACKGROUND: Ammonia, one of the pathogenic factors in Helicobacter pylori-induced mucosal injury, induces acute mucosal lesions in the rat glandular stomach. METHODS: The effect of ammonia administered intragastrically on gastric peptides was investigated in urethane-anesthetized rats. RESULTS: Gastric mucosal lesions were observed 5 min after 0.3% ammonia (4 ml/kg, intragastrically). Immunoreactive endothelin-1 (ET-1) and immunoreactive thyrotropin-releasing hormone (TRH) concentrations in the gastric wall decreased significantly 2 min and 5 min after ammonia, respectively. A significant increase in gastric juice immunoreactive ET-1 and TRH levels was reciprocally observed. The severity of gastric mucosal injury and changes in gastric immunoreactive ET-1 and TRH concentrations were shown to be concentration-dependent 30 min after ammonia. Atropine (5 mg/kg, intraperitoneally, -20 min) prevented ammonia-induced injury accompanied by a block of changes in gastric immunoreactive ET-1 and TRH concentrations. BQ-485 (ET(A) receptor antagonist; 2 mg/kg, subcutaneously) also abolished ammonia-induced lesions and gastric immunoreactive TRH changes. CONCLUSIONS: These findings suggested that gastric ET-1 and TRH play a role in ammonia-induced gastric mucosal injury mediated via a muscarine and an ET(A) receptor.

Ammonia↗
PubMed1992

Fecal ammonia in patients with adenomatous polyps and cancer of the colon.

The correlation between high intakes of protein and high incidence of human colonic cancer is unexplained. Appreciable amounts of ammonia are generated in the large bowel through bacterial degradation of proteins and peptides, and experimental studies indicate that ammonia may select for neoplastic growth. Fecal concentrations of ammonia did not differ among 17 patients with former colonic adenomas [40.6 +/- 4.5 (SE) mM], 17 patients with former colonic cancer (51.4 +/- 3.9 mM), and 16 healthy controls (46.4 +/- 6.1 mM). By use of an in vitro fecal incubation system, possible alterations in bacterial fermentation and formation of ammonia were investigated. Fecal suspensions were incubated for 6 and 24 hours with and without addition of fermentable substrates (ispaghula husk, wheat bran, albumin, and glucose; 10 mg/ml). The in vitro production of ammonia in unsupplemented fecal homogenates from both groups of patients was comparable with the production found in homogenates from healthy controls, and the response to fermentable substrates was similar in all three groups. Addition of albumin caused a marked increase in the production of ammonia, and addition of glucose increased bacterial assimilation of ammonia considerably. These well-known characteristics of bacterial metabolism of ammonia apparently did not differ between healthy individuals and patients investigated more than three months after colonoscopic polypectomy or colonic cancer resection.

Adenoma↗
PubMed2005

Ammonia flux from open-lot dairies: development of measurement methodology and emission factors.

Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 microg m(-3) and from 2 to 43% of total PM2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head(-1) day(-1), showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.

Air Pollutants↗
PubMed2002

Studies on the use of neem products for removal of ammonia from brackishwater.

Laboratory experiments were carried out to investigate the ammonia removal from brackishwater (Salinity 16 +/- 1 ppt) using natural plant products such as seed powder and seed oil from neem (Azadirachta indica) and commercially available neem products-neemazal and neemgold. The experimental results showed that ammonia removal was effective with 90 mg/l of neem oil, whereas, neem seed powder at 90 mg/l registered an increase in ammonia levels throughout the course of the experiment. Neem oil, neemazal, and neemgold at 90 mg/l were effective in decreasing the total ammonia nitrogen (TAN) level of 0.40-0.45 mg/l in 96 h. The effect of initial ammonia concentrations on the ammonia removal using neem oil revealed that percentage ammonia removal decreased with an increase in initial ammonia concentration.

Ammonia↗
PubMedDate not supplied

Ammonia and urea in the maternal-fetal trophic relationship of the viviparous blenny (eelpout) Zoarces viviparus.

A high correlation was observed between the concentration of urea in the maternal plasma and the concentration of urea in the ovarian fluid during post-yolk sac growth of the embryos in the ovary of the viviparous blenny (eelpout) Zoarces viviparus. A high correlation was observed between maternal plasma and ovarian fluid ammonia as well. Ammonia but not urea was excreted to the external medium by the mother fish during pregnancy. Intraovarian loading with either urea or ammonia resulted in a steady decrease from initial high concentrations in the ovarian fluid and a concomitant increase in the maternal plasma levels of both nitrogenous compounds. Injected ammonia was eliminated much faster from the ovarian fluid than urea. No significant effect of any ammonia could be observed on urea excretion rates by embryos in vitro. Patterns of accumulation for urea and ammonia in the external medium were investigated by exposure of embryos in vitro to concentrations of urea and ammonia similar to those normally found in the ovarian fluid. No significant changes could be observed in the external urea or ammonia levels during the experiment. The results indicate that during post-yolk sac development of embryos in vivo, net catabolism of nitrogen-containing organics and formation of urea may be reduced by high ambient concentrations of urea in the ovarian fluid.

Ammonia↗
PubMed1995

Absorption of ammonia by high water content hydrogel lenses: an inexpensive method of analysis.

Few studies have been done on the absorption and release of chemical vapors by high water content hydrogel lenses. In this study we investigated the absorption of ammonia vapors by this type of contact lens (CL). Ten high water content hydrogel lenses were exposed to vapor generated in a cuvette by 1 drop of aqueous ammonia. The contact lens was transferred to a 0.9% saline solution containing a colorometric indicator for ammonia and the amount of ammonia released into the saline was measured. We found that significant quantities of ammonia were absorbed into the lenses and the relation between average concentration of ammonia vapor and amount absorbed per contact lens was nearly linear from 50 parts per million (ppm) to 250 ppm ammonia vapor. For concentrations greater than 250 ppm there appears to be a saturation effect. Our findings indicate that high water contact lenses will absorb ammonia and release it into a solution similar to tears.

Absorption↗
PubMed2001

Ammonia oxidation by Nitrosomonas eutropha with NO(2) as oxidant is not inhibited by acetylene.

The effect of acetylene ((14)C(2)H(2)) on aerobic and anaerobic ammonia oxidation by Nitrosomonas eutropha was investigated. Ammonia monooxygenase (AMO) was inhibited and a 27 kDa polypeptide (AmoA) was labelled during aerobic ammonia oxidation. In contrast, anaerobic, NO(2)-dependent ammonia oxidation (NO(2)/N(2)O(4) as oxidant) was not affected by acetylene. Further studies gave evidence that the inhibition as well as the labelling reaction were O(2)-dependent. Cells pretreated with acetylene under oxic conditions were unable to oxidize ammonia with O(2) as oxidant. After these cell suspensions were supplemented with gaseous NO(2), ammonia oxidation activity of about 140 micromol NH(4)(+) (g protein)(-1) h(-1) was detectable under both oxic and anoxic conditions. A significantly reduced acetylene inhibition of the ammonia oxidation activity was observed for cells incubated in the presence of NO. This suggests that NO and acetylene compete for the same binding site on AMO. On the basis of these results a new hypothetical model of ammonia oxidation by N. eutropha was developed.

Acetylene↗
PubMed2001

ThermoEnergy Ammonia Recovery Process for municipal and agricultural wastes.

The Ammonia Recovery Process (ARP) is an award-winning, low-cost, environmentally responsible method of recovering nitrogen, in the form of ammonia, from various dilute waste streams and converting it into concentrated ammonium sulfate. The ThermoEnergy Biogas System utilizes the new chemisorption-based ARP to recover ammonia from anaerobically digested wastes. The process provides for optimal biogas production and significantly reduced nitrogen levels in the treated water discharge. Process flows for the ammonia recovery and ThermoEnergy biogas processes are presented and discussed. A comparison with other techniques such as biological nitrogen removal is made. The ARP technology uses reversible chemisorption and double salt crystal precipitation to recover and concentrate the ammonia. The ARP technology was successfully proven in a recent large-scale field demonstration at New York City's Oakwood Beach Wastewater Treatment Plant, located on Staten Island. This project was a joint effort with Foster Wheeler Environmental Corporation, the Civil Engineering Research Foundation, and New York City Department of Environmental Protection. Independent validated plant data show that ARP consistently recovers up to 99.9% of the ammonia from the city's centrate waste stream (derived from dewatering of sewage sludge), as ammonium sulfate. ARP technology can reduce the nitrogen (ammonia) discharged daily into local bodies of water by municipalities, concentrated animal farming operations, and industry. Recent advances to ARP enhance its performance and economic competitiveness in comparison to stripping or ammonia destruction technologies.

Agriculture↗
PubMed1995

Ammonia prevents activation of NMDA receptors by glutamate in rat cerebellar neuronal cultures.

Acute ammonia toxicity is mediated by activation of NMDA receptors and is prevented by chronic moderate hyperammonaemia. The aim of this work was to assess whether the protective effect of chronic hyperammonaemia is due to impaired activation of the NMDA receptor. It is shown that chronic hyperammonaemia in rats decreases the binding of [3H]MK-801 to synaptosomal membranes from the hippocampus but not the amount of NMDAR1 receptor protein as determined by immunoblotting. In primary cultures of cerebellar neurons, long-term treatment with 1 mM ammonia also decreased significantly the binding of [3H]MK-801. These results suggest that ammonia impairs NMDA receptor activation. To confirm this possibility we tested the effect of long-term treatment of the cultured neurons with 1 mM ammonia on three well known events evoked by activation of the NMDA receptor: neuronal death induced by glutamate, increase in aspartate aminotransferase activity and increase in free intracellular [Ca2+]. Long-term treatment with ammonia prevented noticeably the effects of glutamate or NMDA on all these parameters. These results indicate that long-term treatment of neurons with 1 mM ammonia leads to impaired function of the NMDA receptor, which cannot be activated by glutamate or NMDA. Activation of protein kinase C by a phorbol ester restored the ability of the NMDA receptor to be activated in neurons treated with ammonia. This suggests that ammonia impairs NMDA receptor function by decreasing protein kinase C-dependent phosphorylation.

Ammonia↗
PubMed1991

Ammonia levels in paediatric ureterosigmoidostomy patients: a screen for hyperammonaemia?

Hyperammonaemia in the urological patient is a rare and potentially grave condition. It has been reported most frequently in association with ureterosigmoidostomy, where clinical neurological symptoms have developed abruptly in association with markedly elevated plasma ammonia levels. The purpose of this study was to determine whether ureterosigmoidostomy patients might have subclinically elevated plasma ammonia levels, which would put them at risk of subsequently developing hyperammonaemic encephalopathy. Both urine and plasma ammonia levels were assayed in 10 asymptomatic paediatric urological patients with ureterosigmoidostomy. Ten paediatric colocystoplasty patients served as controls. Urine pH and urine ammonia levels were significantly higher in the ureterosigmoidostomy group. There was no significant difference in plasma ammonia levels between ureterosigmoidostomy and colocystoplasty patients. In none of the patients was the plasma ammonia level elevated, but 1 ureterosigmoidostomy patient had an exceedingly high urine ammonia level. It was concluded that an annual serum ammonia level in an asymptomatic ureterosigmoidostomy patient is probably not a valuable screen for subclinical hyperammonaemia.

Adolescent↗
PubMed2004

Acute ammonia intoxication induces an NMDA receptor-mediated increase in poly(ADP-ribose) polymerase level and NAD metabolism in nuclei of rat brain cells.

Acute ammonia toxicity is mediated by excessive activation of NMDA receptors. Activation of NMDA receptors leads to activation of poly(ADP-ribose) polymerase (PARP) which mediates NMDA excitotoxicity. PARP is activated following DNA damage and may lead to cell death via NAD+ and ATP depletion. The aim of the present work was to assess whether acute ammonia intoxication in vivo leads to increased PARP in brain cells nuclei and to altered NAD+ and superoxide metabolism and the contribution of NMDA receptors to these alterations. Acute ammonia intoxication increases PARP content twofold in brain cells nuclei.NAD+ content decreased by 55% in rats injected with ammonia. This was not due to decreased NAD+ synthetase nor increased NAD+ hydrolase activities and would be due to increased NAD+ consumption by PARP. Superoxide radical formation increased by 75% in nuclei of brains of rats injected with ammonia, that also induced protein nitrotyrosylation and DNA damage. Blocking NMDA receptors prevented ammonia-induced PARP, superoxide and nitrotyrosylation increase, DNA damage and NAD+ decrease. These results show that acute ammonia intoxication in vivo leads to activation of NMDA receptors, leading to increased superoxide formation and PARP content and depletion of NAD+ in brain cells nuclei that contribute to ammonia toxicity.

Amide Synthases↗
PubMed1996

Determinants of ammonia clearance by hemodialysis.

Ammonia toxicity appears to contribute to the genesis of brain edema, a leading cause of death in fulminant hepatic failure. Because dialysis has been recommended for acute hyperammonemia in other conditions, we have conducted a study to analyze the determinants of ammonia clearance with the use of a single-pass dialyzer. We have used an ionic solution with a constant concentration of ammonia to estimate clearance at different blood flow rates, at dialysate flow rates, and with different dialyzer surfaces. Once hemodialysis had been optimized, we estimated ammonia, glutamine, and urea removal by using a single-compartment model. Our results show that the clearance of ammonia is blood flow dependent and is also influenced by dialysate flow rate and dialyzer surface. At clinically feasible conditions, ammonia can be extracted by more than 80% by setting the dialysate flow at a high rate. In addition to ammonia removal, hemodialysis allows the clearance of urea and glutamine, molecules that can be regarded as ammonia equivalents and that also undergo flow-dependent elimination.

Ammonia↗
PubMed1999

Helicobacter pylori infection, plasma ammonia levels, and psychometric testing in cirrhotic patients.

OBJECTIVE: The role of Helicobacter pylori (H. pylori) infection as a cause of hepatic encephalopathy is still debated. This study focused on the relationship between H. pylori, plasma ammonia levels, and intellectual function in cirrhotic patients. METHODS: Forty-seven cirrhotics with latent or mild hepatic encephalopathy were enrolled in the study, upon H. pylori assessment at endoscopy. Plasma ammonia level determinations and psychometric testing were performed at entry in all patients. Patients with H. pylori infection received a 2-wk standard dual therapy and bacterial eradication was assessed at endoscopy 6-8 wk later. On this occasion, plasma ammonia levels and psychometric assessments were repeated. Patients without H. pylori infection at entry were also studied after 6-8 wk for ammonia level assessment and psychometric testing, as a control group. Patients receiving lactulose therapy and those without therapy were grouped separately for statistical analysis. RESULTS: Among 21 patients without lactulose therapy (group A), basal plasma ammonia levels and psychometric testing scores did not significantly differ between 13 infected and eight uninfected patients. Similarly, among 26 patients undergoing lactulose therapy (group B), basal plasma ammonia concentration and psychometric testing scores did not significantly differ between 13 infected and 13 uninfected patients. Moreover, in group B, both the prevalence of previous overt hepatic encephalopathy episodes and the mean daily dose of lactulose therapy were similar between infected and uninfected patients. In addition, no significant reduction in the plasma ammonia concentrations and in psychometric testing scores emerged in both groups A and B after bacterial eradication. CONCLUSIONS: This study failed to find a relationship between H. pylori, plasma ammonia levels, and psychometric testing scores in cirrhotic patients with latent or mild hepatic encephalopathy.

Adult↗
PubMed2005

Two beta-alanyl-CoA:ammonia lyases in Clostridium propionicum.

The fermentation of beta-alanine by Clostridium propionicum proceeds via activation to the CoA-thiol ester, followed by deamination to acryloyl-CoA, which is also an intermediate in the fermentation of l-alanine. By shifting the organism from the carbon and energy source alpha-alanine to beta-alanine, the enzyme beta-alanyl-CoA:ammonia lyase is induced 300-fold (approximately 30% of the soluble protein). The low basal lyase activity is encoded by the acl1 gene, whereas the almost identical acl2 gene (six amino acid substitutions) is responsible for the high activity after growth on beta-alanine. The deduced beta-alanyl-CoA:ammonia lyase proteins are related to putative beta-aminobutyryl-CoA ammonia lyases involved in lysine fermentation and found in the genomes of several anaerobic bacteria. beta-Alanyl-CoA:ammonia lyase 2 was purified to homogeneity and characterized as a heteropentamer composed of 16 kDa subunits. The apparent K(m) value for acryloyl-CoA was measured as 23 +/- 4 microm, independent of the concentration of the second substrate ammonia; k(cat)/K(m) was calculated as 10(7) m(-1) x s(-1). The apparent K(m) for ammonia was much higher, 70 +/- 5 mm at 150 microm acryloyl-CoA with a much lower k(cat)/K(m) of 4 x 10(3) m(-1) x s(-1). In the reverse reaction, a K(m) of 210 +/- 30 microM was obtained for beta-alanyl-CoA. The elimination of ammonia was inhibited by 70% at 100 mm ammonium chloride. The content of beta-alanyl-CoA:ammonia lyase in beta-alanine grown cells is about 100 times higher than that required to sustain the growth rate of the organism. It is therefore suggested that the enzyme is needed to bind acryloyl-CoA, in order to keep the toxic free form at a very low level. A formula was derived for the calculation of isomerization equilibra between L-alanine/beta-alanine or D-lactate/3-hydroxypropionate.

Ammonia-Lyases↗
PubMed2002

Ammonia inhibits sodium and chloride absorption in rat distal colon.

It was recently demonstrated that ammonia inhibits sodium absorption in the proximal colon of rats. In order to investigate the effect of luminal ammonia in the distal colon, sodium and chloride transport were measured in Ussing chambers. Under short-circuit conditions, distal colon absorbed sodium and chloride. When luminal ammonia (30 mmol l(-1)) was present, sodium and chloride absorption was diminished. Inhibition of the two Na(+)-H(+) exchanger isoforms NHE2 and NHE3, which are known to be located in the apical membrane of the distal colon epithelium, failed to influence the effect of ammonia on transepithelial sodium and chloride fluxes. The inhibitory effect of ammonia was eliminated under the following conditions: after block of carbonic anhydrases with acetazolamide, in the presence of an unspecific blocker of Na(+)-H(+) exchangers, and under chloride-free conditions. Ammonia did not alter electrogenic sodium absorption. These results demonstrate that luminal ammonia inhibits sodium and chloride absorption in rat distal colon. We suggest that ammonia inhibits NaCl absorption by interfering with a Na(+)-H(+) exchanger that is not NHE2 or NHE3

Ammonia↗
PubMed1994

Influence of Yucca shidigera extract on ruminal ammonia concentrations and ruminal microorganisms.

An extract of the desert plant Yucca shidigera was assessed for its possible benefit in ruminal fermentation. The extract bound ammonia in aqueous solution when concentrations of ammonia were low (up to 0.4 mM) and when the extract was added at a high concentration to the sample (20%, vol/vol). The apparent ammonia-binding capability was retained after autoclaving and was decreased slightly following dialysis. Acid-precipitated extract was inactive. No evidence of substantial ammonia binding was found at higher ammonia concentrations (up to 30 mM). When Y. shidigera extract (1%, vol/vol) was added to strained rumen fluid in vitro, a small (6%) but significant (P < 0.05) decrease in ammonia concentration occurred, apparently because of decreased proteolysis. Inclusion of Y. shidigera extract (1%, vol/vol) in the growth medium of the rumen bacterium Streptococcus bovis ES1 extended its lag phase, while growth of Butyrivibrio fibrisolvens SH13 was abolished. The growth of Prevotella (Bacteroides) ruminicola B(1)4 was stimulated, and that of Selenomonas ruminantium Z108 was unaffected. Protozoal activity, as measured by the breakdown of 14C-leucine-labelled S. ruminantium in rumen fluid incubated in vitro, was abolished by the addition of 1% extract. The antimicrobial activities were unaffected by precipitating tannins with polyvinylpyrrolidone, but a butanol extract, containing the saponin fraction, retained its antibacterial and antiprotozoal effects. Saponins from other sources were less effective against protozoa than Y. shidigera saponins. Y. shidigera extract, therefore, appears unlikely to influence ammonia concentration in the rumen directly, but its saponins have antimicrobial properties, particularly in suppressing ciliate protozoa, which may prove beneficial to ruminal fermentation and may lead indirectly to lower ruminal ammonia concentrations.

Ammonia↗
PubMed1999

Effect of toxic metals on indigenous soil beta-subgroup proteobacterium ammonia oxidizer community structure and protection against toxicity by inoculated metal-resistant bacteria.

Contamination of soils with toxic metals is a major problem on military, industrial, and mining sites worldwide. Of particular interest to the field of bioremediation is the selection of biological markers for the end point of remediation. In this microcosm study, we focus on the effect of addition of a mixture of toxic metals (cadmium, cobalt, cesium, and strontium as chlorides) to soil on the population structure and size of the ammonia oxidizers that are members of the beta subgroup of the Proteobacteria (beta-subgroup ammonia oxidizers). In a parallel experiment, the soils were also treated by the addition of five strains of metal-resistant heterotrophic bacteria. Effects on nitrogen cycling were measured by monitoring the NH3 and NH4+ levels in soil samples. The gene encoding the alpha-subunit of ammonia monooxygenase (amoA) was selected as a functional molecular marker for the beta-subgroup ammonia oxidizing bacteria. Community structure comparisons were performed with clone libraries of PCR-amplified fragments of amoA recovered from contaminated and control microcosms for 8 weeks. Analysis was performed by restriction digestion and sequence comparison. The abundance of ammonia oxidizers in these microcosms was also monitored by competitive PCR. All amoA gene fragments recovered grouped with sequences derived from cultured Nitrosospira. These comprised four novel sequence clusters and a single unique clone. Specific changes in the community structure of beta-subgroup ammonia oxidizers were associated with the addition of metals. These changes were not seen in the presence of the inoculated metal-resistant bacteria. Neither treatment significantly altered the total number of beta-subgroup ammonia-oxidizing cells per gram of soil compared to untreated controls. Following an initial decrease in concentration, ammonia began to accumulate in metal-treated soils toward the end of the experiment.

Ammonia↗