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PubMed1990

The effect of pH on the toxicity of ammonia to a murine hybridoma.

The growth inhibition of a murine hybridoma mediated by ammonium chloride was shown to vary with the pH of the culture medium. Values for the initial media concentration causing 50% growth inhibition (IC50) ranged from 4 mM to 7.6 mM as the pH was reduced from 7.8 to 6.8. A significant negative correlation was observed between the IC50 and the NH3 concentration of the medium, suggesting that ammonia and not ammonium may be the toxic species in the culture medium. The optimum initial pH for cell growth was 7.4. However, this optimum shifts to lower pH as ammonia accumulates in culture as a metabolic by-product. This suggests that in order to obtain high cell yields, it may be beneficial to adopt a culture strategy of lowering pH during cell growth to offset the inhibitory effects of accumulated ammonia.

Ammonia↗
PubMedDate not supplied

Effect of ammonia on endocytosis and cytokine production by immortalized human microglia and astroglia cells.

Ammonium acetate decreased in a concentration-dependent manner the phagocytic uptake of mannosylated latex microspheres and of yeast by immortalized human microglia (CHME-5) and astroglioma (GL-15) cells. In both cell lines ammonium acetate affected also the secretion of certain cytokines. The most conspicuous effects were the following: in both cell lines ammonium acetate enhanced greatly the secretion of tumor necrosis factor-alpha in the absence of any other stimulus. in the human microglia cells ammonia decreased the constitutive secretion of interleukin-6, but it enhanced the stimulated (interleukin-1 alpha, tumor necrosis factor-alpha, gamma-interferon and gamma-interferon + tumor necrosis factor-alpha) secretion of interleukin-8. In the astroglioma cell line, the stimulated release of tumor necrosis factor-alpha, interleukin-6 and interleukin-8 was diminished by ammonium acetate. The magnitude of the ammonia-effect depended on the stimulating agent (lipopolysaccharide, interleukin-1 alpha, tumor necrosis factor-alpha, gamma-interferon). The results are discussed with regard to their potential importance in the pathogenesis of human diseases with elevated blood and brain ammonia concentrations.

Acetates↗
PubMed1985

Alterations in behavior produced by inhaled ozone or ammonia.

Ozone, a lower-airway irritant, produces fatigue, lethargy, and increased respiratory rates in several species, including man. Ammonia, an upper-airway irritant, produces burning of the eyes, nose, and throat, and a decrease in respiratory rate. The effects of exposure to these two prototypical irritants were examined to see if behavioral changes during and after exposure occurred at concentrations comparable to those that produce symptoms in humans. Long-Evans rats and Swiss mice, individually housed in running wheels, were exposed either to ozone (0.08, 0.12, 0.25, or 0.5 ppm) or to ammonia (100 or 300 ppm) for 6 hr. Each animal's behavior was compared with its own control performance. Running in both species decreased in a concentration-related manner during exposure to either irritant. The decrease in running activity produced by high concentrations of ozone persisted for several hours after exposure. Concentrations of ammonia that eliminated running during exposure led to an increase in activity following exposure. At comparable concentrations of both compounds, activity in rats decreased more than in mice.

Ammonia↗
PubMed1987

Bacterial tests as indicators for the detoxification of the mycotoxin penicillic acid by ammonia treatment.

The detoxification of penicillic acid by reaction with ammonia was examined by means of a polymerase assay using two strains of Escherichia coli (pol A+ and pol A-1) and a recombination assay using two strains of Bacillus subtilis (rec+ and rec-). A 100-fold surplus of ammonia added to penicillic acid abolished the cytotoxic and genotoxic effects of penicillic acid towards the bacteria under the test conditions. The study presents the possibility of detoxifying mycotoxins in feeds by ammonia treatment and demonstrates the suitability of bacterial assays as indicators for mycotoxins.

Ammonia↗
PubMedDate not supplied

Origin of the ammonia used for mitochondrial citrulline synthesis as revealed by 13C-15N spin coupling patterns observed by 13C NMR.

The sources of ammonia used by isolated, intact rat liver mitochondria in the production of citrulline have been investigated in situ using a novel methodology based on the analysis of 13C-15N heteronuclear couplings observed by 13C NMR. Isolated mitochondria from rat liver were incubated with ornithine, 13CO3H- and 15NH4Cl, using unlabeled glutamate or glutamine as alternative, intramitochondrial nitrogen donors. The production of (7-13C, 8-15N) or (7-13C, 8-14N) citrulline was determined in situ by 13C NMR and the relative proportions of 15N- and 14N-citrullines confirmed by high resolution 13C NMR analysis of the C-7 citrulline resonance observed in perchloric acid extracts prepared at the end of the incubations. The 15N fractional enrichment of the intramitochondrial NH3 pool was manipulated either by modifying the 15N enrichment of added 15NH4Cl, or by altering the concentration of the unlabeled nitrogen donors in the incubation medium. Fractional 15N enrichments measured in the N-8 nitrogen of the resulting (7-13C) citrulline closely paralleled those of the external 15NH4Cl with minor dilutions derived from the unlabeled nitrogen contribution from the alternative substrates. In the presence of 10 mM 15NH4Cl, 10 mM glutamate contributed 4% of the citrulline N-8 nitrogen. Under similar conditions, the contribution of nitrogen from 10 mM glutamine to N-8 citrulline was 6%. These results indicate that the primary source of ammonia used for citrulline synthesis by isolated, intact rat liver mitochondria is extramitochondrial, providing also an illustration of the use of 13C-15N spin coupling patterns observed by 13C NMR, as a new tool in the study of ammonia metabolism.

Ammonia↗
PubMed1989

Permeability of the urinary bladder of the turtle, Pseudemys scripta elegans, to ammonia.

1. The permeability of the isolated turtle urinary bladder to ammonia was investigated by varying the ratio of NH3 to NH4+ concentration in the serosal bath and measuring the flux of ammonia into the mucosal bath. 2. The permeability of the turtle bladder to NH3 was in the range of 5.4-6.1 x 10(-3) cm/sec and the permeability of the unstirred layer to NH4+ was in the range of 1.1-2.1 x 10(-5) cm/sec. 3. The flux of ammonia calculated from the permeability of NH3 can account for the decrease in mucosal H+ secretion observed with addition of NH4Cl to the serosal bath.

Ammonia↗
PubMed1989

Ammonia metabolism during the suckling period in the rat.

1. The time-courses of blood glutamine, glutamate, alanine, ammonia, urea and allantoin concentrations during the first 15 days of extrauterine life were studied. 2. Glutamine and glutamate concentrations followed the same pattern and correlated positively, suggesting that both amino acids are utilized or released synchronously. 3. Alanine concentrations decreased during the first 3 days, reaching levels close to those of adults which persisted up to the end of the observation period. 4. A highly significant correlation was found between ammonia and urea concentrations, suggesting that during the suckling period urea synthesis may be limited by blood ammonia availability. 5. The time-course of allantoin concentrations suggests that the synthesis of purines was enhanced during the first day, decreasing sharply during the 2nd to steeply increase to the end of the suckling period.

Allantoin↗
PubMed1993

The effect of water loss upon the urate, urea and ammonia content of the egg of the Japanese quail Coturnix coturnix japonica.

1. The urate, urea and ammonia content of the whole egg of the Japanese quail was measured in late incubation in eggs subject to different rates of water loss. 2. High rates of water loss substantially increased egg urate content, but had little or no effect on urea or ammonia content. 3. Allopurinol, an inhibitor of urate synthesis, reduced egg urate content to low levels, but produced no effect on urea content, and a small reduction in ammonia content. 4. The urea concentration of the embryo was lower than in allantoic fluid. 5. It is concluded that urate production by the avian embryo is primarily concerned with the modification of allantoic fluid composition.

Allopurinol↗
PubMed1996

Ammonia stimulates glutamine uptake to the cerebral non-synaptic mitochondria of the rat.

The uptake of [3H]glutamine (GLN) to non-synaptic mitochondria isolated from rat cerebral hemispheres was measured in the absence or presence of 3 mM ammonium ion (ammonium chloride; ammonia). Ammonia increased Vmax of the saturable component of GLN uptake by > 20%, without affecting K(m), but did not change a non-saturable component of GLN transport representing diffusion or uptake mediated by a very low affinity carrier. Since GLN is an idiogenic osmole, its increased uptake may contribute to the swelling of astrocytic mitochondria and, subsequently, to a decrease in cerebral energy metabolism usually associated with acute hyperammonemic states. The result is consistent with the recent view that GLN accumulating in the brain in hyperammonemic conditions contributes to ammonia neurotoxicity.

Ammonia↗
PubMed1990

Noninvasive quantification of regional blood flow in the human heart using N-13 ammonia and dynamic positron emission tomographic imaging.

Evaluation of regional myocardial blood flow by conventional scintigraphic techniques is limited to the qualitative assessment of regional tracer distribution. Dynamic imaging with positron emission tomography allows the quantitative delineation of myocardial tracer kinetics and, hence, the measurement of physiologic processes such as myocardial blood flow. To test this hypothesis, positron emission tomographic imaging in combination with N-13 ammonia was performed at rest and after pharmacologically induced vasodilation in seven healthy volunteers. Myocardial and blood time-activity curves derived from regions of interest over the heart and ventricular chamber were fitted using a three compartment model for N-13 ammonia, yielding rate constants for tracer uptake and retention. Myocardial blood flow (K1) averaged 88 +/- 17 ml/min per 100 g at rest and increased to 417 +/- 112 ml/min per 100 g after dipyridamole infusion (0.56 mg/kg) and handgrip exercise. The coronary reserve averaged 4.8 +/- 1.3 and was not significantly different in the septal, anterior and lateral walls of the left ventricle. Blood flow values showed only a minor dependence on the correction for blood metabolites of N-13 ammonia. These data demonstrate that quantification of regional myocardial blood flow is feasible by dynamic positron emission tomographic imaging. The observed coronary flow reserve after dipyridamole is in close agreement with the results obtained by invasive techniques, indicating accurate flow estimates over a wide range. Thus, positron emission tomography may provide accurate and noninvasive definition of the functional significance of coronary artery disease and may allow the improved selection of patients for revascularization.

Adult↗
PubMed1990

Dynamic positron tomographic imaging with nitrogen-13 glutamate in patients with coronary artery disease: comparison with nitrogen-13 ammonia and fluorine-18 fluorodeoxyglucose imaging.

This study was designed to test the usefulness of nitrogen-13 (N-13) glutamate imaging with positron emission tomography in defining myocardial ischemia in humans. Seventeen patients who had undergone coronary arteriography were studied with N-13 glutamate at peak supine exercise using a bicycle ergometer, as well as with the flow tracer N-13 ammonia at peak exercise during a second similar exercise test. Six of the patients also underwent imaging with N-13 glutamate at rest before exercise testing; in the remaining 11 patients imaging with fluorine-18 (F-18) fluorodeoxyglucose was performed to assess glucose metabolism after the second exercise test. Seven patients had classic metabolism-flow mismatches consistent with ischemia (that is, decreased N-13 ammonia uptake in a region with relatively increased F-18 fluorodeoxyglucose uptake). There was no evidence of increased N-13 glutamate uptake in the ischemic mismatched regions in any of these patients. In all 17 patients, the uptake of N-13 glutamate during exercise paralleled the uptake of N-13 ammonia during exercise, suggesting that N-13 glutamate behaves as a flow tracer rather than as a metabolic marker of ischemia in humans.

Aged↗
PubMed1986

Sublethal effect of ammonia on certain biochemical and haematological indicators in common carp (Cyprinus carpio L.).

Carp (Cyprinus carpio L.) fry were exposed for 3 weeks to a sublethal concentration of ammonia (0.102 +/- 0.059 mg NH3/dm3). Ammonia induced considerable changes in the level of free amino acids and unfavourable changes in the blood, i.e. leucopaenia and eosinophy. The observed increase of the concentration of most amino acids in fish intoxicated with NH3 suggests that the process reflects detoxication of ammonia which takes place both in the brain and muscles.

Alanine Transaminase↗
PubMed1986

Ammonia detoxification by accelerated oxidation of branched chain amino acids in brains of acute hepatic failure rats.

BCAA aminotransferase and BCKA dehydrogenase activities are increased in the mitochondrial fractions from the brains of hepatic failure rats treated with two-thirds removal of CCl4-injured liver. Cerebral leucine decarboxylation was accelerated, and it well correlated with arterial blood ammonia levels. Elevation of brain ammonia content following an intraperitoneal injection of ammonium acetate to hepatic failure rats could be prevented by intravenous infusion of BCAA. Significantly increased brain glutamic acid, glutamine, and alanine contents were noted. These results suggested that accelerated brain BCAA catabolism in acute hepatic failure rats reduce the neurotoxicity of ammonia by promoting the synthesis of glutamic acid and glutamine from BCAA.

Acute Disease↗
PubMed1992

Plasma urea and ammonia in epileptic patients and their relatives.

The plasma levels of urea and ammonia were examined in patients with primary generalized epilepsy, patients with partial epilepsy and in the first-degree relatives of these subjects. The results show a significant decrease in plasma urea in both groups of patients and their first-degree relatives as compared to the non-epileptic controls. The plasma ammonia concentrations were significantly higher in both groups of patients and in the relatives of generalized epilepsy patients as compared to the controls. The observed changes in plasma urea and ammonia were found not to be due to the effect of anticonvulsant drugs. The data suggest that a metabolic defect in urea synthesis may constitute one of the genetic components in the multifactorial etiologies of primary generalized and partial epilepsies.

Adolescent↗
PubMed1989

The effect of ammonia on cell-type-specific enzyme accumulation in Dictyostelium discoideum.

We have shown that ammonia inhibits stalk cell formation and promotes spore formation during cyclic AMP induced differentiation of monolayers of sporogenous amoebae (Gross, J.D. et al., Nature (London), 303, 244-245, 1983). Here we show that exposure to ammonia favours the accumulation of prespore- over prestalk-specific enzymes and related products. We conclude that ammonia switches cells from the prestalk to the prespore pathway rather than simply inhibiting stalk cell maturation and hence may act as a morphogen during development.

Acid Phosphatase↗
PubMed1994

Production of [13N]ammonia applicable to low energy accelerators.

We have developed a technique for the rapid conversion of the nitrogen-13 induced in a graphite target into nitrogen oxides. This was accomplished by heating the graphite target in a stream of pure oxygen at 800 degrees C. Less than 20% of the radioactivity was found in the form of [13N]nitrogen. The rest of the radioactivity was efficiently trapped in a solid-phase medium that consisted of an aqueous solution of 5% NaOH dispersed in silica gel. The radioactivity from this solid-phase medium was eluted with water (94% recovery) and found to be in the form of 13NO2- (99%). This was subsequently converted to [13N]ammonia with Raney-nickel, either by a conventional liquid-phase reduction with an overall conversion efficiency to ammonia of 45%, or by an incorporation of the Raney-nickel into the solid-phase medium. The latter system resulted in an overall conversion efficiency to ammonia of 37 +/- 9%, with a radiochemical purity of nearly 100% and a synthesis time under 17 min.

Ammonia↗
PubMed2005

Predicting ammonia losses following the application of livestock manure to land.

A series of experiments was conducted using small wind tunnels to assess the influence of a range of environmental, manure and management variables on ammonia emissions following application of different manure types to grassland and arable land. Wind speed and dry matter content (for cattle slurry in particular) were identified as the parameters with greatest influence on ammonia emissions from slurries. For solid manures, rainfall was identified as the parameter with most influence on ammonia emissions. A Michaelis-Menten function was used to describe emission rates following manure application. Linear regression was then used to develop statistical models relating the Michaelis-Menten function parameters to the experimental variables for each manure type/land use combination. The fitted models accounted for between 62% and 94% of the variation in the data. Validation of the models for cattle slurry to grassland and pig slurry to arable land against independent data sets obtained from experiments using the micrometeorological mass balance measurement technique showed that the models overestimated losses, which was most probably due to inherent differences between the wind tunnel and the micrometerological mass balance measurement techniques.

Agriculture↗
PubMed2005

Pretreatment and fractionation of corn stover by ammonia recycle percolation process.

Corn stover was pretreated with aqueous ammonia in a flow-through column reactor, a process termed as Ammonia Recycle Percolation (ARP). The aqueous ammonia causes swelling and efficient delignification of biomass at high temperatures. The ARP process solubilizes about half of xylan, but retains more than 92% of the cellulose content. Enzymatic digestibility of ARP-treated corn stover is 93% with 10 FPU/g-glucan enzyme loading. The SEM pictures and FTIR spectra confirm swelling and delignification effects of the ARP process. The X-ray crystallography data indicate that the basic crystalline structure of the cellulosic component of corn stover is not altered by the ARP treatment. Low-liquid ARP can reduce the liquid throughput and residence time to 3.3 mL/g-biomass and 10-12 min, without adversely affecting the overall effectiveness. The low-water ARP achieved 73.4% delignification and 88.5% digestibility with 15 FPU/g-glucan. The ethanol yield from the SSF of low-liquid ARP-treated corn stover using Saccharomyces cerevisiae reached 84% of the theoretical maximum. Successive operation of a hot-water treatment and the ARP was applied as a method of biomass fractionation. The two-stage process separated xylan in the first stage (84%) and lignin in the second stage (75%), resulting treated solid that contains 79% glucan.

Ammonia↗