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PubMed1991

Ammonia elimination as a rapid index of viability in liver grafts in dogs.

We examined intraoperative changes in blood ammonia levels and the correlation with graft viability in orthotopic liver transplantation (OLTx) in 29 dogs. Blood ammonia levels following total hepatectomy were examined using five dogs. These levels immediately following hepatectomy (15 min) were significantly higher (212 +/- 29 micrograms/dl) over values noted before hepatectomy (93 +/- 11 micrograms/dl, P less than 0.05). OLTx was performed using the cuff technique. The animals were divided into two groups: Group A (n = 6 pairs), OLTx with a nonpreserved fresh graft; Group B (n = 6 pairs), OLTx with an 8-hr preserved graft with lactated Ringer (4 degrees C). In both groups, the blood ammonia levels before the surgery and at the anhepatic phase data did not differ; however, following reperfusion, the levels in Group B were significantly higher (211 +/- 26 at 15 min, 200 +/- 50 micrograms/dl at 30 min) than those in Group A (121 +/- 10 at 15 min; P less than 0.01, 109 +/- 9 micrograms/dl at 30 min; P less than 0.05). The blood ammonia level highly correlated with adenosine triphosphate contents in the liver tissue, blood level of lactic acid, and amount of bile output, all pertinent indicators of the graft viability. Thus, the potential to eliminate ammonia immediately after reperfusion can serve as an indicator of graft viability. The intraoperative monitoring of blood ammonia levels can be included in management guidelines in cases of liver transplantation.

Adenosine Triphosphate↗
PubMed1996

Airway protective reflexes elicited by laryngeal ammonia: role of C-fiber afferents.

Intralaryngeal ammonia induces an airway protective reflex in rats characterized by apnea, bradycardia and increased laryngeal resistance. Since ammonia is known to stimulate both the myelinated and the nonmyelinated afferents, the role of nonmyelinated afferents in eliciting the above response is unclear. The present study was designed to investigate this by utilizing two techniques that selectively block C-fiber afferents: intravenous ruthenium red and perineural application of capsaicin. Ammonia vapor was introduced into the functionally isolated larynx of anesthetized rats for 10 sec at a flow rate of 5 ml/sec. Changes in expiratory duration were expressed as the ratio between test and control expiratory time (TEmax/control). Perineural application of capsaicin (n = 8) to SLNs attenuated the responses of both intralaryngeal ammonia (TEmax/control: 12.32 +/- 1.67 to 6.89 +/- 1.62; P < 0.05) and capsaicin (8.86 +/- 2.02 to 3.35 +/- 2.17; P < 0.05). Pretreatment with ruthenium red (1 mg/kg, iv., n = 10) significantly reduced the effects of ammonia (20.43 +/- 4.38 vs. 11.66 +/- 3.21; P < 0.05) and nebulized capsaicin (16.28 +/- 4.58 to 3.90 +/- 0.83; P < 0.05). These results suggest that the C-fiber endings of the SLN play an important role in eliciting the airway protective reflexes by irritants such as ammonia.

Airway Resistance↗
PubMed1994

Effects of veratridine and nifedipine on ammonia-induced rapidly adapting pulmonary stretch receptor stimulation in vagotomized rabbits.

We studied the effects of aerosol administration of veratridine (a sodium channel opener) or nifedipine (a calcium channel blocker) on the responses of rapidly adapting pulmonary stretch receptors (RARs) and dynamic lung compliance (Cdyn) to aerosols of 2 and 4% ammonia solutions in anesthetized spontaneously breathing rabbits without intact vagi. The RARs increased their activity following ammonia aerosol, and the increase was concentration-dependent. However, ammonia aerosol did not significantly alter the value of Cdyn. The RARs following aerosol administration of veratridine (about 200 micrograms) showed their characteristic firing pattern with several phases; each phase was characterized by the long high-frequency continuous discharges. Under these conditions, the response was not associated with any significant change in Cdyn. Even though the change in receptor activity produced by veratridine was restored to control level, subsequent aerosol application of ammonia led to similar firing patterns, as veratridine was given by aerosol, but had no significant effect on Cdyn. Following aerosol administration of nifedipine (about 1 and 2 mg) the RAR activity and Cdyn were similar to those during control. Furthermore, the ammonia-induced RAR stimulation was not significantly affected by nifedipine aerosol. These results suggest that the stimulation of RARs by ammonia in vagotomized rabbits is independent of changes in Cdyn and speculate that their excitatory effect is at least in part related to the activation of Na+ influx to the receptive terminals but is not involved in the secondary entry of Ca2+ ions to the receptor membrane, through voltage-dependent calcium channels.

Administration, Inhalation↗
PubMed1995

Methods for reducing the ammonia in hybridoma cell cultures.

The factors which limit the proliferation of eukaryotic cells in vitro are still not well known. Ammonia is believed to be toxic for mammalian cell proliferation and secretion. We have tried two approaches to reducing the ammonia in the medium. We first limited the ammonia produced by the cells by replacing glutamine by glutamate. Then, we used two chemical engineering methods to eliminate accumulated ammonia. In one the used medium was passed through a natural cation exchanger: the clinoptilolite. In the other, the culture medium was passed through a hydrophobic microporous hollow fiber module. Replacing the glutamine by glutamate reduced the medium ammonia concentration. The physicochemical removal of ammonia induced a better cell growth, but not a better specific antibody secretion.

Ammonia↗
PubMed1996

The importance of ammonia in mammalian cell culture.

Ammonia has been reported to be toxic and inhibitory for mammalian cell cultures for many years. Reduction of growth rates and maximal cell densities in batch cultures, changes in metabolic rates, perturbation of protein processing and virus replication have been reported. However, cellular mechanisms of ammonia toxicity are still the subject of controversy and are presented here. The physical and chemical characteristics of ammonia and ammonium are important, with the former capable of readily diffusing across cellular membranes and the latter competing with other cations for active transport by means of carrier proteins. The main source of the ammonia which accumulates in cell cultures is glutamine, which plays an important role in the metabolism of rapidly growing cells. Strategies to overcome toxic ammonia accumulation include substitution of glutamine by glutamate or other amino acids, nutrient control, i.e., controlled addition of glutamine at low concentrations, or removal of ammonia or ammonium from the culture medium by means of ion-exchange resins, ion-exchange membranes, gas-permeable membranes or electrodialysis.

Ammonia↗
PubMed1987

The effect of various ambient ammonia concentrations on the nitrogen metabolism of carp fry (Cyprinus carpio L.).

Authors studied how 125, 375 and 625 micrograms/l amounts of NH4Cl added to the water influenced the ammonia excretion of carp fry with an average weight of 2.4 g, compared to the control. During the course of the experiments the NH4N concentration, the pH and the temperature were measured for three days, twice daily. On the basis of our results the threshold concentration exerting harmful effects on the ammonia household of carp fry (disturbing the normal rate of metabolism in the fishes and decreasing their growth rate) is between 125 and 375 micrograms/l. NH4H (50-100 micrograms/l NH3). The ammonia concentrations exceeding 375 micrograms/l NH4+ (and 100 micrograms/l NH3, respectively) can be regarded as undesirable and harmful in frybreeding fish ponds. With regard to the ambient ammonia, a daily cycle developed in the excretion of ammonia: contrary to the control, a minimum in ammonia excretion was measured in the morning, while a maximum was measured in the afternoon.

Ammonia↗
PubMed1983

Ammonia-induced change in the hepatic glutathione level of an air-breathing freshwater teleost Channa punctatus (Bloch).

Exposure to ammonia (NH4OH) for 48 h resulted in greater than 50% depletion of the hepatic glutathione pool in Channa punctatus (Bloch). Removal of fish to ammonia free ambience induced a rapid and excessive resynthesis of glutathione within 24 h. This level, however, decreased within 5 days of return to ammonia-free fresh water. It is concluded that ammonia stress in a freshwater air-breathing teleost is counteracted by the glutathione system of detoxication of xenobiotics and resynthesis of glutathione is induced by short-term exposure to ammonia followed by transfer to ammonia-free water.

Acclimatization↗
PubMed1995

Noninvasive quantification of regional myocardial flow reserve in patients with coronary atherosclerosis using nitrogen-13 ammonia positron emission tomography. Determination of extent of altered vascular reactivity.

OBJECTIVES: The aim of this study was to evaluate patients with coronary artery disease to 1) determine the relation between flow reserve measured by nitrogen-13 (N-13) ammonia kinetic modeling and stenosis severity assessed by quantitative angiography, and 2) examine whether flow reserve is impaired in regions supplied by vessels without significant angiographic disease. BACKGROUND: With the advent of new therapeutic approaches for coronary disease, an accurate noninvasive approach for absolute quantification of flow and flow reserve is needed to evaluate functional severity and extent of atherosclerosis. Nitrogen-13 ammonia kinetic modeling may permit such evaluation. METHODS: Twenty-seven subjects were classified into three groups: group 1 = 5 young volunteers: group 2 = 7 middle-aged volunteers; and group 3 = 15 patients with coronary artery disease. Dynamic N-13 ammonia positron emission tomographic imaging was performed at rest and during adenosine infusion. A three-compartment model was fit to regional N-13 ammonia kinetic data to determine myocardial flow. Group 3 patients underwent quantitative coronary angiography. RESULTS: The regional blood flow results in patients with coronary disease were classified into four subgroups: no significant detectable disease and mild (50% to 69.9% area stenosis), moderate (70% to 94.9% area stenosis) or severe (95% to 100% area stenosis) coronary disease. Flow reserve was 2.95 +/- 0.65; 2.09 +/- 0.47; 2.02 +/- 0.51; 1.3 +/- 0.32, respectively (p < or = 0.01 except mild vs. moderate). Flow reserve was correlated with percent area stenosis (r = -0.56) and minimal lumen diameter (r = 0.75). In volunteers (groups 1 and 2), flow reserves were greater than in segments without detectable disease in group 3 patients (4.10 +/- 0.71 and 3.79 +/- 0.42, respectively, vs. 2.88 +/- 0.56, p < or = 0.02). CONCLUSIONS: The functional severity of coronary disease measured by N-13 ammonia positron emission tomography varied for a given stenosis but was significantly related to angiographic severity. Among patients with coronary disease, myocardial regions without significant angiographic stenoses displayed reduced flow reserve than did regions in control subjects, indicating that vascular reactivity was more diffusely impaired in group 3 than was suggested by angiography. Noninvasive quantification of myocardial flow reserve using dynamic N-13 ammonia positron emission tomography yields important functional data that permit definition of the extent of disease even when disease is not apparent by angiography.

Adenosine↗
PubMed2006

Structural determinants and modulation of substrate specificity in phenylalanine-tyrosine ammonia-lyases.

Aromatic amino acid ammonia-lyases catalyze the deamination of L-His, L-Phe, and L-Tyr, yielding ammonia plus aryl acids bearing an alpha,beta-unsaturated propenoic acid. We report crystallographic analyses of unliganded Rhodobacter sphaeroides tyrosine ammonia-lyase (RsTAL) and RsTAL bound to p-coumarate and caffeate. His 89 of RsTAL forms a hydrogen bond with the p-hydroxyl moieties of coumarate and caffeate. His 89 is conserved in TALs but replaced in phenylalanine ammonia-lyases (PALs) and histidine ammonia-lyases (HALs). Substitution of His 89 by Phe, a characteristic residue of PALs, yields a mutant with a switch in kinetic preference from L-Tyr to L-Phe. Structures of the H89F mutant in complex with the PAL product, cinnamate, or the PAL-specific inhibitor, 2-aminoindan-2-phosphonate (AIP), support the role of position 89 as a specificity determinant in the family of aromatic amino acid ammonia-lyases and aminomutases responsible for beta-amino acid biosynthesis.

Amino Acid Sequence↗
PubMed2005

Long-term operation of biofilters for biological removal of ammonia.

Biological removal of ammonia was investigated using two types of packing materials, compost and sludge in laboratory-scale biofilters (8l reactor volume). The aim of this study is to investigate the potential of unit systems packed with these supports in terms of ammonia emissions treatment. Experimental tests and measurements included analysis of removal efficiency, metabolic products, and results of long-term operation. The inlet concentration of ammonia applied was 20-200 mg m-3. The ammonia loading rates of 24.9-566 g NH3 m-3 d-1 to compost biofilter (BF3) and 24.9-472 g NH3 m-3 d-1 to sludge biofilter (BF4) were applied for 210 days, respectively. Removal efficiencies of the compost and sludge biofilters were in the range of 97-99% and 95-99%, respectively when the inlet concentration of ammonia was below 110 mg m-3, and the maximum elimination capacities were 288 and 243 g NH3m-3d-1, respectively. However, removal efficiency and elimination capacity of both biofilters significantly decreased as the inlet concentration increased to above 110 mg m-3. By using kinetic analysis, the maximum removal rate of ammonia, Vm, and the saturation constant, Ks, were determined for both packing materials and the value of Vm for compost was found to be larger. Periodic analysis of the biofilter packing materials showed the accumulation of the nitrification product NO3- in the operation. During the experiment, the pressure drops measured were very low. The use of both packing materials requires neither nutritive aqueous solution nor buffer solution.

Air Pollutants↗
PubMed2005

Solubility of volatile organic compounds in aqueous ammonia solution.

The Ostwald solubility coefficient, L of 17 volatile organic compounds (VOCs) from the gas phase into water and dilute aqueous ammonia solutions was determined by the equilibrium partitioning in closed system-solid phase micro extraction (EPICS-SPME) method at 303 K and at 0-2.5 mol dm(-3) ammonia concentrations. Ammonia increased the solubility of all VOCs nearly linearly, but to a different extent. The difference in the solubility values in aqueous ammonia solutions (Lmix) compared to pure water (L) is explained on the basis of a Linear Solvation Energy Relationship (LSER) equation made applicable for solvent mixtures, logLmix - logL = x((sNH3 - sH2O)pi2H + (aNH3 - aH2O)Sigma2H + (bNH3 - bH2O)Sigmabeta2H + (vNH3 - VH2O)Vx). sNH3 - sH2O, aNH3 - aH2O, bNH3 - bH2O, vNH3 - vH2O are the differences of solvent parameters, x is the mole fraction, pi2H is the solute dipolarity-polarizability, Sigmaalpha2H is the effective hydrogen bond acidity of the solute, Sigmabeta2H is the effective hydrogen bond basicity of the solute and Vx, the McGowan characteristic volume. The most significant term was v, the phase hydrophobicity. The solubility behavior was explained by the change in structure of the aqueous solution: the presence of ammonia reduces the cavity effect. These findings show that the presence of compounds such as ammonia, frequently observed in environmental waters, especially wastewaters, affect the fugacity of VOCs, having consequences for the environmental partitioning of VOCs and having technical consequences towards wastewater treatment technologies.

Ammonia↗
PubMed2006

Ammonia triggers the promotion of oxidative stress in the aquatic macrophyte Myriophyllum mattogrossense.

The effect of increased ammonia content on sub-acute biochemical responses was assessed in the rooted submersed aquatic macrophyte Myriophyllum mattogrossense (common name: "Brazil Milfoil" or "Matogrosso Milfoil"), in a seven day aquarium experiment. The pH and temperature were monitored in order to determine the proportions of both ionized (NH4+) and un-ionized (NH3) forms of ammonia. Specific activities of several enzymes such as catalase (CAT), guaiacol peroxidase (POD), glutathione peroxidase (GPx) and glutathione S-transferase (GST's) were measured as well as the content of the soluble antioxidant glutathione and lipid peroxidation were determined as these parameters are considered as indicators of cell-level disorder. The results showed that ammonia is able to generate oxidative stress, expressed through an elevated GSH content and the enhancement of CAT, POD, GPx and GST's activities in treatments with elevated ammonia content. As the toxic mechanism of ammonia is a complex phenomenon, this work adds an additional point of view to explain in parts the oxidative stress generating effect of ammonia promoting oxidative stress. Additionally the different modes of action proposed by other research groups are discussed, thus trying to combine the various points of view.

Ammonia↗
PubMed2006

Potential role of sulfide and ammonia as confounding factors in elutriate toxicity bioassays with early life stages of sea urchins and bivalves.

This work reports some considerations on the possible contribution of sulfide and ammonia to the toxicity of elutriate samples of sediments from the Venice lagoon, tested with a battery of bioassays using early life stages of the sea urchin Paracentrotus lividus and the oyster Crassostrea gigas. A comparison of ammonia or sulfide concentration in the test matrix, matrix toxicity, and the sensitivity limit of bioassays for ammonia or sulfide were used in evaluating toxicity data. Results highlighted that sperm cell and embryo toxicity of elutriates were not affected by sulfides. Neither was any direct relationship shown between elutriate toxicity and ammonia concentration. Most elutriates had ammonia concentrations below the sensitivity limit of acute test methods, while the more sensitive subchronic toxicity tests were affected by ammonia interference in some samples.

Ammonia↗
PubMed2004

Elevated salinity selects for a less diverse ammonia-oxidizing population in aquarium biofilters.

The activity and changes in the structure of the community of the ammonia-oxidizing bacteria belonging to the Betaproteobacteria were monitored in freshwater and artificial seawater biofilters for two months after inoculation with a commercial nitrifying consortium. Both in freshwater and artificial seawater, ammonium oxidation proceeded immediately after addition of the inoculum, although initial activity in artificial seawater was lower than in freshwater. Denaturing gradient gel electrophoresis of the ammonia-oxidizing bacterial community of the inoculum and the freshwater and the artificial seawater aquaria as a function of time showed that initially only one dominant ammonia-oxidizer, closely related to Nitrosomonas marina, was detectable in all the systems. The fingerprint of the ammonia-oxidizing bacterial community in the artificial seawater biofilters continued to be dominated by this single band. In the freshwater aquaria, in contrast, the composition of the ammonia-oxidizer community became more diverse after one month, with 4-7 new bands appearing in the denaturing gradient gel fingerprint. Since the inoculum is cultivated at an average salinity of 11 gl(-1), it is argued that the elevated salinity selects for a less diverse ammonia-oxidizer community in the inoculum and the artificial seawater aquaria.

Ammonia↗
PubMed2006

Ammonia affects the activity and expression of soluble and particulate GC in cultured rat astrocytes.

Neurotoxic effects of ammonia are mediated by increased accumulation of nitric oxide (NO), which combines with free radicals to form a highly toxic compound, peroxynitrite. Previous experiments in vivo and in vitro have suggested that this phenomenon engages neuron-derived NO and is coupled to changes in the accumulation of cGMP. The present study accounted for the facts that: (i) astrocytes, not neurons are the morphological target of ammonia, and (ii) both NO-dependent, soluble (sGC) and NO-independent, particulate guanylate cyclase (pGC) mediate cGMP production in the cells. Neocortical rat astrocytes were treated for 1 or 24 h with 5 mM ammonium chloride ("ammonia") and then subjected to: (i) cGMP measurement, and (ii) mRNA and/or protein expression analysis of alpha1 and beta1 subunits of sGC and two pGC forms: pGC-A and pGC-B. Treatment with ammonia for 1h increased accumulation of cGMP and sGCbeta1 mRNA expression, without producing significant changes in the protein expression. This was followed by a decrease of cGMP level at 24 h treatment, associated with a decreased expression of sGCbeta1 and sGCalpha1 mRNA and sGCbeta1 protein. Expression of pGC-A and pGC-B mRNA was elevated in ammonia-treated astrocytes after 24 h. Accordingly, increased cGMP accumulation was noted in the presence of a specific sGC inhibitor (ODQ). The results show that ammonia affects cGMP production in astrocytes, and that this may involve not only sGC but also pGC.

Acute Disease↗
PubMedDate not supplied

An improved model for the measurement of myocardial perfusion in human beings using N-13 ammonia.

BACKGROUND: Oxygen 15 water and nitrogen 13 ammonia are widely used for the quantitative measurement of myocardial perfusion with positron emission tomography. However, blood flow obtained with N-13 ammonia by use of the conventional 2-compartment model frequently underestimates flow by 30% to 50% compared with O-15 water. We hypothesized that this discrepancy is a result of the model configuration of N-13 ammonia and investigated changes to the mathematical model to determine whether more accurate measurements of perfusion could be obtained. METHODS AND RESULTS: Twelve healthy volunteers were sequentially studied with O-15 water and N-13 ammonia at rest and during maximal coronary vasodilation with adenosine. Perfusion measurements obtained with the conventional and modified models were compared with values obtained with O-15 water. The conventional N-13 ammonia model underestimated flow by 37% +/- 16% at rest and by 20% +/- 24% with stress when compared with flows obtained with O-15 water. The modified model yielded flow values closer to the line of identity than the conventional model (y = 1.07x + 0.04 vs y = 0.69x + 0.08; respectively; P < .01). CONCLUSIONS: Model changes made N-13 ammonia myocardial blood flow estimates more comparable to those obtained with O-15 and may allow for better comparison of flows obtained with these two tracers in the future. Further efforts are warranted to evaluate the accuracy of flow models in human subjects.

Adult↗
PubMed2005

Short-term harmful effects of ammonia nitrogen on activated sludge microfauna.

The response of activated sludge microfauna in terms of abundance and diversity has been analysed to evaluate both the toxic effect of ammonia nitrogen and the acclimatisation capacity of these microorganisms to its toxicity. The harmful effect of ammonia nitrogen was studied by means of two toxicological tests. The ammonia concentrations tested were: 9, 20, 30 and 50mg NH4+-N/l in the first toxicological test and 30, 40, 50 and 80 mg NH4+-N/l in the second. The results suggest that ammonia nitrogen causes a clear but reversible toxic effect on microfauna abundance when its concentrations are around three times higher than that which the microfauna is used to. Chilodonella uncinata and Acineria uncinata were the ciliates least affected by the ammonia nitrogen toxicity. Furthermore, the majority of microfauna groups analysed (gymnamoebae and ciliates) showed capability for acclimatisation to ammonia nitrogen in terms of abundance.

Acclimatization↗
PubMed2002

Amino acids control ammonia pulses in yeast colonies.

Individual yeast colonies produce pulses of volatile ammonia separated by phases of medium acidification. Colonies of Saccharomyces cerevisiae mutant defective in the general amino acid permease, Gap1p, exhibit decreased ammonia production. Mutations in the S. cerevisiae amino acid sensor SPS completely abolish the colony ammonia pulses. In contrast, the ammonia pulse production is independent of external concentrations of ammonium and of its uptake by the ammonium permeases Mep1p, Mep2p, and Mep3p. It is concluded that in S. cerevisiae colonies, the extracellular amino acids, but not the extracellular ammonium, serve as a source for volatile ammonia production. These phenomena are not restricted to S. cerevisiae, since we observe that extracellular levels of 8 out of the 20 tested amino acids are necessary for ammonia pulses produced by Candida mogii colonies.

Amino Acid Transport Systems↗