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PubMed1987

Isolated perfused rat liver: an experimental model for studies on ammonium and amino acid metabolism.

Isolated perfused rat liver is a well-established experimental model for studies on hepatic amino acid and ammonia metabolism. Some aspects and modifications of the liver-perfusion technique are discussed. Perfusion studies with the intact liver have the fundamental advantage that the structural and functional organization of the liver is preserved; however, the experimental system is more complex in view of subcellular and intercellular compartmentation and the recently demonstrated metabolic interactions of different cell populations at the acinar level. These problems of complexity by compartmentation can be largely solved by introducing further techniques such as organ spectrophotometry, the retrograde/antegrade perfusion technique, use of micro-oxygen-electrodes, use of selective inhibitors, radiolabeled compounds, different fractionation techniques of the liver tissue. By means of these approaches, intracellular events can be followed up not only indirectly by analyzing the composition of the perfusate before and after a liver passage, but also directly in the different subcellular and subacinar compartments of a structurally and metabolically intact liver.

Amino Acids↗
PubMed2001

[Cloning sequencing and expression pattern, functional analysis of nifA gene in Azospirillum brasilense Yu62].

The nifA gene of Azospirillum brasilense Yu62 was cloned and sequenced. The expression of nifA gene was investigated in wild type strain Azospirillum brasilense Yu62. The results show that expression of nifA gene is not repressed by ammounium and oxygen completely. But the expression of Yu62 nifA gene is different from that of strain Sp7 nifA gene. Expression of Yu62 nifA seems more sensitive to oxygen than that of Sp7 nifA which shows the highest expression in condition of aerobic, while the Yu62 nifA gene shows the highest expression in the condition of microaerobic. The regulation of NifA protein activity by ammonia and oxygen was investigated. Results showed that the NifA protein is repressed by ammonia, 1 mmol/L NH4Cl can inhibit activity of NifA protein completely. Oxygen concentration affects activity of NifA protein. NifA protein is highly active in 0.4%-0.5% O2.

Ammonium Chloride↗
PubMed1989

Microsomal delta 8,14-sterol delta 14-reductase in higher plants. Characterization and inhibition by analogues of a presumptive carbocationic intermediate of the reduction reaction.

An enzymatic assay for delta 8,14-sterol delta 14-reductase, an enzyme involved in sterol biosynthesis, has been developed for the first time in higher plants. The properties of the microsomal enzyme have been established with respect to cofactor requirements, kinetics and substrate specificity. This enzymatic double-bound reduction is thought to proceed through an electrophilic addition mechanism, involving a C14 putative carbonium ion high-energy intermediate. Using this in vitro assay, ammonium and iminium analogues of this cationic intermediate were shown to be potent inhibitors of the reduction reaction. Thus, compounds of the N-alkyl-8-aza-4 alpha,10-dimethyl-trans-decal-3 beta-ol series strongly inhibited sterol reductase (I50 = 0.07 - 4 microM) (I50/Km = 10(-4) - 10(-3), as did the antimycotic agent 15-azasterol (I50 = 0.03 microM); all of these compounds act as reaction-intermediate analogues of the proposed C14 carbonium ion intermediate. Moreover, the in vitro inhibition of the plant sterol reductase by a series of ammonium-ion-containing fungicides was demonstrated. The relative specificity of these different series of inhibitors toward cycloeucalenol-obtusifoliol isomerase, delta 8----delta 7-sterol isomerase and delta 8,14-sterol delta 14-reductase, was directly studied.

Ammonia↗
PubMedDate not supplied

Liquid chromatographic determination of biogenic amines in dry sausages.

A liquid chromatographic method is described for the determination of biogenic amines found in dry sausages: tryptamine, phenylethylamine, putrescine, cadaverine, histamine, serotonin, tyramine, spermidine, and spermine. Amines were extracted with perchloric acid solution and derivatized with dansyl chloride. After derivatization, ammonia was added to remove an interfering peak near cadaverine. Liquid chromatographic separations were performed by using a Spherisorb ODS2 column and an ammonium acetate-acetonitrile gradient elution program. The limits of determination of the individual amines were 1-5 mg/kg. This method is also applicable to detection of amines in other food samples.

Amines↗
PubMed2002

Reduced encephalopathy in pigs with ischemia-induced acute hepatic failure treated with a bioartificial liver containing alginate-entrapped hepatocytes.

OBJECTIVE: To analyze the effects of an extracorporeal bioartificial liver containing alginate bead-entrapped hepatocytes on pigs with ischemia-induced acute hepatic failure. DESIGN: Prospective animal study. SETTING: University and INSERM laboratory. SUBJECTS: Fifteen Large White/Pietrin female pigs weighing 20-30 kg. INTERVENTIONS: Acute hepatic failure was induced by end-to-side portocaval shunt and ligature of the whole porta hepatitis. The bioartificial liver was in a thermostabilized column, containing a fluidized bed of alginate beads that embedded porcine hepatocytes, connected to a plasmapheresis system. Intracranial pressure; survival; ammonia, total bilirubin, aminotransferases, alkaline phosphatase, and lactate concentrations; and clotting factors were studied. The groups were pigs with acute hepatic failure (group 1, n = 4), pigs with acute hepatic failure treated with bioartificial liver containing empty beads (group 2, n = 4), or porcine hepatocytes (group 3, n = 5). MEASUREMENTS AND MAIN RESULTS: In group 1, survival of pigs averaged 10.9 +/- 1.0 hrs; intracranial pressure reached 32.3 +/- 3.8 mm Hg and was associated with coma and cerebral edema. After connection to the bioartificial liver, the survival of acute hepatic failure pigs was 12.1 +/- 1.4 hrs in group 2 and 14.8 +/- 2.5 hrs in group 3. In group 3, intracranial pressure and bilirubin concentrations were reduced significantly compared with both group 1 and group 2. Neither signs of encephalopathy nor cerebral edema was observed in any animal of group 3. In all animals, plasma ammonium, aminotransferases, alkaline phosphatase, and lactate concentrations increased and clotting factors decreased with no significant differences between the three groups. Autopsy revealed a total necrosis of the liver, which was histologically confirmed. CONCLUSIONS: The ischemia-induced model of acute hepatic failure in pigs is reproducible and provides measurable clinical and biological features. A bioartificial liver containing alginate bead-entrapped hepatocytes improves the signs of encephalopathy in pigs with ischemia-induced acute hepatic failure, suggesting that the bioartificial liver can clear out toxic compounds that are released from necrotic livers.

Alginates↗
PubMed1978

Minimal nitrogen requirements of Corynebacterium renal strains.

Corynebacterium renale strain 10849 was grown in a chemically defined medium containing glucosamine, ammonium sulfate, and 5 amino acids as possible nitrogen sources. Although glucosamine was slightly stimulatory, its omission from the medium had a minimal effect on growth, and washed cells introduced into glucosamine-free medium grew readily through 10 serial transfers, demonstrating that this compound was not required for growth. Individual omissions of isoleucine, valine, methionine, and glutamine resulted in lengthened lag periods and reduced growth rates in initial transfers, but recovery occurred in subsequent serial transfers so that by the 3rd or 4th transfer, growth rates and cell crops were only slightly less than in control cultures in complete medium. Omission of cystine resulted in a permanently low growth rate and reduced cell crop, but this was remedied by substituting various nonnitrogenous compounds containing reduced sulfur. Strain 10849 and 6 additional strains were then serially cultured in a minimal defined medium in which sodium thioglycolate provided reduced sulfur and ammonium sulfate served as sole nitrogen source. Since only ammonium ion was required as the nitrogen source, it could be concluded that C renale, which rapidly hydrolyzes urea, should find an adequate source of nitrogen for growth in the urinary tract of animals.

Ammonia↗
PubMed1988

Pyruvate decarboxylation in astrocytes and in neurons in primary cultures in the presence and the absence of ammonia.

Oxidative decarboxylation of [1-14C]pyruvate was studied in primary cultures of neurons and of astrocytes. The rate of this process, which is a measure of carbon flow into the tricarboxylic acid (TCA) cycle and which is inhibited by its end product, acetyl CoA, was determined under conditions which would either elevate or reduce the components of the malate-aspartate shuttle (MAS). Addition of aspartate (1 mM) was found to stimulate pyruvate decarboxylation in astrocytes whereas addition of glutamate (or glutamine) had no effect. Since aspartate is a precursor for extramitochondrial malate, and thus intramitochondrial oxaloacetate, whereas glutamate and glutamine are not, this suggests that an increase in oxaloacetate level stimulates TCA cycle activity. Conversely, a reduction of the glutamate content by 3 mM ammonia, which might reduce exchange between glutamate and aspartate across the mitochondrial membrane, suppressed pyruvate decarboxylation. This effect was abolished by addition of glutamate or glutamine or exposure to methionine sulfoximine (MSO). These findings suggest that impairment of MAS activity by removal of MAS constituents decreases TCA cycle activity whereas replenishment of these compounds restores the activity of the TCA cycle. No corresponding effects were observed in neurons.

Ammonium Chloride↗
PubMed1996

Hyperammonemia inhibits platelet aggregation in rats.

The effect of hyperammonemia on ex vivo platelet function and in vivo nitric oxide synthesis was evaluated in rats. In addition, mitochondrial energy production was assessed from the fluorescence intensity of tetramethylrhodamine ethyl ester (TMRE). Continuous ammonium acetate infusion significantly reduced ex vivo platelet aggregation concomitant with a decrease of the platelet cytoplasmic ATP level. The serum level of L-arginine, as well as the levels of nitrite and nitrate (oxidative by-products of nitric oxide), increased with ammonium infusion. Prior administration of N omega-nitro-L-arginine methyl ester, a competitive inhibitor of nitric oxide synthase, did not affect the ammonia-induced rise in L-arginine, but substantially attenuated the associated decrease of platelet ATP and TMRE fluorescence as well as diminishing the anti-aggregatory effect of ammonia infusion. These findings suggest that the synthesis of nitric oxide from L-arginine is accelerated by continuous ammonium infusion and inhibits ex vivo platelet aggregation in the rat, probably by reducing mitochondrial energy production.

Acetates↗
PubMed2001

The utilization of aniline, chlorinated aniline, and aniline blue as the only source of nitrogen by fungi in water.

The ability of fungi to degrade aniline and its derivatives in water is reported. Several fungi are able to degrade aniline and its derivatives as a sole nitrogen, carbon and energy source. Some of these fungi were obtained from activated sludge by enrichment technique. Among the 10 studied fungi, Fusarium sp. and Rhizopus sp. utilize aniline as a sole nitrogen, carbon and energy source, with production of acetanilide and catechol. Fusarium sp. utilized 70% of 10 mmol aniline and produced 3.55 mM ammonia during 30 days. Rhizopus sp. utilized 65% of 10 mmol aniline during 30 days. Rhizopus sp. and Fusarium sp. utilized only 2-chloroaniline and 3-chloroaniline as nitrogen source in the presence of glucose, with production of catechol, ammonium and chloride. The utilization of 2-chloroaniline was better than 3-chloroaniline, by Fusarium sp. and Rhizopus sp. Cladosporium sp. was the best isolate which could use aniline blue as the only source of nitrogen. This fungus reduced 89% of aniline blue, and ammonia is produced as the result of aniline blue biodegradation by Cladosporium sp.

Alternaria↗
PubMed2007

Accumulation of ammonium in Norway spruce (Picea abies) seedlings measured by in vivo 14N-NMR.

(14)N-NMR and (31)P-NMR have been used to monitor the in vivo pH in roots, stems, and needles from seedlings of Norway spruce, a typical ammonium-tolerant plant. The vacuolar and cytoplasmic pH measured by (31)P-NMR was found to be c. pH 4.8 and 7.0, respectively, with no significant difference between plants growing with ammonium or nitrate as the N-source. The (1)H-coupled (14) NH 4+ resonance is pH-sensitive: at alkaline pH it is a narrow singlet line and below pH 4 it is an increasing multiplet line with five signals. The pH values in ammonium-containing compartments measured by (14)N-NMR ranged from 3.7 to 3.9, notably lower than the estimated pH values of the P(i) pools. This suggests that, in seedlings of Norway spruce, ammonium is stored in vacuoles with low pH possibly to protect the seedlings against the toxic effects of ammonium ( NH 4+) or ammonia (NH3). It was also found that concentrations of malate were 3-6 times higher in stems than in roots and needles, with nitrate-grown plants containing more malate than plants grown with ammonium.

Ammonium Sulfate↗
PubMed1975

Mechanism for the paradoxical aciduria following alkali administration to prolonged-fasted patients.

Rapidly induced systemic alkalinization due to either sodium-lactate or sodium-bicarbonate infusion in prolonged-fasted subjects with steady-state ketoacidosis was associated with a decrease in urine pH. This decrease in urine pH from 5.50 to 5.20 was the result of a significant decrease in urinary ammonium excretion from 8.40 to 6.35 mEg/hr and was not accompanied by an increase in net acid excretion (11.3 vs. 10.6 mEg/hr). The decreased ammonium excretion is attributed to the raised pH of the proximal tubular fluid resulting in a less favorable pH gradient for gaseous ammonia entry. This would decrease gaseous ammonia generated in the loop of Henle for collecting duct buffering of secreted hydrogen ions.

Acidosis↗
PubMedDate not supplied

Aminonitriles: possible role in chemical evolution.

The formation of HCN, ammonium cyanide, alkylnitriles, aminoacetonitrile and its C- and N-methyl homologs was demonstrated earlier in a simulated Jovian atmosphere. The polymeric material resulting in these experiments was shown to give glycine, alanine, sarcosine, aspacrtic acid and some imino dibasic acids on acid hydrolysis suggesting thereby the participation of the monomeric nitriles into the formation of the polymeric product(s). Further examination of products resulting from semi-corona and arc discharge through a mixture of methane and ammonia has provided evidence for the formation of alkylaminopropionitriles as a complex mixture and also some pyridyl and pyrimidyl type heterocyclic compounds. A GC-MS examination of the heterocylics showed resemblance with those found in some carbonaceous chondrites. The significance of these findings in relation to chemical evolution will be discussed.

Ammonia↗
PubMed2004

Mechanism of ammonia transport by Amt/MEP/Rh: structure of AmtB at 1.35 A.

The first structure of an ammonia channel from the Amt/MEP/Rh protein superfamily, determined to 1.35 angstrom resolution, shows it to be a channel that spans the membrane 11 times. Two structurally similar halves span the membrane with opposite polarity. Structures with and without ammonia or methyl ammonia show a vestibule that recruits NH4+/NH3, a binding site for NH4+, and a 20 angstrom-long hydrophobic channel that lowers the NH4+ pKa to below 6 and conducts NH3. Favorable interactions for NH3 are seen within the channel and use conserved histidines. Reconstitution of AmtB into vesicles shows that AmtB conducts uncharged NH3.

Amino Acid Sequence↗
PubMed2005

Perchlorate and nitrate remediation efficiency and microbial diversity in a containerized wetland bioreactor.

We have developed a method to remove perchlorate (14-27 microg/L) and nitrate (48 mg/L) from contaminated groundwater using a wetland bioreactor. The bioreactor has operated continuously in a remote field location for more than 2 yr with a stable ecosystem of indigenous organisms. This study assesses the bioreactorfor long-term perchlorate and nitrate remediation by evaluating influent and effluent groundwater for oxidation-reduction conditions and nitrate and perchlorate concentrations. Total community DNA was extracted and purified from 10-g sediment samples retrieved from vertical coring of the bioreactor during winter. Analysis by denaturing gradient gel electrophoresis of short, 16S rDNA, polymerase-chainreaction products was used to identify dominant microorganisms. Bacteria genera identified were closely affiliated with bacteria widely distributed in soils, mud layers, and fresh water. Of the 17 dominant bands sequenced, most were gram negative and capable of aerobic or anaerobic respiration with nitrate as the terminal electron acceptor (Pseudomonas, Acinetobacter, Halomonas, and Nitrospira). Several identified genera (Rhizobium, Acinetobactor, and Xanthomonas) are capable of fixing atmospheric nitrogen into a combined form (ammonia) usable by host plants. Isolates were identified from the Proteobacteria class, known for the ability to reduce perchlorate. Initial bacterial assessments of sediments confirm the prevalence of facultative anaerobic bacteria capable of reducing perchlorate and nitrate in situ.

Bacteria↗
PubMed2006

[Influence of temperature, pH value and organic substance on activity of ANAMMOX sludge].

Influence of temperature, pH and organics on ANAMMOX activity was investigated through measuring the anaerobic ammonia oxidation rate of sludge. Results show that temperature and pH could influence ANAMMOX activity dramatically. The optimal temperature was between 30-35 degrees C , and the relationship between the anaerobic ammonia oxidation rate and temperature can be described by revised Arrhenius formula during 20-30 degreee C. The optimal pH was between 7.5 - 8.3, and the relationship between the anaerobic ammonia oxidation rate and pH can be described by two substrates and two inhibitors model during pH 7.0 - 9.0. There was substrata competition between the heterotrophic denitrification bacteria and ANAMMOX bacteria when organics in the

Anaerobiosis↗
PubMed2001

Effects of chronic ammonium and nitrite contamination on the macroinvertebrate community in running water microcosms.

In the present study, during a three-month exposure lethal and sublethal effects of ammonium and its products on typical brook organisms (Gammarus pulex, Amphipoda; Radix ovata, Gastropoda; Limnephilus lunatus Trichoptera) were monitored in microcosms approximating field conditions. Every 24 h during this period the microcosms were contaminated with ammonium at five different nominal concentrations, which by chemical reactions produced a mixture of the toxic products ammonia and nitrite. G. pulex proved the most sensitive to the ammonia and nitrite contamination resulting from the ammonium load. In contrast. L. lunatus and R. ovota exhibited clearly effects only at concentrations 10 times higher. It is appropriate to investigate ammonium pollution with its reaction products as a mixture, because in natural bodies of water receiving ammonium input (e.g., from sewage-treatment plants) the substances ammonium/ammonia and nitrite are likewise present simultaneously.

Animals↗
PubMed2005

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) degradation by Acetobacterium paludosum.

Substrates and nutrients are often added to contaminated soil or groundwater to enhance bioremediation. Nevertheless, this practice may be counterproductive in some cases where nutrient addition might relieve selective pressure for pollutant biodegradation. Batch experiments with a homoacetogenic pure culture of Acetobacterium paludosum showed that anaerobic RDX degradation is the fastest when auxiliary growth substrates (yeast extract plus fructose) and nitrogen sources (ammonium) are not added. This bacterium degraded RDX faster under autotrophic (H2-fed) than under heterotrophic conditions, even though heterotrophic growth was faster. The inhibitory effect of ammonium is postulated to be due to the repression of enzymes that initiate RDX degradation by reducing its nitro groups, based on the known fact that ammonia represses nitrate and nitrite reductases. This observation suggests that the absence of easily assimilated nitrogen sources, such as ammonium, enhances RDX degradation. Although specific end products of RDX degradation were not determined, the production of nitrous oxide (N2O) suggests that A. paludosum cleaved the triazine ring.

Acetobacterium↗
PubMed2002

Continuous spectrometric assays for glutaminyl cyclase activity.

The enzymatic conversion of one chromogenic substrate, l-glutamine-p-nitroanilide, and two fluorogenic substrates, l-glutaminyl-2-naphthylamide and l-glutaminyl-4-methylcoumarinylamide, into their respective pyroglutamic acid derivatives by glutaminyl cyclase (QC) was estimated by introducing a new coupled assay using pyroglutamyl aminopeptidase as the auxiliary enzyme. For the purified papaya QC, the kinetic parameters were found to be in the range of those previously reported for other glutaminyl peptides, such as Gln-Gln, Gln-Ala, or Gln-tert-butyl ester. The assay can be performed in the presence of ammonia up to a concentration of 50 mM. Increasing ionic strength, e.g., potassium chloride up to 300 mM, resulted in an increase in enzymatic activity of about 20%. This is the first report of a fast, continuous, and reliable determination of QC activity, even in the presence of ammonium ions, during the course of protein purification and enzymatic analysis.

Aminoacyltransferases↗