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PubMed1967

Oxidation of pyrimidine nucleosides and nucleotides by osmium tetroxide.

1. Pyrimidine nucleosides such as thymidine, uridine or cytidine are oxidized readily at 0 degrees by osmium tetroxide in ammonium chloride buffer. There is virtually no oxidation in bicarbonate buffer of similar pH. Oxidation of 1-methyluracil yields 5,6-dihydro-4,5,6-trihydroxy-1-methyl-2-pyrimidone. 2. Osmium tetroxide and ammonia react reversibly in aqueous solution to form a yellow 1:1 complex, probably OsO(3)NH. A second molecule of ammonia must be involved in the oxidation of UMP since the rate of this reaction is approximately proportional to the square of the concentration of unprotonated ammonia. 3. 4-Thiouridine reacts with osmium tetroxide much more rapidly than does uridine. The changes of absorption spectra are different in sodium bicarbonate buffer and in ammonium chloride buffer. They occur faster in the latter buffer and, under suitable conditions, cytidine is a major product. 4. Polyuridylic acid is oxidized readily by ammoniacal osmium tetroxide, but its oxidation is inhibited by polyadenylic acid. Pyrimidines of yeast amino acid-transfer RNA are oxidized more slowly than the corresponding mononucleosides, especially the thymine residues. Appreciable oxidation can occur without change of sedimentation coefficient.

Chromatography↗

PubMed1972

Mechanism of nitrification by Arthrobacter sp.

Resting cells of Arthrobacter sp. excrete as much as 60 mug of hydroxylamine-nitrogen per ml when supplied with ammonium. An organic carbon source in abundant supply is necessary for the oxidation. Resting cells oxidize hydroxylamine to nitrite and 1-nitrosoethanol, the former accumulating only when an exogenous carbon source is available. Cell-free extracts contain an enzyme catalyzing the formation of hydroxylamine from acetohydroxamic acid, a hydroxylamine-nitrite oxido-reductase, and an enzyme producing nitrite and nitrate from various primary nitro compounds. Nitrite is not produced from hydroxylamine by the extracts, but 1-nitrosoethanol is formed from hydroxylamine in the presence of acetate. 1-Nitrosoethanol is also produced from acetohydroxamic acid by these preparations. Nitrite was formed from hydroxylamine, however, by extracellular enzymes excreted by the bacterium.

Acetates↗

PubMed1997

Beryllium Chelation by Dicarboxylic Acids in Aqueous Solution.

Maleic and phthalic acids are found to react with Be(OH)(2), generated in situ from BeSO(4)(aq) and Ba(OH)(2)(aq), in aqueous solution at pH 3.0 or 4.4, respectively (25 degrees C), to give solutions containing the complexes (H(2)O)(2)Be[(OOCCH)(2)] (1) and (H(2)O)(2)Be[(OOC)(2)C(6)H(4)] (3). The products can be isolated in high yield and identified by microanalytical data. With 2 equiv of the dicarboxylic acids and the pH adjusted to 5.5 and 5.9, respectively, by addition of ammonia, the bis-chelate complexes [(NH(4))(+)](2){[Be[(OOCCH)(2)](2)}(2)(-) (2) and [(NH(4))(+)](2){Be[(OOC)(2)C(6)H(4)](2)}(2)(-) (4) are obtained, which can also be isolated. The compounds show distinct (9)Be, (1)H, and (13)C resonances in their NMR spectra in aqueous solutions. Layering of an aqueous solution of compound 4 with acetone at ambient temperature leads to the precipitation of single crystals suitable for an X-ray structure determination. This salt (5) was found to contain the bis-chelated dianion {Be[(OOC)(2)C(6)H(4)](2)}(2)(-) with the beryllium atom in the spiro center of two seven-membered rings and an overall geometry approaching closely C(2) symmetry. These anions are associated with two crystallographically independent but structurally similar counterions [MeC(O)CH(2)CMe(2)NH(3)](+), which are the product of a condensation reaction of the ammonium cation with the acetone solvent. In the crystal the ammonium hydrogen atoms of the cations form N-H.O hydrogen bonds with the oxo functions of the dianion.

Journal Article↗

PubMed1991

Effect of chronic non-lethal doses of non-metals and metals on hepatic metallothionein in Channa punctatus (Bloch).

Compared to non-metal toxicants (ammonia, 1.56 ppm; and phenol, 10 ppm), the metals (CdCl2, 30 ppm; HgCl2, 16.7 ppb; and ZnCl2, 6 ppm) significantly induced hepatic metallothionein (MT) concentrations in C. punctatus, exposed independently to non-lethal doses of these toxicants for 28 days. It is suggested that hepatic MT serves as a metal-sequestering protein and is involved in the detoxication of metals only and ensures protection from toxic chemicals in ambience.

Ammonium Hydroxide↗

PubMed1972

Effect of four nematocides on activities of microorganisms in soil.

Tests were conducted to determine the effects of four nematocides, Dasanit, carbofuran, D-D, and Vorlex on microbial activities in a loamy sand. The results indicated that bacterial and fungal populations initially decreased with some nematocide treatments but recovered rapidly to levels similar to those in the controls. In some instances, ammonium production from added peptone increased in the nematocide-treated soils, whereas mineralization of soil organic nitrogen and nitrification and oxidation of elemental sulfur were depressed. Oxygen consumption generally increased in proportion to the concentration of nematocide in the soil. However, with Vorlex, an increase in respiration was evident at the lower concentration, whereas an inhibitory effect occurred at the higher concentration. The study indicated that indigenous soil microorganisms can tolerate these chemicals used for control of nematodes in soil.

Ammonia↗

PubMed2005

Fluorometric determination of ammonium ion by ion chromatography using postcolumn derivatization with o-phthaldialdehyde.

A postcolumn fluorometric derivatization method for the determination of trace amounts of ammonium ion (microg/L level) under matrices with high concentrations of sodium and amino acids has been developed. In this method, ammonium ion was determined by ion chromatography combined with fluorometric detection (IC-FL) in less than 16 min. IC was performed in a high-capacity cation-exchange Dionex IonPac CS16 analytical column (250 mm x 5 mm) under isocratic conditions with 30 mM methanesulfonic acid (MSA) as mobile phase at flow-rate 1.0 mL/min. To remove amino acid interference, the postcolumn derivatization based on the reaction of ammonia with o-phthaldialdehyde (OPA) and sulfite was applied. The excitation and emission wavelengths were 364 and 425 nm, respectively. The effects of pH, reaction temperature and time, OPA-reagent composition and concentration, and sample matrix were studied. The linear range and detection limit of this method were similar to the standard method. The IC-FL method with a postcolumn fluorometric derivatization allows the routine determination of ammonium ion in extreme matrices where the ratios of sodium and amino acids to ammonium are up to 2,800,000:1 and 28,000:1, respectively.

Chromatography, Ion Exchange↗

PubMed2001

Combined phosphate and nitrogen removal in a sequencing batch reactor using the aerobic denitrifier, Microvirgula aerodenitrificans.

A phosphate removal sludge was bioaugmented with the aerobic denitrifier, Microvirgula aerodenitrificans in order to reduce the nitrate produced during the aerobic nitrifying-phosphate uptake phase. Fluorescent in situ hybridization (FISH) was used to follow the fate of the added strain. In order to maintain the pure strain in the complex ecosystem, diverse physiological and kinetic based strategies of bioaugmentation were tested under the sequencing batch reactor (SBR) type culture. The nature of the M. aerodenitrificans inoculum (adapted to nitrate-aerobic conditions or to anoxic one) had no influence on the SBR performances and did not enhance aerobic denitrifying performances. The optimum quantity of the added strain (10% of the total biomass) seemed to have much more positive influence on the long term maintenance of the pure strain than on the SBR performances. A small but daily supply of M. aerodenitrificans gave exactly the same result than a massive and 1-day supply, i.e. no enhancement of performances and no amelioration of the length of maintenance. A continuous supply of carbon during the first hour of the aerobic phase combined to a 10% supply of M. aerodenitrificans gave the best compromise in terms of phosphate removal, nitrification and aerobic denitrification performances. It was accompanied too by a decreased number of the ammonia and nitrite-oxidizing bacteria and a modification of the nitrite-oxidizing floc structure. FISH on M. aerodenitrificans revealed that (i) before bioaugmentation, the strain was already present in the phosphate removal sludge and (ii) the added bacteria almost disappeared from the reactor after 16 HRT. In a last experiment, M. aerodenitrificans embedded in alginate beads allowed enhancement of both aerobic denitrifying performances and length of strain maintenance.

Aerobiosis↗

PubMedDate not supplied

[Effect of amino acids on exoprotease synthesis by Bacillus thuringiensis].

The influence of certain L-amino acids and their mixtures on the synthesis of exoprotease from Bacillus thuringiensis was studied. Physiological experiments showed that the mixture of 20 amino acids added to the artificial medium repressed the synthesis of exoprotease. Among the compounds studied there are both the compounds which stimulate the synthesis of exoprotease (glutamic and aspartic acids, glycine), and the compounds which repress the synthesis of the enzyme (proline, tryptophane, tyrosine, asparagine, serine, cystein). None of the amino acids caused a change in the exoprotease activity. It has been assumed that the repression of the protease synthesis in the presence of the amino acids is accomplished by ammonium ions, which are formed when using the amino acids of Bac. thuringiensis. The glutamine synthetase activity of cells was determined during the growth of Bac. thuringiensis both on a medium containing triptone and after the addition of certain amino acids to the cell suspension. The correlation between the influence of different amino acids on the synthesis of exoprotease and the glutamine synthetase activity was demonstrated.

Amino Acids↗

PubMed1993

Improvement of culture conditions for L-proline production by a recombinant strain of Serratia marcescens.

Serratia marcescens SP511 was previously reported to be an L-proline-producing strain that harbors a recombinant plasmid carrying the mutant type of the proline operon. This strain produced 65 g/L of L-proline in a medium containing 22% sucrose and urea after 5 d of incubation under the conventional culture conditions. We searched for more suitable culture conditions for more abundant L-proline production by SP511. To improve the supply of a nitrogen source to cells, ammonium was used instead of urea and fed to a culture under control of the pH of the medium. The concentrations of MgSO4 and K2HPO4 were increased, and in addition, sucrose was continuously added to the culture at a final concentration of 32%. Under these conditions, the cell amount was increased twofold over that under the previous conditions and L-proline production reached a maximum of more than 100 g/L after 4 d of incubation.

Ammonia↗

PubMed2006

Low nitrification rates in acid Scots pine forest soils are due to pH-related factors.

In a previous study, ammonia-oxidizing bacteria (AOB)-like sequences were detected in the fragmentation layer of acid Scots pine (Pinus sylvestris L.) forest soils (pH 2.9-3.4) with high nitrification rates (>11.0 microg g-1 dry soil week-1), but were not detected in soils with low nitrification rates (<0.5 microg g-1 dry soil week-1). In the present study, we investigated whether this low nitrification rate has a biotic cause (complete absence of AOB) or an abiotic cause (unfavorable environmental conditions). Therefore, two soils strongly differing in net nitrification were compared: one soil with a low nitrification rate (location Schoorl) and another soil with a high nitrification rate (location Wekerom) were subjected to liming and/or ammonium amendment treatments. Nitrification was assessed by analysis of dynamics in NH4+-N and NO3- -N concentrations, whereas the presence and composition of AOB communities were assessed by polymerase chain reaction-denaturing gradient gel electrophoresis and sequencing of the ammonia monooxygenase (amoA) gene. Liming, rather than ammonium amendment, stimulated the growth of AOB and their nitrifying activity in Schoorl soil. The retrieved amoA sequences from limed (without and with N amendment) Schoorl and Wekerom soils exclusively belong to Nitrosospira cluster 2. Our study suggests that low nitrification rates in acidic Scots pine forest soils are due to pH-related factors. Nitrosospira cluster 2 detected in these soils is presumably a urease-positive cluster type of AOB.

Bacteria↗

PubMed1993

Noninvasive detection of acute rejection in a new experimental model of heart transplantation.

We have shown that positron emission scintigraphy detects changes in the uptake of 18-F 2-deoxyglucose and 13-N ammonia by the acutely rejecting myocardium in a nonworking model of heterotopic heart transplantation in the rat. We developed a new working model of heterotopic heart transplantation to determine the possible relevance of these changes to clinical transplantation. Moderate aortic valvular regurgitation was produced allowing the heterotopic left ventricle to fill and eject. Rejecting allografts and nonrejecting isografts (controls) were studied 4 days after transplantation. Histologically, isografts were normal and all allografts showed mild acute rejection. Decay-corrected uptakes of 18-F 2-deoxyglucose and 13-N ammonia reflect glucose metabolism and blood flow, respectively. Values are presented as percent of injected dose per gram of tissue. Uptake of 18-F 2-deoxyglucose was higher in rejecting allografts compared with nonrejecting isografts (3.0 +/- 1.8 versus 1.1 +/- 0.4; p = 0.024). Ammonia uptake was elevated in allografts compared with isografts (2.2 +/- 0.5 versus 1.3 +/- 0.5; p = 0.023). Uptakes of 18-F 2-deoxyglucose and 13-N ammonia are higher in mildly rejecting allografts, implying increased glucose utilization and blood flow during acute rejection. These data support our earlier findings of changes in myocardial metabolism in the absence of diminishing blood flow in acutely rejecting hearts. This model may lead to a better understanding of the physiology and metabolism of acute rejection.

Animals↗

PubMed1977

Synthesis and antimicrobial activity of certain 6H-1,2,4-oxadiazin-3(2H)-ones.

Treatment of 6H-1,2,4-oxadiazin-3(2H)-one-5(4H)-thione (2) with hydroxylamine, hydrazine, methylamine, or benzylamine afforded the corresponding N5-substituted 5-amino-6H-1,2,4-oxadiazin-3(2H)-ones 3c-f. Refluxing a dioxane solution of 6H-1,2,4-oxiazine-3,5(2H,4H)-dione (1) with benzylamine or aminodiphenylmethane and hexamethyldisilazane in the presence of ammonium sulfate gave 5-benzylamino-6H-1,2,4-oxadiazin-3(2H)-one (3f) and the corresponding 5-diphenylmethylamino derivative 3g. Reaction of 1 with methyl iodide, benzyl chloride, dihydropyran, dihydrofuran, or benzyloxycarbonyl chloride afforded the corresponding 2-substituted 6H-1,2,4-oxadiazine-3,5(2H,4H)-diones 6a-e. Reaction of 2-methyl-6H-1,2,4-oxadiazine-3,5(2H,4H)-dione (6a) or the corresponding 2-benzyl derivative 6b with phosphorus pentasulfide in dioxane gave 2-methyl-6H-1,2,4-oxadiazin-3(2H)-one-5(4H)-thione (8a) and the corresponding 2-benzyl derivative 8b, respectively. Reaction of 8a with ammonia in dioxane afforded 2-methyl-5-amino-6H-1,2,4-oxadiazin-3(2H)-one (9). The degree of in vitro activity and the presence of antibacterial activity in the urine of animals given 5-amino-6H-1,2,4-oxadiazin-3(2H)-one (3a) by oral route of administration prompted selection of this compound for further study.

Animals↗

PubMed2003

TOR regulates the subcellular localization of Ime1, a transcriptional activator of meiotic development in budding yeast.

The transcriptional activator Ime1 is a key regulator of meiosis and sporulation in budding yeast. Ime1 is controlled at different levels by nutrients and cell-type signals. Previously, we have proposed that G(1) cyclins would transmit nutritional signals to the Ime1 pathway by preventing the accumulation of Ime1 within the nucleus. We show here that nutritional signals regulate the subcellular localization of Ime1 through the TOR pathway. The inactivation of TOR with rapamycin promotes the nuclear accumulation and stabilization of Ime1, with consequent induction of early meiotic genes. On the contrary, the activation of TOR by glutamine induces the relocalization of Ime1 to the cytoplasm. Thus, TOR may sense optimal nitrogen- and carbon-limiting conditions to modulate Ime1 function. Besides TOR, ammonia induces an independent mechanism that prevents the accumulation of Ime1 in the nucleus. Both TOR and ammonia regulate Ime1 localization in the absence of Cdk1 activity and therefore use mechanisms different from those exerted by G(1) cyclins. Integration of independent mechanisms into a single early controlling step, such as the nuclear accumulation of Ime1, may help explain why yeast cells execute the meiotic program only when the appropriate internal and external conditions are met together.

Antibiotics, Antineoplastic↗

PubMed1983

The amiloride-sensitive Na+/H+ antiport in 3T3 fibroblasts.

BALB/c 3T3 fibroblasts have an amiloride-sensitive Na+ uptake mechanism which is hardly detectable under normal physiological conditions. The activity of this Na+ transport system can be increased to a large extent by treatments that decrease the internal pH such as loss of intracellular NH4+ as NH3 or incubation with nigericin in the presence of a low external K+ concentration. These treatments have made possible an analysis of the interaction of the Na+/H+ antiport with amiloride and of the external pH dependence of the system. The addition of fetal bovine serum to quiescent 3T3 cells stimulates the initial rate of the amiloride-sensitive 22Na+ uptake by only 50%. However, after treatment of the cells with ammonia or nigericin, serum produces a 40-fold stimulation of the rate of the amiloride-sensitive 22Na+ uptake. Control experiments show that serum does not stimulate the activity of the Na+/H+ antiport by an indirect mechanism involving a depolarization of the membrane or a modification of the internal Ca2+ concentration. It is suggested that some serum component directly interacts with the Na+/H+ exchanger to modify its catalytic properties.

Amiloride↗

PubMed2003

In situ distribution and activity of nitrifying bacteria in freshwater sediment.

Nitrification was investigated in a model freshwater sediment by the combined use of microsensors and fluorescence in situ hybridization with rRNA-targeted oligonucleotide probes. In situ nitrification activity was restricted mainly to the upper 2 mm of the sediment and coincided with the maximum abundance of nitrifying bacteria, i.e. 1.5 x 107 cells cm-3 for ammonia-oxidizing Beta-proteobacteria (AOB) and 8.6 x 107 cells cm-3 for Nitrospira-like nitrite-oxidizing bacteria (NOB). Cell numbers of AOB decreased more rapidly with depth than numbers of NOB. For the first time, Nitrospira-like bacteria could be quantified and correlated with in situ nitrite oxidation rates in a sediment. Estimated cell-specific nitrite oxidation rates were 1.2-2.7 fmol NO2- cell-1 h-1.

Bacteria↗

PubMed1976

Further studies of the dynamics of nitrogen metabolism in sheep.

1. A study of ammonia and urea metabolism in sheep was made using isotope dilution techniques with (15NH4)2SO4,[15N]urea and [14C]urea in order to determine quantitatively the movements of urea-N and NH3-N throughout the body of normal, feeding sheep. 2. Single injections of 15N-labelled compounds were made into the rumen fluid NH3, caecal fluid NH3 and the blood urea pools, in order to estimate the rates of flux through, and the transfer of N between, these and other nitrogenous pools in the body. 51CrEDTA was injected into the rumen and caecum with (15NH4)2SO4 to allow estimation of fluid volumes and to provide an indication of mixing, and of times of transit of isotopes between different sampling sites in the digestive tract. 3. The sheep ate approximately 22 g lucerne chaff/h and the mean dietary N intake was 16-3 g/d. 4. The rate of flux of NH3 through the rumen NH3 pool was 15-0 g/d (i.e. 90% of the dietary N ingested; however, this amount also included N from plasma urea (1-1 g/d) and other endogenous sources including NH3 derived from caecal NH3 (0-4 g/d). 5. Only 40% of the N in isolated rumen bacteria was derived from NH3, indicating that a considerable proportion of their N requirements were obtained from compounds other than NH3 (e.g. peptides and amino acids). 6. There was evidence of recycling of N between nitrogenous pools in the rumen, probably through rumen NH3 leads to microbial N leads to NH3. 7. It was estimated that 5-3 g blood urea-N/d entered the digestive tract; 20% of this urea was degraded in the rumen, 25% in the caecum and the remainder was apparently degraded elsewhere; there was evidence of urea degradation in the large intestine posterior to the caecum and it is suggested that urea degradation and absorption of the resultant NH3 may occur in the ileum. 8. Of the 4-8 g N/d entering the caecal NH3 pool, 4-2 g N/d left and did not return and the difference (0-6 g N/d) was recycled, possibly through caecal NH3 leads to microbial N leads to NH3. 9. A large proportion of the NH3 entering the caecal NH3 pool (70% or 3-2 g N/d) was apparently derived from degradation of nitrogenous products, other than urea, including rumen microbial N (1-0 g N/d) passing undigested from the small intestine. 10. Less than half the NH3-N of caecal origin entering the rumen passed through the blood urea pool; the remainder was apparently transported as other nitrogenous compounds in the blood or body fluids. 11. The results of the three experiments were combined in a general three-pool, open-compartment model which formally recognizes an unlimited number of other unspecified, interconnected pools together comprising the whole-animal system. Rates of flux through, and transfer of N between these and other nitrogenous pools in the body were calculated by solving this model and the information derived has been applied to whole-animal models with a view to subsequently using these models in computer simulation studies.

Ammonia↗

PubMed1998

The anaerobic oxidation of ammonium.

From recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'Aerobic' ammonium oxidizers like Nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. The maximum rate for anaerobic ammonium oxidation was about 2 nmol NH4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor. This reaction, which may involve NO as an intermediate, is thought to generate energy sufficient for survival under anoxic conditions, but not for growth. A novel obligately anaerobic ammonium oxidation (Anammox) process was recently discovered in a denitrifying pilot plant reactor. From this system, a highly enriched microbial community with one dominating peculiar autotrophic organism was obtained. With nitrite as electron acceptor a maximum specific oxidation rate of 55 nmol NH4+ min-1 (mg protein)-1 was determined. Although this reaction is 25-fold faster than in Nitrosomonas, it allowed growth at a rate of only 0.003 h-1 (doubling time 11 days). 15N labeling studies showed that hydroxylamine and hydrazine were important intermediates in this new process. A novel type of hydroxylamine oxidoreductase containing an unusual P468 cytochrome has been purified from the Anammox culture. Microsensor studies have shown that at the oxic/anoxic interface of many ecosystems nitrite and ammonia occur in the absence of oxygen. In addition, the number of reports on unaccounted high nitrogen losses in wastewater treatment is gradually increasing, indicating that anaerobic ammonium oxidation may be more widespread than previously assumed. The recently developed nitrification systems in which oxidation of nitrite to nitrate is prevented form an ideal partner for the Anammox process. The combination of these partial nitrification and Anammox processes remains a challenge for future application in the removal of ammonium from wastewater with high ammonium concentrations.

Anaerobiosis↗

PubMed2000

Nitrogen partitioning in Heterorhabditis bacteriophora-infected hosts and the effects of nitrogen on attraction/repulsion.

Entomopathogenic nematode behavior is affected by the condition of their infected hosts. We hypothesized that nitrogen compounds released from infected hosts may be one factor affecting entomopathogenic nematode host-finding and infection behaviors. Our objectives were to (1) investigate the partitioning of nitrogen in Galleria mellonella (L.) infected by Heterorhabditis bacteriophora Poinar and (2) determine attraction and repulsion of H. bacteriophora to various quantities of nitrogen (ammonia). Volatile (ammonia), organic, and inorganic nitrogen forms were monitored during the course of infection. Approximately 0.052 mg of nitrogen was released from a single infected host as volatile ammonia. Most of the ammonia release was detected within the first 3 days postinoculation. Organic nitrogen increased during the course of infection, whereas inorganic nitrogen decreased. The net nitrogen change in the infected host consisted of a loss of approximately 47 mg, most of which was lost within the 1st week of infection. Accelerated loss of nitrogen early in the infection process was likely correlated with activity and growth of bacterial symbionts. Increased organic nitrogen was likely associated with nematode reproduction within the host. Attraction or repulsion of H. bacteriophora to nitrogen (ammonium hydroxide) was measured on agar quadrant plates. Nematodes were attracted to 16 and 160 microg of nitrogen and repelled by concentrations of 1600 and 8000 microg. Our data indicate that nitrogen released from H. bacteriophora-infected hosts attracts nematodes at lower levels (early in the infection) and repels them at higher concentrations (later in the infection process).

Animals↗