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At least 793 records · Page 44Linked to original sources
PubMed2003

Gas chromatographic-mass spectrometric study of the oil fractions produced by microwave-assisted pyrolysis of different sewage sludges.

The pyrolysis of sewage sludge was studied in a microwave oven using graphite as microwave absorber. The pyrolysis temperature ranged from 800 to 1000 degrees C depending on the type of sewage sludge. A conventional electrical furnace was also employed in order to compare the results obtained with both methods. The pyrolysis oils were trapped in a series of condensers and their characteristics such as elemental analysis and calorific value were determined and compared with those of the initial sludge. The oil composition was analyzed by GC-MS. The oils from the microwave oven had n-alkanes and 1-alkenes, aromatic compounds, ranging from benzene derivatives to polycyclic aromatic hydrocarbons (PAHs), nitrogenated compounds, long chain aliphatic carboxylic acids, ketones and esters and also monoterpenes and steroids. The oil from the electric oven was composed basically of PAHs such as naphthalene, acenapthylene, phenanthrene, fluoranthene, benzo[a]anthracene, benzofluoranthenes, benzopyrenes, indenepyrene, benzo[ghi]perylene, and anthanthrene. In contrast, these compounds were not produced in the case of microwave-assisted pyrolysis.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Confirmation of Thiobacillus denitrificans as a species of the genus Thiobacillus, in the beta-subclass of the Proteobacteria, with strain NCIMB 9548 as the type strain.

Thiobacillus denitrificans is physiologically similar to the type species of the genus Thiobacillus, Thiobacillus Thioparus, and both are located in the beta-subclass of the Proteobacteria. T. denitrificans is distinguished from all other Thiobacillus species by its ability to grow as a facultatively anaerobic chemolithotroph, coupling the oxidation of inorganic sulfur compounds to the reduction of nitrate, nitrite and other oxidized nitrogen compounds to dinitrogen. A definitive description of this species is provided and strain NCIMB 9548T is designated as the type strain of the species, thereby correcting an earlier error in the literature.

Base Composition↗
PubMed1989

Regulation of nitrogen catabolic enzymes in Streptomyces clavuligerus.

The levels of several enzymes involved in assimilation of different nitrogen compounds were investigated in Streptomyces clavuligerus in relation to the nitrogen source supplied to the cultures. Threonine dehydratase, serine dehydratase, proline dehydrogenase, histidase and urocanase were not decreased in the presence of ammonium. The latter two enzymes were induced by histidine in the culture medium, while proline dehydrogenase was induced by proline. Glutamine synthetase, urease and ornithine aminotransferase levels were higher with poor nitrogen sources and were repressed by ammonium. Arginase was induced by arginine and repressed by ammonium. Glutamine synthetase was rapidly inactivated upon addition of ammonium to the culture, and could be reactivated in vitro by treatment with snake venom phosphodiesterase, which suggested that adenylylation is involved in the inactivation. Three previously isolated mutants with abnormal glutamine synthetase activities showed pleiotropic effects on urease formation. All these data point to a mechanism controlling preferential utilization of some nitrogen sources in this species.

Ammonia↗
PubMed2003

Biological nitrification and denitrification of opto-electronic industrial wastewater.

Development and application of biological nutrient removal processes accelerated significantly over the past decade due to more stringent nutrients (nitrogen and phosphorus) discharge limits being imposed on wastewater treatment plants. The opto-electronic industry has developed very fast over the past decade in the world. The wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio of over 95% in organic nitrogen (Org-N) to total nitrogen (T-N). In this study, a 2-stage Anoxic/Aerobic pre-denitrification process was established and the efficiency of wastewater treatment was evaluated. Wastewater from an actual LCD-plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment. Hydraulic retention time (HRT) and mixed liquor recycle rate (MLR) were controlled independently to distinguish between the effects of these two factors. Under suitable HRT and mixed liquor recycle ratio, effluents of NH4-N, NOx-N and COD can fall below 20 mg/l, 30 mg/l and 80 mg/l.

Bioreactors↗
PubMed1984

Effect of lipid-coated lysine on digestion and nitrogen metabolism by wethers.

Four mature wethers (70 kg) fitted with permanent abomasal cannulas were assigned to a 4 X 4 Latin square design to study the effect of coating supplemental lysine with coconut oil on nutrient digestion, nitrogen retention and recovery of amino acids in the abomasum and plasma. Dietary treatments were: Control (C) = basal diet; Lysine (LYS) = Control + 1% supplemental lysine; Coconut oil-coated lysine (CN-LYS) = Control + 1% supplemental lysine coated with coconut oil; and Coconut oil + diet (CN-DIET) = Control + 1% supplemental lysine + an equal amount of coconut oil added to the entire diet. Lysine supplementation significantly increased total apparent dry matter, ether extract and energy digestibilities. Total nitrogen and protein nitrogen flows to the abomasum were decreased (p less than .1) in lambs consuming CN-LYS and CN-DIET compared with LYS. Urinary nitrogen excretion (p less than .05), ruminal ammonia nitrogen and plasma urea nitrogen (p less than .05) concentrations were higher for LYS, CN-LYS and CN-DIET compared with C and highest for CN-LYS. There were no differences in nitrogen retention among treatments. Recovery of lysine in the diets after coating (CN-LYS) or lipid addition (CN-DIET) was reduced indicating degradation of supplemental lysine to other nitrogenous compounds during the coating process or storage since total dietary nitrogen content was equivalent to LYS. Flow of abomasal lysine (% of lysine intake) was higher (p = .15) for CN-LYS and CN-DIET than LYS. Flow of total essential amino acids (% of total amino acid flow) was greater (p less than .02) when lysine was added to diets. Essential amino with LYS. Plasma amino acid concentrations did not differ among treatments. Coating lysine with coconut oil did not protect the amino acid from ruminal degradation and was ineffective in improving total nitrogen status of mature wethers.

Abomasum↗
PubMed1998

A Steeply Pyramidal Silylamine: N,O-Dimethyl-N-silylhydroxylamine.

N,O-Dimethyl-N-silylhydroxylamine (H(3)SiMeNOMe) has been prepared by reaction of HMeNOMe with H(3)SiBr and 2,6-lutidine as an auxiliary base. Its identity has been proved by gas-phase IR and solution NMR spectroscopy of the nuclei (1)H, (13)C, (15)N, (17)O, and (29)Si and by mass spectrometry. The solution NMR data indicate aggregation of the compound in solution. H(3)SiMeNOMe decomposes within weeks at ambient temperature, and an extrusion of methylnitrene is probably the mechanistic pathway involved. The final products of this decomposition are an insoluble precipitate and SiH(4). The energy of H(3)SiMeNOMe relative to its potential rearrangement isomer MeHN-H(2)Si-OMe has been estimated by ab initio calculations to be 289 kJ mol(-)(1). The molecular structure of H(3)SiMeNOMe has been determined by gas-phase electron diffraction and by ab initio calculations. The results show H(3)SiMeNOMe to possess a steeply pyramidal nitrogen atom and to adopt a trans conformation. It is thus the first silyl nitrogen compound that adopts a typically pyramidal nitrogen coordination for purely electronic reasons. The Si-N bond is found to be only slightly elongated with respect to those of comparable compounds with planar nitrogen coordination. Important bond length and angles are Si-N 1.742(1), N-O 1.449(4), N-C 1.460(3), and O-C 1.425(4) Å and Si-N-C 121.8(5), Si-N-O 104.3(4), C-N-O 106.2(12), and N-O-C 103.2(12) degrees. Results of an NBO analysis show the silyl group to be bound by a nitrogen sp(2) hybrid, the d-orbital contribution at silicon to be less than 2%, and the N-O bond to comprise mainly p-orbital contribution. The presence of a marked p(lp-N)-sigma(Si-H) hyperconjugation in the NBO description shows that this effect cannot be solely responsible for the generally observed flattening of the nitrogen coordination in silylamines.

Journal Article↗
PubMed1992

Capillary gas chromatographic method for the determination of the thromboxane A2 receptor antagonist S-1452 and its metabolites in human plasma.

A capillary gas chromatographic method for the determination of a newly developed thromboxane A2 antagonist, S-1452, and its metabolites in human plasma has been developed. This nitrogenous compound was detected as the free acid (+)-S-145 using a nitrogen-phosphorus detector. The two metabolites bisnor-(+)-S-145 and tetranor-(+)-145 were also assayed. The three compounds, which all possess carboxylic acid group, were converted into their hexafluoro-2-propyl esters with hexafluoropropan-2-ol-pentafluoropropionic anhydride as reagent. The esterification resulted in a decreased background response from the detector, and hence higher sensitivity and better precision. The glucuronides of the three compounds were also assayed after alkaline hydrolysis. The plasma concentration of the glucuronide of I was more than twice that of the free acid. This method allows determination of the three compounds at more than 2 ng/ml with a precision of 2-6% and an accuracy variation of less than +/- 5%. The analysis was performed within 2 min after injection to assay the sample rapidly from the Phase I test. The method is suitable for pharmacokinetic studies.

Bridged Bicyclo Compounds↗
PubMed1978

Mutagenicity of heterocyclic nitrogen mustards (ICR compounds) in cultured mammalian cells.

The mutagenicity of six heterocylic nitrogen mustards (ICR compounds) has been determined in a cultured mammalian cell system by use of resistance to the purine analog 6-thioguanine to select for mutation induction at the hypoxanthine-guanine phosphoribosyltransferase locus in Chinese hamster ovary cells. The six compounds tested are ICR 191, 170, 292, 372, 191-OH, and 170-OH. The first four contain a single 2-chloroethyl group (nitrogen half-mustard) on the side chain and are mutagenic, with the tertiary amine types (170 and 292) 3 to 5 times more mutagenic than the secondary amine types (191 and 372). The remaining two compounds (191-OH and 170-OH) are not mutagenic, indicating that the 2-chloroethyl group is needed for mutation induction.

Cell Line↗
PubMed2004

Functional characterization of allantoinase genes from Arabidopsis and a nonureide-type legume black locust.

The availability of nitrogen is a limiting factor for plant growth in most soils. Allantoin and its degradation derivatives are a group of soil heterocyclic nitrogen compounds that play an essential role in the assimilation, metabolism, transport, and storage of nitrogen in plants. Allantoinase is a key enzyme for biogenesis and degradation of these ureide compounds. Here, we describe the isolation of two functional allantoinase genes, AtALN (Arabidopsis allantoinase) and RpALN (Robinia pseudoacacia allantoinase), from Arabidopsis and black locust (Robinia pseudoacacia). The proteins encoded by those genes were predicted to have a signal peptide for the secretory pathway, which is consistent with earlier biochemical work that localized allantoinase activity to microbodies and endoplasmic reticulum (Hanks et al., 1981). Their functions were confirmed by genetic complementation of a yeast mutant (dal1) deficient in allantoin hydrolysis. The absence of nitrogen in the medium increased the expression of the genes. In Arabidopsis, the addition of allantoin to the medium as a sole source of nitrogen resulted in the up-regulation of the AtALN gene. The black locust gene (RpALN) was differentially regulated in cotyledons, axis, and hypocotyls during seed germination and seedling growth, but was not expressed in root tissues. In the trunk wood of a mature black locust tree, the RpALN gene was highly expressed in the bark/cambial region, but had no detectable expression in the sapwood or sapwood-heartwood transition zone. In addition, the gene expression in the bark/cambial region was up-regulated in spring and fall when compared with summer, suggesting its involvement in nitrogen mobilization.

Allantoin↗
PubMed1992

Contraluminal transport of organic cations in the proximal tubule of the rat kidney. II. Specificity: anilines, phenylalkylamines (catecholamines), heterocyclic compounds (pyridines, quinolines, acridines).

In order to study the quantitative structure/activity relationship of organic cation transport across the contraluminal side of the proximal renal tubule cell, the stopped-flow capillary microperfusion method was applied and the inhibitory potency (apparent Ki values) of different homologous series of substrates against N1-[3H]methylnicotinamide (NMeN+) transport was evaluated. Aniline and its ring- or N-substituted analogues as well as the aminonaphthalines do not interact with the contraluminal NMeN+ transporter except for the quaternary trimethylphenylammonium and pararosaniline, which bear a permanent positive charge, and for 1,8-bis-(dimethylamino)naphthaline, which forms an intramolecular hydrogen bond. If, however, one or more than one methylene group is interposed between the benzene ring and the amino group, the compounds interact with the contraluminal NMeN+ transporter in proportion to their hydrophobicity parameter, i.e. the octanol/water partition coefficient (log octanol). The catecholamines and other hydroxyl-substituted phenylethyl analogues also follow this rule. In addition, the N-heterocyclic pyridine, quinoline, isoquinoline and acridine analogues also interact with the contraluminal NMeN+ transporter, when their pKa values are higher than 5.0, and, an inverse correlation between pKa and log Ki,NMeN was observed. An exception to this rule are those hydroxy compounds of pyridine, quinoline and isoquinoline that show tautomerism. These compounds slightly inhibit NMeN+ transport despite low pKa values. The quaternary nitrogen compounds of aniline and the N-heterocyclic analogues, as far as tested, all interact with the contraluminal NMeN+ transporter in relation to their hydrophobicity. The data indicate that the contraluminal NMeN+ transporter interacts with N-compounds according to their hydrophobicity and/or according to their basicity (affinity to protons). The reason for deviation of the aniline analogues and the OH-tautomeric heterocyclic N-compounds from this behaviour is discussed.

Aniline Compounds↗
PubMed1997

Crown condition of Norway spruce in relation to sulphur and nitrogen deposition and soil properties in southeast Norway.

Atmospheric deposition of sulphur and nitrogen compounds may lead to enhanced leaching of base cations, accumulation of nitrogen in organic matter, lowered pH and increased concentration of toxic aluminium in soil, which in turn may affect the vitality of forest trees. A general monitoring of forest condition has been initiated in many European countries, partly in order to reveal stresses caused by acidification. However, forest condition is also affected by many other factors. This paper examines a seven-year series of crown-condition data from Local County Monitoring Plots in Norway spruce stands in Norway. Average, time trend and lability variables were calculated for crown density and crown colour for each plot. Wet deposition of sulphate, ammonium and nitrate for each plot were estimated using data from the national air and precipitation monitoring programmes. Soil data are based on soil sampling within the plots. The analysis gave no evident support for the hypothesized negative effect on crown condition from sulphur and nitrogen deposition and related alterations in soil.

Journal Article↗
PubMed1995

Isolation of bacteria degrading carbazole under microaerobic conditions, i.e. nitrogen gas substituted conditions.

Microorganisms degrading carbazole (CA), a model substrate of heterocyclic nitrogen compounds in crude petroleum oil, were screened under microaerobic conditions, i.e. nitrogen gas substituted conditions. Eight bacteria were isolated and identified. For example, Bacillus sp. KUKK-4 degraded 31% of CA when cultivated for 28 days in a medium initially containing CA at 1000 mg/l with shaking under the microaerobic conditions.

Aerobiosis↗
PubMed1992

[Assessment of total mutagenic activity of harmful factors of the industrial environment at the metallurgy plants of South Ural].

Harmful factors of the industrial environment of the steel plants are represented by sulfur- and arsenic-containing compounds, nitrogen and carbon oxides, aerosols of heavy and rare metals, fluorine compounds whose concentrations exceed the maximum allowable ones in the air of the working place. The results of the cytogenetic examination of metallurgists attest to the pronounced total mutagenic activity of unfavourable factors of the industrial environment, among which the key role is played by arsenic, fluorine and heavy metal compounds.

Adult↗
PubMed1993

Biochemical and microbiological events of Parma ham production technology.

Parma ham technology relies on a few basic points. They are: a fresh meat substantially free of microbial deep contamination, a relatively long phase (up to 100 days) at cold temperatures at the beginning of processing, an uncovered muscular surface as reduced as possible, a long period of maturation. The final product, the matured ham, is the result of a slow process of dehydration which, combined with a limited penetration of salt into the muscles, lowers the water activity to values around 0.90. Surface bacterial contamination is mainly made up by Enterobacteriaceae and Pseudomonadaceae. Among them E. agglomerans and S. liquefaciens are able to grow at 2 degrees C and salt concentrations up to 7.5% and can be responsible for taint development. Micrococci penetrate into the meat during salting and can reach values of 10 x 6 but decrease substantially towards the end of maturation. Maturation, from a biochemical point of view, is characterized by hydrolytic phenomena interesting nitrogen compounds and fats. As a result free amino acids, non protein nitrogen, volatile fatty acids and carbonylic molecules are produced. Such products are important for the development of typical organoleptic characters.

Amino Acids↗
PubMed1982

The distribution of oxidized nitrogen in urban air.

This paper describes the distribution of oxidized nitrogen compounds in urban air. The studies reported here have focused on NO, NO2, PAN and NO-3. These species have been monitored for periods of several weeks at a nmber of locations throughout the U.S.A. Oxidized nitrogen distribution is discussed in terms of the daily patterns of nitrogen pollutant concentrations, the fractional conversion of NOx to products and the diurnal profile of the conversion fraction, and lastly, the contribution of the individual compounds to the overall oxidized nitrogen burden. Site to site variations in the distribution are explained by photochemical conversion, distance between the site and the source region, and the proximity of local NOx emission sources.

Air Pollutants↗
PubMed1976

The effect of nitrogen limitation on catabolite repression of amidase, histidase and urocanase in Pseudomonas aeruginosa.

In Pseudomonas aeruginosa, the synthesis of histidase, urocanase and amidase is severly repressed when succinate is added to a culture growing in pyruvate + ammonium salts medium. When growth is nitrogen-limited, catabolite repression by succinate of histidase and urocanase synthesis does not occur but succinate repression of amidase synthesis persists. Amidase synthesis is not regulated in the same way as histidase synthesis by the availability of other nitrogen compounds for growth. Growth of P. aeruginosa strain PACI in succinate + histidine media is nitrogen-limited since this strain is defective in a histidine transport system. When methyl-ammonium chloride is added to succinate + histidine media, growth inhibition occurs. Mutants isolated from succinate + histidine + methylammonium chloride plates were found to be resistant to catabolite repression by succinate even in ammonium salts media. It is suggested that the hut genes of P. aeruginosa may be regulated in the same way as in Klebsiella aerogenes, by induction by urocanate and activation by either the cyclic AMP-dependent activator protein or by glutamine synthetase.

Amidohydrolases↗