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PubMed1976

Ultramicro gas-chromatographic analysis for anticonvulsants, with use of a nitrogen-selective detector.

We describe a procedure for determining phenobarbital, primidone, and diphenylhydantoin simultaneously in 50-mul volumes of serum by use of gas chromatography and a detector with heightened sensitivity and selectivity for nitrogenous compounds. The drugs, together with an internal standard, 5-allyl-5-phenyl barbituric acid, are extracted from serum by the procedure of MacGee [Anal. Chem. 42, 421 (1970)]. The drugs are converted to their methyl derivatives by a modification of the procedure of Greeley [Clin. Chem. 20, 192 (1974)] and then analyzed on a column containing 3% OV-1, with a temperature program, and detected by a nitrogen-selective detector. The method is reproducible to about 7%. Sensitivities of 0.5 mg/liter for 50-mul serum samples are attained routinely. Mephobarbital interferes with the analysis because methylation yields the same product as methylated phenobarbital. Total analysis time for a single sample is 15 min.

Chromatography, Gas↗
PubMed1995

[Automated determination of total nitrogen in milk by the Dumas method].

A nitrogen analyser based on the Dumas method (LECO FP-428) and equipped with a liquid injector has been tested. The intensive steam production during injection may result in poor nitrogen recoveries for volatile nitrogen compounds such as ethylene diamine. However, recoveries could be improved by slow injection and by filling the combustion tube with Cer(IV)-oxide. For the analysis of milk the instrument was calibrated with NaN3 solutions because their response was found to be less sensitive to burning conditions. Dumas-N and Kjeldahl-N of milk showed good correlation (r = 0.998). However, with the Dumas method about 6.7% (+ 0.035% N) higher nitrogen values were obtained. With a standard deviation of repeatability S(r) = 0.002% N (CVr = 0.33) and a between day reproducibility SD = 0.006% N (CVD = 1.1%) the precision of the Dumas method was similar to that reported for the Kjeldahl method. In order to avoid systematic errors the use of standard milk samples for calibration is recommended. It is concluded that modern instruments using the Dumas method allow precise measurements of nitrogen in milk with a high sample throughout.

Animals↗
PubMed1994

Redundancy of the conserved His residue in Azotobacter vinelandii NifL, a histidine autokinase homologue which regulates transcription of nitrogen fixation genes.

The NifL protein of Azotobacter vinelandii inhibits NifA, the activator of nif (nitrogen fixation) transcription, in response to oxygen and fixed nitrogen. NifL shows strong homology in its C-terminal domain to the histidine autokinase domains of the canonical two-component sensor proteins, including the region around His-304, which corresponds to the residue known to be phosphorylated in other systems. To examine the mechanism of sensory transduction by NifL, mutations encoding 10 substitutions for His-304 were introduced into the A. vinelandii chromosome. Regulation of nif transcription was measured using acetylene reduction and RNA blots. The substitutions His-304-->Arg and His-304-->Pro impaired regulation by both fixed nitrogen and oxygen, but substitution of Ala, Phe, Ile, Lys, Asn, Ser, Thr, Val had no effect. None of the mutants, including His-304-->Arg and His-304-->Pro, excreted ammonium during diazotrophy, a phenotype of nifL deletion mutants, suggesting that the molecular basis of this effect differs from that responsible for the inhibition of nif transcription. The data show conclusively that phosphorylation of His-304 is not essential for any of the known functions of A. vinelandii NifL. Homology to the family of histidine autokinases is therefore inadequate evidence for a mechanism of sensory transduction involving phosphorylation of the conserved histidine residue.

Amino Acid Sequence↗
PubMed1991

Murine respiratory mycoplasmosis: a model to study effects of oxidants.

Previous studies have shown that exposure to nitrogen dioxide at concentrations of 5 and 10 parts per million (ppm) decreases intrapulmonary killing of Mycoplasma pulmonis, and that this decrease is related to increased lung lesions and mortality. The specific objectives of the present study were to titrate the effects of nitrogen dioxide on pulmonary clearance of M. pulmonis, determine the mechanisms by which this organism is killed within the lungs, and determine the target that the nitrogen dioxide affects. Pathogen-free C57BL/6N mice were exposed to 0, 0.5, 1, 2, or 5 ppm of nitrogen dioxide (contamination with other oxides of nitrogen compounds was 5% or less) for four hours and then immediately were exposed to aerosols of viable, radiolabeled M. pulmonis strain UAB CT. One-half of the animals in each group were killed immediately after exposure to the infectious aerosols, and the rest were killed 24 hours later. The amount of radioactivity and the number of viable M. pulmonis were determined for each group. Exposure to less than 5 ppm of nitrogen dioxide had no effect on intrapulmonary killing of M. pulmonis, although exposure to 1 ppm of nitrogen dioxide did increase mechanical removal. We were unable to develop a completely in vitro mycoplasma killing method. However, we were able to demonstrate the in vitro killing of M. pulmonis that had been allowed to associate with alveolar macrophages in vivo. Thus, mouse lungs contain unidentified factors that allow cells to kill M. pulmonis. Furthermore, we obtained evidence that suggests that prior exposure to nitrogen dioxide abrogates killing in these experiments. We also have shown that exposure to nitrogen dioxide does not increase the protein content of bronchoalveolar lavage fluid. Using immunofluorescence, more than 95% of the cells recovered by lavage were macrophages; with double-label immunofluorescence, more than 98% of the cell-associated mycoplasmas were on or in alveolar macrophages. In assessing the cytological parameters of lung lavage cells from mice exposed to nitrogen dioxide, M. pulmonis, or both, we found that both insults affected the viability of recovered macrophages. Viability immediately after exposure as measured by trypan blue exclusion or by fluorescein diacetate uptake, was 89% +/- 4% and 88% +/- 4% in the control group, respectively; 56% +/- 19% and 64% +/- 11% in the group receiving M. pulmonis alone; 23% +/- 7% and 48% +/- 9% in the group receiving nitrogen dioxide alone; and 16% +/- 6% and 25% +/- 6% in the group receiving both M. pulmonis and 10 ppm nitrogen dioxide exposures.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollutants↗
PubMed1987

Ischemic heart arrest: nitrogenous metabolism in energy-depleted human myocardium.

Seventeen patients undergoing radical correction of Fallot's tetrad or defects of interventricular septum were investigated. Needle biopsies from the left ventricular apex region were obtained at the 1st min after cross-clamping of the aorta and at the end of cardiac arrest to determine adenosine triphosphate (ATP), glutamate, aspartate, alanine and ammonia. The losses of ATP during clamping period were related to decrease in glutamate. The fall in ATP by more than 20% of the initial level was accompanied by a significant decrease in aspartate, an accumulation of alanine and ammonia in cardiac tissue but did not affect glutamine content. The data obtained prove the participation of specific nitrogenous compounds of human heart, and especially glutamate, in response to energy depletion during ischemia.

Adenosine Triphosphate↗
PubMed2006

Modeling the partial nitrification in sequencing batch reactor for biomass adapted to high ammonia concentrations.

Partial nitrification has proven to be an economic way for treatment of industrial N-rich effluent, reducing oxygen and external COD requirements during nitrification/denitrification process. One of the key issues of this system is the intermediate nitrite accumulation stability. This work presents a control strategy and a modeling tool for maintaining nitrite build-up. Partial nitrification process has been carried out in a sequencing batch reactor at 30 degrees C, maintaining strong changing ammonia concentration in the reactor (sequencing feed). Stable nitrite accumulation has been obtained with the help of an on-line oxygen uptake rate (OUR)-based control system, with removal rate of 2 kg NH4 (+)-N x m(-3)/day and 90%-95% of conversion of ammonium into nitrite. A mathematical model, identified through the occurring biological reactions, is proposed to optimize the process (preventing nitrate production). Most of the kinetic parameters have been estimated from specific respirometric tests on biomass and validated on pilot-scale experiments of one-cycle duration. Comparison of dynamic data at different pH confirms that NH3 and NO2- should be considered as the true substrate of nitritation and nitratation, respectively. The proposed model represents major features: the inhibition of ammonia-oxidizing bacteria by its substrate (NH3) and product (HNO2), the inhibition of nitrite-oxidizing bacteria by free ammonia (NH3), the INFluence of pH. It appears that the model correctly describes the short-term dynamics of nitrogenous compounds in SBR, when both ammonia oxidizers and nitrite oxidizers are present and active in the reactor. The model proposed represents a useful tool for process design and optimization.

Adaptation, Physiological↗
PubMed2005

Investigation of NOx precursor compounds and other combustion by-products in the primary combustion zone of a waste-incineration plant using on-line, real-time mass spectrometry and Fourier-transform infrared spectrometry (FTIR).

On-line analysis of trace and bulk gas compounds in the burning chamber of a waste-incineration plant has been performed, with high temporal resolution, by use of a variety of distinctly different measurement techniques. Time-of-flight mass spectrometry was performed with simultaneous use of three ionization techniques-resonance-enhanced multiphoton ionization (REMPI), single-photon ionization (SPI), and electron-impact ionization (EI). Chemical-ionization mass spectrometry (CIMS), Fourier-transform infrared spectrometry (FTIR), and electrochemical methods were also used. Sampling was conducted by means of a newly developed air-cooled stainless steel lance, to cope with the high temperatures and elevated particle concentrations at the sampling location. Nitrogen species were mainly nitrogen monoxide, ammonia, and hydrogen cyanide (HCN), with a small amount (approximately 0.3%) of aromatic nitrogen compounds. NO, NH(3), and HCN are the main contributors to the NO(x)-formation process in the postulated fuel-NO reaction scheme dominant at this location. The NO recycling process thereby plays a major role. Changes in plant operating conditions have a noticeable impact only when the air supply is varied. For example, reduction of oxygen leads to an increase in the HCN fraction of the total nitrogen content and a decrease in the NO fraction, and vice versa.

Incineration↗
PubMed2003

Microarray analysis of E2Fa-DPa-overexpressing plants uncovers a cross-talking genetic network between DNA replication and nitrogen assimilation.

Previously we have shown that overexpression of the heterodimeric E2Fa-DPa transcription factor in Arabidopsis thaliana results in ectopic cell division, increased endoreduplication, and an early arrest in development. To gain a better insight into the phenotypic behavior of E2Fa-DPa transgenic plants and to identify E2Fa-DPa target genes, a transcriptomic microarray analysis was performed. Out of 4,390 unique genes, a total of 188 had a twofold or more up- (84) or down-regulated (104) expression level in E2Fa-DPa transgenic plants compared to wild-type lines. Detailed promoter analysis allowed the identification of novel E2Fa-DPa target genes, mainly involved in DNA replication. Secondarily induced genes encoded proteins involved in cell wall biosynthesis, transcription and signal transduction or had an unknown function. A large number of metabolic genes were modified as well, among which, surprisingly, many genes were involved in nitrate assimilation. Our data suggest that the growth arrest observed upon E2Fa-DPa overexpression results at least partly from a nitrogen drain to the nucleotide synthesis pathway, causing decreased synthesis of other nitrogen compounds, such as amino acids and storage proteins.

Arabidopsis↗
PubMedDate not supplied

[Colony structure of a consortium of nitrogen-fixing bacteria].

Colonies produced by a consortium of nitrifying bacteria were studied using light and electron microscopy. The colonies were obtained by direct plating of inoculum from a two-stage nonsterile chemostat fermentor and by repeatedly passing the microbial community of the fermentor through selective media containing ammonium or nitrite. The colonies studied can be characterized by a specific combination of six types of cells differing in their ultrastructure and spatial location within the colony. The types of cells occurring within a given colony were found to depend on the nitrogen compound present in the medium. As a result of our study, morphological features of colonial bacterial communities were preliminarily identified. The proposed approach can be viewed as a method to describe microbial associations and communities.

Bacteria↗
PubMed1986

Ruminal degradation of dried brewers grains, wet brewers grains, and soybean meal.

A series of trials was conducted to determine the ruminal degradation of nitrogenous compounds and dry matter of soybean meal, wet brewers grains, and dried brewers grains. In situ and in vitro estimates of degradation were positively correlated but yielded different absolute values for measures of ruminal degradation. Ruminal digestion of protein, predicted from in situ data, was 42, 73, and 83% for brewers dried grains, brewers wet grains, and soybean meal. Drying of wet grains at either 50 or 150 degrees C increased resistance to ruminal digestion equally. Measurements of flow of dry matter and nitrogen of feed origin to the duodenum were made in vivo for diets containing either brewers dried grains or soybean meal. Negative apparent digestibility of nitrogen in the rumen for a 13% crude protein, brewers dried grains ration indicates the potential for using a non-protein nitrogen supplement with this ration. Resistance to digestion of nitrogen from brewers dried grains occurred only in the rumen. Amino acid patterns delivered to the small intestine and digestion of duodenal contents were similar for diets containing brewers dried grains or soybean meal.

Animal Feed↗
PubMed1983

[Current technology of waste water treatment].

For the purification of municipal waste water and industrial waste water predominantly burdened by organic matter, mechanical-biological plants partly based on the method of activation and partly on the trickling filter system are preferably used. Recently overloading of existing plants and tighter water protection requirements imposed the necessity of boosting the performance of conventional biological processes by reducing the sludge burden and the loading per unit volume. This has also resulted in nitrification of the nitrogen compounds and in extensive sludge stabilization. As the oxygen supply to the micro-organisms requires the highest expenditure of energy in the activation process, special attention was given to the development of efficient aeration systems. For waste water containing a high proportion of substances which prove difficult to decompose, or waste water subject to strong fluctuations, multi-stage biological procedures or a combination of various processes are used increasingly. In this context, chemical precipitation for the elimination of phosphorus and biological nitrogen elimination have proven themselves as additional purification methods.

Air↗
PubMed2005

Partition of nitrogen excretion in urine and the feces of holstein replacement heifers.

Increasing public concern has been focused on animal production systems as a major nonpoint source of pollution. These studies were conducted to further our understanding of whole-animal N metabolism, N excretion, and its partition between feces and urine in growing dairy heifers. Isocaloric diets [2.31 Mcal of metabolizable energy (ME)/kg of dry matter (DM)], ranging from 12.4 to 34.2 g of N/kg of DM, were fed to Holstein heifers in 2 experiments at approximately 1.8 times maintenance. Diets were formulated to provide 54 to 143% of the ruminal ammonia requirements as predicted by the Cornell Net Carbohydrate and Protein System. Increasing the N content of the diet increased urinary N excretion and N balance, but did not affect fecal N excretion. Holstein heifers fed low N diets were able to maintain growth rates consistent with current recommendations while at the same time reducing N excretion, in particular nitrogenous compounds that are readily converted to ammonia. However, more research is needed before this type of diet is recommended for growing heifers because of possible changes in body composition that may affect future milk production and performance.

Ammonia↗
PubMedDate not supplied

Formation of heteroaromatic nitrogen after prolonged humification of vascular plant remains as revealed by nuclear magnetic resonance spectroscopy.

In the search for the mechanisms involved in the immobilization of organic nitrogen in humified remains of vascular plants, the efforts of the present investigation were directed toward the examination of the transformation of nitrogenous compounds during the peat and coal stage by means of solid-state nuclear magnetic resonance (NMR) spectroscopy. While accumulation of heteroaromatic-N is not detected in most of the studied peat layers, a clear shoulder in the chemical shift region of pyrrole- or indole-N is observed in the solid-state 15N NMR spectrum of material from the deepest (and thus oldest) peat layer underlying the sapropel from Mangrove Lake, Bermuda (10000 years). This points to the assumption that transformation of nitrogen occurs between an advanced stage of peatification and an early stage of coalification. The observed sudden alteration in nitrogen functionality indicates that continuous accumulation of newly synthesized or selectively preserved biogenic structures is not responsible for the presence of heteroaromatic-N in these fossilized deposits. It seems rather likely that abiotic conditions, occurring during advanced sediment maturation, have an effect on the observed N transformation. With increasing coalification, pyrrole-type-N becomes the dominant form in the macromolecular coal network. Pyridine-type-N was only detected in a coal of anthracite rank.

Biotransformation↗
PubMed1983

Growth responses to nutrients of an auxotroph and a prototroph of a predatory fungus.

The growth responses of a prototroph and an auxotroph of Arthrobotrys dactyloides were compared, on several nutrient media. The prototroph can utilize a variety of nitrogenous compounds almost equally, but the auxotroph has an exacting requirement for several amino acids together. Both strains utilize sucrose best among the three sugars tested as a C-source but the prototroph responds strongly to phospholipid, in addition. They differ in their needs for purines, pyrimidines and B vitamins.

Carbohydrate Metabolism↗
PubMed2005

Calculation and mapping of critical loads of sulphur and nitrogen for forest soils in Galicia (NW Spain).

Calculations of critical loads of acidity within Europe have shown Galicia to be one of the regions in Spain with the highest risk of soil acidification by deposition of atmospheric pollutants. We used the simple mass balance method (SMB) to derive critical loads of sulphur and nitrogen for forest soils in Galicia using available site-specific information. Exceedance of acidic deposition was calculated using the deposition levels of N and S registered in 2001. Most forest ecosystems analysed can support acid loads of more than 2000 eq N ha(-1) year(-1). The lowest critical loads of acidity (1483 eq ha(-1) year(-1)) occurred in coniferous forest stands growing on shallow soils developed on slates, in the interior zone. The highest critical load values (9386 eq ha(-1) year(-1)) were observed in coniferous stands in zones with elevated precipitation rates, in the littoral area. The critical load for acidity was exceeded in 5% of the forest soils. Such exceedances were mainly caused by deposition of nitrogen compounds. The contribution of sulphur deposition to acid exceedance was important in the surroundings of the city of A Coruña. Analysis of rainfall bulk composition revealed that N deposition in Galicia was mainly due to ammonium emissions, probably derived from agricultural and cattle breeding activities.

Acid Rain↗
PubMed2000

[Nitrogen, phosphorus and the C/N ratio in superficial sediments of the lagoon of Chacopata, Sucre, Venezuela].

The basal behaviour and relationship with organic carbon (Corg) content and prevailing granulometric fractions, of organic nitrogen (Norg), total phosphorus (P-total) and C/N ratio in surface sediments of Chacopata lagoon, Sucre State, Venezuela, were studied. Concentrations and spatial gradients were determined in sixteen stations following a common method for marine sediments. Norg concentrations varied between 0.102 and 0.510% (x = 0.237%), total phosphorus between 0.012 and 0.094% (x = 0.058%) and C/N ratio between 9.27 and 44.47 (x = 20.53). The higher contents of Norg and total phosphorus are from sections with an abundance of mangroves, marine phanerogams, macroalgae, benthonic biomass and migratory birds shelters. The C/N ratio shows the typical values for carbonated sediments, indicating that the nitrogenous compounds are rapidly degraded and the organic matter presents itself as humic substances. This parameter was moderately associated with silt and clay, and showed antagonism with sand, whereas Norg and phosphorus showed no correlation with them. The organic contribution is purely autochthonous: no anthropogenous contributions were found.

Biodegradation, Environmental↗
PubMed1983

Influence of nonprotein nitrogen and protein of low rumen degradability on nitrogen flow and utilization in lactating dairy cows.

Four lactating cows, each fitted with a rumen cannula and duodenal and ileal t-cannulae, were used to measure flow and digestion of nitrogenous compounds in the digestive tract. Dietary dry matter contained 17% crude protein and 50:50 forage:concentrate. Treatments were: 1) corn silage-soybean meal; 2) corn silage-heated soybean meal; 3) ammonia-treated corn silage-soybean meal; and 4) ammonia-treated corn silage-heated soybean meal. Flow of organic matter to the duodenum was overestimated when lanthanum or chromium ethylene-diaminetetraacetate was used as an indigestible marker. This resulted in low estimates of ruminal digestion of organic matter and high estimates of nitrogen flow to the duodenum. However, calculations using lanthanum or lignin as markers yielded similar organic matter flow to ileum and feces. With acid-detergent lignin as a marker, estimates of dietary nitrogen degraded in the rumen were: corn silage-heated soybean meal, 55.0% ammonia-treated corn silage-heated soybean meal, 58.8%; ammonia-treated corn silage-soybean meal, 63.3%; and corn silage-soybean meal, 66.0%. Digestion in the small intestine of nonammonia nitrogen was equal for all treatments suggesting that availability of heated soybean meal in the intestine was not different, although ruminal degradability tended to be lower. Feeding diets containing nonprotein nitrogen did not decrease available nitrogen at the duodenum.

Animals↗
PubMed1994

Coordination of nutrient use by peripheral tissues.

The growth of peripheral tissues reflects the combined effect of endogenous and exogenous signals. Limits of endogenous signals are determined by genetics, which define a chronology of growth of individual tissues. Fractional synthesis rate of muscle also follows a chronology. Endogenous mediators are both systemic and local, with tissue response a product of combined effects. Exogenous signals derive from the environment and dietary intake. Exogenous somatotropin or beta-adrenergic agonists change endogenous genetic limits for protein deposition and change partition of absorbed amino acids by stimulating anabolic use of amino acids in peripheral tissues and decreasing catabolism. Peripheral tissues provide a valuable model to study the relationships between tissues and the complexity of in vivo regulation. Shifts in metabolism of nitrogenous compounds by the liver are an example of directed changes in nutrient partitioning that act to increase supply of amino acids to peripheral tissues in conjunction with a stimulus to increase anabolic amino acid use. Further studies should integrate tissue changes with intracellular mechanisms.

Animal Nutritional Physiological Phenomena↗