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PubMed1991

Nitrogen metabolism in the stalk tissue of maize.

During ear development in maize (Zea mays L.), nitrogenous compounds are translocated from vegetative organs to the kernels. At anthesis, the stalk contains approximately 40% of the total plant N, and contributes 45% of the N remobilized to the ear. Therefore, the stalk has an important function as a temporary reservoir for N. Little is known of the metabolism of maize stalks, and this paper describes initial studies of enzymes of N metabolism. High in vitro activity of glutamine synthetase (GS) in maize stalk samples throughout ear development contrasted with a peak in activity of glutamate synthase soon after anthesis and negligible nitrate reductase. With fresh sections of stalk tissue collected at anthesis, (15)N-feeding experiments confirmed high GS and low nitrate reductase activities. Two isoforms of GS were separated from extracts from stalk tissue: GS1, the cytoplasmic form, increased to maximum levels at 2 weeks postanthesis and remained fairly high thereafter; whereas the plastidic form, GS2, declined progressively during kernel development. Western blot analysis confirmed the presence of constantly high levels of GS protein after anthesis. The levels of GS proteins decreased after transfer of N-starved, hydroponically grown plants to N-rich conditions in order to restrict remobilization of N. In contrast, transfer of plants grown under abundant N conditions to N-free medium, which encourages N remobilization, resulted in a relative increase in GS protein. Because glutamine is the major form of N transported in maize, the results indicate that GS, specifically the GS1 isoform, has a central role in the remobilization on nitrogenous compounds from the stalk to the ear.

Journal Article↗
PubMed1983

Myeloperoxidase-dependent effect of amines on functions of isolated neutrophils.

Isolated neutrophilic leukocytes were incubated with primary amines and related nitrogenous compounds. Stimulation of neutrophil oxygen (O2) metabolism with phorbol myristate acetate or opsonized zymosan resulted in production of hydrogen peroxide (H2O2), myeloperoxidase-catalyzed oxidation of chloride (C1-) to hypochlorous acid (HOC1), and the reaction of HOC1 with the added compounds to yield nitrogen-chlorine (N-C1) derivatives. Formation of N-C1 derivatives of low lipid solubility resulted in accumulation of the derivatives in the extracellular medium. These oxidizing agents were identified and measured on the basis of their absorption spectra and their ability to oxidize 5-thio-2-nitrobenzoic acid to the disulfide form. The yield of N-Cl derivatives was in the order: taurine greater than Tris greater than spermidine greater than spermine greater than glucosamine greater than putrescine greater than guanidinoacetate. Accumulation of N-C1 derivatives was also observed in the absence of added amines, owing to the reaction of HOC1 with endogenous taurine and other amines that were released from the cells into the medium. In the presence of compounds that yield lipophilic N-C1 derivatives, little or no accumulation of oxidizing agents was observed. Instead, these compounds inhibited the accumulation of N-C1 derivatives that was obtained with taurine, and their effect was competitive with taurine. Inhibition was in the order: methylamine greater than ethanolamine greater than phenylethylamine greater than p-toluenesulfonamide greater than ammonia greater than guanidine. Formation of lipophilic N-C1 derivatives also resulted in inhibition of O2 uptake and glucose metabolism. Inhibition was prevented by adding catalase to eliminate H2O2, dapsone to inhibit myeloperoxidase, taurine to compete for reaction with HOC1, or compounds that are rapidly oxidized by HOC1 or N-C1 derivatives, to reduce these oxidizing agents. The results indicate that: (a) formation of N-C1 derivatives that do not penetrate biological membranes can protect leukocytes against the cytotoxicity of HOC1 and lipophilic N-C1 derivatives, and (b) formation of membrane-permeable N-C1 derivatives in the absence of target cells or readily oxidized substances results in oxidative attack by the N-C1 derivatives on leukocyte components and inhibition of leukocyte functions.

Adult↗
PubMed2002

Tetrazolylpentazoles: nitrogen-rich compounds.

Tetrazolylpentazole was identified as an intermediate in the reaction of tetrazolediazonium chloride with lithium azide by low-temperature (15)N NMR spectroscopy. The decomposition of (15)N-labeled tetrazolylpentazole to form (15)N-labeled tetrazoleazides and dinitrogen was followed by low-temperature (15)N NMR spectroscopy. The structures of the species involved in this decomposition were optimized at different levels of theory, and the structures of the transition states were identified. The activation barriers for the decomposition were calculated at different levels of theory.

Journal Article↗
PubMed1982

Nitrogen bridgehead compounds. 18. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 1.

A new type of antiallergic agent, 9-hydrazono-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones, was synthesized and evaluated for inhibitory effects in the rat reagenic passive cutaneous anaphylaxis (PCA) screen. Several racemic 6-methyl derivatives were found to be more potent than disodium chromoglycate intravenously and some were also active orally. Structure-activity relationships are discussed. High stereospecificity was observed in the 6-methyl series between the enantiomers with 6S and 6R absolute configuration, the former being more active. Compound 17, (+)-6(S)-methyl-9-(phenylhydrazono)-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid [Chinoin-1045; UCB L140], has an ED50 value of 1.0 mumol/kg po and is now under clinical investigation.

Animals↗
PubMed1983

Nitrogen bridgehead compounds. 33. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 2.

A series of 9-hydrazono-4H-pyrido[1,2-a]pyrimidin-4-ones was prepared. The compounds were evaluated in the rat passive cutaneous anaphylaxis test for antiallergic activity. Structure-activity relationship studies revealed that the presence of a monosubstituted hydrazone moiety in position 9 and an unsubstituted 2-position are necessary for the intravenous activity.

Animals↗
PubMed1983

Nitrogen bridgehead compounds. 38. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 3.

The weak antiallergic activity of 6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carboxylic acid (4) on the rat reaginic passive cutaneous anaphylaxis test was enhanced by the introduction of appropriate functional groups into position 9 of the pyridopyrimidine ring. The most active 9-substituted pyridopyrimidinecarboxylic acids contained an oxime, a phenylamino, or a (phenylamino)thioxomethyl group in position 9. The 9-phenylcarboxamido and 9-phenylhydrazono moieties may be regarded as bioisosteric groups in the pyridopyrimidinone series. In the series of 9-(arylamino)dihydropyridopyrimidines, the structure-activity relationship study revealed similar relationships as found for the 9-(arylhydrazono)tetrahydropyridopyrimidines. The biological activity was due to the 6S enantiomers. A monosubstituted arylamino moiety in position 9 was necessary for the intravenous activity. The most active compound, 9-[(3-acetylphenyl)amino]-6-methyl-4-oxo-6,7,8,9-tetrahydro-4H- pyrido[1,2-a]pyrimidine-3-carboxylic acid (40) was three times as active as the reference sodium chromoglycate (DSCG) in the passive cutaneous anaphylaxis (PCA) test.

Animals↗
PubMed1984

Nitrogen bridgehead compounds. 44. New antiallergic 4H-pyrido[1,2-a]pyrimidin-4-ones. 4.

The weak antiallergic activity of 6-methyl-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3-carbox yli c acid (1) in the rat reaginic passive cutaneous anaphylaxis test was enhanced by the introduction of an (arylamino)methylene moiety into position 9 of the pyridopyrimidine ring. Compound 34, (+)-6(S)-methyl-9-[(m-methylphenyl)-hydrazono]-4-oxo-4H-pyrido[1,2 -a] pyrimidine-3-carboxylic acid, displayed about 10 000 times the activity of the starting compound 1. A structure-activity relationship study of 9-[(arylamino)methylene]tetrahydropyridopyrimidine-3-carb ox ylic acids resulted in conclusions similar to those found for the 9-(arylhydrazono)tetrahydro-and 9-(arylamino)dihydropyridopyrimidine series. Replacement of the 3-carboxy group of 9-(phenylhydrazono)-tetrahydropyridopyrimidin-4-ones with an acrylic acid moiety caused slight increases in potency. In the 6-methyl-substituted series, a high stereospecificity was observed between the enantiomers with 6S and 6R absolute configurations, the former being responsible for the antiallergic activity. The effects of some 9-[(arylamino)-methylene]tetrahydropyridopyrimidine-3-car box ylic acids on the rat passive peritoneal anaphylaxis test were also investigated.

Anaphylaxis↗
PubMed1997

Effect of nitrogen source on biosynthesis of rapamycin by Streptomyces hygroscopicus.

Six non-amino acid nitrogen compounds were examined as nitrogen source for growth of Streptomyces hygroscopicus and biosynthesis of rapamycin. Of the nitrogen sources studied, ammonium sulfate was the best with respect to formation of rapamycin, and supported cell growth comparable to the organic nitrogen sources used in the control chemically defined medium, i.e., aspartate, arginine plus histidine. In the new chemically defined medium, which is buffered with 200 mM 2-(N-morpholino)ethanesulfonic acid to prevent decline of pH during fermentation, an ammonium sulfate concentration of 40 mM was optimal for biosynthesis of rapamycin. Rapamycin production increased by more than 30% on both volumetric and specific bases as compared to the previous medium containing the three amino acids as nitrogen source.

Ammonium Sulfate↗
PubMed2005

Lithium-nitrogen and lithium-boron-nitrogen cage compounds formed using the phenylhydrazido backbone.

Two rare examples of the crystal structures of large molecular clusters formed from the lithium salts of multianions are reported; the first is the dilithium salt of phenylhydrazine, which forms a tetrameric cage with a core of eight Li and eight N centres; the second is a 32-membered cage which forms from the aggregation of two [B(NNPh)3]6- hexaanions, two [NH-NPh]2- dianions and 16 Li+ cations.

Journal Article↗
PubMedDate not supplied

A retention index library for commonly encountered drugs and metabolites using tri-n-alkylamines as reference compounds, nitrogen-phosphorus detectors, and dual capillary chromatography.

The retention index system is a reproducible means for the identification of drugs in toxicology samples analyzed by gas chromatography with flame ionization detectors. Nitrogen-phosphorus (NP) detectors do not respond well to the standard n-alkanes, which lack nitrogen and phosphorus groups and which are used to obtain the Kovats index. A method is presented that creates a retention index library based upon a homologous series of tri-n-alkylamines for a series of 125 drugs and metabolites. Standards were analyzed under temperature programmed conditions by simultaneous dual column chromatography using a 5% phenyl and a 50% phenyl methyl silicone fused-silica capillary column. By increasing the hydrogen and air flows to the NP detectors, the Kovats indices were calculated on the system using the n-alkanes C8 through C32. Tri-n-alkylamine indices calculated under the same conditions were compared to the Kovats indices for 14 drugs on the 5% phenyl column and for 12 drugs on the 50% phenyl column. The correlation was found to be linear. The Kovats indices on the 5% phenyl column were compared to previously reported values and found to be consistent.

Amines↗