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PubMed2004

Trifluoroacetyl-activated nitrogen-nitrogen bond cleavage of hydrazines by samarium(II) iodide.

[reaction: see text] Trifluoroacetyl derivatives of hydrazines undergo clean and efficient reductive cleavage of the N-N bond with SmI(2) in the presence of MeOH. After N-trifluoroacetylation, acyl-, aryl-, and alkyl-substituted hydrazines are reductively cleaved by this method to afford trifluoroacetamides in yields ranging from 70 to 96%. These conditions accommodate alkene functionality, avoid racemization, and furnish chiral amines bearing a readily removable TFA protecting group.

Hydrazines↗
PubMed2006

Thiocyanate cannot inhibit the formation of reactive nitrogen species in the human oral cavity in the presence of high concentrations of nitrite: detection of reactive nitrogen species with 4,5-diaminofluorescein.

In the human oral cavity, nitrite is reduced to nitric oxide (NO) by certain bacteria. 4,5-Diaminofluorescein (DAF-2) was transformed to a fluorescent component triazolfluorescein (DAF-2T) in a bacterial fraction of saliva in the presence of nitrite. No detectable consumption of DAF-2 and formation of DAF-2T were observed in bacterial fraction in the absence of nitrite. The nitrite-dependent transformation of DAF-2 to DAF-2T was inhibited by catalase, SCN(-), and CN(-) suggesting the participation of peroxidases in saliva in the transformation. The formation of DAF-2T, which was observed by the addition of an NO generating reagent (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR 3) to bacterial fraction, was also inhibited by catalase, SCN(-), and CN(-). The degree of the inhibition by SCN(-) decreased as the concentration of nitrite or NOR 3 was increased. Superoxide dismutase (SOD) enhanced nitrite- and NOR 3-induced fluorescence increase in the bacterial fraction, and the degree of the enhancement decreased as the concentrations of nitrite and NOR 3 were increased. In whole saliva filtrate, the inhibitory effects of SCN(-) on the fluorescence increase decreased as the concentration of nitrite was increased, but the enhancement by SOD was not significantly affected by the increase in the concentration of nitrite. As salivary bacteria produce O(2)(-), H(2)O(2), and NO and as peroxidase/H(2)O(2)/nitrite systems in saliva produce NO(2), the effects of SCN(-) are discussed taking SCN(-)-dependent inhibition of NO(2) formation by peroxidases in saliva into consideration and the effects of SOD are discussed taking O(2)(-)-dependent consumption of NO into consideration. It is concluded that when the rate of the formation of NO is high, SCN(-) is not effective enough to inhibit the formation of N(2)O(3) in the oral cavity.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Effect of level and origin of rumen degradable nitrogen on rumen microbial growth and nitrogen utilisation efficiency of animals fed maize silage at maintenance.

Isoenergetic maize silage diets, fed at maintenance to 24 suckling cows (Exp. 1) and to 3 (Exp. 2) or 4 (Exp. 3) rumen fistulated sheep, were compared with a urea and controlled release NPN diet (Exps. 1 and 2) and with a protein-N supplemented diet (Exp. 3). Supplementation increased blood urea concentrations (44.7 +/- 22.3 vs. 97.6 +/- 23.7 mg urea-N x L(-1)) (Exp. 1) and renal urea excretion (2.5 +/- 1.1 vs. 7.6 +/- 1.8 g urea-N x d(-1)) (Exps. 2 and 3), whereas blood allantoin concentrations (286.7 +/- 77.0 micromol x L(-1)) (Exp. 1) and renal excretion of purine derivatives (357.6 +/- 90.7 mg purine-N x d(-1)) (Exps. 2 and 3) were not affected, indicating additional N supplementation did not improve rumen microbial growth. However, some deficiency of rumen degradable N might occur in non supplemented diets as suggested by the reduced rumen NH3-N and RNA concentrations (868 +/- 270 vs. 1466 +/- 466 mg RNA x kg(-1) rumen contents).

Animals↗
PubMed2003

Juvenile nitrogen uptake capacities and root architecture of two open-pollinated families of Picea abies. Effects of nitrogen source and ectomycorrhizal symbiosis.

This study was carried out to find early physiological differences occurring in young seedlings between two contrasting Picea abies open-pollinated families (OPF), one with high- and one with low-growth performance in the field by, determining their N uptake capacities and their root architecture. We used three potential N-sources in forest soil solution, NO3-, NH4+ and amino acids, to establish N uptake rates by the plants, whether or not associated with a fungus isolated from the field and identified as Paxillus involutus. NO3- fluxes were determined locally at the root surface using NO3(-)-selective microelectrodes whereas NH4+ and amino acid (L-glutamate and L-aspartate) uptake rates were calculated from their depletion of the incubation solution by the whole root system. Root systems were digitised in order to determine the number and the length of different root types. In non-mycorrhizal plants, the results showed that the most distinguishing parameters between OPF were NO3- uptake rates measured in the white tip of the secondary roots and the root architecture, with higher values determined in high-growth than in low-growth field performance OPF. The presence of the mycorrhizal fungus decreased NO3- uptake rates in both OPF and had an opposite effect on root architecture by increasing it in low-growth and decreasing it in high-growth field performance OPF, respectively. In non-mycorrhizal plants, NH4+ and amino-acid uptake rates were not different between OPF. Mycorrhizal symbiosis did not change NH4+ uptake rates whereas it increased that of amino acids, specifically that of L-aspartate in the low-growth field performance OPF. Taken together these results suggest that the measurement of local fluxes in roots of young plants could be a good potential tool for the early evaluating of growth capacity of Picea abies OPF.

Amino Acids↗