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At least 559 records · Page 31Linked to original sources
PubMed2006

Seed germination in response to chemicals: effect of nitrogen and pH in the media.

Seed germination generally presents a peak in the next growing season after a fire. Among other factors associated with fire are the increase of soil nitrogen and changes in the pH of the soil. In this study, we addressed the question, whether or not the germination response of eight species is linked with the increase in pH and nitrogenous compounds in the germination media? We assessed the separate and combined effects of nitrogenous compounds and pH on the percentage and rate of germination of seeds of Medicago arabica (L.) Hudson, Epilobium hirsutum L., Foeniculum vulgare Miller, Daucus carota L., Thapsia villosa L., Cynosurus cristatus L., Dactylis glomerata L. and Rumex crispus L. All these species are well represented in the Mediterranean ecosystems of the central-west Spain. Water and CaCl2 were used as controls. Nitrogenous compounds increased percent germination (level) and rate in three of the species studied. High pH negatively affected the germination rate of seeds from most species, but had no effect on the per cent germination of any of the species. The higher concentration of the nutritious solutions affected negatively the germination level and rate. The different germination responses of seeds of the studied species could not be exclusively attributed to pH values in the media, whereas the amount and form of Nitrogen in the media has a greater effect on it. These differences in germination are species dependent.

Apiaceae↗
PubMed1995

Differential susceptibility of yeast and hyphal forms of Candida albicans to macrophage-derived nitrogen-containing compounds.

Candida albicans is a dimorphic fungus capable of transition from the yeast form (Y-Candida) to the hyphal form (H-Candida). Both Y-Candida and H-Candida are known to be growth inhibited by murine macrophages (M phi) in vitro. In the present report, we demonstrate that M phi exposed to interferon gamma (IFN-gamma) plus lipopolysaccharide (LPS) show enhanced anti-Y-Candida and anti-H-Candida activities. To further investigate the phenomenon, Y-Candida and H-Candida were assessed for susceptibilities to M phi-derived supernatants. Only the growth of H-Candida, and not that of Y-Candida, is impaired by cell-free supernatants from M phi treated with IFN-gamma plus LPS. In contrast, no H-Candida growth inhibition occurs when supernatants from M phi exposed to IFN-gamma plus LPS in the presence of NG-monomethyl-L-arginine, an inhibitor of nitric oxide (NO) synthesis, are employed. Finally, supernatants from M phi incubated with sodium nitroprusside, an NO-generating agent, also show anti-H-Candida activity. In conclusion, these results indicate that H-Candida but not Y-Candida is susceptible to extracellular antifungal mechanisms employed by M phi, which likely involve stable nitrogen-containing compounds.

Animals↗
PubMedDate not supplied

[Dynamics of nitrogen-containing compounds in the hemolymph of 2d- and 3d-stage larvae of the reindeer warblefly (Hypodermatidae)].

The content of the total protein, residual and amine nitrogen, urea and ammoniac depends on the physiological state of the warble fly larvae of the reindeer. Metabolism of nitrogen-containing compounds carries out most intensively in the growing organism and during the moulting period. The moulting period is characterized by the fall in the total protein, residual and amine nitrogen and increase of the ammonias and urea.

Amines↗
PubMed2004

Addition reactions of ROPHy/SOPHy oxime ethers: asymmetric synthesis of nitrogen containing compounds.

Oxime ethers prepared from (R)- or (S)-O-(1-phenylbutyl)hydroxylamine (ROPHy or SOPHy) are versatile intermediates for the asymmetric synthesis of a range of nitrogen containing compounds including simple amines, 1,2-aminoalcohols, alpha- and beta-amino acids, heterocyclic building blocks of natural products, piperidine alkaloids, lactams, 5- to 8-membered ring nitrogen heterocycles, imino-sugars, and chiral ferrocene based receptors.

Journal Article↗
PubMed1985

Human milk nonprotein nitrogen: occurrence and possible functions.

Human milk contains a wide variety of nitrogenous compounds in addition to protein. Recognition of the special roles these compounds can perform raises questions about their availability from human milk, and, ultimately, their significance in the development of the human newborn. While it is likely that the major categories of compounds contributing to the nonprotein-nitrogen fraction of human milk have been identified, the true variety of nitrogenous compounds within the peptide fraction of human milk is only beginning to be recognized and appreciated. If predictions can be made from those peptides already identified, epidermal growth factor, delta-sleep inducing peptide, somatomedin-C/insulin-like growth factor I and the peptide hormones, further elucidation of the specific peptides that contribute to this fraction of human milk promises to be especially exciting. With each new published report, the recognized chemical gap between human milk and proprietary formulas increases. There is increasing evidence that human milk produced by a well-nourished woman is a chemical mixture uniquely suited for the developmental stage of her infant. Whether these differences confer developmental advantages to the infant fed human milk, advantages not enjoyed by infants fed formula, is less easily determined. Attempts to answer this question must take into account the relative physiological maturity of the infant at birth. There is a distinct possibility that infants born early in the last intrauterine trimester will derive more benefit from receiving mother's milk than those infants nourished in utero to term.

Amino Acids↗
PubMed2006

Production of alkaline lipase by Corynebacterium paurometabolum, MTCC 6841 isolated from Lake Naukuchiatal, Uttaranchal State, India.

A moderately psychrophilic bacterium Corynebacterium paurometabolum MTCC 6841 (gram positive, short rod type) producing extracellular alkaline lipase was isolated from Lake Naukuchiatal, Uttaranchal, India. The bacterium was able to grow within a broad range of pH (5-10). Soyabean oil and olive oil served as the best carbon sources for lipase production. The bacterium preferred inorganic nitrogenous compounds, NaNO3 and KNO3, over organic nitrogenous compound for its growth. Maximum lipase production occurred at 25 degrees C and 8.5 pH. The enzyme activity was found to be maximum at the same values of temperature and pH. The enzyme was reasonably stable in the presence of various organic solvents. No significant effect of Ca+, Cu++, Fe++, Na+, K+, Mg++, Mn+, NH4+, Co++ ions over enzyme activity was detected. Treatment with EDTA reduced the activity to nearly one half.

Bacterial Proteins↗
PubMed2002

Effects of nitrite and ammonium on methane-dependent denitrification.

For effective application of methane-dependent denitrification (MDD) in the treatment of wastewater containing NO(2)(-) or NH(4)(+), the effect of these inorganic nitrogen compounds on MDD activity needs to be clarified. The MDD activity of sludge acclimatized with CH(4) and O(2) was determined with mineral media of different nitrogen-compound compositions in the presence of 0.21 atm CH(4) and 0.20 atm O(2). Incubations with media containing only NO(2)(-) or two of the three inorganic nitrogen compounds (NO(3)(-)+NO(2)(-), NO(2)(-)+NH(4)(+) or NH(4)(+)+NO(3)(-)) resulted in MDD activity equal to or higher than that with media containing only NO(3)(-). However, there was no MDD activity in media containing NO(2)(-) at 10 degrees C, probably because of serious inhibition of NO(2)(-) on methane oxidation. MDD occurred in media containing only NH(4)(+), although the total nitrogen removal efficiency was very low. These results show that NO(2)(-) and NH(4)(+), in the presence of NO(x)(-), do not inhibit but rather promote MDD. Consequently, NH(4)(+) does not need to be completely oxidized to NO(3)(-) in the nitrification reactor before MDD. However, under psychrophilic conditions, NO(2)(-) seriously inhibited MDD. Therefore, the nitrification reactor must not discharge effluent containing NO(2)(-) under psychrophilic conditions.

Methane↗
PubMedDate not supplied

Redox cycle of stable mixed nitroxides formed from carcinogenic aromatic amines.

1. Of the carcinogenic aromatic nitrogenous compounds investigated, 10 out of 11 were found to be biotransformed in rabbit liver microsomal preparations to nitroxide radicals, as detected by ESR spectroscopy; with non-carcinogenic nitrogenous compounds only 2 out of 8 formed nitroxide radicals. 2. The radicals are stable mixed nitroxides formed by covalent binding of the aromatic nitroxide to endogenous constituents of the microsomal membrane with preservation of the nitroxide radical group (spin-trapping). 3. From the high chemical stability and the observed ESR spectra, spin-label-like structures can be deduced. 4. From this and the known one-electron redox properties of spin-labels, a redox cycle catalysing the production of reactive oxygen species and involved in tumour initiation and/or promotion by aromatic nitrogenous compounds is proposed.

Amines↗
PubMed2006

Kinetics of nitrogen removal from sanitary landfill leachate.

Leachates from municipal landfill 'Lublinek' in Lodz city (Poland) were treated in two-sludge sequence batch reactor systems (type ND). The external carbon source--sodium acetate was used in denitrification. Two versions were tested--with and without supernatant recirculation from D-SBR to N-SBR. The 99% removal of inorganic nitrogen compounds was achieved in both versions. Due to recirculation, the buffering (by means of sodium bicarbonate) was not necessary. Kinetic models for nitrification and denitrification processes were proposed. Kinetic parameters of the models were estimated by the optimization method. The experimental results of both nitrification steps (oxidation of ammonia to nitrites and nitrites to nitrates) were best fitted with the interactive limitation model of nitrogen compounds and oxygen. The denitrification process was limited only by the concentration of nitrogen compounds.

Bioreactors↗
PubMed2007

Study of methylation of nitrogen-containing compounds in the gas phase.

The methyl migration between the protonated N,N-dimethylisopropylamine and other neutral aliphatic amines in the gas phase has been investigated by a hybrid external chemical ionization source ion trap mass spectrometer. Similar reactions have been found in the aqueous solution by Callahan and Wolfenden (J. Am. Chem. Soc. 2003; 125: 310). At the same time, density functional theory (DFT) calculations show that in contrast with the neutral N,N-dimethylisopropylamine, protonated N,N-dimethylisopropylamine is a better methyl donor. These results indicate that protonation promotes the methyl migration between aliphatic amines both in the gas phase and in the aqueous solution. In addition, methyl transfer also exists between the protonated N,N-dimethylisopropylamine and some other nitrogen-containing compounds.

Gases↗