Orientador: Edivaldo Domingues Velini / Banca: Caio Antonio Carbonari / Banca: Fernando Tadeu de Carvalho / Banca: Natália Corniani / Banca: Rubem Silveiro de Oliveira Junior / Resumo: A sensibilidade de plantas daninhas a herbicidas frequentemente se apresenta variável, em função de diversos fatores. O herbicida amônio glufosinate tem ação de contato e inibe a atividade da enzima glutamina sintetase, causando dentre outros efeitos, o acúmulo de amônia nos tecidos foliares, sendo esse um bom indicativo da intoxicação das plantas. Desse modo, o objetivo desse trabalho foi identificar a resposta de plantas de Bidens pilosa e Conyza sumatrensis a diferentes doses do herbicida amônio glufosinate, e a variação da sensibilidade em populações das plantas e de suas progênies ao herbicida. Foram realizados três estudos, todos em casa-de-vegetação e repetidos em diferentes momentos. No primeiro estudo, dois experimentos de dose-resposta foram conduzidos, e foram aplicadas sete diferentes doses do herbicida amônio glufosinate (0, 50, 100, 200, 400, 800, e 1600 g ha-1), com quatro repetições, para cada espécie, sendo realizada análise de amônia e avaliações visuais de fitointoxicação. No segundo estudo, de variação de sensibilidade de B. pilosa e C. sumatrensis ao amônio glufosinate, 44 plantas de B. pilosa e 16 de C. sumatrensis foram aplicadas com a dose de 200 g ha-1 do herbicida, sendo nesse momento a região meristemática e folha mais nova de cada planta protegidas com saco plástico para que não recebessem o herbicida e possibilitasse a manutenção das plantas vivas. Dois dias após a aplicação (DAA) realizou-se a análise do teor de amônia, nas folhas expostas à apli... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The sensitivity of weeds to herbicide is often variable, due to several factors. The glufosinate-ammonium is a contact herbicide and inhibits the activity of the glutamine synthetase enzyme causing, among others, ammonia accumulation in the leaves, an indicator of the plants intoxication. The objective of this study was to evaluate the response of Bidens pilosa and Conyza sumatrensis to different doses of glufosinate ammonium and the sensitivity range of the plants and their progenies to the herbicide. Three studies were conducted, all in a greenhouse and repeated at different times. In the first study, two experiments were conducted to examine the dose-response curve, and the treatments were seven different doses of the herbicide glufosinate ammonium (0, 50, 100, 200, 400, 800, and 1600 g ha-1), with four replicates for each specie. In the second study, which examined the sensitivity range of B. pilosa and C. sumatrensis to glufosinate ammonium, 44 B. pilosa plants and 16 C. sumatrensis plants were sprayed with 200 g ha-1 of the herbicide. At the time of spraying, the meristematic region and the youngest leaf of each plant were protected with a plastic bag so that they would not receive the herbicide, thus keeping the plants alive. At two days after treatment (DAT), an analysis of the ammonium content on the sprayed leaves them was conducted. The protected leaves were kept on the plants enabling to recover from herbicide treatment and to produce seeds used to assess the sensitivity of B. pilosa and C. sumatrensis progenies to glufosinate ammonium. When the plants had reached the reproductive stage, the flower buds were covered with paper bags to prevent cross-pollination and guarantee that only self-pollination would take place. In the third study, the sensitivity range of the progeny of B. pilosa and C. sumatrensis to glufosinate ammonium was investigated; in this experiment, the progenies of ... / Doutor

Magister Scientiae - MSc / This study represents the first structural investigation of any type III glutamine synthetase (GS). The GS, GlnA, from the medically important opportunistic human pathogen Bacteroides fragilis was studied with a view to better understanding its structure/functioning in relation to the extensively characterised GSIs. GSIIIs are the most recently discovered family of GSs and are the most phylogenitically distant GSs from the GSIs. Images (160) of negatively stained rGlnA, expressed in E.coli YMC11 (glnA-), were recorded at 50K magnification using a Leo 912 operating at 120kV with energy filtering coupled to a 4 megapixel CCD camera. An angular refinement based reconstruction strategy was adopted using SPIDER. A reconstruction based on an ab initio starting model, derived by a common-lines based simultaneous minimization of rotationally invariant K-mean clustered class averages, converged to the same structure as a reconstruction based on a GSI starting model to a resolution of 2.1nm as determined by Fourier shell correlation). In contrast to preliminary EM observations, which identified GlnA as a hexamer, this work has revealed a dodecameric structure, with subunits (82.8KDa) arranged in two opposing hexagonal rings with distinct handedness. This is similar to the quaternary structure of GSIs and GlnTs except that the complex is 50% longer and the two rings are not symmetrically related. They differ not only in diameter (16.5 or 15.0nm) but also the degree of separation of subunits and as such the particle possesses only C6 and not D6 symmetry. The finding that particles lie in a preferred orientation, with the larger ring in contact with the carbon support, accounted for this asymmetry, through partial staining. Hexameric views, with similar overall arrangement but larger size in comparison to GSI, were also observed. However, it was uncertain whether these were true hexamers resulting from dissociation of the dodecamers or were a consequence of partial staining. Homology modelling was also undertaken in an attempt to predict the structure of GlnA based on GSI, with a view to interpreting the low resolution EM structure. Due to the failures of state of the art algorithms in detecting the distant homologies between GS families, manual profile-based alignment strategies, incorporating structural information, were employed. Through the first full length alignments of GS sequences from all four families, conservation of all active site residues, core active site αβ barrel fold motifs, and additional previously unreported regions was demonstrated. Docking of these homology models into the 3D structure confirmed the presence of the αβ barrel fold predicted by the bioinformatic analysis of the sequences alone, thus, identifying the indentations between subunits in the volume as putative active sites. In addition to providing unequivocal proof that GlnA is a GS and confirming the presence of putative αβ barrel active site folds, this work has made steps towards understanding the regulation of this enzyme. It is hypothesised that GlnA occurs as both active hexamer and an inactive dodecamer, the interconversion of which, is thought to represent a means of reversible post-translational regulation. / South Africa

This study compared the effects of whey and casein on plasma AA, nitrogen balance (NBAL), glutathione and performance in dieting athletes. Twenty cyclists consumed 40 g·d-1 whey (WHEY) or casein (CAS) for 3 wk. On d 18 – 21 subjects restricted intake to 20 kcal·kg-1·d-1 plus protein supplement. Apparent NBAL was estimated on d 18 – 21 while postabsorptive and 2 h postprandial plasma AA were measured on d 14 and 21. On d 1, 15 and 22 subjects performed an exercise performance test and provided blood for glutathione analysis. Both groups experienced similar negative NBAL (CAS = -19.7 ± 1.4 g, WHEY = -21.4 ± 2.7 g) during energy restriction. There were trends towards a reduction in performance during energy restriction (p = 0.073) and an interaction of group with day (p = 0.072). There were significant main effects of state (postabsorptive = 34.5 ± 2.4 µM, postprandial = 37.1 ± 3.0 µM; p = 0.038) and day (d 14 = 33.8 ± 2.2 µM, d 21 = 37.8 ± 3.2 µM; p = 0.008) on plasma cysteine. There was a significant interaction of state and day on glutamine (p = 0.002), as levels increased 1.3% from postabsorptive to postprandial measurements on d 14, but decreased 4.2% on d 21. The absolute change in postabsorptive cysteine from d 14 to d 21 was correlated with NBAL (r = 0.766, p = 0.01) in CAS but not in WHEY. Plasma glutamine did not correlate with NBAL in either group. / Master of Science

No description available.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.

No description available.

In rodents, stress and corticosteroids rapidly increase excitatory neurotransmission. During excitatory neurotransmission, glutamate concentrations are maintained by conversion of glutamine to glutamate. The hypothesis was that cortisol would alter human prefrontal glutamine or glutamate concentrations. Glutamine and glutamate were measured in prefrontal cortex (n = 12) using 3.0 Tesla proton magnetic resonance spectroscopy (1H-MRS) before and after intravenous cortisol (hydrocortisone 35mg), in a randomized, double blind, placebo-controlled, within-subjects design. Glutamine decreased following cortisol compared with placebo (session by time, F(2,22) = 5.51; p = 0.012), whereas glutamate did not change (F(4,44) = 0.71; p = 0.59). Glutamine may be utilized to maintain glutamate concentrations during increased excitatory neurotransmission following cortisol. A limitation is that 1H-MRS does not measure metabolic flux rates directly. The effects of cortisol on glutamine could be a useful measure of altered central glucocorticoid responses in psychiatric disorders.

No description available.

Thesis (Ph. D.)--Biology, Georgia Institute of Technology, 2005. / Dr Yury Chernoff, Committee Member ; Dr Jung Choi, Committee Member ; Dr Nick Hud, Committee Member ; Dr Roger Wartell, Committee Member ; Dr Harish Radhakrishna, Committee Member. Vita. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 104-132).