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The Global ETD Search service is a free service for researchers
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Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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Showing 131 to 137 of 137 (0.076 seconds)| 131 |
Etude des sources de carbone et d'énergie pour la synthèse des lipides de stockage chez la microalgue verte modèle Chlamydomonas reinhardtii / Study of carbon and energy sources for storage lipid synthesis in model green microalga Chlamydomonas reinhardtiiLiang, Yuanxue 17 January 2019 (has links)
Les triacylglycérols d'algues (TAG) représentent une source prometteuse de biocarburants. Les principales étapes de la synthèse des acides gras et du métabolisme du TAG des algues ont été déduites de celles des plantes terrestres, mais on en sait peu sur les sources de carbones et d’énergie intervenant dans la synthèse de lipides de réserve. Nous avons donc étudié la synthèse des acides gras chez l’algue modèle Chlamydomonas reinhardtii en utilisant une combinaison d'approches génétiques, biochimiques et microscopiques. Plus précisément, j'ai d'abord examiné la localisation subcellulaire de gouttelettes de lipides dans des cellules d'algues exposées à une forte lumière, conditions où une plus grande quantité de pouvoir réducteur est produite. J'ai ensuite contribué à mettre en évidence que la bêta-oxydation des acides gras est un processus peroxysomal, et que pendant une carence en azote réalisée en conditions photoautotrophe, des mutants dépourvus de la malate déshydrogénase 2 peroxysomale (mdh2) accumulent 50% plus TAG que les souches parentales. Ces résultats nous ont permis de mettre en évidence l'importance du contexte redox cellulaire sur la synthèse lipidique. Cette étude a également permis de révéler l’existence d'un échange d’énergie entre le peroxysome et le chloroplaste. Enfin, en caractérisant des mutants déficients dans la dégradation des acides aminés à chaîne ramifiée (BCAA), j'ai montré que le catabolisme des BCAAs joue un double rôle dans la synthèse de TAG en fournissant des précurseurs carbonés et de l'ATP. L'ensemble de ces travaux ouvert de nouvelles pistes pour l'amélioration génétique future de souches d'algues pour la production de biocarburants. / Algal triacylglycerols (TAG) represent a promising source for biofuel. The major steps for fatty acid synthesis and TAG metabolism have been deduced based on that of land plants, but little is known about carbon and energy sources. To address this question, we investigated fatty acid synthesis in algal cells using a combination of genetic, biochemical and microscopic approaches in the model microalga Chlamydomonas reinhardtii. Specifically, I first examined subcellular localization of lipid droplets in algal cells exposed to high light, a condition favoring production of reducing power. Secondly, I contributed to put on evidence that the beta-oxidation of fatty acids is a peroxisomal process, and that during photoautotrophic nitrogen starvation, knock-out mutants of the peroxisomal malate dehydrogenase 2 (mdh2) made 50% more TAG than parental strains, highlighting the importance of cellular redox context on lipid synthesis. This study also revealed for the first time the occurrence of an energy trafficking pathway from peroxisome to chloroplast. And finally, by characterizing mutants defected in degradation of branched-chain amino acids (BCAAs), I showed that BCAA catabolism plays a dual role in TAG synthesis via providing carbon precursors and ATP. Taken together, this work highlighted the complex interplay between carbon and energy metabolism in green photosynthetic cells, and pointed future directions for genetic improvement of algal strains for biofuel productions.
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Die Rolle der beiden Transkriptionsfaktoren AtbZIP1 und AtbZIP53 aus Arabidopsis thaliana in der Anpassung des pflanzlichen Metabolismus an Energiemangelbedingungen / The function of the Arabidopsis thaliana transcription factors AtbZIP1 and AtbZIP53 in reprogramming plant's metabolism during low energy stressDietrich, Katrin 29 April 2010 (has links)
No description available.
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Transcriptional Regulation and Differentiation in Saccharomyces and Aspergillus: jlbA, RPS26, and ARO3/4 / Transkriptionelle Regulation und Differzierung in Saccharomyces und Aspergillus: jlbA, RPS26, and ARO3/4Strittmatter, Axel 06 May 2003 (has links)
No description available.
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Appropriating Judean post-exilic literature in a postcolonial discourse : a case for ZimbabweRugwiji, Temba 06 1900 (has links)
The narratives about the postexilic Judean community are an ancient biblical account of the
socio-economic and political experiences of the Judeans when they were finally restored back to
Judah from Babylonian captivity. Although the Judean restoration was celebrated when they
were restored by King Cyrus’ decree, real freedom did not prevail in the Persian province of
Yehud; corruption, usury, greed, oppression, enslavement and loss of property impacted
negatively on the poor. The leadership expropriated from poor citizens land, vineyards, and
houses in exchange for food. In addition, the governors also charged heavy interest on money
borrowed by poor members of society. Parents and their children were subjected to enslavement.
In response to these corrupt practices, Nehemiah challenged the leadership to stop oppressing the
poor. Nehemiah went further to provide food to the starving Judeans and other people from
surrounding nations which served as a stimulus to strive towards alleviating poverty and starvation among communities.
By employing an approach known as hermeneutics of appropriation, this thesis
appropriates the experience of the postexilic Judean community to the post-independence
Zimbabwean context. Between the years 1999 and 2008 many people lost their lives due to
unemployment and lack of income, shelter, nutrition, and access to health-care facilities because
of the economic meltdown following the controversial fast-track land reform programme in
Zimbabwe. The majority of people are still experiencing the negative impact of the land reform
as people strive to make a living in the absence of jobs and income scarcity. Corruption by the
leadership has continued to further exacerbate starvation among the poor until today.This study attempts to employ the biblical Nehemiah’s social justice reforms (Neh 5) to
challenge the Zimbabwean leadership to focus on rebuilding the country which was ravaged by a
decade of both political and socio-economic crises. Lessons drawn from Nehemiah would be
used to stimulate the leadership in the Zimbabwean government and members of society at large,
to strive towards helping the poor and alleviating poverty. / Biblical and Ancient Studies / D. Litt. et Phil. (Biblical Studies)
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The influence of bottom-up effects on trophic cascades : a case study of Orchestia (Amphipoda) affecting redshank (Tringa totanus) predation risk in a saltmarsh ecosystemKenworthy, Nigel January 2018 (has links)
Previous research into bottom-up processes on saltmarshes has mainly focused on the influence of plant succession on herbivores. This study will present original research exploring the influence of bottom-up processes in a saltmarsh ecosystem between three trophic levels: Orchestia, redshanks, and sparrowhawks. Density dependence, may be the dominant top-down effect when higher numbers of sparrowhawks and redshanks are present, and may mask top-down and bottom-up trait effects which are constant. Bottom-up effects begin to emerge when cold conditions force redshanks from muddy creeks onto the saltmarsh to forage for Orchestia, because their primary prey, Corophium become less available. Larger flocks form and feeding on Orchestia requires them to balance a need to profit from the best available feeding patches and to be vigilant to sparrowhawk attack. Redshank vulnerability is compounded, because Orchestia hide in cold temperatures, so probing in the soil with their heads down makes them more vulnerable to sparrowhawk attack. Larger flocks may be able to exploit areas closer to sparrowhawk-concealing cover at the terrestrial boundary because they feel safer in greater numbers. Warmer temperatures make Orchestia more active which attracts redshanks, which can simultaneously feed and be vigilant because they peck and catch crawling and jumping Orchestia with their heads up. Consequently, increased flock size may temporarily depress Orchestia abundance, so that redshanks become spaced, leaving isolated individuals more vulnerable to attack. Therefore, it is a temperature-dependent bottom-up process which impacts upon both Orchestia and redshank behaviour, which then may influence the hunting success of sparrowhawks. Whether the characteristics of this saltmarsh ecosystem and the trophic dynamics can be compared to other examples is questionable. Saltmarshes probably differ in their topography and the way in which environmental conditions affect them that then defines which species are present and how these species interact.
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Network flux analysis of central metabolism in plantsMasakapalli, Shyam Kumar January 2011 (has links)
The aim of this thesis was to develop stable-isotope steady-state metabolic flux analysis (MFA) based on <sup>13</sup>C labeling to quantify intracellular fluxes of central carbon metabolism in plants. The experiments focus on the analysis of a heterotrophic cell suspension culture of Arabidopsis thaliana (L) Heynh. (ecotype Landsberg erecta). The first objective was to develop a robust methodology based on combining high quality steady-state stable labeling data, metabolic modeling and computational analysis. A comprehensive analysis of the factors that influence the outcome of MFA was undertaken and best practice established. This allowed a critical analysis of the subcellular compartmentation of carbohydrate oxidation in the cell culture. The second objective was to apply the methodology to nutritional perturbations of the cell suspension. A comparison of growth on different nitrogen sources revealed that transfer to an ammonium-free medium: (i) increased flux through the oxidative pentose phosphate pathway (oxPPP) by 10% relative to glucose utilisation; (ii) caused a substantial decrease in entry of carbon into the tricarboxylic acid cycle (TCA); and (iii) increased the carbon conversion efficiency from 55% to 69%. Although growth on nitrate alone might be expected to increase the demand for reductant, the cells responded by decreasing the assimilation of inorganic N. Cells were also grown in media containing different levels of inorganic phosphate (Pi). Comparison of the flux maps showed that decreasing Pi availability: (i) decreased flux through the oxPPP; (ii) increased the proportion of substrate fully oxidised by the TCA cycle; and (iii) decreased carbon conversion efficiency. These changes are consistent with redirection of metabolism away from biosynthesis towards cell maintenance as Pi is depleted. Although published genome-wide transcriptomic and metabolomic studies suggest that Pi starvation leads to the restructuring of carbon and nitrogen metabolism, the current analysis suggests that the impact on metabolic organisation is much less extreme.
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Les écritures de la faim : éléments pour une ontologie de la faim / The writings of hunger : elements for an ontology of hunger / As escrituras da fome : elementos para uma ontologia da fomeLucereau, Jérôme 13 December 2016 (has links)
Le thème de la faim est récurrent dans les littératures du monde entier. primordial, originel, ce thème, dont le champ lexical est souvent convoqué pour attester de l'importance des pulsions humaines, ne fait pourtant l'objet, jusqu'à présent, que de peu d'intérêts de la part des spécialistes de la littérature générale comparée tout comme, d'ailleurs, de la part des philosophes. il s'agit donc d'établir un corpus représentatif des typologies d'écriture de la faim, de proposer une ou plusieurs taxinomie(s) pour, ensuite, approfondir l'analyse critique des différents discours de la faim par plusieurs topiques portant sur l'identité des affamés, les mythes de la faim, la mystique,le jeûne, l'humour de la faim ou bien encore les conséquences particulières de la faim lorsqu'elle est instrumentalisée par un pouvoir politique. cette large analyse critique des différents discours de (et sur) la faim doit permettre d'envisager la crédibilité et les éléments structurants de ce qui pourrait être désigné comme une ‘ontologie de la faim' au sens d'une refondation des rapports de l'homme et de son environnement. le corpus d'œuvres n'est pas restreint à une époque ou à une zone géographique particulière. il s'agit de puiser tout autant dans les littératures anciennes, classiques, modernes, postmodernes que contemporaines dans la mesure où la faim n'est pas l'apanage d'un temps ou d'une civilisation particuliers mais une donnée brute, première et native de l'humain. / The theme of hunger is recurrent in the literatures of the entire world. Primordial, original, this theme, which the lexical field is often summoned to attest to the importance of human impulses, is not yet a subject of great interest on the part of literary scholars General and compared, as well as from the philosophers. The purpose of this work is therefore to establish a representative pattern of writings of the hunger, to define typologies of hunger, to provide one or more taxonomy (s) to then deepen the critical analysis of various speeches from hunger by several topics as the identity of the hungry man, hunger myths, mysticism and fasting, the humour of the hunger, the particular consequences of hunger when it is manipulated by a political power, the ethics of starvation, etc. This broad critical analysis of the different discourses of hunger should allow to consider the credibility and the structuring elements of what could be called an "ontology of hunger" in the sense of a radical reform and rebuilding of the reports of the man and his environment. The references used in this work are not restricted to a time or a particular geographical area. We’ll tap as much in ancient literatures, classical, modern, postmodern, contemporary as well as technical studies because hunger is not the prerogative of a time or a particular civilization but raw, first and original data of the human being. / O tema da fome é quase sistemático nas literaturas do mundo inteiro. Primordial, original, esse assunto (cuja léxico é bastante utilizado como campo metafórico para descrever as pulsões humanas, (amor, paixão, ódio, etc.)foi, portanto, pouco examinado e são poucas as estudas que se focalizam sobre este tema, seja literárias ou filosóficas.O alcance da tese é descrever essa "terra desconhecida" e propor uma taxinomia dos famintos assim que, depois de pesquisar a identidade dos famintos, os mitos da fome, a mística dela, o humor e as consequências sobre a política, o poder e os aspectos jurídicos, elaborar um ontologia da fome ou, pelo menos, os primeiros elementos desse ontologia que poderia liderar uma mudança importante sobre a origem do sentido ética da fome.
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