Détection de l'activité cérébrale par IRMf (EPI) utilisant un algorithme de croissance de régions

- L'Imagerie par Résonance Magnétique fonctionnelle (IRMf) fournit des séries d'images du cerveau. Le traitement de ces séries permet de mettre en évidence et de localiser l'activité cérébrale avec une précision de l'ordre du millimètre. Nous proposons ici un nouvel algorithme fondé sur une méthode de croissance de régions à partir de germes. Il présente l'avantage d'éliminer les activités non significatives (limitées à un seul voxel) et de classer les voxels en fonction de leur comportement temporel

Characterization of a nuclear pore protein sheds light on the roles and composition of the Toxoplasma gondii nuclear pore complex

International audienceThe nuclear pore is a key structure in eukaryotes regulating nuclear-cytoplasmic transport as well as a wide range of cellular processes. Here, we report the characterization of the first Toxoplasma gondii nuclear pore protein, named TgNup302, which appears to be the orthologue of the mammalian Nup98-96 protein. We produced a conditional knock-down mutant that expresses TgNup302 under the control of an inducible tetracycline-regulated promoter. Under ATc treatment, a substantial decrease of TgNup302 protein in inducible knock-down (iKD) parasites was observed, causing a delay in parasite proliferation. Moreover, the nuclear protein TgENO2 was trapped in the cytoplasm of ATc-treated mutants, suggesting that TgNup302 is involved in nuclear transport. Fluorescence in situ hybridization revealed that TgNup302 is essential for 18S RNA export from the nucleus to the cytoplasm, while global mRNA export remains unchanged. Using an affinity tag purification combined with mass spectrometry, we identified additional components of the nuclear pore complex, including proteins potentially interacting with chromatin. Furthermore, reverse immunoprecipitation confirmed their interaction with TgNup302, and structured illuminated microscopy confirmed the NPC localization of some of the TgNup302-interacting proteins. Intriguingly, facilitates chromatin transcription complex (FACT) components were identified, suggesting the existence of an NPC-chromatin interaction in T. gondii. Identification of TgNup302-interacting proteins also provides the first glimpse at the NPC structure in Apicomplexa, suggesting a structural conservation of the NPC components between distant eukaryotes

Isoprenoid biosynthesis via the methylerythritol phosphate pathway: the (E)-4-hydroxy-3-methylbut-2-enyl diphosphate reductase (LytB/IspH) from Escherichia coli is a [4Fe–4S] protein

AbstractThe last enzyme (LytB) of the methylerythritol phosphate pathway for isoprenoid biosynthesis catalyzes the reduction of (E)-4-hydroxy-3-methylbut-2-enyl diphosphate into isopentenyl diphosphate and dimethylallyl diphosphate. This enzyme possesses a dioxygen-sensitive [4Fe–4S] cluster. This prosthetic group was characterized in the Escherichia coli enzyme by UV/visible and electron paramagnetic resonance spectroscopy after reconstitution of the purified protein. Enzymatic activity required the presence of a reducing system such as flavodoxin/flavodoxin reductase/reduced nicotinamide adenine dinucleotide phosphate or the photoreduced deazaflavin radical

GÖÇ VE YAŞAM

Uluslararası Bakalorya Programı, A1 dersi Türk Dili ve Edebiyatı alanında ele alınan bu tezde, Orhan Kemal'in Gurbet Kuşları adlı yapıtında göç olgusu nedenleri ve sonuçlarıyla beraber incelenmiştir. Göç olgusuyla değişen toplumsal yapı, ekonomik ve kültürel farklılıklar çerçevesinde değerlendirilmiştir. Bu tezin amacı, göç olgusunun toplumsal yapıda alt sınıf ve üst sınıflardaki bireyler üzerindeki etkilerini ortaya koymaktır. Üç ana bölümden oluşan tezin ilk bölümünde yapıta adını veren Gurbet Kuşları kavramı üzerinde durulmuştur. Köylülerin aidiyetsizliği ve uyum sorunu bu bölümde aktarılmıştır. Tezin ikinci bölümünde ise köylülerin köyden kente göç sürecinde yaşadıkları kadın ve erkek figürler üzerinden neden ve sonuçlarıyla işlenmiştir. Tezin üçüncü bölümünde şehirliler başlığı altından genel olarak şehirde – İstanbul – yaşayan insanların göç sürecinde köylülerle yaşadıkları uyumsuzluk ve çatışmalara yer verilmektedir. Çalışmada göç sürecinde şehre yerleşen figürlerin şehirlilerle aralarındaki ekonomik ve kültürel farklılıkların sınıflar arasında geçişe olanak tanımadığı sonucuna varılmıştır

Divergent contribution of the MVA and MEP pathways to the formation of polyprenols and dolichols in Arabidopsis

Isoprenoids, including dolichols (Dols) and polyprenols (Prens), are ubiquitous components of eukaryotic cells. In plant cells, there are two pathways that produce precursors utilized for isoprenoid biosynthesis: the mevalonate (MVA) pathway and the methylerythritol phosphate (MEP) pathway. In this work, the contribution of these two pathways to the biosynthesis of Prens and Dols was addressed using an in planta experimental model. Treatment of plants with pathway-specific inhibitors and analysis of the effects of various light conditions indicated distinct biosynthetic origin of Prens and Dols. Feeding with deuteriated, pathway-specific precursors revealed that Dols, present in leaves and roots, were derived from both MEP and MVA pathways and their relative contributions were modulated in response to precursor availability. In contrast, Prens, present in leaves, were almost exclusively synthesized via the MEP pathway. Furthermore, results obtained using a newly introduced here ‘competitive’ labeling method, designed so as to neutralize the imbalance of metabolic flow resulting from feeding with a single pathway-specific precursor, suggest that under these experimental conditions one fraction of Prens and Dols is synthesized solely from endogenous precursors (deoxyxylulose or mevalonate), while the other fraction is synthesized concomitantly from endogenous and exogenous precursors. Additionally, this report describes a novel methodology for quantitative separation of 2H and 13C distributions observed for isotopologues of metabolically labeled isoprenoids. Collectively, these in planta results show that Dol biosynthesis, which uses both pathways, is significantly modulated depending on pathway productivity, while Prens are consistently derived from the MEP pathway

Experiments in artificial theory of mind: From safety to story-telling

© 2018 Winfield. Theory of mind is the term given by philosophers and psychologists for the ability to form a predictive model of self and others. In this paper we focus on synthetic models of theory of mind. We contend firstly that such models-especially when tested experimentally-can provide useful insights into cognition, and secondly that artificial theory of mind can provide intelligent robots with powerful new capabilities, in particular social intelligence for human-robot interaction. This paper advances the hypothesis that simulation-based internal models offer a powerful and realisable, theory-driven basis for artificial theory of mind. Proposed as a computational model of the simulation theory of mind, our simulation-based internal model equips a robot with an internal model of itself and its environment, including other dynamic actors, which can test (i.e., simulate) the robot's next possible actions and hence anticipate the likely consequences of those actions both for itself and others. Although it falls far short of a full artificial theory of mind, our model does allow us to test several interesting scenarios: in some of these a robot equipped with the internal model interacts with other robots without an internal model, but acting as proxy humans; in others two robots each with a simulation-based internal model interact with each other. We outline a series of experiments which each demonstrate some aspect of artificial theory of mind