École Normale Supérieure

About: École Normale Supérieure is a other organization based out in Paris, Île-de-France, France. It is known for research contribution in the topics: Population & Catalysis. The organization has 68439 authors who have published 99414 publications receiving 3092008 citations.

Manipulation of light signal transduction as a means of modifying fruit nutritional quality in tomato

Abstract: Fruit constitutes a major component of human diets, providing fiber, vitamins, and phytonutrients. Carotenoids are a major class of compounds found in many fruits, providing nutritional benefits as precursors to essential vitamins and as antioxidants. Although recent gene isolation efforts and metabolic engineering have primarily targeted genes involved in carotenoid biosynthesis, factors that regulate flux through the carotenoid pathway remain largely unknown. Characterization of the tomato high-pigment mutations (hp1 and hp2) suggests the manipulation of light signal transduction machinery may be an effective approach toward practical manipulation of plant carotenoids. We demonstrate here that hp1 alleles represent mutations in a tomato UV-DAMAGED DNA-BINDING PROTEIN 1 (DDB1) homolog. We further demonstrate that two tomato light signal transduction genes, LeHY5 and LeCOP1LIKE, are positive and negative regulators of fruit pigmentation, respectively. Down-regulated LeHY5 plants exhibit defects in light responses, including inhibited seedling photomorphogenesis, loss of thylakoid organization, and reduced carotenoid accumulation. In contrast, repression of LeCOP1LIKE expression results in plants with exaggerated photomorphogenesis, dark green leaves, and elevated fruit carotenoid levels. These results suggest genes encoding components of light signal transduction machinery also influence fruit pigmentation and represent genetic tools for manipulation of fruit quality and nutritional value.

Reasoning, Learning, and Creativity: Frontal Lobe Function and Human Decision-Making

Abstract: The frontal lobes subserve decision-making and executive control—that is, the selection and coordination of goal-directed behaviors. Current models of frontal executive function, however, do not explain human decision-making in everyday environments featuring uncertain, changing, and especially open-ended situations. Here, we propose a computational model of human executive function that clarifies this issue. Using behavioral experiments, we show that unlike others, the proposed model predicts human decisions and their variations across individuals in naturalistic situations. The model reveals that for driving action, the human frontal function monitors up to three/four concurrent behavioral strategies and infers online their ability to predict action outcomes: whenever one appears more reliable than unreliable, this strategy is chosen to guide the selection and learning of actions that maximize rewards. Otherwise, a new behavioral strategy is tentatively formed, partly from those stored in long-term memory, then probed, and if competitive confirmed to subsequently drive action. Thus, the human executive function has a monitoring capacity limited to three or four behavioral strategies. This limitation is compensated by the binary structure of executive control that in ambiguous and unknown situations promotes the exploration and creation of new behavioral strategies. The results support a model of human frontal function that integrates reasoning, learning, and creative abilities in the service of decision-making and adaptive behavior.

Molecular basis of NMDA receptor functional diversity.

Abstract: NMDA receptors (NMDARs) form glutamate-gated ion channels widely expressed in the central nervous system and highly permeable to calcium ions. NMDARs have always attracted much attention because of their central implications in numerous physiological and pathological processes including synaptic plasticity and excitotoxicity. Ever since the discovery of NMDARs three decades ago, it has been acknowledged that native NMDARs do not form a homogeneous population of receptors but rather exist as multiple subpopulations that differ in their functional properties and, presumably, physiopathological roles. NMDARs are in fact large multi-subunit complexes arranged into heteromeric assemblies composed of four homologous subunits within a repertoire of over 10 different subunits: eight GluN1 isoforms, four GluN2 subunits (A-D) and two GluN3 subunits (A and B). This review gives an overview of our current knowledge of the molecular basis underlying NMDAR functional heterogeneity. The modular architecture and expression profile of NMDAR subunits together with the basic principles of NMDAR operation are first introduced. The influence of subunit composition on receptor functional properties is then described, with emphasis put on the impact of differential incorporation of GluN1 and GluN2 subunits (the roles of GluN3 subunits being less well understood). The final part presents recent studies revealing the central, and largely unsuspected, role of the extracellular N-terminal region in generating functional diversity of NMDARs. Indeed, the identity of this region, which is distal to the membrane and precedes the agonist-binding domains, determines key biophysical and pharmacological attributes of the various NMDAR subtypes.

An integrated process to produce vanillin and lignin-based polyurethanes from Kraft lignin

Abstract: The aim of this manuscript is to present an integrated process that includes reaction and separation steps for producing vanillin and lignin-based polyurethanes from Kraft lignin. It provides details about lignin oxidation and subsequent vanillin recovery, as well as, the synthesis of lignin-based polyurethanes. The oxidation of Kraft lignin in alkaline medium has been carried out in a batch reactor and the optimum operational conditions for vanillin production obtained. The feasibility of a continuous process for vanillin production has been analyzed using a structured bubble column reactor. The generated reaction stream (degraded lignin and sodium vanillate) was further subjected to an ultrafiltration process to recover the vanillate. An ion-exchange process allows recovering the vanillin by passing the vanillate solution through a column packed with an ion-exchange resin in H+ form. The remaining lignin can