25 research outputs found
Thomas Melone, CHINUA ACHEBE et la Tragédie de l’Histoire. Thèse de doctorat d’État, soutenue à Grenoble et publiée aux Éditions Présence Africaine, Paris. 1973, 310 p.
Spodoptera frugiperda transcriptional response to infestation by Steinernema carpocapsae
Steinernema carpocapsae is an entomopathogenic nematode (EPN) used in biological control of agricultural pest insects. It enters the hemocoel of its host via the intestinal tract and releases its symbiotic bacterium Xenorhabdus nematophila. In order to improve our knowledge about the physiological responses of its different hosts, we examined the transcriptional responses to EPN infestation of the fat body, the hemocytes and the midgut in the lepidopteran pest Spodoptera frugiperda. The tissues poorly respond to the infestation at an early time post-infestation of 8 h with only 5 genes differentially expressed in the fat body of the caterpillars. Strong transcriptional responses are observed at a later time point of 15 h post-infestation in all three tissues. Few genes are differentially expressed in the midgut but tissue-specific panels of induced metalloprotease inhibitors, immune receptors and antimicrobial peptides together with several uncharacterized genes are up-regulated in the fat body and the hemocytes. Among the most up-regulated genes, we identified new potential immune effectors, unique to Lepidoptera, which show homology with bacterial genes of unknown function. Altogether, these results pave the way for further functional studies of the responsive genes' involvement in the interaction with the EPN
High-Energy Al/CuO Nanocomposites Obtained by DNA-Directed Assembly
Over the next few years, it is expected that new, energetic, multifunctional materials will be engineered. There is a need for new methods to assemble such materials from manufactured nanopowders. In this article, we demonstrate a DNA-directed assembly procedure to produce highly energetic nanocomposites by assembling Al and CuO nanoparticles into micrometer-sized particles of an Al/CuO nanocomposite, which has exquisite energetic performance in comparison with its physically mixed Al/CuO counterparts. Using 80 nm Al nanoparticles, the heat of reaction and the onset temperature are 1.8 kJ g-1 and 410 degrees C, respectively. This experimental achievement relies on the development of simple and reliable protocols to disperse and sort metallic and metal oxide nanopowders in aqueous solution and the establishment of specific DNA surface-modification processes for Al and CuO nanoparticles. Overall, our work, which shows that DNA can be used as a structural material to assemble Al/Al, CuO/CuO and Al/CuO composite materials, opens a route for molecular engineering of the material on the nanoscale
Spodoptera frugiperda transcriptional response to infestation by Steinernema carpocapsae
Steinernema carpocapsae is an entomopathogenic nematode (EPN) used in biological control of agricultural pest insects. It enters the hemocoel of its host via the intestinal tract and releases its symbiotic bacterium Xenorhabdus nematophila. In order to improve our knowledge about the physiological responses of its different hosts, we examined the transcriptional responses to EPN infestation of the fat body, the hemocytes and the midgut in the lepidopteran pest Spodoptera frugiperda. The tissues poorly respond to the infestation at an early time post-infestation of 8 h with only 5 genes differentially expressed in the fat body of the caterpillars. Strong transcriptional responses are observed at a later time point of 15 h post-infestation in all three tissues. Few genes are differentially expressed in the midgut but tissue-specific panels of induced metalloprotease inhibitors, immune receptors and antimicrobial peptides together with several uncharacterized genes are up-regulated in the fat body and the hemocytes. Among the most up-regulated genes, we identified new potential immune effectors, unique to Lepidoptera, which show homology with bacterial genes of unknown function. Altogether, these results pave the way for further functional studies of the responsive genes' involvement in the interaction with the EPN
Continuous lipase-catalyzed production of esters from crude high-oleic sunflower oil
International audienceThe objective of this work was to develop an economically relevant enzymatic process of butyl ester production using crude high-oleic sunflower oil. Novozym 435, a non-regiospecific biocatalyst, provided the best compromise between activity and butyl-ester yield. The inhibition caused by the presence of phopholipids in crude oil was eliminated by using tert-butanol. It demonstrates the key role of the medium polarity in order to insure the stability of a process. Initial substrate concentrations and their molar ratio were optimized in a continuous packed-bed reactor to maximize product yield and productivity. The best compromise was obtained for an initial oil concentration of 500 mM and a molar ratio of 5. It enabled a high productivity of 13.8 tons year(-1) kg Novozym 435(-1) with a butyl-ester purity of 96.5% to be obtained. Experiments with the continuous reactor were performed over 50 days without any loss of enzyme activity. (C) 2011 Published by Elsevier Ltd
Effects of Rehabilitation on Long-COVID-19 Patient’s Autonomy, Symptoms and Nutritional Observance
Background: Despite significant improvements in COVID-19 therapy, many patients still present with persistent symptoms and quality-of-life alterations. The aim of this study was to simultaneously investigate the long-term evolution of autonomy, malnutrition and long-lasting symptoms in people infected with COVID-19 and hospitalized in the ICU. Method: Patients’ clinical characteristics; extent of their loss of autonomy based on “Autonomie Gérontologie Groupes Iso-Ressources” (AG-GIR) classification; nutritional status while following the French and Global Leadership Initiative on Malnutrition (GLIM) recommendations; and symptom evolutions before infection, during hospitalization and rehabilitation, and up to 6 months after returning home were determined in thirty-seven patients. Results: Prior to a COVID-19 infection, all patients were autonomous, but upon admission to the rehabilitation center (CRM), 39% of them became highly dependent. After discharge from the center and 6 months after returning home, only 6 and 3%, respectively, still required considerable assistance. Of these thirty-seven patients, 11% were moderately malnourished and 81% presented with severe malnutrition, with a significant correlation being observed between malnutrition and autonomy (p < 0.05). Except for fatigue, which persisted in 70% of the patients 6 months after discharge from rehabilitation, all other symptoms decreased significantly. Conclusions: This study shows a striking decrease in autonomy associated with malnutrition after hospitalization for a COVID-19 infection and a clear beneficial effect from personalized rehabilitation. However, although almost all patients regained autonomy 6 months after returning home, they often still suffer from fatigue. Patient compliance with their nutritional recommendations deserves further improvement, preferably through personalized and persistent follow-up with the patient
La protéine FliZ de Xenorhabdus nematophila : un régulateur pléiotropique
International audienc
FliZ is a global regulatory protein affecting the expression of flagellar and virulence genes in individual Xenorhabdus nematophila bacterial cells
Heterogeneity in the expression of various bacterial genes has been shown to result in the presence of individuals with different phenotypes within clonal bacterial populations. The genes specifying motility and flagellar functions are coordinately regulated and form a complex regulon, the flagellar regulon. Complex interplay has recently been demonstrated in the regulation of flagellar and virulence gene expression in many bacterial pathogens. We show here that FliZ, a DNA-binding protein, plays a key role in the insect pathogen, Xenorhabdus nematophila, affecting not only hemolysin production and virulence in insects, but efficient swimming motility. RNA-Seq analysis identified FliZ as a global regulatory protein controlling the expression of 278 Xenorhabdus genes either directly or indirectly. FliZ is required for the efficient expression of all flagellar genes, probably through its positive feedback loop, which controls expression of the flhDC operon, the master regulator of the flagellar circuit. FliZ also up- or downregulates the expression of numerous genes encoding non-flagellar proteins potentially involved in key steps of the Xenorhabdus lifecycle. Single-cell analysis revealed the bimodal expression of six identified markers of the FliZ regulon during exponential growth of the bacterial population. In addition, a combination of fluorescence-activated cell sorting and RT-qPCR quantification showed that this bimodality generated a mixed population of cells either expressing ("ON state") or not expressing ("OFF state") FliZ-dependent genes. Moreover, studies of a bacterial population exposed to a graded series of FliZ concentrations showed that FliZ functioned as a rheostat, controlling the rate of transition between the "OFF" and "ON" states in individuals. FliZ thus plays a key role in cell fate decisions, by transiently creating individuals with different potentials for motility and host interactions
Control of nerve cord formation by Engrailed and Gooseberry-Neuro: A multi-step, coordinated process
One way to better understand the molecular mechanisms involved in the construction of a nervous system is to identify the downstream effectors of major regulatory proteins. We previously showed that Engrailed (EN) and Gooseberry-Neuro (GsbN) transcription factors act in partnership to drive the formation of posterior commissures in the central nervous system of Drosophila. In this report, we identified genes regulated by both EN and GsbN through chromatin immunoprecipitation ("ChIP on chip") and transcriptome experiments, combined to a genetic screen relied to the gene dose titration method. The genomic-scale approaches allowed us to define 175 potential targets of EN-GsbN regulation. We chose a subset of these genes to examine ventral nerve cord (VNC) defects and found that half of the mutated targets show clear VNC phenotypes when doubly heterozygous with en or gsbn mutations, or when homozygous. This strategy revealed new groups of genes never described for their implication in the construction of the nerve cord. Their identification suggests that, to construct the nerve cord, EN-GsbN may act at three levels, in: (i) sequential control of the attractive-repulsive signaling that ensures contralateral projection of the commissural axons, (ii) temporal control of the translation of some mRNAs, (iii) regulation of the capability of glial cells to act as commissural guideposts for developing axons. These results illustrate how an early, coordinated transcriptional control may orchestrate the various mechanisms involved in the formation of stereotyped neuronal networks. They also validate the overall strategy to identify genes that play crucial role in axonal pathfinding