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Search Results: 1 - 10 of 4705 matches for " Laurent Soustelle "
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UV laser mediated cell selective destruction by confocal microscopy
Laurent Soustelle, Beno?t Aigouy, Marie-Laure Asensio, Angela Giangrande
Neural Development , 2008, DOI: 10.1186/1749-8104-3-11
Abstract: Cell selective destruction provides a fruitful approach to study cell-cell interactions, cell function and cell lineages [1,2]. Laser assisted techniques provide fine control over the selective destruction time during development and allow for targeting of any cell(s) in any pattern(s), which is hardly feasible using genetic approaches [3]. This technique, based on the use of pulsed lasers that destroy cells by high energy deposition, has allowed lineage mapping in Caenorhabditis elegans and has been extensively applied to the large cells of the grasshopper nervous system [1,4,5]. This technique was also used in Drosophila to study different processes, such as embryonic morphogenetic movements [6,7] or the development of the nervous [8] and muscular systems [9]. Until recently, such a technique, however, has been limited to cells that can be identified using Nomarski optics. Although this limit has been partially overcome by the advent of green fluorescent protein (GFP) based transgenesis and the development of epifluorescence set-ups, low levels of GFP expression in the targeted cells and/or high levels of autofluorescence still restrict the use of laser assisted cell selective destruction. We here describe a technique that combines UV laser mediated cell destruction and confocal technology. This technique, which relies on the use of common lasers, allows for high resolution and sensitivity and works efficiently in cell cultures as well as in living animals.Currently used laser assisted techniques for selective cell destruction are based on pulsed lasers and conventional microscopes. To circumvent the limits of such an approach (low signal level, autofluorescence), we have devised a simple and efficient UV laser and confocal based technique and used it to study glial development in Drosophila pupal wings. Upon production of a wing glial precursor, proliferation and migration account for the formation of a continuous sheath along axonal fibers, a process that is nec
Plant Insecticide L-Canavanine Repels Drosophila via the Insect Orphan GPCR DmX
Christian Mitri,Laurent Soustelle,Bérénice Framery,Jo?l Bockaert,Marie-Laure Parmentier,Yves Grau
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000147
Abstract: For all animals, the taste sense is crucial to detect and avoid ingesting toxic molecules. Many toxins are synthesized by plants as a defense mechanism against insect predation. One example of such a natural toxic molecule is l-canavanine, a nonprotein amino acid found in the seeds of many legumes. Whether and how insects are informed that some plants contain l-canavanine remains to be elucidated. In insects, the taste sense relies on gustatory receptors forming the gustatory receptor (Gr) family. Gr proteins display highly divergent sequences, suggesting that they could cover the entire range of tastants. However, one cannot exclude the possibility of evolutionarily independent taste receptors. Here, we show that l-canavanine is not only toxic, but is also a repellent for Drosophila. Using a pharmacogenetic approach, we find that flies sense food containing this poison by the DmX receptor. DmXR is an insect orphan G-protein–coupled receptor that has partially diverged in its ligand binding pocket from the metabotropic glutamate receptor family. Blockade of DmXR function with an antagonist lowers the repulsive effect of l-canavanine. In addition, disruption of the DmXR encoding gene, called mangetout (mtt), suppresses the l-canavanine repellent effect. To avoid the ingestion of l-canavanine, DmXR expression is required in bitter-sensitive gustatory receptor neurons, where it triggers the premature retraction of the proboscis, thus leading to the end of food searching. These findings show that the DmX receptor, which does not belong to the Gr family, fulfills a gustatory function necessary to avoid eating a natural toxin.
Plant Insecticide L-Canavanine Repels Drosophila via the Insect Orphan GPCR DmX
Christian Mitri equal contributor,Laurent Soustelle equal contributor,Bérénice Framery,Jo?l Bockaert,Marie-Laure Parmentier,Yves Grau
PLOS Biology , 2009, DOI: 10.1371/journal.pbio.1000147
Abstract: For all animals, the taste sense is crucial to detect and avoid ingesting toxic molecules. Many toxins are synthesized by plants as a defense mechanism against insect predation. One example of such a natural toxic molecule is l-canavanine, a nonprotein amino acid found in the seeds of many legumes. Whether and how insects are informed that some plants contain l-canavanine remains to be elucidated. In insects, the taste sense relies on gustatory receptors forming the gustatory receptor (Gr) family. Gr proteins display highly divergent sequences, suggesting that they could cover the entire range of tastants. However, one cannot exclude the possibility of evolutionarily independent taste receptors. Here, we show that l-canavanine is not only toxic, but is also a repellent for Drosophila. Using a pharmacogenetic approach, we find that flies sense food containing this poison by the DmX receptor. DmXR is an insect orphan G-protein–coupled receptor that has partially diverged in its ligand binding pocket from the metabotropic glutamate receptor family. Blockade of DmXR function with an antagonist lowers the repulsive effect of l-canavanine. In addition, disruption of the DmXR encoding gene, called mangetout (mtt), suppresses the l-canavanine repellent effect. To avoid the ingestion of l-canavanine, DmXR expression is required in bitter-sensitive gustatory receptor neurons, where it triggers the premature retraction of the proboscis, thus leading to the end of food searching. These findings show that the DmX receptor, which does not belong to the Gr family, fulfills a gustatory function necessary to avoid eating a natural toxin.
Gαo Is Required for L-Canavanine Detection in Drosophila
Isabelle Devambez, Moutaz Ali Agha, Christian Mitri, Jo?l Bockaert, Marie-Laure Parmentier, Frédéric Marion-Poll, Yves Grau, Laurent Soustelle
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063484
Abstract: Taste is an essential sense for the survival of most organisms. In insects, taste is particularly important as it allows to detect and avoid ingesting many plant toxins, such as L-canavanine. We previously showed that L-canavanine is toxic for Drosophila melanogaster and that flies are able to detect this toxin in the food. L-canavanine is a ligand of DmXR, a variant G-protein coupled receptor (GPCR) belonging to the metabotropic glutamate receptor subfamily that is expressed in bitter-sensitive taste neurons of Drosophila. To transduce the signal intracellularly, GPCR activate heterotrimeric G proteins constituted of α, β and γ subunits. The aim of this study was to identify which Gα protein was required for L-canavanine detection in Drosophila. By using a pharmacological approach, we first demonstrated that DmXR has the best coupling with Gαo protein subtype. Then, by using genetic, behavioral assays and electrophysiology, we found that Gαo47A is required in bitter-sensitive taste neurons for L-canavanine sensitivity. In conclusion, our study revealed that Gαo47A plays a crucial role in L-canavanine detection.
Marine Biology: A Sub-Sample of a Vast Topic  [PDF]
Laurent Seuront
Open Journal of Marine Science (OJMS) , 2013, DOI: 10.4236/ojms.2013.32A001
Abstract:

Marine Biology: A Sub-Sample of a Vast Topic

Generalized Powers of Substitution with Pre-Function Operators  [PDF]
Laurent Poinsot
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.47A004
Abstract:

An operator on formal power series of the form S \"\" μS , where μ is an invertible power series, and σ is a series of the form t+\"\"(t2) is called a unipotent substitution with pre-function. Such operators, denoted by a pair (μ σ )  , form a group. The objective of this contribution is to show that it is possible to define a generalized powers for such operators, as for instance fractional powers \"\"σ for every\"\" .

The Mediating Role of the Sense of Relatedness and Task Cohesion in the Relation between Psychological Power Distance and Efficicency of a Working Team  [PDF]
Laurent Auzoult
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.410105
Abstract:

Understanding of the effectiveness of work-teams is a major issue in the business world, where they are expected to facilitate developing individual skills and increasing organizations’ efficiency. Eighty-three engineers working in teams have responded to a questionnaire devised to measure perceptual power distances, the sense of relatedness, cohesion measured by integration around the task, and teams’ effectiveness. Results reveal that “task cohesion” and sense of relatedness mediate the relationship between power distance and perceived effectiveness. These results are related with those observed in the context of the self-determination theory and presented in order to highlight their practical implications.

Health 3.0—The patient-clinician “arabic spring” in healthcare  [PDF]
Serge Gagnon, Laurent Chartier
Health (Health) , 2012, DOI: 10.4236/health.2012.42008
Abstract: A growing number of citizen-patients and clinicians use Communication and Self-Managed Health Technologies (CSMHT) in their relationship. Doing so, they shift from the current paradigm of dependency to a co-responsibility paradigm in healthcare. Facing the runaway utilization of health services, we need to think “outside the box” to unblock the system. A Health 3.0 development model of governance that position patients as primary members of the clinicians’ team is presented to map this institutional transformation. At the practical level, an MD 3.0 relational model and a Citizen-Patient 3.0 behavioral profile are presented.
Deploying Safety-Critical Applications on Complex Avionics Hardware Architectures  [PDF]
Robert Hilbrich, Laurent Dieudonné
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.65028
Abstract:

Aviation electronics (avionics) are sophisticated and distributed systems aboard an airplane. The complexity of these systems is constantly growing as an increasing amount of functionalities is realized in software. Thanks to the performance increase, a hardware unit must no longer be dedicated to a single system function. Multicore processors for example facilitate this trend as they are offering an increased system performance in a small power envelope. In avionics, several system functions could now be integrated on a single hardware unit, if all safety requirements are still satisfied. This approach allows for further optimizations of the system architecture and substantial reductions of the space, weight and power (SWaP) footprint, and thus increases the transportation capacity. However, the complexity found in current safety-critical systems requires an automated software deployment process in order to tap this potential for further SWaP reductions. This article used a realistic flight control system as an example to present a new model-based methodology to automate the software deployment process. This methodology is based on the correctness-by-construction principle and is implemented as part of a systems engineering toolset. Furthermore, metrics and optimization criteria are presented which further help in the automatic assessment and refinement of a generated deployment. A discussion regarding a tighter integration of this approach in the entire avionics systems engineering workflow concludes this article.

Estimating firing rates from calcium signals in locust projection neurons in vivo
Laurent Moreaux,Gilles Laurent
Frontiers in Neural Circuits , 2007, DOI: 10.3389/neuro.04.002.2007
Abstract: Combining intracellular electrophysiology and multi-photon calcium imaging in vivo, we studied the relationship between calcium signals (sampled at 500–750?Hz) and spike output in principal neurons in the locust antennal lobe. Our goal was to determine whether the firing rate of individual neurons can be estimated in vivo with calcium imaging and, if so, to measure directly the accuracy and resolution of our estimates. Using the calcium indicator Oregon Green BAPTA-1, we describe a simple method to reconstruct firing rates from dendritic calcium signals with 80–90% accuracy and 50?ms temporal resolution.
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