Alteration in calcium handling at the subcellular level in mdx myotubes.

In this study, we have tested the hypothesis that augmented [Ca(2+)] in subcellular regions or organelles, which are known to play a key role in cell survival, is the missing link between Ca(2+) homeostasis alterations and muscular degeneration associated with muscular dystrophy. To this end, different targeted chimeras of the Ca(2+)-sensitive photoprotein aequorin have been transiently expressed in subcellular compartments of skeletal myotubes of mdx mice, the animal model of Duchenne muscular dystrophy. Direct measurements of the [Ca(2+)] in the sarcoplasmic reticulum, [Ca(2+)](sr), show a higher steady state level at rest and a larger drop after KCl-induced depolarization in mdx compared with control myotubes. The peaks in [Ca(2+)] occurring in the mitochondrial matrix of mdx myotubes are significantly larger than in controls upon KCl-induced depolarization or caffeine application. The augmented response of mitochondria precedes the alterations in the Ca(2+) responses of the cytosol and of the cytoplasmic region beneath the membrane, which become significant only at a later stage of myotube differentiation. Taking into account the key role played by mitochondria Ca(2+) handling in the control of cell death, our data suggest that mitochondria are potential targets of impaired Ca(2+) homeostasis in muscular dystrophy

2es Rencontres FORMIST - 2002 (Actes complets)

Actes des 2èmes Rencontres FORMIST : Le point sur la formation des usagers ; Réseaux.Doc : formation à la recherche documentaire ; Les formations à l\u27information ; Séduction et partenariat : mise en œuvre de la formation des usagers aux bibliothèques de l\u27Université Libre de Bruxelles ; Formation des étudiants à la maîtrise de l\u27information ; l\u27expérience de l\u27Université des Sciences sociales de Toulouse 1 ; Méthodologie documentaire en BU Sciences : l\u27exemple de Nice, témoignage d\u27une expérience de terrain ; Formation à la recherche documentaire au sein de la Faculté de pharmacie de Lyon (Université Claude-Bernard Lyon 1) ; Un module de méthodologie du travail universitaire original : STIM-Sciences de la Terre en images ; Pédagogie classique versus pédagogie par projets et pédagogie inverse : l\u27expérience de l\u27INSA de Lyon ; La méthodologie du travail universitaire à la bibliothèque de Droit et de Lettres de l\u27Université de La Réunion ; Tables-rondes et synthèse

SLI-1 Cbl Inhibits the Engulfment of Apoptotic Cells in C. elegans through a Ligase-Independent Function

The engulfment of apoptotic cells is required for normal metazoan development and tissue remodeling. In Caenorhabditis elegans, two parallel and partially redundant conserved pathways act in cell-corpse engulfment. One pathway, which includes the small GTPase CED-10 Rac and the cytoskeletal regulator ABI-1, acts to rearrange the cytoskeleton of the engulfing cell. The CED-10 Rac pathway is also required for proper migration of the distal tip cells (DTCs) during the development of the C. elegans gonad. The second pathway includes the receptor tyrosine kinase CED-1 and might recruit membranes to extend the surface of the engulfing cell. Cbl, the mammalian homolog of the C. elegans E3 ubiquitin ligase and adaptor protein SLI-1, interacts with Rac and Abi2 and modulates the actin cytoskeleton, suggesting it might act in engulfment. Our genetic studies indicate that SLI-1 inhibits apoptotic cell engulfment and DTC migration independently of the CED-10 Rac and CED-1 pathways. We found that the RING finger domain of SLI-1 is not essential to rescue the effects of SLI-1 deletion on cell migration, suggesting that its role in this process is ubiquitin ligase-independent. We propose that SLI-1 opposes the engulfment of apoptotic cells via a previously unidentified pathway.National Cancer Institute (U.S.) (Award K08CA104890

Symmetric model of compressible granular mixtures with permeable interfaces

International audienceCompressible granular materials are involved in many applications, some of them being related to energetic porous media. Gas permeation effects are important during their compaction stage, as well as their eventual chemical decomposition. Also, many situations involve porous media separated from pure fluids through two-phase interfaces. It is thus important to develop theoretical and numerical formulations to deal with granular materials in the presence of both two-phase interfaces and gas permeation effects. Similar topic was addressed for fluid mixtures and interfaces with the Discrete Equations Method (DEM) [R. Abgrall and R. Saurel, ``Discrete equations for physical and numerical compressible multiphase mixtures,''J. Comput. Phys. 186 (2), 361-396 (2003)] but it seemed impossible to extend this approach to granular media as intergranular stress [K. K. Kuo, V. Yang, and B. B. Moore, ``Intragranular stress, particle-wall friction and speed of sound in granular propellant beds,'' J. Ballist. 4 (1), 697-730 (1980)] and associated configuration energy [J. B. Bdzil, R. Menikoff, S. F. Son, A. K. Kapila, and D. S. Stewart, `` Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues,'' Phys. Fluids 11, 378 (1999)] were present with significant effects. An approach to deal with fluid-porous media interfaces was derived in Saurel et al. [''Modelling dynamic and irreversible powder compaction,'' J. Fluid Mech. 664, 348-396 (2010)] but its validity was restricted to weak velocity disequilibrium only. Thanks to a deeper analysis, the DEM is successfully extended to granular media modelling in the present paper. It results in an enhanced version of the Baer and Nunziato [''A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,'' Int. J. Multiphase Flow 12 (6), 861-889 (1986)] model as symmetry of the formulation is now preserved. Several computational examples are shown to validate and illustrate method's capabilities. (C) 2014 AIP Publishing LLC

Recombinant aequorin as tool for monitoring calcium concentration in subcellular compartments.

not abstract availabl

The function of graphic signs in prehistoric societies: The case of Cantabrian quadrilateral signs

International audienc

Alteration in calcium handling at the subcellular level in mdx myotubes.

In this study, we have tested the hypothesis that augmented [Ca(2+)] in subcellular regions or organelles, which are known to play a key role in cell survival, is the missing link between Ca(2+) homeostasis alterations and muscular degeneration associated with muscular dystrophy. To this end, different targeted chimeras of the Ca(2+)-sensitive photoprotein aequorin have been transiently expressed in subcellular compartments of skeletal myotubes of mdx mice, the animal model of Duchenne muscular dystrophy. Direct measurements of the [Ca(2+)] in the sarcoplasmic reticulum, [Ca(2+)](sr), show a higher steady state level at rest and a larger drop after KCl-induced depolarization in mdx compared with control myotubes. The peaks in [Ca(2+)] occurring in the mitochondrial matrix of mdx myotubes are significantly larger than in controls upon KCl-induced depolarization or caffeine application. The augmented response of mitochondria precedes the alterations in the Ca(2+) responses of the cytosol and of the cytoplasmic region beneath the membrane, which become significant only at a later stage of myotube differentiation. Taking into account the key role played by mitochondria Ca(2+) handling in the control of cell death, our data suggest that mitochondria are potential targets of impaired Ca(2+) homeostasis in muscular dystrophy