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Search Results: 1 - 10 of 5249 matches for " Bernard Payrastre ? "
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A New α5β1 Integrin-Dependent Survival Pathway Through GSK3β Activation in Leukemic Cells
Fabienne De Toni-Costes,Mathieu Despeaux,Jessica Bertrand,Ezzeddine Bourogaa,Lo?c Ysebaert,Bernard Payrastre,Claire Racaud-Sultan
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009807
Abstract: Cell survival mediated by integrin engagement has been implicated in cell adhesion-mediated drug resistance. We have recently demonstrated that the activation of glycogen synthase kinase 3 β (GSK3β) is a new pathway supporting the chemoresistance of leukemic cells adhered to fibronectin.
Phosphatase-Dead Myotubularin Ameliorates X-Linked Centronuclear Myopathy Phenotypes in Mice
Leonela Amoasii equal contributor,Dimitri L. Bertazzi equal contributor,Hélène Tronchère,Karim Hnia,Ga?tan Chicanne,Bruno Rinaldi,Belinda S. Cowling,Arnaud Ferry,Bruno Klaholz,Bernard Payrastre,Jocelyn Laporte ? ,Sylvie Friant ?
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002965
Abstract: Myotubularin MTM1 is a phosphoinositide (PPIn) 3-phosphatase mutated in X-linked centronuclear myopathy (XLCNM; myotubular myopathy). We investigated the involvement of MTM1 enzymatic activity on XLCNM phenotypes. Exogenous expression of human MTM1 in yeast resulted in vacuolar enlargement, as a consequence of its phosphatase activity. Expression of mutants from patients with different clinical progression and determination of PtdIns3P and PtdIns5P cellular levels confirmed the link between vacuolar morphology and MTM1 phosphatase activity, and showed that some disease mutants retain phosphatase activity. Viral gene transfer of phosphatase-dead myotubularin mutants (MTM1C375S and MTM1S376N) significantly improved most histological signs of XLCNM displayed by a Mtm1-null mouse, at similar levels as wild-type MTM1. Moreover, the MTM1C375S mutant improved muscle performance and restored the localization of nuclei, triad alignment, and the desmin intermediate filament network, while it did not normalize PtdIns3P levels, supporting phosphatase-independent roles of MTM1 in maintaining normal muscle performance and organelle positioning in skeletal muscle. Among the different XLCNM signs investigated, we identified only triad shape and fiber size distribution as being partially dependent on MTM1 phosphatase activity. In conclusion, this work uncovers MTM1 roles in the structural organization of muscle fibers that are independent of its enzymatic activity. This underlines that removal of enzymes should be used with care to conclude on the physiological importance of their activity.
Genetic Interaction between MTMR2 and FIG4 Phospholipid Phosphatases Involved in Charcot-Marie-Tooth Neuropathies
Ilaria Vaccari,Giorgia Dina,Hélène Tronchère,Emily Kaufman,Ga?tan Chicanne,Federica Cerri,Lawrence Wrabetz,Bernard Payrastre,Angelo Quattrini,Lois S. Weisman,Miriam H. Meisler,Alessandra Bolino
PLOS Genetics , 2011, DOI: 10.1371/journal.pgen.1002319
Abstract: We previously reported that autosomal recessive demyelinating Charcot-Marie-Tooth (CMT) type 4B1 neuropathy with myelin outfoldings is caused by loss of MTMR2 (Myotubularin-related 2) in humans, and we created a faithful mouse model of the disease. MTMR2 dephosphorylates both PtdIns3P and PtdIns(3,5)P2, thereby regulating membrane trafficking. However, the function of MTMR2 and the role of the MTMR2 phospholipid phosphatase activity in vivo in the nerve still remain to be assessed. Mutations in FIG4 are associated with CMT4J neuropathy characterized by both axonal and myelin damage in peripheral nerve. Loss of Fig4 function in the plt (pale tremor) mouse produces spongiform degeneration of the brain and peripheral neuropathy. Since FIG4 has a role in generation of PtdIns(3,5)P2 and MTMR2 catalyzes its dephosphorylation, these two phosphatases might be expected to have opposite effects in the control of PtdIns(3,5)P2 homeostasis and their mutations might have compensatory effects in vivo. To explore the role of the MTMR2 phospholipid phosphatase activity in vivo, we generated and characterized the Mtmr2/Fig4 double null mutant mice. Here we provide strong evidence that Mtmr2 and Fig4 functionally interact in both Schwann cells and neurons, and we reveal for the first time a role of Mtmr2 in neurons in vivo. Our results also suggest that imbalance of PtdIns(3,5)P2 is at the basis of altered longitudinal myelin growth and of myelin outfolding formation. Reduction of Fig4 by null heterozygosity and downregulation of PIKfyve both rescue Mtmr2-null myelin outfoldings in vivo and in vitro.
Phosphatidylinositol 3-Monophosphate Is Involved in Toxoplasma Apicoplast Biogenesis
Lina Tawk,Jean-Fran?ois Dubremetz,Philippe Montcourrier,Ga?tan Chicanne,Fabrice Merezegue,Véronique Richard,Bernard Payrastre,Markus Meissner,Henri J. Vial,Christian Roy,Kai Wengelnik equal contributor ,Maryse Lebrun equal contributor
PLOS Pathogens , 2011, DOI: 10.1371/journal.ppat.1001286
Abstract: Apicomplexan parasites cause devastating diseases including malaria and toxoplasmosis. They harbour a plastid-like, non-photosynthetic organelle of algal origin, the apicoplast, which fulfils critical functions for parasite survival. Because of its essential and original metabolic pathways, the apicoplast has become a target for the development of new anti-apicomplexan drugs. Here we show that the lipid phosphatidylinositol 3-monophosphate (PI3P) is involved in apicoplast biogenesis in Toxoplasma gondii. In yeast and mammalian cells, PI3P is concentrated on early endosomes and regulates trafficking of endosomal compartments. Imaging of PI3P in T. gondii showed that the lipid was associated with the apicoplast and apicoplast protein-shuttling vesicles. Interference with regular PI3P function by over-expression of a PI3P specific binding module in the parasite led to the accumulation of vesicles containing apicoplast peripheral membrane proteins around the apicoplast and, ultimately, to the loss of the organelle. Accordingly, inhibition of the PI3P-synthesising kinase interfered with apicoplast biogenesis. These findings point to an unexpected implication for this ubiquitous lipid and open new perspectives on how nuclear encoded proteins traffic to the apicoplast. This study also highlights the possibility of developing specific pharmacological inhibitors of the parasite PI3-kinase as novel anti-apicomplexan drugs.
Use of historical data to assess the occurrence of floods in small watersheds in the French Mediterranean area
O. Payrastre, E. Gaume,H. Andrieu
Advances in Geosciences (ADGEO) , 2005,
Abstract: The results of an investigation on historical floods in four watersheds of the Aude region in France are presented herein. Using both, archive documents and field investigations, the discharges of the main historical floods could be estimated for a period ranging from one to two centuries. The use of this data, in addition to systematic discharge measurements (continuous series of about 30 years in each case) shows that the calibration of Gumbel and EVII distributions is highly modified by using historical data, despite of the poor accuracy of discharge estimations for historical floods. In some cases, it is also possible, with a simple test using historical data, to exclude a statistical distribution (Gumbel in the presented case) which is not adapted to represent both historical and systematic data samples. Lastly, the historical data gathered highlights important differences in flood intensities among the four studied watersheds, differences that have now to be explained.
New Formulas for Irregular Sampling of Two-Bands Signals  [PDF]
Bernard Lacaze
Journal of Signal and Information Processing (JSIP) , 2011, DOI: 10.4236/jsip.2011.24035
Abstract: Many sampling formulas are available for processes in baseband (-a,a) at the Nyquist rate a/π. However signals of telecommunications have power spectra which occupate two bands or more. We know that PNS (periodic non-uniform sampling) allow an errorless reconstruction at rate smaller than the Nyquist one. For instance PNS2 can be used in the two-bands case (-a,-b)∪(b,a) at the Landau rate (a-b)/π We prove a set of formulas which are available in cases more general than the PNS2. They take into account two sampling sequences which can be periodic or not and with same mean rate or not.
Pairing Effect on the Binding Energy Curve of N = Z Atomic Nuclei  [PDF]
Bernard Schaeffer
World Journal of Nuclear Science and Technology (WJNST) , 2013, DOI: 10.4236/wjnst.2013.33013

The saw-tooth phenomenon on the binding energy curve of N = Z nuclei is due to the low binding energy between the α-particles. It was suspected by Gamow to be of van der Waals type, found here to be deuteron bonds. The binding energy per nucleon, in absolute value, of an α-particle is larger than any other combination of 4 nucleons. Therefore, the binding energy per nucleon is low for odd-odd N = Z nuclei and maximum for even-even N = Z nuclei. The assumption of N = Z nuclei to be an assembly of α-particles and deuteron bonds predicts the binding energy of the 32 first N = Z nuclei with a rms deviation of 0.25 MeV.

Magic of Language  [PDF]
Bernard Korzeniewski
Open Journal of Philosophy (OJPP) , 2013, DOI: 10.4236/ojpp.2013.34067
Abstract: Language, through the discrete nature of linguistic names and strictly determined grammatical rules, creates absolute, “quantized”, sharply separated “facts” within the external world that is continuous, “fuzzy” and relational in its essence. Therefore, it is similar, in some important sense, to magic, which attributes causal and creative power to magical words and formulas. On the one hand, language increases greatly the effectiveness of the processes of thinking and interpersonal communication, yet, on the other hand, it determines and distorts to a large extent the picture of the world created within the mind. The relatively smallest (but still significant) magical admixture is present in science, because of its relatively reliable methodology, while the largest is found in religion and a large part of philosophy. The magical nature of language also manifests itself in logic and mathematics that refer to ill determined, fuzzy objects, sets and relations in the real world. The meaning of linguistic names is based on the conceptual network—an epiphenomenon (continuous in its essence) of the neural network—where interactions between particular concepts are based on the relation of connotation. The names and formulas of language correspond to these concepts which are best separated and determined. A direct relation of denotation between the elements of language and “facts” of the world is an illusion. While we cannot dispense with language because of its immense usefulness, we must remember about its “fact-creating” nature and influence on our thought and cognitive processes. The picture of the reality created as the result of them is to a large extent formed and deformed by the nature of language, and not by the “immanent” properties of the world in itself.
Formal Similarities between Cybernetic Definition of Life and Cybernetic Model of Self-Consciousness: Universal Definition/Model of Individual  [PDF]
Bernard Korzeniewski
Open Journal of Philosophy (OJPP) , 2013, DOI: 10.4236/ojpp.2013.32049
Abstract: The previously proposed cybernetic definition of a living (biological) individual and the cybernetic model of a psychical individual (a self endowed with subjective consciousness) are extended and compared, and their formal similarities are isolated and highlighted. It is argued that the emergence of the biological level of reality from the physical level and of the psychical level from the biological level is closely analogous. The (biological or psychical) individual is constituted by a network of elements (negative feedbacks/ regulatory mechanisms or neurons/concepts, respectively) that possesses the following common properties: 1) it is intentional (in the operational sense); 2) its elements signify (have sense) by connotation (through relations to each other); 3) it contains an instrumental representation of (some aspects of) the world and 4) it is self-referential i.e. recurrently directed on itself (its own reproduction or representation, respectively). Thus life and self-consciousness have deep, formal, structural similarities when viewed abstractly. The cybernetic definition/model of an individual is also referred to societies/states, companies and other systems. It is postulated that this definition/model is a universal one and can be applied to all possible systems/objects existing in the Universe or constructed in the future by humans.
IUPAC Periodic Table Quantum Mechanics Consistent  [PDF]
Bernard Schaeffer
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.53020

Most periodic tables of the chemical elements are between 96% and 100% in accord with quantum mechanics. Three elements only do not fit correctly into the official tables, in disagreement with the spherical harmonics and the Pauli exclusion principle. Helium, belonging to the s-block, should be placed beside hydrogen in the s-block instead of the p-block. Lutetium and lawrencium belonging to the d-block of the transition metals should not be in the f-block of the lanthanides or the actinoids. With these slight modifications, the IUPAC table becomes quantum mechanics consistent.

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