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Search Results: 1 - 10 of 4693 matches for " Catherine Serres "
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Zona pellucida from fertilised human oocytes induces a voltage-dependent calcium influx and the acrosome reaction in spermatozoa, but cannot be penetrated by sperm
Catherine Patrat, Jana Auer, Patricia Fauque, Roger L Leandri, Pierre Jouannet, Catherine Serres
BMC Developmental Biology , 2006, DOI: 10.1186/1471-213x-6-59
Abstract: The hZP of fertilised oocytes retained their ability to bind sperm (albeit less strongly than that from unfertilised oocytes), to induce an intraspermatic calcium influx through voltage-dependent channels similar to that observed with hZP from unfertilised oocytes and to promote the acrosome reaction at a rate similar to that induced by the ZP of unfertilised oocytes (61.6 ± 6.2% vs60.7 ± 9.1% respectively). Conversely, the rate of hZP penetrated by sperm was much lower for fertilised than for unfertilised oocytes (19% vs 57% respectively, p < 0.01). We investigated the status of ZP2 in the oocytes used in the functional tests, and demonstrated that sperm binding and acrosome reaction induction, but not ZP penetration, occurred whether or not ZP2 was cleaved.The change in ZP function induced by fertilisation could be different in human and mouse species. Our results suggest a zona blocking to polyspermy based at the sperm penetration level in humans.Sperm interaction with the extracellular matrix surrounding the oocyte, the zona pellucida (ZP), is a key step in mammalian fertilisation. The structure and function of the ZP were first studied in mice in the 1980s [1-3]. Mouse ZP contains three glycoproteins: ZP1, ZP2 and ZP3. ZP3 binds to primary receptors on capacitated spermatozoa, inducing a cascade of intraspermatic events including the biphasic calcium influx leading to the acrosome reaction (AR). Following the AR, spermatozoa remain bound to the ZP via ZP2; they then penetrate the ZP and fuse with the egg plasma membrane [4]. The fertilisation is followed by the fusion of peripheral cortical granules with the vitelline membrane, resulting in the discharge of the contents of these granules into the perivitelline space. This exocytosis modifies the ZP matrix such that sperm no longer bind to or penetrate ZP, preventing polyspermy.Our understanding at a molecular level of gamete interaction in humans is much more restricted than for mice and other mammalian species
Gene expression regulation in the context of mouse interspecific mosaic genomes
David L'H?te, Catherine Serres, Reiner A Veitia, Xavier Montagutelli, Ahmad Oulmouden, Daniel Vaiman
Genome Biology , 2008, DOI: 10.1186/gb-2008-9-8-r133
Abstract: Most genes (75%) were not transcriptionally modified either in the IRCSs or in the parent M. spretus mice, compared to M. musculus. The expression levels of most of the remaining transcripts were 'dictated' by either M. musculus transcription factors ('trans-driven'; 20%), or M. spretus cis-acting elements ('cis-driven'; 4%). Finally, 1% of transcripts were dysregulated following a cis-trans mismatch. We observed a higher sequence divergence between M. spretus and M. musculus promoters of strongly dysregulated genes than in promoters of similarly expressed genes.Our study indicates that it is possible to classify the molecular events leading to expressional alterations when a homozygous graft of foreign genome segments is made in an interspecific host genome. The inadequacy of transcription factors of this host genome to recognize the foreign targets was clearly the major path leading to dysregulation.Speciation is defined as the evolutionary process generating new species. It relies on reproductive isolation leading to the separate evolution of genomes. In the 'house mouse species complex' genomic exchanges do occur, and the laboratory mouse itself is considered as a mosaic of other subspecies. Indeed, laboratory mouse strains have originated from a limited number of founder populations of mixed genetic constitution [1,2].A recent analysis of the fine structure of single nucleotide polymorphism (SNP) variation in the mouse genome revealed the existence of long segments with extremely high levels of polymorphism (one-third of the genome). This highly polymorphic subgenome is expected to originate partly from multiple subspecies [2], which suggests that the genomes of inbred strains (that is, Mus musculus) are mosaics of chromosome segments derived from other subspecies [1]. These results have been confirmed and extended to other mouse strains derived from the wild [3].In spite of the accumulating evidence pointing to the mosaic nature of the inbred mouse genome in s
On Zermelo'-like problems: a Gauss-Bonnet inequality and a E. Hopf theorem
Ulysse Serres
Mathematics , 2007,
Abstract: The goal of this paper is to describe Zermelo's navigation problem on Riemannian manifolds as a time-optimal control problem and give an efficient method in order to evaluate its control curvature. We will show that up to change the Riemannian metric on the manifold the control curvature of Zermelo's problem has a simple to handle expression which naturally leads to a generalization of the classical Gauss-Bonnet formula in an inequality. This Gauss-Bonnet inequality enables to generalize for Zermelo's problems the E. Hopf theorem on flatness of Riemannian tori without conjugate points.
Microlocal normal forms for regular fully nonlinear two-dimensional control systems
Ulysse Serres
Mathematics , 2009, DOI: 10.1134/S0081543810030193
Abstract: In the present paper we deal with fully nonlinear two-dimensional smooth control systems with scalar input $\dot{q} = \bs{f}(q,u)$, $q \in M$, $u \in U$, where $M$ and $U$ are differentiable smooth manifolds of respective dimensions two and one. For such systems, we provide two microlocal normal forms, i.e., local in the state-input space, using the fundamental necessary condition of optimality for optimal control problems: the Pontryagin Maximum Principle. One of these normal forms will be constructed around a regular extremal and the other one will be constructed around an abnormal extremal. These normal forms, which in both cases are parametrized only by one scalar function of three variables, lead to a nice expression for the control curvature of the system. This expression shows that the control curvature, a priori defined for normal extremals, can be smoothly extended to abnormals.
Control systems of zero curvature are not necessarily trivializable
Ulysse Serres
Mathematics , 2009,
Abstract: A control system $\dot{q} = f(q,u)$ is said to be trivializable if there exists local coordinates in which the system is feedback equivalent to a control system of the form $\dot{q} = f(u)$. In this paper we characterize trivializable control systems and control systems for which, up to a feedback transformation, $f$ and $\partial f/\partial u$ commute. Characterizations are given in terms of feedback invariants of the system (its control curvature and its centro-affine curvature) and thus are completely intrinsic. To conclude we apply the obtained results to Zermelo-like problems on Riemannian manifolds.
On curvature and feedback classification of two-dimensional optimal control systems
Ulysse Serres
Mathematics , 2005,
Abstract: The goal of this paper is to extend to two-dimensional optimal control systems with scalar input the classical notion of Gaussian curvature of two-dimensional Riemannian surface using the Cartan's moving frame method. This notion was already introduced by A. A. Agrachev and R. V. Gamkrelidze for more general control systems using a purely variational approach. Then we will see that the ``control'' analogue to Gaussian curvature reflects similar intrinsic properties of the extremal flow. In particular if the curvature is negative, arbitrarily long segment of extremals are locally optimal. Finally, we will define and characterize flat control systems.
Fidgetin-Like1 Is a Strong Candidate for a Dynamic Impairment of Male Meiosis Leading to Reduced Testis Weight in Mice
David L'H?te,Magalie Vatin,Jana Auer,Johan Castille,Bruno Passet,Xavier Montagutelli,Catherine Serres,Daniel Vaiman
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0027582
Abstract: In a previous work, using an interspecific recombinant congenic mouse model, we reported a genomic region of 23 Mb on mouse chromosome 11 implicated in testis weight decrease and moderate teratozoospermia (~20–30%), a Quantitative Trait Locus (QTL) called Ltw1. The objective of the present study is to identify the gene underlying this phenotype.
Cholesterol Depletion Disorganizes Oocyte Membrane Rafts Altering Mouse Fertilization
Jorgelina Buschiazzo, Come Ialy-Radio, Jana Auer, Jean-Philippe Wolf, Catherine Serres, Brigitte Lefèvre, Ahmed Ziyyat
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062919
Abstract: Drastic membrane reorganization occurs when mammalian sperm binds to and fuses with the oocyte membrane. Two oocyte protein families are essential for fertilization, tetraspanins and glycosylphosphatidylinositol-anchored proteins. The firsts are associated to tetraspanin-enriched microdomains and the seconds to lipid rafts. Here we report membrane raft involvement in mouse fertilization assessed by cholesterol modulation using methyl-β-cyclodextrin. Cholesterol removal induced: (1) a decrease of the fertilization rate and index; and (2) a delay in the extrusion of the second polar body. Cholesterol repletion recovered the fertilization ability of cholesterol-depleted oocytes, indicating reversibility of these effects. In vivo time-lapse analyses using fluorescent cholesterol permitted to identify the time-point at which the probe is mainly located at the plasma membrane enabling the estimation of the extent of the cholesterol depletion. We confirmed that the mouse oocyte is rich in rafts according to the presence of the raft marker lipid, ganglioside GM1 on the membrane of living oocytes and we identified the coexistence of two types of microdomains, planar rafts and caveolae-like structures, by terms of two differential rafts markers, flotillin-2 and caveolin-1, respectively. Moreover, this is the first report that shows characteristic caveolae-like invaginations in the mouse oocyte identified by electron microscopy. Raft disruption by cholesterol depletion disturbed the subcellular localization of the signal molecule c-Src and the inhibition of Src kinase proteins prevented second polar body extrusion, consistent with a role of Src-related kinases in fertilization via signaling complexes. Our data highlight the functional importance of intact membrane rafts for mouse fertilization and its dependence on cholesterol.
Refined Mapping of a Quantitative Trait Locus on Chromosome 1 Responsible for Mouse Embryonic Death
Magalie Vatin,Gaetan Burgio,Gilles Renault,Paul Laissue,Virginie Firlej,Fran?oise Mondon,Xavier Montagutelli,Daniel Vaiman,Catherine Serres,Ahmed Ziyyat
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043356
Abstract: Recurrent spontaneous abortion (RSA) is defined as the loss of three or more consecutive pregnancies during the first trimester of embryonic intrauterine development. This kind of human infertility is frequent among the general population since it affects 1 to 5% of women. In half of the cases the etiology remains unelucidated. In the present study, we used interspecific recombinant congenic mouse strains (IRCS) in the aim to identify genes responsible for embryonic lethality. Applying a cartographic approach using a genotype/phenotype association, we identified a minimal QTL region, of about 6 Mb on chromosome 1, responsible for a high rate of embryonic death (~30%). Genetic analysis suggests that the observed phenotype is linked to uterine dysfunction. Transcriptomic analysis of the uterine tissue revealed a preferential deregulation of genes of this region compared to the rest of the genome. Some genes from the QTL region are associated with VEGF signaling, mTOR signaling and ubiquitine/proteasome-protein degradation pathways. This work may contribute to elucidate the molecular basis of a multifactorial and complex human disorder as RSA.
Un estudio de la formación profesional de docentes de matemática a través de investigación-acción
Revista de Pedagogía , 2007,
Abstract: abstract this paper analyzes a professional development program for mathematics teachers through action research. the program analyzed was the samuel robinson va al liceo that belongs to the universidad central de venezuela. the information was obtained using field diaries, teachers profiles and interviews that were analyzed using a triangulation method. it was possible to begin an awareness process by having conversations on key pedagogical issues of mathematics education. however, the program did not improve teachers? practices because the original design of the program included different area teams as well as because of the lack of follow up in the high schools. it is recommended the integration of area teams and a follow up of the program in the high schools
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