Accompagner les élèves ? : appropriation de la réforme, ré-élaboration dans le travail réel

La mise en œuvre des réformes n’est souvent regardée que comme application, sous l’angle de la conformité, sans considérer vraiment les richesses d’inventions, de créations ordinaires. Contrairement à ce qui se dit parfois, les professionnels ne sont pas résistants au changement, ils veulent être acteurs et auteurs de leurs contributions à ces améliorations, en puisant dans leurs expériences. Dès qu’ils en ont la possibilité, ils explorent des zones laissées dans l’ombre dans la mesure où ils estiment que cela pourrait constituer des opportunités pour expérimenter de possibles améliorations. Il y a alors des traductions, des expérimentations, des expériences redécouvertes, des ajustements progressifs et des débats sur les qualités des produits visés et réalisés dans le travail.C’est précisément ce que les chercheurs ont rencontré dans le travail ordinaire des professionnels avec qui ils ont partagé cette intervention-recherche d’une durée de trois ans.Après une présentation de l’intervention-recherche et de son déroulement dans quatre établissements et avec un groupe de directeurs-adjoints, le rapport de recherche focalise sur trois domaines : Les dispositifs d’AP et leur élaboration ; Le potentiel d’apprentissages des dispositifs d’AP pour les élèves ; Le travail collectif dans la mise en œuvre de l’accompagnement personnalisé (à l’orientation). La synthèse permet de mettre en lumière les processus d’appropriation de la réforme observés et leurs effets sur la dynamique des rapports entre activité des acteurs et institution. En conclusion, les auteurs ouvrent quelques pistes de réflexion à propos des contenus, modalités et conditions de la mise en œuvre et de l’appropriation d’une réforme éducative par les acteurs

Small Vessel Replacement by Human Umbilical Arteries With Polyelectrolyte Film-Treated Arteries In Vivo Behavior

ObjectiveThe aim of this study was to evaluate the patency of human umbilical arteries treated with polyelectrolyte multilayers (PEMs) after rabbit implantation.BackgroundThe development of small-caliber vascular substitutes with high patency after implantation remains a real challenge for vascular tissue engineering.MethodsCryopreserved human umbilical arteries were enzymatically de-endothelialized and the luminal surfaces were coated with poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers. The PEM-untreated arteries and PEM-treated rabbit carotids were used as graft control. The native rabbit carotids were bypassed by grafts.ResultsThe Doppler ultrasound evaluation, performed in vivo, showed that all PEM-treated grafts remained patent during the full experimental period, whereas after only 1 week, no blood circulation was detected in untreated arteries. Scanning electron microscopy and histological graft examination showed pervasive thrombus formation on the luminal surface of untreated arteries after 1 week and clean luminal surface for treated arteries for at least up to 12 weeks. The arterial wall cells were identified through alpha-smooth muscle actin αυδ platelet endothelial cell adhesion molecule-1 expression. The smooth muscle cells positive to alpha-smooth muscle actin were identified in adventitia and media and the endothelial cells positive to platelet endothelial cell adhesion molecule in intima. Von Kossa reaction didn't reveal any calcium salt deposits on the wall arteries, suggesting a good wall remodelling with no sign of graft rejection.ConclusionsThe in vivo evaluation of human umbilical arteries treated with PSS/PAH multilayers demonstrated a high graft patency after 3 months of implantation. Such modified arteries could constitute a useful option for small vascular replacement

Efficient generation of CD34+ progenitorâ derived dendritic cells from Gâ CSFâ mobilized peripheral mononuclear cells does not require hematopoietic stem cell enrichment

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141647/1/jlb0957.pd

O2 Level Controls Hematopoietic Circulating Progenitor Cells Differentiation into Endothelial or Smooth Muscle Cells

BACKGROUND:Recent studies showed that progenitor cells could differentiate into mature vascular cells. The main physiological factors implicated in cell differentiation are specific growth factors. We hypothesized that simply by varying the oxygen content, progenitor cells can be differentiated either in mature endothelial cells (ECs) or contractile smooth muscle cells (SMCs) while keeping exactly the same culture medium. METHODOLOGY/PRINCIPAL FINDINGS:Mononuclear cells were isolated by density gradient were cultivated under hypoxic (5% O2) or normoxic (21% O2) environment. Differentiated cells characterization was performed by confocal microscopy examination and flow cytometry analyses. The phenotype stability over a longer time period was also performed. The morphological examination of the confluent obtained cells after several weeks (between 2 and 4 weeks) showed two distinct morphologies: cobblestone shape in normoxia and a spindle like shape in hypoxia. The cell characterization showed that cobblestone cells were positive to ECs markers while spindle like shape cells were positive to contractile SMCs markers. Moreover, after several further amplification (until 3(rd) passage) in hypoxic or normoxic conditions of the previously differentiated SMC, immunofluorescence studies showed that more than 80% cells continued to express SMCs markers whatever the cell environmental culture conditions with a higher contractile markers expression compared to control (aorta SMCs) signature of phenotype stability. CONCLUSION/SIGNIFICANCE:We demonstrate in this paper that in vitro culture of peripheral blood mononuclear cells with specific angiogenic growth factors under hypoxic conditions leads to SMCs differentiation into a contractile phenotype, signature of their physiological state. Moreover after amplification, the differentiated SMC did not reverse and keep their contractile phenotype after the 3rd passage performed under hypoxic and normoxic conditions. These aspects are of the highest importance for tissue engineering strategies. These results highlight also the determinant role of the tissue environment in the differentiation process of vascular progenitor cells

Analysis of Virion Structural Components Reveals Vestiges of the Ancestral Ichnovirus Genome

Many thousands of endoparasitic wasp species are known to inject polydnavirus (PDV) particles into their caterpillar host during oviposition, causing immune and developmental dysfunctions that benefit the wasp larva. PDVs associated with braconid and ichneumonid wasps, bracoviruses and ichnoviruses respectively, both deliver multiple circular dsDNA molecules to the caterpillar. These molecules contain virulence genes but lack core genes typically involved in particle production. This is not completely unexpected given that no PDV replication takes place in the caterpillar. Particle production is confined to the wasp ovary where viral DNAs are generated from proviral copies maintained within the wasp genome. We recently showed that the genes involved in bracovirus particle production reside within the wasp genome and are related to nudiviruses. In the present work we characterized genes involved in ichnovirus particle production by analyzing the components of purified Hyposoter didymator Ichnovirus particles by LC-MS/MS and studying their organization in the wasp genome. Their products are conserved among ichnovirus-associated wasps and constitute a specific set of proteins in the virosphere. Strikingly, these genes are clustered in specialized regions of the wasp genome which are amplified along with proviral DNA during virus particle replication, but are not packaged in the particles. Clearly our results show that ichnoviruses and bracoviruses particles originated from different viral entities, thus providing an example of convergent evolution where two groups of wasps have independently domesticated viruses to deliver genes into their hosts

Optimisation of Biochemical Condition and Substrates In Vitro for Tissue Engineering of Ligament

In this work, we analysed the effect of growth factors on in vitro cell proliferation and collagens synthesis by fibroblasts cultured for 72 h on different substrates (silicon sheet with or without 1% gelatin, and glass as control surface) for ligament tissue engineering. A human fibroblast cell line (CRL-2703) was used. The synthesis of type I and type III collagens were evaluated qualitatively and quantitatively by RT-PCR and confocal microscopy, respectively. Cell proliferation was evaluated by two methods: (1) MTT assay (2) cell cycle analysis. It was found that PDGF-AB stimulate the proliferation of fibroblast cultured on gelatin coated silicon sheet in dose dependant manner with a maximum effect at 10 ng ml(−1). The exogenous TGF-β1 induced the expression of type I and type III collagens in a dose and substrate-dependant manner. We deduce from this work that biochemical conditions and substrates have an important impact for optimisation of the tissue neo synthesis

Adhésion leucocyte/endothélium, approches de l'interaction entre molécules d'adhésion LFA-1 et ICAM-1 par micropipette et chambre d'écoulement

NANCY1-SCD Medecine (545472101) / SudocSudocFranceF

Intérêts des films minces multicouches de polyélectrolytes dans la conception de substituts vasculaires

NANCY1-SCD Medecine (545472101) / SudocSudocFranceF

Modification de l'expression et de la phosphorylation de la VASP dans les cellules endothéliales soumises aux écoulements

La phosphoprotéine vasodilatatrice stimulée (VASP) appartient à la famille des protéines ENANASP qui est impliquée dans les modifications du cytosquelette et la transduction du signal lors de changements morphologiques et de migration cellulaire. La VASP s'associe avec les microfilaments d'actine, particulièrement aux points focaux d'adhésion, et aux lamellipodes. Dans cette étude, nous avons étudié l'influence des contraintes de cisaillement sur l'expression, la phosphorylation et la distribution des VASP dans les cellules endothéliales (HUVECs). Par ailleurs, nous avons également exploré deux voies de signalisation possibles pour expliquer la voie de régulation des VASP. Après stimulation par la contrainte de cisaillement, un double marquage immunofluorescence a été utilisé pour démontrer la relation entre l'organisation des fibres d'actine et la distribution des VASP. On observe que dans les HUVECs, après une contrainte de 1,0 Pa pendent 24h, les VASP sont concentrés aux extrémités des fibres de stress. Les résultats de RT-PCR montrent une augmentation significative de la taille du fragment de 482 bp après une exposition d'une heure. La technique de western blotting a été utilisée pour déterminer le taux de l'expression et la phosphorylation de la VASP. En condition statique, les cellules contiennent uniquement des VASP déphosphorylées. Les cellules soumises à une contrainte de 1,0 Pa pour une durée d'une heure présentent le pourcentage de VASP phosphorylées le plus élevé. La contrainte de 1,5 Pa conduit à un taux plus faible de phosphorylation que celle de 1,0 Pa, et la contrainte de 0,2 Pa provoque une augmentation en retard. De plus, cette phosphorylation montre un caractère transitoire et paraît réversible. Par ailleurs, la cytochalasine D (inhibiteur des fibres d'actine) et H89 (un inhibiteur de la PKA) empêchent l'augmentation des VASP provoquée par le cisaillement ('[=1,0 Pa, 1h), tandis que la L-NNA (un inhibiteur de la NOS) présente un effet inverse. Ces résultats suggèrent que la contrainte de cisaillement provoque la phosphorylation des VASP dans la CE, mais cette phosphorylation dépend l'intégrité du cytosquelette et le taux de l'AMPc intracellulaire.NANCY1-SCD Medecine (545472101) / SudocSudocFranceF