RESUMEN
TITLE: Les laboratoires ouverts Tous Chercheurs. ABSTRACT: L'enjeu d'une culture scientifique pour tous est d'importance face à la difficulté des citoyens à critiquer les données de la science avec des arguments rationnels, notamment en ce qui concerne la biologie et la santé (vaccination, procréation médicalement assistée, etc.), car le grand public ne veut plus croire sur parole ce que disent les experts. Dans ce contexte, rapprocher les citoyens de la recherche scientifique représente un réel défi pour l'avenir, que les laboratoires ouverts Tous Chercheurs1 ont voulu relever.
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Acceso a la Información , Investigación Biomédica/educación , Investigación Biomédica/organización & administración , Internado no Médico/organización & administración , Investigación Biomédica/tendencias , Participación de la Comunidad , Educación Continua/organización & administración , Francia , Humanos , Difusión de la Información/métodos , Relaciones Interpersonales , Tutoría , Opinión Pública , Cambio SocialRESUMEN
A French research institute raises the bar for public outreach with an educational laboratory that engages 1,000 high school students per year in mini research projects.
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Creatividad , Investigación , Ciencia/educación , Estudiantes , Adolescente , Humanos , EnseñanzaRESUMEN
The replication origins (ORIs) of Schizosaccharomyces pombe, like those in most eukaryotes, are long chromosomal regions localized within A+T-rich domains. Although there is no consensus sequence, the interacting proteins are strongly conserved, suggesting that DNA structure is important for ORI function. We used atomic force microscopy in solution and DNA modelling to study the structural properties of the Spars1 origin. We show that this segment is the least stable of the surrounding DNA (9 kb), and contains regions of intrinsically bent elements (strongly curved and inherently supercoiled DNAs). The pORC-binding site co-maps with a superhelical DNA region, where the spatial arrangement of adenine/thymine stretches may provide the binding substrate. The replication initiation site (RIP) is located within a strongly curved DNA region. On pORC unwinding, this site shifts towards the apex of the curvature, thus potentiating DNA melting there. Our model is entirely consistent with the sequence variability, large size and A+T-richness of ORIs, and also accounts for the multistep nature of the initiation process, the specificity of pORC-binding site(s), and the specific location of RIP. We show that the particular DNA features and dynamic properties identified in Spars1 are present in other eukaryotic origins.
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Microscopía de Fuerza Atómica , Origen de Réplica , Schizosaccharomyces/genética , Schizosaccharomyces/ultraestructura , Animales , Replicación del ADN , Drosophila/genética , Proteínas del Huevo/genética , Cinética , Conformación de Ácido Nucleico , Complejo de Reconocimiento del Origen , Proteínas de Schizosaccharomyces pombe/genéticaRESUMEN
During neurite elongation, migrating growth cones encounter both permissive and inhibitory substrates, such as laminin and MAG (myelin-associated glycoprotein), respectively. Here, we demonstrated on two neuronal cell lines (PC12 and N1E-115), that laminin and collagen hampered, in a dose-dependent manner, MAG inhibitory activity on several integrin functions, i.e., neurite growth, cell adhesion and cell spreading. Using a function blocking antibody, in PC12 cells, we showed that alpha1beta1 integrin is required in these phenomena. In parallel, we observed that MAG perturbs actin dynamics and lamellipodia formation during early steps of cell spreading. This seemed to be independent of RhoA activation, but dependent of Rac-1 inhibition by MAG. Laminin overrode MAG activity on actin and prevented MAG inhibition NGF-induced Rac1 activation. In conclusion, we evidenced antagonistic signaling between MAG receptors and beta1 integrins, in which Rac-1 may have a central function.
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Integrina beta1/metabolismo , Laminina/metabolismo , Glicoproteína Asociada a Mielina/metabolismo , Neuronas/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Animales , Anticuerpos/farmacología , Bovinos , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Línea Celular , Línea Celular Tumoral , Movimiento Celular/efectos de los fármacos , Movimiento Celular/fisiología , Sistema Nervioso Central/citología , Sistema Nervioso Central/embriología , Sistema Nervioso Central/metabolismo , Colágeno/metabolismo , Colágeno/farmacología , Relación Dosis-Respuesta a Droga , Retroalimentación Fisiológica/efectos de los fármacos , Retroalimentación Fisiológica/fisiología , Conos de Crecimiento/efectos de los fármacos , Conos de Crecimiento/metabolismo , Conos de Crecimiento/ultraestructura , Humanos , Integrina alfa1beta1/metabolismo , Laminina/farmacología , Ratones , Células PC12 , Ratas , Receptores de Superficie Celular/efectos de los fármacos , Receptores de Superficie Celular/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiologíaRESUMEN
The measurement by atomic force microscope of the contour length of DNA fragments adsorbed on mica has been made as accurate as possible by revisiting the different steps of image acquisition and processing. In air, the DNA helical rise was estimated at 2.97 +/- 0.15 A per base pair (bp) (mean +/- standard deviation) by imaging a 648-bp DNA fragment and 2.95 +/- 0.14 A per bp for a 115-bp fragment. This confirms earlier observations suggesting that drying DNA fragments on mica in the presence of nickel induces limited conformational changes. At this point the exact nature of these conformational changes remains unknown. Simple hypotheses are the transconformation of stretches of the DNA molecules to the A-form of the double helix or alteration of the helix structure at the points of contact between DNA and mica. By contrast, in aqueous buffer, the measured helical rise was 3.14 +/- 0.15 A per bp for the 648-bp fragment and 3.17 +/- 0.13 A per bp for the 1115-bp fragment. Thus, measured helical rises do not depend on the fragment length and are significantly shorter than the 3.38 A per bp measured by crystallography, but close to the 3.18 A per bp found in NMR studies. These findings are discussed with respect to discrepancies in earlier results published in the literature.