The Roles of Cyclin A2, B1, and B2 in Early and Late Mitotic Events

This paper presents evidence that chromatin condensation, like nuclear envelope breakdown, is brought about through the combined effects of cyclins A2 and B1, and that cyclins B1 and B2 are largely responsible for maintenance of a spindle assembly checkpoint arrest

Jakaré-Ouassou, ou Les Tupinambas, chronique brésilienne,

Mode of access: Internet

Granulometric Analysis of Maltodextrin Particles Observed by Scanning Electron Microscopy

International audienceMaltodextrin is a substance that is being increasingly used to preserve the physicochemical and biological properties of many active compounds. Therefore, determining the particle size distribution (PSD) of the particles having maltodextrin matrices is a crucial issue to control their end-use properties. This can be done directly by laser diffraction (LD) in a dry way or via SEM image analysis. In this paper, a new method of segmentation of quasi-circular particles from grayscale images called curvature analysis method (CAM) is proposed. This method is compared to two other widely used methods: Circular Hough Transform (CHT) and Stochastic Watershed (SW). It aims in particular to reduce the drawbacks of these two methods: a large number of false detections and an inaccuracy with respect to the mean particle size in case of a large number of overlapping particles. The method is validated using synthetic images generated with a model allowing to simulate gray level images similar to the maltodextrin particle images from the SEM. The CAM method is then applied to real images and the resulting PSD is compared to the one provided by the LD technique. Overall, the results obtained by the CAM method are much better than those proposed by CHT and SW on synthetic images and than the LD method on real images

Une approche pour l’analyse granulométrique de particules condensées sur des images en niveaux de gris

National audienceImageJ Particle Sizer is probably one of the most known and used tools to perform a granulometric analysis ingray-scale images. Although it is a high-performance segmentation method for well separated circles, it produces over-segmentation when applied on images in which the grains are condensed and overlapping. In this paper, we propose a new segmentation algorithm, the Curvature Analysis Method (CAM), to face the problems raised by such images. A stochastic grains simulation model has been developed to compare the accuracy of the CAM’s Particle Size Distribution (PSD) to the ImageJ’s one, regarding the ground truth of simulated images. They are then applied on a provided set of real images of synthesised maltodextrin particles, and compared to the PSD given by Laser Diffraction (LD). The results finally show that the CAM provides much more accurate results than the CHT does on simulated images, and that the LD technique can not be considered as trustworthy as it gives a PSD far from the truth.ImageJ Particle Sizer est probablement l’un des outils les plus utilisés pour effectuer une analyse granulométrique surdes images en niveaux de gris. Bien qu’il s’agisse d’une méthode de segmentation performante pour des cercles bien distincts, elle produit une sur-segmentation lorsqu’elle est appliquée à des images dans lesquelles les grains sont condensés et se chevauchent. Dans cet article, nous proposons un nouvel algorithme de segmentation, la Méthode d’Analyse de Courbure (Curvature Analysis Method - CAM), pour faire face à ce problème. Un modèle stochastique de simulation de grains a été développé pour comparer la précision de la Distribution des Tailles des Particules (PSD) issue de la CAM à celle issue d’ImageJ, par rapport à la vérité terrain des images simulées. Ces deux méthodes sont ensuite appliquées à un ensemble d’images réelles de particules de maltodextrine synthétisées, et comparées à la PSD donnée par Diffraction Laser (DL). Les résultats montrent finalement que la CAM fournit des distributions plus justes qu’ImageJ sur les images simulées, et que la DL fournit une PSD loin de la vérité sur les images réelles

Prolyl endopeptidase is involved in the degradation of neural cell adhesion molecules in vitro

Abstract: Membrane-associated glycoprotein neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) play an important role in brain plasticity by regulating cellcell interactions. Here, we demonstrate that the cytosolic serine protease prolyl endopeptidase (PREP) is able to regulate NCAM and PSA-NCAM. Using a SH-SY5Y neuroblastoma cell line with stable overexpression of PREP, we found a remarkable loss of PSA-NCAM, reduced levels of NCAM180 and NCAM140 protein species, and a significant increase in the NCAM immunoreactive band migrating at an apparent molecular weight of 120\u2005kDa in PREP-overexpressing cells. Moreover, increased levels of NCAM fragments were found in the concentrated medium derived from PREP-overexpressing cells. PREP overexpression selectively induced an activation of matrix metalloproteinase-9 (MMP-9), which could be involved in the observed degradation of NCAM, as MMP-9 neutralization reduced the levels of NCAM fragments in cell culture medium. We propose that increased PREP levels promote epidermal growth factor receptor (EGFR) signaling, which in turn activates MMP-9. In conclusion, our findings provide evidence for newly-discovered roles for PREP in mechanisms regulating cellular plasticity through NCAM and PSA-NCAM