Semaphorins deployed to repel cell migrants at spinal cord borders

In the spinal cord, developing motor neurons extend their axons into the periphery while their cell bodies remain within the motor columns in the spinal cord. Two recent papers show that this partitioning involves forward and reverse semaphorin-plexin signaling between motor neurons and neural crest boundary cap cells

The growth cone: an integrator of unique cues into refined axon guidance

One of the challenges to understanding nervous system development is to establish how a fairly limited number of axon guidance cues can set up the patterning of very complex nervous systems. Most of the recent insights relevant to guidance mechanisms have come from cell biologists focusing on processes and molecular machinery controlling the guidance responses in the growth cone

Cultured microvascular endothelial cells derived from the bovine corpus luteum possess NCAM-140

Previously, five phenotypically different, stable types of microvascular endothelial cells (MVE) were isolated from the bovine corpus and cultured successfully. We found that three out of these five types of MVE express the neural cell adhesion molecule (NCAM). As shown by immunocytochemistry, weak NCAM immunoreactivity occurred mainly in the perinuclear area of cell type 1. Monolayers of types 2 and 5 revealed heavy NCAM immunoreactivity, which was localized predominantly at the lateral cell surface outlining the contact zones of adjacent cells. In contrast, cell types 3 and 4 were not NCAM immunoreactive. Western blot analyses substantiated these results: While cell type 1 showed a weak immunoreactive band, cell types 2 and 5 displayed strong NCAM-immunoreactive bands of a molecular weight of approximately 140 kDa (NCAM-140), which was absent in cell types 3 and 4. These results reveal for the first time that NCAM can be expressed by cultured MVE and may serve in mediating endothelial cell contacts. Since luteal cells also express NCAM-140, this adhesion molecule could in addition be involved in the interactions of luteal cells with MVE

A non-rigid registration approach for quantifying myocardial contraction in tagged MRI using generalized information measures.

International audienceWe address the problem of quantitatively assessing myocardial function from tagged MRI sequences. We develop a two-step method comprising (i) a motion estimation step using a novel variational non-rigid registration technique based on generalized information measures, and (ii) a measurement step, yielding local and segmental deformation parameters over the whole myocardium. Experiments on healthy and pathological data demonstrate that this method delivers, within a reasonable computation time and in a fully unsupervised way, reliable measurements for normal subjects and quantitative pathology-specific information. Beyond cardiac MRI, this work redefines the foundations of variational non-rigid registration for information-theoretic similarity criteria with potential interest in multimodal medical imaging

Endocrine cells share expression of N-CAM with neurones

The reeent explosive interest in eell adhesion molecules (CAMs) is a direet eonsequence of the fundamental roles they are thought to play during early embryogenesis and tissue formation [1,2]. The most weIl known of them, studied independently under the names of N-CAM [3] (neural-CAM), 02 protein [4] and BSP-2 [5], has been shown to consist in brain of a family of three glyeoproteins of Mr 180000, 140000 and 120000 [6,7] which are implicated in neurone-neurone adhesion by a homophilie binding meehanism [8,9]. While N-CAM was originally considered to be limited to neurones in adult tissues, ultrastruetural immunoeytochemical studies have sinee provided unequivocal evidenee that glial cells, both astrocytes [6,10] and Schwann cells [11], also express N-CAM (see also [12,13]). Apart from a very limited expression by skeletal muscle at the neuromuscular junetion [14], its expression in the adult Correspondence address: O.K. Langley, Unite 44 de I'INSERM, and Centre de Neurochirnie du CNRS, 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France has been largely though not exclusively considered to be limited to nervous tissues. N-CAM has been found in eertain eells outside the nervous system (e.g. chromaffin eells in the adrenal medulla [11]) but such eells are derived from the neural crest. Here we extend our previous observations on endocrine eells in the adrenal gland and investigate the possible expression of N-CAM by other endoerine eells whieh have a non-neural origin. The present results indieate a mueh wider distribution of N-CAM in adult tissues than has previously been supposed. N-CAM is shown by immunoeytoehemistry to be expressed by several endoerine eells of non-neural origin. Immunoehemieal data eonfirm the presenee of N-CAM determinants typical of brain in endoerine eells although the relative proportions differ markedly. In addition, in two of the tissues examined a lower molecular mass NCAM positive polypeptide was also detected

Recalage variationnel non rigide statistique référencé région

Les mesures de similarité statistiques classiquement utilisées en recalage non rigide iconique exploitent des statistiques de luminance globales n'intégrant aucune information géométrique. Cette absence de prise en compte du contexte spatial peut conduire dans certains cas à un appariement imprécis voire incohérent de structures géométriques homologues, rendant ces critères mal adaptés à la segmentation par propagation d'atlas. Nous proposons de résoudre cette limitation en injectant dans la mesure de similarité un a priori spatial sous forme d'un modèle étiqueté de scène associé à l'image cible. Ce dernier induit un critère régionalisé fondé sur des densités de probabilité régionales, estimées via des noyaux de Parzen spécifiques sur chaque région du modèle. Nous formalisons ainsi les notions de rapport de corrélation et de f-information régionalisés, dont nous calculons les flots de gradient sur des espaces de transformations non paramétriques et paramétriques. L'application au modèle de scène de la transformation optimale inverse induit de facto une segmentation de l'image source. Nous illustrons les performances de cette approche pour la compensation de mouvements respiratoires et cardiaques complexes lors du transit d'un produit de contraste en IRM de perfusion

Recalage variationnel non rigide d'images par f-information exclusive

Nous nous intéressons à la mise en correspondance non rigide dense d'images dans des contextes monomodaux avec fortes variations photométriques/texturales ou multimodaux, et étudions à cette fin des critères de similarité statistiques fondés sur des mesures d'information généralisées au sein de la classe d'Ali-Silvey. Nous introduisons une nouvelle classe de fonctionnelles, dénommées f-informations exclusives, et développons un cadre variationnel générique bien-posé pour leur optimisation sur des espaces de déformations non paramétriques et paramétriques, généralisant les méthodes par information mutuelle. Cette approche est appliquée à l'alignement aveugle robuste de visages sous éclairement arbitraire et pour des déformations faciales complexes

Estimation paramétrique robuste à support optimal de la structure d'écoulements fluides en imagerie Météosat

Cet article présente une méthodologie d'analyse de la structure lagrangienne d'écoulements fluides dans des séquences d'images météorologiques multispectrales. Adoptant une approche multi-échelles, nous construisons tout d'abord, à partir du tenseur de structure de l'image, un estimateur non ponctuel robuste du champ d'orientation localement dominante, adapté aussi bien à un contexte monospectral que multispectral. Nous estimons ensuite la composante lagrangienne du flot en ajustant un modèle paramétrique vectoriel hiérarchique à ce champ d'orientation. Dans ce but, nous introduisons une approche variationnelle originale permettant l'optimisation conjointe des paramètres du modèle et de son support. La structure du champ de vecteurs résultant est finalement caractérisée au moyen d'outils classiques de géométrie différentielle. Cette méthodologie est appliquée à l'analyse de structures dépressionnaires en zone tempérée en imagerie Météosat

Diversity of innate immune cell subsets across spatial and temporal scales in an EAE mouse model

International audienceIn both multiple sclerosis and its model experimental autoimmune encephalomyelitis (EAE), the extent of resident microglia activation and infiltration of monocyte-derived cells to the CNS is positively correlated to tissue damage. To address the phenotype characterization of different cell subsets, their spatio-temporal distributions and contributions to disease development we induced EAE in Thy1-CFP//LysM-EGFP//CD11c-EYFP reporter mice. We combined high content flow cytometry, immunofluorescence and two-photon imaging in live mice and identified a stepwise program of inflammatory cells accumulation. First on day 10 after induction, EGFP+ neutrophils and monocytes invade the spinal cord parenchyma through the meninges rather than by extravasion. This event occurs just before axonal losses in the white matter. Once in the parenchyma, monocytes mature into EGFP+/EYFP+ monocyte-derived dendritic cells (moDCs) whose density is maximal on day 17 when the axonal degradation and clinical signs stabilize. Meanwhile, microglia is progressively activated in the grey matter and subsequently recruited to plaques to phagocyte axon debris. LysM-EGFP//CD11c-EYFP mice appear as a powerful tool to differentiate moDCs from macrophages and to study the dynamics of immune cell maturation and phenotypic evolution in EAE