Dynamic changes in brain functional connectivity during concurrent dual-task performance.

This study investigated the spatial, spectral, temporal and functional proprieties of functional brain connections involved in the concurrent execution of unrelated visual perception and working memory tasks. Electroencephalography data was analysed using a novel data-driven approach assessing source coherence at the whole-brain level. Three connections in the beta-band (18-24 Hz) and one in the gamma-band (30-40 Hz) were modulated by dual-task performance. Beta-coherence increased within two dorsofrontal-occipital connections in dual-task conditions compared to the single-task condition, with the highest coherence seen during low working memory load trials. In contrast, beta-coherence in a prefrontal-occipital functional connection and gamma-coherence in an inferior frontal-occipitoparietal connection was not affected by the addition of the second task and only showed elevated coherence under high working memory load. Analysis of coherence as a function of time suggested that the dorsofrontal-occipital beta-connections were relevant to working memory maintenance, while the prefrontal-occipital beta-connection and the inferior frontal-occipitoparietal gamma-connection were involved in top-down control of concurrent visual processing. The fact that increased coherence in the gamma-connection, from low to high working memory load, was negatively correlated with faster reaction time on the perception task supports this interpretation. Together, these results demonstrate that dual-task demands trigger non-linear changes in functional interactions between frontal-executive and occipitoparietal-perceptual cortices.

Stem cell populations derived from heart and pancreas show a with a unique phenotype and give rise to functional cardiomyocytes and insulin-producing cells, respectively

Introduction: Recently, mesenchymal stem cells (MSC) of perivascular origin have been identified in several organs not including the heart. Using a novel cell isolation protocol, we have isolated cells sharing common characteristics from mouse hearts and pancreas. The aim of the present study was to characterize these cells in vitro.Methods: Cells were isolated from neonatal and adult mouse hearts and pancreas and cultured for more than 6 months. Surface marker expression was analyzed by flow cytometry and immunocytochemistry. Cell differentiation was tested using multiple differentiation media. Insulin production by pancreas-derived cells was tested by dithizone staining.Results: Cells showing a similar, distinctive morphology were obtained from the heart and pancreas after 4-8 weeks of culture. Cells from the two organs also showed a very similar immunophenotype, characterized by expression of c-kit (stem cell factor receptor), CD44, the common leukocyte marker CD45, and the monocytic markers CD11b and CD14. A significant proportion of cardiac and pancreatic cells expressed NG2, a marker for pericytes and other vascular cells. A significant proportion of cardiac, but not of pancreatic cells expressed stem cell antigen-1 (Sca-1). However, cells did not express T, B or dendritic cell markers. Cells of both cardiac and pancreatic origin spontaneously formed "spheres" (spherical cell aggregates similar to "neurospheres" formed by neural stem cells) in vitro. Cardiosphere formation was enhanced by TNF-alpha. Several cardiospheres (but no "pancreatospheres") derived from neonatal (but not adult) cells showed spontaneous rhythmic contractions, thus demonstrating cardiac differentiation (this was confirmed by immunostaining for alpha-sarcomeric actinin). Beating activity was enhanced by low serum conditions. Cells from both organs formed adipocytes, osteocytes and osteocytes under appropriate conditions, the typical differentiation pattern of MSCs. Pancreas-derived cells also formed dithizonepositive insulin-producing cells.Conclusions: We have defined cardiac and pancreatic cell populations that share a common morphology, growth characteristics, and a unique immunophenotype. Expression of perivascular and monocytic markers, along with stem/priogenitor cell markers by these cells suggests a relationship with pericytes-mesoangioblasts and so-called multipotent monocytes. Cells show MSC-typical growth and differentiation patterns, together with tissue-specific differentiation potential: cardiomyocytes for cardiac-derived cells and insulinproducing cells for pancreas-derived cells.

NS4B Self-Interaction through Conserved C-Terminal Elements Is Required for the Establishment of Functional Hepatitis C Virus Replication Complexes.

Hepatitis C virus (HCV) is an important human pathogen, persistently infecting more than 170 million individuals worldwide. Studies of the HCV life cycle have become possible with the development of cell culture systems supporting the replication of viral RNA and the production of infectious virus. However, the exact functions of individual proteins, especially of nonstructural protein 4B (NS4B), remain poorly understood. NS4B triggers the formation of specific, vesicular membrane rearrangements, referred to as membranous webs, which have been reported to represent sites of HCV RNA replication. However, the mechanism of vesicle induction is not known. In this study, a panel of 15 mutants carrying substitutions in the highly conserved NS4B C-terminal domain was generated. Five mutations had only a minor effect on replication, but two of them enhanced assembly and release of infectious virus. Ten mutants were replication defective and used for selection of pseudoreversions. Most of the pseudoreversions also localized to the highly conserved NS4B C-terminal domain and were found to restore replication competence upon insertion into the corresponding primary mutant. Importantly, pseudoreversions restoring replication competence also restored heterotypic NS4B self-interaction, which was disrupted by the primary mutation. Finally, electron microscopy analyses of membrane alterations induced by NS4B mutants revealed striking morphological abnormalities, which were restored to wild-type morphology by the corresponding pseudoreversion. These findings demonstrate the important role of the C-terminal domain in NS4B self-interaction and the formation of functional HCV replication complexes.

Glibenclamide enhances neurogenesis and improves long-term functional recovery after transient focal cerebral ischemia

Glibenclamide is neuroprotective against cerebral ischemia in rats. We studied whether glibenclamide enhances long-term brain repair and improves behavioral recovery after stroke. Adult male Wistar rats were subjected to transient middle cerebral artery occlusion (MCAO) for 90 minutes. A low dose of glibenclamide (total 0.6mg) was administered intravenously 6, 12, and 24 hours after reperfusion. We assessed behavioral outcome during a 30-day follow-up and animals were perfused for histological evaluation. In vitro specific binding of glibenclamide to microglia increased after pro-inflammatory stimuli. In vivo glibenclamide was associated with increased migration of doublecortin-positive cells in the striatum toward the ischemic lesion 72 hours after MCAO, and reactive microglia expressed sulfonylurea receptor 1 (SUR1) and Kir6.2 in the medial striatum. One month after MCAO, glibenclamide was also associated with increased number of NeuN-positive and 5-bromo-2-deoxyuridine-positive neurons in the cortex and hippocampus, and enhanced angiogenesis in the hippocampus. Consequently, glibenclamide-treated MCAO rats showed improved performance in the limb-placing test on postoperative days 22 to 29, and in the cylinder and water-maze test on postoperative day 29. Therefore, acute blockade of SUR1 by glibenclamide enhanced long-term brain repair in MCAO rats, which was associated with improved behavioral outcome.

Molecular and Functional Characterization of Neuroblastoma-Initiating Cells

Neuroblastoma (NB) is the most common extracranial malignant tumor in young children and arises at any site of the sympathetic nervous system. The disease exhibits a remarkable phenotypic diversity ranging from spontaneous regression to fatal disease. Poor outcome results from a rapidly progressive, metastatic and drug-resistant disease. Recent studies have suggested that solid tumors may arise from a minor population of cancer stem cells (CSCs) with stem cell markers and typical properties such as self-renewal ability, asymmetric division and drug resistance. In this model, CSCs possess the exclusive ability to initiate and maintain the tumor, and to produce distant metastases. Tumor cell subpopulations with stem-like phenotypes have indeed been identified in several cancer including leukemia, breast, brain and colon cancers. CSC hypothesis still needs to be validated in the other cancers including NB.NB originates from neural crest-derived malignant sympatho-adrenal cells. We have identified rare cells that express markers in conformity with neural crest stem cells and their derived lineages within primary NB tissue and cell lines, leading us to postulate the existence of CSCs in NB tumors.In the absence of specific markers to isolate CSCs, we adapted to NB tumor cells the sphere functional assay, based on the ability of stem cells to grow as spheres in non-adherent conditions. By serial passages of spheres from bone marrow NB metastases, a subset of cells was gradually selected and its specific gene expression profile identified by micro-array time-course analysis. The differentially expressed genes in spheres are enriched in genes implicated in development including CD133, ABC-transporters, WNT and NOTCH genes, identified in others solid cancers as CSCs markers, and other new markers, all referred by us as the Neurosphere Expression Profile (NEP). We confirmed the presence of a cell subpopulation expressing a combination of the NEP markers within a few primary NB samples.The tumorigenic potential of NB spheres was assayed by in vivo tumor growth analyses using orthotopic (adrenal glands) implantations of tumor cells into immune-compromised mice. Tumors derived from the sphere cells were significantly more frequent and were detected earlier compared to whole tumor cells. However, NB cells expressing the neurosphere-associated genes and isolated from the bulk tumors did not recapitulate the CSC-like phenotype in the orthotopic model. In addition, the NB sphere cells lost their higher tumorigenic potential when implanted in a subcutaneous heterotopic in vivo model.These results highlighted the complex behavior of CSC functions and led us to consider the stem-like NB cells as a dynamic and heterogeneous cell population influenced by microenvironment signals.Our approach identified for the first time candidate genes that may be associated with NB self-renewal and tumorigenicity and therefore would establish specific functional targets for more effective therapies in aggressive NB.

Lettre d'un ancien professeur en medecine de la faculté de Paris, a M. Vandermonde, auteur du Journal de medecine, censeur royal, &c. Pour servir de réponse à la Lettre d'un médecin de province à un médecin de Paris . Cette lettre fait la troisiéme piéce d'un ecrit intitulé Recueil de plusieurs piéces concernant le Traité des tumeurs & ulceres, &c.

Comprend : Lettre d'un médecin de province à un médecin de Paris