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Chain Migration (chain + migration)
Selected AbstractsSubventricular zone-derived neuroblast migration to the olfactory bulb is modulated by matrix remodellingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Serena Bovetti Abstract In the rodent brain neural progenitor cells are born in the subventricular zone and migrate along a pathway called the rostral migratory stream (RMS) into the olfactory bulb where they differentiate into several classes of interneurones. In the adult, tangential migration in the RMS takes place in ,chains' of cells contained within glial tubes. In contrast, neonatal neuroblasts along the RMS lack these defined glial tubes and chains, migrating instead as individual cells. Time-lapse confocal microscopy of neuroblasts at each of these ages shows that individual cells migrate in a saltatory manner with bursts of high speed followed by periods of slower speed. Tangential migration within a glial tube is 20% faster than migration as individual cells. Neuroblasts may also interact and modify the extracellular matrix during migration through expression of a family of proteins, the matrix metalloproteinases (MMPs). MMPs are present and active along the subventricular zone,olfactory bulb pathway. In the presence of inhibitors of MMPs, neuroblast migration rates were reduced only when cells migrate individually. Chain migration in the adult was unaffected by MMP inhibitors. Taken together, these data suggest that MMPs only influence migration as individual cells and not as chains. [source] Polysialic acid controls NCAM-induced differentiation of neuronal precursors into calretinin-positive olfactory bulb interneuronsDEVELOPMENTAL NEUROBIOLOGY, Issue 9 2008Iris Röckle Abstract Understanding the mechanisms that regulate neurogenesis is a prerequisite for brain repair approaches based on neuronal precursor cells. One important regulator of postnatal neurogenesis is polysialic acid (polySia), a post-translational modification of the neural cell adhesion molecule NCAM. In the present study, we investigated the role of polySia in differentiation of neuronal precursors isolated from the subventricular zone of early postnatal mice. Removal of polySia promoted neurite induction and selectively enhanced maturation into a calretinin-positive phenotype. Expression of calbindin and Pax6, indicative for other lineages of olfactory bulb interneurons, were not affected. A decrease in the number of TUNEL-positive cells indicated that cell survival was slightly improved by removing polySia. Time lapse imaging revealed the absence of chain migration and low cell motility, in the presence and absence of polySia. The changes in survival and differentiation, therefore, could be dissected from the well-known function of polySia as a promoter of precursor migration. The differentiation response was mimicked by exposure of cells to soluble or substrate-bound NCAM and prevented by the C3d-peptide, a synthetic ligand blocking NCAM interactions. Moreover, a higher degree of differentiation was observed in cultures from polysialyltransferase-depleted mice and after NCAM exposure of precursors from NCAM-knockout mice demonstrating that the NCAM function is mediated via heterophilic binding partners. In conclusion, these data reveal that polySia controls instructive NCAM signals, which direct the differentiation of subventricular zone-derived precursors towards the calretinin-positive phenotype of olfactory bulb interneurons. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] Gender and chain migration: the case of ArubaPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 2 2010Haime Croes Abstract Family reunification and family formation form a substantial part of chain migration, as most countries accept this form of settlement on the basis of humanitarian commitment to protecting families. Yet this does not mean that all migrants are treated equally in allowing them to bring over family members. Whether people are allocated this statutory right depends on their social and economic position. Women might be ,triply disadvantaged' as migrant women are often in more marginal jobs, from a different ethnicity, and have a harder time in acquiring these statutory rights. In this contribution we test this gender hypothesis using data from Aruba. Aruba provides an interesting case because the rapid development of the tourist-driven economy has given rise to enormous labour shortages across the various sectors of the economy, and it is now among the ten countries in the world with the highest net immigration rate. Due to its geographical position the island has recruited labour migrants from both Latin and North America and also from Europe. Dutch nationals receive preferential treatment as Aruba is a country within the Kingdom of the Netherlands. This diversity in immigration allows for an analysis of the social, ethnic, economic and legal determinants of family reunification. The results show that women have a disadvantaged position with respect to each of these determinants. On top of that a separate gender effect remains, indicating that it is harder for women migrants to bring over their spouses and children from their home country. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||