Black Americans and Ghanaians: comparative patterns of internal migration.
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"It is widely recognized that many internal migrations are undertaken by individuals whose moves are dependent on those of others. For example, children migrate with their parents and wives with their husbands. This paper suggests two formulations of family migration that permit the introduction of such family dependencies into the population projection process."
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The role of inheritance in neuronal migrational disorders is under intense investigation. Studies on neuronal migrational disorders (NMDs) from developing countries that have a high rate of parental consanguinity are lacking. The present study included 29 children (aged 15 days-12 years, mean age 1.4 years) who were diagnosed to have NMDs, from a non-selected population with seizures and non-selected population of cognitive developmental delay, in the period January 1994 to April 1997. Seventeen (58.6 per cent) patients had lissencephaly, four (13.8 per cent) patients had pachygyria, three (10.3 per cent) patients had neuronal heterotopia, four (13.8 per cent) patients had schizencephaly, one patient (3.4 per cent) had hemimegalencephaly, and 14 (48.2 per cent) patients with NMDs had other associated conditions. Lissencephalic patients had a high rate of parental consanguinity (88.2 per cent) and family history of possible similar cases (76.4 per cent). In conclusion, lissencephaly is probably the commonest neuronal migrational disorder in communities with a high rate of parental consanguinity, adding significant support to the literature on the genetic aetiology of lissencephaly.
Branching morphogenesis is a dynamic developmental process shared by many organs, but the mechanisms that reorganize cells during branching morphogenesis are not well understood. We hypothesized that extensive cell rearrangements are involved, and investigated cell migration using two-color confocal time-lapse microscopy to image cell and extracellular-matrix dynamics in developing salivary glands. We labeled submandibular salivary gland (SMG) epithelial cells with green fluorescent protein and matrix with fluorescent fibronectin. Surprisingly, we observed substantial, rapid and relatively random migration of individual epithelial cells during branching morphogenesis. We predicted that cell migration would decrease after formation of acini and, indeed, found that rapid cell movements do not occur in SMG from newborn mice. However, in embryonic SMG epithelial cells, we observed an absence of choreographed cell migration, indicating that patterned cell migration alone cannot explain the highly ordered process of branching morphogenesis. We therefore hypothesized a role for directional fibronection assembly in branching. Washout and pulse-chase experiments revealed that older fibronectin accumulates at the base of the clefts and translocates inwards as a wedge, with newer fibronectin assembling behind it. These findings identify a new mechanism for branching morphogenesis involving directional fibronectin translocation superimposed on individual cell dynamics.
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Besides specific cellular-mediated T cell responses, B cell related humoral responses have been demonstrated during the course of graft-versus-host disease after semiallogeneic transplantation of cellular antigen. Following semiallogeneic small bowel transplantation, there are, besides others, two specific forms of antigen-presenting cells, namely sinus lining cells (SLCs) and follicular dendritic cells (FDCs) which mediate primary and secondary humoral immune responses, respectively. This study was aimed to clarify the role of these dendritic cell entities after transplantation of small bowel grafts in a one-sided graft-versus-host (GvH) model for untreated and immunosuppressed (15-deoxyspergualin) recipient animals. As graft-versus-host disease progressed, SLCs and FDCs were eliminated in donor and recipient graft-versus-host associated target tissues (spleen and mesenteric lymph nodes) of untreated animals, whereas these dendritic cells prevailed in immunosuppressed recipients. 15-deoxyspergualin successfully prevented GvHD and significantly prolonged the mean survival time of untreated rats (16.0 +/- 4.5 d) for at least 21 d. Based on the immunosuppressive efficacy of 15-deoxyspergualin on the survival and function of SLCs and FDCs, an unaltered development of germinal centers and B cell proliferation within mesenteric lymph nodes and spleen was maintained
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"Using the data of the Indian Census of 1961, this study examines the rate of child migration to the cities of India and the proportion of the migrant children who were engaged in the labour force. The volume of child migration is found to be positively associated with total migration. Just over a fifth of the urban children were migrants but nearly forty percent of the child labourers were migrant children who were found to be concentrated in a few occupational divisions. Rural migrant children were short distance migrants while urban migrant children made long distance moves."
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