996 resultados para neural crest migration


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Lautdem Migrationsmodell des amerikanischen Psychologen Carlos E. Sluzki handelt es sichbei Migrationen um generationsübergreifende Prozesse, die auf die nachfolgendenGenerationen eine belastende Wirkung haben. Diese Belastungen sind gemäß seiner Theorieauf kulturelle Unterschiede zwischen der Familie und der Mehrheitsgesellschaftzurückzuführen. Es gilt diese Theorie anhand folgender Fragestellungen empirisch zuuntersuchen: Gibt es einen Zusammenhang zwischen Belastungen und dem Migrationshintergrund? Werden Kulturunterschiede wahrgenommen? Wie werden Belastungen bewältigt?Die Ergebnisse dieser Untersuchung zeigen, dass der Migrationshintergrund nur geringfügigEinfluss auf Belastungen hat. Es wurde lediglich eine migrationsbedingte Belastung ermittelt,wobei es sich um Probleme beim bilingualen Spracherwerb handelt. Es wurden außerdemeine Reihe von Kulturunterschieden genannt, die nicht per se als Belastung erlebt werden,sondern auch als eine Bereicherung. Alle in der Untersuchung genannten Belastungen werdenunter Anwendung problemlösender oder emotionsregulierender Strategien bewältigt. Einebesondere Bedeutung ist dabei den vorhandenen sozialen Ressourcen beizumessen.Schlüsselwörter:Migration, Migrationshintergrund, Migrant_in, Migrationsmodell, Belastungen,problemlösende/emotionsregulierende Bewältigungsstrategien, persönliche/soziale Ressourcen,Kultur, Dichotomie, Mehrheitsgesellschaft, Wir/Sie - Gruppe, Untersuchung, Leitfaden,qualitative Inhaltsanalyse, Kategorien(system)

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ABSTRACT Based on the hypothesis that diel vertical migration (DVM) is a mechanism of predator avoidance, the objective of the present study was to test for the occurrence of DVM in planktivorous fish larvae of Hypophthalmus edentatus (Spix, 1829) (Siluriformes, Pimelodidae) and Plagioscion squamosissimus (Heckel, 1840) (Perciformes, Sciaenidae), and zooplankton (rotifers, cladocerans and copepods) in an isolated tropical lagoon in the floodplain of the Upper Paraná River, Brazil (region of Parque Nacional de Ilha Grande). We investigated spatial overlap between predators (planktivorous fish larvae) and prey (zooplankton), and tested which physical and chemical variables of the water are related to the DVM of the studied communities. We performed nocturnal (8:00 pm and 4:00 am) and diurnal sampling (8:00 am and 4:00 pm) in the limnetic region of the lagoon for six consecutive months, from October 2010 to March 2011, which comprises the reproductive period of the fish species analyzed. During the day the larvae tried to remain aggregated in the bottom of the lagoon, whereas at night they tried to disperse in the water column. Especially for cladocerans, the diel vertical migration is an important behavior to avoid predation larvae of H. edentatus and P. squamosissimus once decreased spatial overlap between secured and its potential predators, which corroborates the hypothesis that DVM is a mechanism of predator avoidance. Although significant correlations were observed between the abiotic factors and WMD of microcrustaceans at certain times of day, the effect of predation of fish larvae on zooplankton showed more important in this environment, because the small depth and isolation not allow great variation of abiotic factors seasonally and between strata the lagoon.

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MicroRNAs (miRNAs) have been shown to play important roles in both brain development and the regulation of adult neural cell functions. However, a systematic analysis of brain miRNA functions has been hindered by a lack of comprehensive information regarding the distribution of miRNAs in neuronal versus glial cells. To address this issue, we performed microarray analyses of miRNA expression in the four principal cell types of the CNS (neurons, astrocytes, oligodendrocytes, and microglia) using primary cultures from postnatal d 1 rat cortex. These analyses revealed that neural miRNA expression is highly cell-type specific, with 116 of the 351 miRNAs examined being differentially expressed fivefold or more across the four cell types. We also demonstrate that individual neuron-enriched or neuron-diminished RNAs had a significant impact on the specification of neuronal phenotype: overexpression of the neuron-enriched miRNAs miR-376a and miR-434 increased the differentiation of neural stem cells into neurons, whereas the opposite effect was observed for the glia-enriched miRNAs miR-223, miR-146a, miR-19, and miR-32. In addition, glia-enriched miRNAs were shown to inhibit aberrant glial expression of neuronal proteins and phenotypes, as exemplified by miR-146a, which inhibited neuroligin 1-dependent synaptogenesis. This study identifies new nervous system functions of specific miRNAs, reveals the global extent to which the brain may use differential miRNA expression to regulate neural cell-type-specific phenotypes, and provides an important data resource that defines the compartmentalization of brain miRNAs across different cell types.

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Macrophage migration inhibitory factor (MIF), originally identified as a cytokine secreted by T lymphocytes, was found recently to be both a pituitary hormone and a mediator released by immune cells in response to glucocorticoid stimulation. We report here that the insulin-secreting beta cell of the islets of Langerhans expresses MIF and that its production is regulated by glucose in a time- and concentration-dependent manner. MIF and insulin colocalize by immunocytochemistry within the secretory granules of the pancreatic islet beta cells, and once released, MIF appears to regulate insulin release in an autocrine fashion. In perifusion studies performed with isolated rat islets, immunoneutralization of MIF reduced the first and second phase of the glucose-induced insulin secretion response by 39% and 31%, respectively. Conversely, exogenously added recombinant MIF was found to potentiate insulin release. Constitutive expression of MIF antisense RNA in the insulin-secreting INS-1 cell line inhibited MIF protein synthesis and decreased significantly glucose-induced insulin release. MIF is therefore a glucose-dependent, islet cell product that regulates insulin secretion in a positive manner and may play an important role in carbohydrate metabolism.

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Cerebral microangiopathy (CMA) has been associated with executive dysfunction and fronto-parietal neural network disruption. Advances in magnetic resonance imaging allow more detailed analyses of gray (e.g., voxel-based morphometry-VBM) and white matter (e.g., diffusion tensor imaging-DTI) than traditional visual rating scales. The current study investigated patients with early CMA and healthy control subjects with all three approaches. Neuropsychological assessment focused on executive functions, the cognitive domain most discussed in CMA. The DTI and age-related white matter changes rating scales revealed convergent results showing widespread white matter changes in early CMA. Correlations were found in frontal and parietal areas exclusively with speeded, but not with speed-corrected executive measures. The VBM analyses showed reduced gray matter in frontal areas. All three approaches confirmed the hypothesized fronto-parietal network disruption in early CMA. Innovative methods (DTI) converged with results from conventional methods (visual rating) while allowing greater spatial and tissue accuracy. They are thus valid additions to the analysis of neural correlates of cognitive dysfunction. We found a clear distinction between speeded and nonspeeded executive measures in relationship to imaging parameters. Cognitive slowing is related to disease severity in early CMA and therefore important for early diagnostics.

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The Republic of Haiti is the prime international remittances recipient country in the Latin American and Caribbean (LAC) region relative to its gross domestic product (GDP). The downside of this observation may be that this country is also the first exporter of skilled workers in the world by population size. The present research uses a zero-altered negative binomial (with logit inflation) to model households' international migration decision process, and endogenous regressors' Amemiya Generalized Least Squares method (instrumental variable Tobit, IV-Tobit) to account for selectivity and endogeneity issues in assessing the impact of remittances on labor market outcomes. Results are in line with what has been found so far in this literature in terms of a decline of labor supply in the presence of remittances. However, the impact of international remittances does not seem to be important in determining recipient households' labor participation behavior, particularly for women.

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Peripheral nerve injury is a serious problem affecting significantly patients' life. Autografts are the "gold standard" used to repair the injury gap, however, only 50% of patients fully recover from the trauma. Artificial conduits are a valid alternative to repairing peripheral nerve. They aim at confining the nerve environment throughout the regeneration process, and providing guidance to axon outgrowth. Biocompatible materials have been carefully designed to reduce inflammation and scar tissue formation, but modifications of the inner lumen are still required in order to optimise the scaffolds. Biomicking the native neural tissue with extracellular matrix fillers or coatings showed great promises in repairing longer gaps and extending cell survival. In addition, extracellular matrix molecules provide a platform to further bind growth factors that can be released in the system over time. Alternatively, conduit fillers can be used for cell transplantation at the injury site, reducing the lag time required for endogenous Schwann cells to proliferate and take part in the regeneration process. This review provides an overview on the importance of extracellular matrix molecules in peripheral nerve repair.

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Unilateral migration policies impose externalities on other countries. In order to try to internalize these externalities, countries sign bilateral migration agreements. One element of these agreements is the emphasis on enforcing migration policies: immigrant-receiving countries agree to allow more immigrants from their emigrant-sending partner if they cooperate in enforcing their migration policy at the border. I present a simple theoretical model that justifies this behavior in a two-country setting with welfare maximizing governments. These governments establish migration quotas that need to be enforced at a cost. I prove that uncoordinated migration policies are inefficient. Both countries can improve welfare by exchanging a more "generous" migration quota for expenditure on enforcement policy. Contrary to what could be expected, this result does not depend on the enforcement technology that both countries employ.

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This paper proposes a bootstrap artificial neural network based panel unit root test in a dynamic heterogeneous panel context. An application to a panel of bilateral real exchange rate series with the US Dollar from the 20 major OECD countries is provided to investigate the Purchase Power Parity (PPP). The combination of neural network and bootstrapping significantly changes the findings of the economic study in favour of PPP.

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For the development of studies on snail interspecific competition special in-door laboratory channels were built. In the all five channels seeded with adult specimens of Biomphalaria glabrata mass migration of juvenile snails outside the water was observed. Most of the migrant snails presented apertural lamellae. Data collected during the period of two years, showed the regression of the migration phenomenon and the disappearance of the lamellate snails.