A family affair: Evidence of chain migration during the mass emigration from the county of Halland in Sweden to the United States in the 1890s.

This paper examines the influence of individual and household factors on an individual's propensity to emigrate from Halland, a region in south-west Sweden, to the United States during the era of mass migration in the late nineteenth century. The study has a case-control design, using individual-level longitudinal data for a group of emigrants (cases) and a group of non-emigrants (controls). Results indicate the importance of a family's emigration history; individuals whose relatives had previously moved to the United States were more likely to emigrate themselves. In addition, the results also show how this impact varied between groups and how other factors relating to the individual's life situation affected the migration decision. Thus, this paper shows how chain migration and migration networks play important roles during times of mass migration.

Neuraminidase inhibition promotes the collective migration of neurons and recovery of brain function.

In the injured brain, new neurons produced from endogenous neural stem cells form chains and migrate to injured areas and contribute to the regeneration of lost neurons. However, this endogenous regenerative capacity of the brain has not yet been leveraged for the treatment of brain injury. Here, we show that in healthy brain chains of migrating new neurons maintain unexpectedly large non-adherent areas between neighboring cells, allowing for efficient migration. In instances of brain injury, neuraminidase reduces polysialic acid levels, which negatively regulates adhesion, leading to increased cell-cell adhesion and reduced migration efficiency. The administration of zanamivir, a neuraminidase inhibitor used for influenza treatment, promotes neuronal migration toward damaged regions, fosters neuronal regeneration, and facilitates functional recovery. Together, these findings shed light on a new mechanism governing efficient neuronal migration in the adult brain under physiological conditions, pinpoint the disruption of this mechanism during brain injury, and propose a promising therapeutic avenue for brain injury through drug repositioning.

Enteric nervous system development: migration, differentiation, and disease.

The enteric nervous system (ENS) provides the intrinsic innervation of the bowel and is the most neurochemically diverse branch of the peripheral nervous system, consisting of two layers of ganglia and fibers encircling the gastrointestinal tract. The ENS is vital for life and is capable of autonomous regulation of motility and secretion. Developmental studies in model organisms and genetic studies of the most common congenital disease of the ENS, Hirschsprung disease, have provided a detailed understanding of ENS development. The ENS originates in the neural crest, mostly from the vagal levels of the neuraxis, which invades, proliferates, and migrates within the intestinal wall until the entire bowel is colonized with enteric neural crest-derived cells (ENCDCs). After initial migration, the ENS develops further by responding to guidance factors and morphogens that pattern the bowel concentrically, differentiating into glia and neuronal subtypes and wiring together to form a functional nervous system. Molecules controlling this process, including glial cell line-derived neurotrophic factor and its receptor RET, endothelin (ET)-3 and its receptor endothelin receptor type B, and transcription factors such as SOX10 and PHOX2B, are required for ENS development in humans. Important areas of active investigation include mechanisms that guide ENCDC migration, the role and signals downstream of endothelin receptor type B, and control of differentiation, neurochemical coding, and axonal targeting. Recent work also focuses on disease treatment by exploring the natural role of ENS stem cells and investigating potential therapeutic uses. Disease prevention may also be possible by modifying the fetal microenvironment to reduce the penetrance of Hirschsprung disease-causing mutations.

Doublecortin-Expressing Neurons in Human Cerebral Cortex Layer II and Amygdala from Infancy to 100 Years Old.

A cohort of morphologically heterogenous doublecortin immunoreactive (DCX +) "immature neurons" has been identified in the cerebral cortex largely around layer II and the amygdala largely in the paralaminar nucleus (PLN) among various mammals. To gain a wide spatiotemporal view on these neurons in humans, we examined layer II and amygdalar DCX + neurons in the brains of infants to 100-year-old individuals. Layer II DCX + neurons occurred throughout the cerebrum in the infants/toddlers, mainly in the temporal lobe in the adolescents and adults, and only in the temporal cortex surrounding the amygdala in the elderly. Amygdalar DCX + neurons occurred in all age groups, localized primarily to the PLN, and reduced in number with age. The small-sized DCX + neurons were unipolar or bipolar, and formed migratory chains extending tangentially, obliquely, and inwardly in layers I-III in the cortex, and from the PLN to other nuclei in the amygdala. Morphologically mature-looking neurons had a relatively larger soma and weaker DCX reactivity. In contrast to the above, DCX + neurons in the hippocampal dentate gyrus were only detected in the infant cases in parallelly processed cerebral sections. The present study reveals a broader regional distribution of the cortical layer II DCX + neurons than previously documented in human cerebrum, especially during childhood and adolescence, while both layer II and amygdalar DCX + neurons persist in the temporal lobe lifelong. Layer II and amygdalar DCX + neurons may serve as an essential immature neuronal system to support functional network plasticity in human cerebrum in an age/region-dependent manner.

Agent-based approach for elucidating the release from collective arrest of cell motion in corneal epithelial cell sheet.

Changes in cell fluidity have been observed in various cellular tissues and are strongly linked to biological phenomena such as self-organization. Recent studies suggested variety of mechanisms and factors, which are still being investigated. This study aimed to investigate changes in cell fluidity in multi-layered cell sheets, by exploring the collective arrest of cell motion and its release in cultures of corneal epithelial cells. We constructed mathematical models to simulate the behaviors of individual cells, including cell differentiation and time-dependent changes in cell-cell connections, which are defined by stochastic or kinetic rules. Changes in cell fluidity and cell sheet structures were expressed by simulating autonomous cell behaviors and interactions in tissues using an agent-based model. A single-cell level spatiotemporal analysis of cell state transition between migratable and non-migratable states revealed that the release from collective arrest of cell motion was initially triggered by a decreased ability to form cell-cell connections in the suprabasal layers, and was propagated by chain migration. Notably, the disruption of cell-cell connections and stratification occurred in the region of migratable state cells. Hence, a modeling approach that considers time-dependent changes in cell properties and behavior, and spatiotemporal analysis at the single-cell level can effectively delineate emergent phenomena arising from the complex interplay of cells.

Evolution of chain migration in an aerial insectivorous bird, the common swift Apus apus.

Spectacular long-distance migration has evolved repeatedly in animals enabling exploration of resources separated in time and space. In birds, these patterns are largely driven by seasonality, cost of migration, and asymmetries in competition leading most often to leapfrog migration, where northern breeding populations winter furthest to the south. Here, we show that the highly aerial common swift Apus apus, spending the nonbreeding period on the wing, instead exhibits a rarely found chain migration pattern, where the most southern breeding populations in Europe migrate to wintering areas furthest to the south in Africa, whereas the northern populations winter to the north. The swifts concentrated in three major areas in sub-Saharan Africa during the nonbreeding period, with substantial overlap of nearby breeding populations. We found that the southern breeding swifts were larger, raised more young, and arrived to the wintering areas with higher seasonal variation in greenness (Normalized Difference Vegetation Index) earlier than the northern breeding swifts. This unusual chain migration pattern in common swifts is largely driven by differential annual timing and we suggest it evolves by prior occupancy and dominance by size in the breeding quarters and by prior occupancy combined with diffuse competition in the winter.

ß1 integrin signaling promotes neuronal migration along vascular scaffolds in the post-stroke brain.

Cerebral ischemic stroke is a main cause of chronic disability. However, there is currently no effective treatment to promote recovery from stroke-induced neurological symptoms. Recent studies suggest that after stroke, immature neurons, referred to as neuroblasts, generated in a neurogenic niche, the ventricular-subventricular zone, migrate toward the injured area, where they differentiate into mature neurons. Interventions that increase the number of neuroblasts distributed at and around the lesion facilitate neuronal repair in rodent models for ischemic stroke, suggesting that promoting neuroblast migration in the post-stroke brain could improve efficient neuronal regeneration. To move toward the lesion, neuroblasts form chain-like aggregates and migrate along blood vessels, which are thought to increase their migration efficiency. However, the molecular mechanisms regulating these migration processes are largely unknown. Here we studied the role of ß1-class integrins, transmembrane receptors for extracellular matrix proteins, in these migrating neuroblasts. We found that the neuroblast chain formation and blood vessel-guided migration critically depend on ß1 integrin signaling. ß1 integrin facilitated the adhesion of neuroblasts to laminin and the efficient translocation of their soma during migration. Moreover, artificial laminin-containing scaffolds promoted neuroblast chain formation and migration toward the injured area. These data suggest that laminin signaling via ß1 integrin supports vasculature-guided neuronal migration to efficiently supply neuroblasts to injured areas. This study also highlights the importance of vascular scaffolds for cell migration in development and regeneration.

Migration networks: a case study in the Philippines.

"In an attempt to consider contract labor and other forms of temporary migration from the Philippines within the context of several interacting processes, I will first examine aspects of the international economy and government policy that set the stage for labor movement. It will then be argued that international migration flows emerge as a complex set of links that connect individuals and communities to the national capital region and ultimately to places abroad. This approach acknowledges that structural imbalances provide conditions for potential movement, but that this potential is translated into movement flows only when links between various people, places and mediating structures are actually activated through social networks. Once these links are established, a cascading system of migration emerges that is held together by a series of interpersonal relationships."

Family Sponsorship and Late-Age Immigration in Aging America: Revised and Expanded Estimates of Chained Migration.

We use the Immigrants Admitted to the United States (micro-data) supplemented with special tabulations from the Department of Homeland Security to examine how family reunification impacts the age composition of new immigrant cohorts since 1980. We develop a family migration multiplier measure for the period 1981 to 2009 that improves on prior studies by including immigrants granted legal status under the 1986 Immigration Reform and Control Act and relaxing unrealistic assumptions required by synthetic cohort measures. Results show that every 100 initiating immigrants admitted between 1981-85 sponsored an average of 260 family members; the comparable figure for initiating immigrants for the 1996-2000 cohort is 345 family members. Furthermore, the number of family migrants ages 50 and over rose from 44 to 74 per 100 initiating migrants. The discussion considers the health and welfare implications of late-age immigration in a climate of growing fiscal restraint and an aging native population.

Disentangling immigrant status in mental health: psychological protective and risk factors among Latino and Asian American immigrants.

This study aimed to disentangle the psychological mechanisms underlying immigrant status by testing a model of psychological protective and risk factors to predict the mental health prevalence rates among Latino and Asian American immigrants based on secondary analysis of the National Latino and Asian American Study. The first research question examined differences on the set of protective and risk factors between immigrants and their U.S.-born counterparts and found that immigrants reported higher levels of ethnic identity, family cohesion, native language proficiency, and limited English proficiency than their U.S.-born counterparts. The second research question examined the effect of the protective and risk factors on prevalence rates of depressive, anxiety, and substance-related disorders and found that social networking served as a protective factor. Discrimination, acculturative stress, and family conflict were risk factors on the mental health for both ethnic groups. Clinical implications and directions for future research are provided.

Chain migration reconsidered.

PIP: Aspects of migration, particularly chain migration, from Italy to Australia, Latin America, and the United States during the period 1850-1960 are analyzed and compared with migration to countries of the European Community since 1960. Consideration is given to occupational status and other migrant characteristics and to effects on the sending countries.^ieng