Migration Patterns (migration + pattern)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Cardiovascular abnormalities in Folr1 knockout mice and folate rescue,

BIRTH DEFECTS RESEARCH, Issue 4 2007
Huiping Zhu
Abstract BACKGROUND: Periconceptional folic acid supplementation is widely believed to aid in the prevention of neural tube defects (NTDs), orofacial clefts, and congenital heart defects. Folate-binding proteins or receptors serve to bind folic acid and 5-methyltetrahydrofolate, representing one of the two major mechanisms of cellular folate uptake. METHODS: We herein describe abnormal cardiovascular development in mouse fetuses lacking a functional folate-binding protein gene (Folr1). We also performed a dose-response study with folinic acid and determined the impact of maternal folate supplementation on Folr1 nullizygous cardiac development. RESULTS: Partially rescued preterm Folr1,/, (formerly referred to as Folbp1) fetuses were found to have outflow tract defects, aortic arch artery abnormalities, and isolated dextracardia. Maternal supplementation with folinic acid rescued the embryonic lethality and the observed cardiovascular phenotypes in a dose-dependant manner. Maternal genotype exhibited significant impact on the rescue efficiency, suggesting an important role of in utero folate status in embryonic development. Abnormal heart looping was observed during early development of Folr1,/, embryos partially rescued by maternal folinic acid supplementation. Migration pattern of cardiac neural crest cells, genetic signals in pharyngeal arches, and the secondary heart field were also found to be affected in the mutant embryos. CONCLUSIONS: Our observations suggest that the beneficial effect of folic acid for congenital heart defects might be mediated via its impact on neural crest cells and by gene regulation of signaling pathways involved in the development of the pharyngeal arches and the secondary heart field. Birth Defects Research (Part A) 2007. © 2007 Wiley-Liss, Inc. [source]


Primary mesenchyme cell-ring pattern formation in 2D-embryos of the sea urchin

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2000
Hideki Katow
Primary mesenchyme cell (PMC) migration during PMC-ring pattern formation was analyzed using computer-assisted time-lapse video microscopy in spread embryos (2D-embryo) of the sea urchin, Mespilia globulus, and a computer simulation. The PMC formed a near normal ring pattern in the 2D-embryos, which were shown to be an excellent model for the examination of cell behavior in vivo by time-lapse computer analysis. The average migration distance of the ventro-lateral PMC aggregate-forming cells (AFC) and that of the dorso-ventral PMC cable-forming cells (CFC) showed no significant difference. All PMC took a rather straightforward migration path to their destinations with little lag time after ingression. This in vivo cell behavior fitted well to a computer simulation with a non-diffusable chemotaxis factor in the cyber-cell migration field. This simulation suggests that PMC recognize their destination from a very early moment of cell migration from the vegetal plate, and implicates that a chemoattractive region is necessary for making the PMC migration pattern. The left- and right-lateral AFC and dorso and ventral CFC were each derived from an unequally divided one-quarter segment of the vegetal plate. This suggests that AFC and CFC have a distinctive ancestor in the vegetal plate, and the PMC are a heterogeneous population at least in terms of their destination in the PMC-ring pattern. [source]


Effect of habitat fragmentation on spawning migration of brown trout (Salmo trutta L.)

ECOLOGY OF FRESHWATER FISH, Issue 3 2006
C. Gosset
Abstract , Human-induced habitat alteration is one of the main causes of the decline of freshwater fish populations. The watershed of the River Bidasoa (Spain) is an example of heavily fragmented habitat. The local brown trout (Salmo trutta L.) population is disturbed, with evidence of poor recruitment as well as low adult densities in the main stem. Forty male and female adult migratory trout were tagged with external or internal radio transmitters and released. Fixed stations with data loggers and mobile antennae were used with daily surveys to track fish movements during the migration and spawning period (3 months). Migration distances did not exceed 10 km, and half of the fish never entered a tributary in the study area. Fragmentation because of weirs on the main stem apparently prevented fish from reaching their spawning destination. Fish that entered the tributaries were first confronted with an accessibility problem because of low discharge. However, each fish chose one tributary, without making attempts to run up in other tributaries. Once in the tributary, fish were restrained in their upstream movements by dams. The study area appeared to be isolated from the vast upper part of the watershed. Within the study area, upper parts of tributaries also seemed strongly disconnected from the main stem. This study illustrates the negative impact of river fragmentation on S. trutta migration pattern. Population sustainability can be directly affected through the low availability of spawning grounds for migratory fish. Long-term effects of fragmentation may cause reproductive isolation within watersheds, which in the case of trout also means isolated phenotypic population units. [source]


Spatial distribution of the Japanese common squid, Todarodes pacificus, during its northward migration in the western North Pacific Ocean

FISHERIES OCEANOGRAPHY, Issue 2 2006
ATSUSHI KAWABATA
Abstract The spatial distribution of Todarodes pacificus in and near the Kuroshio/Oyashio Transition Zone during its northward migration was examined by comparative surveys using two types of mid-water trawl net and supplementary squid jigging from June to July 2000. The vertical and horizontal distribution patterns varied for different body sizes in relation to the oceanographic structure. Todarodes pacificus of 1,20 cm dorsal mantle length (ML) were widely distributed from the coastal waters of Japan to near 162°E longitude, probably due to transport by the Kuroshio Extension (KE). Todarodes pacificus smaller than 10 cm ML were mainly distributed in temperate surface layers at sea surface temperatures (SSTs) >15°C near the KE meander probably because of their poor tolerance to lower temperatures and limited swimming ability. Squid of 10,15 cm ML were distributed in the offshore waters of 10,15°C SST and in the coastal waters of northern Honshu, and underwent diel vertical migrations between the sea surface at night and deeper layers during the daytime. Squid larger than 15 cm ML were distributed in the coastal feeding grounds of northern Honshu and Hokkaido until they began their southward spawning migration. They also underwent diel vertical migrations, but remained deeper at night than the squid of 10,15 cm ML; this migration pattern closely matched that of their main prey such as euphausiids. We concluded that as T. pacificus grow, they shift their distribution range from the temperate surface layer around the KE toward the colder deeper layers, above 5°C, in the Oyashio and coastal areas. [source]


The role of macroinvertebrates and fish in regulating the provision by macrophytes of refugia for zooplankton in a warm temperate shallow lake

FRESHWATER BIOLOGY, Issue 10 2010
MARÍA de los ÁNGELES GONZÁLEZ SAGRARIO
Summary 1.,The zooplankton often undergoes diel horizontal migration (DHM) from the open water to the littoral of shallow lakes, thus avoiding predators in the former. This behaviour has functional impacts within the lake, as it enhances zooplankton survival, increases their control of phytoplankton and tends to stabilise the clear water state. However, most of the evidence supporting this migration pattern comes from cold north temperate lakes, and more evidence from tropical and subtropical areas, as well as from southern temperate areas, is needed. 2.,We conducted a field study of the diel horizontal and vertical migration of zooplankton, and the horizontal distribution of potential predatory macroinvertebrates and fish, over two consecutive days in the summer in a temperate lake in the southern hemisphere. We took zooplankton samples at two depths, at three sampling stations (inside beds of aquatic macrophytes, at their edge and in open water) along three transects running from the centre of a bed of Ceratophyllum demersum to open water. At each sampling station, we also took samples of macroinvertebrates and fish and measured physical and chemical environmental variables. 3.,Zooplankton (pelagic cladocerans, calanoid copepods and rotifers) avoided the shore, probably because of the greater risk from predators there. Larger and more vulnerable cladocerans, such as Diaphanosoma brachyurum and Moina micrura, were two to four times more abundant in open water than at the edge of or inside beds of macrophytes, respectively, by both day and night. Less vulnerable zooplankton [i.e. of medium body size (Ceriodaphnia dubia) or with the ability to swim fast (calanoid copepods)] were distributed evenly between open water and the edge of the plant beds. Small zooplankton, Bosmina huaronensis and pelagic rotifers, showed an even distribution among the three sampling stations. Accordingly, no DHM of zooplankton occurred, although larger organisms migrated vertically inside C. demersum stands. 4.,Macrophytes contained high densities of predatory macroinvertebrates and fish. The predator assemblage, composed of large-bodied macroinvertebrates (including odonates and shrimps) and small littoral fish, was permanently associated with submerged macrophytes. None of these groups moved outside the plant beds or changed their population structure (fish) over the diel cycle. 5.,Submerged macrophyte beds do not represent a refuge for zooplankton in lakes where predators are numerous among the plants, implying a weaker top-down control of phytoplankton biomass by zooplankton and, consequently, a more turbid lake. The effectiveness of macrophytes as a refuge for zooplankton depends on the associated assemblage of predatory macroinvertebrates and fish among the plants. [source]


Modification of the diel vertical migration of Bythotrephes longimanus by the cold-water planktivore, Coregonus artedi

FRESHWATER BIOLOGY, Issue 5 2008
JOELLE D. YOUNG
Summary 1. The weak diel vertical migration observed in the large cladoceran Bythotrephes longimanus seems contradictory to the predator-avoidance hypothesis that predicts large zooplankton should have long migration amplitudes. However, cold-water planktivores, especially Coregonus spp., are a main source of mortality for Bythotrephes and hence a deeper migration would result in a greater overlap with these hypolimnetic planktivores. We hypothesized that Coregonus artedi (cisco) modifies the normal vertical migration pattern of Bythotrephes, such that the latter stays higher in the water column during the day and thus migrates less extremely at night. 2. The vertical distribution of Bythotrephes during the day was determined from single visits to six lakes in Ontario, Canada, all of which contain warm-water, epilimnetic planktivores but differing in whether they contain cisco. One lake of each fish type was sampled day and night every 2,3 weeks over the ice-free season to examine daytime depths and migration amplitude. 3. The vertical migration of Bythotrephes differed in the presence and absence of cisco. In the lakes with cisco, there were significantly fewer Bythotrephes in the hypolimnion and they were higher in the water column during the day. Migration amplitude was smaller in the cisco than in the non-cisco lake. These observations were not attributable to differences in physical factors, and, although not conclusively attributable to cisco, are consistent with an effect of cisco. 4. We suggest that diurnal depth selection by Bythotrephes in lakes containing cisco is a trade-off between the risk of predation by warm- versus cold-water predators, balanced by the benefits of increased temperature and feeding rates near the surface. Even in lakes without cisco, however, the vertical migration of Bythotrephes was less than expected, suggesting that diurnal depth selection is a balance between the risk from warm-water planktivores and access to sufficient light to feed effectively. [source]


EU Enlargement, Migration, and Lessons from German Unification

GERMAN ECONOMIC REVIEW, Issue 3 2000
Hans-Werner Sinn
The paper studies the role of international implications after EU enlargement. Based on a formal model with migration costs for both capital and labor, it predicts a two-sided migration from the new to the old EU countries which is later reversed. As the migration pattern chosen by market forces turns out to be efficient, migration should not be artificially reduced by means of legal constraints or subsidies to the new member countries. The paper draws the parallel with German unification and points out the lessons to be learned by Europe. The analysis concludes with a brief discussion of the second-best problem posed by the existence of welfare states in the old member countries. [source]


Characterization of the migration of lung and blood T cells in response CXCL12 in a three-dimensional matrix

IMMUNOLOGY, Issue 4 2010
Caroline E. Day
Summary The ability of T cells to microlocalize within tissues, such as the lung, is crucial for immune surveillance and increased T-cell infiltration is a feature of many inflammatory lung conditions. T-cell migration has mainly been studied in two-dimensional assays. Using three-dimensional collagen gels to mimic the extracellular matrix of lung tissue, we have characterized the migration of T lymphocytes isolated from peripheral blood (PBT) and lung (LT) in response to interleukin-2 (IL-2) and CXCL12. Freshly isolated PBT and LT showed a low degree of migration (blood 4·0 ± 1·3% and lung 4·1 ± 1·7%). Twenty-four hours of culture increased the percentage of migrating PBT and LT (blood 17·5 ± 2·9% and lung 17·7 ± 3·8%). The IL-2 stimulation modestly increased migration of PBT after 6 days (32·3 ± 6·0%), but had no effect on the migration of LT (25·5 ± 3·2%). Twenty-four hours of stimulation with anti-CD3/CD28 caused a small but significant increase in the migration of PBT (to 36·4 ± 5·8%). In a directional three-dimensional assay, CXCL12 failed to induce migration of fresh PBT or LT. Twenty-four hours of culture, which increased CXCR4 expression of PBT 3·6-fold, significantly increased the migration of PBT in response to CXCL12. Migration of PBT to CXCL12 was blocked by pertussis toxin, but not by the phosphoinositide 3-kinase inhibitor wortmannin. Twenty-four-hour cultured LT did not respond to CXCL12. CD3/CD28-stimulation inhibited CXCL12-mediated migration of PBT. These results suggest that the migration pattern of PBT is distinct from that of LT. [source]


The orientation system and migration pattern of long-distance migrants: conflict between model predictions and observed patterns

JOURNAL OF AVIAN BIOLOGY, Issue 2 2001
Kasper Thorup
The requirements of the orientation system of naïve long-distance night migrants were analysed by comparing data on Barred Warbler Sylvia nisoria, Marsh Warbler Acrocephalus palustris and Spotted Flycatcher Muscicapa striata with data from a computer model of a clock-and-compass system. These species show, respectively, a rather restricted winter distribution in East Africa, migration through a very narrow corridor in East Africa, and rather widely distributed recoveries in the Mediterranean with more concentrated recoveries south of the Sahara. For all three species, to obtain the observed concentrations either a very high directional migratory concentration was needed in computer simulations to bring the birds successfully to their wintering areas or misorientating individuals would be subjected to a very high mortality. Neither the very high directional concentration nor the high mortality amongst misorientating individuals fit the empirical data sets. On the basis of the present study, the observed patterns seem difficult to explain by a simple clock-and-compass system only, and to account for the exceptionally precise migratory routes shown in this study it is proposed that first-time migrants might be able to use landscape topography on a regional scale in combination with corrections of directional mistakes/wind displacements. [source]


Migratory behaviour and survival rates of wild northern Atlantic salmon Salmo salar post-smolts: effects of environmental factors

JOURNAL OF FISH BIOLOGY, Issue 7 2009
J. G. Davidsen
To study smolt behaviour and survival of a northern Atlantic salmon Salmo salar population during river descent, sea entry and fjord migration, 120 wild S. salar were tagged with acoustic tags and registered at four automatic listening station arrays in the mouth of the north Norwegian River Alta and throughout the Alta Fjord. An estimated 75% of the post-smolts survived from the river mouth, through the estuary and the first 17 km of the fjord. Survival rates in the fjord varied with fork length (LF), and ranged from 97·0 to 99·5% km,1. On average, the post-smolts spent 1·5 days (36 h, range 11,365 h) travelling from the river mouth to the last fjord array, 31 km from the river mouth. The migratory speed was slower (1·8 LF s,1) in the first 4 km after sea entry compared with the next 27 km (3·0 LF s,1). Post-smolts entered the fjord more often during the high or ebbing tide (70%). There was no clear diurnal migration pattern within the river and fjord, but most of the post-smolts entered the fjord at night (66%, 2000,0800 hours), despite the 24 h daylight at this latitude. The tidal cycle, wind-induced currents and the smolts' own movements seemed to influence migratory speeds and routes in different parts of the fjord. A large variation in migration patterns, both in the river and fjord, might indicate that individuals in stochastic estuarine and marine environments are exposed to highly variable selection regimes, resulting in different responses to environmental factors on both temporal and spatial scales. Post-smolts in the northern Alta Fjord had similar early marine survival rates to those observed previously in southern fjords; however, fjord residency in the north was shorter. [source]


Synchrony in the downstream migration of smolts and upstream migration of adult Atlantic salmon in the subarctic River Utsjoki

JOURNAL OF FISH BIOLOGY, Issue 6 2007
P. Orell
Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001,2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300,0900 hours) and high sun (0900,1500 hours), while adults favoured the period of low sun (2100,0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2,3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups. [source]


Habitat use, migration pattern and population dynamics of chevron snakehead Channa striata in a rainfed rice farming landscape

JOURNAL OF FISH BIOLOGY, Issue 2005
E. Amilhat
Habitat use, migration, mortality and growth of the chevron snakehead Channa striata in a rainfed rice farming landscape of north-east Thailand were studied through a tagging experiment. A total of 751 fish were captured, tagged and released during three distinct events in the late dry season, and in the beginning and at the end of the wet season. Rice fields provided the major wet season habitat for C. striata. Small trap ponds built to provide dry season habitat on farms provided 20% of catches and, if not harvested, could increase recruitment to the spawning stock by >30% despite accounting for <1% of dry season habitat by area. Migrations were localized (mostly <500 m). Up-migration from perennial to seasonal water bodies at the beginning of the wet season involved longer distances and took place over a longer time than down-migration at the end of the wet season. Natural mortality rates were extremely high, particularly during the period of down-migration. Fishing mortality rates were high in absolute terms, but contributed only 6,36% to the total mortality. Growth was seasonal with a maximum towards the end of the wet season. Snakeheads have successfully colonized the rainfed rice farming landscape, where populations can withstand intensive exploitation and respond well to aquatic habitat management on farmland. [source]


Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts

JOURNAL OF FISH BIOLOGY, Issue 1 2001
C. Nielsen
Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3,6 days. Burrishoole and Conon fish migrated with a 15,19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na+, K+ -ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter-strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na+, K+ -ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon. [source]


Mutations in GPIIIa molecule as a cause for Glanzmann thrombasthenia in Indian patients

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 3 2005
S. NAIR
Summary.,Background:,Glanzmann thrombasthenia (GT) results from a quantitative or qualitative defect of GPIIb,IIIa complex, the fibrinogen receptor on platelets, which plays a very important role in platelet aggregation. In this report we describe the molecular studies on 22 patients with Glanzmann Thrombasthenia at our institute. Objectives:,The main objective was to identify the mutations present in our GT population in order to establish a strategy for genetic counseling and antenatal diagnosis. Methods:,Twenty-two patients with GT were included in the present study. Complete blood count (CBC), platelet aggregation, flow cytometry, Western blot, single strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) were performed in all the patients. The patients showing an abnormal migration pattern in SSCP or DGGE were sequenced further on an automated sequencer. Results:,Of the 22 patients studied, mutations were detected in 12 individuals. Of these, 11 were novel mutations and one mutation Y115C was reported earlier. Flow cytometric analysis showed the absence of receptors in type I GT, highly reduced levels in type II GT and normal levels in type III GT. The DGGE analysis and SSCP analysis of the patients showed different migration patterns. Sequencing was performed in all patients showing an abnormal migration pattern. Of the 22 cases studied mutations could be detected in 12 cases of GT. We could detect six patients with point mutations, four patients with insertions and five patients with deletion mutations. Exon 4 has been found to be the most common site for mutations in our patients. Conclusion:,This study has shown a wide array of mutations present in our GT patients which would be extremely useful in genetic counseling and prenatal diagnosis, essential in preventing these disorders in succeeding generations. [source]


Direction Sweden: migration fields and cognitive distances of Finland Swedes

POPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 6 2007
Charlotta Hedberg
Abstract This article analyses migration fields and perceptions of distance in the context of the migration process of the Finland-Swedish minority group from Finland to Sweden between 1976 and 1999. The focus of investigation concerns whether the conceptualisation of distance, in terms of socio-historical migration fields and cognitive maps, can contribute to our understanding of migration decision-making. A combination of methods has been employed. Firstly, a quantitative analysis took place of the migration fields of Finland Swedes originating in three case-study areas in Finland. The extension of their migration fields into Sweden is calculated relative to the internal migration pattern within Finland. Secondly, an interview study analysed perceptions of distance among migrants to Sweden. The article shows that a sizeable proportion of the Finland Swedes' migration fields were directed towards Sweden, but that their extension contained regional variations. Further, the decision to migrate to Sweden was strongly influenced by the migrants' perceptions of Sweden prior to migration. Thus, the migrants possessed cognitive maps, with particular sites in Sweden being regarded as distinct and ,close' locations, in contrast to alternative, ,remote' locations in Finland. The perceptions of distance were shaped by the migrants' social, cultural and economic links with Sweden, as well as by their ethnic identity, which included an ethnic affinity with Sweden. It is suggested that the Finland-Swedish migration process to Sweden should be seen as a case of transnational migration. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Dynamics of Mast Cells in Lymph Node Following Antigenic Stimulation

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2004
D. O. Dabak
Summary Dynamics of mast cells in rat cervical lymph nodes were examined using conventional histological techniques after injection of Salmonella paratyphi B-H antigen. There was no significant change in the number of mast cells at sixth hour and on the first day of stimulation compared with the controls. The number of mast cells was increased in all lymph node compartments on the second day of stimulation, which continued in the following 3 days. On the eighth day of stimulation, although the mast cell number decreased in the subcapsular area, it was still high in the paracortical area and medullary sinuses of the lymph nodes. On the second day of stimulation, the mast cell number was apparently increased in the subcapsular area than those of the other compartments. In the following days of stimulation, the highest number of mast cells was seen in the medullary sinuses. The highest paracortical mast cell number was determined on the third day of stimulation and some mast cells were observed near the high endothelial venules (HEVs). The changes of mast cell number among the lymph node compartments after antigenic stimulation support the hypothesis that the migration of mast cells occurred. This migration pattern indicates that mast cells enter the lymph node via afferent lymphatics and migrate to the lymph node compartments following antigenic stimulation. [source]


Coronin is involved in uptake of Mycobacterium bovis BCG in human macrophages but not in phagosome maintenance

CELLULAR MICROBIOLOGY, Issue 12 2001
Stephanie Schüller
By applying density gradient electrophoresis (DGE) to human macrophages infected with Mycobacterium bovis BCG, we were able to separate three different bacterial fractions representing arrested phagosomes, phagolysosomes and mycobacterial clumps. After further purification of the phagosomal population, we found that isolated phagosomes containing live BCG were arrested in maturation as they exhibited only low amounts of the lysosomal glycoprotein LAMP-1 and processing of the lysosomal hydrolase cathepsin D was blocked. In addition, low amounts of MHC class I and class II molecules and the absence of HLA-DM suggest sequestration of mycobacterial phagosomes from antigen-processing pathways. We further investigated the involvement of the actin-binding protein coronin in intracellular survival of mycobacteria and showed that human coronin, as well as F-actin, were associated with early stages of mycobacterial phagocytosis but not with phagosome maintenance. Therefore, we conclude that the unique DGE migration pattern of arrested phagosomes is not as a result of retention of coronin, but that there are other proteins or lipids responsible for the block in maturation in human macrophages. [source]


Characteristics of Important Stopover Locations for Migrating Birds: Remote Sensing with Radar in the Great Lakes Basin

CONSERVATION BIOLOGY, Issue 2 2009
DAVID N. BONTER
ave terrestre migratoria; migración; radar; sitios de escala temporal; WSR-88D Abstract:,A preliminary stage in developing comprehensive conservation plans involves identifying areas used by the organisms of interest. The areas used by migratory land birds during temporal breaks in migration (stopover periods) have received relatively little research and conservation attention. Methodologies for identifying stopover sites across large geographic areas have been, until recently, unavailable. Advances in weather-radar technology now allow for evaluation of bird migration patterns at large spatial scales. We analyzed radar data (WSR-88D) recorded during spring migration in 2000 and 2001 at 6 sites in the Great Lakes basin (U.S.A.). Our goal was to link areas of high migrant activity with the land-cover types and landscape contexts corresponding to those areas. To characterize the landscapes surrounding stopover locations, we integrated radar and land-cover data within a geographic information system. We compared landscape metrics within 5 km of areas that consistently hosted large numbers of migrants with landscapes surrounding randomly selected areas that were used by relatively few birds during migration. Concentration areas were characterized by 1.2 times more forest cover and 9.3 times more water cover than areas with little migrant activity. We detected a strong negative relationship between activity of migratory birds and agricultural land uses. Examination of individual migration events confirmed the importance of fragments of forested habitat in highly altered landscapes and highlighted large concentrations of birds departing from near-shore terrestrial areas in the Great Lakes basin. We conclude that conservation efforts can be more effectively targeted through intensive analysis of radar imagery. Resumen:,Una etapa preliminar en el desarrollo de planes de conservación integrales implica la identificación de áreas utilizadas por los organismos de interés. Las áreas utilizadas por aves terrestres migratorias durante escalas temporales en la migración (períodos de parada) han recibido relativamente poca atención de investigación y conservación. Hasta hace poco, las metodologías para la identificación de sitios de parada en áreas geográficas extensas han sido escasas. Ahora, los avances en la tecnología de radar meteorológico permiten la evaluación de patrones de migración de aves en escalas espaciales grandes. Analizamos datos de radar (WSR-88D) registrados en seis sitios en la cuenca de los Grandes Lagos (E.U.A.) durante la migración en las primaveras de 2000 y 2001. Nuestra meta fue relacionar áreas con gran actividad migratoria con los tipos de cobertura de suelo y los contextos del paisaje correspondientes a esas áreas. Para caracterizar los paisajes circundantes a las localidades de parada, integramos los datos de radar y de cobertura de suelo a un sistema de información geográfica. Comparamos las medidas del paisaje en un radio de 5 km en las áreas que consistentemente albergaron a grandes números de migrantes con los paisajes circundantes a áreas seleccionadas aleatoriamente y que eran utilizadas por relativamente pocas aves durante la migración. Las áreas de concentración se caracterizaron por tener 1.3 veces más cobertura forestal y 9.3 veces más cobertura de agua que las áreas con poca actividad migratoria. Detectamos una fuerte relación negativa entre la actividad de las aves migratorias y los usos de suelo agrícolas. El examen de eventos migratorios individuales confirmó la importancia de los fragmentos de hábitat boscoso en paisajes muy alterados y resaltó las grandes concentraciones de aves partiendo de áreas terrestres cercanas a la costa en la cuenca de los Grandes Lagos. Concluimos que los esfuerzos de conservación pueden ser abordados más efectivamente mediante el análisis intensivo de imágenes de radar. [source]


Rendering the World Unsafe: ,Vulnerability' as Western Discourse

DISASTERS, Issue 1 2001
Gregory Bankoff
Disasters seem destined to be major issues of academic enquiry in the new century if for no other reason than that they are inseparably linked to questions of environmental conservation, resource depletion and migration patterns in an increasingly globalised world. Unfortunately, inadequate attention has been directed at considering the historical roots of the discursive framework within which hazard is generally presented, and how that might reflect particular cultural values to do with the way in which certain regions or zones of the world are usually imagined. This paper argues that tropicality, development and vulnerability form part of one and the same essentialising and generalising cultural discourse that denigrates large regions of world as disease-ridden, poverty-stricken and disaster-prone. [source]


Electrophoretic variants of cardiac myosin heavy chain-, in Sprague Dawley rats

ELECTROPHORESIS, Issue 3 2004
Peter J. Reiser
Abstract Analysis of cardiac myosin revealed differences in gel electrophoretic migration patterns of the ,-isoform of myosin heavy chain, but not the ,-isoform, in Sprague Dawley rats. No differences in the migration patterns of the ,-or ,-isoforms were observed in other rat strains. Three electrophoretic migration patterns of the ,-isoforms were observed in individual rats: a slower migrating isoform alone (4% of all rats tested), a faster migrating isoform alone (55%), and both isoforms (41%). The isoform expression pattern was identical in all myocardial regions in each rat. Frequency of expression patterns suggests multiple gene sequences for ,-cardiac myosin heavy chain in Sprague Dawley rats. Sequence analysis of amplified regions of the Sprague Dawley and Brown Norway rat ,-myosin genes, specifically the 5'-untranslated region, exons 1,3, and associated introns, showed numerous single nucleotide polymorphisms in coding and noncoding regions, including putative regulatory sites in Sprague Dawley rats, but not in Brown Norway rats. All Sprague Dawley rats varied from Brown Norway rats and no heterogeneity was observed in Brown Norway rats. Several deletions and dimorphic positions were also observed. Dimorphic positions were evident on automated sequencing comparisons. The data indicate that at least two ,-myosin heavy chain isoforms exist in Sprague Dawley rats and these rats exhibit sequence diversity within that portion of the ,-myosin heavy chain gene reported in this study. [source]


Site-specific expression of CD11b and SIRP, (CD172a) on dendritic cells: implications for their migration patterns in the gut immune system

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2005
Diane Bimczok
Abstract Dendritic cells (DC) in the intestinal tract play a major role in directing the mucosal immune system towards tolerance or immunity. We analyzed whether different mucosal DC subsets in pigs have specific functions, localizations, or migration patterns in vivo. Therefore, we collected physiologically migrating DC by pseudo-afferent cannulation of the intestinal duct in eight Göttingen minipigs. Lymph DC were phenotypically and functionally characterized and compared to DC found on histological sections of porcine small intestine and mesenteric lymph nodes (MLN). Four different DC subpopulations were detected. Lamina propria (LP) DC were mainly CD11b+ signal regulatory protein,, (SIRP,)+, DC in Peyer's patches were mainly CD11b,/SIRP,+ in subepithelial domes and CD11b,/SIRP,, in interfollicular regions, whereas MLN DC were largely CD11b+/SIRP,,. Of these four subsets, only the CD11b+/SIRP,+ DC and the CD11b+/SIRP,, DC were present in lymph. This suggests that DC migration to MLN largely originates from the LP. Lymph DC expressed high levels of MHC class,II and costimulatory molecules and had a low capacity for FITC-dextran uptake, indicating a mature phenotype. However, lymph DC did not induce PBMC proliferation in MLR, and migration was not significantly influenced by mucosal antigen application. [source]


Migration of cells into and out of peripheral nerve isografts in the peripheral and central nervous systems of the adult mouse

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2001
Natalie A. Symons
Abstract Peripheral nerve (PN) isografts provide a favourable environment for axon regeneration after peripheral and central nervous system (CNS) injury, but definitive information on the extent of cellular intermixing between donor and host tissues is lacking. We wished to compare migration patterns in fresh and predegenerate PN grafts, and also compare the extent of cell migration after transplantation to peripheral nervous system (PNS) versus CNS. To discern how host and donor cells interact after PN transplantation, sciatic nerve segments were transplanted from inbred adult mice into PN defects (PN,PN grafts) or into lesioned cerebral cortex of opposite gender siblings. Migrating male cells were identified using a Y-chromosome-specific probe and in situ hybridization methods, and characterized immunohistochemically. The extent of donor and host cellular intermixing was similar in fresh and predegenerate PN,PN isografts. There was substantial intermixing of donor and host cells by 8 days. Many host cells migrating into epineurial regions of grafts were immunopositive for F4/80 (macrophages). The endoneurium of grafted PN was also colonized by host cells; some were F4/80+ but many were immunostained with S-100 (Schwann cell marker). Donor S-100+ Schwann cells rapidly migrated out into proximal and distal host PN and by 12 weeks were found at least 2 mm from the grafts. Endoneurial microvessels in grafts were mostly donor-derived. By comparison, in male PN grafts to female CNS, even after 6 weeks few donor cells had migrated out into surrounding host cortex, despite the observation that almost all grafts contained regenerating axons and were thus attached to host CNS tissue. [source]


New visions of dental tissue research: Tooth development, chemistry, and structure

EVOLUTIONARY ANTHROPOLOGY, Issue 5 2008
Tanya M. Smith
Abstract Teeth are one of the best preserved and most commonly recovered elements in primate fossil assemblages. Taxonomic, functional, and phylogenetic hypotheses often rely on dental characters, despite considerable evidence of homoplasy in tooth form and large variation in tooth size within and among primates.1,2 Recent studies have led to new areas of research centered on incremental tooth development, chemical composition, and internal structure. Due to rapid technological developments in imaging and elemental sampling, these new approaches have the potential to increase our understanding of developmental biology, including not only changes in the pace of growth and reproduction, but also our assessments of diets, migration patterns, environments, and taxonomy. The integration of these temporal, chemical, and structural approaches heralds a bright future for the role of dental tissue research in evolutionary anthropology. © 2008 Wiley-Liss, Inc. [source]


Genetic diversity and migration patterns of the aquatic macrophyte Potamogeton malaianus in a potamo-lacustrine system

FRESHWATER BIOLOGY, Issue 6 2009
YUANYUAN CHEN
Summary 1.,Previously, the Yangtze River connected thousands of shallow lakes which together formed a potamo-lacustrine system capable of sustaining a rich variety of submerged macrophytes. 2.,Potamogeton malaianus is one of the dominant submerged macrophytes in many lakes of this area. Genetic variation and population structure of P. malaianus populations from ten lakes in the potamo-lacustrine system were assessed using inter-simple sequence repeat markers. 3.,Twelve primer combinations produced a total of 166 unambiguous bands of which 117 (70.5%) were polymorphic. Potamogeton malaianus exhibited a moderate level of population genetic diversity (PP = 70.5%, HE = 0.163 and I = 0.255), as compared with that of plants in the same habitat and range. The main factors responsible for this moderate value were the plant's mixed breeding system (both sexual and asexual) and the hydrological connectivity among habitats. 4.,F statistics, calculated using different approaches, consistently revealed a moderate genetic differentiation among populations, contributing about 20% of total genetic diversity. An estimate of gene flow (using FST) suggested that gene flow played a more important role than genetic drift in the current population genetic structure of P. malaianus (Nm = 1.131). 5.,The genetic diversity of P. malaianus did not increase downstream. A high level of linkage,disequilibrium at the whole population level suggested that metapopulation processes may affect genetic structure. The migration pattern of P. malaianus was best explained by a two-dimensional stepping stone model, indicating that bird-mediated dispersal could greatly influence gene movements among lakes. [source]


Types and Patterns of Later-life Migration

GEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 3 2000
William H. Walters
This paper refines previous typologies of later-life mobility by explicitly evaluating the spatial migration patterns and household characteristics of retired American migrants. Migrants' lifecourse attributes (economic status, disability, presence of spouse), large-scale migration patterns (internal migration) and household characteristics (living arrangements, economic independence, residential independence) are used to identify three types of post-retirement mobility. The first type, amenity migration, has a distinctive spatial pattern that suggests a search for attractive climate and leisure amenities. The second type of mobility, assistance migration, can be traced to low income and the absence of a spouse in the household. It often results in residential and economic dependence , specifically, in co-residence with adult children or other labor force members. The third type of mobility, migration in response to severe disability and spouse absence, tends to result in nursing home residence. While amenity migration has long been associated with good health and favorable economic status, this analysis reveals that many disabled and lower-income retirees share the inmigration pattern typical of amenity migrants. In fact, amenity migration is the predominant type of mobility among those migrants with fewer than two unfavorable lifecourse attributes (low income, severe disability and spouse absence). Unlike previous lifecourse typologies, this study shows no clear relationship between moderate disability and co-residence with adult children. The results suggest that co-residence is primarily a strategy for reducing living costs rather than a means of coping with moderate disability. [source]


Public Education Financing Trends and the Gray Peril Hypothesis

GROWTH AND CHANGE, Issue 4 2009
DAYTON M. LAMBERT
ABSTRACT The effects of migrating seniors on the provision of local public services in rural communities is growing in importance because of the large number of retiring baby boomers and the increasing rate at which these retirees are locating outside traditional retirement destinations. Some communities are optimistic about attracting and retaining retirees as an economic development strategy, but others are concerned that inmigrating seniors may be reluctant to support local public services, such as education, bringing with them "Gray Peril." This article attempts to clarify questions regarding the Gray Peril hypothesis and local ability and willingness to fund education in Tennessee, an increasingly popular retirement destination. To this end, county per pupil education expenditure growth is explained by growth trends in local property tax assessment and sales tax revenue, and migration patterns of the retirement-aged population from 1962 to 2002. [source]


Quality of Life and the Migration of the College-Educated: A Life-Course Approach

GROWTH AND CHANGE, Issue 1 2008
RONALD L. WHISLER
ABSTRACT This paper examines how the college-educated population,segmented into selective demographic groups, from young adults to the elderly,differentially values quality-of-life (QOL) indicators of metropolitan areas in the United States. Using data from the 2000 Census and the 1997 Places Rated Almanac, out-migration patterns are shown to depend jointly upon stage in the life course, the spatial-demographic setting, and QOL characteristics. An abundance of cultural and recreational amenities lowers out-migration rates of young college-educated. For the older college-educated population, the revealed preferences shift toward concerns for safety and a strong preference for milder climates. The study also finds significantly lower out-migration rates for metropolitan areas with growing human capital. In light of shifting age distributions and rising educational attainment levels, the results have important implications for the emergence of new migration patterns and the concentration of human capital. [source]


Migration of naive, effector and memory T cells: implications for the regulation of immune responses

IMMUNOLOGICAL REVIEWS, Issue 1 2001
Jürgen Westermann
Summary: T cells play an important role in protective immune responses and in the pathogenesis of many diseases. Understanding the mechanisms regulating their distribution in vivo may therefore be of therapeutic value. Reviewing studies that have followed the migration of labelled naive, effector and memory T cells in healthy animals reveals that all T-cell subsets enter all organs investigated. Within the tissue, two principally different migration patterns can be identified. First, naive and memory T cells accumulate in lymphoid organs for about 48 h after injection, as the time needed for migration through lymphoid organs is longer than through non-lymphoid organs. During this time, surface molecule expression is temporarily modified. These changes are reversed before leaving the lymphoid organs and entering the blood to start a new cycle of migration. Second, effector T cells are evenly distributed throughout the body, and most die in the tissues within 24 h. However, depending on the presence of cytokines, some are able to survive and to proliferate, and thereby accumulate in defined microenvironments of the body. Analysing the principles regulating T-cell migration and survival within the tissue may lead to the development of new options for the treatment of disease. [source]


Mobility and the middle classes: a case study of Manchester and the North West

INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 3 2003
Fiona Devine
While much is known about the mobility patterns of the middle classes in London and the South East, far less is certain about middle-class migration patterns in other regions of the country. Nor has the importance of other regional centres in providing opportunities in the professions and management been acknowledged. This article rectifies these omissions by drawing on research with young professionals employed in Manchester in the North West. It explores the migratory patterns of the ,migrant' interviewees. The article will show that the majority of young professionals were ,migrants' in having been geographically mobile at some point in their lives. Different types of migrants are identified: (1) those with family affiliations; (2) those with university roots; and (3) those with (seemingly) no connections to the city or the region. These migratory practices are shaped by different factors: namely, the close proximity of family and friends, attractive job opportunities in Manchester, the role of universities in establishing roots and a sense of belonging and, finally, an identification with the North , widely defined and straddling the Pennines. These factors also shaped the residential patterns of the sample. Si l'on connaît l'essentiel des schémas de mobilité des classes moyennes à Londres et dans le Sud-Est, on a bien moins de certitudes quant aux modèles migratoires de ces populations dans d'autres régions britanniques. Pas plus que n'a été reconnue l'importance d'autres centres régionaux concernant l'offre d'opportunités pour les professions libérales et les cadres. Cet article corrige ces omissions à partir d'une étude réalisée auprès de jeunes diplômés travaillant à Manchester dans le Nord-Ouest. Il étudie les schémas migratoires des ,migrants' interrogés. En majorité, ces jeunes sont des ,migrants', car ils ont été mobiles géographiquement à un moment de leur vie. Parmi eux, différents types sont identifiés: ceux qui ont des attaches familiales, ceux qui ont des racines universitaires, et ceux qui n'ont (en apparence) aucun lien avec la ville ou la région. Plusieurs facteurs façonnent ces pratiques migratoires, à savoir: proximité de famille ou d'amis, propositions d'emploi attirantes à Manchester, fonction d'enracinement et de sentiment d'appartenance des universités et, enfin, identification au Nord , selon une définition large s'étendant de part et d'autre des Pennines. D'après l'échantillon, ces facteurs structurent également les schémas résidentiels. [source]


Migration and Transnational Families in Fiji: Comparing Two Ethnic Groups

INTERNATIONAL MIGRATION, Issue 4 2008
Carmen Voigt-Graf
In the past two decades, international migration patterns out of Fiji have undergone changes with important implications for the formation of transnational families. The focus of this paper is on a comparison between the formation of Indo-Fijian transnational extended families and indigenous Fijian transnational nuclear families. These are discussed within the framework of "transnational corporations of kin." For several decades, Indo-Fijians have permanently migrated to the Pacific Rim as a consequence of the economic and political situation in Fiji. They have resettled in complete nuclear family units and have subsequently attempted to sponsor the migration of their extended family members. Recent years have witnessed an increasing number of indigenous Fijians migrating temporarily for work. In contrast to Indo-Fijians, indigenous Fijian migrate as individuals, leaving their spouses and children behind in Fiji. Women migrate autonomously as caregivers and nurses while men find employment as soldiers and security officers. The main purpose of their mostly temporary migration is to send remittances. However, these economic benefits have to be contrasted with the social and psychological costs associated with the separation of nuclear families. The paper also discusses policy implications arising from the comparative analysis, especially in the light of the current situation in Fiji which is characterised by a lack of policies addressing the implications of migration. Migration et familles transnationales à Fidji: comparaison de deux groupes ethniques Durant ces vingt dernières années, les tendances migratoires internationales au départ de Fidji ont subi des changements qui ont eu d'importantes conséquences sur la constitution de familles transnationales. Le thème central de cette publication porte sur une comparaison entre la constitution de familles transnationales indo-fidjiennes élargies et les familles transnationales fidjiennes indigènes nucléaires. Celles-ci sont examinées dans le cadre de ce que l'on appelle les sociétés familiales transnationales. Depuis plusieurs dizaines d'années, les Indo-Fidjiens migrent à demeure vers la ceinture du Pacifique en raison de la situation économique et politique de Fidji. A partir de là, ils reprennent le schéma de la famille nucléaire complète et tentent ensuite de financer la migration des membres de leur famille élargie. Les dernières années ont mis en évidence une tendance croissante des Fidjiens indigènes àémigrer temporairement en quête de travail. A la différence des Indo-Fidjiens, les Fidjiens indigènes émigrent seuls, en laissant derrière eux femmes et enfants. Les femmes émigrent de façon autonome en quête d'un emploi d'aidante ou d'infirmière tandis que les hommes se font embaucher comme soldats ou agents de sécurité. L'objectif principal de leur migration le plus souvent temporaire est de rapatrier des fonds. Cependant, ces avantages économiques doivent être rapportés aux conséquences sociales et psychologiques découlant de la séparation des familles nucléaires. L'article examine également les répercussions politiques résultant de l'analyse comparative, surtout à la lumière de la situation actuelle à Fidji, laquelle dénote l'absence de politiques appropriées pour faire face aux conséquences de la migration. La migración y las familias transnacionales en Fiji: Comparación de dos grupos étnicos En los últimos veinte años, los patrones de migración internacional desde Fiji han sufrido cambios que han repercutido notablemente en la conformación de familias transnacionales. En este artículo, se establece una comparación entre la conformación de familias indo-fiyianas transnacionales amplias y las familias indígenas fiyianas transnacionales nucleares. Ambas se debaten en el marco de "corporaciones transnacionales de parentesco". Durante varias décadas, los indo-fiyianos emigraron con carácter permanente a la costa del Pacífico a raíz de la situación económica y política prevaleciente en Fiji. Se reasentaron en unidades familiares nucleares completas y, ulteriormente, intentaron patrocinar la migración de sus familiares. En los últimos años, se ha observado un creciente número de fiyianos indígenas que emigran temporalmente por motivos laborales. A diferencia de los indo-fiyianos, los fiyianos indígenas emigran a título individual, dejando atrás a cónyuges e hijos. Las mujeres emigran de manera autónoma para trabajar al cuidado de personas o como enfermeras, mientras que los hombres encuentran trabajo como soldados o guardias. Su migración es mayormente de carácter temporal y tiene por finalidad el envío de remesas. Ahora bien, estos beneficios económicos tienen que examinarse a la luz de los costos sociales y sicológicos asociados con la separación del núcleo familiar. En este artículo también se debaten las consecuencias políticas resultantes del análisis comparativo, especialmente habida cuenta de la situación reinante en Fiji, que se caracteriza por la falta de políticas que encaren las repercusiones que trae consigo la migración. [source]