Cancer cell migration on straight, wavy, loop and grid microfibre patterns

Cell migration plays an important role in physiological and pathological processes where the fibrillar morphology of extracellular matrices (ECM) could regulate the migration dynamics. To mimic the morphological characteristics of fibrillar matrix structures, low-voltage continuous electrospinning was adapted to construct straight, wavy, looped and gridded fibre patterns made of polystyrene (of fibre diameter ca. 3 μm). Cells were free to explore their different shapes in response to the directly-adhered fibre, as well as to the neighbouring patterns. For all the patterns studied, analysing cellular migration dynamics of MDA-MB-231 (a highly migratory breast cancer cell line) demonstrated two interesting findings: first, although cells dynamically adjust their shapes and migration trajectories in response to different fibrillar environments, their average step speed is minimally affected by the fibre global pattern; secondly, a switch in behaviour was observed when the pattern features approach the upper limit of the cell body’s minor axis, reflecting that cells’ ability to divert from an existing fibre track is limited by the size along the cell body’s minor axis. It is therefore concluded that the upper limit of cell body’s minor axis might act as a guide for the design of microfibre patterns for different purposes of cell migration.

Understanding the Socioeconomics of International Migration Decisions and Outcomes Through the Capability-Based Migration Framework

This dissertation critically reviews neoclassical migration theories and conceptualises the capability-based framework as a prospect in migration theory. I show that most of the neoclassical migration theories were formed in the twentieth century. They therefore require an update to accommodate contemporary migration dynamics. I argue that a multifaceted and multidimensional capability-based approach that centralises human agency and capabilities can address the earlier theories’ shortcomings. Hence, I adopt the capability-based migration framework as the main framework in my dissertation. The dissertation differs from previous empirical studies in its unique methodology and exceptional attention to the grey areas in the migration discourse. Using data from prospective Nigerian migrants living in Nigeria, actual migrants living in Italy and a collection of secondary data sources, the dissertation addresses three research questions: how do capabilities influence migration decisions in the home country; what are the capability-depriving constraints faced by migrants in the host country; and how do migrants contribute to capability improvement in the home country?

The propagation velocity of seismic activity migrating along the directions of the geodynamic forces prevailing in the northeastern Baikal rift system, Russia

The recent tectonic stress field in the northeastern Baikal rift system (BRS) corresponds to the crustal deformation field. The stress-strain state of the Earth’s crust determines the fault network geometry and spatiotemporal structure of the epicentral field characterized by many earthquake swarms and earthquake migrations in the study area. In order to study the seismic process dynamics in different directions of the crustal deformation, the spatiotemporal analysis of earthquake time series has been made over the 1964–2015 instrumental period. To determine the relationship between crustal stress and spatiotemporal features of the epicentral field the seismic data were projected along horizontal stress tensor axes σ3 and σ2, consistent with major directions of the crustal deformation, a strike of major rifting structures, and a general azimuth of active fault groups. The NE-SW direction along the intermediate horizontal stress axes and main faulted arears exhibits slow earthquake migrations up to 60 km long, propagating with a modal velocity of about 30 kilometers per year. The NW-SE direction along the principal horizontal stress axes, orthogonal to the main faulted areas, is characterized by shorter migration sequences of less duration, propagating with a higher velocity than sequences registered in the NE-SW. The difference between the migration dynamics in mutually orthogonal directions can be attributed to the fault network configuration and the differences in the deformation process.

Impacts of Covid-19 on Migration Dynamics and Remittances in Sub-Saharan Africa (SSA)

The paper therefore x-rays the impacts of the COVID-19 pandemic on migration dynamics by analyzing types and trends dynamics of migrants’ movement, demographic dynamics of migration as related to the inflow of remittances (both cash and in-kind) to SSA countries prior to the pandemic. Also discusses the constraints of transferring cash remittances and subsequent decline posed by the COVID-19 outbreak during and beyond the pandemics. Secondary evidence from Somali and Nigeria were analyzed on the constraints of remitting cash, while in-kind remittance from the Republic of Chad was evaluated. The importance of remittances to the home communities was established. Measures to safeguard SSA migrants’ mobility and their remittances, citing some selected countries of destination, were exploited. The paper concludes that COVID-19 impacts on migration should be opportunities for policymakers (both home and destination countries) to reset their efforts towards protecting migrants and their future activities.

Age and Sex Influence Natal and Breeding Dispersal of Purple Martins

Dispersal patterns deepen our understanding of population dynamics. Dispersal by all age and sex classes enhances a species’ ability to respond to environmental changes, such as in habitat availability, artificial nest sites, and climate. The migration dynamics of the eastern subspecies of the Purple Martin (Progne subis subis) are well known, but we know less about its patterns of annual dispersal. We compared the frequency, distance, and direction of dispersal by each age/sex cohort of martins in central Alberta, at the northwestern limit of their breeding range. We used two datasets: (1) adult martins banded in central Alberta as nestlings and encountered during the summers of 2017 and 2018, and (2) records of encounters of banded martins in Canada from 1935 to 2016 from the Canadian Wildlife Service’s Bird Banding Office. In Alberta, 36% of birds dispersed from natal sites (by an average distance of 24 km), most commonly to the northeast. Across Canada, 29% of birds dispersed (by an average distance of 183 km), most commonly to the east and northeast. In Alberta, martins at least two years old dispersed less frequently than yearlings since some older martins returned to their natal site after first breeding elsewhere. Dispersal distances of after-second-year martins, which represent natal plus breeding dispersal, were greater than those of second-year birds, which represent natal dispersal alone. Thus some martins continue to disperse after their second year and do not maintain complete fidelity to a breeding site, which is different from our current understanding.

First person – Bram van Steen and Lanette Kempers

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Bram van Steen and Lanette Kempers are co-first authors on ‘ Transendothelial migration induces differential migration dynamics of leukocytes in tissue matrix’, published in JCS. Bram is a PhD student in the laboratory of Jaap van Buul at Sanquin Research, Amsterdam, The Netherlands, investigating the secrets of cell behavior and migration using advanced models and microscopy. Lanette is a PhD student in the same lab studying the process of sprouting and angiogenesis using various microscopy approaches.

Mauritania’s internal migration dynamics and trends in response to rainfall variability and change

The northwest African country of Mauritania is a vast, desert territory, which was historically been dominated by pastoral nomads. Since independence in 1960, the country has witnessed a dramatic sedentarization of its nomadic population, as well as settlements in and movements to urban centers. This vast sedentarization movement coupled with internal and interregional migration has resulted in the growth of Mauritania’s urban population from less than 10 percent of the total population in 1965 to nearly 90 percent in 2013. Factors that have caused this rapid urbanization, include the droughts that spanned the late 1960s through to the early 1980s, and the turbulent transformation of Mauritania’s political economy. The aim of this study is to determine and examine internal migration flows to analyze the relationship between long-term rainfall changes and dynamic spatial demographic shifts in terms of movements toward urban centers. In this regard, we propose an assessment approach that integrates official statistics from the decennial census and rainfall data, with available socioeconomic variables, to characterize interregional migration flows. Our result confirms that rates of interregional migration remain elevated and are expected to increase. In 2013, 702,575 individuals were documented as having participated in interregional migration, comprising 17.5 percent of the total population. In comparison, there were 477,814 individuals, which migrated inter-regionally in 2000, and 208,039 in 1988. These results demonstrate distinct interactions between climate variability and interregional migration in Mauritania throughout the past four decades.