Relationship between Blood Vessels and Migration of Neuroblasts in the Olfactory Neurogenic Region of the Rodent Brain

Neural precursors originating in the subventricular zone (SVZ), the largest neurogenic region of the adult brain, migrate several millimeters along a restricted migratory pathway, the rostral migratory stream (RMS), toward the olfactory bulb (OB), where they differentiate into interneurons and integrate into the local neuronal circuits. Migration of SVZ-derived neuroblasts in the adult brain differs in many aspects from that in the embryonic period. Unlike in that period, postnatally-generated neuroblasts in the SVZ are able to divide during migration along the RMS, as well as they migrate independently of radial glia. The homophilic mode of migration, i.e., using each other to move, is typical for neuroblast movement in the RMS. In addition, it has recently been demonstrated that specifically-arranged blood vessels navigate SVZ-derived neuroblasts to the OB and provide signals which promote migration. Here we review the development of vasculature in the presumptive neurogenic region of the rodent brain during the embryonic period as well as the development of the vascular scaffold guiding neuroblast migration in the postnatal period, and the significance of blood vessel reorganization during the early postnatal period for proper migration of RMS neuroblasts in adulthood.

Multi-scale habitat assessment of pronghorn migration routes

We studied the habitat selection of pronghorn (Antilocapra americana) during seasonal migration; an important period in an animal’s annual cycle associated with broad-scale movements. We further decompose our understanding of migration habitat itself as the product of both broad- and fine-scale behavioral decisions and take a multi-scale approach to assess pronghorn spring and fall migration across the transboundary Northern Sagebrush Steppe region. We used a hierarchical habitat selection framework to assess a suite of natural and anthropogenic features that have been shown to influence selection patterns of pronghorn at both broad (migratory neighborhood) and fine (migratory pathway) scales. We then combined single-scale predictions into a scale-integrated step selection function (ISSF) map to assess its effectiveness in predicting migration route habitat. During spring, pronghorn selected for native grasslands, areas of high forage productivity (NDVI), and avoided human activity (i.e., roads and oil and natural gas wells). During fall, pronghorn selected for native grasslands, larger streams and rivers, and avoided roads. We detected avoidance of paved roads, unpaved roads, and wells at broad spatial scales, but no response to these features at fine scales. In other words, migratory pronghorn responded more strongly to anthropogenic features when selecting a broad neighborhood through which to migrate than when selecting individual steps along their migratory pathway. Our results demonstrate that scales of migratory route selection are hierarchically nested within each other from broader (second-order) to finer scales (third-order). In addition, we found other variables during particular migratory periods (i.e., native grasslands in spring) were selected for across scales indicating their importance for pronghorn. The mapping of ungulate migration habitat is a topic of high conservation relevance. In some applications, corridors are mapped according to telemetry location data from a sample of animals, with the assumption that the sample adequately represents habitat for the entire population. Our use of multi-scale modelling to predict resource selection during migration shows promise and may offer another relevant alternative for use in future conservation planning and land management decisions where telemetry-based sampling is unavailable or incomplete.

Giving voice to migrant children during reception and asylum procedures. Illustrations on the implementation of Art. 12 CRC in Greece and Belgium

According to a children’s rights’ approach, asylum-seeking children are entitled to special protection. However, reality dictates that as soon as they enter a host country irregularly, they are often criminalised, thus becoming part of the crimmigration debate and as a result they are further deprived of basic human rights including the right to be heard, as enshrined in the UN Convention on the Rights of the Child. This paper starts from a discussion on the fact that children on the migratory pathway need to be granted a central and active role in research, especially in times when new theoretical concepts in the field of juvenile justice and migration policing are introduced. We continue by delving into both an illustration from Greece and Belgium on how the right of the child to participate and to be heard is applied during reception and asylum procedures. We draw attention to the existing peculiarities of rights-based research methods in immigration studies, whilst arguing for holistic approaches that aim to move beyond the decorative concept of voicing children and towards a positive change concerning asylum processes for migrant minors.

Flying through hurricane central: impacts of hurricanes on migrants with a focus on monarch butterflies

Hurricanes are becoming more frequent and intense, so understanding the consequences for biodiversity, including migratory species, has become critical. Studies suggest that migrants may avoid most of the direct harm of hurricanes by shifting their flight trajectories to less-impacted regions, but the majority of this research has focused on birds. We review the literature on migratory bird responses to hurricanes and also describe other taxa likely to be affected. We then focus on the monarch butterfly (Danaus plexippus), whose fall migratory pathway goes through Texas during hurricane season. Like birds, monarchs may be able to avoid direct damage from hurricanes. However, it may be more important to determine how they respond to shifts in availability of critical resources during migration. In fall, when a storm-triggered flush of out-of-season vegetation growth is especially likely, hurricanes could reasonably cause indirect impacts that could be positive (increased nectar) or negative (out-of-season host plants that could disrupt migration), or both. The monarch butterfly is an especially good target for this research because of its distinct migratory phases, the importance of hurricane-impacted zones to its annual cycle, and the large quantity of data available through an extensive network of citizen science programs.

Early Subset of Cerebellar Nuclei Neurons Derived from Mesencephalon in Mice

ABSTRACTDuring cerebellar development, cerebellar nuclei (CN) neurons and Purkinje cells are the earliest born among the different neuronal subtypes. Purkinje cells are the sole output of the cerebellar cortex and project to the CN. The CN represents the main output of the cerebellum, which is generated from the rhombic lip and the ventricular zone. We used immunohistochemistry, embryonic cultures, dye tracers and in situ hybridization to examine the origin of a new subset of CN neurons from the mesencephalon during early cerebellar development. Our results show that a subset of CN neurons, which are immunopositive for α-synuclein (SNCA) and Otx2, originate from the mesencephalon and cross the isthmus toward the rostral end of the nuclear transitory zone. Double immunostaining of the SNCA with Otx2 or p75 neurotrophin receptor (p75ntr) indicates that these cells are derived from neural crest cells. We also showed that this population of neurons with nerve fibers terminates at the subpial surface of putative lobules VI/VII. The SNCA+/Otx2+/p75+ cells, which divide the cerebellar primordium into rosterodorsal and caudoventral compartments, show increased cleaved caspase-3 activation, which suggests temporary presence of these cells due to apoptosis. These results strongly suggest that early CN neurons originate from the mesencephalic neural crest population and cross the isthmus to contribute as a subset of the CN. Their temporary presence in the nuclear transitory zone suggests that these neurons/fibers play a regulatory role as a signaling center to attract early afferent pioneer axons and provide neuronal migratory pathway during early cerebellar development.Significance StatementDuring cerebellar development two germinal zones are involved in cerebellar neurogenesis: the rhombic lip and the ventricular zone, which are located in the developing cerebellum itself. Our findings indicate that a subset of cerebellar nuclei neurons have an external origin, the mesencephalon, and they are the earliest born neurons that enter to the developing cerebellum. In this study, we focused on the origin of these cells and traced their migratory pathway from the mesencephalon while crossing the isthmus, followed them when they entered to the developing cerebellum. We also demonstrated their potential role on later born cells during cerebellar development.

Spatial distribution of narwhal (Monodon monoceros) diving for Canadian populations helps identify important seasonal foraging areas

In Canada, narwhals (Monodon monoceros L., 1758) are divided into the Baffin Bay (BB) and northern Hudson Bay (NHB) populations. Satellite tracking of 21 narwhals from BB and NHB provided information on their diving behaviour and was used to identify foraging regions. Previous research from hunted narwhals indicated that narwhals in both populations depend on benthic prey to meet their dietary needs. To evaluate home ranges and define areas important for benthic foraging, we conducted kernel density analysis on narwhal locations and focused on areas where deep diving occurs, as a proxy for foraging, in the winter, spring, and migratory periods. These analyses revealed important areas for foraging for BB narwhals on the summer grounds in Eclipse Sound, and the winter grounds in Davis Strait, as well as on the migratory pathway between regions. Similarly, important areas were identified for the NHB narwhal population in northwestern Hudson Bay in summer, in NHB and Hudson Strait on the migration, and to the east of the entrance to Hudson Strait in the winter. This, along with an analysis of the absolute dive depths, provides information on seasons and regions important for foraging, which is particularly relevant with increasing industrial activities in the Arctic.

Bidirectional radial Ca2+ activity regulates neurogenesis and migration during early cortical column formation

Cortical columns are basic cellular and functional units of the cerebral cortex that are malformed in many brain disorders, but how they initially develop is not well understood. Using an optogenetic sensor in the mouse embryonic forebrain, we demonstrate that Ca2+ fluxes propagate bidirectionally within the elongated fibers of radial glial cells (RGCs), providing a novel communication mechanism linking the proliferative and postmitotic zones before the onset of synaptogenesis. Our results indicate that Ca2+ activity along RGC fibers provides feedback information along the radial migratory pathway, influencing neurogenesis and migration during early column development. Furthermore, we find that this columnar Ca2+ propagation is induced by Notch and fibroblast growth factor activities classically implicated in cortical expansion and patterning. Thus, cortical morphogens and growth factors may influence cortical column assembly in part by regulating long-distance Ca2+ communication along the radial axis of cortical development.

Proliferation and Glia-Directed Differentiation of Neural Stem Cells in the Subventricular Zone of the Lateral Ventricle and the Migratory Pathway to the Lesions after Cortical Devascularization of Adult Rats

We investigated the effects of cortical devascularization on the proliferation, differentiation, and migration of neural stem cells (NSCs) in the subventricular zone (SVZ) of the lateral ventricle of adult rats. 60 adult male Wistar rats were randomly divided into control group and devascularized group. At 15 and 30 days after cerebral cortices were devascularized, rats were euthanized and immunohistochemical analysis was performed. The number of PCNA-, Vimentin-, and GFAP-positive cells in the bilateral SVZ of the lateral wall and the superior wall of the lateral ventricles of 15- and 30-day devascularized groups increased significantly compared with the control group (P<0.05andP<0.01). The area density of PCNA-, Vimentin-, and GFAP-positive cells in cortical lesions of 15- and 30-day devascularized groups increased significantly compared with the control group (P<0.05andP<0.01). PCNA-, GFAP-, and Vimentin-positive cells in the SVZ migrated through the rostral migratory stream (RMS), and PCNA-, GFAP-, and Vimentin-positive cells from both the ipsilateral and contralateral dorsolateral SVZ (dl-SVZ) migrated into the corpus callosum (CC) and accumulated, forming a migratory pathway within the CC to the lesioned site. Our study suggested that cortical devascularization induced proliferation, glia-directed differentiation, and migration of NSCs from the SVZ through the RMS or directly to the corpus callosum and finally migrating radially to cortical lesions. This may play a significant role in neural repair.