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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.05.028 Byline: Leigh J. Wilson, Richard J.T. Wingate Keywords: Rhombomere 1; Cerebellar granule cell; Cell migration; Quail-chick chimaera; Green fluorescent protein Abstract: The rhombic lip is a discrete strip of neuroepithelium bordering the roofplate of the fourth ventricle, which gives rise to a defined sequence of migratory neuronal derivatives. In rhombomere 1 of the chick, early born cells give rise to post-mitotic hindbrain nuclei, while later derivatives comprise of cerebellar granule cell precursors, a unique proliferative, migratory precursor population that forms the external granule cell layer. We have examined the temporal specification of these two populations using a heterochronic grafting strategy, in ovo. When transplanted into younger neural tube, rhombic lip cells maintain their characteristic molecular markers and migrate into the hindbrain. Granule cell precursor derivatives of late grafts are, in addition, able to exploit neural crest streams to populate the branchial arches. Within the neural tube, derivatives of early and late rhombic lip progenitors display patterns of migration and process extension, characterised by specific trajectories and targets, which are consistent with their temporal origin. However, the normal temporal progression of cell production is disrupted in grafted progenitors: transplanted early rhombic lip fails to subsequently produce granule cell precursors. This indicates that, while the behaviour of derivatives is intrinsically specified at the rhombic lip, the orderly temporal transition in cell type production is dependent on extrinsic cues present only in the later embryo. Author Affiliation: MRC Centre for Developmental Neurobiology, King's College London, UK Article History: Received 9 January 2006; Revised 9 May 2006; Accepted 22 May 2006

We describe the essential features of and the molecules involved in dorsoventral (DV) patteming in the neural tube. The neural tube is, from its very outset, patterned in this axis as there is a roof plate, floor plate, and differing numbers and types of neuroblasts. These neuroblasts develop into different types of neurons which express a different range of marker genes. Early embryological experiments identified the notochord and the somites as being responsible for the DV patterning of the neural tube and we now know that 4 signaling molecules are involved and are generated by these surrounding structures. Fibroblast growth factors (FGFs) are produced by the caudal mesoderm and must be down-regulated before neural differentiation can occur. Retinoic acid (RA) is produced by the paraxial mesoderm and is an inducer of neural differentiation and patterning and is responsible for down-regulating FGF. Sonic hedgehog (Shh) is produced by the notochord and floor plate and is responsible for inducing ventral neural cell types in a concentration-dependent manner. Bone morphogenetic proteins (BMPs) are produced by the roof plate and are responsible for inducing dorsal neural cell types in a concentration-dependent manner. Subsequently, RA is used twice more. Once from the somites for motor neuron differentiation and secondly RA is used to define the motor neuron subtypes, but in the latter case it is generated within the neural tube from differentiating motor neurons rather than from outside. These 4 signaling molecules also interact with each other, generally in a repressive fashion, and DV patterning shows how complex these interactions can be. Keywords: Dorsoventral patterning; Neural tube; Retinoic acid; FGF; Shh; BMP

The development of neural subtypes in the dorsoventral (DV) axis of the vertebrate central nervous system (CNS) involves the integration of signalling pathways coupled with the combinatorial expression of horneodornain transcription factors. Previous studies have implicated a ole for retinoic acid in the specification of a subtype of motor neurons (MN) and in the patterning of a group of interneurons within the ventral spinal cord. In this study, we use the vitamin A-deficient (VAD) quail model to further investigate the role of retinoids in the patterning of the neural tube. Using genetic markers specific to neuronal cell populations, we demonstrate that in the absence of retinoic acid, there is a disruption to the molecular mechanisms associated with the dorsoventral patterning of the spinal cord. In particular, we observe an uneven dorsal expansion of ventral-specific genes, accompanied by a reduction in the domain of roof plate and dorsal patterning genes, both of which are rescued upon addition of retinoids during development. In addition, there is a loss of V1 interneuron-specific gene expression and a decrease in the ventricular zone expression of motor neuron patterning genes. Interestingly, these effects are localised to the rostral half of the spinal cord, indicating that RA is integrated in both anteruposterior (AP) and dorsoventral patterning processes. Using differential display techniques, we have isolated 27 retinoic acid-regulated genes within the spinal cord that together reveal several interesting potential biological functions for retinoids within the avian neural tube. In summary, we propose that retinoids have an essential role in the patterning of the dorsoventral axis of the spinal cord, and are also required for the correct integration of anteroposterior patterning signals with dorsoventral determinants in the rustral spinal cord. Keywords: Dorsoventral patterning; Spinal cord; Retinoic acid; Quail embryo; Vitamin A deficiency

Improving the health of children in foster care requires close collaboration between pediatrics and the child welfare system. Propelled by recent health care and child welfare policy reforms, there is a strong foundation for more accountable, collaborative models of care. Over the last 2 decades health care reforms have driven greater accountability in outcomes, access to care, and integrated services for children in foster care. Concurrently, changes in child welfare legislation have expanded the responsibility of child welfare agencies in ensuring child health. Bolstered by federal legislation, numerous jurisdictions are developing innovative cross-system workforce and payment strategies to improve health care delivery and health care outcomes for children in foster care, including: (1) hiring child welfare medical directors, (2) embedding nurses in child welfare agencies, (3) establishing specialized health care clinics, and (4) developing tailored child welfare managed care organizations. As pediatricians engage in cross-system efforts, they should keep in mind the following common elements to enhance their impact: embed staff with health expertise within child welfare settings, identify long-term sustainable funding mechanisms, and implement models for effective information sharing. Now is an opportune time for pediatricians to help strengthen health care provision for children involved with child welfare. [ABSTRACT FROM AUTHOR]

Examines the relationship between troglitazone (TGZ) and early-growth response 1 (Egr-1) expression and the effect of TGZ-induced apoptosis. Demonstration that TGZ induces Egr-1 expression by transcriptional and post-transcriptional regulation; Conclusion that the up-regulation kf Egr-1 may provide an explanation for the anti-tumorigenic properties of TGZ.