Guidance of trunk neural crest migration requires neuropilin 2/semaphorin 3F signaling

In vertebrate embryos, neural crest cells migrate only through the anterior half of each somite while avoiding the posterior half. We demonstrate that neural crest cells express the receptor neuropilin 2 (Npn2), while its repulsive ligand semaphorin 3F (Sema3f) is restricted to the posterior-half somite. In Npn2 and Sema3f mutant mice, neural crest cells lose their segmental migration pattern and instead migrate as a uniform sheet, although somite polarity itself remains unchanged. Furthermore, Npn2 is cell autonomously required for neural crest cells to avoid Sema3f in vitro. These data show that Npn2/Sema3f signaling guides neural crest migration through the somite. Interestingly, neural crest cells still condense into segmentally arranged dorsal root ganglia in Npn2 nulls, suggesting that segmental neural crest migration and segmentation of the peripheral nervous system are separable processes

Screening Seniors for Risk of Functional Decline: Results of a Survey in Family Practice

To measure functional status, determine risk of functional decline and assess consistency between responses and standardized instruments. Design: A mailed survey which measured functional impairment, recent hospitalization and bereavement. A positive response on at least one of these factors indicated that the individual was “at risk” for functional decline. A random sample (n=73) of “at risk” subjects (specifically, family practice patients aged 70 and older) were assessed by a nurse. Results: The response rate was 89% (369/415), 59% of seniors were female and the mean age was 77.1 (SD=5.5) years. Self-reported risk, based on activities of daily living (ADLs), was associated with impairment in at least one basic ADL (p\u3c0.0005) using a standardized instrument. The positive predictive value of the survey for ADL impairment was 65%. Conclusion: Response to a mailed survey was high and self-reported ADL risks were consistent with findings from standardized assessment tools

Mass segregation trends in SDSS galaxy groups

It has been shown that galaxy properties depend strongly on their host environment. In order to understand the relevant physical processes driving galaxy evolution it is important to study the observed properties of galaxies in different environments. Mass segregation in bound galaxy structures is an important indicator of evolutionary history and dynamical friction timescales. Using group catalogues derived from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) we investigate mass segregation trends in galaxy groups at low redshift. We investigate average galaxy stellar mass as a function of group-centric radius and find evidence for weak mass segregation in SDSS groups. The magnitude of the mass segregation depends on both galaxy stellar mass limits and group halo mass. We show that the inclusion of low mass galaxies tends to strengthen mass segregation trends, and that the strength of mass segregation tends to decrease with increasing group halo mass. We find the same trends if we use the fraction of massive galaxies as a function of group-centric radius as an alternative probe of mass segregation. The magnitude of mass segregation that we measure, particularly in high-mass haloes, indicates that dynamical friction is not acting efficiently.Comment: 6 pages, 2 figures, accepted for publication in MNRAS Letter

What is bad in cancer is good in the embryo: Importance of EMT in neural crest development

Although the epithelial to mesenchymal transition (EMT) is famous for its role in cancer metastasis, it also is a normal developmental event in which epithelial cells are converted into migratory mesenchymal cells. A prime example of EMT during development occurs when neural crest (NC) cells emigrate from the neural tube thus providing an excellent model to study the principles of EMT in a nonmalignant environment. NC cells start life as neuroepithelial cells intermixed with precursors of the central nervous system. After EMT, they delaminate and begin migrating, often to distant sites in the embryo. While proliferating and maintaining multipotency and cell survival the transitioning neural crest cells lose apicobasal polarity and the basement membrane is broken down. This review discusses how these events are coordinated and regulated, by series of events involving signaling factors, gene regulatory interactions, as well as epigenetic and post-transcriptional modifications. Even though the series of events involved in NC EMT are well known, the sequence in which these steps take place remains a subject of debate, raising the intriguing possibility that, rather than being a single event, neural crest EMT may involve multiple parallel mechanisms

Roundtable Discussion – The Great War and Education

The panelists will discus their experiences in teaching the First World War to students at the secondary and post-sencondary level

A Computer-Assisted Legal Research and Writing Course

In this paper, the authors describe and assess their experience with the use of WebCT (a computer program that facilitates the creation and management of courses using the Internet) in the Dalhousie Legal Research and Writing Program. They explain what WebCT is, why they decided to use it, and how they used it. They assess its inaugural use and conclude that, despite some difficulties, the pilot project was a success and WebCT can be a useful tool for other teachers of legal research and writing

Code Critters: A Block-Based Testing Game

Learning to program has become common in schools, higher education and individual learning. Although testing is an important aspect of programming, it is often neglected in education due to a perceived lack of time and knowledge, or simply because testing is considered less important or fun. To make testing more engaging, we therefore introduce Code Critters, a Tower Defense game based on testing concepts: The aim of the game is to place magic mines along the route taken by small "critters" from their home to a tower, such that the mines distinguish between critters executing correct code from those executing buggy code. Code is shown and edited using a block-based language to make the game accessible for younger learners. The mines encode test inputs as well as test oracles, thus making testing an integral and fun component of the game

A Computer-Assisted Legal Research and Writing Course

In this paper, the authors describe and assess their experience with the use of WebCT (a computer program that facilitates the creation and management of courses using the Internet) in the Dalhousie Legal Research and Writing Program. They explain what WebCT is, why they decided to use it, and how they used it. They assess its inaugural use and conclude that, despite some difficulties, the pilot project was a success and WebCT can be a useful tool for other teachers of legal research and writing

Standard setting in Australian medical schools

Background: Standard setting of assessment is critical in quality assurance of medical programs. The aims of this study were to identify and compare the impact of methods used to establish the passing standard by the 13 medical schools who participated in the 2014 Australian Medical Schools Assessment Collaboration (AMSAC). Methods: A survey was conducted to identify the standard setting procedures used by participating schools. Schools standard setting data was collated for the 49 multiple choice items used for benchmarking by AMSAC in 2014. Analyses were conducted for nine schools by their method of standard setting and key characteristics of 28 panel members from four schools. Results: Substantial differences were identified between AMSAC schools that participated in the study, in both the standard setting methods and how particular techniques were implemented. The correlation between the item standard settings data by school ranged from − 0.116 to 0.632. A trend was identified for panel members to underestimate the difficulty level of hard items and overestimate the difficulty level of easy items for all methods. The median derived cut-score standard across schools was 55% for the 49 benchmarking questions. Although, no significant differences were found according to panel member standard setting experience or clinicians versus scientists, panel members with a high curriculum engagement generally had significantly lower expectations of borderline candidates (p = 0.044). Conclusion: This study used a robust assessment framework to demonstrate that several standard setting techniques are used by Australian medical schools, which in some cases use different techniques for different stages of their program. The implementation of the most common method, the Modified Angoff standard setting approach was found to vary markedly. The method of standard setting used had an impact on the distribution of expected minimally competent student performance by item and overall, with the passing standard varying by up to 10%. This difference can be attributed to the method of standard setting because the ASMSAC items have been shown over time to have consistent performance levels reflecting similar cohort ability. There is a need for more consistency in the method of standard setting used by medical schools in Australia