Late-emigrating trunk neural crest cells in turtle embryos generate an osteogenic ectomesenchyme in the plastron.

BACKGROUND: The turtle plastron is composed of a keratinized epidermis overlying nine dermal bones. Its developmental origin has been controversial; recent evidence suggests that the plastral bones derive from trunk neural crest cells (NCCs). RESULTS: This study extends the observations that there is a turtle-specific, second wave of trunk NCC delamination and migration, after the original NCCs have reached their destination and differentiated. This second wave was confirmed by immunohistochemistry in whole-mounts and serial sections, by injecting DiI (1,1', di-octadecyl-3,3,3',3',-tetramethylindo-carbocyanine perchlorate) into the lumen of the neural tube and tracing labeled cells into the plastron, and by isolating neural tubes from older turtle embryos and observing delaminating NCCs. This later migration gives rise to a plastral ectomesenchyme that expresses NCC markers and can be induced to initiate bone formation. CONCLUSIONS: The NCCs of this second migration have properties similar to those of the earlier NCCs, but also express markers characteristic of cranial NCCs. The majority of the cells of the plastron mesenchyme express neural crest markers, and have osteogenic differentiation capabilities that are similar or identical to craniofacial ectomesenchyme. Our evidence supports the contention that turtle plastron bones are derived from a late emigrating population of cells derived from the trunk neural crest.

eXclusion: toward integrating the X chromosome in genome-wide association analyses.

The X chromosome lags behind autosomal chromosomes in genome-wide association study (GWAS) findings. Indeed, the X chromosome is commonly excluded from GWAS analyses despite being assayed on all current GWAS microarray platforms. This raises the question: why are so few hits reported on the X chromosome? This commentary aims to examine this question through review of the current X chromosome results in the National Human Genome Research Institute Catalog of Published Genome-Wide Association Studies (NHGRI GWAS Catalog). It will also investigate commonly cited reasons for exclusion of the X chromosome from GWAS and review the tools currently available for X chromosome analysis. It will conclude with recommendations for incorporating X chromosome analyses in future studies.

Symbiosis as a source of selectable epigenetic variation: taking the heat for the big guy.

Evolutionary developmental biology is based on the principle that evolution arises from hereditable changes in development. Most of this new work has centred on changes in the regulatory components of the genome. However, recent studies (many of them documented in this volume) have shown that development also includes interactions between the organism and its environment. One area of interest concerns the importance of symbionts for the production of the normal range of phenotypes. Many, if not most, organisms have 'outsourced' some of their developmental signals to a set of symbionts that are expected to be acquired during development. Such intimate interactions between species are referred to as codevelopment, the production of a new individual through the coordinated interactions of several genotypically different species. Within the past 2 years, several research programmes have demonstrated that such codevelopmental schemes can be selected. We will focus on symbioses in coral reef cnidarians symbiosis, pea aphids and cactuses, wherein the symbiotic system provides thermotolerance for the composite organism.

Training in difficult conversations: a national survey of pediatric hematology-oncology and pediatric critical care physicians.

BACKGROUND: In pediatric oncology and critical care, physicians give difficult news, including discussions regarding palliative care and comfort measures, but there are minimal data regarding fellowship program preparation for this task. PURPOSE: We surveyed graduates of pediatric hematology/oncology and critical care fellowships regarding communication training to describe teaching methods, assess which were helpful, and determine whether comfort level is related to training experiences. METHODS: A 12-question Web survey was sent to physicians completing fellowship in the previous 5 years. RESULTS: Of 345 fellows identified, 171 (50%) responded. Prior training included observing senior physicians (100%), being observed (78%), reading (56%), lectures (46%), role-play (20%), workshops (16%), simulation (13%), and videos (13%). Observing senior physicians was thought most helpful. More years since training (p < 0.0005) and frequent difficult conversations (p = 0.009) were predictors of current comfort. Only workshops were associated with feeling better prepared at the end of training (p = 0.019). CONCLUSIONS: Training may help physicians feel prepared for difficult conversations, but ongoing experience was strongly associated with comfort level.