The early stages of heart development: insights from chicken embryos

The heart is the first functioning organ in the developing embryo and the detailed understanding of the molecular and cellular mechanisms involved in its formation provides insights into congenital malformations affecting its function and therefore the survival of the organism. Because many developmental mechanisms are highly conserved, it is possible to extrapolate from observations made in invertebrate and vertebrate model organisms to human. This review will highlight the contributions made through studying heart development in avian embryos, particularly the chicken. The major advantage of chick embryos is their accessibility for surgical manipulations and functional interference approaches, both gain- and loss-of-function. In addition to experiments performed in ovo, the dissection of tissues for ex vivo culture, genomic or biochemical approaches, is straightforward. Furthermore, embryos can be cultured for time-lapse imaging, which enables tracking of fluorescently labeled cells and detailed analyses of tissue morphogenesis. Owing to these features, investigations in chick embryos have led to important discoveries, often complementing genetic studies in mouse and zebrafish. As well as including some historical aspects, we cover here some of the crucial advances made in understanding of early heart development using the chicken model

Stability and Formation of the Resonant System HD 73526

Based on radial velocity measurements it has been found recently that the two giant planets detected around the star HD 73526 are in 2:1 resonance. However, as our numerical integration shows, the derived orbital data for this system result in chaotic behavior of the giant planets, which is uncommon among the resonant extrasolar planetary systems. We intend to present regular (non-chaotic) orbital solutions for the giant planets in the system HD 73526 and offer formation scenarios based on combining planetary migration and sudden perturbative effects such as planet-planet scattering or rapid dispersal of the protoplanetary disk. A comparison with the already studied resonant system HD 128311, exhibiting similar behavior, is also done. The new sets of orbital solutions have been derived by the Systemic Console (www.oklo.org). The stability of these solutions has been investigated by the Relative Lyapunov indicator, while the migration and scattering effects are studied by gravitational N-body simulations applying non-conservative forces as well. Additionally, hydrodynamic simulations of embedded planets in protoplanetary disks are performed to follow the capture into resonance. For the system HD 73526 we demonstrate that the observational radial velocity data are consistent with a coplanar planetary system engaged in a stable 2:1 resonance exhibiting apsidal corotation. We have shown that, similarly to the system HD 128311, the present dynamical state of HD 73526 could be the result of a mixed evolutionary process melting together planetary migration and a perturbative event.Comment: 12 pages, 14 figures, accepted in A&A, v2: technical change

Teachers teaching teachers : a case study of the 2011 ProEd professional learning community and its influence on creating a culture for organizational learning in schools in the Republic of Panama

Title from PDF of title page (University of Missouri--Columbia, viewed on August 30, 2012).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Phillip MessnerIncludes bibliographical references.Vita.Ed. D. University of Missouri-Columbia 2012."May 2012"While evidence of organizational learning through empowered teacher collaboration has been established in many international school studies, no such relationship has been investigated in public and/or low-middle socioeconomic private schools in the Republic of Panama. This observation provides a framework for exploring how schools in Panama learn. This qualitative ethnomethodological case study was driven by the void in empirical knowledge and the guiding question that asked: How and to what extent does participation in the monthly 2011 ProEd Professional Learning Community influence a culture for organizational learning in schools in Panama. Data were collected in a three-step interview process conducted with a sample of 25 randomly selected 2011 ProEd PLC teachers from 5 low-middle socioeconomic public and/or private schools in Panama. Data analysis included open coding of emerging themes from the interviews and field notes. Walkthrough observations of ProEd PLC teachers and focus groups with non-2011 ProEd PLC members were conducted to triangulate for trustworthiness of this study. The participant researcher of this study was involved as lead facilitator and coach of all monthly PLC workshops and in data collection during the interview process. Emerging themes surfaced from conversations with teachers who created meanings from stories shared about their roles as educators in a developing nation.Includes bibliographical reference

On the dynamics of Extrasolar Planetary Systems under dissipation. Migration of planets

We study the dynamics of planetary systems with two planets moving in the same plane, when frictional forces act on the two planets, in addition to the gravitational forces. The model of the general three-body problem is used. Different laws of friction are considered. The topology of the phase space is essential in understanding the evolution of the system. The topology is determined by the families of stable and unstable periodic orbits, both symmetric and non symmetric. It is along the stable families, or close to them, that the planets migrate when dissipative forces act. At the critical points where the stability along the family changes, there is a bifurcation of a new family of stable periodic orbits and the migration process changes route and follows the new stable family up to large eccentricities or to a chaotic region. We consider both resonant and non resonant planetary systems. The 2/1, 3/1 and 3/2 resonances are studied. The migration to larger or smaller eccentricities depends on the particular law of friction. Also, in some cases the semimajor axes increase and in other cases they are stabilized. For particular laws of friction and for special values of the parameters of the frictional forces, it is possible to have partially stationary solutions, where the eccentricities and the semimajor axes are fixed.Comment: Accepted in Celestial Mechanics and Dynamical Astronom

Assay for Neural Induction in the Chick Embryo

The chick embryo is a valuable tool in the study of early embryonic development. Its transparency, accessibility and ease of manipulation, make it an ideal tool for studying the formation and initial patterning of the nervous system. This video demonstrates how to graft organizer tissue into a host, a method by which Hensen s node (the organizer in the chick embryo) is grafted to a host competent ectoderm. The organizer graft instructs overlying na ve tissue to adopt a neural fate via neural inducing signals. This mechanism is referred to as neural induction, and constitutes the initial step in the formation of brain and spinal cord in amniotes. This method is essentially used for the characterization of putative neural inducing molecules in chick. This video demonstrates the different steps in the assay for neural induction; First, the donnor embryo is explanted and pinned on a dish. Then, the host embryo is prepared for New culture. The graft is excised and transplanted to the host area pellucida margin. The host is cultured for 18-22 hrs. The assembly is fixed and processed for further applications (e.g. in situ hybridization). This method was originally devised by Waddington 1,2 and Gallera 3,4

Higher Education Collaboration for Digital Transformation in Pandemic Panamá

Panama’s Ministry of Education unnecessarily complicates its work with non-governmental entities, even when the entities are noted higher education institutions (HEIs). Bureaucratic impediments, lack of transparency and payment terms all present obstacles. During COVID-19, however, the crisis conditions and limited resources available propelled a period of streamlined public-private cooperation, resulting in some unparalleled innovation. This article presents a case study of one such HEI-ministry partnership on a digital transformation mobile literacy project, detailing its components and achievements and providing insights on specific success factors. Situating this discussion within the discourse on collaboration during crisis, the authors conclude that replicating and promoting this type of productive effort beyond periods of crisis will depend on public reform in two areas: (1) streamlining and professionalizing ministry-HEI interactions, and (2) increasing support for research and development, particularly in education. This discussion is relevant for Panama and most of Latin America as well as much of the developing world.Panama’s Ministry of Education unnecessarily complicates its work with non-governmental entities, even when the entities are noted higher education institutions (HEIs). Bureaucratic impediments, lack of transparency and payment terms all present obstacles. During COVID-19, however, the crisis conditions and limited resources available propelled a period of streamlined public-private cooperation, resulting in some unparalleled innovation. This article presents a case study of one such HEI-ministry partnership on a digital transformation mobile literacy project, detailing its components and achievements and providing insights on specific success factors. Situating this discussion within the discourse on collaboration during crisis, the authors conclude that replicating and promoting this type of productive effort beyond periods of crisis will depend on public reform in two areas: (1) streamlining and professionalizing ministry-HEI interactions, and (2) increasing support for research and development, particularly in education. This discussion is relevant for Panama and most of Latin America as well as much of the developing world