다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Zernicka-Goetz and colleagues report an in vitro culture system that recapitulates hallmarks of human embryo morphogenesis before gastrulation, including formation of the pro-amniotic cavity and appearance of the prospective yolk sac.

/pdf/self-organization-of-the-human-embryo-in-the-absence-of-zuuhk2abw5.pdf

Self-organization of the human embryo in the absence of maternal tissues

INTRODUCTION Early mammalian development requires the formation of embryonic and extraembryonic tissues and a highly coordinated partnership between them. This close partnership is a prerequisite for successful construction of embryo architecture, with the embryonic tissue generating cells of the embryo proper and the extraembryonic tissues, trophectoderm, and primitive endoderm forming the placenta and the yolk sac. Each of these components and the interactions between them are critical for embryonic development to birth. Embryonic stem cells (ESCs) in culture have the potential to participate in development when introduced into the early embryo. However, when cultured in vitro on their own, they do not recapitulate the spatial and temporal events of early embryogenesis. RATIONALE We hypothesized that in order to faithfully model with stem cells the morphogenetic steps involved in mammalian embryogenesis, we would need to establish a developmental dialogue between ESCs and extraembryonic trophoblast stem cells (TSCs) in a three-dimensional (3D) extracellular matrix (ECM) scaffold, to potentially substitute for the basement membrane normally provided by the primitive endoderm. RESULTS We combined embryonic and extraembryonic stem cells in vitro on such a 3D matrix and found that these cells were capable of self-assembly into a structure whose development and architecture were similar to that of the natural embryo, leading us to name them in vitro ESC and TSC stem cell–embryos (ETS-embryos). By building ETS-embryos from genetically modified stem cells and using specific inhibitors, we identify morphogenetic events and signaling pathways involved in these early developmental stages. Furthermore, we show that in vitro stem cell embryogenesis can be broken down into a sequence of key steps from implantation stage to germ layer specification. First is the self-organization of ESCs, which leads to polarization and lumenogenesis of ESC-derived embryonic compartment, followed by cavitation in the TSC-derived extraembryonic compartment. Second is the unification of embryonic and extraembryonic cavities into the equivalent of the embryo’s proamniotic cavity. Third is the requirement for a dialogue between embryonic and extraembryonic compartments, involving Nodal signaling, that builds characteristic embryo architecture. Fourth is the patterning of the embryonic compartment, revealed by the localized expression of mesoderm markers at the boundary between embryonic and extraembryonic compartments that, as in the natural embryo, is preceded by and dependent upon Wnt signaling. Fifth is the specification of a small cluster of PGC-like cells at the embryonic and extraembryonic boundary in a bone morphogenetic protein (BMP) signaling–dependent manner. Remarkably, such events in in vitro stem cell embryogenesis occur with very similar spatial and temporal dynamics to those taking place in natural embryogenesis. CONCLUSION In this work, we demonstrate that establishing a close cross-talk between embryonic and extraembryonic stem cells in a 3D ECM scaffold is necessary and sufficient for the self-assembly of a structure that recapitulates many of the key spatial and temporal steps of early mammalian embryogenesis. This in vitro ETS-embryo models embryonic architecture and patterning more accurately than has been possible before using ESCs alone. They also provide a simplified platform to dissect the physical, cellular, and molecular mechanisms mediating the critical cross-talk between embryonic and extraembryonic cells during development, and hence are a powerful tool for the future study of mammalian embryogenesis.

/pdf/assembly-of-embryonic-and-extraembryonic-stem-cells-to-mimic-2plgmupm9f.pdf

Assembly of embryonic and extraembryonic stem cells to mimic embryogenesis in vitro

In the present chapter we consider the well-posedness of an abstract boundary-value problem for differential equations of elliptic type

$$- \upsilon ''\left( t \right) + A\upsilon \left( t \right) = f\left( t \right)\left( {0 \leqslant t \leqslant T} \right),\upsilon \left( 0 \right) = {{\upsilon }_{0}},\upsilon \left( T \right) = {{\upsilon }_{T}}$$

in an arbitrary Banach spaceEwith the positive operator A. The high order of accuracy two-step difference schemes generated by an exact difference scheme or by the Taylor decomposition on three points for the numerical solutions of this problem are presented. The well-posedness of these difference schemes in various Banach spaces are studied. The stability and coercive stability estimates in Holder norms for solutions of the high order of accuracy difference schemes of the mixed type boundary-value problems for elliptic equations are obtained.

Partial Differential Equations of Elliptic Type

During early life, animals develop from a single fertilized egg cell to hundreds, millions or even trillions of cells. These cells specialize to do different tasks; forming different tissues and organs like muscle, skin, lungs and liver. For more than a century, scientists have strived to understand the details of how animal cells become different and specialize, and have created many new techniques and technologies to help them achieve this goal. Limbs – such as arms, legs and wings – form from small lumps of cells called limb buds. Scientists use the shrimp-like crustacean, Parhyale hawaiensis, to study development, including limb growth. This species is useful because it is easy to grow, manipulate and observe its developing young in the laboratory. Understanding how its limbs develop offers important new insights into how limbs develop in other animals too. Wolff, Tinevez, Pietzsch et al. have now combined advanced microscopy with custom computer software, called Massive Multi-view Tracker (MaMuT) to investigate this. As limbs develop in Parhyale, the MaMuT software tracks how cells behave, and how they are organized. This analysis revealed that for cells to produce a limb bud, they need to split at an early stage into separate groups. These groups are organized along two body axes, one that goes from head to tail, and one that runs from back to belly. The limb grows perpendicular to these main body axes, along a new ‘proximal-distal’ axis that goes from nearest to furthest from the body. Wolff et al. found that the cells that contribute to the extremities of the limb divide faster than the ones that stay closer to the body. Finally, the results show that when cells in a limb divide, they mostly divide along the proximal-distal axis, producing one cell that is further from the body than the other. These cell activities may help limbs to get longer as they grow. Notably, the groups of cells seen by Wolff et al. were expressing genes that had previously been identified in developing limbs. This helps to validate the new results and to identify which active genes control the behaviors of the analyzed cells. These findings reveal new ways to study animal development. This approach could have many research uses and may help to link the mechanisms of cell biology to their effects. It could also contribute to new understanding of developmental and genetic conditions that affect human health.

/pdf/multi-view-light-sheet-imaging-and-tracking-with-the-mamut-zwikg1ax0f.pdf

Multi-view light-sheet imaging and tracking with the MaMuT software reveals the cell lineage of a direct developing arthropod limb

The goal of this paper is to present the finite element scheme for solving the Earth potential problems in 3D domains above the Earth surface. To that goal we formulate the boundary-value problem (BVP) consisting of the Laplace equation outside the Earth accompanied by the Neumann as well as the Dirichlet boundary conditions (BC). The 3D computational domain consists of the bottom boundary in the form of a spherical approximation or real triangulation of the Earth’s surface on which surface gravity disturbances are given. We introduce additional upper (spherical) and side (planar and conical) boundaries where the Dirichlet BC is given. Solution of such elliptic BVP is understood in a weak sense, it always exists and is unique and can be efficiently found by the finite element method (FEM). We briefly present derivation of FEM for such type of problems including main discretization ideas. This method leads to a solution of the sparse symmetric linear systems which give the Earth’s potential solution in every discrete node of the 3D computational domain. In this point our method differs from other numerical approaches, e.g. boundary element method (BEM) where the potential is sought on a hypersurface only. We apply and test FEM in various situations. First, we compare the FEM solution with the known exact solution in case of homogeneous sphere. Then, we solve the geodetic BVP in continental scale using the DNSC08 data. We compare the results with the EGM2008 geopotential model. Finally, we study the precision of our solution by the GPS/levelling test in Slovakia where we use terrestrial gravimetric measurements as input data. All tests show qualitative and quantitative agreement with the given solutions.

/pdf/finite-element-method-for-solving-geodetic-boundary-value-56aufb2ovd.pdf

Finite element method for solving geodetic boundary value problems

In this paper, we introduce a set of methods for processing and analyzing long time series of 3D images representing embryo evolution. The images are obtained by in vivo scanning using a confocal microscope where one of the channels represents the cell nuclei and the other one the cell membranes. Our image processing chain consists of three steps: image filtering, object counting (center detection) and segmentation. The corresponding methods are based on numerical solution of nonlinear PDEs, namely the geodesic mean curvature flow model, flux-based level set center detection and generalized subjective surface equation. All three models have a similar character and therefore can be solved using a common approach. We explain in details our semi-implicit time discretization and finite volume space discretization. This part is concluded by a short description of parallelization of the algorithms. In the part devoted to experiments, we provide the experimental order of convergence of the numerical scheme, the validation of the methods and numerous experiments with the data representing an early developmental stage of a zebrafish embryo.

http://www.kybernetika.cz/content/2010/2/226/paper.pdf

4d embryogenesis image analysis using pde methods of image processing

A conventional value for the geoid reference potential W0

During the 2011 IUGG General Assembly, GGOS, the IAG Commissions 1 (Reference Frames) and 2 (Gravity Field) and the IGFS established a joint working group devoted to the Vertical Datum Standardisation. This working group supports the activities of GGOS Theme 1 Unified Height System; in particular, to recommend a reliable geopotential value W 0 to be introduced as the conventional reference level for the realisation of the GGOS Vertical Reference System. At present, the most commonly accepted W 0 value corresponds to the best estimate available in 2004; however, this value presents discrepancies of about 2 m2 s−2 with respect to recent computations based on the latest Earth’s surface and gravity field models. According to this, as a first approach, four different teams working on the computation of a global W 0 value were brought together in order to compare methodologies and models, and to establish the reliability of the individual computations. Results of this comparison show that the four individual estimates present a maximum discrepancy of about 0.5 m2 s−2. They also confirm that the W 0 value declared as the best estimate in 2004 corresponds to an equipotential surface located about 17 cm beneath the sea surface scanned by satellite altimetry, while the potential value U 0 of the GRS80 ellipsoid realises an equipotential surface located about 67 cm lower. In this context, the need to provide a new better estimate of W 0 is evident.

W0 Estimates in the Frame of the GGOS Working Group on Vertical Datum Standardisation

The paper presents a numerical solution of the oblique derivative boundary value problem on and above the Earth’s topography using the finite volume method (FVM) It introduces a novel method for constructing non-uniform hexahedron 3D grids above the Earth’s surface It is based on an evolution of a surface, which approximates the Earth’s topography, by mean curvature To obtain optimal shapes of non-uniform 3D grid, the proposed evolution is accompanied by a tangential redistribution of grid nodes Afterwards, the Laplace equation is discretized using FVM developed for such a non-uniform grid The oblique derivative boundary condition is treated as a stationary advection equation, and we derive a new upwind type discretization suitable for non-uniform 3D grids The discretization of the Laplace equation together with the discretization of the oblique derivative boundary condition leads to a linear system of equations The solution of this system gives the disturbing potential in the whole computational domain including the Earth’s surface Numerical experiments aim to show properties and demonstrate efficiency of the developed FVM approach The first experiments study an experimental order of convergence of the method Then, a reconstruction of the harmonic function on the Earth’s topography, which is generated from the EGM2008 or EIGEN-6C4 global geopotential model, is presented The obtained FVM solutions show that refining of the computational grid leads to more precise results The last experiment deals with local gravity field modelling in Slovakia using terrestrial gravity data The GNSS-levelling test shows accuracy of the obtained local quasigeoid model

Numerical solution to the oblique derivative boundary value problem on non-uniform grids above the Earth topography

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