Endodermal movements during foregut formation in the chick embryo |
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| Authors: | H Stalsberg R L DeHaan |
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| Affiliation: | 1. Key Laboratory of Plant Protection Resources and Pest Management, Ministry of Education, Entomological Museum, Northwest A&F University, Yangling, Shaanxi 712100, China;2. State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China;1. School of Biomedical Sciences, University of Hong Kong, Pokfulam, Hong Kong SAR, China;2. Department of Statistics and Actuarial Science, University of Hong Kong, Pokfulam, Hong Kong SAR, China;3. Center for Translational Stem Cell Biology, Hong Kong Science and Technology Park, Hong Kong SAR, China;3. Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112 and;4. Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115;1. Smart Structures and Systems Laboratory, Department of Mechanical Engineering, Inha University, Incheon 402-751, South Korea;2. Department of Electrical and Electronics Engineering, National Institute of Technology Puducherry, Karaikal, Puducherry 609605, India;1. Heidelberg Institute for Theoretical Studies, Heidelberg, Germany;2. Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Mathematikon, Heidelberg, Germany;1. Unité de Chronobiologie théorique, Faculté des Sciences, Université Libre de Bruxelles (ULB), Campus Plaine, Brussels, Belgium;2. Laboratoire Génétique, Reproduction et Développement, Université Clermont Auvergne, Clermont-Ferrand, France;3. Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1103, Clermont-Ferrand, France;4. Centre National de la Recherche Scientifique (CNRS), UMR6293, Clermont-Ferrand, France;5. Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch, South Africa |
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| Abstract: | Insoluble particles of ferric oxide were placed on the endodermal surface of chick embryos in in vitro culture at stage 5–7. The position of the particles which adhered to the endoderm was recorded by photographing the embryos at frequent intervals during the subsequent 20 hours of development, to trace the movements and infoldings of that layer during formation and elongation of the foregut.From stage 6+ to 11+ the length of the foregut increases from about 0.1 mm to about 1.0 mm, during which time its length remains a constant proportion (80%) of the length of the head. During that period the mean areal surface of the subcephalic yolk sac endoderm increases by more than 3-fold, indicating that the elongation of the subcephalic endoderm and floor of the foregut is not accomplished merely by stretching of the tissue present when the AIP first forms.From stage 6+ to about stage 8, endoderm rolls in over the ventral fold of the AIP from the subcephalic yolk-sac endoderm to contribute a substantial—but decreasing—fraction of the elongating floor of the foregut. By the time the foregut has increased in length to 0.7 mm (about stage 9−), in-rolling contributes little or nothing to its subsequent elongation.A model of the events occurring in the endoderm is proposed, based upon the behavior of an elastic band, fixed at its two ends and stretched into a U-shape by applying tension near the middle. It is demonstrated that the curve relating the amount of foregut elongation and the fraction of that elongation contributed by in-rolling, obtained from measurements of the experimental embryos fits well with a theoretical curve derived from the model. It is postulated that regression of primitive streak and subjacent endoderm exerts a posteriorly directed tension on the lateral endoderm which is transmitted as a pulling force to the endodermal fold of the AIP, and acts to lengthen the foregut. |
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