These studies have also shown that in the operated embryos, none of the remaining cells can replace the missing 2d and 4d and that both 2d and 4d are determined as ectodermal and mesodermal precursors, respectively, at the time of their birth. That 2d and 4d play a pivotal role in Tubifex embryonic development was first suggested from the classic cell-ablation experiments carried out in the early 1920s, and this has been confirmed by the recent cell-ablation/restoration experiments using cell-labeling with lineage tracers. Various studies have suggested that the D quadrant functions as the organizer of the embryonic axes in molluscs and annelids, and it has recently been demonstrated that the D quadrant micromeres, 2d 11 and 4d, which had been transplanted to an ectopic position in an otherwise intact embryo induce a secondary embryonic axis to give rise to the formation of duplicated heads and/or tails. In spiralian embryos, it has long been known that one blastomere at the four-cell stage, the D cell, and its direct descendants play an important role in axial pattern formation. Because its developing eggs are easily obtained in the laboratory, this animal has long been used as material for developmental studies, especially spiralian embryology. The annelid Tubifex tubifex is a cosmopolitan freshwater oligochaete and a member of the Spiralia, a large group of invertebrate phyla displaying spiral development. Lenka Radonova, Tereza Svobodova and Martin AngerġDepartment of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan and 2Department of Molecular and Cellular Biology, University of Arizona, Tucson, USA Abstract.Regulation of the cell cycle in early mammalian embryos and its clinical implications.Early mammalian development: from basic research to the clinic.Eszter Posfai, Isidora Rovic and Andrea Jurisicova.The mammalian embryo’s first agenda: making trophectoderm.Annalaura Mancia, Giulia Zuccon, Denise Lunardi, Barbara Biancani, Claudia Gili, Roscoe Stanyon, Daniel García-Parraga, Mara Mellado, Luigi Abelli and Victoria Moreno-Manzano.Isolation and phenotyping of potential stem cells from the umbilical cord of the bottlenose dolphin (Tursiops truncatus).
Cell population growth regulates dorsalization and caudalization during chick morphogenesis and programmed cell death in lens fibres.
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