Electrophysiological evidence is presented for the exchange of small ions directly between cells interiors, i.e. "electrical coupling," in the early chick embryo. Experiments with intracellular marking show that coupling is widespread, occurring between cells in the same tissue, e.g. ectoderm, notochord, neural plate, mesoderm, and Hensen's node, and between cells in different tissues, e.g. not...

it is well known that glycoconjugate components of the cell surface and extracellular matrix, play an essential role(s) in many developmental phenomena such as cell differentiation, migration, and cellular interactions. the purpose of this study was to investigate distribution of this macromolecules during differentiation of the notochord and paraxial mesoderm. formalin fixed paraffin sections ...

The notochord, a conserved axial structure required for embryonic axis elongation and spine development, consists of giant vacuolated cells surrounded by an epithelial sheath [1-3]. During morphogenesis, vacuolated cells maintain their structural integrity despite being under constant mechanical stress [4]. We hypothesized that the high density of caveolae present in vacuolated cells [5, 6] cou...

Basement membranes are thought to be essential for organ formation, providing the scaffold on which individual cells organize to form complex tissues. Laminins are integral components of basement membranes. To understand the development of a simple vertebrate organ, we have used positional cloning to characterize grumpy and sleepy, two zebrafish loci known to control notochord formation, and fi...

The appearance of the notochord represented a milestone in Deuterostome evolution. The notochord is necessary for the development of the chordate body plan and for the formation of the vertebral column and numerous organs. It is known that the transcription factor Brachyury is required for notochord formation in all chordates, and that it controls transcription of a large number of target genes...

The node and notochord (and their equivalents in other species) are essential signaling centers, positioned along the plane of bilateral symmetry in developing vertebrate embryos. However, genes and mechanisms regulating morphogenesis of these structures and their placement along the embryonic midline are not well understood. In this work, we provide the first evidence that the position of the ...

Members of the paired box (Pax) gene family are expressed in discrete regions of the developing central nervous system, suggesting a role in neural patterning. In this study, we describe the isolation of the chicken homologues of Pax-3 and Pax-6. Both genes are very highly conserved and share extensive homology with the mouse Pax-3 and Pax-6 genes. Pax-3 is expressed in the primitive streak and...

In embryos of the ascidian Halocynthia roretzi, the competence of isolated presumptive notochord blastomeres to respond to fibroblast growth factor (FGF) for induction of the primary notochord decays by 1 hour after cleavage from the 32- to 64-cell stage. This study analyzes the molecular mechanisms responsible for this loss of competence and provides evidence for a novel mechanism. A forkhead ...

This year is the centenary of Edward G. Conklin's signal findings in embryology: the elucidation of complete cell lineages and the discovery of localized maternal determinants. Conklin used ascidian embryos to elucidate universal principles in embryology. A century later, ascidians, or sea squirts, have not only entered the post-genome era, but in many ways are leading the way to the promise of...