Formation of the primitive streak in the explanted chick blastoderm marked with carbon particles

Abstract

The dolitis Hopkiiiv l l n i v f m i t y , Baltiiizore, Mnrylatrd FOURTEEN FIGURESWhen tranverse strips of the pre-and early streak blastoderiri are explanted in vitro, the structures (fore-brain, hindbrain, spinal cord, notochord, etc.) which develop in the isolated pieces correspond to their location along the einbryonic axis at the much later definitive primitive streak stage (Spratt, '42). Thus, most of the neural plate and all of the notochord-forming regions are shown by this method to be located quite far anterior to the original anterior end of the short-beginning primitive streak. These experiments rather strongly indicated then that the anterior end of the short streak, just after its appearance, is only a transitory structure and not the equivalent of the definitive anterior end (Hensen's node). The most plausible manner in which the streak could grow forward and establish those relationships with the notochord and neural plate regions characteristic of the definitive streak stage seemed to be through a progressive differentiation of the epiblast into streak material anterior to the original short streak. In order to obtain more direct evidence on the manner of growth in length of the streak, a series of experiments was begun in which explanted pre-and early streak blastodernis were marked with carbon particles (powdered blood charcoal). The direction, extent, and rate 'It is a pleasure to thank Mr. John Spurheek, artist-photographer, for hie valuable assistance in the preparation of the illustrative material. 359

Primitive and definitive erythropoiesis in the yolk sac: a birds eye view

“…Fates of mesoderm precursors in the primitive streak vary depending on the stages. Generally speaking, posterior part (1/2 to 1/3) of the primitive streak continues to give rise to extraembryonic fated mesoderm from HH2 to at least HH9 (Murray, 1932;Nakazawa et al, 2006;Nocolet, 1970;Peebles, 1898;Psychoyos and Stern, 1996;Rawles, 1936;Rosenquist, 1966;Rudnick, 1938;Sawada and Aoyama, 1999;Schoenwolf et al, 1992;Spratt, 1942;Spratt, 1946;Spratt, 1947;Spratt and Haas, 1965). Relative to more axially located mesoderm lineages (the axial, paraxial, intermediate and lateral plate mesoderm), extraembryonic mesoderm precursors are of the ventralmost fate and populate the lateralmost regions of the developing embryo.…”

Hensen's node

“…With his ingenious techniques for culturing and manipulating the chick embryo, Waddington had established the basis for experimental analysis of the higher vertebrate embryo. Following this work, experimental analysis of induction and axis formation in amniotes was for many years mainly carried out in the avian system (e.g., Wetzel, 1929;Pasteels, 1936;Spratt, 1946;Joubin and Stern, 1999), which in the latter half of the 20th century was helped enormously by the simplification in embryo culture brought about with New's (1955) ring technique and by the cell marking technique made possible by quail-chick transplantation chimeras (Le Douarin and Teillet, 1974). In the course of the publication of these studies, it became customary to use the term Hensen's node for the avian embryo only.…”

Early epochal maps of two different cell adhesion molecules.

“…4A) based on the fate map described by Rudnick (14) was constructed, taking into account marking with carbon or iron particles (6,15), grafts labeled by tritiated thymidine (16), experiments with chimeric chicken-quail blastoderm (11), and unpublished work of L. Vakaet (personal communication). This map revealed a well-delineated central area of blastoderm that will later express N-CAM.…”