Dissociation and Reaggregation of Embryonic cells of Triturus alpestris

Cell movement and migration seem to play an important role in the formation of tissue-patterns during embryogenesis. Phenomena such as the appearance of loosely attached cells in the mesoderm, or of the freely migrating neural crest cells, are quite common in embryonic development. Since the tissues of adult organs are mostly rather compact in structure it seems that the capacity of isolated or loosely arranged cells to reassociate is an obligatory condition for many developmental processes. This capacity, under experimental conditions, was extensively studied by Holtfreter (1947, 1948). He has shown that cells of newt blastulae and early gastrulae can be made to dissociate and can then become reaggregated and proceed with their morphogenetic development. His experiments were carried out, for the most part, either with cells prior to histogenetic determination or with determined cells of a single tissue.

The Uptake of Methionine-S35 by the Chick Embryo and its Inhibition by Ethiònine

It seems probable that the synthesis of new proteins must play one of the most fundamental roles in embryonic development. As part of a programme of investigating protein metabolism in morphogenesis (see Waddington & Sirlin, 1954), a study has begun on the incorporation into the early chick embryo of amino-acids labelled with radioactive isotopes and the effect of some of their structural analogues on their metabolism. It seems that for this particular aspect of study the chick embryo has two main advantages over the amphibian: (1) Since it depends for metabolites on external sources (yolk, albumen, culture medium), it is much easier to interfere with the normal pathway of protein synthesis by means of specific antimetabolites. (2) Unlike the amphibian embryo, it does not possess a surface coat, which greatly inhibits the absorption of substances of even small molecular size in amphibian embryos (Friedberg & Eakin, 1949).