Introduction

This chapter outlines one approach to the study of the basic physiology of the early avian embryo, but, due to limitations of space this has to be a restricted view. No attempt has been made to provide a comprehensive review of all the literature but simply to describe some new results obtained from our laboratory which suggest areas for future study. This physiological approach towards an understanding of embryogenesis assumes that embryonic cells will possess ion transporting mechanisms similar to those which have been observed in adult cells. Our hypothesis suggests that the embryonic cells will utilise the ion regulatory mechanisms to effect growth, promote morphogenic movements and regulate cell proliferation, migration and differentiation (Moolenaar, Tsein & Van der Saag, 1983; Busa, 1986).

Interest in the basic physiology of the early embryo can be traced back for over 60 years. Much of the experimental work on the early embryo deals with amphibian (Barth & Barth, 1974; Turin & Warner, 1980; Gillespie, 1984) and echinoderm blastulae (Rapkine & Prenant, 1925), amphibian gastrula (Gillespie, 1984) and pre-implantation mammalian blastocyst (Cross, 1973; Borland, Biggers & Lechene, 1976, 1977) and has centred on the characterisation of the mechanisms regulating ion and water movements across the developing embryonic epithelia. There is considerable interest in the hydrogen and calcium ion concentrations of the interstitial fluid of blastulae and gastrulae.