Nutritional requirements for the realization of regulative (repair) capacities of young chick blastoderms

Abstract

Studies of the regulative (repair) capacities of young chick blastoderms in ovo and explanted i n vitro on culture media varying in their growth promoting properties clearly indicate that these capacities are realized fully only under the most optimal nutrient conditions. Thus the ability of an explanted part of a young blastoderm to form a bilaterally symmetrical embryo body depends not only on the region of the blastoderm isolated, on its intrinsic growth potentiality and on its size (cell number) but also on the growth promoting properties of the culture medium. Realization of regulative potentiality goes hand-in-hand with realization of growth (or other synthetic) potentiality.The growth and regulative capacities of separated parts (halves, quarters, etc.) of unincubated and early streak chick blastoderms explanted on an egg-extract culture medium are pronounced (Spratt and Haas, '60c; '61a, b). In general, any part of the unincubated blastoderm which includes the growth center or a segment of the marginal zone ( pellucid-opaque area junction) and is larger than one-sixteenth of the area of the blastoderm may form a bilateraIIy symmetrical and essentially complete embryo body axis. More recently, it was discovered that an isolated and explanted central part of a very young unincubated blastoderm (from a winter egg) which included neither the growth center nor part of the marginal zone could form an embryo axis (Eyal-Giladi and Spratt, '65). Chick and duck (Lutz et al., '63) blastoderms thus seem to have similar regulative capacities to the extent that both are almost equipotential (or totipotential).Older sudies of organ-forming capacities of parts of prestreak and early streak blastoderms (stages 1 +-2+, Hamburger and Hamilton, '51) explanted on a blood plasma and embryo extract medium suggested that the young blastoderm had mosaic properties (Spratt, '42 p. 83). Parts of the embryo body axis seemed to be localized in the blastoderm during and even before streak-formation. Separated anterior and posterior parts developed in accord with their prospective fates, i.e., there was little increase in size of the explants J. EXP. ZOOL., 164: 31-46 and regulative capacity was minimal. The primary difference between the older experiments and more recent ones seems to be the kind of culture medium used. This suggested the need for a study of the infiuence of the nutritional composition of a culture medium on growth and regulative ~apacities.~ METHODSExplantation procedures were the same as those reported earlier (Spratt, '47a, b; Spratt and Haas, '60a, b). In all in vitro experiments the blastoderms or fractions thereof were explanted upper layer (epiblast) down on the solid agar medium. This position is important in unincubated and prestreak blastoderms, less important in older blastoderms (Spratt and Haas, '60a, b; '65; Spratt, '66). The upside-down position of the explant simulates that of the in ovo blastoderm. The surface of the solid culture medium corresponds to the underside of the vitelline membr...

Protein Nutrition in Growth Regulation During Early Development

“…The literature would suggest that this has been achieved in that the in vitro culture of chick embryo has been reported with such diverse media as plasma (Waddington, 1932;Spratt, 1942), sera (Gallera and Nicolet, 1961), embryo extract (Spratt, 1942;Wolff and Simon, 1955), egg white (Spratt, 1947;Reporter and Ebert, 1965)i yolk (Spratt, 1947), and mixtures of egg yolk and white (Britt and Herrmann, 1959;Spratt and Haas, i960). However, it should be clearly noted that the relative ability of these various media to support embryo growth could not be compared because most of these studies lacked quantitative determinations of growth.…”

“…Spratt and Haas (1967) observed that the ability of parts of early chick blastoderms to form an embryonic axis (regulative and repair capacities) depended on the ability of the culture medium to support growth. In this study, extract of whole egg was found.to be superior to extract of egg white.…”