Growth and development of chick embryo explants on various protein substrates

Abstract

Chick embryo explants of 11 to 13 somites were cultured on various sources of protein in an attempt to determine if these proteins could replace the proteins of egg yolk as a nutrient substrate for the developing embryo. Various approaches were employed to provide a favorable low molecular weight supplement to the non-yolk sources of protein. After 48 hours of cultivation, the protein nitrogen and DNA contents of the embryo and the extraembryonic membrane were determined and the stages of morphological development were estimated. The growth and development of embryos cultured on yolk or a mixture of yolk and white were not surpassed with the other sources of protein tested. However, a mixture of horse serum and ovalbumin which first had been equilibrated across a cellophane membrane with an homogenate of whole egg supported levels of embryo growth and development which closely approximated that achieved with yolk and white. Individually, serum supported the growth and development of the extraembryonic membrane while ovalbumin supported the embryo proper. The response of embryo explants to sera derived from laying hens, roosters, or rabbits was similar to that observed with horse serum.

Protein nutrition in growth regulation during early development

“…In the initial experiments the procedure of Bernardi and Cook (i960) was used to separate fresh yolk into a high density and low density fraction. Employing various procedures to supply the low molecular weight supplement, as previously discussed (Klein, 1968), the high density fraction but not the low density fraction supported embryo growth and development. In fact, during 48 hours of culture embryo growth on the high density fraction was comparable to that achieved with the whole egg homogenate medium.…”

“…In combination, serum and ovalbumin supported embryo growth comparable to that achieved on whole egg homogenate medium with a somewhat larger extraembryonic membrane. Klein, 1966) suggested that the active component was associated with the globulins rather than the albumins which might be expected from the observation that bovine serum albumin not only failed to support the growth of the embryo proper but the extraembryonic membrane as well (Klein, 1968).…”

“…When the level of amino acids was increased above 1.69 mg per ml, embryo growth was not improved and the medium appeared toxic. Thus, in order to compare the chemically defined and whole egg media at comparable levels of amino acid nitrogen, the whole egg medium was diluted to 2.5% (Klein, 1968). In this study an attempt was made to maintain medium constituents other than amino acids as similar as possible by supplementing the 2.5% whole egg medium with the chemically defined medium constituents less the amino acids.…”

Protein Nutrition in Growth Regulation During Early Development

“…When the growth of embryos was quantitatively evaluated, large differences were observed in the response of embryos to various protein sources (Table II) (Klein, 1968). The accumulation of protein nitrogen during a 48 hour culture period was greatest for embryos provided with whole egg homogenate medium (a mixture of yolk and white).…”

“…The first demonstration that a combination of proteins or sources of protein would support a higher level of embryo growth than could be achieved when these materials were individually provided in the medium was made with ovalbumin and serum (Klein, 1968). The combination of these two proteinaceous materials was not fortuitous but was based on the observation that serum and ovalbumin supported different parts of the chick embryo explant system.…”