The in vitro developmental potential of mouse blastocyst-derived embryonic stem cell lines has been investigated. From 3 to 8 days of suspension culture the cells form complex embryoid bodies with endoderm, basal lamina, mesoderm and ectoderm. Many are morphologically similar to embryos of the 6- to 8-day egg-cylinder stage. From 8 to 10 days of culture about half of the embryoid bodies expand into large cystic structures containing alphafoetoprotein and transferrin, thus being analagous to the visceral yolk sac of the postimplantation embryo. Approximately one third of the cystic embryoid bodies develop myocardium and when cultured in the presence of human cord serum, 30 % develop blood islands, thereby exhibiting a high level of organized development at a very high frequency. Furthermore, most embryonic stem cell lines observed exhibit similar characteristics. The in vitro developmental potential of embryonic stem cell lines and the consistency with which the cells express this potential are presented as aspects which open up new approaches to the investigation of embryogenesis.
Differentiation of individual retina neurons is closely linked to development of retina function. This differentiation may be intrinsic to the cell or determined by the position of the cell within the developing tissue. Retina cognin, a cell-cell recognition protein, which may itself mediate position-dependent cell interactions in vivo exhibits a characteristic change in distribution during embryonic chick development. Cognin is progressively lost from the outer retina in a manner which appears position-dependent. We asked if this change in cognin distribution was actually position-dependent or intrinsic to the retina cells. Neural retina cells from 8-day-old chick embryos were cultured in vitro. Continued differentiation of the cultured cells was demonstrated by neurite outgrowth and characteristic increases in choline acetyltransferase and glutamic acid decarboxylase activity. In such cultures, the characteristic developmentally related disappearance of retina cognin occurred as in vivo. This indicated that this aspect of retina neuronal differentiation was independent of position within the tissue and likely intrinsic to individual cells after 8 days of embryonic development.
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