The origin of the presumptive nephrogenic cells in the epiblast of the chick embryo was traced by radioautographic analysis of the movements of tritiated thymidine-labelled grafts excised from medium-streak to 5-somite stage embryos and transplanted to epiblast, streak, and the endoderm-mesoderm layer of similarly staged recipient embryos. The nephrogenic cells originate near the area pellucida...

Three areas, composed of all three germ layers, were isolated from Fischer strain rat embryonic shields at the head-fold stage, and grafted separately under the kidney capsule of adult male rats of the same strain. The areas were from the neural plate, Hensen's node and the primitive streak. The resulting teratomas were examined histologically for the presence of derivatives of the primitive gu...

Whole mount in situ hybridisation was used to study the embryonic expression of the mouse HMG box-containing genes Sox1, Sox2 and Sox3 between 6.5 and 9.0 days post coitum (dpc). Sox2 and Sox3 are expressed in the epiblast and extraembryonic ectoderm of the egg cylinder, becoming restricted to the prospective neural plate and chorion at the onset of gastrulation. Sox3 is upregulated in the post...

We cloned the chick homologue of the mouse Otx2 gene, c-otx2, and analyzed its expression pattern during gastrulation. During mouse embryogenesis, Otx2 expression is first detected in the entire epiblast and after the formation of the primitive streak becomes confined to the most anterior region of the embryo corresponding to presumptive fore- and mid-brain. Similarly, two distinct phases of c-...

Chick embryos were removed from the egg at stages 6-11 and explanted in culture. The greater part of the postnodal primitive streak of each embryo was replaced with a similar region taken from a corresponding quail embryo. The reciprocal experiment was also carried out, chick primitive streak being grafted in place of quail. After further incubation, the grafted primitive streak cells were foun...

The use of a conventional streak camera for subnanosecond timeresolved fluorimetry is extended to the single-photon counting regime by utilizing intensified readout of the phosphor. The system achieves the usual k e y advantages of photon counting, namely single-photon sensitivity, large dynamic range and shot noise limited statistics, but also permits measurements of lower repetition rate and ...

Previous studies on neural induction have identified regionally localized inducing activities, signaling molecules, potential competence factors and various other features of this important, early differentiation event. In this paper, we have developed an improved model system for analyzing neural induction and patterning using transverse blastoderm isolates obtained from gastrulating chick emb...

IT has recently been shown (Waddington, 1932) that in the chick embryo a developing primitive streak can cause any ectoderm lying above it (provided only that the ectoderm is of the right age) to differentiate into a neural plate. It was shown that in all successful cases the grafted primitive streak had yielded both neural tissue and mesoderm, but that in some specimens the grafted neural tiss...

Snail and Zeb transcription factors induce epithelial-to-mesenchymal transition (EMT) in embryonic and adult tissues by direct repression of E-cadherin transcription. The repression of E-cadherin transcription by the EMT inducers Snail1 and Zeb2 plays a fundamental role in defining embryonic territories in the mouse, as E-cadherin needs to be downregulated in the primitive streak and in the epi...

The cardiogenic potency of cells in the epiblast of the early primitive-streak stage (early PS) embryo was tested by heterotopic transplantation. The results of this study show that cells in the anterior and posterior epiblast of the early PS-stage embryos have similar cardiogenic potency, and that they differentiated to heart cells after they were transplanted directly to the heart field of th...