Fig. 2.

The nephric duct primordium is determined already in the primitive streak. (A-K) Explants from stage 8 (A-D) or stage 4 (E-K) quail mid-primitive streak were stained with DiI and transplanted into the equivalent location in the primitive streak of stage 8 chick embryos. DiI images in B, F and I indicate that the grafted cells remained below the region of the nephric duct primordia at axial level of somites 8-10 (arrow indicates somite 10). Embryos were sectioned and stained for Lim1 (C,G,J, green), the quail marker QCPN (C,G,J, red) and DAPI (D,H,K). Stage 4 donors formed nephric duct tissue (E-K), whereas stage 8 donors did not (A-D). c, nephrogenic cord; d, nephric duct; lp, lateral plate; nt, neural tube; psm, presomitic mesoderm; som, somite.