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Fig. 1. Endoderm is not necessary for in vivo angioblast specification. (A) Diagram of the dissection used to remove endoderm. The vegetal core (red), comprising future endoderm, was removed from embryos at the onset of gastrulation, and the resulting endoderm-depleted embryos were incubated until stage 34. (B,D,F) Control embryos assayed with X-msr, erg and flk-1 probes, respectively. These show elaborate vascularization, including posterior cardinal veins (pcv; closed arrowheads), intersomitic vessels (is; open arrowheads) and a ventrolateral vascular plexus. (C,E,G) Endoderm-depleted embryos, assayed with X-msr, erg and flk-1 probes, respectively, contain angioblasts (white open arrowheads), but these are not organized into patent blood vessels. |