Fig. 2 Expression of DM-GRASP protein on the left and rtk2 mRNA on the right in endodermal precursors of the visceral organs. Dorsal views of whole-mounted embryos, anterior to the left. (A) zn-5 immunoreactive cells (brown) are found in both the atrium and ventricle of the heart tube, the endodermal lining of the pharyngeal arches, as well as a cluster of 15–20 cells lying to the left of the notochord (arrow). (B) Higher magnification view of zn-5-labeled cells on the left side just posterior to the pharyngeal arches at the level of the second somite (arrow). (C) rtk2 expression (arrow) is found in a cluster of 5–10 cells lying ventrally and to the right of the midline at the level of somite 3. a, atrium; e, eye; fp, floor plate; n, notochord; pa, pharyngeal arch; s1–s3, somites 1–3; v, ventricle. Scale bars, 100 μm.
Reprinted from Developmental Biology, 210(2), Schilling, T.F., Concordet, J.-P., and Ingham, P.W., Regulation of left-right asymmetries in the zebrafish by Shh and BMP4, 277-287, Copyright (1999) with permission from Elsevier. Full text @ Dev. Biol.