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Fig. 4. Expression of XSmad3 in the heart is restricted to the endocardium. Panels (A–F) represent serial 10 μm transverse sections from anterior to posterior respectively through the heart region of a stage 33 embryo previously stained for XSmad3 by the whole-mount procedure used in the previous panels. e, endocardium; m, myocardium; aa, aortic arch. In panel (C) note that endocardial staining, which is strong in the outflow tract (arrowhead) does not extend into the aortic arches (aa). In panel (E), the section has cut through the endocardium twice as it is a spirally looped tube (both indicated ‘e’): The blue staining is seen specifically in the endocardium. |
