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Figure 2. Cardiac induction from animal caps and in vivo transplantation. A: Animal caps excised from blastulae were placed in physiologic saline that lacked calcium, to loosen the cell adhesions. The culture medium was replaced with 100 ng/ml activin dissolved in physiologic saline that contained calcium, and the cells were dissociated by pipetting. Individual cells were then reaggregated, and the reaggregates began to beat approximately 2 days later. Reaggregates that had been cultured for 1 day were broken into appropriate sizes and transplanted through an incision that had already been made anterior to the cloaca in the neurula. B: XcTnI, a marker gene for myocardial differentiation, is expressed specifically in the myocardium of a normal 3-day-old embryo (left). The dissociated animal cap cells form spherical reaggregates, regardless of whether they have been treated with activin. XcTnI signals are detected exclusively in the activin-treated reaggregates (right). C: The internal anatomy of a 1-year-old frog with a well-developed ectopic heart. The ectopic heart adjacent to the host's intestine is incorporated into the host's vascular system. The blood from the host's mesenteric artery (black arrows) flows into the host's anterior abdominal vein (white arrows) by means of the ectopic heart (h). D: Histologic section of an ectopic heart. The heart can be divided into multiple chambers: a ventricle-like chamber (v) that comprises a thick and deeply penetrating layer of myocardium; and an atrium-like chamber (a) that is surrounded by a thin layer of myocardium. |
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tnni3 (troponin I type 3 (cardiac)) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 37 & 38, lateral view, anterior left, dorsal up. |
