3-D Rendering of the Adult Zebrafish Heart. Example of a reconstructed heart. (A) The anatomic relationship of the intact atrium, ventricle, and bulbus arteriosus is shown in a surface view. (B) A cross-section through the atrium, ventricle, and bulbus arteriosus demonstrates the 2 leaflets of the AV valve (red) and of the VB valve (orange). (C) Magnification at the level of the cardiac valves showing the ventricular inflow through the AV valve (dashed arrow) and the ventricular outflow through the VB valve (solid arrow). (D) Magnification of a ventricular segment with highlighted trabeculae. AV: atrioventricular. VB: ventriculobulbar. Scale bar: 100 μm.

Cardiac Architecture Following Doxorubicin Treatment. Adult zebrafish hearts were harvested at days 3, 30, and 60 following treatment with doxorubicin or control vehicle. (A) Control hearts exhibit preserved architecture throughout the study period. In contrast, doxorubicin-treated hearts demonstrate a profound cardiac remodeling leading to acute decrease in size at day 3, followed by progressive increase at day 30, and return to control levels at day 60. (B) Quantitative analysis of the total heart, myocardial, and endocardial volumes normalized to control values demonstrating the cardiac regeneration process following response to chemotherapeutic injury. **P < 0.01. Doxo: doxorubicin. Scale bar: 200 μm.