Fig. 3

(A) The number of zebrafish embryos that survived with no heartbeat or mild contractions was assessed. Number of embryos with mild contraction increased from 36% (16/44) to 51% (21/41), suggesting that the washout partially restores heart contractility. (B) The heart rate (n = 7) dropped by 25% within 30 minutes of treatment at 2 dpf. At 5 dpf, the heart rate of treated hearts before washout (n = 15) was far lower than that of control (n = 20) but washout increased heart rate by 19% (n = 20). Note that the treated embryos with no heartbeats were excluded in this calculation. (C) Ventricular fractional area changes from systole to diastole of control (n = 10) and treated hearts (n = 10), calculated from 2D microscopy, evaluated based on the end-systole which was normalized to the end-diastole at 2, 3, and 5 dpf, respectively. For B-C, mean and standard deviations were presented and a two-sample t-test was used, where *P < 0.05. (D) Fractional shortening, a metric of myocardial contractility, measured from cardiac motion tracking of 3D LSFMM microscopy images, taking the end-diastole state as the zero stretch reference, at 3 and 5 dpf