Physiological effects of aging in zebrafish. (A) Experimental setup to assess voluntary swimming. Individual fish were placed in a 3-litre tank, with white paper below and digital video captured from above. The position of the head was tracked manually using Fiji/ImageJ. (B) Voluntary swimming speeds in body lengths per second for 6-month and 18-month-old zebrafish. Sample size (n) was ten for both 6- and 18-month age groups. (C,D) Quantitative RT-PCR analysis of nppa and nppb gene expression in whole hearts. Sample size (n) was ten for both 6- and 18-month age groups. All individual data points are shown, mean±s.e.m. Normal distribution of data (D'Agostino–Pearson), no difference in variance (F-test). *P<0.05; **P<0.02; ns, not significant (unpaired two-tailed Student's t-test).
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