In vivo tracking of individual sarcomeres in an LV myocyte of a mouse under deep anesthesia. (A) Top: Confocal image of a myocyte expressing α-actinin-AcGFP in a mouse with ΔLVP 7.2 mm Hg. During eight cardiac cycles, ΔLVP was 7.2 ± 0.1 mm Hg, and HR was 159 ± 45.4 bpm (Table 1). In the yellow-outlined rectangle, nine sequentially connected sarcomeres were analyzed for both M1 and M2. Numbers indicate longitudinal positions of sarcomeres (i.e., nos. 1–9 for both M1 and M2). Scale bar, 10 µm. See Video 8. Bottom: Color diagram showing CI between average and individual SLs, from nos. 1 to 9, during eight cardiac cycles for M1 (left) and M2 (right). Sarcomere numbers are indicated on top and cardiac cycle numbers on left. Data on the average of eight cycles are shown on bottom. (B) Top: Same as in A, in a mouse with ΔLVP 4.7 mm Hg. During three cardiac cycles, ΔLVP was 4.7 ± 0.2 mm Hg, and HR was 80 ± 14.2 bpm (Table 1). In the yellow-outlined rectangle, seven sequentially connected sarcomeres were analyzed for M1, M2, and M3. Numbers indicate longitudinal positions of sarcomeres (i.e., nos. 1–7 for M1, M2, and M3). Scale bar, 10 µm. See Video 9. Bottom: Color diagram showing CI between average and individual SLs, from nos. 1 to 7, during three cardiac cycles for M1 (left), M2 (middle), and M3 (right). Sarcomere numbers are indicated on top and cardiac cycle numbers on left. Data on the average of three cycles are shown on bottom. Arrowheads (with numbers) indicate longitudinal positions of sarcomeres.