Figure 4.
Figure 4. Cell-SPOC in neonatal cardiomyocytes. (A, top left) Epi-illumination image of an AcGFP-treated myocyte after ionomycin treatment in the presence of 200 µM ryanodine and 4 µM thapsigargin. The area in the yellow outlined rectangle was used for the SL analysis. (top right) Time course of changes in the positions of the Z discs, 1–6. Amplitude of the movement of Z disc 4 was 0.960 ± 0.023 and 0.385 ± 0.055 µm (P < 0.05) in time phases 1 and 2, respectively. Amplitude of the movement of Z disc 5 was 0.904 ± 0.041 and 0.461 ± 0.031 µm (P < 0.05) in time phases 1 and 2, respectively. (bottom) Waveform properties during cell-SPOC in time phases 1 and 2. Numbers in graphs indicate the mean values of the SL amplitude during cell-SPOC (P > 0.05). See Video 10. (B) Relationship of frequency versus amplitude in cell-SPOC. Individual data were fitted by a curve Y = 0.974X−1 (R = 0.618; black line). The red squares were taken from Fig. 3 C (bottom). (C) Relationship of frequency versus the ratio of shortening time to lengthening time in cell-SPOC. The red diamonds were obtained from Fig. S9 (A and B). Gray line, shortening time/lengthening time = 1. (B and C) *, P < 0.05 compared with the values for cell-SPOC. #, P < 0.05; †, P < 0.05; ‡, P < 0.05 compared with 1, 2, and 3 Hz, respectively. (D) Relationship of frequency versus shortening (or lengthening) velocity in cell-SPOC. A significant linear relationship was obtained: Y = 0.511X + 0.425 (R = 0.788; P < 0.0001) for shortening (solid line) and Y = −0.853X + 8.456 (R = 0.390; P < 0.0001) for lengthening (dashed line). (E) Relationship of frequency versus maximal (or minimal) SL in cell-SPOC. Maximal and minimal SL values were obtained at peak lengthening (dashed line) and shortening (solid line), respectively. A significant linear relationship was obtained: Y = 0.041X + 1.598 (R = 0.315; P < 0.002) for minimal SL and Y = −0.090X + 2.480 (R = 0.539; P < 0.0001) for maximal SL. Note that minimal SL is <1.6 µm (1.58 µm; Luther et al., 2008); i.e., the length of the cardiac A band. Error bars indicate means ± SEM.

Cell-SPOC in neonatal cardiomyocytes. (A, top left) Epi-illumination image of an AcGFP-treated myocyte after ionomycin treatment in the presence of 200 µM ryanodine and 4 µM thapsigargin. The area in the yellow outlined rectangle was used for the SL analysis. (top right) Time course of changes in the positions of the Z discs, 1–6. Amplitude of the movement of Z disc 4 was 0.960 ± 0.023 and 0.385 ± 0.055 µm (P < 0.05) in time phases 1 and 2, respectively. Amplitude of the movement of Z disc 5 was 0.904 ± 0.041 and 0.461 ± 0.031 µm (P < 0.05) in time phases 1 and 2, respectively. (bottom) Waveform properties during cell-SPOC in time phases 1 and 2. Numbers in graphs indicate the mean values of the SL amplitude during cell-SPOC (P > 0.05). See Video 10. (B) Relationship of frequency versus amplitude in cell-SPOC. Individual data were fitted by a curve Y = 0.974X−1 (R = 0.618; black line). The red squares were taken from Fig. 3 C (bottom). (C) Relationship of frequency versus the ratio of shortening time to lengthening time in cell-SPOC. The red diamonds were obtained from Fig. S9 (A and B). Gray line, shortening time/lengthening time = 1. (B and C) *, P < 0.05 compared with the values for cell-SPOC. #, P < 0.05; †, P < 0.05; ‡, P < 0.05 compared with 1, 2, and 3 Hz, respectively. (D) Relationship of frequency versus shortening (or lengthening) velocity in cell-SPOC. A significant linear relationship was obtained: Y = 0.511X + 0.425 (R = 0.788; P < 0.0001) for shortening (solid line) and Y = −0.853X + 8.456 (R = 0.390; P < 0.0001) for lengthening (dashed line). (E) Relationship of frequency versus maximal (or minimal) SL in cell-SPOC. Maximal and minimal SL values were obtained at peak lengthening (dashed line) and shortening (solid line), respectively. A significant linear relationship was obtained: Y = 0.041X + 1.598 (R = 0.315; P < 0.002) for minimal SL and Y = −0.090X + 2.480 (R = 0.539; P < 0.0001) for maximal SL. Note that minimal SL is <1.6 µm (1.58 µm; Luther et al., 2008); i.e., the length of the cardiac A band. Error bars indicate means ± SEM.

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