Effects of high-pressure treatment on the structure and function of myofibrils

Figures

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  Figure 1. Structural changes in myofibrils during pressurization. (a,b) Phase contrast optical microscope images of myofibrils when a pressure of 60 MPa was applied in relaxing solution (a) and rigor solution (b). Images at 0, 30, 60 and 90 s, from left to right. The scale bar is 2 μm. (c–e) Time series changes in sarcomere length (c), A-band length (d) and A-band width ratio (e) during pressurization. The A-band width ratio was standardized based on the A-band width immediately after pressurization. The following numbers of sarcomeres were used in the analysis: 40 MPa, n=17; 50 MPa, n=13; 60 MPa, n=21; 70 MPa, n=16; 60 MPa (ATP(–)), n=16. (f–h) Rate of change in sarcomere length (c), A-band length (d) and A-band width ratio (e) during pressurization. Tukey’s test was used for comparisons between groups. When there was a significant difference from the following pressure treatment groups, the following symbol marks were added: 40 MPa (*), 50 MPa (†), 60 MPa (‡), 70 MPa (#).

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  Figure 2. Structural change in the Z line by continuing to apply a pressure of 80 MPa under rigor solution. (a) Photographs of myofibrils in rigor solution at 80 MPa. Image immediately after pressurization (left) and image 13.3 min after pressurization (right). The scale bar is 2 μm. (b) Brightness distribution in the long-axis direction of the yellow frame in (a). The black line shows the brightness distribution immediately after pressurization, and the red line shows the brightness distribution 13.3 min after pressurization.

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  Figure 3. Changes in sarcomeric oscillation of sarcomeres caused by pressure treatment of myofibrils. (a–d) Typical waveform example of sarcomeric oscillation. The results are shown for no pressurization (a), for 40 MPa pressurization in relaxing solution for 10 min (b) or 30 min (c), and for 100 MPa pressurization in rigor solution for 5 min (d). (e–h) PSD of sarcomeric oscillation for each myofibril in a–d. Each represents the average of the PSDs of the following numbers of sarcomeres: e–g, n=30; h, n=21. (i–k) Average frequency (i) and total power (j) and average of peak frequencies (k) of sarcomeric oscillation of each myofibril in a–d. When Steel’s test showed a significant difference from the control group, the result is marked with *.

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  Figure 4. Characteristics of sarcomeric oscillation of during pressurization. (a–d) Typical waveform example of sarcomeric oscillation. Before pressurization (a), during pressurization at 40 MPa (b), during pressurization at 50 MPa (c), and when depressurized to 0.1 MPa (d). (e–h) PSD of sarcomeric oscillation for each myofibril in a–d. Each represents the average of the PSDs of the following numbers of sarcomeres: e–h, n=40. (i–k) Average frequency (i), total power (j) and peak power (k) of sarcomeric oscillation in each state shown in a–d. When Dunnett’s test (i) and Steel’s test (j, k) were significantly different from the control group, the result is marked with *. For the analysis, 20 sarcomeres were used for each group.