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

Abstract

The effects of high pressure (40–70 MPa) on the structure and function of myofibrils were investigated by high pressure microscopy. When this pressure was applied to myofibrils immersed in relaxing solution, the sarcomere length remained almost unchanged, and the A band became shorter and wider. The higher the applied pressure, the faster the change. However, shortening and widening of the A band were not observed when pressure was applied to myofibrils immersed in a solution obtained by omitting ATP from the relaxing solution. However, even under these conditions, structural loss, such as loss of the Z-line structure, occurred. In order to evaluate the consequences of this pressure-treated myofibril, the oscillatory movement of sarcomere (sarcomeric oscillation) was evoked and observed. It was possible to induce sarcomeric oscillation even in pressure-treated myofibrils whose structure was destroyed. The pressurization reduced the total power of the sarcomeric oscillation, but did not change the average frequency. The average frequency did not change even when a pressure of about 40 MPa was applied during sarcomeric oscillation. The average frequency returned to the original when the pressure was returned to the original value after applying stronger pressure to prevent the sarcomere oscillation from being observed. This result suggests that the decrease in the number of myosin molecules forming the crossbridge does not affect the average frequency of sarcomeric oscillation. This fact will help build a mechanical hypothesis for sarcomeric oscillation. The pressurization treatment is a unique method for controlling the structure of myofibrils as described above.

Observation of sarcomere chaos induced by changes in calcium concentration in cardiomyocytes

“…The procedure for preparing myofibrils from rabbit psoas muscle was approved by the Institutional Animal Care and Use Ethical Committee of Waseda University and followed the Waseda University animal experimentation rules [ 16 ]. Experiments using myofibrils were approved by the Institutional Animal Care and Use Ethical Committees of Waseda University and the University of Tokyo [ 16 ].…”

“…The procedure for preparing myofibrils from rabbit psoas muscle was approved by the Institutional Animal Care and Use Ethical Committee of Waseda University and followed the Waseda University animal experimentation rules [ 16 ]. Experiments using myofibrils were approved by the Institutional Animal Care and Use Ethical Committees of Waseda University and the University of Tokyo [ 16 ]. Myofibrils were obtained from the intestinal psoas muscle of male Japanese White (JW) rabbits (2.5–3.0 kg, conventional) decapitated after anesthesia induced by injection of 25 mg/kg sodium pentobarbital into the ear vein.…”

“…We used previous data [ 16 ] acquired as briefly described below. ADP-SPOCs were induced by exchanging the relaxing solution in which the myofibrils were immersed with the ADP-SPOC solution.…”

Mechanical stress concealed force enhancement and ionic transient membrane potential and metabolism in akinesia of stress cardiomyopathy

“…The cardiac muscle percentage increment of the oxygen consumption/concentration 16 relation is correlative with its basic metabolic rate. The muscle lengthening stretch enhances the oxygen consumption and the metabolic rate (Figure 13) [72] .…”

Does the Hyperthermal Sarcomeric Oscillations Manifested by Body Temperature Support the Periodic Ventricular Dilation With Each Heartbeat?

“…It has been reported that sarcomere becomes an oscillation state that repeats contraction and relaxation under a solution with intermediate conditions between contraction and relaxation ( Fabiato and Fabiato, 1978 ; Okamura and Ishiwata, 1988 ; Linke et al, 1993 ; Sasaki et al, 2006 ; Shintani et al, 2014 ; Shintani, 2021 ). Details are given in the cited paper, but “intermediate conditions between contraction and relaxation” are solution conditions in which sarcomere can exert a contractile force of about half of the maximum contractile force.…”