“Deep‑Sea Responses” of Myofibrils Deciphered by High‑Pressure Microscopy — Structural Transformations and the Mystery of Self‑Oscillations at 40–80 MPa (BPPB, 2021)

This fundamental study used a high‑pressure microscope that can observe isolated myofibrils in real time while applying hydrostatic pressures of 40–80 MPa—equivalent to depths of 4 000–8 000 m in the ocean. It investigates how the sarcomere, the minimal contractile unit, changes shape yet preserves function under such conditions.

Structural findings

• Relaxing solution: When pressurized, sarcomere length remained almost constant, but the A‑band shortened axially and expanded laterally.

• Rigor solution (ATP‑free): A‑band length was maintained, yet Z‑lines collapsed and lattice order loosened.

• The deformation rate increased proportionally with both pressure and time, revealing a “pressure dial”: structural relaxation progresses over tens of minutes at 40 MPa but within tens of seconds at 70 MPa.

Functional findings

Raising temperature to 35 °C and supplying ATP/ADP/Pi induced sarcomeric self‑oscillations (SO). Although pressurized myofibrils showed reduced amplitude, their mean oscillation frequency matched that of untreated controls, implying that the chemical reaction cycle, not cross‑bridge number, governs periodicity.
When SOs were subjected to pressure in real time, they persisted at 40 MPa but vanished at 50 MPa, instantly reappearing upon decompression. This reversibility suggests that dynamic adjustment of myosin–actin lattice spacing acts as an energy “switch” for oscillations.

Top: Schematic of the high‑pressure cell and the sarcomere model.

Bottom: Time‑lapse images showing pressure‑dependent deformation under relaxing and rigor conditions.

Significance

The work exemplifies “piezophysiology,” employing hydrostatic pressure as a powerful yet gentle means of uniform, reversible structural control over macromolecular assemblies. It offers foundational insights for functional remodeling of protein complexes and for ultra‑high‑pressure technologies in food and medical applications. Moreover, the data serve as critical validation for sarcomere‑oscillation models, bridging molecular mechanisms with macroscopic rhythmic behavior.

Article information & citation

Seine A. Shintani. Effects of high‑pressure treatment on the structure and function of myofibrils. Biophysics and Physicobiology, 18, 85‑95, 2021. 

https://doi.org/10.2142/biophysico.bppb-v18.010 

Press release

Japanese Physiological Society — Science Topics