Mechanical Strength of Sarcomere Structures of Skeletal Myofibrils Studied by Submicromanipulation

Abstract

ABSTRACT. The mechanical strength of sarcomere structures of skeletal muscle was studied by rupturing single myofibrils of rabbit psoas muscle by submicromanipulation techniques. Microbeads coated with α-actinin were attached to the surface of myofibrils immobilized to coverslip. By use of either optical tweezers or atomic force microscope, the attached beads were captured and detached from the myofibrils. During the detachment of the beads, the actin filaments bound specifically to the beads were peeled off from the bulk structures of myofibrils, thus rupturing the peripheral components of the myofibrils bound to the actin filaments. By analyzing the ruptures thus produced in various myofibril preparations, it was found that the sarcomere structure of myofibrils is maintained by numerous molecular components having the mechanical strength sufficient to sustain the contractile force produced by the actomyosin system. The present techniques could be applied to study the mechanical strength of cellular organelles containing actin filaments as their component.

Reduced Graphene-Oxide-Doped Elastic Biodegradable Polyurethane Fibers for Cardiomyocyte Maturation

“…Cardiomyocytes cultured on the conductive membranes (PU-rGO) exhibited signs of maturation and improved functionality compared to nonconductive membranes (PU). The conductive membranes promoted mature sarcomere structure with increased sarcomere length close to 2 μm and z-line lengths, which are associated with stronger contractions and cardiac maturation. , To assess protein expression levels, we utilized quantitative fluorescent intensity analysis, a method that has been commonly employed in numerous studies. − In both NRCMs and hiPSC-CMs, there were increased α-actinin and troponin-I expressions observed on the PU-10%rGO membrane, consistent with previous reports. , The electrical communication between cardiomyocytes can be tracked from the formation of gap junctions . Enhanced gap junction formation, indicated by increased CX-43 fluorescent intensity on the conductive membranes, aligned with previous studies using rGO-doped membranes. , Beating behavior on the PU-rGO membrane was uniform and synchronous, while nonconductive membranes exhibited asynchronous beatings .…”

“…The conductive membranes promoted mature sarcomere structure with increased sarcomere length close to 2 μm and z-line lengths, which are associated with stronger contractions and cardiac maturation. 95,96 To assess protein expression levels, we utilized quantitative fluorescent intensity analysis, a method that has been commonly employed in numerous studies. 97−100 In both NRCMs and hiPSC-CMs, there were increased αactinin and troponin-I expressions observed on the PU-10%rGO membrane, consistent with previous reports.…”

A discrete sarcomere model reveals internal unbinding dynamics and conditions for regularity of spontaneous oscillatory contractions

“…[14] (133 − −479nN/µm) and divide it by the approximate number of thick filaments in the rabbit psoas muscle sarcomere used in Ref. [14] (200 − 400 [40,41]). This provides a range of 9.75 • 10 −3 nN/µm to 73 • 10 −3 nN/µm or B = 0.33 to 2.395 per filament.…”