miofibrilláris

Miofibrilláris is the term used in Portuguese and Spanish to describe anything relating to myofibrils, the long, rod-like structures inside muscle cells that form the core contractile apparatus of skeletal and cardiac muscle. Myofibrils are organized into repeating units called sarcomeres, which contain thick (myosin) and thin (actin) filaments. The orderly arrangement of sarcomeres along the length of a myofibril produces the characteristic striated appearance of contractile muscle tissue. Contraction occurs through the sliding-filament mechanism, driven by calcium signaling and ATP-powered cross-bridge cycling between actin and myosin.

In medical and scientific contexts, the adjective also appears in reference to myofibrillar pathology and myopathies. Myofibrillar myopathy (MFM) is a group of hereditary muscle disorders marked by progressive weakness and distinctive muscle fiber changes, including disintegration of myofibrils and the accumulation of protein aggregates. Mutations in several genes encoding cytoskeletal and sarcomeric proteins have been associated with MFM, including DES (desmin), MYOT (myotilin), LDB3/ZASP, FLNC (filamin C), CRYAB, and BAG3, among others. These conditions highlight the importance of proper myofibrillar structure for muscle integrity and function.

Beyond disease, the term also appears in discussions of myofibrillogenesis, the development and assembly of myofibrils during muscle differentiation, and in studies of muscle physiology, growth, and repair. Understanding myofibrillar structure and dynamics is fundamental to muscle biology and related clinical disciplines.