抄録
The three components of skeletal muscle fiber, that is, sarcolemma, myofibril and sarcoplasma, different among themselves in their viscoelastic properties, have been separately studied.
A myofibril bundle with properties of living muscle fiber can be separated by removing the sarcolemma of a muscle fiber in liquid paraffine, the smallest sample obtained by this method being about 1μ in diameter.
Myofilaments as thin as 100Å in diameter can be separated by spreading out the myofibril bundle on metal net in air.
The breaking length of a muscle fiber is 180-200% of its resting length, its breaking stress being 0.5∼5×106 dynes/cm2.
The ratio of initial elongation to creep by load is a function of the load itself, for example, the maximum of the ratio is 3 to 2, the load and the breaking stress being 1.5×105 and 5×105dynes/cm2 respectively.
The thermal expansion coefficient (α) of a muscle fiber of M. sartorius of Bufo is -10-4∼-10-5, its absolute value being inversely proportional to its birefringence.
The length-tension diagram of a myofibril bundle coincides with that of intact muscle fiber, as far as the extension is less than 140% of its resting length.
Concerning the time course of creep by loading and the thermo-elasticity, the myofibril bundle and the single muscle fiber resemble each other.
The striated pattern with periodical intervals of about 100Å can be electronmicroscopically observed in the separated myofilament in its resting state.
This periodical intervals increase to 170% of that in its resting state, when the myofilament is extended.
The viscoelasticity of muscle has been discussed on the basis of the results mentioned above and the relevant references.
