Summary
The findings reported here represent the ultrastructural demonstration of a well-oriented mammalian skeletal muscle cytoskeleton. This muscle framework is difficult to preserve and several different fixation procedures have been used on rat diaphragm stretched at right angles to the fibre axis. By using these procedures, however, the preservation of the ultrastructural detail of the muscle is very poor.
The transverse filamentous material is organized at Z- and M-band levels. It is seen to run at these levels and to attach to the plasma membrane. In some cases dense plaques are observed in this position.
The filamentous material, ‘Z-cables’ and ‘M-cables’, appears very irregular in thickness, often apparently branched and with a length-dependent shape. Some ultrastructural images are suggestive of a tight structural integration of the transverse systems with myofibrils at the Z- and M-levels. The major contribution of these structural components to the muscle architecture may now be interpreted in terms of anchorage sarcomere systems. Further ultrastructural studies must be made to provide a basis for demonstrating clearly the three-dimensional arrangement and the role of these filaments.
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Pierobon-Bormioli, S. Transverse sarcomere filamentous systems: ‘Z- and M-cables’. J Muscle Res Cell Motil 2, 401–413 (1981). https://doi.org/10.1007/BF00711967
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DOI: https://doi.org/10.1007/BF00711967