Some Mitochondrial Changes in Denervated Muscle
An electron-microscopic study was made of the mitochondria in normal and denervated rat diaphragm muscles. Two types of structurally different muscle fibres were found: one type had a well-defined M-line, while the other did not. The mitochondria in normally innervated muscle are regularly arranged at both sides of the Z-line. The mitochondria are very long and branched, and surround the myofibrils at the level of the Z-line. In transverse sections of the muscle fibres the worm-like mitochondria give a very characteristic picture. After denervation the mitochondria are smaller and less regularly arranged. In transverse sections of the muscle fibres the mitochondria have small circular profiles. This contrasts sharply with the normal appearance and makes it possible to distinguish normal from denervated fibres. The mitochondrial changes can be detected less than 24 h after denervation.