Figure 4.

εL269F-mice have degeneration of the neuromuscular synapse. Neuromuscular junctions from forelimb flexor muscles of 4-month-old εL269F-transgenic mice. To facilitate orientation all nerve termini are indicated using white arrowheads. In all three views the postsynaptic folds are simplified, whereas the adjacent the nerve termini (white arrowheads) seem normal. A) Large vacuoles containing membranous or granular debris fill the junctional sarcoplasm. The composition of the vacuoles can be seen more clearly in the enlargement from the boxed section. B) The mitochondria in the muscle fiber in (A) and in (B) (inset) are greatly enlarged compared with those in the nerve termini. Black arrows indicate what seem to be two degenerating mitochondria. Three mitochondria are massively enlarged and have densely packed cristae (black arrowheads). C) A degenerating myonucleus (black arrow) filled with autophagic debris and cytoplasmic contents lies immediately beneath a neuromuscular junction and adjacent to a relatively normal-appearing nucleus (white arrow). Calibration bars: A, 20 nM; B, 10 nM; C, 15 nM. (Figure 4 is reproduced by permission from Gómez et al. (1997) Journal of Neuroscience 17: 4170–4179).