Fig. 4.

Selective vulnerability of fast-type MGC synapses in SOD1 model. a, Widespread vacuole formation in vulnerable and resistant synapses of SOD1 mice. Ultrastructure of neuromuscular junctions at P50. Note presence of large vacuoles (arrowheads) at nerve terminals of MGC and soleus.b, Distribution of denervated synapses in SOD1 mice from P50 (nonsymptomatic) to P120 (extensive paralysis and motoneuron death). Color code as in Figure 2. c, Time course of force decline in limbs of SOD1 mice (open squares) and wild-type littermates (filled squares). Loaded grid test; total load, Σ(tw ×W); n = 26.d, Dying-back features of denervation (top row) and sprouting with reinnervation (bottom row; arrows, sprouts; stars, synapses innervated by sprouts) in SOD1 mice. Scale bar:a, 1.1 μm; d, 16 μm.