title: Ultrastructure of the "active zone" in the frog neuromuscular junction.
mesh_terms: D000818:Animals; D001001:Anura; D005613:Freeze Etching; D008854:Microscopy, Electron; D009469:Neuromuscular Junction / Q000166:cytology*; D013570:Synaptic Membranes; D013572:Synaptic Vesicles