title: An ultrastructural and cytochemical study of neuromuscular junctions in echinoderms.
abstract: The ultrastructure of neuromuscular junctions in various organs of a starfish and a holothurian was studied. All neurons were found to contain large (100-250 nm), dense-core vesicles. Cytochemical tests for acetylcholinesterase were negative for these neurons. The presence of proteinaceous neurosecretory material was contested by enzymatic digestion (pepsin) which did not attack the dense-core vesicles, as well as by incubation in phosphotungstic acid (PTA) which did not stain these structures. Staining with dichromate produced a positive reaction for 5-hydroxytryptamine. In the absence of synaptic modifications even after specific staining with PTA, the transmission of nervous impulses is effectuated through exocytosis of 5-hydroxytryptamine at nerve endings in the muscle tissue.
mesh_terms: D000110:Acetylcholinesterase / Q000032:analysis; D000818:Animals; D001369:Axons / Q000648:ultrastructure; D002462:Cell Membrane / Q000648:ultrastructure; D004447:Echinodermata / Q000648:ultrastructure*; D005089:Exocytosis; D006651:Histocytochemistry; D009469:Neuromuscular Junction / Q000648:ultrastructure*; D009474:Neurons / Q000648:ultrastructure; D009489:Neurosecretion; D009940:Organoids / Q000648:ultrastructure; D010455:Peptides / Q000032:analysis; D013194:Staining and Labeling; D013215:Starfish / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure; D009435:Synaptic Transmission
chemical_list: D010455:Peptides; D000110:Acetylcholinesterase