title: Electron microscopic observations of the mesencephalic nucleus of the fifth nerve in the Selachian brain.
abstract: The mesencephalic nucleus of the trigeminal nerve (mes V) in the brain of the skate (Raja oscellata) was studied by electron microscopy. Mes V neurons are large (40-80 mum diameter) and are located in the periventricular grey matter. Their perikaryal cytoplasm is rich in Golgi apparatus, small mitochondria, rough endoplasmic reticulum, polysomes and bundles of neurofilaments. A striking feature is the presence of masses of glycogen granules, at times surrounded by membrane wrappings and lysosomal bodies. Two types of conventional synaptic contacts were made onto mes V perikarya and dendrites. One had round, agranular vesicles and usually also contained dense-cored vesicles, the other had flattened, pleomorphic, agranular vesicles and usually lacked dense-cored vesicles. Additional membrane complexes consisting of a region of gap junction flanked by sites of desmosomal attachment were observed to link neighbouring mes V neurons. Somato-somatic, dendro-somatic, axo-somatic, and dendro-dendritic junctions were noted. Except for the somato-somatic union, one or more chemical synapses were located close to the sites of gap junctions.
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D003712:Dendrites / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000648:ultrastructure; D005399:Fishes / Q000033:anatomy & histology*; D006003:Glycogen / Q000032:analysis; D006056:Golgi Apparatus / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000648:ultrastructure; D008247:Lysosomes / Q000648:ultrastructure; D008928:Mitochondria / Q000648:ultrastructure; D009474:Neurons / Q000648:ultrastructure; D012270:Ribosomes / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure; D014276:Trigeminal Nerve / Q000648:ultrastructure*
chemical_list: D006003:Glycogen