title: Regional differences in myelination of chick vestibulocochlear ganglion cells.
abstract: In vertebrates, vestibular and cochlear ganglion (VG and CG, respectively) cells are bipolar neurons with myelinated axons and perikarya. The time course of the myelination of the VG and CG cells during development of chick embryos was investigated. Chick VG and CG from embryonic day at 7-20 (E7-20) were prepared for a transmission electron microscopy, myelin basic protein immunohistochemistry, and real-time quantitative RT-PCR. In the VG cells, myelination was first observed on the peripheral axons of the ampullar nerves at E10, on the utricular and saccular nerves at E12, and on the lagenar and neglecta nerves at E13. In the VG central axons, myelination was first seen on the ampullar nerves at E11, on the utricular and saccular nerves at E13, and on the lagenar nerves at E13. In the CG cells, the myelination was first observed on the peripheral and central axons at E14. In both VG and CG, myelination was observed on the perikarya at E17. These results suggest that the onset of the axonal myelination on the VG cells occurred earlier than that on the CG cells, whereas the perikaryal myelination occurred at about the same time on the both types of ganglion cells. Moreover, the myelination on the ampullar nerves occurred earlier than that on the utricular and saccular nerves. The myelination on the peripheral axons occurred earlier than that on the central axons of the VG cells, whereas that on the central and peripheral axons of the CG cells occurred at about the same time. The regional differences in myelination in relation to the onset of functional activities in the VG and CG cells are discussed.
authors.affiliation: Department of Anatomy and Structural Science, Yamagata University School of Medicine, 2-2-2 Iida-nishi, Yamagata 990-9585, Japan. Electronic address: sun@med.id.yamagata-u.ac.jp.
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Sun
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Saori
authors.initials: S
authors.lastname: Yoshida
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Shirasawa
authors.forename: Akira
authors.initials: A
authors.lastname: Naito
mesh_terms: D000367:Age Factors; D000818:Animals; D002642:Chick Embryo; D002645:Chickens; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D004676:Myelin Basic Protein / Q000378:metabolism* / Q000648:ultrastructure; D009413:Nerve Fibers, Myelinated / Q000502:physiology* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D000159:Vestibulocochlear Nerve / Q000166:cytology / Q000196:embryology*
chemical_list: D004676:Myelin Basic Protein; D012333:RNA, Messenger
keywords: Chick; Cochlear ganglion; Development; Myelin basic protein; Myelination; Vestibular ganglion