Changes in the acoustic nerve after hair cell regeneration. 1992

B M Ryals, and E W Westbrook, and S Stoots, and R F Spencer
Department of Speech Pathology and Audiology, James Madison University, Harrisonburg, Virginia 22807.

Hair cells of the avian inner ear have been shown to regenerate following acoustic or ototoxic insult. The consequences of this regeneration on the acoustic nerve have yet to be defined. The purpose of the present study was to use TEM analysis following cochlear damage and hair cell regeneration to describe afferent and efferent neural terminals on hair cells in the newly repopulated sensory epithelium. Following acoustic overstimulation (12 h, 115 dB SPL, 1500 Hz) adult quail were sacrificed immediately (0 day), or at 2, 12, or 24 weeks. Serial thin sections were taken from the embedded papilla in a plane tangential to the basilar membrane in the area consistent with regenerative activity. Immediately following noise exposure very few hair cells could be seen within the epithelia; afferent terminals on remaining cells appeared normal. Two weeks later afferent terminals showed signs of degeneration; efferent terminals were rarely seen on tall hair cells but remained relatively normal on short hair cells. Three to six months later afferent terminals had regained a more normal appearance but were less numerous on tall hair cells; some return of efferent-like terminals was seen often contacting two tall hair cells. Large normal appearing, efferent terminals remained on short hair cells. These results suggest that regenerated hair cells are likely to receive neural innervation. It would appear that some degeneration of afferent terminals takes place prior to final innervation of new hair cells.

UI MeSH Term Description Entries
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D009416 Nerve Regeneration Renewal or physiological repair of damaged nerve tissue. Nerve Tissue Regeneration,Nervous Tissue Regeneration,Neural Tissue Regeneration,Nerve Tissue Regenerations,Nervous Tissue Regenerations,Neural Tissue Regenerations,Regeneration, Nerve,Regeneration, Nerve Tissue,Regeneration, Nervous Tissue,Regeneration, Neural Tissue,Tissue Regeneration, Nerve,Tissue Regeneration, Nervous,Tissue Regeneration, Neural
D003051 Cochlea The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH. Cochleas
D003370 Coturnix A genus of BIRDS in the family Phasianidae, order GALLIFORMES, containing the common European and other Old World QUAIL. Japanese Quail,Coturnix japonica,Japanese Quails,Quail, Japanese,Quails, Japanese
D006198 Hair Cells, Auditory Sensory cells in the organ of Corti, characterized by their apical stereocilia (hair-like projections). The inner and outer hair cells, as defined by their proximity to the core of spongy bone (the modiolus), change morphologically along the COCHLEA. Towards the cochlear apex, the length of hair cell bodies and their apical STEREOCILIA increase, allowing differential responses to various frequencies of sound. Auditory Hair Cells,Cochlear Hair Cells,Auditory Hair Cell,Cell, Cochlear Hair,Cells, Cochlear Hair,Cochlear Hair Cell,Hair Cell, Auditory,Hair Cell, Cochlear,Hair Cells, Cochlear
D006317 Hearing Loss, Noise-Induced Hearing loss due to exposure to explosive loud noise or chronic exposure to sound level greater than 85 dB. The hearing loss is often in the frequency range 4000-6000 hertz. Acoustic Trauma,Hearing Loss, Noise Induced,Noise-Induced Hearing Loss
D000159 Vestibulocochlear Nerve The 8th cranial nerve. The vestibulocochlear nerve has a cochlear part (COCHLEAR NERVE) which is concerned with hearing and a vestibular part (VESTIBULAR NERVE) which mediates the sense of balance and head position. The fibers of the cochlear nerve originate from neurons of the SPIRAL GANGLION and project to the cochlear nuclei (COCHLEAR NUCLEUS). The fibers of the vestibular nerve arise from neurons of Scarpa's ganglion and project to the VESTIBULAR NUCLEI. Cranial Nerve VIII,Eighth Cranial Nerve,Cochleovestibular Nerve,Statoacoustic Nerve,Cochleovestibular Nerves,Cranial Nerve VIIIs,Cranial Nerve, Eighth,Cranial Nerves, Eighth,Eighth Cranial Nerves,Nerve VIIIs, Cranial,Nerve, Cochleovestibular,Nerve, Eighth Cranial,Nerve, Statoacoustic,Nerve, Vestibulocochlear,Nerves, Cochleovestibular,Nerves, Eighth Cranial,Nerves, Statoacoustic,Nerves, Vestibulocochlear,Statoacoustic Nerves,VIIIs, Cranial Nerve,Vestibulocochlear Nerves
D000161 Acoustic Stimulation Use of sound to elicit a response in the nervous system. Auditory Stimulation,Stimulation, Acoustic,Stimulation, Auditory
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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