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Electron microscopy of degenerative changes in the chick basilar papilla after gentamicin exposure
Author(s) -
Hirose Keiko,
Westrum Lesnick E.,
Cunningham Dale E.,
Rubel Edwin W
Publication year - 2004
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.11046
Subject(s) - biology , basal lamina , anatomy , hair cell , ultrastructure , reticular connective tissue , electron microscope , dermal papillae , microbiology and biotechnology , hair follicle , cochlea , physics , optics
We present a sequential study of the substructural alterations in the chick basilar papilla at the earliest signs of hair cell degeneration. Three‐day posthatch chicks received a single injection of gentamicin (300 mg/kg) and were killed at 6, 8, 12, 15, 18, 21, and 24 hours after the injection. The basilar papillae were studied by conventional transmission electron microscopy. Examination was limited to the basal region, where all hair cells are eliminated by this treatment. As early as 8 hours and clearly by 12 hours, altered fine structure was seen in hair cells. Changes included rounding and swelling of the hair cells, condensation of nuclear chromatin, dissolution of ribosomes, dilatation of the mitochondria, and accumulation of inclusion bodies and lysosomes. By 15–18 hours, lysosomes increased and became denser, afferent terminals appeared swollen, and the first cell extrusion was seen. Efferents were unaffected, and supporting cells, though having inclusion bodies now, retained normal intercellular junctions. By 21–24 hours, large regions of complete hair cell loss were composed of expanded supporting cell processes with normal‐appearing intercellular junctions and portions of extruded hair cells, partially attached to the supporting cell surface. These observations demonstrate that auditory hair cells undergo a rapid and controlled process of hair cell extrusion that allows preservation of the reticular lamina and minimal contamination of surrounding structures by intracytoplasmic contents of the damaged hair cells. J. Comp. Neurol. 470:164–180, 2004. © 2004 Wiley‐Liss, Inc.