Abstract
Located on the sensory epithelium of the sickle-shaped cochlea of a 7- to 10-d-old chick are approximately 5,000 hair cells. When the apical surface of these cell is examined by scanning microscopy, we find that the length, number, width, and distribution of the stereocilia on each hair cell are predetermined. Thus, a hair cell located at the distal end of the cochlea has 50 stereocilia, the longest of which are 5.5 microns in length and 0.12 microns in width, while those at the proximal end number 300 and are maximally 1.5 microns in length and 0.2 micron in width. In fact, if we travel along the cochlea from its distal to proximal end, we see that the stereocilia on successive hair cells gradually increase in number and width, yet decrease in length. Also, if we look transversely across the cochlea where adjacent hair cells have the same length and number of stereocilia (they are the same distance from the distal end of the cochlea), we find that the stereocilia of successive hair cells become thinner and that the apical surface area of the hair cell proper, not including the stereocilia, decreases from a maximum of 80 microns2 to 15 microns2. Thus, if we are told the length of the longest stereocilium on a hair cell and the width of that stereocilium, we can pinpoint the position of that hair cell on the cochlea in two axes. Likewise, if we are told the number of stereocilia and the apical surface of a hair cell, we can pinpoint the location of that cell in two axes. The distribution of the stereocilia on the apical surface of the cell is also precisely determined. More specifically, the stereocilia are hexagonally packed and this hexagonal lattice is precisely positioned relative to the kinocilium. Because of the precision with which individual hair cells regulate the length, width, number, and distribution of their cell extensions, we have a magnificent object with which to ask questions about how actin filaments that are present within the cell are regulated. Equally interesting is that the gradient in stereociliary length, number, width, and distribution may play an important role in frequency discrimination in the cochlea. This conclusion is amplified by the information presented in the accompanying paper (Tilney, L.G., E.H. Egelman, D.J. DeRosier, and J.C. Saunders, 1983, J. Cell Biol., 96:822- 834) on the packing of actin filaments in this stereocilia.
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Selected References
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- Cohen G. M., Fermin C. D. The development of hair cells in the embryonic chick's basilar papilla. Acta Otolaryngol. 1978 Nov-Dec;86(5-6):342–358. doi: 10.3109/00016487809107513. [DOI] [PubMed] [Google Scholar]
- DeRosier D. J., Tilney L. G., Egelman E. Actin in the inner ear: the remarkable structure of the stereocilium. Nature. 1980 Sep 25;287(5780):291–296. doi: 10.1038/287291a0. [DOI] [PubMed] [Google Scholar]
- DeRosier D. J., Tilney L. G. How actin filaments pack into bundles. Cold Spring Harb Symp Quant Biol. 1982;46(Pt 2):525–540. doi: 10.1101/sqb.1982.046.01.049. [DOI] [PubMed] [Google Scholar]
- Flock A., Cheung H. C. Actin filaments in sensory hairs of inner ear receptor cells. J Cell Biol. 1977 Nov;75(2 Pt 1):339–343. doi: 10.1083/jcb.75.2.339. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hirokawa N. The ultrastructure of the basilar papilla of the chick. J Comp Neurol. 1978 Sep 15;181(2):361–374. doi: 10.1002/cne.901810208. [DOI] [PubMed] [Google Scholar]
- Jahnke V., Lundquist P. G., Wersäll J. Some morphological aspects of sound perception in birds. Acta Otolaryngol. 1969 Jun;67(6):583–601. doi: 10.3109/00016486909125485. [DOI] [PubMed] [Google Scholar]
- Khanna S. M., Leonard D. G. Basilar membrane tuning in the cat cochlea. Science. 1982 Jan 15;215(4530):305–306. doi: 10.1126/science.7053580. [DOI] [PubMed] [Google Scholar]
- Mulroy M. J. Cochlear anatomy of the alligator lizard. Brain Behav Evol. 1974;10(1-3):69–87. doi: 10.1159/000124303. [DOI] [PubMed] [Google Scholar]
- Peake W. T., Ling A., Jr Basilar-membrane motion in the alligator lizard: its relation to tonotopic organization and frequency selectivity. J Acoust Soc Am. 1980 May;67(5):1736–1745. doi: 10.1121/1.384300. [DOI] [PubMed] [Google Scholar]
- Russell I. J., Sellick P. M. Tuning properties of cochlear hair cells. Nature. 1977 Jun 30;267(5614):858–860. doi: 10.1038/267858a0. [DOI] [PubMed] [Google Scholar]
- Tanaka K., Smith C. A. Structure of the avian tectorial membrane. Ann Otol Rhinol Laryngol. 1975 May-Jun;84(3 Pt 1):287–296. doi: 10.1177/000348947508400302. [DOI] [PubMed] [Google Scholar]
- Tanaka K., Smith C. A. Structure of the chicken's inner ear: SEM and TEM study. Am J Anat. 1978 Oct;153(2):251–271. doi: 10.1002/aja.1001530206. [DOI] [PubMed] [Google Scholar]
- Tilney L. G., Derosier D. J., Mulroy M. J. The organization of actin filaments in the stereocilia of cochlear hair cells. J Cell Biol. 1980 Jul;86(1):244–259. doi: 10.1083/jcb.86.1.244. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tilney L. G., Egelman E. H., DeRosier D. J., Saunder J. C. Actin filaments, stereocilia, and hair cells of the bird cochlea. II. Packing of actin filaments in the stereocilia and in the cuticular plate and what happens to the organization when the stereocilia are bent. J Cell Biol. 1983 Mar;96(3):822–834. doi: 10.1083/jcb.96.3.822. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Turner R. G., Muraski A. A., Nielsen D. W. Cilium length: influence on neural tonotopic organization. Science. 1981 Sep 25;213(4515):1519–1521. doi: 10.1126/science.7280673. [DOI] [PubMed] [Google Scholar]
- Weiss T. F., Mulroy M. J., Turner R. G., Pike C. L. Tuning of single fibers in the cochlear nerve of the alligator lizard: relation to receptor morphology. Brain Res. 1976 Oct 8;115(1):71–90. doi: 10.1016/0006-8993(76)90823-4. [DOI] [PubMed] [Google Scholar]