MORPHOLOGY OF THE UNFIXED COCHLEA

Our knowledge of cochlear geometry is based largely upon anatomical ob servations derived from fixed, dehydrated, embedded and/or sputter-coa ted material. We have now developed a novel preparation, the hemicochl ea, where for the first time living cochlear structures can be observe d in situ and from a radial perspective. The experiments were performe d on the Mongolian gerbil. Ion substitution experiments suggest that n o significant swelling or shrinkage occurs when the preparation is bat hed in normal culture medium, so long as calcium concentration is kept at endolymph-like (20 mu M) levels. The tectorial membrane-reticular lamina relationship appears to remain well preserved. Hensen's stripe maintains a close relationship with the inner hair cell stereociliary bundle, unless the mechanical coupling becomes disturbed. In addition, standard fixation and/or dehydration procedures are used to quantify changes due to shrinkage artifacts. Various morphometric gradients are examined in unfixed specimens from apical, middle, and basal turns. ( C) 1998 Elsevier Science B.V. All rights reserved.