Figure 6 Figure 8a Figure 8b

Fig. 6. Photomicrographs illustrate normal development of the cat organ of Corti from untested newborn pigmented kitten (pk-0), PN30 hearing pigmented kitten (hpk-30), PN150 hearing pigmented kitten (hpk-150), and hearing pigmented adult (hp-adult). During this time, the spiral vessel recedes, the tunnel of Corti develops its characteristic shape, and cells of the organ of Corti assume their adult-like structure. Morphological development appears complete by PN30. Scale bar equals 50 µm. Abbreviations: OS, outer sulcus; GER, greater epithelial ridge; IS, internal sulcus; RM, Reissnerís membrane; SL, spiral limbus; SM, scala media; SP, spiral prominence; SV, spiral vessel; TM, tectorial membrane.

Fig. 8. Photomicrographs illustrate the organ of Corti in cats from newborn (wk-0/1) through 5 months of age. Kittens too young to be tested are indicated as wk. A confirmed deaf kitten is indicated as dwk. In our colony, some white cats displayed abnormalities at birth that presaged deafness, and two types of structural abnormalities were clearly evident by PN10. One type (left column) was more common (80%) and featured a collapsed Reissnerís membrane onto an abnormal organ of Corti. The other type (right column) occurred less frequently (20%) and exhibited a thickened yet still highly convoluted Reissnerís membrane as well as enlarged epithelial cells covering scala tympani and scala media. Both abnormalities were always associated with deafness. It should be noted that both were observed in the same litter, and occasionally in the same cochlea. In three such special cases, the spongiform epithelium was found in the apex, whereas the collapsed Reissnerís membrane was found in the base. Scale bar equals 50 µm. Abbreviations: EP, epithelial cells; GER, greater epithelial ridge; IS, inner sulcus; OC, organ of Corti; RM, Reissnerís membrane; SP, spiral prominence; TM, tectorial membrane.

Ryugo DK, Cahill HB, Rose LS, Rosenbaum BT, Schroeder ME, Wright AL (2003) Separate forms of pathology in the cochlea of congenitally deaf white cats. Hearing Research 181: 73-84.

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