PMC

Specimens in low magnification (left) and the areas highlighted by squares in high magnification (right). (A) Saccule and parts of semicircular ducts stained with hematoxylin and eosin (HE). (B) Saccule, parts of semicircular ducts, and cochlea stained with HE. (C) Utricle, saccule, and parts of semicircular ducts stained with HE. (D) Utricle, saccule, the ampulla of a semicircular duct (arrowhead), and parts of semicircular ducts stained with HE. (D-300 μm) All compartments of vestibular organs disappeared after further 300 μm sectioning; stained with HE. Labels: Tympanic cavity (t), Utricle (u), Saccule (s), Semicircular ducts (d), Cochlea (c).

Reduced β-galactosidase staining in Nor-1^−/− mouse semicircular canals (A to D). Cross-sections through anterior semicircular canals of Nor-1^+/− (A and C) and Nor-1^−/− (B and D) mice show comparable β-galactosidase staining in mice of both genotypes at E15.5 (A and B). However, by P1 (C and D), the Nor-1^lacZ staining is greatly decreased in the Nor-1^−/− mouse semicircular ducts. Altered cell morphology of the Nor-1-expressing cells in the Nor-1^−/− mouse semicircular canals (E to H). Hematoxylin-eosin-stained cross-sections of anterior semicircular canals of Nor-1^+/− (E and G) and Nor-1^−/− (F and H) animals. The Nor-1-expressing cells at the inner edge of the semicircular ducts of Nor-1^−/− mice have the normal columnar shape at E15.5 (F); however, at P1, these cells have lost their specialized cell shape and appear flattened (H) compared to corresponding Nor-1^+/− mouse sections at E15.5 (E) and P1 (G). E-cadherin staining of cross-sections of the anterior semicircular canals shows similar staining at E15.5 in Nor-1^+/− (I) and Nor-1^−/− (J) mouse ducts. Together with loss of the columnar cell shape in the Nor-1^−/− mouse ducts, there is a decrease in E-cadherin staining at P1 (L) while staining for E-cadherin is seen in the Nor-1^+/− mouse cells (K). (M to P) Comparison of Nor-1 (M) and Netrin1 (N) expression in Nor-1^+/− mouse anterior semicircular canals shows an overlapping pattern on the inner side of the semicircular duct; however, Nor-1 is more limited to the small group of columnar cells. Netrin1 expression is retained in the Nor-1^−/− mouse ducts (O). Panel P is a bright-field image of Panel O. Scale bars are 25 μm (A to D), 12.5 μm (E to L), and 50 μm (M to P).

Loss of TSK signaling in the vestibules caused defects in the posterior semicircular canal. a The cochlea in TSK-KO mice were smaller than that in WT mice at P30. PSC was defective in TSK-KO mice at P30 (indicated with asterisks). b, c Representative HE-stained cross-sectional images through the cochleae and vestibules in WT mice show that all three epithelial ducts were surrounded by periotic mesenchyme-derived cartilaginous cells, forming the SCs at P30. In contrast, PSC was absent in all TSK-KO mice (indicated with an asterisk; n = 5). SC, semicircular canal; ASC, anterior semicircular canal; LSC, lateral semicircular canal; PSC, posterior semicircular canal. Scale bar: 100 μm

Diagrammatic survey of fluid flow in glass models of two-duct semicircular ducts. The flow in pitch rotation is shown by continuous arrows, the flow in roll by broken arrows. Abbreviations are the same as in Fig. . A: original model with equal ducts a and p. Reference planes with rotations are shown. B: Enlargement of duct a, as in the angler fish (Lophius). C: the same system as in A but points A and C reversed. D: duct a enlarged, as in birds. E: the same system as in D but duct a exaggeratedly enlarged. F: the same system as in D but part of duct a has been cut off. In all cases, except F in roll, the flow in ducts a and p is the same: after Muller and Verhagen ()