Ultrastructure of airway cilia in Cby^−/− mice. (A and B) TEM analysis of cross sections of nasopharyngeal motile cilia and basal bodies in 4-wk-old Cby^+/+ and Cby^−/− mice. Blue arrows and arrowheads indicate central microtubule pairs and outer dynein arms, respectively. Pink arrows point to microtubule triplets in the basal body. (C and D) TEM analysis of nasopharyngeal motile cilia in adult Cby^+/+ and Cby^−/− mice. (E and F) Scanning EM analysis of ciliated cells in the large proximal airways of adult Cby^+/+ and Cby^−/− mice. Blue arrowheads indicate ciliated cells. In addition to cilia, the apical surface of ciliated cells contains microvilli of variable number and length. (G and H) TEM analysis of nasopharyngeal basal bodies from adult Cby^+/+ and Cby^−/− mice. Pink arrows highlight abnormally localized basal bodies. KO, knockout.