(A) When whole-mounted control saccular explants (incubated in ACM only for 24 hours) are viewed perpendicular to the luminal surface at low magnification, hair bundles appear as intensely fluorescent dots (arrowheads). Regions with missing hair bundles can also be identified (small arrows), and are more frequent in explants treated with gentamicin (B) or with gentamicin plus microtubule disruption agents (E, H) compared to non-gentamicin-treated control explants (A,D,G). (C, F, I) High resolution imaging of the sensory epithelium reveals characteristic multi-cellular rings/cartwheels of labeled actin (white arrows) at the site of missing hair bundles. Scale bars in µm.