Postnatal alterations in subsurface cisternae. (a) Absence of cisterns in two adjacent OHCs at birth (P0). Lateral wall indicated by arrowheads. (b) One noncontiguous layer of cisterns in a P6 OHC. Cisterns were present just below the tight junctions associated with apical membrane of the OHC, as indicated by arrows. (c) Subsurface cisternae in the subnuclear region of a P6 OHC. (d) One layer of cisterns in a P12 OHC. Outer hair cell (OHC), tight junction (TJ), subsurface cisternae (SSC), nucleus (N), arrow heads = lateral wall, scale bars = 500 nm.