Cochlear ganglion and nerve fibers. (A–C) Cresyl violet staining of midmodiolar methacrylate sections of the cochlear ganglion at the cochlear basal turn in Irs2+/+Ptpn1+/+ (A), Irs2−/−Ptpn1+/+ (B) and Irs2−/−Ptpnr−/−mice (C) at postnatal wk 11. A slight reduction in the cellular density was more evident in both mutants (B, C) compared with wild-type (A). (D–F) Myelin P0 immunostaining of the cochlear ganglion shows less intense labeling in Irs2−/−Ptpn1+/+ (E) and Irs2−/−Ptpn1−/− (F) mice than in control mice (D). (G–I) Accordingly, myelin P0 immunostaining of nerve fibers projecting from the cochlear ganglion to the sensory cells is less intense in Irs2−/−Ptpn1+/+ and Irs2−/−Ptpn1−/− (arrows in H and I) than in wild-type mice (G). (J–L) Similarly, a weaker neurofilament 200-kDa immunostaining is observed in Irs2+/+Ptpn1−/− (K, white arrow) and Irs2−/−Ptpn1−/− (L, white arrow) mice compared with wild-type mice (J). Scale bars: A–I, 50 µm; J–L, 75 µm.