SUBEPITHELIAL FIBER COMPONENTS OF THE ROUND WINDOW MEMBRANE OF THE GUINEA-PIG - AN ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY

Subepithelial fiber components of the round window membrane (RWM) of t he guinea pig were studied by the following methods: transmission elec tron microscopy (TEM), scanning electron microscopy (SEM) with NaOH tr eatment, high-voltage electron microscopy (HVEM) and immunohistochemic al staining. SEM observation revealed intersecting collagen fibers and a vascular network in the middle layer. TEM observation showed that a t the attachment region to the bone fibroblasts, collagen fibers and e lastic fibers were intermingled with each other, and mesenchymal cells (bone-lining cells) were scattered on the surface of the bone. The cy toplasmic processes of fibroblasts and bone-lining cells were connecte d by interdigitations. HVEM demonstrated that collagen fibers of the R WM were directly linked to the fibers of the bone matrix. Immunohistoc hemically, the middle layer was positive for antibody to type I collag en. Immunoreaction for fibronectin was also positive at the middle lay er and most intense in the region attached to the bone. Thus, the RWM is securely attached to the bone by type I collagen fibers together wi th the bone-lining cells and fibroblasts.