Polymorphism of fiber cell junctions in mammalian lens

Abstract

Previous studies of junctional specializations between bovine lens fiber cells have indicated that pentalamellar profiles in isolated membranes correspond to gap junctions (GJs), undulating square array junctions (SAJs) and thin symmetric junctions (TSJs). We show here that this same junctional diversity occurs in the intact tissue and that the differences in thickness and staining patterns can be documented by density profiles from thin-section TEM images of in vivo and isolated membranes.Fresh bovine lenses were mounted on edge and vibratome sectioned parallel the optic axis. Sections near the center were fixed (paraformaldehyde, glutaraldehyde, and tannic acid) for thin-section analysis or were dissected on a glass slide to select a group of fiber cells within a narrow region, such as the deep cortex about 2 mm from the lens surface. Membranes were isolated from this small fraction of cells using a new procedure, essentially, suspending in buffer, washing 30 min in 4M urea and pelleting at low speed in an AirFuge (Beckman).