A Globular Substructure of the Retinal Receptor Outer Segment Membranes and some other Cell Membranes in the Tadpole

Abstract

A TRIPLE-LAYERED structure of membranes after potassium permanganate fixation was discovered by Robertson¹. A globular substructure of mouse kidney tubular cell mitochondrial membranes and smooth-surfaced cytomembranes after potassium permanganate fixation and section staining was demonstrated by Sjöstrand^2–4. A similar pattern was found in α-cyto-membranes of frozen-dried mouse pancreatic cells by Sjöstrand and Elfvin⁵. Fernández-Morán⁶ described an intermediate dense line in the disks of osmium-cryofixed retinal rod outer segments, in which the disk membranes were closely packed. With respect to the structure of potassium permanganate-fixed retinal receptor outer segment disks, the membranes are triple-layered when separated. In case they are closely packed, they form a five-layered structure, which was independently shown by Moody and Robertson⁷ and by Sjöstrand⁸. The same structural pattern of the disks could also be obtained just as clearly and regularly after routine fixation in osmium tetroxide, if section staining were used^9–11. In this communication, a globular substructure observed in cross-sectioned outer segment disk membranes of tadpole retinæ will be described.