Structural Aspects of Islet Cell Membranes

Abstract

DR. ORCI: Despite a growing body of data on islet cell structure and function in spontaneous and experimental diabetes (100, 101 113, 114, 115), the basic lesion(s) responsible for endocrine pancreatic dysfunction in this disease remain(s) to be unraveled. Although membrane systems are known to be of major importance in the control of cellular activities, no information is so far available concerning the possible role of the membranes as a crucial factor in the impairment of islet function in diabetes mellitus. In this presentation, attention is paid to some structural aspects of such membranes in normal and diabetic animals. One of the most useful techniques in the morphological study of membranes is the freeze-fracture technique (88, 132), which exposes large areas of the inside of membranes in three-dimensional view (Figs. XVI and XVII provide a comparison of conventional and freeze-fracturing techniques) and reveals individual components of these membranes down to a macromolecular size, namely 20 to 30 angstroms. With this technique, the interior of the membranes (middle of the bilayer) is exposed (13, 109), and appears structurally differentiated into smooth areas interrupted by particles 60 to 180 angstrom in diameter (Fig. XVIII). It is now accepted that the smooth areas represent the membrane phospholipids whereas the particles constitute at least in part, the morphological counterparts of proteins (26, 34, 86, 124, 139). Together, proteins and phospholipids are the building blocks of the membrane. Membranes rich in proteins, thus functionally complex, contain numerous particles.KeywordsTight JunctionIslet CellIntercellular SpaceDiabetic AnimalAlpha CellThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.