FORMATION OF MYELIN-SHEATH-LIKE SPIRAL STRUCTURES BY LAMELLAR ASTROCYTE EXTENSIONS IN SUBPIAL AND PERIVASCULAR GLIOSES OF MAMMALIAN BRAINS

Peculiar spiral structures could be observed by electron microscopy in the cerebral cortex of rabbits with an experimentally produced marginal siderosis of the central nervous system. These spirals were found predominantly within areas of subpial and perivascular gliosis. They consisted of extremely thin lamellar astrocyte extensions winding around other astroglial processes or dendrites. The spirally coiled astrocyte extensions exhibited within their interior fine filaments having a rather regular arrangement. In the radial direction, the astrocytic lamellae spirals showed a periodic stratification somewhat resembling that of true myelin-sheaths. They were considered to represent the submicroscopic equivalent of the socalled plaques fibromyéliniques. © 1969 Springer-Verlag.