ELECTRON MICROSCOPIC STUDY ON GLIOSOME FORMATION IN POSTNATAL DEVELOPMENT OF SPINAL CORD IN CAT

The CNS of cats including newly‐born, 2 day‐, 4 day‐, 10 day‐, 18 day‐, 3 week‐, 6 week‐ and 3 month‐old kittens and adults, were fixed by perfusion from the aorta with 1% osmium tetroxide in acetate‐veronal buffer, or with 2.5 to 3% glutaraldehyde or 4% formaldehyde in phosphate buffer and retreatment with osmium tetroxide after removal. The astrocytes in the intermediolateral horn of the thoracic spinal cord and in the neighboring lateral funiculus were examined under the electron microscope. The astrocytic mitochondria are larger than the neuronal ones at birth. They have a finely granular matrix and dispersed cristae mitochondriales. During the first 4 to 10 days after birth many of the astrocytic mitochondria enlarge, with an increase in the amount of matrix material and its crystallization into a filamentous array, forming “gliosomes.” Within two to three weeks, a bundle of crystalline filaments with a regular periodicity are formed in the matrix. The rough surfaced endoplasmic reticulum seems to be closely associated with the processes of gliosome formation. Namely, cisterane of the rough endoplasmic reticulum first accompany the growing mitochondria, then lose ribosomes on their proximal membranes, and finally change into vesicles of the smooth endoplasmic reticulum around the gliosomes and gliofilaments. The possible significance of these structural changes is discussed. Copyright © 1969 The Wistar Institute Press