Membranous stacks in human glioblastoma multiforme

Summary

Curious, characteristic stacks of membranes were found, mainly in the perinuclear cytoplasm of the cells of some human glioblastomas multiforme. The membranes were arranged either in concentric rings or extended haphazardly in several directions. They consisted of closely apposed cisternae, the outermost membranes of which were studded sparsely with ribosomes. The interspaces, formed by the close apposition of adjacent cisternae, were about 160–180 A in width and of intermediate density.

The nuclear envelopes of a small percentage of glioblastoma multiforme cells projected in a complicated fashion into the cytoplasm to form unusual layered structures. The surface of each projection consisted of a membrane continuous with the outer nuclear membrane. A laminated dense zone about 160–180 A wide, sandwiched between the two spaces, was continuous with the nucleoplasm at the point of origin of the projection. Consequently, the stacks of membranes were similar in appearance with the projected nuclear envelope.