title: Endothelial tubuloreticular structures in intracranial germinomas.
abstract: In studying three human intracranial germinomas tubuloreticular structures were observed within the cisterns of granular endoplasmic reticulum (RER), as well as occasionally within dilated perinuclear spaces of capillary endothelial cells. These tubuloreticular structures seen as a network of branching, convoluted, tubular profiles appear to originate from amorphous material. The development of these structures could be classified into three stages. In Stage I, the precursor substance appears as dense amorphous material within the cisterns of RER. Stage II is marked by the transformation of the amorphous material to coarse particulate material which aggregates to form tubular units. During the first and second stages, the distended RER that participates in the formation of these structures is accompanied by numerous attached ribosomes and is closely associated with mitochondria. In Stage III, the tubular units fuse with one another to form the tubuloreticular structure. In this third stage both ribosomes and mitochondria are almost absent. As a result of the almost complete disappearance of these organelles at this time, both the attached ribosomes and mitochondria may play an important role in the synthesis of the precursor substance as well as in its transformation to the tubuloreticular structure.
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000648:ultrastructure*; D004407:Dysgerminoma / Q000648:ultrastructure*; D004721:Endoplasmic Reticulum / Q000648:ultrastructure*; D004727:Endothelium / Q000648:ultrastructure; D005260:Female; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D010871:Pinealoma / Q000648:ultrastructure*