[Electronmicroscopic detection of a special kind of cytoplasmic vesicle in Micrasterias denticulata].

Electronmicroscopic studies of growing and non-growing cells of Micrasterias denticulata Bréb., fixed with glutaraldehyde-OsO4, showed a special kind of cytoplasmic vesicle which has so far not been found in other cells. These particles (1000-1200 Å in diameter) are characterized, by an unusual, multilayered membrane and a rod-like content of high electronoptic density. The vesicles are found to be accumulated in the vicinity of the nucleus and in a positional relationship to the nuclear pores. Although no evidence could be found either for a direct passage of the vesicles through the pores or for a "blebbing"-process from the nuclear membrane, the rod-containing vesicles could be functional in the process of nuclearcytoplasmic exchange.