Reaggregation of fetal rat brain cells in a stationary culture system. II: Ultrastructural characterization.

Ultrastructural characteristics of fetal rat brain cell aggregates in a three-dimensional stationary culture system are described. Transmission electron microscopy showed immature cells which developed into mature astrocytes, oligodendrocytes, and neurons during 20 d in culture. This was accompanied by the development of a neuropil where myelinated axons and synaptic complexes were observed. In addition to confirming earlier ultrastructural investigations on fetal rat brain cell aggregates, the stationary culture system also showed the presence of histiotypic regions within the aggregates. These regions consisted of ependymal cells where cilia were observed on the cell surfaces. Structures resembling subependymal basement membrane labyrinths were also observed. Macrophages seemed to be more numerous in the stationary cultures as compared to other culture systems. The stationary culture system may provide aggregates that are ultrastructurally more complex than those obtained by rotation mediated systems.