Cell junction and ultrastructural development of reaggregated mouse brain cultures.

The morphological development of reaggregated embryonic mouse brain cells was followed by scanning and transmission electron microscopy. Initially, the reaggregated cells are loosely packed and lack specialized cell junction; however, after 2-4 days puncta adhaerens junctions are numerous. The first immature synapses are seen at 8-9 days of culture. These synaptic complexes mature in appearance and increase approximately 3-fold in number during the next 3 weeks of culture. Two distinct, electron dense, intercellular specialization, apparently unique to neural cell cultures, are observed in these older cultures. Brain cell reaggregates observed at 2, 3, and 5 months of culture show signs of aging, i.e., a gradual decrease in the number of synapses, myelin degeneration and increased lipofuscin granules.