Neurons and glial cells in long term cultures of previously dissociated newborn mouse cerebral cortex.

In long term cultures of newborn mouse spinal cord neurons, glial cells and macrophage-like cells may frequently be located in their entirety. Many neurons possessed processes which could be traced from their cell bodies to their growth cones, a feature which indicated that the cells remained immature. The identification of neurons with certainty is a major problem when live cells are observed by light microscopy, but their size, nuclear and cytoplasmic content and the arrangement and number of their processes were features which helped to locate them. After many weeks in culture, however, astrocytes also became extremely large and it became increasingly difficult to separate them from neurons unless features within the cells were clearly seen. The shape and size of glial cells, especially astrocytes, may alter rapidly in culture, and a wide range of features was present for each cell type. It was therefore often impossible to categorize them with certainty when viewed live, but the identification of many was subsequently confirmed with the use of electron microscopic sections. Macrophage-like cells were numerous in older cultures where they engulfed the ever increasing number of dead cells. The size of the cell bodies of many macrophages matched those of neurons, but their stumpy processes and largely granular content were generally adequate to identify them. The persistent immaturity of the neurons and their apparent dependence both on environmental conditions and synaptic relations, and the characteristics of glial cells in long term cell cultures are discussed.