The differentiation of glial cells and glia limitans in organ cultures of chick spinal cord

Differentiation of glial cells and the glia limitans in organ cultures of chick spinal cord explanted at early neural tube stages, alone or with adjacent tissues, was studied by electron microscopy. Oligodendrocytes and astrocytes comparable to those seen in the chicken in vivo were observed, mainly in areas of good neuronal differentiation. A glia limitans with basal lamina, comparable to that in vivo, was found when spinal cord was bordered by normally adjacent tissues. When it was surrounded by vitelline membrane only, a characteristic limiting layer of glial processes, but no basal lamina, was seen. Contact with a filter membrane (Millipore) elicited excessive differentiation of glial filaments and modified cell fine structure; no glia limitans was formed.