The effects of amethopterin, actinomycin D, and 5-bromodeoxyuridine on the differentiation of a cloned line of rat glioma is described. Amethopterin caused spongioblasts to develop rapidly into cells resembling astroblasts in culture. In time, these cells progressively differentiated into sheets of intertwining astrocytes that are morphologically like astroglia from normal rat brain grown under similar conditions. Exposure of glioma cells to low concentrations of actinomycin D resulted in the accumulation of glycogen in the cell bodies and their process without cell degeneration. 5-Bromodeoxyuridine caused a striking change in the surface membrane of the tumor cells. Many desmosomes and close junctions were found. These findings indicate that further morphological differentiation of this rat glioma can be induced by manipulating the environment in which the cells are grown, in this case, by exposure to appropriate antitumor agents.

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These studies were supported by USPHS Grant RO1-CA10755-04 and the Research Fund of the Veterans Administration.

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