PROCESS EXTENSION BY RAT CG-4 LINE PROGENITOR OLIGODENDROCYTES - A POSITIVELY-CHARGED SURFACE PROMOTES A BIPOLAR BUT NOT A DIFFERENTIATED MULTIPOLAR MORPHOLOGY AND IS NOT NECESSARY FOR CELL-GROWTH

Rat CG-4 line progenitor oligodendrocytes passaged in neuroblastoma-co nditioned medium onto a poly-l-lysine-coated surface adopt a bipolar m orphology with long processes and proliferate. On untreated or albumin - or poly-L-glutamate-coated surfaces in the same medium such cells sh ow Little process extension but still proliferate forming clumps of ce lls in the medium or loosely attached to the substratum. Transfer of t hese cell clumps onto a poly-L-lysine-coated surface results in cell m igration out of the clumps and rapid process elaboration to a bipolar morphology. In differentiation medium containing 1% foetal bovine seru m CG-4 line cells extend numerous short processes equally well on poly -L-lysine-, poly-L-glutamate-, albumin-coated or untreated cell cultur e surfaces and divide more slowly. A positively charged substratum thu s may contribute signals initiating development of a bipolar morpholog y: such signals are not needed for the multiprocess morphology of diff erentiated CG-4 cells.