Fig. 6. Outgrowth in the presence of CD and laminin is correlated with the presence of actin-based protrusions. The advance of a single process during a spurt of growth was recorded live by DIC video microscopy. The advance and appearance of actin-based structures were quantitated. A small area of lamellipodium appears immediately prior to advance and is present throughout advance. Single filopodia (three in all) extend during the growth spurt.