ULTRASTRUCTURAL CONSEQUENCES OF RADICAL DAMAGE BEFORE AND AFTER DIFFERENTIATION OF NEUROBLASTOMA B-104 CELLS

There is abundant evidence that the pathophysiology leading to neurona l death during post-ischemic brain reperfusion involves radical-mediat ed damage. Although the ultrastructural alterations accompanying brain ischemia and reperfusion are well characterized, little is known abou t the ultrastructural alterations that are specific to radical damage. This study examines in differentiated and undifferentiated neuroblast oma B-104 cells the viability (by dye exclusion) and ultrastructural c onsequences of radical damage initiated by 50 mu M cumene hydroperoxid e (CumOOH). Differentiation was most notably associated with formation of neurites and an extensive cytoskeletal feltwork. CumOOH-induced ce ll death was increased after differentiation and was blocked by the ir on chelator DETAPAC. The ultrastructural characteristics of radical da mage here included: (1) plasmalemmal holes that appear to undergo ''pa tching'' by well-organized membrane whorls, (2) accumulation of numero us free ribosomes, (3) markedly increased vesicular trafficking about the Golgi accompanied by Golgi transformation from cisternal organizat ion to clusters of vacuoles with numerous fusing vesicles, (4) develop ment of large multi-layered vacuoles that include damage membranes and organelles and appear to undergo extrusion from the cell, and (5) a g eneral loss of cytoplasmic volume. These ultrastructural alterations d eveloped more rapidly and were consistently more advanced in different iated cells throughout the 6-h time course. In differentiated cells ra dical damage also induced the disorganization and subsequent loss of t he extensive feltwork of cytoskeletal elements. There was little damag e to the membranes of the nuclear envelope and mitochondria. Our obser vations in this system are strikingly similar to ultrastructural alter ations in Golgi and ribosomal organization seen in vulnerable neurons during post-ischemic brain reperfusion and suggest that these alterati ons during reperfusion reflect the consequence of radical-mediated dam age.