Surface ultrastructure and cytochemistry of isolated nucleoli from Novikoff hepatoma ascites cells

Surface ultrastructure and cytochemistry of isolated Novikoff hepatoma cell nucleoli were examined using scanning electron microscopy (SEM). Nuclear preparations were examined at 15 sec intervals during the sonication procedure for isolation of nucleoli. In the initial stages of nuclear disruption the nucleoli were attached to large chromatin masses. A compact nucleoprotein nucleolar stalk relatively resistant to shear was observed in association with many nucleoli. Further sonication disrupted these structures and left tightly coiled, helical filaments still attached to the purified nucleoli. These filaments were removed by DNase digestion but were resistant to RNase digestion. The present study provides a new perspective of nucleolar ultrastructure, its surface organization, and its relationships to other nuclear components.