Fine structural localization of RNA in myeloma cells detected by the enzyme-gold method

The ultrastructural localization of RNA in myeloma cells was studied by the RNase-gold method. Gold particles indicating the presence of RNA were observed in large numbers, particularly in the granular component of the nucleolus and periphery of the rough endoplasmic reticulum, but not in the Golgi area, mitochondria, intranuclear inclusion bodies, cytoplasmic inclusion bodies, dense bodies, or cisternae of the rough endoplasmic reticulum. In the nuclear chromatin and nucleolus, gold particles were more numerous as these structures were less mature. They were found in larger numbers also in the cytoplasm of immature cells. In plasma cells from patients with macroglobulinemia, gold particles were fewer than in myeloma cells of multiple myeloma, but there was no difference in their distribution pattern.