STUDIES ON INTRACELLULAR STRUCTURES OF COS CELLS BY X-RAY MICROSCOPY

COS-7 cells, fixed with glutaraldehyde, were studied using the transmi ssion X-ray microscope at the electron storage ring BESSY, Berlin. The border of the cell, the nucleus, nucleoli and mitochondria of the cel ls were clearly visualized with the X-ray microscope. In addition, we found many X-ray dense granules preferentially located around the nucl eus. Electron microscopy showed that numerous multivesicular bodies, w hose structures belong to the endosome-lysosomal system, were present around the nucleus. The size and localization patterns of the X-ray de nse granules were quite similar to those of multivesicular bodies. The se results strongly suggest that the X-ray dense granules are multives icular bodies.