Increase in the dense cytoplasmic bodies in radiation-induced giant cells of the cultured fibroblast.

Abstract

In giant cells developed from fibroblasts after irradiation, the nucleus is large and convoluted so that thin sections often give an impression of multi-nucleation. Individually the cytoplasmic structures are identical with those of the nonirradiated cells, though the Golgi apparatus may appear more diffuse. The striking feature of these cells is the in crease in the number of the dense bodies, which occur in groups of 12 to 15 in each cell in the thin sections. As in the normal cell, they are approximately 0.5 m mu in diameter, with a smooth outer membrane and opaque ground substance. Their internal structure is more variable, most have some lamellations, and myeloid bodies are fairly common. After Thorotrast treatment for l hr, the dense bodies of the giant cells show a considerable concentration of granules. It is concluded that, as a result of continuous pinocytosis, when cell division in cultured fibroblasts is prevented by radiation, the dense cytoplasmic bodies increase in number.