Virusähnliche Partikel in Ra-224-induzierten Osteosarkomen der Maus.

Electron microscopic investigation of osteosarcomas from 3 mice, induced by the incorporation of 224Ra, and an osteosarcoma metastasis from the liver of one of the animals revealed peculiar intracellular particles in all of the tumors. The particles were spherical, measured about 80 nm in diameter and consisted of 2 electron dense, ring shaped, membrane like shells which concentrically surrounded an electron lucent core. Nearly all of the particles with this doughnut like ultrastructural appearance occurred in cisternae of the rough surfaced endoplasmic reticulum (RER) of tumor cells. They were seldom observed in intracytoplasmic smooth surfaced vacuoles or located freely in the cytoplasmic matrix. Crescent shaped particles were occasionally found, presumably in the stage of formation by budding into cisternae of the RER from its membrane component. The ultrastructure, size and formation of particles, as well as their location in relation to intracellular structures, are similar to those described for type A viral particles. The significance of the virus like particles, especially in relation to the pathogenesis of the malignant bone tumors, is not known