Ultrastructure of the sinus wall of murine bone marrow in myelogenous leukemia

The ultrastructure of bone marrow of RF mice having an acute myelogenous leukemia induced by inoculation with leukemic cells was investigated. In several respects sinuses of leukemic marrow are similar to normal marrow. Sinuses are present in numbers approximating that of the normal; the lining cells of the sinus wall have organelles similar in distribution and number to those of normal lining cells; the sinus wall is continuous, having openings only in conjunction with blood cells that are migrating through it (migration pores); migration pores occur within and not between lining cells. Abnormalities observed in leukemic marrow are the occurrence of virus-like particles in leukemic cells, the presence of numerous particles 300 to 500 A in diameter in the extracellular space, reduction in the number of adventitial cells of the sinus wall and an increase in the thickness and distribution of extracellular material located near the basal surface of lining cells.