Leukemic environment mildly and transiently increases osteoclastic numbers in vivo. (A) Serum levels of carboxy-terminal collagen cross-link CTX, a marker of bone resorption as measured by ELISA. (B) Representative images of paraffin sections stained for the osteoclastic marker TRAP. TRAP⁺ cells are pink and highlighted by arrowheads. Top panels 20×, and bottom panels 60× objectives. (C) Quantification of multinucleated TRAP⁺ cells in a 1-mm² area just proximal of the distal growth plate in the femur from sections represented by the panels in B. (D) Serum levels of TRACP 5b, the osteoclast specific TRAP enzyme, measured by ELISA. *P ≤ .05. ***P ≤ .001. Each point indicates an individual mouse in this and subsequent experiments; n = 5 mice per experiment.