Bone changes in mice after prolonged continuous exposure to a high concentration of carbon monoxide

Quantitative and qualitative pathological changes in mouse bones are described after continuous exposure to 0.24% v/v of carbon monoxide in air for periods of up to 180 days. Planimetric measurements of five bones (parietal bone, sternum, lumbar vertebrae, ribs and shafts of femurs) showed a considerable increase in the amount of bone tissue in all bones except the femurs. The greatest amount of new bone formation was found, in decreasing order, in the skull, ribs, lumbar vertebrae and sternal segments. The cortex of the femur shafts showed some thinning, although there was more trabecular bone in the metaphyses. At the same time an expansion of marrow cavities was found in ribs, parietal bones and femurs. Possible pathomechanisms responsible for the excessive bone formation are explored. It is suggested that an increased rate of blood flow through the bone and marrow tissues played an important role.