The Effect of 2000 r of X-rays on the Internal Structure of the Mouse Tibia

SummaryThe effects of 2000 r of x-rays on the structure of the epiphyseal plate of the tibiae of 3 weeks and 12 weeks old mice are described. The initial effects were the disorganization of the epiphyseal plate due to the death of actively dividing cells and the cessation of cell erosion at the metaphyseal edge of the plate and of endochondral ossification, resulting in the formation of a wide plate with a low cell : matrix ratio, and diminished glycogen content. The resorption of bone in the metaphysis continued. This irradiated plate did not always persist and in some animals, clusters of cartilage cells appeared after about 9 weeks and initiated a new plate, the old one being split off and resorbed. It is considered that the formation of a new plate was dependent on the survival of stem cells with an intact reproductive mechanism and the maintenance of an adequate metaphyseal circulation. Where the blood supply was seriously reduced degenerative changes appeared in the bone marrow, cartilage and bone matrix and eventually culminated in necrosis of the lower part of the limb.