Histopathology of bone and brain in late-term aborted Red Angus calves. A-D (distal aspect, femur): Abnormal morphology of few remaining osteoclasts persisting in bone. A. Osteoclast with scant cytoplasm and no obvious Howship's lacuna. B. Osteoclast with scant, lightly vacuolated cytoplasm that partially occupies lacuna. C. Osteoclast with nuclear degeneration. Myeloid cells are interposed between osteoclast and lacuna. D. Two osteoclasts associated with fragment of cartilage. One (black arrow; bottom left) is relatively normal. The other (white arrow; top right) exhibits nuclear changes consistent with apoptosis. E (mid-section, rib). Scant, widely separated osteoblasts (arrowhead) associated with osteoid. F-G (brain, medulla oblongata at obex). F. Chromatolysis of large neurons (asterisks). G. Widespread axonal spheroids in reticular formation (asterisks).