Osteoclasts with ruffled borders from above the tip of the erupting incisors of osteopetrotic mice and rats.

Electron microscopy of the bone above the incisor of 10-day-old microphthalmic mice (mi) and incisors absent rats (ia) demonstrated that in both osteopetrotic mutants, osteoclasts indistinguishable from normal and with well-developed ruffled borders were present. Study of the same region in younger and older animals showed the type of abnormal osteoclast typical of the respective mutant strain.