The supravital staining of osteoclasts with neutral-red: their distribution on the parietal bone of normal growing mice, and a comparison with the mutants grey-lethal and hydrocephalus-3

Abstract

Skullroofs of either-killed mice were stained at 37[degree]C for 1 hr. in 1:10,000 neutral-red in Ringer and transferred to 2% HgCl2 the dura being removed after 3 hrs. Osteoclasts remain sharply stained in this soln. for several weeks, but fade in strong light. Observations were made on the internal surface of the parietal bone, using alizarin transparencies of the opposite side to reveal bone structure. Normal phenotypes from gray-lethal (Gruneberg, 1936) stock show a fine lattice of osteoclasts at birth, which disappear from the solidifying central area at 7 days, become concentrated in the areas traversed by the radial canals which move outwards as the bone grows as a result of osteoclastic erosion of their overhanging margin. By the 18th day most of the osteoclasts have disappeared. Total number of osteoclasts increased from 500 at birth to 2000 at 7 days, dropping to 200 at 14 days. In gray-lethal mice, where bone absorption is very defective, osteoclasts were fewer (800 at 7 days) but larger, estimated at 60% of the mass of osteoclasts in normal mice. A single 15-day-old specimen of hydrocephalus-3 (GrUneberg, 1943) mouse showed great increase in total number and density of osteoclasts as compared to its normal litter mate. Osteoclast location is relatable to the formation of vascular foramina and the underlying diploe, and osteoclasts follow behind the zone of bone deposition at the margins.