Effect of 4-methylumbelliferyl-beta-D-xylopyranoside on the morphology of embryonic cartilage in limb bud cultures.

Limb buds of 11-day-old mouse embryos were cultured for six days in the presence of 0.1, 0.5 or 2 mg/kg 4-methylumbelliferyl-beta-D-xylopyranoside. A dose-dependent decrease in chondrogenesis could be observed in preparations stained with methylene blue and cleared. A reduction or even disappearance (after 2 mg/kg) of intercellular spaces and a change in shape and size of chondroblasts was striking in the light microscopical picture. The electron microscopical findings reveal a decrease in the number, size, and electron-density of the ruthenium-red-positive proteoglycan granules as well as an alteration in the collagen morphology. Up to 1,000 A thick fibrils occur which partly show a so-called continuous cross-striation. In addition, bundles of thin (50-100 A) collagen filaments without cross-striation occur. The number, distribution and packing density of the cell organelles in the chondroblasts are very variable. The vacuoles of the Golgi apparatus are dilated. These effects may be attributed to the xyloside-induced alterations of proteoglycans.