Histochemistry of bone formation in normal and tetracycline-treated chick embryos—I: Lipids

Abstract

The localization of lipid components in the developing femurs of normal and tetracycline-treated chick embryos has been described. A lipid component readily extractable with ethanol, possibly neutral fat, was found in the cytoplasm of osteoblasts and osteocytes, in bone matrix, and to a much lesser extent in osteoid. Phospholipids were found in the cytoplasm of the chondrocytes. A sudanophilic bound lipid, which is unmasked by ethanol but removed by pyridine extraction, was found in the calcified bone of both normal and experimental animals, and in the calcified cartilage matrix of the experimental femurs. A sudanophilic bound lipid, which is resistant to pyridine extraction with the techniques used, was found in the rapidly calcifying bone and cartilage matrix. It was reduced in amount in the older, less rapidly calcifying bone. A similar pyridine-resistant, sudanophilic, bound lipid was found in cytoplasmic granules of the chondrocytes, and those osteocytes situated in a calcified matrix. There appears to be a direct relationship between the size and possibly the number of these granules and the degree and rate of calcification of the surrounding matrix.