Chondroitin sulfate and electron lucent bodies in the pericellular rim about unshrunken hypertrophied chondrocytes of chick long bone.

Direct observation of unstained, 1 mm thick blocks of fresh epiphyseal cartilage from tibia of 15- and 18-day-old chick embryos revealed shrunken chondrocytes on its cut surfaces but unshrunken chondrocytes deep within the tissue blocks. The unshrunken hypertrophied chondrocytes are rimmed with refractile substance identified as chondroitin sulfate removable with hyaluronidase. This substance is stained metachromatically red with toluidine blue, and is stained with ruthenium red and with ruthenium red-OsO4. The latter, observed with the electron microscope, is present as an electron dense rim, specifically about the unshrunken, hypertrophied chondrocytes between the plasma membrane and lacunar wall. By rendering the chondroitin sulfate electron dense with RR-OsO4, electron lucent bodies (ELB) were revealed specifically about the hypertrophied chondrocytes. The ELB contain an electron dense core with radiating fibrils. The content and source of ELB, also found in the intercellular matrix, are not known. The 0.1% toluidine blue solution containing 0.2 M MgC12 or 0.4% NaCl or KCl stained juxtanuclear clusters of granules metachromatically red. The location of intracellular granules was believed to represent a cluster of Golgi-derived vesicles. The pericellular metachromatic, RR-OsO4-positive rim is believed to be an accumulation of externalized juxtanuclear metachromatic granules. The possibility that the ELB may also be externalized content of Golgi vesicles was entertained.