Distribution of acidic glycosaminoglycans in rabbit growth plate cartilage

Glucosaminidase, galactosaminidase, and glucuronidase in the growth plate

The activities of glucosaminidase, galactosaminidase, and glucuronidase were determined in fractions of bovine growth plate cartilage. Glucosaminidase and galactosaminidase activities were lowest in the area corresponding to the reserve cartilage and increased from the upper to the lower portions of the hypertrophic zones of the growth plate, reaching a maximum in the calcifying cartilage. Glucuronidase activity showed a distinct spike of activity in the calcifying cartilage. The spatial distribution of these activities suggests a role in calcification and in the dissolution of the extracellular matrix at the chondro-osseous junction of the growth plate.

Cartilage and bone formation in arterial wall. 1. Morphological and histochemical aspects

Cartilaginous and/or osseous foci were observed in eight aortas from 20 rabbits immunized against heterologous aorta homogenates and sacrificed 11 to 24 months later. They were studied by means of histological and histochemical methods and compared with normal aortas, cartilage and bone. Some of the observed changes seemed to be true markers of these transformations. Chondroid metaplasia was characterized by 1) generalized increase in alcianophilic hyaluronidase sensitive substances. 2) Appearance of Dermatan and/or Keratan sulfates round some isolated cells. 3) Advent of G6 Pase and Alk. Phase activities in cells adjacent to osseous foci. Osteous metaplasia was characterized by 1) decrease, then disappearance of alcianophilic and PAS positive material, 2) increase in osteoblastic alkaline Pase-activities.

Correlation of lysozyme activity with proteoglycan biosynthesis in epiphyseal cartilage

Pig epiphyseal cartilage (proximal ulna epiphysis) previously incubated into vitro in the presence of sodium [35S]sulfate or [3H]thymidine was either analyzed by autoradiography or separated into 9 morphologically defined consecutive layers and investigated for 35S-incorporation into the guanidinium chloride-extractable proteoglycans and for lysozyme activity. The lowest 35S incorporation and lysozyme activity were determined in the zone of resting cells, but there is a consecutive increase in the rate of proteoglycan synthesis and lysozyme activity toward the diaphyseal cartilage-bone junction, with the maximum at the lower columnar cell zone and a sharp reduction of both parameters at the hypertrophic zone. The maxima of 35S incorporation and [3H]thymidine incorporation do not coincide. The guanidinium chloride-soluble proteoglycans exhibit macromolecular polydispersity. Fractions excluded from as well as retarded by Sepharose 2B gel could be separated and were detected in all zones. The results indicate a correlation of proteoglycan biosynthesis and lysozyme activity in epiphyseal cartilage.