Adult rabbit articular cartilage slice and plug explants were cultured in MEM/NCTC 109/fetal calf serum at 37°C in various oxygen tensions. In both the slice and plug explants, 85S04 incorporation exhibited a broad tolerance to oxygen tensions varying from 5 (38 mm. Hg) to 60 (456 mm Hg) per cent. Significantly (P 0.01) less 35S04 was incorporated in 1 (7.6 mm Hg) and 90% (684 mm Hg) oxygen than in 21 % (160 mm Hg) oxygen. No histologic or autoradiographic differences, and only slight histochemical differences, were discernible after seven days culture in the various oxygen tensions. It is suggested that low synovial fluid oxygen tension is detrimental to articular cartilage glycosaminoglycan metabolism. suggest that articular cartilage follows an anaerobic metabolic pathway (1-3). Glycolytic enzymes and high concentrations of lactic acid (1) are found in articular cartilage, and articular cartilage is little affected by short periods of oxygen deprivation (2), is relatively tolerant to high concentrations of potassium cyanide(3), and is very sensitive to monoiodoacetate (3), an agent that prevents glycolysis. Recent investigations (4-6) indicate that synovial fluid oxygen tensions decrease to very low levels in inflammatory joint diseases. These last studies present the possibility that synovial fluid hypoxia might cause chondrocyte damage and death.This report describes a series of experiments in which an in vitro articular cartilage model was cultured in various oxygen tensions. The results indicate that while articular cartilage sulfate incorporation is quite tolerant to rather wide variations in the prevailing oxygen tension, sulfate incorporation is significantly diminished at 1% and 90% oxygen.

The effect of collagen modification on the magnitude of stress-generated potentials has been studied. A whole bone model has been developed for determining the effects of collagen crosslinking on the electrical signals. Increased crosslinking results in larger electrical signals, and such increases result whether in vivo or in vitro changes in the collagen are made.