. Calcified tissues; proceedings. Bone; Collagen; Calcification. Indirect evidence for the role of lysosomes in skeletal morphogenesis is provided by the work of Moscona and Karnofsky (1959). Administration of cortisone to the chick embryo, in ovo, prevented the formation of the marrow cavity. In some species cortisone produces mcreased thickness of the epiphyseal plate due to failure of resorption on the metaphyseal side (Hulth and Olerud, 1963). Both of these findings I would interpret as due to the stabilizing effect of cortisone on the membranes of cartilage lysosomes exposed to the relati
. Calcified tissues; proceedings. Bone; Collagen; Calcification. Indirect evidence for the role of lysosomes in skeletal morphogenesis is provided by the work of Moscona and Karnofsky (1959). Administration of cortisone to the chick embryo, in ovo, prevented the formation of the marrow cavity. In some species cortisone produces mcreased thickness of the epiphyseal plate due to failure of resorption on the metaphyseal side (Hulth and Olerud, 1963). Both of these findings I would interpret as due to the stabilizing effect of cortisone on the membranes of cartilage lysosomes exposed to the relative hyperoxia of a highly vascularized region. In conclusion, it is suggested that exposure of cartilage to elevated partial pressures of oxygen results in tissue degra- dation by enzymes released by lipid peroxidation of the lyso- somal membrane. The often ob- served association between vas- cular invasion and degradation of skeletal tissues and suscep- tibility of cartilage to necrosis in hyperoxia may therefore be related. I would suggest that this phenomenon has important physiological as well as patho- logical implications. Cases in point would be the increased vascularity of the resorbing epiphyseal plate, the formation of the marrow cavity, the shedding of decidious teeth in humans and antlers in deer, and the erosion caused by the vascular pannus in rheumatoid arthritis. ,^^ â ^^?ii-. 8-day rudiment r 6 days. Osteo( cavitv formati on natural medium, exposed to S5"/o oxy- lasts can be seen participating in marrow >n. Haematoxvlin and Eosin. â 110 Acknowledgements The author is a Fellow of The Medical Foundation Inc. of Boston, Massachusetts. I thank Dame Honor B. Fell, F. R. S. and Mr. J. T. Dingle for their interest and advice. Certain aspects of this work were investigated in collaboration with Mr. Dingle. References Ali, S. Y.: The degradation of cartilage matrix by an intracellular protease. Biochem. J. 93, 611 (1964). Allison, A. C: Role of lysosomes in oxy
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