. Calcified tissues; proceedings. Bone; Collagen; Calcification. 54 C. B. Sledge «. unchanged from control figures. What about the cell membrane? Allison (1965), working with cell cultures in 95'''o oxygen, found increased permeability of the lysosomes to the Gomori substrate 12 hrs. before the cell membrane became permeable to eosin. It was, therefore, suspected that the effect of hyperoxia was a direct one on the lysosomal membrane. Mr. Dingle and I (Slldge and Dingle, 1965) prepared lysosome-rich fractions from chick embryonic cartilage and incubated them with oxygen or nitrogen. Similar fr
. Calcified tissues; proceedings. Bone; Collagen; Calcification. 54 C. B. Sledge «. unchanged from control figures. What about the cell membrane? Allison (1965), working with cell cultures in 95'''o oxygen, found increased permeability of the lysosomes to the Gomori substrate 12 hrs. before the cell membrane became permeable to eosin. It was, therefore, suspected that the effect of hyperoxia was a direct one on the lysosomal membrane. Mr. Dingle and I (Slldge and Dingle, 1965) prepared lysosome-rich fractions from chick embryonic cartilage and incubated them with oxygen or nitrogen. Similar fractions from liver, kidney, spleen and brain were run as controls. Only in the case of lysosomes from cartilage was there activation by oxygen. When Vitamin E, a lipid solu- ble anti-oxidant, or vitamin C, a water-soluble anti-oxidant, were added to the culture medium, pro- tection from hyperoxia was ob- served (Fig. 3). Tappel et al. (1963) have found increased lipid per- oxidation in vitamin E deficiency. It therefore seems likely that the effect of hyperoxia is mediated through increased release of hydro- lytic enzymes by lipid peroxida- dation of the lysosomal membrane. The protective effect of vitamin C IS perhaps due to a re-cycling phenomenon whereby a membrane constituent, sus- ceptible to oxidation, is protected by lipidsoluble reducing substance (perhaps vit- amin E) which, in turn, is maintained in a reduced state by vitamin C in the cytoplasm. The role of the osteoclast in these experiments has been most interesting. They are not normally seen in chick limb-bones in culture. However, in all of the rudiments exposed to hyperoxia alone, osteoclasts appear — never in great number and always after resorption is well underway. They are not due to hyperoxia, per se, as they are not seen in rudiments exposed to hyperoxia but protected from matrix degradation by Cortisol, EACA, or vitamins E or C. From this it would appear that some product of matrix degradation is respo
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