Studies on the mode of action of excess of vitamin A. 1. Effect of excess of vitamin A on the metabolism and composition of embryonic chick-limb cartilage grown in organ culture

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Abstract
After 6 days'' cultiva-tion in medium containing added vitamin A (10 international units/ml) the wet and dry weights and amino sugar content of cartilaginous limb-bone (chick) rudiments were half those of controls on normal medium. Compared with the control cultures, the amount of deoxyribonucleic acid was 80% and the amount of ribonucleic acid was 40%. The vitamin depressed the rate of oxygen uptake but increased that of lactic acid formation. There was twice as much acid-soluble nitrogen in the used culture medium (plasma-embryo extract clot) of the vitamin A-treated explants as in that of the control, indicating a greater proteolytic activity in the presence of the vitamin.