The deoxyribonucleic acid content of the rat cell nucleus and its use in expressing the results of tissue analysis, with particular reference to the composition of liver tissue

I953 activity of diphosphopyridinenucleotidase is greatly increased (Nason et al. 1951)-there is no reason to attribute invariably the disorders of metabolism which occur in zinc deficiency to a primary impairment of protein synthesis.Copper deficiency has been claimed to have marked effects on the protein metabolism of green plants (Gilbert, Sell & Drosdoff, 1946;Wood & Womersley, 1946;Lucas, 1948;Gilbert, 1951), and so the observation that the aldolase activity in the leaves of copper-deficient oats remains unimpaired, suggests that the lowered aldolase activity in the leaves of zinc-deficient oats is not due primarily to a decreased protein synthesis; although zinc might be specifically involved in the synthesis of the enzyme itself.The third possibility that the aldolases of green leaves are activated by Zn2+ or by zinc-containing co-enzymes is being examined.SUMMARY Aldolase activity was found to be materially decreased in tissue suspensions prepared from the leaves of zinc-deficient plants of Trifolium sub- terrane,um and of Avena 8ativa, but was unchanged by copper deficiency.The author is grateful to K. Powrie for supplying some of the experimental material: to G. B. Jones for the polaro- graphic estimation of zinc and copper and to V. Stephen who set up the aeration apparatus and is particularly indebted to H. R.