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 subterrane,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 polarographic estimation of zinc and copper and to V. Stephen who set up the aeration apparatus and is particularly indebted to H. R. Marston, F.R.S., Chief of the Division of Biochemistry and General Nutrition, C.S.I.R.O., for his advice and criticism during the experiment and his help in preparation of the manuscript. Glasshouse accommodation was made available by Prof. J. G. Wood of the Botany Department of the University of Adelaide, and this courtesy is gratefully acknowledged.

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OF CONTENTS Scope 01 the review and general survey of methods The preparation of tissue samples for nucleic acid determinations l'recautions during removal of tissues Extraction of acid-soluble compounds Extraction of phospholipids removed as the sparingly soluble potassium perchlorate by acidifying with perchloric acid at the end of alkaline digestion.

IN this review (ArtaZyst, 1961, 86, 768), the concentrations of perchloric acid (PCA) were quoted in all cases both as percentages (w/v) and as normalities by calculation from the authors' published data. The majority of authors quoted did not specify w/v or w/w concentrations and it was incorrectly assumed that 10 per cent. PCA was equivalent to 1.6 N, and pro rata for other concentrations. The figures quoted in the review for concentrations and normalities should in fact be adjusted on the basis that 10 per cent. (w/v) PCA is equivalent to 1.0 N. Where authors quote percentages in their original papers (references 11,

Treatment of female rats with adrenocorticotrophin (ACTH) increased the RNA content of the adrenal glands progressively during a period of 3 days, the DNA content increased only after prolonged administration. By contrast, ACTH caused a decrease in the uptake of [32P]orthophosphate into the total RNA of the gland and into most of the RNA fractions of the subcellular components.A method of analysis for RNA and DNA based on the Schmidt\p=m-\Thann-hauser procedure has been evolved which eliminates extraction of nucleic acid by lipid solvents.