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The Journal of Cell Biology
The Rockefeller University Press
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MALNUTRITION : INCORPORATION OF THYMIDINE 3H INTO NUCLEAR AND MITOCHONDRIAL DNA PETER R. DALLMAN . From the Department of Pediatrics, University of California, San Francisco, California 94199 INTRODUCTION Protein-calorie malnutrition or fasting leads to a readily detectable decrease in the rate of body growth and cellular proliferation, particularly in young animals (32, 33) . In contrast, disorders in cell and organ function have generally been more difficult to demonstrate, perhaps partly due to limitations in methodology (8, 16, 22) . Mito- chondria are the primary energy source for the work of differentiated cells . Normally, mito- chondria continue to proliferate even in non- dividing cells, presumably under the regulation of their own DNA (2, 17, 23) . If energy-requiring cell functions are favored over cell proliferation in undernourished animals, the renewal of mito- chondria might continue even if cell division is decreased . Comparative rates of DNA production in the nuclei and in the mitochondria of hepato- cytes were studied to test the hypothesis that malnutrition might have different effects on the synthesis of DNA in these two intracellular sites . MATERIALS AND METHODS All experiments were performed with female albino rats of the Sprague-Dawley strain fed either a stock pelleted diet (Berkeley diet rat and mouse food, Feedstuffs Processing Company, San Francisco) or a semisynthetic diet containing 3 .5% or 26% protein (General Biochemicals, Div. North American Mogul Products Co ., Chagrin Falls, Ohio : Protein Test Diet, Low (No . 170580), 3.5% protein ; and Protein Test Diet, Normal (No. 170390), 26% protein) . Animals were killed by decapitation . Liver mito- chondria were isolated as previously described (29) by differential centrifugation, washed four times and THE JOURNAL OF CELL BIOLOGY . VOLUME 51, 1971 . pages 549-558 BRIEF NOTES The Brief Notes section of this issue is printed by photolithog

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