350 



RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



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Fig. 7-16. Autoradiogram (X1220) of cell of gastric caecum fixed l}^ hr after feeding 

 of Drosophila on P^^. (a) Phase photograph of cell, indicating A, cytoplasm; B, 

 nuclear membrane ; C, nucleolus ; D, chromatin. (6) Distribution of silver grains above 

 same cell. [Frotn J. Herbert Taylor, Intracellular Localization of Labeled Nucleic Acid 

 Determined with Autoradiographs, Science, 118: 555-557 (1953).] 



larvae in Carney's fluid, embedding in paraffin, sectioning at 7 n, and 

 washing in hot ether alcohol, lower grades of alcohol, cold 5 per cent tri- 

 chloroacetic acid, and water, followed by the usual stripping-film proce- 

 dure. By study of similar sections that were treated with ribonuclease, 

 it was possible to show the most of the P^- found within the nucleolus, 

 cytoplasm, and chromatin of the cell was probably present in the ribo- 

 nucleic acids. At early periods after exposure of the larvae to labeled 



