|"Macromolecules are the biological molecules synthesized by the plants and animals to meet their metabolic and energy needs, and to carry out their day to day activities in a normal manner.
The animal bodies, including both human body as well as the bodies of any experimental animals such as mice and rats consist of various macromolecules. They are classified into nucleic acids (both DNA and RNA), proteins, glucides and lipids, according to their chemical structures. These macromolecules can be demonstrated by specific histochemical staining techniques for respective molecules such as Feulgen reaction (Feulgen and Rossenbeck 1924) that stains the entire DNA contained in the cells. Each compounds of macromolecules such as DNA, RNA, proteins, glucides, lipids can be demonstrated by respective specific histochemical staining and such reactions can be quantified by microscpectrophotometry using specific wave-lengths demonstrating the total amount of respective compounds. To the contrary, radioautography can only demonstrate the newly synthesized macromolecules such as synthetic DNA or RNA or proteins depending upon the RI-labeled precursors incorporated specifically into these macromolecules such as 3H-thymidine into DNA or 3H-uridine into RNA or 3H-amino acid into proteins.
(Tetsuji Nagata- Light and Electron Microscopic Radioautographic Studies on the Cell Aging of the Neuro-Sensory System of Mice)