An Autoradiographic Study of Nucleic Acid and Protein Turnover in the Mammalian Neuraxis

Abstract

The turnover of nucleic acids and proteins in the central nervous system has been explored by autoradiography following the subarachnoid injection of tagged precursors. Nuclear PNA of neurons and oligodendrocytes becomes radioactive earlier than cytoplasmic PNA after injection of adenine-C¹⁴ and orotic-C¹⁴ acid. By 24 hours following injection, cytoplasmic PNA is radioactive. Radioactivity persists with little decrease for as long as 51 days after an injection of adenine-C¹⁴. The cells of the ependymal lining, choroidal plexus, leptomeninges, blood vessel walls, and Schwann cells also exhibit radioactivity in PNA as judged by the loss of radioactivity following ribonuclease digestion. From the 3rd day on, increasing numbers of the aforementioned cells, with the exception of nerve cells, exhibit ribonuclease-resistant nuclear radioactivity which is abolished by deoxyribonuclease. This radioactivity indicates labelling of nuclear DNA.