Dynamic Analysis of RNA Turnover in the Neuron as Shown by 3H-Uridine Autoradiography
1965 Volume 25 Issue 3 Pages 325-332
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1965 Volume 25 Issue 3 Pages 325-332
The processes of RNA synthesis and dynamics of synthesized RNA in the neuron of the kitten and mouse brain have been studied by autoradiography after injection of 3H-uridine which is specific precursor of RNA.
1. When 3H-uridine was injected into subarachnoid space, almost all of the cells including neurons, glial cells and endothelial cells of the parts of the brain where the 3H-uridine infiltrated were labeled, and the density of reduced silver grains in the neurons was remarkably lower at a distance from the injected point.
2. In the mice which received the injection of 3H-uridine subcutaneously on the back, almost all cells in various parts of the brain had the label, and the neurons in the cerebral cortex, hypocampus and basal ganglia were far active in the synthesis of RNA as compared to PURKINJE cells and granular cell neurons in the cerebellum.
3. Within short time as thirty minutes after the injection of 3H-uridine, grains were found to be concentrated in the nuclei of neurons as other kinds of cells, but when the time elapsed the grains appeared gradually in cytoplasm.
4. The silver reducing RNA first appeared on the nucleus after injectiou of 3H-uridine migrated into the cytoplasma with the lapse of time but there was no evidence that only the RNA in the nucleolus predominantly migrated into the cytoplasm as reported by many investigators.
5. In nerve cells the silver reducing RNA which had migrated into the cytoplasm were found both at the dendritic side and the axonal side.
6. Different kinds of neuron had their own rapidity of RNA turnover, and this may be due to difference in function. The turnover of RNA in the neurons of cerebral cortex and hippocampus was more rapid than in the neuron of the brain stem.
7. By the facts that the silver grains first appeared in the nucleus migrates gradually into the cytoplasm and that 3H-uridine is not incorporated into the nucleus of dividing cells in which DNA is inactive, newly synthesized RNA in which 3H-uridine has been incorporated is therefore considered to be messenger RNA.
