The fine structure of isolated HeLa cell nuclei

Abstract

Nuclei were isolated from HeLa cells and were examined in the electron microscope. During the isolation procedure which was carried out in a hypotonic solution, swelling of the nuclei occurred and there was a reduction of approximately 30 per cent in their dry mass. This reduction in dry mass was due to a loss of soluble protein. Experiments with radioactive precursors demonstrated that no appreciable amount of nucleic acid was lost. The structures seen in thin sections of the swollen nuclei appeared to be a dispersed system of fine filaments. A statistical analysis of the structures seen in the thin sections was consistent with this interpretation. The swollen nuclei returned to normal size when they were placed in an isotonic solution, but their contents then became severely clumped. Swelling and contraction appeared not to be an osmotic phenomenon since the nuclear membrane of the isolated nuclei was not intact.