Nucleolus Extrusion: An Electron-microscopic Study of Human Esophageal Cancer Cell Lines under Hypothermia.

Neoplastic cells from human esophageal cancer cell lines, SGF-3, SGF-4 and SGF-5, maintained in a hypothermic state at 21.5°C were examined under electron microscope. Ultrastructural alterations, including nucleolar lesions, were found in the cells. SGF cell nucleoli showed characteristic changes under hypothermia, consisting of a segregation of the granular component, the fibrillar center and the fibrillar component. Both morphological apoptotic features and regenerative features were disclosed by electron microscopy. Segregated nucleoli extruded from the nucleus into the cytoplasm were revealed in these hypothermic cells. RNA staining distinguished the nucleoli from the nuclear material extruded into the cytoplasm, indicating the nucleoli in the nucleus, the migration of the nucleoli into the cytoplasm and a RNA-positive material, probably nucleolus origin of budding with the cytoplasmic membrane under hypothermia.