MITOSIS IN RAT-THYROID EPITHELIAL-CELLS INVIVO .2. CENTRIOLES AND PERICENTRIOLAR MATERIAL

The growth, movements, and orientations of centrioles and the behavior of pericentriolar material during mitosis in vivo was studied at the ultrastructural level in stimulated rat thyroid epithelial cells. Apparent biogenesis of daughter centrioles was first observed in interphase and by very early prophase, daughter centrioles had elongated to about two-thirds of their mature length. They appeared to retain this intermediate length throughout most of mitosis and were observed to reach their mature length only in very late telophase or interphase. Very early in mitosis, centriolar diplosomes left their interphase position near the cell apex and individual diplosomes were observed in various locations, including close to the base of the cell. However, by metaphase (and later) diplosomes were consistently found about midway between the apex and the base, corresponding to the establishment of a spindle axis parallel to the follicular luminal surface. Measurements of the distance between centriolar diplosomes during mitosis revealed a steadily increasing separation until mid-telophase. © 1979 Academic Press, Inc.