The behavior of the nucleolus during mitosis was studied by electron microscopy in neuroblast cells of the grasshopper embryo, Chortophaga viridifasciata. Living neuroblast cells were observed in the light microscope, and their mitotic stages were identified and recorded. The cells were fixed and embedded; alternate thick and thin sections were made for light and electron microscopy. The interphase nucleolus consists of two fine structural components arranged in separate zones. Concentrations of 150 A granules form a dense peripheral zone, while the central regions are composed of a homogeneous background substance. Observations show that nucleolar dissolution in prophase occurs in two steps with a preliminary loss of the background substance followed by a dispersal of the granules. Nucleolar material reappears at anaphase as small clumps or layers at the chromosome surfaces. These later form into definite bodies, which disappear as the nucleolus grows in telophase. Evidence suggests both a collecting and a synthesizing role for the nucleolus-associated chromatin. The final, mature nucleolar form is produced by a rearrangement of the fine structural components and an increase in their mass.
Article| March 01 1965
THE FINE STRUCTURE OF THE NUCLEOLUS DURING MITOSIS IN THE GRASSHOPPER NEUROBLAST CELL
Barbara J. Stevens
From the Department of Anatomy, Cornell University Medical College, New York, and the Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Dr. Stevens' present address is the Whitman Laboratory, University of Chicago, Chicago
Received: February 21 1964
Online Issn: 1540-8140
Print Issn: 0021-9525
Copyright © 1965 by The Rockefeller Institute Press
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Barbara J. Stevens; THE FINE STRUCTURE OF THE NUCLEOLUS DURING MITOSIS IN THE GRASSHOPPER NEUROBLAST CELL . J Cell Biol 1 March 1965; 24 (3): 349–368. doi: https://doi.org/10.1083/jcb.24.3.349
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