Electron Microscopic Studies of Mitosis in Amebae: II. The Giant Ameba Pelomyxa caolinensis

Journal Article · Mon Jan 01 00:00:00 EST 1962 · Journal of Cell Biology

DOI:https://doi.org/10.1083/jcb.12.1.57· OSTI ID:1629415

Roth, L. E. ^[1]; Daniels, E. W. ^[2]

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1. Argonne National Laboratory (ANL), Argonne, IL (United States); DOE/OSTI
2. Argonne National Laboratory (ANL), Argonne, IL (United States); Iowa State Univ., Ames, IA (United States)

Dividing nuclei from the giant ameba Pelomyxa carolinensis were fixed in osmium tetroxide solutions buffered with veronal acetate to pH 8.0. If divalent cations (0.002 M calcium, magnesium, or strontium as chlorides) were added to the fixation solution, fibrils that are 14 mµ in diameter and have a dense cortex are observed in the spindle. If the divalent ions were omitted, oriented particles of smaller size are present and fibrils are not obvious. The stages of mitosis were observed and spindle components compared. Fibrils fixed in the presence of calcium ions are not so well defined in early metaphase as later, but otherwise have the same diameter in the late metaphase, anaphase, and early telophase. Fibrils are surrounded by clouds of fine material except in early telophase, when they are formed into tight bundles lying in the cytoplasm unattached to nuclei. Metaphase and anaphase fibrils fixed without calcium ions are less well defined and are not observably different from each other. Further, the observations are consistent with the concept that spindle fibrils are composed of polymerized, oriented protein molecules that are in equilibrium with and bathed in non-oriented molecules of the same protein. Partially formed spindle fibrils and ribosome-like particles were observed in the mixoplasm when the nuclear envelope had only small discontinuities. Remnants of the envelope are visible throughout division and are probably incorporated into the new envelope in the telophase. Ribosome-like particles are numerous in the metaphase and anaphase spindle but are not seen in the telophase nucleus, once the envelope is reestablished, or in the interphase nucleus.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1629415
• Journal Information: Journal of Cell Biology, Journal Name: Journal of Cell Biology Journal Issue: 1 Vol. 12; ISSN 0021-9525
• Publisher: Rockefeller University Press
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES