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Except that the nuclear envelope remains intact micronuclear mitosis
occurs in a normal way passing through the four stages of prophase,
metaphase, anaphase and telophase. In this example a micronucleus was
sectioned in early anaphase and shows condensed daughter chromosomes
(arrowheads) at each pole. Chromosomes are separated by a large
bundle of microtubules making up an intranuclear spindle. The
separation spindle will become a very long thin tube (see Fig.20 in
Allen, Ueno and Fok, J. Protozool. 35:400-407, 1988). The image shown
here has very low contrast because the cell was taken from a culture
in which a 15 minute treatment in ammonium chloride was used to see
what effect this base would have on its acidic compartments. The cell
was then incubated in diaminobenzidine. As usual the cristae of
mitochondria become electron-opaque following this treatment (see
chapter on cytoplasmic organelles). EM taken on 6/11/86 by R. Allen
with Zeiss 10A TEM. Neg. 4,000X. Bar = 1µm.
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