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Fliedner, Cronkite, Bond and Andrews
mained in the equatorial layer without being movedto oneofthe poles, In interphase such cells which lost chromosomal fragments could be observed as chromatin
clumps inside the cytoplasm. Whether or not these clumps in the red cell precursors are identical with Jolly-bodies is not known but suggestive (Fig. 2). In
some metaphases and anaphases the fragmentation was incomplete and in these
cases very thin chromatin strands stretched from one part of the chromosome
over the fragment to the other chromosome.
In some mitotic figures entire chromosomes remained between the two poles
without being movedto oneside or the other (Fig. 2). This abnormality probably
is due to an injury to the centromere and thus one or several chromosomes werelost
from the dividing cell. In some cases the nuclei of interphase cells were completely
fragmented forming chromatin clumps. Comparison studies in rats? (Fig. 3)
suggested that these are altered chromosomes due to abnormalcell division. unable
to move to the poles, but still able to synthesize desoxyribonucleic acid. It is uncertain whether or not such ‘fragmented nuclei” can survive through one or
more mitoses.
In some cases the arrangement of chromosomes in anaphase and telophase
was disordered. Here the abnormality was probably due to an injury to the formation
of the spindle giving rise to unequal daughter nuclei.
In many mitotic figures the abnormalities described were combined. Therefore it was not always possible to trace the probable pathogenesis of the observed
abnormalities.
Abnormal mitotic figures suggesting multipolar mitoses were observed in some
cases. In these the surrounding cytoplasm was normalin its color but abnormal
in its size. A probably tetrapolar polychromatic normoblast division the cytoplasm of which is about 4 times the normalsize is shownin Fig. 4.
Radiation Effects Reflected in Interphase Cells.
The first marrow smears were
performed 12 hours after the accident. Obvious morphologic abnormalities were
observed in erythroid and myeloid precursors. Some of the immature nuclei
showed an increased diameter and the chromatin pattern was abnormal with
loose nuclear edema or chromatin dissociation or both (Fig. 4). In somecells
transitional stages to karyolysis could be observed (Fig. 4e); it was, however.
rare to see definite karyorrhexis and pyknosis of nuclei. This nuclear swelling was
similarly seen in white cell precursors, in which it often became more and more
difficult to recognize the outline of the nucleus, which often looked rather
homogeneous and washed out (Fig. 4d).
Nuclear swelling with chromatin dissociation became less frequent after
44 hours, and disappeared in the 3 day marrow smears. After 44 hours, and less
frequently after 12 hours many large myeloid and erythroid precursors were
found. Frequently the nuclear structure and staining characteristics of the cytoplasm corresponded to a more maturecell than indicated by the nuclear diameter.