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Fliedner, Cronkite, Bond and Andrews, Mitotic Activity and Cytology
Since under normal conditions the mean nuclear volume. and thus the mean
nuclear diameter decreases from one maturation stage to the next in both the
myeloid and erythroid series: 5, the presence of large nuclei with a more mature
structure and a more mature cytoplasm indicated an inhibition of nuclear division
without disturbance of nuclear and cytoplasmic maturation. Giant neutrophils appeared
in the peripheral blood after 4 to 5 days. Since giant mature myelocytes and
metamyelocytes were found in the earlier marrow smears it is probable that the
formation of giant blood cells is due to the inhibition of nuclear division without
interference of the nuclear and cytoplasmic maturation. The same pathogenesis
would cause giant red cells in the red cell series (Fig. 4, b and c).
In other cases, binucleated red and white cell precursors were seen in the
early marrowsmears. In these only the cytoplasmic division was altered (Fig. 2).
These binucleated precursors apparently can mature and form binucleated white
blood cells.
Less frequently chromatin drops were found, especially in the cytoplasm
of normoblasts. Since in somecases these drops seem to be attachedto the nucleus,
almost like ‘‘released” chromatin, they may be the result of damageto the nuclear
membrane, with release of nuclear material (Fig. 4d). Whether or not these drops
consist of ‘“‘released”” nuclear material or of chromosomal material due to a lost
chromosome fragment during abnormal cell division, was uncertain.
Discussion
The findings of atypical mitoses and abnormalcells in interphase in the 12
and 44 hour bone marrow aspirates of five men accidentally exposed to mixed
neutron-gammairradiation indicate the value of early marrow examinations for
the diagnosis of doubtful radiation exposure.
The clinical course demonstrated that the exposure resulted in the acute
radiation syndrome in its hematological form, with leucopenia and thrombocytopenia. Although none of the persons exposed died, their health was cause for
some concern at approximately 30 days and the exposures were probably in the
high sublethal or low lethal region®.
It was found in studies on the marrow of rats? exposed to 550, 1000, and
1500 r, that only lethal and supralethal doses caused immediate damage of many
nucleated marrow cells, with signs of karyorrhexis and karyolysis. In the bone
marrow smears of men examined the cellularity remained within normal limits
for the first few days and no obvious abnormalities were observedatfirst glance.
A closer examination, however, demonstrated significant signs of injury. No
detailed studies have been reported so far aboutthe initial changes in bone marrow
cytology of man after lethal and supralethal doses, but abnormalities described
here might occur with greater frequency at higher dose levels. Thus a careful
examination of bone marrow smears within hours after radiation exposure of
doubtful severity might help with a quantitative study of mitotic and cellular
abnormalities for a better assessment of the clinical situation.
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