EFFECTS OF WHOLE BODY IRRADIATION ON MARROW
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In agreement with previous experimentalfindings,’®° two types of cytologic
abnormalities were distinguished: “Cells injured directly” and “mitotically
connected abnormalities.” 1n all five marrow smears of the high dose group,
prepared 12 hours after the accident, and less frequent in the 2-day sample,
cells were found, mainly erythroblasts, showing a marked degree of clumping
or dissociation of the nuclear chromatin with transition into frank karyolysis.
These findings were not quantitated because it was judged that their evaluation was too subjective. However, it was the impression that about 5 per
centof all erythroblasts in the 12-hour samples showed nuclear changes which
were not impressive in the smears of the low dose group or of “normal” controls. From animal studies it was derived that such immediate cytologic
changes presumably progressing to cell death occur before further cell division could occur and are apparently dose-dependent.
Easily recognized and quantitated without doubt were mitotically connected abnormalities. In mitoses found in marrow smears, an abnormality was
considered to exist if a chromosomal bridge was found in ana- or telophase
or if a chromosome and/or chromosomal fragments were apparently discarded
from further karyokinesis and “left behind” between the poles of the mitosis
or elsewhere in the cytoplasm, Examples of such abnormal mitoses are given
in figures 1 and 2. During interphase, cells were considered to present a M.C.
Abn. if one or more nuclear fragment, termed “karyomere” (E. Schwarz*°),
was found. Examples of such abnormalcells in the erythropoietic series are
given in figure 1 and in myelopoietic and lymphopoietic cells in figure 2. Another type of M. C. Abn. was the occurrence of binucleated cells, seen in the
early studies primarily in myelocytic elements, and in the late studies primarily in the erythropoietic cells. Examples are shown in figures 2 and 4. “Giant
cells” were also classified under this type of abnormality. They were defined
as cells significantly larger in overall size than normal cells of identical
nuclear structure and apparent cytoplasmic maturity. They are easily recognized in the myelopoietic series and examples are given in figure 2. They occur also among erythropoietic forms, as shown in figure 1, but these were not
included in the quantitative analysis of abnormalities since there is considerable disagreement aboutthe relation of cell size and maturity in erythro-
blasts.
Figure 3 gives the results of M. C. Abn. during the counting of 500 erythro-
blasts in the smears of each of the irradiated persons. In the erythropoietic
series only the cells showing one or more karyomeres are included. These
structures were found in the first marrow smears 12 hours after the accident.
Their frequency rose to maximum in the 2nd day samples when about 12 per
cent of all erythroblasts had at least one karyomere, and decreased subse-
quently. Among 10,000 erythroblasts counted in the marrow smears of four
normals for comparison, only 11 were found to contain one karyomere
(= 0.115), the frequency varying from 0.05 to 0.2 per cent. Most of these were
in oxyphilic normoblasts; none were found to contain more than one karyo-
mere. These karyomeres may appear roundlike a droplet (fig. 1, D, F, G, J), or
elongated (fig. 1, I). They may be single (fig. 1, L) or multiple (fig. 1, H,