472,
FLIEDNER, ANDREWS, CRONKITE AND BOND
and preliminary results of these cytologic studies have been published previously.23-27
MATERIALS AND METHODS
(a) Exposed persons:* Eight men received a mixed neutron-gammairradiation as a result
of a critical excursion during the processing of waste Uranium?35 solution. The doses were
estimated to be (whole body): Patient A: 365 rads; B; 270 rads; C: 339 rads; D: 327 rads;
E: 236 rads (“high dose” group), and Patient F; 68.5 rads; G: 68.5 rads; and H: 22.8
rads (“low dose” group).
{b) Early studies: Bone marrow aspirations were performed in the high dose group 12
hours, and 2, 4 or 5, 9 or 10, 16, and 23 days after the accident, and in the low dose
group 4 and 10 days after the accident. The general findings in the marrow smears and
sections have been published,? as well as the results of mitotic index studies?*® using
Feulgen-stained squash preparations, In this study marrow smears were prepired on
cover slips, dried and stained with Wright’s stain. They were evaluated in two ways.
(1) In each smear, 500 erythroblasts (including proerythroblast, early and late basophilic
normoblasts, polychromatic and oxyphilic normoblast) were counted. All “mitotically
connected abnormalities” (M. C. Abn) seen during this counting in this and any other
marrow cell line were recorded and are reported per 100 erythroblasts. Other cytologic abnormalities were described qualitatively. (2) In each smear made during the first few days
after exposure, 2000 nucleated cells were counted to determine the initial mitotic indices.
(c) Late studies: Three and one-half years after the accident (Nov. 1, 1961) some of
the studies performed early after exposure were repeated. Marrow aspirations were per-
formed and the smears scanned for cytologic abnormulities. For these studies, at Teast
2000 nucleated red cell precursors were counted in each smear and the abnormalities
recorded. In addition, at least 100 mitotic figures were examined in each smear for cytologic
abnormalities and classified into erythrocytic, myelocytic, and “others” (not identified with
certainty). The mitotic indices were determined in Feulgen-stained squash preprrations
with the same technic as used before,28 by counting a total of 5000 nucleated cells (1000
on five different slides). From these total mitotic index values and from the differential
count of mitoses performed on the Wright-stained smears, the specific mitotic index for
ervthropoiesis and myelopoiesis was computed.
(d) Normal controls: Control values for the mitotic index determinations in Feulgenstained squash preparations, and of the distribution of mitoses in marrow smears prepared
and stained by standard methods, have been reported.28.28 These were derived from
studies in seven healthy males in an age group comparable to that of the exposed persons.
In the marrow smears of four of these men, a total of 10,000 nucleated red cell precursors
were counted to determine the frequency of cytologic abnormalities in interphase cells
and mitoses,
,
RESULTS
A. Cytologic Manifestations of Radiation Injury Early after Exposure
As reported previously’ the cellularity of the marrow did not appear to
be markedly abnormal in the 12-hour and 2-day samples while a mild decrease wasfelt to be present on days 3 and 4. In these samples, the erythroidmyeloid ratio decreased during the Ist week. A more detailed cytologic ex-
amination disclosed a number of abnormalities. These are characteristic of
radiation injury, although not “specific” for exposure to ionizing radiation
since they can be seen in patients receiving cytotoxic chemotherapy.
*The clinical management of the exposed persons was performed at the Medical
Division, Oak Ridge Institute of Nuclear Studies. The continuous support and collaboration
of the medicalstaff, in particular Drs. Sitterson and Kretchmar, is gratefully acknowledged.