EFFECTS OF WHOLE BODY IRRADIATION ON MARROW 479 Table 2.—“Mitotically Connected” Abnormalities in Bone Marrow Cells 3.5 Years after Accidental Exposure to Radiation Individuals Number of Ery throblasts Counted . Binucleated “Early” Erythroblasts per 1000 Binucleated “Late” Erythroblasts per 1000 Total Binucleated Erythroblasts per 1000 High dose group A 4050 4000 1.25 4.25 Cc D E 2000 2000 3000 2.5 0.5 1.3 4.0 1.0 4.0 B Low dose group F G H 1.4 5.1 6.5 1.5 5.3 x = 5.08 + 2.1 0.01 > p > 0.001 (compared to normal} 2006 3050 2000 0.5 0 0 ; 2.0 2.0 _ 0,0 F and G only: Comparisons SAK TMF EPC CRC 6.6 5.0 3000 4160 1000 2000 0 0.2 0 0 0.7 0.9 1.0 2.0 2.5 2.0 0.0 x2=15+10 x = 2.25 + 0.63 p > 0.05 (comparedto normal) 0.7 1.1 1.0 2.0 x = 12 + 0.48 group. From these numbers it appears that there is evidence for an increase in the frequency of multinucleated red cell precursors 3.5 years after the radiation accident in the high dose group whereas the findings are not significant in the low dose group. In contrast, the differences in the frequency of binucleated myelocytic cells between the normal and irradiated persons was not significant. It should be pointed out that the occurrence of early binucleated erythroblasts must be considered abnormal in particular, Such cells are shown in figure 4. Their nuclear and cytoplasmic characteristics correspond to those of proerythroblasts, and early and late basophilic normoblasts. Such immature binucleated cells are extremely rare in completely normal marrow smears in which they are mostly polychromatic or oxyphilic.®* Erythroblasts with three nuclei were found 3 times, and tripolar mitoses in three instances in smears of the high dose group. Among 53,167 erythroblasts of eight “normal” persons, not one pluripolar mitosis was seen by Berman.°? Mitotic indices in all eight men were determined in Feulgen-stained squash preparations, using the same technics as in 1958 to study mitotic indices early after the accident.** The results are given in table 3. The mitotic indices in the high dose group andin the low dose group were notstatistically different (p > 0.05) from the values found in seven healthy comparisons.”® In the squash preparations of the high dose group, the mitoses were distributed between the phases of the mitotic cycle in the proportions: prophase 15.3 per

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