922 
GENETIC AND BIOLOGICAL EFFECTS OF RADIATION 
oped detectable bone tumors. Five of the ani- 
mals were 125 /itCi/day offspring, and two of 
these had multicentric tumors. They had re- 
ceived ^Sr throughout their life and died at 
744-1210 days of age. The remaining two ani- 
mals with bone neoplasia were 625 ju,Ci/day 
offspring that received 156 jnCi ^^Sr/day for 
approximately 6 weeks after weaning and then 
were removed from further radionuclide inges- 
tion for 1,093 and 1,561 days before death. Ac- 
cumulated skeletal radiation doses ranged from 
9,000-15,000 rads in both the 125 and 625 fiGi 
offspring. Nine of the eleven bone tumors were 
located in the head region, and one each in a rib 
and ulna. 
Histologically, 73% of these tumors were 
classified as osteosarcomas, 27% as giant cell 
tumors or osteoclastomas, and in most cases 
they appeared to arise from the periosteal sur- 
face. A detailed description of these tumors has 
been previously reported. 
Chromosomal Effects 
Bone marrow cells obtained from animals at 
the higher dose levels (625 and 125 yuCi/day) 
contain a greater number of one-break abnor- 
malities than are observed in the control swine. 
However, no consistent chromosomal abbera- 
tions have been noted in those animals that 
have developed hematopoietic neoplasms. 
Hematopoietic Effects 
Peripheral Blood. The effects of chronic ''"Sr 
ingestion on the peripheral blood values are 
best demonstrated at the highest feeding level, 
i.e., 3100 /xCi/day (Figure 1). Four weeks after 
9-month-old animals were started on ^''Sr 
ingestion, the platelet, segmented neutrophil, 
and lymphocyte values were reduced to approxi- 
mately 50% of the preexposure levels. These 
continued a steady decline until death occurred 
approximately 3 months later. There was a lag 
in erythrocyte response, compared with other 
cellular elements, and the effect was less pro- 
nounced until near the time of death. Erythro- 
cyte depression was, however, similar in magni- 
tude to that observed in leukocytes and platelets. 
These animals failed to survive the gestation 
period so there was no Fl generation for study. 
A similar sequence of events was observed 
with 625, 250 and 125 (jlCi ^oSr/day, although 
the magnitude of change and time of death 
shifted to a longer interval as the daily ^"Sr 
feeding level was reduced. Original animals 
started on 625 fiCi/day survived 9-12 months, 
so were able to produce an Fl generation, which 
if maintained on ^^Sr after weaning, survived 
only about three months. 
The Fl generation, 250 /^Ci 9«Sr/day, ani- 
mals experienced pronounced depression in 
platelets and leukocytes, and 6 of 20 died of a 
hemorrhagic syndrome by 7 months of age. With 
the exception of two animals, ^^Sr feeding was 
discontinued at 200 days of age. This resulted 
in partial recovery of peripheral blood leuko- 
cytes and platelets. One of the animals removed 
from further ^^Sr feeding developed a neopla- 
sia characterized by an abnormal serum protein 
and plasmacytoid cells in the blood and marrow, 
which has been tentatively diagnosed as multi- 
ple myeloma. 
At 125 /u,Ci/day, original animals lived 4-6 
years with moderate development of thrombo- 
il 1 1 > 
0 4 8 12 
WEEKS ON Sr^ 
HEMATOLOGIC EFFECTS OF 3100 uCi Sr'^/DAY ' 
I 
Figure 1. — Hematologic Response of a Miniature Pig , 
Ingesting 3,100 ^Ci ""Sr/day. 
