920 
GENETIC AND BIOLOGICAL EFFECTS OF RADIATION 
their dams' level. This was increased by 25 % of 
the destined '"'Sr dose every six weeks, so that 
by 6 months of age they were at full level. This 
regimen permitted the dietary calcium-stron- 
tium ratio to remain constant during the rapid 
growth of adolescence. 
Over 700 miniature swine representing 3 gen- 
erations have been exposed to ^°Sr at 1, 5, 25, 
125, 625, and 3100 /xCi/day over the past 13 
years. In addition, there have been approxi- 
mately 200 female controls. 
A second major group, comprising 47 minia- 
ture swine, have been exposed to ^°Sr at 5 dif- 
ferent periods: (1) in utero only, (2) nursing 
only, (3) in utero and during the nursing pe- 
riod only, (4) from conception throughout 
adult life, and (5) from the nursing period and 
throughout adult life (Table I). The dams, and 
those oiTspring continuing on ^°Sr, received 125 
/iCi/day. The offspring are being held for life- 
time observation. 
The animals were kept in groups of 3 to 6 
swine per pen within controlled temperature 
buildings. Individual feeding stalls were utilized 
within each pen so that strict dietary control 
could be maintained. The ^°Sr chloride solution 
fed these pigs was absorbed into a large feed 
pellet which was fed with the morning ration. 
Blood samples were obtained at intervals 
from the anterior vena cava using commercially 
available evacuated tubes.* Routine hematologic 
and serum biochemistry parameters were deter- 
mined using the Coulter Model B, and more re- 
cently the Coulter Model S, and the Technicon 
Autoanalyzer. Methods of analysis have been 
previously reported.^ Bone marrow samples 
were aspirated, (without the use of anticoagu- 
lants) , from the sternum using a Rosenthal nee- 
dle. 
About 250 animals have been killed at various 
♦ Becton-Dickinson Vacutainer 
Table I. — Experimental Design Uterine-Milk Exposure 
Study 
GROUP 
DAM 
Sr™ EXPOSURE 
NO. 
RUCF 
125 ^Ci 
IN UTERO ONLY 
10 
CURN 
CONTROL 
NURSING ONLY 
10 
RURN 
125 ^Ci 
IN UTERO & NURSING 
8 
CURE 
CONTROL 
NURSING & FEED 
10 
RUFi 
125 ^Ci 
IN UTERO, NURSING & FEED 
9 
ages for the express purpose of determing the 
tissue distribution of the deposited ®^Sr, and to 
evaluate the early effects of the radionuclide 
ingestion. The remainder have been maintained 
for lifetime observation and killed as their clini- 
cal condition dictated. At death, complete gross 
and histologic examinations were performed on 
all tissues and autoradiograms made on selected 
cases. 
Cytogenetic studies were performed by stand- 
ard methods on peripheral leukocytes and as- 
pirated bone marrow.® 
RESULTS 
Radiation Dose 
The methods of dosimetry and assays for skel- 
etal ^^S>r accumulation in miniature swine in- 
gesting 1 thru 625 fiCi ^"Sr per day from birth 
to approximately 8 years of age have been re- 
ported by Palmer et al.^ Original sows started 
on daily '•'^Sr at 9 months of age accumulated a 
^°Sr body burden approximately 7.5 times the 
daily intake, whereas the Fl and F2 genera- 
tions reached about 10 times their daily intake. 
Less than 1% of the absorbed ^"Sr was located 
in soft tissue, so that the radiation dose to extra- 
osseous tissue was approximately 1/1,000 that 
received by bone. The radiation received by the 
ovaries was essentially the same as other soft 
tissues. 
Thermoluminescent dosimeters were used to 
determine the radiation dose to fetuses at var- 
ious periods during gestation. At approximately 
midway in gestation (55 days) , the dose rate to 
the fetuses of dams ingesting 125 )LiCi/day was 
approximately 28 mrad/day, whereas at term a 
mean dose rate of approximately 50 mrad/day 
was obtained. The osseous tissue dose rate at 55 I 
days was approximately 50 times that received I 
by soft tissue, and 500 times greater at term. I 
There was no significant maternal contribution i 
to the radiation dose received by the fetal i 
thymic area. The accumulated radiation to a j 
term fetus would be about 50 rads from a 125 t 
/LtCi/day dam, and approximately 400 mrads 
from a 1 /iCi/day dam. ' 
1 
