OBSERVATIONS ON CHROMOSOMAL MORPHOLOGY 
DURING SIMULATED INTRACORPOREAL RADIATION 
FROM NUCLEAR-POWERED ARTIFICIAL HEARTS 
Farouk A. Molokhia, William J. Robinson, Fred N. Huffman 
and John C. Norman* 
The study of chromosomal aberrations may offer a 
useful means of evaluating the effects of exposure to 
ionizing radiation. Chromosome studies were carried 
out in (1) two dogs with implanted 16 and 24- watt ^ Pu 
sources for 25 and 26 months, respectively, (2) four dogs 
with thoracic radiation equivalent sources (RES) com- 
parable to 24-watt "'■^ Pu sources but with negligible heat 
output for periods up to three years and continuing, (3) 
two dogs with abdominal RES capsules for 16 months 
I and continuing, (4) surviving offspring of RES-bearing 
: dogs for periods up to three years and continuing, and 
(5) three primates with abdominal RES comparable to 
50-watt Pu capsules for six months and continuing. 
Peripheral lymphocytes were cultured and prepared for 
karyotyping by the technique of Moorhead et al.' Fifty 
I mitoses were scored to detect aberrations in each prepa- 
I ration. Some chromosomal anomalies were noted in 
i cultures early in the observation period. These included 
chromosome gaps, breaks, rings and fragmentation, and 
chromatid gaps. Studies later in the observation period, 
however, showed normal chromosomal morphology in all 
radioisotope-bearing animals. The offsprings of RES 
parents also showed normal morphology and karyotypes, 
although the fetuses were 5-14 cm from the RES cap- 
sules during two months of gestation. Taken together, 
the accumulating data from multiple cultures over a 
three-year period suggest that prolonged intracorporeal 
irradiation of the magnitudes employed does not affect 
chromosomal morphology as determined by the tech- 
niques employed. 
INTRODUCTION** 
A totally implanted nuclear-powered artificial 
, heart or circulatory assist device would expose 
the patient to intracorporeal reject heat and 
radiation. Because the potential dangers have 
not yet been thoroughly documented, we have 
been studying the long-term effects of intra- 
corporeal heat and radiation in experimental 
* Prom the Department of Surgery, Harvard Medical School; the 
Cardiovascular Division, Sears Surgical Research Laboratories, Har- 
vard Surgical Unit, Boston City Hospital and the Thermo Electron 
I Research and Development Center, Waltham, Massachusetts. 
' *• Supported in part by N.I.H. contracts PH 43-66-982 and PH 43- 
67-1116. 
animals. Plutonium-238 (^^spu) heat exchang- 
ers with thermal outputs of 16 and 24 watts 
were implanted in dogs.^ At the same time, we 
have been studying effects of continuous intra- 
corporeal radiation in primates as well as in 
dogs at neutron and gamma exposure dose rates 
equivalent to 24 and 50 watt Plutonium-238 heat 
exchanger sources but with negligible thermal 
outputs.2'^ Radiation from the latter source is 
equivalent to projected clinical requirements 
for a proposed implantable nuclear-powered 
circulatory-assist device.^'^ 
The production of chromosomal aberrations 
by ionizing radiation offers a useful means of 
diagnosing radiation exposure.* In general, in 
the absence of complicating factors, an increase 
in chromosomal aberrations can be taken as an 
indication of radiation exposure.^ Under some 
circumstances, the frequency of chromosomal 
aberrations may even be used as a "biological 
dosimeter" to Jjrovide quantitative estimates of 
the magnitude of exposure.^ 
The purpose of this paper is to report hema- 
tologic and chromosomal data obtained to date 
from animals subjected to intracorporeal radia- 
tion for as long as 36 months. 
MATERIAL AND METHODS 
Implantation of Radioactive Capsules 
Blood-cooled nuclear-powered heat exchang- 
ers were implanted in series with the descend- 
ing thoracic aorta in two mongrel dogs. A 16- 
watt 238py capsule was implanted in one, an 
85-pound female (Plutina, #3779). She was 
monitored for 25 months, at which point she 
succumbed to pulmonary embolism, apparently 
unrelated to prolonged intracorporeal heat or 
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