K. T. LEE, J. JARMOLYCH, D. N. KIM AND W. M. LEE 
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in this fine model to determine the exact point 
just before a pig is going to have an infarct so 
that you could study the effects of ischemia? Do 
you have, for example, some set protocol when- 
ever you do coronary angios every set period of 
time, or say a stress test of this type? 
Dr. Lee: The answer is we cannot predict 
when a particular pig is going to drop dead. 
Quite a number of our final electrocardio- 
grams were taken before or during a pro- 
cedure involving strain such as when we pull the 
pigs out of the cage for anesthesia for the angio- 
grams and at that time some of the pigs develop 
ventricular fibrillation. But it is diflftcult to 
determine by looking at the pig whether he is 
going to die suddenly. We lose pigs sometimes 
while doing angiograms as a result of lethal 
arrhythmia's which we have not been able to 
prevent entirely. We sometimes use anti-arrhy- 
thmic drugs, but their effectiveness is ques- 
tionable. 
Chairman : Dr. Lee, what is the actual time 
sequence of your experimental protocol ? Do you 
irradiate and then start feeding, and would you 
assume that if you started feeding, say for eight 
months, and if you then irradiated, would the 
time needed for producing the occlusion be de- 
creased or remain unchanged? 
Dr. Lee : I failed to mention my time schedule 
for feeding and X-ray. When we get the pigs, 
we condition them until they reach about 10 
kilograms in weight. Then they are fed an 
atherogenic diet for approximately two months 
in order to increase their cholesterol levels to 
those levels that I showed you earlier. At the 
end of this time the first x-irradiation is given 
and this is followed by the second x-irradiation 
in one month. Approximately 2 months after the 
last x-irradiation the pigs begin to die suddenly. 
The entire experimental procedure takes about 
five to six months. 
D. M. Kramsch, Boston University Medical 
Center, University Hospital, Boston, Mass. : 
Dr. Lee, we know from your previous work that 
you could use irradiation without uracil, bile 
acids, and cholesterol, which will cause quite se- 
vere coronary artery lesions in pigs, yet no my- 
ocardial infarction. Now this makes one wonder 
whether true X-ray irradiations damage only 
the arteries or the myocardial muscle cells as 
well? You showed lesions in the intimal small 
vessels ; the same agent must have gone through 
the myocardial muscle cells. My question is, did 
you perhaps study, by electron microscopy or 
biochemically, any irreversible damage in the 
myocardial muscle cells? What happened to the 
CBK enzyme system? 
Dr. Lee : Yes, we produced quite a severe le- 
sion, previously without x-irradiation as I men- 
tioned in my introduction, but none was fol- 
lowed by myocardial infarction. We like to 
believe that with X-ray and with this regimen, 
the lesion is more severe, and also, in this way, 
possibly not only large vessels but also smaller 
vessels are involved, as I demonstrated in the 
picture. Accordingly, this would increase the 
chances of an infarct. 
Myocardial biochemical studies are done in 
our laboratory at present. We are finding some 
decreased production of ATP and increased ox- 
ygen uptake on these myocardiums. But whether 
or that has a direct impact on infarction, I do 
not know. 
