ARTERIOSCLEROSIS AND OTHER VASCULAR DISEASES IN 
ZOO AND LABORATORY ANIMALS 
C. stout and F. 6ohorquez* 
The material to be presented was gathered during a 
five-year period from autopsies on animals dying in the 
Oklahoma City Zoo and the psychological research lab- 
oratory of Dr. W. B. Lemmon at the University of 
Oklahoma. Aortas and epicardial coronary arteries 
from large hearts were removed, flattened on card- 
board, stained with Sudan IV and graded for intimal in- 
volvement using a modification of the method originally 
described by Holman. Contiguous microscopic sections 
of the various arterial lesions were stained with Oil Red 
O, H & E and Weigert's elastic stain. Typical athero- 
sclerotic lesions were found in many of the birds, and 
smaller atherosclerotic lesions were found in a variety 
of other mammals, including anteaters, aardvarks and 
Zebu cattle. Atherosclerotic lesions were also common 
in nonhuman primates, particularly squirrel monkeys 
and chimpanzees. Chimpanzees were the only animals 
in which significant atherosclerotic lesions were present 
in the large coronary and cerebral arteries. None of 
these lesions were of clinical importance, however. Pro- 
liferative intimal lesions consisting primarily of smooth 
muscle cells were found in almost every species exam- 
ined. In seals and sea lions, these lesions were distrib- 
uted in the aorta in a fashion similar to that seen in ath- 
erosclerosis in man. It was interesting that no lipid was 
present in the lesions of the seals and sea lions, particu- 
larly since lipid insudation is thought to stimulate 
smooth muscle cell proliferation in the early stages of 
human atherosclerosis. It was also interesting that 
mural thrombi were almost never seen. 
INTRODUCTION** 
Studies of spontaneous vascular lesions in an- 
imals are important for several reasons. Con- 
ducted in a particular species, such as the work 
of Clarkson in pigeons,^ Middleton in squirrel 
monkeys,^ McGill in baboons,^ Moreland in 
miniature svi^ine,* Malinow in hoM^ler mon- 
keys,'^ and others,*' they provide baseline 
data for comparison with experimentally in- 
duced arterial lesions in that species. Conducted 
• Department of Pathology, University of Oklatioma Health 
Sciences Center, 800 N. E. 13th Street, P. O. Box 26901, Oklahoma 
City, Oklahoma 73190. 
** Supported by Grant HE 08725 from the National Heart In- 
stitute, U.S. Public Health Service. 
in a large number of species, such as the work 
of Fox'' and Ratcliffe^ at the Philadelphia Zoo, 
Vastesaeger^ at the Antwerp Zoo, Finlayson^*' 
at the London Zoo, and others,®'^^'^^ they pro- 
vide a panorama of the types of lesions which 
may occur in the animal kingdom. Studies of 
the latter type may also identify animals or dis- 
eases which are suitable for more intensive in- 
vestigation, the so-called animal models. A list 
of such animal models has recently been com- 
piled by Cornelius. Most importantly, studies 
of animals in natural or captive surroundings 
may provide insights into mechanisms opera- 
tive in health and disease. Examples of the lat- 
ter would include the association of adequate 
nutrition with the decreasing incidence of death 
from infectious disease, and the association of 
social stress with the increasing incidence of 
myocardial fibrosis and stenosis of the small in- 
tramyocardial arteries in mammals and birds in 
the Philadelphia Zoo." 
The studies to be reported in this communica- 
tion were done between 1964 and 1968 at the 
Oklahoma City Zoo. From over 500 autopsies, a 
variety of arterial intimal and medial lesions 
have been selected for presentation. In addition, 
two animal models will be described, one with 
morphologic changes similar to those in pre- 
eclampsia in humans, and the other with morph- 
ologic changes similar to those in essential hy- 
pertension in humans. 
MATERIALS AND METHODS 
In 1964, the University of Oklahoma Health 
Sciences Center opened the Institute for Com- 
parative Pathology in conjunction with, and on 
the grounds of the Oklahoma City Zoo. The lab- 
oratory was remodeled for pathologic studies 
with funds from the National Heart Institute 
(HE 08725) and the Oklahoma Zoological So- 
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