E.S. Morrison

Experimental atherosclerosis in rhesus monkeys: I. Gross and light microscopy features and lipid values in serum and aorta☆

Abstract Forty-five rhesus monkeys were divided into five groups fed four different high-fat diets and a stock diet. The duration of feeding varied from 33 to 70 weeks. All monkeys fed the high-fat diets developed aortic proliferative lesions composed predominantly of spindle-shaped cells, most of them laden with lipid. The thickest of these proliferative lesions measured 0.85 mm, and most were thinner, suggesting that in the monkey receiving these high-fat diets some proliferative lesions can reach this range of thickness before undergoing necrosis. Atheromatous aortic lesions characterized by necrosis and the accumulation of lipid debris were found only in monkeys receiving high-fat diets for 70 weeks. In monkeys receiving a diet in which the lipid component was 30% peanut oil and 5% cholesterol, the fatty acid composition of the aorta was similar tothat in humans developing coronary artery atherosclerosis, in that the fatty acids showing the greatest accumulation were oleic and linoleic. The largest number of atheromatous lesions, however, was associated with a diet otherwise identical to the peanut oil-cholesterol diet but containing as its lipid component 30% butter and 5% cholesterol. This latter diet also resulted in higher serum lipid levels and higher aortic lipid levels per milligram of DNA than did peanut oil diet. High-fat diets fed to rhesus monkeys appear to produce both proliferative and atheromatous aortic lesions similar to those seen in the human as regards both light microscopy features and lipid composition. Work is now in progress assessing some of the metabolic features of these lesions.

Short-term feeding of unsaturated versus saturated fat in the production of atherosclerosis in the rat☆

Abstract Complex diets containing either 40% peanut oil, corn oil, or butter were fed to weanling rats for 3 months. The rats fed the peanut oil-containing diets developed intimal spindle cell lesions similar in many respects to early human atherosclerotic lesions. Rats receiving the butter-containing diets developed foam cell lesions which do not resemble human atherosclerosis. Under electron microscopy the spindle cells were of the smooth muscle type. They appeared more undifferentiated than the smooth muscle cells seen in aortic lesions in rats fed butter-containing diets for 12 months in a previous experiment. The primitive nature of the cells in the present experiment may have been due to their age, their unsaturated fatty acid environment, or other factors. The difference in serum fatty acids was possibly an important factor determining the type of lesion produced, since both the peanut oil- and butter-fed rats had much the same degree of hyperlipemia as shown by similar serum cholesterol and triglyceride levels. Both the peanut oil- and butter-fed rats showed a sharp drop in the relative percentage of serum arachidonic acid, even though the peanut oil-fed group had excessively high levels of serum linoleates. The absolute level of serum arachidonic acid, however, changed very little.

Coronary arteries of children and young adults: A comparison of lipids and anatomic features in New Yorkers and East Africans☆

Abstract Lipid classes (including fatty acids), crude protein, and calcium were measured in the coronary arteries of a total of 246 New Yorkers and East Africans from stillborn to 39 years of age. In subjects stillborn to 19 years of age a histological comparison of the arteries in the two groups was made. 1. (1) Starting at the end of the second decade New Yorker coronary arteries accumulate increasing amounts of cholesterol, in contrast to the findings in age-matched East Africans. 2. (2) The kinds of lipids (including fatty acids) in the coronary arteries of New Yorkers and East Africans were in general similar. This suggests that (as far as lipids are concerned), the type of arteriosclerosis is the same in both groups; the same conclusion is suggested by light microscopy observations. 3. (3) The selective accumulation of certain cholesterol esters and not of other lipids in the coronary artery suggests that the process is a dynamic one, and does not depend on simple filtration from the blood.

Glucose degradation in normal and atherosclerotic aortic intima-media

Abstract Pathways of glucose degradation and 0 2 uptake were measured in intimamedia of normal swine, rabbits and monkeys, and in atherosclerotic intima-media of rabbits and monkeys. In the normal aortas most of the glucose was degraded to lactic acid, with very little entering the Krebs cycle or pentose shunt systems. Only small amounts ended up as lipid, RNA-DNA-protein, or glycogen. In the atherosclerotic aortas, glucose utilization more than doubled per mg DNA, but again virtually all of it was converted to lactic acid. The 0 2 uptake per mg DNA sharply increased in the atherosclerotic tissue, but no more glucose entered the Krebs cycle than in the normal artery tissue. It thus appears that neither in normal nor in atherosclerotic artery wall is glucose an important substrate for oxidative phosphorylation.

Uptake, oxidation, and esterification of free fatty acids in normal and atherosclerotic rabbit aorta.

Abstract Intimamedia tissue from atherosclerotic rabbits showed a 15-fold increase in the amount of [U- 14 C]palmitic acid oxidized to CO 2 compared to normal intimamedia. The findings suggest that oxidation of free fatty acids may at least in part contribute to the increased oxygen uptake seen in atherosclerotic tissue. The concentration of endogenous free fatty acids in atherosclerotic tissue was much higher than in normal tissue. The higher level may have been partly due to the increased levels of serum free fatty acid in the atherosclerotic rabbits, and to the increased permeability of atherosclerotic intimamedia to free fatty acids demonstrated in vitro . The tissue from atherosclerotic rabbit aortas exhibited a different pattern of fatty acid esterification than did that obtained from control aortas. In atherosclerotic tissue more cholesterol ester than triglyceride was formed from palmitate. In determining the specific activity of the free fatty acid tissue pool(s), equilibration of medium and tissue free fatty acid was found to be slow. In addition, the amount of free fatty acid in aorta was substantial and somewhat variable from animal to animal. Therefore, it was necessary to base calculations of fatty acid metabolic pathways on the specific activity of the palmitate in the tissue and not on that of the medium.

Aortic respiration and glycolysis in the pre-proliferative phase of diet-induced atherosclerosis in swine

Summary Cholesterol or stock diets were fed to fourteen pairs of miniature swine for periods varying from 3 to 112 days. Measurements of respiration, aerobic and anaerobic net lactic acid production and lipid content were done in grossly normal intima-media from the upper thoracic aorta in both dietary groups. Intima-media respiration was significantly higher per unit of DNA in the cholesterol-fed swine than in stock-fed swine. This was so even before any grossly visible atherosclerotic lesions were apparent and before there was any light microscopy or biochemical evidence of cell proliferation, but when pre-proliferative changes were presumably present. The aerobic and anaerobic net lactic acid production however were the same in the aortic tissue of both the cholesterol and stock-fed groups. Both total cholesterol and phospholipid were increased in concentration in the grossly normal intima-media after 44 days of feeding the cholesterol diet. The increased tissue respiration before the appearance of atherosclerotic lesions characterized by smooth muscle cell proliferation may mean that the intima media of the swine is synthesizing more ATP or high energy intermediates. That there might be an increased demand for energy in the artery associated with cholesterol diets in swine is suggested by electron microscopy and autoradiographic studies of the pre-proliferative phase of cholesterol-induced atherosclerosis in the same animals as were used in this experiment.

Chemico-anatomic studies of arteriosclerosis and thrombosis in diabetics: II. Fatty acids of adipose tissue and plasma lipids in several groups of North American diabetics and nondiabetics

Abstract It has been well established by both clinical and autopsy studies that myocardial infarction is much more common in North American white diabetics compared with nondiabetics. In this study the possible interrelationships between myocardial infarcts, diabetes and adipose tissue fatty acids and plasma lipids were studied by comparing diabetics unselected as to the presence or absence of complications with age- and sex-matched nondiabetics. Adipose tissue fatty acids were measured because of the suggested abnormal release of fatty acids from tissue stores in the diabetic. Only palmitic acid of six adipose tissue fatty acids compared in diabetics and nondiabetics was found to be significantly different, and this only in female diabetics, compared to female nondiabetics. The biologic significance of this finding is questionable. The finding of similar linoleic acid values in North American diabetics and nondiabetics suggests that there is no deficiency of linoleic acid in the diabetic adipose tissue stores contributing to the greater incidence of myocardial infarction in this group. Among plasma lipids, no difference was found in comparing plasma cholesterol levels. However, triglycerides (in both male and female diabetics) and lipid phosphorus (in female diabetics) were found to be elevated when compared to levels in nondiabetics. The elevated serum triglycerides in the diabetic group in this study is in keeping with the serum triglyceride levels found in other groups of diabetics who have strikingly different frequencies of myocardial infarction. North American white, North American Negro, and East African diabetics, with a high, intermediate, and low frequency of myocardial infarction respectively showed high, intermediate, and low levels of serum triglyceride. Although the evidence is far from complete, there is at least some reason to believe that plasma lipids are involved in the clotting mechanism. It is possible that the elevated plasma lipids found in this group of diabetics may explain the greater susceptibility to coronary artery thrombosis and myocardial infarction in diabetes.

Effects of methyl prednisolone and colchicine on the development of aortic atherosclerosis in swine

The effect of methyl prednisolone and colchicine on the development of both the early proliferative and advanced atherosclerotic lesion in swine aorta was studied. In order to accelerate the development of atherosclerosis, the abdominal aortic endothelium was partially denuded by a balloon before the animals were placed on either a moderate or severe hypercholesterolemic diet. Neither drug in either dietary group inhibited the development of atherosclerosis. Swine receiving methyl prednisolone and severe hypercholesterolemic diet actually had a significantly greater number of the advanced necrotic lesions and more arterial calcification than the group receiving the atherogenic diet alone. In addition, the thoracic aorta of swine receiving the moderate hypercholesterolemic diet and methyl prednisolone showed larger amounts of lipid than did the non-drug fed control group. In swine receiving the moderate hypercholesterolemic diet, methyl prednisolone significantly raised serum cholesterol levels. Colchicine only slightly worsened the atherosclerosis in swine aorta and had no effect on serum cholesterol levels.

A method for isolating aortic mitochondria exhibiting high respiratory control.

Abstract A method for isolating tightly coupled mitochondria from an intima-media strip of swine aorta has been devised. The most important differences from previous methods were the use of a special device for mincing the aorta into a fine gruel before the homogenization, the incubation of the homogenate with elastase before centrifugation, and the use of an electrolyte-based medium for homogenization and centrifugation of the tissue rather than sucrose. The method resulted in the recovery of enough mitochondria from a single aorta so that a number of determinations could be performed. The respiratory control ratios using succinate, glutamate, glutamatemalate, and pyruvate-malate were 4.3, 8.2, 8.8, and 9.2, respectively. β-OH butyrate functioned very poorly as an electron donor under the conditions used in this experiment. Judging from their functional characteristics after rather rigorous treatment during isolation, swine aortic mitochondria, like cardiac mitochondria, are relatively resistant to damage.

Chemico-anatomic studies in geographic pathology. A comparison of lipids in New Yorker and African coronary arteries.

Abstract Many young adult New Yorkers have previously been shown to have a greater amount of arteriosclerosis than young adult Africans. This study of 5 Africans and 20 New Yorkers was carried out to learn if rather complex chemico-anatomical comparisons of coronary arteries of New Yorkers and Nigerians might provide some insight into the quantiative differences in arteriosclerosis in the two groups, and provide information to enable us to plan a large scale study of such groups. As expected, some of the coronary arteries of New Yorkers of comparable age to the Africans showed considerably more arteriosclerosis and higher total lipid contents than the Nigerian coronary arteries. The fatty acid content of the two groups of arteries, New Yorker and Nigerian, were also somewhat different. The New Yorker coronary arteries had higher oleic acid, and a lower palmitic and stearic acid than did the Nigerian arteries. The fatty acid patterns suggested that the kind of arteriosclerosis, as well as its amount, might be different in the two groups of arteries analyzed. While more investigation needs to be done with much larger numbers, and a broader range of fatty acids, this qualitative difference in the coronary arteries of young New Yorkers and Nigerians may in part explain the different biologic behavior of arteriosclerosis in the two groups.