Production of atheromatosis in the aorta of the bird by the administration of diethylstilbestrol

Sustained hyperlipemia induced in rabbits by means of intravenously injected surface-active agents

The intravenous injection of the surface-active agents Tween 80 and Triton A20 into rabbits fed a normal diet resulted in marked and sustained elevations of the cholesterol, phospholipid, and total lipid content of their blood. The increase in phospholipid in general paralleled that of the blood cholesterol. The implications of the findings are briefly discussed.

The effect of alloxan diabetes on experimental cholesterol atherosclerosis in the rabbit. III. The mechanism of the inhibition of experimental cholesterol atherosclerosis in alloxan-diabetic rabbits

A study of the serum lipids in normal and alloxan-diabetic rabbits during the course of cholesterol feeding is presented, particular attention being paid to the factors considered to be responsible for the stability of the serum lipids; namely, (1) their interrelations and (2) their association with the serum proteins. As far as the interrelations of the lipids were concerned a definite correlation was found between the development of atherosclerosis and an increase of serum cholesterol that was out of all proportion to the increase of serum lipid phosphorus and neutral fat. When these last two lipid constituents rose almost parallel with the serum cholesterol (as they did in some alloxan-diabetic rabbits), then the development of atherosclerosis was inhibited. This correlation was independent of the diabetic state, per se. It appeared likely that the marked elevation of serum neutral fat and lipid phosphorus in the diabetic animals was due to mobilization of body fat because of the disturbed carbohydrate metabolism. Because of their hydrophilic and emulsifying properties, it was thought probable that the elevation of the phospholipids was the important factor responsible for the stability of serum cholesterol. That neutral fat played a role, however, could not be denied. In normal rabbit sera, as we have previously shown, only small proportions of the lipid phosphorus and cholesterol are "readily extractable" (i.e., unattached or only loosely attached to protein). On the other hand, in every case in which the serum lipids were elevated, the greater proportion of the lipid phosphorus and cholesterol was "readily extractable," irrespective of whether atherosclerosis developed or was inhibited. Analysis of the lipid content of the aorta of rabbits not fed cholesterol, whether diabetic or non-diabetic, and from alloxan-diabetic rabbits fed cholesterol but protected from the development of atherosclerosis, showed that there was no significant difference in lipid content or composition among the animals of these groups. When atherosclerosis developed following cholesterol feeding, the lipid composition of the aortas was essentially the same in both control and diabetic animals. The deposited lipid consisted predominantly of cholesterol with small and fairly constant proportions of other lipids that did not vary significantly regardless of the quantities of these other lipids present in the circulating blood. In the less severe lesions the proportion of ester cholesterol was greater than that of free cholesterol, but in advanced lesions the reverse was true. The following conclusions are drawn concerning the pathogenesis of experimental cholesterol atherosclerosis in the rabbit: 1. Instability of cholesterol in the blood rather than hypercholesterolemia, per se, is the general condition responsible for the deposition of this substance in the arterial walls. 2. Of the two factors considered to be responsible for the stability of the lipids in the blood, the interrelations of the lipids appear to be more important than their relation to the serum proteins, at least in so far as the development of experimental cholesterol atherosclerosis is concerned. The importance of these conclusions in relation to the pathogenesis of human atherosclerosis is discussed.

The influence of intravenously administered surface-active agents on the development of experimental atherosclerosis in rabbits

A study was made of the relationship of blood lipids to the development of experimental atherosclerosis. Rabbits fed a diet containing cholesterol were found to develop hyperlipemia characterized by a great increase in blood cholesterol and a much lesser increase in blood phospholipids; after several weeks they manifested conspicuous atherosclerosis of the aorta, as has often been observed by others. Comparable rabbits fed the same diets containing added cholesterol were given in addition repeated intravenous injections of the surface-active agents Tween 80 and Triton A20; these animals developed hyperlipemia which was characterized by a great increase in blood cholesterol and an equivalent or even greater increase in phospholipids, and they had much less atherosclerosis than did the control rabbits fed cholesterol alone. In further experiments it was observed that repeated intravenous injections of Tween 80 did not result in resorption of previously induced atherosclerosis in rabbits. The findings are discussed in relation to the pathogenesis of natural and experimental atherosclerosis.

Angiotoxicity and atherogenicity of cholesterol oxides

Cholesterol in the diet can readily autoxidize and be absorbed and transported in plasma lipoproteins. Cholesterol oxides can also be endogenously produced in tissues via free-radical-induced reactions. Some cholesterol oxides, notably cholestane-3 beta, 5 alpha, 6 beta-triol and 25-hydroxycholesterol, have been shown to cause injury to vascular endothelial and smooth muscle cells, to alter LDL receptor function, to enhance cholesteryl ester accumulation, to inhibit prostacyclin production, and to induce experimental atherosclerosis alone or in combination with cholesterol. An epidemiological study examining relationships between atherosclerosis and plasma levels of cholesterol oxides as independent risk factors may provide additional insights regarding the roles of cholesterol oxides in atherogenesis.

Occurrence of lipid oxidation products in foods

Lipid oxidation products are ubiquitous in foods, although much variation exists in the levels present. Although these levels are generally low, the problem of lipid oxidation severely compromises the quality of some foods and limits the shelf-life of others. Lipid oxidation represents a key barrier in the development of new food products and processes, especially convenience items and processes required to manufacture them. Deleterious changes in foods caused by lipid oxidation include loss of flavour, development of off-flavours, loss of colour, nutrient value and functionally, and the accumulation of compounds which may be detrimental to the health of consumers. All foods that contain lipids are susceptible to oxidation but especially affected are foods which are dehydrated, subjected to high temperatures or cooked and subsequently stored, e.g. dehydrated eggs, cheeses and meats, foods fried in frying oils, and cooked (uncured) meats. Specific examples of compounds which are of health concern include lipid peroxides and the free radicals involved in their formation and propagation, malonaldehyde, and several cholesterol oxidation products. Coronary artery disease (CAD) may be in part caused by the consumption of lipid oxidation products.

Effects of estrogen administration on the lipoproteins and apoproteins of the chicken

The plasma lipoproteins of estrogen-treated and untreated sexually immature hens have been compared with respect to their concentration in plasma, protein and lipid composition, particle size, and and apoprotein composition. Administration of diethylstilbestrol resulted in a 400-fold rise in the concentration of very low density lipoprotein (VLDL), a 70-fold rise in low density lipoprotein (LDL), and a marked reduction in high density lipoprotein (HDL) protein. It also resulted in the production of LDL and HDL which were enriched in triacylglycerol, while the proportion of cholesterol in all three lipoprotein fractions decreased. In contrast to the lipoproteins from untreated birds, lipoproteins of density less than 1.06 g/ml from estrogen-treated birds were not clearly separable into discrete VLDL and LDL fractions, but appeared to be a single ultracentrifugal class. The apoprotein composition of VLDL and LDL from untreated birds differed from each other; however, the apoprotein patterns of VLDL and LDL from estrogen-treated birds were indistinguishable: both contained a large amount of low molecular weight protein in addition to the high molecular weight component that predominates in the untreated state. The apoprotein composition of HDL was also markedly altered by estrogen administration: the 28,000 mol. wt. protein (apo A-I) decreased in amount from 65% to less than 5% of the total, while a low molecular weight (Mr = 14,000) protein and as yet poorly defined high molecular weight components became predominant. These observations indicate that the hyperlipidemia induced by estrogen administration is accompanied by marked alterations, both qualitative and quantitative, in the plasma lipoproteins.

Degenerative Changes in the Cardiovascular System of the Spawning Pacific Salmon ( Oncorhynchus tshawytscha )

In a stndy of the cardiovascular system of spawning Pacific salmon, degenerative changes were found in the heart muscle, coronary and visceral arteries, and capillaries of the kidney glomeruli. The heart muscle showed vacuolization of the muscle fibers with loss of fibrils, deposition of collagen, and cartilaginous meta plasia. Changes in the coronary and visceral arteries consisted of intimal hyperplasia with deposition of mucopolysaccharides, disruption of the internal elastic membrane, and destruction of adjacent muscle fibers in the media. The glomerular capillaries showed marked sclerosis. The resemblance of the arterial changes in the salmon to the beginning mani festations of arteriosclerosis in man, mammals, and birds is pointed out, and the relationship of the salmon's state of hyperadrenoeorticism to the occurrence of the vascular lesions is discussed.

Prolonged Δ 4 -Cholestenone Feeding in Birds

The pathologic changes in the aorta, liver, and adrenal glands, and the changes in sterols of plasma and liver induced in birds by the prolonged feeding of a diet containing 0.5 per cent Δ 4 -cholestenone are described. Lesions were found in the media of thoracic aortas and intima of the abdominal aortas of the sterol-fed birds and evidence is presented to show that the crystalline material in the abdominal plaques is not cholesterol. There was enlargement of both liver and adrenal glands with a pronounced deposition of total digitonin-precipitable sterols which could not be accounted for by Liebermann-Burchard reacting sterols (LBRS). In the Δ 4 -cholestenone-fed birds the level of LBRS in plasma, fell to about 50 per cent of that in control birds, whereas the levels of total digitonin-precipitable sterols (TDPS) rose to values of 200 mg. per 100 ml. The fraction of the TDPS present as non-LBRS was quite constant in the plasma of the sterol-fed birds (63-69 per cent). By means of isotope dilution procedures the non-LBRS in the livers of sterol-fed birds was identified as dihydrocholesterol.

Does the ingestion of alcohol influence the development of arteriosclerosis in fowls?

The effect of alcohol ingestion upon the development of naturally occurring and stilbestrol-induced arteriosclerosis was studied in the domestic fowl. In two experiments, a 15 per cent ethyl alcohol solution was used for drinking purposes, and in a third experiment wine containing 12 per cent of it was administered. The caloric intake of both food and alcohol was carefully controlled by pair-feeding, a glucose solution being used for drinking purposes to equalize the caloric intakes of the control birds with those of the alcohol-treated birds. A total of 224 cockrels was studied, and the period of observation for each experiment lasted 12 months. The degree of arteriosclerosis in the thoracic and abdominal aortas was determined in the gross and microscopically, and the degree of lipide infiltration was determined microscopically. The gross grading of arteriosclerotic lesions agreed closely with the microscopic analysis of intimal thickening and lipide infiltration of the arterial wall. The gross gradings were subjected to a critical statistical analysis which allowed precise statements to be made on the probability that a real effect would be overlooked. This analysis yielded no evidence that alcohol or the wine used had affected the degree of gross arteriosclerosis or lipide infiltration.

The inhibition of coronary atherosclerosis by estrogens in cholesterol-fed chicks

Chronic administration of estrogens parenterally inhibits coronary atherogenesis in cockerels fed a cholesterol-supplemented diet, although no such prophylactic effect was observed against aorta atherogenesis. This protection of the coronary vessels is associated with depression of the plasma total cholesterol-lipid phosphorus ratio toward normal levels consequent upon estrogen-induced hyperphospholipemia.