S. Lindsay

Naturally occurring arteriosclerosis in nonhuman primates

Summary (1) Arteriosclerotic lesions are described and illustrated in the coronary arteries and in the thoracic and abdominal segments of aortas in the majority of the members of 17 families of primates (a total of 67 primates were studied). (2) The arteriosclerotic process seemed to be initiated by degeneration of the internal elastic membrane, or in the case of the thoracic aorta, of the innermost medial elastic tissue. This was associated with intimal accumulations of mucopoly-saccharide, followed by intimal proliferation of fibroblasts and smooth muscle cells, and by development of intimal connective tissue fibrils. (3) Extreme variability was observed in the amounts of lipids deposited in intimas with the same degree of thickening, from mild to severe. Pronounced intimal thickening in some cases showed little or no lipid involvement. (4) Continuing intimal lipid infiltration in some primates seemed responsible for the eventual mobilization of macrophages and deposition of cholesterol crystals in the intima — and hence eventually for the development of the mature, athero-matous plaques closely resembling those seen in the human being. (5) The pathogenesis of naturally occurring arteriosclerosis in primates differs significantly from that induced in them by feeding cholesterol. The initial degenera-tive intimal process in the naturally occurring disease appears clearly primary , and seems neither associated with nor caused by lipid deposition in the intimal layer.

Production of Arteriosclerosis in Birds by the Prolonged Feeding of DihydrocholesteroL

Summary 1. The feeding of a diet containing 0.5% dihydrocholesterol (DHC) for 6 months resulted in the development of severe arteriosclerosis of the thoracic and abdominal aortas in 12 birds. 2. The aortic lesions observed were identical with those induced in the bird by the feeding of cholesterol, and appeared to have resulted from deposition of dihydrocholesterol in the vascular wall. 3. Hepatic enlargement in DHC-fed birds was similar to that observed previously in cholesterol-fed birds, and was due in part to reticuloendothelial storage of dihydro-cholesterol.

The effect of dietary protein level on the development of naturally-occurring aortic arteriosclerosis in the chicken

Summary In other laboratories it has been demonstrated that the protein level of the diet can influence the development of aortic atherosclerosis experimentally induced by the feeding of large amounts of cholesterol. In the present study we sought to examine the role of protein on the naturally-occurring aortic arteriosclerosis that develops in chickens fed diets low in cholesterol content (similar to those ingested by man). Two levels of dietary protein were employed: 14.5 %, an adequate level, and 7.3 %, a sub-optimal level. No difference was noted in the gross size of the atheromata or of microscopic lipid deposition in the thoracic and abdominal portions of the aortas of the birds fed the two levels of protein. The need for caution in drawing conclusions ou naturally-occurring aortic arteriosclerosis from experiments in animals fed excessive amounts of cholesterol is pointed out. A higher score of non-lipid intimal thickening was observed in the abdominal aortas in the birds fed the lower-protein diet. The significance of this non-lipid intima thickening is discussed. Throughout the study the average total plasma-cholesterol levels were highest for the birds fed the lower-protein diet. This consistent relationship was significant below the 5% level.

A histochemical study of the heart and thoracic aorta of the chick from hatch to 39 days of age

Summary The high lipid levels in the plasma of the newly-hatched chick are accompanied by a widespread deposition of lipids in the cardiovascular system, namely, in the coronary vessels, myocardium, and thoracic aorta. None of the lipids in these tissues was cholesterol. The lipid deposits completely disappeared from these cardiovascular tissues by the time the bird had attained an age of 39 days.

Prolonged Δ4-Cholestenone Feeding in Birds The Effects on Plasma and Liver Sterols and the Induction of Aortic Arteriosclerosis

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 Δ4-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 Δ4-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.

Pituitary Cytology of Rats with Leydig-Cell Tumors Induced by Low-Level Testicular Irradiation

Summary The pituitary gland cytology of rats subjected to local testicular irradiation was studied. Although rats treated with 500 R X-rays had a high incidence of testicular atrophy, interstitial-cell hyperplasia, and Leydig-cell tumors, increased incidences of gonadotropic hyperplasia and adenomas were not found. We could find no statistical relationship between degenerative, hyperplastic, and neoplastic lesions of the testes and pituitary gonadotropic hyperplasia and adenomas.