Intimal Plaque Research Articles

Histologische Untersuchungen über die Wirkung von Solanum Melongena auf die cholesterininduzierte Atheromatose des Kaninchens im Mittel- und Langzeitversuch: Effect of Solanum Melongena on experimental atheromatosis

In earlier studies [see literature (2, 20, 21, 22)] observations concerning the effect of Solanum Melongena (Sol. Mel.) (violet egg plants) on experimentally induced artheromatosis in rabbits were reported. This study aims to investigate histologically the effect of Sol. Mel. on experimental atheromatosis in mean-term (2--4 weeks) and long-term (8--12 weeks) tests. For details of the test arrangement see AUBOCK and MITSCHEK, Exp. Path. 9, 323--335 (1974). From one portion of the material for histological examination cryostat sections were prepared, the other portion was fixed in Bouin's solution or in Baker's formol and paraffin-embedded at 58--60 degrees C (cross sections of the aorta). The specimens were stained as follows: erythrosin in conjunction with haematoxylin; aqueous or alcoholic solutions of toluidine blue (pH 3.5 to 5, and 7); methylene blue (pH 2.5 to 5, and 8); alcian blue (pH 2.5); Schiff-PAS; alcian blue and PAS in combination; Sudan III; elastica-van Gieson (blue) and Weigert's iron haematoxylin. For demonstration of mucopolysaccharides (MPS) the control sections were pretreated in a 10% Takadiastase solution for 10 minutes at 37 degrees C. In liver sections PAS-reactivity was additionally blocked by dimedone (cyclohexanedione) for elective demonstration of glycogen. The tissue sections were studied in transmission--, incident- and dark field illumination. lipid deposits as demonstrated by surface preparation technique could not be seen in paraffin sections after just one day. In the vascular wall histological changes were earliest visible after 10 to 14 days (enlargement of the subendothelial space and honeycombed edema with fine dispersed lipids). At this stage a "haematoxylin-effect" did yet not develop. Sometimes these alterations were also present in the upper layers of the media. They always first occurred in the aortic arch. At this time the Sol. Mel.-treated animals of group II only occasionally developed superficial edemas. Enlargement of the media with edematous infiltration and loosening of the elastic fibers was similar in both cases (figs. 1a and 1b). Fatty degeneration of the liver was already macroscopically visible on day 14; in untreated animals of group I it was more expressive than in group II (figs. 2a and 2b) -- this likewise applied to the cholesterol content (figs. 3a and 3b). After about 30 days in group I the earliest macroscopically visible plaques occurred prevailingly in the aortic arch and in the thoracic aorta. The development of such small foam cell plaques could be continuously observed with a hand lens (fig. 4a). In group II, however, it was not possible to observe any development of plaques with a hand lens, persistence of edemas was demonstrable with such (fig. 4b). Within these, fine dispersed droplets were present (fig. 5) but exact localization was only possible by electron microscopy [see literature(2)].

Scanning electron microscopic observations of endothelial changes in experimentally induced atheromatosis of rabbit aortas.

Following the administration of cholesterol for a period of 6-7 weeks, Scanning Electron Microscopic (S.E.M.) observations revealed mono-cellular, crater-like and dome-shaped endothelial changes on top of the large intimal plaques in the rabbit aortas. Finger-like and other shaped cell protrusions were observed at the edges of these crater-like and dome-shaped endothelial changes, giving the intimal plaques a rough appearance. At other sites, normal, smooth, although irregularly arranged, endothelial cells covered the lesions. By impregnating the cell borders with silver-nitrate or silver proteinate containing perfusates, it was possible in most cases to ascertain that the lesions were derived from changes in one cell or from changes in a small collection of cells. S.E.M.-observations further revealed crater-like and dome-shaped endothelial changes to be present in large fields or as isolated cell changes in normal areas at sites where no gross lesions were observed with the light microscope. In addition large, multi-cellular, crate-like endothelial changes were observed at the edges of the large intimal plaques. At these sites several endothelial cells were lacking, leaving behind a crater in which sometimes cells and a few fibrin threads were found. Following the administration of cholesterol for periods of 4-5 and 2-3 weeks similar monocellular changes were observed, some extending over large areas, other as single cells in apparently normal surroundings. Quantitatively the number of lesions was less than when the cholesterol was administered for a longer period. Transmission electron microscopic studies revealed the presence of large amounts of membrane-bound lipid globules in the subendothelial spaces and within some endothelial cells, structures which were assumed to be cross-sections of the crater-like or dome-shaped endothelial cell protrusions, visible with the S.E.M.

Organization of valve pocket thrombi and the anomalies of double thrombi and valve cusp involvement.

Abstract Organization and resolution were studied histologically in 48 valve pocket thrombi from femoral veins. The great majority were essentially single structures and the overlying cusps were normal and uninvolved, Thrombus adherence to the distal part of the vein wall in the pocket is followed by cellular and vascular invasion and progressive organization. At the same time many thrombi continue to grow by proximal addition, whilst others regress fully to fibrous intimal plaques. Central fibrinolytic changes are frequent. Focal organic fragmentation following endothelial cell surfacing is not uncommon and is a potential cause of thrombus detachment. Eight thrombi differed in that 5 were anchored to part of the cusp and 4 had a double structure resulting from two demarcated thrombotic events. One thrombus showed both features. In 3 thrombi with anchored cusps scarred intimal remnants of old thrombosis were present nearby. In 3 double structures recent thrombus had been laid down on organizing or organized thrombus, whilst the fourth was unique in that one part was composed solely of a large mass of platelets. The role of endothelium-induced fibrinolysis in preventing cusp adherence and of intact endothelium in preventing second thrombi are discussed.

Mechanisms and frequency of thrombosis in the coronary circulation

The development of coronary thrombi is related to the pathogenesis of the underlying lesions of the arterial wall. Intimal hemorrhage and rupture of atherosclerotic plaques are two of the main factors thought to precipitate thrombosis. Another class of thrombi can be identified that is unassociated with plaque rupture. These thrombi usually occur on fibrous intimal plaques and appear to be influenced by antithrombotic therapy. Recurrent thrombosis is an important factor in the build-up of stenotic lesions. Many thrombi grow in episodes and may produce symptoms before complete occlusion and infarction occur. Microembolic thrombi either originating from proximal in situ thrombi or arising entirely in the bloodstream also may have ischemic effects. The frequency of recent coronary thrombosis is considered in relation to community studies, age and sex, geographic and racial factors, sudden cardiac death and myocardial infarction. In time, the resolution of thrombi and the conversion of residual thrombi to atherosclerotic plaques obscures the true incidence of coronary thrombosis in any given case.

Investigations of free and elastin-bound fluorescent substances present in the atherosclerotic lipid and calcium-plaques.

The nature and behavior of two fluorescent substances, present in the intimal plaques of atherosclerotic human aortas were studied. The maximum activation and emission wavelength of the first peak was 350/405 which is characteristic for pure elastin, while the specific fluorescence of the other peak was 380/450. Only a small part of the latter was readily extractable from the plaques while the major portion was tightly bound in a complex. After digestion with elastase the fluorescent material and associated hydrophobic peptides could be extracted by chloroform:methanol 3:1 The elastase treatment hydrolyzed both elastin and associated proteins. The fluorescent compound resembled other tissue pigments in its emission, and in giving a positive reaction in the thiobarbituric acid test, a red spot characteristic for malonaldehyde.

Cell proliferation 1n the atherosclerotic lesions of cholesterol-fed rabbits: Part 2. histological, ultrastructural and radidautographic observations on epinephrine-treated rabbits

Tritiated thymidine radioautography was employed to study the effect of epinephrine on cellular proliferation in the aorta and pulmonary artery of rabbits with cholesterol atherosclerosis. Rabbits fed cholesterol for 90 days were given epinephrine intravenously in a single large dose or in multiple low daily doses. Labeled cell counts in animals killed at intervals ranging from one to twelve days after the start of treatment showed that both treatments, as compared with controls, increase the deoxyribonucleic acid synthesis both in intimal plaques and in the media. This effect was particularly evident in the animals treated with low daily doses which, otherwise, in light and electron microscopy studies showed less marked structural changes of the medial coat. No definite relationship was found to exist between increased rate of DNA synthesis and serum cholesterol levels. It is suggested that the increased DNA synthesis induced in the atherosclerotic vessels by epinephrine is not merely a consequence of the structural damage, but should also be regarded as a response of the arterial wall to functional and/or metabolic stimuli that are as yet undetermined. On the other hand it is concluded that the contributing or enhancing effect of epinephrine on cholesterol atherogenesis might be due, at least partly, to the increased mitotic rate into the arterial wall.

Electron microscopy of intimal plaques following induction of large superficial mechanical injury (transverse injury) in the rabbit aorta.

As has been shown previously, the induction of a superficial injury extending over a large area in the aorta of normolipidemic rabbits is followed by characteristic and reproducible sequential patterns of light-microscopic changes. After a short phase of thickening of the intima and partial regeneration of injured endothelium and injured media, repair is arrested and a phase of delayed repair ensues. The latter is characterized by delayed reendothelialization, excessive thickening of the intima, and accumulation of lipids, mainly extracellularly, in the non-reendothelialized regions.

Adaptive features in the turkey aorta which precede plaque formation

Posterior aortas taken from broad breasted white turkey poults were examined histologically in order to better define the early events which precede and accompany intimal plaque formation in this species. As early as 3 weeks after hatching, disproportionate thickenings appeared in the ventral portion of the outer aortic wall (outer media and adventitia). These thickenings were associated with a relative increase in non-elastic elements, especially collagen, and were found in over half the birds examined. Since the earliest recognizable intimal plaques made their appearance subsequent to and on the same side (ventral) of the aorta as the foregoing medial and adventitial features, there may be a causal relationship. The authors believe that these composite phenomena, perhaps initially adaptive and developmental in nature, may progress to a point where they weaken the wall to the extent that, by acting in conjunction with hypertension, aortic rupture can occur.

Observations with the scanning electron microscope on the development of cholesterol aortic atherosclerosis in the guinea-pig.

By means of scanning electron microscope “en face” examination of aortic intimal surface, two phases are recognizable in the development of experimental cholesterol atherosclerosis in the guinea-pig. During the first phase, after about two months of hypercholesterolic diet, no intimal plaques are to be found, and an amorphous substance (fibrin? — lipoproteins?) is deposited as a diffuse covering of wide areas of the aortic intimal surface along with erythrocytes and platelets. During this first phase, localized “flattenings” of the intimal folds are also evident.

Histologisch-statistische untersuchungen der koronarsklerose in abhängigkeit von alter und geschlecht

Statistical investigation into the histology of intimal changes in coronary arteriosclerosis in the anterior descending branch and in the originating part of the right coronary artery of 146 hearts (75 women and 71 men) of the 20–90 age group. The evaluation was concerned with the counting of proliferations, fibroses, hyalinoses, foam cell foci, intumescent necroses and calcium deposits. The counted values were statistically checked for significance.It was evident that focal proliferations of the intima are the earliest changes to which other typical changes are added with increasing age. Apart from insights into the course of coronary arteriosclerosis it was found that the histological composition of the intimal plaques is significantly dependent on sex. However these sexual differences do not apply to the formation of various types of sclerotic intimal plaque but give expression to a sex-linked course of the arteriosclerotic process.

Coronary artery hyalinosis in rats fed allylamine

Different concentrations of allylamine in corn oil or as a fumarate salt was fed to 75 rats for periods up to 284 days. A majority of these rats developed focal hyalinosis of the proximal coronary arteries and conspicuous medial edema of the smaller branches together with myocardial infarction. Repeated attempts to produce comparable arterial hyalinosis in other parenchymatous organs were unsuccessful. Intimal cartilagenous plaques in the aortic arch were seen in 18 test rats. Coronary arteritis and intimal fibrosis usually produced by parenteral administration of allylamine to dogs did not develop when the durg was fed in the diet to rats. On the basis of a limited and focal arterial involvement and the character of cytologic alterations observed in the media of the coronary arteries, there is a suggestion that the smooth muscle fibers are selectively injured. Prolonged ingestion of allylamine therefore promotes a focal degeneration of the coronary arteries which closely resembles the morphologic alterations seen in aging rats.

Reaction of the arterial intima of the rabbit to trauma and hyperlipemia

The effect of trauma to the aortic intima of the rabbit and the combination of trauma and hyperlipemia were studied with the electron microscope. It was found that the cells engaged in the repair processes and eventually forming intimal plaques were apparently derived from smooth muscle. Hyperlipemia led to the accumulation of foam cells in these plaques. During the experimental period such foam cells were confined almost entirely to the luminal surfaces of the plaques. Reasons are advanced for considering that many of these foam cells are derived from blood borne cells.

Fatty acid composition of tissues in cholesterol-fed rabbits

Summary (1) The fatty acid pattern of cholesteryl esters, triglycerides and phospholipids of aortic plaques, liver, serum and leucocytes, and triglycerides of adipose tissue were determined in rabbits fed a cholesterol-supplemented diet. (2) In the cholesterol-fed group an increase in oleic acid was found in the cholesteryl esters of the tissues analysed. (3) On comparing the fatty acid pattern of aortic plaques to that of the other tissues it was found that the triglycerides and possibly the phospholipids were similar in composition to those of leucocytes while the cholesteryl esters resembled those of liver. (4) It is very likely that in rabbits maintained for relatively short periods of time on cholesterol, the lipids of the intimal plaques, produced by such dietary means, are not indiscriminately deposited from serum but that a selective uptake and active metabolism are operative locally.

Skeletal and cardiovascular lesions in turkeys induced by feeding beta-aminopropionitrile

Beta-aminopropionitrile toxicosis in turkeys induced skeletal and cardiovascular lesions. Enlarged hocks with widening of the epiphyseal plate and articular cartilage, green tinting of the skin over swollen joints, and synovitis were the skeletal defects that were found. Joint lesions apparently resulted from impediment of endochondral mineralization and maturation of chondrocytes in the epiphyseal plate and articular cartilage. Cardiovascular alterations resulting from BAPN feeding included ground substance increase, swelling and disorganization of collagenous fibers, and elastolysis. These changes cause polypoid intimal thickenings and the induction of dissecting aneurysms. Intimal arteriosclerotic plaques were found in the posterior aorta of “normal” turkey poults. There is a possibility that such lesions are a prerequisite for the development of dissecting aneurysms.

Interrelationships between the two diseases, hypertension and atherosclerosis ∗

Atherosclerosis is the major specific entity in the generic grouping of the arterioscleroses. It is a disease process and not a manifestation of physiologic senescence. Its pathologic hallmark is the lipidand cholesterol-containing, focal intimal plaque.’ Hypertension is the disease process characterized by sustained blood pressure elevation, of known or unknown cause, involving diastolic and, in most cases, systolic pressure.“-4 It is now generally accepted that atherosclerosis and hypertension are two separate and distinct entities with different pathogenetic and etiologic mechanisms. Reference to older literature quickly reveals that, until recently, medicine had great difficulty defining and disentangling the two diseases.5,6 There have been long-standing tendencies to confuse atherosclerosis and the other arterioscleroses, and to confuse atherosclerosis and hypertension. There have also been tendencies to oversimplify, that is, to regard the two as a single entity with a common cause or to regard one simply as the result of the other. These confusions and the difficulties in overcoming them are understandable since in the Western centers of medicine it has been common clinical experience to observe the two processes coexisting in the same patients. Recent contributions, particularly from animal experimental and epidemiological investigations, clearly demonstrate that atherosclerosis and hypertension are two distinct disease processes with different etiologic and pathogenetic mechanisms. Based on the clarification of this cardinal fact, it has become possible to delineate the complex ways in which these two diseases interact and influence each other.

Aortic arteriosclerosis in the dog after localized aortic x-irradiation.

Localized segments of the abdominal aortas of 18 dogs were irradiated with 50-kv. x-rays in doses ranging from 1,500 to 5,500 r (at the ventral surface of the aorta), and were examined histologically at intervals ranging from 2 to 48 weeks after irradiation. Arteriosclerosis developed at the irradiated sites and was significantly more severe than that which occurred in nonirradiated control sites in the abdominal aorta. There was evidence that severity of arteriosclerosis increased with time following irradiation of the aorta. There was less pronounced arteriosclerosis after 3,000 to 5,500 r than after 1,500 to 2,500 r. It appeared that the larger doses of x-rays inhibited the full development of the late lesions, although presumably causing more initial primary damage. X-irradiation appeared to be followed by the development of arteriosclerotic lesions similar to those that occur naturally in old dogs. It is proposed that irradiation may selectively cause injury of the internal elastic membrane, and that this degenerative phenomenon is followed by the development of intimal fibrosis and plaque formation.

Aortic Arteriosclerosis in the Dog After Localized Aortic Irradiation with Electrons

The distal segments of the abdominal aortas of 15 dogs were irradiated with electrons in doses ranging from 1,000 to 9,500 rads and were examined histologically at intervals ranging from 2 weeks to 17 months following irradiation. Pronounced aortic arteriosclerosis developed and was sharply localized to the aortic segment irradiated. Except in one dog, radiation-induced arteriosclerosis was more pronounced on the dorsal than on the ventral aortic wall. There was no evidence that severity of aortic arteriosclerosis was related to the dose of irradiation or was increased with time following irradiation. The development of arteriosclerotic lesions of the aorta induced by electron irradiation was similar to that observed after x-irradiation and to that occurring naturally in old dogs. It is suggested that electron irradiation may have caused selective injury of the internal elastic lamina, which was then followed by intimal fibrous proliferation and formation of intimal plaques.

Arterial Lesions in the Kenya Baboon

One hundred sixty-three baboons ( Papio doguera were sacrificed and autopsied immediately after being trapped in their natural habitat in Kenya, British East Africa. Approximately three-fourths of the 67 adults had some degree of aortic intimal lipid deposition, as indicated by gross Sudan IV staining, and a few animals had extensive fatty streaks. These fatty streaks were more frequent with advancing age, but there was no sex difference. Electron microscopy disclosed most of the intimal lipid droplets to be intracellular. Fibrous plaques were infrequent and had a variable but usually low lipid content. One elderly male had fibrous plaques with hemorrhage into their bases. Histologic sections of the coronary arteries showed many small musculo-elastic intimal plaques in which lipid could only rarely be demonstrated. The aortic intimal lipid deposits cannot be attributed to the consumption of excessive animal fat or to hypercholesterolemia. These results indicate that the baboon, like man, is highly susceptible to arterial intimal lipid deposition and that it promises to be an excellent animal for the experimental investigation of atherosclerosis. They further more caution that adequate controls be used in all experimental work involving arterial lesions in primates.

The Hypercholesteremic and Atherogenic Properties of Various Purines and Pyrimidines

The hypercholesteremic and atherogenic properties of RNA, DNA, four purines, and three pyrimidines were assayed in rats fed moderately atherogenic diets for 10 weeks. It was found that either RNA or DNA supplementation alone favors a mild increase in hypercholesteremic response and cardiovascular sudanophilia. When RNA and DNA were combined in such diets, the level of cardiovascular sudanophilia was reduced to levels seen among the control rats. Among the four purines studied, adenine was found to be the most atherogenic and hypercholesteremic. In addition, these animals displayed severe obstructive renal lesions and medionecrosis of the aorta and its branches, including the coronary arteries. The aortic lesions were associated with aneurysmal dilatation, fibrous intimal plaque formation, and lipid deposition. On the other hand, the rats fed either guanine, uric acid, or xanthine all demonstrated significant elevations in the serum cholesterol response and only mild increases in the amount of cardiovascular sudanophilia without the above renal damage or vascular necrosis. Among the rats fed pyrimidines, uracil treatment resulted in a marked hypercholesteremia and cardiovascular sudanophilia. The nature of these changes as supported by thyroidal hyperplasia is reminiscent of the changes seen among rats treated with dietary thiouracil. This uracil effect on the thyroid therefore may account for the singular properties noted in this pyrimidine. The rats fed thymine demonstrated a mild increase in hypercholesteremia and cardiovascular sudanophilia, while the cytosine group's response was not significantly higher than the control rats. Significant thyroidal changes were not noted among these latter two pyrimidine groups.

Response of arterial wall to intramural cholesterol.

SummaryA technic is described for study of response of avian arteries to intramural injection of cholesterol. This material, when injected into the wall of the artery, causes a foreign body reaction at site of injection. In addition, a localized proliferation of collagenous connective tissue is found in the intima. These intimal plaques resemble some forms of human atherosclerosis. The development of the plaques is not affected by adding cholesterol or various fats to the diet. These findings suggest that the lesions are the result of the local metabolic alteration.