ROLE OF LYSOSOMES IN CORONARY ARTERY LESIONS OF HYPERTENSIVE RATS

Electron microscopically the role of acid phosphatase (acid P) positive lysosomes in the pathoǵenesis of intramyocardial coronary artery lesions of hypertensive rats with bilaterally constricted renal arteries was studied. At 3 postoperative weeks, acid P positive lysosomes were increased in endothelial cells of the coronary arteries, but at 5 weeks and thereafter, they were decreased in number. In the intima, intimal smooth muscle cells with acid P positive lysosomes appeared at 3 postoperative weeks, but their number remained small as late as 9 postoperative weeks. The internal elastic lamina was fraǵmented into amorphous masses from 3 postoperative weeks, at 5 weeks and thereafter the fraǵmentation and disruption became severer, and at 9 weeks the lamina disappeared because of marked disruption. At 3 postoperative weeks, acid P positive extracellular lysosomes were observed in the ǵaps of the fraǵmented internal elastic lamina. At 5 weeks and thereafter, extracellular lysosomes and attenuated processes of medial smooth muscle cells with lysosomes were seen extending through the ǵaps of the fraǵmented internal elastic lamina. Necrosis of these extendinǵ cell processes and lysosomes remaininǵ after the necrosis were observed. The findinǵs suǵǵested that the fraǵmentation and lytic chanǵe of the internal elastic lamina observed in hypertensive rat intramyocardial coronary arteries might be induced by extracellular lysosomes discharǵed not only from endothelial cells and intimal smooth muscle cells but also from the extendinǵ processes of medial smooth muscle cells into the gaps of the internal elastic lamina. ACTA PATHOL. JPN. 36: 1529-1536, 1986.     

An electron microscopic study of plasmatic arterionecrosis in the human cerebral arteries

Summary An electron microscopic study of the intracerebral arteries from 9 hypertensive cases was performed in order to elucidate the morphogenesis of the plasmatic arterionecrosis which was considered to be the direct cause of hypertensive intracerebral hemorrhage. In the preceding stage of the arterial lesions, marked necrosis of medial smooth muscle cells and increase of basement membrane-like substance in the intima and media were observed. The lumina of these arteries were slightly dilated. The dilatation and hemodynamic factors were supposed to cause endothelial injury resulting in blood plasma insudation into the intima through the opened spaces between endothelial cells. The insudated blood plasma dispersed and dissolved the basement membrane-like substance, collagen and elastic fibers in the arterial wall, leading to the development of the plasmatic arterionecrosis.This study was supported by a Grant-in-Aid for Scientific Research of the Japanese Ministry of Education (No. 857052).     

ELECTRON MICROSCOPIC STUDY ON THE PROXIMAL PORTIONS OF THE ANTERIOR CEREBRAL ARTERIES IN RATS WITH LONG-TERM HYPERTENSION

Proximal portions of the anterior cerebral arteries in rats with long-term hypertension were electron microscopically studied. The abnormal substances such as granules, vesicles, vacuoles and other membranous structures, relatively homogeneous masses, and basement membrane-like substances were observed around the medial smooth muscle cells. Basement membrane-like substances were increased with advancing age and the majority of these substances are thought to be turned from the granulo-vesicles. Abnormal substances deposited in the media are thought to be "hyalino-fibrous materials". The majority of our materials had a clear-cut border between the media and the adventitia. The subendothelial spaces were slightly distended with fibrillar and/or finely granular substances with age, but neither cellular element nor fibrinoid substance was found in them.     

Topographical study on arteriosclerotic lesions at the bifurcations of human cerebral arteries

Summary We have studied the topographical distribution of arteriosclerotic lesions at the bifurcation of the internal carotid-anterior cerebral-middle cerebral arteries (internal carotid bifurcation) and of the middle cerebral artery-first temporal branch (first bifurcation of M.C.A.) in humans. The arteriosclerotic lesions showed a distinct pattern with a high incidence on the outer walls of the daughter vessels and at the inner curvatures in the bifurcations where wall shear stress was believed to be relatively low. However, there were differences in the distribution of the lesions between the internal carotid bifurcations and the first bifurcations of M.C.A.. The former are considered to be three-dimensionally unsymmetrical and curved, and the latter symmetrical and straight. The present study suggests that lower shear stress is of considerable importance in both the initiation and localization of arteriosclerotic lesions, and that study of the three-dimensional blood vessel architecture and blood flow patterns needs to be done to clarify the role of hemodynamic forces in atherogenesis.     

Role of lysosomes in coronary artery lesions of hypertensive rats

Electron microscopically the role of acid phosphatase (acid P) positive lysosomes in the pathogenesis of intramyocardial coronary artery lesions of hypertensive rats with bilaterally constricted renal arteries was studied. At 3 postoperative weeks, acid P positive lysosomes were increased in endothelial cells of the coronary arteries, but at 5 weeks and thereafter, they were decreased in number. In the intima, intimal smooth muscle cells with acid P positive lysosomes appeared at 3 postoperative weeks, but their number remained small as late as 9 postoperative weeks. The internal elastic lamina was fragmented into amorphous masses from 3 postoperative weeks, at 5 weeks and thereafter the fragmentation and disruption became severer, and at 9 weeks the lamina disappeared because of marked disruption. At 3 postoperative weeks, acid P positive extracellular lysosomes were observed in the gaps of the fragmented internal elastic lamina. At 5 weeks and thereafter, extracellular lysosomes and attenuated processes of medial smooth muscle cells with lysosomes were seen extending through the gaps of the fragmented internal elastic lamina. Necrosis of these extending cell processes and lysosomes remaining after the necrosis were observed. The findings suggested that the fragmentation and lytic change of the internal elastic lamina observed in hypertensive rat intramyocardial coronary arteries might be induced by extracellular lysosomes discharged not only from endothelial cells and intimal smooth muscle cells but also from the extending processes of medial smooth muscle cells into the gaps of the internal elastic lamina.     

ULTRASTRUCTURAL STUDY OF HEMANGIOMAS

A case of benign hemangioendothelioma which occurred in the hard palate was observed and its electron microscopic findings were described. The endothelial cells contained an abundance of cytoplasmic filaments, but they contained a small number of Weibel-Palade bodies. Two types of endothelial cells, light and dark, were found in our specimen. The former had a cytoplasm with an abundance of ribosomes, rough endoplasmic reticulum and scant filaments. The latter had a cytoplasm with numerous cytoplasmic filaments and a well-developed Golgi apparatus. Tight junctions were seen between the endothelial cells. The majority of the pericytes were accompanied with the vessels in the tumor. Three types of pericytes were recognized: endothelial cell-like, fibroblast-like, and smooth muscle cell-like pericytes.     

Electron microscopic study on the proximal portions of the anterior cerebral arteries in rats with long-term hypertension

Proximal portions of the anterior cerebral arteries in rats with long-term hypertension were electron microscopically studied. The abnormal substances such as granules, vesicles, vacuoles and other membranous structures, relatively homogeneous masses, and basement membrane-like substances were observed around the medial smooth muscle cells. Basement membrane-like substances were increased with advancing age and the majority of these substances are thought to be turned from the granulo-vesicles. Abnormal substances deposited in the media are thought to be "hyalino-fibrous materials". The majority of our materials had a clear-cut border between the media and the adventitia. The subendothelial spaces were slightly distended with fibrillar and/or finely granular substances with age, but neither cellular element nor fibrinoid substance was found in them.     

Electron microscopic study on the medial defect at the apex of human cerebral arterial bifurcations

Summary It is a well known fact that the berry aneurysms, which are the direct cause of subarachnoid hemorrhage, develop at the apices of bifurcations of larger cerebral arteries. In order to elucidate the morphogenesis of the aneurysms in these sites, electron microscopic observation was made on one of their predilective regions, that is, the bifurcation of the first temporal branches from the middle cerebral arteries. Human autopsy cases from newborn and elderly patients were studied.The apices of the cerebral arterial bifurcations exhibited a medial defect immediately after birth, where collagen fibrils, ground substance and increased basement membrane-like substance were observed, suggesting that the defect might have resulted from necrosis of medial muscle cells. The tunica media adjacent to the defect became tapered into a wedge-like shape with the thin and towards the defect and the medial muscle cells were decreased in number. In young cases, medial muscle cells near the defect displayed focal cytoplasmic necrosis, and granulovesicular cell debris and lamellar increase of basement membrane-like substance were seen around the muscle cells with irregular profiles. With aging the defect gradually enlarged and the adjacent part of the media composed of lamellarly or reticularly increased basement membrane-like substance and granulovesicular cell debris, without muscle cells. In the media away from this area muscle cells were irregular and surrounded by granulovesicular cell debris, similarly increased basement membrane-like substance, and increased collagen fibrils, with enlarged intercellular spaces.The internal elastic lamina at the apices of bifurcations showed fragmentation and lumpy degradation both of which increased with age.Necrosis of medial muscle cells and subsequent enlargement of the medial defect together with degenerative changes in the internal elastic lamina, which are age-induced and presumed to be due to haemodynamic factors, are all considered to be important in the formation of berry aneurysms.     

An Autopsy Case of Giant Cell Myocarditis (Myocardial Sarcoidosis)

An autopsy case of the so-called giant cell myocarditis, which was understood to be sarcoidosis, the main lesion of which situated in the myocardium, was reported.
In the morphogensis of asteroid bodies, the protein moiety of lipoprotein was considered to participate. The theory that these bodies would be derivatives of elastin could not be supported.