Ultrastructural alterations of endothelium covering advanced atherosclerotic plaque in human carotid artery visualised by scanning electron microscope.

Human atherosclerotic plaque morphology at its various stages was extensively documented using light microscopy. However, much less is known of the ultrastructure of the human atherosclerotic plaque, in particular of ultrastructure of endothelial cells in atherosclerosis. Here, we analysed alterations of endothelial cells covering advanced atherosclerotic plaque in carotid artery using scanning electron microscope. Examination was performed on specimens from atherosclerotic lesions of the interior carotid artery, collected from 8 patients who had undergone endarterectomy. We found wide spectrum of pathological alterations of the luminal surface of atherosclerotic plaque. In dominant part of the vessel, endothelial layer was preserved but displayed pronounced irregularities in endothelial architecture including appearance of cuboidal cells. Some endothelial cells were covered by numerous microvilli and/or contained "craters" disrupting continuous surface of the endothelium. Platelets and leukocytes adhering to endothelium were frequently observed. There were also areas of the vessel lumen with endothelial denudation, in which the subendothelial surface containing fibrin proteins and collagen fibrils were visible. Interestingly, signs of proliferation of endothelial cells tending to cover the partially denuded vessel were observed. In summary, in scanning electron microscope, preserved endothelial cells of advanced atherosclerotic plaque displayed pronounced pathology; whether any of these changes represent the ultrastructural correlate of endothelial dysfunction remains to be established.

Light and electron microscopic picture of atherosclerotic plaque in stable and unstable angina.

By presenting this series of 127 cases of coronary atherectomy the authors join the workers who study morphological differences between the atherosclerotic plaques in stable and unstable angina. Routine staining of formalin-fixed, paraffin-embedded material was completed by the detection of T lymphocytes, macrophages, mast cells, smooth myocytes and grown-in capillaries using monoclonal antibodies (DAKO), as well as by the immunofluorescent demonstration of fibrinogen in the plaques. The plaques derived from patients with unstable angina showed a higher incidence of mast cells (significant) and macrophages (insignificant). These cells render the plaque more susceptible to rupture or fissuring. There was also significantly more frequent and quantitatively more abundant permeation of the plaque by fibrinogen that raises the chance of thrombosis. These findings support the view that unstable angina correlates with the phenomena that favour the rupture of the plaque and thrombosis. Electron microscopy has not been used so far to study coronary atherosclerotic plaques. This material includes 15 plaques from stable and 18 plaques from unstable angina. A cover of fibrin and blood platelets is a regular formation on the surface and in the superficial layer of the plaque from unstable angina. It contributes to the "thrombotic proneness" of the coronary artery. These plaques also show abundant elastic fibres. This pattern corresponds to myo-elastic intimal hyperplasia ("intimal thickening") where the production of intimal elastin constitutes an essential phenomenon. Intimal thickening is interpreted as a preatherosclerotic event. The presence of elastin reflects an early stage of the development of the plaque. The plaque from stable angina shows abundant collagen fibres, which aggravate the lesion.

The presence of Chlamydia pneumoniae in atherosclerotic plaques--a report of three cases of ischaemic heart disease.

The report presents three cases of ischaemic heart disease in which Chlamydia pneumoniae infections were detected first serologically, later the bacteria were shown in atherosclerotic plaques with electron microscopy, and finally C. pneumoniae strains were isolated from the tissues.

The perivascular fibrotic reaction in rat brain in the late period after experimental clinical death. II. Precapillary vessels.

The aim of the study was to investigate the area surrounding precapillary vessels in the temporal cortex of rat-brains. The material consisted of animals that survived a 10-minute cardiac arrest and then lived on for 10 to 12 months. In the specimens that survived 10 month we observed dilatation of the pericapillary space pervaded with unidentified cells surrounded by multiple collagen fibrils. In the close vicinity of these vessels we often discerned cells participating in the process of phagocytosis. Smooth muscle cells held numerous pinocytic vesicles which contained microfibrillar material. Collagen fibrils were also discerned beneath their basement membrane. In the animals that survived 12 months in many cases the spaces between blood vessel mural myocytes and brain cells were filled with numerous collagen fibrils. In some cases these fibrils formed bridge-like structures between vessel walls and surrounding nerve cells. These compartments were often accompanied by brain phagocytes, the cytoplasm of which contained single fibres or bundles of collagen located in the close proximity of the phagolysosomes. We discussed the role of myocytes, myofibroblasts and phagocytes in the production of reparative collagen following the destruction of precapillary vessels and brain continuity.

The perivascular fibrotic reaction in rat brain in the late period after experimental clinical death. I. Capillary vessels.

In this paper we studied the pericapillary zone of the hypothalamic neurosecretory nuclei and temporal cerebral cortex of rats 6-12 months after experimentally evoked cardiac arrest of 10 minutes duration. The most significant ultrastructural findings were presence of single collagen fibrils and collagen bundles in the compartment between endothelia and pericytes, pericytes and basement membrane and also inside the phagocytic cells. In the animals that survived at least 10 months after resuscitation the capillaries filled with thrombocytes were encountered. Moreover, in the vicinity of these capillaries the dead cells and collagen bundles were observed. We interpret these findings as the evidence of the reparatory process in the border between capillaries and the surrounding brain cells. We discuss the hypothesis that the non-fibroblastic cells present in rat brain are able to synthesize collagen that leads to a process comparable with the fibrosis of parenchymal organs.

Ultrastructure of phagocytizing cells of the rat hypothalamic neurosurgery nuclei in a remote period after the sustained clinical death.

Ultrastructural studies were carried out on neurosecretory nuclei taken from brains of rats which have survived for 16 weeks following clinical death of 5 or 10 min duration. The reported observations indicate that brain lesions were caused by changes due to ischemia and superimposed secondary changes resulting from the maturation of pathological processes. In animals subjected to clinical death for 5 min the observed cells in the perivascular area were integrated in the capillary wall and wrapped by the basement membrane. Sometimes they were accompanied by cells engaged in the process of phagocytosis. Phagocytizing cells were more frequently noted in the animals subjected to clinical death for 10 min and then their cytoplasmic processes were connected with the adjacent capillaries. We assume that these cells, which may represent cerebral macrophages occur by transformation of pericytes or blood derived monocytes.

Ultrastructural alterations of pulmonary surfactant in rat lungs after inhibition of protein synthesis by puromycin.

The effects of systematically administered puromycin on the fine structure of the lung were studied. The effects varied depending on the duration of exposure and the time interval between the last injection and sacrifice. After short term exposure most surfactant had separated from the epithelial surface and profound alterations in the tubular myelin structure were seen. After moderate duration of exposure a previously undescribed multilamellar lining layer was observed which was often detached from the alveolar epithelium. Six hours after the last injection the regular tubular myelin pattern reappeared. Puromycin treatment results in inhibition of various proteins synthesized by type II epithelial cells. Inhibition of synthesis of some proteins, most probably that of glycoprotein A, causes a primary effect on the structure of surfactant. The loss of at least some of the cytoskeletal proteins in Type II epithelial cells apparently results in interference with exocytosis of lamellar body contents.

Studies on the hypothalamus and secretory nuclei of rat in the remote period following clinical death.

Ultrastructural studies of hypothalamic secretory nuclei were carried out on rats which survived 16 weeks after 5- or 10-min-long clinical death. Active neurosecretory cells were noted without any signs of injury. In perikaryonic area numerous polymorphic lysosomes and "nucleolus-like bodies" were observed. Attention was called to significant changes in the structure of cytoskeleton and observations were discussed in relation to biochemical data. In both groups of the studied animals neurosecretory cells with features of apoptosis were found. Apoptotic cells appeared more often in animals which survived 10-min-long clinical death. Characteristic morphological features of the process of apoptosis are shown in illustrations.