Scanning and Transmission Electron Microscopic Observation of Endothelial Cells in the Normal Condition and in Initial Stages of Atherosclerosis

Abstract

The fine structures of vascular endothelial surface with linear endothelial folds, were clearly shown by scanning and transmission electron microscopes in large arteries and veins of man and other mammals and the nuclear parts of endothelial cells were shown in the gullies in scanning electron microscopical observation. The effects of substances promoting or inhibiting transendothelial leakage were studied in relation to these structures. Immediately after the challenge their nuclear parts were transiently enlarged and prolonged and the linear endothelial folds became irregular by edematous swelling of endothelial cells and subendothelial structures. Pyridinolcarbamate pretreatment prevented these changes. Administration of cholesterol for 2 weeks induced edematous and spherical change of endothelial cells of aorta; and then localized flat lesions of endothelial cells with flattening of their degenerated nuclear parts in localized areas exposed to mechanical stress from the arterial blood stream. After 3 to 4 weeks the flat lesions changed into elevated lesions, fatty spots or streaks. These endothelial changes were significantly inhibited by pyridinolcarbamate. At the margin of the elevated lesions, nuclear parts of the endothelial cells were exposed on the endothelial fold by elevation of gullies. The exposed nuclear part exhibited a highly deformed and swollen shape and such changes may be followed by an increase in local transendothelial infiltration resulting in expansion of elevated lesions. Chemical inJuries induce weakness of the resistance of endothelial cells and the mechanical stress from the arterial blood stream may aggravate the injury in a special area facing the strong mechanical stress from the blood stream. Summation of such injuries may initiate atherosclerosis in such a special area followed by expansion of atherosclerotic lesion to all directions.

Intimal Pits of Aorta in Rabbits: Imprints of Vortices of Blood Flow?

“…The endothelial cells at the crest of folds between the pits could be missing. Within the pits abundant bridge like structures as described by Shimamoto et al (13) and Chisholm et al…”

Preparation of vascular endothelium for scanning electron microscopy: a comparison of the effects of perfusion and immersion fixation

“…It is generally accepted that, for T E M study of vascular endothelium (and indeed all tissues where practicable), fixation in situ by intravascular perfusion is superior to fixation by immersion for the prevention of artifacts due to postmortem autolysis (Pease, 1960;Hayat, 1970). However, no such consensus is apparent concerning the advisability of perfusion fixation for preparation of specimens for SEM (Shimamoto et al, 1971;Boatman & Carter, 1973;Weber et al, 1974;Still, 1972). Consequently, accurate interpretation and useful comparisons of the results of these SEM studies are extremely difficult.…”

Focal Endothelial Cell Injury in Rabbit Aorta, Aggravation of Injury by 2 Days of Cholesterol Feeding

“…The excess plasma cholesterol may also have a direct ))toxic(( effect upon the endothelial cells. Previous reports support this assumption (3,26,27,30).…”