Ultrastructural observations on bifurcations in rat cerebral arteries

Abstract

The bifurcation pads ("valve-like projections") in the anterior cerebral arteries of rats with long-term hypertension were studied electron microscopically. The rats ranging in age from 2 to 10 months were sacrificed after bilateral renal artery constriction at 5-week-old. In the bifurcation pads (intimal pads) of hypertensive rats, smooth muscle cell damage first appeared in the roots of the pads as well as underlying media in the form of granular, vesicular, and somewhat tubular structures (200-1500 A in diameter).Thereafter, with a lapse in time after the operation, these abnormal substances increased around the smooth muscle cells which were arranged in the marginal zones of the pads. Deeply arranged intimal smooth muscle cells which were embedded in an abundance of ground substances were only damaged in rats with very long-term hypertension. The medial smooth muscle cells beneath the pads manifested lesions which were more marked and diffuse than in the intima. These smooth muscle cells were bizarrely atrophied and abnormal substances which might be derived from necrotic smooth muscle cells were found around them. Basement membrane-like substances, either thick or multilaminated, were also present around them. ACTA PATHOL. JPN. 32: 31-39, 1982. 36 RIFURCATIONS I N HYPERTENSIVE RAT ARTERIESAcfa Pathol. Jpn.

Scanning electron microscopic study of arterial cushions in rats: A novel application of the corrosion‐replication technique

“…Furrows (i.e., "cushions") similar to those found in renal casts were observed in a variety of organs. Our identification of these furrows as indentations of cushions in replicated cerebral, coronary, and ophthalmic arteries is consistent with previous histological studies Azzam, 1963a, 1963b;Rosen, 1967;Kojimahara and Ooneda, 1980;Yohro and Burnstock, 1973;Moffat, 1969;Jellinger, 1974;Lange and Halata, 1979). Although cushions have never been described in adrenals, testes, liver, spleen, and intestinal tract, their presence in these organs may be inferred from the present studies.…”

“…Cushions guarding the entrance of collateral arteries have been found in a variety of organs and species including man (for brief review see Moffat, 1969 andKojimahara andOoneda, 1980). Many studies have been dedicated to the elucidation of the fine structure of cushions in relation to their evolution with age (Nanda and Getty, 1972;Kojimahara and Ooneda, 1980) or to their possible involvement in atherogenesis (Stehbens, 1965;Kottke et al, 1977). Paradoxically, few data are available about their hemodynamic or rheological properties (Wagenvoort, 1954;Fourman and Moffat, 1961).…”

Thalamic arterial pattern: An endocast and scanning electron microscopic study in normotensive male rats

“…Examination of the vascular endocasts reveals the imprints of endothelial cells and their nuclei on the lumenal surface in thalamic vessels, a feature characteristic of endocasts from other tissues of the rat (Hodde et al, 1977;Rieke et al, 1981). Endothelial cushions observed at thalamic arteriolar branch points represent the structural components of precapillary arteriolar sphincters (Rhodin, 1967;Kojimahara and Ooneda, 1980;Rieke et al, 1981). These sphincters are thought to be one means of regulating blood flow into the capillary beds (Kojimahara and Ooneda, 1980).…”

“…Endothelial cushions observed at thalamic arteriolar branch points represent the structural components of precapillary arteriolar sphincters (Rhodin, 1967;Kojimahara and Ooneda, 1980;Rieke et al, 1981). These sphincters are thought to be one means of regulating blood flow into the capillary beds (Kojimahara and Ooneda, 1980). The smooth muscle cells in the tunica media of penetrating arterioles contain significant amounts of myosin ATPase (Cook et al, 1978;Rieke et al, 1981), which provides the muscle with the potential for sustained contraction.…”