Three‐dimensional structural changes in cerebral microvessels after transient focal cerebral ischemia in rats: Scanning electron microscopic study of corrosion casts

Abstract

Pathological changes of cerebral microvessels in transient ischemia were investigated by scanning electron microscopy of vascular corrosion casts. Wistar rats were treated with middle cerebral artery (MCA) occlusion for 30 min, 1 h, 3 h, 4 h, 5 h or 7 h and subsequent reperfusion for 2 h. The ultrastructures of the cast were observed and computer-aided montage micrographs were obtained for visualization of the whole microvasculature in the ischemic brain hemisphere. Avascular areas representing ischemic areas were detected in the frontotemporal cortex and caudate putamen in the groups from 30 min to 5 h occlusion. Extravasation of the resin, which probably corresponded to the leakage of plasma or hemorrhage, was seen as spheroidal, conglomerative, large massive and worm-like types. The spheroidal type, which probably indicated a small leakage or minor hemorrhage, began to appear in the 30-min occlusion group. The conglomerative type, which probably indicated a larger leakage or moderate hemorrhage, appeared in the 3- to 5-h occlusion groups. The large massive and worm-like types, which probably indicated a significant hemorrhage, appeared in the 4- and 5-h occlusion groups. The number of these extravasations increased significantly in the 4-h occlusion group. Arterioles near the avascular area frequently showed vasospastic appearances, such as corrugations, fusiform indentations of endothelial nuclei, continuous circulatory constrictions and severe narrowing with interrupted branches. Arteriolar vasospasm possibly caused prolonged hypoperfusion even if reperfusion was achieved. The capillaries had a thin stringy appearance in the 4- and 5-h occlusion groups. These changes seemed to relate closely with increased intracranial pressure by brain edema or hemorrhage. The present study suggested that the risk of brain edema or hemorrhagic infarction increased beyond 3 h of MCA occlusion, and vasospasm of the arterioles might participate in stroke pathophysiology.

Can Restoring Incomplete Microcirculatory Reperfusion Improve Stroke Outcome after Thrombolysis?

“…Briefly, precapillary arterioles generally remain open, 9,25 although circular constrictions have been observed after prolonged permanent ischemia. 30 Capillaries show constrictions and luminal narrowing, which are attributed to compression by swollen astrocyte endfeet. 9,15 Their narrowed lumina are filled with entrapped erythrocytes, leukocytes, and fibrin-platelet deposits.…”

Protective effects of morphine preconditioning in delayed phase on myocardial ischemia-reperfusion injury in rabbits

“…Myocardial ultrastructure change is an effective indicator of the degree of myocardium injury (Ohtake et al, 2004). In the present study, electron microscoscopic examination showed markedly swollen myocardial cells, interstitial edema, vacuolar degeneration of the cytoplasm, disordered arrangement of myofilaments, high levels of edema and vacuolar degeneration in the sarcoplasm and mitochondria, as well as obvious interstitial edema in the I/R group.…”

Quantitative assessments of cerebral vascular damage with a silicon rubber casting method in photochemically-induced thrombotic stroke rat models

“…In such cases, the method resulted in no artificial effects on vascular diameter (Ono et al, 1997). Another published report showed precise microvasculature obtained by a casting method following focal cerebral ischemia and reperfusion in rats (Ohtake et al, 2004); this report confirmed the presence of avascular zones in the ischemic region, but precise quantitative analyses were not performed. Since these studies suggest that casting methods offer features ideal for assessing microvascular disturbances in rats, exert no artificial effects on cerebral vasculature, and permit precise observation of microvessels, this study sought to investigate quantitatively the persistence and spatial distribution of microvascular disturbances and their relationship to brain infarct formation, applying a casting technique to photochemicallyinduced thrombotic (PIT) stroke rat models.…”