Abstract
Experimental cerebral infarction has been produced in dogs by clipping the middle cerebral artery and lowering the systemic blood pressure to 50mmHg for one hour. In this study, changes in microvasculatures in or near the ischemic area of the experimental animals were examined with light and electron microscope. All the dogs were sacrificed 24 hours after restoration of blood pressure. They were devided into three groups: the clip was permanently placed (Group 1); the clip was removed at the time of sacrifice (Group 2); and the clip was removed 4 hours after restoration (Group 3).
Hemorrhage from venules at the boundary zone between the gray and white matters was the common and conspicuous finding in all groups. Venules showed severe ischemic damages including disruption of the limiting membrane of the swollen perivascular glial processes. The enlarged perivascular space was filled with erythrocytes. The capillaries of this boundary zone were occluded by erythrocytes and by the endothelial swelling, but were not ruptured.
In the ischemic cortex, capillaries of Group 1 and 2 were packed with erythrocytes and platelets, but were not broken down. In the third group, on the other hand, hemorrhage from necrotic capillaries was one of the characteristic findings; Endothelial flattening and discontinuity and destruction of the basement membrane were observed under electronmicroscope. Marked brain edema was also seen.
These results indicated that changes in the fine structure of the microvasculature in the area of focal cerebral ischemia varies according to the location of the area and the degree of ischemia.
