Tohru Okuyama

Regional ischemia in cerebral venous hypertension due to embolic occlusion of the superior sagittal sinus in the rat

To determine the pathophysiological changes in brain tissue that characterize damage following cerebral venous hypertension, a model of cerebral venous hypertension in the rat was devised. This experimental model has the advantage of simultaneously measuring the regional changes in cerebral blood flow as well as the metabolism. The ischemic area demonstrated by the accumulation of NADH is confined to the cerebral cortex and becomes enlarged in proportion to the increase in venous pressure. This metabolic disturbance appears even in the very early period following cerebral venous hypertension. These pathophysiological features are different from those observed in the case of intracranial hypertension.

Changes in cerebral microvasculature in congenital hydrocephalus of the inbred rat LEW/Jms: light and electron microscopic examination.

The vascular apparatus in congenitally hydrocephalic rat brains was studied. The characteristic findings were structural changes in the small vessels with formation of an intracerebral cavity in the periventricular white matter. Stenotic or occluded blood vessels were located in an edematous area adjacent to the dilated lateral ventricles. Electron microscopically, the endothelial cells of capillaries and venules in the periventricular edematous region showed an irregular surface with indentations, and contained numerous plasmalemmal vesicles. Occluded capillaries were found in the border zone between the edematous and nonedematous area. These vascular changes indicate the presence of a disturbed microcirculation in the hydrocephalic brain.

Characteristics of Brain Tissue Damage in Kaolin-induced Infantile Rat Hydrocephalus

Experimental hydrocephalus was induced by an intracisternal injection of 4% or 40% kaolin suspension in 2 days old Wistar rats. They were examined histologically and microangiographically 2 weeks after the injection of kaolin. Hydrocephalic rats were classified into 2 groups, severe hydrocephalic group A and mild hydrocephalic group B. In group A, a marked enlargement of the entire ventricular system with a thinning of the cerebral mantle was observed. On the other hand, the dilatation of the fourth ventricle was more pronounced compared with the other ventricles in group B. In group A, a spongy appearance of brain tissue was observed in the periventricular white matter accompanied with an intracerebral cavity. In these edematous areas, the lack of carbon black perfusion was apparent indicating an occurrence of microcirculatory disturbances. These microcirculatory disturbances and mechanical compression to the cerebral parenchyma may produce defective brain tissue (intracerebral cavity formation). The ependymal cell walls and subependymal glial cell layers were well preserved in spite of the damaged periventricular white matter. In group A, kaolin was present in the fourth ventricle and Sylvian aqueduct. Subependymal gliosis containing macrophages and newly produced blood vessels were observed in the region between the periventricular brain tissue and kaolin granules. These findings indicate that kaolin may produce changes in the ependymal cell and cerebral parenchyma as well as fibrosis and meningitis in the subarachnoid space.

Morphological Study on Congenital Hydrocephalus of the Inbred Rat, LEW/Jms

The morphological changes of the cerebral gray matter in congenital hydrocephalic rat were studied. Dilatation of the ventricle with thinned cerebral mantle was observed. The characteristic finding was the “intracerebral cavity formation” in the gray matter as well as in the cerebral white matter.