We studied ultrastructurally cerebral perforating arteries in 60 stroke-prone spontaneously hypertensive rats (SHRSP), which were sequentially killed at 4-52 weeks of age before showing symptoms of stroke. Another 24 SHRSP were killed soon after they showed symptoms of cerebral infarction. The initial vascular lesions included focal cytoplasmic necrosis in the outer layers of the media. This change progressed to widespread medial necrosis with time although endothelial cells were well-preserved. The adherence of monocytes to the endothelium, having advanced medial damages, triggered the accumulation of the plasma components in the arterial wall. The accumulation thickened the wall, narrowed the lumen and resulted in arterial occlusion. These results suggest that the monocytes may affect the endothelium, disturbing the so-called blood-brain barrier to proteins.
Furthermore we measured the blood pressure and histologically examined the brains, hearts, and kidneys in normotensive WKY and SHRSP rats fed on a diet containing L-N-nitroarginine (L-NNA: EDRF inhibitor). In addition we examined L-NNA-treated SHRSP, the blood pressure of which was lowered using hydralazine. Moreover we examined Goldblatt's renal hypertensive rats, which were of a different type from those resulting from the L-NNA treatment. Both WKY and SHRSP rats fed on a diet containing L-NNA suffered from hypertension and cerebral infarctions in a dose-dependent manner. Cerebral infarctions occurred whether or not SHRSP rats were treated with an antihypertensive agent when they were fed a high dosage of L-NNA. In contrast there were no cerebral infarctions in Goldblatt's renal hypertensive rats, although they suffered from advanced hypertension. The data indicate that the inhibition of EDRE injures the vessel walls and encourages platelet adhesion to the damaged areas. The adhering platelets narrow the lumen with resultant thrombotic occlusions.

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The influence of blood flow to the thrombus formation was analyzed using hybrid vascular model (HVM). HVM was made by silica glass and endothrialization was performed. HVM was implanted into femoral artery and vein of mongrel dog respectively. HVM from artery was not recognized thrombus formation. Minimal platelets adhesion was observed by scanning electron micro scope (SEM) (Fig. 1). In contrast, line shaped thrombus was observed on the inferior area of the venous specimen (Fig. 2). Different flow patterm, artery and vein, effect the different shesr stress on the vessel wall. Those findings suggested that diminution of shear stress induced the thrombus initiation in vein.
Pathological changes of vessels, i, e. aneurysm and stenosis, are influenced to thrombus formation in clinical experience. Pathological model, eccentric dilatation or stenosis in the center of the tube, were connected to in vitro flow visualizing system. Flow pattern through the model was recorded by video (Fig. 3). Significant flow stagnation was observed in dilatation and just after stenosis (Fig. 4). Pathological HVM (D-HVM and S-HVM) were implanted into femoral arteries. The specimen demonstrated that thrombus was located the same area of the flow stagnation in vitro (Fig. 5). Those results surmised that flow stagnation related with thrombus formation.
Owing to estmate the thrombin production on the endothelial cell (EC), HVM was incubated with thrombomodulin monochronal antibody (TMmAb20: Mitsubishi Gas Chemical). HVM was implanted into femoral vein. Immediate thrombus formation was occurred and obvious fibrin network on the EC was observed (Fig. 7). This finding suggested hat the thrombin was produced on the EC in physiologically. However, thrombomodulin on the EC affected with thrombin and thrombin was altered non-active form in physiological flow. This finding suspected that the flow stagnation would diminish the clearance of thrombin on the EC.

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Influence of blood flow in the intravascular thrombus formation was evaluated in vivo study using cultured endothelialized glass tube vascular model and the in vitro study using the flow visualizing model (FVM). 1) 1.5×50mm straight silica glass tube were used as a physiological hybrid vascular model (P-HVM). Endothelialization were performed by rotator cultivation using bovine aorta endotherial cells suspended in RPM1 1640. The femoral artery and vein of eighteen mongrel dogs were interposed by the model respectively. The model were exposed to blood flow for 1 to 24 hours. The average blood flow of femoral artery and vein were both 30ml per minute and not significant dif f errence between artery and vein in blood flow was found. Arterial replacement P-HVM demonstrated 100% patency for 24 hours. SEM micro graphs showed a fairly clean surface morphology with minimal platelets adhesion. In contrast, the longest patency of P-HVM in the vein was 18 hours, and line shaped thrombus was observed inferior area 1 hour after replacement. 2) 2.0×50mm tube which has eccentric dilatation or stenosis in the center were used as pathological model (D-/S-HVM). After endotheliazation, the model were interposed. FVM was developed using open circuit which connected with the artificial heart and scale up model of D-/S-HVM. The correlation between in vitro hydrodynamic events and in vivo results were evaluated. FVM demonstrated the stagnation in the dilatation area of D-HVM and peripheral area of the stenosis in the S-HVM. Initial thrombus formations in vivo model observed just on the flow stagnation area of FVM. It would be concluded that the difference in the shear stress between artery and vein on the vessel wall leaded to the difference of the thrombus formation in P-HVM. The shear stress diminution on the vessel wall by flow disturbance from dilatation or stenosis would cause of initial intravascular thrombus formation.

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Recently a rapid decline of thrombotest values in several patients on warfarin therapy with benzbromarone was observed. Since conbination therapy with benzbromarone appeared to give rise to a bleeding tendency, both drugs were investigated for interactions.
The study subjects included 8 patients who had been treated with warfarin for cardiovascular disease and were also given benzbromarone for gout. The doses of warfarin averaged 1.94mg, with a range of 1.0 to 3.0mg/day, and the average dose of benzbromarone was 62.5mg, with a range of 50 to 100mg/day. While keeping the patients on warfarin therapy, benzbromarone was withdrawn for one week only, and changes in the blood coagulation systems were determined before and after withdrawal of benzbromarone.
The mean thrombotest value was increased from 22.3% (PT-INR 2.0) to 43.0% (1.4) after drug withdrawal, coagulation factor II increased from 57.3% to 74.5%, PIVKA-II decreased from 11.5AU/ml to 7.0 AU/ml, and the blood concentration of warfarin decreased from 656.5ng/ml to 563.6ng/ml. All the changes were statistically significant (p<0.05). These results indicate that benzbromarone strongly potentiates warfarin. When both drugs are to be combined clinically, patients should be carefully observed for a bleeding tendency.

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