Ryusuke Ogawa

Role of the endothelium on extraluminal and intraluminal vasoactive mechanisms in the perfused rabbit basilar artery.

In order to investigate the role of the endothelium in the regulation of cerebrovascular tone, we studied selective intraluminal and extraluminal vasoactive mechanisms of acetylcholine, potassium and serotonin. We also examined the effects of removal of the endothelium on these vasoactive responses. With 0.75 g of tension, isolated rabbit basilar arteries were fixed in a perfusion system with the ability to isolate the intraluminal and extraluminal surfaces, and perfused at 8 ml-1 min-1 under a pressure of 8 mmHg. To remove the endothelium, we applied several concentrations of saponin. The endothelium was completely removed by 0.05 mg-1 ml-1 saponin, confirmed histologically. Extraluminal and intraluminal acetylcholine induced endothelium-dependent relaxations. Intraluminal potassium induced greater contraction than extraluminal potassium in both saponin denuded (p < 0.01) and intact preparations (p < 0.05, n = 8). Intraluminal and extraluminal serotonin induced symmetric contractions, and for both sides the response was enhanced by removal of the endothelium (p < 0.05, n = 6). Our results suggest that inhibitory (relaxant) contribution of the endothelium to contractile responses varies depending on the vasoactive agent. The fact that the effects of some extraluminal agents were enhanced when the endothelium was denuded, may be of some importance in potentiating the mechanism of vasospasm following subarachnoid haemorrhage.

Development of a new perfusion system for pharmacological study on rabbit basilar arteries.

We developed a constant-flow perfusion system to measure vascular responses to vasoactive agents applied intraluminally or extraluminally. The intraluminal and extraluminal sides of a cylindrical section of rabbit basilar artery were isolated completely. By loading with 0.75 g of tension, the resting condition of each preparation was made constant. The intraluminal side was perfused at a constant flow of 8 ml/min and under an intraluminal pressure of 8 mm Hg. When 30 mM KCl was administered intraluminally the preparation showed marked contraction, whereas only slight contraction was observed with extraluminal administration. When 2 x 10(-7) M 5-hydroxytryptamine was administered, no significant differences in contraction could be detected between the intraluminal and extraluminal routes. Application of 10(-6) to 10(-4) M acetylcholine after precontraction with 30 mM KCl resulted in much stronger dilatation upon intraluminal application. Thus, it was demonstrated that under certain conditions significant differences exist in the responses of rabbit basilar arteries to vasoactive agents applied intraluminally or extraluminally. This system can detect the effects of vasoactive agents administered intraluminally and extraluminally at a high level of sensitivity and shows good reproducibility as a means of analyzing vascular functions and characteristics.

Aphasia following left putaminal hemorrhage. Statistical analysis of factors affecting prognosis

Abstract Multivariate and single variable analyses were employed to investigate the recovery mode of aphasia in right-handed patients with putaminal hemorrhage on the left side. Speech disturbance was evaluated using the standard language test for aphasia (SLTA) at intervals of 1, 3 and 6 months after the ictus. Recovery was assessed in relation to age, gender, volume and location of hematoma, and treatment modalities. Extension of the hematoma into the corona radiata was the factor that dominated the prognosis of aphasia at all intervals during the follow-up period. Good recovery was documented in patients with less than 2 cm2 of the hematoma volume located in the corona radiata. Recovery was poor, however, in patients with more than 12 cm2 of the hematoma in the corona radiata. While aphasia continued to improve over 6 months after the ictus, recovery was more prominent in the first 3 months. Our study precisely demonstrated that the extension into the corona radiata independently and strongly influenced the outcome of aphasia in patients with left putaminal hemorrhage.

Effect of Ebselen on Contractile Responses in Perfused Rabbit Basilar Artery

OBJECTIVE To evaluate the possible role of the antioxidant ebselen in the treatment of cerebral vasospasm, we examined the effects of ebselen on the vasoactive mechanisms induced by endothelin (ET)-1, oxyhemoglobin, and oxygen-derived radicals. METHODS Isolated rabbit basilar arteries with intact endothelium were fixed in a perfusion system and perfused intraluminally. Contraction of the artery was detected as an increase in perfusion pressure. RESULTS Ebselen, in a certain concentration range (3 x 10(-6) and 10(-5) mol/L), significantly reduced the contractile response to ET-1 (10(-10) to 10(-8) mol/L) but not the contraction induced by 40 mmol/L potassium. It reduced the contraction induced by 10(-4) mol/L 1,2-dioctanoyl-sn-glycerol, a protein kinase C activator. Addition of 10(-5) mol/L dithiothreitol, a sulfhydryl-reducing agent, partially reversed the inhibitory effects of ebselen on ET-1- and 1,2-dioctanoyl-sn-glycerol-induced contractions. Ebselen (10(-5) mol/L) as well as a combination of catalase (1000 units/mL) and superoxide dismutase (150 units/mL) inhibited the potentiating effects of oxyhemoglobin (10(-5) mol/L) on ET-1-induced contraction. Both ebselen and catalase inhibited the contractile response to hydroxyl radical generated by ferrous ion (10(-3) mol/L) plus hydrogen peroxide (10(-2) mol/L). Ebselen reduced the response to potassium when a high dose (3 x 10(-5) mol/L) was applied and failed to preserve contractility of the preparation after exposure to hydroxyl radical. CONCLUSION Ebselen suppressed ET-1-induced contraction and synergetic interaction between oxyhemoglobin and ET-1, where free radical formation was involved. These effects may result from modification of the intracellular regulatory system including protein kinase C, as well as from protection against free radicals.

Pressure gradients between intraluminal and extraluminal spaces may affect the potassium induced contraction in the rabbit’s basilar arteries

In order to investigate the different contactile effects between intraluminal and extraluminal vasoactive agents, we studied the contractile responses of rabbit basilar artery to selective intraluminal and extraluminal administration of potassium, serotonin and histamine in vitro. We also studied how the physical pressure gradients, such as hydrostatic or osmotic pressure gradients between intraluminal and extraluminal spaces, affect potassium-induced contraction. Intraluminal potassium (30 mM) induced a significantly greater contraction than extraluminal potassium. Serotonin (2 x 10(-7) M) and histamine (10(-5) M) applied intraluminally caused the same magnitude of the contraction as those applied extraluminally and no significant differences were noted between these applications. These differences in potassium-induced contraction were more significant when the intraluminal hydrostatic pressure was elevated by 20 mmHg. Contraction by either intraluminal or extraluminal potassium was significantly decreased when intraluminal pressure was raised by 40 mmHg. As the osmotic pressure gradients between the extraluminal and the intraluminal spaces were increased, these differences in potassium-induced contraction were decreased. Our findings suggest that physical pressure gradients may affect potassium-induced contraction in a different manner from pharmacologically-induced contraction and that free ions can penetrate the vascular wall by physical pressure gradients between the intraluminal and extraluminal spaces of cerebral artery.