Keiji Kohno

Neuroprotective nitric oxide synthase inhibitor reduces intracellular calcium accumulation following transient global ischemia in the gerbil

By observing the ultrastructural intracellular Ca2+ distribution with Ca(2+)-oxalate-pyroantimonate method, we examined whether the protective mechanism of the nitric oxide (NO) synthase inhibitor, N omega-nitro-L-arginine (LNNA), involves change of the intracellular Ca2+ movement in delayed neuronal death (DND) in gerbil hippocampal CA1 neurons following 5-min forebrain ischemia. In the group intraventricularly administered 5.0 mg/ml LNNA, 15 min after reperfusion the intracellular Ca2+ deposits and the mitochondrial Ca2+ uptake index increased to levels similar to those in the control group administered only artificial cerebro-spinal fluid, but by 180 min after reperfusion they had returned to the preischemic level. By 15 min after reperfusion Ca2+ deposits in the endoplasmic reticulum (ER) had almost disappeared in both groups, but at 180 min of reperfusion, the ER in only the LNNA group showed Ca2+ deposits. It is suggested that the neuronal toxicity of NO involves the dysfunction of the intracellular Ca2+ transport system including the mitochondria and ER.

Calcium Movement in Ischemia-Tolerant Hippocampal CA1 Neurons After Transient Forebrain Ischemia in Gerbils

Hippocampal CA1 neurons exposed to a nonlethal period (2 min) of ischemia, acquired tolerance to a subsequent lethal 5-min period of ischemia, which usually causes delayed-type neuronal death. Intracelluar Ca2+ movements before and after the 5 min of forebrain ischemia were evaluated in gerbil hippocampal CA1 pyramidal neurons, had acquired tolerance in comparison with nonischemia-tolerant CA1 neurons. Evaluation was performed by observing the ultrastructural intracellular Ca2+ distribution and the Ca2+ adenosine triphosphatase (Ca2+-ATPase) activity using electron microscopic cytochemistry. In comparison with nonischemia-tolerant CA1 neurons, mitochondria of ischemia-tolerant CA1 neurons sequestered more Ca2+ from the cytosomal fraction 15 min after the 5-min period of ischemia, and Ca2+ deposits in these mitochondria were rapidly decreased. Plasma membrane Ca2+-ATPase activities were already significantly elevated before the 5 min of ischemia, and remained at a higher level subsequently compared to nonischemia-tolerant CA1 neurons. Changes in the mitochondrial Ca2+ distribution and Ca2+-ATPase activities in ischemia-tolerant CA1 neurons after the 5-min period of ischemia showed a strong resemblance to those in CA3 neurons, which originally possess resistance to such periods of ischemia. These findings suggest that enhanced or maintained activities of mitochondrial Ca2+ sequestration and plasma membrane Ca2+-ATPase reduced Ca2+ toxicity following 5-min ischemia in terms of time, resulting in escape from delayed neuronal death.

Endovascular treatment for acute thrombotic occlusion of the middle cerebral artery: local intra-arterial thrombolysis combined with percutaneous transluminal angioplasty

Abstract We report our experience in treating 15 patients with acute thrombotic occlusion of the M1 or M2 segment of the middle cerebral artery who underwent intra-arterial thrombolytic therapy alone or in combination with percutaneous transluminal angioplasty (PTA). The results were compared with those of 30 patients with acute embolic occlusion of the same artery. Intra-arterial thrombolysis was performed in 10 patients and thrombolysis combined with PTA in 5 in whom symptoms reappeared due to restenosis or reocclusion, or in whom recanalisation was not successfully accomplished by thrombolysis alone. In the patients with embolism recanalisation was observed in 28 (93 %) and there was no patient with reocclusion. In the patients with thrombosis recanalisation immediately after thrombolysis alone was observed in 9 of 15 (60 %). Restenosis, with reappearance of symptoms, occurred in 2 of these (22 %). In the patients who also underwent PTA, angiography after 1 month did not demonstrate any restenosis or reocclusion. Thrombolysis combined with PTA for acute thrombotic stroke may provide an effective procedure for restoring patency and preventing reocclusion of the occluded artery.

Intracellular calcium levels in canine basilar artery smooth muscle following experimental subarachnoid hemorrhage : an electron microscopic cytochemical study

SummaryChanges in intracellular calcium levels in canine basilar arterial smooth muscle were semiquantitatively measured by an electron microscopic cytochemical technique using a combined oxalate-pyroantimonate method. Measurements made after subarachnoid hemorrhage were compared with those made after contraction induced by prostaglandin F2α. Fifteen minutes after topical application of the drug, when the basilar artery was constricted by 20%, 15% of smooth muscle cells contained a large amount of intracellular calcium. One hour later, the diameter of the basilar artery and intracellular calcium precipitation returned almost to control levels. Fifteen minutes after the first intracisternal injection of autologous blood, when acute vasospasm was angiographically evident, 13% of smooth muscle cells contained a large amount of calcium. After 1 h, when acute vasospasm had already abated, the number of smooth muscle cells containing a large amount of calcium markedly increased to 37% and some smooth muscle cells showed early degenerative findings such as intracytoplasmic vacuoles including calcium accumulation. After 48 h, when delayed vasospasm had already started, the calcium deposits and early degenerative changes had decreased significantly. After 49 h and 4 days (1 h and 48 h after the second injection of blood), the change in the amount of calcium was the same as at 1 h and 48 h after the first injection, respectively, but degeneration of smooth muscle cells increased. Therefore, acute vasospasm after subarachnoid hemorrhage may be caused by an initial elevation of intracellular calcium levels, as is the case with drug-induced contraction. Delayed vasospasm may be initiated by an excessive influx of calcium accompanied by early degeneration of cells within a few hours after subarachnoid hemorrhage. This may be followed by persistent contraction of smooth muscle cells in a low concentration of intraccllular calcium and by progressive structural derangement.

Nitric oxide synthase inhibitor reduces delayed neuronal death in gerbil hippocampal CA1 neurons after transient global ischemia without reduction of brain temperature or extracellular glutamate concentration

We planned a study to determine whether or not the mechanism of nitric oxide (NO) neurotoxicity involves the elevation of extracellular glutamate or changes of brain temperature in the pathogenesis of delayed neuronal death of gerbil hippocampal CA1 neurons following 5-min transient forebrain ischemia. Intraventricular injection of 5 microliters of 5.0 mg/ml N omega-nitro-L-arginine (LNNA) significantly preserved neuronal density in the central part of the CA1 region examined 7 days after 5-min ischemia [188.5 +/- 8.5/mm: 90.0% of the 209.5 +/- 11.1/mm density in the sham-operated controls vs. 16.7 +/- 6.4/mm in those injected with artificial cerebrospinal fluid (CSF) only]. There was no difference between these two groups in hippocampal temperature before, during or after 5-min ischemia. The glutamate concentration ([Glu]) during 5-min ischemia measured by a microdialysis technique was similar in the two groups (peak [Glu.] = 2.76 +/- 0.62 pmol/microliters dialysate in the artificial CSF group and = 2.93 +/- 0.64 pmol/microliters dialysate in the LNNA group). It was found that the neuronal toxicity of NO does not involve hyperthermia or the increase of extracellular glutamate concentration in the hippocampal CA1 region during 5-min ischemia.

Intraventricular administration of nitric oxide synthase inhibitors prevents delayed neuronal death in gerbil hippocampal CA 1 neurons

We performed experiments to investigate the participation of nitric oxide (NO) in the delayed neuronal death (DND) of gerbil hippocampal CA1 neurons, following 5-min forebrain ischemia with pretreatment of stereotaxic intraventricular administration of several types of NO synthase inhibitors and biologically inactive control drugs. The number of surviving neurons in the control drug groups administered NG-monomethyl-D-arginine or NG-nitro-D-arginine methyl ester was comparable to that in the group administered artificial cerebro-spinal fluid, while the groups administered NOS inhibitors, such as NG-monomethyl-L-arginine or NG-nitro-L-arginine methyl ester, showed significant preservation of the neuronal densities compared with the control drug groups, to over 60% of the sham operation group value. Furthermore, intraventricular administration of N omega-nitro-L-arginine at various concentrations disclosed a dose-dependent protection against the DND. These results suggest that the generation of NO may act to promote the establishment of DND.

Early detection of cerebral ischemic lesion using diffusion-weighted MRI.

We performed serial diffusion-weighted imaging (DWI) in a patient with right middle cerebral arterial occlusion using 1.0 T MRI. The initial DWI demonstrated suppression of water diffusion in the gray matter in the ischemic lesion as a high signal area 4 h after stroke onset, when T2-weighted imaging failed to detect any parenchymal injury. Repeat DWI 9 h after onset demonstrated the whole infarct, whereas it was not demonstrated by T2-weighted imaging until 48 h. Furthermore, the regional apparent diffusion coefficient (ADC) had already decreased significantly in both the gray and white matters of the ischemic lesion 4 h after onset, even though hyperintensity was not visible in the white matter on the DWI. The features in this case indicate that DWI in conjunction with the assessment of regional ADC can provide important information regarding the evolving infarct at a very early stage even when a relatively low tesla clinically available MRI unit is used.

Bilateral vertebral artery dissecting aneurysm with subarachnoid hemorrhage treated with staged bilateral vertebral artery coil occlusion: a case report

BACKGROUND Vertebral artery dissecting aneurysm is now increasingly recognized as a cause of posterior circulation stroke in young adults. Here, we report a case of bilateral VADA with SAH, treated by bilateral coil occlusion using GDCs. CASE DESCRIPTION A 64-year-old woman was admitted to our hospital with consciousness disturbance (Hunt and Kosnik: grade 4). Computed tomography showed diffuse SAH with a thick hematoma in the left C-P angle. Magnetic resonance angiography, 3D-CTA, and cerebral angiography revealed bilateral VADAs. First, the ruptured left VADA involving the PICA and a perforating branch was treated by occluding the lower half of the VADA and the proximal VA with GDCs in the acute stage. Thereafter, the residual VADA and contralateral VADA exhibited enlargement on cerebral angiography and MRA for 2 months after the initial surgery; thus, the right VADA was occluded by GDCs just proximal to the right PICA after confirming BTO tolerance. CONCLUSION Staged bilateral VA coil occlusions combined with BTO may be one of the treatment strategies for bilateral VADA with SAH in cases presenting surgical difficulty due to anatomical factors or severe grade of SAH.

Magnetic resonance angiography in patients with acute stroke treated by local thrombolysis

Abstract Although magnetic resonance angiography (MRA) is accepted for showing chronic intracranial stenotic or occlusive lesions, the method has not been practically examined in patients with acute cerebral ischaemia. We carried out three-dimensional time-of-flight MRA in six patients with acute ischaemia treated by local thrombolysis, and compared the findings with those of digital subtraction angiography (DSA). In all patients, MRA before thrombolysis clearly demonstrated the occluded arteries, which corresponded precisely to those shown by DSA. In four patients with complete recanalisation of the occluded vessels after thrombolysis, the recanalisation could be demonstrated by postoperative MRA. In one patient with reocclusion of the recanalised artery, repeat MRA also demonstrated the reocclusion, confirmed by DSA. These results suggest that MRA may be helpful for noninvasive investigation before and after thrombolysis.

Correlation between magnetic resonance angiography and cerebral blood flow change in patients who underwent bypass surgery

To evaluate bypass function, we examined the relationship between postoperative magnetic resonance angiography (MRA) and postoperative change in cerebral blood flow (CBF) using 133Xe-SPECT in nine patients who underwent bypass surgery. MRA was obtained through the methods of three-dimensional time-of-flight (3D-TOF), and 2D-TOF with selective presaturation and phase contrast. The findings of postoperative MRA were classified into marked, moderate and poor flow groups according to the degree of blood flow supplied via the bypass. Patients in the marked or moderate flow groups exhibited a postoperative improvement in CBF, but those in the poor flow group did not. As postoperative MRA correlated well with postoperative change in CBF in patients who underwent bypass surgery, it was useful for evaluation of bypass function.