Shigeki Imaizumi

Liposome-entrapped superoxide dismutase reduces cerebral infarction in cerebral ischemia in rats.

We studied the role of superoxide radicals in the pathogenesis of ischemic brain injury using a model of focal cerebral ischemia in 102 rats and liposome-entrapped CuZn-superoxide dismutase, which can penetrate the blood-brain barrier and cell membranes efficiently. The bolus intravenous administration of 25,000 units of liposome-entrapped CuZn-superoxide dismutase elevated superoxide dismutase activities in the blood and brain 1, 2, 8, and 24 hours later as well as in the ischemic hemisphere and contralateral cortex. Determined 24 hours after right middle cerebral and bilateral common carotid artery occlusion by the lack of staining for mitochondrial dehydrogenase activity with 2,3,5-triphenyltetrazolium chloride, infarct sizes were reduced by 33%, 25%, and 18% in the anterior, middle, and posterior brain slices, respectively, by treatment with liposome-entrapped CuZn-superoxide dismutase. Our data demonstrate that superoxide radicals are important determinants of infarct size following focal cerebral ischemia and that liposome-entrapped CuZn-superoxide dismutase may have pharmacologic value for the treatment of focal cerebral ischemic injury.

Chemiluminescence in hypoxic brain--the second report: cerebral protective effect of mannitol, vitamin E and glucocorticoid.

The effect of vitamin E, betamethasone and mannitol upon a series of pathological free radical reactions within hypoxic brain tissue was evaluated by the chemiluminescence method. Hypoxia was induced by arterial hypoxemia (PaO2 17-22 mmHg) with normocapnia (PaCO2 28-38 mmHg) and normotension (MABP 100-140 mmHg). 4% O2-96% N2 mixed gas was used to obtain the lowered PaO2. In the untreated group, increased chemiluminescence was measured in the hypoxic state and the early stage of the initial post-hypoxic state. In the groups administered vitamin E, betamethasone, mannitol and a combination of them reduced chemiluminescence was detected. To explore the reaction stage at which the drugs act in lipid peroxidation, chemiluminescence spectra was analyzed using the brain homogenate with the drugs added. Intensity peaks of the spectra were around at 480, 520-530, 570, 620-640, 680-700 nm before addition of the drugs. All the intensity peaks diminished after addition of vitamin E and betamethasone, but very little decrease occurred after mannitol. The lowered chemiluminescence value may indicate the free radical scavenging action of vitamin E, betamethasone and mannitol in vivo. Chemiluminescence spectrum analysis shows that vitamin E and betamethasone act on the late chain reaction following hydroperoxide and mannitol acts on the early reaction--generation of active oxygens.

Chapter 6 Role of superoxide dismutase in ischemic brain injury: reduction of edema and infarction in transgenic mice following focal cerebral ischemia

Publisher Summary During the past few decades, a large accumulated body of experimental data has indicated that the biological reduction of molecular oxygen can yield dangerously reactive free radicals. About 2–5% of the electron, flow in isolated brain mitochondria produces superoxide (O 2 · – ) and hydrogen peroxide (H 2 O 2 ). These constantly produced oxygen radicals are scavenged by endogenous antioxidants including antioxidative enzymes such as superoxide dismutases (SOD S ), catalase, glutathione peroxidase, and non-enzymatic antioxidants such as reduced glutathione, ascorbic acid and α-tocopherol. Superoxide dismutase scavenges superoxide radicals at a rate close to diffusion, whereas glutathione peroxidase and catalase are specific scavengers for H 2 O 2 and other lipid peroxides. Both enzymatic and non-enzymatic antioxidants are located in cellular membranes, cytoplasmic compartments and subcellular organelles such as mitochondria and peroxisomes. Based on the metal ion requirements and the anatomical distribution, two types of SOD exist in brain cells. CuZn-SOD is a cytosolic enzyme that requires both copper and zinc ions as cofactors, whereas manganese (Mn)-SOD is a mitochondria1 enzyme with requirement for Mn 2+ . Recent studies have demonstrated that CuZn-SOD is primarily localized in peroxisomes, a subcellular organelle that also contains high levels of catalase in plants. Both CuZn-SOD and Mn-SOD from various sources have been fully characterized biochemically and the cDNAs of both human enzymes have been successfully cloned. Both cDNA and genomic DNA of human CuZn-SOD have been used to successfully generate transgenic mice.

THE INFLUENCE OF OXYGEN FREE RADICALS ON THE PERMEABILITY OF THE MONOLAYER OF CULTURED BRAIN ENDOTHELIAL CELLS

Free radicals have been implicated in the pathogenesis of vasogenic brain edema caused by ischemic or traumatic injury. It has been reported that in transgenic mice overexpressing the human CuZn-superoxide dismutase, brain edema is decreased in many cerebral disorders. To investigate the effects of free radicals on the permeability of the blood brain barrier, we established an in vitro model system of the blood-brain barrier using brain endothelial cells cultivated from transgenic mice and non-transgenic mice. The blood-brain barrier model is originated by a monolayer of brain endothelial cells cultured on a membrane which has 0.45-micron pores. Electrical resistance across the cell monolayer, which reflects the paracellular flux of ionic molecules, was measured. The blood-brain barrier models were incubated with menadione (vitamin K3, an intracellular O2- producing agent), and segmental changes in the electrical resistance across the monolayer were compared between the transgenic and the non-transgenic mice. Superoxide dismutase activity of the cultured brain endothelial cells was 1.7 times higher in the transgenic than in the non-transgenic mice (n = 3, P < 0.001). The electrical resistance was reduced by menadione in the transgenic but not in the non-transgenic mice (n = 7, P < 0.05) in the early stage. Moreover, desferroxamine mesylate (Fe2+ chelating agent) inhibited the menadione-induced early decrease in electrical resistance in the transgenic mice (n = 7, P < 0.05). These results suggest that the permeability of the blood-brain barrier may be affected by hydroxyl radicals and/or peroxynitrite rather than the O2- itself.

Effect of calcitonin gene-related peptide on delayed cerebral vasospasm after experimental subarachnoid hemorrhage in rabbits.

BACKGROUND Calcitonin gene-related peptide (CGRP) is an intrinsic vasodilatory substance contained in perivascular nerve fibers of intracranial arteries. It is suggested that CGRP plays a role in cerebral vasospasm after subarachnoid hemorrhage (SAH). METHOD An experimental SAH was produced by intracisternal injection of arterial blood in rabbits. The animals were treated with intrathecal administration of CGRP solution 3 days after SAH. The degree of vasospasm and the effect of CGRP were evaluated angiographically by measuring the basilar artery diameter. RESULTS The basilar artery constricted to 73.0% of the pre-SAH values 3 days after SAH. Fifteen minutes after injection of 10(-10) mol/kg CGRP, the basilar artery dilated to 117.1% (n = 8), which was significantly larger than 67.1% in the vehicle group (n = 8) (p < 0.01). The significant vasodilatory effect of CGRP, compared with the vehicle group, lasted for 6 hours. CONCLUSIONS Intrathecal administration of CGRP has therapeutic potential for treating cerebral vasospasm.

A distal anterior cerebral artery aneurysm in infant: disappearance and reappearance of the aneurysm.

The incidence of intracranial aneurysms in childhood is rare, especially in infancy. Spontaneous thrombosis of a cerebral aneurysm in a child is very rare, particularly in a non-giant aneurysm. We report a case of a 1-month-old girl with a distal anterior cerebral artery aneurysm which disappeared spontaneously after subarachnoid hemorrhage and reappeared 6 months later. Surgical resection of the aneurysm was performed and she discharged uneventfully 10 days later. Histological examination revealed an aneurysm with a fibrous muscular layer, absence of the internal elastic lamina and partial hypertrophy of the intimal layer. Though the pathogenesis of this aneurysm is uncertain, two hypotheses are discussed.

Unruptured carotid-duplicated middle cerebral artery aneurysm: case report.

We demonstrate the first case with unruptured carotid-duplicated middle cerebral artery (IC-Dup MCA) aneurysm combined with ruptured opposite carotid aneurysm. Eleven IC-Dup MCA aneurysm reported until now had all ruptured. It is noteworthy that 8 patients of the 11 were Japanese.

Growth of small unruptured intracranial aneurysm: case report.

Magnetic resonance angiography (MRA) revealed silent but rapid growth of a small unruptured intracranial aneurysm until it was surgically treated to prevent rupture. Modern neuroimaging methods such as MRA and 3-dimensional computed tomography have increased opportunity to detect small unruptured cerebral aneurysms. Strict follow up is an option for the incidentally discovered small intact aneurysms using these methods.

Free hand aspiration for large periventricular hemorrhage: case report

BACKGROUND At present, there are several therapeutic options, including craniotomy and stereotactic aspiration, for large intracerebral hemorrhage perforating into the lateral ventricle. In the cases with Glasgow Coma Scale (GCS) scores under 6 with anisocoria, external ventricular drainage would be the first choice [2-4]. We have also performed anterior ventricular horn puncture in a standard manner. The target was the foramen of Monro, at a depth of 5.5 cm from the inner table of the skull. The point of insertion was located just anterior to the coronal suture, approximately 10 cm above the nasion, and 3 cm from the midline [1]. However, we noticed that the insertion of a catheter into the periventricular hematoma adjacent to the lateral ventricle was made easier by tilting the catheter 30 degrees laterally as in the first case (Figure 1). METHODS In our method, inclining the catheter by 30 degrees laterally, we used a silicone tube 3.5 mm in internal diameter (Silascon ventricle drainage tube, Kaneka Medix Corp., Osaka, Japan) and then replaced it with another Silascon tube with a 2.5 mm-internal diameter. From January 1999 through December 2000, eleven patients who all had GCS scores under 6 and anisocoria preoperatively were treated by this method. The series included two patients who were undergoing hemodialysis because of renal failure, two with bleeding tendency because of liver dysfunction, and one with heart failure. RESULTS The insertion itself caused no complications. Cerebrospinal fluid was drained smoothly after removal of hematoma because the hematoma cavity connecting with the lateral ventricle was opened. Two typical cases using this technique are shown (Figures 1 and 2). All patients recovered favorable consciousness postoperatively compared with the preoperative state but hemiparesis remained. Postsurgical follow up at 3 months revealed the outcomes evaluated by Glasgow Outcome Scale (GOS) were moderate disability in 5 patients and severe disability in 6 patients . CONCLUSION This direct aspiration and drainage of a large intracerebral hematoma that ruptures into the lateral ventricle is superior to simple ventricular drainage in regard to the removal of the hematoma clot. This technique would be the choice especially in patients with serious complications such as cardiac disease and renal failure.

Symptom changes caused by movement of a calcified lateral ventricular meningioma: Case report

BACKGROUND Large calcified psammomatous meningioma in the left lateral ventricle with a long silent interval of 16 years was presented. The symptoms varied by its moving not enlargement, which was described by sequential images of the brain computer tomography. Combined approaches of transcallosal and transinferior temporal sulcus routes were superior to prevent injury of the speech center in the dominant hemisphere.