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S Oi

Publications and source records attributed to S Oi.

At least 19 recordsLinked to original sources
PubMed2003

Distribution of intracellular and extracellular water molecules in developing rat's midbrain: comparison with fraction of multicomponent T(2) relaxation time and morphological findings from electron microscopic imaging.

OBJECTIVE: In the present study, we examined the behavior and state of water molecules in immature and mature rat brains by measuring the components of magnetic resonance (MR) water proton transverse relaxation time ( T(2)). We also performed morphological examination of immature and mature rat brains using electron microscopy (EM). We then compared the fraction of T(2) component and the EM findings. METHODS: Midbrains of male Wistar rats were examined at various time points ranging from 4 h to 12 weeks after birth. T(2) was measured by MR, and the ratios of intra- to extracellular spaces were determined by EM in each stage. RESULTS: T(2) consisted of two components: fast T(2) (<100 ms), and slow T(2) (>100 ms). During maturation, values of fast T(2) decreased dramatically, but slow T(2) remained constant. However, the fraction accounted for by slow T(2) decreased from 59% to 9% during maturation. Morphological examination showed that the extracellular space fraction of the midbrain decreased from 49% to 5% during maturation. Thus, morphological change correlated well with changes in slow T(2); in other words, multicomponent T(2) results showed a close correlation with tissue compartmentalization. CONCLUSION: MR relaxation times obtained by means of multicomponent analysis can thus be used to measure intra- and extracellular space fractions.

Animals↗
PubMed2001

NGF, NT-3 and Trk C mRNAs, but not TrkA mRNA, are upregulated in the paraventricular structures in experimental hydrocephalus.

OBJECTS: This study was designed to detect possible alterations in the expression of neurotrophins and trks in kaolin-induced hydrocephalus by in situ hybridization. METHODS AND RESULTS: Sixteen rats were treated by injection of 25 mg kaolin suspended in 0.1 ml of physiological saline into the cisterna magna. Four rats were injected with saline and served as controls. The kaolin-treated rats were divided into two groups studied 1 and 4 weeks after treatment. Rats were anesthetized and killed, and their brains were rapidly dissected and frozen. DNA oligonucleotide probes for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and trkA, trkB, and C were labeled with [(35)S]dATP using terminal deoxyribonucleotidyl transferase for in situ hybridization. Hydrocephalic brains were also classified according to the degree of ventricular enlargement. The results observed were as follows. (1) The medial septal and striatal NGF mRNA levels increased with severity in animals. (2) Hippocampal trkB and BDNF mRNA levels increased with time in animals with moderate ventricular enlargement. (3) Expression of hippocampal trkB, trkC, and NT-3 mRNA increased in animals with moderate ventricular enlargement, while it apparently decreased in the large ventricular enlargement group reaching normal ranges. (4) In the corpus callosum there was an apparent increase in NGF, NT-3 and trkC mRNA, but not in trkA, in hydrocephalic animals. NT-3 EIA confirmed the presence of NT-3 protein increases in corpus callosum. It is therefore possible that simultaneous NGF, NT-3, and trkC receptor upregulation occurred in glial elements of the white matter. CONCLUSIONS: These results demonstrate that neurotrophins and their receptors are overexpressed in many damaged structures of the severely hydrocephalic brain. There were discrepancies in the distribution of NGF and trkA mRNA, and we hypothesize that NGF mRNA in the damaged white matter structure might be due to the reduced availability of other receptors, such as the low-affinity NGF receptors.

Animals↗
PubMed2001

Neuroendoscopic anatomy and surgery in pineal region tumors: role of neuroendoscopic procedure in the 'minimally-invasive preferential' management.

The therapeutic modalities for pineal region tumors in Western countries differ from those in far-eastern countries, that is, Japan and Korea, mainly because of the different patient populations. The majority of pineal region tumors in Japan and Korea are radio sensitive and/or chemosensitive, and adjuvant therapy rather than extensive surgery plays the main part in the treatment of these tumors. The authors have applied minimally-invasive preferential management in pineal region tumors in last 8 years. For the therapeutic regimen, if the tumor markers alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) were not detected in serum and there was significant ventricular dilation visualized on neuroimages, neuroendoscopic surgery was first applied for tumor debulking with tissue diagnosis and gross morphological analysis of the tumor and the intraventricular structures, followed by third-ventriculostomy. In the results, our minimally-invasive preferential regimen clarified the precise indication for neuroendoscopic procedures, and the majority of our patients with dilated ventricles and no evidence of tumor markers were treated satisfactorily with effective neuroendoscopic procedures as the initial procedure. Then avoided unnecessary craniotomy and radiotherapy and promised excellent therapeutic outcomes. Neuroendoscopic procedures have a great advantage in the management of chemo- or radiosensitive tumors, such as germinoma, pineoblastoma, or primitive neuroectodermal tumor. The neuroendoscopic anatomy including the lateral and third ventricles with a pineal region tumor with or without tumor dissemination was described in detail, together with the neuroendoscopic surgical technique.

Brain Neoplasms↗
PubMed2001

Moyamoya disease complicated with renal artery stenosis and nephrotic syndrome: reversal of nephrotic syndrome after nephrectomy.

A 7-year-old boy with moyamoya disease developed sustained hypertension, nephrotic syndrome, hyperreninemia, and occlusion of the right renal artery. After right nephrectomy, hyperreninemia and hypertension improved. Proteinuria was resolved after nephrectomy, in parallel with the decrease in plasma renin activity. Moyamoya disease can cause nephrotic-range proteinuria, which is caused hemodynamically by hyperreninemia.

Child↗
PubMed2000

Microvascular Doppler ultrasound-assisted neuroendoscopic surgery.

To achieve endoscopic procedures more safely and less invasively, an operative strategy with ultrasound-assisted neuroendoscopic surgery is described. The improvement in the endoscope unit is that endoscopic viewing can be stopped on the display, anytime we choose and simultaneously visualize the ongoing view on the same display. The ultrasound unit, using a miniature Doppler probe, is to able to detect even invisible vessels in real-time, easily and non-invasively. The information from both units can be switched intraoperatively, whenever required.

Arachnoid Cysts↗
PubMed2000

Isolated dilation of the trigono-inferior horn--four case reports.

Four patients presented with isolated dilation of the trigono-inferior horn associated with either mass lesion at the trigone of the lateral ventricle or with shunt over-drainage. We investigated clinical symptoms, course, and neuroradiological findings of these cases. The pressure of the isolated ventricle was measured or estimated at surgery in all cases. The common symptoms were recent memory disturbance and contralateral homonymous hemianopia. Contralateral hemiparesis was observed occasionally. Rapid deterioration of the isolation caused uncal herniation in one case. Comma-shaped dilation of the inferior horn was observed in all cases. Midline shift was not conspicuous except in one case. Intraventricular pressure at surgery was 18 cmH2O, 35 cmH2O, 3 cmH2O, and within normal range. These cases had very similar clinical symptoms and neuroradiological findings. The pathophysiology of isolation suggested three types of isolation (high-, normal-, and low-pressure isolation), depending on the pressure of the isolated ventricle. The isolation of trigono-inferior horn is an important clinical entity as it may cause uncal herniation in patients with high-pressure lesions.

Aged↗
PubMed2000

Pathophysiology of long-standing overt ventriculomegaly in adults.

OBJECT: Long-standing overt ventriculomegaly in adults (LOVA) is a unique form of hydrocephalus that develops during childhood and manifests symptoms during adulthood. The aim of the present study was to analyze the specific pathophysiological characteristics of LOVA. METHODS: The specific diagnostic criteria for LOVA include severe ventriculomegaly in adults that is associated with macrocephalus measuring more than two standard deviations in head circumference and/or neuroradiological evidence of a significantly expanded or destroyed sella turcica. Twenty patients who fulfilled these criteria, 14 males and six females, were retrospectively studied. These patients' ages at diagnosis ranged from 15 to 61 years (mean 39.4 years). All had symptoms and/or signs indicating that hydrocephalus first occurred at birth or during infancy in the absence of any known underlying disease. The authors performed a pathophysiological study that included specific variations of magnetic resonance (MR) imaging, such as fluid-attenuated inversion recovery and cardiac-gated cine-mode imaging; intracranial pressure (ICP) monitoring; three-dimensional computerized tomography (CT) scanning; and other techniques. Hydrocephalus was caused by aqueductal stenosis in all patients. Severe ventriculomegaly involving the lateral and third ventricles was associated with a marked expansion or destruction of the sella turcica in 17 cases. Cardiac-gated cine-MR imaging did not reveal any significant movements of cerebrospinal fluid in the aqueduct. Three-dimensional CT ventriculography confirmed that the expanded third ventricle protruded into the sella and, sometimes, extended a diverticulum. Fourteen patients revealed symptoms and signs that indicated increased ICP with prominent pressure waves. Dementia or mental retardation was seen in 11 patients, gait disturbance in 12, and urinary incontinence in eight; all three of these symptoms were observed in seven patients. Thirteen patients experienced visual disturbance. Nine patients underwent ventriculoperitoneal shunt implantation as the initial treatment, leading to postoperative subdural hematoma in all seven cases in which a differential pressure valve was used. Nine patients, three of whom were initially treated by shunt placement, underwent a neuroendoscopic procedure, mainly for third ventriculostomy. Postoperatively, ICP returned to normal, and marked to-and-fro pulsatile movements at the site of ventriculostomy were recognized on cine-MR imaging in patients treated endoscopically. However, the ventriculomegaly was little improved. Consequently, all patients eventually demonstrated improvement in response to either a shunt equipped with a pressure-programmable valve or an endoscopic procedure; however, depression appeared in six patients, who required psychiatric consultation or medication. CONCLUSIONS: Such remarkably decreased intracranial compliance but relatively high ICP dynamics are the pathophysiological characteristics of LOVA. The therapeutic regimen should be determined based on the individual's specific pathophysiological makeup.

Adolescent↗
PubMed2000

Efficacy of neuroendoscopic procedures in minimally invasive preferential management of pineal region tumors: a prospective study.

OBJECT: This prospective study is based on a consecutive series of 20 patients with pineal region tumors who underwent minimally invasive preferential management. The purpose of this report is to discuss the role of neuroendoscopic procedures in the management of pineal region tumors. METHODS: If the tumor markers alpha-fetoprotein and human chorionic gonadotropin were not detected in serum and there was significant ventricular dilation visualized on neuroimages, neuroendoscopic surgery was first applied for tumor debulking with tissue diagnosis and gross morphological analysis of the tumor and the intraventricular structures, followed by third ventriculostomy. Subsequent procedures were determined on the basis of verified individual tumors. For treatment of germinomas and pineoblastomas, if no tumor dissemination was confirmed by pre-, intra-, or postoperative findings, stereotactic radiotherapy or radiosurgery was performed after one course of chemotherapy with the ICE regimen (isofomid, cisplatin, and etoposide) and followed by two additional courses of chemotherapy. For treatment of malignant germ cell tumors, after extensive surgery, adjuvant chemotherapy with the ICE regimen was performed in three courses in all cases. Then radiotherapy was started using various methods, depending on the evidence of tumor dissemination. For treatment of teratomatous and neuroectodermal tumors other than pineoblastomas, extensive surgical removal was performed. As for adjuvant therapy, if the tumor was a low-grade glioma or if the patient was younger than 5 years of age, postoperative treatment did not include radiotherapy. If the tumor was a malignant teratoma or high-grade glioma, conventional focal radiotherapy was performed, followed by chemotherapy with ICE for 1 year. All but two treated patients had ventriculomegaly. Neuroendoscopic procedures were performed in six of 15 treated patients. Neuroendoscopic biopsy with tumor debulking offered enough material for tissue diagnosis, including immunohistochemical analysis and, in one case, revealed evidence of tumor dissemination undetectable on neuroimaging. With one exception, no shunt was required in any patient undergoing endoscopic third ventriculostomy. Stereotactic radiotherapy was performed in indicated cases. Favorable therapeutic outcomes were obtained in all cases of germinoma and pineoblastoma, with follow-up periods ranging from 24 months to 6.5 years. CONCLUSIONS: Our minimally invasive preferential regimen clarified the precise indication for neuroendoscopic procedures, and the majority of our patients with dilated ventricles and no evidence of tumor markers were treated satisfactorily with effective neuroendoscopic procedures as the initial procedure, avoiding unnecessary craniotomy and radiotherapy and promising excellent therapeutic outcomes. The treatment for malignant pineal region tumors remains a subject for further study.

Adolescent↗
PubMed2000

[Independent compartment phenomena: characteristics of dynamics in cerebral tissue oxygen metabolism under increased intracranial pressure in immature brain: an experimental study].

The aim of this study is to clarify the specific pathophysiology of increased intracranial pressure in an immature brain in relation to its unique cerebral blood flow dynamics and brain tissue oxygen metabolism. Thirteen puppies were used for an experimental model of brain herniation due to a massive intracerebral hematoma. Along with increasing size of the hematoma, the intracranial pressure (ICP), carotid blood flow (CBF) and cerebral tissue oxygen (CTPO2) were measured simultaneously and continuously. The tolerance capacity for an acutely expanding mass lesion, or intracranial compliance, was studied. The ratio of hematoma volume/body weight was obviously higher by more than 200% in a group of younger puppies with open cranial sutures. Dynamic changes of CTPO2 were noted to be independent in the cerebral subcortical region and the medulla oblongata, when Doppler detection of arterial pulsations showed no flow in the anterior circulation in association with increased intracranial pressure caused by a supratentorial expanding mass lesion. A case with open cranial sutures (1,500 g of body weight) clearly demonstrated this and survived over 24 hours. With acutely increasing ICP CTPO2 was elevated modestly in the cerebral subcortical region (p < 0.1) and prominently in the medulla oblongata (p < 0.005). In conclusion, the posterior fossa structure (brain stem and cerebellum) in the immature age group is protected from an acutely expanding mass lesion in the supratentorial compartment. The posterior fossa behaves as an independent compartment with more prominent CBF and CTPO2 reactivity in the dynamic changes. The author proposed to name these findings as "independent compartment phenomena".

Age Factors↗
PubMed1999

Prerequisites for fetal neurosurgery: management of central nervous system anomalies toward the 21st century.

With the dramatic technical advances in neuroimaging, it has become possible to diagnose central nervous system (CNS) anomalies in the fetus in utero with more precise morphological analysis. A new technique, high-resolution magnetic resonance (MR) imaging using heavily T2-weighted fast spin echo sequences, has been reported to solve motion artifact of the fetus. However, it has also been recognized that the morphological fetal CNS findings detected in early development are not always the final features: occasionally they may not be determined in diagnosis and may change developmentally or chronologically during the fetal life in utero. Certain factors of the fetal chronology of CNS anomalies can cause irreversible changes during fetal life. These include: (1) significant delay in the neuronal maturation process in fetal hydrocephalus developed in clinicoembryological stage II in the Perspective Classification of Congenital Hydrocephalus (PCCH), (2) secondary neural injury in the intactly developing spinal cord above the neural placode in fetus with spina bifida aperta (myeloschisis), (3) histological "evolution" of tumors or dysgenetic CNS, and (4) deformity of the normally developed intracranial or intraspinal CNS structures. Considering the current status of fetal surgery in general and technical advances promising improved outcomes, fetal neurosurgery can also be applied in the above-mentioned progressive pathology or pathophysiology in the fetal CNS. However, since the failure of the first trial of fetal neurosurgery in the 1980s, the prerequisites have still not been clarified. In order to use advanced neurosurgery techniques in the management of fetal CNS anomalies, these prerequisites have to be established.

Journal Article↗
PubMed1999

Lovastatin prevents angiotensin II-induced cardiac hypertrophy in cultured neonatal rat heart cells.

Angiotensin II activates p21ras, and mediates cardiac hypertrophic growth through the type 1 angiotensin II receptor in cardiac myocytes. An inhibitor of 3-hydroxy-3-methyglutaryl-coenzyme A (HMG-CoA) reductase has been shown to block the post-translational farnesylation of p21ras and inhibit protein synthesis in several cell types. Primary cultures of neonatal cardiac myocytes were used to determine whether HMG-CoA reductase inhibitors, lovastatin, simvastatin and pravastatin inhibit the angiotensin II-induced hypertrophic growth. Angiotensin II (10(-6) M) significantly increased protein-DNA ratio, RNA-DNA ratio, ratios of protein synthesis and mitogen-activated protein (MAP) kinase activity. Lipid-soluble HMG-CoA reductase inhibitors, lovastatin (10(-6) M) and simvastatin (10(-6) M) partially and significantly inhibited the angiotensin II-induced increases in these parameters, but a water-soluble HMG-CoA reductase inhibitor, pravastatin (10(-6) M) did not. Mevalonate (10(-4) M) overcame the inhibitory effects of lovastatin and simvastatin on angiotensin II-induced increases in these parameters. A selective protein kinase C inhibitor, calphostin C (10(-6) M) partially and significantly prevented angiotensin II-induced increases in these parameters, and treatment with both lovastatin and calphostin C inhibited completely. Angiotensin II increased p21ras activity and membrane association, and lovastatin inhibited them. These studies demonstrate that a lipid-soluble HMG-CoA reductase inhibitor, lovastatin, may prevent angiotensin II-induced cardiac hypertrophy, at least in part, through p21ras/MAP kinase pathway, which is linked to mevalonate metabolism.

Angiotensin II↗
PubMed1999

Neuroendoscopic surgery for specific forms of hydrocephalus.

Neuroendoscopic surgery was used to treat patients with various forms of hydrocephalus with specific pathophysiology, including long-standing overt ventriculomegaly in adulthood (LOVA), isolated unilateral hydrocephalus (IUH), isolated IV ventricle (IFV), disproportionately large IV ventricle (DLFV), isolated rhombencephalic ventricle (IRV), isolated quarto-ventriculomegaly (IQV), dorsal sac in holoprosencephaly (DS), and loculated ventricle (LV). A total of 26 operative procedures were performed, with neuroendoscopic surgery in 22 patients, 12 with unique forms of noncommunicating hydrocephalus and 10 with various types of postshunt isolated compartment. These procedures included III ventriculostomy, aqueductal plasty by both rostral and caudal approaches, foraminal plasty in the foramen of Monro/foramen of Magendie, septostomy, IV ventriculostomy, fenestration of septation in the loculated ventricle, fenestration of arachnoid cyst or cystic tumor obstructing a ventricle with or without tumor removal, and dorsal sac ventriculostomy. The characteristics of the cerebrospinal fluid (CSF) dynamics in the individual specific pathophysiologies were delineated by cardiac-gated cine-mode magnetic resonance imaging (MRI) before and after the endoscopic procedure. The consequent success rate (success = restoration of communication of the CSF pathway in the individual patients) was 19/22 (86.4%). The progression of ventricular dilatation was stopped in 17 of 19 patients (89.5%) in whom the endoscopic procedure was successful (radiologically arrested hydrocephalus). Improvement in the clinical symptoms and signs (clinically arrested hydrocephalus) was obtained in 15 of the patients (68.2% of all patients: 5 with LOVA, 3 with IQV, 5 with IUH and 2 with LV). Seven patients (2 LOVA, 2 IFV, 1 DS, 1 DFLV and 1 IRV) underwent a shunt procedure after the neuroendoscopic procedure(s). The postoperative changes of ventriculomegaly were complicated, reflecting the differences in the brain parenchymal compliance and postoperatively corrected CSF flow dynamics in the major CSF pathway.

Adult↗
PubMed1999

A new experimental model of obstructive hydrocephalus in the rat: the micro-balloon technique.

We used three types of specialized micro-balloons 0.7-1.35 mm in outer diameter instead of kaolin to develop a reproducible rat model of hydrocephalus with a low experimental mortality. The micro-balloon was inserted 6 mm deep into the cisterna magna via a burr hole immediately behind the lambda. The angle of introduction was 50 degrees. We also set up kaolin-induced hydrocephalic models in 25 rats as controls. The kaolin model revealed 52% mortality with an 80% induction rate of hydrocephalus, while the balloon model showed 9% mortality with a 60% induction rate. Balloon-induced hydrocephalus was maximal at 1 week and tended to decrease after 2-3 weeks. The pathological findings were not different between the two models. We concluded that the micro-balloon model for hydrocephalus is an easily reproducible model with low experimental mortality.

Animals↗
PubMed1999

[Clinical application and future prospect of neuroendoscopic surgery].

The clinical application and future prospect of neuroendoscopic surgery are described. In the historical trend, it is emphasized that the neuroendoscopic surgery has become one of the major or leading procedures in "minimally-invasive approaches" to the intracranial lesions. The presently-available instrument include procedures using an endoscope of three different types: rigid-rod, steerable/flexible-fiber-rod and semi-rigid-rod. To use a rigid-rod or fiber-rod scope, it is available to apply forceps, laser, a microballoon and other fine instruments. The indication for neuroendoscopic surgery has been expanded to almost all neurosurgical procedures, as "endoscope-assisted" procedures are applied more to micro neurosurgical procedures (endoscope-assisted microsurgery). The realistic indication for "pure neuroendoscopic surgery" includes reconstruction of cerebrospinal fluid (CSF) pathway such as third ventriculostomy, septostomy, foramen reconstruction, fenestration of septation; removal or biopsy of tumor/cystic lesion, mainly in the intraventricular regions; and removal of hematoma involving the cerebral parenchyma (intracerebral hematoma), ventricles/(intraventricular hematoma) or subdural space (subdural hematoma). The intraparenchymal or deep-seated intracisternal lesions can be the realistic indication for "pure neuroendoscopic surgery" when the instrument are further developed in future. Neuroendoscopic surgery will play a promising and major role in the "minimally-invasive neurological procedure" in the 21st century.

Brain↗
PubMed1999

Delayed ischemic neurological deficit of short duration in patients with subarachnoid hemorrhage.

We retrospectively examined the duration of delayed ischemic neurological deficits (DIND) attributed to vasospasm following subarachnoid hemorrhage (SAH) in order to delineate the nature and involved factors. Among 605 patients with SAH, 201 developed DIND, and 137 of these had undergone early aneurysmal obliteration. In these 137, duration of DIND was clearly determined in 67 cases. Hypervolemic therapy was instituted only after the onset of DIND. In the 67 patients, the mean duration of DIND was 5.2 days (ranging from 2 to 13 days); 22 patients had DIND lasting only 2 to 3 days, 26 patients had DIND lasting 4 to 6 days, and in 19, DIND lasted 7 to 13 days. Clinical factors associated with short DIND duration (2 to 3 days) as determined by multivariate analysis included internal carotid artery or middle cerebral artery aneurysm, age under 60, and a good World Federation of Neurological Surgeons grade on admission. No patients developed pulmonary edema from hypervolemic therapy, and the outcomes of all 67 patients were extremely favorable. In SAH patients developing DIND after early aneurysmal surgery, 16% (22 of 137) had a documented brief duration of DIND. We believe DIND rapidly improved and resolved with hypervolemic therapy because antecedent brain damage from SAH or surgical manipulation had been minimal.

Female↗