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T Nariai

Publications and source records attributed to T Nariai.

At least 37 records · Page 2Linked to original sources
PubMed1998

Brain surgery simulation system using VR technique and improvement of presence.

A computer aided brain surgery system using virtual reality techniques is developed. This system is aimed to be used to support the surgeons' decision for the operational strategies, or used in the training of medical students to learn how to operate the brain surgery for the patients. In constructing the whole system, high speed graphical computer is equipped. For input 3D data from MRI or CT are used to display 3D images, HMD (head-mounted display) and 3D CRT display with glass are equipped. To improve the 3D images, colors and optical properties of the voxel are refined.

Brain↗
PubMed1998

Evaluation of carbon-11-labeled KF17837: a potential CNS adenosine A2a receptor ligand.

UNLABELLED: The 11C-labeled KF17837 ([7-methyl-11C](E)-8-(3,4-dimethoxystyryl)-1,3-dipropyl-7-methylxa nthine) was evaluated as a PET ligand for mapping adenosine A2a receptors in the central nervous system (CNS). METHODS: The regional brain distribution of [11C]KF17837 and the effect of adenosine antagonists on the distribution were measured in mice by the tissue sampling method. In rats, the regional brain uptake of [11C]KF17837 and the effect of carrier KF17837 was visualized by autoradiography. Imaging of the monkey brain with [11C]KF17837 was performed by PET. RESULTS: In mice, a high uptake of [11C]KF17837 was found in the striatum in which A2a receptors were highly enriched. The uptake was decreased by co-injection of carrier KF17837 or a xanthine-type A2a antagonist CSC but not by nonxanthine-type A2a antagonists ZM 241385 or SCH 58261, or an A1 antagonist KF15372. In the rat brain, [11C]KF17837 was accumulated higher in the striatum than in other brain regions, and the uptake was blocked by co-injection of carrier KF17837. In a monkey PET study, a high striatal uptake of radioactivity was observed. CONCLUSION: Carbon-11-KF17837 binds to adenosine A2a receptors in the striatum. However, the presence of an unknown but specific binding site for xanthine-type compounds also was suggested in the other brain regions. The results also suggested that the in vivo receptor-binding sites of xanthine-type ligands are slightly different from those of nonxanthine-type A2a antagonists.

Animals↗
PubMed1997

Long-term intelligence outcome of post-encephalo-duro-arterio-synangiosis childhood moyamoya patients.

Long term post-encephalo-duro-arterio-synangiosis (EDAS) intelligence quotient (IQ) evaluated by Wechsler tests stays around the normal range (mean full intelligence quotient (FIQ), verbal intelligence quotient (VIQ) and performance intelligence quotient (PIQ) at 100.0 +/- 155, 100.0 +/- 15.7 and 100.2 +/- 163, respectively) at more than 9.5 years after the operation, provided that the patient has FIQ above 70 pre-operatively. This fact encourages us to employ operative treatment for this difficult disease in which intelligence deterioration has been reported to be a common occurrence.

Cerebral Revascularization↗
PubMed1997

[Dural arteriovenous fistula involving the superior sagittal and transverse-sigmoid sinuses, treated by thrombolysis: case report].

A rare case of dural arteriovenous fistula (DAVF) in the superior sagittal sinus (SSS), the transverse sinus and the sigmoid sinus is reported. A 64-year-old man, who had had an episode of temporary visual disturbance after moderate fever for a week about 20 years before, was aware of loss of visual acuity and reduced field of view in the right eye. When he was introduced to our outpatient service, increased intracranial pressure (ICP) was detected by lumbar puncture. Cerebral angiograms showed bilateral DAVFs both in the posterior fossa and the SSS concomitant with thrombosis in the transverse sinus, sigmoid sinus and SSS. Afterwards, endovascular transarterial embolization through bilateral occipital, posterior auricular and left middle meningeal, superior temporal arteries was carried out. In addition, transvenous thrombolytic therapy using a catheter inserted into SSS resulted in the improvement of his visual problems. Although he was discharged at once, he was readmitted to our department with Foster Kennedy syndrome and increased ICP. Cerebral angiograms showed recurrence of both DAVF and sinus thrombosis. Transarterial embolization was performed again resulting in a significant reduction of DAVF, and his visual acuity was recovered to a moderate degree. The origin of DAVF is still controversial. Although two theories, "congenital" and "acquired", are put forward, it has been thought that both factors play important roles. In our case, the patient had stenosis in the jugular canal portions of the sigmoid sinus. In addition, sinus thrombosis seemed to have occurred. It is thought that increased intrasinus pressure may have lead to communication with surrounding arteries through existing dural vessels. We applied transvenous thrombolytic therapy in this case. Our result suggests that we should consider this therapy for some cases of DAVF.

Arteriovenous Fistula↗
PubMed1997

Three-dimensional imaging of cortical structure, function and glioma for tumor resection.

UNLABELLED: A three-dimensional brain imaging protocol with PET and MRI was used to visualize the cortical structure in relation to brain function and glioma infiltration to determine tumor resectability. METHODS: Sixteen patients with glioma had a PET scan with 11C-methionine to visualize tumor infiltration. The PET images were co-registered to the patients' own MRI reconstructed to the three-dimensional brain surface images to indicate the gyral structure and the extent of tumor infiltration. Thirteen patients, who bore tumors adjacent to the language or motor cortex, had H2 15O activation study to locate the eloquent cortex. The area of tumor infiltration was superimposed on the brain surface images together with the language and/or motor cortex. RESULTS: When a tumor was located within a single gyrus without influencing surface cortical gyrus pattern, the motor and language areas were identified morphologically by three-dimensional surface image alone. However, when the tumor caused swelling and deformation of cortical structure, functional mapping with H2(15)O activation technique was essential in locating them correctly. In such cases, the combined mapping of the facial motor area with oral movement and the language area with word repetition was the most useful method to identify the parasylvian structure in the dominant hemisphere. Total or near total resection of low-grade glioma in eight patients and the effective decompression of the active part of the malignant glioma in four patients was completed without causing functional neurological deterioration. CONCLUSION: The three-dimensional expression of cortical structure and function combined with PET glioma imaging with 11C-methionine is useful for radical resection of cerebral glioma.

Adult↗
PubMed1996

Xe-CT in cerebrovascular disease and moyamoya disease.

(1) Negative response to acetazolamide challenge test using Xe-CT is a reliable indicator for identifying the hemodynamic compromise. (2) The hemodynamic compromise may be a cause of TIAs in some patients with chronic cerebrovascular occlusive diseases. (3) The brain suffering from hemodynamic compromise actively works to induce collateral blood channels.

Acetazolamide↗
PubMed1996

Magnetic resonance imaging and pathologic studies on lateral fluid percussion injury as a model of focal brain injury in rats.

In this study, morphologic changes in brain lesions initiated by moderate lateral fluid percussion injury in rats were investigated chronologically using high-resolution magnetic resonance imaging (MRI) and histopathologic methods. Rats were subjected to moderate fluid percussion injury (average 2.80 +/- 0.48 atmospheres) over the exposed dura overlying the right parietal cortex. MRI obtained in vivo were compared with corresponding pathologic findings at 1, 6, and 24 h and at 3, 6, 14 and 80 days after injury. T2-weighted images showed scattered low-signal intensity in the injured cortex within a few hours after injury, whereas histologic findings revealed intraparenchymal hemorrhages. T2-weighted images of the ipsilateral cerebral cortex and/or corpus callosum showed a high-signal-intensity area 4 h after injury. The high-signal-intensity area became largest in size between 6 and 24 h, then declined gradually, and almost disappeared 14 days after injury. Histologic examination revealed pyknosis, retraction of the cell body of neurons with vacuolated neuropil in the corresponding regions 6 and 24 h after injury, and cystic necrosis 14 days after injury. The location and extent of these pathologic changes were depicted accurately by MRI in vivo. In the hippocampus, pyknosis and retraction of the cell body of pyramidal neurons were observed on the injured side 24 h after injury, and the number of neurons in the CA1 and CA2-CA3 regions decreased significantly on the same side by 14 days after injury. It is concluded that morphologic changes in the brain following experimental traumatic brain injury in rats are detectable in vivo by high-resolution MRI, and that MRI may be useful for the evaluation of treatment effects in experimental brain injury.

Animals↗
PubMed1996

Surgical approaches for treatment of ischaemic cerebral stroke other than moyamoya disease in children.

Ischaemic cerebral strokes in children are relatively uncommon. With the exception of patients with moyamoya disease, there is no effective treatment for these lesions. One potential approach is encephalo-duro-arterio-synangiosis (EDAS). This is a safe neurosurgical procedure that promotes spontaneous transdural anastomosis that may provide additional blood flow to ischaemic regions. We present eight children with ischaemic strokes other than moyamoya disease, and discuss surgical attempts to treat this entity. The mean age of the eight children was 3.6 years (range: 13 months to 9 years). All children presented with acute childhood hemiplegia. Ischaemic stroke had occurred in association with a head injury in three children, but without an apparent cause in five. Five children underwent stable xenon-enhanced computed tomography to evaluate cerebral blood flow and all but one patient underwent EDAS. One child with no angiographic abnormalities recovered to a normal neurological state without surgery. Following surgery, another child also fully recovered, and the remaining six children recovered with only a slight hemiparesis. Revascularization was observed on a follow-up angiogram in three children. Our surgical experiences suggest that revascularization is influenced by haemodynamic demand and recanalization of the occluded artery. We favour the use of indirect anastomosis (EDAS) for selected patients and suggest that chronic ischaemia probably contributes to surgical success.

Anastomosis, Surgical↗
PubMed1995

Vascular reserve in chronic cerebral ischemia measured by the acetazolamide challenge test: comparison with positron emission tomography.

PURPOSE: To determine the value of the acetazolamide challenge test with stable xenon-enhanced CT (Xe CT) for making therapeutic decisions in patients with chronic cerebrovascular disease. METHODS: We compared the Xe CT-measured acetazolamide response with various measures obtained by positron emission tomography. We performed both a positron emission tomographic scan and a Xe CT study in 11 patients with chronic cerebral ischemic diseases within a 1-week interval. An increase of cerebral blood flow after injection of acetazolamide was expressed as delta AT. Regional cerebral blood flow, cerebral oxygen metabolism, oxygen extraction fraction, and cerebral blood volume were measured with oxygen-15-labeled gases by positron emission tomography. RESULTS: In low-cerebral blood flow regions, decreased delta AT was accompanied by a significant elevation of oxygen extraction fraction and cerebral blood volume, compared with oxygen extraction fraction and cerebral blood volume in regions of normal delta AT. Plotting of regional data indicated that delta was significantly dependent on oxygen extraction fraction and cerebral blood volume. The area of decreased vascular reserve determined by the Xe CT image corresponded to the area of "misery perfusion" determined by positron emission tomography. CONCLUSION: The acetazolamide challenge test with Xe CT may offer an alternative to positron-emission tomography in detecting lesions with elevated oxygen extraction fraction and cerebral blood volume (misery perfusion) that result from chronic hemodynamic stress.

Acetazolamide↗
PubMed1994

Differences in rates of incorporation of intravenously injected radiolabeled fatty acids into phospholipids of intracerebrally implanted tumor and brain in awake rats.

This study investigates the incorporation of three intravenously administered radiolabeled fatty acids, [9,10-3H]palmitate (3H-PAM), [1-14C]arachidonate (14C-ACH) and [1-14C]docosahexaenoate (14C-DHA), into lipids of intracerebrally implanted tumor and contralateral brain cortex in awake rats. A suspension of Walker 256 carcinosarcoma cells (1 x 10(6) cells) was implanted into the right cerebral hemisphere of an 8- to 9-week-old Fischer-344 rat. Seven days later, the awake rat was infused intravenously for 5 min with 3H-PAM (6.4 mCi/kg), 14C-ACH (170 microCi/kg) or 14C-DHA (100 microCi/kg). Twenty min after the start of infusion, the rat was killed and intracranial tumor mass and brain cortex were removed for lipids analysis. Each radiolabel was incorporated more into tumor than into brain cortex. Ratios of net incorporation rate coefficients (k*) into tumor as compared with brain were 4.5, 3.4 and 1.7 for 3H-PAM, 14C-ACH and 14C-DHA, respectively. Lipid radioactivity comprised more than 80% of total tumor or brain radioactivity for each probe. Phospholipids contained 58%, 89% and 68% of tumor lipid radioactivity, and 58%, 82% and 74% of brain lipid radioactivity, for 3H-PAM, 14C-ACH and 14C-DHA, respectively. Incorporation coefficients (k*i) for a phospholipid class (i)--choline phosphoglycerides (PC), inositol monophosphoglycerides (PI), ethanolamine phosphoglycerides (PE), serine phosphoglycerides (PS), and sphingomyelin (SM)--were greater in tumor than in brain for each fatty acid probe, except that values for k*PE and k*PS using 14C-DHA were equivalent. Differences in k*i between tumor and brain were largest for SM and PC and the change in k*PC accounted for 65-90% of the increase in the net phospholipid incorporation rate for each probe. Differences in k*PI, k*PE and k*PS were smaller than those in were smaller than those in k*PC and k*SM, and varied with the probe. Differences in k*i were related to differences in tumor and brain phospholipid composition and metabolism. The results indicate that suitably radiolabeled fatty acids may be used to image and characterize metabolism of lipid compartments of a brain tumor in vivo using positron emission tomography.

Animals↗
PubMed1994

Surgically induced angiogenesis to compensate for hemodynamic cerebral ischemia.

BACKGROUND AND PURPOSE: The ischemic brain may stimulate angiogenesis to compensate for impaired circulation. We examined the conditions promoting such angiogenesis to provide the basis for surgical treatment. METHODS: The degree of cerebral hemodynamic stress was studied in patients with moyamoya disease using the stable xenon-enhanced computed tomographic acetazolamide tolerance test and positron emission tomography. Patients were subjected to surgery in which scalp arteries were placed on the cerebral cortex without vessel-to-vessel anastomosis. Formation of the newly vascularized collateral network connecting the implanted artery to cortical arteries was assessed angiographically 12 to 17 months after surgery. RESULTS: Preoperative average resting cerebral blood flow for cortex that developed revascularization of cortical arteries was not significantly different from that for cortex that did not. However, cortex that developed revascularization had an average preoperative increase of blood flow by acetazolamide treatment of -3.29 +/- 4.6 mL/min per 100 cm3 (n = 20), which was significantly less (P = .0034) than that of cortex that did not show revascularization (20.7 +/- 4.3 mL/min per 100 cm3; n = 9). Good revascularization developed when the cortex showed increase of blood flow by acetazolamide treatment of less than 0 (steal phenomenon). Preoperative positron emission tomography data indicated that revascularization developed when the cortex was under "misery perfusion." Postoperative hemodynamics were ameliorated by revascularization. CONCLUSIONS: Angiogenesis to connect the implanted scalp arteries to the cerebral cortical arteries was selectively initiated when ischemia of hemodynamic origin existed.

Acetazolamide↗
PubMed1993

Intravenously injected radiolabelled fatty acids image brain tumour phospholipids in vivo: differential uptakes of palmitate, arachidonate and docosahexaenoate.

This paper investigates the incorporation of intravenously (i.v.) administered radiolabelled fatty acids--[9,10(3)-H]palmitate (3H-PA), [1-14C]arachidonate (14C-AA) and [1-14C]docosahexaenoate (14C-DHA)--into intracerebrally implanted tumours in awake Fischer-344 rats. A suspension of Walker 256 carcinosarcoma tumour cells (1 x 10(6) cells) was implanted into the right cerebral hemisphere of 8- to 9-week-old rats. Seven days after implantation, the awake rat was infused i.v. for 5 min with 3H-PA (6.4 mCi/kg), 14C-AA (170 microCi/kg) or 14C-DHA (100 microCi/kg). Twenty minutes after the start of infusion, the rat was killed and coronal brain sections were obtained for quantitative autoradiography and histology. Each fatty acid showed well-demarcated incorporation into tumour tissue. Areas of necrosis or haemorrhage showed no or small levels of incorporation. The ratios of incorporation into the tumour to incorporation into contralateral brain regions were 2.8-5.5 for 3H-PA, 2.1-3.3 for 14C-AA and 1.5-2.2 for 14C-DHA. The mean ratios differed significantly between the fatty acids (P < 0.01). 3H-PA was not incorporated into necrotic tumours despite the presence of an open blood-tumour barrier, indicated by extravasated horseradish peroxidase. The incorporation rate constant of 3H-PA was similar for small intracerebral and large extracerebral tumours. The results show that 3H-PA, 14C-AA and 14C-DHA are incorporated more readily into tumour tissue than into brain, and that the increase is primarily due to increased utilization of fatty acids by tumour cells and not due to a high blood-tumour permeability. The relative increases in rates of incorporation for the different fatty acids may be related to lipid composition of the tumour and to the requirement of and specific role of these fatty acids in tumour cell growth and division.

Animals↗
PubMed1992

Membrane trapping of carbon-11-labeled 1,2-diacylglycerols as a basic concept for assessing phosphatidylinositol turnover in neurotransmission process.

The uptake mechanism of 1,2-[11C]diacylglycerols (DAG) was studied and its use as a probe for the measurement of phosphatidylinositol (PI) turnover was verified. A method of synthesis for producing rac-1,2-[11C]DAG using [11C]ethylketene was developed to label the 1- or 3-hydroxyl group of 2-monoacylglycerol. After intravenous injection, these tracers were metabolized rapidly in the rat brain cortex to phosphatidic acids, phosphatidylinositols and phosphatidylinositol phosphates. The brain cortex anesthetized by barbiturate, which represents inhibited state of synaptic transmission, did not produce differences in uptake values between sn-1,2-[11C]DAG and rac-1,2-[11C]DAG. However, in the liver, lung, and pancreas under the same conditions, the uptake values of rac-1,2-[11C]DAG were higher than those of sn-1,2-[11C] DAG, in which the labeling position was on the 2-hydroxyl group in the sn type. These findings suggest that the lipase activity in the brain should be disregarded because lipase predominantly hydrolyzes the 1- or 3-position of rac-1,2-[11C] DAG, which should be the main factor producing the differences in uptake values in other organs. Cholinergic stimulation prompted accumulation of 1,2-[11C]DAG in the conscious rat brain. In conclusion, sn-1,2-[11C]DAG, administered even in the racemic mixture, could serve as a tracer that becomes mixed with receptor-linked PI turnover and could accumulate in the brain based on the membrane trapping mechanism.

Animals↗
PubMed1991

In vivo brain incorporation of [1-14C]arachidonate in awake rats, with or without cholinergic stimulation, following unilateral lesioning of nucleus basalis magnocellularis.

Regional brain incorporation of a radiolabeled unsaturated fatty acid, [1-14C]arachidonic acid (14C-AA), was measured in awake rats following unilateral lesioning of the nucleus basalis magnocellularis (NBM). Right-sided lesions were produced in 3-month-old, male rats by stereotaxic injection of 10 micrograms ibotenic acid. Two weeks after lesioning, rats were subjected to one of two protocols: (1) 5 min intravenous infusion of 14C-AA (170 microCi/kg); or (2) i.p. injection of arecoline (5 mg/kg), a cholinergic agonist, followed by 5 min intravenous infusion of 14C-AA. All animals were killed 15 min postinfusion. Brains were frozen and sectioned for quantitative autoradiography or were stained for acetylcholinesterase (AChE). Animals with unilateral NBM lesions displayed reduced AChE staining in prefrontal, frontal and parietal cortices of the lesioned side, but there was no right-left difference in incorporation of 14C-AA without cholinergic stimulation. Arecoline administration increased 14C-AA incorporation into the prefrontal and frontal cortices ipsilateral to the NBM lesion as compared to the contralateral side and the increase was most prominent in deeper cortical layers such as layers IV and V. Right-left differences in incorporation were not apparent in parietal, temporal, or occipital cortices, where reduction of AChE activity was minimal or absent, nor in subcortical structures. The results suggest that the intravenous 14C-AA technique combined with cholinergic stimulation can be used to detect compensatory regulation of phospholipid-coupled signal transduction caused by a deficit in cholinergic input into the cerebral cortex.

Acetylcholinesterase↗
PubMed1991

Arecoline-stimulated brain incorporation of intravenously administered fatty acids in unanesthetized rats.

Brain incorporation of [1-14C]arachidonate ([14C]AA; 170 microCi/kg), [1-14C]docosahexaenoate ([14C]DA; 100 microCi/kg), or [9,10-3H]palmitate ([3H]PA; 6.4 mCi/kg) infused intravenously for 5 min was examined in the awake rat following systemic administration of the cholinomimetic arecoline (15 mg/kg i.p.). The rat was killed 15 min after infusion, and the brain was removed, frozen, and prepared for biochemical analysis and autoradiography. Brain radioactivity, normalized for plasma exposure, was increased by 41 and 45% in arecoline-treated rats given [14C]AA and [14C]DA, respectively. Pretreatment with atropine prevented the increase in fatty acid incorporation. Arecoline treatment had no effect on brain incorporation of [3H]PA. Quantitative autoradiography indicated regionally selective increases in brain [14C]AA and [14C]DA incorporation in response to arecoline. The results suggest that intravenously administered radiolabeled fatty acids can be used to study neurotransmitter-stimulated brain lipid metabolism in vivo.

Animals↗
PubMed1991

In vivo incorporation of [9,10(-3)H]-palmitate into a rat metastatic brain-tumor model.

Lipid metabolism of an intracerebrally implanted brain tumor and normal brain was investigated in awake Fischer 344 rats using intravenously injected [9,10(-3)H]-palmitate as a probe. A suspension of Walker 256 carcinosarcoma cells (250 cells in 5 microliters medium), with or without 1% low-melting-point agar, was implanted into the caudate nucleus of rats 8 to 9 weeks old. Control animals received an intracerebral injection without tumor cells. Seven days after implantation, awake rats were infused intravenously for 5 minutes with [9,10(-3)H]-palmitate (6.4 mCi/kg). The rats were killed 20 minutes after initiation of the infusion and coronal brain slices were obtained for quantitative autoradiography and light histological study. Tumor cell masses were histologically well demarcated from the surrounding brain tissue. Tumor tissue incorporation of [9,10(-3)H]-palmitate was heterogeneous, ranging on average from 3.1- to 6.1-fold greater than in the corresponding contralateral brain. In addition, incorporation corresponded to regional tumor cell density. The incorporation rate constant of [9,10(-3)H]-palmitate in tumor was significantly increased compared to control brain and was independent of tumor size. Necrotic areas within tumors showed no incorporation of radiolabeled palmitate. Brain surrounding the tumors and control injection sites showed reactive gliosis, and possessed 30% greater incorporation of [9,10(-3)H]-palmitate than contralateral normal brain. These results suggest that [9,10(-3)H]-palmitate can be used to image brain tumors in vivo, measuring turnover and/or synthesis of tumor and brain lipid.

Animals↗