30 results on '"Nakakita, K."'
Search Results
2. Restenosis of the sigmoid sinus after stenting for treatment of intracranial venous hypertension: case report
- Author
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Tsumoto, T., Miyamoto, T., Shimizu, M., Inui, Y., Nakakita, K., Hayashi, S., and Terada, T.
- Published
- 2003
- Full Text
- View/download PDF
3. Simultaneous Visualization of Transonic Buffet on a Rocket Faring Model Using Unsteady PSP Measurement and Schlieren Method.
- Author
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Nakakita, K.
- Published
- 2017
- Full Text
- View/download PDF
4. Three dimensional observation of the nerve fibers along the cerebral blood vessels
- Author
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Hakura, T., Nakakita, K., Imai, H., Nakai, K., Kamei, I., Naka, Y., Okuno, T., Komai, N., Hirai, T., Arai, T., and Komi, H.
- Published
- 1986
- Full Text
- View/download PDF
5. Development of Bi-Luminophore Pressure-Sensitive Paint Systems.
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Mitsuo, K., Kurita, M., Nakakita, K., Fujii, K., Watanabe, S., Katagiri, S., and Wada, Y.
- Published
- 2007
- Full Text
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6. Temperature Correction of PSP Measurement for Low-Speed Flow Using Infrared Camera.
- Author
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Mitsuo, K., Kurita, M., Nakakita, K., and Watanabe, S.
- Published
- 2005
- Full Text
- View/download PDF
7. Image Measurement of Unsteady Pressure Fluctuation on a Delta Wing by an Anodized Aluminum PSP.
- Author
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Kameda, M., Tabei, T., Nakakita, K., Sakaue, H., and Asai, K.
- Published
- 2005
- Full Text
- View/download PDF
8. Recent topics in fast-responding pressure-sensitive paint technology at National Aerospace Laboratory.
- Author
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Asai, K., Nakakita, K., Kameda, M., and Teduka, K.
- Published
- 2001
- Full Text
- View/download PDF
9. In-cylinder stratification of external exhaust gas recirculation for controlling diesel combustion.
- Author
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Fuyuto, T., Nagata, M., Hotta, Y., Inagaki, K., Nakakita, K., and Sakata, I.
- Subjects
DIESEL motor exhaust gas ,AUTOMOBILE engine cylinders ,COMPUTATIONAL fluid dynamics ,DIESEL motor combustion ,SMOKE prevention - Abstract
A technique for achieving the in-cylinder stratification of external exhaust gas recirculation (EGR) gas in direct-injection (DI) diesel engines has been developed to reduce toxic exhaust emissions. The external EGR gas is supplied from one of the two intake ports which can create a swirl flow in either the upper or lower portion of the cylinder during the intake stroke. In the final stage of the compression stroke, a squish flow conveys the vertically stratified EGR gas into the piston cavity, generating a radially stratified EGR gas in the piston cavity at the end of the compression stroke. This strategy for achieving EGR gas stratification in the piston cavity was developed by using an unsteady computational fluid dynamics (CFD) code. Prior to the exhaust emission tests, the accuracy of the simulation was evaluated by planer laser-induced fluorescence (LIF) imaging. The exhaust emission tests showed that there was less smoke emission under medium load conditions when the EGR gas was delivered to the inner part of the piston cavity. The mechanism of this smoke reduction was investigated using CFD simulation, which is based on a series of calculations related to the internal flow of the injector nozzle, the in-cylinder fuel spray, and mixture formation and combustion. It has been shown that, at the beginning of the combustion, the higher concentration of EGR gas in the inner part of the cavity lowers the combustion temperature and reduces the soot formation rate. Air, which exists in the outer part of the cavity at the start of fuel injection, enhances the oxidation of the soot cloud in the piston cavity periphery in the latter half of the combustion period. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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10. Effect of the hydrocarbon molecular structure in diesel fuel on the in-cylinder soot formation and exhaust emissions.
- Author
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Nakakita, K., Akihama, K., Weissman, W., and Farrel, J. T.
- Subjects
HYDROCARBONS ,DIESEL motors ,DIESEL fuels ,CYCLOALKANES ,SHOCK tubes ,DIESEL motor exhaust gas - Abstract
Evaluations of diesel fuel effects on combustion and exhaust emissions in single-cylinder direct-injection diesel engines led to the unexpected result that a Swedish 'class 1' fuel generated more particulate matter (PM) than a fuel denoted 'improved', even though 'class 1' fuel had much lower distillation temperatures, aromatic concentration, sulphur level, and density than the 'improved' fuel. Little differences were observed in the combustion characteristics between these fuels, but detailed compositional analyses showed that 'class 1' fuel contains higher levels of cyclic and/or branched paraffins. Subsequent investigations in a laboratory flow reactor showed that 'class 1' fuel produces more soot precursors such as benzene and acetylene than the 'improved' fuel. In addition, experiments in a low-pressure laminar flame apparatus and shock tube with model (single-molecule) paraffin fuels showed that isoparaffins and cycloparaffins generate more soot precursors and soot than n-paraffins do. These results strongly suggested that the effect of molecular structure on exhaust PM formation should be more carefully examined. Therefore, a new series of investigations were performed to examine exhaust emissions and combustion characteristics in single-cylinder engines, with well characterized test fuels having carefully controlled molecular composition and conventional distillation characteristics and cetane numbers (CNs). These investigations revealed the following. Firstly, under low and medium lo ads, cycloparaffins (naphthenes) have a higher PM formation tendency than isoparaffins and n-paraffins. Under high-load conditions, however, the paraffin molecular structure has a very small effect. Secondly, a highly n-paraffinic fuel does not yield PM reductions as high as expected, due to its high CN and corresponding shorter ignition lag, which initiates combustion under a state of insufficient fuel-air mixing. This finding was corroborated by laser-induced incandescence analyses. Thirdly, the lowest PM emissions were observed with a paraffinic fuel containing 55 per cent isoparaffins and 39 per cent n-paraffins. Fourthly, aromatics give higher soot and PM levels than paraffins do at high and medium load conditions. Smaller differences are observed at lower speeds and loads. Fifthly, the best fit to the PM emissions was obtained with an equation containing the regression variables CN, aromatic rings, and naphthene rings. This expression of the fuel effects in chemical terms allows well-to-wheel analyses of refining and vehicle impacts resulting from molecularly based fuel changes. [ABSTRACT FROM AUTHOR]
- Published
- 2005
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11. Identification of time and spatial varying heat flux from surface measurements based on temperature-sensitive paint technology.
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Kojima, F., Fukuda, S., Asai, K., and Nakakita, K.
- Published
- 2004
12. Simulation studies on surface heat flux for highly dynamical heat diffusion system under surface temperature measurements.
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Kojima, F., Fukuda, S., Asai, K., and Nakakita, K.
- Published
- 2003
13. Dual-luminophore pressure-sensitive paint measurement using three-gate lifetime method with photodegradation correction.
- Author
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Uchida K, Nakakita K, Sugioka Y, Asai K, and Nonomura T
- Abstract
In this paper, we propose a photodegradation correction method for the dual-luminophore pressure-sensitive paint (PSP) measurement using lifetime-based imaging, which was proposed for correction of the temperature-induced error but has suffered from photodegradation in the previous studies. We introduced a parameter that characterizes the photodegradation of a dual-luminophore PSP as the intensity ratio between the two luminophores. The changes in the calibration coefficients for the pressure and the temperature due to photodegradation were corrected based on this parameter. In this study, a coupon-based calibration test was performed, and the luminescence characteristics of the dual-luminophore PSP including photodegradation were investigated. Then, the proposed method was applied to a coupon-based validation test and a jet impingement test, and the effectiveness of the method was evaluated by comparing results with and without correction. The pressure measurement accuracy was significantly improved by photodegradation correction., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)
- Published
- 2024
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14. Photoelctrochemically Fabricated and Heated Cu 2 O/CuO Bilayers with Enhanced Photovoltaic Characteristics.
- Author
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Izaki M, Abe S, Nakakita K, and Khoo PL
- Abstract
Cu
2 O/CuO bilayers were fabricated by electrodeposition of the CuO layer in a copper(II)-ammonia complex aqueous solution, followed by photoelectrochemical deposition of the Cu2 O layer at potentials ranging from -0.3 to -1.0 V referenced to a Ag/AgCl electrode in a copper(II)-lactate complex aqueous solution under light irradiation, and the effects of varied potentials of the photoelectrochemical Cu2 O depositions and post-heating conditions on their structural, optical, and photovoltaic characteristics were investigated with X-ray diffraction, field emission-scanning electron microscopy, optical absorption measurements, and external quantum efficiency (EQE) measurements with and without applied bias voltage. The Cu2 O layers with a characteristic 2.1 eV band gap energy were adhesively stacked on the thorn-like grains of the CuO layers possessing a characteristic 1.5 eV band gap energy, and dense and defect-free Cu2 O/CuO bilayers could be fabricated at the potentials of -0.4 and -0.5 V, but the grain size of Cu2 O decreased at -0.5 V. In addition, the metallic Cu was deposited simultaneously at potentials less than -0.7 V. The Cu2 O/CuO bilayer fabricated at -0.4 V revealed photovoltaic features at wavelengths ranging from 350 nm to approximately 900 nm, and a maximum EQE value of 56.8% was achieved at 510 nm in wavelength with a bias voltage of -0.1 V. The maximum EQE value, however, decreased to 1.2% accompanied with the peak wavelength shift to 580 nm, and no photovoltaic feature was observed at potentials of -0.3, -0.7, and -1.0 V. The photovoltaic performance for the Cu2 O/CuO bilayer fabricated at -0.4 V was ameliorated by heating at 423 K, and the maximum EQE values were enhanced to 87.7% at 550 nm and 89.8% at 530 nm in an ambient atmosphere and vacuum. Both the Cu2 O and CuO layers acted as photovoltaic layers in the Cu2 O/CuO bilayer fabricated at -0.4 V and heated at 423 K, and the electrical characteristic including the carrier mobility affected the photovoltaic performance. The photovoltaic feature, however, disappeared by heating above 523 K due to the formation of nanopores inside the CuO layer and near the CuO heterointerface to the Cu2 O and fluorine-doped tin oxide substrate., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)- Published
- 2021
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15. Investigation of Factors Causing Nonuniformity in Luminescence Lifetime of Fast-Responding Pressure-Sensitive Paints.
- Author
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Egami Y, Yamazaki Y, Hori N, Sugioka Y, and Nakakita K
- Subjects
- Temperature, Luminescence, Paint
- Abstract
Factors that cause nonuniformity in the luminescence lifetime of pressure-sensitive paints (PSPs) were investigated. The lifetime imaging method of PSP does not theoretically require wind-off reference images. Therefore, it can improve measurement accuracy because it can eliminate errors caused by the deformation or movement of the model during the measurement. However, it is reported that the luminescence lifetime of PSP is not uniform on the model, even under uniform conditions of pressure and temperature. Therefore, reference images are used to compensate for the nonuniformity of the luminescence lifetime, which significantly diminishes the advantages of the lifetime imaging method. In particular, fast-responding PSPs show considerable variation in luminescence lifetime compared to conventional polymer-based PSPs. Therefore, this study investigated and discussed the factors causing the nonuniformity of the luminescence lifetime, such as the luminophore solvent, luminophore concentrations, binder thickness, and spraying conditions. The results obtained suggest that the nonuniformity of the luminophore distribution in the binder caused by the various factors mentioned above during the coating process is closely related to the nonuniformity of the luminescence lifetime. For example, when the thickness of the binder became thinner than 8 μm, the fast-responding PSPs showed a tendency to vary significantly in the luminescence lifetime. In addition, it was found that the luminescence lifetime of fast-responding PSP could be changed in the depth direction of the binder depending on the coating conditions. Therefore, it is important to distribute the luminophore uniformly in the binder layer to create PSPs with a more uniform luminescence lifetime distribution.
- Published
- 2021
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16. Evaluation of the Characteristics and Coating Film Structure of Polymer/Ceramic Pressure-Sensitive Paint.
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Sugioka Y, Arakida K, Kasai M, Nonomura T, Asai K, Egami Y, and Nakakita K
- Abstract
Polymer/ceramic pressure-sensitive paint (PC-PSP), which incorporates a high percentage of particles in the binder layer, is proposed in order to improve the characteristics of PSP. The procedure for embedding particles into the binder layer was modified. In the conventional procedure, dye is adsorbed onto a polymer/ceramic coating film (denoted herein as a dye-adsorbed (D-adsorbed) PSP). In the new procedure, the mixture of a dye and particles is adsorbed onto a polymer coating film (denoted herein as the particle/dye-adsorbed (PD-adsorbed) PSP). The effect of particle mass content on PSP characteristics was investigated. In addition, the effect of solvent on PSP characteristics and film structure were evaluated for the PD-adsorbed PSP. As a result, the difference in the PSP characteristics between the two types of PSP was clarified. Although surface roughness and time response increase with increased mass content of particles for both D- and PD-adsorbed PSPs, the critical pigment volume concentration (CPVC) for the PD-adsorbed PSP is smaller than that of the D-adsorbed PSP (88 wt% and 93 wt%, respectively). The PD-adsorbed PSP has a higher frequency response comparing with the D-adsorbed PSP while maintaining the same surface roughness. Observation by scanning electron microscope showed that the CPVC of the PC-PSP is governed primarily by surface structure. The coating film structure can be roughly classified into two states depending on the particle mass content. One is a state in which the coating film consisted of two layers: a lower particle-rich layer and an upper polymer-rich layer. This type of structure was observed in the PD-adsorbed PSP as well as in the D-adsorbed PSP. In the other state, polymer and particles are homogeneously distributed in the film, and pores are formed. This difference in the coating structure results in a change in the time response.
- Published
- 2018
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17. De novo vertebral artery dissecting aneurysm after contralateral vertebral artery occlusion--two case reports.
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Inui Y, Oiwa Y, Terada T, Nakakita K, Kamei I, and Hayashi S
- Subjects
- Adult, Humans, Male, Middle Aged, Radiography, Vertebral Artery Dissection diagnostic imaging, Embolization, Therapeutic adverse effects, Vertebral Artery Dissection etiology, Vertebral Artery Dissection therapy
- Abstract
Two patients developed de novo vertebral artery dissecting aneurysm after contralateral vertebral artery occlusion. A 36-year-old man presented with brainstem ischemia and was treated non-surgically. Subsequent angiography showed spontaneous vertebral artery occlusion at the site of dissection. A 45-year-old man developed subarachnoid hemorrhage due to vertebral artery dissecting aneurysm. He underwent endovascular occlusion of the vertebral artery proximal to the dissecting aneurysm. These patients developed de novo dissecting aneurysm on the contralateral vertebral artery at 13 months and 11 days after unilateral vertebral artery occlusion, respectively. These cases strongly suggest that changes in hemodynamic stress due to unilateral vertebral artery occlusion are related to de novo dissecting aneurysm on the contralateral side. The risk of de novo dissecting aneurysm may be increased by proximal occlusion or trapping of dissecting aneurysm of the contralateral vertebral artery.
- Published
- 2006
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18. Bone defect associated with middle meningeal arteriovenous fistula treated by embolization--case report.
- Author
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Tsumoto T, Nakakita K, Hayashi S, and Terada T
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- Arteriovenous Fistula complications, Arteriovenous Fistula diagnosis, Head Injuries, Closed complications, Humans, Magnetic Resonance Imaging, Male, Meningeal Arteries injuries, Middle Aged, Osteolysis diagnosis, Osteolysis etiology, Osteolysis therapy, Tomography, X-Ray Computed, Arteriovenous Fistula therapy, Embolization, Therapeutic, Frontal Bone blood supply, Frontal Bone pathology, Meninges blood supply
- Abstract
A 57-year-old male presented with a frontal bone defect associated with a middle meningeal arteriovenous fistula (AVF) manifesting as headache. The patient had a history of head injury 19 years previously. Skull radiography and computed tomography demonstrated a left frontal bone defect. Left external carotid angiography demonstrated a middle meningeal AVF at the frontal region, at the same location as the bone defect. The AVF was fed by the bilateral middle meningeal and left deep temporal arteries, and drained by the superior sagittal and ipsilateral cavernous sinuses. The minor feeding artery, the left deep temporal artery, was embolized with polyvinyl alcohol particles, then 0.4 ml of a 1:3 mixture of n-butyl cyanoacrylate and lipiodol was injected from the left middle meningeal artery. Follow-up angiography 3 months after the embolization revealed complete obliteration of the fistula. The bone defect may have been caused by erosion of the frontal bone by the pulsating effect of the feeding and draining vessels of the fistula, or by inadequate nutrition to the bone tissue because of the arteriovenous shunt.
- Published
- 2001
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19. Peptidergic innervation in the cerebral blood vessels of the guinea pig: an immunohistochemical study.
- Author
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Nakakita K
- Subjects
- Animals, Brain Chemistry, Calcitonin Gene-Related Peptide metabolism, Guinea Pigs, Immunohistochemistry, Neuropeptide Y metabolism, Substance P metabolism, Vasoactive Intestinal Peptide metabolism, Brain blood supply, Brain ultrastructure, Cerebral Arteries innervation, Nerve Fibers ultrastructure
- Abstract
The distribution of peptidergic nerve fibers containing substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in the cerebral arteries and veins of the guinea pig was studied using immunohistochemical techniques. The ultrastructure of these immunoreactive nerve terminals was also compared. The cerebral arteries were innervated by abundant peptidergic nerve fibers with characteristic running patterns, i.e., SP fibers in a meshwork, VIP and NPY fibers in a spiral fashion. Only CGRP fibers showed both meshwork and spiral patterns. In the cerebral veins, the abundant SP fibers innervated the cortical veins, deep cerebral veins, and dural sinuses. However, CGRP, VIP, and NPY fibers in extremely low density were noted merely in the cortical veins. Electron microscopic observations demonstrated that SP-immunoreactive nerve terminals existed apart from the arterial smooth muscle cells, while VIP- and NPY-immunoreactive nerve terminals adjoined them. As for CGRP nerve terminals, some existed close to the arterial smooth muscle cells, and others were found some distance from them. These morphological characteristics observed by light and electron microscopy suggest that SP fibers are not related directly to the vasomotor function, but VIP and NPY fibers are, and that CGRP fibers have a more complicated function. The distribution patterns of the peptidergic nerve fibers are consistent with the suggestion that vasomotor peptidergic fibers may function actively on cerebral arteries and passively on cerebral veins and that SP fibers regarded as sensory fibers may provide information regarding cerebral vascular conditions, innervating every part of both cerebral arteries and veins.
- Published
- 1990
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20. Three dimensional observation of the nerve fibers along the cerebral blood vessels.
- Author
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Itakura T, Nakakita K, Imai H, Nakai K, Kamei I, Naka Y, Okuno T, Komai N, Hirai T, and Arai T
- Subjects
- Animals, Cerebral Arteries ultrastructure, Guinea Pigs, Histocytochemistry, Microscopy, Electron, Scanning, Nerve Fibers analysis, Substance P immunology, Vasoactive Intestinal Peptide immunology, Vasoconstriction, Vasodilation, Cerebral Arteries innervation, Nerve Fibers ultrastructure, Substance P analysis, Vasoactive Intestinal Peptide analysis
- Abstract
Three dimensional observation of the nerve fibers along the cerebral blood vessels was investigated by scanning electron microscopy. Electron probe X-ray microanalysis was also performed in the cerebral blood vessels treated with peroxidase-antiperoxidase immunohistochemistry intensified by nickel ammonium sulfate. Nerve fibers (2-8 microns in diameter) formed a plexus on the outer surface of the adventitia. After branching, the nerve fibers penetrated the blood vessel adventitia. Substance P-immunoreactive nerve fibers showed a meshwork pattern in the outer layer of the adventitia, and vasoactive intestinal polypeptide (VIP)-immunoreactive nerve fibers revealed a spiral running pattern in the inner layer of the adventitia. Taken together with previous studies, these findings suggest that substance P nerve fibers in the cerebral arteries may not be related to arterial dilatation or constriction, but VIP nerve fibers may be vasodilative.
- Published
- 1986
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21. A light and electron microscopic immunohistochemical study of vasoactive intestinal polypeptide- and substance P-containing nerve fibers along the cerebral blood vessels: comparison with aminergic and cholinergic nerve fibers.
- Author
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Itakura T, Okuno T, Nakakita K, Kamei I, Naka Y, Nakai K, Imai H, Komai N, Kimura H, and Maeda T
- Subjects
- Animals, Blood Vessels innervation, Guinea Pigs, Histocytochemistry, Immunochemistry, Microscopy, Electron, Nerve Fibers ultrastructure, Parasympathetic Nervous System metabolism, Cerebrovascular Circulation, Nerve Fibers metabolism, Substance P metabolism, Sympathetic Nervous System metabolism, Vasoactive Intestinal Peptide metabolism
- Abstract
Vasoactive intestinal polypeptide (VIP)- and substance P-containing nerve fibers were observed in the cerebral blood vessels using an immunohistochemical technique. VIP-containing nerve fibers distributed in a spiral pattern, similar to that of muscle cells. Under electron microscopic observation, VIP-immunoreactive terminals lay close to a muscle cell in the inner layer of the adventitia. In contrast, substance P-containing nerve fibers showed a meshwork pattern in the outer layer of the adventitia. Using both acetylcholinesterase (AChE) staining and VIP immunohistochemistry, AChE-positive and VIP-immunoreactive nerve fibers revealed almost the same distribution in the same specimen. The present data suggest that VIP-containing nerve fibers may play a role in the smooth muscle control of the blood vessels, whereas substance P-containing nerve fibers may not take part in muscle control.
- Published
- 1984
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22. The distribution of adrenergic receptors in cerebral blood vessels: an autoradiographic study.
- Author
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Nakai K, Itakura T, Naka Y, Nakakita K, Kamei I, Imai H, Yokote H, and Komai N
- Subjects
- Animals, Arteries innervation, Autoradiography, Cerebral Arteries innervation, Humans, Male, Pia Mater blood supply, Radioligand Assay, Rats, Rats, Inbred Strains, Vertebral Artery innervation, Brain blood supply, Receptors, Adrenergic analysis
- Abstract
The first morphological evidence of the existence of adrenergic receptors (alpha 1, alpha 2 and beta) within the vascular walls of the central nervous system were presented using the in vitro receptor autoradiographic technique. In the rat pial arteries all three types of adrenergic receptors were demonstrated, whereas the human pial arteries failed to show significant autoradiographic grains of alpha 1 type of adrenergic receptors indicating a considerable inter-species difference in the distribution of adrenergic receptors. alpha 2 and beta receptors in human pial arteries were found not only in the arterial smooth muscle layers but also in the endothelial layers. This suggests a possibility that circulating sympathomimetic agents play some role in controlling the tone or permeability of vascular walls within the central nervous system. A distinct distribution of alpha 1 receptors in cortical layer IV where the vascular plexus was richest may suggest a relation of alpha 1 receptors and blood flow of brain parenchyma.
- Published
- 1986
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23. Regional cerebral blood flow in the persistent vegetative state.
- Author
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Sato M, Kuroda R, Ioku M, Kim A, Tanaka S, Nakakita K, Kohama A, Fujii C, Ono S, and Fukunaga M
- Subjects
- Adult, Aged, Female, Humans, Male, Middle Aged, Tomography, Emission-Computed, Single-Photon, Cerebrovascular Circulation, Coma physiopathology
- Abstract
Regional cerebral blood flow (CBF) in eight patients in a persistent vegetative state was measured and compared with that in five healthy volunteers. The patients were classified into three groups: Group 1 (locked-in syndrome) consisted of a single patient, Group 2 (typical vegetative state) of five patients, and Group 3 (prolonged coma) of two patients. CBF was measured early after onset by single photon emission computed tomography with 123I-N-isopropyl-p-iodo-amphetamine and/or 99mTc-hexamethyl-propyleneamine oxime. The regions of interest (ROIs) were the bilateral frontal, temporal, parietal, occipital, and cerebellar areas and basal ganglia. The values obtained in these areas were averaged, and the ratio for each ROI [(the value in the ROI/the mean value) x 100] was calculated. "Hyperfrontal distribution" of CBF was found to be rare in both the normal condition and the vegetative state. Higher CBF values were noted in the left than in the right frontal area in four of the five volunteers but in only four of the eight patients. CBF distribution in the frontal lobe was characteristic for each group: Group 1 showed high CBF bilaterally, although the elevation was statistically significant only on the right side, and Group 3 exhibited significantly low values. In Group 2, CBF was variable but, for the most part, within normal limits. Awareness was closely correlated with frontal lobe function and alteration of CBF in the frontal region.
- Published
- 1989
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24. Regulation of rCBF by intracortical vasoactive intestinal polypeptide-containing neurons. Immunohistochemical and hydrogen clearance study in rats.
- Author
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Itakura T, Yokote H, Okuno T, Naka Y, Nakakita K, Kamei I, Nakai K, Imai H, and Komai N
- Subjects
- Animals, Cerebral Cortex cytology, Cerebral Cortex physiology, Hydrogen, Immunoenzyme Techniques, Nerve Fibers physiology, Rats, Rats, Inbred Strains, Cerebral Cortex analysis, Cerebrovascular Circulation, Nerve Fibers analysis, Vasoactive Intestinal Peptide analysis
- Abstract
The role of intracortical vasoactive intestinal polypeptide (VIP)-containing neurons in the regulation of cortical blood flow was investigated in rats by immunohistochemical and hydrogen clearance methods. Immunohistochemical studies revealed an intimate association between intracortical VIP-containing neurons and small blood vessels. Intracortical injection of a VIP solution (10(-5) M) produced significantly higher blood flow in the treated cortex (mean +/- standard error of the mean: 46.2 +/- 4.0 ml/100 gm/min) than in the untreated cortex (36.9 +/- 2.4 ml/100 gm/min). These data suggest that intracortical VIP-containing neurons produce dilatation of intracortical blood vessels.
- Published
- 1987
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25. Innervation of the cerebral veins as compared with the cerebral arteries: a histochemical and electron microscopic study.
- Author
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Nakakita K, Imai H, Kamei I, Naka Y, Nakai K, Itakura T, and Komai N
- Subjects
- Animals, Catecholamines physiology, Fluorescence, Histocytochemistry, Microscopy, Electron, Nerve Fibers physiology, Rats, Rats, Inbred Strains, Cerebral Arteries innervation, Cerebrovascular Circulation, Veins innervation
- Abstract
The distribution of nerve fibers in the cerebral veins was studied by catecholamine fluorescence simultaneously with acetylcholinesterase (AChE) histochemistry. A comparison of nerve fibers in the cerebral arteries was made. The ultrastructure of terminal boutons in the veins fixed with potassium permanganate was also studied. In the adventitia of the cerebral artery, green fluorescent aminergic fibers and brownish AChE-reactive (probably cholinergic) fibers were observed. In contrast, the cerebral venous system showed no AChE-positive fibers. Catecholamine fluorescent varicose fibers were detected in the dural sinus, the internal cerebral vein, and the superficial vein of Labbé. The highest density of aminergic fibers was found in the dural sinus and the second highest in the internal cerebral vein. Most of the terminal boutons in the adventitia of the cerebral veins were found adjacent to a muscle-like cell and showed only cored vesicles under electron microscopy. Results of our study suggest that the cerebral venous system has a neurogenic innervation, mainly from aminergic fibers, which is different from the neurogenic supply to the cerebral arterial system.
- Published
- 1983
- Full Text
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26. Autotransplantation of the superior cervical ganglion into the brain. A possible therapy for Parkinson's disease.
- Author
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Itakura T, Kamei I, Nakai K, Naka Y, Nakakita K, Imai H, and Komai N
- Subjects
- 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine, Animals, Catecholamines metabolism, Caudate Nucleus metabolism, Caudate Nucleus pathology, Cerebral Cortex metabolism, Fluorescence, Ganglia, Sympathetic metabolism, Hydroxydopamines pharmacology, Nerve Fibers pathology, Oxidopamine, Parkinson Disease, Secondary chemically induced, Parkinson Disease, Secondary pathology, Pyridines pharmacology, Transplantation, Autologous, Cerebral Cortex physiology, Ganglia, Sympathetic transplantation, Parkinson Disease therapy
- Abstract
The superior cervical ganglion (SCG) of rats was transplanted into their own parietal cortex. Four weeks after implantation, catecholamine histofluorescence revealed many transplanted catecholamine cells in the cortex. However, no fibers extended from the transplanted tissue to the cerebral cortex. In a second group of rats which had been pretreated with 6-hydroxydopamine (a specific neurotoxin to the catecholamine neuron), some showed extension of catecholamine fibers to the cerebral cortex. To simulate an animal model of Parkinson's disease, MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine) was administered to five monkeys. Two weeks after MPTP administration, dopamine terminals in the caudate nucleus disappeared. After autotransplantation of the SCG into the caudate nucleus of these monkeys, many of the transplanted SCG cells extended axons beyond the graft into the caudate nucleus. These results show that transplanted SCG cells survived well in the brain. Under special circumstances, such as a shortage of catecholamine in the brain, implanted SCG cells extended their axons into the brain. It is suggested that autotransplantation of SCG grafts may be a new therapy for Parkinson's disease.
- Published
- 1988
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27. Immunohistochemical demonstration of vasopressin nerve fibers in the cerebral artery.
- Author
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Itakura T, Okuno T, Ueno M, Nakakita K, Nakai K, Naka Y, Imai H, Kamei I, and Komai N
- Subjects
- Animals, Immunohistochemistry, Nerve Fibers anatomy & histology, Pia Mater blood supply, Cerebral Arteries innervation, Nerve Fibers metabolism, Vasopressins metabolism
- Abstract
Vasopressin-immunoreactive nerve fibers were demonstrated in the cerebral pial arteries by peroxidase immunohistochemistry. In the large pial artery (proximal part of the middle cerebral artery), they ran longitudinally to the long axis of the vessel. They ran in a spiral pattern in the distal part of the middle cerebral artery. Even in small arteries, vasopressin nerve fibers were found arranged in a longitudinal fashion. The present morphological data suggest that vasopressin nerve fibers in the cerebral artery may play a role in cerebral circulation.
- Published
- 1988
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28. 5-Hydroxytryptamine innervation of vessels in the rat cerebral cortex. Immunohistochemical findings and hydrogen clearance study of rCBF.
- Author
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Itakura T, Yokote H, Kimura H, Kamei I, Nakakita K, Naka Y, Nakai K, Imai H, and Komai N
- Subjects
- Animals, Brain Chemistry, Carbon Dioxide metabolism, Immunochemistry, Rats, Rats, Inbred Strains, Cerebral Arteries innervation, Cerebral Cortex analysis, Cerebrovascular Circulation, Serotonin analysis
- Abstract
The role of the central 5-hydroxytryptamine (5-HT) neuron system in cerebral microcirculation of the rat was examined by immunohistochemical and hydrogen clearance methods. Immunohistochemical studies demonstrated 5-HT-immunoreactive nerve fibers along intraparenchymal blood vessels (arterioles, capillaries, and venules). Ultrastructural observation revealed that 5-HT-immunoreactive terminal boutons (0.3 to 1.0 micron in diameter) made contact with the basement membrane of the capillaries. After an intracerebral injection of 5,7-dihydroxytryptamine (5,7-DHT), a neurotoxin to the 5-HT neuron system, no 5-HT-immunoreactive nerve fibers were found around the injection site with immunohistochemical techniques. With the hydrogen clearance method, the 5,7-DHT-injected cortex showed no significant change in regional cerebral blood flow (rCBF) in the presence of normocapnia, but a significant increase in rCBF with hypercapnia, compared with the untreated cortex. These facts strongly suggest that the central 5-HT neuron system has an important role in carbon dioxide reactivity of the cerebral blood vessels.
- Published
- 1985
- Full Text
- View/download PDF
29. Microangioarchitecture of the feline spinal cord. Three-dimensional observation of blood vessel corrosion casts by scanning electron microscopy.
- Author
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Naka Y, Itakura T, Nakai K, Nakakita K, Imai H, Okuno T, Kamei I, and Komai N
- Subjects
- Animals, Microscopy, Electron, Scanning, Spinal Cord ultrastructure, Cats anatomy & histology, Spinal Cord blood supply
- Abstract
The microangioarchitecture of corrosion casts of the cat spinal cord was studied by scanning electron microscopy. On the ventral surface of the spinal cord, the anterior spinal artery and the anterior spinal vein ran parallel along the anterior median fissure. Many central arteries branching from the anterior spinal artery coursed in a wavelike manner in the anterior median fissure. The number of central arteries was lowest in the thoracic spinal cord. Central arteries at some spinal cord levels revealed well-developed anastomoses with other central arteries in the anterior median fissure. These well-developed anastomotic central arteries were frequently observed in the thoracic spinal cord, in which the number of central arteries was lowest. On the dorsal surface of the spinal cord, the posterior spinal vein ran longitudinally at the midline and was drained by circumferential veins and posterior central veins. This vein formed a characteristic anastomotic plexus. Small arterioles (20 microns in diameter) in the spinal parenchyma revealed a ring-like compression at the branching site.
- Published
- 1987
- Full Text
- View/download PDF
30. Aminergic innervation of cerebral veins. Histochemical comparison with extracranial veins.
- Author
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Itakura T, Nakakita K, Kamei I, Naka Y, Nakai K, Komai N, Yokoi H, Nishimura O, and Okada N
- Subjects
- Amines, Animals, Nerve Fibers anatomy & histology, Rats, Rats, Inbred Strains, Brain blood supply, Veins innervation
- Abstract
The density and distribution pattern of aminergic nerve fibers in intracranial and extracranial veins were compared by means of catecholamine histofluorescence studies. Extracranial veins (internal jugular, inferior caval, portal, renal, internal iliac, and femoral veins) showed quite a uniform distribution pattern. Large veins (jugular, caval, renal, and iliac veins) revealed a spiral pattern, and small veins presented as a meshwork (femoral vein) or in a longitudinal pattern (a branch of the femoral vein). In contrast, intracranial veins displayed more complex patterns: the dural sinus showed a longitudinal pattern and the internal cerebral vein and the superficial vein of Labbé revealed a meshwork of nerve fibers. The aminergic fibers were denser in cerebral veins (dural sinus and internal cerebral vein) than in extracranial veins. The complex distribution and the density of aminergic fibers in cerebral veins suggest that the aminergic innervation of the circulatory system may be more important in the brain than in the extracranial organs.
- Published
- 1984
- Full Text
- View/download PDF
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