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Search Results: 1 - 10 of 2013 matches for " Masahiro Kawahara "
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Object-Spatial Imagery Types of Japanese College Students  [PDF]
Masahiro Kawahara, Kazuo Matsuoka
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.43024

This study investigated the object-spatial imagery types found among Japanese college students. First, we examined the descriptive statistics of the Japanese version of the Object-Spatial Imagery Questionnaire object-spatial imagery scales, which measure respondents’ tendencies with respect to object-spatial imagery types. Although the means of these subscales were lower than those of the original versions, the raw score distributions and gender differences were similar to those obtained using the original version. Additionally, we compared imagery types among students in seven different academic departments. Specifically, the results showed specific patterns of imagery type among students in each department, indicating that the object-spatial imagery type model is applicable to Japanese college students and that individual imagery type data would be helpful for career guidance.

The Molecular Mechanisms of Zinc Neurotoxicity and the Pathogenesis of Vascular Type Senile Dementia
Dai Mizuno,Masahiro Kawahara
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms141122067
Abstract: Zinc (Zn) is an essential trace element that is abundantly present in the brain. Despite its importance in normal brain functions, excess Zn is neurotoxic and causes neurodegeneration following transient global ischemia and plays a crucial role in the pathogenesis of vascular-type dementia (VD). We have investigated the molecular mechanisms of Zn-induced neurotoxicity using immortalized hypothalamic neurons (GT1-7 cells) and found that carnosine (β-alanyl histidine) and histidine (His) inhibited Zn 2+-induced neuronal death. A DNA microarray analysis revealed that the expression of several genes, including metal-related genes (metallothionein and Zn transporter 1), endoplasmic reticulum (ER)-stress related genes ( GADD34, GADD45, and p8), and the calcium (Ca)-related gene Arc (activity-related cytoskeleton protein), were affected after Zn exposure. The co-existence of carnosine or His inhibited the expression of GADD34, p8, and Arc, although they did not influence the expression of the metal-related genes. Therefore, ER-stress and the disruption of Ca homeostasis may underlie the mechanisms of Zn-induced neurotoxicity, and carnosine might be a possible drug candidate for the treatment of VD.
Link between Aluminum and the Pathogenesis of Alzheimer's Disease: The Integration of the Aluminum and Amyloid Cascade Hypotheses
Masahiro Kawahara,Midori Kato-Negishi
International Journal of Alzheimer's Disease , 2011, DOI: 10.4061/2011/276393
Abstract: Whilst being environmentally abundant, aluminum is not essential for life. On the contrary, aluminum is a widely recognized neurotoxin that inhibits more than 200 biologically important functions and causes various adverse effects in plants, animals, and humans. The relationship between aluminum exposure and neurodegenerative diseases, including dialysis encephalopathy, amyotrophic lateral sclerosis and Parkinsonism dementia in the Kii Peninsula and Guam, and Alzheimer's disease (AD) has been suggested. In particular, the link between aluminum and Alzheimer's disease has been the subject of scientific debate for several decades. However, the complex characteristics of aluminum bioavailability make it difficult to evaluate its toxicity and therefore, the relationship remains to be established. Mounting evidence has suggested that significance of oligomerization of -amyloid protein and neurotoxicity in the molecular mechanism of AD pathogenesis. Aluminum may play crucial roles as a cross-linker in -amyloid oligomerization. Here, we review the detailed characteristics of aluminum neurotoxicity based on our own studies and the recent literatures. Our aim is to revisit the link between aluminum and AD and to integrate aluminum and amyloid cascade hypotheses in the context of -amyloid oligomerization and the interactions with other metals.
Neurosteroids block the increase in intracellular calcium level induced by Alzheimer’s β-amyloid protein in long-term cultured rat hippocampal neurons
Midori Kato-Negishi,Masahiro Kawahara
Neuropsychiatric Disease and Treatment , 2008,
Abstract: Midori Kato-Negishi1, Masahiro Kawahara21Department of Developmental Morphology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu-shi, Tokyo 183- 8526, Japan; 2Department of Analytical Chemistry, School of Pharmaceutical Sciences, Kyushu University of Health and Welfare, 1714-1 Yoshino-cho, Nobeoka-shi, Miyazaki 882-8508, JapanAbstract: The neurotoxicity of β-amyloid protein (AβP) is implicated in the etiology of Alzheimer’s disease. We previously have demonstrated that AβP forms Ca2+-permeable pores on neuronal membranes, causes a marked increase in intracellular calcium level, and leads to neuronal death. Here, we investigated in detail the features of AβP-induced changes in intracellular Ca2+ level in primary cultured rat hippocampal neurons using a multisite Ca2+- imaging system with fura-2 as a fluorescent probe. Only a small fraction of short-term cultured hippocampal neurons (ca 1 week in vitro) exhibited changes in intracellular Ca2+ level after AβP exposure. However, AβP caused an acute increase in intracellular Ca2+ level in long-term cultured neurons (ca 1 month in vitro). The responses to AβP were highly heterogeneous, and immunohistochemical analysis using an antibody to AβP revealed that AβP is deposited on some but not all neurons. Considering that the disruption of Ca2+ homeostasis is the primary event in AβP neurotoxicity, substances that protect neurons from an AβP-induced intracellular Ca2+ level increase may be candidates as therapeutic drugs for Alzheimer’s disease. In line with the search for such protective substances, we found that the preadministration of neurosteroids including dehydroepiandrosterone, dehydroepiandrosterone sulfate, and pregnenolone significantly inhibits the increase in intracellular calcium level induced by AβP. Our results suggest the possible significance of neurosteroids, whose levels are reduced in the elderly, in preventing AβP neurotoxicity.Keywords: neurotoxicity, pore, calcium homeostasis, channel, aging
Starspots - Transit Depth Relation of the Evaporating Planet Candidate KIC 12557548b
Hajime Kawahara,Teruyuki Hirano,Kenji Kurosaki,Yuichi Ito,Masahiro Ikoma
Physics , 2013, DOI: 10.1088/2041-8205/776/1/L6
Abstract: Violent variation of transit depths and an ingress-egress asymmetry of the transit light curve discovered in KIC 12557548 have been interpreted as evidences of a catastrophic evaporation of atmosphere with dust (M_p gtrsim 1 M_oplus/Gyr) from a close-in small planet. To explore what drives the anomalous atmospheric escape, we perform time-series analysis of the transit depth variation of Kepler archival data for ~ 3.5 yr. We find a ~ 30% periodic variation of the transit depth with P1 = 22.83 pm 0.21 days, which is within the error of the rotation period of the host star estimated using the light curve modulation, Prot = 22.91 pm 0.24 days. We interpret the results as evidence that the atmospheric escape of KIC 12557548b correlates with stellar activity. We consider possible scenarios that account for both the mass loss rate and the correlation with stellar activity. X-ray and ultraviolet (XUV)-driven evaporation is possible if one accepts a relatively high XUV flux and a high efficiency for converting the input energy to the kinetic energy of the atmosphere. Star-planet magnetic interaction is another possible scenario though huge uncertainty remains for the mass loss rate.
Use of FDG-PET in Radiation Treatment Planning for Thoracic Cancers
Katsuyuki Shirai,Akiko Nakagawa,Takanori Abe,Masahiro Kawahara,Jun-ichi Saitoh,Tatsuya Ohno,Takashi Nakano
International Journal of Molecular Imaging , 2012, DOI: 10.1155/2012/609545
Abstract: Radiotherapy plays an important role in the treatment for thoracic cancers. Accurate diagnosis is essential to correctly perform curative radiotherapy. Tumor delineation is also important to prevent geographic misses in radiotherapy planning. Currently, planning is based on computed tomography (CT) imaging when radiation oncologists manually contour the tumor, and this practice often induces interobserver variability. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been reported to enable accurate staging and detect tumor extension in several thoracic cancers, such as lung cancer and esophageal cancer. FDG-PET imaging has many potential advantages in radiotherapy planning for these cancers, because it can add biological information to conventional anatomical images and decrease the inter-observer variability. FDG-PET improves radiotherapy volume and enables dose escalation without causing severe side effects, especially in lung cancer patients. The main advantage of FDG-PET for esophageal cancer patients is the detection of unrecognized lymph node or distal metastases. However, automatic delineation by FDG-PET is still controversial in these tumors, despite the initial expectations. We will review the role of FDG-PET in radiotherapy for thoracic cancers, including lung cancer and esophageal cancer. 1. Introduction Radiotherapy plays an important role in the treatment of thoracic cancers, such as non-small-cell lung cancer (NSCLC), small-cell lung cancer (SCLC), and esophageal cancer [1, 2]. Recent advances in accurate diagnosis improve the practice of curative radiotherapy, because patients with unsuspected metastases may avoid unnecessary local therapies and receive necessary systemic treatment. Accurate delineation of tumor volume is also important to prevent geographic misses in treatment planning. Indeed, an underestimation of tumor extension will result in tumor recurrence. In contrast, overestimation of the extension may increase unnecessary side effects. Therefore, delineation of tumor volumes is a crucial factor in curative radiotherapy. Currently, treatment planning is based on computed tomography (CT) imaging to contour the tumor. Tumor delineation is manually performed by each radiation oncologist in clinical practice, which leads to interobserver variability in tumor delineation. Accurate delineation of tumor volume requires the identification of anatomic borders of tumors based on accurate diagnosis. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and PET/CT have been reported to enable accurate staging and
Membrane Incorporation, Channel Formation, and Disruption of Calcium Homeostasis by Alzheimer's β-Amyloid Protein
Masahiro Kawahara,Isao Ohtsuka,Shoko Yokoyama,Midori Kato-Negishi,Yutaka Sadakane
International Journal of Alzheimer's Disease , 2011, DOI: 10.4061/2011/304583
Abstract: Oligomerization, conformational changes, and the consequent neurodegeneration of Alzheimer's β-amyloid protein (AβP) play crucial roles in the pathogenesis of Alzheimer's disease (AD). Mounting evidence suggests that oligomeric AβPs cause the disruption of calcium homeostasis, eventually leading to neuronal death. We have demonstrated that oligomeric AβPs directly incorporate into neuronal membranes, form cation-sensitive ion channels (“amyloid channels”), and cause the disruption of calcium homeostasis via the amyloid channels. Other disease-related amyloidogenic proteins, such as prion protein in prion diseases or α-synuclein in dementia with Lewy bodies, exhibit similarities in the incorporation into membranes and the formation of calcium-permeable channels. Here, based on our experimental results and those of numerous other studies, we review the current understanding of the direct binding of AβP into membrane surfaces and the formation of calcium-permeable channels. The implication of composition of membrane lipids and the possible development of new drugs by influencing membrane properties and attenuating amyloid channels for the treatment and prevention of AD is also discussed. 1. Introduction Alzheimer’s disease (AD) is a severe type of senile dementia, affecting a large portion of elderly people worldwide. It is characterized by profound memory loss and inability to form new memories. The pathological hallmarks of AD are the presence of numerous extracellular deposits, termed senile plaques, and intraneuronal neurofibrillary tangles (NFTs). The degeneration of synapses and neurons in the hippocampus or cerebral cortex is also observed [1]. The major components of NFTs are phosphorylated tau proteins, and that of senile plaques are β-amyloid proteins (AβPs). Although the precise cause of AD remains elusive, it is widely accepted that oligomerization of AβP and the consequent neurodegeneration might be the cause of neuronal death in AD patients [2, 3]. There is considerable interest regarding the mechanism by which AβPs cause neurodegeneration. AβPs have been reported to cause various adverse effects on neuronal survivals, such as the production of reactive oxygen species, the induction of cytokines, the induction of endoplasmic reticulum (ER) stresses, and the abnormal increase in intracellular calcium levels ([Ca2+]i) [4]. These adverse effects are complex and may be interwoven. Of these effects, the disruption of calcium homeostasis could be the earliest and primary event, since Ca2+ ions are essential for various neuronal functions. The
Utility and Limitation of Cumulative Stone Diameter in Predicting Urinary Stone Burden at Flexible Ureteroscopy with Holmium Laser Lithotripsy: A Single-Center Experience
Hiroki Ito, Takashi Kawahara, Hideyuki Terao, Takehiko Ogawa, Masahiro Yao, Yoshinobu Kubota, Junichi Matsuzaki
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0065060
Abstract: Purpose To retrospectively assess the clinical utility in ureteroscopy (URS) planning of cumulative stone diameter (CSD), which does not account for stone width or depth, as a predictor of URS outcome and compare it with stone volume. Materials and Methods Patients with renal stones treated at a single institute by flexible URS were retrospectively evaluated. To assess the clinical utility of CSD, relationships between stone-free (SF) status and stone burden (CSD and volume) were analyzed using the area under the receiver operating characteristics (AUROC) curve. To identify stone number impact on CSD, the AUROC of CSD divided by stone number was evaluated. Correlation coefficients of CSD and stone volume were also calculated for groups by stone number. Results In cases with CSD <20.0 mm, CSD and stone volume revealed equal ability to predict SF status. In cases with CSD ≥20.0 mm, stone volume showed higher predictive ability. The ROC curves for cases with ≥4 stones showed that CSD was less predictive of SF status than stone volume. The correlation coefficients of CSD and stone volume by stone number were 0.922 for 1 stone, 0.900 for 2–3 stones, and 0.661 for ≥4 stones. Conclusions In cases with CSD ≥20.0 mm or ≥4 stones, we should evaluate stone volume for a more predictive stone burden, and pretreatment non-contrast CT seems sufficient. In cases with CSD <20.0 mm or 1–3 stones, CSD was as valid a predictor of preoperative stone burden as stone volume, so preoperative kidney-ureter-bladder (KUB) films may be sufficient.
Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
Yuichi Ito,Masahiro Ikoma,Hajime Kawahara,Hiroko Nagahara,Yui Kawashima,Taishi Nakamoto
Physics , 2015, DOI: 10.1088/0004-637X/801/2/144
Abstract: Motivated by recent detection of transiting high-density super-Earths, we explore the detectability of hot rocky super-Earths orbiting very close to their host stars. In the environment hot enough for their rocky surfaces to be molten, they would have the atmosphere composed of gas species from the magma oceans. In this study, we investigate the radiative properties of the atmosphere that is in the gas/melt equilibrium with the underlying magma ocean. Our equilibrium calculations yield Na, K, Fe, Si, SiO, O, and O$_2$ as the major atmospheric species. We compile the radiative-absorption line data of those species available in literature, and calculate their absorption opacities in the wavelength region of 0.1--100~$\mathrm{\mu m}$. Using them, we integrate the thermal structure of the atmosphere. Then, we find that thermal inversion occurs in the atmosphere because of the UV absorption by SiO. In addition, we calculate the ratio of the planetary to stellar emission fluxes during secondary eclipse, and find prominent emission features induced by SiO at 4~$\mathrm{\mu m}$ detectable by Spitzer, and those at 10 and 100~$\mathrm{\mu m}$ detectable by near-future space telescopes.
Simulation of Human Phonation with Vocal Nodules  [PDF]
Shinji Deguchi, Yuki Kawahara
American Journal of Computational Mathematics (AJCM) , 2011, DOI: 10.4236/ajcm.2011.13022
Abstract: The geometric and biomechanical properties of the larynx strongly influence voice quality and efficiency. A physical understanding of phonation natures in pathological conditions is important for predictions of how voice disorders can be treated using therapy and rehabilitation. Here, we present a continuum-based numerical model of phonation that considers complex fluid-structure interactions occurring in the airway. This model considers a three-dimensional geometry of vocal folds, muscle contractions, and viscoelastic properties to provide a realistic framework of phonation. The vocal fold motion is coupled to an unsteady compressible respiratory flow, allowing numerical simulations of normal and diseased phonations to derive clear relationships between actual laryngeal structures and model parameters such as muscle activity. As a pilot analysis of diseased phonation, we model vocal nodules, the mass lesions that can appear bilaterally on both sides of the vocal folds. Comparison of simulations with and without the nodules demonstrates how the lesions affect vocal fold motion, consequently restricting voice quality. Furthermore, we found that the minimum lung pressure required for voice production increases as nodules move closer to the center of the vocal fold. Thus, simulations using the developed model may provide essential insight into complex phonation phenomena and further elucidate the etiologic mechanisms of voice disorders.
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