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Search Results: 1 - 10 of 3015 matches for " Katsunori Kobayashi "
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Behavioral destabilization induced by the selective serotonin reuptake inhibitor fluoxetine
Katsunori Kobayashi, Yumiko Ikeda, Hidenori Suzuki
Molecular Brain , 2011, DOI: 10.1186/1756-6606-4-12
Abstract: We chronically treated adult male mice with fluoxetine, and examined its effect on several forms of behavior of mice. During fluoxetine treatments, mice showed a marked increase in day-to-day fluctuations of home cage activity levels that was characterized by occasional switching between hypoactivity and hyperactivity within a few days. This destabilized cage activity was accompanied by increased anxiety-related behaviors and could be observed up to 4 weeks after withdrawal from fluoxetine. As reported previously, the granule cell dematuration by fluoxetine includes a reduction of synaptic facilitation at the granule cell output, mossy fiber, synapse to the juvenile level. Mossy fiber synaptic facilitation examined electrophysiologically in acute hippocampal slices also remained suppressed after fluoxetine withdrawal and significantly correlated with the fluctuation of cage activity levels in individual mice. Furthermore, in mice lacking the 5-HT4 receptor, in which the granule cell dematuration has been shown to be attenuated, fluoxetine had no significant effect on the fluctuation of cage activity levels.Our results demonstrate that the SSRI fluoxetine can induce marked day-to-day changes in activity levels of mice in the familiar environment, and that the dematuration of the hippocampal granule cells is closely associated with the expression of this destabilized behavior. Based on these results, we propose that the granule cell dematuration can be a potential cellular basis underlying switching-like changes in the behavioral state associated with SSRI treatments.Selective serotonin reuptake inhibitors (SSRIs) have been commonly used to treat mood and anxiety disorders, while some severe adverse effects have been reported [1,2]. Although SSRIs can immediately change extracellular levels of serotonin in the central nervous system, therapeutic effects of these drugs usually require weeks of treatments [3]. Some of adverse psychiatric effects of SSRIs also emerge wit
Impaired synaptic clustering of postsynaptic density proteins and altered signal transmission in hippocampal neurons, and disrupted learning behavior in PDZ1 and PDZ2 ligand binding-deficient PSD-95 knockin mice
Nagura Hitoshi,Ishikawa Yasuyuki,Kobayashi Katsunori,Takao Keizo
Molecular Brain , 2012, DOI: 10.1186/1756-6606-5-43
Abstract: Background Postsynaptic density (PSD)-95-like membrane-associated guanylate kinases (PSD-MAGUKs) are scaffold proteins in PSDs that cluster signaling molecules near NMDA receptors. PSD-MAGUKs share a common domain structure, including three PDZ (PDZ1/2/3) domains in their N-terminus. While multiple domains enable the PSD-MAGUKs to bind various ligands, the contribution of each PDZ domain to synaptic organization and function is not fully understood. Here, we focused on the PDZ1/2 domains of PSD-95 that bind NMDA-type receptors, and studied the specific roles of the ligand binding of these domains in the assembly of PSD proteins, synaptic properties of hippocampal neurons, and behavior, using ligand binding-deficient PSD-95 cDNA knockin (KI) mice. Results The KI mice showed decreased accumulation of mutant PSD-95, PSD-93 and AMPA receptor subunits in the PSD fraction of the hippocampus. In the hippocampal CA1 region of young KI mice, basal synaptic efficacy was reduced and long-term potentiation (LTP) was enhanced with intact long-term depression. In adult KI mice, there was no significant change in the magnitude of LTP in CA1, but robustly enhanced LTP was induced at the medial perforant path-dentate gyrus synapses, suggesting that PSD-95 has an age- and subregion-dependent role. In a battery of behavioral tests, KI mice showed markedly abnormal anxiety-like behavior, impaired spatial reference and working memory, and impaired remote memory and pattern separation in fear conditioning test. Conclusions These findings reveal that PSD-95 including its ligand binding of the PDZ1/2 domains controls the synaptic clustering of PSD-MAGUKs and AMPA receptors, which may have an essential role in regulating hippocampal synaptic transmission, plasticity, and hippocampus-dependent behavior.
Cytosolic chaperonin CCT possesses GTPase activity  [PDF]
Susumu Noguchi, Kazuyoshi Toyoshima, Soh Yamamoto, Toshio Miyazaki, Michiro Otaka, Sumio Watanabe, Katsunori Imai, Haruki Senoo, Ryoji Kobayashi, Mitsutoshi Jikei, Yasushi Kawata, Hiroshi Kubota, Hideaki Itoh
American Journal of Molecular Biology (AJMB) , 2011, DOI: 10.4236/ajmb.2011.13013
Abstract: Cytosolic chaperonin CCT (also known as TRiC) is a hetero-oligomeric cage-like molecular chaperone that assists in protein folding by ATPase cycle-dependent conformational changes. However, role of the nucleo-tide binding and hydrolysis in CCT-assisted protein folding is still poorly understood. We purified CCT by using ATP-Sepharose and other columns, and found that CCT possesses ability to hydrolyze GTP, with an activity level very similar to the ATPase activity. CCT was more resistant to proteinase K treatment in the presence of GTP or ATP. These results suggest that the GTPase activity of CCT may play a role in chaperone-assisted protein folding.
Correlated Alterations in Serotonergic and Dopaminergic Modulations at the Hippocampal Mossy Fiber Synapse in Mice Lacking Dysbindin
Katsunori Kobayashi,Satomi Umeda-Yano,Hidenaga Yamamori,Masatoshi Takeda,Hidenori Suzuki,Ryota Hashimoto
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018113
Abstract: Dysbindin-1 (dystrobrevin-binding protein 1, DTNBP1) is one of the promising schizophrenia susceptibility genes. Dysbindin protein is abundantly expressed in synaptic regions of the hippocampus, including the terminal field of the mossy fibers, and this hippocampal expression of dysbindin is strongly reduced in patients with schizophrenia. In the present study, we examined the functional role of dysbindin in hippocampal mossy fiber-CA3 synaptic transmission and its modulation using the sandy mouse, a spontaneous mutant with deletion in the dysbindin gene. Electrophysiological recordings were made in hippocampal slices prepared from adult male sandy mice and their wild-type littermates. Basic properties of the mossy fiber synaptic transmission in the mutant mice were generally normal except for slightly reduced frequency facilitation. Serotonin and dopamine, two major neuromodulators implicated in the pathophysiology of schizophrenia, can potentiate mossy fiber synaptic transmission probably via an increase in cAMP levels. Synaptic potentiation induced by serotonin and dopamine was very variable in magnitude in the mutant mice, with some mice showing prominent enhancement as compared with the wild-type mice. In addition, the magnitude of potentiation induced by these monoamines significantly correlated with each other in the mutant mice, indicating that a subpopulation of sandy mice has marked hypersensitivity to both serotonin and dopamine. While direct activation of the cAMP cascade by forskolin induced robust synaptic potentiation in both wild-type and mutant mice, this forskolin-induced potentaition correlated in magnitude with the serotonin-induced potentiation only in the mutant mice, suggesting a possible change in coupling of receptor activation to downstream signaling. These results suggest that the dysbindin deficiency could be an essential genetic factor that causes synaptic hypersensitivity to dopamine and serotonin. The altered monoaminergic modulation at the mossy fiber synapse could be a candidate pathophysiological basis for impairment of hippocampus-dependent brain functions in schizophrenia.
ITGAV polymorphism and disease susceptibility in a Japanese rheumatoid arthritis population
Noriko Iikuni, Shu Kobayashi, Katsunori Ikari, Taisuke Tomatsu, Masako Hara, Hisashi Yamanaka, Naoyuki Kamatani, Shigeki Momohara
Arthritis Research & Therapy , 2007, DOI: 10.1186/ar2303
Abstract: One feature of the pathophysiology of RA is the hyper-angiogenesis observed in the synovial tissue and, along with excess macrophages and T lymphocytes, αvβ3 ligands are also abundant in synovial fluid [2]. As a key player in angiogenesis [3], it has been suggested that ITGAV may be a RA susceptibility gene. The linkage study also supports this view because the 2q31 region containing ITGAV exhibited linkage in a dense genome scan [4].Although the European association study by Jacq and colleagues [1] indicated ITGAV to be a new minor RA susceptibility gene, a replication study conducted in a population of different ethnicity is helpful in exploring whether the association is caused by a common variance through various ethnic groups. We therefore undertook a large population-based study to investigate the association between ITGAV and RA in a Japanese population.DNA samples were obtained from 1,504 Japanese RA patients and 449 population control individuals [5]. Genotypes were determined using the TaqMan method, in accordance with the manufacturer's instructions (Applied Biosystems, Tokyo, Japan). Table 1 shows the genotype distributions and allelic frequencies of patients and control individuals. Unlike the European population, the rs3738919-C allele was more frequent in control individuals in our Japanese population, and no significant differences were observed in allele frequencies for Japanese RA patients and control individuals (0.908 and 0.922, respectively).There are several factors that must be accounted for when a study fails to corroborate a previously identified association. One of these is an ethnicity-specific effect. Ethnic differences can result in differences in allele frequencies, and the genetic background of the disease itself may vary between ethnic groups. Another issue that must be considered is that, usually, negative association studies of a target gene outside the HLA region lack sufficient power to detect the genetic effect because the diseas
Correlation between mood and heart rate variability indices during daily life  [PDF]
Kohzoh Yoshino, Katsunori Matsuoka
Health (Health) , 2011, DOI: 10.4236/health.2011.39094
Abstract: We investigated the correlation between mood and heart rate variability (HRV) indices during daily life. The RR-interval and body acceleration of 40 normal male subjects were recorded using ambulatory device for 48 to 72 hours. Every hour that the subjects were awake they registered their current mood on a Visual Analogue Scale questionnaire. The questionnaire scales eight of the subjects’ current moods. Those are happiness, tension, fatigue, worry, depression, anger, vigor, and confusion. The following four HRV indices were calculated. Those are heart rate, root mean square of successive differences of RR-interval sequence, the normalized high-frequency (0.15 - 0.4 Hz) power of RR-in- terval variability, and mean frequency in the high-frequency band of RR-interval variability. The calculated HRV indices data and the mood data were normalized individually, the data with body acceleration exceeding 30 mG were excluded from the analysis to reduce the effect of exercise, and the differences from the first day (?mood and ?HRV-index) were taken to reduce the effect of circadian rhythm. The most three highly correlated combinations were ?vigor and ?HFnu (R = –0.24, p < 0.0001), ?vigor and ?RMSSD (R = –0.24, p < 0.0001), and ?vigor and ?HR (R = 0.22, p < 0.001). Vigor exhibited the most significant correlations with HRV indices of eight moods.
Brain activity following esophageal acid infusion using positron emission tomography
Shigeyuki Kobayashi, Yasuhiko Abe, Manabu Tashiro, Tomoyuki Koike, Katsunori Iijima, Akira Imatani, Shuichi Ohara, Satoshi Watanabe, Shin Fukudo, Tooru Shimosegawa
World Journal of Gastroenterology , 2010,
Abstract: AIM: To investigate symptoms and brain activity following esophageal acid infusion.METHODS: Fifteen healthy volunteers were recruited for the study. Hydrochloric acid (pH 1 and 2) and distilled water (pH 7) were randomly and repeatedly infused into the esophagus. The brain activity was evaluated by positron emission tomography. The severity of heartburn elicited by the infusion was rated on an auditory analog scale of 0-10.RESULTS: The severity of heartburn following each infusion showed a step-wise increase with increasing acidity of the perfusate. The heartburn scores were significantly higher in the second pH 1 infusion compared with the first infusion. Acid and distilled water infusion induced activation of various brain areas such as the anterior insula, temporal gyrus, and anterior/posterior cingulate cortex. At pH 1 or 2, in particular, activation was observed in some emotion-related brain areas such as the more anterior part of the anterior cingulate cortex, parahippocampal gyrus, or the temporal pole. Strong activation of the orbitofrontal cortex was found by subtraction analysis of the two second pH 1 infusions, with a significant increase of heartburn symptoms.CONCLUSION: Emotion-related brain areas were activated by esophageal acid stimulation. The orbitofrontal area might be involved in symptom processing, with esophageal sensitization induced by repeated acid stimulation.
Distance to G14.33-0.64 in the Sagittarius Spiral Arm: H2O Maser Trigonometric Parallax with VERA
Mayumi Sato,Tomoya Hirota,Mark J. Reid,Mareki Honma,Hideyuki Kobayashi,Kenzaburo Iwadate,Takeshi Miyaji,Katsunori M. Shibata
Physics , 2010, DOI: 10.1093/pasj/62.2.287
Abstract: We report on trigonometric parallax measurements for the Galactic star forming region G14.33-0.64 toward the Sagittarius spiral arm. We conducted multi-epoch phase-referencing observations of an H2O maser source in G14.33-0.64 with the Japanese VLBI array VERA. We successfully detected a parallax of 0.893+/-0.101 mas, corresponding to a source distance of 1.12+/-0.13 kpc, which is less than half of the kinematic distance for G14.33-0.64. Our new distance measurement demonstrates that the Sagittarius arm lies at a closer distance of ~1 kpc, instead of previously assumed ~2-3 kpc from kinematic distances. The previously suggested deviation of the Sagittarius arm toward the Galactic center from the symmetrically fitted model (Taylor & Cordes 1993) is likely due to large errors of kinematic distances at low galactic longitudes. G14.33-0.64 most likely traces the near side of the Sagittarius arm. We attempted fitting the pitch angle of the arm with other parallax measurements along the arm, which yielded two possible pitch angles of i=34.7+/-2.7 degrees and i=11.2+/-10.5 degrees. Our proper motion measurements suggest G14.33-0.64 has no significant peculiar motion relative to the differential rotation of the Galaxy (assumed to be in a circular orbit), indicating that the source motion is in good agreement with the Galactic rotation.
Obituary: Yukio Mano (1943–2004)
Katsunori Ikoma
Journal of NeuroEngineering and Rehabilitation , 2005, DOI: 10.1186/1743-0003-2-1
Abstract: Associate Editor, Journal of NeuroEngineering and RehabilitationI was terribly shocked to hear of the tragic and sudden passing of Yukio Mano on November 7, 2004, at the age of 61. He had not been well this past year but had been working continuously until just ten days before his death.Yukio Mano (Figure 1) was born on August 26, 1943 in Aichi Prefecture, Japan. He studied medicine at Nagoya University School of Medicine, and graduated in 1968. After he completed his basic medical training in Japan, he began his medical career in the USA in 1972. He first worked as a resident at the Institute of Rehabilitation Medicine at New York University for two years, then in 1974 he moved to the Department of Neurology at Baylor College of Medicine working as an assistant instructor and resident for one year. In 1975, he became a research fellow at the University of Maryland School of Medicine, in the Neuromuscular Research Unit. Yukio Mano studied the most advanced techniques in the fields of rehabilitation medicine and neurology during his four-year stay in the USA. Upon returning to Japan in 1976, he resumed his research in rehabilitation medicine at Nagoya University and the National Center of Neurology and Psychiatry, Japan. In 1981, he became an associate professor in the Department of Neurology at Nara Medical University. He was responsible for running the rehabilitation department there as a specialist in rehabilitation medicine. Finally, he was granted a full professorship in Rehabilitation and Physical Medicine at Hokkaido University (Graduate) School of Medicine in 1995. Yukio Mano was committed to helping researchers studying rehabilitation medicine, as well as young medical doctors and therapists in the rehabilitation field. He extensively expanded the Rehabilitation Department of Hokkaido University, and my colleagues and I had expected his leadership to continue into the future.His research interest was rehabilitation medicine, especially brain plasticity. He w
Forgotten and unattended: refugees in post-earthquake Japan
Katsunori Koike
Forced Migration Review , 2011,
Abstract: Despite being a world leader in disaster preparedness, Japan paid scant attention to the needs of one of its most marginalised social groups after the 2011 earthquake.
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