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Search Results: 1 - 10 of 418 matches for " Hiroto Kita "
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Endoscopic Submucosal Dissection for Early Gastric Cancer  [PDF]
Kouichi Nonaka, Hiroto Kita
Journal of Cancer Therapy (JCT) , 2013, DOI: 10.4236/jct.2013.41A004
Abstract: The field of endoscopy has progressed markedly and become widespread in recent years, and the role of minimally invasive endoscopic treatment has become increasingly more important with the increase in the number of patients in whom gastric cancer is detected at an early stage. In addition, the characteristics of early gastric cancer, which can be curably treated by mucosal resection alone just as by surgical cancer resection, were clarified, and endoscopic submucosal dissection (ESD) was developed as a highly curable, minimally invasive treatment, that is gaining popularity. In this paper, we describe the technical details and complications of ESD for early gastric cancer, including their management.
Role of narrow band imaging in endoscopic submucosal dissection
Kouichi Nonaka,Makoto Nishimura,Hiroto Kita
World Journal of Gastrointestinal Endoscopy , 2012, DOI: 10.4253/wjge.v4.i9.387
Abstract: Narrow band imaging (NBI) is a new image enhancement system employing optic digital methods to enhance images of blood vessels on mucosal surfaces, allowing improved visualization of mucosal surface structures. Studies have progressed over the last several years, and the clinical usefulness has been demonstrated. NBI has become frequently applied for preoperative diagnosis before endoscopic submucosal dissection (ESD) of digestive tract cancers, as well as for assessment of the range of ESD for en-bloc resection of large lesions. Consensus has been reached with regard to the usefulness of NBI for detecting micro-lesions of esophageal squamous cell carcinoma indicated for ESD, for the diagnosis of the range and depth. NBI has also been attracting attention for diagnosing gastric cancer based on the observation of micro blood vessels on the mucosal surface and mucosal surface microstructures. The usefulness of NBI has been reported in relation to various aspects of colon cancer, including diagnoses of the presence, quality, range, and depth of lesions. However, as NBI has not surpassed diagnostic methods based on magnifying observation combined with the established and widely employed dye method, its role in ESD is limited at present. Although NBI is very useful for the diagnosis of digestive tract cancers, comprehensive endoscopic diagnosis employing the combination of conventional endoscopy including dye spraying, EUS, and NBI may be important and essential for ESD.
Evolution of Homo sapiens in Asia: an alternative implication of the “Out-of-Africa” model based on mitochondrial DNA data  [PDF]
Hiroto Naora
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.26072
Abstract: Cann et al. have claimed on the basis of mitochondrial DNA (mtDNA) data that our direct ancestral Homo sapiens evolved in the African continent and spread to other continents, followed by the total replacement of the indigenous population. Their “Out-of-Africa” model is based on the assumption that mtDNA inheritance is simply maternal. Recent findings suggest the possibility that in between-population, e.g. African and Asian, mating, the African paternal mtDNA was transferred to the egg cell of an Asian together with Y-chromosomal DNA in the human past. Considering that Y-chromos- omal DNA and mtDNA sequences of African origin coexist together with Asian X-chromos- omal and autosomal DNA sequences in a current Asian, the observations by Cann et al. suggest the full/near full replacement of mtDNA in the human past, but do not necessarily imply the total replacement of indigenous populations with African migrants.
A Reaction-Diffusion Algorithm for Segmentation of Three-Dimensional Sinusoidal Networks in Rats Fed a High-Fat and High-Cholesterol Diet: New Insights and Evaluation  [PDF]
Hiroto Shoji
Journal of Biosciences and Medicines (JBM) , 2018, DOI: 10.4236/jbm.2018.610004
Abstract: Microstructures in the liver are primarily composed of hepatocytes, hepatic blood, and biliary vessels. Because each hepatocyte comes in contact with both vessels, these vessels form three-dimensional (3D) periodic network patterns. Confocal microscope images are useful for observing 3D structures; however, it is necessary to explicitly describe the vessel structures using 3D images of sinusoidal endothelial cells. For this purpose, we propose a new approach for image segmentation based on the Turing reaction-diffusion model, in which temporal and spatial patterns are self-organized. Turing conditions provided reliable tools for describing the 3D structures. Moreover, using the proposed method, the sinusoidal patterns of rats fed a high-fat/high-cholesterol diet were examined; these rats exhibited pathological features similar to those of human patients with nonalcoholic steatohepatitis related to metabolic syndrome. The findings showed that the parameter in diffusion terms differed significantly among the experimental groups. This observation provided a heuristic argument for parameter selection leading to pattern recognition problems in diseased rats.
Status of the Gastric Mucosa with Endoscopically Diagnosed Gastrointestinal Stromal Tumor
Kouichi Nonaka,Shinichi Ban,Yoshimitsu Hiejima,Rei Narita,Michio Shimizu,Masayasu Aikawa,Ken Ohata,Nobuyuki Matsuhashi,Shin Arai,Hiroto Kita
Diagnostic and Therapeutic Endoscopy , 2014, DOI: 10.1155/2014/429761
Abstract: Background. Since gastrointestinal stromal tumor (GIST) is a mesenchymal submucosal tumor, the endosonographic, CT, and MRI features of gastric GISTs have been widely investigated. However, the GIST-bearing gastric mucosa status has not been reported. Objective. To characterize the GIST-bearing gastric mucosa status in terms of the degree of inflammation and atrophy, assessed endoscopically. Subjects and Methods. The subjects were 46 patients with submucosal tumors (histologically proven gastric GISTs) who had undergone upper gastrointestinal endoscopy in our hospital between April 2007 and September 2012. They were retrospectively evaluated regarding clinicopathological features, the endoscopically determined status of the entire gastric mucosa (presence or absence and degree of atrophy), presence or absence and severity of endoscopic gastritis/atrophy (A-B classification) at the GIST site, and presence or absence of H. pylori infection. Results. Twenty-three patients had no mucosal atrophy, but 17 and 6 had closed- and open-type atrophy, respectively. Twenty-six, 5, 12, 1, 1, and 1 patients had grades B0, B1, B2, B3, A0, and A1 gastritis/atrophy at the lesion site, respectively, with no grade A2 gastritis/atrophy. Conclusion. The results suggest that gastric GISTs tend to arise in the stomach wall with H. pylori-negative, nonatrophic mucosa or H. pylori-positive, mildly atrophic mucosa. 1. Introduction Gastric gastrointestinal stromal tumor (GIST) is a mesenchymal tumor arising from the muscularis propria of the gastric wall and is covered with normal mucosa, giving the endoscopic appearance of a submucosal tumor with bridging folds. Since gastric GIST is a submucosal tumor, its endosonographic, CT, and MRI features have been widely investigated [1–4]. However, the status of the GIST-bearing gastric mucosa itself has not been reported. Based on our experience, many GIST patients often show no evidence of H. pylori infection, gastritis, or mucosal atrophy on upper gastrointestinal endoscopy, and even H. pylori-infected patients may show mild gastritis in the background gastric mucosa. We consider that it is necessary to evaluate the GIST-bearing gastric mucosa using available data before testing the validity of this empirical rule and investigate the reason for it, if it is valid. In this study, we retrospectively evaluated patients with submucosal tumors (histologically proven gastric GISTs) regarding the age, gender, site and size of the lesion, risk classification of GISTs, presence or absence and degree of endoscopic atrophy in the entire gastric
Increased Frequency of Pre–Pro B Cells in the Bone Marrow of New Zealand Black (NZB) Mice: Implications for aDevelopmental Block in B Cell Differentiation
Zhe-Xiong Lian,Hiroto Kita,Tomoyuki Okada,Tom Hsu,Leonard D. Shultz,Kenneth Dorshkind,Aftab A. Ansari,Susumu Ikehara,Mitsuru Naiki,M. Eric Gershwin
Clinical and Developmental Immunology , 2002, DOI: 10.1080/1044667021000003961
Abstract: Reductions in populations of both Pre-B cell (Hardy fractions D) and Pro-B cells (Hardy fractions B–C) have been described in association with murine lupus. Recent studies of B cell populations, based on evaluation of B cell differentiation markers, now allow the enumeration and enrichment of other stage specific precursor cells. In this study we report detailed analysis of the ontogeny of B cell lineage subsets in New Zealand black (NZB) and control strains of mice. Our data suggest that B cell development in NZB mice is partially arrested at the fraction A Pre–Pro B cell stage. This arrest at the Pre-Pro B cell stage is secondary to prolonged lifespan and greater resistance to spontaneous apoptosis. In addition, expression of the gene encoding the critical B cell development transcription factor BSAP is reduced in the Pre–Pro B cell stage in NZB mice. This impairment may influence subsequent B cell development to later stages, and thereby accounts for the down-regulation of the B cell receptor component Igα (mb-1). Furthermore, levels of expression of the Rug2, λ5 and Igβ (B29) genes are also reduced in Pre–Pro B cells of NZB mice. The decreased frequency of precursor B cells in the Pre–Pro B cell population occurs at the most primitive stage of B cell differentiation.
Self-consistent perturbation expansion for Bose-Einstein condensates satisfying Goldstone's theorem and conservation laws
Takafumi Kita
Physics , 2009, DOI: 10.1103/PhysRevB.80.214502
Abstract: Quantum-field-theoretic descriptions of interacting condensed bosons have suffered from the lack of self-consistent approximation schemes satisfying Goldstone's theorem and dynamical conservation laws simultaneously. We present a procedure to construct such approximations systematically by using either an exact relation for the interaction energy or the Hugenholtz-Pines relation to express the thermodynamic potential in a Luttinger-Ward form. Inspection of the self-consistent perturbation expansion up to the third order with respect to the interaction shows that the two relations yield a unique identical result at each order, reproducing the conserving-gapless mean-field theory [T. Kita, J. Phys. Soc. Jpn. 74, 1891 (2005)] as the lowest-order approximation. The uniqueness implies that the series becomes exact when infinite terms are retained. We also derive useful expressions for the entropy and superfluid density in terms of Green's function and a set of real-time dynamical equations to describe thermalization of the condensate.
Entropy in Nonequilibrium Statistical Mechanics
Takafumi Kita
Physics , 2006, DOI: 10.1143/JPSJ.76.067001
Abstract: Entropy in nonequilibrium statistical mechanics is investigated theoretically so as to extend the well-established equilibrium framework to open nonequilibrium systems. We first derive a microscopic expression of nonequilibrium entropy for an assembly of identical bosons/fermions interacting via a two-body potential. This is performed by starting from the Dyson equation on the Keldysh contour and following closely the procedure of Ivanov, Knoll and Voskresensky [Nucl. Phys. A {\bf 672} (2000) 313]. The obtained expression is identical in form with an exact expression of equilibrium entropy and obeys an equation of motion which satisfies the $H$-theorem in a limiting case. Thus, entropy can be defined unambiguously in nonequilibrium systems so as to embrace equilibrium statistical mechanics. This expression, however, differs from the one obtained by Ivanov {\em et al}., and we show explicitly that their ``memory corrections'' are not necessary. Based on our expression of nonequilibrium entropy, we then propose the following principle of maximum entropy for nonequilibrium steady states: ``The state which is realized most probably among possible steady states without time evolution is the one that makes entropy maximum as a function of mechanical variables, such as the total particle number, energy, momentum, energy flux, etc.'' During the course of the study, we also develop a compact real-time perturbation expansion in terms of the matrix Keldysh Green's function.
Principle of Maximum Entropy Applied to Rayleigh-Bénard Convection
Takafumi Kita
Physics , 2006, DOI: 10.1143/JPSJ.75.124005
Abstract: A statistical-mechanical investigation is performed on Rayleigh-B\'enard convection of a dilute classical gas starting from the Boltzmann equation. We first present a microscopic derivation of basic hydrodynamic equations and an expression of entropy appropriate for the convection. This includes an alternative justification for the Oberbeck-Boussinesq approximation. We then calculate entropy change through the convective transition choosing mechanical quantities as independent variables. Above the critical Rayleigh number, the system is found to evolve from the heat-conducting uniform state towards the convective roll state with monotonic increase of entropy on the average. Thus, the principle of maximum entropy proposed for nonequilibrium steady states in a preceding paper is indeed obeyed in this prototype example. The principle also provides a natural explanation for the enhancement of the Nusselt number in convection.
Entropy Change through Rayleigh-Bénard Convective Transition with Rigid Boundaries
Takafumi Kita
Physics , 2007, DOI: 10.1143/JPSJ.76.064006
Abstract: The previous investigation on Rayleigh-B\'enard convection of a dilute classical gas [T. Kita: J. Phys. Soc. Jpn. {\bf 75} (2006) 124005] is extended to calculate entropy change of the convective transition with the rigid boundaries. We obtain results qualitatively similar to those of the stress-free boundaries. Above the critical Rayleigh number, the roll convection is realized among possible steady states with periodic structures, carrying the highest entropy as a function of macroscopic mechanical variables.
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