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Search Results: 1 - 10 of 234 matches for " Yuzo Ninomiya "
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Genetic and Molecular Basis of Individual Differences in Human Umami Taste Perception
Noriatsu Shigemura, Shinya Shirosaki, Keisuke Sanematsu, Ryusuke Yoshida, Yuzo Ninomiya
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006717
Abstract: Umami taste (corresponds to savory in English) is elicited by L-glutamate, typically as its Na salt (monosodium glutamate: MSG), and is one of five basic taste qualities that plays a key role in intake of amino acids. A particular property of umami is the synergistic potentiation of glutamate by purine nucleotide monophosphates (IMP, GMP). A heterodimer of a G protein coupled receptor, TAS1R1 and TAS1R3, is proposed to function as its receptor. However, little is known about genetic variation of TAS1R1 and TAS1R3 and its potential links with individual differences in umami sensitivity. Here we investigated the association between recognition thresholds for umami substances and genetic variations in human TAS1R1 and TAS1R3, and the functions of TAS1R1/TAS1R3 variants using a heterologous expression system. Our study demonstrated that the TAS1R1-372T creates a more sensitive umami receptor than -372A, while TAS1R3-757C creates a less sensitive one than -757R for MSG and MSG plus IMP, and showed a strong correlation between the recognition thresholds and in vitro dose - response relationships. These results in human studies support the propositions that a TAS1R1/TAS1R3 heterodimer acts as an umami receptor, and that genetic variation in this heterodimer directly affects umami taste sensitivity.
Sour Taste Responses in Mice Lacking PKD Channels
Nao Horio,Ryusuke Yoshida,Keiko Yasumatsu,Yuchio Yanagawa,Yoshiro Ishimaru,Hiroaki Matsunami,Yuzo Ninomiya
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020007
Abstract: The polycystic kidney disease-like ion channel PKD2L1 and its associated partner PKD1L3 are potential candidates for sour taste receptors. PKD2L1 is expressed in type III taste cells that respond to sour stimuli and genetic elimination of cells expressing PKD2L1 substantially reduces chorda tympani nerve responses to sour taste stimuli. However, the contribution of PKD2L1 and PKD1L3 to sour taste responses remains unclear.
Genetically-increased taste cell population with Gα-gustducin-coupled sweet receptors is associated with increase of gurmarin-sensitive taste nerve fibers in mice
Keiko Yasumatsu, Tadahiro Ohkuri, Keisuke Sanematsu, Noriatsu Shigemura, Hideo Katsukawa, Noritaka Sako, Yuzo Ninomiya
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-152
Abstract: Here, we investigated whether the increased taste cell population with Gα-gustducin-coupled sweet receptors would be associated with selective increment of GS fiber population or nonselective shift of gurmarin sensitivities of overall sweet-responsive fibers by examining the classification of GS and GI fiber types in dpa CG and BALB mice. The results indicated that dpa CG, like C57BL, possess two distinct populations of GS and GI types of sweet-responsive fibers with almost identical sizes (dpa CG: 13 GS and 16 GI fibers; C57BL: 16 GS and 14 GI fibers). In contrast, BALB has only 3 GS fibers but 18 GI fibers. These data indicate a marked increase of the GS population in dpa CG.These results suggest that the increased cell population expressing T1r2/T1r3/Gα-gustducin in dpa CG mice may be associated with an increase of their matched GS type fibers, and may form the distinct GS sweet reception pathway in mice. Gα-gustducin may be involved in the GS sweet reception pathway and may be a key molecule for links between sweet taste receptors and cell type-specific-innervation by their matched fiber class.Gurmarin (Gur) is a peptide isolated from a plant, gymnemma sylvestre. This peptide was shown to selectively inhibit the taste responses to sweet substances without affecting the responses to other basic taste stimuli, such as NaCl, HCl and quinine in rodents [1-4]. In mice, the Gur sensitivity differs among tongue regions and strains [2-4]. That is, the Gur inhibition of whole nerve integrated responses to sweet compounds is clearly evident only in the chorda tympani (CT) nerve innervating the anterior tongue, but not in the glossopharyngeal nerve innervating the posterior tongue. The responses of the CT nerve to sucrose (0.01 - 1.0 M) significantly decrease to about ~50% of control after Gur treatment in C57BL but only slightly if at all in BALB/c (BALB) mice [2,5]. In C57BL mice, sweet-responsive CT fibers can be classified into two distinct populations, Gur-sensitive (
The chemical mechanism of oxidative stress due to the non-transferrin-bound iron (NTBI)  [PDF]
Yuzo Nishida
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.327131
Abstract: Plasma iron is normally bound to the iron transport protein transferrin, but there are some iron ions not associated with transferrin. The latter ions are generally termed as non-transferrin-bound iron (NTBI) or labile plasma iron. The NTBI has been thought to play an important role in iron-induced cell damage with resultant peroxidation of cell membrane lipids and other biomolecules, and such oxidative damage is implicated as an important contributor in the pathogenesis of cancer, cardiovascular disease, aging and other degenerative disorders, but little is understood about the chemical composition of NTBI and the origin of toxicity due to NTBI. In this review, we demonstrated the several chemical models for NTBI, and elucidated the chemical mechanism of iron toxicity due to NTBI in human body on the basis of my concept on the mechanism of oxygen activation in biological oxygenases. This has lead to the conclusion that 1) NTBI are divided into two groups, water-in-soluble and water-soluble ones, 2) some of the water-soluble NTBI react with oxygen or hydrogen peroxide, changing these molecules to those exhibiting the reactivity similar to singlet oxygen (1△g), and this is the main reason for NTBI to induce the oxidative stress, and 3) the responsibility of hydroxyl radical or free singlet oxygen is negligible as a “reactive oxygen species” in the human body. Based on the discussions described in this article we have proposed a new technique to prevent the oxidative damage due to NTBI. In order to achieve the purpose, we have synthesized the new superpolyphenols which contain more than 100 molecules of catechol derivative in one polymeric compound; these are sometimes water-insoluble, and in another cases, water-soluble. We have observed that some of these compounds can eliminate NTBI effectively from the plasma, and also some of these derivatives can remove hydrogen peroxide from the solution. Thus, we can hope that our new super-polyphenols should depress greatly the oxidative stress due to NTBI, which may be consistent with the facts that the Japanese tea catechins which contain polyphenols exhibit high preventing effects against lifestyle-related diseases, and that some polyphenols have been known to protect the pathogenesis of Alzheimer’s disease. We also discussed the antioxidative function by zinc(II) ion, which depresses the oxidative damage by NTBI by promoting the formation of iron deposition.
Sweet Taste Receptor Expressed in Pancreatic β-Cells Activates the Calcium and Cyclic AMP Signaling Systems and Stimulates Insulin Secretion
Yuko Nakagawa, Masahiro Nagasawa, Satoko Yamada, Akemi Hara, Hideo Mogami, Viacheslav O. Nikolaev, Martin J. Lohse, Noriatsu Shigemura, Yuzo Ninomiya, Itaru Kojima
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005106
Abstract: Background Sweet taste receptor is expressed in the taste buds and enteroendocrine cells acting as a sugar sensor. We investigated the expression and function of the sweet taste receptor in MIN6 cells and mouse islets. Methodology/Principal Findings The expression of the sweet taste receptor was determined by RT–PCR and immunohistochemistry. Changes in cytoplasmic Ca2+ ([Ca2+]c) and cAMP ([cAMP]c) were monitored in MIN6 cells using fura-2 and Epac1-camps. Activation of protein kinase C was monitored by measuring translocation of MARCKS-GFP. Insulin was measured by radioimmunoassay. mRNA for T1R2, T1R3, and gustducin was expressed in MIN6 cells. In these cells, artificial sweeteners such as sucralose, succharin, and acesulfame-K increased insulin secretion and augmented secretion induced by glucose. Sucralose increased biphasic increase in [Ca2+]c. The second sustained phase was blocked by removal of extracellular calcium and addition of nifedipine. An inhibitor of inositol(1, 4, 5)-trisphophate receptor, 2-aminoethoxydiphenyl borate, blocked both phases of [Ca2+]c response. The effect of sucralose on [Ca2+]c was inhibited by gurmarin, an inhibitor of the sweet taste receptor, but not affected by a Gq inhibitor. Sucralose also induced sustained elevation of [cAMP]c, which was only partially inhibited by removal of extracellular calcium and nifedipine. Finally, mouse islets expressed T1R2 and T1R3, and artificial sweeteners stimulated insulin secretion. Conclusions Sweet taste receptor is expressed in β-cells, and activation of this receptor induces insulin secretion by Ca2+ and cAMP-dependent mechanisms.
Functional Microvascular Anatomy of the Horse Eye: A Scanning Electron Microscopic Study of Corrosion Casts  [PDF]
Hiroyoshi Ninomiya, Tomo Inomata
Open Journal of Veterinary Medicine (OJVM) , 2014, DOI: 10.4236/ojvm.2014.45011

Objective: This study presents the microvasculature of the horse iris, ciliary process, retina, and choroid and discusses the functional significance of the vasculature. Procedure: Seven horses were used for this study. The ocular vascular system was injected with methylmethacrylate resin via the carotid artery, and the vascular corrosion casts were observed using a scanning electron microscope. Results: The iridial vessels showed a wavy course. The ciliary process was supplied by 2 arterial routes: the iridial and ciliary arterial circles. The subjects displayed a paurangiotic retina with retinal vessels extending only a short distance around the disc. The retinal arterioles and venules ran in closely related pairs, and the capillaries formed hairpin loops. No central retinal artery was seen in the equine eyes examined. The choriocapillaris in the avascular retina was arranged in honeycomb hexagon lobules and formed a more densely packed network than that in the vascular retina. There were 2 distinct venous drainage systems in the horse choroid: the vortex veins and the posterior ciliary veins. The vortex vein ampulla was flattened and showed a slit-like lumen at the merge site with the ophthalmic vein. The vortex veins demonstrated a marked constriction before leaving the eye. Discussion: The 2 choroidal drainage systems may compensate each other in event of occlusion. The ampulla and the constriction in the vortex veins may act as a valve regulating the blood flow to keep the eye at an optimum size and the intraocular pressure within the normal physiological range.

Magnet Formation by the Surface Modification of Diamond with Manganese Detected by the Magnetic Flux Density on the Surface  [PDF]
Takahisa Yamazaki, Ryusei Ninomiya
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.88045
Abstract: A surface modification of diamond with manganese powder was attempted to make a magnetic functional surface for handling diamond. Manganese carbide, Mn7C3, was formed on diamond (110) by near-infrared radiation heating, resulting in a layered material with suppressing formation of Mn5C2. Investigated by a Hall-effect sensor, the magnetic flux density on the modified diamond surface showed ferromagnetic properties.
A new weak approximation scheme of stochastic differential equations and the Runge-Kutta method
Mariko Ninomiya,Syoiti Ninomiya
Mathematics , 2007,
Abstract: In this paper, authors successfully construct a new algorithm for the new higher order scheme of weak approximation of SDEs. The algorithm presented here is based on [1][2]. Although this algorithm shares some features with the algorithm presented by [3], algorithms themselves are completely different and the diversity is not trivial. They apply this new algorithm to the problem of pricing Asian options under the Heston stochastic volatility model and obtain encouraging results. [1] Shigeo Kusuoka, "Approximation of Expectation of Diffusion Process and Mathematical Finance," Advanced Studies in Pure Mathematics, Proceedings of Final Taniguchi Symposium, Nara 1998 (T. Sunada, ed.), vol. 31 2001, pp. 147--165. [2] Terry Lyons and Nicolas Victoir, "Cubature on Wiener Space," Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences 460 (2004), pp. 169--198. [3] Syoiti Ninomiya, Nicolas Victoir, "Weak approximation of stochastic differential equations and application to derivative pricing," Applied Mathematical Finance, Volume 15, Issue 2 April 2008, pages 107--121
Oxygen Activation in Lipoxygenase Model Reaction Studied with Density Functional Theory
Yuzo Nishida
International Journal of Chemistry , 2012, DOI: 10.5539/ijc.v4n4p1
Abstract: Density Functional Computational studies were performed for the systems containing an iron (III) complex with (cyclam), 1,4-pentadiene and oxygen, where cyclam represents 1,4,8,11-tetraazacyclotetradecane. The calculations have indicated that bond formation between oxygen and carbon atom of the 1,4-pentadiene anion where methylene-proton is removed, occurs in the presence of the FeIII-(cyclam) complex, giving the hydroperoxy derivative of the 1,4-pentadiene. Based on these results it seems quite reasonable to assume that deprotonation of the methylene proton should be a trigger for the peroxidation of the 1,4-pentadiene moiety and the electron transfer reaction between iron(III) atom and the substrate is unnecessary in the lipoxygenases.
Role of Zinc(II) Ion for the Formation of Iron Deposition in Human Body and Its Significance
Yuzo Nishida
International Journal of Chemistry , 2012, DOI: 10.5539/ijc.v4n6p1
Abstract: Iron depositions, one of the non-transferrin-bound iron (NTBI), are frequently observed for the patients with thalassemia, hemochromatosis and other iron-overloading disorders. In this article, we have pointed out that zinc(II) ion and hydrogen peroxide play a critical role in the formation of the iron deposition, and that the formation of iron deposition by zinc(II) ion should be one of the important method to protect the oxidative stress by water-soluble NTBI. This implies that the zinc(II) ions contribute to depress the oxidative stress by NTBI.
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