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Search Results: 1 - 10 of 753 matches for " Keiko Yasumatsu "
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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 (
NSC-induced D-neurons are decreased in striatum of schizophrenia: Possible cause of mesolimbic dopamine hyperactivity  [PDF]
Keiko Ikemoto
Stem Cell Discovery (SCD) , 2012, DOI: 10.4236/scd.2012.22009
Abstract: Neural stem cell (NSC) hypofunction is an etiological hypothesis of schizophrenia. Although dopamine (DA) dysfunction is also a widely accepted hypothesis, molecular background of mesolimbic DA hyperactivity has not yet been well known. Here, the author proposes “D-cell hypothesis”, accounting for molecular basis of mesolimbic DA hyperactivity of schizophrenia, by NSC hypofunction and decrease of putative NSC-induced D-cells. The “D-cell” is defined as “non-monoaminergic aromatic L-amino acid decarboxylase (AADC)-containing cell”. D-cells produce trace amines, and also take up amine precursors and convert them to amines by decarboxylation. The author reported “dopa-decarboxylating neurons specific to the human striatum”, that is, “D-neurons” in the human striatum, and decrease of striatal D-neurons in patients with schizophrenia. Trace amine-associated receptor, type 1 (TAAR1), a subtype of trace amine receptors, having a quite number of ligands such as tyramine, β-phenylethylamine (PEA) and methamphetamine, has modulating functions on monoamine neurons. It has been known that reduced binding of ligands to TAAR1 receptors on DA terminal of DA neurons of the midbrain ventral tegmental area (VTA) increased firing frequency of VTA DA neurons. In brains of schizophrenia, NSC hypofunction in the subventricular zone of lateral ventricle may cause decrease of D-neurons in the striatum and nucleus accumbens, and may result in decrease of trace amine signals. Decrease of trace amine signals to TAAR1 on VTA DA neurons may increase firing frequency of VTA DA neurons, and may finally cause mesolimbic DA hyperactivity. Increased stimulation to DA D2 receptors of NSCs might suppress NSC proliferation, and may induce additional mesolimbic DA hyperactivity as well as D-cell decrease. This novel theory, “D-cell hypothesis”, possibly explains mesolimbic DA hyperactivity in pathogenesis of schizophrenia.
D-Cell Hypothesis: Pathogenesis of Mesolimbic Dopamine Hyperactivity of Schizophrenia  [PDF]
Keiko Ikemoto
Journal of Behavioral and Brain Science (JBBS) , 2012, DOI: 10.4236/jbbs.2012.23048
Abstract: In the present article, the author proposes a new “D-cell hypothesis” for mesolimbic dopamine (DA) hyperactivity of schizophrenia, of which relevant molecular mechanism has not yet been known. The “D-cell” is defined as “the non-monoaminergic aromatic L-amino acid decarboxylase (AADC)-containing cell”. The D-cell contains AADC but not dopaminergic nor serotonergic. D-cells produce trace amines, and also take up amine precursors and convert them to amines by decarboxylation. The author reported “dopa-decarboxylating neurons specific to the human striatum”, that is, “D-neurons” in the human striatum, and preliminarily the number reduction of D-neurons in the striatum and nucleus accumbens of postmortem brains of patients with schizophrenia. Trace amine-associated receptor, type 1 (TAAR1), a subtype of trace amine receptors, having a large number of ligands, including tyramine, β-phenylethylamine (PEA), and methamphetamine, is a target receptor for the latest neuroleptic discovery. Recent studies have shown that the decreased stimulation of TAAR1 on cell membranes or nerve terminals of DA neurons in the midbrain ventral tegmental area (VTA) increased firing frequency of VTA DA neurons. In brains of schizophrenia, dysfunction of neural stem cells in the subventricular zone of lateral ventricle may cause reduction of the number of D-neurons in the striatum and nucleus accumbens, and may result in decrease of trace amine synthesis. The decrease of stimulation of TAAR1 on terminals of VTA DA neurons caused by trace amine reduction may increase firing frequency of VTA DA neurons, and may finally cause mesolimbic DA hyperactivity. This innovative theory, “D-cell hypothesis” might explain mesolimbic DA hyperactivity in pathogenesis of schizophrenia.
“D-cell hypothesis” of schizophrenia: possible theory for mesolimbic dopamine hyperactivity  [PDF]
Keiko Ikemot
World Journal of Neuroscience (WJNS) , 2012, DOI: 10.4236/wjns.2012.23021
Abstract: The author proposes a new “D-cell hypothesis” for mesolimbic dopamine (DA) hyperactivity of schizophrenia. The “D-cell” is defined as “non-monoaminergic aromatic L-amino acid decarboxylase (AADC)-containing cell”. D-cells produce trace amines, such as tyramine and β-phenylethylamine, and may also take up amine precursors and convert them to amines by decarboxylation. Trace amine-associated receptor, type 1 (TAAR1), a subtype of trace amine receptors, has a large number of ligands, including tyramine, β-phenylethylamine and methamphetamine, that influence on human mental states, and is now regarded to be a target receptor for novel neuroleptics. Recent studies revealed that the reduced stimulation of TAAR1 on DA neurons in the midbrain ventral tegmental area (VTA) increased firing frequency of VTA DA neurons. The author and her colleagues reported the decrease of D-neurons in the striatum and nucleus accumbens of postmortem brains of patients with schizophrenia. This may imply the decrease of trace amine synthesis, resulting the reduced stimulation of TAAR1 on terminals of midbrain VTA DA neurons, and may lead to mesolimbic DA hyperactivity in schizophrenia. The decrease of striatal D-neurons of postmortem brains of schizophrenia is supposed to be due to neural stem cell dysfunction in the subventricular zone of lateral ventricle. The decrease of striatal D-neurons and acts of TAAR1 signals on DA neurons-might explain mesolimbic DA hyperactivity of schizophrenia.
Why D-neuron? Importance in schizophrenia research  [PDF]
Keiko Ikemoto
Open Journal of Psychiatry (OJPsych) , 2012, DOI: 10.4236/ojpsych.2012.224055
Abstract: Recent pharmacological discovery on trace amine-associated receptor, type 1(TAAR1) has emphasized importance of trace amines in pathogenesis of psychoses, such as schizophrenia. TAAR1 has many ligands, including tyramine, β-phenylethylamine (PEA), amphetamines, and 3’-iodothyronamine. So-called D-neurons are putative producer of trace amines, endogenous ligands of TAAR1. The D-neuron is defined “the aromatic L-amino acid decarboxylase (AADC)-containing neuron, but not dopaminergic nor serotonergic”, i.e. not containing tyrosine hydroxylase nor tryptophan hydroxylase. AADC is an enzyme, also called dopa decarboxylase (DDC). The localization of D-neurons in the central nervous system has been specified into 15 groups, from the spinal cord (D1) to striatum (D15). We showed the decrease of D-neurons in D15 in postmortem brains of schizophrenia, where midbrain dopamine (DA) neurons are heavily innervated. Decrease of D-neurons may cause reduction of trace amines in the striatum, and may also decrease stimulation of TAAR1 on striatal terminals of ventral tegmental area (VTA) DA neurons. This might increase firing frequency of VTA DA neurons, and causes DA hyperactivity in the striatum and nucleus accumbens. In the present article, the author introduces the novel theory, “D-cell hypothesis”, for mesolimbic DA hyperactivity of schizophrenia. Some clinical and/or experimental evidences that support this hypothesis are mentioned. The D-neuron, as a trace amine producer, is a clue for elucidating pathogenesis of psychoses, as well as human mental functions. Thus, signal transduction of D-neurons should be investigated.
Overexpression of the Orotate Phosphoribosyl-Transferase Gene Enhances the Effect of 5-Fluorouracil in Head and Neck Squamous Cell Carcinoma In Vitro
Ryuji Yasumatsu,Torahiko Nakashima,Shizuo Komune
Journal of Oncology , 2012, DOI: 10.1155/2012/649605
Abstract: 5-Fluorouracil (5-FU) is a widely used drug in head and neck squamous cell carcinoma (HNSCC). In the anabolic pathway of 5-FU, the first step in activation of the drug is phosphorylation of 5-FU by orotate phosphoribosyltransferase (OPRT), which directly metabolizes 5-FU to 5-fluorouridine monophosphate (FUMP) in the presence of 5-phosphoribosyl-1-pyrophosphate. To date, OPRT expression in the tumors has been related to the clinical response or survival of cancer patients receiving 5-FU-based chemotherapy. In this study, we examined whether OPRT expression correlates with the chemosensitivity to 5-FU and cell proliferation in HNSCC. We constitutively expressed an OPRT cDNA in an HNSCC cell line. The effects of OPRT expression on in vitro cell growth and 5-FU cytotoxicity were examined. OPRT transfection increases the cytotoxicity of 5-FU without affecting cell proliferation of HNSCC cells in vitro. These results indicate that OPRT expression plays an important role in the sensitivity of HNSCC to 5-FU chemotherapy. 1. Introduction 5-Fluorouracil (5-FU) has been used most frequently for treating head and neck squamous cell carcinoma (HNSCC) in a form of single agent or in combination with cisplatin [1] and the drug of choice for systemic therapy in colorectal cancer [2]. However, nowadays 5-FU resistance during the course of treatment has become common, which is an important cause of failure for cancer therapies [3]. It has been reported that response rate of 5-FU and its derivatives are due to interindividual difference in the enzyme activities for anabolism and catabolism. In the anabolic pathway of 5-FU, the first step in activation of the drug is phosphorylation of 5-FU by orotate phosphoribosyltransferase (OPRT), which directly metabolizes 5-FU to 5-fluorouridine monophosphate (FUMP) in the presence of 5-phosphoribosyl-1-pyrophosphate [4]. This step is the most important mechanism of 5-FU activation. To date, OPRT expression in the tumors has been related to the clinical response or survival of cancer patients receiving 5-FU-based chemotherapy [5, 6]. However, no study has confirmed directly whether the regulation of intratumoral OPRT expression level affects the efficacy of 5-FU and the cell activity in HNSCC. We therefore investigated whether overexpression of the OPRT enhances sensitivity to 5-FU. In this study, to assess the role of OPRT in the biological regulation of HNSCC, we constitutively expressed the OPRT complementary DNA (cDNA) in HNSCC cell line. The effect of OPRT on in vitro cell growth and 5-FU cytotoxicity was examined. 2. Materials
Effects of oleic acid on murine macrophage dysfunction  [PDF]
Naofumi Shiomi, Keiko Watanabe
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.66080
Abstract:

Obese individuals exhibit much higher risks not only for metabolic syndrome, but also for cancer and allergies, than normal-weight subjects. This fact suggests that signals secreted from adipocytes change the characteristics of lymphocytes, such as macrophages and T-cells. We focused on a free fatty acid, oleic acid, as a signal inducing such changes and examined its effects on murine J774.2 macrophages. When the cells were cultured in medium containing high concentrations (1, 2 and 4 mM) of oleic acid, apoptosis occurred, and the apoptotic cells were gathered into clusters of very large size by the work of enzymes for phagocytosis. When the cells were cultured in medium containing 0.5 mM of oleic acid, the fatty acid did not affect cell growth; however, it inhibited nitrogen monoxide (NO) secretion and the gene expressions of interleukins and TNF-α. NO disturbs the invasion of macrophages into blood vessels, and interleukins promote the differentiation and proliferation of T- and B-cells. Therefore, these results suggest that the high risks for cancer and allergies observed in obese subjects are associated with the dysfunction of macrophages induced by fatty acids. Moreover, we also examined the protective effects of carnitine against dysfunction. However, carnitine did not exhibit sufficient effects.

Distinct Transforming Activity of ABL Family Tyrosine Kinase Oncogenes Is Induced by Their C-Terminal Domain*  [PDF]
Keiko Okuda, Hideyo Hirai
Open Journal of Blood Diseases (OJBD) , 2013, DOI: 10.4236/ojbd.2013.33A005
Abstract: The TEL/ARG oncogene is similar in structure to the TEL/ABL fusion found in human leukemia, however, we have demonstrated previously that the expression of TEL/ARG in Ba/F3 cells does not sustain strong activity of proliferation, whereas, that of TEL/ABL appeared to induce immediate cell proliferation. To study the molecular basis of the difference in the transforming activity of TEL/ARG and TEL/ABL, TEL/ARG mutants that swapped the kinase domain or C-terminus of ARG with the corresponding domain in ABL were generated, and each mutant was expressed in Ba/F3 cells. A TEL/ARG mutant containing the ABL kinase domain was similar to TEL/ARG in this study, but replacing the ARG C-terminal domain with that of ABL resulted in accelerated proliferation that was similar to that of TEL/ABL. When expressed in primary mouse bone marrow cells by retroviral transduction, spontaneous colony formation in methylcellulose culture was observed, in a fashion dependent on the C-terminal portion of ABL. These results indicate that distinct bio-phenotypes associated with these oncogenes are likely to be regulated by their C-termini, and the C-terminus of ARG contains a functional subdomain that impairs the growth signal induced by ABL family tyrosine kinase.
Effects of Hydrocortisone, Glycerophosphate and Retinol on the Differentiation of Mesenchymal Stem Cells and Vascular Endothelial Cells to Osteoblasts  [PDF]
Naofumi Shiomi, Keiko Watanabe
Journal of Biomedical Science and Engineering (JBiSE) , 2014, DOI: 10.4236/jbise.2014.713103
Abstract: Vascular calcification, which causes occlusion and rupture of the vascular, is often observed in patients in the advanced stages of arteriosclerosis. One of the best procedures for inhibiting the accumulation of vascular calcification is to obstruct the differentiation of mesenchymal stem cells (MSCs) and/or vascular endothelial cells (VECs) in the vascular to osteoblasts. In this study, we evaluated the biochemical and genetic characteristics of the process of differentiation of MSCs and VECs to osteoblasts. C3H10T1/2 MSCs, TKD2 VECs and MC3T3-E1 preosteoblasts (POBs) were cultured in medium containing both hydrocortisone and glycerophosphate. These compounds showed strong effects promoting the differentiation of VECs as well as POBs, although the effect was weak in the MSCs. Moreover, C3H10T1/2 MSCs and TKD2 VECs were cultured in medium containing 10 mM retinol, after which the alkali phosphatase (ALP) activity of the MSCs and production of calcified nodules of TKD2 were significantly increased, whereas the marker genes for the osteoblasts were not. These results suggest that retinol does not have an effect in inducing the differentiation of VECs to osteoblasts, but rather exhibits a strong promoting effect on differentiation.
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