Y. Tomioka

National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan

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Publications (357)1156.18 Total impact

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    ABSTRACT: We report on a thermoelectric investigation of the stripe and superconducting phases of the cuprate La$_{2-x}$Ba$_{x}$CuO$_{4}$ near the $x=1/8$ doping known to host stable stripes. We use the doping and magnetic field dependence of field-symmetric Nernst effect features to delineate the phenomenology of these phases. Our measurements are consistent with prior reports of time-reversal symmetry breaking signatures above the superconducting $T_{{\rm c}}$, and crucially detect a sharp, robust, field-invariant peak at the stripe charge order temperature, $T_{{\rm {\scriptscriptstyle CO}}}$. Our observations suggest the onset of a nontrivial charge ordered phase at $T_{{\rm {\scriptscriptstyle CO}}}$, and the subsequent presence of spontaneously generated vortices over a broad temperature range before the emergence of bulk superconductivity in LBCO.
  • YAKUGAKU ZASSHI 04/2015; DOI:10.1248/yakushi.15-00001 · 0.31 Impact Factor
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    ABSTRACT: We present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010] and TA2 along [110]) and two low energy optic phonon modes (LO and TO1) have been mapped out between 300 K and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN = 640 K. This suggests that the magnetic and low-energy lattice dynamics in this multiferroic material are coupled.
    Physical Review B 02/2015; 91:064301. DOI:10.1103/PhysRevB.91.064301 · 3.66 Impact Factor
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    ABSTRACT: Genetic variations in cytochrome P450 4A11 (CYP4A11) contributes to inter-individual variability in the metabolism of fatty acids such as arachidonic acid. CYP4A11 metabolizes arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), which is important for the regulation of blood pressure. Polymorphisms in CYP4A11 are associated with susceptibility to hypertension. In this study, we evaluated the in vitro ω-hydroxylation of arachidonic acid by 10 CYP4A11 allelic variants, which cause amino acid substitutions in the encoded proteins. CYP4A11 variants were heterologously expressed in COS-7 cells and the kinetic parameters of arachidonic acid ω-hydroxylation were estimated. Among 10 CYP4A11 variants, 5 (CYP4A11-v1, CYP4A11-v2, CYP4A11-v3, CYP4A11-v4, and CYP4A11-v7) showed no or markedly lower activity compared to wild-type CYP4A11. This functional analysis of CYP4A11 variants could provide useful information for the effective prevention and treatment of hypertension. Copyright © 2014 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.
    Drug Metabolism and Pharmacokinetics 02/2015; 30(1):119-122. DOI:10.1016/j.dmpk.2014.09.001 · 2.86 Impact Factor
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    ABSTRACT: The accumulation of uremic toxins is involved in the progression of CKD. Various uremic toxins are derived from gut microbiota, and an imbalance of gut microbiota or dysbiosis is related to renal failure. However, the pathophysiologic mechanisms underlying the relationship between the gut microbiota and renal failure are still obscure. Using an adenine-induced renal failure mouse model, we evaluated the effects of the ClC-2 chloride channel activator lubiprostone (commonly used for the treatment of constipation) on CKD. Oral administration of lubiprostone (500 µg/kg per day) changed the fecal and intestinal properties in mice with renal failure. Additionally, lubiprostone treatment reduced the elevated BUN and protected against tubulointerstitial damage, renal fibrosis, and inflammation. Gut microbiome analysis of 16S rRNA genes in the renal failure mice showed that lubiprostone treatment altered their microbial composition, especially the recovery of the levels of the Lactobacillaceae family and Prevotella genus, which were significantly reduced in the renal failure mice. Furthermore, capillary electrophoresis-mass spectrometry-based metabolome analysis showed that lubiprostone treatment decreased the plasma level of uremic toxins, such as indoxyl sulfate and hippurate, which are derived from gut microbiota, and a more recently discovered uremic toxin, trans-aconitate. These results suggest that lubiprostone ameliorates the progression of CKD and the accumulation of uremic toxins by improving the gut microbiota and intestinal environment. Copyright © 2014 by the American Society of Nephrology.
    Journal of the American Society of Nephrology 12/2014; DOI:10.1681/ASN.2014060530 · 9.47 Impact Factor
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    ABSTRACT: Lysophospholipids (LPLs) serve as lipid mediators and precursors for synthesis of diacyl phospholipids (PLs). LPLs detected in cells have various acyl chains attached at either the sn-1 or sn-2 position of the glycerol backbone. In general, acyl chains at the sn-2 position of 2-acyl-1-LPLs readily move to the sn-1 position, generating 1-acyl-2-lyso isomers by a non-enzymatic reaction called intra-molecular acyl migration, which has hampered the detection of 2-acyl-1-LPLs in biological samples. In this study, we developed a simple and versatile method to separate and quantify 2-acyl-1- and 1-acyl-2-LPLs. The main point of the method was to extract LPLs at pH 4 and 4 degree, conditions that was found to completely eliminate the intra-molecular acyl migration. Under the present conditions, the relative amounts of 2-acyl-1-LPLs and 1-acyl-2-LPLs did not change at least for 1 week. Further, in LPLs extracted from cells and tissues under the present conditions, most of the saturated fatty acids (16:0 and 18:0) were found in the sn-1 position of LPLs, while most of the polyunsaturated fatty acids (18:2, 20:4, 22:6) were found in the sn-2 position. Thus the method can be used to elucidate the in vivo role of 2-acyl-1-LPLs.
    The Journal of Lipid Research 08/2014; 55(10). DOI:10.1194/jlr.D048439 · 4.73 Impact Factor
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    ABSTRACT: Tissue damage by oxidative stress is a key pathogenic mechanism in various diseases, including AKI and CKD. Thus, early detection of oxidative tissue damage is important. Using a tRNA-specific modified nucleoside 1-methyladenosine (m1A) antibody, we show that oxidative stress induces a direct conformational change in tRNA structure that promotes subsequent tRNA fragmentation and occurs much earlier than DNA damage. In various models of tissue damage (ischemic reperfusion, toxic injury, and irradiation), the levels of circulating tRNA derivatives increased rapidly. In humans, the levels of circulating tRNA derivatives also increased under conditions of acute renal ischemia, even before levels of other known tissue damage markers increased. Notably, the level of circulating free m1A correlated with mortality in the general population (n=1033) over a mean follow-up of 6.7 years. Compared with healthy controls, patients with CKD had higher levels of circulating free m1A, which were reduced by treatment with pitavastatin (2 mg/d; n=29). Therefore, tRNA damage reflects early oxidative stress damage, and detection of tRNA damage may be a useful tool for identifying organ damage and forming a clinical prognosis.
    Journal of the American Society of Nephrology 05/2014; DOI:10.1681/ASN.2013091001 · 9.47 Impact Factor
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    ABSTRACT: We have studied the microscopic magnetic state of a double perovskite Sr2FeMoO6 by x-ray magnetic circular dichroism (XMCD). An Fe L3,2-edge XMCD reveals that the formal Fe3+ ions have an appreciable orbital moment (morb) parallel to their large spin moment (mspin), showing the charge-transfer-induced, minority-spin (↓) Fe t2g electrons. A weak but undoubted O K-edge XMCD was successfully detected, showing an O 2p-hole morb induced by 2p-3d hybridization. Along with information obtained from the observed Mo M3,2-edge XMCD, our findings verify the partially filled Fe 3d t2g↓-O 2pπ↓-Mo 4d t2g↓ hybridized bands at the Fermi level, which mediates ferrimagnetism.
    Journal of Physics Conference Series 04/2014; 502(1):012003. DOI:10.1088/1742-6596/502/1/012003
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    ABSTRACT: Electronic orderings of charges, orbitals and spins are observed in many strongly correlated electron materials, and revealing their dynamics is a critical step toward undertsanding the underlying physics of important emergent phenomena. Here we use time-resolved resonant soft x-ray scattering spectroscopy to probe the dynamics of antiferromagnetic spin ordering in the manganite Pr0.7Ca0.3MnO3 following ultrafast photo-exitation. Our studies reveal a glass-like recovery of the spin ordering and a crossover in the dimensionality of the restoring interaction from quasi-1D at low pump fluence to 3D at high pump fluence. This behavior arises from the metastable state created by photo-excitation, a state characterized by spin disordered metallic droplets within the larger charge- and spin-ordered insulating domains. Comparison with time-resolved resistivity measurements suggests that the collapse of spin ordering is correlated with the insulator-to-metal transition, but the recovery of the insulating phase does not depend on the re-establishment of the spin ordering.
    Scientific Reports 02/2014; 4:4050. DOI:10.1038/srep04050 · 5.58 Impact Factor
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    ABSTRACT: 5-Hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC) represent important epigenetic modifications to DNA, and a sensitive analytical method is required to determine the levels of 5hmC in the genomic DNA of tumor cells or cultured cell lines because 5hmC is present at particular low levels in these cells. We have developed a sensitive liquid chromatography-tandem quadrupole mass spectrometric method for quantifying 5-hydroxymethyldeoxycytidine (5hmdC), 5-methyldeoxycytidine (5mdC), and deoxyguanosine (dG) levels using stable isotope labeled internal standards, and used this method to estimate the global level of 2 modified cytosines in genomic DNA prepared from small number of cells. The quantification limits for 5hmdC, 5mdC and dG were 20pM, 2nM and 10nM, respectively. MRM transitions for isotopologue (isotopologue-MRM) were used to quantify the 5mdC and dG levels because of the abundance of these nucleosides relative to 5hmdC. The use of isotopologue-MRM for the abundant nucleosides could also avoid the saturation of the detector, and allow for all three nucleosides to be analyzed simultaneously without the need for the dilution and re-injection of samples into the instrument. The global ratios of modified cytosine nucleosides to dG were estimated following the quantification of each nucleoside in the hydrolysate of genomic DNA. The limit of estimation for the global 5hmC level was less than 0.001% using 200ng of DNA. Using this method, we found that MLL-TET1, which a fusion protein in acute myelogenous leukemia, did not produce 5hmC, but interfered with TET1 activity to produce 5hmC in cells. Our analytical method is therefore a valuable tool for further studies aiming at a deeper understanding of the role of modified cytosine in the epigenetic regulation of cells.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 02/2014; 953-954C:38-47. DOI:10.1016/j.jchromb.2014.01.050 · 2.69 Impact Factor
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    ABSTRACT: We have performed an angle-resolved photoemission spectroscopy (ARPES) study of BaNi$_2$P$_2$ which shows a superconducting transition at $T_c$ $\sim$ 2.5 K. We observed hole and electron Fermi surfaces (FSs) around the Brillouin zone center and corner, respectively, and the shapes of the hole FSs dramatically changed with photon energy, indicating strong three-dimensionality. The observed FSs are consistent with band-structure calculation and de Haas-van Alphen measurements. The mass enhancement factors estimated in the normal state were $m^*$/$m_b$ $\leq$ 2, indicating weak electron correlation compared to typical iron-pnictide superconductors. An electron-like Fermi surface around the Z point was observed in contrast with BaNi$_2$As$_2$ and may be related to the higher $T_c$ of BaNi$_2$P$_2$.
    Physical Review B 01/2014; 89(19). DOI:10.1103/PhysRevB.89.195138 · 3.66 Impact Factor
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    ABSTRACT: Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are second-generation lysophospholipid mediators that exert multiple biological functions through their own cognate receptors. They are both present in the blood stream, activate receptors with similar structures (endothelial differentiation gene receptors), have similar roles in the vasculature and are vasoactive. However, it is unclear whether these lysophospholipid mediators cross-talk downstream of each receptor. Here, we provide in vivo evidence that LPA signaling counteracted S1P signaling. When autotaxin (Atx), an LPA-producing enzyme, was overexpressed in zebrafish embryos by injecting atx mRNA, the embryos showed cardia bifida, a phenotype induced by down-regulation of S1P signaling. A similar cardiac phenotype was not induced when catalytically inactive Atx was introduced. The cardiac phenotype was synergistically enhanced when antisense morpholino oligonucleotides (MO) against S1P receptor (s1pr2/mil) or S1P transporter (spns2) was introduced together with atx mRNA. The Atx-induced cardia bifida was prominently suppressed when embryos were treated with an lpar1 receptor antagonist, Ki16425, or with MO against lpar1. These results provide the first in vivo evidence of cross-talk between LPA and S1P signaling.
    Journal of Biochemistry 01/2014; DOI:10.1093/jb/mvt114 · 3.07 Impact Factor
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    ABSTRACT: We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2(As1-xPx)2 (x = 0.30, Tc = 30 K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent with horizontal nodes but are consistent with modified s± gap with nodal loops. We have shown that the complicated gap modulation can be theoretically reproduced by considering both spin and orbital fluctuations.
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    ABSTRACT: Electron correlation often produces a variety of electrically insulating states caused by self-organization of electrons, which are particularly stable at commensurate fillings. Although collapsing such ordered states by minute external stimuli has been a key strategy toward device applications, it is difficult to access their true electronic phase boundaries due to the necessity of fine-tuning of material parameters. Here, we demonstrate the ambipolar resistance switching in Pr1-xSrxMnO3 thin films (x = 0.5; an effectively 1/4-filled state) by quasi-continuous control of the doping level x and band-width W using gate-voltage and magnetic field, enabled by the extreme electric-field formed at the nanoscale interface generated in an electrolyte-gated transistor. An electroresistance peak with unprecedented steepness emerges on approaching a critical point in the x-W phase diagram. The technique opens a new route to Mott-insulator based transistors and to discovering singularities hitherto unnoticed in conventional bulk studies of strongly correlated electron systems.
    Scientific Reports 10/2013; 3:2904. DOI:10.1038/srep02904 · 5.58 Impact Factor
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    ABSTRACT: MD-2 is essential for lipopolysaccharide (LPS) recognition of Toll-like receptor 4 (TLR4) but not for cell surface expression. The TLR4/MD-2 complex is formed intracellularly through co-expression. Extracellular complex formation remains a matter for debate because of the aggregative nature of secreted MD-2 in the absence of TLR4 co-expression. We demonstrated extracellular complex formation using three independent monoclonal antibodies (mAbs), all of which are specific for complexed TLR4 but unreactive with free TLR4 and MD-2. These mAbs bound to TLR4-expressing Ba/F3 cells only when co-cultured with MD-2-secreting Chinese hamster ovary cells or incubated with conditioned medium from these cells. All three mAbs bound the extracellularly formed complex indistinguishably from the intracellularly formed complex in titration studies. In addition, we demonstrated that two mAbs lost their affinity for TLR4/MD-2 on LPS stimulation, suggesting that these mAbs bound to conformation-sensitive epitopes. This was also found when the extracellularly formed complex was stimulated with LPS. Additionally, we showed that cell surface TLR4 and extrinsically secreted MD-2 are capable of forming the functional complex extracellularly, indicating an additional or alternative pathway for the complex formation.
    Biochemical and Biophysical Research Communications 09/2013; 440(1). DOI:10.1016/j.bbrc.2013.09.004 · 2.28 Impact Factor
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    ABSTRACT: The nonlinear lattice dynamics of La0.7Sr0.3MnO3, as initiated by strong mid-infrared femtosecond pulses made resonant with a specific lattice vibration, are measured with ultrafast X-ray diffraction at the LCLS free electron laser. Our experiments show that large amplitude excitation of an infrared-active stretching mode leads also to a displacive motion along the coordinate of a second, anharmonically coupled, Raman mode. This rectification of the vibrational field is described within the framework of the Ionic Raman Scattering theory and explains how direct lattice excitation in the nonlinear regime can induce a structural phase transition.
    09/2013; 169:24-27. DOI:10.1016/j.ssc.2013.06.024
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    ABSTRACT: We carried out a comparative study of the in-plane resistivity and optical spectrum of doped BaFe2As2 and investigated the doping evolution of the charge dynamics. For BaFe2As2, charge dynamics is incoherent at high temperatures. Electron (Co) and isovalent (P) doping into BaFe2As2 increase coherence of the system and transform the incoherent charge dynamics into highly coherent one. On the other hand, charge dynamics remains incoherent for hole (K) doping. It is found in common with any type of doping that superconductivity with high transition temperature emerges when the normal-state charge dynamics maintains incoherence and when the resistivity associated with the coherent channel exhibits dominant temperature-linear dependence.
    Scientific Reports 08/2013; 4. DOI:10.1038/srep05873 · 5.58 Impact Factor
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    ABSTRACT: The accumulated uremic toxins inhibit the expression of various renal transporters and this inhibition may further reduce renal function and subsequently cause the accumulation of uremic toxins. However, the precise mechanism of the nephrotoxicity of uremic toxins on renal transport has been poorly understood. Here we report that indoxyl sulfate, one of the potent uremic toxins, directly suppresses the renal-specific organic anion transporter SLCO4C1 expression through a transcription factor GATA3. The promoter region of SLCO4C1 gene has several GATA motifs, and indoxyl sulfate up-regulated GATA3 mRNA and subsequently down-regulated SLCO4C1 mRNA. Overexpression of GATA3 significantly reduced SLCO4C1 expression, and silencing of GATA3 increased SLCO4C1 expression vice versa. Administration of indoxyl sulfate in rats reduced renal expression of slco4c1 and under this condition, plasma level of guanidinosuccinate, one of the preferable substrates of slco4c1, was significantly increased without changing plasma creatinine. Furthermore, in 5/6 nephrectomized rats, treatment with oral adsorbent AST-120 significantly decreased plasma indoxyl sulfate level and conversely increased the expression of slco4c1, following the reduction of plasma level of guanidinosuccinate. These data suggest that the removal of indoxyl sulfate and blocking its signal pathway may help to restore the SLCO4C1-mediated renal excretion of uremic toxins in CKD.
    PLoS ONE 07/2013; 8(7):e66518. DOI:10.1371/journal.pone.0066518 · 3.53 Impact Factor
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    ABSTRACT: The nature of the pseudogap in high transition temperature (high-Tc) superconducting cuprates has been a major issue in condensed matter physics. It is still unclear whether the high-Tc superconductivity can be universally associated with the pseudogap formation. Here we provide direct evidence of the existence of the pseudogap phase via angle-resolved photoemission spectroscopy in another family of high-Tc superconductor, iron-pnictides. Our results reveal a composition dependent pseudogap formation in the multi-band electronic structure of BaFe2(As1-xPx)2. The pseudogap develops well above the magnetostructural transition for low x, persists above the nonmagnetic superconducting dome for optimal x and is destroyed for x ~ 0.6, thus showing a notable similarity with cuprates. In addition, the pseudogap formation is accompanied by inequivalent energy shifts in xz/yz orbitals of iron atoms, indicative of a peculiar iron orbital ordering which breaks the four-fold rotational symmetry.
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    ABSTRACT: In Fe-based superconductors, electron doping is often realized by the substitution of transition-metal atoms for Fe. In order to investigate how the electronic structure of the parent compound is influenced by Zn substitution, which supplies nominally four extra electrons per substituted atom but is expected to induce the strongest impurity potential among the transition-metal atoms, we have performed an angle-resolved photoemission spectroscopy measurements on Ba(Fe_{1-x}Zn_x)_2As_2 (Zn-122). In Zn-122, the temperature dependence of the resistivity shows a kink around T~135 K, indicating antiferromagnetic order below the Neel temperature of T_N ~ 135 K. In fact, folded Fermi surfaces (FSs) similar to those of the parent compound have been observed below T_N. The hole and electron FS volumes are, therefore, different from those expected from the rigid-band model. The results can be understood if all the extra electrons occupy the Zn 3d state ~10 eV below the Fermi level and do not participate in the formation of the FSs.
    Physical review. B, Condensed matter 04/2013; 87(20). DOI:10.1103/PhysRevB.87.201110 · 3.66 Impact Factor

Publication Stats

13k Citations
1,156.18 Total Impact Points

Institutions

  • 2002–2015
    • National Institute of Advanced Industrial Science and Technology
      • Nanoelectronics Research Institute
      Tsukuba, Ibaraki, Japan
  • 1993–2015
    • Tohoku University
      • • Graduate School of Pharmaceutical Sciences
      • • Division of Physiological Sciences
      • • Department of Life and Pharmaceutical Science
      Miyagi, Japan
  • 2014
    • University of Shizuoka
      • Department of Clinical Pharmacology and Genetics
      Sizuoka, Shizuoka, Japan
  • 1994–2014
    • Tohoku Pharmaceutical University
      Miyagi, Japan
  • 2012–2013
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 2010
    • University of Hyogo
      • Graduate School of Applied Informatics
      Kōbe, Hyōgo, Japan
  • 2006
    • Tokai University
      Hiratuka, Kanagawa, Japan
  • 1995–2004
    • The University of Tokyo
      • Department of Applied Physics
      Tōkyō, Japan
  • 2003
    • University of Groningen
      • Materials Science Group
      Groningen, Province of Groningen, Netherlands
  • 2001
    • Ukrainian Academy of Agrarian Sciences
      Kievo, Kyiv City, Ukraine
  • 2000
    • RIKEN
      Вако, Saitama, Japan
  • 1997
    • Princeton University
      • Department of Physics
      Princeton, New Jersey, United States