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Search Results: 1 - 10 of 146 matches for " Soichiro Ushio "
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L type Ca2+ channel blockers prevent oxaliplatin-induced cold hyperalgesia and TRPM8 overexpression in rats
Takehiro Kawashiri, Nobuaki Egashira, Kentaro Kurobe, Kuniaki Tsutsumi, Yuji Yamashita, Soichiro Ushio, Takahisa Yano, Ryozo Oishi
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-7
Abstract: Cold hyperalgesia was assessed by the acetone test. Oxaliplatin (4 mg/kg), sodium oxalate (1.3 mg/kg) or vehicle was injected i.p. on days 1 and 2. Ca2+ (diltiazem, nifedipine and ethosuximide) and Na+ (mexiletine) channel blockers were administered p.o. simultaneously with oxaliplatin or oxalate on days 1 and 2.Oxaliplatin (4 mg/kg) induced cold hyperalgesia and increased in the transient receptor potential melastatin 8 (TRPM8) mRNA levels in the dorsal root ganglia (DRG). Furthermore, oxalate (1.3 mg/kg) significantly induced the increase in TRPM8 protein in the DRG. Treatment with oxaliplatin and oxalate (500 μM for each) also increased the TRPM8 mRNA levels and induced Ca2+ influx and nuclear factor of activated T-cell (NFAT) nuclear translocation in cultured DRG cells. These changes induced by oxalate were inhibited by nifedipine, diltiazem and mexiletine. Interestingly, co-administration with nifedipine, diltiazem or mexiletine prevented the oxaliplatin-induced cold hyperalgesia and increase in the TRPM8 mRNA levels in the DRG.These data suggest that the L type Ca2+ channels/NFAT/TRPM8 pathway is a downstream mediator for oxaliplatin-induced cold hyperalgesia, and that Ca2+ channel blockers have prophylactic potential for acute neuropathy.Oxaliplatin, a platinum-based chemotherapeutic agent, is widely used for treatment of colorectal cancer. However, oxaliplatin frequently causes severe acute and chronic peripheral neuropathies. Acute neuropathy is peculiar to oxaliplatin and includes acral paresthesias enhanced by exposure to cold [1-4]; the acute neuropathy is not attributed to morphological damage to the nerve [5,6]. On the other hand, the chronic neuropathy is characterized by loss of sensory and motor function after long-term oxaliplatin treatment, and it is similar to cisplatin-induced neurological symptoms [4]. Recently, we reported that repeated administration of oxaliplatin induced cold hyperalgesia in the early phase and mechanical allodynia in the l
Inhibition of Ca2+/Calmodulin-dependent protein kinase II reverses oxaliplatin-induced mechanical allodynia in Rats
Masafumi Shirahama, Soichiro Ushio, Nobuaki Egashira, Shota Yamamoto, Hikaru Sada, Ken Masuguchi, Takehiro Kawashiri, Ryozo Oishi
Molecular Pain , 2012, DOI: 10.1186/1744-8069-8-26
Abstract: An increase of CaMKII phosphorylation was found in the spinal cord (L4-6) of oxaliplatin-treated rats. This increased CaMKII phosphorylation was reversed by intrathecal injection of a selective CaMKII inhibitor KN-93 (50 nmol, i.t.) and a selective NR2B antagonist Ro 25-6981 (300 nmol, i.t.). Moreover, acute administration of KN-93 (50 nmol, i.t.) strongly reversed the oxaliplatin-induced mechanical allodynia in von Frey test, while it did not affect the oxaliplatin-induced cold hyperalgesia in acetone test. Similarly, oral administration of trifluoperazine (0.1 and 0.3 mg/kg, p.o.), which is an antipsychotic drug and inhibits calmodulin, reduced both mechanical allodynia and increased CaMKII phosphorylation. On the other hand, trifluoperazine at the effective dose (0.3 mg/kg) had no effect on the paw withdrawal threshold in intact rats. In addition, trifluoperazine at the same dose did not affect the motor coordination in rota-rod test in intact and oxaliplatin-treated rats.These results suggest that CaMKII is involved in the oxaliplatin-induced mechanical allodynia, and trifluoperazine may be useful for the treatment of oxaliplatin-induced peripheral neuropathy in clinical setting.Oxaliplatin, a platinum-based chemotherapeutic agent, has widely been used for colorectal cancer. However, oxaliplatin causes severe peripheral neuropathy. After multiple cycles, the patients develop a chronic neuropathy that is characterized by a sensory and motor dysfunction. This chronic neuropathy is a dose-limiting toxicity and a major clinical problem in oxaliplatin-based chemotherapy [1].We previously reported that repeated administration of oxaliplatin induced cold hyperalgesia in the early phase and mechanical allodynia in the late phase in rats [2]. Recently, we reported that spinal NR2B-containing N-methyl-D-aspartate (NMDA) receptors are involved in the oxaliplatin-induced mechanical allodynia [3]. The NMDA receptor antagonists (MK-801 and memantine) and selective NR2B antago
Involvement of spinal NR2B-containing NMDA receptors in oxaliplatin-induced mechanical allodynia in rats
Yuki Mihara, Nobuaki Egashira, Hikaru Sada, Takehiro Kawashiri, Soichiro Ushio, Takahisa Yano, Hiroaki Ikesue, Ryozo Oishi
Molecular Pain , 2011, DOI: 10.1186/1744-8069-7-8
Abstract: Repeated administration of oxaliplatin (4 mg/kg, i.p., twice a week) caused mechanical allodynia in the fourth week, which was reversed by intrathecal injection of MK-801 (10 nmol) and memantine (1 μmol), NMDA receptor antagonists. Similarly, selective NR2B antagonists Ro25-6981 (300 nmol, i.t.) and ifenprodil (50 mg/kg, p.o.) significantly attenuated the oxaliplatin-induced pain behavior. In addition, the expression of NR2B protein and mRNA in the rat spinal cord was increased by oxaliplatin on Day 25 (late phase) but not on Day 5 (early phase). Moreover, we examined the involvement of nitric oxide synthase (NOS) as a downstream target of NMDA receptor. L-NAME, a non-selective NOS inhibitor, and 7-nitroindazole, a neuronal NOS (nNOS) inhibitor, significantly suppressed the oxaliplatin-induced pain behavior. The intensity of NADPH diaphorase staining, a histochemical marker for NOS, in the superficial layer of spinal dorsal horn was obviously increased by oxaliplatin, and this increased intensity was reversed by intrathecal injection of Ro25-6981.These results indicated that spinal NR2B-containing NMDA receptors are involved in the oxaliplatin-induced mechanical allodynia.Glutamate is a major excitatory transmitter in the spinal cord and N-methyl-D-aspartate (NMDA) receptors are known to be involved in the painful neuropathy [1,2]. The NMDA receptor antagonist inhibits the pain hypersensitivity in chronic constriction injury (CCI) model. Moreover, the expression of spinal NR2B-containing NMDA receptors is increased with the pain hypersensitivity induced by CCI or chronic compression of the dorsal root ganglia (CCD) [3-6]. Selective NR2B antagonists inhibit mechanical allodynia without causing motor dysfunction in CCI, CCD and spinal nerve-ligated (SNL) neuropathic models [5-8]. In addition, the NR2B subunits are localized to the superficial dorsal horn of the spinal cord [7,9], suggesting a possible involvement in pain transmission. Thus, the NR2B-containing NMDA re
A Synthesis Method for Time-Domain Passive Filters Compensating for Waveform Distortion
Ushio Sangawa
PIER B , 2012, DOI: 10.2528/PIERB12051001
Abstract: A novel synthesis method for a class of time-domain passive filters that compensates for waveform distortion caused by frequency dependencies of the transmission properties of signal propagation paths, is formulated. The method is based on the linear response theory and mathematical properties of scattering matrices for passive circuits. This paper focuses on the formulation and theoretical consistency of the method. The causal transfer functions for the filters can be extracted by "regularizing" the inverse of a transfer function of the path. To fulfill the necessary restrictions imposed on the causal functions, regularization is realized by multiplying the function of linear phase filters comprising a sufficient number of resonators by the inverse. The filter circuits are easily derived from the regularized transfer functions through numerical optimization techniques and the coupling matrix synthesis method to determine transmission poles and extract each lumped element value, respectively. The method is then applied to practically designing a filter that compensates for the frequency dependencies of a two-port radio propagation path having a pair of wideband antennas. In addition, applications of the filter and the scope of further developments of this technology are discussed.
The Origin of Electromagnetic Resonances in Three-Dimensional Photonic Fractals
Ushio Sangawa
PIER , 2009, DOI: 10.2528/PIER09062203
Abstract: After a report on strange electromagnetic resonances emerging in an isotropic paraelectric Menger sponge (MS) now known as a photonic fractal, vigorous studies began to reveal their properties. However, the mechanics of how the resonances occur is still unknown. This report focuses on the findings that the resonances can be perturbation-theoretically identified as those originally occurring in an isolated dielectric cube, and that they arise within band gaps and uncouple with Bloch modes for a certain multiperiodic lattice. This interpretation is justified by the fact that the MS can be considered as a cube embedded in the lattice rather than the outcome of conventional recursive fractal structuring operations. An experimental formula for resonance conditions already reported can be derived from this interpretation.
Asymptotic pointwise behavior for systems of semilinear wave equations in three space dimensions
Soichiro Katayama
Mathematics , 2011, DOI: 10.1142/S0219891612500099
Abstract: In connection with the weak null condition, Alinhac introduced a sufficient condition for global existence of small amplitude solutions to systems of semilinear wave equations in three space dimensions. We introduce a slightly weaker sufficient condition for the small data global existence, and we investigate the asymptotic pointwise behavior of global solutions for systems satisfying this condition. As an application, the asymptotic behavior of global solutions under the Alinhac condition is also derived.
Asymptotic bahavior for systems of nonlinear wave equations with multiple propagation speeds in three space dimensions
Soichiro Katayama
Mathematics , 2012, DOI: 10.1016/j.jde.2013.04.003
Abstract: We consider the Cauchy problem for systems of nonlinear wave equations with multiple propagation speeds in three space dimensions. Under the null condition for such systems, the global existence of small amplitude solutions is known. In this paper, we will show that the global solution is asymptotically free in the energy sense, by obtaining the asymptotic pointwise behavior of the derivatives of the solution. Nonetheless we can also show that the pointwise behavior of the solution itself may be quite different from that of the free solution. In connection with the above results, a theorem is also developed to characterize asymptotically free solutions for wave equations in arbitrary space dimensions.
Global existence for coupled systems of nonlinear wave and Klein-Gordon equations in three space dimensions
Soichiro Katayama
Mathematics , 2009, DOI: 10.1007/s00209-010-0808-0
Abstract: We consider the Cauchy problem for coupled systems of wave and Klein-Gordon equations with quadratic nonlinearity in three space dimensions. We show global existence of small amplitude solutions under certain condition including the null condition on self-interactions between wave equations. Our condition is much weaker than the strong null condition introduced by Georgiev for this kind of coupled system. Consequently our result is applicable to certain physical systems, such as the Dirac-Klein-Gordon equations, the Dirac-Proca equations, and the Klein-Gordon-Zakharov equations.
IMPACT OF SWAPPING RISKS FOR FACILITATING
Hideyuki Takada,Ushio Sumita
International Journal of Electronic Commerce Studies , 2011,
Abstract: A swapping scheme is proposed so as to facilitate the capital flow into e-commerce by controlling credit risks associated with e-commerce corporations. More specifically, we develop and analyze a mathematical model for swapping credit risks across two industrial sectors A without involving e-commerce and another industrial sector B which relies upon e-commerce. When two Banks X and Y provide loans to corporations in A and B, a swapping scheme can be devised between Bank X and Y so as to improve the Value-at-Risk for both of them. Exploiting the dynamic stochastic model based on a Markov Modulated Poisson Process (MMPP) developed by Takada, Sumita and Takahashi (2010) and Takada and Sumita (2010), the efficient computational procedures are established for solving the Value-at-Risk problems.
Model for the occurrence of Fermi pockets without the pseudogap hypothesis in underdoped cuprate superconductors - Interplay of Jahn-Teller physics and Mott physics -
Hiroshi Kamimura,Hideki Ushio
Physics , 2010,
Abstract: Central issues in the electronic structure of underdoped cuprate superconductors are to clarify the shape of the Fermi surfaces and the origin of a pseudogap. Based on the model proposed by Kamimura and Suwa which bears important characteristics born from the interplay of Jahn-Teller Physics and Mott Physics, we show that the feature of Fermi surfaces is the Fermi pockets constructed by doped holes under the coexistence of a metallic state and of the local antiferromagnetic order. Below $T_{\rm c}$ the holes on Fermi pockets form Cooper pairs with d-wave symmetry in the nodal region. In the antinodal region all the states below the Fermi level are occupied by electrons so that there is no gap, not even pseudo both below and above $T_{\rm c}$. Calculated angle-resolved photoemission spectrum below $T_{\rm c}$ show a coherent peak at the nodal region while a broad hump in antinodal region. From this feature the origin of the two distinct gaps in observed ARPES is elucidated. The finite-size-effects of a spin-correlation length coexisting with a metallic state are discussed. In particular, we discuss a possibility of the spatially inhomogeneous distribution of Fermi-pocket-states and of large-Fermi-surface-states above $T_{\rm c}$ which changes with time. Finally a new phase diagram for underdoped cuprates is proposed.
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