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Search Results: 1 - 10 of 7661 matches for " Takashi Takahashi "
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Function of Membrane Rafts in Viral Lifecycles and Host Cellular Response
Tadanobu Takahashi,Takashi Suzuki
Biochemistry Research International , 2011, DOI: 10.1155/2011/245090
Abstract: Membrane rafts are small (10–200 nm) sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process) and the late stage (assembly, budding, and release processes of virus particles). In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction.
Function of Membrane Rafts in Viral Lifecycles and Host Cellular Response
Tadanobu Takahashi,Takashi Suzuki
Biochemistry Research International , 2011, DOI: 10.1155/2011/245090
Abstract: Membrane rafts are small (10–200?nm) sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Membrane rafts play an important role in viral infection cycles and viral virulence. Viruses are divided into four main classes, enveloped DNA virus, enveloped RNA virus, nonenveloped DNA virus, and nonenveloped RNA virus. General virus infection cycle is also classified into two sections, the early stage (entry process) and the late stage (assembly, budding, and release processes of virus particles). In the viral cycle, membrane rafts act as a scaffold of many cellular signal transductions, which are associated with symptoms caused by viral infections. In this paper, we describe the functions of membrane rafts in viral lifecycles and host cellular response according to each virus classification, each stage of the virus lifecycle, and each virus-induced signal transduction. 1. Introduction Relationships between virus infection mechanisms and lipid rafts had often been studied in complexes with caveolae [1, 2]. Lipid rafts, membrane microdomains enriched in cholesterol, and sphingolipids represented by GM1 and globotriaosylceramide (Gb3Cer) were defined at the Keystone Symposium on Lipid Rafts and Cell Function (March 23–28, 2006 in Steamboat Springs, CO) as follows: “Membrane rafts are small (10–200?nm), heterogeneous, highly dynamic, sterol- and sphingolipid-enriched domains that compartmentalize cellular processes. Small rafts can sometimes be stabilized to form larger platforms through protein-protein and protein-lipid interactions.” This definition led to the term “lipid raft” being discarded in favor of the term “membrane raft”. The term “membrane raft” underlies the concept that both proteins and lipids, rather than solely lipid-driven interactions, play an important role in the formation of these membrane microdomains. The caveola, a cholesterol/sphingolipid-rich small pit, depression, or invagination, is a site on the cell surface that provides a platform for proteins and lipids to interact and transmit signals. In the symposium, the range of 10–200?nm, which was adopted as the size of membrane rafts, included the upper limit on the surface of a caveola. Here, membrane rafts include caveolae [3]. Membrane rafts have been shown to be involved in the virus entry, assembly, or/and budding process in infection lifecycles of various viruses, such as retroviruses (Retroviridae), RNA viruses (Arenaviridae, Astroviridae, Bunyaviridae, Caliciviridae, Coronaviridae, Filoviridae, Flaviviridae, Orthomyxoviridae, Paramyxoviridae,
Deci hertz Laser Interferometer can determine the position of the Coalescing Binary Neutron Stars within an arc minute a week before the final merging event to Black Hole
Ryuichi Takahashi,Takashi Nakamura
Physics , 2003, DOI: 10.1086/379112
Abstract: It may be possible to construct a laser interferometer gravitational wave antenna in space with $h_{rms}\sim 10^{-23}$ at $ f\sim 0.1{\rm Hz}$ in $\sim 2020$. This deci hertz antenna may be called DECIGO/BBO,which stand for DECi hertz Interferometer Gravitational wave Observatory and Big Bang Observer, respectively. The analysis of 1-10 years observational data of the coalescing binary neutron stars or black holes at the distance of $\sim$ 300Mpc will give us the spatial position within $\sim$ an arc minute and the time of the coalescence within $\sim 0.1$ sec beforehand. With the knowledge of the accurate position and the time of final merging event, the follow up simultaneous observation using high frequency ($ f\sim 100{\rm Hz}$) gravitational wave antennae as well as electro-magnetic wave antennae from the radio frequency to the ultra high energy gamma ray will reveal the physics in the enigmatic event of the coalescence and the formation of the black hole.
Wave Effects in Gravitational Lensing of Gravitational Waves from Chirping Binaries
Ryuichi Takahashi,Takashi Nakamura
Physics , 2003, DOI: 10.1086/377430
Abstract: In the gravitational lensing of gravitational waves, the wave optics should be used instead of the geometrical optics when the wavelength $\lambda$ of the gravitational waves is longer than the Schwarzschild radius of the lens mass $M_L$. For the gravitational lensing of the chirp signals from the coalescence of the super massive black holes at the redshift $z_S\sim 1$ relevant to LISA, the wave effects become important for the lens mass smaller than $\sim 10^8 M_{\odot}$. For such cases, we compute how accurately we can extract the mass of the lens and the source position from the lensed signal. We consider two simple lens models: the point mass lens and the SIS (Singular Isothermal Sphere). We find that the lens mass and the source position can be determined within $\sim 0.1% [(S/N)/10^3]^{-1}$ for the lens mass larger than $10^8 M_{\odot}$ and $\gsim 10% [(S/N)/10^3]^{-1}$ for the lens mass smaller than $10^7 M_{\odot}$ due to the diffraction effect, where $(S/N)$ is the signal to noise ratio of the unlensed chirp signals. For the SIS model, if the source position is outside the Einstein radius, only a single image exists in the geometrical optics approximation so that the lens parameters can not be determined. While in the wave optics cases we find that the lens mass can be determined even for $M_L < 10^8 M_{\odot}$. For the point mass lens, one can extract the lens parameters even if the source position is far outside the Einstein radius. As a result, the lensing cross section is an order of magnitude larger than that for the usual strong lensing of light.
Evidence of one-step replica symmetry breaking in a three-dimensional Potts glass model
Takashi Takahashi,Koji Hukushima
Physics , 2014, DOI: 10.1103/PhysRevE.91.020102
Abstract: We study a 7-state Potts glass model in three dimensions with first, second, and third neighbor interactions with a bimodal distribution of couplings by Monte Carlo simulations. Our results show the existence of a spin-glass transition at a finite temperature T_c, a discontinuous jump of an order parameter at T_c without latent heat, and a non-trivial structure of the order-parameter distribution below T_c. They are compatible with a one-step replica symmetry breaking.
Determination of the equation of the state of the Universe using ~ 0.1 Hz Gravitational Wave Detectors
Ryuichi Takahashi,Takashi Nakamura
Physics , 2004, DOI: 10.1143/PTP.113.63
Abstract: We show that ten(one) years operation of the ultimate DECIGO (DECihertz Interferometer Gravitational wave Observatory) can determine the cosmic equation of the state with such accuracy that 0.06%(3%), 0.08%(4%) and 0.06%(3%) for $\Omega_m$, $\Omega_w$ and $w$, respectively. In more realistic case of practical DECIGO or BBO (Big Bang Observer), $w$ will be determined within $\sim 10%$ by ten years observation assuming the flat universe model. Hence, the DECIGO or BBO will give an independent determination of the cosmic equation of the state.
Critical blowup exponent to a class of semilinear elliptic equations with constraints in higher dimension - local properties
Takashi Suzuki,Ryo Takahashi
Mathematics , 2014,
Abstract: We study a class of semilinear elliptic equations with constraints in higher dimension. It is known that several mathematical structures of the problem are closed to those of the Liouville equation in dimension two. In this paper, we establish a classification of entire solutions, the $\sup + \inf$ type inequality and the quantized blowup mechanism.
Activation of ERK and P38 by the Addition of Arsenic Trioxide in Flt3-ITD Cells  [PDF]
Sawami Suzuki, Hiroko Inaba, Takashi Satoh, Toshio Okazaki, Shinichiro Takahashi
Open Journal of Blood Diseases (OJBD) , 2011, DOI: 10.4236/ojbd.2011.12003
Abstract: Flt3-internal tandem duplications (Flt3-ITD) is a prevalent mutation in acute myeloid leukemia (AML). We recently reported arsenic trioxide (ATO) and Flt3 inhibition synergize to induce apoptosis in Flt3-ITD cells. However, the signaling effect of ATO in these cells has not been elucidated. Here, we demonstrate that the treatment of ATO potently induces the activation of extracellular regulated kinase (ERK)- mitogen activated protein kinase (MAPK), and modestly activates p38-MAPK in BaF3-Flt3-ITD cells, among other major (PI3-kinase-Akt, c-jun N-terminal kinase [JNK]) signaling pathways examined. In contrast, in BaF3-Flt3-wild type (WT) cells, slight activation of p38, but none for others, was observed. As MAPK kinase (MEK), as well as p38 inhibition is reported to enhance ATO-induced apoptosis in AML and various hematological malignancies, our results suggest that Flt3 mutation status is important for the effect of these combinations.
Safe Hydroformylation of Aliphatic Alkene in a Flow Reactor  [PDF]
Hisashi Masui, Eiki Honda, Sakura Niitsu, Mitsuru Shoji, Takashi Takahashi
International Journal of Organic Chemistry (IJOC) , 2018, DOI: 10.4236/ijoc.2018.81009
Abstract: Despite hydroformylation being a very efficient method for the transformation of alkenes, it is not commonly employed in laboratories owing to the flammable/toxic nature of hydrogen and carbon monoxide gases and the necessity of high-pressure equipment in a batch system. Flow chemistry often raises the safety profiles against high-pressure and toxic gases because the diameter of the flow reactor is small. Herein, we show that aliphatic alkenes can be safely hydroformylated in a flow reactor. In our flow method, although the target hydroformylated product was obtained in a low yield (19%), toxic gases were safely treated using a flow reactor. Better yields could possibly be achieved by recycling of the unreacted alkene.
Suppressive effects of saliva against enamel demineralization caused by acid beverages  [PDF]
Shoji Takahashi, Shigeru Watanabe, Takashi Ogihara, Koji Watanabe, Kun Xuan, Xiaojing Wang
Health (Health) , 2011, DOI: 10.4236/health.2011.312123
Abstract: This study aimed to clarify the ability of the buffer systems of saliva to inhibit enamel demineralization after intake of an acid beverage. In the first experiment, titrable acidity tests were carried out. Ten milliliters of saliva stimulated by chewing gum base was obtained from 10 healthy adult subjects and the pH of each saliva sample was measured. The beverages used for the experiment were a carbonated soft drink (pH 2.2), a sports drink (pH 3.5), and 100% orange juice (pH 3.8). Distilled water adjusted to the pH of each saliva sample was used as a control. In the second experiment, the suppressive ability of saliva against enamel demineralization was quantitatively analyzed using quantitative light- induced fluorescence (QLF). Aliquots of stimulated saliva obtained from a subject were mixed with 15 ml of 100% orange juice in saliva:orange juice ratios of 1/30, 1/15, 1/10 and 1/5, and bovine teeth were soaked for 24 hours in the solutions. The △Q of the QLF analyses of the enamel was then measured. The lowest titrant volume which reduced the pH of the initial saliva (7.7 on average) to pH 5.4 was that of the orange juice. No relationship was found between the buffer capacity and the pH of the acid beverages. From the QLF measurement, the saliva-orange juice group showed a significantly decreased amount of enamel demineralization (p < 0.01 at 20% level) compared with the distilled water-orange juice group. In conclusion, saliva acts as a buffer to suppress enamel demineralization caused by low-pH beverages.
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