Alteration of gene expression profiles in the brain of Japanese medaka (Oryzias latipes) exposed to KC-400 or PCB126     

Nakayama K  Sei N  Oshima Y  Tashiro K  Shimasaki Y  Honjo T 《Marine pollution bulletin》2008,57(6-12):460-466

Polychlorinated biphenyls (PCBs) are known as neurotoxic chemicals and possibly alter animal behavior. We previously reported that PCB-exposure induced abnormal schooling behavior in Japanese medaka (Oryzias latipes). This abnormal behavior might be caused by the functional alteration of central or terminal nervous system. To understand the mechanism(s) of behavioral change by PCB-exposure, we analyzed the gene expression profiles in the brain of medaka exposed to 3,3',4,4',5-pentachlorobiphenyl (PCB126) or a PCB mixture (Kanechlor-400: KC-400) using a cDNA microarray that we constructed. Twelve FLF-II strain medaka (six individuals per treatment) were dietary exposed to PCB126 (0.01 microg/g b.w./day) or KC-400 (1 microg/g b.w./day) for three weeks. For the control, six fish were fed a control diet. After the exposure period, fish were dissected, and the brain samples were collected. The samples from control fish were pooled and used as a common reference in the microarray experiment. Microarray data were normalized by the LOWESS method, and we screened the genes whose expression levels were altered more than 1.5-fold. Gene expression profiling showed 97 down-regulated and 379 up-regulated genes in the brain of medaka exposed to PCB126. KC-400 exposure suppressed 15 genes and induced 266 genes in medaka brain. Among these genes, the expression levels of 7 and 188 genes were commonly down- or up-regulated, respectively in both treatment groups. On the other hand, 31 gene expressions were significantly different between PCB126 and KC-400 treatment groups, and three out of 31 genes were received opposite effects. In addition, the microarray data showed that thyroid hormone-responsive genes were up-regulated by PCB-exposure, which may imply that PCBs or their metabolites mimic thyroid hormone effects in the brain of PCB-exposed medaka.  相似文献   

Numerical model of local scour considering the unsteady sediment inflow and sediment sorting: Application to scour upstream of slit weir     

Kazuyuki Ota  Takahiro Sato  Ryosuke Arai 《国际泥沙研究》2022,37(4):469-483

The current study proposes a novel framework for the numerical model for estimating the temporal scour considering unsteady sediment inflow and the sediment sorting process. The framework was applied to local scour upstream of a slit weir. The scour model is based on an ordinary nonlinear differential equation derived from sediment continuity and scour rate equations. A one-dimensional(1-D)Boussinesq-type model coupled with nonequilibrium sediment transport was incorporated in the scour model to...  相似文献   

Interhemispheric observations of field line resonance frequencies as a continuous function of ground latitude in the auroral zones     

S. Takasaki  N. Sato  A. Kadokura  H. Yamagishi  H. Kawano  Y. Ebihara  Y.-M. Tanaka 《Polar Science》2008,2(2):73-86

In the austral summer of 2006–2007, the 48th Japanese Antarctic Research Expedition (JARE-48) installed two unmanned low-power magnetometers to form a closely spaced magnetometer network in combination with the permanent sites at Japan's Syowa Station in Antarctica. To identify field line resonances (FLRs), gradient methods are applied to the data from three adjacent sites in Antarctica and data from conjugate points in Antarctica and Iceland. By analyzing the data from the Antarctic and Icelandic sites individually, the structure of FLRs with high coherence is clearly identified. However, by analyzing the data from closely spaced Antarctic sites, it is more difficult to identify the signature of FLRs because of the inclusion of multiple signals related to the local geomagnetic pulsations over a broad frequency range. The frequency and resonance width of FLRs are determined by applying the amplitude phase gradient method (APGM) to the data from Antarctic sites. This yields the eigenfrequency as a continuous function of ground latitudes in the area surrounding Syowa Station. The mass density in the equatorial region at the L of the auroral zones is estimated from the obtained FLR frequency by numerically solving the standing Alfvén wave equation. The mass density thus obtained is consistent with observational results from previous in situ measurements by spacecraft. The results of the present study demonstrate that data from geomagnetic conjugate points are helpful in identifying FLR in cases in which the magnetometers are too close to each other to enable identification. Once FLR is identified, APGM can be applied to the identified FLR, yielding the FLR frequency as a continuous function of ground latitudes. Therefore, the magnetospheric equatorial mass density is readily estimated with high spatial resolution.  相似文献   

Synoptic distribution of dayside aurora: Multiple-wavelength all-sky observation at Yellow River Station in Ny-Ålesund,Svalbard     

Z.-J. Hu  H. Yang  D. Huang  T. Araki  N. Sato  M. Taguchi  E. Seran  H. Hu  R. Liu  B. Zhang  D. Han  Z. Chen  Q. Zhang  J. Liang  S. Liu 《Journal of Atmospheric and Solar》2009,71(8-9):794-804

Observations acquired from three-wavelength (427.8, 557.7 and 630.0 nm) all-sky imagers (ASIs) at Yellow River Station (YRS) in Ny-Ålesund, Svalbard, are used to examine the synoptic distribution of dayside aurora. The results demonstrate that the maximum emission regions (MERs) at each wavelength are all located in the postnoon sector, but have rather different magnetic local time (MLT) distributions from each other. The so-called 15 MLT “hot spot” is the overlapping region of the MERs at three wavelengths, and the prenoon “warm spot” is characterized uniquely by an increase of emissions at the 557.7 nm wavelength. The detailed dayside auroral spectra and morphology as a function of MLT are discussed.  相似文献   

Electrical conductivities of pyrolitic mantle and MORB materials up to the lowermost mantle conditions     

Kenji Ohta  Kei Hirose  Masahiro Ichiki  Katsuya Shimizu  Nagayoshi Sata  Yasuo Ohishi 《Earth and Planetary Science Letters》2010,289(3-4):497-502

The electrical conductivities of natural pyrolitic mantle and MORB materials were measured at high pressure and temperature covering the entire lower mantle conditions up to 133 GPa and 2650 K. In contrast to the previous laboratory-based models, our data demonstrate that the conductivity of pyrolite does not increase monotonically but varies dramatically with depth in the lower mantle; it drops due to high-spin to low-spin transition of iron in both perovskite and ferropericlase in the mid-lower mantle and increases sharply across the perovskite to post-perovskite phase transition at the D″ layer. We also found that the MORB exhibits much higher conductivity than pyrolite. The depth–conductivity profile measured for pyrolite does not match the geomagnetic field data below about 1500-km depth, possibly suggesting the existence of large quantities of subducted MORB crust in the deep lower mantle. The observations of geomagnetic jerks suggest that the electrical conductivity may be laterally heterogeneous in the lowermost mantle with high anomaly underneath Africa and the Pacific, the same regions as large low shear-wave velocity provinces. Such conductivity and shear-wave speed anomalies are also possibly caused by the deep subduction and accumulation of dense MORB crust above the core–mantle boundary.  相似文献   

Gravitational wave background from neutrino-driven gamma-ray bursts     

Takashi Hiramatsu  Kei Kotake  Hideaki Kudoh  Atsushi Taruya 《Monthly notices of the Royal Astronomical Society》2005,364(3):1063-1068

We study cosmic microwave background (CMB) secondary anisotropies produced by inhomogeneous reionization by means of cosmological simulations coupled with the radiative transfer code crash . The reionization history is consistent with the Wilkinson Microwave Anisotropy Probe Thomson optical depth determination. We find that the signal arising from this process dominates over the primary CMB component for   l ≳ 4000  and reaches a maximum amplitude of   l ( l + 1) C_l /2π≃ 1.6 × 10⁻¹³  on arcmin scales (i.e. l as large as several thousands). We then cross-correlate secondary CMB anisotropy maps with neutral hydrogen 21-cm line emission fluctuations obtained from the same simulations. The two signals are highly anticorrelated on angular scales corresponding to the typical size of H  ii regions (including overlapping) at the 21-cm map redshift. We show how the CMB/21-cm cross-correlation can be used: (i) to study the nature of the reionization sources; (ii) to reconstruct the cosmic reionization history; (iii) to infer the mean cosmic ionization level at any redshift. We discuss the feasibility of the proposed experiment with forthcoming facilities.  相似文献   

Non-destructive monitoring of trace element levels in short-tailed albatrosses (Phoebastria albatrus) and black-footed albatrosses (Phoebastria nigripes) from Torishima Island, Japan using eggs and blood     

Ikemoto T  Kunito T  Tanabe S  Tsurumi M  Sato F  Oka N 《Marine pollution bulletin》2005,51(8-12):889-895

Concentrations of 18 trace elements (V, Cr, Mn, Co, Cu, Zn, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Hg, Tl and Pb) were determined in abandoned eggs of short-tailed albatrosses and abandoned eggs and blood of black-footed albatrosses from Torishima Island, Japan in 2002. Mercury concentration was highest among the toxic elements in egg content of both the two species. In some egg contents of black-footed albatrosses, Hg concentrations were higher than the threshold level that may cause decreased hatchability and aberrant nesting behavior in some avian species. Concentrations of Cd in egg content and Ba in egg content and shell increased with an increase in egg breadth/length ratio, whereas Hg in egg content showed an opposite trend in black-footed albatrosses. Since egg breadth/length ratio is known to increase with the age of mother bird, this result may imply that concentrations of these elements in eggs vary with age of mother bird. In blood of black-footed albatross chicks, concentration of Hg was highest among the toxic elements and the Hg concentration showed an increase in the later growth stages. In contrast, concentration of Sr in blood decreased with growth stage. Since the behaviour of Sr is similar to that of Ca in animals, it is conceivable that Sr was used along with Ca for the formation of bone.  相似文献   

Mapping of micro topography using airborne laser scanning   总被引：2，自引：1，他引：1  

Tatsuo?SekiguchiEmail author  Hiroshi?P.?Sato 《Landslides》2004,1(3):195-202

Intense rainfall conditions and seismic activity commonly trigger fluidised landslides which are characterized by rapid movement and long run-out. They are potentially a very dangerous form of landslide phenomena and may result in extensive damage due to their sudden movement. Until now, photogrammetry has been used to produce maps and investigate such landslides in areas where these disasters occur. Recently, however, airborne laser scanning technology has become a promising technique for making topographical maps and investigating the micro topographic details of these landslide disasters, particularly on slopes around urban areas where the potential risk is high. In this study, airborne laser scanning was carried out in the Tama Hills, near Tokyo, Japan, which is extensively affected by this type of landsliding. The effectiveness of this technique was tested and compared with a laser contour map and aerial photograph interpretations.  相似文献   

Amplitude of Body Waves in a Heterogeneous Sphere Comparison of Wave Theory and Ray Theory     

Ryosuke Sato 《Geophysical Journal International》1969,17(5):527-544

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Overlaying landslides distribution on the earthquake source, geological and topographical data: the Mid Niigata prefecture earthquake in 2004, Japan   总被引：4，自引：3，他引：4  

Hiroshi P. Sato  Tatsuo Sekiguchi  Ryoichi Kojiroi  Yoshinori Suzuki  Makoto Iida 《Landslides》2005,2(2):143-152

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