Hokkaido University

About: Hokkaido University is a education organization based out in Sapporo, Hokkaidô, Japan. It is known for research contribution in the topics: Catalysis & Population. The organization has 53925 authors who have published 115403 publications receiving 2651647 citations. The organization is also known as: Hokudai & Hokkaidō daigaku.

Perpetuation of influenza A viruses in Alaskan waterfowl reservoirs.

Abstract: To provide information on the mechanism of perpetuation of influenza viruses among waterfowl reservoirs in nature, virological surveillance was carried out in Alaska during their breeding season in summer from 1991 to 1994. Influenza viruses were isolated mainly from fecal samples of dabbling ducks in their nesting places in central Alaska. The numbers of subtypes of 108 influenza virus isolates were 1 H2N3, 37 H3N8, 55 H4N6, 1 H7N3, 1 H8N2, 1 H10N2, 11 H10N7, and H10N9. Influenza viruses were also isolated from water samples of the lakes where they nest. Even in September of 1994 when the most ducks had left for migration to south, viruses were still isolated from the lake water. Phylogenetic analysis of the NP genes of the representative isolates showed that they belong to the North American lineage of avian influenza viruses, suggesting that the majority of the waterfowls breeding in central Alaska migrate to North America and not to Asia. The present results support the notion that influenza viruses have been maintained in waterfowl population by water-borne transmission and revealed the mechanism of year-by-year perpetuation of the viruses in the lakes where they breed.

Collective Josephson plasma resonance in the vortex state of Bi2Sr2CaCu2O8+ delta.

Abstract: We have measured the microwave surface resistance (30-60 GHz) for different crystallographic orientations in the vortex state of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$. A sharp magnetoabsorption resonance is observed below ${T}_{c}$ when ac electric fields and magnetic fields are applied parallel to the $c$ axis (${E}_{\mathrm{ac}}\ensuremath{\parallel}B\ensuremath{\parallel}c$). We argue that the observed resonance arises from collective Josephson plasma oscillations generated by interlayer Josephson currents. From the frequency and temperature dependence of the resonance, we discuss the interlayer phase coherence in the vortex liquid and solid states quantitatively.

Molecular Orientation and Ordered Structure of Benzenethiol Adsorbed on Gold(111)

Abstract: The adsorption of benzenethiol on Au(111) from aqueous solution has been investigated by using surface-enhanced infrared absorption spectroscopy (SEIRAS), scanning tunneling microscopy (STM), and cyclic voltammetry (CV). This molecule is dissociatively adsorbed on the surface as a Au benzenethiolate and forms a well-ordered monolayer with a commensurate (√13×√13)R13.9° symmetry. The ordered phase is formed within a few minutes in 0.1 mM aqueous solution, and further immersion of the substrate results in the deposition of multilayers. The phenyl ring is tilted about 30° from the surface normal in the monolayer. The coverage of this molecule is calculated to be 0.31 (or 0.71 nmol cm-2) from the (√13×√13)R13.9° symmetry, but it was estimated to be 0.23 (or 0.53 nmol cm-2) from the reductive desorption of the monolayer in alkaline solution. The discrepancy between the two measurements may be ascribed to the coadsorption of sulfur atoms and the presence of vacancies.

Single-Molecule Fluorescence Photoswitching of a Diarylethene−Perylenebisimide Dyad: Non-destructive Fluorescence Readout

Abstract: Single-molecule fluorescence photoswitching plays an essential role in ultrahigh-density (Tbits/inch2) optical memories and super-high-resolution fluorescence imaging. Although several fluorescent photochromic molecules and fluorescent proteins have been applied, so far, to optical memories and super-high-resolution imaging, their performance is unsatisfactory because of the absence of “non-destructive fluorescence readout capability”. Here we report on a new molecular design principle of a molecule having non-destructive readout capability. The molecule is composed of acceptor photochromic diarylethene and donor fluorescent perylenebisimide units. The fluorescence is reversibly quenched when the diarylethene unit converts between the open- and the closed-ring isomers upon irradiation with visible and UV light. The fluorescence quenching is based on an electron transfer from the donor to the acceptor units. The fluorescence photoswitching and non-destructive readout capability were demonstrated in solutio...

Short-Chain Fatty Acids Suppress Cholesterol Synthesis in Rat Liver and Intestine

Abstract: We previously showed that plasma cholesterol levels decreased following ingestion of a short-chain fatty acid (SCFA) mixture composed of sodium salts of acetic, propionic, and butyric acids simulating cecal fermentation products of sugar-beet fiber (SBF). In the present study, we investigated whether hepatic and small intestinal cholesterol synthesis is involved in the cholesterol-lowering effects of SCFA and SBF. In vitro (expt. 1) and in vivo (expt. 2) cholesterol synthesis rates and the diurnal pattern of SCFA concentrations in portal plasma (expt. 3) were studied in three separate experiments in rats fed diets containing the SCFA mixture, SBF (100 g/kg diet), or the fiber-free control diet. Cholesterol synthesis was measured using 3H2O as a tracer. The in vitro rate of cholesterol synthesis, measured using liver slices, was greater in the SBF group, but not in the SCFA group, than in the fiber-free control group. In contrast, the hepatic cholesterol synthesis rate in vivo was lower in the SCFA group, but not in the SBF group, than in the control group. The mucosal cholesterol synthesis rate for the whole small intestine was <50% of the hepatic rate. The rate in the proximal region was slightly but significantly lower in the SCFA group, and was significantly higher in the SBF group than in the fiber-free group. The rate in the distal small intestines was also significantly greater in the SBF group than in the fiber-free group. Plasma total cholesterol concentrations were lower in the SCFA and SBF groups than in the fiber-free group in both experiments 2 and 3. Diurnal changes in portal SCFA and cholesterol levels were studied in the experiment 3. SCFA concentrations increased rapidly after the start of feeding the SCFA diet, and changes in plasma cholesterol were the reciprocal of those observed in SCFA. These results show that a decrease in hepatic cholesterol synthesis rate mainly contributes to the lowering of plasma cholesterol in rats fed the SCFA mixture diet. Changes in portal SCFA and cholesterol concentrations support this conclusion. In SBF-fed rats, SCFA produced by cecal fermentation are possibly involved in lowering plasma cholesterol levels by negating the counteractive induction of hepatic cholesterol synthesis caused by an increase in bile acid excretion.