Cells of the central nervous system (CNS) normally do not express detectable levels of major histocompatibility complex (MHC) Class I antigens. However, MHC Class I expression can be induced after virus infection. We tested the hypothesis that virus-induced Class I expression is mediated by lymphocytes or cytokines using lymphocyte- and cytokine-deficient mice. We used Theiler's murine encephalomyelitis virus (TMEV), which induces CNS demyelination that maps genetically to the D region of MHC Class I and is associated with high levels of Class I products. TMEV infection of severe combined immunodeficiency (SCID) and recombination activation gene-1-deficient mice, which lack B and T lymphocytes, resulted in equivalent H-2D and H-2K expression in brain and spinal cord, according to analysis of the area and intensity of immunoperoxidase staining. Class I antigens were demonstrated as early as 6 hours after infection, and they were more widely distributed than viral RNA, indicating that expression was induced indirectly via a soluble factor. To determine whether cytokines induced the expression, we infected mice lacking receptors for interferon-alpha/beta (IFN-alpha/beta R (-/-)), interferon-gamma (IFN-gamma R(-/-)), and tumor necrosis factor-alpha (TNFRp55(-/-)). TMEV-infected IFN-gamma R(-/-) and TN-FRp55(-/-) mice expressed Class I antigens in the CNS, whereas IFN-alpha/beta R(-/-) mice did not, establishing that IFN-alpha/beta mediated the expression. In contrast to the equivalent expression in SCID mice, we observed greater area and higher intensity of H-2D versus H-2K antigens in infected SCID mice reconstituted with normal spleen cells. Collectively, the data indicate that after TMEV infection, early generalized MHC Class I expression is mediated by IFN-alpha/beta independently of lymphocytes, but the differential regulation of H-2D over H-2K may be controlled by B and/or T lymphocytes. 相似文献
A novel chirped return-to-zero transmitter with a simplified configuration that uses an electro-absorption modulator is proposed. Using this transmitter, high fibre input power is achieved (up to +14 dbm) in repeaterless 20 Gbit/s transmission over standard singlemode fibres 相似文献
This work presents a gain-cell solution in which a novel ultrathin polysilicon film transistor provides the basis for dense and low-power embedded random-access memory (RAM). This is made possible by the new transistor's 2-nm-thick channel, which realizes a quantum-confinement effect that produces a low leakage current value of only 10/sup -19/ A at room temperature. The memory has the potential to solve the power and stability problems that static RAM (SRAM) is going to face in the very near future. 相似文献
We disclose herein an efficient enantioselective conjugate addition reaction between coumarin‐3‐carboxylic acids and malonic acid half thioesters (MAHTs). The reaction was catalyzed by N‐heteroarenesulfonyl Cinchona alkaloid amides to afford double‐decarboxylative conjugate addition products in good yield with high enantioselectivity. The reaction of various coumarin‐3‐carboxylic acids with MAHTs gave products in high yield with high enantioselectivity.
Endo-beta-N-acetylglucosaminidase from Arthrobacter protophormiae (Endo-A) has transglycosylation activity, and high-mannose-type oligosaccharides are transferred to suitable glycosides as acceptor substrates. The acceptor specificity of Endo-A-catalyzed transglycosylation toward various disaccharides was investigated. To identify an effective acceptor for the transglycosylation by Endo-A, the reaction was carried out using various disaccharides. Endo-A transferred high-mannose-type oligosaccharides more efficiently to beta-linked disaccharides (cellobiose, gentiobiose, sophorose, and laminaribiose) than to alpha-linked disaccharides (isomaltose, maltose, nigerose, kojibiose, and trehalose) as acceptor substrates. The transglycosylation products, (Man)6GlcNAc-Glc-beta-Glc, were more rapidly hydrolyzed than (Man)6GlcNAc-Glc-alpha-Glc. These results indicate that Endo-A recognizes the anomeric configuration of the acceptor substrates, and beta-linked glycosides are suitable for the synthesis of transglycosylation products. 相似文献
Based on the previous success of adding ultra-fine carbon–PVA (polyvinyl alcohol) colloid solution to restore performance of weak batteries, a large scale test programme of practical batteries including those used in forklift, golf cart, taxi cab, truck and bus applications from 150 companies was carried out. More than 95% of the tested batteries exhibited excellent recovery in performance parameters including the specific gravity (S.G.), voltage and operation time (Ah capacity). The work reported here includes basic research studies to understand better the beneficial action of the carbon–PVA colloid additive. 相似文献
Effect of monoolein surfactant which promotes n-hexane to dissolve in water was investigated to enhance the carbon nanoparticle (CNP) synthesis by arc discharge in liquid. The production rate of CNPs consisting of multi-shelled fullerenes and multi-walled carbon nanotubes was increased by the addition of the n-hexane to water with support of monoolein surfactant. An optimal amount of monoolein led to the maximal production rate of CNPs which was ca. two-fold higher than that obtained from a pure water system. This effect is ascribed to the role of n-hexane and monoolein to provide carbon clusters to the arc reactive zone. The hydrodynamic particle sizes of CNPs and their crystallinity were also enhanced by the addition of these organic compounds. As the vapor pressure of the organic component is significantly suppressed, the proposed method is much safer than that using pure organic liquid. 相似文献
Abstract— By applying an energy‐recovery method to their driver circuits, the circuit power consumption of plasma displays can be reduced. However, further power reduction is necessary for large‐sized higher‐resolution displays such as used for Super HDTV. The ideal adiabatic charge method has been proven to be able to minimize circuit resistive element power consumption to 81 % of the conventional energy‐recovery‐circuit resistive‐element loss. An experimental pseudo‐adiabatic charge circuit that reduces the power consumption to about 90% of a conventional circuit has been demonstrated. The power consumption caused by both the resistance loss and the discharge loss of the switching‐element parasitic capacitances was analyzed. 相似文献
We report on the experimental observation of surface plasmon resonance in Cu nanowires fabricated by shadow deposition method. When the incident light is polarized perpendicular to the wire axes, plasmon maxima appeared at about 2.3 eV in the absorption spectra. Plasmon resonance appeared at lower photon energy when the incident light is polarized parallel to the wire axes. Resonance peaks move to lower energy when the nanowire widths are increased. We have found that finite-difference time-domain (FDTD) simulation gives better results than Maxwell–Garnett model in explaining the relation between the light polarization and the energies of the observed absorption maxima. 相似文献