Developmental change of the inhibition by lead of NMDA-activated currents in cultured hippocampal neurons

The inhibition of N-methyl-D-aspartate (NMDA)-activated current in cultured fetal rat hippocampal neurons by Pb2+ was investigated at various stages of cell development. Pb2+ selectively inhibited NMDA currents recorded from young cultured neurons. In the first week of culture, Pb2+ showed the most prominent inhibition, which was gradually attenuated in the following weeks. Pb2+'s action was selective for NMDA- as opposed to either kainate- or quisqualate-induced currents. The current-voltage relationship for NMDA-induced currents in the presence of Pb2+ revealed that the effect of this cation was voltage-independent, which suggested that the site of interaction of Pb2+ with the NMDA receptor/channel is located outside the membrane electric field. Single channel studies showed that Pb2+ reduced the frequency but not the lifetime of the NMDA-activated single channel currents. Further evaluation of the mechanism of action of Pb2+ on the NMDA receptor demonstrated that this cation is a noncompetitive antagonist of both NMDA and glycine. We have demonstrated that the NMDA-induced whole cell currents change along with cell development, and the effects of Pb2+ are also dependent upon age of culture. The NMDA-induced currents in cultured rat hippocampal neurons had two components, one that decayed rapidly and another that decayed slowly. The fast component was clearly observed at concentrations of glycine higher than 1 microM, whereas the slow component reached its maximum amplitude at the glycine concentration of 1 microM. Moreover, the rapidly decaying component of NMDA-evoked whole cell currents was predominant in young cultured neurons, and its contribution to the total current was reduced in old cultured neurons.(ABSTRACT TRUNCATED AT 250 WORDS)     

Human tyrosinase inhibitor in rum distillate wastewater

An inhibitor of human tyrosinase activity in rum distillate wastewater was isolated and identified as (S)-(+)-imperanene (1). (S)-(+)-Imperanene significantly inhibited tyrosinase isolated from HMV-II cells (IC(50) 1.85 mM). Inhibition kinetics studies revealed that imperanene is a competitive inhibitor of tyrosinase when L-3,4-dihydroxyphenylalanine is used as the substrate. The inhibitory activities of 1, O-beta-D-glucopyranosyl imperanene (2) and O-beta-D-glucopyranosyl-3-methoxyl imperanene (3) were 1>2>3.     

Quantum theory of spontaneous emission from a two-level atom in aone-dimensional cavity with output coupling

A nonperturbative fully quantum-theoretical analysis describing the transient spontaneous emission of an initially excited two-level atom in a one-dimensional cavity with output coupling is presented. A delay-differential equation for the probability amplitude of the upper atomic state is strictly derived from the Schrodinger equation. With this equation, both the time evolution of the atomic state and the emission spectrum are calculated. Furthermore, the mode function makes the calculations of emitted fields both inside and outside the cavity possible. The calculated result of the vacuum Rabi oscillation in an underdamped cavity and the result of enhanced spontaneous emission rate in an overdamped cavity are presented. A retardation-governed revival of the upper atomic state is predicted. The calculated results also show the inhibition of spontaneous emission by detuning or by setting the atom at a node     

Power enhancement in argon II narrow-tube lasers due to zeeman effect by a transverse magnetic field

The role of the Zeeman effect for the power enhancement of a small-bore argon ion laser (488.0 nm) by applying the transverse magnetic field has been investigated both experimentally and theoretically. The σ-polarized laser has a larger output power than the π-polarized laser in the wide range of magnetic field strength. Specifically, at weak magnetic fields, enhancement occurred only for the σ-polarized laser. The experimental results are interpreted in terms of the semiclassical theory of the Zeeman laser. A narrow spectrum envelope is observed in the σ-polarized laser. In the case of internal mirrors without Brewster window, it is demonstrated experimentally that π and σ polarization coexist and compete with each other.     

Subjective Evaluation of Multi-Channel Stereophony for HDTV

In order to develop sound systems for HDTV, experiments were carried out with seven sound reproduction systems to assess their sensation of reality, sound spaciousness and other qualities. The results suggest that (1) it is desirable to use four sound signals in order to reproduce a better sensation of reality, (2) it is desirable to use three sound signals in front of observers and one sound signal at the rear of observers in order to maintain a better correspondence between the picture direction and the sound localization.     

Hierarchical structures of dendritic polymers

Dendritic polymers' highly specific and three‐dimensional architectures set them apart from linear and slightly branched polymers. Their unique properties also allow them to form hierarchical organizations, which can be classified as planar or non‐planar. The preparation of a planar hierarchy consisting of dendritic polymers can be achieved by conventional techniques of adsorption or Langmuir monolayer and Langmuir–Blodgett accumulation, and the resultant hierarchy is well ordered. Non‐planar hierarchies are built on non‐planar scaffolds, for example by self‐assembly. In this mini‐review, the practical/potential applications of dendritic polymers such as for electrical or optical devices, sensing systems, or medical diagnosis are also reviewed in association with their structures. Copyright © 2009 Society of Chemical Industry     

Synthesis of beta-cyclodextrin-modified water-dispersible Ag-TiO2 core-shell nanoparticles and their photocatalytic activity

The beta-cyclodextrin-modified Ag-TiO2 core-shell nanoparticles were prepared by sodium borohydrate reduction of AgNO3 and the subsequent hydrolysis of the tetraisopropyl orthotitanate in an aqueous medium. Inversely in the preparation of beta-cyclodextrin-modified TiO2-Ag core-shell nanoparticles, first hydrolysis and then following reduction were carried out. The synthesized spherical core-shell nanoparticles were highly water-dispersible and had an average diameter in the range of 9 to 12 nm. A significant shifting of surface plasmon band was observed for the synthesized Ag-TiO2 and TiO2-Ag core-shell nanoparticles. On a model reaction, namely, the photodegradation of phenol by the UV light irradiation, the photocatalytic property of TiO2 nanoparticles was enhanced, when the Ag nanoparticle was embedded in the core of TiO2 nanoparticles but TiO2 nanoparticles coated by Ag shell decreased the photocatalytic property of TiO2 nanoparticles. The mechanism is ascribed to the surface plasmon characteristics of Ag in the core of the TiO2 nanoparticles under the acceleration by host-guest inclusion characteristics.     

Mean field theory of optical bistability in a phase-conjugate resonator using nearly degenerate four-wave mixing

A mean field theory of nearly-degenerate four-wave mixing is developed for the optical bistability, which has recently been found in a phase-conjugate resonator consisting of a normal mirror and a phase-conjugate mirror under relatively strong pumping. The bistability in transmission of the probe beam occurs as the mirror separation or the probe offset frequency is changed, but for a limited range of probe beam intensity. This behavior is explained as occurring under injection-locked conditions because of combined effects of tilting and broadening, or narrowing of the resonance curves due to nonlinearities in the phase-conjugate reflectivity arising from pump depletion.     

Stacked Ge islands for photovoltaic applications

Stacked Ge islands formed via the Stranski–Krastanov growth mode were incorporated into the intrinsic layer of Si-based pin diode to improve the performance of the solar cells in the near-infrared regime. The onset of the external quantum efficiency was extended up to around 1.4 mm for the solar cells with stacked Ge islands. The quantum efficiency was found to increase with increasing number of stacking, and the onset of the photocurrent response was in good agreement withroom-temperature photoluminescence energy of the Ge islands. These results manifest that the Ge islands did play a role toincrease the quantum efficiency. Furthermore, a part of electron-hole pairs generated within Ge islands was separated by the internal electric field and contribute to the photocurrent.