稀土元素镧在植物细胞中超微结构定位及与钙、铝关系研究

本文主要利用等离子体发射光谱元素含量分析( ICP)、亚细胞定位观察技术、以及电镜与能谱分析相结合技术，研究镧在绿豆(Phmeatus radiatus L.)幼苗不同部位组织细胞中的进入、运转、分配、含量和超微结构定位及与钙、铝关系。在全营养液加镧和缺钙营养液加镧处理的幼苗中，细胞超微结构受到不同程度影响，但其内未检测到镧。无离子水加镧处理幼苗，在低浓度、短时间条件下，镧进入、分布在质膜以外质外体系统中。高浓度镧处理时，镧沉淀能进入细胞内，并常看到堵塞胞间连丝，在质膜以外发现解体物质穿壁转移，并在壁中形成明暗相间的染色带。镧在植株中运输层层受阻，由根向叶其含量逐渐减少，而钙含量变化呈负相关，表明镧钙之间存在拮抗作用。 用焦锑酸钙的电镜细胞化学方法与能谱分析技术相结合，研究镧对细胞内Ca2+定位分布的影响，发现镧、钙沉淀颗粒的差异。在镧胁迫下，细胞质和核中Ca2+增多，液泡中Ca2+趋向于沿被膜分布，细胞结构受到破坏，说明镧胁迫下Ca2+水平增加与膜透性变化和Ca2+_CaM相关的许多生理生化过程有关。 初步探讨铝的毒害机理，发现铝也能进行超微结构定位观察，铝通过拮抗钙起作用，其作用机制与镧相似。

Fluid flow induced calcium response in bone cell network

In our previous work, bone cell networks with controlled spacing and functional intercellular gap junctions had been successfully established by using microcontact printing and self assembled monolayers technologies [Guo, X. E., E. Takai, X. Jiang, Q. Xu, G. M. Whitesides, J. T. Yardley, C. T. Hung, E. M. Chow, T. Hantschel, and K. D. Costa. Mol. Cell. Biomech. 3:95-107, 2006]. The present study investigated the calcium response and the underlying signaling pathways in patterned bone cell networks exposed to a steady fluid flow. The glass slides with cell networks were separated into eight groups for treatment with specific pharmacological agents that inhibit pathways significant in bone cell calcium signaling. The calcium transients of the network were recorded and quantitatively evaluated with a set of network parameters. The results showed that 18 alpha-GA (gap junction blocker), suramin (ATP inhibitor), and thapsigargin (depleting intracellular calcium stores) significantly reduced the occurrence of multiple calcium peaks, which were visually obvious in the untreated group. The number of responsive peaks also decreased slightly yet significantly when either the COX-2/PGE(2) or the NOS/nitric oxide pathway was disrupted. Different from all other groups, cells treated with 18 alpha-GA maintained a high concentration of intracellular calcium following the first peak. In the absence of calcium in the culture medium, the intracellular calcium concentration decreased slowly with fluid flow without any calcium transients observed. These findings have identified important factors in the flow mediated calcium signaling of bone cells within a patterned network.

Multicolor luminescence in oxygen-deficient Tb3+;doped calcium aluminogermanate glasses

In this paper, we report on the multicolor luminescence in oxygen-deficient Tb3+-doped calcium aluminogermanate glasses. A simple method was proposed to control oxygen-deficient defects in glasses by adding metal Al instead of the corresponding oxide (Al2O3), resulting in efficient blue and red emissions from Tb3+-undoped glasses with 300 and 380 nm excitation wavelengths, respectively. Moreover, in Tb3+-doped oxygen-deficient glasses, bright three-color (sky-blue, green or yellow, and red) luminescence was observed with 300, 380, and 395 nm excitation wavelengths, respectively. These glasses are useful for the fabrication of white light-emitting diode (LED) lighting.

Spectral investigation of Yb-doped calcium pyroniobate crystal

Ytterbium-doped calcium pyroniobate single crystal has been grown for the first time. Spectral properties of Yb: Ca2Nb2O7 were investigated by emission and absorption spectra. Its cooperative luminescence and fluorescence lifetime were also studied. Yb ions in Ca2Nb2O7 showed very broad absorption and emission bandwidth and relatively large absorption and emission cross-sections. Along with other optical properties, this Yb-doped crystal would be a potential self-frequency doubling femtosecond laser gain material. (C) 2007 Published by Elsevier B.V.