Nitrate and phosphate supplementation to increase toxin production by the marine dinoflagellate Alexandrium tamarense

Alexandrium tamarense toxins have great value in biotechnology research as well as important in connection with shellfish poisoning. The influence of nitrate or nitrate and phosphate supplementation on cell biomass and toxin content were investigated in batch cultures. When cultures at low nitrate (88.2 mu M NaNO3) Were supplemented with 793.8 mu M NaNO3 at day 10 the cell density and cellular toxin contents were increased by 6-29% and 20-76%, respectively, compared with controls, and maximal values were 43,600 cells/ml (day 38) and 0.91 pg/cell (day 31). Supplementation with nitrate at day 14 or with nitrate and phosphate at day 10/14 to the cultures did not increase the cell density compared with the non-supplemented middle nitrate or high phosphate (108 mu M NaH2PO4) cultures, respectively, but increased the cellular toxin contents by an average of 52%. The results showed that supplementation with nitrate or with nitrate and phosphate at different growth phases of the cultures increased toxin yield by an average of 46%. Supplementation with nitrate at selected times to maintain continuous low level of nitrate might contribute to the effective increase of toxin yield of A. tamarense. (c) 2005 Elsevier Ltd. All rights reserved.

Monitoring organochlorine pesticides and polychlorinated biphenyls in Baiyangdian Lake using microbial communities

We used polyurethane foam units (PFUs) to collect persistent organic pollutants (POPs) from four sites in Baiyangdian Lake in July 2003. Following extraction from the PFUs, relative concentrations of seven organochlorine pesticides (OCPs) and ten polychlorinated biphenyls (PCBs) were determined by gas chromatography. OCPs and PCBs were detected in the microbial communities from all the four sampling stations. In terms of the total concentration of POPs (OCPs+ PCBs), two river estuary stations had more POP (18.45 mu g/L and 9.77 mu g/L) than the two mid-lake stations (4.75 mu g/L and 5.21 mu g/L), indicating that Baiyangdian Lake was significantly impacted by inflow from the Fu River and Baigou River.

Electroabsorption modulator integrated with buried-ridge-stripe dual-core spot-size converter by quantum-well intermixing

A single shallow ridge electroabsorption modulator monolithically integrated with a buried-ridge-stripe dual-core spot-size converter at the input and output port was fabricated by combining quantum-well intermixing and dual-core integration techniques simultaneously, using only a two-step low-pressure metal-organic vapor phase epitaxial process, conventional photolithography, and a chemical wet etching process. The optical insertion loss of the modulator in the on-state and the dc extinction ratio between 0 and -3 V at 1550 nm was -7.5 and 16 dB, respectively. The 3-dB modulation bandwidth was more than 10.0 GHz in electrical-optical response.

InP-based optoelectronic devices for optical fiber communications

In this contribution we report the research and development of 1.55 mu m InGaAsP/InP gain-coupled DFB laser with an improved injection-carrier induced grating and of high performance 1.3 mu m and 1.55 mu m InGaAsP/InP FP and DFB lasers for communications. Long wavelength strained MQW laser diodes with a very low threshold current (7-10 mA) have been fabricated. Low pressure MOVPE technology has been employed for the preparation of the layered structure. A novel gain-coupled DFB laser structure with an improved injection-carrier modulated grating has been proposed and fabricated. The laser structures have been prepared by hybrid growth of MOVPE and LPE techniques and reasonably good characteristics have been achieved for resultant lasers. High performance 1.3 mu m and 1.55 mu m InGaAsP/InP DFB lasers have successfully been developed for CATV and trunk line optical fiber communication.

猕猴胚胎干细胞培养以及定向分化成神经细胞的研究

灵长类胚胎干细胞（Es）的研究不仅对理解生殖发育生物学的基础理论、而且对实现细胞替代治疗具有重要意义。当前灵长类ES细胞还有很多问题需要解决，如ES细胞培养体系的改进、ES细胞定向分化成高纯度特定组织细胞的可能性、有效性以及分化机制等问题。本文一方面概述了灵长类ES细胞相关领域的研究进展；另一方面，以称猴胚胎干细胞（rEs）为材料，在改善rES细胞的培养体系、提高其定向分化成神经前体细胞（NPs）和少突细胞的比率进行了研究。实验采用同源称猴细胞系作为饲养层培养rES细胞，并在此基础上利用肝生长因子（HGF）和GS诱导rES细胞定向分化成高纯度的NPs和少突细胞，并评价了NPs是否具有移植功能。主要结论如下：1）四种称猴细胞系（MOF、MESF、MFG和CMESF）可作为饲养层支持rES细胞的生长，保持ES自我更新的能力和分化的多能性。而且这几种称猴饲养层支持ES细胞生长的能力存在明显的差异，进一步的研究表明这些差异主要是由于基因表达种类以及表达量上的差异而导致的。2）采用HGF和GS作为诱导因子添加到NDCM液中，诱导rES细胞分化成可移植的NPs。实验结果如下：单独的HGF或GS仅能诱导ES细胞分化成65±8.3％和69±14％NPs，而HGF和GS的联合使用NPs的比率达到88.3±8.1％，进一步纯化后获得98±1.2％的NPs。获得的NPs能在体内、外分化成三个谱系神经细胞，并能整合到大鼠脑部，发生迁移和分化。25％的NPs细胞8周后仍保持存活状态，其中65-80％的细胞发生了不同程度的迁移，而且细胞在脑部的分化种类以及数目与细胞在体内所处的微环境具有重要的关系。亚克隆实验也进一步证明采用HGF＋GS获得的部分单个NPs具有神经干细胞的特性，也能在体内、外分化成三个谱系的神经细胞，而另外的却只能分化成其中的一、两种谱系的细胞。3）利用五步法，ES细胞能分化成75±6.8％的少突祖细胞和81土8．6％的成熟少突细胞。HGF通过抑制NPs的凋亡和缩短NPs的复制周期，共同促进NPs的增殖。HGF也能诱导HGF+G5获得的NPs分化成少突祖细胞和成熟少突细胞，并且促进少突细胞成熟。而且HGF促进NPs分化成少突细胞的能力受到GS的调控，单独HGF作用将导致ES细胞分化成神经元。本实验的结果为促进rES细胞相关领域的研究，以及ES细胞在神经系统疾病临床应用上提供信息，也为研究NPs和少突细胞的发育提供典型的细胞模型。

InP-based optoelectronic devices for optical fiber communications

In this contribution we report the research and development of 1.55 mu m InGaAsP/InP gain-coupled DFB laser with an improved injection-carrier induced grating and of high performance 1.3 mu m and 1.55 mu m InGaAsP/InP FP and DFB lasers for communications. Long wavelength strained MQW laser diodes with a very low threshold current (7-10 mA) have been fabricated. Low pressure MOVPE technology has been employed for the preparation of the layered structure. A novel gain-coupled DFB laser structure with an improved injection-carrier modulated grating has been proposed and fabricated. The laser structures have been prepared by hybrid growth of MOVPE and LPE techniques and reasonably good characteristics have been achieved for resultant lasers. High performance 1.3 mu m and 1.55 mu m InGaAsP/InP DFB lasers have successfully been developed for CATV and trunk line optical fiber communication.

不同长度β_2整合素_M亚基与ICAM-1的亲和性比较

<正>整合素作为细胞表面糖蛋白受体,介导细胞-细胞、细胞-胞外基质以及细胞-病原体间粘附和信息传递,在免疫应答、凝血反应、炎症反应、肿瘤转移和创伤愈合等许多病理生理过程中起重要作用。整合素是由α、β两个亚基非共价结合而成的异源二聚体,其结构类似于两条近平行的腿部支撑着一个球形的头部。研究表明,β_2整合素_M亚基头部的.domain为与配体直接作用的结构域,并可通过"open"或"close"的构象变化