Bis(7)-tacrine/tacrine对大鼠DRG神经元延时整流钾通道电流的调制作用

目的研究乙酰胆碱酯酶抑制剂bis(7)-tacrine/tac-rine[bis(7)-tetrahydroaminacrine]对大鼠DRG神经元的延时整流钾通道电流的调制作用。方法在急性分离的DRG神经元标本上,采用全细胞膜片钳技术记录钾通道电流,研究bis(7)-tacrine/tacrine对DRG神经元延时整流钾通道电流的影响和作用。结果 bis(7)-tacrine对延迟整流钾通道电流IDR具有浓度依赖性的抑制作用,其半量效浓度为(IC50)(0.72±0.05)μmol.L-1,而tacrine抑制的半量效浓度(IC50)(58.3±3.7)μmol.L-1。结论两种药物对DRG延时整流钾通道电流有浓度依赖性的抑制作用,bis(7)-tacrine的抑制强度高一个数量级,有利于抑制神经元的钾通道过于激活和兴奋,预防胞内钾离子过度丢失而引起的神经元凋亡,起到神经保护的作用。

Bis(7)-tacrine protects retinal ganglion cells against excitotoxicity via NMDA receptor inhibition

AIM: To investigate whether bis (7)-tacrine, a multifunctional drug, inhibits N-methyl-D-aspartate (NMDA) -activated current in retinal ganglion cells (RGC) and provides neuroprotection against retinal cell damage. METHODS: Purified RGC cultures were obtained from retinas of 1-3 days old Sprague-Dawley (SD) rats, following a two-step immunopanning procedure. After 7 days of cultivation, the inhibition of NMDA-activated current by bis(7) -tacrine was measured by using patch-clamp recording techniques. In animal experiments, RGCs were damaged after intravitreal injection of NMDA (5 mu L, 40nmol) in adult rats. Bis (7)-tacrine(0.05, 0.1, 0.2mg/kg) or memantine(20mg/kg) was intraperitoneal administered to the rats fifteen minutes before intravitreally injection of NMDA. RGC damage was analyzed by histologic techniques, TUNEL and retrograde labeling techniques. RESULTS: Whole-cell patch-clamp recordings demonstrated that NMDA (30 mu mol/L) resulted in approximately -50 pA inward currents that were blocked by bis (7)-tacrine (1 mu mol/L). Histological examination and retrograde labeling analysis revealed that bis (7)-tacrine induced a significant neuroprotective effect against NMDA-induced cell damage 7 days after NMDA injection. TUNEL staining showed that pretreatment with bis(7)-tacrine was effective in ameliorating NMDA-induced apoptotic cell loss in the retinal ganglion cell layer 18 hours after injection. CONCLUSION: Bis (7)-tacrine possesses remarkable neuroprotective activities against retinal excitotoxicity through inhibition of NMDA receptors.

Bis(7)-Tacrine, a Promising Anti-Alzheimer's Agent,Attenuates Glutamate-Induced Cell Injury in Primary Cultured Cerebrocortical Neurons of Rats

The effects of bis(7) tacrine, a novel dimeric acetylcholinesterase (AChE) inhibitor, on glutamate induced cell injury were investigated in primary cerebral cortical neurons of rats. Exposure of cultured neurons (12 days after plating) to 0.5 mmol/L glutamate for 30 min resulted in significant cell damage. Pretreatment with bis(7) tacrine (0.03 1.0 μmol/L) reduced the glutamate induced neurotoxicity in a concentration dependent manner and the maximal response was seen at 1 μmol/L with approximately 30% protection. A receptor binding assay showed that bis(7) tacrine can completely displace MK 801 binding to rat cortical membrane with an IC 50 of 0.57 μmol/L. These findings suggest that bis(7) tacrine can directly interact with N methyl D aspartate receptor channel complex, which may contribute to the inhibitor's protective effects against glutamate induced excitotoxicity. Thus, it is possible that anti glutamate/anti AChE synergism is responsible for potentially better Alzheimer's therapy of bis(7) tacrine relative to tacrine.

Bis(7)-Tacrine Ameliorates Cognitive Impairment Caused by Cerebral Hypoperfusion in Rats

The effects ofbis(7)-tacrine, a novel acetylcholinesterase inhibitor, on cognitive impairment and neuronal degeneration induced by permanent ligation of bilateral common carotid arteries (2VO) were investigated using the Morris water maze in rats. Once daily oral administration ofbis(7)-tacrine (0.025, 0.05 and 0.1 mg?kg?1) was started 14 days after 2VO operation. Over a three-week treatmentbis(7)-tacrine effectively reversed 2VO-induced spatial memory deficits in a dose-dependent fashion. Furthermore, histological observation showedbis(7)-tacrine decreased the neuropathological changes in the 2VO rats brain. These results suggest thatbis(7)-tacrine has therapeutic potential for the treatment of dementia caused by chronic cerebral hypoperfusion.

Inhibition of N-methyl-D-aspartate-activated Current by Bis(7)-tacrine in HEK-293 Cells Expressing NR1/NR2A or NR1/NR2B Receptors

In normal rat forebrain, the NR1/NR2A and NR1/NR2B dimmers are the main constitutional forms of NMDA receptors. The present study was carried out to determine the functional properties of the heteromeric NMDA receptor subunits and their inhibition by bis(7)-tacrine (B7T). Rat NR1, NR2A and NR2B cDNAs were transfected into human embryonic kidney 293 cells (HEK-293).The inhibition of NMDA-activated currents by B7T was detected in HEK-293 cell expressing NR1/NR2A or NR1/NR2B receptors by using whole-cell patch-clamp techniques. The results showed that in HEK-293 cells expressing NR1/NR2A receptor, 1μmol/L B7T inhibited 30μmol/L NMDA- and 1000μmol/L NMDA-activated steady-state currents by 46% and 40%, respectively (P>0.05; n=5), suggesting that the inhibition of B7T on NR1/NR2A receptor doesn’t depend on NMDA concentration, which is consistent with a non-competitive mechanism of inhibition. But for the NR1/NR2B receptor, 1μmol/L B7T inhibited 30μmol/L NMDA- and 1000 μmol/L NMDA-activated steady-state currents by 61% and 13%, re-spectively (P<0.05; n=6), showing that B7T appears to be competitive with NMDA. In addition, simultaneous application of 1μmol/L B7T and 1000μmol/L NMDA produced a moderate inhibition of peak NMDA-activated current, followed by a gradual decline of the current to a steady state. However, the gradual onset of inhibition produced by B7T applied simultaneously with NMDA was eliminated when B7T was given 5s before NMDA. These results suggested that B7T inhibition of NMDA current mediated by NR1/NR2B receptor was slow onset, and it did not depend on the presence of the agonist. With holding potentials ranging from -50 to +50 mV, the B7T inhibition rate of NMDA currents didn’t change significantly, and neither did the reversal potential. We are led to conclude that the NR1/NR2B recombinant receptor can serve as a very useful model for studying the molecular mechanism of NMDA receptor inhibition by B7T.

Promoting dynamic recrystallization and improving strength and ductility of Mg-7Bi alloy through Al addition

This study investigated the influence of the addition of Al to a Mg-7Bi(B7,wt%)alloy,particularly its recrystallization behavior during extrusion and its resulting mechanical properties.The addition of 2 wt%Al to the B7 alloy resulted in a lower grain size,a reduction in the number density of fine Mg3Bi2 particles,and a higher area fraction of relatively coarse Mg3Bi2 particles in the extrusion billet.These microstructural changes increased the nucleation sites for recrystallization,reduced the Zener pinning effect,and enhanced particle-stimulated nucleation,all of which promoted dynamic recrystallization behavior during extrusion.As a result,the area fraction of recrystallized grains in the extruded alloy increased from 77%to 94%.The extruded B7 alloy exhibited a strong<10-10>fiber texture,whereas the extruded Mg-7Bi-2Al(BA72)alloy had a weak<10-10>-<2-1-10>texture,which was attributed to the minimal presence of unrecrystallized grains and the dispersed orientation of the recrystallized grains.The tensile yield strength(TYS)of the extruded BA72 alloy was higher than that of the extruded B7 alloy(170 and 124 MPa,respectively),which resulted from the enhanced grain-boundary and solid-solution strengthening effects.The tensile elongation(EL)of the BA72 alloy also exceeded that of the B7 alloy(20.3%and 6.1%,respectively),the result of the uniform formation of fine twins under tension in the former and the formation of a few coarse twins among the unrecrystallized grains in the latter.Consequently,the addition of a small amount of Al to the B7 alloy significantly improved both the strength and ductility of the extruded alloy,resulting in a remarkable increase in the product of the TYS and EL from 756 to 3451 MPa%and expanding its potential range of applications as a lightweight extruded structural component.

Extraction of Cesium from the Irradiated Nuclear Waste by 4(5),4'(5')-Bis[1-hydroxyalkylbenzo]-21-crown-7

Bis[1-hydroxyalkylbenzo]-21-crown-7 (A-C) have been synthesized by ) two-step reactions from dibenzo-21-crown-7 (DB21C7). Extraction of cesium cation from nitric acid solutions by A-C has been investigated in nitromethane. Under the conditions of various concentration of HNO3 or NaNO3, the extractabilities of A and B were superior to that of DB21C7.

A SENSITIZED PHOTOINITIATION SYSTEM ——BIS (7-DIETHYLAMINO COUMARIN ) KETONE-3 AND DIPHENYLIODONIUM SALT COMBINATION

Bis (7- diethylaminocoumarin) ketone- 3(DACK) and diphenyliodonium salt (DPIO)combination as an effective photoinitiation system for radical polymerization has been investigated. The sensitized photolysis of DACK/DPIO leads to bleaching of DACK and decomposition of DPIO to generate initiating radical species. The electron transfer sensitization occurs mainly from the triplet state of DACK. The photobleaching obeyed a second-order kinetics and the rate constant was evaluated to be 31.3mol^(-1)·1·s^(-1) Photopolymerization of MMA initiated by DACK/DPIO was carried out in acetonitrile solution. The polymerization rate was found to be proportional to the concentration of DACK, DPIO and MMA with the exponents of 0.34, 0.40 and 1.0 respectively. The initiated efficiency is comparable to those of small molecular ketones.The sensitized photoinitiation mechanism has been discussed.

Bi_2Ti_2O_7/TiO_2复合纤维:原位水热合成及光催化性能

采用静电纺丝技术制备的TiO2纤维作为模板和反应物,通过原位水热合成了具有异质结构的Bi2Ti2O7/TiO2复合纤维。利用X射线衍射(XRD)、扫描电镜(SEM)、能量散射光谱(EDS)、高分辨透射电镜(HRTEM)和紫外可见吸收光谱(UV-Vis)等分析测试手段对样品的结构和形貌进行表征。以罗丹明B为模拟有机污染物进行光催化降解实验。结果表明:花状Bi2Ti2O7纳米结构均匀地生长在TiO2纤维上,制备了Bi2Ti2O7与TiO2相复合的光催化材料,其光谱响应范围拓宽至可见光区,与纯TiO2纤维相比可见光催化活性显著提高,且易于分离、回收和循环使用。初步探讨了Bi2Ti2O7/TiO2异质结的生长机制和光催化活性提高机理。

Bi_2Ti_2O_7/TiO_2异质结对盐酸四环素的光催化降解效果评价

采用溶剂热法通过控制溶剂比获得3种不同形貌的Bi_2Ti_2O_7/TiO_2异质结(BT-0、BT-5、BT-10).采用X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)、低温氮气吸附-脱附(BET)、Zeta电位仪和循环伏安实验等对催化剂的晶型结构、形貌和性能进行表征.研究了异质结对盐酸四环素(TC)的吸附和光催化降解性能,考察了溶液的初始p H、盐酸四环素的初始浓度和催化剂投加量对盐酸四环素光催化降解效率的影响.实验结果表明,橄榄球状Bi_2Ti_2O_7/TiO_2异质结具有更大的比表面积和较多孔型,对盐酸四环素的吸附去除率更大.在异质结加入量为0.1 g/L,250 W金卤灯下反应180 min,BT-0、BT-5和BT-10异质结对浓度为0.05 g/L初始pH为8.9的盐酸四环素去除率分别为92.4%、99.8%、97%.异质结对盐酸四环素的光降解反应符合拟一级动力学规律.

脉冲激光沉积法合成Bi2Ti2O7介电薄膜及其光吸收特性

控制单脉冲能量为350mJ,脉冲频率为5Hz,控制合适的基底温度,利用脉冲激光沉积法制备出Bi2Ti2O7薄膜材料.结果发现,SiO2基底温度控制在500～600℃,均能获得纯的Bi2Ti2O7薄膜.其介电常数约18.2左右,随频率变化比较稳定,介电损耗约0.015左右,并且在紫外波段200～450nm有着较强的紫外吸收能力,有望在微电子器件中获得应用.

沉积氧压对Bi_(1.5)ZnNb_(1.5)O_7薄膜的结构和介电特性的影响

采用固相反应法合成具有焦绿石立方结构的Bi1.5ZnNb1.5O7(BZN)陶瓷靶材,采用脉冲激光沉积法在Pt/SiO2/Si(100)基片上制备立方BZN薄膜。研究了沉积氧压的变化对薄膜的结晶性能,微观形貌以及介电性能的影响。结果表明:沉积的BZN薄膜都呈现出立方焦绿石单相结构,但是薄膜的取向随氧压变化而变化。当沉积氧压为10 Pa时,薄膜的(222)晶面拥有最强的择优取向。随着氧压的升高,BZN薄膜的介电常数明显降低。在10 Pa氧压下沉积的BZN薄膜展示出介电可调特性为5%(500 kV/cm)。

Bi_2Ti_2O_7薄膜的自组装法制备及表征(英文)

以Bi(NO3)3·5H2O和Ti(OC4H9)4为原料,采用自组装单层膜技术,在负载有功能化三氯十八烷基硅烷(octadecyl-trichloro-silane,OTS)的FTO基板上制备了Bi2Ti2O7薄膜。基板表面的亲水性测试表明,紫外照射使OTS自组装单层膜表面由疏水转变为亲水,实现功能化。借助X射线衍射(XRD)、X射线能量色散谱(EDS)、扫描电子显微镜(SEM)和原子力显微镜(AFM)分析分别对Bi2Ti2O7薄膜的组成、结构和微观形貌进行了表征。结果表明,沉积溶液浓度为0.02 mol·L-1时,所得Bi2Ti2O7薄膜均匀致密。560℃热处理1 h、厚度为0.4μm的Bi2Ti2O7薄膜在100 kHz的介电常数为153,介电损耗为0.089。

不同衬底温度下生长的Bi_(1.5)Zn_(1.0)Nb_(1.5)O_(7.0)薄膜的XPS研究

采用固相反应法合成具有焦绿石立方结构的Bi1.5Zn1.0Nb1.5O7（BZN）陶瓷靶材,采用脉冲激光沉积法在Pt/TiO2/SiO2/Si（100）基片制备立方BZN薄膜,衬底温度在500~700℃范围内变化。X射线衍射测量结果表明：当在500℃沉积BZN薄膜时,薄膜呈现出无定形态结构。随着衬底温度增加到550℃,薄膜开始晶化,并且显示出立方焦绿石结构。X射线光电子能谱也被用来研究BZN薄膜的结构状态和元素价态。测试得到的全谱表明：在BZN薄膜中,除了用于定标的C元素之外,只有Bi、Zn、Nb、O元素的特征峰,此外有Ti2p特征峰出现,可能来自底电极的TiO2缓冲层。各元素的窄谱扫描表明：Bi,Zn,Nb,O四种元素的化学价态分别是＋3,＋2,＋5,-2。BZN薄膜在550℃结晶,随着衬底温度升高到600℃,金属阳离子的结合能的峰位向高能方向移动,然而O1s的特征峰位也向高能方向移动,这归因于薄膜中存在的氧空位。

熔盐法制备Bi_(1.5)ZnNb_(1.5)O_7陶瓷粉体

以Bi2O3,ZnO和Nb2O5为原料,KCl为熔盐,用熔盐法合成了单相Bi1.5ZnNb1.5O7陶瓷粉体。XRD和SEM分析表明,在950～1000℃,合成了单相Bi1.5ZnNb1.5O7粉体,粉体呈颗粒状,尺寸约2～5μm。研究了合成温度、熔盐含量和保温时间对粉体颗粒形貌和尺寸的影响。结果表明,合成温度对Bi1.5ZnNb1.5O7粉体形貌和尺寸影响较大,熔盐含量和保温时间对其形貌和尺寸的影响相对较小。

具有非对称中心结构的硼酸盐Bi_2ZnB_2O_7的合成、晶体结构和光学性质(英文)

具有非对称中心结构的硼酸盐Bi2ZnB2O7由固相反应法在低于700℃下制备得到。X射线单晶结构分析表明,该化合物以正交空间群Pba2结晶,晶体学参数为:a=1.0819(2)nm,b=1.1023(2)nm,c=0.4890(1)nm,Z=4。其晶体结构中包含分别由[BO3]3-和[BO4]5-组成的[B2O5]4-和[B2O7]8-基团,它们被[ZnO4]四面体通过共用O原子的方式连接成二维2∞[ZnB2O7]6-层,这些层由Bi3 +离子进一步结合形成三维网。红外光谱证实了[BO3]3-和[BO4]5-基团的存在,粉末倍频效应测试表明,其强度为KDP(KH2PO4)的4倍,UV漫反射光谱表明该物质吸收边约为360 nm。

Bi^(3＋)掺杂对Sr2MgSi2O7：Eu^(2＋)荧光粉的结构及发光性能的影响(英文)

采用溶胶-凝胶法在还原气氛下制备了Sr2MgSi2O7∶Eu2+,xBi3+(x=0,0.02,0.04,0.06,0.08,0.1)荧光粉,并用XRD、TG-DTA及激发与发射谱仪对样品的结构及发光性能进行了表征。结果发现:单掺杂Bi3+的Sr2MgSi2O7样品的发射光谱所用的材料的激发光谱为一主峰为286 nm的宽带谱,这是由于激发态时Bi3+的3P1→1S0电子能级跃迁而造成的;单掺杂Eu2+的Sr2MgSi2O7样品的发射光谱所用的材料的激发光谱为一主峰为358 nm的宽带谱,这是典型的Eu2+的4f65d1→4f7跃迁而引起的。当Bi3+离子掺杂到Sr2MgSi2O7∶Eu2+样品的摩尔分数为0.04时,样品的发射强度是未掺杂Bi3+离子样品的1.9倍。

脉冲激光沉积法制备立方焦绿石结构的Bi_(1.5)ZnNb_(1.5)O_7薄膜

采用固相反应法合成具有焦绿石立方结构的Bi1.5ZnNb1.507（BZN）陶瓷靶材，采用脉冲激光沉积法在Pt／SiO2／si（100）基片制备立方BZN薄膜。研究了随衬底温度的变化，薄膜的结晶性能，微观形貌以及介电性能的差异。结果表明当衬底温度在550-650℃时，薄膜具有纯的立方BZN结构，并且在600℃时薄膜的晶粒发育比较完整，此时薄膜具有较高的介电常数和较低的损耗。

自组装单层膜表面的Bi_2Ti_2O_7薄膜制备与表征

以硝酸铋和钛酸四丁酯为原料,以三氯十八烷基硅烷(OTS)为模板,采用自组装单层膜(self-as-sembled monolayers,SAMs)技术,在玻璃基板上成功制备了Bi2Ti2O7晶态薄膜。借助X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、X射线能谱(EDS)及原子力显微镜(AFM)等测试手段对Bi2Ti2O7薄膜进行了表征。结果表明,以OTS为模板利用自组装技术,经540℃煅烧2h可成功制得立方相Bi2Ti2O7晶态薄膜,且薄膜表面平整光滑,均匀致密。

Bi_(1.6)La_(0.4)Ti_2O_7薄膜的制备及性能研究

采用化学溶液沉积法在ITO基片上制备不同退火温度的掺镧钛酸铋Bi1.6La0.4Ti2O7(BLT)薄膜。研究了其结构、介电性能、漏电流密度与外加电压I-V关系曲线和光学带隙。XRD射线衍射测试结果表明,经500、550、600℃1 h退火后的薄膜的主晶相为烧绿石结构,无杂相生成,600℃时BLT薄膜衍射峰比其他两种温度的强。在1 kHz频率下测得的介电常数、损耗因子分别为114,3%;129,3%;194,6%。BLT薄膜的漏电流密度与外加电压关系曲线表明,BLT薄膜600℃的漏电流比550和500℃稍微减小。通过透射谱分析得到BLT薄膜的光学带隙几乎不受温度影响,均为3.7 eV。这些结果表明制备BLT固溶体薄膜较佳为退火温度600℃,具有较好的性能,在光电器件有良好的应用前景。