叶绿体遗传转化：植物导入外源基因的新途径

叶绿体转化系统,独立于传统的核转化,为植物导入外源基因提供了新途径,它有如下优点：超量表达目的的基因;以定点整合方式导入外源基因从而消除了位置效应及基因沉默;具有原核表达方式,能以多 反子的形式表达多个基因;母系遗传方式可防止基因扩散;基因产物区域化并能提供适于某些产物发挥功能的小环境等。随着这项技术在越来越多的领域发挥作用,其优势性逐渐得到认同。本文着重对此技术的特点,发展及应用作一综述。     

三江平原沼泽湿地岛状林植物多样性

 基于Quick Bird影像选择样地区域,采用样方法进行群落学调查。选取丰富度指数（R）、Simpson指数（D）、Shannon-Wiener指数（H′）、Pielou均匀度指数（J_sw）测度多样性水平。结果表明：19个岛状林共记录到维管植物140种,隶属于44科,102属,与相邻的洪河自然保护区内的同类型群落相比较有些物种已经消失。山杨林(Ass. Populus davidiana)、白桦林(Ass. Betula platyphylla)和杨桦林(Ass. P. davidiana+B. platyphylla)3种群落类型多样性指数在灌木层之间差异显著（p<0.05）。岛状林总体3个层次之间的R、D、H′大小顺序均为草本层>灌木层>乔木层,3者之间差异极显著（p<0.01）。岛状林斑块的物种丰富度与斑块面积（r=0.591, p<0.01）、周长（r=0.674 , p<0.01）和形状指数（r=0.584,p<0.01）极显著相关,而D、H′、J_sw与周长、面积和形状指数相关均不显著。受到一定人为干扰的岛状林群落仍具有较高的植物多样性,其中草本层植物多样性占有重要地位。林窗干扰是导致林下植物多样性较高的重要原因。边缘效应可能是引起群落斑块物种丰富度随着斑块面积、周长和形状指数的增大而增加的重要原因。岛状林群落斑块对于维持该地区的植物多样性具有重要意义。     

胍丁胺对大鼠心室肌细胞内游离钙浓度的影响

本研究旨在观察胍丁胺 (agmatine ,Agm)对分离大鼠心室肌细胞内游离钙浓度 ( [Ca2 +]i)的影响。用酶解方法分离大鼠心室肌细胞 ,用Fluo 3 AM负载 ,然后用激光共聚焦法测定单个心室肌细胞 [Ca2 +]i 的荧光强度 (fluorescenceintensity ,FI) ,结果以FI或相对荧光强度 (F/F0 % )表示。实验结果表明 ,在正常台氏液 (含钙 1 0mmol/L)和无钙台氏液中 ,单个大鼠心室肌细胞的荧光密度分别为 12 8 8± 13 8和 119 6± 13 6,两者无差异。Agm 0 1、1和 10mmol/L浓度依赖性地显著降低细胞的钙浓度 ;在正常台氏液中加入EGTA 3mmol/L ,Agm同样降低细胞的钙浓度。KCl 60mmol/L ,PE 3 0 μmol/L ,和Bay K 864 410 μmol/L均升高心室肌细胞的[Ca2 +]i。Agm同样降低高浓度KCl、Bay K 864 4和PE诱发的心室肌细胞 [Ca2 +]i 升高。当细胞外液钙浓度由 1mmol/L增加到 10mmol/L时 ,诱发心室肌细胞钙超载 ,同时部分心室肌细胞产生可传播的钙波 (Ca2 +wave) ,Agm 1mmol/L降低钙波的传播速度和持续时间 ,最终阻断钙波。以上结果提示 ,Agm对心室肌细胞的胞浆[Ca2 +]i具有抑制作用 ,此作用通过阻断电压依赖性钙通道而实现 ;并可能与抑制大鼠心室肌细胞内钙释放有关     

黑河上游祁连山区青海云杉生长状况及其潜在分布区的模拟

根据Hutchinson的n维超体积概念以及物种与资源利用之间的关系, 构建了青海云杉(Picea crassifolia)在三维环境资源空间中的生物-地理模型, 并利用该模型模拟了青海云杉的潜在分布及其对环境资源的利用状况。结果表明: 青海云杉在生长季平均气温、多年平均降水量及太阳直接辐射三维环境资源空间上的最佳配置为9 ℃、360 mm和1.9 × 10³ kW·h·m^-2; 用三元方程式的拟合结果在大范围上预测了青海云杉的潜在分布区, 并给出了其在对应地理位置上的生长状况。     

Category and Perceptual Learning in Subjects with Treated Wilson's Disease

To explore the relationship between category and perceptual learning, we examined both category and perceptual learning in patients with treated Wilson''s disease (WD), whose basal ganglia, known to be important in category learning, were damaged by the disease. We measured their learning rate and accuracy in rule-based and information-integration category learning, and magnitudes of perceptual learning in a wide range of external noise conditions, and compared the results with those of normal controls. The WD subjects exhibited deficits in both forms of category learning and in perceptual learning in high external noise. However, their perceptual learning in low external noise was relatively spared. There was no significant correlation between the two forms of category learning, nor between perceptual learning in low external noise and either form of category learning. Perceptual learning in high external noise was, however, significantly correlated with information-integration but not with rule-based category learning. The results suggest that there may be a strong link between information-integration category learning and perceptual learning in high external noise. Damage to brain structures that are important for information-integration category learning may lead to poor perceptual learning in high external noise, yet spare perceptual learning in low external noise. Perceptual learning in high and low external noise conditions may involve separate neural substrates.     

Enabling High Grayscale Resolution Displays and Accurate Response Time Measurements on Conventional Computers

Display systems based on conventional computer graphics cards are capable of generating images with 8-bit gray level resolution. However, most experiments in vision research require displays with more than 12 bits of luminance resolution. Several solutions are available. Bit++ ¹ and DataPixx ² use the Digital Visual Interface (DVI) output from graphics cards and high resolution (14 or 16-bit) digital-to-analog converters to drive analog display devices. The VideoSwitcher ³ described here combines analog video signals from the red and blue channels of graphics cards with different weights using a passive resister network ⁴ and an active circuit to deliver identical video signals to the three channels of color monitors. The method provides an inexpensive way to enable high-resolution monochromatic displays using conventional graphics cards and analog monitors. It can also provide trigger signals that can be used to mark stimulus onsets, making it easy to synchronize visual displays with physiological recordings or response time measurements.Although computer keyboards and mice are frequently used in measuring response times (RT), the accuracy of these measurements is quite low. The RTbox is a specialized hardware and software solution for accurate RT measurements. Connected to the host computer through a USB connection, the driver of the RTbox is compatible with all conventional operating systems. It uses a microprocessor and high-resolution clock to record the identities and timing of button events, which are buffered until the host computer retrieves them. The recorded button events are not affected by potential timing uncertainties or biases associated with data transmission and processing in the host computer. The asynchronous storage greatly simplifies the design of user programs. Several methods are available to synchronize the clocks of the RTbox and the host computer. The RTbox can also receive external triggers and be used to measure RT with respect to external events. Both VideoSwitcher and RTbox are available for users to purchase. The relevant information and many demonstration programs can be found at http://lobes.usc.edu/.     

子痫前期动物模型的研究进展

子痫前期是一种非常严重的妊娠疾病,主要症状有高血压、蛋白尿、内皮功能障碍、肾小球血管内皮细胞增生以及滋养层细胞浸润不足等,动物模型是研究本病发病机理与开发诊治手段的主要工具.长期以来,针对子痫前期主要症状已经建立了多种动物模型,但不同的动物模型各有优缺点,至今仍没有一个理想的子痫前期动物模型,这也是子痫前期病因不明和缺乏有效治疗手段的主要原因之一.本文就已有的模型进行了归纳总结,旨在为不同研究需要而选择合适的模型,并为开发更为理想的子痫前期动物模型提供参考.     

植物细胞中的膜联蛋白（annexin）

膜联蛋白（annexin）是存在于动植物细胞中的钙依赖性磷脂结合蛋白,广泛参与受钙离子调控的生命活动,如囊泡运输、膜融合、信号转导、钙离子通道的形成、细胞分化和细胞骨架蛋白间的相互作用等。本文就植物细胞中annexin的研究进展进行了介绍。