Barrier function of porcine choroid plexus epithelial cells is modulated by cAMP-dependent pathways in vitro

In the present paper, we demonstrate that the barrier properties of primary cultured epithelial cells isolated from porcine choroid plexus are regulated by cAMP-dependent signal transduction pathways in vitro. Triggering cAMP-connected cascades in cell layers grown on permeable filters with cAMP-analogues or forskolin led to a significant increase of transepithelial electrical resistances and a pronounced reduction in the permeation rate of a 4 kDa-dextran probe. In dose-response experiments using the cAMP-analogue 8-(4-chlorophenylthio)-cAMP transepithelial electrical resistances were observed to increase above a threshold concentration ranging between 10(-5.5) and 10(-5) M. Additional impedance studies performed with confluent cell layers grown on gold-film electrodes revealed that the observed changes in transepithelial resistances and presumably also in macromolecular permeation rates were not entirely caused by a reinforcement of intercellular junctions but also contained contributions from changes in the cell-substrate adhesion pattern. These inherent contributions to the electrical resistance and macromolecular permeability are caused by a restricted diffusion pathway between basal plasma membrane and culture substrate that have to be considered in data analysis, especially when leaky cell layers on filter substrates with low pore densities are used.     

The effect of two low-dose propofol infusions on the relationship between six-pulse transcranial electrical stimulation and the evoked lower extremity muscle response

BACKGROUND: Transcranial stimulation of the motor cortex using high-voltage electrical stimuli given in train is a method of monitoring the integrity of the motor pathways during thoracoabdominal aortic aneurysm surgery. The purpose of this study was to assess the relationship between the stimulus intensity and the corresponding amplitude of the myogenic motor evoked potential (tcMEP) in response to six-pulse transcranial electrical stimulation during two levels of low-dose propofol infusion and stable fentanyl/nitrous oxide anaesthesia. METHODS: Nine patients (37-78 yr) scheduled to undergo surgery on the thoracoabdominal aorta were studied. After achieving a stable anaesthetic state the output voltage was decreased with 50 V intervals from 350 V to 200 V during a target propofol infusion aimed at a plasma steady-state concentration of 0.7 microg x ml(-1) and increased with 50 V intervals from 200 V to 450 V during a target propofol infusion aimed at a plasma steady-state concentration of 1.4 microg x ml(-1). TcMEPs were recorded from the right tibialis anterior muscle. RESULTS: Doubling the target propofol infusion to 1.4 microg x ml(-1) resulted in a 30-50% decrease in tcMEP amplitude. The largest tcMEP amplitude using the six-pulse paradigm was found during a propofol infusion aimed at a plasma concentration of 0.7 microg x ml(-1) and demanded a stimulus output of 350 V, corresponding to a charge density of 7.5 microC x cm(-2) per phase. CONCLUSION: Doubling the target propofol infusion to 1.4 microg x ml(-1) provides less robust, but still recordable tcMEPs in response to six-pulse electrical stimulation. Safety guidelines are discussed.     

生物电阻抗测量技术

以人体组织的阻抗特性为基础,阐明了简化模型,血液电阻率,细胞膜容抗以及呼吸干扰等对血流图测量准确性和重复性的影响;比较了采用全身测量、分段测量和多频率方法行人体成分分析(BIA)测量时的优缺点;提出采用阻抗测量建立有效的胃动力学评价方法;展现了代表生物阻抗测量技术发展方向的电阻抗断层成像技术(EIT)的诱人应用前景.     

镀银导电纤维的制备和性能

对短切聚酯纤维进行化学镀银,制备了用于导电高分子材料的导电填料,探讨了氨水浓度、装载量及稳定剂对纤维化学镀银的影响。实验表明,φ=0.10的氨水有利于化学镀银;通过调整装载量,可提高纤维的增重量率和硝酸银的利用率;稳定剂的加入可阻止镀液自分解,但对包覆层的均匀性和致密性有影响。电性能测试表明,镀银纤维的体积电阻率可达3.35×1-0 3Ω.cm,以其作为导电橡胶填料,当含量为w=0.40时,其电阻率为1.54×1-0 1Ω.cm。     

用市电干扰校准心电图机走纸速度

校准心电图走纸速度的方法,在实际操作中,钟表检查法不宜掌握、浪费记录纸、误差较大;正弦波检查法因条件所限,无正弦波发生器或频率不准,不易实现。经过多年实践,总结出用市电50Hz交流干扰法校准心电图走纸速度,其方法简单实用、容易掌握、不用任何设备、准确度高、适用于维修人员和临床医务人员,减少误诊,提高临床诊断率。     

宫颈上皮内瘤变阴道镜下活检与电环切除术后病理的对比分析

目的 对比分析宫颈上皮内瘤变（CIN）阴道镜下活检与电环切除术后病理，提高CIN诊断的准确性。方法 回顾性对比分析216例宫颈上皮内瘤变阴道镜下活检与电环切除术后病理，探讨影响两者符合率的相关因素。结果 两者对比，宫颈电环切除术（LEEP）后病理结果与阴道镜下活检相符的74例，升级的18例，降级的124例。阴道镜下检查不满意者活检与电环切除术后病理对比，升级率大于阴道镜下检查满意者，差异有显著性（P〈0．01）。结论 宫颈转化区向宫颈管上移者，要注意宫颈管内的病变。宫颈电环切除术可以部分弥补阴道镜下活检的缺陷，且有治疗作用。     

电阻抗断层成像脑出血模型的仿真研究

目的：建立脑出血有限元模型,对其进行电阻抗断层成像仿真研究.方法：基于4层同心圆头模型,利用有限元方法和动态NOSER算法重构成像.结果：单病灶脑出血模型的病灶能够被准确重构呈现,而多病灶模型中邻近病灶间的边界重构较为模糊.结论：动态NOSER算法是一种有效检测脑出血的电阻抗断层成像方法.     

一种电阻抗断层成像的图像后处理算法

目的：研究电阻抗断层成像的图像处理方法,改善图像显示效果.方法：先利用相邻三角形单元的电导率估计节点的电导率,然后根据三角形单元3个顶点的电导率进行二维线性插值获得单元内任意点的电导率.结果：原始的按三角形单元分块显示的电阻抗断层成像的图像,可转换为光滑的图像.结论：图像显示效果得到很大的改善;此方法适用于所有三角形剖分的电阻抗断层成像的图像处理.     

电热蒸汽发生器的研制及应用

指出使用锅炉高压蒸汽灭菌器的缺点，重点介绍了利用电热蒸汽法进行消毒的研制过程及实际应用价值。     

医学成像技术的进展

医学成像技术在最近几年中有了飞速的发展，新的成像方法不断涌现，已有的成像方式不断完善。从平面到立体、从局部到整体、从静态到动态、从形态到功能已成为医学成像技术发展的趋势。文中简要介绍分子成像、近红外热成像等新的成像方式。