生物医学工程学

0500862 心外膜电位重构中边界条件不完全的仿真研究，0500863 麻醉期心率变异性的复杂性研究，0500864 锥形血管内血液脉动流的数值模拟，0500865 高强度聚焦超声在肿瘤治疗中的焦域模型，0500866 骨骼肌介电行为的理论模型仿真。     

心外膜电位仿真研究

以往的心电理论研究，一方面强调从体表电位分布到心外膜电位分布的求逆；另一方面利用计算机心脏仿真模型只侧重于体表电位的仿真，而忽视了对心外膜电位的仿真，不利于心电逆问题研究的发展。本文阐明了心外膜电位对临床诊断和心电逆问题研究的重要性，并在ＬＦＸ计算机心脏仿真模型［１～３］的基础上建立了心外膜电位仿真的数学描述和心外膜模型。文中对正常心脏和左束支传导阻滞的心外膜电位进行了仿真研究，获得了一些有价值的结论     

心脏外膜电势传播过程的三维立体显示

我们借助于一组心脏的X－CT图片重构人体心脏的几何模型，并采用边界元算法从体表电位求得心外膜电位的数值解，利用计算机图形技术在1BM－PC／XT微型机上实现了心外膜电势传播过程的三维立体显示。     

心脏位置的改变对体表电位分布的影响

作者在所建三维仿真人体躯干模型的基础上，利用边界元方法对诸如深吸气等引起的心脏位置的改变而对体表电位产生的影响进行了正向模拟计算。文中给出了心脏分别处在中间位、垂位及横位时的体表电位分布图以及相应的心电图（QRS期间）。结果表明心脏处在不同的位置时，体表电位分布在极化方向的幅值等方面的变化都非常明显。     

体表心电图机及心外膜心电图机

体表及心外膜(或心表面)心电图机是一种同时测量胸部体表及心外膜(或心表面)上若干测试点的电位,并表示出电位分布图及心表兴奋传播图的装置。对于用标准12导心电图机及矢量心电图机测不出来的心脏兴奋电位的详细信息,可用表体心电图机进行测量这对心脏电生理的研究及心脏病变诊断精度的提高无疑是有益的。再有,心外膜心电图机主要用于心律失常的外科治疗,其方法是在开胸后,作外科手术之前,测量心外膜上的心电图,目的是将刺激兴奋异常部位及付传导通路,传导障     

心电体外层电位仿真研究：一种检测心脏电位活动的新方法

体表电位测量中常要面对一些难以克服的问题。例如电极数量受限、电极与人体体表固定困难以及人体体形个体差异对测量数据影响较大等。为解决上述问题，本文提出了一种检测心电活动的新方法：心电体外层电位法。并建立了体外层电位标测系统的仿真模型，对不同的人体体形算例进行了仿真计算。结果表明，体外层电位法是比传统体表电位测量更可行的一种新方法。     

体表心电峰值等电位图的描绘及临床应用研究

作者首先讨论了体表心电峰值等电位图的描绘方法，其中包括将２－Ｄ展开平面网格化、建立边表、等位线上点的插值、建立等位值序列表及最后生成峰值等电位图等，利用该方法作者以３２例临床病例对五种异常心电信号进行了研究，得到了一些启发性结果。     

求解心外膜电位的有限元方法研究

由体表电位分布求解心电源 称力心电逆问题 它是现代心电理论研究的方向之一 具有重要的理论价值和临床意义 本文推导了用有限元方法求解心外膜电位的算法 着重介绍了为改善逆问题解的稳定性所做的努力 在作者研制的100通道体表电位系统上 利用实测的体表电位数据进行了心外膜电位的实际计算 得到了具有生理意义的结果 从而证明本算法是合理的。     

基于真实心脏—躯干模型的体表Laplacian图的理论基础

０　引言体表电位是心脏电兴奋事件在人体表面的粗略投影，而且体表电位容易受到躯干的不均匀性、胸腔组织电导率不均匀性、胸腔模型的不规则性等各个方面的影响，因此很难由体表电位分布图反映心脏电兴奋的具体细节。５年前ＢｉｎＨｅ和Ｒ．Ｊ．Ｃｏｈｅｎ采用同心环电极首次记录了体表Ｌａｐｌａｃｉａｎ图（ＢＳＬＭ）。此后便形成了国际生物医学工程界研究ＢＳＬＭ的一股热潮，像１９９６年６月芬兰召开的第一届国际生物电磁学学术会议上就安排了一个ＢＳＬＭ专题。ＢＳＬＭ可以看成是体表等效电荷密度或体表电流密度法向分量的微分。从…     

Laplacian心电图的研究进展

Laplacian心电图技术是利用表面Laplacian值的概念，通过对体表电位进行微分，得以更准确、全面地反映心脏电活动的情况。本详细介绍了Laplacian心电图研究的发展和现状，主要包括理论背景、实际测量、数据处理方法以及临床应用等方面，并指出了Laplacian心电图的研究困难及发展前景。     

Role of ventral hippocampal NMDA receptors in anxiolytic-like effect of morphine

The possible role of ventral hippocampal N-methyl-d-aspartate (NMDA) receptors on morphine-induced anxiolytic-like behavior in an elevated plus maze (EPM) task was investigated in the present study. Adult male mice (7 per group) with cannulas aimed at the ventral hippocampus (VH) received NMDA or a competitive NMDA receptor antagonist D-AP5 with or without morphine and 30 min later were subjected to an EPM task. Intraperitoneal injection (i.p.) of morphine (3-9 mg/kg) increased the percentage of open arm time (%OAT) and open arm entries (%OAE), which suggested an anxiolytic-like effect. Intra-VH microinjection of NMDA (0.5-1 μg/mouse) with an ineffective dose of morphine (3 mg/kg, i.p.) significantly increased %OAT and %OAE. However, microinjections of the same doses of NMDA into the VH in the absence of morphine had no effect on %OAT and %OAE. Intra-VH microinjection of D-AP5 (0.5-2 μg/mouse) decreased the anxiolytic-like effect of morphine, while intra-VH microinjection of the same doses of D-AP5 alone increased %OAT and %OAE, which indicated an anxiolytic response. Furthermore, intra-VH microinjection of D-AP5 reversed the effect of NMDA response to the administration of a lower morphine dose as seen in the EPM task. It should be noted that intra-VH microinjection of D-AP5 plus NMDA, 5 min before morphine increased locomotor activity, while other treatments had no effect on this parameter. The results suggest that VH-NMDA receptors participate in the mediation of morphine-induced anxiolytic-like behavior.     

The anterior cingulate cortex is a target structure for the anxiolytic-like effects of benzodiazepines assessed by repeated exposure to the elevated plus maze and Fos immunoreactivity

Prior experience with the elevated plus maze (EPM) increases the avoidance of rodents to the open arms and impairs the anxiolytic-like effects of benzodiazepines on the traditional behaviors evaluated upon re-exposure to the maze, a phenomenon known as one-trial tolerance. Risk assessment behaviors are also sensitive to benzodiazepines. During re-exposure to the maze, these behaviors reinstate the information-processing initiated during the first experience, and the detection of danger generates stronger open-arm avoidance. The present study investigated whether the benzodiazepine midazolam alters risk assessment behaviors and Fos protein distribution associated with test and retest sessions in the EPM. Naive or maze-experienced Wistar rats received either saline or midazolam (0.5 mg/kg i.p.) and were subjected to the EPM. Midazolam caused the usual effects on exploratory behavior, increasing exploratory activity of naive rats in the open arms and producing no effects on these conventional measures in rats re-exposed to the maze. Risk assessment behaviors, however, were sensitive to the benzodiazepine during both sessions, indicating anxiolytic-like effects of the drug in both conditions. Fos immunohistochemistry showed that midazolam injections were associated with a distinct pattern of action when administered before the test or retest session, and the anterior cingulate cortex, area 1 (Cg1), was the only structure targeted by the benzodiazepine in both situations. Bilateral infusions of midazolam into the Cg1 replicated the behavioral effects of the drug injected systemically, suggesting that this area is critically involved in the anxiolytic-like effects of benzodiazepines, although the behavioral strategy adopted by the animals appears to depend on the previous knowledge of the threatening environment.     

Influence of circadian phase and test illumination on pre-clinical models of anxiety

Pre-clinical models of anxiety, particularly the elevated plus-maze (EPM), have been shown to be sensitive to a variety of methodological variations. Recent research has implicated circadian phase of testing in influencing the behavioural profile of 5-HT(1A) ligands on the EPM. The present study investigated the effects of testing animals during the dark and light phases and in light and subjective dark test conditions on baseline behaviour in animal models of anxiety. Eighty singly housed male Sprague-Dawley rats were exposed to a battery of unconditioned, exploratory tests (EPM, open field arena, holeboard) and a new model of extreme anxiety, the unstable elevated exposed plus-maze (UEEPM). Circadian phase of testing failed to consistently alter behaviour on any model. Level of test illumination had no effect on subjects' response to the open field arena, holeboard or UEEPM. Dark testing increased locomotor activity on the EPM (total arm entries, closed arm entries and distance moved) without decreasing open-arm avoidance. The construct of anxiety as measured by a number of different paradigms withstood major intra-laboratory manipulation of circadian phase of testing and illumination of apparatus. It is suggested that the effects of circadian rhythmicity may be confined to the behavioural profiles of serotonergic, particularly 5-HT(1A), ligands on the EPM.     

下颌颏部骨折内固定的三维有限元模型及边界约束的建立

通过Pro／E和ANSYS建立下颌骨颏部骨折内固定的三维有限元模型，并模拟了各种功能状态下的边界约束。使用计算机图像处理软件对CT扫描图像进行预处理，然后采用自编程序获取下颌骨解剖结构的三维坐标数据，用ANSYS建立下颌骨的三维有限元模型。采用数值化建模软件Pro／E建立小型接骨板-螺钉固定体系统的实体模型。模拟下颌骨颏部正中骨折坚强内固定治疗，建立该内固定治疗的有限元模型。通过改变各组咀嚼肌力的大小，进行了三种咬合状态的边界约束。获得了形态逼真、相似性好的下颌颏部骨折内固定后的三维有限元模型，并模拟了各功能状态下的边界约束，为后期的生物力学分析奠定了基础。     

听觉新奇事件相关电位的研究进展

就人脑对听觉新奇事件的事件相关电位(Event-related potentials,ERP)响应的研究进展进行了综述。介绍了新奇性响应的实验方案设计和新奇性响应ERP在认知方面的一系列问题。对反映偏离检测的非匹配负波电位(MMN)以及与新奇性响应的关系也进行了讨论。熟悉度和注意力两个因素影响着大脑的新奇性ERP响应。研究表明,随熟悉程度的加强,在脑前区体现出信号明显的减小,而脑后区无明显变化。注意的作用有助于信号的加强,使大脑相应的部位产生激活。本文进一步讨论了ERP响应的功能意义,包括大脑对新奇事件的估价等内容。     

Peanut agglutinin (PNA)-binding properties of murine thymocyte subpopulation.

Surface receptors for peanut agglutinin (PNA), a lectin with D-galactose specificity, were detected on mouse thymocytes using fluorescence microscopy. Depending on mouse strain, 69-85% of unseparated thymocytes could thus be characterized as PNA+. Electrophoretic fractionation of thymocytes from normal or immunosuppressive drug-treated donors revealed an inverse relationship between PNA-binding properties and cell electrophoretic mobility (EPM). Thus, all thymocytes recovered in the lowest EPM fractions were strongly PNA+ whereas those in the highest EPM fractions were in the majority PNA-. Most of the cells collected in the intermediate EPM range were PNA+ but staining with the fluoresceinated lectin appeared weaker than for the low EPM thymocytes. Reciprocal experiments in which thymocytes were separated by PNA-mediated aggregation into fractions with different affinities for the lectin and then subjected to physical analysis, definitely established that PNA+ cells are of lower EPM than PNA- cells and that these two cell types also differ in size distribution. These data show that the four physical subpopulations of thymocytes previously described present distinctive PNA-binding properties: Th1 and Th2 cells can be classified as strongly PNA+, Th3 cells as less intensely PNA+, and Th4 cells as mostly PNA-.     

Reduced levels of nitric oxide metabolites in cerebrospinal fluid are associated with equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is a disease of horses that is primarily associated with infection with the apicomplexan Sarcocystis neurona. Infection with this parasite alone is not sufficient to induce the disease, and the mechanism of neuropathogenesis associated with EPM has not been reported. Nitric oxide (NO) functions as a neurotransmitter, a vasodilator, and an immune effector and is produced in response to several parasitic protozoa. The purpose of this work was to determine if the concentration of NO metabolites (NO(x)(-)) in the cerebrospinal fluid (CSF) is correlated with the development of EPM. CSF NO(x)(-) levels were measured before and after transport-stressed, acclimated, or dexamethasone-treated horses (n = 3 per group) were experimentally infected with S. neurona sporocysts. CSF NO(x)(-) levels were also compared between horses that were diagnosed with EPM after natural infection with S. neurona and horses that did not have clinical signs of disease or that showed no evidence of infection with the parasite (n = 105). Among the experimentally infected animals, the mean CSF NO(x)(-) levels of the transport-stressed group, which had the most severe clinical signs, was reduced after infection, while these values were found to increase after infection in the remaining groups that had less severe signs of EPM. Under natural conditions, horses with EPM (n = 65) had a lower mean CSF NO(x)(-) concentration than clinically normal horses with antibodies (Abs) against S. neurona (n = 15) in CSF, and horses that developed ataxia (n = 81) had a significantly lower mean CSF NO(x)(-) concentration than horses that did not have neurologic signs (n = 24). In conclusion, lower CSF NO(x)(-) levels were associated with clinical EPM, suggesting that measurement of CSF NO(x)(-) levels could improve the accuracy of diagnostic tests that are based upon detection of S. neurona-specific Abs in CSF alone and that reduced NO levels could be causally related to the development of EPM.     

Activity in prelimbic cortex is required for adjusting the anxiety response level during the elevated plus-maze retest

The prelimbic (PL) subregion of medial prefrontal cortex has been implicated in anxiety regulation. It is unknown, however, whether PL cortex also serves to fine-tuning the level of anxiety-related behavior exhibited on the next exposure to the same potentially threatening situation. To address this, we infused cobalt (1.0 mM) to temporarily inactivate the PL cortex during testing, post-testing or retesting in the elevated plus-maze (EPM). This protocol was chosen because it allowed us to concurrently investigate anxiety and the process of aversive learning and memory. PL cortex inactivation during the EPM testing increased the exploration of open-arms, substantiating its role in anxiety. PL cortex inactivation during the EPM retesting counteracted the further avoidance to open-arms exhibited by rats. Interestingly, as evidenced by min-by-min analysis, the cobalt-treated group behaved on EPM retesting as did the vehicle-treated group on EPM testing. This result may imply that activity in PL cortex is necessary for retrieving previously learned information that adjusts the anxiety response level on EPM retesting. Alternatively, a simple reduction in anxiety could explain the cobalt-induced increase in retest open-arms exploration. Neither test nor post-test PL cortex inactivation affected the further avoidance to open-arms observed on EPM retesting. To extend the investigation of PL cortex role in the regulation of open-arms avoidance, we infused other drugs prior to testing or retesting in the EPM. Antagonism of PL cortex adrenergic beta-1 receptors with atenolol (10 nmol), cholinergic muscarinic receptors with scopolamine (20 nmol) or glutamatergic N-methyl-d-aspartic acid (NMDA) receptors with AP5 (6.0 nmol) interfered with the level of open-arms exploration on testing, but not on retesting.     

老年人坐立转换时股骨近端应力分布的有限元分析

目的 通过建立股骨近端有限元模型,分析在坐立（sit-to-stand, STS）转换站立阶段初期,股骨近端在自选速度起立和快速起立条件下的损伤风险。方法 将老年人股骨近端CT影像三维重建、逆向建模完成实体模型。通过材料赋值和网格划分建立有限元模型,基于有限元分析软件ANSYS,通过边界条件约束,并加载1.733、1.837 kN载荷,得到不同起立速度下股骨近端的应力分布和应变。结果 应力集中区域均为大转子内侧边缘和股骨颈。应力和微应变峰值出现在大转子内侧边缘。快速起立下应力峰值为30.16 MPa,微应变峰值为2 553.5;自选速度起立下应力和微应变峰值较低,分别为28.69 MPa和2 430.4。对于股骨颈应力集中区,快速、自选速度起立下应力范围分别为13.42~23.46、12.76~25.51 MPa。结论 频繁的STS转换会使老年人股骨近端有疲劳性骨折的风险;快速STS转换比自选速度STS转换对股骨近端有更高的损伤风险。     

Species differences in anxiety-related responses in male prairie and meadow voles: the effects of social isolation

Prairie (Microtus ochrogaster) and meadow voles (M. pennsylvanicus) are closely related species that differ in life strategy and social behaviors, and thus provide an excellent comparative model for the study of neuronal and hormonal mechanisms underlying behavior. In the present study using the elevated plus maze (EPM) test, we found that male prairie voles entered the open arms of the EPM more and remained there longer, and showed a higher level of overall locomotor activity than did male meadow voles. In addition, two weeks of social isolation induced an increase in open arm entries in prairie, but not meadow, voles. Prairie voles also had a higher level of circulating corticosterone compared to meadow voles, and the EPM test increased circulating corticosterone in prairie voles. Finally, social isolation coupled with the EPM test influenced Fos-immunoreactive expression in several brain areas, including the medial preoptic area, ventromedial hypothalamus, amygdala, and prefrontal cortex differently between the two species. Together, these data indicate a neural circuit involved in mediating anxiety-associated behavior in voles, and that the functioning of this circuit is influenced by social environment differently between social and non-social species.