心室肌细胞膜电位与膜通道的动力学结构研究

本文利用Beeler-Reuter模型，对心室肌细胞膜电位及膜通道在恒定的Na^ 电导下进行了双参数分岔分析，发现五个动力学性质不同的区域，其中两个区域具有双稳吸引子，当漏电流及慢电导选择适合的参数，心肌纤维会产生自发节律，此为某些异位起博点产生的原因，在漏电流及慢电导参数平面上存在一个小的区域，振荡态与静息态共存，揭示临床上房性停搏的内在机理。     

基于磋感应相位移谱方法的脑出血模拟测试系统的性能研究

目的 基于脑出血模拟物理模型和研制的脑出血检测系统,实验研究和评估脑出血检测系统的性能.方法 采用磁感应相位移谱(PSSMI)方法,在3个频率(f1、f2和f3)下进行检测,脑出血的程度用0～ 100 mL NaCl溶液进行模拟.结果 检测系统的相位差分辨率可以达0.005°,增益在-10～35 dB范围可调,而且检测...     

心脏电活动正问题仿真研究进展

近年来随着心脏疾病越来越为人们所重视，用心脏仿真模型研究各种心脏疾病的应用新研究成为热点；与此同时，在仿真理论方面也向着更加真实地反映复杂的人体环境和更加简单易操作两方面发展，研究者们发表了很多新的研究成果。从源、容积导体及算法等方面综述了心脏仿真建模理论的最新发展。     

Nuss手术矫正漏斗胸过程的数值模拟

目的 建立漏斗胸患者前胸廓三维实体模型,进行生物力学有限元分析,为Nuss手术提供可参考的依据,并提出可行的手术方案.方法 首先利用Mimics和GeomagicStudi0软件的三维造型功能,构建出漏斗胸患者前胸廓三维模型,包括患者前胸廓数据采集,生成点云数据,构建前胸廓三维实体造型;然后利用有限元分析软件ANSYS...     

基于传输线模型的脉搏波传播数值仿真及参数分析

目的通过提出一种传输线模型和输入阻抗递归算法的计算方法,数值仿真人体动脉树中脉搏波的传播过程,分析个体差异性和动脉树各参数对脉搏波的影响,为动脉树生理和病理变化分析提供参考。方法利用由大中动脉构成的55段人体动脉树建立传输线模型,采用递归算法计算动脉树各点的输入阻抗,仿真计算动脉树中各段血压和血流的分布图。在此基础上比较不同身高、心率、每搏量、内径、壁厚等参数对脉搏波传播和血压分布的影响。结果仿真结果和一般脉搏波传播规律相一致,验证了该方法的有效性。不同参数对动脉树中脉搏波传播的影响有较大差异且呈现各自特征。结论基于传输线模型和递归算法的计算方法能有效仿真动脉树中脉搏波的传播过程,并准确反映个体差异性和动脉树血液动力学参数的变化对脉搏波的影响,是人体动脉树生理病理分析和诊断的重要辅助手段。     

Immunohistochemical cellular distribution of proteins related to M phase regulation in early proliferative lesions induced by tumor promotion in rat two-stage carcinogenesis models

We have previously reported that 28-day treatment with hepatocarcinogens increases liver cells expressing p21^Cip1, a G₁/S checkpoint protein, and M phase proteins, i.e., nuclear Cdc2, Aurora B, phosphorylated-Histone H3 (p-Histone H3) and heterochromatin protein 1α (HP1α), in rats. To examine the roles of these markers in the early stages of carcinogenesis, we investigated their cellular distribution in several carcinogenic target organs using rat two-stage carcinogenesis models. Promoting agents targeting the liver (piperonyl butoxide and methapyrilene hydrochloride), thyroid (sulfadimethoxine), urinary bladder (phenylethyl isothiocyanate), and forestomach and glandular stomach (catechol) were administered to rats after initiation treatment for the liver with N-diethylnitrosamine, thyroid with N-bis(2-hydroxypropyl)nitrosamine, urinary bladder with N-butyl-N-(4-hydroxybutyl)nitrosamine, and forestomach and glandular stomach with N-methyl-N′-nitro-N-nitrosoguanidine. Numbers of cells positive for nuclear Cdc2, Aurora B, p-Histone H3 and HP1α increased within preneoplastic lesions as determined by glutathione S-transferase placental form in the liver or phosphorylated p44/42 mitogen-activated protein kinase in the thyroid, and hyperplastic lesions having no known preneoplastic markers in the urinary bladder, forestomach and glandular stomach. Immunoreactive cells for p21^Cip1 were decreased within thyroid preneoplastic lesions; however, they were increased within liver preneoplastic lesions and hyperplastic lesions in other organs. These results suggest that M phase disruption commonly occur during the formation of preneoplastic lesions and hyperplastic lesions. Differences in the expression patterns of p21^Cip1 between thyroid preneoplastic and proliferative lesions in other organs may reflect differences in cell cycle regulation involving G₁/S checkpoint function between proliferative lesions in each organ.     

Numerical simulation of the effect of sodium profile on cardiovascular response to hemodialysis

PURPOSE: We developed a numerical model that predicts cardiovascular system response to hemodialysis, focusing on the effect of sodium profile during treatment. MATERIALS AND METHODS: The model consists of a 2-compartment solute kinetics model, 3-compartment body fluid model, and 12-lumped-parameter representation of the cardiovascular circulation model connected to set-point models of the arterial baroreflexes. The solute kinetics model includes the dynamics of solutes in the intracellular and extracellular pools and a fluid balance model for the intracellular, interstitial, and plasma volumes. Perturbation due to hemodialysis treatment induces a pressure change in the blood vessels and the arterial baroreceptors then trigger control mechanisms (autoregulation system). These in turn alter heart rate, systemic arterial resistance, and cardiac contractility. The model parameters are based largely on the reported values. RESULTS: We present the results obtained by numerical simulations of cardiovascular response during hemodialysis with 3 different dialysate sodium concentration profiles. In each case, dialysate sodium concentration profile was first calculated using an inverse algorithm according to plasma sodium concentration profiles, and then the percentage changes in each compartment pressure, heart rate, and systolic ventricular compliance and systemic arterial resistance during hemodialysis were determined. A plasma concentration with an upward convex curve profile produced a cardiovascular response more stable than linear or downward convex curves. CONCLUSION: By conducting numerical tests of dialysis/cardiovascular models for various treatment profiles and creating a database from the results, it should be possible to estimate an optimal sodium profile for each patient.     

Accuracy of single-dipole inverse solution when localising ventricular pre-excitation sites: simulation study

Different factors are investigated that may affect the accuracy of an inverse solution that uses a single-dipole equivalent generator, in a standardised inhomogeneous torso model, when localising the pre-excitation sites. An anatomical model of the human ventricular myocardium is used to simulate body surface potential maps (BSPMs) and magnetic field maps (MFMs) for 35 pre-excitation sites positioned on the epicardial surface along the atrioventricular ring. The sites of pre-excitation activity are estimated by the single-dipole method, and the measure for the accuracy of the localisation is the localisation error, defined as the distance between the location of the best-fitting single dipole and the acutal site of pre-excitation in the ventricular model. The findings indicate that, when the electrical properties of the volume conductor and lead positions are precisely known and the ‘measurement’ noise is added to the simulated BSPMs and MFMs, the single-dipole method optimally localises the pre-excitation activity 20 ms after the onset of pre-excitation, with 0.71±0.28 cm and 0.65±0.30 cm using BSPMs and MFMs, respectively. When the standard torso model is used to localise the sites of onset of the pre-excitation sequence initiated in four individualised torso models, the maximum errors are as high as 2.6–3.0 cm (even though the average error, for both the BSPM and MFM localisations, remains within the 1.0–1.5 cm range). In spite of these shortcomings, it is thought that single-dipole localisations can be useful for non-invasive pre-interventional planning.     

不同骨密度下人体脊柱着陆冲击响应的数值模拟

目的 用数值模拟方法探讨人体骨密度改变对人体脊柱着陆冲击响应的影响。方法 通过人体扫描CT图片构建人体头骨、颈椎、胸椎、腰椎、尾椎、盆骨、韧带的三维物质点模型,并将这些模型固定连接作为人体脊柱模型固定置于利用MPM3D程序构建的长方体椅背物质点模型上,构建人体脊柱着陆冲击模型。在椅背上施加加速度载荷,模拟人体脊柱仰卧于椅背受到着陆冲击载荷的情况。通过改变脊柱骨骼密度及对应骨骼弹性模量模拟计算不同骨密度下人体脊柱的着陆冲击响应。结果 正常骨骼密度时,人体脊柱的整体损伤评价γ值为1.589 3;骨密度分别减小2%、4%、6%、8%、10%时,对应人体脊柱的整体损伤评价γ值分别为1.608 6、1.634 7、1.641 0、1.662 5、1.680 5。结论 在受到相同的冲击载荷时,人体骨骼密度越小,人体对冲击载荷的响应越大,越容易受伤。