Myocilin蛋白在小梁网组织中的作用

Myocilin基因是与原发性开角型青光眼成因有关的基因.其蛋白产物myocilin蛋白是一种分泌型糖蛋白,具有特征性区域:N端亮氨酸拉链区,中央链接区,C端类嗅质蛋白(嗅素)区.眼组织中,小梁网myocilin蛋白表达水平最高且在细胞内外均可检测到.细胞内myocilin蛋白由小梁网细胞以外泌体样囊泡形式释放至胞外,...     

小梁网组织表面力学特性及其各向异性模型

目的 探讨小梁网组织表面弹性模量的变化趋势,并使用各向异性模型模拟,验证各向异性模型的合理性。方法 对2只大鼠的4个小梁网样本在表面不同位置进行原子力显微镜(atomic force microscope, AFM)压痕实验,并使用本课题组提出的各向异性小梁网力学模型对小梁网组织表面不同位置处测得的弹性模量进行模拟实验。结果 测试得到的小梁网组织表面弹性模量会随着位置不同而变化,并且在小梁网中段达到最小值;各向异性小梁网力学模型可以较好地模拟这一现象。结论 各向异性小梁网力学模型在描述小梁网力学特性方面具有较强的理论意义与实用价值。同时,该模型可以解释对小梁网组织进行单轴拉伸与AFM压痕实验获得的弹性模量之间的巨大差别。因此,各向异性小梁网模型是对小梁网力学特性的一种更好描述。     

基于双光子共聚焦成像的大鼠小梁网三维重建及有限元分析

青光眼是一组威胁视神经视觉功能、与眼压升高密切相关的眼病。目前认为临床上大部分眼压的升高与房水流出阻力增加有关,特别是小梁网流出阻力的增加。因此,研究高眼压下影响房水外流阻力的重要区域小梁网的形态学信息尤为重要。通过前房灌注的方法制造大鼠急性高眼压动物模型,将6只SD大鼠分成两组(A组和B组),B组大鼠处死后于左眼球加压60 mmHg处理,其余眼球均为未加压对照组,利用双光子共聚焦成像系统采集正常眼压和高眼压下小梁网组织的断层序列图,通过图像处理方法,定量分析眼压对小梁网组织孔隙率变化的影响。通过三维重建获取正常眼压下的小梁网结构模型,并利用有限元方法,探讨眼压对于小梁网组织形态结构的影响。结合实验数据与模拟计算的结果,综合分析眼压的变化对于小梁网外流阻力的影响。高眼压组数据显示,部分小梁与周围组织融合,胶原纤维出现塌缩,越是靠近前房的小梁组织损伤越严重。有限元分析结果表明,孔隙越多的区域变形越大,而且压力越大,小梁变形程度越明显。眼内压升高可能会引起房水外流通道结构发生异常,主要表现为小梁网胶原纤维发生塌缩。高眼压与正常眼压情况相比,小梁网区域外流阻力增大的可能性较大。     

Effect of Ethacrynic Acid on Plasma Renin Activity during Supine Exercise in Normal Subjects

Plasma renin activity, clearances of inulin (cin) and para-aminohippuric acid (cpah) , free water clearance (ch₂o) and urinary excretion of sodium and potassium were measured in 6 normal subjects at rest and during exercise in the supine position on a bicycle ergometer. The mean work load was 667 kpm/min and the duration of exercise 45 min. Ethacrynic acid, 50 mg, was injected i.v. at the start of exercise. Ethacrynic acid did not influence the normally occurring decrease in Cpah and C_in during exercise but abolished the renal concentration mechanism, indicating an inhibition of sodium reabsorption in the ascending loop of Henle. The urinary sodium cxcrction increased markedly, indicating an increased load of sodium in distal tubules. This was coincident with increased plasma renin activity. The findings indicate that changes in plasma sodium concentration or sodium load in the distal tubules are of minor importance for the increase in plasma renin activity during exercise.     

In Vitro Experiments and Numerical Simulations of Airflow in Realistic Nasal Airway Geometry

Pressure–flow relationships measured in human plastinated specimen of both nasal cavities and maxillary sinuses were compared to those obtained by numerical airflow simulations in a numerical three-dimensional reconstruction issued from CT scans of the plastinated specimen. For experiments, flow rates up to 1500 ml/s were tested using three different gases: HeO₂, Air, and SF₆. Numerical inspiratory airflow simulations were performed for flow rates up to 353 ml/s in both the nostrils using a finite-volume-based method under steady-state conditions with CFD software using a laminar model. The good agreement between measured and numerically computed total pressure drops observed up to a flow rate of 250 ml/s is an important step to validate the ability of CFD software to describe flow in a physiologically realistic binasal model. The major total pressure drop was localized in the nasal valve region. Airflow was found to be predominant in the inferior median part of nasal cavities. Two main vortices were observed downstream from the nasal valve and toward the olfactory region. In the future, CFD software will be a useful tool for the clinician by providing a better understanding of the complexity of three-dimensional breathing flow in the nasal cavities allowing more appropriate management of the patient's symptoms.     

Complexation of Mefenamic Acid by Low‐Generation PAMAM Dendrimers: Insight from NMR Spectroscopy Studies and Molecular Dynamics Simulations

The complexation of mefenamic acid (MA) with poly(amido amine) dendrimers of the second and third generation (PAMAM‐G2 and PAMAM‐G3) at pH 7.0 is studied by aqueous solubility experiments, DOSY and 2D‐NOESY spectroscopy, and fully atomistic molecular dynamics (MD) simulations. Solubility profiles account for the formation of MA:PAMAM complexes of the type 10:1 and 15:1, for PAMAM‐G2 and PAMAM‐G3, respectively, with a maximum solubilization enhancement of 14.6 mol of MA per mol dendrimer. Diffusion ordered sepectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments suggest that MA association occurs through both external electrostatic interactions with the PAMAM surface and internal encapsulation into the deep dendrimer cavities. MD simulations are consistent with these experimental findings and show that the internal drug encapsulation is enhanced as the dendrimer generation increases. The involvement of internal and external interactions in the complexation of MA with low‐generation PAMAM dendrimers differs from the general behavior expected for acidic anionic guests, for which external electrostatic contacts with the positively charged PAMAM surface have been postulated as the most relevant factor for drug association.

     

Three-dimensional Numerical Modeling and Computational Fluid Dynamics Simulations to Analyze and Improve Oxygen Availability in the AMC Bioartificial Liver

A numerical model to investigate fluid flow and oxygen (O₂) transport and consumption in the AMC-Bioartificial Liver (AMC-BAL) was developed and applied to two representative micro models of the AMC-BAL with two different gas capillary patterns, each combined with two proposed hepatocyte distributions. Parameter studies were performed on each configuration to gain insight in fluid flow, shear stress distribution and oxygen availability in the AMC-BAL. We assessed the function of the internal oxygenator, the effect of changes in hepatocyte oxygen consumption parameters in time and the effect of the change from an experimental to a clinical setting. In addition, different methodologies were studied to improve cellular oxygen availability, i.e. external oxygenation of culture medium, culture medium flow rate, culture gas oxygen content (pO₂) and the number of oxygenation capillaries. Standard operating conditions did not adequately provide all hepatocytes in the AMC-BAL with sufficient oxygen to maintain O₂ consumption at minimally 90% of maximal uptake rate. Cellular oxygen availability was optimized by increasing the number of gas capillaries and pO₂ of the oxygenation gas by a factor two. Pressure drop over the AMC-BAL and maximal shear stresses were low and not considered to be harmful. This information can be used to increase cellular efficiency and may ultimately lead to a more productive AMC-BAL.     

雾化治疗中气溶胶在深层肺泡输运特性 的数值模拟研究

目的 基于计算流体动力学的方法,模拟计算单个肺泡中的气体与气溶胶颗粒输运情况,研究深层肺泡内气体流动和气溶胶颗粒输运特性。方法 采用一端有周期性扩张/收缩半球形壁的长直导管作为单一肺泡及肺泡管的简化近似,建立二维数学模拟模型。考虑呼吸气体在半球边界上的扩散,采用欧拉 欧拉方法对肺泡管中气体以及气溶胶颗粒的输运方程进行求解。结果 整个呼吸过程中,管道中空气的成分比率以稳定的周期方式随时间变化。气溶胶在管道输运主要依赖于颗粒的扩散系数,平流输运只有微小的影响。气溶胶颗粒尺寸减小时,气溶胶的扩散速度与深度均有提高,粒径小于4 μm时该现象尤为明显,且呼吸频率和幅度的增大可以显著提升颗粒的输运能力。结论 雾化治疗中,粒径较小的气溶胶颗粒可以增强药物扩散速度。深呼吸有助于提升颗粒的输运效果,治疗中应鼓励患者深呼吸。     

A Contrastive Analysis of Laser Heating Between the Human and Guinea Pig Cochlea by Numerical Simulations

<正>The photo-thermal effect has been hypothesised to be one of the most possible biophysical mechanisms for laser-cochlea stimulation.The majority focus on animals like the guinea pig,from which a number of valuable results have been gained.However,in light of the increasing need to improve laser safety,it has became necessary to find out whether studies on animals can shed light on safe laser pa-     

Keratinocyte Differentiation and Proliferation are Regulated by Adhesion to the Three-Dimensional Meshwork Structure of Type IV Collagen

We examined the behavior of human foreskin keratinocytes (HFKs) on reconstituted type IV collagen gel. HFKs survived for several days and the upper layer cells expressed a differentiation marker, involucrin. Apoptosis was induced after involucrin expression while cell proliferation was suppressed. On molecular type IV collagen, integrins shifted from α2β1 to α3β1 during HFK culture. On type IV collagen gel, HFKs initially expressed integrin α2β1, and later expressed integrin α3β1 in the presence of α2β1 did not disappear. Using synthetic peptides, we examined integrin α2-mediated adhesion to type IV collagen gel. Addition of synthetic peptide dose-dependently inhibited cell adhesion both on type IV collagen gel and on molecular type IV collagen. On type IV collagen gel, weaker phosphorylation of focal adhesion kinase, paxillin, and Akt was observed compared with the molecular forms. Based on these observations, we think type IV collagen gel is a novel culture substrate that mimics the physiological environment for HFKs.     

Trabecular bone remodelling simulated by a stochastic exchange of discrete bone packets from the surface

Human bone is constantly renewed through life via the process of bone remodelling, in which individual packets of bone are removed by osteoclasts and replaced by osteoblasts. Remodelling is mechanically controlled, where osteocytes embedded within the bone matrix are thought to act as mechanical sensors. In this computational work, a stochastic model for bone remodelling is used in which the renewal of bone material occurs by exchange of discrete bone packets. We tested different hypotheses of how the mechanical stimulus for bone remodelling is integrated by osteocytes and sent to actor cells on the bone's surface. A collective (summed) signal from multiple osteocytes as opposed to an individual (maximal) signal from a single osteocyte was found to lead to lower inner porosity and surface roughness of the simulated bone structure. This observation can be interpreted in that collective osteocyte signalling provides an effective surface tension to the remodelling process. Furthermore, the material heterogeneity due to remodelling was studied on a network of trabeculae. As the model is discrete, the age of individual bone packets can be monitored with time. The simulation results were compared with experimental data coming from quantitative back scattered electron imaging by transforming the information about the age of the bone packet into a mineral content. Discrepancies with experiments indicate that osteoclasts preferentially resorb low mineralized, i.e. young, bone at the bone's surface.     

Exosomes Transport Anti-Human Immunodeficiency Virus Factors from Human Cervical Epithelial Cells to Macrophages

The female reproductive tract (FRT) is a major site of HIV sexual transmission. As the outermost layer of cells in the FRT, the human cervical epithelial cells (HCEs) have direct contact with HIV or infected cells. Our early work showed that supernatant (SN) from TLR3-activated HCEs contain the antiviral factors that could potently inhibit HIV replication in macrophages. However, it remains to be determined how HCEs transport the anti-HIV factors to macrophages. This follow-up study examined the role of exosomes in HCE-mediated anti-HIV activity. We found that TLR3 activation of HCEs resulted in the release of exosomes that contained multiple IFN-stimulated genes (ISGs: ISG56, OAS1, MxA, and Mx2) and the HIV restriction microRNAs (miR-28, miR-29 family members, miR-125b, miR-150, miR-382, miR-223, miR-20a, and miR-198). The depletion of exosomes from SN of TLR3-activated HCEs diminished HCE-mediated anti-HIV activity in macrophages, indicating that HCE-derived exosomes are responsible for transporting the antiviral molecules to macrophages. These in vitro findings suggest a novel antiviral mechanism by which HCEs participate in the FRT innate immunity against HIV infection. Further in vivo studies are necessary in order to develop an exosome-based delivery system for prevention and treatment of HIV infection through sexual transmission.     

脑电高阶Lyapunov指数的估计及其仿真计算

本研究从一维时间序列中估算了相应混沌系统的前3阶最大Lyapunov指数λ1、λ2和λ3,以两个高维混沌模型:4×3 Lorenz方程高维混沌系统和HyperR ssler超混沌系统作为仿真系统,对算法的可行性和有效性进行了验证。然后,应用λ1、λ2和λ3对脑电的高维混沌特性进行了研究:从脑电中分别重构了对应的时间延迟吸引子,计算了癫痫脑电组和正常对照组脑电的1λ、λ2和3λ,应用Y-K公式给出的混沌系统分数维和Lyapunov指数谱jλ的关系,估计了癫痫脑电和正常对照脑电对应系统的分数维的范围,对癫痫脑电的高维混沌状况进行了分析。结果表明:癫痫脑电对应混沌吸引子的维数低于正常脑电(高维混沌)的维数;可以分属于高维混沌和低维混沌两类情况,因此研究这两类不同的情况,应采用高维和低维两种不同的混沌理论和方法。     

Transport of inhaled dust to extrapulmonary sites

A histological study of the lungs of guinea-pigs that inhaled carbon, chrysotile asbestos or crocidolite asbestos dust indicated that dust particles in macrophages move through alveolar walls towards the pleura. After some weeks accumulations of dust-filled macrophages were found near to pulmonary blood vessels. Macrophages that ingested carbon appeared to be much less mobile than those that ingested asbestos. In sections from the animals that inhaled asbestos, macrophages were found that were penetrating the wall of blood vessels, some carrying asbestos fibres. It is probable that some inhaled dust is transferred to extrapulmonary sites by macrophages in the blood.