Immunophenotypic,immunocytochemistry, ultrastructural,and cytogenetic characterization of mesenchymal stem cells from equine bone marrow

The aim of this study was to isolate, culture, and characterize mesenchymal stem cells (MSCs) from horse bone marrow (BM) using the techniques of flow cytometry, immunocytochemistry, cytogenetics, and electron microscopy. Immunophenotypic analysis revealed the presence of MSCs with high expression of the CD90 marker, lower expression of the CD44 marker, and absent expression of the CD34 marker. In assays of differentiation, the positive response to osteogenic (OST), chondrogenic (CDG), and adipogenic (ADP) differentiation signals was observed and characterized by deposition of calcium‐rich extracellular matrix (OST), proteoglycans and collagen II (CDG) and intracellular deposition of fat drops (ADP). In immunocytochemical characterization, MSCs were immunopositive for CD44, vimentin, and PCNA, and they were negative for CD13. In the ultrastructural analysis of MSCs, the most outstanding characteristic was the presence of rough endoplasmic reticulum with very dilated cisterns filled with a low electrodensity material. Additionally, MSCs had normal karyotypes (2n = 64) as evidenced by cytogenetic analysis, and aneuploidy in metaphase was not observed. The protocols for isolating, culturing, and characterizing equine MSCs used in this study were shown to be appropriate for the production of a cell population with a good potential for differentiation and without aneuploidy that can be used to study future cellular therapies. Microsc. Res. Tech. 76:618–624, 2013. © 2013 Wiley Periodicals, Inc.     

APPLICATION OF FORCE-STATE MAPPING TO A NON-LINEAR FLUID–ELASTIC SYSTEM

The damping mechanisms associated with flow/structure interactions are, in general, considered to be non-linear. In this paper, the fluid–elastic instability of a tube in a heat exchanger is controlled using a tunable damper and the stiffness and damping associated with the flow-induced non-linearities are determined using the force-state mapping technique. The analysis of the results clearly indicates a linear destabilising fluid mechanism but also identifies non-linear damping and stiffness forces which are consistent with both the experimental behaviour and theoretical models for the instability.     

Mechanical and histological properties of an electrospun scaffold with a modified surface by plasma polymerization implanted in an <i>in vivo</i> model

This article presents the construction of scaffolds composed of polylactic acid (PLA) with different concentrations of hydroxyapatite (HA) by electrospinning, which were superficially modified with polypyrrole (PPy/I) by plasma polymerization. A preliminary study was conducted of the biological and mechanical behavior of the scaffolds when they were implanted in the back of rabbits for 30 days; bone cells differentiated from mesenchymal stem cells (MSCs) were used. The bone cell and scaffold structures were characterized by histological, immunohistochemical, and mechanical stress tests. Hematoxylin–eosin staining showed good tissue conformation. The immunohistochemical tests highlighted the presence of the main bone tissue proteins, such as collagen, osteocalcin, and osteopontin. The PLA/HA scaffolds were observed to exhibit cell adhesion and proliferation properties; however, the response was much better in the scaffolds that had a higher concentration of HA and that were coated with PPy/I. The results of the mechanical tests of the scaffolds indicated that the plasma treatment improved the adhesion and cell proliferation properties and contributed to the mechanical support, allowing the formation of neotissues with good viability of cell growth.     

Brief Note: CD44 is involved in CXCL-12 induced acute myeloid leukemia HL-60 cell polarity

CXCL-12 and its receptor CXCR4 participate in breast cancer and melanoma cell metastasis to bone and lymphoid nodes. CD44, as a receptor for hyaluronic acid, is involved in lymphocyte recirculation, homing, adhesion and migration. But the role of CD44 in CXCL-12 induced leukemia cell migration still remains unclear. The present study showed that CXCL-12 stimulation induced the rapid internalization of CXCR4 and facilitated the formation of lamellipodia and uropod in acute leukemia cell line HL-60. CXCL12 also induced CD44 translocation into the uropod, while CD44 remained evenly distributed on the untreated cell membranes. Results suggest that CD44 participates in CXCL-12 induced cell polarization and subsequent cell migration.     

Development of preparation methods for and insights obtained from atomic force microscopy of fluid spaces in cortical bone

Several preparation methods were developed to investigate the dimensions and surface structure of fluid spaces within cortical bone, using atomic force microscopy (AFM). Of special interest was the morphology of the lacunocanalicular system, which serves as a conduit between osteocytes encased in bone tissue, the intramedullary cavity, blood vessels running through the bone, and the periosteal surface of bone. Fracture and the removal of either the mineral or the organic component is a method by which each component can be investigated at a very high resolution in situ. Although fractured bone was too rough to image details of the lacunocanalicular system, post-treatment with ethylene diamine tetraacetic acid (EDTA) or papain allowed for investigation of the collagen matrix or the mineral crystals of bone, respectively. Cut and polished bone was smooth enough for identifying the lacunae of bone using AFM, but unambiguous differentiation between the canaliculi and cracks in the bone surface was not possible. However, when the lacunocanalicular system was filled with polymethylmethacrylate (PMMA), it was possible to image casts of the lacunocanalicular system by selectively etching away the surrounding bone matrix. Using this method, we identified individual canaliculi and measured their dimensions. Furthermore, by carefully etching away the bone matrix in successive etches, it was shown that the wall structure of the canaliculus is dominated by collagen fibrils. These observations have important implications for fluid flow in bone.     

Stratified steady and unsteady two-phase flows between two parallel plates

To understand fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. Stratified steady and unsteady two-phase flows between two parallel plates have been studied to investigate the general characteristics of the flow related to flow-induced vibration. Based on the spectral collocation method, a numerical approach has been developed for the unsteady two-phase flow. The method is validated by comparing numerical result to analytical one given for a simple harmonic two-phase flow. The flow parameters for the steady two-phase flow, such as void fraction and two-phase frictional multiplier, are evaluated. The dynamic characteristics of the unsteady two-phase flow, including the void fraction effect on the complex unsteady pressure, are illustrated.     

用概率分析研究克服流体诱发调节阀振动

按流体诱发振动的流体力学理论 ,应用概率分析和数理统计方法 ,研制了异径多束流调节阀。使用表明 ,其克服流体诱发调节阀的振动效果十分显著     

Mechanotransduction-The relationship between gravity,cells and tensile loading in extracellular matrix

Gravity plays a central role in vertebrate development and evolution. Mechanotransduction involves the tensile tethering of veins and arteries, connections between the epidermis and dermis in skin, tensile stress concentrations that occur at tissue interfaces, cell-cell interactions, cell-collagen fiber stress transfer in extracellular matrix and fluid shear flow. While attention in the past has been directed at understanding the myriad of biochemical players associated with mechanotransduction pathways, less attention has been focused on determining the tensile mechanical behavior of tissues in vivo. Fibroblasts sit on the surface of collagen fibers in living skin and exert a retractile force on the fibers. This retractile force pulls against the tension in collagen fibers in skin. After fibroblast-collagen fiber interactions are altered either by changes in fibroblast adhesion or after formation of cancer associated fibroblasts, and changes in cell junctions, alterations in the retractive force leads to changes in mechanotransduction. The purpose of this paper is to present a model of tensile forces that occur at the fibroblast-collagen fiber interface and how these forces are important in extracellular matrix physiology in health and disease.     

Rheology of synthetic lubricating oils

A lubricating fluid's flow characteristics are affected by fluid deformation resulting from the action of mechanical forces: flow resistance, dissipation of mechanical energy, transfer and dampening of mechanical disturbances. These in turn affect the lubricating ability of the fluid through energy absorption, power transfer and other properties. Synthetic fluids can display various thixotropic characteristics and non-Newtonian effects. In this paper, experimental work on these phenomena are reported.     

节气门急速开启过程流动噪声数值分析与研究

研究了节气门运动对流动噪声的影响。采用计算流体力学与计算声学耦合方法,并结合运动网格技术,实现对节气门由关闭向全开位置急速转动过程时空气瞬态流动引起噪声形成的三维数值模拟,分析了节气门处于不同转角时刻,空气流场与流动噪声的变化规律。在节气门转动初期,节气门后侧流动区域有涡流形成,节气门前后两侧的压力发生陡降,在节气门上边缘和下边缘附近产生两个流动噪声区,随后在节气门下游逐渐合并。流动噪声声功率级先增加然后逐渐减小,并接近稳定,节气门开度在40°附近时,声功率级达到最大。随着节气门开度的继续增加,节气门后侧的涡流逐渐减弱,节气门前后两侧的压力降逐渐减小。噪声场时域-频域计算结果发现,节气门噪声属于中低频段宽频噪声,其中大约100Hz以下的低频噪声占主要贡献量,声压级较高,并且声压没有随着测点与节气门的距离增加而明显衰减。控制节气门流动噪声的重点在于减少低频噪声。     

基于离散单元法多孔陶瓷微球骨支架的微观结构分析

人工骨支架的孔隙率是评价体液在人工骨内部循环和细胞生长能力的重要参数,利用离散单元法分析模拟人工骨支架制备过程中HA微球的堆积过程,实现了对堆积内部微观情况的预测。本文以PFC3D软件为平台对HA石微球人工骨支架的微观结构进行了模拟仿真,从而通过改变HA微球和可速溶性小球的数量比及半径值,实现孔隙率可控,得出配位数为6时,HA微球人工骨支架的孔隙率为0．59,在满足力学性能的条件下,与人骨组织的孔隙率最为接近。     

Experimental investigation on the flow-induced noise under variable conditions for centrifugal pumps

With extensively using of centrifugal pumps,noise generation in these pumps is increasingly receiving research attention in recent years.The noise sources in centrifugal pumps are mainly composed of mechanical noise and flow-induced noise.And the study of flow-induced noise has become a hotspot and important domain in the field.The flow-induced noise closely related to the inner pressure pulses and vibration of volute in pumps,therefore,it is necessary to research the interaction and mechanism among them.To investigate the relationships,a test system is designed which includes a test loop and a measurement system.The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body.Via these instruments,the signals of noise,pressure pulses and vibration are collected and analyzed.The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations,and it is steadily close to the design point,then it increases with the growing of flow rate in high flow rate conditions.Furthermore,there are some similar peak points in the power spectrum charts of noise,pressure pulses and vibration.The broadband noise at low flow rate is mostly focused on the region of 0-40 times shaft frequency,which is mostly made by rotating stall and vortex;while the noise at high flow rate conditions is focused on the region of 60-100 times shaft frequency,which may be mostly made by cavitations.The proposed research is of practical and academic significance to the study of noise reduction for centrifugal pumps.     

基于流-固耦合模型的人工骨力学数值仿真

根据力学平衡条件推出应力场方程,并建立孔隙率和渗透率的动态模型;依据流体力学连续性方程,考虑流-固耦合情形下多孔介质骨架变形特性和流体的可压缩性,得到了孔隙流体的连续性方程,即渗流场方程。在此基础上辅以定解条件,建立了人工骨完备的饱和多孔介质流-固全耦合渗流的数学模型,进而分析人工骨在承受各种载荷时,其骨质应力场、变形场以及孔间骨液压力场的分布规律。     

Design and Simulation of Flow Field for Bone Tissue Engineering Sca old Based on Triply Periodic Minimal Surface

A novel method was proposed to design the structure of a bone tissue engineering scafold based on triply periodic minimal surface.In this method,reverse engineering software was used to reconstruct the surface from point cloud data.This method overcomes the limitations of commercially available software packages that prevent them from generating models with complex surfaces used for bone tissue engineering scafolds.Additionally,the fluid feld of the scafolds was simulated through a numerical method based on fnite volume and the cell proliferation performance was evaluated via an in vitro experiment.The cell proliferation and the mass flow evaluated in a bioreactor further verifed the flow feld simulated using computational fluid dynamics.The result of this study illustrates that the pressure value drops rapidly from 0.103 Pa to 0.011 Pa in the y-axis direction and the mass flow is unevenly distributed in the outlets.The mass flow in the side outlets is observed to be approximately 24.3 times higher thanthe bottom.Importantly,although the mean value of wall shear stress is signifcantly more than 0.05 Pa,there is stil a large area with a suitable shear stress below 0.05 Pa where most cells can proliferate well.The result shows that th inlet velocity 0.0075 m/s is suitable for cell proliferation in the scafold.This study provides an insight into the design analysis,and in vitro experiment of a bone tissue engineering scafold.     

A new bioreactor for the controlled application of complex mechanical stimuli for cartilage tissue engineering

Mechanical stimuli have been shown to enhance chondrogenesis on both animal and human chondrocytes cultured in vitro. Different mechanical stimuli act simultaneously in vivo in cartilage tissue and their effects have been extensively studied in vitro, although often in a separated manner. A new bioreactor is described where different mechanical stimuli, i.e. shear stress and hydrostatic pressure, can be combined in different ways to study the mechanobiology of tissue engineered cartilage. Shear stress is imposed on cells by forcing the culture medium through the scaffolds, whereas a high hydrostatic pressure up to 15 MPa is generated by pressurizing the culture medium. Fluid-dynamic experimental tests have been performed and successful validation of the bioreactor has been carried out by dynamic culture of tissue-engineered cartilage constructs. The bioreactor system allows the investigation of the combined effects of different mechanical stimuli on the development of engineered cartilage, as well as other possible three-dimensional tissue-engineered constructs.     

Flow-induced vibration and stability analysis of multi-wall carbon nanotubes

The free vibration and flow-induced flutter instability of cantilever multi-wall carbon nanotubes conveying fluid are investigated and the nanotubes are modeled as thin-walled beams. The non-classical effects of the transverse shear, rotary inertia, warping inhibition, and van der Waals forces between two walls are incorporated into the structural model. The governing equations and associated boundary conditions are derived using Hamilton’s principle. A numerical analysis is carried out by using the extended Galerkin method, which enables us to obtain more accurate solutions compared to the conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for a flow velocity below a certain critical value. However, beyond this critical flow velocity, flutter instability may occur. The variations in the critical flow velocity with respect to both the radius ratio and length of the carbon nanotubes are investigated and pertinent conclusions are outlined. The differences in the vibration and instability characteristics between the Timoshenko beam theory and Euler beam theory are revealed. A comparative analysis of the natural frequencies and flutter characteristics of MWCNTs and SWCNTs is also performed.     

快速成形中PAN基碳纤维/HA力学性能模拟研究

在人工骨支架增材制造过程中,为了制造出具有不同力学性能的人造骨支架适合不同病患,提出利用分子动力学(Molecular dynamics,MD)模拟方法,研究所用基体复合材料(聚丙烯腈(Poly acrylonitrile,PAN)基碳纤维和羟基磷灰石(Hydroxyapatite, HA))表面之间的相互作用及力学性能。分别在原子模拟凝聚相优化分子势能力场(Condensed-phase optimized molecular potentials for atomistic simulation studies,COMPASS)和通用力场(Universal force field,UFF)下,对比计算HA和PAN基碳纤维/HA的力学性能,并比较其弹性模量和泊松比,证明羟基磷灰石是一种各向异性材料,并给出羟基磷灰石中添加PAN基碳纤维可以有效改善其力学性能。针对沿不同剪切方向上的PAN基碳纤维/羟基磷灰石进行动力学计算,表明在不同的力场下,羟基磷灰石均是在沿(110)剪切面上与聚丙烯腈纤维产生的结合能值较大。结合径向分布函数分析,揭示了PAN/HA复合材料主要是通过PAN中的N原子与HA表面发生强作用,从而提高PAN/HA基体力学性能。     

A structural analysis on the leaflet motion induced by the blood flow for design of a bileaflet mechanical heart valve prosthesis

This paper presents a structural analysis on the rigid and deformed motion of the leaflet induced by the blood flow required in the design of a bileaflet mechanical heart valve (MHV) prosthesis. In the study on the design and the mechanical characteristics of a bileaflet mechanical heart valve, the fluid mechanics analysis on the blood flow passing through leaflets, the kinetodynamics analysis on the rigid body motion of the leaflet induced by the pulsatile blood flow, and the structural mechanics analysis on the deformed motion of the leaflet are required sequentially and simultaneously. Fluid forces computed in the previous hemodynamics analysis on the blood flow are used in the kinetodynamics analysis on the rigid body motion of the leaflet. Thereafter, the structural mechanics analysis on the deformed motion of the leaflet follows to predict the structural strength variation of the leaflet as the leaflet thickness changes. Analysis results show that structural deformations and stresses increase as the fluid pressure increases and the leaflet thickness decreases. Analysis results also show that the leaflet becomes structurally weaker and weaker as the leaflet thickness becomes smaller than 0.6 mm.     

Vortex-induced vibration control by micro actuator

The control of vortex-induced vibration of two side-by-side circular cylinders in a cross flow is carried out experimentally. One cylinder is elastically supported and the other is fix-supported at both ends. The two cylinders vibrate under the action of the unsteady flow-induced forces. A micro actuator is embedded on the surface of each cylinder to perturb the boundary layer. The spacing ratio is set at 1.2. The measurement shows that the structural vibration can be suppressed significantly when the reduced excitation frequency is around 2.655.     

氟羟基磷灰石的稳定性及细胞反应

模仿天然骨和牙齿的组成成分,构建复合的牙、骨修复材料。采用羟基磷灰石和胶原蛋白复合构建。因氟离子被认为有一定的防龋齿以及较好的热学和化学稳定性,引入氟羟基磷灰石构建复合材料,并与羟基磷灰石复合材料进行比较并分别用X射线衍射法以及红外光谱分析复合材料的结合情况。用MTT法验证羟基磷灰石和氟羟基磷灰石的细胞安全性。