兔眼角膜生物力学特性的年龄相关性

目的 利用兔眼角膜条的单轴拉伸实验数据,研究角膜生物力学特性与年龄的相关性。 方法 分别取3月龄和7~8月龄兔眼角膜条,实施单轴拉伸实验,获得实验数据;用指数模型和幂模型对应力 应变数据进行分析;用黏弹性力学模型对应力松弛数据进行分析。结果 兔眼角膜条呈现非线性黏弹性特征。在实验误差允许的范围内,不同月龄兔眼角膜条的非线性应力-应变关系差别不明显,7~8月龄兔眼角膜的切线模量略偏大,但其应力衰减得明显快。不同的拉伸速率对3月龄兔眼角膜条非线性应力-应变关系的影响不明显,但快速拉伸后的角膜条应力衰减明显变快。结论 兔眼角膜随月龄增加会轻微变硬,而角膜的松弛特性随月龄变化明显。     

层粘连蛋白对兔角膜内皮细胞bcl-2表达的影响

目的：观察层粘连蛋白（LN）对兔角膜内皮细胞bcl-2表达的影响。 方法： 将体外培养的兔角膜内皮细胞分成3组：正常对照组、层粘连蛋白(LN)处理组、阴性对照组,采用免疫组化法和酶联免疫法分别检测3组的染色深浅及吸光度大小，以显示各组间bcl-2表达的水平。 结果： 免疫组织化学染色及评分结果显示LN组bcl-2为强阳性表达，正常对照组bcl-2为弱阳性表达，阴性对照组bcl-2为阴性表达。酶联免疫吸附试验检测3组吸光度分别为1.21±0.18（LN组）、1.05±0.14（正常对照组）和0.04±0.01（阴性对照组）。 结论： 层粘连蛋白能促进兔角膜内皮细胞bcl-2基因表达，从而可以有效地抗细胞凋亡。     

猪肝动脉的弹性模量与性别的关系

目的探讨猪肝动脉弹性模量与性别的关系,为猪到人异种肝移植提供理论依据。方法取23例4、7月龄雌性、雄性、去势湖北白猪的肝动脉,将其按从近心端到远心端的方向分成近、中、远3段,各段置于4℃冰箱中待用。在软组织生物力学试验机上测定中段动脉的压力-直径关系,计算出增量弹性模量(Einc)、压力-应变弹性模量(Ep)和容积弹性模量(Ev)。结果 7月龄各组肝动脉的弹性模量有显著性差异(P0.01):雌性组最低,雄性组居中,去势组最高;7月龄各组与4月龄各组的弹性模量相比显著减小(P0.05)。结论 7月龄不同性别猪肝动脉弹性模量存在差异,从生物力学方面考虑,在猪到人异种肝移植时,应选择性别相匹配的猪肝脏作为供体材料,使移植材料肝动脉间的弹性模量尽可能相近,降低肝动脉并发症,有可能提高移植肝的存活率。     

Metabolic component in the epithelial intracellular potential of rabbit cornea

Summary Effects of the change of external ionic composition and the addition of metabolic inhibitors on rabbit cornea were studied by recording the epithelial intracellular potential. High K and Li Ringer's solutions, applied to the corneal endothelial side, caused a marked depolarization of the epithelial cells, but no potential change was seen when applied to the epithelial side. Ouabain, MIAA and NaCN applied to the endothelial side reduced the epithelial potential, while those applied to the epithelial side did not change the potential. DNP and FDNB also had no effect when applied to the epithelial side only. The thermal dependence of the epithelial intracellular potentials of whole eye (0.85 mV/°C) and excised cornea (2.01 mV/°C) preparations were greater than about 0.2 mV/°C predicted by the Nernst equation. It is concluded that the epithelial cell layers of rabbit cornea act as a tight barrier against diffusion of K ion and metabolic inhibitors from the tear side to the epithelial basal cell. A high thermal dependence of the epithelial intracellular potential may depend greatly on the pump inhibition.     

人体松质骨矿质密度与弹性模量关系

目的 测量人体多部位松质骨矿质密度、轴向弹性模量,建立矿质密度与轴向弹性模量相关关系的本构方程,为国人有限元材料属性赋值提供依据。方法 采取10例成人新鲜尸体作为样本源,选取胫骨近端、大转子、股骨颈、肱骨头和椎体5个部位的松质骨,加工成直径约6 mm、长约30或40 mm的准试样。测量尺寸并计算体积,CT扫描试样骨矿质密度。对松质骨试样进行力学性能测试,分析不同部位松质骨弹性模量。对矿质密度与轴向弹性模量关系进行线性与幂次回归分析。结果 测试成功的试样来自5个部位,共169枚,其中胫骨近端52枚,大转子31枚,股骨颈15枚,肱骨头17枚,椎体54枚;5个部位松质骨矿质密度、轴向弹性模量均有所差异,线性相关性均较好（0.850>r2>0.785）,3个部位（胫骨近端、大转子、椎体）的幂次相关性较好（0.871>r2>0.825）,2个部位（肱骨头、股骨颈）的幂次相关性较弱(0.671>r2>0.643)。结论 各个部位骨矿质密度与轴向弹性模量的线性和幂次回归的相关性均较高,且同部位两种回归的r2值之间无明显差异;可应用于体外检测患者的骨骼质量,准确分辨骨质变化的部位,配合有限元建模能够预测骨折的风险。     

不同部位骨盆骨静态弹性模量及其相关生物力学性质的测定

采用生物力学实验的方法研究骨盆骨的轴向刚度、不同部位骨盆骨的压缩及拉伸弹性模量以及强度,从而为骨盆的临床及实验研究提供理论依据.试验采用12具防腐骨盆骨,利用万能材料试验机测量不同载荷下骨盆骨的位移,计算其轴向刚度;之后截取耻骨、坐骨、髋臼骨前柱及后柱、以及骶髂关节两侧骨,制成10 mm×5mm×10mm大小试件,分成12组,利用杠杆引伸仪、万能材料试验机、电阻应变仪上分别进行压缩及拉伸弹性模量以及强度的测定.在静态载荷状态下,500 N的生理载荷时,骨盆刚度值为181.28±21.4 N.mm-1,1500N时,刚度值增加到352.32 N.mm-1;耻骨、坐骨、髂骨、髋臼前、后柱以及骶髂关节两侧骨质的压缩弹性模量依次为26.7、18.4、31.7、21.3、23.1、31.7、29.6 GPa;压缩强度均值依次为64.27、124.26、91.73、94.22、50.39、107.37、84.23 GPa;拉伸弹性模量依次为29.3、20.4、25.4、23.3、21.2、19.3、17.6 GPa;拉伸强度均值依次为132.53、93.26、95.72、74.22、40.39、84.23、64.27 GPa.静态载荷状态下,刚度值随着载荷的增加逐渐加大;坐骨的抗压缩强度最大,而耻骨的抗拉伸强度最大,髋臼前柱抗压缩及拉伸的强度(94.22、74.22)均明显高于髋臼后柱.     

腰背部肌筋膜疼痛综合征激痛点的剪切波弹性模量研究

目的 通过剪切波弹性成像(SWE)技术研究肌筋膜疼痛综合征激痛点的弹性特征,探索弹性超声技术在肌筋膜疼痛综合征临床诊断中的应用价值.方法 对8例女性健康志愿者的8个正常点和15例女性肌筋膜疼痛综合征患者腰背部30个激痛点行弹性超声检查,分别获得正常点、激痛点病灶区及邻近区定量分析取样框(Q-box)内弹性模量的均值(Mean)、最小值(Min)、最大值(Max)及标准差(SD);比较正常点、激痛点病灶区及临近区的弹性模量差异,探索激痛点弹性模量与患者年龄、所在部位的关系.结果 激痛点病灶区弹性模量的均值、最小值、最大值、标准差显著高于邻近区及正常点,其差异具有统计学意义(P＜0.05);而邻近区与正常点的弹性模量差异无统计学意义(P＞0.05),两个年龄组和3个不同部位激痛点的弹性模量差异亦无统计学意义(P＞0.05).结论 剪切波弹性模量值可用于激痛点病灶区与临近区及正常组织的鉴别,为激痛点的定位提供了新方法,也为肌筋膜疼痛综合征的触诊提供了新依据,具有较高的临床应用价值和研究前景.     

A Microplate Compression Method for Elastic Modulus Measurement of Soft and Viscoelastic Collagen Microspheres

Hydrogel-based microspheres are commonly used for drug and cell delivery in regenerative medicine. Characterization of their physical and mechanical properties is important in monitoring their quality during fabrication and in predicting their performance upon injection. However, existing methods have limitations in measuring these micron-sized, soft and viscoelastic spherical structures. In this study, a protocol is developed to measure the elastic modulus of non-linear viscoelastic spheres by microplate compression, and is applied to collagen microspheres fabricated with or without cells. During the measurement, a microsphere is placed on a rigid surface and is compressed by a calibrated flexible microplate gripped to a rigid end. A step increase in the displacement rate of the rigid end of the flexible microplate is introduced and the reduced elastic modulus of the microsphere is calculated from the deformation response of the microsphere, using an equation derived in this study. The reduced elastic modulus of collagen microspheres with and without mesenchymal stem cells measured by this method was 9.1 kPa and 132 Pa, respectively.     

Thalamic inputs to the rabbit visual cortex: Identification and organization using horseradish peroxidase (HRP)

Summary Horseradish peroxidase (HRP) has been injected in visual cortical area 1 (V1, striate cortex) of 33 rabbits (16 received a unilateral injection, 17 bilateral injections) in order to identify its thalamic inputs and to determine their retinotopic organization. This study has shown that when HRP is injected into different portions of V1: 1. Labeled cells are consistently seen in the dorsal lateral geniculate nucleus (LGNd) and are always organized into horizontal columns arranged perpendicularly to the long axis of the LGNd; although the columns are always present in the alpha sector of the LGNd, they extend into the beta sector of this nucleus only occasionally. 2. With a series of injection sites that lie on or near the medial edge of V1 and run rostrocaudally, cell columns shift from ventromedial to dorsolateral within the LGNd. With a series of injection sites that are located along the lateral border of V1 and run from rostral to caudal, columns of labeled cells move from ventral to dorsal along the medial edge of the LGNd. 3. In some of the experiments, with injections in either medial or lateral portions of V1, columns of HRP-labeled cells have also been found within the pulvinar.A preliminary report of this study (Karamanlidis and Giolli, 1976) has been presented at the sixth annual meeting of the Society for Neurosciences, Toronto, Canada, November 1976     

自体静脉移植后管壁超微结构的变化

目的　探讨自体静脉移植后内皮形态特征和中膜SMC增生特点 ,为静脉搭桥后再狭窄的防治提供资料。方法　兔 18只 ,随机分 6组 ,均作模拟血管搭桥手术 ,即将颈外静脉移植于颈总动脉 ,术后取材 ,光电镜观察。结果　移植后 1～ 4周管壁渐增厚 ,4～ 6周时达最厚 ,随后管壁不再继续增厚。对照侧静脉无微绒毛梭形内皮被移植段具有丰富微绒毛呈不同形态的内皮细胞所替代。移植后 1～ 2周 ,SMC肌丝和致密体减少 ,与合成和分泌有关的细胞器异常丰富 ,SMC从收缩型转变成合成型 ,四周时分泌型细胞器略有减少 ,但细胞间的胶原纤维明显增多。第 6～ 12周 ,SMC又渐从分泌型向收缩型转变。结论　自体静脉移植后 4～ 6周管壁厚度达高峰 ,内皮微绒毛增多。中膜SMC在 1～ 2周转型增殖最明显。提示术后 2周内是药物抑制SMC增殖的良机     

Comparison of mechanical and ultrasound elastic modulus of ovine tibial cortical bone

Finite element models of bones can be created by deriving geometry from an X-ray CT scan. Material properties such as the elastic modulus can then be applied using either a single or set of homogeneous values, or individual elements can have local values mapped onto them. Values for the elastic modulus can be derived from the CT density values using an elasticity versus density relationship.Many elasticity–density relationships have been reported in the literature for human bone. However, while ovine in vivo models are common in orthopaedic research, no work has been done to date on creating FE models of ovine bones. To create these models and apply relevant material properties, an ovine elasticity–density relationship needs to be determined.Using fresh frozen ovine tibias the apparent density of regions of interest was determined from a clinical CT scan. The bones were the sectioned into cuboid samples of cortical bone from the regions of interest. Ultrasound was used to determine the elastic modulus in each of three directions – longitudinally, radially and tangentially. Samples then underwent traditional compression testing in each direction.The relationships between apparent density and both ultrasound, and compression modulus in each direction were determined. Ultrasound testing was found to be a highly repeatable non-destructive method of calculating the elastic modulus, particularly suited to samples of this size.The elasticity–density relationships determined in the longitudinal direction were very similar between the compression and ultrasound data over the density range examined. A clear difference was seen in the elastic modulus between the longitudinal and transverse directions of the bone samples, and a transverse elasticity–density relationship is also reported.     

Immunohistochemical expression of matrix metalloproteinases in the rabbit corneal epithelium upon UVA and UVB irradiation

Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in tissue remodeling and wound healing. These enzymes degrade and also synthesize components of the extracellular matrix. Overexpression of MMPs results in excessive extracellular matrix degradation and tissue destruction. In the cornea, destructive processes may lead to scarring and loss of vision. In this study MMPs (types 1, 2, 7, 8, 9 and 14) were examined immunohistochemically in the normal rabbit corneal epithelium and in epithelium irradiated in vivo with similar doses of UVB or UVA radiation (UVB rays 312 nm, UVA rays 365 nm, daily dose 1.01 J/cm² for four days). Results show that MMPs studied revealed low expression in the normal corneal epithelium, whereas after repeated UVB irradiation the expression of MMPs was significantly increased in the corneal epithelium, in ascending order: MMP-2, MMP-9, MMP-1, and MMP-7 with MMP-8. In contrast, compared to normal corneas, repeated UVA radiation did not significantly change the expression of MMPs in the irradiated corneal epithelium. MMP-14 was expressed at very low levels in all studied corneas, whereas no significant changes were detected upon UV exposure. In conclusion, UV radiation of shorter wavelength (UVB) induced an increase in expression of all MMPs except MMP-14. It is suggested that overexpression of MMPs in the corneal epithelium contributes to the damaging effect of UVB radiation to the cornea.     

植体弹性模量变化对牙种植体和骨组织应力分布的影响

目的通过三维有限元法分析,探讨植体弹性模量变化对牙种植体和骨组织应力分布的影响,为新型牙种植系统的研究提供实验依据。方法应用螺旋CT数据,建立下颌骨和种植体模型。设定植体弹性模量分别为110、90、70、55和40 GPa,模拟咬合状态,在垂直、水平、斜向分别施加300、100、130 N静止载荷,计算并分析各组在3种载荷下植体周围骨组织和牙种植体各部分的应力。结果随着植体弹性模量的降低,水平和斜向载荷下牙种植体周围皮质骨受到的应力会随之降低,种植体的应力也呈逐渐减小趋势。结论降低牙种植体材料的弹性模量有利于载荷在种植体和周围骨组织中的传导,降低种植义齿晚期失败的风险。     

A new method to evaluate the elastic modulus of cortical bone by using a combined computed tomography and finite element approach

This study attempted to estimate the elastic modulus of cortical specimens directly from the computed tomography (CT) number (CT). Cubic specimens of fresh bovine femora were tested under compressive loading. The corresponding three-dimensional mesh models of these specimens were established with the aid of CT images. The elastic modulus of each element was determined using the following transfer formula: E=A×(CT)^B. The A and B were determined by matching the simulation results with the experimental force-displacement curves. An optimization approach was used to match the entire specimen sets between simulations and experiments. The results indicated that the elastic modulus of cortical bone can be effectively estimated using a power relationship (E=1.26×10⁻³×(CT)^1.93) directly from the CT number. This procedure eliminates the need to determine the bone density, and therefore reduces the computational time required to define mechanical properties in finite element methods.     

Morphological organization of the neuropil in laminae II-V of rabbit visual cortex

Summary A combined light- and electronmicroscopic study of tangential serial sections through the visual cortex of the rabbit has been performed in order to find out whether or not the vertical bundles of apical dendrites in laminae IV/V and II/III on one hand and the areas between these bundles on the other differ with respect to composition and/or spatial organization of the neuropil. Lightmicroscopically only thick profiles such as apical dendrites of pyramidal cells and myelinated axons contribute to the structural characteristics of the neuropil. The appearance of the areas between the dendrite bundles is determined by the presence or absence of radiate bundles of myelinated axons. Lamina-dependent variations were seen in the neuropil of the dendrite bundles as well as in that of the areas between them. Ultrastructurally, the dendrite bundles and the areas between them were observed to be different also with respect to the distribution of the various types of small dendritic profiles and thin axons. The neuropil within the dendrite bundles except for the shafts and thick branches of apical dendrites contains thin unmyelinated axons and numerous spines of apical dendrites contacted by axon terminals. Small irregularly shaped dendrites are few in number. The neuropil between the dendrite bundles contains a larger number of thin unmyelinated axons than that within the bundles, and, instead of spines of apical dendrites, small irregularly shaped smooth and spiny dendrites represent the prevailing postsynaptic structures. Hence, areas within dendrite bundles differ from areas between them 1. by the thickness and orientation of their profiles and 2. by the quantitative relation of the various kinds of processes accumulating in each compartment.     

Artificial neural network for modeling the elastic modulus of electrospun polycaprolactone/gelatin scaffolds

Scaffolds for tissue engineering (TE) require the consideration of multiple aspects, including polymeric composition and the structure and mechanical properties of the scaffolds, in order to mimic the native extracellular matrix of the tissue. Electrospun fibers are frequently utilized in TE due to their tunable physical, chemical, and mechanical properties and porosity. The mechanical properties of electrospun scaffolds made from specific polymers are highly dependent on the processing parameters, which can therefore be tuned for particular applications. Fiber diameter and orientation along with polymeric composition are the major factors that determine the elastic modulus of electrospun nano- and microfibers. Here we have developed a neural network model to investigate the simultaneous effects of composition, fiber diameter and fiber orientation of electrospun polycaprolactone/gelatin mats on the elastic modulus of the scaffolds under ambient and simulated physiological conditions. The model generated might assist bioengineers to fabricate electrospun scaffolds with defined fiber diameters, orientations and constituents, thereby replicating the mechanical properties of the native target tissue.     

Substrate modulus of 3D-printed scaffolds regulates the regenerative response in subcutaneous implants through the macrophage phenotype and Wnt signaling

The growing need for therapies to treat large cutaneous defects has driven recent interest in the design of scaffolds that stimulate regenerative wound healing. While many studies have investigated local delivery of biologics as a restorative approach, an increasing body of evidence highlights the contribution of the mechanical properties of implanted scaffolds to wound healing. In the present study, we designed poly(ester urethane) scaffolds using a templated-Fused Deposition Modeling (t-FDM) process to test the hypothesis that scaffolds with substrate modulus comparable to that of collagen fibers enhance a regenerative versus a fibrotic response. We fabricated t-FDM scaffolds with substrate moduli varying from 5 to 266 MPa to investigate the effects of substrate modulus on healing in a rat subcutaneous implant model. Angiogenesis, cellular infiltration, collagen deposition, and directional variance of collagen fibers were maximized for wounds treated with scaffolds having a substrate modulus (K_s = 24 MPa) comparable to that of collagen fibers. The enhanced regenerative response in these scaffolds was correlated with down-regulation of Wnt/β-catenin signaling in fibroblasts, as well as increased polarization of macrophages toward the restorative M2 phenotype. These observations highlight the substrate modulus of the scaffold as a key parameter regulating the regenerative versus scarring phenotype in wound healing. Our findings further point to the potential use of scaffolds with substrate moduli tuned to that of the native matrix as a therapeutic approach to improve cutaneous healing.     

Expression and organization of muscle specific proteins during the early developmental stages of the rabbit heart

Summary The expression and intracellular distribution patterns of muscle-specific proteins were studied during rabbit embryo development (7–13 dpc) using monoclonal antibodies against titin, myosin, tropomyosin and actin, as well as the intermediate filament proteins desmin, keratin and vimentin. From our panel, titin appeared to be the first muscle-specific protein to be exclusively expressed in the embryonic rabbit heart. Upon differentiation (myocyte and myotube formation), titin reorganizes from dot-like aggregates into a cross-striated pattern (in 9- to 30-somite embryos) via a transiently filamentous distribution. When the expression and organization of the other muscle proteins was studied in relation to titin, it became apparent that tropomyosin followed upon titin with respect to its exclusive expression in the heart anlagen and its organization into a striated pattern. Myosin and desmin were organized into cross-striated patterns after titin and tropomyosin, but this arrangement had not reached its final form in 13-dpc embryos. Actin, keratin and vimentin were distributed in cytoplasmic filaments in the embryonic stages we investigated. Since the first pulsations are already detected in 3-somite embryos, we conclude that the organization of titin, tropomyosin, myosin and desmin into a striated pattern does not seem to be essential for the initiation of muscle cell contraction in the heart anlagen. Furthermore, this study shows that, in comparison with studies on mouse, chick and rat, the sequence of expression of muscle-specific and intermediate filament proteins during cardiomyogenesis is species-dependent, and that their expression and organization varies in time in different regions of the developing heart.Abbreviations IFP intermediate filament proteins - PBS phosphate-buffered saline - FITC fluorescein isothiocyanate - TRITC tetramethylrhodamine isothiocyanate - TxRd texas red - dpc days post conception