低氧及运动致大鼠骨骼肌形态学改变的实验研究

目的观察低氧及低氧复合运动时,大鼠体重及腓肠肌显微、超微结构的变化,旨在探讨低氧状态下适当运动对骨骼肌的影响。方法建立大鼠低氧及低氧复合运动模型,运用光镜及透射电镜观察大鼠腓肠肌显微、超微结构的变化。结果低氧复合运动组较低氧安静组大鼠体重差异有显著性意义(P<0.05)。低氧复合运动组骨骼肌结构正常,线粒体数量增加,骨骼肌纤维增粗,毛细血管增生。结论低氧复合适当的运动能够维持骨骼肌的正常形态,增强骨骼肌的有氧代谢,起到保护骨骼肌的作用,从而提高骨骼肌的低氧适应能力,促进低氧习服。     

PBT／PC共混体系流变性能与形态结构研究

采用毛细管流交仪测定了ＰＢＴ／ＰＣ共混物的表观粘度、剪切应力，观察了不同共混物组成和不同温度下共混物的流变行为，并借助扫描电镜对共混物和微观形态结构进行分析。结果表明：ＰＢＴ／ＰＣ熔体共混物的流变行为接近假塑性流体．温度对共混物的流变行为影响很大，共混物的熔体粘度在ＰＢＴ／ＰＣ为９０／１０和６０／４０时呈双极值．共混物为两相结构，ＰＣ含量为４－５０％时呈两互锁结构。     

Quantitative assessment of the microstructure of rat behavior: I.f(d), The extension of the scaling hypothesis

Previous studies demonstrated that drug effects on the movement sequences of rats in unconditioned motor activity paradigms can be quantified by scaling measures that describe the average relationship between a variable of interest and an experimental parameter. However, rats engage in a wide variety of geometrically distinct movements that can be influenced differentially by drugs. In this investigation, the extended scaling approach is presented to capture quantitatively the relative contributions of geometrically distinct movement sequences to the overall path structure. The calculation of the spectrum of local spatial scaling exponents,f(d), is based on ensemble methods used in statistical physics. Results of thef(d) analysis confirm that the amount of motor activity is not correlated with the geometrical structure of movement sequences. Changes in the average spatial scaling exponent,d, correspond to shifting the entiref(d) function, and indicate overall changes in path structure. With the extended scaling approach, straight movement sequences are assessed independently from highly circumscribed movements. Thus, thef(d) function identifies drug effects on particular ranges of movement sequences as defined by the geometrical structure of movements. More generally, thef(d) function quantifies the relationship between microscopically recorded variables, in this paradigm consecutive (x, y) locations, and the macroscopic behavioral patterns that constitute the animal's response topography.Exemplary calculations of path segments with different geometrical characteristics can be obtained from the authors. Questions regarding the computational implementation of this method should be addressed to MPP preferably via email (martin@rat.ucsd.edu) or FAX (619-543-2493)     

胶原基真皮再生支架的微结构控制

综述了影响胶原基真皮再生支架微结构的各种因素及其控制方法。胶原基真皮支架的生物活性和修复创面的能力受到诸如除胶原外的其它主要材料 (第二组分 )、支架的孔径和孔隙率、支架厚度、生物活性因子以及交联度等多方面因素的综合影响。从材料学、生物学和医学的角度综合地应用物理、化学和生物学的手段探索各种影响因素的控制方法是组织工程皮肤研究的重点。     

纯钛表面激光合成钙磷生物陶瓷涂层的组成与结构

目的 采用廉价的CaCO_3和CaHPO_4·2H_2O作为原料,在激光的作用下通过反应制备HA生物陶瓷涂层。方法 利用X射线衍射仪和电子探针分析仪对涂层进行相分析、组织观察和成分分析。结果CaCO_3和CaHPO_4·2H_2O按20:80的质量比混合时,在功率为600W、扫描速度为3.5mm/s的激光作用下可一步合成钙磷生物陶瓷涂层。结论 在一定实验条件下,CaCO_3和CaHPO_4·2H_2O可合成组织致密、结合状态良好的钙磷生物陶瓷涂层。     

电针对糖尿病大鼠坐骨神经传导速度和神经超微结构的影响

目的 :观察固本通络电针法对实验性糖尿病周围神经病变的防治作用。方法 :大鼠分为正常组、电针组和模型对照组 ,运用链脲菌素造成大鼠实验性糖尿病模型 ,用桥式鼠架使大鼠在清醒、安静的自然状态下接受电针“肾俞”“环跳”穴 ,用神经电生理方法观察坐骨神经传导速度 ,用透射电镜观察神经纤维的超微结构。结果 :电针组与模型组相比 ,左、右两侧NCV均明显加快 (P <0 .0 5) ,潜伏期均明显缩短 (P <0 .0 5) ,但未达到正常组的水平 ;电针组有髓纤维髓鞘脱失的程度有所减轻 ,神经纤维内微血管内皮细胞肿胀程度较轻。结论 :固本通络电针法对实验性糖尿病周围神经病变具有一定的防治作用。     

Microstructure,mechanical and corrosion properties of Mg–Dy–Gd–Zr alloys for medical applications

In previous investigations, a Mg–10Dy (wt.%) alloy with a good combination of corrosion resistance and cytocompatibility showed great potential for use as a biodegradable implant material. However, the mechanical properties of Mg–10Dy alloy are not satisfactory. In order to allow the tailoring of mechanical properties required for various medical applications, four Mg–10(Dy + Gd)–0.2Zr (wt.%) alloys were investigated with respect to microstructure, mechanical and corrosion properties. With the increase in Gd content, the number of second-phase particles increased in the as-cast alloys, and the age-hardening response increased at 200 °C. The yield strength increased, while the ductility reduced, especially for peak-aged alloys with the addition of Gd. Additionally, with increasing Gd content, the corrosion rate increased in the as-cast condition owing to the galvanic effect, but all the alloys had a similar corrosion rate (～0.5 mm year^?1) in solution-treated and aged condition.     

Scanning Electron Microscopic Characterization of Healing and Normal Rat Ligament Microstructure Under Slack and Loaded Conditions

The objective of this study was to observe and compare behavior of the collagen fiber microstructure in normal and healing ligaments, both in situ and ex vivo, in order to add insight into the structure-function relationship in normal and healing ligaments. Fifty-two ligaments from 26 male rats were investigated. Eleven animals underwent surgical transection of both medial collateral ligaments (MCLs) (22 ligaments), which were allowed to heal for a period of 2 weeks. An additional 15 animals (30 ligaments) were used as normals. Ligaments were placed into six groups: Slack ( n = 6 control, n = 6 healing), Reference ( n = 4 control, n = 4 healing), Loaded ( n = 4 control, n = 4 healing), 15° Flexion ( n = 4 control, n = 4 healing), 120° Flexion ( n = 4 control, n = 4 healing), and Tissue Strain vs. Flexion Angle ( n = 8 normals). All ligaments, except those in the Tissue Strain vs. Flexion Angle group, were prepared for scanning electron microscopy. Tissues were harvested, mounted in a load frame, and chemically fixed in one of five states: (1) slack, (2) reference (onset of loading), (3) loaded, (4) 15° knee flexion, or (5) 120° knee flexion. After fixation the tissues were prepared for electron microscopy (SEM). The micrographs from the slack, reference, and loaded groups show fiber straightening with loading in normal ligaments as well as in both scar and "retracted" regions of healing ligaments. Collagen fibers' diameter and crimp patterns were dramatically changed in the scar region of healing ligaments: Width decreased from 19.4 &#45 1.7 &#119 m to 6.5 &#45 2.1 &#119 m ( p < .000001), period from 51.4 &#45 15.1 &#119 m to 11.0 &#45 2.4 &#119 m ( p < .000001), and amplitude from 9.8 &#45 0.8 &#119 m to 3.9 &#45 0.8 &#119 m ( p < .000001). Normal ligaments fixed in situ show wavy regions at 120° but less so at 15° flexion. Healing ligaments fixed in situ show regions of fiber waviness in the scar region at 120° and also at 15° flexion, indicating ligament laxity persists toward both extremes of the range of motion. The data suggest that straightening of crimped fibers is a functionally relevant phenomenon, not only in normal but also in healing ligaments.     

A Comparative Study on Morphochemical Properties and Osteogenic Cell Differentiation within Bone Graft and Coral Graft Culture Systems

The objective of this study was to compare the morphological and chemical composition of bone graft (BG) and coral graft (CG) as well as their osteogenic differentiation potential using rabbit mesenchymal stem cells (rMSCs) in vitro. SEM analysis of BG and CG revealed that the pores in these grafts were interconnected, and their micro-CT confirmed pore sizes in the range of 107-315 µm and 103-514 µm with a total porosity of 92% and 94%, respectively. EDS analysis indicated that the level of calcium in CG was relatively higher than that in BG. FTIR of BG and CG confirmed the presence of functional groups corresponding to carbonyl, aromatic, alkyl, and alkane groups. XRD results revealed that the phase content of the inorganic layer comprised highly crystalline form of calcium carbonate and carbon. Atomic force microscopy analysis showed CG had better surface roughness compared to BG. In addition, significantly higher levels of osteogenic differentiation markers, namely, alkaline phosphatase (ALP), Osteocalcin (OC) levels, and Osteonectin and Runx2, Integrin gene expression were detected in the CG cultures, when compared with those in the BG cultures. In conclusion, our results demonstrate that the osteogenic differentiation of rMSCs is relatively superior in coral graft than in bone graft culture system.     

A mechanism for effective cell-seeding in rigid,microporous substrates

Seeding cells into porous ceramic substrates has been shown to improve outcomes in surgical repair of large bone defects, but the physics underlying cellular ingress into such scaffolds remains elusive. This paper demonstrates capillary forces as a novel, yet simple, self-loading or self-seeding mechanism for rigid, microporous substrates. Capillary forces were found to draw cells through a microporous network with interconnections smaller than the diameter of the cells in suspension. Work here emphasizes CaP-based bone scaffolds containing both macroporosity (>100 μm) and microporosity (5–50 μm); these have been shown to improve bone formation in vivo as compared to their macroporous counterparts and also performed better than microporous scaffolds containing BMP-2 by some measures of bone regeneration. We hypothesize that capillary force driven self-seeding in both macro- and micropores may underlie this improvement, and present a mathematical model and experiments that support this hypothesis. The cell localization and penetration depth within these two-dimensional substrates in vitro depends upon both the cell type (size and stiffness) and the capillary forces generated by the microstructure. Additional experiments showing that cell penetration depth in vitro depends on cell size and stiffness suggest that microporosity could be tailored to optimize cell infiltration in a cell-specific way. Endogenous cells are also drawn into the microporous network in vivo. Results have important implications for design of scaffolds for the healing of large bone defects, and for controlled release of drugs in vivo.