Design characteristics for temporomandibular joint disc tissue engineering: learning from tendon and articular cartilage

Tissue engineering of chondrocytic or fibroblastic musculoskeletal tissues has been relatively well studied compared with that of the temporomandibular joint (TMJ) disc. Early attempts at tissue engineering the disc have been misguided owing to a lack of understanding of the composition and function of the TMJ disc. The objective of this review is to compare the TMJ disc with a chondrocytic tissue (hyaline articular cartilage) and a fibroblastic tissue (tendon) to understand better the properties of this fibrocartilaginous tissue. The TMJ disc has 25 times more glycosaminoglycan (GAG) per dry weight than tendon but half that of articular cartilage. The disc's tensile modulus is six times more than cartilage but orders less than tendon. The GAG content and tensile modulus suggest that the TMJ disc is characterized as a tissue between hyaline cartilage and tendon, but the disc appears more tendon like when considering its collagen make-up and cell content. Like tendon, the TMJ disc contains primarily collagen type I at 85 per cent per dry weight, while articular cartilage has 30 per cent less collagen, which is type II. Knowledge of quantitative comparisons between joint tissues can give extensive insight into how to improve tissue engineering of the TMJ disc.     

Effects of the ascorbic acid supplementation on NADH-diaphorase myenteric neurons in the duodenum of diabetic rats.

We assessed the ascorbic acid (AA) supplementation on the myenteric neurons in the duodenum of rats. Fifteen rats with 90 days of age were divided into three groups: control (C), diabetics (D) and ascorbic acid treated diabetics (DA). After 120 days of daily treatment with AA, the duodenum was submitted to the NADH-diaphorase (NADH-d) histochemical technique, which allowed us to evaluate the neuronal density in an area of 8.96 mm2 for each duodenum, and also to measure the cellular profile area of 500 neurons per group. The supplementation promoted an increase on AA levels. The neuronal density (p < 0.05) was higher in the group DA when compared to group D. There were no significant differences in the neuronal areas, when we compared groups C (204 +/- 16.5) and D (146.3 +/- 35.84) to groups D and DA (184.5 +/- 5.6) (p > 0.05). The AA-supplementation avoided the density reduction of the NADHd myenteric neurons in the duodenum of diabetic rats.     

Angioarchitecture and morphology of temporomandibular joint of Monodelphis domestica

The opossum Monodelphis domestica presents movement of the temporomandibular joint (TMJ) reflecting adaptation to eating habits similar to movement in humans, but the structure of the TMJ is not yet known. Thus, nine young M. domestica, of both sexes were weighed, anesthetized with xylazine (10 mg kg^?1), and ketamine (70 mg kg^?1) and processed for: 1. The analyses of the macroscopic angioarchitecture after latex injection, as well as the topography of the TMJ; 2. The analysis of microvascularization after injection of Mercox resin and corrosion of soft tissue with NaOH using scanning electron microscopy and; 3. The histological evaluation of the TMJ with an optical microscope. Macroscopic analysis of the latex injected vessels revealed the distribution of the arteries from the common carotid artery, receiving branches of the superficial temporal and maxillary arteries. The mandibular condyle has the long axis in the lateral–lateral direction, and is convex in the anterior–posterior direction. Its topography was determined in relation to the eye and external acoustic meatus. With scanning electron microscopy, microvascularization consists of arterioles of varying diameter (85–15 µm) of the meandering capillary network in the retrodiscal region, and a network of straight capillaries in the TMJ anterior region. Via light microscopy the TMJ has similar histological features to those of humans. These macroscopic, microscopic and ultrastructural data from TMJ of the M. domestica could be a suitable model for TMJ physiology and pathophysiology studies for then speculate on possible human studies. Microsc. Res. Tech. 79:806–813, 2016. © 2016 Wiley Periodicals, Inc.     

高效液相色谱法测定水果中的抗坏血酸

用高效液相色谱法测定了几种水果中的维生素C,并研究了不同的色谱条件、不同的提取液对测定结果的影响,结果表明用0.25%的偏磷酸浸提样品以及作为流动相效果较好,测得Vc的保留时间为4.35,回收率为92%～98%,线性范围0.0001～1.68mg/ml.     

胶接技术在工程中的应用

简要介绍胶接技术,在实例的基础上详细阐述它的特性,以及在现代工程中的应用和未来发展前景。     

Tissue engineering of the synovial joint: the role of cell density

The ultimate goal in the tissue engineering of the synovial joint is to fabricate biologically derived analogues that can replace severely degenerated or traumatized synovial joint components. A number of challenges must be addressed before reaching this ultimate goal. In this report, the relevance of cell seeding density in the synthesis of chondrogenic and osteogenic matrices from human mesenchymal stem cells is explored. Human mesenchymal stem cells (hMSCs) were differentiated into chondrogenic cells and osteogenic cells ex vivo and encapsulated in poly(ethylene glycol) diacrylate (PEGDA) hydrogel at densities of 5 x 106 cells/ml, 40 x 10(6) cells/ml, and 80 x 10(6) cells/ml, in addition to a cell-free poly(ethylene glycol) (PEG) control group (0 x 10(6) cells/ml). Cell-seeded or cell-free PEG constructs were separately incubated in vitro for 4 weeks or implanted in vivo in the dorsum of immunodeficient rats for 4 weeks. In-vitro data demonstrated that hMSC-derived chondrocytes or hMSC-derived osteoblasts maintained their lineages per Safranin O and von Kossa staining after incubation for 4 weeks. The general pattern of initial cell seeding densities of 5 x 10(6) cells/ml, 40 x 10(6) cells/ml, and 80 x 10(6) cells/ml were preserved following in-vitro cultivation. Similarly, in-vivo data revealed that hMSC-derived chondrocytes and hMSC-derived osteoblasts maintained their respective lineages and the pattern of cell-seeding densities. An attempt was made to fabricate a composite construct with PEGDA hydrogel and polycaprolactone (PCL) with designed internal porosity for an osteochondral graft. Various cell-seeding densities as delineated in this report can be realized in the composite PEG-PCL graft. The findings demonstrate that cell-seeding density is likely a key parameter to consider in tissue-engineering design. The source of cells can either be transplanted cells or internally recruited cells.     

Fretting wear behaviors of mandibular condylar cartilage of nature temporomandibular joint in vitro

Torsional fretting tests of condylar cartilage against a ZrO₂ ball were carried out. The damage characteristics were discussed based on an analysis of frictional kinetics behavior, SEM observations, and histological stainings. The results indicated that fretting behaviors were strongly dependent on the angular displacement amplitudes and the number of cycles. The worn surface was characterized by netlike shape ridges along the radial direction, and three parts were detected. The wear mechanism of condylar cartilage performed mainly as delamination and micro-fracture of collagenous fibers. As the damage characters are very special, a model of the condylar cartilage surface damage was established.     

Investigation of polyelectrolyte for electrochemical detection of uric acid in presence of ascorbic acid

Uric acid (UA) was detected in the presence of ascorbic acid (AA) at GC electrode by cyclic voltametry (CV) and differential pulse voltametry (DPV) in aqueous media of cationic polyelectrolyte (poly(diallyldimethylammonium chloride) (PDDA)). Both, UA and AA are anionic nature and electro-static attraction with cationic solution. This lowered their oxidation potentials and increased anodic current. In CV studies, the UA oxidation potential was decreased by 400 mV in the presence of PDDA along with increase in peak current. Effect of PDDA and pH on E_pa and I_pa were also studied. About 360 mV difference in oxidation peak potentials was observed for AA and UA in PDDA media, which established a quick method for their simultaneous determination. The detection limit of UA in the presence of 200 folds AA was found as 1 μM with correlation coefficient of 0.994 and sensitivity of 0.05 μA μM⁻¹. The proposed method has been also applied for determining the UA in human urine without any pretreatment, and found to be satisfactory.     

组织工程支架的快速成形制备方法

这篇文章介绍了组织工程的概念及组织工程支架的重要性.与传统的组织工程支架制备方法相比,提出了新的快速成形技术.主要阐述了3维打印技术、熔融沉积技术及选择性激光烧结技术的原理及其在构建组织工程支架的应用及特点.     

Spectrofluorometric determination of ascorbic acid using thiamine and potassium ferricyanide

A simple and sensitive spectrofluorometry method for the determination of ascorbic acid was reported. In alkaline solution, the nonfluorescent thiamine was oxidized by potassium ferricyanide and formed the fluorescent thiochrome with an excitation maximum at 367?nm and an emission peak at 441?nm. However, the fluorescence intensity gradually decreased in the presence of ascorbic acid. The decreased fluorescence was linearly dependent under the optimum conditions with the concentration of ascorbic acid from 0.086–1.5?µmol?L^?1 with a correlation coefficient of 0.9996. The detection limit of 0.026?µmol?L^?1 was lower than many other methods. Additionally, the mechanism underlying the enhancement and quenching of this method was discussed. The protocol was used to determine ascorbic acid in tablets and juice with satisfactory results.     

组织工程支架的低温沉积制造工艺参数研究

低温沉积制造是一种新的快速成形技术。为了将这项技术更好地应用于组织工程支架的制造,根据支架孔隙率的要求,按照一定比例将PLGA和珍珠粉混合,配制成浆料,然后利用低温沉积制造工艺制备了网格型的组织工程支架,并得出了适于加工这种材料的一组工艺参数。主要从软件设定、浆料性质、温控调节和速度匹配4个方面入手,研究了在材料配制、分层和成形机制造等一系列工艺过程中参数对成形结果的影响。实验结果表明,制造出的支架结构规则能满足孔隙率的要求。     

Cell proliferation of the ileum intestinal mucosa of diabetic rats treated with ascorbic acid

The objective of this work was to evaluate the effect of the ascorbic acid supplementation on the cellular proliferation on the ileum mucosa of diabetic rats. Fifteen 90-days rats were divided in the groups: control, diabetic and diabetic supplemented with ascorbic acid (DA). Two hours prior the sacrifice, they were injected with Vincristin. Semi-seriate histological cuts stained with HE were accomplished. About 2500 crypt cells from the intestinal mucosa were counted in order to obtain the metaphasic indexes. The height and depth of 30 villi and 30 crypts were measured for each animal, respectively. The metaphasic indexes showed no significant changes when we compared the three groups: 20.2 +/- 0.7 (control), 18 +/- 1.9 (diabetic) and 17 +/- 1.4 (DA) (p > 0.05). The values obtained from the crypts measurement were 221.2 +/- 8.5 (control), 225.3 +/- 9.5 (diabetic) and 222 +/- 34 (DA). The villi of the control, diabetic and DA animals presented the following results: 301.7 +/- 25.33, 304.8 +/- 25.63 and 322.1 +/- 45.77 respectively. The morphometric data were not different statistically (p > 0.05). Summing up, the present work showed that there was no alteration in the cellular proliferation of the ileum of diabetic-induced rats supplemented with ascorbic acid.     

Stem cells for tissue engineering of articular cartilage

Articular cartilage injuries are one of the most common disorders in the musculo-skeletal system. Injured cartilage tissue cannot spontaneously heal and, if not treated, can lead to osteoarthritis of the affected joints. Although a variety of procedures are being employed to repair cartilage damage, methods that result in consistent durable repair tissue are not yet available. Tissue engineering is a recently developed science that merges the fields of cell biology, engineering, material science, and surgery to regenerate new functional tissue. Three critical components in tissue engineering of cartilage are as follows: first, sufficient cell numbers within the defect, such as chondrocytes or multipotent stem cells capable of differentiating into chondrocytes; second, access to growth and differentiation factors that modulate these cells to differentiate through the chondrogenic lineage; third, a cell carrier or matrix that fills the defect, delivers the appropriate cells, and supports cell proliferation and differentiation. Stem cells that exist in the embyro or in adult somatic tissues are able to renew themselves through cell division without changing their phenotype and are able to differentiate into multiple lineages including the chondrogenic lineage under certain physiological or experimental conditions. Here the application of stem cells as a cell source for cartilage tissue engineering is reviewed.     

基于逆向工程的个性化人工关节三维CAD数模的建立

通过螺旋CT扫描人体股骨关节,得到二维断层图像数据,利用数据处理软件将二维图片转换成三维点云数据,继而依据点云数据,采用计算机三维重构技术,构建了股骨的三维CAD数字模型.     

Effects of joint on dynamics of space deployable structure

Joints are necessary components in large space deployable truss structures which have significant effects on dynamic behavior of these joint dominated structures.Previous researches usually analyzed effects of one or fewer joint characters on dynamics of jointed structures.Effects of joint stiffness,damping,location,number,clearance and contact stiffness on dynamics of jointed structures are systematically analyzed.Cantilever beam model containing linear joints is developed based on finite element method,influence of joint on natural frequencies and mode shapes of the jointed system are analyzed.Analytical results show that frequencies of jointed system decrease dramatically when peak mode shapes occur at joint locations,and there are cusp shapes present in mode shapes.System frequencies increase with joint damping increasing,there are different joint damping to achieve maximum system damping for different joint stiffness.Joint nonlinear force-displacement is described by describing function method,one-DOF model containing nonlinear joints is established to analyze joints freeplay and hysteresis nonlinearities.Analysis results show that nonlinear effects of freeplay and hysteresis make dynamic responses switch from one resonance frequency to another frequency when amplitude exceed demarcation values.Joint contact stiffness determine degree of system nonlinearity,while exciting force level,clearance and slipping force affect amplitude of dynamic response.Dynamic responses of joint dominated deployable truss structure under different sinusoidal exciting force levels are tested.The test results show obvious nonlinear behaviors contributed by joints,dynamic response shifts to lower frequency and higher amplitude as exciting force increasing.The test results are further compared with analytical results,and joint nonlinearity tested is coincident with hysteresis nonlinearity.Analysis method of joint effects on dynamic characteristics of jointed system is proposed,which can be used in optimal design of joint parameters     

The use of acellular matrices for the tissue engineering of cardiac valves

Tissue-engineering approaches to cardiac valve replacement have made considerable advances over recent years and it is likely that this application will realize clinical success in the near future. Research in this area has been driven by the inadequacy of the currently available cardiac valve prostheses for younger patients who require multiple reoperations as they grow and develop. Tissue engineering has the potential to provide a valve capable of the same growth, repair, and regeneration as a natural valve and could improve outcomes for patients of all ages. Owing to the function and physical environment of the cardiac valve, the development of tissue-engineered replacements is unusual in that the biomechanical properties of the construct must dominate the biological properties in order for the valve to be functional at the time of implantation. As a result of this, conventional tissue-engineering scaffolds based on biodegradable polymers or collagen may not at present be suitable in this situation because of their initial limited strength. Research into the use of acellular xenogeneic and allogeneic matrices for tissue-engineered heart valves has consequently become extremely popular since the biomechanical properties of the valve can potentially be preserved with an optimal decellularization technique that removes the cells without damaging the matrix. A number of acellular scaffolds have already been tested clinically both unseeded and preseeded with cells and these have met with variable results. This article reviews the concepts involved and the advantages and disadvantages of the different approaches to tissue engineering a living cardiac valve.