胰岛素对链脲佐菌素诱导的糖尿病大鼠骨转换和骨力学性能的影响

 目的 探讨胰岛素对于链脲佐菌素(streptozotocin,STZ)诱导的糖尿病大鼠骨量、骨转换状态和骨力学性能的影响。方法 单次尾静脉注射STZ制造糖尿病大鼠模型,成模后分为糖尿病大鼠组(DM)、胰岛素治疗组(INS)与正常对照组(CON),8周后处死,测定3组大鼠血清骨钙素和尿Ⅰ型胶原氨基末端交联肽(NTx)/肌酐(Cr)比值,DEXA方法测定大鼠离体腰椎和股骨骨密度。骨形态计量学方法分析大鼠骨量和骨转换变化情况。采用股骨三点弯曲试验和腰椎压缩试验分析各组大鼠骨力学性能。结果 与CON组相比,DM大鼠血清骨钙素和尿NTx/Cr比值降低,DM大鼠腰椎和股骨骨密度降低。与DM组大鼠相比,INS组大鼠血清骨钙素水平增高,尿NTx/Cr比值无变化,INS组大鼠腰椎和股骨骨密度显著增大(P＜0.01),但未达CON组水平。骨形态计量学分析提示与CON组相比,DM大鼠骨小梁骨量[TBV/TTV(12.06±2.48)% vs (24.12±1.84)%, P＜0.01]减少,骨形成速率减低[(0.44±0.11) vs (0.78±0.14)μm/d, P＜0.01]。与DM组大鼠相比,INS组大鼠骨小梁骨量显著增加[TBV/TTV(19.75±2.43) %, P＜0.01],骨形成速率亦增加[(0.70±0.16) μm/d, P＜0.01]。股骨三点弯曲试验显示,与CON组大鼠相比,DM组大鼠最大载荷、弹性载荷、弯曲能量、最大应力均显著减低(P＜0.01)。与DM组相比,INS组上述各力学指标均显著增加(P＜0.01),但均未达CON组水平。椎体压缩实验提示与CON组大鼠相比,DM组大鼠最大载荷、弹性载荷、能量吸收、弹性模量均显著减低(P＜0.01)。与DM组相比,INS组上述各指标亦显著增加,差异有统计学意义(P＜0.01)。结论 DM大鼠表现为低转换型骨量减少,且骨力学性能下降,胰岛素治疗可以促进骨形成,增加骨量,且能改善DM大鼠的骨力学性能。     

三种眼压计测量高眼压儿童眼压及其与中央角膜厚度的关系

目的：探讨经Topcon眼压计(non-contact tonometry,NCT)初筛高眼压的屈光不正儿童的中央角膜厚度(central corneal thickness,CCT)分布,以及NCT、Goldmann压平眼压计(Goldmann applanation tonometry,GAT)与OCULUS Corvis ST角膜生物力学分析仪(CST)所测眼压值的差异,并分析眼压和CCT的相关性。

方法：选择经NCT测量单眼或双眼眼压高于21mmHg的非青光眼屈光不正儿童39例78眼,用CST和GAT再次进行眼压测量,两种仪器的测量顺序随机,同时用CST测量CCT并根据CCT进行眼压校正。根据CCT分成正常组和较厚组,分析经NCT初筛高眼压的屈光不正儿童的总体CCT分布情况,探讨三种仪器所测眼压值的不同及其与CCT的相关性。

结果：正常CCT组,CST低于GAT和NCT的眼压测量值,差异有统计学意义(F=5.12,P=0.01); 较厚组,三种眼压测量方式的眼压测量值比较,差异均有统计学意义(F=15.72,P<0.001)。NCT和GAT眼压值与CCT呈明显正相关(r_NCT=0.298,P_NCT=0.04; r_GAT=0.408,P_GAT= 0.01); CST校正眼压值与CCT无明显相关性(r_CST=0.062,P_CST=0.593)。

结论：NCT初筛高眼压的屈光不正儿童的CCT偏厚,CST校正眼压低于NCT和Goldmann眼压,NCT和GAT所测眼压与CCT呈正相关; 对于CCT偏厚的儿童患者,CST校正眼压比NCT和GAT更接近于真实眼压值。     

人工关节金属磨损颗粒体外制备分离方法的实验研究

[目的]设计一种体外制备、分离人工关节金属磨损颗粒的方法，并验证这种颗粒用于医学实验的可行性。[方法]用钛铝钒合金、钴铬钼合金材料分别制成球磨罐（国家发明专利，申请号：03142073．7），球磨罐内装有用同种材料制成的磨块；向该球磨罐内注入模拟生物体液；震动球磨得到颗粒混悬液。梯度离心获得金属颗粒。对颗粒进行：（1）元素成分鉴定；（2）颗粒大小鉴定和粒度分析；（3）扫描电镜对颗粒的表面形态观察；（4）将颗粒与J774A．1巨噬细胞共同培养，观察细胞吞噬颗粒的情况。[结果]通过此方法成功产生并分离出大量直径1μm左右的钛合金和钴铬钼合金颗粒。（1）元素分析证实整个处理过程中无杂质成分污染；（2）钛合金颗粒的平均直径Dv90：1．009，钴铬钼颗粒的平均直径Dv90：1．008，粒度分布曲线基本成正态；（3）扫描电镜图象显示颗粒大小均匀，形状多为不规则，与体内颗粒极为相似；（4）J774A．1巨噬细胞能完整吞噬2种材料的颗粒。[结论]此方法能持续大量产生人工关节假体金属材料的磨损颗粒，产生的颗粒能在各方面很好地模拟体内磨损颗粒，为今后人工关节假体松动相关研究的体内、体外研究提供可靠的颗粒来源。     

Preparation and characterization of human scar acellular dermal matrix

Introduction: Acellular dermal matrix (ADM) is commonly used to treat burn injuries and wounds. In this study, we aimed to analyze the structural and biomechanical characteristics of an ADM from human scars.

Methods: We randomly selected human mature scars, human proliferative scars, and human normal skin as experimental specimens. Split-thickness dermal grafts were obtained using a free-hand graft knife. Samples were subjected to cell lysis to obtain ADMs. Structural analysis was performed via light microscopy, fluorescence microplate reader and scanning electron microscopy. Thereafter, human epithelial stem cells were incubated on these ADMs. Finally, the biomechanical characteristics of the ADMs were analyzed using a tensile machine.

Results: Normal skin ADM fibers were arranged in order, whereas proliferative scar ADM fibers were dense and disordered, and mature scar ADM fibers were porous and slightly disordered. The residual DNA of three ADM meet the residual DNA standard of biological material. After incubating human epithelial stem cells on ADMs, cells grew in an aggregated state in both normal skin ADMs and mature scar ADMs; however, cells adhered only on the surface of proliferative scar ADMs. No significant differences were observed in the Young’s modulus, relaxation slope, creep slope, creep, or maximum tensile stress among the three ADMs, although significant differences in stress–strain elongation and relaxation were noted.

Conclusions: Our findings showed that mature scar ADMs were similar to proliferative scar ADMs, showing a slight lag compared with normal skin ADMs, providing insights into the biomechanical features of these scar tissues. Abbreviations ADM Acellular dermal matrix

H&E Hematoxylin and eosin

PBS Phosphate-buffered saline

SEM Scanning electron microscopy

     

自体腘绳肌腱修复兔巨大肩袖缺损的实验研究

目的研究自体腘绳肌腱修复兔巨大肩袖缺损腱骨愈合的早期实验效果。方法将40只成年雄性新西兰大白兔随机分为3组,分别为正常组(n=8)、模型组(n=8)和实验组(n=24)。正常组相同方式饲养但不予手术处理;模型组将大白兔双前肢肱骨头大结节处切取1.5 cm×1.0 cm的肩袖组织缺损,不予缝合修补后直接缝合皮肤;实验组在模型组的基础上用自体腘绳肌腱修复巨大肩袖缺损。实验组分别于术后第8、16、24周时安乐死8只大白兔后取出双肩标本。将标本处理后分别进行组织形态学分析和生物力学研究测试。结果组织形态学分析结果显示:实验组术后24周腱骨界面胶原纤维明显增多,腱骨隧道连接处可见Sharpey纤维、纤维软骨细胞及纤维软骨等腱骨愈合成分。生物力学研究结果显示实验组肌腱最大负荷随时间延长呈持续增大趋势(各时间点之间比较,P<0.05),术后24周可以获得较强的力学强度。结论应用自体腘绳肌腱修复兔巨大肩袖缺损可以获得良好的腱骨愈合。     

The bioengineering theory of the key modes of action of a cyanoacrylate liquid skin protectant

The objective of this article is to formulate a new bioengineering theoretical framework for modelling the biomechanical efficacy of cyanoacrylate skin protectants, with specific focus on the Marathon technology (Medline Industries, Inc., Northfield, Illinois) and its modes of action. This work details the bioengineering and mathematical formulations of the theory, which is based on the classic engineering theories of flexural stiffness of coated elements and deformation friction. Based on the relevant skin anatomy and physiology, this paper demonstrates: (a) the contribution of the polymerised cyanoacrylate coating to flexural skin stiffness, which facilitates protection from non‐axial (eg, compressive) localised mechanical forces; and (b) the contribution of the aforementioned coating to reduction in frictional forces and surface shear stresses applied by contacting objects such as medical devices. The present theoretical framework establishes that application of the cyanoacrylate coating provides considerable biomechanical protection to skin and subdermally, by shielding skin from both compressive and frictional (shearing) forces. Moreover, these analyses indicate that the prophylactic effects of the studied cyanoacrylate coating become particularly strong where the skin is thin or fragile (typically less than ~0.7 mm thick), which is characteristic to old age, post‐neural injuries, neuromuscular diseases, and in disuse‐induced tissue atrophy conditions.     

Biomechanical Modeling to Improve Coronary Artery Bifurcation Stenting: Expert Review Document on Techniques and Clinical Implementation

Treatment of coronary bifurcation lesions remains an ongoing challenge for interventional cardiologists. Stenting of coronary bifurcations carries higher risk for in-stent restenosis, stent thrombosis, and recurrent clinical events. This review summarizes the current evidence regarding application and use of biomechanical modeling in the study of stent properties, local flow dynamics, and outcomes after percutaneous coronary interventions in bifurcation lesions. Biomechanical modeling of bifurcation stenting involves computational simulations and in vitro bench testing using subject-specific arterial geometries obtained from in vivo imaging. Biomechanical modeling has the potential to optimize stenting strategies and stent design, thereby reducing adverse outcomes. Large-scale clinical studies are needed to establish the translation of pre-clinical findings to the clinical arena.     

Towards Customized Footwear with Improved Comfort

A methodology enabling the customization of shoes for comfort improvement is proposed and assessed. For this aim, 3D printed graded density inserts were placed in one of the critical plantar pressure zones of conventional insoles, the heel. A semi-automated routine was developed to design the 3D inserts ready for printing, which comprises three main stages: (i) the definition of the number of areas with different mesh density, (ii) the generation of 2D components with continuous graded mesh density, and (iii) the generation of a 3D component having the same 2D base mesh. The adequacy of the mesh densities used in the inserts was previously assessed through compression tests, using uniform mesh density samples. Slippers with different pairs of inserts embedded in their insoles were mechanically characterized, and their comfort was qualitatively assessed by a panel of users. All users found a particular pair, or a set, of prototype slippers more comfortable than the original ones, taken as reference, but their preferences were not consensual. This emphasizes the need for shoe customization, and the usefulness of the proposed methodology to achieve such a goal.     

Comparative Effects of Ibandronate and Paclitaxel on Immunocompetent Bone Metastasis Model

Purpose

Bone metastasis invariably increases morbidity and mortality. This study compares the effects of ibandronate and paclitaxel on bone structure and its mechanical properties and biochemical turnover in resorption markers using an immunocompetent Walker 256-Sprague-Dawley model, which was subjected to tumor-induced osteolysis.

Materials and Methods

Seventy rats were divided equally into 4 groups: 1) sham group (SHAM), 2) tumor group (CANC), 3) ibandronate treated group (IBAN), and 4) paclitaxel treated group (PAC). Morphological indices [bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp)] and mechanical properties (failure load, stiffness) were evaluated after thirty days of treatment period. Bone resorption rate was analysed using serum deoxypyridinoline (Dpd) concentrations.

Results

Morphological indices showed that ibandronate (anti-resorptive drug) had a better effect in treating tumor-induced architectural changes in bone than paclitaxel (chemotherapeutic drug). The deterioration in bone architecture was reflected in the biomechanical properties of bone as studied with decreased failure load (F_x) and stiffness (S) of the bone on the 30th day post-surgery. Dpd concentrations were significantly lower in the IBAN group, indicating successful inhibition of bone resorption and destruction.

Conclusion

Ibandronate was found to be as effective as higher doses of paclitaxel in maintaining stiffness of bone. Paclitaxel treatment did not appear to inhibit osteoclast resorption, which is contrary to earlier in-vitro literature. Emphasis should be placed on the use of immunocompetent models for examining drug efficacy since it adequately reflects bone metastasis in clinical scenarios.