强肌Ⅰ、Ⅱ号中药改善尾吊大鼠比目鱼肌血流量和肌肉力学特性的作用

航天员因失重而产生肌肉萎缩,引起了国内外很多学者的关注,并进行了广泛研究。本文观察尾吊大鼠服用中药后比目鱼肌血流量和肌肉力学特性的变化。实验采用45只SD 品系雄性大鼠,体重240-300g,将鼠按体重分为3组。尾吊大鼠头低位20-25°。三组鼠每天按固定时间分别灌水和强肌Ⅰ、Ⅱ号中药(30g/kg),悬吊15天后,用戊巴比妥钠(4mg/100g)麻醉,用张力、位移传感器测量肌肉力学特性各参数,用标有~(51)Cr 同位素青蛙红血球方法测比目鱼肌的血流量。结果表明:强肌Ⅰ、Ⅱ号中药对尾吊大鼠比目鱼肌血流量、肌肉力学特性有改善作用。其中强肌Ⅱ号效果更明显。比目鱼肌的血流量与等长单收缩、强直收缩张力峰值呈正相关,相关系数分别为0.81、0.84。本结果为防护肌肉萎缩措施提供了实验依据。     

壳聚糖-鞣质复合膜的止血促愈合作用

目的 制备壳聚糖-鞣质复合膜,研究其止血及促愈合作用.方法 从中药蒲黄中提取鞣质,与壳聚糖混合后冷冻干燥制成复合膜.通过测定体外血液凝固时间和在体肝脏止血时间,评价复合膜的止血效果.制作大鼠皮肤损伤模型,敷以复合膜治疗,观察伤口HE染色结果,测定肉芽组织蛋白质和经脯氨酸含量,评价复合膜的促愈合作用.结果 所制复合膜能明...     

同种异体骨-中1/3髌腱-骨、骨-跟腱移植重建羊膝关节后交叉韧带的比较研究

目的对同种异体骨-中1／3髌腱-骨(B-PT-B)、骨-跟腱移植重建后交叉韧带(PCL)后的组织学演变及力学特性进行初步分析．以了解其临床应用的可行性及影响因素：方法选用健康成年羊25只，A组为取材组(5只)．B、C组为实验组(各10只)；分别以新鲜冷冻异体B-PT-B和异体骨-跟腱移植重建PCL．分别以健侧为自身对照组．采用形态学及生物力学手段、对术后1个月和6个月两组移植物(供体)重建PCL后的组织学演变及术后6个月力学特性进行初步分析。结果常规组织学染色显示：重建PCL6个月后两种移植物与正常PCL结构相似；生物力学测试结果表明，同种异体骨-跟腱移植重建后的PCL的抗拉伸强度比同种异体B-PT-B重建的PCL高，且具有与正常PCL接近的力学特性。结论同种异体骨-跟腱移植重建的PCL具有与正常PCL接近的力学特性．更适合临床应用。     

关节—肌肉系统的生物力学效率

如何评定关节-肌肉系统在不同施力条件下所产生的外力效率,是从事人-机系统工程和运动医学研究人员十分关心的问题。关节-肌肉产生外力的效率不仅受机械因素的影响,而且与肌肉本身的生理特性有着密切的关系。测出关节-肌肉系统产生外力的“绝对”效率是人们十分希望的,但有许多困难;对人-机系统工程设计人员而言,知道关节-肌肉系统在不同施力条件下所产生的外力的效率也是极有意义的。本文提出了关节-肌肉系统“生物-力学”效率的概念,给出了测定和计算方法,以上臂肱二头肌和肘关节为主要对象,用6名被试者进行了实验研究。以测得的皮肤表面肌电信号的平均积分电位(mIEMG)及所产生的外力为参数,结合肌肉不同施力条件,对关节-肌肉系统产生外力的生物-力学效率进行了相应的计算。结果表明,在肌肉静态(等长)收缩条件下,其效率与肘关节的角度和所给出外力的大小有关,在各种用力水平条件下,生物—力学效率达到最大值时的肘角为45°或75°。随着所施外力的加大,效率下降;但下降速度却随力的加大而变慢。在所施外力较小时(<60%最大值),45°肘角条件下的效率高于90°肘角时的相应值;但当所施外力加大后(>60%),两肘角条件下的效率无差异。在动态(等张)收缩条件下,在不同用力水平,效率和运动速度之间的关系表现出不同的趋势。当所施外力较小时(<20%最大值),效率随所施外力的加大而减小;但当用力水平较高时,效率随运动速度变化不明显。在相同运动速度下,效率随所施外力的增加而下降,但与静态收缩条件下的结果类似,当所施外力增加后(>50%),效率不再随力的加大而明显的下降。在相同用力水平,动态收缩效率低于静态的值。讨论了可能影响关节-肌肉系统生物-力学效率的机制进行了较深入详细提出了生物-力学效率的可能应用范围。     

多曲方丝弓简单受力有限元分析模型的建立

目的建立多曲方丝弓简单受力的有限元分析模型,并分析其力学特性。方法利用Pro/E软件建立初始化图形交换规范(IGES)格式的牙列-托槽-弓丝三维几何实体模型,将多曲方丝弓通过托槽粘接在下牙列上,弓丝和托槽采用四点四面体单元划分后,采用ANSYS对模型进行力学分析。结果建立了多曲方丝弓简单受力的有限元分析模型,多曲方丝弓在在某个局部(如3、4牙间)受力较大时,在其他牙位托槽处(1、2、5、6、7)的支反力并不大,力量轻柔,尤以第一磨牙处明显。结论本研究建立的多曲方丝弓简单受力的有限元分析模型可为临床更好地研究其整体力学特性、揭示其技术矫治特点、探讨其作用机制提供理论依据。     

力量训练对运动性骨骼肌损伤的影响及其机制研究

目的观察在不同张力下 ,离心收缩力量训练对骨骼肌组织结构、血清CK及生物力学特性的影响 ,研究运动性骨骼肌损伤与力学因素的内在联系。方法本文建立了一个活体大鼠骨骼肌力量训练及其生物力学性质的动态、定量测试模型 ,将SD雄性大鼠的踝关节背伸肌群在两组不同外加载荷下 ,进行循环式离心力量训练。结果离心运动后即刻— 1 4d ,大鼠骨骼肌的组织结构、血清CK及其力学性质变化在高张力组和低张力组之间的差异无统计学意义 (P >0 .0 5 )。结论离心收缩产生的高张力本身 ,并非是造成骨骼肌损伤的首要因素     

渐消记忆递推最小二乘法在呼吸力学参数估计中的应用

油酸及组胺两种急性肺损伤犬模型检验了渐消记忆递推最小二乘算法辨识跟踪慢时变呼吸力学参数的效果,除肺力学参数外,还对胸-肺系统总的呼吸力学参数进行了估计。此外,还与用最小二乘曲线拟合法得出的参数估计结果作了比较。结果表明:渐消记忆递推最小二乘(RLS)法精度高、收敛速度快,适于跟踪慢时变的呼吸力学参数。作者认为,针对临床监测目的,以选用一室一阶线性呼吸力学模型跟踪呼气相的呼吸力学参数为宜。     

胞质分裂的细胞力学实验技术及其柑关理论研究进展

胞质分裂是一个典型的力学过程,涉及细胞皮质力学特性的明显改变,胞质分裂过程中不同刚度或黏弹性区域的形成对细胞形态的改变至关重要.胞质分裂研究在不断深入的过程中,利用不断革新的研究技术,积累了大量数据,要求研究在精细化、定量化的基础上实现模型化,随着相应理论模型的建立和完善,量化蛋白控制胞质分裂的过程将成为可能.本文针对胞质分裂研究中涉及的力学研究技术及主要研究进展加以综述.     

人工髋臼接触力学特性的有限元分析

目的 考察人工超高分子量聚乙烯髋关节臼的接触力学特性.方法 建立人工髋臼模型,对模型进行网格划分,在接触区域建立接触对,按真实人体关节对模型进行边界条件的设定后进行有限元接触力学分析.对不同条件下(摩擦系数0～0.25,髋臼厚度6～12 mm,髋臼直径26～32 mm)的髋臼分别进行步态分析.结果 计算结果显示压缩变形量在接触面摩擦系数增大、髋臼直径增加情况下均呈现下降趋势.接触层厚及接触面积受髋臼厚度的影响在不同尺寸处体现不同的特性,接触面积和层厚对于植入假体的稳定性及磨粒的产生有重要影响.结论 综合考虑两者的作用效果认为7～9 mm厚的髋臼表现效果较好.     

对细胞施加力学作用的实验方法

对细胞施加力学作用的实验方法有很多种,但大多是对体内、体外环境中某一力学因素的模拟.按照所模拟力的来源不同,分为模拟体内力学环境的实验方法和模拟体外力学环境的实验方法两类.模拟体内力学环境的实验方法主要有:流动剪切力法、静水压法、圆周应力法、基底拉伸法;模拟体外力学环境的实验方法主要有:微重力细胞培养法、离心力场法、气体加压法、声波刺激法、微光束辐照法.另外,还有一类用于研究单细胞力学特性的实验方法,主要有微管吸吮法、原子力显微镜悬臂刺激法、磁珠扭转法和光钳法.本文针对这些主要的实验方法进行综述.     

Stent conformity in curved vascular models with simulated aneurysm necks using flat-panel CT: an in vitro study

BACKGROUND AND PURPOSE: Radiographic visibility of self-expandable intracranial stents is insufficient for assessment of conformability and deployment characteristics. The purpose of this study was to evaluate stent mechanics in a curved vessel model by using Flat-Panel CT (FPCT). MATERIALS AND METHODS: The following stents were used: Neuroform 2, Neuroform Treo, Enterprise, and LEO. All stents were bent in the same polytetrafluoroethylene tubes with various angles ranging from 150 degrees to 30 degrees . To visualize potential prolapse of the stent struts, 4-, 5-, and 8-mm openings were created. FPCTs were obtained using a C-arm with flat detector. RESULTS: FPCT scans provided excellent visualization of deployment characteristics and stent mechanics and was superior to digital subtraction angiography (DSA) and digital radiography (DR). The Neuroform2/Treo showed, with increasing angle and diameter of the opening, a continuous increase in cell size. These stents also showed an outward prolapse at the convexity and an inwards prolapse of struts at the concavity of the curvature. The Enterprise showed an increasing trend to flatten and to kink with curvatures that are more acute. The LEO showed fewer trends to kink but an inward crimping of its ends with more acute angles. CONCLUSIONS: Deployment characteristics and conformability to a curved vessel model vary considerably, depending on the angle and the stent design. Adverse mechanics such as increased cell opening, strut prolapse, flattening, and kinking occur during stent placement in a curved vessel model, and may gain clinical importance. FPCT is superior to DSA and DR in visualizing small metallic stents and enables accurate detection of adverse stent mechanics.     

Mechanical Characteristics of Composite Knitted Stents

We used metal wires and fibers to fabricate a composite knitted stent and then compare the mechanical characteristics of this stent with those of a pure metallic stent of the same construction in order to develop a stent that offers a comparable degree of expandability as metallic stents but can be used for highly curved lesions that cannot be treated using metallic stents. We fabricated two types of composite knitted stent (N–Z stents), using nitinol wire with a diameter of 0.12 mm and polypara-phenylene-benzobisoxazole (PBO) multifilament fiber (Zyron AS; Toyobo, Osaka, Japan). Stents were knitted into a cylindrical shape using the same textile pattern as a Strecker stent. Two loop lengths (L) of nitinol wire were used in the N–Z stents: L = 1.84 mm (N–Z stent L = 1.84) and L = 2.08 mm (N–Z stent L = 2.08). For the sake of comparison, we fabricated a metallic stent of nitinol using the same textile pattern (N–N stent L = 1.92). We applied a radial compression force diametrically to each stent and applied a bending force diametrically at the free end of a stent with one end fixed in order to evaluate the relationship between stent elasticity and load values. In addition, we macroscopically evaluated the generation of kinks when the stent was bent 180°. The radial compressive force when the stent diameter was reduced by 53% was 6.44 N in the case of N–Z stent L = 1.84, 6.14 N in the case of N–Z stent L = 2.08, and 4.96 N in the case of N–N stent L = 1.92 mm. The composite stent had a radial compressive force higher than that of a metallic stent. The restoring force to longitudinal direction at a 90° bending angle was 0.005 N for N–Z stent L = 1.84, 0.003 N for N–Z stent L = 2.08, and 0.034 N for N–N stent L = 1.92. The restoring force of the composite stent was significantly lower. Finally, the composite stent generated no definitive kinks at a bending angle of 180°, regardless of loop length. However, the N–N stent clearly produced kinks, causing blockage of the inner cavity. In conclusion, the use of a metal and fiber composite in the construction of a knitted stent ensures an expansion performance comparable to that of metallic stents, while providing better kink resistance.     

Bile resistance of coated transjugular intrahepatic portosystemic shunt stents in a flow-model

PURPOSE: We sought to test the bile resistance of transjugular intrahepatic portosystemic shunt (TIPS) stents with 3 different coatings. MATERIALS AND METHODS: Three stents with different coating materials (monolayer polyethylene terephthalate [PETP], monolayer polytetrafluoroethylene [PTFE], and double layer [PTFE]) were tested in a flow model. After testing the sealing of the system with isotonic saline solution, fresh human bile was circulated. Constant pressure was 50 cm H2O. Bile resistance of the stent membranes was analyzed. RESULTS: Two of the 3 stents proved completely resistant to water. Only the PETP stent was resistant to bile. The PTFE-coated stents were not bile resistant. CONCLUSION: The bile resistance of coated TIPS stents and, thus, the dependency of TIPS shunt patency is called into question. The stent with the reported superior patency rates does not show experimental bile resistance.     

Changes in wall mechanics after endovascular stenting in the rabbit aorta: comparison of three stent designs

OBJECTIVE: The aim of this study was to evaluate changes in the wall mechanics of small-diameter arteries after endovascular placement of three different stents. SUBJECTS AND METHODS: Five self-expandable stents (Wallstent), five balloon-expandable noncovered Palmaz stents, and three balloon-expandable covered stents (Jostent) were placed in the infrarenal aorta of 13 New Zealand white rabbits. Systolic blood pressure changes, blood-flow velocity, systolic diameter, and diameter changes were measured and used to calculate the diameter compliance, the distensibility coefficient, and the pulsatility index. RESULTS: Compliance (10(-3) mm kPa(-1)) was 75.3 +/- 20.1 before stenting and reached 94.7 +/- 42.2 upstream, 38.8 +/- 14.2 at the stent level (p < 0.05), and 70.8 +/- 23.2 downstream from the stent. Distensibility (10(-3) kPa(-1)) was 24.3 +/- 6.3 before stenting and reached 27.8 +/- 10.3 upstream, 10.5 +/- 4.4 at the stent level (p < 0.001), and 21.9 +/- 8.6 downstream from the stent. Compliance and distensibility were significantly lower at the stent level than upstream and downstream (p < 0.05). Aortic diameter increased significantly at the stent level from 3.11 +/- 0.40 mm before to 3.76 +/- 0.42 mm after stenting. No significant difference was found among the three stent designs for all the studied data. CONCLUSION: Regardless of the three tested stent designs, endovascular stenting produces a significant decrease in arterial wall compliance of the rabbit aorta.     

The Nitinol SMART stent vs Wallstent for suboptimal iliac artery angioplasty: CRISP-US trial results

PURPOSE: The Cordis Randomized Iliac Stent Project-US (CRISP-US) trial evaluated, with an equivalence design, the performance of the shape memory alloy recoverable technology (SMART) nitinol self-expanding stent and the stainless steel Wallstent for treating iliac artery disease after suboptimal percutaneous transluminal angioplasty (PTA). MATERIALS AND METHODS: This multicenter, prospective, randomized trial comprised 203 patients with chronic limb ischemia who received either the SMART stent (n = 102) or the Wallstent (n = 101) after suboptimal PTA. The primary equivalence end point was a composite of 9-month restenosis, 30-day death, and 9-month target vessel revascularization. Functional, clinical, and hemodynamic assessments were made at hospital discharge and at 1, 6, 9, and 12 months. RESULTS: The 9-month composite end point rate was equivalent for the SMART stent and Wallstent (6.9% vs 5.9%), with low rates of restenosis (3.5% vs 2.7%), death (2.0% vs 0.0%), and revascularization (2.0% vs 4.0%) in the two groups. Primary patency at 12 months was 94.7% and 91.1% with the SMART stent and Wallstent, respectively. Functional and hemodynamic improvement was also comparable between the groups. The acute procedural success rate was higher in the SMART stent group (98.2% vs 87.5%; P =.002). The frequency of major adverse events was similar at 1 year (4.9% vs 5.9%). CONCLUSIONS: The performance of the SMART stent was equivalent to that of the Wallstent for treating iliac artery stenosis. The design characteristics of the SMART stent may contribute to greater procedural success and more accurate stent deployment.     

Utilization of and Outcomes Associated with Intravascular Ultrasound during Deep Venous Stent Placement among Medicare Beneficiaries

PurposeTo evaluate temporal trends, practice variation, and associated outcomes with the use of intravascular ultrasound (US) during deep venous stent placement among Medicare beneficiaries.Materials and MethodsAll lower extremity deep venous stent placement procedures performed between January 1, 2017, and December 31, 2019 among Medicare beneficiaries were included. Temporal trends in intravascular US use were stratified by procedural setting and physician specialty. The primary outcome was a composite of 12-month all-cause mortality, all-cause hospitalization, or repeat target vessel intervention. The secondary outcome was a composite of 12-month stent thrombosis, embolization, or restenosis.ResultsAmong the 20,984 deep venous interventions performed during the study period, 15,184 (72.4%) utilized intravascular US. Moderate growth in intravascular US use was observed during the study period in all clinical settings. There was a variation in the use of intravascular US among all operators (median, 77.3% of cases; interquartile range, 20.0%–99.2%). In weighted analyses, intravascular US use during deep venous stent placement was associated with a lower risk of both the primary (adjusted hazard ratio, 0.72; 95% confidence interval [CI], 0.69–0.76; P < .001) and secondary (adjusted hazard ratio, 0.32; 95% CI, 0.27–0.39; P < .001) composite end points.ConclusionsIntravascular US is frequently used during deep venous stent placement among Medicare beneficiaries, with further increase in use from 2017 to 2019. The utilization of intravascular US as part of a procedural strategy was associated with a lower cumulative incidence of adverse outcomes after the procedure, including venous stent thrombosis and embolization.     

Hemodynamics and wall mechanics after stent placement in swine iliac arteries: comparative results from six stent designs.

PURPOSE: To compare the hemodynamics and wall mechanics of swine iliac arteries after placement of six types of stent. MATERIALS AND METHODS: Stents were placed in the iliac artery of 18 pigs (three pigs each underwent placement with one of six types of stent); 16 untreated pigs served as control animals. Iliac arterial hemodynamics and wall mechanics were measured 4 days after placement. RESULTS: Four stents (Palmaz-Schatz, Cordis, Warren, NJ; and Strecker, Cragg, and Symphony, Boston Scientific/Vascular, Natick, Mass) caused decreased pulsatile flow rate in the treated and contralateral iliac arteries; one (Memotherm; Bard, Covington, Ga) caused increased flow pulsatility; and one (Wallstent; Schneider, Plymouth, Minn) had no effect. No compliance mismatching was noted for the Cragg, Symphony, and Memotherm stents, whereas a decrease in compliance was noted for the Palmaz-Schatz, Strecker, and Wallstent designs. The Palmaz-Schatz and Strecker stents caused increased arterial wall rigidity, the Symphony and Wallstent designs had no effect, and the Memotherm and Cragg stents caused decreased wall rigidity. Stents made of stiff metal yielded different early results than did stents made of the less rigid nitinol. CONCLUSION: Soon after implantation, the six stent designs elicited varying changes in blood flow, arterial compliance, and arterial wall mechanics. Contralateral arterial flow also was affected.     

MR safety and imaging of neuroform stents at 3T

The Neuroform stent is a self-expanding nitinol stent designed for use in wide-necked intracranial aneurysms. Heating and imaging artifacts were evaluated by using a porcine carotid artery aneurysm model in a 3T MR system. A suspended Neuroform stent was tested for deflection. No heating was measured, and no evidence of deflection of the stent was found. Imaging artifacts were minimal. MR imaging in patients with Neuroform stent-treated aneurysms is safe and feasible.     

Endovascular treatment of superficial femoral artery occlusive disease with stents coated with diamond-like carbon

A major consideration in the reduction of early stent thrombosis and in-stent restenosis is the improvement of biocompatibility of the devices. Diamond-like carbon is a novel material for coating stent surfaces in order to increase biocompatibility. The authors report on the endovascular treatment of two individuals with superficial femoral artery occlusions, using stents coated with diamond-like carbon. Technical and clinical success was achieved in both cases, with primary patency rates of 100% 12 months after intervention.     

Electron-microscopic study on the effect of an expandable metallic stent placement in the aortic wall]

As part of a series of basic experiments on using metallic stents for treatment of vascular stenosis, a chronological examination of changes in dog aorta following implantation of a self-expandable metallic stent was conducting using transmission and scanning electron microscopy. The Giantruco stent was placed in the abdominal aorta via the right carotid artery. One week after insertion, the aortic intima was depressed and degenerative changes observed in both endothelial and medial smooth muscle cells. After 2 weeks, except for the bend portion, the stent was covered with neointima. The neointimal surface was covered by premature endothelial cells with abundant microvilli and prominent nuclear protrusions. Under the endothelial cells, immature mesenchymal cells, such as fibroblast, were scattered throughout the edematous intercellular space. At 4 weeks, the stent was completely covered by neointima and the endothelial cells had flattened and few microvilli were in evidence. In this thickened intima, premature smooth muscle cells with myofilaments and basement membranes were observed but, around them, few collagen fibers and only occasional elastic fibers were found. At 6 weeks, the intimal surfaces were flat and smooth with a slight intimal elevation over the stent. No thrombus was observed throughout the period of the experiment. The above results indicate that dilation using metallic stents may be a useful method for treatment of vascular stenosis.