Predicting Skull Loading: Applying Multibody Dynamics Analysis to a Macaque Skull

Evaluating stress and strain fields in anatomical structures is a way to test hypotheses that relate specific features of facial and skeletal morphology to mechanical loading. Engineering techniques such as finite element analysis are now commonly used to calculate stress and strain fields, but if we are to fully accept these methods we must be confident that the applied loading regimens are reasonable. Multibody dynamics analysis (MDA) is a relatively new three dimensional computer modeling technique that can be used to apply varying muscle forces to predict joint and bite forces during static and dynamic motions. The method ensures that equilibrium of the structure is maintained at all times, even for complex statically indeterminate problems, eliminating nonphysiological constraint conditions often seen with other approaches. This study describes the novel use of MDA to investigate the influence of different muscle representations on a macaque skull model (Macaca fascicularis), where muscle groups were represented by either a single, multiple, or wrapped muscle fibers. The impact of varying muscle representation on stress fields was assessed through additional finite element simulations. The MDA models highlighted that muscle forces varied with gape and that forces within individual muscle groups also varied; for example, the anterior strands of the superficial masseter were loaded to a greater extent than the posterior strands. The direction of the muscle force was altered when temporalis muscle wrapping was modeled, and was coupled with compressive contact forces applied to the frontal, parietal and temporal bones of the cranium during biting. Anat Rec, 291:491–501, 2008. © 2008 Wiley‐Liss, Inc.     

Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy

Direct visualization of crystal growth in poly(L ‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.

     

Muscular fatigue and rate of tension development

Summary The effects of long-term fatigue upon maximal force and peak rate of tension development (PRTD) (dF/dt max) are studied in man (elbow flexors), in the rat (pseudo-isolated gastrocnemius muscle) and in the frog (isolated sartorius muscle). The muscles are fatigued by voluntary anisometric anisotonic contractions against an elastic resistance in man, and by maximal tetanic contractions in the frog and the rat. In man, the excitation level of the muscle is controlled by the integrated surface EMG of the biceps brachii. In the animals, the muscles are stimulated by a neurostimulator. The PRTD and the maximal isometric force are measured during fatigue tests.In man, frog and rat, the maximal voluntary isometric torque or the maximal force and the PRTD decrease initially more or less rapidly according to the power developed during the fatigue process, and then less rapidly. The relationship between PRTD and maximal force is linear in the animals and curvilinear in man.The variations of maximal force and PRTD are discussed in relation to the level of excitation of the muscles and of the composition in different motor units types and their spatio-temporal recruitment. From a biomechanical point of view, it seems necessary to study the behavior of the series elastic component during the evolution of long term fatigue.     

培养大鼠皮层神经元NMDA受体蛋白单分子原子力显微镜定位研究

为在纳米尺度对 NMDA受体蛋白分子进行神经细胞膜表面原位定位和探讨原子力显微镜在生物单分子操纵和调控中的应用 ,本研究应用原子力显微镜分别对分布在云母表面的膜 NMDA受体蛋白分子标记物抗 NMDAR1Ig G-葡萄球菌蛋白 A-胶体金复合物分子和结合标记物分子后的神经元膜进行扫描 ,三维形貌测定 ,通过颗粒度分析结果 ,明确标记物分子的特征性三维形貌 ,对比确定经过免疫胶体金结合后的 NMDA受体蛋白单分子在神经元膜表面的定位。结果显示 ,空白云母表面标记物分子为分散均匀的平均粒径为 49nm的球形颗粒 ,在神经元膜表面结合 NMDA目的受体蛋白分子后 ,免疫复合物分子呈现出粒径为 5 3 nm的散在分布球形或短棒状颗粒 ,长径约为宽径的 2倍 ,长轴截面可见典型的双峰三维结构。上述结果表明 ,NMDA受体蛋白单分子可以结合 1个或 1个以上的胶体金标记物分子 ;原子力显微镜可以在纳米尺度对神经元膜 NMDA受体蛋白进行标记和其免疫复合物的三维形貌测定。胶体金颗粒标记 ,原子力显微镜测定是免疫细胞化学新方法。     

Molecular weights of individual proteins correlate with molecular volumes measured by atomic force microscopy

 Proteins are usually identified by their molecular weights, and atomic force microscopy (AFM) produces images of single molecules in three dimensions. We have used AFM to measure the molecular volumes of a number of proteins and to determine any correlation with their known molecular weights. We used native proteins (the TATA-binding protein Tbp, a fusion protein of glutathione-S-transferase and the renal potassium channel protein ROMK1, the immunoglobulins IgG and IgM, and the vasodilator-stimulated phosphoprotein VASP) and also denatured proteins (the red blood cell proteins actin, Band 3 and spectrin separated by SDS-gel electrophoresis and isolated from nitrocellulose). Proteins studied had molecular weights between 38 and 900 kDa and were imaged attached to a mica substrate. We found that molecular weight increased with an increasing molecular volume (correlation coefficient = 0.994). Thus, the molecular volumes measured with AFM compare well with the calculated volumes of the individual proteins. The degree of resolution achieved (lateral 5 nm, vertical 0.2 nm) depended upon the firm attachment of the proteins to the mica. This was aided by coating the mica with suitable detergent and by imaging using the AFM tapping mode which minimizes any lateral force applied to the protein. We conclude that single (native and denatured) proteins can be imaged by AFM in three dimensions and identified by their specific molecular volumes. This new approach permits detection of the number of monomers of a homomultimeric protein and study of single proteins under physiological conditions at the molecular level. Received: 14 February 1997 / Received after revision: 8 September 1997 / Accepted: 8 September 1997     

Force- and moment-generating capacities of muscles in the distal forelimb of the horse

A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarpal, intercarpal, carpometacarpal, metacarpophalangeal (MCP), proximal interphalangeal (pastern) and distal interphalangeal (coffin)). Bone surfaces were reconstructed from computed tomography scans obtained from the left forelimb of a Thoroughbred horse. The model was actuated by nine muscle-tendon units. Each unit was represented as a three-element Hill-type muscle in series with an elastic tendon. Architectural parameters specifying the force-producing properties of each muscle-tendon unit were found by dissecting seven forelimbs from five Thoroughbred horses. Maximum isometric moments were calculated for a wide range of joint angles by fully activating the extensor and flexor muscles crossing the carpus and MCP joint. Peak isometric moments generated by the flexor muscles were an order of magnitude greater than those generated by the extensor muscles at both the carpus and the MCP joint. For each flexor muscle in the model, the shape of the maximum isometric joint moment-angle curve was dominated by the variation in muscle force. By contrast, the moment-angle curves for the muscles that extend the MCP joint were determined mainly by the variation in muscle moment arms. The suspensory and check ligaments contributed more than half of the total support moment developed about the MCP joint in the model. When combined with appropriate in vivo measurements of joint kinematics and ground-reaction forces, the model may be used to determine muscle-tendon and joint-reaction forces generated during gait.     

Atomic force microscopy for imaging human metaphase chromosomes

The present study introduces the principle of atomic force microscopy (AFM) and reviews our results of human metaphase chromosomes obtained by AFM. AFM imaging of the chromosomes revealed that the chromatid arm was not uniform in structure but had ridges and grooves along its length, which was most prominent in the late metaphase. The arrangement of these ridges and grooves was roughly symmetrical with the counterpart of the paired sister chromatids. AFM imaging of banded chromosomes also showed that the ridges and grooves were related to the G/Q-positive and G/Q-negative bands, respectively. At high magnification, the chromatid was seen to be produced by the compaction of highly twisted chromatin fiber loops, and its compaction tended to be stronger in the ridged regions of the chromosomes than in the grooved regions. Our AFM studies also showed the presence of catenation of chromatin fibers between the ridged portions of the chromatid in the late metaphase. Thus, AFM is useful for obtaining the three-dimensional surface topography not only in ambient conditions but also in physiological liquid conditions, and is expected to be an attractive tool for investigating the structure of chromosomes.     

Scanning and synthesizing Canadian policies that address the school-to-work transition of youth and young adults with disabilities

BackgroundDisability faced by a young person can impact the school-to-work transition and shape health and well-being over the life course. Unique barriers to entry and advancement within the labor market that are relevant to young people with disabilities underscore the need for tailored policy-level supports.ObjectivesTo examine and describe policies that support the school-to-work transition of young people with disabilities in Canada.MethodsA scan of policies which focused on the school-to-work transition of young people with disabilities across Canada was conducted between June 2019 and January 2020. Searches were completed within federal, provincial and territorial policy portals. Each policy relating to employment participation of people with disabilities was summarized. Policies that focused on the school-to-work-specific were synthesized using Bemelmans-Vidic, Rist and Vedung's policy tool framework.ResultsA total of 36 policies were identified by our scan that focused on the employment of people with disabilities. Only five policies explicitly addressed the school-to-work transition. All existing policies were implemented at the provincial level and aimed to promote entry into employment. The synthesis of policies revealed that financial policy tools were primarily used to incentivize employment, provision of workplace accommodations, or the development and implementation of job readiness programs.ConclusionOur analysis of federal, provincial and territorial policies in Canada uncovered a limited number of policies that specifically support the school-to-work transition. Addressing these policy gaps can increase the inclusion of young people with disabilities in the labor market.     

一种脉象全信息触力传感器

根据中医脉象生理信号的采集原理和特点,结合国际标准脉搏波触力传感器ISO 19614:2017-05的要求,研制了一种可将脉象生理信号进行完整客观化采集的专用触力传感器组件,并符合产业化要求。该传感器可采集人体寸口部位的脉象幅度和宽度信号,能同时进行三部九候的脉象采集。对该传感器经验证后,其相关技术性能指标的检测结果符合国际标准规定的相关要求,并与临床中医专家的诊断结果一致性为92.3%。     

对促宫颈成熟与引产孕产妇的全程分娩管理模式

目的探讨在全程分娩管理模式下,为孕产妇提供促宫颈成熟与引产服务的可行性。方法选择2018年1月1日至2020年12月31日,在南京大学医学院附属鼓楼医院接受待产、分娩到产后康复(LDRP)一体化全程分娩管理模式(以下简称为LDRP管理)的848例孕产妇为研究对象。根据孕产妇进入产房时是否进入自然产程,将其分为自然临产组(n=441)和引产组(n=407)。采用回顾性分析法,对2组孕产妇的一般临床资料,如分娩年龄、孕次、孕龄、妊娠并发症,以及母儿结局进行比较。本研究遵循的程序符合2013年修订的《世界医学协会赫尔辛基宣言》的要求,并经过南京大学医学院附属鼓楼医院伦理委员会审核批准(审批文号:201702001)。结果①2组孕产妇分娩年龄、孕次和高龄孕产妇所占比例比较,差异无统计学意义(P>0.05)。2组孕产妇分娩孕龄、经产妇占比、早产率、缩宫素使用率、分娩时长比较,差异有统计学意义(P<0.05)。②引产组孕产妇均使用前列腺素类药物促宫颈成熟或缩宫素进行引产,其中使用地诺前列酮栓、米索前列醇、缩宫素、地诺前列酮栓+米索前列醇分别为26.5%(108/407)、10.3%(42/407)、60.0%(244/407)、3.2%(13/407)。③2组接受LDRP管理孕产妇总剖宫产术分娩率(2.9%vs 7.1%)、会阴侧切率(20.1%vs 28.6%)、新生儿出生体重[3410 g(3180~3650 g)vs 3340 g(3040~3640 g)]、总住院时间[4 d(3~4 d)vs 4 d(4~5 d)]比较,差异均有统计学意义(χ^(2)=7.846、χ^(2)=7.894、Z=-2.730、Z=-5.112,P<0.05)。④2组LDRP管理孕产妇临产后剖宫术分娩产率、产后24 h出血率、产后24 h出血量≥1000 mL、异体红细胞悬液输注率和宫腔水囊压迫率和产后住院天数比较,差异均无统计学意义(P>0.05)。结论为符合纳入、排除标准孕产妇LDRP管理具有一定可行性,孕产妇及其分娩新生儿均可获得良好妊娠结局。