A Coupling Analysis of the Biomechanical Functions of Human Foot Complex during Locomotion

This study represents a functional analysis of the human foot complex based on in-vivo gait measurements, finite element (FE) modeling and biological coupling theory, with the objective of achieving a comprehensive understanding of the impact attenuation and energy absorption functions of the human foot complex. A simplified heel pad FE model comprising reticular fiber structure and fat cells was constructed based on the foot pad Magnetic Resonance (MR) images. The model was then used to investigate the foot pad behaviors under impact during locomotion. Three-dimensional (3D) gait measurement and a 3D FE foot model comprising 29 bones, 85 ligaments and the plantar soft tissues were used to investigate the foot arch and plantar fascia deformations in mid-stance phase. The heel pad simulation results show that the pad model with fat cells (coupling model) has much stronger capacity in impact attenuation and energy storage than the model without fat cells (structure model). Furthermore, the FE simulation reproduced the deformations of the foot arch structure and the plantar fascia extension observed in the gait measurements, which reinforces the postulation that the foot arch structure also plays an important role in energy absorption during locomotion. Finally, the coupling mechanism of the human foot functions in impact attenuation and energy absorption was proposed.     

Work-Related Pain in Extrinsic Finger Extensor Musculature of Instrumentalists Is Associated with Intracellular pH Compartmentation during Exercise

Background

Although non-specific pain in the upper limb muscles of workers engaged in mild repetitive tasks is a common occupational health problem, much is unknown about the associated structural and biochemical changes. In this study, we compared the muscle energy metabolism of the extrinsic finger extensor musculature in instrumentalists suffering from work-related pain with that of healthy control instrumentalists using non-invasive phosphorus magnetic resonance spectroscopy (³¹P-MRS). We hypothesize that the affected muscles will show alterations related with an impaired energy metabolism.

Methodology/Principal Findings

We studied 19 volunteer instrumentalists (11 subjects with work-related pain affecting the extrinsic finger extensor musculature and 8 healthy controls). We used ³¹P-MRS to find deviations from the expected metabolic response to exercise in phosphocreatine (PCr), inorganic phosphate (Pi), Pi/PCr ratio and intracellular pH kinetics. We observed a reduced finger extensor exercise tolerance in instrumentalists with myalgia, an intracellular pH compartmentation in the form of neutral and acid compartments, as detected by Pi peak splitting in ³¹P-MRS spectra, predominantly in myalgic muscles, and a strong association of this pattern with the condition.

Conclusions/Significance

Work-related pain in the finger extrinsic extensor muscles is associated with intracellular pH compartmentation during exercise, non-invasively detectable by ³¹P-MRS and consistent with the simultaneous energy production by oxidative metabolism and glycolysis. We speculate that a deficit in energy production by oxidative pathways may exist in the affected muscles. Two possible explanations for this would be the partial and/or local reduction of blood supply and the reduction of the muscle oxidative capacity itself.     

Activity of Motor Units in Human Elbow Flexor and Extensor Muscles during Task-Dependent Unloading

Neurophysiology - Surface EMGs and activity of 73 single motor units (MUs) of the m. triceps brachii caput laterale (TBcl) and 25 units of the m. biceps brachii caput longum (BBcl) were recorded in...     

Isometric strength and endurance during the menstrual cycle.

Seven healthy young women, 3 whom had been taking oral contraceptives, were examined during the course of 2 menstrual cycles to assess their isometric strength, their endurance during a series of 5 fatiguing isometric contractions at a tension of 40% MVC, and their blood pressures and heart rates during those fatiguing contractions. Two sets of experiments were performed, one in which the subject's forearm temperature was allowed to vary as a function of T A, and one with the muscle temperature stabilized by immersion of the forearm in water at 37 degrees C. During exposure to ambient temperatures, isometric strength and both the heart rate and blood pressure responses at rest and at the end of a fatiguing, sustained isometric exercise, were not significantly different during any phase of the menstrual cycle in any subject. In contrast, the isometric endurance in the women not taking oral contraceptives varied sinusoidally in all 5 contractions with a peak endurance midway through the ovulatory phase and the lowest endurance mid-way through the luteal phase of the menstrual cycle. The isometric endurance of the women taking oral contraceptives did not vary during their menstrual cycle. After stabilization of the temperature of the muscles of the forearm in water at 37 degrees C, the isometric endurance of the normal subjects showed a hyperbolic response with the maximal endurance at the beginning and end of their cycles, and the shortest endurance at mid-cycle. Here again, however, the isometric endurance of the women taking oral contraceptives did not vary after immersion of their forearms in the 37 degree C water.     

缝线治疗粉碎性髌骨骨折并修复伸膝装置

目的:探讨缝线治疗严重粉碎性髌骨骨折并修复伸膝装置的临床疗效.方法:采用缝线治疗严重粉碎性髌骨骨折伴伸膝装置损伤19例.术后影像学检查及术后功能恢复情况综合判定治疗效果,并予以临床分级标准评分.结果:术后平均随访23.5个月,术后无需石膏托外固定,无骨折移位,全部达到临床愈合,膝关节功能恢复良好.术后功能恢复情况:优ll例,良6例,可2例.临床分级标准评分平均26.3分.结论:运用缝线治疗严重粉碎性髌骨骨折并修复伸膝装置是一种较为理想的手术方法.     

人锌指蛋白ZNF256基因克隆、表达谱分析及其功能研究

人ZNF256 基因属于C2H2 型锌指蛋白家族.该家族里面的基因大部分为转录因子,它们能够促进细胞分化、参与胚胎及心脏的发育,与精子的形成有关,并且与肿瘤相关.本文采用实时定量 PCR 方法分析了ZNF256 基因在各个组织和不同细胞系中的表达情况,亚细胞定位发现 ZNF256 定位于细胞核,萤光素酶实验分析确定 ZNF256 可以抑制 AP1 的转录活性.这些研究结果为进一步研究 ZNF256 基因在疾病发生中的作用奠定了一定的基础.     

Neuromuscular Activation of the Vastus Intermedius Muscle during Isometric Hip Flexion

Although activity of the rectus femoris (RF) differs from that of the other synergists in quadriceps femoris muscle group during physical activities in humans, it has been suggested that the activation pattern of the vastus intermedius (VI) is similar to that of the RF. The purpose of present study was to examine activation of the VI during isometric hip flexion. Ten healthy men performed isometric hip flexion contractions at 25%, 50%, 75%, and 100% of maximal voluntary contraction at hip joint angles of 90°, 110° and 130°. Surface electromyography (EMG) was used to record activity of the four quadriceps femoris muscles and EMG signals were root mean square processed and normalized to EMG amplitude during an isometric knee extension with maximal voluntary contraction. The normalized EMG was significantly higher for the VI than for the vastus medialis during hip flexion at 100% of maximal voluntary contraction at hip joint angles of 110° and 130° (P < 0.05). The onset of VI activation was 230–240 ms later than the onset of RF activation during hip flexion at each hip joint angle, which was significantly later than during knee extension at 100% of maximal voluntary contraction (P < 0.05). These results suggest that the VI is activated later than the RF during hip flexion. Activity of the VI during hip flexion might contribute to stabilize the knee joint as an antagonist and might help to smooth knee joint motion, such as in the transition from hip flexion to knee extension during walking, running and pedaling.     

Biomechanical analysis of women weightlifters during the snatch

The majority of the research to date on weightlifting has focused on men competitors. This study attempted to bridge the sex-based gap evident in the scientific literature. The performances of 10 women weightlifters competing in the 1999 United States national championships were analyzed. The performance of the athletes competing in the 69-kg class was recorded and analyzed using a Peak5 2D Motion Analysis system. The purpose of this study was 3-fold: (a) analyze the horizontal bar displacement of women weightlifters, (b) analyze key kinematic variables related to performance, and (c) compare the power outputs of the first, second, and total pulls in the snatch. Less than half (<50%) of the snatch attempts demonstrated by the women weightlifters in this study displayed the optimal toward-away-toward horizontal bar trajectory reported elsewhere. The women in this study demonstrated greater drop displacement and drop under times than those previously reported for men weightlifters. They also demonstrated lesser maximal vertically velocities of the barbell than those reported for world class women weightlifters. These women weightlifters demonstrated statistically significant differences (p < 0.05) during each phase of the snatch, and total power output values were comparable to values previously reported. The results of this study suggest that women demonstrate performance characteristics that differ subtly from those reported in men weightlifters. Knowledge of performance measures during the snatch may help coaches and athletes more fully refine the training leading to competition.     

一个新的人类锌指蛋白基因ZNF474的cDNA克隆和表达分析

数据库消减杂交就是利用NCBI中的Unigene数据库中大量的数据资源,收集各种细胞或组织的基因表达谱进行两两比较或多重比较,获得两组文库间有统计学意义的差异表达基因。运用NCBI中的数据库消减杂交分析方法,从人睾丸组织中分离了一个含有C2H2结构的新型锌指蛋白基因-ZNF474(GenBank登录号：AY461732)．通过推导和进一步的RT—PCR实验证实：该基因含2个外显子,gDNA在染色体上跨度30065bp,定位于人染色体5q23．1-q23。2．cDNA编码一个含364个氨基酸的新蛋白,分子质量是40．3kDa,等电点为9．59。Northem杂交结果显示：该基因含有2．37kb大小的唯一转录本,主要在睾丸中很强表达,卵巢中有弱表达,而其他组织中该基因无表达．结果提示：ZNF474基因对精子发生和卵母细胞的发育可能起重要作用、     

Biomechanical analysis of the knee during the power clean

To our knowledge, no scientific literature has examined the 3-dimensional forces acting at the knee joint during a power clean. Ten male weightlifting subjects (25.9 years, SD 3.54) performed 1 set of the power clean at 60 and 70% of their maximal collegiate level for 5 repetitions. The subjects displayed a large compressive, moderate anterior, and a small degree of lateral and medial force at the knee during both percentage lifts. The majority of these forces occurred during the second pull phase or the catching phase of the lift. Lifters with decreased weight/system weight percentages displayed a more efficient lift that placed less stress on the knees. This analysis may provide invaluable information in the assessment of weight percentages used for Olympic weightlifters throughout the training year. the power clean.     

The Finger Domain of the Human Deubiquitinating Enzyme HAUSP is a Zinc Ribbon

Human deubiquitinating enzyme HAUSP is a cysteine protease that regulates the levels of the tumor suppressor protein p53. By comparative sequence and structural analysis, we show that the previously uncharacterized finger domain insert to the catalytic core of HAUSP is a zinc ribbon that has lost its zinc-binding ability.     

The Human Ankle-Foot Complex as a Multi-Configurable Mechanism during the Stance Phase of Walking

<正> The objective of this study is to investigate the biomechanical functions of the human ankle-toot complex during the stancephase of walking. The three-dimensional (3D) gait measurement was conducted by using a 3D infrared multi-camera system anda force plate array to record the Ground Reaction Forces (GRF) and segmental motions simultaneously. The ankle-foot complexwas modelled as a four-segment system, connected by three joints: talocrural joint, sub-talar joint and metatarsophalangeal joint.The subject-specific joint orientations and locations were determined using a functional joint method based on the particleswarm optimisation algorithm. The GRF moment arms and joint moments acting around the talocrural and sub-talar joints werecalculated over the entire stance phase. The estimated talocrural and sub-talar joint locations show noticeable obliquity. Thekinematic and kinetic results strongly suggest that the human ankle-foot complex works as a mechanical mechanism with twodifferent configurations in stance phase of walking. These lead to a significant decrease in the GRF moment arms therebyincreasing the effective mechanical advantages of the ankle plantarflexor muscles. This reconfigurable mechanism enhancesmuscle effectiveness during locomotion by modulating the gear ratio of the ankle plantarflexor muscles in stance. This studyalso reveals many factors may contribute to the locomotor function of the human ankle-foot complex, which include not only itsre-configurable structure, but also its obliquely arranged joints, the characteristic heel-to-toe Centre of Pressure (COP) motionand also the medially acting GRF pattern. Although the human ankle-foot structure is immensely complex, it seems that itsconfiguration and each constitutive component are well tuned to maximise locomotor efficiency and also to minimise risk ofinjury. This result would advance our understanding of the locomotor function of the ankle-foot complex, and also the intrinsicdesign of the ankle-foot musculoskeletal structure. Moreover, this may also provide implications for the design of bionicprosthetic devices and the development of humanoid robots.     

Biomechanical interactions of cancer cells with the microvasculature during metastasis

Metastasis is a major, life-threatening complication of cancer. The bloodstream is the most important disseminative route for cancer cells liberated from their parent tumors. Single circulating cancer cells are arrested in the microvasculature, where the vast majority are killed by rapid or slow processes, and the relatively few survivors grow into micrometastases. We review the underlying causes of one type of rapid cancer cell death in the microcirculation, namely, that caused by biomechanical interactions of cancer cells with microvessel walls, which may result in cell surface membrane expansion and lethal rupture. These lethal interactions appear to be important rate-regulators in hematogenous metastasis, and to dictate some aspects of metastatic patterns. Although these are not the only interactions involving cancer cells, in contrast to others involving cellular and humoral defense mechanisms, they have received comparatively little attention.     

Biomechanical interactions of cancer cells with the microvasculature during metastasis

Metastasis is a major, life-threatening complication of cancer. The bloodstream is the most important disseminative route for cancer cells liberated from their parent tumors. Single circulating cancer cells are arrested in the microvasculature, where the vast majority are killed by rapid or slow processes, and the relatively few survivors grow into micrometastases. We review the underlying causes of one type of rapid cancer cell death in the microcirculation, namely, that caused by biomechanical interactions of cancer cells with microvessel walls, which may result in cell surface membrane expansion and lethal rupture. These lethal interactions appear to be important rate-regulators in hematogenous metastasis, and to dictate some aspects of metastatic patterns. Although these are not the only interactions involving cancer cells, in contrast to others involving cellular and humoral defense mechanisms, they have received comparatively little attention.     

一种新型锌指蛋白基因——人ZNF313的克隆、定位及表达(英文 )

运用正常可育男性和无精症病人睾丸组织的mRNA差异显示和cDNA末端快速扩增 (RACE)等方法 ,从人睾丸组织中分离了一个同时含有指环结构和C2 H2 结构域的新型锌指蛋白基因———人ZNF3 13。运用荧光原位杂交 (FISH)方法 ,将该基因定位到人染色体 2 0q13。该基因含 6个外显子 ,编码 2 2 8个氨基酸。基因组结构分析显示 ,外显子 6含有的 2个加尾信号 ,产生 2种不同的 3′端非翻译区。Northern杂交及多组织RT PCR的结果显示该基因含有 0 .75kb和 2 .4kb两种转录本 ,其中0 .75kb转录本在正常睾丸中高表达 ,而其他组织、无精症患者及胎儿睾丸组织中该基因低表达。结果提示 :人ZNF3 13基因对精子发生和男性可育性可能起重要作用     

Finger photoplethysmography during the Valsalva maneuver reflects left ventricular filling pressure

It is often challenging to assess cardiac filling pressure clinically. An improved system for detecting or ruling out elevated cardiac filling pressure may help reduce hospitalizations for heart failure. The blood pressure response to the Valsalva maneuver reflects left heart filling pressure, but its underuse clinically may be due in part to lack of continuous blood pressure recording along with lack of standardization of expiratory effort. In this study, we tested whether Valsalva-induced changes in the pulse amplitude of finger photoplethysmography (PPG), a technology already widely available in medical settings, correlate with invasively measured left ventricular end-diastolic pressure (LVEDP). We tested 33 subjects before clinically scheduled cardiac catheterizations. A finger photoplethysmography waveform was recorded during a Valsalva effort of 20 mmHg expiratory pressure sustained for 10 s, an effort most patients can achieve. Pulse amplitude ratio (PAR) was calculated as the PPG waveform amplitude just before release of expiratory effort divided by the waveform amplitude at baseline. PAR was well correlated with LVEDP (r = 0.68; P < 0.0001). For identifying LVEDP > 15 mmHG, PAR > 0.4 was 85% sensitive [95% confidence interval (95CI): 54-97%] and 80% specific (95CI: 56-93%). In conclusion, finger PPG, a technology already ubiquitous in medical centers, may be useful for assessing clinically meaningful categories of left heart filling pressure, using simple analysis of the waveform after a Valsalva maneuver effort that most patients can achieve.