Predicting cortical bone adaptation to axial loading in the mouse tibia

The development of predictive mathematical models can contribute to a deeper understanding of the specific stages of bone mechanobiology and the process by which bone adapts to mechanical forces. The objective of this work was to predict, with spatial accuracy, cortical bone adaptation to mechanical load, in order to better understand the mechanical cues that might be driving adaptation. The axial tibial loading model was used to trigger cortical bone adaptation in C57BL/6 mice and provide relevant biological and biomechanical information. A method for mapping cortical thickness in the mouse tibia diaphysis was developed, allowing for a thorough spatial description of where bone adaptation occurs. Poroelastic finite-element (FE) models were used to determine the structural response of the tibia upon axial loading and interstitial fluid velocity as the mechanical stimulus. FE models were coupled with mechanobiological governing equations, which accounted for non-static loads and assumed that bone responds instantly to local mechanical cues in an on–off manner. The presented formulation was able to simulate the areas of adaptation and accurately reproduce the distributions of cortical thickening observed in the experimental data with a statistically significant positive correlation (Kendall's τ rank coefficient τ = 0.51, p < 0.001). This work demonstrates that computational models can spatially predict cortical bone mechanoadaptation to a time variant stimulus. Such models could be used in the design of more efficient loading protocols and drug therapies that target the relevant physiological mechanisms

Effects of acute fatigue on the volitional and magnetically-evoked electromechanical delay of the knee flexors in males and females

Neuromuscular performance capabilities, including those measured by evoked responses, may be adversely affected by fatigue; however, the capability of the neuromuscular system to initiate muscle force rapidly under these circumstances is yet to be established. Sex-differences in the acute responses of neuromuscular performance to exercise stress may be linked to evidence that females are much more vulnerable to ACL injury than males. Optimal functioning of the knee flexors is paramount to the dynamic stabilisation of the knee joint, therefore the aim of this investigation was to examine the effects of acute maximal intensity fatiguing exercise on the voluntary and magnetically-evoked electromechanical delay in the knee flexors of males and females. Knee flexor volitional and magnetically-evoked neuromuscular performance was assessed in seven male and nine females prior to and immediately after: (i) an intervention condition comprising a fatigue trial of 30-seconds maximal static exercise of the knee flexors, (ii) a control condition consisting of no exercise. The results showed that the fatigue intervention was associated with a substantive reduction in volitional peak force (PFV) that was greater in males compared to females (15.0%, 10.2%, respectively, p < 0.01) and impairment to volitional electromechanical delay (EMDV) in females exclusively (19.3%, p < 0.05). Similar improvements in magnetically-evoked electromechanical delay in males and females following fatigue (21%, p < 0.001), however, may suggest a vital facilitatory mechanism to overcome the effects of impaired voluntary capabilities, and a faster neuromuscular response that can be deployed during critical times to protect the joint system

A novel malaria vaccine candidate antigen expressed in Tetrahymena thermophila

Development of effective malaria vaccines is hampered by the problem of producing correctly folded Plasmodium proteins for use as vaccine components. We have investigated the use of a novel ciliate expression system, Tetrahymena thermophila, as a P. falciparum vaccine antigen platform. A synthetic vaccine antigen composed of N-terminal and C-terminal regions of merozoite surface protein-1 (MSP-1) was expressed in Tetrahymena thermophila. The recombinant antigen was secreted into the culture medium and purified by monoclonal antibody (mAb) affinity chromatography. The vaccine was immunogenic in MF1 mice, eliciting high antibody titers against both N- and C-terminal components. Sera from immunized animals reacted strongly with P. falciparum parasites from three antigenically different strains by immunofluorescence assays, confirming that the antibodies produced are able to recognize parasite antigens in their native form. Epitope mapping of serum reactivity with a peptide library derived from all three MSP-1 Block 2 serotypes confirmed that the MSP-1 Block 2 hybrid component of the vaccine had effectively targeted all three serotypes of this polymorphic region of MSP-1. This study has successfully demonstrated the use of Tetrahymena thermophila as a recombinant protein expression platform for the production of malaria vaccine antigens

Centre of pressure characteristics in normal, planus and cavus feet

Background The aim of this study was to compare centre of pressure (COP) characteristics between healthy adults with normal, planus or cavus feet who were allocated to groups based on reliable foot posture measurement techniques. Methods Ninety-two healthy adult participants (aged 18 to 45) were recruited and classified as either normal (n = 35), pes planus (n = 31) or pes cavus (n = 26) based on Foot Posture Index, Arch Index and normalised navicular height truncated measurements. Barefoot walking trials were conducted using an emed®-x 400 plantar pressure system (Novel GmbH, Munich, Germany). Average, maximum, minimum and range (difference between maximum and minimum) values were calculated for COP velocity and lateral-medial force index during loading response, midstance, terminal stance and pre-swing phases of stance. The COP excursion index was also calculated. One-way analyses of variance were used to compare the three foot posture groups. Results The cavus foot exhibited the slowest average and minimum COP velocity during terminal stance, but this pattern was reversed during pre-swing, when the cavus foot exhibited the fastest maximum COP velocity. The planus foot exhibited the smallest lateral medial force index range during terminal stance. There were no differences between the groups for COP excursion index. Conclusion These findings indicate that there are differences in COP characteristics between foot postures, which may represent different mechanisms for generating force to facilitate forward progression of the body during the propulsive phases of gait

International Foot and Ankle Biomechanics Community (i-FAB): past, present and beyond

The International Foot and Ankle Biomechanics Community (i-FAB) is an international collaborative activity which will have an important impact on the foot and ankle biomechanicscommunity. It was launched on July 2nd 2007 at the foot and ankle session of the International Society of Biomechanics (ISB) meeting in Taipei, Taiwan. i-FAB is driven by the desire to improve our understanding of foot and ankle biomechanics as it applies to health, disease, and the design,development and evaluation of foot and ankle surgery, and interventions such as footwear, insoles and surfaces

Temporal estimation with two moving objects: overt and covert pursuit

The current study examined temporal estimation in a prediction motion task where participants were cued to overtly pursue one of two moving objects, which could either arrive first, i.e., shortest [time to contact (TTC)] or second (i.e., longest TTC) after a period of occlusion. Participants were instructed to estimate TTC of the first-arriving object only, thus making it necessary to overtly pursue the cued object while at the same time covertly pursuing the other (non-cued) object. A control (baseline) condition was also included in which participants had to estimate TTC of a single, overtly pursued object. Results showed that participants were able to estimate the arrival order of the two objects with very high accuracy irrespective of whether they had overtly or covertly pursued the first-arriving object. However, compared to the single-object baseline, participants’ temporal estimation of the covert object was impaired when it arrived 500 ms before the overtly pursued object. In terms of eye movements, participants exhibited significantly more switches in gaze location during occlusion from the cued to the non-cued object but only when the latter arrived first. Still, comparison of trials with and without a switch in gaze location when the non-cued object arrived first indicated no advantage for temporal estimation. Taken together, our results indicate that overt pursuit is sufficient but not necessary for accurate temporal estimation. Covert pursuit can enable representation of a moving object’s trajectory and thereby accurate temporal estimation providing the object moves close to the overt attentional focus

Design and implementation of a low-cost mechatronic shoe for biomechanical analysis of the human locomotion

In this paper the development of a low-cost and easy wearable mechatronic system for the measurement of ground reaction forces (GRF) for the biomechanical analysis of the human locomotion is presented. The system consists of an insole, a conditioning device for the signals produced by the sensors applied to the insole and a data acquisition system connected to a USB portable storage. The sensors applied to the insole can measure the reaction forces in the horizontal and vertical directions during locomotion. The prototype was validated by comparing the data from the sensors with the values obtained using a force platform