Injection of macromolecular anabolic enzymes is a promising treatment for disc degeneration. However, macromolecular diffusion within the degraded or crosslinking-augmented discs remains unclear. In this study, healthy porcine anular fibrosus (AF) and nucleus pulposus (NP) were prepared. After a 24 hr trypsin-induced matrix degradation and a following 24 hr genipin-induced crosslinking augmentation, the diffusion of 0.37 kDa fluorescein sodium, 4.4 kDa dextran and 40 kDa dextran in the AF and NP were evaluated. Regardless of molecular weight, macromolecular diffusion was highest along the circumferential AF followed by the radial AF and NP. Matrix degradation and the crosslinking-augmentation decreased macromolecular diffusion. Scanning electric microscopic (SEM) images revealed that the intact circumferential AF contained oval-shaped pores, while the intact radial AF included long and narrow cavities. These porous diffusion paths collapsed after matrix degradation. The following crosslinking augmentation recovered matrix hydration and the area encircled by pore contour. Nevertheless, the diffusion paths were still occluded by detached collagen fibrils. In conclusion, pore shapes regulate macromolecular diffusion in discs. The decrease of macromolecular diffusion after matrix degradation is due to pore deformation. The following crosslinking augmentation makes the macromolecules more easily trapped within the diffusion paths.
The purpose of this study was to determine the neuromuscular and metabolic changes among three selected preferred transition speeds (PTS) and two types of gait (walk and run). Twelve male subjects were enrolled to participate in this study. Vicon® motion capture system, Biopac® Electromyography and Cosmed® Indirect Calorimeter were used to determine the kinematics, neuromuscular control and metabolic expenditure, respectively. Subjects were asked to walk and run repeatedly under three different speed (75, 100, 125% PTS). The results show that thigh/shank iEMG ECC/CON ratio illustrates the metabolic change among different PTSs. A significant inefficient shank muscle activation was initially occurred under 100% PTS, furthermore thigh muscle became inefficient under 125% PTS. It is suggested that “muscle elastic capacity” may contribute to the changes in muscle activation between walking and running under different PTSs. During walking, the increase in walking speed may lead to decreased utilization of muscle elastic energy, whereas it is opposite the case for running. This study provides a different approach to clarify the unexplored area between physiological and neuromuscular system on PTS.
Treadmill-based training protocols have played an important role in gait and balance training in rehabilitation settings, and the position of the body’s center of mass (COM) relative to the base of support provides an important measurement of postural stability. With the advance in wearable technology, the movement of the COM has been estimated using inertial measurement units (IMU) or by placing a single marker on the pelvis. However, there has not been a consensus over the differences in the movement control of COM relative to pelvis between treadmill walking (TW) and over-ground walking (OW). The current study aimed to quantify and compare the motions of the COM with respect to the pelvic reference frame during TW and OW. Fifteen young male adults walked barefoot on an 8-meter walkway, as well as on an instrumented treadmill at their self-selected speed while their pelvis position, COM positions, and center of pressure (COP) positions were measured. Paired t-tests were performed between OW and TW for all the variables. The results showed that compared to OW, treadmill walking produced significantly greater variations of COM displacements in every direction, namely anterior/posterior, proximal/distal, and medial/lateral, and significantly greater excursions of the COM in the medial/lateral direction with respect to the pelvis coordinate system. The results suggest that the estimation of the COM position with an IMU attached to the pelvis is more accurate during OW than TW.
Anterior cruciate ligament reconstruction (ACL-R) surgery can improve knee joint stability; however, altered sensory feedback after reconstruction surgery might affect the movement control which is required by proper multijoint coordination to compensate for the impaired sensorimotor function. The purpose of this study was to determine how interjoint coordination changed during stair walking in individuals with ACL-R compared with the control group and how interjoint coordination was affected by the stair height. Sixteen individuals with unilateral ACL-R and 16 healthy age- and sex-matched controls were recruited. Participants were instructed to ascend and descend a 4-step stairs with two different heights at their self-selected speed. Kinematic data were collected during stair walking using a motion analysis system. Interjoint coordination and muscle strength of the lower extremities were investigated. The root-mean-squared difference, cross-correlation coefficient, and deviation phase of the relative phase angles were used to quantify the interjoint coordination pattern. A mixed-model analysis of variance was used to compare the difference among variables. Muscle strength in the vastus femoris and biceps femoris of the affected side of the patient group was significantly decreased, compared with that of the healthy control. Higher variability of the knee-ankle interjoint coordination was observed in the affected side during stair walking in individuals with ACL-R than the healthy control. The findings suggested that the variation in interjoint coordination patterns between the patient group and control group was more distinct at a high stair height than a lower stair height. Inadequate muscle strength could affect the neuromuscular control and could not provide stability at the joints, which increases the variability of interjoint movement and changes the interjoint coordination.
In this paper, we evaluate the performance of the rigid and soft exoskeleton by measuring electromyography (sEMG) signal of human lower limb muscles. sEMG represents the degree of muscle activation and the higher sEMG level can be measured if the greater muscle force generated. We compared the sEMG activation level whether wearing the rigid exoskeleton or soft exoskeleton. First, we manufactured the rigid inspired by ‘Berkeley Lower Extremity Exoskeleton (BLEEX)’ and soft exoskeleton motivated by ‘Exosuit’ respectively. After developed the systems, sEMG signals on VM, HAM, GAS, and TA with the rigid lower limb exoskeleton were measured during walking. As a result, up to 150 % muscle activation level increased and it implies that the resistance occurred between human and the rigid lower limb exoskeleton and the user should make an effort to generate more force. After validate the limitation of the rigid lower limb exoskeleton, we did isometric experiment with the soft lower limb exoskeleton, there was 3.4 % normalized MAV decrease at GAS muscle. From this result, we concluded that developed soft lower limb exoskeleton assisted the subject with lower muscle activation level. In addition, the density of the sEMG signal was lower when the subject was assisted by the developed system. It implies that lower fatigue human can feel to maintain isometric condition. Therefore, soft lower limb exoskeleton can assist human more effective than the rigid lower limb exoskeleton.
Decubitus ulcer is a disease that causes the necrosis of skin tissue through the disorder of blood circulation on a certain part of the body where bones protrude. This study is aimed at obtaining an optimal design of a set composed of a rubber air-cell seat cushion and back-supporter, showing even distribution of the interface pressure and minimizing its peak value on the buttocks through optimization using the simulation. The finite element (FE) human model was a human body model developed by the MADYMO (mathematical dynamic model; TASS, Netherlands) and consisted of 44 FE models such as skeletal structures, flesh, muscles, and internal organs. For the optimization of a seat cushion and a back-supporter, a basic model for seat cushion and back-supporter were designed using 50th percentile European male model. To design an optimal seat cushion and back-supporter system, the optimization was performed considering the design factors such as the air-cell height of buttocks and thighs, air-cell height of back-supporter, and angle of back-supporter. The results of the sensitivity analysis confirmed the two design factors (height of buttock air-cell and height of thigh air-cell). The optimization result was 55 mm for the buttock air-cell's height, 60 mm for the thigh air-cell's height, 90 mm for the back-supporter air-cell's height, and 100° for the back-supporter's angle. Based on this study, there is preliminary evidence to show that the design of seat cushion and back-supporter is necessary to reflect biomechanical characteristics, such as body shape (difference of body shape between thigh and buttocks). A main advantage of air-cell type for seat cushion and back-supporter is the good effect of interface pressure distribution.
Although early diagnosis and treatment of hearing disorders in neonates is highly effective for realization of linguistic competence and intellectual development, the diagnostic accuracy in the initial period of life is low. To overcome this problem, extensive research studies to diagnose the neonatal hearing with tympanometry, multi-frequency tympanometry, the wideband acoustic transfer function technique, the sweep frequency impedance (SFI) technique and others have been conducted. However, since the results obtained are not consistent with those obtained in adults/children, diagnosis of hearing in neonates has been problematic. The difference in the dynamic characteristics of the hearing apparatus between adults/children and neonates, especially due to the morphological difference in the external ear canal, has been suggested as a possible reason for such problem. However, the dynamics of the neonatal hearing system has not yet been clarified. In the present study, therefore, three types of finite-element models of the neonatal external ear were developed and their dynamic characteristics (i.e., natural frequencies and mode shapes) were investigated. Frequency analyses of the constructed models revealed that the neonatal external ear canal wall has a resonance of around 0.3 kHz and that this resonance leads to the volume change of such canal. This result suggests that the neonatal external ear canal wall may exhibit intrinsic oscillatory behavior if conventional tympanometry with a probe tone of 226 Hz is performed, affecting the diagnostic data in neonates.
The endoscopic optical coherence tomography (OCT) has been developed for early detection of digestive system cancer. However, it is difficult to detect cancerous tissue due to complicated speckle patterns contributed by optical properties of scattering and absorption in the morphological images of OCT. In our previous papers, 2-color optical coherence dosigraphy (2C-OCD) was proposed, which quantified OCT signal as scattering and absorption coefficients and could provide drug distribution at the micro-scale spatial resolution. In this study, an in vivo tomographically diagnosing technique of early cancer is presented, in which 2C-OCD is applied to cancerous tissue with selective uptake of photosensitizer. The feasibility study was demonstrated and investigated, based on 2C-OCD visualization of the subcutaneous tumor-implanted nude mice with photosensitizer AlPcS administered. Consequently, it was confirmed that drug absorption coefficient obtained by 2C-OCD was correlated with fluorescence intensity from accumulated AlPcS (r = 0.918), comparing with their histological images. Additionally, 2C-OCD could diagnose tumor tissue significantly with sensitivity of 82.5% and specificity of 78.3%, respectively. Therefore, 2C-OCD can detect photosensitizer infiltration into cancerous tissue, and thus has a promising modality for in vivo tomographically diagnosing technique of early cancer.
Cell-substrate adhesions are a mechanosensitive protein complex that regulates various cellular functions. Molecular mechanisms underlying the physical force-dependent regulation remain elusive partly because endogenous forces are distributed in a spatially heterogeneous manner within cells, thus complicating the interpretation on the effect of forces. Here we use a micropatterning technique to focus spatially distributed intracellular contractile forces onto a particular subcellular area, with which mechanical and pharmacological effects are separately analyzed. Single human osteosarcoma U2OS cells were plated within square micropatterns, and phosphorylation of an adhesion-associated adaptor protein paxillin was analyzed. Paxillin, visualized with immunostaining, was highly accumulated in the proximity of the corners of the square micropatterns where cellular forces are concentrated, but the huge paxillin-labeled adhesions were less phosphorylated compared to those present elsewhere as a small patch. Pharmacological inhibition of the endogenous forces resulted in disassembly of the huge dephoshorylated paxillin clusters; in contrast, the small, highly phosphorylated paxillin patches persisted. Similar negative regulation of paxillin phosphorylation is also induced upon loading of exogenous forces. Unexpectedly, on the other hand, immunoblot of cell lysates showed a tendency of a reduction in paxillin phosphorylation upon the same pharmacological inhibition of the endogenous forces. Thus, the response of paxillin phosphorylation to mechanical forces was the opposite between the immunostaining and immunoblot data; i.e., the phosphorylation is reduced and enhanced at subcellular level and whole-cell level, respectively, in response to loading of mechanical forces. To reconcile the contradictory results, we submit a simple model that is consistent with not only the present but also previous reports on the regulation of paxillin. The model implies that similar opposite response can generally emerge if the protein activation is negatively regulated at a local place while the activation trigger alters the assembly of the protein to the local place.
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