This study as primary research to propose a non-invasive technique to diagnose the Outerbridge grade of cartilage damage by impact signals. A knee model was experimented with the novel attempt instead of a real knee. The knee model is made by a 3D model converted from magnetic resonance images (MRI) and then assembled by true scale and position. The impact signal is input from the calf and output from the thigh, and the absorption of the impact signal is contended differently by different Outerbridge grades of cartilage. The absorbed impact signals collected by sensors were time-frequency analyzed by continuous Gabor transform (CGT). In addition, the absorbed jerk signal is interpreted by the singular spectrum analysis (SSA) for its oscillation components. The analysis of the signals in this study found that the features derived have abilities to distinguish Outerbridge classification. Therefore, the proposed method can be considered for carrying the experiment onto real knees. This study provides a novel idea to make the diagnostic technique of cartilage damage efficient. Combined with the feature engineering and classification technique, it will help in the clinical diagnosis of knees, this study expects that the method can be applied not only to the diagnosis of the overall knee, but also that the method can diagnose more tiny areas in the early stages of the knee disorder.
Phase-contrast magnetic resonance imaging (PC-MRI) allows us to acquire biofluid flow velocity maps, whereas MRI data is restricted by spatiotemporal resolution limitations and contains theoretically inevitable errors. Although various approaches to estimating actual velocity from MR velocity maps using the mass and momentum conservation laws have been proposed, practically reasonable methodologies are still not well established. This study investigates a practical strategy for estimating physically consistent velocities from MR velocity maps based on variational optimal boundary control through examples of the 2D steady Stokes flow as an incompressible viscous fluid. We defined a minimization problem of the sum of squared residuals between MR and the estimated velocity at all pixels (voxels) considering the image data structure with respect to the Dirichlet boundary velocity condition subject to flow governing equations based on variational formulations. This optimization problem is treated as an unconstrained optimization problem by deriving the Lagrange functional, including the cost function, regularization term, and constraint conditions. The optimality condition is computed using the adjoint variable method in a finite element manner. The boundary velocity profile is iteratively updated by the optimality condition using gradient-based optimization until convergence. Numerical examples for 2D Poiseuille flow with noise-free and noisy reference data demonstrated good convergencies of the cost function minimization. The estimated flow velocities were in excellent agreement with reference data. Finally, we demonstrated the viability of the velocity estimation using the actual MR velocity of the cerebrospinal fluid flow. The proposed approach with further considerations specialized for the MRI may be feasible in providing physically consistent velocity profiles in a versatile target of the biofluid flow.
Although the role of biarticular muscles during squatting and its variations have received considerable attention, the function of these muscles during squatting is not well understood. Closed kinetic chain exercises like squats are commonly preferred for knee rehabilitation and strength training for athletes. Squat exercises require both the hip and knee extensors, such as the gluteus maximus, hamstrings, and quadriceps femoris. For the hip extension strategy, the gluteus maximus and hamstrings have an important role, while the hamstrings and quadriceps co-contract at the knee. The same co-contraction occurs at the hip, between the rectus femoris and the hip extensors. These co-contractions do not seem to be effective, in terms of minimum energy expenditure, minimum muscle fatigue, and minimum sense of effort. However, muscular co-contraction is often seen in human movement, and the co-contractions were measured using electromyography (EMG). Although muscle co-contraction is important to modulate joint stability, the co-contraction cannot be predicted in simulations using a musculoskeletal model where the sum of the muscle activations or metabolic energies is minimized. Thus, the activations of those biarticular muscles are clearly underestimated. In this study, EMG were measured during squatting, and interpretations to understand biarticular muscles activations are discussed.
Complex blood flow patterns play a significant role in atherogenesis. Multiple studies have reported that early lesion occurs primarily in the regions of flow separation, vortex, and complex flow patterns. To elucidate these dynamic factors in detail and at a cellular level, the responses of endothelial cells to complex flow patterns should be investigated. In this study, an immediately expanding flow chamber was designed to investigate the effects of vortex and shear stress gradient on the morphological response of cultured endothelial cells. In the flow chamber, a pair of vortices were observed in the immediately expanding area. The shear stress profile and streamline were confirmed through computational fluid dynamics analysis. Human umbilical vein endothelial cells (HUVECs) were cultured on a cell culture dish, and the dish was set in the flow channel. The shear stress in the outlet and main flow regions was set to 2 Pa, and HUVECs were exposed to the flow for 24 h. After flow exposure, the F-actin structure and cell morphology of HUVECs were observed. After exposure to shear stress for 24 h in the central region, HUVECs showed elongation and alignment parallel to the flow direction, accompanied by the development of actin stress fibers. In contrast, the HUVECs exposed to the flow in the vortex region were randomly oriented and exhibited the formation of stress fibers; thus, it can be concluded that the vortex flow suppressed the flow-induced morphological remodeling of cells and induced the inflammatory response of HUVECs.
Actin filaments play significant roles in many essential cellular processes including muscle contraction, cell motility, vesicle and organelle movement, cell signaling, and mechano-sensing mechanism of cells. However, one of the important cellular processes, the mechano-sensing mechanism of cells, is still debatable. To elucidate these mechanisms of cellular processes, it is important to observe the remodeling of the F-actin structure in cells. Although there are many reports about the remodeling of the F-actin structure during cellular processes, it needs to consider that the intracellular and extracellular proteins are fluctuating with thermal energy. We assumed that these small fluctuations affect the mechano-transduction in cells. We focused on an F-actin small fluctuation and tried to observe that in a living cell. Here, we propose the analyzing method of F-actin fluctuation in a living cell using the quasi super-resolution technique. To visualize F-actin filaments in living cells, Lifeact-GFP plasmid vector was transfected to NIH3T3 cells. Ten images of F-actin in living cells were taken every second under static culture conditions. First, we analyzed the small fluctuation of F-actin in living cells with Gaussian smoothed images. In this analysis, the amplitude of F-actin fluctuation was approximately 0.2 to 0.3 μm, which is almost the same as the optical resolution. Therefore, we have reconstructed the F-actin image in cell from a cross-sectional fluorescent profile with the quasi super-resolution technique. We analyzed the fluorescent profile at several points along one F-actin filament, and the X and Y coordinates were picked up from the peak fluorescent in each fluorescent profile. From these X and Y coordinates in images, F-actin filament was approximated as a quadratic curve. We reconstructed the F-actin filament each time. The obtained spatial resolution was 0.08 μm which was 2.5 times higher than the optical resolution. In quasi super-resolution images, the fluctuation amplitude of F-actin was 0.42 to 0.53 μm in the peripheral region and 0.27 μm in the center region. The frequency of F-actin fluctuation in both center and peripheral regions was approximately 3 Hz. The F-actin fluctuation was irregular, and several fluctuation patterns were observed. These phenomena might be caused due to the influence of restriction of the cytoskeletal network.
Neutrophil motion toward inflamed regions by cytokine concentration gradient is one of the most important problems in immune function. When the velocity of neutrophil motion is high, it is considered that the immune function of neutrophils is also high. In addition, shock waves have been required to be applied more widely to medical fields. To find out the possibility of the enhancement of the immune function by working shock waves, the effects of shock waves on neutrophil propulsion (translational velocity) are investigated by changing the pressure ratio and the shot numbers of shock waves. In the experiments, the neutrophil’s motion is observed under a microscope after working plane shock waves. The translational velocity, rotational speed, and cytokine concentration gradient on the membrane are measured. From the equation of the Marangoni effect, the sensitivity of the neutrophil membrane is explained by the ratio of the translational velocity to the concentration gradient. We call this ratio the “membrane function coefficient (MFC)”. From the measurements, it was found that there is a maximum translational velocity, rotational speed, and MFC with a pressure ratio 2.5 in the range of 2.5 to 3.5. It was also found that the translational velocity, rotational speed, and MFC are decreased by increasing shot numbers by more than 1. In conclusion, it is considered that the immune function of neutrophils can be enhanced by shock waves with an optimized pressure ratio and proper shot numbers.
We investigate difference in the chemotactic behavior between peritrichous bacteria (Salmonella typhimurium SJW1103) and monotrichous bacteria (Vibrio alginolyticus YM4). Bacterial chemotaxis occurs by suppressing the directional change and continue the straight swimming (run) when approaching the favorable region. The manner of the directional change differs between peritrichous and monotrichous bacteria, which may cause the difference in chemotaxis. The turn angle of a peritrichous bacterium tends to be random that change the posture by loosening the flagellar bundle, whereas a monotrichous bacterium with a single flagellum tend to turn behind by the rotational change of the flagellum. In the microscopic observation, chemotactic behavior of the cells is measured in the concentration gradient of the chemoattractant (L-serine) formed by diffusion from the tip of the glass capillary. V. alginolyticus cells accumulate around the attractant more rapidly and more densely than S. typhimurium. The numerical simulation where the observed run length and turn angle distribution were taken into account, well reproduces the observed result of the cells’ distribution. The reason for the higher number density in the monotrichous bacteria is the backward directional changes when receding from the attractant source. The degree of prolongation of average duration of runs toward the attractant source does not differ significantly between V. alginolyticus and S. typhimurium cells. Considering the probability with which the swimming direction changes in terms of approaching or receding from the attractant, we are able to relate quantitatively between the degree of accumulation and the turn angle distribution.