Broadband Dielectric Study of Dynamics of Polymer and Solvent in Poly(vinyl pyrrolidone)/Normal Alcohol Mixtures

Broadband dielectric measurements of poly(vinyl pyrrolidone) (PVP)-monohydroxyl alcohol mixtures of various normal alcohols with the number of carbon atoms per molecule ranging from 1 to 9 were made in the frequency range of 20 Hz to 20 GHz at 25 degrees C. Two relaxation processes due to the reorientation of dipoles on the PVP and alcohol molecules were observed. The relaxation process at frequencies higher than 100 MHz is the primary process of alcohols, and that at frequencies lower than 10 MHz is attributed to the local chain motion of PVP. For mixtures of alcohol molecules that are smaller than propanol, the relaxation time of the alcohol increases with increasing PVP concentration, whereas for mixtures of alcohol molecules larger than butanol, the relaxation time of the alcohol decreases with increasing PVP concentration. The increase in the density of hydrogen-bonding sites upon the addition of PVP reduces the relaxation time of alcohol in the mixture, and vice versa. The relaxation time of the local chain motion of PVP increases with PVP concentration and solvent viscosity. Different time scales of the molecular motions of polymer and solvent coexist in homogeneous mixtures with hydrogen-bonded polar solvent and polymer.

Phosphorylation of chemoattractant receptors regulates chemotaxis, actin reorganization and signal relay

Migratory cells, including mammalian leukocytes and Dictyostelium, use G-protein-coupled receptor (GPCR) signaling to regulate MAPK/ERK, PI3K, TORC2/AKT, adenylyl cyclase and actin polymerization, which collectively direct chemotaxis. Upon ligand binding, mammalian GPCRs are phosphorylated at cytoplasmic residues, uncoupling G-protein pathways, but activating other pathways. However, connections between GPCR phosphorylation and chemotaxis are unclear. In developing Dictyostelium, secreted cAMP serves as a chemoattractant, with extracellular cAMP propagated as oscillating waves to ensure directional migratory signals. cAMP oscillations derive from transient excitatory responses of adenylyl cyclase, which then rapidly adapts. We have studied chemotactic signaling in Dictyostelium that express non-phosphorylatable cAMP receptors and show through chemotaxis modeling, single-cell FRET imaging, pure and chimeric population wavelet quantification, biochemical analyses and TIRF microscopy, that receptor phosphorylation is required to regulate adenylyl cyclase adaptation, long-range oscillatory cAMP wave production and cytoskeletal actin response. Phosphorylation defects thus promote hyperactive actin polymerization at the cell periphery, misdirected pseudopodia and the loss of directional chemotaxis. Our data indicate that chemoattractant receptor phosphorylation is required to co-regulate essential pathways for migratory cell polarization and chemotaxis. Our results significantly extend the understanding of the function of GPCR phosphorylation, providing strong evidence that this evolutionarily conserved mechanism is required in a signal attenuation pathway that is necessary to maintain persistent directional movement of Dictyostelium, neutrophils and other migratory cells.

Comparative mapping of crawling-cell morphodynamics in deep learning-based feature space

Navigation of fast migrating cells such as amoeba Dictyostelium and immune cells are tightly associated with their morphologies that range from steady polarized forms that support high directionality to those more complex and variable when making frequent turns. Model simulations are essential for quantitative understanding of these features and their origins, however systematic comparisons with real data are underdeveloped. Here, by employing deep-learning-based feature extraction combined with phase-field modeling framework, we show that a low dimensional feature space for 2D migrating cell morphologies obtained from the shape stereotype of keratocytes, Dictyostelium and neutrophils can be fully mapped by an interlinked signaling network of cell-polarization and protrusion dynamics. Our analysis links the data-driven shape analysis to the underlying causalities by identifying key parameters critical for migratory morphologies both normal and aberrant under genetic and pharmacological perturbations. The results underscore the importance of deciphering self-organizing states and their interplay when characterizing morphological phenotypes.

Migratory cells that move by crawling do so by extending and retracting their plasma membrane. When and where these events take place determine the cell shape, and this is directly linked to the movement patterns. Understanding how the highly plastic and interconvertible morphologies appear from their underlying dynamics remains a challenge partly because their inherent complexity makes quantitatively comparison against the outputs of mathematical models difficult. To this end, we employed machine-learning based classification to extract features that characterize the basic migrating morphologies. The obtained features were then used to compare real cell data with outputs of a conceptual model that we introduced which describes coupling via feedback between local protrusive dynamics and polarity. The feature mapping showed that the model successfully recapitulates the shape dynamics that were not covered by previous related models and also hints at the critical parameters underlying state transitions. The ability of the present approach to compare model outputs with real cell data systematically and objectively is important as it allows outputs of future mathematical models to be quantitatively tested in an accessible and common reference frame.

Gait training using a stationary, one-leg gait exercise assist robot for chronic stroke hemiplegia: a case report

[Purpose] The Gait Exercise Assist Robot (GEAR) is a stationary, one-leg robot for gait training. The purpose of this case study was to evaluate the efficacy of rehabilitation using GEAR training for chronic stroke hemiplegia. [Participant and Methods] The participant was a 66-year-old male stroke survivor with left hemiparesis due to a right putaminal hemorrhage. He could walk slowly under supervision, although his gait had a constant forward trunk lean, with flexed knee, and a lack of hip extension movement on the affected side. Gait training using GEAR and physical therapy were performed for 14 days. Under both training conditions, the physical therapist made the participant conscious of extension movement of the hip joint in the affected-side stance phase. The robotic assistance was adjusted to maximize voluntary movement while observing gait. Physical function and gait ability parameters were evaluated before and after training. [Results] After training, extension motion of the hip joint increased in the affected-side stance phase, and body weight was transferred smoothly onto the affected-side limb, leading to an improvement in gait speed. [Conclusion] Gait training using GEAR and physical therapy may improve gait pattern and speed in patients with chronic stroke hemiplegia.

Changes in postural strategy during exercise against perturbation using the balance exercise assist robot: a pilot study

[Purpose] To clarify the changes in postural strategy by evaluating leg joint motion and muscle activity before and after continuous exercise against perturbation using the Balance Exercise Assist Robot (BEAR). [Subjects and Methods] Nine healthy subjects (male 7, female 2; mean age 23 ± 1 years) performed a postural perturbation coping exercise only. In the task, the robot leaned and moved automatically. Participants were instructed to maintain their default upright position and they performed the exercise five times in a row (1 minute/trial). Changes in total movement distance, range of motion of each joint (hip, knee, ankle), and mean activity of each muscle for the first and fifth trials were compared. [Results] The total movement distance of BEAR and range of motion in the hip decreased significantly from the first trial to the last trial. No change in muscle activity was observed in the rectus femoris, biceps femoris, tibialis anterior or gastrocnemius. [Conclusion] The results for exercise against perturbation using BEAR in this study suggest that BEAR may be a promising method to improve the ankle strategy for maintaining a standing posture.

Factors associated with falls in Japanese polio survivors

Purpose: To identify factors associated with falls in Japanese polio survivors and assess the extent of their impact.Materials and methods: Subjects were 128 polio survivors. Fall history and fear of falling, lower limb muscle strength, gait ability (determined by walking speed and number of steps per day), post-polio syndrome incidence, and orthosis or walking aid use were assessed, and factors associated with falls were identified using logistic regression analysis.Results: The fall rate was 64%. Fallers (subjects with one or more falls in the preceding 12 months) had low lower limb muscle strength, slow walking speed, high total scores on the Fall Efficacy Scale-International, which assesses fear of falling, and a high orthosis use rate. Knee extension muscle strength on the weaker side was identified as a main factor influencing risk of falls (odds ratio: 0.72, 95% confidence interval: 0.56-0.96). Receiver operating characteristic curve analysis gave a cutoff value for knee extension muscle strength on the weaker side of 0.42 N/kg or lower.Conclusion: Low knee extension muscle strength on the weaker side was associated with falls, but predictive ability using a single internal factor might be poor. It appears that a comprehensive examination, including other factors, is required.Implications for rehabilitationAs polio survivors age, their risk of falling increases.To identify polio survivors who are at risk of falls, it is important to determine the factors associated with falls and their influence on fall risk.The results of this study showed that reduced knee extension muscle strength on the weaker side was a risk factor for falls in polio survivors.To precisely predict the risk of falls in polio survivors, a comprehensive evaluation of both internal and external factors is required.

A novel gait analysis system for detecting abnormal hemiparetic gait patterns during robot-assisted gait training: A criterion validity study among healthy adults

INTRODUCTION

Robot-assisted gait training has been reported to improve gait in individuals with hemiparetic stroke. Ideally, the gait training program should be customized based on individuals' gait characteristics and longitudinal changes. However, a gait robot that uses gait characteristics to provide individually tailored gait training has not been proposed. The new gait training robot, "Welwalk WW-2000," permits modification of various parameters, such as time and load of mechanical assistance for a patient's paralyzed leg. The robot is equipped with sensors and a markerless motion capture system to detect abnormal hemiparetic gait patterns during robot-assisted gait training. Thus, it can provide individually tailored gait training. This study aimed to investigate the criterion validity of the gait analysis system in the Welwalk WW-2000 in healthy adults.

MATERIALS AND METHODS

Twelve healthy participants simulated nine abnormal gait patterns that were often manifested in individuals with hemiparetic stroke while wearing the robot. Each participant was instructed to perform a total of 36 gait trials, with four levels of severity for each abnormal gait pattern. Fifteen strides for each gait trial were recorded using the markerless motion capture system in the Welwalk WW-2000 and a marker-based three-dimensional (3D) motion analysis system. The abnormal gait pattern index was then calculated for each stride from both systems. The correlation of the index values between the two methods was evaluated using Spearman's rank correlation coefficients for each gait pattern in each participant.

RESULTS

Using the participants' index values for each abnormal gait pattern obtained using the two motion analysis methods, the median Spearman's rank correlation coefficients ranged from 0.68 to 0.93, which corresponded to moderate to very high correlation.

CONCLUSION

The gait analysis system in the Welwalk WW-2000 for real-time detection of abnormal gait patterns during robot-assisted gait training was suggested to be a valid method for assessing gait characteristics in individuals with hemiparetic stroke.

CLINICAL TRIAL REGISTRATION

[https://jrct.niph.go.jp], identifier [jRCT 042190109].

Kinematic, kinetic, and electromyographic characteristics during quiet standing on a balance exercise assist robot

[Purpose] The balance exercise assist robot is a training device based on a personal transport assistance robot ridden in the standing position. The personal transport assistance robot uses an inverted pendulum control system and moves in response to movements of the user's center of gravity. The purpose of this study was to describe the characteristics of postural control during the action of stopping the personal transport assistance robot. [Participants and Methods] Eleven healthy male participants were required to maintain a standing position for 30 s; each task was performed 10 times. The measurement conditions were as follows: (1) on the floor; (2) on the robot, touching the handlebars; and (3) on the robot, not touching the handlebars. [Results] During the robotic tasks, the total locus lengths of the center of gravity and total joint momentums of the hip, knee, and ankle joints were larger, and the amount of displacement of the center of pressure was smaller than that during the floor task. Posture control on the robot was performed actively by mechanical interaction of the ankle, knee, and hip joints within a small base of support. [Conclusion] The balance exercise assist robot can be useful for postural control exercises because maintaining a standing position on the personal transport assistance robot required active postural control.

Pre-set estimation-based in-silico silhouette-based methodology for improving the robustness to viewing direction difference for assisting forensic gait analysis

Forensic gait analysis is used to visually and quantitatively analyze information regarding the appearance and style of walking that can be presented as evidence in the court. The demand for analyzing CCTV pedestrian footage in video surveillance has been increasing. The dependence of the accuracy of semiautomatic silhouette-based analysis, often used in forensic science, on the differences in the viewing directions is a very challenging issue that is yet to be resolved for real case applications. Currently, the different viewing directions used in comparison footage significantly decrease the accuracy of same person analysis when using the silhouette-based method, often used in the Japanese forensic science domain. A calibration-based method was previously prosed to resolve this problem, but it requires performing an elaborate measurement procedure at the camera installation site for an accurate analysis. In this study, we propose a novel in-silico silhouette-based analysis method that significantly expands the number of viewing direction pre-set settings to 900 from the 24 used in the previous method. Several software tools have been developed to ensure that all the procedures can be executed on a computer. The experimental results confirm that the accuracy of the proposed method is comparable to that of the calibration-based method. Furthermore, the practical comparison results from actual consultation confirmed the effectiveness of the proposed method under existing viewing direction differences. We therefore anticipate that the proposed method will be beneficial for improving the analysis accuracy in real cases and therefore serve as a substitute of the previous method.

Motion analysis of operating a balance exercise assist robot system during forward and backward movements

[Purpose] Stand-and-ride personal mobility devices controlled by movements of the user's center of gravity are used for balance training. We aimed to describe the physical activity required to operate this type of mobility device. [Participants and Methods] Eleven healthy males performed the following tasks: 1) moving their center of gravity forward or backward while standing on the floor (control task) and, 2) moving the mobility device forward or backward by moving their center of gravity (experimental task). [Results] We observed that the displacement of the center of gravity and the center of pressure, as well as angular displacements of the hips and knee joints, and maximum muscle activities of the biceps femoris, the medial head of the gastrocnemius and peroneus longus muscles were lesser during the experimental than during the control task. The distance moved by the device was significantly greater than the displacement of the user's center of gravity during the experimental task. [Conclusion] We observed that moving the device forward or backward required lesser physical activity than that required to shift the user's center of gravity forward or backward while standing on the floor. Additionally, we observed that even a small displacement of the user's center of gravity produced a large displacement of the device. We concluded that during balance training, the greater and more easily perceived movement of the mobility device would provide helpful feedback to the user.

Effect of gait training using Welwalk on gait pattern in individuals with hemiparetic stroke: a cross-sectional study

Introduction

We aimed to explore the effect of gait training using Welwalk on gait patterns by comparing differences in gait patterns between robotic-assisted gait training using Welwalk and gait training using an orthosis in individuals with hemiparetic stroke.

Methods

This study included 23 individuals with hemiparetic stroke who underwent gait training with Welwalk combined with overground gait training using an orthosis. Three-dimensional motion analysis on a treadmill was performed under two conditions for each participant: during gait training with Welwalk and with the ankle-foot orthosis. The spatiotemporal parameters and gait patterns were compared between the two conditions.

Results

The affected step length was significantly longer, the step width was significantly wider, and the affected single support phase ratio was significantly higher in the Welwalk condition than in the orthosis condition. The index values of abnormal gait patterns were significantly lower while using Welwalk than in the orthosis condition. The following four indices were lower in the Welwalk condition: contralateral vaulting, insufficient knee flexion, excessive hip external rotation during the paretic swing phase, and paretic forefoot contact.

Discussion

Gait training using Welwalk increased the affected step length, step width, and single support phase while suppressing abnormal gait patterns as compared to gait training using the ankle-foot orthosis. This study suggests that gait training using Welwalk may promote a more efficient gait pattern reacquisition that suppresses abnormal gait patterns.

Trial registration

Prospectively registered in the Japan Registry of Clinical Trials (https://jrct.niph.go.jp; jRCTs042180152).

Survey of changes in subjective symptoms among Japanese polio survivors over 10 years

OBJECTIVE

To define long-term changes in subjective symptoms among polio survivors in Japan.

DESIGN

Prospective cohort study.

PATIENTS

Sixty-five polio survivors.

METHODS

Surveys were conducted on subjective symptoms including muscle weakness and limb atrophy during 2007 and 2021. The results of manual muscle tests of the upper and lower limbs on both sides during 2007 were summed and scored, and the side with lower scores was defined as the poor side. The participants were classified as younger or older groups based on the median age at the first survey (i.e., 58 years old) and the subjective symptoms were compared between the two groups.

RESULTS

As a whole, muscle atrophy and weakness progressed in the lower and upper limbs while fatigue was reduced. Muscle weakness progressed especially in the lower limbs on the poor side in the younger group, and in the older group it progressed in the lower limbs on the good side and the upper limbs on the poor side.

CONCLUSION

The timing of progressive muscle weakness differed between the upper and lower limbs of younger and older polio survivors.

Random walk and cell morphology dynamics in Naegleria gruberi

Amoeboid cell movement and migration are wide-spread across various cell types and species. Microscopy-based analysis of the model systems Dictyostelium and neutrophils over the years have uncovered generality in their overall cell movement pattern. Under no directional cues, the centroid movement can be quantitatively characterized by their persistence to move in a straight line and the frequency of re-orientation. Mathematically, the cells essentially behave as a persistent random walker with memory of two characteristic time-scale. Such quantitative characterization is important from a cellular-level ethology point of view as it has direct connotation to their exploratory and foraging strategies. Interestingly, outside the amoebozoa and metazoa, there are largely uncharacterized species in the excavate taxon Heterolobosea including amoeboflagellate Naegleria. While classical works have shown that these cells indeed show typical amoeboid locomotion on an attached surface, their quantitative features are so far unexplored. Here, we analyzed the cell movement of Naegleria gruberi by employing long-time phase contrast imaging that automatically tracks individual cells. We show that the cells move as a persistent random walker with two time-scales that are close to those known in Dictyostelium and neutrophils. Similarities were also found in the shape dynamics which are characterized by the appearance, splitting and annihilation of the curvature waves along the cell edge. Our analysis based on the Fourier descriptor and a neural network classifier point to importance of morphology features unique to Naegleria including complex protrusions and the transient bipolar dumbbell morphologies.

Effects of robot-assisted gait training within 1 week after stroke onset on degree of gait independence in individuals with hemiparesis: a propensity score-matched analysis in a single-center cohort study

BACKGROUND

Robot-assisted gait training (RAGT) is an effective method for treating gait disorders in individuals with stroke. However, no previous studies have demonstrated the effectiveness of RAGT in individuals with acute stroke. This study aimed to investigate the effects of RAGT initiation within 1 week after onset on degree of gait independence in individuals with hemiparetic stroke.

METHODS

This retrospective cohort study used propensity-score matching. Individuals admitted to Fujita Health University Hospital after stroke onset and underwent RAGT between March 2017 and June 2023 were enrolled. Ninety-two individuals were eligible and grouped into the acute (≤ 7 days after the onset) and subacute groups (8-90 days after onset). RAGT was conducted using Welwalk, primarily comprising a knee-ankle-foot orthosis type robot worn on one paralyzed lower extremity, with training sessions lasting approximately 40 min/day, occurring 3-7 days/week. The primary outcome was the gait under supervision within 90 days of onset, which was compared between groups using the log-rank test.

RESULTS

After propensity-score matching, 36 individuals were included in the analysis, including 18 each in the acute and subacute groups; the participant demographics were not significantly different between the groups. RAGT was initiated at a median of 6 and 25 days after onset in the acute and subacute groups, respectively. The Kaplan-Meier curves after the log-rank test showed a significantly higher percentage and shorter median days to achieve gait under supervision in the acute group than in the subacute group. The cumulative incidence of gait under supervision events at 90 days after onset was 82.2% and 55.6% in the acute and the subacute groups, respectively. Half of the individuals achieved gait under supervision within 49 days and 75 days in the acute and subacute groups, respectively (p = 0.038). No significant differences were observed in the dose of rehabilitation program and gait training per day from onset to achieving gait under supervision.

CONCLUSION

Initiation of RAGT within 1 week after stroke onset in individuals with hemiparesis may reduce the number of days required to achieve gait under supervision and increase the percentage of gait under supervision.

Effects of robot-assisted gait training using the Welwalk on gait independence for individuals with hemiparetic stroke: an assessor-blinded, multicenter randomized controlled trial

BACKGROUND

Gait disorder remains a major challenge for individuals with stroke, affecting their quality of life and increasing the risk of secondary complications. Robot-assisted gait training (RAGT) has emerged as a promising approach for improving gait independence in individuals with stroke. This study aimed to evaluate the effect of RAGT in individuals with subacute hemiparetic stroke using a one-leg assisted gait robot called Welwalk WW-1000.

METHODS

An assessor-blinded, multicenter randomized controlled trial was conducted in the convalescent rehabilitation wards of eight hospitals in Japan. Participants with first-ever hemiparetic stroke who could not walk at pre-intervention assessment were randomized to either the Welwalk group, which underwent RAGT with conventional physical therapy, or the control group, which underwent conventional physical therapy alone. Both groups received 80 min of physical therapy per day, 7 days per week, while the Welwalk group received 40 min of RAGT per day, 6 days per week, as part of their physical therapy. The primary outcome was gait independence, as assessed using the Functional Independence Measure Walk Score.

RESULTS

A total of 91 participants were enrolled, 85 of whom completed the intervention. As a result, 91 participants, as a full analysis set, and 85, as a per-protocol set, were analyzed. The primary outcome, the cumulative incidence of gait-independent events, was not significantly different between the groups. Subgroup analysis revealed that the interaction between the intervention group and stroke type did not yield significant differences in either the full analysis or per-protocol set. However, although not statistically significant, a discernible trend toward improvement with Welwalk was observed in cases of cerebral infarction for the full analysis and per-protocol sets (HR 4.167 [95%CI 0.914-18.995], p = 0.065, HR 4.443 [95%CI 0.973-20.279], p = 0.054, respectively).

CONCLUSIONS

The combination of RAGT using Welwalk and conventional physical therapy was not significantly more effective than conventional physical therapy alone in promoting gait independence in individuals with subacute hemiparetic stroke, although a trend toward earlier gait independence was observed in individuals with cerebral infarction.

TRIAL REGISTRATION

This study was registered with the Japan Registry of Clinical Trials ( https://jrct.niph.go.jp ; jRCT 042180078) on March 3, 2019.