Poroelastic osmoregulation of living cell volume

Cells maintain their volume through fine intracellular osmolarity regulation. Osmotic challenges drive fluid into or out of cells causing swelling or shrinkage, respectively. The dynamics of cell volume changes depending on the rheology of the cellular constituents and on how fast the fluid permeates through the membrane and cytoplasm. We investigated whether and how poroelasticity can describe volume dynamics in response to osmotic shocks. We exposed cells to osmotic perturbations and used defocusing epifluorescence microscopy on membrane-attached fluorescent nanospheres to track volume dynamics with high spatiotemporal resolution. We found that a poroelastic model that considers both geometrical and pressurization rates captures fluid-cytoskeleton interactions, which are rate-limiting factors in controlling volume changes at short timescales. Linking cellular responses to osmotic shocks and cell mechanics through poroelasticity can predict the cell state in health, disease, or in response to novel therapeutics

A new framework for characterization of poroelastic materials using indentation

To characterize a poroelastic material, typically an indenter is pressed onto the surface of the material with a ramp of a finite approach velocity followed by a hold where the indenter displacement is kept constant. This leads to deformation of the porous matrix, pressurization of the interstitial fluid and relaxation due to redistribution of fluid through the pores. In most studies the poroelastic properties, including elastic modulus, Poisson ratio and poroelastic diffusion coefficient, are extracted by assuming an instantaneous step indentation. However, exerting step like indentation is not experimentally possible and usually a ramp indentation with a finite approach velocity is applied. Moreover, the poroelastic relaxation time highly depends on the approach velocity in addition to the poroelastic diffusion coefficient and the contact area. Here, we extensively studied the effect of indentation velocity using finite element simulations which has enabled the formulation of a new framework based on a master curve that incorporates the finite rise time. To verify our novel framework, the poroelastic properties of two types of hydrogels were extracted experimentally using indentation tests at both macro and micro scales. Our new framework that is based on consideration of finite approach velocity is experimentally easy to implement and provides a more accurate estimation of poroelastic properties

The effect of 1-year tailored exercise training, on according to cytokine levels and immune function at emphasis on IL-6 in breast cancer patients: A meta-analysis

Physical activity performance of patients during and after breast cancer treatment is common and is associated with increased toxicity from treatment, shorter time to tumor progression, and decreased survival. Exercise is a potential intervention to maintain or increase physical performance. We conducted a meta-analysis review of the 1-year tailored exercise training, according to cytokine levels and immune function with emphasis on IL-6 in breast cancer patients. A comprehensive search was performed in September 2022 for randomized controlled trials reporting the effects of structured exercise training on breast cancer effect with cytokine levels and immune function with an emphasis on IL-6 during or after cancer treatment. A random-effects meta-analysis was completed using the absolute net difference in the change between intervention and control groups as the outcome measure. Sensitivity and subgroup analyses were also performed. Data from 18 studies involving 1833 breast cancer survivors were included in the meta-analysis. Overall, there was a significant benefit of exercise training compared with the control (I2 = 71.3%, 95% CI = 38.4% to 77.6%, P < 0.001). Subgroup analysis showed positive effects for resistance training and aerobic training and for exercise training conducted during or after cancer treatment. Compared with usual care, exercise training has a beneficial effect on in women with breast cancer, both during and after cancer treatment. Given the physiological and functional importance of women with breast cancer, oncologists should encourage their patients to engage in regular exercise training, with particular emphasis on resistance training

Quantitative Analysis of Lateral Pinch Force in Quadriplegic Patients Using Functional Neuromuscular Stimulation with Computer Stimulation

Objective: In some applications of functional neuromuscular stimulation (FNS), the distal joint of the thumb (IP) in quadriplegic patients is sometimes surgically fused at zero degrees and the FPL is stimulated. This prevents hyperextension and extreme flexion of the IP joint during lateral pinch. However, IP joint fusion removes one degree of freedom from the thumb and may reduce the grip force. An alternative approach, preferably without surgical alterations, using sufficient electrical stimulation of selected muscles was investigated. A 3D model of prehensile lateral pinch was developed. Computer simulation of the model was used to find an approach providing the appropriate posture and adequate lateral grip force for quadriplegic patients using FNS. Materials & Methods: The model consists of a multi-rigid-body system connected by one or two degree(s) of freedom joints acted upon by passive resistive moments, active muscle moments and moments of external contact forces. Passive resistive moments were measured at each joint, active muscle moments were computed using a simple muscle model, and moments of external force were computed based on a force-displacement relationship for finger pads. In addition to the current strategy, two possible alternatives were studied: increasing the fused joint angle and activation of multiple muscles without joint fusion. Normal component of the grip force and its angle with respect to the horizontal plane were computed and compared for the studied cases. Results: Results showed, by using the current FNS strategy, a convenient posture and a grip force of 10.1 (N) are achieved which is comparable to what is measured experimentally and introduced in the literature. Increasing the joint fusion angle from 0 to 15 and 30 degrees in parallel with the activation of FPL increased the grip force from 10.1 to 10.7 and 11.2 (N), respectively, but resulted in inconvenient posture. Among all different combinations of the muscles with no joint fusion, only synchronous activation of ADP, APB, and FPL resulted in a convenient posture and a higher grip force of 16.6 (N). Conclusion: An alternative approach stimulating a combination of the named muscles without any need for surgical alterations might exist

Investigating the Interference control in Internet Addiction Disorder: Evidence from Brain Oscillatory Activity associated with Stroop Task

It is common for individuals with internet addiction disorder (IAD) to demonstrate impairments in interference and inhibitory control. A major objective of this study was to explore how interference control is related to event-related spectral perturbations (ERSPs) and whether participants with IAD experience changes in these spectral dynamics. Twenty-one IAD participants and twenty healthy controls (HCs) administered a Stroop task while their brains’ electroencephalographic activity (EEG) was recorded. ERSPs were extracted from the EEG and a cluster-based random permutation test was performed to test the difference in power between the two groups at each time frequency point. ERSP Stroop effect in theta was significantly reduced for the IAD group in an earlier time window, comparing to what was observed in the HC group. According to these results, IADs were unable to successfully inhibit their brain activation for stimulus conflict detection. Furthermore, IAD participants displayed a significant ERSP Stroop effect at beta2 and gamma frequencies - with the main contribution coming from bilateral dorsal frontal and parietal cortex over the scalp when compared to HC participants. In our study, IADs displayed reduced conflict detection and response selection compared to HCs, as measured by theta band indices, as well as impaired conflict resolution, as revealed by altered interaction dynamics between beta2 and gamma bands. This study is one of the first studies to use cluster-based random permutation tests to investigate oscillatory dynamics in conflict processing for IAD group

Quantitative assessment of deep brain stimulation on tremor in multiple sclerosis disease

Background and Purpose: Multiple sclerosis (MS) is a chronic disease that gives rise to anumber of unpleasant symptoms that can be difficult to manage by conventional means. There aresome aspects of MS-related disability which can be improved by using Deep Brain Stimulation(DBS); particularly movement disorders, such as tremor. The research aim is to study the effectof DBS on MS tremor with a quantitative approach.Methods: Raw tremor data was provided by the Surgical Center for Movement Disorders atthe University of British Columbia, Canada. The hand tremor signal was collected on 8 MSsubjects and 10 healthy individuals during finger-to-nose test (FNT) by using motion analysissystem. Patients executed the FNT with DBS OFF and ON. Nonlinear and statistical featureswere extracted from tremor spectrum as tremor indexes. Tremor reduction by using DBS wasdetermined by classifying mentioned features into three groups of healthy, DBS ON and DBSOFF.Results: Several dominant peaks were observed in power spectrum of the recorded signals whichindicate MS tremor consists of several tremor subtypes due to different sites of demyelinatinglesions affecting cerebellum and its output pathways. Results of frequency analysis revealedtremor spectrum dominant frequency in healthy group was significantly greater than for thepatients with DBS ON and OFF (p&lt;0.05). Additionally, classification results demonstrated thattremor of 6 patients out of 8 decreased significantly when their DBS was ON.Conclusion: Overall, in 75% of patients with MS who suffered from tremor, thalamic DBSsignificantly reduced their tremor. In addition, power spectrum dominant frequency has highpotential for a quantitative and objective measure of MS tremor

Original Article

Objectives: This paper describes further improvement and preliminarily evaluation of a novel viscoelastic ankle-foot prosthesis prototype. The objective was to control the ankle hysteresis at slow and normal walking speeds. Methods: Inspired by the ankle biomechanics, in which the hysteresis differs based on the gait speeds, a manually damping control mechanism imbedded in the prosthesis for adjusting the ankle damping at slow and normal walking speeds. The prototype was then preliminarily tested on an able-bodied subject wearing an adaptor which simulates the amputee walking. The ankle joint kinetics and kinematics were measured in a gait analysis lab at different walking speeds. Results: The results suggest that the viscoelastic ankle foot prosthesis prototype could provide a smooth normal-like walking for most of the measured gait characteristics in slow and normal speeds. Discussion: Therefore, it is suggested to apply a controllable damping mechanism based on the gait speeds in the design of new prosthetic feet

Evaluation of a Viscoelastic Ankle-Foot Prosthesis at Slow and Normal Walking Speeds on an Able-Bodied Subject

Objectives: This paper describes further improvement and preliminarily evaluation of a novel viscoelastic ankle-foot prosthesis prototype. The objective was to control the ankle hysteresis at slow and normal walking speeds. Methods: Inspired by the ankle biomechanics, in which the hysteresis differs based on the gait speeds, a manually damping control mechanism imbedded in the prosthesis for adjusting the ankle damping at slow and normal walking speeds. The prototype was then preliminarily tested on an able-bodied subject wearing an adaptor which simulates the amputee walking. The ankle joint kinetics and kinematics were measured in a gait analysis lab at different walking speeds. Results: The results suggest that the viscoelastic ankle foot prosthesis prototype could provide a smooth normal-like walking for most of the measured gait characteristics in slow and normal speeds. Discussion: Therefore, it is suggested to apply a controllable damping mechanism based on the gait speeds in the design of new prosthetic feet