Age-related DNA methylation changes: Potential impact on skeletal muscle aging in humans

Human aging is accompanied by a decline in muscle mass and muscle function, which is commonly referred to as sarcopenia. Sarcopenia is associated with detrimental clinical outcomes, such as a reduced quality of life, frailty, an increased risk of falls, fractures, hospitalization, and mortality. The exact underlying mechanisms of sarcopenia are poorly delineated and the molecular mechanisms driving the development and progression of this disorder remain to be uncovered. Previous studies have described age-related differences in gene expression, with one study identifying an age-specific expression signature of sarcopenia, but little is known about the influence of epigenetics, and specially of DNA methylation, in its pathogenesis. In this review, we will focus on the available knowledge in literature on the characterization of DNA methylation profiles during skeletal muscle aging and the possible impact of physical activity and nutrition. We will consider the possible use of the recently developed DNA methylation-based biomarkers of aging called epigenetic clocks in the assessment of physical performance in older individuals. Finally, we will discuss limitations and future directions of this field

Stretch Evoked Potentials in Healthy Subjects and After Stroke: A Potential Measure for Proprioceptive Sensorimotor Function

Sensory feedback is of vital importance in motor control, yet rarely assessed in diseases with impaired motor function like stroke. Muscle stretch evoked potentials (StrEPs) may serve as a measure of cortical sensorimotor activation in response to proprioceptive input. The aim of this study is: 1) to determine early and late features of the StrEP and 2) to explore whether StrEP waveform and features can be measured after stroke. Consistency of StrEP waveforms and features was evaluated in 22 normal subjects. StrEP features and similarity between hemispheres were evaluated in eight subacute stroke subjects. StrEPs of normal subjects had a consistent shape across conditions and sessions (mean cross correlation waveforms > 0.75). Stroke subjects showed heterogeneous StrEP waveforms. Stroke subjects presented a normal early peak (40 ms after movement onset) but later peaks had abnormal amplitudes and latencies. No significant differences between stroke subjects with good and poor motor function were found (P > 0.14). With the consistent responses of normal subjects the StrEP meets a prerequisite for potential clinical value. Recording of StrEPs is feasible even in subacute stroke survivors with poor motor function. How StrEP features relate to clinical phenotypes and recovery needs further investigatio

Stretch reflex augmentation by subthreshold TMS is evidence for corticospinal signal integration

Reflex adaptation to environment and task at hand plays a key role in motor control. In search for cortical reflex modulation mechanisms, transcranial magnetic stimulation (TMS) has been found to augment muscle stretch reflexes as recorded by electromyography (EMG). However, instead of reflecting true integration of efferent sensory with cortical activity, this augmentation can alternatively be explained by spinal summation of the stretch response with TMS induced motor evoked potentials (MEP). The goal of this study was to confirm true peripheral-cortical signal integration by combining muscle reflex responses with timed subthreshold TMS. Mechanically induced ramp-and-hold stretches (duration: 40 ms, velocity: 1.5 rad/s) of the m. flexor carpi radialis were combined with TMS pulses at 96% of active motor threshold applied between 10 ms before and 120 ms after stretch onset with a resolution of 5 to 10 ms. Significant MEP like augmentation of the EMG response was found when TMS was timed to arrive between 60 and 90 ms after stretch onset with a consistent and short delay between estimated TMS arrival time and peak EMG activity of 5 to 10 ms. Timing and nature of muscle stretch reflex activity augmentation by subthreshold TMS reflect supraspinal integration of peripheral sensory afferent with cortical efferent signals as a mechanism of supraspinal reflex adaptation

Recovery Map for Fermionic Gaussian Channels

A recovery map effectively cancels the action of a quantum operation to a partial or full extent. We study the Petz recovery map in the case where the quantum channel and input states are fermionic and Gaussian. Gaussian states are convenient because they are totally determined by their covariance matrix and because they form a closed set under so-called Gaussian channels. Using a Grassmann representation of fermionic Gaussian maps, we show that the Petz recovery map is also Gaussian and determine it explicitly in terms of the covariance matrix of the reference state and the data of the channel. As a by-product, we obtain a formula for the fidelity between two fermionic Gaussian states. We also discuss subtleties arising from the singularities of the involved matrices.Comment: 13 pages and 11 pages of appendices. Updated references and footnotes in v2. Updated for a new paragraph of twisted recovery map and change of format in v

Pulse transit time as a proxy for vasoconstriction in younger and older adults

Objectives: Changes of vasoconstriction may be measured non-invasively using pulse transit time. This study assessed the sensitivity, test-retest reliability and validity of pulse transit time during vasoconstriction provocation and active standing, and the predictive value of pulse transit time for blood pressure drop. Methods: Fifty-five younger (age 70 years) underwent electrocardiography, wrist and finger photoplethysmography and continuous blood pressure and total peripheral resistance measurements during vasoconstriction provocation using a cold pressor test (21 younger adults), or active stand tests (all other participants). Pulse transit tim

Requirements for home-based upper extremity rehabilitation using wearable motion sensors for stroke patients:a user-centred approach

Purpose: Telerehabilitation systems have the potential to enable therapists to monitor and assist stroke patients in achieving high-intensity upper extremity exercise in the home environment. We adopted an iterative user-centred approach, including multiple data sources and meetings with end-users and stakeholders to define the user requirements for home-based upper extremity rehabilitation using wearable motion sensors for subacute stroke patients. Methods: We performed a requirement analysis consisting of the following steps: 1) context &amp; groundwork; 2) eliciting requirements; 3) modelling &amp; analysis; 4) agreeing requirements. During these steps, a pragmatic literature search, interviews and focus groups with stroke patients, physiotherapists and occupational therapists were performed. The results were systematically analysed and prioritised into “must-haves”, “should-haves”, and “could-haves”. Results: We formulated 33 functional requirements: eighteen must-have requirements related to blended care (2), exercise principles (7), exercise delivery (3), exercise evaluation (4), and usability (2); ten should-haves; and five could-haves. Six movement components, including twelve exercises and five combination exercises, are required. For each exercise, appropriate exercise measures were defined. Conclusion: This study provides an overview of functional requirements, required exercises, and required exercise measures for home-based upper extremity rehabilitation using wearable motion sensors for stroke patients, which can be used to develop home-based upper extremity rehabilitation interventions. Moreover, the comprehensive and systematic requirement analysis used in this study can be applied by other researchers and developers when extracting requirements for designing a system or intervention in a medical context.</p

Pulse transit time as a proxy for vasoconstriction in younger and older adults

Objectives: Changes of vasoconstriction may be measured non-invasively using pulse transit time. This study assessed the sensitivity, test-retest reliability and validity of pulse transit time during vasoconstriction provocation and active standing, and the predictive value of pulse transit time for blood pressure drop. Methods: Fifty-five younger (age 70 years) underwent electrocardiography, wrist and finger photoplethysmography and continuous blood pressure and total peripheral resistance measurements during vasoconstriction provocation using a cold pressor test (21 younger adults), or active stand tests (all other participants). Pulse transit tim

Optical Hand Tracking: A Novel Technique for the Assessment of Bradykinesia in Parkinson's Disease

Neurological Motor Disorder

Knee extension strength measurements should be considered as part of the comprehensive geriatric assessment

Pathophysiology, epidemiology and therapy of agein