Characterisation of a multi-channel multiplexed EMG recording system: towards realising variable electrode configurations

First steps towards osseointegrated myoelec-trically-controlled prostheses: Bone anchor conduit conveys EMG signals from implanted electrodes [1]. In vivo selection of electrode configurations would improve signal-to-noise ratio (SNR) of EMG recordings [2]; optimal electrode config-urations are not known before implantation. The CAPITel system: Control of Active Prostheses using Implant-able Telemetry [3,4]. Implantable EMG amplifier with a novel multi-plexed frontend. In vivo selection of monopolar, bipolar or tripolar configurations. Designed using commercially available com-ponents for use in animal models. After further research design will be imple-mented as an ASIC

The use of a bone-anchored device as a hard-wired conduit for transmitting EMG signals from implanted muscle electrodes.

The use of a bone-anchored device to transmit electrical signals from internalized muscle electrodes was studied in a sheep model. The bone-anchored device was used as a conduit for the passage of a wire connecting an internal epimysial electrode to an external signal-recording device. The bone-anchored device was inserted into an intact tibia and the electrode attached to the adjacent M. peroneus tertius. "Physiological" signals with low signal-to-noise ratios were successfully obtained over a 12-week period by walking the sheep on a treadmill. Reliable transmission of multiple muscle signals across the skin barrier is essential for providing intuitive, biomimetic upper limb prostheses. This technology has the potential to provide a better functional and reliable solution for upper limb amputee rehabilitation: attachment and control

Myoelectric Signal Transmission from Implanted Epimysial Electrodes Using a Bone-Anchor as a Conduit

Introduction Current Upper-limb myoelectric prostheses rely on only 2 control signals from surface electrodes, placed over antagonistic muscles in the amputation stump, for limb control. While this has benefits over the traditional body-powered control, there are disadvantages; electrode lift-off, impedance variation, cross-talk, reliability, and limitations in intuitive control. To address these problems, electrodes can be implanted directly on individual muscles responsible for specific actions. Not only does this address skin-related issues, it reduces cross-talk and greatly increases the number of control channels for multi degrees of freedom intuitive control. Bone-anchored devices can be used to overcome problems with prosthetic attachment and additionally used to transfer control signals from these implantable electrodes to the prosthesis. [1] In above-elbow amputees, targeted muscle reinnervation (TMR) enables more signal generation by redirecting nerves previously controlling the amputated muscles in the forearm, to surrogate muscles in the torso (e.g. pectoralis major). [2] We describe in vivo model using implantable electrodes to record myoelectric signals (MES) in normal muscles and following TMR, utilizing a bone-anchor as a conduit to carry signals across the skin barrier. Materials and Methods An in vivo n=6 ovine model was used. A bone-anchor was placed trans-tibially and bipolar electrodes sutured to M. Peroneus Tertius (PT). In a further n=1, motor nerve to PT was divided and coapted with a motor branch from peroneal nerve. MES were recorded over a 12-week period. Functional recovery in the TMR model was assessed by MES and force-plate analysis (FPA). Results In the n=6 group, there was a positive correlation between signal to noise ratio (SNR) and time since implantation (p < 0.005), with a mean SNR of 7 by week 12. In the TMR model, functional recovery was observed after 6 weeks. Difference between legs returned to normal (pre-op: left 4.7 N/kg, right 4.8 N/kg; 80 days post-op: left 4.1 N/kg, right 4.3 N/kg). Recorded MES from TMR muscle compared favourably with healthy muscle. Conclusions We have demonstrated that a bone-anchor is a reliable and robust conduit for transmitting MES over a period of 12 weeks. The combination of implanted electrodes & direct skeletal fixation offers clear advantages over current systems for prosthetic attachment & control. This system forms the basis of a complete solution for prosthetic rehabilitation, which can also be used in the context of TMR. References 1. Al Ajam et. al., 2013. PMID: 23358938 2. Kuiken et. al., 2004. PMID: 1565863

Impairment of Immunoproteasome Function by β5i/LMP7 Subunit Deficiency Results in Severe Enterovirus Myocarditis

Proteasomes recognize and degrade poly-ubiquitinylated proteins. In infectious disease, cells activated by interferons (IFNs) express three unique catalytic subunits β1i/LMP2, β2i/MECL-1 and β5i/LMP7 forming an alternative proteasome isoform, the immunoproteasome (IP). The in vivo function of IPs in pathogen-induced inflammation is still a matter of controversy. IPs were mainly associated with MHC class I antigen processing. However, recent findings pointed to a more general function of IPs in response to cytokine stress. Here, we report on the role of IPs in acute coxsackievirus B3 (CVB3) myocarditis reflecting one of the most common viral disease entities among young people. Despite identical viral load in both control and IP-deficient mice, IP-deficiency was associated with severe acute heart muscle injury reflected by large foci of inflammatory lesions and severe myocardial tissue damage. Exacerbation of acute heart muscle injury in this host was ascribed to disequilibrium in protein homeostasis in viral heart disease as indicated by the detection of increased proteotoxic stress in cytokine-challenged cardiomyocytes and inflammatory cells from IP-deficient mice. In fact, due to IP-dependent removal of poly-ubiquitinylated protein aggregates in the injured myocardium IPs protected CVB3-challenged mice from oxidant-protein damage. Impaired NFκB activation in IP-deficient cardiomyocytes and inflammatory cells and proteotoxic stress in combination with severe inflammation in CVB3-challenged hearts from IP-deficient mice potentiated apoptotic cell death in this host, thus exacerbating acute tissue damage. Adoptive T cell transfer studies in IP-deficient mice are in agreement with data pointing towards an effective CD8 T cell immune. This study therefore demonstrates that IP formation primarily protects the target organ of CVB3 infection from excessive inflammatory tissue damage in a virus-induced proinflammatory cytokine milieu

Obesity in mammaplasty : a study of complications following breast reduction

Original article can be found at : http://www.sciencedirect.com/ Copyright British Association of Plastic, Reconstructive and Aesthetic Surgeons [Full text of this article is not available in the UHRA]Background : Access to effective surgical treatments such as breast reduction is often restricted on the grounds of patient obesity. However, there is a lack of unambiguous data on the surgical risks of obesity in patients undergoing breast reduction. The aim of this study was to assess the relationship between patient obesity, as determined by body mass index (BMI), and surgical outcome following bilateral breast reduction (BBR). Methods : Retrospective review of case notes was conducted for 306 patients who underwent BBR in our unit over a 5-year period. BMI, resection weight, smoking history, technique, complications and outcomes were determined from records of follow-up assessment. Results : Overall complication rate was 53.9%, with multiple complications of 22.9%. A significant increase in complications after BBR with increasing BMI was identified (p = 0.019 any complication, p = 0.002 multiple complications). The effect of BMI on multiple complications was significant and independent of resection weight (p = 0.031) and reduction technique (p = 0.020). Smoking was associated with higher wound dehiscence and multiple complications. We developed a model for predicting risk of complications based on key variables. Despite higher complications, there was no significant difference in aesthetic outcome at follow-up between the BMI groups. Conclusions : These findings add to the body of evidence that obesity is associated with an increased risk of post-operative complications. This has implications for surgeons and healthcare payers. However the majority of complications were minor and aesthetic outcomes were satisfactory in the majority of cases. The use of a ‘target’ BMI as exclusion criteria should therefore be treated with caution.Peer reviewe

Characterisation of a multi-channel multiplexed EMG recording system: towards realising variable electrode configurations

An implantable EMG amplifier with a novel multiplexed frontend for in vivo selection of optimal electrode configurations, was designed using commercially available components. The multiplexers are advantageous as optimal electrode configuration are not known before implantation. The system has 6 ADC recording channels (ADS1298 biopotential amplifier, 2 kHz sampling frequency, 16-bit resolution), and three 8 × 8 multiplexer arrays (ADG2188), 2 channels per MUX. The system was characterised by measuring input impedance (5.8 MOhm) and frequency response (CMRR 49.0 dB; SNR 51.4 dB). EMG recordings from implanted epimysial electrodes showed lower signal quality (13.5 dB) compared with a commercial EMG recorder (19.5 dB), nonetheless the signals appeared suitable for myoelectric control applications. An implantable version of the EMG recorder, housed within a hermetically sealed ceramic package, should improve signal quality

Assessment of bioaccessibility and exposure risk of arsenic and lead in urban soils of Guangzhou City, China

Soil ingestion is an important human exposure pathway of heavy metals in urban environments with heavy metal contaminated soils.This study aims to assess potential health risks of heavy metals in soils sampled from an urban environment where high frequency of human exposure may be present. A bioaccessibility test is used, which is an in vitro gastrointestinal (IVG) test of soluble metals under simulated physiological conditions of the human digestion system. Soil samples for assessing the oral bioaccessibility of arsenic (As) and lead (Pb) were collected from a diverse range of different land uses, including urban parks, roadsides, industrial sites and residential areas in Guangzhou City, China. The soil samples contained a wide range of total As (10.2 to 61.0 mg kg) and Pb (38.4 to 348 mg kg) concentrations. The bioaccessibility of As and Pb in the soil samples were 11.3 and 39.1% in the stomach phase, and 1.9 and 6.9% in the intestinal phase, respectively. The As and Pb bioaccessibility in the small intestinal phase was significantly lower than those in the gastric phase. Arsenic bioaccessibility was closely influenced by soil pH and organic matter content (r = 0.451, p residential area/road side. Although the risk of heavy metal exposure from direct ingestion of urban soils is relatively low, the risk of inhalation of fine soil particulates in the air remains to be evaluated