Forearm

Background Posttranslational protein modification with O-linked N-acetylglucosamine (O-GlcNAc) is linked to high glucose levels in type 2 diabetes mellitus (T2DM) and may alter cellular function. We sought to elucidate the involvement of O-GlcNAc modification in endothelial dysfunction in patients with T2DM. Methods and Results Freshly isolated endothelial cells obtained by J-wire biopsy from a forearm vein of patients with T2DM (n=18) was compared with controls (n=10). Endothelial O-GlcNAc levels were 1.8-ford higher in T2DM patients than in nondiabetic controls (P=0.003). Higher endothelial O-GlcNAc levels correlated with serum fasting blood glucose level (r=0.433, P=0.024) and hemoglobin A1c (r=0.418, P=0.042). In endothelial cells from patients with T2DM, normal glucose conditions (24 hours at 5 mmol/L) lowered O-GlcNAc levels and restored insulin-mediated activation of endothelial nitric oxide synthase, whereas high glucose conditions (30 mmol/L) maintained both O-GlcNAc levels and impaired insulin action. Treatment of endothelial cells with Thiamet G, an O-GlcNAcase inhibitor, increased O-GlcNAc levels and blunted the improvement of insulin-mediated endothelial nitric oxide synthase phosphorylation by glucose normalization. Conclusions Taken together, our findings indicate a role for O-GlcNAc modification in the dynamic, glucose-induced impairment of endothelial nitric oxide synthase activation in endothelial cells from patients with T2DM. O-GlcNAc protein modification may be a treatment target for vascular dysfunction in T2DM.

Upper limb amputation deprives individuals of their innate ability to manipulate objects. Such disability can be restored with a robotic prosthesis linked to the brain by a human-machine interface (HMI) capable of decoding voluntary intentions, and sending motor commands to the prosthesis. Clinical or research HMIs rely on the interpretation of electrophysiological signals recorded from the muscles. However, the quest for an HMI that allows for arbitrary and physiologically appropriate control of dexterous prostheses, is far from being completed. Here we propose a new HMI that aims to track the muscles contractions with implanted permanent magnets, by means of magnetic field sensors. We called this a myokinetic control interface. We present the concept, the features and a demonstration of a prototype which exploits six 3-axis sensors to localize four magnets implanted in a forearm mockup, for the control of a dexterous hand prosthesis. The system proved highly linear (R2 = 0.99) and precise (1% repeatability), yet exhibiting short computation delay (45 ms) and limited cross talk errors (10% the mean stroke of the magnets). Our results open up promising possibilities for amputees, demonstrating the viability of the myokinetic approach in implementing direct and simultaneous control over multiple digits of an artificial hand.

BackgroundGiven the potential benefits of introducing ultrasound in the clinical assessment of muscle disorders, this study aimed to assess the feasibility and reliability of measuring forearm muscle thickness by ultrasound in a geriatric clinical setting.MethodsCross-sectional pilot study in 25 participants (12 patients aged ≥ 70 years in an acute geriatric ward and 13 healthy volunteers aged 25-50 years), assessed by three raters. Muscle thickness measurement was estimated as the distance between the subcutaneous adipose tissue-muscle interface and muscle-bone interface of the radius at 30% proximal of the distance between the styloid process and distal insertion of the biceps brachii muscle of the dominant forearm. Examinations were repeated three times by each rater and intra- and inter-rater reliability was calculated. Feasibility analysis included consideration of technological, economic, legal, operational, and scheduling (TELOS) components.ResultsMean muscle-thickness measurement difference between groups was 4.4 mm (95% confidence interval [CI] 2.4 mm to 6.3 mm], p ConclusionOur findings suggest that US is a feasible tool to assess the thickness of the forearm muscles with good inter-rater and excellent intra-rater reliability in a sample of hospitalized geriatric patients, making it a promising option for use in clinical practice.

Exposing the skin to high levels of ultraviolet B (UVB) radiation induces an inflammatory response that upregulates local nociceptive processing; this, in turn, facilitates protective responses to limit further injury. In this study, the UVB model was used to explore additional effects of inflammation on supraspinal nociceptive processing. Thirty-one healthy participants attended two sessions approximately 24 h apart. In each session, pressure-pain thresholds and sensitivity to sharp stimulation and heat were assessed in both forearms, and pressure-pain thresholds and sensitivity to sharp stimulation were assessed on each side of the forehead. In a novel paradigm, supraspinal nociceptive processing was explored by assessing pain and blink reflexes to electrical stimulation of the forehead, paired with acoustic startle stimuli. At the end of the first session, UVB radiation at a dose sufficient to induce erythema at the most exposed site was administered to one forearm. Consistent with local sensitization, sensitivity to heat and sharp stimulation had increased at the maximally exposed site 24 h later. This local response was accompanied by changes in supraspinal nociceptive processing-pressure-pain thresholds were lower on the ipsilateral than contralateral side of the forehead, and acoustic startle stimuli augmented electrically evoked pain. Blink reflexes weakened from the first to the second session, but decreases were smaller on the UVB-treated than contralateral side. Together, these findings suggest that acoustic startle stimuli facilitated activity in sensitized supraspinal nociceptive pathways. Potentially, this supraspinal mechanism adds to the burden of chronic nociplastic pain during states of heightened arousal and stress.