Average Contraction Research Articles

Age as a dominant factor affecting gastric motility and emptying

Gastric motility is the process of continuous propagation of peristaltic waves from the anterior part of the stomach to the pylorus region. These waves aid in the digestion of foods, importantly play a major role in gastric emptying of foods. The present study aimed to investigate whether ageing influences gastric motility in response to apple consumption. Subjects were asked to consume apple and water in the ratio of 3:1 followed by MRI scanning in the right lying position. Antral contraction wave characteristics like speed, frequency, amplitude and width of the wave and occlusion percentage were calculated. Average contractions per minute were obtained as 2.67±0.06 for young age and 2.43±0.22 for middle-aged healthy humans. From the obtained results, no significant difference was found between the assessed motility parameters.

Decreased urothelial expression of caveolin 1 and 2 in aging rats showing detrusor overactivity: Potential association with aging bladder.

PurposeThe purpose of this study was to investigate the effect of aging on bladder function and caveolin protein expression in rat urothelium.Materials and MethodsFemale Sprague-Dawley rats were divided into the following two groups: young age control group (12 weeks) and old-aged group of rats (80 weeks). Urodynamic measurements were taken to compare the contraction interval and the contraction pressure between the two groups. The expression and cellular localization of caveolin 1 and 2 in the urothelium of the rat urinary bladder were determined by Western blot and immunofluorescence microscopy.ResultsIn cystometrograms, the contraction interval (min) was significantly shorter in the old-aged group (3.7±0.5 min) than in the young age control group (6.2±0.8 min). Also, the average contraction pressure (mmHg) was lower in the old-aged group (8.4±0.6 mmHg) than in the young age control group (13.2±1.3 mmHg). Caveolin 1 and 2 were expressed in the subepithelial area in the urothelium. The protein expression of both caveolin 1 and 2 was significantly lower in the old-aged group than in the young age control group.ConclusionsAging caused a significant change in the expression of caveolin 1 and 2 in the urothelium of the rat urinary bladder. These findings suggest that these molecules might have specific roles in the functional change of the urinary bladder that occurs in association with aging.

Activity Evaluation of Facial Muscles by Surface Electromyography.

Background:Surface electromyography (sEMG) is an easy, noninvasive, and reproducible way to assess spontaneous electrical activity of muscles in real time. In this study, we report data on the correlation between sEMG and mimetic muscle activity during specific tasks so as to create a case–control reference for future studies on acute, chronic, and congenital facial palsy.Methods:Twelve healthy participants were enrolled (6 women and 6 men) with a mean age of 42.75 (range, 26–58 years) years. sEMG signals were recorded at rest and while performing voluntary and specific tasks that elicited selective contraction of frontalis, orbicularis oculi, zygomaticus major, orbicularis oris, and platysma muscles simultaneously and bilaterally for each muscle group. Statistical analysis was performed to evaluate if there was a statistically significant difference of the average contraction values between left- and right-side data sets and between male and female participants.Results:No statistically significant difference was found between male and female participants or between the right and left sides at rest and while performing the requested tasks, even though they were not identical. No participant complained about the procedure.Conclusions:Interindividual and intraindividual variability of the sEMG signal as well as crosstalk between muscles groups were reported downsides that we did not encounter. The absolute noninvasiveness of our procedure makes it feasible to be applied even to young children. This dataset obtained in healthy participants might also be useful in the observation of patients undergoing regeneration/reinnervation procedure following recently acquired facial palsy or mimetic muscle reconstruction for congenital/inveterate one.

Altered Lymphatic Vessel Anatomy and Markedly Diminished Lymph Clearance in Affected Hands of Patients With Active Rheumatoid Arthritis

To assess differences between lymphatic function in the affected hands of rheumatoid arthritis (RA) patients with active synovitis and that of healthy controls, using indocyanine green (ICG) dye and near-infrared (NIR) imaging. NIR imaging of the hands of 8 patients with active RA and 13 healthy controls was performed following web space injection of 0.1 ml of 100 μM ICG. The percentage of ICG retention in the web spaces was determined by NIR imaging at baseline and at 7 days (±1 day) after the initial injections; image analysis provided contraction frequency. ICG+ lymphatic vessel (LV) length and branching architecture were assessed. Retention of ICG in RA hands was higher compared to controls (P < 0.01). The average contraction frequency of ICG+ LVs in RA patients and in controls did not differ (mean ± SD 0.53 ± 0.39 contractions/minute versus 0.51 ± 0.35 contractions/minute). Total ICG+ LV length in RA hands was lower compared to healthy controls (58.3 ± 15.0 cm versus 71.4 ± 16.1 cm; P < 0.001), concomitant with a decrease in the number of ICG+ basilic LVs in the hands of RA patients (P < 0.05). Lymphatic drainage in the hands of RA patients with active disease was reduced compared to controls. This reduction was associated with a decrease in total length of ICG+ LVs on the dorsal surface of the hands, which continued to contract at a similar rate to that observed in controls. These findings provide a plausible mechanism for exacerbation of synovitis and joint damage, specifically the accumulation and retention of inflammatory cells and catabolic factors in RA joints due to impaired efferent lymphatic flow. NIR/ICG imaging of RA hands is feasible and warrants formal investigation as a primary outcome measure for arthritis disease severity and/or persistence in future clinical trials.

Climate niche mismatch and the collapse of primate seed dispersal services in the Amazon

Animal-plant interactions are threatened by ongoing climate change, deforestation, and defaunation. The disruption of biotic interactions leads to loss of ecosystem services but estimates of the magnitude of reductions are rarely available. Using a seed disperser primate community in the Amazon as study case, we forecast the magnitude of seed dispersal services to be lost as function of the future redistribution of species. In the most likely scenario, our projections indicate average contractions of 56% (23 to 100% reduction) on the suitable areas for the studied primates. As result, we found billions of seeds of a model tree (Manilkara bidentata) might fail to be dispersed by this primate community on each fruiting season. Primate contribution to seed dispersal was, however, uneven among species, highlighting the endangered large-bodied woolly monkey Lagothrix cana as a keystone disperser. That species alone was responsible for about 64% of all Manilkara seeds dispersed in the present and up to 71% in the future. Niche mismatch will, however, lead to 37% of the future plant distribution not being able to host its second top disperser (the tufted capuchin Sapajus apella), exacerbating losses on potential seed dispersal. Our projections indicate that seed dispersal in tropical forests might be hampered by global changes, even if defaunation by poaching is controlled. The forecasted magnitude of loss in seed dispersal services is alarming and may have been overlooked in conservation assessments. In a similar manner, niche mismatch and disruption of biotic interactions will likely impair ecosystems functions and resilience worldwide.

Weakly contractive iterated function systems and beyond: a manual

ABSTRACT We give a systematic account of iterated function systems (IFS) of weak contractions of different types (Browder, Rakotch, topological). We show that the existence of attractors and asymptotically stable invariant measures, and the validity of the random iteration algorithm (‘chaos game’), can be obtained rather easily for weakly contractive systems. We show that the class of attractors of weakly contractive IFSs is essentially wider than the class of classical IFSs' fractals. On the other hand, we show that, in reasonable spaces, a typical compact set is not an attractor of any weakly contractive IFS. We explore the possibilities and restrictions to break the contractivity barrier by employing several tools from fixed point theory: geometry of balls, average contractions, remetrization technique, ordered sets, and measures of noncompactness. From these considerations it follows that while the existence of invariant sets and invariant measures can be assured rather easily for general iterated function systems under mild conditions, to establish the existence of attractors and unique invariant measures is a substantially more difficult problem. This explains the central role of contractive systems in the theory of IFSs.

Effect of foods on selected dynamic parameters of mandibular elevator muscles during symmetric incisal biting

The paper focuses on research that enables the relationship between food and selected mechanical parameters do be determined. The main aim of the study was to designate, depending on the food: (1) the work of a single muscle (i.e. masseter, medial pterygoid, temporalis), and (2) the energy balance of mandibular elevator muscles based on the dynamic patterns of muscles. In turn, the indirect goal was to determine: (1) the muscle contraction, and (2) the average muscle contraction velocity based on the specified kinematic parameters, i.e. incisal biting velocity and incisal biting time.A hybrid model, consisting of a phenomenological model of the masticatory system and a behavioural model of incisal biting, was used in the calculations. The phenomenological model was based on an anatomically and physiologically normal mandible and healthy muscles, while the behavioural model was represented by the dynamic patterns of food.Calculations showed that muscle force is an important, but not the only, parameter that enables the quantitative and qualitative assessment of the functioning of the mandibular elevator muscles during symmetric incisal biting. Based on the obtained results, it can be stated that the dynamic patterns of muscles are a very important parameter, because on their basis, among others, muscle contraction, contraction time, work, and energy can be determined. The conducted calculations and analyses showed that the above-mentioned parameters depend on the mechanical properties of food (the dynamic patterns of food).

Comparative visualized investigation of impact-driven high-speed liquid jets injected in submerged water and in ambient air

This paper is a comparative study on the characteristics of high-speed liquid jets injected in surrounding water and air using shadowgraph technique. One of the main objectives is to investigate the effects of liquid’s physical properties, used to generate the high-speed liquid jets, on jet generation’s characteristics. Moreover, comparative investigations on effects of those liquid jets after injected in water and air are reported. The high-speed liquid jets were generated by the impact of a projectile launched by a horizontal single-stage power gun. The impact-driven high-speed liquid jets were visualized by shadowgraph technique and images were recorded by a high-speed digital video camera. The process of impact-driven high-speed liquid jet injection in air and water, oblique shock waves, jet-induced shock waves, shock waves propagation, the bubble behavior, bubble collapse-induced rebound shock waves and bubble cloud regeneration were clearly observed. It was found that different properties of liquid (surface tension and kinematic viscosity) affect the jet maximum velocity and shape of the jet. Bubble behaviors were only found for the jet injected in water. From the shadowgraph images, it is found that the maximum average jet velocity, expansion and contraction velocities of bubble in axial direction increase when the value of the multiplied result of surface tension by kinematic viscosity increases. Therefore, surface tension and kinematic viscosity are the significant physical properties that affect characteristics of high-speed liquid jets.

Prediction of the level of consciousness using pupillometer measurements in patients with impaired consciousness brought to the emergency and critical care center.

AimWe investigated whether the level of consciousness can be predicted using pupillometer measurements in patients with severe disturbance of consciousness.MethodsPatients with a Glasgow Coma Scale (GCS) of 3–8, except for those after cardiac arrest, were included. Pupillary contraction rate and contraction velocity were each measured using a pupillometer.ResultsThirty‐five patients were analyzed. At the time of discharge or changing hospitals, 16 patients had a GCS score of 3–13 and 19 patients had a GCS score of 14–15. In the non‐sedative group at about the time of arrival at our hospital, average pupillary contraction rates were 18.36% in the GCS 3–13 group and 19.67% in the GCS 14–15 group (P = 0.739), and average pupillary contraction velocities were 1.02 and 1.48, respectively (P = 0.182). Approximately 48 h after arrival, average pupillary contraction rates were 21.18% and 29.27%, respectively (P = 0.058), and average pupillary contraction velocities were 1.37 and 1.91, respectively (P = 0.172). Among the sedative group, at about the time of arrival, average pupillary contraction rates were 8.75% in the GCS 3–13 group and 19.75% in the GCS 14–15 group (P = 0.032). Average pupillary contraction velocities were 0.34 and 1.48, respectively (P = 0.001). Approximately 48 h after arrival, average pupillary contraction rates were 13.50% and 13.50%, respectively (P = 1.00), and average pupillary contraction velocities were 0.80 and 0.82, respectively (P = 0.93).ConclusionsPupillometer measurements could predict level of consciousness of patients with severe consciousness disorder.

Is Government Contracting Fair? Estimating the Value of Female Politicians for Women-Owned Firms

This paper provides novel evidence that female politicians increase the proportion of US government procurement contracts allocated to women-owned firms. The identification strategy uses close elections for the US House of Representatives. The effect concentrates in local contractors and persists after the female’s politician departure. The more gender-balanced representation in government contracting does not seem to be associated with economic costs, as the firm characteristics of the average contractor and contract performances are unchanged. By analyzing congressional requests from legislators to federal agencies, we show that female politicians affect procurement contract allocation through individual oversight.

Neural and muscular determinants of maximal rate of force development.

The ability to produce rapid forces requires quick motor unit recruitment, high motor unit discharge rates, and fast motor unit force twitches. The relative importance of these parameters for maximum rate of force development (RFD), however, is poorly understood. In this study, we systematically investigated these relationships using a computational model of motor unit pool activity and force. Across simulations, neural and muscular properties were systematically varied in experimentally observed ranges. Motor units were recruited over an interval starting from contraction onset (range: 22-233 ms). Upon recruitment, discharge rates declined from an initial rate (range: 89-212 pulses per second), with varying likelihood of doublet (interspike interval of 3 ms; range: 0-50%). Finally, muscular adaptations were modeled by changing average twitch contraction time (range: 42-78 ms). Spectral analysis showed that the effective neural drive to the simulated muscle had smaller bandwidths than the average motor unit twitch, indicating that the bandwidth of the motor output, and thus the capacity for explosive force, was limited mainly by neural properties. The simulated RFD increased by 1,050 ± 281% maximal voluntary contraction force per second from the longest to the shortest recruitment interval. This effect was more than fourfold higher than the effect of increasing the initial discharge rate, more than fivefold higher than the effect of increasing the chance of doublets, and more than sixfold higher than the effect of decreasing twitch contraction times. The simulated results suggest that the physiological variation of the rate by which motor units are recruited during ballistic contractions is the main determinant for the variability in RFD across individuals.NEW & NOTEWORTHY An important limitation of human performance is the ability to generate explosive movements by means of rapid development of muscle force. The physiological determinants of this ability, however, are poorly understood. In this study, we show using extensive simulations that the rate by which motor units are recruited is the main limiting factor for maximum rate of force development.

What's next for Cuba? And this issue's contents

In April the United Nations Economic Commission for Latin America and the Caribbean (ECLAC) reported that the Cuban economy was expected to shrink by 3.7 percent in 2020 (which, if reflected on as a comment on the robustness of the Cuban economy to such an external shock, should be considered against the expected 5.3 percent average contraction of the Latin America and the Caribbean region as a whole that the Island is part of). [...]contrary to those who blame every problem Cuba ever faces on 'errors by the government', the data do not support that the serious contraction that Cuba is facing from COVID-19 is the result of, or even has been primarily exacerbated by, the country's economic policies. [...]beyond that, and once again independent of one's views about the desirability of tourism as a human economic activity (which this author has great concerns with, though more with its nature than with its amount), the data do not support that the development of the tourism industry in Cuba over the last quarter century has left its economy 'overdependent' on tourism by any meaningful comparative economic measure. Worldwide, a rounded approximate number for tourism's total contribution to world economic activity (or more correctly, the part of that which standard national accounting keeps track of as GDP) and of world employment is 10 percent of each.

Increased Platelet Force Is Associated with Decreased Bleeding Severity in Pediatric Immune Thrombocytopenia

Background: Immune Thrombocytopenia Purpura (ITP) can result in severely low platelet counts and while most of the 4,000 new cases of pediatric ITP diagnosed each year self-resolve, 10% of these patients have major bleeding episodes. The platelet count remains the mainstay method for predicting hemorrhage and unfortunately has only proven to be loosely correlated to bleeding severity. Consequently, there currently exists no biomarker that accurately and reliably predicts which patients need immediate medical treatment, all of which have side effects, and which patients only require monitoring. To that end, we leveraged our Platelet Contraction Cytometer (PCC), a versatile system that measures platelet contraction forces at the single-cell level and at high-throughput, to study platelets of patients with ITP prospectively. Buchanan bleeding scores were used to distinguish patients with severe symptoms from asymptomatic patients. With 49 patients, we observed two significant findings: 1) Tracking both single platelet force measurements and platelet count enables stratifying patients into having major, minor, or no risk for bleeding. Accordingly, patients in the major risk category have a combined low platelet force and low platelet count. 2) Longitudinal studies showed that when major risk patients had increased platelet force or higher platelet counts, this was associated with the alleviation of major symptoms. Thus, when utilized together, platelet force and platelet count can more accurately predict bleeding severity in pediatric ITP patients. Platelet Contraction Cytometry: Our PCC utilizes a large array of fibrinogen "microdot" pairs patterned on a flat hydrogel of known stiffness. Thrombin-activated platelets adhere to these microdots, spread to the neighboring microdot, and contract, pulling the microdots closer together. As platelet force is directly proportional to the microdot displacement, only a single microscopy measurement is necessary to determine the force applied by each single platelet (Fig 1). As such, hundreds of platelets are measured in a controlled mechanical and biochemical environment (Myers et al, 2017) Results: With our cohort of 49 ITP patients, we observed that low average single cell platelet contraction forces highly correlate with severe bleeding symptoms (Buchannan scores 2-4). Using a regression tree, we found that an average force of 26nN best separates symptomatic from asymptomatic patients with a diagnostic sensitivity of 100% and specificity of 86.8% (AUC 0.97, 95% CI: 0.9361-1). However, platelets from some asymptomatic patients exerted forces of less than 26nN as well. In a more thorough examination, we found that majority of those asymptomatic patients with low platelet forces had platelet counts &gt; 40,000/uL. Although our data shows that platelet count alone is a poor predictor of severe bleeding symptoms (AUC 0.8, 95% CI: 0.6757-0.9189), when a platelet count &lt;40k/uL is coupled alongside our criterion of average contraction force &lt;26 nN, we find that the specificity of our system increases to 94.7% and thus platelet count and platelet force synergistically predict which patients are symptomatic with high accuracy. Using a logistic regression model, we also found that with each 1nN decrease in average contraction force, the odds of the patient bleeding increases 2.1 (95% CI: 1.1-4.0) times that of being asymptomatic and when this decrease in contraction force is increased 5nN, the odds of a patient bleeding is 44.4 (95% CI: 1.8-1066.5) times that of being asymptomatic (Fig 2A-B). Moreover, when tracking individual patients (n=4) over time, we demonstrate that whenever a patient's blood sample is associated with increased single platelet average contraction force &gt;26 nN or platelet count &gt;40k/uL, bleeding symptoms are alleviated. Conversely, whenever a patient exhibited high platelet contractile force and low platelet count, the onset of bleeding symptoms correlated with a decrease in platelet forces. Unlike bulk or micro-clot assays, our assay functions as a "stress test" of single platelets by placing them in conditions that maximize contractility, and in both cases, the reduction in the subpopulation of highly contractile platelets is correlated with bleeding severity. As such, our work suggests that single platelet forces could be used as a diagnostic biomarker to assess bleeding risk in patients with ITP regardless of count (Fig 2C-D). Disclosures Bennett: Novartis: Research Funding. Lam:Sanguina, LLC: Equity Ownership.

Iterated Function Systems with the Weak Average Contraction Conditions

This paper concerns the chaos game of random iterated function systems. We consider a random iterated function system IFS() generated by a finite family of Lipschitz maps on a compact ball of ℝn with the weak average contraction condition and show that it admits a quasi-attractor satisfying the deterministic chaos game. In particular, these properties are preserved under small perturbations of the iterated function system IFS() with respect to the Lipschitz topology.

Effects of Foot Instability Variations on Muscle Activation during Front Plank Exercise

Adding instability is a common method of increasing the difficulty of an exercise. Front plank exercise is often performed with various instability types and levels; however, how induced instability influences muscle activation during front plank is not well-understood. PURPOSE: To examine how 4 different foot stability variations of front plank influence activation of 5 different muscles. METHODS: 19 physically active, healthy individuals (8 males, 11 females; age 39±16.0 years; height 1.68±0.1 m; mass 75±17.51 kg) performed each of 4 plank variations in a randomized order. The foot stability was modified by placing the feet: 1) on a level, stable floor (FLOOR); 2) on an elevated stable step (STEP); 3) in elevated suspension straps (SUSPEND); 4) on a rubber dome (DOME). STEP, SUSPEND and DOME were height-matched for foot placement. Electromyography of 5 muscles, rectus abdominis (RA), external oblique abdominis (EO), rectus femoris (RF), serratus anterior (SA) and erector spinae (ES) during front plank with 4 different foot stability conditions was examined and normalized as % maximal voluntary isometric contraction (%MVIC). Foot stability variation effect on normalized average muscle contraction of 5-second static plank trials was assessed using one-way repeated measure ANOVA and Friedman test for normally and non-normally distributed data respectively. RESULTS: SUSPEND was associated with greater muscle activation than DOME in RF (43.2±25.8 vs. 32.9±25.9 %MVIC), p<0.05) and in RA (39.5±18.2 vs. 30.3±18.5 %MVIC, p<0.05). Compared to FLOOR, SUSPEND was associated with higher activation of SA (57.2±27.5 vs. 48.2±23.1 %MVIC, p<0.05) and ES (8.9±4.3 vs. 7.5±3.4 %MVIC, p<0.05). CONCLUSIONS: Plank with suspended feet increased average activation of muscles used in the front plank. The use of RF and RA increased primarily due to foot instability induced by suspension, and the activation of SA and ES increased with combination of instability and increased weight distribution to the upper body.

Data Center Demand Response in Deregulated Electricity Markets

With the development of deregulated electricity markets, a customer can enter a contract with one of several competing utility companies. Meanwhile, a utility company is motivated to increase its market share by helping its customers manage their energy usage and save money through demand response programs. In this paper, we study the demand response program in deregulated electricity markets for data centers that often have significant flexibility in workload scheduling. We consider the real-time pricing and model the data centers’ coupled decisions of utility company choices and workload scheduling as a many-to-one matching game with externalities . To solve such a game, we show that it admits an exact potential function, whose local minima correspond to the stable outcomes of the game. We further develop a distributed algorithm that guarantees to converge to a stable outcome. Compared with the scenario without data centers’ demand response, we show through simulation that the proposed algorithm can reduce the average contract payment of data centers by 18.7% and increase the revenue of the utility companies that offer lower electricity tariffs up to 80% by attracting more data centers as customers.

Does managed competition constrain hospitals' contract prices? Evidence from the Netherlands.

In the Dutch health care system, health insurers negotiate with hospitals about the pricing of hospital products in a managed competition framework. In this paper, we study these contract prices that became for the first time publicly available in 2016. The data show substantive price variation between hospitals for the same products, and within a hospital for the same product across insurers. About 27% of the contract prices for a hospital product are at least 20% higher or lower than the average contract price in the market. For about half of the products, the highest and the lowest contract prices across hospitals differ by a factor of three or more. Moreover, hospital product prices do not follow a consistent ranking across hospitals, suggesting substantial cross-subsidization between hospital products. Potential explanations for the large and seemingly random price variation are: (i) different cost pricing methods used by hospitals, (ii) uncertainty due to frequent changes in the hospital payment system, (iii) price adjustments related to negotiated lumpsum payments and (iv) differences in hospital and insurer market power. Several policy options are discussed to reduce variation and increase transparency of hospital prices.

Caudal Lumbar Splanchnic Nerves Provide Primary Control of the Porcine Bladder Neck

BackgroundFunctional infertility caused by retrograde ejaculation (RE) is the most significant postoperative complication following surgery for advanced stage testis cancer. This occurs because of iatrogenic injury to the sympathetic nerves of the aortic‐ and superior hypogastric plexuses in control of internal urethral sphincter (IUS) contraction, thus impairing bladder neck closure.Despite recent advancements in our anatomical understanding of these plexuses to inform nerve‐sparing surgical technique, complete preservation of all nerves is not always possible due to the extent of some cancers. As such, the most effective approach would spare only the nerves required to prevent RE (i.e., the sympathetic innervation to the bladder neck). However, the relative contribution of the nerves comprising the the aortic plexus — the intermesenteric nerves (IMN) and caudal‐most lumbar splanchnic nerves (LSN) — in control of bladder neck closure remain unknown, thus directed nerve‐sparing cannot be yet be achieved.AimTo investigate the contribution of the IMNs and LSNs in bladder neck closure.MethodUsing a translational porcine model that has been shown to have homology to the human aortic plexus, the first objective evaluated the role of the contributing nerves (the IMN &amp; LSN) in IUS contraction compared to the hypogastric nerves (HN; homologous to the human superior hypogastric plexus). For the second objective, we determined the arrangement of the fibers supplying the IUS within the ipsilateral and contralateral HNs.To achieve this, we measured IUS contraction following electrostimulation [10Hz, 30mA, 1ms pulse width, 200V, 30s] of the (1) HN, (2) LSN, and (3) IMN in an intact state (Obj #1) and following an ipsilateral HN lesion to test if relevant axons decussate proximal to the HNs (Obj #2) in three boars (85.6 ± 6.4 kg). Direct electrostimulation was performed using a bipolar electrode, and the resultant contraction was monitored using a pressure‐sensing balloon catheter.ResultsImportantly, the average IUS contraction following LSN stimulation was approximately 3.5 fold greater (157.3 ± 79.7 mmHg□s) than the ipsilateral IMN stimulation (44.0 ± 70.2 mmHg□s; p&lt;0.05). Moreover, ipsilateral LSN stimulation produced an average IUS contraction integral that rivaled the maximal response generated by ipsilateral HN stimulation (82.1% of total; 193.4 ± 107.9 mmHg□s; p&gt;0.05). Lastly, a lesion to the ipsilateral HN significantly reduced (in some cases, abolished) the response (87.2% reduction; 13.8 ± 14.2 mmHg□s; p&lt;0.05) indicating minimal decussation of fibers at the level of the aortic plexus.ConclusionThese data demonstrate that the most caudal LSNs provide the majority of sympathetic innervation to the IUS in comparison to the IMNs. In addition, few fibers within the LSNs pass contralaterally, but rather continue through an ipsilateral HN to supply the bladder neck. These findings position the LSNs as major contributors to the maintenance of normal bladder neck function in the boar. Future studies seek to test this hypothesis in retrospective clinical studies to verify the translatability to humans.Support or Funding InformationCIHR; LRCP Catalyst; Lawson IRFThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 22: Real-time Dextrous Fine Motor Control of an Advanced Prosthetic Arm Using Regenerative Peripheral Nerve Signals

PURPOSE: Peripheral nerves provide a promising source for neuroprosthetic control given that they are functionally selective and easy to access. However, current interface methods, such as penetrating electrodes, are limited either by low signal amplitude or interface instability. In contrast, Regenerative Peripheral Nerve Interfaces (RPNIs) are constructed by suturing a graft of devascularized, denervated muscle to the residual end of a severed nerve. The graft then regenerates, revascularizes, and is reinnervated by the nerve, creating a stable bioamplifier that produces high amplitude electromyography (EMG) signals. In addition, nerves can be surgically divided into fascicles to construct multiple independent RPNIs. Here, we demonstrate the extraction of hand level prosthetic control signals from RPNIs. We also demonstrate for the first time control of the DEKA Luke Prosthetic Arm from RPNIs with indwelling wires. METHODS: We implanted RPNIs in two individuals with upper limb amputations. P1 had a proximal transradial amputation and underwent implantation of 9 RPNIs implanted, with the median, ulnar, and radial nerves subdivided into four, three, and two branches, respectively. P2 had a distal transradial amputation and was implanted with a single graft on each of the median, ulnar, and radial nerves (3 total RPNIs). During acute recording sessions, we used ultrasound to locate and visualize RPNI motor contractions, and implant percutaneous fine-wire bipolar electrodes into each RPNI. P1 was subsequently implanted with 8 indwelling electrodes from Synapse Biomedical (IDE #:G160229). RESULTS: P1’s ulnar RPNIs produced signals with an average maximum voluntary contraction (MVC) of 211µV and signal-to-noise ratio (SNR) of 3.48. P2’s ulnar RPNI produced EMG signals with an average MVC of 49.2µV and SNR 7.45. Likewise, the median RPNI produced signals with an average MVC of 145µV and SNR 16.8. Using a combination of RPNI and available residual muscle signals, subjects successfully controlled a virtual prosthesis in real-time. P1 could hit targets with a virtual small finger using a position/velocity Kalman filter with 98.2% accuracy over 56 trials. Similarly, P2 could hit targets with a virtual thumb with 80.6% accuracy over 108 trials. All decoders used temporal features of the EMG waveform within 300-1500Hz and binned at 50ms. Implanted electrodes in P1 enabled real-time control of the DEKA Luke prosthetic arm. CONCLUSION: Overall, we have demonstrated that RPNIs produce motor specific contractions and high amplitude signals. Implanted electrodes enable an amputee to control numerous independent degrees of freedom in real-time with an advanced prosthetic arm.

Effect of habitual foot-strike pattern on the gastrocnemius medialis muscle-tendon interaction and muscle force production during running.

The interaction between gastrocnemius medialis (GM) muscle and Achilles tendon, i.e., muscle-tendon unit (MTU) interaction, plays an important role in minimizing the metabolic cost of running. Foot-strike pattern (FSP) has been suggested to alter MTU interaction and subsequently the metabolic cost of running. However, metabolic data from experimental studies on FSP are inconsistent, and a comparison of MTU interaction between FSP is still lacking. We, therefore, investigated the effect of habitual rearfoot and mid-/forefoot striking on MTU interaction, ankle joint work, and plantar flexor muscle force production while running at 10 and 14 km/h. GM muscle fascicles of 9 rearfoot and 10 mid-/forefoot strikers were tracked using dynamic ultrasonography during treadmill running. We collected kinetic and kinematic data and used musculoskeletal models to determine joint angles and calculate MTU lengths. In addition, we used dynamic optimization to assess plantar flexor muscle forces. During ground contact, GM fascicle shortening ( P = 0.02) and average contraction velocity ( P = 0.01) were 40-45% greater in rearfoot strikers than mid-/forefoot strikers. Differences in contraction velocity were especially prominent during early ground contact. Moreover, GM ( P = 0.02) muscle force was greater during early ground contact in mid-/forefoot strikers than rearfoot strikers. Interestingly, we did not find differences in stretch or recoil of the series elastic element between FSP. Our results suggest that, for the GM, the reduced muscle energy cost associated with lower fascicle contraction velocity in mid-/forefoot strikers may be counteracted by greater muscle forces during early ground contact. NEW & NOTEWORTHY Kinetic and kinematic differences between foot-strike patterns during running imply (not previously reported) altered muscle-tendon interaction. Here, we studied muscle-tendon interaction using ultrasonography. We found greater fascicle contraction velocities and lower muscle forces in rearfoot compared with mid-/forefoot strikers. Our results suggest that the higher metabolic energy demand due to greater fascicle contraction velocities might offset the lower metabolic energy demand due to lower muscle forces in rearfoot compared with mid-/forefoot strikers.