Unit Recruitment Research Articles

Abstract TP69: Change Over Time Feature Of A Range Of The Recruited Motor Unit In The Recovery Period Of Hemispheric Stroke

The paralysis after the stroke makes loss adjustment of the force in the voluntary movement and disturbs the physical activity. The voluntary force is regulated by the motor unit (MU) recruitment and firing rate. Therefore, we should evaluate MU firing patterns to understand a part of the mechanism of the force adjustment disorders of the paralysis side. It might be possible to evaluate the change of the force adjustment function on the paralysis side in the convalescence if we considered a range of the recruited MU over time. This pilot study hypothesizes that a range of the recruited MU spreads depending on a recovery stage. Two-stroke patients participated in this study. We measured the muscle activity of the biceps using surface EMG with three-time points during the recovery period after stroke. The raw EMG data were decomposed into motor unit action potential (MUAP). Then mean firing rate (MFR) and peak amplitude of MUAP were calculated by decomposed MUAP. Additionally, coefficients of the regression line were calculated by MFR and MUAP's peak amplitude. The coefficient of the linear regression line was adopted as the outcome to evaluate a range of the recruited MU size. We also analyzed the change over time of a range of the recruited MU size. The range of the recruited MU of the recovery stage changed over time but became wide during the recovery stage. These data showed that it varied from a restrictive style to a comprehensive recruitment style over time. Therefore, a range of the recruited MU with the stroke of the recovery stage was suggested to be a tendency to enlarge over time. Expanding the diachronic range of the recruited MU may let you enrich a variation of the force in the recovery process.

Mechanosensitive recruitment of stator units promotes binding of the response regulator CheY-P to the flagellar motor

Reversible switching of the bacterial flagellar motor between clockwise (CW) and counterclockwise (CCW) rotation is necessary for chemotaxis, which enables cells to swim towards favorable chemical habitats. Increase in the viscous resistance to the rotation of the motor (mechanical load) inhibits switching. However, cells must maintain homeostasis in switching to navigate within environments of different viscosities. The mechanism by which the cell maintains optimal chemotactic function under varying loads is not understood. Here, we show that the flagellar motor allosterically controls the binding affinity of the chemotaxis response regulator, CheY-P, to the flagellar switch complex by modulating the mechanical forces acting on the rotor. Mechanosensitive CheY-P binding compensates for the load-induced loss of switching by precisely adapting the switch response to a mechanical stimulus. The interplay between mechanical forces and CheY-P binding tunes the chemotactic function to match the load. This adaptive response of the chemotaxis output to mechanical stimuli resembles the proprioceptive feedback in the neuromuscular systems of insects and vertebrates.

INTERFERENCES EFFECTS BETWEEN OSTEOCYTES LOCATED AT THE SAME ZONE DURING BONE REMODELING PERIOD: A THEORETICAL AND NUMERICAL STUDY

Background: Several analytical models have been developed in the past to analyze the specific role of osteocytes in the process of bone remodeling, which can be considered as the response of bone material to functional requirements. Most of them considered both the number of osteocytes and their spatial distribution in one area of influence, while others suggested in addition to include considerations of the size of the basic multi-cellular unit. Methods: Taking advantage of previous works, the standard model equation is revisited by incorporating two complementary parameters: (a) the possibility of resorption of osteocytes, apoptosis or function inhibition during remodeling process triggered by the transduction phase of osteocytes embedded within the bone matrix and; (b) the interference of influence zones for the same osteocyte. Results: Bone density evolution has been calculated starting with a medical imaging of an implanted femur. It is shown that the management of interference zone and the possibility of resorption or inhibition of osteocytes have a direct impact upon the value of the mechanical stimulus and hence on the recruitment of Bone Multicellular Units (BMUs). From a mathematical point of view, this effect has been considered by modifying mechanical stimulus of the standard model such that it is impacted by a scalar factor ranged in the interval (0.5–1). Conclusion: It is clearly demonstrated that predicted of the added bone mass amount shows that the new model is more active in low density regions where requiring rapid adaptation to the behavior of the implant, and that the standard model takes the lead in the regions with high density.

P80-F The spectrum of involuntary movements in patients with motor neuron disease – A cross-sectional study

Background We have commonly observed involuntary jerks and tremor in patients with otherwise typical motor neuron disease (MND). We conducted prospective clinical study to explore their prevalence and phenomenology. Materials and methods Seventy-four consecutive patients were clinically examined by movement disorders specialists. Based on regularity and distribution, movements observed at rest were classified as minipolymioclonus (MPMC) or rest thumb tremor (RTT) and movements present during action as action MPMC or action tremor. Results Involuntary movements (IMs) were present in 54 patients (73%). Rest MPMC was present in 26 (35%), RTT in 22 (31%), action MPMC in 22 (30%) and action tremor in 20 patients (27%), with some overlap. Sixteen patients (22%) reported negative impact of IMs on their ability to use hands. Regression model showed that lower distal muscle power and less prominent upper motor neuron (UMN) signs significantly increased the probability of I. Conclusions IMs are common yet largely overlooked feature of MND and may have negative impact on patient’s functional abilities. Lower distal muscle power increased the probability of IMs of fingers and wrist, suggesting that generation of IMs in MND patients is associated with muscle weakness. The presence of UMN signs decreased the probability of IMs, possibly by increasing muscle and joint stiffness. Overall, our findings suggest IMs in MND patients are of peripheral origin. We propose that IMs are caused by activation of enlarged motor units without sufficient previous recruitment of smaller units to smooth their contraction during action and by their spontaneous firing at rest.

2025

OBJECTIVES/SPECIFIC AIMS: To establish a state-wide research registry of diverse participants. METHODS/STUDY POPULATION: We garnered broad institutional and community support by involving TRI’s Community Engagement team, its Community Advisory Board (CAB), and 3 UAMS patient CABs in selecting Web site content, images, and colors. Using this feedback, the TRI Recruitment Unit (RU), in conjunction with UAMS Communications and the Center for Health Literacy, developed the materials and crafted comprehensive communication and recruitment strategies. The UAMS Center for Pacific Islander Health, Hispanic faculty, and CAB members translated materials. UAMS IT programmed the user-friendly site to allow registration from smartphones and i-Pads and linked to UAMS patient electronic health messages. RESULTS/ANTICIPATED RESULTS: The RU committee implemented successful innovative strategies, including recruiting at the Arkansas State Fair and ballgames, attended by people of all races, ages, and socio-economic levels. Using i-Pads at the sites, recruitment took <5 minutes/registrant. Within 8 months, >2400 participants from across Arkansas had joined the registry: 14% African-Americans, 8% Pacific Islanders, 5% Hispanic, and 3% Native American. DISCUSSION/SIGNIFICANCE OF IMPACT: Involving CAB multidisciplinary input to design and implement recruitment materials was highly successful. Despite challenges of recruiting under-represented groups, the registry includes 30% minorities. By tracking registrants’ demographics with Lime Survey software, the RU will prioritize future recruitment events to maximize diversity of registrants.

144-P A cost-benefit analysis for recruitment of adult donors versus cord blood units in the be the match registry

144-P A cost-benefit analysis for recruitment of adult donors versus cord blood units in the be the match registry

The Armies of al-Mamūn in Khurāsān (193-202/809 — 817-18): Recruitment of its Contingents and their Commanders and their Social-Ethnic Composition

The following subjects are elaborated on in this article: a) The recruitment of commanders and military units in Marw. The most important was āhir b. al-usayn and other members of his family; b) The mobilization of a non-Arab army from Khurāsān and Transoxiana; c) A discussion on the three chief commanders of al-Mamūn (and also others), āhir b. al-usayn, and two of the most honoured commanders of al-Abnā, Harthama b. Ayan and Zuhayr b. al-Musayyab b. Zuhayr; d) The armies of al-asan b. Sahl in al-Irāq from 198 or 199/813-814, which at the beginning mainly consisted of the armies of Harthama and Zuhayr b. al-Musayyab, the Abnāwīs; e) The stiff opposition to al-Mamūn and to al-Fal b. Sahl in Khurāsān.A notable opposition to al-Mamūn and al-Fal b. Sahl was that of Harthama b. Ayan and another senior Abnāwī. It seems that the main reason for this opposition, which eventually ended in Harthama’s execution in Marw, was his opposition to the murder of al-Amīn that was carried out with the agreement and approval of al-Mamūn. Close study of the evidence on the senior commanders who were sent by al-Mamūn from Marw to al-Irāq (between 200-203/815-818) reveals that most of them were in fact Arabs, or belonged to veteran families of the Abnā. Only rare information is given about the ethnic nature of their contingents; there is no evidence of non-Arab commanders or troops sent from Marw.

Long-term effects of two protective-ventilation strategies in an ARDS model: Open Lung Approach by EIT versus ARDSnet

Different ventilatory strategies for the acute respiratory distress syndrome have been proposed. The Open Lung Approach (OLA) emphasizes the recruitment of airway units with avoidance of tidal recruitment. The ARDSnet strategy simply emphasizes the reduction of and hyperdistension. We studied the long-term VT consequences of both strategies in a controlled experiment where pigs where randomized and submitted to one of both strategies for 48 hours. Lung injury was induced by saline lavage followed by 3 hours of injurious mechanical ventilation. In the OLA arm, PEEP was selected by the EIT after a recruitment maneuver (RM), trying to keep lung collapse to a minimum, while the ARDSnet group followed a PEEP × FiO2 table. We scrutinized lung function at the end of a 48-hour period of lung protection, after a standardized RM. The concept was to provide equivalent conditions for lungs to perform, irrespective of lung history or treatment in previous days, in terms of gas exchange or alveolar stability during slow-deflation maneuvers. Before sacrifice and after maximum RM, we collected blood gases and expiratory pressure versus ΔZ (impedance changes by electric impedance tomography). Oxygenation and alveolar stability were equally impaired in both arms after injury. However, at the end of the 48 hours there was significant improvement in the capacity of oxygenation in the OLA arm (mean = 494 mmHg; P = 0.043), but not in the ARDSNet arm (mean = 278; P = 0.285). The potential to maintain airspace volumes improved along the protective period in the OLA arm, but deteriorated in the ARDSnet arm. (See Figure ​Figure11.) Figure 1

A registry of high-frequency oscillatory ventilation in adults

High-frequency oscillatory ventilation (HFOV) theoretically provides the ideal mode of ventilation for patients with acute lung injury. By avoiding repeated recruitment and de-recruitment of lung units it has the potential to reduce ventilator-associated lung injury. In the vast majority of centres, however, it is still only used as rescue therapy for patients failing conventional ventilation (CV). In our 29-bed university hospital ITU we maintain a registry of patients receiving HFOV, and the first 25 entries are presented here.

The role of motor unit rate modulation versus recruitment in repeated submaximal voluntary contractions performed by control and spinal cord injured subjects

The relative roles of motor unit firing rate modulation and recruitment were evaluated when individuals with cervical spinal cord injury (SCI) and able-bodied controls performed a brief (6 s), 50% maximal voluntary contraction (50% MVC; target contraction) of triceps brachii every 10 s until it required maximal effort to achieve the target force. Mean (±SD) endurance times for SCI and control subjects were 34±26 and 15±5 min, respectively, at which point significant reductions in maximal triceps force had occurred. Twitch occlusion analysis in controls indicated that force declines resulted largely from peripheral contractile failure. In SCI subjects, triceps surface EMG and motor unit potential amplitude declined in parallel suggesting failure at axon branch points and/or alterations in muscle membrane properties. The force of low threshold units, measured by spike-triggered averaging, declined in SCI but not control subjects, suggesting that higher threshold units fatigued in controls. Central fatigue was also obvious after SCI. Mean (±SD) MVC motor unit firing rates declined significantly with fatigue for control (24.6±7.1 to 17.3±5.1 Hz ), but not SCI subjects (25.9±12.7 to 20.1±9.7 Hz ). Unit firing rates were unchanged during target contractions for each subject group, but with the MVC rate decreases, units of SCI and control subjects were activated intensely at endurance time (88% and 99% MVC rates, respectively). New unit recruitment also maintained the target contractions although it was limited after SCI because many descending inputs to triceps motoneurons were disrupted. This resulted in sparse EMG, even during MVCs, but allowed the same unit to be recorded throughout. These EMG data showed that both unit recruitment and rate modulation were important for maintaining force during repeated submaximal intermittent contractions of triceps brachii muscles performed by SCI subjects. Similar results were found for control subjects. Muscles weakened by SCI may therefore provide a useful model in which to directly study motor unit rate modulation and recruitment during weak or strong voluntary contractions.

Motor Skill Learning of Concentric and Eccentric Isokinetic Movements in Older Adults

Neuromuscular adaptation at the onset of resisted exercise can be observed as increases in torque and surface electromyography. The effect of learning the motor task has been hypothesized to contribute to these early increases, especially for older people. Thus, the purpose of this study was to investigate the facilitatory effects of practice on motor performance in older adults during short-term isokinetic training of the ankle dorsiflexors (DF). Twenty-eight men and women (M = 76.3 +/- 4.6 years) volunteered for a 2-week, 3-days/week strength training program. They were tested in a sitting position on a KinCom isokinetic dynamom eter at 30, 90, and 180° s-1 through 40° of DF movement (concentric and eccentric contractions). Criterion curves of lever arm angle patterns were cross-correlated with subject-generated angle patterns, showing significantly better correlations on posttest versus baseline. Smoothness and proficiency of muscle contraction improved with practice by fewer hesitations in movement and increased ability to change between concentric and eccentric muscle contractions. Increased agonist electromyography and torque were hypothesized to be secondary to greater neural drive and/or synchronization of motor unit firing rate and/or recruitment during maximal voluntary contraction, improved coordination, and adapted neural control of concentric and eccentric muscle contraction.

Analysis of free forward flight ofSchistocerca gregaria employing telemetric transmission of muscle potentials

The free flight of mature female Schistocerca gregaria loaded with a transmitter device has been video-monitored for short periods of time in the laboratory. Several flight parameters, such as body angles to horizontal and to flight path, ascent angle, and flight speed, have been analysed. These flight parameters and their interrelationships coincide with those revealed during steady free flight in the field (Baker et al. 1981. J Comp Physiol 141:233–237). Therefore, these short free flights in the laboratory represent free autonomous flight performance, but offer the possibility of controlling environmental conditions. During free flight, the firing patterns of four selected powerful depressor and elevator muscles of the fore- and hindwings were obtained by a transmitter device fixed to the prothorax of the locust. Based on the recruitment of individual motor units, a correlation of the muscle-specific activity with the aerodynamic flight parameters can be accomplished. Wing-beat frequency is positively correlated to ascent angle and to speed. The recruitment of the motor units of the forewing muscles shows a correlation with some of the flight parameters, whereas the hindwing muscles are activated in a rather immutable pattern. This argues for the importance of the forewings for maneuvering, whereas the hindwings mainly serve to provide the basic power output in flight. J. Exp. Zool. 284:119–129, 1999. © 1999 Wiley-Liss, Inc.

The effects of sciatic nerve section on the contraction force of gastrocnemius muscle in cats

The experiments were performed on anaesthetised cats gastrocnemiur muscles. Both muscles were stimulated directly through silver plate electrodes by brief trains (0.33 s) of rectangular-wave electrical impulses (0.1 ms, 100 Hz) once every 2 s. The muscles contracted in steady state conditions with force 25-30% of max contraction force. The svmnathetic nervous system was treated with ganglion _ biockator benzohexony (2.5%; 13.5-68.2 mg 2.2-15.5 mg/kg). Subsequent injection of 0.3 ml Novocain (2%) in the sciatic nerve after 30 min caused an increase of muscle contraction force (MCF) in 7 of 9 experiments by 26+4% (n=7). After section of sciatic nerve at the place of novocainization in the next 30 min the MCF further increased to 29*5% (n=5). The putting of a tourniquet on the thigh for 7 min (ischemic conditions) caused an transient increase of MCF by lOI* 1.4% (n=l7). This reaction appeared with 34k1.4 s latency and persisted for 7lk3.9 s (n=l7). The denervation of these muscles resulted in the increase of the reaction to the application of tourniquet: MCF rised by 180*3.7% (n=6); the duration of enhanced reaction was 182+19.2 sand the latent period was 144+21.4 s. Cardiac arrest by injection of air into thk v,jugularis induced a greater effect in denervated muscles (increase of MCF bv 169-205%. duration 202-306 s) as compared to that in inehated muscles (increase of MCF II l-151%, duration 98-240 s). The fast elevated effect caused by denervation is thought to result from (i) recruitment of additional neiromotor units; (ii) the rise of adrenergetic chemosensitivity of extrajunctional area; (iii) additional loss of [Ca2’], from intracellular stores.

Clustering of slowly adapting type II mechanoreceptors in human peripheral nerve and skin.

The intrafascicular organization of human peripheral nerves was studied with percutaneous microneurography in the median, radial and peroneal nerves with one-surface or two-surface thin diameter concentric needle electrodes. Data from 33 recording sites containing 47 slowly adapting type II (SAII) units were analysed. At many sites two, sometimes even three, neighbouring SAII units were recorded from the explored nerve fascicle and they had adjacent or even overlapping cutaneous receptive fields. Among pairs of SAII units found at the same site, one unit often had ongoing discharge, whereas the other was silent under resting conditions. The neighbouring SAII units were optimally activated by stretching the skin in different directions. Stretching the same skin area in different directions produced different unit recruitment. Clustered SAII units were often found in sites where Pacinian afferents and skin sympathetic activity were also recorded. No significant difference was observed in the degree of grouping of SAII units either between recordings obtained with one-surface versus two-surface electrodes or between glabrous and hairy skin. The data do not support the notion that myelinated fibres are randomly organized in peripheral nerve fascicles. Instead, the findings suggest that SAII units tend to be clustered in human peripheral nerves. Furthermore, the response of groups of SAII units to skin stretch suggests that they play a role in proprioception. Dual channel recordings with two-surface concentric needle electrodes may provide a novel approach to study fibre organization in human peripheral nerves and the behaviour of groups of nerve fibres.

Plasticity and Function-The Fate of a Free, Neurovascular Muscle Graft Ten Years Post-Reconstruction

A 16-year-old female sustained a subtotal amputation of the left thigh. Debridement resulted in a bone and soft-tissue defect of 20 cm in length. The whole quadriceps muscle was lost, and the knee joint was open. The femur was stabilized by transfer of corticocancellous bone grafts. A latissimus dorsi muscle was harvested and transferred to reconstruct the lost quadriceps muscle. The thoracodorsal nerve was coaptated to the motor branch of the femoral nerve. The years after trauma, the muscle provides excellent motor function. EMG evaluation reveals no sign of denervation; macro-electromyography reveals only a moderate enlargement of motor units. There is recruitment of all motor units. Maximum voluntary torque of the transplanted muscle has decreased, compared to the contralateral rectus femoris. Histologic evaluation demonstrates a normal skeletal muscle with typical fiber distribution. These results indicate complete adaptability of the muscle at an atypical site, with a high degree of functional and structural plasticity of the skeletal muscle. The decreased voluntary torque of the transferred latissimus dorsi depends on the lower, total-fiber, cross-sectional area--the result of a parallel fiber structure.

Motor unit forces and recruitment patterns after cervical spinal cord injury

Motor unit forces and recruitment patterns after cervical spinal cord injury

Temporal winner-take-all networks: a time-based mechanism for fast selection in neural networks

Winner-take-all (WTA) networks frequently appear in neural network models. They are primarily used for decision making and selection. As an alternative to the conventional activation-based winner-take-all mechanisms (AWTA), we present a time-based temporal-winner-take-all mechanism with O(n) space complexity and roughly O(log n) time complexity. The mechanism exploits systematic and stochastic differences between time delays within different units and connections. The TWTA and the AWTA networks are shown to be logically equivalent, but the TWTA mechanism may be more suitable than the latter for various selection tasks, especially the selection of an arbitrary unit from a set (e.g., as in unit recruitment). TWTA avoids various problems with conventional WTA, notably the difficulty of making it converge rapidly over a large range of conditions. Here we report a probabilistic analysis of the TWTA mechanism along with experimental data obtained from numerous massively parallel simulations of the TWTA mechanism on the connection machine.

Input-output relation of the somatosensory system for mechanical air-puff stimulation of the index finger in man.

This study examined input-output relation of the somatosensory system in response to mechanical air-puff stimuli applied to the volar aspect of the tip of the index finger. Compound sensory nerve action potentials (SNAPs) from the median nerve at the wrist and cerebral somatosensory evoked potentials (SEPs) were simultaneously recorded at six levels of stimulus intensity above threshold. Using the time-integral of the SNAPs and SEPs as measures of peripheral and central neural activity, a strongly accelerating power function with an exponent of 1.35 was found to describe peripheral neural function, while central neural function was described by a negatively accelerating function with a power exponent of 0.50, suggesting suppression of SEPs by recruitment of units with increasing stimulus intensity. It was concluded that input-output relation of the somatosensory system can be described by a decelerating power function with the exponent of 0.37.

Electromyogram power spectrum during dynamic contractions at different intensities of exercise

During dynamic contractions performed on a cycle ergometer, we studied the influence of motor unit (MU) recruitment on the electromyographic (EMG) spectral content by exerting mechanical power of different intensities, which was chosen to remain below the maximal aerobic power (VO2max). The spectral parameters: EMG total power (PEMG), mean (MPF) and median (MED) power frequencies, which are the most representative of the EMG spectral content, were calculated according to the EMG activity of the vastus medialis muscle (VM) and soleus muscle (SOL) of the right leg. For VM and SOL, PEMG increased linearly with exerted power demonstrating an enhancement of MU recruitment. Moreover these relationships were less scattered when exerted power was expressed as a percentage of VO2max. Changes in MPF and MED with varying exercise intensities were different from one subject to another. For a set of subjects, MPF and MED were found to be independent of exerted power. Although VM and SOL muscles are different in fibre type composition, similar results were obtained for both EMG activities. We have concluded that for dynamic contractions performed at different intensities below VO2max, the recruitment of the MU has a poor effect on the EMG spectral content whatever the predominant type of fibre.

Plasma volume expansion and PEEP in a canine model of acutePseudomonas pneumonia

Four groups of anesthetized, ventilated dogs (n = 6 in each group) inoculated endotracheally with Pseudomonas aeruginosa were studied over 5 h as bilateral, hemorrhagic pneumonia developed. Groups I and II were ventilated with zero end-expiratory pressure (ZEEP) and groups III and IV with positive end-expiratory pressure (PEEP) (8 cmH2O). Hetastarch (6%) in saline was infused intravenously to maintain similar transmural pulmonary wedge pressures (Pwtm) in groups I and III (approximately 5 mmHg) and groups II and IV (approximately 10 mmHg) throughout the experiment. The effects of plasma volume expansion were analyzed by comparing groups I and III with groups II and IV and of PEEP by comparing groups I and II with groups III and IV. The number of lobes with gross consolidation was greater in groups II (4.8 +/- 1.2) and IV (5 +/- 0.9) than in groups I (2 +/- 1.1) and III (3.3 +/- 1). The mean lung wet weight/body weight ratio was greater in groups II (40 +/- 11 g/kg) and IV (48 +/- 12 g/kg) than in groups I (19 +/- 3 g/kg) and III (32 +/- 6 g/kg) and in groups III and IV than in groups I and II. Plasma volume expansion, in the absence of PEEP (group II vs. group I), dramatically increased intrapulmonary shunt (Qs/Qt 5 h after inoculation: group II, 62 +/- 13%; group I, 25 +/- 12%). However, overall gas exchange 5 h after inoculation was not significantly different between PEEP-treated groups and ZEEP-treated groups despite more extensive disease in the former. Despite maintenance of Pwtm, cardiac output fell significantly over the 5 h study period in groups III (4.3 +/- 0.7 to 3.3 +/- 1.0 L/min) and IV (7.2 +/- 1.7 to 3.8 +/- 2.4 L/min) compared to groups I (3.8 +/- 1.0 to 3.5 +/- 1.2 L/min) and II (6.9 +/- 3.2 to 7.3 +/- 2.6 L/min). We conclude that plasma volume expansion, within the normal physiological range of Pwtm, increases the extent of pneumonia. Positive end-expiratory pressure with maintenance of Pwtm also independently increases pneumonia size, possibly by increasing pulmonary capillary hydrostatic pressure, but masks this effect by maintaining arterial oxygenation through recruitment of additional lung units for gas exchange. The data also suggest that PEEP adversely affects cardiac performance in this model of acute pneumonia.