Mechanism and significance of early, rapid shortening in sensitized airway smooth muscleThis article is one of a selection of papers published in the Special Issue on Recent Advances in Asthma Research.

2007 ◽  
Vol 85 (7) ◽  
pp. 747-753 ◽  
Author(s):  
Lincoln E. Ford ◽  
Susan H. Gilbert
Keyword(s):  
Myosin Light Chain ◽  
Force Production ◽  
Muscle Length ◽  
Airway Disease ◽  
Shortening Velocity ◽  
Reactive Airway Disease ◽  
Activation Rate ◽  
Contractile Parameters ◽  
Stage Process ◽  
Selection Of

It has been reported that sensitization of animals to allergens increases both early shortening velocity and myosin light-chain kinase of their airway smooth muscle without increasing force generated by these muscles. Since early shortening sets muscle length for the duration of a contraction, these responses might be expected to produce greater airway obstruction. Here, it is explained how the more rapid early shortening without increased force production is predicted by the 2-stage process of activation followed by contraction posited by the crossbridge theory of contraction when the rate, but not the extent, of activation is increased. The experimental results are reproduced by a simple model in which activation rate is increased 1.6-fold without any other changes in contractile parameters. These results reinforce suggestions that sensitized animals are a model for reactive airway disease.

The EMG-force relationship of the cat soleus muscle and its association with contractile conditions during locomotion.

1995 ◽  
Vol 198 (4) ◽  
pp. 975-987 ◽  
Author(s):  
A C Guimaraes ◽  
W Herzog ◽  
T L Allinger ◽  
Y T Zhang
Keyword(s):  
Soleus Muscle ◽  
Adaptive Filtering ◽  
Muscle Activation ◽  
Stance Phase ◽  
Force Production ◽  
Muscle Length ◽  
Force Transducer ◽  
Shortening Velocity ◽  
Integrated Emg ◽  
Filtering Approach

The relationship between force and electromyographic (EMG) signals of the cat soleus muscle was obtained for three animals during locomotion at five different speeds (154 steps), using implanted EMG electrodes and a force transducer. Experimentally obtained force-IEMG (= integrated EMG) relationships were compared with theoretically predicted instantaneous activation levels calculated by dividing the measured force by the predicted maximal force that the muscle could possibly generate as a function of its instantaneous contractile conditions. In addition, muscular forces were estimated from the corresponding EMG records exclusively using an adaptive filtering approach. Mean force-IEMG relationships were highly non-linear but similar in shape for different cats and different speeds of locomotion. The theoretically predicted activation-time plots typically showed two peaks, as did the IEMG-time plots. The first IEMG peak tended to be higher than the second one and it appeared to be associated with the initial priming of the muscle for force production at paw contact and the peak force observed early during the stance phase. The second IEMG peak appeared to be a burst of high muscle activation, which might have compensated for the levels of muscle length and shortening velocity that were suboptimal during the latter part of the stance phase. Although it was difficult to explain the soleus forces on the basis of the theoretically predicted instantaneous activation levels, it was straightforward to approximate these forces accurately from EMG data using an adaptive filtering approach.

Work-dependent deactivation of a crustacean muscle

1999 ◽  
Vol 202 (18) ◽  
pp. 2551-2565 ◽  
Author(s):  
R.K. Josephson ◽  
D.R. Stokes
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Carcinus Maenas ◽  
Stimulus Frequency ◽  
Force Production ◽  
Muscle Length ◽  
Background Level ◽  
Shortening Velocity ◽  
Shortening Deactivation ◽  
Work Done

Active shortening of respiratory muscle L2B from the crab Carcinus maenas results in contractile deactivation, seen as (1) a decline of force during the course of isovelocity shortening, (2) a reduction in the rate of force redevelopment following shortening, (3) a depression of the level of isometric force reached following shortening, and (4) an accelerated relaxation at the end of stimulation. The degree of deactivation increases with increasing distance of shortening, decreases with increasing shortening velocity, and is approximately linearly related to the work done during shortening. Deactivation lasts many seconds if stimulation is maintained, but is largely although not completely removed if the stimulation is temporarily interrupted so that the force drops towards the resting level. Deactivation for a given distance and velocity of shortening increases with increasing muscle length above the optimum length for force production. Stimulating muscle L2B at suboptimal frequencies gives tetanic contractions that are fully fused but of less than maximal amplitude. The depression of force following shortening, relative to the force during an isometric contraction, is independent of the stimulus frequency used to activate the muscle, indicating that deactivation is not a function of the background level of stimulus-controlled muscle activation upon which it occurs. Deactivation reduces the work required to restretch a muscle after it has shortened, but it also lowers the force and therefore the work done during shortening. The net effect of deactivation on work output over a full shortening/lengthening cycle is unknown.

Myosin phosphorylation, force, and maximal shortening velocity in neurally stimulated tracheal smooth muscle

1985 ◽  
Vol 249 (3) ◽  
pp. C238-C247 ◽  
Author(s):  
K. E. Kamm ◽  
J. T. Stull
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Isometric Force ◽  
Muscle Length ◽  
Temporal Correlation ◽  
Tracheal Smooth Muscle ◽  
Shortening Velocity ◽  
Bathing Medium ◽  
Myosin Phosphorylation

Field stimulation of intrinsic nerves in bovine tracheal smooth muscle strips elicited atropine-sensitive contractions that were more rapid than those obtained by addition of carbamylcholine to the bathing medium. These stimulus conditions were used to improve estimates of maximal rates of activation as indicated by myosin light chain phosphorylation, maximal shortening velocity (Vo), and isometric force. Maximal values of Vo [0.25 X optimal muscle length X s-1] and light chain phosphorylation (0.65 mol phosphate/mol light chain) were attained after 5 s of stimulation and preceded maximal force (60 s). Force gradually fell to 0.85 times maximal values during 30 min of stimulation, while both light chain phosphorylation and Vo declined to 0.3 times the maximal value. The temporal correlation between light chain phosphorylation and Vo supports the hypothesis that myosin phosphorylation in smooth muscle functions in regulating cross-bridge cycling rates. Myosin was dephosphorylated during relaxation with a half time of 2.7 s. Calculated maximal cellular rates of light chain phosphorylation were similar to measured values, indicating that most of the kinase was activated on stimulation.

scholarly journals Ultrasound imaging links soleus muscle neuromechanics and energetics during human walking with elastic ankle exoskeletons

2020 ◽  
Author(s):  
R.W. Nuckols ◽  
T.J.M Dick ◽  
O.N. Beck ◽  
G.S. Sawicki
Keyword(s):  
Metabolic Rate ◽  
Ultrasound Imaging ◽  
Soleus Muscle ◽  
Force Production ◽  
Metabolic Cost ◽  
Flexor Muscle ◽  
Shortening Velocity ◽  
Activation Rate ◽  
Force Activation ◽  
Muscle Contractile

ABSTRACTUnpowered exoskeletons with springs in parallel to human plantar flexor muscle-tendons can reduce the metabolic cost of walking. We used ultrasound imaging to look ‘under the skin’ and measure how exoskeleton stiffness alters soleus muscle contractile dynamics and shapes the user’s metabolic rate during walking. Eleven participants (4F, 7M; age: 27.7 ± 3.3 years) walked on a treadmill at 1.25 m s-1 and 0% grade with elastic ankle exoskeletons (rotational stiffness: 0-250 Nm rad-1) in one training and two testing days. Metabolic savings were maximized (4.2%) at a stiffness of 50 Nm rad-1. As exoskeleton stiffness increased, the soleus muscle operated at longer lengths and improved economy (force/activation) during early stance, but this benefit was offset by faster shortening velocity and poorer economy in late stance. Changes in soleus activation rate correlated with changes in users’ metabolic rate (p = 0.038, R2 = 0.44), highlighting a crucial link between muscle neuromechanics and exoskeleton performance; perhaps informing future ‘muscle-in-the loop’ exoskeleton controllers designed to steer contractile dynamics toward more economical force production.

Surgical Techniques for Tonsillectomy and Perioperative Respiratory Complications in Children

2021 ◽  
pp. 019459982110151
Author(s):  
Rahul G. Baijal ◽  
Karla E. Wyatt ◽  
Teniola Shittu ◽  
Eugenia Y. Chen ◽  
Eric Z. Wei ◽  
...  
Keyword(s):  
Surgical Technique ◽  
Chart Review ◽  
Surgical Techniques ◽  
Retrospective Chart Review ◽  
Airway Disease ◽  
Respiratory Complications ◽  
Patient Factors ◽  
Children's Hospital ◽  
Reactive Airway Disease ◽  
Children’S Hospital

Objectives The aim of this study was to determine the incidence of perioperative respiratory complications in children following tonsillectomy with cold and hot dissection surgical techniques. Study Design The study was a retrospective cohort study. Setting Retrospective chart review was performed for all children presenting for a tonsillectomy at Texas Children’s Hospital from November 2015 to December 2017. Methods Pre- and intraoperative patient factors, including surgical technique with cold or hot dissection (electrocautery or radiofrequency ablation), and perioperative anesthetic factors were collected to determine the incidence of perioperative respiratory complications. Results A total of 2437 patients underwent a tonsillectomy at Texas Children’s Hospital from November 2015 to December 2017. The incidence of perioperative respiratory complications was 20.0% (n = 487). Sickle cell disease, cardiac disease, reactive airway disease, pulmonary disease, age >2 and <3 years, and obesity, defined as a body mass index >95th percentile for age, were significant for overall perioperative respiratory complications. There was no difference in the incidence of perioperative respiratory complications in children undergoing tonsillectomy by cold or hot dissection. Conclusion Perioperative respiratory complications following tonsillectomy are more affected by patient factors than surgical technique.

The effects of pH on force and stiffness development in mouse muscles

1987 ◽  
Vol 65 (8) ◽  
pp. 1798-1801 ◽  
Author(s):  
J. M. Renaud ◽  
R. B. Stein ◽  
T. Gordon
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Force Production ◽  
Muscle Length ◽  
Low Ph ◽  
Muscle Stiffness ◽  
Average Force ◽  
Cross Bridge ◽  
Effects Of Ph ◽  
Cross Bridges

Changes in force and stiffness during contractions of mouse extensor digitorum longus and soleus muscles were measured over a range of extracellular pH from 6.4 to 7.4. Muscle stiffness was measured using small amplitude (<0.1% of muscle length), high frequency (1.5 kHz) oscillations in length. Twitch force was not significantly affected by changes in pH, but the peak force during repetitive stimulation (2, 3, and 20 pulses) was decreased significantly as the pH was reduced. Changes in muscle stiffness with pH were in the same direction, but smaller in extent. If the number of attached cross-bridges in the muscle can be determined from the measurement of small amplitude, high frequency muscle stiffness, then these findings suggest that (a) the number of cross-bridges between thick and thin filaments declines in low pH and (b) the average force per cross-bridge also declines in low pH. The decline in force per cross-bridge could arise from a reduction in the ability of cross-bridges to generate force during their state of active force production and (or) in an increased percentage of bonds in a low force, "rigor" state.

Selected Contribution: Effect of chronic passive length change on airway smooth muscle length-tension relationship

2001 ◽  
Vol 90 (2) ◽  
pp. 734-740 ◽  
Author(s):  
Lu Wang ◽  
Peter D. Paré ◽  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Force Production ◽  
Muscle Length ◽  
Electrical Field Stimulation ◽  
Length Change ◽  
Electrical Field ◽  
Optimal Length ◽  
Active Length ◽  
Reference Length ◽  
Relationship Of

The ability of rabbit trachealis to undergo plastic adaptation to chronic shortening or lengthening was assessed by setting the muscle preparations at three lengths for 24 h in relaxed state: a reference length in which applied force was ∼1–2% of maximal active force (Po) and lengths considerably shorter and longer than the reference. Passive and active length-tension ( L-T) curves for the preparations were then obtained by electrical field stimulation at progressively increasing muscle length. Classically shaped L-T curves were obtained with a distinct optimal length ( L o) at which Podeveloped; however, both the active and passive L-T curves were shifted, whereas Po remained unchanged. L o was 72% and 148% that of the reference preparations for the passively shortened and lengthened muscles, respectively. The results suggest that chronic narrowing of the airways could induce a shift in the L-T relationship of smooth muscle, resulting in a maintained potential for maximal force production.

Delivering Nebulized Medication to Infants and Toddlers

1996 ◽  
Vol 17 (9) ◽  
pp. 327-327
Author(s):  
James Seidel
Keyword(s):  
Young Children ◽  
Airway Disease ◽  
Dose Inhaler ◽  
Systemic Effects ◽  
Infants And Toddlers ◽  
Metered Dose Inhaler ◽  
Reactive Airway Disease ◽  
Reactive Airway ◽  
Metered Dose ◽  
Infants And Young Children

Several aerosolized drugs are available for the management of reactive airway disease. Nebulized drugs are given directly into the airway, which minimizes the systemic effects of musculoskeletal tremor, anxiety, and cardiovascular stimulation in most patients. Although infants and young children can be given medication via a metered dose inhaler that has a spacer, these children may not generate enough inspiratory pressure to open the oneway valve on the spacer fully.

Proposed guidelines for treatment of recurrent failures for sustainability of results in the post-project improvement stage process

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Caio Melo Almeida ◽  
Fernando Oliveira Araujo ◽  
Chrystyane Gerth Silveira Abreu ◽  
Haydee Maria Correia da Silveira Batista
Keyword(s):  
Process Improvement ◽  
Process Performance ◽  
Mining Company ◽  
Improvement Project ◽  
Content Type ◽  
Stage Process ◽  
Improvement Programs ◽  
Low Performance ◽  
Methodological Aspects ◽  
Selection Of

PurposeThe maintenance of process improvement programs within organizations is not an easy task. Some processes do not maintain the results achieved with the improvement project and again present low performance shortly after completion of the project. This paper aims to identify the socio-technical causes responsible for the loss of process performance after applying improvement projects, in order to support the mitigation of the problem.Design/methodology/approachA systematic review of the literature was carried out, which allowed the selection of 28 articles. The empirical stage used the benchmarking technique, along a large Brazilian mining company with an international standard of production and quality. This organization has been using improvement projects for more than ten years.FindingsThe research complements the literature regarding the prioritization of the 26 identified failures and the identification of seven new failure factors and two resources. Findings in this study can be an inspiration for other organizations, considering the similarity of methodological aspects of improvement projects since internationally standardized methodologies such as Six Sigma, Lean, Kaizen and 5S are used.Originality/valueThe research presented a proposal of guidelines that corroborate to the mitigation of loss of process performance after improvement project.

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