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Richard L Lieber - One of the best experts on this subject based on the ideXlab platform.
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intraoperative and biomechanical studies of human vastus lateralis and vastus medialis Sarcomere Length operating range
Journal of Biomechanics, 2018Co-Authors: Jongsang Son, Richard L Lieber, Samuel R Ward, Andy Indresano, Kristin SheppardAbstract:The vast majority of musculoskeletal models are not validated against primary experimental data. Conversely, most human experimental measurements are not explained theoretically using models to provide a mechanistic understanding of experimental results. Here we present a study with both primary human data and primary modeling data. Intraoperative Sarcomere Length was measured on the human vastus lateralis (VL) and vastus medialis (VM) muscles (n = 8) by laser diffraction. These data were compared to a biomechanical model based on muscle architecture and moment arms obtained independently from cadaveric specimens (n = 9). Measured VL Sarcomere Length ranged from about 3.2 µm with the knee flexed to 45° to 3.8 µm with the knee flexed to 90°. These values were remarkably close to theoretical predictions. Measured VM Sarcomere Length ranged from 3.6 µm with the knee flexed to 45° to 4.1 µm with the knee flexed to 90°. These values were dramatically longer than theoretical predictions. Our measured Sarcomere Length values suggest that human vasti may have differing functions with regard to knee extension and patellar stabilization. This report underscores the importance of validating experimental data to theoretical models and vice versa.
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In Vivo Sarcomere Length Measurement in Whole Muscles during Passive Stretch and Twitch Contractions
Biophysical Journal, 2017Co-Authors: Kevin W. Young, Bill P.p. Kuo, Shawn M. O'connor, Stojan Radic, Richard L LieberAbstract:Muscle force is dictated by micrometer-scale contractile machines called Sarcomeres. Whole-muscle force drops from peak force production to zero with just a few micrometers of Sarcomere Length change. No current technology is able to capture adequate dynamic Sarcomere data in vivo, and thus we lack fundamental data needed to understand human movement and movement disorders. Methods such as diffraction, endoscopy, and optical coherence tomography have been applied to muscle but are prohibitively invasive, sensitive to motion artifact, and/or imprecise. Here, we report dynamic Sarcomere Length measurement in vivo using a combination of our recently validated resonant reflection spectroscopy method combined with optical frequency domain interferometry. Using a 250-μm-wide fiber optic probe, we captured nanometer Sarcomere Length changes from thousands of Sarcomeres on the sub-millisecond timescale during whole-muscle stretch and twitch contraction. We believe that this demonstrates the first large-scale sensing of Sarcomere dynamics in vivo, which is a necessary first step to understand movement disorders and to create patient-specific surgical interventions and rehabilitation.
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Polarization gating enables Sarcomere Length measurements by laser diffraction in fibrotic muscle
Journal of biomedical optics, 2014Co-Authors: Kevin W. Young, Sudarshan Dayanidhi, Richard L LieberAbstract:Sarcomere Length is a key parameter commonly measured in muscle physiology since it dictates striated muscle active force. Laser diffraction (LD)–based measurements of Sarcomere Length are time-efficient and sample a greater number of Sarcomeres compared with traditional microscopy–based techniques. However, a limitation to LD techniques is that signal quality is severely degraded by scattering events as photons propagate through tissue. Consequently, Sarcomere Length measurements are unattainable when the number of scattering events is sufficiently large in muscle tissue with a high scattering probability. This occurs in fibrotic skeletal muscle seen in muscular dystrophies and secondary to tissue trauma, thus eliminating the use of LD to study these skeletal muscle ailments. Here, we utilize polarization gating to extract diffracted signals that are buried in noise created by scattering. Importantly, we demonstrate that polarization-gated laser diffraction (PGLD) enables Sarcomere Length measurements in muscles from chronically immobilized mice hind limbs; these muscles have a substantial increase of intramuscular connective tissue that scatter light and disable Sarcomere Length measurements by traditional LD. Further, we compare PGLD Sarcomere Lengths to those measured by bright field (BF) and confocal microscopy as positive controls and reveal a significant bias of BF but not of confocal microscopy.
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the external anal sphincter operates at short Sarcomere Length in humans
Neurogastroenterology and Motility, 2011Co-Authors: Ravinder K Mittal, Richard L Lieber, Geoff Sheean, Bikram S Padda, Raj M RajasekaranAbstract:Background The Length at which a muscle/Sarcomere operates in vivo (operational Length) and the Length at which it generates maximal stress (optimal Length) can be quite different. In a previous study, we found that the rabbit external anal sphincter (EAS) operates on the ascending limb of the Length–tension curve, in other words at Lengths shorter than its optimal Length (short Sarcomere Length). In this study, we tested whether the human EAS muscle also operates at a short Sarcomere Length. Methods The Length–tension relationship of the EAS muscle was studied in vivo in 10 healthy nullipara women. EAS muscle Length was altered by anal distension using custom-designed probes of 5, 10, 15, and 20 mm diameter. Probes were equipped with a sleeve sensor to measure anal canal pressure. The EAS muscle electromyograph (EMG) was recorded using wire electrodes. Ultrasound images of anal canal were obtained to measure EAS muscle thickness and anal canal diameter. EAS muscle stress was calculated from the anal canal pressure, inner radius, and thickness of the EAS muscle. Key Results Rest and squeeze stress of the anal canal increased with the increase in probe size. Similarly, the change in anal canal stress, i.e. the difference between the rest and the squeeze, which represents the active contribution of EAS to the anal canal stress, increased with the increase in probe size. However, increase in probe size was not associated with an increase in the external anal sphincter EMG activity. Conclusions & Inferences Increase in EAS muscle stress with the increase in probe size, in the presence of constant EMG (neural input), demonstrates that the human EAS muscle operates on the ascending limb of the Length–tension curve or at low Sarcomere Lengths. We propose that surgically adjusting EAS Sarcomere Length may represent a novel strategy to treat fecal incontinence in humans.
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novel applications of external anal sphincter muscle Sarcomere Length to enhance the anal canal function
Neurogastroenterology and Motility, 2011Co-Authors: Mahadevan Rajasekaran, Richard L Lieber, Yanfen Jiang, Valmik Bhargava, Ravinder K MittalAbstract:Background Our recent studies show that the external anal sphincter muscle (EAS) operates at a Sarcomere Length range which is below optimal. In this study, we tested the hypothesis that by surgically increasing Sarcomere Length and bringing it close to the optimal Length, EAS muscle function and anal canal pressure can be enhanced. Methods Rabbits (n = 25) were anesthetized and subjected to either a sham or an EAS plication of different Length by placing sutures at two locations, at a distance of 13%, 20%, 28%, or 35% of the circumferential Length of the anal canal. Anal canal pressures were recorded before and after the plication. Anal canal was harvested and the EAS muscle Sarcomere Length was measured using laser diffraction. Key Results Electrical stimulation of the EAS muscle resulted in a stimulus-dependent increase in the anal canal pressure (mmHg) and EAS muscle stress (mN mm−2). A significant increase in maximal pressure (212 ± 13 after compared with 139 ± 22 before plication) as well as stress (166 ± 10 after as compared with 88 ± 14 before plication) was recorded at 20% plication Length. Passive anal canal stress at 20% plication was not significantly different compared with the sham group. The mean Sarcomere Lengths with sham and 20% plication were 2.11 and 2.60 μm, respectively. Conclusions & Inferences EAS plication resulted in a Length-dependent increase in EAS muscle Sarcomere Length with an optimal Sarcomere Length at 20% plication. These considerations may help guide repair of anal sphincter muscle defects in the humans.
Jan Fridén - One of the best experts on this subject based on the ideXlab platform.
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Sarcomere Length in wrist extensor muscles
1997Co-Authors: Richard L Lieber, Björn-ove Ljung, Jan FridénAbstract:Since the etiology of tennis elbow (lateral epicondylitis) is poorly understood, we studied the anatomical changes in the extensor carpi radialis brevis (ECRB) muscle during elbow joint rotation. Specifically, we measured ECRB Sarcomere Length, using an intraoperative laser diffraction procedure that measures muscle Sarcomere Length with an accuracy off 0.05 pm. We found an unexpected biphasic response in ECRB Sarcomere Length as the elbow was rotated from full extension to full flexion. The initial Sarcomere Length of 3.49 pm, with the elbow extended, was gradually changed to 3.68 pm, 3.34 pm, 3.81 pm, and 3.45 km with progressive elbow flexion. Based on the very nonlinear mechanical properties of skeletal muscle, this "double Lengthening" of the ECRB during progressive flexion would impose intense eccentric contractions on the muscle itself. Given that eccentric contractions cause muscle injury and subsequent inflammation, these findings may provide insights into the etiology of lateral epicondylitis.
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Sarcomere Length in wrist extensor muscles changes may provide insights into the etiology of chronic lateral epicondylitis
Acta Orthopaedica Scandinavica, 1997Co-Authors: Richard L Lieber, Björn-ove Ljung, Jan FridénAbstract:Since the etiology of tennis elbow (lateral epicondylitis) is poorly understood, we studied the anatomical changes in the extensor carpi radialis brevis (ECRB) muscle during elbow joint rotation. Specifically, we measured ECRB Sarcomere Length, using an intraoperative laser diffraction procedure that measures muscle Sarcomere Length with an accuracy of ± 0.05 |xm. We found an unexpected biphasic response in ECRB Sarcomere Length as the elbow was rotated from full extension to full flexion. the initial Sarcomere Length of 3.49 μm, with the elbow extended, was gradually changed to 3.68 μm, 3.34 |xm, 3.81 μrn, and 3.45 um with progressive elbow flexion. Based on the very nonlinear mechanical properties of skeletal muscle, this “double Lengthening” of the ECRB during progressive flexion would impose intense eccentric contractions on the muscle itself. Given that eccentric contractions cause muscle injury and subsequent inflammation, these findings may provide insights into the etiology of lateral epicondylitis.
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Sarcomere Length changes after flexor carpi ulnaris to extensor digitorum communis tendon transfer
Journal of Hand Surgery (European Volume), 1996Co-Authors: Richard L Lieber, Thomas J Burkholder, Eva Ponten, Jan FridénAbstract:Sarcomere Length was measured intraoperatively on five patients undergoing tendon transfer of the flexor carpi ulnaris (FCU) to the extensor digitorum communis (EDC) for radial nerve palsy. The most significant result was that the absolute Sarcomere legnth and Sarcomere Length operating range of the FCU increased after transfer into the EDC (p
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in vivo measurement of human wrist extensor muscle Sarcomere Length changes
Journal of Neurophysiology, 1994Co-Authors: Richard L Lieber, G J Loren, Jan FridénAbstract:1. Human extensor carpi radialis brevis (ECRB) Sarcomere Length was measured intraoperatively in five subjects using laser diffraction. 2. In a separate cadaveric study, ECRB tendons were loaded to...
Walter Herzog - One of the best experts on this subject based on the ideXlab platform.
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does partial titin degradation affect Sarcomere Length nonuniformities and force in active and passive myofibrils
American Journal of Physiology-cell Physiology, 2018Co-Authors: Venus Joumaa, Fanny Bertrand, Shuyue Liu, Sophia Poscente, Walter HerzogAbstract:The aim of this study was to determine the role of titin in preventing the development of Sarcomere Length nonuniformities following activation and after active and passive stretch by determining t...
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Does partial titin degradation affect Sarcomere Length nonuniformities and force in active and passive myofibrils
American journal of physiology. Cell physiology, 2018Co-Authors: Venus Joumaa, Fanny Bertrand, Shuyue Liu, Sophia Poscente, Walter HerzogAbstract:The aim of this study was to determine the role of titin in preventing the development of Sarcomere Length nonuniformities following activation and after active and passive stretch by determining the effect of partial titin degradation on Sarcomere Length nonuniformities and force in passive and active myofibrils. Selective partial titin degradation was performed using a low dose of trypsin. Myofibrils were set at a Sarcomere Length of 2.4 µm and then passively stretched to Sarcomere Lengths of 3.4 and 4.4 µm. In the active condition, myofibrils were set at a Sarcomere Length of 2.8 µm, activated, and actively stretched by 1 µm/Sarcomere. The extent of Sarcomere Length nonuniformities was calculated for each Sarcomere as the absolute difference between Sarcomere Length and the mean Sarcomere Length of the myofibril. Our main finding is that partial titin degradation does not increase Sarcomere Length nonuniformities after passive stretch and activation compared with when titin is intact but increases the extent of Sarcomere Length nonuniformities after active stretch. Furthermore, when titin was partially degraded, active and passive stresses were substantially reduced. These results suggest that titin plays a crucial role in actively stretched myofibrils and is likely involved in active and passive force production.
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An Examination of Sarcomere Length Non-Uniformities in Actively Stretched Muscle Myofibrils
Biophysical Journal, 2014Co-Authors: Kaleena Johnston, Azim Jinha, Walter HerzogAbstract:Residual force enhancement (RFE) is a characteristic of skeletal muscle describing the increase in force exhibited following an active stretch on the descending limb of the force-Length relationship, compared to the force of an isometric contraction at the final Length. It has previously been argued that RFE is a result of instable Sarcomeres on the descending limb, causing longer, weaker Sarcomeres to Lengthen to a greater extent than shorter, stronger Sarcomeres, when a myofibril is actively stretched. If this were the mechanism of RFE, then Sarcomeres should become more non-uniform in Length after an active stretch. The purpose of this study was to investigate Length non-uniformities between Sarcomeres within a myofibril in isometric contractions pre- and post-active stretch. We hypothesized that Sarcomere Lengths would be less uniform in the post-stretch condition. Rabbit psoas muscle myofibrils were stretched passively to an average Sarcomere Length of 3.2 μm. The myofibrils were then activated. Five seconds after full activation, myofibrils were rapidly shortened to an average Sarcomere Length of 2.4 μm, held at that Length for ten seconds and then stretched back to 3.2 μm. Individual Sarcomere Lengths were then determined during the initial isometric contraction and again following the active stretch. Standard deviations of Sarcomere Lengths were compared to analyze non-uniformity. Preliminary results gave normalized Sarcomere Length standard deviations of 5.7 % and 10.2 % for the initial isometric contraction and following active stretch respectively (103 % RFE). This supports the hypothesis that Sarcomere Lengths might be less uniform after active stretch; however, further testing will increase the sample size to 20. This will allow for a more general idea of the development of Sarcomere Length non-uniformities following active stretch and might provide additional insight into the mechanism of RFE.
Wenji Dong - One of the best experts on this subject based on the ideXlab platform.
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Sarcomere Length dependent effects on ca2 troponin regulation in myocardium expressing compliant titin
The Journal of General Physiology, 2019Co-Authors: Mei Methawasin, Bertrand C W Tanner, Hendrikus Henk Granzier, John R Solaro, Wenji DongAbstract:Cardiac performance is tightly regulated at the cardiomyocyte level by Sarcomere Length, such that increases in Sarcomere Length lead to sharply enhanced force generation at the same Ca2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how Length-dependent Ca2+-induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca2+-induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and Sarcomere Length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca2+-troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of Sarcomere Length–dependent enhancement of troponin regulation with both Ca2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted Sarcomere Length–dependent effects. These results suggest that titin-based passive tension contributes to Sarcomere Length–dependent Ca2+-troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca2+-troponin regulation of the myocardium.
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Sarcomere Length dependent effects on the interaction between ctnc and ctni in skinned papillary muscle strips
Archives of Biochemistry and Biophysics, 2016Co-Authors: Nazanin Bohlooli Ghashghaee, John R Solaro, Wenji DongAbstract:Sarcomere Length dependent activation (LDA) of myocardial force development is the cellular basis underlying the Frank-Starling law of the heart, but it is still elusive how the Sarcomeres detect the Length changes and convert them into altered activation of thin filament. In this study we investigated how the C-domain of cardiac troponin I (cTnI) functionally and structurally responds to the comprehensive effects of the Ca(2+), crossbridge, and Sarcomere Length of chemically skinned myocardial preparations. Using our in situ technique which allows for simultaneous measurements of time-resolved FRET and mechanical force of the skinned myocardial preparations, we measured changes in the FRET distance between cTnI(167C) and cTnC(89C), labeled with FRET donor and acceptor, respectively, as a function of [Ca(2+)], crossbridge state and Sarcomere Length of the skinned muscle preparations. Our results show that [Ca(2+)], cross-bridge feedback and Sarcomere Length have different effects on the structural transition of the C-domain cTnI. In particular, the interplay between crossbridges and Sarcomere Length has significant impacts on the functional structural change of the C-domain of cTnI in the relaxed state. These novel observations suggest the importance of the C-domain of cTnI and the dynamic and complex interplay between various components of myofilament in the LDA mechanism.
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Sarcomere Length dependent effects on ca2 induced troponin regulation within chemically skinned cardiac muscle fibers
Biophysical Journal, 2016Co-Authors: John R Solaro, Wenji DongAbstract:Sarcomere Length dependent activation (LDA) of myocardial force development is the cellular basis underlying the Frank-Starling law of the heart, but it is still elusive how Sarcomere detects the SL changes and converts it into altered activation of thin filament. Among the myofilament proteins, troponin and myosin are two key components that are likely involved in the LDA. The two components are functionally linked through Ca2+ activation and cross-bridge feedback. Although the active cross-bridge feedback has been strongly implicated in LDA, there was no evidence linking Sarcomere Length changes and troponin regulation until our recent study showing that Ca2+-cTnC interaction in cardiac muscle can be modulated by Sarcomere Length through cross-bridge feedback [Biophysical Journal, 107(3), 682-93 (2014)]. In this study, we continue our efforts to understand the role of the C-domain of cTnI in LDA. Specifically, we used in situ time-resolved FRET measurements to determine how the switch region of cTnI is affected by Ca2+, Sarcomere Length, and cross-bridge in skinned cardiac muscle fibers. To monitor the Ca2+-induced structural transition of the switch region, skinned myocardial fibers were reconstituted with troponin complex containing FRET donor (AEDANS) modified cTnI(167C)AEDANS and acceptor (DDPM) modified cTnC(89C)DDPM. The measured FRET distance changes show that Ca2+, strong cross-bridges and Sarcomere Length all influence the structural transition of the switching region of cTnI within myocardial fibers. The results provide a mechanism by which Sarcomere Length can modulate Ca2+-troponin regulation via strong cross-bridge binding and suggest that the Sarcomere Length dependent cross-bridge effect plays an important role in the Frank-Starling law of the heart.
Samuel R Ward - One of the best experts on this subject based on the ideXlab platform.
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intraoperative and biomechanical studies of human vastus lateralis and vastus medialis Sarcomere Length operating range
Journal of Biomechanics, 2018Co-Authors: Jongsang Son, Richard L Lieber, Samuel R Ward, Andy Indresano, Kristin SheppardAbstract:The vast majority of musculoskeletal models are not validated against primary experimental data. Conversely, most human experimental measurements are not explained theoretically using models to provide a mechanistic understanding of experimental results. Here we present a study with both primary human data and primary modeling data. Intraoperative Sarcomere Length was measured on the human vastus lateralis (VL) and vastus medialis (VM) muscles (n = 8) by laser diffraction. These data were compared to a biomechanical model based on muscle architecture and moment arms obtained independently from cadaveric specimens (n = 9). Measured VL Sarcomere Length ranged from about 3.2 µm with the knee flexed to 45° to 3.8 µm with the knee flexed to 90°. These values were remarkably close to theoretical predictions. Measured VM Sarcomere Length ranged from 3.6 µm with the knee flexed to 45° to 4.1 µm with the knee flexed to 90°. These values were dramatically longer than theoretical predictions. Our measured Sarcomere Length values suggest that human vasti may have differing functions with regard to knee extension and patellar stabilization. This report underscores the importance of validating experimental data to theoretical models and vice versa.
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A novel muscle biopsy clamp yields accurate in vivo Sarcomere Length values
Journal of biomechanics, 2008Co-Authors: Samuel R Ward, Mitsuhiko Takahashi, Taylor M. Winters, Alan Kwan, Richard L LieberAbstract:The measurement of in vivo muscle Sarcomere Length facilitates the definition of in vivo muscle functional properties and comparison of muscle designs amongst functional muscle groups. In vivo Sarcomere Lengths are available for just a handful of human muscles, largely due to the technical challenges associated with their measurement. The purpose of this report was to develop and test a muscle biopsy clamp that can quickly and accurately measure in vivo muscle Sarcomere Length. To test the device, muscle biopsies (n=23) were removed from the tibialis anterior muscles of New Zealand White rabbits immediately after Sarcomere Length measurements were made using laser diffraction. The muscle biopsy contained within the clamp was immediately fixed in Formalin for subsequent Sarcomere Length measurement. Comparisons of clamp-based and diffraction-based Sarcomere Lengths demonstrated excellent agreement between the two techniques, especially when the biopsy was obtained at relatively long Lengths (above 2.6 microm). Given the intraoperative speed and simplicity of this technique and the relatively low-cost of the biopsy clamp, this method of measuring muscle Sarcomere Length should help investigators generate much-needed in vivo muscle structural and functional data.
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Intraoperative Single-Site Sarcomere Length Measurement Accurately Reflects Whole-Muscle Sarcomere Length in the Rabbit
Journal of Hand Surgery (European Volume), 2007Co-Authors: Mitsuhiko Takahashi, Samuel R Ward, Richard L LieberAbstract:Purpose To compare single-site intraoperative Sarcomere Length values with Sarcomere Lengths measured from systematic sampling of the entire transferred muscle. Methods The tendon of the rabbit second toe extensor muscle was transposed to the ankle extensor retinaculum under levels of stretch over the Sarcomere Length range of about 2.5 μm to about 4.0 μm. Intraoperative Sarcomere Length was measured at a single site with a laser diffraction device. Whole-muscle Sarcomere Length measurement was then determined by sampling across the muscle in the proximal, middle, and distal regions. Linear regression analysis and intraclass correlation coefficients were used to validate single intraoperative Sarcomere Lengths relative to whole-muscle Sarcomere Lengths. Results Single intraoperative Sarcomere Lengths correlated strongly with average whole-muscle Sarcomere Length, although there was a systematic tendency to overestimate intraoperative Sarcomere Length. Intraoperative Sarcomere Length also matched well with all regions sampled, indicating that there was no tendency for intraoperative Sarcomere Length to better represent one region of the muscle compared with another. Conclusions These results show that intraoperative Sarcomere Lengths accurately represent the entire muscle. The relatively small Sarcomere Length variations validate the use of intraoperative Sarcomere Length measurement during tendon transfer in which the entire muscle is not available for measurement because of limited surgical exposure.
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Sarcomere Length measurement permits high resolution normalization of muscle fiber Length in architectural studies
Journal of Experimental Biology, 2005Co-Authors: Amanda Felder, Samuel R Ward, Richard L LieberAbstract:SUMMARY The use of Sarcomere Length to normalize fiber Length in architectural studies is commonly practiced but has not been explicitly validated. Using mouse hindlimb muscles as a model system, ankle joints were intentionally set to angles ranging from 30° to 150° and their muscles fixed. Tibialis anterior (TA), extensor digitorum longus (EDL) and soleus muscles were removed and their raw fiber Length measured. Sarcomere Length was then measured for each fiber Length sample and fiber Length was normalized to a standard Sarcomere Length. As expected, raw fiber Length was dependent on tibiotarsal angle ( P r 2 range 0.22–0.61), while Sarcomere Length normalization eliminated the joint-angle dependent variation in fiber Length ( P >0.24, r 2 range 0.001–0.028). Similarly, one-way ANOVA revealed no significant differences in normalized fiber Length among ankle angles for any of the three muscles ( P >0.1), regardless of animal size. To determine the resolution of the method, power calculations were performed. For all muscles studied, there was >90% chance of detecting a 15% fiber Length difference among muscles and >60% chance of detecting fiber Length differences as small as 10%. We thus conclude that the use of Sarcomere Length normalization in architectural studies permits resolution of fiber Length variations of 15% and may even be effective at resolving 10% fiber Length variations.
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Sarcomere Length measurement permits high resolution normalization of muscle fiber Length in architectural studies.
The Journal of experimental biology, 2005Co-Authors: Amanda Felder, Samuel R Ward, Richard L LieberAbstract:The use of Sarcomere Length to normalize fiber Length in architectural studies is commonly practiced but has not been explicitly validated. Using mouse hindlimb muscles as a model system, ankle joints were intentionally set to angles ranging from 30 degrees to 150 degrees and their muscles fixed. Tibialis anterior (TA), extensor digitorum longus (EDL) and soleus muscles were removed and their raw fiber Length measured. Sarcomere Length was then measured for each fiber Length sample and fiber Length was normalized to a standard Sarcomere Length. As expected, raw fiber Length was dependent on tibiotarsal angle (P < 0.0005 for all muscles, r2 range 0.22-0.61), while Sarcomere Length normalization eliminated the joint-angle dependent variation in fiber Length (P > 0.24, r2 range 0.001-0.028). Similarly, one-way ANOVA revealed no significant differences in normalized fiber Length among ankle angles for any of the three muscles (P > 0.1), regardless of animal size. To determine the resolution of the method, power calculations were performed. For all muscles studied, there was >90% chance of detecting a 15% fiber Length difference among muscles and >60% chance of detecting fiber Length differences as small as 10%. We thus conclude that the use of Sarcomere Length normalization in architectural studies permits resolution of fiber Length variations of 15% and may even be effective at resolving 10% fiber Length variations.
