scholarly journals The Effect of Low-Level Activation on the Mechanical Properties of Isolated Frog Muscle Fibers

1971 ◽  
Vol 58 (2) ◽  
pp. 145-162 ◽  
Author(s):  
J. Lännergren
Keyword(s):  
Mechanical Properties ◽  
Sarcomere Length ◽  
Length Change ◽  
Ringer Solution ◽  
Tension Development ◽  
Low Level ◽  
Tension Response ◽  
Resting Tension ◽  
Hypertonic Solutions ◽  
Length Changes

The mechanical properties, as revealed by minute length changes, of isolated twitch fibers of the frog have been studied at rest and during low-level activation. Resting tension is 77 ± 23 mN/cm2 (mean ± SD) at 2.2 µm sarcomere length.1 The slope of the tension curve (ΔP/ΔL) recorded during a constant-speed length change of a resting fiber is initially large. At length changes exceeding about 0.18 % of the initial length of the fiber ΔP/ΔL falls abruptly and remains close to zero during the rest of the length change. The amplitude of the tension response is reduced after a length change and returns to normal in about 3 min. Hypertonic sucrose-Ringer solutions cause a small, maintained rise in tension up to 1.4–1.6 times normal osmotic strength. Higher sucrose concentrations cause relatively large, transient tension responses. The initial ΔP/ΔL is increased in moderately hypertonic solutions; it may be reduced in more strongly hypertonic solutions. Elevated [K]o (range 10–17.5 mM) causes a marked reduction in ΔP/ΔL. In this range of [K]o the reduction is not accompanied by changes in resting tension. Addition of 1–1.5 mM caffeine to the Ringer solution affects the resting tension very little but also reduces ΔP/ΔL. The results suggest that stiffness and tension development are not related in a simple way.

scholarly journals Local movement in stimulated frog sartorius muscle.

1981 ◽  
Vol 78 (2) ◽  
pp. 151-170 ◽  
Author(s):  
G J Stienen ◽  
T Blangé
Keyword(s):  
Relative Length ◽  
Length Change ◽  
Sartorius Muscle ◽  
Tension Development ◽  
Frog Sartorius Muscle ◽  
Local Movement ◽  
Length Changes ◽  
Two Phases ◽  
Frog Sartorius ◽  
Relative Length Change

Local movement was recorded in tetanically contracting frog sartorius muscle to estimate the nonuniformity in the distribution of compliance in the muscle preparation and the compliance that resides in the attachments of the preparation to the measuring apparatus. The stimulated muscle was also subjected to rapid length changes, and the local movements and tension responses were recorded. The results indicate that during tension development at resting length the central region of the muscle shortens at the expense of the ends. After stimulation the "shoulder" in the tension, which divided the relaxation into a slow decline and a subsequent, rather exponential decay toward zero, was accompanied by an abrupt increase in local movement. We also examined the temperature sensitivity of the two phases of relaxation. The results are consistent with the view that the decrease in tension during relaxation depends on mechanical conditions. The local movement brought about by the imposed length changes indicates that the peak value of the relative length change of the uniformly acting part was approximately 20% less than the relative length change of the whole preparation. From these observations, corrections were obtained for the compliance data derived from the tension responses. These corrections allow a comparison with data in the literature obtained from single fiber preparations. The implications for the stiffness measured during the tension responses are discussed.

Dynamic relations among length, tension, and intracellular Ca2+ in activated ferret papillary muscles

1998 ◽  
Vol 275 (6) ◽  
pp. H1957-H1962 ◽  
Author(s):  
Yasutake Saeki ◽  
Satoshi Kurihara ◽  
Kimiaki Komukai ◽  
Tetsuya Ishikawa ◽  
Kiyohiro Takigiku
Keyword(s):  
Cardiac Troponin ◽  
Muscle Length ◽  
Length Change ◽  
Troponin C ◽  
Cardiac Troponin C ◽  
Mechanical Constraints ◽  
Tension Response ◽  
Cardiac Muscles ◽  
Length Changes ◽  
Cross Bridges

To study the effects of mechanical constraints on the Ca2+ affinity of cardiac troponin C, we analyzed the tension and aequorin light (AL) responses to sinusoidal length changes (5–10% of the initial muscle length) in aequorin-injected, tetanized cardiac muscles. The amplitude of the quasi-sinusoidal tension and AL responses decreased with increasing length-perturbation frequency from 0.5 to 1 Hz at 24°C and from 1 to 3 Hz at 30°C. The increase in AL corresponded well to the decrease in tension; likewise, the decrease in AL to the increase in tension and the tension response lagged behind the length change. A further increase in frequency (>1 Hz at 24°C and >3 Hz at 30°C) markedly increased the amplitude of the tension responses but decreased the amplitude of the AL responses. The increase in AL lagged behind the decrease in tension; likewise, the decrease in AL lagged behind the increase in tension, and the tension response led the length change. From previous mechanistic interpretations of the frequency dependence of the amplitude of tension response, we argue that the Ca2+affinity of cardiac troponin C changes in parallel with the active tension (i.e., the number of active cross bridges) but not with the passive tension produced by the length perturbation-induced cross-bridge strain.

Transient tension responses of heart muscle in Ba2+ contracture to step length changes

1980 ◽  
Vol 238 (3) ◽  
pp. H340-H347 ◽  
Author(s):  
Y. Saeki ◽  
K. Sagawa ◽  
H. Suga
Keyword(s):  
Heart Muscle ◽  
Muscle Length ◽  
Length Change ◽  
Step Length ◽  
Second Phase ◽  
Tension Response ◽  
Third Phase ◽  
Different Temperatures ◽  
Length Changes ◽  
Stretch Response

To characterize mechanical properties of activated heart muscle, kitten papillary muscles in Ba2+ contracture were stretched or released stepwise, and the transient tension responses were analyzed. Various amplitudes of step length change (0.1-1.0% of Lmax) were tested from different initial lengths and at different temperatures. The tension response to either stretch or release showed four different phases, which were nearly symmetric when the input length change was 0.1% of Lmax. When the length changes was 1%, the second phase of stretch response became shorter, whereas that of release became longer. The third phase of stretch response was prolonged, whereas that of release response became obscure. The peak tension (F1) in the first phase was linearly related to the amplitude, whereas those in the second and third phase were not. Increasing temperature markedly decreased F1 and shortened the second and third phase independently of initial muscle length. These results were consistent with those properties of heart muscle in Ba2+ contracture previously characterized with sinusoidal length changes.

scholarly journals Microendoscopy reveals positive correlation in multiscale length changes and variable sarcomere lengths across different regions of human muscle

2018 ◽  
Vol 125 (6) ◽  
pp. 1812-1820 ◽  
Author(s):  
Glen A. Lichtwark ◽  
Dominic J. Farris ◽  
Xuefeng Chen ◽  
Paul W. Hodges ◽  
Scott L. Delp
Keyword(s):  
Tibialis Anterior ◽  
Sarcomere Length ◽  
Length Change ◽  
Human Muscle ◽  
Fascicle Length ◽  
Needle Probe ◽  
Distal Location ◽  
Length Changes ◽  
Sarcomere Number

Sarcomere length is a key physiological parameter that affects muscle force output; however, our understanding of the scaling of human muscle from sarcomere to whole muscle is based primarily on cadaveric data. The aims of this study were to explore the in vivo relationship between passive fascicle length and passive sarcomere length at different muscle-tendon unit lengths and determine whether sarcomere and fascicle length relationships are the same in different regions of muscle. A microendoscopy needle probe capable of in vivo sarcomere imaging was inserted into a proximal location of the human tibialis anterior muscle at three different ankle positions [5° dorsiflexion, 5° plantar flexion (PF), and 15° PF] and one distal location at a constant ankle position (5° PF distal). Ultrasound imaging of tibialis anterior fascicles, centered on the location of the needle probe, was performed for each condition to estimate fascicle length. Sarcomere length and fascicle length increased with increasing muscle-tendon unit length, although the correlation between sarcomere length change and muscle fascicle length change was only moderate ( r2 = 0.45). Passive sarcomere length was longer at the distal imaging site than the proximal site ( P = 0.01). When sarcomere number was estimated from sarcomere length and fascicle length, there were fewer sarcomeres in the fibers of distal location than the proximal location ( P = 0.01). These data demonstrate that fascicle length changes are representative of sarcomere length changes, although significant variability in sarcomere length exists within a muscle and sarcomere number per fiber is region-dependent. NEW & NOTEWORTHY Sarcomere and fascicle lengths were measured in vivo from human muscle to examine the relationship between the different scales of organization. Changes in fascicle length were moderately related to sarcomere length changes; however, sarcomere length and number per fiber varied from proximal to distal regions of the muscle. Differences in average sarcomere operating lengths across the muscle suggest potentially different stresses or strains experienced within different regions of muscle.

Decreased auxotonic sarcomere shortening in hypertrophied rabbit myocardium

1985 ◽  
Vol 249 (4) ◽  
pp. H820-H826
Author(s):  
P. B. Hultgren ◽  
B. B. Hamrell
Keyword(s):  
Right Ventricular ◽  
Sarcomere Length ◽  
Pressure Overload ◽  
Length Change ◽  
Isometric Tension ◽  
Ventricular Free Wall ◽  
Free Wall ◽  
Right Ventricular Free Wall ◽  
Tension Development ◽  
The Right

Auxotonic sarcomere length change occurs during isometric twitches of isolated cardiac muscle preparations. To assess the amount of internal work in hypertrophied myocardium, we measured auxotonic sarcomere length change during isometric tension development over a range of initial muscle and sarcomere lengths. Hypertrophy was produced by banding the pulmonary artery, which resulted in an increase in the ratio of right ventricular free wall weight to total ventricular weight (normal 0.19 +/- 0.004; hypertrophy 0.35 +/- 0.008; P less than 0.001). Right ventricular free wall trabeculae and papillary muscles were studied with optical and mechanical instrumentation, including a helium-neon laser, to measure sarcomere length and isometric twitch parameters. The resting sarcomere length-resting tension relationship was shifted to the left of normal in the hypertrophied preparations (P less than 0.001). The relationship of sarcomere length at the peak of the twitch with total tension at the same instant was shifted downward and to the right of normal in hypertrophy (P less than 0.01). For the same amount of total tension development there was less than normal sarcomere shortening in the hypertrophied preparations (P less than 0.001). Consequently, there is less than normal work per sarcomere during auxotonic sarcomere shortening in hypertrophied heart muscle. Less sarcomere work for a particular functional state is important to consider in the assessment of the basis of myocardial function in compensated pressure overload hypertrophy.

scholarly journals Medial collateral ligament reconstruction graft isometry is effected by femoral position more than tibial position

2021 ◽  
Author(s):  
Christoph Kittl ◽  
James Robinson ◽  
Michael J. Raschke ◽  
Arne Olbrich ◽  
Andre Frank ◽  
...  
Keyword(s):  
Medial Collateral Ligament ◽  
Knee Flexion ◽  
Length Change ◽  
Collateral Ligament ◽  
Complex Behaviour ◽  
Femoral Attachment ◽  
Attachment Sites ◽  
Custom Made ◽  
Length Changes ◽  
Graft Length

Abstract Purpose The purpose of this study was to examine the length change patterns of the native medial structures of the knee and determine the effect on graft length change patterns for different tibial and femoral attachment points for previously described medial reconstructions. Methods Eight cadaveric knee specimens were prepared by removing the skin and subcutaneous fat. The sartorius fascia was divided to allow clear identification of the medial ligamentous structures. Knees were then mounted in a custom-made rig and the quadriceps muscle and the iliotibial tract were loaded, using cables and hanging weights. Threads were mounted between tibial and femoral pins positioned in the anterior, middle, and posterior parts of the attachment sites of the native superficial medial collateral ligament (sMCL) and posterior oblique ligament (POL). Pins were also placed at the attachment sites relating to two commonly used medial reconstructions (Bosworth/Lind and LaPrade). Length changes between the tibiofemoral pin combinations were measured using a rotary encoder as the knee was flexed through an arc of 0–120°. Results With knee flexion, the anterior fibres of the sMCL tightened (increased in length 7.4% ± 2.9%) whilst the posterior fibres slackened (decreased in length 8.3% ± 3.1%). All fibre regions of the POL displayed a uniform lengthening of approximately 25% between 0 and 120° knee flexion. The most isometric tibiofemoral combination was between pins placed representing the middle fibres of the sMCL (Length change = 5.4% ± 2.1% with knee flexion). The simulated sMCL reconstruction that produced the least length change was the Lind/Bosworth reconstruction with the tibial attachment at the insertion of the semitendinosus and the femoral attachment in the posterior part of the native sMCL attachment side (5.4 ± 2.2%). This appeared more isometric than using the attachment positions described for the LaPrade reconstruction (10.0 ± 4.8%). Conclusion The complex behaviour of the native MCL could not be imitated by a single point-to-point combination and surgeons should be aware that small changes in the femoral MCL graft attachment position will significantly effect graft length change patterns. Reconstructing the sMCL with a semitendinosus autograft, left attached distally to its tibial insertion, would appear to have a minimal effect on length change compared to detaching it and using the native tibial attachment site. A POL graft must always be tensioned near extension to avoid capturing the knee or graft failure.

scholarly journals Enhancement of Mechanical Properties and Porosity of Concrete Using Steel Slag Coarse Aggregate

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2865
Author(s):  
Md Jihad Miah ◽  
Md. Munir Hossain Patoary ◽  
Suvash Chandra Paul ◽  
Adewumi John Babafemi ◽  
Biranchi Panda
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Microstructural Analysis ◽  
Steel Slag ◽  
Physical And Mechanical Properties ◽  
Length Change ◽  
Sustainable Building ◽  
Burnt Clay ◽  
Lower Porosity ◽  
Furnace Steel

This paper investigates the possibility of utilizing steel slags produced in the steelmaking industry as an alternative to burnt clay brick aggregate (BA) in concrete. Within this context, physical, mechanical (i.e., compressive and splitting tensile strength), length change, and durability (porosity) tests were conducted on concrete made with nine different percentage replacements (0%, 10%, 20%, 30%, 40%, 50%, 60%, 80%, and 100% by volume of BA) of BA by induction of furnace steel slag aggregate (SSA). In addition, the chemical composition of aggregate through X-ray fluorescence (XRF) analysis and microstructural analysis through scanning electron microscopy (SEM) of aggregates and concrete were performed. The experimental results show that the physical and mechanical properties of concrete made with SSA were significantly higher than that of concrete made with BA. The compressive and tensile strength increased by 73% when SSA fully replaced BA. The expansion of concrete made with SSA was a bit higher than the concrete made with BA. Furthermore, a significant lower porosity was observed for concrete made with SSA than BA, which decreased by 40% for 100% SSA concrete than 100% BA concrete. The relation between compressive and tensile strength with the porosity of concrete mixes are in agreement with the relationships presented in the literature. This study demonstrates that SSA can be used as a full replacement of BA, which is economical, conserves the natural aggregate, and is sustainable building material since burning brick produces a lot of CO2.

The Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Potentiation of Potassium-Induced Contractures by Preexposure to Subthreshold Potassium Concentrations

1972 ◽  
Vol 50 (1) ◽  
pp. 37-44 ◽  
Author(s):  
E. C. Vos ◽  
G. B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Ringer Solution ◽  
Frog Skeletal Muscle ◽  
Contractile Apparatus ◽  
Tension Development ◽  
Eventual Loss ◽  
Active Processes ◽  
Muscle Potentiation ◽  
Small Bundle

A brief exposure (about 10–30 s) of a frog's toe muscle or a small bundle of fibers from the semi-tendinosus muscle to just subthreshold potassium concentrations potentiated contractures subsequently produced by exposing the muscles to a potassium concentration slightly above the threshold. The contractures thus potentiated had greater maximum tensions, and greater rates of tension development and relaxation than control contractures elicited by the same final potassium concentration. The resistance to stretch (R.T.S.) in the first few seconds of the potentiated contractures was about twice that of control contractures. Maximum potentiation occurred with preexposures of about 30 s; longer preexposures led to a decrease of potentiation and eventually to a depression of the contracture. The potentiation was not immediately abolished when the muscle was reexposed to Ringer solution but persisted for 2 min or longer (the 'washout effect'). It was concluded that exposing a muscle to low subcontracture threshold concentrations of potassium for a few seconds primes the intracellular contractile apparatus, probably by causing an increased sarcoplasmic concentration of Ca2+ ions, resulting in a potentiation of subsequently induced submaximal potassium contractures. The increase in metabolism (or 'Solandt effect') seen under these conditions is temporally related to the decline and eventual loss of the potentiation and is probably a reflection of active processes involved in reducing the sarcoplasmic concentration of Ca2+ ions.

The location and mechanism of electromotility in guinea pig outer hair cells

1993 ◽  
Vol 70 (2) ◽  
pp. 549-558 ◽  
Author(s):  
R. Hallworth ◽  
B. N. Evans ◽  
P. Dallos
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Outer Hair Cell ◽  
Length Change ◽  
Opposite Polarity ◽  
Outer Hair Cells ◽  
Response Amplitude ◽  
Change Function ◽  
Length Changes ◽  
Diameter Change

1. The microchamber method was used to examine the motile responses of isolated guinea pig outer hair cells to electrical stimulation. In the microchamber method, an isolated cell is drawn partway into a suction pipette and stimulated transcellularly. The relative position of the cell in the microchamber is referred to as the exclusion fraction. 2. The length changes of the included and excluded segments were compared for constant sinusoidal stimulus amplitude as functions of the exclusion fraction. Both included and excluded segments showed maximal responses when the cell was excluded approximately halfway. Both segments showed smaller or absent responses when the cell was almost fully excluded or almost fully included. 3. When the cell was near to, but not at, the maximum exclusion, the included segment response amplitude was zero, whereas the excluded segment response amplitude was nonzero. In contrast, when the cell was nearly fully included, the excluded segment response amplitude was zero, but the included segment response amplitude was still detectable. A simple model of outer hair cell motility based on these results suggests that the cell has finite-resistance terminations and that the motors are restricted to a region above the nucleus and below its ciliated apex (cuticular plate). 4. The function describing length change as a function of command voltage was measured for each segment as the exclusion fraction was varied. The functions were similar at midrange exclusions (i.e., when the segments were about equal length), showing nonlinearity and saturability. The functions were strikingly different when the segment lengths were different. The effects of exclusion on the voltage to length-change functions suggested that the nonlinearity and saturability are local properties of the motility mechanism. 5. The diameter changes of both segments were examined. The segment diameter changes were always antiphasic to the length changes. This finding implies that the motility mechanism has an active antiphasic diameter component. The diameter change amplitude was a monotonically increasing function of exclusion for the included segment, and a decreasing function for the excluded segment. 6. The voltage to length-change and voltage to diameter-change functions were measured for the same cell and exclusion fraction. The voltage to diameter-change function was smaller in amplitude than the voltage to length-change function. The functions were of opposite polarity to each other, but were otherwise similar in character. Thus it is likely that the same motor mechanism is responsible for both axial and diameter deformations.

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