Rate of heat production related to degree of filament overlap in chick ALD muscle

1977 ◽  
Vol 233 (1) ◽  
pp. C1-C7 ◽  
Author(s):  
Y. Matsumoto ◽  
A. M. McPhedran
Keyword(s):  
Heat Production ◽  
Length Change ◽  
Heat Liberation ◽  
Heavy Meromyosin ◽  
Thin Filaments ◽  
Cross Bridge ◽  
Single Cross ◽  
Anterior Latissimus Dorsi ◽  
Cross Bridges ◽  
Degree Of Overlap

The anterior latissimus dorsi (ALD) of chicks (2 wk old) was examined for rate of heat liberation when the muscle was reversibly stretched from L0 to about 1.6 L0. The "plateau" forces of isometric tetani were related to the corresponding rates of heat liberation. Presumably, in this region of length change the degree of overlap between the thick and thin filaments is changing. If the amount of overlap is known, the number of heavy meromyosin cross bridges in activity can be estimated. From this information, the amount of liberated energy can be calculated for a single cross-bridge cycling. In all of our measurements, there was heat production even at muscle lengths so great that no filament overlap would have to be assumed. This finding was incorported into the estimate for energy release per cross-bridge cycling.

Heat production of rat anococcygeus muscle during isometric contraction

1988 ◽  
Vol 255 (4) ◽  
pp. C536-C542 ◽  
Author(s):  
J. S. Walker ◽  
I. R. Wendt ◽  
C. L. Gibbs
Keyword(s):  
Energy Expenditure ◽  
Heat Production ◽  
Progressive Increase ◽  
Isometric Contractions ◽  
Shortening Velocity ◽  
Anococcygeus Muscle ◽  
Cross Bridge ◽  
Time Integral ◽  
Rat Anococcygeus Muscle ◽  
Cross Bridges

Heat production, unloaded shortening velocity (Vus), and load-bearing capacity (LBC) were studied in the isolated rat anococcygeus muscle during isometric contractions at 27 degrees C. The relation between the total suprabasal heat produced and the stress-time integral for isometric contractions of various durations was curvilinear, demonstrating a decreasing slope as contractile duration increased. The rate of heat production at 600 s was approximately 68% of the peak value of 6.55 mW/g that occurred at 10 s. At the same time, force rose from a mean of 92 mN/mm2 at 10 s to a value of 140 mN/mm2 at 600 s. This produced a nearly threefold increase in the economy of force maintenance. The decline in the rate of heat production was accompanied by a decline in Vus from 0.56 Lo/s at 10 s to 0.28 Lo/s at 600 s, where Lo is the length for optimal force development. This suggests the fall in the rate of heat production was caused, at least in part, by a slowing of cross-bridge kinetics. The ratio of LBC to developed tension at 10 s was not significantly different from the ratio at 600 s, suggesting that the increase in tension was due to an increased number of attached cross bridges. The decline in heat production, therefore, appears contradictory, since an increased number of attached cross bridges would predict an increased rate of energy expenditure. The observations can be reconciled if either 1) the increase in force is caused by a progressive increase in the attachment time of a constant number of cross bridges that cycle at a lower frequency or 2) the decline in energy expenditure caused by the slowing of cross-bridge cycling is sufficient to mask the increase caused by the recruitment of additional cross bridges.

scholarly journals Stiffness-distortion sarcomere model for muscle simulation

1999 ◽  
Vol 87 (5) ◽  
pp. 1861-1876 ◽  
Author(s):  
Maria V. Razumova ◽  
Anna E. Bukatina ◽  
Kenneth B. Campbell
Keyword(s):  
Differential Equations ◽  
Kinetic Scheme ◽  
Simple Method ◽  
Thin Filaments ◽  
Cross Bridge ◽  
Model Predictions ◽  
Force Velocity ◽  
Cross Bridges ◽  
Shearing Motion ◽  
State Kinetic

A relatively simple method is presented for incorporating cross-bridge mechanisms into a muscle model. The method is based on representing force in a half sarcomere as the product of the stiffness of all parallel cross bridges and their average distortion. Differential equations for sarcomeric stiffness are derived from a three-state kinetic scheme for the cross-bridge cycle. Differential equations for average distortion are derived from a distortional balance that accounts for distortion entering and leaving due to cross-bridge cycling and for distortion imposed by shearing motion between thick and thin filaments. The distortion equations are unique and enable sarcomere mechanodynamics to be described by only a few ordinary differential equations. Model predictions of small-amplitude step and sinusoidal responses agreed well with previously described experimental results and allowed unique interpretations to be made of various response components. Similarly good results were obtained for model reproductions of force-velocity and large-amplitude step and ramp responses. The model allowed reasonable predictions of contractile behavior by taking into account what is understood to be basic muscle contractile mechanisms.

scholarly journals Stretch of active muscle during the declining phase of the calcium transient produces biphasic changes in calcium binding to the activating sites.

1990 ◽  
Vol 96 (5) ◽  
pp. 1013-1035 ◽  
Author(s):  
A M Gordon ◽  
E B Ridgway
Keyword(s):  
Calcium Binding ◽  
Time Course ◽  
Control Level ◽  
Calcium Transient ◽  
Length Change ◽  
Positive Phase ◽  
Active Force ◽  
Cross Bridge ◽  
Calcium Affinity ◽  
Cross Bridges

In voltage-clamped barnacle single muscle fibers, muscle shortening during the declining phase of the calcium transient increases myoplasmic calcium. This extra calcium is probably released from the activating sites by a change in affinity when cross-bridges break (Gordon, A. M., and E. B. Ridgway, 1987. J. Gen. Physiol. 90:321-340). Stretching the muscle at similar times causes a more complex response, a rapid increase in intracellular calcium followed by a transient decrease. The amplitudes of both phases increase with the rate and amplitude of stretch. The rapid increase, however, appears only when the muscle is stretched more than approximately 0.4%. This is above the length change that produces the breakpoint in the force record during a ramp stretch. This positive phase in response to large stretches is similar to that seen on equivalent shortening at the same point in the contraction. For stretches at different times during the calcium transient, the peak amplitude of the positive phase has a time course that is delayed relative to the calcium transient, while the peak decrease during the negative phase has an earlier time course that is more similar to the calcium transient. The amplitudes of both phases increase with increasing strength of stimulation and consequent force. When the initial muscle the active force. A large decrease in length (which drops the active force to zero) decreases the extra calcium seen on a subsequent restretch. After such a shortening step, the extra calcium on stretch recovers (50 ms half time) toward the control level with the same time course as the redeveloped force. Conversely, stretching an active fiber decreases the extra calcium on a subsequent shortening step that is imposed shortly afterward. Enhanced calcium binding due to increased length alone cannot explain our data. We hypothesize that the calcium affinity of the activating sites increases with cross-bridge attachment and further with cross-bridge strain. This accounts for the biphasic response to stretch as follows: cross-bridges detached by stretch first decrease calcium affinity, then upon reattachment increase calcium affinity due to the strained configuration brought on by the stretch. The experiments suggest that cross-bridge attachment and strain can modify calcium binding to the activating sites in intact muscle.

scholarly journals Activation Dependence of Stretch Activation in Mouse Skinned Myocardium: Implications for Ventricular Function

2006 ◽  
Vol 127 (2) ◽  
pp. 95-107 ◽  
Author(s):  
Julian E. Stelzer ◽  
Lars Larsson ◽  
Daniel P. Fitzsimons ◽  
Richard L. Moss
Keyword(s):  
Isometric Force ◽  
Force Characteristic ◽  
Stretch Activation ◽  
Thin Filaments ◽  
Cross Bridge ◽  
Steady Level ◽  
Myocardial Stretch ◽  
Myosin Subfragment 1 ◽  
Activation Response ◽  
Cross Bridges

Recent evidence suggests that ventricular ejection is partly powered by a delayed development of force, i.e., stretch activation, in regions of the ventricular wall due to stretch resulting from torsional twist of the ventricle around the apex-to-base axis. Given the potential importance of stretch activation in cardiac function, we characterized the stretch activation response and its Ca2+ dependence in murine skinned myocardium at 22°C in solutions of varying Ca2+ concentrations. Stretch activation was induced by suddenly imposing a stretch of 0.5–2.5% of initial length to the isometrically contracting muscle and then holding the muscle at the new length. The force response to stretch was multiphasic: force initially increased in proportion to the amount of stretch, reached a peak, and then declined to a minimum before redeveloping to a new steady level. This last phase of the response is the delayed force characteristic of myocardial stretch activation and is presumably due to increased attachment of cross-bridges as a consequence of stretch. The amplitude and rate of stretch activation varied with Ca2+ concentration and more specifically with the level of isometric force prior to the stretch. Since myocardial force is regulated both by Ca2+ binding to troponin-C and cross-bridge binding to thin filaments, we explored the role of cross-bridge binding in the stretch activation response using NEM-S1, a strong-binding, non-force–generating derivative of myosin subfragment 1. NEM-S1 treatment at submaximal Ca2+-activated isometric forces significantly accelerated the rate of the stretch activation response and reduced its amplitude. These data show that the rate and amplitude of myocardial stretch activation vary with the level of activation and that stretch activation involves cooperative binding of cross-bridges to the thin filament. Such a mechanism would contribute to increased systolic ejection in response to increased delivery of activator Ca2+ during excitation–contraction coupling.

The Z band in skeletal muscle in rigor exhibits the activated lattice form

1989 ◽  
Vol 47 ◽  
pp. 252-253
Author(s):  
R. J. Edwards
Keyword(s):  
Skeletal Muscle ◽  
Cross Sections ◽  
Active Tension ◽  
Thin Filaments ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges ◽  
Glycerinated Muscle

The Z band of skeletal muscle is a tetragonal array of interdigitating thin filaments from adjacent sarcomeres held together by cross connecting filaments. Two visually unique forms of the Z band (small square, ss, and basketweave, bw) can be observed by TEM of cross sections. The ss form is found in relaxed muscle and the bw is found in maximally activated muscle. The average Z spacing in the bw form is 20% largerthan in the ss form. There is a correlation between active tension and the form of the Z band. This correlation suggests that cross bridge binding in the A band is directly related to the form of the Z band. In rigor, the cross bridges are completely bound; therefore, we predicted that the Z band would exhibit the bw form. To test this hypothesis we compared unstimulated muscle to glycerinated muscle in rigor.

Direct interaction between troponin and myosin enhances the ATPase activity of heavy meromyosin

Biologia ◽  
2017 ◽  
Vol 72 (6) ◽  
Author(s):  
Nazanin Bohlooli Ghashghaee ◽  
King-Lun Li ◽  
Wen-Ji Dong
Keyword(s):  
Atpase Activity ◽  
Heart Muscle ◽  
Direct Interaction ◽  
Heavy Meromyosin ◽  
Thin Filaments ◽  
Cross Bridge ◽  
The Cross ◽  
Contractility Of The Heart

AbstractContractility of the heart muscle is a result of sliding movements between thick and thin filaments, produced by interactions between actin and myosin during the cross-bridge cycle. Activation of the myofilament is triggered by Ca

scholarly journals Phosphorylation of myosin regulatory light chain has minimal effect on kinetics and distribution of orientations of cross bridges of rabbit skeletal muscle

2014 ◽  
Vol 306 (4) ◽  
pp. R222-R233 ◽  
Author(s):  
Divya Duggal ◽  
Janhavi Nagwekar ◽  
Ryan Rich ◽  
Krishna Midde ◽  
Rafal Fudala ◽  
...  
Keyword(s):  
Light Chain ◽  
Ex Vivo ◽  
Muscle Relaxation ◽  
Force Production ◽  
Regulatory Light Chain ◽  
Power Stroke ◽  
Rabbit Muscle ◽  
Thin Filaments ◽  
Cross Bridge ◽  
Cross Bridges

Force production in muscle results from ATP-driven cyclic interactions of myosin with actin. A myosin cross bridge consists of a globular head domain, containing actin and ATP-binding sites, and a neck domain with the associated light chain 1 (LC1) and the regulatory light chain (RLC). The actin polymer serves as a “rail” over which myosin translates. Phosphorylation of the RLC is thought to play a significant role in the regulation of muscle relaxation by increasing the degree of skeletal cross-bridge disorder and increasing muscle ATPase activity. The effect of phosphorylation on skeletal cross-bridge kinetics and the distribution of orientations during steady-state contraction of rabbit muscle is investigated here. Because the kinetics and orientation of an assembly of cross bridges (XBs) can only be studied when an individual XB makes a significant contribution to the overall signal, the number of observed XBs was minimized to ∼20 by limiting the detection volume and concentration of fluorescent XBs. The autofluorescence and photobleaching from an ex vivo sample was reduced by choosing a dye that was excited in the red and observed in the far red. The interference from scattering was eliminated by gating the signal. These techniques decrease large uncertainties associated with determination of the effect of phosphorylation on a few molecules ex vivo with millisecond time resolution. In spite of the remaining uncertainties, we conclude that the state of phosphorylation of RLC had no effect on the rate of dissociation of cross bridges from thin filaments, on the rate of myosin head binding to thin filaments, and on the rate of power stroke. On the other hand, phosphorylation slightly increased the degree of disorder of active cross bridges.

Oxytocin-mediated recruitment of slowly cycling cross bridges and isometric force in rat myometrium

1996 ◽  
Vol 270 (2) ◽  
pp. E203-E208
Author(s):  
A. L. Ruzycky ◽  
B. T. Ameredes
Keyword(s):  
Isometric Force ◽  
Additional Stress ◽  
Shortening Velocity ◽  
Cycling Rate ◽  
Quick Release ◽  
Cross Bridge ◽  
Cross Bridges ◽  
Unit Stress ◽  
Release Method ◽  
The Relationship

The relationship between cross-bridge cycling rate and isometric stress was investigated in rat myometrium. Stress production by myometrial strips was measured under resting, K+ depolarization, and oxytocin-stimulated conditions. Cross-bridge cycling rates were determined from measurements of maximal unloaded shortening velocity, using the quick-release method. Force redevelopment after the quick release was used as an index of cross-bridge attachment. With maximal K+ stimulation, stress increased with increased cross-bridge cycling (+76%; P < 0.05) and attached cross bridges (+112%; P < 0.05). Addition of oxytocin during K+ stimulation further increased stress (+30%; P < 0.05). With this force component, the cross-bridge cycling rate decreased (-60%; P < 0.05) similar to that under resting conditions. Attached cross-bridges did not increase with this additional stress. The results suggest two distinct mechanisms mediating myometrial contractions. One requires elevated intracellular calcium and rapidly cycling cross bridges. The other mechanism may be independent of calcium and appears to be mediated by slowly cycling cross bridges, supporting greater unit stress.

Cross-bridge blocker BTS permits direct measurement of SR Ca2+ pump ATP utilization in toadfish swimbladder muscle fibers

2003 ◽  
Vol 285 (4) ◽  
pp. C781-C787 ◽  
Author(s):  
Iain S. Young ◽  
Claire L. Harwood ◽  
Lawrence C. Rome
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Direct Measurement ◽  
Motor Behavior ◽  
Force Generation ◽  
Skinned Fibers ◽  
Control Value ◽  
Cross Bridge ◽  
Direct Measurements ◽  
Hill Coefficients ◽  
Cross Bridges

Because the major processes involved in muscle contraction require rapid utilization of ATP, measurement of ATP utilization can provide important insights into the mechanisms of contraction. It is necessary, however, to differentiate between the contribution made by cross-bridges and that of the sarcoplasmic reticulum (SR) Ca2+ pumps. Specific and potent SR Ca2+ pump blockers have been used in skinned fibers to permit direct measurement of cross-bridge ATP utilization. Up to now, there was no analogous cross-bridge blocker. Recently, N-benzyl- p-toluene sulfonamide (BTS) was found to suppress force generation at micromolar concentrations. We tested whether BTS could be used to block cross-bridge ATP utilization, thereby permitting direct measurement of SR Ca2+ pump ATP utilization in saponin-skinned fibers. At 25 μM, BTS virtually eliminates force and cross-bridge ATP utilization (both <4% of control value). By taking advantage of the toadfish swimbladder muscle's unique right shift in its force-Ca2+ concentration ([Ca2+]) relationship, we measured SR Ca2+ pump ATP utilization in the presence and absence of BTS. At 25 μM, BTS had no effect on SR pump ATP utilization. Hence, we used BTS to make some of the first direct measurements of ATP utilization of intact SR over a physiological range of [Ca2+]at 15°C. Curve fits to SR Ca2+ pump ATP utilization vs. pCa indicate that they have much lower Hill coefficients (1.49) than that describing cross-bridge force generation vs. pCa (∼5). Furthermore, we found that BTS also effectively eliminates force generation in bundles of intact swimbladder muscle, suggesting that it will be an important tool for studying integrated SR function during normal motor behavior.

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