Theoretical determination of force-length relations of intact human skeletal muscles using the cross-bridge model

1990 ◽  
Vol 416 (1-2) ◽  
pp. 113-119 ◽  
Author(s):  
Walter Herzog ◽  
Sheila K. Abrahamse ◽  
Henk E. D. J. ter Keurs
Keyword(s):  
Skeletal Muscles ◽  
Theoretical Determination ◽  
Cross Bridge ◽  
Bridge Model ◽  
The Cross ◽  
Human Skeletal Muscles

scholarly journals Investigation of the molecular motor of muscle: from generating life in a test tube to myosin structure over beers

2021 ◽  
Vol 45 (4) ◽  
pp. 730-743
Author(s):  
Jack A. Rall
Keyword(s):  
Molecular Motor ◽  
Test Tube ◽  
In Vitro Motility Assay ◽  
Cross Bridge ◽  
Lever Arm ◽  
Bridge Model ◽  
The Cross ◽  
Cross Bridges ◽  
Globular Head

This article traces 60 years of investigation of the molecular motor of skeletal muscle from the 1940s through the 1990s. It started with the discovery that myosin interaction with actin in the presence of ATP caused shortening of threads of actin and myosin. In 1957, structures protruding from myosin filaments were seen for the first time and called “cross bridges.” A combination of techniques led to the proposal in 1969 of the “swinging-tilting cross bridge” model of contraction. In the early 1980s, a major problem arose when it was shown that a probe attached to the cross bridges did not move during contraction. A spectacular breakthrough came when it was discovered that only the cross bridge was required to support movement in an in vitro motility assay. Next it was determined that single myosin molecules caused the movement of actin filaments in 10-nm steps. The atomic structure of the cross bridge was published in 1993, and this discovery supercharged the muscle field. The cross bridge contained a globular head or motor domain that bound actin and ATP. But the most striking feature was the long tail of the cross bridge surrounded by two subunits of the myosin molecule. This structure suggested that the tail might act as a lever arm magnifying head movement. Consistent with this proposal, genetic techniques that lengthened the lever arm resulted in larger myosin steps. Thus the molecular motor of muscle operated not by the tilting of the globular head of myosin but by tilting of the lever arm generating the driving force for contraction.

Cardiac quick-release contraction mechanoenergetics analysis using a cardiac muscle cross-bridge model

1995 ◽  
Vol 268 (6) ◽  
pp. H2544-H2552
Author(s):  
T. W. Taylor ◽  
Y. Goto ◽  
K. Hata ◽  
T. Takasago ◽  
A. Saeki ◽  
...  
Keyword(s):  
Cardiac Muscle ◽  
Muscle Fiber ◽  
Rate Constants ◽  
Fiber Length ◽  
Atp Hydrolysis ◽  
Energy Utilization ◽  
Quick Release ◽  
Cross Bridge ◽  
Bridge Model ◽  
The Cross

Huxley's sliding filament cross-bridge muscle model coupled with parallel and series elastic components was simulated to examine the conflicting reports on the amount of energy saved by quick release at the peak contraction time. Cross-bridge energy utilization was determined by considering the ATP hydrolysis for the cross-bridge cycling. The quick-release cases were simulated by letting the muscle fiber suddenly shorten to the resting fiber length at peak systole, and then the contraction was allowed to continue at the resting length. Simulation results demonstrated that, using realistic parameter values, typically approximately 15% of the muscle fiber energy is used after peak systole (and approximately 30% of the cross-bridge energy), but this is also a function of the muscle fiber properties characterized by cross-bridge association and dissociation rate constants. Increasing the kinetic rate constants, the series elasticity, the initial fiber length, or the time of peak intracellular calcium will increase the amount of energy left, which may explain some of the discrepancies in the literature. Cardiac muscle hypertrophy will increase the fraction of muscle fiber energy left after peak systole to approximately 30%. The strongest indicator of the percent energy left at peak systole was the time the fiber reached peak systole, and as the fiber reached peak systole faster, the amount of energy saved by quick release increased.

scholarly journals Alignment determination of the Hayabusa2 laser altimeter (LIDAR)

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hirotomo Noda ◽  
Hiroki Senshu ◽  
Koji Matsumoto ◽  
Noriyuki Namiki ◽  
Takahide Mizuno ◽  
...  
Keyword(s):  
Altimeter Data ◽  
Gravity Assist ◽  
Laser Altimeter ◽  
Trajectory Error ◽  
Flight Data ◽  
Camera Image ◽  
Operation Period ◽  
The Cross ◽  
Along Track

AbstractIn this study, we determined the alignment of the laser altimeter aboard Hayabusa2 with respect to the spacecraft using in-flight data. Since the laser altimeter data were used to estimate the trajectory of the Hayabusa2 spacecraft, the pointing direction of the altimeter needed to be accurately determined. The boresight direction of the receiving telescope was estimated by comparing elevations of the laser altimeter data and camera images, and was confirmed by identifying prominent terrains of other datasets. The estimated boresight direction obtained by the laser link experiment in the winter of 2015, during the Earth’s gravity assist operation period, differed from the direction estimated in this study, which fell on another part of the candidate direction; this was not selected in a previous study. Assuming that the uncertainty of alignment determination of the laser altimeter boresight was 4.6 pixels in the camera image, the trajectory error of the spacecraft in the cross- and/or along-track directions was determined to be 0.4, 2.1, or 8.6 m for altitudes of 1, 5, or 20 km, respectively.

scholarly journals Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis

2021 ◽  
Author(s):  
Daiani de Campos ◽  
Lucas B.R. Orssatto ◽  
Gabriel S. Trajano ◽  
Walter Herzog ◽  
Heiliane de Brito Fontana
Keyword(s):  
Systematic Review ◽  
Skeletal Muscles ◽  
Meta Analysis ◽  
Force Enhancement ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Human Skeletal Muscles

Theoretical progress in the H2+ molecular ion: towards electron to proton mass ratio determinationThis paper was presented at the International Conference on Precision Physics of Simple Atomic Systems, held at École de Physique, les Houches, France, 30 May – 4 June, 2010.

2011 ◽  
Vol 89 (1) ◽  
pp. 103-107 ◽  
Author(s):  
J.-Ph. Karr ◽  
L. Hilico ◽  
V. I. Korobov
Keyword(s):  
High Resolution ◽  
Mass Ratio ◽  
Theoretical Determination ◽  
Atomic Systems ◽  
The Road ◽  
Theoretical Progress ◽  
Proton Mass ◽  
Accuracy Level ◽  
Ratio Determination

High resolution ro-vibrational spectroscopy of H 2+ or HD+ can lead to a significantly improved determination of the electron to proton mass ratio me/mp if the theoretical determination of transition frequencies becomes sufficiently accurate. We report on recent theoretical progress in the description of the hyperfine structure of H 2+ , as well as first steps in the evaluation of radiative corrections at order mα7. Completion of the latter calculation should allow us to reach the projected 10−10 accuracy level and open the road to mass ratio determination.

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