Hand-held model of a sarcomere to illustrate the sliding filament mechanism in muscle contraction

2009 ◽  
Vol 33 (4) ◽  
pp. 297-301 ◽  
Author(s):  
Karnyupha Jittivadhna ◽  
Pintip Ruenwongsa ◽  
Bhinyo Panijpan
Keyword(s):  
Muscle Contraction ◽  
Striated Muscle ◽  
Computer Graphic ◽  
Alternative Conceptions ◽  
Two Dimensional ◽  
Thin Filaments ◽  
Transverse Expansion ◽  
Thin Elements ◽  
Common Items ◽  
Graphic Displays

From our teaching of the contractile unit of the striated muscle, we have found limitations in using textbook illustrations of sarcomere structure and its related dynamic molecular physiological details. A hand-held model of a striated muscle sarcomere made from common items has thus been made by us to enhance students' understanding of the sliding filament mechanism as well as their appreciation of the spatial arrangements of the thick and thin filaments. The model proves to be quite efficacious in dispelling some alternative conceptions held by students exposed previously only to two-dimensional textbook illustrations and computer graphic displays. More importantly, after being taught by this hand-held device, electronmicrographic features of the A and I bands, H zone, and Z disk can be easily correlated by the students to the positions of the thick and thin elements relatively sliding past one another. The transverse expansion of the sarcomere and the constancy of its volume upon contraction are also demonstrable by the model.

The Filament Lattice of Striated Muscle

1998 ◽  
Vol 78 (2) ◽  
pp. 359-391 ◽  
Author(s):  
BARRY M. MILLMAN
Keyword(s):  
Muscle Contraction ◽  
Structural Changes ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Lattice Stability ◽  
X Ray Diffraction ◽  
Thin Filaments ◽  
Intact Muscle ◽  
Radial Forces ◽  
Speed Of Shortening

Millman, Barry M. The Filament Lattice of Striated Muscle. Physiol. Rev. 78: 359–391, 1998. — The filament lattice of striated muscle is an overlapping hexagonal array of thick and thin filaments within which muscle contraction takes place. Its structure can be studied by electron microscopy or X-ray diffraction. With the latter technique, structural changes can be monitored during contraction and other physiological conditions. The lattice of intact muscle fibers can change size through osmotic swelling or shrinking or by changing the sarcomere length of the muscle. Similarly, muscle fibers that have been chemically or mechanically skinned can be compressed with bathing solutions containing very large inert polymeric molecules. The effects of lattice change on muscle contraction in vertebrate skeletal and cardiac muscle and in invertebrate striated muscle are reviewed. The force developed, the speed of shortening, and stiffness are compared with structural changes occurring within the lattice. Radial forces between the filaments in the lattice, which can include electrostatic, Van der Waals, entropic, structural, and cross bridge, are assessed for their contributions to lattice stability and to the contraction process.

scholarly journals Estimation of Forces on Actin Filaments in Living Muscle from X-ray Diffraction Patterns and Mechanical Data

2019 ◽  
Vol 20 (23) ◽  
pp. 6044
Author(s):  
Srboljub M. Mijailovich ◽  
Momcilo Prodanovic ◽  
Thomas C. Irving
Keyword(s):  
Muscle Contraction ◽  
Striated Muscle ◽  
Thin Filaments ◽  
X Ray ◽  
Cytoskeletal Network ◽  
Molecular Events ◽  
Mechanisms Of Adaptation ◽  
Length Changes ◽  
Diffraction Patterns ◽  
Intracellular Forces

Many biological processes are triggered or driven by mechanical forces in the cytoskeletal network, but these transducing forces have rarely been assessed. Striated muscle, with its well-organized structure provides an opportunity to assess intracellular forces using small-angle X-ray fiber diffraction. We present a new methodology using Monte Carlo simulations of muscle contraction in an explicit 3D sarcomere lattice to predict the fiber deformations and length changes along thin filaments during contraction. Comparison of predicted diffraction patterns to experimental meridional X-ray reflection profiles allows assessment of the stepwise changes in intermonomer spacings and forces in the myofilaments within living muscle cells. These changes along the filament length reflect the effect of forces from randomly attached crossbridges. This approach enables correlation of the molecular events, such as the current number of attached crossbridges and the distributions of crossbridge forces to macroscopic measurements of force and length changes during muscle contraction. In addition, assessments of fluctuations in local forces in the myofilaments may reveal how variations in the filament forces acting on signaling proteins in the sarcomere M-bands and Z-discs modulate gene expression, protein synthesis and degradation, and as well to mechanisms of adaptation of muscle in response to changes in mechanical loading.

scholarly journals Comparative Biomechanics of Thick Filaments and Thin Filaments with Functional Consequences for Muscle Contraction

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Mark S. Miller ◽  
Bertrand C. W. Tanner ◽  
Lori R. Nyland ◽  
Jim O. Vigoreaux
Keyword(s):  
Mechanical Properties ◽  
Muscle Contraction ◽  
Material Properties ◽  
Muscle Function ◽  
Striated Muscle ◽  
Muscle Performance ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Functional Consequences

The scaffold of striated muscle is predominantly comprised of myosin and actin polymers known as thick filaments and thin filaments, respectively. The roles these filaments play in muscle contraction are well known, but the extent to which variations in filament mechanical properties influence muscle function is not fully understood. Here we review information on the material properties of thick filaments, thin filaments, and their primary constituents; we also discuss ways in which mechanical properties of filaments impact muscle performance.

scholarly journals CAP2 is a regulator of actin pointed end dynamics and myofibrillogenesis in cardiac muscle

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mert Colpan ◽  
Jessika Iwanski ◽  
Carol C. Gregorio
Keyword(s):  
Muscle Contraction ◽  
Cardiac Muscle ◽  
Adenylyl Cyclase ◽  
Thin Filament ◽  
Essential Role ◽  
Striated Muscle ◽  
Actin Dynamics ◽  
Actin Assembly ◽  
Thin Filaments ◽  
Pointed End

AbstractThe precise assembly of actin-based thin filaments is crucial for muscle contraction. Dysregulation of actin dynamics at thin filament pointed ends results in skeletal and cardiac myopathies. Here, we discovered adenylyl cyclase-associated protein 2 (CAP2) as a unique component of thin filament pointed ends in cardiac muscle. CAP2 has critical functions in cardiomyocytes as it depolymerizes and inhibits actin incorporation into thin filaments. Strikingly distinct from other pointed-end proteins, CAP2’s function is not enhanced but inhibited by tropomyosin and it does not directly control thin filament lengths. Furthermore, CAP2 plays an essential role in cardiomyocyte maturation by modulating pre-sarcomeric actin assembly and regulating α-actin composition in mature thin filaments. Identification of CAP2’s multifunctional roles provides missing links in our understanding of how thin filament architecture is regulated in striated muscle and it reveals there are additional factors, beyond Tmod1 and Lmod2, that modulate actin dynamics at thin filament pointed ends.

scholarly journals ULTRASTRUCTURAL STUDIES ON THE CONTRACTILE MECHANISM OF SMOOTH MUSCLE

1969 ◽  
Vol 42 (3) ◽  
pp. 683-694 ◽  
Author(s):  
Robert E. Kelly ◽  
Robert V. Rice
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Striated Muscle ◽  
Smooth Muscle Contraction ◽  
Nuclear Chromatin ◽  
Taenia Coli ◽  
Thin Filaments ◽  
Ultrastructural Studies ◽  
Thick Filaments ◽  
Morphological Differences

Fresh taenia coli and chicken gizzard smooth muscle were studied in the contracted and relaxed states. Thick and thin filaments were observed in certain (but not all) cells fixed in contraction. Relaxed smooth muscle contained only thin filaments. Several other morphological differences were observed between contracted and relaxed smooth muscle. The nuclear chromatin is clumped in contraction and evenly dispersed in the relaxed state. The sarcolemma is more highly vesiculated in contraction than in relaxation. In contraction, the sarcoplasm also appears more electron opaque. Over-all morphological differences between cells fixed in isometric and in unloaded contraction were also noticeable. The results suggest a sliding filament mechanism of smooth muscle contraction; however, in smooth muscle, unlike striated muscle, the thick filaments appear to be in a highly labile condition in the contractile process. The relation between contraction and a possible change in pH is also discussed.

Introductory Remarks

1980 ◽  
Vol 38 ◽  
pp. 598-599
Author(s):  
H. Mohri
Keyword(s):  
Muscle Contraction ◽  
Experimental Evidence ◽  
Sea Urchin ◽  
Constant Length ◽  
Thin Filaments ◽  
Bridge Formation ◽  
Thick Filaments ◽  
Sliding Mechanism ◽  
Radial Spokes ◽  
Cilia And Flagella

In 1959, Afzelius observed the presence of two rows of arms projecting from each outer doublet microtubule of the so-called 9 + 2 pattern of cilia and flagella, and suggested a possibility that the outer doublet microtubules slide with respect to each other with the aid of these arms during ciliary and flagellar movement. The identification of the arms as an ATPase, dynein, by Gibbons (1963)strengthened this hypothesis, since the ATPase-bearing heads of myosin molecules projecting from the thick filaments pull the thin filaments by cross-bridge formation during muscle contraction. The first experimental evidence for the sliding mechanism in cilia and flagella was obtained by examining the tip patterns of molluscan gill cilia by Satir (1965) who observed constant length of the microtubules during ciliary bending. Further evidence for the sliding-tubule mechanism was given by Summers and Gibbons (1971), using trypsin-treated axonemal fragments of sea urchin spermatozoa. Upon the addition of ATP, the outer doublets telescoped out from these fragments and the total length reached up to seven or more times that of the original fragment. Thus, the arms on a certain doublet microtubule can walk along the adjacent doublet when the doublet microtubules are disconnected by digestion of the interdoublet links which connect them with each other, or the radial spokes which connect them with the central pair-central sheath complex as illustrated in Fig. 1. On the basis of these pioneer works, the sliding-tubule mechanism has been established as one of the basic mechanisms for ciliary and flagellar movement.

A method for determining the periodicity of a troponin component in isolated insect flight muscle thin filaments by gold/Fab labelling

1992 ◽  
Vol 101 (3) ◽  
pp. 503-508
Author(s):  
R. Newman ◽  
G.W. Butcher ◽  
B. Bullard ◽  
K.R. Leonard
Keyword(s):  
Gold Particle ◽  
Colloidal Gold ◽  
Striated Muscle ◽  
Flight Muscle ◽  
Insect Flight ◽  
Insect Flight Muscle ◽  
Fab Fragment ◽  
Thin Filaments ◽  
Gold Particles ◽  
Almost All

Insect flight muscle has a large component (Tn-H) in the tropomyosin-troponin complex that is not present in vertebrate striated muscle thin filaments. Tn-H is shown by gold/Fab labelling to be present at regular intervals in insect flight muscle thin filaments. The Fab fragment of a monoclonal antibody to Tn-H was conjugated directly with colloidal gold and this probe used to label isolated thin filaments from the flight muscle of Lethocerus indicus (water bug). The distribution of gold particles seen in electron microscope images of negatively stained thin filaments was analysed to show that the probe bound to sites having a periodicity of approximately 40 nm, which is the expected value for the tropomyosin-troponin repeat. Conjugates of Fab with colloidal gold particles of 3 nm diameter labelled almost all sites. Conjugates with gold particles of 5 nm and 10 nm diameter labelled less efficiently (70% and 30%, respectively) but analysis of the distribution of inter-particle intervals among a number of filaments again gave the same fundamental spacing of 40 nm. The error in the measurements (standard deviation approximately +/− 4.2 for 5 nm gold/Fab) is less than earlier estimates for the size of the gold/Fab complex. Measurements on gold/Fab in negative stain suggest that the bound Fab contributes a shell about 2 nm in thickness around the gold particle. The radius of the probe (about 4.5 nm for 5 nm gold/Fab) would then be consistent with the value of error found. The size of the probe suggests that the gold particle binds to the side of the Fab molecule, rather close to the antibody combining site. The potential resolution of the technique may thus be better than originally expected.

scholarly journals Calcium ion-dependent myosin from decapod-crustacean muscles

1977 ◽  
Vol 163 (2) ◽  
pp. 291-296 ◽  
Author(s):  
W Lehman
Keyword(s):  
Calcium Ion ◽  
Adenosine Triphosphatase ◽  
Striated Muscle ◽  
Decapod Crustacean ◽  
Regulatory System ◽  
Thin Filaments ◽  
Fast Muscles

Ca2+ regulation of arthropod actomyosin adenosine triphosphatase is associated with both the thin filaments, as in vertebrates, and with the myosin, as in molluscs. The actomyosin of decapod-crustacean fast muscles was previously considered to be an exception, displaying only a Ca2+-regulatory system linked to the thin filaments and not a myosin-linked regulatory system. In the present study, myosin regulation is demonstrated in a variety of decapod muscles when they are tested under more physiological ionic conditions. Myosin regulation is shown by using mixtures of pure rabbit actin with myofibrils, with actomyosin and with purified myosin, and in each case the adenosine triphosphatase is Ca2+ dependent. Myosin regulation may also occur in vertebrate striated muscle, but seemingly is lost during purification of the myosin.

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