scholarly journals Regulation of muscular contraction. Distribution of actin control and myosin control in the animal kingdom.

1975 ◽  
Vol 66 (1) ◽  
pp. 1-30 ◽  
Author(s):  
W Lehman ◽  
A G Szent-Györgyi
Keyword(s):  
Atpase Activity ◽  
Control Systems ◽  
Striated Muscle ◽  
Muscular Contraction ◽  
Striated Muscles ◽  
Functional Tests ◽  
Simple Correlation ◽  
Thin Filaments ◽  
Fast Muscles

The control systems regulating muscle contraction in approximately 100 organisms have been categorized. Both myosin control and actin control operate simultaneously in the majority of invertebrates tested. These include insects, chelicerates, most crustaceans, annelids, priapulids, nematodes, and some sipunculids. Single myosin control is present in the muscles of molluscs, brachiopods, echinoderms, echiuroids, and nemertine worms. Single actin control was found in the fast muscles of decapods, in mysidacea, in a single sipunculid species, and in vertebrate striated muscles. Classification is based on functional tests that include measurements of the calcium dependence of the actomyosin ATPase activity in the presence and the absence of purified rabbit actin and myosin. In addition, isolated thin filaments and myosins were also analyzed. Molluscs lack actin control since troponin is not present in sufficient quantities. Even though the functional tests indicate the complete lack of myosin control in vertebrate striated muscle, it is difficult to exclude unambiguously the in vivo existence of this regulation. Both control systems have been found in animals from phyla which evolved early. We cannot ascribe any simple correlation between ATPase activity, muscle structure, and regulatory mechanisms.

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.

scholarly journals THE PATHOGENESIS OF WAXY DEGENERATION OF STRIATED MUSCLES (ZENKER'S DEGENERATION)

1909 ◽  
Vol 11 (1) ◽  
pp. 1-9 ◽  
Author(s):  
H. Gideon Wells
Keyword(s):  
Lactic Acid ◽  
Striated Muscle ◽  
Negative Evidence ◽  
Striated Muscles ◽  
Positive Evidence ◽  
Striated Muscle Fibers ◽  
Positive Results ◽  
Stimulation Of

In view of theoretical deductions and the positive results obtained in the above experiments, it would seem probable that the production of waxy degeneration depends upon the action of lactic acid which is formed by the living muscle under the stimulation of infecting bacteria or their toxins, the formation of large amounts of lactic acid and its accumulation being perhaps favored by defective circulation through the injured muscle. The hyaline transformation of muscle acted upon by lactic acid is analogous to the swelling of fibrin placed in dilute acids. This view is supported by both negative and positive experimental evidence—the negative evidence being that simple anemic necrosis, aseptic or antiseptic autolysis whether in vivo or in vitro, or the action of bacteria of various sorts on muscle in vitro, are all incapable of causing changes in muscle cells resembling those characteristic of waxy or hyaline degeneration of striated muscle. The positive evidence consists in the demonstration that lactic acid, even in dilutions comparable to the amounts that can be formed in living muscle, can produce a similar or identical waxy transformation of the striated muscle fibers, both in vitro and in vivo; and also the observation that muscles stimulated to exhaustion, under which condition lactic acid is known to accumulate in the muscle, show microscopically changes identical with those of Zenker's waxy degeneration.

scholarly journals THE ULTRASTRUCTURE OF FROG VENTRICULAR CARDIAC MUSCLE AND ITS RELATIONSHIP TO MECHANISMS OF EXCITATION-CONTRACTION COUPLING

1968 ◽  
Vol 38 (1) ◽  
pp. 99-114 ◽  
Author(s):  
Nancy A. Staley ◽  
Ellis S. Benson
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Striated Muscle ◽  
Structural Features ◽  
Mammalian Skeletal Muscle ◽  
Striated Muscles ◽  
Thin Filaments ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Dense Granules

Frog ventricular cardiac muscle has structural features which set it apart from frog and mammalian skeletal muscle and mammalian cardiac muscle. In describing these differences, our attention focused chiefly on the distribution of cellular membranes. Abundant inter cellular clefts, the absence of tranverse tubules, and the paucity of sarcotubules, together with exceedingly small cell diameters (less than 5 µ), support the suggestion that the mechanism of excitation-contraction coupling differs in these muscle cells from that now thought to be characteristic of striated muscle such as skeletal muscle and mammalian cardiac muscle. These structural dissimilarities also imply that the mechanism of relaxation in frog ventricular muscle differs from that considered typical of other striated muscles. Additional ultrastructural features of frog ventricular heart muscle include spherical electron-opaque bodies on thin filaments, inconstantly present, forming a rank across the I band about 150 mµ from the Z line, and membrane-bounded dense granules resembling neurosecretory granules. The functional significance of these features is not yet clear.

scholarly journals Analysis of myofibrillar structure and assembly using fluorescently labeled contractile proteins.

1984 ◽  
Vol 98 (3) ◽  
pp. 825-833 ◽  
Author(s):  
J W Sanger ◽  
B Mittal ◽  
J M Sanger
Keyword(s):  
Actin Filaments ◽  
Striated Muscle ◽  
Contractile Proteins ◽  
Actin Binding ◽  
Thin Filaments ◽  
In Vitro System ◽  
Self Association ◽  
Cross Bridges

To study how contractile proteins become organized into sarcomeric units in striated muscle, we have exposed glycerinated myofibrils to fluorescently labeled actin, alpha-actinin, and tropomyosin. In this in vitro system, alpha-actinin bound to the Z-bands and the binding could not be saturated by prior addition of excess unlabeled alpha-actinin. Conditions known to prevent self-association of alpha-actinin, however, blocked the binding of fluorescently labeled alpha-actinin to Z-bands. When tropomyosin was removed from the myofibrils, alpha-actinin then added to the thin filaments as well as the Z-bands. Actin bound in a doublet pattern to the regions of the myosin filaments where there were free cross-bridges i.e., in that part of the A-band free of interdigitating native thin filaments but not in the center of the A-band which lacks cross-bridges. In the presence of 0.1-0.2 mM ATP, no actin binding occurred. When unlabeled alpha-actinin was added first to myofibrils and then labeled actin was added fluorescence occurred not in a doublet pattern but along the entire length of the myofibril. Tropomyosin did not bind to myofibrils unless the existing tropomyosin was first removed, in which case it added to the thin filaments in the l-band. Tropomyosin did bind, however, to the exogenously added tropomyosin-free actin that localizes as a doublet in the A-band. These results indicate that the alpha-actinin present in Z-bands of myofibrils is fully complexed with actin, but can bind exogenous alpha-actinin and, if actin is added subsequently, the exogenous alpha-actinin in the Z-band will bind the newly formed fluorescent actin filaments. Myofibrillar actin filaments did not increase in length when G-actin was present under polymerizing conditions, nor did they bind any added tropomyosin. These observations are discussed in terms of the structure and in vivo assembly of myofibrils.

scholarly journals Troponin Variants as Markers of Skeletal Muscle Health and Diseases

2021 ◽  
Vol 12 ◽  
Author(s):  
Monica Rasmussen ◽  
Jian-Ping Jin
Keyword(s):  
Skeletal Muscle ◽  
Troponin I ◽  
Striated Muscle ◽  
Troponin T ◽  
Muscle Quality ◽  
Striated Muscles ◽  
Thin Filaments ◽  
Age Related ◽  
Development And Aging ◽  
Regulation Of Muscle Contraction

Ca2+-regulated contractility is a key determinant of the quality of muscles. The sarcomeric myofilament proteins are essential players in the contraction of striated muscles. The troponin complex in the actin thin filaments plays a central role in the Ca2+-regulation of muscle contraction and relaxation. Among the three subunits of troponin, the Ca2+-binding subunit troponin C (TnC) is a member of the calmodulin super family whereas troponin I (TnI, the inhibitory subunit) and troponin T (TnT, the tropomyosin-binding and thin filament anchoring subunit) are striated muscle-specific regulatory proteins. Muscle type-specific isoforms of troponin subunits are expressed in fast and slow twitch fibers and are regulated during development and aging, and in adaptation to exercise or disuse. TnT also evolved with various alternative splice forms as an added capacity of muscle functional diversity. Mutations of troponin subunits cause myopathies. Owing to their physiological and pathological importance, troponin variants can be used as specific markers to define muscle quality. In this focused review, we will explore the use of troponin variants as markers for the fiber contents, developmental and differentiation states, contractile functions, and physiological or pathophysiological adaptations of skeletal muscle. As protein structure defines function, profile of troponin variants illustrates how changes at the myofilament level confer functional qualities at the fiber level. Moreover, understanding of the role of troponin modifications and mutants in determining muscle contractility in age-related decline of muscle function and in myopathies informs an approach to improve human health.

scholarly journals Molecular-scale visualization of sarcomere contraction within native cardiomyocytes

2020 ◽  
Author(s):  
Laura Burbaum ◽  
Jonathan Schneider ◽  
Sarah Scholze ◽  
Ralph T Böttcher ◽  
Wolfgang Baumeister ◽  
...  
Keyword(s):  
Thin Filament ◽  
Striated Muscle ◽  
Hexagonal Lattice ◽  
Muscular Contraction ◽  
Neonatal Rat ◽  
Molecular Architecture ◽  
Thin Filaments ◽  
Rat Cardiomyocytes ◽  
Thick Filaments ◽  
Activated State

Sarcomeres, the basic contractile units of striated muscle, produce the forces driving muscular contraction through cross-bridge interactions between actin-containing thin filaments and myosin II-based thick filaments. Until now, direct visualization of the molecular architecture underlying sarcomere contractility has remained elusive. Here, we use in situ cryo-electron to-mography to unveil sarcomere contraction in frozen-hydrated neonatal rat cardiomyocytes. We show that the hexagonal lattice of the thick filaments is already established at the neonatal stage, with an excess of thin filaments outside the trigonal positions. Structural assessment of actin polarity by subtomogram averaging reveals that thin filaments in the fully activated state form overlapping arrays of opposite polarity in the center of the sarcomere. Our approach provides direct evidence for thin filament sliding during muscle contraction and may serve as a basis for structural understanding of thin filament activation and actomyosin interactions inside unperturbed cellular environments.

scholarly journals Downsizing the molecular spring of the giant protein titin reveals that skeletal muscle titin determines passive stiffness and drives longitudinal hypertrophy

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Ambjorn Brynnel ◽  
Yaeren Hernandez ◽  
Balazs Kiss ◽  
Johan Lindqvist ◽  
Maya Adler ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Mouse Model ◽  
Striated Muscle ◽  
Super Resolution ◽  
Editorial Note ◽  
Passive Stiffness ◽  
Thin Filaments ◽  
In Series ◽  
Active Force Generation

Titin, the largest protein known, forms an elastic myofilament in the striated muscle sarcomere. To establish titin’s contribution to skeletal muscle passive stiffness, relative to that of the extracellular matrix, a mouse model was created in which titin’s molecular spring region was shortened by deleting 47 exons, the TtnΔ112-158 model. RNA sequencing and super-resolution microscopy predicts a much stiffer titin molecule. Mechanical studies with this novel mouse model support that titin is the main determinant of skeletal muscle passive stiffness. Unexpectedly, the in vivo sarcomere length working range was shifted to shorter lengths in TtnΔ112-158 mice, due to a ~ 30% increase in the number of sarcomeres in series (longitudinal hypertrophy). The expected effect of this shift on active force generation was minimized through a shortening of thin filaments that was discovered in TtnΔ112-158 mice. Thus, skeletal muscle titin is the dominant determinant of physiological passive stiffness and drives longitudinal hypertrophy.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (<xref ref-type="decision-letter" rid="SA1">see decision letter</xref>).

scholarly journals ULTRASTRUCTURAL ORGANIZATION OF OBLIQUELY STRIATED MUSCLE FIBERS IN ASCARIS LUMBRICOIDES

1965 ◽  
Vol 25 (3) ◽  
pp. 495-515 ◽  
Author(s):  
Jack Rosenbluth
Keyword(s):  
Plasma Membrane ◽  
Striated Muscle ◽  
Muscle Fibers ◽  
Electron Microscopic Examination ◽  
Thick Filament ◽  
Ultrastructural Organization ◽  
Striated Muscles ◽  
Three Dimensional Model ◽  
Electron Microscopic ◽  
Thin Filaments

The somatic musculature of the nematode, Ascaris, is currently thought to consist of smooth muscle fibers, which contain intracellular supporting fibrils arranged in a regular pattern. Electron microscopic examination shows that the muscle fibers are, in fact, comparable to the striated muscles of vertebrates in that they contain interdigitating arrays of thick and thin myofilaments which form H, A, and I bands. In the A bands each thick filament is surrounded by about 10 to 12 thin filaments. The earlier confusion about the classification of this muscle probably arose from the fact that in one longitudinal plane the myofilaments are markedly staggered and, as a result, the striations in that plane of section are not transverse but oblique, forming an angle of only about 6° with the filament axis. The apparent direction of the striations changes with the plane of the section and may vary all the way from radial to longitudinal. A three-dimensional model is proposed which accounts for the appearance of this muscle in various planes. Z lines as such are absent but are replaced by smaller, less orderly, counterpart "Z bundles" to which thin filaments attach. These bundles are closely associated with fibrillar dense bodies and with deep infoldings of the plasma membrane. The invaginations of the plasma membrane together with intracellular, flattened, membranous cisternae form dyads and triads. It is suggested that these complexes, which also occur at the cell surface, may constitute strategically located, low-impedance patches through which local currents are channeled selectively.

Interstitial anion distribution in striated muscle determined with [35S]sulfate and [3H]sucrose

1979 ◽  
Vol 237 (3) ◽  
pp. C125-C130 ◽  
Author(s):  
D. D. Macchia ◽  
E. Page ◽  
P. I. Polimeni
Keyword(s):  
Left Ventricle ◽  
Striated Muscle ◽  
Extracellular Volume ◽  
Striated Muscles ◽  
Double Labeling ◽  
Fixed Charges ◽  
Anion Exclusion ◽  
Anion Distribution ◽  
Rat Ventricle

The distributions of a charged and an uncharged extracellular tracer in the interstitial spaces of skeletal and heart muscles were examined in vivo by a double-labeling technique. 35SO4(2-) and [3H]sucrose were simultaneously injected intraperitoneally into rats and toads, and extracellular volume was determined in the rat gastrocnemius and left ventricle and in the toad semitendinosus. In nephrectomized rats and in toads with intact kidneys, sucrose and SO4(2-) spaces were constant for several hours. Sucrose and SO4(2-) spaces did not significantly differ in rat ventricle (P greater than 0.80); in rat gastrocnemius the sucrose space was much larger than SO4(2-) space (2P less than 0.0005), while in toad semitendinosus sucrose space was somewhat smaller than SO4(2-) space (2P less than 0.005). These observations suggest that fixed charges in the interstitial compartment can lead to extracellular anion exclusion in some tissues and perhaps to accumulation in others. The magnitude and direction of these effects differ for different striated muscles.

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