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.

scholarly journals THE ORGANIZATION OF CONTRACTILE FILAMENTS IN A MAMMALIAN SMOOTH MUSCLE

1970 ◽  
Vol 47 (1) ◽  
pp. 183-196 ◽  
Author(s):  
Robert V. Rice ◽  
Joan A. Moses ◽  
G. M. McManus ◽  
Arlene C. Brady ◽  
Lorraine M. Blasik
Keyword(s):  
Smooth Muscle ◽  
Thin Filament ◽  
Nearest Neighbor ◽  
Striated Muscle ◽  
Taenia Coli ◽  
X Ray Diffraction ◽  
Thin Filaments ◽  
Ordered Arrays ◽  
Thick Filaments ◽  
Filament Spacing

Ordered arrays of thin filaments (65 A diameter) along with other apparently random arrangements of thin and thick filaments (100–200 A diameter) are observed in contracted guinea pig taenia coli rapidly fixed in glutaraldehyde. The thin-filament arrays vary from a few to more than 100 filaments in each array. The arrays are scattered among isolated thin and thick filaments. Some arrays are regular such as hexagonal; other arrays tend to be circular. However, few examples of rosettes with regular arrangements of thin filaments surrounding thick filaments are seen. Optical transforms of electron micrographs of thin-filament arrays give a nearest-neighbor spacing of the thin filaments in agreement with the "actin" filament spacing from x-ray diffraction experiments. Many thick filaments are closely associated with thin-filament arrays. Some thick filaments are hollow circles, although triangular shapes are also found. Thin-filament arrays and thick filaments extend into the cell for distances of at least a micron. Partially relaxed taenia coli shows thin-filament arrays but few thick filaments. The suggestion that thick filaments aggregate prior to contraction and disaggregate during relaxation is promoted by these observations. The results suggest that a sliding filament mechanism operates in smooth muscle as well as in striated muscle.

scholarly journals LOCALIZATION OF MYOSIN FILAMENTS IN SMOOTH MUSCLE

1968 ◽  
Vol 37 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Robert E. Kelly ◽  
Robert V. Rice
Keyword(s):  
Smooth Muscle ◽  
Cross Section ◽  
Striated Muscle ◽  
Thick Filament ◽  
Longitudinal Axis ◽  
Thin Filaments ◽  
Chicken Gizzard ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Muscle Myosin

Thick myosin filaments, in addition to actin filaments, were found in sections of glycerinated chicken gizzard smooth muscle when fixed at a pH below 6.6. The thick filaments were often grouped into bundles and run in the longitudinal axis of the smooth muscle cell. Each thick filament was surrounded by a number of thin filaments, giving the filament arrangement a rosette appearance in cross-section. The exact ratio of thick filaments to thin filaments could not be determined since most arrays were not so regular as those commonly found in striated muscle. Some rosettes had seven or eight thin filaments surrounding a single thick filament. Homogenates of smooth muscle of chicken gizzard also showed both thick and thin filaments when the isolation was carried out at a pH below 6.6, but only thin filaments were found at pH 7.4. No Z or M lines were observed in chicken gizzard muscle containing both thick and thin filaments. The lack of these organizing structures may allow smooth muscle myosin to disaggregate readily at pH 7.4.

Blebbistatin, a myosin II inhibitor, suppresses contraction and disrupts contractile filaments organization of skinned taenia cecum from guinea pig

2010 ◽  
Vol 298 (5) ◽  
pp. C1118-C1126 ◽  
Author(s):  
Masaru Watanabe ◽  
Masatoshi Yumoto ◽  
Hideyuki Tanaka ◽  
Hon Hui Wang ◽  
Takeshi Katayama ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Smooth Muscle Contraction ◽  
Myosin Light Chain Phosphorylation ◽  
Thin Filaments ◽  
Tension Development

To explore the precise mechanisms of the inhibitory effects of blebbistatin, a potent inhibitor of myosin II, on smooth muscle contraction, we studied the blebbistatin effects on the mechanical properties and the structure of contractile filaments of skinned (cell membrane permeabilized) preparations from guinea pig taenia cecum. Blebbistatin at 10 μM or higher suppressed Ca2+-induced tension development at any given Ca2+ concentration but had little effects on the Ca2+-induced myosin light chain phosphorylation. Blebbistatin also suppressed the 10 and 2.75 mM Mg2+-induced, “myosin light chain phosphorylation-independent” tension development at more than 10 μM. Furthermore, blebbistatin induced conformational change of smooth muscle myosin (SMM) and disrupted arrangement of SMM and thin filaments, resulting in inhibition of actin-SMM interaction irrespective of activation with Ca2+. In addition, blebbistatin partially inhibited Mg2+-ATPase activity of native actomyosin from guinea pig taenia cecum at around 10 μM. These results suggested that blebbistatin suppressed skinned smooth muscle contraction through disruption of structure of SMM by the agent.

The influence of temperature on the thick filaments of vertebrate smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 197-202 ◽  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pigs ◽  
Taenia Coli ◽  
Thin Filaments ◽  
Influence Of Temperature ◽  
Thick Filaments ◽  
Influence Of Temperature On ◽  
10 Nm Filaments ◽  
Ion Analysis

When fixation of taenia coli from adult guinea-pigs is initiated at 37 °C only thin filaments and 10 nm filaments are preserved. At 37 °G (i.e. as in vivo ) thick filaments are very labile; to preserve them during fixation much thinner muscles must be used such as taenia coli from very young animals. The thick filaments from taenia coli of adult guinea-pigs can however be stabilized by pre-cooling the living muscles before fixation at 37 °C. An ion analysis of these muscles in vivo, and during fixation at 37 and 4 °C, showed that there is a K and Na ion exchange in the tissue both on cooling and during fixation; the exchange is most rapid on fixation particularly when it takes place at 37 °C. The Mg 2+ content appears to be unaffected by these conditions, but the Ca 2+ content rises both on cooling and during fixation (when the uptake is unexpectedly large). The selective destruction of the cell membrane is greatest when fixation is carried out at 37 °C. It is suggested that pre-cooling may alter thick filaments.

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 THICK FILAMENTS IN VASCULAR SMOOTH MUSCLE

1971 ◽  
Vol 49 (3) ◽  
pp. 636-649 ◽  
Author(s):  
Carrick E. Devine ◽  
Andrew P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Actin Filaments ◽  
Vas Deferens ◽  
Average Diameter ◽  
Physiological Salt Solution ◽  
Taenia Coli ◽  
Striated Muscles ◽  
Thin Filaments ◽  
Thick Filaments

Two sets of myofilaments were demonstrated after incubation of strips of rabbit portal-anterior mesenteric vein under moderate stretch in a physiological salt solution. Thick filaments had a mean diameter of 18 nm and reached a maximum length of 1.4 µm with a mean length of 0.61 µm. In transverse sections, 2.5–5 nm particles were resolved as subunits of the thick filaments. Thin filaments had an average diameter of 8.4 nm and generally conformed to the structure believed to represent actin filaments in smooth and striated muscles. In the areas of maximum concentration there were 160–328 thick filaments/µm2 and the lowest ratio of thin to thick filaments was 12:1. Thick filaments were present in approximately equal numbers in vascular smooth muscle relaxed by theophylline, in Ca++-free solution, or contracted by norepinephrine. The same preparatory procedures used with vascular smooth muscle also enabled us to visualize thick filaments in guinea pig and rabbit taenia coli and vas deferens.

scholarly journals The Huxley crossbridge model as the basic mechanism for airway smooth muscle contraction

2019 ◽  
Vol 317 (2) ◽  
pp. L235-L246 ◽  
Author(s):  
Ling Luo ◽  
Lu Wang ◽  
Peter D. Paré ◽  
Chun Y. Seow ◽  
Pasquale Chitano
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Airway Smooth Muscle ◽  
Time Course ◽  
Striated Muscle ◽  
Isometric Force ◽  
Smooth Muscle Contraction ◽  
Time Dependent ◽  
Shortening Velocity ◽  
Mlc20 Phosphorylation

The cyclic interaction between myosin crossbridges and actin filaments underlies smooth muscle contraction. Phosphorylation of the 20-kDa myosin light chain (MLC20) is a crucial step in activating the crossbridge cycle. Our current understanding of smooth muscle contraction is based on observed correlations among MLC20 phosphorylation, maximal shortening velocity ( Vmax), and isometric force over the time course of contraction. However, during contraction there are changes in the extent of phosphorylation of many additional proteins as well as changes in activation of enzymes associated with the signaling pathways. As a consequence, the mechanical manifestation of muscle contraction is likely to change with time. To simplify the study of these relationships, we measured the mechanical properties of airway smooth muscle at different levels of MLC20 phosphorylation at a fixed time during contraction. A simple correlation emerged when time-dependent variables were fixed. MLC20 phosphorylation was found to be directly and linearly correlated with the active stress, stiffness, and power of the muscle; the observed weak dependence of Vmax on MLC20 phosphorylation could be explained by the presence of an internal load in the muscle preparation. These results can be entirely explained by the Huxley crossbridge model. We conclude that when the influence of time-dependent events during contraction is held constant, the basic crossbridge mechanism in smooth muscle is the same as that in striated muscle.

Smooth muscle: contraction hypothesis based on the arrangement of actin and myosin filaments in different states of contraction*

1973 ◽  
Vol 265 (867) ◽  
pp. 213-217 ◽  
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Hexagonal Lattice ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Thin Filaments ◽  
Random Fashion ◽  
Filament Bundles ◽  
Small Contraction ◽  
Electron Microscopical

Electron microscopical studies were m ade of the changes occurring during contraction of mouse taenia coli. In relaxed fibres actin filaments were found clearly ordered into bundles. W ithin the bundles the filaments were often arranged in rows or in a hexagonal lattice. In the areas between the filament bundles thick filaments were detected. The shortened fibres showed a different appearance. Thick and thin filaments were interm ingled in a random fashion. By com paring these findings with observations m ade on invertebrate smooth muscles, a model for smooth muscle contraction is proposed. According to this hypothesis the contractile apparatus of smooth muscles is composed of small contraction units of interdigitating bundles of thick and thin filaments. They seem to be irregularly shaped and random ly arranged. During the contraction the sets of filaments slide into each other. The result is the intermingling of the thick and thin filaments found in contracted fibres.

scholarly journals Myosin Crossbridge, Contractile Unit, and the Mechanism of Contraction in Airway Smooth Muscle: A Mechanical Engineer's Perspective

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Airway Smooth Muscle ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Structural Data ◽  
Smooth Muscle Contraction ◽  
Shortening Velocity ◽  
Mathematical Analyses ◽  
Myosin Motors

Muscle contraction is caused by the action of myosin motors within the structural confines of contractile unit arrays. When the force generated by cyclic interactions between myosin crossbridges and actin filaments is greater than the average load shared by the crossbridges, sliding of the actin filaments occurs and the muscle shortens. The shortening velocity as a function of muscle load can be described mathematically by a hyperbola; this characteristic force–velocity relationship stems from stochastic interactions between the crossbridges and the actin filaments. Beyond the actomyosin interaction, there is not yet a unified theory explaining smooth muscle contraction, mainly because the structure of the contractile unit in smooth muscle (akin to the sarcomere in striated muscle) is still undefined. In this review, functional and structural data from airway smooth muscle are analyzed in an engineering approach of quantification and correlation to support a model of the contractile unit with characteristics revealed by mathematical analyses and behavior matched by experimental observation.

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