scholarly journals A filamentous cytoskeleton in vertebrate smooth muscle fibers.

1976 ◽  
Vol 68 (3) ◽  
pp. 539-556 ◽  
Author(s):  
P Cooke
Keyword(s):  
Molecular Weight ◽  
Smooth Muscle ◽  
Muscle Protein ◽  
Muscle Fibers ◽  
Thin Filaments ◽  
The Third ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Cell Fractions

There are three classes of myofilaments in vertebrate smooth muscle fibers. The thin filaments correspond to actin and the thick filaments are identified with myosin. The third class of myofilaments (100 A diam) is distinguished from both the actin and the myosin on the basis of fine structure, solubility, and pattern of localization in the muscle fibers. Direct structural evidence is presented to show that the 100A filament constitute an integrated filamentous network with the dense bodies in the sarcoplasm, and that they are not connected to either the actin or myosin filaments. Examination of (a) isolated dense bodies, (b) series of consecutive sections through the dense bodies, and (c) redistributed dense bodies in stretched muscle fibers supports this conclusion. It follows that the 100-A filaments complexes constitute a structrally distinct filamentous network. Analysis of polyacrylamide gels after electrophoresis of cell fractions that are enriched with respect to the 100-A filaments shows the presence of a new muscle protein with a molecular weight of 55,000. This protein can form filamentous segments that closely resemble in structure the native, isolated 100-A filaments. The results indicate that the filamentous network has a structure and composition that distinguish it from the actin and myosin in vertebrate smooth 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.

scholarly journals Dense bodies and actin polarity in vertebrate smooth muscle.

1982 ◽  
Vol 95 (2) ◽  
pp. 403-413 ◽  
Author(s):  
M Bond ◽  
A V Somlyo
Keyword(s):  
Smooth Muscle ◽  
Vas Deferens ◽  
Dense Body ◽  
Thin Filaments ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1 ◽  
10 Nm Filaments ◽  
Rabbit Vas Deferens

The arrangement of cytoplasmic dense bodies in vertebrate smooth muscle and their relationship to the thin filaments was studied in cells from rabbit vas deferens and portal vein which were made hyperpermeable (skinned) with saponin and incubated with myosin subfragment 1 (S-1). The dense bodies were obliquely oriented, elongated structures sometimes appearing as chains up to 1.5 microns in length; they were often continuous across the cell for 200 to 300 nm and were interconnected by an oblique network of 10-nm filaments. The arrowheads, formed by S-1 decoration of actins, which inserted into both the sides and ends of dense bodies, always pointed away from the dense body, similar to the polarity of the thin filaments at the Z-bands of skeletal muscle. These results show that the cytoplasmic dense bodies function as anchoring sites for the thin filaments and indicate that the thin filaments, thick filaments, and dense bodies constitute a contractile unit.

Models of contractile units and their assembly in smooth muscle

2005 ◽  
Vol 83 (10) ◽  
pp. 825-831 ◽  
Author(s):  
Farah Ali ◽  
Peter D Paré ◽  
Chun Y Seow
Keyword(s):  
Smooth Muscle ◽  
Striated Muscle ◽  
Dense Body ◽  
Unit Length ◽  
Muscle Length ◽  
Thick Filament ◽  
Contractile Apparatus ◽  
Thin Filaments ◽  
Dense Bodies ◽  
In Series

It is believed that the contractile filaments in smooth muscle are organized into arrays of contractile units (similar to the sarcomeric structure in striated muscle), and that such an organization is crucial for transforming the mechanical activities of actomyosin interaction into cell shortening and force generation. Details of the filament organization, however, are still poorly understood. Several models of contractile filament architecture are discussed here. To account for the linear relationship observed between the force generated by a smooth muscle and the muscle length at the plateau of an isotonic contraction, a model of contractile unit is proposed. The model consists of 2 dense bodies with actin (thin) filaments attached, and a myosin (thick) filament lying between the parallel thin filaments. In addition, the thick filament is assumed to span the whole contractile unit length, from dense body to dense body, so that when the contractile unit shortens, the amount of overlap between the thick and thin filaments (i.e., the distance between the dense bodies) decreases in exact proportion to the amount of shortening. Assembly of the contractile units into functional contractile apparatus is assumed to involve a group of cells that form a mechanical syncytium. The contractile apparatus is assumed malleable in that the number of contractile units in series and in parallel can be altered to accommodate strains on the muscle and to maintain the muscle's optimal mechanical function.Key words: contraction model, ultrastructure, length adaptation, plasticity.

scholarly journals THE STRUCTURE OF INTERSEGMENTAL MUSCLE FIBERS IN AN INSECT, PERIPLANETA AMERICANA L

1966 ◽  
Vol 29 (3) ◽  
pp. 449-459 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Periplaneta Americana ◽  
Flight Muscle ◽  
Muscle Fibers ◽  
Structural Features ◽  
Mitochondrial Content ◽  
Thin Filaments ◽  
Transverse Tubular System ◽  
Thick Filaments ◽  
Tubular System ◽  
Contraction And Relaxation

The organization of intersegmental muscle fibers associated with the dorsal abdominal sclerites of the cockroach is described. These fibers correspond closely, in the disposition and derivation of the membranes of the transverse tubular system and sarcoplasmic reticulum cisternae, with insect synchronous flight muscle fibers, but differ markedly from these in their fibrillar architecture and mitochondrial content. The mitochondria are small and generally aligned alongside the prominent I bands of the sarcomere, and, in the best-oriented profiles of the A bands, thick filaments are associated with orbitals of twelve thin filaments, a configuration that has also been observed in striated fibers of insect visceral muscle. These structural features of insect muscles are compared and discussed in terms of possible variations in the control of contraction and relaxation, and in the nature of their mechanical role.

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.

Band Patterns in Chick Muscle at Short Sarcomere Length

1970 ◽  
Vol 28 ◽  
pp. 144-145
Author(s):  
M. Hagopian ◽  
D. Spiro ◽  
P. Yau
Keyword(s):  
Electron Microscopy ◽  
Actin Filaments ◽  
Sarcomere Length ◽  
Pectoral Muscle ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Contraction Band

Glycerinated chick pectoral muscle was prepared for electron microscopy. Sarcomere lengths varied from 2.3 to 1.1μ reflecting various degrees of shortening. Over a sarcomere range of 2.3 to 1.3μ the thin actin filaments which measure 1.0μ and the thick myosin filaments which measure 1.5μ are constant in length (Fig. 1). At sarcomere lengths below 2μ the thin filaments penetrate through the center of the A band into the opposite halves of the sarcomere producing A contraction bands as previously described. In sarcomeres which measure 1.5 to 1.3μ additional contraction bands are noted adjacent to the Z lines. In longitudinal sections the array of filaments in the Z contraction band appears orderly (Fig. 2). It is our impression that these Z contraction bands result from penetration of the tapered lateral ends of the myosin filaments through the Z lines into the adjacent sarcomere rather than a crumpling of thick filaments as has been previously stated. Below 1.3μ in length the sarcomeres are disorganized, and it is not possible to define filament lengths.

A comparison of isolated and in situ thick filaments from smooth muscle

1986 ◽  
Vol 44 ◽  
pp. 156-157
Author(s):  
E.L. Buhle ◽  
A.V. Somlyo ◽  
A.P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Actin Filaments ◽  
Muscle Actin ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Rabbit Portal Vein ◽  
Stable Structures

Early ultrastructural studies of smooth muscle are consistent with the sliding filament mechanism of contraction. Myosin filaments are stable structures in situ and can be found in both relaxed and contracted muscle. Actin filaments can be decorated with SI subfragments of myosin to show a polarity similar to the Z-lines of skeletal muscle. The work presented here is a comparison of isolated thick filaments from relaxed chick amnion with thick filaments obtained in situ from longitudinal thin sections (∽50nm thick) of rabbit portal vein in rigor.

scholarly journals Kinase-related protein (telokin) is phosphorylated by smooth-muscle myosin light-chain kinase and modulates the kinase activity

1997 ◽  
Vol 328 (2) ◽  
pp. 425-430 ◽  
Author(s):  
Apolinary SOBIESZEK ◽  
Y. Oleg ANDRUCHOV ◽  
Krzysztof NIEZNANSKI
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Muscle Protein ◽  
Smooth Muscle Myosin ◽  
Phosphorylation Reaction ◽  
Myosin Filaments ◽  
Separate Protein ◽  
Muscle Myosin

Telokin is an abundant smooth-muscle protein with an amino acid sequence identical with that of the C-terminal region of smooth-muscle myosin light-chain kinase (MLCK), although it is expressed as a separate protein [Gallagher and Herring (1991) J. Biol. Chem. 266, 23945-23952]. Here we demonstrate that telokin is also similar to smooth-muscle myosin regulatory light chain (ReLC) not only in its gross physical properties but also as an MLCK substrate. Telokin was slowly phosphorylated by MLCK in the presence of Ca2+ and calmodulin and could be readily dephosphorylated by myosin light-chain phosphatase. A threonine residue was phosphorylated with up to 0.25 mol/mol stoichiometry. This low stoichiometry, together with the observed dimerization of telokin [Sobieszek and Nieznanski (1997) Biochem. J. 322, 65-71], indicates that the telokin dimer was acting as the substrate with a single protomer being phosphorylated. Our enzyme kinetic analysis of the phosphorylation reaction confirms this interpretation. Because telokin phosphorylation also required micromolar concentrations of MLCK, which also facilitates the formation of kinase oligomers, we concluded that the oligomers are interacting with telokin. Thus it seems that telokin modulates the phosphorylation rate of myosin filaments by a mechanism that includes the direct or indirect inhibition of the kinase active site by the telokin dimer, and that removal of the inhibition is controlled by slow phosphorylation of the telokin dimer, which results in MLCK dimerization.

The site and state of myosin in intestinal smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 219-222 ◽  
Keyword(s):  
Smooth Muscle ◽  
Cross Sections ◽  
Striated Muscle ◽  
Mechanical Tension ◽  
Constant Length ◽  
Substantial Modification ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Resting Muscle ◽  
Longitudinal Layer

The longitudinal layer of the guinea-pig ileum represents a highly advantageous specimen for the study of vertebrate smooth muscle structure. In this muscle we regularly observed thick filaments, consisting presumably of myosin, in longitudinal as well as in cross-sections, if the samples were fixed at constant length, i.e. standing under mechanical tension. Thick filaments were regularly present also in muscles relaxed by atropine. On the other hand, thick filaments were absent in many cases in slack muscles in K+ contracture. As a consequence, we regard myosin filaments as regular constituents of smooth muscle, independently of the functional state. Their absence in electronmicrographs taken from slack muscles seems an artefact due to processing. We observed the same artefact in bee-wing muscle, i.e. in a striated muscle, too. This fact indicates the importance of mechanical tension and polymer crystallization in the survival of myosin filaments. On the basis of a recent work of Ladik, Biczó and Garamvölgyi we discuss how tension may be exerted on the myosin filaments of the resting muscle. Anyway, the sliding model seems valid also for vertebrate smooth muscle, without any substantial modification.

scholarly journals LOCUS AND STATE OF AGGREGATION OF MYOSIN IN TISSUE SECTIONS OF VERTEBRATE SMOOTH MUSCLE

1970 ◽  
Vol 44 (1) ◽  
pp. 52-61 ◽  
Author(s):  
Bernard J. Panner ◽  
Carl R. Honig
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Low Ph ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tissue Sections ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
And Storage

Structures with the characteristics of molecular myosin were identified by electron microscopy in tissue sections of vertebrate smooth muscle. No thick filaments of myosin were found regardless of preparative procedures, which included fixation at rest and in contraction, glycerine extraction, and storage at low pH prior to fixation. Absence of thick myosin filaments and presence of what appear to be myosin molecules is in accord with conclusions based on X-ray diffraction (3, 12) and birefringence data (4) from living smooth muscles at rest and in contraction. Explanations are provided for appearances thought by others (6, 20, 21) to represent thick myosin filaments. Our present observations are in accord with the model for smooth muscle contraction which we have previously proposed (1).

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