scholarly journals Z‐line‐like Structures Are Distinct from α‐actinin‐rich Dense Bodies in Nematode Obliquely Striated Muscle

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Shoichiro Ono ◽  
Emily Nickoloff ◽  
Kanako Ono
Keyword(s):  
Striated Muscle ◽  
Dense Bodies

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 Zeugmatin: a new high molecular weight protein associated with Z lines in adult and early embryonic striated muscle.

1985 ◽  
Vol 101 (5) ◽  
pp. 1871-1883 ◽  
Author(s):  
P A Maher ◽  
G F Cox ◽  
S J Singer
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Biochemical Characterization ◽  
Striated Muscle ◽  
High Molecular Weight Protein ◽  
Adult Skeletal Muscle ◽  
Intercalated Discs ◽  
Dense Bodies ◽  
Weight Protein

Monoclonal antibodies were generated to a purified preparation of the fascia adherens domains of the intercalated discs of chicken cardiac cell membranes. One of these antibodies, McAb 20, immunofluorescently labeled the Z lines of adult skeletal muscle, the Z lines and intercalated discs of adult cardiac muscle, and the dense bodies and dense plaques of adult gizzard smooth muscle. In addition, McAb 20 was found to label regenerating muscle cells in a cross-striated pattern much like that of Z lines in 24-h muscle cell cultures before the appearance of Z lines was detectable by phase or Nomarski optics and before the concentration of alpha-actinin occurred at the Z lines. Thus, McAb 20 appears to be directed against an antigen involved in early myofibrillar organization. Preliminary biochemical characterization of the antigen recognized by McAb 20 indicates that it is a high molecular weight doublet of over 5 X 10(5) kD that is highly susceptible to proteolysis. By virtue of its presence in Z lines, and its possible role in the end-on attachment of microfilaments to Z lines and membranes, we have named this protein zeugmatin (xi epsilon nu gamma mu alpha identical to yoking).

scholarly journals OBLIQUELY STRIATED MUSCLE

1968 ◽  
Vol 36 (1) ◽  
pp. 245-259 ◽  
Author(s):  
Jack Rosenbluth
Keyword(s):  
Electron Microscopy ◽  
Sarcoplasmic Reticulum ◽  
Connective Tissue ◽  
Striated Muscle ◽  
Muscle Cells ◽  
Body Muscle ◽  
Dense Bodies ◽  
Thick Filaments ◽  
Predominant Type ◽  
Physiological Differences

Body muscle cells of the bloodworm Glycera, a polychaete annelid, were studied by electron microscopy and compared with muscle cells of the more slowly acting nematode Ascaris, which have been described previously. Both muscles are obliquely striated. The predominant type of bloodworm fiber is characterized by a prominent transversely oriented sarcoplasmic reticulum with numerous dyads at the surface of each cell. Thick myofilaments are ∼3 µ long and overlap along ∼60% of their length in extended fibers and ∼80% in shortened fibers. There is virtually no endomysium and very little intracellular skeleton, and the cells are attached by desmosomes to one another rather than to connective tissue. Dense bodies are absent from the fibers and in their place are Z lines, which are truly linear rather than planar. Scattered among the predominant fibers are others, less orderly in arrangement, in which the SR is much less prominent and in which the thick filaments are thicker and longer and overlap to an even smaller degree. It is suggested that physiological differences between bloodworm and Ascaris muscles derive from differences in the proportion of series to parallel linkages between the contractile elements, differences in the amount and disposition of the SR, and differences in the impedance to shear within the myofibrils.

Dense-body aggregates as plastic structures supporting tension in smooth muscle cells

2010 ◽  
Vol 299 (5) ◽  
pp. L631-L638 ◽  
Author(s):  
Jie Zhang ◽  
Ana M. Herrera ◽  
Peter D. Paré ◽  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Striated Muscle ◽  
Dense Body ◽  
Muscle Cells ◽  
Cell Length ◽  
Structural Basis ◽  
Airway Smooth Muscle Cells ◽  
Dense Bodies ◽  
Large Length

The wall of hollow organs of vertebrates is a unique structure able to generate active tension and maintain a nearly constant passive stiffness over a large volume range. These properties are predominantly attributable to the smooth muscle cells that line the organ wall. Although smooth muscle is known to possess plasticity (i.e., the ability to adapt to large changes in cell length through structural remodeling of contractile apparatus and cytoskeleton), the detailed structural basis for the plasticity is largely unknown. Dense bodies, one of the most prominent structures in smooth muscle cells, have been regarded as the anchoring sites for actin filaments, similar to the Z-disks in striated muscle. Here, we show that the dense bodies and intermediate filaments formed cable-like structures inside airway smooth muscle cells and were able to adjust the cable length according to cell length and tension. Stretching the muscle cell bundle in the relaxed state caused the cables to straighten, indicating that these intracellular structures were connected to the extracellular matrix and could support passive tension. These plastic structures may be responsible for the ability of smooth muscle to maintain a nearly constant tensile stiffness over a large length range. The finding suggests that the structural plasticity of hollow organs may originate from the dense-body cables within the smooth muscle cells.

Three muscle isoforms of α-actinin form unipolar actin bundles

1995 ◽  
Vol 53 ◽  
pp. 706-707
Author(s):  
K. A. Taylor ◽  
D. W. Taylor
Keyword(s):  
Cell Membrane ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Subcellular Location ◽  
Binding Activity ◽  
Actin Binding ◽  
Physiological Importance ◽  
Terminal Domain ◽  
Dense Bodies ◽  
Membrane Anchoring

α-Actinin is an F-actin binding protein that is ubiquitous in eucaryotic cells. It is the smallest member of the spectrin superfamily and consists of two, identical polypeptide chains of 95-103 kDa. α-Actinin is an elongated molecule of 34 nm length and consists of a string of peptide domains with different functions. The N-terminal domain of ˜255 residues has actin binding activity, the central core consists of four 122 residues triple-helical repeats and the C-terminal domain contains two E-F hand Ca2+ binding motifs.The physiological importance α-actinin lies in its subcellular location and its interactions with other proteins. The F-actin crosslinking activity of α-actinin is its best known function. In striated muscle aactinin is found in the Z-disk. In smooth muscle, α-actinin is found in both cytoplasmic dense bodies, which are analogs of the Z-disk, and adhesion plaques, which are cell membrane anchoring sites of actin filaments. In dense bodies and Z-disks, oppositely oriented, unipolar bundles of actin filaments overlap so it has been commonly assumed that α-actinin is functioning as a bipolar crosslinker but the unipolar orientation of actin filaments at the cell membrane implies a unipolar bundling activity.

scholarly journals The Regulation of Catch in Molluscan Muscle

1967 ◽  
Vol 50 (6) ◽  
pp. 157-169 ◽  
Author(s):  
Betty M. Twarog
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Neural Activation ◽  
Thin Filaments ◽  
Dense Bodies ◽  
Thick Filaments

Molluscan catch muscles are smooth muscles. As with mammalian smooth muscles, there is no transverse ordering of filaments or dense bodies. In contrast to mammalian smooth muscles, two size ranges of filaments are present. The thick filaments are long as well as large in diameter and contain paramyosin. The thin filaments contain actin and appear to run into and join the dense bodies. Vesicles are present which may be part of a sarcoplasmic reticulum. Neural activation of contraction in Mytilus muscle is similar to that observed in mammalian smooth muscles, and in some respects to frog striated muscle. The relaxing nerves, which reduce catch, are unique to catch muscles. 5-Hydroxytryptamine, which appears to mediate relaxation, specifically blocks catch tension but increases the ability of the muscle to fire spikes. It is speculated that Mytilus muscle actomyosin is activated by a Ca++-releasing mechanism, and that 5-hydroxytryptamine may reduce catch and increase excitability by influencing the rate of removal of intracellular free Ca++.

Ultrastructural Localization of Acid Mucosubstance in Skeletal Muscle

1967 ◽  
Vol 25 ◽  
pp. 52-53 ◽  
Author(s):  
William J. Dougherty ◽  
Samuel S. Spicer
Keyword(s):  
Striated Muscle ◽  
Divalent Cations ◽  
Ultrastructural Localization ◽  
Major Elements ◽  
Frozen Sections ◽  
Thorium Dioxide ◽  
Iron Solution ◽  
Coupling System ◽  
Psoas Muscles ◽  
Formalin Fixed

In recent years, considerable attention has focused on the morphological nature of the excitation-contraction coupling system of striated muscle. Since the study of Porter and Palade, it has become evident that the sarcoplastic reticulum (SR) and transverse tubules constitute the major elements of this system. The problem still exists, however, of determining the mechamisms by which the signal to interdigitate is presented to the thick and thin myofilaments. This problem appears to center on the movement of Ca++ions between myofilaments and SR. Recently, Philpott and Goldstein reported acid mucosubstance associated with the SR of fish branchial muscle using the colloidal thorium dioxide technique, and suggested that this material may serve to bind or release divalent cations such as Ca++. In the present study, Hale's iron solution adapted to electron microscopy was applied to formalin-fixed myofibrils isolated from glycerol-extracted rabbit psoas muscles and to frozen sections of formalin-fixed rat psoas muscles.

Ultrastructure of Liver in Lactosyl Ceramidosis

1971 ◽  
Vol 29 ◽  
pp. 312-313
Author(s):  
Z. Hruban ◽  
J. R. Esterly ◽  
G. Dawson ◽  
A. O. Stein
Keyword(s):  
Connective Tissue ◽  
Liver Biopsy ◽  
Osmium Tetroxide ◽  
Close Contact ◽  
Multivesicular Bodies ◽  
Bile Canaliculi ◽  
Dense Bodies ◽  
Marginal Plates ◽  
Membranous Material ◽  
Perichromatin Granules

Samples of a surgical liver biopsy from a patient with lactosyl ceramidosis were fixed in paraformaldehyde and postfixed in osmium tetroxide. Hepatocytes (Figs. 1, 2) contained 0.4 to 2.1 μ inclusions (LCI) limited by a single membrane containing lucid matrix and short segments of curved, lamellated and circular membranous material (Fig. 3). Numerous LCI in large connective tissue cells were up to 11 μ in diameter (Fig. 2). Heterogeneous dense bodies (“lysosomes”) were few and irregularly distributed. Rough cisternae were dilated and contained smooth vesicles and surface invaginations. Close contact with mitochondria was rare. Stacks were small and rare. Vesicular rough reticulum and glycogen rosettes were abundant. Smooth vesicular reticulum was moderately abundant. Mitochondria were round with few cristae and rare matrical granules. Golgi complex was seen rarely (Fig. 1). Microbodies with marginal plates were usual. Multivesicular bodies were very rare. Neutral lipid was rare. Nucleoli were small and perichromatin granules were large. Small bile canaliculi had few microvilli (Fig. 1).

Copper Localization in Cirrhotic Rat Liver by Scanning Electron Microscopy

1969 ◽  
Vol 27 ◽  
pp. 38-39 ◽  
Author(s):  
J. C. Russ ◽  
E. McNatt
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Copper Acetate ◽  
Lead Citrate ◽  
Dense Bodies ◽  
Transmission Electron ◽  
Electron Mode ◽  
Scanning Electron

In order to study the retention of copper in cirrhotic liver, rats were made cirrhotic by carbon tetrachloride inhalation twice weekly for three months and fed 0.2% copper acetate ad libidum in drinking water for one month. The liver tissue was fixed in osmium, sectioned approximately 2000 Å thick, and stained with lead citrate. The section was examined in a scanning electron microscope (JEOLCO JSM-2) in the transmission electron mode.Figure 1 shows a typical area that includes a red blood cell in a sinusoid, a disse, and a portion of the cytoplasm of a hepatocyte which contains several mitochondria, peribiliary dense bodies, glycogen granules, and endoplasmic reticulum.

A complex network of “snake-like tubules” revealed by the NADPase cytochemical reaction in the acinar cell of pancreas

1984 ◽  
Vol 42 ◽  
pp. 666-667
Author(s):  
A.R. Beaudoin ◽  
G. Grondin ◽  
A. Lord ◽  
M. Pelletier
Keyword(s):  
Acinar Cell ◽  
Lead Acetate ◽  
Ultrastructural Localization ◽  
Sodium Acetate Buffer ◽  
Zymogen Granules ◽  
Sprague Dawley ◽  
Dense Bodies ◽  
Sprague Dawley Rats ◽  
Cytochemical Reaction ◽  
Cellular Organelles

We have recently described the ultrastructural localization of NADPase activity in the exocrine pancreas of rat. The enzyme was found in the intermediate saccules of the Golgi apparatus, in dense bodies and lysosomes but was absent from zymogen granules. A very intense reaction was noticed in a peculiar structure which was termed “Snake-Like Tubule” (SLT). The purposes of the present study were firstly to delineate SLT distribution in the acinar cell and secondly to define any possible relationship or association with other cellular organelles.NADPase cytochemical reaction was performed on the pancreas of adult Sprague Dawley rats. Small lobules were excised and fixed for 50 min, at 4°C, in 2% glutaraldehyde buffered with 0.1M cacodylate at pH 7.2. Lobules were rinsed several times with the same buffer containing 570 sucrose and cut with a Mcllwayn tissue chopper. Sections were washed several times with buffer and incubated for 2 hr at 37°C in the following medium: 4mM NADPH; 40mM sodium acetate buffer, pH 5.0; 4mM lead acetate and 5% sucrose.

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