scholarly journals Polarity of actin filaments at the initial stage of myofibril assembly in myogenic cells in vitro.

1977 ◽  
Vol 72 (3) ◽  
pp. 777-785 ◽  
Author(s):  
Y Shimada ◽  
T Obinata
Keyword(s):  
Actin Filaments ◽  
Muscle Cells ◽  
Spatial Position ◽  
Myogenic Cells ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Initial Stage ◽  
The Right ◽  
Developing Muscle

The polarity of thin filaments in relation to thick filaments in developing muscle cells in vitro was investigated. The majority of thin filaments exhibited the right polarity and spatial position similar to that seen in mature myofibrils. It appears that the interaction between thick and thin filaments exists in the initial phases of myofibrillogenesis. Cortical microfilaments are found to have their polarities arranged randomly.

scholarly journals Involvement of transglutaminase in myofibril assembly of chick embryonic myoblasts in culture.

1995 ◽  
Vol 130 (5) ◽  
pp. 1127-1136 ◽  
Author(s):  
S J Kang ◽  
K S Shin ◽  
W K Song ◽  
D B Ha ◽  
C H Chung ◽  
...  
Keyword(s):  
Competitive Inhibitor ◽  
Minimal Level ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Tetradecanoyl Phorbol Acetate ◽  
Cross Striation ◽  
The Cross ◽  
Triton X ◽  
Developing Muscle

Involvement of transglutaminase in myofibrillogenesis of chick embryonic myoblasts has been investigated in vitro. Both the activity and protein level of transglutaminase initially decreased to a minimal level at the time of burst of myoblast fusion but gradually increased thereafter. The localization of transglutaminase underwent a dramatic change from the whole cytoplasm in a diffuse pattern to the cross-striated sarcomeric A band, being strictly colocalized with the myosin thick filaments. For a brief period prior to the appearance of cross-striation, transglutaminase was localized in nonstriated filamental structures that coincided with the stress fiber-like structures. When 12-o-tetradecanoyl phorbol acetate was added to muscle cell cultures to induce the sequential disassembly of thin and thick filaments, transglutaminase was strictly colocalized with the myosin thick filaments even in the myosacs, of which most of the thin filaments were disrupted. Moreover, monodansylcadaverine, a competitive inhibitor of transglutaminase, reversibly inhibited the myofibril maturation. In addition, myosin heavy chain behaved as one of the potential intracellular substrates for transglutaminase. The cross-linked myosin complex constituted approximately 5% of the total Triton X-100-insoluble pool of myosin molecules in developing muscle cells, and its level was reduced to below 1% upon treatment with monodansylcadaverine. These results suggest that transglutaminase plays a crucial role in myofibrillogenesis of developing chick skeletal muscle.

scholarly journals AN ELECTRON MICROSCOPE STUDY OF MYOFIBRIL FORMATION IN EMBRYONIC CHICK SKELETAL MUSCLE

1967 ◽  
Vol 32 (3) ◽  
pp. 557-575 ◽  
Author(s):  
Donald A. Fischman
Keyword(s):  
Self Assembly ◽  
Actin Filaments ◽  
Electron Microscope Study ◽  
Embryonic Chick ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Leg Muscle ◽  
Cross Bridges ◽  
Developing Muscle ◽  
Band Material

The formation of myofibrils in the developing leg muscle of the 12-day chick embryo was studied by electron microscopy. Myofilaments of two varieties, thick (160–170 A in diameter) and thin (60–70 A in diameter), which have been designated myosin and actin filaments, respectively, on the basis of their similarity to natural and synthetic myosin and actin filaments, appear in the cytoplasm of developing muscle cells. There is a greater than 7:1 ratio of thin to thick filaments in these young myofibers. The free myofilaments become aligned in the long axis of the cells, predominantly in subsarcolemmal locations, and aggregate into hexagonally packed arrays of filaments. The presence of Z band material or M band cross-bridges do not appear to be essential for the formation or spacing of these aggregates of filaments. Formation of the Z band lattices occurs coincidentally with the back-to-back apposition of thin filaments. An hypothesis concerning myofibril growth, based on the self-assembly characteristics of the filaments, is presented.

Phenotypic Modulation of Smooth Muscle Cells after Arterial Injury Is Associated with Changes in the Distribution of Laminin and Fibronectin

1997 ◽  
Vol 45 (6) ◽  
pp. 837-846 ◽  
Author(s):  
Johan Thyberg ◽  
Karin Blomgren ◽  
Joy Roy ◽  
Phan Kiet Tran ◽  
Ulf Hedin
Keyword(s):  
Smooth Muscle ◽  
Basement Membrane ◽  
Smooth Muscle Cells ◽  
Actin Filaments ◽  
Cell Structure ◽  
Muscle Cells ◽  
Arterial Injury ◽  
Internal Elastic Lamina ◽  
Contractile Phenotype

Earlier in vitro studies suggest opposing roles of laminin and fibronectin in regulation of differentiated properties of vascular smooth muscle cells. To find out if this may also be the case in vivo, we used immunoelectron microscopy to study the distribution of these proteins during formation of intimal thickening after arterial injury. In parallel, cell structure and content of smooth muscle α-actin was analyzed. The results indicate that the cells in the normal media are in a contractile phenotype with abundant α-actin filaments and an incomplete basement membrane. Within 1 week after endothelial denudation, most cells in the innermost layer of the media convert into a synthetic phenotype, as judged by loss of actin filaments, construction of a large secretory apparatus, and destruction of the basement membrane. Some of these cells migrate through fenestrae in the internal elastic lamina and invade a fibronectin-rich network deposited on its luminal surface. Within another few weeks a thick neointima forms, newly produced matrix components replace the strands of fibronectin, and a basement membrane reappears. Simultaneously, the cells resume a contractile phenotype, recognized by disappearance of secretory organelles and restoration of α-actin filaments. These findings support the notion that laminin and other basement membrane components promote the expression of a differentiated smooth muscle phenotype, whereas fibronectin stimulates the cells to adopt a proliferative and secretory phenotype.

scholarly journals Transverse sarcomere splitting. A possible means of longitudinal growth in crab muscles.

1979 ◽  
Vol 80 (3) ◽  
pp. 736-742 ◽  
Author(s):  
S S Jahromi ◽  
M P Charlton
Keyword(s):  
Electron Microscope ◽  
Blue Crab ◽  
Actin Filaments ◽  
Muscle Cells ◽  
Contractile Properties ◽  
Longitudinal Growth ◽  
Thick Filaments

Transversely split sarcomeres are seen in mouthpart muscles of the blue crab in the electron microscope. Sarcomeres split only at the H zone. Two new sarcomeres are formed by a Z disk which appears in the H zone of the splitting sarcomere. Splitting may involve breaking of the thick filaments in the H zone, elongation of these filaments, and formation of both new actin filaments and Z-disk materials, Sarcomere splitting would allow longitudinal growth of muscle cells without lengthening of sarcomeres and concomitant changes in contractile properties.

scholarly journals DIFFERENTIATION OF THE SARCOPLASMIC RETICULUM AND T SYSTEM IN DEVELOPING CHICK SKELETAL MUSCLE IN VITRO

1967 ◽  
Vol 35 (2) ◽  
pp. 405-420 ◽  
Author(s):  
Elizabeth B. Ezerman ◽  
Harunori Ishikawa
Keyword(s):  
Skeletal Muscle ◽  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Osmium Tetroxide ◽  
Muscle Cells ◽  
Simultaneous Occurrence ◽  
Chick Embryos ◽  
Developing Muscle ◽  
T System

The electron microscope was used to investigate the first 10 days of differentiation of the SR and the T system in skeletal muscle cultured from the breast muscle of 11-day chick embryos. The T-system tubules could be clearly distinguished from the SR in developing muscle cells fixed with glutaraldehyde and osmium tetroxide. Ferritin diffusion confirmed this finding: the ferritin particles were found only in the tubules identified as T system. The proliferation of both membranous systems seemed to start almost simultaneously at the earliest myotube stage. Observations suggested that the new SR membranes developed from the rough-surfaced ER as tubular projections. The SR tubules connected with one another to form a network around the myofibril. The T-system tubules were formed by invagination of the sarcolemma. The early extension of the T system by branching and budding was seen only in subsarcolemmal regions. Subsequently the T-system tubules could be seen deep within the muscle cells. Immediately after invaginating, the T-system tubule formed, along its course, specialized connections with the SR or ER: triadic structures showing various degrees of differentiation. The simultaneous occurrence of myofibril formation and membrane proliferation is considered to be important in understanding the coordinated events resulting in the differentiated myotube.

scholarly journals A 295-kDA intermediate filament-associated protein in radial glia and developing muscle cells in vivo and in vitro

2000 ◽  
Vol 219 (4) ◽  
pp. 514-525 ◽  
Author(s):  
Grazyna Chanas-Sacr� ◽  
Marc Thiry ◽  
Sandrine Pirard ◽  
Bernard Rogister ◽  
Gustave Moonen ◽  
...  
Keyword(s):  
Intermediate Filament ◽  
Radial Glia ◽  
Muscle Cells ◽  
Developing Muscle

scholarly journals THE FINE STRUCTURE OF EMBRYONIC CHICK SKELETAL MUSCLE CELLS DIFFERENTIATED IN VITRO

1967 ◽  
Vol 35 (2) ◽  
pp. 445-453 ◽  
Author(s):  
Y. Shimada ◽  
D. A. Fischman ◽  
A. A. Moscona
Keyword(s):  
Electron Microscopy ◽  
Skeletal Muscle ◽  
Fine Structure ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Chick Embryos ◽  
Embryonic Chick ◽  
Developing Muscle

Dissociated myoblasts from 12-day chick embryos were cultured in monolayer, and the differentiation of skeletal muscle cells was studied by electron microscopy. The results have revealed a striking ultrastructural similarity between the in vivo and the in vitro developing muscle, particularly with respect to the myofibrils and sarcoplasmic reticulum. This study demonstrates that all the characteristic organelles of mature skeletal muscle can develop in vitro in the absence of nerves.

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.

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.

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