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.

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 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.

scholarly journals Structure and paramyosin content of tarantula thick filaments.

1983 ◽  
Vol 97 (1) ◽  
pp. 186-195 ◽  
Author(s):  
R J Levine ◽  
R W Kensler ◽  
M C Reedy ◽  
W Hofmann ◽  
H A King
Keyword(s):  
Evolutionary Relationship ◽  
Radial Distance ◽  
Thick Filament ◽  
Optical Diffraction ◽  
Thin Filaments ◽  
Biochemical Characteristics ◽  
Thick Filaments ◽  
Cross Bridges ◽  
Centers Of Mass ◽  
Relationship Of

Muscle fibers of the tarantula femur exhibit structural and biochemical characteristics similar to those of other long-sarcomere invertebrate muscles, having long A-bands and long thick filaments. 9-12 thin filaments surround each thick filament. Tarantula muscle has a paramyosin:myosin heavy chain molecular ratio of 0.31 +/- 0.079 SD. We studied the myosin cross-bridge arrangement on the surface of tarantula thick filaments on isolated, negatively stained, and unidirectionally metal-shadowed specimens by electron microscopy and optical diffraction and filtering and found it to be similar to that previously described for the thick filaments of muscle of the closely related chelicerate arthropod, Limulus. Cross-bridges are disposed in a four-stranded right-handed helical arrangement, with 14.5-nm axial spacing between successive levels of four bridges, and a helical repeat period every 43.5 nm. The orientation of cross-bridges on the surface of tarantula filaments is also likely to be very similar to that on Limulus filaments as suggested by the similarity between filtered images of the two types of filaments and the radial distance of the centers of mass of the cross-bridges from the surfaces of both types of filaments. Tarantula filaments, however, have smaller diameters than Limulus filaments, contain less paramyosin, and display structure that probably reflects the organization of the filament backbone which is not as apparent in images of Limulus filaments. We suggest that the similarities between Limulus and tarantula thick filaments may be governed, in part, by the close evolutionary relationship of the two species.

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.

Plasticity in smooth muscle, a hypothesis

1994 ◽  
Vol 72 (11) ◽  
pp. 1320-1324 ◽  
Author(s):  
Lincoln E. Ford ◽  
Chun Y. Seow ◽  
Victor R. Pratusevich
Keyword(s):  
Smooth Muscle ◽  
Preliminary Finding ◽  
Muscle Length ◽  
Shortening Velocity ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Initial Hypothesis ◽  
In Series ◽  
Cross Bridges ◽  
Muscle Myosin

The controversial finding that the thick filaments of smooth muscle can be evanescent leads to the hypothesis that the large functional range of this muscle is accommodated by plastic rearrangements that place more thick filaments in series at longer lengths. Our preliminary finding that the shortening velocity and compliance of dog tracheal muscle were strongly dependent on adapted muscle length, while force was much less length dependent, supports this hypothesis (V.R. Pratusevich, C.Y. Seow, and L.E. Ford. Biophys. J. 66: A139, 1994). The hypothesis leads to two further corollaries. The first is that the lengthening of the thick filaments that must accompany their reformation will cause a series to parallel transition: fewer long filaments span the muscle length, but the longer filaments have more cross bridges acting in parallel. The second is that there is more than one activating mechanism in smooth muscle. It is known that myosin light chain phosphorylation activates the actomyosin ATPase, but this same phosphorylation also causes a structural change that facilitates filament formation. The consideration that the unaggregated, phosphorylated myosin must be prevented from competing with myosin in thick filaments and hydrolyzing ATP suggests that there must be a second mechanism that must allow the thin filaments to interact selectively with filamentous myosin. This need for a second activating mechanism may explain the presence of tropomyosin, calponin, and caldesmon on thin filaments. Although the two corollaries follow from the initial hypothesis, it should be emphasized that the three are not mutually dependent, and that the proof or disproof of any one of them would not prove or disprove the others.Key words: smooth muscle, myosin, thick filaments, contraction.

scholarly journals Bridgelike interconnections between thick filaments in stretched skeletal muscle fibers observed by the freeze-fracture method.

1986 ◽  
Vol 102 (3) ◽  
pp. 1093-1098 ◽  
Author(s):  
S Suzuki ◽  
G H Pollack
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Freeze Fracture ◽  
Thick Filament ◽  
Rapid Freezing ◽  
Semitendinosus Muscle ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Cross Bridges ◽  
Half Length

The ultrastructure of frog semitendinosus muscle was explored using the freeze-fracture, deep-etch, rotary-shadowing technique. Mechanically skinned fibers were stretched to decrease or eliminate the overlap of thick and thin filaments before rapid freezing with liquid propane. In relaxed, contracting, and rigor fibers, a significant number of bridgelike interconnections, distinct from those observed in the M-region, were observed between adjacent thick filaments in the non-overlap region. Their half-length and diameter corresponded approximately to the known dimensions of the cross-bridge (or myosin S-1). The interconnection may thus be formed by the binding of two apposed cross-bridges projecting from adjacent thick filaments. Fixation with 0.5% glutaraldehyde for 5-10 min before freezing effectively preserved these structures. The results indicate that the interconnections are genuine structures that appear commonly in stretched muscle fibers. They may play a role in stabilizing the thick filament lattice, and possibly in the contractile process.

scholarly journals Mechanisms of thin filament assembly in embryonic chick cardiac myocytes: tropomodulin requires tropomyosin for assembly.

1995 ◽  
Vol 129 (3) ◽  
pp. 683-695 ◽  
Author(s):  
C C Gregorio ◽  
V M Fowler
Keyword(s):  
Actin Filaments ◽  
Thin Filament ◽  
Striated Muscle ◽  
Cell Model ◽  
Significant Proportion ◽  
Embryonic Chick ◽  
Permeabilized Cell ◽  
Thin Filaments ◽  
Filament Assembly ◽  
Cell Biol

Tropomodulin is a pointed end capping protein for tropomyosin-coated actin filaments that is hypothesized to play a role in regulating the precise lengths of striated muscle thin filaments (Fowler, V. M., M. A. Sussman, P. G. Miller, B. E. Flucher, and M. P. Daniels. 1993. J. Cell Biol. 120:411-420; Weber, A., C. C. Pennise, G. G. Babcock, and V. M. Fowler. 1994, J. Cell Biol. 127:1627-1635). To gain insight into the mechanisms of thin filament assembly and the role of tropomodulin therein, we have characterized the temporal appearance, biosynthesis and mechanisms of assembly of tropomodulin onto the pointed ends of thin filaments during the formation of striated myofibrils in primary embryonic chick cardiomyocyte cultures. Our results demonstrate that tropomodulin is not assembled coordinately with other thin filament proteins. Double immunofluorescence staining and ultrastructural immunolocalization demonstrate that tropomodulin is incorporated in its characteristic sarcomeric location at the pointed ends of the thin filaments after the thin filaments have become organized into periodic I bands. In fact, tropomodulin assembles later than all other well characterized myofibrillar proteins studied including: actin, tropomyosin, alpha-actinin, titin, myosin and C-protein. Nevertheless, at steady state, a significant proportion (approximately 39%) of tropomodulin is present in a soluble pool throughout myofibril assembly. Thus, the absence of tropomodulin in some striated myofibrils is not due to limiting quantities of the protein. In addition, kinetic data obtained from [35S]methionine pulse-chase experiments indicate that tropomodulin assembles more slowly into myofibrils than does tropomyosin. This observation, together with results obtained using a novel permeabilized cell model for thin filament assembly, indicate that tropomodulin assembly is dependent on the prior association of tropomyosin with actin filaments. We conclude that tropomodulin is a late marker for the assembly of striated myofibrils in cardiomyocytes; its assembly appears to be linked to their maturity. We propose that tropomodulin is involved in maintaining and stabilizing the final lengths of thin filaments after they are assembled.

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.

The length-tension relationship of the dorsal longitudinal muscle of a leech

1975 ◽  
Vol 62 (1) ◽  
pp. 43-53
Author(s):  
JB Miller
Keyword(s):  
Body Wall ◽  
Longitudinal Muscle ◽  
Muscle Fibres ◽  
Passive Tension ◽  
Active Tension ◽  
Thin Filaments ◽  
Thick Filaments ◽  
Tension Curve ◽  
Cross Bridges ◽  
Relationship Of

The length-tension relationship of a preparation of the dorsal body wall of the leech Haemopis sanguisuga was determined. Passive tension is low except at very long lengths of the preparation, when it rises steeply. It is due mainly to the epidermis present in the preparation. The active tension curve is very flat, with tension being reduced only at very short and very long lengths. This shape is explained in the context of the myofilament arrangement of the muscle fibres. It may be that thin filaments can form cross-bridges with different thick filaments at different lengths of the preparation.

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