Z Disc Ultrastructure in Scutal Depressor Fibers of the Barnacle

Leyton, Robert A.; Ullrick, William C.

doi:10.1126/science.168.3927.127

Cited by 16 publications

(7 citation statements)

References 11 publications

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“…It appears that this point of inflection in the length-tension curve in the present study results from the penetration of the myosin filaments into the Z lines . Z line penetration by the thick filaments was reported in barnacle muscle (Hoyle et al ., 1965 ;Leyton and Ullrick, 1970), and in an insect muscle (Zebe et al ., 1968) . In the barnacle supercontracted sarcomeres, large spaces open in the Z lines .…”

Section: Resultsmentioning

confidence: 99%

“…However, once the sarcomeres shorten to less than 1 .5 µ, the myosin filaments, which are approximately 1 .6 u in length (Page and Huxley, 1963), hit the Z discs, and they are bent back. Exceptions to the crumpling of the thick filaments as they hit the Z line have been reported in barnacle muscle (Hoyle et al ., 1965 ;Leyton and Ullrick, 1970) and in an insect muscle (Zebe et al ., 1968) . In barnacle muscle, spaces opened up in the Z line for the penetration of the thick filaments whereas, in the insect muscle, electron micrographs suggest penetration of the Z lines by thick filaments .…”

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confidence: 99%

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Contraction Bands at Short Sarcomere Length in Chick Muscle

Hagopian

1970

The Journal of Cell Biology

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Contraction Bands at Short Sarcomere Length in Chick Muscle

Hagopian

1970

The Journal of Cell Biology

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“…The resemblance between Limulus telson muscle fibers and slow fibers of arthropodan (Fahrenbach, 1967 ;Hagopian and Spiro, 1968) and even vertebrate (Page, 1965) (Hoyle et al, 1965 ;Leyton and Ullrick, 1970) especially in long sarcomeres than they do the totally separate Z disks found in obliquely striated muscles (Rohlich, 1962 ;Reger, 1964) .…”

Section: Discussionmentioning

confidence: 97%

STRUCTURE OF LIMULUS STRIATED MUSCLE

Dewey

Levine

Colflesh

1973

The Journal of Cell Biology

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The musculature of the telson of Limulus polyphemus L. consists of three dorsal muscles: the medial and lateral telson levators and the telson abductor, and one large ventral muscle; the telson depressor, which has three major divisions: the dorsal, medioventral, and lateroventral heads. The telson muscles are composed of one type of striated muscle fiber, which has irregularly shaped myofibrils. The sarcomeres are long, with discrete A and I and discontinuous Z bands. M lines are not present. H zones can be identified easily, only in thick (1.0 µm) longitudinal sections or thin cross sections. In lengthened fibers, the Z bands are irregular and the A bands appear very long due to misalignment of constituent thick filaments. As the sarcomeres shorten, the Z lines straighten somewhat and the thick filaments become more aligned within the A band, leading to apparent decrease in A band length. Further A band shortening, seen at sarcomere lengths below 7.4 µm may be a function of conformational changes of the thick filaments, possibly brought about by alterations in the ordering of their paramyosin cores.

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“…1 b). While tarantula thick filaments do not appear "hollow" as do the thick filaments of many other arthropid muscles, notably insect and crustacean muscles (20,23,27), they do exhibit slightly decreased electron density at their cores. The filament cortices are very electron-dense and a cloud of moderately electron-dense material, presumably cross-bridges, extends from the thick-filament surfaces toward the surrounding thin filaments (Fig.…”

Section: Electron Microscopy Of Sectioned Musclementioning

confidence: 99%

Structure and paramyosin content of tarantula thick filaments.

Levine¹,

Kensler²,

Reedy³

et al. 1983

The Journal of Cell Biology

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Muscle fibers of the tarantula femur exhibit structural and biochemical characteristics similar to those of other Iong-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 fi.laments, 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.Using a modified isolation procedure and improved electron microscopic techniques together with computer image and optical diffraction analyses, we recently described the structure of the myosin cross-bridge arrangement on the surface of negatively stained thick filaments isolated from unstimulated Limulus telson levator muscle (15,22,30). Four crossbridges extend from the surface of these filaments at each level, with an axial rise of 14.5 nm between adjacent levels and a helical repeat period of 43.5 nm, as predicted by Wray et al. (36) and confirmed by computer image reconstruction (30). Furthermore, by unidirectional metal-shadowing we determined that the myosin cross-bridges are disposed in a major right-handed helix, having 12 subunits per complete turn (175 nm), on the filament surface (16).Wray (35) recently reported that the x ray patterns from glycerinated, relaxed tarantula leg muscle resemble those he earlier obtained from similar preparations of Limulus muscle (36). Here we present the results of an electron microscopic, optical diffraction, and biochemical analysis of the structure and paramyosin content, respectively, of thick filaments from tarantula femur muscle fibers and compare them with those from our previous analysis of Limulus telson muscle thick filaments (15,16,22,30). MATERIALS AND METHODSTarantula (Eurypelma sp.) specimens (sex unknown) were purchased from C...

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Z Disc Ultrastructure in Scutal Depressor Fibers of the Barnacle

Cited by 16 publications

References 11 publications

Contraction Bands at Short Sarcomere Length in Chick Muscle

Contraction Bands at Short Sarcomere Length in Chick Muscle

STRUCTURE OF LIMULUS STRIATED MUSCLE

Structure and paramyosin content of tarantula thick filaments.

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