The structure of actin filaments and the origin of the axial periodicity in the
            <i>I</i>
            -substance of vertebrate striated muscle

Hanson, Jean; Lowy, J.

doi:10.1098/rspb.1964.0055

Cited by 76 publications

(8 citation statements)

References 8 publications

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“…The functional implications of these varying filament arrays as regards active tension per unit area of contractile substance cannot be assessed at present, although Lowy et al (1964) speculate on this matter with regard to fast and slow muscles. In accord with the studies of Hanson and Lowy (1964), it is noted that the diameters of the thin filaments are the same in all species although there is variation in thin filament length.…”

Section: Discussionsupporting

confidence: 71%

The Filament Lattice of Cockroach Thoracic Muscle

Hagopian

Spiro

1968

The Journal of Cell Biology

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The fine structure of the tergo-coxal muscle of the cockroach, Leucophaea maderae, has been studied with the electron microscope. This muscle differs from some other types of insect flight muscles inasmuch as the ratio of thin to thick filaments is 4 instead of the characteristic 3. The cockroach flight muscle also differs from the cockroach femoral muscle in thin to thick filament ratios and diameters and in lengths of thick filaments. A comparison of these latter three parameters in a number of vertebrate and invertebrate muscles suggests in general that the diameters and lengths of the thick filaments and thin to thick filament ratios are related.

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Section: Discussionsupporting

confidence: 71%

The Filament Lattice of Cockroach Thoracic Muscle

Hagopian

Spiro

1968

The Journal of Cell Biology

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“…In thin sections the fine structure of the masses that contain the myofilaments of the myoepithelial cell resembles that of the I band of striated muscle (11) (9)). The 50-A filaments have the same density and diameter as the F-actin filaments present in all smooth and striated muscle cells that have been investigated (12). The dense zones that appear randomly within the filamentous masses share the characteristic density seen at the Z line of striated skeletal muscle.…”

Section: Correlations With Striated Musclementioning

confidence: 71%

“…In this respect, striated muscle has been investigated intensively and some progress is now being made in elucidating the structure and function of smooth muscle (21,34), but for lack of information or from oversight the myoepithelial cell has often been neglected (12). Superficially, myoepithelial cells resemble smooth muscle cells, but close examination reveals that they are not alike in their fine structure.…”

Section: Introductionmentioning

confidence: 99%

Fine Structure of the Myoepithelium of the Eccrine Sweat Glands of Man

Ellis

1965

The Journal of Cell Biology

115

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A B S T R A C TThe secretory coils of glutaraldehyde-osmium tetroxide-fixed and Epon-Araldite-embedded eccrine sweat glands from the palms of young men were studied with the electron microscope. The myoepithclial cells lie on the epithelial side of the basement membrane and abut other epithelial elements directly. The irregularly serrated base of the cell has dense thickenings along the plasma membranc which alternate with zones bcaring pits; the smooth apical surface lacks dense thickenings, is studded with pits, and conjoined to secretory cells by cccasional desmosomes. Masses of myofilaments, 50 A in diameter, fill most of the cell and are associated with irregular dense zones. In cross-section the arrangement of the myofilaments seems identical with that of the I band of striated muscle, and the dense zone has typical Z band structure. A few microtubules and cytoplasmic cores bearing profiles of the endoplasmic reticulum, filamentous mitochondria, and glycogen granules penetrate the fibrillar masses and run parallel to the oriented myofilaments. In the perinuclear zone, Golgi membranes, rough-and smooth-surfaced elements of the endoplasmic reticulum, mitochondria, glycogen, microtubules, lipid, pigment, and dense granules are variable components in the cytoplasm. The interrelationships of the myoepithelial cells with the secretory cells suggest that the former may act as regulators, controlling the flow of metabolites to the secretory epithelium. I N T R O D U C T I O NMyoepithelial cells are common components of many vertebrate glands that take their origin from the embryonic ectoderm. They have been studied by cytochemical and the electron microscopic techniques in salivary glands (24,(40)(41)(42)(44)(45)(46); in lacrimal glands (25,26,40); in mammary glands (5,11,15,22,42,44); in the prostate (38); in the Harderian gland (4, 25); and in apocrine) (14,16,19,48) and eccrine (8,13,18,30,32,33 sweat glands. All of these investigators agree that the myoepithelial cells lie on the epithelial side of the basement membrane, and most authors note the similarity between filaments in the cytoplasm of smooth muscle and myoepithelium. The literature shows that although the myoepithelial cells of various glands may differ in size and shape, they are essentially similar in their fine structure. In some glands the contractile function of the myoepithelial elements has been clearly demonstrated (16,27,46) and the similarities in fine structure between the myoepithelial elements of the different glands suggest that they all are contractile cells.In studies seeking the elements basic to all intracellular contractile systems, the organization of every type of contractile cell should be considered. In this respect, striated muscle has been investigated intensively and some progress is now being made in elucidating the structure and function of smooth muscle (21, 34), but for lack of information or from oversight the myoepithelial cell has often 551

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“…The outlines of the model received subsequent support from electron microscopy and fiber diffraction work (described later), all suggesting that coiled-coil tropomyosin molecules interact end-to-end to form a continuous cable at a ∼40Å radius from the filament's central axis while following the helical path of F-actin. The 40-to 41-nmlong periodicity of end-to-end linked tropomyosin molecules (69,70,73,75) is slightly shorter than the 42 nm contour length of the tropomyosin molecule. However, EM observations by Flicker et al (51) showed that this small discrepancy can be accounted for by successive tropomyosin molecules overlapping end-to-end in forming the continuous cable, as originally predicted by McLachlin and Stewart (149,206) and later confirmed by Greenfield and Hitchcock (68,85).…”

Section: Striated Muscle Thin-filament Organizationmentioning

confidence: 98%

“…About a year later, the essence of the newly formulated steric blocking model of muscle regulation was proposed by Jean Hanson and Jack Lowy at a meeting of the Royal Society in 1963 organized by Hugh Huxley and the Nobel Laureate Andrew Huxley "On the Physical and Chemical Basis of Muscle Contraction" (92). Hanson and Lowy (75) suggested that coiled-coil tropomyosin (30), the first actin-binding protein to be described (by Kenneth Bailey 5,6), sterically regulates myosin-cross-bridge movement on actin and consequently controls muscle contraction. In their written contribution for the conference proceedings, Hanson and Lowy suggested (75) that "If tropomyosin B (Bailey's name for tropomyosin) forms some sort of complex with actin in the intact muscle, as seems very probable, then it might exert some control over the contractile function of actin, say by masking certain monomers in the filament and thereby selecting the sites for interaction with myosin".…”

Section: Introductionmentioning

confidence: 99%

Thin Filament Structure and the Steric Blocking Model

Lehman

2016

Comprehensive Physiology

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By interacting with the troponin-tropomyosin complex on myofibrillar thin filaments, Ca2+ and myosin govern the regulatory switching processes influencing contractile activity of mammalian cardiac and skeletal muscles. A possible explanation of the roles played by Ca2+ and myosin emerged in the early 1970s when a compelling "steric model" began to gain traction as a likely mechanism accounting for muscle regulation. In its most simple form, the model holds that, under the control of Ca2+ binding to troponin and myosin binding to actin, tropomyosin strands running along thin filaments either block myosin-binding sites on actin when muscles are relaxed or move away from them when muscles are activated. Evidence for the steric model was initially based on interpretation of subtle changes observed in X-ray fiber diffraction patterns of intact skeletal muscle preparations. Over the past 25 years, electron microscopy coupled with three-dimensional reconstruction directly resolved thin filament organization under many experimental conditions and at increasingly higher resolution. At low-Ca2+, tropomyosin was shown to occupy a "blocked-state" position on the filament, and switched-on in a two-step process, involving first a movement of tropomyosin away from the majority of the myosin-binding site as Ca2+ binds to troponin and then a further movement to fully expose the site when small numbers of myosin heads bind to actin. In this contribution, basic information on Ca2+-regulation of muscle contraction is provided. A description is then given relating the voyage of discovery taken to arrive at the present understanding of the steric regulatory model.

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The structure of actin filaments and the origin of the axial periodicity in the I -substance of vertebrate striated muscle

Cited by 76 publications

References 8 publications

The Filament Lattice of Cockroach Thoracic Muscle

The Filament Lattice of Cockroach Thoracic Muscle

Fine Structure of the Myoepithelium of the Eccrine Sweat Glands of Man

Thin Filament Structure and the Steric Blocking Model

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