Distribution of mass within native thick filaments of vertebrate skeletal muscle

Knight, Peter J.; Erickson, Martha A.; Rodgers, Michael E.; Beer, M; Wiggins, J. W.

doi:10.1016/0022-2836(86)90388-8

Cited by 9 publications

(10 citation statements)

References 37 publications

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“…This is in agreement with our experimental results, indicating that the density distribution of the myosin rods is crucial in defining the SHG intensity profile. Regarding both the apparent A-and M-band lengths, only the simulated profiles based on the packing model by Knight et al, 29 with LMM þ S2 as SHG active regions resulted in similar lengths as found in the experimental data. This suggests that the S2 region should be taken into account as a significant contributor, a fact that is currently still under debate.…”

Section: Discussionsupporting

confidence: 63%

“…30 It is known that only the LMMs assemble into the backbone of the thick filament, but how this packing is organized is still under debate. 19,29,30,33 A general consensus is that the myosin density decreases at the distal parts of the myosin filament. 19,30 We tested two possible packing schemes, both based on the complete bipolar model suggested by Skubiszak and Kowalczyk 30 in which the myosin rod takes a helical form.…”

Section: Myosin Density Distributionmentioning

confidence: 99%

“…29,30 The step between successive myosin rods is 14.33 nm and the antiparallel overlap in the central zone is maximal 7 × 14.33 nm. Due to the helical rod shape, the LMM and S2 have projected axial lengths of 88.44 and 53.17 nm, respectively.…”

Section: Myosin Density Distributionmentioning

confidence: 99%

“…The thick filament is then composed of a total of 270 myosin rods. The second packing model is based on observations done by Knight et al 29 Each crown has three sets of globular heads and a gap is present before the last two distal crowns. A total of 294 myosin molecules are then contained in the thick filament.…”

Section: Myosin Density Distributionmentioning

confidence: 99%

“…For this, the effect of the density distribution of myosin rods along the thick filament axis was studied. We performed simulations by implementing the myosin packing according to models by Knight et al 29 and Skubiszak and Kowalczyk, 30 considering either the LMM or the LMM and S2 as SHG active regions (Fig. 1) Female Lewis rats of age 6 to 7 weeks and body weight 100 to 120 g (Harlan CPB, Zeist, The Netherlands) were housed in the animal facilities at Hasselt University.…”

Section: Introductionmentioning

confidence: 99%

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On the interpretation of second harmonic generation intensity profiles of striated muscle

et al. 2015

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Abstract. Recently, a supramolecular model was developed for predicting striated skeletal muscle intensity profiles obtained by label-free second harmonic generation (SHG) microscopy. This model allows for a quantitative determination of the length of the thick filament antiparallel range or M-band (M), and results in M ¼ 0.12 μm for single-band intensity profiles when fixing the A-band length (A) to A ¼ 1.6 μm, a value originating from electron microscopy (EM) observations. Using simulations and experimental data sets, we showed that the objective numerical aperture (NA) and the refractive index (RI) mismatch (Δn ¼ n 2ω − n ω ) between the illumination wave (ω) and the second harmonic wave (2ω) severely affect the simulated sarcomere intensity profiles. Therefore, our recovered filament lengths did not match with those observed by EM. For an RI mismatch of Δn ¼ 0.02 and a moderate illumination NA of 0.8, analysis of single-band SHG intensity profiles with freely adjustable A-and M-band sizes yielded A ¼ 1.40 AE 0.04 μm and M ¼ 0.07 AE 0.05 μm for skeletal muscle. These lower than expected values were rationalized in terms of the myosin density distribution along the myosin thick filament axis. Our data provided new and practical insights for the application of the supramolecular model to study SHG intensity profiles in striated muscle.

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Section: Discussionsupporting

confidence: 63%

Section: Myosin Density Distributionmentioning

confidence: 99%

Section: Myosin Density Distributionmentioning

confidence: 99%

Section: Myosin Density Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the interpretation of second harmonic generation intensity profiles of striated muscle

et al. 2015

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Structural transitions in myosin and the origin of contractile force in muscle

Harrington

Ueno

1987

Biopolymers

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SynopsisForce generation in actively contracting muscle very likely involves a structural transition in each cycling cross-bridge while it is attached to actin. T w o different types of force-generating mechanisms are discussed in this paper: (1) the force-generating event results from a change in the effective angle of the myosin head (S-1 subunit) and (2) a conformational change in the a-helical S-2 region of the crossbridge occurs when this portion of the bridge is released from the thick-filament surface. This process causes shortening in S-2 and produces force. Evidence supporting mechanism 2 has been obtained from recent studies of actively contracting muscle fibers and of isolated my& rod subfragments using an enzyme-(chymotrypsin) probe technique to detect and pinpoint local melting within the a-helical structure. The kinetics of proteolysis and the site of cleavage were determined at various temperatures (5 to 40°C) by electrophoresis of digestion products on SDS gels. We found the cleavage sites to be localized in a restricted segment of S-2 spanning the LMM/HMM hinge region (64,OOO-9O,OOO M,./polypeptide chain from the C-terminus of the myosin rod). The cleavage rate constant for activated muscle fibers in the presence of an ATP-regenerating system was about 100 times larger at each temperature than that for rigor or relaxed muscle fibers, and it showed a marked increase in magnitude with increasing temperature. Comparative plots of the apparent rate constant for cleavage within the 5-2 hinge domain and the isometric force generated by active fibers vs MgATP concentration gave closely similar profiles, suggesting a close coupling between the conformational transitions within the S-2 hinge domain and contractile force when the cross-bridges undergo cycling.

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Calibration methods for quantitative image processing in electron microscopy

Lamvik

Davilla

1989

J. Elec. Microsc. Tech.

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An image can be represented digitally as a matrix of numbers. When those numbers are linearly related to a property of the object, such as mass per unit area, a simple integration of an image area leads to a total of that property, such as the mass of a particle that is represented in a selected area. Following techniques pioneered by Bahr and Zeitler, we illustrate the use of photographic densitometry of films exposed in an electron microscope to measure electron scattering. The transmission of an electron micrograph will be linear with respect to mass thickness for a particular value of background brightfield density, hence allowing determination of the mass of microscopic particles. We show here a digital computer method for conveniently establishing the linear condition by quantitative image processing using micrographs of polystyrene spheres. The method also serves to produce calibration curves for cases where the transfer from transmission to mass thickness is not linear. We also illustrate how an inexpensive computer is used to display and integrate regions of micrographs to determine particle mass.

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Distribution of mass within native thick filaments of vertebrate skeletal muscle

Cited by 9 publications

References 37 publications

On the interpretation of second harmonic generation intensity profiles of striated muscle

On the interpretation of second harmonic generation intensity profiles of striated muscle

Structural transitions in myosin and the origin of contractile force in muscle

Calibration methods for quantitative image processing in electron microscopy

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