scholarly journals Bilaterally Asymmetric Helical Myofibrils in Ascidian Tadpole Larvae

2021 ◽  
Vol 9 ◽  
Author(s):  
Koichi Matsuo ◽  
Ryota Tamura ◽  
Kohji Hotta ◽  
Mayu Okada ◽  
Akihisa Takeuchi ◽  
...  
Keyword(s):  
Phase Contrast ◽  
Longitudinal Axis ◽  
Biological Molecules ◽  
Cell Alignment ◽  
Cell Nuclei ◽  
Locomotor System ◽  
X Ray ◽  
Left Handed ◽  
Symmetrical Cell ◽  
Left Right Asymmetry

The locomotor system is highly bilateral at the macroscopic level. Homochirality of biological molecules is fully compatible with the bilateral body. However, whether and how single-handed cells contribute to the bilateral locomotor system is obscure. Here, exploiting the small number of cells in the swimming tadpole larva of the ascidian Ciona, we analyzed morphology of the tail at cellular and subcellular scales. Quantitative phase-contrast X-ray tomographic microscopy revealed a high-density midline structure ventral to the notochord in the tail. Muscle cell nuclei on each side of the notochord were roughly bilaterally aligned. However, fluorescence microscopy detected left-right asymmetry of myofibril inclination relative to the longitudinal axis of the tail. Zernike phase-contrast X-ray tomographic microscopy revealed the presence of left-handed helices of myofibrils in muscle cells on both sides. Therefore, the locomotor system of ascidian larvae harbors symmetry-breaking left-handed helical cells, while maintaining bilaterally symmetrical cell alignment. These results suggest that bilateral animals can override cellular homochirality to generate the bilateral locomotor systems at the supracellular scale.

scholarly journals Nuclear incorporation of iron during the eukaryotic cell cycle

2016 ◽  
Vol 23 (6) ◽  
pp. 1490-1497 ◽  
Author(s):  
Ian Robinson ◽  
Yang Yang ◽  
Fucai Zhang ◽  
Christophe Lynch ◽  
Mohammed Yusuf ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Fluorescence Microscopy ◽  
Phase Contrast ◽  
Eukaryotic Cell ◽  
Inhomogeneous Distribution ◽  
Cell Nuclei ◽  
X Ray ◽  
Microscopy Images ◽  
Different Levels

Scanning X-ray fluorescence microscopy has been used to probe the distribution of S, P and Fe within cell nuclei. Nuclei, which may have originated at different phases of the cell cycle, are found to show very different levels of Fe present with a strongly inhomogeneous distribution. P and S signals, presumably from DNA and associated nucleosomes, are high and relatively uniform across all the nuclei; these agree with X-ray phase contrast projection microscopy images of the same samples. Possible reasons for the Fe incorporation are discussed.

Which is Better for Protein Imaging: Phase Contrast TEM or Annular Dark Field STEM?

2001 ◽  
Vol 7 (S2) ◽  
pp. 382-383
Author(s):  
P. Rez
Keyword(s):  
Phase Contrast ◽  
Protein Structure Determination ◽  
Dark Field ◽  
Biological Molecules ◽  
Contrast Imaging ◽  
Bright Field ◽  
Low Contrast ◽  
X Ray ◽  
Contrast Microscopy ◽  
Annular Dark Field

In a landmark paper Henderson compared X-ray, neutrons and electrons for protein structure determination. He showed that electron microscopy should be superior to X-ray or neutron diffraction in terms of dose for a given resolution. in addition he presented a theoretical analysis to determine the smallest size molecule whose structure could be determined by phase contrast microscopy. Although he qualitatively considered amplitude contrast mechanisms and concluded they were inferior to phase contrast, no explicit numerical analysis was performed. It has been implicitly assumed that bright field phase contrast imaging is the optimal technique for imaging small biological molecules. Protein specimens are usually embedded in some medium such as ice or glucose. Since they must give a very low contrast it seems reasonable to expect that bright field techniques for these weakly scattering objects would be inferior, given that a weak signal is sitting on large background.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

Direct visualization of phase-separated domains in lipid membranes

1978 ◽  
Vol 36 (2) ◽  
pp. 290-291
Author(s):  
S. W. Hui ◽  
T. P. Stewart
Keyword(s):  
Lipid Membranes ◽  
Structural Information ◽  
Freeze Fracture ◽  
Biological Molecules ◽  
Vacuum Drying ◽  
Direct Visualization ◽  
X Ray Diffraction ◽  
Electron Microscopic ◽  
X Ray ◽  
Hydrocarbon Chains

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

Correction of the contrast transfer function to determine the radial density distribution of frozen-hydrated tobacco mosaic virus

1992 ◽  
Vol 50 (1) ◽  
pp. 536-537
Author(s):  
Michael F. Smith ◽  
John P. Langmore
Keyword(s):  
Transfer Function ◽  
Phase Contrast ◽  
Heavy Atom ◽  
Biological Molecules ◽  
Frequency Compensation ◽  
Contrast Transfer Function ◽  
High Background ◽  
Low Contrast ◽  
Radial Density Distribution ◽  
Excellent Preservation

The purpose of image reconstruction is to determine the mass densities within molecules by analysis of the intensities within images. Cryo-EM offers this possibility by virtue of the excellent preservation of internal structure without heavy atom staining. Cryo-EM images, however, have low contrast because of the similarity between the density of biological material and the density of vitreous ice. The images also contain a high background of inelastic scattering. To overcome the low signal and high background, cryo-images are typically recorded 1-3 μm underfocus to maximize phase contrast. Under those conditions the image intensities bear little resemblance to the object, due to the dependence of the contrast transfer function (CTF) upon spatial frequency. Compensation (i.e., correction) for the CTF is theoretically possible, but implementation has been rare. Despite numerous studies of molecules in ice, there has never been a quantitative evaluation of compensated images of biological molecules of known structure.

Image Quality Analysis of X-ray Grating Interferometer Using Integrating-bucket Method

2020 ◽  
Vol 64 (2) ◽  
pp. 20503-1-20503-5
Author(s):  
Faiz Wali ◽  
Shenghao Wang ◽  
Ji Li ◽  
Jianheng Huang ◽  
Yaohu Lei ◽  
...  
Keyword(s):  
Image Quality ◽  
Phase Contrast ◽  
Quality Analysis ◽  
Phase Contrast Imaging ◽  
Phase Image ◽  
Contrast Imaging ◽  
High Quality ◽  
Image Quality Analysis ◽  
X Ray ◽  
Grating Interferometer

Abstract Grating-based x-ray phase-contrast imaging has the potential to enhance image quality and provide inner structure details non-destructively. In this work, using grating-based x-ray phase-contrast imaging system and employing integrating-bucket method, the quantitative expressions of signal-to-noise ratios due to photon statistics and mechanical error are analyzed in detail. Photon statistical noise and mechanical error are the main sources affecting the image noise in x-ray grating interferometry. Integrating-bucket method is a new phase extraction method translated to x-ray grating interferometry; hence, its image quality analysis would be of great importance to get high-quality phase image. The authors’ conclusions provide an alternate method to get high-quality refraction signal using grating interferometer, and hence increases applicability of grating interferometry in preclinical and clinical usage.

Numerical analysis of shift error in X-ray phase contrast imaging for large field of view

2017 ◽  
Vol 34 (1) ◽  
pp. 8
Author(s):  
Jianheng Huang ◽  
Yaohu Lei ◽  
Xin Liu ◽  
Jinchuan Guo ◽  
Ji Li ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Phase Contrast ◽  
Field Of View ◽  
Phase Contrast Imaging ◽  
Large Field ◽  
Contrast Imaging ◽  
X Ray
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