scholarly journals CONFIGURATION OF A FILAMENTOUS NETWORK IN THE AXOPLASM OF THE SQUID (LOLIGO PEALII L.) GIANT NERVE FIBER

1969 ◽  
Vol 43 (3) ◽  
pp. 480-505 ◽  
Author(s):  
J. Metuzals
Keyword(s):  
Nerve Fiber ◽  
Protein Structures ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Uranyl Acetate ◽  
Nerve Fibers ◽  
Acetate Solution ◽  
Thin Sections ◽  
Resolution Electron ◽  
Specific Affinity

High-resolution electron microscopy is integrated with physicochemical methods in order to investigate the following preparations of the giant nerve fibers of the squid (Loligo pealii L.): (1) Thin sections of fibers fixed in four different fixatives; (2) fresh axoplasm stained negatively in solutions of different pH and composition; (3) chemically isolated threadlike elements of the axoplasm. A continuous, three-dimensional network can be identified in all these preparations of the axoplasm. The network is composed of coiled or looped unit-filaments ∼30 A wide. The unit-filaments are intercoiled in strands ∼ 70–250 A wide. The strands are oriented longitudinally in the axoplasm, often having a sinuous course and cross-associations. Microtubules are surrounded by intercoiled unit-filaments and filamentous strands. Calcium ions cause loosening and disintegration of the network configuration. UO2++ ions of a 1% uranyl acetate solution at pH 4.4 display a specific affinity for filamentous protein structures of the squid giant nerve fiber axoplasm, segregating the filamentous elements of the axoplasm in a coiled, threadlike preparation. The uranyl ions combine probably with the carboxyl groups of the main amino acids of the protein—glutamic and aspartic acids. It is proposed that by coiling/decoiling and folding/unfolding of the unit-filaments, shifts in physicochemical properties of the axoplasm are maintained.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

Role of the Small (40S) Subunits in the Structure of the Interface of Eukaryotic Ribosomes

1980 ◽  
Vol 38 ◽  
pp. 548-549
Author(s):  
M. Boublik ◽  
N. Robakis ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Structural Similarity ◽  
High Resolution Electron Microscopy ◽  
Peptide Bond ◽  
Uranyl Acetate ◽  
Mutual Orientation ◽  
Mutual Position ◽  
Peptide Bond Formation ◽  
Resolution Electron ◽  
Direct Technique ◽  
Structural Details

Ribosomes are ribonucleoprotein particles which process the genetic information coded in mRNA into protein synthesis. The analogy in function and composition of ribosomes from various sources, both prokaryotic and eukaryo-tic, imply a structural similarity. At present, high resolution electron microscopy is the most direct technique with a potential to resolve the extent of the structural homology of ribosomal particles at a macromolecular level. The structure of ribosomes is highly complex as a result of the large number of their constituents. In general, 80S eukaryotic monosomes consist of two uneven subunits - large (60S) and small (40S) - accomodating four different RNAs and approximately 80 different proteins. Mutual orientation of both subunits on the monosome is of particular interest because it determines the interface, the supposed site of interactions of ribosomes with other macro-molecules involved in peptide bond formation. Since entrapping of the contrasting solution (0.5% aqueous uranyl acetate) obscures all structural details in the interface, information on its architecture is limited to an indirect reconstruction based on the established 3-D structure of both sub-units and their mutual position after association.

High-Resolution Electron Microscopy on Thin Sections of Monodisperse CdS Particles

1996 ◽  
Vol 183 (1) ◽  
pp. 295-298 ◽  
Author(s):  
Jun-Mo Yang ◽  
Daisuke Shindo ◽  
Grace E. Dirige ◽  
Atsushi Muramatsu ◽  
Tadao Sugimoto
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Thin Sections ◽  
Resolution Electron

Atomic Scale Aluminum and Strain Distribution in a Gan/AlxGa1−XN Heterostructure

1997 ◽  
Vol 482 ◽  
Author(s):  
Christian Kisielowski ◽  
Olaf Schmidt ◽  
Jinwei Yang
Keyword(s):  
Three Dimensional ◽  
Chemical Vapor ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Organic Chemical ◽  
Well Test ◽  
Lattice Constants ◽  
Resolution Electron ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition

AbstractA GaN/AlxGalxN multi-quantum well test structure with Al concentrations 0 ≤ xAl ≤ 1 was utilized to investigate the growth of AlxGal–xN barrier layers deposited by metal organic chemical vapor deposition (MOCVD). A transition from a two dimensional (2D) to a three dimensional (3D) growth mode was observed in AlxGa1–xN barriers with XAl ≥ 0.75. It is argued that the transition occurs because of growth at temperatures that are low compared with the materials melting points Tmelt. The resulting rough AlxGa1–xN surfaces can be planarized by overgrowth with GaN. Quantitative high resolution electron microscopy (HREM) was applied to measure composition and strain profiles across the GaN/AlxGa1−xN stacks at an atomic level. The measurements reveal a substantial variation of lattice constants at the AlxGa1−xN/GaN interfaces that is attributed to an Al accumulation.

Changes in Myelin Ultrastructure Produced by a Series of Physical and Chemical Agents

1970 ◽  
Vol 28 ◽  
pp. 118-119
Author(s):  
Vincenzo Di Carlo
Keyword(s):  
Synaptic Vesicles ◽  
Plasma Membranes ◽  
Brain Cortex ◽  
High Resolution Electron Microscopy ◽  
Mammalian Brain ◽  
Thin Sections ◽  
Chemical Agents ◽  
Resolution Electron ◽  
Physical And Chemical ◽  
Granule Diameter

High-resolution electron microscopy of ultra-thin sections of fixed and plastic-embedded tissue shows that myelin consists essentially of an orderly aggregate of osmiophilic granules and osmiophobic globules. Frequently, granules and globules can be seen organized in hexagonal formations (diameter of about 90-120 A), which have an osmiophilic granule (diameter of about 30 A) in the center and six osmiophobic globules (diameter of about 40-45 A) around it. These formations are morphologically very similar to the “polyhedric-globular” (P-G) units (approx. 40-50 A high hexagonal prisms) which were described in the membrane of synaptic vesicles and mitochondria and in the plasma membranes of frog brain cortex as well as in the ribosomes of neurons of mammalian brain cortex. The P-G units were postulated to be an important, if not the exclusive, constituent of many biological membranes, which would be essentially a mosaic of such hexagonal prisms. Since ribosomes, which are believed to contain no lipid, also show the presence of P-G units in their structure, one wonders whether these units might possibly reflect mainly the presence of protein.

The Three-Dimensional shape of carbon nanotubes by High Resolution Electron Microscopy

1993 ◽  
Vol 51 ◽  
pp. 754-755
Author(s):  
Z. G. Li ◽  
L. Liang ◽  
P.J. Fagan ◽  
M. van Kavelaar
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
High Resolution ◽  
Large Scale ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Dimensional Shape ◽  
Dimensional Object ◽  
Three Dimensional Shape

Following the discovery of a large scale synthesis of fullerenes, the existence of the related carbon nanotubes was suggested by high resolution electron microscopy (HREM). Larger scale syntheses of these nanotube-rich materials has now been reported and has sparked interest worldwide. Because the HREM technique essentially observes the projection of a three dimensional object onto a two-dimensional plane, the three dimensional shape of the object is usually not apparent in typical HREM images. However, as we report here, by rotating along the axis of single carbon nanotube, and recording the images in succession by HREM, the non-cylindrical nature of these tubes is revealed, especially near the sealed ends of the nanotubes. In addition, from electon diffraction and X-ray diffraction, we find the spacing between the planes to be 3.398(8) Å on average. This is in contrast to earlier reports which suggested an interlayer distance of 3.35 Å, similar to the graphite interplanar spacing.

Brain Nerve Fiber Tracking Algorithm Based on Improved Optical Flow in Combination of Bayesian Prior Constraints

2020 ◽  
Vol 10 (2) ◽  
pp. 452-457
Author(s):  
Shen Jian ◽  
Chen Huan ◽  
Zuo Jianjian ◽  
Pan Xuming
Keyword(s):  
Optical Flow ◽  
Nerve Fiber ◽  
Diffusion Tensor ◽  
Three Dimensional ◽  
Fiber Tracking ◽  
Nerve Fibers ◽  
Tracking Algorithm ◽  
Brain Diseases ◽  
Field Estimation ◽  
The Brain

Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) can track the brain nerve fiber and reconstruct non-invasively the three-dimensional image by tracing the local tensor orientation. The commonly used tracking method is usually based on the local diffusion information and insufficient to consider the geometrical structure and fractional anisotropy which is constrained by anatomical structure and physiological function of human. Therefore, a novel brain nerve fiber tracking algorithm based on Bayesian optical-flow constrained framework is proposed. The construction of energy function is the core step of global optical flow field estimation technology. In this paper, data fidelity constraint, prior constraint, penalty function and weight factor are introduced to construct Bayesian constraint function. The fiber trend model is displayed intuitively to obtain the structure and direction of the inner nerve fibers of the brain, which can better assist in the diagnosis and treatment of clinical brain diseases, and lay a foundation for subsequent brain tissue research.

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