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.

High resolution electron microscopy of lanthanum phosphate crystals

1978 ◽  
Vol 36 (1) ◽  
pp. 274-275
Author(s):  
J. C. Wheatley ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
High Resolution ◽  
Petroleum Industry ◽  
High Resolution Electron Microscopy ◽  
Lanthanum Phosphate ◽  
Good Catalyst ◽  
Resolution Electron ◽  
Good Catalytic Activity ◽  
Physical And Chemical

Rare-earth phosphates are of particular interest because of their catalytic properties associated with the hydrolysis of many aromatic chlorides in the petroleum industry. Lanthanum phosphates (LaPO4) which have been doped with small amounts of copper have shown increased catalytic activity (1). However the physical and chemical characteristics of the samples leading to good catalytic activity are not known.Many catalysts are amorphous and thus do not easily lend themselves to methods of investigation which would include electron microscopy. However, the LaPO4, crystals are quite suitable samples for high resolution techniques.The samples used were obtained from William L. Kehl of Gulf Research and Development Company. The electron microscopy was carried out on a JEOL JEM-100B which had been modified for high resolution microscopy (2). Standard high resolution techniques were employed. Three different sample types were observed: 669A-1-5-7 (poor catalyst), H-L-2 (good catalyst) and 27-011 (good catalyst).

scholarly journals Initial events during phagocytosis by macrophages viewed from outside and inside the cell: membrane-particle interactions and clathrin.

1982 ◽  
Vol 94 (3) ◽  
pp. 613-623 ◽  
Author(s):  
J Aggeler ◽  
Z Werb
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Cell Attachment ◽  
High Resolution Electron Microscopy ◽  
Peritoneal Macrophages ◽  
Coated Pits ◽  
Thin Sections ◽  
Particle Uptake ◽  
Freeze Dried

The initial events during phagocytosis of latex beads by mouse peritoneal macrophages were visualized by high-resolution electron microscopy of platinum replicas of freeze-dried cells and by conventional thin-section electron microscopy of macrophages postfixed with 1% tannic acid. On the external surface of phagocytosing macrophages, all stages of particle uptake were seen, from early attachment to complete engulfment. Wherever the plasma membrane approached the bead surface, there was a 20-nm-wide gap bridged by narrow strands of material 12.4 nm in diameter. These strands were also seen in thin sections and in replicas of critical-point-dried and freeze-fractured macrophages. When cells were broken open and the plasma membrane was viewed from the inside, many nascent phagosomes had relatively smooth cytoplasmic surfaces with few associated cytoskeletal filaments. However, up to one-half of the phagosomes that were still close to the cell surface after a short phagocytic pulse (2-5 min) had large flat or spherical areas of clathrin basketwork on their membranes, and both smooth and clathrin-coated vesicles were seen fusing with or budding off from them. Clathrin-coated pits and vesicles were also abundant elsewhere on the plasma membranes of phagocytosing and control macrophages, but large flat clathrin patches similar to those on nascent phagosomes were observed only on the attached basal plasma membrane surfaces. These resulted suggest that phagocytosis shares features not only with cell attachment and spreading but also with receptor-mediated pinocytosis.

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

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.

Synaptic and Extra-Synaptic Intercellular Filaments in Brain Cortex

1969 ◽  
Vol 27 ◽  
pp. 306-307
Author(s):  
Vincenzo Di Carlo
Keyword(s):  
Focal Plane ◽  
Messenger Rna ◽  
Brain Cortex ◽  
The Other ◽  
Mammalian Brain ◽  
Thin Filaments ◽  
Dense Bodies ◽  
Resolution Electron ◽  
Neuronal Processes ◽  
Electron Microscopical

In the course of high-resolution electron microscopical investigations on the morphology and distribution of RNA-containing organelles in the neuropil of mammalian brain cortex, thin filaments were observed bridging the intercellular gap between non-synaptic areas of neuronal processes as well as between neuronal processes and glial cells. Some among them are over 200 mμ long. Morphologically these intercellular filaments are quite similar to the filaments which, inside polysomes, connect one ribosome to the others and which other investigators interpreted as being messenger-RNA. As a matter of fact, the intercellular filaments are often closely associated with dense bodies which can be identified as ribosomes (Fig. 2 and 3). Some of the filaments, however, appear to be only a few hundred A long and appear not to contact ribosomes. On the other hand, at present one cannot exclude that these apparently short filaments may actually be longer and be connected with ribosomes in areas outside the focal plane of the electron micrographs or even outside the very thin section of tissue under observation.

Microstructure and Lattice Defects in Polycrystalline Nuclear Ceramics

1968 ◽  
Vol 26 ◽  
pp. 270-271
Author(s):  
J. L. Daniel ◽  
S. J. Mayhan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Thin Sections ◽  
Small Areas ◽  
Physical Measurements ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Mechanical Thinning

Transmission electron microscopy of several nuclear ceramics has been extended to thin sections of as - fabricated poly-crystalline materials, by use of a thinning technique utilizing only common metallographic practices. The method is based on work by Doherty and Leombruno. However, while mechanical thinning (polishing) produces large, evenly thinned specimens, the surface of ceramic materials retains many shallow scratches and defects introduced by the polishing medium. On the other hand, the chemical thinning methods commonly applied produce only very small areas which are thin enough for examination by transmission electron microscopy, since preferential attack occurs on grain boundaries, inclusions, second phases, etc. By combining the chemical polish with the mechanical thinning procedures, large, relatively clean areas of ceramic materials can be produced. Another significant advantage is that in the course of thinning, the same specimens can be examined frequently and in detail by light microscopy, some physical measurements can be made along the way (e.g., microhardness, spectral transmission, autoradiography), and all observations can be closely correlated finally with the high resolution electron microscopy.

New Insights on the Morphology of Nanocomposite Prepared by In Situ Emulsion Polymerization

2015 ◽  
Vol 775 ◽  
pp. 170-175
Author(s):  
José Costa de Macêdo Neto ◽  
João Evangelista Neto ◽  
Nayra Reis do Nascimento ◽  
Sheila Contant ◽  
Liliane Maria Ferrareso Lona
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
Nanocomposite Powder ◽  
Thin Sections ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Level Of Details ◽  
High Level

In order to better understand the morphology and properties of polymer nanocomposites it is necessary to conduct their characterization by Transmission Electron Microscopy (TEM). This work shows a technique through which the nanocomposite powder is mixed with a resin, and after cured, thin sections can be obtained by ultramicrotomy. Another technique presented in this work deals with the observation of clay powder in solution. In this work High Resolution Electron Microscopy (HRTEM) was used to obtain images of the nanocomposites and clay. Images with a high level of details were showed. Through the use of such techniques, it was possible to observe two types of clay morphology in polymer matrix and its distribution. The dimensions and hexagonal layers of the natural clay used as nanofiller for the nanocomposite were also observed. The X-ray Diffraction (XRD) was used to investigate the kaolinite and nanocomposite.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

One Million Direct Magnification Microscopy

1971 ◽  
Vol 29 ◽  
pp. 166-167
Author(s):  
J. A. Hugo ◽  
V. A. Phillips
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Illumination Level ◽  
Level Of Detail ◽  
Photographic Emulsion ◽  
Low Contrast ◽  
Fluorescent Screen ◽  
Resolution Electron ◽  
Lattice Images ◽  
Electron Microscopes

A continuing problem in high resolution electron microscopy is that the level of detail visible to the microscopist while he is taking a picture is inferior to that obtainable by the microscope, readily readable on a photographic emulsion and visible in an enlargement made from the plate. Line resolutions, of 2Å or better are now achievable with top of the line 100kv microscopes. Taking the resolution of the human eye as 0.2mm, this indicates a need for a direct viewing magnification of at least one million. However, 0.2mm refers to optimum viewing conditions in daylight or the equivalent, and certainly does not apply to a (colored) image of low contrast and illumination level viewed on a fluorescent screen through a glass window by the dark-adapted eye. Experience indicates that an additional factor of 5 to 10 magnification is needed in order to view lattice images with line spacings of 2 to 4Å. Fortunately this is provided by the normal viewing telescope supplied with most electron microscopes.

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