Freeze-Fracture Replication of Frozen Outer Segments of Rat Retinal Rods

1969 ◽  
Vol 27 ◽  
pp. 392-393
Author(s):  
Thomas S. Leeson ◽  
C. Roland Leeson
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Outer Segment ◽  
Freeze Fracture ◽  
X Ray Diffraction ◽  
X Ray ◽  
Outer Segments ◽  
Retinal Rods ◽  
Temperature Electron ◽  
Freeze Etching

Numerous previous studies of outer segments of retinal receptors have demonstrated a complex internal structure of a series of transversely orientated membranous lamellae, discs, or saccules. In cones, these lamellae probably are invaginations of the covering plasma membrane. In rods, however, they appear to be isolated and separate discs although some authors report interconnections and some continuities with the surface near the base of the outer segment, i.e. toward the inner segment. In some species, variations have been reported, such as longitudinally orientated lamellae and lamellar whorls. In cross section, the discs or saccules show one or more incisures. The saccules probably contain photolabile pigment, with resulting potentials after dipole formation during bleaching of pigment. Continuity between the lamina of rod saccules and extracellular space may be necessary for the detection of dipoles, although such continuity usually is not found by electron microscopy. Particles on the membranes have been found by low angle X-ray diffraction, by low temperature electron microscopy and by freeze-etching techniques.

scholarly journals The crystal lattice of Paramecium trichocysts before and after exocytosis by X-ray diffraction and freeze-fracture electron microscopy.

1987 ◽  
Vol 105 (4) ◽  
pp. 1649-1662 ◽  
Author(s):  
L Sperling ◽  
A Tardieu ◽  
T Gulik-Krzywicki
Keyword(s):  
Electron Microscopy ◽  
Freeze Fracture ◽  
X Ray ◽  
Before And After ◽  
Ordered Array ◽  
Extracellular Form ◽  
Freeze Etching ◽  
Freeze Fracture Electron Microscopy ◽  
Genetically Determined ◽  
Fracture Electron

Paramecium trichocysts are unusual secretory organelles in that: (a) their crystalline contents are built up from a family of low molecular mass acidic proteins; (b) they have a precise, genetically determined shape; and (c) the crystalline trichocyst contents expand rapidly upon exocytosis to give a second, extracellular form which is also an ordered array. We report here the first step of our study of trichocyst structure. We have used a combination of x-ray powder diffraction, freeze-etching, and freeze-fracture electron microscopy of isolated, untreated trichocysts, and density measurements to show that trichocyst contents are indeed protein crystals and to determine the elementary unit cell of both the compact intracellular and the extended extracellular form.

scholarly journals Structural states of myelin observed by x-ray diffraction and freeze-fracture electron microscopy.

1979 ◽  
Vol 82 (1) ◽  
pp. 140-149 ◽  
Author(s):  
D A Kirschner ◽  
C J Hollingshead ◽  
C Thaxton ◽  
D L Caspar ◽  
D A Goodenough
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Freeze Fracture ◽  
Intermediate Structure ◽  
X Ray Diffraction ◽  
Membrane Unit ◽  
X Ray ◽  
Critical Measure ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Coordinated freeze-fracture electron microscopy and x-ray diffraction were used to visualize the morphological relation between compacted and native period membrane arrays in myelinated nerves treated with dimethylsulfoxide (DMSO). Comparison of x-ray diffraction at room temperature and at low temperature was used as a critical measure of the extent of structural preservation. Our x-ray diffraction patterns show that in the presence of cryoprotective agents, it is possible to preserve with only small changes the myelin structure which exists at room temperature. These changes include a slight increase in packing disorder of the membrane, a small, negative thermal expansion of the membrane unit, and some reorganization in the cytoplasmic half of the bilayer. The freeze-fracture electron microscopy clearly demonstrates continuity of compact and native period phases in DMSO-treated myelin. Finally, the use of freezing to trap the transient, intermediate structure during a structural transition in glycerol is demonstrated.

Palygorskite from Warren Quarry, Enderby, Leicestershire, England

Clay Minerals ◽  
1973 ◽  
Vol 10 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Pei-Lin Tien
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Structural Formula ◽  
Filling Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rock Fragments ◽  
Monoclinic Form ◽  
Dolomitic Rock ◽  
Transversal Cross Section

AbstractSpecimens of palygorskite from Warren Quarry, Enderby, Leicestershire, have been studied in the laboratories. The mineral is found in dioritic rocks in association with angular dolomitic rock fragments as the filling material of a joint, the walls of which are sometimes lined with calcite and dolomite. Palygorskite occurs as 3-10 mm long bundles of fibres, 0·03-0·1μm wide. X-ray diffraction data indicate that the mineral may occur in the monoclinic form. The structural formula for the half-unit cell is Si8(Al1.89Fe0.053+Ti0.01Mg1.99)O20(OH)2(OH2)43·61 H2O.Ca0.07. Data obtained from differential thermal and infrared analyses are comparable with those for palygorskite in the literature, but the six-sided transversal cross-section of the fibres as revealed by electron microscopy is unexpected. The mineral was formed after the deposition of the overlying basal Triassic rocks when ground waters penetrated cracks in the dioritic rocks, causing Si and Mg to be released there and above the unconformity.

Elucidation of Crystal Packing by X-ray Diffraction and Freeze-etching Electron Microscopy. Studies on GTP Cyclohydrolase I ofEscherichia coli

1995 ◽  
Vol 253 (1) ◽  
pp. 208-218 ◽  
Author(s):  
Winfried Meining ◽  
Adelbert Bacher ◽  
Luis Bachmann ◽  
Cornelia Schmid ◽  
Sevil Weinkauf ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Crystal Packing ◽  
Ofescherichia Coli ◽  
X Ray Diffraction ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
X Ray ◽  
Freeze Etching

Selective Laser Sintering of Different Powders of Co-Cr-Mo

2014 ◽  
Vol 802 ◽  
pp. 338-342
Author(s):  
Claudinei dos Santos ◽  
Paula Cipriano da Silva ◽  
Luciane Carvalho de Paula ◽  
Alexandre Fernandes Habibe ◽  
Jefferson Fabrício C. Lins ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Particle Size ◽  
Size Distribution ◽  
Cross Section ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

In this work, different commercial Co-Cr-Mo powders were used in selective laser sintering. Commercial powders with particle size distribution between 5 and 50μm were sintered by laser sintering, and characterized. The samples were characterized by X-ray diffraction, indicating Co as the only crystalline phase. Relative density was measured by Archimedes method showing values between 90 and 96% of TD, depending on the powder used. Scanning electron microscopy performed on the cross section of the sintered samples, indicates that the microstructural features are similar, but the surface finish of the samples differ significantly due to the morphology and size distribution of the starting powders used.

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