scholarly journals Carbon replicas reveal double stranded structure of tight junctions in phase-contrast electron microscopy

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Evan S. Krystofiak ◽  
J. Bernard Heymann ◽  
Bechara Kachar
Keyword(s):  
Electron Microscopy ◽  
Tight Junctions ◽  
Phase Contrast ◽  
Carbon Replicas

New challenges to image processing posed by cryo-Electron microscopy of single particles

1991 ◽  
Vol 49 ◽  
pp. 422-423
Author(s):  
Joachim Frank
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Particle Orientation ◽  
Single Particles ◽  
Contrast Transfer Function ◽  
Virtual Absence ◽  
Cryo Electron Microscopy ◽  
Spatial Frequencies ◽  
New Challenges ◽  
Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

Imaging sub-micron objects with light microscopy: Visualization of the T-4 bacteriophage

1989 ◽  
Vol 47 ◽  
pp. 834-835
Author(s):  
Malcolm Brown ◽  
Reynolds M. Delgado ◽  
Michael J. Fink
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Focal Plane ◽  
Phase Contrast ◽  
Dark Field ◽  
E Coli ◽  
Polystyrene Beads ◽  
Television Camera ◽  
Transmission Electron ◽  
Universal Microscope

While light microscopy has been used to image sub-micron objects, numerous problems with diffraction-limitations often preclude extraction of useful information. Using conventional dark-field and phase contrast light microscopy coupled with image processing, we have studied the following objects: (a) polystyrene beads (88nm, 264nm, and 557mn); (b) frustules of the diatom, Pleurosigma angulatum, and the T-4 bacteriophage attached to its host, E. coli or free in the medium. Equivalent images of the same areas of polystyrene beads and T-4 bacteriophages were produced using transmission electron microscopy.For light microscopy, we used a Zeiss universal microscope. For phase contrast observations a 100X Neofluar objective (N.A.=1.3) was applied. With dark-field, a 100X planachromat objective (N.A.=1.25) in combination with an ultra-condenser (N.A.=1.25) was employed. An intermediate magnifier (Optivar) was available to conveniently give magnification settings of 1.25, 1.6, and 2.0. The image was projected onto the back focal plane of a film or television camera with a Carl Zeiss Jena 18X Compens ocular.

scholarly journals THE SUBMICROSCOPIC ORGANIZATION OF AXON MATERIAL ISOLATED FROM MYELIN NERVE FIBERS

1953 ◽  
Vol 98 (3) ◽  
pp. 269-276 ◽  
Author(s):  
E. De Robertis ◽  
C. M. Franchi
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Phase Contrast ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Dense Granules ◽  
Small Clusters ◽  
Membranous Material ◽  
The Way

A technique has been developed for the extrusion of axon material from myelinated nerve fibers. This material is then compressed and prepared for observation with the electron microscope. All the stages of preparation and purification of the axon material can be checked microscopically and in the present paper they are illustrated with phase contrast photomicrographs. Observation with the electron microscope of the compressed axons showed the presence of the following components: granules, fibrils, and a membranous material. Only the larger granules could be seen with the ordinary microscope. A considerable number of dense granules were observed. Of these the largest resemble typical mitochondria of 250 mµ by 900 mµ. In addition rows or small clusters of dense granules ranging in diameter from 250 to 90 mµ were present. In several specimens fragments of a membrane 120 to 140 A thick and intimately connected with the axon were found. The entire axon appeared to be constituted of a large bundle of parallel tightly packed fibrils among which the granules are interspersed. The fibrils are of indefinite length and generally smooth. They are rather labile structures, less resistant in the rat than in the toad nerve. They varied between 100 and 400 A in diameter and in some cases disintegrated into very fine filaments (less than 100 A thick). The significance is discussed of the submicroscopic structures revealed by electron microscopy of the material prepared in the way described.

HIGH RESOLUTION ELECTRON MICROSCOPE STUDY OF CdTe-Cd0.6Mn0.4 Te SUPERLATTICES

1985 ◽  
Vol 56 ◽  
Author(s):  
C. CHOI ◽  
N. OTSUKA ◽  
L. A. KOLODZIEJSKI ◽  
R. L. GUNSHOR-a
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Contrast ◽  
Electron Microscope Study ◽  
Lattice Mismatch ◽  
Thick Layer ◽  
High Resolution Electron Microscopy ◽  
Misfit Dislocations ◽  
Resolution Electron ◽  
High Resolution Electron Microscope

AbstractStructures of CdTe-Cd0.6Mn0.4Te superlattices which are caused by the lattice mismatch between suterlattice layers have been studied by high resolution electron microscopy (HREM). In thin-layer superlattices, the crystal lattice in each layeris elastically distorted, resulting in the change of the crystal symmetry from cubic to rhombohedral. The presence of the small rhombohedral distrotion has been confirmed through a phase contrast effect in HREM images. In a thick-layer superlattice, the lattice mismatch is accommodated by dissociated misfit dislocations. Burgers vectors of partial misfit dislocations have been identified from the shift of lattice fringes in HREM images.

Phase-contrast and electron-microscopic observations on a membranous complex in primary spermatocytes of the mouse

1975 ◽  
Vol 18 (1) ◽  
pp. 1-17
Author(s):  
A. Pleshkewych ◽  
L. Levine
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Phase Contrast ◽  
Cultured Cells ◽  
Light And Electron Microscopy ◽  
Cytoplasmic Inclusion ◽  
Electron Microscopic ◽  
Secondary Spermatocyte ◽  
Living Mouse ◽  
Circular Contour

A prominent cytoplasmic inclusion present in living mouse primary spermatocytes has been observed by both light and electron microscopy. It began to form at prometaphase and continued to increase in thickness and length as the cells developed. By metaphase it was a distinct sausage-shaped boundary that enclosed a portion of the cytoplasm between the spindle and the cell membrane. At the end of metaphase, the inclusion reached its maximum length. At telophase, it was divided between the daughter secondaries. The inclusion persisted as a circular contour in the interphase secondary spermatocyte. Electron microscopy of the same cultured cells that were previously observed with light microscopy revealed that the inclusion was a distinctive formation of membranes. It consisted of agranular cisternae and vesicles, and was therefore a membranous complex. Many of the smaller vesicles in the membranous complex resembled those found in the spindle. The cisternae in the membranous complex were identical to the cisternal endoplasmic reticulum of interphase primary spermatocytes. Nevertheless, the organization of vesicles and cisternae into the membranous complex was unique for the primaries in division stages, since such an organization was not present in their interphase stages.

Coelomomyces canadense stat. et comb. nov. (Blastocladiales: Coelomomycetaceae) from Psectrocladius sp. G (Diptera: Chironomidae)

1978 ◽  
Vol 56 (18) ◽  
pp. 2303-2306 ◽  
Author(s):  
Richard A. Nolan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Contrast ◽  
Field Phase ◽  
Species Status ◽  
Bright Field ◽  
Latin Diagnosis ◽  
Taxonomic Criterion ◽  
Sporangial Wall ◽  
Scanning Electron

Resistant sporangia of Coelomomyces chironomi var. canadense Weiser and McCauley were examined by bright-field, phase-contrast, and scanning electron microscopy (SEM). The use of SEM facilitated the observation of previously undescribed complex furrows in the sporangial wall. The taxonomic criterion for varietal status is discussed, and the variety is elevated to species status. Coelomomyces canadense (Weiser and McCauley) Nolan stat. et comb. nov. is described with an emended Latin diagnosis.

scholarly journals Comparative Electron Microscopy of Synapses in the Vertebrate Spinal Cord

1966 ◽  
Vol 1 (1) ◽  
pp. 67-80
Author(s):  
B. T. CHARLTON ◽  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Spinal Cord ◽  
Synaptic Transmission ◽  
Tight Junctions ◽  
Presynaptic Inhibition ◽  
Grey Matter ◽  
Rare Occurrence ◽  
Lower Vertebrates ◽  
Mode Of Transmission ◽  
Comparative Electron

Synapses with a cleft with ‘thickened’ membranes and presynaptic vesicles and mitochondria occur commonly throughout the grey matter of the spinal cord of goldfish, frog and various mammals studied. Such synapses are generally thought to have a chemical mode of transmission. The absence or rare occurrence of presynaptic neurofilaments in fish and frog accounts for the failure to detect boutons by silver methods, and there is no need to postulate morphologically unspecialized synaptic contacts in the lower vertebrates as some light microscopists did. Both fish and frog show axo-somatic or axo-dendritic tight junctions, which could be sites of electrical synaptic transmission. No neuronal tight junctions have yet been seen in the mammalian spinal cord. Axo-axo-dendritic synapses have been seen in the frog and mammalian cord, but not so far in the fish. Such serial synapses may be responsible for presynaptic inhibition. Neuroglia of fish, frog and mammals have tight junctions at their apposed surfaces. These differ structurally from neuronal tight junctions. Neuroglia in fish cord have, in addition, desmosomes at their apposed surfaces.

scholarly journals Antibody-induced membrane fusion in Paramecium

1984 ◽  
Vol 65 (1) ◽  
pp. 153-162
Author(s):  
A. Barnett ◽  
E. Steers
Keyword(s):  
Electron Microscopy ◽  
Membrane Fusion ◽  
Phase Contrast ◽  
Immobilized Cells ◽  
Living Cells ◽  
Immune Serum ◽  
Induced Membrane ◽  
Transmission Electron ◽  
Membrane Changes ◽  
Antigen Antibody

Immobilization of cells by specific immune serum involves crosslinking between immunoglobulin G (IgG) and the i-antigen in the cell membrane. Globular material is seen to accumulate at the ciliary tips by phase-contrast and fluorescence microscopy in a manner analogous to ‘capping’ in more typical eukaryotes. When immobilized cells of Paramecium are examined by scanning electron microscopy, the fused ciliary tips are seen to be distended, discoidal membranes. Transmission electron microscopy often reveals several ciliary axonemes enclosed within a single, enlarged membrane that is oriented with the ferritin-labelled second antibody directed against the i-antigen antibody on the outer surface only. Fixed cells or living cells treated with immune Fab do not show membrane changes, but do bind antibody. Membrane fusion occurs only if cells are alive and the i-antigen is directly or indirectly cross-linked by intact immune IgG.

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