Dark-Field Chest Radiography in the Detection of Emphysema

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

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Protamine-DNA interaction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081863 ◽

1978 ◽

Vol 36 (2) ◽

pp. 200-201

Author(s):

D.P. Bazett-Jones ◽

F.P. Ottensmeyer

Keyword(s):

Small Volume ◽

Double Helix ◽

Dna Interaction ◽

Dark Field ◽

Sperm Head ◽

Nuclear Proteins ◽

Field Electron Microscopy ◽

Dark Field Electron ◽

Dna Double Helix ◽

Positively Charged

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.

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Evaluation of the dark field method for large association of spread DNA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081814 ◽

1978 ◽

Vol 36 (2) ◽

pp. 190-191

Author(s):

Douglas C. Barker

Keyword(s):

Electron Microscopy ◽

Molecular Weight ◽

Mitochondrial Dna ◽

Extraction Method ◽

Field Method ◽

Dark Field ◽

Kinetoplast Dna ◽

Field Electron ◽

Field Electron Microscopy ◽

Dark Field Electron

A number of satisfactory methods are available for the electron microscopy of nicleic acids. These methods concentrated on fragments of nuclear, viral and mitochondrial DNA less than 50 megadaltons, on denaturation and heteroduplex mapping (Davies et al 1971) or on the interaction between proteins and DNA (Brack and Delain 1975). Less attention has been paid to the experimental criteria necessary for spreading and visualisation by dark field electron microscopy of large intact issociations of DNA. This communication will report on those criteria in relation to the ultrastructure of the (approx. 1 x 10-14g) DNA component of the kinetoplast from Trypanosomes. An extraction method has been developed to eliminate native endonucleases and nuclear contamination and to isolate the kinetoplast DNA (KDNA) as a compact network of high molecular weight. In collaboration with Dr. Ch. Brack (Basel [nstitute of Immunology), we studied the conditions necessary to prepare this KDNA Tor dark field electron microscopy using the microdrop spreading technique.

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Thin Pyrolytic Graphite Films for Electron Microscope Substrates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065183 ◽

1971 ◽

Vol 29 ◽

pp. 226-227 ◽

Cited By ~ 1

Author(s):

George H. N. Riddle ◽

Benjamin M. Siegel

Keyword(s):

Vacuum Chamber ◽

Pyrolytic Graphite ◽

High Vacuum ◽

Dark Field ◽

Ultra High Vacuum ◽

Graphite Substrate ◽

Nickel Substrate ◽

Routine Procedure ◽

Field Electron Microscopy ◽

Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

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Two Investigations into Grain Boundary Structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080833 ◽

1977 ◽

Vol 35 ◽

pp. 688-691

Author(s):

P. Humble

Keyword(s):

Grain Boundary ◽

Dark Field ◽

Boundary Structure ◽

Boundary Dislocation ◽

Bright Field ◽

Intrinsic Structure ◽

Weak Beam ◽

Grain Boundary Structure ◽

Independent Information ◽

Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

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Elastic Scattering in Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071703 ◽

1973 ◽

Vol 31 ◽

pp. 252-253

Author(s):

J. Langmore ◽

M. Isaacson ◽

J. Wall ◽

A. V. Crewe

Keyword(s):

Electron Microscopy ◽

Elastic Scattering ◽

Cross Section ◽

Quantum Noise ◽

Dark Field ◽

Elastic Cross Section ◽

Biological Molecules ◽

Dark Field Microscopy ◽

Field Systems ◽

Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

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