Dark electron microscopes

Figure 3 Bright-field (a) and dark-field (b) STEM images of crushed ceramic particles dispersed on a "holey" carbon film supported on an electron microscope grid (shown at the right).

Figure 48-6. Dark field electron micrograph of a proteoglycan aggregate in which the proteoglycan subunits and filamentous backbone are particularly well extended. (Reproduced, with permission, from Rosenberg L, Heilman W, Kleinschmidt AK Electron microscopic studies of proteoglycan aggregates from bovine articular cartilage. J Biol Chem 1975 250 1877.)...

Figure 9.3. Characterization of mesoporous Ti02 films templated by Pluronics block copolymers using diverse characterization techniques XRD pattern (a), transmission electron microscope (TEM) image (b), dark-field TEM image (c), and isotherms of Kr adsorption (d).The Pluronic-templated Ti02 films were calcined at 400°C (solid points) and 600°C (open points). The films were prepared according to Alberius et al. (Ref. 14).

Information concerning myelin structure is also available from electron microscope studies, which visualize myelin as a series of alternating dark and less dark lines (protein layers) separated by unstained zones (the lipid hydrocarbon chains) (Figs 4-4 to 4-7). There is asymmetry in the staining of the protein layers. The less dark, or intraperiod, line represents the closely apposed outer protein... 

Figure 1.11 Longitudinal section through a flight muscle of an insect as seen under an electron microscope. The dark, approximately circular, objects are mitochondria packed between two myofibrils. Electron micrograph kindly provided by Professor David Smith, Oxford University. (For details, see Chapter 13).

Fig. 13. On the left, representation of the ferritin molecule the subunits form a spherical shell containing a ferrihydrite crystal. On the right, a Transmission Electron Microscope picture showing the iron core contained inside the proteic shell, appearing as electron-dense dark spots.

Figure 5.10. Accumulation of a radiolabelled LMWP in the lysosomes of the proximal tubular cell. Electron microscope autoradiography of renal proximal tubular cells from a rat injected i.v. with [1251]-tyramine-cellobiose-labelled cytochrome-c, 4 h prior to fixation throngh the abdominal aorta. An intense lysosomal accumulation of the protein is observed in three dark electron-dense lysosomes. A few grains are seen over the apical endocytic apparatus. Part of the luminal brush border is found in the upper right hand corner. Magnification, x 25 000. Unpublished data from E. I. Christensen, Arhus, Denmark, and M. Haas, Groningen, Netherlands.

Marlies Teichmuller. We have observed dark spots in vitrinites (especially in anthracites) under the electron microscope without impregnating the coal. The technique was to grind the coal in a rocking ball mill, and treat the very fine particles obtained by this process as thin sections, (cf. R. Meldau and M. Teichmuller, Ol Kofde 37, 751 (1961)). 

When viewed with an electron microscope after thin-sectioning and staining, membranes typically have a trilaminar appearance of two dark lines separated by a lighter space, with a total thickness on the order of 40 A (see fig. 17.1). 

Clearly, a number of chromogenic systems are available and may be varied between laboratories. The horseradish peroxidase-DAB system is probably the most widely favored as the brown reaction product contrasts well against a wide range of counterstains and mountants. DAB is not only alcohol resistant but can be visualized in the electron microscope. Osmification can produce a more intense dark brown-black color and a similar effect is achieved by post-treatment with nickel sulphate or cobalt chloride but such enhancement is seldom necessary. The reaction product is relatively stable with fading occurring only after years in routine storage. 

Fig. 7.6 Scheme of a scanning transmission electron microscope with bright- and dark-field detectors. ADF annular dark field HAADF high-angle annular dark field. (Adapted from [7]). 

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