Scanning electron mirror microscopy

The working principles, instrument designs, and applications of scanning electron mirror microscopy are reviewed. The capability of this technique for direct imaging of topographical surface structures as well as electrostatic and magnetic surface strayfields is demonstrated by a number of examples.     

Scanning transmission electron microscopy

The scanning transmission electron microscope is of quite recent origin, and it is only in the last few years that it has been shown that this instrument is capable of giving the same high resolution as the conventional electron microscope. In this article we examine the conditions necessary for the achievement of high resolution and also the various modes of contrast which can be obtained from this instrument. Finally, we suggest other ways in which the microscope can be used in future investigations.     

Scanning electron microscopy of intestinal microvilli

The usual simple methods for the preparation of soft tissues for scanning electron microscopy failed to demonstrate the presence of microvilli on intestinal epithelial cells from rats. Treatment with a mucolytic agent or surface-section methods also failed. However, the isolation of the brush borders as the first step in the preparatory procedure did allow a study of the microvilli. The width and height of the microvilli differed from those seen by transmission microscopy and it is suggested that these differences are related to both the shadow-material used and the presence of a mucopolysaccharide on the surface of the membrane. The technique illustrates the possible use of fractionation methods as part of the preparative procedures in scanning electron microscopy.     

Scanning electron microscopy of vascular casts

Corrosion casts provide three dimensional replicas that can be examined readily by scanning electron microscopy (SEM). They are prepared by filling vascular networks with polymerizing plastic and then digesting away the tissue. As based on our studies of ocular vessels, this report describes the vascular anatomy, as well as the artifacts, that are encountered during SEM studies of such preparations.     

Scanning electron microscopy of freeze-dried aortic elastin

As part of a larger project aimed at claryfying some of the uncertainties that exist concerning the structural basis for an explanation of the mechanical behaviour of elastin, an examination was made of purified porcine aortic elastin under the scanning electron microscopy. In order to avoid structural changes caused by impregnation with organic solvents, specimens were prepared directly from their water-saturated state by either air-drying of freeze-drying processes. Comparison of the results obtained by these techniques demonstrates that freeze-drying of elastin has the advantage of enhancing fine detail, minimizing distortion and reducing specimen shrinkage.     

Scanning electron microscopy of blood cells.

Scanning electron microscopy (SEM) is an invaluable tool for studying the surface morphology of isolated blood cells. We have used a simple preparative technique for SEM to study the erythrocytes from a case of Congenital Dyserythropoietic Anaemia type II and the leucocytes from healthy individuals or patients with leukaemia or lymphoma. This rapid and inexpensive technique for fixation and dehydration of blood cells was found to be equally reliable for obtaining micrographs of healthy or diseased leucocytes or erythrocytes.     

Scanning electron microscopy of renal vascular casts

The use of Cementex to form casts of the renal vascular system is described. These casts are useful in delineating the vascular microarchitecture of the kidney including that of the glomerular capillaries, but do not appear to reproducibly reflect physiological vascular tone. The postglomerular vascular system is often incompletely filled using this technique. The amount of filling can be altered by the techniques used in cast preparation. The effect of perfusion pressure, concentration of Cementex, fixation, and type of colour additive are compared with respect to the cast structure.     

Scanning electron microscopy of two-dimensional magnetic stray fields

Methods used in metrology of two-dimensional magnetic microfields and based on direct interaction of the electron beam of scanning electron microscope (SEM) with the studied fields are described. An analytical expression for calculating the value of the field is presented. The errors and applicability of the methods have been estimated. The concepts discussed are illustrated by the experimental results of the measurements of some types of statistical and dynamic stray fields.     

Scanning electron microscopy studies of protein-functionalized atomic force microscopy cantilever tips

Protein-functionalized atomic force microscopy (AFM) tips have been used to investigate the interaction of individual ligand-receptor complexes. Herein we present results from scanning electron microscopy (SEM) studies of protein-functionalized AFM cantilever tips. The goals of this study were (1) to examine the surface morphology of protein-coated AFM tips and (2) to determine the stability of the coated tips. Based on SEM images, we found that bovine serum albumin (BSA) in solution spontaneously adsorbed onto the surface of silicon nitride cantilevers, forming a uniform protein layer over the surface. Additional protein layers deposited over the initial BSA-coated surface did not significantly alter the surface morphology. However, we found that avidin-functionalized tips were contaminated with debris after a series of force measurements with biotinylated agarose beads. The bound debris presumably originated from the transfer of material from the agarose bead. This observation is consistent with the observed deterioration of functional activity as measured in ligand-receptor binding force experiments.     

Scanning electron microscopy of Vicia faba nuclei structure

Using a simple and fast technique, chromosomes and nuclei of V. faba were isolated and examined under various magnifications with SEM. Details of chromatin construction were observed.     

Scanning electron microscopy 1928–1965

This article gives an account of the origins of the scanning electron microscope (SEM) and traces its development up to 1965 when the first SEM was marketed by the Cambridge Instrument Company. The survey concentrates on the SEM, as distinct from the microanalytic electron probe instruments that were also being developed during this period.     

Scanning electron microscopy of uncoated human metaphase chromosomes.

Human metaphase chromosomes were processed with a 3% glutaraldehydetannic acid technique and examined in a scanning electron microscope at 20 kV either without added metal coating or with 2 nm of sputtered gold coating. Several substrates--aluminum mnium foil, silver mirror deposit and sputtered gold-provided good conductive backgrounds for chromosomal spreads. Silver mirror deposit was the best conductive substrate tested. This method should prove to be a useful tool for monitoring the three-dimensional morphology of mitotic chromosomes with the possibility of studying various banding techniques, chromosomal uncoiling and secondary constrictions currently being examined in chromosomal studies.     

Scanning electron microscopy and transmission electron microscopy study of hot-deformed γ-TiAl-based alloy microstructure

The aim of this work was to assess the changes in the microstructure of hot‐deformed specimens made of alloys containing 46–50 at.% Al, 2 at.% Cr and 2 at.% Nb (and alloying additions such as carbon and boron) with the aid of scanning electron microscopy and transmission electron microscopy techniques. After homogenization and heat treatment performed in order to make diverse lamellae thickness, the specimens were compressed at 1000 °C. Transmission electron microscopy examinations of specimens after the compression test revealed the presence of heavily deformed areas with a high density of dislocation. Deformation twins were also observed. Dynamically recrystallized grains were revealed. For alloys no. 2 and no. 3, the recovery and recrystallization processes were more extensive than for alloy no. 1.     

Scanning electron microscopy in biomedical research and routine pathology

After 15 years of development, scanning electron microscopy now plays a major role in biomedical science. This brief review highlights some aspects of the contribution of SEM to the teaching of morphology, to experimental scientific research and to pathological diagnosis.     

Scanning electron microscopy of nerve fibers in human fetal cochlea

The cochleas of four human fetuses ranging 22–25 weeks gestation were studied by scanning electron microscopy (SEM) for the purpose of obtaining a better understanding of the nerve fiber arrangement in the human ear. After critical point drying, the specimens were dissected and the floor of the tunnel of Corti and the outer wall of Nuel's space were exposed for observation. Upper cochlear turns, especially the apical turn, seemed to be still immature. Observed nerve fibers were classified into three types:

• 1 Spiral fibers: Fibers traveling basalward and following the shape of the cochlea were found in both the tunnel of Corti and Nuel's space and believed to be the afferent nerves responsible for innervating the outer hair cells
• 2 Radial fibers: radiating outward from the osseous spiral lamina—one such radial fiber transversing high in the tunnel space (supposedly the efferent nerve servicing the outer hair cells), and another sort of radial fiber (found crossing the tunnel floor), the nature of which was uncertain.
• 3 Irregular fibers: Consisting of thin, randomly running fibers within the cochlea. The destination of these fibers was not determined, but possibly they represent transitory nerve branchings of afferent or more probably efferent nerves, which would later regress during maturation.

     

Scanning electron microscopy of piliated Neisseria gonorrhoeae processed with hexamethyldisilazane

Piliated Neisseria gonorrhoeae are virulent and attach readily to some human mucosal cells. The study of interactions between piliated Neisseria gonorrhoeae and surface structures of eukaryotic cells in tissue culture requires consistent high resolution imaging in scanning electron microscopy (SEM). The combination of the fixatives glutaraldehyde, osmium, tannic acid, and uranyl acetate improves preservation of pili and other delicate structures. Following the critical point drying (CPD) process, pili bundles remained intact, but charging produced image distortion in most of the specimens. The use of hexamethyldisilazane (HMDS) with air drying substantially reduced charging and image distortion. Less contrast and greater resolution of pili bundles and surface structures of bacteria or tissue culture cells were obtained at magnifications of 10,000 or higher. As an alternative to CPD, HMDS processing of cell culture monolayers was simple and was more efficient when a large number of samples was processed.