Scanning and transmission electron microscopy study of antibody-dependent lymphocyte-mediated cytotoxicity on measles virus-infected cells.

The structural events related to antibody-dependent lymphocyte-mediated cytotoxicity (ADLC) have been studied on measles virus-infected cells using human peripheral blood lymphocytes (PBL) and anti-measles virus serum. The first event in ADLC was a recognition process occurring with 15 min after contact between the infected cells and lymphocytes. Plasma membrane and microvilli of adsorbed PBL were specifically attached to virus-induced ridges over nucleocapsids and to viral buds. After 30 min, a fraction of adsorbed PBL (K cells) changed shape and extended long filipodia toward the target cells which, in turn, showed long villi contacting the PBL. At 4 h, when cytotoxicity as measured by chromium release was maximum, K cells had flattened and numerous blebs and ruffles formed on their surface. The K-cell alterations varied in intensity with the type of measles-infected target cell, but frequently the K cells appeared irreversibly damaged. T- and non-T-cell fractions were separated, and in situ erythrocyte rosettes were used as markers for subpopulations which were easily recognized by scanning electron microscopy. Most of the cytotoxic K cells were identified as non-T cells carrying Fc receptors for immunoglobulin G. However, a small subpopulation of cells bearing both sheep erythrocyte and Fc receptors was also found to be involved in ADLC by chromium release assay as well as by electron microscopy. Some of these interacting T cells extended a long uropod on the target cell, but their intracellular structure remained unaltered through ADLC, in contrast with the other T cells and the non-t killer cells. This suggests that perhaps some T killer cells might remain functional after the cytotoxic interaction with a target cell.     

Scanning electron microscopy

The technology of scanning electron microscopy (SEM) is described in brief. Its application to the study of cell and tissue structure is demonstrated and the evolution of the concept of 'topographical histology' is discussed. Some current literature on the applications of SEM is reviewed under the headings of experimental pathology and human pathology. While SEM has become an indispensable technique for the experimental morphologist, its application to diagnostic pathology and cytology is still at an early exploratory stage.     

Scanning electron microscopy of red blood cells from eleven species of marsupial

Samples of red of blood cells (RBC), washed free of plasma, from eleven marsupial species were examined in a Jeol JSM-6300 F scanning electron microscope. The diameters of the RBC, lying completely flat or exactly on edge, were measured on photographs using a binocular enlarging optical system with a calibrated eye piece. RBC from the following species were studied: bandicoot (Isoodon macrourus), bilby (Macrotis lagotis sagitta), Bennett's wallaby (Macropus rufogriseus), Goodfellow's tree kangaroo (Dendrolagus goodfellowi), koala (Phascolarctos cinereus), parma wallaby (Macropus parma), red kangaroo (Macropus rufus), swamp wallaby (Wallabia bicolor), Tammar wallaby (Macropus eugenii), Tasmanian devil (Sarcophilus harrish) and whiptail wallaby (Macropus parryi). In all species the RBC were biconcave discs. The major morphological difference was in the size of the cells. Taking the human RBC as a reference (with a diameter of 8.0 m), the RBC of the Tasmanian devil, bilby, bandicoot and Goodfellow's tree kangaroo were 7 m in diameter, whereas those of the other marsupials ranged from 7.8 to 8.6 m.     

Scanning electron microscopy of synaptonemal complexes

The novel application of scanning electron microscopy to study whole-mount surface-spread synaptonemal complex complements of rye (Secale cereale) and rat (Rattus norvegicus) is described. Scanning electron microscopy is able to resolve the third dimension in such preparations and improve the tracing of the continuity of lateral elements without losing information that could be obtained by conventional transmission electron microscopy. This improvement is likely to benefit detailed studies of chromosome synapsis and karyology, and may provide a means of circumventing technical obstacles inhibiting the use of surface-spreads as substrates forin situ hybridization under the electron microscope.     

Scanning electron microscopy of cytoplasmic filaments in rat anterior pituitary cells

In order to demonstrate the occurrence of cytoplasmic filaments and their relationship to secretory granules, rat anterior pituitaries perfused with a detergent solution containing 0.5% Triton X-100 were observed with the scanning electron microscope. Thin section images and quick-freeze, deep-etching replica images were also studied. Scanning electron microscopy clearly demonstrated complicated networks of numerous cytoskeletal filaments in the cytoplasm of all the secretory cells of the anterior pituitary. These filaments can be classified into two groups on the basis of their diameter: thick filaments measuring 30-40 nm in diameter, and thin filaments 15-25 nm in diameter, each including the thickness of the platinum coat. The thick filaments, which run rather straight, are considered to be microtubules. The thin filaments attached to the surface of a secretory granule may connect it with an adjacent secretory granule, with cyto-organelles, with the nucleus, or with the plasma membrane. Transmission electron microscopic images of thin sections and quick-freeze, deep-etching replicas confirm the occurrence of filamentous structures associated with the limiting membrane of the secretory granule. The fine filaments associated with the limiting membrane of the secretory granule might participate in the support and transport of the granule.     

Scanning electron microscopy in oral cytology

Sixty-three cell smears from oral mucosa were studied by scanning electron microscopy. Among them, smears from ten healthy controls showed three kinds of cells: flat (superficial) cells with linear anastomosing microridges and microvilli; polygonal (intermediate) cells with well-defined crests between their faces and numerous microvilli; and round (parabasal) cells entirely covered by microvilli. Twenty-five smears from patients with untreated squamous-cell carcinoma showed enlarged polymorphous cells (round, globular, and elongated); microvilli, variable in their dimensions, were irregularly distributed on their surfaces. Eighteen smears from patients with severe epithelial dysplasia showed polymorphous cells with discontinuous but obvious edges separating their faces and with irregular microvilli and ridges. Nine smears were also performed in patients with various other mucosal lesions (lichen planus, leukoplakia, white sponge naevus, pemphigus vulgaris, and herpes). All of these smears were studied comparatively between examination of smears and biopsies by light microscopy. The smears were truly reliable, particularly for distinguishing between dysplastic and tumoral cells.     

Scanning electron microscopy of Blastocystis hominis cysts

Scanning electron microscopy of Blastocystishominis cysts reveals that some cysts have an outer coat, whereas others are naked. If intact, the outer coat forms a fan-like structure around the cyst and its surface is granular. The fragmented outer coat adheres to other cysts and bacteria, forming irregular clumps. Received: 15 September 1997 / Accepted: 2 December 1997