Scanning electron microscopy of dissociated pancreatic acinar cell surfaces

Summary The pancreatic acinar cell surfaces have been studied by SEM with a dissection technique and correlated with results obtained by TEM. The SEM results demonstrate characteristic arrangement of microplicae which in some areas are densely packed.In many areas, the microplicae are distributed in such a manner that they create zones with typical geometrical shapes and show a relatively smooth surface.These smooth areas may coincide, as indicated by correlated TEM results, with the limits of intimate contact between adjacent acinar cells which, in turn, represent part of the junctional complex. Another aspect revealed by these SEM preparations concerns the presence of groups of densely packed microplicae, arranged in regular rows and distributed along some grooves and/or infoldings of the cellular surface. On the basis of SEM and TEM information, it is likely that these structures correspond to intercellular (and possibly, in some cases, intracellular) canaliculi which topographically form a kind of extensive microlabyrinthine arrangement running along all the cell sides.One final point revealed by fractured samples concerns the finding of spherical zymogen droplets within the vesicles of the Golgi complex. Because in many scanning images these vesicles appear connected by small openings, it is suggested that they may represent a system of intercommunicating chambers (vacuoles) through which the zymogen droplets can be continuously accumulated and discharged into the acinar lumen.     

Scanning electron microscopy of the integumental surfaces of Schistosoma haematobium.

The integumental surfaces of critical point dried S. haematobium were studied by scanning electron microscopy at 34 to 8,000 magnifications. There are marked differences between the surface structures of male and female as well as from one part of the same parasite to another. The surface of the male schistosome is moderately rough while that of the female is relatively smooth. SEM reveals certain basic features such as spines in the oral sucker and the acetabulum of both sexes which may facilitate rasping and/or attachment of the parasite for residence in the bloodstream of the definitive host. The lining of the gynecophoral canal is roughened by minute spines. The presence of a gynecophoral fold may enhance anchorage of the female in the grasp of the male. The significance of visualization of surface features by SEM as a means for differentiating species is not yet known.     

Megalodiscus temperatus: Scanning electron microscopy of the tegumental surfaces

The tegumental surface of Megalodiscus temperatus forms cobblestonelike areas with rows of indentations encircling the worm. This pattern merges in several areas into folds and ridges, some of which represent the musculature of the posterior sucker and genital pore. Papillae surrounding the base of the oral sucker appear as two types: one with a bulb-like base and a short apical knob; the second typified by a hair-like structure (cilium?) of variable length projecting from a pit. From their location on the oral sucker and the resemblance to previously described structures, they are presumed to be sensory receptors. A circle of papillae on the closed posterior sucker was also observed. Rod-shaped bacteria were seen adhering to some of the worms observed but they were not found to be in any special association with the tegument or in any specific areas of the worm's surface.     

Modifications of mammalian cell surfaces induced by sugars: Scanning electron microscopy

Substitution of galactose, xylose, or mannose for glucose in the growth medium of L cells or the addition of equal concentrations of the alternate sugars to glucose-containing medium results in marked morphologic changes. The changes are revealed by conventional staining for light microscopy and by scanning electron microscopy.L cells grow indefinitely on combinations of equal concentrations of glucose and galactose, xylose, or mannose. There appear to be no significant differences in growth rate on glucose compared to the combinations of sugars cited. Cells subcultured from glucose to the combinations while undergoing rapid multiplication show marked morphologic changes by light and scanning electron microscopy within 36 hr.Of particular note are the loss of microvilli; flattening of the cells; assumption of polygonal shape; prominence of nuclei and nucleoli; and changes in the structure and distribution of filopodia. Virtually all cells in the population exhibit the changes noted.     

Scanning electron microscopy of dairy equipment surfaces contaminated by two milk-borne micro-organisms

Ethanol dehydration followed by argon replacement induced drying (ARID) was found to be a suitable method for the preparation of glass, stainless steel and rubber surfaces which had been in contact with inoculated milk and which were to be examined using scanning electron microscopy (SEM). This technique was used to examine samples of all three materials which had been subjected to both single and repeated inoculation with whole milk containing a Pseudomonas sp. or a Micrococcus sp. and incubated for various periods. Some samples were also prepared for SEM using a cryofixation technique. The Pseudomonas sp. was found to proliferate on glass and stainless steel surfaces but not on rubber. Due to the clumping tendency of the Micrococcus sp. proliferation of this organism was more difficult to assess accurately. In general there was no difference in results obtained between single and repeated inoculation. Various factors which may have aided attachment of micro-organisms to surfaces were identified viz. , surface channels present in stainless steel, milk deposits and the production of extracellular material. The value of using both the cryofixation and chemical preparatory techniques for the identification of artifacts is discussed.     

Scanning electron microscopy of the chick embryo

Internal anatomical features of developing chick embryos can be examined using the scanning electron microscope in embryos that have been sectioned at varying levels. Standard paraffin sectioning techniques are used. After removal of paraffin, embryos are dried by the critical point method and examined. The resulting scanning electron micrographs have proved to be exceptionally useful in teaching anatomy of embryos.     

Scanning electron microscopy of the rat retina

Summary Fixed and unfixed, freeze-dried pieces of isolated retina and the posterior part of the eye bulb from adult rats were examined in a scanning electron microscope.The inner limiting membrane shows distinct cell borders, protrusions, and scattered microvilli-like structures. Different types of nerve cells are observed in the ganglion cell layer and the inner nuclear layer. They all lack synaptic boutons on the surface of their perikarya. There is an intercellular space between the processes in the nerve fiber layer.The inner and outer segments are surrounded by a space with extracellular material. Their surface is smooth or slightly undulated. There is no evidence indicating the existence of basal infoldings continuous with the membraneous structures inside the rod outer segments. The connecting piece between the inner and outer segments resemble a symmetrically shaped hour-glass. The surface of the epithelial cells is covered by microvilli forming a honeycomb-like structure and each outer segment is surrounded by several microvilli.The results obtained are discussed in relation to those obtained by transmission electron microscopy. The probable existence of a significant extracellular space and the distribution of extracellular material between the segments and the microvilli are discussed.Supported by grants from H. Jeanssons Stiftelse Riksföreningen mot Cancer (265-B69-OIX) and the Swedish Medical Research Council (B70-12X-2534-02). I would like to thank the Swedish Silicate Research Institute, Göteborg, for using their scanning electron microscope, and Miss. M. Persson for skilful technical assistance.     

Scanning electron microscopy of Penicillium conidia

The morphology of conidia in 211 species and 12 varieties belonging to the genus Penicillium Link ex Gray have been studied and compared.According to surface ornamentation, conidia have been classified into six groups: A, smooth-walled (7% of the species); B, delicately roughened (13%); C, warty (28%); D, echinate (10%); E, striate with low irregular ridges (36%); and F, striate with scarce high ridges or bars (6%). Whereas the first two groups are closely related in both shape and average size, a gradual reduction was observed in size and in the length/width (l/w) ratio in the remaining groups. Echinate conidia were globose, having the largest average size. Only four species produced conidia not surpassing 2 m in diameter. Maximum length observed was 8 m, and most elongated conidia had a l/w ratio of 3.5. Forty per cent of the species studied had globose conidia.Conidia of the monoverticillate species were generally smaller, more globose and frequently with ridges. In the Asymmetrica, the conidia were generally larger, and showed ridges in comparatively few species. Conidia of the Symmetrica, which were frequently striate with ridges, presented the most elongated forms. The largest average size was found in the conidia of the Polyverticillata which were generally warty. Finally, we have considered the variations in surface ornamentation of conidia during the evolution of the genus Penicillium and drawn attention to their possible relationship with certain habitats and ways of conidial dispersion.     

Scanning electron microscopy of barley protoplasts

Summary Scanning electron micrographs of barley protoplasts were compared using various preparatory techniques. Numerous features were observed which turned out to be artifactual characteristics of the processing procedure used in collecting and dehydrating the samples. The most successful technique gave protoplasts which presumably maintained their natural structural integrity, as judged by retention of sphericity and absence of holes in the plasma membrane. The relative numbers of fragmented protoplasts and cellular organelles was also greatly reduced.