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PubMed1988

Reflection high resolution analytical electron microscopy: a technique for studying crystal surfaces.

Reflection electron microscopy (REM), reflection high energy electron diffraction (RHEED), reflection electron energy-loss spectroscopy (REELS), and energy dispersion x-ray spectroscopy (EDX) have been comprehensively used as a technique, termed reflection high resolution analytical electron microscopy (RHRAEM), for studying the structures of the bulk crystal GaAs (110) surfaces by transmission electron microscopy (TEM). The simultaneous observations of surface topography imaging, the surface diffraction mechanism with RHEED, surface atomic inner-shell excitations with REELS, and surface chemical compositions with EDX provide a systematic description of the atomic structure and chemical structure of the surface. The surface channelling effect has been observed in GaAs (110) with REELS, which may provide a basis for localizing surface foreign atoms with ALCHEMI. The theoretically predicted surface-resonance wave has been observed directly in the RHEED pattern; the surface-captured Bragg reflection wave have been identified. It is shown that surface chemical compositions can be determined by analyzing the EDX spectra obtained in the REM case. Finally, the surface monolayer resonance characteristic of the RHRAEM has been confirmed by calculations with dynamical RHEED theory.

Arsenic↗
PubMed1977

The rat epithalamus. I. Correlative scanning-transmission electron microscopy of supraependymal nerves.

Transmission and scanning electron microscopy of the rat epithalamus shows a regional variation in the distribution of supraependymal nerves (SN) which correlates well with supraependymal yellow fluorescence reported by Richards et al. (1974). The medial habenular nucleus, the intercommissural and suprahabenular recesses, the habenular commissure and the fibrae periventriculares thalami have the greatest density of SN/100micron of ependymal surface. The floor of the suprahabenular and intercommisural recesses is covered by non-ciliated ependyma. The significance of these findings is discussed with respect to (1) a direct functional relationship of SN with ependyma, and (2) a possible participation of the non-ciliated ependyma of the suprahabenular and intercommissural recesses in secretory activity whereby the CSF serves as a vehicle for neuroendocrine communication.

Animals↗
PubMed1989

Electron microscopy in the diagnosis of pediatric disease.

Electron microscopy, although not able to solve all diagnostic dilemmas, is an essential adjunct to the analysis of pathologic processes. The importance of correct specimen handling for ultrastructural study is highlighted. Some diseases encountered in pediatrics, in which the ultrastructural findings are well established, are illustrated. New technologies that show promise for wider application to problems in pathology also are considered in this article.

Child↗
PubMed1979

[Study of an oral protozoan Trichomonas tenax using scanning and transmission electron microscopy].

The study with scanning and transmission electron microscopy of Trichomonas tenax gave morphological information on this protozoon. The oval-shaped cell body showed at the anterior pole four free flagella and a trailing flagellum which had an undulating membrane. The axostyle which consisted of microtubules and produced the cellular rigidity emerged at the posterior pole. An ovoid nucleus and a well-developed Golgi apparatus were located at the anterior pole. At the latter, a pelta consisting of horizontal microtubulus surrounding the kinetoplats from which started the flagella was also found. No mitochondria were observed: they were replaced by chromatin granules or hydrogenosomes. Numerous vacuoles and developing vesicles were found in the cytoplasm. Phagocytized bacteria were in an advanced stage of lysis. Others seemed intact showing even division phases.

Bacteria↗
PubMed1983

The small bowel mucosa in disease states characterized by chronic diarrhea: observations by scanning electron microscopy.

This paper summarizes observations by scanning electron microscopy (SEM) of surface ultrastructure of small bowel mucosa in patients (mostly children) with disorders characterized by chronic diarrhea. Included are chronic nonspecific diarrhea; conditions associated with villous damage, such as gluten-, milk protein- and soy protein-intolerance; giardiasis; cystic fibrosis and Crohn's disease. SEM has proven most useful to characterize pathologic processes on the surface of the small bowel mucosa, and thus has helped gain more insight to explain clinical symptoms. This was particularly true for chronic nonspecific diarrhea. It is predicted that SEM will become a valuable tool to aid in the diagnosis of diseases of the intestinal tract, which is considered one of the principal domains for such surface ultrastructure research.

Child↗
PubMed1993

Ultrastructural study of rabbit buccal epithelial cells and intercellular junction by scanning and transmission electron microscopy.

We observed by scanning and transmission electron microscopy the ultrastructure on the upper and lower surfaces of buccal epithelial superficial layer cells and the arrangement of intercellular junction apparatuses. In the superficial layer cells of the rabbit buccal epithelium, microvillus-like processes were observed on the lower surface and microridges on the upper surface. The distal portion of the microvillus-like process on the lower cell surface formed a wedge-like structure. At the intermicroridge areas on the upper cell surface, wedge-like depressions were observed. These depressions were interdigitated with the wedge-like structures of the microvillus-like processes. From the observation of the serial ultrathin sections, most interdigitation sites have two demosomes per microvillus-like process (89.5%). The desmosomes were located in the distal portion of the microvillus-like processes (99.3%). The wedge-like structures of the microvillus-like processes and wedge-like depressions on the inter-microridge areas seem to increase the junctional surface and enhance cell cohesion against external forces from various directions.

Animals↗
PubMed1991

Peripheral chondrosarcoma: ultrastructural investigation by transmission and scanning electron microscopy.

Ultrastructural analysis by transmission and scanning electron microscopy was performed on two grade 1 peripheral chondrosarcomas which had arisen from a preexisting osteochondroma. This analysis allowed us to determine the morphologic changes in both the cell and the matrix and suggested a low grade of malignancy. We emphasize that ultrastructural analysis with scanning and electron microscopy is only valid when conducted on representative areas of the tumor.

Adult↗
PubMed1987

Cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. A study using simultaneous scanning electron microscopy and fluorescence microscopy.

An instrument combining scanning electron microscopy (SEM) and light microscopy (LM) was used to study the cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. After a quantitative Feulgen DNA staining, the DNA content of the individual macrophages was measured and their cell surface morphology was studied immediately thereafter with the SEM part of the instrument. The cells were divided into six groups according to the number of microvilli and/or microridges present on their surface. A proportion of macrophages showed a DNA content more than occurs in diploid cells, which could indicate a future division. No special surface morphology could be detected in this cell type.

Animals↗
PubMed1992

Scanning force microscopy and cryo-electron microscopy of tobacco mosaic virus as a test specimen.

In this study, tobacco mosaic virus (TMV) provides a resolution criterion for specimen preparation methods as well as for imaging parameters of the scanning force microscope (SFM). We present scanning force microscopic images of the virus embedded in 0.5% buffered phosphotungstic acid solution adsorbed on a freshly cleaved mica surface, and imaged under atmospheric conditions. Individual TMV particles were clearly identified with a characteristic shape of long rods of about 300 nm long and 60-70 nm in apparent width due to the geometric parameters of the tip. The structure of the virus was compared with cryo-electron microscopic data of vitrified suspensions observed to a resolution of 1.15 nm. Uncoated TMV particles were also deposited on evaporated titanium thin films and imaged by SFM.

Cryopreservation↗
PubMed2007

Morphology and ultrastructure of Siberian sturgeon (Acipenser baerii) spermatozoa using scanning and transmission electron microscopy.

BACKGROUND INFORMATION: Available data concerning the sperm morphology of teleost fishes demonstrate wide variation. In the present study, the spermatozoa of Siberian sturgeon (Acipenser baerii Brandt, 1869), a chondrostean fish, was investigated. In contrast with teleost fish, chondrostean spermatozoa have a head with a distinct acrosome, whereas other structures, such as a midpiece and a single flagellum, are present in spermatozoa of most species. RESULTS: The average length of the head including the acrosome and the midpiece was 7.01+/-0.83 microm. Ten posterolateral projections derived from the acrosome were present on a subacrosomal region, with mean lengths of 0.94+/-0.15 microm and widths of 0.93+/-0.11 microm. The nucleus consisted of electrodense homogeneous nuclear chromatin. Three intertwining endonuclear canals, bound by membranes, traversed the nucleus longitudinally from the acrosomal end to the basal nuclear fossa region. There were between three and six mitochondria, two types of centrioles (proximal and distal) in the midpiece and two vacuoles composed of lipid droplets. The flagellum (44.75+/-4.93 microm in length), originating from the centriolar apparatus, had a typical 9+2 eukaryotic flagellar organization. In addition, there was an extracellular cytoplasm canal between the cytoplasmic sheath and the flagellum. CONCLUSIONS: A principal components analysis explained the individual morphological variation fairly well. Of the total accumulated variance, 41.45% was accounted for by parameters related to the head and midpiece of the sperm and the length of the flagellum. Comparing the present study with previous studies of morphology of sturgeon spermatozoa, there were large inter- or intra-specific differences that could be valuable taxonomically.

Acrosome↗
PubMedDate not supplied

The endolymphatic sac: a scanning and transmission electron microscopy study.

A recent investigation has suggested that the chief cells of the endolymphatic sac produce an endogenous inhibitor of sodium resorption in the kidneys, tentatively named saccin. In the current study, the ultrastructure of the endolymphatic sac and in particular the chief cells are described to demonstrate that this organ fulfils the morphological criteria of a potential endocrine gland. Accordingly, the chief cells are shown to exhibit all the organelles and characteristics of cells that simultaneously synthesize, secrete, absorb and digest proteins.

Acid Phosphatase↗
PubMed1980

Electron microscopy of negatively stained and unstained fibrinogen.

Electron microscope images of negatively stained fibrinogen are predominantly asymmetric rods 450 A in length and about 60 A in width. The molecules appear to have considerable flexibility, and mass distribution along the major axis is not uniquely distinguished despite apparent beading in some particles. Scanning transmission electron microscopy of unstained fibrinogen again demonstrates that a majority of molecules are rodlike. The results differ from those obtained by negative staining in that a substantial fraction of images are trinodular with striking resemblance to those obtained by C. E. Hall and H. S. Slayter [J. Biophys. Biochem. Cytol. (1959) 5, 11--16] using the mica replica technique. The above results were obtained on glow-discharged carbon substrate films by a simple low-concentration, long-attachment-time modification of standard deposition methods that is diffusion controlled and depends on concentration and time but is independent of pH, buffer, and other staining conditions. Evidence is presented that standard attachment procedures result in artifactual images. Any models of fibrinogen in solution consequently must encompass properties that permit its visualization as an asymmetetric rod by electron microscopy as first suggested by Hall and Slayter 20 years ago.

Animals↗
PubMedDate not supplied

Imaging faces of shadowed magnetite (Fe(3)O(4)) crystals from magnetotactic bacteria with energy-filtering transmission electron microscopy.

We used energy-filtering transmission electron microscopy to image magnetite crystals isolated from uncultured magnetotactic bacteria. These magnetite crystals were shadowed in high vacuum with platinum at 45 degrees. The shadowed crystals were observed in a Zeiss (Thornwood, NY) CEM902 transmission electron microscope. Imaging shadowed crystals with inelastically scattered electrons provided information of the decoration pattern of small platinum particles over crystal surfaces, and thus information on surface characteristics of crystals. Results were comparable to those obtained from scanning electron microscopy using a field emitter gun. Electron energy loss spectra of the crystals as well as of the supporting film were recorded to evaluate variations of image contrast with energy losses. Results indicated that the contrast is attenuated with inelastic imaging and that the effect of contrast tuning caused a contrast inversion at a given point between 100 and 150 eV. We believe this approach can be useful for studying multilayered materials by transmission electron microscopy.

Bacteria↗
PubMed1975

Scanning electron microscopy of mast cell degranulation.

Scanning and transmission electron microscopy were used to study the morphologic changes occurring in isolated mast cells after stimulation by compound 48/80. Two approaches were used to obtain cells for scanning electron microscopy. Cells incubated in suspension were collected on Millipore filters and air-dried from isopropyl alcohol. Other cells were allowed to attach to cover slips, stimulated, fix in situ, and dried from Freon at its critical point. Resting mast cells prepared by the latter method were covered by a tracery of shelflike ridges, whereas cells prepared by the first method had no ridges but presented a bumpy surface disclosing the underlying granules. Stimulation by compound 48/80 caused marked changes in the surface configuration of the cells, with loss of the regular pattern of ridges, extrusion of granules, and the appearance of openings leading to the interior of the cell. Correlation with transmission electron microscopy indicates that these openings lead to channels containing granules and lined by an intact membrane. These openings give extracellular cations access to granules within the confines of the cell, where the cations may exchange for histamine.

Animals↗
PubMedDate not supplied

Tissue response in sporotrichosis: light and electron microscopy studies.

On the basis of electron microscopy examination of human tissue affected by sporotrichosis, we have proposed a classification, at the light microscopy level, of fungal cells in tissue. Light and electron microscopy observations clarified the following five points: (1) in sporotrichosis lesions in man, the fungal cells are frequently phagocytized by polymorphonuclear leucocytes (PMNs); (2) phagocytosis of phagocytes by other phagocytes was common, and giant cells phagocytized both fungal cells and PMNs; (3) fungal cells in the tissues of lesions were thought to be highly viable, and their budding was frequently observed within macrophages and giant cells; (4) it was highly probable that PMNs participated in asteroid body formation; (5) few free fungal cells were present in the tissues. We believe that the classification of fungal cells in sporotrichosis tissue into the five categories below is useful for correctly understanding the pathological condition in a sporotrichosis lesion: (1) fungal cells in PMNs, (2) fungal cells in PMNs within macrophages, (3) fungal cells in macrophages, (4) fungal cells in giant cells, and (5) free fungal cells.

Giant Cells↗
PubMed1987

Morphometrical evaluation of acute leukemic cells by electron microscopy. Discrepancy between morphological characteristics in FAB classification and electron microscopic morphometry.

Leukemic cells from 39 patients with acute leukemia (20 lymphocytic and 19 myelogenous) were examined by transmission electron microscopy and the nucleus and cytoplasm were measured on the micrographs with a computer-controlled image analyzer. The ratios between the areas of the nucleus and whole cell profile (nucleus/cell ratio), heterochromatin and euchromatin, the nucleolus and nucleus, and the degree of irregularity of the nucleus were compared between the two major types of leukemia studied. Acute lymphocytic leukemia (ALL) cells had a relatively larger nucleus and relatively less cytoplasm than acute myelogenous leukemia (AML) cells, and a greater proportion of the area of the nucleus was occupied by heterochromatin in ALL cells than in AML cells. According to the FAB classification, L1 cells are characterized by narrow, and L2 cells by wide cytoplasm based on light microscopic observation of smeared cells, and we confirmed these features by morphometry of May-Giemsa-stained blood smears. However, by electron microscopy there was no difference in the nucleus/cell ratio between L1 and L2 cells, this constituting a discrepancy between the results obtained by electron and light microscopic morphometry. In addition there was no difference in the degree of nuclear irregularity between L1 and L2 cells. Among AML subtypes, significant differences were observed only in the nucleus/cell ratio between M3 and M1, M2 or M4 cells, and in the heterochromatin/euchromatin ratio between M5 and M1, M2 or M3 cells. In conclusion, electron microscopic morphometry revealed marked differences between ALL and AML, but the differences among their subtypes defined by the FAB classification based on nonmorphometric light microscopy were less evident by electron microscopic morphometry.

Cell Nucleus↗
PubMed1993

[Electron microscopy of needle biopsies from cancer patients with unknown primary tumors].

The aim of the present study was to evaluate the diagnostic value of electron microscopy (EM) performed on Surecut biopsies from patients without known primary tumour. The material consisted of 108 consecutive biopsies, obtained over a period of two years, from patients with tumour(s) in the liver or lymph nodes (on the neck, in the axilla or retroperitoneum). From each patient fine needle aspirations and Surecut biopsies for light microscopy and electron microscopy were taken. Only biopsies in which material for both electron microscopy and light microscopy was sufficient were included (60%). Immunohistochemical reactions were performed on paraffin sections when indicated. Final diagnoses were confirmed on surgically removed specimens and/or autopsies. Electron microscopy was necessary for obtaining the final histological diagnosis in 15% of the cases. It is therefore recommended to obtain additional ultrasound guided biopsies for EM from cancer patients with tumours in the liver or lymph nodes in cases where the primary origin of the tumour is unknown.

Biopsy, Needle↗
PubMed2006

Scanning electron microscopy imaging of dislocations in bulk materials, using electron channeling contrast.

The imaging and characterization of dislocations is commonly carried out by thin foil transmission electron microscopy (TEM) using diffraction contrast imaging. However, the thin foil approach is limited by difficult sample preparation, thin foil artifacts, relatively small viewable areas, and constraints on carrying out in situ studies. Electron channeling imaging of electron channeling contrast imaging (ECCI) offers an alternative approach for imaging crystalline defects, including dislocations. Because ECCI is carried out with field emission gun scanning electron microscope (FEG-SEM) using bulk specimens, many of the limitations of TEM thin foil analysis are overcome. This paper outlines the development of electron channeling patterns and channeling imaging to the current state of the art. The experimental parameters and set up necessary to carry out routine channeling imaging are reviewed. A number of examples that illustrate some of the advantages of ECCI over thin foil TEM are presented along with a discussion of some of the limitations on carrying out channeling contrast analysis of defect structures.

Electrons↗