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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this report, conditions for attaining high resolution in scanning electron microscopy with soft biological specimens are described using the currently available high resolution scanning electron microscopes in emission mode of low energy electrons (secondary and charging electrons). Retinal rod outer segments, red blood cells, intestinal mucosa, and ferritin molecules were all used as biological test specimens. From uncoated specimens a new source of signal, referred to as a discharge signal, can provide a high yield of low energy electrons from an excitation area approximately the size of the beam's cross section. Additionally, under these conditions sufficient topographic contrast can be achieved by applying ultra thin metal coatins. A 0.5 nm thick gold film is found sufficient for generating the total signal, whereas increased coating thickness causes additional topographic background signal. However, a 2.0 nm film is needed for imaging surface details with the present instrument. Ultra thin, even, and grainless tantalum films have been found effective in eliminating the charging artifacts caused by external fields, and the decoration artifacts caused by crystal growth as seen in gold films. To improve, in high magnification work on ultra thin coated specimen, signal-to-noise ratio, methods for obtaining saturation of the signal with discharge electrons are shown. The necessity of confirming the information obtained in SEM by independent techniques (TEM of stereo-replicas or ultra thin sections) is discussed.
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PMID:Scanning electron microscopy at macromolecular resolution in low energy mode on biological specimens coated with ultra thin metal films. 39 3

The present resolution (75-100 A) of the conventional scanning electron microscope (SEM) and its ability to image the surfaces of large numbers of whole cells in situ permits the approach of problems such as viral and cell surface antigen localization by immunological labeling with visual markers. Identification of virus and cell surface antigens in situ has been accomplished in indirect reactions by conjugated and unconjugated markers. Hemocyanin (Hcy) from whelk, Busycon canniculatum, has been developed as an immunospecific marker for virion and cell surface labeling in the electron microscope. Its size (approximately 30 x 50 nm) and distinct cylindrical shape permit easy visualization in the SEM and TEM. The Hcy method involves the preparation of antisera to Hcy in appropriate hosts for use in an unlabeled antibody macromolecular procedure based exclusively on antigen-antibody affinity to couple the macromolecule to the antigen site. Further correlative data from fluorescence microscopy can be obtained from similarly labeled samples by binding fluorescein to the bridging antibodies used in the Hcy technique. The usefulness of the Hcy marker system was demonstrated using antisera to the major envelope and cell surface glycoprotein (gp70) of Rauscher murine leukemia virus (R-MuLV), a type C retrovirus. The antiserum was shown to bind to the virion and cell surfaces of virus-infected cells in the homologous virus-infected cell system. It also demonstrated the expression of R-MuLV gp70-related antigens on a murine cell line Mm5mt/c1 which produces mouse mammary tumor virus (MuMTV), A type B retrovirus. Furthermore, when used in the Hcy marker system this antiserum was able to distinguish type B from type C budding virus on the same cell. Examples of other marker systems (ferritin, peroxidase, colloidal gold, and latex) used to show anti-gp70 serum reactivity will be presented to demonstrate their applicability to cell surface labeling studies. Methods for the preparation of immunoreagents and labeling of cells are discussed.
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PMID:Immunologic techniques for the identification of virion and cell surface antigens by correlative fluorescence, transmission electron and scanning electron microscopy. 39 19

The water-rich phase (tissue channels) of the intersititial tissue in rat ileum, knee joint capsules, kidneys, and implanted Guyton's capsules was examined electron microscopically by the SEM of plastic injection models, and by TEM and HVEM of ferrocyanide and ferritin as tracers. It was shown that the channels do in fact exist, and are not just vacuoles. Quantitative estimations of their numbers and diameters were made. These agreed well with estimates made by other methods.
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PMID:The quantitative morphology of interstitial tissue channels in some tissues of the rat and rabbit. 72 12

Picric acid-paraformaldehyde-glutaraldehyde (PA-P-G) was used to stabilize chemically ocular surface-associated mucus in mice of various ages. Transmission electron microscopy was then used to examine those specimens stained with cationic ferritin (CF), dialysed iron and Alcian Blue. Collectively, all of these stains are markers for anionic sulfate or carboxyl groups. With each of them, positive labeling of the ocular surface was observed for all ages examined, even when mucus cannot be morphologically demonstrated. Except for dialysed iron, staining was weak in the youngest animals and heaviest in young adult and aged mice. The ocular surface was negative for high iron diamine (HID) in pups and older mice through 1 year of age. Scant positive staining for HID was seen at the ocular surface in 14-month-old mice indicating that mucus became slightly sulfated with aging. Treatment of eyes with neuraminidase prior to fixation reduced the number of CF binding sites in all ages of mice examined, confirming that many of the carboxyl groups at the ocular surface are associated with sialic acid residues. Comparison of percentage reduction in CF labeling following neuraminidase treatment of the eyes of 5- and 10-postnatal day mice with all other ages of mice suggested that fewer removable carboxyl groups at the ocular surface are associated with sialic acid residues in pups. The ocular surface of all eyes also stained positively at the TEM level when a periodic acid-thiocarbohydrazide-silver protein (PA-T-SP) staining sequence was used. Collectively, these data are of significance with respect to further characterization of the ocular surface, particularly with regard to development-associated changes and their possible role in defence of the eye surface.
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PMID:Ocular surface complex carbohydrates are modified with aging. 243 68

A method using low concentrations of formaldehyde and dithiothreitol was applied to obtain 'right-side out' luminal plasmalemma-derived vesicles from bovine aortic endothelial cells (EC) in culture, and from human umbilical vein and bovine or porcine aortas perfused ex vivo with the vesiculation solution. Vesicle formation and shedding were examined by phase-contrast microscopy and by transmission (TEM) and scanning electron microscopy (SEM). Vesicles showed the characteristic trilaminar pattern of the unit membrane and did not contain cellular organelles. As detected in freeze-fracture preparations, vesicle membrane displayed intramembrane particles and filipin-detectable cholesterol. Like EC plasmalemma, vesicle surface was heavily stained by Ruthenium Red and bound under a normal pattern cationized ferritin and ferritin hydrazide. As indicated by lectin agglutination assays and by ultrastructural cytochemistry, vesicles maintained on their ectodomains glycoconjugates bearing monosaccharides such as N-acetyl-neuraminic acid, beta-N-acetylglucosamine and beta-D-galactose, and expressed 5'-nucleotidase activity. The electrophoretic profiles of externally disposed 125I-labelled polypeptides of vesicles were found to be similar to those of intact EC. Chemically-induced vesiculation appears as a suitable method to obtain EC plasmalemma for studying its composition and functions in various vascular beds.
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PMID:Endothelial cell plasma membrane obtained by chemically induced vesiculation. 359 39

It is not so difficult to operate on the hydrosalpinx with macrosurgical or microsurgical methods, but difficult to initiate pregnancy after the operation because little is known about the post-operative condition of the hydrosalpinx. In this study time sequential observations of the growing experimental hydrosalpinx with the two hemoclip method was performed during morphological change using the microscope, sequential electron microscope and transmission electron microscope with cationized ferritin as an ultrastructural marker. The following results were obtained: Size of hydrosalpinx: Until 15 weeks after the operation, the hemo-clipping hydrosalpinx became longer but thereafter there was no change. The maximum diameter of the hydrosalinx became wider until 20 weeks after treatment. Peristaltic of hydrosalpinx: Tubal peristaltics were observed until 7 weeks after treatment, but not thereafter. SEM findings: Decreases in the amount of cilia started 1 week after treatment, and 7 weeks after treatment partial excoriations of epithelium were observed. 20 weeks after treatment excoriations of epithelium were observed widely. A decrease in the amount of cilia was observed but no loss was observed. The negative charges on the tubal endometrium due to TEM using cationized ferritin: The negative charges on the tubal endometrium were decreasing both on the secretory cells and ciliary cells.
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PMID:[Variations in ultrastructures and negative charges in experimental hydrosalpinx]. 379 49

Sporozoites of Eimeria tenella were incubated for 10, 20, or 30 min with parasite-specific monoclonal IgG antibody 3D3II from mice and then rinsed in a Tris-buffered glucose saline solution (TBGS). Some sporozoites were then incubated for 10, 20, or 30 min with ferritin- or colloidal gold-conjugated goat anti-mouse IgG antibody and then fixed in 2.5% glutaraldehyde and prepared for transmission (TEM) or scanning (SEM) electron microscopy. Other sporozoites that had been previously exposed to monoclonal antibody were prefixed with 0.25% glutaraldehyde, incubated with ferritin- or colloidal gold-conjugated anti-mouse IgG antibody and then fixed and prepared for TEM or SEM. Control preparations consisted of sporozoites exposed only to TBGS, monoclonal antibody 3D3II or to ferritin- or colloidal gold-conjugated anti-mouse IgG antibody. Capping of immune complexes occurred only on the surface of those sporozoites exposed to monoclonal antibody 3D3II followed by ferritin- or gold-conjugated antibody. Immune complexes moved laterally and posteriorly on the outer surface of the parasite plasma membrane to form a cap at the posterior end of the sporozoite. Capping did not occur in TBGS controls nor in sporozoites treated with monoclonal antibody 3D3II and prefixed in 0.25% glutaraldehyde before exposure to ferritin- or gold-conjugated antibody. Thus, capping of surface antigens did not occur in the presence of monoclonal 3D3II antibody only, whereas specimens exposed to both monoclonal and ferritin- or colloidal gold-conjugated antibodies were able to cap immune complexes.
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PMID:Capping of immune complexes by sporozoites of Eimeria tenella. 398 46

We used concanavalin A (con A)-peroxidase-iron dextran-diaminobenzidine (DAB) technique for the electron microscopic detection of con A binding sites on cell membranes. Normal bladder mucosa showed a sparse distribution of con A binding sites with both transmission (TEM) and scanning (SEM) electron microscopy, but bladder tumors showed a higher concentration in the distribution of con A binding sites in proportion to the histopathological grade of transitional cell carcinoma. Quantitative estimation of the con A binding sites was attempted using scanning X-ray pulse analysis of iron elements contained in the reaction complexes. Con A binding sites were quantitatively the smallest in normal mucosa, increasing proportionate to the grade of the bladder tumor. Some specimens were compared by the ferritin-labelled method and the pattern of ferritin conjugates distribution was similar to that seen with the con A-peroxidase-iron dextran method.
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PMID:Distribution of concanavalin A binding sites on normal human urinary bladder mucosa and bladder tumors by transmission and scanning electron microscopy and X-ray microanalysis. 674 Aug 37

In long-term cultures of bone marrow, the adherent stromal cells provide support for the proliferation and maintenance of hemopoietic stem cells. These stromal cells and their interactions were characterized by means of scanning (SEM) and transmission (TEM) electron microscopy in correlation with functional studies. Cultures were initiated by establishing the adherent stromal layer as a "soil" which was then "seeded" after 3 weeks by the addition of another marrow-cell suspension. Clonal assay of the supernatant demonstrated the continuous proliferation of the hemopoietic stem cell. The stroma essentially consisted of two cell types, macrophages and epithelioid cells. Macrophages were smaller, 10-15 microns, phagocytosed latex and carbon particles, and contained lysosomes. Their surface did not stain with polycationic ferritin (PCF). Epithelioid cells were much larger, more than 100 microns; contained numerous thin, elongated mitochondria; did not phagocytose latex particles; but did display strong surface staining with PCF. The appearance of epithelioid cells in TEM depended on their state of development and whether the section was parallel or perpendicular to the substratum. Epithelioid cells displayed a maturational spectrum, at two ends of which were synthetic and storage phases. In the synthetic phase, the cell contained numerous profiles of rough endoplasmic reticulum, and in the storage phase, numerous storage granules. These two phases were best appreciated in sections perpendicular to the substratum, demonstrating synthetic cells on top settling over the substratum upon maturation into the storage cells. Both macrophages and epithelioid cells contained fat globules which increased in number and size with the addition of hydrocortisone to the culture medium. A distinct fat-cell type, as has been claimed, was not found in this study. Granulopoiesis was observed in the culture system in the absence of colony-stimulating activity in the supernatant, suggesting direct cellular interaction or short-range factors in the induction of granulopoiesis. Widespread cellular interactions were noted between macrophages and epithelioid cells, the latter often completely embracing the former and both extending cytoplasmic processes toward each other. This is reminiscent of the cooperative interaction of endoderm and mesoderm in chick embryo hemopoiesis and may be necessary for the maintenance of stem cells in these cultures.
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PMID:Morphological studies on long-term culture of marrow cells: characterization of the adherent stromal cells and their interactions in maintaining the proliferation of hemopoietic stem cells. 710 79

High quality of secondary electron (SE) images, taken at useful magnifications of 100,000 to 200,000, require new signal generation and collection methods and new metal coating procedures. High quality is defined as the condition under which image contrast describes accurately the topographic features of the specimen in a size range that approximates the beam diameter. Such high resolution contrasts are produced by the SE (SE-I) generated by a small electron probe on the specimen surface. Tobacco mosiac virus and ferritin molecules deposited on bulk substrates were introduced as test specimens to check the image quality obtained. The SE-I signal contrast could be imaged when SE (SE-III), produced by backscattered electrons (BSE) at the pole piece of the final lens, were eliminated with an electron absorption device attached to the pole piece. This signal collection procedure will be referred to as "Secondary Electron-I Image" (SE-I image) mode. In addition to the SE-III, BSE generate SE-II in the specimen itself. On specimens deposited on bulk gold or platinum, and coated with the same metals SE-II produced a microroughness contrast that limited particle resolution in the SE-I image mode to approximately 10 nm. Reduction of SE-II and enrichment of the signal in SE-I was achieved by using continuous fine crystalline coatings of tantalum, niobium and chromium. By applying these metals in films of approximately 2.0 nm thickness, the SE-I contrast generation was found to be indepedent of the atomic number of the metal. Edge sharpness was improved when the specimens were coated with low atomic number metals. Under these conditions, the quality of images obtained in SE-I image mode equals that of images obtained in TEM from identically coated specimens and was limited only by the size of the topographic details, beam diameter and beam current.
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PMID:Conditions required for high quality high magnification images in secondary electron-I scanning electron microscopy. 718 36


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