Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The surface charge of heart muscle cells (HMC) and Trypanosoma cruzi trypomastigotes was estimated during their interaction by means of zeta potential (ZP). Metacyclic and bloodstream trypomastigote, but not amastigote forms, are able to decrease the surface charge of HMC as well as other nonphagocytic cells. However, no alteration could be detected on T. cruzi-infected macrophage cell line. Trypomastigote forms collected from the supernatant after 20 h of contact with HMC also have their ZP value decreased. The analysis of the surface components of both the parasite and HMC involved in such interaction was also carried out. Assays concerning the kinetics of the cell-parasite interaction demonstrated the influence of parasite surface anionogenicity during its interaction with HMC. The binding of bloodstream forms to HMC was enhanced after their incubation with cationized ferritin (CF), whereas phospholipase C and neuraminidase treatments improved and trypsin treatment inhibited parasite uptake in HMC. Conversely, the incubation of HMC with phospholipase C impaired, and with trypsin enhanced, the interiorization of the parasites. These results suggest that trypomastigote forms of T. cruzi may process the surface of HMC and its own surface either by removing molecules or by exposing ligands for their internalization.
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PMID:Alterations in the surface charge of heart muscle cells during interaction with Trypanosoma cruzi. 775 89

We have used a neuraminidase-deficient influenza virus, NWS-Mvi, which was selected by supplying bacterial neuraminidase in the medium (C. Liu and G. M. Air, Virology 194:403-407, 1993), to define the role of neuraminidase in influenza virus replication. Electron microscopy showed that virions of the NWS-Mvi mutant assembled normally and formed large aggregates associated with cell surfaces. The NWS-Mvi virus grown in the absence of neuraminidase was able to carry out a second round of replication in MDCK cells without added neuraminidase, indicating that the virus particles contained in these aggregates were infectious. Aggregates of virus were also found in cytoplasmic vacuoles. When virus-infected cells were incubated in the presence of ferritin, such aggregates were found to be labeled with ferritin, indicating that they are derived from uptake at the cell surface. When the neuraminidase-deficient virus was administered intranasally to C57BL/6 mice, low titers of virus were recovered from the lungs and major histocompatibility complex class I-restricted cytotoxic T cells were generated: evidence that cells were infected in vivo. In C57BL/6 nu/nu mice, the low level of virus persisted for at least 28 days but never increased. These results suggest that neuraminidase is not required for influenza virus entry, replication, or assembly in cell culture or in mice.
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PMID:Influenza type A virus neuraminidase does not play a role in viral entry, replication, assembly, or budding. 781 89

The distribution and internalization of anionic sites in heart muscle cells (HMC) were studied by direct measurements of their zeta potential (ZP) and by ultrastructural cytochemistry. Our data showed that HMC are negatively charged and that their anionic sites are distributed over the entire sarcolemma. Treatments with neuraminidase and trypsin altered the ZP value and also reduced binding of cationized ferritin (CF) to the sarcolemma. Sialic acid was shown to be an important component on the surface of HMC, since its removal reduced the cell surface negative charge by 25%. Phospholipase C did not significantly change the surface charge, nor did it alter HMC reactivity to CF particles when compared with control cells. Endocytosis of anionic sites was investigated using two different protocols that allow follow-up of this dynamic process. Incubation of HMC with cationized ferritin particles at 37 degrees C induced a redistribution of ligand-bound anionic sites, followed by their internalization or detachment. The clustering of anionic sites on the surface of HMC indicates that these cells are characterized by a high level of membrane fluidity. CF particles were localized inside early and late endosomes, lysosomes, and also in ferritin-enriched vesicles near the sarcolemma. An endocytic pathway for anionic sites in HMC is discussed.
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PMID:The nature of anionic sites and the endocytic pathway in heart muscle cells. 814 29

Structure and composition of stereocilia cross-links were investigated cytochemically in normal and hydropic cochleas of the guinea pig. The electron-dense markers colloidal thorium and cationized ferritin were used for visualization. Side links as well as tip links were visualized using both markers. Cationized ferritin allowed a better visualization of the delicate cross-link substructure than did colloidal thorium. Following digestion with neuraminidase, cross-link reactivity for colloidal thorium was virtually abolished. However, the basic structure of the cross-links could still be observed as a result of routine post-fixation and contrast staining. In both 3- and 6-month hydropic cochleas glycocalyx reactivity of the stereocilia appeared to be unaltered, provided that stereocilia were still present. However, loss of cross-links of the outer hair cells - resulting in disarrangement of the stereociliary bundles - was observed in hydropic cochleas. Our results suggest that cross-links are a separate morphological and cytochemical entity, which is different from the glycocalyx. Furthermore, loss of stereocilia cross-links, with concomitant disarrangement of the outer hair cell stereociliary bundle, appears to be one of the early pathological features of surgically induced endolymphatic hydrops, which might be responsible for permanent sensorineural hearing loss.
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PMID:Structure and composition of stereocilia cross-links in normal and hydropic cochleas of the guinea pig. 850 69

Adhesion of microcrystals to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones. The role of membrane surface charge as a determinant of the interaction between renal epithelial cells (BSC-1 line) and the most common crystal in kidney stones, calcium oxalate monohydrate (COM), was studied in a tissue culture model system. Adhesion of COM crystals to cells was blocked by cationized ferritin. Other cations that bind to cells including cetylpyridinium chloride and polylysine, as well as cationic dyes such as Alcian blue, also inhibited adhesion of COM crystals, but not all polycations shared this effect. Specific lectins including Triticum vulgaris (wheat germ agglutinin) blocked crystal binding to the cells. Furthermore, treatment of cells with neuraminidase inhibited binding of crystals. Therefore, anionic cell surface sialic acid residues appear to function as COM crystal receptors that can be blocked by specific cations or lectins. In vivo, alterations in the structure, function, quantity, or availability of these anionic cell surface molecules could lead to crystal retention and formation of renal calculi.
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PMID:Adhesion of calcium oxalate monohydrate crystals to anionic sites on the surface of renal epithelial cells. 876 39

(1) Neurogenic inflammation has been implicated in the pathogenesis of the vascular headaches of migraine and cluster headaches. (2) Dural blood vessels are both pain-sensitive and show neurogenic plasma extravasation. (3) Endothelial cell (EC) surface anionic sites appear to be a determinant of vascular permeability. We therefore examined the anionic sites of dural EC to determine whether they are different from those of pial and parenchymal vessels. Luminal anionic sites of rat optic nerve EC were labelled with cationic colloidal gold (CCG) and cationic ferritin (CF) and examined by electron microscopy. Employing a battery of enzymes, the effects of digestion of ultrathin sections on subsequent labelling with CCG was quantified using image analysis software. In addition, a gold-labelled lectin, wheat-germ agglutinin (WGA), was employed to locate specific saccharide residues. Of the enzymes with a narrow specificity, only neuraminidase substantially reduced CCG binding. Of the proteolytic enzymes, papain was most effective in reducing labelling. These results show that the luminal EC anionic sites are chiefly composed of sialoglycoproteins. The labelling with biotinylated WGA-streptavidin gold was similar to that with CCG without enzyme digestion. This suggests that WGA is binding to N-acetylneuraminic (sialic) acid residues and not to the neutral N-acetylglucosamine (since CCG would not label uncharged molecules). These results do not differ significantly from those for pial and parenchymal EC. It is therefore likely that factors other than anionic site molecular composition account for the susceptibility of dural vessels to neurogenic plasma extravasation. The relevance of these observations in an experimental animal model to the human clinical condition remains to be determined.
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PMID:Dural microvessels: molecular properties of their luminal anionic sites. 883 82

Adhesion of microcrystals that nucleate in tubular fluid to the apical surface of renal tubular cells could be a critical step in the formation of kidney stones, 20% of which contain hydroxyapatite (HA). HA crystals bound rapidly to monolayer cultures of monkey kidney epithelial cells (BSC-1 line), used to model the surface of the nephron, in a concentration-dependent manner. Adhesion was blocked by diverse polyanions including heparin, pentosan polysulfate, polyaspartate, and polyglutamate, as well as many found in tubular fluid such as chondroitin sulfates A and B, heparan sulfate, citrate, nephrocalcin, and osteopontin. The polycations cetylpyridinium chloride and cationized ferritin, as well as the cationic dyes alcian blue, polyethylenimine, and brilliant blue R, also inhibited adhesion of HA crystals, as did specific lectins including Triticum vulgaris (wheat germ agglutinin). Anions that inhibited adhesion of crystals appeared to act on the crystal surface, whereas cations and lectins exerted their effect on the cell. Treatment of cells with neuraminidase inhibited binding of crystals, suggesting that anionic cell surface sialic acid residues function as HA crystal receptor sites that can be blocked by specific cations or lectins. Adherence of HA crystals to cells of another renal line (MDCK) and, to 3T3 fibroblasts was also inhibited by heparin, polyaspartate, alcian blue, and T vulgaris lectin, suggesting that these crystals bind to analogous molecules on the surface of different types of cells. These results suggests that the structure, quantity, and/or function of soluble anions in tubular fluid, as well as those anchored to the cell surface, could be critical determinants of HA crystal retention in the nephron and the subsequent formation of a renal stone.
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PMID:Adhesion of hydroxyapatite crystals to anionic sites on the surface of renal epithelial cells. 927 83

Monomeric single chain antibody (scFv) fragments lack both the avidity of the bivalent IgG, or (Fab')2 fragment, and the effector functions conferred by the Fc domain. For certain diagnostic or therapeutic applications it may be desirable to link these molecules to other proteins, antibodies, enzymes or peptide ligands, and chemical or recombinant methods have been developed to produce many of these crosslinked reagents. One approach has been to link an antibody fragment to streptavidin which can bind a second biotinylated molecule to create a higher affinity, bifunctional or bispecific molecule. To demonstrate the applicability of this technology, an anti-neuraminidase NC10 scFv-streptavidin fusion was expressed in E. coli and the product was refolded and purified to homogeneity from 6 M guanidine hydrochloride. Analysis in a BIAcore biosensor showed that the NC10 scFv moiety reacted with immobilised neuraminidase and that the core streptavidin moiety was able to bind biotinylated anti-ferritin Fab' to produce a new model bispecific reagent which bound ferritin. Conceptually, this design principle can be applied to the creation of useful diagnostic and possibly therapeutic molecules.
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PMID:Linear gene fusions of antibody fragments with streptavidin can be linked to biotin labelled secondary molecules to form bispecific reagents. 930 36

The surface anionogenic groups and sialoglycoconjugate structures of Paracoccidioides brasiliensis yeast forms were analysed by cell microelectrophoresis, binding assays with lectins and viral particles, ultrastructural cytochemistry, enzymic digestion and flow cytofluorimetry. P. brasiliensis yeast forms, particularly the budding primordia, reacted strongly with cationized ferritin. Binding assays showed that the reaction with sialic-acid-specific Limax flavus lectin (LFA) was distributed over the entire P. brasiliensis cell wall. Treatment of yeast forms with neuraminidase significantly reduced their negative surface charge and LFA labelling, which suggests that sialic acid residues are major anionogenic groups exposed on the P. brasiliensis surface. Furthermore, after neuraminidase treatment, labelling with Arachis hypogaea (peanut) agglutinin increased due to unmasking of subterminal beta-D-galactopyranosyl residues. The sialic acid linkages to galactose are alpha 2,6 and alpha 2,3 as assessed, respectively, by fungal attachment to M1/5 and M1/5 HS8 strains of influenza A virus and binding of Sambucus niger and Maackia amurensis agglutinins. The alpha 2,6 linkage clearly predominated in both experiments. Flow cytofluorimetry analysis revealed the heterogenicity of P. brasiliensis yeast cell populations, which comprised young and mature budding yeasts. Both express binding sites to LFA and Limulus polyphemus agglutinin.
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PMID:Anionogenic groups and surface sialoglycoconjugate structures of yeast forms of the human pathogen Paracoccidioides brasiliensis. 949 68

Among the wall-less mycoplasmas only a few species have been identified with a capsule at their cell surface. Mycoplasma penetrans is a recently identified mycoplasma with unique morphology, isolated from HIV-infected patients. Using transmission electron microscopy, it was found that M. penetrans is surrounded by capsular material 11 nm (strain GTU-54-6A1) to 30 nm (strain HF-2) thick, which can be stained with ruthenium red and labelled with cationized ferritin. The polysaccharide composition of this capsule was indicated by its staining with periodic acid-thiocarbohydrazide silver proteinate and the abolition of ruthenium red staining of the cell surface by neuraminidase treatment. In addition, proteinase K treatment of the M. penetrans cells resulted in removal of the capsule, suggesting that polypeptides may contribute in anchoring it to the membrane or in its stability. Two different types of glycosylated material were detected in mycoplasma extracts by SDS-PAGE and periodic acid-Schiff staining. The first component was a high-molecular-mass material, which was heat- and proteinase-K-labile and which probably constitutes the capsular polymer. The other component was a low-molecular-mass glycolipid fraction, which was proteinase-K-, heat- and EDTA-resistant. The identification of a capsule at the M. penetrans cell surface is of particular interest for a mycoplasma which has been shown to adhere to various host cells and to penetrate into their intracellular compartments. The capsule may have significance in the pathogenesis of disease associated with infection by this organism.
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PMID:Identification of two glycosylated components of Mycoplasma penetrans: a surface-exposed capsular polysaccharide and a glycolipid fraction. 961 99


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