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

Trypanosoma lewisi bloodstream and culture forms were agglutinated differentially with low concentrations of the cationic compounds: ruthenium red, ruthenium violet, Alcian blue chloride, 1-hexadecylpyridinium chloride, lanthanum chloride, and cationized ferritin. The bloodstream form trypanosomes gave the highest agglutination levels with each of the compounds tested. Ruthenium red was the most effective inducer of cell agglutination among the several cations used. Trypsin-treated bloodstream forms were agglutinated less in the presence of ruthenium red than untreated controls. Ruthenium red-induced cell agglutination also was lowered with chondroitin sulphate and dextran sulphate, but not with alpha-D-glucose, alpha-D-mannose or with several methyl glycosides. Treatment of the bloodstream trypanosomes with alpha-amylase, dextranase, or neuraminidase had little effect on agglutination levels obtained with ruthenium red. Fine-structure cytochemical staining with ruthenium red, ruthenium violet, and Alcian blue-lanthanum nitrate was used to ascertain the presence and distribution of presumptive carbohydrates in the trypanosome cell surface. The extracellular surface coat of the bloodstream forms stained densely with each of the polycationic dyes. Trypsin treatment removed the surface coat from bloodstream trypanosomes; however, the surface membranes of the organisms were stained densely with the several dyes. Similar surface-membrane staining was obtained with the cationic compounds and the culture forms, which lack a cell surface coat. Cationized ferrin was used at the fine-structure level to visualize the negative surface charge present in the cell surface coat and external membrane of the several trypanosome stages. Results obrained from the agglutination and cytochemistry experiments indicate that complex polysaccharides are present in the surface membranes and cell surface coat of T. lewisi bloodstream forms. Similar conclusions also pertain to the surface membranes of the T. lewisi culture from trypanosomes. The carbohydrates probably represent glycopeptide and glycoprotein structural components of the surface membrane of this organism.
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PMID:Cell surface saccharides of Trypanosoma lewisi. I. Polycation-induced cell agglutination and fine-structure cytochemistry. 5 63

A carbohydrate-containing fraction was extracted from the trypanosomatid Crithidia fasciculata by a phenol-water procedure. Ion-exchange chromatography separated this fraction into three components: a polysaccharide which was not retained on the column; RNA which eluted upon addition of salt; and, another polysaccharide which eluted upon addition of detergent. The unretained fraction was shown to be composed solely of D-mannose. The mannan, which was heterodisperse on Sephadex G-100, had an average molecular weight of approx. 14 000 as based on analysis of reducing groups. The detergent-eluted material yielded arabinose and galactose upon acid hydrolysis. The arabinogalactan was excluded from Sephadex G-100 and Sephacryl S-200 molecular sieve columns, suggesting a molecular weight greater than or equal to 200 000. Cell fractionation studies showed the bulk of extractable polysaccharide was associated with a particulate fraction. Further determination of the cellular localization of the polysaccharide was accomplished by employing a specific antiserum prepared from rabbits immunized with the polysaccharide extract. The cell surface localization of the arabinogalactan was demonstrated by cell agglutination studies as well as immunocytochemical techniques using fluorescein and ferritin conjugated antibodies.
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PMID:Polysaccharides of crithidia fasciculata. Identification and partial characterization of a cell surface constituent. 9 71

An affinity-purified plant lectin from Ricinus communis (RCAII) was shown to exhibit differential toxicity toward SV40-transformed 3T3 fibroblasts grown in vitro. When macromolecular synthesis was examined in SV3T3 and 3T3 cells, RCAII suppressed cell protein synthesis in the transformed line at lower concentrations (1/50 to 1/100) compared to the 3T3 line, and these effects were blocked by the RCAII inhibitors D-galactose or lactose. RNA and DNA synthesis and L-leucine transport were relatively unaffected by RCAII concentrations (greater than 1 mug/ml) that completely suppressed protein synthesis in both cell lines. The RCAII-mediated inhibition of cell protein synthesis required incubation times longer than 60 min, but quantitative cell binding studies with 125-I-RCAII indicated that the lectin binds to maximal levels in approximately 5 to 10 min, even at 4 degrees. During 10-min labeling experiments with 125-I-RCAII (1 mug/ml), it was demonstrated that the cell-bound lectin could be almost quantitatively removed from cells up to an additional 15 min after labeling without subsequent inhibition of protein synthesis. However, longer incubation times (greater than 30 min) after RCAII cell labeling and washing resulted in incomplete removal of cell-bound lectin (less than 20 to 30% of cell-bound lectin could be removed after a 60-min incubation). The longer incubation times (greater than 60 min) also resulted in almost complete inhibition of protein synthesis. Ferritin-conjugated RCAII (ferritin-RCAII) was used to follow the fate of the cell-bound lectin. Ferritin-RCAII bound rapidly (less than 10 min) to SV3T3 cell surfaces and could be blocked from labeling with lactose. After a 10-min incubation at 4 degrees in ferritin-RCAII solutions, the ferritin label was exclusively located at the extracellular surface in a random distribution. After washing and incubation at 37 degrees, the ferritin-RCAII induced clustering of its receptors (15 to 30 min) and eventually induced endocytosis (30 to 60 min). Further incubation (greater than 60 min) resulted in a predominantly intracellular localization of ferritin-RCAII inside endocytotic vesicles and free in the cell cytoplasm. That RCAII acts directly on protein synthesis after cell entry was confirmed with rabbit reticulocyte and mouse Krebs II ascites S30 cell-free protein synthesis system in diameter wit
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PMID:Mechanism of cell entry and toxicity of an affinity- purified lectin from Ricinus communis and its differential effects on normal and virus-transformed fibroblasts. 16 59

The uptake in vitro of various substances by Brugia pahangi was investigated using infective larvae obtained from Aedes aegypti and worms removed from Meriones unguiculatus at 2, 3, 10, 20 and 90 days post-infection. Worms incubated in growth medium 199 containing 1% Trypan blue possessed demonstrable dye in the oral orifice, the anterior oesophageal lumen and the external openings of the vulva and the cloaca or anus but the dye was not found in the gut lumen even after incubation for 24 h. No uptake of ferritin particles into the intestine of the worms was found and no fluorescence could be demonstrated in the gut lumen of worms incubated in medium containing 50% (v/v) fluorescein isothiocyanate-conjugated calf serum for up to 24 h. Trypan blue uptake by the gut of Aspiculuris tetraptera was clearly observed after incubation for several hours. The uptake of D-glucose and L-leucine by B. pahangi was demonstrated using autoradiographic and scintillation counting techniques and incorporation into worm tissues was detected. Glucose was found to be readily incorporated in the apical, glycogen-rich areas of the myocytes of worms of all ages studied and in the uterine epithelium of the adult female. In contrast, a lower incorporation of D-glucose was found in the eggs, embryos and vas deferens and especially in the gut. The incorporation of L-leucine occurred throughout the tissue of the worms during a 30 min incubation. Labelling was also located over the surface of the cuticle of the worms, when incubated for a period of 15 to 60 min in L-[H]leucine. Scintillation counting techniques demonstrated that there was no uptake of 14C-labelled L-glucose or sucrose by B. pahangi. The data presented on the uptake in vitro of nutrients or other compounds by infective larvae and adult stages of B. pahangi did not demonstrate an intestinal route of uptake but indicated that the transcuticular route of uptake may be employed.
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PMID:The uptake in vitro of dyes, monosaccharides and amino acids by the filarial worm Brugia pahangi. 48 11

In the present study ultrastructural localization of binding sites for 5 lectins was studied in rat liver cell surface membrane fractions. For this purpose ferritin-coupled Concanavalin A, wheat germ agglutinin, soybean agglutinin, Ricinus communis agglutinin 120 and Lotus tetragonolobus agglutinin I were used as probes for mannose, N-acetyl glucosamine, N-acetyl galactosamine, galactose and fucose moieties in glycoproteins and glycolipids. Although recent reports suggest presence of glycogroups on the cytoplasmic surface of cellular membranes ultrastructural identification of membrane surfaces in the present study indicated an asymmetric localization of lectin-binding sites exclusively on the extracellular side of the membranes.
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PMID:Lectin-binding sites are found in rat liver cell plasma membrane only on its extracellular surface. 62 8

Carbohydrate-containing structures in rat liver rough microsomes (RM) were localized and characterized using iodinated lectins of defined specificity. Binding of [125I]Con A increased six- to sevenfold in the presence of low DOC (0.04--0.05%) which opens the vesicles and allows the penetration of the lectins. On the other hand, binding of [125I]WGA and [125I]RCA increased only slightly when the microsomal vesicles were opened by DOC. Sites available in the intact microsomal fraction had an affinity for [125I]Con A 14 times higher than sites for lectin binding which were exposed by the detergent treatment. Lectin-binding sites in RM were also localized electron microscopically with lectins covalently bound to biotin, which, in turn, were visualized after their reaction with ferritin-avidin (F-Av) markers. Using this method, it was demonstrated that in untreated RM samples, binding sites for lectins are not present on the cytoplasmic face of the microsomal vesicles, even after removal of ribosomes by treatment with high salt buffer and puromycin, but are located on smooth membranes which contaminate the rough microsomal fraction. Combining this technique with procedures which render the interior of the microsomal vesicles accessible to lectins and remove luminal proteins, it was found that RM membranes contain binding sites for Con A and for Lens culinaris agglutinin (LCA) located exclusively on the cisternal face of the membrane. No sites for WGA, RCA, soybean (SBA) and Lotus tetragonobulus (LTA) agglutinins were detected on either the cytoplasmic or the luminal faces of the rough microsomes. These observations demonstrate that: (a) sugar moieties of microsomal glycoproteins are exposed only on the luminal surface of the membranes and (b) microsomal membrane glycoproteins have incomplete carbohydrate chains without the characteristic terminal trisaccharides N-acetylglucosamine comes from galactose comes from sialic acid or fucose present in most glycoproteins secreted by the liver. The orientation and composition of the carbohydrate chains in microsomal glycoproteins indicate that the passage of these glycoproteins through the Golgi apparatus, followed by their return to the endoplasmic reticulum, is not required for their biogenesis and insertion into the endoplasmic reticulum (ER) membrane.
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PMID:Spatial orientation of glycoproteins in membranes of rat liver rough microsomes. I. Localization of lectin-binding sites in microsomal membranes. 70 63

Ferritin conjugates of a lectin from mistletoe (Viscum album L.) were used for the electron-microscopic demonstration of carbohydrate receptors on the cell surface of human erythrocytes and murine tumor cells. Human A1 erythrocytes showed only a slight focal binding of ferritin. Cells of the mouse ascites tumor strain L 1210 were labelled very tightly on their surface and incorporate the ferritin by pinocytosis. Furthermore they showed cytotoxic changes in their ultrastructure. In the presence of galactose the labelling on the surface, the incorporation of the conjugate within the cell as well as the cytotoxicity were inhibited.
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PMID:[Use of ferritin conjugates of a lectin from mistletoe (Viscum album L.) for the electron microscopic localization of cell surface receptors]. 75 6

Concanavalin A (Con A) is taken up by endocytosis in mature erythrocytes of newborn humans but not in adult red cells. Thin sections of neonatal cells incubated with ferritin-conjugated Con A at 37 degrees show ferritin clusters on invaginations at the surface and in intracellular vesicles, but such invaginations and vesicles are absent with adult cells. The endocytosis induced by ferritin-conjugated Con A is inhibited at 0 degrees, and by methyl-alpha-D-mannopyranoside at 37 degrees. Succinylation of Con A, which is known to convert it from the tetrameric to dimeric form, renders Con A inactive in cell agglutination and endocytotic vesicle formation, presumably by reducing the number of oligosaccharide chains simultaneously bound by a single Con A molecule. Ferritin-conjugated succinyl Con A binds to neonatal erythrocytes but does not induce endocytosis; if, however, antibodies to ferritin are now added, endocytosis occurs. These results are consistent with a greater lateral mobility of at least a fraction of Con A recptors in the membrane of the intact neonatal erythrocyte compared to the adult. The results also support the hypothesis that the clustering of receptors is obligatory for endocytosis to occur. No discernible difference was found in the sodium dodecyl sulfate/polyacrylamide gel patterns of the membrane proteins of the neonatal and adult cells.
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PMID:Clustering and endocytosis of membrane receptors can be induced in mature erythrocytes of neonatal but not adult humans. 106 94

The use of Lens culinaris lectin for electron microscopic detection of D-mannose,- D-glucose and N-acetyl-D-glucosamine like sites on tumor cells, erythrocytes, erythrocyte ghosts, cultured rat liver cells and various tissues of mice is demonstrated. In addition to Lens culinaris lectin-peroxidase reaction (LeL-po reaction) the preparation of active Lens culinaris lectin-ferritin conjugate are described and the specificity of cytochemical reactions are demonstrated. Furthermore experiments by immuno freeze-etching are reported for topological analysis of the lectin receptors.
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PMID:Electron microscopic demonstration of cell surface carbohydrates by means of peroxidase and ferritin complexes of the Lens culinaris lection. 115 Apr 86

Various lactoferrin preparations (iron-saturated and iron-depleted human milk lactoferrins and bovine milk and colostrum lactoferrins) were bound by Aeromonas hydrophila. Binding was (i) reversible (65% of bound lactoferrin was displaced by unlabeled lactoferrin), (ii) specific (lactoferrin but not other iron-containing glycoproteins such as ferritin, transferrin, hemoglobin, and myoglobin inhibited binding), and (iii) significantly reduced by pepsin and neuraminidase treatment of the bacteria. The glycosidic domains of the lactoferrin molecule seem to be involved in binding since precursor monosaccharides of the lactoferrin oligosaccharides (mannose, fucose, and galactose) and glycoproteins which have homologous glycosidic moieties similar to those of the lactoferrin oligosaccharides (asialofetuin or fetuin) strongly inhibited lactoferrin binding. A. hydrophila also binds transferrin, ferritin, cytochrome c, hemin, and Congo red. However, binding of these iron-containing compounds seems to involve bacterial surface components different from those required for lactoferrin binding. Expression of lactoferrin binding by A. hydrophila was influenced by culture conditions. In addition, there was an inverse relationship between lactoferrin binding and siderophore production by the bacterium.
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PMID:Characterization of lactoferrin binding by Aeromonas hydrophila. 131 45


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