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

Plasmalemmal differentiation of the enucleating normoblast of rabbit and rat was studied by means of cytochemical methods and freeze-etching. Staining with colloidal iron revealed about identical amounts of iron particles bound to various areas of the normoblast membrane. Cationized ferritin and ruthenium red, likewise, failed in the demonstration of significant changes of the enucleating normoblast glycocalyx. Despite these findings the topo-optical staining with toluidine blue showed the plasmalemmal envelope of the protruding normoblast nucleus moderately birefringent, clearly discriminated from the intense anisotropic staining of the future reticulocyte membrane. The ferritin-labeled snail lectin anti AHP localized a great number of binding sites at the plasmalemmal envelope of the nucleus under extrusion. That is in sharp contrast with rather low lectin binding to the future reticulocyte membrane which amounts to about 30 to 50% of the nuclear envelope label. The findings provide evidence of unmasking of bindings sites of the normoblast membrane. Apparently, the effect is due to conformational changes of the cell membrane, rather than it could be attributed to degradation of glycoproteins. Moreover, enucleation kinetics may also be related to supramolecular changes of membrane structure albeit missing evidence for the rearrangement of membrane particles.
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PMID:Alteration of the enucleating erythroblast glycocalyx. 11 25

Since the trophoblast-uterine adhesion is as nearly a universal phenomenon in implantation as can be found, an attempt was made to determine whether or not there was a reduction in cell surface glycoproteins in the rat, as can be observed in the ferret. Neither colloidal iron nor cationized ferritin revealed the type of pattern anticipated for a localized reduction in surface negativity in the imprint of the blastocyst in the implantation chamber. The use of lectin-coated latex beads also proved disappointing in defining regional differences in adhesiveness. However, a number of observations on the changing shape of the implantation chamber, the secretion of periluminal material by decidual cells, and the penetration of the residual basal lamina of the luminal epithelium by the decidual cells were made in the course of these studies. The implantation chamber of the rabbit, in which the blastocyst does not make an imprint, was contrasted with that of the rat. The areas of fusion of trophoblast knobs with uterin epithelial cells shown to be visible by scanning electron microscopy. Finally, some observations on the hypertrophy of maternal epithelial cells to form the uterine plaque in the rhesus monkey are described, and the hypertrophy of endothelial cells to form admirably suited to protein secretion is presented.
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PMID:Comparative aspects of blastocyst-endometrial interactions at implantation. 11 57

For electron microscopic demonstration of complex carbohydrates and simple sugars in the mouse lung, anionic dye and lectins were used. After immersion fixation of small lung tissue blocks, the alveolar surfactant system was destroyed and only membrane bound carbohydrates (cell coat) could be demonstrated by means of colloidal iron and ruthenium red. Fixation of the whole lung via the visceral pleura preserved the alveolar surfactant system. Only this technique afforded a distinction between cell coat components and hypophase components. After performance of the Concanavalin A-peroxidase technique and after incubation in ferritin-labed Concanavalin A, Lens culinaris lectin or Ricinus communis lectin, various saccharide moieties were demonstrable by immune electron microscopy in the hypophase of the alveolar surfactant system.
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PMID:Electron microscopic demonstration of a saccharide moieties in the hypophase of the alveolar surfactant system. 12 9

The lectin receptors of confluently grown hamster BHK, wild type polyoma virus transformed PyBHK, and temperature-sensitive polyoma transformed ts3-PyBHK fibroblasts were investigated using cell agglutination, quantitative (125I)lectin binding, and ferritin-lectin labeling. PyBHK and permissively grown ts3-PyBHK cells agglutinated more strongly with Ricinus communis I agglutinin (RCA-I)compared to BHK and nonpermissively grown ts3-PyBHK, although saturation binding of (125I)RCA-I to these cells at 4 degrees resulted in a twofold difference in lectin-binding sites on BHK and nonpermissively grown ts3-PyBHK cells (1.0-1.3 x 10 7 sites/cell) compared to PyBHK and permissively grown ts3-PyBHK (0.4-0.6 x 10 7 sites/cell). These cells bound equivalent amounts of (125I)concanavalin A (0.8-1 x 10 7 sites/cell) and (125I)wheat germ agglutinin (1-2.2 x 10 7 sites/cell). Under these binding conditions little endocytosis occurred, as judged by the subsequent release of greater than 90% cell-bound (125I)RCA-I by the RCA-I inhibitor lactose and localization of ferritin-RCA-I exclusively to the extracellular plasma membrane surface. However, if the binding is performed at 22 degrees, only 50% of the bound lectin can be removed by lactose, and ferritin-RCA-I is localized inside the cell within endocytotic vesicles. The relative mobility of RCA-I receptors was examined on ts3-PyBHK cells by the ability of ferritin-RCA-I to induce clustering of its receptors at 22 degrees. RCA-I receptors on permissively grown ts3-PyBHK cells appeared to be more mobile than on nonpermissively grown cells. BHK and PyBHK cells were treated with neuraminidase, and the resulting enzyme-treated cells were assayed for lectin agglutinability and quantitative binding of RCA-I, concanavalin A, and wheat germ agglutinin. Neuraminidase treatment resulted in decreased concanavalin A and wheat germ agglutinability and a slight increase in RCA-I agglutinability. The enzyme-treated BHK and PyBHK cells bound less (125I)wheat germ agglutinin (2.8 x 10 6 and 2.2 x 10 6 sites/cell, respectively) and 2.5 and 6.2 times more (125I)RCA-I (2.5-3 x 10 7) and 3.5-4 x 10 7 sites/per cell, respectively). There was no change in the number of concanavalin A binding sites after neuraminidase treatment. The increase in RCA-I binding sites approximated the decrease in wheat germ agglutinin binding sites indicating that the predominant penultimate oligosaccharide residue to sialic acid on these cells is D-Gal.
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PMID:Qualitative and quantitative interactions of lectins with untreated and neuraminidase-treated normal, wild-type, and temperature-sensitive polyoma-transformed fibroblasts. 16 28

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

Concanavalin A (Con A) has been popularly used as a cell surface probe for normal and neoplastic cells. Differences between normal fibroblasts and their transformed derivatives were examined using Con A agglutination, quantitative labeling with 125I-Con A and ultrastructural labeling with fluorescent- or ferritin-Con A. Con A agglutinates confluent-SV3T3 and 3T3 cells at midpoints of 20-60 and greater than, 500-2,000 mug/ml, respectively, and sparse cells at 5-15 and 1,200-1,500 mg/ml, respectively. Quantitative binding of 125I-Con A at 4 degrees C (10 or 15 min) with saturating lectin concentrations does not indicate a difference in the number of Con A receptors on sparse or confluent 3T3 and SV3T3 cells similar to many publications, but contrary to Noonan and Burger (1973). Under these conditions of labeling, ferritin-Con A is not internalized, indicating absence of endocytosis. The lateral mobility of Con A receptors and their relative ability to be aggregated on the cell surface by Con A was investigated with fluorescent- and ferritin-Con A. The initial distribution of Con A receptors on 3T3, SV3T3 and MSV3T3 cells under conditions of labeling at low temperature (0-5 degrees C) or to fixed cells was essentially randomly dispersed, but changes quickly to aggregated on SV3T3 and MSV3T3 (but not 3T3) after shifting the temperature to 20-37 degrees C, indicating, in general, a greater relative mobility of Con A receptors on SV3T3 and MSV3T3 cells. The aggregated Con A receptors seem to be directly involved in cell agglutination because they are usually found at the sites of cell-to-cell contact during 10 min agglutination experiments with ferritin-Con A. When confluent-3T3 cells are labeled on monolayer with ferritin-Con A at 0-4 degrees C, washed and then shifted to 20-37 degrees C for 10-15 min prior to in situ embedding, two classes of Con A receptors can be identified. One class appears to have low relative mobility and is associated with the 3T3 cell's extensive subplasma membrane microfilament network, while the other is capable of being aggregated and eventually endocytosed. On confluent-SV3T3 cells, only the latter class of receptors appears to be present, indicating a possible loss of cytoplasmic control over the distribution and mobility of lectin-binding sites on transformed cell surfaces.
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PMID:Concanavalin A as a quantitative and ultrastructural probe for normal and neoplastic cell surfaces. 16 43

Lectins, plant proteins that bind specific saccharide determinants, have been utilized to examine the effect of neuraminidase digestion on the structure and/or expression of oligosaccharide moieties present at the periphery of Novikoff ascites hepatoma cells. Five lectins were utilized: concanavalin A (Con A), specific for alpha-D-manno- or alpha-D-glucopyranosyl residues; wheat germ agglutinin, specific for 2-acetamido-2-deoxy-D-glucopyranosyl residues; Ricinus communis agglutinin I (RCAI), specific for D-glucopyranosyl residues; R. communis agglutinin II (RCAII), specific for D-galacto- or 2-acetamido-2-deoxy-D-galactopyranosyl residues; and soybean agglutinin, specific for 2-acetamido-2-deoxy-D-galactopyranosyl residues. Neuraminidase treatment of Novikoff cells did not alter their agglutination by Con A or wheat germ agglutinin. Similar treatment produced only a 2-fold increase in their agglutination by RCAI but a 12-fold increase in their agglutination by RCAII, indicating that 2-acetamido-2-deoxy-D-galactopyranosyl residues become expressed upon neuraminidase treatment. This conclusion was confirmed by the observation that neuraminidase-treated Novikoff cells acquired agglutinability by soybean agglutinin. Binding studies using ferritin-conjugated RCAII indicated that neuraminidase treatment exposed cryptic cell surface receptors for RCAII. To ascertain the role of cell surface glycoproteins in lectin-induced agglutination of Novikoff cells, glycopeptides cleaved from the cell surface by papain were assayed for lectin receptor activity. The cell surface glycopeptides exhibited receptor activity for Con A, wheat germ agglutinin and RCAI but not for RCAII and soybean agglutinin. A cell surface macrosialoglycopeptide fraction, resolved by gel filtration and ion-exchange chromatography, possessed a major portion of the Con A and RCAI receptor activity.
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PMID:Effect of neuraminidase and papain treatment on lectin-induced agglutination of Novikoff tumor cells and assay of lectin receptor activity of the glycopeptides released from the cell surface by papain. 17 11

Human glioblastoma cells in long-term monolayer culture showed an even distribution of intramembrane particles (IMP) on all surfaces of the plasma membrane; junctional complexes were rarely observed and rectilinear arrays were not seen. Cells treated with Con A-ferritin and Ricin II-ferritin showed an even distribution of lectin receptors and under conditions used no capping occurred. Lectin-ferritin complexes were taken up into pinocytotic vesicles. Cleaved preparations of Ricin II-ferritin treated cells showed no change in the distribution of IMP.
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PMID:Intramembrane particle distribution and lectin binding of glioblastoma cells after long term subculture. 18 99

To determine the fluidity of the membrane lipid phase, chicken erythrocytes were labeled with a stearic acid derivative spin label. When chicken erythrocytes were treated with concanavalin A (Con A), ESR spectra showed a change in the peaks of the labels in membrane lipids, indicating an increase of membrane fluidity. The degree of the increase in fluidity of the membrane lipid phase depended on the valency of the lectin used. Tetravalent Con A induced an increase of membrane fluidity at a concentration as low as 30 micrograms/ml, while a monovalent derivative of Con A did not affect membrane fluidity. This increase in membrane fluidity was observed within 10 min after the addition of Con A. If bound Con A was removed with methyl alpha-D-mannoside later than 60 min after its addition, a complete return of the fluidity to the normal level could not be observed. However, no change was found in the composition of phospholipids or in the fatty acid compositions of phosphatidylcholine and phosphatidylethanolamine of chicken erythrocytes after the addition of Con A, indicating that this increase in membrane fluidity is not caused by a change of lipid composition. The clustering of membrane receptors of chicken erythrocytes for Con A was demonstrated when the two-dimensional distribution of ferritin-conjugated Con A on the membranes was assayed by transmission electron microscopy. Furthermore, it was shown that major receptors for Con A of chicken erythrocytes were transmembrane glycoproteins having apparent molecular weights of 100K, 45, and 33K.
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PMID:Concanavalin A-induced increase in the membrane fluidity of chicken erythrocytes. 23 Oct 35

Pathogenic strains of Entamoeba histolytica are more easily agglutinated with concanavalin A (Con A) than strains isolated from human asymptomatic carriers. All three pathogenic strains studied here were found to agglutinate with low concentrations of Con A in contrast to various nonpathogenic axenic strains of amebas, characterized by their ability to grow at room temperature. Our present observations suggest that the extreme susceptibility of pathogenic strains of E. histolytica to agglutinate with Con A is related to their higher capacity for lectin binding and to their lack of detectable repulsive charges at the cell surface. The amount of fluorescein-tagged Con A bound to the surface was much higher in pathogenic strains. Only nonpathogenic strains showed a detectable negative surface charge as studied both by means of cell microelectrophoresis and by labeling cells with cationized ferritin at 0 degrees C. The mobility of surface Con A receptors estimated as the percentage of caps was comparable in all strains. Results of one strain cultured in axenic and monoxenic conditions suggested that bacteria can modify the behaviour of E. histolytica trophozoites by altering surface properties of the amebas.
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PMID:Surface properties related to concanavalin A-induced agglutination. A comparative study of several Entamoeba strains. 23 19


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