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)

This report records for the first time double-label freeze-etch electron microscopy of cells in culture. On L6 rat myoblasts, receptors for wheat germ agglutinin and concanavalin A were found distributed together in irregular granular microclusters of cell surface material up to 60 nm in diameter. Simultaneous localization of two different receptor families to such small regions using colloidal gold and ferritin to differentiate between lectin markers proved difficult in our hands. We were able to achieve the desired result using native concanavalin A and ferritin-conjugated wheat germ agglutinin, whose shadowed diameters are measurably different.
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PMID:Double label freeze-etch study of the relative topography of concanavalin A and wheat germ agglutinin receptors at the myoblast surface. 362 Apr 68

Ricinus communis agglutinin I (RCA-I), a lectin that binds to D-galactosyl residues, intensely stained capillaries in cryostat sections of canine cerebral cortex when evaluated by the avidin-biotin-peroxidase complex method. Of seven lectins tested, only RCA-I gave strong staining of vessels and capillaries with little staining of other cortical cells. Ultrastructural studies using ferritin-, biotin-, and peroxidase-labeled RCA-I indicated that this lectin was bound to the luminal membrane of the cerebral capillary endothelial cell and that lectin receptors were distributed continuously along this membrane. Plasmalemma invaginations that bound RCA-I were also present in endothelial cells. Primary cultures of cerebral capillary endothelial cells grown on plastic or gelatin-coated glass substrates demonstrated staining of the cell membrane and perinuclear structures which appeared to be the Golgi complex and secondary lysosomes. These staining characteristics were retained when the cells were subcultured and were confirmed by ultrastructural studies. In contrast, light microscopy showed that fibronectin was more widely distributed in the cytoplasm, a finding consistent with its occurrence in the endoplasmic reticulum. This work provides support for the concept that lectins may be useful endothelial cell markers in both intact tissue and cell culture.
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PMID:Light and electron microscopic localization of D-galactosyl residues in capillary endothelial cells of the canine cerebral cortex. 370 Oct 30

The osteoclast is a large multinucleate cell that is widely accepted as the primary effector cell responsible for normal bone resorption. In a previous study, we demonstrated that concanavalin A (con A) has a dose-dependent biphasic effect on the bone-resorbing capacity of osteoclasts, using a 45Ca bone-organ culture system; bone resorption was stimulated at low concentrations and inhibited at high concentrations. The mitogenic property of con A in lymphocyte cultures is well documented; therefore con A has been used extensively to study the manner in which lymphocytes and other mononuclear cells process the cell-bound lectin. In this study, we have investigated the processing of con A-receptor complexes by osteoclasts in culture, using con A-FITC to evaluate the redistribution of cell-bound con A via epifluorescence microscopy and using con A-ferritin to determine whether the lectin receptor complexes are internalized. The osteoclasts were obtained from the long bones of newborn rats and allowed to attach to glass coverslips at 37 degrees C. Following attachment, the nonadherent cells were removed by rinsing. The adherent osteoclasts were preincubated in 50 micrograms/ml con A-FITC or con A-ferritin at 4 degrees C for 10 min, washed to remove unbound con A, and incubated at 37 degrees C for 15 or 30 min in the absence of con A. Positive controls were fixed immediately after preincubation at 4 degrees C; negative controls were preincubated in con A-FITC and alpha-methyl mannoside, the haptenic inhibitor of con A binding. The results demonstrate that redistribution and endocytosis of con A-receptor complexes occurs within 30 min. These findings confirm the hypothesis that cell-bound con A can alter the structure and activity of osteoclast membrane components in a manner similar to that observed in mononuclear cell cultures. The internalization of con A may be important in altering osteoclastic activity by mediating intracellular mechanisms involved in the bone-resorbing process.
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PMID:Processing of concanavalin A-receptor complexes by rat osteoclasts in vitro. 372 43

The molecular basis for the acquisition of adhesiveness between blastocysts and uterine luminal epithelium is an interesting problem in reproductive biology. It is rather difficult to study implantation-stage blastocysts of mice because during the implantation period each blastocyst becomes lodged within a crypt formed by decidualizing stroma. After trophectoderm adheres to uterine luminal epithelium, it is not possible to flush intact blastocysts from the uterus by standard recovery procedures. By identifying implantation sites with the Evans blue technique and splitting or gently separating the apposed epithelium of finely trimmed sites, it was possible to expose nonadhesive and adhesive trophectoderm to polycationized ferritin (PCF) and a series of ferritin-conjugated lectins. Examination by transmission electron microscopy revealed that both adhesive and nonadhesive trophectoderm bound PCF, concanavalin A, wheat-germ agglutinin, Ricinus communis agglutinin I, and Limulus polyhemus agglutinin, but not Dolicos biflorus agglutinin or peanut agglutinin. Nonadhesive trophectoderm bound succinylated wheat germ agglutinin but adhesive trophectoderm did not. There was no apparent difference in the relative amounts of each lectin bound to adhering and nonadhering cells.
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PMID:Cell surface of mouse blastocysts at the trophectoderm-uterine interface during the adhesive stage of implantation. 373 44

A new two-step method using an Fc-fragment/ferritin conjugate as a marker for the visualization of lectin-binding sites on neuronal and other cell membranes is described. In this study of rat synaptosomes, three lectins were tested: concanavalin A, mistletoe lectin I and wheat germ agglutinin. The specificity of the method was proved by control experiments.
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PMID:A method for the fine-structural demonstration of lectin receptors. 375 56

The distribution of anionic sites detected in vitro with cationized ferritin and lectin-binding sites on the endothelial cell (EC) surface of brain micro-blood vessels was studied by electron microscopy. Gold-labeled lectins and glycoproteins and Lowicryl K4M-embedded brain samples obtained from mouse embryos (19th day), and from 1-, 5-, 12-, 24- and 48-day-old and adult mice were used. It was shown that the functional maturation of the blood-brain barrier (BBB) occurring in the mouse after birth between the 12th and 24th day of life is accompanied by a disappearance of vesicular transport in capillaries and by the formation of a uniform, thin, negatively charged layer on the surface of the EC. Concomitantly the binding of lectins specific for beta-D-galactosyl (RCA) and sialyl (LFA and WGA) residues become progressively more intense and uniform on both luminal and abluminal fronts of the EC. The concentration of HPA-binding sites on the abluminal side of the EC and in the basement membrane increases. Similarly the binding of Con A becomes more intense on abluminal than on luminal front of the EC. These observations suggest that extensive remodeling of anionic sites and surface glycoprotein layer and also the elaboration of ECs polarity occur during BBB maturation.
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PMID:Distribution of anionic sites and glycoconjugates on the endothelial surfaces of the developing blood-brain barrier. 375 33

D-mannose, D-galactose, N-acetyl-D-galactosamine, N-acetyl-D-glucosamine and L-fucose which are sugar determinants of receptors were found on the surface of neuroblastoma cells by means of four carbohydrate-specific lectin groups. Labeling of lectins was performed by horseradish peroxidase, ferritin and colloidal gold. Peculiarities of the lectin receptors distribution on the surface of immature neuroblastoma cells were detected.
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PMID:[Localization of lectin receptors on the surface of C1300 neuroblastoma cells]. 375 84

Cell surface sugar residues in neurulating ectoderms of bantam chick embryos of stage 4-11 were examined using ferritin-labeled Ricinus communis (RCAI) and Wheat germ agglutinin (WGA). RCAI binding sites densely covered the apical surfaces of the basal plate cells during the neural plate stage (1,322.8 +/- 28.8 ferritin particles/micron 2). As neural tube formation advanced, the number of receptors decreased as a result of an increase in the extent of the sparsely covered regions. The decrease in receptors for WGA occurred in a similar manner but more rapidly. By the stage of development at which the opposite sides of the neural ridges meet at the dorsal midline, the receptors for WGA were reduced to about half. After this period, the two lectin receptors did not show significant changes. This result suggests that sugar residues or the sugar-chain skeleton on basal plate cells are altered during neurulation.
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PMID:Binding pattern of ferritin-labeled lectins (RCAI and WGA) during neural tube closure in the bantam embryo. 376 85

We explored the luminal surface of liver sinus endothelium for the presence of lectin receptors and lectinlike substances capable of interacting with specific sugars. We used ferritin-conjugated lectins and glycosylated ferritins as probes. Incubation of small blocks of rat liver with these probes led to the binding of concanavalin A (on A), Ricinus communis (RCA), wheat germ agglutinin (WGA), phytohemagglutinin (PHA) and mannosyl ferritins to the luminal surface of endothelium. Ulex europaeus agglutinin I (UEA), fucosyl, galactosyl, and chitobiosyl-ferritins did not bind. The binding was patchy and sparse in the case of Con A and mannosyl-ferritins but uniform for others. Binding density did not correlate with hemagglutinability of lectins, suggesting that the difference in the hemagglutinability of these lectins did not account for the difference in their binding densities. Bindings were all completely inhibited in the presence of excess specific sugar inhibitors, indicating the specificity of binding. The distribution of binding was segregated on the endothelial membrane, being heaviest on luminal pits. To define the functional significance of this segregated distribution, sinus endothelium was compared to portal-vein endothelium in which endothelial fenestrations are also seen; and these fenestrations as well as pits may be covered by a thin diaphragm. Of interest was the total absence of binding to the diaphragm. The significance of these findings is discussed.
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PMID:Mapping of the rat liver endothelial membrane with lectins and glycosylated ferritins. 379 91

Selective transport of proteins is a major mechanism by which biochemical differences are maintained between the cytoplasm and nucleus. To begin to investigate the molecular mechanism of nuclear transport, we used an in vitro transport system composed of a Xenopus egg extract, rat liver nuclei, and a fluorescently labeled nuclear protein, nucleoplasmin. With this system, we screened for inhibitors of transport. We found that the lectin, wheat germ agglutinin (WGA), completely inhibits the nuclear transport of fluorescently labeled nucleoplasmin. No other lectin tested affected nuclear transport. The inhibition by WGA was not seen when N-acetylglucosamine was present and was reversible by subsequent addition of sugar. When rat liver nuclei that had been incubated with ferritin-labeled WGA were examined by electron microscopy, multiple molecules of WGA were found bound to the cytoplasmic face of each nuclear pore. Gel electrophoresis and nitrocellulose transfer identified one major and several minor nuclear protein bands as binding 125I-labeled WGA. The most abundant protein of these, a 63-65-kD glycoprotein, is a candidate for the inhibitory site of action of WGA on nuclear protein transport. WGA is the first identified inhibitor of nuclear protein transport and interacts directly with the nuclear pore.
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PMID:Inhibition of in vitro nuclear transport by a lectin that binds to nuclear pores. 380 21


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