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)

A fluorescent enzyme-linked immunosorbent assay is described for the rapid measurement of serum ferritin. Increased sensitivity was achieved by using 4-methyl-umbelliferyl-beta-D-galactopyranoside as the substrate for beta-galactosidase coupled to the purified antiferritin antibody. Further enhancement of the specific antigen-antibody reaction was attained by the addition of 4% polyethylene glycol 6000 to the antiferritin-beta-galactosidase conjugate. The procedure is performed in microELISA plates. These modifications of the method permit the measurement of serum ferritin at concentrations ranging from 0.25 to 50 microgram/liter with a coefficient of variation of 8% or less. The entire procedure is performed at ambient temperature and is completed within one working day. The cost of the assay is less than 10% of the immunoradiometric assay for serum ferritin.
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PMID:A rapid and sensitive ELISA for serum ferritin employing a fluorogenic substrate. 681 55

The avidin-biotin complex was used for the selective ultrastructural labeling of terminal cell surface galactosyl residues. Rabbit bone marrow cells were treated with the enzyme galactose oxidase in the presence of biotin hydrazide. Subsequent treatment with ferritin-avidin conjugates enabled the electron microscopic visualization of terminal membrane-based galactose and/or N-acetylgalactosamine on these cells. All stages of erythroid development were characterized by high levels of exposed cell surface galactose, whereas all leukoid cells in the same preparations were virtually unlabeled by the above method. Modulations in the distribution of these surface determinants during differentiation and maturation of rabbit erythroid cells were found to concur in inverse fashion with respect to that of terminal sialic acids. Neuraminidase treatment, before the above labeling procedure, resulted in the exposure of additional galactosyl residues on the surface of all bone marrow cell types. The results indicate that a galactose-bearing glycoconjugate(s) may comprise an erythroid-specific membrane constituent of rabbit bone marrow cells. The high density of galactose on the surface of even the earliest erythroid precursors may eventually enable the identification and isolation of a stem cell, which already contains the erythroid-specific galactoconjugate(s). The results suggest that variations in the spectrum of cell surface carbohydrates may serve as recognition signals in the complex set of intercellular interactions which occur during the development and maturation of the erythrocyte. The occurrence of similar but species-specific variations in the complement of surface heterosaccharides during erythroid development of humans and other mammals supports this contention.
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PMID:Cell-type-related segregation of surface galactosyl-containing components at an early developmental stage in hemopoietic bone marrow cells in the rabbit. 682 46

Carbohydrate-directed endocytosis is mediated by a receptor, the hepatic binding protein; it is responsible for the clearance of galactose-terminated glycoproteins from the circulation. This process was investigated by using lactosaminated ferritin which is recognized by this receptor. Ferritin was seen in elements of an extensive "lysosomal compartment" that includes secretory vacuoles, coated vesicles, and GERL. The compartment marked in hepatocytes by the distribution of ligand is similar to that previously described in Kupffer cells (marked by acid phosphatase reaction product and horseradish peroxidase reaction product).
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PMID:Carbohydrate-specified endocytosis: localization of ligand in the lysosomal compartment. 694 68

Acidic isoferritins have been identified as leukemia-associated inhibitory activity (LIA), which suppresses colony and cluster formation of colony-forming unit-granulocyte macrophages from normal donors but not from patients with leukemia. LIA was detected in all ferritin preparations tested, including ferritin isolated from normal heart, spleen, liver, and placental tissues, and from the spleens of patients with chronic myelogenous leukemia and Hodgkin's disease. Purified preparations of LIA were composed almost entirely of acidic isoferritins, as determined by immunoassay, radioimmunoassay, and isoelectric focusing. The inhibitory activity in the LIA and ferritin samples was inactivated by a battery of antisera specific for ferritin, including those prepared against acidic isoferritins from normal heart and spleen tissues from patients with Hodgkin's disease, and those previously absorbed with basic isoferritins. Antisera absorbed with acidic isoferritins did not inactivate the inhibitory activity. Separation of LIA and chronic myelogenous leukemia and normal spleen ferritin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing confirmed that the regions of peak inhibitory activity corresponded in each to an apparent molecular weight of approximately 550,000 and to a pI value of 4.7. Similar physicochemical characteristics included inactivation by methods that dissociate ferritin molecules into subunits and by treatment with trypsin, chymotrypsin, pronase, and periodate. The purified preparations were extremely stable to heat treatment. The glycoprotein nature of the inhibitory activity was substantiated because it bound to concanavalin A-Sepharose and was eluted off by alpha-methyl mannose. Inhibitory activity of the activity of the acidic isoferritins was detected at concentrations as low as 10(-17)-10(-19) M and iron saturation did not appear to be necessary for its action. These results implicate acidic isoferritins in the regulation of normal myelopoiesis and suggest a role for them in the progression of leukemia.
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PMID:Identification of leukemia-associated inhibitory activity as acidic isoferritins. A regulatory role for acidic isoferritins in the production of granulocytes and macrophages. 697 99

The binding characteristics of lectins with varying sugar specificities were investigated in muscle biopsies from normal individuals and from patients with neuromuscular disorders. Horseradish peroxidase (HRPA) and fluorescein isothiocyanate (FITC)-conjugated lectins were used for light microscopy and ferritin-conjugated Concanavalin A (Con A) for electron microscopy. In normal and diseased muscle a lectin specific for alpha-D-mannosyl residues (Con A) and a group of lectins specific for beta-D-galactosyl residues were found to bind to the perimysial and endomysial connective tissue, blood vessels and capillaries and clearly demonstrated the perimeter of each muscle fibre. Wheat germ agglutinin (WGA), specific for N-acetylglucosamine and N-acetyl-neuraminic acid residues, had a similar distribution of staining although it appeared to stain the capillaries more strongly. In contrast, lectins specific for alpha-L-fucose and N-acetyl-galactosamine did not stain specifically any structures in normal or diseased muscle. In biopsies from dystrophic patients Con A, WGA and the beta-D-galactose specific lectins were always associated with splits and in biopsies from a variety of disorders discontinuities in staining were observed at the periphery of occasional fibers. These were not found in normal muscle. Electron microscopy showed Con A bound to the basement membrane of muscle fibres and capillaries and the connective tissue. The plasma membranes themselves were unstained. These preliminary investigations of lectin binding in muscle have shown important differences in diseased muscle and demonstrate the application of lectin chemistry to the study of membrane structure.
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PMID:Cytochemical studies of lectin binding by diseased human muscle. 713 Oct 29

Incubation of horse spleen ferritin and rat liver ferritin with [14C]glucose, [14C]mannose or [14C]fucose resulted in the covalent incorporation of the sugar into ferritin. The rate of reaction depended on the concentrations of ferritin and sugar and time of incubation. The order of this nonenzymic incorporation was glucose greater than mannose greater than or equal to fucose. Glucosylated or mannosylated ferritin was not retained by concanavalin A. The plasma half-life of rat liver ferritin and apoferritin was found to be 20 min. This value remained unaffected by in vitro glucosylation or mannosylation of ferritin. It is suggested that varying degrees of glycosylation might account for the occurrence of isoferritins.
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PMID:Non-enzymic glycosylation of horse spleen and rat liver ferritins. 728 31

The cell surface of Tritrichomonas foetus was characterized by using 18 highly purified lectins with specificities for N-acetyl glucosamine, N-acetyl galactosamine, galactose, mannose, and sialic acid. The specificity of the lectin-induced cell agglutination was verified by inhibition of the agglutination with the specific sugars. By using cytochemical techniques associated with electron microscopy, carbohydrates were detected on the cell surface of T. foetus. The following techniques were used: periodic acid--thiosemicarbazide--silver proteinate, concanavalin A--horseradish peroxidase, and ruthenium red. Anionic sites were detected on the cell surface of the protozoan at pH's 1.8 and 7.2 with the use of colloidal iron hydroxide and cationized ferritin particles, respectively. The binding of colloidal iron particles, as well as the agglutination induced by the lectin from Limulus polyphemus, indicated the presence of sialic acid on the cell surface of T. foetus.
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PMID:Cell surface carbohydrates in Tritrichomonas foetus. 731 Jul 44

We have used two electron microscopic tracers, asialoorosomucoid covalently coupled to horseradish peroxidase (ASOR-HRP) and lactosaminated ferritin (Lac-Fer), to investigate the internalization of proteins bound by the asialoprotein receptor of rat hepatocytes. Both ligands are cleared rapidly from the circulation of rats, are retarded in their clearance by an excess of ASOR and accumulate principally in the liver. Morphological examination of the livers of rats after injection of the probes confirmed that the hepatocyte is the principal liver cell involved in the clearance of galactose-terminating proteins. Internalization occurred via coated pits and coated vesicles of 1000 A diameter. At 30 sec to 2 min the tracers began to accumulate in a complex arrangement of larger smooth-surfaced vesicles and tubular structures at the sinusoidal periphery of the cell. Fluid phase pinocytosis did not appear to account for any of the uptake into larger vesicles. The particulate tracer, Lac-Fer, was closely apposed to the membrane of coated pits and vesicles, but was found scattered throughout the lumen of the larger vesicles, possibly indicating dissociation of the ligand from its receptor. Although occasional lysosomes were detected cytochemically in the cell periphery, vesicles containing Lac-Fer showed no demonstrable aryl sulfatase activity. At 5 min, the tracers began to appear in Golgi-lysosome regions of the hepatocyte and were present in small vesicles of <2000 A in diameter, larger irregular vesicles and tubules. Serial sectioning indicated that tubular structures in Golgi-lysosome regions were often interconnected to the larger vesicles, but that tubules in the peripheral cytoplasm were only occasionally connected to larger structures. Some of the Lar-Fer-containing vesicles in Golgi-lysosome areas at 15 min after injection were found to contain aryl sulfatase reaction product, indicating fusion with lysosomes.
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PMID:The galactose-specific recognition system of mammalian liver: the route of ligand internalization in rat hepatocytes. 740 14

Exopolysaccharide (EPS) synthesis by Erwinia amylovora depends on environmental and genetic predispositions. To measure the amount of the acidic EPS amylovoran synthesized by E. amylovora cell cultures, a turbidity assay using cetylpyridinium salt was developed. The EPS produced by bacteria grown on solid media was additionally characterized by its water content. The amylovoran capsules were visualized in situ by staining with fluorescein isothiocyanate (FITC)-labelled lectin from Abrus precatorius, which reacts with the galactose residue of the EPS side chain. The staining and the turbidity assays were applied to suspension cell cultures or to cells from colonies and did not require any purification steps. Lectin staining was superior to electron microscopic (EM) techniques for visualization of capsules. For EM, the capsule was stabilized with polycationic ferritin. In contrast to lectin staining, only a small fraction of the cells was found to be EPS-coated in the EM assay. An increase in capsulation and in amylovoran production was found in conjunction with mutations in a ribosomal protein conferring resistance to streptomycin. Furthermore, the presence of sorbitol in the growth environment resulted in high synthesis of amylovoran. Cells in the stationary growth phase continued to produce amylovoran. Apparently, the strong dependence of the fireblight pathogen on capsules requires the capacity for EPS synthesis in all growth stages in order to escape plant defence reactions.
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PMID:Visualization of capsule formation by Erwinia amylovora and assays to determine amylovoran synthesis. 753 77

Exponential-growth-phase cultures of Bacillus subtilis 168 were probed with polycationized ferritin (PCF) or concanavalin A (localized by the addition of horseradish peroxidase conjugated to colloidal gold) to distinguish surface anionic sites and teichoic acid polymers, respectively. Isolated cell walls, lysozyme-digested cell walls, and cell walls treated with mild alkali to remove teichoic acid were also treated with PCF. After labelling, whole cells and walls were processed for electron microscopy by freeze-substitution. Thin sections of untreated cells showed a triphasic, fibrous wall extending more than 30 nm beyond the cytoplasmic membrane. Measurements of wall thickness indicated that the wall was thicker at locations adjacent to septa and at pole-cylinder junctions (P < 0.001). Labelling studies showed that at saturating concentrations the PCF probe labelled the outermost limit of the cell wall, completely surrounding individual cells. However, at limiting PCF concentrations, labelling was observed at only discrete cell surface locations adjacent to or overlying septa and at the junction between pole and cylinder. Labelling was rarely observed along the cell cylinder or directly over the poles. Cells did not label along the cylindrical wall until there was visible evidence of a developing septum. Identical labelling patterns were observed by using concanavalin A-horseradish peroxidase-colloidal gold. Neither probe appeared to penetrate between the fibers of the wall. We suggest that the fibrous appearance of the wall seen in freeze-substituted cells reflects turnover of the wall matrix, that the specificity of labelling to discrete sites on the cell surface is indicative of regions of extreme hydrolytic activity in which alpha-glucose residues of the wall teichoic acids and electronegative sites (contributed by phosphate and carboxyl groups of the teichoic acids and carboxyl groups of the peptidoglycan polymers) are more readily accessible to our probes, and that the wall of exponentially growing B. subtilis cells contains regions of structural differentiation.
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PMID:Structural differentiation of the Bacillus subtilis 168 cell wall. 811 82


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