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

Avian tumour virus-infected chick embryo fibroblasts express new antigens, identical with the viral envelope antigens, in their plasma membranes. Electron-microscopic examination of carbon-platinum replicas of cells labelled with haemocyanin-marked antibody has shown the distribution of these antigens to be diffuse over the cell surface with an increased concentration on peripheral cell processes. However, antigen-antibody complexes (AAC), resulting from reaction with specific antibody, may be redistributed into a variety of patterns. Observation of the time course of antibody-induced antigen mobility revealed a rapid and a delayed phase of redistribution. During the rapid phase (10 min or less) some of the antigen-bearing cells reorganized AAC into patches, while the remainder maintained a diffuse distribution. A fraction of the cells with either diffuse or patchy distribution also redistributed AAC into a pattern of 'marginal redistribution (MR)', consisting of linear aggreagation of AAC, at the cell edge. During the 'late' phase of redistribution (after about 20 min), AAC began to condense into one or more foci of coalescence (FC) on each cell. As the number of cells with FC increased with time, the fraction of cells which were labelled decreased. Electron-microscopic observation of thin sections of ferritin-labelled specimens indicated that AAC were lost by endocytosis and that this process was probably related to FC formation. Inhibitors of oxidative phosphorylation, protein synthesis, RNA synthesis, or microtubule assembly had no significant effect on the patterns or the course of redistribution. Iodoacetic acid (IAA), which depletes cellular ATP, and cytochalasin B (CB), which is believed to depolymerize microfilaments, partially inhibited MR and completely prevented FC formation and endocytosis. Paradoxically, IAA or CB-treated cells lost AAC very rapidly by some alternate mechanism not involving FC formation but which may entail a centrifugal migration of complexes to the cell extremities during the process of AAC disposal.
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PMID:The dynamics of antibody-induced redistribution of viral envelope antigens in the plasma membranes of avian tumour virus-infected chick embryo fibroblasts. 17 78

The transfer of iron between horse spleen [55Fe]ferritin and human apotransferrin or [59Fe]transferrin in homogeneous solution was investigated. Transfer between the two proteins in the presence of citrate, ATP, or ascorbate occurs in both direction, but the net flow is always from ferritin to transferrin. Ferritin which is ca. 1/3 to 1/2 saturated with iron appears to be most reactive. Chemically prepared apoferritin does not accept iron from diferric transferrin. Citrate-mediated transfer of iron from ferritin to apotransferrin is first order with respect to ferritin, zero order with respect to transferrin, and has a complex dependence upon citrate concentration. Direct transfer of iron from native or reconstituted ferritin to apotransferrin in the absence of any identifiable mediating agent was observed to occur at about half the rate attained in the presence of 1 mM citrate. No transfer of iron between the two proteins occurs across a dialysis membrane in the absence of a mediating agent. No binding of transferrin and ferritin to each other was demonstrable. One possible explanation for these observations is that iron from the core of ferritin is in equilibrium with iron near the outer surface of the protein, where the metal would be available to transferrin.
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PMID:Iron exchange between ferritin and transferrin in vitro. 69 86

Apo horse spleen ferritin undergoes a 6.3 +/- 0.5 electron redox reaction at -310 mV at pH 6.0-8.5 and 25 degrees C to form reduced apoferritin (apoMFred). Reconstituted ferritin containing up to 50 ferric ions undergoes reduction at the same potential, taking up one electron per ferric ion and six additional electrons by the protein. We propose that apo mammalian ferritin (apoMF) contains six redox centers that can be fully oxidized forming oxidized apoferritin (apoMFox) or fully reduced forming apoMFred. ApoMFred can be prepared conveniently by dithionite or methyl viologen reduction. ApoMFred is slowly oxidized by molecular oxygen but more rapidly by Fe(CN)6(3-) to apoMFox. Fe(III)-cytochrome c readily oxidizes apoMFred to apoMFox with a stoichiometry of 6 Fe(III)-cytochrome c per apoMFred, demonstrating a rapid interprotein electron-transfer reaction. Both redox states of apoMF react with added Fe3+ and Fe2+. Addition of eight Fe2+ to apoMFox under anaerobic conditions produced apoMFred and Fe3+, as evidenced by the presence of a strong g = 4.3 EPR signal. Subsequent addition of bipyridyl produced at least six Fe(bipyd)3(2+) per MF, establishing the reversibility of this internal electron-transfer process between the redox centers of apoMF and bound iron. Incubation of apoMFred with the Fe(3+)-ATP complex under anaerobic conditions resulted in the formation and binding of two Fe2+ and four Fe3+ by the protein. The various redox states formed by the binding of Fe2+ and Fe3+ to apoMFox and apoMFred are proposed and discussed. The yellow color of apoMF appears to be an integral characteristic of the apoMF and is possibly associated with its redox activity.
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PMID:Redox reactions of apo mammalian ferritin. 132 25

Red cells (RBCs) of individuals with the In(Lu) gene are characterized by suppression of the Lutheran, P1, i, and other blood group antigens, acanthocytosis, and abnormal electrolyte metabolism. To determine the clinical significance of these abnormalities, the survival of autologous RBCs was determined by 51Cr in two siblings with the dominant Lu(a-b-) [In(Lu)] phenotype. Both subjects studied had normal hemoglobin, hematocrit, reticulocyte count, haptoglobin, and ferritin values. RBC indices were mildly hypochromic. Examination of the peripheral smear showed mild acanthocytosis in one individual. Analysis of RBC distribution on discontinuous density gradients showed a shift to lighter fractions than normal control RBCs. Storage of these Lu (a-b-) RBCs at 4 degrees C showed significant hemolysis within a few days; this was confirmed by increased autohemolysis, which was reduced by glucose and ATP. RBC cation content (sodium and potassium) was higher than that in control cells, which indicated increased cell hydration, which explains the lighter density and mild hypochromia of the Lu(a-b-) RBCs. 51Cr survival of autologous Lu(a-b-) RBCs was normal in both subjects studied. The data indicate that the morphologic and cation abnormalities of RBCs of persons with the In(Lu) gene are clinically insignificant, as these cells have normal in vivo survival. Such RBCs, however, are susceptible to increased hemolysis in vitro under standard blood banking storage conditions. Individuals of the Lu(a-b-) phenotype, associated with In(Lu), may not be suitable candidates for routine blood donation.
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PMID:In vitro storage and in vivo survival studies of red cells from persons with the In(Lu) gene. 151 24

Neuroblastoma cells accumulate ascorbic acid and iron. It was hypothesized that these features could be exploited for sensitizing neuroblastoma cells for therapy in combination with reactive oxygen intermediates. In the present study the effects of 6-hydroxydopamine (6-OHDA) and H2O2 on metabolic parameters critical for cell survival were investigated in cells with low and high ferritin content in the presence and absence of ascorbate. Human neuroblastoma SK-N-SH cells were pretreated with 100 microM FeSO4 and 10 microM desferrioxamine, respectively, for 24 h yielding cells with different ferritin contents. The effects of 6-OHDA and H2O2 (25 microM-250 microM) in the absence and presence of 1 mM ascorbic acid on DNA strand break formation, activation of poly(ADP-ribose) polymerase, and finally decrease in NAD+ and ATP concentration were investigated. All these parameters were influenced by 6-OHDA and H2O2 in a concentration-dependent manner in a similar way. The effects were most pronounced in ferritin-rich cells and in the presence of ascorbic acid. Using isolated CCC PM2 DNA, 6-OHDA and ascorbic acid caused strand breaks that were prevented in the presence of mannitol or desferrithiocine. H2O2-mediated strand breaks were observed only in the presence of ascorbic acid. Based on these data and data published by others a model explaining the deleterious effects of ascorbic acid on neuroblastoma cells is presented. It is suggested that continuous application of a high dosage of ascorbic acid might be a useful approach in neuroblastoma therapy.
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PMID:Ascorbic acid enhances the effects of 6-hydroxydopamine and H2O2 on iron-dependent DNA strand breaks and related processes in the neuroblastoma cell line SK-N-SH. 193 70

Effects of endurance training on O2 transport and on iron status are well documented in the literature. Only a few data are available concerning the consequences of strenuous anaerobic muscular exercise on red cell function. This study was performed to test the influence of strength training alone on parameters of red cell O2 transport and iron status. Twelve healthy untrained males participated in a strength-training programme of 2-h sessions four times a week lasting 6 weeks. After 6 weeks a small but significant reduction of haemoglobin (Hb; -5.4 g.l-1) was found (p less than 0.05). Mean red cell volume did not change, but a pronounced decrease of mean cell Hb concentration (from 329.2 g.l-1, SE 2.5 to 309.8 g.l-1, SE 1.2; p less than 0.001) and mean corpuscular Hb (from 29.6 pg, SE 0.4 to 27.7 pg, SE 0.3; p less than 0.01) was observed. Serum ferritin decreased significantly by 35% (p less than 0.01); transferrin, serum iron and iron saturation of transferrin were unaltered. Serum haptoglobin concentration was diminished significantly by 30.5% (p less than 0.01). The reticulocyte count had already increased after 3 weeks of training (p less than 0.05) and remained elevated during the following weeks. Strength training had no significant influence on the O2 partial pressure at which Hb under standard conditions was 50% saturated, red cell 2,3-diphosphoglycerate and ATP concentration as well as on erythrocytic glutamate-oxalacetate transaminase activity. The data demonstrate that mechanical stress of red cells due to the activation of large muscle masses led to increased intravascular haemolysis, accompanied by a slightly elevated erythropoiesis, which had no detectable influence on Hb-O2 affinity. Training caused an initial depletion of body iron stores (prelatent iron deficiency). Although Hb had decreased by the end of the training phase a true "sports anaemia" could not be detected.
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PMID:Consequences of 6 weeks of strength training on red cell O2 transport and iron status. 234 15

This article briefly describes the use of a photon counting system (ARGUS-100) in the detection of low levels of light. The ARGUS-100 was used in determining ATP in cell sections from tumor tissues and in measuring a luminescence-enhanced immunoluminometric assay, using ferritin as the analyte, based on the luminol-peroxide-4-iodophenol reaction with peroxidase as the enzyme. The aim is not so much the presentation of data, but rather to show the potentials of the photon counting camera in increasing our knowledge of the cellular and subcellular levels, as well as lowering the detection limits in already sensitive systems, such as immunoassays.
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PMID:Low light level in vitro monitoring of cellular and antigen-antibody reactions using a photon detection camera system--new perspectives for clinical diagnosis and research. 240 95

A monoclonal antibody named TM60, which inhibited both thrombin- and ristocetin-induced platelet aggregations, was obtained by hybridoma technique. TM60 inhibited binding of von Willebrand factor to platelets under the presence of ristocetin. The subclass of TM60 was IgG2a. TM60 did not inhibit ADP-, collagen-A-23187-, arachidonic acid- and PAF-induced platelet aggregations, but inhibited polylysine-, polybrene- and cationized ferritin-induced platelet aggregations. ATP-release from platelets induced by thrombin was also inhibited by TM60. Immunoprecipitation and SDS-PAGE experiments demonstrated that TM60 recognized an epitope on GPIb whose molecular weight was 165,000 under non-reduced and 145,000 under reduced conditions.
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PMID:Monoclonal antibody to glycoprotein Ib inhibits both thrombin- and ristocetin-induced platelet aggregations. 241 61

Physiologic concentrations of ATP stimulate the translocation of gallium-67 (67Ga) from human transferrin (TF) to horse ferritin (HoFE). The mechanism of this translocation was examined. One millimolar ATP did not speed the binding of 67Ga or indium-111 (111In) to HoFE. ATP and pyrophosphate (PPi) at 1 mM, did not form high affinity complexes with 67Ga or 111In. ATP and PPi interacted directly with the [67Ga]TF complex and could within minutes increase the amount of nonprotein-bound 67Ga. Serum HCO3- concentration, 30 mM, prevented the ATP-induced dissociation of 67Ga from TF, whereas intracellular concentrations (0.4 and 5 mM) did not. Using a dialysis technique, ATP also stimulated the translocation of 111In from TF to HoFE; however, this process was much slower than with 67Ga. ATP caused an increase in the nonprotein-bound 111In compared to the control. These results suggest the formation of nonprotein-bound nuclide by these phosphate-containing compounds in a kinetically labile form is important to the translocation mechanism.
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PMID:Role of phosphate-containing compounds in the transfer of indium-111 and gallium-67 from transferrin to ferritin. 253 83

Reduction of iron is important in promoting xenobiotic-enhanced, microsomal lipid peroxidation, yet there is little evidence that Fe3+ chelates that promote lipid peroxidation can be reduced by the microsomal system. We have shown that rat liver microsomes catalyse NADPH-dependent reduction of Fe3+ without chelator, as well as Fe3+(ADP), Fe3+(ATP), Fe3+(citrate), Fe3+(EDTA), and ferrioxamine in N2. The NADPH oxidation that accompanied Fe3+ reduction was inhibited by CO for all chelates, except Fe3+ (EDTA). This implies that, except for Fe3+ (EDTA), cytochrome P450 was involved in reduction of the complexes. Adriamycin, paraquat, and anthraquinone 2-sulfonate (AQS) enhanced reduction of all the Fe3+ chelates, whereas menadione enhanced reduction only of Fe3+(ADP) and Fe3+(citrate). All the compounds enhanced oxidation of NADPH in the presence or absence of iron. This was not inhibited by CO, and the results are compatible with Fe3+ reduction occurring via the xenobiotic radicals produced by cytochrome P450 reductase. Microsomal reduction of the xenobiotics, except menadione, enabled the reduction and release of iron from ferritin. Fe3+ chelate reduction, both with and without xenobiotic, was inhibited by O2, although it still proceeded in air at 10-20% of the rate in N2. Iron-dependent lipid peroxidation was promoted by ADP and ATP, inhibited 50% by citrate, and completely inhibited by EDTA and desferrioxamine. Of the xenobiotics, only Adriamycin enhanced microsomal lipid peroxidation. These results indicate that the effects of chelators and xenobiotics on Fe3+ reduction do not correlate with lipid peroxidation and, although reduction is necessary, there must be other factors involved.
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PMID:Microsomal reduction of low-molecular-weight Fe3+ chelates and ferritin: enhancement by adriamycin, paraquat, menadione, and anthraquinone 2-sulfonate and inhibition by oxygen. 285 Jul 67


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