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)

Diaphragmed fenestrae (DF) are sites of increased vascular permeability. The anionic charge distribution at the luminal aspect of the DF of the endothelium of the bone marrow vessels has been studied after aldehyde fixation by means of colloidal iron (CI), native ferritin (NF), and polycationic ferritin (PCF). At pH 1.8, these cationic agents are bound by the nonmodified luminal endothelial cell surface but not at the sites of the DF. PCF was used over a pH range of 1.8--7.2 (CI is unstable at higher pH levels, whereas NF which has a pI of 4.5 is anionic above this point). PCF shows increased binding at the DF from pH 3.5 upwards. PCF binding at pH 1.8 at the nonmodified luminal cell surface is significantly diminished by neuraminidase treatment which, however, does not perceptibly reduce PCF binding at the higher pH levels. It is concluded that there are exposed sialic acid groups at the lunimal cell surface which are absent or significantly fewer at the sites of the DF, whereas other anionic materials possibly with a pKa higher than that of sialic acid (pKa 2.6) are present both at the DF and at the nonmodified endothelial cell surface.
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PMID:Changes in the random distribution of sialic acid at the surface of the myeloid sinusoidal endothelium resulting from the presence of diaphragmed fenestrae. 4 43

Cationized ferritin (CF) of narrow pI range (7.3-7.5) and the basic dye ruthenium red (RR) have been used as cationic probes to partially characterize anionic sites previously demonstrated in the glomerular basement membrane (GBM). When CF was given i.v. to normal rats and the left kidney was fixed by perfusion 15 min thereafter, clusters of CF molecules were found throughout the lamina rara interna (LRI), lamina rara externa (LRE), and mesangial matrix distributed at regular (approximately 60 nm) intervals. When kidneys were perfused with aldehyde fixative containing RR, small (20 nm) RR-stained particles were seen in the same locations distributed with the same 60 nm repeating pattern, forming a quasiregular, lattice-like arrangement. Fine (approximately 3 nm) filaments connected the sites and extended between them and the membranes of adjoining endothelial and epithelial cells. When CF was given i.v. followed by perfusion with RR in situ, both probes localized to the same sites. CF remained firmly bound after prolonged perfusion with 0.1-0.2 M KCl or NaCl. It was displaced by perfusion with buffers of high ionic strength (0.4-0.5 M KCl) or pH (less than 3.0 or greater than 10.0). CF also bound (clustered at approximately 60 nm intervals) to isolated GBM's, and binding was lost when such isolated GBM's were treated with buffers of high ionic strength or pH. These experiments demonstrate the existence of a quasi-regular, lattice-like network of anionic sites in the LRI and LRE and the mesangial matrix. The sites are demonstrable in vivo (by CF binding), in fixed kidneys (by RR staining), and in isolated GBM's (by CF binding). The results obtained with CF show that the binding of CF (and probably also RR) to the laminae rarae is electrostatic in nature since it is displaced by treatment with buffers of high ionic strength or pH. With RR the sites resemble in morphology and staining properties the proteoglycan particles found in connective tissue matrices and in association with basement membranes in several other locations.
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PMID:Anionic sites in the glomerular basement membrane. In vivo and in vitro localization to the laminae rarae by cationic probes. 9 48

Receptors for Ricinus communis agglutinin I (RCAI), concanavalin A (Con A), and wheat germ agglutinin (WGA) were localized on the zonae pellucidae and plasma membranes of hamster, mouse, and rat eggs with ferritin-lectin conjugates. Intact eggs labeled with the ferritin conjugates showed dense concentrations of RCAI and WGA receptors in the outermost regions of their zonae pellucidae and sparse distributions of Con A receptors throughout the zonae. Ferritin-lectin labeling was specific, since inhibitory saccharides effectively blocked labeling. The asymmetric density of RCAI receptors across the zona was confirmed by ferritin-RCAI and fluorescein-RCAI labeling of mechanically isolated zonae pellucidae, indicating that the RCAI-binding sites are more densely distributed in the exterior zona regions. Plasma membranes of rodent eggs contained RCAI, WGA, and Con A receptors. These receptors were found to be more or less randomly distributed on surfaces of aldehyde-fixed eggs or on eggs labeled near 0 degrees C. However, eggs incubated at 25 degrees C showed aggregated WGA- and Con A-binding site distributions on their plasma membranes. This indicates that lectin-induced receptor redistribution occurs at this temperature. The possibility that plasma membrane receptor mobility is a requirement for sperm-egg fusion is discussed.
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PMID:Ultrastructural localization of lectin-binding sites on the zonae pellucidae and plasma membranes of mammalian eggs. 109 97

Alcohol abuse is associated with disturbances to iron metabolism in man, ranging from anemia to siderosis. Also seen in these patients are increased serum ferritin levels. Since the liver not only stores iron in cytosolic ferritin, but has also been shown to take up this molecule from the plasma by an active transport mechanism, it has been suggested that the iron in this circulating ferritin may contribute to the increased incidence of siderosis seen in alcoholics. As part of an ongoing study of these disturbances, using a rat model, we have examined the uptake of ferritin by freshly isolated hepatocyte suspension to test the hypothesis that increased hepatocyte uptake of ferritin iron contributes to the siderosis seen in some alcoholics. Incubation of hepatocytes in the presence of ethanol resulted in a progressive reduction in uptake with increasing alcohol concentration, from 1.23 +/- 0.05 ng of ferritin/10(6) cells/min to 0.65 +/- 0.02 ng/10(6) cells/min (mean +/- SD) at an ethanol concentration of 100 mM. 4-Methylpyrazole (0.1 mM) restored 70% of this activity, but higher concentrations also decreased ferritin uptake in the absence of ethanol. The addition of 5 microM cyanamide decreased ferritin uptake slightly in the presence of ethanol (0.82 +/- 0.04 ng of ferritin/10(6) hepatocytes/min vs. 0.86 +/- 0.03 ng/10(6) cells/min for ethanol alone), while having no effect in the absence of ethanol (1.01 +/- 0.04 vs. 1.12 +/- 0.05 ng/10(6) cells/min). Preincubation of the hepatocytes with acetaldehyde resulted in a dose-dependent reduction to a maximum reduction of approximately 25% at 300 microM acetaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effect of ethanol metabolism on ferritin uptake by freshly isolated rat hepatocytes: is acetaldehyde responsible for this alteration? 159 May 51

Superoxide radicals, a species known to mobilize ferritin iron, and their interaction with catalytic iron have been implicated in the pathogenesis of alcohol-induced liver injury. The mechanism(s) by which ethanol metabolism generates free radicals and mobilizes catalytic iron, however, is not fully defined. In this investigation the role of hepatic aldehyde oxidase in the mobilization of catalytic iron from ferritin was studied in vitro. Iron mobilization due to the metabolism of ethanol to acetaldehyde by alcohol dehydrogenase was increased 100% by the addition of aldehyde oxidase. Iron release was favored by low pH and low oxygen concentration. Mobilization of iron due to acetaldehyde metabolism by aldehyde oxidase was completely inhibited by superoxide dismutase but not by catalase suggesting that superoxide radicals mediate mobilization. Acetaldehyde-aldehyde oxidase mediated reduction of ferritin iron was facilitated by incubation with menadione, an electron acceptor for aldehyde oxidase. Mobilization of ferritin iron due to the metabolism of acetaldehyde by aldehyde oxidase may be a fundamental mechanism of alcohol-induced liver injury.
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PMID:Ethanol-induced iron mobilization: role of acetaldehyde-aldehyde oxidase generated superoxide. 217 Feb 42

The oxidation of acetaldehyde (generated from the metabolism of ethanol) by oxidases such as xanthine oxidase generates free radicals which can mobilize ferritin iron, alter hepatic glutathione and produce lipid peroxidation. The stomach, a site of ethanol metabolism and rich in xanthine oxidase, was studied with respect to the effects of ethanol on intrinsic factor (IF) binding of vitamin B-12 as well as gastric glutathione (GSH). Incubations of gastric homogenates with acetaldehyde-xanthine oxidase inhibited the B-12 binding ability by IF. A large acute dose of ethanol in vivo (5 g/kg, conc. greater than 40% w/v) decreased gastric IF binding of B-12 and depressed gastric GSH; these effects were markedly attenuated by the feeding of sodium tungstate which inhibited xanthine oxidase. Changes in B-12 binding paralleled changes in gastric GSH. Scatchard plots of IF binding of B-12 for homogenates suggested decreased number of binding sites rather than altered affinity. In conclusion, the gastric metabolism of ethanol generates free radicals which alter IF binding of B-12, depress gastric GSH and may play a role in alcohol-induced gastric injury.
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PMID:Effect of ethanol-generated free radicals on gastric intrinsic factor and glutathione. 232 89

A simple post-embedding technique for the electron microscopical detection of lectin-binding sites using thin sections of tissues embedded in the resin LR White is described. With this technique, no prior etching of the sections is necessary. The cellular fine structure is well preserved and permits close correlation of the labelling to distinct cellular compartments. After mild aldehyde fixation (4% formaldehyde and 0.5% glutaraldehyde for 30 min), enterocyte brush border, vesicles and lysosomes as well as goblet cell Golgi apparatus and mucin are intensely stained after 30-60 min. The hydrophilia and penetrability of LR White is shown by the formation of oxidized diaminobenzidine reaction product arising from horseradish peroxidase-conjugated lectins. The precipitate not only covers the surface of the sections but is also formed within the resin, as is revealed on cross-sections through thin and semithin sections. The addition of 0.2 M solutions of the appropriate inhibitory sugars prevented staining, which indicates a specific binding. Examples are given of the binding of gold-, ferritin- and peroxidase-conjugated lectins for the purpose of detecting glycoconjugates in various intracellular compartments.
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PMID:Post-embedding localization of glycoconjugates by means of lectins on thin sections of tissues embedded in LR white. 242 41

Although folate deficiency and increased requirements for folate are observed in most alcoholics, the possibility that acetaldehyde generated from ethanol metabolism may increase folate catabolism has not been previously demonstrated. Folate cleavage was studied in vitro during the metabolism of acetaldehyde by xanthine oxidase, measured as the production of p-aminobenzoylglutamate from folate using h.p.l.c. Acetaldehyde/xanthine oxidase generated superoxide, which cleaved folates (5-methyltetrahydrofolate greater than folinic acid greater than folate) and was inhibited by superoxide dismutase. Cleavage was increased by addition of ferritin and inhibited by desferrioxamine (a tight chelator of iron), suggesting the importance of catalytic iron. Superoxide generated from the metabolism of ethanol to acetaldehyde in the presence of xanthine oxidase in vivo may contribute to the severity of folate deficiency in the alcoholic.
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PMID:Cleavage of folates during ethanol metabolism. Role of acetaldehyde/xanthine oxidase-generated superoxide. 253 25

Increasing evidence points to a major role for free radicals in the pathogenesis of alcohol-induced liver injury. In vitro, free radicals may be generated during ethanol metabolism by the further metabolism of acetaldehyde by molybdenum-dependent oxidases such as xanthine oxidase. Ferritin iron mobilized by such free radicals may serve as catalytic iron. Increased stores of ferritin iron and induction of microsomal P-450 reductase activity are mechanisms by which chronic alcohol feeding may potentiate the acute effects of alcohol.
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PMID:Lipid peroxidation, iron mobilization and radical generation induced by alcohol. 255 83

Xanthine oxidase is able to mobilize iron from ferritin. This mobilization can be blocked by 70% by superoxide dismutase, indicating that part of its action is mediated by superoxide (O2-). Uric acid induced the release of ferritin iron at concentrations normally found in serum. The O2(-)-independent mobilization of ferritin iron by xanthine oxidase cannot be attributed to uric acid, because uricase did not influence the O2(-)-independent part and acetaldehyde, a substrate for xanthine oxidase, also revealed an O2(-)-independent part, although no uric acid was produced. Presumably the amount of uric acid produced by xanthine oxidase and xanthine is insufficient to release a measurable amount of iron from ferritin. The liberation of iron from ferritin by xanthine oxidase has important consequences in ischaemia and inflammation. In these circumstances xanthine oxidase, formed from xanthine dehydrogenase, will stimulate the formation of a non-protein-bound iron pool, and the O2(-)-produced by xanthine oxidase, or granulocytes, will be converted by 'free' iron into much more highly toxic oxygen species such as hydroxyl radicals (OH.), exacerbating the tissue damage.
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PMID:Superoxide-dependent and -independent mechanisms of iron mobilization from ferritin by xanthine oxidase. Implications for oxygen-free-radical-induced tissue destruction during ischaemia and inflammation. 302 67


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