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

The interactions of horse spleen ferritin and its derivative apoferritin with H+ ions were studied by potentiometric and spectrophotometric titration; to aid in data analysis, heats of ionization over a limited pH range and amide content were also determined. Per apoferritin subunit, all tyrosine and cysteine side chains, two of the nine lysine side chains and at least three of the six histidine side chains were found not to titrate; a preliminary but self-consistent analysis of the titration data is proposed. The titration curve of ferritin was identical with that of apoferritin in the pH range 5.5 to 3. In addition, under the conditions used, the reactivities of ferritin histidines to bromoacetate and of ferritin lysines to formaldehyde were identical with those in apoferritin. Above pH 8, a time-dependent titration of the ferritin core occurs which prevents comparison of the titration curves of the two proteins in this region. However, in the pH regions 5.5 to 7.5, two extra groups per subunit titrate reversibly in ferritin relative to apoferritin. Moreover, although the isoionic points of ferritin and apoferritin are identical in water, the isoionic point of ferritin is 0.5 pH unit lower than that of apoferritin in 0.16 to 1 M KCl. The different effects of KCl and NaCl on the two proteins indicate the presence of cation binding sites in ferritin that are absent in apoferritin and possibly also the presence of anion binding sites in apoferritin that are occupied in ferritin by anions of the core. The difference between the isoionic points of the two proteins in KCl has been interpreted to indicate the presence of approximately 2 phosphate residues per ferritin subunit which serve as cation binding sites and which are negatively charged at the isoionic point in KCl. These phosphates may also represent the additional residues that titrate in ferritin between pH 5.5 and 7.5, or may interact with positively charged residues on the inner surface of the ferritin shell, or both.
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PMID:Hydrogen ion interactions of horse spleen ferritin and apoferritin. 1 Dec 12

A test for demonstrating ringed sideroblasts was developed, using the dye bromchlorphenol blue. The test is based upon the ability of the dye to form a colored water-insoluble precipitate with iron. Because it is rapid and permits localization of ferritin-containing cytoplasmic inclusions, the reaction may be useful in the assessment of sideroblastic anemias.
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PMID:Rapid detection of ringed sideroblasts with bromchlorphenol blue. 8 98

The transcapillary flux of horseradish peroxidase (HRP, mol. diam. 50--60 A) and ferritin (mol. diam. 110--120 A), microinjected interstitially into the biceps femoris muscle of rats, was analyzed in the electron microscope. From 1 min postinjection HRP was observed to occupy endothelial plasmalemmal vesicles in all positions to be expected if a vesicular transendothelial transport of material occurs in the interstitium-to-lumen direction. Permeation of HRP through the intercellular clefts of the endothelium could not be demonstrated unequivocally. The periendothelial basement membrane appeared to constitute a significant permeability barrier against ferritin. The endothelial ultrastructure in muscle capillaries was analysed morphometrically after artificial perfusions of rat hindquarters at venous outflow pressures of -4 cm H2O and +10 cm H2O. In the "high pressure" material the endothelium was thinner and the frequency of vesicles open towards the interstitium was lower than after perfusion at low outflow pressure. The findings may indicate that net transendothelial transport via vesicles varies with hemodynamics.
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PMID:Capillary permeability to interstitial microinjections of macromolecules and influence of capillary hydrostatic pressure on endothelial ultrastructure. 8 86

A carbohydrate-containing fraction was extracted from the trypanosomatid Crithidia fasciculata by a phenol-water procedure. Ion-exchange chromatography separated this fraction into three components: a polysaccharide which was not retained on the column; RNA which eluted upon addition of salt; and, another polysaccharide which eluted upon addition of detergent. The unretained fraction was shown to be composed solely of D-mannose. The mannan, which was heterodisperse on Sephadex G-100, had an average molecular weight of approx. 14 000 as based on analysis of reducing groups. The detergent-eluted material yielded arabinose and galactose upon acid hydrolysis. The arabinogalactan was excluded from Sephadex G-100 and Sephacryl S-200 molecular sieve columns, suggesting a molecular weight greater than or equal to 200 000. Cell fractionation studies showed the bulk of extractable polysaccharide was associated with a particulate fraction. Further determination of the cellular localization of the polysaccharide was accomplished by employing a specific antiserum prepared from rabbits immunized with the polysaccharide extract. The cell surface localization of the arabinogalactan was demonstrated by cell agglutination studies as well as immunocytochemical techniques using fluorescein and ferritin conjugated antibodies.
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PMID:Polysaccharides of crithidia fasciculata. Identification and partial characterization of a cell surface constituent. 9 71

Measurements of filtration coefficients (Lp) and osmotic reflexion coefficients (sigma) of single capillaries in the frog mesentery suggest that fluid flows through the walls of these vessels in two types of channel. One channel type (representing about 10% of Lp) appears to be exclusively available for water whereas the other channels appear available for both water and hydrophilic solutes though they severely restrict the passage of albumin (sigma = 0.81). The effects of proteins in the perfusate upon Lp and studies on the passage of ferritin into the surface vesicles of the endothelial cells, suggest that an important component of capillary permeability may reside in an endocapillary layer.
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PMID:The investigation of capillary permeability in single vessels. 38 45

In the proximal tubular cells of rats or mice given a single, parenteral dose of lead, clusters of ferritin are frequently associated with characteristic cytoplasmic fibrillar bodies. To learn more about this relationship, we have investigated content and synthesis of ferritin protein and incorporation of iron into ferritin in rat kidneys 48 hours after a single parenteral dose of lead (10 microgram/g). By immunoradiometric assays, we found that the kidneys of female rats, whether treated with lead or not, contained significantly more ferritin protein than did kidneys of males of the same age and provenance. Administration of lead diminished (or did not significantly alter) the incorporation of 14C-amino acids into newly synthesized ferritin protein. Contrary to expectation, administration of lead tended to depress incorporation of 59Fe into kidney ferritin in rats maintained on standard rations and distilled water. Electron microscopy confirmed the presence of clusters of ferritin in close association with dense fibrillar bodies in the cytoplasm of proximal tubular cells of rats given lead. Considered together, the findings indicate that clustering of ferritin next to the dense fibrillar cytoplasmic lesions is a selective effect of lead that requires neither augmented synthesis of ferritin protein nor increased incorporation of iron into preexisting ferritin.
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PMID:Ferritin in rat kidneys with specific lesions due to a single dose of lead. 42 36

The permeability of Octopus microvasculature was investigated by intravascular injection of carbon and ferritin. Vessels were tight to carbon while ferritin penetrated the pericyte junction, and was found extravascularly 1-2 min after its introduction. Vesicles occurred rarely in pericytes; fenestrae were absent. The discontinuous endothelial layer did not consitute a permeability barrier. The basement membrane, although retarding the movement of ferritin, was permeable to it; carbon did not penetrate the basement membrane. Evidence indicated that ferritin, and thus similarly sized and smaller water soluble materials, traverse the pericyte junction as a result of bulk fluid flow. Comparisons are made with the convective (or junctional) and slower, diffusive (or vesicular) passage of materials known to occur across the endothelium of continuous capillaries in mammals. Previous macrophysiological determinations concerning the permeability of Octopus vessels are questioned in view of these findings. Possible reasons for some major structural differences in the microcirculatory systems of cephalopods and vertebrates are briefly discussed.
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PMID:Octopus microvasculature: permeability to ferritin and carbon. 47 69

In mice fed a low iron diet, the addition of low levels of cadmium chloride (10 micrometer) to the drinking water impaired growth and accentuated the development of anemia. Cadmium had no effect on mice given a similar diet supplemented with iron. Iron deficiency increased the concentration of cadmium in the duodenal mucosa, the transfer of cadmium to the body from the intestinal tract, and the deposition of absorbed cadmium in the kidneys. In human subjects, the average absorption of 25 microgram of cadmium, labeled with 115mCd, from a test meal was 8.9 +/- 2.0% (mean +/- SE) in 10 people with low body iron stores (serum ferritin less than 20 ng per ml) and 2.3 +/- 0.3% in 12 subjects with normal iron stores (serum ferritin greater than 23 ng per ml). The biological half-time of the radiocadmium in 3 of the subjects ranged from 90 to 202 days. Thus, the intestinal adaptive response to iron deficiency in both experimental animals and human subjects leads to the increased absorption of cadmium, a potentially toxic element.
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PMID:Increased dietary cadmium absorption in mice and human subjects with iron deficiency. 64 Mar 39

1. When lead is administered in drinking-water iron-deficient rats retain more Pb than Fe-replete rats (Six & Goyer, 1972; Klauder & Petering, 1975). In the present study the relationship between the absorption of Pb and Fe was investigated. 2. Adult male rats were transfered to a milk-based diet fed with or without supplementary Fe (180 mg Fe/kg as ferrous sulphate). After 7--9 d the absorption of duodenally-administered 203Pb and 59Fe was measured as uptake of radioactivity from the gastrointestinal tract after 90 min. 59Fe absorption was increased in rats given the unsupplemented diet for 7 d and was further increased in rats kept on the diet for up to 7 weeks. 203Pb absorption was not consistently increased by either short- or long-term Fe deprivation. 3. Much of the 203Pb in homogenates of the upper small intestine was bound to soluble protein of which up to 85% was dialysable. In contrast little 59Fe was dialysable. Only a small proportion of the soluble musosal Pb was associated with ferritin during gel-filtration chromatography although 203Pb precipitated together with carrier rat-liver ferritin with an antibody to rat-liver ferritin. 4. There appeared to be no direct relationship between the transfer of Fe and Pb across the small intestine of the adult rat.
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PMID:Lead and iron absorption from rat small intestine: the effect of dietary Fe deficiency. 69 63

The water-rich phase (tissue channels) of the intersititial tissue in rat ileum, knee joint capsules, kidneys, and implanted Guyton's capsules was examined electron microscopically by the SEM of plastic injection models, and by TEM and HVEM of ferrocyanide and ferritin as tracers. It was shown that the channels do in fact exist, and are not just vacuoles. Quantitative estimations of their numbers and diameters were made. These agreed well with estimates made by other methods.
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PMID:The quantitative morphology of interstitial tissue channels in some tissues of the rat and rabbit. 72 12


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