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

Cell fractions were prepared from ACI rat livers and from rat hepatoma cell clone M-5123-C1. Radioimmunoassays of ferritin and of its protein subunits in various cell fractions after biosynthetic labeling with [14C]leucine were done by means of ferritin-specific and subunit-specific rabbit antibody. In both ACI rat livers and M-5123-C1 hepatoma cells free polyribosomes synthesized approximately 81% of the protein subunits of ferritin, and membrane-bound polyribosomes synthesized the rest. In both polyribosomal fractions, [14C]leucine-labeled subunits were detected earlier than [14C]leucine-labeled ferritin and apoferritin (5 min as against 30 min after initiation of a pulse). Time sequence studies of the shifts of biosynthetically labeled subunits and ferritin through different cell compartments provided evidence for vectorial transport of subunits and of ferritin, the direction of transport being from the two polyribosomal systems to the smooth membrane compartment and to the cytosol.
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PMID:Biosynthesis of ferritin in rat hepatoma cells and rat livers. I. Synthesis and assembly of protein subunits of ferritin. 19 50

Ferritin and its protein subunits in rat hepatoma cell clone M-5123-C1 were biosynthetically labeled with [14C]leucine and 59Fe. Radioimmunoassays of ferritin/apoferritin and of protein subunits in the free polyribosome, membrane-bound polyribosome, smooth membrane, and cytosol fractions were done with ferritin-specific and subunit-specific rabbit IgG antibodies at various time intervals after pulsing. Much more 59Fe was bound by ferritin/apoferritin than by subunits in all of the cell fractions. Binding of iron to subunits may have been a random process. When hepatoma cells were simultaneously pulse-labeled with 59Fe and [14C]leucine, uptake of much of the 59Fe by ferritin occurred relatively early, in comparison to incorporation of [14C]leucine, in all of the cell fractions examined. Thus, 59Fe was readily incorporated into pre-existing ferritin. We conclude that most, if not nearly all, of the iron is incorporated after assembly of protein subunits.
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PMID:Biosynthesis of ferritin in rat hepatoma cells and rat livers. II. Binding of iron by ferritin protein. 19 51

Human plasma low density lipoprotein (LDL) that had been rendered polycationic by coupling with N, N-dimethyl-1, 3-propanediamine (DMPA) was shown by electron microscopy to bind in clusters to the surface of human fibroblasts. The clusters resembled those formed by polycationic ferritin (DMPA-feritin), a visual probe that binds to anionic site on the plasma membrane. Biochemical studies with (125)I-labeled DMPA-LDL showed that the membrane-bound lipoprotein was internalized and hydrolyzed in lysosomes. The turnover time for cell bound (125)I-DMPA-LDL, i.e., the time in which the amount of (125)I-DMPA-LDL degraded was equal to the steady-state cellular content of the lipoprotein, was about 50 h. Because the DMPA-LDL gained access to fibroblasts by binding nonspecifically to anionic sites on the cell surface rather than by binding to the physiologic LDL receptor, its uptake failed to be regulated under conditions in which the uptake of native LDL was reduced by feedback suppression of the LDL receptor. As a result, unlike the case with native LDL, the DMPA-LDL accumulated progressively within the cell, and this led to a massive increase in the cellular content of both free and esterified cholesterol. Studies with (14)C-oleate showed that at least 20 percent of the accumulated cholesteryl esters represented cholesterol that had been esterified within the cell. After 4 days of incubation with 10 mug/ml of DMPA-LDL, fibroblasts had accumulated so much cholesteryl ester that neutral lipid droplets were visible at the light microscope level with Oil Red O staining. By electron microscopy, these intracellular lipid droplets were observed to lack a tripartite limiting membrane. The ability to cause the overaccumulation of cholesteryl esters within cells by using DMPA-LDL provides a model system for study of the pathologic consequences at the cellular level of massive deposition of cholesteryl ester.
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PMID:Metabolism of cationized lipoproteins by human fibroblasts. Biochemical and morphologic correlations. 19 5

Electron and immunoelectron microscopic studies were carried out on liver tissues from three marmosets, experimentally infected with hepatitis A virus and sacrificed during the acute phase of illness. Ultrastructurally, the liver cells demonstrated marked cisternal dilation of endoplasmic reticulum and vesicular transformation and contortion of endoplasmic reticulum profiles. Clusters of virus-like particles of 24 to 27 nm. in diameter, both "solid" and "empty" forms, were found in membrane-bound cytoplasmic vesicles. In one animal, the virus-like particles were significantly smaller, measuring 17 to 22 nm. in size, and almost all were solid forms embedded in an amorphous matrix. Clusters of virus-like particles were found in the bile canaliculi of liver cell cords and in lysosomal structures of monocytes or Kupffer cells in the hepatic sinusoids. The latter correlated with the immunofluorescent microscopic finding. Indirect immunoferritin staining was carried out on fresh and formalin-fixed liver tissues, using convalescent phase serum from patients recovered from hepatitis A virus infection as the primary antibody, and the ferritin-labeled rabbit anti-human IgG or ferritin-labeled staphylococcal protein A as the secondary antibody. Specific stainings were observed with the virus-like particles, indicating that the particles were probably antigenically related to hepatitis A virus. Our findings are in agreement with the immunofluorescent and immunoelectron microscopic studies reported by others and support the concept that hepatitis A virus is produced in the liver. The infection seems to produce cytopathic effect especially to the endoplasmic reticulum organelle of hepatocytes.
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PMID:Electron and immunoelectron microscopic study on liver tissues of marmosets infected with hepatitis A virus. 22 41

Previous electron-microscopic studies on the liver have shown that following excessive administration of iron to experimental animals, small particles believed to represent ferritin and/or hemosiderin (electron-dense iron-containing particles [IPs]) accumulate in membrane-bound bodies--many with a lysosome-like structure--in liver parenchymal and Kupffer cells. Further identification of the IP-containing bodies has been facilitated by the application of histochemical techniques for the demonstration of acid phosphatase. The results have shown that reaction product was deposited over organelles similar in appearance to the IP-containing ones, indicating that they were lysosomes. However, the granular nature of the reaction product makes it difficult or impossible to decide whether IPs are present simultaneously with reaction product in the organelle. In order to clarify this qualitative aspect, x-ray microanalysis has been utilized to identify iron and lead (reaction product) in the various structures thought to represent lysosomes. The results indicate that all IP-containing bodies also show the presence of reaction product, and thus can be regarded as lysosomes. However, in the parenchymal cells there may exist a small population of iron-deficient lysosomes (only lead could be shown). The latter may correspond to "primary lysosomes."
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PMID:Studies on the rat liver following iron overload. Electron probe x-ray microanalysis of acid phosphatase and iron. 47 12

We describe the sequential ultrastructural changes in villus absorptive cells of human fetal small intestine between 9 and 22 weeks of gestation. In concert with villus formation at 9 to 10 weeks, a complex membranous system designated the apical tubular system appeared in the apical cytonous system designated the apical tubular system appeared in the apical cytoplasm of absorptive cells. The apical tubular system consisted of deep invaginations of plasma membrane and membrane-bounded vesicles and tubules. Some elements of this system were characterized by linear arrays of particles on the inner (luminal) membrane leaflet. After villus formation, many lysosomal elements designated "meconium corpuscles" also appeared in the apical cytoplasm. Modified morphometric studies suggested that both the apical tubular system and the lysosomal elements were more extensively developed in the distal than in the proximal intestine, were most abundant at 15 to 17 weeks, and decreased by 18 to 22 weeks. Morhpometry also showed an inverse relationship between the relative surface density of the apical tubular system and microvillus membrane, suggesting the possible derivation of elements of the former from the apical plasma membrane. Exposure of intestine to ferritin for 8 to 40 minutes in vitro revealed ferritin in elements of the apical tubular system of 12- to 20-week fetuses. There was no evidence of transport of ferritin across absorptive cells. Distinctive membranous bodies composed of convoluted membrane-bound cisternae separated by narrow channels of cytoplasmic matrix were seen in the Golgi region and apical cytoplasm of fetal absorptive cells between 14 and 22 weeks. In a single 22-week fetus, there was marked proliferation of smooth endoplasmic reticulum, a decrease in cytoplasmic glycogen and loss of most lysosomal and apical tubular elements in the proximal but not the distal intestine. Thus, by the end of the second trimester, the structure of absorptive cells in proximal intestine was remarkably similar to absorptive cells in adult intestine.
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PMID:Development of villus absorptive cells in the human fetal small intestine: a morphological and morphometric study. 50 2

The in vitro events of phagocytosis of ferritin and of cationized ferritin by normal eosinophils and the eosinophilic cells of two patients with hypereosinophilic syndrome are described. After one minute of incubation, the cells showed a noticeable pseudopod formation, while after five minutes, ferritin-containing vacuoles were seen in both the normal and the patients' eosinophils. No alterations of the specific granules were observed in cells incubated for 90 minutes or less. Ferritin was observed in the membrane-bound vacuoles, but not in the specific granules of the cells. There was no difference in phagocytic activity of the patients' eosinophils as compared with the normal eosinophils, as well as between phagocytosis of ferritin and of cationized ferritin.
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PMID:Ferritin phagocytosis. 57 89

Iron overload of the rat liver following parenteral administration of Jectofer (an iron sorbitol citric acid complex) was studied in the electron microscope. Abundant ferritin-like granules were present in parenchymal and Kupffer cells, partly free in the cell sap and partly concentrated in 3 types of membrane-bound organelles, with characteristic appearances. In the parenchymal cells these organelles consisted of lysosome-like structures, apparent autophagic vacuoles, and vacuoles lacking features linking them to specific cytoplasmic elements. Organelle-bound ferritinlike granules in the Kupffer cells were demonstrated in lysosomelike structures, in phagocytic vacuoles, and in tubular and vacuolar elements referred to as "type 1" and "type 2" bodies. No ferritin-like granules were observed in other cell types than parenchymal and Kupffer cells.
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PMID:Studies on the rat liver following iron overload. 1. Fine structural appearance. 69 16

The fine structure of the pore cells in connective tissue in the kidney of Achatina achatina and the skin of the slug Arion hortensis is described and evidence is presented which shows that these cells, in the latter species, are involved in the synthesis of the respiratory blood pigment, haemocyanin. The involvement of these cells in phagocytosis of colloidal particles, was demonstrated following introduction of ferritin and colloidal gold into the blood. The extracellular coat which surrounds the cells is permeable to ferritin, but is impermeable to colloidal gold. Following penetration of the extracellular coat the ferritin enters the sub-surface cisternae and is taken into the cells where it crystallises within membrane-bound vesicles.
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PMID:On the functions of the pore cells in the connective tissue of terrestrial pulmonate molluscs. 112 26

The degradation of intramuscularly injected autogenic and xenogenic red blood cells are studied with electron microscopy and immunoferritin technique. Autogenic red blood cells are phagocytosed and completely degradated by macrophages within the draining lymph node in a relatively short time. Phagocytosis and initial degradation of xenogeneic red blood cells by macrophages in the draining lymph node are similar; however, portions of the degradation products persist in macrophages as characteristic myelinic-like figures. After 4 days, identical figures appear in large numbers in the adjacent lymphocytes within membrane-bound vacuoles. With the conjugated ferritin antibody technique, these myelinic-like figures are shown to contain antigens of the xenogeneic red blood cells. Subsequently, lymphocytes containing the inclusions are found in the peripheral blood, the marginal zone of the spleen, other lymph nodes, and the bone marrow. As in the draining lymph node the number of plasma cells increases in these organs in areas adjacent to lymphocytes with the inclusions. In a parallel study, uncoated polystyrene spheres injected intramuscularly accumulate and remain localized in macrophages of the draining lymph node. When coated with xenogeneic hemoglobin and membranes, these spheres appear in lymphocytes of the draining lymph node and subsequently in lymphocytes of the blood and spleen.
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PMID:Xenogeneic red blood cell degradation in a regional lymph node and dissemination of antigens by circulating lymphocytes. 118 18


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