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

Recently, we suggested that the cell coat of the surface epithelial cells of the palatal shelves and especially its sialyl groups are implied in the adhesion process which initiates the constitution of the secondary palate. In this work, use of cationized ferritin which interacts with anionic receptors of the plasma membrane give us the possibility to render these sialic acids visible. After five minutes incubation in presence of cationized ferritin, the labeling particles are distributed in monolayer over the plasmalemma of epithelial cells. Subsequent incubation in cationized ferritin free medium results in clustering of the marker followed by the detachment of the labeled patches. Otherwise, incubation in the presence of neuraminidase from Clostridium perfringens before the polycationic ligand contact prevents labeling. We think that lateral migration modifications of the anionic receptor could be associated with changes of the shelves capacity to adhere.
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PMID:[Binding of cationized ferritin to the surface of the palatine crest in the rat]. 713 38

The surface charge of Tritrichomonas foetus was evaluated by means of the binding of colloidal iron hydroxide particles at pH 1.8 and cationized ferritin particles at pH 7.2 to the cell surface, as visualized by electron microscopy and by direct measurements of the electrophoretic mobility (EPM), of cells suspended in solutions of different ionic strength and pH. At pH 7.2, T. foetus has a negative surface charge with a mean EPM of -1.03 micrometer . s-1 . V-1 . cm. At lower pH, there is a decrease in the negative surface charge with an isoelectric point at pH 1.2. At higher pH (greater than 9.0), there is an increase in the surface charge reaching an EPM of -2.5 micrometers . s-1 . V-1 . cm. These results indicate that the surface of T. foetus contains both negatively and positively charged dissociating groups. Binding of colloidal iron hydroxide and cationized ferritin particles throughout the cell surface of the protozoon was observed. Treatment of T. foetus with neuraminidase or trypsin reduced significantly the EPM of the cells. Enzyme-treated cells recovered their normal EPM when incubated for 6 h in fresh culture medium by a process that is inhibited by puromycin.
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PMID:The surface charge of Tritrichomonas foetus. 717 70

Monolayer cultures of Ehrlich ascites tumor cells in exponential growth phase were treated with X-rays and neuraminidase alone or in combination. A radiation dose of 2 Gy (200 rd) and higher effected a significant inhibition of DNA synthesis and cell proliferation. Neuraminidase treatment in addition to irradiation did not modify the growth-inhibitory irradiation effect. Cells pretreated for 0.5 to 1.0 hours with neuraminidase (in Earle's salt solution) and cultured thereafter (4h) in serum-containing growth medium exhibited an enhanced development of the microtubule-microfilament-system. Morphometric analysis of microtubules on electronmicroscopic sections revealed a nearly 4-fold increased number in neuraminidase treated cells while the average length of microtubules was similar to controls. Pinocytosis as measured by the ultrastructural uptake of ferritin appeared to be increased following neuraminidase treatment. A connection between neuraminic acid containing components (glycoproteins or glycolipids?) of the cell membrane or cell surface, on the one hand, and the cytoskeleton and the endocytotic process of these tumor cells, on the other hand, is suggested.
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PMID:[Action of x-rays and neuraminidase on pinocytotic activity and microtubule-microfilament system of Ehrlich ascites tumor cells in monolayer culture (author's transl)]. 719 7

The purpose of this study was to examine the distribution and mobility of anionic sites on the surface of fetal trophoblast in contact with maternal blood using polycationic ferritin (PCF) as a probe. Pieces of human placental villi were washed to remove maternal blood, and fresh, unfixed tissue was exposed to PCF for varying times, concentrations, and temperatures to determine the effects on labeling patterns. The major findings were: 1) anionic sites were localized almost exclusively on the microvillous portion of the trophoblast surface; inter-microvillous regions of the surface, including the coated pits, were generally not labeled with PCF; 2) PCF binding present as small clusters on the microvilli. This pattern was observed in tissue incubated 5-10 sec at 4 degrees C and 23 degrees C. The size of the clusters was increased with increased incubation time, suggesting some aggregation or patching can occur; 3) following the formation of patches, the anionic sites showed no evidence of being cleared from the membrane by endocytosis during incubation subsequent to labeling; 4) the binding of PCF to the surface was reduced by pretreatment of the tissue with neuraminidase. Tissue fixed in glutaraldehyde prior to PCF exposure showed both clustered and more dispersed labeling. The results indicate that anionic sites on human trophoblast surface have a non-random distribution and have restricted mobility on the surface. This may be indicative of a segregation of different membrane proteins and functions within different structural regions of the placental cell surface.
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PMID:The distribution and mobility of anionic sites on the surface of human placental syncytial trophoblast. 722 98

The distribution and effects of polycationized ferritin (PCF) bound ot anionic sites on living plasmalemmas and basal laminae of normal and puromycin aminonucleoside nephrotic (PAN) kidneys were studied using an in vitro model system. Immersion of normal glomeruli in physiological saline solutions containing low concentrations of PCF (0.01 to 0.1 mg/ml) for 10 seconds results in preferential binding of PCF to microvillous projections on the glomerular epithelium (i.e., podocytes). Exposure to higher concentrations of PCF (1.0 mg/ml) for 10 seconds results in several layers of PCF distributed evenly over the urinary aspect of epithelial podocytes. In these short treatment times, the thin slit diaphragms which span the filtration slits appear to be impermeable to PCF. Within several minutes after PCF treatment, ferritin is found within caveolae on the surface of epithelial podocytes and within numerous pinosomes and larger endocytic vesicles within these cells. Longer treatment with PCF results in the narrowing of filtration slit spaces and the formation of junctions between adjacent podocyte foot processes. Occurringg coincident with these structural changes is a gradual accumulation of PCF in regular patches along the lamina rara externa (LRE) of the glomerular basement membrane. Loss of foot processes and accumulation of PCF in the LRE are prevented by treatment with either cytochalasin B (25 micro g/ml), D (2 micro g/ml) or incubation at low temperatures (0-4 degrees C). When PCF-coated glomeruli are incubated in PCF-free media, the ferritin coat is shed form the free surfaces within 1/2 to 1 hour except at the tips and sides of microvillous projections. Pretreatment of normal glomeruli with neuraminidase or protamine sulfate results in a dramatic reduction in the binding of PCF to the glomerular epithelial free surface. Treatment of PAN glomeruli with PCF often results in patchlike distributions of PCF over the glomerular epithelial free surface. High concentrations of PCF (1.0 mg/ml) bind preferentially to microvillous projections on the parietal epithelial luminal surface and in distinct patchlike patterns along the basal laminae of parietal and tubular epithelial cells.
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PMID:Cationized ferritin binding to anionic surfaces in normal and aminonucleoside nephrotic kidneys. 730 71

The entry of fowl plague virus, and avian influenza A virus, into Madin-Darby canine kidney (MDCK) cells was examined both biochemically and morphologically. At low multiplicity and 0 degrees C, viruses bound to the cell surface but were not internalized. Binding was not greatly dependent on the pH of the medium and reached an equilibrium level in 60-90 min. Over 90% of the bound viruses were removed by neuraminidase but not by proteases. When cells with prebound virus were warmed to 37 degrees C, part of the virus became resistant to removal b neuraminidase, with a half-time of 10-15 min. After a brief lag period, degraded viral material was released into the medium. The neuraminidase-resistant virus was capable of infecting the cells and probably did so by an intracellular route, since ammonium chloride, a lysosomotropic agent, blocked both the infection and the degradation of viral protein. When the entry process was observed by electron microscopy, viruses were seen bound primarily to microvilli on the cell surface at 0 degrees C and, after warming at 37 degrees C, were endocytosed in coated pits, coated vesicles, and large smooth-surfaced vacuoles. Viruses were also present in smooth-surfaced invaginations and small smooth-surfaced vesicles at both temperatures. At physiological pH, no fusion of the virus with the plasma membrane was observed. When prebound virus was incubated at a pH of 5.5 or below for 1 min at 37 degrees C, fusion was, however, detected by ferritin immunolabeling. t low multiplicity, 90% of the prebound virus became neuraminidase-resistant and was presumably fused after only 30 s at low pH. These experiments suggest that fowl plague virus enters MDCK cells by endocytosis in coated pits and coated vesicles and is transported to the lysosome where the low pH initiates a fusion reaction ultimately resulting in the transfer of the genome into the cytoplasm. The entry pathway of fowl plague virus thus resembles tht earlier described for Semliki Forest virus.
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PMID:Infectious entry pathway of influenza virus in a canine kidney cell line. 732 11

1. Ferritin has been partially purified from the serum of patients with idiopathic haemochromatosis. 2. Incubation with neuraminidase of this partially purified serum ferritin eliminated much of the microheterogeneity of the protein so that only ferritin of isoelectric point approximately 5.8 was present. 3. There was no change in the total amount of ferritin present (measured immunologically) or in the percentage of ferritin binding to concanavalin A. 4. Incubation of liver, spleen or heart ferritin with neuraminidase did not change the isoelectric focusing patterns.
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PMID:Sialic acid and the microheterogeneity of human serum ferritin. 736 68

Antigens A and B, shown to be associated with the progestagen-dominated human endometrium, were partly purified and their properties studied. The antigens were recovered in the crude nuclei, the heavy particulate fraction and cytosol of decidua-rich tissue from early pregnancy. The antigens in cytosol were enriched by a combination of Concanavalin A-Sepharose chromatography and polyacrylamide gel electrophoresis. The immunological reactivity of the antigens after partial purification by Concanavalin A-Sepharose chromatography was retained after 30 min exposure to 4-85 degrees C at pH 7.4, or after 2 h to pH 2-12 at 22 degrees C. Trypsin, but not pepsin, RNase, DNase or neuraminidase, completely destroyed immunological reactivity of both antigens. The apparent molecular weight of both antigens determined by filtration on Sephadex G100 was 48 000. The isoelectric point of both antigens was approximately 4.9. The antigens were not immunologically related to transferrin, ceruloplasmin, alpha-1-antitrypsin, ferritin, uteroglobin, alpha-fetoprotein, human chorionic gonadotrophin, pregnancy-associated plasma proteins or pregnancy zone protein. Furthermore, the antisera to Antigens A and B did not react with the decidual cytosol of pregnant baboons or of pseudopregnant rats.
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PMID:Properties of the progestagen-dependent protein of the human endometrium. 743 Dec 86

The selective entry of mature blood cells into the peripheral circulation of the bone marrow is a transcellular process. The mature blood cells penetrate the cytoplasm of the endothelial cells lining the myeloid sinuses and form a migration pore in the cell body of the lining cell, which closes after the blood cell reaches the intravascular space. The changes at the surfaces of the cells involved in this selective transcellular process were studied by means of the cationic cell surface markers colloidal iron (CI) and polycationic (high isoelectric point) ferritin (PCF). The anionic cell surface charges resulting from the presence of sialated glycoproteins remain, as shown by the application of these markers at low pH (1.8), evenly distributed at the cell surfaces of both the blood cell and the sinus lining cell. However, there is at the advancing margin of the diapedesing blood cells a marked accumulation of a nonsialated anionic material binding PCF at high pH (7.2). This material first accumulates extravascularly beneath the endothelium at an area of the blood cell surface near the site of the migration pore formation, remains at the cell surface during the initial phases of transcellular passage and disappears, either through shedding in the vascular lumen or through redistribution on the cell surface, when the cell reaches the intravascular space. This anionic material, which is neuraminidase resistant and has a pKa higher than sialic acid, is a characteristic concommitant in the selective transcellular blood cell passage in bone marrow.
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PMID:An anionic material at the advancing front of blood cells entering the bone marrow circulation. 744 7

The binding of cationized ferritin (CF) to the cell-coat (glycocalyx) glycoproteins of human and rat intestinal absorptive cells was investigated in relation to the amount of sialic acid in these macromolecules. The cell coat of human absorptive cells exhibited poor binding of CF and contained a small amount of sialic acid. The cell coat of rat absorptive cells had about ten times more sialic acid than that of human cells and showed a strong affinity for the marker. The removal of sialic acid from the cell-coat glycoproteins of rat intestinal cells by neuraminidase treatment abolished CF binding. These results suggest that sialic acid is necessary for CF binding and that human and rat intestinal absorptive cells show a species-specific difference in the sugar composition of the cell coat.
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PMID:Binding of cationized ferritin to the cell-coat glycoproteins of human and rat small-intestinal absorptive cells. 746 7


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