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

Short asbestos fibers isolated by a sedimentation procedure have a strong hemolytic activity. In the presence of ferritin particles, hemolysis by chrysotile fibers is inhibited at least during the first 10 min. Freeze-fracture studies show that after 20 sec or 2 min of contact between the fibers and the RBC membrane, the intramembranous particles remain randomly distributed over the whole surface of the P-face. On the E-face of the asbestos-treated red blood cell membranes, the number of intramembranous particles is significantly reduced. With the transmission electron microscopy, it is not possible to resolve the trilaminar structure of the ghost membrane around the deeply buried asbestos fibers. It is postulated that the membrane defects brought about by asbestos are caused by the adsorption of one membrane constituent, possibly phospholipids, on the chrysotile fibers.
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PMID:The hemolytic activity of chrysotile asbestos fibers: a freeze-fracture study. 630 72

During the last week of gestation of the fetal rat, the epithelium of the colon is rapidly remodeled. At 16 days a primitive stratified epithelium surrounds a small central lumen. Over the next 3 days, the main lumen extends narrow clefts down to the basal cell layer and small secondary lumina appear within the stratified epithelium between these clefts. At 19 and 20 days, secondary lumina enlarge but remain discrete; an infusion of cationic ferritin into the main lumen does not enter secondary lumina. During the 2 days prior to birth (21-22), the secondary lumina join the main lumen as superficial cells are sloughed, and the epithelium becomes simple columnar. Freeze-fracture replicas indicate that luminal and nonluminal membrane domains of epithelial cell plasma membranes are separated by continuous tight junctions throughout the conversion process. Cytochemical analysis of tissue slices from 16- to 22-day fetal colon demonstrated the appearance and segregation of two phosphatases on apical and basolateral membrane domains during epithelial conversion. Cysteine-sensitive pH 9.0 (alkaline) phosphatase activity was first detected along the luminal membranes of cells bordering both primary and secondary lumina at 18 days gestation and increased to a maximum at 20-21 days; weaker activity was present on basolateral membranes. Phosphatase activity at pH 8.0 also appeared at 18 days and increased thereafter, but was localized primarily on nonluminal membranes. At pH 8.0, reaction product appeared on both inner and outer sides of the membrane, and was only partially abolished by omission of K+ or addition of ouabain; thus the reaction may be only partially due to K+-dependent ATPase activity. Biochemical analysis of the cytochemical media confirmed the appearance of phosphatase activities at 18 days. Thus, plasma membrane phosphatase activities appear while the epithelium is still stratified, but are segregated to luminal and nonluminal membrane domains at the onset of activity. Segregation is maintained throughout the process of conversion of a simple columnar epithelium.
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PMID:Epithelial differentiation in the fetal rat colon. I. Plasma membrane phosphatase activities. 630 78

Freeze-fracturing and deep-etching have been used to characterize the internal morphology and surface charge of the plasma membrane of GH3-cells from cell culture in fixed and unfixed material. Glutaraldehyde does not effect intramembrane particle pattern but induces structural modifications on the cell surface in a way that additional attachment sites for cationized ferritin are exposed at specific areas of the membrane. Negative surface charges are not directly linked to the intramembrane particles, but to other (surface-) proteins, independently enough to be dislocated by external ligands; this process is restricted to the membrane surface. Thermotropic phase changes induce separation of lipidic regions from proteinaceous regions. Peripheral and integral protein are thus aggregated simultaneously, resulting in clustered membrane particles and aggregated surface charges.
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PMID:Morphological characterization of the plasma membrane of a pituitary tumor cell line (GH3). 678 62

Treatment of rat liver rough microsomes (3.5 mg of protein/ml) with sublytical concentrations (0.08%) of the neutral detergent Triton X-100 caused a lateral displacement of bound ribosomes and the formation of ribosomal aggregates on the microsomal surface. At slightly higher detergent concentrations (0.12-0.16%) membrane areas bearing ribosomal aggregates invaginated into the microsomal lumen and separated from the rest of the membrane. Two distinct classes of vesicles could be isolated by density gradient centrifugation from microsomes treated with 0.16% Triton X-100: one with ribosomes bound to the inner membrane surfaces ("inverted rough" vesicles) and another with no ribosomes attached to the membranes. Analysis of the fractions showed that approximately 30% of the phospholipids and 20-30% of the total membrane protein were released from the membranes by this treatment. Labeling with avidin-ferritin conjugates demonstrated that concanavalin A binding sites, which in native rough microsomes are found in the luminal face of the membranes, were present on the outer surface of the inverted rough vesicles. Freeze-fracture electron microscopy showed that both fracture faces had similar concentrations of intramembrane particles. SDS PAGE analysis of the two vesicle subfractions demonstrated that, of all the integral microsomal membrane proteins, only ribophorins I and II were found exclusively in the inverted rough vesicles bearing ribosomes. These observations are consistent with the proposal that ribophorins are associated with the ribosomal binding sites characteristic of rough microsomal membranes.
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PMID:Recovery of ribophorins and ribosomes in "inverted rough" vesicles derived from rat liver rough microsomes. 706 49

Pinocytosis was studied in cultured human skin fibroblasts in order to obtain more information about uptake in these cells of non-specific ligands with different net surface charge. The fibroblasts were obtained from a normal person and a patient homozygous for familial hypercholesterolemia. No ultrastructural differences were observed between the two cell types. The ratio between coated and smooth pits at the cell surface was about 1:6. Freeze-fracture revealed that whereas smooth pits were devoid of intramembrane particles, the coated pits occupying 1-5% of the total cell surface area showed numerous intramembrane particles. Cationized ferritin (pI = 8.5) bound to the cell surface and to coated pits of both types of fibroblasts at 4 degrees C. Either type internalized CF at 37 degrees C. Vacuoles (lysosomal elements) containing CF were seen already after 5 min at 37 degrees C, but were much numerous after 30 min of incubation at 37 degrees C, and appeared with the same frequency in both cell types. Smooth (uncoated) pits at the cell surface remained unlabeled. In contrast to CF, native ferritin (pI = 4.6) was internalized to a very limited extent in both cell types, even after 3.5 h of incubation at 37 degrees C. These results indicate that both normal and FH fibroblasts internalize CF exclusively by coated pits, and adsorptive uptake mechanism that apparently is nonspecific but clearly cation-selective.
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PMID:Coated pits and pinocytosis of cationized ferritin in human skin fibroblasts. 711 70

The cellular sites of the glycoproteins Group 1 allergen (glycoprotein 1) and Antigen A (glycoprotein 2) in mature ryegrass pollen have been investigated by immunoelectron microscopy. Radioimmunoassays confirm previous findings of cross-reactivity between the purified glycoprotein antigens at the high immunoglobulin G (IgG) concentrations used for localization. Freeze-drying of anthers followed by anhydrous processing has been employed because of the water solubility and mobility of the glycoproteins. A double-embedding technique has been developed. This involves, first, embedding anthers in the water-soluble plastic resin JB-4, sectioning and incubating in ferritin-labelled antisera by the indirect method. The sections are then embedded in Spurr's resin for ultra-thin sectioning. Both glycoproteins are found in the following sites: (1) exine and intine wall layers; (2) pollen cytoplasm; (3) the orbicules and anther loculus; and (4) the anther cuticle. In the exine arcades and surface and in the anther loculus, the ferritin label is bound to pollenkitt. The finding that the glycoproteins are in similar sites is predictable in view of the cross-specificity of the antisera. The extent of antibody penetration of the plastic sections has been examined; labelling is confined to cut grains and absent from intact grains.
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PMID:Immunocytochemical localization of water-soluble glycoproteins, including group 1 allergen, in pollen of ryegrass, Lolium perenne, using ferritin-labelled antibody. 717 55

Studies on plasmalemmal expansion in isolated nerve growth cones identified large, clear vesicles characteristically found in growth cones as the plasmalemmal precursor. The present article examines these plasmalemmal precursor vesicles (PPVs) in greater detail in the intact cell. (a) Pulse-chase experiments with the phospholipid precursor, [3H]glycerol, followed by radioautographic analysis show that PPVs in distal neurites and growth cones are labeled prior to equilibration of the label with the plasmalemma. (b) Pulse-chase experiments with lectin-ferritin conjugates demonstrate that PPVs are not endocytotic, that they contain lectin receptors, and that, during growth, patches of lectin receptors appear on the plasmalemma covering PPV clusters. (c) Freeze-fracture studies show that this plasmalemma shares with PPVs a paucity of intramembrane particles. (d) Lectin labeling experiments and freeze-fracture analysis demonstrate, furthermore, that the plasmalemma forms a network of invaginations at the base of PPV clusters. (e) Correlative studies indicate that the refractive 'vacuoles' seen in growth cones by phase-contrast light microscopy correspond to the PPV clusters seen at the ultrastructural level. These results confirm the identity of the plasmalemmal precursor in the intact cell and demonstrate that PPV clusters form distinct, dynamic organelles specialized for plasmalemmal expansion in the growth cone.
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PMID:Sites of plasmalemmal expansion in growth cones. 849 Oct 40

Reference values for Ferritin Flex on the Dimension RxL analyzer calibrated against the 3rd International Standard for Ferritin (recombinant) and N-Latex Ferritin on the BNA II nephelometer calibrated against the 2nd International Standard for Ferritin (spleen) both from Dade Behring (Marburg, Germany) were established (77 men and 182 women). Exclusion criteria were iron deficiency or iron deficiency anemia, inflammation, liver disease, malignancy, and other hematological or chronic disorders. The reference values (5.0th-95th percentiles) were as follow: for N-Latex Ferritin - men, 12-399 microg/l; women <50 years, 11-102 microg/l and women > or =50 years, 17-219 microg/l; for Ferritin Flex - men, 14-415 microg/l; women <50 years, 11-111 microg/l and women > or =50 years, 22-224 microg/l. Both assays correlated very closely with each other (r=0.993). The linearity was acceptable down to 2 microg/l for the Ferritin Flex method, but only down to 15 microg/l for the N-Latex Ferritin assay. The mean recovery of the 3rd International Standard by N-Latex Ferritin and Ferritin Flex was comparable (approximately 80%). We conclude that the new Ferritin Flex assay, which is based on the new 3rd International Standard, should be used for ferritin measurement in the routine medical laboratories in the future.
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PMID:Reference values for a heterogeneous ferritin assay and traceability to the 3rd International Recombinant Standard for Ferritin (NIBSC code 94/572). 1205 77

In this communication, we examine the fate of iron during soft rot pathogenesis caused by Erwinia chrysanthemi on its host, Saintpaulia ionantha. The spread of soft rot caused by this enterobacterium was previously shown to depend on a functional genetic locus encoding a high-affinity iron assimilation system involving the catechol-type siderophore chrysobactin. Leaf intercellular fluid from healthy plants was analyzed with regard to the iron content and its availability for bacterial growth. It was compared to the fluid from diseased plants for the presence of strong iron ligands, using a new approach based on the iron-binding property of an ion-exchange resin. Further characterization allowed the identification of chrysobactin in diseased tissues, thus providing the first evidence for the external release of a microbial siderophore during pathogenesis. Competition for nutritional iron was also studied through a plant-bacterial cell system: iron incorporated into plant ferritin appeared to be considerably reduced in bacteria-treated suspension soybean cells. The same effect was visualized during treatment of soybean cells with axenic leaf intercellular fluid from E. chrysanthemi-inoculated saintpaulia leaves or with chrysobactin.
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PMID:Iron Deficiency Induced by Chrysobactin in Saintpaulia Leaves Inoculated with Erwinia chrysanthemi. 1223 82

To isolate bovine oocyte marker genes, we performed suppressive and subtractive hybridization between oocytes and somatic tissues (i.e., intestine, lung, muscle, and cumulus cells). The subtracted library was characterized by sequencing 185 random clone inserts, representing 146 nonredundant genes. After Blast analysis within GenBank, 64% could be identified, 21% were homologous to unannotated expressed sequence tag (EST) or genomic sequences, and 15% were novel. Of 768 clone inserts submitted for differential screening by macroarray hybridization, 83% displayed a fourfold overexpression in the oocyte. The 40 most preferential nonredundant ESTs were submitted to GenBank analysis. Several well-known oocyte-specific genes were represented, including growth differentiation factor 9, bone morphogenetic protein 15, or the zona pellucida glycoprotein genes. Other ESTs were not identified. We investigated the expression profile of several candidates in the oocyte and a panel of gonadal and somatic tissues by reverse transcription-polymerase chain reaction. B-cell translocation gene 4, cullin 1, MCF.2 transforming sequence, a locus similar to snail soma ferritin, and three unidentified genes were, indeed, preferentially expressed in the oocyte, even though most were also highly expressed in testis. The transcripts were degraded throughout preimplantation development and were not compensated for by embryonic transcription after the morula stage. These profiles suggest a role in gametogenesis, fertilization, or early embryonic development.
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PMID:Genes preferentially expressed in bovine oocytes revealed by subtractive and suppressive hybridization. 1593 Mar 21


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