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

Ferritin extracted from rat heart containes two species separable by gel electrophoresis. These were purified and examined for structural characteristics. As in gel electrophoresis, cardiac ferritin preparations yielded only two bands on isoelectric focusing in gels, with pI values of 4.6 and 4.8. After separation by preparative electrophoresis, the two species were found to have a different amino acid composition from each another and from liver ferritin. Similarly, peptide maps showed several components not found in liver ferritin. On dissociation and electrophoresis with sodium dodecyl sulfate, heart ferritins were found to contain subunits of the same sizes as in other rat ferritins but also some larger components. Since cardiac ferritins have apparent molecular weights greater than those of other ferritins, it is concluded they probably contain more subunits, and possibly some of larger size not present in ferritins of other tissues.
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PMID:Structural features of rat cardiac ferritins. 84 69

In adult mice suffering from a phenylhydrazine (PHZ)-induced hemolytic anemia, erythropoietic islands were observed in the liver. These islands were studied with the light and electron microscope. Within two days after the beginning of four daily injections of PHZ, erythoid elements appeared in the sinusoids and central veins. A maximum number of erythroblasts was found on day 7. Light and electron microscopic observations revealed that the erythropoietic islands consisted of centrally located macrophages(CM) with a Kupffer cell-like morphology, surrounded by erythroblasts, which were often of the same maturation stage. CM in central veins (CM-V) and in sinusoids (CM-S) were found to have a different morphology. The CM-V phagocytized less circulating red blood cells and were in contact with a smaller number of erythroblasts. Furthermore, the contact areas between erythroblasts and CM-S extended for a much longer distance than those between erythroblasts and CM-V. The progenitor cell for the CM-V is most likely a monocyte, since cells which were morphologically determined as monocytes were found to appear on the first day of the PHZ treatment and differentiated into macrophages within about 2 days. The origin of the CM-S population was less clear, but could be monocytic as well. These data are tentatively explained as a migration of a progenitor of a cellular component of the erythroid micro-environment into the liver after appropriate stimuli. In contrast to fetal liver erythropoiesis, erythroblasts in the adult liver occurred only incidentally extrasinusoidally. Furthermore, specialized membrane contacts between erythroblasts and CM or hepatocytes could not be observed in adult liver. Ferritin could not be detected on the erythroid cell membrane or located in coated vesicles. Also, no ferritin could be observed within or attached to the finger-like processes of CM. The observations suggest that the coated vesicles in erythoid elements are partly exocytotic vesicles and are not specific for ferritin transport. The morphological aspects of PHZ-induced extramedullary erythropoiesis is discussed in relation to the hemopoietic microenvironment.
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PMID:Morphological investigation on phenylhydrazine-induced erythropoiesis in the adult mouse liver. 87 Feb 1

In Glasgow, the iron stores in healthy women and in normal pregnant women on prophylactic iron supplementation have been assessed by measurement of plasma ferritin. Ferritin concentration fell progressively to a low level in late pregnancy suggesting that the average iron store was inadequate to meet the demands of pregnancy and that dietary iron supplements were therefore required. There was no evidence that iron supplementation led to excessive iron stores.
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PMID:Ferritin as an assessment of iron stores in normal pregnancy. 88 38

Peripheral blood lymphocytes from patients with all stages of untreated Hodgkin's disease and from normal healthy adults were shown to synthesize and release ferritin in vitro. Ferritin synthesis was confirmed by immunoelectrophoresis, double immunodiffusion and autoradiography. Hodgkin's disease lymphocytes synthesized ferritin 4.2 times faster and released it 2.4 times faster than did normal lymphocytes, whereas total protein synthesis was faster in normal lymphocytes. Patients with nodular sclerosis and perhaps those with absence of fever had the highest synthetic rates; however no relationship was observed between relative rates of lymphocyte ferritin synthesis and sex, age, anatomical stage and presence of splenic or hepatic involvement by tumor. Addition of iron to normal human lymphocytes produced little or no change in ferritin synthesis. These data indicate that part of the intracellular ferritin detected in peripheral blood lymphocytes from patients with Hodgkin's disease and from normal individuals resulted from de novo synthesis rather than from uptake and storage of serum ferritin, and suggests that elevated ferritin levels detected in the serum and tumor tissue of Hodgkin's disease patients originate from lymphocytes.
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PMID:Increased ferritin synthesis and release by Hodgkin's disease peripheral blood lymphocytes. 90 87

MODIFICATIONS IN RABBIT SPERM PLASMA MEMBRANES DURING EPIDIDYMAL PASSAGE AND AFTER EJACULATION WERE INVESTIGATED BY USED OF THREE LECTINS: concanavalin A (Con A); Ricinus communis I (RCA(I)); and wheat germ agglutinin (WGA). During sperm passage from caput to cauda epididymis, agglutination by WGA drastically decreased, and agglutination by RCA(I) slightly decreased, although agglutination by Con A remained approximately unchanged. After ejaculation, spermatozoa were agglutinated to a similar degree or slightly less by Con A, WGA, and RCA(I), compared to cauda epididymal spermatozoa. Ultrastructural examination of sperm lectin-binding sites with ferritin- lectin conjugates revealed differences in the densities of lectin receptors in various sperm regions, and changes in the same regions during epididymal passage and after ejaculation. Ferritin-RCA(I) showed abrupt changes in lectin site densities between acrosomal and postacrosomal regions of sperm heads. The relative amounts of ferritin-RCA(I) bound to heads of caput epididymal or ejaculated spermatozoa. Tail regions were labeled by ferritin RCA(I) almost equally on caput and cauda epididymal spermatozoa, but the middle-piece region of ejaculated spermatozoa was slightly more densely labeled than the principal-piece region, and these two regions on ejaculated spermatozoa were labeled less than on caput and cuada epididymal spermatozoa. Ferritin-WGA densely labeled the acrosomal region of caput epididymal spermatozoa, although labeling of cauda epidiymal spermatozoa was relatively sparse except in the apical area of the acrosomal region. Ejaculated spermatozoa bound only a few molecules of ferritin-WGA, even at the highest conjugate concentrations used. Caput epididymal, but not cauda epididymal or ejaculated spermatozoa, bound ferritin-WGA in the tail regions. Dramatic differences in labeling densities during epididymal passage and after ejaculation were not found with ferritin-Con A.
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PMID:Lectin-binding sites on the plasma membranes of rabbit spermatozoa. Changes in surface receptors during epididymal Maturation and after ejaculation. 90 74

Although large hemoglobin inclusions are observed in intraerythrocytic Babesia microti parasites, they are absent from parasites freed of hamster red cells by immune lysis with anti-hamster erythrocyte serum. Babesia microti has no cytostome. This parasite, therefore, does not appear to feed by phagocytosis of large boluses of hemoglobin, as does Plasmodium. To determine whether Babesia can pinocytose protein, free parasites were fed ferritin in an in vitro system. Ferritin was taken up from the entire cell surface into narrow channels within 15 min at 37 C. Only merozoites, with their pellicular complex, failed to take up the protein. By 60 min, the ferritin was highly concentrated in many channels and vesicles, which formed interconnecting stacks. The ferritin-containing channels became associated with membrane whorls of the multimembranous structure. Membrane whorls were also observed in the process of extrusion in samples incubated for longer times. These events may represent steps in the digestion and excretion of the pinocytosed protein. Empty channels formed when Babesia was fed albumin. The diaminobenzidine reaction for hemoprotein was positive for the channels in both free and intraerythrocytic babesias. The staining reaction was completely inhibited by cyanide, but not at all by aminotriazole. These results further suggest that Babesia pinocytoses hemoglobin in vivo. Plasmodium lophurae parasites freed of red cells by immune lysis are surrounded by 2 membranes and apparently can ingest ferritin only through the cytostome. Extracellular cytostomal feeding involves both membranes, as it does in vivo. Ferritin was found in food vacuoles, some of which contained hemoglobin ingested before parasite isolation, connected to or near the cytostome. In both Plasmodium and Babesia low temperature inhibited ferritin uptake.
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PMID:Feeding mechanisms in extracellular Babesia microti and Plasmodium lophurae. 93 77

Proteins are selectively sequestered by a number of cell types. However, only in oocytes is the process sufficiently aggravated and specific to be readily studied. In these cells certain serum proteins are taken up in proportions different from those found in the serum. In vitro incubations of hormonally stimulated and synchronous mosquito oocytes show that the only protein capable of initiating the transport process is the female specific yolk protein. Heterologous proteins such as IgG, bovine serum albumin, cytochrome C, and ferritin are inactive. The female specific protein is a phosphoglycolipoprotein. It is synthesized in the fat body, a liver analog in the insect, and passed into the serum before being transported into the oocytes. Preliminary kinetic analysis shows the uptake process to be specific with an apparent Km of about 10(-7) M. Glycolytic inhibitors stop protein uptake. The receptor-mediated binding steps in the transport process are most easily studied in the chicken because of the enormous amount of oocyte membrane available from a given oocyte and because up to 1 gm of protein is normally transported per day per oocyte. IgG and the hen specific phosvitin lipovitellin are two of the physiologically important proteins that are transported intact into the chicken oocytes. The uptake appears selective as shown by studies with iodinated proteins. Ferritin conjugated to IgG is shown by electron microscopy to bind to isolated plasma membranes only where coated pits have formed, whereas ferritin alone is not seen localized on any membrane surface. These very specialized regions of the membrane are similar to micropinocytotic pits but, in addition, possess on their cytoplasmic side dense ridges that form the coat. Transport involves binding to the coated pits, the pinching off of the pits, and the subsequent movement of the coated vesicles in the cytoplasm.
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PMID:Protein transport: a selective membrane mechanism. 93 39

This paper comprises a part of our study to examine whether ferritin can be used as an immunological surface marker for high resolution scanning electron microscopy. In the first part of the study individual ferritin particles in a sample of purified ferritin were demonstrated as spheres with a diameter of about 170 A by use of fixation by glutaraldehyde and thin coating by ion sputtering. In the second part of this study, ferritin particles as indicating the antigen sites of blood group A were also recognized on the erythrocytes by the same techniques as in the first part. Ferritin deposition differed in amount among the erythrocytes, but without regard to the shape of the cells. On the individual erythrocytes, heavier depositions tended to occur in the concavity of the cell. In conclusion, ferritin is useful as a surface marker in immunoscanning electron microscopy. It has the benefit, in comparison with the other markers hitherto reported, of allowing us to observe the fine features of the cell surface under immunological reaction.
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PMID:Ferritin as a surface marker for immunoscanning electron microscopy. observation of individual ferritin particles on erythrocytes. 96 9

The Fleischer ring of keratoconus was studied with the transmission electron microscope in four corneal buttons. The ring was characterized by accumulations of ferritin particles in the widened intercellular spaces and/or in the cytoplasmic vacuoles of the corneal epithelium. Both changes were prominent in basal layers in three cases; in one case, ferritin-containing vacuoles were noted in wing cell layers. Ferritin particles were also scattered over the corneal epithelium in all cases. For comparison, normal human corneas and conjunctivas were studied. Ferritin particles were scattered over the corneal epithelium and throughout the basal cells of the conjunctiva. They were not found in corneal stroma or endothelium. In conjunctival stroma, numerous ferritin particles were observed in the cytoplasm of some macrophages. Possible origin of these particles and the cause of their deposition are discussed.
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PMID:Electron microscopical study of the Fleisher ring. 96 67

1. Ferritin has been isolated from the serum of four patients with iron overload by using two methods. 2. In method A, the serum was adjusted to pH 4.8 and heated to 70 degrees C. After removal of denatured protein, ferritin was concentrated and further purified by ion-exchange chromatography and gel filtration. In most cases, only a partial purification was achieved. 3. In method B, ferritin was extracted from the serum with a column of immuno-adsorbent [anti-(human ferritin)] and released from the column with 3M-KSCN. Further purification was achieved by anion-exchange chromatography followed by the removal of remaining contaminating serum proteins by means of a second immunoadsorbent. Purifications of up to 31 000-fold were achieved, and the homogeneity of the final preparations was demonstrated by polyacrylamide-gel electrophoresis. 4. Serum ferritin purified by either method has the same elution volume as human spleen ferritin on gel filtration on Sephadex G-200. Serum ferritin has a relatively low iron content and iron/protein ratios of 0.023 and 0.067 (mug of Fe/mug of protein) were found in two pure preparations. On anion-exchange chromatography serum ferritin has a low affinity for the column when compared with various tissue ferritins. Isoelectric focusing has demonstrated the presence of a high proportion of isoferritins of relatively high pI. 5. Possible mechanisms for the release of ferritin into the circulation are briefly discussed.
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PMID:The purification and properties of ferritin from human serum. 96 66


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