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

4-Dimethylaminoazobenzene was fed to Wistar-derived, male, albino rats after hepatic siderosis had been induced by including ferric citrate in the diet. Iron-free foci of hepatocytes developed and this characteristic enabled them to be recognized macroscopically in the brown parenchyma. Five such lesions, each 1 mm or less in diameter, were studied by light and electron microscopy. The cells in the foci were larger than those surrounding the foci and had a granular and moderately basophilic cytoplasm. Ultrastructurally, the cells closely resembled normal hepatocytes. They possessed well-developed rough endoplasmic reticulum, numerous free ribosomes, peroxisomes, bile canaliculi, and cytoplasmic junctional complexes, but only small stores of glycogen were observed. Occasional ferritin-laden lysosomes persisted in some cells. These foci were regarded as hyperplastic. Possibly, they evolved into hyperplastic nodules either of the basophilic or vacuolated type. These foci should be clearly distinguished from hyperbasophilic foci that consisted of very poorly differentiated cells.
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PMID:Hyperplastic foci in precancerous rat liver: light microscopic and electron microscopic study. 9 41

Morphological studies were carried out on fibroblasts from chick embryo tendons, cells which have been used in a number of recent studies on collagen biosynthesis. The cells were relatively rich in endoplasmic reticulum and contained a well-developed Golgi complex comprised of small vesicles, stacked membranes, and large vacuoles. Techniques were then devised for preparing cell fragments which were penetrated by ferritin-antibody conjuates but which retained the essential morphological features of the cells. Finally, the new procedures were employed to develop further information as to how collagen is synthesized. As reported elsewhere, preliminary studies with ferritin-labeled antibodies showed that prolyl hydroxylase was found in the endoplasmic reticulum of freshly isolated fibroblasts and that procollagen is found in both the cisternae of the endoplasmic reticulum and the large Golgi vacuoles. In the experiments described here, the cells were manipulated so that amino acids continued to be incorporated into polypeptide chains but assembly of the molecule was not completed because hydroxylation of prolyl and lysyl residues was prevented. The results indicated that these manipulations produced no change in the distribution of prolyl hydroxylase. Examination of the cells with ferritin conjugated to antibodies which reacted with protocollagen, the unhydroxylated form of procollagen, demonstrated that protocollagen was retained in the cisternae of the endoplasmic reticulum during inhibition of the prolyl and lysyl hydroxylases. Assays for prolyl hydroxylase with an immunologic technique demonstrated that although the enzyme is found within the endoplasmic reticulum, it is not secreted along with procollagen. The observations provided further evidence for a special role for prolyl hydroxylase in the control of collagen biosynthesis.
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PMID:Further characterization of embryonic tendon fibroblasts and the use of immunoferritin techniques to study collagen biosynthesis. 16 30

The bone marrow macrophages of patients with homozygous beta-thalassaemia were frequently situated adjacent to collagen fibres and sometimes formed intrasinusoidal cytoplasmic protrusions. They also appeared to phagocytose processes of erythroblast cytoplasm (at times containing precipitated alpha-chains) which projected into them from neighbouring erythroblasts. The cytoplasm of the macrophages included large numbers of heavily-iron-loaded secondary lysosomes of various sizes and shapes in addition to phagocytosed erythroblasts, erythrocytes and extruded erythroblast nuclei. Numerous ferritin molecules were found in the cytoplasmic matrix but there were hardly any in the mitochondria, endoplasmic reticulum or golgi saccules. A small number of ferritin molecules were present within the nucleus. Electron microscope autoradiographs of marrow fragments which had been incubated with [3H]leucine for 1 h revealed the presence of newly-synthesized protein molecules in all types of secondary lysosomes. Light microscope autoradiographs showed the [3H]thymidine labelling index of the bone marrow macrophages was less than 1% and suggested that only a very small proportion of these cells were actively preparing for division.
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PMID:Some features of bone marrow macrophages in patients with homozygous beta-thalassaemia. 20 37

The mechanism of tumor localization of gallium-67 (67Ga) is not known with certainty, although much information has been derived regarding the biodistribution and subcellular fate of 67Ga in a variety of tumors and other tissues from experimental animals. After intravenous administration, 67Ga is bound to transferrin in the blood, and distributed to liver, lacrimal glands, salivary glands, and soft tissue tumors. Within the cells of the liver and tumors, gallium is found in lysosomes, and rough endoplasmic reticulum. Within these organelles, 67Ga is bound to a variety of macromolecules, including transferrin, ferritin, and a 45,000 molecular weight glycoprotein. Recent studies of tumor cells growing in tissue culture suggest an important role for transferrin in 67Ga tumor uptake. This uptake is mediated by a transferrin specific cellular receptor.
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PMID:Mechanisms of localization of gallium-67 in tumors. 21 49

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

The distribution of glutathione-insulin transhydrogenase (glutathione: protein-disulphide oxidoreductase, EC 1.8.4.2) in isolated rat hepatocytes that had been first treated with rabbit antiserum against purified rat liver transhydrogenase and then with ferritin-conjugated goat anti-rabbit gamma-globulin was examined by electron microscopy. In cells with intact plasma membrane, the immunoferritin labeling of glutathione-insulin transhydrogenase was observed on a few external microvillous projections at the outside of the cell. In cells with breaks in the plasma membrane, the immunoferritin labeling appeared extensively on smooth vesicles just inside the plasma membrane and on smooth endoplasmic reticulum extending to and including the outer nuclear membrane, in addition to the external microvillous projections. There was some immunoferritin labeling on rough endoplasmic reticulum and on the inner surface of the plasma membrane. The mitochondria and the outer surface of the plasma membrane of the cell did not show the ferritin labeling. Control parallel samples in which the antiserum was substituted with normal (i.e. non-immune) serum or with neutralized antiserum (prepared by absorption with the transhydrogenase) showed little or no immunoferritin labeling. These results are consistent with the idea that gluthalione-insulin transhydrogenase probably synthesized in the endoplasmic reticulum and that the transhydrogenase accessible to cell surface (or found in the isolated plasma membrane preparations) probably represents a functional continuity between the endoplasmic reticulum and the plasma membrane.
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PMID:Insulin degradation. XXIII. Distribution of glutathione-insulin transhydrogenase in isolated rat hepatocytes as studied by immuno-ferritin and electron microscopy. 33 61

The distribution of cytochrome b5 reductase in rat liver microsomes purified by density gradient centrifugation was studied using anti-cytochrome b5 reductase/anti-ferritin hybrid antibodies labeled with ferritin. Electron micrographs show that the outer surface and the polar cap of tangential sections of essentially all vesicles derived from endoplasmic reticulum are specifically marked with a few ferritin grains which are not localized in large patches but arranged randomly. This finding was correlated with morphometrical and biochemical measurements. The results, supporting our earlier investigations, suggest that cytochrome b5 reductase may be clustered at the most in very small assemblies consisting of a few molecules which, in turn, are statistically uniformly distributed over the total membrane system.
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PMID:Immunohistological studies on the distribution of cytochrome b3 reductase in rat liver microsomes. 34 93

Nonspecific binding of ferritin to chromatin and the cytoplasmic aspect of the nuclear envelope was observed when nonantigenic, serum-washed hepatocyte nuclei were incubated in ferritin-antibody conjugates. This labeling was duplicated when nuclei from a wide range of species and cell types were exposed to unconjugated ferritin. Unconjugated ferritin binding to nuclei did not depend on a subpopulation of denatured molecules or on the ferritin purification procedure. Binding occurred equally on unfixed and formaldehyde-fixed nuclei, but no ferritin bound to glutaraldehyde-fixed nuclei. Inconjugated ferritin also bound to the cytoplasmic aspects of the rough endoplasmic reticulum and the plasma membrane. The tracer did not bind to lysosomes, mitochondria, Golgi vesicles, the extracellular surface of plasma membranes, or the intracisternal surfaces of ruptured nuclear envelopes. The addition of 0.4 M KCl or 0.7 M NaCl to ferritin solutions and washing media at neutral pH reduced the binding of conjugated and unconjugated ferritin to nuclei to about 3% of that seen in 0.10 M phosphate buffer alone. The added salts caused little extraction of nuclear contents from formaldehyde-fixed nuclei. The use of one of these salts in ferritin conjugates should considerably improve the specificity of intracellular labeling.
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PMID:Intracellular labeling with ferritin conjugates. A specificity problem due to the affinity of unconjugated ferritin for selected intracellular sites. 46 31

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

A combined electron microscopic and cytochemical study of the thrombocytes of the mature chicken has demonstrated the existence of two membrane systems, the surface connected system (SCS) and the dense tubular system (DTS). The SCS consists of light tubules and vacuoles which are in continuity with the plasmalemma. A ruthenium red-positive reaction product was observed on the inner surface of this membrane system. Ferritin particles were present in the tubules and the vacuoles of the SCS after the thrombocytes had been incubated in vitro with ferritin. The DTS consisted of the nuclear envelope, the rough-surfaced endoplasmic reticulum, dense tubules and concentric double membrane structures, all of which give a peroxidase-positive reaction. Although actual continuity between the DTS and the SCS of thrombocytes was not observed in this study, close approximation between the two systems was observed at many points. These results are discussed in relation to those from comparable studies of human platelets.
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PMID:Electron microscopic and cytochemical observations on the membrane systems of the chicken thrombocyte. 63 7


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