Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ultrastructure of Kupffer liver cells of adult frogs collected in winter and Kupffer cells during amphibian metamorphosis when larval red cells are replaced by adult red cells were investigated. It was revealed that Kupffer cells of the animals investigated had very large size and consisted of either the whole senescent erythrocyte or many phagosomes with small electron dense granules resembling ferritin. Phagosomes are oriented among numerous vesicular and vermiform profiles of agranular endoplasmic reticulum and big Golgi complex. Comparing our morphologic evidence with data of the literature that granules of melanin are synthesized and localized in frog liver Kupffer cells, we came to conclusion that pigment cells were formed as a result of erythrophagocytosis and therefore they were the depo of catabolism products. The comparison of functions of melano-macrophage centers of fish liver and of pigment cells of amphibia liver were discussed.
 ...
PMID:[Erythrophagocytosis and pigment cells of the amphibian liver]. 139 74

Mammalian olfactory neurons possess a well-developed system of endocytic vesicles, endosomes, and lysosomes in their dendrites and perikarya. Vomeronasal neurons are similar and also contain much perikaryal agranular endoplasmic reticulum (AER). Olfactory supporting cells contain endocytic vesicles and endosomes associated closely with abundant fenestrated AER, and vesicles and numerous large dense vacuoles are present basally. Vomeronasal supporting cells have little AER, and few dense vacuoles occur in their bases. In olfactory neurons, ultrastructural tracers (0.08% horseradish peroxidase, thorium dioxide, ferritin) are endocytosed by olfactory receptor endings and transported to the cell body, where their movement is halted in lysosomes. Higher concentrations (1%) of horseradish peroxidase penetrate olfactory receptor plasma membranes and intercellular junctions. In olfactory supporting cells, endocytosed tracers pass through endosomes to accumulate in dense basal vacuoles. These observations indicate that olfactory sensory membranes are rapidly cycled and that endocytosed materials are trapped within the epithelium. It is proposed that in the olfactory epithelium, endocytosis presents redundant odorants to the enzymes of the supporting cell AER to prevent their accumulation, whereas in the vomeronasal epithelium the receptor cells carry out this activity.
 ...
PMID:Endocytic pathways in the olfactory and vomeronasal epithelia of the mouse: ultrastructure and uptake of tracers. 142 52

Brefeldin A (BFA) rapidly blocks secretion, induces disassembly of the Golgi complex and causes a redistribution of Golgi components into the endoplasmic reticulum (ER). In addition to these effects on the exocytotic pathway, BFA has been shown to induce fusion of endosomal membranes with the trans-Golgi network in some cell types. To better understand the mechanism through which BFA disrupts the exocytotic traffic, we have examined its effects on the ultrastructural organization of the Golgi complex. Within minutes of exposure to BFA, the Golgi cisternae were fragmented into a number of small tubules and vesicles, many of which had a non-clathrin coat on their cytosolic surface. In addition, a complex structure consisting of anastomosing tubules and associated vesicles appeared in the cytoplasm of cells incubated with BFA for 10 min or longer. These tubular networks were permanent, distinct structures separated from the ER cisternae. They contained cis, middle, and trans Golgi proteins as well as the lipid analogue C5-DMB-ceramide. Furthermore, secretory proteoglycans en route through the Golgi were retained in the lumen of the tubular networks. As judged by the endocytosis of cationized ferritin, endosomes do not contribute to the formation of these tubular networks. Reassembly of the Golgi complex after BFA incubation involved fragmentation and reorganization of the tubular networks as well as fusion with vesicles budded from the ER. We conclude that although in the presence of BFA the bulk of Golgi membranes are induced to fuse with the ER, as indicated by the detection of Golgi markers in this organelle, a fraction of these membranes remain in the cytoplasm organized as Golgi remnants.
 ...
PMID:Presence of Golgi remnant membranes in the cytoplasm of brefeldin A-treated cells. 142 63

The evidence that ferritin is synthesized both on free polyribosomes and on polyribosomes attached to the endoplasmic reticulum is reviewed. Evidence that some ferritin is secreted from cells after synthesis on bound polyribosomes was found to be inconclusive.
 ...
PMID:Ferritin synthesis on polyribosomes attached to the endoplasmic reticulum. 143 82

We have examined the distribution of ferritin mRNA to free and endoplasmic reticulum (ER)-bound liver polyribosomes during inflammation and iron treatment of rats. Postnuclear tissue supernatants were fractionated on a discontinuous sucrose gradient developed to separate free and bound polyribosomes. Total RNA recovered averaged 3.2 mg/g tissue, 40% of which was with ER and 30% with the free polyribosomes, about 25% being with the postribosomal/RNP fraction. Slot-blot hybridization of equal portions of RNA revealed that 12 h after injection of turpentine to induce inflammation, ferritin mRNA was concentrated on the ER-bound polyribosomes, while it was concentrated on the free polyribosomes 2 h after injection of ferric ammonium citrate. Differences were highly significant, based on multiple determinations and densitometry. Profiles of ferritin mRNA distribution on linear sucrose gradients corroborated the differential findings. Concentrations of total ferritin mRNA per gram liver doubled with iron treatment but were not significantly different 12 h after turpentine treatment. At the same time point after turpentine, ferritin protein synthesis was increased twofold, as measured by the 1 h incorporation of [14C]leucine. We conclude that a significant portion of ferritin mRNA always associates with the ER-bound polyribosomes, and that inflammation and iron differentially alter the polysomal distribution of ferritin mRNA, suggesting that two different kinds of mRNA may be involved.
 ...
PMID:Differential effects of iron and inflammation on ferritin synthesis on free and membrane-bound polyribosomes of rat liver. 144 58

Ferritin is a typical intracellular protein but small amounts are also present in serum and other biological fluids. The source and physiological significance of serum ferritin are still obscure. The presence of ferritin mRNAs on polysomes bound to endoplasmic reticulum (ER) could be relevant for the secretion of ferritin. By Northern blot analysis we found significant amounts of both L and H subunit mRNAs on rat liver membrane-bound polysomes. Immunoprecipitation of translational products of membrane-bound polysomes with anti-rat liver ferritin antibody showed that ferritin is actually synthesized on ER membranes. Analysis of RNA extracted from salt-washed rat liver microsomes demonstrated that ferritin mRNAs are translated by polysomes tightly bound to ER membranes. Following iron treatment, both the amount of H and L subunit mRNAs and ferritin synthesis increased sharply in both free and bound polysomal fractions. Translation of membrane-bound polysomes in the presence of microsomal membranes indicated that ferritin is not processed by signal sequence cleavage or glycosylation and is not translocated into ER membranes. Ferritin mRNAs found on membrane-bound polysomes are associated with ER in a specific way, however, their products do not seem to follow the classic secretory pathway and therefore the significance of the large amount of ferritin mRNAs in the bound ribosome fraction remains unclear.
 ...
PMID:Ferritin mRNAs on rat liver membrane-bound polysomes synthesize ferritin that does not translocate across membranes. 161 Aug 92

Ferritin in 119 astrocytoma cases was studied by immunocytochemical PAP and immunogold silver staining (IGSS) methods. In 57% of the cases, ferritin was found in the cytoplasm of the tumor cells. The higher the differentiation of the tumor cells, the less ferritin they contained. Contrary to the reaction of glial fibrillary acidic protein (GFAP), the positive rate of ferritin in various types and grades of astrocytomas was inversely proportional to their degree of differentiation. Electron microscopic observation in 30 cases showed ferritin in the cell sap, cytocavity network, endoplasmic reticulum, Golgi apparatus and also in lysosomes. Some of the cases had extraordinary high level of ferritin in their blood serum.
 ...
PMID:Ferritin in astrocytomas. 164 65

Electron microscopy has shown that normal mouse liver cells contain abundant cytosolic and lysosomal holoferritin but none in cisternae of the rough endoplasmic reticulum (RER). This does not mean that ferritin is absent from the secretory pathway, since the low contrast of apoferritin and ferritin containing little iron makes it difficult to resolve using standard transmission electron microscopy. We hypothesized that treatment of permeabilized cells and cell fractions with iron should make apoferritin visible by converting it to holoferritin. The iron treatment caused particles resembling the cores of holoferritin to appear in RER and in RER microsomes from mouse liver. We conclude that ferritin occurs in the endoplasmic reticulum and could be secreted, allowing the liver to be a source of serum ferritin.
 ...
PMID:The visualization of apoferritin in the secretory pathway of vertebrate liver cells. 176 77

Bromadiolone damaged the erythrocytes, resulting in a probable saturation of transferrin, a deposit of iron in the connective tissue and in a few cells of the proximal tubules of the kidneys and an increased storage of ferritin in the spleen. In the hepatocytes, mitochondria were distorted, their lipid inclusions being granular; a large depletion of glycogen may be considered a reflection of an elevated phosphorylase a ascribable to the proliferation of the smooth endoplasmic reticulum. In the kidneys, pyelonephritis may be irrelevant to the poisoning of the animals. Bromine could not be detected using microanalytical methods.
 ...
PMID:[Effects of bromadiolone on some organs and tissues (liver, kidney, spleen, blood) of coypu (Myocastor coypus)]. 190 55

Previous ultrastructural investigations have shown that the erythroblastic island is composed of erythroblasts at different stages of maturation which are intimately associated with a central macrophage. However, it is still unclear at which stage of erythroid differentiation this interaction occurs, mainly because of the lack of purified populations of normal erythroid progenitors [erythroid colony-forming units (CFU-E) and erythroid burst-forming units (BFU-E)] and early precursor cells (proerythroblasts) and because of our limited knowledge of their ultrastructural characteristics. In the present work we analyzed the ultrastructure of CFU-E enriched from normal human bone marrow by avidin-biotin immune rosetting and leukemic blasts of erythroid origin from two patients. Normal and leukemic CFU-Es were defined as glycophorin A (GPA)-negative blasts, devoid of rhopheocytosis, containing some ferritin molecules, either free in the cytoplasm or associated with theta-granules (theta-Gr) in the Golgi zone. Peroxidase activity was detected in the endoplasmic reticulum of these blasts. A preproerythroblast stage was identified, which corresponded to an intermediate phenotype with few GPA sites and rhopheocytosis. In contrast to hemoglobin synthesis, which was absolutely dependent on the presence of erythropoietin (Epo) during culture for 24 hours, ferritin molecules accumulated in the absence of Epo. Interestingly, leukemic CFU-E-like blasts were always in contact with bone marrow macrophages and adhesion between these cell types resisted mechanical dissociation. This result suggests that erythroid progenitors may be part of the erythroblastic island. The mechanisms involved in erythroblast-macrophage binding are still unknown, but the expression by macrophages and erythroid progenitors of receptors for fibronectin and thrombospondin (TSP), as well as their respective ligands in the case of macrophages, suggests that these molecules could be involved in the formation of the erythroblastic island.
 ...
PMID:Association between leukemic erythroid progenitors and bone marrow macrophages. 201 49


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>