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

A 4-hour in vivo test for iron chelator activity in the rat is described. The amount of radioiron in the gut and urine that results from chelator-induced excretion of previously injected radioiron labelled ferritin is measured. Hepatocyte localization and desferrioxamine-induced radioiron mobilization from in vitro tagged homologous ferritin is shown to be similar to that from in vivo tagged ferritin. Non-homologous ferritin preparations labelled in vitro proved unsatisfactory. Radioiron mobilization by chelator occurred regardless of the iron status of the animal. Employing this measurement, the effectiveness of three iron chelators, pyridoxal isonicotinoyl hydrazone, the dimethyl ester of ethylene diamine-N, N'-dis (3-hydroxyphenyl acetic acid), and the dimethyl ester N, N'-di (3-hydroxybenzyl) ethylene-1, ethylene-1, 2-diamine-N, N'-diacetic acid, given orally was determined. All three chelators, when given in comparable dosage, induced iron excretion similar in amount to that observed with parenteral desferrioxamine. In addition, pyridoxal isonicotinoyl hydrazone administered in the diet over a period of 4 weeks was shown to reduce hepatic and splenic iron of normal animals by about one third, providing further validation of this method of evaluating chelator effectiveness.
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PMID:Effectiveness of oral iron chelators assayed in the rat. 382 55

Two protein antigens, horseradish peroxidase (HRP) and ferritin, have been administered to the digestive tract of carp. Electron-microscopical observations reveal considerable absorption of both antigens in the second segment of the gut (from 70 to 95% of the total length) and also, although to a lesser extent, in the first segment (from 0 to 70% of the total length). Even when administered physiologically with food, a large amount of ferritin is absorbed by enterocytes in the second gut segment. HRP and ferritin are processed by enterocytes in different ways. HRP seems to adhere to the apical cell membrane, probably by binding to receptors, and is transported in vesicles to branched endings of lamellar infoldings of the lateral and basal cell membrane. Consequently, most of the HRP is released in the intercellular space where it contacts intra-epithelial lymphoid cells. Only small amounts of HRP become localized in secondary lysosomes of enterocytes. Ferritin does not bind to the apical cell membrane; after uptake by pinocytosis, it is present in small vesicles or vacuoles that appear to fuse with lysosome-like-bodies. In the second segment, intact ferritin ends up in the large supranuclear vacuoles (after 8 h), where it is digested slowly. Although no ferritin is found in the intercellular space, ferritin-containing macrophages are present between the epithelial cells, in the lamina propria and also to a small extent in the spleen. The transport of antigens from the intestinal lumen, through enterocytes, to intra-epithelial lymphoid cells or macrophages may have immunological implications, such as induction of a local immune response and prospectives for oral vaccination.
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PMID:Uptake and transport of intact macromolecules in the intestinal epithelium of carp (Cyprinus carpio L.) and the possible immunological implications. 398 79

In adult germfree C(3)H mice immunized with horse spleen ferritin, either subcutaneously or intraperitoneally, plasma cells containing specific antibodies were found in lymph nodes and spleen and, in smaller numbers, also in the lamina propria of the intestine. In extraintestinal sites, these antiferritin-containing plasma cells were mainly of the IgM class after a single stimulation, and of the IgG(1) class after repeated stimulation. In the intestine, all the anti-ferritin-containing cells appeared to be of the IgA class. Circulating antibodies, after repeated stimulation, were for the major part IgG(1) and IgG(2). In germfree mice given ferritin in their drinking water, antiferritin-containing cells were abundant in the intestinal mucosa, much less numerous in the mesenteric lymph nodes, and extremely scarce in other lymphoid tissues. All these cells, whatever their location, appeared to belong exclusively to the IgA class. Similarly, all the circulating antibody in these animals was found to be IgA. These findings illustrate the role of the gut as a site of antibody synthesis, as well as its selective commitment to the production of antibodies of the IgA class.
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PMID:Antibodies of the IgA type in intestinal plasma cells of germfree mice after oral or parenteral immunization with ferritin. 418 43

Feeding of baboons with crocidolite showed small numbers of asbestos needles 0.5-1 mum in ashed tissue of the gut wall, which probably came from iron-containing macrophages. It is suggested that pleural plaques and hyaline nodules in the peritoneum represent a hypersensitivity reaction to ferritin protein coating on asbestos fibers. In South Africa only a few peritoneal mesotheliomas come from the asbestos areas, and the incidence of gastrointestinal carcinomas is no greater than normal. Intrapleural and intraperitoneal injection produces unrealistic situations. Calcium salts are deposited on asbestos cement pipes from hard water and organic material from soft water. It is difficult to envisage asbestos contamination of the water so reticulated.
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PMID:The ingestion of asbestos fibers. 447 Sep 36

Germfree BALB/c mice have been treated from birth with intraperitoneal injections of purified goat antibodies to mouse IgM. The treated mice, and controls which had received an equivalent amount of goat gamma-globulin, were sacrificed at 8 or 13 wk of age. Compared to controls, mice given anti-micro (a) had very few germinal centers in spleen and lymph node, (b) had decreased numbers of mature plasma cells synthesizing IgM and IgG1 in spleen, and virtual absence of IgA-synthesizing plasma cells in the gut, (c) had greatly diminished numbers of B lymphocytes bearing membrane-bound immunoglobulins of the IgM, IgG1, IgG2, and IgA classes in spleen, (d) had reduced synthesis of IgM, IgG2, and IgA by in vitro spleen cultures, and (e) had significant decreases in serum levels of IgM, IgG1, IgG2, and IgA. The treated animals failed to make antibodies to ferritin after hyperimmunization, and lacked natural antibodies to sheep erythrocytes. These results indicate that cells ultimately committed to synthesis of IgG1, IgG2, and IgA immunoglobulins are derived from cells which have expressed IgM determinants at an earlier stage of differentiation. They are consistent with a proposed two-stage model for plasma cell differentiation. The first stage is antigen independent, involves sequential activation of Cmicro, Cgamma, and Calpha genes by progeny of a single stem cell, and results in the formation of B lymphocytes bearing membrane-bound recognition antibodies of each class. The second, antigen-dependent, stage results in formation of mature plasmacytes and memory cells.
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PMID:Suppression of immunoglobulin class synthesis in mice. I. Effects of treatment with antibody to -chain. 455 Dec 16

Within the epithelium that overlies the dome regions of Peyer's patches, exist specialized surface epithelial cells (M) which function to take up macromolecules from the gut lumen. These cells may be of great importance in processing antigenic material in the gut. The predominant lymphoid structures of the small intestine are isolated lymphoid follicles, by virtue of their frequency. These follicles are difficult to study because they are not grossly visible. In the present study, three guinea pigs drank India ink mixed into their water for 1, 3, and 5 months. Two hours prior to sacrifice, animals were given an intraintestinal injection of ferritin or India ink. Using a hand lens, the Peyer's patches and isolated follicles were clearly identified among the villi of the intestine. Light microscopy revealed ink in the surface epithelium covering the isolated follicles and within the substance of the follicles. Transmission electron microscopy demonstrated M cells over isolated follicles and Peyer's patches. These cells had lighter staining cytoplasm, while the mitochrondria stained darker with prominent cristae, and the microvilli were shorter. Therefore, M cells do exist within isolated follicles and structurally appear the same as those found in Peyer's patches. This implicates the isolated follicles in the overall antigen processing role of gut-associated lymphoid tissues. The present method facilitates identification of isolated lymphoid follicles which will allow functional studies to be performed on these structures.
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PMID:Demonstration of M cells in the specialized follicle-associated epithelium overlying isolated lymphoid follicles in the gut. 620 May 55

Three insect tissues have particular roles as filters to maintain the fluid composition of the hemolymph. Water and ions enter and leave through the midgut. The pericardial cells filter circulating hemolymph. Malpighian tubules, often with the rectum, allow resorption from a hemolymph filtrate that passes to the hindgut. All three tissues have plasma membrane infolds making a reticulum on their hemolymph surfaces, and all three have RER leading to SER extensions into their reticula. SER is a catch-all description for membranes lacking ribosomes in the pre-Golgi complex set of compartments of the vacuolar system. Some kinds of SER are well known for their role in housing enzymes for steroid metabolism and for detoxification. The SER ramifying within the plasma membrane reticular systems of tissues concerned with hemolymph filtration contains ferritin, suggesting that this SER has another, different function. In contrast to vertebrate cells, where ferritin is confined to the cytosol and lysosomes, we have found that in Calpodes and perhaps in most insects, ferritin occurs in the vacuolar system and not in the cytosol. Ferritin occurs naturally in the RER and SER of cells at the hind end of the midgut, in pericardial cells and in the yellow region of the Malpighian tubules. Additional ferritin is induced by loading the gut or hemolymph with iron. Overloading with iron causes ferritin secretion to the gut lumen. We propose that the SER in these cells functions in iron homeostasis by holding ferritin for loading and unloading as it moves to and from the reticulum at the cell surface where it can be maximally exposed to extracellular fluid flow.
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PMID:The induction and distribution of an insect ferritin--a new function for the endoplasmic reticulum. 651 41

Organized lymphoid tissue in the rat colon exists as clusters (colonic lymphoid patches) of intramucosal and submucosal follicles in the proximal, mid, and distal colon, interspersed by solitary follicles. The follicular lymphoid cells of colonic lymphoid patches are separated from the gut lumen by a highly specialized lymphoepithelium which lacks mature goblet cells. Cells of this epithelium are of two types: those characterized by an electron-dense cytoplasm, large numbers of apical vesicles and lysosomes, and prolonged extensions of the apical cytoplasm forming thin partitions between the gut lumen and underlying intercellular spaces; and cells with a less electron-dense cytoplasm, distorted mitochondria, and little endoplasmic reticulum. Both cell types bear normal microvilli and have numerous lateral membrane processes which penetrate large intercellular spaces. A ferritin-India ink label infused into the colonic lumen was preferentially adsorbed onto the surface of this follicle-associated epithelium. Indigenous colonic bacteria were observed penetrating the superficial cytoplasm of the electron-dense cells where they were enclosed in lysosomes and digested. An antigen-sampling role is proposed for the colonic lymphoid patch epithelium.
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PMID:Morphological study of antigen-sampling structures in the rat large intestine. 669 72

A multicompartment model describing the physiological processes of intestinal iron absorption has been developed. The model accounts for uptake by the intestinal mucosa of iron in the lumen, followed by either iron incorporation into a mucosal storage pool (presumably ferritin) or direct iron transfer to the plasma. To enable analysis of iron absorption from noninvasive measurements, plasma iron kinetics were also analyzed. The model was validated in studies of three beagle dogs given oral 59Fe-citrate and intravenous 55Fe-transferrin simultaneously. Model parameters were estimated from the best (least-squares) fit of the model outputs to the tracer iron activity in venous blood samples and in the whole body. The parameter values show that both incorporation of iron into the mucosal storage pool and transfer of iron from the mucosa to the plasma occur at rates approximately 100 times greater than mucosal uptake of iron from the gut lumen. Further, release of iron from mucosal storage, while measurable, occurs at a slow rate. The study demonstrates the practicality of this noninvasive approach for the simultaneous study of iron absorption and plasma iron kinetics.
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PMID:A model of intestinal iron absorption and plasma iron kinetics: optimal parameter estimates for normal dogs. 669 1

A mechanism is proposed by which apotransferrin is secreted from mucosal cells, loaded with iron in the intestinal lumen, and then the intact complex is taken into the cell. Within the cell, iron is released and transferred to the blood stream, whereas iron-free transferrin returns to the brush border to be recycled. We have investigated this hypothesis by measuring intestinal absorption of radioiron and 125I-labeled plasma transferrin using tied-off gut segments in normal and iron-deficient rats. There was no absorption of diferric transferrin from the ileum, but high absorption from the duodenum and jejunum segments. Jejunal absorption occurred as a function of the dose offered and showed saturation kinetics. In normal animals, 4 micrograms of the 50 micrograms of transferrin iron was absorbed over 1 hr. In iron-deficient animals, mean values as high as 13 micrograms were observed. Radioiron content of the jejunal mucosa bore a linear relationship to the dose administered and was inversely proportional to the amount of iron entering the plasma. Recycling of transferrin was indicated by the presence of labeled apotransferrin in the lumen, first observed between 15 and 60 min after the injection of diferric transferrin. A high resistance of diferric and apotransferrin to proteolytic degradation within the gut lumen was demonstrated. Comparative studies with lactoferrin and ferritin disclosed poor availability of their iron for absorption. The small amount that was absorbed did not relate to the iron status of the recipient animal. These studies support the role of mucosal transferrin as a shuttle protein for iron absorption.
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PMID:The significance of transferrin for intestinal iron absorption. 682 98


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