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

The transport of immunoglobulin and ferritin across the intestinal mucosa of adult rats provides an excellent model for transcellular protein transport study. Intestinal uptake and transcellular transport have been extensively studied in the neonatal rat, but not to such an extent in the adult rat. The transport of 125I labelled bovine immunoglobulin G and ferritin was studied in 100 days old rats using intestinally administered proteins. Antigen was estimated in the tissues by reacting extracts against specific immune antiserum prepared in rats, and visualization studies were carried out by fluorescence microscopy and direct deposition autoradiography at electron microscopic level. From these studies, it can be seen that these proteins are taken up by the intestinal cells and transported, antigenically intact, across the barriers to the body organs.
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PMID:Intestinal uptake and transport of proteins in the adult rat. 3 90

A scanning transmission electron microscope (STEM) equipped with a field emission gun has been employed for the examination of biological macromolecules at high resolution. The quality of micrographs obtained with the STEM is dependent upon the quality of the substrate used to support biological objects because the image contrast in dark field is proportional to the mass density of the specimen. In order to reduce deleterious effects of the substrates on the image quality, we have developed a method of fabricating substrates consisting of very thin, very clean carbon films supported on very clean fenestrated plastic films. These films are approximately 15 A thick. Well-known biological macromolecules such as glutamine synthetase and tobacco mosaic virus (both stained) and low-density lipoprotein and ferritin (both unstained were placed on these substrates and examined with the STEM by using various modes of contrast. The micrographs obtained by using the dark field mode of contrast employing an annular detector were free from phase contrast, as expected. Using this contrast mode, we have been able to directly observe (in-focus) 2.5- to 4.4-A lattice spacings in the ferritin core. The effect of electron radiation damage on the helical structure of tobacco mosaic virus was also examined. Micrographs as well as corresponding optical diffraction patterns obtained with moderately low doses showed very clear helical structure from both sides of the virus. In addition, the (11.5 A)(-1) layer lines indicated the effective resolution attained on these particles.
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PMID:Dark field imaging of biological macromolecules with the scanning transmission electron microscope. 3 88

Ionic iron at physiological pH hydrolyzes into insoluble aggregates, which disperse on slight acidification. Uncontrolled ionic iron promotes autoxidation, which crosslinks biomolecules and produces destructive activated oxygen. Defenses against autoxidative crosslinking include: 1. ferritin, the macromolecular scavenger of iron; 2. metabolic turnover, which prevents irreversible crosslinking through early catabolic degradation and replacement; and 3. enzymatic deactivation of oxygen. I am proposing that the anticrosslinking defenses are defeated by transient actions of metabolic perturbations, toxicants, oxidants and "foreign bodies", which cause oxidative crosslinking of proteins and lipids into irreversible tissue imprint: indigestible bodies containing porous limited-access spaces (LASs). The pores exclude the macromolecular ferritin and the digestive and antiautoxidation enzymes but admit ionic iron which, sheltered from ferritin, accumulates into decontrolled-iron pathogen (DIP). DIP utilizes the energy of ambient pH fluctuations to erupt from the LAS, swamp the available ferritin, poison the surroundings, catalyze autoxidation and crosslink cell components into additional LAS carriers. With time and sufficient promotion by pH fluctuations or metal-complexing agents, DIP and LAS expand. DIP injures through heavy-metal inhibition of life processes and catalysis of autoxidation. Typically, carcinogenic initiators are protein denaturants, cell poisons, "foreign bodies" and autoxidation catalysts. These are DIP-initiating properties, and DIP may be a preneoplastic stage of carcinogenesis. A DIP-model interpretation is given for the growth of asbestos bodies. DIP is an inorganic parasite. It may envelope and attack phagocytized particles.
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PMID:Biological autoxidation. I. Decontrolled iron: an ultimate carcinogen and toxicant: an hypothesis. 3 81

Neuronal antigens can be demonstrated histologically by numerous direct and indirect immunocytochemical techniques in which a specific antibody is identified by a marker compound such as fluorescein isothiocyanate, ferritin, or horseradish peroxidase. One of the more sensitive methods for the light and electron microscopic localizations of antigens in sections of tissue is the peroxidase-antiperoxidase (PAP) technique. The experimental procedures and the results obtained using this technique for the localization of the catecholamine synthesizing enzyme, tyrosine hydroxylase, are described. The cellular and ultrastructural localization of the enzyme is demonstrated in perikarya, processes, and terminals of catecholaminergic neurons in rat brain. The immunocytochemical localization of tyrosine hydroxylase is compared to the localization of two peptides, substance P and [Met5]-enkephalin, in the A2 region of the medulla. These studies suggest that a synaptic interaction exists between the catecholaminergic neurons and neurons showing positive immunoreactivity for the peptides. The limitations of the PAP immunocytochemical technique are also discussed in relation to the immunocytochemical localization of tyrosine hydroxylase and other antigens.
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PMID:Immunocytochemical localization of neuronal antigens: tyrosine hydroxylase, substance P, [Met5]-enkephalin. 3 6

Rat liver mitochondria and rat liver mitoplasts mobilize iron from ferritin by a mechanism which depends on a respiratory substrate (preferentially succinate), a small molecular weight electron mediator (FMN, phenazine methosulphate or methylene blue) and (near) anaerobic conditions. The release process under optimized conditions (approx. 50 mumol/1 FMN, 1 mmol/l succinate, 0.35 mmol/1 Fe(III) (as ferritin iron), 37 degrees C and pH 7.40) amounts to 0.9--1.2 nmol iron/mg protein per min. The results suggest that ferritin might function as an intermediate in the cytosolic transport of iron to the mitochondria.
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PMID:Studies on the mobilization of iron from ferritin by isolated rat liver mitochondria. 4 94

Diaphragmed fenestrae (DF) are sites of increased vascular permeability. The anionic charge distribution at the luminal aspect of the DF of the endothelium of the bone marrow vessels has been studied after aldehyde fixation by means of colloidal iron (CI), native ferritin (NF), and polycationic ferritin (PCF). At pH 1.8, these cationic agents are bound by the nonmodified luminal endothelial cell surface but not at the sites of the DF. PCF was used over a pH range of 1.8--7.2 (CI is unstable at higher pH levels, whereas NF which has a pI of 4.5 is anionic above this point). PCF shows increased binding at the DF from pH 3.5 upwards. PCF binding at pH 1.8 at the nonmodified luminal cell surface is significantly diminished by neuraminidase treatment which, however, does not perceptibly reduce PCF binding at the higher pH levels. It is concluded that there are exposed sialic acid groups at the lunimal cell surface which are absent or significantly fewer at the sites of the DF, whereas other anionic materials possibly with a pKa higher than that of sialic acid (pKa 2.6) are present both at the DF and at the nonmodified endothelial cell surface.
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PMID:Changes in the random distribution of sialic acid at the surface of the myeloid sinusoidal endothelium resulting from the presence of diaphragmed fenestrae. 4 43

Oesophageal epithelial cells from biopsies from normal patients showed the presence of randomly distributed anionic groups, mostly sialic acid on the cell membrane in fixed material shown by cationized ferritin. When biopsies were pulse labelled, patching occurred in all three cell layers. Patching was energy dependent and did not occur at 4 degrees C. Pulse labelled material incubated on an unlabelled medium showed progressive loss of cationized ferritin from the cell membrane. This was mostly into the medium, although some was internalized in membrane profiles. A second pulse of cationized ferritin produced further patching suggesting regeneration of cell membrane. Superficial cells were leaky, but their organelles were not.
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PMID:The distribution and mobility of surface anionic groups of normal human oesophageal epithelium following interaction with cationized verritin. 4 21

Major surface antigens of Bactmbrane complex by gentle methods, purified, and characterized immunochemically. A lipopolysaccharide (LPS) was found to be chemically distinct from the LPS of facultative gram-negative bacteria in that it lacked two core sugars, 2-keto-3-deoxyoctonate and heptose, as well as beta-hydroxymyristic acid, the predominant fatty acid in the lipid A moiety. The LPS was further atypical in that it had a very low level of biologic activity. A capsular polysaccharide was demonstrated morphologically by electron microscopy with ruthenium red staining and a ferritin-labeled antibody technique. This antigen was shown to be subspecies-specific by indirect immunofluorescence. Antibody to the capsular polysaccharide was measured by an enzyme-linked immunospecific assay. The presence of a relatively impotent LPS and a surface capsular antigen may partly explain the rarity of bacteremia and septic shock due to B. melaninogenicus subspecies asaccharolyticus and the common association of this organism with abscess formation.
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PMID:Immunochemical characterization of surface antigens of Bacteroides melaninogenicus. 4 22

Thoracic duct and spleen cells of normal (unimmunized) adult rats were fractionated according to size by 1 times G velocity sedimentation. Fractions were tested for their ability to restore the adoptive antibody response of irradiated hosts to horse spleen ferritin. A constant source of T cells (small numbers of unfractionated thoracic duct cells) was added to each fraction in order to monitor the B cell activity of the latter. Although large and small cell fractions of the spleen showed restorative activity, only the small cell fractions of the thoracic duct lymph showed activity. The turnover rate of the spleen cell fractions was determined by treating donors with high specific-activity 3H-thymidine for 48 hr before splenectomy. Rapidly dividing cells are preferentially killed by this treatment. The results suggest that a considerable proportion of large, intermediate, and small virgin B cells turn over within 48 hr. The cell surface of the various spleen cell fractions was examined for the presence of immunoglobulin (Ig) and a receptor for complement. The percentage of Ig-bearing cells in the large cell fractions was similar to the percentage of cells bearing IgM and a receptor for complement. However, the majority of Ig-bearing cells in the small cell fractions did not show the latter two surface markers. Experiments with the fluorescence-activated cell sorter showed that the large functionally active B cells bore surface IgM. The experimental findings suggest that there are subpopulations of virgin B cells in the spleen of the adult rat which differ with respect to size, migration pattern, turnover rate, and cell surface characteristics. The relationship of these cells to one another is discussed in the framework of an antigen-independent model of B cell maturation in the rat.
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PMID:Maturation of B lymphocytes in the rat. II. Subpopulations of virgin B lymphocytes in the spleen and thoracic duct lymph. 4 56

Prostaglandin and prostaglandin receptors were localized on unwashed ejaculate rabbit sperm utilizing ferritin conjugated antibody to prostaglandin. Reaction was obtained over the acrosomal portion of the plasma membrane, with a greater aggregation over the apex of the head. The remainder of the head plasmalemma and flagellum showed no deposits of of reaction product. The reaction did not occur if the sperm were washed prior to incubation with the labelled antisera. However enhanced binding of ferritin was demonstrated if washed sperm were pre-incubated in PGE1. No reaction was seen in similar studies with human sperm.
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PMID:Localization of prostaglandin on the plasmalemma of rabbit sperm. 4 69


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