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

The fracture-permeation method was applied in order to assess changes in nuclear compactness associated with different metabolic conditions. Rat ventral prostate was used as a model because transcription in the secretory cells of this organ is highly dependent on androgens. Two major problems that raise important questions concerning the validity of the method were encountered: (1) poorly preserved cells are massively permeated by ferritin and (2) within the same experimental group the permeation pattern was quite variable. In order to objectify such variability, the percentage of permeated nuclear cross-fractures was quantified. Different permeation patterns could be detected in nuclei from normal, castrated, and testosterone-treated prostatic cells, possibly reflecting changes in chromatin compactness.
J Ultrastruct Mol Struct Res 1988 Oct
PMID:Nuclear compactness as assessed by ferritin permeation: a critical evaluation of the method. 324 38

Based upon the observation that the multivalent ligand cationized ferritin (CF) alters the cell surface distribution of anionic domains and significantly enhances the adsorptive endocytosis of 125I-labeled human serum albumin, these studies were undertaken to probe the influence of CF on receptor-mediated low-density lipoprotein (LDL) endocytosis and the nature of the mechanisms involved. A brief 1-min exposure of normal receptor upregulated fibroblasts to CF (0.2 mg/ml) resulted in a significant decrease (P less than 0.001) in the subsequent internalization and degradation of 125I-LDL. Studies with receptor downregulated normal fibroblasts indicated that CF pretreatment did not measurably influence 125I-LDL internalization and only slightly inhibited its degradation (P less than 0.05). In contrast, CF pretreatment of FH receptor-negative mutant skin fibroblasts resulted in a modest but significant increase in both 125I-LDL internalization and degradation (P less than 0.05). Scatchard analyses of binding data indicated that CF-pretreated upregulated normal fibroblasts exhibit a single class of LDL binding sites with an affinity, Kd = 24.7 +/- 4.1 nM, almost 10-fold lower than the affinity of binding sites in untreated controls, Kd = 3.2 +/- 0.06 nM. Increasing either the concentration or the duration of CF exposure resulted in additional inhibition of LDL internalization and degradation associated primarily with a decrease in the number of LDL binding sites without any further change in binding affinity. Total cellular LDL receptor-mediated binding, measured using an octylglucoside solubilization-filtration assay, confirmed the CF-induced decrease in high-affinity LDL binding. Pulse-chase experiments showed that CF had no direct influence on LDL degradation, nor did it influence targeting of the LDL-containing endosome toward exocytosis. Further, restoration of LDL receptor function to control values after CF pretreatment required de novo protein synthesis. The normal feedback inhibition of HMG-CoA reductase activity was nearly abolished by CF pretreatment. Additionally, CF pretreatment was found to induce not only a redistribution of surface anionic sites, but also a very rapid internalization of surface components labeled with 4,4'-[3H]diisothiocyano-1,2..diphenylethane-2,2'-disulfonic acid. It is concluded that the inhibitory influence of CF on LDL endocytosis is mediated via a decrease in the affinity and in the number of functional LDL receptors.
Exp Mol Pathol 1988 Jun
PMID:Low-density lipoprotein endocytosis. I. Influence of the multivalent ligand cationized ferritin on normal and receptor-negative human fibroblasts. 337 59

Interactions of the basic multivalent ligand cationized ferritin (CF) with cultured cells markedly alter their endocytic function. In this study, the influence of CF treatment on the binding, internalization, and degradation of chemically modified (acetylated) low-density lipoproteins (Ac-LDL) was examined in aortic smooth muscle cells (SMC); and in normal and FH mutant LDL receptor-negative human skin fibroblasts, which lack the Ac-LDL (scavenger) receptor; and in vascular endothelial cells, which normally express the receptor. Although CF treatment of all three cell types at 37 degrees C resulted in the induction of Pronasesensitive, high-capacity, high-affinity binding (Kd = 12.0 +/- 2.0 nM at 4 degrees C) of labeled Ac-LDL, which at 37 degrees C was accompanied by significant internalization and degradation, these processes were not receptor-mediated. CF-induced high-affinity binding was inhibited by unlabeled Ac-LDL, fucoidan, carrageenan, and dextran sulfate but was unaffected by native LDL and albumin and only partially inhibited by acetylated albumin. However, analysis of membrane preparations of the cells for "scavenger" receptor protein by solid-phase filtration assay and Western blotting identified the receptor in endothelial cells and in granuloma (positive control) macrophages, but not in either CF-treated or untreated SMC. In addition, studies with both glutaraldehyde-fixed cells and CF bound to culture dishes indicated that Ac-LDL avidly binds to CF. Further, ultrastructural studies using colloidal gold-conjugated Ac-LDL showed Ac-LDL preferentially binding to CF aggregates on the cell surface. Thus, these studies indicate that treatment of cells with CF induces an endocytic process which, although remarkably similar to the scavenger pathway, is mediated by Ac-LDL binding to membrane-associated CF. These observations have implications in terms of mechanisms that might regulate the endocytosis of modified low-density lipoproteins.
Exp Mol Pathol 1988 Jun
PMID:Low-density lipoprotein endocytosis. II. Influence of the multivalent ligand cationized ferritin on acetylated low-density lipoprotein endocytosis in cultured cells. 337 60

The ultrastructure of the crystalline surface layer (S-layer) of Bacillus stearothermophilus strain NRS 2004/3a has been characterized by electron microscopy supplemented by optical and computer image analysis. The S-layer, composed of glycoprotein subunits, has oblique symmetry, and can be extracted by guanidine hydrochloride. Upon dialysis, this extract produced both flat and cylindrical mono- and double-layer self-assembly products. Optical diffraction analysis of negatively stained preparations showed five types of double-layered assembly products. Computer filtering separated the double-layer complexes and revealed them to be composed of a common monolayer with p2-symmetry (a = 9.4 nm, b = 11.6 nm, and gamma = ca. 78 degrees). By analysis of freeze-dried and heavy metal-shadowed self-assemblies the surface topography and the characteristic "handedness" of the morphological units have been determined. Labeling with polycationic ferritin has shown that each surface of the S-layer possessed a different net charge. The results indicate that S-layers in vivo could prevent autoagglutination of cells.
J Ultrastruct Mol Struct Res
PMID:Characterization of the ultrastructure and the self-assembly of the surface layer of Bacillus stearothermophilus strain NRS 2004/3a. 345 74

Although the genomes of many species contain multiple copies of ferritin heavy (H)- and light (L)-chain sequences, the chicken genome contains only a single copy of the H-subunit gene. The primary transcription unit of this gene is 4.6 kilobase pairs and contains four exons which are posttranscriptionally spliced to generate a mature transcript of 869 nucleotides. Chicken and human ferritin H-subunit genomic loci are organized with similar exon-intron boundaries. They exhibit approximately 85% nucleotide identity in coding regions, which yield proteins 93% identical in amino acid sequence. We have identified a sequence of 22 highly conserved nucleotides in the 5' untranslated sequences of chicken, human, and tadpole ferritin H-subunit genes and propose that this conserved sequence may regulate iron-modulated translation of ferritin H-subunit mRNAs.
Mol Cell Biol 1987 May
PMID:Structure and expression of the chicken ferritin H-subunit gene. 360 Jun 43

A brief exposure of low dose methylmercuric chloride to monolayer cultures of mouse fetal astrocytes caused a marked shift in the distribution of anionic groups on the surface membrane as evidenced by irregular disruption of cationized ferritin. It is suggested that one of the earliest changes following methyl mercury exposure in embryonic astrocytes includes alterations in the surface charge which may in turn trigger cascading toxic actions of methyl mercury in the developing brain.
Exp Mol Pathol 1986 Apr
PMID:Surface charge alterations in mouse fetal astrocytes due to methyl mercury: an ultrastructural study with cationized ferritin. 369 41

The luminal surface properties of aortic and mitral valve endothelium in hypercholesterolemic rabbits were examined with the aid of cationic ferritin (CF), ferritin-lectins (FWGA, FRCA, FSBA), and low density lipoprotein-colloidal gold (LDL-Gold) conjugates. Based upon comparative studies with normocholesterolemic rabbit valves, the number of CF and wheat germ agglutinin (FWGA) particles per 100 nm of endothelial surface was found to be reduced in moderate hypercholesterolemia (450 mg/dl). Conversely, the number of Ricinus communis agglutinin (FRCA) and soybean agglutinin (FSBA) conjugates were increased. Quantitation of the CF and FWGA particles demonstrated that the endothelium lining of the valve surfaces (i.e., the arterial surfaces of the aortic cusps, AA, and the ventricular surfaces of the mitral cusps, MV) exposed to more turbulent hemodynamic conditions displayed the greatest densities of particle counts. Cholesterol levels of 400-500 mg/dl produced a loss of characteristic differences in the number of ferritin particles that existed between the two surfaces of a cusp. Especially prominent over the AA and MV surfaces, these changes represented a reduction in the anionic properties of the endothelial glycocalyx. Enzymatic digestion demonstrated the reduction in surface sialic acid residues to be one of the major factors responsible for these early changes at the blood-endothelium interface. More severe hypercholesterolemia (700-900 mg/dl) resulted in even further reductions in the number of ferritin particles over the AA and MV surfaces but enhanced the binding of LDL-Gold. Chondroitinase studies of these specimens demonstrated that the initial loss of sialic acids at moderate serum levels unmasks deeper lying components of the glycocalyx (e.g., sulfated glycosaminoglycans) and augments the attachment of LDL molecules to the endothelial surface. The findings of this study suggest that specific macromolecular changes in the endothelial glycocalyx in diet-induced hypercholesterolemia occur at vascular locales where hemodynamic forces such as eddy formations and blood stagnation impinge against the vascular wall.
Exp Mol Pathol 1986 Jun
PMID:A cytochemical study of the surface properties of aortic and mitral valve endothelium from hypercholesterolemic rabbits. 372 Sep 17

Interactions between fibrin and arterial endothelial cells of rat iliac arteries in vivo were studies electron microscopically using a newly devised method. The microvilli became attached to the fibrin threads in an initial period of fibrinolysis. These threads had a fine granular appearance in the lysed areas. Fibrinolytically active endothelial cells had an active vesicular transport for ferritin particles injected concomitantly with the fibrinogen-thrombin mixture, thereby implying the enhancement of endothelial permeability in the lysed areas. However, fibrinolytically inactive endothelial cells coexisted in the same arteries. The denuded intima showed no lytic changes in the fibrin threads. These results indicate that the microvilli of the endothelial cells may plan an important role in the releasing plasminogen tissue activator from the endothelial cells and that there is a heterogeneity with regard to reactivity of each endothelial cell to fibrin.
Exp Mol Pathol 1986 Jun
PMID:Pathophysiological effects of fibrin on arterial endothelial cells in vivo: an electron microscopic study. 372 Sep 24

We found in preliminary studies using 125I-labelled antibodies that an antibody bound to a solid-phase antigen was recognized more efficiently than an antibody adsorbed directly to the solid phase. The present study was designed therefore to quantitate the differential recognition of an antibody adsorbed directly to the solid phase and an antibody bound to antigen on the solid phase using the amplified enzyme-linked immunosorbent assay (a-ELISA), and to compare results with the amounts of specific antibody determined by quantitative immunoprecipitation. The degree of differential recognition was quantitated for rabbit IgG and SIgA anti-ovalbumin (anti-OA) and anti-fluorescein, and was found to be dependent upon the isotype of the antibody and not its specificity. The ratio describing the differential recognition of SIgA antibodies (1.8) was much less than for IgG antibodies (greater than 30) and remained constant over the titration range analyzed while the ratios obtained for IgG varied substantially (25-60) over the same range. These ratios of differential recognition were used to estimate rabbit IgG antibody levels to OA, bovine serum albumin, ferritin and alpha-lactalbumin. The estimates obtained were consistently much less than total antibody levels measured by quantitative precipitation. The use of glutaraldehyde-aggregated OA in the ELISA, however, increased the amount of IgG anti-OA and SIgA anti-OA capable of recognizing OA adsorbed on plastic from 12 to 50 and from 30 to 80%, respectively.
Mol Immunol 1986 Apr
PMID:Altered recognition of surface-adsorbed compared to antigen-bound antibodies in the ELISA. 372 58

Antisera were raised in rabbits against histamine conjugated to human serum albumin (HSA) by the carbodiimide (ECDI) method. The specificity of the antisera was studied in a radioimmunoassay using 125I-protein A for detection of IgG binding. The HIS-HSA antisera reacted with histamine-HSA conjugates prepared by either the carbodiimide or diisocyanate coupling procedure, as well as with carbodiimide-prepared histamine-ferritin and histamine-ovalbumin conjugates. On the contrary, the antisera were unreactive with unconjugated HSA, ECDI-reacted HSA, or HSA conjugated to ethanolamine or pentylamine. Free unconjugated histamine significantly inhibited antibody binding to histamine-HSA and 50% inhibition of antibody binding (IC50) was recorded at 3 mM histamine concn. On a histamine molar concn basis a much lower inhibitory potency of free histamine was recorded, as compared to histamine-protein conjugates (IC50 = 3 X 10(-6) mM). This probably reflected amplification of antibody binding to the multivalent ligand, but possibly also that the protein carrier adds some common features to the antigenic determinant. Histidine, ornithine, glutamine, asparagine, sterylamine and several other amino acids lacked inhibitory effects. Histamine H1 and H2 receptor antagonists inhibited histamine binding to the histamine antibodies. The antagonists varied in their affinity for the histamine antibodies and 50% inhibition of antibody binding was recorded in the range of 1-50 mM concn of the antagonists. Comparing one H1 and one H2 antagonist (diphenhydramine and cimetidine, respectively) two of the sera were preferentially inhibited by cimetidine whereas the third serum seemed to be more prone to inhibition by diphenhydramine.
Mol Immunol 1986 Aug
PMID:Production and characterization of rabbit antibodies against histamine. 379 25


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