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

The surface charge of epimastigote and trypomastigote forms of Trypanosoma cruzi was analysed by three approaches: a) visualization by electron microscopy of the binding of cationic particles (cationized ferritin at pH 7.2 and colloidal iron hydroxyde at pH 1.8) to the parasite's surface, b) visualization of the binding of fluorescein-labeled lectins (PNA and LPA) to the parasite's surface, and c) by cell electrophoresis. In all cases control, trypsin and neuraminidase-treated cells were analysed. The results obtained indicate that sialic acid residues located on the parasite's surface are responsible for the binding of cationic particles to it and the major component responsible for the net negative surface charge presented by T. cruzi. Phosphate groups, associated to phospholipids, also contribute to the negative surface charge. The effect of previous incubation of the parasites in the presence of lectins (ConA, WGA, PNA, RCA and LPA) on their surface charge was also analysed by cell electrophoresis.
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PMID:The surface charge of Trypanosoma cruzi: analysis using cell electrophoresis, lectins and ultrastructural cytochemistry. 309 34

Carbohydrates were located on the surface of Phytomonas davidi using ultrastructural cytochemistry, and agglutination induced by lectins which bind to residues of mannose, N-acetylglucosamine, galactose, N-acetylgalactosamine, fucose and sialic acid. The surface charge of the cells was analysed by the binding of cationic particles (colloidal iron and cationized ferritin) to the cell surface and by cell electrophoretic mobility (EPM). Based on observations of binding of cationic particles to the cell surface; a decrease in the binding of these particles to the cell surface; a decrease in the mean EPM of the cells after their incubation in the presence of neuraminidase; and detection of N-acetylneuraminic acid by paper and gas-liquid chromatography, it was concluded that sialic acid residues are exposed on the surface of P. davidi. These residues may be glycolipids or are masked on the cell surface since only after brief trypsinization were the cells agglutinated by the lectin from Limulus polyphemus.
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PMID:The cell surface of Phytomonas davidi. 313 69

The adhesion of immunoglobulins (IgG) and beta-migrating very low density lipoproteins (beta-VLDL) to aortic valve cusps from normolipidemic and hypercholesterolemic rabbits is associated with cytochemical changes in the endothelial glycocalyx. Endothelial surface changes are characterized by (1) enzymatic degradations with neuraminidase (NEU), chondroitinase ABC (CABC) or AC, and heparitinase (HPT); and (2) affinity cytochemistry with avidin-ferritin, protein A-HRP, and beta-VLDL-colloidal gold. NEU facilitated IgG deposition on cells from normolipid animals; however, tandem treatment with NEU and CABC increased beta-VLDL but prevented IgG interactions. The addition of HPT was required to eliminate beta-VLDL activity. The cells lining the arterial surfaces of cusps from hypercholesterolemic animals were reactive for endogenous IgG and beta-VLDL-gold. CABC enhanced the binding of the latter but removed most of the IgG. All reactivity was prevented by CABC and HPT. These findings suggest that the reduction of sialic acid residues and exposure of deeper lying glycosaminoglycans in the endothelial glycocalyx favor the interaction of blood-borne elements at natural sites of disturbed blood flow in dietary hypercholesterolemia.
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PMID:Interactions of IgG and beta-VLDL with aortic valve endothelium from hypercholesterolemic rabbits. 332 1

The structure, relative density, and distribution of anionic sites on the surface of epididymal and ejaculated spermatozoa were studied using polycationic ferritin (CF), colloidal iron hydroxide (CIH), various enzymatic treatments, methylation, and de-acetylation. Macro-molecules containing sugar residues, probably sialic acid, are part of the sperm membrane and show a characteristic distribution and density that is dependent of the sperm region and of its origin. Unlike the spermatozoa of other eutheria examined, the exposure of the stallion spermatozoa to neuraminidase treatment did not produce significant changes in the density of the negative charge of the sperm surface. The ability of purified neuraminidase to act only after saponification suggests that sialic acid may be present in the acetylated form. When CIH was used it is seen that the density of the negative charge is rather uniform within a particular segment of the spermatozoa and abruptly changes at the junction of morphologically distinct segments (Between the acrosomal and post acrosomal region of the sperm head and between the post acrosomal region and middle piece of the flagellum). The acrosome presented more negative groups dissociated at pH 1.8 than the postacrosomal region. A greater concentration of anionic sites over the flagellum was also observed when CIH and CF were used. This asymmetry probably represents different domains that may be related to specific functions. The cytochemical observations and the cellular electrophoretic mobility measurements did not show striking differences on the negative charge of sperm obtained from different regions of epididymis and ejaculates in contrast to previous results in other species. The spermatozoa collected from caput epididymidis bind CIH but not all population present equal response. In corpus and cauda region of epididymis the population displaying the capacity to bind CIH or CF significantly over the head and tail surface was the majority. This study corroborates that the distribution and density of terminal oligosaccharide residues on the sperm plasma membrane has species specific characteristics. The surface charge of the spermatozoa obtained either during the breeding or nonbreeding season, determined by measurements of cellular electrophoretic mobility and by the binding pattern of CIH and CF, does not show significant differences.
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PMID:Cytochemical analysis of the anionic sites on the membrane of the stallion spermatozoa during the epididymal transit. 350 80

Terminal saccharide sequences in rat photoreceptor cell surface glycoconjugates were characterized. Lectin cytochemistry and electron microscopy were used for preembedding cytochemical localization of surface carbohydrates. Neuraminidase digestion was employed for the exposure of penultimate saccharides in sialoglycoconjugates. Isolated rat retinas were incubated with ferritin-labeled wheat germ agglutinin (WGA), peanut agglutinin (PNA), and soybean agglutinin (SBA) prior to and after neuraminidase digestion. PNA and SBA did not label untreated photoreceptors. WGA densely labeled the photoreceptor surface and interphotoreceptor matrix (IPM) components. Following neuraminidase treatment, PNA, but not SBA, labeled the photoreceptor surface and the IPM. WGA labeling of the IPM was abolished, and the labeling of the photoreceptor surface was reduced. Based on the lectin specificity, it was concluded that photoreceptor surface glycoconjugates in the rat retina contain a terminal trisaccharide: sialic acid-D-galactose-(beta 1----3)-N-acetyl-D-galactosamine.
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PMID:Cytochemical characterization of sialoglycoconjugates on rat photoreceptor cell surface. 355 69

In order to study differences in cell-surface sugars which may be involved in the phagocytic defect in Royal College of Surgeons (RCS) retinas, we have examined the presence or absence of lectin binding to carbohydrates on retinal pigment epithelial (RPE) plasma membranes of dystrophic (RCS-p+) and normal (Long-Evans) rats. A lectin which binds to both sialic acid and N-acetylglucosamine sugar residues, wheat germ agglutinin-ferritin (WGA-fe), was used. The specificity of WGA-fe binding to each sugar was studied by either pre-treating the tissue with neuraminidase enzyme which removes sialic acid residues, or by incubating the WGA-fe lectin with one of the haptens, N-acetylglucosamine. In non-enzyme-treated tissue, RPE cell-surface membranes from RCS retinas were densely labeled with WGA-fe as compared with the labeling on normal RPE, which appeared less dense and patchy in distribution. Wheat germ agglutinin-ferritin labeling in the presence of N-acetylglucosamine was blocked on both RCS and normal RPE surface membranes. After pre-treatment with neuraminidase, WGA-fe labeling on dystrophic RPE membranes was similar to non-enzyme-treated tissue but was enhanced on normal RPE. Labeling was blocked when N-acetylglucosamine was present with the lectin after enzyme pre-treatment. Other lectins which specifically bind to sialic acid, Limulus polyphemus agglutinin-ferritin (LPA-fe) and Limax flavus agglutinin (LFA) demonstrated sparse or no labeling on both RCS and normal RPE membranes. Our data suggests that N-acetylglucosamine residues predominate on RCS and normal RPE cell-surface membranes and that sialic acid binding sites are either not accessible to the lectins or may not be present.
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PMID:Examination of sialic acid binding on dystrophic and normal retinal pigment epithelium. 359 57

We propose here the use of freeze-fracture to gain access and to label in vitro glomerular components and locate WGA receptors and anionic sites. Tissues are frozen, fractured under liquid nitrogen, and thawed. Freeze-fracture rendered all glomerular structures directly accessible to the reagents. This made possible study of the nature and topology of cationized ferritin and WGA binding sites. WGA-gold complexes were observed over plasma membranes of podocytes and of endothelial and mesangial cells. Labeling of podocytes and endothelial cells was similar in the mesangial area and in the peripheral part of the capillary loop. Cross-fractures of extracellular matrices showed that WGA bound uniformly to the glomerular basement membrane (GBM) as well as to mesangial matrix. In fractured specimens treated with neuraminidase, WGA was no longer observed over podocytes but it consistently labeled the surface of endothelial and mesangial cells. Whereas in GBM cross-sections WGA binding was greatly reduced or even abolished, it remained unmodified in the mesangium. This shows that only NeuNAc (sialic acid) might account for the binding of WGA to podocytes, whereas GlcNAcs appear to be the main WGA binding sites on endothelial and mesangial cells and in the mesangial matrix. Both NeuNAc and GLcNAc residues are probably associated in GBM. With cationized ferritin (pI 8.3) at pH 7.4, intense, continuous labeling was seen all over the different plasma membranes, denser in podocytes than in endothelial cells. CF was also observed in cross-fractured profiles of extracellular matrices and never appeared agglutinated in discrete sites.
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PMID:Freeze-fracture cytochemistry of rat glomerular capillary tuft. Determination of wheat germ agglutinin binding sites and localization of anionic charges. 368 Sep 32

Sialic acids were characterized on the cell surface of conidia and hyphae of Fonsecaea pedrosoi, one of the agents of chromoblastomycosis. Neuraminidase-treated conidia had a reduced negative electrophoretic mobility and, in comparison with untreated cells, bound fewer particles of colloidal iron hydroxide and of cationized ferritin. Sialic acid residues in conidia are linked to galactopyranosyl units as indicated by the increased reactivity of neuraminidase-treated cells with peanut agglutinin. N-acetylneuraminic acid was the only derivative found in the mycelium whereas conidia contained both N-glycolyl- and N-acetylneuraminic acids.
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PMID:Identification of sialic acids on the cell surface of hyphae and conidia of the human pathogen Fonsecaea pedrosoi. 372 89

The polycation hexadimethrine (HDM) binds to anionic sites in the glomerular basement membrane (GBM) and causes heavy proteinuria when infused in vivo. An in vitro assay of 3H-HDM binding to isolated dog GBM was developed, to permit further analysis of the GBM components binding HDM. 3H-HDM binding to isolated GBM was saturable, reversible in dose-dependent fashion by competing polycations, and inhibited by increasing salt concentration and low pH. The pH dependence of binding suggested that most of the HDM binds to carboxyl groups rather than to the sulfate groups of proteoglycans. Removal of heparan sulfate by heparinase or purified heparatinase had no detectable effect on HDM binding. Treatment of GBM with neuraminidase, hyaluronidase, or chondroitinase reduced binding of HDM by a maximum of 20 to 38%. However, substitution of carboxyl anions with nonionizable glycine methyl ester residues resulted in complete elimination of HDM binding. Parallel results were obtained in studies of glomerular localization of cationized ferritin (CatF), pI 8.5. After carboxyl substitution, GBM did not bind CatF; heparinase-treated GBM bound CatF in a distribution not demonstrably different from normal. Cellulose acetate electrophoresis of glycosaminoglycan fractions prepared from treated GBM confirmed that carboxyl modification did not alter the content or charge of the heparan sulfate of GBM, but heparinase treatment removed at least 90% of heparan sulfate. The results indicate that carboxyl groups are quantitatively more important than heparan sulfate for binding of HDM in vitro. Since HDM causes proteinuria in vivo, carboxyl groups may be important for maintenance of normal permselectivity.
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PMID:Polycation binding to glomerular basement membrane. Effect of biochemical modification. 380 16

The acrosome is a large secretory vesicle of the sperm head that carries enzymes responsible for the digestion of the oocyte's investments. The event leads to sperm penetration and allows fertilization to occur. Release of the acrosomal enzymes is mediated by the interaction between sperm acrosomal and plasma membranes (acrosome reaction). Biochemical characterization of the acrosomal membrane has been restrained by a lack of methods to isolate uncontaminated fractions of the membrane. Here, we use new methods to expose the membrane to in situ cytochemical labeling by lectin-gold complexes. We study the topology and relative density of glycoconjugates both across and along the plane of the acrosomal membrane of boar sperm. Detachment of the plasma membrane from glutaraldehyde-fixed cells exposed the cytoplasmic surface of the acrosome to the lectin markers; freeze-fractured halves of the acrosomal membrane were marked by "fracture-label" (Aguas, A. P., and P. Pinto da Silva, 1983, J. Cell Biol. 97:1356-1364). We show that the cytoplasmic surface of the intact acrosome is devoid of binding sites for both concanavalin A (Con A) and wheat germ agglutinin (WGA). By contrast, it contains a high density of neuraminidase-resistant anionic sites detected by cationic ferritin. On freeze-fractured sperm, the receptors for Con A partitioned with the exoplasmic membrane half of the acrosomal membrane. The Con A-binding glycoconjugates were accumulated on the equatorial segment of the membrane. A low density of WGA receptors, as well as of intramembrane particles, was found on the freeze-fracture halves of the acrosomal membrane. The plasma membrane displayed, in the same preparations, a high density of receptors for both Con A and WGA. We conclude that the acrosome is limited by a membrane poor in glycoconjugates, which are exclusively exposed on the exoplasmic side of the bilayer. Regionalization of Con A receptors on the acrosome shows that sperm intracellular membranes, like the sperm surface, express domain distribution of glycocomponents.
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PMID:The acrosomal membrane of boar sperm: a Golgi-derived membrane poor in glycoconjugates. 383 77


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