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

Scanning and transmission electron microscopy were used to evaluate free surface microprojections on the kidney glomerular epithelium in response to various experimental situations. Normally glomerular epithelial podocytes exhibit a rather sparse population of finger-like or bleb-like projections. Some investigations, however, have suggested that microvillous projections may increase in number during the differentiation of podocytes and in the aging kidney. With the onset of puromycin aminonucleoside induced nephrotic syndrome, podocyte microprojections become very knob-like and irregular in their shapes. In response to the in vitro environment, the number of podocyte microprojections increases dramatically. Neuraminidase removal of the sialic acid component of the glomerular glycocalyx and exposure to either cytochalasin B (25 microgram/ml) or cytochalasin D (2 microgram/ml), prevent the in vitro formation of podocyte microprojections. In vitro incubation in compounds which depolymerize cytoplasmic microtubules (e.g. vinblastine sulfate 10(-5); colchicine 10(-5) M), however, result in the formation of unusually long glomerular epithelial microprojections. Investigations utilizing the cationic ligand polycationized ferritin (PCF) have shown that podocyte microprojections are the most anionic sites on the free surfaces of these cells. During prolonged incubation of PCF treated glomeruli, the tips of podocyte microprojections are the last sites to shed the anionically bound PCF. It is suggested that the highly anionic sialic acid components of the glomerular free surface glycocalyx may play principal roles in the formation, maintenance and shapes of glomerular podocyte microprojections.
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PMID:Characterization of free surface microprojections on the kidney glomerular epithelium. 702 99

Previous work has shown that when chick embryo mesoderm tissue is seeded onto the free, dorsal surface of established sheets of embryonic epithelial endoblast, the former penetrates the latter and spreads on the underlying artificial substratum. In this work, the surface charge on the epithelial sheet has been altered, prior to seeding the mesoderm, to ascertain whether such a change could alter the behavior of the mesoderm with respect to the free surface of the epithelium. Charge alteration was accomplished using the polycations, poly-L-lysine. Surface charge characteristics were examined ultrastructurally using cationized and anionized ferritin. Results showed that although surface charge changes were detectable, there was no difference in the behavior of the mesoderm with respect to the endoblast. Neuraminidase did not detectably affect the epithelial surface charge. These results are consistent with the view that changes in substratum surface charge are not necessarily correlated with changes in adhesiveness.
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PMID:Inability of mesoderm cells to locomote on the modified free surface of epithelial cell sheets in vitro. 718 49

Monolayer cultures of Ehrlich ascites tumor cells in exponential growth phase were treated with X-rays and neuraminidase alone or in combination. A radiation dose of 2 Gy (200 rd) and higher effected a significant inhibition of DNA synthesis and cell proliferation. Neuraminidase treatment in addition to irradiation did not modify the growth-inhibitory irradiation effect. Cells pretreated for 0.5 to 1.0 hours with neuraminidase (in Earle's salt solution) and cultured thereafter (4h) in serum-containing growth medium exhibited an enhanced development of the microtubule-microfilament-system. Morphometric analysis of microtubules on electronmicroscopic sections revealed a nearly 4-fold increased number in neuraminidase treated cells while the average length of microtubules was similar to controls. Pinocytosis as measured by the ultrastructural uptake of ferritin appeared to be increased following neuraminidase treatment. A connection between neuraminic acid containing components (glycoproteins or glycolipids?) of the cell membrane or cell surface, on the one hand, and the cytoskeleton and the endocytotic process of these tumor cells, on the other hand, is suggested.
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PMID:[Action of x-rays and neuraminidase on pinocytotic activity and microtubule-microfilament system of Ehrlich ascites tumor cells in monolayer culture (author's transl)]. 719 7

An in vitro model system for studying the glomerular epithelium exposed on the surfaces of kidney slices is described. In the first 12 hours of incubation at 37 degrees C, glomerular podocytes exhibit an increase in number of free surface microprojections and number of cytoplasmic lipid inclusions. During the next several days these cells undergo a series of morphological alterations which resemble a dedifferentiation of the glomerular epithelium. By one week of incubation, the glomerular epithelium has been transformed into a compact group of rounded cells. These cells remain rounded but viable throughout several weeks of subsequent incubation. The glomerular endothelium becomes thickened but also remains viable throughout several weeks of incubation. Surface epithelial cells in both cortical and medullary regions become modified into a thin layer of viable cells. At lower incubation temperatures (e.g. 15 to 33 degrees C), the dedifferentiation of glomerular podocytes and formation of a viable surface layer of cells are significantly inhibited. Both undifferentiated and puromycin aminonucleoside nephrotic glomerular podocytes survive and adapt to the in vitro environment. The in vitro response of glomerular epithelial cells to various compounds added to the incubation media are briefly described. Compounds which induce a loss of cytoplasmic microtubules (e.g. vinblastine, colchicine), cause a loss of podocyte cell body and major process morphological integrity. Neuraminidase removal of the glomerular sialic acid surface coat inhibits the formation of free surface microvilli and results in an early loss of podocyte foot processes. The nephrotoxic agent puromycin aminonucleoside has no effect on the viability or morphology of glomerular cells except at very high concentrations (300 micrograms/ml). The distribution and effects of polycationized ferritin on living glomeruli are briefly described. Finally, in vitro treatment with cytochalasin B appears to inhibit cation-induced loss of podocyte foot processes.
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PMID:In vitro studies of kidney glomerular epithelial cells. 742 17

Incorporated in the luminal glycocalyx of vascular endothelia (EC) are negatively charged microdomains (anionic sites). These sites are considered functionally important (a) in their interaction with circulating blood constituents, and (b) as a determinant of vascular permeability. The molecular composition of these EC sites, described for a number of tissues, has demonstrated a heterogeneity dependent on their anatomical location. Luminal anionic sites have not been characterized for EC of optic nerve. Optic nerves were removed from Sprague-Dawley rats previously fixed by vascular perfusion. EC anionic sites were labelled with the probes cationic colloidal gold (CCG) and cationic ferritin (CF), using the pre- and post-embedding techniques, and examined by electron microscopy. The effects of enzyme digestion of ultrathin sections on subsequent CCG labelling were determined using a battery of enzymes in association with the post-embedding technique. CCG labelling was quantified following each enzyme treatment using image analysis software. The biotinylated lectin wheat germ agglutinin (WGA) with streptavidin gold was also used to localize specific monosaccharide residues. The luminal front of intraneural EC showed a uniform labelling with CCG and CF which was greater than on the abluminal surface. Extracellular matrix components and basal laminae were moderately labelled. Digestion of tissue sections with heparitinase and trypsin had no significant effect on subsequent CCG labelling. Proteinase K was less effective than papain but both produced a significant reduction. Neuraminidase almost completely eliminated labelling. CCG binding to the luminal plasma membrane of optic nerve EC can be significantly reduced with proteolytic and glycolytic enzymes. The results demonstrate that sialoglycoproteins principally constitute these luminal EC anionic sites. Biotinylated WGA-streptavidin gold, which detects both N-acetylneuraminic (sialic) acid and N-acetylglucosamine, gave a similar pattern of labelling to CCG alone on the luminal versus abluminal EC fronts. These findings suggest that WGA is binding predominantly to N-acetylneuraminic acid residues since CCG would not label the neutral (uncharged) N-acetylglucosamine.
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PMID:Optic nerve microvessels: a partial molecular definition of cell surface anionic sites. 854 80

An alternative to identify the critical processes necessary to the parasite establishment of the host is to focus on the evolutionary stage responsible for the primary invasion, i.e. the infection structure. The objective of this study was to ultrastructurally characterize Schistosoma mansoni cercariae, using cytochemical techniques. In order to identify basic proteins, techniques such as ethanolic phosphotungstic acid (EPTA) and ammoniacal silver staining were used. Calcium sites location was achieved using the Hepler technique and to evidence anionic groups, we used cationic ferritin particles and enzyme treatment with trypsin Vibrio cholerae, chondroitinase and neuraminidase. The EPTA technique highlighted the presence of basic tegument proteins, nucleus and nucleolus from subtegumental cells, inclusion bodies and preacetabular glands. After using ammoniacal silver, we observed a strong staining in all infective larvae, particularly in the nuclei of muscle cells, circular muscle tissue and preacetabular glands. Calcium site locations were shown to be uniform, thereby limiting the inner spaces of the larvae, especially muscle cells. Samples treated with cationized ferritin particles presented strong staining at the cuticular level. Neuraminidase treatment did not alter the stained shape of such particles on the trematode surface. However, trypsin or chondroitinase treatment resulted in absence of staining on the larval surface. This information on the biochemical composition of the infecting S. mansoni larvae provides data for a better understanding of the biology of this parasite and background on the intriguing parasite-host relationship.
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PMID:Ultrastructural and cytochemical aspects of Schistosoma mansoni cercaria. 1908 Dec 61


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