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)

In isolated perfused rat lungs we have examined the effect of inhibition of receptor-mediated endocytosis and of intracellular acidic compartments activity on adsorptive and fluid-phase uptake and transport of macromolecules by capillary endothelium. Cationized and native ferritin were used as electron-dense tracers of adsorptive and fluid-phase transport, respectively. Luminal endothelial vesicles were labeled with tracers at 4 degrees C for 2 minutes and the density of ferritin particles in endothelial multivesicular bodies and in the capillary basement membrane, after a 60-minute chase with tracer-free perfusate at 37 degrees C, was determined by electron microscopic morphometry. Fluid-phase transport of native ferritin in 60-minute perfusions at 37 degrees C was also investigated. Adsorptive endocytosis was inhibited in chase experiments with hypertonic (800 mOsm) perfusate. Endothelial acidic compartments activity was decreased by adding either dextran sulfate or chloroquine to the chase media. We found that hypertonic solutions, dextran sulfate, and chloroquine inhibit cationized ferritin accumulation in multivesicular bodies and in the extravascular space. Hypertonic buffer or dextran sulfate have no effect on native ferritin uptake and transport in either pulse-chase or continuous perfusions. Since adsorptive or receptor-mediated mechanisms play a role in the transendothelial movement of plasma proteins, and other plasma constituents, our findings suggest a general role of the endothelial acidic compartments in modulating microvascular permeability to macromolecules.
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PMID:Inhibition of adsorptive endocytosis and transcytosis in pulmonary microvessels. 246 Jun 97

Studies were designed to examine fluid-phase pinocytosis in proximal tubular cells. Canine proximal tubules were obtained from the band IV of Percoll gradient centrifugation of the dispersed renal cortex, and were seeded on collagen-coated polycarbonate membranes. Integrity of monolayers was confirmed by electrophysiologic measurements, and by scanning electron microscopy. At confluence cell monolayers were studied in Ussing chambers. The rate of transfer of a marker of fluid-phase pinocytosis, Lucifer Yellow CH, from the luminal to the basolateral bath was three times higher than that occurring in the opposite direction. Fluorescence microscopy demonstrated that Lucifer Yellow was trapped exclusively in the vesicular compartment. Electron microscopy of the monolayers incubated with cationized ferritin added to the luminal or to the basolateral both revealed that endocytic vesicles were formed only at the luminal surface. Luminal-to-basolateral transfer of Lucifer Yellow was almost completely blocked at 0 degrees C, and was significantly diminished by K+ depletion. Transcytosis of Lucifer Yellow was stimulated twofold by 1-oleoyl-2-acetyl-glycerol. Transfer of quin-2 acetoxymethylester across the monolayer was used as a marker of the paracellular pathway, demonstrating the lack of directional selectivity of this transport route. In summary, vectorial fluid-phase pinocytosis in proximal tubular cells represents an additional mechanism contributing to fluid transport in this segment of the nephron.
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PMID:Transcytosis in cultured proximal tubular cells. 382 Feb 80

Luminal uptake and degradation of protein in proximal tubules is well documented. However, abluminal uptake has only been demonstrated in a few species and probably only amounts to a few percent of luminal absorption. To investigate this absorptive pathway, isolated perfused proximal tubules from rabbit kidney were exposed to either cationized ferritin or horseradish peroxidase in the bath for 30 min. The tubules were then fixed and processed for electron microscopy. Peroxidase and small amounts of ferritin were found in the intercellular spaces, in endocytic vesicles located in the abluminal part of the cells and in multivesicular bodies. No tracer was found in the lumina or in the apical part of the cells. The tubules were ultrastructurally intact thus excluding the possibility that the proteins were absorbed via the luminal endocytic pathway or as a result of damaged cell membranes. In conclusion, this study presents evidence that ferritin and peroxidase can be absorbed via the basolateral membranes in rabbit proximal tubules.
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PMID:Basolateral endocytosis of protein in isolated perfused proximal tubules. 398 72

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

(1) Neurogenic inflammation has been implicated in the pathogenesis of the vascular headaches of migraine and cluster headaches. (2) Dural blood vessels are both pain-sensitive and show neurogenic plasma extravasation. (3) Endothelial cell (EC) surface anionic sites appear to be a determinant of vascular permeability. We therefore examined the anionic sites of dural EC to determine whether they are different from those of pial and parenchymal vessels. Luminal anionic sites of rat optic nerve EC were labelled with cationic colloidal gold (CCG) and cationic ferritin (CF) and examined by electron microscopy. Employing a battery of enzymes, the effects of digestion of ultrathin sections on subsequent labelling with CCG was quantified using image analysis software. In addition, a gold-labelled lectin, wheat-germ agglutinin (WGA), was employed to locate specific saccharide residues. Of the enzymes with a narrow specificity, only neuraminidase substantially reduced CCG binding. Of the proteolytic enzymes, papain was most effective in reducing labelling. These results show that the luminal EC anionic sites are chiefly composed of sialoglycoproteins. The labelling with biotinylated WGA-streptavidin gold was similar to that with CCG without enzyme digestion. This suggests that WGA is binding to N-acetylneuraminic (sialic) acid residues and not to the neutral N-acetylglucosamine (since CCG would not label uncharged molecules). These results do not differ significantly from those for pial and parenchymal EC. It is therefore likely that factors other than anionic site molecular composition account for the susceptibility of dural vessels to neurogenic plasma extravasation. The relevance of these observations in an experimental animal model to the human clinical condition remains to be determined.
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PMID:Dural microvessels: molecular properties of their luminal anionic sites. 883 82

Light and electron microscopy was used to examine the apical luminal epithelial surface of the uterus at preovulatory and preimplantation stages in the marmoset monkey. Luminal surface charge, detected by cationic ferritin staining, progressively decreased from preovulation to day 11 of pregnancy. The smooth, regular apical plasma membrane at preovulatory stages was in contrast to the convoluted, irregular surface observed during early pregnancy, especially at 1 day before blastocyst implantation. Profiles of microvilli were also altered, becoming thicker and more irregular during early pregnancy. Within the epithelial cell body, cyclic morphologic changes were seen, largely in association with secretory organelles. Giant phagocytic bodies were prominent at all stages examined, although their composition and intensity of staining varied throughout the cycle. Weak to moderate estrogen alpha and progesterone receptor immunostaining of the luminal epithelium was found during preovulatory and early pregnancy stages. This study describes complex cyclic changes in the morphology and biochemical make-up of the uterine luminal epithelial surface in a New World monkey in preparation for blastocyst attachment.
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PMID:Characteristics of the uterine luminal surface epithelium at preovulatory and preimplantation stages in the marmoset monkey. 1150 74