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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Immunology 14 (1996), S. 275-300 
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract Epithelial barriers on mucosal surfaces at different sites in the body differ dramatically in their cellular organization, and antigen sampling strategies at diverse mucosal sites are adapted accordingly. In stratified and pseudostratified epithelia, dendritic cells migrate to the outer limit of the epithelium, where they sample antigens for subsequent presentation in local or distant organized lymphoid tissues. In simple epithelia, specialized epithelial M cells (a phenotype that occurs only in the epithelium over organized lymphoid follicles) deliver samples of foreign material by transepithelial transport from the lumen to organized lymphoid tissues within the mucosa. Certain pathogens exploit the M cell transport process to cross the epithelial barrier and invade the mucosa. Here we review the features of M cells that determine antigen and pathogen adherence and transport into mucosal lymphoid tissues.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 16 (2000), S. 301-332 
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract M cells are distinctive epithelial cells that occur only in the follicle-associated epithelia that overlie organized mucosa-associated lymphoid tissues. They are structurally and functionally specialized for transepithelial transport, delivering foreign antigens and microorganisms to organized lymphoid tissues within the mucosae of the small and large intestines, tonsils and adenoids, and airways. M cell transport is a double-edged sword: Certain pathogens exploit the features of M cells that are intended to promote uptake for the purpose of immunological sampling. Eludication of the molecular architecture of M cell apical surfaces is important for understanding the strategies that pathogens use to exploit this pathway and for utilizing M cell transport for delivery of vaccines to the mucosal immune system. This article reviews the functional and biochemical features that distinguish M cells from other intestinal cell types. In addition it synthesizes the available information on development and differentiation of organized lymphoid tissues and the specialized epithelium associated with these immune inductive sites.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 123 (1991), S. 93-103 
    ISSN: 1432-1424
    Keywords: transcytosis ; epithelium ; membrane traffic ; endocytosis ; receptors ; antibodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Conclusions Our current understanding of vesicular transport across polarized epithelial cells is largely derived from studies of various cell lines in vitro and rat liver in vivo. It may be assumed that the basic mechanisms and cellular machineries which control membrane protein sorting, coated pit-mediated internalization, membrane fusion and fission, play important roles in the phenomenon of selective transcytosis. At the present, however, no general rules have been established that explain the traffic of different membrane proteins and ligands across specific epithelial cell types. For example, the pattern of protein movement that seems to represent a default pathway in certain cell types appears to be signal-mediated in others. The dissection at the molecular level of the components involved in transepithelial traffic of membrane proteins will require complementary experimental approaches, including the isolation of specific transcytotic carrier vesicles, their biochemical characterization, the reconstitution of the various steps in cell-free systems, and analysis of the traffic patterns of transcytotic proteins in different cell types after transfection and in transgenic animals.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 193 (1979), S. 367-381 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Distinctive linear arrays of intramembrane particles were present in microvillar membranes of approximately 5% of surface columnar cells observed in freeze-fracture replicas of monkey colon and human rectum. On these cells, longitudinally-oriented rows of P face particles and corresponding E face grooves appeared on all exposed microvilli. The constituent particles varied from round (8-9 nm in diameter) to rod-shaped (18 nm long). Microvilli of the great majority of columnar cells displayed randomly distributed P face particles similar to those previously observed in small and large intestine of birds and small mammals. The significance of the linear arrays is not known. It is postulated that they may represent protein assemblies which are specific to a functionally-distinct subpopulation of primate intestinal columnar cells.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 213 (1985), S. 520-528 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The luminal membrane of ileal absorptive cells in suckling rats includes two domains: microvillar membranes and deep invaginations between microvilli. We examined the fates of foreign macromolecules that bind to anionic or saccharide sites on these domains after infusion into ligated loops in vivo. Cationized ferritin (CF) and ferritin-RCAI (β-galactosyl) binding sites were distributed over the entire apical membrane. Ligands bound to apical invaginations were rapidly endo cytosed, but ligands on microvilli were not. After CF binding, anionic sites on microvilli were mobile in the plane of the membrane and formed CF clusters at the tip and base of each microvillus. RCAI binding sites did not cluster. Wheat germ agglutinin (WGA, sialic acid) labeling was restricted to microvillus tips of mature cells but was dispersed over the microvillar surfaces of lower villus cells. Ferritin conjugates of Concanavalia ensiformis (Con A), Ulex europaeus agglutinin (UEA), and Dolichos biflorus agglutinin (DBA) did not bind to cell surfaces in vivo. Aldehyde fixation dramatically altered lectin binding patterns, resulting in unmasking and labeling of Con A, WGA, and DBA binding sites that were unavailable in vivo.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Peyer's patch ; M cell ; Transepithelial transport ; Lectins ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary M cells in Peyer's patch epithelium conduct transepithelial transport of luminal antigens to cells of the mucosal immune system. To determine the distribution of specific lectin-binding sites on luminal membranes of living M cells and to follow the transport route of membranebound molecules, lectin-ferritin conjugates and cationized ferritin were applied to rabbit Peyer's patch mucosa in vivo and in vitro. The degree to which binding enhances transport was estimated by comparing quantitatively the transport of an adherent probe, wheat germ agglutinin-ferritin, to that of a nonadherent BSA-colloidal gold probe. When applied to fixed tissue, the lectins tested bound equally well to M cells and columnar absorptive cells. On living mucosa, however, ferritin conjugates of wheat germ agglutinin and Ricinus communis agglutinins I and II bound more avidly to M cells. Absorptive cells conducted little uptake and no detectable transepithelial transport. Lectins on M cell membranes were endocytosed from coated pits, rapidly transported in a complex system of tubulocisternae and vesicles, and remained adherent to M cell basolateral membranes. Cationized ferritin adhered to anionic sites and was similarly transported, but was released as free clusters at M cell basolateral surfaces. When applied simultaneously to Peyer's patch mucosa, wheat germ agglutinin-ferritin was transported about 50 times more efficiently than was bovine serum albumin-colloidal gold.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0878
    Keywords: Goblet cells ; Small intestine ; Tight junctions ; Peroxidase ; Cholinergic drugs ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Crypt, but not villus, goblet cells in the ileum accelerate their secretion of mucus within 5 min following cholinergic stimulation. This study was done to determine whether the macromolecular permeability and structure of occluding junctions in the ileum are altered during accelerated secretion. Rats were injected intravenously with horseradish peroxidase followed by carbachol (250 μg/kg, subcutaneous) and the intestinal mucosa was fixed 3–12 min later. In control mucosa (saline-injected), peroxidase filled lateral intercellular spaces up to the occluding junctions of both crypt and villus epithelium, but did not enter occluding junctions or pass into the lumen. In 3 of 8 carbachol-stimulated rats, peroxidase was present within occluding junctions in crypt epithelium and in the crypt lumen, although all intermembrane junctional fusion sites appeared intact. Villus epithelial occluding junctions, in contrast, continued to exclude peroxidase. In freeze-fracture replicas of crypt cells prepared after carbachol stimulation, we detected no structural changes in strand networks of occluding junctions that could account for increased paracellular permeability.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 160 (1981), S. 461-472 
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Scanning electron microscopy (SEM) was used to investigate the epithelial topography of the surface and crypt in rabbit and monkey colon. Crypt openings in monkey colon are arranged in a hexagonal pattern, in sharp contrast to rabbit colon where they are randomly arrayed and frequently hidden by epithelial folds. Crypt lumens were exposed by freezing ethanol-dehydrated tissue in liquid nitrogen and fracturing the tissue with a razor blade. The resulting overview of crypt-cell luminal surfaces showed that as columnar cells mature and migrate up the crypt and onto the colonic surface, their microvilli become progressively more abundant. Goblet cells were readily identified in the cross-fractured crypt epithelium; their luminal surfaces are characterized by short, sparse microvilli. The changing appearance of the luminal surface of goblet cells was visualized by SEM during the exocytosis of single mucous granules from unstimulated crypt goblet cells, and during the compound exocytosis of multiple granules in response to acetylcholine.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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