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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Inflammation research 42 (1994), S. 141-145 
    ISSN: 1420-908X
    Keywords: Bradykinin ; Mucin ; Mucus ; HT29 ; Goblet cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of the inflammatory mediator bradykinin on glycoprotein synthesis and mucin secretion in the human colonic adenocarcinoma cell line HT29–18N2 was examined. Bradykinin, at a threshold of 0.01 μM, accelerated the rate of mucin discharge as assessed by a mucin-specific ELISA. Using immunofluorescence microscopy, a thick meshwork of extracellular mucus was observed over bradykinin-treated monolayers but not mock-treated controls. Morphometric analysis of bradykinin-treated monolayers revealed no decreases in intracellular mucin stores or any other easily discernable morphological alteration. The ability of the cyclooxygenase inhibitors indomethacin and naproxen to decrease the response to bradykinin by approximately 68% indicates the effect is mediated, at least partially, through the generation of prostaglandins. Bradykinin did not alter the rate of incorporation of3H-glucosamine into newly synthesized glycoproteins. Bradykinin-accelerated mucin secretion may be linked to the depletion of intracellular mucin stores in the inflammatory bowel disease ulcerative colitis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Digestive diseases and sciences 38 (1993), S. 1046-1054 
    ISSN: 1573-2568
    Keywords: mucus ; HT29 ; cholinergic ; calcium ; protein kinase C ; exocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cholinergic stimulation of the HT29-18N2 goblet cell line increased mucin secretion as assessed: (1) with a mucin-specific immunoassay, (2) using whole-mount immunocytochemistry, or (3) by morphometric quantification of intracellular mucous granule stores. Cholinergic stimulation did not, however, result in the apical plasmalemmal membrane cavitation that is characteristic of recent compound exocytotic activity. The resposse was not dependent on protein kinase C activation since it was not inhibited by the kinase C antagonist H7 or potentiated by the diaacylglycerol kinase antagonist R59022. Calcium ionophore A23187 also accelerated mucin secretion by a noncompound exocytotic pathway. Activation of protein kinase C by phorbol 12-myristate 13-acetate, on the other hand, increased mucin secretion by a compound exocytotic pathway. The results provide insight into the signal transduction pathways underlying secretory responses of goblet cells observedin situ.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 1 (1983), S. 352-360 
    ISSN: 0736-0266
    Keywords: Autografts ; Azathioprine immunosuppression ; Bone labeling ; Free vascular allografts ; Microvascular anastomoses ; Transplants ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An area of experimental bone grafting that needs further study is the use of free vascularized allografts of bone. In 35 outbred mongrel dogs, the viability of vascularized bone allografts with and without azathioprine immunosuppression was compared to vascularized autogenous bone grafts. Viability was assessed by histologic techniques, fluorochrome bone labeling, and electron microscopy. Autogenous vascularized bone grafts remained viable, and it was concluded that microvascular technique was not the limiting factor in attaining survival of the grafts. The behavior of autogenous vascularized bone grafts with and without the influence of azathioprine was similar. Allogenic vascularized bone transplants uniformly failed at a period between 2 and 3 weeks. Immunosuppression with azathioprine did not appreciably affect survival of the osteocytes. However, the host response to the foreign tissue was slightly modified. The clinical ramifications of bone transplantations in humans are not analogous to the clinical situation of transplantation of other organs. If vascularized bone transplants are performed in humans, a relatively safe form of immunosuppression is necessary. This study suggests that azathioprine alone does not offer sufficient immunosuppression to insure viability of the vascularized transplant.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 16 (1990), S. 25-36 
    ISSN: 0741-0581
    Keywords: Lectins ; Collodial gold ; LR White ; Lowicryl ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The plasmalemmal glycoconjugates of the HT29-18N2 (N2) cell line were characterized on cells grown as (1) undifferentiated multilayers in glucose-containing culture media and (2) monolayers of columnar cells acquiring the goblet cell phenotype in glucose-free media. Lectins were unable to bind sheets of detached N2 cells in the absence of fixation. Following fixation with aldehydes, a dramatic unmasking of lectin binding sites was seen. When fixed monolayers were stained prior to embedding, biotinylated lectins, visualized by the avidin-biotin-complexed peroxidase technique, were more efficient than collodial gold-coupled lectins. Lectin binding sites could also be detected by using collodial gold-coupled lectins to stain monolayers embedded in LR White, Lowicryl K4M, and Lowicryl HM20. The binding of 5 lectins (wheat germ, Dolichos bifluros, peanut, soybean, and Ulex europeus) was found to be independent of the stage of differentiation; “pre-differentiated” columnar cells which had prominent microvilli and no or few mucous secretory granules had identical staining patterns as well-differentiated goblet cells with large numbers of secretory granules. Ricinus communis I was the only lectin whose binding was influenced by the stage of differentiation; it intensely labeled undifferentiated multilayers of N2 cells but only weakly labeled basolateral membranes of differentiated monolayers. Canavalia ensiformas (ConA) caused a moderate and even labeling of both apical and basolateral membranes of fixed monolayers stained prior to embedding, but post-embedding labeling revealed heavy labeling along the lateral margins of all columnar cells and weak to moderate binding along the apical and basal cell surface.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 1 (1984), S. 9-29 
    ISSN: 0741-0581
    Keywords: Quick freezing ; Synaptic vesicles ; Cholinergic nerve terminals ; Electric organ ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The limitations of chemical fixation in permitting the 1:1 quantitative correlations required for convincing ultrastructural explanations of cell biological processes are noted. We describe techniques for obtaining highly reproducible direct quick freezing on the polished surface of pure copper bars dipping into a static dewar of liquid N2. The importance and the ease of testing and obtaining bounce suppression with commerically available equipment is emphasized. Artefacts caused by tissue damage and bad freezing are illustrated, and a hitherto unrecognized population of presynaptic membrane attached vesicles is described in Torpedine electric organ. Between 15 and 20% of the synaptic vesicles are attached to ca. 30% of the cytoplasmic face of the presynaptic terminal membrane. There is a close correlation between the occurrence of such attachments and the application of electrocyte basal lamina to the external face. We suggest that these vesicles are the ‘membrane operators,’ ‘vesigates,’ and ‘highly active subpopulation’ of vesicles whose existence has been invoked to explain biochemical data in other laboratories. We further speculate that relatively selective Ca pumping by this immediately submembranous population leads to displacement of acetylcholine (ACh) and reloading with newly synthesized ACh. The preferential release of the latter would then be expected.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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