Regeneration of colonic mucosa in the rat

As part of a study of ulcer formation and healing, regeneration of colonic mucosa in rats was studied following placement of a surgical lesion. Alterations in mucosubstances and connective tissue were examined and their possible significance discussed. The sequence of events in healing was: (1) The mucosa adjacent to the lesion tipped into the lesioned area. The crypts in this mucosa became lined with cells which contained no mucus and had no striated borders. Later in the experimental period, these undifferentiated cells gave rise to cells containing carboxymucins. Cells containing sulfomucin, neutral mucin, or having striated borders arose from the carboxymucin cells. (2) An epithelial ledge of undifferentiated cells migrated onto a sulfated glycosaminoglycan, fibrous interface between necrotic and living tissue in the lesion. (3) Crypt formation began with the appearance of intraepithelial anlagen. (4) Crypts lengthened by a process of epithelial-connective tissue proliferation from the base of the crypt upwards. Following completion of connective tissue regeneration, crypts formed by invading the reestablished lamina propria. (5) The first mucous cells in the ledge contained carboxymucins. As crypt formation occurred, these cells gave rise to typical columnar absorptive cells, to cells containing sulfomucins, and to cells containing neutral mucins. (6) Lengthening of crypts ceased following the appearance of a sulfated acid glycosaminoglycan—collagenous layer deep in the submucosa.     

Localization of nitric oxide synthase immunoreactivity in mast cells of human nasal mucosa

Nitric oxide (NO)-synthase immunoreactivity has been detected for the first time in mast cells of human normal nasal mucosa, with an antibody specific for neuronal NO-synthase. Intense immunoreactivity was revealed in secretion granules of mast cells but was found in mast cell granules free in the extracellular matrix only in some instances; no reactivity was found in the cytoplasm of this or other cell types. These findings suggest that human nasal mast cells contain a particulate isoform of NO-synthase, which shares epitopes with neuronal NO-synthase and is rapidly removed from granules upon exocytosis.     

Vasoactive intestinal polypeptide (VIP) immunoreactivity of endocrine-like cells in the feline pyloric mucosa

Summary Immunoreactivity to VIP by endocrine-like cells in the feline pyloric mucosa was examined by using three kinds of region-specific anti-porcine VIP sera. VIP-immunoreactive endocrine-like cells were detected clearly with all of the VIP antisera used. They were located mainly around the neck of the pyloric glands. Some of these endocrine-like cells showed dilution-dependent immunoreactivity against VIP antisera. The immunostaining intensity of VIP-immunoreactive endocrine-like cells showing dilution-independence could not be distinguished from those of nerve elements. The present results suggest that the immunoreactivity with properties very similar to those of authentic VIP may be present in the endocrine-like cells of the feline pyloric glands.     

Calcium secretion in canine tracheal mucosa

Calcium (Ca) affects many cellular functions of the respiratory tract mucosa and might alter the viscoelastic properties of mucus. To evaluate Ca homeostasis in a respiratory epithelium we investigated transport of Ca by the canine tracheal mucosa. Mucosal tissues were mounted in Ussing-type chambers and bathed with Krebs-Henseleit solution at 37 degrees C. Unidirectional fluxes of 45Ca were determined in tissues that were matched by conductance and short-circuit current (SCC). Under short-circuit conditions there was a significant net Ca secretion of 1.82 +/- 0.36 neq . cm-2 . h-1 (mean +/- SE). Under open-circuit conditions, where the spontaneous transepithelial potential difference could attract Ca toward the lumen, net Ca secretion increased significantly to 4.40 +/- 1.14 compared with 1.54 +/- 1.17 neq . cm-2 . h-1 when the preparation was short-circuited. Addition of a metabolic inhibitor, 2,4-dinitrophenol (2 mM in the mucosal bath), decreased tissue conductance and SCC and slightly decreased the unidirectional movement of Ca from submucosa to lumen. Submucosal epinephrine (10 microM) significantly enhanced Ca secretion by 2.0 +/- 0.63 neq . cm-2 . h-1. Submucosal ouabain (0.1 mM) failed to inhibit Ca secretion. The data suggest that canine tracheal mucosa secretes Ca; this secretory process is augmented by epinephrine or by the presence of a transepithelial potential difference as found under in vivo conditions.     

Nitroxidergic vasodilator nerve in the canine nasal mucosa

The canine nasal mucosa was studied by in vitro bioassay. Non-adrenergic, non-cholinergic (NANC) vasodilator response to transmural electrical stimulation was observed in the presence of guanethidine and atropine. This vasodilator response was abolished by N^G-nitro-l-arginine (l-NA) which is an inhibitor of nitric oxide (NO) formation but not by N^G-nitro-d-arginine. The inhibitory effect of l-NA was partially reversed by treatment with l-arginine but not with d-arginine. The vasodilator response was significantly suppressed by tetrodotoxin. The present results indicate that NO may mediate neurogenic vasodilation in the canine nasal mucosa.     

Induction of caveolae in the apical plasma membrane of Madin-Darby canine kidney cells

In this paper, we have analyzed the behavior of antibody cross-linked raft-associated proteins on the surface of MDCK cells. We observed that cross-linking of membrane proteins gave different results depending on whether cross-linking occurred on the apical or basolateral plasma membrane. Whereas antibody cross-linking induced the formation of large clusters on the basolateral membrane, resembling those observed on the surface of fibroblasts (Harder, T., P. Scheiffele, P. Verkade, and K. Simons. 1998. J. Cell Biol. 929-942), only small ( approximately 100 nm) clusters formed on the apical plasma membrane. Cross-linked apical raft proteins e.g., GPI-anchored placental alkaline phosphatase (PLAP), influenza hemagglutinin, and gp114 coclustered and were internalized slowly ( approximately 10% after 60 min). Endocytosis occurred through surface invaginations that corresponded in size to caveolae and were labeled with caveolin-1 antibodies. Upon cholesterol depletion the internalization of PLAP was completely inhibited. In contrast, when a non-raft protein, the mutant LDL receptor LDLR-CT22, was cross-linked, it was excluded from the clusters of raft proteins and was rapidly internalized via clathrin-coated pits.Since caveolae are normally present on the basolateral membrane but lacking from the apical side, our data demonstrate that antibody cross-linking induced the formation of caveolae, which slowly internalized cross-linked clusters of raft-associated proteins.     

DNA damage in human colonic mucosa cells induced by bleomycin and the protective action of vitamin E

Using the alkaline comet assay, we showed that bleomycin at 0.1-5 microg/ml induced DNA strand breaks and/or alkali-labile sites, measurable as the comet tail moment, in human colonic mucosa cells. This DNA damage was completely repaired during a 120-minute post-treatment incubation of the cells. Post-treatment of the bleomycin-damaged DNA with 3-methyladenine-DNA glycosylase II (AlkA), an enzyme recognizing alkylated bases, gave rise to a significant increase in the extent of DNA damage, indicating that the drug could induce alkylative bases in DNA. We did not observe any change in the comet tail moment in the presence of catalase. Vitamin E ((+)-alpha -tocopherol) decreased DNA damage induced by bleomycin. The results obtained suggest that hydrogen peroxide might not be involved in the formation of DNA lesions induced by bleomycin in the colonic mucosa cells.     

Dendritic cells derived from murine colonic mucosa have unique functional and phenotypic characteristics

Dendritic cells (DCs) residing in different tissues and exposed to different organisms are likely to have different reactivities to their surrounding environment. Many studies use in vitro generated DCs to examine functions of these cells, but such cells may not truly reflect the nature of DCs and their in situ activities in vivo. We have used magnetic label-based technique to isolate colonic DCs to conduct derailed characterization of these cells. Colonic DCs comprise mainly CD11b+ DCs with few CD8alpha+ DCs or plasmacytoid DCs. Functionally, isolated colonic DCs are able to endocytose and process proteins, undergo maturation, and stimulate T cells to proliferate. Importantly, expression of TLRs by colonic DCs is significantly lower than that of their spleen counterparts; however, they appear to be as, or more, responsive to stimulation by oligodeoxynucleotides containing CpG motif based on their cytokine production. We speculate that colonic DCs have unique reactivities differing from DCs residing in other lymphoid tissues and are adapted for the unique microenvironment of the colonic mucosa and that these cells react uniquely to their environment.     

Carbohydrate-rich compounds in the colonic mucosa of man. III. A preliminary report of some biochemical characteristics of the carbohydrate-rich components in normal colonic mucosa

Synopsis Preparations of human colonic epithelial cells were obtained virtually free from contamination by connective tissue. A trichloroacetic acid-soluble carbohydrate-rich fraction was prepared after defatting, proteolytic digestion and trichloroacetic acid precipitation of proteins by precipitating the polysaccharides with ethanol and potassium acetate. Four components of acid mucosubstances were revealed on electrophoresis, three of them showing the presence of sulphate radicals. The periodate consumption rate of the preparation was over four times greater after methanolytic desulphation, and confirms previous results concerning the blocking of periodate reactivity by acid radicals. The analysis of the sample showed the presence of 15% protein, 14% hexose, 9% sialic acid, 6% hexosamine, 3% fucose and 3% uronic acid.     

Apical junction complex protein expression in the canine colon: differential expression of claudin-2 in the colonic mucosa in dogs with idiopathic colitis.

Canine idiopathic lymphocytic-plasmacytic colitis (LPC) is a well-recognized clinical and pathological entity in the dog, associated with altered immune cell populations and cytokine expression profiles. Clinical and experimental data indicate that alterations in the permeability of the intestinal epithelium contribute to the pathogenesis of a range of related conditions. The apical junction complex plays a significant role in regulating epithelial paracellular permeability, and we have characterized the distribution of a number of its component tight junction (ZO-1, occludin, claudin-2) and adherens junction (E-cadherin and beta-catenin) proteins in normal colon and colon from dogs with idiopathic LPC. ZO-1, occludin, E-cadherin, and beta-catenin exhibited a distribution in normal canine colon similar to that described previously in humans and rodents. In contrast to the situation in humans, claudin-2-specific labeling was observed in the normal canine colonic crypt epithelium, decreasing in intensity from the distal to the proximal crypt and becoming barely detectable at the luminal surface of the colon. There was little evidence for significant changes in ZO-1, occludin, E-cadherin, or beta-catenin expression in dogs affected by idiopathic LPC. However, claudin-2 expression markedly increased in the proximal crypt and luminal colonic epithelium in affected dogs, suggesting a role in the pathogenesis of canine LPC.     

Ultrastructural findings in the wound healing of the colonic mucosa of rabbits

The wound healing of the rabbit colonic mucosa after experimental excision was observed with the electron microscope. Between 5 and 7 days, considerable numbers of undifferentiated mesenchymal cells (group I), differentiating muscle cells (group II) and histiocyte-like cells (group III) appear in the regions where the muscularis mucosae is re-establishing. Our electron micrographs indicate that group I cells are stem cells which differentiate to group II cells involved in muscle regeneration or to group III cells involved in phagocytosis. The mitotic proliferation of pre-existing smooth-muscle cells at the ulcer margin does not seem to be the major reason for the re-establishment of the muscular layer. Multinucleated cells occurring in this healing mucosa are considered to be formed by successive fusions between the group III cells and to play a role in enclosure of cell debris such as fragments of elastin.