Analysis of the effects of food and of digestive secretions on the small intestine of the rat. 1. Mucosal morphology and epithelial replacement.
A modified Roux-en-Y repositioning of rat small intestine was performed so that the proximal segment of bowel (A) received only bile and pancreastic secretions, the second (B) received food direct from the stomach, and these two segments drained into a third (C). Four to five weeks after operation, cell production was assessed by injection of vincristine into operated, sham-operated and unoperated rats, and counts of blocked metaphases were made on isolated microdissected crypts. Villus height, crypt depth, and the number of crypts per villus (crypt/villus ratio) were also measured. Most of segment A showed no significant differences from sham-operated intestine, although the normal proximo-distal gradient of villus height was abolished. At the distal end (near the anastomosis with segments B and C), crypt depth and cell production were increased. The villus height gradient in segment B was also abolished, although crypt depth and cell production were significantly increased, especially at the proximal end. Crypt/villus ratio was also increased. Segment C showed all the characteristics of small bowel promoted to a more proximal position: increased villus height, crypt depth and cell production. Increased crypt/villus ratio was also observed. These results are discussed in terms of the role of food and of digestive secretions in the control of mucosal morphology and epithelial replacement. (+info)
PKCdelta acts as a growth and tumor suppressor in rat colonic epithelial cells.
We have analysed the expression of three calcium-independent isoforms of protein kinase C (PKC), PKCdelta, PKCepsilon and PKCzeta, in an in vitro model of colon carcinogenesis consisting of the nontumorigenic rat colonic epithelial cell line D/WT, and a derivative src-transformed line D/src. While PKCzeta and PKCepsilon showed similar protein levels, PKCdelta was markedly decreased in D/src cells when compared to the D/WT line. To assess whether down-regulation of PKCdelta was causally involved in the neoplastic phenotype in D/src cells, we prepared a kinase-defective mutant of PKCdelta. Stable transfection of this sequence caused morphological and growth changes characteristic of partial transformation in D/WT cells. Moreover, to test whether PKCdelta was involved in growth control and transformation in this model, we overexpressed PKCdelta in D/src cells. Transfected cells underwent marked growth and morphological modifications toward the D/WT phenotype. In a late stage in culture, transfected cells ceased to proliferate, rounded up and degenerated into multinucleated, giant-like cells. We conclude that PKCdelta can reverse the transformed phenotype and act as a suppressor of cell growth in D/src cells. Moreover, our data show that downregulation of this isoenzyme of PKC may cooperate in the neoplastic transformation induced by the src oncogene in D/WT cells. (+info)
Expression of nitric oxide synthase in inflammatory bowel disease is not affected by corticosteroid treatment.
AIM: To examine the effect of corticosteroid treatment on the expression of inducible nitric oxide synthase (iNOS) in the colon of patients with inflammatory bowel disease. METHODS: Four groups of patients were studied: (1) ulcerative colitis treated with high dose corticosteroids (six patients, 10 blocks); (2) ulcerative colitis patients who had never received corticosteroids (10 patients, 16 blocks); (3) Crohn's disease treated with high dose corticosteroids (12 patients, 24 blocks); (4) Non-inflammatory, non-neoplastic controls (four patients, six blocks). Full thickness paraffin sections of colons removed at surgery were immunostained with an antibody raised against the C terminal end of iNOS. Sections were assessed semiquantitatively for the presence and degree of inflammation and immunoreactivity for nitric oxide synthase. RESULTS: Cases of ulcerative colitis and Crohn's disease with active inflammation showed strong staining for nitric oxide synthase. The staining was diffuse in ulcerative colitis and patchy in Crohn's disease, in accordance with the distribution of active inflammation. Staining was seen in epithelial cells and was most intense near areas of inflammation such as crypt abscesses. Non-inflamed epithelium showed no immunoreactivity. Treatment with corticosteroids made no difference to the amount of nitric oxide synthase. CONCLUSIONS: Expression of nitric oxide synthase is increased in both ulcerative colitis and Crohn's disease and appears to be unaffected by treatment with corticosteroids. Disease severity necessitated surgery in all the cases included in this study, regardless of whether or not the patients had received long term corticosteroid treatment. It seems therefore that a high level of iNOS expression and, presumably, production of nitric oxide characterise cases which are refractory to clinical treatment; this suggests that specific inhibition of the enzyme may be a useful therapeutic adjunct. (+info)
Interleukin-8 controls bacterial transepithelial translocation at the cost of epithelial destruction in experimental shigellosis.
In shigellosis, the network of cellular interactions mediated by a balance of pro- and anti-inflammatory cytokines or chemokines is clearly tipped toward acute destructive inflammation of intestinal tissues by the bacterial invader. This work has addressed the role played by interleukin-8 (IL-8) in a rabbit model of intestinal invasion by Shigella flexneri. IL-8, which is largely produced by the epithelial cells themselves, appears to be a major mediator of the recruitment of polymorphonuclear leukocytes (PMNs) to the subepithelial area and transmigration of these cells through the epithelial lining. Neutralization of IL-8 function by monoclonal antibody WS-4 caused a decrease in the amount of PMNs streaming through the lamina propria and the epithelium, thus significantly attenuating the severity of epithelial lesions in areas of bacterial invasion. These findings are in agreement with our previous work (31). In contrast to the PMNs, the bacteria displayed increased transepithelial translocation, as well as overgrowth in the lamina propria and increased passage into the mesenteric blood. By mediating eradication of bacteria at their epithelial entry site, although at the cost of severe epithelial destruction, IL-8 therefore appears to be a key chemokine in the control of bacterial translocation. (+info)
The postnatal development of the alimentary canal in the opossum. I. Oesophagus.
The oesophageal epithelium of the newborn opossum generally is two to three cells in depth and in some regions appears pseudostratified. By the 9th postnatal day the epithelium shows two distinct strata. Ciliated cells and occasional goblet cells also are observed within the epithelium during this stage and in subsequent stages. Cilia persist in the oesophagus of the adult opossum, but are restricted to the depths of the transverse folds found in the distal part of the organ. The epithelium covering the transverse folds of the adult likewise has an immature appearance. By 4-5 cm (ca. 20 days), the epithelium has assumed a more mature appearance and is of greater depth. This and later stages show three basic strata: a germinal layer, a spinous layer and, adjacent to the lumen, a flattened layer of cells that retain their nuclei. The epithelium throughout the postnatal period and in the adult does not undergo complete keratinization. The oesophageal glands begin as outgrowths from the epithelium just prior to 4-5 cm (ca. 20 days). The glands continue their development throughout the remainder of the postnatal period. The secretory units of the oesophageal glands of the the major portion of the secretory elements, and a light, rounded cell type which is less numerous and which occupies the terminal portions of the secretory units. Secretory material of the former appears complex, consisting of both neutral and acid glycoproteins. The secretory product of the light cell type is unknown at present. Both cell types are encompassed by myoepithelial cells. The relationship of the mitotic sequences to the observations made by microscopic examination of the developing oesophagus is discussed. (+info)
Giardia induces proliferation and interferon gamma production by intestinal lymphocytes.
BACKGROUND: Murine intraepithelial lymphocytes kill Giardia lambia; responses of human intestinal lymphocytes to this parasite are unknown. AIMS: To examine giardia induced proliferation, interferon gamma production, migration, and cytotoxicity by lymphocytes from the human intestine and peripheral blood. METHODS: Giardia were added to intraepithelial lymphocytes, lamina propria lymphocytes, and peripheral blood lymphocytes, obtained from jejunal mucosa and blood of otherwise healthy patients undergoing gastric bypass surgery for morbid obesity. Proliferation was measured by 3H-thymidine incorporation; frequency of proliferation precursors, by limiting dilution analysis; interferon gamma production, by ELISA; cytotoxicity, by 51Cr release of radiolabelled giardia and by release of serine esterases by effector lymphocytes that mediate cytotoxicity. RESULTS: The CD4+ T lymphocytes from intestine and blood proliferated in response to giardia. The stimulus by the parasite was mitogenic rather than antigenic due to the fact that the peak response was on day 3 rather than day 6, and the large number of precursors was in the range of that for mitogens. CD4+ T lymphocytes from both sites produced interferon gamma in response to giardia. Lymphocytes did not migrate towards or kill the parasite. CONCLUSIONS: Giardia induced the same degree of proliferation and interferon gamma production by CD4+ T lymphocytes in intestine and blood, but did not trigger cytotoxicity or migration. (+info)
Expression of CD44 in Apc and Tcf mutant mice implies regulation by the WNT pathway.
Overexpression of cell surface glycoproteins of the CD44 family is an early event in the colorectal adenoma-carcinoma sequence. This suggests a link with disruption of APC tumor suppressor protein-mediated regulation of beta-catenin/Tcf-4 signaling, which is crucial in initiating tumorigenesis. To explore this hypothesis, we analyzed CD44 expression in the intestinal mucosa of mice and humans with genetic defects in either APC or Tcf-4, leading to constitutive activation or blockade of the beta-catenin/Tcf-4 pathway, respectively. We show that CD44 expression in the non-neoplastic intestinal mucosa of Apc mutant mice is confined to the crypt epithelium but that CD44 is strongly overexpressed in adenomas as well as in invasive carcinomas. This overexpression includes the standard part of the CD44 (CD44s) as well as variant exons (CD44v). Interestingly, deregulated CD44 expression is already present in aberrant crypt foci with dysplasia (ACFs), the earliest detectable lesions of colorectal neoplasia. Like ACFs of Apc-mutant mice, ACFs of familial adenomatous polyposis (FAP) patients also overexpress CD44. In sharp contrast, Tcf-4 mutant mice show a complete absence of CD44 in the epithelium of the small intestine. This loss of CD44 concurs with loss of stem cell characteristics, shared with adenoma cells. Our results indicate that CD44 expression is part of a genetic program controlled by the beta-catenin/Tcf-4 signaling pathway and suggest a role for CD44 in the generation and turnover of epithelial cells. (+info)
Developmental changes in mucosubstances revealed by immunostaining with antimucus monoclonal antibodies and lectin staining in the epithelium lining the segment from gizzard to duodenum of the chick embryo.
The mucosubstances in the epithelium lining the segment from gizzard to duodenum during development of the chick embryo was studied histochemically using monoclonal antibodies against gizzard mucus and lectins, with attention to the regional differentiation of the epithelium in this segment. The anterior limit of epithelial CdxA mRNA expression detected by in situ hybridisation, which served as the position of the gizzard-duodenal boundary, was clearly found from d 3. Granules positive for some antibodies or lectins were found in the region ranging from the posterior part of the gizzard to the duodenum at d 3, which was followed by an increase in the number of granules and a gradual enlargement of the granule-positive area to the anterior part of the gizzard over 4-6 d. From d 4, the epithelia of the gizzard body and of the pyloric or duodenal region came to be differently stained with some antibodies or lectins. From d 10, each region showed a specific pattern of staining. The epithelia of the gizzard body and pyloric region contained abundant mucus granules with a different staining pattern. In the duodenum the number of stained granules was low except in occasional goblet cells. Thus the epithelia of the gizzard body, pyloric region and duodenum may produce different mucosubstances and the regional differentiation in these epithelia may start at rather early stages soon after the formation of digestive tube. (+info)