| 1. |
- Azerkan, Leila, et al.
(author)
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Characterization of oxyntic glands isolated from the rat gastric mucosa
- 2001
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In: Comparative Biochemistry and Physiology A. - 1095-6433 .- 1531-4332. ; 128:2, s. 349-357
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Journal article (peer-reviewed)abstract
- A simple and reproducible method for isolating oxyntic glands from the rat gastric mucosa was developed. The mucosa was incubated with pronase and EGTA, and then treated mechanically to release glands that were separated from single cells by sedimentation. Parietal cells were identified by immunostaining using a monoclonal antibody against H,K-ATPase. The glandular cells appeared morphologically intact. By careful control of the conditions of gland isolation, long glandular structures comprising hundreds of cells surrounding the lumen were obtained. Intraperitoneal injection of Br-deoxyuridine in the rat 1.5 h before the isolation procedure resulted in glands with a labeling of cells in their neck region. The glands were viable, as demonstrated by their ability to respond to various hormones. Histamine dose-dependently stimulated the acid formation which was measured as the accumulation of [14C]aminopyrine. At 100 microM histamine the accumulation was increased 5-10-fold. At 100 nM, pentagastrin potentiated the histamine stimulated accumulation by approximately 40% but pentagastrin alone did not stimulate. The oxyntic glands obtained by the present procedure appear useful for studies on cell physiology, including regulation of acid secretion, cellular interactions, and possibly also differentiation and proliferation mechanisms since long glandular fragments that contained the proliferative zone could be isolated.
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| 2. |
- Tømmerås, Karin, et al.
(author)
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Effects of Extracellular Matrix Proteins on Development of Fetal Rat Gastric Epithelial Cells in Culture
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Other publication (other academic/artistic)abstract
- Undifferentiated fetal gastric epithelial cells and stem cells of adult gastric glands give rise to surface mucous, parietal, mucous neck, zymogenic, caveolated, and endocrine cells by yet-unknown mechanisms. Our aim was to establish an in vitro model for investigating the effects of extracellular matrix proteins on development of gastric epithelial cells, and to determine whether collagen type I affects growth and maturation of undifferentiated epithelial cells. Fetal rat gastric cells were isolated and then cultured for 15 days on uncoated glass coverslips or on collagen types I or IV, fibronectin, or laminin. The appearance of epithelial cells was investigated by means of Alcian blue-periodic acid Schiff (AB-PAS) staining, inununostaining for cytokeratin, H,K-ATPase and chromogranin A, acridine orange accumulation, and by transmission and scamting electron microscopy. AB-PAS-positive cells containing mucous-type granules were detected. These mucoid cells were abundant on uncoated coverslips and collagen, but scarce on fibronectin and laminin. No cytokeratin, H,K-ATPase or chromogranin A, or increased acridine orange accumulation in response to secretagogues were observed. Rarely, endocrine cells were observed by electron microscopy. In conclusion, undifferentiated epithelial cells did proliferate and differentiate, and mucoid and endocrine cells matured in the established in vitro system. Moreover, development of mucoid cells from undifferentiated gastric epithelial cells was stimulated by collagen matrices but inhibited by fibronectin and laminin.
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| 3. |
- Tømmerås, Karin, et al.
(author)
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Expression of extracellular matrix proteins in the fetal rat gastric mucosa
- 2000
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In: Anatomy and Embryology. - 0340-2061 .- 1432-0568. ; 201:3, s. 149-156
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Journal article (peer-reviewed)abstract
- At gestational day 16 the epithelium of the rat stomach consists of a stratified layer of undifferentiated cells, and two days later glandular structures appear. The present study was carried out to identify extracellular matrix proteins that could be involved in the epithelial cell proliferation and differentiation processes that occur in the fetal rat stomach during this period. For comparative purposes the expression of the same components in the adult gastric mucosa was examined. Pregnant Sprague-Dawley rats received an intraperitoneal injection of 5-bromo-2’-deoxyuridine to label proliferating cells. One, 3.5, or 6 h post-injection the stomachs were excised and immediately frozen. The specimens were sectioned and stained with hematoxylin and eosin or for 5-bromo-2’-deoxyuridine, cytokeratin no. 8, H,K-ATPase, and the extracellular matrix proteins fibronectin, laminin, and collagens type I and IV. A stratified layer of proliferating cells was observed in the epithelium of the fetal stomachs, while in adult stomachs proliferating cells were detected in the isthmus/neck region of the glands. Cytokeratin, an epithelial cell marker, was sparse at gestational day 16 but abundant both at gestational day 18 and in the isthmus/neck region of gastric glands of the adult stomach. The parietal cell marker H,K-ATPase could not be detected in the fetal stomachs during this period. Fibronectin was observed in the stroma of both fetal and adult stomachs. Collagen type I could only be detected in the stroma close to the oesophagus at gestational day 16. Two days later, collagen type I was abundant in the lamina propria, the submucosa and in the serosa of the fetal stomachs. In adult tissue collagen type I was detected in the surface epithelium, the submucosa and in the serosa of the stomach. Collagen type IV and laminin were expressed in the lamina propria, the basement membranes around blood vessels, muscle cells, and nerve bundles, as well as in the serosa of both 16- and 18-day-old fetal and adult rat stomachs. In conclusion, a high cell proliferation rate was observed in the epithelium at both gestational days 16 and 18. The increased expression of cytokeratin observed during this period indicates that the epithelial character of the embryonic cells becomes more distinct, while the remarkable change in the expression of collagen type I might reflect an important role of collagen type I in the development of the gastric epithelium.
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| 4. |
- Tømmerås, Karin, et al.
(author)
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Immunolocalization of Cholecystokinin-2 Receptors in Rat Gastric Mucosa
- 2002
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In: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 37:9, s. 1017-1024
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Journal article (peer-reviewed)abstract
- BACKGROUND: Gastrin exerts trophic effects on the gastric mucosa by mechanisms not yet completely elucidated. Our aim was to localize the cholecystokinin-2 (CCK2) receptor in epithelial cells of foetal and adult rat stomachs in order to determine the cell types that are directly affected by gastrin.METHODS: Gastric tissue was subjected to indirect double immunofluorescence staining with antiserum against the C-terminal decapeptide of the CCK2 receptor and antibodies against 5' bromo-2-deoxyuridine, which had been injected into the rats I h before they were killed, the acid pump H,K-ATPase, the membrane-cytoskeletal linker ezrin, pepsin/pepsinogen or histidine decarboxylase.RESULTS: Undifferentiated foetal gastric epithelial cells expressed CCK2 receptors, whereas stem cells of adult gastric glands did not exhibit immunoreactivity. However, other epithelial cells in the progenitor zone of adult gastric glands did express CCK2 receptors. Some of these cells were faintly stained for H,K-ATPase; pepsin/pepsinogen was also detected in this region. Parietal cells in the isthmus/pit region of the glands contained ezrin, and some showed weak immunoreactivity for the CCK2 receptor. As expected, enterochromaffin-like cells also expressed CCK2 receptors.CONCLUSION: Our findings are consistent with the hypothesis that a CCK2 receptor mediates direct effects of gastrin on gastric epithelial cells during both stomach organogenesis and adult life.
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| 5. |
- Tømmerås, Karin, et al.
(author)
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Proliferation and differentiation of cells from explants of fetal rat stomach
- 1997
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In: Acta Physiologica. - 1748-1708 .- 1748-1716. ; 159:2, s. 155-161
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Journal article (peer-reviewed)abstract
- The current understanding of the mechanisms controlling the proliferation and differentiation of the stem cells of the gastric oxyntic glands is limited. The aim of the present study was to develop a method for investigating proliferation and differentiation of undifferentiated cells from fetal rat stomach. Outgrowth of cells was initiated from explants of 16-day-old fetal rat stomachs. At this stage of the fetal development the gastric epithelial cells are undifferentiated. The explants were cultured in DMEM/F-12 medium supplemented with fetal calf serum only, or fetal calf serum combined with either hydrocortisone or pentagastrin. Morphological characterization by means of light microscopy, dye staining and immunostaining was used to identify the growing cells. Both hydrocortisone and pentagastrin accelerated the differentiation towards H,K-ATPase-positive cells, mucus-producing cells and other epithelial cells. H,K-ATPase-positive cells, which were identified by immunostaining with a monoclonal antibody reacting with the α-subunit of the H,K-ATPase, grew on top of the confluent layer of epithelioid and fibroblastoid cells. With this method in vitro investigations of the mechanisms of proliferation and differentiation of gastric mucosal cells are possible. Although by different mechanisms, both hydrocortisone and pentagastrin appear to play a regulatory role in these processes.
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| 6. |
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| 7. |
- Tømmerås, Karin
(author)
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The role of gastrin and extracellular matrix proteins in proliferation and differentiation of gastric epithelial cells
- 2000
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Doctoral thesis (other academic/artistic)abstract
- The mechanisms regulating the proliferation and differentiation processes that give rise to and maintain the gastric epithelium have not yet been completely elucidated.In the present studies, in vitro models were established and the influence of growth factors and extracellular matrix proteins on these processes were investigated. Pentagastrin and hydrocortisone were found to accelerate the development of H,KTPase-positive parietal cells and other epithelial cells from undifferentiated gastric epithelial cells of foetal rats. These undifferentiated cells and also presumably immature epithelial cells in the progenitor zone of adult gastric glands were shown to express cholecystokinin-2 (CCK2) receptors and are therefore targets for the trophic action of gastrin.H,K-ATPase-positive parietal cells in the progenitor zone of adult glands were also found to express CCK2 receptors, indicating that gastrin may stimulate maturation of the parietal cell lineage even during adult life. Parietal cells located in the upper region of the glandular unit are probably responsible for most of the acid secretion, because these cells were found to express the membrane-cytoskeletallinker ezrin, reported to be present in the canaliculi of stimulated parietal cells.Pulse-labelling with 5-bromo-2'-deoxyuridine showed that during the gestational period, when the main motphological conformations and maturation of the gastric epithelium occur, proliferating cells appear at the basal epithelial cell layer and migrate towards the gastric lumen. This indicates that epithelial-mesenchymal cell and cell-matrix interactions may be involved in regulation of the cell proliferation and differentiation. Investigation of the expression of extracellular matrix proteins in foetal rat stomachs revealed a marked increase in collagen type I, suggesting that collagen, which is known to stimulate epithelial cell proliferation, is involved in the initial folding of the embryonic epithelium and formation of glandular structures.In experiments in vitro, development of mucus-producing cells from undifferentiated gastric epithelial cells was stimulated by collagens but inhibited by fibronectin and laminin. In adult gastric epithelium, collagen type I was present only in the pit region of the glandular unit, where surface mucous cells are located. Thus, collagen type I, which is overexpressed in gastric ulcers and gastric cancers, likely stimulates proliferation of mucus-producing cells.In conclusion, expression of CCK2 receptors was detected in foetal gastric epithelium and in the progenitor zone of adult gastric epithelium, implying that gastrin exerts trophic effects on immature gastric epithelial cells, during both stomach organogenesis and adult life. The spatial and temporal expression of extracellular matrix proteins and the effects of these proteins on development of mucus-producing cells in vitro indicate that extracellular matrix proteins may play an important role in regulation of epithelial cell proliferation and differentiation, and thus in the maintenance of normal cellular composition and function ofthe gastric epithelium.
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