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At least 55 records · Page 3Linked to original sources
PubMed2000

Integrins as mediators of epithelial cell-matrix interactions in the human small intestinal mucosa.

The intestinal epithelium is a highly dynamic tissue, which depends on a variety of factors for the regulation of its rapid renewal and expression of digestive functions. Over the last 10 years, it has become evident that among these factors are cell interactions with the extracellular matrix, more specifically with the underlying basement membrane, through a series of specific cell membrane receptors, many of which are integrins. Integrins regulate the assembly of adhesive junctions as well as the activation of various signaling pathways, leading to the modulation of gene expression. The analysis of the integrin repertoire along the crypt-villus axis in the human small intestinal epithelium identifies a number of beta1 and beta4 integrins, showing differential patterns of expression relative to its two functional compartments. Among them are the integrins alpha3beta1, alpha7Bbeta1 and the functional form of alpha6beta4 that appear to be related, in concert with the distribution of their ligands, to the process of intestinal cell differentiation, and the integrins alpha2beta1, alpha1beta1, alpha5beta1, and the non-functional form of alpha6beta4 that seem to be coupled with the undifferentiated/proliferative status of crypt cells. These observations delineate the potential complexity of the organization of epithelial cell-matrix interactions involved in the maintenance of the human intestinal crypt-villus axis.

Basement Membrane↗
PubMed1991

Neuroimmunomodulation in the intestinal mucosa.

The intestine contains major subdivisions of the nervous and immune systems. The lymphoid compartments of the intestine contain functionally distinguishable populations of immunologic cells and are innervated differently. The lamina propria has an extensive network of nerves using the neuropeptides SOM, SP, and VIP. Subpopulations of T cells, B cells, cells of the monocyte/macrophage line, and several other immunologically relevant cells have the ability to recognize and respond to these neuropeptide signals. SOM, SP, and VIP can act as potent regulators of lymphoid cell proliferation and interleukin and immunoglobulin production. The unusual effector lymphocytes in the epithelial layer of the intestine can be exposed to SP and VIP, and their responses may be regulated by these peptides. In the organized lymphoid compartments such as Peyer's patches, the neuropeptides VIP and SP may regulate the accumulation or recirculation of affector lymphocytes from the central compartment of the immune system and their subsequent response to antigens. The large array of immunoregulatory effects that have been found with these neuropeptides suggest that local neurophysiologic signals in the intestinal lymphoid microenvironments can regulate selected aspects of immune responses. The intestine is likely to be a highly specialized venue for neuroimmunomodulation in intact animals, and this has important implications in the physiologic and pathologic responses of the gut. Further investigations of these regulatory pathways will lead to new concepts concerning neural-immune interactions in general and the regulation of mucosal immunology in particular.

Animals↗
PubMedDate not supplied

Differentiation and aging of the intestinal mucosa of the rat. I. Morphological, enzyme-histochemical and disc electrophoretic aspects of the prenatal and postnatal differentiation of the intestinal mucosa.

The large and small intestines of fetal, newborn, juvenile and adult rats were investigated at various points by means of enzyme histochemistry, disc electrophoretic separations of enzymes and electron microscopy. The results obtained permit division of the morphological and enzymatic differentiation of the rat intestinal epithelium into four periods of development. 1. The period of prenatal development from the 19th to the 21st fetal day with a continuous increase of the enzyme activities in the enterocytes of the entire intestinal mucosa. 2. The period of postnatal development from the first day of life until the end of the second week with enzyme activity remaining roughly the same compared with the 21st day of life. 3. The period of adaptation from the beginning of the third week of life up to the middle of the fourth week of life. During this phase the transition into the stage of adult maturity occurs both morphologically and enzymatically. 4. The stage of adult maturity, which is fully developed in the middle of the fourth week of life.

Acid Phosphatase↗
PubMed1997

Organization of the lamina propria mucosae of rat intestinal mucosa, with special reference to the subepithelial connective tissue.

Light microscopy, scanning electron microscopy and transmission electron microscopy have been used to delineate the structure and function of the lamina propria mucosae in the rat jejunum. In silver-impregnated sections, the adepithelial surface of the lamina propria mucosae was framed by a sheet of reticular fibers (reticular sheet). Short-term (3-hour) immersion of jejunal tissues in 2 N NaOH solution enabled us to simultaneously view networks of reticular fibrils and fibroblasts residing in the subepithelial connective tissue under a scanning electron microscope. The reticular fibrils, which measured about 40 nm in diameter and were interwoven in dense networks, formed a sheet 2-3 microns thick. In the villi, this sheet contained numerous foramina ranging from 3 to 7 microns in diameter, through which lymphocytes, macrophages, basal extensions of epithelial cells and fat particles traversed. The reticular sheet in the domes of isolated lymphoid nodules was markedly porous, and many lymphocytes migrated into or out of the epithelium through the foramina. The formaina of the reticular sheet may participate in the communication between the intestinal epithelium and the lamina propria mucosae. It was noted that the foramina of the reticular sheet in the villi were surrounded by end feet of the cytoplasmic processes of fibroblasts. In addition, these fibroblasts were combined with lymphocytes or dendritic cells in the lamina propria mucosae.

Animals↗
PubMed1996

Impaired defense of intestinal mucosa in mice lacking intestinal trefoil factor.

The mechanisms that maintain the epithelial integrity of the gastrointestinal tract remain largely undefined. The gene encoding intestinal trefoil factor (ITF), a protein secreted throughout the small intestine and colon, was rendered nonfunctional in mice by targeted disruption. Mice lacking ITF had impaired mucosal healing and died from extensive colitis after oral administration of dextran sulfate sodium, an agent that causes mild epithelial injury in wild-type mice. ITF-deficient mice manifested poor epithelial regeneration after injury. These findings reveal a central role for ITF in the maintenance and repair of the intestinal mucosa.

Animals↗
PubMed2001

Antioxidative properties of pig vesical mucosa: a comparison with gastric and intestinal mucosa.

The antioxidative properties of pig urinary bladder mucosa were compared with those of gastric and intestinal mucosa using nitroxide radicals. Electron paramagnetic resonance (EPR) method was used to monitor the metabolic processes of nitroxides in mucosae. The reduction of nitroxides was measured on intact luminal surfaces of gastric, intestinal, and urinary bladder mucosa, as well as in homogenates of mucosa surface layer. Furthermore, N-ethylmaleimide and ascorbate oxidase have been used to characterize the reducing agents in urinary bladder mucosa homogenates. The nitroxide concentration decrease on intact mucosa of the urinary bladder was significantly different from those of the gastric and the intestinal mucosa. The concentration decrease was the largest for intestinal mucosa and the smallest for bladder mucosa. On the other hand, homogenates exhibit the largest nitroxide reduction rates for the bladder mucosa and the smallest for the gastric mucosa. In the bladder surface layer homogenates ascorbate and thiol-containing reducing agents were found and their coupled action in the nitroxide reduction process was established. The mucosa of urinary bladder is protected against nitroxide free radicals by a relatively low permeability and very active endogenous reducing agents. The gastric and intestinal mucosa are more permeable and/or have greater antioxidant activity on their surface. The reduction of nitroxides in the urinary bladder mucosa occurs via the ascorbate-thiol coupled reducing system.

Animals↗
PubMed1987

[Disaccharidases and peptidases of intestinal mucosa after experimental subtotal small intestinal resection with and without retardation of the passage].

Several operating methods for retardation of the passage were compared together after resection of 75% of the mid-small-bowel for preventing a malabsorption syndrome. Morphologic and enzyme-histochemical findings of the intestinal mucosa allow conclusions on the absorptive capacity of the residual intestine. The investigations were carried out one year after the operation. The lay-out of an antiperistaltic segment for the surgical therapy of the short bowel syndrome appears specially suitable after the results of this investigation.

Animals↗
PubMed2002

Interactions between the microbiota and the intestinal mucosa.

The intestinal microflora can be considered as a postnatally aquired organ composed of a large diversity of bacterial cells that can perform different functions for the host. This organ is highly exposed to environmental influences and thus modulated in its composition and functions by external factors, such as nutrition. Specific components of the intestinal microflora, including lactobacilli and bifidobacteria, have been associated with beneficial effects on the host, such as promotion of gut maturation and integrity, antagonisms against pathogens and immune modulation. In addition, the microflora seem to play a significant role in the maintenance of intestinal immune homeostasis and prevention of inflammation. At the present time, the contribution of intestinal epithlial cell in the first line of defence against pathogenic bacteria and microbial antigens has been recognized, in contrast, the interactions of intestinal epithelial cells with commensal bacteria are less understood. The present work summarizes the increasing scientific attention for mechanisms of the innate immune response of the host to different components of the autochthonous microflora and suggests a potential role for selected probiotic bacteria in the regulation of intestinal inflammation.

Bifidobacterium↗