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Query: UMLS:C0029713 (immaturity)
 4,335 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The differentiation status of epithelial cells in intestinal adaptation remains unclear. To determine whether enterocytes reach optimum maturity following adaptation after 85% shortening of the rat gut by jejunoileal bypass surgery, activities of two brush border enzymatic markers of differentiation, alkaline phosphatase and sucrase, were examined in subpopulations of epithelial cells isolated sequentially from the villus/crypt axis of normal (sham operated) and hyperplastic mucosa. In jejunal villi, adaptational hyperplasia was associated with an increase in total epithelial alkaline phosphatase, but not total sucrase, activity; alkaline phosphatase activity increased most obviously in cells at the 11-50% position (from the tip) on villi. In hyperplastic ileal villi, total alkaline phosphatase activity fell, although sucrase activity did not change significantly. Specific activity (per mg protein) of sucrase on jejunal villus epithelium was reduced by the adaptational changes to bypass; alkaline phosphatase specific activity remained unchanged. In the ileum, despite adaptational changes to bypass, there was no increase in the normally low specific activities of sucrase and alkaline phosphatase. Bypass surgery did not change the major site of expression of either enzyme on jejunal or ileal villi. In conclusion, enzymatic markers of functional differentiation are not all equally affected by adaptational hyperplasia. Hypertrophy of villi and increased cell proliferation seen in jejunum remaining exposed to luminal contents resulted in an increase in the alkaline phosphatase but not the sucrase content. This is not, therefore, the result of a simple immaturity of villus cells. Morphological adaptation in the ileum, however, is not accompanied by adaptation of brush border enzyme markers of differentiation, confirming a functional immaturity of these cells. Strategies for increasing the expression of these markers may have clinical value.
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PMID:Differentiation status of rat enterocytes after intestinal adaptation to jejunoileal bypass. 148 65

Mucosal histology, crypt cell proliferation and brush border enzymes were measured in rats with varying degrees of jejunoileal bypass, in order to compare the effect of systemic and luminal factors on adaptive growth and differentiation (brush border enzymes) in small intestinal epithelium. Eighty five percent jejunoileal bypass caused a functional short gut; in intestine remaining in continuity there were significant increases in segmental weight, villus area and crypt depth, compared with sham operated controls and 25% jejunoileal bypass rats. Despite villus cell hyperplasia in 85% bypass rats, mucosal sucrase and alkaline phosphatase fell in jejunum and remained low in ileum, while leucine amino peptidase rose in ileum. There was a significant fall in villus area (p less than 0.01) and crypt cell production (p less than 0.001) in self emptying loops of 25% bypass rats not exposed to luminal contents compared with control segments of sham operated rats. In contrast, self emptying loops of 85% bypass rats were not atrophied despite the much greater distance from luminal nutrients; the villus area (p less than 0.01) and crypt cell production (p less than 0.005) were higher than in 25% bypass rats, and at least as great as in sham operated rats. These results indicate that adaptive hyperplasia has a variable effect on expression of brush border enzymes which might reflect villus cell immaturity. The atrophic effect of diversion of luminal contents can be counteracted by systemic growth factors released as part of the adaptive response; thus systemic growth factors are not dependent on a permissive effect of luminal contents.
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PMID:Systemic factors are trophic in bypassed rat small intestine in the absence of luminal contents. 238 26

The ability of adapting ileal enterocytes to express different digestive enzymes in their brush border membranes was tested in young female Wistar rats (n = 72) receiving 60% proximal small bowel resection. In control rats with intestinal transection both neutral aminopeptidase and alpha-glucosidase activities were shown, by quantitative cytochemistry, to increase during enterocyte migration over the lower part of the villus; thereafter enzyme activities declined or remained approximately constant. Proximal enterectomy increased the amount of alpha-glucosidase but not neutral aminopeptidase activity appearing during early enterocyte development. Thymidine labelled autoradiography showed that the rate of enterocyte migration along the ileal villus nearly doubled after jejunal resection (19.3 v 11.1 microns/h). Nevertheless, the time taken for both peptidase and saccharidase activities to appear at maximal rates in the brush border membrane was diminished by about five hours. Thus ileal enterocytes adapt to proximal small bowel resection by selective increments in enzyme expression, findings that contradict the previous hypothesis of simple metabolic immaturity.
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PMID:Increased activity of digestive enzymes in ileal enterocytes adapting to proximal small bowel resection. 288 50

During the suckling period in mammals, the immaturity of the digestive function as well as several functional pecularities lead the gastrointestinal physiology to adapt to milk digestion and absorption. The dietary transition which occurs at weaning is accompanied by wide modifications as neonatal properties are lost and mature digestive functions are acquired. The involvement of factors like tissue interaction, hormones and nutritional substrates in the onset and subsequent maturation of intestinal brush border hydrolases is discussed.
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PMID:[Development of the digestive function: regulation of the maturation of intestinal brush border enzymes]. 308 91

The transport of ions and solutes at the epithelial surface of the renal proximal tubule increases during periods of reduced dietary intake and decreases with dietary excess. We have used the sulfur-containing beta-amino acid, taurine, as a probe of this renal adaptive response to altered dietary sulfur amino acid intake to better understand the mechanisms of renal amino acid reabsorption. There exists an age-related precession of taurine uptake values by brush border membrane vesicles prepared from nursing rats from youngest to oldest. However, despite the immaturity of this transport mechanism, epithelial membranes become able to display a full renal adaptive response to altered sulfur amino acid intake sometime between the 7th and 14th day of life. This adaptive response is expressed in both "up regulation" and "down regulation" by means of a change in the initial rate of Na(+)-taurine cotransport. No changes in the lipid microenvironment of the membrane, as assessed by measurements of membrane fluidity, are evident. The lack of adaptation observed in 7-day-old pups may be due to immaturity of the Na+ transporting mechanism which energizes the uptake of amino acids.
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PMID:Renal adaptation to dietary amino acid alteration is expressed in immature renal brush border membranes. 315 88

Taurinuria is characteristic of the immature rat. The excessive taurine loss could be the result of brush border or basal lateral membrane immaturity. The beta-amino acid, taurine, and D-glucose were examined using isolated brush border membrane vesicles (BBMV), slices and tubules prepared from 28-day-old rats. In BBMV, taurine accumulation was inversely proportional to osmolarity, indicating uptake rather than binding, and taurine accumulation was Na+-dependent. BBMV from 28-day rats did not accumulate D-glucose to the same degree as in adult BBMV, and the initial rate of uptake was slower. Taurine uptake had a similar Km and Vmax in BBMV from immature rats. Despite similarities in the kinetics of taurine uptake, higher urinary taurine concentrations are found in younger rats. The efflux of taurine from slices and tubules was much slower than in adults and probably accounts for the taurinuria of young animals. A diet low in methionine and taurine (LTD) given for seven days resulted in a lower excretion and fractional excretion of taurine than in animals fed a normal sulfur amino acid diet (NTD). A high-taurine diet (HTD) causes excessive taurinuria. These patterns of excretion are reflected at the brush border membrane surface with greater uptake after the LTD and reduced uptake after the HTD. A kinetic analysis of adult and 28-day-old animal BBMV reveals that the Vmax of accumulation is altered by diet, whereas the Km remains unchanged. The Vmax is higher in BBMV from LTD animals and lower in BBMV from HTD animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Divergent membrane maturation in rat kidney: exposure by dietary taurine manipulation. 403 Feb 27

The "in situ" kinetic constants (app. Km and Vmax) of brush border neutral alpha-glucosidase (EC 3.2.1.20) and lactase/beta-glucosidase (EC 3.2.1.21) were determined 4,6 (only alpha-glucosidase), and 12 days after 60% proximal intestinal resection in rat ileum at the villus base and the transition zone between middle and upper villus third by use of a quantitative biochemical analysis of enzymes in tissue sections (section biochemistry). Sham-operated rats served as controls, and the kinetic data (means per rat, time and villus position) were compared (n = 4 animals in each experimental group) first by an overall factorial analysis of variance and thereafter in detail using nonparametric test procedures. Both enzyme activities exhibited a differential response: No changes of lactase/beta-glucosidase kinetics, but a significant decrease in both Vmax- and Km-values of neutral alpha-glucosidase, which was already fully expressed on day 4 after resection and confined to the apical villus region still implying a basoapical increase of Vmax and thus maintaining the normal activity gradient on a lower level. In conclusion, a complex pattern of enzymatic adaptation to proximal intestinal resection ensues in the hyperplastic ileal mucosa which cannot be explained simply in terms of the hypothesis of cellular immaturity.
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PMID:The adaptive response of disaccharidase activities at different sites along the villus epithelium after proximal intestinal resection in the rat. A microdensitometric study of enzyme kinetics. 641 38

Mucin secretion was examined in three functional models relevant to human disease, using rat small intestinal rings or in situ loops, [3H]glucosamine precursor labelling, gel chromatography and a specific radioimmunoassay for mucin. As a model for acute bacterial secretory diarrhoea, tissues were exposed to cholera toxin for up to 4 h. Both stored and newly synthesized radioactive glycoproteins were secreted in amounts twofold to threefold above control levels. Immunoreactive mucin secretion increased fivefold to eightfold. Other agents known to raise cAMP levels did not stimulate mucin secretion, suggesting that cholera may release mucin by a non-cAMP-dependent mechanism. Sepharose 2B chromatography indicated that secreted mucin was smaller in size than intracellular mucin and had compositional differences suggestive of 'immaturity' or protein contamination. In chronically (seven days) reserpinized rats, used as a model of glycoprotein abnormalities relevant to cystic fibrosis, mucin secretion increased twofold to threefold, but the most prominent abnormality was a marked increase in [3H]glucosamine incorporation into all tissue glycoproteins. On purification, the intracellular mucin of reserpine-treated rats had the same composition as mucin from control rats, but the former was smaller in size and had a higher specific radioactivity. Mucin hypersecretion in reserpinized rats may therefore be secondary to a primary and chronic hyperstimulation of mucin biosynthesis. A model of intestinal 'anaphylaxis' or immune-mediated diarrhoea was created in Hooded Lister rats by immunizing with egg albumin (10 micrograms) and challenging with the same antigen in intestinal loops 14 days later. After 4 h, total protein, DNA and brush border sucrase were increased in the lumen. Enhancement of mucin secretion did not occur, however, and therefore does not seem to be a particular feature of the pathophysiology of this model.
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PMID:Acute and chronic models for hypersecretion of intestinal mucin. 656 39

In an attempt to correlate host and parasite-related events occurring during the course of a primary Giardia infection in the mouse we have measured epithelial cell kinetics, enzymes, and intraepithelial lymphocytes at different stages of the infection. New methods were developed for the accurate measurement of parasite numbers and distribution within the gut. In jejunum a modest decrease in villus length and intraepithelial lymphocytes at week 1 preceded a pronounced disaccharidase deficiency at week 2, the time of maximum trophozoite numbers, whereas crypt lengthening and increased cell production became maximal at week 3. As trophozoite numbers fell the intraepithelial lymphocyte count and disaccharidase values rose. With the exception of the intraepithelial lymphocyte count, which followed the same pattern as in jejunum but two weeks later, the changes seen in the ileum were the opposite of those in jejunum, suggesting rapid ileal adaptation. The results indicate that the disaccharidase deficiency associated with giardiasis is likely to represent a direct effect of the parasite on the brush border rather than enterocyte immaturity, whereas the intraepithelial lymphocyte response reflects host immunity to the parasite. Profound adaptive changes occur throughout the small intestine in response to a relatively localised insult.
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PMID:Features of small intestinal pathology (epithelial cell kinetics, intraepithelial lymphocytes, disaccharidases) in a primary Giardia muris infection. 707 25

Literature reports that chronically ingested ethanol induces changes in the morphology of the small bowel mucous membranes. It has a topical toxic effect on the epithelium of the proximal jejunum and a blood-borne effect on the epithelium of the ileum because its absorption is almost complete in the stomach, duodenum and proximal jejunum. In addition there are also reports showing stimulation of enterocyte proliferation after segmental intestine resection. In this report we compare a group of rats submitted to resection of the proximal jejunum and fed a liquid diet containing 35% of the total calories intake as ethanol for four weeks to its control pair-fed group. In both groups we studied the mucosal alkaline phosphatase (APase) activity by histochemical as well as biochemical methods. We found a decreased APase activity in the homogenate of the intestinal mucous membrane in the alcoholic group and a reduced enzymatic activity in the brush border of the ileum enterocytes, as demonstrated by histochemical qualitative and densitometric assays. The result suggests that this change in APase activity of the brush border may represent enterocyte immaturity induced by long-standing ethanol intake in the remnant ileum after proximal resection.
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PMID:Ileum brush border alkaline phosphatase activity in an experimental model of chronic alcoholism after small bowel proximal resection in the rat. 778 32


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