Gene/Protein Disease Symptom Drug Enzyme Compound
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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

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

Ethanol consumption has a toxic effect on the epithelium of the small bowel, but enterocyte maturity is very difficult to measure under these circumstances. However, when ethanol intake is combined with enterectomy, enterocyte immaturity is greater, permitting an easier separation of these two effects. In a group of rats (13 male Wistar rats weighing approximately 220 g) fed a liquid diet containing 35% ethanol for 4 weeks after resection of the proximal jejunum, the residual small intestine brush border maltase, sucrase, and lactase activities were similar to those of a pair-fed control group (13 animals). However, alkaline phosphatase activity was decreased in the mucosa and in the enterocyte brush border, probably because of the lower activity of this enzyme in the jejunum-ileum remnant of the alcoholic group.
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PMID:Effect of chronic ethanol consumption on the activities of residual small bowel brush-border enzymes after proximal jejunum resection in the rat. 865 45

It has been hypothesized that human mucosal glucoamylase (EC 3.2.1. 20 and 3.2.1.3) activity serves as an alternate pathway for starch digestion when luminal alpha-amylase activity is reduced because of immaturity or malnutrition and that maltase-glucoamylase plays a unique role in the digestion of malted dietary oligosaccharides used in food manufacturing. As a first step toward the testing of this hypothesis, we have cloned human small intestinal maltase-glucoamylase cDNA to permit study of the individual catalytic and binding sites for maltose and starch enzyme hydrolase activities in subsequent expression experiments. Human maltase-glucoamylase was purified by immunoisolation and partially sequenced. Maltase-glucoamylase cDNA was amplified from human intestinal RNA using degenerate and gene-specific primers with the reverse transcription-polymerase chain reaction. The 6,513-base pair cDNA contains an open reading frame that encodes a 1,857-amino acid protein (molecular mass 209,702 Da). Maltase-glucoamylase has two catalytic sites identical to those of sucrase-isomaltase, but the proteins are only 59% homologous. Both are members of glycosyl hydrolase family 31, which has a variety of substrate specificities. Our findings suggest that divergences in the carbohydrate binding sequences must determine the substrate specificities for the four different enzyme activities that share a conserved catalytic site.
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PMID:Human small intestinal maltase-glucoamylase cDNA cloning. Homology to sucrase-isomaltase. 944 24