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 survival and prognosis of the prematurely born human infant are dependent on a successful transition from the intrauterine to the extrauterine environment. This is largely a consequence of the maturation of sufficient gastrointestinal function to provide adequate nutrition. However, the gastrointestinal tract of the premature infant, and to some extent, of the full-term infant, may be unprepared to provide the requisite absorptive function. Data presented in this symposium emphasize the dissociations in the development of human gastrointestinal function. Morphological maturation is completed early in gestation while glucose absorption increases with gestational age. Sucrase and maltase activities appear early; lactase activity begins to increase at 30 weeks and increases steadily to term. The latter pattern is accompanied by increased production of cortisol and thyroid in the fetus. The intraluminal phase of fat digestion is immature even in the full-term neonate. Both pancreatic secretory function and bile salt metabolism mature postnatally. Despite this relative immaturity, breast milk fat is absorbed with great efficiency by the term infant, and breast milk provides other important influences on intestinal development: mitogenic factor, immunological support, control of intestinal flora. The goals of nutrition support of the premature infant have been to maintain intrauterine growth standards; yet premature infants receiving pooled breast milk from mothers at 40 weeks or more may be given too little protein for their needs. Human milk from mothers of premature infants may be a more appropriate nutrient source. Supplements with higher contents of amino acids may lead to amino acid imbalance or hyperammonaemia. Additional stresses and requirements are imposed by illness or congenital anomalies. While we must apply current research findings to clinical care, we must also extend our knowledge of extrauterine human development. The ultimate measure of success in this field will be the physical and neurological capacities of infants followed prospectively.
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PMID:The immature intestine: implications for nutrition of the neonate. 9 85

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

Circulating non-T lymphocytes had higher activities of 5'nucleotidase (plasma membrane), neutral alpha-glucosidase (endoplasmic reticulum) and basal leucine amino-peptidase than did T lymphocytes. Activities of catalase (peroxisomes), malate dehydrogenase (mitochondria), lactate dehydrogenase (cytosol) and N-acetyl-beta-glucosaminidase, beta-glucuronidase and acid phosphatase (lysosomes), were similar in the lymphocyte subfractions. Lymphocyte 5'nucleotidase (plasma membrane) in patients with common variable hypogammaglobulinaemia is much lower than normal. However, the decrease is less marked in X-linked hypogammaglobulinaemia, chronic lymphatic leukaemia or protein loosing enteropathy or in lymphocytes isolated from cord blood. Cells from patients with nephrotic syndrome had normal levels of 5'nucleotidase. Other plasma membrane marker enzymes (gamma-glutamyl transferase, leucine amino-peptidase) were normal in lymphocytes from patients with common variable hypogammaglobulinaemia. There is a selective reduction of mitochondrial (malate dehydrogenase) and cytosolic (lactate dehydrogenase) enzymes, with normal activities of lysosomal, peroxisomal and endoplasmic reticulum enzymes, in patients with common variable hypogammaglobulinaemia. The lymphocyte subcellular organelles in normal subjects and patients with common variable hypogammaglobulinaemia have similar properties on sucrose density gradient centrifugation. It is suggested that lymphocytes from patients with common variable hypogammaglobulinaemia show a specific enzymopathy and that this is not simply a reflection of cellular immaturity.
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PMID:Lymphocyte enzyme activities in immunodeficiency syndromes with particular reference to common variable hypogammaglobulinaemia. 630 45

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

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

Intestinal epithelial brush border hydrolases are important and sensitive enzyme markers of gastrointestinal development and function. Little is know about the mechanisms that regulate the induction of these enzymes during human fetal development, as these events occur primarily in utero. The present work used ectopically grafted human fetal jejunal xenografts (median age,13.3 wk of gestation), maintained in severe-combined immunodeficient mice, to study the differential expression of five different hydrolases after 10 wk of xenotransplantation. The spatio-temporal distribution of brush border alkaline phosphatase, aminopeptidase-N, alpha-glucosidase, lactase-phlorizin hydrolase, and dipeptidyl peptidase IV enzyme activities were measured quantitatively using scanning microdensitometry along the crypt-villus axes of fetal, xenograft, and pediatric (median age, 34 mo) biopsies. Ectopic grafting of fetal jejunum closely recapitulated the development of these enzymes in utero, with alkaline phosphatase, aminopeptidase-N, alpha-glucosidase, and dipeptidyl peptidase IV enzyme activities closely matching the spatio-temporal distribution and levels recorded in pediatric duodenal biopsies. Lactase-phlorizin hydrolase was the only enzyme not to reach values recorded in pediatric brush border membranes, although activities were significantly (5.6-fold) higher than in pretransplanted fetal bowel. Human jejunal xenografts therefore demonstrate an appropriate developmental induction of brush border hydrolase activity and may represent a useful model to study trans-acting factors that promote human epithelial differentiation and function in vivo. Characterization of such agents may be of potential therapeutic use in the treatment of diseases associated with gastrointestinal immaturity, notably necrotizing enterocolitis.
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PMID:Developmental regulation of intestinal epithelial hydrolase activity in human fetal jejunal xenografts maintained in severe-combined immunodeficient mice. 1147 3