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Diabetes stimulates the functional activity of the intestinal brush border membrane with enhancement of both hydrolytic enzyme activity and membrane transport systems. To determine the mechanism of this effect, we studied the effects of streptozotocin diabetes on the metabolism of one membrane protein, sucrase-isomaltase, which increases its activity in diabetes. The protein was purified and an antiserum prepared. Sucrase-isomaltase from control and diabetic rats was immunologically identical as shown by Ouchterlony double-diffusion analysis of papain-solubilized mucosal proteins. The increase in sucrase enzyme activity in diabetic animals (31.0+/-1.4 U SEM 5 days after streptozotocin vs. 13.1+/-1.0 in controls) was the consequence of increased enzyme protein and not an alteration in catalytic efficiency as demonstrated by quantitative immunoprecipitin reactions. To account for increased sucrase-isomaltase protein in diabetes we studied papain-solubilized mucosal proteins labeled by injection of [(14)C]carbonate and [(14)C]leucine and analyzed incorporation into sucrase-isomaltase protein (anti-serum precipitable) and total protein (trichloroacetic acid precipitable). We found that diabetes did not affect the decay of labeled total protein, but prolonged the decay of labeled sucrase-isomaltase. t((1/2)) of sucrase-isomaltase was 4.4 h in control animals after [(14)C]carbonate injection and 8.8 and 10.2 h, respectively, 2 and 5 days after induction of streptozotocin diabetes. We obtained similar results in experiments with [(14)C]leucine with diabetes increasing t((1/2)) from 6 to 13.6 h. Diabetes did not appear to increase the rate of addition of sucrase-isomaltase to the brush border membrane, since it did not affect the 10- and 60-min incorporations of isotope into sucrase-isomaltase protein relative to incorporation into total protein and did not alter rate constants for synthesis calculated from the t((1/2)) and the change in enzyme mass over time.Thus, enhanced sucrase activity in the diabetic animal is the consequence of an increase in sucrase-isomaltase protein which develops because of a decrease in its rate of degradation.
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PMID:The intestinal brush border membrane in diabetes. Studies of sucrase-isomaltase metabolism in rats with streptozotocin diabetes. 14 62

RDEC-1 is a piliated strain of Escherichia coli that was isolated from and produces diarrhea in rabbits without invading the mucosa or synthesizing one of the classical enterotoxins. Previous histological and fluorescent-antibody studies of RDEC-1 diarrhea revealed an acute inflammatory response and large numbers of RDEC-1 associated with (adhering to) the mucosal surface of the ileum, cecum, and colon. The purpose of the present investigation was to further elucidate the histopathology by scanning (SEM) and transmission (TEM) electron microscopy. SEM revealed aggregates of bacteria on the surface of the gut; their distribution was patchy in the ileum and diffuse in the cecum and colon. Bacteria were in contact with each other and appeared to be closely associated with the epithelial surface. TEM showed that the brush border region of the epithelial cells was found to be in varying stages of degeneration, and the bacteria could not be seen adhering to the mucosal cells unless the brush border was absent. Bacteria were in close contact only with epithelial cells that had lost their brush border. The space between the bacteria and the epithelial cells was 11 nm, and it appeared to be filled, in most cases, with densely stained material. This E. coli rarely penetrated epithelial cells, but when it did; it was found in the supranuclear region and never reached the lamina propria. From previous and present studies, it seems probable that RDEC-1 produces diarrhea in rabbits by a mechanism that may be cytotoxic and differs from the classic mechanisms by which E. coli produces diarrhea.
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PMID:Scanning and transmission electron microscopic study of Escherichia coli O15 (RDEC-1) enteric infection in rabbits. 34 19

The in vivo effects of the anthelmintics taenifugin, VUFB 14170 and VUFB 15269 on the tegument of Hymenolepis fraterna have been examined by SEM, TEM and cytochemistry. The drugs were given to H. fraterna-infected mice on the 14th day post-infection in a single oral dose of 150, 200 and 200 mg/kg, respectively. By 72 h post-treatment, the drug-induced pathomorphological changes in the tegument indicated that all three drugs had a significant effect. Changes were most pronounced on the brush border and in the intercellular material. On the apical surface, there was blebbing as well as accumulation of membrane fragments over the microthrix tips and erosion of the brush border. The intercellular material was changed in structure, showing increased electron density in some areas and oedema of the intercellular spaces in other areas. There were also fractures of the tegument of variable depth, sometimes reaching to the parenchyma. These results suggest altered tegumental integrity and, occasionally, complete disruption of the selective permeability barrier created by the normal tegument. This suggestion is further supported by the penetration of ruthenium red into some tegumental areas and its distribution into the intercellular spaces, down to the parenchyma. The intrategumental lysosomes also appeared to be significantly activated. There was evidence of autophagy in both distal cytoplasm and tegumental cells. Mature and gravid proglottides were more susceptible to drug damage than those in the anterior strobila and neck.
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PMID:Effects of three anthelmintics on the tegument of Hymenolepis fraterna (Cestoda). 137 75

The small intestine of healthy adult Beagles was examined to determine whether subclinical abnormalities might exist that would be relevant to the use of Beagles in pharmacologic studies. Duodenal juice was obtained for qualitative and quantitative bacteriologic examinations; jejunal mucosa was taken for morphologic and biochemical investigation, and intestinal permeability was assessed by quantification of 24-hour urinary excretion of 51Cr-labeled EDTA after its oral administration. Comparisons were made with findings in healthy adult dogs of other breeds that served as controls. Small intestinal bacterial overgrowth was found in 14 of the 21 Beagles examined, and represented a mixed flora that included obligate anaerobic bacteria in 8 dogs and exclusively aerobic bacteria in 6 dogs. Intestinal permeability (percentage urinary recovery of 51Cr-labeled EDTA; mean +/- SEM) was considerably higher (P < 0.01) in Beagles with anaerobic overgrowth (37.6 +/- 3.2%) or aerobic overgrowth (30.5 +/- 4.8%), compared with Beagles with no overgrowth (17.3 +/- 1.6%) and with controls (11.1 +/- 1.0%). In Beagles, significant (r = 0.54, P = 0.03) correlation was observed between 24-hour urinary recovery of 51Cr-labeled EDTA and bacterial numbers in duodenal juice. Morphologic changes in jejunal mucosa were minimal, and specific activities of brush border enzymes were not significantly decreased, apart from aminopeptidase N, but activities of lysosomal and endoplasmic reticular marker enzymes were higher in the 3 groups of Beagles with anaerobic, aerobic, or no overgrowth, compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Small intestinal bacterial overgrowth and enhanced intestinal permeability in healthy beagles. 145 44

To clarify the possible role of intrarenal renin-angiotensin system (RAS) in the evolution of renal hemodynamic alteration in diabetes, we investigated the change of tissue angiotensin-converting enzyme (ACE) activity, a key enzyme of RAS, in the kidneys obtained from streptozotocin-induced diabetic rats. Tissue ACE activity was significantly reduced in both outer cortex (0.29 +/- 0.04, mean +/- SEM, n = 6) and inner cortex with outer medulla (2.43 +/- 0.28, n = 6) of the kidneys from diabetic rats 2 weeks after induction of diabetes compared with those from control rats (0.47 +/- 0.05, n = 7, in outer cortex; 3.68 +/- 0.32, n = 7, in inner cortex with outer medulla). ACE activities in the lung and aorta of diabetic rats were not different from those of control rats. ACE activities in the serum and urine were significantly elevated in diabetic rats. Treatment of diabetic rats with insulin to achieve near euglycemia completely prevented these alterations in ACE activity, except that, in the urine, the elevation of ACE was partially corrected with insulin. In contrast to ACE activity, activity of N-acetyl-beta-D-glucosaminidase (a lysosomal enzyme of the tubule) and r-glutamyl transpeptidase (a brush border enzyme) in the kidney were not reduced in diabetic rats, whereas in the urine both enzyme activities were significantly elevated in diabetic rats. It is likely, therefore, that the reduction of ACE activity in the kidneys of diabetic rats may reflect the impairment of vascular endothelial cells in the kidney, rather than tubular damage.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reduced activity of renal angiotensin-converting enzyme in streptozotocin-induced diabetic rats. 168 36

Gamma-L-glutamyl-L-dopa (or gludopa), a dopamine (DA) prodrug, is selectively metabolized in vivo by the kidney through the sequential action of two renal enzymes, gamma-glutamyl transpeptidase (gamma-GT) and aromatic L-amino acid decarboxylase (AADC). This study was designed to analyze, in vitro, the factors regulating gludopa metabolism and its renal vascular effects. Rat kidneys were perfused in closed circuit with a cell-free perfusion buffer containing 6% bovine serum albumin (BSA). Adding gludopa (final concentration 10(-5) M in the perfusate) led to the release of DA both into urine and perfusate (0.53 +/- 0.21 and 1.38 +/- 0.28 nmol/min/g kidney wt, respectively, during the first 5 min after substrate addition, N = 5, mean +/- SEM). Total DA release (urine plus perfusate) was 73.7 +/- 15.8 nmol/g kidney wt within 30 minutes of recirculation. In non-filtering kidneys, total DA release in the recirculating medium was lower (12.5 +/- 1.4 nmol/g kidney wt, P less than 0.01). Glomerular filtration and access to the gamma-GT on the brush border membrane of proximal tubular cells are therefore required for the maximal conversion rate of gludopa. On filtering kidneys, L-dopa was also converted to DA, but at a higher rate than gludopa (total DA formed within 30 min of recirculation = 131.2 +/- 31.9 nmol/g kidney wt) and this rate was not reduced in non-filtering kidneys (224.2 +/- 41.7 nmol/g kidney wt DA formed within 30 min). Metabolic conversion of L-dopa by AADC is thus preserved in the case of an approach via the basolateral side of the proximal tubular cells. The renal vascular effects of gludopa were studied after vascular tone had been restored by continuous perfusion of PGF2 alpha and after the inhibition of alpha- and beta-adrenoceptors. Gludopa (3.10(-6) to 4.10(-5) M) elicited concentration-dependent renal vasodilatation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism and vascular effects of gamma-L-glutamyl-L-dopa on the isolated rat kidney. 197 67

1. This study investigates the acetylation of 5-aminosalicylic acid by isolated human colonic epithelial cells. 2. After incubation of intact cells with 0.1 mmol/l 5-aminosalicylic acid, N-acetyl-5-aminosalicylic acid was detected in a concentration of 141 (+/- 23.8 SEM) nmol/g dry weight in the incubation medium, and 34.8 (+/- 5.5 SEM) nmol/g dry weight intracellularly. No unchanged 5-aminosalicylic acid was detected inside the cell. 3. Acetylation of 5-aminosalicylic acid by a cell homogenate was very poor, but the addition of 1 mmol/l acetyl-CoA resulted in complete conversion of 0.1 mmol/l 5-aminosalicylic acid to N-acetyl-5-aminosalicylic acid. 4. N-Acetyltransferase activity was detected in the cytosol, with a mean of 3.3 nmol min-1 mg-1 of protein. There was no N-acetyltransferase activity in the brush border. There was no difference in enzyme activity between epithelial cells derived from normal, Crohn's disease or ulcerative colitis patients. 5. Preliminary characterization of the N-acetyltransferase enzyme suggests a molecular weight of 150,000.
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PMID:Acetylation of 5-aminosalicylic acid by isolated human colonic epithelial cells. 215 87

Intestinal calcium transport, renal tubular calcium reabsorption, and plasma 1.25 (OH)2 vitamin D3 (calcitriol) levels have all been reported to be diminished in the spontaneously hypertensive rat (SHR) compared with its genetic control the Wistar Kyoto rat (WKY). In the present study, absorptive duodenal and renal tubular epithelia of 12- to 14-week-old male SHR and WKY were examined by electron microscopy to determine whether such disturbances could be related to structural abnormalities. Patchy loss of microvilli in both duodenal and proximal tubular epithelia was observed in the SHR, whereas brush border membrane was entirely normal in the WKY. Irregular spaces were observed between the basal aspects of SHR intestinal epithelial cells and their basement membrane. In addition, the average height of duodenal and renal microvilli was reduced in the SHR. Two specific markers of the brush border membrane, alkaline phosphatase and villin, as well as the cytoplasmic vitamin-D dependent calcium-binding proteins, CaBP9K and CaBP28K were determined. Duodenal alkaline phosphatase activity was reduced in the SHR, compared with the WKY: 0.145 +/- 0.002 vs. 0.186 +/- 0.002 IE/min.microns 3 x 10(3) brush border, mean +/- SEM, N = 10 pairs, P less than 0.001. However, duodenal villin expression was not different from that of the WKY. Duodenal CaBP9K and renal CaBP28K content was diminished in the SHR: 21.0 +/- 0.80 vs. 29.9 +/- 2.19 micrograms/mg protein, N = 6 pairs, P less than 0.01 for duodenum, and 4.47 +/- 0.39 vs. 7.67 +/- 0.54 micrograms/mg protein, N = 6 pairs, P less than 0.001 for kidney. These data showing structural and functional abnormalities of intestinal and kidney cells in the SHR appear to reflect a disorder of transporting epithelia which may be either intrinsic or related to reduced circulating calcitriol.
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PMID:Ultrastructural and functional abnormalities of intestinal and renal epithelium in the SHR. 236 1

Endopeptidase 24.11, a widely distributed membrane-bound peptidase is found in low levels in the serum of normal individuals. Although increased levels of the enzyme have been found in sera of patients with sarcoidosis and adult respiratory distress syndrome, the cellular origin of circulating endopeptidase 24.11 remains unknown. As the brush border of the proximal tubular epithelial cells have the highest endopeptidase specific activity, we investigated the possible contribution of the kidney to the release of endopeptidase 24.11 in the systemic circulation. Therefore, we measured serum levels of the enzyme in patients with end-stage renal failure (ESRF) treated by haemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). Increased serum levels of endopeptidase 24.11 were observed both in HD patients (mean +/- SEM: 74.6 +/- 20.9 ng/ml) and in CAPD patients (mean +/- SEM: 45.1 +/- 8.1 ng/ml) as compared to normal individuals (mean +/- SEM: 13.6 +/- 1.4 ng/ml). Endopeptidase levels remain stable during haemodialysis sessions on two different dialysis membranes. Finally, serum levels of the enzyme in anephric patients tend to be lower than in ESRF patients, suggesting that the kidney may contribute to the generation of the circulating form of endopeptidase 24.11.
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PMID:Increased serum levels of endopeptidase 24.11 ('enkephalinase') in patients with end-stage renal failure. 254 94

The effects of exocrine pancreatic insufficiency on the small intestinal mucosa were examined in dogs following pancreatic duct ligation. There were no significant changes either in villus architecture or enterocyte height after duct ligation, but numbers of bacteria in duodenal juice increased then subsequently decreased following treatment with exogenous pancreatic enzymes. Pancreatic insufficiency resulted in a considerable increase in the proportion of microvillar membrane proteins of molecular mass over 200 kDa from 3.3 +/- 4 per cent (mean +/- SEM) to 13.6 +/- 7.2 per cent, and this decreased to 6.9 +/- 5.2 per cent following pancreatic enzyme supplementation. However, anticipated increases in activities of maltase and sucrase were not observed following duct ligation, and there was a reduction in lactase activity which was reversed by pancreatic supplementation. Activities of marker enzymes for the other subcellular organelles showed relatively minor or no changes throughout the study. These findings are consistent with a specific role for pancreatic enzymes in the post-translational processing of intestinal microvillar membrane proteins, and suggest that reduced degradation of brush border proteins in the absence of pancreatic secretions may be masked by quantitative and qualitative changes in the intestinal microflora.
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PMID:Biochemical changes in the jejunal mucosa of dogs with exocrine pancreatic insufficiency following pancreatic duct ligation. 259 94

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