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Biomedical subjects

G G Forstner

Publications and source records attributed to G G Forstner.

At least 37 records · Page 2Linked to original sources
PubMed1989

Late gastrointestinal bleeding and protein loss after distal small-bowel resection in infancy.

Four children who underwent extensive small-bowel resection in infancy developed recurrent iron deficiency anemia due to gastrointestinal bleeding between 4 and 12 years later. The initial resections were required for multiple ileal atresia (n = 2) and gastroschisis (n = 2). Three patients have had melena and one had persistently guaiac-positive stools. Three patients had protein-losing enteropathy, and in one there was persistent hypoalbuminemia. Colonoscopy identified circumferential ulcerative lesions at the surgical anastomosis (n = 2) and at laparotomy another patient had well-defined linear ulcers close to the surgical anastomosis. Histology demonstrated focal ulceration with chronic inflammation, but did not show granulomata, crypt abscesses, or malignancy. Multiple imaging procedures and gastroduodenoscopy failed to identify an alternative bleeding source. Medical therapy including iron, antacids, sucralfate, H2 antagonists, and cholestyramine was ineffective. Two patients have undergone anastomotic resection. One experienced symptomatic recurrence 4 months after surgery. Repeat colonoscopy found ulceration at the new anastomosis with similar histology. The other patient remains asymptomatic 7 months postsurgery. Recurrent gastrointestinal hemorrhage due to anastomotic ulceration, of unknown etiology, appears to be a late complication of small-bowel resection in infancy.

Abdominal Muscles↗
PubMed1988

Effect of dietary restriction on total and bacterium-specific mucosal secretory immunoglobulin A in bile-diverted intestinal self-filling blind loops.

The effect of starvation on the mucosal secretory immunoglobulin A (sIgA) response to bacterial antigens was studied in bile-free rat self-filling blind loops constructed at the end of a Roux-en-Y branch of jejunum. Rats were fed a 50% restricted diet for 1 to 4 weeks after surgery. sIgA was measured in the mucosa and lumen by an enzyme-linked immunosorbent assay. Dietary restriction caused a final rise of luminal sIgA which was less than 50% of that of normally fed controls Luminal bacteria counts were not different in the two groups. The percentage of total sIgA precipitated with intestinal bacteria was not significantly affected by dietary restriction, and there was no change in the specific binding of sIgA to several bacterial species. Nonprecipitated sIgA exhibited a low but significant specific binding to bacteria in both diet-restricted and fed rats. Diet restriction therefore reduced the total sIgA response to luminal bacteria, but the specific bacterial binding capacity per microgram of sIgA was not altered. In these short-term experiments diet-restricted animals appeared to be capable of secreting sIgA in excess of requirement, since the nonprecipitable luminal fraction contained free sIgA with binding capacity for bacteria. The ability of sIgA to react with specific antigens may therefore be of more significance as an indicator of bacterial susceptibility than the measurement of total sIgA.

Animals↗
PubMed1987

Structural and compositional differences between intracellular and secreted mucin of rat small intestine.

An investigation was undertaken to discover whether mucin purified from secretions in the lumen of rat small intestine differed in structure or composition from intracellular mucin purified from rat intestinal tissue. To do this, ligated loops were constructed in situ from previously washed intestinal segments and mucin purified separately from tissue homogenates or loop fluid. Secreted mucin (SM) differed from intracellular mucin (IM) by having a higher proportion of 'minor' mucin amino acids (aspartic acid, glutamic acid, glycine and alanine) and a lower proportion of 'major' amino acids (serine, proline and threonine). SM also contained less N-acetylgalactosamine and a small, but measureable, amount of mannose. Gel electrophoresis showed that SM penetrated the gel more readily and, unlike IM, gave a rather prominent, but diffuse, band having a midpoint position of Mr 200,000. After reduction both IM and SM gave rise to the putative 'link' component of Mr 118,000 and the 200,000-Mr band of SM disappeared. SM was included to a greater extent than IM on Sepharose CL-2B chromatography, suggesting a smaller size. With the use of CsCl-density-gradient ultracentrifugation of SM, a lighter species [buoyant density (rho) = 1.38 g/ml] enriched in the 200,000-Mr component, was separated from a heavier, more glycosylated, species (rho = 1.50 g/ml). Purified 200,000-Mr component had a composition identical with that of the 118,000-Mr 'link' component of IM, reacted in Western blots with an antibody specific for the 118,000-Mr 'link' component, and after reduction gave rise to a 118,000-Mr component on gel electrophoresis. Thus secreted mucin contains a 200,000-Mr component which appears to represent a disulphide-linked dimer of the previously described 118,000-Mr 'link' component of intracellular mucin.

Amino Acids↗
PubMed1987

Characterization and localization of the putative 'link' component in rat small-intestinal mucin.

Rat intestinal mucin is polymerized by a putative 'link' component of Mr 118,000 that can be released from the native mucin by thiol reduction [Fahim, Forstner & Forstner (1983) Biochem. J. 209, 117-124]. To confirm that this component is an integral part of the mucin and independent of the mucin purification technique, rat mucin was purified in the present study by three independent techniques. In all cases, the 118,000-Mr component was released after reduction. The 118 kDa band was electroeluted from SDS/polyacrylamide gels and its composition shown to resemble closely that of the link component of human intestinal mucin [Mantle, Forstner & Forstner (1984) Biochem. J. 224, 345-354]. Carbohydrates were present, including significant (10 mol/100 mol) amounts of mannose, suggesting the presence of N-linked oligosaccharides. Monospecific antibodies prepared against the rat 118,000-Mr component established its tissue localization in intestinal goblet cells. Mucins subjected to SDS/polyacrylamide-gel electrophoresis and Western blots using the same antibody, established that the link components of rat and human intestinal mucin are similar antigenically. Brief exposure (10 min) of native rat mucin to trypsin or Pronase (enzyme/mucin protein, 1:500, w/w) also released a 118,000-Mr component that reacted with the monospecific antibody. Thus the 118,000-Mr component is an integral part of the mucin and, although linked to large glycopeptides by disulphide bonds, this component also has proteinase-sensitive peptide bonds, presumably at terminal locations such that brief treatment with proteinases releases the molecule in a reasonably intact form. Under physiological conditions, therefore, one might expect that, after mucin is secreted into the intestinal lumen, luminal proteinases would rapidly remove the link component, thereby causing the mucin to depolymerize.

Amino Acids↗
PubMed1986

Radiation inactivation of human intestinal mucin: determination of the size of the functional antigenic unit.

Previously we have shown that the major antigenic determinant of human intestinal mucin is associated with its glycopeptide monomers and not the 118 kDa 'link' component. In the present study, the size and nature of the functional unit containing the antigenic determinant has been assessed by radiation inactivation and immunological assays. Increasing doses of radiation led to a monoexponential decay in antigenic reactivity due to a progressive loss of antigenic determinants. From three independent mucin preparations, a value of 78500 +/- 7000 was determined for the Mr of the functional antigenic unit. Prolonged pronase digestion of native mucin released large degraded glycopeptide monomers containing all the mucin carbohydrate, and low molecular weight peptides. The antigenicity of the glycopeptides decreased with digestion but could not be recovered in the peptide fractions, suggesting that determinants were released and destroyed by the enzyme. Treatment of native mucin with trifluoromethanesulphonic acid caused a major loss of carbohydrate (approx. 70%), but the protein component was unchanged in amino acid profile and remained antigenic. Subsequent thiol reduction, however, abolished the antigenicity of the deglycosylated mucin. We conclude that antigenicity is associated with a non-glycosylated segment of the peptide backbone of the glycopeptides and that a large functional unit of Mr 78500 which is stabilized by disulphide bonds is important for full antigenic activity.

Amino Acids↗
PubMed1986

Treatment of distal intestinal obstruction syndrome in cystic fibrosis with a balanced intestinal lavage solution.

Conventional treatment of distal intestinal obstruction syndrome (DIOS) with high doses of pancreatic enzymes, mucolytic agents, and enemas is neither predictably effective nor rapid in action. In 6 cystic fibrosis patients with DIOS a balanced, non-absorbable intestinal lavage solution produced clinical and radiological improvement and striking improvement in DIOS scores. It is suggested that a balanced intestinal lavage solution should be considered as an alternative treatment for DIOS in patients with cystic fibrosis.

Adolescent↗
PubMed1986

Serum immunoreactive cationic trypsinogen: a useful indicator of severe exocrine dysfunction in the paediatric patient without cystic fibrosis.

We evaluated serum cationic trypsinogen as a marker of exocrine pancreatic function in children without cystic fibrosis. The ability of this test to determine steatorrhoea of pancreatic origin, and its relationship to a wide range of exocrine pancreatic function were assessed. Serum trypsinogen was measured in 32 children with steatorrhoea, 10 with pancreatic and 22 with non-pancreatic causes. In patients with pancreatic steatorrhoea, serum cationic trypsinogen was 4.9 +/- 4.9 micrograms/l (mean +/- SD), significantly below values in patients with non-pancreatic steatorrhoea (47.0 +/- 22.1 micrograms/l, p less than 0.001) and 50 control subjects (31.4 +/- 7.4 micrograms/l, p less than 0.001). Serum cationic trypsinogen values in patients with pancreatic steatorrhoea all fell below the lower limit of our control range and below all values for patients with non-pancreatic steatorrhoea. Serum cationic trypsinogen was also evaluated against pancreatic trypsin output in 47 patients (range 0.2-17.0 yr who underwent a hormonal pancreatic stimulation test. In 17 patients, serum cationic trypsinogen was low (less than -2SD or less than 16.6 micrograms/l), and associated with greatly impaired pancreatic trypsin output, ranging from 0-8% of mean normal trypsin output. Five of these 17 patients did not have steatorrhoea. In 30 patients with normal or raised serum cationic trypsinogen (greater than or equal to 16.6 micrograms/l), pancreatic trypsin output ranged from 15-183% of mean normal values. In conclusion, low serum cationic trypsinogen suggests severely impaired exocrine pancreatic function, with sensitivity extending above the steatorrhoeic threshold. In the presence of steatorrhoea, low serum cationic trypsinogen indicates a pancreatic aetiology. Normal serum cationic trypsinogen, however, does not exclude impaired pancreatic function, above the steatorrhoeic threshold.

Adolescent↗
PubMed1986

Bile acid secretion in cystic fibrosis: evidence for a defect unrelated to fat malabsorption.

In order to define basic biliary defects not related to steatorrhoea in cystic fibrosis, we studied 12 control and 18 cystic fibrosis subjects, with a wide range of pancreatic function. Duodenal aspirates were collected over three consecutive 20 minute periods, during continuous intravenous infusion of cholecystokinin and secretin using a marker perfusion technique, and analysed for pancreatic enzyme output (colipase, lipase, trypsin), bile acid output and concentration, and biliary lipids. Cystic fibrosis patients, at all levels of pancreatic function, had significantly reduced total bile acid output (mumol/kg/h) with delayed appearance of the bile acid peak, compared with control subjects. Actual duodenal bile acid concentrations were significantly higher in cystic fibrosis subjects than in controls, however, probably because of the markedly reduced water output shown in these patients. The lithogenic index was not raised in cystic fibrosis patients at any level of pancreatic function. The reduced bile acid output and the delayed peak appearance probably reflect a defect in gall bladder responsiveness which is independent of pancreatic function and steatorrhoea. Whether this defect is related to gall bladder filling or a defective peptide hormone response awaits further study.

Adolescent↗
PubMed1986

Age-related alterations of immunoreactive pancreatic cationic trypsinogen in sera from cystic fibrosis patients with and without pancreatic insufficiency.

Serum immunoreactive cationic trypsinogen levels were determined in 99 control subjects and 381 cystic fibrosis (CF) patients. To evaluate the status of the exocrine pancreas all CF patients had previously undergone fecal fat balance studies and/or pancreatic stimulation tests. Three hundred fourteen CF patients had fat malabsorption and/or had inadequate pancreatic enzyme secretion (pancreatic insufficiency) requiring oral pancreatic enzyme supplements with meals. Sixty-seven CF patients did not have fat malabsorption and/or had adequate enzyme secretion (pancreatic sufficiency) and were not receiving pancreatic enzyme supplements with meals. Mean serum trypsinogen in 99 control subjects was 31.4 +/- 14.8 micrograms/liter (+/- 2 SD) and levels did not vary with age or sex. In CF infants (less than 2 yr) with pancreatic insufficiency, mean serum trypsinogen was significantly above the non-CF values (p less than 0.001). Ninety-one percent of the CF infants had elevated levels. Serum trypsinogen values in the pancreatic insufficient group declined steeply up to 5 years, reaching subnormal values by age 6. An equation was developed which described these age-related changes very accurately. Only six CF patients with pancreatic insufficiency had serum trypsinogen levels above the 95% confidence limits of this equation. In contrast, there was no age related decline in serum trypsinogen among the CF group with pancreatic sufficiency. Under 7 yr, serum trypsinogen failed to distinguish the two groups. In those over 7 yr of age, however, serum trypsinogen was significantly higher than the CF group with pancreatic insufficiency (p less than 0.001), and 93% had values within or above the control range.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Bentiromide test for assessing pancreatic dysfunction using analysis of para-aminobenzoic acid in plasma and urine. Studies in cystic fibrosis and Shwachman's syndrome.

We evaluated the bentiromide test by analyzing para-aminobenzoic acid (PABA) in plasma and urine (a) for the identification of patients with complete pancreatic insufficiency and (b) as an alternative to the secretin-cholecystokinin test. Nine control subjects, 18 patients with cystic fibrosis, and 4 patients with Shwachman's syndrome were studied. Based upon the secretin-cholecystokinin test, pancreatic function was judged to be less than 0.1% of normal in 7 patients with cystic fibrosis and malabsorption and between 0.7% and 90% of control values in 11 patients with cystic fibrosis and 4 patients with Shwachman's syndrome without malabsorption. The bentiromide test was performed in two stages: first with bentiromide alone, then with equimolar free PABA. After ingestion of free PABA, the plasma profile and urinary excretion of PABA were comparable in controls, patients with cystic fibrosis, and patients with Shwachman's syndrome. Thirty minutes after oral bentiromide, plasma PABA values in patients with and without malabsorption were significantly lower than in the control group. From 60 to 180 min after ingestion, plasma PABA levels in patients without malabsorption were no different from controls; whereas levels in patients with malabsorption were significantly lower than in controls and in those without malabsorption, reaching the highest significance at 90 min. Similar results were obtained when the urinary excretion of PABA was considered. Only the 90-min plasma test reliably detected cystic fibrosis patients with steatorrhea, however. Duodenal colipase output was highly correlated with both the 90-min plasma test and the urinary excretion of PABA, with similar results for lipase and trypsin output. Reliable detection of pancreatic dysfunction, nevertheless, was not obtained even with the plasma test, in cystic fibrosis patients with greater than 5%-10% of the mean normal enzyme output. In patients with Shwachman's syndrome, none of whom had malabsorption, the plasma and urinary test failed to detect pancreatic dysfunction even with enzyme output as low as 1% of normal.

4-Aminobenzoic Acid↗
PubMed1985

Elevated serum immunoreactive pancreatic cationic trypsinogen in acute malnutrition: evidence of pancreatic damage.

We used a sensitive probe of pancreatic dysfunction, serum immunoreactive cationic trypsinogen, to study 50 infants and children with varying degrees of malnutrition. Patients were classified into subgroups according to the severity of malnutrition. Mean serum trypsinogen concentration was significantly elevated in 25 patients with "severe" malnutrition (77.4 +/- 42.0 ng/ml, P less than 0.001) and in 23 with "moderate" malnutrition (55.2 +/- 16.1 ng/ml, P less than 0.02) compared with the mean value (32.5 +/- 10.4 ng/ml) for well-nourished controls. The level of circulating trypsinogen tended to rise with increasing severity of malnutrition. There was no relationship between serum trypsinogen and other variables such as age, specific diagnosis, or mode of feeling. Elevated serum trypsinogen levels could not be attributed to renal disease or cystic fibrosis. In patients who showed an improvement in nutritional status, serum trypsinogen tended to revert toward normal. Elevated serum trypsinogen values in acutely malnourished infants and children may result from pancreatic acinar cell damage or regurgitation of enzymes from obstructed pancreatic ducts.

Acute Disease↗
PubMed1985

Serial alterations in the forms of immunoreactive pancreatic cationic trypsin in plasma from patients with acute pancreatitis.

We employed a radioimmunoassay for human cationic trypsin to define the time course for alterations in the molecular forms of this enzyme in plasma from patients with pancreatitis. Six patients developed acute pancreatitis as a complication of a known disorder [three, Reye's syndrome; two, hemolytic uremic syndrome (HUS); one, choledochal cyst]. The immunoreactive forms of cationic trypsin were determined by gel filtration of each plasma sample followed by radioimmunoassay of the column fractions. Early in the course of the disease, predominantly free trypsinogen was released into the circulation in five patients. In the three patients with Reye's syndrome, subsequent plasma samples showed, in addition to free trypsinogen, increasing amounts of immunoreactive trypsin complexed to alpha 2-macroglobulin and alpha 1-protease inhibitor. In contrast, subsequent samples from the two patients with HUS contained little or no inhibitor-bound trypsin. The remaining patient had intermediate concentrations of cationic trypsin complexed to these two circulating protease inhibitors. Five patients died and postmortem studies showed a striking correlation between the histological severity of acute pancreatic inflammation and the amount of immunoreactive trypsin complexed to alpha 2-macroglobulin and alpha 1-protease inhibitor. This preliminary study suggests that measurement of alpha 2-macroglobulin or alpha 1-protease inhibitor-bound trypsin may be a useful method of monitoring the progression and severity of disease in patients with acute pancreatitis. Characterization of serial changes in the forms of circulating pancreatic proteases may enhance our understanding of time-dependent pathophysiologic events, possibly leading to improved forms of specific therapy.

Acute Disease↗
PubMed1984

Biochemical characterization of the component parts of intestinal mucin from patients with cystic fibrosis.

Previous studies have shown that human small-intestinal mucin consists of high-Mr glycoproteins and a smaller S-S-bonded protein of 118 kDa. The major antigenic determinants of the mucin were associated with the large glycoproteins, but depended for stability on intact disulphide bonds, and were destroyed by digestion with Pronase. In the present study we isolated and analysed the component parts of mucin from patients with cystic fibrosis with special attention being paid to the peptide constituents. After reduction with 0.2 M-beta-mercaptoethanol [5 min, 100 degrees C in 1% SDS (sodium dodecyl sulphate)], the large glycoproteins and smaller peptide with an apparent molecular size of 118 kDa were separated by equilibrium density-gradient centrifugation in CsCl, Sepharose 4B chromatography or preparative SDS/polyacrylamide-gel electrophoresis. The large glycoproteins contained about 70% of the protein of the native mucin. Digestion with Pronase resulted in a further loss of 'naked' protein (10% of the native mucin protein) from the C-terminal end of the glycoprotein peptide core, and left behind highly glycosylated proteins comprised mainly (70 mol%) of threonine, serine and proline. The 118 kDa component, which contained about 30% of the native mucin protein, consisted mainly of aspartic acid, serine, glutamic acid and glycine (40 mol%), plus threonine, proline, alanine, valine and leucine (35 mol%). Together with the 'naked' protein segment, the 118 kDa component contained most of the cysteine residues of the native mucin. Surprisingly, the peptide also contained carbohydrate (less than or equal to 5% of the native mucin carbohydrate but 50% by weight of the 118 kDa component), which included 9 mol% mannose, suggesting the presence of N-linked oligosaccharides. The peptide exhibited strong non-covalent interactions with the high-Mr glycoproteins and a tendency to self-aggregate in the absence of dissociating agents. Our findings therefore suggest that native mucin consists of large glycoproteins capable of forming disulphide bridges from their C-terminal 'naked' (antigenic) regions to a smaller glycopeptide having an Mr of 118 000.

Amino Acids↗
PubMed1984

Antigenic and structural features of goblet-cell mucin of human small intestine.

With the use of a newly developed solid-phase radioimmunoassay method, the major antigenic determinants of human small-intestinal goblet-cell mucin were investigated and related to the overall tertiary structure of the mucin. Preliminary hapten inhibition studies with various oligosaccharides of known sequence and structure suggested that the determinants did not reside in carbohydrate. Exhaustive thiol reduction, however, almost abolished antigenicity, caused breakdown of the mucin into small heterogeneous glycopeptides, and liberated a 'link' peptide of Mr 118000. Western 'blots' of reduced mucin from polyacrylamide gels on to nitrocellulose sheets showed that a small amount of residual antigenicity remained in large-Mr glycopeptides (Mr greater than 200000). The 'link' peptide was not antigenic. Timed Pronase digestion of native mucin resulted in a progressive loss of antigenic determinants. Gel electrophoresis revealed that after 8h of digestion the 118000-Mr peptide had disappeared, whereas antigenicity, which was confined to large-Mr glycopeptides, was destroyed much more slowly with time (70% by 24h, 100% by 72h). Despite the loss of antigenicity, 72h-Pronase-digested glycopeptides retained all of the carbohydrate of the native mucin. Therefore the antibody to human small-intestinal mucin appears to recognize a 'naked' (non-glycosylated and Pronase-susceptible) peptide region(s) of mucin glycopeptides. For full antigenicity, however, disulphide bonds are required to stabilize a specific three-dimensional configuration of the 'naked' region.

Amino Acids↗
PubMed1984

Pancreatic function testing in cystic fibrosis.

None of the currently available clinical techniques for measuring pancreatic function in patients with CF can be considered "ideal". The "direct" pancreatic stimulation test provides the most information and remains the only truly accurate test of exocrine function, particularly in those individuals with pancreatic sufficiency. The invasive, complex nature of the pancreatic stimulation tests precludes its use as a routine method of assessing pancreatic function in all patients and limits its value for monitoring function in those individuals who are expected to deteriorate with time. Many of the indirect tests of pancreatic function are of value for identifying CF patients with complete pancreatic insufficiency who may require therapy with pancreatic enzyme supplements and fat soluble vitamins. However, none of the currently available "indirect" tests of exocrine function are sensitive enough to evaluate or monitor CF patients with pancreatic sufficiency. Blood tests, capable of measuring pancreatic enzymes in the circulation, such as immunoreactive trypsinogen, may be of value for monitoring pancreatic function in patients with CF, but further longitudinal studies are necessary to fully evaluate this approach. More sophisticated "indirect" tests of exocrine pancreatic function are vitally needed to facilitate adequate assessment of this important digestive organ in patients with cystic fibrosis.

Cystic Fibrosis↗