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Biomedical subjects

G Forstner

Publications and source records attributed to G Forstner.

At least 37 records · Page 2Linked to original sources
PubMed1988

Impaired chloride secretion, as well as bicarbonate secretion, underlies the fluid secretory defect in the cystic fibrosis pancreas.

Pancreatic fluid and electrolyte secretion was assessed in 56 patients with cystic fibrosis (CF) and 56 non-CF control subjects undergoing pancreatic function testing while stimulated with cholecystokinin and secretin. Both CF patients and control subjects exhibited a wide range of pancreatic function. Fluid and trypsin outputs were positively correlated in both groups. Fluid output in CF subjects was significantly lower, however, than that of control subjects at any given level of trypsin output. Sodium, bicarbonate, and chloride secretions were all significantly decreased in CF subjects. Bicarbonate and chloride were important determinants of fluid secretion, but at any given bicarbonate or chloride output CF subjects secreted significantly less fluid than control subjects. When bicarbonate and chloride were analyzed as simultaneous predictor variables, adjusted fluid secretion was not significantly different in CF and control subjects. Diminished fluid secretion in CF subjects is therefore caused by impaired chloride, as well as bicarbonate, secretion.

Bicarbonates↗
PubMed1987

Bacteria and the mucus blanket in experimental small bowel bacterial overgrowth.

Self-filling blind loops were created experimentally in jejunal segments of specific pathogen-free male Wistar rats, and the loop contents and mucosa were examined over an 8-week period for evaluation of the interaction between mucus and luminal bacteria. Corresponding jejunal segments from rats that did not undergo surgery were used as controls. Proliferation of anaerobic bacteria developed in the test animals by the first week after surgery. Despite anaerobic bacterial proliferation, no adherence by bacteria to the intestinal microvillus surface was observed by scanning or transmission electron microscopy. Rather, bacteria were present within the mucus layer overlying the intestinal mucosal surface. Immunoassay of goblet cell mucin demonstrated an increase in the proportion of mucin present in the intestinal lumen and a decrease in mucin levels in the jejunal mucosa. These results suggest that the interaction of bacteria with mucus is an important mechanism of protection of the mucosal surface in experimental small bowel bacterial overgrowth.

Animals↗
PubMed1987

Quaternary structure of intestinal maltase-glucoamylase in pancreatectomized rats.

Detergent-solubilized intestinal maltase-glucoamylase was isolated 1 week postpancreatectomy (dMpanc) and purified in the presence of detergent and protease inhibitors. Upon sodium dodecyl sulfate - polyacrylamide gel electrophoresis under nondissociating conditions, the major band had a molecular weight of 280,000, slightly smaller than similar bands from detergent (dM) and papain (pM) solubilized maltase from nonpancreatectomized rats. Upon octyl-Sepharose CL-4B chromatography, 57% of the enzyme was eluted by aqueous buffer, unlike pM which was almost completely eluted or dM, 95% of which bound to the column. All fractions of dMpanic from octyl-Sepharose 4B were reduced, by boiling +/- beta-mercaptoethanol, to monomeric subunits, indicating that processing by pancreatic enzymes at the level of the brush border is not a requirement for the appearance of subunits in the rat. As well, under these dissociating conditions, the 145,000 subunit previously identified with the apolar terminus was present in all fractions of dMpanc, including the aqueous fraction, whereas pM contained only the 130,000 subunit. The presence of dMpanc in the aqueous fraction cannot be explained, therefore, by proteolytic cleavage of an apolar anchor segment from the 145,000 subunit. Pancreatic enzymes may affect the enzyme in a minor fashion, however, since aqueous solubility was enhanced and the apparent molecular weight was reduced by pancreatectomy, suggesting a more compact conformation with shielding of apolar segments.

Animals↗
PubMed1986

Production of secretory immunoglobulin A in rat self-filling blind loops. Local secretory immunoglobulin A immune response to luminal bacterial flora.

The immunoglobulin A (IgA) response to small intestinal bacteria was studied in rats with self-filling blind loops (SFBLs), surgically constructed in continuity with the intestine or at the end of a Roux-en-Y loop (RY-SFBL) so as to avoid filling with chyme. Total bile salt in the RY-SFBL lumen was much lower (4.35 +/- 0.8 mumol) than in the SFBL lumen (116 +/- 15 mumol), but other parameters, such as the number of anaerobic bacteria and disaccharidase activities were similar. Within 1 wk of establishing the blind loops, they had accumulated at least 14 times as much IgA as found in the normal jejunum. Luminal IgA per milligram mucosal protein was almost as high in the RY-SFBL as in the SFBL, indicating that a significant proportion of the IgA must be nonbiliary and probably mucosal in origin. Oral treatment with lincomycin significantly reduced luminal IgA accumulation in the RY-SFBL. Column chromatography and enzyme-linked immunosorbent assay (ELISA), which employed antirat secretory component antibody, established that the majority of the luminal IgA was nonmonomeric and complexed with secretory component. Centrifugation of luminal contents to separate soluble and particulate bound IgA showed that the RY-SFBL contained a higher proportion of precipitable IgA than either the SFBL or lincomycin-treated RY-SFBL. Immunoglobulin A eluted from the precipitates by KSCN was bound to a greater extent by bacterial sonicates than IgA in the supernatant. For either precipitate or supernatant IgA, the greatest binding was observed when the IgA was obtained from the RY-SFBL. These observations indicate that rat intestinal mucosa rapidly responds to bacterial overgrowth by secreting secretory immunoglobulin A (sIgA) with specificity for luminal bacterial antigens. As the sIgA present within the SFBL is to a certain extent derived from bile, the lower proportion of SFBL sIgA bound by bacterial antigens than of RY-SFBL sIgA suggests that biliary sIgA is less specific for local antigens than the sIgA that is secreted by the local mucosa.

Animals↗
PubMed1986

Hydrophobic binding domains of rat intestinal maltase-glucoamylase.

Rat intestinal microvillus maltase-glucoamylase was isolated by detergent extraction and purification in the presence of protease inhibitors as previously described and incorporated into phospholipid vesicles. After purification of the vesicles on Sephadex G-50, maltase was labelled with 3-trifluoromethyl-3-(m-[125I]iodophenyl) diazirine ([125I]TID) by photolysis using a water-jacketed mercury vapour lamp with a saturated CuSO4 filter. The labelled enzyme was extracted with acetone, resuspended in 1% Triton X-100, reincorporated into phospholipid vesicles, and digested with activated papain to release the hydrophilic polar head of the enzyme from the vesicle bilayer. Vesicle-bound and free enzyme components were separated on Sepharose 4B. Ninety percent of the enzymatic activity was free, while a similar percentage of radioactive label remained with the vesicles in keeping with the separation of an active polar headpiece from a labelled apolar peptide in the lipid bilayer. The vesicle fractions were subjected to chromatography on Sephadex LH-60 with ethanol--formic acid (7:3) as the eluant. A single radioactive peak (14 kilodaltons (kDa)) was separated from labelled lipid. Sodium dodecyl sulfate--polyacrylamide gel electrophoresis of the peak showed a radioactive doublet of 26-28 kDa, possibly representing a dimer. No other labelled peptides were found. These results suggest that detergent-solubilized maltase-glucoamylase is inserted into the phospholipid bilayer via an apolar peptide with a minimum molecular mass of 14 kDa. The peptide probably represents a terminal anchor segment of the 145-kDa subunit which is converted to 130 kDa when the membrane-bound enzyme is solubilized by papain.

Affinity Labels↗
PubMed1986

Serum immunoreactive pancreatic lipase and cationic trypsinogen for the assessment of exocrine pancreatic function in older patients with cystic fibrosis.

Indirect and qualitative tests of pancreatic function are commonly used to screen patients with cystic fibrosis for pancreatic insufficiency. In an attempt to develop a more quantitative assessment, we compared the usefulness of measuring serum pancreatic lipase using a newly developed enzyme-linked immunosorbent immunoassay with that of cationic trypsinogen using a radioimmunoassay in the assessment of exocrine pancreatic function in patients with cystic fibrosis. Previously, we have shown neither lipase nor trypsinogen to be of use in assessing pancreatic function prior to 5 years of age because the majority of patients with cystic fibrosis in early infancy have elevated serum levels regardless of pancreatic function. Therefore, we studied 77 patients with cystic fibrosis older than 5 years of age, 41 with steatorrhea and 36 without steatorrhea. In addition, 28 of 77 patients consented to undergo a quantitative pancreatic stimulation test. There was a significant difference between the steatorrheic and nonsteatorrheic patients with the steatorrheic group having lower lipase and trypsinogen values than the nonsteatorrheic group (P less than .001). Sensitivities and specificities in detecting steatorrhea were 95% and 86%, respectively, for lipase and 93% and 92%, respectively, for trypsinogen. No correlations were found between the serum levels of lipase and trypsinogen and their respective duodenal concentrations because of abnormally high serum levels of both enzymes found in some nonsteatorrheic patients. We conclude from this study that both serum lipase and trypsinogen levels accurately detect steatorrhea in patients with cystic fibrosis who are older than 5 years but are imprecise indicators of specific pancreatic exocrine function above the level needed for normal fat absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Neutral and acidic species of human intestinal mucin. Evidence for different core peptides.

Highly purified human mucins from postmortem intestinal tissue were fractionated on anion exchange columns to generate separate neutral and acidic species. The neutral mucin (less than 1.0 mol % sialic acid) was the major species (greater than 80% by weight) and contained a higher molar proportion of fucose, galactose, and N-acetylglucosamine, and a lower proportion of sialic acid and N-acetylgalactosamine than the acidic species (greater than 10 mol % sialic acid). Amino acid analyses revealed a highly significant enrichment in serine, aspartate, and alanine in the neutral species and proline, threonine, and glycine in the acidic species. Thiol reduction of each species to remove their integral 118,000-dalton component did not alter the essential interspecies differences. Differences in threonine, proline, and serine also remained after removal of all "naked" or pronase-susceptible peptide regions from each species. These results indicate that neutral and acidic mucins contain glycopeptide segments exclusive of their 118,000-dalton and naked peptide components, which differ in amino acid composition. The key amino acid markers are similar to those observed for fuco- and sialoglycopeptides obtained after proteolytic digestion of human colonic mucin by Gold et al. (Gold, D.V., Schochat, D., and Miller, F. (1981) J. Biol. Chem. 256, 6354-6358). The oligosaccharide composition of small intestinal and colonic mucin may therefore depend upon transcriptional control of the synthesis of specific mucin peptides as well as the post-translational activity of glycosyltransferases. These findings may have significance for the quality and functions of mucus produced in a variety of pathological states.

Amino Acids↗
PubMed1985

Pancreatic fluid secretion and protein hyperconcentration in cystic fibrosis.

To study pancreatic protein and water secretion in 28 patients with cystic fibrosis and 21 controls matched for pancreatic acinar function as defined by trypsin secretion, we used a quantitative-marker perfusion technique and continuous intravenous secretin-pancreozymin stimulation. Regardless of the level of pancreatic acinar function, secretions from the patients contained significantly higher concentrations of protein than those from the controls. Total protein output and albumin:protein ratios were not increased in secretions from the patients, but their fluid secretion was significantly decreased at any level of pancreatic function. A significant linear correlation was found between protein and volume secretion in the patients (r = 0.86, P less than 0.001), most of whom had a fluid output of less than 4.2 ml per kilogram of body weight per hour. No such relation was found in the control subjects, whose flow was always above 4.2 ml per kilogram per hour. We conclude that fluid secretion in patients with cystic fibrosis may be a rate-limiting factor in protein output and that a limited flow of hyperconcentrated protein secretions may predispose to protein precipitation and ductal obstruction in the pancreas.

Adolescent↗
PubMed1985

Altered PABA pharmacokinetics in cystic fibrosis. Implications for bentiromide test.

The bentiromide test has been proposed as a useful noninvasive method for assessing exocrine pancreatic function in cystic fibrosis (CF) patients. Following oral administration, this peptide is selectively cleaved by pancreatic chymotrypsin liberating PABA which is passively absorbed. Recent studies have suggested that PABA measured in plasma is superior to the more established method of estimating urinary recovery of this marker. However, in using the plasma test in CF patients, one makes the assumption that the PABA marker has similar distribution and elimination patterns in normal and CF subjects. Since many drugs display altered pharmacokinetics in CF patients, we studied the disposition of PABA following ingestion of free PABA in six controls (age 19-28 years) and 18 CF patients (13-18 years; seven steatorrheic and 11 nonsteatorrheic). Elimination of T1/2 of PABA was significantly shorter in CF patients (58 +/- 21 min) compared to controls (93.5 +/- 28) (P less than 0.005). PABA clearance was similar in the control and CF patients (2.99 +/- 1.21 and 3.27 +/- 1.02 ml/min/kg, respectively). PABA distribution volume was smaller, although not significantly so, than in the controls (268 +/- 107 vs 376 +/- 140 ml/kg). Good correlation was found between PABA distribution volume and T1/2 (r = 0.51 P less than 0.02). Our simulation data suggest that altered pharmacokinetics of PABA in CF patients would cause their PABA levels to be 7% lower than controls at 90 min, 18% at 120 min, 29% at 150 min, and 38% at 180 min.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aminobenzoic Acid↗
PubMed1985

Age-related alterations in immunoreactive pancreatic lipase and cationic trypsinogen in young children with cystic fibrosis.

Serum immunoreactive pancreatic lipase and cationic trypsinogen are elevated in young infants with cystic fibrosis (CF) and may be useful neonatal screening tests for CF. We compared lipase measured by a recently developed ELISA immunoassay with trypsinogen measured by radioimmunoassay in 70 children (ages 0.1 to 9.9 years) with CF who had various degrees of pancreatic dysfunction and in 79 similarly aged children without CF (controls). In the control children, lipase activity increased with advancing age, whereas trypsinogen showed no age-related trend. Lipase and trypsinogen were significantly elevated in the infants with CF who were younger than 1 year, irrespective of pancreatic function (trypsinogen, P less than 0.001; lipase, P less than 0.05). Sensitivities in detecting CF were 76% and 90% for lipase and trypsinogen, respectively. After the first year of life, lipase and trypsinogen values declined toward normal, the rate of decline of lipase being greater than that of trypsinogen; 67% of lipase values were within or below the normal range by 3 years, whereas 67% of trypsinogen values continued to be elevated. We conclude that trypsinogen is an excellent screening test for CF in young infants regardless of pancreatic function, and that the addition of a serum pancreatic lipase determination does not improve the accuracy of trypsinogen as a screening test for cystic fibrosis.

Age Factors↗
PubMed1985

Mapping of proteolytic and cyanogen bromide peptides from subunits of intestinal maltase-glucoamylase: evidence for significant homology.

Rat intestinal maltase-glucoamylase was purified in the presence of detergent and proteolytic inhibitors, and the 130000 and 145000 subunits were separated and isolated by preparative sodium dodecyl sulfate - polyacrylamide gel electrophoresis and electrophoretic elution. Amino acid analyses were very similar, with a small excess of apolar amino acid residues in the 145000 subunit. Peptide mapping with Staphylococcus aureus V8 protease revealed eight similar peptide products for each, with apparent elongation of the five larger peptides in the 145000 subunit by a relative mass (Mr) of 2000-5000. alpha-Chymotrypsin maps showed at least eight identical cleavage products plus one large, shared product which was larger by a Mr of 5000 in the 145000 subunit. Cyanogen bromide cleavage of the 145000 subunit produced a single peptide of Mr 75000. A peptide of Mr 66000, also indicative of a central cleavage, was generated from the 130000 subunit, but a second cleavage into 43000 and 23000 segments was also evident. Several sets of antibodies formed against both antigens consistently gave reactions of identity without spurring on immunodiffusion. These results indicate extreme homology between the central segment of the 145000 subunit and the 130000 subunit. The cyanogen bromide cleavage results suggest, however, that the two central sequences are not absolutely identical and therefore that one subunit may not be a posttranslational derivative of the other.

Amino Acids↗
PubMed1985

Mucin depletion in the intestine of malnourished rats.

The effects of malnutrition on mucosal goblet cell mucin levels were studied in rats deprived of 50% of their daily intake, as judged by pair-fed, age-matched control animals, for 5 wk. Average daily weight gain was 0.7 g/day compared with 5.8 g in age-matched (AM) rats; final weight was 246 +/- 9 g compared with 406 +/- 4 g. Immunoassayable mucin, sucrase, protein, and DNA were assayed in mucosal scrapings from the proximal, middle, and distal segments of the small intestine in malnourished rats, AM rats, and a third group of low-weight, less mature (LM) rats. Total protein, total DNA, and protein-to-DNA ratios in malnourished rats were unchanged compared with AM control rats and often higher than levels in LM control rats. In malnourished animals, mucin concentration per milligram protein was significantly decreased below AM control animals in the upper two segments and below LM control animals in all segments. Mucin concentration per milligram DNA was significantly lower in malnourished rats than in all segments of both control groups. In contrast, sucrase activity per milligram protein or DNA was either unchanged or increased in the malnourished rats, indicating that the reduction in mucin concentration was selective and did not reflect all surface glycoproteins. Isolated mucins from malnourished and AM control rats were chemically similar, and the affinity and number of antigenic determinants were the same. Malnutrition therefore leads to an absolute decrease in intestinal mucin rather than reduced molecular antigenicity. Impaired capacity to maintain mucosal mucin content may be a factor in reducing intestinal resistance to enteric infection in malnutrition.

Animals↗
PubMed1985

Sequential disaccharidase loss in rat intestinal blind loops: impact of malnutrition.

We studied lactase, maltase, and sucrase activities in the mucosa of self-filling blind loops (SFBL) in adult rats at weekly intervals after SFBL formation in order to determine the sequence in which disaccharidase activities fall. The studies were carried out on nourished and malnourished rats and extended to a recovery period induced by antibiotics to determine the effects of malnutrition on the establishment and repair of disaccharidase deficiencies caused by bacterial overgrowth. Malnutrition was produced by feeding 50% of the intake of paired rats fed ad libitum. Disaccharidase activities were determined in SFBL from nourished and malnourished rats at 7-day intervals until pandisaccharidase deficiency was established and during a 2-wk recovery period induced by antibiotics. Maximal SFBL bacterial counts in both nourished and malnourished groups of rats and brush-border glycoprotein degradation ratios were established at 7 days. In nourished rats only lactase was deficient at 7 days; maltase and sucrase fell later and sequentially. In malnourished rats all three disaccharidases were reduced at 7 days. Disaccharidase activities in self-emptying blind loops (SEBL), used as operated controls, were not decreased 28 days after surgery. Malnutrition had no effect on disaccharidase activities in the SEBL, and malnutrition did not affect recovery rates with antibiotic therapy. We conclude that small intestinal bacterial overgrowth causes a staggered loss of disaccharidase activities beginning with the loss of lactase activity. In the presence of bacterial overgrowth, malnutrition accelerates the conversion of a mono- to a pan-disaccharidase deficiency.

Animals↗
PubMed1984

Acute and chronic models for hypersecretion of intestinal mucin.

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.

Anaphylaxis↗
PubMed1984

Improved prognosis in CF patients with normal fat absorption.

CF patients with normal fat absorption, as a group, have lower mean sweat chloride levels, maintain better pulmonary function and weight for their age, and appear to survive longer than CF patients with steatorrhea. The prognostic advantage for CF males in general is not seen in the pulmonary function data for patients with normal fat absorption, but may be reflected in the smaller number of females in this group. Males in both groups are clearly better at maintaining good weight than are females. Whether this means that nutritional intervention can improve pulmonary course or that other factors (genetic, endocrinological, environmental) dictate nutritional and pulmonary state, as well as sex differences, remains to be shown. Non-steatorrheic patients are far less likely than steatorrheic patients to have Pseudomonas infecting their lungs. This is a significant prognostic advantage since the progressive lung disease and eventual mortality of most CF patients can be charted by their acquisition of P. aeruginosa and the increasing frequency of exacerbation and attempts to eradicate this organism. CF has been called a lethal genetic disease because affected homozygotes did not generally survive to procreate. However, increasing numbers of young women with CF are surviving to an age where pregnancy and child-rearing are options for them. The majority of patients who reach this stage with sufficiently good health to embark on a pregnancy are patients with normal fat absorption. They also appear to be more likely to remain well throughout pregnancy and as young mothers. There is no doubt that CF patients with normal fat absorption have a better prognosis than those with typical CF malabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Rat intestinal maltase--glucoamylase. Purification of the detergent-solubilized enzyme in the presence of protease inhibitors: properties and identification of a protease-sensitive subunit.

Failure to develop clear-cut, distinguishing characteristics for hydrophobic and hydrophilic forms of maltase-glucoamylase led us to attempt the purification of the detergent-extracted enzyme in the continuous presence of protease inhibitors (phenylmethylsulfonyl fluoride and N-ethylmaleimide). The enzyme was purified by molecular exclusion, anion-exchange, and affinity column chromatography to a final specific maltase activity of 80 U/mg protein, comparable to previously solubilized enzymes. Both detergent (d-maltase) and proteolytically (p-maltase) solubilized enzymes had identical Km's for maltose and similar glycogenase activity. d-Maltase was clearly amphipathic. Whereas 95% of p-maltase was eluted with aqueous buffer from an octyl-Sepharose CL-4B column, the elution of d-maltase required solutions containing Triton X-100 and ethylene glycol. On density gradient centrifugation and sodium dodecyl sulfate (SDS)--polyacrylamide gels, p-maltase migrated as one high molecular weight species of 500,000. In contrast d-maltase migrated heterogeneously and the smallest maltase-active forms delineated by these two techniques, as well as by high pressure liquid chromatography, had molecular weights which ranged from 120,000 to 15,0000. Both p- and d-maltase were dissociated by heat in SDS, forming five prominent species as we have previously described. In contrast to p-maltase, in which the smallest species, band 1, equalled 36.7% of the total mass, band 1 of d-maltase accounted for 66.5%. Band 1 was separable when smaller amounts of enzyme were applied to slab gels and stained with silver, into two proteins of 130,000 and 145,000 daltons. The 145,000 dalton protein was absent in p-maltase and was replaced by a faint band of 140,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1984

Abnormal mucus: nominated but not yet elected.

Mucus secretions of the intestine may contribute to plug formation in CF, through several mechanisms acting alone or simultaneously. Excessive mucin secretion and relative dehydration of secretions would elevate mucin concentration and enhance mucus gel formation. Deficient pancreatic enzymes combined with intrinsic hyperglycosylation of mucin or an increase in covalently bound fatty acid groups on mucins, would retard normal proteolytic degradation of mucins. Excessive calcium ions in the ducts would tend to decrease mucin solubility, while excessive hydrogen ions and protein (especially albumin) together with mucins, may be responsible for the appearance of proteinaceous ductal 'plugs' characteristic of CF pathology.

Albumins↗