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Biomedical subjects

D L Hogan

Publications and source records attributed to D L Hogan.

62 records · Page 4Linked to original sources
PubMed1984

Effect of sodium taurocholate on the human gastric mucosa at acid and neutral pH's.

This study was conducted to determine whether taurocholate alters human gastric function and structure at a neutral pH, when ionized, and to contrast this with its effect at an acid intraluminal pH, when pronated. Five fasted healthy subjects were studied on 4 days in random order. Net ion fluxes, mucosal damage (as quantitated endoscopically), and potential difference were measured. The control solution instilled into the stomach in the first, third, and fourth 15-min periods contained 200 ml of 100 mM HCl, 54 mM mannitol, and [14C]polyethylene glycol. Taurocholate (10 mM) was added to the control solution (pH 1.1) or citrate buffer (pH 7.0) during the second 15-min period. The effect of citrate buffer alone or control solution alone was also tested. Because hydrogen and sodium fluxes could not be quantitated at pH 7 in the presence of citrate buffer, the net ion fluxes during the 15 min immediately after exposure to the test agent were measured. At both pH 1.1 and 7.0 taurocholate produced similar and significant increases in net hydrogen ion flux (-1.7 +/- 0.4 and -1.8 +/- 0.3 mmol/15 min, respectively), net sodium ion flux (1.8 +/- 0.4 and 1.7 +/- 0.2 mmol/15 min, respectively), decreases in potential difference, and mucosal erosions. The net hydrogen ion fluxes were significantly greater than occurred after citrate buffer alone or the HCl control. The net sodium fluxes after taurocholate in citrate were significantly greater than the pH 1.1 acid control, but not citrate buffer alone. These findings indicate that pronated (pH 1.1) or ionized (pH 7.0) taurocholate significantly damaged the in vivo human gastric mucosa. Taurocholate at pH 7 could in part be responsible for the gastric mucosal injury that occurs in patients with bile reflux gastritis.

Adult↗
PubMed1984

Protective effect of acetaminophen against aspirin- and ethanol-induced damage to the human gastric mucosa.

Aspirin and ethanol damage the gastric mucosa in humans, whereas acetaminophen does not. Acetaminophen increases prostacyclin activity in animals and thus may increase endogenous prostaglandin synthesis. The effect of acetaminophen was examined in five healthy subjects after intragastric aspirin or ethanol. Hydrogen and sodium ion fluxes were measured in the pylorus-occluded stomach that prevents duodenogastric reflux and gastric fluid losses. Studies were in random order and on 8 separate days. Potential difference was measured throughout and mucosal erosions were endoscopically quantitated (endoscopist masked, no premedication). The isoosmolar test solution (200 ml, 100 mM HC1, 54 mM mannitol, [14C]polyethylene glycol) was instilled into the stomach and removed 15 min later for four 15-min periods. Either aspirin (1300 mg) or ethanol (20% vol/vol) was added to the test solution only during the second 15 min. Acetaminophen (2600 mg) was given orally 1 h before aspirin or ethanol administration. To determine if the effect of acetaminophen was related to prostaglandin synthesis, prostaglandin production was inhibited with indomethacin (50 mg orally 12 h and 1 h before acetaminophen). Aspirin and ethanol alone each produced significant changes in net hydrogen and sodium fluxes, potential difference, and endoscopic changes. Acetaminophen significantly inhibited hydrogen ion flux, change in potential difference, and endoscopic damage; however, it did not totally abolish these changes. The protective effect of acetaminophen was abolished by pretreatment with indomethacin, suggesting that the effect of acetaminophen is likely to be prostaglandin-mediated. Indomethacin alone was without effect. These results demonstrate that oral acetaminophen protects the human gastric mucosa against the damaging effects of aspirin and ethanol.

Acetaminophen↗
PubMed1983

Comparison of the serial dilution indicator and intragastric titration methods for measurement of meal-stimulated gastric acid secretion in man.

Two in vivo methods that permit quantitation of gastric acid secretion immediately after the meal are currently in use: intragastric titration and the serial dilution indicator method. During intragastric titration, intragastric pH is artificially maintained at 5.5 to 7 by the continuous addition of alkali to the gastric contents, while during serial dilution the intragastric pH is permitted to seek its natural pH. This study compared gastric acid secretion and serum gastrin in response to a liquid protein meal measured by both techniques in 10 subjects. Mean (+/- SE) 3-hr acid outputs were almost identical (53.6 +/- 6.0 mmol/3 hr with intragastric titration and 52.0 +/- 8.5 mmol/3 hr with serial dilution indicator). Furthermore, 30 min secretory responses in individual subjects were highly correlated (r = 0.98 +/- 0.01, P less than 0.001). Also, in spite of intragastric pH being less than 1.5 by 90 min after the meal during the serial dilution method, total integrated serum gastrin concentrations after the meal were similar (intragastric titration = 20.6 +/- 7.3 ng min/ml versus serial dilution indicator = 23.5 +/- 9.8 ng min/ml) and individual 30-min gastrins during the two separate tests were highly correlated (r = 0.80 +/- 0.06, P less than 0.01). It is concluded that both meal-stimulated gastric acid secretion and serum gastrin concentrations as measured by intragastric titration and by the serial dilution indicator method produced similar results.

Dietary Proteins↗
PubMed1983

Intravenous infusion of L-isomers of phenylalanine and tryptophan stimulate gastric acid secretion at physiologic plasma concentrations in normal subjects and after parietal cell vagotomy.

To determine whether intravenous infusion of individual amino acids stimulated gastric acid secretion in man, graded doses of phenylalanine, tryptophan, glycine, alanine, histidine, and NaCl control were infused on separate days in nine healthy subjects. Intravenous infusion of phenylalanine and tryptophan significantly stimulated gastric acid secretion to 50 and 52%, respectively, of the acid secretory response to intragastric peptone. Intravenous alanine and histidine were without effect, whereas glycine produced a slight response. Serum gastrin concentrations did not significantly change during intravenous amino acid infusion, except in response to 0.1 M phenylalanine. However, the increase in serum gastrin occurred 2 h after acid secretion had significantly increased in response to the 0.025 M phenylalanine infusion. Plasma amino acid concentrations were measured during intravenous amino acid infusion and in response to a steak meal in five of the subjects. At a time when acid secretion was significantly increased during intravenous infusion of phenylalanine and tryptophan, plasma amino acids were similar to, or less than, that observed after the steak meal, suggesting that circulating levels of these three amino acids have a physiologic effect on gastric secretion in man. Intravenous infusion of a combination of graded doses of phenylalanine plus a continuous infusion of 0.01 M tryptophan shifted the dose-response curve to the left and resulted in a significantly greater response than to either amino acid alone. In five subjects with parietal cell vagotomy, intravenous phenylalanine and tryptophan stimulated acid secretion, whereas histidine was without effect, similar to normal subjects. These studies indicate that intravenous infusion of small amounts of phenylalanine (0.025 M, 3.1 mmol/h) and tryptophan (0.01 M, 1.25 mmol/h) stimulated gastric acid secretion at plasma concentrations similar to those observed after a steak meal, suggesting a physiologic role for circulating levels of these amino acids on gastric acid secretion. Because acid secretion increased at a time when serum gastrin was unchanged and since there was no correlation between changes in serum gastrin and acid secretion, the responses to phenylalanine and tryptophan are probably mediated by a nongastrin-related mechanism(s). Since both phenylalanine and tryptophan stimulated secretion in vagotomized subjects, the response is vagally independent. These observations suggest that circulating levels of these two amino acids have either a direct or indirect effect on or near the human parietal cell.

Amino Acids↗
PubMed1982

Rapid gastric emptying in duodenal ulcer patients.

Isosmotic liquid peptone meals adjusted to pH 7, 3, and 1.5 were instilled on separate days into the stomachs of 8 duodenal ulcer patients and 7 healthy controls. Using a marker-dilution method, duodenal acid load (DAL) was measured as the amount of unbuffered hydrogen ions delivered to the duodenum per unit time. Gastric emptying was measured as the total volume of gastric contents, including meal plus gastric secretion, passing through the pylorus per unit time (VPP). Mean pentagastrin-stimulated acid output was significantly different between the two groups. However, after all three tests meals, mean DAL was significantly greater in duodenal ulcer than in normal subjects in both hours of the test, and VPP was significantly greater in ulcer than in normal subjects in the first 40 min. In both groups, following peptone meals of pH 7 and 3, the volume of gastric contents delivered through the pylorus decreased as the amount of free hydrogen ions entering the duodenum increased, but a given load of acid was less effective in slowing emptying duodenal ulcer patients than in controls. These studies indicate that duodenal ulcer patients empty liquid meals more rapidly than do normal subjects, independent of the initial pH of the meals, and that, in addition, acid inhibition of gastric emptying is defective in duodenal ulcer.

Adult↗
PubMed1982

Unconventional application of standard light and electron immunocytochemical analysis to aldehyde-fixed, araldite-embedded tissues.

A simple procedure for the immunocytochemical analysis of glutaraldehyde/formaldehyde-fixed, Araldite- or Epon-embedded tissues by either light or electron microscopy is presented. Retention of immunoreactive antigen in deplasticized sections was achieved by use of a low concentration of glutaraldehyde in the fixative in combination with a seldom-used plastic solvent. This protocol produced good ultrastructural preservation in tissues and large, high-quality, 2-micrometers thick, plastic-free sections. These semithin sections provided a level of structural and antigenic preservation, image resolution, and labeling intensity that surpassed all other conventional sectioning methods used for immunocytochemistry. The capacity to use a single tissue sample in studies designed for light and electron immunocytochemistry, in conjunction with existing autoradiographic and cytochemical techniques, makes this a very desirable method for routine tissue preparation in research and clinical applications.

Animals↗
PubMed1979

Ultrastructure of myofibroblasts and decidualized cells in leiomyomatosis peritonealis disseminata.

A case of leiomyomatosis peritonealis disseminata studied by light and transmission electron microscopy is reported. The lesion, from a pregnant woman, was found to contain predominantly myofibroblasts and decidualized cells in a rich collagen stroma, while relatively few leiomyocytes and fibroblasts were observed. The development and fate of this entity are discussed in view of the present findings and those previously reported.

Adult↗