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Biomedical subjects

K F Sewing

Publications and source records attributed to K F Sewing.

At least 91 records · Page 5Linked to original sources
PubMed1993

Isolation, identification and quantitative evaluation of specific cell types from the mammalian gastric mucosa.

Functional in vitro studies with isolated gastric mucosal cells require cytological identification of different cell types in suspension or primary culture. Since suitable techniques have not been well established, different staining methods for the discrimination of dispersed pig and guinea pig gastric cells have been developed on the basis of modified previous protocols for enzymatic cell dispersion. Chief and parietal cells were visualized by combined periodic acid-Schiff stains. Surface mucous and mucous neck cells were identified by affinity-labelling, using lectins with selective staining properties in situ. Two of the lectins were found to be specific markers for gastric polymorphonuclear cells. The following vital tests were found to be useful: succinic dehydrogenase for parietal cells, Nile blue/brilliant cresyl blue stains for chief cells, and different phagocytosis assays for endothelial cells and gastric phagocytes. Endocrine cells were characterized by immunocytochemistry using specific antibodies against gastrin, somatostatin, histamine and serotonin. The same technique using a vimentin antibody was performed for the identification of fibroblasts. Proliferation of mucosal cells in primary culture was monitored by the incorporation of bromo-deoxyuridine, which was subsequently detected by a monoclonal antibody.

Animals↗
PubMed1993

Cholinergic regulation of guinea pig duodenal bicarbonate secretion.

Although it is well known that vagal stimulation induces duodenal HCO3- secretion, there is presently no information about the nature of the cholinoceptor and the intracellular signals involved. In a series of experiments performed in a guinea pig duodenal loop model in situ, intravenous carbachol, atropine, pirenzepine, and hexamethonium were used to determine the extent of cholinergic stimulation and the types of cholinoceptors. Carbachol (2 micrograms.kg-1.5 min-1) stimulated HCO3- secretion threefold, and atropine (0.1 mg.kg-1.5 min-1) and pirenzepine (1 mg.kg-1.5 min-1) both abolished this effect. In addition, hexamethonium (0.3 mg.kg-1.5 min-1) inhibited carbachol-stimulated duodenal HCO3- secretion. Vasoactive intestinal peptide (VIP, 5 micrograms.kg-1.5 min-1) stimulated duodenal HCO3- secretion, and this action was partly inhibited by atropine (0.1 mg.kg-1.5 min-1) but not by pirenzepine (1 mg.kg-1.5 min-1). [4Cl-D-Phe6,Leu17]VIP (3.3 mg/kg), an antagonist to VIP, reduced basal, VIP-stimulated, and carbachol-stimulated HCO3- secretion. To examine the role of Ca2+ in this process, Ca2+ ionophore A23187, verapamil, and nifedipine were employed. A23187 (5, 50, 500 micrograms.kg-1.5 min-1) stimulated duodenal HCO3- secretion, an effect blocked by the VIP antagonist, and modestly augmented the effect of carbachol. Verapamil (0.2 mg.kg-1.5 min-1) and nifedipine (1.7 mg.kg-1.5 min-1) stopped the effect of carbachol on duodenal HCO3- secretion. These results suggest, that in cholinergic regulation of duodenal HCO3- secretion, the M-cholinoceptor pathway, Ca2+, and VIP are involved.

Animals↗
PubMed1993

Studies on the mechanism of action of colloidal bismuth subcitrate. I. Interaction with sulfhydryls.

The present study was designed to examine the reaction pathway of colloidal bismuth subcitrate (CBS) with thiols. Studies were performed using the monothiol glutathione (GSH), the dithiol dithiothreitol (DTT) and the thiol enzymes papain and H+/K(+)-ATPase. UV-vis spectra showed that CBS forms complexes with GSH and DTT. The GSH/CBS complex but not the DTT/CBS complex was cleared by 5,5'-dithiobis-(2-nitrobenzoic acid). CBS inhibited H+/K(+)-ATPase (IC50: 23 +/- 6.5 mumol/l) but failed to inhibit papain activity. The inhibitory action of CBS on H+/K(+)-ATPase-mediated proton transport was prevented by the dithiol dithioerythritol but not by GSH. These results indicate that CBS forms stable complexes with dithiols and instable complexes with monothiols. We suggest that some of the effects of CBS (i.e., stimulation of prostaglandin production, antibacterial action against Helicobacter pylori) are mediated via the blockade of SH-groups.

Animals↗
PubMed1993

Studies on the mechanism of action of colloidal bismuth subcitrate. II. Interaction with pepsin.

The effects of colloidal bismuth subcitrate (CBS) on porcine pepsin have been studied in vitro. CBS inhibited pepsin activity in a pH-dependent manner. CBS was not active at pH 4.0 but inhibited pepsin activity at pH 1.0 (IC50: 2.3 +/- 0.09 mmol/l) and pH 2.0 (IC50: 8.9 +/- 0.7 mmol/l). This inhibition was reversible. In the presence of the sulfhydryl ligand mercaptoethanol, which prevents precipitation of CBS, the inhibitory potency of CBS increased. CBS bound to both positively (Amberlite) and negatively charged (Dowex) ion exchangers in a pH-dependent manner. With increasing acidity, binding to Amberlite increased, whereas binding to Dowex decreased. From these data we conclude that negatively charged bismuth salts derived from CBS bind at pH 2.0 and 1.0 via an ionic interaction to positively charged groups of pepsin, thereby inactivating the enzyme.

Animals↗
PubMed1993

[Effects of the histamine H2 receptor antagonist roxatidine acetate on stomach and liver alcohol dehydrogenase and serum alcohol level].

Some histamine-H2-receptor antagonists block gastric first-pass metabolism of ethanol and lead to increased blood alcohol concentrations after ingestion of a low dose (0.15 and 0.3 g/kg) of alcohol. To investigate whether the histamine-H2-receptor antagonist roxatidine acetate has a similar effect, we administered a low dose (0.3 g/kg) of ethanol to eleven volunteers before and after seven days treatment with roxatidine acetate (150 mg once daily). No effect of the drug on mean peak serum alcohol concentrations or on areas under the serum alcohol curves was found. In vitro, roxatidine acetate and its active metabolite roxatidine had almost no effect on guinea-pig gastric alcohol dehydrogenase activity. We conclude that roxatidine acetate does not block gastric first-pass metabolism of ethanol and can be considered as a safe histamine-H2-receptor antagonist in individuals who do not refrain from alcohol consumption under treatment for gastric or duodenal ulcer disease.

Adult↗
PubMed1993

Tolerance of antacids.

The use of aluminium containing antacids raises the question of toxicity. Uptake of excessive quantities of aluminium may produce neurological symptoms and osteomalacia. Provided that renal function is intact ingested aluminium from antacids is absorbed to a small extent from the gastrointestinal tract resulting in a transient increase in plasma aluminium levels which never reach toxic concentration, and therefore can be regarded as safe.

Aluminum↗
PubMed1993

Cyclosporine metabolite pattern in blood from patients with acute GVHD after BMT.

The cyclosporine (CYA) metabolite patterns in blood were evaluated in patients with liver dysfunction after allogeneic BMT. Fifty-five BMT patients were included in the study until discharge from hospital. Blood trough levels of CYA and 12 of its metabolites were quantified using HPLC. The patients were assigned to three groups: group I (no acute GVHD, n = 23), group II (acute GVHD of the skin and good liver function, overall acute GVHD: grade I: n = 18, grade II: n = 2) and group III (acute GVHD and liver dysfunction, overall acute GVHD: grade II: n = 2, grade III/IV: n = 8). Analysis of the trough blood concentrations of CYA and its metabolites revealed higher concentrations of metabolite AM19 in group III than in the other groups without reaching statistical significance. During acute GVHD of the liver, the metabolites AM19 (p < 0.01), AM1c9 (p < 0.05) and AM1A (p < 0.05) were significantly elevated compared with patients with normal liver function while CYA and all other metabolites did not differ. The CYA metabolite pattern in patients with acute GVHD and liver involvement was identical with that of liver graft patients during acute graft rejection, while the metabolite patterns of the patients without acute GVHD paralleled that of kidney grafted patients with normal liver function. Acute GVHD of the liver leads to an impaired elimination of CYA with increased blood concentrations of single CYA metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Pantoprazole: a novel H+/K(+)-ATPase inhibitor with an improved pH stability.

The action of the H+/K(+)-ATPase inhibitors pantoprazole and omeprazole was compared in different in vitro test systems. In gastric membrane vesicles under conditions shown to result in acidification of the vesicle interior, pantoprazole and omeprazole inhibited H+/K(+)-ATPase activity with IC50 values of 6.8 and 2.4 microM, respectively. When intravesicular acidification was reduced by inclusion of imidazole (5 mM), a membrane permeable weak base, the inhibitory action of omeprazole was partially lost (IC50 30 microM) and that of pantoprazole almost completely lost. After incubation for 40 min with pumping membrane vesicles, a half-maximal reduction in intravesicular H+ concentration occurred at pantoprazole and omeprazole concentrations of 1.1 and 0.6 microM, respectively. Again, when the intravesicular H+ concentration was reduced by inclusion of imidazole (2.5 mM), pantoprazole (20 and 60 microM) did not reduce the remaining intravesicular proton concentration, whereas omeprazole (10 and 30 microM) did. Both drugs inhibited, with similar potency, papain activity at pH 3.0 and inactivated the enzyme in a similar time-dependent manner; at pH 5.0 omeprazole (IC50 17 microM) was more potent than pantoprazole (IC50 37 microM) and enzyme inhibition was faster than with pantoprazole. These results indicate that pantoprazole is a potent inhibitor of H+/K(+)-ATPase under highly acidic conditions and that it is more stable than omeprazole at a slightly acidic pH such as pH 5.0.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1992

Gastric prostaglandin E2 receptors are the common antisecretory target of mucosal prostanoids.

The gastric mucosa produces all principal prostaglandin (PG) types, but receptor binding studies in this tissue have as yet been performed exclusively with [3H]PGE2. Therefore we compared the binding of different 3H-labelled prostanoids to fundic mucosal plasma membranes from the porcine stomach. Binding sites for [3H]PGE2, [3H]iloprost and [3H]PGF2 alpha had similar nanomolar dissociation constants with high affinities for unlabelled PGE2. Iloprost and PGF2 alpha were 10- and 100-fold less potent competitors with Hill slopes near unity in all cases. In further [3H]PGE2 competition studies the affinities of prostanoid ligands with selectivity for different PG receptor types correlated closely with their respective antisecretory potencies, as tested by [14C]aminopyrine uptake in isolated porcine parietal cells. We conclude that parietal cell PGE2 receptors are the common antisecretory target for all prostanoid types in the porcine stomach. There was no evidence for other mucosal PG receptors possibly involved in acid secretion.

Animals↗
PubMed1992

[Treatment of acid-related diseases of the gastrointestinal tract. Observations in patients receiving a single evening dose of 300 mg ranitidine].

UNLABELLED: Testing of the effectiveness and tolerability of ranitidine treatment in acid-related diseases of the gastrointestinal tract in non-selected outpatients. STUDY DESIGN: Observations made by 15,180 general practitioners and internists in the Länder of former West Germany in the period January 1989 to December 1990. PATIENTS: 23,783 patients with acid-related diseases of the gastrointestinal tract for which treatment with ranitidine is indicated (no further diagnostic or therapeutic requirement). TREATMENT: 300 mg ranitidine administered in the form of a single evening dose. RESULTS: A duodenal ulcer presented in 50.1%, a gastric ulcer in 26%, and reflux esophagitis in 29.6% of the patients; in 17.5% some other gastrointestinal disease (for the most part gastritis) was diagnosed. Six weeks of treatment was associated with a high rate of healing (more than 90%). The total incidence of side effects was a very low 0.77% (183 cases). These results confirm the effectiveness and good tolerability of ranitidine.

Adult↗
PubMed1992

Effects of EP-receptor subtype specific agonists and other prostanoids on adenylate cyclase activity of duodenal epithelial cells.

Rank order of agonist potency for activation of adenylate cyclase by the naturally occurring prostanoids PGE2, PGF2 alpha, PGD2, the stable PGI2 analogue iloprost, and the TXA2 mimetic U 46619, provides evidence for the existence of a distinct PGE-receptor on guinea-pig duodenal enterocytes. The PGE-receptor is likely to be of the EP2-subtype since the specific EP2-agonist 11-deoxy-PGE1 stimulated adenylate cyclase activity with a 20-fold higher potency than the EP1-agonist 17-phenyltrinor-PGE2 and the EP3-agonists MB 28767 and GR 63799. In addition, sulprostone (acting on both EP1- and EP3-receptors) was ineffective. Since the specific EP1-antagonist SC 19220 did not inhibit PGE2-stimulated adenylate cyclase activity, the involvement of EP1-receptors could be further excluded. The synthetic prostaglandin E-analogues misoprostol and nocloprost stimulated adenylate cyclase almost identically, though they were about 10-fold less potent than the natural PGE2.

Adenylyl Cyclases↗
PubMed1992

The synergistic immunosuppressive potential of cyclosporin metabolite combinations.

Out of the 29 cyclosporin (CS) metabolites defined so far seven representatives were isolated from the bile of liver grafted patients, purified by HPLC and characterized by FAB-MS and/or 1H-NMR. These were used to determine the growth inhibitory effects on concanavalin A stimulated rat lymphocytes (LN). Metabolites diluted in culture medium at concentrations re-checked by HPLC at the respective assay time were added and proliferation determined by [3H]-thymidine incorporation after 48 h. A 50% growth inhibition of LN by single metabolites (AM) was achieved at the following concentrations (mg/l): CS: 0.023; primary metabolites AM1: 0.11; AM1c: 0.65; AM9: 1.05; secondary metabolites AM19: 1.02; AM4N9: 1.02; H355: 1.85; AM1A: 4.5. Although all metabolites were immunosuppressive at higher concentrations in vitro on a single metabolite level, only AM1 with 20% of the activity of native CS seemed to play a role in vivo. However, when we tested the antiproliferative effects of double or triple metabolite combinations, we found a strong synergism not only of primary metabolites, but even with combinations including secondary metabolites. The concentration of the participating metabolites necessary to decrease LN growth by 50% was far below the trough levels observed in vivo. Finally, to mimic to some extent the in vivo situation we determined the interaction of native CS with single metabolites or double combinations. In contrast to the clear synergism in the absence of CS the combinations of metabolites with native CS resulted in an additive growth inhibition. These results indicate an immunosuppressive potential of all metabolites tested and a clear synergism of metabolites in the absence of CS. Although up to double metabolite combinations did only additively enhance CS induced immunosuppression, the combination of 29 metabolites occurring in vivo might have significant immunosuppressive effects in situations where CS levels drop below active concentrations.

Bile↗
PubMed1992

Interaction of the non-steroidal anti-inflammatory drug flufenamic acid with gastric acid secretion and H+/K(+)-ATPase.

1. The effects of the non-steroidal anti-inflammatory drug (NSAID) flufenamic acid on H+ production in isolated and enriched guinea-pig parietal cells and on H+/K(+)-ATPase activity in ion-tight inside-out membrane vesicles from pig gastric mucosa were studied. 2. At low concentrations (0.1 and 1.0 mumol/L), flufenamic acid increased the secretory response of parietal cells to dibutyryl cyclic AMP (dbcAMP). At higher concentrations (10 and 100 mumol/L) it progressively inhibited basal and dbcAMP-stimulated acid production. 3. Flufenamic acid (10 mumol/L) increased K+ (0.5-10.0 mmol/L) and K+ (0.5-1.0 mmol/L) plus gramicidin-stimulated ATPase activity in gastric membrane vesicles. The Km value for K+ (1.6 and 1.0 mmol/L in the absence and presence of gramicidin, respectively) was decreased to 0.8 and 0.5 mmol/L, respectively. At higher concentrations (greater than or equal to 50 mumol/L), flufenamic acid inhibited K+ plus gramicidin-stimulated ATPase activity (inhibited concentration at 50% [IC50] = 186 mumol/L) and reduced the proton concentration (IC50 = 50 mumol/L). 4. It is concluded that flufenamic acid-induced enhancement of dibutyryl cyclic AMP-stimulated H+ production in the parietal cell reflects the stimulation of H+/K(+)-ATPase. We suggest that activation of the enzyme involves increased affinity of K+ towards the K(+)-binding site of the enzyme and/or increased KCl permeability at the vesicle membrane. The inhibitory action of the drug on H+ production in parietal cells results from a detergent and/or protonophoric-like action at the apical parietal cell membrane, and from inhibition of H+/K(+)-ATPase activity.

Adenosine Triphosphatases↗
PubMed1992

Subcellular localization of prostaglandin E2 receptors in the gastric mucosa.

Gastric mucosal PG E2 receptors are the common antisecretory working point of all prostanoid types and may also be involved in "protective" effects. We investigated the subcellular localization of these receptors, as measured by displaceable 3H-PG E2 binding, and identified different organelles by monitoring the activities of specific marker enzymes. Porcine mucosal homogenates were subdivided by differential centrifugation into fractions P1 (1000 x g), P2 (20,000 x g), P3 (300,000 x g) and the supernatant S1. P3 was further fractionated over a series of sucrose step gradients. Mitochondria and lysosomes were enriched in P2 (maximum specific activities of cytochrome-c-oxidase of beta-glucosidase, beta-glucuronidase, beta-galactosidase, respectively). Plasma membranes (alkaline phosphatase, gamma-glutamyl-transpeptidase, 5-nucleotidase), tubulovesicles (H+/K(+)-ATPase) and rough endoplasmic reticulum (NADPH-cytochrome-c-reductase) were mainly found in P3, which also contained the majority of 3H-PG E2 binding sites. In contrast, prostanoid binding was barely detectable in S1. Density fractionation of P3 revealed that 3H-PG E2 binding sites shared a similar sedimentation profile with plasma membranes and tubulovesicular markers. No or negative correlation was found with lysosomes, rough endoplasmic reticulum and mitochondria. We conclude that mucosal PG E2 receptors are predominantly located at the cell surface. This supports the view that prostanoids inhibit gastric secretion through membrane receptors, but gives no clue for intracellular "protective" working points.

Animals↗
PubMed1992

Specific and sensitive measurement of FK506 and its metabolites in blood and urine of liver-graft recipients.

A specific and sensitive assay for quantifying the immunosuppressant FK506 and its metabolites in blood and urine was developed. 32-O-Acetyl FK506 was synthesized and used as internal standard. FK506 and its metabolites were purified from the samples by solid-liquid extraction and were injected into a high-performance liquid chromatographic (HPLC) system linked to a mass spectrometer (MS) by particle-beam interface. The FK506 derivatives were separated from interfering material by use of a 100 x 4 mm C8 analytical column and water/acetonitrile or water/methanol gradient elution; they were detected by negative chemical ionization with methane as reagent gas. The limit of detection was 25 pg in a standard solution, and the limit of quantification in blood was 250 pg (extracted from 1 mL of blood). The CV was 11.3% at 5 ng, and no interferences with other drugs were found.

Chromatography, High Pressure Liquid↗
PubMed1991

FK 506.

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Anti-Bacterial Agents↗