An artificial stomach-duodenum model for the in-vitro evaluation of antacids

To improve the dynamic in-vitro evaluation of the effects of antacids, we have developed the 'artificial stomach' model by adding a 'duodenal reservoir' to receive the gastric emptying flux and simulated bicarbonate secretion, thus constituting an 'artificial stomach-duodenum' model. With this model we measured antacid-induced resistance to gastric acidification, and simultaneously evaluated the effect of antacid activity on the duodenal milieu. The model also permitted evaluation of the antacid effects of proteins (as natural antacids), and of drugs containing aluminium phosphate, alone or combined with magnesium oxide, or aluminium and magnesium hydroxides. At the gastric site, these drugs, as well as the proteins (that is, meat extract), induced a strong resistance to acidification due to the gastric emptying flux and to antacid composition. At the duodenal site, the decrease of the acid load penetrating into the duodenum varied, depending on the efficacy of gastric antacid activity. Duodenal pH was related to the equilibrium between bicarbonate secretion and the emptying of acid load. Proteins and aluminium phosphate induced the same duodenal pH as in the control tests without antacids, but magnesium-containing antacids increased it, thus decreasing bicarbonate consumption. The antacid mechanisms within the stomach, and the fate of antacids in the duodenal milieu, might explain the variation in duodenal pH in response to antacid administration.

[In vitro evaluation of antacid activity in gastric acid secretion in static and dynamic systems]

A valid in vitro evaluation of antacid capacity should consider: 1) the intragastric pH-range; 2) the antacid mechanism; 3) the dependence of antacid activity from intraluminal flux variations; 4) the interaction between proteins and antacids. Pharmacologically, a static method allows 1) to quantify H+ binding sites at different pH-end points of the titration: pH 3.0, 2.0 and 1.0 and 2) to characterize the antacid mechanism, neutralizing activity and/or buffering capacity. In dynamic conditions, using the "artificial stomach-duodenum" model the antacid-induced resistance to acidification was measured, the antacid mechanisms were characterized in regard to intraluminal gastroduodenal flux variations and the incidence of antacid activity on duodenal pH was evaluated. These procedures were applied to antacid evaluation of proteins, as natural antacids, and of drugs containing aluminium salts alone or combined with magnesium salts. Pharmacologically, antacid drugs exhibited a greater amount of H+ binding sites when titration end-point was pH 1.0 than pH 3.0 corresponding to the development of neutralizing activity and/or buffering capacity. In dynamic conditions, the drugs, like proteins, induced a potent resistance to acidification related to gastric emptying fluxes. Antacid effect was supported by neutralizing activity and/or by buffering capacity. It was prolonged by removal of H+ ions since lagtimes for recovering initial pH were longer than antacid total emptying, the dilution of intragastric content by H+ impoverished secretory flux contributing thus to prevent gastric acidification. At duodenal site, proteins and aluminium-containing antacids induced the same duodenal pH as controls, without antacids, while magnesium-containing antacids increased it.

Controlled trial comparing two types of enteral nutrition in treatment of active Crohn's disease: elemental versus polymeric diet

To determine whether an elemental diet or a polymeric defined formula diet would be more effective for treating active Crohn's disease, we conducted a prospective randomised clinical trial in 30 patients with active Crohn's disease unresponsive to steroids and/or complicated by malnutrition. They received a four to six week enteral nutrition course with either an elemental diet or a polymeric diet. Clinical remission occurred in 10 of the 15 patients on elemental diet compared with 11 of the 15 patients assigned to polymeric diet. Both groups showed similar improvements in nutritional status, biological inflammation, alpha 1 antitrypsin clearance, and colonoscopic lesions (diminished in 17 out of 24 patients). Most patients relapsed during the year after discharge. We conclude that enteral nutrition, whatever the diet, is an efficient primary therapy for active Crohn's disease but does not influence the long term outcome.

Assessment of mucus glycoprotein erosion by measurement of sialic acid in gastric secretions: pathophysiologic and therapeutic aspects

The quantification of mucus glycoproteins (GPs) faces paramount difficulties in terms of methods and interpretation. Mucus glycoprotein erosion, however, might be quantified in gastric juice by measurement of GP-bound sialic acid. Basal sialic acid content was low in normal healthy subjects (N) and in nonulcer dyspepsia (NUD) patients. They were five to six times higher in duodenal ulcer (DU), or more in Zollinger-Ellison patients. Pentagastrin stimulation induced a five- to sixfold rise in N and NUD patients although it did not affect DU patient sialic acid contents. Relationships between sialic acid content and pepsin output in DU indicate that pepsin exerts a variable mucolytic activity depending on disease evolution. In addition to pepsin, duodenogastric reflux exerts a potent mucolytic effect. Therapeutically, highly selective vagotomy without recurrent ulcer markedly reduced mucus erosion. The reduction of mucus erosion by protective drugs has been observed in some cases but in other cases sialic acid measurement did not allow to verify a protective effect. Adherent mucus analysis by high-performance liquid chromatography (HPLC) should allow one to appreciate GP fractions qualitatively. Combination of both methods should allow further determination of the mucus protective role, simultaneously investigating the adherent mucus quality and eroded GPs.

Gastric secretory investigation of recurrent ulcer after surgery for duodenal ulcer

The results of gastric secretory studies in 192 cases of recurrent ulcer after surgery for duodenal ulcer were analyzed and compared with the secretory data collected in a control group of 74 duodenal ulcer patients who had undergone various forms of gastric surgery, but who did not develop a recurrent ulcer (controls). The patients studied comprised 46 cases of recurrent ulcer after partial gastrectomy, 10 cases of recurrent ulcer after partial gastrectomy and bilateral truncal vagotomy, 56 cases of recurrent ulcer after truncal vagotomy and drainage, 52 cases of recurrent ulcer after highly selective vagotomy, and finally 28 cases in which the recurrent ulcer led to the diagnosis of the Zollinger-Ellison syndrome. The entire study was based upon an analysis of the basal acid output, the response to maximal stimulation by pentagastrin or by histalog and by insulin in the case of previous vagotomy, and finally on an assessment of basal serum gastrin. The analysis has suggested minimal secretory levels with discriminative values useful for the postoperative diagnosis of recurrent ulcer and for an assessment of the completeness of vagotomy (ratio PAO Insulin/PAO pentagastrin or histalog). Moreover, an analysis of various elements of the sequential basal pentagastrin-insulin test permitted us to approach the pathophysiological mechanism responsible for ulcer recurrence, and to identify suitable criteria for selection of the best treatment.

[Which diagnostic and therapeutic approach to the Zollinger-Ellison syndrome should be adopted in 1990?]

A diagnostic and therapeutic strategy for ZES is proposed based on the vast experience (180 cases) of this rare disease gained at hospital Bichat (Paris, France). The first step is diagnostic and relies essentially a) upon measurements of gastric acid and serum gastrin in the basal state and b) upon the results of secretin test because of the overlap between ZES and duodenal ulcer disease in a large proportion of cases. In sporadic ZES cases, after adequate control of acid overproduction and attempt to localize the tumoral process(es), surgery is indicated (at the exception of patients with advanced metastatic disease). Surgery aims essentially at eradicating gastrinoma(s) as often as possible and whenever it is feasible without endangering patient's life. An apparently definite cure is attained in 60 to 80% in extrapancreatic gastrinoma(s) and 20 to 30% when gastrinomas are located within the pancreas. Liver involvement (25% of ZES cases) remains the major concern and death cause in these patients. Although liver metastases frequently stabilize and sometimes regress upon chemotherapy and chemoembolization, liver transplantation may, in the future, represent the major chance for these patients; but in this frequently slowly evolving condition, the time for liver transplantation is exceptionally difficult to settle.

New approach for the in vitro evaluation of antacids

Evidence is given that the in vitro evaluation of antacids has been incomplete, not regarding physiopathological conditions. As a consequence arbitrary antacid potency classifications were introduced and in clinical practice high dosages of antacid drugs were prescribed. The main reason is that the in vitro evaluation procedures used did not take into account the actual conditions of gastric acid secretion. The proposed methods allow to assess antacid activity under conditions similar to those during gastric secretion. "Pharmacologically", the capacity of binding H+ ions in acid milieu can be quantified and the antacid mechanism can be characterized. "Therapeutical efficacy" might be analysed under acid conditions taking into account gastric intraluminal flux variations by using the "artificial stomach" model. This procedure also allows to evaluate the influence of gastric protein content on antacid activity and to simulate the actual gastric conditions by using human gastric juice as gastric content and as simulated "secretion". The antacid-induced resistance to acidification largely corresponds to the therapeutical antacid activity. Data obtained with aluminum containing antacids are presented.

Assessment of antacid characteristics of drugs containing a combination of aluminium and magnesium salts using the "artificial stomach" model

Antacid characteristics of three drugs containing aluminium and magnesium salts (combination of clay with aluminium and magnesium hydroxides, aluminium and magnesium hydroxide mixture and hydrotalcite) have been studied in a dynamic situation simulated by the "artificial stomach" model, simultaneously taking into account both gastric fluxes, a constant secretory flux and variable emptying fluxes. Therapeutic doses of the drugs were added 1. to 100 ml of 0.1 N HCl, without or with 1% or 5% meat extract, and 2. 100 ml of pooled human gastric juice (96 mmol/l, pH 1.1). In addition, antacid activity of 0.5 g aluminium and magnesium hydroxides, taken alone or in combination, were evaluated when added to 100 ml of 0.1 N HCl. In aqueous HCl solution or in human gastric juice, the three antacid drugs exhibited 1. a neutralising activity characterised by pH-rise and 2. a buffering capacity close to pH 3.8. In addition, hydrotalcite exhibited also buffering capacity at pH 1.2. The antacid-induced capacity, expressed as H+ mmol, to recover initial pH were very similar, indicating that antacid physiochemical properties are similar in HCl solution or in gastric juice. H+ consumption depended upon emptying fluxes. The same antacid characteristics were observed when antacids were mixed with 1% meat extract while 5% meat extract resulted in a modification of antacid characteristics. Therefore the antacid capacities of respective mixtures were of smaller magnitude (50-60%) than the sum of the activities of antacids plus meat extracts.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical characterization of gastrinomas with antibodies specific to different fragments of progastrin

The characterization of the tumors and their metastasis in patients with the Zollinger-Ellison syndrome is currently based on the immunohistochemical identification of gastrin cells. However, sometimes tumoral cells fail to react with common C-terminal gastrin antibodies. In order to clarify this failure, we carried out morphologic, morphometric and immunocytochemical analyses performed on light and electron microscope levels of 6 pancreatic and 1 metastatic gastrinomas, using antibodies raised against various sequences of human progastrin. On the basis, in light microscopy, of qualitative analysis of immunostaining within cells and of immunostained cell numbers, gastrin 34 residue seemed to be the prominent form in 2 of the tumor tissues, G-17 in 1 tumor which was not responsive with C terminus progastrin and N terminus G-34 antisera, and progastrin in the metastatic tissue that did not contain typical gastrin (G-like) cells. Two tumors failed to react with all antisera used. At the electron microscope level, immunogold staining revealed that progastrin was present only in the progranules and gastrin 34 in both progranules and intermediate granules. Quantitative studies performed on 3 tumors showed that, within a given tumoral cell, about 25 percent of progranules contained progastrin while 75 percent contained gastrin 34. We concluded that different forms of gastrin can be immunodetected in a gastrinoma tissue, depending on the regions, and that the distribution of progastrin fragments is variable from tumor to tumor. So, specific antibodies to different fragments of progastrin may help to the characterization of gastrinomas.

[Tri-annual rhythm of basal acid secretion and secretion stimulated by pentagastrin in duodenal ulcer]

Duodenal ulcer is a recurrent disease with seasonal periodicity for pain and complications such as hemorrhage and perforation. Ulcer craters or symptoms seem to occur preferentially in early spring and autumn. Since acid secretion is one of the pathogenetic factors of the disease, we analyzed retrospectively basal and maximal (pentagastrin) acid secretion data obtained in 341 consecutive patients according to the month in which they were obtained. The patients were classified according to the activity of their ulcer (active, non active) and to the level of the peak acid secretion (hypersecretors, normosecretors). Basal acid concentration and output, and peak acid output were, both overall and month by month, higher in patients with active duodenal ulcer disease than in those who were non active, and in hypersecretors than in normosecretors. For all 341 patients as well as for normosecretors and non active ulcer patients, a triannual rhythm was detected for stimulated acid concentration and peak acid output. The highest values were noted in February, June, and October (period: 4 months). The amplitude of these rhythms was 3 to 4 percent, with differences between highest and lowest values of 30.4 mmol/l for concentration and 17.1 mmol/h for peak acid output. These rhythms for acid secretion during the year may contribute to the periodicity of duodenal ulcer events and should be analyzed in association with other factors which could be implied in ulcerogenesis. Moreover, this seasonal periodicity of acid secretion in duodenal ulcer should be taken into account in all therapeutic trials in which acid secretion is analyzed.

[Long-term efficacy and tolerability of omeprazole in 20 patients with severe Zollinger-Ellison syndrome]

Omeprazole efficacy and tolerance were evaluated in 20 patients with longstanding Zollinger-Ellison syndrome (ZES) committed to long-term antisecretory therapy. The study included 13 men and 7 women, aged 53 (30-74) years (median and range). Nineteen patients presented with epigastric pain, 14 with vomiting, and 9 with diarrhea. All patients had gastroduodenal ulcerations, associated with esophagitis in 9 cases. Median and extreme values for basal acid output (BAO) and serum gastrin (SG) levels before omeprazole treatment were 41 (3.7-80) mmol H+/h and 413 (111-11,490) pg/ml, respectively. In 18 patients, omeprazole treatment was initiated because of resistance to H2-antagonists, and in 2 patients because of carbothioamide RP 40749 discontinuation. Initial doses of omeprazole were 60 mg per day in 10 patients and ranged from 80 to 160 mg per day in the others. Esophagogastrectomy was performed in one patient at day 15 because of esophageal stenosis. In the remaining 19 patients, median duration of treatment was 16 (7-54) months and median doses of omeprazole were 70 (20-160) mg per day during the survey. Omeprazole therapy was highly effective in inducing rapid disappearance of clinical abnormalities in 18 of 19 patients. Twenty-two days after initiation of treatment, median BAO was 4 (0-14) mmol/h and ulcerations had healed in 17 of 19 patients. Median BAO was less than 5 mmol/h during follow-up. However, asymptomatic ulcer recurrence was noted in 4 patients, but disappeared quickly after omeprazole doses were increased. Median basal gastrin level was 700 (116-36.625) pg/ml at the least determination and was statistically higher than pretreatment values (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric endocrine cell behavior in Zollinger-Ellison patients upon long-term potent antisecretory treatment

Serum gastrin and gastric endocrine cell numerical densities were examined in 22 patients with long-standing Zollinger-Ellison syndrome who were receiving either ranitidine, omeprazole, or other antisecretory drugs (SMS 201-995 or pirenzepine with or without ranitidine) for long periods of time. Fifteen patients had iterative biopsies. Twenty-one subjects with normal endoscopy, serum gastrin, and acid secretion served as controls. Individual fundic argyrophil cell density was above the highest control value in 77% of the patients, whatever the treatment. Argyrophil cell densities tended to be higher in women than in men. During the survey, fundic carcinoids developed in one ranitidine- and in one omeprazole-treated patient. Fundic argyrophil cell densities were correlated with serum gastrin levels (r' = 0.730, p less than 0.001). Antral somatostatin cell density was not modified in any patients as compared with controls, nor was antral gastrin cell density except in omeprazole-treated patients. In these patients, gastrin cell density and gastrin to somatostatin cell ratio were significantly higher than in all other patients or controls. Such increases may indicate true gastrin cell hyperplasia in relation to drug-induced profound acid inhibition.

[Sigmoid motility stimulated by luminal distention. Changes in the motility response in constipation by the slowing down of left colonic transit]

The aim of our study was to develop a new technique of sigmoid manometry using standardized luminal distensions and to compare patterns of colonic motility following distension in normal subjects and in constipated patients. Eight subjects without colonic disturbances and 8 constipated patients with delayed transit time of the left colon as shown by radiopaque markers were investigated. Sigmoid motor activity was recorded by measuring pressure in a distending latex balloon placed at 25 cm from the anus. Inflations were maintained during 250 s and separated by 60 s recovery periods of deflation. Volumes of air (V) were increased until the patient reported abdominal pain (VMT). For each distension level, the resistance to distension of the bowel wall evaluated by the baseline adaptative pressure (P) and the contractile activity (A) quantified by planimetry of the active contractile activity (A) quantified by planimetry of the active contraction waves superimposed to P were assessed. In normal subjects, VMT was 147 +/- 9 ml. P increased linearly with V (p less than 0.03) up to 4,336 +/- 876 Pa. A increased with V until VMT/2 reached the maximum of 389 +/- 72 Pa*; for higher volumes A decreased significantly with to 166 +/- 46 Pa for VMT. Reference to controls, the constipated patients had a decreased VMT (61 +/- 4 ml). P increase at VMT (5,084 +/- 753 Pa) and A maximal value (387 +/- 176 Pa) were not different.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of the antacid properties of Gelox in a dynamic milieu using the artificial stomach apparatus]

Gelox antacid activity has been evaluated in a dynamic procedure by using the "artificial stomach" model that mimics both gastric fluxes, gastric secretion and gastric emptying. At time 0, the gastric reservoir has been filled by 100 ml of 0.1 N hydrochloric acid solution without or with protein, or by 100 ml of human gastric juice (pH 1.1). Gastric secretion was simulated by a constant 3 ml/min flux of HCl solution or of human gastric juice. Gastric emptying fluxes varied from 1.5 to 4.5 ml/min. Gelox addition to 100 ml of 0.1 N HCl or of human gastric juice induced 1) a pH-rise from 1.0 to 4.5-5.8, 2) a buffering capacity close to pH 3.6-4.0 and 3) the consumption of an acid amount between 25 and 50 mmol according to emptying fluxes, for recovering initial pH. In a mixture of HCl 0.1 N and protein extract 1 or 5%, Gelox induced 1) a pH-rise related to the protein concentrations, 2) a buffering capacity close to pH 3.2-3.9 when 1% protein extract has been used, and close to pH 5.0-5.9 with 5% protein extract and 3) a greater acid consumption with 1% than with 5% protein extract. For both protein concentrations, the resistance for recovering the initial pH, expressed as the amount of consumed mmol H+, was therefore less than the sum of individual capacities of proteins and Gelox.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastrin processing in primary culture of gastrinoma cells

There is a general agreement on the cell specificity of gastrin processing. In order to investigate this processing in Zollinger-Ellison (ZE) patients, we have studied in two primary gastrinoma cultures (one from a pancreatic tumor, the other from a liver metastasis) the proportion of progastrin fragments using immunochemical and immunohistological methods. In tumor extracts as well as in sera, the predominant gastrin form differed between the two patients (i.e. being G17 and G34, respectively). In the two gastrinoma cultures, RIA determinations and electron microscopic observations indicated that the proportion of progastrin increased with time while that of G17 and G34 decreased. On the other hand, as the culture time extended, an increasing proportion of nonimmunostained secretory granules was observed suggesting the presence of other gastrin precursors (e.g. Gly-extended progastrin). From these findings, we suggest that gastrinoma culture cells could be a valuable tool in the biochemical approach to gastrin processing in ZE tumors.

Gastrin secretion by gastrinoma cells in long-term culture

Gastrinoma cells from surgical specimens of a primary pancreatic tumor and an hepatic metastasis in two patients with a Zollinger-Ellison syndrome were grown and subcultured for 7 mo. Cultured cells displayed a strong reactivity to heptadecapeptide gastrin antibody and maintained an ultrastructural appearance resembling that of the original tumor cells with the presence of secretory granules of variable size and electron density. Cultured cells also showed the ability to secrete immunoreactive gastrin, and this secretion was further concentration-dependently stimulated by secretin (10(-10)-10(-6) M), carbachol (10(-6) M), and bombesin (10(-10)-10(-6) M). The latter peptide was the more potent stimulant with a maximal effect at 10(-9) M (460 +/- 20% of basal release; P less than 0.05). This stimulation occurred in the absence of extracellular Ca2+ and was potentiated by the addition of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; 10(-3) M) into the culture medium. The somatostatin analogue, somatostatin-(201-995), did not alter basal gastrin release but inhibited secretin, carbachol, and bombesin stimulation. Moreover, DBcAMP (10(-3) M) and Ca2+ (1-3 mM) stimulated gastrin release; Ca2+ ionophore A23187 (6 micrograms/ml) enhanced gastrin response to Ca2+ in the early time intervals of incubation. Furthermore the phorbol ester derivative, 12-O-tetradecanoyl phorbol-13-acetate, dramatically stimulated gastrin release (10 times the basal value). We conclude that gastrinoma cells can be cultured over an extended period with maintenance of their capacity to secrete gastrin in response to various hormones and mediators.(ABSTRACT TRUNCATED AT 250 WORDS)