Immunocytochemical and morphometric studies of gastrin-, somatostatin- and serotonin-producing cells in the stomach and duodenum of patients with acid peptic disorders

Gastric and duodenal biopsies from 90 patients with various acid peptic disorders-reflux esophagitis (n = 24), gastric ulcer (n = 13), duodenal ulcer (n = 47) and nonulcer dyspepsia (n = 6)-were examined. Seven patients with minimal dyspeptic symptoms and an endoscopically and histologically normal stomach and duodenum served as controls. Immunoperoxidase staining for gastrin-producing G cells, somatostatin-producing D cells and serotonin-producing EC cells was carried out on fundic, antral and duodenal biopsies, and was quantified using a Zeiss MOP Videoplan using the peroxidase-antiperoxidase technique of Sternberger. In the gastric antrum, a G:D:EC cell ratio of approximately 1.6:1:1-was observed. In the duodenum the corresponding ratio was 1:1:2.4. No significant differences were observed within any of the major diagnostic categories. Patient age, sex, duration of symptoms, smoking habits, alcohol consumption and nonsteroidal anti-inflammatory drug use had no effect on endocrine cell densities. Reduced G cell density in the descending duodenum was observed in the presence of mild duodenitis in four patients. In four patients with evidence of antral intestinal metaplastic changes, a significant increase in duodenal G cell densities was found. These results suggest that a change in the number of G, D or EC cells does not play a primary role in the pathophysiology of acid peptic disorders in the majority of patients.

Nutrients and intestinal adaptation

The authors review the physiological, cellular and molecular aspects of the patterns, mechanisms and signals of the adaptation of intestinal transport of sugars and lipids, especially in response to manipulations of dietary lipid content. In models of intestinal adaptation, nutrient uptake is enhanced by an up- or down-regulation of the maximal rate of carrier-mediated transport or by alterations in the passive permeability properties (Pd) of the intestinal brush border membrane (BBM). The importance of unstirred water layers has been demonstrated. Alterations in the Pd for lipid uptake are due to changes in the lipid content of the BBM, which in turn are associated with alterations in the activity of lipid-metabolizing enzymes in the enterocyte microsomal membrane (EMM), and, therefore, alterations in the lipid composition of the EMM. Lipid uptake is also mediated by at least two proteins in the BBM, the sodium-hydrogen exchangers and the membrane-fatty-acid-binding protein. Alterations in the maximal transport rate for glucose and fructose transporters are associated with variations in the abundance of their transporters (including sodium-dependent glucose transporter, glucose and fructose transporter and fructose transporter) in the basolateral membrane sodium-potassium adenosine triphosphatase, and in the abundance of the messenger RNA of the transporters. Isocaloric changes in dietary lipids, such as switching from a saturated to a polyunsaturated diet, within the range seen in human consumption, leads to major alterations in passive and active transport processes. In a proposed model, changes in dietary lipids stimulate intracellular second messengers, modifying gene expression of the transporter carriers and of the EMM lipid-metabolizing enzymes. Thus, an understanding of the mechanisms of intestinal adaptation lays the groundwork for future studies of dietary manipulations. It may also lead to dietary interventions to prevent unwanted or to enhance desirable intestinal adaptation, thereby preventing disease.

Intravenous ursodeoxycholic acid reduces cholestasis in parenterally fed newborn piglets

BACKGROUND & AIMS

Cholestasis complicates total parenteral nutrition (TPN) in preterm infants. Ursodeoxycholic acid (UDCA) is used for several cholestatic problems. The hypothesis of this study was that intravenous UDCA prevents TPN-induced cholestasis by (1) maintaining normal basal and stimulated bile flow, (2) altering bile composition, and (3) changing hepatocyte membrane composition and Na+,K(+)-adenosine triphosphatase (ATPase) activity.

METHODS

Three groups of piglets were studied: group 1 received sow's milk, groups 2 and 3 received TPN, and group 3 also received 100 mumol.kg-1.day-1 UDCA intravenously. After 3 weeks, basal and stimulated bile flow were measured. Cholesterol, bile acids, phospholipids, and phospholipid fatty acids were analyzed in bile, and fluidity, phospholipid fatty acid composition, and Na+,K(+)-ATPase were analyzed in hepatocyte membranes.

RESULTS

Bile acid secretion and basal and stimulated bile flow were similar in control and UDCA-treated animals but reduced to < 50% in the TPN group. Bile acid-dependent and -independent bile flow were lower in the TPN group. UDCA did not normalize abnormalities in TPN-induced bile composition. Sinusoidal but not canalicular membrane fluidity was different in TPN than in control and UDCA-treated animals. UDCA also increased Na+,K(+)-ATPase activity. Bile and membrane phospholipid fatty acids reflected dietary fatty acids.

CONCLUSIONS

Intravenous UDCA improves bile flow and reduces bilirubin levels in the serum and liver in piglets with TPN-induced cholestasis.

Comparison of the utilization of endoscopy units in selected teaching hospitals across Canada

There is no information on the number of endoscopic procedures performed at major teaching hospitals across Canada. The directors of endoscopy units at eight teaching hospitals from Halifax to Vancouver volunteered demographic information on the unit at their location. There was a very wide range of endoscopic utilization, with approximately comparable rates of out-patient versus in-patient procedures and of gastroscopies versus colonoscopies, but there was no obvious linking of the ratios of in-patients:out-patients versus total number of designated gastrointestinal beds or total number of hospital beds. Thus, the appropriateness of endoscopic procedures needs to be based on standards of practice and accepted indications. The number of endoscopies performed per endoscopy unit support staff varied widely (from 323.7 to 1065.3 per year), and it would be interesting to learn whether this represents an opportunity for cost-saving in some units.

Total parenteral nutrition impairs bile flow and alters bile composition in newborn piglet

Cholestatic liver disease complicates total parenteral nutrition (TPN) in premature neonates. We investigated TPN-induced liver disease in the newborn piglet, hypothesizing that: (1) TPN impairs bile flow by reducing the bile acid-dependent (BADF) and the bile acid-independent component of bile flow (BAIF); and (2) TPN changes bile composition. For three weeks, eight piglets received TPN and nine piglets were fed milk. Basal bile flow was measured and bile composition analyzed for bile acids, cholesterol (C), phospholipids (PL), and PL fatty acids. Bile flow was also measured after stimulation with 20, 50, and 100 mu/kg taurocholic acid (TCA). Liver histology and bilirubin content were examined. Basal bile flow was reduced from 11.6 +/- 1.2 microliters/g liver/10 min in orally fed animals to 1.6 +/- 0.4 microliters/g liver/10 min in the TPN group. The stimulated bile flow in the TPN group did not respond to TCA and was lower than in the orally fed animals at each TCA dose. Both BADF and BAIF were significantly lower in the TPN group. Bile acid secretion was less than 50% of control values and total C and PL secretions were less than 5% of control. Liver and serum bilirubin were elevated in the TPN group. The newborn piglet is a valid model to study TPN-induced cholestasis, characterized by decreased bile acid secretion, impaired BADF and BAIF, and reduced bile flow stimulation after intravenous TCA.

Calcium channel blockers modify jejunal uptake of D-galactose in rabbits

Calcium channel blockers modify the intestinal uptake of lipids. This study was undertaken to test the hypothesis that two different types of calcium channel blockers influence the uptake of D-galactose, a sugar absorbed by the sodium-dependent glucose transporter (SGLT1) in the intestinal brush border membrane. Nisoldipine (1 mg/kg/day) or verapamil (4 mg/kg/day) were given by mouth to New Zealand white rabbits for three weeks, and then the rates of uptake of varying concentrations (2-64 mM) of galactose were examined in an in vitro preparation of jejunum using the incorporation of 14C-labeled substrate into intact tissue segments. The maximal transport capacities (Vmax) for D-galactose were increased in animals given nisoldipine or verapamil, as compared to controls. The value of the apparent Michaelis constant Km* for D-galactose was higher with nisoldipine group and lower with verapamil, than in controls. The apparent passive permeability (Pd*) of D-galactose was estimated from the uptake of L-glucose: Pd* was lower with nisoldipine and higher with verapamil, as compared to controls. The effect of these drugs on sugar uptake is not due to differences in the animals' food intake, body weight gain, or mucosal surface area. Thus, the two different classes of calcium channel blockers, the dihydropyridine nisoldipine and the phenylalkylamine verapamil, have different effects on the K(m)* and Pd*, but not on the Vmax of D-galactose uptake.

Short-chain fatty acids increase proglucagon and ornithine decarboxylase messenger RNAs after intestinal resection in rats

BACKGROUND

Intestinal adaptation is a complex physiological process that is not completely understood. Systemic administration of short-chain fatty acids (SCFAs) has been shown to facilitate adaptation to small bowel resection; however the mechanisms underlying this phenomena are unknown.

METHODS

Forty-six male Sprague-Dawley rats underwent an 80% jejunoileal resection and jugular catheterization. After surgery, rats were randomly assigned to receive standard total parenteral nutrition (TPN) or an isoenergetic, isonitrogenous TPN supplemented with SCFAs. On day 3 or 7 after surgery, ileal samples were removed for determination of mucosal wet weight, DNA, RNA, and protein concentrations. Total cellular RNA was extracted for use in Northern blot analysis to quantify proglucagon and ornithine decarboxylase messenger RNAs (mRNAs).

RESULTS

Total, mucosal, and submucosal weights were increased (p < .05) in the SCFA group both 3 and 7 days after surgery. Ileal DNA and RNA concentrations were increased (p < .05) in the SCFA group at both time points; however ileal protein concentration did not differ between groups until 7 days after resection. Levels of proglucagon and ornithine decarboxylase messenger RNAs were higher (p < .05) in the SCFA group at both time points.

CONCLUSION

The upregulation of proglucagon and ornithine decarboxylase gene expression may be the mechanism by which SCFAs facilitate intestinal adaptation.

Review article: older systemic and newer topical glucocorticosteroids and the gastrointestinal tract

Systemic steroids have been used in gastrointestinal disorders, such as ulcerative colitis and Crohn's disease. However, glucocorticosteroids are associated with potentially serious adverse effects. For that reason there is a search for a steroid which would have rapid first-pass metabolism in the intestine and liver, low systemic bioavailability, high topical activity and rapid excretion. This review will consider the absorption, transport, metabolism, mechanisms of action, general effects and effects of steroids on the intestine, and the new steroids in particular.

Intestinal morphology and transport after ileal resection in rat is modified by dietary fatty acids

The authors tested the hypothesis that the intestinal morphology and uptake of nutrients after resection of the distal half of the small intestine of rats responds to alterations in the dietary content of saturated (SFA) and polyunsaturated (PUFA) fatty acids. Adult female Sprague-Dawley rats were subjected to a sham operation or to the surgical resection of the distal half of the small intestine, leaving the ileocecal valve intact. The animals were fed chow for 3 weeks, then either chow or isocaloric semisynthetic SFA or PUFA diets for a further 2 weeks. Food consumption, weight gain and jejunal mucosal surface area were unchanged after ileal resection. A microdensitometric autoradiographic technique was used to examine the distribution of 3H-leucine and 3H-lysine along the villus: approximately 70% of uptake occurred in the upper 30% of the enterocytes of the villus in chow-fed rats, and this portion was unchanged by ileal resection. The jejunal uptake of 40 mM of glucose, observed in vitro, was twice as high in animals that had undergone resection and were fed SFA than in those fed PUFA. In summary, (1) there is a separation between the adaptation of intestinal transport function and dynamic/static morphology after ileal resection, and (2) glucose uptake after ileal resection is enhanced by SFA in the diet and is not explained by any changes in the animals' food intake, weight gain or intestinal morphology.

Ileal recovery of nutrients and mucin in humans fed total enteral formulas supplemented with soy fiber

The objective of this study was to determine whether soy fiber supplementation of total enteral nutrition formulas affected small intestinal recovery of nitrogen, amino acids, and carbohydrates or mucin output in eight human subjects (four males, four females) with ileostomies. The subjects ingested five test diets to provide 1.0-16.5 g soy fiber/L for 2 consecutive days each. The five test diets, each with a different soy fiber content were formulated by varying the relative proportion (1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75, and 0:1) of two commercially available formulas. Effluent dry matter increased with soy fiber intake as a result of the quantitative recovery of soy fiber nonstarch polysaccharide. Nitrogen and amino acid digestibilities were unchanged by the ingestion of soy fiber. Nutrients from the total enteral nutrition formulas were well digested in the small intestine with true nitrogen and amino acid digestibilities in excess of 90% and starch digestibilities approaching 100%. Ileal mucin output was higher in male subjects and was unaffected by soy fiber intake. In summary, soy fiber supplementation does not compromise protein and carbohydrate absorption from the small intestine of humans.

Small intestinal function following syngeneic transplantation in the rat

Improvements in immunosuppression have led to the use of small intestinal transplantation clinically. Previous studies have suggested that the transplantation process and immunosuppression with cyclosporin independently affect small intestinal function. This study describes the effects of syngeneic small intestinal transplantation and cyclosporine in rats on intestinal permeability and nutrient transport. Orthotopic transplantation of the small intestine was performed between syngeneic (Lewis) rats. Transplanted animals received chronic treatment with cyclosporine (10 mg/kg) or vehicle on alternate days. Sham operated controls received treatment with vehicle. Animals were followed for 60 days monitoring weight gain, feed intake, intestinal permeability, in vivo absorption of dietary fat and carbohydrate, and at sacrifice in vitro transmural flux of 3-O-methyl-D-glucose. Weight gain, feed intake, and absorption of fat and carbohydrate from the diet were not altered by intestinal transplantation alone; transplantation plus cyclosporine treatment caused a slight reduction in dietary fat absorption. Both the transplant and transplant plus cyclosporine groups demonstrated increased permeability to 51Cr-EDTA and mannitol but not lactulose. Jejunal and ileal 3-O-methyl-D-glucose net transmural flux was decreased in both transplant and transplant plus cyclosporin groups. Intestinal transplantation and cyclosporin treatment reduce mucosal glucose transport and increase intestinal permeability. These altered transport characteristics could affect dietary choices and the selection of immunosuppressive drugs during clinical transplantation efforts, however, the overall impact on animal well-being was minimal, and support the continued study of intestinal transplantation for clinical application.

Oral budesonide as maintenance treatment for Crohn's disease: a placebo-controlled, dose-ranging study. Canadian Inflammatory Bowel Disease Study Group

BACKGROUND & AIMS

Budesonide is a corticosteroid with high topical anti-inflammatory activity and low systemic activity due to rapid hepatic metabolism. The efficacy and safety of an oral controlled-release preparation of budesonide for maintenance of remission was evaluated in patients with ileal or ileocecal Crohn's disease.

METHODS

In a double-blind, multicenter trial, 105 patients were randomly assigned to receive placebo or budesonide at doses of 3 or 6 mg daily for 1 year. The primary outcome measure was relapse defined by a Crohn's Disease Activity Index score of > 150 and a minimum increase of 60 points.

RESULTS

Patients receiving 6 mg of budesonide had a median time to relapse or discontinuation of therapy of 178 days compared with 124 days in those receiving 3 mg of budesonide and 39 days in those receiving placebo. However, at 1 year, the rate of relapse in the group receiving 6 mg of budesonide was similar to the rates in the 3-mg and placebo groups. Basal plasma cortisol levels and incidence of corticosteroid-associated effects were similar in the three groups.

CONCLUSIONS

Oral controlled-release budesonide (6 mg/day) was well tolerated and prolonged remission in Crohn's disease of the ileum and proximal colon, but this effect was not sustained at 1-year follow-up.

Mesalazine (Mesasal/Claversal) 1.5 g b.d. vs. placebo in the maintenance of remission of patients with Crohn's disease

INVESTIGATORS: This multicentre study was conducted by 29 principal investigators in 11 countries.

AIMS

To compare the safety and efficacy of oral mesalazine (Mesasal/Claversal, 5-ASA) 1.5 g b.d. in comparison with placebo in the maintenance of remission in 286 patients with Crohn's disease.

MATERIALS AND METHODS

Patients had to score less than 150 in their Crohn's Disease Activity Index (CDAI), and had to have had one period of clinical activity (CDAI > 150) within 18 months of the study start. Patients were randomized to receive 5-ASA 1.5 g b.d. daily or matching placebo for 12 months. Study visits were scheduled for months 1, 3, 6, 9 and 12, or when symptoms suggested a relapse of the disease. Relapse was defined as a CDAI score greater than 150, with at least a 60-point increase from the baseline index score. None of the patients used glucocorticoids or immunosuppressants during the trial.

RESULTS

In the first group, 207 patients with Crohn's colitis or ileocolitis were randomized: there were 101 females and 106 males, in age range 18-71 years. A total of 106 patients (51 in the 5-ASA group and 55 in the placebo group) were withdrawn from the study due to adverse events, insufficient therapeutic effect, or for other reasons. This left 101 patients (51 in the 5-ASA group and 50 in the placebo group) who completed the 12-month trial. In the second group, 79 patients with Crohn's ileitis were randomized to treatment. There were 53 females and 26 males, age range 18-66 years. A total of 41 patients (19 in the 5-ASA group and 22 in the placebo group) were withdrawn from the study. This left 38 patients (17 in the 5-ASA group and 21 in the placebo group) who completed the 12-month trial. The primary efficacy variable was the CDAI. A protocol-eligible analysis and an intent-to-treat analysis were performed. No statistical differences were noted between the two analyses. In patients with Crohn's colitis or ileocolitis, or in those with ileitis, no statistically significant differences were noted with respect to the relapse rates between the 5-ASA and the placebo treatment groups. Adverse events in the gastrointestinal system were the most frequently reported in both treatment groups. Many of the events such as diarrhoea or abdominal pain are symptoms of Crohn's disease. The majority of the events reported were mild or moderate in severity. In neither study was the prevalence of adverse events or the proportion of drop-outs different between patients in the treatment or in the placebo groups. The site of the Crohn's disease had no effect on the frequency of adverse events.

CONCLUSION

The relapse rates of Crohn's disease were similar for up to 12 months in both the 5-ASA 1.5 g b.d. and the placebo treatment groups.

Diurnal variation in the pharmacokinetics of nizatidine in healthy volunteers and in patients with peptic ulcer disease

Six healthy volunteers and six patients with asymptomatic duodenal ulcer disease received placebo or 300 mg nizatidine once at night or twice daily (morning and evening) for a week in a random, cross-over fashion. Steady-state serum nizatidine concentrations and gastric pH were measured over a 24-hour period. No significant differences in the pharmacokinetic indices were observed between the healthy volunteers and patients with duodenal ulcer disease. In patients with duodenal ulcers, significantly lower peak serum concentrations, longer half-life (t1/2) and larger volume of distribution (Vd) were observed after the night doses compared with the daytime doses. The diurnal variation in drug kinetics between the nighttime and daytime doses in the twice daily regimen may be caused by a slower absorption rate, paralleled with a higher extent of distribution. Despite lower serum nizatidine concentrations, gastric pH was higher in the evening than in the daytime; it is speculated that this was due to a time-dependent enhanced distribution of the H2-receptor blocker into the site of action.

Na(+)-K(+)-ATPase alpha 1- and beta 1-mRNA and protein levels in rat small intestine in experimental ileitis

Na(+)-K(+)-adenosinetriphosphatase (ATPase) plays a key role in the absorption of electrolytes, water, and nutrients from the small intestine. The expression of Na(+)-K(+)-ATPase was examined in isolated enterocytes during the course of the ileal inflammatory response elicited by intraluminal administration of 2,4,6-trinitrobenzenesulfonic acid. The ileal inflammatory response was characterized by a marked cellular infiltrate, villous atrophy, and crypt hyperplasia along with fibrosis and smooth muscle hypertrophy. Peak levels of myeloperoxidase were observed at day 7, and ileal mucosal injury was paralleled by increases in ileal mucosal permeability. Ileal enterocytes were harvested from days 3 to 30 after the induction of ileitis. Decreases in Na(+)-K(+)-ATPase functional activity were observed from days 3 to 21 and were accompanied by corresponding decreases in Na(+)-K(+)-ATPase pump abundance, alpha 1- and beta 1-protein expression, and mRNA abundance, whereas Na(+)-K(+)-ATPase turnover, Michaelis-Menten constant values, and inhibition constant values for Na+ and ouabain, respectively, were unaltered. Alterations in transcriptional and posttranscriptional events may determine the changes in Na(+)-K(+)-ATPase activity in this particular model. Additionally observed increases in thymidine kinase and ornithine decarboxylase activities appear to signify alterations in the state of differentiation of the ileal epithelium and may determine the phenotypic expression of enterocyte transporters and permeability in the setting of inflammation.

Role of a brush border membrane fatty acid binding protein in oleic acid uptake into rat and rabbit jejunal brush border membrane

Oleic acid uptake was studied using adult rat and rabbit jejunal brush border membrane vesicles. The intestinal uptake of oleic acid is influenced by the activity of an amiloride-inhibitable brush border membrane Na+/H+ exchanger, NHE3: opposing Na+/H+ gradients (inward Na+ and outward H+ gradients) increased oleic acid uptake by about 40%, as compared with only an inward Na+ gradient, only an outward H+ gradient, or the absence of either Na+ or H+ gradients. This study was undertaken to test the hypothesis that a portion of oleic acid uptake is facilitated by a fatty acid binding protein in the brush border membrane (FABPPM) of adult rat jejunum. There was a reduction in the uptake of oleic acid when brush border membrane vesicles were incubated with a rat liver plasma membrane fatty acid binding protein antibody (anti-FABPPM-Ab) in the absence, but not in the presence, of opposing Na+/H+ gradients. Thus, oleic acid uptake occurs largely by partitioning of the lipid into the brush border membrane, as well as by a process which involves the activation of the brush border membrane Na+/H+ exchanger, and a membrane fatty acid binding protein.

Small bowel permeability--a variable effect of NSAIDS

The baseline permeability of small bowel in 57 healthy volunteers was assessed by measuring the mannitol and chromium-EDTA recovery in a 5-hour urine collection after ingestion of a drink containing a mixture of 1 g of mannitol and 3.7 MBq of 51Cr-EDTA. Subjects were treated with medication for 1 week followed by permeability studies as described above. The regimens used were diclofenac sodium (Voltaren) 50 mg po tid (21 subjects), Voltaren SR 75 mg bid for 1 week (34 subjects), indomethacin 50 mg tid (10 subjects), and tenoxicam (Mobiflex) 20 mg daily (13 subjects). There was no significant difference between the mannitol recoveries at baseline or after any of the drugs. The permeability was clearly increased by indomethacin and by Voltaren SR. Conventional-release Voltaren increased permeability, but the results were not significantly above baseline. Mobiflex had no influence on the measured permeability. Our results suggest that the SR preparation of diclofenac has a more pronounced effect than regular diclofenac sodium; thus different NSAIDs and different preparations of the same NSAID may have different effects on small bowel permeability.

Age of rat influences isolation of jejunal enterocytes from along the villus

Aging is associated with alterations in the functions of the intestine. Also, the functions of the intestine vary along the length of the villus. A method is reported for the isolation of four fractions of enterocytes from along the villus of young (3 months, 300-350 g) and old (8 months, 700-750 g) male Wistar rats. Different qualitative patterns are seen when the activities of alkaline phosphatase (AP), invertase (INV), or [3H]methylthymidine incorporation are expressed on the basis of millimoles per gram protein, percentage of highest activity, percentage of total activity, cumulative activity for each fraction, or millimoles per gram protein versus cumulative percentage of total protein. When expressed on the basis of protein, AP is higher in upper (FI) versus lower (FIV) villus fractions, and in each fraction AP is higher in old versus young animals. INV varies little along the villus or between young and old rats; [3H]methylthymidine incorporation is highest in the crypt cells. The ratio mg protein/mg DNA varies along the villus and is twofold higher in young than in old rats. In contrast, when activities are expressed on the basis of DNA, the same qualitative patterns are seen along the villus, but INV and AP are both higher in young than in old rats. In summary (i) the qualitative and quantitative differences in the activities of AP and INV along the villus of old versus young rats vary when the data are expressed on the basis of DNA rather than protein; (ii) the ratio of protein to DNA varies along the villus in young and old animals, and for this reason it is appropriate to report enzyme activity on the basis of enterocyte DNA; and (iii) INV and AP, when expressed on the basis of DNA, are higher in young than in old animals. Thus, the isolation of rat jejunal enterocytes from along the villus is affected by the age of the animals.

Oleic acid uptake into rat and rabbit jejunal brush border membrane

Oleic acid uptake was studied using adult rabbit and rat jejunal brush border membrane vesicles. There was a reduction of oleic acid uptake following trypsin-treatment. Opposing Na+/H+ gradients (inward Na+ and outward H+ gradients) increased oleic acid uptake by about 40%, as compared with only an inward Na+ gradient, only an outward H+ gradient, or the absence of either Na+ or H+ gradients. The addition of mucin further increased the enhanced uptake of oleic acid observed in the presence of opposing Na+/H+ gradients. Amiloride, an inhibitor of the Na+/H+ exchanger, reduced by about 40% the uptake of oleic acid into sheets of rat jejunum, and this inhibitory effect was observed over a range of rates of stirring of the bulk phase. In rabbit jejunal brush border membrane vesicles, amiloride reduced oleic acid uptake in the presence but not in the absence of opposing Na+/H+ gradients, with a Ki of approx. 36 microM. Thus, oleic acid uptake occurs largely by partitioning of the lipid into the brush border membrane, influenced by a process which involves the activation of the brush border membrane Na+/H+ exchanger.

Orally administered immunosuppressants modify intestinal uptake of nutrients in rabbits

The effect on intestinal nutrient transport of the immunosuppressive drugs cyclosporin A (CsA), cyclosporin G (CsG), and rapamycin (RAP) was determined in New Zealand white rabbits. Rabbits received oral doses of CsA (20 mg/kg/day), CsG (10 mg/kg/day), or RAP (1 mg/kg/day) for 10 days. Animals receiving RAP had decreased food intake and weight gain compared with controls. This correlated with a decrease in both total ileal weight and corresponding mucosal weight. CsA and CsG administration had no effect on food intake, total weight gain, or intestinal weight. Villus surface area was significantly decreased in all groups as compared with controls. Jejunal uptake of D-glucose as well as 1 medium and 4 long chain fatty acids was not affected by drug administration, while both mucosal-to-serosal and net 3-0-methylglucose fluxes were increased (P < 0.05) in the jejunum by all 3 drugs. In the ileum, the rates of uptake of D-glucose as well as stearic and linoleic acids were increased in animals treated with RAP compared with controls. There was an increase in the ileal values of the maximal transport rate (Vmax) and apparent Michaelis constant (Km*) in RAP, and a fall in the Vmax and Km* in CsG. CsG administration resulted in a decreased cholesterol uptake in both jejunum and ileum, and a decreased D-glucose uptake in the ileum compared with controls. These differences in glucose uptake among groups could not be attributed to variations in body, intestinal, or mucosal weights. It is unlikely that the changes observed in CsA- and CsG-treated animals would have nutritional importance, as these animals gained weight normally. In addition, in these animals the changes mainly occurred in the ileum, not in the jejunum, where most glucose is absorbed, and the associated alterations in the values of the Vmax and Km* would lead to reciprocal changes in the rates of uptake of varying luminal concentrations of glucose. In contrast, these changes are likely to be of more importance in RAP-treated animals, since they failed to gain weight normally. The significance of these findings needs to be established in chronically treated animals.

Dietary omega 3 fatty acids and cholesterol modify enterocyte microsomal membrane phospholipids, cholesterol content and phospholipid enzyme activities in diabetic rats

Diabetes-associated changes in intestinal uptake of nutrients are modified by isocaloric variations in the type of dietary lipids, and are associated with alterations in the phospholipid and fatty acyl content of the intestinal brush border membrane. The present study was designed to test the hypothesis that diet- and diabetes-associated changes in enterocyte microsomal membrane phospholipids are due to variations in the activity of two phospholipid metabolizing enzymes, 1,2-diacylglycerol:CDPcholine cholinephosphotransferase (CPT) and phosphatidylethanolamine methyltransferase (PEMT). Adult female Wistar rats were fed one of four semisynthetic diets--beef tallow low in cholesterol (BT), beef tallow high in cholesterol (BTC), fish oil low in cholesterol (FO) or fish oil high in cholesterol. In half of the animals, diabetes mellitus was produced by injection of streptozotocin. Jejunal and ileal enterocyte microsomes (EMM) were isolated and analyzed for cholesterol and phospholipids, as well as for CPT and PEMT activities. In control animals, feeding FO reduced EMM total phospholipids including phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol. Feeding FO resulted in a greater than 95% reduction in the activity of CPT. Diabetes was associated with increased jejunal EMM total phospholipids including sphingomyelin (SM) and PE, without associated changes in CPT or PEMT. Dietary cholesterol supplementation did not affect EMM total cholesterol or phosphlipid composition in control rats fed BT or FO, but was associated with an increase in EMM cholesterol in diabetic rats fed BT or FO. A decrease in total phospholipids due to a decline in SM, PC and PE in diabetic rats fed FO was not associated with changes in the activities of CPT or PEMT in EMM.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral budesonide for active Crohn's disease. Canadian Inflammatory Bowel Disease Study Group

BACKGROUND

Corticosteroids are the most efficacious drugs for inducing remission in active Crohn's disease, but their benefits are frequently offset by serious side effects. Budesonide is a corticosteroid with high topical antiinflammatory activity but low systemic activity because of extensive hepatic metabolism. We investigated the efficacy and safety of an oral controlled-ileal-release preparation of budesonide in patients with active Crohn's disease involving the ileum or ileum and proximal colon.

METHODS

In a double-blind, multicenter trial, 258 patients were randomly assigned to receive placebo or one of three doses of budesonide--3, 9, or 15 mg daily. The primary outcome measure was clinical remission, as defined by a score of 150 or less on the Crohn's disease activity index.

RESULTS

After eight weeks of treatment, remission occurred in 51 percent of the patients in the group receiving 9 mg of budesonide (95 percent confidence interval, 39 to 63 percent), 43 percent of those receiving 15 mg (95 percent confidence interval, 31 to 55 percent), and 33 percent of those receiving 3 mg (95 percent confidence interval, 21 to 44 percent), as compared with 20 percent of those receiving placebo (P < 0.001, P = 0.009, and P = 0.13, respectively). Improvements in the quality of life, as measured by the patients' responses to the inflammatory bowel disease questionnaire, paralleled these remission rates. Location of disease, prior surgical resection, and previous use of corticosteroids did not affect the outcome. A total of 119 patients (46 percent) were withdrawn from the study before the trial ended, 96 because of insufficient therapeutic effects, 13 because of adverse reactions, and 10 because of noncompliance. Budesonide caused a dose-related reduction in basal and corticotropin-stimulated plasma cortisol concentrations but was not associated with clinically important corticosteroid-related symptoms or other toxic effects.

CONCLUSIONS

In an eight-week trial, an oral controlled-release preparation of budesonide at an optimal daily dose of 9 mg was well tolerated and effective against active Crohn's disease of the ileum and proximal colon.

A dose-ranging study of ranitidine and its effect on intragastric and intra-oesophageal acidity in subjects with gastro-oesophageal reflux disease

METHODS

This randomized, double-blind, single-centre, crossover study was designed to assess the effects of three regimens of ranitidine (150 mg b.d., 300 mg b.d. and 300 mg q.d.s.) and placebo on intra-oesophageal and intragastric pH in subjects with gastro-oesophageal reflux disease (GERD). Twenty-six subjects were screened, and 9 were evaluable by the admission criteria. These 9 subjects received each of the regimens for 72 h, and a wash-out period of at least 48 h followed each dosing period. Standard meals and beverages were provided.

RESULTS

With increasing doses of ranitidine, 24-h intragastric mean H+ and integrated H+ fell, and the percentage of the time the pH was equal to or greater than 4 (% time pH > or = 4) rose: the minimum effective dose for these effects was ranitidine 300 mg daily. With increasing doses of ranitidine there was also a progressive decline in mean 24-h intra-oesophageal H+ and integrated H+, and increasing % time pH > or = 4. The minimal effective dose was 300 mg daily for intra-oesophageal mean H+ and integrated H+, and 600 mg for % time pH > or = 4. The minimal effective dose to decrease the number of reflex episodes was 1200 mg ranitidine. For the daytime upright position, a dose effect of increasing ranitidine was also seen, with minimal effective ranitidine doses of 300 mg for a decrease in mean H+, and 1200 mg for % time pH > or = 4.

CONCLUSION

If these higher doses of ranitidine are confirmed to be more effective than the standard 150 mg b.d. regimen for the treatment of patients with gastro-oesophageal reflux disease, then the mechanism of this action probably relates to the lower exposure of the oesophageal mucosa to acid.

The future of clinical investigators and of academic medicine in Canada

Health is part of our own personal well-being, as well as that of the community and of our nation: clinician-investigators lead us forward in new medical developments, and may even be of assistance in developing innovative programs of cost control and outcome analysis. Canada now devotes close to 10% of its gross national product to health expenditures, second only to the United States, and yet there is still the widespread perception within this country that "there is not enough." The issues are how to do more with less, and how to recruit more clinician-investigators from the diminishing pool of potential recruitees. Academic medicine, with its research focus, is well-suited to bring together newer perspectives of education and health, and these clinician-investigators may improve major areas of our health care partnership.

Effect of isradipine on the formation and regression of fatty streaks in cholesterol fed rabbits

OBJECTIVE

The aim was to determine whether the antiatherogenic effect of the calcium channel blocker isradipine on fatty streak formation was dependent upon a temporal relationship between cholesterol feeding and administration of the drug.

METHODS

The study was done in New Zealand White rabbits fed a diet supplemented with cholesterol (2.5% w/w) for three weeks. Such a regimen results in loss of endothelium dependent relaxation and accumulation of cholesterol in the aorta four weeks later. The calcium antagonist isradipine was given in a dose of 0.25 mg.kg-1.d-1 at specified periods during the study to seven subgroups of animals: (1) standard diet + 2.5% cholesterol for three weeks; (2) standard diet + 2.5% cholesterol for three weeks followed by standard diet for four weeks; (3) standard diet + 2.5% cholesterol for three weeks followed by standard diet for 12 weeks; (4) standard diet + 2.5% cholesterol+isradipine for three weeks followed by standard diet alone for four weeks; (5) standard diet + 2.5% cholesterol for three weeks followed by standard diet for four weeks with isradipine given throughout the seven weeks; (6) standard diet + 2.5% cholesterol for three weeks followed by standard diet for four weeks with isradipine given during the final four weeks only; (7) standard diet + 2.5% cholesterol for three weeks followed by standard diet for 12 weeks with isradipine given during the final eight weeks. Aortic tissue was removed for measurement of cholesterol content, endothelium dependent relaxation to acetylcholine and the calcium ionophore A23187, and relaxant responses to sodium nitrite. Serum was collected for measurement of cholesterol and triglyceride concentration.

RESULTS

When isradipine was given either during cholesterol feeding and continued for four weeks following it (subgroup 5) or during the four weeks following cholesterol feeding (subgroup 6), loss of endothelium dependent relaxation and the accumulation of cholesterol in the aorta was prevented. However, administration of isradipine during the period of cholesterol feeding alone (subgroup 4) was without effect. Also, administration of isradipine after lesions of fatty acid streak type were established appeared to have a favourable effect on removal of cholesterol from the aorta.

CONCLUSIONS

Isradipine protects against the development of fatty streaks in rabbits fed a diet supplemented with 2.5% cholesterol. Administration of this drug after fatty streaks are formed also promotes their resolution.