Here we describe an evaluation of the effectiveness, compared with a traditional laboratory, of an interactive computer-assisted learning (CAL) program, which simulates a series of experiments performed using isolated, everted sacs of rat small intestine. The program is aimed at undergraduate students of physiology and is designed to offer an alternative student-centered learning approach to the traditional laboratory-based practical class. The evaluative study compared two groups of second-year undergraduate students studying a module on epithelial transport: one group worked independently using the CAL program and associated learning materials, and the other group followed a conventional practical class approach, working in the laboratory under supervision. Knowledge gain of each group was measured by means of a test consisting of a range of question types (e.g., short-answer factual, calculation, interpretation) given to students before and after the module. Student attitude to both approaches was assessed by questionnaire, and the resource requirements were also compared. It was found that the knowledge gain of both groups of students was the same, that students had a positive attitude toward using CAL programs of this type, and that the cost of the conventional laboratory-based approach was five times greater. The potential for integrating CAL programs into the undergraduate curriculum is discussed.

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SUMMARY1. The involvement of Ca2+ in the regulation of intestinal secretion was investigated in stripped sheets of rat mid-intestine.2. Removal of serosal Ca2+ together with the addition of EGTA at concentrations of 05 and 1 mm inhibited the rise in short-circuit current (s.c.c.) induced by both acetylcholine and theophylline, a similar degree of inhibition being observed with both secretagogues.3. Ca2+-free serosal fluid with 05 mM-EGTA added reduced significantly the rises in s.c.c. induced by A23187, acetylcholine, 5-hydroxytryptamine, theophylline, dibutyryl cyclic AMP and prostaglandin E2, but not the increased s.c.c. associated with glucose absorption. The Ca2+ channel blocker verapamil produced similar results.4. The calmodulin antagonist trifluoperazine inhibited secretagogue action while its sulphoxide derivative was without effect at the same concentration.5. The intracellular Ca2+ antagonist TMB-8 reduced the increased s.c.c. observed with acetylcholine and dibutyryl cyclic AMP.6. The net Cl-secretion, but not the decreased mucosal-to-serosal Na+ flux, induced by acetylcholine was abolished in Ca2+-free conditions. There was no consistent effect on the reduction in the residual ion flux caused by acetylcholine.7. Absence of Ca2+ converted the stimulation of Cl-secretion induced by dibutyryl cyclic AMP observed under control conditions to an enhancement of net Na+ and Cl-absorption.8. It is concluded that intestinal secretagogues, whether they act through cyclic AMP or not, require both internal and external sources of Ca2+ if they are to produce their full effects. Moreover, it appears that the nature of the response to dibutyryl cyclic AMP depends on the prevailing Ca2+ concentration.

The rise in short-circuit current associated with the active transport ofglucose and alanine was measured in intestinal biopsy samples from children with cystic fibrosis. The glucose-induced increase in the short-circuit current was greater in the cystic fibrosis tissues than in control samples over the whole range of concentrations tested (2.5-35 mM), a reflection of an increased maximum rate of transport. Similar results were obtained with alanine. These findings suggest that active Na+-linked nutrient transport is enhanced in cystic fibrosis.

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