ABSTRACT
The aim of this study was to characterise the individual human gastric and duodenal juices to be used in in vitro model digestion and to examine the storage stability of the enzymes. Gastroduodenal juices were aspirated, and individual variations in enzymatic activities as well as total volumes, pH, bile acids, protein and bilirubin concentrations were recorded. Individual pepsin activity in the gastric juice varied by a factor of 10, while individual total proteolytic activity in the duodenal juice varied by a factor of 5. The duodenal amylase activity varied from 0 to 52.6 U/ml, and the bile acid concentration varied from 0.9 to 4.5 mM. Pooled gastric and duodenal juices from 18 volunteers were characterised according to pepsin activity (26.7 U/ml), total proteolytic activity (14.8 U/ml), lipase activity (951.0 U/ml), amylase activity (26.8 U/ml) and bile acids (4.5 mM). Stability of the main enzymes in two frozen batches of either gastric or duodenal juice was studied for 6 months. Pepsin activity decreased rapidly and adjusting the pH of gastric juice to 4 did not protect the pepsin from degradation. Lipase activity remained stable for 4 months, however decreased rapidly thereafter even after the addition of protease inhibitors. Glycerol only marginally stabilised the survival of the enzymatic activities. These results of compositional variations in the individual gastrointestinal juices and the effect of storage conditions on enzyme activities are useful for the design of in vitro models enabling human digestive juices to simulate physiological digestion.
ABSTRACT
BACKGROUND: Invasive coronary angiography is the gold standard for diagnosing coronary artery disease. CT angiography (CTA) is a non-invasive alternative that is more available and less expensive. Previous Norwegian experience with 16-channel CT has been less successful than that reported from other countries. Improved image resolution has increased expectations of a better diagnostic accuracy, but a new local assessment of the method's usefulness is needed before routine usage is implemented. MATERIAL AND METHODS: Patients with suspected stabile coronary disease, referred to invasive coronary angiography, were first assessed with 64-channel CT angiography. Patients with atrial fibrillation or previous bypass operation were not included. All patients who fulfilled the eligibility criteria were included in the study (104), but 13 who had an Agatston calcium score > or = 800 and three for whom the examinations were technically unsuccessful were excluded; the study material therefore consisted of 88 patients. We assessed the method's ability (diagnostic accuracy) to detect diameter stenoses > or = 50% in coronary segments > or = 2 mm (without stent). RESULTS: When 4% non-interpretable segments were interpreted as positive (stenotic), the sensitivity was 97%, the specificity 78% and the positive and negative predictive values were 77 and 98% on a patient level. For 50 patients who did not have significant stenosis, CTA correctly identified 39, but overestimated the degree of stenosis in 11 patients. INTERPRETATION: 64-channel CTA is best at ruling out obstructive coronary artery disease in patients with intermediate risk of such disease. Few patients with significant lesions were missed due to false negative CTA evaluations, but false positive findings are a problem in low risk populations.