Niels Krarup

Open-Book Tests in a University Course.

In the few available studies on the use of books in examinations, open-book tests have been found to reduce pre-test memorization and anxiety during examinations without affecting academic performance. However, these studies were made with students in non-book systems, whereas systems which allowed books in all exams might be thought likely to create a non-fact-learning attitude in students. The present study was undertaken in a book-allowing system with 120 students during a regular course in physiology at a medical school. Each group sat two parallel 60-item multiple choice tests and used books in one test but not in the other. The tests took place about four weeks prior to the final examination, which is of the same type as the experimental tests. Recall items could yield less than 15% of maximum points, so that interpretation and problem-solving items predominated. Total test points with and without books did not differ significantly. An analysis of variance showed that the effect of books on recall items was only slight and that the two tests varied in difficulty, in spite of efforts to secure equality.

Chronic Portal Venous Hypertension: The Effect on Liver Blood Flow and Liver Function and the Development of Esophageal Varices

Portal venous hypertension was induced in Göttingen minipigs by banding the portal vein. The pigs were checked repeatedly during the following 24 weeks. Portal pressure increased immediately on banding, from 8.4 +/- 0.7 mm Hg to 19.4 +/- 0.7 mm Hg, and remained constant throughout the observation period. Within 5 weeks all pigs developed esophageal varices, as demonstrated by portal angiography and endoscopy. The experimentally induced portal hypertension was accompanied by a 65% decrease in hepatic blood flow, most probably caused by almost complete shunting of portal venous blood. The hepatic arterial flow appeared to be within normal limits and sufficient to cover the oxygen demand of the liver; to judge from the splanchnic elimination rate of galactose, the hemodynamic changes did not affect the functional capacity of the liver.

Endoscopic, Portographic, and Hemodynamic Evaluation of Prolonged Propranolol Administration in Pigs with Experimental Portal Hypertension and Esophageal Varices

The effect of long-term propranolol administration on esophageal varices, portocollateral shunting, portal pressure, hepatosplanchnic hemodynamics, and liver function was studied in a pig model with experimentally induced prehepatic portal hypertension and esophageal varices. Five pigs were treated with 160 mg propranolol daily from week 5 to week 24 after portal-vein banding, and five pigs served as nontreated controls. Administration of propranolol caused an initial, significant reduction (20%) of portal venous pressure, followed by a gradual increase to levels not different from control pressures. In contrast, a marked reduction of the caliber of the coronary vein and size of the esophageal varices was noticed. Twenty weeks of propranolol treatment did not change liver blood flow or liver function. We conclude that the size of the varices rather than portal venous pressure depicts the effect of propranolol treatment and suggest that the beneficial effect of propranolol on variceal bleeding can be explained by a reduction in the wall tension of the varices, initiated and maintained by a diminution of splanchnic blood flow.

Effect of Endoscopic Sclerotherapy of Esophageal Varices on Liver Blood Flow and Liver Function: An Experimental Study

In 10 Göttingen mini-pigs esophageal varices developed after banding of the portal vein. In five pigs the varices were treated by paravariceal injection of polidocanol, and the rest served as controls. As judged from endoscopy and portography, the varices disappeared after four sclerotherapy sessions within 4 weeks, and at the same time portal venous pressure rose from 19 to 38 mm Hg. No changes were seen in the control group. After 24 weeks of observation the hepatic blood flow in the untreated group was 10 ml/kg/min, and portal angiography showed that nearly all the portal blood bypassed the liver. In the pigs treated with sclerotherapy the hepatic blood flow increased to 28 ml/kg/min, angiography showed a normal hepatogram, and no filling of the collaterals was seen. Sclerotherapy induced only a few changes in liver function, and these may be related to the concomitant increase in liver blood flow.

Energy requirement of the transport of reducing equivalents from cytosol to mitochondriae in perfused rat liver

Abstract The system transporting reducing equivalents across the mitochondrial membrane was investigated by following the flux of reducing equivalents from cytosol to mitochondriae, estimated from the ethanol elimination, and the redox potentials on both sides of the mitochondrial membrane, estimated from the lactate/pyruvate and β-hydroxybutyrate/acetoacetate ratios in the effluent medium. The power of the transport system was calculated to be 1.8×10 −3 cal/min/g liver (wet wt.), which was about 1% of the metabolic rate. Uncoupling by 2,4 dinitrophenol increased the oxygen consumption 30%, but the ethanol elimination decreased despite a fall in the redox potential gradient, resulting in a 50% decrease in power of the transport system. This indicates that the transport of reducing equivalents from cytosol to mitochondriae is energy dependent.