Christian Olsen

An enzymatic fluorimetric micromethod for the determination of acetoacetate, β-Hydroxybutyrate, pyruvate and lactate

Abstract A simple and rapid method was developed for determining acetoacetate, β-hydroxybutyrate, pyruvate and lactate in whole blood in a sample of 0.2 ml. The procedures were based on enzyme-catalyzed reactions involving changes m the concentration of coenzyme (NADH), which was measured by its native fluorescence. Proportionality between concentration and fluorescence emission was established, problems with non-specific NADH reaction were overcome and the blank fluorescence was markedly reduced. This makes the method highly reliable and well-suited for routine use.

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.

The lactate/pyruvate ratio in muscular work and following injection of lactate in man

SummaryThe concentration of lactate and pyruvate in arterial and in venous blood draining a resting limb were determined in seven young adults at rest, during and after exercise and after injection of sodium-(l+)-lactate.1.The arteriovenous lactate difference was negative at rest but positive during exercise.2.The arteriovenous pyruvate difference was positive both at rest, during and after exercise.3.The L/P ratio was higher in venous than in arterial blood at rest but lower during exercise.4.Following injection of lactate the lactate/pyruvate ratio rose markedly. There was no significant difference between the arterial and venous ratios.5.The concentration of pyruvate rose and reached a maximum 7 min after the injection of lactate. The arteriovenous difference of pyruvate remained positive. The results exclude the concept that the elevated lactate/pyruvate ratio in arterial blood during exercise originates in the resting extremities, and suggest that the lactate/pyruvate ratio in the blood is of limited value as an indicator of the cellular redox level in muscle.

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.