Mechanism of reaction of carcinogen N-acetoxy-2-acetylaminofluorene with DNA

Summary Scavenging studies are supporting the notion that triplet radical cations are formed during the binding of the carcinogen N-acetoxy-2-acetylamino-fluorene to native DNA in vitro.This work was supported by Grant No.3305.78 of the Swiss National Science Foundation and by a grant from The Roche Research Foundation.     

DNA sequence organisation in relation to genome size in birds

Summary DNA sequence interspersion was investigated in pheasant and pelican nuclear DNA. As is typical for birds, these genomes are organized in a long period pattern. Altogether, 5 bird species with genome sizes between 1.6 and 1.9 pg DNA are compared with regard to the extent of repetitive and single copy sequence interspersion. The result indicates that the average length of interspersed repetitive sequences increases with genome size.Acknowledgment. This work was supported by the Deutsche Forschungsgemeinschaft. Mrs H. Tuczynski and Mr J. S. Jackson are thanked for editorial assistance.     

Effect of physical exercise on the specific activity of carbonic anhydrase isozyme in human erythrocytes

Summary Significant decreases in the levels of both carbonic anhydrase type B and total esterase activity of human erythrocytes were observed after physical exercise (bicycle ergometer, 150 W for 30 min). Since carbonic anhydrase B-dependent esterase activity likewise decreased, the decrease in the total esterase activity would be caused by the decrease of carbonic anhydrase B activity. The specific activity of carbonic anhydrase B tended to decrease after the exercise. On the other hand no such effects were noted for carbonic anhydrase type C.     

Leydig cell function in streptozotocin-induced diabetic rats

Summary Streptozotocin diabetic rats were infertile as a result of decreased Leydig cell function of the testes. The major changes found were: decreased number of Leydig cells and their spontaneous secretion of testosterone. No change in the receptors to LH on the Leydig cells was observed. LH was found to be obligatory for the regulation of Leydig cell function and fertility.     

Acetylcholine-induced atrial tachyarrhythmia: A modification to quantitate potency and duration

Résumé La méthode d'induction de fibrillation auriculaire par l'acétylcholine est couramment utilisée pour tester l'action de substances anti-arythmiques. Nous avons modifié cette méthode de telle sorte que la fibrillation peut être induite à plusieurs reprises, à 15 minutes d'intervalle, chez le chien anesthésié. Ceci permet la détermination de l'efficacité et de la durée d'action dans des conditions bien contrôlées.