No abstract

SUMMARYHighly tritium-iabelled oxy tocin and lysine-vasopressin have been synthesized. L-tyrosine-3-3H was prepared from L-3-iodotyrosine and tritium gas in methanolic potassium hydroxide with palladium on active carbon as a catalyst. The tritiated oxytocin and lysinevasopressin were obtained from the tritiated tyrosine and the heptapeptides of oxytocin and lysine-vasopressin, respectively, by the p-nitrophenyl ester method. The peptides had a high degree of purity and the specijic radioactivity was 2.9 Clmmole or 5.9 pC/IU for oxjtocin and 1.9 Clmmole or 6.5 pClIU for lysine-vasopressin. The high radioactivity of the peptides permits extensive studies of their properties in vivo. The stability of the tritium label is discussed.

Lysine vasopressin tritiated at meta position of tyrosine (1.9 Ci/mmole) decomposes during a long storage period, mainly as a result of radiolysis. The loss of specific activity by isotopic exchange with water is slow. The nonlabelled peptide undergoes only very minute decomposition (polymerization). Specific radioactivity declines with a half life of 47.4 months.

No abstract

The aim here was to employ color tissue velocity imaging (TVI), to test the hypothesis that highly trained endurance athletes exhibit enhanced systolic function of the left ventricular (LV) myocardium both at rest and during combined arm-and-leg exercise in comparison with untrained subjects. For each of the ten elite male (EG) and ten matched control participants (CG), LV dimensions and systolic function were assessed at rest using echocardiography. Subsequently, these subjects exercised continuously on a combined arm-and-leg cycle ergometer for 3 min each at 50, 60, 70, 80, 90 and 100% of VO(2max). Oxygen uptake, heart rate, systolic blood pressure (SBP) and peak contraction systolic velocities of the LV myocardium (PSV) were recorded in the end of each level. At rest, the trained and untrained groups differed with respect to LV dimensions, but not systolic function. At 60-100% VO(2max), the EG group demonstrated both higher PSV and SBP. The observation that the EG athletes had higher PSV than CG during exercise at 60-100% VO(2max), but not at rest or at 50% of VO(2max), suggested an enhanced systolic capacity. This improvement is likely to be due to an enhanced inotropic contractility, which only becomes apparent during exercise.