To evaluate the contribution of adenosine (AD) to exercise capacity, plasma concentrations of AD were assessed before, during and after dynamic exercise in 6 healthy men (24-32yr) . The exercise protocol was a symptom-limited ramp exercise test. Blood pressure, heart rate and respiratory gas exchange parameters were monitored throughout the exercise test. The first exercise test (EX 1) was performed to determine the anaerobic threshold (AT) . The second exercise test (EX 2) was performed 2 days after EX 1 and blood samples for assay of AD, lactate and norepinephrine (NE) were taken from the cubital vein at rest, before and after AT, at peak exercise, and 5, 10, 15min after EX 2. Blood for assay of AD was collected into a vaccum tube with EDTA, dipyridamole and 2'-deoxycoformycin. Plasma AD concentrations were measured by the RIA.
The mean AD concentration±S. D. at rest, before and after AT, at peak exercise, 5, 10 and 15min after exercise was 22±11.8pmol/ml, 45±20.7, 63±33.6, 123±82.1, 186±146.9, 154±127.7 and 150±68.5, respectively. A significant increase of AD concentration was observed during the period from before AT until 15 min after exercise, as compared with that at rest. There was a significant relation between AD and lactate (r=0, 54, p<0.01), but there was no significant relation between AD and NE (r=0.08) .
It is concluded that AD may be a contributing factor to increase exercise capacity through its vasodilation effect, suggesting a paracrine interaction between the exercising skeletal muscle and blood vessels.

Problem-based learning (PBL) tutorials were introduced at our university in April 2001. Because a complete PBLbased curriculum could not be adopted, a transitional curriculum incorporating 3-hour PBL tutorial sessions into the traditional curriculum was introduced. More than 80% of students agreed that PBL is an effective way of learning problem solving at the bedside. Twenty percent to 40% of teachers felt that students who took PBL were more motivated for bedside learning and self-directed learning and had better at presentation than were students who did not take PBL. Because of 80% of the curriculum comprised didactic lectures, most students considered PBL tutorials a type of lecture. For this reason, motivating students to learn additional material originating from PBL tutorials was difficult. Although the combination of a traditional curriculum and PBL tutorials may appear to be a new curriculum, this type of PBL has limited value as a method for studying problem solving.