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Little is known about the effectiveness of clinical courses as a learning environment. To accurately assess performance in these courses, equal conditions for all candidates are required. We investigated the influence of the proximity of the course to the students test taking, the students' learning styles, and their self-motivation for learning in relation to performance success. One hundred and eleven students were randomized into eight groups, each attending a 2 week course in otolaryngology with a high proportion of patient-related teaching, and a 2 week long course in neurology with a low level of patient-related teaching. All students took multiple-choice end-of-term exams to assess their knowledge in both subjects. There was a different time interval between the course participation and the test taking for each of the groups. Performance success was correlated with the different groups, as well as with the type of learning style (LIST questionnaire) and with motivation for learning (study interest questionnaire). Explorative rank variance analysis showed a significant correlation between students' performance on the written exam and the time interval between completion of the neurology course and test-taking, with the shortest interval corresponding to highest scores (P = 0.002). There was no such effect on the success rate in otolaryngology (P = 0.28). Study motivation was not the major component for performance success, but a strong correlation between the use of strategic and deep learning styles and success in the exam was observed (R = 0.62; P < 0.001). The duration of time between a clinical course with little practical teaching and the students' taking of the exam plays a significant role on performance success; this effect does not occur in a course with a high proportion of practical patient-related teaching. More studies on clinical courses are needed to establish how students can be given adequate opportunities to develop necessary skills for patient care and for objective success on assessment. With such further information, the effectiveness of clinical courses as a learning experience might be enhanced.

Ecdysone was found to be the major secreted steroid of ring glands dissected from blowfly larvae and incubated in vitro. Other secretory products such as 3-dehydroecdysone and 20-deoxy-makisterone A could not be detected when the glands were labelled with tritiated cholesterol. Ecdysone synthesis and secretion were found to be tightly coupled. The highest rate of secretion was observed a few hours before pupariation. In vitro, the rate of ecdysone secretion by ring glands was affected significantly by coincubation with the central nervous system (CNS). Modulating effects from the CNS to the gland were mediated both by culture medium and by nerve connections. Distinct parts of the CNS revealed multiple and partially opposite effects on ecdysone secretion, suggesting a more complex control than had been anticipated. Multiple neural control systems appear to be involved. Moreover, the observed effects changed with development during the second half of the third instar, reflecting a significant plasticity of neural control.

Endogenous ecdysteroids as well as radiolabelled exogenous ecdysone were crosslinked to a protein when haemolymph from blowfly larvae was irradiated with UV-light under optimized conditions. This indicates that larval haemolymph of blowflies contains an ecdysteroid-binding protein.The crosslinked ecdysteroid-protein complex was shown to form a ternary complex when mixed with ecdysteroid-specific antibodies. Formation of the ternary complex was due to a specific interaction of the binding sites of the antibodies with the steroid. This specific interaction was used to isolate the ecdysteroid-protein complex from irradiated crude larval haemolymph by immunoadsorption. The method described here represents a rapid approach for the isolation of steroid-binding proteins by a combination of photoaffinity labelling and immunoadsorption.