Localized adhesion of nongerminated Venturia inaequalis conidia to leaves and artificial surfaces.

Adhesion to the host surface is the first step for successful plant pathogen development and has been reported to be associated with both passive and active processes. For conidia of Venturia inaequalis, which depend on leaf wetness for germination, this process has not yet been described. Conidia of V. inaequalis adhered to wet hydrophobic surfaces immediately after contact to the surface, hours before initiation of germination. Attachment of nongerminated conidia was much better on hydrophobic surfaces, such as apple leaves and polystyrene, than on hydrophilic glass. Conidia released adhesive material localized in a droplet named spore tip glue (STG) at the spore apex which interacted with a contact surface only when water was present. Histochemical investigations indicated the presence of proteins and carbohydrates in STG, lectin labeling the presence of beta-galactose and N-acetylglucosaminyl residues. Transmission electron microscopy revealed two phases in the STG at the tip of dry mature conidia; as STG was present on the outer side of the intact fungal cell wall its formation should be associated with the secretion of glue through pores of the conidial wall. Surface-active substances affected the adhesion of conidia to hydrophobic surfaces stressing the importance of hydrophobic interactions. The use of protein biosynthesis inhibitors did not affect adhesion of conidia indicating that the adhesive material was preformed. It is concluded that the coincidence of STG, contact to a hydrophobic surface, and free water are essential for the adhesion of V. inaequalis conidia.

The effect of open- vs. closed-book testing on performance on a multiple-choice examination in pediatrics.

A study was undertaken to test the effect of open- vs. closed-book testing conditions on performance on a graduate-level, multiple-choice examination in pediatrics. A group of practicing pediatricians and a group of medical students took the examination. For the practice group, no significant difference between mean scores was observed, and the correlation between scores under the two testing conditions was high. In the student group, however, the mean score was significantly higher under open-book conditions and the correlation between scores under the two testing conditions was positive but low. The mean score obtained by practitioners was significantly higher than the mean score obtained by students under both testing conditions. The effects of time limit and level of motivation were not explored in the present study.

The feasibility of using an American National Board examination for the evaluation of Swiss candidates for licensure.

A test in Internal Medicine of the American National Board of Medical Examiners was given to Swiss medical students as a graduating examination. This study dealing with the feasibility of such an enterprise describes the technical procedures and investigates the problems of translation and the validity of foreign made items. Comparison of item analyses for the 369 Swiss candidates and for a sample of 370 American candidates reveals that most items are of close comparability in difficulty, discrimination and pattern of response to the distractors. In a cross-national comparison of student's responses to the items no systematic content characteristics can be found for items favouring one group or the other. Swiss experts, in judging the validity of the items for testing Swiss students, could indeed identify in advance some of the items that proved to be less valid and more difficult for their--but also the American--students. It is concluded that National Borad examination can be as valid and suited to examine Swiss candidates for licensure as it is to examine American candidates.

The effect of open vs closed-book testing conditions upon performance on a multiple-choice examination in pediatrics.

This study compared the performance of medical students and practicing pediatricians taking a graduate-level examination in pediatrics under open-book vs closed-book conditions. Students performed significantly better under open-book conditions, but there was no significant difference for the practitioner group.

Computerization of a patient management problems examination to prevent 'retracing'.

During 1973, a 10-patient, linear PMP examination was administered in both written and computerized form to 104 candidates for certification by the American Board of Pediatrics and to 122 individuals in their first month of graduate training in paediatrics. Both groups made significantly more errors of omission (failure to select appropriate actions) and fewer correct diagnoses on the computerized version of the test than on the written version. These results suggest that examinees 'retrace' (use clues from problems near the end of the case to make additional correct decisions on earlier problems) when the test is presented in written form and that computerization prevents this phenomenon. Additional analyses indicated that the reliability of the PMP examination was essentially the same for the written and computerized versions, that both forms distinguished about equally well between first-year residents and candidates, and that both forms had about the same magnitude of correlation with the American Board of Pediatrics oral examination. Finally, correlation between both PMP forms and the American Board of Pediatrics multiple-choice examination suggested that the PMP, in either mode of presentation, measures characteristics that are not tapped by the multiple-choice test. Thus, computerization of the PMP provides a means for controlling a variable (retracing) which may be considered extraneous to the desired measurement, but it does not appear to alter the reliability of the test or to modify its relations with other measures.