Biomedical subjects

Si-Mui Sim

Publications and source records attributed to Si-Mui Sim.

4 recordsLinked to original sources

PubMed2006

Relationship between item difficulty and discrimination indices in true/false-type multiple choice questions of a para-clinical multidisciplinary paper.

INTRODUCTION: This paper reports the relationship between the difficulty level and the discrimination power of true/false-type multiple-choice questions (MCQs) in a multidisciplinary paper for the para-clinical year of an undergraduate medical programme. MATERIALS AND METHODS: MCQ items in papers taken from Year II Parts A, B and C examinations for Sessions 2001/02, and Part B examinations for 2002/03 and 2003/04, were analysed to obtain their difficulty indices and discrimination indices. Each paper consisted of 250 true/false items (50 questions of 5 items each) on topics drawn from different disciplines. The questions were first constructed and vetted by the individual departments before being submitted to a central committee, where the final selection of the MCQs was made, based purely on the academic judgement of the committee. RESULTS: There was a wide distribution of item difficulty indices in all the MCQ papers analysed. Furthermore, the relationship between the difficulty index (P) and discrimination index (D) of the MCQ items in a paper was not linear, but more dome-shaped. Maximal discrimination (D = 51% to 71%) occurred with moderately easy/difficult items (P = 40% to 74%). On average, about 38% of the MCQ items in each paper were "very easy" (P > or =75%), while about 9% were "very difficult" (P <25%). About two-thirds of these very easy/difficult items had "very poor" or even negative discrimination (D < or =20%). CONCLUSIONS: MCQ items that demonstrate good discriminating potential tend to be moderately difficult items, and the moderately-to-very difficult items are more likely to show negative discrimination. There is a need to evaluate the effectiveness of our MCQ items.

Adult↗

PubMed2006

A simple instrument for the assessment of student performance in problem-based learning tutorials.

INTRODUCTION: A process-oriented instrument was developed for the summative assessment of student performance during problem-based learning (PBL) tutorials. This study evaluated (1) the acceptability of the instrument by tutors and (2) the consistency of assessment scores by different raters. MATERIALS AND METHODS: A survey of the tutors who had used the instrument was conducted to determine whether the assessment instrument or form was user-friendly. The 4 competencies assessed, using a 5-point rating scale, were (1) participation and communication skills, (2) cooperation or team-building skills, (3) comprehension or reasoning skills and (4) knowledge or information-gathering skills. Tutors were given a set of criteria guidelines for scoring the students' performance in these 4 competencies. Tutors were not attached to a particular PBL group, but took turns to facilitate different groups on different case or problem discussions. Assessment scores for one cohort of undergraduate medical students in their respective PBL groups in Year I (2003/2004) and Year II (2004/2005) were analysed. The consistency of scores was analysed using intraclass correlation. RESULTS: The majority of the tutors surveyed expressed no difficulty in using the instrument and agreed that it helped them assess the students fairly. Analysis of the scores obtained for the above cohort indicated that the different raters were relatively consistent in their assessment of student performance, despite a small number consistently showing either "strict" or "indiscriminate" rating practice. CONCLUSION: The instrument designed for the assessment of student performance in the PBL tutorial classroom setting is user-friendly and is reliable when used judiciously with the criteria guidelines provided.

Education, Medical↗

PubMed2004

Vascular effects of Siberian ginseng (Eleutherococcus senticosus): endothelium-dependent NO- and EDHF-mediated relaxation depending on vessel size.

Siberian ginseng (SG) has been widely and historically consumed as a health food product for the improvement of self well-being, but whether vascular relaxation may contribute to such a therapeutic health effect has not been studied. We therefore investigated the vasorelaxant effect of the aqueous extract of the roots of SG (Eleutherococcus senticosus Maxim) using several in vitro vascular rings prepared from dog carotid artery, rat aorta and rat mesenteric artery. SG extract (0.04-0.8 mg/ml) caused concentration-dependent relaxation in dog carotid arterial rings pre-contracted with 100 microM phenylephrine (PE), and the relaxation was primarily endothelium-dependent. Treatment with 100 microM L-NOARG (a nitric oxide synthase inhibitor) either prevented or totally reverted SG-induced relaxation, suggesting that the endothelium-dependent relaxation was mediated by NO. Similar endothelium-dependent vascular relaxant responses were also obtained with rat aortic and mesenteric arterial rings, except that it occurred over a relatively higher concentration range of SG (0.5-2.0 mg/ml). When tested in the presence of 300 microM L-NAME, the vasorelaxant effect of SG was inhibited totally in rat aorta but only partially in rat mesenteric artery. The relaxation to SG that was insensitive to L-NAME in rat mesenteric arterial rings was eliminated when the rings (both proximal and distal ends) were pre-treated with a combination of 300 microM L-NAME and 15 mM KCl indicating the involvement of endothelium-derived hyperpolarizing factor (EDHF). This vasorelaxant response of the SG extract was inhibited partially by atropine (1 microM), completely by TEA (5 mM), but not by indomethacin (1 microM) or propranolol (10 microM). SG up to 2 mg/ml had no effect on KCl-induced contraction in any of the vascular rings studied. When compared with carbachol-induced (CCh) relaxation, SG resembles CCh in that the sensitivity to L-NAME inhibition is dependent on vascular size, i.e. aorta >proximal end of mesenteric artery >distal end of mesenteric artery. However, SG exhibited different potencies to relaxation while CCh showed similar potency (EC(50) of about 0.2 microM) in all three vascular segments. In conclusion, we have demonstrated that the vascular effect of SG is endothelium-dependent and mediated by NO and/or EDHF depending on the vessel size. Other vasorelaxation pathways, such as inhibition of K(+)-channels and activation of muscarinic receptors, may also be involved.

Animals↗

PubMed2003

In vitro vasodilator mechanisms of the indole alkaloids rhynchophylline and isorhynchophylline, isolated from the hook of Uncaria rhynchophylla (Miquel).

Rhynchophylline (Rhy) and isorhynchophylline (Isorhy), indole alkaloids from Uncaria hooks, reportedly exert hypotensive and vasodilatory effects, but the mechanism of action is unclear. We therefore investigated the relaxant effects of these two isomeric alkaloids in rat arteries in vitro, in particular in respect of the various functional Ca2+ pathways. Both Rhy and Isorhy relaxed aortic rings precontracted with phenylephrine (PE, 1 microM) in a dose-dependent manner (3-300 microM). Removal of endothelium and preincubation with L-NAME (300 microM) slightly inhibited but did not prevent the relaxant response. These results indicate that Rhy and Isorhy act largely in an endothelium-independent manner. Unlike nicardipine, both alkaloids not only inhibited the contraction induced by 60 mM KCl (IC50 20-30 microM), but also that induced by PE and U46619, albeit to a lesser extent (IC50 100 and 200 microM, respectively). These results suggest that Rhy and Isorhy may act via multiple Ca2+ pathways. In contrast to their inhibitory effects on KCl-induced and receptor-mediated contractions, where both isomers were comparably potent, Rhy was more potent than Isorhy at higher concentrations (>100 microM) in inhibiting both caffeine (25 mM)- and cyclopiazonic acid (CPA, 30 microM)-induced contractions. Similar results observed with caffeine in Ca2+-containing medium were also observed in Ca2+-free medium. However, 0.1-0.3 microM nicardipine (which completely inhibited KCl-induced contraction) had no significant inhibitory effect on CPA-induced contractions. Taken together, these results indicate discrimination between these two isomers with respect to Ca2+-induced Ca2+ release and non-L-type Ca2+ channel, but not for IP3-induced Ca2+ release and L-type Ca2+ channels. Similar relaxant responses to KCl- and caffeine-induced contractions were seen when these two alkaloids were tested on the smaller mesenteric and renal arteries. In conclusion, the vasodilatory effects of Rhy and Isorhy are largely endothelium independent and are mediated by L-type Ca2+ channels. At higher concentrations, they also affect other Ca2+-handling pathways, although to a lesser extent. While there is no discrimination between the two isomers with respect to the contraction induced by KCl or agonists (PE and U46619), differential effects between Rhy and Isorhy were seen on caffeine- and CPA-induced contractions.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗