Debra Patten

Anatomy teaching : ghosts of the past, present and future

‘Ghost of the Future,’ he exclaimed, ‘I fear you more than any spectre I have seen. But as I know your purpose is to do me good, and as I hope to live to be another man from what I was, I am prepared to bear you company, and do it with a thankful heart. Will you not speak to me?’ Ebenezer Scrooge (Charles Dickens, A Christmas Carol)

SUBUNIT-SELECTIVE MODULATION OF GABAA RECEPTORS BY THE NON-STEROIDAL ANTI-INFLAMMATORY AGENT, MEFENAMIC ACID

Mefenamic acid (MFA) has anti‐convulsant and pro‐convulsant effects in vivo, and has been shown to potentiate and inhibit GABAA (γ‐aminobutyric acid) receptors in vitro. In this study, whole‐cell currents were recorded from Xenopus oocytes and human embryonic kidney (HEK) cells expressing human recombinant GABAA receptors to resolve the molecular mechanisms by which MFA modulates GABAA receptor function. We demonstrate that MFA potentiated GABA‐activated currents for α1β2 γ2S (EC50 = 3.2 ± 0.5 μm), but not for α1β1 γ2S receptors. MFA also enhanced GABA‐activated responses and directly activated α1β2/β3 GABAA receptors, but inhibited responses to GABA on α1β1 constructs (IC50 = 40 ± 7.2 μm). A comparison of β1, β2 and β3 subunits suggested that the positive modulatory action of MFA involved asparagine (N) 290 in the second transmembrane domain (TM2) of the β2 and β3 subunits. Mutation of N290 to serine (S) markedly reduced modulation by MFA in α1β2(N290S)γ2S receptors, whereas α1β1(S290N)γ2S constructs revealed potentiated responses to GABA (EC50 = 7.8 ± 1.7 μm) and direct activation by MFA. The potentiation by MFA displayed voltage sensitivity. The direct activation, potentiation and inhibitory aspects of MFA action were predominantly conferred by the β subunits as the spontaneously active homomeric β1 and β3 receptors were susceptible to modulation by MFA. Molecular comparisons of MFA, loreclezole and etomidate, agents which exhibit similar selectivity for GABAA receptors, revealed their ability to adopt similar structural conformations. This study indicates that N290 in TM2 of β2 and β3 subunits is important for the regulation of GABAA receptor function by MFA. Our data provide a potential molecular mechanism for the complex central effects of MFA in vivo.

Purification and amino acid sequence of a highly insecticidal toxin from the venom of the Brazilian spider Phoneutria nigriventer which inhibits NMDA-evoked currents in rat hippocampal neurones

A new insecticidal toxin Tx4(5-5) was isolated from the fraction PhTx4 of the venom of the spider Phoneutria nigriventer by reverse phase high performance liquid chromatography (HPLC) and anion exchange HPLC. The complete amino acid sequence determined by automated Edman degradation showed that Tx4(5-5) is a single chain polypeptide composed of 47 amino acid residues, including 10 cysteines, with a calculated molecular mass of 5175 Da. Tx4(5-5) shows 64% of sequence identity with Tx4(6-1), another insecticidal toxin from the same venom. Tx4(5-5) was highly toxic to house fly (Musca domestica), cockroach (Periplaneta americana) and cricket (Acheta domesticus ), producing neurotoxic effects (knock-down, trembling with uncoordinated movements) at doses as low as 50 ng/g (house fly), 250 ng/g (cockroach) and 150 ng/g (cricket). In contrast, intracerebroventricular injections (30 microg) into mice induced no behavioural effects. Preliminary electrophysiological studies carried out on whole-cell voltage-clamped rat hippocampal neurones indicated that Tx4(5-5) (at 1 microM) reversibly inhibited the N-methyl-D-aspartate-subtype of ionotropic glutamate receptor, while having little or no effect on kainate-, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid- or gamma-aminobutyric acid-activated currents.

An electrophysiological study of the effects of propofol on native neuronal ligand-gated ion channels.

1. Pharmacological evidence suggests that some of the clinical actions of propofol may be mediated, at least in part, by positive modulation of the GABAA receptor chloride channel. The effect of propofol at other native neuronal ligand‐gated ion channels is unclear.

Virtual human dissector as a learning tool for studying cross-sectional anatomy

Background: Within diagnostic medicine there is a continuing and marked increase in the use of two-dimensional (2D) images of cross-sectional anatomy. Medical undergraduates should therefore develop skills to interpret such images early in their education. The Virtual Human Dissector© (VHD) software facilitates such learning, permitting users to study actual images of 2D anatomical cross-sections and reconstructed three-dimensional (3D) views simultaneously. This study investigates the use of VHD in facilitating students’ ability to interpret cross-sectional images and understand the relationships between anatomical structures. Methods: First year medical students (n = 89) were randomly divided into two groups. Using a crossover design, the investigation was undertaken as two 20 minute self-directed learning (SDL) activities using VHD in a computer suite and prosections and models in the dissecting room (DR), interspersed between 3 tests identifying anatomical structures in cross-sectional images (pre-, mid- and post-session). Results: Statistical analysis of test performance revealed significant improvements in each group between the pre- and mid-session tests, and again between mid- and post-session tests. There was no significant difference between the two groups at any stage. SDL using the VHD was as effective as SDL using prosections.

What lies beneath: the in living anatomy teaching

T here is considerable debate about the best way of teaching anatomy, and which resources to use, but there is a consensus that electronic representations of the body alone do not offer students a learning experience that enables them to understand completely the complex three-dimensional (3D) relationships within the human body. These electronic resources, however, may be a useful adjunct to other resources employed in anatomical teaching. We have explored the use of one resource in particular, the VH Dissector, Pro edition(VHD) and have developed an interactive and lively anatomy teaching session which, as well as being fun, delivers some powerful learning opportunities for both students and staff.

The impact of wearing scrubs on contextual learning

Background: Godden and Baddeley () suggested strong contextual influence on recall, suggesting learning in an educational context might not transfer well to practice. Aim: To explore the impact of an authentic context (wearing hospital scrubs) on learning and recall. Methods: 82 first year medical students sat a pre-test on renal gross anatomy and imaging, to establish prior knowledge, wearing their own clothes. Students wore either scrubs or their own clothes for the first teaching session on renal gross anatomy. A mid-test on this topic was completed immediately after the teaching session. Students then changed into opposite clothing and attended a self-directed session on renal imaging. An imaging specific mid-test was completed. 5 weeks later students completed two post-tests (gross anatomy and imaging) in their own clothes. Tests were online. Results: Data were analysed using paired t-tests. Results showed no significant difference between test performance immediately after the teaching session, but a significant improvement (p = 0.04) on recall between groups tested in the same clothing versus testing in different clothing. The effect size of the teaching intervention was 0.27, a ‘moderate’ effect in teaching terms. Conclusions: Students examined in the same context as they were taught recalled significantly more information.

An anatomical evaluation of the serratus anterior plane block.

The serratus anterior plane block has been described for analgesia of the hemithorax. This study was conducted to determine the spread of injectate and investigate the anatomical basis of the block. Ultrasound‐guided serratus anterior plane block was performed on six soft‐fix embalmed cadavers. All cadavers received bilateral injections, on one side performed with 20 ml latex and on the other with 20 ml methylene blue. Subsequent dissection explored the extent of spread and nerve involvement. Photographs were taken throughout dissection. The intercostal nerves were involved on three occasions with dye, but not with latex. The lateral cutaneous branches of the intercostal nerve contained dye and latex on all occasions. The serratus plane block appears to be mediated through blockade of the lateral cutaneous branches of the intercostal nerves. Anatomically, serratus plane block does not appear to be equivalent to paravertebral block for rib fracture analgesia.

Student attitudes to peer physical examination: A qualitative study of changes in expressed willingness to participate

Background: A number of studies have explored student attitudes to examining each other (peer physical examination: PPE). Differences have emerged in whether students prefer to be examined by friends or strangers. Changes have been reported in how students feel about PPE if asked before or after the PPE programme commences. Research intention: Since a Grounded Theory paradigm was employed, there was no formal research hypothesis: the research intention was to explore factors which might underlie changes in student willingness to undertake PPE following familiarity with the process. Methods: Students who had completed an Examining Fellow Students Questionnaire at the beginning and end of the academic year, and who had indicated a change in willingness to participate, were invited to attend focus groups. Four focus groups were convened and transcripts were analysed for common themes. Results: Surprisingly, students downplayed the significance of changes. Also unexpectedly, dichotomous views emerged on familiarity, with some students preferring friends for examination and others preferring strangers. Staff embarrassment also emerged as a factor inhibiting student participation. Conclusions: The significance of reported changes in attitudes to PPE may have been exaggerated. Proposals for increasing the willingness of students to participate in PPE are developed from the emergent themes.

Using ultrasound to teach anatomy in the undergraduate medical curriculum: an evaluation of the experiences of tutors and medical students

This paper describes the experiences of staff and students at two UK medical schools, who introduced portable ultrasound (PU) as an imaging technology to deliver clinical anatomy teaching and to aid skill development in interpretation of cross-sectional anatomy (CSA). A sonographer contributed to curriculum design and teaching, but mostly anatomy tutors delivered the teaching. This case study method evaluates staff and student perspectives on the ultrasound-based anatomy teaching. Quantitative data and qualitative data were collected and analysed. Staff were positive about the experience. They described their expectations for students and solutions for practical issues regarding the teaching, but were concerned about their competency in scanning and wanted bespoke training for sonoanatomy teaching. Curriculum development was accelerated through engagement with a sonographer and an ultrasound champion. Students were extremely positive about their experience; they valued the expertise of a sonographer who taught more challenging sonoanatomy, but were equally positive regarding teaching sessions led by well-trained anatomy tutors who taught more simple sonoanatomy. Students affirmed most tutors’ expectations that ultrasound could reinforce existing anatomical knowledge, added clinical contextualisation, but not that use of ultrasound (US) assisted in interpreting CSA. Students valued the introduction to the technology and found sonoimage interpretation challenging, but not insurmountable. Students wanted more instruction on ultrasound physics, an expansion of ultrasound curriculum, with smaller groups and opportunities to scan volunteers. These data support the case for the use of PU to deliver anatomy teaching and to prime medical students for later clinical encounters with PU.