Sally Krasne

Freezing and Melting of Lipid Bilayers and the Mode of Action of Nonactin, Valinomycin, and Gramicidin

An abrupt loss of effectiveness of the presumed carriers, nonactin and valinomycin, in mediating ion conductance occurred at the same temperature as the membrane fluidity, judged visually, was lost. By contrast, the effects of the presumed channel-former, gramicidin, were the same on solid and liquid membranes. Taken together, these findings imply that freezing the membrane primarily reduces the mobility of these antibiotics with little effect on their solubility.

Ionic probes of membrane structures.

In this paper we have examined the possibility of identifying those membrane structural variables (polar head groups and the nature of hydrocarbon tails) that modulate membrane ionic permeability. Altering the bilayer lipid composition produces variations in physical parameters (surface potential, partition coefficient, and mobility) governing the conductance mediated by neutral carriers of anions and cations. Specifically, the effects of the charged polar head groups are shown to be understandable in terms of the surface potential they produce through the formation of a diffuse double layer, whereas the effects of the viscosity may be demonstrated by “freezing” the membrane. The effects of membrane composition on membrane conductance are illustrated by a third, less well understood, example of how cholesterol alters bilayer conductances. The results indicate the possibility of using positive and negative permeant species as probes of membrane structures.

No content without context: Integrating basic, clinical, and social sciences in a pre-clerkship curriculum

Background: The basic science curricula in medical schools ultimately succeed or fail at the bedside when students must draw on their pre-clerkship experiences as they learn to form nuanced clinical decisions. Given this expectation, learning context becomes as decisive as content in determining students’ recall and application. Aims: Using the pre-clerkship medical curriculum at the University of California, Los Angeles, as an example, we illustrate how traditional biomedical sciences can be integrated with clinical sciences in a comprehensive foundational curriculum following curricular design features and teaching methods based on learning principles from cognitive psychology and education. Methods: Multiple planning teams of faculty and students collaborated in the design of the Human Biology and Disease (HB&D) curriculum. Broad participation, careful selection of course chairs, the assistance of educational consultants, ongoing oversight structures, and faculty development were used to develop and sustain the curriculum. Results: The resulting HB&D curriculum features an interdisciplinary spiral block structure including interactive lecture formats, integrative formative and summative examinations, self- and peer-taught laboratories, and problem-based learning with innovative variations. Conclusion: Our fully integrated, spiral, pre-clerkship curriculum built on repeating interdisciplinary blocks and longitudinal threads has yielded encouraging results as well as some specific innovations that other schools or individual teachers may find valuable to adapt for use in their own settings.

Training pattern recognition of skin lesion morphology, configuration, and distribution

BACKGROUND The ability to reliably recognize and classify a range of skin signs and symptoms remains a necessary skill across most clinical disciplines but one that is traditionally mastered via nonsystematic experience over long periods. OBJECTIVE We investigated whether online Perceptual and Adaptive Learning Modules (PALMs) could efficiently train preclerkship medical students to identify and discriminate primary skin lesion morphologies, configurations, and anatomic distributions. METHODS Medical students completed an online skin lesion morphology PALM voluntarily in year 1 and by requirement, along with configuration and anatomic distribution PALMs, in year 2. In controlled before-and-after studies, multiple-choice pretests and posttests using previously unused images, assessed PALM-induced learning. In prospective cohort studies, differences in year-2 performance between students who had and had not completed the morphology PALM in year 1 were also assessed. RESULTS Multiple-choice tests, used to evaluate PALM effectiveness, demonstrated large (effect sizes of 1.1 [±0.1 SE] to 2.2 [±0.1 SE]) and statistically significant (P < .0001) improvements after PALM training, with learning retention when tested after 1 year. LIMITATIONS Results are from self-selected groups and a single class at 1 institution. CONCLUSION PALMs are a useful tool for efficient development of the core clinical skills of pattern recognition and classification of skin lesion characteristics.

Improving medical literature sourcing by first-year medical students in problem-based learning: Outcomes of early interventions

Purpose To describe and report outcomes of interventions implemented in the preclerkship curriculum at the David Geffen School of Medicine at UCLA to guide students toward use of high-quality information sources and build a foundation for developing fluency in applying primary medical literature to answer clinical questions. Method The authors introduced three phases of change to instruction in literature searching and sourcing for beginning medical students writing learning issue essays: in phase 1 (2003–2006), students were introduced to online resources during orientation week and received a lecture on high-yield literature searching midway through their first curricular block; in phase 2 (2007–2008), the high-yield lecture shifted to orientation week, and a resource matrix and librarian-guided workshop on locating authoritative sources were added; and in phase 3 (2009), peer evaluation and collaboration were implemented. To track changes in sourcing skills, the authors analyzed 3,199 references from 665 essays written by 465 first-year students for two problem-based learning (PBL) cases during the first block of one representative year per phase (2006, 2008, 2009). Results Over the study period, the authors found significantly increased citations to peer-reviewed journal articles and guidelines and decreased citations to general public Web sites and highly abstracted resources. Peer feedback and collaboration in phase 3 were associated with maintenance of these gains. Conclusions Early introduction of instruction on medical literature searching and sourcing, a librarian-guided workshop, and peer collaboration and feedback improved the quality of references cited by students in PBL essays during their first curricular block.