In vivo measurement of apolipoprotein E from the brain interstitial fluid using microdialysis

BACKGROUND: The APOE4 allele variant is the strongest known genetic risk factor for developing late-onset Alzheimer’s disease. The link between apolipoprotein E (apoE) and Alzheimer’s disease is likely due in large part to the impact of apoE on the metabolism of amyloid β (Aβ) within the brain. Manipulation of apoE levels and lipidation within the brain has been proposed as a therapeutic target for the treatment of Alzheimer’s disease. However, we know little about the dynamic regulation of apoE levels and lipidation within the central nervous system. We have developed an assay to measure apoE levels in the brain interstitial fluid of awake and freely moving mice using large molecular weight cut-off microdialysis probes. RESULTS: We were able to recover apoE using microdialysis from human cerebrospinal fluid (CSF) in vitro and mouse brain parenchyma in vivo. Microdialysis probes were inserted into the hippocampus of wild-type mice and interstitial fluid was collected for 36 hours. Levels of apoE within the microdialysis samples were determined by ELISA. The levels of apoE were found to be relatively stable over 36 hours. No apoE was detected in microdialysis samples from apoE KO mice. Administration of the RXR agonist bexarotene increased ISF apoE levels while ISF Aβ levels were decreased. Extrapolation to zero-flow analysis allowed us to determine the absolute recoverable concentration of apoE3 in the brain ISF of apoE3 KI mice. Furthermore, analysis of microdialysis samples by non-denaturing gel electrophoresis determined lipidated apoE particles in microdialysis samples were consistent in size with apoE particles from CSF. Finally, we found that the concentration of apoE in the brain ISF was dependent upon apoE isoform in human apoE KI mice, following the pattern apoE2>apoE3>apoE4. CONCLUSIONS: We are able to collect lipidated apoE from the brain of awake and freely moving mice and monitor apoE levels over the course of several hours from a single mouse. Our technique enables assessment of brain apoE dynamics under physiological and pathophysiological conditions and in response to therapeutic interventions designed to affect apoE levels and lipidation within the brain

The Efficacy of Table Top Simulation as a Didactic Adjunct for an Undergraduate Emergency Medicine Clerkship Curriculum: A Prospective Cross-Over Study

Introduction: Simulation is used by many medical specialties, throughout the world, as an effective educational adjunct to clinical learning experiences. There is limited prospective research to support the use of table-top, low fidelity, simulation experiences as a suitable replacement for traditional lecture-based modalities in the context of undergraduate emergency medical education. We designed, implemented and evaluated sections of a table-top simulation-based curriculum for fourth year medical students participating in the department’s advanced emergency medicine clerkship. Methods: A prospective, randomized, cross over study comparing lecture-based learning activities to an experimental table-top simulation exercises based on a primary outcome objective, considering the quantitative acquisition of clinical knowledge, and a secondary outcome looking at the results of survey data, considering student perspectives on learning experience. Four student cohorts participated in the study, each spending one month in the department’s advanced emergency medicine medical student elective.Results: Medical knowledge learning outcomes did not show a significant improvement in the experimental modality when compared to the traditional format. Likert scale survey data showed, with statistical significance (P<.05), that students preferred the simulation modality over the traditional lectures finding it to be more interactive, and a more effective format for teaching medical knowledge and applicable clinical information. Conclusion: Findings showed, with statistical significance, that students preferred this learning modality but that more research would be needed to further evaluate our findings of improved learning outcomes. Further research should be pursued to characterize this modality’s benefit, as compared to traditional small group lecture and high-fidelity simulation modalities, in order to evaluate its possible effectiveness for furthering the development of undergraduate emergency medicine education in the future

Pleiotropy, Homeostasis, and Functional Networks Based on Assays of Cardiovascular Traits in Genetically Randomized Populations

A major problem in studying biological traits is understanding how genes work together to provide organismal structures and functions. Conventional reductionist paradigms attribute functions to particular proteins, motifs, and amino acids. An equally important but harder problem involves the synthesis of data at fundamental levels of biological systems to understand functionality at higher levels. We used subtle, naturally occurring, multigenic variation of cardiovascular (CV) properties in a panel of genetically randomized strains that are derived from the A/J and C57BL/6J strains of mice to perturb CV functions in nonpathologic ways. In this proof-of-concept study, computational analysis correctly identified the known relations among CV properties and revealed functionality at higher levels of the CV system. The network was then used to account for pleiotropies and homeostatic responses in single gene mutant mice and in mice treated with a pharmacologic agent (anesthesia). The CV network accounted for functional dependencies in complementary ways to the insights obtained from genetic networks and biochemical pathways. These networks are therefore an important approach for defining and characterizing functional relations in complex biological systems in health and disease

Learning Outcomes of High-fidelity versus Table-Top Simulation in Undergraduate Emergency Medicine Education: Prospective, Randomized, Crossover-Controlled Study

Introduction: Over the last several decades simulation, in both graduate and undergraduate emergency medicine education, has continued to develop as a leading and highly effective teaching modality. Limited research exists to evaluate the efficacy of low-fidelity (table-top) simulation, as compared to high-fidelity standards, as it relates to medical knowledge learning outcomes. We sought to assess the efficacy of a low-fidelity simulation modality in undergraduate emergency medicine education, based on quantitative medical knowledge learning outcomes. Methods: A prospective, randomized, crossover-control study comparing objective medical knowledge learning outcomes between simulation modalities. Analysis was designed to evaluate for the statistical equivalence of learning outcomes between the two cohorts. This was done by comparing a calculated 95% confidence interval (CI) around the mean difference in post-test scores, between experimental and control modalities, to a pre-established equivalence margin.  Results: Primary outcomes evaluating student performance on post-test examinations demonstrated a total cohort CI (95% CI, -0.22 and 0.68). Additional course-subject subgroup analysis demonstrated non-inferior CIs with: Shortness of Breath (95% CI, -0.35 and 1.27); Chest Pain (95% CI, -0.53 and .94); Abdominal Pain (95% CI, -0.88 and 1.17); Cardiovascular Shock (95% CI, -0.04 and 1.29). Secondary outcome analysis was done to evaluate medical knowledge acquisition by comparing the difference in pre and post-test examination between the cohorts. CI of the full cohort ranged from (95% CI, -0.14 and 0.96). Conclusion: The student’s performance on quantitative medical-knowledge assessment was equivalent between the high-fidelity control and low-fidelity experimental simulation groups. Analysis of knowledge acquisition between the two groups also demonstrated statistical equivalence.&nbsp