Developing Technical Expertise in Emergency Medicine—The Role of Simulation in Procedural Skill Acquisition

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72919/1/j.1553-2712.2008.00218.x.pd

Shear Forces during Blast, Not Abrupt Changes in Pressure Alone, Generate Calcium Activity in Human Brain Cells

Blast-Induced Traumatic Brain Injury (bTBI) describes a spectrum of injuries caused by an explosive force that results in changes in brain function. The mechanism responsible for primary bTBI following a blast shockwave remains unknown. We have developed a pneumatic device that delivers shockwaves, similar to those known to induce bTBI, within a chamber optimal for fluorescence microscopy. Abrupt changes in pressure can be created with and without the presence of shear forces at the surface of cells. In primary cultures of human central nervous system cells, the cellular calcium response to shockwaves alone was negligible. Even when the applied pressure reached 15 atm, there was no damage or excitation, unless concomitant shear forces, peaking between 0.3 to 0.7 Pa, were present at the cell surface. The probability of cellular injury in response to a shockwave was low and cell survival was unaffected 20 hours after shockwave exposure

Virology under the microscope—a call for rational discourse

Viruses have brought humanity many challenges: respiratory infection, cancer, neurological impairment and immunosuppression to name a few. Virology research over the last 60+ years has responded to reduce this disease burden with vaccines and antivirals. Despite this long history, the COVID-19 pandemic has brought unprecedented attention to the field of virology. Some of this attention is focused on concern about the safe conduct of research with human pathogens. A small but vocal group of individuals has seized upon these concerns – conflating legitimate questions about safely conducting virus-related research with uncertainties over the origins of SARS-CoV-2. The result has fueled public confusion and, in many instances, ill-informed condemnation of virology. With this article, we seek to promote a return to rational discourse. We explain the use of gain-of-function approaches in science, discuss the possible origins of SARS-CoV-2 and outline current regulatory structures that provide oversight for virological research in the United States. By offering our expertise, we – a broad group of working virologists – seek to aid policy makers in navigating these controversial issues. Balanced, evidence-based discourse is essential to addressing public concern while maintaining and expanding much-needed research in virology

The effect of shear forces on the response of cells to an

<p>∼<b>11 atm peak pressure simulated blast.</b> (<b>A</b>) Sequential fluo-4 calcium imaging of a dissociated primary human fetal CNS cell culture without shear (380 µl well fluid volume); the blast occurred at time 100 seconds. (<b>B</b>) Sequential fluo-4 calcium imaging of the same cells as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039421#pone-0039421-g003" target="_blank">Figure 3A</a> with shear (150 µl well fluid volume) using the same blast parameters; the blast occurred at time 100 seconds. (<b>C</b>) ΔF/F in time of the cells shown in Figures A and B for 10 minutes before, during, and after the blast. (<b>D</b>) Normalized response of two cells shown in Figure B, panel 1, indicating that the calcium response does not occur simultaneously in cells but sequentially; time to peak response is offset by ∼30 seconds in this example and is consistent with propagation (see Video S4). (<b>E</b>) Integrated Ca²⁺ Response, integral of ΔF/F over time following the blast, without and with shear forces in the same well, for n = 6 pair-matched experiments (11 atm; 10 atm above ambient pressure). The first blast was without shear forces. The response to a lethal peak pressure of 15 atm (14 atm above ambient pressure) with no shear forces is also shown (n = 10) (<b>F</b>) Correlation (r² = 0.99) between Integrated Ca²⁺ Response following a 11 atm peak pressure blast and well fluid volume for the 3 volume conditions evaluated; 150–200, 250–300, and 380 µl with n = 14, 7 and 25, respectively. Fluid volume and Ca²⁺ Response error bars are the range and SEM, respectively.</p

(A) Schematic diagram of the pneumatic device and modified 96 well plate attached to a microscope stage

<p>(<b>B</b>) Pressure profile measurements of the simulated open field blast shockwave compared to a classical Friedlander curve of the same peak pressure and positive phase duration. Average of 6 measurements is shown with standard error.</p

Shear forces are regulated by well fluid volume.

<p>Three consecutive frames of 400 msec duration captured beads before (a), during (b), and after (c) the application of a ∼11 atm peak pressure blast with (180 µl fluid volume) and without shear (380 µl fluid volume). Significant bead motion due to shear is registered in top frame b. Note, a single bead did not move (arrow); this bead, presumably immobilized due to adhesion to the surface, allows one to check for stability of the stage during the blast. In the absence of shear, the application of the same peak pressure blast does not show any bead displacement (bottom frame b).</p