Förster resonance energy transfer efficiency of the vinculin tension sensor in cultured primary cortical neuronal growth cones.

Significance: Interaction of neurons with their extracellular environment and the mechanical forces at focal adhesions and synaptic junctions play important roles in neuronal development. Aim: To advance studies of mechanotransduction, we demonstrate the use of the vinculin tension sensor (VinTS) in primary cultures of cortical neurons. VinTS consists of TS module (TSMod), a Förster resonance energy transfer (FRET)-based tension sensor, inserted between vinculin's head and tail. FRET efficiency decreases with increased tension across vinculin. Approach: Primary cortical neurons cultured on glass coverslips coated with poly-d-lysine and laminin were transfected with plasmids encoding untargeted TSMod, VinTS, or tail-less vinculinTS (VinTL) lacking the actin-binding domain. The neurons were imaged between day in vitro (DIV) 5 to 8. We detail the image processing steps for calculation of FRET efficiency and use this system to investigate the expression and FRET efficiency of VinTS in growth cones. Results: The distribution of fluorescent constructs was similar within growth cones at DIV 5 to 8. The mean FRET efficiency of TSMod ( 28.5 ± 3.6 % ) in growth cones was higher than the mean FRET efficiency of VinTS ( 24.6 ± 2 % ) and VinTL ( 25.8 ± 1.8 % ) ( p < 10 - 6 ). While small, the difference between the FRET efficiency of VinTS and VinTL was statistically significant ( p < 10 - 3 ), suggesting that vinculin is under low tension in growth cones. Two-hour treatment with the Rho-associated kinase inhibitor Y-27632 did not affect the mean FRET efficiency. Growth cones exhibited dynamic changes in morphology as observed by time-lapse imaging. VinTS FRET efficiency showed greater variance than TSMod FRET efficiency as a function of time, suggesting a greater dependence of VinTS FRET efficiency on growth cone dynamics compared with TSMod. Conclusions: The results demonstrate the feasibility of using VinTS to probe the function of vinculin in neuronal growth cones and provide a foundation for studies of mechanotransduction in neurons using this tension probe.

Lazarus phenomenon in trauma.

Lazarus phenomenon embodies auto-resuscitation, aka the return of spontaneous circulation following termination of cardiopulmonary resuscitation. Limited or no literature exists that describes auto-resuscitation in trauma. In the current report, we describe a case of an older woman that presented with poly-traumatic injuries following a motor vehicle collision. The aggressive resuscitation efforts failed, and the patient witnessed a pulseless electrical activity; however, nine-minutes after cessation of resuscitation efforts, the patient experienced auto-resuscitation. In addition to the sequel of events following the presentation, the report highlights the management dilemma and ethical implications relating to the observation period for auto-resuscitation in cases of donation after circulatory death, where the urgency to harvest the organs to ensure maximum viability is in direct opposition to ensuring enough time has elapsed to rule out auto-resuscitation. Guidelines on an appropriate period for observation in auto-resuscitation patients queued for organ donation are warranted, keeping in lieu viability of organs following death.