[cid:image001.jpg@01D87988.7EF7C5B0] BME Summer Seminar Series Wednesday, June 8th, 2022 9:30-10:30AM EST Via Zoom Meeting - link below* Evaluation links: Awadh Al Hawwash: https://purdue.ca1.qualtrics.com/jfe/form/SV_54KHkKA4gWNPP8O Worapat Sawatwong: https://purdue.ca1.qualtrics.com/jfe/form/SV_ePQ84UmokUO6W5o Characterization of Peripheral Motor Nerve Activation Using Sinusoidal Low Frequency Alternating Currents Awadh Al Hawwash (K. Yoshida / H. Lee, advisor) [cid:image002.jpg@01D87988.7EF7C5B0] Abstract: Electrical stimulation (ES) of peripheral nerves is an established therapeutic and rehabilitative technology to restore functional movements, and treat other neurological disorders. Historically, ES relied on the use of classical rectangular pulse stimulation. Although it provides an efficient means to activate nerve fibers, the activation is synchronous to the pulse, and generally activates nerve fibers within the nerve trunk in a non-physiological order. As a result, ES based muscle activation results in a rapid muscle fatigue. Recently, we reported that using a novel continuous sinusoidal Low Frequency Alternating Current (LFAC) waveform was able to activate autonomic nerve fibers and to elicit the Hering-Breuer reflex when presented at 5, 10, and 20 Hz in the swine animal model. Interestingly, the results suggest that LFAC might activate nerve fibers in the normal physiological order, and has a frequency dependency. Therefore, the present work describes the use of LFAC waveform to produce motor nerve activity that evoke muscle contractions. Acute in-vivo experiments were conducted where direct LFAC stimulation was applied to the sciatic nerve of anesthetized Sprague Dawley rats. LFAC waveforms were applied through bipolar cuff electrodes at frequency ranging from 1 to 20 Hz. The physiological responses to the LFAC waveform were quantified by measuring the electromyogram (EMG) and force output from the triceps surae muscle. Observed in the preliminary results were muscle responses to LFAC stimulation that were en masse phase locked to the sinusoidal cycle, but of two different modes: 1) A burst mode, and 2) A unitary mode of activation. LFAC activation threshold was not only frequency dependent, but also influenced by the geometry of the cuff electrodes. Our future work aims to characterize the muscle force fatigue rate and muscle type recruitment order to systematically explore the order of nerve fiber activation using LFAC. Effects of bone strain distribution on osteogenic transcriptome-level responses to two different loading modes Worapat Sawatwong (R. Main, advisor) [cid:image003.jpg@01D87988.7EF7C5B0] Abstract: Worapat Sawatwong1,2, and Russell P Main1,2 1Musculoskeletal Biology and Mechanics Lab, Department of Basic Medical Sciences, Purdue University, West Lafayette, IN, USA 2Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA Mechanical loading is an effective stimulus to induce new bone formation and inhibit bone loss. Osteocytes (Ots) are recognized as the key regulator for sensing and transducing the mechanical signals and mediating new bone formation in response to mechanical loading. Among various in vivo loading models, bone appears to be more sensitive to non-physiological strain distribution compared to strains elicited during normal locomotion. However, the effect of tissue-level strain distribution on cellular function and activity of Ots remains unclear. This study aims to reveal the effects of strain distribution on the skeletal osteogenic response on gene expression. A pilot study of female C57BL/6 mice (n = 4) with strain gauges attached to the tibiae were subjected to the tibial axial compressive (AC, physiological) and medial-lateral cantilever-type (ML, non-physiological) loading to obtain load-strain calibrations. The AC model requires a relatively higher load (~7N) than the ML model (~2N) to generate the absolute strain magnitude of 1000 ** on the medial midshaft of the tibia. Gauge-attached tibiae were analyzed by finite element modeling for the whole-bone strain distribution. Our next step will be to acquire 15wk old C57Bl/6 mice to be subjected to either tibial AC and ML loading for five days (n=3/group). Tibiae will be dissected after loading and the cross-sectional (CS) surface of the tibial cortical bone will be collected by cryosection. Ots located at the posterior-lateral region of the CS surface, where they are exposed to distinct directions of strain in the two loading models, will be isolated by the laser capture microdissection (LCM). We will perform RNA-Seq on these Ots to analyze the transcriptome-level response influenced by strain distribution. The outcome of this study is essential for understanding mechanosensation and mechanotransduction at the Ot, which could contribute to better osteoporosis clinical intervention through mechanical stimulation or drug development. *Join Zoom Meeting https://purdue-edu.zoom.us/j/92168739019?pwd=cnBOaFBxN3FWVVVTWC8wWWhaekdIdz0... Meeting ID: 921 6873 9019 Passcode: biomedical Liz Rowen She/Her Graduate Program Assistant Weldon School of Biomedical Engineering Martin C. Jischke Hall of Biomedical Engineering 206 S. 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