Compact Electrochromic Optical Recording of Bioelectric Potentials.

Electrochromic optical recording (ECORE) is a label-free method that utilizes electrochromism to optically detect electrical signals in biological cells with a high signal-to-noise ratio and is suitable for long-term recording. However, ECORE usually requires a large and intricate optical setup, making it relatively difficult to transport and to study specimens on a large scale. Here, we present a Compact ECORE (CECORE) apparatus that drastically reduces the spatial footprint and complexity of the ECORE setup whilst maintaining high sensitivity. An autobalancing differential photodetector automates common-mode noise rejection, removing the need for manually adjustable optics, and a compact laser module conserves space compared to a typical laser mount. The result is a simple, easy-to-use, and relatively low cost system that achieves a sensitivity of 16.7 µV (within a factor of 5 of the shot noise limit), and reliably detects action potentials from Human-induced pluripotent stem cell (HiPSC) derived cardiomyocytes. This setup can be further improved to within 1.5 dB of the shot noise limit by filtering out power-line interference.

Dual-Color Optical Recording of Bioelectric Potentials by Polymer Electrochromism.

Optical recording based on voltage-sensitive fluorescent reporters allows for spatial flexibility of measuring from desired cells, but photobleaching and phototoxicity of the fluorescent labels often limit their sensitivity and recording duration. Voltage-dependent optical absorption, rather than fluorescence, of electrochromic materials, would overcome these limitations to achieve long-term optical recording of bioelectrical signals. Electrochromic materials such as PEDOT:PSS possess the property that an applied voltage can either increase or decrease the light absorption depending on the wavelength. In this work, we harness this anticorrelated light absorption at two different wavelengths to significantly improve the signal detection. With dual-color detection, electrical activity from cells produces signals of opposite polarity, while artifacts, mechanical motions, and technical noises are uncorrelated or positively correlated. Using this technique, we are able to optically record cardiac action potentials with a high signal-to-noise ratio, 10 kHz sampling rate, >15 min recording duration, and no time-dependent degradation of the signal. Furthermore, we can reliably perform multiple recording sessions from the same culture for over 25 days.

The effect of dynamic intermittent hypoxic conditioning on arterial oxygen saturation.

BACKGROUND: Increases in arterial oxygen saturation (SaO2) in response to intermittent hypoxic exposure (IHE) are well established. However, IHE protocols have historically involved static hypoxic environments. The effect of a dynamic hypoxic environment on SaO2 is not known. OBJECTIVE: The purpose of this study was to examine the effect of dynamic IHE conditioning on SaO2 using the Cyclical Variable Altitude Conditioning Unit. METHODS: Thirteen trained participants (9 males, age 30.1 +/- 9.2 years; 4 females, age 30.3 +/- 8.9 years) residing at or near sea level were exposed to a 7-week IHE conditioning protocol (mean total exposure time = 30.8 hours). Participants were exposed to a constantly varying series of hypobaric pressures simulating altitudes from sea level to 6858 m (22 500 feet) in progressive conditioning tiers, creating a dynamic hypoxic environment. SaO2 was evaluated using pulse oximetry (SpO2) 4 times: at 2740, 3360, and 4570 m, prior to and following the first 3 weeks of IHE, and at 4570, 5490, and 6400 m at the start and end of the final 4 weeks. RESULTS: SpO2 improved 3.5%, 3.8%, and 4.1% at 2470, 3360, and 4570 m, respectively (P < .05), and 3.3%, 3.4%, and 5.9% at 4570, 5490, and 6400 m, respectively (P < .05). At 4570 m, SpO2 increased from 81.7% +/- 6.5% to 89.1% +/- 3.2% over the entire 7-week conditioning period. DISCUSSION: The dynamic intermittent hypoxic conditioning protocol used in the present study resulted in an acclimation response, such that SpO2 was significantly increased at all altitudes tested, with shorter exposure times than generally reported.

Selective serotonin reuptake inhibitors and rhabdomyolysis after eccentric exercise.

PURPOSE: The purpose of this report was to review three cases of clinically significant rhabdomyolysis that developed in research subjects after completing an eccentric exercise protocol. All three cases occurred in subjects who reported use of selective serotonin reuptake inhibitors (SSRI). METHODS: Sixty-three subjects enrolled in the study. Subjects performed 15 sets of 15 repetitions of maximal eccentric contractions of the elbow flexors. Subjects were then monitored on a daily basis for development of delayed onset muscle soreness (DOMS). Subjects received either microcurrent electrical neuromuscular stimulation (MENS) or sham treatment. RESULTS: Three subjects developed clinically significant rhabdomyolysis after performing this exercise protocol. Affected subjects were the only subjects who reported use of SSRI during the study period. CONCLUSION: This report raises suspicion of SSRI use as a predisposing factor to muscle injury after eccentric exercise.

Physiologic considerations of therapeutic slideboard rehabilitation with an external loading device.

CONTEXT: Slideboard exercise is consistent with the American College of Sports Medicine guidelines for exercise intensity of 55% to 90% of maximal heart rate or 40% to 85% of maximal oxygen uptake. OBJECTIVE: To determine if slideboard exercise while in a leg harness increases the metabolic and cardiorespiratory demands. DESIGN: Repeated-measures design. SETTING: Athletic Training Research Laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixteen volunteers from the university community. INTERVENTION(S): Subjects performed 2 graded slideboard exercise tests with and without the leg harness, each 2-minute stage ranging from 46 to 90 slides per minute. MAIN OUTCOME MEASURE(S): We measured maximal oxygen uptake, heart rate, blood lactate, respiratory exchange ratio, ratings of perceived exertion, and total time to exhaustion during each session. RESULTS: Significant decreases in maximal oxygen uptake and blood lactate were observed when the leg harness was used. CONCLUSIONS: Performance was hindered when subjects wore the leg harness during the slideboard exercise.