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Electrophysiology
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
Microelectrodes consist of an ultrafine-tapered tip and are used for either signal acquisition in single cells or electrical stimulations of nerve tissues (Plieth, 2008). The electrode tip must be small when compared to the cell dimension to avoid cell damage and to enable easy penetration into the cell wall. There are three categories of microelectrodes namely, glass micropipettes, metal microelectrodes and solid-state microprobes (Enderle & Bronzino, 2012), as shown in Figure 3.4. Mostly, solid-state microelectrodes are used for multi-channel recordings of biopotential or electrical stimulation of neuron cells in brain or spinal cord (Enderle & Bronzino, 2012; Manahan-Vaughan, 2018). The major advantage of using solid-state microelectrodes instead of other two microelectrode types is the capability to manufacture small size electrodes in a mass quantity.
Isolated Atrial Preparations
Published in John H. McNeill, Measurement of Cardiac Function, 2020
M.K. Pugsley, E.S. Hayes, M.J.A. Walker
Electrical activity can be measured in atrial tissue by a variety of techniques. Electrograms and monophasic action potential recordings can easily be obtained from atrial tissue. These are probably poor alternatives to the use of intracellular microelectrodes. Intracellular potentials can be recorded from whole atrium or from a variety of atrial preparations using routine techniques. If the mechanical activity of the preparation makes recording difficult, floating electrodes can be used.
Intestine Microcirculation
Published in John H. Barker, Gary L. Anderson, Michael D. Menger, Clinically Applied Microcirculation Research, 2019
Measurement of tissue oxygen tension with the Whalen54 microelectrode is not a particularly difficult technique, but construction of the microelectrodes is difficult. The microelectrodes must be calibrated at oxygen tensions of 0 to 100 mmHg, with particular attention to the calibration at oxygen tensions below 40 mmHg where most tissue oxygen tensions reside.31 Details of construction of the microelectrodes are published54 and commercial microelectrodes are available. The principal of operation is that the gold anode, which is plated within the electrode tip, will facilitate reduction of oxygen and the higher the oxygen tension, the higher the microelectrode current; theoretical and practical aspects of electrode design and physics are available.37 The typical current range is 10−11 to 10−9 amps at physiological oxygen tensions and, as a result of such low currents, electronic shielding equivalent to that used in membrane potential and patch clamp technology is essential.
Lithium upregulates growth-associated protein-43 (GAP-43) and postsynaptic density-95 (PSD-95) in cultured neurons exposed to oxygen-glucose deprivation and improves electrophysiological outcomes in rats subjected to transient focal cerebral ischemia following a long-term recovery period
Published in Neurological Research, 2022
Shih-Huang Tai, Sheng-Yang Huang, Liang-Chun Chao, Yu-Wen Lin, Chien-Chih Huang, Tian-Shung Wu, Yan-Shen Shan, Ai-Hua Lee, E-Jian Lee
SSEP recordings were conducted before the ischemic insult as the baseline and post-insult for 28 days using a previously described method [18]. Rats were anesthetized with 0.5–2% halothane mixed with 70% N2O and 30% O2 and placed in a cage (60 × 45 × 45 cm) made of aluminum columns and copper mesh. Appropriate stereotactic coordinates were measured from the bregma, and four holes were created in the parietal bones at appropriate stereotaxic coordinates (AP 0–1 mm, LM 4–5 mm and AP −1 to −2 mm, LM 2–3 mm for the fore- and hindpaw receptive fields, respectively). A recording microelectrode was then positioned 0.5 mm below the cortical surface. The signal was filtered with bandpass (10–2000 Hz) and notch (60 Hz) filters, and the signals were recorded digitally on a computer (Medelec Synergy Suite EMG/EP; Oxford Instruments, UK). The somatosensory stimuli consisted of transcutaneous electrical stimulation (1–3 mA direct current, 0.1 ms duration, 1 Hz) of the fore- and hindpaws contralateral to the side of the recording. At least 20 evoked potentials were averaged and recorded to obtain the latency and intensity of the field potentials. The SSEP waves, which consist of the first negative peak (N1) and first positive (P1) peak, were used to measure the latency and amplitude (negative up). The potential latency and amplitude were defined as the time difference between the stimulation to N1 and the intensity difference between N1 and P1, respectively.
Uncontrolled Oxygen Levels in Cultures of Retinal Pigment Epithelium: Have We Missed the Obvious?
Published in Current Eye Research, 2022
The optimum O2 level for most primary cell cultures has been reported to be 2–5%.75 In retina and RPE studies, more attention has been paid to characterizing O2 consumption rate 76,77 than to determining O2 partial pressure in the microenvironment of the cells. For example, the utilization of O2 has been examined in retina isolated from rabbit 78 and rat.79 These studies have considered the metabolism of the entire retina rather than spatial resolution.80 To address the spatial issue, a micro electrode array system has been used to evaluate, for instance, the RPE functionality in a co-culture of mice retina with human embryonic stem cell-derived RPEs cells.81 In this regard, microelectrodes are advantageous because of providing detailed PO2 mapping with high spatial resolution and particularly for the possibility of providing information on metabolism when integrated with mathematical models of diffusion and consumption.80 Nonetheless, O2 reduction by almost all electrodes limits the polarographic measurements to produce current, therefore requiring samples with significantly higher O2 consumption than that of the electrode. To overcome drawbacks, a microfluidics-based respirometry has recently been introduced for RPE cell cultures.82
Experience to prevent wire tethering in deep brain stimulation from a single center
Published in Neurological Research, 2021
Dongliang Wang, Jiayu Liu, Qingpei Hao, Hu Ding, Bo Liu, Zhi Liu, Haidong Song, Jia Ouyang, Ruen Liu
Briefly, the 3.0 T magnetic resonance imaging (MRI) was carried out 1–3 days before surgery. The imaging scanner was aligned parallel to the anterior commissure–posterior commissure line as closely as possible and used a specific sequence (3DT1, axial, coronal and sagittal T2-weighted images with 1.0 mm slice thickness and no spacing). A Leksell stereotactic head frame was mounted on the patient’s skull on the day of surgery under local anesthesia and then underwent stereotactic cranial computed tomography (1.0 mm slice thickness and no spacing). The MRI was integrated into the computed tomography (CT)-based three-dimensional stereotactic coordinate system by landmark-based image fusion. The targets and trajectory of the electrode implantation were calculated and determined using the Leksell SurgiPlan station (Elekta, Stockholm, Sweden). Under local anesthesia, the surgical incision was made according to the calculated target coordinates, and a hole was drilled through the skull. The electrodes for subthalamic nucleus (STN) were PINS L301 with four platinum–iridium cylindrical surface contacts, and each contact was 1.27 mm in diameter and 1.5 mm in length and separated by 0.5 mm. The electrodes for globus pallidus internus (GPi) were PINS L302, which had contacts of the same size but separated by 1.5 mm. The ultimately precise target was confirmed by anatomical location, and the signal of intraoperative microelectrode stimulation and the symptoms were relieved intraoperatively.