Ion channel involvement in the temperature-sensitive response of the rabbit corneal endothelial cell resting membrane potential

1993 ◽  
Vol 135 (1) ◽  
Author(s):  
MitchellA. Watsky ◽  
JamesL. Rae
Keyword(s):  
Membrane Potential ◽  
Endothelial Cell ◽  
Ion Channel ◽  
Corneal Endothelial Cell ◽  
Resting Membrane Potential ◽  
Temperature Sensitive

Temperature-sensitive properties of rat suprachiasmatic nucleus neurons

2001 ◽  
Vol 281 (3) ◽  
pp. R706-R715 ◽  
Author(s):  
Penny W. Burgoon ◽  
Jack A. Boulant
Keyword(s):  
Membrane Potential ◽  
Firing Rate ◽  
Suprachiasmatic Nucleus ◽  
Interspike Interval ◽  
Slow Component ◽  
Resting Membrane Potential ◽  
Temperature Sensitive ◽  
Tissue Slices ◽  
Hypothalamic Tissue ◽  
Potential Threshold

The hypothalamic suprachiasmatic nucleus (SCN) contains a heterogeneous population of neurons, some of which are temperature sensitive in their firing rate activity. Neuronal thermosensitivity may provide cues that synchronize the circadian clock. In addition, through synaptic inhibition on nearby cells, thermosensitive neurons may provide temperature compensation to other SCN neurons, enabling postsynaptic neurons to maintain a constant firing rate despite changes in temperature. To identify mechanisms of neuronal thermosensitivity, whole cell patch recordings monitored resting and transient potentials of SCN neurons in rat hypothalamic tissue slices during changes in temperature. Firing rate temperature sensitivity is not due to thermally dependent changes in the resting membrane potential, action potential threshold, or amplitude of the fast afterhyperpolarizing potential (AHP). The primary mechanism of neuronal thermosensitivity resides in the depolarizing prepotential, which is the slow depolarization that occurs prior to the membrane potential reaching threshold. In thermosensitive neurons, warming increases the prepotential's rate of depolarization, such that threshold is reached sooner. This shortens the interspike interval and increases the firing rate. In some SCN neurons, the slow component of the AHP provides an additional mechanism for thermosensitivity. In these neurons, warming causes the slow AHP to begin at a more depolarized level, and this, in turn, shortens the interspike interval to increase firing rate.

scholarly journals MicroRNA Biophysically Modulates Cardiac Action Potential by Direct Binding to Ion Channel

Circulation ◽  
2021 ◽  
Vol 143 (16) ◽  
pp. 1597-1613 ◽  
Author(s):  
Dandan Yang ◽  
Xiaoping Wan ◽  
Adrienne T. Dennis ◽  
Emre Bektik ◽  
Zhihua Wang ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Rna Interference ◽  
Action Potential ◽  
Ion Channel ◽  
Cardiac Electrophysiology ◽  
Ex Vivo ◽  
Proximity Ligation Assay ◽  
Resting Membrane Potential ◽  
Seed Region ◽  
Single Nucleotide

Background: MicroRNAs (miRs) play critical roles in regulation of numerous biological events, including cardiac electrophysiology and arrhythmia, through a canonical RNA interference mechanism. It remains unknown whether endogenous miRs modulate physiologic homeostasis of the heart through noncanonical mechanisms. Methods: We focused on the predominant miR of the heart (miR1) and investigated whether miR1 could physically bind with ion channels in cardiomyocytes by electrophoretic mobility shift assay, in situ proximity ligation assay, RNA pull down, and RNA immunoprecipitation assays. The functional modulations of cellular electrophysiology were evaluated by inside-out and whole-cell patch clamp. Mutagenesis of miR1 and the ion channel was used to understand the underlying mechanism. The effect on the heart ex vivo was demonstrated through investigating arrhythmia-associated human single nucleotide polymorphisms with miR1-deficient mice. Results: We found that endogenous miR1 could physically bind with cardiac membrane proteins, including an inward-rectifier potassium channel Kir2.1. The miR1–Kir2.1 physical interaction was observed in mouse, guinea pig, canine, and human cardiomyocytes. miR1 quickly and significantly suppressed I K1 at sub–pmol/L concentration, which is close to endogenous miR expression level. Acute presence of miR1 depolarized resting membrane potential and prolonged final repolarization of the action potential in cardiomyocytes. We identified 3 miR1-binding residues on the C-terminus of Kir2.1. Mechanistically, miR1 binds to the pore-facing G-loop of Kir2.1 through the core sequence AAGAAG, which is outside its RNA interference seed region. This biophysical modulation is involved in the dysregulation of gain-of-function Kir2.1–M301K mutation in short QT or atrial fibrillation. We found that an arrhythmia-associated human single nucleotide polymorphism of miR1 (hSNP14A/G) specifically disrupts the biophysical modulation while retaining the RNA interference function. It is remarkable that miR1 but not hSNP14A/G relieved the hyperpolarized resting membrane potential in miR1-deficient cardiomyocytes, improved the conduction velocity, and eliminated the high inducibility of arrhythmia in miR1-deficient hearts ex vivo. Conclusions: Our study reveals a novel evolutionarily conserved biophysical action of endogenous miRs in modulating cardiac electrophysiology. Our discovery of miRs’ biophysical modulation provides a more comprehensive understanding of ion channel dysregulation and may provide new insights into the pathogenesis of cardiac arrhythmias.

scholarly journals Suppression of spikes during posttetanic hyperpolarization in auditory neurons: the role of temperature, Ih currents, and the Na+-K+-ATPase pump

2012 ◽  
Vol 108 (7) ◽  
pp. 1924-1932 ◽  
Author(s):  
Jun Hee Kim ◽  
Henrique von Gersdorff
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Atpase Activity ◽  
Brain Stem ◽  
High Frequency ◽  
Afferent Fiber ◽  
Resting Potential ◽  
Effect Of Temperature ◽  
Resting Membrane Potential ◽  
Temperature Sensitive

In vivo recordings from postsynaptic neurons in the medial nucleus of the trapezoid body (MNTB), an auditory brain stem nucleus, show that acoustic stimulation produces a burst of spikes followed by a period of hyperpolarization and suppressed spiking activity. The underlying mechanism for this hyperpolarization and reduced spiking is unknown. Furthermore, the mechanisms that control excitability and resting membrane potential are not fully determined for these MNTB neurons. In this study we investigated the excitability of principal neurons from the MNTB after high-frequency afferent fiber stimulation, using whole cell recordings from postnatal day 15–17 rat brain stem slices. We found that Na+-K+-ATPase activity mediates a progressive hyperpolarization during a prolonged tetanic train and a posttetanic hyperpolarization (PTH) at the end of the train, when postsynaptic action potentials failed to fire. Raising the temperature to more physiological levels (from 22 to 35°C) depolarized the resting membrane potential of both presynaptic and postsynaptic cells and decreased the latency of action potential firing during PTH. Higher temperatures also reduced the presynaptic calyx action potential failure rates by 50% during presynaptic PTH, thus increasing the safety-factor for presynaptic spiking. The effect of temperature on hyperpolarization-activated cation current ( Ih) is reflected in the resting potential at both pre- and postsynaptic neurons. We thus propose that temperature-sensitive Na+-K+-ATPase activity and Ih contribute to set the resting membrane potential and produce a brief period of suppressed spiking (or action potential failures) after a prolonged high-frequency afferent tetanus.

Rabbit corneal endothelial cell membrane potential

1993 ◽  
Vol 13 (3) ◽  
pp. 305-308 ◽  
Author(s):  
Chris C. Wigham ◽  
Keith Green ◽  
Stuart Hodson
Keyword(s):  
Membrane Potential ◽  
Endothelial Cell ◽  
Cell Membrane ◽  
Corneal Endothelial Cell ◽  
Cell Membrane Potential

scholarly journals Myopia, corneal endothelial cell density and morphology in a Japanese population-based cross-sectional study: the JPHC-NEXT Eye Study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Naohiko Aketa ◽  
Miki Uchino ◽  
Motoko Kawashima ◽  
Yuichi Uchino ◽  
Kenya Yuki ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Cell Density ◽  
Contact Lenses ◽  
Population Based ◽  
Cross Sectional Study ◽  
Corneal Endothelial Cell ◽  
Endothelial Cell Density ◽  
Sectional Study ◽  
Cross Sectional ◽  
Corneal Endothelial Cell Density

AbstractThis population-based cross-sectional study was performed to determine the mean corneal endothelial cell density (ECD), coefficient of variation (CV), and hexagonality (HEX), and their associations with myopia in Japanese adults living in Chikusei city. Of 7109 participants with available data, 5713 (2331 male and 3382 female) participants were eligible for analysis. After assessing the relationship between participant characteristics and spherical equivalent refraction (SER), the association of SER with the abnormal value of ECD (< 2000 cells/mm), CV (≥ 0.40), and HEX (≤ 50%) were determined using the logistic regression models adjusting for potential confounders (age, intraocular pressure, keratometric power, height, and antihypertensive drug use). In male participants, there was no statistically significant relationships between SER and endothelial parameters. In female participants, compared to emmetropia, SER ≤ − 6 D had significantly higher odds ratio (OR) of having the abnormal value of CV (OR = 2.07, 95% confidence interval [CI] 1.39–3.10) and HEX (OR = 2.04, 95% CI 1.29–3.23), adjusted for potential confounders, indicating that the high myopia was associated with the abnormal values of CV and HEX. Further adjustment for contact lenses wear partly attenuated these associations. Association between the SER and ECD was not detected.

scholarly journals 27-gauge trocar-assisted sutureless intraocular lens fixation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Tatsuya Jujo ◽  
Jiro Kogo ◽  
Hiroki Sasaki ◽  
Reio Sekine ◽  
Keiji Sato ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Endothelial Cell ◽  
Cell Density ◽  
Intraocular Lens ◽  
Vitreous Hemorrhage ◽  
Corneal Endothelial Cell ◽  
Endothelial Cell Density ◽  
Corneal Endothelial Cell Density ◽  
The Mean ◽  
Iol Fixation

Abstract Backgrounds However there have been numerous investigations of intrascleral intraocular lens (IOL) fixation techniques, there is room for improvement in terms of simplifying complicated techniques and reducing the high levels of skill required. This study aimed to report a novel technique for sutureless intrascleral fixation of the IOL using retinal forceps with a 27-gauge trocar. Methods Nineteen eyes of 18 patients underwent intrascleral fixation of the IOL from July 2018 to September 2019 were enrolled in this study. A 27-gauge trocar formed 3-mm scleral tunnels positioned at 4 and 10 o’clock, 2 mm from the corneal limbus. We used a 3-piece IOL haptic grasped by a 27-gauge retinal forceps and pulled from the 27-gauge trocar. The IOL was fixed by making a flange. Main outcome measures were visual acuity, corneal endothelial cell density, IOL tilt, decentration, predicted error of refraction and complications. Results The 19 eyes were followed up for 1 month. The mean pre- and postoperative logMAR uncorrected visual acuity (UCVA) was 1.06 ± 0.63 and 0.40 ± 0.26, respectively (p < 0.01), while the mean pre- and postoperative logMAR best corrected visual acuity (BCVA) was 0.27 ± 0.51 and 0.06 ± 0.15, respectively (p = 0.09). The mean corneal endothelial cell density was 2406 ± 625 to 2004 ± 759 cells/mm2 at 1 month (p = 0.13). The mean IOL tilt was 3.52 ± 3.00°, and the mean IOL decentration was 0.39 ± 0.39 mm. There was no correlation among IOL tilt, decentration and BCVA (p > 0.05). The mean prediction error of the target refraction was − 0.03 ± 0.93 D. The complications were vitreous hemorrhage (3 eyes), hyphema (1 eye), IOP elevation (1 eye), iris capture of the IOL (1 eye) and hypotony (2 eyes). No IOL dislocation occurred. Conclusions IOL intrascleral fixation with a flange achieved good IOL fixation and visual outcome in the scleral tunnels created with the 27-gauge trocar.

scholarly journals Age-Stratified Analysis of Diabetes and Pseudophakia Effects on Corneal Endothelial Cell Density

Cornea ◽  
2017 ◽  
Vol 36 (3) ◽  
pp. 367-371 ◽  
Author(s):  
Yicheng Chen ◽  
Sean W. Tsao ◽  
Moonseong Heo ◽  
Patrick K. Gore ◽  
Mitchell D. McCarthy ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Cell Density ◽  
Corneal Endothelial Cell ◽  
Endothelial Cell Density ◽  
Corneal Endothelial Cell Density ◽  
Stratified Analysis
Sign in / Sign up

Export Citation Format

Share Document