scholarly journals A dynamic clamp protocol to artificially modify cell capacitance

2021 ◽  
Author(s):  
Paul Pfeiffer ◽  
Federico José Barreda Tomás ◽  
Jiameng Wu ◽  
Jan-Hendrik Schleimer ◽  
Imre Vida ◽  
...  
Keyword(s):  
Neuron Model ◽  
Granule Cells ◽  
Membrane Resistance ◽  
Dynamic Clamp ◽  
Excitable Cells ◽  
Genetic Manipulations ◽  
Novel Technique ◽  
Ionic Conductances ◽  
Cell Capacitance

Dynamics of excitable cells and networks depend on the membrane time constant, set by membrane resistance and capacitance. Whereas pharmacological and genetic manipulations of ionic conductances are routine in electrophysiology, experimental control over capacitance remains a challenge. Here, we present capacitance clamp, an approach that allows to mimic a modified capacitance in biological neurons via an unconventional application of the dynamic clamp technique. We first demonstrate the feasibility to quantitatively modulate capacitance in a mathematical neuron model and then confirm the functionality of capacitance clamp in in vitro experiments in granule cells of rodent dentate gyrus with up to threefold virtual capacitance changes. Clamping of capacitance thus constitutes a novel technique to probe and decipher mechanisms of neuronal signaling in ways that were so far inaccessible to experimental electrophysiology.

Cable properties of layer V neurons from cat sensorimotor cortex in vitro

1984 ◽  
Vol 52 (2) ◽  
pp. 278-289 ◽  
Author(s):  
C. E. Stafstrom ◽  
P. C. Schwindt ◽  
W. E. Crill
Keyword(s):  
Voltage Clamp ◽  
Time Constant ◽  
Neuron Model ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Voltage Range ◽  
Cable Properties ◽  
Layer V ◽  
Specific Membrane

The passive cable properties of neurons from layer V of cat neocortex were studied in an in vitro slice preparation using current-clamp techniques and a single-microelectrode voltage clamp. Neurons were examined in the presence and absence of several agents that block time- and voltage-dependent conductances. The charging response to an injected current pulse was well fitted by a single exponential in 12 of 17 cells examined. By itself, this result would suggest that most of the neurons are isopotential. However, the existence of a nonisopotential region was demonstrated in all neurons examined using two alternative, independent methods: application of voltage-clamp steps and current impulses. The decay of the capacitive charging transient following a voltage-clamp step reflects charge redistribution solely in the nonisopotential region and had a mean time constant about 17% of the membrane time constant, tau m. The voltage decay following a current impulse was always fitted by (at least) two exponentials, the shorter of which was about 9% of tau m. These results suggest that a nonisopotential region exists but is electrotonically short, of relatively low-input conductance, or both, independent of a particular neuron model. Adopting Rall's (23, 24) idealized neuron model (isopotential compartment attached to a finite-length uniform cable) resulted in a mean value for the equivalent electrotonic length (L) of the nonisopotential compartment of 0.72 space constants from voltage-clamp data and 1.21 space constants from impulse-response data. A dendrite-to-soma conductance ratio (p) of 2-4 was obtained from either procedure. There were no significant differences in the cable parameters between normal cells and those where conductance-blocking agents were present. A specific membrane resistance (Rm) ranging from 2,300 to 11,700 omega X cm2 was estimated by assuming values of specific membrane capacitance reported in the literature. We conclude that large layer V neocortical neurons in vitro are electrotonically compact in the voltage range near resting potential and in the absence of significant tonic synaptic input. In this respect, their electrotonic cable properties resemble those of other mammalian neurons in vitro.

scholarly journals Development of a gel dedicated to gel immersion endoscopy

2021 ◽  
Vol 09 (06) ◽  
pp. E918-E924
Author(s):  
Tomonori Yano ◽  
Atsushi Ohata ◽  
Yuji Hiraki ◽  
Makoto Tanaka ◽  
Satoshi Shinozaki ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Porcine Model ◽  
Ex Vivo ◽  
In Vitro Experiments ◽  
Efficacy And Safety ◽  
Coagulative Necrosis ◽  
Novel Technique ◽  
In Vivo Experiments

Abstract Backgrounds and study aims Gel immersion endoscopy is a novel technique to secure the visual field during endoscopy. The aim of this study was to develop a dedicated gel for this technique. Methods To identify appropriate viscoelasticity and electrical conductivity, various gels were examined. Based on these results, the dedicated gel “OPF-203” was developed. Efficacy and safety of OPF-203 were evaluated in a porcine model. Results  In vitro experiments showed that a viscosity of 230 to 1900 mPa·s, loss tangent (tanδ) ≤ 0.6, and hardness of 240 to 540 N/cm2 were suitable. Ex vivo experiments showed electrical conductivity ≤ 220 μS/cm is appropriate. In vivo experiments using gastrointestinal bleeding showed that OPF-203 provided clear visualization compared to water. After electrocoagulation of gastric mucosa in OPF-203, severe coagulative necrosis was not observed in the muscularis but limited to the mucosa. Conclusions OPF-203 is useful for gel immersion endoscopy.

scholarly journals The Expression of the Cancer-Associated lncRNA Snhg15 Is Modulated by EphrinA5-Induced Signaling

2021 ◽  
Vol 22 (3) ◽  
pp. 1332
Author(s):  
Daniel Pensold ◽  
Julia Gehrmann ◽  
Georg Pitschelatow ◽  
Asa Walberg ◽  
Kai Braunsteffer ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Intracellular Signaling ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Membrane Receptors ◽  
In Vitro Assays ◽  
Eph Receptor ◽  
Medulloblastoma Cell Line ◽  
And Migration

The Eph receptor tyrosine kinases and their respective ephrin-ligands are an important family of membrane receptors, being involved in developmental processes such as proliferation, migration, and in the formation of brain cancer such as glioma. Intracellular signaling pathways, which are activated by Eph receptor signaling, are well characterized. In contrast, it is unknown so far whether ephrins modulate the expression of lncRNAs, which would enable the transduction of environmental stimuli into our genome through a great gene regulatory spectrum. Applying a combination of functional in vitro assays, RNA sequencing, and qPCR analysis, we found that the proliferation and migration promoting stimulation of mouse cerebellar granule cells (CB) with ephrinA5 diminishes the expression of the cancer-related lncRNA Snhg15. In a human medulloblastoma cell line (DAOY) ephrinA5 stimulation similarly reduced SNHG15 expression. Computational analysis identified triple-helix-mediated DNA-binding sites of Snhg15 in promoters of genes found up-regulated upon ephrinA5 stimulation and known to be involved in tumorigenic processes. Our findings propose a crucial role of Snhg15 downstream of ephrinA5-induced signaling in regulating gene transcription in the nucleus. These findings could be potentially relevant for the regulation of tumorigenic processes in the context of glioma.

scholarly journals Topography and Response Timing of Intact Cerebellum Stained With Absorbance Voltage-Sensitive Dye

2009 ◽  
Vol 101 (1) ◽  
pp. 474-490 ◽  
Author(s):  
Michael E. Brown ◽  
Michael Ariel
Keyword(s):  
Time Course ◽  
Granule Cells ◽  
Physiological Activity ◽  
Timing Analysis ◽  
Molecular Layer ◽  
Stimulus Position ◽  
Voltage Sensitive Dye ◽  
Limited Region ◽  
Response Timing

Physiological activity of the turtle cerebellar cortex (Cb), maintained in vitro, was recorded during microstimulation of inferior olive (IO). Previous single-electrode responses to such stimulation showed similar latencies across a limited region of Cb, yet those recordings lacked spatial and temporal resolution and the recording depth was variable. The topography and timing of those responses were reexamined using photodiode optical recordings. Because turtle Cb is thin and unfoliated, its entire surface can be stained by a voltage-sensitive dye and transilluminated to measure changes in its local absorbance. Microstimulation of the IO evoked widespread depolarization from the rostral to the caudal edge of the contralateral Cb. The time course of responses measured at a single photodiode matched that of single-microelectrode responses in the corresponding Cb locus. The largest and most readily evoked response was a sagittal band centered about 0.7 mm from the midline. Focal white-matter (WM) microstimulation on the ventricular surface also activated sagittal bands, whereas stimulation of adjacent granule cells evoked a radial patch of activation. In contrast, molecular-layer (ML) microstimulation evoked transverse beams of activation, centered on the rostrocaudal stimulus position, which traveled bidirectionally across the midline to the lateral edges of the Cb. A timing analysis demonstrated that both IO and WM microstimulation evoked responses with a nearly simultaneous onset along a sagittal band, whereas ML microstimulation evoked a slowly propagating wave traveling about 25 cm/s. The response similarity to IO and WM microstimulation suggests that the responses to WM microstimulation are dominated by activation of its climbing fibers. The Cb's role in the generation of precise motor control may result from these temporal and topographic differences in orthogonally oriented pathways. Optical recordings of the turtle's thin flat Cb can provide insights into that role.

Selective Modulation of Tonic and Phasic Inhibitions in Dentate Gyrus Granule Cells

2002 ◽  
Vol 87 (5) ◽  
pp. 2624-2628 ◽  
Author(s):  
Zoltan Nusser ◽  
Istvan Mody
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Hippocampal Slices ◽  
Tonic Inhibition ◽  
Adult Rats ◽  
Adult Rat ◽  
Phasic Inhibition ◽  
The Mean

In some nerve cells, activation of GABAA receptors by GABA results in phasic and tonic conductances. Transient activation of synaptic receptors generates phasic inhibition, whereas tonic inhibition originates from GABA acting on extrasynaptic receptors, like in cerebellar granule cells, where it is thought to result from the activation of extrasynaptic GABAA receptors with a specific subunit composition (α6βxδ). Here we show that in adult rat hippocampal slices, extracellular GABA levels are sufficiently high to generate a powerful tonic inhibition in δ subunit–expressing dentate gyrus granule cells. In these cells, the mean tonic current is approximately four times larger than that produced by spontaneous synaptic currents occurring at a frequency of ∼10 Hz. Antagonizing the GABA transporter GAT-1 with NO-711 (2.5 μM) selectively enhanced tonic inhibition by 330% without affecting the phasic component. In contrast, by prolonging the decay of inhibitory postsynaptic currents (IPSCs), the benzodiazepine agonist zolpidem (0.5 μM) augmented phasic inhibition by 66%, while leaving the mean tonic conductance unchanged. These results demonstrate that a tonic GABAA receptor–mediated conductance can be recorded from dentate gyrus granule cells of adult rats in in vitro slice preparations. Furthermore, we have identified distinct pharmacological tools to selectively modify tonic and phasic inhibitions, allowing future studies to investigate their specific roles in neuronal function.

scholarly journals Deletion of Jdp2 enhances Slc7a11 expression in Atoh-1 positive cerebellum granule cell progenitors in vivo

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chia-Chen Ku ◽  
Kenly Wuputra ◽  
Kohsuke Kato ◽  
Jia-Bin Pan ◽  
Chia-Pei Li ◽  
...  
Keyword(s):  
Granule Cell ◽  
Granule Cells ◽  
Apoptotic Cell ◽  
Redox Homeostasis ◽  
Critical Role ◽  
Glutamate Transporter ◽  
Developmental Abnormalities ◽  
Oxidative Stresses

Abstract Background The cerebellum is the sensitive region of the brain to developmental abnormalities related to the effects of oxidative stresses. Abnormal cerebellar lobe formation, found in Jun dimerization protein 2 (Jdp2)-knockout (KO) mice, is related to increased antioxidant formation and a reduction in apoptotic cell death in granule cell progenitors (GCPs). Here, we aim that Jdp2 plays a critical role of cerebellar development which is affected by the ROS regulation and redox control. Objective Jdp2-promoter-Cre transgenic mouse displayed a positive signal in the cerebellum, especially within granule cells. Jdp2-KO mice exhibited impaired development of the cerebellum compared with wild-type (WT) mice. The antioxidation controlled gene, such as cystine-glutamate transporter Slc7a11, might be critical to regulate the redox homeostasis and the development of the cerebellum. Methods We generated the Jdp2-promoter-Cre mice and Jdp2-KO mice to examine the levels of Slc7a11, ROS levels and the expressions of antioxidation related genes were examined in the mouse cerebellum using the immunohistochemistry. Results The cerebellum of Jdp2-KO mice displayed expression of the cystine-glutamate transporter Slc7a11, within the internal granule layer at postnatal day 6; in contrast, the WT cerebellum mainly displayed Sla7a11 expression in the external granule layer. Moreover, development of the cerebellar lobes in Jdp2-KO mice was altered compared with WT mice. Expression of Slc7a11, Nrf2, and p21Cip1 was higher in the cerebellum of Jdp2-KO mice than in WT mice. Conclusion Jdp2 is a critical regulator of Slc7a11 transporter during the antioxidation response, which might control the growth, apoptosis, and differentiation of GCPs in the cerebellar lobes. These observations are consistent with our previous study in vitro.

The chemokine SDF1 regulates migration of dentate granule cells

Development ◽  
2002 ◽  
Vol 129 (18) ◽  
pp. 4249-4260 ◽  
Author(s):  
Anil Bagri ◽  
Theresa Gurney ◽  
Xiaoping He ◽  
Yong-Rui Zou ◽  
Dan R. Littman ◽  
...  
Keyword(s):  
Cell Migration ◽  
Dentate Gyrus ◽  
Granule Cell ◽  
Granule Cells ◽  
Ectopic Expression ◽  
Dentate Granule Cell ◽  
Vitro Assay ◽  
Dentate Granule Cells ◽  
Cell Position

The dentate gyrus is the primary afferent pathway into the hippocampus, but there is little information concerning the molecular influences that govern its formation. In particular, the control of migration and cell positioning of dentate granule cells is not clear. We have characterized more fully the timing and route of granule cell migration during embryogenesis using in utero retroviral injections. Using this information, we developed an in vitro assay that faithfully recapitulates important events in dentate gyrus morphogenesis. In searching for candidate ligands that may regulate dentate granule cell migration, we found that SDF1, a chemokine that regulates cerebellar and leukocyte migration, and its receptor CXCR4 are expressed in patterns that suggest a role in dentate granule cell migration. Furthermore, CXCR4 mutant mice have a defect in granule cell position. Ectopic expression of SDF1 in our explant assay showed that it directly regulates dentate granule cell migration. Our study shows that a chemokine is necessary for the normal development of the dentate gyrus, a forebrain structure crucial for learning and memory.

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