Optical single-channel recording: imaging Ca[sup 2+] flux through individual ion channels with high temporal and spatial resolution

2005 ◽  
Vol 10 (1) ◽  
pp. 011002 ◽  
Author(s):  
Angelo Demuro ◽  
Ian Parker
Keyword(s):  
Ion Channels ◽  
Spatial Resolution ◽  
Single Channel ◽  
Single Channel Recording ◽  
Individual Ion ◽  
Temporal And Spatial

Single-channel recording of ligand-gated ion channels

2007 ◽  
Vol 2 (11) ◽  
pp. 2826-2841 ◽  
Author(s):  
Martin Mortensen ◽  
Trevor G Smart
Keyword(s):  
Ion Channels ◽  
Single Channel ◽  
Single Channel Recording ◽  
Gated Ion Channels ◽  
Ligand Gated Ion Channels

scholarly journals Homomeric GluA2(R) AMPA receptors can conduct when desensitized

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ian D. Coombs ◽  
David Soto ◽  
Thomas P. McGee ◽  
Matthew G. Gold ◽  
Mark Farrant ◽  
...  
Keyword(s):  
Steady State ◽  
Ion Channels ◽  
Ampa Receptors ◽  
Single Channel ◽  
Fluctuation Analysis ◽  
Single Channel Recording ◽  
Auxiliary Subunits ◽  
Steady State Current ◽  
The Brain ◽  
Silent State

Abstract Desensitization is a canonical property of ligand-gated ion channels, causing progressive current decline in the continued presence of agonist. AMPA-type glutamate receptors (AMPARs), which mediate fast excitatory signaling throughout the brain, exhibit profound desensitization. Recent cryo-EM studies of AMPAR assemblies show their ion channels to be closed in the desensitized state. Here we present evidence that homomeric Q/R-edited AMPARs still allow ions to flow when the receptors are desensitized. GluA2(R) expressed alone, or with auxiliary subunits (γ-2, γ-8 or GSG1L), generates large fractional steady-state currents and anomalous current-variance relationships. Our results from fluctuation analysis, single-channel recording, and kinetic modeling, suggest that the steady-state current is mediated predominantly by conducting desensitized receptors. When combined with crystallography this unique functional readout of a hitherto silent state enabled us to examine cross-linked cysteine mutants to probe the conformation of the desensitized ligand binding domain of functioning AMPAR complexes.

scholarly journals Homomeric Q/R edited AMPA receptors conduct when desensitized

2019 ◽  
Author(s):  
Ian D. Coombs ◽  
David Soto ◽  
Thomas P. McGee ◽  
Matthew G. Gold ◽  
Mark Farrant ◽  
...  
Keyword(s):  
Steady State ◽  
Ion Channels ◽  
Ampa Receptors ◽  
Single Channel ◽  
Fluctuation Analysis ◽  
Single Channel Recording ◽  
Steady State Current ◽  
The Brain ◽  
Surprising Finding ◽  
Silent State

Desensitization is a canonical property of ligand-gated ion channels, causing progressive current decline in the continued presence of agonist. AMPA-type glutamate receptors, which mediate fast excitatory signaling throughout the brain, exhibit profound desensitization. Recent cryo-EM studies of AMPAR assemblies show their ion channels to be closed in the desensitized state. Here we report the surprising finding that homomeric Q/R edited AMPARs still allow ions to flow when the receptors are desensitized. GluA2(R) expressed alone, or with auxiliary subunits (γ-2, γ-8 or GSG1L), generates large steady-state currents and anomalous current-variance relationships. Using fluctuation analysis, single-channel recording, and kinetic modeling we demonstrate that the steady-state current is mediated predominantly by ‘conducting desensitized’ receptors. When combined with crystallography this unique functional readout of a hith-erto silent state enabled us to examine cross-linked cysteine mutants to probe the conformation of the desensitized ligand binding domain of functioning AMPAR complexes within the plasma membrane.

scholarly journals Semi-automated classification of colonial Microcystis by FlowCAM imaging flow cytometry in mesocosm experiment reveals high heterogeneity during seasonal bloom

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yersultan Mirasbekov ◽  
Adina Zhumakhanova ◽  
Almira Zhantuyakova ◽  
Kuanysh Sarkytbayev ◽  
Dmitry V. Malashenkov ◽  
...  
Keyword(s):  
Machine Learning ◽  
Flow Cytometry ◽  
Spatial Resolution ◽  
Mesocosm Experiment ◽  
Imaging Flow Cytometry ◽  
Leibler Divergence ◽  
Temporal And Spatial ◽  
High Level ◽  
Training Sets

AbstractA machine learning approach was employed to detect and quantify Microcystis colonial morphospecies using FlowCAM-based imaging flow cytometry. The system was trained and tested using samples from a long-term mesocosm experiment (LMWE, Central Jutland, Denmark). The statistical validation of the classification approaches was performed using Hellinger distances, Bray–Curtis dissimilarity, and Kullback–Leibler divergence. The semi-automatic classification based on well-balanced training sets from Microcystis seasonal bloom provided a high level of intergeneric accuracy (96–100%) but relatively low intrageneric accuracy (67–78%). Our results provide a proof-of-concept of how machine learning approaches can be applied to analyze the colonial microalgae. This approach allowed to evaluate Microcystis seasonal bloom in individual mesocosms with high level of temporal and spatial resolution. The observation that some Microcystis morphotypes completely disappeared and re-appeared along the mesocosm experiment timeline supports the hypothesis of the main transition pathways of colonial Microcystis morphoforms. We demonstrated that significant changes in the training sets with colonial images required for accurate classification of Microcystis spp. from time points differed by only two weeks due to Microcystis high phenotypic heterogeneity during the bloom. We conclude that automatic methods not only allow a performance level of human taxonomist, and thus be a valuable time-saving tool in the routine-like identification of colonial phytoplankton taxa, but also can be applied to increase temporal and spatial resolution of the study.

Potential of Arabic documentary sources for reconstructing past climate in the western Mediterranean region from AD 680 to 1815

The Holocene ◽  
2021 ◽  
pp. 095968362110332
Author(s):  
Yassin Meklach ◽  
Chantal Camenisch ◽  
Abderrahmane Merzouki ◽  
Ricardo Garcia Herrera
Keyword(s):  
Spatial Resolution ◽  
Mediterranean Region ◽  
Climate Extremes ◽  
Western Mediterranean ◽  
Historical Documents ◽  
Atmospheric Conditions ◽  
Documentary Sources ◽  
Drought Conditions ◽  
Temporal And Spatial ◽  
Climate Proxies

Archival records and historical documents offer direct observation of weather and atmospheric conditions and have the highest temporal and spatial resolution, and precise dating, of the available climate proxies. They also provide information about variables such as temperature, precipitation and climate extremes, as well as floods, droughts and storms. The present work studied Arab-Islamic documentary sources covering the western Mediterranean region (documents written by Arab-Islamic historians that narrate social, political and religious history) available for the period AD 680–1815. They mostly provide information on hydrometeorological events. In Iberia the most intense droughts were reported during AD 747–753, AD 814–822, AD 846–847, AD 867–874 and AD 914–915 and in the Maghreb AD 867–873, AD 898–915, AD 1104–1147, AD 1280–1340 and AD 1720–1815 had prevalent drought conditions. Intense rain episodes are also reported.

scholarly journals Single-channel Ca2+ imaging implicates Aβ1–42 amyloid pores in Alzheimer’s disease pathology

2011 ◽  
Vol 195 (3) ◽  
pp. 515-524 ◽  
Author(s):  
Angelo Demuro ◽  
Martin Smith ◽  
Ian Parker
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Ion Channels ◽  
Single Channel ◽  
Membrane Integrity ◽  
Cytosolic Calcium ◽  
Xenopus Laevis Oocytes ◽  
Permeable Membrane ◽  
Membrane Pores ◽  
Pathological Mechanism

Oligomeric forms of Aβ peptides are implicated in Alzheimer’s disease (AD) and disrupt membrane integrity, leading to cytosolic calcium (Ca2+) elevation. Proposed mechanisms by which Aβ mediates its effects include lipid destabilization, activation of native membrane channels, and aggregation of Aβ into Ca2+-permeable pores. We distinguished between these using total internal reflection fluorescence (TIRF) microscopy to image Ca2+ influx in Xenopus laevis oocytes. Aβ1–42 oligomers evoked single-channel Ca2+ fluorescence transients (SCCaFTs), which resembled those from classical ion channels but which were not attributable to endogenous oocyte channels. SCCaFTs displayed widely variable open probabilities (Po) and stepwise transitions among multiple amplitude levels reminiscent of subconductance levels of ion channels. The proportion of high Po, large amplitude SCCaFTs grew with time, suggesting that continued oligomer aggregation results in the formation of highly toxic pores. We conclude that formation of intrinsic Ca2+-permeable membrane pores is a major pathological mechanism in AD and introduce TIRF imaging for massively parallel single-channel studies of the incorporation, assembly, and properties of amyloidogenic oligomers.

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