Fluorescence imaging of cardiac propagation: spectral properties and filtering of optical action potentials

2006 ◽  
Vol 291 (1) ◽  
pp. H327-H335 ◽  
Author(s):  
Sergey F. Mironov ◽  
Frederick J. Vetter ◽  
Arkady M. Pertsov
Keyword(s):  
Action Potential ◽  
Wave Front ◽  
Fluorescence Imaging ◽  
High Frequency ◽  
Action Potentials ◽  
High Signal ◽  
Fluorescence Signal ◽  
Signal To Noise ◽  
Right Ventricular Free Wall ◽  
Spectral Components

Fluorescence imaging using voltage-sensitive dyes is an important tool for studying electrical propagation in the heart. Yet, the low amplitude of the voltage-sensitive component in the fluorescence signal and high acquisition rates dictated by the rapid propagation of the excitation wave front make it difficult to achieve recordings with high signal-to-noise ratios. Although spatially and temporally filtering the acquired signals has become de facto one of the key elements of optical mapping, there is no consensus regarding their use. Here we characterize the spatiotemporal spectra of optically recorded action potentials and determine the distortion produced by conical filters of different sizes. On the basis of these findings, we formulate the criteria for rational selection of filter characteristics. We studied the evolution of the spatial spectra of the propagating wave front after epicardial point stimulation of the isolated, perfused right ventricular free wall of the pig heart stained with di-4-ANEPPS. We found that short-wavelength (<3 mm) spectral components represent primarily noise and surface features of the preparation (coronary vessels, fat, and connective tissue). The time domain of the optical action potential spectrum also lacks high-frequency components (>100 Hz). Both findings are consistent with the reported effect of intrinsic blurring caused by light scattering inside the myocardial wall. The absence of high-frequency spectral components allows the use of aggressive low-pass spatial and temporal filters without affecting the optical action potential morphology. We show examples where the signal-to-noise ratio increased up to 150 with <3% distortion. A generalization of our approach to the rational filter selection in various applications is discussed.

Spatial Frequency Content in Optical Mapping of Cardiac Cell Monolayers

2006 ◽  
Vol 291 (3) ◽  
pp. H1484-H1485 ◽  
Author(s):  
Harold Bien ◽  
Emilia Entcheva
Keyword(s):  
Action Potential ◽  
Wave Front ◽  
High Frequency ◽  
Optical Mapping ◽  
Coronary Vessels ◽  
High Signal ◽  
Fluorescence Signal ◽  
Signal To Noise ◽  
Right Ventricular Free Wall ◽  
Spectral Components

Fluorescence imaging using voltage-sensitive dyes is an important tool for studying electrical propagation in the heart. Yet, the low amplitude of the voltage-sensitive component in the fluorescence signal and high acquisition rates dictated by the rapid propagation of the excitation wave front make it difficult to achieve recordings with high signal-to-noise ratios. Although spatially and temporally filtering the acquired signals has become de facto one of the key elements of optical mapping, there is no consensus regarding their use. Here we characterize the spatiotemporal spectra of optically recorded action potentials and determine the distortion produced by conical filters of different sizes. On the basis of these findings, we formulate the criteria for rational selection of filter characteristics. We studied the evolution of the spatial spectra of the propagating wave front after epicardial point stimulation of the isolated, perfused right ventricular free wall of the pig heart stained with di-4-ANEPPS. We found that short-wavelength (<3 mm) spectral components represent primarily noise and surface features of the preparation (coronary vessels, fat, and connective tissue). The time domain of the optical action potential spectrum also lacks high-frequency components (>100 Hz). Both findings are consistent with the reported effect of intrinsic blurring caused by light scattering inside the myocardial wall. The absence of high-frequency spectral components allows the use of aggressive low-pass spatial and temporal filters without affecting the optical action potential morphology. We show examples where the signal-to-noise ratio increased up to 150 with <3% distortion. A generalization of our approach to the rational filter selection in various applications is discussed.

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

Resilient RTN Fast Spiking in Kv3.1 Null Mice Suggests Redundancy in the Action Potential Repolarization Mechanism

2002 ◽  
Vol 87 (3) ◽  
pp. 1303-1310 ◽  
Author(s):  
Darrell M. Porcello ◽  
Chi Shun Ho ◽  
Rolf H. Joho ◽  
John R. Huguenard
Keyword(s):  
Action Potential ◽  
High Frequency ◽  
Action Potentials ◽  
Brain Slices ◽  
Firing Frequency ◽  
Wild Type ◽  
Genetic Redundancy ◽  
Fast Spiking ◽  
Deficient Mice ◽  
Action Potential Repolarization

Fast spiking (FS), GABAergic neurons of the reticular thalamic nucleus (RTN) are capable of firing high-frequency trains of brief action potentials, with little adaptation. Studies in recombinant systems have shown that high-voltage-activated K+ channels containing the Kv3.1 and/or Kv3.2 subunits display biophysical properties that may contribute to the FS phenotype. Given that RTN expresses high levels of Kv3.1, with little or no Kv3.2, we tested whether this subunit was required for the fast action potential repolarization mechanism essential to the FS phenotype. Single- and multiple-action potentials were recorded using whole-cell current clamp in RTN neurons from brain slices of wild-type and Kv3.1-deficient mice. At 23°C, action potentials recorded from homozygous Kv3.1 deficient mice (Kv3.1−/−) compared with their wild-type (Kv3.1+/+) counterparts had reduced amplitudes (−6%) and fast after-hyperpolarizations (−16%). At 34°C, action potentials in Kv3.1−/− mice had increased duration (21%) due to a reduced rate of repolarization (−30%) when compared with wild-type controls. Action potential trains in Kv3.1−/− were associated with a significantly greater spike decrement and broadening and a diminished firing frequency versus injected current relationship ( F/I) at 34°C. There was no change in either spike count or maximum instantaneous frequency during low-threshold Ca2+ bursts in Kv3.1−/− RTN neurons at either temperature tested. Our findings show that Kv3.1 is not solely responsible for fast spikes or high-frequency firing in RTN neurons. This suggests genetic redundancy in the system, possibly in the form of other Kv3 members, which may suffice to maintain the FS phenotype in RTN neurons in the absence of Kv3.1.

scholarly journals Intracellular calcium movements during relaxation and recovery of superfast muscle fibers of the toadfish swimbladder

2014 ◽  
Vol 143 (5) ◽  
pp. 605-620 ◽  
Author(s):  
Frank E. Nelson ◽  
Stephen Hollingworth ◽  
Lawrence C. Rome ◽  
Stephen M. Baylor
Keyword(s):  
High Frequency ◽  
Action Potentials ◽  
Slow Rate ◽  
Water Volume ◽  
Fluorescence Signal ◽  
High Affinity ◽  
Mating Call ◽  
Stimulus Train ◽  
The Stability ◽  
Repetitive Stimulus

The mating call of the Atlantic toadfish is generated by bursts of high-frequency twitches of the superfast twitch fibers that surround the swimbladder. At 16°C, a calling period can last several hours, with individual 80–100-Hz calls lasting ∼500 ms interleaved with silent periods (intercall intervals) lasting ∼10 s. To understand the intracellular movements of Ca2+ during the intercall intervals, superfast fibers were microinjected with fluo-4, a high-affinity fluorescent Ca2+ indicator, and stimulated by trains of 40 action potentials at 83 Hz, which mimics fiber activity during calling. The fluo-4 fluorescence signal was measured during and after the stimulus trains; the signal was also simulated with a kinetic model of the underlying myoplasmic Ca2+ movements, including the binding and transport of Ca2+ by the sarcoplasmic reticulum (SR) Ca2+ pumps. The estimated total amount of Ca2+ released from the SR during a first stimulus train is ∼6.5 mM (concentration referred to the myoplasmic water volume). At 40 ms after cessation of stimulation, the myoplasmic free Ca2+ concentration ([Ca2+]) is below the threshold for force generation (∼3 µM), yet the estimated concentration of released Ca2+ remaining in the myoplasm (Δ[CaM]) is large, ∼5 mM, with ∼80% bound to parvalbumin. At 10 s after stimulation, [Ca2+] is ∼90 nM (three times the assumed resting level) and Δ[CaM] is ∼1.3 mM, with 97% bound to parvalbumin. Ca2+ movements during the intercall interval thus appear to be strongly influenced by (a) the accumulation of Ca2+ on parvalbumin and (b) the slow rate of Ca2+ pumping that ensues when parvalbumin lowers [Ca2+] near the resting level. With repetitive stimulus trains initiated at 10-s intervals, Ca2+ release and pumping come quickly into balance as a result of the stability (negative feedback) supplied by the increased rate of Ca2+ pumping at higher [Ca2+].

scholarly journals Basis for the Induction of Tissue-Level Phase-2 Reentry as a Repolarization Disorder in the Brugada Syndrome

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Alfonso Bueno-Orovio ◽  
Elizabeth M. Cherry ◽  
Steven J. Evans ◽  
Flavio H. Fenton
Keyword(s):  
Action Potential ◽  
Right Ventricular ◽  
Brugada Syndrome ◽  
Action Potentials ◽  
Human Action ◽  
Three Dimensions ◽  
Phase 2 ◽  
Three Dimensional Model ◽  
Right Ventricular Free Wall ◽  
The Right

Aims. Human action potentials in the Brugada syndrome have been characterized by delayed or even complete loss of dome formation, especially in the right ventricular epicardial layers. Such a repolarization pattern is believed to trigger phase-2 reentry (P2R); however, little is known about the conditions necessary for its initiation. This study aims to determine the specific mechanisms that facilitate P2R induction in Brugada-affected cardiac tissue in humans.Methods. Ionic models for Brugada syndrome in human epicardial cells were developed and used to study the induction of P2R in cables, sheets, and a three-dimensional model of the right ventricular free wall.Results. In one-dimensional cables, P2R can be induced by adjoining lost-dome and delayed-dome regions, as mediated by tissue excitability and transmembrane voltage profiles, and reduced coupling facilitates its induction. In two and three dimensions, sustained reentry can arise when three regions (delayed-dome, lost-dome, and normal epicardium) are present.Conclusions. Not only does P2R induction by Brugada syndrome require regions of action potential with delayed-dome and lost-dome, but in order to generate a sustained reentry from a triggered waveback multiple factors are necessary, including heterogeneity in action potential distribution, tissue coupling, direction of stimulation, the shape of the late plateau, the duration of lost-dome action potentials, and recovery of tissue excitability, which is predominantly modulated by tissue coupling.

Trans-illumination fluorescence imaging of deep-seated tumors in small animals

2015 ◽  
Vol 4 (1) ◽  
Author(s):  
Mikhail Kleshnin ◽  
Marina Shirmanova ◽  
Ilya Fiks ◽  
Anna Orlova ◽  
Vladimir Plekhanov ◽  
...  
Keyword(s):  
Fluorescence Imaging ◽  
Light Absorption ◽  
Light Emitting Diode ◽  
Small Animal ◽  
Ccd Camera ◽  
The Body ◽  
Laser Source ◽  
High Signal ◽  
Fluorescence Signal ◽  
Animal Body

AbstractBackground:Fluorescence diffuse tomography (FDT) is the most accurate technique for the imaging of labeled tumors in the small animal body. However, the procedure for reconstruction of the spatial distribution of the fluorophore requires a high signal-to-noise ratio due to the ill-condition of the inverse problem. Therefore, the FDT technique is ineffective for imaging tumors of small size or with dim fluorophores because of the low intensity of their fluorescence compared with the high level of tissue autofluorescence. In these cases, the size and position of a marked tumor in the animal body can be estimated from two-dimensional fluorescence images obtained using trans- or epi-illumination techniques.Material and methods:A versatile system for small animal fluorescence imaging which combines planar epi- and trans-illumination geometries of the light source and of the fluorescence receiver was created and tested. For epi-illumination imaging, light-emitting diode sources were used to provide homogeneous and stable illumination of the experimental animal, in combination with a cooled CCD camera which covers the entire illuminated area. For trans-illumination imaging, mechanical raster-scanning devices modulated at a low frequency were used for the laser source, together with a cooled photomultiplier tube, which provided outstanding sensitivity.Results:Monitoring the orthotopic tumor growth in animal bodies has demonstrated the efficacy of trans-illumination imaging in comparison with the epi-illumination technique. The results obtained also showed that the effective use of the trans-illumination technique requires Born normalization of the fluorescence signal and the exclusion of lateral illumination by surrounding the animal with additional light absorption material using light-absorption pads on both sides of the body.

scholarly journals Intracellular action potential recordings from cardiomyocytes by ultrafast pulsed laser irradiation of fuzzy graphene microelectrodes

2021 ◽  
Vol 7 (15) ◽  
pp. eabd5175
Author(s):  
Michele Dipalo ◽  
Sahil K. Rastogi ◽  
Laura Matino ◽  
Raghav Garg ◽  
Jacqueline Bliley ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Field Effect Transistors ◽  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Pulsed Laser ◽  
Extracellular Recording ◽  
High Signal ◽  
Intimate Contact ◽  
Potential Shape

Graphene with its unique electrical properties is a promising candidate for carbon-based biosensors such as microelectrodes and field effect transistors. Recently, graphene biosensors were successfully used for extracellular recording of action potentials in electrogenic cells; however, intracellular recordings remain beyond their current capabilities because of the lack of an efficient cell poration method. Here, we present a microelectrode platform consisting of out-of-plane grown three-dimensional fuzzy graphene (3DFG) that enables recording of intracellular cardiac action potentials with high signal-to-noise ratio. We exploit the generation of hot carriers by ultrafast pulsed laser for porating the cell membrane and creating an intimate contact between the 3DFG electrodes and the intracellular domain. This approach enables us to detect the effects of drugs on the action potential shape of human-derived cardiomyocytes. The 3DFG electrodes combined with laser poration may be used for all-carbon intracellular microelectrode arrays to allow monitoring of the cellular electrophysiological state.

A compact guided-wave EMAT with pulsed electromagnet for ferromagnetic tube inspection

2020 ◽  
Vol 64 (1-4) ◽  
pp. 951-958
Author(s):  
Tianhao Liu ◽  
Yu Jin ◽  
Cuixiang Pei ◽  
Jie Han ◽  
Zhenmao Chen
Keyword(s):  
Power Plants ◽  
Signal To Noise Ratio ◽  
Small Diameter ◽  
Performance Testing ◽  
Guided Wave ◽  
High Signal ◽  
Receiver Coil ◽  
Signal To Noise ◽  
Corrosion Defects

Small-diameter tubes that are widely used in petroleum industries and power plants experience corrosion during long-term services. In this paper, a compact inserted guided-wave EMAT with a pulsed electromagnet is proposed for small-diameter tube inspection. The proposed transducer is noncontact, compact with high signal-to-noise ratio and unattractive to ferromagnetic tubes. The proposed EMAT is designed with coils-only configuration, which consists of a pulsed electromagnet and a meander pulser/receiver coil. Both the numerical simulation and experimental results validate its feasibility on generating and receiving L(0,2) mode guided wave. The parameters for driving the proposed EMAT are optimized by performance testing. Finally, feasibility on quantification evaluation for corrosion defects was verified by experiments.

Computationally Assisted Design of High Signal-to-Noise Photoinduced Electron Transfer-Based Voltage-Sensitive Dyes

2020 ◽  
Author(s):  
Rishikesh Kulkarni ◽  
Anneliese Gest ◽  
Chun Kei Lam ◽  
Benjamin Raliski ◽  
Feroz James ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dft Calculations ◽  
Photoinduced Electron Transfer ◽  
Density Functional ◽  
Embryonic Stem ◽  
High Sensitivity ◽  
Md Simulations ◽  
High Signal ◽  
Signal To Noise ◽  
Green Fluorescent

<p>High signal-to-noise optical voltage indicators will enable simultaneous interrogation of membrane potential in large ensembles of neurons. However, design principles for voltage sensors with high sensitivity and brightness remain elusive, limiting the applicability of voltage imaging. In this paper, we use molecular dynamics (MD) simulations and density functional theory (DFT) calculations to guide the design of a bright and sensitive green-fluorescent voltage-sensitive fluorophore, or VoltageFluor (VF dye), that uses photoinduced electron transfer (PeT) as a voltage-sensing mechanism. MD simulations predict an 11% increase in sensitivity due to membrane orientation, while DFT calculations predict an increase in fluorescence quantum yield, but a decrease in sensitivity due to a decrease in rate of PeT. We confirm these predictions by synthesizing a new VF dye and demonstrating that it displays the expected improvements by doubling the brightness and retaining similar sensitivity to prior VF dyes. Combining theoretical predictions and experimental validation has resulted in the synthesis of the highest signal-to-noise green VF dye to date. We use this new voltage indicator to monitor the electrophysiological maturation of human embryonic stem cell-derived medium spiny neurons. </p>

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