Global ETD Search

1	Chemical Targeting of Voltage Sensitive Dyes in the Brain Wang, Jihang January 2020 (has links) Voltage sensitive dyes are a family of chemical sensors which enable optical recording of electrical activities from large populations of neurons, but nevertheless suffer from the lack of delivery and targeting strategies in brain tissue due to their generally high lipophilicity. In this dissertation, I present a purely chemical approach to target voltage sensitive dyes to natively expressed protein targets in live brain tissue and achieve functional voltage imaging with the limited photon budget afforded by the small number of sensors targeted to endogenous molecular targets. To our knowledge, this study represents the first example of functional optical recording from specific neuronal types and their axons in live brain tissue without any genetic manipulation. Such approach is vastly significant in the long run when we ultimately need to translate findings from model animals in research laboratories to benefit real human patients in clinical settings, to which imaging and diagnostic methods requiring genetic modification are and will remain problematic in the foreseeable future. In addition, we demonstrate the high modularity and versatility of our chemical approach in targeting different voltage sensitive dyes to various molecular targets in the brain. We believe that the same concept can be applied to the targeting and delivery of other important lipophilic cargos, such as drugs and other sensors, to enable genetic modification-free, cell- or molecule-specific imaging and pharmacology in the brain. Neurosciences Chemistry, Organic Voltage-sensitive dyes Neurons Drug lipophilicity
2	Can optical recordings of membrane potential be used to screen for drug-induced action potential prolongation in single cardiac myocytes? Hardy, Matthew E., Lawrence, C.L., Standen, N.B., Rodrigo, G.C. January 2006 (has links) No / Introduction: Potential-sensitive dyes have primarily been used to optically record action potentials (APs) in whole heart tissue. Using these dyes to record drug-induced changes in AP morphology of isolated cardiac myocytes could provide an opportunity to develop medium throughout assays for the pharmaceutical industry. Ideally, this requires that the dye has a consistent and rapid response to membrane potential, is insensitive to movement, and does not itself affect AP morphology. Materials and methods: We recorded the AP from isolated adult guinea-pig ventricular myocytes optically using di-8-ANEPPS in a single-excitation dual-emission ratiometric system, either separately in electrically field stimulated myocytes, or simultaneously with an electrical AP recorded with a patch electrode in the whole-cell bridge mode. The ratio of di-8-ANEPPS fluorescence signal was calibrated against membrane potential using a switch-clamp to voltage clamp the myocyte. Results: Our data show that the ratio of the optical signals emitted at 560/620 nm is linearly related to voltage over the voltage range of an AP, producing a change in ratio of 7.5% per 100mV, is unaffected by cell movement and is identical to the AP recorded simultaneously with a patch electrode. However, the APD90 recorded optically in myocytes loaded with di-8-ANEPPS was significantly longer than in unloaded myocytes recorded with a patch electrode (355.6 ± 13.5 vs. 296.2 ± 16.2ms; p< 0.01). Despite this effect, the apparent IC50 for cisapride, which prolongs the AP by blocking IKr, was not significantly different whether determined optically or with a patch electrode (91 ± 46 vs. 81 ± 20 nM). Discussion: These data show that the optical AP recorded ratiometrically using di-8- ANEPPS from a single ventricular myocyte accurately follows the action potential morphology. This technique can be used to estimate the AP prolonging effects of a compound, although di-8-ANEPPS itself prolongs APD90. Optical dyes require less technical skills and are less invasive than conventional electrophysiological techniques and, when coupled to ventricular myocytes, decreases animal usage and facilitates higher throughput assays. Action potential Arrythmia Cardiac muscle Guinea-pig myocyte Voltage-sensitive dyes
3	Imaging membrane potential Wilkinson, James Daniel January 2014 (has links) Imaging membrane potential is a promising technique in the elucidation of the interactions of large networks of neurons. The membrane potential in a neuron varies as an action potential, the basic electrical signal of neuronal communication, travels along the length of the cell. Voltage sensitive dyes play a key role by providing an optical readout of the electric field generated across a neuron membrane by the action potential. However, none of the dyes reviewed in Chapter 1 generate sufficient signal change with changes in membrane potential; this sensitivity problem limits the ability of the imaging membrane potential technique to allow the high spatial and temporal resolution necessary for neuronal networks to be better understood. This thesis features two avenues of research that are expected to result in the necessary enhancements to voltage sensitive dyes to improve the signal change. The first avenue is based on the effect of an electric field upon the non-linear optical properties of a porphyrin macromolecule. The encouraging field sensitivity of a previous porphyrin monomer voltage sensor inspired an investigation which identified optimisations to enhance the voltage sensitivity (Chapter 2). The design, synthesis and initial characterisation of optimised porphyrin voltage sensors is detailed in Chapter 3. The second avenue is based on the effect of an electric field upon the rate of intermolecular electron transfer. In a suitably designed dye, the competition between electron transfer and fluorescence, following excitation by incoming light, allows the fluorescence intensity to act as an optical indicator of the electron transfer rate. New dyes were rationally designed and synthesised, as this effect had not been applied to voltage sensitive imaging before the research detailed in Chapter 4. The challenging purification of the new amphiphilic dyes synthesised also inspired research into a novel testing method which does not require amphiphilic dyes (Chapter 5). 547
4	Měření membránového napětí pomocí napěťově citlivých barviv ve fluorescenční mikroskopii / Membrane potential measurement with voltage sensitive dyes in fluorescence microscopy Tkáč, Jan January 2013 (has links) The aim of this work is to make a literature search in the measurement of membrane voltage using voltage-sensitive dyes and suggest a method for measuring the membrane voltage on the available cells using the voltage-sensitive dye di 4 ANEPPS and its further implementation. The work contains an introduction to electrophysiology of cells, and explains typical fluorescence characteristics. The thesis contains the description of a fluorescence microscope. The document presents characteristics of voltage-sensitive dyes and their distribution. A large part of the work describes the implementation and measurement of the experiment. The document also includes different methods for measuring and processing of all results.
5	Měření membránového napětí pomocí napěťově citlivých barviv / Membrane potential measurement with voltage sensitive dyes in confocal microscopy Heczková, Monika January 2013 (has links) The aim of this work is to make a literature search in the measurement of membrane voltage using the voltage-sensitive dyes and suggest a method of measuring the membrane voltage on the available cells using the voltage-sensitive dye Di-4-ANEPPS and RH237. The work contains an introduction to electrophysiology of cell, explains fluorescence and typical fluorescence characteristics. The thesis contains the description of a fluorescence microscope. The document was largely devoted to characterization and distribution of voltage-sensitive dyes. The output of a design solution is a real experiment.
6	NaV1.5 Modulation: From Ionic Channels to Cardiac Conduction and Substrate Heterogeneity Raad, Nour 16 January 2014 (has links) No description available. 571.4 Antiarrhythmic drugs Optical Mapping Action potential duration Spatial dispersion of repolarization Cardiac depolarization Conduction velocity Anisotropy Duchenne muscular dystrophy mdx - mouse model Dystrophin ΔKPQ mouse model Long QT Syndrome 3 Cardiac Sodium Channel (NaV1.5) Flecainide Maximum upstroke velocity Least Squares Ellipsis Fitting Method Area Fitting Method Plane Fitting Method Conduction abnormalities Voltage sensitive dyes Cardiac arrhythmia Functional heterogeneity Spatial-temporal heterogeneity Proarrhythmia Activation maps Symmetry breaking Intrinsic cardiac heterogeneity Biologie (PPN619462639)

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