Thesis (M.Sc.) -- University of Adelaide, 1948. / Typewr. copy.

The vibrating probe voltmeter for the measurement of bioelectric potentials by Bluh and Scott has been used in an improved form for measurements of frog skin potential differences. In good agreement with earlier findings the observed frog skin potential differences were found to be of the order of 100 millivolts, and the polarity such that the inside of the skin was positive relative to the outside. Bioelectric potential measurements were made during the influx of sodium chloride and amino acids in aqueous solutions into frog skin in either direction. Characteristic potential changes were observed for different substances and opposite directions of flux, and have been used to demonstrate the asymmetry of frog skin permeability. Transfer mechanisms for sodium chloride and amino acids have been advanced from the standpoint of the assumption that an electrical field exists in the frog skin membrane. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Yip Pak Yam Pelen. / "Running head: Nature of interval timing." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 39-43). / Abstracts in English and Chinese. / Introduction --- p.6-16 / Method --- p.17-20 / Results --- p.21-22 / Discussion --- p.23-27 / Experiment Two --- p.28-30 / Results and Discussion --- p.31-33 / General Discussion --- p.34-38 / References --- p.39-43 / Tables --- p.44-56 / Figure Caption --- p.57 / Figures --- p.58-62

Hodgkin-Huxley (HH) 模型對於電流生理學的發展有著深遠的影響。它能精確地模擬離子通道的變化。然而，隨著多年來的反覆驗證，研究人員發現HH模型亦有其局限性和不足之處。有見及此，本論文提出一個建基於變形動力學的模型，藉此以更深入的物理層面解釋Hodgkin與Huxley的實驗數據。新的模型為鉀與鈉離子通道建立了新的電導方程。在這模型的詮釋下，HH模型的鉀離子通道電導方程[附圖] 被[附圖]取代，而HH模型的鈉離子通道電導方程 [附圖] 則被 [附圖] 取而代之。縱使 n(t), m(t)和 h(t)在兩個模型中被授予不同的物理意義，但它們均是一階微分方程。此論文詳細闡述模型的建立過程及參數的推導，並論證它能準確地描繪Hodgkin與Huxley對於烏賊巨軸突的實驗數據。模型參數經由遺傳演算法優化後，新的模型不僅能夠準確描述離子通道的電導變化，還能闡述Cole-Moore shift現象。在相同強度的去極化刺激和溫度下，新的模型比HH模型能接近地模擬膜動作電位的實驗數據。 / Hodgkin-Huxley (HH) model has a profound influence on the development of electrophysiology. It is capable of modeling the transient responses of voltage-gated ion channels precisely. Nevertheless, limitations and deficiencies of the model were found as researchers conducted subsequent experiments. In this regard, a new model based on deformation kinetic has been put forth to help explaining the HH experimental data with a deeper level of physical insight. Under the proposed model, the famous HH equation [with formula] for the description of potassium conductance was replaced by [with formula] and the HH sodium conductance equation [with formula] was substituted by [with formula]. Meanwhile, n(t), m(t) and h(t) are still first order differential equations as the HH case. This thesis contributes to illustrate the capability of the new model in approximating HH’s experimental data on squids’ giant axons. Detailed derivation of the new model and identification of the parametric functions are summarized in this report. A customized genetic algorithm was utilized to optimize the model parameters. After fine tuning the new model, we are able to describe the conductance behaviors of voltage-gated ion channels closely, and manage to account for the Cole-Moore shift phenomenon. Under identical initial depolarizing stimuli and temperature as stated in HH’s experiments, close approximations of membrane action potential can also be obtained by the new model. / Detailed summary in vernacular field only. / Yu, Cheuk Him Derek. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 69-70). / Abstracts also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of Electrophysiological Models --- p.4 / Chapter 1.2 --- The Hodgkin-Huxley Membrane Current Model --- p.4 / Chapter 1.2.1 --- Hodgkin-Huxley Potassium Channel --- p.6 / Chapter 1.2.2 --- Hodgkin-Huxley Sodium Channel --- p.8 / Chapter 1.3 --- Proliferation of the Deformation Kinetic Based Model --- p.10 / Chapter 1.4 --- Thesis Outline --- p.12 / Chapter 2 --- The Deformation Kinetic Based Model --- p.13 / Chapter 2.1 --- The Molecular Theory --- p.13 / Chapter 2.1.1 --- Application of Deformation Kinetics --- p.13 / Chapter 2.1.2 --- The Energy Function E{U+2093} (q) --- p.14 / Chapter 2.1.3 --- The Population Distribution Function P{U+2093} (N,t) --- p.17 / Chapter 2.1.4 --- Conductance Model for Voltage-gated Ion Channels --- p.18 / Chapter 2.2 --- The Approximate Solutions --- p.19 / Chapter 2.2.1 --- Approximation of the General Solution for G{U+2093} (N) --- p.19 / Chapter 2.2.2 --- Approximation of the General Solution for P{U+2093} (N,t) --- p.19 / Chapter 2.2.3 --- The Approximate Solution for Molecular g{U+2093} (t) --- p.23 / Chapter 2.2.4 --- A Convenient Form of the Approximate Solutions --- p.24 / Chapter 2.3 --- Chapter Summary --- p.25 / Chapter 3 --- Voltage-gated Ion Channel Modeling --- p.27 / Chapter 3.1 --- Voltage-gated Potassium Channel Modeling --- p.27 / Chapter 3.2 --- Voltage-gated Sodium Channel Modeling --- p.29 / Chapter 3.3 --- Chapter Summary --- p.31 / Chapter 4 --- The Parametric Functions --- p.32 / Chapter 4.1 --- The Curve Fitting References - HH Experimental Data --- p.32 / Chapter 4.2 --- Curve Fitting through Genetic Algorithm --- p.34 / Chapter 4.3 --- Functional Approximations w.r.t. HH Experimental Data --- p.37 / Chapter 4.3.1 --- Parametric Functions for Voltage-gated Potassium Channel --- p.37 / Chapter 4.3.2 --- Parametric Functions for Voltage-gated Sodium Channel --- p.39 / Chapter 4.4 --- Chapter Summary --- p.46 / Chapter 5 --- The Tracing Results --- p.47 / Chapter 5.1 --- Voltage Clamp Tracings --- p.47 / Chapter 5.1.1 --- Potassium Conductance Tracings --- p.48 / Chapter 5.1.2 --- Sodium Conductance Tracings --- p.49 / Chapter 5.2 --- Membrane Action Potential Tracings --- p.54 / Chapter 5.3 --- Propagated Action Potential Tracings --- p.56 / Chapter 5.4 --- Chapter Summary --- p.59 / Chapter 6? --- The Cole-Moore Shift Phenomenon --- p.60 / Chapter 6.1 --- Cole-Moore shift Phenomenon of Voltage-gated Potassium Channel --- p.61 / Chapter 6.2 --- Cole-Moore Shift Phenomenon of Voltage-gated Sodium Channel --- p.62 / Chapter 6.3 --- Chapter Summary --- p.64 / Chapter 7 --- Discussions --- p.65 / Conclusion --- p.67 / Future Works --- p.68 / References --- p.69 / Chapter Appendix I --- Hodgkin-Huxley’s Analysis of Voltage-gated Channels’ Voltage Clamp Data / Chapter (a) --- HH’s Analysis of Potassium Conductance Change in Voltage Clamp Experiments --- p.71 / Chapter (b) --- HH’s Analysis of Sodium Conductance Change in Voltage Clamp Experiments --- p.71 / Chapter Appendix II --- Numerical Estimations of Hodgkin-Huxley’s Experimental Data / Chapter (a) --- Numerical Estimations of Podium Conductance Change in Voltage Clamp Experiments for HH axon 17 --- p.72 / Chapter (b) --- Numerical Estimations of Sodium Conductance Change in Voltage Clamp Experiments for HH axon 17 --- p.73 / Chapter (c) --- Numerical Estimations of Membrane Action Potential with Different Initial Depolarizations for HH axon 17 --- p.74 / Chapter Appendix III --- Verification of the Replica of HH Model’s Simulations Results / Chapter (a) --- Comparison between HH Membrane Action Potential and Its Replica --- p.75 / Chapter (b) --- Comparison between HH Propagated Action Potential and Its Replica --- p.76

A passive system that may be useful for measuring electrochemical changes occurring in in vivo, extracellular plant tissue has been developed within the past few years. The technique involves the placement of a small (250 μm diameter) noble metal probe into the anatomical region of interest. The electrode potential of this probe is then established relative to a reference electrode. The time variation of this potential (up to 100 mV or more per day) is termed an electrophytogram. The changes are coherent and reproducible. In this dissertation theoretical physiological bases for the voltage fluctuations have been developed. One theory involves modeling the electrophytogram as a chemical thermodynamic system passing through a series of "frozen" equilibria. The electron is considered as the chemical species of interest in this system and changes in the redox potential are interpreted in terms of an electron electrochemical potential (μ̃ₑ).The relationship between changes in the electrochemical nature of the solution contiguous with the probe and the μ̃ₑ intensity variable is then represented for several limiting cases. In the case of a redox reaction accompanied by a proton exchange, the limiting equation shows that pH changes well within the physiological range for extracellular plant fluid can account for the observed voltage fluctuations. An alternative representation of the electrophytogram as an electrostatic field phenomenon is more difficult to analyze due to a lack of information about the three dimensional structure and the probe/tissue interface. However, a cylindrical capacitor model shows that fluxes in the range of a few hundred monovalent ions per um³ of extracellular volume could easily explain the measured voltage changes. The third model involves the polyelectrolyte gel nature of the plant cell wall. The electrophytogram voltage signal is considered to result from surface interactions between the metal probe and the cell wall. This interaction is analyzed by using the theory of interacting electrochemical double layers. Output from a computer simulation shows that if these two surfaces approach within two Debye lengths, a voltage signal will be generated at the electrophytogram probe. Furthermore, slight fluctuations in the surface to surface distance result in voltage fluctuations of a magnitude equal to those observed in vivo. Physiological processes known to occur in plants are discussed with respect to the generation of electrochemical potential gradients and other physical conditions necessary to "drive" the various models. I conclude that the electrophytogram is most likely the result of surface interactions between the probe and the polyelectrolyte gel components of the cell wall. Elucidation of the physiological basis for electrophytograms must also involve an accurate anatomical interpretation of the position of the probe relative to the plant tissue. Therefore the results of a freeze-fracture electron microscopic (FFSEM) examination of the probe/tissue interface after wound healing are included. Electron micrographs show cell wall material appressed directly against the probe, indicating that the electrophytogram provides a method for monitoring the electrochemical status of the cell wall space. Since cell wall material is hygroscopic, it is reasonable to assume that the smallest probe/tissue separation distance observed in the FFSEM's represents a maximum in vivo value. Since this distance is less than 10nm, these data support the hypothesis that the metal surface is within two Debye lengths of the cell wall surface in vivo. Insertion of the probe into mature, fully elongated tissue appears to cause minimal damage to nonxylem tissue beyond the adjacent cell layers and virtually no damage to the xylem region.

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