Numerical simulation of excitation-contraction coupling in a locus of the small bowel

A mathematical model for the excitation-contraction coupling within a functional unit (locus) of the small bowel is proposed. The model assumes that: the functional unit is an electromyogenic syncytium; its electrical activity is defined by kinetics of L- and T-type Ca2+-channels, mixed Ca2+-dependent K+-channels, potential-sensitive K+-channels and Cl--channels; the basic neural circuit, represented by the cholinergic and adrenergic neurones, provides a regulatory input to the functional unit via receptor-linked L-type Ca2+-channels; the smooth muscle syncytium of the locus is a null-dimensional contractile system. With the proposed model the dynamics of active force generation is determined entirely by the concentration of cytosolic calcium. The model describes electrical processes of the propagation of excitation along the neural circuit, chemical mechanisms of nerve-pulse transmission at the synaptic zones and the dynamics of active force generation. Numerical simulations have shown that it is capable of displaying different electrical patterns and mechanical responses of the locus. The simulated effects of: tetrodotoxin, β-bungarotoxin, salts of divalent cations, inhibitors of catechol-O-methyltransferase and neuronal uptake mechanisms, and changes in the concentration of external Ca2+ on the dynamics of force generation have been analysed. The results are in good qualitative and quantitative agreement with results of experiments conducted on the visceral smooth muscle of the small bowel. © Springer-Verlag 1996

A survey of small bowel modelling and its applications for capsule endoscopy

This is the final version. Available on open access from Elsevier via the DOI in this recordThe small intestine, an anatomical site previously considered inaccessible to clinicians due to its small diameter and length, is the part of the gastrointestinal tract between the stomach and the colon. Since its introduction into clinical practice two decades ago, capsule endoscopy has become established as the primary modality for examining the surface lining of the small intestine. Today, researchers continue to develop ground-breaking technologies for novel miniature devices aiming for tissue biopsy, drug delivery and therapy. The purpose of this paper is to provide researchers and engineers in this area a comprehensive review of the progress in understanding the anatomy and physiology of the small intestine and how this understanding was translated to virtual and physical test platforms for assessing the performance of these intestinal devices. This review will cover both theoretical and practical studies on intestinal motor activities and the work on mathematical modelling and experimental investigation of capsule endoscope in the small intestine. In the end, the requirements for improving the current work are drawn, and the expectations on future research in this field are provided.Engineering and Physical Sciences Research Council (EPSRC)China Scholarship Counci

A quantitative model of human jejunal smooth muscle cell electrophysiology

10.1371/journal.pone.0042385PLoS ONE78

Pattern formation in electrically coupled pacemaker cells : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mathematics at Massey University, Manawatū, New Zealand

Figures are re-used with permission.In this thesis we study electrical activity in smooth muscle cells in the absence of external stimulation. The main goal is to analyse a reaction-diffusion system that models the dynamical behaviour where adjacent cells are coupled through passive electrical coupling. We first analyse the dynamics of an isolated muscle cell for which the model consists of three first-order ordinary differential equations. The cell is either excitable, nonexcitable, or oscillatory depending on the model parameters. To understand this we reduce the model to two equations, nondimensionalise, then perform a detailed numerical bifurcation analysis of the nondimensionalised model. One parameter bifurcation diagrams reveal that even though there is no external stimulus the cell can exhibit two fundamentally distinct types of excitability. By computing two-parameter bifurcation diagrams we are able to explain how the cell transitions between the two types of excitability as parameters are varied. We then study the full reaction-diffusion system first through numerical integration. We show that the system is capable of exhibiting a wide variety of spatiotemporal behaviours such as travelling pulses, travelling fronts, and spatiotemporal chaos. Through a linear stability analysis we are able to show that the spatiotemporal patterns are not due to diffusion-driven instability as is often the case for reaction-diffusion systems. It is as a consequence of the nonlinear dynamics of the reaction terms and coupling effect of diffusion. The precise mechanism is not yet well understood, this will be subject of future work. We then examine travelling wave solutions in detail. In particular we show how they relate to homoclinic and heteroclinic solutions in travelling wave coordinates. Finally we review spectral stability analysis for travelling waves and compute the essential spectrum of travelling waves in our system

Dynamics of a self-propelled capsule robot in contact with different folds in the small intestine

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: Data will be made available on request.Considering the anatomy of small intestine involving lesions, circular folds and tumours are the major sources resisting the locomotion of capsule robots. By mimicking the small-bowel tumours as cone folds, this paper presents a comparative study on the dynamics of a vibro-impact capsule robot in contact with different circular and cone folds. With the aid of GPU parallel computing and path-following techniques, extensive bifurcation and basin stability analyses are performed to identify different capsule-fold interactions and unravel the parametric influences on the robot, such as fold shape, Young’s modulus and robot’s control parameters (e.g., excitation period and amplitude). It is found that fold shape and Young’s modulus may only affect capsule’s dynamics significantly when robot’s excitation period is large. Two essential locomotion modes, a period-one motion with capsule-fold contact in the small region of excitation amplitude and a fold crossing motion in the large region of excitation amplitude, dominating the dynamics of the robot regardless of fold shape and Young’s modulus are observed. In addition, the instability mechanism of this period-one motion is revealed in detail. The numerical study presented in this work will provide a solid basis for the locomotion control of the robot when encountering different types of circular folds and small-bowel tumours. It also offers the potential of utilising robot’s dynamics for bowel cancer detection.European Union Horizon 2020National Natural Science Foundation of Chin

FIBER-OPTIC BUNDLE FLUORESCENCE MICROSCOPY FOR FUNCTIONAL BRAIN ACTIVITY MAPPING

Understanding the relationship between cellular activities in the animal brain and the emerging patterns of animal behavior is a critical step toward completing the Brain Activity Map. This dissertation describes the development of fiber-bundle microscopy capable of high-resolution cellular imaging, for mapping of functional brain activity in freely moving mice. As a part of this work, several fiber-bundle microscope systems and image processing algorithms were proposed and developed. These optical imaging methods and system performance were tested and evaluated by performing in vivo animal brain imaging. Several fiber-bundle imaging devices, including a dual-mode confocal reflectance and fluorescence micro-endoscope, a single ball-lens imaging probe, and a spatially multiplexed fiber-bundle imager, were designed and developed for high-resolution imaging of brain cells and visualization of brain activity. A dual-mode micro-endoscope, simultaneously achieving laser scanning confocal reflectance and fluorescence imaging, was developed to quantitatively assess gene transfection efficacy using human cervical cancer cells. A single ball-lens integrated imaging probe was designed for endoscopic brain imaging. Lastly, a spatially multiplexed fiber-bundle imager that allows concurrent monitoring of astrocytic activities in multiple brain regions and enables optical manipulation with cell-specific targeting was proposed and experimentally demonstrated. Novel image-processing algorithms were used along with the developed imaging systems. Structured illumination employing a digital micro-mirror device (DMD) was integrated into the system to achieve depth-resolved imaging with a wide-field illumination fiber-bundle microscope. Data from super-resolution fiber-bundle microscopy based on the linear structured illumination were numerically processed to extend the lateral resolution beyond the diffraction limit. To evaluate the performance of the developed fiber-bundle microscope systems and image reconstruction algorithms, the systems and methods were each tested and validated on in vivo animal models, namely transgenic mice expressing a genetically encoded Calcium indicator (GCaMP3) within astrocytes. We showed that locomotion triggers simultaneous activation of astrocyte networks in multiple brain regions in mice. We have also demonstrated real-time cellular-resolution dual-color functional brain imaging in mice. Finally, we established a platform that allows real-time and non-invasive imaging of the intact central nervous system of freely behaving mice. Using this platform, we observed, for the first time, physiologically relevant activation of astrocytes during behaviorally relevant tasks and in the natural setting. In addition, we present a proof-of-concept study by using a fiber-bundle ring light-guided portable multispectral imaging (MSI) platform capable of tissue characterization and preoperative surgical planning for intestinal anastomosis

Modelling, Simulation and Data Analysis in Acoustical Problems

Modelling and simulation in acoustics is currently gaining importance. In fact, with the development and improvement of innovative computational techniques and with the growing need for predictive models, an impressive boost has been observed in several research and application areas, such as noise control, indoor acoustics, and industrial applications. This led us to the proposal of a special issue about “Modelling, Simulation and Data Analysis in Acoustical Problems”, as we believe in the importance of these topics in modern acoustics’ studies. In total, 81 papers were submitted and 33 of them were published, with an acceptance rate of 37.5%. According to the number of papers submitted, it can be affirmed that this is a trending topic in the scientific and academic community and this special issue will try to provide a future reference for the research that will be developed in coming years

Computational Intelligence in Electromyography Analysis

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG may be used clinically for the diagnosis of neuromuscular problems and for assessing biomechanical and motor control deficits and other functional disorders. Furthermore, it can be used as a control signal for interfacing with orthotic and/or prosthetic devices or other rehabilitation assists. This book presents an updated overview of signal processing applications and recent developments in EMG from a number of diverse aspects and various applications in clinical and experimental research. It will provide readers with a detailed introduction to EMG signal processing techniques and applications, while presenting several new results and explanation of existing algorithms. This book is organized into 18 chapters, covering the current theoretical and practical approaches of EMG research

Multi-Scale Modelling of Gastric Electrophysiology

Ph.DDOCTOR OF PHILOSOPH

COMPUTATIONAL BIOENGINEERING OF THE GASTROINTESTINAL TRACT

Ph.DDOCTOR OF PHILOSOPH