No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 96-114). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 96-114). Also available on the Internet.

Vagus nerve stimulation (VNS) is an approved therapy for patients suffering from refractory epilepsy. While VNS is currently an open loop system, making the system closed loop can improve the therapeutic efficacy. Electrical recording of peripheral nerve activity using a nerve cuff electrode is a potential long-term solution for implementing a closed-loop controlled VNS system. However, the clinical utility of this approach is significantly limited by various factors, such as poor signal-to-noise ratio (SNR) of the recorded electroneurogram (ENG). In this study, we investigated the effects of (1) modifying the electrode contact dimensions, (2) implementing an external shielding layer on the nerve cuff electrode and (3) exploring shielded bipolar nerve cuff designs on the recorded ENG. Findings from both computer simulations and animal experiments suggest that significant improvements in peripheral nerve recordings can be achieved.

The field of food intake and satiety has received increasing interest from the research community in recent years. The mechanisms and factors that regulate satiety gains their importance from the crucial role they play in food consumption and consequently control of body weight. Leukotrienes are mediators that are released in inflammatory conditions. One of the receptors on which Leukotrienes perform their actions is Cysteinyl Leukotriene Receptor Type 2 (CysLT2Rs). Recently, our colleagues made the observation that CysLT2Rs are expressed in vagal afferent neurons. In addition, CysLT2R-/- mice appeared to be heavier than WT (Moos and Funk, unpublished observations). Based on these findings, I hypothesized that CysLT2Rs play a role in regulating food intake via vagal afferent activity. In-vivo studies were performed to characterize body weight gain and investigate whether weight gain was associated with increased food intake. I found that CysLT2R-/- mice not only have significantly higher body weight, but also eat significantly more than CysLT2R+/+ mice. Using calcium imaging techniques, I demonstrated that LTD4 and LTC4 increased calcium Ca2+ influx in nodose ganglion neuron. Moreover, the level of neuronal activation in the brainstem (NTS area) was measured in both groups of mice using immunohistochemical techniques, which suggested less postprandial neuronal activity in KO mice. These data suggest that CysLT2Rs take part in regulating body weight and food intake. In addition these results implicate vagal afferents as a possible pathway. These findings may have implications for the control of food intake in both health and disease and may lead to novel insights in the causes and treatment of disordered weight such as overweight and obesity, or even anorexia. / Thesis (Master, Physiology) -- Queen's University, 2011-02-04 10:48:47.018

Vagus nerve stimulation (VNS) is an approved therapy for patients suffering from refractory epilepsy. While VNS is currently an open loop system, making the system closed loop can improve the therapeutic efficacy. Electrical recording of peripheral nerve activity using a nerve cuff electrode is a potential long-term solution for implementing a closed-loop controlled VNS system. However, the clinical utility of this approach is significantly limited by various factors, such as poor signal-to-noise ratio (SNR) of the recorded electroneurogram (ENG). In this study, we investigated the effects of (1) modifying the electrode contact dimensions, (2) implementing an external shielding layer on the nerve cuff electrode and (3) exploring shielded bipolar nerve cuff designs on the recorded ENG. Findings from both computer simulations and animal experiments suggest that significant improvements in peripheral nerve recordings can be achieved.

Thesis (Ph. D.)--University of Adelaide, Dept. of Physiology, 1984. / Includes bibliographical references (leaves 118-161).

No description available.

The current enthusiasm for vagotomy as treatment for peptic ulcer disease has been dampened by several problems, the most serious of which is recurrent ulceration. As this is due in most instances to incomplete vagal section, it is clear that the development of a reliable method to assess completeness of vagotomy during the course of surgery is an essential step toward reducing the 10-15% incidence of recurrent ulcer. The problem has been approached by studying some of the gastric effects of vagal stimulation during operation. These include changes in intragastric pressure, acid secretion, and electrical activity. The investigation as outlined in this thesis was aimed at developing a reliable, reproducible intraoperative method for assessing the completeness of vagotomy. The plan of the experiment was essentially twofolds: (i) to determine whether complete vagotomy would alter the gastric electrical activity in some reproducible manner such as would indicate that all vagal connectionshad been severed; (ii) to divide one vagus nerve at the level of the esophageal hiatus, assess the effect on electrical activity of stimulation of its distal or peripheral end, and then stimulate the central end with view to eliciting a response in the electrical activity via reflex pathways through the brainstem, vagal nuclei, and along the remaining intact efferent vagal fibres; these remaining fibres would then be divided, central stimulation of either vagal trunk repeated, and presumably the previously observed "characteristic" response of the gastric electrical activity would no longer be obtained, indicating complete division of all vagal fibres. Vago-vagal reflex responses to afferent vagal stimulation have been documented with respect to influence on both gastric tone and secretion. One may reasonably expect to be able to demonstrate the existence of a vago-vagal reflex pathway where by one might alter gastric electrical activity by central or reflex stimulation of the afferent vagal fibres. Gastric electrical activity has been recorded, and the effects of vagal section on this electrical activity have been assessed. The reduction in the frequency of the basic electrical rhythm (BER) observed following complete vagotomy, though of significance statistically, was found to be caused as well by other non-related factors, and was in any case of such a low order as to be of limited value in assessing any individual case. It could therefore not be considered indicative of complete vagal section. The disorganization of the BER observed following vagotomy was both temporary and inconsistent, and could not be interpreted as pathognomonic of complete vagotomy. The observations recorded during electrical stimulation of afferent vagal fibres have demonstrated the existence of a vago-vagal reflex pathway whereby gastric electrical and motor activity can be modified by afferent vagal stimulation. These effects are presumably conveyed via pathways through the central nervous system and along the intact efferent vagal fibres. The effects on gastric electrical activity are neither consistent nor reproducible, whereas the effects on gastric motor activity appear to be considerably more reliable. In the light of these observations, it would seem more appropriate to study the changes in the contractile force of gastrointestinal smooth muscle subsequent to afferent vagal stimulation in the search for a method to assess completeness of vagotomy during the course of surgery. The development of such a test will be a major factor in preventing this form of treatment from falling into disrepute because of a continued high rate of recurrent ulceration. / Surgery, Department of / Medicine, Faculty of / Graduate

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