Motility and absorption in the autotransplanted canine jejunoileum

Transplantation of the upper gut will soon become a clinical reality, yet little is known about the effects on enteric physiology. This study addresses relevant and complementary long-term objectives with respect to the physiology of the transplanted jejunoileum, particularly neural and humoral control of the upper gastrointestinal tract

Investigation of non-traditional roles of the neural gut-brain axis

The neural gut-brain axis is an important bidirectional pathway through which the gastrointestinal (GI) tract communicates with the central nervous system (CNS). This axis includes sensory nerves that send information from the GI tract to the brain and motor nerves that transmit descending information from the brain to the GI tract. Traditional research has focused on nutrient-induced changes in sensory neural signaling and the subsequent motor response altering muscular and secretory functions. These nerves, though, may also play novel, non-traditional roles in the function of the gut-brain axis. Just as nutrients have been shown to induce neuroplasticity of CNS neurons, long-term alterations in nutrition may do more than just change signaling, and ultimately lead to modifications in fiber density, branching, and terminal morphology. These neuroplastic changes may underlie aberrant signaling and could be associated with GI diseases, as has been found with CNS-associated neuroplasticity and disease. The GI tract also has to perform many functions beyond muscular contraction/relaxation and secretion. One essential function in maintaining GI homeostasis is the constant renewal of the cells lost due to normal apoptosis, a process whereby entire GI tissues can be replaced every few days. Because loss of the motor nerves of the gut-brain axis results in changes in the rate of tissue renewal and the location of the nerves are in close contact with the GI stem cells responsible for cell renewal, these motor nerves may play a direct role in inducing proliferation and differentiation of the GI tissue. I hypothesized that there are indeed new, non-traditional roles of the sensory and motor nerves of the gut-brain axis in neuroplasticity and tissue regeneration and tested the mechanisms underlying these processes. Specifically, I used rodents and swine mammalian models to develop new methods by which to investigate multiple hypotheses about nutrient-induced vagal sensory neuroplasticity and found a direct mechanism by which the autonomic motor nerves induce changes in intestinal epithelial renewal. The results of the experiments included in this dissertation establish roles for the neural gut-brain axis that are outside those that are traditionally studied, which can expand the available methods to manipulate gut-brain system for therapeutic purposes

THE EFFECTS OF GASTRIC AND HOMEOSTATIC AUTONOMIC AFFERENT REFLEXES ON CARDIAC AUTONOMIC EFFERENT ACTIVITY IN HEALTHY HUMAN VOLUNTEERS

A thesis submitted in partial fulfilment of the requirements of the University of Wolverhampton for the degree of Doctor of PhilosophyThe effects of gastric autonomic afferent reflexes on cardiovascular autonomic efferent activity are regarded as a direct neural effect of the activation of gastric receptors which send afferent inputs to the central nervous system (CNS) to cause various cardiovascular changes (Van Orshoven et al., 2004; McHugh et al., 2010; Girona et al., 2014). However, the cardiovascular responses to liquid ingestion in humans may be related to gastric distension, volume loading effects, or to its osmotic proprieties. The purpose of this study was to investigate cross autonomic reflex function and to elucidate the effects of the resulting cardiac efferent autonomic activity in resting young healthy subjects. The ingestion of 300 mL of isothermic water increased both the cardiac vagal tone as indicated by increased RMSSD (mean 23.95 ± 20.50 msec increase, p<0.05) and sympathetic activity shown by increased QTc interval (mean 9.86 ± 8.59 msec increase, p< 0.05) during the first 40 minutes post-ingestion. These effects were absent with an identical volume of a physiological (0.9% w/v) saline solution which would increase plasma volume more, indicating that the cardiovascular responses to water drinking are influenced by its hypo-osmotic properties, rather than being related to the volume loading effects. Nevertheless, subjects responded to gastric distension with an ingestion of 300 mL of Fybogel solution with an increase in sympathetic activity during the first 20 minutes post-ingestion, but not in cardiac vagal tone. These results indicate that the mechanisms underlying the cardiovascular responses to water ingestion have additional components to the gastric stretch effect. Contrarily, the cold mediated sympathetic inhibition after drinking the same volume of either cold water or cold Fybogel solution probably happened in the NTS where the two branches of the ANS meet for the first time during their central pathway (Kubin et al., 2006; Thayer and Lane, 2009). In conclusion, the cardiovascular responses to water drinking are influenced by its hypo-osmolality properties and temperature, not by the volume loading effects

Volume 30, issue 4

The mission of CJS is to contribute to the effective continuing medical education of Canadian surgical specialists, using innovative techniques when feasible, and to provide surgeons with an effective vehicle for the dissemination of observations in the areas of clinical and basic science research. Visit the journal website at http://canjsurg.ca/ for more.https://ir.lib.uwo.ca/cjs/1218/thumbnail.jp