The complex interaction between the central nervous system, the enteric nervous system and local and endocrine hormones enables drugs affecting gastrointestinal motility to produce their effects through multiple sites and mechanisms of action. Opiates are one class of drugs which can have dramatic effects on gastrointestinal function and the mechanisms for these actions have been the subject of intense study in recent years. These changes in motility have assumed increased importance following the discovery of several endogenous opioid peptides. In the present studies, centrally-administered morphine was more potent than peripherally-administered morphine at inhibiting intestinal propulsion and gastric emptying in rats. Direct measurement of intestinal motility revealed that the antipropulsive effects of morphine were due to an inhibition of intestinal contractions. The opioid peptide, β-endorphin, and a stabilized enkephalin analog, [D-Ala², Met⁵] enkephalinamide, also inhibited intestinal propulsion only after central administration. These effects were not blocked by a peripherally selective opioid receptor antagonist, diallylnormorphinium. These data indicated that there is an opioid sensitive mechanism in the brain of rats that, when activated, can inhibit intestinal motility. Physiological activation, by electroconvulsive shock or inescapable footshock, or pharamcological activation by kyotorphin (Tyr-Arg) treatment, did not affect gastrointestinal motility but did produce naloxone-reversible analgesia. These data indicate that the opioid mechanisms mediating analgesia and inhibition of intestinal motility are independent and may be a function of different receptor systems. Several opioid receptor selective agonists were used to determine the specific receptors mediating the analgesic and motility effects of centrally-administered opioids. Mu selective agonists produced analgesia and inhibition of intestinal transit, while delta receptor agonists produced analgesia only. Kappa agonists did not produce analgesia or an inhibition of intestinal motility. Mu receptors mediate the analgesic and intestinal motility effects of exogenously administered opioids, while delta receptors can mediate analgesia without altering gut motility. It appears then, that electroconvulsive shock, inescapable footshock and kyotorphin may produce their analgesic effects by releasing enkephalins, which are delta selective agonists. This accounts for the failure of these treatments to alter gastrointestinal motility while still producing the analgesic effects reported here.

Motility of the small intestine is a result of complex neurochemical and hormonal interactions within the intestine. The net motility (contraction) of the intestine is a balance of the influences from the central nervous system, enteric nervous system and hormonal changes in the body. Recently, the discovery of several peptide neurotransmitters common to the brain and the intestine has stimulated new research into the influence of these novel neurotransmitter candidates on intestinal motility at the level of the enteric (intestinal) nervous system. The present studies examined the contractile actions of three families of peptides, the opioids, tachykinins and motilin. Each of these peptide groups has been localized in the intestine, and suggested to function in the control of intestinal motility. The peptides were administered by intraarterial injection to isolated segments of canine small intestine and the resulting contractile activity measured. The results of these experiments demonstrate that all of these peptides may elicit contractile activity of the intestine in very low doses. These actions were further examined, using pharmacological antagonists, to determine the mechanism of action and the receptor types involved in the contractile actions. The opioid peptide induced responses were found to be mediated by two receptor types, mu and delta, located on the enteric nerve and smooth muscle, respectively. Similarly, the tachykinin induced contractions were also found to be due to actions on two receptor types, SP-P and SP-K, located on the nerve and muscle layers, respectively. These data suggest that the opioids and tachykinins may have multiple functions in the intestine dependent on the site of action and the receptor type involved in the response. Administration of motilin induced long-lasting contractile patterns in the intestine. The results also suggest that the actions of motilin are mediated by intermediate neurons of the enteric plexes which synapse on terminal cholinergic motor neurons.

The purpose of this investigation was to determine the effect of solute carbonation and carbohydrate (CHO) concentration on gastric emptying during prolonged cycling. Eight highly trained male cyclists completed four two hour cycling bouts during which one of four test solutions were consumed. The test solutions consisted of a carbonated 10 % CHO solution (CK), a non-carbonated 10 % CHO solution (NCK), a carbonated non-CHO solution (CNK), and a noncarbonated non-CHO solution (NCNK). Approximately 150 ml (8.5 ml/kg/hr) of one of the test solutions were consumed every fifteen minutes. The first 105 minutes of each trial was a continuous ride on an electrically braked cycle ergometer at 70 % V02 max. The last fifteen minutes of each trial was a self paced "performance ride" on an isokinetic cycle ergometer. The subjects were instructed to complete as much work (kilojuoles) as possible during the performance ride. Gastric contents were aspirated within five minutes following the performance ride and analyzed to determine the amount of the original test solution emptied.Of the original1273 ml ingested during each trial, the volumes emptied were 993.6 ±78.1, 1064.6 ±75.3, 1097.4 ±94.2, and 1147.2 ±95.9 ml (±SE) for CK, NCK, CNK, NCNK, respectively. The only significant difference was between trials CK and NCNK (P < 0.05). There were no statistically significant differences in total work output between any of the trials. However, when the performance data from the CHO trials were pooled and compared to the combined data from the non-CHO trials, total work output was significantly greater (P < 0.05) in the CHO group (1185.19 + 21.81, and 1092.85 + 21.52 Kj (+ SE) for the CHO and non-CHO groups, respectively). These data suggest that carbonated or 10 % CHO solutions, independent of one another, may not significantly inhibit gastric emptying. They also suggest that there may be some interaction between carbonation and CHO concentration which caused an additional inhibition of emptying. In addition, the potential for improved performance exists with the consumption of 10 % CHO solutions. / Human Performance Laboratory

No description available.

The gut microbiome is an integral component of the human body that plays a role in many physiological processes. Dysbiosis, an imbalance of the microbiome, has been associated with disease states including inflammatory bowel disease, type II diabetes, and obesity, and moreover, contributes to the pathogenesis of these states. Understanding the functional mechanisms governing microbial ecology and microbe-host interactions is essential to understanding the microbiome’s role in health and disease. However, at present, functional genetic studies of diverse natural mammalian gut microbiomes remain challenging, due to a lack of genetic tools for bacteria outside of a handful of well-studied model organisms. Altering the metagenome of a complex microbial community requires novel platform technologies for genetic engineering which can operate in a generalized fashion across many different host organisms. In this thesis, I present two novel genetic tools designed for genetic modification of bacterial communities. The first, the Cas-Transposon platform, is a host-independent targeted genome editing tool that utilizes programmable, targeted transposases to mediate site-specific gene insertions into user-defined loci. The Himar1 transposase naturally inserts transposases into random TA dinucleotides in a genome, but when fused to the dCas9 RNA-guided, DNA-binding protein, the fusion protein Himar1-dCas9 targets transposon insertions to a single TA site. The activity of Himar1-dCas9 was characterized using in vitro experiments, demonstrating that site-specific transposition is dependent on guide RNA (gRNA) orientation relative to the target site and the sequence surrounding the target site, but robust to variations in DNA and protein concentration, presence of background DNA, and temperature. We additionally showed that the Cas-Transposon platform is capable of performing site-specific transposition into a plasmid in vivo in E. coli, although further optimization of the system may be necessary to effect site-specific transposition into a genomic locus. The Himar1-dCas9 protein is the first example of a transposase that inserts transposons into locations programmable by an RNA, making it a novel tool for gene insertion and knockout in potentially any organism, without relying on DNA repair by a host cell. Metagenomic Alteration of Gut microbiome by In situ Conjugation (MAGIC) is an approach to directly modify gut bacteria in their native habitat by harnessing naturally occurring horizontal gene transfer activity to deliver engineered DNA. Because many gut bacteria are difficult to cultivate and thus difficult to genetically manipulate in the laboratory, MAGIC uses donor bacteria, delivered directly into the gut environment, to conjugate mobile vectors bearing engineered genetic payloads. Using payloads with selectable markers, we identified organisms across 4 major phyla of gut bacteria that were amenable to genetic modification with libraries of conjugative vectors we created. Using a lab-adapted E. coli strain as a donor, we achieved transient expression of the engineered payload in the microbiome. We also demonstrated that engineered native gut bacteria containing conjugative vectors could be deployed back into the gut to stably recolonize and mediate secondary transfer of the payload into other microbes, potentially enabling long-term infiltration of the payload into the metagenome. The results from this study suggest that both short-term and long-term genetic alteration of the metagenome are possible by choosing different donors, and that the MAGIC platform could enable development of more diverse microbial chasses for synthetic biology applications. MAGIC could also be used to create personalized engineered probiotics for diagnostic or therapeutic applications. In Chapter 4 of this thesis, we explored the targeted use of MAGIC to genetically modify Segmented Filamentous Bacteria, a gut commensal that is important for immune regulation but recalcitrant to in vitro cultivation. The Cas-Transposon and MAGIC technologies expand our capabilities in the areas of targeted genome editing and gene delivery into bacteria, respectively. Together, they form a suite of complementary approaches to genetically engineer undomesticated gut commensal bacteria and probe the functional genetic networks in the gut microbiome, which will enhance our understanding of microbiome ecology and host-microbiome interactions. In addition, the expanded range of genetic manipulations made possible by these tools may enable production of more diverse, perhaps personalized, probiotics containing engineered functions, such as sensing disease markers or drug delivery.

Probiotic bacteria such as Lactobacillus and Bifidobacterium species are normal inhabitants of healthy gastrointestinal (GI) tract, which may promote beneficial effects on host through limiting the growth of undesirable micro-organisms and modulating the immune system. In the present study, Lactobacillus and Bifidobacterium strains were screened for their in vitro acid and bile tolerance, autoaggregation, coaggregation and hydrophobic abilities to identify potential probiotic bacteria. Lactobacillus acidophilus LAFTI L10 and Lactobacillus paracasei LAFTI L26 were selected based on their overall tolerance to in vitro acidic conditions to further investigate their influence on various immune functions and gene expression in mice. Immunofluorescent analysis of small intestine in mice fed with L. acidophilus or L. paracasei demonstrated an increase of immunoglobulin (Ig)-A, interleukin (IL)-10 and interferon (IFN)- producing cells compared to control mice. In summary, L. acidophilus and L. paracasei showed tolerance to various gastric conditions and bile salts. Lactobacillus acidophilus and L. paracasei enhanced gut and systemic immune functions, particularly non-specific and specific immune responses in normal and CT mice. Moreover, L. acidophilus regulated the genes involved in various biological functions in small bowel of normal and CT mice, which provided a basis in understanding the pathways through which these bacteria are beneficial to the host. / Doctor of Philosophy (PhD)

Bibliography: leaves 159-192. / viii, 192 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines aspects of the control and measurement of pyloric motor function believed to be relevant to the role(s) of the pylorus in the regulation of normal gastric emptying. / Thesis (M.D.)--University of Adelaide, Dept. of Medicine, 1992

Bibliography: leaves 216-250. / xii, 250 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / To determine the acute and subacute effects of therapeutic irradiation on oescophageal, gastric and intestinal function; the chronic effects of irradiation on gastric, intestinal and anorectal function, and, the effects of loperamide-N-oxide in patients with diarrhoea due to chronic radiation enteritis. / Thesis (M.D.)--University of Adelaide, Dept. of Medicine, 1996?

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 65-71).

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy