Thesis (M. Sc.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 139-147). Also available via the World Wide Web.

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Non-Latin script record Includes bibliographical references (p. 76-87).

No description available.

The purpose of this investigation was to provide direct experimental evidence for or against the suggestion that amino acids and B vitamins are among the nutrients absorbed from the rumen of the ruminant. The investigation was subdivided into two parts: (1) six ruminal fistula experiments and (2) nine blood-sampling experiments. The goat (Capra) was the experimental animal. In the ruminal fistula experiments, solutions of amino acids, B vitamins, and usually propionic acid were added to an empty rumen for 120 or 150 minutes. Propionic acid, a substance known to be absorbed from the rumen, was included in most of the solutions to provide a positive control for ruminal absorption. In addition, in all but the first two experiments, polyethylene glycol was added to the solutions in order to provide a marker substance for differential water movement into or out of the rumen. Controls for the experiments included the taking of a sample from the solution in the rumen at zero time and incubating the sample for the duration of the experiment in a water-bath held at 37°C. The ruminal and control solutions were sampled at periodic intervals during the experiment. The results demonstrated not only marked decreases in the concentrations of propionic acid in the ruminal solutions but also, in most cases, marked decreases in the concentrations of the amino acids and the B vitamins assayed: tryptophan, methionine, tyrosine, glycine, lysine, riboflavin, nicotinic acid, and pantothenic acid. In contrast, the concentrations of these constituents in the control solutions usually demonstrated either no decrease or a small increase. In the first three blood-sampling experiments, the concentrations of amino acids and nicotinic acid in the plasma draining the rumen were compared with the concentrations in the peripheral plasma. The results demonstrated that seldom were the concentrations of an amino acid or nicotinic acid higher in the plasma draining the rumen than in the peripheral plasma. The results did suggest, however, that there had been slight increases in the plasma concentrations of the amino acids with time. Accordingly, the next six blood-sampling experiments were designed to determine if time-related increases in the blood concentration of alpha amino nitrogen occurred after the addition of amino acids to the rumen. Blood samples were removed periodically from anesthetized goats, both before and after the addition of a solution of amino acids to an empty rumen. The results demonstrated time-related increases in the blood concentrations of alpha amino nitrogen. These results and those obtained for the ruminal fistula experiments are interpreted as supporting the suggestion that amino acids and B vitamins are absorbed from the rumen. In the General Discussion, a preliminary attempt is made to answer three questions: 1) What is the manner of the passage of amino acids and B vitamins across the ruminal epithelium? 2) Does this passage of amino acids and B vitamins occur under normal feeding conditions? 3) How does this passage of amino acids and B vitamins across the ruminal epithelium fit into the scheme pictured for the metabolism and final fate of these compounds in the ruminal contents? As a part of the attempt to answer the first question, literature reviews are presented on the manner of absorption of amino acids and B vitamins in the small intestine, kidney, placenta, and other tissues. Then, after a literature review on the manner of absorption of substances other than amino acids and B vitamins from the rumen, the data of the present investigation are examined for evidence as to the manner of absorption of amino acids and B vitamins from the rumen. The examination led to the following statement: the movement of amino acids across the ruminal wall of the goat is determined by a summation of the effects of chemical, electrical, and possibly metabolic potentials. Unfortunately, other than to suggest that the process of simple diffusion is involved, the nature of the data for the B vitamins was not such as to yield much information on their manner of absorption. In the attempt to answer the second question, the fulfillment or non-fulfillment of the following conditions is considered: (1) the demonstration of the presence of amino acids and B vitamins in the rumen, (2) the demonstration of the relation of the concentrations of individual amino acids and B vitamins in the ruminal liquor to their concentrations in the blood plasma, and (3) the demonstration of the absorption of individual amino acids and B vitamins from an ingesta-filled rumen. Although fulfillment of the third condition was not obtained, fulfillment of the first two conditions was obtained and led to the statement that a strong possibility exists that the absorption of amino acids and B vitamins occurs from the rumen under normal feeding conditions. In the attempt to answer the third question, a number of factors are discussed in turn: (1) the environmental conditions of the rumen, (2) the influence of the diet on the composition of the population of microorganisms in the rumen, (3) the physical and chemical nature of the dietary constituents, (4) the relative stability of amino acids and B vitamins in the ruminal ingesta, and (5) the physiological state of the animal. Evidence is presented to demonstrate that each of these factors probably exerts an important influence on the content of amino acids and B vitamins in the rumen. It is suggested that, when the interaction of the many factors is such as to produce higher concentrations of amino acids and B vitamins in the rumen, the proportions of amino acids and B vitamins that pass from the rumen by absorption through its wall will be an important pathway for these nutrients. To conclude the General Discussion, the possible nutritional implications of the absorption of amino acids and B vitamins from the rumen are considered. One suggestion made is that a general absorption of nutrients from the rumen would permit the simultaneous arrival at the liver, or elsewhere in the body, of volatile fatty acids, amino acids, B vitamins, and inorganic ions. This should promote more efficient utilization of each of the nutrients. Another suggestion made is that ruminal absorption of amino acids and B vitamins places the host ruminant in a better competitive position relative to its contained microbial population in the competition for nutrients. Finally, a suggestion is made that the action of the ruminal wall in absorbing amino acids helps to explain the results that have been obtained for certain nitrogen retention experiments in ruminants. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Adelaide, 1986. / Includes bibliographical references.

Crohn’s disease (CD) and ulcerative colitis (UC) constitute the two major forms of inflammatory bowel disease (IBD), which are disorders of chronic inflammation in the gastrointestinal tract that are associated with significant morbidity and socioeconomic burden. IBD patients with long-standing intestinal inflammation are more prone to developing colorectal cancer (CRC). Until now, none of the existing IBD treatments is able to heal the mucosal ulcerations satisfactorily. The endocannabinoid system (ECS), which comprises of endogenous cannabinoid ligands, their receptors, and metabolic enzymes, has been implicated in gut homeostasis, visceral sensation, inflammation and gastrointestinal motility. Available studies in rodent models of IBD suggest that enhancing the ECS tone may reduce inflammation and improve mucosal integrity. This evidence indicates that the components of the ECS seem well positioned to exert a protective role in IBD and also to offer a great opportunity for therapeutic exploitation. Despite the role of the ECS in the gut, the presence and function of the components of the ECS is not well characterised in human IBD. The primary aim of the study was to investigate the state of the major components of the ECS in human IBD and to establish whether IBD is associated with any changes of the components of the ECS. Cannabinoid CB1 and CB2 receptors, enzymes for endocannabinoid biosynthesis PLC, “LRAT”, NAPE-PLD and DAGL, and endocannabinoid metabolic enzymes FAAH and MAGL were analysed from colonic tissue samples of CD, UC and control patients by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to determine the relative mRNA expression of the above genes. The RT-qPCR analysis showed that the mRNA expression of PLC, LRAT, and NAPE-PLD were unchanged in both CD and UC, whiles DAGL mRNA was decreased in UC but was unchanged in CD. The endocannabinoid degradation enzymes, FAAH mRNA expression was also unchanged in CD but decreased in UC, whereas the mRNA expression of MAGL was significantly decreased in both CD and UC. NAPE-PLD/FAAH and DAGL/MAGL ratios, an estimation of the balance of AEA and 2-AG levels, showed that AEA and 2-AG levels could be increased and unchanged, respectively, in IBD. The mRNA expression of CB1 was significantly decreased in CD and UC whilst CB2 mRNA expression was unchanged in both forms of IBD. The study demonstrated that the components of the ECS which were investigated were present in colonic tissues of both IBD patients and healthy individuals, but they appear to be off balance in CD and UC patients. The decreased CB1 receptors in IBD patients could be an important modifier in the disease and could also provide a possible pathoaetiological mechanism linking IBD and CRC. Although these findings look promising, more studies with larger sample size are required to characterise the components of the ECS in human IBD.

Noncholinergic neurotransmission was studied in vitro in the guinea pig inferior mesenteric ganglion (IMG) using the technique of intracellular recording. First, the role of substance P (SP) in noncholinergic transmission was examined. Forty-four percent of IMG neurons depolarized upon superfusion of SP (1-10 x 10⁻⁷M); however, some neurons that were insensitive to SP still exhibited slow excitatory potentials (EPSPs) in response to nerve stimulation. During exposure to SP, slow EPSPs were depressed by 52% compared to paired control EPSPs. In animals treated with systemic doses of capsaicin (50-350 mg/kg), mean slow EPSP amplitude was 3.5 mV compared to 6.8 mV in untreated animals. Arginine-vasopressin (AVP) was tested for its electrophysiological effects on IMG neurons and synaptic transmission. AVP (0.5-10 x 10⁻⁷M) produced a depolarization in 67% of neurons, accompanied by an increase in membrane resistance of 44%. The depolarizations and increase in resistance were blocked by a specific V₁ receptor antagonist. During AVP-induced depolarizations, slow EPSPs were reversibly depressed in the majority of neurons by a mean of 71% relative to paired control EPSPs. The V₁ antagonist blocked slow EPSPs in only 10% of neurons tested. A group of neurons exhibiting slow EPSPs was exposed separately to both AVP and SP. Some neurons were exclusively sensitive to either SP or AVP, others were sensitive to both peptides, and still others were sensitive to neither peptide. The physiologic role of noncholinergic transmission was examined using a preparation consisting of a segment of distal colon attached to the IMG. Distension of the colon segment produced a slow depolarization resistant to cholinergic antagonists in 44% of IMG neurons. Distension-induced noncholinergic depolarizations increased in amplitude with colonic intraluminal pressure and with membrane hyperpolarization, and were accompanied by an increase in membrane input resistance of 21%. Capsaicin in vivo reduced the number of neurons exhibiting the noncholinergic mechanosensory depolarization, and in vitro capsaicin and SP desensitization reduced the amplitude of the depolarization. These results suggest that (1) both SP and AVP may be transmitters of noncholinergic potentials in the IMG, (2) some IMG neurons receive heterogeneous peptidergic innervation, and (3) noncholinergic transmission in the IMG is involved in sensory regulation of visceral autonomic function.

The non-starch polysaccharide (NSP) components from apple, oat, broccoli and plantain were tested as growth substrates for representatives of the major groups of intestinal bacteria, none of which was able to fully utilise the NSPs for growth.  More bacteria were able to use the soluble plantain NSP fraction for growth than any other NSP tested, with the <i>Bacteroides </i>group showing the strongest growth response.  <i>E. coli</i> strains isolated from healthy people and Inflammatory bowel disease (IBD) patients were all able to utilise the soluble plantain substrate to the same high extent. A wide range of commensal anaerobes were able to bind to the insoluble plantain NSP in a strain specific manner that was independent of the ability to utilize the soluble plantain NSP for growth, with <i>E. coli </i>binding in the highest numbers to the insoluble NSP. The effects of plantain NSP were monitored <i>in vivo</i>, and only the <i>Bacteroides </i>group increased significantly after soluble plantain supplementation.  <i>E. coli </i>populations were volunteer-specific and unaltered after plantain supplementation. <i>Bacteroides </i>and <i>E. coli</i> were the two main groups affected by plantain NSP after the <i>in vitro </i>work, both of which have been implicated in IBD.  Binding to, and growth on plantain may therefore selectively alter the composition of the gut microbiota in patients.  Despite the stimulation of <i>E. coli</i> growth, addition of plantain to the diet may help to prevent colonization of the gut wall by providing this alternative binding substrate.