The enrichment of egg with folate is a viable option for supplying the general population of a food product rich in natural folates. However, attempts to increase the concentration of folate in egg beyond the achieved level of enrichment had been unsuccessful because egg folate reached a maximum plateau when folic acid (FA) was increased in the diet. Thus, experiments were conducted to determine the factors regulating the deposition of dietary FA into the eggs. In the first study, the effect of feeding equimolar intake of FA and 5-methyltetrahydrofolate (5-methylTHF), the biologically active form of folate; on egg folate concentrations, indices of folate status, and activities of folate-dependent enzymes was evaluated. Folic acid and 5-methylTHF demonstrated equivalent effects in enhancing the egg folate concentrations and improving the indices of folate status in the laying hen. The activities of folate-dependent enzymes were similar between the two forms of folate except for hepatic dihydrofolate reductase (DHFR) activity which increased in FA-fed birds compared to 5-methylTHF-fed birds. However, this demonstrated the ability of the laying hen to metabolically convert FA into its biologically active forms. Therefore, the influence of intestinal FA absorption in the regulation of FA deposition in the egg was subsequently evaluated. Using the in vitro everted intestinal sac technique, FA was absorbed in all regions of the intestine. Absorption was maximum at acidic pH 6.0, and increased in the duodenum and jejunum compared to the ileum and cecum. The rate of FA absorption in the jejunum diminished at higher FA concentrations. Therefore, further study was conducted to determine the regulation of FA absorption when levels of FA in the laying hen diet are increased. Supplementation of increased FA levels resulted to a down-regulation of FA absorption in the duodenum, but not in the jejunum of the laying hen. This down-regulation was not associated to a decreased mRNA gene expression of the duodenal folate transporters. Overall, decreased intestinal rate of FA absorption possibly associated to a post-transcriptional or translational regulation of specific folate transporters in the intestine of the laying hen may contribute to the saturation in the egg folate concentration.

Glucagon-like peptide-2 (GLP-2) augments intestinal adaptation in animal models of short bowel syndrome (SBS) and in adult patients with SBS. However, GLP-2 has not been used as a therapy for pediatric SBS. In this thesis, it is hypothesized that exogenous GLP-2 therapy will improve outcomes of intestinal adaptation in proximal intestinal resection (JI) and distal intestinal resection (JC) neonatal piglet models of SBS. Improvements in morphological parameters (increased small intestinal length) and histological parameters (increased jejunal villus length or jejunal crypt depth) of intestinal adaptation in JI and JC neonatal piglets treated with GLP-2 were observed. However, improved clinical outcomes (fewer days of diarrhea, fewer days on parenteral nutrition, more days on enteral nutrition alone) were only observed in GLP-2 treated JC animals. Since the JC anatomical subtype (no remnant ileum) represents the majority of clinical cases of neonatal SBS, these results support a potential role for GLP-2 therapy in pediatric SBS.

Two different feeding trials were conducted to evaluate the effects of dietary supplementation with the dairy/yeast prebiotic GroBiotic-A (GBA) to Nile tilapia diets. A nutritionally complete basal diet was supplemented with GBA at either 1 or 2% of dry weight, and all three diets were fed to triplicate groups of juvenile fish in two consecutive trials. Trial 1 continued for 8 weeks, while Trial 2 was conducted for 5 weeks to more specifically assess immunological responses, intestinal characteristics and disease resistance of tilapia. At the conclusion of Trial 1, there were no differences in weight gain (WG) or feed efficiency (FE) among fish fed the three diets. However, fish fed the diet with GBA at 2% had significantly increased survival and noticeably elevated levels of plasma lysozyme compared to fish fed the basal diet or the diet with GBA at 1%. Similarly, at the conclusion of Trial 2, WG and FE were unaffected by GBA supplementation; however, fish fed the diet with GBA at 2% also exhibited elevated plasma lysozyme as well as significantly (P < 0.05) increased levels of extracellular superoxide anion production (EX-SOAP) by macrophages. Dendrogram analysis of denaturing gradient gel electrophoresis (DGGE) images detected a significantly different microbial community within the intestine of fish fed the diet with GBA at 2% compared to fish fed the basal diet and diet with GBA at 1%. None of the experimental diets resulted in significant improvements to survival after exposure to Streptococcus iniae due to within treatment variability. However, fish fed the diet with GBA at 2% did tend to experience reduced mortality (12.5%) as compared to fish fed the basal diet (35%). Thus, supplementation of GBA at 2% of diet did alter the gut microbiota of tilapia and enhanced immunological responses and disease resistance to S. iniae.

Cyclosporine forms the cornerstone of therapy to prevent rejection after organ transplantation. However, the clinical use of the drug is compromised by a narrow therapeutic window and a wide inter- and intra-individual variation in metabolism. Cyclosporine is metabolised by the CYP3A4 isoenzymes in both the liver and intestine, while it has been reported that the metabolism of the drug can be inhibited by certain furocoumarin derivatives in grapefruit juice. Methoxsalen (8-methoxypsoralen) is a furocoumarin and a potent inhibitor of the cytochrome P450 system in both the liver and intestine. The study was conducted to investigate the possibility whether methoxsalen may inhibit the metabolism of cyclosporine and thereby increase the bioavailability of the drug. The interaction is of clinical relevance since both drugs are used in the treatment of psoriases. The study, conducted in 12 healthy male volunteers, was a three-way comparative bioavailability study with a wash out period of one week between treatments. The patients received 40 mg methoxsalen, 200 mg cyclosporine or a combination of the two on three separate occasions. Blood samples of 10 ml were collected by venupuncture at the following times: 0, 0.5, 1, 1.5, 2, 2.5, 3.4, 5,6, 8, 12 and 24 hours after drug administration. Methoxsalen was analysed by a high pressure liquid chromatograph method (HPLC) with UV detection (LOQ = 10 ng/ml), while cyclosporine was analysed using a fluorescence polarisation immunoassay (FPIA) technique. There was a statistical significant difference in AUCo-00 and Cmax ' for cyclosporine when methoxsalen was added to the drug regimen. When the methoxsalen levels were compared with those in the presence of cyclosporine, the levels were lower, although the difference was not statistical significant. We conclude that methoxsalen increase the levels of cyclosporine by inhibiting the P450 system enzymes in the liver and intestine. However, the absorption of methoxsalen is highly variable in the same individual which needs to be considered before this interaction can be regarded as being of any clinical relevance. / Thesis (M.Sc.(Pharmacology))--North-West University, Potchefstroom Campus, 2004.

The enrichment of egg with folate is a viable option for supplying the general population of a food product rich in natural folates. However, attempts to increase the concentration of folate in egg beyond the achieved level of enrichment had been unsuccessful because egg folate reached a maximum plateau when folic acid (FA) was increased in the diet. Thus, experiments were conducted to determine the factors regulating the deposition of dietary FA into the eggs. In the first study, the effect of feeding equimolar intake of FA and 5-methyltetrahydrofolate (5-methylTHF), the biologically active form of folate; on egg folate concentrations, indices of folate status, and activities of folate-dependent enzymes was evaluated. Folic acid and 5-methylTHF demonstrated equivalent effects in enhancing the egg folate concentrations and improving the indices of folate status in the laying hen. The activities of folate-dependent enzymes were similar between the two forms of folate except for hepatic dihydrofolate reductase (DHFR) activity which increased in FA-fed birds compared to 5-methylTHF-fed birds. However, this demonstrated the ability of the laying hen to metabolically convert FA into its biologically active forms. Therefore, the influence of intestinal FA absorption in the regulation of FA deposition in the egg was subsequently evaluated. Using the in vitro everted intestinal sac technique, FA was absorbed in all regions of the intestine. Absorption was maximum at acidic pH 6.0, and increased in the duodenum and jejunum compared to the ileum and cecum. The rate of FA absorption in the jejunum diminished at higher FA concentrations. Therefore, further study was conducted to determine the regulation of FA absorption when levels of FA in the laying hen diet are increased. Supplementation of increased FA levels resulted to a down-regulation of FA absorption in the duodenum, but not in the jejunum of the laying hen. This down-regulation was not associated to a decreased mRNA gene expression of the duodenal folate transporters. Overall, decreased intestinal rate of FA absorption possibly associated to a post-transcriptional or translational regulation of specific folate transporters in the intestine of the laying hen may contribute to the saturation in the egg folate concentration.

Inflammatory Bowel Diseases (IBD) result from the nexus of a genetic predisposition, dysregulated immunologic insult against commensal microflora, and an environmental trigger. The intestinal epithelium is a single cell layer that separates a highly active mucosal immune system from a large antigenic load in the intestinal lumen. Innate immune recognition combined with a highly regulated adaptive immune response maintains this tolerance. The intestinal epithelium in collusion with antigen presenting cells primarily modulates this activity. In this thesis, we show that, in response to DNA isolated from bacteria, innate toll like receptor 9 (TLR9) activation in intestinal epithelial cells modulates both arms of the immune system, to regulate intestinal homeostasis, and through this mechanism, Bifidobacteria breve DNA exerts its anti-inflammatory function. / Experimental Medicine

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 6 uppsatser.

Thesis (Ph.D.)--University of Western Australia, 2004.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [78]-93).