No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Intestinal Peyer's patches, through their specialized M cell-rich epithelium, can act as a portal of entry for bacteria, viruses, macromolecules and particles. Particles can be further classified as exogenous particles such as those derived from the diet in the form of food additives or endogenous particles which result from calcium and phosphate precipitation in the mid-distal intestinal lumen. Although exogenous dietary particles have been found to accumulate in "pigment cells" at the base of the human Peyer's patch, little is known about calcium phosphate particles. This thesis aimed (i) to investigate and compare the micro-anatomical site of exogenous and endogenous particles within the Peyer's patch, and (ii) to analyse the phenotype of cells involved in their uptake. Following an Introduction chapter (Chapter 1) and Methods chapter (Chapter 2), the focus of chapter 3 was to look for the presence of both calcium phosphate and exogenous particles in human intestinal Peyer's patches using the Von Kossa staining method and dark field microscopy, respectively. The elemental makeup of the endogenous particles was investigated by X-Ray Microanalysis (XRMA). This study revealed a sub-epithelial Peyer's patch dome-associated population of Von Kossapositive particle cells, the majority of which appeared to be calcium-rich, and more especially calcium- and phosphorus- rich. Exogenous particles associated with the usual basal pigment cells could similarly be found in the sub-epithelial dome cells and suggested that the exogenous particles made their way through the patch via intermediary cells. Following work concentrated on the phenotyping of cells responsible for the uptake of exogenous and endogenous particles (Chapters 4 and 5, respectively). Pigment cells of the Peyer's patch base were found to be macrophages, chiefly of a mature phenotype, and appeared metabolically and immunologically of low activation status. In contrast, calcium phosphate particles were found mainly in dendritic cells of the sub epithelial dome region of the Peyer's patch. The cell phenotype (CDIlc+, CDl lb+) was consistent with immune tolerance-inducing dendritic cells reported in the literature - the specific mechanism being induction of regulatory T cells. I have speculated on how the uptake of endogenous particles may influence such process.

A substantial percentage of the UK population are overweight or obese, and research indicates that behaviours associated with energy intake rather than expenditure account for this weight gain. Aberrant eating behaviours have been associated with disturbances in peripheral signals of hunger and satiety, but it is not yet clear if these mechanisms underlie individual differences in appetite control. Thus, the objective of this thesis was to identify healthy weight adults who were likely to overeat (scoring high on the TFEQ-disinhibition scale) or eat less than desired (scoring high on the TFEQ-restraint scale), and to examine the eating behaviours and peripheral appetite signals associated with these eating styles. Experiments 1 and 2 confirmed that TFEQ-disinhibition predicts overeating and indicated that this overeating was dependent on physiological context. Furthermore, these studies suggested that TFEQ-restraint was a weak predictor of energy intake, and had no impact on the overeating associated with TFEQ-disinhibition. Consequently, Experiments 3 and 4 examined whether the TFEQ-disinhibition and TFEQ-restraint eating styles were associated with disturbances in leptin, ghrelin and PYY3-36, peripheral peptides that influence the experience of appetite. Together, these Experiments indicated that TFEQ-restraint predicts low fasting levels of PYY3-36 and that TFEQ-disinhibition predicts low post-meal leptin levels, suggesting that both these eating styles are related to weak signals of satiety. Furthermore, the interaction of TFEQ-restraint and TFEQ-disinhibition predicted post-meal ghrelin levels, with individuals scoring low on both the TFEQ-restraint and TFEQ-disinhibition scales having low post-meal levels of ghrelin, which is associated with weak hunger signals. Experiment 5 was designed to determine the real-world eating styles associated with TFEQ-restraint and TFEQ-disinhibition. This food diary study provided some evidence that TFEQ-restraint and TFEQ-disinhibition predicted patterns of energy intake, implying that the physiological findings from Experiment 3 and 4 reflected differences in habitual eating patterns. Alternately, it is equally as likely that the physiology associated with the TFEQ determined the inter-individual differences in eating styles. Further work is required to validate these interpretations.

No description available.