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Title: Studies on the effect of diet on exfoliation in the human colon
Author: Bailey, J. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2006
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In this Thesis a non-invasive, reliable and reproducible technique for the isolation of exfoliated colonocytes from human stool was developed. Exfoliated colonocytes were shown histologically and immunocytochemically to be gut derived although the exact area of the large bowel from which they were derived was not clear. To investigate factors determining the numbers of recovered exfoliated cells, cells were obtained from three studies in which diet was carefully controlled in human volunteers over periods of 10-15 days. On analysis of variance, there was a significant individual effect (p < 0.001), indicating that the recovery technique was reliable. High polyunsaturated diets supplemented with vitamin E, and low starch high sugar diets were probably associated with increased cell recoveries (p < 0.002). In a fourth study, there was a clear effect of alcohol on increasing the numbers of cells recovered (p = 0.004). Transit time and stool weight were not reliably associated with increased cell recovery, but stool consistency was a significant (p < 0.010) factor influencing cell recovery in all three studies investigated. Exfoliated cells are a source of genomic DNA which was successfully isolated from 93.3% of samples, but only 11.7% of these extractions produced DNA yields of 3μg or more, so that quantification of adduct levels could not be determined by a sensitive immunoslot blot analysis. However, direct visualization of diet related adduct formation was possible, and could be quantified as percentages of cells staining positive for the N-nitroso compound (NOC) related adduct, O6 carboxymethyl guanine. A red meat diet significantly (p = 0.001) increased percentages of isolated cells staining positive for this adduct compared with a vegetarian diet, and there was a significant correlation (r = 0.66) between measures of faecal ATNC concentration and the percentages of positive cells on an individual basis.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available