Dietary protein intake has been observed to influence the induction of cancer in animals exposed to carcinogens, presumably by affecting the activities of enzyme systems which metabolize them. One such carcinogen is aflatoxin B₁ (AFB₁) a mold metabolite and frequent contaminant of foodstuffs. Variations in the levels of dietary proteins fed rats and rainbow trout (Salmo gairdneri) influence the induction of hepatocellular carcinoma by AFB, in these animals. The following work was undertaken to provide an explanation of these results in terms of AFB₁ in vitro metabolism. The effect of dietary casein and fish protein concentrate (FPC) levels upon the activities of potential AFB₁ metabolizing enzyme systems were studied in the rainbow trout (Salmo gairdneri). Hepatic subcellular protein and cytochrome P-450 contents, and the activities of glutathione-S-epoxide transferase (GTr) epoxide hydrase (EH) cytochrome c reductase and aldrin epoxidase (AE) enzymes were determined in trout fed varying levels of casein or FPC. In addition, the reduction of AFB₁ to aflatoxicol (AFL) and conversion to an active mutagen for Salmonella typhimurium TA 98 were examined. A prerequisite for this study was the adaptation of the Ames mutagen assay system for use with fish hepatic enzymes. Lowered hepatic GTr and AE activities and increased conversion of AFB₁ to AFL and to a microbial mutagen were noted in trout fed high protein diets relative to those fed low protein diets. Cytochrome P-450 content was observed to decrease with increasing dietary casein and increase with increasing dietary FPC. Hepatic EH activity remained constant and decreased in trout fed increasing levels of casein or FPC respectively. These changes in enzyme activity are discussed in relation to dietary influences upon AFB₁ carcinogenesis in the rainbow trout. / Graduation date: 1978

Graduation date: 1979

Photocopy of typescript. / Digitized by Kansas Correctional Industries

This investigation studies the effects of diets containing varying amounts of linoleic acid (a polyunsaturated fatty acid) and stearic acid (a saturated fatty acid) on tumorigenesis, weight and longevity in strain A/ST mice. Linoleic acid [ 18 carbons and 2 double bonds (18:2)] was chosen to represent a fatty acid known to enhance tumorigenesis and obesity in certain strains of mice. Stearic acid [ 18 carbons and no double bonds (18:0)] represents a saturated fatty acid known to increase the latency period for mammary tumor development and to decrease the rate of tumor growth. This study was conducted to determine whether the effects of fatty acids observed in younger mice on time to tumor, survival and body weights were also found in aging animals. Further, by varying the amount of linoleic acid in the diet, this study examined whether the tumor enhancing effects of increasing amounts of linoleic acid could be overcome by the incorporation of dietary stearic acid. All diets had equal percentages, by weight, of protein, salt, sucrose, mineral salt, and vitamin levels and an equal number of calories per gram of food. The SF diet was rich in linoleic acid. The SA-1 diet contained enough linoleic acid to prevent essential fatty acid deficiency, and the SA-4 diet contained the maximal amount of linoleic acid for tumor enhancement. Total body weight and tumor production in the three dietary groups show a relationship between an increase in body weight and tumor production as the amount of dietary linoleic acid increases. There also is an inverse relationship between animal survival and body weight as the amount of dietary linoleic acid increases. Survival thus appears to be dependent on tumor production in the three dietary groups, where there appears to be an inverse relationship between survival and time to tumor as the amount of dietary linoleic acid increases at each timepoint. These results suggest that the inclusion of stearic acid in the diet can, in part, overcome this enhancing effect of linoleic acid, even at the optimal tumor producing level of linoleic acid. The results of this study indicate that that effects of linoleic and stearic acid in aging mice are similar to those in younger animals. / Department of Biology

Not available / text

Thesis (MNutr (Interdisciplinary Health Sciences. Human Nutrition))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: See full text for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

[Truncated abstract] This thesis examines the potential role of dietary intake in the development of two common conditions affecting the prostate gland; prostate cancer and benign prostatic hyperplasia (BPH). Diet is of interest as a potential risk factor for prostate cancer because of geographical variations in prostate cancer incidence and increased prostate cancer risks associated with migration from Asian to western countries. Some geographical variation has been suggested for BPH, but this is less certain. However, both prostate cancer and BPH have potential links with diet through their positive associations with sex hormone levels, metabolic syndrome, increased insulin levels and chronic inflammation. In addition, zinc is an essential dietary micronutrient required for semen production in the prostate gland. The original work for this thesis is presented in six manuscripts of which, four have been published in peer-reviewed journals (at the time of thesis completion). BPH investigated in this thesis is defined as surgically-treated BPH. The following hypotheses were investigated. Regarding foods, nutrients and the risk of prostate cancer and BPH: 1. Increasing intakes of fruits, vegetables and zinc are inversely associated with the risk of prostate cancer and BPH 2. Increasing intakes of total fat and calcium are positively associated with the risk of prostate cancer and BPH. 3. Dietary patterns characterised by high meat, processed meat, calcium and fat content are positively associated with the risk of prostate cancer and BPH. 4. Dietary patterns characterised by high fruit and vegetable and low meat content are inversely associated with the risk of prostate cancer and BPH. v Regarding methodological issues related to the study of diet-disease relationships: 5. Dietary patterns (overall diet) elicited from principal components analysis yield stronger diet-disease associations than when studying isolated nutrients. 6. Remotely recalled dietary intake is reliable enough to be used in studies of chronic disease with long latency periods, such as prostate cancer and BPH. Methods: Data from two studies was used to address the hypotheses above. ... Based on the literature reviewed and the original work for this thesis, the most important dietary risk factors for prostate cancer and BPH appear to be those common to western style diets, i.e. diets high in red meat, processed meat, refined grains, dairy products, and low in fruit and vegetables. This type of diet is likely to result in marginal intakes of antioxidants and fibre, excess intakes of fat and possibly, moderate intakes of carcinogens associated with processed meat and meat cooked at high temperatures. These dietary factors have been linked with biomarkers of inflammation, and they support the hypotheses that chronic inflammation is involved in the development of both prostate cancer and BPH. In addition, this work builds on evidence that zinc is an important factor in prostate health. There is scope for more investigation into the reliability of dietary patterns and the use of nutrient patterns as an alternative to focussing on single food components. Further studies on the reliability of remote dietary intake would also be useful. Because of the latency of chronic disease, it can be theorised that remote dietary recall may uncover more robust diet-disease relationships.

No description available.

Bibliography: leaves 150-166. / ix, 166, xxii leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / To assess the role of acetylator status and glutathione S-transferase[mu] (GST[mu]) null phenotype on the risk for development of colorectal neoplasms in humans and to determine whether this was influenced by the dietary intake of meat. / Thesis (M.D.)--University of Adelaide, Dept. of Medicine, 1995?

Bibliography: leaves 253-286 / vi, 299 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (M.D.)--University of Adelaide, Faculty of Medicine, 1988