Browsing by Subject "Colon (Anatomy)"
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Item Dietary fat and antioxidant status relating to colon carcinogenesis(Texas Tech University, 1993-05) Tsai, Shwu-yarEpidemiological evidence has linked dietary fat with colorectal cancer in humans but with mixed results. Studies using animal models have shown that high fat diets containing predominantly corn oil, beef tallow or lard induce colon tumorigenesis to a greater extent than corresponding low fat diets; however, these findings are still inconclusive. Recently, some research indicated differences according to the types of fat used and support the concept that diets high in unsaturated fatty acids have a greater tumor-promoting capability than diets high in saturated fatty acids. The mechanism was proposed that free radicals were involved in colon carcinogenesis. Therefore, a polyunsaturated fatty acid (PUFA) diet would increase antioxidant activity to prevent free radical damage. Several studies have indicated that dietary lipids influence the liver microsomal mixed function oxidase system. It has been reported that the elevation of dietary polyunsaturated fatty acid intake increases the activity of the liver microsomal enzymes responsible for carcinogen metabolism. Some studies directed the diet-related effect on the susceptibility of colonic cells to nuclear-damaging agents. However, there have been very few studies on the effects of dietary fat and nuclear aberrations due to xenobiotics challenge. The purpose of this study was to examine the effect of amount and type of dietary fat on the (1) colon mucosal antioxidant status; (2) liver microsomal demethylase activity; (3) liver microsomal and cytosolic mutagenic activation; and (4) colonic epithelial nuclear aberrations during colon carcinogenesis.Item Heme iron from beef and its role in colon carcinogenesis(Texas Tech University, 1996-08) Lai, Chih-HueiRed meat is an important dietary source of iron compared to other animal products (Table 1). Animal products contribute about 28% of the total iron to the food supply (National Research Council, 1988) Iron is an essential metal in mammals for oxygen and cart>on dioxide transport by hemoglobin and for the function of many enzymes, including catalase and cytochromes Iron also is required for the growth of all living cells, including tumor cells. In fact, the role of iron in cell proliferation is thought to represent an important factor in the clonal expansion of cancer cells. Studies have shown that transferrin, the major serum iron binding protein, is one of the essential substances required for the growth of cells in serum free media (Hann et al., 1988). Results of some studies have been consistent with the hypothesis that increased body iron stores are associated with an increased risk of cancer (Stevens et al, 1986; Selby and Friedman, 1988). Stevens et al. (1988) stated that iron may influence the risk for some cancer sites, including colon, bladder and lung Kapsokefalou and Miller (1993) stated that the interaction of lean beef and beef fat enhances nonheme iron absorption in rats. Cermak et al (1993) reported that chronic exposure of tumor cells to iron may, by induction of the intracellular iron scavenger, ferritin, contribute to the resistance of various tumors to oxidant-producing immune effector cells that require iron for their cytotoxic effect. Some studies show that dietary iron enhances the tumor rate in DMH-induced (1,2-dimethylhydrazine dihydrochloride) colon carcinogenesis in mice (Siegers et al, 1988). However, the role of heme iron from beef in colon carcinogenesis still is not clear. The objective of this study was to investigate the effects of beef as a dietary iron source and its contribution to colon carcinogenesis.Item Lack of colon promoting carcinogenesis by beef in the rat model(Texas Tech University, 1995-12) Butler, Micah JohnThe possibility that eating red meat might cause colon cancer has received much attention by the popular press. An article in Time magazine carried the headline "Red Alert on Red Meat" (Toulexis, 1990). Additionally, a cartoon accompanying a New York Times column showed a man using a saw to cut away the section of a dining table that held a platter of steak. When articles and pictures such as these are appearing in major newspapers and magazines, it is understandable that people have become concerned or even fiightened about eating red meat and rightly so as cancer is second only to heart disease as the leading cause of death in the United States (American Cancer Society, 1992). Colorectal cancer is the third leading cancer in both men and women (Figures 1 and 2) and accounted for 11% of all cancer deaths in males and 13% in females in 1992(Anonymous, 1992). Recent epidemiological studies have implicated red meat consumption as a risk factor for colon cancer in both men and women. A recent analysis of mortality data has identified animal fat in particular as the factor most strongly correlated with the risk for colon cancer (McKeon-Eyssen et al., 1984). The association between animal fat and colon cancer was said to be largely due to red meat consumption. However, a comparative study by Kinlin (1982) of strict religious orders in Britain showed that colon cancer mortality was not lower in religious orders that consumed no meat as compared to orders that regularly consumed meat as part of their dietary intake. Furthermore, it has been difficult to separate the effects of meat as a protein source from the accompanying fat content of the diets analyzed in these studies. Very little information has been published on the dietary effects of beef consumption on experimental colon cancer, so the issue still remains controversial. Therefore, the goal of this study was to rigorously study the effects of beef as a protein source, and the effects of fat source (beef tallow and com oil) at fat levels of 5 and 20%> and their contributions as dietary factors, as either promoters that increase the risk or protectors that reduce the risk, for colon carcinogenesis.