Many substances in the plant kingdom and in man's diet occur as glycosides. Recent studies have indicated that many glycosides that are not mutagenic in tests such as the Salmonella/microsome test become mutagenic upon hydrolysis of the glycosidic linkages. The Salmonella/microsome test utilizes a liver homogenate to approximate mammalian metabolism but does not provide a source of the enzymes present in intestinal bacterial flora that hydrolyze the wide variety of glycosides present in nature. This investigation was designed to study the effect of stable cell-free extracts from enteric bacteria of human feces, fecalase, which was shown to contain glycosidases which bioactivate in vitro many natural diet glycosides to compounds which are mutagenic in the Salmonella/ liver homogenate test. Cantaloupe (Cucumis melo); Raspberry (Rubus idaeus), Red and Yellow Onion (Allium cepa) varieties all contain quercetin which presumably forms mutagenic flavonol glycosides in the gut. The White Onion does not contain quercetin. Flavonol extract of Cantaloupe, Raspberry, Red and Yellow varieties of onion were mutagenic in the test when fecalase was added. Frameshift mutagenicity (TA 1537, TA 98, and TA 97) among the flavonoid extracts tests was mainly confined to the flavonols (flavon-3-ols). The base-pair mutants (TA 1535, TA 100) did not show mutagenic activity upon testing the flavonoid extracts of the samples investigated in this study. Since the flavonols are probably the single largest group of flavonoids, and the mutagenic agent detected, quercetin, is the most common flavonol aglycone, plant breeding has been suggested to reduce the amount of flavonoids present in the food we eat. / Graduation date: 1983

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1954. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1949. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 43-45).

Thesis (Ph. D.)--Illinois State University, 1992. / Title from title page screen, viewed January 30, 2006. Dissertation Committee: Herman E. Brockman (chair), Alan J. Katz, Brian J. Wilkinson, Lynne A. Lucher, Radheshaym Jayaswal. Includes bibliographical references (leaves 115-123) and abstract. Also available in print.

Thesis (M.S.)--University of Iowa, 2007. / Supervisor: Gabriele Ludewig. Includes bibliographical references (leaves 56-61).

Numerous studies on bacterial systems have shown that cell survival following exposure to various mutagens is greatly influenced by the capacity of the cells to repair the induced DNA lesions. Caffeine (1-3-7-trimethyI xanthine), has been shown to reduce this repair-capacity thereby producing mutagenic, and cytotoxic effects. The question was raised as to whether or not caffeine might reduce the repair-capacity of mammalian cells by interacting with the DNA lesions produced by either the carcinogenic, and oncogenic 4-nitroquinoIine l-oxide, or ultraviolet light (UV) irradiation. This was of interest due to the potential applications that synergistic relationships may hold for chemotherapy. An established line of Syrian-hamster cells (BHK-21, clone 13), was used throughout the experiments. Arginine deprivation was employed to arrest the cultured cells at G₁-phase. The mutagenic 4NQO, UV, and caffeine were applied to these non-dividing cells. The caffeine exposure was at varying time intervals prior to, during, and after 4NQO-induced DNA-repair synthesis (unscheduled DNA synthesis). Similarly, caffeine was added to cells immediately following UV-induced DNA-repair synthesis. Exposure of BHK-21 cells to caffeine, and 4NQO appeared to reduce their colony-forming ability to a greater extent than when the cells were exposed to either chemical alone. The addition of caffeine combined with 4NQO to cells, in G₁-phase, did not appear to significantly influence their rate of flow into S-phase, or through to metaphase. The effect of caffeine on 4NQO- (but not UV-) induced DNA-repair synthesis, using isotope labelling, and autoradiography suggested a reduction in the amount of DNA-repair synthesis. This reduction appeared to be dependent on the caffeine concentration, and on the time of exposure of the cells to this chemical. An initial inquiry was made into whether or not this synergistic effect between caffeine and 4NQO-induced DNA-repair synthesis could be detected in human lymphocytes in vitro. However, very low levels of 4NQO-induced DNA-repair synthesis were observed in these cells. It was therefore not conducive for the autoradiographic analysis of DNA-repair synthesis following 4NQO exposure. A model explaining the apparent caffeine suppression of 4NQO-induced DNA-repair synthesis is postulated. The potential medical implications are discussed. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

No description available.

The sweet potato has become a major international crop and it is also the main staple food for many people in the developing world. This crop is desirable as it is high yielding, easy to grow and has a low cost of production. However, the tubers have a low protein content and a low concentration of amino acids, particularly the aspartate amino acid. This has contributed to malnutrition in some areas. To help overcome this problem this study had the aim of producing lines of sweet potato with increased nutritional values. Two varieties, Beauregard and LO322, were selected for study as they have a good flavour and a high beta-carotene content. The conditions for the tissue culture of these varieties were determined by altering the mineral and hormonal composition of the culture medium. Increases in nutritional composition were induced by treating calli with mutagenic agents which included : colchicine, ethylmethanesulphonate, UV radiation and two levels of gamma radiation. Putative mutants with reduced feedback inhibition in the pathways which lead to the synthesis of the aspartate amino acids were selected by placing calli on media containing increasing concentrations of lysine and threonine. During the final stage of the selection process, calli were placed on a medium without the addition of selection agents. The results from the tissue culture study suggest that media, 2, 4-D and explant size affect callus growth. MSMA medium (a modified Murashige and Skoog medium) was the most suitable for growing the callus of Beauregard whilst modified White's medium (MW) was better for the growth of LO322 calli. The most prolific callus growth was exhibited by explants of the cultivar Beauregard when placed on MSMA medium. This combination was used to determine the potential of mutagenic treatments to improve the nutritional qualities of the sweet potato. Results from treatments with mutagenic agents showed that all mutagens used had the capability of increasing the soluble protein content of callus. These treatments also had the capacity to increase the concentration of aspartate and other amino acids. Of the mutagens trialed, a treatment with 500 rad gamma radiation appears to be the most suitable for increasing protein and amino acid concentrations. Therefore, once the conditions for regeneration of shoots from calli have been determined this study suggests that it should be possible to produce lines of sweet potato with increased nutritional values using this agent / Master of Science (Hons)

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Daniel T. Simmons, Dept. of Biological Sciences. Includes bibliographical references.