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Educational Freedom in an Age of Anxiety . Twelfth Yearbook of the John Dewey Society, ed.
Freedom, Power, and democratic Planning . By K. Mannheim, Internat. Lib. of Sociol. & Soc. Reconstr.
Improving Teaching-Learning Processes . By Ray H. Simpson. 相似文献
Freedom, Power, and democratic Planning . By K. Mannheim, Internat. Lib. of Sociol. & Soc. Reconstr.
Improving Teaching-Learning Processes . By Ray H. Simpson. 相似文献
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Chemoprevention represents a new intervention strategy to control some type of carcinogenesis especially in subjects at high
risk for cancer development. Experimental and epidemiological data indicate that a variety of nutritional factors including
vitamin C and E are effective to lower the risk of some types of cancer. However large prospective studies have failed to
find such significant association. A comparative and combined in vitro antimutagenic potential of two antioxidant vitamins
ascorbic acid (vitamin C) and α-tocopherol (vitamin E) were evaluated using Ame’s Salmonella typhimurium test assay. Directly
acting mutagens such as sodium azide (NaN3) and 4-Nitro-o-phenylenediamine (NPDA), and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) were used to induce mutation in salmonella strains
TA 98 and TA 100. Vitamin C significantly (P < 0.01) and dose dependently inhibited the mutagenicity induced by all the three mutagens. The percent inhibitions of vitamin
C at 15 mg/plate were 33.8% (NaN3), 52.5 % (MNNG) and 55.4 % (NPDA). Vitamin E (15 mg/plate) was effective to inhibit mutagenicity induced by NaN3 and MNNG
but did not inhibit mutation induced by NPDA. Combination of vitamins (vitamin C plus vitamin E) produced only an additive
antimutagenic activity when compared to their activity at 5 mg/plate. The results of the study concluded that vitamin C is
a better antimutagenic agent than vitamin E and combination of vitamins did not produce any synergistic activity. 相似文献
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