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OBJECTIVES: To assess the value of the cervical smear test to women, taking account of the positive and negative aspects of the cervical screening service. DESIGN: A postal survey. SETTING: Tayside Health Board region of Scotland. PARTICIPANTS: A sample of 2000 women aged 20-59. MAIN OUTCOME MEASURES: Maximum willingness to pay (WTP) for a cervical smear test. RESULTS: Women were prepared to pay 50.20 British pounds per smear on a 3-yearly basis. Willingness to pay was positively related to income, but unrelated to age and whether or not the respondent had previously had a smear. CONCLUSIONS: Previous studies have estimated the cost per screen or cost per life year saved by cervical screening. This study used the economic instrument of WTP to take account of other potential (dis)benefits to women. The value women place on having a smear was more than the cost to the National Health Service (NHS) of providing the service. The output of a WTP study is potentially useful at the policy level. Future work should explore both the value of alternative approaches to cervical screening, and the value of competing health care interventions. 相似文献
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The rate of the aerobic metabolism of pyruvic acid by bakers' yeast cells is determined mainly by the amount of undissociated acid present. As a consequence, the greatest rate of oxidation was observed at pH 2.8. Oxidation, at a slow rate, started at pH 1.08; at pH 9.4 there was no oxidation at all. The anaerobic metabolism, only a fraction of the aerobic, was observed only in acid solutions. There was none at pH values higher than 3. Pyruvic acid in the presence of oxygen was oxidized directly to acetic acid; in the absence of oxygen it was metabolized mainly by dismutation to lactic and acetic acids, and CO2. Acetic acid formation was demonstrated on oxidation of pyruvic acid at pH 1.91, and on addition of fluoroacetic acid. Succinic acid formation was shown by addition of malonic acid. These metabolic pathways in a cell so rich in carboxylase may be explained by the arrangement of enzymes within the cell, so that carboxylase is at the center, while pyruvic acid oxidase is located at the periphery. Succinic and citric acids were oxidized only in acid solutions up to pH 4. Malic and α-ketoglutaric acids were not oxidized, undoubtedly because of lack of penetration. 相似文献
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Dilute solutions of sulfhydryl enzymes (phosphoglyceraldehyde dehydrogenase, adenosinetriphosphatase, succinoxidase) showed reduced activity on irradiation by small amounts of x-rays. When the inhibition was partial the enzyme was reactivated on addition of glutathione. When the inhibition was more complete, reactivation was only partial. These observations are interpreted as being due to oxidation of the -SH groups of the protein by the products of water irradiation, the radicals OH and O(2)H, and H(2)O(2) and atomic oxygen. The irreversible inhibition which occurs when the dose of x-rays is increased is attributed to protein denaturation. Inhibition of the non-sulfhydryl enzymes trypsin, catalase, and ribonuclease, which required larger amounts of x-rays, is attributed to protein denaturation. These experiments are further evidence that inhibition of enzymes by ionizing radiations is due to the indirect action of the products of irradiated water rather than to direct ionization of the enzyme through collision with the ionizing radiation. 相似文献
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Thiol compounds, such as glutathione, 2,3-dimercaptopropanol (BAL), propane-1,3-dithiol, and N-phenylaminopropanedithiol, were readily oxidized by x-rays, beta rays, and gamma rays. The ionic yield for this oxidation was about the same, 3 at pH 7, on irradiation with x-rays and with beta rays; it was 23 per cent less on irradiation with gamma rays. The ionic yield varied with the hydrogen ion concentration, increasing as the pH value increased. There was no reduction of oxidized glutathione on irradiation with dosages of x-rays and gamma rays which produced oxidation of the reduced compound. In the absence of oxygen, the oxidation of thiols by ionizing radiations was only 33 per cent of that obtained in the presence of dissolved oxygen. When the thiol solutions were irradiated in the presence of dissolved oxygen, catalase protected them from oxidation by 17 to 27 per cent. 相似文献
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Aqueous dilute solutions of ferrocytochrome c were easily oxidized by x-rays, the oxidation being proportional to the intensity of irradiation. The ionic yield was 0.54. The oxidation produced by 10,000 r. was completely reversed on addition of dithionate. The oxidation seems to be brought about only by OH radicals produced on x-irradiation of water, because catalase offered no protection and the absence of oxygen did not reduce the extent of oxidation.X-Irradiation attacked also the protein and porphyrin components of cytochrome. The protein portion was more sensitive in alkaline solutions, whereas the porphyrin portion was more sensitive in acid solutions. X-irradiation seems to produce an oxidation of the chromophore double bond groups of porphyrin, which is manifested by a decrease of all the absorption bands characteristic of this substance. The ionic yield, as calculated from a decrease of the Soret band, was rather low: 0.015 in neutral solutions, and 0.046 in acid solutions. 相似文献
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