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JK Sugden 《Biotechnic & histochemistry》2004,79(2):71-90
An overview of the basic principles of photochemistry is presented to facilitate discussion of fluorescence, quenching and quantum yields. These topics in turn provide the foundation for an account of fluorescence spectroscopy and its application to microscopy. A brief overview of light microscopy and the application of fluorescence microscopy is given. The influences of molecular features, such as aromatic character and substitution patterns, on color and fluorescence are described. The concept of color fading is considered with particular reference to its effect on microscopic preparations. A survey of representative fluorescent probes is provided, and their sensitivity, application, and limitations are described. The phototoxicity of fluorescent molecules is discussed using biomembranes and DNA as examples of targets of toxicity. Photodynamic therapy, a relatively new clinical application of phototoxicity, is described. Both anticancer and antimicrobial applications are noted, and an assessment is given of the current ideas on the ideal physicochemical properties of the sensitizing agents for such applications. 相似文献
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The histological effect on and stress response of post juvenile Clarias gariepinus exposed to Qua Iboe crude oil and rig wash were investigated. Fish weighing 60–90 g and measuring 16–18 cm were exposed for 7–28 days to 8.00 ml?1 Qua Iboe crude oil and 0.0018 ml–1 rig wash, both being 0.1 of the 96 hr LC50. Blood samples of C. gariepinus were collected every seven days and evaluated for stress by measuring cortisol concentration. The gills and liver were studied and scored for Gill Alteration Index (GAI) and Hepatic Alteration Index (HAI), respectively. There was an increase in cortisol level up to the 7th and 14th day among the group exposed to Qua Iboe crude oil, with a decrease on the 21st and 28th day. The rig wash group increased in cortisol level up to the 7th day and decreased slightly on the 14th day, after which the trend became irregular. The toxic effects of the Qua Iboe crude oil and rig wash were time dependent, as shown by the histopathological alteration index (HAI) of gill and liver. After 28 days of exposure, the gills had irreparable damage due to high frequency of cellular necrosis and degeneration, whereas the liver had from moderate to severe damage due to the high frequency of cellular degeneration and inflammation. Qua Iboe crude oil and rig wash are both toxic to C. gariepinus, therefore their indiscriminate discharge to the environment must be discouraged. 相似文献
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Hypomethylation of DNA during differentiation of friend erythroleukemia cells 总被引:14,自引:0,他引:14
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JK Christman N Weich B Schoenbrun N Schneiderman G Acs 《The Journal of cell biology》1980,86(2):366-370
DNA from mammalian cells has been shown to contain significant amounts of 5-methyl cytosine resulting from enzymatic transfer of methyl groups from s-adenosylmethionine to cytosine residues in the DNA polymer. The function of this modification is not known. We have found that DNA synthesized during chemically induced differentiation of friend erythroleukemia cells is hypomethylated, as measured by its ability to accept methyl groups transferred by homologous DNA methyltransferases in vitro. The extent of hypomethylation detected by this sensitive method is small, a decrease of less than 1.6 percent in 5-methylcytosine content. Hypomethylated DNA can be isolated from friend erythroleukemia cells grown in the presence of dimethyl sulfoxide, butyrate, hexamethylene-bis- acetamide, pentamethylene-bis acetamide, and ethionine. However, hypomethylated DNA is found only under conditions where differentiation is actually induced. DNA isolated from cells of a dimethyl sulfoxide- resistant subclone grown in the presence of that agent is not hypomethylated, although DNA of these cells becomes hypomethylated after growth in the presence of inducers that can trigger their differentiation. We also find that the DNA of friend erythroleukemia cells does not become hypomethylated when the cells are exposed to inducing agents in the presence of substances that inhibit differentiation. These results suggest a close link between genome modification by methylation and differentiation of friend erythroleukemia cells. 相似文献
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Miguel DC Ferraz ML Alves Rde O Yokoyama-Yasunaka JK Torrecilhas AC Romanha AJ Uliana SR 《Memórias do Instituto Oswaldo Cruz》2010,105(7):945-948
The activity of the antineoplastic drug tamoxifen was evaluated against Trypanosoma cruzi. In vitro activity was determined against epimastigote, trypomastigote and amastigote forms of CL14, Y and Y benznidazole resistant T. cruzi strains. Regardless of the strain used, the drug was active against all life-cycle stages of the parasite with a half maximal effective concentration ranging from 0.7-17.9 μM. Two experimental models of acute Chagas disease were used to evaluate the in vivo efficacy of treatment with tamoxifen. No differences in parasitemia and mortality were observed between control mock-treated and tamoxifen-treated mice. 相似文献
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