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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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Lupron depot prevention of antispermatogenic/antifertility activity of the indenopyridine, CDB-4022, in the rat. 总被引:2,自引:0,他引:2
The goals of this study were to determine the CDB-4022 dose-response relationship for induction of acute decreases in testicular weight and germ cell depopulation in rats; establish the threshold dose of CDB-4022 required to induce infertility; and investigate whether CDB-4022-induced testicular damage could be prevented by a GnRH agonist (Lupron Depot). Reduction of testis weight and germ cell depopulation were observed 7 days after a single oral dose of 1 mg CDB-4022/kg, whereas 0.5 mg/kg had no observable effect. These effects were maximal at 12.5 or 25 mg CDB-4022/kg. After a single oral dose of either 2.5 or 5 mg/kg, CDB-4022 induced infertility in five of five treated rats by Week 5, whereas only one of five males was rendered infertile at a dose of 1 mg/kg. Proven fertile male rats (6/group) were treated with vehicle, CDB-4022 alone (2.5 mg/kg on Day 0), CDB-4022 plus Lupron Depot (on Weeks -1, 2, 5, and 8), or Lupron Depot alone. Control males demonstrated normal fertility throughout a 32-wk cohabitation period. Five of six rats were rendered transiently infertile with Lupron Depot alone, but all recovered fertility. CDB-4022 treatment resulted in infertility in all six rats, and only one of six regained fertility. Combined treatment also caused infertility in all six rats, but four of six recovered fertility (P = 0.08 compared to CDB-4022 alone). Testicular weight was decreased in the three treatment groups compared to vehicle controls; testicular weights were ranked from highest to lowest as follows: vehicle > Lupron Depot > Lupron Depot + CDB-4022 > CDB-4022. The tubule differentiation index of Lupron Depot-treated rats (96 +/- 4%) was not different from vehicle-treated rats (100%). CDB-4022 treatment decreased the number of differentiating tubules (15 +/- 8%). Lupron Depot plus CDB-4022 treatment resulted in a greater number of differentiating tubules (53 +/- 12%) than CDB-4022 alone, but this was still lower than vehicle- or Lupron Depot-treated rats. These data indicate that 2.5 mg/kg of CDB-4022 was the oral threshold dose that caused testicular damage rendering the majority of adult male rats permanently infertile within the study interval; 12.5 mg/kg of CDB-4022 induced maximal testicular damage. Suppression of gonadotropins and/or testosterone production by treatment with Lupron Depot before and after CDB-4022 prevented the CDB-4022-induced irreversible testicular damage. 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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