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11.
Activation of human ribosomal genes by 5-azacytidine 总被引:2,自引:0,他引:2
Cultured human fibroblasts were exposed to 5-azacytidine which inhibits methylation of newly synthesized DNA. A significant increase in the mean number of Ag-stained active nucleolus organizers has been observed in treated cells. This suggests that DNA methylation is involved in modulation of human rRNA synthesis. 相似文献
12.
Bruna Tadolini Diana Fiorentini Laura Landi Luciana Cabrini 《Free radical research》1989,5(4):245-252
To find experimental conditions to selectively study the propagation phase of lipoperoxidation we studied the lipoperoxidation, catalyzed by FeCl2, of liposomes in a buffering condition where Fe2+ autoxidation and oxygen active species generation does not occur. Liposomes from egg yolk phosphatidylcholine. prepared by vortex mixing, do not oxidize Fe2+: on the contrary they oxidize Fe2+ when prepared by ultrasonic irradiation. Dimyristoyl phosphatidylcholine liposomes prepared by ultrasonic irradiation do not oxidize Fe2+. During sonication polyunsaturated fatty acid residues autoxidize and lipid hydroperoxides (LOOH) are generated. Only when LOOH are present in the liposimes Fe2+ oxidizes and its rate of oxidation depends on the amount of LOOH in the assay. The reaction results in the generation of both LOOH and thiobarbituric acid reactive material (TBAR): it is inhibited by butylated hydroxytoluene and has a acidic pH optimum; it is not inhibited by catalase and OH' scavengers. The reaction studied. thus, appears to be the chain branching and propagation phase of lipoperoxidation. When we studied the dependence of Fe2+ oxidation, LOOH and TBAR generation on FeCl2 concentration, we observed that at high FeCl2 concentrations the termination phase of lipoperoxidation was prevalent. Thus. by selecting the appropriate FeCl2 concentration the proposed experimental system allows study of either the propagation or the termination phase of lipoperoxidation. 相似文献
13.
Nicoletta zini Patrizia Sabatelli Irene Faenza Andrea Ognibene Nadir M. Maraldi 《The Histochemical journal》1996,28(7):495-504
Summary Some key elements of signal transduction have been identified within the nucleus and demonstrated to be responsive to specific
agonists in numerous cell types. In particular, mitogenic stimuli have been reported to induce, a transient increase of the
nuclear phospholipase C β1 activity, causing the release of inositide-derived second messengers, whereas differentiating stimuli induced a decrease
of the enzyme activity and an increase of nuclear phosphatidylinositol 4,5-bisphosphate (PIP2). Recently, we reported evidence, in human osteosarcoma Saos-2 cell lines, on the presence of specific nuclear phospholipase
C isoforms and on the activation of phospholipase C β1 in the nucleus following the exposure to interleukin-1α. In this study we report immunocytochemical ultrastructural evidence on quantitative variations of PIP2 and phospholipase C β1 amounts in the nucleus of Saos-2 cells at different times of exposure to interleukin-1α. After short periods of culture in the presence of the agonist, the intranuclear amount of PIP2 is decreased, while a translocation of phospholipase C β1 occurs from the cytoplasm to the nucleus, in correspondence with the increased hydrolyzing activity of the enzyme. After
longer periods of incubation with interleukin-1α, on the other hand, the intranuclear amount of PIP2 is restored to initial level, while the amount of phospholipase C β1 is increased both at the nuclear and cytoplasmic level, when its activation is no longer effective. The results, compared
with those obtained in other cell types responsive to given agonists, account for a cell-specific modulation of signal transduction
based on polyphosphoinositide breakdown at the nuclear level. 相似文献
14.
M. Sari-Gorla S. Ferrario E. Frascaroli C. Frova P. Landi M. Villa 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,88(6-7):812-817
In order to assess the efficiency of male gametophytic selection (MGS) for crop improvement, pollen selection for tolerance to herbicide was applied in maize. The experiment was designed to test the parallel reactivity to Alachlor of pollen and plants grown in controlled conditions or in the field, the response to pollen selection in the sporophytic progeny, the response to a second cycle of MGS, and the transmission of the selected trait to the following generations. The results demonstrated that pollen assay can be used to predict Alachlor tolerance under field conditions and to monitor the response to selection. A positive response to selection applied to pollen in the sporophytic progeny was obtained in diverse genetic backgrounds, indicating that the technique can be generally included in standard breeding programs; the analysis of the data produced in a second selection cycle indicated that the selected trait is maintained in the next generation. 相似文献
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P. Pasquali L. Landi L. Cabrini G. Lenaz 《Journal of bioenergetics and biomembranes》1981,13(3-4):141-148
Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms ofK
M, although a decrease ofV
max is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant ofS. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III. 相似文献
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Long single-stranded DNA molecules have been observed at electron microscope in DNA preparations from synchronized Chinese hamster cells. The amount of single strandedness in parental DNA increases following a prolonged block of DNA synthesis by hydroxyurea as judged by the results obtained using an improved hydroxyapatite chromatography (Hanania et al., 1975). As far as newly replicated DNA is concerned, an increase of the single strand amount has been observed in DNA preparations from cells actively synthesizing DNA. 相似文献
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