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Inhibitors of protein synthesis block action of cholera toxin 总被引:4,自引:0,他引:4
Prior treatment of macrophages with cycloheximide blocked the activation of adenylate cyclase by choleragen. The effect of cycloheximide was time and dose dependent and also caused by puromycin. Toxin receptors and the catalytic and regulatory components of the cyclase were still present. As degradation and generation of the A1 subunit of choleragen was also blocked, we propose the existence of a membrane component that mediates the translocation of choleragen across the membrane. 相似文献
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In Chinese hamster cells, hydroxyurea and 5-fluorodeoxyuridine have both been shown to induce nuclear membrane associated DNA synthesis after release from different periods of inhibition. This synthesis occurs in cells which have lost their ability to form clones. The DNA precursors in the medium, the cell pools and the effectiveness of the inhibitors influence the time of expression of these effects. In cells with pre-labelled DNA, nuclear swelling occurs followed by an association of labelled DNA with the nuclear membrane. Eventually degraded DNA, expressed as a reduction in grain counts, is lost from the cells. It is suggested that cell nucleases are responsible for this process. DNA synthesis can still occur in these cells for a certain period while the DNA is associated with the nuclear periphery. 相似文献
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The activity levels of DNA polymerases α and β have been measured by autoradiography in squash preparations from rat testis of sexually mature animals. Similar results were obtained with ‘fixed’ samples (dipped in acetone: ethanol for 5 min at 25 °C) or ‘unfixed’ samples (frozen in liquid nitrogen and freeze-dried). The activities of DNA polymerases α and β in situ were distinguished by differential assay conditions and by selective inhibition with compounds such as N-ethylmaleimide and aphidicolin. Using the endogenous chromatin as template, maximal activity for both enzymes was obtained in the presence of all four deoxyribonucleoside triphosphates, MgCl2 and ethylene glycol. When DNA polymerase activities in several predominant testicular cell types (pre-leptotene primary spermatocytes, pachytene primary spermatocytes, round spermatids and elongated spermatids) were quantitatively compared, on a per cell basis, the following percentage distribution was observed:
Pre-leptotene primary spermatocyte % | Pachytene primary spermatocyte % | Round spermatid % | Elongated spermatid % | |
DNA polymerase α | 25 | 42 | 30 | 3 |
DNA polymerase β | 29 | 34 | 36 | 1 |