【摘要】 近年发现Ｃａ２＋、钙调蛋白参与细胞核内的许多生命活动，其中可能与染色质的凝集与去凝集有关，我们利用爪蟾卵非细胞体系研究了Ｃａ２＋对体外核重建的影响。分别含３ｍＭ的ＥＧＴＡ（低钙）与含２．５ｍＭ的ＣａＣｌ２（高钙）的核重建反应体系呈现的结果明显不同。在正常对照与加入ＥＧＴＡ的样品中，非洲爪蟾去膜精子在卵提取物中均能去浓缩并形成典型间期核结构，而加入Ｃａ２＋的样品中，去膜精子永远呈浓缩状态，不能形成间期样核。用电镜观察，在正常对照样品中，去膜精子染色质能完全去浓缩，形成重构核，有完整的双层核膜和核孔复合体。含ＥＧＴＡ的样品中，去膜精子也能形成重构核，其形态与正常核无明显区别，而加入Ｃａ２＋的样品中，去膜精子却处于高度凝集的状态，不能形成双层核膜与核孔复合体。在对照样品与含ＥＧＴＡ（低钙）的样品中形成的重构核均有ＤＮＡ复制的活性，而在高浓度Ｃａ２＋的样品中没有ＤＮＡ复制的迹象。以上结果说明高浓度Ｃａ２＋对染色体的去凝集、间期核形成有抑制作用，而降低Ｃａ２＋浓度对核重建没有明显的影响。更多还原

【Abstract】 Ca 2+ and camodulin have been found to play an important role in many activities relating to cell nuclei such as chromatin condensation and decondensation.Here we foucus on the effect of Ca 2+ on cell free nuclear reassembly in Xenopus laevis egg extracts.When EGTA(final conc.3mM) were introduced into the cell free system,demembranated sperms of Xenopus decondensed and formed interphase nuclei which was similar to those formed in normal extracts.In contrast,the sperms in the extracts with extra added Ca 2+ (final conc.2 5mM) retained their condensation forms and could not change into interphase nuclei.By electron microscopy,no difference could be found in the nuclei formed in EGTA extracts with normal ones,while in Ca 2+ extracts,some membrane vesicles attached to the surface of sperms but could not fuse each other,neither double nuclear membrane nor nuclear pore complexes could be found,the sperm chromatin were staying in a high condensation state.The nuclei from the extracts with low Ca 2+ concentration had DNA replication activity but those from Ca 2+ extract did not.These results show that high Ca 2+ concentration could inhibit nuclear formation while low Ca 2+ concentration have no effect.更多还原