Longo F J, Mathews L, Palazzo R E
Department of Anatomy, University of Iowa, Iowa City 52252.
Dev Biol. 1994 Mar;162(1):245-58. doi: 10.1006/dbio.1994.1082.
Following their incorporation into oocytes, sperm nuclei (SN) of the surf clam, Spisula solidissima, undergo an initial expansion, followed by condensation and then a dramatic enlargement during their development into male pronuclei. These changes are temporally correlated with alterations in the maternal chromatin: germinal vesicle breakdown (GVBD), meiotic maturation, and female pronuclear development, respectively. To analyze possible changes occurring in SN at fertilization, surf clam oocyte extracts, prepared before and after parthenogenetic activation, were examined for their ability to affect SN in vitro. Sperm heads were incubated in extracts for variable periods up to 5 hr. Extracts prepared from oocytes following GVBD (15 min postactivation) induced an expansion in approximately 90% of SN by 60 min incubation. However, when SN were incubated in extracts from unactivated or 4-min-activated oocytes only approximately 30% underwent expansion. Ultrastructural examination of specimens taken at increasing periods of incubation in oocyte extracts revealed that SN expansion in vitro resembled chromatin decondensation in vivo. SN incubated 1 to 5 hr in extracts prepared from oocytes following GVBD consisted of decondensed chromatin surrounded to varying degrees by membranous cisternae. Staining with anti-lamin antibody was variable: some specimens (60-70%) were positive while others (30-40%) were weak to negative. In contrast, all decondensed SN incubated in extracts from postmeiotic oocytes (65 min postactivation) were delimited by an intact nuclear envelope possessing nuclear pores and reactive to anti-lamin antibody. Decondensation of SN in 15- or 65-min extracts was blocked by EDTA, 2,6-dimethyl-ami-nopurine, histone, and protamine. The presence (65-min extract) and absence (unactivated, 4- and 15-min extracts) of sperm nuclear envelope assembly in vitro is consistent with events in vivo, where such a structure forms after meiotic maturation in concert with the development of the female pronucleus.
在被纳入卵母细胞后，厚壳蛤（Spisula solidissima）的精核（SN）会经历最初的膨胀，随后凝聚，然后在发育成雄原核的过程中急剧增大。这些变化在时间上分别与母本染色质的改变相关：生发泡破裂（GVBD）、减数分裂成熟和雌原核发育。为了分析受精时SN可能发生的变化，对孤雌激活前后制备的厚壳蛤卵母细胞提取物影响SN的体外能力进行了检测。将精子头部在提取物中孵育不同时长，最长可达5小时。从GVBD后（激活后15分钟）的卵母细胞制备的提取物，孵育60分钟后可使约90%的SN发生膨胀。然而，当SN在未激活或激活4分钟的卵母细胞提取物中孵育时，只有约30%会发生膨胀。对在卵母细胞提取物中孵育时间不断增加的标本进行超微结构检查发现，体外SN膨胀类似于体内染色质解聚。在GVBD后从卵母细胞制备的提取物中孵育1至5小时的SN由解聚的染色质组成，周围有不同程度的膜性池包围。用抗核纤层蛋白抗体染色的结果各不相同：一些标本（60 - 70%）呈阳性，而其他标本（30 - 40%）呈弱阳性或阴性。相比之下，在减数分裂后卵母细胞（激活后65分钟）的提取物中孵育的所有解聚SN都由具有核孔且对抗核纤层蛋白抗体有反应的完整核膜界定。15分钟或65分钟提取物中SN的解聚被EDTA、2,6 - 二甲基氨基嘌呤、组蛋白和鱼精蛋白阻断。体外精子核膜组装的存在（65分钟提取物）和不存在（未激活、4分钟和15分钟提取物）与体内事件一致，在体内这种结构在减数分裂成熟后与雌原核的发育同时形成。
