中国对虾受精过程中精卵核的细胞学变化

中国对虾精子以其棘部顶端随机附着在卵上,精子在凝胶膜形成后,第一极体排出前入卵,精子入卵后,絮状的精核经过重建形成雄原核,中国对虾卵子排放时处于第一次成熟分裂的中期,卵子入海水时,纺锤体的长轴与质膜平行,卵子激活后,纺锤体的长轴开始旋转,旋转至纺鲑体长轴与质膜垂直时,由纺锤丝牵引着染色体向两极移动,外侧的染色体由质膜包裹形成第一极体,受膜举起后,由次级卵母细胞排放出第二极体,此后,单倍雌核重建形成雌原核,雄原核形成早于雌原核,雌雄原核于卵子中央联会形成联合核,受精后的50分钟纺锤丝牵关染色体称向两极,质膜内缢断裂形成两个细胞的胚胎。     

复合四倍体异育银鲫两种不同生殖方式的细胞学观察

在复合四倍体异育银鲫（）×银鲫（）的受精过程中,精子入卵后经过解凝、核化,最终形成雄性原核,并可与卵子的雌性原核融合,证明了复合四倍体异育银鲫卵子具有与两性融合生殖极为相似的拟两性融合生殖的能力;而在复合四倍体异育银鲫（）×兴国红鲤（）的组合中,精子入卵后以固缩状态存在,又表现出典型的雌核发育型生殖行为。因此我们认为复合四倍体异育银鲫具有两种不同的生殖发育机制。此外,我们还观察到在第一次有丝分裂中期有核物质被排斥到纺锤体之外的现象。本文就复合四倍体异育银鲫生殖发育的机制进行了初步的探讨。     

银鲫雌核发育的细胞学观察

在受精卵内,精子核呈凝缩状态,不形成雄性原核,没有看到两性原核融合。在刚产出的成熟卵子中没有看到极体,直到受精后10分钟(在水温19°—21℃)才有唯一的一个极体排出。在同一尾银鲫产出的同批卵子中,绝大多数具有成熟分裂中期的卵核,并在精子入卵后继续进行发育(雌核发育),接着排出唯一的一个极体;授精7分钟的少数卵子具有三极纺锤体状的核。根据现在的观察,双凤水库的银鲫是以雌核发育方式繁殖的种群。       

星射线、纺锤丝和纺锤体

动物细胞有丝分裂时"由两组中心粒之间的星射线形成了纺锤体",植物细胞是"从细胞的两极发出许多纺锤丝,纺锤丝,纺锤丝纵行排列在细胞的中央,形成一个梭形的纺锤体".(见高中全一册《生物学》P·32和P·28).所以教材把这作为动物细胞与植物细胞有丝分裂区别的特征之一.构成动物细胞纺锤体的丝状结构教材为不称纺锤丝?是否由星射线形     

文蛤受精及早期胚胎发育过程的细胞学观察

用普通光镜、荧光显微镜技术和石蜡切片技术三种方法,对文蛤卵在受精及早期胚胎发育过程中的外形和核相变化进行了详细观察。结果表明:文蛤成熟未受精卵呈圆球形,直径90.06μm±5.59μm,核相处于第一次成熟分裂中期;精子为鞭毛型,全长48.05μm±1.60μm,头部呈狭茧形,长度为3.06μm±0.17μm;精卵混合后,精子迅速附着于卵子表面,受精后5min-10min,精子进入卵内并明显膨胀,激活卵子启动两次成熟分裂;分别在受精后20min、30min,受精卵完成第一次和第二次成熟分裂,先后排出第一、第二极体;成熟分裂完成之后,精、卵核体积迅速膨胀到最大,核膜重新出现,形成弥散状的雌、雄原核;受精后35min左右,雌、雄原核在卵子中央发生染色体联合,共同排列在纺锤体的赤道板上,形成第一次有丝分裂的中期分裂相;受精后40min-45min,在纺锤丝的牵引下染色体被拉向两极,结果形成2个大小不等的卵裂球;受精后55min-60min,第二次卵裂结束,形成1大3小4个卵裂球,卵裂过程中的核相变化与第一次卵裂基本相同,只是卵裂方向是与第一次卵裂的卵裂沟呈基本垂直的纵裂;受精后80min-90min,第三次卵裂完成,仍为不等全裂,但自此次起开始进行螺旋分裂。此外,实验中也发现了少量的多精入卵、多极分离和天然三倍体等异常现象。     

小鼠卵母细胞成熟和受精过程中Ca^2＋分布变化的研究

用焦锑酸钾原位定位法、膜结合Ｃａ＾２＋荧光探针金霉素标记法,分别在电镜和光镜水平对小鼠卵成熟和卵受精过程中结合态Ｃａ＾２＋的分布及其变化进行了研究,发现：１）Ｃａ＾２＋分布于线粒体、胞质、内质网囊泡、微绒毛和透明带等部位,其中以线粒体基质中分布密度为最大;２）减数分裂Ｉ中、后期于纺锤体极区结合有较多的Ｃａ＾２＋;３）生发泡、纺锤体和原核内膜结合态Ｃａ＾２＋含量很少,但纺锤体和原核周围分布较多;４）     

Cytological Mechanism on the Integration of Heterologous Genome or Chromosomes in the Unique Gynogenetic Carassius auratus gibelio

银鲫（ＣａｒａｓｉｕｓａｕｒａｔｕｓｇｉｂｅｌｉｏＢｌｏｃｈ）是行天然雌核发育生殖的两性型三倍体鱼类,与普通两性融合生殖鱼类相比,具有独特的育种优势。八十年代以来,异育银鲫、复合四倍体异育银鲫的发现表明,雌核发育卵子不但具有保持自身全部染色体的能力,还能整合异源精子的部分遗传物质或整个基因组,影响雌核发育后代的性状。因此,搞清楚异源基因组的整合机制对于进一步弄清其发育模式以及诱导复合多倍体银鲫均具有十分重要的作用。两性融合发育鱼类的精子入卵后,精核在促精核活化因子的诱导下,可以逐渐解凝并形成雄性原核;而在天然雌核发育银鲫受精卵中,精核的解凝和原核化却被抑制。去掉卵壳的控制作用后,精核虽能在卵质中解凝却仍不能形成雄性原核（Ｆｉｇ．１）。可见,雌核发育银鲫与两性融合发育鱼类的卵质间必定存在某些差异。对哺乳类和两栖类卵质诱导精核原核化作用的研究表明,ＤＴＴ和蛋白水解酶能够分别还原精核组蛋白中ＳＳ和水解精核组蛋白,从而诱导精核在卵质中形成雄性原核。本文通过显微注射以及冷休克处理等诱导方法,探讨了人工诱导外源精核在银鲫卵中解凝和原核化,培育银鲫复合种的细胞学机制。实验结果显示,向银鲫卵质中注入胰蛋白酶、ＤＴＴ和     

谈谈遗传学中若千基本间题

人们对细胞分裂的认识,开始时只看到它 有,I接分裂”与“间接分裂”。直接分裂的例子 再没有比原生动物纤毛虫的大核（营养核）的分 裂为最典型的了。间接分裂后改称为有丝分 裂,因为这种分裂总伴随着纺锤休的形成,而 纺锤体上的微管束在光学显微镜下观察固定后 的切片标本都呈显为丝线状,由此这种分裂就 被称为有丝分裂。在某些特定的纺锤体内微管 束的支配下,细胞核膜逐渐消失,使核内形成的 染色体和其他产物与细胞质的物质直接得到接 触,这一过程很值得注意。     

孤雌活化诱导恢复的小鼠减数分裂期间细胞骨架的动态与作用

减数分裂的顺利完成是胞质分裂和核分裂在时间和空间上的协调结果,细胞骨架系统在减数分裂的一系列事件中具有重要的调节作用.实验通过孤雌活化诱导小鼠MⅡ期卵减数分裂恢复,采用激光共聚焦显微术检测了减数分裂期间的微管、微丝和核的动态变化,并通过细胞骨架药物处理,以分析微管和微丝在减数分裂事件中的不同作用.结果显示：纺锤体微管为核的定位、分离和运动所必需;纺锤体从与质膜平行旋转至与质膜垂直是极体排放的前提;微丝是控制纺锤体旋转的关键因素;纺锤体旋转完成后微丝随即解聚,不参与极体的最后排出,形成原核后再重新组装.     

唇鱼骨受精的细胞学研究

唇精孔器属深凹陷、短孔径型。精子在受精后2s到达精孔管、5s进入卵子。受精后8—15min,卵子进入第二次减数分裂后期。受精后10min,开始形成雄性原核。受精后20min,进入第二次减数分裂末期。受精后25min,雌性原核形成。受精后30—35min,雌性原核向雄性原核移动。受精后40min,雌雄原核接近。受精后50min,雌雄原核结合。受精后70min,受精卵进入第一次有丝分裂中期,受精后80min,进入第一次有丝分裂后期,受精后120min,进入末期。卵黄降解与其内部或外周小泡的泡状缺口紧密相关。雌雄原核结合是精子星光扩张、牵引和细胞质流动的共同结果。有多精入卵的现象。     

雌核发育和两性融合发育鱼卵调控精核受精发育的生化特性研究

两性融合生殖的鱼卵受精后,精核能疏松、解凝,形成雄性原核：雌核发育银鲫卵子受精后,精核发育受到抑制,无法形成原核。采用显微注射去膜精核以及细胞学和电镜观察的方法,本文对两类鱼卵受精后精核早期发育的生化性质进行了初步探讨,并着重研究了雌核发育银鲫卵子控制精核发育的生化特征。实验结果显示,两性融合生殖鱼类卵质中,一定量的Ｃａ２＋的存在,二硫键的还原作用对于精核的发育显然是必要的;而在雌核发育银鲫卵中,Ｃａ２＋的功能和二硫键的还原作用与精核发育受到抑制之间并无直接联系。银鲫卵质中似乎显示出异常的磷酸酶脂解活性,导致磷酸化过程无法进行,使精核解凝受到阻碍。另外,两性融合生殖的鱼卵重质层中具有大量诱导精核原核化的有关因子,而银鲫卵质中则缺少该因子（或活性极低）。银鲫卵质中还可能缺乏某些与雄性原核的核膜重组装有关的大分子物质。     

Remodeling of sperm chromatin after fertilization involves nucleosomes formed by sperm histones H2A and H2B and two CS histone variants

The composition of nucleosomes at an intermediate stage of male pronucleus formation was determined in sea urchins. Nucleosomes were isolated from zygotes harvested 10 min post-insemination, whole nucleoprotein particles were obtained from nucleus by nuclease digestion, and nucleosomes were subsequently purified by a sucrose gradient fractionation. The nucleosomes derived from male pronucleus were separated from those derived from female pronucleus by immunoadsorption to antibodies against sperm specific histones (anti-SpH) covalently bound to Sepharose 4B (anti-SpH-Sepharose). The immunoadsorbed nucleosomes were eluted, and the histones were analyzed by Western blots. Sperm histones (SpH) or alternatively, the histones from unfertilized eggs (CS histone variants), were identified with antibodies directed against each set of histones. It was found that these nucleosomes are organized by a core formed by sperm histones H2A and H2B combined with two major CS histone variants. Such a hybrid histone core interacts with DNA fragments of approximately 100 bp. It was also found that these atypical nucleosome cores are subsequently organized in a chromatin fiber that exhibits periodic nuclease hypersensitive sites determined by DNA fragments of 500 bp of DNA. It was found that these nucleoprotein particles were organized primarily by the hybrid nucleosomes described above. We postulate that this unique chromatin organization defines an intermediate stage of male chromatin remodeling after fertilization.     

天然雌核发育银鲫卵子控制异源精核发育的受精学机制

作者对两性融合生殖鱼和雌核发育银鲫脱膜卵受精的精核发育进行了观察,并采用鱼类卵子无细胞系对以上两类卵质提取物体外诱导经Ｔｒｉｔｏｎ—Ｘ１００处理的精子及其发育进行了初步研究,结果表明在两性融合生殖型脱膜鱼卵中精核通过解凝最终形成原核,而在雌核发育的银鲫脱膜卵子中部分精核体积虽有一定程度的增加,但始终没有观察到原核的发育;在体外诱导实验中,经Ｔｒｉｔｏｎ—Ｘ１００处理的精子在两类卵质提取物中充分发育,都出现了类似体内原核的状态。该现象提示在银鲫卵质中存在有促使精核形成原核的因子,但在正常受精状态下,由于银鲫卵质促使精核核膜解体的功能的异常,使覆盖精子头部的核膜不能象在两性融合生殖受精卵子中进行崩解,精核进一步的原核发育受到抑制。另外,建立体外诱导系统的重要意义,在于它为研究雌核发育调控的分子学机制提供了一条有效途径。     

Pronuclear formation in starfish eggs inseminated at different stages of meiotic maturation: correlation of sperm nuclear transformations and activity of the maternal chromatin

Changes in sperm nuclei incorporated into starfish, Asterina miniata, eggs inseminated at different stages of meiosis have been correlated with the progression of meiotic maturation. A single, uniform rate of sperm expansion characterized eggs inseminated at the completion of meiosis. In oocytes inseminated at metaphase I and II the sperm nucleus underwent an initial expansion at a rate comparable to that seen in eggs inseminated at the pronuclear stage. However, in oocytes inseminated at metaphase I, the sperm nucleus ceased expanding by meiosis II and condensed into chromosomes which persisted until the completion of meiotic maturation. Concomitant with the formation and expansion of the female pronucleus, sperm chromatin of oocytes inseminated at metaphase I enlarged and developed into male pronuclei. Condensation of the initially expanded sperm nucleus in oocytes inseminated at metaphase II was not observed. Instead, the enlarged sperm nucleus underwent a dramatic increase in expansion commensurate with that taking place with the maternal chromatin to form a female pronucleus. Fusion of the relatively large female pronucleus and a much smaller male pronucleus was observed in eggs fertilized at the completion of meiotic maturation. In oocytes inseminated at metaphase I and II, the male and female pronuclei, which were similar in size, migrated into juxtaposition, and as separate structures underwent prophase. The chromosomes in each pronucleus condensed, intermixed, and became aligned on the metaphase palate of the mitotic spindle in preparation for the first cleavage division. These observations demonstrate that the time of insemination with respect to the stage of meiotic maturation has a significant effect on sperm nuclear transformations and pronuclear morphogenesis.     

Breakdown of the sperm nuclear envelope is a prerequisite for male pronucleus formation: direct evidence from the gynogenetic crucian carp Carassius auratus langsdorfii

The gynogenetic fish, Carassius auratus langsdorfii (the ginbuna, a crucian carp), provides an interesting model for the study of the mechanisms controlling male pronucleus formation. When the sperm nucleus of a different subspecies (C. a. cuvieri) is incorporated into the gynogenetic egg, the nuclear envelope of the spermatozoon is not broken down, and the pronucleus fails to develop, although dispersion of the sperm chromatin occurs to some extent within the space limited by the nuclear envelope. When spermatozoa without plasma membranes and nuclear envelopes were microinjected into mature activated eggs, the sperm nuclei underwent chromatin dispersion, nuclear envelope formation, DNA synthesis, and transformation into male pronuclei. These results indicate that the failure of the male pronucleus to form in ginbuna is primarily due to the failure of sperm nuclear envelope breakdown. We conclude that sperm nuclear envelope breakdown is an indispensable step for the development of the male pronucleus.     

雌核发育银鲫的受精生物学研究——天然雌核发育银鲫繁殖方式的讨论

本文研究了同源雌核发育银鲫精子在4种类型的雌核发育银鲫卵中的发育特征。初步揭示了天然雌核发育银鲫根据精子的来源不同而分别具有二种不同的繁殖方式,对其在维持雌核发育银鲫种群生存,促使克隆分化等方面的独特的生物学意义进行了讨论。     

An ultrastructural study of cross-fertilization (Arbacia female x Mytilus male)

Insemination of sea urchin (Arbacia) ova with mussel (Mytilus) sperm has been accomplished by treating eggs with trypsin and suspending the gametes in seawater made alkaline with NaOH. Not all inseminated eggs undergo a cortical granule reaction. Some eggs either elevate what remains of their vitelline layer or demonstrate no cortical modification whatsoever. After its incorporation into the egg, the nucleus of Mytilus sperm undergoes changes which eventually give rise to the formation of a male pronucleus. Concomitant with these transformations, a sperm aster may develop in association with the centrioles brought into the egg with the spermatozoon. Both the male pronucleus and the sperm aster may then migrate centrad to the female pronucleus. Evidence is presented which suggests that fusion of the male pronuclei from Mytilus sperm with female pronuclei from Arbacia eggs may occur, although this was not directly observed. These results demonstrate that Mytilus sperm nuclei are able to react to conditions within Arbacia eggs and differentiate into male pronuclei.