减数分裂

To investigate whether the expression of cdc2 and cyclin B1 in spermatogenic cells during spermatogenesis is actually a temperature dependent event, in situ hybridization, Western blotting and immunohistochemistry analysis were used to study the expression of cdc2 and cyclin B1 in normal and cryptorchid testis. Results showed that heat would differentially hurt male germ cells in different developmental stages during spermatogenesis, especially the pachytene primary spermatocytes. Most of spermatogonia in contralateral cryptorchid testis were not harmed fatally by heat as yet, indicating that spermatogonia could resist to beat to a certain extent. In this case spermatogonia could develop to pachytene/diplotene primary spermatocytes, but they could not acquire the ability to complete the transition from mitosis to meiosis, and then appeared to go through apoptosis. Therefore, we could not find the descendants of meiosis: secondary spermatocytes and round spermatids, elongated spermatids and spermatozoon. The abdominal temperature had no significant influence on the transcription of cdc2 and cyclin B1 in the spermatogonia and pachytene/diplotene primary spermatocytes. In normal rabbit testis, cyclin B1 increased in the pachytene/diplotene primary spermatocytes before meiosis and reached its peak in the spermatids.

为了解精子正常发生过程中cdc2和cyclin B1表达的低温依赖性，我们利用原位杂交和免疫组化等方法，研究了正常和隐睾精子发生过程中cdc2和cyclin B1的转录和翻译调控活动，结果表明：（1）热对各阶段的雄性生殖细胞都有损害，粗线期的初级精母细胞尤为敏感，实验性隐睾内的精原细胞尚未完全受到"致命"影响，说明精原细胞对热有一定的耐受性，但即使成为粗线期／双线期初级精母细胞，却未能获得由有丝分裂过渡到减数分裂的能力，呈现不同程度的凋亡，所以在整个切片中找不到源自减数分裂的产物----次级精母细胞、圆形精子细胞，更谈不上长形精子细胞和精子的形成；（2）腹腔高温未明显地影响隐睾精原细胞和粗线期/双线期初级精母细胞中cyclinB1和cdc2的转录，说明高温并不是通过影响cyclin B1和cdc2的转录活动而导致生精过程阻断的；（3）正常兔睾丸组织中，〓在精原细胞和粗线期／双线期精母细胞中均有表达：cyclin B1蛋白在减数分裂前期的粗线期／双线期初级精母细胞中的表达量增加，于变态末期的精子细胞中达高峰。

Genes important for male gametogenesis involved in highly con-served landmark events such as meiotic recombination, formation of the synaptonemal complex, sister chromatid cohesion, spermiogenesis during postmeiotic stages, and checkpoints and factors required for the meiotic cell cycle .

精子发生中的重要基因与一系列精子发生过程中阶段性的细胞事件密切相关，例如减数分裂重组、联会丝复合物的形成、姊妹染色体的结合、减数分裂后精子的变态以及减数分裂周期中的关键点和必需因子等。

Megaspore mother cell just enters leptotene as The meiosis of microspore mother cell develop into tetrads . The meiosis of megaspore mother cell develop into pachytene while that of microspores develop into a single nuclear adjacent to cell wall.

当白杨小孢子母细胞减数分裂至四分体时，大孢子母细胞开始进入减数分裂细线期；而当小孢子发育至单核靠边期上时，大孢子母细胞减数分裂达到粗线期。

Meiotic division is composed of two successive, and are called meiosis meiosis Ⅰ and Ⅱ.

减数分裂是由相继的两次分裂组成的，分别称为减数分裂Ⅰ和减数分裂Ⅱ。

At the same time, the existence of respective specific proteins during the development of pistillate and staminate flowers shed some light on the difference of further development direction between these two kinds of flowers.

在减数分裂期前和减数分裂期荔枝的雌雄花的发育都有一个相似的历程，即该时期都有两性花原基，都能正常减数分裂，因而这2个时期都有出现和消失同样的特异蛋白，同时，雌雄花的发育又存在着各自特有的蛋白，从大分子水平上阐明了它们进一步的发育方向的不同。

Reduction division The first division of meiosis , including prophase, metaphase I, and anaphase I. It results in a haploid number of chromosomes gathering at each end of the nuclear spindle.

减数分裂：减数分裂中的第一次分裂，包括分裂前期，中期 I 和后期 I ，形成单倍数目的染色体在每一个核纺锤体末端聚集。

In conclusion, these results suggested that (1) the ageing-associated decline in fertility of female KM mouse was due to a decrease in both quantity and quality of oocytes;(2) the ooplasm from young mice did not correct the meiotic errors of aged mice, and the ooplasm from aged mice did not induce abnormal segregation of meiotic chromosome of young mice, indicating that meiotic anomalies found in the oocytes of aged mice might be related to nucleus or chromosomes and relevant factors;(3) a critical nucleocytoplasmic ratio was essential for normal maturation and segregation of meiotic chromosomes of oocytes and development to 2-cell embryos.

本研究结果表明：（1）昆明白小鼠与衰老相关的生育力下降是其卵母细胞数量减少和质量下降的综合结果；（2）年轻小鼠卵母细胞细胞质不能纠正老龄小鼠GV的减数分裂错误，老龄小鼠卵母细胞细胞质也不诱导年轻小鼠的GV发生减数分裂错误，老龄小鼠卵母细胞减数分裂异常很可能与细胞核或染色体及其相关因素有关；（3）关键的核质比对卵母细胞正常的成熟、减数分裂染色体分离及2-细胞期胚的发育是绝对必需的。

Thus it is obvious that the weak homology existedamong genomes A, B, D and 〓. However, the rare unreduced gemetes and near-unreduced ones with the loss of several chromosomes could be produced by the highlyunequtional division of univalents at the first meisis and the normal second division,which gave the F1 hybrid the partial fertility.

但通过第一次减数分裂时单价体的极不对称的分离及正常的第二次分裂，可形成少量未减数配子和丢失了少数几条染色体的近未减数配子，使杂种〓表现部分可育性。

For further studying the genetic mechanism of the reproductive isolation phenomenon of interspecific hybrid, paraffin sections of testes from 13 sexually mature male mules (Equus asinus×Equus caballus) and 12 hinnies (Equus caballus×Equus asinus) were prepared, and the samples of Giemsa meiosis and AgNO 3 synaptonemal complexes were observed and compared with spermatocyte meiosis of horse and donkey under light microscope and electronic microscope.

为了进一步探讨种间杂种生殖隔离现象的遗传机理，本研究采用性成熟公骡的睾丸为材料，制备组织切片和减数分裂联会复合体标本进行观察，发现个别性腺发育较好的个体虽然减数分裂存在大量异常，但确有少数精母细胞完成了减数分裂并产生精子。

The events occurring during these stages differ in meiosis and mitosis, notably in that bivalents (pairs of homologous chromosomes) are formed in meiosis, whereas homologous chromosomes remain separate in mitosis.

在减数分裂和有丝分裂中，前期发生的事件是不同的，尤其是二价染色体区别最为明显，在减数分裂中形成，而在有丝分裂中同源染色体是分离的。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。