赤点石斑鱼精子发生和形成的超微结构研究

用透射电镜研究了赤点石斑鱼Epinephelus妇精子发生和精子形成过程。结果表明，赤点石斑鱼精子发生经历了初级精原细胞、次级精原细胞、初级精母细胞、次级精母细胞、精子细胞阶段。精子细胞再经过精子形成过程成为精子。在初级精原细胞、次级精原细胞阶段，细胞核释放出拟染色体。拟染色体分布于精原细胞和前期Ⅰ的初级精母细胞的细胞质中。初级精母细胞减数分裂早期同源染色体配对明显可见，并形成联会复合体。精子细胞之间存在细胞联系（桥粒）。赤点石斑鱼成熟精子的特点是细胞核圆形，核内染色质致密，没有核泡（核空隙）。精子尾部细长，横切面为典型的“9＋2”轴丝结构。     

短尾鮠精子发生的超微结构研究

用透射电镜观察了短尾鮠的精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子的形态以及细胞核、拟染色体和线粒体等的结构变化规律．结果表明：精原细胞时期细胞器较丰富，到精子细胞后期，细胞器的形态和数量发生了较大变化；随着精母细胞的发育，核质凝聚程度逐渐增强．短尾鮠的精子具有椭圆的头部和复杂的中片，近侧中心粒和远侧中心粒靠近核的中央，鞭毛呈9＋2轴丝结构，并具有由外膜折迭形成的波浪形的结构．表明短尾鮠精子发生中具有某些区别于其它鱼类精子的不同结构．     

黑条小车蝗Oedaleus decorus(Gevm)精母细胞减数分裂观察研究

1、遗传学教学过程中希望学生具有遗传学的牢固基础知识。减数分裂是遗传学的三个基本原则的共同的细胞学基础。减数分裂中染色体的行为变化与生物遗传变异密切相关。熟悉减数分裂过程,掌握制片观察技术,是从事遗传育种的基本功之一。特别是细胞遗传学的优势反映在概念和技术的融合和促进。2、能否准确观察到蝗虫精母细胞的减数分裂,至关重要的是把握住蝗虫合适的发育时期:若虫末期,成虫最早期,如失之过早或偏晚都将观察不到精母细胞的减数分裂。黑条小车蝗精细管多为46条。解剖之后,凭观感可以初步判断偏晚已经退化的精细管或过早发育不良的精细管。3、黑条小车蝗精母细胞减数分裂初期Ⅰ,n=11,n=12,多为短棒状和两头带尖的端化染色体、以及少数近端着丝粒拉成括弧状的染色体图象(参见照片)。     

遗传的基本规律在解习题中的运用

遗传的两大基本规律：基因的分离规律和基因的自由组合规律。这两大规律是高中生物必修本的重点和难点。本文通过几个实例帮助学生突破难点,灵活运用分离规律和自由组合规律。例1一个基因型为AaBbC。的初级精母细胞,减数分裂形成的精子种类及个数。解析生殖细胞种类的分化发生在减数分裂第一次分裂形成次级性母细胞过程。此过程中,等位基因随同源染色体的分离而分离,非同源染色体上的非等位基因自由组合。一个初级精母细胞经减数第一次分裂形成两个次级精母细胞,再经第二次分裂各形成两个种类相同的精子。由此可知：一个基因型为AaBb…     

棕色田鼠减数分裂及精细胞染色体数目的研究

以棕色田鼠精母细胞为研究对象，观察减数分裂各时期染色体特征性变化，特别对精细胞染色体构成及数目进行了研究．结果表明，ｘ型和ｙ型精细胞均显示了染色体数目的多态性（２ｎ＝２４，２５，２６），可以认为这是造成棕色田鼠体细胞染色体数目多态性的原因之一．     

云斑车蝗精母细胞减数分裂过程的观察与分析

本文研究了云斑车蝗（Ｇａｓｔｒｉｍａｒｇｕｓｍａｒｍｏｒａｔｕｓ）精母细胞的减数分裂过程，阐述了该蝗虫减数分裂各时期的染色体行为和细胞学特征，特别是Ｘ染色体在细线期、偶线期、双线期和中期Ｉ、后期Ｉ的特殊表现，以及中期Ｉ各种染色体的形态特征。     

蟋蟀雄性生殖系统的结构和精子发生

研究了蟋蟀雄性生殖系统的结构和精子发生的动态过程 .成熟的雄性生殖系统主要由一对精巢 ,一对输精管 ,一对附腺 ,一对储精囊和一根射精管组成 .精巢乳白色由许多精巢管盘曲组成 ,精巢管包括原精区、生长区、成熟区和变形区四个区域 .其主要特点是处于不同发育时期的精母细胞呈放射状密集排列在圆球形的育精囊中 .精子发生的动态是 :一龄期 ,精巢小管仅具一些精原细胞 ;二～三龄期 ,精原细胞不断通过有丝分裂增殖 ;四龄期 ,初级精母细胞形成 ,并由减数分裂形成次级精母细胞 ;五龄期 ,精细胞大量形成 ,并变形成为精子 .其主要特点是成虫期的精巢管中存在所有各期生殖细胞 ,当下端的精子成熟时 ,上端部分的精母细胞再发育形成精子 ,表明从五龄开始蟋蟀便能连续不断地产生精子     

一例恒河猴生殖器官畸形的分析报告

发现一例生殖器官畸形的恒河猴（Ｍ．ｍｕｌａｔｔａ）。具有正常大小的睾丸但缺阴茎；阴囊袋伸缩性不明显且缺皮皱。尿道口位于阴裂中、尿道口下方有一肉质突起长１．ｌｃｍ粗０．４ｃｍ，类似于雌性的阴蒂。睾丸的组织学观察表明精小叶结构正常，生殖季节虽有大量分裂相的初级精母细胞但只有少数的精子和精子细胞出现；大量的初级精母细胞和次级精母细胞停留于减数分裂期并落入曲细精管管腔。来发现有生殖腺导管开口；腹腔镜检查未发现卵巢或其它雌性生殖器官。推测本例畸形个体是由于染色体异常引起。     

近江牡蛎受精细胞学研究

用醋酸－地衣红染色的方法对近江牡蛎人工授精的卵子减数分裂和受精过程进行了详细细胞学观察。精子入卵前，卵子处于第一次减数分裂的前期（胚泡期），精子入卵后，胚泡消失，然后进行两次减数分裂，在海水温度为２８．８℃的情况下，授精后３３ｍｉｎ和４５ｍｉｎ，绝大部分受精卵已排出第一极体和第二极体，雄原核可在第一极体排出后及第二极体排出前任何时期内形成，雌雄原核以联合的方式将两组染色体合并，授精后１ｈ，大部分卵     

棕色田鼠减数分裂及精细胞染色体数目的研究

以棕色田鼠精母细胞的研究对象，观察减数分裂各时期染色体特征性变化，特别对精细胞染色体构成及数目进行了研究，结果表明，Ｘ型和Ｙ型精细胞均显著了染色体数目的多态性（２ｎ＝２４，２５，２６）可以认为这是造成棕色田鼠体细胞染色体数目多态性的原因之一。     

Protein phosphatase 2A protects centromeric sister chromatid cohesion during meiosis I

Segregation of homologous maternal and paternal centromeres to opposite poles during meiosis I depends on post-replicative crossing over between homologous non-sister chromatids, which creates chiasmata and therefore bivalent chromosomes. Destruction of sister chromatid cohesion along chromosome arms due to proteolytic cleavage of cohesin's Rec8 subunit by separase resolves chiasmata and thereby triggers the first meiotic division. This produces univalent chromosomes, the chromatids of which are held together by centromeric cohesin that has been protected from separase by shugoshin (Sgo1/MEI-S332) proteins. Here we show in both fission and budding yeast that Sgo1 recruits to centromeres a specific form of protein phosphatase 2A (PP2A). Its inactivation causes loss of centromeric cohesin at anaphase I and random segregation of sister centromeres at the second meiotic division. Artificial recruitment of PP2A to chromosome arms prevents Rec8 phosphorylation and hinders resolution of chiasmata. Our data are consistent with the notion that efficient cleavage of Rec8 requires phosphorylation of cohesin and that this is blocked by PP2A at meiosis I centromeres.     

孔雀鱼精子发生的显微与超微结构

对卵胎生硬骨鱼孔雀鱼精子的发生进行了显微与超微结构研究.成鱼精巢呈肾形,腹面有输精管伸出,内部构造为小管型.孔雀鱼精子发生经过精原细胞,初级精母细胞,次级精母细胞,精子细胞及变态精子阶段;初级精母细胞和精子细胞高尔基体和囊泡丰富;从精母细胞到精子细胞有细胞质不完全分裂现象;成熟精子头部较长,袖套部分长度是头部的2倍,直径与精子头部相同,线粒体多.鞭毛有侧鳍,其轴丝为典型的“9+2”结构.     

Rec8 phosphorylation and recombination promote the step-wise loss of cohesins in meiosis

During meiosis, cohesins--protein complexes that hold sister chromatids together--are lost from chromosomes in a step-wise manner. Loss of cohesins from chromosome arms is necessary for homologous chromosomes to segregate during meiosis I. Retention of cohesins around centromeres until meiosis II is required for the accurate segregation of sister chromatids. Here we show that phosphorylation of the cohesin subunit Rec8 contributes to step-wise cohesin removal. Our data further implicate two other key regulators of meiotic chromosome segregation, the cohesin protector Sgo1 and meiotic recombination in bringing about the step-wise loss of cohesins and thus the establishment of the meiotic chromosome segregation pattern. Understanding the interplay between these processes should provide insight into the events underlying meiotic chromosome mis-segregation, the leading cause of miscarriages and mental retardation in humans.     

秉氏环毛蚓(Pheretima pingi Stephenson)雄性生殖细胞减数分裂

以秉氏环毛蚓雄性生殖细胞为实验材料,通过石蜡连续切片方法,对雄性生殖细胞的减数分裂进行了初步研究,并分折了雄性生殖细胞在精巢囊、贮精囊中从形成到成熟的过程。进一步了解秉氏环毛蚓的染色体数2n=8。这为促进蚯蚓生物学研究、人工养殖和综合利用,以及蚯蚓的远缘杂交和育种选种提供理论依据。     

银杏精原细胞和精细胞的初步研究

0　引　言由于银杏(ＧｉｎｋｇｏｂｉｌｏｂａＬ.)独特的系统学地位及精子结构的特殊性,对银杏生殖生物学的研究工作一直是裸子植物胚胎学研究的热点之一[1～12]。这些研究表明,银杏精原细胞从产生到最后形成精子历时3个月左右[1～5]。在此期间,其体积增大数倍,结构发生了...     

A contractile nuclear actin network drives chromosome congression in oocytes

Chromosome capture by microtubules is widely accepted as the universal mechanism of spindle assembly in dividing cells. However, the observed length of spindle microtubules and computer simulations of spindle assembly predict that chromosome capture is efficient in small cells, but may fail in cells with large nuclear volumes such as animal oocytes. Here we investigate chromosome congression during the first meiotic division in starfish oocytes. We show that microtubules are not sufficient for capturing chromosomes. Instead, chromosome congression requires actin polymerization. After nuclear envelope breakdown, we observe the formation of a filamentous actin mesh in the nuclear region, and find that contraction of this network delivers chromosomes to the microtubule spindle. We show that this mechanism is essential for preventing chromosome loss and aneuploidy of the egg--a leading cause of pregnancy loss and birth defects in humans.     

一粒小麦小孢子发生过程中的细胞并合

经检测,在正常的一粒小麦(TriticummonococumL.)中有细胞并合发生.细胞并合仅存在于减数分裂的凝线期,核物质从一个花粉母细胞到邻近花粉母细胞的转移是通过胞质通道进行的.细胞并合的发生是自发的,且在花粉母细胞中有方向性.本次调查中未观察到花粉败育现象,具细胞并合的植株结实也未受影响.中期Ⅰ一些花粉母细胞的染色体数目有变化,这造成一些花粉母细胞在后期Ⅰ时出现非正常分离.由于异常花粉母细胞很少,孟德尔分离比例仍然成立.这被认为是在常规遗传分析中不能检测出细胞并合的效应的原因.     

两种环缘蝽的染色体研究(半翅目:姬缘蝽科)

本文研究了中国姬缘蝽科开环缘蝽Stictopleurus punctatonervosus minutus Blote和闭环缘S．viridictatus(Uhler)的核型及其染色体的减数分裂行为．结果表明：两个种的染色体数目均为2n(♂)=13，具有一对m染色体和XO性别决定机制，但是在染色体行为方面却表现出了各自的特异性．     

Generation of GTP-bound Ran by RCC1 is required for chromatin-induced mitotic spindle formation.

Chromosomes are segregated by two antiparallel arrays of microtubules arranged to form the spindle apparatus. During cell division, the nucleation of cytosolic microtubules is prevented and spindle microtubules nucleate from centrosomes (in mitotic animal cells) or around chromosomes (in plants and some meiotic cells). The molecular mechanism by which chromosomes induce local microtubule nucleation in the absence of centrosomes is unknown, but it can be studied by adding chromatin beads to Xenopus egg extracts. The beads nucleate microtubules that eventually reorganize into a bipolar spindle. RCC1, the guanine-nucleotide-exchange factor for the GTPase protein Ran, is a component of chromatin. Using the chromatin bead assay, we show here that the activity of chromosome-associated RCC1 protein is required for spindle formation. Ran itself, when in the GTP-bound state (Ran-GTP), induces microtubule nucleation and spindle-like structures in M-phase extract. We propose that RCC1 generates a high local concentration of Ran-GTP around chromatin which in turn induces the local nucleation of microtubules.     

Function of c-mos proto-oncogene product in meiotic maturation in Xenopus oocytes

The c-mos proto-oncogene is expressed as a maternal mRNA in oocytes and early embryos of Xenopus laevis, but its translation product pp39mos is detectable only during progesterone-induced oocyte maturation. Microinjection of mos-specific antisense oligonucleotides into oocytes not only prevents expression of pp39mos, but also blocks germinal vesicle breakdown, indicating that it functions during reinitiation of meiotic division.