褐斑大蠊精母细胞联会复合体研究

采用表面铺展法结合银染技术制备联会复合体标本,在光镜、电镜下进行观察。发现褐斑大蠊精母细胞联会复合体(SC)的结构及演变符合一般规律;SC的相对长度与有丝分裂染色体的相对长度之间存在着良好的吻合性;电镜下可观察到SC侧线本身的双股结构;分类描述了核内的几种颗粒,并对相关的一些问题进行了讨论。     

利用黑色斑蚕作亲本、选育日系普斑限性品系

根据家蚕Bombyx moli斑纹互作原理,利用2032限性品种的雌,与自然突变体雄杂交。F2代出现分离,于是淘汰所有黑色斑蚕,只留下普斑蚕和素斑蚕,即得到新限性普斑系。新限性品系得到后,做连续3代的系统选育,其中F3代为蛾区混合育,F4～F5代采用单蛾育。蛾区混合育着重个体选择,单蛾育以蛾区选择为主,个体选择为辅。性状基本稳定后,即初步对其作主要经济性状的测定。结果显示:新限性品系在5龄经过、全龄经过上比两亲本略短。在全茧量、茧层量、茧层率几项指标上较两亲本为优,分别比两亲本平均值提高31%、38%、5%。     

激光诱导家蚕孤雌生殖的研究 Ⅳ.Lamp 1的遗传学研究

通过杂交和解剖试验,我们发现Ｌａｍｐ１为一常染色体（Ⅱ）和Ｗ易位片段同时缺失或突变的斑纹限性孤雌生殖突变体。与亲本回交后代分离比,１浓普♀：３正常普♀或：３淡普♀或：１素蚕♀或１＋ｐ＋ｐ／：２Ｗ＋ｐ／：１＋ｐ＋ｐ／ＺＺ：１ＰＰ／：ＺＷ＋ｐ／ＺＺ：１ＰＰ／ＺＺ。联会复合体分析仅浓普斑雌蚕表型个体中发现染色体易位片段。     

对减数分裂的新理解

减数分裂历来被认为是：同源染色体联会－重组－分离。染色体配对是其中最早的事件,配对又叫联会,联会由联会复合体（ＳＣ）引起或促进。联会复合体又是减数分裂重组所必需的。重组引起细胞学上可见的交叉,能够确保同源染色体分离。这些经典观点在９０年代受到了严重挑战,对减数分裂的许多新理解正在取而代之。按照新观点,减数分裂的过程可以用下图表示。１　同源性搜索是减数分裂的第一步减数分裂最早的事件不是同源染色体的配对,其前在细线期还发生了同源性搜索。它是在全染色体组内识别染色体上同源性位点的过程。搜索不仅仅限于染…     

二种抗有丝分裂化合物诱发小鼠联会复合体损伤的研究

以抗有丝分裂化合物秋水仙素和对苯二酚处理雄性小鼠,分析了减数分裂前期细胞联会复合体出现的各类损伤。二种化合物在减数分裂前期都诱发各种特殊倾向性的联会复合体损伤(如联会复合体断裂、联会异常等现象)。联会复合体分析,可以作为监测减数分裂过程中源染色体联会异常所引起的染色体异常分离和染色体结构损伤的手段。 Abstract:Two anti-mitotic chemicals(colchicines and hydroquinone)were assayed for their effects on synaptonemal complex(SC)damage in male mice.The tested chemicals significantly induced SC anomalies including SC breakage,asynapsis and non-homologous.It is concluded that SC analysis could be used to pre-screen aneugenes and clastogenes in mammalian germinal cells.     

二种抗有丝分裂化合物诱发小鼠联会复合体损伤的研究

以抗有丝分裂化合物秋水仙素和对苯二酚处理雄性小鼠,分析了减数分裂前期细胞联会复合体出现的各类损伤。二种化合物在减数分裂前期都诱发各种特殊倾向性的联会复合体损伤(如联会复合体断裂、联会异常等现象)。联会复合体分析,可以作为监测减数分裂过程中源染色体联会异常所引起的染色体异常分离和染色体结构损伤的手段。 Abstract:Two anti-mitotic chemicals(colchicines and hydroquinone)were assayed for their effects on synaptonemal complex(SC)damage in male mice.The tested chemicals significantly induced SC anomalies including SC breakage,asynapsis and non-homologous.It is concluded that SC analysis could be used to pre-screen aneugenes and clastogenes in mammalian germinal cells.     

联会复合体:减数分裂的结构基础

减数分裂是有性生殖生物产生单倍体配子的特殊分裂方式,其第一次分裂(减数分裂I)过程中同源染色体的行为是最突出的特征。在减数分裂I,同源染色体间形成的联会复合体通过促进和调控程序性DNA双链断裂的形成和修复,确保同源染色体正确的识别、配对、重组和分离,从而为减数分裂I的顺利完成提供保障。本综述对联会复合体的组成和功能研究进展进行了回顾,探讨了联会复合体的组装如何影响程序性DNA双链断裂的修复和交叉互换的形成,并总结了与人类生殖障碍相关的联会复合体成分突变,还对该领域未来研究方向进行了展望。     

褐斑大蠊精母细胞联会复合体研究

采用表面铺展法结合银染技术制备联会复合体标本,再光镜、电镜下进行观察。发现褐斑大蠊精母细胞连会复合体(SC)的结构及演变符合一般规律;SC的相对长度与有丝分裂染色体的相对长度之间存在着良好的吻合性;电镜下可观察到SC侧线本身的双股结构;分类描述了核内的几种颗粒并对相关的一些问题进行了讨论。     

猕猴精母细胞联会复合体的银染色观察

作者以银染的雄性猕猴减数分裂标本,研究联会复合体的形成和行为,特别是性泡内X、Y染色体有规律的变化。指出常染色体联会复合体的形成开始于偶线期,成熟于粗线期,开始消失于弥散期。在粗线期可见20条清晰的常染色体联会复合体,其中1条带有呈深黑色的核仁组织者。X、Y染色体同源区段的配对,开始于早粗线期。随着粗线期的发展,由侧面配对转为端部配对状。性染色体配对的解体也比常染色体联会复合体晚,在弥散期仍清晰可见。在整个前期,X、Y的着色也比常染体联会复合体深。在一些细胞中,X染色体显示一种特殊的“发夹状”结构。这是在性染色体进化过程中X染色体由于易位得到的重复片段在粗线期同源配对的一种细胞学表现。     

联会复合体——原发无精症发病中的重要角色

联会复合体(synaptonemal complex,SC)是一种减数分裂特异性超分子蛋白质结构,与减数分裂I(改罗文)中同源染色体的凝缩、配对、重组和分离密切相关。近年来,联会复合体的研究取得了一系列重要的进展,包括在其组成成分和功能上的一些新发现。在小鼠不育模型中联会复合体及其编码基因的异常可引起精子发生障碍。更重要的是,联会复合体编码基因之一SCP3单个碱基缺失导致的无精症已在人类原发不育患者中得到证实。对联会复合体基因SCP1的进一步研究也正在进行之中。      

Identification of 2chromosome region translocated onto the W chromosome by RFLP with EST-cDNA clones in the Gensei-kouken strains of the mulberry silkworm, Bombyx mori L

In silkworms, sex-limited strains are either obtained spontaneously or induced by X-rays or gamma rays. When a fragment of an autosome carrying a dominant allele of those genes responsible for certain characters is translocated onto a W chromosome, the female of the successive generations will express these phenotypic characters and sex discrimination can be facilitated. Gensei-kouken strains are sex-limited strains of silkworms developed by irradiating the pupae with gamma rays, by which a portion of the second chromosome is translocated onto the W chromosome. In these improved strains, the females are yellow-blooded and spin yellow cocoons. By using the EST-cDNA clones mapped on the Z chromosome, we identified the sex according to the polymorphic banding pattern or intensity of the signals. Furthermore, by using the clones on the second chromosome, the region of the second chromosome translocated onto the W chromosome was also defined. In both the A95 and A 96 strains selected for the present study, only the mid-portion of the second chromosome was translocated. The differences in length of the fragments translocated in these strains are discussed.     

Development of the synaptonemal complex of two types of pachytene in oocytes and spermatocytes of Carausius morosus Br. (Phasmatodea)

During oogenesis of the parthenogenetic stick insect Carausius morosus (2n =61+XXX) pachytene is followed by a duplication of the desynapsed chromosomes, which results in a second type of pachytene (tetrapachytene) consisting of paired sister chromosomes (autobivalents). Electron microscopic studies on sections revealed that synaptonemal complexes (SCs) are formed during tetrapachytene only. This means that the parthenogenetically produced progeny have the genetic constitution of the mother. During spermatogenesis of rare fatherless males (2n=61 + XX) and intersexes (2n=61 +XXX) either an incomplete chromosome doubling (demonstrated by up to 10% additional DNA synthesis) or a complete chromosome doubling takes place during zygotene. EM studies on sections and spreads of germ cells of the first type of meiosis showed that unpaired lateral components (LCs), pieces of SCs and complete SCs are formed during pachytene only, the sex chromosomes being represented by unpaired thickened LCs. The incomplete SC formation reflects the complex heterozygosity of the chromosome complement. In the duplicated type SCs are found in tetrapachytene nuclei only; they are wider than the SCs in oocytes. The sex chromosome bivalents are represented by unpaired thickened LCs or partially paired LCs, in which localized chiasma formation was found. The idea is discussed that formation of SCs does not take place as long as a germ cell has been programmed either to replicate or to be able to replicate its chromosomes and that consequently SCs can be formed only once per meiosis.     

Identification of the Z-W bivalent in the silkworm,Bombyx mori

None of the 56 chromosomes including sex chromosomes have been identified in the silkworm so far, though the 28 linkage groups have been determined (Doira, 1986). The present study aims to demonstrate the sex chromosome bivalent in the oocyte by using a particular strain, the sex-limited yellow cocoon (Sy), in which a large fragment of the second chromosome was translocated onto the W chromosome. Among 28 bivalents in the oocyte of the Sy strain, an asymmetrical synaptonemal complex was observed, while in the oocyte of the control strains no such complex was found. We consider this complex as the Z-W bivalent in the silkworm.     

Identification of the female-determining region of the W chromosome in Bombyx mori

The W chromosome of the silkworm Bombyx mori is devoid of functional genes, except for the putative female-determining gene (Fem). To localize Fem, we investigated the presence of W-specific DNA markers on strains in which an autosomal fragment containing dominant marker genes was attached to the W chromosome. We produced new W-chromosomal fragments from the existing Zebra-W strain (T(W;3)Ze chromosome) by X-irradiation, and then carried out deletion mapping of these and sex-limited yellow cocoon strains (T(W;2)Y-Chu, -Abe and -Ban types) from different Japanese stock centers. Of 12 RAPD markers identified in the normal W chromosomes of most silkworm strains in Japan, the newly irradiated W(B-YL-YS)Ze chromosome contained three, the T(W;2)Y-Chu chromosome contained six, and the T(W;2)Y-Abe and -Ban chromosomes contained only one (W-Rikishi). To investigate the ability of the reduced W-chromosome translocation fragments to form heterochromatin bodies, which are found in nuclei of normal adult female sucking stomachs, we examined cells of the normal type p50 strain and the T(W;2)Y-Chu and -Abe strains. A single sex heterochromatin body was found in nuclei of p50 females, whereas we detected only small sex heterochromatin bodies in the T(W;2)Y-Chu strain and no sex heterochromatin body in the T(W;2)Y-Abe strain. Since adult females of all strains were normal and fertile, we conclude that only extremely limited region, containing the W-Rikishi RAPD sequence of the W chromosome, is required to determine femaleness. Based on a comparison of the normal W-chromosome and 7 translocation and W-deletion strains we present a map of Fem relative to the 12 W-specific RAPD markers.     

白腹锦鸡,红腹锦鸡,中国雉鸡SC组型的比较研究

以微铺展—硝酸银染色技术制备三种鸡的SC标本,进行电镜观察。结果表明:三种鸡的SC组非常相似,即2n=82,ZZ/ZW型性别决定,雄性为ZZ。除1号SC和Z-SC为中着丝粒外,其余均为端着丝粒。Z-SC的相对长度有明显的细胞间差异;平均相对长度度介于第3和第4号SC之间。三者SC组型上的差异主要表现在相应SC长度上的不同。并对其亲缘关系及在鸟类进化中的可能地位进行了讨论。此外,在微铺展法制备的锦鸡精母细胞SC标本中还发现了巨大中心粒,这在高等动物尚属首次。     

Meiotic sister chromatid cohesion in holocentric sex chromosomes of three heteropteran species is maintained in absence of axial elements

It has been suggested that in species with monocentric chromosomes axial element (AE) components may be responsible for sister chromatid cohesion during meiosis. To test this hypothesis in species with holocentric chromosomes we selected three heteropteran species with different sex-determining mechanisms. We observed in surface-spreads and sections using transmission electron microscopy that the univalent sex chromosomes form neither AEs nor synaptonemal complexes (SCs) during pachytene. We also found that a polyclonal antibody recognizing SCP3/Cor1, a protein present at AEs and SC lateral elements of rodents, labels the autosomal SCs but not AEs or SC stretches corresponding to the sex chromosomes. Cytological analysis of the segregational behaviour of the sex univalents demonstrates that although these chromosomes segregate equationally during anaphase I they never show precocious separation of sister chromatids during late prophase I or metaphase I. These results suggest that AEs are not responsible for sister cohesion in sex chromosomes. The segregational behaviour of these chromosomes during both meiotic divisions also indicates that different achiasmate modes of chromosome association exist in heteropteran species. Received: 22 September 1999; in revised form: 20 December 1999 / Accepted: 21 December 1999     

Heterosynapsis and axial equalization of the sex chromosomes of the northern bobwhite quail.

The pairing behavior of the Z and W chromosomes in the female northern bobwhite quail (Colinus virginianus) was analyzed by electron microscopy of silver-stained synaptonemal complexes (SCs). After autosomal pairing was completed, synapsis of the sex chromosomes initiated at the short-arm end of the W chromosome and one end of the Z chromosome. Synapsis then progressed unidirectionally, producing a sex bivalent in which the entire length of the W axis was paired with an equivalent length of the Z axis. Progressive contraction and asymmetrical twisting of the Z axis ultimately resulted in a fully paired configuration with aligned axial ends. Further contraction of the Z axis reduced the extent of asymmetrical twisting such that only the nonaligned centromeric regions distinguished the SC of the ZW bivalent from SCs of similar-sized autosomes in late-pachytene nuclei. Quantitative analyses indicated that the length of the Z axis shortened significantly during the adjustment process, whereas no significant difference occurred in the length of the W axis. The nonalignment of the centromeric regions during transitional stages of ZW synapsis indicates that direct heterosynapsis of nonhomologous segments, followed by axial equalization of the length inequality, is responsible for the length adjustment during synapsis in the sex chromosomes of the bobwhite quail.     

Synaptonemal complex analysis in spermatocytes of tilapia, Oreochromis niloticus (Pisces, Cichlidae).

Some adaptations of the synaptonemal complex (SC) whole-mounting technique first used in plants permitted its application to meiotic studies in tilapia, Oreochromis niloticus. Direct observation of the chromosome pairing process and bivalent structure during the meiotic prophase of this fish species by light and electron microscopy permitted the analysis of SCs in autosomes and the possible identification of sex chromosomes. The analysis of SCs in spermatocytes of O. niloticus revealed that all 22 bivalent chromosomes completely paired, except for the occurrence of a size heteromorphism in the terminal region of the largest bivalent associated with the presence of an incompletely paired segment during the synapsis process, which may be the cytological visualization of an XX/XY sex chromosome system in this species.     

黑眉锦蛇的有丝分裂染色体和减数分裂联会复合体的观察

本工作以C带、硝酸银染色、对黑眉锦蛇(Elaphe taeniura)的有丝分裂染色体进行了显微观察。其二倍体染色体数目2n=36,核型组成为16(8m+6sm+2t)大染色体+20微小染色体。C带显现于几乎所有染色体的着丝粒区,有一对插入型C带位于第6对端着丝粒染色体。一个银染核仁组织区(NORs)位于No.12小染色体。同时以界面铺张——硝酸银染色技术,对黑届锦蛇减数分裂精母细胞联会复合体(SC)的结构进行了亚显微观察。发现黑眉锦蛇的SC结构与其他动物的SC相似,是由两股平行的侧线组成,SC组型与有丝分裂染色体组型有较好的一致性。     

Ultrastructure of the synaptic autosomes and the ZW bivalent in chicken oocytes

Chromosomal axes of chicken oocytes from pre- and post-hatching chickens were analyzed with a microspreading technique for electron microscopy. At leptotene, chromosomal axes begin to be formed as discontinuous, non-polarized axial segments. During zygotene synaptonemal complex (SC) formation begins at the axial ends attached to the nuclear envelope. Polarization of axial ends is nearly simultaneous with the beginning of SC formation. The complete SC set is found at pachytene and it consists of 38 SC's and an unequal SC which has been identified as the ZW pair. This unequal SC is formed by two axes of different length. The Z and W axes represent 6.2% and 4.5% respectively of the combined length of the SC set plus the Z axis. The unpaired segment of the Z axis shortens markedly from early to mid-pachytene and becomes thicker than the lateral elements of SCs. In the paired region the Z axis forms most of the twists around a straighter W axis, suggesting some extent of non-homologous pairing between the Z and W chromosomes in this region. The existence of partial synapsis of the Z and W axes without heteropycnosis of the sex chromosomes is in marked contrast to partial synapsis in the heteropycnotic XY body of mammalian spermatocytes.