葱小孢子的染色体和核型研究

本文用胰酶－尿素双重处理法和ＳＳＧ法,分别进行了葱小孢子染色体螺旋的染色体Ｃ－带的显带研究。首次成功地获得了葱小孢子染色体螺旋和染色体Ｃ－带,螺旋图象清晰;染色本Ｃ－带与体细胞的基本一致,所有染色体上均显示出明显的末端带,但未出现次缢痕带,另外,研究了葱小孢子的核型,其结果与体细胞的核型基本一致,但有差异。作者认为小孢子的核型比体细胞的核型准确,更能反映出葱的核型特征。     

一种显示染色体螺旋结构的简易方法

染色体是遗传基因的载体,对生物的生长、发育、遗传和变异起着决定作用,因此染色体结构的研究就显得十分重要。过去,人们对于染色体结构提出了许多种模型^[1,2,3,5]。大多数作者认为染色体的最高级结构为螺旋结构。关于显示染色体螺旋结构的方法,国外已有报道^[4,6],本文将介绍一种显示染色体最高级结构为螺旋结构的简易方法。     

鸡胚发育中染色体长度的变化及螺旋结构

对孵育3-72小时家鸡胚胎染色体长度及螺旋结构进行了比较研究,同时还考察了染色体DNA含量的变化。结果表明：(1)家鸡染色体的最高一级结构是螺旋结构。(2）随胚胎发育的进展,染色体绝对长度逐渐缩短。(3）伴随染色体的缩短,其螺旋数目亦相应地减少,而螺旋直径却有一定程度增加。(4）每个中期板的染色体DNA含量并不随发育进展而变化。本文还讨论了发育中染色体缩短与螺旋结构间的相互关系。     

蒜有丝分裂前期和前中期染色体的螺旋结构

本文研究了蒜(Allium sativum)根端细胞有丝分裂前期和前中期染色体的螺旋结构及其形成过程。在光镜和电镜下都看到前期核内存在螺旋化的染色线。从早前期到晚前期染色线的螺旋化是逐渐进行的。开始只有部分染色线螺旋化,螺幅直径约为1.2-1.5微米,以后螺幅增大,达1.8～2微米,并且螺旋结构变得更为紧密。前中期染色体中可见由直径600 nm左右的染色线形成的螺旋结构,螺旋比晚前期更加紧密。本文对中期染色体的高层次结构进行了讨论。     

红翅皱膝蝗减数分裂染色体的螺旋与轴结构

用低渗处理和苯酚品红染色,在经过卡诺液(甲醇3∶冰醋酸1)固定和未经固定的红翅皱膝蝗减数分裂染色体上都看到了螺旋结构。观察和测量结果表明,每条染色单体都是由430nm左右的染色线螺旋形成的。由染色线到染色体的压缩率为4∶1。低渗处理后固定的材料经过银染,则显示了染色体轴结构。同样,未经低渗处理直接固定的材料银染时也出现了轴结构。银染的轴结构位于每个染色单体的中央,并贯穿整个染色单体。在光镜下,这个轴并不是直径均一的棒状结构,而似乎是由许多大小相近的颗粒相连而成。本文对染色体结构的有关模型、骨架和轴结构的真实性以及轴和螺旋的关系等问题进行了讨论。     

蚕豆染色体集缩和解集缩过程中的螺旋结构

运用常规电镜技术观察到,在有丝分裂前期的集缩过程中,蚕豆(Vicia faba)染色体横切面为直径约0.5μm的染色质纤维形成的环状结构;染色体纵切面上存在着平行排列的0.5μm染色质纤维,它们与染色体长轴所成的角度近似直角。通过立体电镜观察可清晰辨认出这些纤维盘绕成的螺旋结构。在有丝分裂末期至间期的解集缩过程中,染色体横切面由环形变为“C”形。这种“C”形构造显示了染色体螺旋结构的解螺旋过程。在染色体集缩和解集缩过程中均可观察到0.5μm染色质纤维和直径约0.2μm的染色质纤维。本文讨论了放射环模型和多级螺旋模型。     

小麦染色体轴结构的观察

对普通小麦 ( Triticum aestivum L.)中期染色体进行常规制片银染的结果显示 ,染色体中存在着染色深的轴结构 ,每个染色单体一条 ,轴在有些部位似乎是螺旋的。研究结果对染色体轴结构的真实性提供了证据     

早熟凝集染色体和诱导凝集的染色体扫描电镜研究

应用细胞融合技术和扫描电镜研究了ＢＫ（牛肾）细胞早熟凝集染色体（ＰＣＣ）和诱导ＰＣＣ的ＣＨＯ中期染色体的超微结构。所用电镜标本制备方法,尽可能使之减少人工效应,故首次观察到ＰＣＣ超微结构,特别是早、中、晚Ｓ－ＰＣＣ超微结构的自然状态,从早、中、晚Ｓ－ＰＣＣ的染色体片段所显示的ＰＣＣ的多级亚结构,进一步了解了ＢＫ细胞染色体的超微结构。诱导ＰＣＣ的ＣＨＯ中期染色体表面显示出整齐的小毛样由螺旋纤维形成的环状突起。     

植物染色体G带及螺旋的研究

本文报道了采用胰酶,尿素,SDS和NaOH原位诱导黑麦,小麦和蚕豆染色体G带和螺旋的结果,所得的G带带纹众多,分布于整个染色体上,带纹数目与染色体收缩程度相关,个别细胞的同源染色体带纹可以配对,一些晚前期染色体的带纹已达高分辨水平,G显带处理时间过长,染色体螺旋结构往往被诱导出来,螺纹数与染色体收缩程序有关,螺旋方向具有多样性,本文还首次报道了植物染色体G带到螺旋的转化现象,在光镜下显G带的染色体在扫描电镜下呈现出螺旋的特征,作者还对植物染色体G带与螺旋的关系作了初步的讨论。     

植物染色体G带及螺旋的研究

本文报道了采用胰酶,尿素,SDS和NaOH原位诱导黑麦,小麦和蚕豆染色体G带和螺旋的结果,所得的G带带纹众多,分布于整个染色体上,带纹数目与染色体收缩程度相关,个别细胞的同源染色体带纹可以配对,一些晚前期染色体的带纹已达高分辨水平,G显带处理时间过长,染色体螺旋结构往往被诱导出来,螺纹数与染色体收缩程序有关,螺旋方向具有多样性,本文还首次报道了植物染色体G带到螺旋的转化现象,在光镜下显G带的染色体在扫描电镜下呈现出螺旋的特征,作者还对植物染色体G带与螺旋的关系作了初步的讨论。     

Helical Structure Revealed upon the Condensation and Decondensation of Chromosomes of Vicia faba

By using conventional and stereo electron microscopy, helical structures were revealed in prophase and telophase chromosomes of root tip cells of Vicia faba. Longitudinal and transverse sections of the chromosomes showed that both prophase and telophase chromosomes were composed of chromatin fibres about 0.5μm in diameter and among the 0.5μm chromatin fibre thinner chromatin fibres with a diameter of about 0.2μm were found. In transverse sections, prophase chromosomes appeared to be a circular structure which contained a low electron density centre encircled by the 0.5 μm fibre. In longitudinal section of the chromosomes, the 0.5 μm fibres were seen to be orientated parallel to each other while constituted roughly a right angle to the long axis of the chromosome. Helical coils consisting of the 0.5μm fibre were identified easily by stereo electron microscopy. In transverse sections of telophase chromosomes, both the circular structure similar to that of the prophase chromosomes and the hoof-shaped structure composed of the 0.5μm fibre were observed, demonstrating4 the de-spiralization of the helical coils in the decondensation of the chromosomes. Based on these observations, the radial loop. model and the multiple coiling model are discussed.     

Nucleosomelike structures associated with chromosomes of the archaebacterium Halobacterium salinarium.

Chromosomes of the halophilic archaebacterium Halobacterium salinarium were examined by electron microscopy after being spread onto water. The major part of the chromosomal DNA was associated with protein particles with diameter of 9.4 nm, arranged tandemly along the DNA fibers. Thus, the primary structure of the chromosome resembles that of eucaryote chromosomes.     

Characteristics of the ultrastructural organization of metaphase chromosomes in mouse embryos in the early cleavage stages

The structural organization of the mouse metaphase chromosomes in the early embryonic development (I-IV cleavages) was studied using serial ultrathin section. It was shown that in the first cleavage the metaphase chromosomes consist of DNP fibrils 20-25 nm in diameter, which are distributed nonuniformly along the chromosomes. It was suggested that parts of chromosomal arms formed by tightly packing DNP fibrils may correspond to the G-bands revealed by the routine Giemsa staining. In metaphase chromosomes of 8-16-cell embryos DNP fibrils form chromonema--thick threads about 90 nm in diameter. The chromonemata are evenly organized along chromosomal arms. The centromeric heterochromatin always consists of DNP fibrils tightly arranged in a block having no chromonemal level of organization. In all the cells studied chromosomes form structural contacts (associations) by their centromeric heterochromatin regions.     

Studies on Ribonucleoprotein and Argyrophilic Proteins in the Chromosomes of Prorocentrum sp.

The chromosomal ultrastructure and the chromosomal substances of ribonucleoprotein (RNP) and argyrophilic proteins of Prorocentrum sp. were studied using the techniques of conventional staining, RNP preferential staining and Ag-staining. Most part of the RNP in the chromosomes of Prorocentrum sp. was in the form of fibril distributed around the DNP throughout the chromosone. The RNP in the periphery of the chromosomes was found to form a closed membrane-like structure. Many kinds of the argyrophilic proteins were distributed regularly in the chromosome of Prorocentrum sp., but varied greatly in quantity from cell to cell. The amount of argyrophilic proteins in the chromosomes of some cells was much more than that in the nucleoplasm, but in other cells the amount of argyrophilic proteins was less than that in the nucleoplasm. The results indicated that in addition to argyrophilic proteins, RNA might play a role in the maintenance of the chromosome structure at a high level.     

草鱼染色体的包装（间期—中期）

以草鱼ＺＣ７９０１细胞株为材料,观察鱼类细胞从间期染色质到中期染色体的包装过程。主要通过（１）分裂期与间期细胞融合,诱导染色体早熟凝集;（２）染色体“伸长”处理;（３）培养细胞的低渗处理;（４）染色质辅展等方法,制作染色体标本,进行扫描和透射电镜观察。观察表明,鱼类染色质的基本结构与哺乳类细胞相同,也是直径约１０ｎｍ的核丝。染色体的色装有两种形式：一种是多级螺旋化形成直径约３００ｎｍ的染色单体,     

The dynamics of the structural reconstruction of mitotic chromosomes after their artificial decondensation in vitro

The treatment of isolated metaphase chromosomes with 5 mM Tris buffer caused their decondensation into DNP fibers 10 nm in diameter. The following increase in CaCl2 concentration induced the transition of nucleosomic DNP fibers into DNP fibers 20 nM and 40-50 nM in diameter, and the recovery of the whole chromosomes. However, in the similar conditions, the typical chromosomes (threads about 100 nm thick), chromomeres and G-bands were not reconstructed. According to these data, we assume that DNP threads 40-50 nm in diameter may be artificial (i.e. "pseudochromonemes"). The treatment of isolated chromosomes with 0.35 and 0.6 M NaCl prevents from formation of nucleomeric and pseudochromomeric fibers, although bodies of chromosomes can be recovered after the removal of HMG and H1 proteins. These observations point to a high stability of chromosomal fasteners providing the structural integrity of mitotic chromosomes.     

Chromosomes for molecular hybridization

Summary Specific recombinant DNA sequences (5S rRNA, B1, albumin) were assigned to flow sorted chromosomes of the Chinese hamster cell line CHV79. For this purpose, a rapid protocol was developed using filterbound chromosomal DNA and probing with various nucleic acids, that allows sequence identification in chromosomes. A flow histogram and a flow karyogram of the CHV79 cell line were established by flow analysis in order to calculate the amount of DNA per CHV79 cell and their chromosomes. Subsequently, metaphase chromosomes or chromosomal groups were fractionated by electronic sorting and a defined number of chromosomes was directly bound to nitrocellulose filters for sequence homology analysis by a dot blot hybridization procedure. This procedure not only allows the assigning of specific DNA sequences to particular chromosomes, it is also applicable to studies of changes in karyotypes, for example translocations of given sequences.Some results shown constituted a Diploma Thesis by G.L. submitted to and accepted by the Department of Biology, University of Kaiserslautern     

Localization of DNA in the condensed interphase chromosomes of Euglena

The localization of DNA in the condensed interphase chromosomes of Euglena was determined by immunoelectron microscopy. Deposits of gold particles that coincided with the localization of DNA followed threads that corresponded to the chromatin fibers. The threads were 55–80 nm in diameter and were assumed to be supersolenoids. The localization of gold deposits on chromosomes that had been sectioned in various directions suggested that the chromatin fibers coiled around the surface of chromosomes, with a wide central axial region of the chromosomes remaining free of DNA. These findings are discussed in relation to current models of chromosomal structure.