Three-dimensional helical coiling structures and band patterns of hydrous metaphase chromosomes observed by low vacuum scanning electron microscopy.
Three-dimensional helical coiling structures and band patterns of hydrous metaphase chromosomes observed by low vacuum scanning electron microscopy.
复制标题
低真空扫描电镜观察含水中期染色体的三维螺旋卷曲结构和带型。
DOI：
--
复制
发表时间：
2002
影响因子：
--
通讯作者：
A. Iino
中科院分区：
文献类型：
--
作者：
S. Inaga;Kéiichi Tanaka;A. Iino
用低真空扫描电镜（SEM）三维观察了含水中期染色体的螺旋卷曲结构和带型。将固定或未固定的分离的中国仓鼠中期染色体用铂蓝（Pt蓝）染色，并在低真空SEM的背散射电子模式下观察，无需任何低渗处理或干燥过程。固定和未固定含水染色体均显示纤维结构;特别是在具有对比鲜明的明暗交替带的固定染色体中，螺旋染色单体卷曲及其亚卷曲被澄清，而在未固定染色体中识别出半透明的染色体周基质和紧凑的纤维结构。螺旋卷曲在中期染色体松散的染色单体中表现得更为清楚。用Tris-HCl缓冲液处理，在含水条件下进行铂蓝染色，成功地在中期染色体上产生了类似于G-带的带型。用低真空扫描电镜观察到的这些带化染色体，在临界点干燥后，也用场发射扫描电镜进行了立体分析。这些调查结果表明：1）天然或未固定的染色体保持着紧密排列的高级螺旋结构，并被染色体周围的基质所覆盖：2）以往文献中经常观察到的染色单体螺旋卷曲现象可能是由于中期染色体的高级结构的最后一层松动所致;（3）在提取某些染色体成分后，染色质纤维在30 nm纤维水平上的重排或重组可能产生带型，这些染色体成分包括胞内或胞间的染色体材料在显带过程中。
Helical coiling structures and band patterns of hydrous metaphase chromosomes were documented three-dimensionally by low vacuum scanning electron microscopy (SEM). Fixed or unfixed isolated Chinese hamster metaphase chromosomes were stained with platinum blue (Pt blue) and observed in the backscattered electron mode for low vacuum SEM without any hypotonic treatment or drying processes. Fibrous structures were shown both in the fixed and unfixed hydrous chromosomes; helical chromatid coils and their subcoils were clarified especially in the fixed chromosomes having contrasting alternative bands of light and darkness, while the translucent perichromosomal matrix and compact fibrous structures were recognized in the unfixed chromosomes. The helical coils were more clearly represented in a loosened chromatid of metaphase chromosomes. Treatment with a tris-HCl buffer solution and Pt blue staining in a hydrous condition successfully produced banding patterns similar to G-bands on metaphase chromosomes. These banded chromosomes observed by low vacuum SEM were also analyzed stereoscopically by field emission SEM after critical point drying. These findings indicate that: 1) native or unfixed chromosomes maintain the compact arrangement of high-order helical structures covered with the peri-chromosomal matrix; 2) helical coiling appearances of chromatids frequently observed in previous papers might be caused by loosening of the final level of the high-order structure of the metaphase chromosome; and 3) banding patterns might be produced by the rearrangement or reorganization of chromatin fibers at the 30 nm fiber level after the extraction of some chromosomal components including the peri- or intra-chromosomal materials during the banding procedure.