黄瓜花粉母细胞减数分裂过程中微核仁现象的研究

在黄瓜(CucumissativusL.)高代自交系花粉母细胞减数分裂过程中,首次观察到了微核仁现象。在被观察的430个花粉母细胞(PMCs)中,有279个含有微核仁,占64.9%。微核仁在PMCs中数目变化范围在1～7之间。从细线期到四分孢子期都可观察到微核仁,其数量和大小在分裂的不同时期有所差异,但在第一次和第二次减数分裂时期内的变化趋势相似。在微核仁的周期性变化过程中,染色体的行为正常,并没有发现染色体畸变或染色体桥等现象。将此高代自交材料与3个商品种对照,分别在不同的季节种植在不同的地点,证明微核仁仅在此高代自交系上发生,且不受栽培季节和环境的影响。

人卵母细胞前期染色体和核仁、微核仁的观察

多年来,许多生物学家采用压片法(Ohno等,1961,1962;Baker 1963),空气干燥法(Luciani等,1974;Vebele-Kaelhardt,1978;Speed,1985)连续切片的电镜观察(Baker和Franchi,1967)等相继对人卵母细胞染色体进行过研究。Hart-ung等(1978)曾经以;H-尿嘧啶核苷标记人卵母细胞前期核,观察了RNA的进行性变化。

蚕豆根端细胞核中微核仁的研究

以蚕豆(Vicia faba)根端分生组织细胞为材料研究了微核仁的超微结构和细胞化学特点。结果表明;微核仁是直径0.3—0.5μm 的卵圆形或球形结构。常规染色时,微核仁与集缩染色质的电子密度相仿,但两者之间在结构上没有任何联系。细胞化学研究指出,微核仁含有 RNA 和蛋白质,其结构成分主要是与核仁颗粒组分十分相似的 RNP 颗粒。报道了植物细胞核中微核仁发生于核仁的过程并对微核仁的本质和功能进行了讨论。

微核仁是富含剪接因子SC35的核内小体

许多植物细胞核中存在一些较小的球形或卵圆形的结构，不同作者分别将其称为球体（ｓｐｈｅｒｕｌｅｓ）［１］、核体（ｋａｒｙｏｓｏｍｅ）［２］、核仁附着小体（ｎｕｃｌｅｏｌｕｓａｓｏｃｉａｔｅｄｂｏｄｉｅｓ）［３］、螺旋小体（ｃｏｉｌｅｄｂｏｄｉｅｓ）［４...

Electron Microscopic Studies on the Silver-stained Nucleolar Cycle of Physarum polycephalum

The dynamic changes of nucleolar ultrastructure in the cell cycle of Physarum polycephalum Schw. were studied by an en bloc silver-staining method. The results showed that the nucleolus was large in size and situated in the center of the nucleus in late G(2)-phase, and the fibrillar centers, dense fibrillar components and granular components could be observed in the nucleolus. During prophase, the nucleolus moved towards the periphery of the nucleus and in late prophase disintegrated near the nuclear envelope. in metaphase, the disintegrated nucleolar components were dispersed in masses and located at the periphery of the chromosomal region of the nucleus. No specifically silver-stained area and argentophilic protein sheath were observed on the chromosomes, but there were some big dispersed silver particles within the chromosomes. During telophase the nucleolar components moved towards the two poles along with the chromosomes and co-existed with the decondensing chromatin in daughter nuclei. The nucleolar components then gradually converged with one another and separated from the chromatin. A big nucleolus was formed in the nucleus about 120 min after the completion of mitosis.

^3H的辐射生物学效应的研究：Ⅲ.^3H—Thymidine诱发水绵（Spiro…

利用电子显微镜研究＾３Ｈ－Ｔｈｙｍｉｄｉｎｅ对水绵细胞核仁的辐射效应。结果明显，水绵细胞分裂间期的核仁为近球形，由核仁颗粒区和立体网状的核仁纤维区组成。水绵在含有１０μｃｉ／ｍＬ的＾３Ｈ－Ｔｈｙｍｉｄｉｎｅ培养基培养１４００ｈ以后，受到细胞内外，细胞核内外＾３Ｈ的辐射作用，分裂间期核仁增大，核仁中小部分纤维区或颗粒区的物质成团离开核仁，在核中，核仁旁形成“微核仁”。

放射卫生

在北京市按网格布点调研了环境辐射水平。北京原野γ辐射及宇宙射线室外剂量率按网点加权均值分别为56.2及32.3nGy·h-1,全市土壤中233U、232Th、226Ra、40K及137Cs含量按面积加权均值分别为19.4、34.1、21.4、622及8.3Bq·kg-1,各类水体水中U、Th及226Ra、40K浓度范围分别是0.12～8.94、0.02～0.66μg·L-1及6.0～98.1、19.2～643mBq·L-1。