烟草表皮细胞薄层培养中第一次无丝分裂时的核及核外微丝骨架变化的观察

通过Hoechst33258和TRITC－Phalloidin对烟草茎表皮薄层培养细胞的非固定染色观察，发现细胞无丝分裂过程中核及其外围微丝鞘发生了很大变化．染色质在分裂时形成卷曲拉裂状，此时核外微丝鞘完全消失．直至染色质分开后，两组染色质由伸张状态回缩时，微丝鞘才重新聚合排列，并最后形成两个子核的微丝鞘．     

荧光染色观察钝节拟丽藻中无丝分裂的研究

用DAPI荧光染色法对处于不同生长时期钝节拟丽藻(Nitellopsis obtuse)的节间,小枝,苞片,节部及假根中细胞的细胞核的分裂方式进行了研究,发现无丝分裂是钝节拟丽藻藻体细胞核的唯一分裂方式.在细胞核无丝分裂过程中,染色质不发生浓缩,不形成染色体,核膜不解体,核的分裂部位不定,产生的子核大小,形状各异.     

烟草表皮细胞薄层培养中第一次无丝分裂时的核及核外微丝骨…

通过Ｈｏｅｃｈｓｔ３３２５８和ＴＲＩＴＣ－Ｐｈａｌｌｏｉｄｉｎ对烟草茎表皮薄层２细胞的非固定染色观察，发现细胞无丝分裂过程中核及其外围微丝鞘发生了很大变化，染色质在分裂时形成卷曲拉裂状，此时核外微丝鞘完全消失，直至染色质分开后，两组以持同伸张状态回缩时，微丝才重新聚合排列，并最后形成两个子核的微丝鞘。     

半夏绒毡层细胞降解的显微观察及花粉活力检测

本文对三叶半夏的变形绒毡层的降解过程进行了显微观察，发现绒毡层细胞随着花粉母细胞的减数分裂和小孢子发育的进行，其细胞位置、细胞壁和核的形态发生改变．Feulgen反应显示变化过程中细胞核内染色质结构是完整的，染色质与细胞结构随着花粉的成熟逐渐降解．FCR法检测，发现花粉活力在散落后逐渐降低．本文探讨了绒毡层与花粉活力的关系，以及半夏在自然情况下有性繁殖能力较低的原因．     

爪蟾卵非细胞体系诱导凋亡与27kD凋亡相关核酸酶的发现

通过向正常爪瞻卵提取物Ｓ－１５０中加入ｄＡＴＰ和细胞色素ｃ，得到能有效诱导外源细胞核半亡的非细胞体系。温育在上述非细胞体系中的小鼠肝细胞表现出明显的凋亡特征。细胞核的绝大部分染色质ＤＮＡ凝集并排出，只在核膜边级残留一些ＤＮＡ成分，而温育体系中充满高度凝集的凋亡小体。     

斑马鱼体细胞核移植——头肾细胞和尾鳍细胞核移入成熟具核卵子发育能力的初步研究

将经直接消化的斑马鱼头肾细胞或经短暂培养的尾鳍细胞核移植到同种成熟具核卵子中，移核卵可发育到原肠晚期；将移核卵发育成的囊胚细胞核作供体进行第2次核移植，受体卵可发育到尾芽期或肌肉感应期。流式细胞仪测定DNA含量表明，受体卵发育形成的囊胚细胞DNA含量与正常囊胚细胞DNA含量相同，由此可知，移核卵中的雌原核没有参与移核胚胎的发育。     

泥蚶精母细胞与精细胞的超微结构

用透射电镜研究了泥蚶精母细胞与精细胞的超微结构变化。精母细胞时期，胞质中线粒体呈极性分布，高尔基体结构典型，染色质多数团块状、少数颗粒状分布于核质中；精细胞时期，胞质中线粒体数目较少，基质电子密度高，并逐渐迁移至细胞核的后端，参于精于中段的形成，核内染色质从粗团块状→颗粒状均匀分布→高电子密度的均质体；初级精母细胞发育至后期精细胞的过程中，细胞及核的体积各期依次变小。     

荔枝雌花发育过程中花药败育的超微结构观察

应用扫描电镜、透射电镜和DAPI荧光染色方法对荔枝雌花发育过程中花药败育进行了研究,结果发现:败育的花药在减数分裂之前其药壁细胞即开始解体,减数分裂后,药壁组织发生细胞程序性死亡,导致对营养物质竞争力的减弱;发生凋亡的细胞,细胞核染色质固缩,其电子密度高于正常,核仁消失,染色质趋边化的双层核膜降解,有的核变形而凹陷,核膜破裂,在核膜破裂处可见到由核物质组成的凋亡小体.正在凋亡的细胞中,几乎都可观察到细胞核周围有许多线粒体,一些线粒体变形拉长,嵴肿胀,有的线粒体发生缢缩,线粒体膜降解而变得模糊,有的已破裂.表明线粒体与细胞凋亡可能有直接的关系.     

台湾桤木无丝分裂与细胞多核现象研究

利用去壁低渗-火焰干燥法在台湾桤木根尖细胞中观察到除有丝分裂外,还存在无丝分裂和细胞多核现象.在进行无丝分裂的根尖细胞核中,不发生染色质凝集,不形成可见的染色体,整个过程中核膜保持完整.其无丝分裂产生形状、大小相似的子核,形成了不同类型的多核细胞.     

水稻单细胞培养及植株再生

对以水稻幼穗为外植体诱导的愈伤组织进行振荡培养,分离出单细胞。观察到两种细胞类型:一类细胞呈圆形,其核较大,细胞质较致密,分裂活性较强;另一类细胞呈长形或不规则形,其核较小,细胞质较少,很少见到分裂现象。这两类细胞数目与培养基中大量元素、肌醇和2.4-D浓度有很密切的关系。通过半连续悬浮培养使圆形细胞增加,培养40～60天后圆形细胞数达95%。观察到单细胞活体连续分裂的过程及从悬浮培养细胞液中滤出的单细胞再生成了植株。     

Nicotiana ovule extracts in duce nuclear reconstitution of demembranated Xenopus sperm in cell-free system

s Nicotiana tabaccum ovule extracts induced nuclear reconstitution of demembranated Xenopus leavis sperm in a ceil-free system. Demembranated Xenopus sperm began to swell after 15 rmin of incubation with Nicotiana ovulde extracts. Accompanying the process of incubation,Xenopus sperm decondensed and their shapes changed gradually from long and ellipse to round. The completely decondensed chromatin was surrounded with membrane structure, which was a mixture envelope of a double membrane and a single membrane. Nucleosome assembly was verified by means of micrococcal nuclease digestion to reconstituted nuclei and DNA electrophoresis. Nicotiana ovule extracts supplied one more experimental model and system.The new system could promote powerfully the research on mechanisms of cell division and cell cycle regulation.     

CUL-4 ubiquitin ligase maintains genome stability by restraining DNA-replication licensing

To maintain genome stability, DNA replication is strictly regulated to occur only once per cell cycle. In eukaryotes, the presence of 'licensing proteins' at replication origins during the G1 cell-cycle phase allows the formation of the pre-replicative complex. The removal of licensing proteins from chromatin during the S phase ensures that origins fire only once per cell cycle. Here we show that the CUL-4 ubiquitin ligase temporally restricts DNA-replication licensing in Caenorhabditis elegans. Inactivation of CUL-4 causes massive DNA re-replication, producing cells with up to 100C DNA content. The C. elegans orthologue of the replication-licensing factor Cdt1 (refs 2, 3) is required for DNA replication. C. elegans CDT-1 is present in G1-phase nuclei but disappears as cells enter S phase. In cells lacking CUL-4, CDT-1 levels fail to decrease during S phase and instead remain constant in the re-replicating cells. Removal of one genomic copy of cdt-1 suppresses the cul-4 re-replication phenotype. We propose that CUL-4 prevents aberrant re-initiation of DNA replication, at least in part, by facilitating the degradation of CDT-1.     

DMSO诱导烟草BY-2悬浮细胞的凋亡

烟草BY-2悬浮细胞经不同浓度的DMSO处理后发现,2％DMSO处理可导致细胞核染色质凝集或核结构解体,琼脂糖凝胶电泳显示基因组DNA降解成明显的梯状条带,从而表现出典型的细胞凋亡特征．对微丝骨架的进一步观察发现,2％DMSO处理引起细胞内微丝骨架分布异常,造成微丝骨架不同程度地断裂．这些结果为进一步研究微丝骨架在植物细胞凋亡中的功能奠定了基础．     

EC109细胞株细胞周期DNA代谢和形态改变的研究

人食管癌细胞株 EC109以显微分光光度计测定癌细胞核 DNA 含量,以放射自显影测定细胞核摄取~3H-TdR 和扫描电镜检查细胞表面的超微结构.大多数 EC109瘤细胞间期细胞核的 DNA 含量增加,主要干系细胞 DNA 含量为2 C,属 G_1期,也可见低于四倍体(3 C),高于四倍体(>4 C).甚至多倍体(>8 C)的瘤细胞.~3H-TdR 加入培养基10分钟后,许多瘤细胞核有银粒出现(S 期细胞).大量细胞进入细胞周期反映其恶性程度高.扫描电镜可见 EC109在细胞周期不同阶段其细胞大小形状和微绒毛也不同.本文结果说明用细胞核 DAN 含量测定,~3H-TdR 掺入和细胞表面超微结构可测定肿瘤周期.也可用这些方法判定瘤细胞的恶性程度.     

外阴硬化性苔藓基底细胞核DNA含量分析

运用图像分析技术,通过Feulgen染色检测外阴硬化性苔藓组织及正常外阴皮肤组织角朊细胞基底细胞核积分光密度、DNA含量.结果显示,与外阴正常皮肤组织比较,硬化性苔藓组织的角朊细胞基底细胞核积分光密度、DNA含量明显降低,差异有显著性(P＜0.05),硬化性苔藓组织的角朊细胞基底细胞核增生能力较正常皮肤低下.     

Apoptosis in suspension culture of tobacco cells induced by heat shock

The induction of apoptosis in suspension culture of tobacco cells by heat shock is reported for the first time. Heat treatment (48℃ for 4 h) of tobacco cells led to the appearance of typical hallmarks of apoptosis. It was demonstrated by DNA laddering analysis that the cells treated with heat shock at 48℃ for 4 h had a serious degradation of nuclear DNA into multi-nu-cleosomal sizes, suggesting that heat shock activated endogenous nuclease which led to DNA cleavage at the linkage sites between the nucleosomes, but ladders were very faint for DNA from 2 and 9 h heat-treated cells. The terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labelling (TUNEL) detection also showed that most of these treated cells (48℃ for 4 h) displayed positive reactions, indicating a serious DNA 3'-OH cleavage in their nuclei. Moreover, some other cytological changes in apoptotic cells, such as cell shrinkage, chromatin aggregation, nucleus collapse, have also been observed by 4', 6'-diamidino-2-phenyl-indole (DAPI) staining.     

Nicotiana ovule extracts induce nuclear reconstitution of demembranated Xenopus sperm in cell-free system

Nicotiana tabaccum ovule extracts induced nuclear reconstitution of demembranated Xenopus leavis sperm in a cell-free system. Demembranated Xenopus sperm began to swell after 15 min of incubation with Nicotiana ovule extracts. Accompanying the process of incubation, Xenopus sperm decondensed and their shapes changed gradually from long and ellipse to round. The completely decondensed chromatin was surrounded with membrane structure, which was a mixture envelope of a double membrane and a single membrane. Nucleosome assembly was verified by means of micrococcal nuclease digestion to reconstituted nuclei and DNA electrophoresis. Nicotiana ovule extracts supplied one more experimental model and system. The new system could promote powerfully the research on mechanisms of cell division and cell cycle regulation.     

Chromatin dynamics during epigenetic reprogramming in the mouse germ line

A unique feature of the germ cell lineage is the generation of totipotency. A critical event in this context is DNA demethylation and the erasure of parental imprints in mouse primordial germ cells (PGCs) on embryonic day 11.5 (E11.5) after they enter into the developing gonads. Little is yet known about the mechanism involved, except that it is apparently an active process. We have examined the associated changes in the chromatin to gain further insights into this reprogramming event. Here we show that the chromatin changes occur in two steps. The first changes in nascent PGCs at E8.5 establish a distinctive chromatin signature that is reminiscent of pluripotency. Next, when PGCs are residing in the gonads, major changes occur in nuclear architecture accompanied by an extensive erasure of several histone modifications and exchange of histone variants. Furthermore, the histone chaperones HIRA and NAP-1 (NAP111), which are implicated in histone exchange, accumulate in PGC nuclei undergoing reprogramming. We therefore suggest that the mechanism of histone replacement is critical for these chromatin rearrangements to occur. The marked chromatin changes are intimately linked with genome-wide DNA demethylation. On the basis of the timing of the observed events, we propose that if DNA demethylation entails a DNA repair-based mechanism, the evident histone replacement would represent a repair-induced response event rather than being a prerequisite.