小鼠生精细胞染色质与染色体构筑的扫描电镜研究(简报)

正常情况下,染色质和染色体在细胞内呈高度致密状态,在光镜和透射电镜下常呈浓染的斑块状。由于方法学上的困难,至今对染色质乃至染色体的微细结构,仍缺乏清楚的了解。特别是关于染色质如何凝缩形成染色体方面,现仍存在有争论。扫描电镜的冷冻割断技术,曾被用于对游离细胞间期核染色质的观察,并取得了较好的     

Mitochondrial dysfunction leads to reduced chronological lifespan and increased apoptosis in yeast

We previously isolated a Saccharomyces cerevisiae mutant (HsTnII), which displays 40% reduced chronological lifespan as compared to the wild type (WT). In this study, we found HsTnII cultures to be characterized by fragmented and dysfunctional mitochondria, and by increased initiation of apoptosis during chronological aging as compared to WT. Expression of genes encoding subunits of mitochondrial electron transport chain and ATP synthase is significantly downregulated in HsTnII, and as a consequence, HsTnII is not able to respire ethanol. All these data confirm the importance of functional mitochondria and respiration in determining yeast chronological lifespan and apoptosis.     

The tkNeo gene, but not the pgkPuro gene, can influence the ability of the beta-globin LCR to enhance and confer position-independent expression onto the beta-globin gene

Whether drug-selectable genes can influence expression of the beta-globin gene linked to its LCR was assessed here. With the tkNeo gene placed in cis and used to select transfected cells, the beta-globin gene was expressed fourfold lower when it was positioned upstream of the LCR rather than downstream. This difference did not occur when the pgkPuro gene replaced tkNeo. Moreover, the beta-globin gene situated upstream of the LCR was transcribed without position effects when it was cotransfected with a pgkPuro-containing plasmid, whereas cotransfection with a tkNeo plasmid gave measurable position effects. Previous results from transfected cells selected via a linked tkNeo gene suggested that the 3' end of the beta-globin gene has no impact on LCR-enhanced expression. Here, removal of the 3' end of the beta-globin gene resulted in lower and much more variable expression in both transgenic mice and cells cotransfected with pgkPuro. Together, the results suggest that tkNeo, but not pgkPuro, can strongly influence expression of the beta-globin gene linked to its LCR. The findings could partly explain why data on beta-globin gene regulation obtained from transfected cells have often not agreed with those obtained using transgenic mice. Hence, one must be careful in choosing a drug-selectable gene for cell transfection studies.     

Identification of microRNAs in Wool Follicles during Anagen,Catagen, and Telogen Phases in Tibetan Sheep

Background

Wool quality is one of the most important economic traits in sheep. The wool fiber is derived from specialized skin cells that are referred to as wool follicles. To understand the roles of microRNAs (miRNAs) in wool fiber growth, we detected the expression patterns of miRNAs in wool follicles at the anagen, catagen, and telogen stages from Tibetan sheep through Solexa sequencing.

Results

A total of 244 mature miRNAs were identified. Of these, only five miRNAs are listed in the database of sheep miRNAs (miRBase Database V19), and the other 239 miRNAs have not been previously described in this species. Further analyses indicated that 204 miRNAs are evolutionarily conserved among mammal species, whereas 35 of the identified miRNAs were first found specifically in sheep. The expression pattern analyses showed that the expression levels of 39, 34, and 20 of the miRNAs significantly change between anagen and catagen, between anagen and telogen, and between catagen and telogen, respectively. The results of the bioinformatics analysis show that these differentially expressed miRNAs might regulate wool follicle development by targeting genes in many different pathways, such as the MAPK and Wnt pathways, as well as the pathways that regulate the actin cytoskeleton, focal adhesion, and tight junctions. Furthermore, we identified six differentially expressed miRNAs (oar-miR-103-3P, oar-miR-148b-3P, oar-miR-320-3P, oar-miR-31-5P, oar-novel-1-5P, and oar-novel-2-3P) that might target the key genes of the Wnt pathway. It has been reported that the Wnt pathway is critical for wool follicle development. Therefore, these miRNAs may regulate wool development through the Wnt pathway.

Conclusions

Our results provide new information on the identification and expression pattern of miRNAs in wool follicles. Our data might therefore aid in the understanding of the mechanisms of wool follicle development in sheep.     

东北红豆杉(Taxus cuspidata)中四种紫杉烷类化合物抑制妇科肿瘤细胞增殖活性研究及其作用机制的初步探讨

通过四唑盐(MTT)比色法检测东北红豆杉中四种紫杉烷类化合物对人子宫颈癌细胞、人子宫内膜癌细胞、人卵巢透明癌细胞和人卵巢囊腺癌细胞增殖的影响,不仅探讨了这些化合物作用的构效关系,还初步探讨了其抑制肿瘤细胞增殖的作用机制。结果发现9,10-去乙酰紫杉宁对人子宫颈癌细胞、人子宫内膜癌细胞和人卵巢囊腺癌细胞的增殖均有明显的抑制作用,与紫杉宁和1β-羟基紫杉宁即使在100μmol/L的高浓度下,对五种妇科肿瘤细胞的增殖不显示抑制活性;流式细胞学检查发现9,10-去乙酰紫杉宁作用后的HeLa细胞出现凋亡现象。因此推测:1.C-9,10位的羟基和C-5位的肉桂酰基侧链是该类化合物抑制肿瘤细胞增殖所必需的;2.9,10-去乙酰紫杉宁有可能是通过诱导肿瘤细胞凋亡来实现其抑制HeLa细胞的增殖作用。     

细胞因子基因转导对人乳腺癌细胞MHC抗原及细胞膜糖蛋白表达的影响

为探讨细胞因子基因(人IL-2、IL-6)转导对于肿瘤细胞膜MHC抗原及细胞膜糖蛋白表达调控的影响,本文利用脂质体介导的方法,将含人IL-6、IL-2基因的逆转录病毒载体分别导入人乳腺癌细胞系MCF-7细胞中,采用间接免疫荧光染色流式细胞仪测定法,对基因转导的瘤细胞细胞膜糖蛋白及MHC抗原表达进行测定。结果表明经两种基因修饰的MCF-7细胞MHCⅠ型抗原表达均获得增强,此外,基因转导细胞可程度不同地表现出细胞膜多种糖蛋白表达的变化。提示肿瘤细胞膜抗原及糖蛋白表达的改变可能是细胞因子基因转导影响肿瘤细胞免疫原性的重要结构基础。     

HCV编码病毒结构蛋白的DNA免疫研究

应用HCVC (pC)和HCVCE1E2 (pCE1E2 )重组体转染真核细胞并且通过肌注免疫BALB/C小鼠 ,对其体液免疫和细胞免疫进行检测。所用的 pC和 pCE1E2 均可在真核细胞内表达出特异性HCVC蛋白 ;肌注DNA免疫后均可诱导出BALB/C小鼠的体液和细胞免疫反应 ,抗体反应的A值 :pC组为 0 .358± 0 .0 96 ,pCE1E2 组为 0 .4 15± 0 .12 7;CTL活力 pC组为 18.6 5%± 5.72 % ,pCE1E2 组为 2 0 .0 7%± 11.11% ;通过免疫鼠荷瘤检测体内CTL反应 ,可观察到免疫组鼠发瘤时间滞后 ,发瘤部位减少和存活时间延长。在开发和研制HCV疫苗的过程中 ,DNA免疫是在快速构建、评价和筛选免疫原方面的有效办法。     

Membrane Rafts Are Involved in Intracellular Miconazole Accumulation in Yeast Cells

Azoles inhibit ergosterol biosynthesis, resulting in ergosterol depletion and accumulation of toxic 14α-methylated sterols in membranes of susceptible yeast. We demonstrated previously that miconazole induces actin cytoskeleton stabilization in Saccharomyces cerevisiae prior to induction of reactive oxygen species, pointing to an ancillary mode of action. Using a genome-wide agar-based screening, we demonstrate in this study that S. cerevisiae mutants affected in sphingolipid and ergosterol biosynthesis, namely ipt1, sur1, skn1, and erg3 deletion mutants, are miconazole-resistant, suggesting an involvement of membrane rafts in its mode of action. This is supported by the antagonizing effect of membrane raft-disturbing compounds on miconazole antifungal activity as well as on miconazole-induced actin cytoskeleton stabilization and reactive oxygen species accumulation. These antagonizing effects point to a primary role for membrane rafts in miconazole antifungal activity. We further show that this primary role of membrane rafts in miconazole action consists of mediating intracellular accumulation of miconazole in yeast cells.