人完全性葡萄胎中c-myc的表达及意义

目的研究c-myc基因在人完全性葡萄胎中的表达及其意义。方法取人完全性葡萄胎30例,正常早孕流产标本10例,用SABC免疫组织化学染色方法,检测c-myc基因在两种组织中的表达情况,并采用图像分析技术,对正常早孕绒毛组和完全性葡萄胎组c-myc的表达情况进行对比分析。结果与正常绒毛相比,c-myc基因在完全性葡萄胎组织中的表达量和表达的空间特异性有明显不同。结论 c-myc基因可能与完全性葡萄胎的发生密切相关。     

Hypoxia-responsive AIEgens for precise disease theranostics

Specific biomarker-activatable probes have revolutionized theranostics, being beneficial for precision medicine. Hypoxia is a critical pathological characteristic prevalent in numerous major diseases such as cancers, cardiovascular disorders, inflammatory diseases, and acute ischemia. Aggregation-induced emission luminogens (AIEgens) have emerged as a promising tool to tackle the biomedical issues. Of particular significance are the hypoxia-responsive AIEgens, representing a kind of crucial probe capable of delicately sensing and responding to the hypoxic microenvironment, thereby enhancing the precision of disease diagnosis and treatment. In this review, we summarize the recent advances of hypoxia-responsive AIEgens for varied biomedical applications. The hypoxia-responsive structures based on AIEgens, such as azobenzene, nitrobenzene, and N-oxide are presented, which are in response to the reduction property to bring about significant alternations in response spectra and/or fluorescence intensity. The bioapplications including imaging and therapy of tumor and ischemia diseases are discussed. Moreover, the review sheds light on the future challenges and prospects in this field. This review aims to provide comprehensive guidance and understanding into the development of activatable bioprobes, especially the hypoxia-responsive AIEgens for improving the diagnosis and therapy outcome of related diseases.     

Dancing on the platform: Lability of floral organs of Beilschmiedia appendiculata (Lauraceae)

Floral characters are important for the systematics of the Lauraceae. However, structure and development of the flowers remain poorly known in the family. In this study, we observed the variation and early development of flowers of Beilschmiedia appendiculata, which belongs to the Cryptocarya clade of the family. The results indicate that the shoot apical meristems (SAMs) of the floral buds are enlarged and become a platform for the programmed initiation of the floral organs; floral organs develop basically in an acropetal pattern; phyllotaxis is whorled, initiation of floral primordia within a whorl is asynchronous; floral merosity is extremely variable, for example, dimerous, trimerous, tetramerous, dimerous plus trimerous, and trimerous plus tetramerous. In addition, this species has lost the innermost staminal whorl and glands are not closely associated with stamens of the third staminal whorl, which is unusual in the family Lauraceae. Our new observations broaden our knowledge of the variation of floral structure in Beilschmiedia and pose a fundamental question regarding the ecology underlying the lability of floral organs in B. appendiculata.     

Down-regulation of epidermal growth factor receptor-signaling pathway by binding of GRP78/BiP to the receptor under glucose-starved stress conditions

GRP78/BiP, a molecular chaperone in the endoplasmic reticulum, is induced under such adverse conditions for cell survival as glucose starvation. Induction of GRP78 has been shown to coincide with G1 cell cycle arrest, which is an important cellular defense system. In this study, we investigated involvement of GRP78 in the mechanism of growth arrest by using human epidermoid carcinoma A431 cells. Under a chemical stress condition with 2-deoxyglucose, GRP78 was induced 3–4-fold. In the stressed cells, an underglycosylated form of epidermal growth factor receptor (EGFR) was produced and the mature form was decreased. We found that the molecular chaperone GRP78 in the endoplasmic reticulum formed a stable complex with the underglycosylated EGFR but did not with the mature form. This complex formation occurred specifically under the stress conditions, and the complex was dissociated upon removal of the stress. Treatment of the GRP78-underglycosylated EGFR complex with ATP resulted in a release of the underglycosylated EGFR from GRP78, indicating that the complex could be formed through the chaperone function of GRP78. In accordance with the complex formation with endoplasmic reticulum-resident GRP78, the underglycosylated EGFR could not be translocated to the cell surface. As a result, EGF could not induce expression of cyclin D3, a G1 cyclin, in the stressed cells, whereas it did in non-stressed cells. These results indicated that, in the stressed cells, GRP78 participated in down-regulation of EGF-signaling pathway by forming a stable complex with EGFR and inhibiting EGFR translocation to the cell surface. J. Cell. Physiol. 177:282–288, 1998. © 1998 Wiley-Liss, Inc.     

Fas stimulation induces RB dephosphorylation and proteolysis that is blocked by inhibitors of the ICE protease family

Fas antigen is a member of the tumor necrosis factor/nerve growth factor receptor family. Stimulation of Fas by Fas ligand or agonistic antibodies results in the activation of interleukin-1β converting enzyme-like (ICE-like) proteases, and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP). Ultimately, Fas activation leads to apoptotic cell death. The importance of PARP cleavage to the death process remains unclear. We have hypothesized that the cleavage of other cellular substrates may be important for Fas-mediated apoptosis. Here we show that stimulation of Fas results in significant alterations of retinoblastoma protein (RB). Treatment of Jurkat cells, a human leukemic T cell line, with anti-Fas induces dephosphorylation of RB, followed by proteolytic cleavage. These events precede internucleosomal DNA fragmentation. Dephosphorylation and cleavage of RB are inhibited by a specific tetrapeptide inhibitor of ICE-like proteases or by expression of cowpox virus CrmA protein or the Bcl-2 oncoprotein. Inhibition of these RB changes correlates with inhibition of apoptosis. We propose that cleavage of RB may represent an important step in the pathway of Fas-mediated apoptotic cell death. J. Cell. Biochem. 64:586–594. © 1997 Wiley-Liss, Inc.     

Bacteriophage Twort protein Gp168 is a β-clamp inhibitor by occupying the DNA sliding channel

Bacterial chromosome replication is mainly catalyzed by DNA polymerase III, whose beta subunits enable rapid processive DNA replication. Enabled by the clamp-loading complex, the two beta subunits form a ring-like clamp around DNA and keep the polymerase sliding along. Given the essential role of β-clamp, its inhibitors have been explored for antibacterial purposes. Similarly, β-clamp is an ideal target for bacteriophages to shut off host DNA synthesis during host takeover. The Gp168 protein of phage Twort is such an example, which binds to the β-clamp of Staphylococcus aureus and prevents it from loading onto DNA causing replication arrest. Here, we report a cryo-EM structure of the clamp–Gp168 complex at 3.2-Å resolution. In the structure of the complex, the Gp168 dimer occupies the DNA sliding channel of β-clamp and blocks its loading onto DNA, which represents a new inhibitory mechanism against β-clamp function. Interestingly, the key residues responsible for this interaction on the β-clamp are well conserved among bacteria. We therefore demonstrate that Gp168 is potentially a cross-species β-clamp inhibitor, as it forms complex with the Bacillus subtilis β-clamp. Our findings reveal an alternative mechanism for bacteriophages to inhibit β-clamp and provide a new strategy to combat bacterial drug resistance.     

一步法RT-PCR克隆水稻线粒体磷转运蛋白基因及其序列特征分析

以水稻广亲和品种Cpslo17幼穗为材料,用一步法RT—PCR（逆转录聚合酶链式反应）克隆了一个长度为1118bp的编码线粒体磷转运蛋白的OsMPT基因。序列分析表明其包含了基因完整的编码序列,编码由368个氨基酸组成的线粒体磷转运蛋白,它与玉米、大豆、Lotus japonicus、Betula pendula、拟南芥的线粒体磷转运蛋白氨基酸序列相似率分别为93．5％,85．6％,83．8％,83．7％,81．1％。氨基酸疏水谱分析显示它有线粒体磷转运蛋白家族高度保守的6个跨膜结构域。水稻线粒体磷转运蛋白N端富含精氨酸（Arginine）、丙氨酸（Alanine）和丝氨酸（Serine）。iPSORT预测其蛋白N端具有定位于线粒体的信号肽序列,进一步分析表明此编码区段有6个外显子和5个内含子。RT—PCR结果表明,OsMPT基因在水稻两个亚种粳稻和籼稻的叶片中均有表达,在Cpslo17营养器官和生殖器官中都有高水平表达。水稻线粒体磷转运蛋白的克隆和表达分析将为研究其结构和生物学功能奠定基础。     

基于三代测序的食蟹猴Mafa-B等位基因共表达与进化分析

【背景】主要组织相容性复合体(major histocompatibility complex,MHC)的多态性在很大程度上会影响生物医学实验的结果,而且特定的MHC-B等位基因与多种疾病的发展进程密切相关。食蟹猴(Macaca fascicularis,Mafa)是一种开展生物医学研究的重要实验动物,与人类相比,目前尚缺乏对食蟹猴Mafa-B等位基因的综合表征。【目的】获得全面的食蟹猴Mafa-B等位基因信息,鉴定Mafa-B等位基因共表达与进化关系。【方法】基于三代测序获得的食蟹猴MHC-B基因组信息,设计特异性引物扩增33只越南食蟹猴群体中的Mafa-B序列,并结合多种生物信息学方法进行分析。【结果】基于92个Mafa-B等位基因信息,鉴定了65个新的Mafa-B等位基因。其中,8个Mafa-B等位基因与其他地理来源的食蟹猴群体中已报道的序列相同,32个Mafa-B等位基因与其他猕猴物种中已报道的序列相同。此外,鉴定了7个高频Mafa-B谱系和7对共表达的Mafa-B等位基因,并检测到了一个潜在的重组事件。进化分析表明不同地理来源的食蟹猴群体Mafa-B序列具有很高的相似性。【结论】越南食蟹猴群体中共表达的Mafa-B等位基因经历了某些抗原的选择,不同地理来源的食蟹猴群体可能微调其Mafa-B序列以适应病原体的选择压力,本文为食蟹猴MHC遗传背景研究奠定了基础。     

乌檀的化学成分研究

从珍稀药用植物乌檀(Nauclea officinalis)的枝叶中分离得到1个甾醇类、3个三萜类、2个酚类和1个生物碱类化合物。通过光谱分析,分别鉴定为豆甾-4-烯-3-酮(1)、铁冬青酸(2)、常春藤皂苷元(3)、3-羰基奎诺瓦酸(4)、2,5-二甲氧基苯甲酸(5)、3,4,5-三甲氧基苯甲酸(6)和Strictosamide(7)。7个化合物均是首次从乌檀中得到。     

黄独微型块茎低温离体保存的GC/MS代谢组学分析

GC/MS检测方法采用初步探明黄独低温离体保存微型块茎的差异代谢物。与黄独微型块茎25℃离体保存相比较,黄独微型块茎4℃离体保存的差异性代谢物有丙氨酸（Alanine）、儿茶素（Catechin）、N,N-双（2-羟乙基）甲胺（N,N-Di-（2-Hydroxyethyl）-methanamine）、水杨酸（Salicylic acid）、柠檬酸（Citric acid）和山梨糖（Sorbose）等。在黄独微型块茎4℃离体保存中,丙氨酸（Alanine）参与氰基氨基酸代谢;儿茶素（Catechin）参与次生代谢产物生物合成、黄酮类化合物的生物合成和苯丙素的生物合成;水杨酸（Salicylic acid）参与多环芳烃降解、微生物在不同环境中的代谢、植物激素信号转导、次生代谢产物生物合成、二恶英降解、苯丙氨酸代谢、芳烃降解、植物激素生物合成、铁载体组非核糖体肽合成和苯丙素的生物合成等。柠檬酸（Citric acid）参与来自鸟氨酸、赖氨酸和烟酸的生物碱生物合成、组氨酸和嘌呤的生物碱生物合成、微生物在不同环境中的代谢、植物次生代谢产物的生物合成、2-氧代羧酸代谢、萜类和类固醇的生物合成、原核生物固碳途径、次生代谢产物生物合成、来自莽草酸途径的生物碱生物合成、来自萜类化合物和聚酮的生物碱生物合成、柠檬酸循环（TCA循环）、植物激素生物合成、乙醛酸和二羧酸代谢、双组分系统、苯丙素的生物合成以及来自鸟氨酸,赖氨酸和烟酸的生物碱生物合成等。黄独低温离体保存微型块茎差异代谢物的初步发现为进一步了解其低温离体保存的分子机制奠定了基础,也为低温离体保存黄独微型块茎的破除休眠以及其后续萌发提供了理论依据。