电子束辐射对大妻种胚核酸合成活性的损伤效应

电子束辐射损伤大麦种胚核酸合成能力的效应主要表现在使ＤＮＡ复制合成启动推迟,使ＤＮＡ复制、ＲＮＡ合成活性下降,吸涨过程中大麦种胚的ＤＮＡ复动过程。２００与４００Ｇｙ电子束辐射分别使ＤＮＡ复制合成活性的抑制作用强于对ＲＮＡ合成活性的抑制。在５０－５００Ｇｙ范围内,大麦种胚ＤＮＡ复制、ＲＮＡ合成活性均随辐射剂量呈指数下降,其半对数斜率分别为－０．００３９与－０．００１４。根据实验计算,电子束辐射对ＤＮ     

RNA的生物合成与加工(一)

所有细胞的RNA都是按照DNA模板的指令,由RNA聚合酶催化合成的。RNA的生物合成(转录)过程的有些地方与DNA复制相似,如底物是核苷三磷酸,合成方向是5′→3′。但,RNA聚合酶不需要引物,也不具备有校正作用的核酸外切酶活力。DNA模板在RNA合成中是全保留的,而在DNA复制中则是半保留的。原核生物的转录原核生物转录的源料主要是从大肠杆菌取得的。大肠杆菌的所有RNA都是由同一种RNA聚合酶催化合成的。这种酶的分子量为460KDa,全酶的亚基组成为α_2ββ′σ,核心酶为α_2ββ′。σ亚基只在转录的启动中起作用,     

玉米花粉胚状体发育过程中DNA,RNA蛋白质含量及合成动态变化

继代培养的玉米花粉胚状体的发育过程可划分为6个时期:胚性细胞团时期、球形胚时期、心形胚时期、梨形胚时期、子叶形胚时期以及分化期。我们应用微量生化分析技术以及放射性同位素液体闪烁计数技术研究了玉米花粉胚状体发育过程的DNA、RNA、蛋白质含量及合成动态,发现DNA、RNA和蛋白质含量在胚性细胞团期较高,然后下降,但到了分化期时又有所升高。DNA合成速度在胚性细胞团时期较高,在以后的各时期降低并保持平稳。RNA和蛋白质的合成动态呈相似的变化规律。这个结果说明DNA、RNA和蛋白质在胚状体发育早期的活跃代谢,可能与胚性细胞的快速分裂以及胚性结构的形成有关,而后期的活跃代谢可能与胚状体的分化有关。     

抗菌肽BuforinⅡ衍生物抑制大肠杆菌大分子合成的研究

【目的】研究抗菌肽BuforinⅡ的衍生物BF2-A/B作用大肠杆菌后对胞内生物大分子合成的影响。【方法】紫外分光光度法检测抗菌肽对细胞DNA、RNA合成能力的影响, 考马斯亮蓝法检测抗菌肽对细胞总蛋白合成能力的影响, 分别用邻硝基苯-β-D-吡喃半乳糖苷法和对硝基苯磷酸二钠法检测抗菌肽对β-半乳糖苷酶及碱性磷酸酶表达活性的影响。【结果】BF2-A/B不优先抑制DNA合成, 而是优先抑制RNA和蛋白的合成。在相同浓度下, BF2-B抑制RNA合成的能力比BF2-A强, BF2-A抑制蛋白合成的能力比BF2-B强。胞内酶β-半乳糖苷酶和碱性磷酸酶的表达活性都在下降。【结论】BF2-A/B结合胞内核酸后, 没有首先影响DNA的复制功能, 而是优先抑制基因转录功能, 主要在转译水平上抑制蛋白的合成。     

花生种子萌发早期胚轴DNA合成与种子活力的关系

随着花生种子萌发率和活力指数的下降,胚轴DNA开始合成的时间推迟,其合成水平也降低。但DNA合成都是先于吸胀的12h(高活力胚)或18h(低活力胚)出现一个峰,然后再持续上升。腐胺预处理明显地促进老化胚轴萌发早期(12～2dh)的DNA合成。钙离子预处理则有一定抑制作用,但两种预处理均能提高种子的活力指数,并能促进吸胀30h以后的DNA合成。     

苯噻草胺与水稻DNA和稗草DNA作用的谱学研究

提出了苯噻草胺用于水田除草的新除草机理 ,BTMPA在DNA和RNA分子表面堆积 ,抑制DNA复制 ,阻止RNA参与植物体内的蛋白质合成 ,造成稗草等杂草细胞不能分裂 ,从而杀除杂草。发现水稻DNA对BTMPA有解毒作用。用苯噻草胺除草时 ,在植物体内的有效浓度为 1 7× 10 - 5mol L - 5 1× 10 - 5mol L ,最宜施药期为芽期至三叶期 ,最宜施药温度为 2 0℃ - 2 5℃。     

杉木雌配子体与后胚发育过程中核酸、蛋白质和类脂的消长

在杉木胚胎分化期至成熟期,每个雌配子体总核酸和DNA,RNA含量在初期增加,后期则随着胚的分化发育逐渐下降,而蛋白质和类脂则一直上升。每胚总核酸、DNA,RNA则相应增加,而蛋白质、类脂的含量和干重亦逐渐增加。在胚分化早期RNA的迅速合成与细胞的分化及器官形成有关。但以胚干重为单位的DNA、RNA含量却随着胚的发育而有所减少;蛋白质含量先增加,至成熟后才下降。授粉前的胚珠,以及雌配子体、胚中都发现有凝集素存在。     

平贝母体细胞胚胎发生中的核酸与蛋白质合成研究

在获得比较理想的平贝母体细胞胚胎发生体系的基础上,我们应用放射性同位素液体闪烁计数技术测定了平贝母体细胞胚胎发生过程中球形胚、心形胚、鱼雷胚、子叶胚和成熟胚等时期的DNA、RNA和蛋白质合成动态,实验表明,从球形胚到子叶胚,核酸与蛋白质的合成速度递增。在子叶胚前期RNA合成达到高峰,在子叶胚期蛋白质合成达到高峰,在子叶胚后期DNA合成达到高峰,核酸与蛋白质合成速度的变化与胚体细胞增殖及器官分化相关联。     

雌激素受体α抑制剂MPP对小鼠合子型基因组激活的影响可能与S期启动相关

目的观察雌激素受体α(ERα)特异性抑制剂甲基哌啶吡唑(Methyl-Piperidino-Pyrazole,MPP)对小鼠早期胚胎发育的影响与合子型基因组激活(ZGA)发生的时间是否相关,并检测与小鼠ZGA密切相关的2-细胞胚DNA复制是否受MPP处理的影响,为进一步探讨ERα在小鼠ZGA过程中的作用机制提供实验基础。方法 1收集昆明小鼠1-细胞胚、2-细胞胚和4-细胞胚,以空白KSOM培养液(单纯型优化的胚胎培养基)为对照组,以KSOM中添加MPP为实验组;将各时间点收集的早胚培养3h后再移入新KSOM培养液中继续培养至囊胚阶段,并记录囊胚数;2收集昆明小鼠末期1-细胞胚,分别置于上述两组培养液中培养15h至2-细胞胚S期后期,用荧光显微镜技术检测2-细胞胚核像变化;Brd U标记法分析DNA复制情况。结果1于不同时间段经MPP 3h处理后,在1-细胞胚末期、2-细胞早期和2-细胞胚中后期,MPP处理对小鼠早胚发育具有显著的抑制作用,其阶段特异性影响与小鼠ZGA发生的时间一致。另外,MPP对2-细胞胚G1/S过渡期(36~39h)抑制明显,但是对S期中后期(39~42h)进程无显著影响。2与KSOM组相比,经MPP处理15h后,2-细胞胚核变圆;Brd U标记水平明显下降。结论MPP在小鼠早胚中的阶段性作用与ZGA有关;ERα可能通过促进S期启动来调控ZGA。     

X射线辐射对仔鼠体重、皮毛生长及肝、肾脏组织SOD、CAT活力及MDA含量的影响

本文采用比色法测定不同剂量（0．0、0．5、2．0、3．5、5．0、6．5Gy）X射线辐射对不同发育期（1、5、10和20d）仔鼠肝脏及肾脏组织超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活力和丙二醛（MDA）含量的影响,探讨X射线辐射后小鼠的体重、皮毛及肝、肾组织抗氧化酶活性的动态变化,为电离辐射防治提供实验依据。结果表明：经2．0、3．5、5．0和6．5GyX射线辐射后的仔鼠体重降低;3．5、5．0和6．5Gy辐射后3d开始脱毛,10d脱毛处开始长出新毛,6．5Gy辐射组鼠脱毛处皮肤出现紫斑;0．5Gy辐射组仔鼠肝脏及肾脏中SOD活性在辐射初期升高,后逐渐降低至近似正常水平,其它各组则先降低,后缓慢升高但始终低于对照组;0．5Gy辐射组仔鼠肝脏及肾脏MDA含量先降低,后升高至近似正常水平,其它各组则先升高,后缓慢降低,始终高于对照组;0．5、2．0Gy辐射组其仔鼠肝脏及肾脏CAT活性在辐射后初期降低,后升高,最终至近似正常水平;其它各组则在初期升高,后降低。辐射后一段时间内检测各组仔鼠肝脏及肾脏中各种酶的活性均有不同程度恢复正常的趋势。表明X射线影响生长发育中仔鼠的体重、皮毛生长及肝、肾组织的抗氧化酶活性,且剂量因素的影响大于时间因素。大剂量电离辐射对发育期仔鼠具有损伤作用[动物学报54（6）：1029-1037,2008]。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.