美国紫踵劈蚌与三角帆蚌和褶纹冠蚌的形态比较与判别分析

描述了紫踵劈蚌(Potamilus alatus)贝壳外部和内部特征,并对紫踵劈蚌、三角帆蚌(Hyriopsis cumingii)和褶纹冠蚌(Cristaria plicata)进行了形态学比较。运用多变量形态度量学方法分析了3种淡水育珠蚌的形态差异。主成分分析构建了2个主成分,其中第一主成分的方差贡献率为66·90%,第二主成分的贡献率为33·10%,2个主成分的累计贡献率达到100%;采用逐步判别法,从11个比例性状中筛选出6个主要性状建立了3种育珠蚌的形态判别函数,其综合判别准确率达到100%。     

中国沿海双齿近相手蟹9个群体形态差异分析

针对双齿近相手蟹Perisesarma bidens 9个群体(龙海、深圳、珠海、阳江、徐闻、企水、清澜港、北海、防城港)228只个体的22项形态比例参数,采用聚类分析、判别分析和主成分分析对群体间形态差异进行了比较。结果表明,聚类分析不能把群体明显地分群;9个群体提取的6个主成分的累积贡献率为84.09%,第一、二主成分绘制的散点图显示,各群体互相重叠,无法区分开来;综合判别准确率为40.8%,判别准确率不高,无法有效地运用判别函数依据个体形态特征进行分类;单因子方差分析显示,各群体大多数变量的差异具有统计学意义(P<0.05),说明双齿近相手蟹群体间个体形态有一定差异,可能是受环境影响;差异系数(CD)值均小于亚种分类的阈值1.28,说明群体间的形态差异小,未达到亚种水平。     

中华小长臂虾(Palaemonetes sinensis)4个群体的形态差异

本文采用3种多元分析方法,分析了中华小长臂虾4个群体(鞍山、大连、沈阳和盘锦群体)的形态差异,探讨了它们的形态亲缘关系。聚类分析的结果表明,盘锦群体和鞍山群体的形态差异最小,而与大连和沈阳群体的差异程度逐渐增大。Mantel检验的结果表明,各群体的欧氏距离和地理距离之间没有显著相关性(r=0.576,P=0.901)。经主成分分析得到7个主成分,累计方差贡献率为84.74%,4个群体的形态学分化主要集中在头胸甲部的特征上。经判别分析建立了4个群体的判别函数,判别准确率为66.00%~97.00%,综合判别率为77.83%。本研究可为中华小长臂虾的资源保护和遗传育种提供依据。     

甘蔗品种(系)叶片形态特征数学分析

本文对48份甘蔗品种(系)的叶片形态特征进行主成分、聚类和判别分析.结果表明,品种(系)间的叶片形态特征差异达到极显著水平(P＞0.01);主成分分析选出了3个主成分,方差累积贡献率达到97.52%,叶长、叶宽及形态因子分别是第一、二、三主成分的主导因子;在聚类分析基础上用判别分析选出对甘蔗品种(系)叶片形态分类有极显著影响的面积、长度、宽度、周长、长宽比及形态因子参数,同时建立了4个判别能力较高的判别模型.     

濒危鱼类稀有白甲鱼沅江种群与西江种群形态度量学性状的差异性

分别以采自沅江水系142例和西江水系92例稀有白甲鱼标本为材料,采用差异系数法、方差分析法、判别分析法和主成分分析法,研究了稀有白甲鱼沅江种群、西江种群包括10个可数性状和31个比例性状等形态度量学性状的差异性.方差分析表明,2个种群之间共有6个可数性状和27个比例性状存在着显著性差异(P＜0.05).判别分析筛选出了9个对区分2个种群贡献较大的比例性状,并建立了2个种群的判别函数式.主成分分析显示,稀有白甲鱼种群鱼体沿背腹轴、头尾轴分别有16和6个比例性状表现出了明显的变化,在尾部有2个比例性状差异明显.可见2个种群之间形态度量学性状已显示了明显的分化.这可能是两个种群长期隔离,在不同水系生态环境中产生了适应性进化的结果.然而,差异系数的计算结果表明,两个种群之间形态度量学性状的差异尚未达到亚种分化的水平.     

板栗和锥栗天然同域居群的叶表型变异研究

对分布于湖北省秭归县境内的一个由169株板栗（Castanea mollissima）和281株锥栗（C.henryi）组成的天然同域居群的20个叶表型性状的变异进行了研究。根据叶片背面和叶柄的被毛情况及叶缘形状3个定性性状,在总共450个个体中,共得到18个（4%）中间过渡类型个体。利用17个数量性状进行逐步判别分析（SDA）表明：根据定性性状得到的中间型个体中分别有7个和11个被归入板栗和锥栗;板栗和锥栗在叶形上的差异较大,有8个数量性状被选入判别方程,判别方程对板栗和锥栗的判别准确率都达93%以上,判别结果较为理想;综合20个表型性状进行主成分分析（PCA）,构建了3个主成分,主成分1和2的贡献率分别为53.5%和18.7%,累计贡献率达72.2%。前2个主成分的散布图中,有6个（1/3）中间型个体位于板栗和锥栗的重叠分布区域,可能是二者之间存在杂交的表型证据。     

四川裂腹鱼和重口裂腹鱼形态差异的多元分析

通过聚类分析、判别分析和主成分分析3种多元分析方法,对乌江总溪河89尾四川裂腹鱼(Schizothorax kozlovi)和岷江青衣江33尾重口裂腹鱼(S.davidi)的10个常规可量性状与20个框架性状进行了比较研究。聚类分析结果显示,3次采集的四川裂腹鱼聚为一支,而重口裂腹鱼单独为一支;主成分分析结果显示,提取的8个主成分对总方差的累计贡献率为73.762%,贡献率大的性状集中在吻端和躯干后侧;通过两次判别分析,最终建立四川裂腹鱼和重口裂腹鱼两个判别方程,综合判别率为100%。研究结果显示,四川裂腹鱼和重口裂腹鱼是独立的两个种,在形态上的主要差异体现在吻端和躯干后侧,运用多元分析方法能有效地将其区分开来,而3次采样的四川裂腹鱼为同一种群。     

基于形态学差异探讨秦岭细鳞鲑亚种有效性问题

秦岭细鳞鲑(Brachymystax lenok tsinlingensis Li)的亚种分类地位自命名以来一直饱受争议。研究运用单因素方差分析、主成分分析、判别分析、聚类分析及差异系数检验法, 对秦岭细鳞鲑和黑龙江流域的尖吻细鳞鲑(B. lenok lenok)和钝吻细鳞鲑(B. tumensis)的5项可数性状和34项标准化后的比例性状进行统计分析。单因素方差分析结果表明, 尖吻细鳞鲑、钝吻细鳞鲑和秦岭细鳞鲑在32项比例性状和5项可数性状上存在极显著差异(P<0.01); 主成分分析结果显示, 贡献率较大的前3个主成分的累计贡献率为92.779%; 以逐步判别分析方法选用14个判别效果较好的比例性状构建了3个细鳞鲑类群的判别函数, 综合判别率为99.4%。基于欧式距离矩阵法构建的形态学聚类图显示, 秦岭细鳞鲑和尖吻细鳞鲑距离较近, 而与钝吻细鳞鲑距离较远。据Mayr 75%亚种识别和划分规则, 34项比例性状和5项可数性状中, 尖吻细鳞鲑和秦岭细鳞鲑第一鳃弓外鳃耙数目的差异系数大于1.28, 而钝吻细鳞鲑和秦岭细鳞鲑有31项比例性状和2项可数性状的差异系数高于1.28。据分析结果, 结合秦岭细鳞鲑地理隔离的事实及其与尖吻细鳞鲑和钝吻细鳞鲑的形态差异, 推断秦岭细鳞鲑与黑龙江流域内的尖吻细鳞鲑的形态差异程度至少已达亚种水平。     

基于耳石形态的鱚属鱼类鉴别

利用9个耳石形状指标对我国鱚属鱼类少鳞鱚、多鳞鱚及斑鱚共78个个体的矢耳石形态进行了多元统计分析,同时对3个群体的74个少鳞鱚矢耳石形态进行了判别分析。单因子方差分析结果显示,少鳞鱚与多鳞鱚矢耳石的9个形状指标均存在显著差异(P<0.05);反映耳石长、短轴差异程度的第1主成分与反映耳石三维特征的第2主成分解释了85.943%的形态差异;9个指标在种间判别分析中的综合判别正确率为93.6%,种内判别分析中的综合判别正确率为93.2%。研究表明形状指标法可以作为中国鱚属鱼类鉴别的有效手段。     

甘蔗品种（系）叶片形态特征数学分析

本对48份甘蔗品种(系)的叶片形态特征进行主成分、聚类和判别分析。结果表明,品种(系)间的叶片形态特征差异达到权显水平(P＞O．01);主成分分析选出了3个主成分,方差累积贡献率达到97．52％,叶长、叶宽及形态因子分别是第一、二、三主成分的主导因子;在聚类分析基础上用判别分析选出对甘蔗品种(系)叶片形态分类有权显影响的面积、长度、宽度、周长、长宽比及形态因子参数,同时建立了4个判别能力较高的判别模型。     

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.