对虾病毒病和细菌合并感染的病理特点和诊断价值

应用电镜超薄切片及光学石蜡切和环氧树脂薄片技术,观察健康对照组,疾病始发组和濒临死亡组的草虾,中国对虾、日本对虾和肝胰腺和中肠。结果在３组４种对虾中均检测到病毒,只在濒临死亡组的４种对虾中发现病毒与细菌的合并感染。合并染的病毒有ＭＢＶ,球形病毒和淋细胞核型杆状病毒。细菌以弧菌为主。其病理变化表现为器官和组织的保护层受损、溶解样坏死和凝固样坏死,仅以病毒和细菌合并感染徐为养殖对虾病毒病早期诊断的指标     

养殖对虾病毒致病性的初步研究

用从日本对虾分离的杆伏病毒扣长毛对虾分离的球伏病毒分别感染健康无病毒的日本对虾,对虾死亡率分别为６５％（杆状病毒组）和５０％（球状病毒组）,而对照组的死亡率仅为２５％,在诸环境因素中,温度的上升和低压可能是对虾病毒病发作的最重要诱因之一。     

改良染色显示中国对虾病毒核酸DNA

对虾病毒病的诊断 ,只根据患病对虾群体的表现症状 ,是不能确诊的。目前最基本又广为采用的诊断技术是通过组织病理检查来找到病毒包涵体 ,或应用细胞病理技术在电子显微镜下观察到病毒颗粒。在组织切片检查中 ,对虾病毒核酸 DNA的 Schiff's反应已有报道。但对于稳定可能的快速显示对虾病毒 DNA成分的改良染色技术还未见报道。我们采用龚志锦等 (1994 )研究的改进染色液配制方法 ,首次进行中国对虾病毒核酸DNA显示实验 ,得到了较好的 DNA染色结果。1　材料与方法1.1　材料选用　取患病或室内感染的中国对虾 ,分别进行冰冻切片和 3种不…     

养殖对虾一种新杆状病毒的研究

应用超薄切片、负染色和蔗糖梯度超离心技术,在自然发病和人工感染的对虾肝、肠、淋巴样器官、鳃和肌肉组织中,发现并纯化了一种新杆状病毒.该病毒直径96～112nm,是已知对虾病毒中最粗的一种.中央是高电子密度的核心,外裹衣壳和囊膜,两膜之间有宽阔的间隙,这是已报道的任何一种对虾杆状病毒所没有的.纯化的病毒核衣壳表面有螺旋排列的亚单位,这也是本病毒特有的.主要靶细胞是淋巴样细胞,未在肝、肠和鳃上皮细胞中观察到,这与对虾杆状病毒无一例外地侵染某一种上皮细胞迥然不同.病毒仅在靶细胞核内增殖,不形成封入体或包涵体,它是一种迄今未曾报道的新病毒,称之为“淋巴样细胞核型杆状病毒”.     

1996年中国对虾暴发性流行病病毒病原研究

１９９６年６月至８月,青岛地区养殖的中国对虾大面积暴发流行病,死亡率达９０％以上。发病对虾典型表征为甲壳白斑。病虾鳃组织匀浆滤液经微孔滤膜过滤除菌后,注射给健康对虾进行人工感染试验,９天内累计死亡率达１００％,发病症状及体征与自然发病对虾相似。电镜下自然发病对虾鳃、胃、头胸甲下表皮、淋巴样器官、触角腺等组织细胞核内发现大量杆状病毒,未见包涵体;人工感染对虾相同组织中可见大量同样病毒。切片中病毒粒子     

二温式多重PCR检测对虾白斑综合征病毒和桃拉病毒的研究

正对虾白斑综合征(WSS)和桃拉病(TS)是两种严重危害当前对虾养殖业的对虾病毒性疾病。目前对虾病毒病的诊断手段主要包括病理学和生物学方法、免疫学方法、分子杂交方法及PCR方法1-4等。其中PCR方法是这些方法中特异性最强、敏感最高的病原检测手段,在国外已被广泛应用于对虾病毒病的检测和诊断。多重PCR是一种特殊PCR形式,其最突出特点,即一次PCR反应,就可同时检测、鉴别出多种病原体,在临床混合感染的鉴别诊断上具有其独特优势和很高的实用价值5,6。本试验建立了二温式多重PCR同时检测鉴别WSSV和TSV的方法,并用该多重PCR方法对广西沿海地区对虾养殖业WSSV和TSV感染状况进行了初步调查。现将结果报告如下。       

中国对虾中一种球状病毒的分离提纯与检测

从人工养殖生长比较缓慢的对虾与病虾的肝胰腺和消化道中,分离出一种大小为８０ｎｍ的球状病毒。同时采用超薄切片技术可在对虾中肠细胞中发现大量的球状病毒,这些病毒聚集成片,在同一细胞内的细胞器,如线粒体等均发生病变。此外,将分离提取的球状病毒进行感染试验,感染死亡率为６０％。并且从感染致死的对虾消化腺及肠道中,同样可以观察到大小相同、形态一致的球状病毒颗粒。     

中国对虾呼肠孤样病毒感染的电镜观察

呼肠孤病毒在自然界广泛存在于脊椎动物、无脊椎动物和植物中.水产动物呼肠孤病毒感染曾见于鱼、贝、蟹.近几年随着对对虾病毒病害研究的日益重视,在对虾中也发现呼肠孤病毒的感染.Tsing等[1]最早于1987年在法国南部养殖的日本对虾(P.japonicus)幼虾中发现呼肠孤病毒感染.Krol等[2]于1990年在试验感染的南美白对虾(P.vannamei)中发现呼肠孤样病毒与对虾杆状病毒混合感染.中国大陆养殖的中国对虾自1993年全面暴发流行病以来,许多学者进行了对虾流行病的病原学、流行病学及诊断和防治方法的研究,部分学者曾在中国对虾(P.chinensis)中观察到呼肠孤样病毒颗粒[3],但未报道较详细的电子显微镜观察资料.     

PCR法检测对虾皮下和造血器官坏死杆状病毒

皮下和造血器官坏死杆状病毒（ＨＨＮＢＶ）［１］、对虾杆状ＤＮＡ病毒（ＰＲＤＶ）［２］和白斑杆状病毒（ＷＳＢＶ）［３］是近年来引起全球对虾暴发性死亡的病原。这三种病毒同属杆状病毒属Ｃ杆状病毒亚群中的新病毒,在流行病学和病理学特征上十分类似,因此,我们...     

对虾杆状病毒病暴发式大流行的生态机理初步研究

初步探讨中国和沿海和对虾杆状病毒病暴发式大流行的生理机理。分析了病毒病特性与对虾免疫功能的关系;病毒在虾池间的传染机制。着重说明了虾病的群体感染过程,给出模式化的群体传染模型,简要阐述了与虾病相关的社会生态经济问题。     

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.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.