Virion glycosylation governs integrity and infectivity of infectious pancreatic necrosis virus

The possible importance of the O-linked glycosylation in virion stability and infectivity of infectious pancreatic necrosis virus (IPNV) was analysed. Enzymatic treatment with O-glycosidase of radiolabelled virions under different ionic conditions, to allow for possible alternative exposure of glycosidic enzyme cleavage sites, did not alter the specific infectivity of virions re-isolated after rate-zonal centrifugation in glycerol gradients. As an alternative method to assess the significance of carbohydrates in IPNV integrity, periodate oxidation in the presence of an aldehyde quencher was chosen. Following re-isolation of viruses, a 3-5 (10)log-unit reduction in specific infectivity was revealed and, at higher concentrations, a total disruption or virion aggregation was observed. The loss of infectivity of intact virions was not because of a lack of attachment to cells. Additionally, re-evaluation of reading values from UV-spectra of purified IPNV yielded a specific infectivity of 3 × 10(11) TCID(50)-units mg(-1) of protein and a ratio of 40 virions per TCID(50)-unit in the CHSE-214 cell system.     

The persistence of infectivity of Tetracapsulabryosalmonae-infected water for rainbow trout, Oncorhynchus mykiss (Walbaum)

Proliferative kidney disease (PKD) is caused by the infection of susceptible salmonid fish with spores of the myxozoan Tetracapsula bryosalmonae , a parasite harboured and released by several species of bryozoans. Under natural conditions, PKD is a water-borne infection of fish, whose outcome and spatio-temporal dissemination depend on the viability of spores present in the water. In order to evaluate the duration of parasite infectivity, juvenile rainbow trout, Oncorhynchus mykiss , were exposed for 20 h to T. bryosalmonae -infected water at various times post-water collection or after different filtration procedures. When infected water was held in a temperature range of 14.5–17 °C for up to 14 days, PKD was transmitted to the fish only between 0 and 12 h post-water collection and its infectivity vanished between 12 and 24 h. Similarly, the infectivity of water passed through 25 μm but not through 1 μm mesh filters, and was lost in the material eluted from the 1 μm filtration membrane although the parasite's DNA was amplified from this material. The parasitic infectivity in water appears to be fragile and this may offer opportunities to decrease the impact of PKD in trout farms by the implementation of management procedures aimed at reducing the number of the bryozoan-holding surfaces located in the river, immediately upstream from these farms.     

基于GIS的松树萎蔫病发生格局研究

通过GIS对发病信息的空间定位以及发病林型几何质心的挖掘,对空间点(单元)发病属性数据建立距离矩阵,利用空间自相关性指数研究探询安徽滁州地区松树萎蔫病发生的空间扩散机制,结果表明:松树萎蔫病在安徽滁州和马鞍山地区的发病率从0.18%到46%不等,严重发病的区域主要集中在明光县管店林业总厂及其相邻的鲁山林厂和老嘉山林场,发病率都在40%～46%;其次为马鞍山地区的横山林场及其附近的薛津镇.在安徽滁州地区和马鞍山地区松树萎蔫病的发生和扩散有适宜的生境条件,该地区松材线虫易感植被集聚分布的特点使松树萎蔫病持续发生和蔓延成为可能.空间自相关性的分析发现,松树萎蔫病在该区域内发病的Moran's Ⅰ的空间自相关指数高达74.86%(0.05水平检验),推断在安徽滁州和马鞍山地区1316个以林型为发病单元的发病点的分布格局为高度聚集型,同时也说明松树萎蔫病在安徽滁州和马鞍山地区的发生具有一定强度的传染性.     

Endomycorrhizae in a newly cultivated acidic meadow: Effects of three years of barley cropping,tillage, lime,and phosphorus on root colonization and soil infectivity

The dynamics of mycorrhizae under disturbance created by crop production is not well understood. A 3-year experiment was undertaken on a nutrient-poor and acidic land that had last been cultivated in the early 1970s. We observed the effects of cropping spring barley (Hordeum vulgare L.) under four P-fertilizer levels and four levels of lime, in a minimum (rototillage), a reduced (chisel), or a conventional tillage system, on the mycorrhizal receptiveness of the host (maximum level of mycorrhizal colonization, as measured at harvest) and soil infectivity most probable number method. The host receptiveness decreased with time, while crop yields and soil infectivity increased simultaneously with time. Liming increased mycorrhizal colonization of barley roots and soil infectivity. P additions decreased root colonization but did not significantly affect the most probable number valuse. Slightly higher soil infectivity estimates were found under reduced tillage.     

Epidemiological studies of piglet diarrhoea in intensively managed Danish sow herds. IV. Pathogenicity of porcine rotavirus

Colostrum-deprived piglets inoculated with rotavirus 24 h after birth developed a profuse diarrhoea that spread to non-inoculated, colostrum-deprived litter mates and, occassionally, to colostrum-fed piglets. Case fatality rates in these 3 categories of piglets were 63.2%, 35.7% and 8.3%, respectively. Surviving piglets recovered in 1-2 weeks, but shedded virus via the faeces for up to 3 weeks p.i. The D-xylose test revealed severe malabsorption, with extremely flat absorption curves for up to 3-4 weeks p.i. Malabsorption was more marked in piglets with a long-lasting faecal virus excretion than in piglets where virus disappeared from the faeces within 10 days p.i. Infected piglets (colostrum-fed and colostrum-deprived) had decreased weight gains and were 5 days older at a bodyweight of 25 kg than non-inoculated controls. It is concluded that rotavirus is probably of significance in diarrhoeal syndromes in suckling piglets, alone or in combination with E. coli or other pathogens.     

嗜菌异小杆线虫的分离鉴定及生物学特性分析

为了发掘具有耐高温特性的昆虫病原线虫,本实验室对在山东地区采集的122份土样进行了线虫分离,得到异小杆线虫JNR,扩增其ITS基因和D2-D3基因,并构建系统进化树,分析可得:线虫JNR与嗜菌异小杆线虫Heterorhabditis bacteriophora在同一分支,同源性达到98%以上,为嗜菌异小杆线虫品系。为进一步了解该线虫品系的生物学特性,本试验研究了其侵染力、高温耐受力及水平运动能力。结果表明,线虫JNR有较好的耐热性,38℃条件下处理16 h,存活率最高54%,24 h时为32%;40℃水浴处理2 h,低浓度500 IJs/mL下存活率28%,3 h后全部死亡。对大蜡螟和小菜蛾的生测结果显示,在10、15、20、25、30、35、40、60、120、240 IJs/头剂量下处理24 h,蔬菜害虫小菜蛾先出现死亡,大蜡螟则在48 h后出现死亡;大于20 IJs/头剂量下,处理48 h后线虫对大蜡螟的校正死亡率达到59.5%,高于对小菜蛾的侵染效果。在剂量120 IJs/头以上,72 h后寄主的校正死亡率均能达到100%。异小杆线虫JNR在30℃条件下水平运动能力比在18、25℃时强,48 h时有31%的个体运动到3.6 cm处。以上研究表明,该线虫有较强的侵染力,特别是在温度相对较高时具有较好的耐热力和水平运动能力,对防治蔬菜田小菜蛾具有应用开发潜力。     

Pathogenesis of experimental bovine spongiform encephalopathy (BSE): estimation of tissue infectivity according to incubation period

This paper reports the results of tissue infectivity assays of bovine spongiform encephalopathy (BSE) agent in orally exposed cattle at stages during the incubation period. Estimations of the titre of infectivity in central nervous system (CNS), certain peripheral nerve ganglia and distal ileum tissue were made according to time post exposure from the relationship between incubation period and dose for RIII mice and C57bl mice using data from titrations of brain material from cases of BSE. The rate of increase of infectivity in the bovine CNS was then estimated, taking into account these tissue infectivity titres, the variability of the brain titre of clinical field cases of BSE, and the probability density of the expected number of months before clinical onset of each infected bovine. The doubling time for CNS was shown to equal 1.2 months. The titre in the thoracic dorsal root ganglia (DRG) was, on average, approximately 1 log units less than CNS, and cervical DRG approximately 0.5 log less than thoracic DRG. The pattern of increase of infectivity in the distal ileum is that of an initial increase up to 14-18 months post exposure, followed by a decrease, which is likely to be highly variable between animals. These results will be informative for future risk assessments of BSE, especially in relation to reviewing current control measures.     

土壤温湿度对南方根结线虫侵染能力的影响

研究了土壤温度和湿度对南方根结线虫侵染番茄根部能力的影响.结果表明,在42℃和-15℃处理3 d后可使二龄幼虫丧失侵染能力,在0℃、400℃和土壤含水量20.7%～36.2%时,可有效降低二龄幼虫的侵染能力;当土壤含水量较低时有利于二龄幼虫对番茄根部的侵染;当根结数量较多时根重显著增加,株高下降.     

8种硫酸化多糖对新城疫病毒感染鸡胚成纤维细胞能力的影响

用氯磺酸-吡啶法修饰当归多糖(CAPS)和枸杞多糖(LBPS),得到4种硫酸化当归多糖sCAPS0.6、sCAPS1.1、sCAPS1.9、sCAPS2.2和4种硫酸化枸杞多糖sLBPS0.7、sLBPS1.1、sLBPS1.5和sLBPS1.9。分别以CAPS和LBPS为对照,采用MTT法比较了这8种硫酸化多糖对新城疫病毒感染鸡胚成纤维细胞能力的影响。结果表明:硫酸化修饰能显著提高当归多糖和枸杞多糖的抗病毒活性,且与硫酸基取代度有一定的相关性。sCAPS2.2、sLBPS1.5、sCAPS1.9和sLBPS1.9的活性较好,可以作为进一步研究的材料。     

杨树黄叶病害症状及侵染性研究初报

在野外详细调查和定量测试基础上,对杨树黄叶病害症状进行了描述,修改了过去对杨树黄叶病害症状描述中的"叶脉保持绿色"、"叶片变薄"和"丛枝"等不确切说法。进行了病树枝条的硬枝、嫩枝扦插,病接穗嫁接、病苗换土盆栽、病树移植、病苗造林及病树自然恢复现象观测等试验,连续跟踪观测3 a未发现杨树黄叶病害具有侵染性。