斜带石斑鱼溶藻弧菌病的研究

从患病的斜带石斑鱼肝和肾组织分离的两株病原菌,进行纯化培养、人工感染、VITEK-AMS-32自动微生物分析鉴定及药敏试验,经形态和生理生化测定,确定为溶藻弧菌(Vibrioalginolyticus)。组织病理变化主要表现为鳃、肝和肾细胞变性、坏死,病变组织炎性细胞浸润,呈变质性炎症。     

常用中草药对4种病原弧菌体外抗菌效果的研究

采用琼脂扩散法(打孔法)测定了五倍子等18种中草药对鳗弧菌、副溶血弧菌、河口弧菌及霍乱弧菌等4种病原弧菌的抑制作用。结果表明,五倍子、苏木、地锦草、石榴皮、黄芩、虎杖和山楂等7种中草药对病原弧菌具有较好的抑菌效果,而金银花等11种中草药抑菌作用较弱;同时采用试管连续稀释法,测定了五倍子等抑菌效果较强的7种中草药对4种病原弧菌的抑菌和杀菌浓度。结果表明,苏木、五倍子、地锦草和石榴皮4种中药具有较好的抑菌和杀菌作用,此4种中药对鳗弧菌、副溶血弧菌、河口弧菌及霍乱弧菌等4种病原弧菌的最小抑菌浓度(MIC)为0.78～6.25mg/ml,最小杀菌浓度(MBC)为3.12～12.5mg/ml。     

Effect of in vitro exposure to Vibrio vulnificus on hydroelectrolytic transport and structural changes of sea bream (Sparus aurata L.) intestine

The everted gut sac technique has been used to investigate the effect of Vibrio vulnificus on water and electrolyte (Na⁺, K⁺, Cl⁻, HCO₃ ⁻) transport on the intestine of sea bream (Sparus aurata L.). Both the anterior and the posterior intestine were incubated in a medium containing 10⁸ V. vulnificus cells ml⁻¹ at 25°C for 2 h. The presence of V. vulnificus resulted in a significant reduction (P < 0.05) of water absorption in the anterior intestine, while sodium absorption in the anterior (P < 0.01) and posterior (P < 0.05) intestine was elevated. Chloride absorption was increased, but the changed was not significant, while potassium absorption decreased significantly (P < 0.05), but only in the posterior intestine. Incubation the sea bream intestine with V. vulnificus did not affect carbonate secretion in the anterior segment, whereas high secretion was stimulated in the posterior segment (P < 0.01). Histological evaluations demonstrated damage in the anterior intestine of sea bream that was characterized by the detachment of degenerative enterocytes, alterations in the microvilli, and the presence of a heterogenous cell population, indicating inflammation. Based on our results, we conclude that V. vulnificus caused cell damage to the intestine of sea bream and that the anterior intestine is more susceptible than the posterior part of the intestine. Several hypotheses are suggested to explain our observations, such as the presence of higher numbers of villosities in the anterior intestine than in the posterior one and/or the presence of endogenous bacteria in the posterior intestine which may have a protector role.     

A role for Toll-like receptor 4 in the host response to the lung infection of Yersinia pseudotuberculosis in mice

Although a Yersinia pseudotuberculosis (Yptb) lung infection model has been developed to study Y. pestis pathogenesis, it is still necessary to establish a new animal model to mimic the pathophysiological features induced by Y. pestis infection. Here, we provide a new lung infection model using the Yptb strain, IP2777, which displayed rapid spread of bacteria to the liver, spleen, and blood. In addition, we examined whether TLR4 is involved in Yptb-induced pathogenesis in the lung infection model of mice we generated. Following lung infection of WT and TLR4-deficient mice with the Yptb strain IP2777, the survival rate, bacterial colonization, histopathology, and level of cytokines and chemokines in the lung, spleen, liver, and blood were analyzed. TLR4-deficient mice had a lower survival rate than WT mice in response to Yptb lung infection. Although the bacterial colonization and pathology of the lung were comparable between WT and TLR4-deficient mice, those of the spleen and liver were more severe in TLR4-deficient mice. In addition, the levels of TNF-α and CXCL2 in the liver and IL-6 and CXCL2 in the blood were higher in TLR4-deficient mice than in WT mice. Our results demonstrate that TLR4 is necessary for optimal host protection against Yptb lung infection and TLR4-deficient mice may serve as a better genetic model of Yptb infection for mimicking Y. pestis infection.     

Genetic diversity and mixed infections of begomoviruses infecting tomato, pepper and cucurbit crops in Nicaragua

Begomoviruses were detected in Nicaraguan fields of tomato ( Lycopersicon esculentum ) and adjacently growing plants of pepper ( Capsicum annuum ), chilli pepper ( C . baccatum ), cushaw ( Cucurbita argyrosperma ) and Mexican fireplant ( Euphorbia heterophylla ) using polymerase chain reaction (PCR) and universal begomovirus primers. All tomato and Mexican fireplant plants showing symptoms were infected with begomoviruses, while only 30–46% of the pepper, chilli pepper and cushaw plants showing symptoms tested virus-positive. No begomoviruses were found in potato. The virus species were provisionally identified by sequencing 533 bp of the viral coat protein gene ( AV1 ). Tomato severe leaf curl virus (ToSLCV), Tomato leaf curl Sinaloa virus (ToLCSinV) and Pepper golden mosaic virus (PepGMV) were found to infect both tomato and pepper. A new provisional species designated Tomato leaf curl Las Playitas virus (ToLCLPV) was detected in a tomato plant. Squash yellow mottle virus (SYMoV) and PepGMV were found in cucurbits, the latter for the first time in this host. Euphorbia mosaic virus (EuMV) was detected in Mexican fireplant. Sequencing of a larger number of PCR-amplified clones from selected plants revealed intraspecific viral sequence variability, and also multiple begomovirus infections which could represent up to three species in a single tomato or cushaw plant. Phylogenetic grouping of virus sequences did not correlate with the host of origin.     

大豆疫霉菌对大豆下胚轴侵染过程的细胞学研究

 接种后1.5~24h,用光镜和电镜研究了2个大豆品种与大豆疫霉菌Ps411的亲和性和非亲和性互作。观察结果表明,大豆疫霉菌对大豆下胚轴的侵染过程可分为侵入前、侵入、皮层组织中的扩展和进入维管束组织4个连续阶段。大豆下胚轴接种后在25℃保湿培养,1.5h后游动孢子即形成休止孢并萌发产生附着孢,3h后侵入表皮细胞,6h后进入皮层组织,24h后进入维管束组织。病原菌主要以侵染菌丝直接侵入表皮,表皮细胞间隙是主要侵入部位。皮层细胞是病原菌定殖和发展的主要场所,胞间菌丝侵入皮层细胞并形成吸器。在菌丝与寄主细胞接触部位的寄主细胞壁与质膜之间常有胞壁沉积物的形成。在抗病品种上病菌的侵染事件与感病品种基本一致,但不能形成正常的吸器,胞壁沉积物明显多于感病品种,菌丝在寄主组织内的扩展明显受到抑制。利用β-1,3-葡聚糖免疫金标记单克隆抗体进行的免疫细胞化学的研究表明,胞壁沉积物内含有大量的β-1,3-葡聚糖,在大豆疫霉菌菌丝壁中也存在β-1,3-葡聚糖。以上结果表明,病原菌的侵染可诱导抗病寄主细胞内β-1,3-葡聚糖迅速的合成与积累、并形成胞壁沉积物,以抵御病菌的侵染与扩展。     

The role of fungal endophyte infection in the evolution of Lolium multiflorum resistance to diclofop-methyl

Diclofop-methyl resistance was evaluated in populations of Italian ryegrass ( Lolium multiflorum Lam.) infected and uninfected with fungal endophyte ( Neotyphodium ). Survival was tested in susceptible populations using herbicide screening. The results served as inputs to a model for investigating the role of endophyte infection in the evolution of L. multiflorum resistance to herbicide. The tolerance of infected plants varied depending on the origin of the population and the herbicide dose. Only in some populations and at some diclofop-methyl doses did plants infected with these endophytes have higher survivorship than endophyte-free plants. The model demonstrated that endophytes might indeed play an important role in the evolution of herbicide-resistant weeds, delaying the appearance of herbicide resistance.     

Components of resistance to late blight (Phytophthora infestans) in eight South AmericanSolanum species

Four components of partial resistance toPhytophthora infestans were measured after inoculation in the greenhouse and in the field ofSolanum arnezii x hondelmannii, S. berthaultii, S. circaeifolium, S. leptophyes, S. microdontum, S. sparsipilum, S. sucrense andS. vernei, and four hybrid progenies ofS. microdontum withS. tuberosum. The four components were infection efficiency, lesion growth rate, generation time and sporulation capacity. The results were compared with resistance ratings derived from field experiments, and with observations made on the potato cultivars Bintje, Bildstar, Libertas and Pimpernel. Genetic variation for all components was found, while the relative importance of the components of partial resistance appeared to vary between the species. InS. microdontum, generation time, infection efficiency and lesion growth rate, and inS. tuberosum infection efficiency, lesion growth rate and sporulation capacity appeared positively associated, but in other species no such association was found. A strong hypersensitive reaction, the expression of which appeared to depend on environmental conditions, was found inS. microdontum. ForS. berthaultii, infection efficiency appeared to be the main resistance component.Abbreviations ADPC area under the disease progress curve - IE infection efficiency - LGR lesion growth rate - GT generation time - SC sporulation capacity     

Infection of Linseed by Alternaria linicola; Effects of Inoculum Density, Temperature, Leaf Wetness and Light Regime

Controlled environment studies were conducted to determine the effects of inoculum density, temperature, leaf wetness and light regime on the infection of linseed by Alternaria linicola. The % cotyledons and leaves with symptoms, and the disease severity (% leaf area with symptoms) increased linearly when the inoculum density increased from 1×10³ to 1×10⁵ conidiaml^–1. The first symptoms appeared on cotyledons and leaves 4 and 6 days after inoculation, respectively. Eight hours of leaf wetness were sufficient to initiate the disease at 25°C but not at 15°C, when 10-h periods of leaf wetness were required. % leaf area with symptoms was lower at 15°C than that at 25°C irrespective of the leaf wetness periods tested. Interruption of a continuous leaf wetness period by a 12-h dry period, occurring at any time between 1 and 18h after inoculation, decreased the % cotyledons with symptoms and the disease severity, with the greatest reductions (60% and 100%, respectively) being observed when the dry period began 6h after inoculation. A. linicola conidia were able to exploit successive 12-h periods of leaf wetness cumulatively to infect linseed plants. Disease incidence and severity were positively correlated with the dark period following inoculation, but they were negatively related to the length of the initial light period. Our findings suggest that infection of linseed by A. linicola and further development of symptoms can occur under unfavourable environmental conditions.     

人工感染雏鹅新型病毒性肠炎的病理形态学发展规律的研究

40只2日龄四川白鹅口服感染雏鹅新型病毒性肠炎病毒，在不同阶段解剖发病和死亡雏鹅，电镜观察组织器官的病理变化发展规律，接种后第2天，十二指肠绒毛顶部上皮细胞发生坏死、脱落。随着感染时间延长，上皮细胞的坏死、脱落迅速向绒毛基部发展，并伴随固有膜炎性细胞浸润和坏死，病变向着空肠段发展，进一步发展为纤维素性坏死性肠炎，于小肠中后段形成假膜包裹肠内容物的栓塞物或直接由纤维素性渗出物与地不死肠粘膜混合凝固形成栓塞物阻塞肠腔，使外观膨大，肺充血和出血，肾充血、出血及肾小管上皮细胞变性。部分病例肝颗粒变性、脂肪变性，后期部分病例气管、腺胃上皮细胞脱落，早期部分病例心充血和出血，食道、胰腺及脑正常，电镜下可观察到小肠上皮细胞核畸形、固缩、核仁消失、核膜模糊和胞核崩解；胞浆严重空化，形成含有很多病毒粒子的“封入体”；粗面内质网扩张呈囊状，其上的核蛋白体严重脱落；线粒体外膜破裂或嵴断裂及空化，部分受到损害的线凿全充满大量的病毒粒子；形成肠道栓子的外层假膜有大量的病毒粒子、细菌以及坏死的肠上皮细胞，肝脏细胞粗面内质网严重扩张及部分线粒体肿胀、脊断裂；而心肌细胞粗面内质网的轻度扩张及胞核畸形。本文还对雏鹅新型病毒性肠炎与小鹅瘟的病理变化进行了比较分析。