Atypical myxomatosis--virus isolation, experimental infection of rabbits and restriction endonuclease analysis of the isolate

Atypical form of myxomatosis, which caused non-lethal and clinically mild disease in domestic rabbits 1 month after immunization with a commercially available vaccine MXT, is described. The isolated myxoma virus designated as Litovel 2 (Li-2) did not induce systemic disease following subcutaneous and intradermal applications in susceptible experimental rabbits but led to the immune response demonstrated by ELISA. No severe disease was induced in those Li-2 inoculated rabbits by challenge with the virulent strains Lausanne (Lu) or Sanar (SA), while the control animals showed nodular form of myxomatosis with lethal course of the illness. Restriction fragment length polymorphism (RFLP) of genomic DNA with KpnI and BamHI endonucleases was used for genetic characterization of the Li-2 isolate, the vaccine strain MXT and both virulent strains Lu and SA, respectively. In general, RFLP analysis has shown to be informative for inferring genetic relatedness between myxoma viruses. Based on restriction endonuclease DNA fragment size distribution, it was evident that the pathogenic strain SA is genetically related to the reference strain Lu and the isolate Li-2 is more related, but not identical, to the vaccination strain MXT.     

An ELISA optimized for porcine epidemic diarrhoea virus detection in faeces

Monoclonal antibodies to porcine epidemic diarrhoea virus (PEDV) membrane protein M were prepared and used for the comparative assessment of three blocking ELISA variants to detect PEDV. The competitive blocking ELISA (CB-ELISA) format showed the highest sensitivity, allowing detection of 10(2.5) plaque-forming units of PEDV/ml in culture medium. Its specificity was verified by inclusion of control samples containing transmissible gastroenteritis virus (TGEV) and rotavirus A in each analysis. Eighty porcine field samples of faeces obtained from 38 herds affected with diarrhoea were examined, and PEDV was found in 15 (19%) samples from 6 (16%) herds. The suitability of the CB-ELISA for the screening herds in epizootiologic situations is discussed.     

Use of immunoenzyme (ELISA) diagnosis of Aujeszky's disease in pigs during the recovery period

Samples of blood and blood serums of pigs were examined for the presence of antibodies to the Aujeszky's disease virus. The virus-neutralizing (VN) test and the enzymoimmunologic (ELISA) method were used for this examination. As indicated by comparison of the average titres of antiviral antibodies determined by both methods, the ELISA method is 60 to 600 times more sensitive than the VN test. The high sensitivity of the ELISA method enabled to detect antiviral antibodies even in samples considered as negative after VN-testing. The method has been used with success for the sanitation of three swine stocks where the Aujeszky's disease was eradicated without interruption of operation.     

糖类和骤冷对红茶冷后浑形成的影响

研究了添加糖类和骤冷对红茶冷后浑形的影响，结果表明，还原糖抑制红茶冷后浑比非还原糖有效。还原糖中的双糖一旦与多糖作用结合后，对防止多酚类分子相互聚集具有立体障碍作用，其抑制冷后浑的效果优于单糖，淀粉促进茶汤冷后浑形成。冷后浑随冷却速率加快而增加．     

Immunoenzyme (ELISA) diagnosis of spring viremia in carp

The enzymoimmunologic (ELISA) method was used to diagnose spring viremia in carp. The specific antibodies to Rhabdovirus carpio in the fish sera were detected by this method. Reaction specificity was tested by the use of viral and control antigens, by examination of positive and negative sera and by serum-free control incubation. Applying the ELISA method, the antiviral antibodies can be detected after infection or vaccination: this method is therefore suitable for thorough studies and when choosing the appropriate treatments and preventive measures.     

Habitat proximity exerts opposing effects on key ecological functions

Context

Connectivity is an important property of landscapes that shapes populations and ecosystem functioning. We do not know, however, whether and how different types of spatial linkages combine to influence ecological functions, and this hampers their integration into conservation planning.

Objectives

We used coral reef seascapes in eastern Australia as a model system to test whether the proximity of other reefs (habitat proximity) or the proximity of other habitats (seascape proximity) exert stronger effects on two key ecological functions (herbivory and piscivory).

Methods

We measured rates of herbivory (on fleshy macroalgae) and piscivory (on prey fish) on reefs that differed in their proximity to both other reefs and nearby mangroves and seagrass.

Results

The extent of habitat proximity between reefs significantly influenced both ecological functions, but in different ways: isolated reefs supported high herbivory but low piscivory, whilst, conversely, reefs that were closer to other reefs supported high piscivory but low herbivory. This was not caused by herbivores avoiding their predators, as the dominant piscivores (small predatory snappers) were too small to consume the dominant herbivores (large rabbitfishes). Seascape proximity (e.g., distance to mangroves or seagrass) was less important in shaping ecological functions on reefs in this system.

Conclusions

We suggest that the effects of seascape configuration on ecological functions depends on the type of spatial linkage, and the ecological functions in question. To better integrate connectivity into conservation, we must develop a deeper understanding of how different spatial linkages combine to shape ecosystem functioning across landscapes.

     

Variability of Cuban and International Populations of Alternaria solani from Different Hosts and Localities: AFLP Genetic Analysis

As causal agent of early blight disease in tomato and potato, Alternaria solani is an internationally important horticultural pathogen. Genetic variability was surveyed by amplified fragment length polymorphism analysis in a total of 112 isolates from potato and tomato, representing pathogen populations from different Cuban provinces together with isolates from the USA, Brazil, Turkey, Greece and China. Also included in the analysis were isolates from catenulated Alternaria spp. from Brazil, Canada, Greece and Russia, along with single isolates of Alternaria porri, Alternaria alternata and a Curvularia sp. UPGMA clustering revealed a differentiation between the isolates of A. solani and all other species with the exception of A. porri which could not be distinguished from A. solani. Among the isolates of A. solani, two distinct subclusters were formed, with high genetic significance revealed by bootstrapping, corresponding to a general subdivision based on the respective solanaceous host. The results are discussed with regard to potential host specificity of A. solani on tomato and potato, and in terms of the comparative contributions of regional and international genetic variability in populations of this ubiquitous plant pathogen.     

A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are potential increases in tree mortality associated with climate-induced physiological stress and interactions with other climate-mediated processes such as insect outbreaks and wildfire. Despite this risk, existing projections of tree mortality are based on models that lack functionally realistic mortality mechanisms, and there has been no attempt to track observations of climate-driven tree mortality globally. Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world's forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks. Our review also identifies key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system. Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide.     

Assessing the Extent of Substitution Rate Variation of Retrotransposon Long Terminal Repeat Sequences in Oryza sativa and Oryza glaberrima

Long Terminal Repeat retrotransposons (LTR-RTs) are a major component of several plant genomes. Important insights into the evolutionary dynamics of these elements in a genome are provided by the comparative study of their insertion times. These can be inferred by the comparison of pairs of LTRs flanking intact LTR-RTs in combination with an estimated substitution rate. Over the past several years, different substitution rates have been proposed for LTRs in crop plants. However, very little is known about the extent of substitution rate variation and the factors contributing to this variation, so the rates currently used are generally considered rough estimators of actual rates. To evaluate the extent of substitution rate variation in LTRs, we identified 70 orthologous LTRs on the short arms of chromosome 3 of both Oryza sativa and Oryza glaberrima, species that diverged ～0.64 Ma. Since these orthologous sequences were present in a common ancestor prior to species divergence, nucleotide differences identified in comparing these regions must correspond to mutations accumulated post-speciation, thereby giving us the opportunity to study LTR substitution rate variation in different elements across these short arms. As a control, we analyzed a similar amount of non-repeat-related sequences collected near the orthologous LTRs. Our analysis showed that substitution rate variation in LTRs is greater than 5-fold, is positively correlated with G+C content, and tends to increase near centromeric regions. We confirmed that in the vast majority of cases, LTRs mutate faster than their corresponding non-repeat-related neighboring sequences.