Immunosuppression abrogates resistance of young rabbits to Rabbit Haemorrhagic Disease (RHD)

Rabbit Haemorrhagic Disease (RHD) is caused by a calicivirus (RHDV) that kills 90% of infected adult European rabbits within 3 days. Remarkably, young rabbits are resistant to RHD. We induced immunosuppression in young rabbits by treatment with methylprednisolone acetate (MPA) and challenged the animals with RHDV by intramuscular injection. All of these young rabbits died within 3 days of infection due to fulminant hepatitis, presenting a large number of RHDV-positive dead or apoptotic hepatocytes, and a significant seric increase in cytokines, features that are similar to those of naïve adult rabbits infected by RHDV. We conclude that MPA-induced immunosuppression abrogates the resistance of young rabbits to RHD, indicating that there are differences in the innate immune system between young and adult rabbits that contribute to their distinct resistance/susceptibility to RHDV infection.     

Intramembrane cleavage of AMA1 triggers Toxoplasma to switch from an invasive to a replicative mode

Apicomplexan parasites invade host cells and immediately initiate cell division. The extracellular parasite discharges transmembrane proteins onto its surface to mediate motility and invasion. These are shed by intramembrane cleavage, a process associated with invasion but otherwise poorly understood. Functional analysis of Toxoplasma rhomboid 4, a surface intramembrane protease, by conditional overexpression of a catalytically inactive form produced a profound block in replication. This was completely rescued by expression of the cleaved cytoplasmic tail of Toxoplasma or Plasmodium apical membrane antigen 1 (AMA1). These results reveal an unexpected function for AMA1 in parasite replication and suggest that invasion proteins help to promote parasite switch from an invasive to a replicative mode.     

Triacylglycerol composition of walnut (Juglans regia L.) cultivars: characterization by HPLC-ELSD and chemometrics

A total of 26 walnut (Juglans regia L.) samples from 9 cultivars (Arco, Franquette, Hartley, Lara, Marbot, Mayette, Mellanaise, Parisienne, and Rego) harvested in the 2001, 2002, and 2003 crop years and grown in two geographical origins (Braganca and Coimbra, Portugal) were evaluated with regard to their triacylglycerol composition. The methodology employed was reversed-phase high-performance liquid chromatography coupled to an evaporative light-scattering detector (RP-HPLC-ELSD) after extraction of the lipidic fraction of the nuts. Nine compounds were separated, identified, and quantified. All samples presented an identical qualitative profile composed by LLnLn, LLLn, LLL, OLLn, OLL, PLL, OOL, and PLO (P = palmitoyl; O = oleoyl; L = linoleoyl; Ln = linonenoyl). Trilinolein (LLL) was the major triglyceride, followed by dilinoeoyl-oleoyl-glycerol (OLL) and dilinoleoyl-linolenoyl-glycerol (LLLn), with mean values of 37.7, 18.5, and 18.4%, respectively. Significant differences in composition were found between cultivars, and these differences were also significant when cultivars were grouped by year of production, showing that besides genetic factors, the triacylglycerol composition can be strongly influenced by environmental factors.     

Effects of multiple factors on plant diversity of forest fragments in intensive farmland of Northern Portugal

The joint and independent effects of dominant tree species, forest patch spatial attributes, and forest structure and management as drivers of plant species richness and composition in small forest patches scattered within an intensive agricultural landscape were addressed.In a landscape with scattered urban and intensive dairy agricultural areas in north-west Portugal, within which small forest patches (dominated by pines, eucalypts, or both) represent semi-natural habitat islands, 50 small forest patches, with areas ranging between 0.3 and 3 ha, were selected and surveyed for vascular plant diversity, within dairy farming landscape mosaics dominated by annual forage crops. Explanatory variables were composed of three datasets derived either from GIS mapping or field observations: forest type (dominant tree species), forest patch spatial attributes (patch area and shape index), and measures of forest management and structure (diameter at breast height, tree density per hectare, and percentage cover of vegetation strata). Variations in these forest patch attributes were assessed across forest types, and related to measures of plant diversity (total, native, alien, woody, and herbaceous species richness). Redundancy analysis with variance partitioning was applied to evaluate the joint and independent effects of the three sets of variables on species assemblages. The recent shift in canopy dominance from pine to eucalypt observed in the region appears to be related to a (nonsignificant) tendency for the increase of patch area and to the decrease of patch complexity, as well as several changes in forest structure and management, expressed as a trend to denser tree canopies and lower cover of understory plants. Dominant tree species and attributes related to forest structure and management were the most important factors determining plant diversity. The joint effect of the dominant tree species and forest structure and management resulted in lower levels of plant species richness in eucalypt plantations. These were also more prone to invasion by alien species, probably due to decreased biotic resistance from unsaturated native plant assemblages. Our results draw attention to the importance of dominant tree species and management practices for the maintenance of plant diversity levels (species richness and composition) in dairy landscape mosaics, highlighting the importance of the remnants of semi-natural forests as refuges for plant diversity in the landscape context. Nonetheless, forest plant diversity could further be fostered by promoting naturalness of pine stands and the regeneration of native oak woodlands in some forest areas. This would also diversify the range of ecosystem services that could be provided by forest areas in these peri-urban farmlands.     

Sialylation of Helicobacter bizzozeronii lipopolysaccharides modulates Toll-like receptor (TLR) 2 mediated response

Sialic acid in lipopolysaccharides (LPS) of mucosal pathogens is known to be an important virulence factor. Few strains of Helicobacter pylori express sialyl-Lewis-X and we have reported that human and canine Helicobacter bizzozeronii strains express sialyl-lactoseamine in their LPS. However, the role of sialyation of Helicobacter LPS in the interaction with the host cells is still unknown. In this study H. bizzozeronii LPS is shown to activate the TLR2 in a dose and strain dependent manner in the in vitro HEK-293 cells model expressing TLR2, but not the cells expressing TLR4. These results indicate that TLR2 is the specific receptor for H. bizzozzeronii LPS, as previously described for H. pylori. To further explore the role of sialylation of H. bizzozeronii LPS on TLR2 response, H. bizzozeronii Δhbs2 mutant strains deficient in sialyltransferase activity were constructed by homologous recombination. LPS from H. bizzozeronii Δhbs2 strains enhanced the NF-ĸB induction via TLR2 compared to the respective wild types, leading to the conclusion that the sialylation of H. bizzozeronii LPS in wild-type strains may modulate host immune response.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-014-0133-4) contains supplementary material, which is available to authorized users.     

Assessment of the diversity of comfrey (Symphytum officinale L. and S. × uplandicum Nyman)

Genetic Resources and Crop Evolution - Comfrey Symphytum officinale L. (true comfrey) and S.?×?uplandicum Nyman (a hybrid between S. asperum Lepech?×?S. officinale...     

Cnidarians as a source of new marine bioactive compounds--an overview of the last decade and future steps for bioprospecting

Marine invertebrates are rich sources of bioactive compounds and their biotechnological potential attracts scientific and economic interest worldwide. Although sponges are the foremost providers of marine bioactive compounds, cnidarians are also being studied with promising results. This diverse group of marine invertebrates includes over 11,000 species, 7500 of them belonging to the class Anthozoa. We present an overview of some of the most promising marine bioactive compounds from a therapeutic point of view isolated from cnidarians in the first decade of the 21st century. Anthozoan orders Alcyonacea and Gorgonacea exhibit by far the highest number of species yielding promising compounds. Antitumor activity has been the major area of interest in the screening of cnidarian compounds, the most promising ones being terpenoids (monoterpenoids, diterpenoids, sesquiterpenoids). We also discuss the future of bioprospecting for new marine bioactive compounds produced by cnidarians.     

Influence of two fertilization regimens on the amounts of organic acids and phenolic compounds of tronchuda cabbage (Brassica oleracea L. Var. costata DC)

A phytochemical study was undertaken on tronchuda cabbage (Brassica oleracea L. var. costata DC) cultivated under conventional and organic practices and collected at different times. Six organic acids (aconitic, citric, ascorbic, malic, shikimic, and fumaric acids) were identified and quantified by HPLC-UV. Qualitative and quantitative differences were noted between internal and external leaves. Analysis of the phenolics of the internal leaves was achieved by HPLC-DAD, and the phenolic profile obtained was revealed to be distinct from that of the external leaves. By this means were identified and quantified 11 compounds: 3-p-coumaroylquinic acid, kaempferol 3-O-sophoroside-7-O-glucoside, kaempferol 3-O-(caffeoyl)sophoroside-7-O-glucoside, kaempferol 3-O-(sinapoyl)sophoroside-7-O-glucoside, kaempferol 3-O-(feruloyl)sophoroside-7-O-glucoside, kaempferol 3-O-sophoroside, two isomeric forms of 1,2-disinapoylgentiobiose, 1-sinapoyl-2-feruloylgentiobiose, 1,2,2'-trisinapoylgentiobiose, and 1,2'-disinapoyl-2-feruloylgentiobiose. In general, internal leaves exhibited more constant chemical profiles.     

Seed dispersal networks in an urban novel ecosystem

The conflict resulting from the expansion of human activities into natural habitats affects the structure and functioning of ecosystems. Similarly, the anthropogenic redistribution of many species all over the world affects the composition of biological communities, possibly altering their capacity to sustain key ecological functions, such as seed dispersal. Urban parks are extreme examples of such novel ecosystems resulting from the anthropogenic redistribution of species in a new ecological framework. Here, we describe the avian seed dispersal network in an urban recreational woodland in central Portugal (c.79 ha). Four quantitative seed dispersal networks were assembled by identifying intact seeds in the droppings of mist-netted birds throughout the year. Overall, 1,244 seeds were identified, representing 33 links between 15 plant species and 11 bird species. Most birds dispersed alien seeds, but these represented a small proportion of the overall network (20 % of the seeds and 13 % of the droppings). Blackcap (Sylvia atricapilla) was the main disperser of native and alien seeds in all seasons, particularly those of the invasive Phytolacca americana. Fleshy fruits were more abundant in summer, but were more consumed in winter, presumably when other foods were difficult to find. Our study suggests that even in a highly managed urban park, seed dispersal networks can be temporally complex and variable and that a network approach can be an important monitoring tool to detect the status of crucial ecosystem functions in rapidly changing habitats such as urban parks.     

Susceptibility of larvae and adults of Monochamus galloprovincialis to entomopathogenic fungi under controlled conditions

Six entomopathogenic fungal isolates were tested under controlled conditions, as biological control agents against Monochamus galloprovincialis (Coleoptera: Cerambycidae) (Olivier), the vector of the pine wood nematode Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) (Steiner and Buhrer). The fungi Beauveria bassiana (Bals.-Criv.) Vuill, Metarhizium anisopliae (Metchnikoff) Sorokin, Metarhizium sp. and Fusarium sp. were tested against larvae and adults of the insect, by comparing two exposure techniques: continuous contact and spraying. Regarding the larvae, only Fusarium sp. and Metarhizium sp. killed more than 40% of the individuals, while B. bassiana and M. anisopliae were found to kill 50% of the adults (LT₅₀) within five days. Exposure to B. bassiana reduced adult longevity by 19 days, when compared to untreated beetles, and had a direct efficacy of 46%. Continuous contact with the fungi proved to be more effective than spraying. A larval disinfection protocol was developed to eliminate other fungal isolates from the wood-collected tested individuals. The implications of the results and possible applications of selected strains as bio-control agents against M. galloprovincialis are discussed.