Extracellular matrix alterations in experimental Leishmania amazonensis infection in susceptible and resistant mice

ABSTRACT: Leishmania is inoculated, by the bite of an infected sandfly, into the skin of the host, where the promastigotes are phagocyted by dermal macrophages. The dermal region comprises cells and abundant extracellular matrix. Studies show that matrix metalloproteinases play an important role in host defense responses against pathogens in mammals and that their activities lead to the production of antimicrobial peptides. The aim of this study is to evaluate the changes in the distribution of fibronectin and laminin as well as in the elastic system fibres during the course of infection caused by Leishmania amazonensis in mice with distinct genetic backgrounds of susceptibility to this parasite. The results showed that BALB/c presented an enhancement of fibronectin during the course of infection when compared to their control group while the infected or non-infected C3H.He showed a decrease of this protein at end of the experiment. Laminin, on the other hand, remained unaltered in both strains. Also in both BALB/c and C3H.He mice the elastic and elaunin fibres remained unchanged while the oxytalan fibres decreased along the experiment. Ninety days after the infection C3H.He mice had recovered their capacity to produce oxytalan fibres.     

Comparative and collaborative studies for the validation of a nested PCR for the detection of Xanthomonas axonopodis pv. dieffenbachiae from Anthurium samples

Efficient control of Xanthomonas axonopodis pv. dieffenbachiae, the causal agent of anthurium bacterial blight, requires sensitive and reliable diagnostic tools. The European standard EN ISO 16140:2003 has been followed to compare a nested PCR assay (N‐PCR) to a reference method (isolation and serological identification of bacterial colonies) and to other alternative serological detection methods. The evaluation was performed in two steps: a comparative study and a collaborative study involving 15 European laboratories. Although inclusivity was maximal (100%) for all methods, a maximal exclusivity was obtained only with N‐PCR followed by an enzymatic restriction digestion of the amplicons. Exclusivity indices of 90·6, 88·7 and 47·2% were found for indirect ELISA, immunofluorescence and double antibody sandwich ELISA, respectively. An exclusivity of 92·5% was obtained with the reference method, further increased to 100% if pathogenicity tests were performed as a supplemental assay. The best level of sensitivity (relative detection level) was obtained with the reference method followed by the N‐PCR assay. The N‐PCR performance in terms of relative accuracy, accordance and concordance was very similar to that of the reference method. Moreover, N‐PCR had undeniable advantages compared to the reference method (less labour‐intensive and less time‐consuming). In addition, post‐test probabilities of infection were calculated to select the most appropriate detection scheme related to the prevalence of the pathogen. The N‐PCR assay has since been included in a revised version of the EPPO detection protocol.     

Substrate-Dependent Bioavailability of Deltamethrin for the Epigeal Spider Oedothorax apicatus (Blackwall) (Aranaea,Erigonidae)

Terrestrial arthropods are mainly exposed to pesticides by uptake from the substrate e.g. “residual” uptake, which depends on the bioavailability of the pesticide. The residual uptake of deltamethrin by female Oedothorax apicatus (Blackwall), a linyphiid spider, was studied in relation to dependence on soil cover, soil moisture, walking behaviour, time after spraying and deposition rate. C¹⁴-labelled deltamethrin was used to quantify the uptake processes. Data were analysed using multiple regression analysis. Uptake was markedly higher from soil covered with fungi or moss than from uncovered soil. From uncovered soils with moisture contents varying from 7 to 49% dry weight, low uptake was measured, while at 63% moisture, the uptake was high. The bioavailability half-life was 157 min. The rate of uptake decreased with distance walked. The possible consequences of these results for field experiments are discussed.     

Water balance,respiration and immobilisation in relation to deltamethrin poisoning and physical conditions in the epigeal spider Oedothorax apicatus

The effect of a pyrethroid insecticide, deltamethrin, on water loss, metabolic rate and immobilisation was studied, using the epigeal spider Oedothorax apicatus (Blackwall) (Linyphiidae) as a test species. Water loss was measured gravimetrically at different temperatures, air humidities, and doses of deltamethrin. Metabolic rate and immobilisation were measured at different temperatures and doses. Immobilisation was measured at different relative humidities and temperatures. Water loss due to evaporation increased linearly with vapour pressure deficit. The slope of the latter relationship increased with temperature, indicating an increase in cuticle permeability with temperature. In addition to water loss by evaporation, deltamethrin treatment induced water excretion. This was positively related to dose and temperature, but independent of air humidity. Metabolic rate increased with temperature and dose. Immobilisation was highest at low temperatures in combination with low air humidity. The consequences of pesticide-induced water excretion are discussed with respect to field- and laboratory-based dose-effect relationships for pyrethroids presented in the literature. The present results seem to offer an explanation for hitherto unexplained minima in temperature-response curves in pyrethroid toxicity in some arthropod species. It is concluded that simultaneous measurements of metabolic rate, water-loss rate and pesticide effects are a prerequisite for an understanding of the effects of pesticides on arthropods.     

LysM-type mycorrhizal receptor recruited for rhizobium symbiosis in nonlegume Parasponia

Rhizobium-root nodule symbiosis is generally considered to be unique for legumes. However, there is one exception, and that is Parasponia. In this nonlegume, the rhizobial nodule symbiosis evolved independently and is, as in legumes, induced by rhizobium Nod factors. We used Parasponia andersonii to identify genetic constraints underlying evolution of Nod factor signaling. Part of the signaling cascade, downstream of Nod factor perception, has been recruited from the more-ancient arbuscular endomycorrhizal symbiosis. However, legume Nod factor receptors that activate this common signaling pathway are not essential for arbuscular endomycorrhizae. Here, we show that in Parasponia a single Nod factor-like receptor is indispensable for both symbiotic interactions. Therefore, we conclude that the Nod factor perception mechanism also is recruited from the widespread endomycorrhizal symbiosis.     

Changing patterns in insect pests on trees in The Netherlands since 1946 in relation to human induced habitat changes and climate factors—An analysis of historical data

In The Netherlands, insect pests on trees and shrubs are being monitored continuously since 1946. During these years, almost all insect pest populations showed marked changes, which may be the result of changes in forest management, shifts in forest composition, climate change and the arrival of new pests from the Mediterranean region or from other continents. In order to generate hypothesis about possible relationships between species ecology and environmental factors, we have analyzed 61 years of population development of the 98 most abundant species in the database while paying attention to life history traits and preferred host plants. The 22 species with infestations lasting a few years only were excluded from the analysis. Of the remaining 76 species, 18 were present over the entire observation period of 61 years. Of the other species, 27 showed a decline and 31 showed an increase. On coniferous trees most species showed decreasing populations. Increasing populations were found most on deciduous trees. Not directly climate-related factors such as changes in forest age, tree composition and forest management were identified as the most important causes for the fluctuations in pest insect populations. Climate change is a possible driver of the population increase in Thaumetopoea processionea, Haematoloma dorsatum and of the population decrease in Euproctis chrysorrhoea. The recently increasing exotic species Eupulvinaria hydrangeae and Pulvinaria regalis were exclusively found on trees in cities, presumably in relation to the higher temperatures of the urban habitat.     

Water absorption characteristics of kenaf core to use as animal bedding material

Kenaf is grown these days as a minor fibre crop in some Asian countries, but also in the US and recently in Southern European countries such as Italy. The yield of extracted bast fibres is below 1/3 of that of the kenaf stem weight. In the US and Europe a profitable outlet for the remaining woody core is important for economical production of the crop. The use of kenaf core as animal bedding material is considered here as potential market outlet. An important aspect for this application is the moisture absorption capacity of the material. This paper describes evaluation of the water absorption capacity of different kenaf core fractions in comparison with other commercial animal bedding materials like straw and wood shavings. The water absorption of kenaf core particles is shown to be in the range of the other tested materials and especially the soft pith material showed very high absorbency.     

Dissimilar response of plant and soil biota communities to long-term nutrient addition in grasslands

The long-term effect of fertilizers on plant diversity and productivity is well known, but long-term effects on soil biota communities have received relatively little attention. Here, we used an exceptional long-lasting (>40 years) grassland fertilization experiment to investigate the long-term effect of Ca, N, PK, and NPK addition on the productivity and diversity of both vegetation and soil biota. Whereas plant diversity increased by liming and decreased by N and NPK, the diversity of nematodes, collembolans, mites, and enchytraeids increased by N, PK, or NPK. Fertilization with NPK and PK increased plant biomass and biomass of enchytraeids and collembolans. Biomass of nematodes and earthworms increased by liming. Our results suggest that soil diversity might be driven by plant productivity rather than by plant diversity. This may imply that the selection of measures for restoring or conserving plant diversity may decrease soil biota diversity. This needs to be tested in future experiments.     

Stored water use and transpiration in Scots pine: a modeling analysis with ANAFORE

We estimated daily use of stored water by Scots pine (Pinus sylvestris L.) trees growing in a temperate climate with the ANAFORE model (ANAlysis of FORest Ecosystems) and compared the simulation results with sap flow measurements. The original model was expanded with a dynamic water flow and storage model that simulates sap flow dynamics in an individual tree. ANAFORE was able to accurately simulate diurnal patterns of measured sap flow under microclimatic conditions that differ from those of the calibration period. Strong relationships were found between stored water use and several tree characteristics (diameter at breast height, sapwood area, leaf area), but not with tree height. Relative to transpiration, stored water use varied over time (between < 1% and 44% of daily transpiration). On days when transpiration was high, trees were more dependent on stored water, indicating that the contribution of internal water to transpiration is not a constant in the water budget of trees.