Risk assessment of dietary exposure to pesticides using a Bayesian method

Risk assessment of pesticides can be a statistically difficult problem because pesticides occur only occasionally, but they may occur on multiple components in the diet. A Bayesian statistical model is presented which incorporates multivariate modelling of food consumption and modelling of pesticide measurements which are for a large part below a measurement threshold. It is shown that Bayesian modelling is feasible for a limited number of food components, and that in a data-rich situation the model compares well with an empirical Monte Carlo modelling.     

Development of specific PCR primers for identification and detection of <Emphasis Type="Italic">Phytophthora capsici</Emphasis> Leon

A PCR-based method was developed for the identification and detection of Phytophthora capsici in pepper plants. Three PCR primers (CAPFW, CAPRV1 and CAPRV2) specific for P. capsiciwere designed based on the sequence of its internal transcribed spacer regions. CAPFW/CAPRV1 amplify a 452 bp product from P. capsici DNA whereas CAPFW/CAPRV2 a 595 bp fragment; neither set amplifies DNA from pepper or several fungi pathogenic to pepper. In conventional (single-round) PCR, the limit of detection was 5 pg DNA for both primer sets, whereas in nested PCR the detection limit for both was of 0.5 fg. However, when the dilution series of target DNA were spiked with plant DNA, amplification declined two-fold in both conventional and nested PCR. The CAPFW/CAPRV2 set in conventional PCR was used to detect P. capsici DNA in inoculated plants. Detection occurred as soon as 8h post-inoculation in stem samples from infected but still symptomless plants. The method was also tested to detect fungal DNA in infected soils.     

Estimated BVDV-prevalence, -contact and -vaccine use in dairy herds in Northern Portugal

A study to evaluate BVDV-prevalence, recent -contact and -vaccine use in dairy herds in the "Entre Douro e Minho" (EDM) region in North Portugal was carried out in 124 dairy herds in 2003. Herds were visited to ascertain BVDV-vaccine use and to collect a bulk tank milk (BTM) sample and serum from 1268 cattle to analyse BVDV-antibodies using an NS2-3 ELISA. Fifty-three percent of farmers used inactivated BVDV-vaccines whilst the remaining farmers were not presently using BVDV-vaccines. BMT-antibody results included 35% positives, 25% negative and 39% inconclusive, and were similar in vaccinated and non-vaccinated herds (p>0.05) and allowed estimating a 10% BVDV herd-prevalence from prior knowledge of the relationship between BMT-antibody results and probability of PI cattle in the herd. Overall individual seroprevalence was 27% and was 23% in non-vaccinated and 36% in vaccinated cattle (p<0.05). Contact of the herd with BVDV was assessed according to seroprevalence in young and adult cattle in the herd and it was estimated that 35% of herds were infected or had recent contact with BVDV, 40% were not infected and did not have recent contact with BVDV and the BVDV-infection and -contact status of remaining herds was undetermined. The results from this study indicate BVDV is endemic and BVDV-vaccines are widespread in the dairy-cattle population in EDM region in Portugal.     

Integrating Fire Risk Considerations in Forest Management Planning in Spain – A Landscape Level Perspective

It is reasonable to assume that there is a relationship between the spatial distribution of forest fuels and fire hazards. Therefore, if fire risk is to be included into numerical forest planning, the spatial distribution of risky and non-risky forest stands should be taken into account. The present study combines a stand-level fire risk model and landscape level optimization to solve forest planning problems in which the fire risk plays an important role. The key point of the method was to calculate forest level fire resistance metrics from stand level indices and use these metrics as objective variables in numerical optimization. This study shows that maximizing different landscape metrics produces very different landscape configurations with respect to the spatial arrangement of resistant and risky stands. The landscapes obtained by maximizing different metrics were tested with a fire spread simulator. These tests suggested that the mean fire resistance of the landscape, which is a non-spatial metric, is the most important factor affecting the burned area. However, spatial landscape metrics that decrease the continuity of fire resistance in the landscape can significantly improve the fire resistance of the landscape when used as additional objective variables.     

Detection of the enterotoxins A, B, and C genes in Staphylococcus aureus from goat and bovine mastitis in Brazilian dairy herds

To determine the distribution of genes that encode enterotoxins A, B and C, 36 strains of Staphylococcus aureus isolated from goat mastitis and 64 isolated from bovine mastitis were analyzed by Multiplex PCR. Of the total strains studied, 37 (37%) were detected to have some of the SEs genes. From the bovine mastitis strains, 4 (6.3%) co-amplified the sea and seb genes and 2 (3.1%) were positive for the sec gene. From the goat mastitis strains, 31 (86%) tested positive to the Multiplex, and the sec gene was detected in all of them. The production of SE was detected in all strains harboring the corresponding gene. The results demonstrated that S. aureus isolated from goat mastitis had a higher enterotoxigenic potential than those isolated from bovine mastitis. Additionally, the presence of the sec gene in the majority of goat mastitis strains suggests a possible involvement of SEC in goat mastitis pathogenesis.     

Biological and DNA evidence of two dissimilar populations of the Rhipicephalus sanguineus tick group (Acari: Ixodidae) in South America

In this work, the biology, mitochondrial DNA and fertility of hybrids from two strains of Rhipicephalus sanguineus, from Brazil and Argentina, were compared. Engorged larvae, nymphs and adults from Argentina weighed more and the engorgement period of adult females was significantly longer than those of their Brazilian counterparts, whereas adult female tick yield rate was higher for the Brazilian strain. High intraspecific divergence of mitochondrial DNA was detected between R. sanguineus from Brazil and Argentina. On the other hand, a strong genetic relationship was detected between European and Argentinean R. sanguineus populations while the Brazilian population appeared to be related to the African Rhipicephalus turanicus. Adult hybrid females laid eggs, which were mostly unviable, whereas a mean of more than 1400 larvae hatched per egg mass from pure Brazilian and Argentinean strains. These results showed that differences between these strains are greater than previously assumed and that the biosystematic status of R. sanguineus ticks from South America should be re-evaluated. Wide variations, such as these might account for the reported worldwide differences in biology and vector capacity of this species.     

Etude submicroscopique de la structure des reserves nutritives de l'orge

Résumé Dans notre étude submicroscopique des réserves nutritives de l'orge, nous avons pu mettre en évidence d'une façon précise, l'existence des films protéiques longitudinaux et transversaux se trouvant à l'intérieur du grain d'amidon. Un film transversal semble trancher une partie du corps du grain d'amidon, ce qui a été confirmé par l'étude d'une suspension alcoolique (préparée aux Ultra-Sons) et ombragée (métalisée) avec du chrome.Des coupes fines démontrent que les lamelles protéiques sont disposées radialement à l'intérieur des grains d'amidon, et que la structure de l'amidon d'orge est disposée en couches concentriques.Une fissure médiane caractéristique pour les Hordeae a été mise en évidence, ainsi que celle d'une bande pectique à l'intérieur des parois cellulaires. La structure fine de la cellulose en forme de lattice, a pu être ressortie, de même que l'existence de Ponts Intercellulaires avec des Desmosomes.La fixation (OsO₄ suivie de AWP) et l'inclusion dans du methacrylate (buthyl+methyl) 4:1 a été choisie, vu que ce procédé donnait les meilleurs résultats.La fixation avec UO₂ (NO₃)₂ donne aussi de bons résultats, tandis que celle à l'iode doit encore être développée.

---

Summary Submicroscopic studies of barley endosperm showed that protein membranes are radialy disposed inside the starch granules. A perpendicular membrane seems to separate a part of the starch granule. The granular consistency of these starch granules has been put into evidence, as well as a medial fissure, caracteristic for Hordeae, well defined.Besides, it was possible to show that the interior of the cell wall consists of a pectic band, and that adjacent cells are connected by intercellular bridges with desmosomes.No great difference was found between fixation with OsO₄ followed by AWP, and the one with H₂ Pt Cl₆.Fixation with uranil nitrate UO₂ (NO₃)₂ was also tried, but the material not yet studied.The fixation with iodide has still to be developped as it is known that iodide, even in dilute concentrations, may form an undesirable coat arround the starch grain.Methacrylate was prefered to araldite, as it can be evaporated under the electronic beam and is well recommended byWykoff (32) andBahr (3). Plexiglas inclusions have still to be tried out.The staining with (O_SO₄+AWP) and evaporation of the inclusion material, gives the possibility to obtain pictures of the cell interior tel quel, which opens new pathways for the future.

---

Zusammenfassung Elektronenmikroskopische Studien des Gerstenendosperms zeigten, daß Proteinfilme im Stärkekorn radial gelegen sind. Haftproteine und Lipoproteide konnten besser zur Geltung gebracht werden. Zwickelprotein dagegen nur in einigen Fällen.Ein konzentrischer Aufbau der Stärkekörner, sowie die für die Hordeae charakteristische Medianspalte, wurde nachgewiesen.Es scheint, daß eine Proteinmembran einen Teil der großen Stärkekörner, von der Hauptmasse trennt. Diese Erscheinung konnte außerdem durch Oberflächenstudien hervorgehoben werden.Der Feinbau der Zellwände und das Vorhandensein einer Pektinschicht im Inneren der Zellmembranen konnte durch Fixierung mittels (OsO₄+AWP) und Verdunstung des Methacrylats, hervorgehoben werden.Diese neue Technik erlaubte noch das Vorhandensein von Interzellularbrücken und Desmosomen zu zeigen.Kein großer Unterschied konnte zwischen der Fixierung mit (OsO₄+AWP) und H₂Pt Cl₆, gefunden werden.Wegen Zeitmangel konnte das mit Uranyl-Nitrat UO₂(NO₃)₂ fixierte Material nicht untersucht werden.Methacrylat wurde dem Araldit und Plexiglas als Einbettungsmittel vorgezogen, da es durch Elektronenstrahlen verdampft werden kann.Diese Methode ermöglicht in der Zukunft das Studium der Änderungen, die im Inneren von Zellen durch physikalische und chemische Mittel hervorgerufen werden.

     

Spatial patterns of fire occurrence in Catalonia,NE, Spain

In this paper, we analyse spatial patterns of fire occurrence in Catalonia (NE Spain) during 1975–98. Fire scar maps, discriminated by means of 30–60 m resolution remote sensing imagery, have been used as a source of fire occurrence. We employ several visual or analytical approaches to interpret fire occurrence in this region, such as those of Minnich and Chou (1997), Ricotta et al. (2001) or Krummel et al. (1987). Crucial spatial patterns such as fire size distribution, fire frequency distribution, spots and residual vegetation islands are documented. In addition, several geographical layers were overlaid with burned area maps in order to determine interactions between fire occurrence and environmental parameters such as altitude, slope, solar radiation, and burned land cover. Assuming that fire occurrence is well determined by such a posteriori empirical factors we detect areas most prone to fire in this region and aim to enhance the local forest management and conservation plans.     

Bird assemblages in forest fragments within Mediterranean mosaics created by wild fires

The role of habitat heterogeneity as a key factor in determining species pools in habitat mosaics has been acknowledged, but we still know little on the relative importance of the different ecological processes acting within such complex landscapes. We compared species richness and distribution in forest fragments imbedded in shrub-lands to those in continuous forests or in continuous shrublands. We examined the consistency of our data with the predictions of two hypotheses: 1) the Habitat fragmentation hypothesis which states that fragmentation has negative effects on the species from the original continuous habitat; 2) the Habitat supplementation /complementation hypothesis which stipulates that the presence of a matrix habitat around the fragments will mitigate negative effects on the species from the original habitat (supplementation) or allow the presence of species that depend on the presence of both the fragment and matrix habitats (complementation). We show that: 1) species richness in forest fragments did not differ from species richness in segments of continuous forests of equal area; 2) the bird community of forest fragments got impoverished in some forest species but a higher proportion of species common in continuous forests were not affected by fragmentation; 3) fragment communities had a significant proportion of common species that were scarce in, or absent from both continuous forests and shrublands. While, a few forest species supported predictions from the fragmentation hypothesis, occurrence patterns observed in several other species were consistent with either the supplementation or the complementation hypotheses. Our results suggest that there is no single hypothesis that properly captures the consequences of a shift from continuous forests to a mosaic of forest fragments and shrublands and that different ecological mechanisms act in conjunction to determine species pools in habitat mosaics. Habitat heterogeneity at a local scale appears a key factor in maintaining bird diversity in fire driven Mediterranean landscapes.     

Host-parasite relationships in tobacco plants infected with a root-knot nematode (<Emphasis Type="Italic">Meloidogyne incognita</Emphasis>) population from the Azores

During a nematode survey, severe infections of tobacco feeder roots and heavy soil infestations byMeloidogyne incognita race 1 were found in S. Miguel (Azores islands, Portugal). This is the first record ofM. incognita infection of tobacco in Azores. Morphology of various life stages, analysis of the esterase electrophoretic pattern and differential host tests were used for nematode characterization and identification. Nematode-induced mature galls were spherical and/or ellipsoidal and usually contained more than one female, males and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. Giant cell cytoplasm was aggregated along a thickened cell wall. Vascular tissues within galls appeared disorganized. The relationship between the initial nematode population density and growth of tobacco plants was tested in a glasshouse experiment in which inoculum levels varied from 0 to 512 eggs and juveniles (J₂) cm⁻³ of soil. Seinhorst’s model was fitted to height and top fresh weight data of the inoculated and control plants. Tolerance limits with respect to plant height and fresh top weight of tobacco cv. ‘Erzegovina’ plants toM. incognita race 1 were estimated as 1.25 eggs and J₂ cm⁻³ of soil. The maximum nematode reproduction rate was 404.7 at an initial population density of 4 eggs and J₂ cm⁻³ of soil. http://www.phytoparasitica.org posting March 2, 2004.