Host plant determines the phytoplasma transmission competence of Empoasca decipiens (Hemiptera: Cicadellidae).

Phytoplasmas are phloem-restricted plant pathogens transmitted by leafhoppers, planthoppers, and psyllids (Hemiptera). Most known phytoplasma vectors belong to the Cicadellidae, but many are still unknown. Within this family, Empoasca spp. (Typhlocybinae) have tested positive for the presence of some phytoplasmas, and phytoplasma transmission has been proven for one species. The aim of this work was to investigate the ability of Empoasca decipiens Paoli in transmitting chrysanthemum yellows phytoplasma (CYP, "Candidatus Phytoplasma asteris", 16SrI-B) and Flavescence dorée phytoplasma (FDP, 16SrV-C) to Chrysanthemum carinatum Schousboe (tricolor daisy) and Viciafaba (L.) (broad bean). Euscelidius variegatus Kirschbaum, a known vector of CYP and FDP, was caged together with Em. decipiens on the same source plants as a positive control of acquisition. Em. decipiens acquired CYP from daisies, but not from broad beans, and inoculated the pathogen to daisies with alow efficiency, but not to broad beans. Em. decipiens did not acquire FDP from the broad bean source. Consistent with the low transmission rate, CYP was found in the salivary glands of very few phytoplasma-infected Em. decipiens, indicating these organs represent a barrier to phytoplasma colonization. In the same experiments, the vector Eu. variegatus efficiently acquired both phytoplasmas, and consistently CYP was detected in the salivary glands of most samples of this species. The identity of the CYP strain in leafhoppers and plants was confirmed by polymerase chain reaction (PCR)-restriction fragment length polymorphism. The CYP titer in Em. decipiens was monitored over time by real-time PCR. The damage caused by Em. decipiens feeding punctures was depicted. Differences in feeding behavior on different plant species may explain the different phytoplasma transmission capability. Em. decipiens proved to be an experimental vector of CYP.

Ecotoxicological assessment for receiving waters with the premetamorphic tadpoles acute assay.

The toxicity of receiving waters was evaluated by means of the young tadpoles assays. The sentinel organism was Bufo arenarum, an indigenous anuran species. The assayed water samples were taken from a highly polluted urban watercourse (Reconquista River, Buenos Aires, Argentina), characterized by high concentration of nitrites, phosphates and heavy metals. The toxicity of water samples was assessed performing the pass-fail test and by means of the NOEC and LC(50); TUs (toxic units) were also calculated. The effect of the addition of a positive control (Cd) on the toxicity of the river water samples was also examined. Water samples of three sites, characterised by their different degree of pollution, were assayed. The lethal response had a clear cut correspondence with the water quality of the sample evaluated by means of physicochemical parameters. In most cases, the dilution of the samples resulted in a significant reduction of their toxicity to TU values compatible to those stated by the USEPA for industrial effluents. It was concluded that (a) the used Bufo arenarum bioassay was an adequate method for assessing the toxicity of natural polluted water samples and (b) the three considered endpoints showed no important differences after 48 or 96 h of exposure, therefore we concluded that it may not be necessary to extend the assay for a longer period than 48 h.

Oil spill in the Rio de la Plata estuary, Argentina: 1. Biogeochemical assessment of waters, sediments, soils and biota.

Aliphatic (ALI) and aromatic (ARO) hydrocarbon concentrations, composition and sources were evaluated in waters, sediments, soils and biota to assess the impact of approximately 1000 tons of oil spilled in Rio de la Plata coastal waters. Total ALI levels ranged from 0.4-262 microg/l in waters, 0.01-87 microg/g in sediments, 5-39 microg/g in bivalves, 12-323 microg/g in macrophytes to 948-5187 microg/g in soils. ARO varied from non-detected 10 microg/l, 0.01-1.3 mug/g, 1.0-16 microg/g, 0.5-6.9 microg/g to 22-67 microg/g, respectively. Offshore (1, 5, 15 km) waters and sediments were little affected and contained low background hydrocarbon levels reflecting an effective wind-driven transport of the slick to the coast. Six months after the spill, coastal waters, sediments, soils and biota still presented very high levels exceeding baseline concentrations by 1-3 orders of magnitude. UCM/resolved aliphatic ratio showed a clear trend of increasing decay: coastal waters (3.3) < macrophytes (6.7) < soils (9.4) < offshore sediments (13) < coastal sediments (17) < clams (52). All environmental compartments consistently indicated that the most impacted area was the central sector close to Magdalena city, specially low-energy stream embouchures and bays which acted as efficient oil traps. The evaluation of hydrocarbon composition by principal component analysis indicated the predominance of biogenic (algae, vascular plant cuticular waxes), background anthropic, pyrogenic and diagenetic hydrocarbons, offshore and in non-impacted coastal sites. In contrast, polluted stations presented petrogenic signatures characterized by the abundance of isoprenoids, low molecular weight n-alkanes and methylated aromatics in different stages of alteration. The petrogenic/biogenic ratio ( n-C23) and petrogenic/pyrogenic relationship (methylated/unsubstitued PAH) discriminated the samples according to the different degree of impact. The following paper present the results of the study of the progress of hydrocarbon disappearance in sediments and soils 13 and 42 months after the spill.

Tadpoles assay: its application to a water toxicity assessment of a polluted urban river.

The acute toxicity assay with premetamorphic tadpoles of Bufo arenarum as sentinel organism was applied to evaluate the quality of two water samples taken from three sites of the Reconquista River, an urban watercourse which is recipient of both untreated industrial effluents and domestic wastes. The results of the 96 hr bioassays were compared with the physicochemical parameters determined in the samples. Mortality rates in each sample were compared using the Bonferroni's test and a stepwise regression analysis of mortality and physicochemical parameters was done. In this way, it was possible to build up consistent descriptive models which showed that pH, Cl- Cd2+ and Cu2+ concentrations in the river water were significant independent variables and might explain, under the experimental conditions, the recorded toxicity effects of the tested samples. Because of its simplicity, low cost and reliability it was suggested the tadpoles bioassay be included in the set of tests used in integrated program of freshwater pollution.

IgM anti-phenolic glycolipid I and IgG anti-10-kDa heat shock protein antibodies in sera and immune complexes isolated from leprosy patients with or without erythema nodosum leprosum and contacts.

The aim of the present work was to evaluate the levels of anti-PGL-I and anti-10-kDa heat shock protein antibodies in serum and immune complexes isolated from leprosy patients, convivients and controls. Leprosy patients with erythema nodosum leprosum or without it were included and a comparative study was done to investigate intergroup differences. Immune complexes were precipitated from serum by polyethylene glycol 3.5%; antibody levels were measured in sera and in dissociated immune complexes by ELISA. Serum antibody levels were then correlated with immune complex-associated antibody levels. The results showed that the erythema nodosum leprosum group differed from controls, contacts and non-erythema patients in their immune complex levels. IgM anti-PGL-I and IgG anti-10-kDa heat shock protein antibodies were constituents of the immune complexes in patients with erythema nodosum leprosum, who exhibited a significant difference in their immune complex composition compared with controls, contacts and non-erythema patients; while free antibody levels (anti-PGL-I and anti-10-kDa) did not differentiate between erythema and non-erythema patients, the measurement of immune complex-associated antibodies demonstrated a significant difference between the two clinical conditions. Furthermore, the measurement of immune complex-associated anti-PGL-I IgM made it possible to differentiate between contacts and controls. The significance of these results is discussed.

Cross-reactivity of anti-10kD heat shock protein antibodies in leprosy and tuberculosis patients.

The response to recombinant 10-kD heat shock protein (HSP) of Mycobacterium leprae (rML10) was evaluated by indirect ELISA in sera from leprosy patients, household contacts, tuberculosis patients and healthy controls in a leprosy-endemic area in the North East of Argentina. Some technical parameters were analyzed: within-assay and between-assay variability, dose-response curves and detectability indexes (specificity and sensitivity) of ELISA applied to measure anti-10 kDa antibodies. High levels of these antibodies have already been reported in positive bacilloscopy patients; herein we have also demonstrated that tuberculosis patients sera cross-react with this M. leprae antigen. This test seems to have a low sensitivity and specificity for leprosy detection; it confirms that antibodies against highly conserved HSP antigens are important in the polyclonal response against mycobacterial epitopes in leprosy as well as in tuberculosis.