Silvia Laura Fanelli

Insecticide concentrations in stream sediments of soy production regions of South America.

Concentrations of 17 insecticides were measured in sediments collected from 53 streams in soy production regions of South America (Argentina in 2011-2014, Paraguay and Brazil in 2013) during peak application periods. Although environmental regulations are quite different in each country, commonly used insecticides were detected at high frequencies in all regions. Maximum concentrations (and detection frequencies) for each sampling event ranged from: 1.2-7.4 ng/g dw chlorpyrifos (56-100%); 0.9-8.3 ng/g dw cypermethrin (20-100%); 0.42-16.6 ng/g dw lambda-cyhalothrin (60-100%); and, 0.49-2.1 ng/g dw endosulfan (13-100%). Other pyrethroids were detected less frequently. Banned organochlorines were most frequently detected in Brazil. In all countries, cypermethrin and/or lambda-cyhalothrin toxic units (TUs), based on Hyalella azteca LC50 bioassays, were occasionally>0.5 (indicating likely acute toxicity), while TUs for other insecticides were <0.5. All samples with total insecticide TU>1 were collected from streams with riparian buffer width<20 m. A multiple regression analysis that included five landscape and habitat predictor variables for the Brazilian streams examined indicated that buffer width was the most important predictor variable in explaining total insecticide TU values. While Brazil and Paraguay require forested stream buffers, there were no such regulations in the Argentine pampas, where buffer widths were smaller. Multiple insecticides were found in almost all stream sediment samples in intensive soy production regions, with pyrethroids most often occurring at acutely toxic concentrations, and the greatest potential for insecticide toxicity occurring in streams with minimum buffer width<20 m.

A liver nuclear ethanol metabolizing system. Formation of metabolites that bind covalently to macromolecules and lipids

Recent studies from the laboratory reported the presence in highly purified liver nuclear preparations free of endoplasmic reticulum, mitochondria or cytosol, of an ethanol metabolizing group of enzymes (NEMS) leading to acetaldehyde and to hydroxyl and 1-hydroxyethyl (1HEt) free radicals. In the present study it is reported that when NEMS metabolize [14C]ethanol using NADPH as cofactor, its reactive metabolites bind covalently to nuclear proteins and lipids. No covalent binding to DNA was detected with presently used procedures. The covalent binding to nuclear proteins was acid labile and is mostly attributable to acetaldehyde. Additional evidence was attempted through studies where the acetaldehyde was identified as its 2,4-dinitrophenylhydrazone or as its pentafluorphenylhydrazone and gas chromatography (GC) analysis using electron capture detection. Values obtained were close to detection limit and of variable nature. The covalent binding to nuclear lipids involved phospholipids, fatty acids and esters and cholesterol free and esterified and it was only partially labile to acid treatment. Production of ethanol reactive metabolites such as acetaldehyde and free radicals, nearby liver nuclear DNA and nuclear proteins or lipids, might have significant toxicological consequences.

Species at Risk (SPEAR) index indicates effects of insecticides on stream invertebrate communities in soy production regions of the Argentine Pampas

We investigated relationships among insecticides and aquatic invertebrate communities in 22 streams of two soy production regions of the Argentine Pampas over three growing seasons. Chlorpyrifos, endosulfan, cypermethrin, and lambda-cyhalothrin were the insecticides most frequently detected in stream sediments. The Species at Risk (SPEAR) pesticide bioassessment index (SPEARpesticides) was adapted and applied to evaluate relationships between sediment insecticide toxic units (TUs) and invertebrate communities associated with both benthic habitats and emergent vegetation habitats. SPEARpesticides was the only response metric that was significantly correlated with total insecticide TU values for all three averaged data sets, consistently showing a trend of decreasing values with increasing TU values (r2=0.35 to 0.42, p-value=0.001 to 0.03). Although pyrethroids were the insecticides that contributed the highest TU values, toxicity calculated based on all insecticides was better at predicting changes in invertebrate communities than toxicity of pyrethroids alone. Crustaceans, particularly the amphipod Hyalella spp., which are relatively sensitive to pesticides, played a large role in the performance of SPEARpesticides, and the relative abundance of all crustaceans also showed a significant decreasing trend with increasing insecticide TUs for two of three data sets (r2=0.30 to 0.57, p-value=0.003 to 0.04) examined. For all data sets, total insecticide TU was the most important variable in explaining variance in the SPEARpesticides index. The present study was the first application of the SPEAR index in South America, and the first one to use it to evaluate effects of pesticides on invertebrate communities associated with aquatic vegetation. Although the SPEAR index was developed in Europe, it performed well in the Argentine Pampas with only minor modifications, and would likely improve in performance as more data are obtained on traits of South American taxa, such as pesticide sensitivity and generation time.

Liver nuclear and microsomal CYP2E1-mediated metabolism of xenobiotics in rats chronically drinking an alcohol-containing liquid diet

In previous studies from our laboratory, the presence in highly purified liver nuclei of metabolic pathways for processing ethanol (EtOH), N-nitrosodimethylamine (NDMA), carbon tetrachloride and chloroform was reported. All these chemicals are known to be metabolized in liver microsomes, via cytochrome P450 2E1 (CYP2E1)-mediated processes. In the present work we checked whether rat liver nuclei from rats chronically drinking an alcohol-containing liquid diet exhibited an enhanced ability to metabolize chemicals known to require CYP2E1 participation for given metabolic transformations. The nicotinamide adenosine dinucleotide phosphate (NADPH)-requiring metabolism of p-nitrophenol to p-nitrocathecol; the activation of carbon tetrachloride to trichloromethyl radicals, covalently binding to proteins; and the ring hydroxylation of aniline and o-toluidine were studied. Comparison of the obtained nuclear activities against the one present in the microsomal counterpart, and their respective response to the EtOH inductive effect after repetitive exposure to it, was studied. The obtained results showed that rat liver nuclei exhibited less pnitrophenol hydroxylase activity than microsomes, but it was inducible by repetitive alcohol drinking to equivalent levels of those of microsomes from control animals. Nuclei exhibited the ability to activate CCl4, which was significantly enhanced by alcohol drinking. Aniline was ring hydroxylated in liver microsomes but not in nuclei from either control or EtOH-treated animals. In contrast, nuclei and microsomes metabolized o-toluidine to ring hydroxylated products. They are considered less toxic in nature but other authors reported a genotoxic effect for one of them. The production of the ring hydroxylated metabolites was enhanced by repetitive EtOH drinking. Results suggest that nuclear metabolism of xenobiotics might be relevant for either activations or detoxications mediated by CYP2E1 and that repetitive exposure to EtOH might significantly modulate those processes. Toxicology and Industrial Health 2006; 22: 367-374.

Land use effect on invertebrate assemblages in Pampasic streams (Buenos Aires, Argentina).

Agriculture and livestock may contribute to water quality degradation in adjacent waterbodies and produce changes in the resident invertebrate composition. The objective of the present study was to assess land use effects on the stream invertebrate assemblages in rural areas of the Argentine Pampa. The four sampling events were performed at six sites in four streams of the Pampa plain; two streams were sampled inside a biosphere reserve, and another one was surrounded by extensive livestock fields. The fourth stream was sampled at three sites; the upstream site was adjacent to agricultural plots, the following site was adjacent to an intensive livestock plot and the downstream site was adjacent to extensive breeding cattle plots. Higher pesticide concentrations were found at the site adjacent to agricultural plots and higher nutrient concentrations at the sites adjacent to agricultural and intensive breeding cattle plots. The invertebrate fauna were also different at these sites. Multivariate analysis showed a relationship between nutrient concentrations and taxonomic composition. Amphipoda (Hyalella curvispina) was the dominant group in the reserve and extensive breeding cattle sites, but was not present in the agricultural site. Also, Chironomidae were absent from the agricultural site while present at other sites. Gasteropoda (Biomphalaria peregrina), Zygoptera, and Hirudinea were dominant at the most impacted agricultural and intensive breeding cattle sites.

Diallyl Disulfide Prevention of Cis-Diammine Dichloroplatinum–Induced Nephrotoxicity and Leukopenia in Rats: Potential Adjuvant Effects

Cisplatin (CisPt) is an effective chemotherapeutic agent against several human cancers, but it produces important nephrotoxicity, leukopenia, and mortality. In this work, we report initial results on the potential ability of diallyl disulfide (DADS) to block these toxicities without compromising chemotherapy. Male Sprague Dawley rats were used (control, DADS, CisPt, and CisPt/DADS). CisPt was administered sc as a single dose (10.5 mg/kg) in saline. DADS was given daily intragastrically in olive oil (292.5 mg/kg) 1 h before CisPt administration the first day and 146.25 mg/kg during the next 3 days. The animals were sacrificed at the fifth day after CisPt administration. DADS significantly decreased CisPt-induced nephrotoxicity as evaluated by histology and by seric urea (CisPt: 11.05 ± 3.59; CisPt/DADS: 6.53 ± 1.74) and creatinine (CisPt: 24.74 ± 3.03; CisPt/DADS: 14.83 ± 2.07). DADS also decreased leukopenia (CisPt: 13.5% and CisPt/DADS: 43.4% respect the control), and mortality (CisPt: 50%; CisPt/DADS: 29%). DADS showed ability to interact with reactive oxygen species (H2O2, hydroperoxides, OH•) and with iron. DADS treatment does not change Platinum levels in kidney (CisPt: 15.2 ± 5.1; CisPt/DADS: 13.9 ± 4.5). Because DADS is known to inhibit cellular replication and to promote apoptosis of tumor cells, results suggest that DADS merit to be tested as a potential coadjuvant of CisPt chemotherapy in tumor-bearing animals.

Cholesterol interaction with free radicals produced from carbon tetrachloride or bromotrichloromethane by either catalytic decomposition or via liver microsomal activation

The reaction between cholesterol (Ch) and trichloromethyl or trichloromethyl peroxyl radicals was studied. The latter were generated from CCl4 either by benzoyl peroxide (BP) catalysis or via thermal activation or by liver microsomal NADPH-dependent biotransformation of CBrCl3. The structure of the products formed was elucidated by gas chromatography-mass spectrometry (GC/MS). Under aerobic conditions and using thermal activation of CCl4, the formation of 6 products was observed. Two (I and II) were dehydrated Ch derivatives (one also having a third double bond) (I). Another product was a delta(5)-3 ketone derivative of Ch (III). Two additional reaction products were determined as ketocholesterols (IV and V). One chloro Ch was also formed (VI). At low concentrations of BP, reaction was more extensive than under thermal activation, and the formation of peaks I to IV was also observed. When the reaction was conducted anaerobically and using thermal activation of CCl4 to generate radicals, only products I and II were formed in low yield. Under anaerobic conditions, but using catalyst, compounds I and III were produced plus two new isomeric ketocholesterol derivatives (VIII and IX) and also a compound having an extra hydroxyl group on the Ch structure (X). In order to check whether similar reactions are observable under biological experimental conditions, we used activation of CBrCl3 by liver microsomes. The incubation using only microsomes (without CBrCl3 or NADPH) showed two ketocholesterol peaks (A and B). In the presence of CBrCl3 we could detect peak B and hydroxycholesterol (C) and two others, ketocholesterols (D and E). D was the only peak showing close similarity (spectrum and retention time) to one of those observed in the chemical reaction system (V). The reaction of CBrCl3 in the presence of NADPH showed peaks B, C, D and E, in low abundance and a 7-ketocholesterol (F). If some of the reaction products reported here were formed during the intoxication with these haloalkanes, significant biological consequences might be expected.

Benznidazole levels in blood vary with age in rats

Benznidazole (Bz) exhibits toxic side effects in animal studies and clinical use. Reductive metabolism of Bz in liver microsomes modulates the duration of its chemotherapeutic effect and its toxicity. The rate of this metabolism depends on age and is less intense in newborns and youngsters than in adults. In the present study, we determined Bz blood levels in rats of different ages that received Bz intragastrically (100 mg/kg). We developed and validated a high-pressure liquid chromatography with UV detector method for determination of Bz levels in whole blood. Bz levels were significantly higher and persisted for longer periods of time in the blood of young rats when compared to that of adult animals.

Effect of agrochemicals on macroinvertebrate assemblages in Pampasic streams, Buenos Aires, Argentina

Agricultural practices have been intensified in recent decades in Argentina. The Pampa plain is the main agricultural region of the country. The effect of increased application of agrochemicals on the invertebrate fauna of the Pampasic streams remains unreported. In the present study, we compared the abundance and composition of invertebrate assemblages in seven Pampasic streams with contrasting soil use in their basins. Two streams run through intensively cropped plots, two drain basins with livestock fields, while the other three are located within a biosphere Reserve. Higher nutrient and insecticide concentrations were measured in the streams draining cropped basins, related with pesticide applications and crop fertilization. The invertebrate assemblage composition of the cropped streams differed significantly from the others and between the two. Present evidence suggests that the impact of agrochemicals results in a change in composition with decreased abundance or absence of sensitive species such as Hyalellidae, Caenidae, Baetidae and Curculionidae and increased abundance of more tolerant taxa: Ostracoda, Glossiphoniidae (Hirudinea), Ancylidae (Gundlanchia), Ampullariidae (Pomacea canaliculata), Sphaeriidae and Dugesiidae. Available information suggests that macrophyte cover and composition also influence the invertebrate assemblages of the Pampasic streams.

Acute toxicity of roundup to the nontarget organism Hyalella curvispina. Laboratory and field study

Glyphosate is the most used pesticide in Argentina. Hyalella curvispina is a widely distributed and commonly abundant component of the invertebrate assemblages in shallow waters of southern South America. The aim of this study was to assess the acute toxicity of the increasingly common Roundup Full II®, commercial formulation of the herbicide glyphosate (66.2% active ingredient), to H. curvispina in laboratory and field assessments. The mean estimated 48-h LC50 of Roundup was 9.9 ± 1.7 mg L−1. In a field experiment Roundup was applied to soybean plots. Simulated rain was generated the following day by means of irrigation sprinkler equipment. H. curvispina was exposed to runoff water and soy leaves. No mortality was observed. It is suggested that Roundup crop applications represent a low risk of acute toxicity to H. curvispina adults inhabiting water bodies adjacent to crop fields.