Ecotoxicological evaluation of contaminated soil using the legume root nodule symbiosis as effect parameter

The legume root nodules are the site of biological nitrogen fixation in the legume—rhizobium symbiosis. They are a structure unique to this symbiosis and morphologically as well as physiologically distinct from other plant organs. We will present evidence that the formation of nodules (nodulation) may serve for ecotoxicological evaluation of contaminated soil. Substances affecting the macro- and/or microsymbionts vitality, such as certain heavy metals or polycyclic aromatic hydrocarbons (PAHs), reduce nodulation before visible damage of the plant occurs. Tests were performed in petri dishes that were planted with alfalfa seedlings and inoculated with Rhizobium meliloti. Mineral agar served as substrate. Test substances were added to the mineral agar before pouring it into petri dishes (application of heavy metals), or were sprayed as etheral solutions onto the surface of solidified medium (application of PAHs). For investigation of contaminated soil, the soil material was first mixed with mineral agar and then poured into petri dishes. Appropriate controls were made by extracting an aliquot of soil with methylene chloride to remove hazardous substances. Data from stressed plants were taken after 15 days of cultivation on contaminated substrate. A dose-responsive decrease in nodulation was found after application of CdCl₂, NaAsO₂, fluoranthene, and other PAHs. PAH-contaminated soil (75 mg/kg) caused only a slight reduction in nodulation of alfalfa. But when PAHs were extracted and restored into the extracted soil material, toxicity and uptake of PAHs into roots and shoots dramatically increased. Toxicity and uptake of PAHs were also enhanced by reducing the amount of humic matter added to the test system. © by John Wiley & Sons, Inc.     

Acute Nose-Only Exposure of Rats to Phosgene. Part I: Concentration × Time Dependence of LC50s,Nonlethal-Threshold Concentrations,and Analysis of Breathing Patterns

Groups of young adult Wistar rats were acutely exposed to phosgene gas using a directed-flow nose-only mode of exposure. The exposure durations used were 10, 30, 60, and 240 min and the corresponding C × t products bracketed a range from 1538 to 2854 mg/m³× min. The postexposure period was 2 wk. Subgroups of rats were subjected to respiratory function measurements. With few exceptions, mortality occurred within 24 h after exposure. The median lethal concentration (LC₅₀) and the estimated nonlethal threshold concentrations (LC₀₁) for 10, 30, 60, and 240 min were 253.3 (105.3), 54.5 (29.2), 31.3 (21.1), and 8.6 (5.3) mg/m³, respectively. With regard to the fixed outcome Cⁿ× t product, the exponent n was found to be ～0.9 for both the LC₅₀ and the LC₀₁. Due to an apparent rodent-specific transient depression in ventilation, results from 10-min exposures were excluded for the calculation of average C × t products. The average LCt₅₀ (and confidence interval 95%) and LCt₀₁ were 1741 (1547–1929) mg/m³× min and 1075 mg/m³× min, respectively, with a LCt₅₀/LCt₀₁ ratio of 1.6. Respiratory function measurements revealed an increased apnea time (AT), which is typical for lower respiratory tract irritants. This response was associated with transiently decreased respiratory minute volumes. Borderline, although distinct, changes in AT occurred at 1.2 × 30 mg/m³ × min and above, which did not show evidence of recovery during a 30-min postexposure period at 47.6 × 30 mg/m³× min and above. In an ancillary study, one group of rats was exposed to 1008 mg/m³× min (at 4.2 mg/m³ for 240 min; postexposure period 4 wk). Emphasis was on the time course of nonlethal endpoints (bronchoalveolar lavage, BAL) and histopathology of the lungs of rats sacrificed at the end of the 4-wk postexposure period. The climax of BAL protein was on the first postexposure day and exceeded approximately 70 times the control without causing mortality. The changes in BAL protein resolved within 2 wk. Histopathology did not show evidence of lung remodeling or progressive, potentially irreversible changes 4 wk postexposure. In summary, the analysis of the C × t dependent mortality revealed a steep C × t mortality relationship. The C × t product in the range of the nonlethal threshold concentration (1008 mg/m³ × min) caused pulmonary injury as indicated by markedly increased protein in BAL. Changes resolved almost entirely within the 4-wk postexposure period.     

中药白头翁对体外大肠杆菌生物膜抑制作用研究

目的：在Φ30培养皿和96孔板表面建立大肠杆菌生物被膜（E.coli biofilm,EBF）,形成体外模型,并开展白头翁对EBF抑制作用的初步研究。方法选取临床分离的大肠杆菌菌株,在Φ30培养皿和96孔板中分别复制体外EBF模型,将白头翁作用于EBF体外模型,分别采用银染法和MTT法考察白头翁对EBF的影响。结果Φ30培养皿中,表面观察到黑色呈棉絮状的膜样物,空白组没有此样物质;96孔板中,模型组的OD值为0.079,空白组的OD值为1.548;白头翁醇提组抑制率为25.79%,白头翁水提组抑制率为53.11%;750μg/mL的白头翁对大肠杆菌生物被膜有最佳抑制作用,抑制率为55.17%;药物作用12h后开始白头翁组的EBF明显少于空白对照组,24h效果最好。结论Φ30培养皿和96孔板表面可以形成大肠杆菌生物被膜体外模型,白头翁可以抑制和破坏早期及成熟的细菌生物膜,且其抑制作用表现出了一定的量效关系。     

Acute Nose-Only Exposure of Rats to Phosgene. Part II. Concentration × Time Dependence of Changes in Bronchoalveolar Lavage During a Follow-Up Period of 3 Months

Groups of young adult male Wistar rats were acutely exposed to phosgene gas for either 30 or 240 min using a directed-flow nose-only mode of exposure. In 30-min exposed rats the concentrations were 0.94, 2.02, 3.89, 7.35, and 15.36 mg/m³, which relate to C × t products of 28.2, 60.6, 116.7, 220.5, and 460.8 mg/m³ × min. In 240-min exposed rats the concentrations were 0.96, 0.387, 0.786, 1.567, and 4.2 mg/m³, which relate C × t products of 47.0, 92.9, 188.6, 376, and 1008 mg/m³ × min. Six rats/group were sacrificed on postexposure days 1, 3, 7, 14, and 84, while the rats of the 1008 mg/m³ × min group where sacrificed on postexposure days 1, 7, 14, and 28. The focus of measurements was directed toward indicators of inflammatory response and increased transmucosal permeability in bronchoalveolar lavage (BAL), including lung weights. Lungs from rats sacrificed at the end of the postexposure period were additionally examined by histopathology. Mortality did not occur at any C × t product. The most pronounced changes were related to C × t-dependent increases in the following markers in BAL: protein, soluble collagen, polymorphonuclear leukocytes (PMN) counts, and alveolar macrophages with foamy appearance. These indicators were maximal on the first postexposure day, while total cell counts and alveolar macrophages containing increased phospholipids reached their climax around post-exposure day 3. At 1008 mg/m³ × min the most sensitive indicators in BAL, that is, protein, PMN, and collagen, resolved within 2 wk, whereas at lower C × t products they reached the level of the control by postexposure day 7. At 1008 mg/m³ × min (day 28), histopathology revealed a minimal to slight hypercellularity in terminal bronchioles with focal peribronchiolar inflammatory infiltrates and focal septal thickening. At lower C × t products (day 84) the rats from all groups were indistinguishable and Sirius red-stained lungs did not provide evidence of late-onset sequelae, such as fibrotic changes or collagen deposition. At similar C × t products the changes in BAL were slightly less pronounced using 30-min exposure periods when compared to 240-min exposure periods. In summary, the phosgene-induced transmucosal permeability caused a C × t-dependent increase of several BAL indicators, of which those of protein, PMN, and soluble collagen were most pronounced. Exposure intensities up to 116.7 mg/m³ × min did not cause changes different from those observed in controls, while at 188.6 mg/m³ × min distinct differences to the control existed. Despite the extensively increased airway permeability, histopathology did not provide evidence of lung tissue remodeling or irreversible sequelae.     

Biotransformation of chlorpyrifos and diazinon by human liver microsomes and recombinant human cytochrome P450s (CYP)

1. The cytochrome P450 (CYP)-mediated biotransformation of the organophosphorothioate insecticides chlorpyrifos and diazinon was investigated. Rates of desulphuration to the active oxon metabolite (chlorpyrifos-oxon and diazinon-oxon) and dearylation to non-toxic hydrolysis products were determined in human liver microsome preparations from five individual donors and in recombinant CYP enzymes.

2. Chlorpyrifos and diazinon underwent desulphuration in human liver microsome with mean K_m = 30 and 45 μM and V_max = 353 and 766 pmol min^?1 mg^?1, respectively. Dearylation of these compounds by human liver microsome proceeded with K_m = 12 and 28 μM and V_max = 653 and 1186?pmol min^?1 mg^?1, respectively. The apparent intrinsic clearance (V_max/K_m) of dearylation was 4.5- and 2.5-fold greater than desulphuration for chlorpyrifos and diazinon, respectively.

3. Recombinant human CYP2B6 possessed the highest desulphuration activity for chlorpyrifos, whereas CYP2C19 had the highest dearylation activity. In contrast, both desulphuration and dearylation of diazinon were catalysed at similar rates, in the rank order CYP2C19 > CYP1A2 > CYP2B6 > CYP3A4.

4. Both organophosphorothioates were more readily detoxified (dearylation) than bioactivated (desulphuration) in all human liver microsome preparations. However, the role of individual CYP enzymes in these two biotransformation pathways varied according to the structure of the organophosphorothioate, which was reflected in different activation/detoxification ratios for chlorpyrifos and diazinon. Variability in activity of individual CYP enzymes may influence interindividual sensitivity to the toxic effects of chlorpyrifos and diazinon.     

Qualitative Effects Associated with Red Phosphorus Smoke Inhalation Exposures in Two Wildlife Species: Prairie Dogs and Rock Doves

Abstract

Effects of red phosphorus/butyl rubber (RPIBR) smoke on two wildlife species, prairie dogs and rock doves (pigeons), were evaluated in laboratory range-finding experiments. Prairie dogs exposed to either 2.0, 4.0, or 6.0 mg/L concentrations of smoke showed no mortality within 30 days after one to four 1-h exposure sessions. Rock doves exposed to either 3.0 or 6.0 mg/L concentrations over 1–4 sessions, however, showed 26% mortality within 8 days postexposure. Male rock doves were much more vulnerable to RP/BR smoke effects, with 42% mortali% in contrast to 6% in the females. Assessments indicated affected or lost vocalization capability in both species, abnormal body postures in rock doves, and increased respiratory congestion in prairie dogs postexposure. Neither species showed definite, consistent effects in gross necropsy and histopathology assessments. Only a few of the rock doves in 6.0 mg/L groups showed signs of excess mucus or exudate in their nasal passages and larynges.     

Serially Passaged Human Nasal Epithelial Cell Monolayer for in Vitro Drug Transport Studies

Purpose. To evaluate the feasibility of using a serially passaged culture of human nasal epithelial cell monolayers on a permeable support for in vitro drug transport studies. The optimum conditions for passaged culture as well as the correlation between the transepithelial electrical resistance (TEER) value and drug permeability (P_app) were evaluated. Methods. Fresh human nasal epithelial cells were collected from normal inferior turbinates and were subcultured repeatedly in serum-free bronchial epithelial cell growth media (BEGM) in petri dishes. The subcultured cells of each passage were seeded onto permeable supports at 5 × 10⁵ cells/cm² and grown in Dulbecco's modified Eagle medium (DMEM). Morphologic characteristics were observed by scanning electron microscopy (SEM). To verify the formation of tight junctions, actin staining and transmission electron microscopy (TEM) studies were conducted. In the drug transport study, [¹⁴C]mannitol and budesonide were selected as the paracellular and the transcellular route markers, respectively. Results. Serially passaged cells were successfully cultured on a permeable support and showed significantly high TEER values up to passage 4. After 14 days of seeding, SEM showed microvilli, and protrusions of cilia and mucin granules were detected by TEM. The paracellular marker [¹⁴C]mannitol showed a nearly constant permeability coefficient (P_app) when the TEER value exceeded 500 ·cm² regardless of the passage number. However, as expected, budesonide showed a higher permeability coefficient compared to [¹⁴C]mannitol and was less affected by the TEER value. Conclusions. Human nasal epithelial cell monolayers were successfully subcultured on a permeable support up to passage 4. These cell culture methods may be useful in high-throughput screening of in vitro nasal transport studies of various drugs.     

Development of a field test kit for coliphage detection in natural waters

Coliphages may be suitable alternative indicators of fecal pollution in natural waters. The relationship between coliphage and fecal coliform numbers may be expressed by log₁₀ transformed linear regression equations in surface waters (correlation coefficient, r² = 0.5872; p < 0.001) and in well waters (r² = 0.4767; p < 0.001). Using the American Public Health Association 919C single agar layer method, coliphages can be enumerated easily and at less cost and more rapidly than coliform enumeration methods. In adapting this test for use in a field test kit, however, further modifications and simplifications are required. The use of 2,3,5-triphenyl tetrazolium chloride (TPTZ) to enhance plaque visibility while helpful, was not essential. Matched-pair t-test analysis showed no significant difference between the plaque numbers enumerated with or without TPTZ to help plaque visibility. The Escherichia coli C host bacteria can be maintained either as a frozen preparation or dried on to paper disks with protective milk colloids. In the latter procedure, a resuscitation period of 18–24 h in broth at 30°C was found to be satisfactory in giving plaque numbers in the test that were not significantly different than when frozen host was used. A portable field kit has been designed to carry out a total of eight tests. The kit includes the media, the bacterial host, petri dishes, syringes, receptacles, and a camping gas cylinder. It measures 38 cm by 25.5 cm by 33.5 cm and weighs about 6.4 kg. Using the kit, the test procedure for a water sample can be carried out in under 15 min.     

Acute nose-only inhalation exposure of rats to di- and triphosgene relative to phosgene

Groups of young adult Wistar rats were acutely exposed to trichloromethyl chloroformate (diphosgene) and bis(trichloromethyl) carbonate (triphosgene) vapor atmospheres using a directed-flow nose-only mode of exposure. The exposure duration used was 240?min. The median lethal concentration (LC₅₀) of diphosgene and triphosgene was 13.9 and 41.5?mg/m³, respectively. Based on the molar exposure concentrations, the LC₅₀s of phosgene (previously published), diphosgene, and triphosgene were 0.07, 0.07, and 0.14 mmol/m³, respectively. Although the principal toxic mode of action of the volatile diphosgene was similar to phosgene gas, the vapor phase of triphosgene appeared to be different to that of phosgene and diphosgene based on a more persistent occurrence of signs of respiratory distress and a biphasic onset of mortality. While all substances caused mortality within 1 day postexposure, triphosgene induced a second phase of mortality 11–14 days postexposure. The vapor saturation concentration of triphosgene at ambient temperature is ≈100 times its LC₅₀. In summary, triphosgene-induced lung injury patterns are different from that of phosgene and diphosgene. More research is needed to close the substantial data gaps of triphosgene.     

Hematological,biochemical and histopathological changes in Caspian brown trout (Salmo trutta caspius Kessler, 1877) following exposure to sublethal concentrations of chlorpyrifos

The main objective of this study was to survey the acute and sublethal effect of chlorpyrifos (CPF) on Caspian brown trout (Salmo trutta caspius). Toxicity tests were performed for the determination of 96?h median lethal concentration (96hLC50). For this purpose, nominal concentrations of CPF including 0.0125, 0.025, 0.05, 0.1, 0.2 and 0.3?mgL^??¹. The 96hLC50 value of CPF was 0.026?mgL^?1. The sublethal effect was determined on the basis of acute toxicity, hematological effects, biochemical plasma profile, behavioral and histopathological changes. The experimental group exposed to CPF at nominal concentration of 0.0026?mgL^?1 (10% 96hLC50) for 30 days showed significant changes in hematological and biochemical profiles and caused histopathological changes in liver, gill and kidney. Based on these data, CPF is acute toxic for Caspian trout.     

Respiratory Irritation Associated with Inhalation of Boron Trifluoride and Fluorosulfonic Acid

The objectives of this study were to examine the respiratory irritancy of boron trifluoride (BF₃) and fluorosulfonic acid (FSA) following acute inhalation exposure. Testing was conducted using groups of 10 male and 10 female rats (BF₃) or groups of 6 male rats (FSA). Rats were exposed for a single 4-h period (BF₃) or a single 1-h period (FSA) and necropsied 1 or 14 days after exposure (BF₃) or 14 days after exposure (FSA). Measurements consisted of clinical signs, body weight, kidney and lung weight, histopathology (BF₃), and breathing parameters (FSA) and were used to evaluate the possible irritating effects of these compounds. The results indicated treatment-related findings in the larynx and trachea in the rats exposed to 74.4 mg/m³ BF₃, consisting of ventral cartilage necrosis, hemorrhage, and an increase in ventral epithelial hyperplasia and ventral inflammatory cell inflammation 24 h postexposure. In the animals sacrificed 14 days postexposure, the only notable observation was ventral cartilage necrosis, present in 2 animals. The next lower level tested, 24.6 mg/m³ BF, was considered a no-observed-adverse-effects level (NOAEL). A concentration of 4125 mg/m³ FSA resulted in a clearly decreased breathing rate during and shortly after exposure with 67% (4/6) mortality on days 5–9 after exposure. A concentration of 845 mg/m³ FSA resulted in only minor signs of irritation, consisting of slight changes in breathing pattern shorlty after exposure. The results of the present 4-h inhalation study with BF₃ indicated that respiratory irritation was present at a level of 74.4 mg/m³ whereas 24.6 mg/m³ was a NOAEL. A single 1-h exposure to 845 mg/m³ FSA resulted in only minor signs of respiratory irritation, indicating that on a mass basis FSA is no more toxic or irritating than hydrogen fluoride (HF) or sulfuric acid.     

Ultrafine organic aerosol particles inhaled by mice at low doses remain in lungs more than half a year

Experimental results of the second series of experiments on the penetration of monodisperse polymeric particles, inhaled at low dose by mice, to different organs using direct way of particle registration, based on the ultra‐sensitive accelerator mass spectrometer (AMS), are presented. Polystyrene (PS) beads, composed of radiocarbon‐labeled styrene, were produced for testing them as model organic aerosols. Mice inhaled ¹⁴C‐PS aerosol of 3·10⁵ ultrafine particles per 1 cm³ for 30 minutes every day during 5 days. Long‐term investigation showed that PS ultrafine particles have been effectively accumulated in lungs with the maximum content in the fifth day of postexposure, and have also appeared in liver on the fifth day of exposure and in the brain on the 30th day of experiments. No particles have been detected in kidneys, spleen, and excrements. Thirty‐five millions of particles remained in the lungs after half a year of postexposure showing extremely slow removal of such particles from the organ.     

In vitro and in vivo effects of cadmium on cholinesterases in Nile tilapia fingerlings: implications for biomonitoring aquatic pollution

Effects of cadmium on in vitro and in vivo cholinesterase (ChE) activities of brain and muscle tissues of Oreochromis niloticus fingerlings were evaluated, considering its potential use in biomonitoring tropical water pollution. Results show that in vitro ChE activities were depressed significantly by millimolar concentration ranges of Cd²⁺. The IC₅₀ values of Cd²⁺ on in vitro ChE activity in brain and muscle tissues were 1.56 and 4.31 mM, respectively. Exposure of fish to environmentally relevant concentrations of Cd²⁺ (5–30 μg l^−l) for 28 days evoked only a transient inhibition (21–34%) of in vivo ChE activities. Prior exposure and co-exposure of fish to 15 μg l⁻¹ of Cd²⁺ enhanced the extent of inhibition of ChE levels induced by the organophosphorous insecticide chlorpyrifos. As high concentrations of cadmium have the potential to depress ChE activities, monitoring of metal levels in water bodies with suspected high levels of metal inputs is necessary to accurately interpret the fish ChE inhibition data in relation to insecticide contaminations.     

Chlorpyrifos exposure reduces reproductive capacity owing to a damaging effect on gametogenesis in the nematode Caenorhabditis elegans

Previous studies have revealed that chlorpyrifos exposure adversely affects the reproductive capacity of male rodents. The present study investigated the reproductive toxicity of chlorpyrifos exposure and possible related mechanisms using the nematode Caenorhabditis elegans. L4 nematode larvae were exposed to chlorpyrifos at concentrations of 0.003, 0.03, 0.3 and 3.0 mg l^?1 for different durations. In addition to decreased brood size, reduced spermatid size, increased percentage of abnormal spermatids, suppressed spermatid activation and motility of sperm, damaged oocyte morphology, increased numbers of apoptotic cells and unfertilized oocytes were observed in nematodes exposed to various concentrations of chlorpyrifos. Moreover, expression patterns of the genes spe‐10, spe‐15, fer‐1, prg‐1, glp‐1, mlh‐1, cyb‐3, ced‐3, ced‐4 and ced‐9 (which are associated with spermatid size, spermatid activation and morphology, oocyte morphology, oocyte function, and apoptosis) were altered after chlorpyrifos exposure. Therefore, chlorpyrifos exposure may adversely affect fertility in nematodes by influencing both spermatogenesis and oogenesis. Alterations in the expression patterns of genes involved in gametogenesis may explain the corresponding changes in gametogenesis in nematodes exposed to chlorpyrifos. Hence, the model organism Caenorhabditis elegans is recommended for assessment of reproductive toxicity relating to gametogenesis. Copyright © 2011 John Wiley & Sons, Ltd.     

Lethal and sublethal effects of pesticides on <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> larvae (Neuroptera: Chrysopidae) and the influence of rainfastness in their degradation pattern over time

The predator Chrysoperla carnea is a model species for the study of non-target effects of pesticides under different scenarios: registration of plant protection products under the European Union and effects of the Bt toxin. Laboratory and persistence studies were carried out with six pesticides currently used in corn crops in Spain that were applied at their maximum field recommended concentrations. The assessed end-points were larval mortality, survivorship until adult stage, duration of the larval and pupal periods, fecundity, fertility and sex ratio of the emerged adults. Based on the total effect (lethal and sublethal) caused to L₃ larvae in contact with fresh residues in the laboratory, pendimethalin was harmless (IOBC 1), lambda-cyhalothrin, abamectin, and hexythiazox were slightly harmful (IOBC 2), deltamethrin was moderately harmful (IOBC 3) and chlorpyrifos was harmful (IOBC 4). Afterwards, the residues of the two most toxic pesticides in the lab (deltamethrin and chlorpyrifos) were aged under greenhouse conditions (22 ± 2 °C, 40 ± 10 % R.H., 16.9 μmol m^?2 s^?1 UV radiation) in the presence and absence of artificial rainfall (10 l m^?2 h^?1, applied 24 h after pesticide application). Deltamethrin was classified as short lived (IOBC A) in both cases. However, degradation of chlorpyrifos residues was accelerated in the presence of rainfall, leading to the classification as slightly persistent (IOBC B), while in absence of rainfall it behaved as persistent (IOBC D). Every pesticide can be recommended for inclusion in corn IPM programs where the predator is present except chlorpyrifos that exhibited high direct toxicity in the lab and prolonged residual action even in the presence of rainfall.     

The pathological response and fate in the lung and pleura of chrysotile in combination with fine particles compared to amosite asbestos following short-term inhalation exposure: interim results

The pathological response and translocation of a commercial chrysotile product similar to that which was used through the mid-1970s in a joint compound intended for sealing the interface between adjacent wall boards was evaluated in comparison to amosite asbestos. This study was unique in that it presents a combined real-world exposure and was the first study to investigate whether there were differences between chrysotile and amosite asbestos fibers in time course, size distribution, and pathological response in the pleural cavity. Rats were exposed by inhalation 6?h/day for 5 days to either sanded joint compound consisting of both chrysotile fibers and sanded joint compound particles (CSP) or amosite asbestos. Subgroups were examined through 1-year postexposure. No pathological response was observed at any time point in the CSP-exposure group. The long chrysotile fibers (L > 20?µm) cleared rapidly (T_1/2 of 4.5 days) and were not observed in the pleural cavity. In contrast, a rapid inflammatory response occurred in the lung following exposure to amosite resulting in Wagner grade 4 interstitial fibrosis within 28 days. Long amosite fibers had a T_1/2 > 1000 days and were observed in the pleural cavity within 7 days postexposure. By 90 days the long amosite fibers were associated with a marked inflammatory response on the parietal pleural. This study provides support that CSP following inhalation would not initiate an inflammatory response in the lung, and that the chrysotile fibers present do not migrate to, or cause an inflammatory response in the pleural cavity, the site of mesothelioma formation.     

Impact of five insecticides used to control citrus pests on the parasitoid <Emphasis Type="Italic">Ageniaspis citricola</Emphasis> Longvinovskaya (Hymenoptera: Encyrtidae)

The parasitoid Ageniaspis citricola Longvnovskaya is a main biological control agent of the citrus leafminer Phyllocnistis citrella Stainton, an insect pest that causes considerable damage to citrus worldwide. However, the use of pesticides to control arthropod pests can reduce the effectiveness of parasitoids and disrupt integrated pest management in citrus groves. This study evaluated the impact on A. citricola of five insecticides that are used to control arthropod pests in citrus. Our results indicated that imidacloprid, chlorpyrifos, bifenthrin and β-cyfluthrin were harmful (mortality >89 %) to A. citricola adults; whereas abamectin did not cause significant mortality and was considered harmless to the parasitoid. In addition to causing high mortality, imidacloprid and bifenthrin were considered moderately persistent, because they caused <25 % mortality to 17 and 24 days after spraying (DAS), respectively. Chlorpyrifos and β-cyfluthrin were considered slightly persistent (mortality <25 %, 7 DAS). Although abamectin was considered harmless to A. citricola adults, had a short life (mortality <25 %, 3 DAS), and did not significantly affect the parasitism rate, the number and viability of pupae, or the longevity of A. citricola, this insecticide significantly reduced the proportion of females in the progeny compared to the control treatment. Therefore, semi-field and field studies that consider demographic parameters are needed to evaluate the impacts of these insecticides on the A. citricola parasitoid.     

Genotoxicity of chlorpyrifos and cypermethrin to ICR mouse hepatocytes

Massive application of pesticides had generated a considerable concern in the public. Potentials of chlorpyrifos [O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl) phosphorothionate] and cypermethrin [(RS)-α-cyano-3-phenoxybenzyl (1RS)-cis-trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] to induce the excision-repairable DNA damage, DNA strand breakage, and DNA hypomethylation in ICR mouse hepatocytes were investigated. It was showed that chlorpyrifos and cypermethrin didn’t increase the incorporation of ³H-TdR into DNA of ICR mouse hepatocytes but increased the frequency of comet cells and decreased the 5MeC percentage of ICR mouse hepatocytes. In conclusion, chlorpyrifos and cypermethrin induced no excision-repairable DNA damage but led to DNA strand breakage and DNA hypomethylation in ICR mouse hepatocytes.     

Effects of Ambient Particles and Carbon Monoxide on Supraventricular Arrhythmias in a Rat Model of Myocardial Infarction

The association between short-term increases in particulate air pollution and increased cardiovascular morbidity and mortality is well documented. Recent studies suggest an association between particulate matter with aerodynamic diameter < 2.5 μm (PM_2.5) and supraventricular arrhythmias (SVA), but the results have been inconsistent. We evaluated this hypothesis in a rat model of acute myocardial infarction (AMI). Diazepam-sedated Sprague-Dawley rats with AMI were exposed (1 h) to either filtered air (n = 16), concentrated ambient fine particles (CAPS; mean = 645.7 μg/m³; n = 23), carbon monoxide (CO; 35 ppm; n = 19), or CAPs and CO (n = 24). Each exposure was immediately preceded and followed by a 1-h exposure to filtered air (baseline and postexposure periods, respectively). Surface electrocardiograms were recorded and the frequency of supraventricular premature beats was quantified. Among rats in the CAPS group, the probability of observing any SVA decreased from baseline to the exposure and postexposure periods. This patterm was significantly different than that observed for the filtered air group during the exposure period (p = .048) only. In the subset of rats with one or more SVA during the baseline period, the change in SVA rate from baseline to exposure period was significantly lower in the CAPS (p = .04) and CO (p = .007) groups only, as compared to the filtered air group. No significant effects were observed in the group simultaneously exposed to CAPS and CO. Thus, the results of this study do not support the hypothesis that exposure to ambient air pollution increases the risk or frequency of supraventricular arrhythmias.     

Impacts of seven insecticides on Cotesia flavipes (Cameron) (Hymenoptera: Braconidae)

The endoparasitoid wasp Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) is inundatively released in Brazilian sugarcane plantations to control the sugarcane borers Diatraea saccharalis (Fabricius) and Diatraea flavipennella (Box) (Lepidoptera: Crambidae). In conjunction with these releases, several synthetic insecticides are used to control the neonate larvae of these pests. We assessed the lethal and transgenerational sublethal effects of seven of these insecticides on C. flavipes. Leaf discs were sprayed at the highest field concentrations of chlorantraniliprole, lambda-cyhalothrin + chlorantraniliprole, chlorfluazuron, triflumuron, lambda-cyhalothrin + thiamethoxam, tebufenozide, and novaluron. Distilled water was used as a negative control. Newly emerged females (24 h old) were placed in Petri dishes containing the treated leaves, and the lethal and transgenerational sublethal effects were assessed for the next two generations. Lambda-cyhalothrin + chlorantraniliprole and lambda-cyhalothrin + thiamethoxam caused 100% mortality of the parasitoid and were highly persistent, causing more than 30% mortality at 30 days after spraying. Chlorantraniliprole, chlorfluazuron, novaluron, and triflumuron did not cause significant mortality compared to the negative control, but did have transgenerational sublethal effects. The length of the tibia of the right posterior leg, used as a growth measurement, was reduced in the progeny (F₁ generation) of exposed female parasitoids. In addition, chlorantraniliprole increased and chlorfluazuron reduced the proportion of females in the F₁ generation, whereas novaluron reduced the proportion of females in the F₂ generation. Overall, only tebufenozide was considered harmless to C. flavipes. The results of this study suggest that lambda-cyhalothrin + chlorantraniliprole and lambda-cyhalothrin + thiamethoxam are harmful to C. flavipes, although field studies are needed to obtain results for actual sugarcane crops.