Bipyridylium Dichloride Research Articles

The effect of water molecules on paraquat salts: from physicochemical properties to environmental impact in the Brazilian Cerrado.

Introduction: The green revolution model that is followed in the Brazilian Cerrado is dependent on mechanization, chemical fertilization for soil dressing and correction, and the use of herbicides. Paraquat is a methyl viologen herbicide marketed as bipyridylium dichloride salts and used (in low doses) to combat weeds in their post-emergence stage. It is a non-selective pesticide that causes the peroxidation of the lipids that make up the cell membrane, and when it comes into contact with foliage, it results in the death of the plant. Methods: The effect of water molecules co-crystallized in Paraquat salt structures was analyzed in anhydrous, dihydrate, and trihydrate forms to understand those physicochemical properties in its redox activity. The frontier molecular orbitals were also carried out using DFT to obtain the chemical reactivity of the bipyridylium cation. Finally, the supramolecular arrangements were evaluated to analyze the physicochemical stability and acquire insights on superoxide anions. Results and discussion: The electronic structure indicated that the BP cation presents an acidic character due to its low ELUMO value, while the salt has a more basic character due to its high EHOMO value. For this reason, the BP ion is more susceptible to reduction during the weeds' photosynthesis process. During the process of plant photosynthesis, PQ is reduced to form a stable radical cation. In the supramolecular arrangement, the presence of water molecules increases the number of strong H-bonds, while the weak/moderate H-bonds are stabilized. PQ's toxic effects are observed in wildlife, domesticated animals, human populations, and ecosystems. The influence of PQ on the terrestrial environment is limited because of the soil adsorption capacity associated with good agricultural practices. The current use of good agricultural practices in the Cerrado seems not to prevent the environmental impacts of herbicides like PQ because it aims for the expansion and profitability of large-scale farming based on input-intensive practices instead of sustainable agriculture processes.

Occurring the paraquat residues in various Nigerian

Abstract: Because pesticides are ubiquitous and focused on the food chain, they are a substantial source of possible environmental danger to humans and animals. The highest extremely hazardous herbicides to be launched in 60 years ago is paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride). Although most nations have prohibited or severely limited the use of paraquat (PQ), it is still used in others, particularly in Nigeria. As a result, the present study used a spectrophotometric method to look for PQ in some vegetables, crops, and fruits in Abeokuta that are commonly consumed. The presence and amounts of PQ residues were assessed in 150 samples of various vegetables, crops, and fruits (harvested at Fadama field of the University of Agriculture, Abeokuta). PQ residues were detected in Talinum triangulare, Corchorus olitorius, Amaranthus caudatus, Cratylia argentea, Capsicum frutescens, Lycopersicum esculentum, Raphanus sativus, Zea may, and Dioscorea alata at 0.130.02, 0.27+0.02, 0.06+0.01, 0.10+0.03, 0.15+0.03, 0. Using this technique, no paraquat residues were found in M. paradisicica or C. papaya. At 0.05-1.0 ppm fortification level, the technique yields a mean recovery of over 80% and is reproducible with a total coefficient of variation of 8.0 percent (n=10). All residual levels found were under the PQ tolerance or pesticide maximum limits.

Filamentous fungi with high paraquat-degrading activity isolated from contaminated agricultural soils in northern Thailand.

The contamination of paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) herbicide from the farming area has become a public concern in many countries. This herbicide harms to human health and negatively effects the soil fertility. Several methods have been introduced for the remediation of paraquat. In this study, 20 isolates of the paraquat-tolerant fungi were isolated from the contaminated soil samples in northern Thailand. We found that isolate PRPY-2 and PFCM-1 exhibited the highest degradation activity of paraquat on synthetic liquid medium. About 80 and 68% of paraquat were removed by PRPY-2 and PFCM-1 respectively after 15days of cultivation. Based on the morphological characteristic and molecular analysis, the fungal isolate PRPY-2 and PFCM-1 were identified as Aspergillus tamarii and Cunninghamella sp. respectively. The biosorption of paraquat on these fungal mycelia was also investigated. It was found that only 8-10% of paraquat could be detected on their mycelia, while 24-46% of paraquat was degraded by fungal mycelia. This is the first report on paraquat degrading ability by A. tamarii and Cunninghamella sp. It is demonstrated that these filamentous fungi are promising microorganisms available for remediation of paraquat contaminated environment.

Metabolitic profiling of amino acids in paraquat-induced acute kidney injury.

The herbicide paraquat (1, 1'-dimethyl-4, 4'-bipyridylium dichloride; PQ) is a poison well-known to cause delayed mortality due to acute kidney injuries (AKI). This study examines the changes in serum amino acids (AAs) metabolite profiles as surrogate markers of renal cell metabolism and function after paraquat poisoning. To identify the metabolic profiling of free serum AAs and its metabolites, serum from 40 paraquat-poisoned patients with or without AKI is collected. LC-MS/GC-MS is performed to analyze AA molecules. A Cox proportional hazard model was used to assess for incidence of AKI. Receiver operating characteristic (ROC) curve is applied to evaluate AKI occurrence and prognosis. A total of 102 serum AAs and its metabolites were identified. Compared with non-AKI patients, 37 varied significantly in AKI patients. The univariate Cox proportional hazard model analysis revealed that the estimated PQ amount, plasma PQ concentration, urine PQ concentration, APACHE, SOFA scores and 16 amino acids correlated with the incidence of AKI. Further analyses revealed that 3-methylglutarylcarnitine, 1-methylimidazoleacetate, and urea showed higher cumulative hazard ratios for the occurrence of AKI during follow-up (P < 0.05). The area under the curve (AUC) of 3-methylglutarylcarnitine, 1-methylimidazoleacetate and urea were 0.917, 0.857, 0.872, respectively. 3-methylglutarylcarnitine, 1-methylimidazoleacetate and urea were associated with AKI in patients with paraquat intoxication.

Viologen-Based Photochromic Coordination Polymers for Inkless and Erasable Prints.

Four coordination polymers, namely, [Zn(HL1)(L2)0.5]·H2O (1), [Cd(HL1)(L2)0.5]·H2O (2), [Zn(L1)(L3)0.5]·H2O (3), and [Cd(L1)(L3)0.5] (4) (H3L1 = (3,5-dicarboxyl-phenyl)-(4-(2'-carboxyl-phenyl)-benzyl)ether, H2L2Cl2 = 1,1'-bis(4-carboxy-benzyl)-4,4'-bipyridinium dichloride, and L3Cl2 = 1,1'-dimethyl-4,4'-bipyridylium dichloride), have been synthesized hydrothermally. The structures of compounds 1-4 have been determined by single-crystal X-ray diffraction analyses, and further characterized by elemental analyses, infrared (IR) spectra, powder X-ray diffraction (PXRD) analyses, and thermogravimetric analyses. Compounds 1 and 2 display three-dimensional 2-fold interpenetrating frameworks, whereas compounds 3 and 4 exhibit two-dimensional layer structures. These compounds display photochromic behaviors from pale yellow to green under UV light, visible light, or sunlight. The photochromic mechanisms of these compounds have been studied by IR spectra, PXRD analyses, UV-vis absorption spectra, electron paramagnetic resonance spectra, density functional theory calculations, and X-ray photoelectron spectroscopy. The capabilities of compounds 1 and 2 as inkless and erasable printing media have also been tested. Moreover, the photomodulated fluorescence of these compounds has also been investigated.

133 INCIDENCE AND OUTCOME OF ACUTE KIDNEY INJURY IN PATIENTS WITH ACUTE PARAQUAT POISONING

Category: Research in AKI (Basic, translational, clinical including clinical trials) Presenter: Dr SHERILLIA SHARIF Keywords: acute kidney injury, paraquat poisoning Paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) is widely used as a herbicide. Paraquat poisoning is associated with high mortality varying from 35% to 50%. Multiple organ (cardiac, respiratory, hepatic, and renal) failure may occur, although pulmonary features predominate and are the usual cause of death. 1.To ascertain the incidence of acute kidney injury (AKI) in patients with acute paraquat poisoning as confirmed by presence of positive urine paraquat sample.2.To ascertain the renal outcome and patient outcome of the acute kidney injury. This retrospective study was performed on all patients admitted from 1st January 2007 to 8thApril 2017.Patients with positive urine paraquat sample were identified from the Hospital Laboratory Information System (LIS). Patients' demography, relevant clinical data, laboratory results, renal outcome and patient outcome were retrieved from hospital electronic medical record. Results were analysed using SPSS version 23. Thirty-four patients have been hospitalized with documented positive urine paraquat sample. Twenty-six patients (76.5%) died. Twenty-eight patients (82%) had AKI. Mean age in AKI group was 37.9±14.1 years. Twenty-one (75%) were male. Twenty-three patients with AKI (82.1%) died. Seventeen (60.7%) were Indian while Chinese, Malay and others accounted 7 (25%), 3 (10.7%) and 1 (3.6%) respectively. Of the 5 patients who remained alive, at time of discharge, 4 (80%) had complete renal recovery, 1 (20%) developed chronic kidney disease. There was no significant difference in mortality rates between patients who develop AKI and those without AKI (P value = 0.220). The incidence of acute kidney injury and mortality rate is high with acute paraquat poisoning. Some patients died from cardiorespiratory collapse before the development of acute kidney injury. This study is limited by the small sample size.

Environmental Health Risk Analysis of Paraquat Exposure in Palm Oil Plantations

Paraquat (1, 1’-dimethyl-4, 4’-bipyridylium dichloride) is a highly toxic herbicide. Recently, Paraquat is still used widely in the plantations area, mainly in palm oil plantations. Paraquat application continuously can be increased Paraquat concentration and contaminated in soil and water. This study aimed was to analysis Paraquat exposure in environmental media water and soil, and the calculation of risk quotient of Paraquat in palm oil plantation. The study design of this research was a cross sectional with the laboratory examination Paraquat concentrations in soil and water. Soil and water samples taken by grab sampling with random composites. Water samples were taken from three sources in palm oil plantations area. Whereas soil samples were taken at a depth of 0-10 cm (top soil) and the number of soil samples as much as 5 samples. Furthermore, the risk quotient of Paraquat concentration in the water used in the palm oil plantation. The laboratory tests of Paraquat concentration were in water and soil with gas chromatography. The results of laboratory tests showed that Paraquat concentration in water samples were found between &amp;lt;0.005 to 0.01 mg/l and Paraquat concentration in soil samples were found between &amp;lt;0.005 to 0.08 ppm. The calculation of risk quotient was 0.058 mg/body weight/day. Although, the calculated of risk quotient showed less than one. Therefore, prior to use the water must be treatment first. While the recommended water to consumption as much as 2 liters/day for a 55 kg body weight to Indonesian workers.

Environmental Health Risk Analysis of Paraquat Exposure in Palm Oil Plantations

Paraquat (1, 1’-dimethyl-4, 4’-bipyridylium dichloride) is a highly toxic herbicide. Recently, Paraquat is still used widely in the plantations area, mainly in palm oil plantations. Paraquat application continuously can be increased Paraquat concentration and contaminated in soil and water. This study aimed was to analysis Paraquat exposure in environmental media water and soil, and the calculation of risk quotient of Paraquat in palm oil plantation. The study design of this research was a cross sectional with the laboratory examination Paraquat concentrations in soil and water. Soil and water samples taken by grab sampling with random composites. Water samples were taken from three sources in palm oil plantations area. Whereas soil samples were taken at a depth of 0-10 cm (top soil) and the number of soil samples as much as 5 samples. Furthermore, the risk quotient of Paraquat concentration in the water used in the palm oil plantation. The laboratory tests of Paraquat concentration were in water and soil with gas chromatography. The results of laboratory tests showed that Paraquat concentration in water samples were found between &amp;lt;0.005 to 0.01 mg/l and Paraquat concentration in soil samples were found between &amp;lt;0.005 to 0.08 ppm. The calculation of risk quotient was 0.058 mg/body weight/day. Although, the calculated of risk quotient showed less than one. Therefore, prior to use the water must be treatment first. While the recommended water to consumption as much as 2 liters/day for a 55 kg body weight to Indonesian workers.

Influence of Zirconium Doped Titanium Oxide towards Photocatalytic Activity of Paraquat

The heterogeneous photocatalyst based on titanium dioxide has been widely investigated as an attractive treatment method for water pollution. Herbicide like paraquat dichloride is one of the toxic organic pollutants which is harmful to human and animal and is still being used in agricultural sectors. TiO2 doped with zirconium element has been proven to enhance the photocatalytic activity of TiO2 from the previous study. Therefore in this study, photodegradation of paraquat dichloride (1,1-dimethyl-4,4’-bipyridylium dichloride) under UV irradiation was studied using TiO2 and Zr doped TiO2 prepared via modified sol gel method as photocatalysts. The photocatalytic activity was increased in the presence of zirconium as dopant compared to TiO2. Various calcination temperatures range from 450°C to 1000°C and dopant ratio (10:90, 20:80 and 30:70) were applied to optimize the working condition. Significant enhancement was obtained using Zr doped TiO2 (20:80) calcined at 750°C which gave 79.63% degradation of paraquat compared to TiO2 calcined at 450°C and 750°C which were 22.31% and 11.57%. X-ray diffraction (XRD) diffratogram of Zr doped TiO2 photocatalyst showed a mixture of anatase/rutile TiO2 crystalline structures at 750°C. Nanosized photocatalyst with spherical morphology was observed by Field Emission Scanning Electron Microscopy (FESEM). The surface area measured by nitrogen adsorption analysis showed an increment from 8.43m2/g to 46.35m2/g compared to undoped catalyst calcined at 450°C.

Daily Subacute Paraquat Exposure Decreases Muscle Function and Substantia Nigra Dopamine Level

The use of the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride; PQ) which is widely used in agriculture is known to cause dopaminergic neurotoxicity. However, the mechanisms underlying this effect are not fully understood. This present study investigated the behavioral manifestations, motor coordination, and dopaminergic neurodegeneration following exposure to PQ. Male rats were injected with PQ (10 mg/kg i.p.) daily for three weeks. Rotarod systems were used for measuring locomotor activity and motor coordination. The effects of PQ on dorsiflexor, electrophysiologically-induced muscle contraction were studied. Dopamine concentrations in the ventral mesencephalon were measured by high performance liquid chromatography and the number of dopaminergic neurons in substantia nigra pars compacta was estimated by tyrosine hydroxylase immunohistochemistry. PQ induced difficulty in movement and significant reduction in motor activity and twitch tension at the dorsiflexor skeletal muscle. The number of tyrosine hydroxylase positive neurons was significantly less in the substantia nigra pars compacta and nigral dopamine level was significantly reduced in PQ treated animals (20.4+/-3.4 pg/mg) when compared with control animals (55.0+/-2.4 pg/mg wet tissue). Daily treatment of PQ for three weeks induces selective dopaminergic neuronal loss in the substantia nigra and significant behavioral and peripheral motor deficit effects.

Protection of HeLa cells against ROS stress by CuZnSOD mimic system.

A new copper zinc complex (CZpbi), [(bipyridinyl)2Cu-μ-pbi-Zn(pbi)](ClO4)2, pbi = 2-(2-pyridyl)-benzimidazole, was synthesized to mimic copper zinc superoxide dismutase (CuZnSOD). CZpbi was then encapsulated onto a dye (fluorescein isothiocyanate, FITC) functionalized mesoporous silica nanoparticles (MSN) where MSN serves as a nanofactory platform for delivering the catalytic action of the center copper complex. We examined the inhibition of oxidative damage of HeLa cells in the presence of paraquat (PQ, 1,1'-dimethyl-4,4'-bipyridylium dichloride, an oxidative stressor). We further studied the cell viability and cell cycle process under the influence of paraquat stress in the presence of the SOD-mimic FITC-MSN-CZpbi material by flow cytometry and western blot test. We found the nano-sized FITC-MSN is an excellent nano-carrier for delivering the mimic SOD complexes to HeLa cells. Here the reactants are already inside the cell and the result is a promotion of cell function. We present the methodology of encapsulating bio-inspired SOD-mimic in FITC-MSN to achieve a better drug delivery vehicle and catalytic (detoxification) activity. The potency and the stability of SOD-mimic FITC-MSN-CZpbi may provide a new avenue in the future development of artificial antioxidant enzymes.

Paraquat research: do recent advances in limiting its toxicity make its use safer?

The use of the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride; PQ) has been fiercely challenged due to its severe acute toxicity, putative neurotoxicity after long-term exposure and lack of antidotes. Breakthrough research on PQ is therefore required for an effective risk control and to allow a safer use of PQ in the future. The silencing or inhibition of quinone oxidoreductase 2, a NAD(P)H-independent flavoenzyme, was shown to significantly attenuate PQ toxicity in vitro, in primary pneumocytes and astroglial U373 cells, and to strongly antagonize PQ-induced systemic toxicity and animal mortality. The novel results reported in this issue of BJP, added to recent findings using sodium salicylate and lysine acetylsalicylate, in which full survival of PQ-intoxicated rats was also achieved, open the door for new preventative and therapeutic strategies that may lead to safer use of this effective pesticide.

Evaluation of substitutes for paraquat in soil microbial ATP determinations using the trichloroacetic acid based reagent of Jenkinson and Oades (1979)

The trichloroacetic acid (TCA) based reagent proposed by Jenkinson and Oades (1979) fits all the criteria required to measure soil microbial biomass ATP (biomass ATP). Amongst other components it contains paraquat (0.1 M 1,1′ dimethyl-4,4′ bipyridylium dichloride), usually extracted from the herbicide Gramoxone. Paraquat is added as an analogue of ATP. It is tightly fixed to soil and so decreases ATP fixation. However, Gramoxone is now banned as an agricultural chemical in both Europe and North America. Our aim was to find an effective replacement for paraquat to measure biomass ATP. The best replacement was 0.6 M imidazole in 1.10 M TCA containing 0.25 M P (termed the TIP reagent). Biomass ATP concentrations were not significantly different in five soils extracted by either reagent 10.37 and 11.17 μmol ATP g −1 biomass C, respectively; standard error of differences of means = 0.36; p = 0.091. ► Limitation of Jenkinson and Oades (1979) reagent (TPP) is now overcome. ► Imidazole shown to be a suitable analogue for paraquat to extract biomass ATP. ► A new method to measure soil ATP is thus provided (termed TIP method). ► Both TIP and TPP methods give same soil ATP results.

Adsorption study of 14C-paraquat in two Malaysian agricultural soils

The adsorption equilibrium time and effects of pH and concentration of (14)C-labeled paraquat (1,1(')-dimethyl-4,4(')-bipyridylium dichloride) in two types of Malaysian soil were investigated. The soils used in the study were clay loam and clay soils from rice fields. Equilibrium studies of paraquat in a soil and pesticide solution were conducted. Adsorption equilibrium time was achieved within 2 h for both soil types. The amount of (14)C-labeled paraquat adsorbed onto glass surfaces increased with increasing shaking time and remained constant after 10 h. It was found that paraquat adsorbed by the two soils was very similar: 51.73 (clay loam) and 51.59 μ g g(-1) (clay) at 1 μ g/ml. The adsorption of paraquat onto both types of soil was higher at high pH, and adsorption decreased with decreasing pH. At pH 11, the amounts of (14)C-labeled paraquat adsorbed onto the clay loam and clay soil samples were 4.08 and 4.05 μ g g(-1), respectively, whereas at pH 2, the amounts adsorbed were 3.72 and 3.57 μ g g(-1), respectively. Results also suggested that paraquat sorption by soil is concentration dependent.

Hydrogen Bonding in the Water Stabilized Structure of the Modified Unsymmetrically Substituted Viologen Chromophore, N-ethyl-N′-(2-phosphonoethyl)-4,4′-bipyridylium Dichloride

The crystal structure of the modified unsymmetrically N,N′-substituted viologen chromophore, N-ethyl-N′-(2-phosphonoethyl)-4,4′-bipyridinium dichloride 0.75 hydrate (1) has been determined. Crystals are triclinic, space group P−1 with Z = 2 in a cell with a = 7.2550(1), b = 13.2038(5), c = 18.5752(7) A, α = 86.495(3), β = 83.527(2), γ = 88.921(2)°. The two independent but pseudo-symmetrically related cations in the asymmetric unit form one-dimensional hydrogen-bonded chains through short homomeric phosphonic acid O–H···O links [2.455(4), 2.464(4) A] while two of the chloride anions are similarly strongly linked to phosphonic acid groups [O–H···Cl, 2.889(4), 2.896(4) A]. The other two chloride anions together with the two water molecules of solvation (one with partial occupancy) form unusual cyclic hydrogen-bonded bis(Cl···water) dianion units which lie between the layers of bipyridylium rings of the cation chain structures with which they are weakly associated. The crystal structure determination of unsymmetrically substituted viologen N-ethyl-N′-(2-phosphonoethyl)-4,4′-bipyridylium dichloride 0.75 hydrate shows the presence of strong intermolecular phosphonate O–H···O and O–H···Cl interactions together with unusual cyclic hydrogen-bonded bis(chloride···water) dianion units giving one-dimensional chain structures.

Comparative effects of the herbicides dicamba, 2,4-D and paraquat on non-green potato tuber calli

The effects of the herbicides 1,1'-dimethyl-4,4'-bipyridylium dichloride (paraquat), 3,6-dichloro-2-metoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) on cell growth of non-green potato tuber calli are described. We attempted to relate the effects with toxicity, in particular the enzymes committed to the cellular antioxidant system. Cell cultures were exposed to the herbicides for a period of 4 weeks. Cellular integrity on the basis of fluorescein release was strongly affected by 2,4-D, followed by dicamba, and was not affected by paraquat. However, the three herbicides decreased the energy charge, with paraquat and 2,4-D being very efficient. Paraquat induced catalase (CAT) activity at low concentrations (1 microM), whereas at higher concentrations, inhibition was observed. Dicamba and 2,4-D stimulated CAT as a function of concentration. Superoxide dismutase (SOD) activity was strongly stimulated by paraquat, whereas dicamba and 2,4-D were efficient only at higher concentrations. Glutathione reductase (GR) activity was induced by all the herbicides, suggesting that glutathione and glutathione-dependent enzymes are putatively involved in the detoxification of these herbicides. Paraquat slightly inhibited glutathione S-transferase (GST), whereas 2,4-D and dicamba promoted significant activation. These results indicate that the detoxifying mechanisms for 2,4-D and dicamba may be different from the mechanisms of paraquat detoxification. However, the main cause of cell death induced by paraquat and 2,4-D is putatively related with the cell energy charge decrease.

Photocatalytic degradation of paraquat and genotoxicity of its intermediate products

The photocatalytic degradation of paraquat (1,1-dimethyl-4,4′-bipyridylium dichloride) aqueous solutions in the presence of polycrystalline TiO 2 Degussa P25 irradiated by near-UV light was investigated. The substrate and total organic carbon concentrations were monitored by UV spectroscopy and TOC measurements, respectively: the complete photocatalytic mineralization of paraquat (20 ppm) was achieved after ca. 3 h of irradiation by using 0.4 g l −1 of catalyst amount at natural pH (ca 5.8). On the contrary no significant photodegradation of paraquat was observed in the absence of TiO 2 under similar experimental conditions. To evaluate the genotoxicity of paraquat and its intermediates produced during heterogeneous photocatalytic treatment, in vitro tests such as Ames test, with and without rat liver microsomal fractions (S9 mix), and micronucleus test, were used. Results obtained with Salmonella typhimurium (strain TA100) showed that paraquat and photocatalytic products were unable to induce gene mutations when photocatalysis was used in the presence of the optimum amount of TiO 2, i.e. 0.4 g l −1, whereas an increase of revertants his + per plate was observed after 300 min irradiation in the presence of very low amount of TiO 2 (0.04 g l −1). The negative results from micronucleus test suggest that mutagenic, but non-clastogenic, late intermediates of paraquat photo-oxidation were formed when the photocatalytic runs of paraquat degradation were carried out by using 0.04 g l −1 of photocatalyst.

Effect of Genetic Variation on Human Cytochrome P450 Reductase-Mediated Paraquat Cytotoxicity

Paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride) is a widely used herbicide and is highly toxic to human and animals. The mechanisms of paraquat toxicity involve the generation of superoxide anion through the process of redox cycling. NADPH-cytochrome P450 oxidoreductase (POR) has been reported to be a major enzyme for one-electron reduction of paraquat that initiates the redox cycling. Recently, a total of six missense variants of human POR have been identified in patients with discorded steroidogenesis. However, the effect of these genetic variations on POR-mediated paraquat toxicity is not known. Using the Flp-In Chinese hamster ovary (CHO) cells stably expressing either mouse or human POR and the cells with POR knockdown by siRNA, we confirmed that POR is responsible for paraquat-induced cytotoxicity. We further used this validated system to compare paraquat-induced toxicity among the cells that stably expressed wild-type human POR and its natural variants. While there was no difference in paraquat-induced toxicity between the cells expressing wild-type human POR and the Cys569Tyr variant, the toxicity in cells expressing all the other variants (Tyr181Asp, Ala287Pro, Arg457His, Val492Glu, and Val608Phe) was significantly decreased. Our results provide further evidence on the important role of POR in paraquat-induced toxicity and suggest that individuals carrying the functional variant POR alleles may have an altered susceptibility to paraquat exposure.

A modeling study of soil temperature and moisture effects on population dynamics of Paronychiurus kimi (Collembola: Onychiuridae)

The effect of soil moisture on population dynamics of Paronychiurus kimi (Collembola) was examined by combining an empirical soil moisture model with a temperature-sensitive, stage-structured population model. Field observations of soil temperature were used to drive the population model, and simulations were compared to field observations of juvenile and adult densities. Simulations without soil moisture effects produced stable, interyear population dynamics and a significant correlation between simulations and observations (n=12, r2=0.40, P<0.05) but overestimated densities during much of the year. Adding responses to soil moisture improved the fit between simulations and observations (n=13, r2=0.40), suggesting that soil moisture is a major limiting factor on field populations of P. kimi. Moreover, an observed temporary decline in field populations during spring could be explained partly by the effects of an herbicide, paraquat (N,N′-dimethyl-gamma,gamma′-bipyridylium dichloride) (r2=0.45), suggesting that paraquat imposes additional limits on collembolan populations.

Assessment of Herbicidal Toxicity Based on Non-Destructive Measurement of Local Chlorophyll Content in Photoautotrophic Hairy Roots

Changes in local chlorophyll (Chl) content in photoautotrophic hairy roots of pak-bung (Ipomoea aquatica) were evaluated at incident light intensities of I=11 and 22 W/m2 by non-destructive measurement of the pigment based on color image analysis. Upon addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 1-1′-dimethyl-4,4′-bipyridylium dichloride (paraquat) and 2,4-dichlorophenoxyacetic acid (2,4-D) to the medium at the median effective concentrations (0.40, 0.37 and 0.45 μmol/dm3 for DCMU, paraquat and 2,4-D, respectively), the roots showed different Chl pigmentation responses when the Chl content was measured at longitudinal lengths of l0=2.5 mm (Chl accumulation position) and l0=35 mm (Chl saturation position) under light irradiation. Chl accumulation index (β) and Chl degradation index (γ) were determined from the changes in Chl content at l0=2.5 and 35 mm, respectively, during the cultures for 96 h: β=0% (DCMU), 93.6% (paraquat) and 93.8% (2,4-D), and γ=98.4% (DCMU), 282% (paraquat) and 86.5% (2,4-D) at I=22 W/m2. Moreover, the bioassay system with the hairy roots was applied to the evaluation of a model sample of field water. The values of β and γ for the field water were determined, respectively, to be 105% and 217% at I=22 W/m2, from which the field water tested was judged to be a “paraquat-like” toxicant against the roots.