Photochemically-induced fluorescence properties of two benzoyl- and phenylurea pesticides and determination in natural waters.

A photo-induced fluorescence (PIF) method was developed for the determination of two benzoyl- and phenylurea pesticides, namely diflubenzuron (DFB) and fenuron (FEN). The photoconversion under UV irradiation of both pesticides into strongly fluorescent photoproducts was performed in several media (methanol, ethanol, acetonitrile, pH4 aqueous solution and pH4 water-methanol (30:70, v/v) mixture). PIF parameters were optimized. Analytical figures of merit for the PIF determination of DFB and FEN were satisfactory, with rather wide linear dynamic range (LDR) values of one to two orders of magnitude, relatively low limit of detection (LOD) values of, respectively, 9-24 ng/mL for DFB and 1-28 ng/mL for FEN, and limit of quantification (LOQ) values of, respectively, 30-80 ng/mL for DFB and 4-95 ng/mL for FEN, according to the medium. Relative standard deviation (RSD) values were in the range 1.7-5.6%. PIF was validated by comparing its analytical performances to those of a standard UV absorption spectrophotometric method. The optimized PIF method was applied to the quantitative analysis of both pesticides in various spiked natural water samples collected in a Senegal agricultural area by the standard addition procedure prior to extraction steps in dichloromethane, with satisfactory mean recovery percentage values (97.0-105.3 for DFB and 98.3-102.8% for FEN). An interference study of foreign species, including pesticides and inorganic ions, likely to be present in natural waters, was also carried out.

Widespread sex dimorphism across single-cell transcriptomes of adult African turquoise killifish tissues.

The African turquoise killifish (Nothobranchius furzeri), the shortest-lived vertebrate that can be bred in captivity, is an emerging model organism for aging research. Here, we describe a multitissue, single-cell gene expression atlas of female and male blood, kidney, liver, and spleen. We annotate 22 cell types, define marker genes, and infer differentiation trajectories. We find pervasive sex-dimorphic gene expression across cell types. Sex-dimorphic genes tend to be linked to lipid metabolism, consistent with clear differences in lipid storage in female vs. male turquoise killifish livers. We use machine learning to predict sex using single-cell gene expression and identify potential markers for molecular sex identity. As a proof of principle, we show that our atlas can be used to deconvolute existing bulk RNA sequencing (RNA-seq) data to obtain accurate estimates of cell type proportions. This atlas can be a resource to the community that could be leveraged to develop cell-type-specific expression in transgenic animals.

Widespread sex-dimorphism across single-cell transcriptomes of adult African turquoise killifish tissues.

The African turquoise killifish (Nothobranchius furzeri), the shortest-lived vertebrate that can be bred in captivity, is an emerging model organism to study vertebrate aging. Here we describe the first multi-tissue, single-cell gene expression atlas of female and male turquoise killifish tissues comprising immune and metabolic cells from the blood, kidney, liver, and spleen. We were able to annotate 22 distinct cell types, define associated marker genes, and infer differentiation trajectories. Using this dataset, we found pervasive sex-dimorphic gene expression across cell types, especially in the liver. Sex-dimorphic genes tended to be involved in processes related to lipid metabolism, and indeed, we observed clear differences in lipid storage in female vs. male turquoise killifish livers. Importantly, we use machine-learning to predict sex using single-cell gene expression in our atlas and identify potential transcriptional markers for molecular sex identity in this species. As proof-of-principle, we show that our atlas can be used to deconvolute existing liver bulk RNA-seq data in this species to obtain accurate estimates of cell type proportions across biological conditions. We believe that this single-cell atlas can be a resource to the community that could notably be leveraged to identify cell type-specific genes for cell type-specific expression in transgenic animals.

Application of flow injection analysis--photo-induced fluorescence (FIA-PIF) for the determination of α-cypermethrin pesticide residues in natural waters.

Flow injection analysis combined with photo-induced fluorescence (FIA-PIF) has been applied for the determination of α-cypermethrin pesticide residues in Senegalese natural waters, using organic solutions and cyclodextrin (ß-cyclodextrin and 2-hydroxypropyl-ß-cyclodextrin) aqueous media. The α-cypermethrin insecticide has a very weak natural fluorescence, but it is converted into strongly fluorescent photoproduct(s) by UV irradiation. Cyclodextrins were found to enhance the PIF signal. FIA parameters, including mobile phase flow rate, injected volume, and reactor length, were optimized. Analytical performances of the FIA-PIF method for the determination of α-cypermethrin were satisfactory, with concentration linear dynamic ranges over one to two orders of magnitude and with rather low limits of detection and limits of quantification, in the ng mL(-1) range, and relative standard deviations comprised between 1.2% and 3.8%. Application of FIA-PIF for the analysis of fortified natural water samples collected from Senegal yielded good recovery values (84-112%). Because of its high sampling rate, the FIA-PIF method constitutes a rapid analytical tool, useful for quantification of α-cypermethrin residues in natural waters.

Study of the toxicity of sulfamethoxazole and its degradation products in water by a bioluminescence method during application of the electro-Fenton treatment.

Sulfamethoxazole (SMX) is a synthetic antibiotic widely applied as a bacteriostatic drug to treat a number of diseases. SMX can persist in the environment for long periods of time because of its low biodegradability, which may result in various, direct and indirect, toxicological effects on the environment and on human health. Therefore, we have developed the electrochemical advanced oxidation process (AOP) "electro-Fenton" to degrade SMX in aqueous media. In this work, a detailed study of the evolution of toxicity of SMX and its degradation products in aqueous solutions, during treatment by the electro-Fenton AOP, is described, using the bioluminescence Microtox® method, based on the inhibition of luminescence of marine bacteria Vibrio fischeri. Samples were collected at various electrolysis times and analyzed by HPLC for quantifying the evolution of the degradation products, and their toxicity was measured by the Microtox® method. Our results demonstrated that the toxicity of SMX aqueous solutions varied considerably with the electrolysis time and the applied current intensity. This phenomenon could be explained by the formation and disappearance of several degradation products, including cyclic and/or aromatic intermediates, and short-chain acid carboxylic acids, having a toxicity different of the initial antibiotic. The curves of the % of bacterial luminescence inhibition vs. electrolysis time, corresponding to the evolution of the toxicity of the formed degradation products, were investigated and tentatively interpreted.

Transplanted Human Neural Progenitor Cells Attenuate Motor Dysfunction and Lengthen Longevity in a Rat Model of Ataxia.

The spastic Han Wistar (sHW) rat serves as a model for human ataxia presenting symptoms of motor deterioration, weight loss, shortened lifespan, and Purkinje neuron loss. Past studies revealed that human neural progenitor cells (NPCs) improved ataxic symptoms at 20 d posttransplantation in sHW rats. In this study, we investigated the fate and longer-term effectiveness of these transplanted NPCs. Rats were placed into four treatment groups: an untreated normal control group (n = 10), an untreated mutant rat control (n = 10), a mutant group that received an injection of dead NPCs (n = 9), and a mutant group that received live NPCs (n = 10). Bilateral cerebellar injections containing 500,000 of either live or dead NPCs were performed on mutant sHW rats at 40 d of age. Motor activity for all mutant rats started to decline in open field testing around day 35. However, at day 45, the live NPC-treated mutants exhibited significant improvements in open field activity. Similar improvements were observed during rotarod testing and weight gain through the completion of the experiments (100 d). Immunohistochemistry revealed few surviving human NPCs in the cerebella of 80- and 100-d-old NPC-treated mutants; while cresyl violet staining revealed that live NPC-treated mutants had significantly more surviving Purkinje neurons compared to mutants that were untreated or received dead NPCs. Direct stereotactic implantation of NPCs alleviated the symptoms of ataxia, acting as a neuroprotectant, supporting future clinical applications of these NPCs in the areas of ataxia as well as other neurodegenerative diseases.

Toxicological study of pesticides in air and precipitations of Paris by means of a bioluminescence method.

A detailed toxicological study on several pesticides, including chlorothalonil, cyprodynil, dichlobénil, pendimethaline, trifluraline, and alpha-endosulfan, present at trace levels in air and total atmospheric precipitations of Paris is presented. The pesticides contained in the atmospheric samples, collected during sampling campaigns in February-March 2007, are identified and quantified by a high-performance liquid chromatographic (HPLC)-UV detection method. The toxicity measurements are performed by means of the Microtox bioluminescence method, based on the evaluation of the bioluminescence inhibition of the Vibrio fischeri marine bacteria at two exposure times to the pesticide solutions. The specific toxicity, corresponding to the particular toxicity of the compound under study and represented by the EC(50) parameter, is determined for these pesticides. Also, the global toxicity, which is the toxicity of all micro-pollutants present in the sample under study, is estimated for the extracts of air and atmospheric precipitation (rainwater) samples. The specific toxicities strongly vary with the nature of the pesticide, the EC(50) parameter values being comprised between 0.17 and 0.83 mg/mL and 0.15 and 0.66 mg/mL, respectively, for exposure times of 5 and 15 min. The importance of the atmospheric samples' global toxicity and the respective contribution of the toxic potency of the various pesticides contained in these samples are discussed.

Development of a new automatic on-site detector of pesticides in natural waters by photo induced fluorescence, application to three phenylurea and benzoylurea herbicide.

Prototypes of on-site automatic photo induced fluorescence detectors of pesticide in natural waters are set up and applied for the determination of the benzoyl- and phenylurea pesticides, namely fluometuron, monolinuron and diflubenzuron. As these pesticides present no native fluorescence the set up system use the photo conversion under UV irradiation of these pesticides into highly fluorescent photoproducts. A first system, called AUTOPIF, (evolution the commercial AQUAPOD system) is develop using a detection via a diode array spectrometer. To improve the sensitivity of the method, a second system, called AUTOPIF+, is developed with a more resolute spectrometer and an intensified CCD camera detection. Analytical applications were carried out in aqueous solution and detected on line with the AUTOPIF and AUTOPIF+ system. The calibration curves are linear over one order of magnitude, and the limits of detection are in the µg mL-1 range. The analytical performances of these methods for the determination of the three pesticides are satisfactory in comparison to other classical PIF methods published for the determination of phenylurea pesticides in aqueous solutions. Our results show that the AUTOPIF and AUTOPIF+ methods are versatile, sensible and can be easily applied as an alert system to detect pollutant residues in naturals waters over a threshold value.

A new direct laser photo-induced fluorescence method coupled on-line with liquid chromatographic separation for the simultaneous determination of anilides pesticides.

A new direct laser photo-induced fluorescence high performance liquid chromatography (DL-PIF-HPLC) method is developed for the simultaneous determination of three anilide pesticides, namely carboxin, monalide and propanil. DL-PIF-HPLC uses a tunable Nd:YAG-OPO laser to obtain fluorescent photoproduct(s) and to simultaneously analyze their fluorescence in a short acquisition time with an intensified CCD camera, which improves the selectivity (by choosing the suitable excitation wavelength), increases the sensitivity (due to the high energy of the laser beam) and reduces the time of analysis, relative to the classical PIF methods. However, one of the main drawbacks of PIF methods is the presence of interferences with other compounds, such as other pesticides from the same group yielding similar fluorescent photoproducts, which reduces their selectivity. The analytical interest of DL-PIF-HPLC to avoid these interferences is demonstrated. The DL-PIF spectra, chromatographic conditions and analytical performances of DL-PIF-HPLC are presented for the simultaneous determination of three anilide pesticides. The calibration curves are linear over one order of magnitude and the limits of detection are in the ng mL(-1) range. The new DL-PIF-HPLC system has the advantage to combine the performances of both techniques, DL-PIF and liquid chromatography, and to improve the analysis selectivity.

An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers.

Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension.

Relationship between tumor (T) antigen expression and substituent effects on benzo [a] phenothiazines.

Human adenovirus, oncogene-type 12 infected HEp-2 cells were exposed to six benzo[a]phenothiazines. 5-Oxo-5H-benzo[a]phenothiazine (4) and 6-hydroxy-5-oxo-5H-benzo[a]phenothiazine (5) were moderately toxic. 9-Methyl-12H-benzo[a]phenothiazine (2), 10-methyl-12H-benzo[a]phenothiazine (3), 6-methyl-5-oxo-5H-benzo[a]phenothiazine (6), and 12H-benzo[a]phenothiazine (1) were not toxic in the system tested. 6-Methyl-5-oxo-5H-benzo[a]phenothiazine (6) enhanced the expression of viral oncogene product (tumor antigen) in the adenovirus infected cells. 5-Oxo-5H-benzo[a]phenothiazine (4) and 6-hydroxy-5-oxo-5H-benzo[a]phenothiazine (5) reduced this effect. 6-Methyl-5-oxo-5H-benzo[a]phenothiazine (6), with hyperconjugation due to the methyl group, increased the T antigen activity at higher dose concentrations, whereas 6-hydroxy-5-oxo-5H-benzo[a]phenothiazine (5) with a hydroxy substituent had the opposite effect on T antigen expression. The methyl substitution at positions C9 or C10 increased the T antigen expression of adenovirus infected cells.

Antimutagenicity of benzo[a]phenothiazines in chemically induced mutagenesis.

The antimutagenicity of seven benzo[a]phenothiazines was screened against Salmonella typhimurium strain TA98 treated with 4-nitro-o-phenylenediamine which is a specific mutagen to the strain, and the results were compared to the antimutagenic activity of chlorpromazine (8), one of the 2-chlorophenothiazine derivatives-which have been shown to be the most effective mutagen inhibitors. Benzo[a]phenothiazines with methyl, oxo or hydroxyl substituent(s) at position 5, 6, 9 or 10 were used in the screening tests. 6-Hydroxy-5-oxo-5H-benzo[a]phenothiazine (6) reduced the induced mutation by 27%, being a more potent antimutagenic agent than chlorpromazine (8). The study of antimutagenicity is of great interest for the development of cancer chemopreventive agents which stop cancer progression in multistage carcinogenesis in which successive mutation sequences are required for a progression into full-fledged metastatic cancer.

Photochemically-induced fluorescence determination of sulfonylurea herbicides using micellar media.

An analytical method based on the use of UV irradiation to produce fluorescent derivatives from four non-fluorescent sulfonylurea herbicides, including chlorsulfuron, metsulfuron methyl, 3-rimsulfuron and sulfometuron methyl is described. Their photochemically-induced fluorescence (PIF) properties in several solvents (water, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), acetonitrile, methanol, ethanol, propan-2-ol and their binary mixtures with water) and micellar solutions of sodium dodecyl sulfate (SDS), and cetyltrimethylammonium chloride (CTAC) are reported. Physicochemical variable influencing the sensitivity of the method have been optimized. A PIF method is developed for the determination of the four herbicides under study. Micellar media are found to provide the best analytical figures of merits. Linear dynamic ranges are established over about two orders of magnitude. The limit of detection (LOD) range from 0.2 to 6 ng ml(-1) according to the compound, with relative standard deviation (RSD) between 1.2 and 3.9%. Examples of applications to the analysis of these herbicides in spiked river water samples are given. The mean recoveries range from 80 to 104%.

Analysis of mixtures of purines and pyrimidines by first- and second-derivative ultraviolet spectrometry.

Zero-order, first-derivative and second-derivative ultraviolet absorption spectra of a series of purines, pyrimidines and their binary mixtures in aqueous solution have been recorded at 298 K. It is shown that second-derivative spectra can be used for the identification of eight mixtures of purines and pyrimidines. Several graphical procedures are tested for evaluating derivative spectra in quantitative measurements of single compounds and mixtures. Linear log-log calibration plots are obtained with correlation coefficients generally larger than 0.99. Second-derivative spectra appear to provide a precise and simple method for determination of purines and pyrimidines, at concentrations ranging between 5 x 10(-6) and 5 x 10(-4)M.

The effect of pH on the room-temperature phosphorescence properties of several purine and pyrimidine derivatives.

Room-temperature phosphorescence (RTP) spectra of eleven purines and pyrimidines adsorbed on Whatman No. 40 filter paper have been determined in acidic, neutral and basic media. RTP excitation and emission wavelengths do not vary significantly with pH. For most compounds, use of basic (pH approximately 13) solutions yields stronger RTP signals than use of neutral or acidic (pH approximately 1.6) solutions. Exceptions are adenine, theobromine and theophylline, which give larger RTP signals when in neutral than in basic conditions. The existence of differences in phosphorescence quantum yields between the various ionic species as well as of specific pH-related interactions with the substrate is discussed. Absolute limits of detection, ranging between 0.4 and 38 ng for selected compounds, depend on the pH of the analyte solution.

Evaluation of filter papers as substrates for solid-surface room-temperature fluorimetry and photochemical fluorimetry.

Filter papers (Whatman Nos. 1 and 41, S & S 904) and anion-exchange filter paper (Whatman DE-81) have been evaluated for their use as substrates in solid-surface room-temperature fluorescence (RTF) and photochemical fluorescence (RTPF). Several chemical treatments of filter papers are found not to reduce significantly their background fluorescence signal. Analyte fluorescence signals are 2-4 times higher on filter papers than on silica-gel TLC plates. Absolute limits of detection range between 0.6 and 40 ng on the Whatman filter papers, depending on the test compound. Filter papers are proposed as convenient, inexpensive, and easy-to-handle substrates for RTF and RTPF measurements.

Fluorimetric determination of aromatic pesticides in technical formulations. Effects of solvent and of ultraviolet photolysis.

The effects of solvent and of ultraviolet (UV) photolysis on the fluorescence intensity of several aromatic pesticides including bendiocarb, chlorophacinone, coumatetralyl and pirimiphos-methyl were investigated. The type and polarity of solvent (acetonitrile, dimethylsulfoxide, methanol, ethanol and 2-propanol) were shown to play an important role in the limits of detection (LOD) of the method. UV photolysis provoked a decrease of the fluorescence signal more or less marked, depending of the structure of the pesticide. Analytical figures of merit were evaluated for the determination of pesticides under optimal conditions. The method exhibited satisfactory analytical performances. The linear dynamic ranges were obtained over more than two orders of magnitude. The LOD ranged from 0.03 to 20 ng/ml, according to the compound. The relative standard deviations were between 5.5 and 6.1%. Examples of application to the determination of pesticides in technical formulations are presented. The mean recoveries ranged from 86 to 116%. It shows the usefulness of this technique for pesticide analysis.

Photochemical analysis studies-III A fluorimetric and ultraviolet spectrophotometric study of the photolysis of chloroquine on silica-gel thin layers, and its analytical application.

The photolysis of chloroquine on silica-gel thin layers has been studied by ultraviolet spectrophotometry and fluorimetry. It has been shown that a reversible photoisomerization of chloroquine takes place and yields a fluorescent photoproduct. The effect of pH, alkali-metal halides, and the eluent system on the fluorescence intensity of chloroquine and its photoproduct was investigated. The fluorescence on silica-gel thin layers is quenched by high concentrations of sodium hydroxide; this is explained in terms of interference of sodium ions in the hydrogen-bonded adsorption of chloroquine on the silica gel. The results have been used to develop a method for determination and separation of chloroquine at the nanogram level. Linear calibration plots are obtained, covering the range between 4 and 10(4) ng.

Determination of bromophos residues by fluorogenic labelling with dansyl chloride and thin-layer. Chromatography.

The use of a highly sensitive and inexpensive method for determination of residues of bromophos (an organophosphate pesticide) in peanut crops, by fluorogenic labelling and thin-layer chromatography (TLC) is described. The bromophos is hydrolysed and the product 4-bromo-2,5-dichlorophenol (BDCP) dansylated with dansyl chloride. The fluorescent dansylated BDCP is separated by TLC and detected fluorimetrically. Linear fluorimetric analytical curves are obtained for bromophos weights ranging between 0.5 and 50 ng. The minimum detectable quantity is estimated to be 0.5 ng. The method can be used to recover as little as 400 ng of bromophos residue from 25 g of peanut seeds.

Fluorimetric determination of dissociation constants and ph-controlled fluorescence analysis of purines and pyrimidines.

Fluorimetrically determined pH-titration curves have been obtained for twelve purines and pyrimidines at room temperature, in aqueous solution. The pK(a) values for these compounds have been determined fluorimetrically and potentiometrically. Except for 6-mercaptopurine and uric acid, there is close agreement between the two sets of pK(a) values, but a large difference for the corresponding excited singlet-state values, pK(S1)(a), which were calculated previously. This indicates that the excited singlet-state proton-transfer rate is much slower than the fluorescence-decay rate of purines and pyrimidines in our experimental conditions. A direct, simple, pH-controlled fluorimetric method is proposed for the determination of purines and pyrimidines. The limits of detection vary between 60 ng ml and 5.4 mug ml .