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PubMed2001

Development of an ELISA for the detection of the residues of the insecticide imidacloprid in agricultural and environmental samples.

A competitive enzyme-linked immunosorbent assay (ELISA) for the chloronicotinyl insecticide imidacloprid was developed using a polyclonal antibody produced against a hapten conjugated through the imidazolidine to keyhole limpet hemocyanin. In the standard curve of imidacloprid, an IC(50) of 17.3 ng/mL was obtained using a competitive heterologous system at pH 10. Very low cross-reactivity was found for some structurally related compounds including the insecticide thiacloprid. The high cross-reactivity with a metabolite containing the carbonyl group in the imidazolidine moiety suggests the involvement of its polarity and stereochemical fitness in forming the antibody--antigen complex. The effects of various assay conditions, including organic solvents, detergent content, salt concentration, and pH on the sensitivity were evaluated. High-performance liquid chromatography was run for comparison to validate the ELISA with fortified water samples, the correlation being 0.997-0.998 (n = 15) with a slope of 1.10--1.38. The ELISA turned out to be a convenient tool for monitoring imidacloprid residues in agricultural and environmental samples.

Chromatography, High Pressure Liquid↗

PubMed2002

Single-channel microchip for fast screening and detailed identification of nitroaromatic explosives or organophosphate nerve agents.

A single-channel chip-based analytical microsystem that allows rapid flow injection measurements of the total content of organic explosive or nerve agent compounds, as well as detailed micellar chromatographic identification of the individual ones, is described. The protocol involves repetitive rapid flow injection (screening) assays--to provide a timely warning and alarm--and switching to the separation (fingerprint identification) mode only when harmful compounds are detected. While micellar electrokinetic chromatography, in the presence of sodium dodecyl sulfate (SDS), is used for separating the neutral nitroaromatic explosive and nerve agent compounds, an operation without SDS leads to high-speed measurements of the "total" explosives or nerve agent content. Switching between the "flow injection" and "separation" modes is accomplished by rapidly exchanging the SDS-free and SDS-containing buffers in the separation channel. Amperometric detection was used for monitoring the separation. Key factors influencing the sample throughput, resolution, and sensitivity have been assessed and optimized. Assays rates of about 360 and 30/h can thus be realized for the "total" screening and "individual" measurements, respectively. Ultimately, such development will lead to the creation of a field-deployable microanalyzer and will enable transporting the forensic laboratory to the sample source.

Chemical Warfare Agents↗

PubMed2000

Denitrobacterium detoxificans gen. nov., sp. nov., a ruminal bacterium that respires on nitrocompounds.

A new group of anaerobic, Gram-positive, high G + C (56-60 mol%) bacteria was isolated from the bovine rumen. Of four strains characterized, all were non-motile and none produced spores. The isolates did not produce indole or H2S and did not hydrolyse gelatin. Cells of each strain exhibited similar rod-shaped morphology (0.5-1.0 x 1.0-1.5 microns) although bulbous ends were sometimes present. None of the four strains were able to grow via oxidation of a variety of potentially fermentable substrates but rather obtained energy for growth via anaerobic respiration processes, oxidizing hydrogen, formate or lactate for reduction of various oxidized nitrogen compounds. Trimethylamine oxide and DMSO were also used as electron acceptor. All four strains shared greater than 99% 16S rRNA gene sequence identity. The closest match found between the 16S rRNA gene sequence of all four strains, NPOH1T, NPOH2, NPOH3 and MAJ1, to sequences available in GenBank was that of Coriobacterium glomerans (86% sequence similarity), a phenotypically dissimilar anaerobe within the class Actinobacteria. To accommodate these bacteria the creation of a new genus and species, Denitrobacterium detoxificans, for placement within the family Coriobacteriaceae is proposed. The type strain, NPOH1T (ATCC 700546T), grew equally well over a narrow range of incubation temperatures tested (32-39 degrees C).

Actinomycetaceae↗

PubMed2006

On-line strategies for determining trace levels of nitroaromatic explosives and related compounds in water.

We report the development and tests of several systems for the simultaneous determination of 18 energetic compounds and related congeners in untreated water samples. In these systems a Restricted Access Material trap or liquid-chromatography precolumn (with a C(18) or porous graphitic carbon, PGC, stationary phase) followed by a PGC analytical column are used for sample clean-up, enrichment and separation of the trace level analytes, which are then analyzed by mass spectrometry (MS). The relative merits of two MS ionization interfaces (atmospheric pressure chemical ionization, APCI, and atmospheric pressure photoionization, APPI) were also compared for the MS identification and quantification of these analytes. APCI was found to be superior in cases where both alternatives are applicable. A major drawback when applying APPI is that no signal is obtained for the cyclic nitramines and nitrate esters. Using APCI, a wide spectrum of unstable compounds can be determined in a single analysis, and the feasibility of using large volume samples (up to 100 mL) in combination with the sensitivity of the MS detection system provide method detection limits ranging from 2.5 pg/mL (for 2,4-dinitrotoluene and 2,6-diamino-6-nitrotoluene) to 563 pg/mL (for pentaerythritol tetranitrate, PETN), with repeatability ranging from 2 to 7%. Other chemometric parameters such as robustness, selectivity, repeatability, and intermediate precision were also evaluated in the validation of the extraction methods for use in water analysis. Tests with untreated groundwater and drinking water samples, spiked with 20 ng of the analytes, yielded results similar to those obtained with high purity water samples.

Analytic Sample Preparation Methods↗

PubMedDate not supplied

The genotoxicity of unsubstituted and nitrated polycyclic aromatic hydrocarbons.

To determine the DNA damaging properties of unsubstituted and substituted polycyclic hydrocarbons, 61 aromatic and heterocyclic compounds were examined for the induction of the SOS system in E. coli PQ37. PAH such as benzo[ghi]fluoranthene, benzo[j]fluoranthene, benzo[c]phenanthrene, benzo[a]pyrene, chrysene, dibenzo[a,1]pyrene, fluoranthene and triphenylene showed relatively high genotoxicity. With respect to the nitroarenes, the highest genotoxic potencies were exhibited by the dinitropyrenes. The SOS-inducing potency of nitroarenes increased from the bicyclic to the tetracyclic ring system. Additionally, it was seen that any increase in the extent of nitration is paralleled by an increase of genotoxicity. Whereas PAH required metabolic activation by hepatic cytochrome P-450 enzymes, nPAH were direct-acting genotoxicants.

Animals↗

PubMed1999

Effects of imidacloprid on adult and larval stages of the flea Ctenocephalides felis after in vivo and in vitro application: a light- and electron-microscopy study.

The effects of imidacloprid (Advantage) on the larval and adult stages of cat fleas (Ctenocephalides felis) were studied in vivo and in vitro by means of light and electron microscopy. It was found that: 1. The compound acted rapidly on both larval and adult fleas, killing both stages within 20 min of contact. 2. When applied as a spot-on to the skin of dogs, the compound localized in the water-resistant lipid layer of the skin surface and in the hairs but not in the blood. 3. Thus, the compound was not taken up during sucking of the flea but was absorbed via the thin intersegmental membranes, since larval and adult fleas that had only external contact with imidacloprid-impregnated paper or with shaved hairs from imidacloprid-treated dogs showed reactions similar to those shown by fleas sitting on treated skin. 4. The compound led to a continuous blockage of insect-specific nicotinic-acetylcholine receptors (nAChR), causing tetanic muscle cotractions within minutes of exposure. This manifested as intense trembling of the legs and pumping movements of the body. The affected flea stages remained motionless while the nerves and muscles were constantly and irreversibly destroyed due to hyperactivity. The ganglia of the head and thorax and the striated muscles of the flea body and legs were damaged first, whereas the intestinal movements (e.g., visible in larvae) took longer to exhibit damage. In summary, these studies show that imidacloprid kills larval and adult flea stages rapidly via the same mode of action and thus prevents the development of flea populations in human or animal dwellings.

Animals↗

PubMed2005

Photodegradation of nitroaromatic compounds in aqueous solutions in the UV/ H2O2 process.

Photodegradation of nitrobenzene and nitrophenols in aqueous solutions by means of UV/H2O2 process was studied in the Rayox batch reactors. Three nitrophenol isomers were identified as main photoproducts in the irradiated NB aqueous solutions. The distribution of nitrophenol isomers follows the order p- > m- > o-nitrophenol. Other intermediates detected include nitrohydroquinone, nitrocatechol, catechol, benzoquinone, phenol, nitrate/nitrite ions, formic acid, glyoxylic acid, maleic acid, oxalic acid and some aliphatic ketones and aldehydes. The degradation of nitrobenzene and nitrophenols at initial stages follows the first-order kinetics and the decay rate constants for nitrobenzene(NB) are around 10(-3)-10(-2) s(-1) and for nitrophenols are around 10(-2) s(-1). The decomposition of H2O2 in the presence of NB and each nitrophenol isomers follows zero-order kinetics. The quantum yields at initial stages for NB decay were estimated around 0.30 to 0.36, and for NPs decay is around 0.31-0.54.

Chromatography, High Pressure Liquid↗

PubMed2004

Comparison of electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization for the analysis of dinitropyrene and aminonitropyrene LC-MS/MS.

The only relevant source for human exposure to dinitropyrenes is diesel engine emissions. Due to this specificity, dinitropyrenes may be used as biomarkers for monitoring human exposure to diesel engine emissions. Only few analytical methods have been described for the quantitation of dinitropyrenes and their metabolites, aminonitropyrenes, and diaminopyrenes. Therefore, for dinitropyrenes, aminonitropyrenes, and diaminopyrenes were selected as model compounds for the development of a sensitive HPLC-MS/MS method (high performance liquid chromatography coupled to triple quadrupole mass spectrometry) was to quantify polyaromatic amines and nitroarenes in biological matrices was developed optimal methods by comparing electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) sources. Dinitropyrene was not effectively ionized and diaminopyrene yielded mainly [M(.)](+) ions by electrospray ionization. With APCI and APPI, precursor ions of diaminopyrene and aminonitropyrene were [M + H](+) and [M(.)](-) for dinitropyrene. Precursor ions with [M - 30(.)](-) for dinitropyrene and [M - 30 + H](+) for aminonitropyrene were observed. Reversed and normal phase HPLC-MS/MS with ESI, APCI and APPI were optimized separately with respect to unequivocal analyte identification and sensitivity. Normal phase HPLC coupled to APPI-MS/MS gave the highest precision and sensitivity for aminonitropyrene (6%/0.2 pg on column) and dinitropyrene (9%/0.5 pg on column). The limit of detection in spiked rat plasma was 5 pg/100 microL for aminonitropyrene (accuracy 82%) and 10 pg/100 microL for dinitropyrene (accuracy 105%). In plasma of rats treated with dinitropyrene by oral administration, no detectable levels of dinitropyrene but higher aminonitropyrene levels compared with intratracheal instillation were observed. These findings clearly demonstrate that dinitropyrene was absorbed after oral and intratracheal application and that a reduction of nitro groups occurs to a high extent in the reductive environment of the intestine. To our knowledge, this is the first time that aminonitropyrene was observed in plasma after intratracheal or oral administration directly demonstrating the reductive metabolism of dinitropyrene in vivo.

Air Ionization↗

PubMed2005

Efficacy of imidacloprid, imidacloprid/permethrin and phoxim for flea control in the Mustelidae (ferrets, mink).

Farmed mink (Mustela vison), a close relative of the domestic ferret (Mustela putorius furo), naturally infested with the squirrel flea (Ceratophyllus sciurorum) were included in a study to investigate three compounds for flea control. The test products were imidacloprid in a 10% (w/v) solution, an imidacloprid 10% (w/v)/permethrin 50% (w/v) solution, and phoxim; all three are well-known compounds for the control of different ectoparasites in a wide range of animals. Two groups of mink received 0.1 ml per animal of the imidacloprid or the imidacloprid/permethrin combination at days 0 and 28, respectively. Two groups of mink were sprayed with 25 ml of a 0.1% phoxim solution at day 0 and either 1x25 ml or 2x25 ml, respectively, of a 0.05% phoxim solution at day 28. One group of mink served as an untreated control. At assessment on day 56 the efficacy was 91.9% in the imidacloprid group, 89.3% in the imidacloprid/permethrin group, 92.2% in the phoxim 1x25-ml group and 99.3% in the phoxim 2x25 ml group, respectively. In the untreated control group an average of 757 fleas per mink nesting material was recorded.

Administration, Topical↗

PubMed1998

6-Hydroxydopamine injections into the nigrostriatal pathway attenuate striatal malonate and 3-nitropropionic acid lesions.

The mitochondrial inhibitors malonate and 3-nitropropionic (3NP) acid are potent neurotoxins in vivo. Administration of these compounds results in neuronal loss similar to that seen in Huntington's disease. Although the mechanism of cell death produced by these compounds likely involves activation of N-methyl-D-aspartate receptors, it remains unclear why the striatum demonstrates regional susceptibility to the toxicity of these and other mitochondrial poisons. We hypothesized that dopamine, a weak neurotoxin that occurs in high concentrations in the striatum, may contribute to the neuronal damage caused by mitochondrial inhibition. We investigated whether depletion of striatal dopamine using the catecholaminergic toxin 6-hydroxydopamine would attenuate lesions induced by mitochondrial inhibition. We found that dopamine depletion reduced significantly the extent of histological damage in the striatum elicited by both intraparenchymal injections of 0.8 micromol malonate and 20 mg/kg systemic administration of 3NP. These data suggest that dopamine or one of its metabolites may contribute to mitochondrial toxin-induced cell death.

Animals↗

PubMed2004

[Identification of the structure of two new nitro group phenolic glycosides from Schisandra propinqua (Wall. ) Baill var. intermidia A. C. Smith].

AIM: To study the bioactive components from Schisandra propinqua (Wall.) Baill var. intermidia A. C. Smith. METHODS: Compounds were separated with a combination of multichromatography. Their chemical structures were determined on the basis of spectral analysis and chemical evidence. RESULTS: Seven compounds were isolated from the leaves of Helicia nilagirica. The structures were elucidated as 6'-O-alpha-L-arabinofuranosylthalictoside (1), 6'-O-beta-D-apiofuranosylthalictoside (2), thalictoside (3), icariside D2 (4), prinsepiol (5), (+)-1-hydroxypinoresinol (6) and (+)-medioresinol (7). CONCLUSION: Two compounds are new nitro phenolic glycosides.

Disaccharides↗

PubMed1986

Effect of different nitroheterocyclic compounds on aerobic, microaerophilic, and anaerobic bacteria.

The antibacterial activities of different nitroheterocyclic compounds were assessed by an agar dilution method against aerobic, microaerophilic, and anaerobic bacteria. Nitronaphthofurans inhibited the multiplication of aerobic bacteria at low concentrations (MIC for 50% of strains tested [MIC50], 1 mg/liter). Under anaerobic growth conditions the MICs were found to be even lower. The rough, DNA repair-deficient mutants of Salmonella typhimurium were more susceptible, whereas nitroreductase-deficient strains were resistant. Microaerophilic campylobacter isolates could be divided into two groups, one of which was as susceptible as aerobic bacteria (MIC50, 1 mg/liter) and the other of which was more highly susceptible (MIC50, 0.015 mg/liter). All anaerobic bacteria tested were susceptible to nitronaphthofurans (MIC50, 0.125 mg/liter). Nitrothiazole exerted antibacterial activities similar to those of the nitronaphthofurans. Metronidazole, a nitroimidazole derivative, and nitrofurans were definitely less active. Nitrobenzofurans showed relatively high MICs.

Anti-Bacterial Agents↗

PubMed2005

Protective effect of S-allylcysteine on 3-nitropropionic acid-induced lipid peroxidation and mitochondrial dysfunction in rat brain synaptosomes.

3-Nitropropionic acid is a neurotoxin that irreversibly inhibits succinate dehydrogenase, a relevant enzyme constituting the complex II of the respiratory chain during mitochondrial electron transport. 3-Nitropropionic acid is known to produce oxidative/nitrosative stress and evokes an experimental model of Huntington's disease. In this work we evaluated the effects of the antioxidant compound and major organosulfur garlic derivative, S-allylcysteine, on lipid peroxidation and mitochondrial dysfunction induced by 3-nitropropionic acid in synaptosomal fractions from rat brain. 3-Nitropropionic acid, at concentrations ranging 0.75-2.5 mM, produced enhanced levels of lipid peroxidation, while increasing concentrations of S-allylcysteine (0.1-2 mM) decreased the peroxidative action of 3-nitropropionic acid (1 mM) in synaptosomal fractions in a concentration-dependent manner. S-Allylcysteine (0.75 mM) also prevented the 3-nitropropionic acid (1mM)-induced mitochondrial dysfunction. These findings suggest that the protective actions that S-allylcysteine exert on the in vitro neurotoxicity induced by 3-nitropropionic acid are mediated by its antioxidant properties.

Animals↗

PubMed1995

Protective actions of L-carnitine and acetyl-L-carnitine on the neurotoxicity evoked by mitochondrial uncoupling or inhibitors.

The mechanism for the pathological increase in cell death in various disease states e.g. HIV immunodefficiency or even ageing or Alzheimer's disease, occurs by complex and as yet undefined mechanism(s) related to immunological, virological or biochemical disturbances (i.e. energy depletion, oxidative stress, increased protein degradation). We have studied mitochondrial uncoupling or inhibitor toxicity on neurones at the cellular level and at the mitochondrial level using rhodamine (Rh123) and 10-nonylacridine orange (NAO) fluorescence with confocal microscopy. Blockade of the mitochondrial chain complexes at various points was studied. The possible protective effects of the compound L-carnitine, which plays a central role in mitochondrial function, was tested in this form of neurotoxicity. It appears that L-carnitine and its acetylated form, acetyl-L-carnitine, can attenuate the cell damage, as assessed by lactate dehydrogenase (LDH) release, evoked by the uncoupler, p-(trifluoromethoxy)phenylhdyrazone (FCCP), or by the inhibitors, 3-nitropropionic acid (3-NPA) or rotenone. Further, the FCCP-induced inhibition of Rh123 uptake was antagonized by the preincubation of cells with L-carnitine. Since such neurotoxic mechanisms may be operating in the various pathological forms of myotoxicity and neurotoxicity, these observations suggest potential for a therapeutic approach.

Acetylcarnitine↗

PubMed2001

Comparative study on the effects of three insecticides (fipronil, imidacloprid, selamectin) on developmental stages of the cat flea (Ctenocephalides felis Bouché 1835): a light and electron microscopic analysis of in vivo and in vitro experiments.

The effects of three insecticides (fipronil, imidacloprid and selamectin) on developmental stages of cat fleas (Ctenocephalides felis) were studied in vivo, in vitro and by means of light and electron microscopy. The results were documented by video. Adult fleas were attached to the skin of dogs that had been treated 7 days before with one of the three compounds. Furthermore, adult fleas were exposed exclusively to the hair and skin debris of such treated dogs or were placed on filter papers that had been impregnated with one of these three compounds or with the blood of treated dogs. Larval fleas were exposed to hair of treated dogs, to debris obtained by combing treated dogs, to dried blood samples of treated dogs or were placed onto filter papers impregnated with one of the three compounds. In these experiments with adult and larval fleas, it was noted that none of the three insecticides had a repellent effect on adult or larval fleas. Imidacloprid was the only compound that acted exclusively by body contact, and was apparently taken up by adult and larval fleas via the thin, non-sclerotized intersegmental membranes of the flea's body, shown when flea stages were exposed to hairs taken from dogs treated with one of the compounds or placed onto drug-impregnated filter papers. Imidacloprid killed larvae and adult fleas within 1 h, while it took at least 24 h until all adult fleas had died on fipronil- or selamectin-treated dogs, thus allowing longer feeding periods, increasing the risk of transmission of flea-derived diseases. Flea larvae covered with debris from dogs topically treated 7 days before with fipronil, imidacloprid or selamectin died, like the untreated control, within 16-28 h after exposure. This was, however, probably mainly due to a drying effect. Adult and larval fleas exposed to filter papers impregnated with the blood of treated dogs survived longer than 7 days, as did the untreated controls. All three drugs apparently acted on nerves and muscles and thus stopped motility.

Animals↗

PubMed1975

Carcinogenicity of nitrosation products of ephedrine, sarcosine, folic acid, and creatinine.

Carcinogenic activity of several synthetic N-nitroso compounds was evaluated in C57BL/6J X C3HeB/FeJ F1 mice. Test substances, suspended in trioctanoin, were injected i.p. in three equal doses given on Days 1, 4, and 7 after birth and animals were held without further treatment for up to 85 weeks. Nitrosoephedrine at a total dose of 600 mg/kg induced metastasizing liver cell carcinomas in 28 of 30 animals. Nitrososarcosine (225 mg/kg) induced similar tumors in 8 of 14 animals. Nitrosofolic acid (375 mg/kg) induced lung adenocarcinomas in 4 of 28 mice. Creatinine-5-oxime (600 mg/kg) showed no evidence of carcinogenic activity. Diethylnitrosamine (12 mg/kg given in four doses), included as a positive control, caused metastasizing liver cell tumors in 23 of 25 animals.

Adenoma, Bile Duct↗

PubMed1998

Modulation of the neuronal nicotinic acetylcholine receptor-channel by the nitromethylene heterocycle imidacloprid.

Nitromethylene heterocycle insecticides are known to act on the nicotinic acetylcholine receptor-channel. The effects of the nitromethylene heterocycle, imidacloprid, on the nicotinic acetylcholine receptor-channel of clonal rat phaeochromocytoma (PC12) cells were studied using whole-cell and single-channel patch clamp methods. Imidacloprid suppressed carbachol-induced whole-cell currents in a dose-dependent manner, and this compound itself generated small currents. Multiple conductance states of single-channel currents were also evoked by imidacloprid at the nicotinic acetylcholine receptor-channels. The most frequently generated single-channel currents showed two conductance states, 25.4 and 9.8 pS, which were identical to the conductance states of acetylcholine-generated currents. The mean open time and burst duration of the main conductance currents induced by imidacloprid were shorter than those induced by acetylcholine. Co-application of imidacloprid and acetylcholine caused some interactions at the two conductance states. Mean open time and mean burst duration of the main conductance state currents evoked by acetylcholine were decreased by the co-application of imidacloprid as compared with those induced by acetylcholine alone. In conclusion, imidacloprid has both multiple agonist and antagonist effects on the neuronal nicotinic acetylcholine receptor-channels.

Acetylcholine↗

PubMed2001

Chemistry and biology of thiamethoxam: a second generation neonicotinoid.

Thiamethoxam is the first commercial neonicotinoid insecticide from the thianicotinyl subclass. It was discovered in the course of our optimisation program on neonicotinoids started in 1985. Novel variations of the nitroimino-heterocycle of imidacloprid led to 4-nitroimino-1,3,5-oxadiazinanes exhibiting high insecticidal activity. Among these, thiamethoxam (CGA 293433) was identified as the best compound and selected for worldwide development. The compound can be synthesised in only a few steps and high yield from easily accessible starting materials. Thiamethoxam acts by binding to nicotinic acetylcholine receptors. It exhibits exceptional systemic characteristics and provides excellent control of a broad range of commercially important pests, such as aphids, jassids, whiteflies, thrips, rice hoppers, Colorado potato beetle, flea beetles and wireworms, as well as some lepidopteran species. In addition, a strong preventative effect on some virus transmissions has been demonstrated. Thiamethoxam is developed both for foliar/soil applications and as a seed treatment for use in most agricultural crops all over the world. Low use rates, flexible application methods, excellent efficacy, long-lasting residual activity and favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.

Animals↗