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PubMed2004

Foetal rat lung epithelial (FRLE) cells: partial characterisation and response to pneumotoxins.

Cultured cell lines are routinely used for in vitro toxicity screens, reducing the requirement for animal studies during the development of new pharmaceutical, agrochemical and cosmetic products. The foetal rat lung epithelial (FRLE) cell line was originally derived from alveolar type II cells (ATII) of the lung. The aims of this study were to further characterise FRLE cells and investigate their potential for screening for pneumotoxins. The cells were found to have retained some of the features of their progenitor cells, namely the expression of cytokeratin proteins, specifically cytokeratin 18, and the ability to actively accumulate the non-selective contact herbicide paraquat. However, the cells have lost the ability to synthesise surfactant protein mRNA and no longer contain multiple lamellar bodies. Toxins that damage ATII cells in vivo (cadmium chloride, cobalt chloride and paraquat) were found to induce cytotoxicity in FRLE cells, as did the non-specific pneumotoxin nitrofurantoin, and hydrogen peroxide. However, the cells were less sensitive to the effects of compounds that require metabolic activation (1-nitronaphthalene, coumarin and butylated hydroxytoluene) and the hepatotoxin bromobenzene. Thus, FRLE cells appear to be a good in vitro model for monitoring the potential toxicity to ATII cells and could be used as an initial screen for pneumotoxicity.

Animals↗

PubMed2005

Sorption of pesticides in tropical and temperate soils from Australia and the Philippines.

The sorption behavior of diuron, imidacloprid, and thiacloprid was investigated using 22 soils collected in triplicate from temperate environments in Australia and tropical environments in Australia and the Philippines. Within the temperate environment in Australia, the soils were selected from a range of land uses. The average KOC values (L/kg) for imidacloprid were 326, 322, and 336; for thiacloprid, the values were 915, 743, and 842; and for diuron, the values were 579, 536, and 618 for the Ord (tropical), Mt. Lofty (temperate), and Philippines (tropical) soils, respectively. For all soils, the sorption coefficients decreased in the following order: thiacloprid > diuron > imidacloprid. There were no significant differences in sorption behavior between the tropical soils from the Philippines and the temperate soils from Australia. Sorption was also not significantly related with soil characteristics, namely, organic carbon (OC) content, clay content, and pH, for any of the three chemicals studied. When the data were sorted into separate land uses, the sorption of all three chemicals was highly correlated (P < 0.001) with OC for the rice soils from the Philippines. Sorption coefficients for all three chemicals were highly correlated with OC in temperate, native soils only when one extreme value was removed. The relationships between sorption of all three chemicals and OC in temperate, pasture soils were best described by a polynomial. Sorption coefficients for imidacloprid and thiacloprid determined in the temperate pasture soils remained fairly consistent as the OC content increased from 3.3 to 5.3%, indicating that, although the total OC in the pasture soils was increasing, the component of OC involved with sorption of these two compounds may have been remaining constant. This study demonstrated that the origin of the soils (i.e., temperate vs tropical) had no significant effect on the sorption behavior, but in some cases, land use significantly affected the sorption behavior of the three pesticides studied. The impact of land use on the nature of soil OC will be further investigated by NMR analysis.

Adsorption↗

PubMed1991

Electrochemical studies of nitroheterocyclic compounds of biological interest. VII. Effect of electrode material.

The electrochemical behaviour of three nitrofuran compounds, nitrofurazone, nitrofurantoin and furazolidone, has been studied in three solvent types; aprotic, aqueous and mixed, and at four working electrodes. Particular attention has focused on the 1-electron RNO2/RNO2.- couple as measured by the cyclic voltammetric mode. Using Hg in aqueous buffer, reduction of the NO2 group proceeds directly to the hydroxylamine with no intermediate stages being identified. Addition of an aprotic solvent gave a 2-stage reduction, initially forming the RNO2.- species. At all solid electrodes, however, the RNO2/RNO2.- couple was identified under simple aqueous conditions. The switch to a mixed aqueous/aprotic solvent medium produced only minor changes in the response compared with the situation on Hg. This presents the opportunity of using nitrofuran complexes as model systems for the redox behaviour of nitro aromatic compounds in general at solid electrode surfaces where the latters' more negative reduction potentials makes direct study difficult. The conditions have been defined whereby we can examine pH effects and RNO2.- biological target interactions in simple aqueous media to allow the further refinement of the electrolytic model system for studying bio-reducible drug action.

Carbon↗

PubMed2006

Immunization with soot from a non-combustion process provokes formation of antibodies against polycyclic aromatic hydrocarbons.

The emission of soot during combustion processes used in transportation, manufacturing, and power generation is of increasing concern because of its serious adverse health effects. In particular, the ability to modulate the immune system has recently been established. In the present investigation, an artificial soot sample that was prepared by fragmentation of acetylene in a laser-induced plasma was used as an antigen for the immunization of a rabbit. A highly sensitive competition curve in an indirect competitive ELISA using a benzo[a]pyrene-BSA conjugate as a coating antigen could be constructed for benzo[a]pyrene with an IC50 of 2.94 mug/l (11.65 nmol/l). In contrast to the high affinity, the soot antiserum dilution (antibody titer) of 1:750 was rather low. The cross-reactivity was tested with 16 parent polycyclic aromatic hydrocarbons, 7 nitrated polycyclic aromatics, and 3 methylated, hydroxylated or butyric acid derivatives. The results obtained suggest that the vertebrate immune system can respond to an immunization with soot by the generation of high affinity IgG class antibodies against polycyclic aromatics. It is likely that antibodies are raised against the molecular structures which form the framework of the soot particles and not against adsorbed and extractable polyaromatic compounds. The experiments suggest that if soot is considered a T-independent antigen, the isotype switch, essentially from IgM to IgG, could have been caused by co-inoculation with a T-dependent antigen, i.e., mycobacteria contained in Freunds complete adjuvant. However, at the cellular level the mechanism remains to be uncovered.

Acetylene↗

PubMed2001

7-Nitrobenzofurazan (NBD) derivatives of 5'-N-ethylcarboxamidoadenosine (NECA) as new fluorescent probes for human A(3) adenosine receptors.

New fluorescent ligands for adenosine receptors (ARs), obtained by the insertion, in the N(6) position of NECA, of NBD-moieties with linear alkyl spacers of increasing length, proved to possess a high affinity and selectivity for the A(3) subtype expressed in CHO cells. In fluorescence microscopy assays, compound 2d, the most active and selective for human A(3)-AR, permitted visualization and localization of this human receptor subtype, showing its potential suitability for internalization and trafficking studies in living cells.

Adenosine-5'-(N-ethylcarboxamide)↗

PubMed2002

Therapy and prevention of parasitic insects in veterinary medicine using imidacloprid.

Ectoparasitic insects play a major role in veterinary medicine. The flea, especially the cat flea (Ctenocephalides felis felis Bouch 1835) is the most important ectoparasite worldwide. The cat flea parasitizes not only on dogs and cats but also on other warm-blooded animals including humans. The veterinary importance of flea infestation are dermatological conditions due to allergic reactions to antigens in the flea saliva and the transmission of infectious agents like bacteria, viruses and helminths. Insecticides used in veterinary medicine today have to fulfil criteria of elimination of a existing flea infestation (therapy) and prevention (prophylaxis) of new infestation for weeks. Imidacloprid is a compound of the chemical class of CNI (chloronicotinyl insecticides syn. neonicotinoids) that fits these criteria. The high selectivity towards the site of action within insects together with the high safety margin on mammals allowed to develop imidacloprid as an insecticide for agricultural use and finally for the application as a veterinary medicine. The major features of imidacloprid chemistry, toxicology and the development and use as a veterinary medicinal remedy are described.

Animals↗

PubMed1988

Synthesis of spin traps specific for hydroxyl radical.

Two nitrones, 3,3-diethyl-5,5-dimethylpyrroline 1-oxide (DEDMPO) and 3,3,5,5-tetramethylpyrroline 1-oxide (M4PO), were synthesized by the zinc/ammonium chloride reduction of appropiately substituted gamma-nitrocarbonyl compounds, followed by addition of methylmagnesium bromide to the resulting intermediate nitrones. The lipophilicities of these nitrones were estimated by determining their partition coefficients in an 1-octanol/water system. They were found to be considerably more lipophilic than 5,5-dimethylpyrroline 1-oxide (DMPO). The spin trapping of hydroxyl and superoxide radicals with these nitrones was investigated, and the hyperfine coupling constants were determined. M4PO was found to spin trap both free radicals, while DEDMPO spin trapped only hydroxyl radical. DEDMPO was used to determine if hydroxyl radical was produced during the metabolism of menadione or nitrazepam by porcine thoracic aorta endothelial cells. Our results indicate, in conjunction with spin-trapping studies utilizing DMPO, that only superoxide is generated during cellular metabolism of quinones and aromatic nitro-containing compounds by endothelial cells.

Cyclic N-Oxides↗

PubMed1993

Synthesis and pharmacological evaluation of (nitrooxy)alkyl apovincaminates.

A series of (nitrooxy)alkyl apovincaminates has been synthesized and evaluated for their effects on vertebral and femoral blood flow. These derivatives were prepared from apovincaminic acid (4). In cerebral circulation, compound 5 (0.03-1.0 mg/kg iv) caused a dose-dependent increase in cerebral blood flow (CerBF) without affecting the blood pressure. It was more potent than vinpocetine (2). The structures of 2 and 5, determined by X-ray crystallography, showed differences in the electrostatic potential image and in the conformation of the ethyl group at the 16-position.

Animals↗

PubMed1998

Radiation-activated prodrugs as hypoxia-selective cytotoxins: model studies with nitroarylmethyl quaternary salts.

Bioreductive drugs are designed to be activated by enzymatic reduction in hypoxic regions of tumours, but activation of these drugs is not always fully suppressed by oxygen in normal tissues. A further limitation is that bioreductive drug activation depends on suitable reductases being expressed in the hypoxic zone. This essay proposes an alternative approach in which prodrugs are reduced, and thereby activated, in hypoxic regions by ionizing radiation rather than by enzymes. This strategy is theoretically attractive, but design requirements for such radiation-activated cytotoxins are challenging. In particular, the reducing capacity of radiation at clinically relevant doses is small, which necessitates the development of prodrugs capable of releasing very potent cytotoxins efficiently in hypoxic tissue. It is shown that nitroarylmethyl quaternary (NMQ) salts possess many of the features required of a radiation-activated prodrug. In some heterocyclic NMQ compounds the cytotoxicity of the latent cytotoxic amine effector is suppressed by > 100-fold in the prodrug form, and the effector is released rapidly by fragmentation following reduction by a single electron. Appreciable cytotoxic activation of NMQ prodrugs can be achieved by irradiation at clinically relevant doses in anoxic plasma. Some of the further drug design challenges required to develop a clinical agent based on this approach are outlined.

Animals↗

PubMed2003

The mutagenic potential of the furylethylene derivative 2-furyl-1-nitroethene in the mouse bone marrow micronucleus test.

The compound 2-furyl-1-nitroethene (G-0) has been tested to determine its ability to induce clastogenic or aneugenic effects in vivo, through the induction of micronucleated polychromatic erythrocytes (MNPCE) in mouse bone marrow. Groups of five CD-1 male mice were administered once intraperitoneally at a dose range of 5-20 mg/kg and bone marrow was sampled at 24 and 48 h after the treatment. G-0 was dissolved in corn oil, thus a vehicle control group received only corn oil at 10 ml/kg. The positive control group was administered with cyclophosphamide (40 mg/kg). All animals dosed with the highest concentration of the test agent (20 mg/kg) showed evident clinical symptoms of toxicity. Although evidences of bone marrow toxicity were observed, no statistically significant increases in the incidence of MNPCE over the vehicle control group were observed at any sampling time with any of the assayed doses of the G-0 compound. Cyclophosphamide treatment increased the incidence of MNPCE in all treated animals, demonstrating the sensitivity of the assay conditions in which it was carried out. From the results obtained, it is concluded that the test agent G-0 is neither clastogenic nor aneugenic in the erythrocytes from the bone marrow of treated mice at the doses tested.

Animals↗

PubMed1982

Comparative tumor initiating activity on mouse skin of 6-nitrobenzo[a]pyrene, 6-nitrochrysene, 3-nitroperylene, 1-nitropyrene and their parent hydrocarbons.

6-Nitrobenzo[a]pyrene, 6-nitrochrysene, 3-nitroperylene, 1-nitropyrene, and the corresponding parent hydrocarbons were tested for tumor initiating activity on mouse skin with promotion by tetradecanoylphorbol acetate. The initiating doses of 6-nitrobenzo[a]pyrene and benzo[a]pyrene were 0.05 mg each; for all other compounds the initiating doses were 1.0 mg. 6-Nitrochrysene induced tumors in 60% of the mice (2.1 tumors per mouse), but was significantly less tumorigenic than chrysene. 3-Nitroperylene induced tumors in 42% of the mice (0.5 tumors per mouse) and was significantly more active than perylene. Neither 1-nitropyrene nor 6-nitrobenzo[a]pyrene exhibited significant tumorigenic activity in the concentrations tested.

Animals↗

PubMedDate not supplied

Determination of the concentration of explosives in air by isotope dilution analysis.

The concentrations in air of dinitrotoluene (DNT), trinitrotoluene (TNT), nitroglycerin (NG), ethylene glycol dinitrate (EGDN), and pentaerythritol tetranitrate (PETN) were measured at 25 degrees C under equilibrium conditions, and that of cyclomethylene trinitramine (RDX) was measured at elevated temperature by means of an isotope dilution technique. Isotopically multi-labeled compounds were synthesized and used as diluents. Field ionization mass spectrometry was used to measure the abundance ratios of the unlabeled materials. The concentrations in air at 25 degrees C of DNT, TNT, NG, EDGN, PETN, and RDX are 184, 4, 31, 37,000, 7, and 0.8 ppb v/v, respectively. The data obtained may be used for the assessment of the required sensitivity of air-monitoring detection systems.

Air Pollutants↗

PubMed2001

Neurotoxicity of glutamate uptake inhibition in vivo: correlation with succinate dehydrogenase activity and prevention by energy substrates.

Impairment of glutamate uptake or the reverse action of its transporters has been suggested as the mechanism responsible for the increased glutamate extracellular levels associated with ischemic neuronal damage. In previous studies we have shown that glutamate uptake inhibition by L-trans-pyrrolidine-2,4-dicarboxylate (PDC) in the rat striatum and hippocampus in vivo does not induce neuronal death despite the notable increase in the extracellular levels of glutamate and aspartate. However, PDC intracerebral administration leads to neuronal death in rats chronically injected with the mitochondrial toxin 3-nitropropionic acid (3-NP), an inhibitor of succinate dehydrogenase (SDH). In the present study we have determined the time course of inhibition of SDH activity in the striatum of rats acutely injected with a single dose of 3-NP (20 mg/kg), and studied its relation to PDC neurotoxicity. PDC induced larger lesions when administered during maximum inhibition of SDH activity while smaller lesions were found when it was injected during recovery of enzyme activity. We also studied the neuroprotective effect of different energy substrates such as creatine, pyruvate, and the ketone bodies beta-hydroxybutyrate and acetoacetate in this experimental model. Our results show partial protection with all compounds except for beta-hydroxybutyrate that showed no protection, while MK-801 completely prevented PDC-induced neuronal damage. We believe that the present results might be of relevance for the understanding of the mechanisms responsible for ischemic neuronal death and its prevention.

3-Hydroxybutyric Acid↗

PubMed1991

Comparison of oxidative damage to rat liver DNA and RNA by primary nitroalkanes, secondary nitroalkanes, cyclopentanone oxime, and related compounds.

The hepatocarcinogen 2-nitropropane causes oxidative damage to liver DNA and RNA after administration to rats; increases in 8-hydroxydeoxyguanosine and formation of an unknown moiety (DX1) in DNA, plus increases in 8-hydroxyguanosine and the appearance of two unidentified peaks (RX1 and RX2) in RNA were observed by high-performance liquid chromatography of nucleosides from 2-nitropropane-treated rats using electrochemical detection (E. S. Fiala et al, Cancer Res., 49:5518-5522, 1989). In the present study, damage to Sprague-Dawley rat liver RNA and DNA was assessed to determine whether the characteristic pattern of oxidative nucleic acid damage caused by 2-nitropropane also occurred after i.p. administration of primary nitroalkanes, other secondary nitroalkanes, 2-methyl-2-nitropropane (a tertiary nitroalkane), and cyclopentanone oxime. All of the secondary nitroalkanes and cyclopentanone oxime significantly increased levels of 8-hydroxyguanine in both DNA and RNA and caused the appearance of DX1, RX1 and RX2. The primary nitroalkanes and the tertiary nitroalkane 2-methyl-2-nitropropane did not cause a similar pattern of nucleic acid damage. The rates of reprotonation of nitronates of the secondary nitroalkanes to the respective un-ionized neutral forms at pH 7.7 were more than 20-fold less than the rates of reprotonation of primary nitroalkane nitronates, suggesting that the anionic nitronates, rather than neutral compounds, are more immediately responsible for the DNA and RNA damage observed in vivo. Since 8-hydroxyguanine is a miscoding lesion in DNA, these results suggest the possibility, still to be rigorously tested, that hepatocarcinogenicity may be associated not only with 2-nitropropane but also with other secondary nitroalkanes as well as with those ketoximes that are capable of being converted to secondary nitroalkanes in vivo.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2006

New method for calculating densities of nitroaromatic explosive compounds.

A new model has been introduced for simple calculation of crystal density of an important class of organic explosives, namely nitroaromatic energetic compounds. This model is based on the fundamental correlation. The introduced procedure has been applied to 60 well-known and new synthesized organic nitroaromatic explosives. The results show that the present method gives comparable prediction respect to well-developed group additivity method for estimation of crystal density of organic explosives. The introduced simple method can be applied to any complex nitroaromatic explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties.

Crystallization↗

PubMed1976

Structural identification and synthesis of luciferin from the bioluminescent earthworm, Diplocardia longa.

For the first time, luciferin from a bioluminescent earthworm has been purified, identified, and synthesized. This luciferin from the North American species, Diplocardia longa, is a simple aldehyde compound, N-isovaleryl-3-aminopropanal, with an amide functional group. It is a clear, odorless oil at room temperature. It is nonvolatile and has no near-uv-visible absorption or fluorescence. Derivatives of this compound were made to facilitate its identification: the luciferin 2,4-dinitrophenylhydrazone (mp 174 degrees C), a yellow crystalline solid; and the luciferin alcohol, a clear oil. Synthesis of Diplocardia luciferin yielded an oil of identical spectroscopic (proton nuclear magnetic resonance (NMR), 13C NMR, mass, and ir), chemical (dinitrophenylhydrazone and alcohol derivatives, bioluminescence activity), and physical (thin-layer chromatography, volatility) properties to those of the purified native Diplocardia luciferin.

Animals↗

PubMed2005

Self-assembly and multistage redox chemistry of strong electron acceptors on metal surfaces: polynitrofluorenes on gold and platinum.

Nitrofluoren-9-one and nitrofluoren-9-dicyanomethylene electron acceptors 7, 8, and 11 functionalized with a terminal thioctic acid unit have been synthesized from 2,4,5,7-tetranitrofluorenone. The self-assembled monolayers (SAMs) of these compounds on gold, formed via gold-sulfur interaction, have been fully characterized by electrochemical, FTIR, ellipsometry, and contact angle measurements. Cyclic voltammetry of SAMs reveals two reversible single-electron reduction waves for fluorenone derivatives 7a,b and 11, and three single-electron reductions for the dicyanomethylene-fluorene 8b, providing the first observation of a radical trianion species in SAMs. The tendency of the thioctic anchor to form multilayers via disulfide links is noted.

Electrochemistry↗

PubMed2000

4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) inhibits peroxynitrite-mediated phenol nitration.

Peroxynitrite (PN), a very reactive oxidant formed by the combination of superoxide and nitric oxide, appears to play a role in producing tissue damage in a number of inflammatory conditions. Pharmacological scavenging and decomposition of PN within these areas has therapeutic value in several tissue injury models. Recently, we have been interested in nitroxide free radical-containing compounds as possible scavengers of PN decomposition products. Nitroxides can undergo redox reactions to the corresponding hydroxylamine anion or oxoammonium cation in biological systems as shown by its ability to react with superoxide, leading to the formation of hydrogen peroxide and molecular oxygen. We found that 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) inhibits PN-mediated nitration of phenolic compounds in the presence of a large molar excess of PN, suggesting a catalytic-like mechanism. In these experiments, Tempol inhibited PN-mediated nitration over the pH range of 6.5-8.5. This inhibition was specific for nitration and had no effect on hydroxylation. After the inhibition of PN-mediated nitration, Tempol was recovered from the reaction mixtures unmodified. In addition, Tempol was effective in protecting PC-12 cells from death induced by SIN-1, a PN-generating compound. The exact mechanism of Tempol's interaction with PN is not clear; however, we propose that an intermediate in this reaction may be a nitrogen dioxide radical-Tempol complex. This complex could react with water to form either nitrite or nitrate, or with a phenol radical to produce nitrophenol or nitrosophenol products and regenerate the nitroxide.

Animals↗