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PubMed1979

N-mineralization of formaldehyde-releasing N-compounds.

The mineralization of several N-compounds, such as MMU, DMU, and HMT, as well as their respective nitrificide action, have been investigated. It has been proved that the amount of available formaldehyde, as well as its rate of release, are responsible for the specific action of these compounds on the N-mineralization process. Factors affecting the rate of release, namely molecular structure, solubility, and temperature, are discussed as well. Importance of these N-compounds as slow-release N-fertilizers based on a new molecular-microbiological approach is described.

Bacteria↗

PubMed1998

Analysis of the in vivo nitrosation capacity of the larvae used in the wing somatic mutation and recombination test of Drosophila melanogaster.

The in vivo nitrosation capacity of third-instar larvae of Drosophila melanogaster was assessed using the wing somatic mutation and recombination test (SMART). Larvate derived from two different crosses, the standard cross (ST) and the high bioactivation cross (HB) both involving the recessive wing cell markers multiple wing hairs (mwh) and flare (flr3), were used. The HB cross is characterised by an increased cytochrome P450-dependent bioactivation capacity for promutagens and procarcinogens. The larvae were treated either with methyl urea, sodium nitrite or its combination. N-Nitrosomethylurea was used as a positive control. The wings of the resulting flies were analysed for the occurrence of mutant spots produced by various types of mutational events or by mitotic recombination. Methyl urea is negative in the ST and the HB cross, whereas sodium nitrite is weakly genotoxic in both crosses. However, the combination of both compounds produces highly increased frequencies of mutations and recombinations predominantly in the HB cross. The genotoxic effects produced by the combined treatments were considerably increased when mashed potatoes or an agar-yeast medium were used for the treatment instead of the standard instant medium. Treatment of larvae with the mixture resulting from the in vitro reaction of nitrosation precursors also resulted in high frequencies of induced spots comparable to those recorded with the potent genotoxin N-nitrosomethylurea. Further experiments showed that the genotoxic effect resulting from the in vivo exposure to nitrosation precursors can be reduced by co-treatment with catechin, a known nitrosation inhibitor. The present study demonstrates that the wing spot test is well suited for the determination of genotoxicity produced by in vivo nitrosation processes and for the study of their modulation by individual compounds or dietary complex mixtures.

Animals↗

PubMed1989

Inhibition of chemical Epstein-Barr virus induction by dimethyl sulfoxide and related polar compounds.

Dimethyl sulfoxide and twelve related polar compounds, capable of inducing differentiation of murine erythroleukemia cells, markedly inhibited induction of Epstein-Barr virus antigens in virus producer and nonproducer lymphoblastoid cells exposed to 12-O-tetradecanoylphorbol-13-acetate, n-butyric acid, 5-iodo-2'-deoxyuridine, and a combination of 12-O-tetradecanoylphorbol-13-acetate and n-butyric acid. The concentration at which these compounds caused 90% inhibition of antigen induction corresponded to that optimal for induction of differentiation. At the same concentrations, polar compounds did not affect cell viability or virus induction by superinfection with Epstein-Barr virus recovered from P3HR-1 cells. The inhibitory activity was reversible. Three nonpolar differentiating compounds revealed no inhibitory activity.

Acetamides↗

PubMed2002

Biotransformation of phenylurea herbicides by a soil bacterial strain, Arthrobacter sp. N2: structure, ecotoxicity and fate of diuron metabolite with soil fungi.

In order to assess the influence of the aromatic substitution on the ability of a soil bacterial strain, Arthrobacter sp. N2, to degrade phenylurea herbicides, biotransformation assays were performed in mineral medium with resting cells of this soil bacterial strain on three phenylurea herbicides (diuron, chlorotoluron and isoproturon). Each herbicide considered, led to the formation of only one metabolite detected by HPLC analysis. After isolation, the metabolites were identified by NMR and MS, as the corresponding substituted anilines. According to the Microtox test (realized on the bacterium Vibrio fischeri), these metabolites presented non-target toxicity far more important (up to 600 times higher for 4-isopropylaniline) than the parent molecule. For isoproturon and chlorotoluron, the amount of substituted anilines obtained at the end of the biotransformation was very low, whereas the biotransformation of diuron into 3,4-dichloroaniline was almost quantitative. In this last case, the degradation product accumulated in the medium. In soil, other microorganisms are present that might degrade it. So the biotransformation of 3,4-dichloroaniline was then tested with four fungal strains: Aspergillus niger, Beauveria bassiana, Cunninghamella echinulata var. elegans and Mortierella isabellina. The aniline was further transformed with all the microorganisms tested. Only one metabolite was detected by HPLC analysis and after isolation, it was identified to be 3,4-dichloroacetanilide. This acetylated compound led to biological effects less important on V. fischeri than 3,4-dichloroaniline. These results stress the importance of identifying the degradation products to assess the impact of a polluting agent. Indeed, the pollutant may undergo transformation yielding compounds more toxic than the parent molecule.

Arthrobacter↗

PubMed1982

The selectivity of amino acid and peptide amidination with O-methylisourea.

Selectivity of amidination using ornithine as model amino acid was investigated in detail. The results obtained were taken advantage of for studying the reactions with other polyfunctional amino acids: beta-tyrosine, isoserine, 2,3-diaminopropionic acid, 2,6-diamino-7-hydroxyazelaic acid and with the pentapeptide amide, edeine A. It was found that, if the appropriate conditions are maintained, selective amidination of more basic amino groups of polyamino compounds is possible when these groups are bound to the primary alkyl.

Amides↗

PubMed2002

Effects of the formaldehyde releasing preservatives dimethylol urea and diazolidinyl urea in several short-term genotoxicity tests.

The two formaldehyde (FA)-releasers dimethylol urea (DMU) and diazolidinyl urea (DZU) are widely used as preservatives or additives. They were tested for genotoxicity in three short-term test systems, i.e. in the Salmonella typhimurium mutagenicity assay, in the in vitro micronucleus test with V79 Chinese hamster cells and in the in vitro tubulin assembly assay using isolated tubulin from pig brains. The polymerization products obtained in the tubulin assembly assay were examined additionally by electron microscopy. In the S. typhimurium mutagenicity assay with the pre-incubation assay both FA-releasers tested show a clear and concentration-dependent increase in the number of revertants in strains TA98, TA100 and TA102 with and without metabolic activation (rat liver S9 mix). In all cases, a biologically relevant increase in the number of revertants was achieved within the concentration range tested (DZU: 0.04-1.8 micromol per plate, DMU: 0.21-8.33 micromol per plate). FA was tested at 0.06-2.5 micromol per plate and lead to similar effects.Both compounds induce the formation of micronuclei (concentration range tested: DZU: 2.5-50 micromol/l, DMU: 3.3-333 micromol/l). However, DMU shows a comparatively weaker effect exclusively in the absence of the metabolizing enzymes. By contrast, DZU yields a distinct increase of the micronucleus rate in the absence and in the presence of S9. In addition, DZU predominantly causes an increase of large micronuclei, which suggests that this compound has a marked aneugenic potential. Cytotoxic effects accompany the clastogenic effects of both DMU and DZU. The examination of DMU and DZU in view of a possible aneugenic potential in the tubulin assembly assay yielded the following results: DMU at concentrations up to 10 mmol/l did not influence the formation of microtubuli, whereas DZU inhibited this process completely at 3 mmol/l. FA at 6 mmol/l completely inhibited the tubulin assembly. These results could clearly be confirmed by electron microscopy examination. The different potential of the two compounds with respect to the inhibition of tubulin formation is apparently due to a significant difference in the degree of FA release. According to these results, both compounds have to be considered as genotoxic in vitro. On account of these data and because of the widespread use of these two compounds in various products used in daily life, a reevaluation of the risk associated with these compounds seems to be necessary.

Animals↗

PubMed2002

Exploiting plant metabolism for the phytoremediation of persistent herbicides.

Weed control by herbicides has helped us to create the green revolution and to provide food for at least the majority of human beings living today. However, some herbicides remain in the environment and pose an ecological problem. The present review describes the properties and fate of four representative herbicides known to be presistent in ecosystems. Metabolic networks are depicted and it is concluded that removal of these compounds by the ecologically friendly technique of phytoremediation is possible. The largest problem is seen in the uptake of the compounds into suitable plants and the time needed for such an approach.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1963

FLAVIN SENSITIZED PHOTOREACTIONS: EFFECTS OF 3-(P-CHLOROPHENYL)- 1,1-DIMETHYLUREA.

Photooxidation reactions, which were inhibited by high concentrations of oxygen, were affected by the addition of 3-(p-chlorophenyl)-1,1-dimethylurea (CMU), but the response varied with the substrate being oxidized. With ascorbic acid and 2,3-diketogulonic acid, CMU reversed the inhibition caused by high concentrations of oxygen. With ethylenediaminetetraacetic acid (EDTA), tetraethylene tetramine, or Mn(++) as reductant, CMU itself inhibited the reactions. The photoreduction of flavins by EDTA and the bleaching of flavin mononucleotide under anaerobic conditions were also inhibited by CMU. Corresponding photoreactions sensitized by phthaleine dyes or methylene blue were completely insensitive to CMU. This compound therefore seems to change specifically the reactivity of excited flavin molecules.

Antimetabolites↗

PubMed2004

Chromatographic and column stability at pH 7 of a C18 dimethylurea polar stationary phase.

Chromatographic evaluations of a C18 dimethylurea phase in 150 mm x 3.9 mm HPLC columns were performed using the Tanaka and Engelhardt test mixtures. The applicability of the new C18 dimethylurea phase was also evaluated with a mixture of some herbicides and their metabolites. An artificial aging procedure was also performed by passing a potassium phosphate mobile phase buffered at pH 7.0 through C18 50 mm x 3.9 mm dimethylurea columns. The column stability was evaluated by means of the chromatographic parameters obtained for the separation of some compounds from the Neue test mixture, using apolar, polar and highly basic analytes.

Chromatography, High Pressure Liquid↗

PubMed2001

Penetration of herbicides to groundwater in an unconfined chalk aquifer following normal soil applications.

The persistence and penetration of the herbicides isoproturon and chlorotoluron in an unconfined chalk aquifer has been monitored over a 4-year period through soil sampling, shallow coring and groundwater monitoring. Chlorotoluron was applied on plots as a marker compound, having never been used previously on that, or surrounding fields. The fieldsite had a 5 degree slope with soil depths of 0.5 to 1.5 m and a water table between 20 and 5 m from the soil surface. Where the water table was deepest (9-20 m below surface (mbs)) little or no positive herbicide detections were made. However, where the water table was at only 4-5 mbs, a regular pesticide signal of around 0.1 microg/l for isoproturon and chlorotoluron could be distinguished. Over the winter recharge period automatic borehole samplers revealed a series of short-lived peaks of isoproturon and chlorotoluron reaching up to 0.8 microg/l. This is consistent with a preferential flow mechanism operating at this particular part of the field. Such peaks were occurring over 2 years after the last application of these compounds. Shallow coring failed to uncover any significant pesticide pulse moving through the deep unsaturated zone matrix at the fieldsite.

Environmental Monitoring↗

PubMed2006

HPLC-DAD and Q-TOF MS techniques identify cause of Daphnia biomonitor alarms in the River Meuse.

Several water companies in The Netherlands use a combination of specifically targeted compound analysis (HPLC-UV and GC-MS) and effect monitoring (continuous biotests) to monitor source water quality and to screen for unknown compounds. In spring 2004, the Daphnia biomonitor at Keizersveer monitoring station alongside the River Meuse recorded several alarms. In this study, the combination of HPLC-DAD and Q-TOF MS techniques was used to identify the so-far unknown microcontaminant related to this Daphnia alarm as 3-cyclohexyl-1,1-dimethylurea. The maximum concentration of this compound in the River Meuse at the time of the alarm was estimated to be 5 microg/L. The response of the waterfleas to this compound was confirmed with a short-term and a long-term verification test. The origin of the pollutant is still unknown. This paper shows that the combined application of on-line continuous biotests and advanced chemical analysis is an effective tool for the detection and identification of unknown, potentially hazardous compounds for surface water quality monitoring. Biological effect monitoring and specific compound analysis complement each other and together provide the best possible insight in rapid surface water quality changes.

Animals↗

PubMed1977

Individual susceptibility of mice to a mutagen in both germ and somatic cells.

Male Swiss mice received simultaneously, by gavage, 500 mg methylurea/kg body weight and 25 mg sodium nitrite/kg body weight, and in a further experiment 330 mg of methylurea/kg and 17 mg sodium nitrite/kg, for 5 consecutive days. This treatment resulted in a dose-dependent mutagenic effect in both the dominant-lethal and the micro-nucleus tests. Furthermore, in both mammalian tests, some animals were more susceptible to the mutagenic compounds than were others. However, the liver microsomal metabolizing system did not seem to be responsible for this variation of mutagenic induction.

Animals↗

PubMed1996

Design, synthesis, and resistance patterns of MP-134 and MP-167, two novel inhibitors of HIV type 1 protease.

Inhibitors of HIV-1 protease represent a new class of antiretroviral compounds. Here, we report the design and synthesis of two novel C2 symmetry-based inhibitors, MP-134 and MP-167, specifically targeted against HIV-1 variants with reduced sensitivity to another related protease inhibitor, A-77003. In addition, we describe the in vitro selection of viral variants with reduced sensitivity of these two protease inhibitors. An isoleucine-to-valine substitution at residue 84 (I84V) of the HIV-1 protease confers resistance to MP-134, whereas a glycine-to-valine substitution at residue 48 (G48V) confers resistance to MP-167. Testing other protease inhibitors against these variants has revealed specific overlapping patterns of resistance among these agents. These findings have important implications in the design of combination regimens using multiple protease inhibitors and underscore the need to develop non-cross-resistant compounds to be used toward this goal.

Amino Acid Sequence↗

PubMed1998

DNA damaging effects of pesticides measured by the single cell gel electrophoresis assay (comet assay) and the chromosomal aberration test, in CHOK1 cells.

One herbicide (isoproturon), two fungicides (carbendazim and chlorothalonil) and etoposide (an effective antitumor agent used as a positive control), were tested for their ability to induce cytotoxic and genotoxic effects in Chinese Hamster Ovary (CHOK1) cells. Etoposide induced DNA damage detectable both by the alkaline Single Cell Gel Electrophoresis (SCGE) assay and the chromosomal aberration (CA) test in absence of noticeable cytotoxicity. With the SCGE assay, a clear induction of DNA damage was observed for chlorothalonil within a 0.2 to 1 microM concentration range. In the CA test, chlorothalonil gave also positive results, inducing mainly chromosome breaks. In contrast, no DNA damage was observed with the SCGE assay for carbendazim and isoproturon. In the CA test, carbendazim induced only numerical aberrations in the concentration range of 25 microM to 100 microM, and isoproturon did not induce any significant increase in CA. In conclusion, chlorothalonil appears genotoxic in proliferative CHOK1 cells, and as expected, the aneugenic compound, carbendazim, did not induce DNA strand breaks in the SCGE assay.

Animals↗

PubMed2001

Mineralization of 2,4-D, mecoprop, isoproturon and terbuthylazine in a chalk aquifer.

The potential to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D), mecoprop, isoproturon and terbuthylazine was studied in soil and aquifer chalk sampled at an agricultural field near Aalborg, Denmark. Laboratory microcosms were incubated for 258 days under aerobic conditions at 10 degrees C with soil and chalk from 0.15-4.45 m below the surface. The [ring-U-14C]-labeled herbicides were added to obtain a concentration of 6 micrograms kg-1 and mineralization was measured as evolved [14C]carbon dioxide. The herbicides were readily mineralized in soil from the plough layer, except for terbuthylazine, which was mineralized only to a limited extent. In the chalk, lag periods of at least 40 days were observed, and a maximum of 51%, 33% and 6% of the added 2,4-D, mecoprop and isoproturon, respectively, were recovered as [14C]carbon dioxide. Large variations in both rate and extent of mineralization were observed within replicates in chalk. No mineralization of terbuthylazine in chalk was observed. As a measure of the general metabolic activity towards aromatic compounds, [ring-U-14C]-benzoic acid was included. It was readily mineralized at all depths.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2001

Spatial requirements of the antagonist binding site of the NK2 receptor.

Computer-aided modelling has been used to identify a putative antagonist binding site in the tachykinin NK2 receptor. In order to validate the implied spatial requirements for this region, a series of compounds, based on the potent antagonist GR 149861 have been synthesised and their binding affinities established. Our findings suggest the presence of a large hydrophobic cavity in the putative binding crevice of GR 149861.

Binding Sites↗

PubMed2006

Structure-activity relationship (SAR) studies of benzoxazinones, their degradation products, and analogues. Phytotoxicity on problematic weeds Avena fatua L. and Lolium rigidum Gaud.

Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.

Benzoxazines↗

PubMed1995

Synthetic chemical diversity: solid phase synthesis of libraries of C2 symmetric inhibitors of HIV protease containing diamino diol and diamino alcohol cores.

Solid phase synthesis of non-oligomeric organic compounds has been pursued for high-efficiency generation of large numbers of structurally diverse compounds for drug screening. Known as chemical diversity libraries or combinatorial libraries (when the synthesis is carried out in a combinatorial fashion), these compounds can be used for de novo discovery of drug leads or for expedient structure--activity relationship (SAR) studies. To expand the scope of solid phase synthesis beyond the capability of the traditional method of solid phase synthesis for peptides, a strategy was developed for bi-directional solid phase synthesis starting with diamino alcohol or diamino diol core structures. The strategy relies on using bifunctional linkers to modify the core structures, simultaneously protecting the hydroxyl group or the diol moiety of the core and providing a carboxyl group for attachment of the modified cores to a solid support. The two NH2 groups of the modified cores attached to the solid support were then deprotected and reacted with a wide variety of amine-reactive reagents (carboxylic acids, sulfonyl chlorides, isocyanates, chloroformates, etc.) to extend the molecule in both directions. This strategy was successfully applied to automated parallel synthesis of a library of C2 symmetric inhibitors of HIV protease containing the known symmetry-based diamino diol and diamino alcohol core structures, thus enabling expedient access of large numbers of analogs in this series. A library of over 300 discrete compounds was synthesized using this methodology in order to identify potent (IC50 < 100 nM) HIV protease inhibitors with reduced size. This paper describes the technical aspects of this technology.

Alcohols↗