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PubMed1996

In vitro metabolism of atrazine, terbuthylazine, ametryne, and terbutryne in rats, pigs, and humans.

The in vitro metabolism of four s-triazine herbicides (atrazine, terbuthylazine, ametryne, and terbutryne) was studied using liver microsomes from rats, pigs, and humans. New HPLC methods with UV detection were developed for the analyses of the incubations. Principal phase I reactions were N-monodealkylation, hydroxylation of the isopropyl or tert-butyl moiety, and sulfoxidation of the substrates in all species. Bidealkylation, 2-hydroxylation, or cleavage of the tert-butyl moiety could not be found in this system. The sulfoxidation of the 2-methylthio-s-triazines exceeded catalysis of the other metabolic reactions by 3-4-fold in all species. In general, all species produced the same types of metabolites, but with species-specific differences in the ratios of the metabolites. Species-specific stereoselective formation of a new chiral isopropyl-hydroxylated metabolite from atrazine was investigated using chiral HPLC techniques. The stereoselective production of this metabolite was different in the different species, with S/R ratios of 76:24 in rats, 49:51 in pigs, and 28:72 in humans.

Animals↗
PubMed2001

The discovery of thiamethoxam: a second-generation neonicotinoid.

Neonicotinoids represent a novel and distinct chemical class of insecticides with remarkable chemical and biological properties. In 1985, a research programme was started in this field, in which novel nitroimino heterocycles were designed, prepared and assayed for insecticidal activity. The methodology for the synthesis of 2-nitroimino-hexahydro-1,3,5-triazines, 4-nitroimino-1,3,5-oxadiazinanes and 4-nitroimino-1,3,5-thiadiazinanes is outlined. Bioassays demonstrated that 3-(6-chloropyridin-3-ylmethyl)-4-nitroimino-1,3,5-oxadiazinane exhibited better insecticidal activity than the corresponding 2-nitroimino-hexahydro-1,3,5-triazine and 4-nitroimino-1,3,5-thiadiazinane. In most tests, this compound was equally or only slightly less active than imidacloprid. A series of structural modifications on this lead structure revealed that replacement of the 6-chloro-3-pyridyl group by a 2-chloro-5-thiazolyl moiety resulted in a strong increase of activity against chewing insects, whereas the introduction of a methyl group as pharmacophore substituent increased activity against sucking pests. The combination of these two favourable modifications led to thiamethoxam (CGA 293 343). Thiamethoxam is the first commercially available second-generation neonicotinoid and belongs to the thianicotinyl sub-class. It is marketed under the trademarks Actara for foliar and soil treatment and Cruiser for seed treatment. The compound has broad-spectrum insecticidal activity and offers excellent control of a wide variety of commercially important pests in many crops. Low use rates, flexible application methods, excellent efficacy and the favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.

Anabasine↗
PubMed1984

Evolution of herbicide-resistant weeds.

The first generation of species-selective phenoxy herbicides went into use at the same time as modern antibiotics, chlorinated hydrocarbon insecticides and new fungicides and rodenticides. No resistance has appeared to the still widely used phenoxy herbicides. However, resistance has developed, in many isolated areas around the world, to s-triazine herbicides and, in a few small areas, to bipyridillium herbicides. The parameters of population genetics that govern herbicide resistance and those that govern resistance of microorganisms and fungi to other xenobiotics are the same: generations, selection pressure and fitness. Even though generation times are longer with plants, a sufficient number has passed for resistance to be apparent. The only special factor that controls the development of herbicide resistance in weeds is the spaced germination of seed throughout many seasons. The reason that resistance has not developed to the phenoxy herbicides is probably because of a low effective selection pressure; germination of susceptible seeds occurs late in the season after the herbicide is biodegraded. The highly persistent triazines, and the monthly used, highly ephemeral bipyridillium, paraquat, have exerted much stronger selection pressures. Different modes of tolerance and resistance seem to have evolved in the same species. Crop and herbicide rotation can considerably delay the possibility of resistance development until it is effectively precluded.

Adaptation, Biological↗
PubMedDate not supplied

Dye-ligand affinity chromatography on continuous beds.

Continuous beds derivatized with three triazine dyes (Cibacron Blue 3G-A, Pricon Red HE-3B and Pricon Red H-3B) were used for chromatographic purification of dehydrogenases from yeast enzyme concentrate. All three columns, which were prepared by a very simple and cost-effective method, provided strong binding of glucose-6-phosphate dehydrogenase and lactate dehydrogenase. The Cibacron Blue 3G-A column showed high affinity for alcohol dehydrogenase. Under the same conditions, the Pricon Red HE-3B column showed a lower affinity and the Pricon Red H-3B column showed none. The adsorbed dehydrogenases were eluted specifically from the columns in high yields (71-113% by desorption with the coenzymes NADP, NADH and NAD respectively). Non-specific binding of human serum albumin and transferrin to these columns was also investigated. Enzyme assays and analyses by capillary electrophoresis showed that the continuous beds derivatized with triazine dyes gave a high degree of purification.

Alcohol Dehydrogenase↗
PubMed2003

Symmetrical electron-deficient materials incorporating azaheterocycles.

To investigate the potential of di- and tri-azaheterocycles as building blocks for pi-conjugated materials with high electron affinity, linear oligomers incorporating pyrazine and a C(3)-symmetric discotic molecule based on triazine were synthesized. The tridodecyloxyphenyl end-capped ethynylene pyrazinylene oligomers showed remarkable solvatochroism in absorption and emission in solution. The oligomers containing one and two pyrazine rings displayed liquid crystallinity in the solid state. The largest ethynylene pyrazinylene oligomer containing three pyrazine rings had the lowest first reduction potential at -1.08 V. The triazine-derived discotic molecule exhibited UV/Vis and fluorescence behavior comparable to that of the linear oligomers and featured a first reduction potential at -1.49 V, somewhat lower than expected.

Journal Article↗
PubMed2007

Tuning the excited-state energy of the organic chromophore in bichromophoric systems based on the Ru(II) complexes of tridentate ligands.

A series of new heteroleptic and homoleptic Ru(II) complexes containing variously substituted bis(pyridyl)triazine ligands has been prepared and their absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in a rigid matrix at 77 K) have been investigated. For some compounds, X-ray structures have also been determined. The new bis(pyridyl)triazines incorporate additional chromophores, such as biphenyl, phenanthrene, anthracene and bromoanthracene derivatives, so the Ru(II) species can be considered as multichromophoric species. The absorption spectra and redox properties of all the metal complexes have been assigned to features belonging to specific subunits, thus suggesting that these species can be regarded as multicomponent, supramolecular assemblies from an electronic coupling point of view. Whereas most of the complexes exhibit luminescence properties that can be attributed to metal-to-ligand charge-transfer (MLCT) states involving the metal-based subunit(s), the species containing the anthryl and, even more, the brominated anthryl chromophores exhibit complicated luminescence behaviour. For example, 2 d (the anthryl-containing heteroleptic metal compound) exhibits MLCT emission at room temperature and emission from the anthracene triplet at 77 K; 2 e (the bromo-substituted anthryl-containing heteroleptic metal compound) exhibits anthryl-based emission at 77 K and MLCT emission at room temperature, but with a prolonged lifetime, thus suggesting equilibration between two triplet states that belong to different chromophores. The equilibration regime between MLCT and aromatic hydrocarbon triplet states is therefore reached by suitable substitution on the organic chromophore.

Journal Article↗
PubMed1989

Isotachophoretic determination of herbicides prometryne, desmetryne, terbutryne and hydroxy-derivatives of atrazine and simazine in extracts of milk.

A method is described for the determination of the triazine herbicides prometryne, desmetryne, terbutryne, OH-atrazine and OH-simazine in purified extracts of milk using analytical capillary isotachophoresis. The reproducibility of isotachophoretic analyses was 3.5% and the detection sensitivity reached 2 ng. Recovery of triazines from fortified samples of homogenized full milk (0.05 mg/L) was about 65%.

Animals↗
PubMed1993

Design of novel cationic ligands for the purification of trypsin-like proteases by affinity chromatography.

A number of new cationic ligands have been designed and synthesized for the selective resolution and purification of the trypszin-like proteases. A series of ligands based on 4-[2'-methyl-4'-(2'',4''-dichloro-1'',3'',5''-triazin-6-ylamino ) phenylazo]benzamidine were able to bind to trypsin and the trypsin-like proteases, thrombin and urokinase, but bound pancreatic kallikrein only weakly. Ligands possessing a second cationic group (either 4-aminophenyltrimethylammonium or 4-aminobenzamidine) substituted onto the triazine ring displayed higher affinities than the parent compound for trypsin in solution but bound the enzyme weakly or not at all after immobilization. In contrast, these bis-cationic ligands bound pancreatic kallikrein in solution and following immobilization. The presence of the second cationic group was crucial, since its replacement by neutral or anionic groups led to loss of affinity for pancreatic kallikrein. One of the bis-cationic ligands was used to purify pancreatic kallikrein 9.5-fold from a crude pancreatic extract in 79% yield, to generate a product 99.9% free of contaminating trypsin activity.

Affinity Labels↗
PubMed2005

Simazine biodegradation in soil: analysis of bacterial community structure by in situ hybridization.

Pesticide and nitrate contamination of soil and groundwater from agriculture is an environmental and public health concern worldwide. Simazine, 6-chloro-N2,N4-diethyl-1,3,5-triazine-2,4-diamine, is a triazine herbicide used in agriculture for selective weed control with several types of crops and it is frequently applied to soils receiving N-fertilizers. Degradation experiments were performed in the laboratory to assess whether the biodegradation of simazine in soil may be influenced by the presence of urea. Simazine degradation rates under different experimental conditions (presence/absence of urea, microbiologically active/sterilized soil) were assessed together with the formation, degradation and transformation of its main metabolites in soil. Simazine degradation was affected by the presence of urea, in terms both of a smaller half-life (t(1/2)) and of a higher amount of desethyl-simazine formed. The soil bacterial community was also studied. Microbial abundances were determined by epifluorescence direct counting. Moreover in situ hybridization with rRNA-targeted fluorescent oligonucleotide probes was used to analyze the bacterial community structure. Fluorescent in situ hybridization (FISH) was used to detect specific groups of bacteria such as the alpha,beta,gamma-subdivisions of Proteobacteria, Gram-positive bacteria with a high G + C DNA content, Planctomycetes, Betaproteobacterial ammonia-oxidizing bacteria and nitrifying bacteria. The presence of the herbicide and/or urea affected the bacterial community structure, showing that FISH is a valuable tool for determining the response of bacterial populations to different environmental conditions.

Bacteria↗
PubMed2006

Characterisation of new strains of atrazine-degrading Nocardioides sp. isolated from Japanese riverbed sediment using naturally derived river ecosystem.

A Gram-positive bacterial strain able to degrade the herbicide atrazine was isolated using a simple model ecosystem constituted with Japanese riverbed sediment and its associated water (microcosm). Treatment of the water phase of the microcosm with 1 mg litre-1 [ring-14C]atrazine resulted in the rapid degradation of atrazine after a 10 day lag phase period. The [ring-14C]cyanuric acid formed was transiently accumulated as an intermediary metabolite in the water phase and was subsequently mineralised through triazine ring cleavage. Possible atrazine-degrading microbes suspended in the water phase of the microcosm were isolated by the plating method while rapid degradation of atrazine was in progress. Among the 48 strains that were isolated, 47 exhibited atrazine-degrading activity. From these 47 isolates, 12 strains that were randomly selected were found to identically convert atrazine to cyanuric acid via hydroxyatrazine. Polymerase chain reaction (PCR) amplification of the genes corresponding to atrazine degradation revealed that these strains at least carried the genes trzN (atrazine chlorohydrolase from Nocardioides C190) and atzC (N-isopropylammelide isopropyl amidohydrolase from Pseudomonas ADP). Physiological characteristics and 16S rDNA partial sequences of six strains that were further selected strongly suggested that all these isolates originated from the same Nocardioides sp. strain. Additionally, only one isolate could mineralise the triazine ring of cyanuric acid. Based on microscopic observations, this strain appears to be a two-membered microbial consortium consisting of Nocardioides sp. and a Gram-negative bacterium. In conclusion, atrazine biodegradation in the microcosm appeared to occur predominantly by Nocardioides sp. to yield cyanuric acid, which could be mineralised by the other relatively ubiquitous microbes.

Actinomycetales↗
PubMed2001

Dynamics and mechanism of ultraviolet photolysis of atrazine on soil surface.

The photolysis of atrazine in the soil surface under UV light and the factors affecting this has been studied. A rate constant of 0.09-0.17 min-1, photolytic depth of 0.1-0.3 mm and half-life of 4-8 min were determined. The results show that soil granularity, pH, humidity, organic content, humic acid and surface-active agents could affect the photolysis of atrazine in soil. GC-MS showed three photolytic products: 1-sec-butyl-4,4-diethyl-1-tetrazene, N2,N4-diethyl-6-methyl-1,3,5-triazine-2,4-diamine and 6-chloro-N2-propyl-1,3,5-triazine-2,4-diamine. The mechanism of the photolytic process is discussed.

Atrazine↗
PubMed1994

Minimum structural requirements for minoxidil inhibition of lysyl hydroxylase in cultured fibroblasts.

The structural features of minoxidil contributing to its inhibitory effect on lysyl hydroxylase in cultured fibroblasts were investigated. Minoxidil analogs in which the pyrimidine ring (two nitrogens) was replaced with a pyridine ring (one nitrogen) or a sym-triazine ring (three nitrogens) suppressed lysyl hydroxylase activity without affecting prolyl hydroxylase activity, as did an analog in which the piperidine ring was replaced with an N,N-diethyl group. By contrast, minoxidil analogs bearing an N-monoalkyl (ethyl or butyl) group in place of the piperidine substituent failed to suppress lysyl hydroxylase activity. The results indicate that nitroxides of pyridine and triazine, in addition to pyrimidine, having an ortho amino group can act as specific inhibitors of lysyl hydroxylase in the cell. The minimum structural requirement for inhibitory activity appears to be an organic moiety containing a tertiary nitrogen para to the nitroxide oxygen, a condition that is best fulfilled by the piperidine ring in minoxidil. Hydroxylation of minoxidil at the 3 or 4 position of the piperidine ring had no impact on its ability to inhibit the post-translational hydroxylation of lysine during collagen biosynthesis. Fibroblasts treated with minoxidil, 3'-hydroxyminoxidil, or 4'-hydroxyminoxidil synthesized a collagen specifically deficient in hydroxylysine by approximately 70%, which completely accounted for the diminished lysyl hydroxylase activity. The percentage of total proteins synthesized as collagen was reduced minimally by minoxidil but not by 3'- or 4'-hydroxyminoxidil. The studies offer a potential means for therapeutic intervention of excessive collagen deposition during fibrosis, using minoxidil or preferably its hydroxy derivatives to limit the supply of hydroxylysine for collagen crosslink formation.

Cell Line↗
PubMed1995

Epidemiology of atrazine.

Chronically exposed workers in chemical plants have revealed no increased incidence of benign or malignant disease attributable to atrazine. Some case-control studies showed a slight increase of non-Hodgkin's lymphoma (NHL) incidence while others were negative. Weighted evidence supports no causal association of malignant changes in farming populations with atrazine. Two studies on a rural population suggested an increase of ovarian tumors in exposed women. Neither statistics nor exposure data are satisfactory, however, and no other studies present supporting evidence. New studies under clearly defined conditions are desirable. Very high doses of atrazine ingested in suicidal attempts had no acute clinical effect, suggesting that atrazine is virtually innocuous to humans. Sporadic reports on suspected acute poisoning leave too many questions open to be convincing: they reflect coincidence rather than causality. The tolerance of ruminants to triazine is limited. Severe poisoning in case of accidental intake of concentrated products is to be expected. Poisoning through ingestion has been controlled with activated charcoal. Adsorption on fodder enhances tolerability of triazines. Suspected poisoning through spray-contaminated fodder requires differential diagnosis to avoid confusion with other pasture toxins, electrolyte problems, or gastrointestinal infection.

Acute Disease↗
PubMed1978

Residues of atrazine and N-deethylated atrazine in water from five agricultural watersheds in Québec.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and N-deethylated atrazine (2-chloro-4-amino-6-isopropylamino-s-triazine) were monitored (1974 and 1975) in five rivers which drained agricultural areas in the Yamaska river basin of Québec. Water samples were collected frequently from April to December each year from sites near the outflow of each river. The water samples were extracted with benzene, chloroform, or ethyl acetate and the extracts were analyzed by gas chromatography using a Hall electrolytic conductivity detector and an alkali-flame detector. Atrazine and N-deethylated atrazine residues ranged in concentration from 0.01 to 26.6 microgram/L and less than 0.01 to 1.34 microgram/L, respectively, over the monitoring period. The highest levels of atrazine were observed in July each year and they coincided with the herbicide spraying season in this region and with occasional heavy rainfall events. Discharges (kg/yr) of atrazine from the five rivers were related to corn-growing area in each watershed. Losses of atrazine ranged from 0.1 to 2.9% of the atrazine that was estimated to have been applied in each watershed.

Atrazine↗
PubMed1996

Seasonal atrazine contamination of drinking water in pig-breeding farm surroundings in agricultural and industrial areas of Croatia.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) a s-triazine herbicide, has been widely used in Croatian agriculture. Due to atrazine extensive use and its biodegradation in nature within at least one year (Klassen and Kodoum 1979), atrazine residues are found in ground, surface, drain and drinking water (Vidacek et al. 1994; Gojmerac et al. 1994). Groundwater downgradient from atrazine treated fields may show seasonal concentration peaks which could exceed the safe level (Wehtje et al. 1983). Therefore, the use of atrazine includes permanent control of its residues in water, particularly in relation to its use as a herbicidal chemical and groundwater contamination (Graham 1991). Furthermore, the presence of atrazine in the environment and its possible ingestion via the water, food and feed chain, may present a risk for the animal and human health. The analysis of atrazine residues in soil can be performed by either colorimetry or high performance liquid chromatography (HPLC) (Vickrey et al. 1980), and in water, soil and food by immunoassay in comparison with HPLC or gas chromatography/mass spectrometry (GS-MS) (Bushway et al. 1988; Bushway et al. 1989; Bushway et al. 1992; Thurman et al. 1990). We describe the use of enzyme-linked immunosorbent assay (ELISA) for one-year seasonal monitoring of atrazine residues in drinking water from two differently situated pig-breeding farms (agricultural and industrial areas) in Croatia. Results obtained by ELISA were compared to those produced by HPLC.

Agriculture↗
PubMed1996

Respiratory effects of a synthetic metalworking fluid and its components.

A synthetic metalworking fluid, MWF "A", and its major components were evaluated using a previously developed mouse bioassay. This fluid and its components evoked sensory (S) and pulmonary (P) irritation in mice. For MWF "A" and each of its components, a concentration-response relationship was developed on the basis of respiratory frequency (fR) responses. From such relationships, the concentration capable of evoking a 50% decrease in mean fR was determined for MWF "A" and each component (RD50). RD50S or RD50P was used to distinguish decreases in fR that were due to sensory irritation (S) from those due to pulmonary irritation (P). From RD50P values, it was concluded that the fatty acid alkanolamide condensates, tolutriazole, and triazine-type biocide components were similar in potency to one another and similar in potency to MWF "A". By examining potency and fractional composition, it was concluded that the fatty acid alkanolamide condensates and the triazine-type biocide largely contributed to the irritancy of MWF "A". From RD50P values, occupational exposure limits were proposed for MWF "A" and each of its components. The current Threshold Limit Value of 10 mg/m3 established by the American Conference of Governmental Industrial Hygienists for "particulates not otherwise classified" (PNOC) would be inadequate to protect workers from the irritating properties of MWF "A" and most of its components.

Aerosols↗
PubMed2004

Low-level atrazine exposure decreases cell proliferation in human fibroblasts.

There is continuing concern that release of certain chemicals into the environment leads to human exposure to toxins, particularly through contaminated ground and surface waters. The triazine herbicide atrazine (2-chloro-4-ethylamine-6-isopropylamino-S-triazine) is routinely found as a contaminant in many surface and groundwaters. Little is known of the long-term effects of atrazine exposure on human cells. The objective of this research was to examine whether low-level exposure of atrazine to normal human fibroblast cells in culture had measurable deleterious effects. We show that low-level, short-term exposure of atrazine to normal fibroblasts results in decreased cell proliferation. In two separate assays to measure cell proliferation, either a 1.5-fold decrease in the cell number occurred (saturation density analysis) or a 2-fold decrease in cell proliferation was found (MTT analysis). Experiments to measure apoptosis in cells exposed to low levels of atrazine did not show DNA fragmentation or increased caspase activity. Thus, this analysis shows that short-term exposure to environmentally relevant, low levels of atrazine can be assessed by a decrease in cellular proliferation of normal human cells.

Apoptosis↗
PubMed2002

Molecular basis for multiple resistance to acetolactate synthase-inhibiting herbicides and atrazine in Amaranthus blitoides (prostrate pigweed).

Amaranthus blitoides S. Watson (prostrate pigweed) populations resistant to acetolactate synthase (ALS; EC 4.1.3.18)-inhibiting herbicides and triazines (SuR/TR) were found in Israel. The Ganot population was 6- to 790-fold more resistant to ALS inhibitors than the wild type due to an altered target site. Molecular analyses showed that the Ganot population was a mixture of two biotypes: (i) SuRA/TR in which domain A of the als gene differed in one nucleotide, resulting in substitution of Pro by Ser 188; (ii) SuRB/TR in which a mutation in domain B led to a substitution of Trp by Leu 569. The mutation in domain A resulted in resistance to all ALS inhibitors except imidazolinones, whereas the mutation in domain B led to resistance to all ALS inhibitors tested. SuRA/TR and SuRB/TR are multiple-resistant with an additional single mutation in the plastidic psbA gene that changes Ser 264 to Gly in the D1 protein, leading to triazine resistance. It is evident that plants within a population exposed to a similar selection pressure may show different patterns of cross-resistance due to three different point mutations. This unique phenomenon renders planning of rational weed management difficult or even impossible.

Acetolactate Synthase↗