Products of the photolysis of 3,6-dichloropicolinic acid (the herbicide lontrel) in aqueous solutions

We studied the composition of products of the photochemical degradation of 3,6-dichloropicolinic acid (DCPA), the active principle of Lontrel, a herbicide broadly used in agriculture. Ultraviolet irradiation (mimicking the natural sunlight action) did not degrade DCPA completely to environmentally safe products. The rate of DCPA degradation was notably lower when distilled water was replaced by river water and even lower in sea water. Chromatomass spectrometry revealed 9 compounds among the photolysis products, in addition to undegraded DCPA.     

A plant selectable marker gene based on the detoxification of the herbicide dalapon

Summary A gene from Pseudomonas putida coding for a dehalogenase capable of degrading 2,2 dichloropropionic acid (2,2DCPA), the active ingredient of the herbicide dalapon, has been isolated and characterised. In plant transformation experiments the gene was shown to confer resistance to 2,2DCPA at a tissue culture level where 2,2DCPA could be used to select for transformants. At the whole plant level, transformed plants showed resistance to 2,2DCPA at concentrations up to 5 times the recommended dose rate of dalapon when it was sprayed on their leaves. At lower concentrations, the herbicide caused a non-lethal yellowing of sensitive plants which clearly distinguished them from resistant plants. The mode of action of chlorinated aliphatic acids is not known but they probably affect many enzyme pathways. The results described here are the first example of engineering a plant resistant to a herbicide that does not have one specific enzyme as its target site. This gene has several advantages as a marker in plant breeding and genetic studies. For example, the herbicide is readily available and has low toxicity, transformants can be selected at both the tissue culture and the whole plant level, a large number of transformed plants can easily be screened even in the field, and there is a very low probability of selecting spontaneous mutants.Abbreviations 2MCPA 2, monochloropropionic acid - 2,2DCPA 2,2 dichloropropionic acid - TCA trichloroacetic acid     

Survival ofAlcaligenes xylosoxidans degrading 2,2-dichloropropionate and horizontal transfer of its halidohydrolase gene in a soil microcosm

A soil microcosm, containing a mixture of sand and a well-characterized phaeozem soil from loess, was developed for biodegradative applications. It was inoculated with soil-borneAlcaligenes xylosoxidans AB IV, degrading 2,2-dichloropropionate (DCPA), by a plasmid-encoded haloalkanoic acid halidohydrolase. In long-term microcosm experiments, survival ofAlcaligenes xylosoxidans ABIV in the presence and absence of selective pressure by the xenobiotic compound could be demonstrated as well as its capacity to maintain degradation of DCPA. At the same time its plasmid, pFL40, containing the degradative gene,dhlC, was horizontally transferred toPseudomonas fluorescens in sterilized soil and also to different indigenous soil bacteria in nonsterilized soil.     

Comparison of the Disruption of Mitosis and Cell Plate Formation in Oat Roots by DCPA, Colchicine and Propham

Holmsen, J. D. and Hess, F. D. 1985. Comparison of the disruptionof mitosis and cell plate formation in oat roots by DCPA, colchicineand propham.—J. exp. Bot. 36: 1504–1513. Concentrationsof DCPA, propham and colchicine were selected to cause from0% to greater than 60% inhibition of oat (Avena sativa L. ‘Victory’)root growth after 24 h exposure. Root growth progressively declinedas concentrations were raised from 1·0 to 5·6mmol m^–3 DCPA, 1·0–5·0 mmol m^–3propham, and 50–500 mmol m^–3 colchicine. In additionto inhibiting root growth each mitotic disrupter caused theroot tips to swell to an extent dependent upon concentration.All three compounds effectively disrupted mitosis at concentrationsthat caused less than maximal root growth inhibition. Mitoticdisruption was manifest as a reduction in the number of normalmitotic figures and an increase in the number of condensed prophase,multipolar and anaphase bridge division figures. The frequencyof each type of division figure was different for each of thethree compounds. DCPA disrupted mitosis more effectively whencompared with propham and colchicine at concentrations whichcaused the same amount of root growth inhibition. Each mitoticdisrupter also induced the formation of aberrant cell walls.DCPA was the most effective at disrupting cell plate formation,whereas colchicine was least effective. These data suggest thatthe mechanism of action of DCPA is distinct from the mechanismof colchicine or propham Key words: Avena sativa L., mitotic disruption, DCPA, colchicine, propham     

Inhibition of Respiration of Yeast by Photosynthesis Inhibiting Herbicides

In order to elucidate the mode of action of some herbicides, effect of several anilide type herbicides on the respiration of yeast cells was studied. The results obtained were as follows: 1) DCPA (3,4-dichloropropionanilide) and DCMU (3-(3,4-dichlorophenyl)-1,1- dimethylurea), the powerful inhibitors of the Hill reaction in photosynthesis, inhibited the oxygen uptake of yeast cells at low concentrations. 2) DCPA and DCMU inhibited the enzymic reduction of cytochrome-c by the yeast cell-free preparation, but not the reduction of dye. 3) The oxidation of cytochrome-b was inhibited in the yeast cells treated with DCPA or DCMU.     

Tuning the polylactide hydrolysis rate by plasticizer architecture and hydrophilicity without introducing new migrants

The possibility to tune the hydrolytic degradation rate of polylactide by plasticizer architecture and hydrophilicity without introduction of new degradation products was investigated by subjecting polylactide with cyclic oligolactide and linear oligolactic acid additives to hydrolytic degradation at 37 and 60 °C for up to 39 weeks. The more hydrophilic oligolactic acid plasticizer led to larger water uptake and rapid migration of plasticizer from the films into the aging water. This resulted in a porous material more susceptible to further hydrolysis. During hydrolysis at 37 °C the mass loss was generally 10-20% higher for the material containing linear oligolactic acid plasticizers. The hydrolysis accelerating effect of the linear oligolactic acid is probably counteracted by the higher degree of crystallinity in the films containing oligolactic acid additives. The degradation process was monitored by measurements of mass loss, water uptake, molar mass changes, material composition changes, surface changes, and thermal properties. The water-soluble degradation products were analyzed by following pH changes and identified by electrospray ionization-mass spectrometry (ESI-MS). The time frame for formation of water-soluble products was influenced by the architecture and hydrophilicity of the plasticizer. Furthermore, the advantage with oligolactide and oligolactic acid plasticizers was clearly demonstrated as they do not introduce any new migrants into the degradation product patterns.     

Studies in the Physiological Action of 2,2-Dichloropropionic Acid: II. THE EFFECTS OF LIGHT AND TEMPERATURE ON THE FACTORS RESPONSIBLE FOR THE INHIBITION OF GROWTH

When Lemna minor and Salvinia natans, grown in a constant environment,are subjected to sub-lethal concentrations of 2,2-dichioropropionicacid (DCPA), the relative growth-rates are progressively reduced.These cumulative reductions, which are greater for S. natans,are correlated with decreases in (1) the rate of leaf or frondformation, (2) the mean area per leaf or frond, and (3) thenet assimilation rate. Of these components, the first is themost important and the third is the least. The effects of light intensity (300, 600, 900 f.c.), temperature(20, 25, and 30°C), and concentration of DCPA on both therelative growth-rate and rate of leaf or frond multiplicationhave been examined in multi-factorial experiments. Over theconcentration range selected (100, 200, and 400 mg/l for S.natans and 100, 300, and 6oo mg/l for L. minor) there are positiveeffects of light intensity, temperature, and concentration.For each concentration the order of the depression is maximalunder a combination of the highest temperature and the greatestintensity. Using radioactive DCPA it has been established that uptake isalso a cumulative process, and that S. natans has a greatercapacity to absorb DCPA. The rate of uptake is independent ofthe light intensity but increases with temperature and concentration. DCPA brings about morphological and structural changes. In S.natans, many of the leaves become submerged and the proportionis positively dependent on light, temperature, and concentration.This failure to float is associated with a reduction in thedensity of epiderrnal hairs. It is concluded that the inhibitory effects of DCPA are maximalunder conditions which are optimal for both meristematic activityand accumulation.     

Selective medium for isolation of Fusarium species and dematiaceous hyphomycetes from cereals

A selective medium containing 2 micrograms of dichloran per ml, 200 micrograms of chloramphenicol per ml, and 1.5% bacteriological peptone was developed for the isolation of Fusarium species and dematiaceous hyphomycetes from cereals. The medium, designated DCPA, was shown to select against species of Aspergillus, Penicillium, Cladosporium, and mucoraceous fungi. DCPA was evaluated for use as an enumeration medium and compared satisfactorily with dichloran-rose bengal-chloramphenicol agar when both media were tested with a range of cereal samples. Fusarium species and dematiaceous hyphomycetes produced well-formed colonies with good conidial production on DCPA, permitting rapid identification of such isolates on this medium.     

Studies in the Physiological Action of 2,2-Dichloropropionic Acid: III. FACTORS AFFECTING THE LEVEL OF ACCUMULATION AND MODE OF ACTION

The factors determining the pattern of uptake by Lemna minorof 2,2-dichloropropionic acid (DCPA), containing chlorine-36,have been examined. Entry takes place via both the roots andfrond and is largely in the ionic form. Initially, the net ratesare high and are replaced by slower but steady rates. It isconcluded that over the first 30 minutes, net uptake is dependenton the physico-chemical processes since (i) the rate is directlyproportional to the external concentration, (ii) on transferenceto buffer containing non-radioactive DCPA up to 90 per centof the radioactivity is exchangeable, (iii) the temperaturecoefficients for the rates of net influx and efflux range from1.2 to 1.4. During the second phase, the net rates of uptakeare curvilinearly related to concentration, the temperaturequotients are higher and the rates of efflux markedly lowerthan in the first phase. Phenylmercuric nitrate and cupric sulphateat 5x10^–6 M halve the net rate of uptake but higher concentrationsare demanded for dinitrophenol, arsenite, aside, and iodoacetate.The depression induced by phenylmercuric nitrate can to somedegree be reversed by the addition of either glutathione orcysteine. For pyruvic acid to halve the rate of uptake of DCPA,it requires more than a three hundredfold greater concentration.It is postulated that in the second phase, uptake is mediatedby metabolic processes involving thiol groups. The ability ofcalcium pantothenate and ß-alanine to reverse theinhibitory effects of DCPA on the growth of L. minor were investigatedin multifactorial experiments. Over a narrow range of concentrations,calcium pantothenate partially offset the inhibitions of growthbut the interactions for ß-alanine were not significant.These results do not support the view that the primary actionof DCPA is to interfere with the biosynthesis of Co-enzyme A.In a comparison of the maximal capacity of different speciesto accumulate DCPA in their roots, up to a six-fold differencewas recorded in the eight species examined. On the basis ofthese findings, the mechanisms determining selective actionand the inhibition of meristematic activity are discussed.     

A derivative of amiloride blocks both the light-regulated and cyclic GMP-regulated conductances in rod photoreceptors

Vertebrate rod photoreceptors in the dark maintain an inward current across the outer segment membrane. The photoresponse results from a light-induced suppression of this dark current. The light-regulated current is not sensitive to either tetrodotoxin or amiloride, potent blockers of Na+ channels. Here, we report that a derivative of amiloride, 3',4'-dichlorobenzamil (DCPA), completely suppresses the dark current and light response recorded from rod photoreceptors. DCPA also blocks a cyclic GMP-activated current in excised patches of rod plasma membrane and a cGMP-induced Ca++ flux from rod disk membranes. These results are consistent with the notion that the Ca++ flux mechanism in the disk membrane and the light-regulated conductance in the plasma membrane are identical. DCPA also inhibits the Na/Ca exchange mechanism in intact rods, but at a 5-10-fold-higher concentration than is required to block the cGMP-activated flux and current. The blocking action of DCPA in 10 nM Ca++ is different from that in 1 mM Ca++, which suggests either that the conductance state of the light-regulated channel may be modified in high and low concentrations of Ca++, or that there may be two ionic channels in the rod outer segment membrane.     

The impact of dilute sulfuric acid on the selectivity of xylooligomer depolymerization to monomers

The disappearance of xylose and xylooligosaccharides with degrees of polymerization (DP) ranging from 2 to 5 was followed at 160 degrees C with sulfuric acid added to adjust the pH from near neutral to 1.45, and the impact on the yields of lower DP xylooligomers and xylose monomer was determined. In addition, the experimental data for the disappearance of these xylooligomers was kinetically modeled assuming first-order reaction kinetics for xylose degradation and xylooligomer hydrolysis to evaluate how the pH affected the selectivity of monomer formation from xylooligomers and direct oligomer degradation to unknown products. The yield of xylose from xylooligomers increased appreciably with increasing acid concentration but decreased with increasing xylooligomer DP at a given acid concentration, resulting in more acid being required to realize the same xylose yields for higher DP species. For example, the maximum xylose yields were 49.6%, 28.0%, 13.2% and 3.2% for DP values of 2, 3, 4, and 5, respectively, at pH 4.75. Kinetic modeling revealed that all the xylooligomers disappeared at a higher rate compared to xylose monomer and the disappearance rate constant increased with DP at all pH. The kinetics for lower DP oligomers of 2 and 3 showed that these species directly degrade to unknown compounds in the absence of acid. On the other hand, higher oligomers of DP 4 and 5 exhibited negligible losses to degradation products at all pH. Therefore, only xylooligomers of DP 2 and 3 were found to directly degrade to undesired products in the absence of acid, but more work is needed to determine how higher DP species behave. This study also revealed that the source of water and the material used for the construction of the reactor impacted xylose degradation kinetics.     

Selective medium for isolation of Fusarium species and dematiaceous hyphomycetes from cereals.

A selective medium containing 2 micrograms of dichloran per ml, 200 micrograms of chloramphenicol per ml, and 1.5% bacteriological peptone was developed for the isolation of Fusarium species and dematiaceous hyphomycetes from cereals. The medium, designated DCPA, was shown to select against species of Aspergillus, Penicillium, Cladosporium, and mucoraceous fungi. DCPA was evaluated for use as an enumeration medium and compared satisfactorily with dichloran-rose bengal-chloramphenicol agar when both media were tested with a range of cereal samples. Fusarium species and dematiaceous hyphomycetes produced well-formed colonies with good conidial production on DCPA, permitting rapid identification of such isolates on this medium.     

Hydrolytic degradation of ricinoleic-sebacic-ester-anhydride copolymers

The degradation process of poly(ricinoleic-co-sebacic-ester-anhydride)s in buffer solution was investigated by following the composition of the degradation products released into the degradation medium and the degraded polymer. The first week of degradation was characterized by the hydrolysis of the anhydride bonds and significant release of sebacic acid (SA). The remaining oligoesters of SA and ricinoleic acid (RA) degraded into shorter oligoesters composed of RA ester dimers, trimers, and tetramers as well as dimers of RA-SA. To confirm and determine the hydrolytic behavior of the degradation products, short oligoesters of sebacic and ricinoleic acid were synthesized and degraded. It was established that during the hydrolysis under physiological conditions the degradation products have a composition and water absorption similar to those of the synthesized oligoesters.     

Characterization and comparison of leuprolide degradation profiles in water and dimethyl sulfoxide.

The effect of solvent on the rate of leuprolide degradation and on the structure of the degradation products was explored. Leuprolide solutions (370 mg/mL) were prepared in water and dimethyl sulfoxide (DMSO) for delivery in DUROS osmotic implants. Both solvent systems demonstrated better than 90% stability after 1 year at 37 degrees C, where the DMSO formulation afforded better stability than the aqueous formulation and was used in subsequent clinical trials. The rate of leuprolide degradation in DMSO was also observed to accelerate with increasing moisture content, indicating that the aprotic solvent minimized chemical degradation. Interestingly, leuprolide degradation products varied with formulation vehicle. The proportions of leuprolide degradation products observed to form in water and DMSO at 37 degrees C were hydrolysis > aggregation > isomerization > oxidation and aggregation > oxidation > hydrolysis > isomerization, respectively. Specifically, more N-terminal hydrolysis and acetylation were observed under aqueous conditions, and increased Trp oxidation and Ser beta-elimination were seen under non-aqueous conditions. Furthermore, the major chemical degradation pathway changed with temperature in the DMSO formulation (decreasing oxidation with increasing temperature), but not in the aqueous formulation.     

Effect of Fe(III) on 1,1,2,2-Tetrachloroethane Degradation and Vinyl Chloride Accumulation in Wetland Sediments of the Aberdeen Proving Ground

1,1,2,2-Tetrachloroethane (TeCA) contaminated groundwater at the Aberdeen Proving Ground discharges through an anaerobic wetland in West Branch Canal Creek (MD), where dechlorination occurs. Two microbially mediated pathways, dichloroelimination and hydrogenolysis, account for most of the TeCA degradation at this site. The dichloroelimination pathways lead to the formation of vinyl chloride (VC), a recalcitrant carcinogen of great concern. The goal of this investigation was to determine whether microbially-available Fe(III) in the wetland surface sediment influenced the fate of TeCA and its daughter products. Differences were identified in the TeCA degradation pathway between microcosms treated with amorphous ferric oxyhydroxide (AFO-treated) and untreated (no AFO) microcosms. TeCA degradation was accompanied by a lower accumulation of VC in AFO-treated microcosms than untreated microcosms. The microcosm incubations and subsequent experiments with the microcosm materials showed that AFO treatment resulted in lower production of VC by (1) shifting TeCA degradation from dichloroelimination pathways to production of a greater proportion of chlorinated ethane products, and (2) decreasing the microbial capability to produce VC from 1,2-dichloroethene (DCE). VC degradation was not stimulated in the presence of Fe(III). Rather, VC degradation occurred readily under methanogenic conditions and was inhibited under Fe(III)-reducing conditions.     

Degradation kinetics of the main carbohydrates in birch wood during hot water extraction in a batch reactor at elevated temperatures

Hot water extraction of wood at elevated temperatures may be a suitable method to produce hemicellulose-lean pulps and to recover xylan-derived products from the water extract. In this study, water extractions of birch wood were conducted at temperatures between 180 and 240 °C in a batch reactor. Xylan was extensively removed, whereas cellulose was partly degraded only at temperatures above 180 °C. Under severe extraction conditions, acetic acid content in the water extract was higher than the corresponding amount of acetyl groups in wood. In addition to oligo- and monosaccharides, considerable amounts of furfural and 5-hydroxymethylfurfural (HMF) were recovered from the extracts. After reaching a maximum, the furfural yield remained constant with increasing extraction time. This maximum slightly decreased with increasing extraction temperature, suggesting the preferential formation of secondary degradation products from xylose. Kinetic models fitting experimental data are proposed to explain degradation and conversion reactions of xylan and glucan.     

Stability of the Transthyretin Molecule as a Key Factor in the Interaction with A-Beta Peptide - Relevance in Alzheimer's Disease

Transthyretin (TTR) protects against A-Beta toxicity by binding the peptide thus inhibiting its aggregation. Previous work showed different TTR mutations interact differently with A-Beta, with increasing affinities correlating with decreasing amyloidogenecity of the TTR mutant; this did not impact on the levels of inhibition of A-Beta aggregation, as assessed by transmission electron microscopy. Our work aimed at probing differences in binding to A-Beta by WT, T119M and L55P TTR using quantitative assays, and at identifying factors affecting this interaction. We addressed the impact of such factors in TTR ability to degrade A-Beta. Using a dot blot approach with the anti-oligomeric antibody A11, we showed that A-Beta formed oligomers transiently, indicating aggregation and fibril formation, whereas in the presence of WT and T119M TTR the oligomers persisted longer, indicative that these variants avoided further aggregation into fibrils. In contrast, L55PTTR was not able to inhibit oligomerization or to prevent evolution to aggregates and fibrils. Furthermore, apoptosis assessment showed WT and T119M TTR were able to protect against A-Beta toxicity. Because the amyloidogenic potential of TTR is inversely correlated with its stability, the use of drugs able to stabilize TTR tetrameric fold could result in increased TTR/A-Beta binding. Here we showed that iododiflunisal, 3-dinitrophenol, resveratrol, [2-(3,5-dichlorophenyl)amino] (DCPA) and [4-(3,5-difluorophenyl)] (DFPB) were able to increase TTR binding to A-Beta; however only DCPA and DFPB improved TTR proteolytic activity. Thyroxine, a TTR ligand, did not influence TTR/A-Beta interaction and A-Beta degradation by TTR, whereas RBP, another TTR ligand, not only obstructed the interaction but also inhibited TTR proteolytic activity. Our results showed differences between WT and T119M TTR, and L55PTTR mutant regarding their interaction with A-Beta and prompt the stability of TTR as a key factor in this interaction, which may be relevant in AD pathogenesis and for the design of therapeutic TTR-based therapies.     

Application of the Kinetic Triplets and Geometrical Characteristics of Thermal Analysis Curves in Identifying the Main Bioactive Compounds (BC) that Govern the Thermal and Thermo-Oxidative Degradation Mechanism of <Emphasis Type="Italic">Aronia melanocarpa</Emphasis> (Black Chokeberry)

Thermal and thermo-oxidative kinetics of Aronia melanocarpa fresh samples was investigated. The current investigation was based on the application of kinetic triplets and geometrical characteristics of thermal analysis curves in identifying the main bioactive compounds that govern the thermal and thermo-oxidative degradation mechanisms. From established kinetic model in an argon atmosphere, it was found that released products arise from decomposition of phenolic compounds where autocatalysis may occurs from the inevitable presence of water already in the early stages of the process through the hydrolysis reaction pathway. In the case of thermo-oxidative degradation, it was found that the main mechanistic scheme can be presented with two different forms of reaction mechanism function, such as: nth order reaction model (with n > 1) (in lower heating mode) and ?esták-Berggren autocatalytic model (in higher heating mode). Isoconversional analysis has been shown that neochlorogenic acid represents the governed bioactive compound which has a strong hydrogen-donating activity. Based on the mechanistic conclusions, it was established that in an air atmosphere, the cyanidin-3-glucosylrutinoside (Cy-3-GR) degradation significantly participates in overall complex mechanism.     

Impact of the longitudinal and seasonal changes of the water quality on the benthic macroinvertebrate assemblages of the Andorran streams

The ecological quality of the Andorran streams was assessed in 1998-1999, based on the survey of the water chemistry and the benthic macroinvertebrate assemblages. Two types of modification of the water quality were observed in the Andorran rivers: (i) a progressive degradation along the longitudinal gradient with a chronic degradation in the lower water courses; (ii) a seasonal modification in the mid-elevation sites. Two responses of the benthic macroinvertebrate assemblages to these disturbances were observed: an extreme simplification of the composition and a change of the trophic structure of the assemblages in the more impacted sites.     

Customizing the hydrolytic degradation rate of stereocomplex PLA through different PDLA architectures

Stereocomplexation of poly(L-lactide) (PLLA) with star shaped D-lactic acid (D-LA) oligomers with different architectures and end-groups clearly altered the degradation rate and affected the degradation product patterns. Altogether, nine materials were studied: standard PLLA and eight blends of PLLA with either 30 or 50 wt % of four different D-LA oligomers. The influence of several factors, including temperature, degradation time, and amount and type of D-LA oligomer, on the hydrolytic degradation process was investigated using a fractional factorial experimental design. Stereocomplexes containing star shaped D-LA oligomers with four alcoholic end-groups underwent a rather slow hydrolytic degradation with low release of degradation products. Materials with linear D-LA oligomers exhibited similar mass loss but released higher concentrations of shorter acidic degradation products. Increasing the fraction of D-LA oligomers with a linear structure or with four alcoholic end-groups resulted in slower mass loss due to higher degree of stereocomplexation. The opposite results were obtained after addition of D-LA oligomers with carboxylic chain-ends. These materials demonstrated lower degree of stereocomplexation and larger mass and molar mass loss, and also the release of degradation products increased. Increasing the number of alcoholic chain-ends from four to six decreased the degree of stereocomplexation, leading to faster mass loss. The degree of stereocomplexation and degradation rate were customized by changing the architecture and end-groups of the D-LA oligomers.