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1.
The reactions of captan, folpet, and thiophosgene with calf thymus histones and total rat liver histones were investigated. The binding of radioactivity from [35S]captan or [14C]folpet and changes in polyacrylamide gel patterns of captan-treated calf thymus histones were pH dependent. At pH 7.5, gel patterns of captan-treated histones were not different from those of non-treated histones; whereas, at pH 9.0 the Amido Schwartz-staining bands of captan- and thiophosgene-treated histones in polyacrylamide gels were characterized by band diffusion, loss of staining definition, band migration, and aggregate formation. Nearly equal amounts of radio-activity from [14C]folpet and [35S]captan were bound to lysine-rich histones at pH 9.0, while at pH 7.5 there was little binding of radioactivity to the proteins. Approximately equal amounts of radioactivity were removed from histones in the presence of the low-molecular-weight thiol, dithiothreitol. Reconstitution experiments using captan-treated lysine-rich histones and non-treated calf thymus DNA yielded less stable complexes, as well as smaller nucleohistone-nucleohistone complexes. These data suggest that the intact molecule binds to deprotonated sites on the lysine-rich histones. This binding causes changes in the configuration of the protein molecule which alters the ability of nuclear histones to stabilize DNA structure.  相似文献   

2.
The reactions of chlorothalonil with calf thymus histones, DNA, and isolated rat liver nuclei were studied utilizing labeled fungicide, polyacrylamide gel electrophoresis, and nucleohistone thermal denaturation. The reaction was dependent on pH, type of histones, and the histone and fungicide concentrations. In addition, two types of fungicide-histone binding patterns were observed. These patterns were characterized by the amount of label bound to protein after dialysis or after dialysis and acid precipitation. There was little binding of chlorothalonil to DNA. Polyacrylamide gel patterns of treated lysine-rich calf thymus histones were characterized by a loss of up to 80% of the stained protein without a change in the migration of the bands. Gel patterns of treated calf thymus whole histones were characterized by small variations in band density and minor loss of stained protein. The results of thermal denaturation experiments using chlorothalonil-treated lysine-rich histones and nontreated calf thymus DNA were not different from those using nontreated histones. Almost all of the radioactivity from [14C]chlorothalonil was bound by isolated rat liver nuclei. The binding patterns observed with rat liver nuclei were very similar to those using purified histones. Fractionation of proteins from treated nuclei revealed that the label was unequally distributed between the nuclear sap protein, ribonucleoprotein, and deoxyribonucleoprotein.  相似文献   

3.
The effects on DNA synthesis of the fungicide captan and several structurally related compounds were investigated in isolated bovine liver nuclei. Captan, folpet, captafol, and trichloromethanesulfenyl chloride inhibited DNA synthesis to the same degree with ID50 values of approximately 50 μM in a 40-min assay. The inhibition is concentration dependent and the degree of inhibition increases with time. Studies with structural analogs of captan indicated that inhibition of DNA synthesis by captan is mediated through the trichloromethylthio moiety of the captan molecule. In addition, the data indicate thiophosgene is probably not the toxic species involved in the inhibition of DNA synthesis. The isolated nuclei used in this study were shown to exhibit only a single DNA polymerase activity which was determined to be of the β or low-molecular-weight type. In addition to its inhibition in intact nuclei, captan inhibited the activity of the β polymerase in nuclear extracts as well as in partially purified enzyme preparations. These results indicate that captan inhibits DNA synthesis in our preparation of isolated nuclei by acting directly on the DNA polymerase-catalyzed reaction rather than by causing a nonspecific or indirect effect in the nuclear system such as alterations in the nuclear membrane or aggregation of the nuclei. The site of captan's inhibitory action is the DNA polymerase molecule. The interaction of captan with the polymerase results in irreversible inhibition of the enzyme. Interaction of captan with the template, if it occurs, does not appear to be involved in mediating the inhibition.  相似文献   

4.
A study was conducted concerning the inhibition of calf thymus nuclear DNA synthesis by captan. Captan was shown to be toxic to the in vitro incorporation of [3H]dTTP into calf thymus DNA, with an ID50 value of 0.16 mM being measured. This inhibition was determined to be independent of Mg2+ concentration. Although intact nuclear activities were affected, the soluble DNA polymerizing activity isolated from calf thymus nuclei exhibited no inhibition when exposed to captan. Treatment of purified calf thymus DNA with 10?5 and 10?4M captan caused an elevation of the Tm by 2 and 6°C, respectively. The inhibitory characteristic of captan on DNA polymerizing activities and the influence of this compound on the thermostability of DNA indicate a mechanism of inhibition which is located in the nucleus and is possibly related to the template function of DNA and/or with the nuclear DNA polymerizing enzymes.  相似文献   

5.
Ring- and carboxyl-labelled [14C]2,4-D were incubated under laboratory conditions, at the 2 g/g level, in a heavy clay, sandy loam, and clay loam at 85% of field capacity and 20 1C. The soils were extracted at regular intervals for 35 days with aqaeous acidic acetonitrile, and analysed for [14C]2,4-D and possible radioactive degradation products. Following solvent extraction, a portion of the soil residues were combusted in oxygen to determine unextracted radioactivity as [14C]carbon dioxide. The remaining soil residues were then treated with aqueous sodium hydroxide, and the radioactivity associated with the fulvic and humic soil components determined. In all soils there was a rapid decrease in the amounts of extractable radioacitivity, with only 5% of that applied being recoverable after 35 days. All recoverable radioactivity was attributable to [14C]2,4-D, and no [14C]-containing degradation products were observed. This loss of extractable radioactivity was accompanied by an increase in non-extractable radioactivity. Approximately 15% of the applied radioactivity, derived from carboxyl-labelled [14C]2,4-D, and 30% from the ring-labelled [14C]2,4-D was associated with the soil in a non-extractable form, after 35 days of incubation. After 35 days, less than 5% of the radioactivity from the carboxyl-labelled herbicide, and less than 10% of the ringlabelled material, was associated with the fulvic components derived from the three soils. Less than 5% of the applied radioactivities were identifiable with any of the humic acid components. It was considered that during the incubation [14C]2,4-D did not become bound or conjugated to soil components, and that non-extractable radioactivity associated with the three soil types resulted from incorporation of radioactive degradation products, such as [14C]carbon dioxide, into soil organic matter.  相似文献   

6.
A method is described for the simultaneous determination of residues of five fungicides used for foliar treatment of apple and pear trees, and for postharvest application. After extraction, the mixture of these fungicides is cleaned-up on a ‘SEP PAK C18’ cartridge and the components determined by gas-liquid chromatography with electron-capture detection. The minimum detectable amounts in apples and pears, on a fresh weight basis, were 0.005mg kg−1 for vinclozolin, 0.010mg kg−1 for captan, folpet and iprodione, and 0.020 mg kg−1 for captafol. The percentage recovery for each fungicide (calculated by analysing four samples of untreated apples and pears, to which varying concentrations of each active ingredient had been added) varied for vinclozolin between 70.0 and 89.2, for captan between 72.0 and 83.8, for folpet between 73.0 and 93.0, for captafol between 70.8 and 91.8, and for iprodione between 75.1 and 97.1.  相似文献   

7.
Captan, folpet, and perchloromethylmercaptan were effective inhibitors of Penicillium duponti p-nitrophenylpropionate esterase activity (I50 = 0.5 – 2 μM) whereas α-naphthyl acetate esterase activity was not affected by the presence of these compounds. Captan and folpet are both equally effective at pH 7.3 and 8.3. The ionic composition of the medium had strong effects on the degree of inhibition produced by all inhibitors but did not alter esterase activity. Neither succinamide nor phthalimide caused inhibition of the p-nitrophenylpropionate esterase activity: The trichloromethylmercaptan portion of these fungicides appears to be responsible for the observed inhibition. The rapidity of captan and folpet inhibition of esterase activity (complete in < 1 min) compared to the rates of spontaneous decomposition (t12 > 1 min) and the insensitivity of captan and folpet inhibition to hydrogen ion concentration suggest that generation of spontaneous decomposition products is not required for inhibition. The results are consistent with a mechanism in which the entire fungicide molecule binds to the protein followed by enzyme-promoted reactions of captan and folpet which result in loss of esterase activity.  相似文献   

8.
A single oral dose of 0.14 mg kg?1 of [14C] flocoumafen to rat, which gave a transient, non-lethal, effect, was rapidly absorbed, radioactivity appearing in the blood maximally at 4 h and falling to half maximum value by 8 h. The maximum effect on prothrombin time was at 24 h and the value returned to normal by 48 h. Elimination of radioactivity was very slow, with less than 0.5% of the dose in the urine up to 7 days after dosing, and 23-26% in the faeces (more than half of which appeared in the first 24 h). Most of the administered radioactivity (74-76%) was retained 7 days after dosing. Approximately half of the dose was in the liver; it was eliminated with a halflife of 220 days. At 48 h after dosing, most of the hepatic radioactivity comprised unchanged flocoumafen. Treatments of flocoumafen-dosed rats with warfarin or with cytochrome P450-inducing doses of phenobarbitone were without effect on the hepatic residue of flocoumafen.  相似文献   

9.
The tissue distribution and excretion of 14C-labeled propham and chlorpropham were investigated in the adult female rat after a single oral dosage. The average 3-day urinary excretions of radioactivity were 55.9%, 82.6%, 79.5%, and 85.4% of an oral dose of chain [14C] chlorpropham, ring [14C] chlorpropham, chain [14C] propham, and ring [14C] propham, respectively. With chain [14C] chlorpropham 35.4 ± 7.5% of the administered radioactivity appeared in the respired air, whereas only 5.0 ± 0.8% was found in CO2 from chain [14C] propham. There was no significant difference in the rate of excretion or the route of elimination among rats receiving different oral dosages, ranging from less than 4 mg/kg to 200 mg/kg. The radioactivity was distributed in all tissues with highest concentration found in the kidney. The average biological half-life of 14C from chlorpropham and propham in most organs was short, ranging between 3 and 8 hr; however, in brain, fat, and muscle, the half-life was about twice the value for other organs.Both compounds were metabolized by hydrolytic and oxidative mechanisms and the resulting metabolites were excreted either as free forms or as conjugates.Subcellular distribution of 14C in the rat liver and kidney after an oral administration of chlorpropham and propham was investigated. The percentage distribution of 14C in the particulate and soluble fractions was dependent on the elapsed time after dosing.  相似文献   

10.
Addition of cysteine to the fungicides captan, folpet, dichlofluanid and captafol antagonizes the activity of these fungicides and results in the formation of volatile fungitoxicants. There is no relationship, however, between the vapour action upon reaction with cysteine and the fungitoxicity of these compounds.Samenvatting Cysteine heeft een antagonerend effect op de werking van captan, folpet, dichlofluanid en captafol (Tabel 1). Bij proeven in afgesloten ruimtes (twee petri schaaltjes, waarvan de één ongekeerd op de ander, Fig. 1) bleek vooral captan als gevolg van een reactie met cysteine een voorFusarium culmorum toxische damp af te geven, folpet deed dit daarentegen niet, en de twee andere fungiciden alleen in de hoogste concentratie (Tabel 1, Fig. 1). Er is dus weinig verband tussen de fungicide werking en de productie van fungicide dampen als gevolg van de reactie met thiolen.  相似文献   

11.
The fate of the di-n-butylaminosulfenyl moiety in 2,3-dihydro-2,2-dimethyl-7-benzofuranyl (di-n-butylaminosulfenyl)(methyl)carbamate (DBSC or Marshal) was studied in the cotton plant at 1, 3, 6, and 10 days following foliage treatment with [di-n-butylamino-14C]DBSC. Dibutylamine and two major radioactive metabolites were obtained following extraction of the plant tissue with a methanol-buffer containing N-ethylmaleimide (NEM), a sulfhydryl scavenger which was added to prevent the cleavage of the NS bond during the workup procedure. The most adundant radioactive material recovered from plants was identified as a product arising from the reaction between NEM and dibutylamine. Extraction of plant tissue with straight methanol-buffer solution or with methol-buffer containing other sulfhydryl scavengers resulted in 57–86% of the applied radioactivity being recovered as dibutylamine in the organosoluble fraction. When [14C]dibutylamine was applied to cotton leaves, most of the radioactivity, i.e., 96% of the total recovered radioactivity, was found in the organosoluble fraction as dibutylamine. Dibutylamine is the major metabolite of [di-n-butylamino-14C]DBSC in the cotton plant.  相似文献   

12.
The effects of two pesticides, dieldrin and captan, upon the growth and macromolecular syntheses of the vegetative cells of Dictyostelium discoideum strain Ax-2 were investigated. Dieldrin at a concentration of 5 μg/ml inhibited growth as well as the synthesis of RNA, DNA, and protein, while as little as 1 μg/ml of captan produced the same effects. After a 1-hr exposure to either pesticide, all macromolecular syntheses ceased. Within a period of 5 to 10 hr the amoebae began to shrink, and eventually some lysis occurred. Lysis was most pronounced in cells incubated with captan. When the amoebae were grown in the presence of 5 μg/ml of either pesticide and then washed and resuspended in fresh medium, the effects on growth were annulled. No growth inhibition was observed when 0.05 M cysteine was added prior to the addition of 5 μg/ml of captan. Further experimentation to study possible degradation effects of these two synthetic pesticides upon RNA and protein molecules showed that breakdown of these macromolecules into TCA-soluble units did not occur. Preliminary studies have also shown that [2-14C]uracil and [14C]amino acids are taken up in their respective pools in the presence of captan or dieldrin.  相似文献   

13.
Toxicity tests revealed up to 40-fold resistance to a number of cyclodiene insecticides in a laboratory-reared, cyclodiene-resistant (CYW) housefly strain (Musca domestica L.). Using [35S] TBPS as a probe for convulsant sites in insects, saturable specific binding was detected in thorax and abdomen membranes prepared from housefly strains susceptible (CSMA) and resistant (CYW) to cyclodienes. Scatchard analysis of[35S] TBPS binding data to CSMA and CYW membranes failed to provide evidence for significant differences between the two strains in either the affinity (Kd) or density (Bmax) of saturable binding sites. For several polychlorocycloalkane insecticides, the ligand displacement profile of [35S] TBPS binding was almost identical for the CSMA and CYW houseflies. Therefore, using [35S] TBPS as a probe for convulsant sites, a 40-fold resistance to cyclodienes in the CYW housefly strain cannot be accounted for only in terms of alterations in TBPS binding sites.  相似文献   

14.
When [14C]F3-fluorodifen (2,4′-dinitro-4-trifluoromethyl diphenylether), carbonyl-[14C]CDAA (N,N-diallyl-2-chloroacetamide), and carbonyl-14C-propachlor (2-chloro-N-isopropylacetanilide) were fed to rats, 57 to 86% of the 14C was excreted via the urine within 48 hr. Although very little radioactivity was excreted in the feces of CDAA-treated rats, 15–22% of the 14C was excreted in the feces of propachlor- of fluorodifentreated rats and an average of 8% of the 14C remained in these rats 48 hr after treatment. Oxidation of the 14C label to [14C]O2 was not a major process in the metabolism of these herbicides. The only major radioactive metabolite present in the 24-h urine of fluorodifen-treated rats, 2-nitro-4-trifluoromethylphenyl mercapturic acid, accounted for 41% of the administered dose of 14C. In the metabolism of CDAA, the corresponding mercapturic acid accounted for 76% of the dose; it was the only major metabolite present in the 24-h urine. In contrast, three major metabolites were detected in the 24-h urine of propachlortreated rats, and the mercapturic acid accounted for only 20% of the dose. The mercapturic acid of each herbicide was identified by mass spectrometry.  相似文献   

15.
Dimethoate [O,O-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate] was oxidatively metabolized by primary human embryonic lung cells in culture. Over 95% of the recovered radioactivity after incubation with 14C-labeled dimethoate resulted from oxidative metabolites, with the remainder being water soluble. Thus, oxidative metabolism of dimethoate predominated over hydrolytic metabolism in the cell culture system, in contrast to the whole rat where the opposite is true. The sequence of reactions was similar to that found in rats. Dimethoate was desulfurated to yield dimethoxon and both compounds were N-demethylated. Metabolism of dimethoate in mouse fibroblast L-929 cell cultures revealed up to 35% of dimethoate carboxylic acid as the only compound other than dimethoate present.  相似文献   

16.
Sugar beet plants were grown in the field, after in-furrow application of [14C]- aldicarb (3 kg of aldicarb ha?1) at planting. The ripe sugar beet plants were harvested, and the roots were analysed. The roots were fractionated according to a procedure similar to the normal beet-sugar manufacturing process. Expressed as a proportion of the total radioactivity incorporated into the root, the pulp contained 29.7%, the lime cake 9.7%, the crystallised sugar 17.7% (which gave, with the radioactivity found in the sugar in the molasses, a total of 20.7% of the radioactivity in the total sugar), and the molasses, 42.9%. A part of the labelled carbon from the radio- active aldicarb and its metabolites had thus been metabolised and incorporated into sugar molecules. Except for the radioactivity in the sugar and in the lime cake from the processing, the proportion of radioactive non-conjugated organosoluble compounds was very low (2.6%), and perhaps partially corresponded to the very low amount of aldoxycarb (aldicarb sulphone) in the root (less than 0.001 mg of [14C]-aldicarb equivalents kg?1 fresh weight). Hydrolysis of the molasses yielded free radioactive 2-methyl-2-(methylsulphinyl)propan-1-ol (3.1%), 2-mesyl-2-methyl-propan-I-ol (8.9%) and 2-mesyl-2-methylpropionic acid (12.0%) which had been conjugated to plant constituents in the root. The corresponding concentrations (expressed as mg of [14C]aldicarb equivalents kg?1 fresh weight of root) were 0.004, 0.011, and 0.016, respectively. No aldicarb, aldicarb sulphoxide or aldoxycarb (nor the corresponding nitrile, generated from aldicarb during the fractionation procedure) was liberated by the hydrolysis, indicating the absence of conjugates of these compounds in the root.  相似文献   

17.
Phthalimide fungicides (captafol, captan and folpet) enhanced the accumulation of fenarimol by the mycelium of a wild-type strain and a fenarimol-resistant strain of Aspergillus nidulans. The accumulation is ascribed to inhibition of active efflux of fenarimol from the mycelium. It is assumed that the synergistic action observed between the phthalimide fungicides and fenarimol with respect to fungitoxicity, was caused by the increased accumulation of fenarimol.  相似文献   

18.
The disposition of the pyrethroid insecticide cypermethrin, (RS)-a-cyano-3-phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinly)-2, 2-dimethylcyclopropane-carboxylate, has been studied in male and female rats following a single toxic oral dose (200mg kg−1) of two radiolabelled forms ([14C-benzyl] and [14C-cyclopropyl]) of the insecticide. The bioaccumulation and elimination of 14C-benzyl-labelled cypermethrin, following repeated administration at a sub-toxic dose (2mg kg−1), has also been studied in male and female rats. Although, at the toxic dose, radioactivity from the two radiolabelled forms was rapidly eliminated in urine and faeces, the increased excretion in the faeces, over that for low doses, was evidence that absorption was incomplete. The major pathways of metabolism involved cleavage of the ester bond, with subsequent hydroxylation and glucuronidation of the cyclopropyl acid moieties, together with hydroxylation and sulphation of the 3-phenoxybenzyl moiety. The absence of sex- or dose-dependent changes was reflected by the constant proportions of these metabolites found in the urine. Constant levels of radioactivity in tissues were achieved rapidly, generally within the first week of repeated administration. Elimination was rapid on the cessation of dosing, although less rapid from the fat and skin. The material in the fat was mainly the cis-isomers of cypermethrin, which were eliminated with a mean half-life of 18.2 days, compared with 3.4 days for the trans-isomers.  相似文献   

19.
Comparisons were made between the amounts of abamectin and total radioactivity recovered from Spodoptera littoralis and Heliothis armigera larvae after topical application of [3H]abamectin. Penetration (as shown by wash-off experiments) did not differ significantly between the Spodoptera instars. Significantly more abamectin was recovered from ventral nerve cord samples of larvae showing symptoms of poisoning than from larvae not showing these symptoms. Fifth-instar S. littoralis larvae had a significantly lower proportion of radioactivity as abamectin in the ventral nerve cord than in sixth-instar S. littoralis or fifth- and sixth-instar H. armigera. The proportion of radioactivity present as abamectin (but not total radioactivity) was significantly increased when the fifth-instar S. littoralis larvae were pre-treated with piperonyl butoxide (PB) suggesting that the relative insensitivity of fifth-instar S. littoralis larvae to abamectin is due at least in part to greater metabolism, particularly by microsomal oxidases. Fat body samples consistently had a greater proportion of radioactivity as abamectin than the nerve cord and the former may act as storage sites for abamectin.  相似文献   

20.
The degradation of bis(tri[1-14C]butyltin) oxide in two soils (1 mg tin kg?1) has been studied under laboratory conditions. Half of the applied compound disappeared from unsterilised silt loam and sandy loam in approximately 15 and 20 weeks, respectively; it disappeared also from the sterilised soils but to a lesser extent. The formation of small amounts of dibutyltin derivatives was established by thin-layer chromatography both in the unsterilised and sterile soils. The amount of unextractable radioactivity increased with time in the unsterilised and sterile soils. In the unsterilised soils 14C was released as [14C]carbon dioxide in amounts equivalent to 20% of the applied radioactivity for silt loam and 10.7% for sandy loam over a period of 42 weeks. Almost no [14C]carbon dioxide was released from the sterile soils, confirming microbial participation in the degradation of the compound in the unsterilised soils.  相似文献   

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