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1.
A hydrophilic form of acetylcholinesterase (AChE) was purified from N-methyl carbamate susceptible (SA) and highly N-methyl carbamate-resistant (N3D) strains of the green rice leafhopper (GRLH), Nephotettix cincticeps Uhler. Both of purified AChE from SA and N3D strains displayed the highest activities toward acetylthiocholine (ATCh) at pH 8.5. In the SA strain, the optimum concentrations for ATCh, propionylthiocholine (PTCh), and butyrylthiocholine (BTCh) were about 1 × 10−3, 2.5 × 10−3, and 1 × 10−3 M, respectively. However, in the N3D strain, substrate inhibition was not identified for ATCh, PTCh, and BTCh to 1 × 10−2 M. The Km value in the SA strain was 51.1, 39.1, and 41.6 μM and that in the N3D strain was 91.8, 88.1, and 85.2 μM for ATCh, PTCh, and BTCh, respectively. The Km value in the N3D strain indicated about 1.80-, 2.25-, and 2.05-fold lower affinity than that of the SA strain for ATCh, PTCh, and BTCh, respectively. The Vmax value in the SA strain was 70.2, 30.5, and 4.6 U/mg protein and that in the N3D strain was 123.0, 27.0, and 14.5 U/mg protein for ATCh, PTCh, and BTCh, respectively. The Vmax value in the N3D strain was 1.75- and 3.15-fold higher for ATCh and BTCh than that in the N3D strain. However, it was 1.13-fold lower for PTCh. The increased activity of AChE in the N3D strain is due to the qualitatively modified enzyme with a higher catalytic efficiency. The bimolecular rate constant (ki) for propoxur was 27.1 × 104 and 0.51 × 104 M−1 min−1 in the SA and N3D strain and that for monocrotophos was 0.031 × 104 and 2.0 × 104 M−1 min−1 in the SA and N3D strain. AChE from the N3D strain was 53-fold less sensitive than SA strain to inhibition by propoxur. In contrast, AChE from the N3D strain was 65-fold more sensitive to inhibition by monocrotophos than AChE from the SA strain. This indicated negatively correlated cross-insensitivity of AChE to propoxur and monocrotophos.  相似文献   

2.
Potential genotoxicity of sulcotrione 2-(2-chloro-4-(methylsulfonyl)benzoyl)-1,3-cyclohexanedione, a selective triketonic herbicide was evaluated on Vicia faba seedlings in hydroponic culture conditions. Sulcotrione (10−5, 10−4 and 2 × 10−4 M) treatments for 45 h, caused a dose dependent increase in micronuclei frequencies in root meristematic cells. Cytological analysis of root tips cells showed aneugenic effects of the sulcotrione on the plant root meristems. Sulcotrione induced chromosomal alterations at the lowest concentration used (10−5 M) when incubated for 42 h, indicating the potent mutagenic effect of this element. This is the first report for the genotoxicity of such a sulcotrione herbicide.  相似文献   

3.
The in vitro inhibition potency of some organophosphates (OPs) and carbamates (CAs) which are widely used to control plant-parasitic nematodes on acetylcholinesterase (AChE) of Meloidogyne javanica, Heterodera avenae and Tylenchulus semipenetrans, the major pathogens responsible for the damage of a wide range of crops in Al-Qassim region, Saudi Arabia was examined. AChE of H. avenae activity was 1.58- and 1.51-fold greater than that of T. semipenetrans or M. javanica, respectively. The order of inhibition potency of the tested compounds against T. semipenetrans AChE was: carbofuran > paraoxon > oxamyl > fenamiphos > phorate-sulfoxide > aldicarb, where the corresponding concentrations that inhibited 50% of the nematode AChE activity (I50) were 5 × 10−8, 7 × 10−7, 7.5 × 10−7, 2 × 10−6, 2 × 10−4 and 2 × 10−3 M, respectively. Paraoxon, fenamiphos and carbofuran exhibited high inhibition potency against M. javanica AChE where the I50 values were below 1 nM. Phorate-sulfoxide and aldicarb were potent inhibitors of M. javanica AChE with I50 values of 3.8 and 8 nM, respectively, while oxamyl exhibited low inhibition potency with I50 of 15 nM. Fenamiphos and paraoxon showed the highest I50 values of <100 μM against H. avenae followed by oxamyl (I50 < 1 mM), whereas paraoxon, carbofuran and aldicarb showed low potency with I50 values >1 mM. All the tested compounds exhibited high inhibition potency to AChE of M. javanica than T. semipenetrans or H. avenae. Except phorate-sulfoxide in M. javanica the inhibition pattern and implied mechanism for all the tested compounds for the three nematodes is suggested to be a linear mixed type (a combination of competitive and non-completive type).  相似文献   

4.
In the present study cytogenetic effects of atrazine herbicide, were examined on the root meristem cells of Allium cepa and Vicia faba. Test concentrations were chosen by calculating EC50 values of formulated atrazine against both the test systems which determined to be 30 mg l−1 for A. cepa and 35 mg l−1 for V. faba, respectively. For cytogenetic effects root meristem cells of A. cepa were exposed to 15, 30 or 60 mg l−1 whereas V. faba to 17.5, 35 or 70 mg l−1 for 4 or 24 h. Roots exposed for 4 or 24 h, after sampling, were left in water for 24 h recovery and sampled at 24 h post-exposure. A set of onion bulbs or seedlings of V. faba exposed to DMSO (0.3%) was run parallel for negative control. Treatment of atrazine significantly and dose-dependently inhibited the mitotic index (MI) and induced micronucleus formation (MN) chromosome aberrations (CA) and mitotic aberrations (MA) in both the test systems at 4 or 24 h. Root meristem cells examined at 24 h post-exposure also revealed significant (p < 0.001) frequencies of MN, CA or MA despite considerable decline. Chromosome breaks and fragments were found to be major CA whereas C-metaphase, chromosome bridges and laggards were prevalent MA. Results of our study, indicate that atrazine may produce genotoxic effects in plants. Further, both the plant bioassays found to be sensitive indicators for the genotoxicity assessment as the outcome of majority of in vivo/in vitro mammalian tests are comparable.  相似文献   

5.
The present study was conducted to determine the 96 h-LC50 of benomyl to the Nile tilapia, Oreochromis niloticus and to investigate the biochemical or hematological indices of blood and the alterations in the antioxidant enzymes of this fish in response to sublethal concentrations of benomyl. Fish weighing 71.61 ± 12.05 g were used in this study; they were subjected to fasting for 4 weeks before treatment. An aqueous solution of benomyl (0, 0.5, 1, 2, 4, 8, and 16 mg L−1) was administered for 96 h to determine the LC50. The 96 h-LC50 value of benomyl was 4.39 (3.23-5.60) mg L−1 in the present study. For 5 weeks, the aqueous solution of benomyl (0, 100, 200, and 400 μg L−1) was administered to investigate its effect on the hematological parameters and antioxidant enzymes. The predominant hematological findings in fish exposed to benomyl were as follows: no significant change in the Hb (g dL−1) level, MCV (μm3), MCH (pg) and MCHC (%) as compared to the control. Benomyl exposure led to greater increases in the GPT, GOT (Karmen-unit), LDH (Wroblewski unit), total cholesterol, Fe, and Ca (mg dL−1) values, whereas the levels of ALP (KA unit), total protein, triglyceride, albumin, and Mg (mg dL−1) did not increase. Benomyl increased the in vivo HSI (%), GST (nmol min−1 mg protein−1), and SOD (U mg protein−1) values in the fish livers in the test group, unlike those in the control group for 5 weeks. At concentrations higher than 100 μg L−1, benomyl affected the GST and SOD levels of Nile tilapia in a dose- and time-dependent manner. The present findings suggest that the in vivo hepatotoxicity associated with benomyl may, in part, result from the hematological index, and antioxidants may provide limited protection against benomyl toxicity.  相似文献   

6.
The continuous increase in the number of new chemicals as well as the discharges of solid and liquid wastes triggered the need for simple and inexpensive bioassays for routine testing. In recent years, there has been increasing development of methods (particularly rapid tests) for testing environmental samples. This paper describes the quick toxic evaluation of an organophosphorus insecticide, acephate (O,S-dimethyl acetylphosphoramidothioate) on Paramecium caudatum for acute and sub-acute toxicity studies with reference to morphology, behaviour, and its generation time. The lethal concentrations for 10 min and 2 h were determined by probit method, as 500 mg L−1 and 300 mg L−1, respectively. Higher concentrations of 10 min exposure caused cell lysis with disintegration of cell membrane and precipitation of protoplasm. Combination of conventional light microscopy and computerized video tracking systems were used to study the locomotor behaviour of paramecia. The test organism was under stress and exhibited an initial increase and subsequent decrease in the swimming speed when exposed to 1/4, 1/2, 3/4, and LC50 concentrations for 10 min (125, 250, 375, and 500 mg L−1, respectively). Similar changes were also noticed when paramecia were exposed to LC50 for 2 h. In a separate set of experiments, the number of generations and generation time in 24 h was evaluated with respect to the different sub-lethal concentrations (30, 60, 120, and 240 mg L−1). The number of generations decreased and generation time extended significantly in a concentration dependent manner. The results indicate that the Paramecium toxicity assay could be used as a complimentary system to rapidly elucidate the cytotoxic potential of insecticides. The major advantages associated with these tests are: they are inexpensive, simple, user-friendly, space saving, and seem to be attractive alternatives to conventional bioassays.  相似文献   

7.
Multiwalled carbon nanotubes-polymeric methyl red film modified electrode (MWNT-PMRE) was made. The electrochemical behavior of carbendazim on modified electrode was studied with Cyclic Voltammetry, Linear Sweep Voltammetry, Stable Polarization Method and Chronocoulometry. The results indicated that the electrical oxidation of carbendazim on MWNT-PMRE in H2SO4 supporting electrolyte with concentration of 0.6 mol/L was irreversible and was mainly controlled by diffusion. Some parameters of the electrochemical process were evaluated. The impacts of experiment conditions on the electrochemical behavior of carbendazim were studied. A good linearity relationship between peak current and concentration of carbendazim in the range of 2.0 × 10−7-1.0 × 10−5 mol/L was found, of which the equation was Ip(A) = −1.149 × 10−5 − 2.301c (mol/L), the correlative coefficient R = −0.9953 and detection limit was 9.0 × 10−9 mol/L. The recovery was between 90.3% and 94.7%.  相似文献   

8.
Effects of deltamethrin on voltage-sensitive calcium channels (VSCC) from rat brain (Cav2.2) expressed in Xenopus oocytes were assessed electrophysiologically. Deltamethrin reduced peak current of wild-type Cav2.2 in a stereospecific and concentration-dependent manner with an EC50 of 1 × 10−9 M. Phosphorylation of threonine 422 enhances voltage-sensitive calcium current, increases the probability that Cav2.2 will open under depolarizing conditions and antagonizes the inhibition of the channel by the betagamma subunit of heterotrimeric G-protein (Gβγ). Site-directed mutagenesis of threonine 422 to glutamic acid (T422E) results in a channel that acts as if it were permanently phosphorylated. Deltamethrin (10−7 M) significantly enhanced peak current via the T422E channel (1.5-fold) compared to the nontreated control and the increase was significantly greater than for either the wild-type (T422) or T422A (permanently unphosphorylated mutant) channels. The effect of deltamethrin on T422E Cav2.2 was stereospecific and concentration-dependent with an EC50 of 9.8 × 10−11 M. Thus, Cav2.2 is modified by deltamethrin but the resulting perturbation is dependent upon the phosphorylation state of threonine 422.  相似文献   

9.
Recovery study was performed at regular intervals to establish the time course of 50% and 100% recovery in neurotransmitter enzyme (acetylcholinesterase, AChE, EC 3.1.1.7) and locomotor behaviour response of mosquito fish, Gambusia affinis exposed to lethal concentration (20.49 mg L−1) of an organophosphorous pesticide, monocrotophos (MCP) for 96 h. In vitro AChE activity studies indicated that MCP could cause 50% inhibition (I50) at 10.2 × 10−5 M. A positive correlation was observed between brain AChE activity and swimming speed during the recovery study. Also, the recovery response of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) as well as lipid peroxidation (LPO) as biomarkers of oxidative stress were assessed in viscera of G. affinis. The results showed that the MCP besides its inhibitory effect on target enzyme AChE activity and induction in antioxidant enzyme activities as a characteristic of oxidative stress, which can be used as biomarkers in the pesticide contaminated aquatic streams.  相似文献   

10.
Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to sublethal concentrations of glyphosate were examined in order to evaluate the possibilities of using a response pattern in plants as a measure of exposure to glyphosate through the growth media, more sensitive than the well-known biomarker shikimate. Rapeseed seedlings were grown in hydroponic nutrient solutions containing varying sublethal concentrations of glyphosate (1-50 μM). After 9 days of glyphosate exposure, the shoots of the seedlings were analysed with respect to the effects on selected metabolites downstream from the primary affected metabolite shikimate, which accumulated linearly in response to glyphosate exposure (from 0 to ∼126 μmol/g DW). The selected metabolites analysed, comprising the free amino acids, and the glucosinolates derived therefrom, showed complex patterns in response to glyphosate exposure. Most noteworthy was though that they responded at the lowest concentrations of exposure to glyphosate (1 μM), where no visual effects, decrease in shoot DW or shikimate could be detected, indicating that a biomarker response more sensitive than that of shikimate can be established for plants exposed to glyphosate.  相似文献   

11.
In vitro inhibition of electric eel acetylcholinesterase (AChE) by single and simultaneous exposure to organophosphorus insecticides diazinon and chlorpyrifos, and their transformation products, formed due to photoinduced degradation, was investigated. Increasing concentrations of diazinon, chlorpyrifos and their oxidation products, diazoxon and chlorpyrifos-oxon, inhibited AChE in a concentration-dependent manner. IC50 (20 min) values, obtained from the inhibition curves, were (in mol/l): (5.1 ± 0.3) × 10−8, (4.3 ± 0.2) × 10−6 and (3.0 ± 0.1) × 10−8 for diazoxon, chlorpyrifos and chlorpyrifos-oxon, respectively, while maximal diazinon concentration was lower than its IC50 (20 min). Calculated KI values, in mol/l, of 7.9 × 10−7, 9.6 × 10−6 and 4.3 × 10−7 were obtained for diazoxon, chlorpyrifos and chlorpyrifos-oxon, respectively. However, 2-isopropyl-4-methyl-6-pyrimidinol (IMP) and 3,5,6-trichloro-2-pyridinol, diazinon and chlorpyrifos hydrolysis products, did not noticeably affect the enzyme activity at all investigated concentrations. Additive inhibition effect was achieved for lower concentrations of the inhibitors (diazinon/diazoxon ?1 × 10−4/1 × 10−8 mol/l i.e., chlorpyrifos/chlorpyrifos-oxon ?2 × 10−6/3 × 10−8 mol/l), while an antagonistic effect was obtained for all higher concentrations of the organophosphates. Inhibitory power of 1 × 10−4 mol/l diazinon irradiated samples can be attributed mostly to the formation of diazoxon, while the presence of non-inhibiting photodegradation product IMP did not affect diazinon and diazoxon inhibitory efficiencies.  相似文献   

12.
The brown planthopper (BPH), Nilaparvata lugens Stål, is a primary insect pest of cultivated rice, and its effective control is essential for crop production. However, in recent years, outbreaks of the brown planthopper have occurred more frequently in China. In order to determine the causes and mechanisms of insecticide-induced BPH resurgence and perform population management, we conducted the following studies. By the topical application method, our results showed that, fenvalerate acted as stimulus of fecundity from 3.50 × 10−3 to 2.02 × 10−2 μg/female in the BPH. Apart from 7.00 × 10−3 μg/female, the number of hatched nymphs was increased gradually with an increase in application dose from 3.50 × 10−3 to 1.74 × 10−2 μg/female. After continuous selection with fenvalerate for 11 generations by the rice-stem dipping method, a resistant strain was achieved with medium resistance to fenvalerate (RR 39.22). Life table study indicated that the resistant strain (G4 and G8) showed reproductive advantages, including increased female ratio, copulation rate and fecundity. But the hatchability of resistant strain was lower. The survival rate and emergence rate were significantly lower in G4 and G8 resistant strain. Resistant strains in G4 and G8 showed a fitness advantage (1.04 and 1.11), and the number of offspring in G8 generation was higher than that in G4 generation. The significant difference detected between resistant insects (G4, G5, G8 and G9) and S-strain contains not only the effect of resistant selection but also the effect of continuous rearing itself. Hence it was concluded that the BPH had the potential to develop high resistance against fenvalerate and the induction of the nymphs by sublethal doses of fenvalerate was of importance in the BPH population management, particularly in the predicting. Further studies demonstrated that triphenyl phosphate (TPP) and diethyl maleate (DEM) had no synergism on fenvalerate. However, piperonyl butoxide (PBO) displayed significant synergism in susceptible strain (1.97) and resistant strain (2.73). We concluded that esterase and glutathione S-transferase play little role in fenvalerate detoxification. The increase of the P450-monooxygenases detoxification is an important mechanism for fenvalerate resistance. Because their resistant populations had a fitness advantage, we should pay close attention to the occurrence of BPH and use other functionally different insecticides to control the BPH.  相似文献   

13.
Aclonifen belongs to the diphenylether (DPE) chemical family among which potent herbicides with a photodependent mode of action can be found. For years aclonifen has been used in several types of cultures. However its biochemical mode of action remains unclear although it was listed as a carotenoid synthesis inhibitor by the Herbicide Resistance Action Committee (HRAC). As a matter of fact, corn seedling leaves treated with 10−4 M aclonifen and maintained in the dark no longer contained carotenoids but showed an accumulation of a compound having all the characteristics of phytoene. That demonstrated aclonifen ability to inhibit the desaturases catalyzing the transformation of phytoene into carotenoids. Moreover, aclonifen (5 × 10−5 M) was responsible for a photodependent cell destruction (necrosis) of cucumber cotyledons typically due to protoporphyrin IX accumulation. The same phenomenon was demonstrated in aclonifen-treated etiolated corn seedlings (10−4 M) that showed an accumulation of protoporphyrin IX, reaching 62 ng/g of leaf fresh mass and reactive oxygen species production under light. On these two cases (cucumber cotyledons and etiolated corn seedlings), aclonifen was acting as a typical DPE, as demonstrated by the accumulation of protoporphyrin IX. As a whole, aclonifen was shown here, to act on two different biochemical pathways including carotenoid synthesis on the one hand, as well as protoporphyrinogen oxidase, in the chlorophyll synthesis pathway, on the other for the same range of concentrations.  相似文献   

14.
Amitraz is a pesticide targeting the octopaminergic receptors. In a previous study, octopamine, a biogenic amine, was found to induce a biphasic effect on the honeybee heart, inhibition at low concentrations and excitation at high concentrations. Furthermore, the honeybee heart was found to be far more sensitive to octopamine compared to other insect hearts. The objective of the present study was to investigate the effects of amitraz on the electrical and mechanical properties of the honeybee heart ex vivo and on the heart rate in vivo. In ex vivo conditions, amitraz at 10−12 M caused a significant inhibition in the mechanical (p < 0.05, n = 4) and electrical properties (p < 0.05, n = 4). Higher concentrations such as 10−9 and 10−6 M induced a biphasic effect, with total inhibition for 7.86 ± 1.26 min (n = 7), followed by strong excitation of spontaneously-generated contractions (n = 7). The initial elimination of heart activity was caused by strong hyperpolarization, while the subsequent excitation was caused by a depolarization in the membrane potential of pacemaker cells at 10−9 M (n = 8). In the in vivo experiments, abdominal injection or oral application of 0.20 ng of amitraz per bee induced a persistent increase of 134.28 ± 4.07% (p < 0.05, n = 4) in the frequency of the cardiac action potentials. The above responses clearly show that the heart of the honeybee is extremely vulnerable to amitraz, which is nevertheless still used inside beehives, ostensibly to “protect” the honeybees against their main parasite, Varroa destructor.  相似文献   

15.
Elevated oxidative detoxification is a major mechanism responsible for pyrethroid resistance in Helicoverpa armigera from Asia. Constitutive overexpression of CYP9A12 and CYP9A14 was associated with pyrethroid resistance in the YGF strain of H. armigera. CYP9A12 and CYP9A14 were functionally expressed in the W(R) strain of yeast (Saccharomyces cerevisiae) transformed with a plasmid shuttle vector pYES2. The cell lysates prepared from yeast transformed with CYP9A12 and CYP9A14, respectively, exhibited considerable O-demethylation activities against two model substrates p-nitroanisole (0.59 and 0.42 nmol p-nitrophenol min−1 mg protein−1) and methoxyresorufin (2.98 and 5.41 pmol resorufin min−1 mg protein−1), and clearance activity against the pyrethroid esfenvalerate (8.18 and 4.29 pmol esfenvalerate min−1 mg protein−1). These results provide important evidence on the role of CYP9A12 and CYP9A14 in conferring pyrethroid resistance in H. armigera, and also demonstrate that the yeast expression system can provide necessary redox environment for insect P450s to metabolize xenobiotics.  相似文献   

16.
Nile Tilapia (Oreochromis niloticus) juveniles were exposed to different concentrations of Folidol 600® in static toxicity tests. The 24, 48, 72 and 96 h LC50 values of Folidol 600® to O. niloticus were 17.82, 8.91, 4.00 and 2.70 mg L−1, respectively. The values of hematological parameters increased, and inhibition of cholinesterases activity (AChE, BChE and PChE) in plasma of fish exposed to the higher concentrations of pesticide reached 94%. Furthermore, the exposure of Tilapia to Folidol 600® caused an increase of 4%, 20% and 38.4% in oxygen consumption at 0.1, 0.5 and 1.0 mg L−1, respectively. However, exposure to 2.5, 5.0 and 10 mg L−1 caused a decrease of 33.6%, 35.2% and 42.4% in oxygen consumption relative to the control. The ammonium excretion of fish exposed to 0.0, 0.1, 0.5, 1.0, 2.5, 5.0 and 10.0 mg Folidol 600®/L was 0.12, 0.18, 0.30, 0.33, 0.37, 0.36 and 0.33 μg/g/min, i.e., 50%, 150%, 175%, 208%, 200% and 175% increase, respectively, relative to the control.  相似文献   

17.
In order to gain insight into the development of insecticides with novel modes of action, the effects of salicylidene aniline (a), salicylidene-4-chloroaniline (b), salicylidene-4-bromoaniline (c), and salicylidene-4-nitroaniline (d) on partially purified phenoloxidase (PO) from Pieris rapae L. were investigated. The results showed that the 4 compounds could inhibit PO activity, and the inhibitor concentrations leading to a loss of 50% activity (IC50) were estimated to be 0.025 mmol L−1, 0.732 mmol L−1, 0.471 mmol L−1, and 0.675 mmol L−1, respectively. Meanwhile, all the inhibitors showed reversible competitive inhibition, except (d), which showed reversible mixed inhibition. The KI values were determined as 0.106 mmol L−1, 10.059 mmol L−1, 8.390 mmol L−1, and 20.198 mmol L−1 for the four compounds, respectively. The UV-vis spectra of (a) and (d) in the presence of copper ions and the enzyme showed that (a) could directly chelate the copper ions of PO; however, (d) could neither chelate the additional copper ions nor the copper ions of PO.  相似文献   

18.
The oriental tobacco worm, Helicoverpa assulta Guenée, is one of the most destructive pests of tobacco and peppers in China. We determined the susceptibility of H. assulta reared on an artificial diet, chili pepper and tobacco to four insecticides (fenvalerate, phoxim, methomyl, indoxacarb) under laboratory conditions associated with the activities of acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione S-transferase (GST) in its larvae. H. assulta larvae that were fed with chili pepper were more susceptible to fenvalerate, indoxacarb, and phoxim than those that were fed with tobacco and the artificial diet, but not to methomyl. The larvae that were fed with chili pepper were 3.65-, 2.49-, 1.92- and 2.44-fold more susceptible to fenvalerate, phoxim, methomyl, and indoxacarb than those fed with tobacco, respectively. The AChE activities of H. assulta larvae that were fed with chili pepper and tobacco were 2.12 and 1.07 μmol mg−1 15 min−1, respectively, almost 2-fold difference. The CarE activity of H. assulta larvae that were fed with chili pepper, tobacco and the artificial diet was 4.12, 7.40 and 7.12 μmol mg−1 30 min−1, respectively. Similarly, the GST activities of H. assulta larvae that were fed with chili pepper, tobacco and the artificial diet was 52.02, 79.37 and 80.02 μmol mg−1 min−1, respectively. H. assulta larvae that were fed with chili pepper were more resistance to the tested insecticides. The low activities of AChE and the high activities of CarE and GST lead to H. assulta become more susceptible to the tested insecticides.  相似文献   

19.
The effect of chitosan (0.5, 1.0 and 2.0 mg ml−1) on mycelium growth, potassium efflux, pH of the incubation medium, and activity of plasma membrane H+-ATPase of Rhizopus stolonifer was evaluated. The mycelium growth of R. stolonifer was reduced on media amended with chitosan at 1.0 and 2.0 mg ml−1. The highest antifungal index (65%) was obtained on media containing chitosan at 2.0 mg ml−1. Potassium efflux induced by the addition of the three chitosan concentrations was demonstrated. The highest potassium effluxes were observed with addition of chitosan at 2.0 mg ml−1. R. stolonifer grown 72 h on Potato Dextrose Broth without chitosan generated a decrease in the medium’s pH from 5.4 to 4.8. However, the addition of chitosan at all concentrations caused increases on pH of medium cultures. The highest pH increases were observed on media amended chitosan at 2.0 mg ml−1 resulting in the raising of pH level to 6.9. Additionally, there was an important inhibitory effect of chitosan (1.0 and 2.0 mg ml−1) on H+-ATPase activity in the plasma membrane of R. stolonifer (32.70%).  相似文献   

20.
Valienamine, an aminocyclitol with similar configuration to α-glucose, has a strong inhibitory effect on α-glucosidase. α-Glucosidase plays an important role in insect carbohydrate metabolism. The inhibitory effect of valienamine on the enzymatic activity of honeybee (Apis cerana Fabr.) α-glucosidase was investigated. Our results show that valienamine inhibition of honeybee α-glucosidase was pH- and dose-dependent, but temperature-independent. Valienamine is shown to be a potent and competitive reversible inhibitor of honeybee α-glucosidase in vitro with an IC50 value of 5.22 × 10−5 M and Ki value of 3.54 × 10−4 M at pH 6.5, 45 °C. Valienamine has the potential to be developed into novel insecticides.  相似文献   

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