Protective effect of vitamin C against chlorpyrifos oxidative stress in male mice

Pesticides may induce oxidative stress leading to generate free radicals and alternate antioxidant or oxygen free radical scavenging enzyme system. This study was conducted to investigate the acute toxicity of chlorpyrifos toward male mice and the oxidative stress of the sub-lethal dose (1/10 LD₅₀) on the lipid peroxidation level (LPO), reduced glutathione content (GSH) and antioxidant enzymes; catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PD), and glutathione-S-transferase (GST) activities. Also, the protective effects of vitamin C (200 mg/kg body weight, bw) 30 min before or after administration of chlorpyrifos were investigated. The results demonstrated that the LD₅₀ value of chlorpyrifos was 134.95 mg/kg bw. The oral administration of 13.495 mg/kg chlorpyrifos significantly caused elevation in LPO level and the activities of antioxidant enzymes including CAT, SOD and GST. However, GPx activity remained unchanged, while the level of GSH and G6PD activity were decreased. Vitamin C treatment to chlorpyrifos intoxicated mice decreased LPO level and GST activity, normalized CAT, SOD and G6PD activities, while GSH content was increased. We conclude that vitamin C significantly reduces chlorpyrifos-induced oxidative stress in mice liver and the protective effect of the pre-treatment with vitamin C is better than the post-treatment.     

Subacute chlorpyrifos-induced oxidative stress in rat erythrocytes and the protective effects of catechin and quercetin

This study examined the effects of chlorpyrifos in the rat erythrocyte antioxidant system and evaluated the ameliorating effects of catechin and quercetin on the oxidative damage induced by chlorpyrifos. Sexually mature male Wistar rats were given chlorpyrifos (5.4 mg/kg, 1/25 of the oral LD₅₀), catechin (20 mg/kg), quercetin (20 mg/kg), catechin plus chlorpyrifos, and quercetin plus chlorpyrifos daily via gavage for four weeks. No statistical differences were found in the catechin-only and quercetin-only groups compared with the control group. By the end of the fourth week, chlorpyrifos alone increased the levels of malondialdehyde (MDA) and decreased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities compared with the control group in rat erythrocytes. In the catechin-plus-chlorpyrifos and quercetin-plus-chlorpyrifos groups, there were statistically significantly decreased MDA levels and increased SOD, CAT, and GPx activities compared with the chlorpyrifos-only group. Thus, it appears that catechin and quercetin ameliorate chlorpyrifos-induced oxidative stress in rat erythrocytes in vivo.     

Induction of antiviral resistance and stimulary effect by oligochitosan in tobacco

Oligochitosan was applied by spraying it on tobacco leaves for inhibition of tobacco mosaic virus (TMV). The maximum inhibition of TMV by oligochitosan was observed when inoculation occurred at 24 h after spraying 50 μg ml⁻¹ oligochitosan. The production of H₂O₂ and NO in epidermal tobacco cells induced by oligochitosan was investigated by epidermal strip bioassay and LSCM, using cell permeable fluorophore diaminofluorescein diacetate (DAF-2D) and 2′,7′-dichlorofluorescin diacetate (H₂DCF-DA), respectively. Epidermal tobacco cells treated with oligochitosan resulted in a strong increase of intracellular NO and H₂O₂. Oligochitosan and NO donor sodium nitroprusside (SNP) induced the defense reaction against tobacco mosaic virus (TMV), and increased phenylalanine ammonia-lyase (PAL) activity. Co-treatment of the tobacco cells with oligochitosan and NO scavenger CPTIO blocked the inducing resistance. The results indicated that the defense response induced by oligochitosan was connected with NO pathway.     

Antioxidant role of propolis extract against oxidative damage of testicular tissue induced by insecticide chlorpyrifos in rats

Pesticides induce oxidative stress leading to generate free radicals and alternate the antioxidant or oxygen free radical scavenging enzyme system. This study was conducted to investigate the oral toxicity of chlorpyrifos toward male rat and the oxidative stress of the sub-lethal dose (9 mg/kg; 1/25 LD₅₀) on the lipid peroxidation level (LPO), reduced glutathione content (GSH) and antioxidant enzymes; catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities of testicular tissue. Also, the protective effects of propolis extract (50 mg/kg b.w.) alone or in combination with chlorpyrifos were investigated. The oral administration of chlorpyrifos significantly caused elevation in LPO level by 1.79-fold as compared to control. The activities of antioxidant enzymes including CAT, SOD, GPx and GST were decreased significantly (23.66%, 27.75%, 29.13% and 11.52%) as well as the level of GSH decreased by 21.97% in testicular tissue as compared to control animals. Co-administration of propolis extract with chlorpyrifos or alone in male rats decreased LPO level, normalized CAT, SOD GPx and GST activities, while GSH content was increased in testicular tissue. We conclude that propolis extract significantly reduces chlorpyrifos-induced oxidative stress in rat testis and the protective effect of the pre-treatment with propolis extract as attenuating agent could be due to its antioxidant properties.     

Oligochitosan induces cell death and hydrogen peroxide accumulation in tobacco suspension cells

Oligochitosan has been shown to induce several plant defense responses. In the present work, the effect of oligochitosan on tobacco cell survival was investigated. The results showed that oligochitosan caused tobacco cell death in a dose-dependent manner. About 40.6 % tobacco cells died when cultured for 72 h after 500 μg ml⁻¹ oligochitosan treatment. Certain aspects of this cell death process appeared to be similar to apoptosis in animal cells. These included shrinkage of cytoplasm and condensation of chromatin. Oligochitosan also induced H₂O₂ accumulation in tobacco cell suspension culture. The role of H₂O₂ in the signal transduction that leads to cell death was investigated. Co-treatment of tobacco cells with oligochitosan and catalase inhibited H₂O₂ accumulation but did not inhibit the induction of cell death. The results suggested that apoptosis-like cell death of tobacco cells induced by oligochitosan is independent of H₂O₂ signal pathway.     

Protective effects of Nigella sativa oil on propoxur-induced toxicity and oxidative stress in rat brain regions

Propoxur (PPr) is a widely used broad spectrum carbamate insecticide mainly used to control household pests. Because of the widespread use of pesticides for domestic and industrial applications, evaluation of their neurotoxic effects is of major concern to public health. The aim of the present study was to evaluate the possible protective effects of Nigella sativa oil (NSO), an antioxidant agent, against PPr-induced toxicity and oxidative stress in different brain regions of rats including cerebellum, cortex and hippocampus. In the present study, 32 male Sprague-Dawley rats were used and divided into four equal groups. Group 1 was allocated as the control group. Groups 2-4 were orally administered 1 ml/kg/bw/day NSO, 8.51 mg/kg/bw/day PPr or NSO plus PPr, respectively, for 30 days. Lipid peroxidation (LPO), protein carbonyl content (PCC) and acetylcholine esterase activity (AChE) were determined. Enzymatic antioxidant activities [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST)] and non-enzymatic antioxidants [reduced glutathione (GSH)] were determined. PPr treatment significantly increased the levels of LPO, PCC and oxidized glutathione (GSSG) in brain regions. On the contrary, levels of GSH and the activities of SOD, CAT, GSH-Px, GST and AChE were significantly decreased. NSO treatment to PPr intoxicated rats restored such biochemical parameters to within control levels except GST activity, emphasizing its antioxidant role. We conclude that NSO significantly reduces PPr-induced toxicity and oxidative stress in rat brain regions via a free radicals scavenging mechanism.     

Biochemical effects of acute phoxim administration on antioxidant system and acetylcholinesterase in Oxya chinensis (Thunberg) (Orthoptera: Acrididae)

The study was undertaken to evaluate the effects of different concentrations of phoxim on acetylcholinesterase (AChE) and esterase (EST) activities, and antioxidant system after topical application to Oxya chinensis. The results showed that phoxim inhibited AChE activity, and did not cause significant changes in the EST activity and the levels of malondialdehyde (MDA) and reduced glutathione (GSH). After phoxim administration, superoxide (SOD) and catalase (CAT) activities showed a biphasic response with an initial increase followed by a decline in their activities. Glutathione reductase (GR) and glutathione peroxidase (GPx) activities were inhibited in comparison with the control. Glutathione S-transferase (GST) activity showed irregular changes. Its activity increased significantly at the concentrations of 0.06 and 0.12 μg/μL and decreased at the concentrations of 0.09 and 0.24 μg/μL compared with the control. Changes in SOD, CAT, GST, GPx, and GR activities indicated that phoxim caused oxidative damage in O. chinensis. However, no significant changes in MDA content suggested that these enzymes played important roles in scavenging the oxidative free radicals induced by phoxim in O. chinensis. The formation of oxygen free radicals might be a factor in the toxicity of phoxim.     

Co-stressors chilling and high light increase photooxidative stress in diuron-treated red alga Kappaphycus alvarezii but with lower involvement of H2O2

Diuron is one of the most commonly found N-phenylurea herbicides in marine/estuarine waters that promotes toxic effects by inhibiting photosynthesis and affecting the production of reactive oxygen species (ROS) in autotrophs. Since photo- and thermoacclimation are also ROS-mediated processes, this work evaluates a hypothetical additive effect of high light (HL) and chilling (12 °C) on 50 nM diuron toxicity to the highly-photosynthetically active apices of the red alga Kappaphycus alvarezii. Additive inhibition of photosynthesis was mainly evidenced by significant decreases of quantum yield of photosystem II and electron transfer rates upon co-stressors exposure to diuron-treated algae. Under extreme 12 °C/HL/diuron conditions, unexpected lower correlations between H₂O₂ concentrations in seawater and radical-sensitive protein thiols were concomitantly measured with the highest indexes of photoinhibition (parameter β). Altogether, these data support the hypothesis that co-stressors chilling/HL additively inhibit photosynthesis in diuron-exposed K. alvarezii but with less involvement of H₂O₂ in injury effects than with only chilling or HL.     

Methylparathion- and carbofuran-induced mitochondrial dysfunction and oxidative stress in Helicoverpa armigera (Noctuidae: Lepidoptera)

The cotton bollworm, Helicoverpa armigera is a polyphagous pest of several crops in Asia, Africa, and the Mediterranean Europe. Organophosphate and carbamate insecticides are used on a large-scale to control Helicoverpa. Therefore, we studied the effect of methylparathion and carbofuran, an organophosphate and carbamate insecticide, respectively, on oxidative phosphorylation and oxidative stress in H. armigera larvae to gain an understanding of the different target sites of these insecticides. It was observed that state III and state IV respiration, respiratory control index (RCI), and P/O ratios were inhibited in a dose-dependent manner by methylparathion and carbofuran under in vitro and in vivo conditions. Methylparathion and carbofuran inhibited complex II by ∼45% and 30%, respectively. Lipid peroxidation, H₂O₂ content, and lactate dehydrogenase (LDH) activity increased and glutathione reductase (GR) activity decreased in a time- and dose-dependent manner in insecticide-fed larvae. However, catalase activity was not affected in insecticide-fed larvae. Larval growth decreased by ∼64% and 67% in larvae fed on diets with 100 μM of methylparathion and carbofuran. The results suggested that both the insecticides impede the mitochondrial respiratory functions and induced lipid peroxidation, H₂O₂, and LDH leak, leading to oxidative stress in cells, which contribute to deleterious effects of these insecticides on the growth of H. armigera larvae, along with their neurotoxic effects.     

Effect of waterborne benomyl on the hematological and antioxidant parameters of the Nile tilapia, Oreochromis niloticus

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.     

向日葵与锈菌互作过程中活性氧的积累

为了探讨向日葵品种与锈菌互作中活性氧的产生和积累与向日葵抗锈病性的关系,采用分光光度计法及联苯胺蓝(DAB)、氮兰四唑(NBT)染色法对过氧化氢(H2O2)及超氧阴离子自由基(O2-)诱导积累的过程进行了检测.结果表明:接种后抗、感病品种均出现H2O2和O2-双峰,侵染早期积累明显,最高峰出现在16 h,在抗病品种中活性氧产生和积累明显高于感病品种;在抗病品种中侵染位点活性氧的产生及积累较明显,接种后16h,侵染位点周围的染色范围较大,染色较深,H2O2及O2-的染色比例均达到最高,分别为65.5%和41%;而在感病品种的侵染位点没有检测到明显的活性氧积累.     

Inhibitory effects of Schiff analogs of salicylidene aniline on phenoloxidase from Pieris rapae L. (Lepidoptera: Pieridae)

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 K_I 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.     

Ultra-structural changes in the integument induced by the use of three of six forms of allylisothiocyanate tested against Plutella xylostella and Pieris rapae larvae

The insecticidal activity of four forms of Hong Jing (HJ) allylisothiocyanate (AITC), AITC + cypermethrin (HJ_A, HJ_B, and HJ_C) with ratio of (1:1, 4:1, and 2:1), pure AITC (HJ_D), and two forms of Hong Du (HD) AITC, AITC + chlorpyrifos (HD_A and HD_B) with ratio of (2:1 and 2:1), respectively, were studied on the major cruciferous insect larvae Plutella xylostella (L.) and Pieris rapae (L.) by combining both spraying and dipping methods. The P. rapae was more susceptible than P. xylostella larvae. The LC₅₀ values 72 h after treatment of AITC forms (HJ_B, HJ_A, HJ_C, HJ_D, HD_B, and HD_A) on the P. rapae were; 0.07, 0.08, 0.16, 0.83, 0.26, 1.08 gL⁻¹, and 0.69, 0.26, 5.45, 0.93, 3.01, 5.98 gL⁻¹ on the P. xylostella, respectively. The toxicity of some of the AITC forms was very close to or better than that of the commercial contact insecticides such as chlorpyrifos (LC₅₀ = 0.03 and 0.04 gL⁻¹ on P. rapae and P. xylostella, respectively), and cypermethrin (0.65 and 0.78 gL⁻¹, respectively, against P. rapae and P. xylostella). The ultrastructural studies on the integument of the third larval instar of P. xylostella treated by sub-lethal concentration (LC₂₀) of HJ_B, HJ_D, and HD_B were carried out by using transmission electron microscope. The more pronounced alterations in the hypodermis and mitochondria cells. They exhibited changes in all treated samples. The hypodermis was almost completely destroyed, and the mitochondria exhibited morphological alterations, represented by enlargement, matrix rarefaction and vacuolization of the mitochondria matrix, quantity of cristae reduced, and density electron matrix lessened. These AITC forms have potential as contact insecticides, and the ultra structural observations confirm the insecticidal efficiency of different AITC forms on P. rapae and P. xylostella.     

<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>- mediated reprogramming of oxidative stress response in root apoplast of sunflower enhances defence against <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

Trichoderma harzianum is an effective biocontrol agent against the devastating plant pathogen Rhizoctonia solani. Despite its wide application in agriculture, the mechanisms of biocontrol are not yet fully understood. Mycoparasitism and antibiosis are suggested, but may not be sole cause of disease reduction. In the present study, we investigated the role of oxidant-antioxidant metabolites in the root apoplast of sunflower challenged by R. solani in the presence/absence of T. harzianum NBRI-1055. Analysis of oxidative stress response revealed a reduction in hydroxyl radical concentration (^•OH; 3.6 times) at 9 days after pathogen inoculation (dapi), superoxide anion radical concentration (O₂^•−; 4.1 times) at 8 dapi and hydrogen peroxide concentration (H₂O₂; 2.7 times) levels at 7 dapi in plants treated with spent maize-cob formulation of T. harzianum NBRI-1055 (MCFT), as compared to pathogen-inoculated plants. The protection afforded by the biocontrol agent was associated with the accumulation of the ROS gene network: the catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and ascorbate peroxidase (APx), maximum activity of CAT (11.0 times) was observed at 8 dapi, SOD (7.0 times) at 7 dapi, GPx (5.4 times) and APx (8.1 times) at 7 dapi in MCFT-treated plants challenged with the pathogen. This was further supported by the inhibition of lipid and protein oxidation in Trichoderma-inoculated plants. MCFT stimulated the accumulation of secondary metabolites of phenolic nature that increased up to five-fold and also exhibited strong antioxidant activity at 8 dapi, eventually leading to the systemic accumulation of phytoalexins. These results suggest that T. harzianum–mediated biocontrol may be related to alleviating R. solani-induced oxidative stress.     

Evaluation of molluscicidal activities of Arisaema tubers extracts on the snail Oncomelania hupensis

Four extracts of Arisaema erubescens tubers by acetic acetal (AAE), benzinum (BZE), n-butanol (NBE) and chloroform (CFE) were obtained to evaluate their molluscicidal activities against the snail Oncomlania hupensis. The responses of choline esterase (ChE), alkaline phosphatase (ALP), esterase (EST), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to the extracts (NBE) were also investigated. In the four extracts (AAE, BZE, NBE and CFE), NBE showed the highest toxicity on the snails after 48 h exposure. NBE also showed the time- and concentration-dependent effect, for example, the LC₉₀ values of the NBE were decreased from 365.5 mg/L (24 h) to 36.4 mg/L (96 h). At the end of exposure to NBE (LC₅₀ concentration), the activities of ChE and ALP in snail tissues (cephalopodium and liver) decreased significantly. Isozyme electrophoresis profiles indicated that responses of isozymes (EST, SOD and GSH-Px) to NBE were more intense in liver than in cephalopodium. After 72 h exposure to NBE, the EST activity in snail liver decreased and some enzyme bands (EST1 and EST4) disappeared. But the activities of SOD 1 and GSH 2 in liver increased after 48 h exposure. The results indicated that NBE was the highest toxic component in the four extracts. The decline of the detoxification ability and the oxidative damage in snail tissues might be the main reason for the molluscicidal activities.     

Comparison of kinetic properties of a hydrophilic form of acetylcholinesterase purified from strains susceptible and resistant to carbamate and organophosphorus insecticides of green rice leafhopper (Nephotettix cincticeps Uhler)

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 K_m 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 K_m 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 V_max 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 V_max 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 (k_i) 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.     

Toxic effects of acephate on Paramecium caudatum with special emphasis on morphology, behaviour, and generation time

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.     

BTH处理对甜瓜叶片活性氧代谢的诱导作用

为了明确活性氧（reactive oxygen species,ROS）代谢在甜瓜抗病性诱导中的作用,以抗白粉病甜瓜品种Tam Dew和感病品种卡拉克赛幼苗为材料,通过盆栽试验研究了苯丙噻二唑（BTH）喷雾或白粉菌接种后甜瓜叶片超氧阴离子（O2.-）产生速率、过氧化氢（H2O2）含量及超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、苯丙氨酸解氨酶（PAL）活性的变化。BTH处理或白粉菌接种均可诱导甜瓜叶片SOD、PAL活性升高,抑制CAT活性,导致叶组织O2.-产生速率和H2O2含量增加,BTH喷雾＋白粉菌接种比二者单独处理效果更好。结果表明,BTH处理后叶片O2.-产生速率提高和H2O2积累是甜瓜抗白粉病能力提高的重要机制,BTH通过诱导ROS代谢酶活性调节H2O2含量,且BTH诱导的甜瓜抗病性与品种的基础抗性有关。     

Oxidative stress and locomotor behaviour response as biomarkers for assessing recovery status of mosquito fish, Gambusia affinis after lethal effect of an organophosphate pesticide, monocrotophos

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.     

Amelioratory effect of vitamin E on organophosphorus insecticide diazinon-induced oxidative stress in mice liver

Considering that the involvement of reactive oxygen species (ROS) has been implicated in the toxicity of organophosphate insecticides (OPIs), the aim of this study was to investigate the ameliorative properties of vitamin E (vitE) against the subchronic effect of diazinon (DZN) on oxidative damage markers such as lipid peroxidation (LPO) and the antioxidant defense system (ADS) in the liver of male MFI albino mice. The groups were intraperitoneally (i.p) administered with either vehicle or vitE (100 mg/kg body weight) or ¼ LD₅₀ of DZN (16.25 mg/kg b.w.) or ½ LD₅₀ of DZN; 32.5 mg/kg b.w) or ¼ LD₅₀-DZN + vitE or ½ LD₅₀ + vitE every consecutive day for 14 days. Hepatic damage markers analysis revealed that alanine transferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) were significantly decreased in both DZN doses. Also, the significantly increased levels of biomarkers of oxidative stress as LPO and protein carbonyl (PC) and the decreased antioxidant defenses like reduced glutathione (GSH), and free radical scavenger enzymes viz., catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rx) were noted in DZN-treated groups as compared to control group. Distinctly lower levels of GSH and increased levels of LPO, along with alterations in endogenous antioxidant enzymes were evident in hepatic toxicity of DZN which is dose-dependent. Hepatic specific marker enzymes were restored to normalcy in mice supplemented with vitE following treatment with DZN which otherwise was decreased in the DZN-treated mice. The results show that co-treatment of vitE with DZN prevents or diminishes the oxidative stress of DZN-treated mice and may act as a putative protective agent against DZN-induced liver tissue injury.