Monocrotophos induced lipid peroxidation and oxidative DNA damage in rat tissues

Monocrotophos (dimethyl(E)-1-methyl-2-(methyl carbamoyl) vinyl phosphate, MCP), a substituted vinyl phosphate, is a potent systemic toxicant and used for control of variety of pests. The present study is undertaken to evaluate the genotoxic potential of monocrotophos and time-dependent repair of the damaged DNA in rats, using single cell gel electrophoresis or comet assay. The involvement of oxidative stress was also examined by estimation of thiobarbituric acid reactive substances (TBARS) in the tissues of MCP exposed rats. The rats were given oral exposure of 4.5 and 9 mg MCP/kg body weight once as well as 0.3 and 0.6 mg MCP/kg body weight for 60 days. A dose-dependent increase was recorded in the levels of TBARS in the liver, kidney, spleen and brain of MCP exposed rats. Cytotoxicity of MCP is evident from the histopathological studies of rat tissues. The level of DNA damage was estimated by scoring 50 cells per animal, dividing into five types, Types 0, I, II, III and IV. The results clearly indicated that exposure to MCP, acutely or chronically, caused a dose-dependent increase in the number of damaged nuclei of Types II, III and IV in the liver, kidney, spleen and brain of rats. When the DNA damage was studied 48 and 72 h post MCP treatment, a significant reduction in the number of types III and IV nuclei was observed in all the tissues indicating a time-dependent repair. From the present study, it can be concluded that oxidative stress may be involved in the toxicity of MCP and MCP induces DNA damage in all the rat tissues exhibiting genotoxic potential in vivo.     

Oxidative damage, biochemical and histopathological alterations in rats exposed to chlorpyrifos and the antioxidant role of zinc

The protective effects of zinc on liver and kidney injury induced by chlorpyrifos (CPF) were investigated in rats. Male and female rats were orally administered CPF at a dose of 6.75 mg kg⁻¹ body weight for 28 consecutive days. An additional CPF group received zinc (227 mg l⁻¹) in drinking water throughout the experimental duration. Two groups more served as controls. Administration of CPF resulted in a significant increase in serum lipid peroxidation (LPO) level, while induced significant decreases in the activities of plasma superoxide dismutase (SOD), glutathione-S-transferase (GST) and serum acetylcholinesterase (AChE) either in male or female rats. Similarly, a significant increase in the levels of various serum marker enzymes [e.g. aminotransferases (AST and ALT), lactate dehydrogenase (LDH) and gamma glutamyl transferase (GGT)] and increase the level of total protein, uric acid and creatinine. In contrast, co-administration of zinc to CPF-treated animals restored most of these biochemical parameters to within normal levels. In case of AChE, supplementation of zinc showed little alteration in the activity of this enzyme especially in male rats treated with CPF. CPF caused histopathological change in liver and kidneys of male and female rats. However, zinc administration to CPF-treated animals resulted in overall improvement in liver and kidneys damage, emphasizing its antioxidant role. In light of the available data, it can deduce that CPF-induced lipid peroxidation, oxidative stress, liver and kidneys damage in male and female rats, and conjunction supplementation of zinc has resulted in pronounced ameliorating effect.     

Reactive oxygen species (ROS) generation and ROS-induced lipid peroxidation are associated with plasma membrane modifications in host cells in response to AK-toxin I from Alternaria alternata Japanese pear pathotype

AK-toxin I caused plasma membrane modifications with plasma membrane-derived membrane fragments only in sensitive Japanese pear tissues. H₂O₂ generation was abundant in both the membrane fragments and the plasma membranes of the toxin-treated sensitive tissues. Whether lipid peroxidation was induced in plasma membranes of the toxin-treated sensitive tissues was examined biochemically and histochemically. Lipid peroxidation was caused only in the toxin-treated sensitive tissues or the toxin-treated plasma membrane-enriched fractions from sensitive young pear fruits. The results indicated that the peroxidation was probably induced by reactive oxygen species in the modified plasma membranes by action of toxin, suggesting that peroxidation is closely associated with plasma membrane modifications.     

Phenotypic and genetic characterization of Pseudomonas syringae strains associated with the recent citrus bacterial blast and bacterial black pit epidemics in Tunisia

In the spring of 2012, symptoms of a disease resembling citrus blast and citrus black pit were observed in some orchards in Tunisia. The epidemic spread rapidly in the following years. Twenty‐four commercial citrus orchards from four Tunisian regions showing characteristic symptoms of bacterial diseases were surveyed during a 3‐year study. Eighty‐eight Pseudomonas‐like bacterial isolates were successfully obtained from the northeast and west of Tunisia. No isolates were recovered from the central region. Overall, 46 isolates were identified as Pseudomonas syringae pv. syringae and most of them showed similar phenotypic and genetic profiles. The virulence of three selected isolates differed from one plant cultivar to another as well as from the type of plant organ used for the inoculation. In a bioassay test, all isolates produced syringomycin, which was confirmed by molecular detection based on the syrB and syrD genes. Only EC122 possessed syrD but not syrB. DNA fingerprints, based on repetitive sequence‐based polymerase chain reaction (rep‐PCR) and PCR melting profile (PCR MP), were used to determine the potential genetic diversity among strains. Clustering of PCR MP fingerprinting data matched with rep‐PCR fingerprinting data. The generated distribution tree showed that Tunisian isolates were closely related to the citrus reference strain LMG5496. In contrast, EC112, isolated from citrus, and the almond isolate EC122 were distantly related to the type strain LMG1247^T isolated from lilac. Such studies have not been reported until now for P. syringae from citrus.