Acclimatization of micropropagated plantlets induces an antioxidative burst: a case study with <Emphasis Type="Italic">Ulmus minor</Emphasis> Mill.

In this article, the effects of increased light intensities on antioxidant metabolism during ex vitro establishment of Ulmus minor micropropagated plants are investigated. Three month old in vitro plants were acclimatized to ex vitro conditions in a climate chamber with two different light intensities, 200 μmol m⁻² s⁻¹ (high light, HL) and 100 μmol m⁻² s⁻¹ (low light, LL) during 40 days. Immediately after ex vitro transfer, the increase of both malondialdehyde (MDA) and electrolyte leakage in persistent leaves is indicative of oxidative stress. As the acclimatization continues, an upregulation of the superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) enzyme activities were also observed. Simultaneously, MDA content and membrane permeability stabilized, suggesting that the antioxidant enzymes decrease the deleterious effects of reactive oxygen species (ROS) generation. Unexpectedly, newly formed leaves presented a different pattern of antioxidative profile, with high levels of MDA and membrane leakage and low antioxidant enzyme activity. Despite these differences, both leaf types looked healthy (e.g. greenish, with no necrotic spots) during the whole acclimatization period. The results indicate that micropropagated U. minor plantlets develop an antioxidant enzyme system after ex vitro transfer and that, in general, LL treatment leads to lower oxidative stress. Moreover, new leaves tolerate higher levels of ROS without the need to activate the antioxidative pathway, which suggests that the environment at which leaves are exposed during its formation determinate their ability to tolerate ROS.     

Antioxidant role of astaxanthin in the green alga Haematococcus pluvialis

The green unicellular alga, Haematococcus pluvialis has two antioxidative mechanisms against environmental oxidative stress: antioxidative enzymes in vegetative cells and the antioxidative ketocarotenoid, astaxanthin, in cyst cells. We added a reagent that generates superoxide anion radicals (O₂ ⁻), methyl viologen, to mature and immature cysts of H. pluvialis. Tolerance to methyl viologen was higher in mature than in immature cysts. Mature (astaxanthin-rich) cysts showed high antioxidant activity against O₂ ⁻ in permeabilized cells, but not in astaxanthin-free cell extracts, while immature (astaxanthin-poor) cysts had very low antioxidant activities against O₂ ⁻ in both. The results suggested that astaxanthin accumulated in the cyst cells functions as an antioxidant against excessive oxidative stress. The same levels of antioxidant activities against O₂ ⁻ in both permeabilized cells and cell extracts from vegetative cells suggested the presence of antioxidative enzymes (superoxide dismutase). Received: 13 January 1997 / Received revision: 26 February 1997 / Accepted: 27 March 1997     

Effects of cytokinin on callus proliferation associated with physiological and biochemical changes in <Emphasis Type="Italic">Vitis vinifera</Emphasis> L.

The essential role of 6-benzylaminopurine (BA) in plant tissue culture has been widely known; however, physiological and biochemical mechanisms behind BA requirement have not been fully understood yet. BA may have an important role on callus growth by regulating antioxidant enzyme activities and acting as an effective free radical scavenger. To test this hypothesis, the impact of exogenous BA concentrations on antioxidative system in Vitis vinifera L. cv. ‘Bogazkere’ callus was investigated under in vitro conditions. Relative fresh weight growth (RFWG) of calli, total phenolics (TP) content, endogenous hydrogen peroxide (H₂O₂), malondialdehyde (MDA), proline concentrations, percentage of electrolyte leakage (EL), and some of the antioxidant enzyme activities; such as superoxide dismutase (SOD), and guaiacol peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were measured. Inhibitory effect of high concentrations of BA on antioxidant enzyme activities and RFWG was found. In the presence of BA at 0.1 mg L⁻¹, SOD, POD, and APX activities decreased, while CAT activity increased in comparison with the controls. Exogenous BA treatments higher than 0.1 mg L⁻¹ resulted in an increase in cellular TP, H₂O₂, MDA, proline contents, and percentage of EL, while RFWG of calli decreased. Based on the findings, it may be concluded that only 0.1 mg L⁻¹ BA concentration combined with NAA could play a direct role in reducing the level of free radicals and phenolic production associated with proliferation capacity of grape cells under in vitro conditions. Furthermore, cytokinin was effective in the antioxidative enzyme system, lipid peroxidation, and electrolyte leakage.     

Selenium as an anti-oxidant and pro-oxidant in ryegrass

Selenium is an essential element for antioxidation reactions in human and animals. In order to study its biological role in higher plants, ryegrass (Lolium perenne) was cultivated in a soil without Se or amended with increasing dosages of H₂SeO₄ (0.1, 1.0, 10.0 and 30.0 mg Se kg⁻¹). Ryegrass was harvested twice and the yields were analyzed for antioxidative systems and growth parameters. Selenium exerted dual effects: At low concentrations it acted as an antioxidant, inhibiting lipid peroxidation, whereas at higher concentrations, it was a pro-oxidant, enhancing the accumulation of lipid peroxidation products. The antioxidative effect was associated with an increase in glutathione peroxidase (GSH-Px) activity, but not with superoxide dismutase (SOD) and αα-tocopherol, which was the only tocopherol detected. In the second yield, the diminished lipid peroxidation due to a proper Se addition coincided with promoted plant growth. The oxidative stress found at the Se addition level ≥ 10 mg kg⁻¹ resulted in drastic yield losses. This result indicates that the toxicity of Se can be attributed, in addition to metabolic disturbances, to its pro-oxidative effects. Neither the growth-promoting nor the toxic effect of Se could be explained by the changes in the total chlorophyll concentration. This revised version was published online in June 2006 with corrections to the Cover Date.     

The effects of superoxide dismutase knockout on the oxidative stress parameters and survival of mouse erythrocyt

The erythrocytes of 12-month old Sod1 ^−/− mice showed an increased level of reactive oxygen species (ROS), as estimated by the degree of dihydroethidine and dihydrorhodamine oxidation, and the increased level of Heinz bodies. No indices of severe oxidative stress were found in the red blood cells and blood plasma of Sod1 ^−/− mice as judged from the lack of significant changes in the levels of erythrocyte and plasma glutathione, plasma protein thiol and carbonyl groups and thiobarbituric-acid reactive substances in the blood plasma. However, a decreased erythrocyte lifespan, increased reticulocyte count and splenomegaly were noted, indicating the importance of superoxide dismutase for maintaining erythrocyte viability. The levels of erythrocyte ROS and Heinz bodies and the reticulocyte count were indistinguishable in Sod1 ^+/+ and Sod1 ^+/− mice, suggesting that a superoxide dismutase activity decrease to half of its normal value may be sufficient to secure the protective effects of the enzyme.     

Effects of 28-homobrassinolide on growth, lipid peroxidation and antioxidative enzyme activities in seedlings of Zea mays L. under salinity stress

The effects of 28-homobrassinolide (28-homoBL) on seedling growth, lipid peroxidation and antioxidative enzyme activities in the seedlings of Zea mays L. (var. Partap-1) under salt (NaCl) stress were studied. The surface-sterilized seeds were germinated in petriplates containing different concentrations of NaCl (25, 50, 75 and 100 mM) only, 28-homoBL (10⁻⁷, 10⁻⁹ and 10⁻¹¹ M) only and NaCl supplemented with 28-homoBL for 7 days. The activities of superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (POD, EC 1.11.1.7), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APOX, EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) were analysed in 7 day-old seedlings. It was observed that 28-homoBL treatments reduced the toxicity of salt on seedling growth considerably. Lipid peroxidation level was significantly increased under saline stress, but lowered with 28-homoBL applications revealing less oxidative damage. Further 28-homoBL treatments to the seedlings showed an enhancement in activities of SOD, POD, CAT and APOX. The activities of all antioxidative enzymes were further increased in seedlings treated with solution containing 28-homoBL and salt together as compared to seedlings treated with different concentration of salt solution only.     

Mammalian sex hormones stimulate antioxidant system and enhance growth of chickpea plants

In the present study, it was aimed to investigate the influence of exogenous mammalian sex hormones (MSH) (progesterone, β-estradiol and androsterone) on the morphological (root and shoot growth) and biochemical parameters (protein and sugar content, antioxidant enzyme activities, and lipid peroxidation and H₂O₂ levels) of chickpea (Cicer arietinum L.) plants growing under control conditions. The solutions of hormones prepared at different concentrations (10⁻⁴, 10⁻⁶, 10⁻⁹, 10⁻¹² and 10⁻¹⁵ M) were sprayed once on the leaves of 7-day plants. The plants were harvested on 18 days after the hormone treatment. Although all of the hormones at the tested concentrations significantly increased plant growth, soluble protein and sugar contents, and antioxidant enzyme activities [superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT)], they decreased H₂O₂ content and lipid peroxidation level when compared with control plants. The activities of SOD, POX and CAT reached to the highest levels at 10⁻⁶ M for progesterone, and 10⁻⁹ M for β-estradiol and androsterone, which maximum growth, protein and sugar contents were determined. The same concentrations also resulted in the lowest levels for H₂O₂ content and lipid peroxidation. It can be interpreted that the MSH improve plant growth and development by affecting some biochemical parameters including antioxidative system.     

Plant growth and responses of antioxidants of <Emphasis Type="Italic">Chenopodium album</Emphasis> to long-term NaCl and KCl stress

The effects of long-term NaCl and KCl treatment on plant growth and antioxidative responses were investigated in Chenopodium album, a salt-resistant species widely distributed in semi-arid and light-saline areas of Xinjiang, China. Growth parameters [plant height, branch number, leaf morphology and chlorophyll (Chl) content], the level of oxidative stress [superoxide anion radical (O₂ ⁻), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) concentrations], activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX)], the contents of non-enzymatic antioxidants [carotenoids (Car) and ascorbic acid (AsA)] and expression of selected genes were investigated. Plants were grown in the presence of 0, 50, and 300 mM NaCl or KCl for 2 months. Growth was stimulated by 50 mM NaCl or KCl, maintained stable at 300 mM NaCl, but was inhibited by 300 mM KCl. Three hundred mM NaCl did not affect O₂ ⁻, H₂O₂, MDA, Car and AsA, but increased the activities of SOD, CAT and POX compared to the controls. RT-PCR analysis suggested that expression of some genes encoding antioxidant enzymes could be induced during long-term salt stress, which was consistent with the enzyme activities. Treatment with 300 mM KCl was associated with elevated oxidative stress, and significantly decreased Car and AsA contents. These results suggest that an efficient antioxidant machinery is important for overcoming oxidative stress induced by treatment with high NaCl concentrations in C. album. Other strategies of ion regulation may also contribute to the differential tolerance to Na and K at higher concentrations.     

Cadmium and copper induction of oxidative stress and antioxidative response in tomato (<Emphasis Type="Italic">Solanum lycopersicon</Emphasis>) leaves

We compare cadmium and copper induced oxidative stress in tomato leaves and the antioxidative enzyme response during a time course of 96 h. Plants were subjected to 25 μM of CdCl₂ or CuSO₄ and malondialdehyde (MDA) level and activity of guaiacol peroxidase, superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were determined. The results showed that there was an early increase in the MDA level and in the guaiacol peroxidase activity more pronounced with copper exposure during almost all the time course of the experiment. The activity of superoxide dismutase and catalase was induced very early after cadmium and copper treatment, reached a maximal value after 12 h and then declined but it remained always slightly higher than the control at the end of the experiment. Ascorbate peroxidase activity pathway was similar to superoxide dismutase or catalase with a maximal activity after 48 h of heavy metal exposure. Induction of glutathione reductase activity observed only under copper exposure is maintained during almost all the experimental time. The antioxidative activity developed by tomato leaves is more induced by copper treatment. This can be related to the ability of this metal to induce more than cadmium an accumulation of reactive oxygen species (ROS) at the cellular level. Decline in the antioxidative enzymes activity at the end of the experiment can be a consequence of cadmium- and copper-inducing a further ROS formation that might affect enzymes activity.     

Efficient regeneration and antioxidative enzyme activities in <Emphasis Type="Italic">Brassica rapa</Emphasis> var. <Emphasis Type="Italic">turnip</Emphasis>

The regeneration potential and antioxidative enzyme activities of economically important Brassica rapa var. turnip were evaluated. Calli were induced from leaf explants of seed-derived plantlets on Murashige and Skoog (MS) medium incorporated with different concentrations of various plant growth regulators (PGRs). The highest leaf explant response (83%) was recorded for 2.0 mg l⁻¹ benzyladenine (BA) and 1.0 mg l⁻¹ α-naphthaleneacetic acid (NAA). Subsequent subculturing of callus after 3 weeks of culture, on medium with similar compositions of PGRs, induced shoot organogenesis. The highest shoot induction response (83%) was recorded for 5.0 mg l⁻¹ BA after 5 weeks of transfer. However, 7.8 shoots/explant were recorded for 2.0 mg l⁻¹ BA. The transferring of shoots to elongation medium resulted in 5.1-cm-long shoots on 10 mg l⁻¹ of gibberellic acid (GA₃). Rooted plantlets were obtained on MS medium containing different concentrations of indole butyric acid (IBA). The determination of activities of antioxidative enzymes (superoxide dismutase [SOD], ascorbate peroxidase [APX], catalase [CAT], glutathione peroxidase [GPX], and peroxidase [POD]) revealed involvement of these enzymes in callus formation and differentiation. All of the activities were interlinked with each other and played significant roles in the scavenging of toxic free radicals. This study will help in the advancement of a regeneration protocol for B. rapa var. turnip and the understanding of the functions of antioxidative enzymes in plant differentiation.     

Oral Administration of Lycopene Reverses Cadmium-suppressed Body Weight Loss and Lipid Peroxidation in Rats

Cadmium (Cd) exposure has been recognized to result in a wide variety of cellular responses, including oxidative stress and body weight loss. The aim of the present study was to examine the effect of lycopene supplementation on the antioxidant defense system, lipid peroxidation (LPO) level, nitric oxide (NO), tumor necrosis factor alpha (TNF-α) production, and body weight in Cd-exposed rats. Animals were divided into four groups (n = 7): control, Cd-treated, Cd plus lycopene-treated, and lycopene-treated. Cadmium (as CdCl₂) was administrated orally for 20 days (6.6 mg kg⁻¹ day⁻¹), and lycopene (10 mg kg⁻¹ day⁻¹) was similarly administered. Lycopene administration significantly suppressed Cd-induced LPO in plasma and kidney homogenates. Lycopene also reversed Cd-decreased body weight compared to the control. Cadmium treatment had diverse effects on the antioxidant enzyme activities. Although antioxidant superoxide dismutase activity was unchanged, glutathione peroxidase activity was decreased, and catalase activity was elevated in kidney homogenates of Cd-administrated group. However, lycopene treatment reversed Cd-changed enzyme activities to the control level. Xanthine oxidase activity and TNF-α concentration were not altered by Cd administration, indicating that superoxide anion production and inflammation were not stimulated. Cadmium did not change NO levels in kidney homogenates but decreased those in plasma, and this effect was not prevented by lycopene supplementation. The result suggests that consumption of adequate levels of lycopene may be useful to prevent heavy-metal-induced LPO and body weight loss.     

Effects of Selenium and Vitamin E,in Addıtıon to Melatonin,Against Oxidative Stress Caused by Cadmium in Rats

The present study was carried to evaluate the protective effects of melatonin alone and vitamin E with selenium combination against high dose cadmium-induced oxidative stress in rats. The control group received subcutanous physiological saline. The first study group administered cadmium chloride (CdCl₂) by subcutaneous injection of dose of 1 mg/kg. The second study group administered cadmium plus vitamin E with selenium (1 mg/kg sodium selenite with 60 mg/kg vitamin E); the third study group administered cadmium plus 10 mg/kg melatonin (MLT); the fourth study group administered CdCl₂ plus a combination of melatonin in addition to vitamin E and selenium for a month. Determination levels of plasma malondialdehyde (MDA), glutathione peroxidase (GSH-Px), blood superoxide dismutase (SOD), creatinine alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), blood urea nitrogen (BUN), and urea were measured in serum. In only CdCl₂ administered group, the MDA, creatinine, ALT, AST, ALP, and urea levels in the serum were significantly higher than the control group (p < 0.05). Whereas in all other groups, this values were significantly lower than the only CdCl₂ administered group (p < 0.05). Erythrocytes GSH-Px, serum SOD activities of only CdCl₂ received group were significantly lower than the control group (p < 0.05). In conclusion, vitamin E + Se, melatonin and vitamin E, and Se, in addition to MLT combinations, had protective effects against high dose cadmium-induced oxidative damage.     

A highly stable Cu/Zn superoxide dismutase from <Emphasis Type="Italic">Withania somnifera</Emphasis> plant: gene cloning,expression and characterization of the recombinant protein

A gene from Withania somnifera (winter cherry), encoding a highly stable chloroplastic Cu/Zn superoxide dismutase (SOD), was cloned and expressed in Escherichia coli. The recombinant enzyme (specific activity of ~4,200 U mg⁻¹) was purified and characterized. It retained ~90 and ~70% residual activities after 1 h at 80 and 95°C, respectively. At 95°C, thermal inactivation rate constant (K _d) of the enzyme was 2.46 × 10⁻³ min⁻¹ and half-life of heat inactivation was 4.68 h. The enzyme was stable against a broad pH range (2.5–11.0). It also showed a high degree of resistance to detergent, ethanol and protease digestion. This recombinant Cu/Zn SOD could therefore have useful applications.     

Effects of 28-homobrassinolide on nickel uptake,protein content and antioxidative defence system in <Emphasis Type="Italic">Brassica juncea</Emphasis>

The effects of 28-homobrassinolide (HBL) on nickel uptake, protein content and activities of antioxidative enzymes were determined in the seedlings of Brassica juncea L. The seeds were treated with different concentrations (0, 0.01, 1 and 100 nM) of HBL for 8 h and then sown in the Petri plates containing various concentrations (0, 25, 50 and 100 mg dm⁻³) of nickel. After 7 d, observations were made on shoot and root length, Ni uptake, protein content and activities of antioxidative enzymes (guaiacol peroxidase, catalase, glutathione reductase, ascorbate peroxidase and superoxide dismutase). The growth of seedlings was inhibited by Ni, however, less after HBL pre-treatment. The protein content and antioxidative enzyme activities were also increased by HBL treatment.     

The in vivo and in vitro influence of methyl jasmonate on oxidative processes in Arabidopsis thaliana leaves

In Arabidopsis thaliana leaves a strong increase of H₂O₂ content was induced by application of methyl jasmonate (JAMe) through the root system, but the induction only slightly depended on JAMe concentration. The activity of superoxide dismutase and ascorbic acid peroxidase increased at lower JAMe concentrations and decreased at higher ones. Catalase activity decreased proportionally to JAMe concentration (in comparison with control plants). The sum of ascorbic acid and dehydroascorbate content at 10⁻⁶ M JAMe was similar to the control, but at higher concentrations it increased, especially due to a higher ascorbate accumulation. Methyl jasmonate applied directly to the extract of leaves (in vitro experiment) also induced a strong increase in H₂O₂ level, even at a low concentration (10⁻⁸ M). Since lower JAMe concentrations induced weak superoxide dismutase and did not change catalase and peroxidase activity, it is suggested that in this case a high level of hydrogen peroxide was not the result of the activity of the mentioned enzymes. JAMe-induction of H₂O₂ increase at the highest JAMe concentration resulted from SOD activity. Our in vivo and in vitro experiments suggest that jasmonate can influence oxidative stress not only through gene expression but also by its direct effect on enzyme activity.     

In Vitro and In Vivo Antioxidant Activity of <Emphasis Type="Italic">Bifidobacterium animalis</Emphasis> 01 Isolated from Centenarians

Several studies reported the antioxidant activity of bifidobacteria using assays in vitro. In present study, the in vitro and in vivo antioxidant activity of Bifidobacterium animalis 01 was investigated. Culture supernatant, intact cells, and intracellular cell-free extracts of B. animalis 01 were involved in this study. The antioxidant assays in vitro included lipid peroxidation assay, 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, hydroxyl radical ( ^• OH) assay and superoxide anion ( \textO₂ ^- {\text{O}}_{2}^{ - } ) assay. The antioxidant assays in vivo were conducted using mice model. Activities of antioxidative enzymes, malondialdehyde (MDA) content in serums and livers of aging mice were evaluated. Monoamine oxidase (MAO) activity and lipofuscin level in brains of aging mice were also characterized. Results showed that culture supernatant, intact cells and intracellular cell-free extracts of B. animalis 01 could effectively scavenge free radicals, significantly enhance mice’s activities of antioxidative enzymes and reduce mice’s MDA content, lipofuscin level and MAO activity. Our results indicated that B. animalis 01 has the potential to be developed into a dietary antioxidant supplements.     

Activation of the antioxidant complex in <Emphasis Type="Italic">Pseudomonas aurantiaca</Emphasis>—Producer of phenazine antibiotics

Two Pseudomonas aurantiaca mutant strains overproducing phenazine antibiotics (synthesis levels of 210 and 410 mg/l, respectively) along with wild-type bacteria (production level of 71–75 mg/l) and a phz⁻ mutant not producing phenazines were used to study the changes in the activity of the antioxidant complex components, that is, catalase, superoxide dismutase (SOD), glutathione reductase, and NADH oxidase; glutathione concentration (in both reduced and oxidized forms); and activity of acyl-CoA synthetase, the key enzyme of cell metabolism.     

Characterization of the superoxide dismutase SOD1 gene of Kluyveromyces marxianus L3 and improved production of SOD activity

Superoxide dismutase (SOD) activity is one major defense line against oxidative stress for all of the aerobic organisms, and industrial production of this enzyme is highly demanded. The Cu/Zn superoxide dismutase gene (KmSOD1) of Kluyveromyces marxianus L3 was cloned and characterized. The deduced KmSod1p protein shares 86% and 71% of identity with Kluyveromyces lactis and Saccharomyces cerevisiae Sod1p, respectively. The characteristic motifs and the amino acid residues involved in coordinating copper and zinc and in enzymatic function were conserved. To the aim of developing a microbial production of Cu/Zn superoxide dismutase, we engineered the K. marxianus L3 strain with the multicopy plasmid YG-KmSOD1 harboring the KmSOD1 gene. The production of KmSOD1p in K. marxianus L3 and K. marxianus L3 (pYG-KmSOD1) in response to different compositions of the culture medium was evaluated. The highest specific activity (472 U_SOD mg_prot ⁻¹) and the highest volumetric yield (8.8 × 10⁵ U_SOD l⁻¹) were obtained by the recombinant strain overexpressing KmSOD1 in the presence of Cu²⁺ and Zn²⁺ supplements to the culture media. The best performing culture conditions were positively applied to a laboratory scale fed-batch process reaching a volumetric yield of 1.4 × 10⁶ U_SOD l⁻¹. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of Acrylamide on the Nervous Tissue Antioxidant System and Sciatic Nerve Electrophysiology in the Rat

To investigate the time-dependent effects of acrylamide (ACR) on the antioxidative status in rat nerve tissues, adult male Wistar rats were given ACR (40 mg/kg, i.p., 3 times/week) for 2, 4, 6 and 10 weeks, respectively. The time-dependent changes of the lipid peroxidation (malondialdehyde, MDA) and antioxidative status (glutathione, GSH; glutathione peroxidase, GSH-Px; glutathione reductase, GR; superoxide dismutase, SOD and anti-reactive oxygen species, anti-ROS) in nerve tissues were investigated. The electrophysiology indices (nerve conduction velocity, NCV; compound action potential duration, CAPD; compound action potential amplitude, CAPA; compound action potential latency, CAPL) in the sciatic nerve were determined using BL-420E Biologic Function Determining System. The results showed that MDA levels increased significantly (P < 0.05) in nerve tissues, while GSH levels markedly decreased (P < 0.05) in a time-dependent manner. SOD activity (in the spinal cord and sciatic nerve) and GR activity (in the sciatic nerve) increased significantly after 4 weeks ACR treatment (P < 0.01), but then decreased (P < 0.05). The anti-ROS activity in the sciatic nerve was markedly decreased at the end of week 6 and 10 (P < 0.01). The above indices changed most in the sciatic nerve. The levels of GSH, MDA and anti-ROS in rat sciatic nerve were in high correlation (P < 0.05, |r| > 0.80) with the electrophysiology indices according to the exposure time. Thus, ACR-induced neurotoxicity may be associated with the enhancement of lipid peroxidation and reduction of the antioxidative capacity. Depletion of neural GSH level might be one of the primary events in ACR-induced neuropathy. Ying-Jian Zhu and Tao Zeng––These authors contributed equally to this work.     

Paraquat pre-treatment increases activities of antioxidant enzymes and reduces lipid peroxidation in salt-stressed cucumber leaves

To investigate whether paraquat (PQ) is involved in regulation of antioxidant enzymes and lipid peroxidation under short-term salt stress, and to elucidate the physiological mechanism of salt stress mitigated by PQ, a cucumber cultivar (cv. Chunguang no. 2) was exposed to 100 mM NaCl for 48 h after pre-treatment with 10 μM PQ for 1 h. When compared to the control, salt stress increased the levels of malonaldehyde (MDA), superoxide radical (O₂^·−) and hydrogen peroxide (H₂O₂) and the activities of antioxidant enzymes, such as superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) in the cucumber leaves. Under salt conditions, PQ pre-treatment prevented oxidative stress as observed by the decreases in MDA, H₂O₂ and O₂^·− that correlated with the increase in antioxidant defenses. We propose that, at low concentrations, the PQ pre-treatment can reduce the salt-induced oxidative damage by increasing the antioxidative mechanisms in cucumber plants.