Induction Of Catalase Research Articles

Enhancement Of Normal Hematopoietic Stem Cells By Redox-Active Antioxidants

Injury to hematopoietic tissues is a major problem limiting the success of cancer therapy, including ionizing radiation, chemotherapy, and immunotherapy. Acute injury to hematopoietic cells challenges hematopoietic stem cells (HSCs) to regenerate for self-renewal and differentiate into different lineages of peripheral blood cells. It is well-documented that HSCs reside in a hypoxia niche and have a lower level of reactive oxygen species (ROS) than their mature progeny. Life-long measurements of local oxygen tension (pO2) in the bone marrow of living mice show that the absolute pO2 of bone marrow is Here, we demonstrate that, in transgenic mice expressing the human manganese superoxide dismutase (MnSOD) gene, a scavenger of ROS in mitochondria, the number and function of hematopoietic stem/progenitor cells (HSPCs) under physiological conditions is enhanced. Importantly, giving MnTnBuOE-2-PyP5+ (MnP), a redox- active MnSOD mimetic, to mouse primary bone marrow cells or to C57B/L6 mice significantly enhances the number of HSPCs. Mechanistically, MnP reduces superoxide to hydrogen peroxide, which activates intracellular Nrf2 signaling leading to the induction of antioxidant enzymes, including MnSOD and catalase, and mitochondrial uncoupling proteins. The results reveal a novel aspect of ROS signaling in regulating stem cell function, and suggest possible beneficial effects of MnP in treating pathological bone marrow cell loss and increasing stem cell population for bone marrow transplantation, and the development of redox-based therapies.

Induction of resistance in tomato against Xanthomonas perforans by lipopolysaccharides of the pathogen

The goal of this study was to investigate the role of lipopolysaccharides (LPS) in induction of resistance in tomato against the causal agent of bacterial spot, Xanthomonas perforans. The results showed that pre-treatment with LPS leads to enhancing resistance of tomato against X. perforans. In addition, expression profiling of β-1,3-glucanase (BGL), Phenylalanine ammonia-lyase (PAL) and catalase (CAT) was examined during the induced resistance by LPS. The effect of LPS on induction of BGL, PAL and CAT was demonstrated in the present study. The data suggest that the effect of LPS on resistance of tomato against X. perforans could be through activation of some defence genes such as of BGL, PAL and CAT which afford defence responses against the pathogen. Our findings might help to better understanding the molecular bases of the induced resistance by LPS.

Fenofibrate Administration Reduces Alcohol and Saccharin Intake in Rats: Possible Effects at Peripheral and Central Levels.

We have previously shown that the administration of fenofibrate to high-drinker UChB rats markedly reduces voluntary ethanol intake. Fenofibrate is a peroxisome proliferator-activated receptor alpha (PPARα) agonist, which induces the proliferation of peroxisomes in the liver, leading to increases in catalase levels that result in acetaldehyde accumulation at aversive levels in the blood when animals consume ethanol. In these new studies, we aimed to investigate if the effect of fenofibrate on ethanol intake is produced exclusively in the liver (increasing catalase and systemic levels of acetaldehyde) or there might be additional effects at central level. High drinker rats (UChB) were allowed to voluntary drink 10% ethanol for 2 months. Afterward, a daily dose of fenofibrate (25, 50 or 100 mg/kg/day) or vehicle (as control) was administered orally for 14 days. Voluntary ethanol intake was recorded daily. After that time, animals were deprived of ethanol access for 24 h and administered with an oral dose of ethanol (1 g/kg) for acetaldehyde determination in blood. Fenofibrate reduced ethanol voluntary intake by 60%, in chronically drinking rats, at the three doses tested. Acetaldehyde in the blood rose up to between 80 μM and 100 μM. Considering the reduction of ethanol consumption, blood acetaldehyde levels and body weight evolution, the better results were obtained at a dose of 50 mg fenofibrate/kg/day. This dose of fenofibrate also reduced the voluntary intake of 0.2% saccharin by 35% and increased catalase levels 2.5-fold in the liver but showed no effects on catalase levels in the brain. To further study if fenofibrate administration changes the motivational properties of ethanol, a conditioned-place preference experiment was carried out. Animals treated with fenofibrate (50 mg/kg/day) did not develop ethanol-conditioned place preference (CPP).In an additional experiment, chronically ethanol-drinking rats underwent two cycles of ethanol deprivation/re-access, and fenofibrate (50 mg/kg/day) was given only in deprivation periods; under this paradigm, fenofibrate was also able to generate a prolonged (30 days) decreasing of ethanol consumption, suggesting some effect beyond the acetaldehyde-generated aversion. In summary, reduction of ethanol intake by fenofibrate appears to be a consequence of a combination of catalase induction in the liver and central pharmacological effects.

Mercury induced oxidative stress, DNA damage, and activation of antioxidative system and Hsp70 induction in duckweed (Lemna minor)

Mercury uptake and its effects on physiology, biochemistry and genomic stability were investigated in Lemna minor after 2 and 6d of exposure to 0–30μM Hg. The accumulation of Hg increased in a concentration- and duration-dependent manner, and was positively correlated with the leaf damage. Oxidative stress after Hg exposure was evidenced in L. minor by a significant decrease in photosynthetic pigments, an increase in malondialdehyde and lipoxygenase activities (total enzyme activity and isoenzymes activity). Fronds of L. minor exposed to Hg showed an induction of peroxidase, catalase, and ascorbate peroxidase activities (total enzyme activity and some isoenzymes activities). Exposure of L. minor to Hg reduced the activity (total enzyme activity and some isoenzymes activities) of glutathione reductase, and superoxide dismutase. Exposure to Hg produced a transient increase in the content of glutathione and ascorbic acid. The content of dehydroascorbate and oxidized glutathione in L. minor were high during the entire exposure period. Exposure of L. minor to Hg also caused the accumulation of proline and soluble sugars. The amplification of new bands and the absence of normal DNA amplicons in treated plants in the random amplified polymorphic DNA (RAPD) profile indicated that genomic template stability (GTS) was affected by Hg treatment. The accumulation of Hsp70 indicated the occurrence of a heat shock response at all Hg concentrations. These results suggest that L. minor plants were able to cope with Hg toxicity through the activation of various mechanisms involving enzymatic and non-enzymatic antioxidants, up-regulation of proline, and induction of Hsp70.

Catalase protects Aedes aegypti from oxidative stress and increases midgut infection prevalence of Dengue but not Zika

BackgroundDigestion of blood in the midgut of Aedes aegypti results in the release of pro-oxidant molecules that can be toxic to the mosquito. We hypothesized that after a blood meal, the antioxidant capacity of the midgut is increased to protect cells against oxidative stress. Concomitantly, pathogens present in the blood ingested by mosquitoes, such as the arboviruses Dengue and Zika, also have to overcome the same oxidative challenge, and the antioxidant program induced by the insect is likely to influence infection status of the mosquito and its vectorial competence.Methodology/Principal findingsWe found that blood-induced catalase mRNA and activity in the midgut peaked 24 h after feeding and returned to basal levels after the completion of digestion. RNAi-mediated silencing of catalase (AAEL013407-RB) reduced enzyme activity in the midgut epithelia, increased H2O2 leakage and decreased fecundity and lifespan when mosquitoes were fed H2O2. When infected with Dengue 4 and Zika virus, catalase-silenced mosquitoes showed no alteration in infection intensity (number of plaque forming units/midgut) 7 days after the infectious meal. However, catalase knockdown reduced Dengue 4, but not Zika, infection prevalence (percent of infected midguts).Conclusion/SignificanceHere, we showed that blood ingestion triggers an antioxidant response in the midgut through the induction of catalase. This protection facilitates the establishment of Dengue virus in the midgut. Importantly, this mechanism appears to be specific for Dengue because catalase silencing did not change Zika virus prevalence. In summary, our data suggest that redox balance in the midgut modulates mosquito vectorial competence to arboviral infections.

Early response of wheat antioxidant system with special reference to Fusarium head blight stress

Fusarium head blight (FHB) is a destructive fungal disease of wheat (Triticum aestivum L.) that causes significant grain yield losses and end-use quality reduction associated with contamination by the mycotoxin deoxynivalenol (DON). Three winter wheat varieties (‘Vulkan’, ‘Kraljica’ and ‘Golubica’) were screened for FHB resistance using artificial inoculation technique under field conditions. The aim of this study was to examine a relationship between FHB resistance and the effectiveness of enzyme antioxidant system of wheat varieties under different sampling times (3, 15, 24, 48, 96, 120 and 336 hai). In the time-course experiments FHB-resistant variety ‘Vulkan’ showed rapid induction of ascorbate peroxidase (APX) and polyphenol oxidase (PPO) activity in the early stages after infection (3 hai) and it seems that in ‘Vulkan’ FHB-resistance is associated with antioxidative enzymes activity. Moderately FHB resistant variety ‘Kraljica’ showed the higher guaiacol peroxidase (POD) activity and higher H2O2 content after 24 hai, increased malondialdehyde (MDA) content at the beginning of infection (3, 15 hai) while induction of catalase (CAT), APX and PPO was delayed. FHB-susceptible variety ‘Golubica’ involved antioxidant enzymes in defense response much later. Based on our results the activity of antioxidant enzymes (APX and PPO) was more pronounced in ‘Vulkan’ than in FHB-medium resistant variety ‘Kraljica’ and FHB-susceptible ‘Golubica’. The differences in antioxidant response of wheat varieties under Fusarium infestation could be the result of genetic properties.

A novel redox regulator, MnTnBuOE-2-PyP5+, enhances normal hematopoietic stem/progenitor cell function

The signaling of reactive oxygen species (ROS) is essential for the maintenance of normal cellular function. However, whether and how ROS regulate stem cells are unclear. Here, we demonstrate that, in transgenic mice expressing the human manganese superoxide dismutase (MnSOD) gene, a scavenger of ROS in mitochondria, the number and function of mouse hematopoietic stem/progenitor cells (HSPC) under physiological conditions are enhanced. Importantly, giving MnTnBuOE-2-PyP5+(MnP), a redox- active MnSOD mimetic, to mouse primary bone marrow cells or to C57B/L6 mice significantly enhances the number of HSPCs. Mechanistically, MnP reduces superoxide to hydrogen peroxide, which activates intracellular Nrf2 signaling leading to the induction of antioxidant enzymes, including MnSOD and catalase, and mitochondrial uncoupling protein 3. The results reveal a novel role of ROS signaling in regulating stem cell function, and suggest a possible beneficial effect of MnP in treating pathological bone marrow cell loss and in increasing stem cell population for bone marrow transplantation.

Induction of resistance in pepper against Xanthomonas euvesicatoria by β-aminobutyric acid

Xanthomonas euvesicatoria is one of the most destructive pathogens of pepper that results in serious yield loss worldwide. Previous studies confirmed that β-aminobutyric acid (BABA) induces resistance in plants against a variety of pathogens. A promoted resistance of pepper induced by BABA to X. euvesicatoria was demonstrated in this study. Additionally, induction of catalase and pathogenesis-related gene 1 during the BABA-induced resistance was confirmed. Our data provides useful information for the development of disease management programs.

Canthaxanthin: From molecule to function.

The aim of this review is to summarize the relevant literature about the use of canthaxanthin in food science and nutrition research. Canthaxanthin is a red-orange carotenoid that belongs to the xanthophyll group. This naturally occurring pigment is present in bacteria, algae and some fungi. Canthaxanthin is also responsible for the color of flamingo feathers, koi carp skin and crustacean shells. Canthaxanthin is widely used in poultry (broiler, laying hens) as a feed additive. Canthaxanthin can be obtained by total synthesis. The canthaxanthin-mediated color of foods is an important quality criterion for consumers. Recently, the potential health-promoting effects of canthaxanthin have been discussed. Canthaxanthin enrichment of LDL has the potential to protect cholesterol from oxidation. In addition to its free radical scavenging and antioxidant properties (e.g., the induction of catalase and superoxide dismutase), canthaxanthin's immunomodulatory activity (e.g., enhancing the proliferation and function of immune competent cells) and its important role in gap junction communication (e.g., induction of the transmembrane protein connexin 43) have been reported. Many studies regarding the potential health benefits of canthaxanthin have been conducted in vitro and should be validated in appropriate in vivo models.

Activation of Peroxisome Proliferator-Activated Receptor Alpha Improves Aged and UV-Irradiated Skin by Catalase Induction

Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear hormone receptor involved in the transcriptional regulation of lipid metabolism, fatty acid oxidation, and glucose homeostasis. Its activation stimulates antioxidant enzymes such as catalase, whose expression is decreased in aged human skin. Here we investigated the expression of PPARα in aged and ultraviolet (UV)-irradiated skin, and whether PPARα activation can modulate expressions of matrix metalloproteinase (MMP)-1 and procollagen through catalase regulation. We found that PPARα mRNA level was significantly decreased in intrinsically aged and photoaged human skin as well as in UV-irradiated skin. A PPARα activator, Wy14643, inhibited UV-induced increase of MMP-1 and decrease of procollagen expression and caused marked increase in catalase expression. Furthermore, production of reactive oxygen species (ROS) was suppressed by Wy14643 in UV-irradiated and aged dermal fibroblasts, suggesting that the PPARα activation-induced upregulation of catalase leads to scavenging of ROS produced due to UV irradiation or aging. PPARα knockdown decreased catalase expression and abolished the beneficial effects of Wy14643. Topical application of Wy14643 on hairless mice restored catalase activity and prevented MMP-13 and inflammatory responses in skin. Our findings indicate that PPARα activation triggers catalase expression and ROS scavenging, thereby protecting skin from UV-induced damage and intrinsic aging.

Superoxide serves as a putative signal molecule for plant cell division: overexpression of CaRLK1 promotes the plant cell cycle via accumulation of O2- and decrease in H2 O2.

Reactive oxygen species (ROS) exert both positive and negative effects on plant growth and development and therefore receive a great deal of attention in current research. A hot pepper, Capsicum annuum receptor-like kinase 1 (CaRLK1) was ectopically expressed in Nicotiana tabacum BY-2 cell and Nicotiana benthamiana plants. This ectopic expression of CaRLK1 enhanced cell division and proliferation in both heterologous systems. Apparently, CaRLK1 is involved in controlling the cell cycle, possibly by inducing expressions of cyclin B1, cyclin D3, cyclin-dependent protein kinase 3, condensin complex subunit 2 and anaphase-promoting complex subunit 11 genes. CaRLK1 overexpression also increased transcript accumulation of NADPH oxidase genes, generation of O2- and catalase (CAT) activity/protein levels. In parallel, it decreased cellular H2 O2 levels and cell size. Treatment with Tiron or diphenyleneiodonium (DPI) both decreased the cell division rate and O2- concentrations, but increased cellular H2 O2 levels. Tobacco BY-2 cells overexpressing CaRLK1 were more sensitive to amino-1,2,4-triazole (3-AT), a CAT inhibitor, than control cells, suggesting that the increased H2 O2 levels may not function as a signal for cell division and proliferation. Overexpression of CaRLK1 stimulated progression of the cell cycle from G0 /G1 phase into the S phase. It is concluded that the CaRLK1 protein plays a pivotal role in controlling the level of O2- as signaling molecule which promotes cell division, concomitant with a reduction in H2 O2 by the induction of CAT activity/protein.

Sensitivity and Antioxidant Response of Chlorella sp. MM3 to Used Engine Oil and Its Water Accommodated Fraction.

We exposed the microalgal strain, Chlorella sp. MM3, to unused or used engine oil, or their water accommodated fractions (WAFs) to determine growth inhibition and response of antioxidant enzymes. Oil type and oil concentration greatly affected the microalgal growth. Used oil at 0.04% (0.4g L(-1)) resulted in 50% inhibition in algal growth, measured in terms of chlorophyll-a, while the corresponding concentration of unused oil was nontoxic. Similarly, used oil WAF showed significant toxicity to the algal growth at 10% level, whereas WAF from unused oil was nontoxic even at 100% concentration. Peroxidase enzyme in the microalga significantly increased with used oil at concentrations above 0.04g L(-1) whereas the induction of superoxide dismutase and catalase was apparent only at 0.06g L(-1). Activities of the antioxidant enzymes increased significantly when the microalga was exposed to 75 and 100% WAF obtained from used oil. The used oil toxicity on microalga could be due to the presence of toxic soluble mono- and polyaromatic compounds, heavy metals, and other compounds attained by the oil during its use in the motor engines.

Effects of Standardised Fermented Papaya Gel on Clinical Symptoms, Inflammatory Cytokines, and Nitric Oxide Metabolites in Patients with Chronic Periodontitis: An Open Randomised Clinical Study.

The clinical efficacy of topical administration of standardised fermented papaya gel (SFPG), known to have antioxidant and anti-inflammatory properties, versus conventional therapy was evaluated in a group of 84 patients with moderate-to-severe periodontitis, randomly assigned to control group (n = 45) undergoing traditional pharmacologic/surgical protocols or to experimental group (n = 39), additionally treated with intragingival pocket SFPG (7 g) applications (15 min daily for 10 days). Patients undergoing SFPG treatment showed significant (P < 0.05), durable improvement of three major clinical indices of disease severity: reduced bleeding (day 7), plaque and gingival conditions (day 14), and consistent gingival pocket depth reduction (day 45). Proinflammatory nitric oxide metabolites reached normal values in plasma (day 14) and gingival crevicular fluid (GCF) at day 45 with SFPG applications compared to controls that did not reach normalisation. Levels of highly increased proinflammatory (IL-1B, IL-6) and suppressed anti-inflammatory (IL-10) cytokines normalised in the SFPG group by days 14 (plasma) and 45 (GCF), but never in the control group. Although not acting directly as antibiotic, SFPG acted in synergy with human granulocytes blocking adaptive catalase induction in S. aureus in response to granulocyte-derived oxidative stress, thus enhancing intracellular bacterial killing.

Gene response of CYP360A, CYP314, and GST and whole-organism changes in Daphnia magna exposed to ibuprofen

The fate and ecological impact of non-steroidal anti-inflammatory drugs (NSAIDs) in aquatic environments has gained increasingly concern recently. However, limited information is provided about the toxicity mechanism of NSAIDs to aquatic invertebrates. In the present study, we investigated the expression of CYP360A, CYP314, and GST genes involved in the detoxification process and the responses of their associated enzymes activity, as well as whole-organism changes in Daphnia magna exposed to environmentally relevant concentrations of ibuprofen (IBU). Results showed that the total amount of eggs produced per female, total number of brood per female, and body length were significantly decreased under IBU exposure, suggesting the effects of chronic IBU exposure on growth and reproduction of D. magna cannot be ignored. In gene expression level, the CYP360A gene, homologue to CYP3A in mammalian, showed inhibition at low concentration of IBU (0.5μg·L−1) and induction at high concentration of IBU (50μg·L−1). GST gene also exhibited a similar performance to CYP3A. CYP314 displayed inhibition for short time exposure (6h) and induced with prolonged exposure time (48h) at low concentration of IBU (0.5μg·L−1). Erythromycin N-demethylase (ERND) and aminopyrine N-demethylase (APND) related to cytochrome oxidase P450 (CYPs) were inhibited for short time exposure (6h) to IBU and then activated with prolonged exposure time (48h) at low concentration of IBU (0.5μg·L−1), while EROD showed a dose-dependent pattern under IBU exposure. As for antioxidative system, induction of glutathione S-transferase (GST), superoxide dismutase (SOD), and catalase (CAT) was observed in short-term exposure to IBU. Meanwhile, methane dicarboxylic aldehyde (MDA) content increased with the increasing IBU concentration and the delayed exposure time, displaying obvious dose- and time-dependent pattern. In summary, IBU significantly altered some physiological and biochemical parameters and genes expressions associated with detoxification metabolism in D. magna, the integrated approach combining the response in molecule levels with the performance of the whole organism can help elucidate the toxic effects of IBU and provide more insight into the exact mechanism of toxicity in aquatic organisms.

Enzymatic antioxidant defences are transcriptionally regulated in Es524, a copper-tolerant strain of Ectocarpus siliculosus (Ectocarpales, Phaeophyceae)

:Previous investigations have revealed that Ectocarpus siliculosus strain Es524, isolated from a highly copper (Cu)-polluted location in Chile, displays higher activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) under Cu excess. This partly explains its enhanced tolerance compared with other E. siliculosus strains. However, the transcriptomic basis behind the activity of these antioxidant enzymes is still unknown. We have conducted laboratory experiments with Es524 under control conditions and exposure to 2.4 μM total Cu. Under Cu exposure, Es524 showed a decrease in cell length and cell plasmolysis, revealing a certain level of cytophysiological stress. The genes encoding for iron-SOD, APX and CAT were overexpressed under Cu excess, demonstrating that higher activities of these enzymes are transcriptionally regulated. It is now more apparent that the induction of SOD, APX and CAT are conserved molecular and biochemical mechanisms developed after a long history of Cu exposure which is responsible, at least in part, for intraspecific Cu tolerance in E. siliculosus.

Preconditioning treatment induces chilling tolerance in zucchini fruit improving different physiological mechanisms against cold injury

Zucchini fruit is susceptible to develop chilling injuries (CI) when stored at low temperature. In this study, the effects of a preconditioning treatment during cold storage and its relation with the physiological response to chilling tolerance have been investigated. The commercial variety Sinatra, whose fruit are very sensitive to cold storage, has been used. After harvest, fruit were kept at 4°C or preconditioned during 48 h at 15°C before cold storage. Weight loss, electrolyte leakage and lipid peroxidation were lower in preconditioned at the end of storage time, and CI index was significantly reduced in preconditioned compared to control fruit. The preconditioning treatment improved the energy status of the fruit increasing the pool of ATP, and maintaining the energy charge. The preconditioned fruit improved their antioxidant status with lower H2O2 content and induction of ascorbate peroxidase (APX) and catalase (CAT) activities. A reduction in putrescine was detected in preconditioned fruit along with a lower expression of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) and a rise in activity of diamine oxidase (DAO). The concentrations of glutamate and γ-aminobutyrate (GABA) were lower during preconditioning, while that of proline was higher. In summary, preconditioning treatment induces chilling tolerance in zucchini fruit triggering a defence-response against oxidative stress and increasing ATP pool and proline content.

Antioxidant and oxidative stress related responses in the Mediterranean land snail Cantareus apertus exposed to the carbamate pesticide Carbaryl

The aim of the present work was to study the alterations of the antioxidant defenses and the overall susceptibility to oxidative stress of the terrestrial snail Cantareus apertus exposed to the carbamate pesticide Carbaryl at a low environmentally realistic concentration.The animals were exposed to Lactuca sativa soaked for 1h in 1μM Carbaryl. The temporal dynamics of the responses was assessed by measurements at 3, 7 and 14days of exposure.C. apertus exposed to Carbaryl activates a number of enzymatic antioxidant responses, represented by the early induction of catalase, glutathione peroxidase, glutathione reductase, followed by a delayed induction of superoxide dismutase. Concomitantly, a derangement of the total oxyradical scavenging of the tissues was observed, suggesting an overall impairment of the tissue capability to neutralize ROS probably resulting from the overall negative balance between enzymatic antioxidant defense capability and oxidative stress intensity. This negative balance exposed the animals to the risk of oxidative stress damages including genotoxic damage. Compared to acetylcholinesterase inhibition, the antioxidant responses developed to Carbaryl exposure at the low concentration utilized showed a greater percentage variation in exposed organisms.The results pointed out the high sensitivity of the antioxidant and oxidative stress related responses to Carbaryl exposure at an environmental realistic concentration, demonstrating their usefulness in environmental monitoring and risk assessment. The study highlights also the usefulness of the terrestrial snail C. apertus as potential bioindicator species for assessing the risk of pesticide environmental contamination.

Quorum sensing enhancement of the stress response promotes resistance to quorum quenching and prevents social cheating.

Quorum sensing (QS) coordinates the expression of virulence factors and allows bacteria to counteract the immune response, partly by increasing their tolerance to the oxidative stress generated by immune cells. Despite the recognized role of QS in enhancing the oxidative stress response, the consequences of this relationship for the bacterial ecology remain unexplored. Here we demonstrate that QS increases resistance also to osmotic, thermal and heavy metal stress. Furthermore a QS-deficient lasR rhlR mutant is unable to exert a robust response against H2O2 as it has less induction of catalase and NADPH-producing dehydrogenases. Phenotypic microarrays revealed that the mutant is very sensitive to several toxic compounds. As the anti-oxidative enzymes are private goods not shared by the population, only the individuals that produce them benefit from their action. Based on this premise, we show that in mixed populations of wild-type and the mexR mutant (resistant to the QS inhibitor furanone C-30), treatment with C-30 and H2O2 increases the proportion of mexR mutants; hence, oxidative stress selects resistance to QS compounds. In addition, oxidative stress alone strongly selects for strains with active QS systems that are able to exert a robust anti oxidative response and thereby decreases the proportion of QS cheaters in cultures that are otherwise prone to invasion by cheats. As in natural environments stress is omnipresent, it is likely that this QS enhancement of stress tolerance allows cells to counteract QS inhibition and invasions by social cheaters, therefore having a broad impact in bacterial ecology.

Short term exposure to multi-walled carbon nanotubes induce oxidative stress and DNA damage in Xenopus laevis tadpoles

The potential impact of Multiwalled Carbon NanoTubes (MWCNTs) was investigated on Xenopus laevis tadpoles exposed to 0.1, 1 and 10mg/L. Oxidative stress was measured in entire larvae exposed and DNA damage (Comet assay) was carried out in erythrocytes of circulating blood from 2h to 24h according to standardized recommendations. Results showed significant H2O2 production when larvae were exposed to 1mg/L and 10mg/L of MWCNTs after 4h and 2h of exposure, respectively. Antioxidant enzyme activities showed significant induction of catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) from only 2h of exposure to 10mg/L of MWCNTs. In presence of 1mg/L of MWCNTs, only GR and CAT activities were significantly induced at 4h. Enzyme activities do not follow a simple dose-effect relation, but the time of induction is shortened in relation with the tested concentration. The Comet assay results showed significant DNA damages with a dose dependent response. The profiles of DNA damages show fluctuations, in course of time, which are characteristics of oxidative stress response in relation with the continuous balance between damage and compensation process.

Evaluation of Differences Among Vigna aconitifolia Varieties for Acquired Thermotolerance

The induction of thermotolerance using the efficacy of heat acclimation was analyzed in nine varieties of moth bean (Vigna aconitifolia Jacq.), including those derived through mutation breeding. Seedlings maintained at 27 °C were exposed to lethal temperature with or without heat-acclimation treatment. All the nine varieties sustained an abrupt rise in temperature up to 42 °C; however, 47 °C proved detrimental to all the varieties used, with CZM-99, RMB-75, and RMO-40 showing resistance. Heat acclimation followed by lethal temperature induced acquired thermo-tolerance in all the varieties except RMO-225 and RMO-435. An increase in the protein level was observed up to 37 °C, while no alteration recorded in protein content at heat-acclimation and lethal temperature. The maximum and significant increase in the level of proline content was observed in CZM-99, RMB-75, and RMO-40. Acquired thermotolerance was also found to be associated with the induction of peroxidase (POX), ascorbic peroxidase (APOX), and catalase (CAT) activities. Maximum activities of enzymes were recorded for POX at heat-acclimation temperature (42 °C), and for CAT and APOX at sub-optimal temperature (37 °C). Among all the studied enzymes, only CAT showed greater activity at lethal temperature in all the accessions except var. Jwala.