Screening of Pleurotus ostreatus isolates for their ligninolytic properties during cultivation on natural substrates

Thirteen basidiospore-derived isolates of Pleurotus ostreatus f6 strain differing in the level of ligninolytic enzyme production and other characteristics (mycelium extension rate, colony morphology) from the parental strain were cultivated on natural substrates. Under these conditions ligninolytic enzyme activity, loss of organic mass, polycyclic aromatic hydrocarbons (PAHs) degradation and colonization of sterile and nonsterile soil were studied. The activity of ligninolytic enzymes was substantially higher in straw than in liquid culture, although the differences between the isolates were less pronounced on this substrate. Some of the isolates showed a very good ability to decompose the lignocellulosic substrate (straw) and a relatively high loss of organic mass was found after 50 days of cultivation in these strains. The original strain f6 and isolates B13 and B26 successfully degraded all seven tested PAH compounds present in experimental soil samples, but the higher or lower ligninolytic enzyme production of isolates tested had no substantial effect on the extent of the degradation. In our screening, six basidiospore-derivedisolates growing well in nonsterile soil were found, whichcould be suitable for the prospective biotechnological exploitation.     

Ameliorative effect of vanadyl(IV)–ascorbate complex on high-fat high-sucrose diet-induced hyperglycemia,insulin resistance,and oxidative stress in mice

There is mounting evidence demonstrating causative links between hyperglycemia, oxidative stress, and insulin resistance, the core pathophysiological features of type 2 diabetes mellitus. Using a combinational approach, we synthesized a vanadium–antioxidant (i.e., l-ascorbic acid) complex and examined its effect on insulin resistance and oxidative stress. This study was designed to examine whether vanadyl(IV)-ascorbate complex (VOAsc) would reduce oxidative stress, hyperglycemia, and insulin resistance in high-fat high-sucrose diet (HFSD)-induced type 2 diabetes in mice. Male C57BL/6J mice were fed a HFSD for 12 weeks to induce insulin resistance, rendering them diabetic. Diabetic mice were treated with rosiglitazone, sodium l-ascorbate, or VOAsc. At the end of treatment, fasting blood glucose, fasting serum insulin, homeostasis model assessment-insulin resistance index, and serum adipocytokine levels were measured. Serum levels of nitric oxide (NO) parameters were also determined. The liver was isolated and used for determination of malondialdehyde, reduced glutathione, and catalase levels, and superoxide dismutase and glutathione peroxidase activities. VOAsc groups exhibited significant reductions in serum adipocytokine and NO levels, and oxidative stress parameters compared to the corresponding values in the untreated diabetic mice. The results indicated that VOAsc is non-toxic. In conclusion, we identified VOAsc as a potentially effective adjunct therapy for the management of type 2 diabetes.     

Differential Implication of Glutathione, Glutathione-Metabolizing Enzymes and Ascorbate in Tomato Resistance to Pseudomonas syringae

We studied the response of glutathione‐ and ascorbate‐related antioxidant systems of the two tomato cultivars to Pseudomonas syringae pv. tomato infection. In the inoculated susceptible A 100 cultivar a substantial decrease in reduced glutathione (GSH) content, oxidised glutathione accumulation and GSH redox ratio decline as well as glutathione peroxidase activity increase were found. The enhanced glutathione reductase activity was insufficient to keep the glutathione pool reduced. A transiently increased dehydroascorbic acid (DHA) content and ascorbic acid (AA) redox ratio decrease together with ascorbate peroxidase activity suppression were observed. Adversely to the progressive reduction in GSH pool size, AA content tended to increase but the changes were more modest than those of GSH. By contrast, in interaction with the resistant Ontario cultivar the glutathione pool homeostasis was maintained throughout P. syringae attack and no significant effect on the ascorbate pool was observed. Moreover, in the resistant interaction there was a significantly higher constitutive and pathogen‐induced glutathione‐S‐transferase (GST) activity. The relationship between GST activity and DHA content found in this study indicates that this enzyme could also act as dehydroascorbate reductase. These results reflect the differential involvement of GSH and AA in tomato‐P. syringae interaction and, in favour of the former, they clearly indicate the role of GSH and GSH‐utilizing enzymes in resistance to P. syringae. The maintenance of glutathione pool homeostasis and GST induction appear to contribute to tissue inaccessibility to bacterial attack.     

Drought-inhibited ribulose-1,5-bisphosphate carboxylase activity is mediated through increased release of ethylene and changes in the ratio of polyamines in pakchoi

To study the mechanisms of drought inhibiting photosynthesis and the role of PAs and ethylene, the photosynthetic rate (P_n), the maximal photochemical efficiency of PSII (F_v/F_m), the intercellular CO₂ concentration (C_i), photorespiratory rate (P_r), the amount of chlorophyll (chl), antioxidant enzyme activity, ethylene levels, RuBPC (ribulose-1,5-bisphosphate carboxylase) activity and endogenous polyamine levels of pakchoi were examined, and an inhibitor of S-adenosylmethionine decarboxylase (SAMDC) and an inhibitor of ethylene synthesis and spermidine (Spd) were used to induce the change of endogenous polyamine levels. The results show that drought induced a decrease in P_n and RuBPC activity, an increase in the intercellular CO₂ concentration (C_i), but no change in the actual photochemical efficiency of PSII (Φ_PSII), and chlorophyll content. In addition, drought caused an increase in the free putrescine (fPut), the ethylene levels, a decrease in the Spd and spermine (Spm) levels, and the PAs/fPut ratio in the leaves. The exogenous application of Spd and amino oxiacetic acid (AOAA, an inhibitor of ethylene synthesis) markedly reversed these drought-induced effects on polyamine, ethylene, P_n, the PAs/fPut ratio and RuBPCase activity in leaves. Methylglyoxal-bis(guanylhydrazone) (MGBG), an inhibitor of SAMDC resulting in the inability of activated cells to synthesize Spd and Spm, exacerbates the negative effects induced by drought. These results suggest that the decrease in P_n is at least partially attributed to the decrease of RuBPC activity under drought stress and that drought inhibits RuBPC activity by decreasing the ratio of PAs/fPut and increasing the release of ethylene.     

Plant growth regulator interactions results enhancement of antioxidant enzymes in Catharanthus roseus

Abstract

The present investigation was carried out with the objectives to understand the effect of paclobutrazol, gibberellic acid and Pseudomonas fluorescens on the enzymatic antioxidants like Ascorbate peroxidase (APX, EC: 1.11.1.11), Superoxide dismutase (SOD, EC: 1.15.1.1), Catalase (CAT, EC: 1.11.1.6), Peroxidase (POX, EC 1.11.1.7) and polyphenol oxidase (PPO, Ec 1.10.3.1) activities of Catharanthus roseus plants under field conditions. 10 mg l^?1 paclobutrazol, 5 µM gibberellic acid and 1 mg P. fluorescens concentrations were used for the treatments, and control plants were irrigated with well water. The treatments were given 38, 53, 68 and 83 days after planting (DAP) by soil drenching. The plants were taken randomly 45, 60, 75 and 90 DAP and separated into root, stem, leaves and flowers and used for estimating the antioxidant enzymes. The results showed that these plant growth regulators have significant effects on antioxidant enzymes of C. roseus.     

Generation of Probucol Radicals and Their Reduction by Ascorbate and Dihydrolipoic Acid in Human Low Density Lipoproteins

Probucol, 4.4′-[(1-methylethylidene)bis(thio)]bis-[2,6-bis(1.1-dimethyl)phenol], is a lipid regulating drug whose therapeutic potential depends on its antioxidant properties. Probucol and x-tocopherol were quantitatively compared in their ability to scavenge peroxyl radicals generatcd by the thermal decomposition of the lipid-soluble azo-initiator 2,2′-azo-bis(2,4-dimethyl-valeronitrile), AMVN, in dioleoylphos-phatidylcholine (DOPC) liposomes. Probucol showed 15-times lower peroxyl radical scavenging efficiency than x-tocopherol as measured by the effects on AMVN-induced luminol-dependent chemiluminescence. We suggest that probucol cannot protect x-tocopherol against its loss in the course of oxidation, although probucol is known to prevent lipid peroxidation in membranes and lipoproteins. In human low density lipoproteins (LDL) ESR signals of the probucol phenoxyl radical were detected upon incubation with lipoxygenase + linolenic acid or AMVN. Ascorbate was shown to reduce probucol radicals. Dihydro-lipoic acid alone was not able to reduce the probucol radical but in the presence of both ascorbate and dihydrolipoic acid a synergistic effect of a stepwise reduction was observed. This resulted from ascorbate-dependent reduction of probucol radicals and dihydrolipoic acid-dependent reduction of ascorbyl radicals. The oxidized form of dihydrolipoic acid, thioctic acid, did not affect probucol radicals either in the presence or in the absence of ascorbate.     

Radical Cations in Aromatic Hydrocarbon Carcinogenesis

Most carcinogens, including polycyclic aromatic hydrocarbons (PAH), require metabolic activation to produce the ultimate electrophilic species that bind covalently with cellular macromolecules to trigger the cancer process. Metabolic activation of PAH can be understood in terms of two main pathways: one-electron oxidation to yield reactive intermediate radical cations and monooxygenation to produce bay-region diol epoxides. The reason we have postulated that one-electron oxidation plays an important role in the activation of PAH derives from certain common characteristics of the radical cation chemistry of the most potent carcinogenic PAH. Two main features common to these PAH are: 1) a relatively low ionization potential, which allows easy metabolic removal of one electron, and 2) charge localization in the PAH radical cation that renders this intermediate specifically and efficiently reactive toward nucleophiles. Equally important, cytochrome P-450 and mammalian peroxidases catalyze one-electron oxidation. This mechanism plays a role in the binding of PAH to DNA. Chemical, biochemical and biological evidence will be presented supporting the important role of one-electron oxidation in the activation of PAH leading to initiation of cancer.