Assessment Of Redox Status Research Articles

Targeted Quantification of Glutathione/Arginine Redox Metabolism Based on a Novel Paired Mass Spectrometry Probe Approach for the Functional Assessment of Redox Status.

Glutathione (GSH) redox control and arginine metabolism are critical in regulating the physiological response to injury and oxidative stress. Quantification assessment of the GSH/arginine redox metabolism supports monitoring metabolic pathway shifts during pathological processes and their linkages to redox regulation. However, assessing the redox status of organisms with complex matrices is challenging, and single redox molecule analysis may not be accurate for interrogating the redox status in cells and in vivo. Herein, guided by a paired derivatization strategy, we present a new ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS)-based approach for the functional assessment of biological redox status. Two structurally analogous probes, 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) and newly synthesized 2-methyl-6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (MeAQC), were set for paired derivatization. The developed approach was successfully applied to LPS-stimulated RAW 264.7 cells and HDM-induced asthma mice to obtain quantitative information on GSH/arginine redox metabolism. The results suggest that the redox status was remarkably altered upon LPS and HDM stimulation. We expect that this approach will be of good use in a clinical biomarker assay and potential drug screening associated with redox metabolism, oxidative damage, and redox signaling.

Computational Models on Pathological Redox Signalling Driven by Pregnancy: A Review.

Oxidative stress is associated with a myriad of diseases including pregnancy pathologies with long-term cardiovascular repercussions for both the mother and baby. Aberrant redox signalling coupled with deficient antioxidant defence leads to chronic molecular impairment. Abnormal placentation has been considered the primary source for reactive species; however, placental dysfunction has been deemed secondary to maternal cardiovascular maladaptation in pregnancy. While various therapeutic interventions, aimed at combating deregulated oxidative stress during pregnancy have shown promise in experimental models, they often result as inconclusive or detrimental in clinical trials, warranting the need for further research to identify candidates. The strengths and limitations of current experimental methods in redox research are discussed. Assessment of redox status and oxidative stress in experimental models and in clinical practice remains challenging; the state-of-the-art of computational models in this field is presented in this review, comparing static and dynamic models which provide functional information such as protein-protein interactions, as well as the impact of changes in molecular species on the redox-status of the system, respectively. Enhanced knowledge of redox biology in during pregnancy through computational modelling such as generation of Systems Biology Markup Language model which integrates existing models to a larger network in the context of placenta physiology.

Feasibility of Non-invasive Measurement of Tumour NAD(H) by In Vivo Phosphorus-31 Magnetic Resonance Spectroscopy.

Importance of the redox status of nicotinamide adenine dinucleotide (NAD), including its oxidized (NAD+) and reduced (NADH) forms, has been shown in many biological processes. However, NAD(H) redox status assessment is traditionally limited to biochemical assays in vitro or optical redox imaging (ORI) for superficial tissues in vivo and for deep tissues ex vivo. In recent years, phosphorous-31 magnetic resonance spectroscopy (31P-MRS) was utilized to quantify NAD+, NADH, and the redox ratio NAD+/NADH in normal tissues in vivo. The quantification is based on the spectral fitting of the upfield shoulder of the αATP peak that contains signals of NAD+ (a quartet) and NADH (a singlet), assuming pH-independence of peak positions. To evaluate the feasibility of measuring tumour NAD(H) redox status in vivo, we fitted single voxel 31P-MR spectra of subcutaneous mouse xenografts of human breast cancer cell lines acquired on a 9.4-T horizontal bore preclinical MR scanner. We found larger variations in the chemical shift offsets of NAD+ and NADH from αATP in these tumours than the literature values of normal tissues. Furthermore, our 31P-MR spectra of αATP, NAD+, and NADH solution phantoms indicated that the chemical shift of αATP and thus the offsets between NAD(H) and αATP were pH dependent. Therefore, whether tumour pH should be incorporated into the spectral fitting model should be further evaluated. Additionally, spectral resolution and signal-to-noise ratio should be improved by optimising 31P-MRS protocols, increasing data acquisition time, and using a more sensitive coil for signal detection.

A Novel FACS-Based Workflow for Simultaneous Assessment of RedOx Status, Cellular Phenotype, and Mitochondrial Genome Stability.

Intracellular reduction-oxidation (RedOx) status mediates a myriad of critical biological processes. Importantly, RedOx status regulates the differentiation of hematopoietic stem and progenitor cells (HSPCs), mesenchymal stromal cells (MSCs) and maturation of CD8+ T Lymphocytes. In most cells, mitochondria are the greatest contributors of intracellular reactive oxygen species (ROS). Excess ROS leads to mitochondrial DNA (mtDNA) damage and protein depletion. We have developed a fluorescence-activated cell sorting (FACS)-based protocol to simultaneously analyze RedOx status and mtDNA integrity. This simultaneous analysis includes measurements of ROS (reduced glutathione (GSH)), ATP5H (nuclear encoded protein), MTCO1 (mitochondrial DNA encoded protein), and cell surface markers to allow discrimination of different cell populations. Using the ratio of MTCO1 to ATP5H median fluorescence intensity (MFI), we can gain an understanding of mtDNA genomic stability, since MTCO1 levels are decreased when mtDNA becomes significantly damaged. Furthermore, this workflow can be optimized for sorting cells, using any of the above parameters, allowing for downstream quantification of mtDNA genome copies/nucleus by quantitative PCR (qPCR). This unique methodology can be used to enhance analyses of the impacts of pharmacological interventions, as well as physiological and pathophysiological processes on RedOx status along with mitochondrial dynamics in most cell types.

Redox Status in Canine Leishmaniasis.

The World Health Organization defined leishmaniasis as one of the priority attention diseases. Aiming to clarify some aspects of its pathogenetic mechanisms, our study focused on the assessment of redox status in dogs, the main reservoir for Leishmania infantum. Forty-five dogs from an endemic area in southern Italy were divided into four different groups (from mild disease with negative to low positive antibody levels to very severe disease with medium to high positive antibody levels) according to the LeishVet group guidelines. Their plasma and/or sera were tested for reactive oxygen species (ROS), namely the superoxide anion (O2-), reactive nitrogen species (RNS), such as nitric oxide (NO) and hydroperoxides (ROOH), as well as activity of the detoxifying enzyme superoxide dismutase (SOD), and total nonenzymatic antioxidant capacity, as determined by the ferric reducing-antioxidant power (FRAP) assay. O2- generation was significantly (p < 0.05) reduced in leishmaniasis-affected dogs independently of the clinical stage, while NO production was stimulated (p < 0.05) only in II and III stage patients. No difference could be found for the levels of hydroperoxides and SOD activity between healthy and pathological subjects. FRAP values were lower in affected dogs but only in stage II. Taken together, although we demonstrated that several redox status parameters are altered in the plasma of dog affected by leishmaniasis, the oxidative stress changes that are observed in this disease, are possibly mainly due to cellular blood components i.e., neutrophils responsible for the elimination of the parasite. Further studies are required to assess the clinical values of the collected data.

Redox and apoptotic potential of novel ruthenium complexes in rat blood and heart.

Ruthenium(II) complexes offer the potential for lower toxicity compared with platinum(II) complexes. Our study aimed to compare cardiotoxicity of [Ru(Cl-tpy)(en)Cl][Cl], [Ru(Cl-tpy)(dach)Cl][Cl], [Ru(Cl-tpy)(bpy)Cl][Cl], cisplatin, and saline through assessment of redox status and relative expression of apoptosis-related genes. A total of 40 Wistar albino rats were divided into five groups. Ruthenium groups received a single dose of complexes intraperitoneally (4mg/kg/week) for a 4-week period; cisplatin group received cisplatin (4mg/kg/week) and control group received saline (4mL/kg/week) in the same manner as ruthenium groups. In collected blood and heart tissue samples, spectrophotometric determination of oxidative stress biomarkers was performed. The relative expression of apoptosis-related genes (Bcl-2, Bax, and caspase-3) in hearts was examined by real-time polymerase chain reaction. Our results showed that systemic and cardiac pro-oxidative markers (thiobarbituric acid reactive substances and nitrite) were significantly lower in ruthenium groups compared with cisplatin group, while concentrations of antioxidative parameters (catalase, superoxide dismutase, and oxidized glutathione) were significantly higher. Ruthenium administration led to significantly lower gene expression of Bax and caspase-3 compared with cisplatin-treated rats, while Bcl-2 remained unchanged. Applied ruthenium complexes have less pronounced potential for induction of oxidative stress-mediated cardiotoxicity compared with cisplatin. These findings may help for future studies that should clarify the mechanisms of cardiotoxicity of ruthenium-based metallodrugs.

P-02-67 Redox Status Assessment in Infertile Patients With Non-Obstructive Azoospermia Undergoing Testicular Sperm Extraction: A Prospective Study

P-02-67 Redox Status Assessment in Infertile Patients With Non-Obstructive Azoospermia Undergoing Testicular Sperm Extraction: A Prospective Study

Полиморфный вариант гена GPX2 (rs4902346) и предрасположенность к сахарному диабету 2-го типа

Окислительный стресс служит важной составляющей патогенеза сахарного диабета 2 типа (СД2). Одним из ферментов антиоксидантной защиты является глутатионпероксидаза 2 (GPX2), использующая глутатион в качестве ко-субстрата для восстановления перекиси водорода H2O2 и обладающая наибольшей экспрессией в поджелудочной железе, - органе, имеющем непосредственное отношение к развитию диабета. Тем не менее, данные о связи GPX2 с предрасположенностью к СД2 в литературе отсутствуют. Целью исследования стало изучение ассоциации полиморфного варианта rs4602346 (А&gt;G) в интроне гена GPX2 с риском развития СД2, а также его влияния на показатели редокс-гомеостаза плазмы крови. В исследование включено 3197 неродственных индивидов славянского происхождения, в том числе 1570 пациентов с СД2 и 1609 сопоставимых по полу и возрасту здоровых добровольцев. Генотипирование полиморфизма гена GPX2 проводили методом полимеразной цепной реакции в режиме реального времени с дискриминацией аллелей с помощью TaqMan зондов на термоциклере CFX96 Touch Bio-Rad. Генотип G/G ассоциировался с повышенным риском развития заболевания (OR 1,41, 95%CI 1,02-1,96, р=0,039, рецессивная модель). Выявленная ассоциация сохранила значимость и после введения поправки на пол, возраст и индекс массы тела (ORadj 1,50, 95%CI 1,04-2,16, рadj=0,03). При раздельном сравнении больных СД2 мужчин и женщин с контролем оказалось, что установленная ассоциация rs4902346 была характерна только для мужчин (ORadj 2,09, 95%CIadj 1,22-3,59, рadj=0,0065), в то время как частоты генотипов и аллелей GPX2 больных женщин не отличались от соответствующих показателей здоровых (р&gt;0,05). Оценка редокс-статуса показала увеличение содержания перекиси водорода и снижение уровня общего глутатиона в плазме больных по сравнению с контролем (р&lt;0,05). Корреляционный анализ обнаружил, что уровень перекиси водорода пациентов прямо пропорционален концентрации глюкозы крови натощак. Анализ взаимосвязей между генетическими и биохимическими данными выявил, что генотип G/G rs4902346 ассоциирован со снижением содержания восстановленного глутатиона в плазме больных СД2 женщин (р=0,0086). Таким образом, нами впервые выявлена ассоциация rs4902346 гена GPX2 с развитием СД2 и показаны значительные половые различия в ассоциациях с исследованными фенотипами. Oxidative stress is an important component of the pathogenesis of type 2 diabetes mellitus (T2D). Glutathione peroxidase 2 is one of the antioxidant defense enzymes which uses glutathione as a co-substrate to reduce hydrogen peroxide and has the highest expression in the pancreas, an organ that is directly related to the development of diabetes. However, there is no data on the association of GPX2 with a predisposition to T2D. The aim of the study was to investigate the association of rs4602346 (A&gt;G) in the intron of the GPX2 gene with a risk of T2D, as well as the effect of this SNP on blood plasma redox homeostasis. The study included 3197 unrelated individuals of Slavic origin, including 1570 patients with T2D and 1609 age- and sex-matching healthy volunteers. GPX2 gene polymorphism was genotyped using real-time PCR on a CFX96 Touch Bio-Rad thermal cycler. The G/G genotype was associated with an increased risk of the disease (OR 1,41, 95% CI 1,02-1,96, P=0,039, recessive model). The identified association retained its significance even after correction for gender, age, and body mass index (ORadj 1,50, 95% CI 1,04-2,16, Padj=0,03). Gender-stratified analysis revealed that the established association of rs4902346 was characteristic only for diabetic males (ORadj 2,09, 95% CIadj 1,22-3,59, Padj=0,0065), and was not observed in diabetic females (P&gt;0,05). Assessment of redox status showed an increase in the content of hydrogen peroxide and a decrease in the level of total glutathione in the plasma of patients compared with the control (P &lt;0.05). A correlation analysis found that patients’ hydrogen peroxide levels are directly proportional to their fasting blood glucose concentrations. An analysis of the relationships between genetic and biochemical data showed that the G/G genotype rs4902346 is associated with a decrease in the content of reduced glutathione in the plasma of female patients with T2D (P=0,0086). Thus, we identified for the first time the association of rs4902346 with an increased risk of T2D and showed significant gender differences in the associations of the GPX2 gene with the studied phenotypes.

Redox status assessment in infertile patients with non-obstructive azoospermia undergoing testicular sperm extraction: A prospective study.

Oxidative stress (OS) is one of the most prevalent causes of sperm damage, through the toxic effects of endogenously generated hydrogen peroxide, superoxide anion, and hydroxyl radicals. Peripheral leukocytes represent a feasible model for studying the pathophysiology of OS-mediated homeostasis, which can be responsible for cell dysfunction and cell injury. To evaluate the redox status in patients with non-obstructive azoospermia (NOA), establishing the potential role exerted by reactive oxygen species (ROS) in the genesis of testicular secretory injury. From May 2018 to March 2019, 39 patients were enrolled in this prospective single-center cohort study and divided into two groups. Group 1 included 19 patients with NOA, and Group 2 included 20 normozoospermic men, partners of women with infertility tubal factor. All patients underwent serum blood tests. NOA underwent testicular sperm extraction (TeSE). ROS production (in lymphocytes, monocytes, and granulocytes) was assessed by fluorescence-activated cell sorting (FACS) analysis. Plasma oxidative stress was evaluated by lipid peroxidation markers (MDA) and total antioxidant capacity (TAC) both assessed by fluorometric techniques. Mean lymphocyte ROS production resulted 967.0±224.5 vs 728.0±98.0 (NOA vs Controls, P<.001), monocyte ROS resulted 2102.5±517.5 vs 1253±171 (P<.001), and granulocyte ROS were 2366.5±595.4 vs 1751.0±213.0 (P<.001). Significant increases plasma lipid peroxidation markers were found in NOA patients compared with controls (2.7±0.8 vs 0.37±0.2nmol/mL, P<.001). Significant decreased TAC was evident in NOA compared with controls (13.4±3.9 vs 3.0±0.2µmol/mL Trolox equivalents, P<.001). No significant differences were found in blood leukocyte subpopulations ROS production, plasma lipid peroxidation, and TAC comparing groups (positive vs negative sperm retrieval, P>.05). ROS production can be directly related to disorders of spermatogenesis, leading to severe conditions of male infertility, including azoospermia.

The cardioprotective effects of diallyl trisulfide on diabetic rats with ex vivo induced ischemia/reperfusion injury.

Diallyl trisulfide (DATS) is distinguished as the most potent polysulfide isolated from garlic. The aim of our study was to investigate effects of oral administration of DATS on healthy and diabetic rats, with special attention on heart function. Rats were randomly divided into four groups: CTRL (healthy rats), DATS (healthy rats treated with DATS), DM (diabetic rats), DM + DATS (diabetic rats treated with DATS). DATS (40mg/kg of body weight) was administered every other day for 3weeks, at the end of which rats underwent echocardiography, glycemic measurement and redox status assessment. Isolated rat hearts were subjected to 30min global ischemia and 60min reperfusion, after which heart tissue was counterstain with hematoxylin and eosin and cardiac Troponin T staining (cTnT), while expression of Bax, B cell lymphoma 2 (Bcl-2), caspase-3, caspase-9 and superoxide dismutase-2 were examined in the left ventricle. DATS treatment significantly reduced blood glucose levels of diabetic rats, and improved cardiac function recovery, diminished oxidation status, attenuated cardiac remodeling and inhibited myocardial apoptosis in healthy and diabetic rats. DATS treatment causes promising cardioprotective effects on ex vivo-induced ischemia/reperfusion (I/R) injury in diabetic and healthy rat heart probably mediated by inhibited myocardial apoptosis. Moreover, appropriate DATS consumption may provide potential co-therapy or prevention of hyperglycemia and various cardiac complications in rats with DM.

Crosstalk between cytokine profile, redox, and iron status in β-Thalassemia: relation to frequency/duration of blood transfusion

β-Thalassemia, a blood disease instigated by mutations in β-globin genes or their regulatory regions. Infectious complications, immune abnormalities and iron overload related organ damage are the chief causes of morbidity and mortality. The role of inflammatory cytokines in the pathophysiology of β-thalassemia is still indistinct, so the present study aimed to evaluate immune-inflammatory and redox status in β-thalassemia and their relation to iron status, frequency/duration of blood transfusion. Seventy β-Thalassemia patients (35 β-thalassemia major; 35 β-thalassemia intermedia) and twenty age and sex-matched healthy controls were included. Interleukin4 (IL4), Interleukin10 (IL10), Interleukin 8 (IL8), and Interleukin 13 (IL13) levels were immunoassayed in addition to iron, hematological and redox status assessment. Significantly increased iron, ferritin, IL8, IL13 levels (p value ˂0.001), meanwhile, decreased IL10 level, total anti-oxidant (TAC) and iron binding capacities were observed in β-thalassemia major compared with β-thalassemia intermedia and control groups (p value ˂0.001) . IL4 level was decreased in patients group compared to control. Positive correlation was found between malondialdehyde (MDA), IL8, IL13 and iron load, transfusion frequency/duration, total leucocyte count and lymphocyte (%). Meanwhile, negative correlation was found with IL4, IL10, and TAC. Multiple blood transfusions increased iron stores which may critically impair the immune-regulatory balance with disturbed redox status and cytokine profile.

Reactive oxygen species upregulate expression of muscle atrophy-associated ubiquitin ligase Cbl-b in rat L6 skeletal muscle cells.

Unloading-mediated muscle atrophy is associated with increased reactive oxygen species (ROS) production. We previously demonstrated that elevated ubiquitin ligase casitas B-lineage lymphoma-b (Cbl-b) resulted in the loss of muscle volume (Nakao R, Hirasaka K, Goto J, Ishidoh K, Yamada C, Ohno A, Okumura Y, Nonaka I, Yasutomo K, Baldwin KM, Kominami E, Higashibata A, Nagano K, Tanaka K, Yasui N, Mills EM, Takeda S, Nikawa T. Mol Cell Biol 29: 4798-4811, 2009). However, the pathological role of ROS production associated with unloading-mediated muscle atrophy still remains unknown. Here, we showed that the ROS-mediated signal transduction caused by microgravity or its simulation contributes to Cbl-b expression. In L6 myotubes, the assessment of redox status revealed that oxidized glutathione was increased under microgravity conditions, and simulated microgravity caused a burst of ROS, implicating ROS as a critical upstream mediator linking to downstream atrophic signaling. ROS generation activated the ERK1/2 early-growth response protein (Egr)1/2-Cbl-b signaling pathway, an established contributing pathway to muscle volume loss. Interestingly, antioxidant treatments such as N-acetylcysteine and TEMPOL, but not catalase, blocked the clinorotation-mediated activation of ERK1/2. The increased ROS induced transcriptional activity of Egr1 and/or Egr2 to stimulate Cbl-b expression through the ERK1/2 pathway in L6 myoblasts, since treatment with Egr1/2 siRNA and an ERK1/2 inhibitor significantly suppressed clinorotation-induced Cbl-b and Egr expression, respectively. Promoter and gel mobility shift assays revealed that Cbl-b was upregulated via an Egr consensus oxidative responsive element at -110 to -60 bp of the Cbl-b promoter. Together, this indicates that under microgravity conditions, elevated ROS may be a crucial mechanotransducer in skeletal muscle cells, regulating muscle mass through Cbl-b expression activated by the ERK-Egr signaling pathway.

Effect of sodium metabisulfite on lipid peroxidation and enzyme activities in adult rat stomach and spleen

Sodium metabisulfite (NaMBS) has been used as an antioxidant and antimicrobial agent in a variety of drugs and foods. The aim of our study was to evaluate the effect of subchronic ingestion of NaMBS on lipid peroxidation, protein and enzymatic antioxidants in the gastric tissue and splenic Wistar rat. The rats were divided into four groups (n = 06 rats/group) as follows; Control (C), rats treated with 0.25% NaMBS (S0.25%), rats treated with 1% NaMBS (S1%) and rats treated with 4% NaMBS (S4%). NaMBS was administered to animals via drinking water. At the end of the experimental period, Malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxi-dase (GPx), catalase (CAT) and thiols were determined. Redox status assess-ment revealed that 1% and 4% NaMBS doses induced gastric and spleen lipid peroxidation in animals compared to the control group. On the other hand, activities of SOD, GPx, CAT and thiols were reduced in the S1% and S4% groups in the stomach and spleen compared to the controls. Slight changes were detected in the GPx and CAT in the stomach of S0.25% group compared to the control group. In conclusion, the subchronic consumption of NaMBS has an adverse effect on the spleen and stomach by inducing oxidative damage leading to an increase in lipid peroxidation, protein oxidation and alteration of enzyme activity antioxidant.

Transforming Growth Factor-β1/Smad3 Signaling and Redox Status in Experimentally Induced Nephrotoxicity: Impact of Carnosine.

carnosine has the ability to protect against CCl4-induced nephrotoxicity possibly by alleviating oxidative stress, normalizing kidney histopathological architecture in addition to the disruption of the inflammatory and fibrotic response induced by CCl4.

Comprehensive Plasma Thiol Redox Status Determination for Metabolomics

Thiol homeostasis plays an important role in human health and aging by regulation of cellular responses to oxidative stress. Due to major constraints that hamper reliable plasma thiol/disulfide redox status assessment in clinical research, we introduce an improved strategy for comprehensive thiol speciation using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) that overcomes sensitivity, selectivity and dynamic range constraints of conventional techniques. This method integrates both specific and nonspecific approaches toward sensitivity enhancement for artifact-free quantification of labile plasma thiols without complicated sample handling. A multivariate model was developed to predict increases in ionization efficiency for reduced thiols when conjugated to various maleimide analogs based on their intrinsic physicochemical properties. Optimization of maleimide labeling in conjunction with online sample preconcentration allowed for simultaneous analysis of nanomolar levels of reduced thiols and free oxidized thiols as their intact symmetric or mixed disulfides. Identification of low-abundance thiols and various other polar metabolites detected in plasma was supported by prediction of their relative migration times using CE as a qualitative tool complementary to ESI-MS. Plasma thiol redox status determination together with untargeted metabolite profiling offers a systemic approach for elucidation of the causal role of dysregulated thiol metabolism in the etiology of human diseases.

Heat shock protein 70 regulates cellular redox status by modulating glutathione-related enzyme activities

Heat shock protein (Hsp) 70 has been reported to protect various cells and tissues from ischemic damage. However, the molecular mechanisms of the protection are incompletely understood. Ischemia induces significant alterations in cellular redox status that plays a critical role in cell survival/death pathways. We investigated the effects of Hsp70 overexpression on cellular redox status in Madin-Darby canine kidney (MDCK) cells under both hypoxic and ischemic conditions with 3 different approaches: reactive oxygen species (ROS) measurement by a fluorescence probe, redox environment evaluation by a hydroxylamine spin probe, and redox status assessment by the glutathione/glutathione disulfide (GSH/GSSG) ratio. Results from each of these approaches showed that the redox status in Hsp70 cells was more reducing than that in control cells under either hypoxic or oxygen and glucose deprivation (OGD) conditions. In order to determine the mechanisms that mediated the alterations in redox state in Hsp70 cells, we measured the activities of glutathione peroxidase (GPx) and glutathione reductase (GR), two GSH-related antioxidant enzymes. We found that OGD exposure increased GPx and GR activities 47% and 55% from their basal levels (no stress) in Hsp70 cells, compared to only 18% and 0% increase in control cells, respectively. These data, for the first time, indicate that Hsp70 modulates the activities of GPx and GR that regulate cellular redox status in response to ischemic stress, which may be important in Hsp70's cytoprotective effects.

Characterizing redox status of paddy soils with incorporated rice straw

Redox status is one of the more difficult soil quality criteria to characterize especially in paddy soils. The soil system chosen in this study was an ongoing paddy field trial on alternative practices of incorporating rice straw instead of traditional burning of straw. Upon flooding, rapid changes in redox potential (Eh) occur in paddy soil due to the decomposition of soil organic matter (SOM), including rice straw. This investigation evaluated three methods of characterizing redox status: (i) Eh, a conventional method using Pt black electrode; (ii) terminal electron-accepting processes (TEAPs), a method of diagnosing microbially mediated electron acceptor (oxidized species) consumption, intermediate product concentration of H 2 and accumulation of final products (reduced species); and (iii) oxidative capacity (OXC), a comprehensive analysis of the algebraic sum of oxidized and reduced species into a single descriptive parameter. There was a need to develop a sampling technique for anaerobic soil pore water in rice paddy (without exposure to the atmosphere) to measure all the redox parameters required by these methods. The setup comprised of a capped piezometer (sampling well) back-filled with sand and sealed with bentonite, and vacuum extraction of pore water containing dissolved constituents. The pore water containing dissolved gases was collected into previously evacuated 400-ml two-port PVC bags from which gaseous phase sub-samples were withdrawn with a syringe into 10-ml vacutainers previously flushed with N 2 gas for H 2 and CH 4 determinations in the laboratory. Unstable water quality parameters such as DO, Eh, pH and S 2− were measured on site using fresh samples, while other parameters such as NO 3 −, SO 4 2−, EC, Fe(II) and Fe(III), and Mn(II) were analyzed in the laboratory. The above three methods of evaluating redox status were applied to monitoring the paddy pore water over 3 years of field observations (1997–1999). Eh is a simple measure, but it gives at best only qualitative assessment of redox status because this electrode may not respond to many of the important redox couples. The adaptation of TEAPs to assess non-equilibrium redox conditions in flow pathways in large-scale ground water systems to small-scale rice rootzone was not entirely successful because of differences in the two systems and the significant overlapping among electron acceptors in paddy soils. OXC, a non-equilibrium capacity-type redox parameter, clearly identified geochemical redox classes of oxic, post-oxic, sulfidic and methanic conditions in the paddy pore waters during the course of the rice-growing season. Based on data observed for 3 years, it is concluded that straw incorporation does enhance more reducing conditions development compared to that without straw incorporation. We conclude that OXC provides a better characterization of redox status in paddy soils.