Semen static oxidation-reduction potential is not helpful in evaluating male fertility.

BACKGROUND: Infertility affects a significant percentage of couples worldwide, with male infertility contributing substantially in a considerable number of cases. Research indicates that oxidative stress is a critical factor impacting male fertility. OBJECTIVE: To explore the relationship between semen static oxidation-reduction potential (sORP), sperm parameters, and validated biomarkers of oxidative stress in infertile men. MATERIALS AND METHODS: This cross-sectional study involved 202 men diagnosed with idiopathic male factor infertility and male partners from couples with unexplained infertility. Multivariable linear regression to query the associations between sORP, sperm parameters, and oxidative aggression biomarkers (lipid peroxidation, mitochondrial membrane potential, annexin V, and sperm DNA fragmentation). RESULTS: SORP has no linear association with any semen analysis parameter. Furthermore, its relationship with validated biomarkers of oxidative stress was inconsistent. sORP was inversely related to lipid peroxidation (multivariable linear regression coefficient: -0.64), positively associated with sperm DNA fragmentation (multivariable linear regression coefficient: 3.20), and unrelated to mitochondrial membrane potential or annexin V. CONCLUSIONS: There is no clear or consistent relationship between sORP and validated oxidative aggression biomarkers or sperm parameters. Our findings suggest that sORP is unlikely to be helpful in the evaluation of a male with idiopathic infertility.

Sex-specific responses of Taxus mairei to UV-B radiation involved altering the interactions between the microbiota assembly and host secondary metabolism.

BACKGROUND: To adapt to constantly changing environments, ancient gymnosperms have coevolved with diverse endophytic fungi that are essential for the fitness and adaptability of the plant host. However, the effect of sex on plant-endophyte interactions in response to environmental stressors remains unknown. RNA-seq integrated with ITS analysis was applied to reveal the potential mechanisms underlying the sex-specific responses of Taxus mairei to ultraviolet (UV)-B radiation. RESULTS: Enrichment analysis suggested that sex influenced the expression of several genes related to the oxidation-reduction system, which might play potential roles in sex-mediated responses to UV-B radiations. ITS-seq analysis clarified the effects of UV-B radiation and sex on the composition of endophytic fungal communities. Sex influenced various secondary metabolic pathways, thereby providing chemicals for T. mairei host to produce attractants and/or inhibitors to filter microbial taxa. Analysis of fungal biomarkers suggested that UV-B radiation reduced the effect of sex on fungal communities. Moreover, Guignardia isolate #1 was purified to investigate the role of endophytic fungi in sex-mediated responses to UV-B radiation. Inoculation with spores produced by isolate #1 significantly altered various oxidation-reduction systems of the host by regulating the expression of APX2, GST7 NCED1, ZE1, CS1, and CM1. CONCLUSION: These results revealed the roles of endophytic fungi in sex-mediated responses to UV-B radiation and provided novel insights into the sex-specific responses of Taxus trees to environmental stressors. Video Abstract.

Dataset on the decolorization of Naphthol Green B using a UV/sulfite system: Optimization by response surface methodology.

Naphthol Green B (NGB) is a synthetic azo dye widely used in various industries, including textiles and leathers. NGB poses significant environmental and ecological concerns when released into natural water systems. This paper investigates the decolorization of NGB using UV/sulfite system. The % decolorization of NGB was optimized using 32 Full Factorial Design (FFD), and the ANOVA results show that the model has a good fit for the data (R2 = 99.54 %, R2 (adj) = 98.76 %) and the significant factors contributing to the % decolorization are A, B, A2, and B2 where A = mM sulfite and B = pH. The model predicted ≥100 % decolorization with the optimum conditions 12 mM sulfite and pH 10. An actual experiment was conducted to verify the response, resulting in 96.2 % decolorization which is in good agreement with the model.

A four-step biosynthetic pathway involving C-3 oxidation-reduction reactions from cycloastragenol to astragaloside IV in Astragalus membranaceus.

Astragaloside IV is a significant chemical component derived from the medicinal plant Astragalus membranaceus. Despite the characterization of several glycosyltransferases from A. membranaceus, the complete biosynthetic pathway of astragaloside IV has not been fully elucidated. In this study, we propose a biosynthetic pathway for astragaloside IV that involves a sequence of oxidation-reduction reactions. The biosynthesis pathway from cycloastragenol to astragaloside IV encompasses four key steps: C-3 oxidation, 6-O-glucosylation, C-3 reduction, and 3-O-xylosylation. We identified a hydroxysteroid dehydrogenase AmHSD1 from A. membranaceus. AmHSD1 catalyzes the C-3 oxidation of cycloastragenol, yielding cycloastragenol-3-one, and the C-3 reduction of cycloastragenol-3-one-6-O-glucoside, resulting in cycloastragenol-6-O-glucoside. Additionally, the glycosyltransferases AmGT8 and AmGT1, previously reported by our groups, were identified as catalyzing the 6-O-glucosylation and 3-O-xylosylation steps, respectively. Astragaloside IV was successfully synthesized in transient expression in Nicotiana benthamiana using the combination of AmHSD1, AmGT8 and AmGT1. These results support the proposed four-step biosynthetic pathway and suggest that AmHSD1 probably plays a crucial role in the biosynthesis of astragaloside IV within A. membranaceus.

Analysis on morphological characteristics and identification of candidate genes during the flowering development of alfalfa.

Flower development is a crucial and complex process in the reproductive stage of plants, which involves the interaction of multiple endogenous signals and environmental factors. However, regulatory mechanism of flower development was unknown in alfalfa (Medicago sativa). In this study, the three stages of flower development of 'M. sativa cv. Gannong No. 5' (G5) and its early flowering and multi flowering mutant (MG5) were comparatively analyzed by transcriptomics. The results showed that compared with late bud stage (S1), 14287 and 8351 differentially expressed genes (DEGs) were identified at early flower stage (S2) in G5 and MG5, and 19941 and 19469 DEGs were identified at late flower stage (S3). Compared with S2, 9574 and 10870 DEGs were identified at S3 in G5 and MG5, respectively. Venn analysis revealed that 547 DEGs were identified among the three comparison groups. KEGG pathway enrichment analysis showed that these genes were involved in the development of alfalfa flowers through redox pathways and plant hormone signaling pathways. Key candidate genes including SnRK2, BSK, GID1, DELLA and CRE1, for regulating the development from buds to mature flowers in alfalfa were screened. In addition, differential expression of transcription factors such as MYB, AP2, bHLH, C2C2, MADS-box, NAC, bZIP, B3 and AUX/IAA also played an important role in this process. The results laid a theoretical foundation for studying the molecular mechanisms of the development process from buds to mature flowers in alfalfa.

Protection of Membrane Contact Protein by the Methionine Sulfoxide Reductases.

In this News and Views, I discuss our recent publication that established how steroidogenic acute regulatory-related lipid transfer domain-3 (STARD3), a membrane contact protein situated at lysosomal membranes, plays a role in the detoxification of cholesterol hydroperoxide. STARD3's methionine residues can be oxidized to methionine sulfoxide by cholesterol hydroperoxide, after which methionine sulfoxide reductases reduce the methionine sulfoxide residues back to methionine. The reaction also results in the reduction of the cholesterol hydroperoxide to an alcohol. The cyclic oxidation and reduction of methionine residues in STARD3 at membrane contact sites creates a catalytically efficient mechanism for detoxification of cholesterol hydroperoxide during cholesterol transport, thus protecting membrane contact sites and the entire cell against the toxicity of cholesterol hydroperoxide.

Diagnostic value of oxidation-reduction potential for male infertility: a systematic review and meta-analysis.

Background: In the last few years, studies have initially confirmed the diagnostic significance of oxidation-reduction potential (ORP) in male infertility patients. In this article, we used meta-analysis to clarify the role of ORP in the diagnosis of male infertility. Methods: PubMed, Embase, Web of Science, and Cochrane Library were searched by computer for relevant published literature. Quality assessment of the included literature was performed by Quality Assessment of Diagnostic Accuracy Studies (QUADAS) scale. Heterogeneity analysis of included studies was conducted using Metadisc 1.4 and Stata 12.0, and effective models for quantitative synthesis were selected based on heterogeneity results; the sensitivity and specificity of the synthesis were obtained using the software, and in order to reduce the effects of heterogeneity and thresholds, the information of sensitivity and specificity was integrated. We used the subject receiver operating characteristic (SROC) curve, area under the curve (AUC) and Q* index for comprehensive evaluation. Results: Seven papers were eventually included in the study, and the results showed that ORP had a sensitivity of 0.81 [95% confidence interval (CI): 0.80-0.82] and specificity of 0.66 (95% CI: 0.63-0.69), an AUC of 0.8 and a Q* index of 0.74 for the diagnosis of male infertility. Conclusions: ORP has high sensitivity and specificity for diagnosing male infertility.

Electrical Stimulating Redox Membrane Incorporated with PVA/Gelatin Nanofiber for Diabetic Wound Healing.

Chronic wounds adversely affect the quality of life. Although electrical stimulation has been utilized to treat chronic wounds, there are still limitations to practicing it due to the complicated power system. Herein, an electrostimulating membrane incorporated with electrospun nanofiber (M-sheet) to treat diabetic wounds is developed. Through the screen printing method, the various alternate patterns of both Zn and AgCl on a polyurethane substrate, generating redox-mediated electrical fields are introduced. The antibacterial ability of the patterned membrane against both E. coli and S. aureus is confirmed. Furthermore, the poly(vinyl alcohol) (PVA)/gelatin electrospun fiber is incorporated into the patterned membrane to enhance biocompatibility and maintain the wet condition in the wound environment. The M-sheet can improve cell proliferation and migration in vitro and has an immune regulatory effect by inducing the polarization of macrophage to the M2 phenotype. Finally, when applied to a diabetic skin wound model, the M-sheet displays an accelerated wound healing rate and enhances re-epithelialization, collagen synthesis, and angiogenesis. It suggests that the M-sheet is a simple and portable system for the spontaneous generation of electrical stimulation and has great potential to be used in the practical wound and other tissue engineering applications.

Synthesis of Intrinsically-Fluorescent Aliphatic Tautomeric Polymers for Proton-Conductivity, Dual-State Emission, and Sensing/Oxidation-Reduction of Metal Ions.

Herein, fluorescent conducting tautomeric polymers (FCTPs) are developed by polymerizing 2-methylprop-2-enoic acid (MPEA), methyl-2-methylpropenoate (MMP), N-(propan-2-yl)prop-2-enamide (PPE), and in situ-anchored 3-(N-(propan-2-yl)prop-2-enamido)-2-methylpropanoic acid (PPEMPA). Among as-synthesized FCTPs, the most promising characteristics in FCTP3 are confirmed by NMR and Fourier transform infrared (FTIR) spectroscopies, luminescence enhancements, and computational studies. In FCTP3, ─C(═O)NH─, -C(═O)N<, ─C(═O)OH, and ─C(═O)OCH3 subluminophores are identified by theoretical calculations and experimental analyses. These subluminophores facilitate redox characteristics, solid state emissions, aggregation-enhanced emissions (AEEs), excited-state intramolecular proton transfer (ESIPT), and conductivities in FCTP3. The ESIPT-associated dual emission/AEEs of FCTP3 are elucidated by time correlated single photon counting (TCSPC) investigation, solvent polarity effects, concentration-dependent emissions, dynamic light scattering (DLS) measurements, field emission scanning electron microscopy images, and computational calculations. The cyclic voltammetry measurements of FCTP3 indicate cumulative redox efficacy of ─C(═O)OH, ─C(═O)NH─/-C(═O)N<, ─C(─O─)═NH+─/─C(─O─)═N+, and ─C(═N)OH functionalities. In FCTP3, ESIPT-associated dual-emission enable in the selective detection of Cr(III)/Cu(II) at λem1/λem2 with the limit of detection of 0.0343/0.079 ppb. The preferential interaction of Cr(III)/Cu(II) with FCTP3 (amide)/FCTP3 (imidol) and oxidation/reduction of Cr(III)/Cu(II) to Cr(VI)/Cu(I) are further supported by NMR-titration; FTIR and X-ray photoelectron spectroscopy analyses; TCSPC/electrochemical/DLS measurement; alongside theoretical calculations. The proton conductivity of FCTP3 is explored by electrochemical impedance spectroscopy and I-V measurements.

The contrasting photosynthesis and growth response of young test species irrigated with electro-chemical modified water.

The study evaluated the effects of treating irrigation water with a coaxial flow variator (CFV) on the morpho-physiology of pot-cultivated test species, including cucumber (Cucumis sativus, CU), lettuce (Lactuca sativa, LE), and sorghum (Sorghum vulgare, SO), in early stages of growth. CFV caused a lower oxidation reduction potential (ORP), increased pH and flow resistance and inductance. It induced changes in the absorbance characteristics of water in specific spectral regions, likely associated with greater stretching and reduced bending vibrations compared to untreated water. While assimilation rate and photosynthetic efficiency were not significantly affected at 60 days after sowing, treated water increased the stomatal conductance to water vapour gsw (+79%) and the electron transport rate ETR (+10%) in CU, as well as the non-photochemical quenching NPQ (+33%) in SO. Treated water also reduced leaf temperature in all species (-0.86 °C on average). This translated into improved plant biomass (leaves: +34%; roots: +140%) and reduced leaf-to-root biomass ratio (-42%) in SO, allowing both faster aerial growth and soil colonization, which can be exploited to improve plant tolerance against abiotic stresses. In the C3 species CU and LE, plant biomass was instead reduced, although significantly in LE only, while the leaf-to-root biomass ratio was generally enhanced, a result likely profitable in the cultivation of leafy vegetables. This is a preliminary trial on the effects of functionalized water and much remains to be investigated in other physiological processes, plant species, and growth stages for the full exploitation of this water treatment in agronomy.

Ying and Yang of Ceramide in the Vascular Endothelium.

Ceramides, a group of biologically active sphingolipids, have been described as the new cholesterol given strong evidence linking high plasma ceramide with endothelial damage, risk for early adverse cardiovascular events, and development of cardiometabolic disease. This relationship has sparked great interest in investigating therapeutic targets with the goal of suppressing ceramide formation. However, the growing data challenge this paradigm of ceramide as solely eliciting detrimental effects to the cardiovascular system. Studies show that ceramides are necessary for maintaining proper endothelial redox states, mechanosensation, and membrane integrity. Recent work in preclinical models and isolated human microvessels highlights that the loss of ceramide formation can in fact propagate vascular endothelial dysfunction. Here, we delve into these conflicting findings to evaluate how ceramide may be capable of exerting both beneficial and damaging effects within the vascular endothelium. We propose a unifying theory that while basal levels of ceramide in response to physiological stimuli are required for the production of vasoprotective metabolites such as S1P (sphingosine-1-phosphate), the chronic accumulation of ceramide can promote activation of pro-oxidative stress pathways in endothelial cells. Clinically, the evidence discussed here highlights the potential challenges associated with therapeutic suppression of ceramide formation as a means of reducing cardiovascular disease risk.

Enhanced anaerobic digestion performance and sludge filterability by membrane microaeration for anaerobic membrane bioreactor application.

Slow dissolution/hydrolysis of insoluble/macromolecular organics and poor sludge filterability restrict the application potential of anaerobic membrane bioreactor (AnMBR). Bubble-free membrane microaeration was firstly proposed to overcome these obstacles in this study. The batch anaerobic digestion tests feeding insoluble starch and soluble peptone with and without microaeration showed that microaeration led to a 65.7-144.8% increase in methane production and increased critical flux of microfiltration membrane via driving the formation of large sludge flocs and the resultant improvement of sludge settleability. The metagenomic and bioinformatic analyses showed that microaeration significantly enriched the functional genes and bacteria for polysaccharide and protein hydrolysis, microaeration showed little negative effects on the functional genes involved in anaerobic metabolisms, and substrate transfer from starch to peptone significantly affected the functional genes and microbial community. This study demonstrates the dual synergism of microaeration to enhance the dissolution/hydrolysis/acidification of insoluble/macromolecular organics and sludge filterability for AnMBR application.

Sulfur-carbon loop enhanced efficient nitrogen removal mechanism from iron sulfide-mediated mixotrophic partial denitrification/anammox systems.

This study successfully established Iron Sulfide-Mediated mixotrophic Partial Denitrification/Anammox system, achieving nitrogen and phosphorus removal efficiency of 97.26% and 78.12%, respectively, with COD/NO3--N of 1.00. Isotopic experiments and X-ray Photoelectron Spectroscopy analysis confirmed that iron sulfide enhanced autotrophic Partial Denitrification performance. Meanwhile, various sulfur valence states functioned as electron buffers, reinforcing nitrogen and sulfur cycles. Microbial community analysis indicated reduced heterotrophic denitrifiers (OLB8, OLB13) under lower COD/NO3--N, creating more niche space for autotrophic bacteria and other heterotrophic denitrifiers. The prediction of functional genes illustrated that iron Sulfide upregulated genes related to carbon metabolism, denitrification, anammox and sulfur oxidation-reduction, facilitating the establishment of carbon-nitrogen-sulfur cycle. Furthermore, this cycle primarily produced electrons via nicotinamide adenine dinucleotide and sulfur oxidation-reduction processes, subsequently utilized within the electron transfer chain. In summary, the Partial Denitrification/Anammox system under the influence of iron sulfide achieved effient nitrogen removal by expediting electron transfer through the carbon-nitrogen-sulfur cycle.

Targeted Therapy of Tumors and Cancer Stem Cells based on Oxidant-Regulated Redox Pathway and its Mechanism.

A malignant tumor is a frequent and common disease that severely threatens human health. Many mechanisms, such as cell signaling pathway, anti-apoptosis mechanism, cell stemness, metabolism, and cell phenotype, have been studied to explain the reasons for chemotherapy, radioresistance, and tumor recurrences in antitumor treatment. Cancer stem cells (CSCs) are important tumor cell subclasses that can potentially organize and regulate stem cell properties. Growing evidence suggests that CSCs can initiate tumors and constitute a significant factor in metastasis, recurrence, and treatment resistance. The inability to completely target and remove CSCs is a considerable obstacle in tumor treatment. Therefore, drugs and therapeutic strategies that can effectively intervene with CSCs are essential for the treatment of different tumor types. However, the current strategies and efficacy of targeted elimination of CSCs are very limited. Oxidative stress has been recognized to play a crucial role in cancer pathophysiology. Moreover, reactive oxygen species (ROS) production and imbalance of the built-in cellular antioxidant defense system are hallmarks of tumor and cancer etiology. The current paper will focus on the regulation and mechanism behind oxidative stress in tumors and cancer stem cells and its tumor therapy applications. Additionally, the article discusses the role of CSCs in causing tumor treatment resistance and recurrence based on a redox perspective. The study also emphasizes that targeted modulation of oxidative stress in CSCs has great potential in tumor therapy, providing novel prospects for tumor therapy.

Transcriptome analysis of Gossypium hirsutum cultivar Zhongzhimian No.2 uncovers the gene regulatory networks involved in defense against Verticillium dahliae.

BACKGROUND: Cotton is globally important crop. Verticillium wilt (VW), caused by Verticillium dahliae, is the most destructive disease in cotton, reducing yield and fiber quality by over 50% of cotton acreage. Breeding resistant cotton cultivars has proven to be an efficient strategy for improving the resistance of cotton to V. dahliae. However, the lack of understanding of the genetic basis of VW resistance may hinder the progress in deploying elite cultivars with proven resistance. RESULTS: We planted the VW-resistant Gossypium hirsutum cultivar Zhongzhimian No.2 (ZZM2) in an artificial greenhouse and disease nursery. ZZM2 cotton was subsequently subjected to transcriptome sequencing after Vd991 inoculation (6, 12, 24, 48, and 72 h post-inoculation). Several differentially expressed genes (DEGs) were identified in response to V. dahliae infection, mainly involved in resistance processes, such as flavonoid and terpenoid quinone biosynthesis, plant hormone signaling, MAPK signaling, phenylpropanoid biosynthesis, and pyruvate metabolism. Compared to the susceptible cultivar Junmian No.1 (J1), oxidoreductase activity and reactive oxygen species (ROS) production were significantly increased in ZZM2. Furthermore, gene silencing of cytochrome c oxidase subunit 1 (COX1), which is involved in the oxidation-reduction process in ZZM2, compromised its resistance to V. dahliae, suggesting that COX1 contributes to VW resistance in ZZM2. CONCLUSIONS: Our data demonstrate that the G. hirsutum cultivar ZZM2 responds to V. dahliae inoculation through resistance-related processes, especially the oxidation-reduction process. This enhances our understanding of the mechanisms regulating the ZZM2 defense against VW.

Harnessing solar power for enhanced photocatalytic degradation of coloured pollutants using novel Mg-doped-ZnFe2O4/S@g-C3N4 heterojunction: A facile hydrothermal synthesis approach.

The ability of heterogeneous photocatalysis to effectively remove organic pollutants from wastewater has shown great promise as a tool for environmental remediation. Pure zinc ferrites (ZnFe2O4) and magnesium-doped zinc ferrites (Mg@ZnFe2O4) with variable percentages of Mg (0.5, 1, 3, 5, 7, and 9 mol%) were synthesized via hydrothermal route and their photocatalytic activity was checked against methylene blue (MB) taken as a model dye. FTIR, XPS, BET, PL, XRD, TEM, and UV-Vis spectroscopy were used for the identification and morphological characterization of the prepared nanoparticles (NPs) and nanocomposites (NCs). The 7% Mg@ZnFe2O4 NPs demonstrated excellent degradation against MB under sunlight. The 7% Mg@ZnFe2O4 NPs were integrated with diverse contents (10, 50, 30, and 70 wt.%) of S@g-C3N4 to develop NCs with better activity. When the NCs were tested to degrade MB dye, it was revealed that the 7%Mg@ZnFe2O4/S@g-C3N4 NCs were more effective at utilizing solar energy than the other NPs and NCs. The synergistic effect of the interface formed between Mg@ZnFe2O4 and S@g-C3N4 was primarily responsible for the boosted photocatalytic capability of the NCs. The fabricated NCs may function as an effective new photocatalyst to remove organic dyes from wastewater.

Modification of extracellular matrix proteins by oxidants and electrophiles.

The extracellular matrix (ECM) is critical to biological architecture and determines cellular properties, function and activity. In many situations it is highly abundant, with collagens and elastin being some of the most abundant proteins in mammals. The ECM comprises of multiple different protein species and sugar polymers, with both different isoforms and post-translational modifications (PTMs) providing a large variety of microenvironments that play a key role in determining tissue structure and health. A number of the PTMs (e.g. cross-links) present in the ECM are critical to integrity and function, whereas others are deleterious to both ECM structure and associated cells. Modifications induced by reactive oxidants and electrophiles have been reported to accumulate in some ECM with increasing age. This accumulation can be exacerbated by disease, and in particular those associated with acute or chronic inflammation, obesity and diabetes. This is likely to be due to higher fluxes of modifying agents in these conditions. In this focused review, the role and effects of oxidants and other electrophiles on ECM are discussed, with a particular focus on the artery wall and atherosclerotic cardiovascular disease. Modifications generated on ECM components are reviewed, together with the effects of these species on cellular properties including adhesion, proliferation, migration, viability, metabolic activity, gene expression and phenotype. Increasing data indicates that ECM modifications are both prevalent in human and mammalian tissues and play an important role in disease development and progression.

Properties of the iron-sulfur cluster electron transfer relay in an [FeFe]-hydrogenase that is tuned for H2 oxidation catalysis.

[FeFe]-hydrogenases catalyze the reversible oxidation of H2 from electrons and protons at an organometallic active site cofactor named the H-cluster. In addition to the H-cluster, most [FeFe]-hydrogenases possess accessory FeS cluster (F-cluster) relays that function in mediating electron transfer with catalysis. There is significant variation in the structural properties of F-cluster relays among the [FeFe]-hydrogenases; however, it is unknown how this variation relates to the electronic and thermodynamic properties, and thus the electron transfer properties, of enzymes. Clostridium pasteurianum [FeFe]-hydrogenase II (CpII) exhibits a large catalytic bias for H2 oxidation (compared to H2 production), making it a notable system for examining if F-cluster properties contribute to the overall function and efficiency of the enzyme. By applying a combination of multifrequency and potentiometric electron paramagnetic resonance, we resolved two electron paramagnetic resonance signals with distinct power- and temperature-dependent properties at g = 2.058 1.931 1.891 (F2.058) and g = 2.061 1.920 1.887 (F2.061), with assigned midpoint potentials of -140 ± 18 mV and -406 ± 12 mV versus normal hydrogen electrode, respectively. Spectral analysis revealed features consistent with spin-spin coupling between the two [4Fe-4S] F-clusters, and possible functional models are discussed that account for the contribution of coupling to the electron transfer landscape. The results signify the interplay of electronic coupling and free energy properties and parameters of the FeS clusters to the electron transfer mechanism through the relay and provide new insight as to how relays functionally complement the catalytic directionality of active sites to achieve highly efficient catalysis.

The Reducing Agent Dithiothreitol Modulates the Ventilatory Responses That Occur in Freely Moving Rats during and following a Hypoxic-Hypercapnic Challenge.

The present study examined the hypothesis that changes in the oxidation-reduction state of thiol residues in functional proteins play a major role in the expression of the ventilatory responses in conscious rats that occur during a hypoxic-hypercapnic (HH) gas challenge and upon return to room air. A HH gas challenge in vehicle-treated rats elicited robust and sustained increases in minute volume (via increases in frequency of breathing and tidal volume), peak inspiratory and expiratory flows, and inspiratory and expiratory drives while minimally affecting the non-eupneic breathing index (NEBI). The HH-induced increases in these parameters, except for frequency of breathing, were substantially diminished in rats pre-treated with the potent and lipophilic disulfide-reducing agent, L,D-dithiothreitol (100 µmol/kg, IV). The ventilatory responses that occurred upon return to room air were also substantially different in dithiothreitol-treated rats. In contrast, pre-treatment with a substantially higher dose (500 µmol/kg, IV) of the lipophilic congener of the monosulfide, N-acetyl-L-cysteine methyl ester (L-NACme), only minimally affected the expression of the above-mentioned ventilatory responses that occurred during the HH gas challenge or upon return to room air. The effectiveness of dithiothreitol suggests that the oxidation of thiol residues occurs during exposure to a HH gas challenge and that this process plays an essential role in allowing for the expression of the post-HH excitatory phase in breathing. However, this interpretation is contradicted by the lack of effects of L-NACme. This apparent conundrum may be explained by the disulfide structure affording unique functional properties to dithiothreitol in comparison to monosulfides. More specifically, the disulfide structure may give dithiothreitol the ability to alter the conformational state of functional proteins while transferring electrons. It is also possible that dithiothreitol is simply a more efficient reducing agent following systemic injection, although one interpretation of the data is that the effects of dithiothreitol are not due to its reducing ability.

The influence of pH on the efficacy of oxidation-reduction potential (ORP) to predict chlorine disinfection of surrogate bacteria, Escherichia coli O157:H7 and Listeria monocytogenes in oxidant demand free conditions and fresh produce wash water.

Oxidation-reduction potential (ORP) is commonly used as a rapid measurement of the antimicrobial potential of free chlorine during industrial fresh produce washing. The current study tested the hypothesis that ORP can act as a "single variable" measurement of bacterial (vegetative and endospores) inactivation effectiveness with free chlorine irrespective of the water pH value. This situation has on occasion been assumed but never confirmed nor disproven. Chlorine-dosed pH 6.5 and 8.5 phosphate buffer solutions were inoculated with Escherichia coli (E. coli), Listeria innocua (L. innocua), or Bacillus subtilis (B. subtilis) endospores. ORP, free chlorine (FC), and log reduction were monitored after 5 s (for E. coli and L. innocua) and up to 30 min (for B. subtilis spores) of disinfection. Logistic and exponential models were developed to describe how bacteria reduction varied as a function of ORP at different pH levels. Validation tests were performed in phosphate buffered pH 6.5 and 8.5 cabbage wash water periodically dosed with FC, cabbage extract and a cocktail of Escherichia coli O157:H7 (E. coli O157:H7) and Listeria monocytogenes (L. monocytogenes). The built logistic and exponential models confirmed that at equal ORP values, the inactivation of the surrogate strains was not consistent across pH 6.5 and pH 8.5, with higher reductions at higher pH. This is the opposite of the well-known free chlorine-controlled bacterial inactivation, where the antibacterial effect is higher at lower pH. The validation test results indicated that in the cabbage wash water, the relationship between disinfection efficiency and ORP was consistent with the oxidant demand free systems. The study suggests that ORP cannot serve as a reliable single variable measurement to predict bacterial disinfection in buffered systems. When using ORP to monitor and control the antibacterial effectiveness of the chlorinated wash water, it is crucial to take into account (and control) the pH.