Chemolithotrophic acetogenic H2/CO2 utilization in Italian rice field soil

Acetate oxidation in Italian rice field at 50 °C is achieved by uncultured syntrophic acetate oxidizers. As these bacteria are closely related to acetogens, they may potentially also be able to synthesize acetate chemolithoautotrophically. Labeling studies using exogenous H₂ (80%) and ¹³CO₂ (20%), indeed demonstrated production of acetate as almost exclusive primary product not only at 50 °C but also at 15 °C. Small amounts of formate, propionate and butyrate were also produced from ¹³CO₂. At 50 °C, acetate was first produced but later on consumed with formation of CH₄. Acetate was also produced in the absence of exogenous H₂ albeit to lower concentrations. The acetogenic bacteria and methanogenic archaea were targeted by stable isotope probing of ribosomal RNA (rRNA). Using quantitative PCR, ¹³C-labeled bacterial rRNA was detected after 20 days of incubation with ¹³CO₂. In the heavy fractions at 15 °C, terminal restriction fragment length polymorphism, cloning and sequencing of 16S rRNA showed that Clostridium cluster I and uncultured Peptococcaceae assimilated ¹³CO₂ in the presence and absence of exogenous H₂, respectively. A similar experiment showed that Thermoanaerobacteriaceae and Acidobacteriaceae were dominant in the ¹³C treatment at 50 °C. Assimilation of ¹³CO₂ into archaeal rRNA was detected at 15 °C and 50 °C, mostly into Methanocellales, Methanobacteriales and rice cluster III. Acetoclastic methanogenic archaea were not detected. The above results showed the potential for acetogenesis in the presence and absence of exogenous H₂ at both 15 °C and 50 °C. However, syntrophic acetate oxidizers seemed to be only active at 50 °C, while other bacterial groups were active at 15 °C.     

Crystallographic structure of the turbine C-ring from spinach chloroplast F-ATP synthase

In eukaryotic and prokaryotic cells, F-ATP synthases provide energy through the synthesis of ATP. The chloroplast F-ATP synthase (CF₁F_O-ATP synthase) of plants is integrated into the thylakoid membrane via its F_O-domain subunits a, b, b’ and c. Subunit c with a stoichiometry of 14 and subunit a form the gate for H⁺-pumping, enabling the coupling of electrochemical energy with ATP synthesis in the F₁ sector.Here we report the crystallization and structure determination of the c14-ring of subunit c of the CF₁F_O-ATP synthase from spinach chloroplasts. The crystals belonged to space group C2, with unit-cell parameters a=144.420, b=99.295, c=123.51 Å, and β=104.34° and diffracted to 4.5 Å resolution. Each c-ring contains 14 monomers in the asymmetric unit. The length of the c-ring is 60.32 Å, with an outer ring diameter 52.30 Å and an inner ring width of 40 Å.     

Interactive effects of elevated CO2 and precipitation change on leaf nitrogen of dominant Stipa L. species

Nitrogen (N) serves as an important mineral element affecting plant productivity and nutritional quality. However, few studies have addressed the interactive effects of elevated CO₂ and precipitation change on leaf N of dominant grassland genera such as Stipa L. This has restricted our understanding of the responses of grassland to climate change. We simulated the interactive effects of elevated CO₂ concentration and varied precipitation on leaf N concentration (N_mass) of four Stipa species (Stipa baicalensis, Stipa bungeana, Stipa grandis, and Stipa breviflora; the most dominant species in arid and semiarid grassland) using open-top chambers (OTCs). The relationship between the N_mass of these four Stipa species and precipitation well fits a logarithmic function. The sensitivity of these four species to precipitation change was ranked as follows: S. bungeana > S. breviflora > S. baicalensis > S. grandis. The N_mass of S. bungeana was the most sensitive to precipitation change, while S. grandis was the least sensitive among these Stipa species. Elevated CO₂ exacerbated the effect of precipitation on N_mass. N_mass decreased under elevated CO₂ due to growth dilution and a direct negative effect on N assimilation. Elevated CO₂ reduced N_mass only in a certain precipitation range for S. baicalensis (163–343 mm), S. bungeana (164–355 mm), S. grandis (148–286 mm), and S. breviflora (130–316 mm); severe drought or excessive rainfall would be expected to result in a reduced impact of elevated CO₂. Elevated CO₂ affected the N_mass of S. grandis only in a narrow precipitation range. The effect of elevated CO₂ reached a maximum when the amount of precipitation was 253, 260, 217, and 222 mm for S. baicalensis, S. bungeana, S. grandis, and S. breviflora, respectively. The N_mass of S. grandis was the least sensitive to elevated CO₂. The N_mass of S. breviflora was more sensitive to elevated CO₂ under a drought condition compared with the other Stipa species.     

Anticholinesterse and antioxidant investigations of crude extracts,subsequent fractions,saponins and flavonoids of atriplex laciniata L.: potential effectiveness in Alzheimer’s and other neurological disorders

Background

Atriplex laciniata L. was investigated for phenolic, flavonoid contents, antioxidant, anticholinesterase activities, in an attempt to explore its effectiveness in Alzheimer’s and other neurological disorders. Plant crude methanolic extract (Al.MeF), subsequent fractions; n-hexane (Al.HxF), chloroform (Al.CfF), ethyl acetate (Al.EaF), aqueous (Al.WtF), Saponins (Al.SPF) and Flavonoids (Al.FLVF) were investigated for DPPH, ABTS and H₂O₂ free radical scavenging activities. Further these extracts were subjected to acetylcholinesterase (AChE) & butyrylcholinesterase (BChE) inhibitory activities using Ellman’s assay. Phenolic and Flavonoid contents were determined and expressed in mg Gallic acid GAE/g and Rutin RTE/g of samples respectively.

Results

In DPPH free radicals scavenging assay, Al.FLVF, Al.SPF and Al.MeF showed highest activity causing 89.41 ± 0.55, 83.37 ± 0.34 and 83.37 ± 0.34% inhibition of free radicals respectively at 1 mg/mL concentration. IC₅₀ for these fractions were 33, 83 and 82 μg/mL respectively. Similarly, plant extracts showed high ABTS scavenging potential, i.e. Al.FLVF (90.34 ± 0.55), Al.CfF (83.42 ± 0.57), Al.MeF (81.49 ± 0.60) with IC₅₀ of 30, 190 and 70 μg/ml respectively. further, H₂O₂ percent scavenging was highly appraised in Al.FLVF (91.29 ± 0.53, IC₅₀ 75), Al.SPF (85.35 ± 0.61, IC₅₀ 70) and Al.EaF (83.48 ± 0.67, IC₅₀ 270 μg/mL). All fractions exhibited concentration dependent AChE inhibitory activity as; Al.FLVF, 88.31 ± 0.57 (IC₅₀ 70 μg/mL), Al.SPF, 84.36 ± 0.64 (IC₅₀ 90 μg/mL), Al.MeF, 78.65 ± 0.70 (IC₅₀ 280 μg/mL), Al.EaF, 77.45 ± 0.46 (IC₅₀ 270 μg/mL) and Al.WtF 72.44 ± 0.58 (IC₅₀ 263 μg/mL) at 1 mg/mL. Likewise the percent BChE inhibitory activity was most obvious in Al.FLVF 85.46 ± 0.62 (IC₅₀ 100 μg/mL), Al.CfF 83.49 ± 0.46 (IC₅₀ 160 μg/mL), Al.MeF 82.68 ± 0.60 (IC₅₀ 220 μg/mL) and Al.SPF 80.37 ± 0.54 (IC₅₀ 120 μg/mL).

Conclusions

These results stipulate that A. laciniata is enriched with phenolic and flavonoid contents that possess significant antioxidant and anticholinestrase effects. This provide pharmacological basis for the presence of compounds that may be effective in Alzheimer’s and other neurological disorders.     

Protective effects of L-pGlu-(2-propyl)-L-His-L-ProNH2, a newer thyrotropin releasing hormone analog in in vitro and in vivo models of cerebral ischemia

In the present study, the newly synthesized TRH analog (l-pGlu-(2-propyl)-l-His-l-ProNH₂; NP-647) was evaluated for its effects in in vitro (oxygen glucose deprivation (OGD)-, glutamate- and H₂O₂-induced injury in PC-12 cells) and in vivo (transient global ischemia) models of cerebral ischemic injury. PC-12 cells were subjected to oxygen and glucose deprivation for 6 h. Exposure of NP-647 was given before and during OGD. In glutamate and H₂O₂ induced injury, exposure of NP-647 was given 1, 6 and 24 h prior to exposure of glutamate and H₂O₂ exposure. NP-647, per se found to be non-toxic in 1-100 μM concentrations. NP-647 showed protection against OGD at the 1 and 10 μM. The concentration-dependent protection was observed in H₂O₂- and glutamate-induced cellular injury. In in vivo studies, NP-647 treatment showed protection of hippocampal (CA1) neuronal damage in transient global ischemia in mice and subsequent improvement in memory retention was observed using passive avoidance retention test. Moreover, administration of NP-647 resulted in decrease in inflammatory cytokines TNF-α and IL-6 as well as lipid peroxidation. These results suggest potential of NP-647 in the treatment of cerebral ischemia and its neuroprotective effect may be attributed to reduction of excitotoxicity, oxidative stress and inflammation.     

The combined effect of water deficit stress and TiO2 nanoparticles on cell membrane and antioxidant enzymes in Helianthus annuus L.

Nanotechnology has become one of the several approaches attempting to ameliorate the severe effect of drought on plant''s production and to increase the plants tolerance against water deficit for the water economy. In this research, the effect of foliar application of TiO₂, nanoparticles or ordinary TiO₂, on Helianthus annuus subjected to different levels of water deficit was studied. Cell membrane injury increased by increasing the level of water deficit and TiO₂ concentration, and both types of TiO₂ affected the leaves in analogous manner. Ord-TiO₂ increased H₂O₂ generation by 67–240% and lipid peroxidation by 4–67% in leaves. These increases were more than that induced by Nano-TiO₂ and the effect was concentration dependent. Proline significantly increased in leaves by water deficit stress, reaching at 25% field capacity (FC) to more than fivefold compared to that in plants grown on full FC. Spraying plants with water significantly decreased the activities of enzymes in the water deficit stressed roots. The water deficit stress exerted the highest magnitude of effect on the changes of cell membrane injury, MDA, proline content, and activities of CAT and GPX. Nano-TiO₂ was having the highest effect on contents of H₂O₂ and GPX activity. In roots, the level of water deficit causes highest effect on enzyme activities, but TiO₂ influenced more on the changes of MDA and H₂O₂ contents. GPX activity increased by 283% in leaves of plants treated with 50 and 150 ppm Nano-TiO₂, while increased by 170% in those treated with Ord-TiO₂, but APX and CAT activities increased by 17–197%, in average, with Ord-TiO₂. This study concluded that Nano-TiO₂ didn’t ameliorate the effects of drought stress on H. annuus but additively increased the stress, so its use in nano-phytotechnology mustn’t be expanded without extensive studies.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-022-01153-z.     

Protective effects of cyclosativene on H2O2-induced injury in cultured rat primary cerebral cortex cells

Sesquiterpenes have attracted much interest with respect to their protective effect against oxidative damage that may be the cause of many diseases including several neurodegenerative disorders and cancer. Our previous unpublished work suggested that cyclosativene (CSV), a tetracyclic sesquiterpene, has antioxidant and anticarcinogenic features. However, little is known about the effects of CSV on oxidative stress induced neurotoxicity. We used hydrogen peroxide (H₂O₂) exposure for 6 h to model oxidative stress. Therefore, this experimental design allowed us to explore the neuroprotective potential of CSV in H₂O₂-induced toxicity in new-born rat cerebral cortex cell cultures for the first time. For this aim, MTT and lactate dehydrogenase release assays were carried out to evaluate cytotoxicity. Total antioxidant capacity (TAC) and total oxidative stress (TOS) parameters were used to evaluate oxidative changes. In addition to determining of 8-hydroxy-2-deoxyguanosine (8-OH-dG) levels, the single cell gel electrophoresis (or Comet assay) was also performed for measuring the resistance of neuronal DNA to H₂O₂-induced challenge. Our results showed that survival and TAC levels of the cells decreased, while TOS, 8-OH-dG levels and the mean values of the total scores of cells showing DNA damage (Comet assay) increased in the H₂O₂ alone treated cultures. But pre-treatment of CSV suppressed the cytotoxicity, genotoxicity and oxidative stress which were increased by H₂O₂. On the basis of these observations, it is suggested that CSV as a natural product with an antioxidant capacity in mitigating oxidative injuries in the field of neurodegenerative disorders.     

Hydrogen peroxide primes heart regeneration with a derepression mechanism

While the adult human heart has very limited regenerative potential, the adult zebrafish heart can fully regenerate after 20% ventricular resection. Although previous reports suggest that developmental signaling pathways such as FGF and PDGF are reused in adult heart regeneration, the underlying intracellular mechanisms remain largely unknown. Here we show that H₂O₂ acts as a novel epicardial and myocardial signal to prime the heart for regeneration in adult zebrafish. Live imaging of intact hearts revealed highly localized H₂O₂ (∼30 μM) production in the epicardium and adjacent compact myocardium at the resection site. Decreasing H₂O₂ formation with the Duox inhibitors diphenyleneiodonium (DPI) or apocynin, or scavenging H₂O₂ by catalase overexpression markedly impaired cardiac regeneration while exogenous H₂O₂ rescued the inhibitory effects of DPI on cardiac regeneration, indicating that H₂O₂ is an essential and sufficient signal in this process. Mechanistically, elevated H₂O₂ destabilized the redox-sensitive phosphatase Dusp6 and hence increased the phosphorylation of Erk1/2. The Dusp6 inhibitor BCI achieved similar pro-regenerative effects while transgenic overexpression of dusp6 impaired cardiac regeneration. H₂O₂ plays a dual role in recruiting immune cells and promoting heart regeneration through two relatively independent pathways. We conclude that H₂O₂ potentially generated from Duox/Nox2 promotes heart regeneration in zebrafish by unleashing MAP kinase signaling through a derepression mechanism involving Dusp6.     

Prostaglandin E2 production in astrocytes: regulation by cytokines, extracellular ATP, and oxidative agents

Upregulation and activation of phospholipases A₂ (PLA₂) and cyclooxygenases (COX) leading to prostaglandin E₂(PGE₂) production have been implicated in a number of neurodegenerative diseases. In this study, we investigated PGE₂ production in primary rat astrocytes in response to agents that activate PLA₂ including pro-inflammatory cytokines (IL-1β, TNFα and IFNγ), the P2 nucleotide receptor agonist ATP, and oxidants (H₂O₂ and menadione). Exposure of astrocytes to cytokines resulted in a time-dependent increase in PGE₂ production that was marked by increased expression of secretory sPLA₂ and COX-2, but not COX-1 and cytosolic cPLA₂. Although astrocytes responded to ATP or phorbol ester (PMA) with increased cPLA₂ phosphorylation and arachidonic acid release, ATP or PMA only caused a small increase in levels of PGE₂. However, when astrocytes were first treated with cytokines, further exposure to ATP or PMA, but not H₂O₂ or menadione, markedly increased PGE₂ production. These results suggest that ATP release during neuronal excitation or injury can enhance the inflammatory effects of cytokines on PGE₂ production and may contribute to chronic inflammation seen in Alzheimer's disease.     

H2O2 Sensors of Lungs and Blood Vessels and Their Role in the Antioxidant Defense of the Body

This paper considers the composition and function of sensory systems monitoring H₂O₂ level by the lung neuroepithelial cells and carotid bodies. These systems are localized in the plasma membrane of the corresponding cells and are composed of O ² -generating NADPH-oxidase and an H₂O₂-activated K⁺ channel. This complex structure of the H₂O₂ sensors is probably due to their function in antioxidant defense. By means of these sensors, an increase in the H₂O₂ level in lung or blood results in a decrease in lung ventilation and constriction of blood vessels. This action lowers the O₂ flux to the tissues and, hence, intracellular [O₂]. The [O₂] decrease, in turn, inhibits intracellular generation of reactive oxygen species. The possible roles of such systems under normal conditions (e.g., the effect of O ² in air) and in some pathologies (e.g., pneumonia) is discussed.     

Microsomal Prostaglandin E Synthase Type 2 (mPGES2) Is a Glutathione-dependent Heme Protein,and Dithiothreitol Dissociates the Bound Heme to Produce Active Prostaglandin E2 Synthase in Vitro

An x-ray study indicated that microsomal prostaglandin E synthase type 2 (mPGES2) is a heme-bound protein and catalyzes prostaglandin (PG) H₂ degradation, but not PGE₂ formation (Yamada, T., and Takusagawa, F. (2007) Biochemistry 46, 8414–8424). In response to the x-ray study, Watanabe et al. claimed that mPGES2 is a heme-free protein and that both the heme-free and heme-bound proteins have PGE₂ synthesis activity in the presence of dithiothreitol (Watanabe, K., Ito, S., and Yamamoto, S. (2008) Biochem. Biophys. Res. Commun. 367, 782–786). To resolve the contradictory results, the heme-binding scheme of mPGES2 was further characterized in vivo and in vitro by absorption and fluorescence spectroscopies. A substantial amount of heme-bound mPGES2 was detected in cell extracts. The heme content in mPGES2 was increased along with an increase in Fe³⁺ in the culture medium. Heme-free mPGES2 was converted to the heme-bound form by mixing it with pig liver extract, indicating that mPGES2 is capable of forming a complex with heme in mammalian cells. Heme binds to mPGES2 only in the presence of glutathione. The newly determined heme dissociation constant (2.9 nm) supports strongly that mPGES2 is a heme-bound protein in vivo. The bound heme was not dissociated by oxidation by H₂O₂ or reduction by glutathione or 2-mercaptoethanol. However, reduction by dithiothreitol (an artificial reducing compound) induced the bound heme to dissociate from mPGES2 and released heme-free mPGES2, which exhibited PGE₂ synthesis activity in vitro. Imidazole bound to mPGES2 by stacking on the bound heme and inhibited heme oxidation by H₂O₂ and reduction by dithiothreitol.     

Antioxidant and anticholinesterase investigations of Rumex hastatus D. Don: potential effectiveness in oxidative stress and neurological disorders

Background

Rumex species are traditionally used for the treatment of neurological disorders including headache, migraine, depression, paralysis etc. Several species have been scientifically validated for antioxidant and anticholinestrase potentials. This study aims to investigate Rumex hastatus D. Don crude methanolic extract, subsequent fractions, saponins and flavonoids for acetylcholinestrase, butyrylcholinestrase inhibition and diverse antioxidant activities to validate its folkloric uses in neurological disorders. Rumex hastatus crude methanolic extract (Rh. Cr), subsequent fractions; n-hexane (Rh. Hex), chloroform (Rh. Chf), ethyl acetate (Rh. EtAc), aqueous fraction (Rh. Aq), crude saponins (Rh. Sp) and flavonoids (Rh. Fl) were investigated against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) at various concentrations (125, 250, 500, 1000 μg/mL) using Ellman’s spectrophotometric analysis. Antioxidant potentials of Rh. Sp and Rh. Fl were evaluated using DPPH, H₂O₂ and ABTS free radical scavenging assays at 62.5, 125, 250, 500, 1000 μg/mL.

Results

All the test samples showed concentration dependent cholinesterase inhibition and radicals scavenging activity. The AChE inhibition potential of Rh. Sp and Rh. Fl were most prominent i.e., 81.67 ± 0.88 and 91.62 ± 1.67 at highest concentration with IC₅₀ 135 and 20 μg/mL respectively. All the subsequent fractions exhibited moderate to high AChE inhibition i.e., Rh. Cr, Rh. Hex, Rh. Chf, Rh. EtAc and Rh. Aq showed IC₅₀ 218, 1420, 75, 115 and 1210 μg/mL respectively. Similarly, against BChE various plant extracts i.e., Rh. Sp, Rh. Fl, Rh. Cr, Rh. Hex, Rh. Chf, Rh. EtAc and Rh. Aq resulted IC₅₀ 165, 175, 265, 890, 92, 115 and 220 μg/mL respectively. In DPPH free radical scavenging assay, Rh. Sp and Rh. Fl showed comparable results with the positive control i.e., 63.34 ± 0.98 and 76.93 ± 1.13% scavenging at 1 mg/mL concentration (IC₅₀ 312 and 104 μg/mL) respectively. The percent ABTS radical scavenging potential exhibited by Rh. Sp and Rh. Fl (1000 μg/mL) were 82.58 ± 0.52 and 88.25 ± 0.67 with IC₅₀ 18 and 9 μg/mL respectively. Similarly in H₂O₂ scavenging assay, the Rh. Sp and Rh. Fl exhibited IC₅₀ 175 and 275 μg/mL respectively.

Conclusion

The strong anticholinesterase and antioxidant activities of Rh. Sp, Rh. Fl and various fractions of R. hastatus support the purported ethnomedicinal uses and recommend R. hastatus as a possible remedy for the treatment of AD and neurodegenerative disorders.     

Influence of exogenous application of glycinebetaine on antioxidative system and growth of salt-stressed soybean seedlings (Glycine max L.)

Glycinebetaine is one of the most competitive compounds which play an important role in salt stress in plants. In this study, the enhanced salt tolerance in soybean (Glycine max L.) by exogenous application of glycinebetaine was evaluated. To improve salt tolerance at the seedling stage, GB was applied in four different concentrations (0, 5, 25 and 50 mM) as a pre-sowing seed treatment. Salinity stress in the form of a final concentration of 150 mM sodium chloride (NaCl) over a 15 day period drastically affected the plants as indicated by increased proline, MDA and Na⁺ content of soybean plants. In contrast, supplementation with 50 mM GB improved growth of soybean plants under NaCl as evidenced by a decrease in proline, MDA and Na⁺ content of soybean plants. Further analysis showed that treatments with GB, resulted in increasing of CAT and SOD activity of soybean seedlings in salt stress. We propose that the role of GB in increasing tolerance to salinity stress in soybean may result from either its antioxidant capacity by direct scavenging of H₂O₂ or its role in activating CAT activity which is mandatory in scavenging H₂O₂.     

Study on the heterogeneous degradation of chitosan with H2O2 catalyzed by a new supermolecular assembly crystal: [C6H8N2]6H3[PW12O40]·2H2O

A new supermolecular assembly crystal, [C₆H₈N₂]₆H₃[PW₁₂O₄₀]·2H₂O (DMB-PWA), was synthesized with phosphotungstic acid (PWA) and 1,2-diaminobenzene (DMB) under hydrothermal conditions and was characterized by Fourier-transform infrared spectra (FTIR) and single-crystal X-ray diffraction analysis. DMB-PWA could effectively catalyze oxidative degradation of chitosan with H₂O₂ in the heterogeneous phase. The optimum degradation conditions were determined by orthogonal tests as follows: amount of chitosan 1.00 g, 30% (wt %); H₂O₂, 3.0 mL; dosage of catalyst, 0.06 g; reaction temperature, 85 °C; and reaction time, 30 min. The water-soluble chitosan with a viscosity-average molecular weight (M_v) of 4900 was obtained under the optimum degradation conditions and was characterized by FTIR, ultraviolet-visible diffuse reflection spectra (UV-vis DRS), and X-ray powder diffraction analysis.     

P2Y2 receptor agonist with enhanced stability protects the heart from ischemic damage in vitro and in vivo

Extracellular nucleotides acting via P2 receptors play important roles in cardiovascular physiology/pathophysiology. Pyrimidine nucleotides activate four G protein-coupled P2Y receptors (P2YRs): P2Y₂ and P2Y₄ (UTP-activated), P2Y₆, and P2Y₁₄. Previously, we showed that uridine 5′-triphosphate (UTP) activating P2Y₂R reduced infarct size and improved mouse heart function after myocardial infarct (MI). Here, we examined the cardioprotective role of P2Y₂R in vitro and in vivo following MI using uridine-5′-tetraphosphate δ-phenyl ester tetrasodium salt (MRS2768), a selective and more stable P2Y₂R agonist. Cultured rat cardiomyocytes pretreated with MRS2768 displayed protection from hypoxia [as revealed by lactate dehydrogenase (LDH) release and propidium iodide (PI) binding], which was reduced by P2Y₂R antagonist, AR-C118925 (5-((5-(2,8-dimethyl-5H-dibenzo[a,d][7]annulen-5-yl)-2-oxo-4-thioxo-3,4-dihydropyrimidin-1(2H)-yl)methyl)-N-(1H-tetrazol-5-yl)furan-2-carboxamide). In vivo, echocardiography and infarct size staining of triphenyltetrazolium chloride (TTC) in 3 groups of mice 24 h post-MI: sham, MI, and MI+MRS2768 indicated protection. Fractional shortening (FS) was higher in MRS2768-treated mice than in MI alone (40.0 ± 3.1 % vs. 33.4 ± 2.7 %, p < 0.001). Troponin T and tumor necrosis factor-α (TNF-α) measurements demonstrated that MRS2768 pretreatment reduced myocardial damage (p < 0.05) and c-Jun phosphorylation increased. Thus, P2Y₂R activation protects cardiomyocytes from hypoxia in vitro and reduces post-ischemic myocardial damage in vivo.     

Impairment of ATP hydrolysis decreases adenosine A1 receptor tonus favoring cholinergic nerve hyperactivity in the obstructed human urinary bladder

This study was designed to investigate whether reduced adenosine formation linked to deficits in extracellular ATP hydrolysis by NTPDases contributes to detrusor neuromodulatory changes associated with bladder outlet obstruction in men with benign prostatic hyperplasia (BPH). The kinetics of ATP catabolism and adenosine formation as well as the role of P1 receptor agonists on muscle tension and nerve-evoked [³H]ACh release were evaluated in mucosal-denuded detrusor strips from BPH patients (n = 31) and control organ donors (n = 23). The neurogenic release of ATP and [³H]ACh was higher (P < 0.05) in detrusor strips from BPH patients. The extracellular hydrolysis of ATP and, subsequent, adenosine formation was slower (t_1/2 73 vs. 36 min, P < 0.05) in BPH detrusor strips. The A₁ receptor-mediated inhibition of evoked [³H]ACh release by adenosine (100 μM), NECA (1 μM), and R-PIA (0.3 μM) was enhanced in BPH bladders. Relaxation of detrusor contractions induced by acetylcholine required 30-fold higher concentrations of adenosine. Despite VAChT-positive cholinergic nerves exhibiting higher A₁ immunoreactivity in BPH bladders, the endogenous adenosine tonus revealed by adenosine deaminase is missing. Restoration of A₁ inhibition was achieved by favoring (1) ATP hydrolysis with apyrase (2 U mL⁻¹) or (2) extracellular adenosine accumulation with dipyridamole or EHNA, as these drugs inhibit adenosine uptake and deamination, respectively. In conclusion, reduced ATP hydrolysis leads to deficient adenosine formation and A₁ receptor-mediated inhibition of cholinergic nerve activity in the obstructed human bladder. Thus, we propose that pharmacological manipulation of endogenous adenosine levels and/or A₁ receptor activation might be useful to control bladder overactivity in BPH patients.     

H2 oxidation,O2 uptake and CO2 fixation in hydrogen treated soils

In many legume nodules, the H₂ produced as a byproduct of N₂ fixation diffuses out of the nodule and is consumed by the soil. To study the fate of this H₂ in soil, a H₂ treatment system was developed that provided a 300 cm³ sample of a soil:silica sand (2:1) mixture with a H₂ exposure rate (147 nmol H₂ cm^–3hr^–1) similar to that calculated exist in soils located within 1–4 cm of nodules (30–254 nmol H₂ cm^–3hr^–1). After 3 weeks of H₂ pretreatment, the treated soils had a K_m and V_max for H₂ uptake (1028 ppm and 836 nmol cm^–3 hr^–1, respectively) much greater than that of control, air-treated soil (40.2 ppm and 4.35 nmol cm^–3 hr^–1, respectively). In the H₂ treated soils, O₂, CO₂ and H₂ exchange rates were measured simultaneously in the presence of various pH₂. With increasing pH₂, a 5-fold increase was observed in O₂ uptake, and CO₂ evolution declined such that net CO₂ fixation was observed in treatments of 680 ppm H₂ or more. At the H₂ exposure rate used to pretreat the soil, 60% of the electrons from H₂ were passed to O₂, and 40% were used to support CO₂ fixation. The effect of H₂ on the energy and C metabolism of soil may account for the well-known effect of legumes in promoting soil C deposition.     

NO serves as a signaling intermediate downstream of H2O2 to modulate dynamic microtubule cytoskeleton during responses to VD-toxins in Arabidopsis

Although hydrogen peroxide (H₂O₂) and nitric oxide (NO) can act as an upstream signaling molecule to modulate the dynamic microtubule cytoskeleton during the defense responses to Verticillium dahliae (VD) toxins in Arabidopsis, it is not known the relationship between these two signaling molecules. Here, we show that VD-toxin-induced NO accumulation was dependent on prior H₂O₂ production, NO is downstream of H₂O₂ in the signaling process, and that H₂O₂ acted synergistically with NO to modulate the dynamic microtubule cytoskeleton responses to VD-toxins in Arabidopsis.     

Multiple reactions in vanadyl-V(IV) oxidation by H2O2

Oxidation of vanadyl sulfate by H₂O₂ involves multiple reactions at neutral pH conditions. The primary reaction was found to be oxidation of V(IV) to V(V) using 0.5 equivalent of H₂O₂, based on the loss of blue color and the visible spectrum. The loss of V(IV) and formation V(V) compounds were confirmed by ESR and⁵¹V-NMR spectra, respectively. In the presence of excess H₂O₂ (more than two equivalents), the V(V) was converted into diperoxovanadate, the major end-product of these reactions, identified by changes in absorbance in ultraviolet region and by the specific chemical shift in NMR spectrum. The stoichiometric studies on the H₂O₂ consumed in this reaction support the occurrence of reactions of two-electron oxidation followed by complexing two molecules of H₂O₂. Addition of a variety of compounds—Tris, ethanol, mannitol, benzoate, formate (hydroxyl radical quenching), histidine, imidazole (singlet oxygen quenching), and citrate—stimulated a secondary reaction of oxygen-consumption that also used V(IV) as the reducing source. This reaction requires concomitant oxidation of vanadyl by H₂O₂, favoured at low H₂O₂:V(IV) ratio. Another secondary reaction of oxygen release was found to occur during vanadyl oxidation by H₂O₂ in acidic medium in which the end-product was not diperoxovanadate but appears to be a mixture of VO ₃ ⁺ (–546 ppm), VO³⁺ (–531 ppm) and VO ₂ ⁺ (–512 ppm), as shown by the⁵¹V-NMR spectrum. This reaction also occurred in phosphate-buffered medium but only on second addition of vanadyl. The compounds that stimulated the oxygen-consumption reaction were found to inhibit the oxygen-release reaction. A combination of these reactions occur depending on the proportion of the reactants (vanadyl and H₂O₂), the pH of the medium and the presence of some compounds that affect the secondary reactions.