RESUMO
H2S is a gaseous compound that contributes to air pollution. In this work, the electrochemical oxidation treatment of gaseous streams polluted with H2S is evaluated using a jet mixer and electrochemical cell device, in which the performance of electrolytic and electro-Fenton assisted absorption processes are compared. Results demonstrate the feasibility of both processes to remove H2S, reaching coulombic efficiencies of nearly 100% in the electrolytic assisted absorption, and 70-80% in the electro-Fenton assisted absorption. Aqueous solutions containing phosphate salts as electrolyte were found to be suitable as absorbents for the process. Efficiency in the cathodic production of H2O2 in these solutions using the experimental device was found to be as high as 32.8% (1.184 mgH2O2/min) at 12 °C and atmospheric pressure. Sequential formation of SO2 and SO3 is obtained by the oxidation of H2S contained in the gas. These species are hydrolysed, and a part remained in the absorbent as SO32- and SO42-, while the rest is dragged in the outlet gas. SO3 production is promoted by electrolytic assisted absorption and polysulphides by the electro-Fenton technology. Low concentrations of elemental sulphur are detected in the solid suspensions formed during the process.
Assuntos
Gases , Poluentes Químicos da Água , Peróxido de Hidrogênio/química , Eletrólise , Oxirredução , Eletrodos , Poluentes Químicos da Água/químicaRESUMO
Molybdate (MoO4) and tetrathiomolybdate (MoS4) supplementation of rats via drinking water had opposite effects on the establishment of Nippostrongylus brasiliensis larvae but both induced hypercupraemia, temporarily inhibited activities of superoxide dismutase in liver and duodenum after infection and enlarged the femoral head. Effects of MoO4 and MoS4 on activities of caeruloplasmin oxidase (CpO) in plasma, erythrocyte superoxide dismutase (ESOD) and tissue copper (Cu) and molybdenum (Mo) were compared to test the hypothesis that species lacking a rumen can thiolate MoO4. Three groups of 18 immature Wistar rats were given Mo (70 mg/L as MoO4) or MoS4 (5 mg/L) via drinking water or remained untreated; all received a commercial, cubed diet and 12 from each group were infected with larvae of N. brasiliensis. Rats were killed 7-9 days later and liver, kidney, spleen, heart, muscle (quadriceps), brain and bone (femur) removed for Cu and Mo analysis. Plasma Cu was greatly increased by MoO4 and MoS4, without changing CpO activity, but the effect was more variable with MoO4 and accompanied by a smaller decrease in ESOD. Tissue Cu and Mo were increased by MoS4 in all tissues examined except brain and bone, correlating with plasma Cu and with each other; relationships were strongest in spleen, followed by kidney. MoO4 also increased soft tissue Cu and Mo but increases were generally smaller than those induced by MoS4 and correlations between the two elements and with plasma Cu generally weaker. Since hypercupraemia and correlated increases in liver and kidney Cu and Mo are characteristic of systemic thiomolybdate (TM) exposure, we conclude that MoO4 was partially thiolated to give a different TM profile from that produced by MoS4. The pathophysiological significance of systemic exposure to di- and tri-TM merits investigation in non-ruminants as agents of chelation therapy and in ruminants as agents of short-lived TM toxicity on Mo-rich pastures.
Assuntos
Água Potável , Molibdênio , Animais , Ceruloplasmina/metabolismo , Cobre/metabolismo , Suplementos Nutricionais , Fígado/química , Molibdênio/análise , Molibdênio/metabolismo , Molibdênio/farmacologia , Nippostrongylus/metabolismo , Ratos , Ratos Wistar , Superóxido DismutaseRESUMO
Dissolved gases in the effluent of anaerobic reactors, specifically dissolved methane (D-CH4) and sulphide (S2-), are a drawback for anaerobic-based sewage treatment plants (STPs). This article studied the simultaneous desorption/removal of both gases from anaerobic effluents with hollow fibre membrane contactors (HFMCs), evaluating two types of membrane materials (e.g. microporous and dense) at different operating conditions (atmospheric air as sweeping gas or vacuum, and different gas/liquid flows and vacuum pressures). The transfer of other gases, such as O2 and CO2, was studied as well. Desorption/removal efficiencies up to 99% for D-CH4 and 100% for S2- were obtained, with the higher efficiencies reported for the dense HFMC and with air as sweeping gas. It was found that the removal mechanism for S2- was oxidation with O2 from the air. In addition, the use of air as sweeping gas allowed the obtention of a nearly O2 saturated effluent, with more elevated dissolved oxygen concentrations in the microporous HFMC. Finally, it was found that the higher mass-transfer resistance in the dense membrane was compensated by a better performance in the liquid phase (lower mass-transfer resistance) in this unit, which allowed better D-CH4 desorption efficiencies.
Assuntos
Metano , SulfetosRESUMO
Sulphur (S) dietary excess can limit productive performance and increase polioencephalomalacia (PEM) incidence in feedlot cattle (FC). Sulphur excess ingested is transformed to hydrogen sulphide (H2 S) by sulfo-reducing ruminal bacteria (SRB), being high ruminal H2 S concentration responsible for aforementioned damages. As the ruminal mechanisms involved in H2 S concentrations increase have not been elucidated, this study aimed to evaluate the ruminal environment, and the association between ruminal H2 S and dissimilatory SRB (DSRB) concentration in FC experimentally subjected to S dietary excess. Twelve crossbred steers were randomly assigned to one of two dietary S levels (6 animals per treatment): low (LS, 0.19% S) and high (HS, 0.39% S obtained by sodium sulfate inclusion at 0.86%). The study lasted 38 days, and on days 0, 22 and 38, ruminal gas samples were taken to quantify H2 S concentration, and ruminal fluid to determine total bacteria, DSRB, protozoa, volatile fatty acid and ammonia nitrogen concentration. For ruminal H2 S concentration, S dietary × sampling day interaction was significant (p < 0.001), so that the greater concentration was observed on days 22 and 38 with the HS diet. The remaining ruminal parameters were not affected by dietary S level, and no significant correlation between H2 S and DSRB concentrations was observed. The ruminal adaptation that maximizes H2 S production in FC consuming S excess does not seem to be associated with biological or biochemical alterations, nor DSRB concentration changes. The microbial diversity and ruminal environment were resilient to the S excess evaluated, suggesting that 0.39% of dietary S achieved by 0.86% sodium sulfate addition, could be used without disturbances on digestion nor health of FC.
Assuntos
Ração Animal , Rúmen , Ração Animal/análise , Animais , Bovinos , Dieta/veterinária , Digestão , Ácidos Graxos Voláteis/metabolismo , Fermentação , Rúmen/metabolismo , EnxofreRESUMO
Endothelial dysfunction is a hallmark of preeclampsia and the role of nitric oxide (NO) has been extensively studied in this pregnancy complication. In recent years, hydrogen sulphide (H2 S) has arisen as a new gasotransmitter with an impact on endothelial function. However, the involvement of H2 S in the pathophysiology of preeclampsia is not fully understood, and only a few studies with limited sample size have investigated circulating levels of H2 S in preeclamptic patients. Moreover, H2 S levels have not been previously evaluated in gestational hypertension. Furthermore, the relationship between H2 S and NO in these hypertensive disorders of pregnancy has yet to be determined. We measured H2 S levels in plasma of 120 healthy pregnant women, 88 gestational hypertensive and 62 preeclamptic women. We also measured plasma nitrite in a subset of patients and carried out correlation analysis between plasma H2 S and nitrite in these three groups. We found that plasma H2 S was elevated in preeclampsia and further increased in gestational hypertension compared to healthy pregnancy. Plasma nitrite was reduced in gestational hypertension and preeclampsia, and these levels were negatively correlated with H2 S in both gestational hypertension and preeclampsia, but not in healthy pregnancy. Our results indicate that increases in H2 S may represent a mechanism triggered as an attempt to compensate reduced NO in gestational hypertension and preeclampsia. Future studies are warranted to investigate the mechanisms underlying H2 S/NO interaction on mediating endothelial dysfunction in these hypertensive disorders of pregnancy.
Assuntos
NitritosRESUMO
Hydrogen sulphide (H2 S) is an endogenously produced gasotransmitter that has rapidly emerged as an active signalling component of several plant processes, stomatal movement regulation among them. The guard cells (GCs), pairs of cells that neighbour the stomatal pores, transduce endogenous and environmental signals, through signalling network, to control stomatal pore size. In this complex network, which has become a model system for plant signalling, few highly connected components form a core that links most of the pathways. The evidence summarized in this insight, on the interplay between H2 S and different key components of the GC networks, points towards H2 S as a regulator of the GC core signalling pathway.
Assuntos
Sulfeto de Hidrogênio , Ácido Abscísico , Estômatos de Plantas , Transdução de SinaisRESUMO
Nitric oxide (NO) negatively modulates the secretion of vasopressin (AVP), oxytocin (OT) and atrial natriuretic peptide (ANP) induced by the increase in extracellular osmolality, whereas carbon monoxide (CO) and hydrogen sulphide (H2 S) act to potentiate it; however, little information is available for the osmotic challenge model about whether and how such gaseous systems modulate each other. Therefore, using an acute ex vivo model of hypothalamic and neurohypophyseal explants (obtained from male 6/7-week-old Wistar rats) under conditions of extracellular iso- and hypertonicity, we determined the effects of NO (600 µmol L-1 sodium nitroprusside), CO (100 µmol L-1 tricarbonylchloro[glycinato]ruthenium [II]) and H2 S (10 mmol L-1 sodium sulphide) donors and nitric oxide synthase (NOS) (300 µmol L-1 Nω -methyl-l-arginine [LNMMA]), haeme oxygenase (HO) (200 µmol L-1 Zn(II) deuteroporphyrin IX 2,4-bis-ethylene glycol [ZnDPBG]) and cystathionine ß-synthase (CBS) (100 µmol L-1 aminooxyacetate [AOA]) inhibitors on the release of hypothalamic ANP and hypothalamic and neurohypophyseal AVP and OT, as well as on the activities of NOS, HO and CBS. LNMMA reversed hyperosmolality-induced NOS activity, and enhanced hormonal release by the hypothalamus and neurohypophysis, in addition to increasing CBS and hypothalamic HO activity. AOA decreased hypothalamic and neurohypophyseal CBS activity and hormonal release, whereas ZnDPBG inhibited HO activity and hypothalamic hormone release; however, in both cases, AOA did not modulate NOS and HO activity and ZnDPBG did not affect NOS and CBS activity. Thus, our data indicate that, although endogenous CO and H2 S positively modulate AVP, OT and ANP release, only NO plays a concomitant role of modulator of hormonal release and CBS activity in the hypothalamus and neurohypophysis and that of HO activity in the hypothalamus during an acute osmotic stimulus, which suggests that NO is a key gaseous controller of the neuroendocrine system.
Assuntos
Fator Natriurético Atrial/metabolismo , Monóxido de Carbono/metabolismo , Sulfeto de Hidrogênio/metabolismo , Hipotálamo Médio/metabolismo , Óxido Nítrico/metabolismo , Ocitocina/metabolismo , Vasopressinas/metabolismo , Animais , Cistationina beta-Sintase/metabolismo , Masculino , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo I/metabolismo , Ratos Wistar , Sulfurtransferases/metabolismoRESUMO
Dysregulation of hydrogen sulphide (H2 S) producing enzymes has been related to hypertensive pregnancy, and H2 S donor, sodium hydrosulphide (NaHS) exerts antihypertensive effects, modulates angiogenic factors production and acts as an antioxidant. Moreover, reduction in nitric oxide (NO) bioavailability is related to hypertensive pregnancy and H2 S may interact with NO, modulating its production. We aimed to investigate the NaHS effects in hypertension-in-pregnancy and also in feto-placental parameters. Female Wistar rats (200-250 g) were mated and desoxycorticosterone acetate injections followed by replacement of water by 0.9% saline solution were used to induce hypertensive pregnancy. Rats were divided into four groups: normal pregnant (Norm-Preg), pregnant + NaHS (Preg+NaHS), hypertensive pregnant (HTN-Preg) and HTN-Preg+NaHS. Systolic blood pressure was increased in HTN-Preg and this increase was blunted in HTN-Preg+NaHS. Fetal and placental weights were decreased in HTN-Preg animals, while fetal growth restriction was improved in HTN-Preg+NaHS. Placental weight was lower in HTN-Preg+NaHS than in HTN-Preg; however, placental efficiency was re-established in HTN-Preg+NaHS rats. We observed that a partial contribution of placental NO, but not changes in anti-angiogenic factors may mediate the increases in placental efficiency in HTN-Preg+NaHS. HTN-Preg presented thoracic aorta hyperreactivity to phenylephrine while NaHS treatment blunted this hyperreactivity, which seems not to be related to NO-mediated relaxation induced by acetylcholine. Therefore, changes in vascular responsiveness promoted by NaHS treatment may underlie the beneficial effects in systolic blood pressure and feto-placental parameters in our study.
Assuntos
Sulfeto de Hidrogênio/metabolismo , Hipertensão Induzida pela Gravidez/tratamento farmacológico , Óxido Nítrico/metabolismo , Placenta/efeitos dos fármacos , Sulfetos/farmacologia , Vasodilatação/efeitos dos fármacos , Animais , Anti-Hipertensivos/farmacologia , Anti-Hipertensivos/uso terapêutico , Aorta/efeitos dos fármacos , Aorta/fisiopatologia , Pressão Sanguínea/efeitos dos fármacos , Feminino , Peso Fetal/efeitos dos fármacos , Hipertensão Induzida pela Gravidez/metabolismo , Hipertensão Induzida pela Gravidez/fisiopatologia , Malondialdeído/metabolismo , Neovascularização Fisiológica/efeitos dos fármacos , Nitratos/metabolismo , Nitritos/metabolismo , Placenta/metabolismo , Gravidez , Ratos , Ratos Wistar , Sulfetos/uso terapêuticoRESUMO
Organisms adapted to physiochemical stressors provide ideal systems to study evolutionary mechanisms that drive adaptation and speciation. This review study focuses on livebearing fishes of the Poecilia mexicana species complex (Poeciliidae), members of which have repeatedly colonized hydrogen sulphide (H2 S)-rich springs. H2 S is a potent respiratory toxicant that creates extreme environmental conditions in aquatic ecosystems. There is also a rich history of research on H2 S in toxicology and biomedicine, which has facilitated the generation of a priori hypotheses about the proximate mechanisms of adaptation. Testing these hypotheses through the application of high-throughput genomic and transcriptomic analyses has led to the identification of the physiological underpinnings mediating adaptation to H2 S-rich environments. In addition, systematic natural history studies have provided a nuanced understanding of how the presence of a physiochemical stressor interacts with other sources of selection to drive evolutionary change in a variety of organismal traits, including physiology, morphology, behaviour and life history. Adaptation to extreme environments in P. mexicana also coincides with ecological speciation, and evolutionarily independent lineages span almost the full range of the speciation continuum from panmixia to complete reproductive isolation. Multiple mechanisms of reproductive isolation are involved in reducing gene flow between adjacent populations that are adapted to contrasting environmental conditions. Comparative studies among evolutionarily independent lineages within the P. mexicana species complex and, more recently, other members of the family Poeciliidae that have colonized H2 S-rich environments will provide insights into the factors facilitating or impeding convergent evolution, providing tangible links between micro-evolutionary processes and macro-evolutionary patterns.
Assuntos
Adaptação Fisiológica , Biodiversidade , Ambientes Extremos , Especiação Genética , Nascentes Naturais , Poecilia/genética , Poecilia/fisiologia , Sulfetos/química , Animais , México , FilogeniaRESUMO
The hydrogen sulphide (H2S) levels from wastewater treatment plants (WWTPs) in Curitiba, Brazil have been quantified for the first time. H2S generated by anaerobic decomposition of organic matter in WWTPs is a cause for concern because it is an air pollutant, which can cause eye and respiratory irritation, headaches, and nausea. Considering the requirement for WWTPs in all communities, it is necessary to assess the concentrations and effects of gases such as H2S on populations living and/or working near WWTPs. The primary objective of this study was to evaluate the indoor and outdoor concentration of H2S in the neighbourhood of two WWTPs located in Curitiba, as well as its human health impacts. Between August 2013 and March 2014 eight sampling campaigns were performed using passive samplers and the analyses were carried out by spectrophotometry, presenting mean concentrations ranging from 0.14 to 32µgm-3. Eleven points at WWTP-A reported H2S average concentrations above the WHO recommendation of 10µgm-3, and 15 points above the US EPA guideline of 2µgm-3. At WWTP-B the H2S concentration was above US EPA guideline at all the sampling points. The I/O ratio on the different sampling sites showed accumulation of indoor H2S in some instances and result in exacerbating the exposure of the residents. The highest H2S concentrations were recorded during the summer in houses located closest to the sewage treatment stations, and towards the main wind direction, showing the importance of these factors when planning a WWTP. Lifetime risk assessments of hydrogen sulphide exposure showed a significant non-carcinogenic adverse health risk for local residents and workers, especially those close to anaerobic WWTPs. The data indicated that WWTPs operated under these conditions should be recognized as a significant air pollution source, putting local populations at risk.