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1.
Food Chem ; 303: 125346, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31446364

RESUMO

The effect of a respiratory quotient dynamic controlled atmosphere (DCA - RQ), which induces ethanol production through low oxygen storage, and ethanol application on softening of Braeburn apples stored at different temperatures was investigated. DCA - RQ storage was associated with the activation of the alcohol dehydrogenase (ADH) and greater anaerobic metabolism in comparison with DCA - CF (chlorophyll fluorescence) and controlled atmosphere (CA) storage. Greater anaerobic metabolism resulted in lower ethylene production, ACC oxidase activity, membrane permeability, -galactosidase activity and, therefore, less softening after long-term storage. Ethanol application after CA storage decreased ethylene biosynthesis, respiration rate and membrane permeability. Storage at 3 °C resulted in the lowest soluble solids and acidity, but not softening. In conclusion, Braeburn apples could be stored at 3 °C under DCA - RQ1.5. Additionally, ethanol produced by the fruit, or applied externally, had a significant effect on inhibiting softening during and after storage.


Assuntos
Atmosfera , Etanol/farmacologia , Malus/efeitos dos fármacos , Malus/metabolismo , Oxigênio/metabolismo , Anaerobiose/efeitos dos fármacos , Frutas/efeitos dos fármacos , Frutas/metabolismo
2.
Phys Chem Chem Phys ; 21(41): 22902-22909, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31595895

RESUMO

Broken-symmetry density functional calculations have been used to calculate effective 55Mn hyperfine (A) tensors for a mixed-valence tetranuclear manganese complex, a model system for the S2 state of the oxygen-evolving complex of photosystem II. Recent investigations carried out in our laboratory showed that for calculations within the strong exchange limit, density functional calculations cannot reproduce the relative magnitude of the anisotropy of the hyperfine tensors of the MnIII center compared to the MnIV centers. In this work we therefore go beyond the strong exchange limit and investigate the effect of multiplet mixing, induced by zero-field splitting, on the effective hyperfine tensors through a perturbational treatment within the numerical spin projection procedure. Results show that the inclusion of zero-field splitting leads to a shift of the anisotropy from the MnIII ion towards the three MnIV ions, thus reconciling the calculated and experimentally observed anisotropy pattern. However, the final results are quite sensitive to the energy gap between the ground (doublet) and the first excited (quartet) state and therefore critically depend on the appropriate choice of the isotropic exchange coupling constants.


Assuntos
Anisotropia , Modelos Biológicos , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II , Manganês/química
3.
Medicine (Baltimore) ; 98(42): e17591, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31626131

RESUMO

BACKGROUND: Spinal cord ischemia-reperfusion injury (SCII) is a common complication of spinal surgery as well as thoracic and abdominal surgery. Acute cytotoxic edema is the key pathogenic alteration. Therefore, avoiding or decreasing cellular edema has become the major target for SCII treatment. METHODS: The antiedema activity of ginsenoside Rb1 on aquaporin (AQP) 4, nerve growth factor (NGF), and brain-derived neurotrophic factor expression was detected by western blot and real-time polymerase chain reaction under conditions of oxygen-glucose deprivation/reoxygenation (OGD/R) in a rat astrocyte model in vitro. In addition, the cellular membrane permeability of AQP4 overexpressing cells or AQP4 small interfering RNA-transfected cells was detected. RESULTS: Ginsenoside Rb1 significantly prevented OGD/R-induced AQP4 downregulation in rat astrocytes. In addition, ginsenoside Rb1 treatment or AQP4 overexpression in rat astrocytes significantly attenuated the OGD/R-induced increase of cellular membrane permeability. Moreover, ginsenoside Rb1 obviously prevented the OGD/R-induced decrease of NGF and BDNT expression in rat astrocytes. CONCLUSION: These findings demonstrate that ginsenoside Rb1 can relieve spinal cord edema and improve neurological function by increasing AQP4 expression.


Assuntos
Aquaporina 4/genética , Astrócitos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Ginsenosídeos/farmacologia , Glucose/metabolismo , Oxigênio/metabolismo , Traumatismo por Reperfusão/genética , Animais , Animais Recém-Nascidos , Aquaporina 4/biossíntese , Astrócitos/efeitos dos fármacos , Astrócitos/patologia , Western Blotting , Células Cultivadas , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , RNA/genética , Ratos , Ratos Sprague-Dawley , Traumatismo por Reperfusão/tratamento farmacológico , Traumatismo por Reperfusão/patologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Medula Espinal/metabolismo , Medula Espinal/patologia
5.
J Agric Food Chem ; 67(39): 10823-10831, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31487159

RESUMO

The development of technology to improve the mineralization of organic fertilizer and to enhance crop production is essential to achieve the transition from traditional farming to eco-friendly organic farming. Nanobubble oxygation (NB) was employed for comparison with traditional pump-aerated oxygation (AW) and a control group through both soil incubation and soil column experiments. Plant-available N and P contents in the NB treatment group were higher than those in the AW and control groups. Enzymatic activities including ß-1,4-N-acetyl-glucosaminidase, phosphatase, α-1,4-glucosidase, ß-1,4-xylosidase, peroxidase, and phenol oxidase were significantly higher in both oxygation groups compared with the control. The soil microbial biomass, activity, and diversity were also significantly improved due to the oxygation treatment. Additionally, the microbial metabolic functions were shifted in both oxygation treatments compared with the control group. The final tomato yield increase from the NB treatment group was 23%, and that from the AW treatment was 17%, compared with the control.


Assuntos
Lycopersicon esculentum/crescimento & desenvolvimento , Lycopersicon esculentum/metabolismo , Nanotecnologia/métodos , Oxigênio/metabolismo , Produção Agrícola , Lycopersicon esculentum/enzimologia , Oxigênio/química , Proteínas de Plantas/metabolismo , Solo/química , Microbiologia do Solo
6.
BMC Bioinformatics ; 20(1): 442, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31455206

RESUMO

BACKGROUND: Contemporary biological observations have revealed a large variety of mechanisms acting during the expansion of a tumor. However, there are still many qualitative and quantitative aspects of the phenomenon that remain largely unknown. In this context, mathematical and computational modeling appears as an invaluable tool providing the means for conducting in silico experiments, which are cheaper and less tedious than real laboratory experiments. RESULTS: This paper aims at developing an extensible and computationally efficient framework for in silico modeling of tumor growth in a 3-dimensional, inhomogeneous and time-varying chemical environment. The resulting model consists of a set of mathematically derived and algorithmically defined operators, each one addressing the effects of a particular biological mechanism on the state of the system. These operators may be extended or re-adjusted, in case a different set of starting assumptions or a different simulation scenario needs to be considered. CONCLUSION: In silico modeling provides an alternative means for testing hypotheses and simulating scenarios for which exact biological knowledge remains elusive. However, finer tuning of pertinent methods presupposes qualitative and quantitative enrichment of available biological evidence. Validation in a strict sense would further require comprehensive, case-specific simulations and detailed comparisons with biomedical observations.


Assuntos
Modelos Biológicos , Modelos Teóricos , Neoplasias/patologia , Algoritmos , Proliferação de Células , Simulação por Computador , Difusão , Glucose/metabolismo , Glicólise , Humanos , Necrose , Neoplasias/irrigação sanguínea , Neovascularização Patológica/patologia , Oxigênio/metabolismo , Fatores de Tempo , Remodelação Vascular
7.
An Acad Bras Cienc ; 91(3): e20180395, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31432900

RESUMO

The aquatic environment presents daily and/or seasonal variations in dissolved oxygen (DO) levels. Piava faces different DO levels in the water due to its distributional characteristics. The goal of this study was to describe the effects of low DO levels on plasma ion, biochemical and oxidative variables in piava juveniles. Fish were exposed to different DO levels, including 1.0, 2.0, 3.0, 4.0 and 5.0 mg L-1 of DO for 96 h, after which blood and tissue samples (liver, kidney, gill and muscle) were collected. The decrease in DO levels decreased plasma Na+, Cl-, K+ and NH3 levels as well as protein and glycogen levels in the liver, kidney and muscle; increased Na+/K+-ATPase activity in the gills and kidney as well as glucose and ammonia levels in the liver, kidney and muscle; and increased lactate levels in the kidney and muscle. Thiobarbituric acid-reacting substances, catalase and non-protein thiol levels decreased in the tissues of piavas exposed to low DO levels. It is concluded that piava can apparently cope with hypoxic conditions; however, low DO levels are a stressor, and the tolerance of piava to hypoxia involves iono-regulatory, metabolic and oxidative adjustments.


Assuntos
Adaptação Fisiológica/fisiologia , Caraciformes/fisiologia , Estresse Oxidativo/fisiologia , Oxigênio/fisiologia , Animais , Catalase/metabolismo , Caraciformes/metabolismo , Ácido Láctico/metabolismo , Oxigênio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Superóxido Dismutase/metabolismo
8.
Chem Commun (Camb) ; 55(72): 10792-10795, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31432816

RESUMO

Hypoxia, as an important feature in tumor sites, greatly hinders the performance of photosensitizers, thus affecting the efficacy of photodynamic therapy (PDT). Therefore, designing and preparing new photosensitizer with high photosensitivity under hypoxic condition presents a great challenge that urgently needs to be solved. In this work, a new nano-MOF material using Mn(ii) as the active center can catalytically decompose high concentrations of H2O2 in tumor cells to generate O2, thereby improving the PDT efficacy in hypoxic tumors. The Mn-MOF also produces 1O2 under light irradiation, which finally induces cancer cell apoptosis. This work offers a new strategy for the design and discovery of effective photosensitizers for PDT.


Assuntos
Neoplasias da Mama/tratamento farmacológico , Manganês/farmacologia , Estruturas Metalorgânicas/farmacologia , Fotoquimioterapia , Fármacos Fotossensibilizantes/farmacologia , Hipóxia Tumoral/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Feminino , Peróxido de Hidrogênio/metabolismo , Manganês/química , Estruturas Metalorgânicas/química , Camundongos , Oxigênio/metabolismo , Tamanho da Partícula , Fármacos Fotossensibilizantes/química , Propriedades de Superfície
9.
Bioresour Technol ; 291: 121867, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376671

RESUMO

Nitrous oxide (N2O) is a strong greenhouse gas that is produced in significant quantities through biological nitrogen removal processes in wastewater treatment plants; however, N2O generation within the internal micro-environment of activated sludge flocs (ASFs) is poorly understood. In this study, microelectrodes and molecular techniques were employed to investigate the concentrations of N2O and other chemicals and the composition and distribution of microbes within ASFs, respectively. The results showed that N2O generation was correlated with the ASF micro-environment, and was significantly influenced by the dissolved oxygen (DO) concentration of the bulk wastewater. Equal N2O, DO, NH4+-N, and NO3--N concentrations were found in small flocs (<100 µm). By contrast, higher N2O generation rates and lower DO, NH4+-N, and NO3--N concentrations were detected in the center of large flocs (>200 µm) compared with those at their surfaces. Microbial structures of varying particle sizes were distinct and depended on the micro-environmental characteristics.


Assuntos
Óxido Nitroso/metabolismo , Oxigênio/metabolismo , Esgotos , Nitrogênio/metabolismo , Tamanho da Partícula , Esgotos/química
10.
Int J Nanomedicine ; 14: 5449-5475, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31409998

RESUMO

Purpose: We created and evaluated an enhanced topical delivery system featuring a combination of highly skin-permeable growth factors (GFs), quercetin (QCN), and oxygen; these synergistically accelerated re-epithelialization and granulation tissue formation of/in diabetic wounds by increasing the levels of GFs and antioxidants, and the oxygen partial pressure, at the wound site. Methods: To enhance the therapeutic effects of exogenous administration of GFs for the treatment of diabetic wounds, we prepared highly skin-permeable GF complexes comprised of epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), platelet-derived growth factor-A (PDGF-A), and basic fibroblast growth factor (bFGF), genetically attached, via the N-termini, to a low-molecular-weight protamine (LMWP) to form LMWP-EGF, LMWP-IGF-I, LMWP-PDGF-A, and LMWP-bFGF, respectively. Furthermore, quercetin (QCN)- and oxygen-carrying 1-bromoperfluorooctane (PFOB)-loaded nanoemulsions (QCN-NE and OXY-PFOB-NE) were developed to improve the topical delivery of QCN and oxygen, respectively. After confirming the enhanced penetration of LMWP-GFs, QCN-NE, and oxygen delivered from OXY-PFOB-NE across human epidermis, we evaluated the effects of combining LMWP-GFs, QCN-NE, and OXY-PFOB-NE on proliferation of keratinocytes and fibroblasts, and the chronic wound closure rate of a diabetic mouse model. Results: The optimal ratios of LMWP-EGF, LMWP-IGF-I, LMWP-PDGF-A, LMWP-bFGF, QCN-NE, and OXY-PFOB-NE were 1, 1, 0.02, 0.02, 0.2, and 60, respectively. Moreover, a Carbopol hydrogel containing LMWP-GFs, QCN-NE, and OXY-PFOB-NE (LMWP-GFs/QCN-NE/OXY-PFOB-NE-GEL) significantly improved scratch-wound recovery of keratinocytes and fibroblasts in vitro compared to that afforded by hydrogels containing each component alone. LMWP-GFs/QCN-NE/OXY-PFOB-NE-GEL significantly accelerated wound-healing in a diabetic mouse model, decreasing wound size by 54 and 35% compared to the vehicle and LMWP-GFs, respectively. Conclusion: LMWP-GFs/QCN-NE/OXY-PFOB-NE-GEL synergistically accelerated the healing of chronic wounds, exerting both rapid and prolonged effects.


Assuntos
Diabetes Mellitus/patologia , Hidrogéis/química , Fator de Crescimento Insulin-Like I/farmacologia , Peptídeos e Proteínas de Sinalização Intercelular/farmacologia , Oxigênio/metabolismo , Quercetina/farmacologia , Absorção Cutânea , Cicatrização/efeitos dos fármacos , Animais , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Colágeno/biossíntese , Modelos Animais de Doenças , Emulsões/química , Fator de Crescimento Epidérmico/farmacologia , Epiderme/efeitos dos fármacos , Fator 2 de Crescimento de Fibroblastos/farmacologia , Humanos , Queratinócitos/citologia , Queratinócitos/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Peso Molecular , Nanopartículas/química , Nanopartículas/ultraestrutura , Octanos/química , Fator de Crescimento Derivado de Plaquetas/farmacologia , Protaminas/química , Absorção Cutânea/efeitos dos fármacos
11.
Inorg Chem ; 58(15): 9557-9561, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31313577

RESUMO

An iron(III) methoxide complex reacts with para-substituted triarylmethyl radicals to give iron(II) and methoxyether products. Second-order rate constants for the radical derivatives were obtained. Hammett and Marcus plots suggest the radical transfer reactions proceed via a concerted process. Calculations support the concerted nature of these reactions involving a single transition state with no initial charge transfer. These findings have implications for the radical "rebound" step invoked in nonheme iron oxygenases, halogenases, and related synthetic catalysts.


Assuntos
Compostos Férricos/metabolismo , Compostos Ferrosos/metabolismo , Oxirredutases/metabolismo , Oxigênio/metabolismo , Oxigenases/metabolismo , Biocatálise , Compostos Férricos/química , Compostos Ferrosos/química , Estrutura Molecular , Oxirredutases/química , Oxigênio/química , Oxigenases/química
12.
Bioresour Technol ; 289: 121754, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323714

RESUMO

Acetonitrile (ACN) is a very volatile, toxic and nitrogen-rich organic compound. To enhance ACN wastewater treatment, a novel hybrid membrane-aerated bioreactor (MAB) containing aerated and non-aerated zones was established. A polypropylene hollow fiber membrane module (HF) and a silicone rubber membrane module (SR) were separately used as the bubble-free aeration diffuser and the biofilm carrier, and the non-aerated zones of these two types of reactors were packed with ceramsite. When the influent ACN loading was 1.200 kg/m3·d, under aeration pressures of 20 kPa in the HF-MAB and 40 kPa in the SR-MAB, ACN removal loadings of 1.116 kg/m3·d and 1.004 kg/m3·d, respectively, were achieved, and the TN (total nitrogen) removal loadings were 0.267 kg/m3·d and 0.246 kg/m3·d, respectively. In the MABs, different stratified biofilm structures of the two zones and the diffusion and counter-diffusion of oxygen synergistically promoted ACN degradation, nitrification and denitrification.


Assuntos
Reatores Biológicos , Águas Residuárias/química , Acetonitrilos/metabolismo , Biofilmes , Análise da Demanda Biológica de Oxigênio , Desnitrificação , Nitrificação , Nitrogênio/química , Oxigênio/metabolismo , Eliminação de Resíduos Líquidos
13.
Bioresour Technol ; 289: 121742, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31323725

RESUMO

A novel partial nitritation-anammox (PNA) reactor configuration was piloted for 250 days. Primary effluent from full-scale municipal wastewater treatment plant was treated in a two-stage biofilm system incorporating innovative process control for cold partial nitritation. Partial nitritation was combined with carbon removal in a moving bed biofilm reactor (MBBR) to achieve high-rate treatment and nitritation was obtained with dissolved oxygen to total ammonium nitrogen (DO/TAN) ratio control and free ammonia (FA) for inhibition of nitratation. Effluent from MBBR was directed to an integrated fixed-film activated sludge (IFAS) reactor where nitrogen was removed via anammox. MBBR achieved partial nitritation at 2.0 ±â€¯0.3 g-N m-2 d-1 and nitrogen removal in the IFAS reactor reached 0.45 ±â€¯0.1 g-N m-2 d-1 (55 g-N m-3 d-1). The process performed well at 19 ±â€¯3 °C with an average effluent total inorganic nitrogen (TIN) concentration of 11 ±â€¯4 mg L-1.


Assuntos
Biofilmes , Nitrogênio/metabolismo , Esgotos , Águas Residuárias/química , Amônia/metabolismo , Compostos de Amônio/metabolismo , Reatores Biológicos , Desnitrificação , Oxirredução , Oxigênio/metabolismo , Projetos Piloto
14.
Rev Bras Enferm ; 72(3): 592-599, 2019 Jun 27.
Artigo em Inglês, Português | MEDLINE | ID: mdl-31269121

RESUMO

OBJECTIVE: to describe the influence of oxygen in retinopathy of prematurity (ROP) in premature newborns (PTNB) hospitalized in neonatal units of intensive care and undergoing ophthalmological follow-up procedures after hospital discharge. METHOD: retrospective cohort study, from January 2014 to June 2016, whose data collection totaled 181 charts. Descriptive and inferential statistical analysis. RESULTS: when using oxygen (O2) in 148 PTNB (81.7%), both mask (n=141; 77.9%; p-value <0.001) and the tracheal tube predominated (n=100; 55.25; p-value <0.001) for 15 days in average. The time of use and O2 concentration of the tracheal tube (p-value <0.001), the time of mask use (p-value <0.001) and the time and concentration of O2 of the continuous positive airway pressure (CPAP) (p-value <0.001) were significant to cause ROP in 50 PTNB (11.31%). CONCLUSION: the oxygen therapy has influenced the development and severity of ROP, indicating the need to adopt protocols for its use.


Assuntos
Recém-Nascido Prematuro/fisiologia , Oxigênio/metabolismo , Retinopatia da Prematuridade/etiologia , Brasil , Estudos de Coortes , Idade Gestacional , Humanos , Recém-Nascido Prematuro/crescimento & desenvolvimento , Oxigênio/efeitos adversos , Retinopatia da Prematuridade/fisiopatologia , Estudos Retrospectivos
15.
Adv Exp Med Biol ; 1143: 129-145, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31338818

RESUMO

The relationship of the homing of normal hematopoietic stem cells (HSC) in the bone marrow to specific environmental conditions, referred to as the stem cell niche (SCN), has been intensively studied over the last three decades. These conditions include the action of a number of molecular and cellular players, as well as critical levels of nutrients, oxygen and glucose in particular, involved in energy production. These factors are likely to act also in leukemias, due to the strict analogy between the hierarchical structure of normal hematopoietic cell populations and that of leukemia cell populations. This led to propose that leukemic growth is fostered by cells endowed with stem cell properties, the leukemia stem cells (LSC), a concept readily extended to comprise the cancer stem cells (CSC) of solid tumors. Two alternative routes have been proposed for CSC generation, that is, the oncogenic staminalization (acquisition of self-renewal) of a normal progenitor cell (the "CSC in normal progenitor cell" model) and the oncogenic transformation of a normal (self-renewing) stem cell (the "CSC in normal stem cell" model). The latter mechanism, in the hematological context, makes LSC derive from HSC, suggesting that LSC share SCN homing with HSC. This chapter is focused on the availability of oxygen and glucose in the regulation of LSC maintenance within the SCN. In this respect, the most critical aspect in view of the outcome of therapy is the long-term maintenance of the LSC subset capable to sustain minimal residual disease and the related risk of relapse of disease.


Assuntos
Hipóxia Celular , Leucemia Mieloide Aguda , Leucemia , Células-Tronco Neoplásicas , Glucose/metabolismo , Células-Tronco Hematopoéticas , Humanos , Oxigênio/metabolismo , Nicho de Células-Tronco
16.
World J Microbiol Biotechnol ; 35(8): 116, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31332538

RESUMO

Exploration of renewable energy sources is an imperative task in order to replace fossil fuels and to diminish atmospheric pollution. Hydrogen is considered one of the most promising fuels for the future and implores further investigation to find eco-friendly ways toward viable production. Expansive processes like electrolysis and fossil fuels are currently being used to produce hydrogen. Biological hydrogen production (BHP) displays recyclable and economical traits, and is thus imperative for hydrogen economy. Three basic modes of BHP were investigated, including bio photolysis, photo fermentation and dark fermentation. Photosynthetic microorganisms could readily serve as powerhouses to successively produce this type of energy. Cyanobacteria, blue green algae (bio photolysis) and some purple non-sulfur bacteria (Photo fermentation) utilize solar energy and produce hydrogen during their metabolic processes. Ionic species, including hydrogen (H+) and electrons (e-) are combined into hydrogen gas (H2), with the use of special enzymes called hydrogenases in the case of bio photolysis, and nitrogenases catalyze the formation of hydrogen in the case of photo fermentation. Nevertheless, oxygen sensitivity of these enzymes is a drawback for bio photolysis and photo fermentation, whereas, the amount of hydrogen per unit substrate produced appears insufficient for dark fermentation. This review focuses on innovative advances in the bioprocess research, genetic engineering and bioprocess technologies such as microbial fuel cell technology, in developing bio hydrogen production.


Assuntos
Eletrólise , Hidrogênio/metabolismo , Fontes de Energia Bioelétrica , Reatores Biológicos/microbiologia , Cianobactérias/metabolismo , Fermentação , Hidrogenase/metabolismo , Oxigênio/metabolismo , Fotólise , Fotossíntese
17.
J Plant Physiol ; 239: 92-108, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31255944

RESUMO

Acclimation by plants to hypoxia and anoxia is of importance in various ecological systems, and especially for roots in waterlogged soil. We present evidence for acclimation by roots via 'anoxic' cores rather than being triggered by O2 sensors. The evidence for 'anoxic' cores comes from radial O2 profiles across maize roots and associated metabolic changes such as increases in the 'anaerobic enzymes' ADH and PDC in the 'anoxic' core, and inhibition of Cl- transport to the xylem. These cores are predicted to develop within 15-20 min after sudden transfer of a root to hypoxia, so that the cores are 'anoxically-shocked'. We suggest that 'anoxic' cores could emanate a signal(s), such as ACC the precursor of ethylene and/or propagation of a 'Ca2+ wave', to other tissue zones. There, the signalling would result in acclimation of the tissues to energy crisis metabolism. An O2 diffusion model for tissues with an 'anoxic' core, indicates that the phytoglobin-nitric oxide (Pgb-NO) cycle would only be engaged in a thin 'shell' (annulus) of tissue surrounding the 'anoxic' core, and so would only contribute small amounts of ATP on a whole organ basis (e.g. whole roots). A key feature within this annulus of tissue, where O2 is likely to be limiting, is that the ratio (ATP formed) / (O2 consumed) is 5-6, both when the NAD(P)H of glycolysis is converted to NAD(P)+ by the Pgb-NO cycle or by the TCA cycle linked to the electron transport chain. The main function of the Pgb-NO cycle may be the modulating of NO levels and O2 scavenging, thus preventing oxidative damage. We speculate that an 'anoxic' core in hypoxic plant organs may have a particularly high tolerance to anoxia because cells might receive a prolonged supply of carbohydrates and/or ATP from the regions still receiving sufficient O2 for oxidative phosphorylation. Severely hypoxic or 'anoxic' cores are well documented, but much research on responses of roots to hypoxia is still based on bulk tissue analyses. More research is needed on the interaction between 'anoxic' cores and tissues still receiving sufficient O2 for oxidative phosphorylation, both during a hypoxic exposure and during subsequent anoxia of the tissue/organ as a whole.


Assuntos
Aclimatação/fisiologia , Metabolismo Energético , Óxido Nítrico/metabolismo , Oxigênio/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Anaerobiose
18.
Plant Sci ; 286: 1-6, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31300135

RESUMO

The excessive and harmful light energy absorbed by the photosystem (PS) II of higher plants is dissipated as heat through a protective mechanism termed non-photochemical quenching (NPQ) of chlorophyll fluorescence. PsbS-knock-out (KO) mutants lack the trans-thylakoid proton gradient (ΔpH)-dependent part of NPQ. To elucidate the molecular mechanism of NPQ, we investigated its dependency on oxygen. The development of NPQ in wild-type (WT) rice under low-oxygen (LO) conditions was reduced to more than 50% of its original value. However, under high-oxygen (HO) conditions, the NPQ of both WT and PsbS-KO mutants recovered. Moreover, WT and PsbS-KO mutant leaves infiltrated with the ΔpH dissipating uncoupler nigericin showed increased NPQ values under HO conditions. The experiments using intact chloroplasts and protoplasts of Arabidopsis thaliana supported that the LO effects observed in rice leaves were not due to carbon dioxide deficiency. There was a noticeable 90% reduction in the half-time of P700 oxidation rate in LO-treated leaves compared with that of WT control leaves, but the HO treatment did not significantly change the half-time of P700 oxidation rate. Overall, the results obtained here indicate that the stroma of the PsbS-KO plants could be potentially under O2 deficiency. Because the functions of PsbS in rice leaves are likely to be similar to those in other higher plants, our findings offer novel insights into the role of oxygen in the development of NPQ.


Assuntos
Adaptação Fisiológica/efeitos da radiação , Arabidopsis/metabolismo , Oryza/metabolismo , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Arabidopsis/efeitos da radiação , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Oryza/efeitos da radiação , Complexo de Proteína do Fotossistema II/genética , Folhas de Planta/genética , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Protoplastos/metabolismo , Protoplastos/efeitos da radiação
19.
Food Microbiol ; 83: 113-121, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31202402

RESUMO

Co-cultivation of brewers' yeast (Saccharomyces cerevisiae) with Cyberlindnera fabianii makes it possible to steer aroma and alcohol levels by changing the inoculation ratio of the two yeasts. A dynamic model was developed based on mono-culture performance of brewers' yeast and C. fabianii in controlled bioreactors with aerated wort as medium, describing growth rate, carbohydrate utilization, ethanol production, maintenance, oxygen consumption and ergosterol biosynthesis/use for cell membrane synthesis (the last one only for brewers' yeast). The parameters were estimated by fitting models to experimental data of both mono-cultivations. To predict the fermentation outcome of brewers' yeast and C. fabianii in co-cultivation, the two models were combined and the same parameter settings were used. The co-cultivation model was experimentally validated for the inoculum ratios 1:10 and 1:100 brewers' yeast over C. fabianii. The use of predictive modelling supported the hypothesis that performance of brewers' yeast in co-cultivation is inhibited by oxygen depletion which is required for the biosynthesis of ergosterol. This dynamic modelling approach and the parameters involved may also be used to predict the performance of brewers' yeast in the co-cultivation with other yeast species and to give guidance to optimize the fermentation outcome.


Assuntos
Técnicas de Cocultura , Fermentação , Interações Microbianas , Saccharomyces cerevisiae/metabolismo , Saccharomycetales/metabolismo , Ergosterol/biossíntese , Etanol/metabolismo , Oxigênio/metabolismo
20.
Food Microbiol ; 83: 122-133, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31202403

RESUMO

Sequential fermentation of grape must inoculated with L. thermotolerans and then S. cerevisiae 24 h later (typical wine-making practice) was conducted with or without cell-cell contact between the two yeast species. We monitored cell viability of the two species throughout fermentation by flow cytometry. The cell viability of S. cerevisiae decreased under both conditions, but the decrease was greater if there was cell-cell contact. An investigation of the nature of the interactions showed competition between the two species for nitrogen compounds, oxygen, and must sterols. Volatile-compound analysis showed differences between sequential and pure fermentation and that cell-cell contact modifies yeast metabolism, as the volatile-compound profile was significantly different from that of sequential fermentation without cell-cell contact. We further confirmed that cell-cell contact modifies yeast metabolism by analyzing the exo-metabolome of all fermentations by FT-ICR-MS analysis. These analyses show specific metabolite production and quantitative metabolite changes associated with each fermentation condition. This study shows that cell-cell contact not only affects cell viability, as already reported, but markedly affects yeast metabolism.


Assuntos
Fermentação , Metaboloma , Interações Microbianas , Saccharomyces cerevisiae/metabolismo , Saccharomycetales/metabolismo , Técnicas de Cocultura , Etanol , Viabilidade Microbiana , Oxigênio/metabolismo , Vitis/microbiologia , Vinho/microbiologia
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