Oxygen Stress Research Articles

VvLBD39, a grape LBD transcription factor, regulates plant response to salt and drought stress

Grape (Vitis vinifera L.), as an important deciduous perennial fruit tree, constantly confronts various abiotic stresses such as salinity and drought. The lateral organ boundaries domain (LBD) proteins are a class of plant-specific transcription factors that play pivotal roles in regulating plant growth and responding to abiotic stress. However, the biological function of the LBD transcription factor in grape remains poorly understood. Here, we cloned and characterized the VvLBD39 gene from grape, which contained a highly conserved LBD domain and localized to the cell nucleus. qRT-PCR analyses showed that the expression of VvLBD39 was downregulated upon exposure to NaCl, polyethylene glycol 6000 (PEG6000) and abscisic acid (ABA) treatments, respectively. Overexpression of VvLBD39 in grape calli and Arabidopsis resulted in hypersensitivity to PEG6000 and NaCl stress. Moreover, VvLBD39-overexpressing transgenic tobacco exhibited decreased tolerance to drought and salt stress, as well as insensitivity to exogenous ABA. After drought and salt stress treatments, the chlorophyll content, root length and antioxidant enzyme activity of the transgenic tobacco were lower than those of the wild-type (WT). Conversely, malonic dialdehyde (MDA) content, electronic conductivity, hydrogen peroxide (H2O2) content and superoxide anion (O2-) productivity were markedly elevated in the transgenic tobacco compared to the WT. Further investigations found that VvLBD39 had a negative impact on stomatal closure, ABA biosynthesis and ABA signaling under drought and salt treatments. In addition, the expression of genes related to reactive oxygen species (ROS) scavenging and stress response were significantly downregulated in VvLBD39 transgenic tobacco. Taken together, these results indicated that VvLBD39 functions as a negative regulator of salt and drought tolerance, making it a promising target for drought and salt resistance breeding.

Clostridioides difficile superoxide reductase mitigates oxygen sensitivity.

Clostridioides difficile causes a serious diarrheal disease and is a common healthcare-associated bacterial pathogen. Although it has a major impact on human health, the mechanistic details of C. difficile intestinal colonization remain undefined. C. difficile is highly sensitive to oxygen and requires anaerobic conditions for in vitro growth. However, the mammalian gut is not devoid of oxygen, and C. difficile tolerates moderate oxidative stress in vivo. The C. difficile genome encodes several antioxidant proteins, including a predicted superoxide reductase (SOR) that is upregulated upon exposure to antimicrobial peptides. The goal of this study was to establish SOR enzymatic activity and assess its role in protecting C. difficile against oxygen exposure. Insertional inactivation of sor rendered C. difficile more sensitive to superoxide, indicating that SOR contributes to antioxidant defense. Heterologous C. difficile sor expression in Escherichia coli conferred protection against superoxide-dependent growth inhibition, and the corresponding cell lysates showed superoxide scavenging activity. Finally, a C. difficile SOR mutant exhibited global proteome changes under oxygen stress when compared to the parent strain. Collectively, our data establish the enzymatic activity of C. difficile SOR, confirm its role in protection against oxidative stress, and demonstrate SOR's broader impacts on the C. difficile vegetative cell proteome.IMPORTANCEClostridioides difficile is an important pathogen strongly associated with healthcare settings and capable of causing severe diarrheal disease. While considered a strict anaerobe in vitro, C. difficile has been shown to tolerate low levels of oxygen in the mammalian host. Among other well-characterized antioxidant proteins, the C. difficile genome encodes a predicted superoxide reductase (SOR), an understudied component of antioxidant defense in pathogens. The significance of the research reported herein is the characterization of SOR's enzymatic activity, including confirmation of its role in protecting C. difficile against oxidative stress. This furthers our understanding of C. difficile pathogenesis and presents a potential new avenue for targeted therapies.

The Thioredoxin Fold Protein (TFP2) from Extreme Acidophilic Leptospirillum sp. CF-1 Is a Chaperedoxin-like Protein That Prevents the Aggregation of Proteins under Oxidative Stress.

Extreme acidophilic bacteria like Leptospirillum sp. require an efficient enzyme system to counteract strong oxygen stress conditions in their natural habitat. The genome of Leptospirillum sp. CF-1 encodes the thioredoxin-fold protein TFP2, which exhibits a high structural similarity to the thioredoxin domain of E. coli CnoX. CnoX from Escherichia coli is a chaperedoxin that protects protein substrates from oxidative stress conditions using its holdase function and a subsequent transfer to foldase chaperones for refolding. Recombinantly produced and purified Leptospirillum sp. TFP2 possesses both thioredoxin and chaperone holdase activities in vitro. It can be reduced by thioredoxin reductase (TrxR). The tfp2 gene co-locates with genes for the chaperone foldase GroES/EL on the chromosome. The "tfp2 cluster" (ctpA-groES-groEL-hyp-tfp2-recN) was found between 1.9 and 8.8-fold transcriptionally up-regulated in response to 1 mM hydrogen peroxide (H2O2). Leptospirillum sp. tfp2 heterologously expressed in E. coli wild type and cnoX mutant strains lead to an increased tolerance of these E. coli strains to H2O2 and significantly reduced intracellular protein aggregates. Finally, a proteomic analysis of protein aggregates produced in E. coli upon exposition to oxidative stress with 4 mM H2O2, showed that Leptospirillum sp. tfp2 expression caused a significant decrease in the aggregation of 124 proteins belonging to fifteen different metabolic categories. These included several known substrates of DnaK and GroEL/ES. These findings demonstrate that Leptospirillum sp. TFP2 is a chaperedoxin-like protein, acting as a key player in the control of cellular proteostasis under highly oxidative conditions that prevail in extreme acidic environments.

Low oxygen environment effect on the tomato cell wall composition during the fruit ripening process

BackgroundOxygen concentration is a key characteristic of the fruit storage environment determining shelf life and fruit quality. The aim of the work was to identify cell wall components that are related to the response to low oxygen conditions in fruit and to determine the effects of such conditions on the ripening process. Tomato (Solanum lycopersicum) fruits at different stages of the ripening process were stored in an anoxic and hypoxic environment, at 0% and 5% oxygen concentrations, respectively. We used comprehensive and comparative methods: from microscopic immunolabelling and estimation of enzymatic activities to detailed molecular approaches. Changes in the composition of extensin, arabinogalactan proteins, rhamnogalacturonan-I, low methyl-esterified homogalacturonan, and high methyl-esterified homogalacturonan were analysed.ResultsIn-depth molecular analyses showed that low oxygen stress affected the cell wall composition, i.e. changes in protein content, a significantly modified in situ distribution of low methyl-esterified homogalacturonan, appearance of callose deposits, disturbed native activities of β-1,3-glucanase, endo-β-1,4-glucanase, and guaiacol peroxidase (GPX), and disruptions in molecular parameters of single cell wall components. Taken together, the data obtained indicate that less significant changes were observed in fruit in the breaker stage than in the case of the red ripe stage. The first symptoms of changes were noted after 24 h, but only after 72 h, more crucial deviations were visible. The 5% oxygen concentration slows down the ripening process and 0% oxygen accelerates the changes taking place during ripening.ConclusionsThe observed molecular reset occurring in tomato cell walls in hypoxic and anoxic conditions seems to be a result of regulatory and protective mechanisms modulating ripening processes.

Dual Gallium Drug Treatment Against Carbapenem‐Resistant Klebsiella Pneumoniae: Efficacy and Potential Mechanism(s) of Action and Resistance

AbstractKlebsiella pneumoniae (KLP) is a Gram‐negative pathogen that can be highly antibiotic‐resistant. Our group has worked with gallium‐based compounds as a means of treating bacterial infections. Here the possible mechanism is investigated for dual therapy comprised of gallium nitrate (Ga(NO3)3) and gallium protoporphyrin (GaPP) on KLP. It is found that in vitro the combination of Ga(NO3)3 and GaPP is synergistic against KLP. The in vivo efficacy is of the dual therapy is additionally tested by treating pulmonary KLP infections in mice. Much greater effectiveness are observed in bacterial clearance and survival of mice receiving the dual therapy than that of singly treated or untreated mice. It is found that in in vitro the dual therapy increased reactive oxygen stress in treated bacteria. Combination therapy impacted KLP catalase, but not superoxide dismutase (SOD) activity. Finally, alterations in KLP genes encoding 6‐phosphogluconate phosphatase or cytochrome C assembly protein are found to be associated with increased resistance to combination gallium therapy, raising the MIC to both Ga(NO3)3 and GaPP by 4‐fold. These cumulative data lend validation to the potential for the use of Ga(NO3)3 and GaPP combination therapy against KLP and suggest that increased oxidative stress is involved in the mechanism of action.

Combined analysis of the effects of hypoxia and oxidative stress on DNA methylation and the transcriptome in HTR-8/SVneo trophoblast cells.

The alterations in DNA methylation and transcriptome in trophoblast cells under conditions of low oxygen and oxidative stress have major implications for pregnancy-related disorders. However, the exact mechanism is still not fully understood. In this study, we established models of hypoxia (H group) and oxidative stress (HR group) using HTR-8/SVneo trophoblast cells and performed combined analysis of genome-wide DNA methylation changes using reduced representation bisulphite sequencing and transcriptome expression changes using RNA sequencing. Our findings revealed that the H group exhibited a higher number of differentially methylated genes and differentially expressed genes than the HR group. In the H group, only 0.90% of all differentially expressed genes displayed simultaneous changes in DNA methylation and transcriptome expression. After the threshold was expanded, this number increased to 6.29% in the HR group. Notably, both the H group and HR group exhibited concurrent alterations in DNA methylation and transcriptome expression within Axon guidance and MAPK signalling pathway. Among the top 25 differentially methylated KEGG pathways in the promoter region, 11 pathways were commonly enriched in H group and HR group, accounting for 44.00%. Among the top 25 KEGG pathways in transcriptome with significant differences between the H group and HR group, 10 pathways were consistent, accounting for 40.00%. By integrating our previous data on DNA methylation from preeclamptic placental tissues, we identified that the ANKRD37 and PFKFB3 genes may contribute to the pathogenesis of preeclampsia through DNA methylation-mediated transcriptome expression under hypoxic conditions.

Repeated low oxygen stress on dynamic controlled atmosphere storage of ‘Elstar’ and ‘Nicoter’ apples

Repeated low oxygen stress on dynamic controlled atmosphere storage of ‘Elstar’ and ‘Nicoter’ apples

The impact of HBx protein on mitochondrial dynamics and associated signaling pathways strongly depends on the hepatitis B virus genotype.

Chronic hepatitis B virus (HBV) infections are strongly associated with liver cirrhosis, inflammation, and hepatocellular carcinoma. In this context, the viral HBx protein is considered as a major factor influencing HBV-associated pathogenesis through deregulation of multiple cellular signaling pathways and is therefore a potential target for prognostic and therapeutic applications. However, HBV-associated pathogenesis differs significantly between genotypes, with the relevant factors and in particular the contribution of the genetic diversity of HBx being largely unknown. To address this question, we studied the specific genotype-dependent impact of HBx on cellular signaling pathways, focusing in particular on morphological and functional parameters of mitochondria. To exclusively investigate the impact of HBx of different genotypes on integrity and function of mitochondria in the absence of additional viral factors, we overexpressed HBx in Huh7 or HepG2 cells. Key signaling pathways were profiled by kinome analysis and correlated with expression levels of mitochondrial and pathogenic markers. Conclusively, HBx of genotypes A and G caused strong disruption of mitochondrial morphology alongside an induction of PTEN-induced putative kinase 1/Parkin-mediated mitophagy. These effects were only moderately dysregulated by genotypes B and E, whereas genotypes C and D exhibit an intermediate effect in this regard. Accordingly, changes in mitochondrial membrane potential and elevated reactive oxygen species production were associated with the HBx-mediated dysfunction among different genotypes. Also, genotype-related differences in mitophagy induction were identified and indicated that HBx-mediated changes in the mitochondria morphology and function strongly depend on the genotype. This indicates a relevant role of HBx in the process of genotype-dependent liver pathogenesis of HBV infections and reveals underlying mechanisms.IMPORTANCEThe hepatitis B virus is the main cause of chronic liver disease worldwide and differs in terms of pathogenesis and clinical outcome among the different genotypes. Furthermore, the viral HBx protein is a known factor in the progression of liver injury by inducing aberrant mitochondrial structures and functions. Consequently, the selective removal of dysfunctional mitochondria is essential to maintain overall cellular homeostasis and cell survival. Consistent with the intergenotypic difference of HBV, our data reveal significant differences regarding the impact of HBx of different genotypes on mitochondrial dynamic and function and thereby on radical oxygen stress levels within the cell. We subsequently observed that the induction of mitophagy differs significantly across the heterogenetic HBx proteins. Therefore, this study provides evidence that HBx-mediated changes in the mitochondria dynamics and functionality strongly depend on the genotype of HBx. This highlights an important contribution of HBx in the process of genotype-dependent liver pathogenesis.

IC100, a humanized therapeutic monoclonal anti-ASC antibody alleviates oxygen-induced retinopathy in mice

BackgroundRetinopathy of prematurity (ROP), which often presents with bronchopulmonary dysplasia (BPD), is among the most common morbidities affecting extremely premature infants and is a leading cause of severe vision impairment in children worldwide. Activations of the inflammasome cascade and microglia have been implicated in playing a role in the development of both ROP and BPD. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is pivotal in inflammasome assembly. Utilizing mouse models of both oxygen-induced retinopathy (OIR) and BPD, this study was designed to test the hypothesis that hyperoxia induces ASC speck formation, which leads to microglial activation and retinopathy, and that inhibition of ASC speck formation by a humanized monoclonal antibody, IC100, directed against ASC, will ameliorate microglial activation and abnormal retinal vascular formation.MethodsWe first tested ASC speck formation in the retina of ASC-citrine reporter mice expressing ASC fusion protein with a C-terminal citrine (fluorescent GFP isoform) using a BPD model that causes both lung and eye injury by exposing newborn mice to room air (RA) or 85% O2 from postnatal day (P) 1 to P14. The retinas were dissected on P14 and retinal flat mounts were used to detect vascular endothelium with AF-594-conjugated isolectin B4 (IB4) and citrine-tagged ASC specks. To assess the effects of IC100 on an OIR model, newborn ASC citrine reporter mice and wildtype mice (C57BL/6 J) were exposed to RA from P1 to P6, then 75% O2 from P7 to P11, and then to RA from P12 to P18. At P12 mice were randomized to the following groups: RA with placebo PBS (RA-PBS), O2 with PBS (O2-PBS), O2 + IC100 intravitreal injection (O2-IC100-IVT), and O2 + IC100 intraperitoneal injection (O2-IC100-IP). Retinal vascularization was evaluated by flat mount staining with IB4. Microglial activation was detected by immunofluorescence staining for allograft inflammatory factor 1 (AIF-1) and CD206. Retinal structure was analyzed on H&E-stained sections, and function was analyzed by pattern electroretinography (PERG). RNA-sequencing (RNA-seq) of the retinas was performed to determine the transcriptional effects of IC100 treatment in OIR.ResultsASC specks were significantly increased in the retinas by hyperoxia exposure and colocalized with the abnormal vasculature in both BPD and OIR models, and this was associated with increased microglial activation. Treatment with IC100-IVT or IC100-IP significantly reduced vaso-obliteration and intravitreal neovascularization. IC100-IVT treatment also reduced retinal microglial activation, restored retinal structure, and improved retinal function. RNA-seq showed that IC100 treatment corrected the induction of genes associated with angiogenesis, leukocyte migration, and VEGF signaling caused by O2. IC100 also corrected the suppression of genes associated with cell junction assembly, neuron projection, and neuron recognition caused by O2.ConclusionThese data demonstrate the crucial role of ASC in the pathogenesis of OIR and the efficacy of a humanized therapeutic anti-ASC antibody in treating OIR mice. Thus, this anti-ASC antibody may potentially be considered in diseases associated with oxygen stresses and retinopathy, such as ROP.

Transcriptomic atlas for hypoxia and following re-oxygenation in Ancherythroculter nigrocauda heart and brain tissues: insights into gene expression, alternative splicing, and signaling pathways.

Hypoxia is a mounting problem that affects the world's freshwaters, with severe consequence for many species, including death and large economical loss. The hypoxia problem has increased recently due to the combined effects of water eutrophication and global warming. In this study, we investigated the transcriptome atlas for the bony fish Ancherythroculter nigrocauda under hypoxia for 1.5, 3, and 4.5h and its recovery to normal oxygen levels in heart and brain tissues. We sequenced 21 samples for brain and heart tissues (a total of 42 samples) plus three control samples and obtained an average of 32.40 million raw reads per sample, and 95.24% mapping rate of the filtered clean reads. This robust transcriptome dataset facilitated the discovery of 52,428 new transcripts and 6,609 novel genes. In the heart tissue, the KEGG enrichment analysis showed that genes linked to the Vascular smooth muscle contraction and MAPK and VEGF signaling pathways were notably altered under hypoxia. Re-oxygenation introduced changes in genes associated with abiotic stimulus response and stress regulation. In the heart tissue, weighted gene co-expression network analysis pinpointed a module enriched in insulin receptor pathways that was correlated with hypoxia. Conversely, in the brain tissue, the response to hypoxia was characterized by alterations in the PPAR signaling pathway, and re-oxygenation influenced the mTOR and FoxO signaling pathways. Alternative splicing analysis identified an average of 27,226 and 28,290 events in the heart and brain tissues, respectively, with differential events between control and hypoxia-stressed groups. This study offers a holistic view of transcriptomic adaptations in A. nigrocauda heart and brain tissues under oxygen stress and emphasizes the role of gene expression and alternative splicing in the response mechanisms.

Novel transcriptional regulator OxtR1 regulates potential ferrodoxin in response to oxygen stress in Treponema denticola

ObjectiveTreponema denticola has been strongly implicated in the pathogenesis of chronic periodontitis. Previously, we reported that the potential transcriptional regulator TDE_0259 (oxtR1) is upregulated in the bacteriocin ABC transporter gene-deficient mutant. OxtR1 may regulate genes to adapt to environmental conditions during colonization; however, the exact role of the gene in T. denticola has not been reported. Therefore, we investigated its function using an oxtR1-deficient mutant. MethodsThe growth rates of the wild-type and oxtR1 mutant were monitored under anaerobic conditions; their antibacterial agent susceptibility and gene expression were assessed using a liquid dilution assay and DNA microarray, respectively. An electrophoretic mobility shift assay was performed to investigate the binding of OxtR1 to promoter regions. ResultsThe growth rate of the bacterium was accelerated by the inactivation of oxtR1, and the mutant exhibited an increased minimum inhibitory concentration against ofloxacin. We observed a relative increase in the expression of genes associated with potential ferrodoxin (TDE_0260), flavodoxin, ABC transporters, heat-shock proteins, DNA helicase, iron compounds, and lipoproteins in the mutant. OxtR1 expression increased upon oxygen exposure, and oxtR1 complementation suppressed the expression of potential ferrodoxin. Our findings also suggested that OxtR1 binds to a potential promoter region of the TDE_0259–260 operon. Moreover, the mutant showed a marginal yet significantly faster growth rate than the wild-type strain under H2O2 exposure. ConclusionThe oxygen-sensing regulator OxtR1 plays a role in regulating the expression of a potential ferrodoxin, which may contribute to the response of T. denticola to oxygen-induced stress.

The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics

BackgroundThe presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1).ResultsThe study examined the effects of nitrogen (NH4+ and NO3−) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3−). Specifically, the highest levels of oxygen significantly increased root growth in NO3−-fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3− exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3−-fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3−-grown plants. Interestingly, the NO3−-fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1.ConclusionThis study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3− –supplied culture media or nutrient solutions, respectively.

Apigenin encapsulated in spray‐dried liposomes coated with chitosan: heat, pH, light, oxygen, salt and storage stability

SummaryApigenin (AP) is a natural flavonoid with multiple health benefits that can be used in functional foods. However, the hydrophobicity and poor aqueous solubility of AP have hindered its food application. With ethanol injection and spray drying, encapsulated AP in dried chitosan‐coated liposomes could be promising in delivering AP via foods. By comparing with the unencapsulated AP, this study examined the potential of spray‐dried chitosan‐coated apigenin liposomes (SCAL) in preserving the AP content and antioxidant capacity against food‐related heat, pH, light, oxygen and salt conditions. The moisture sorption isotherms and storage stability of SCAL were also investigated. The results show that the encapsulated AP in SCAL had better stability against pH (pH 2, pH 4, pH 6 and pH 7), light, oxygen and salt stress (0.1, 0.3 and 0.5 M NaCl) than the unencapsulated AP. The limits of relative humidity (RH) for SCAL storage were found to be <50% at 25 °C, <60% at 35 °C and <70% at 45 °C. SCAL could preserve AP over 90 days in room (86.55–95.42%) and chilled (91.54–95.79%) conditions. These findings suggest the potential of spray‐dried chitosan‐coated liposomes in improving the stability of AP, hence SCAL is promising for delivering AP in functional foods.

The Selenoproteome as a Dynamic Response Mechanism to Oxidative Stress in Hydrogenotrophic Methanogenic Communities.

Methanogenesis is a critical process in the carbon cycle that is applied industrially in anaerobic digestion and biogas production. While naturally occurring in diverse environments, methanogenesis requires anaerobic and reduced conditions, although varying degrees of oxygen tolerance have been described. Microaeration is suggested as the next step to increase methane production and improve hydrolysis in digestion processes; therefore, a deeper understanding of the methanogenic response to oxygen stress is needed. To explore the drivers of oxygen tolerance in methanogenesis, two parallel enrichments were performed under the addition of H2/CO2 in an environment without reducing agents and in a redox-buffered environment by adding redox mediator 9,10-anthraquinone-2,7-disulfonate disodium. The cellular response to oxidative conditions is mapped using proteomic analysis. The resulting community showed remarkable tolerance to high-redox environments and was unperturbed in its methane production. Next to the expression of pathways to mitigate reactive oxygen species, the higher redox potential environment showed an increased presence of selenocysteine and selenium-associated pathways. By including sulfur-to-selenium mass shifts in a proteomic database search, we provide the first evidence of the dynamic and large-scale incorporation of selenocysteine as a response to oxidative stress in hydrogenotrophic methanogenesis and the presence of a dynamic selenoproteome.

Physical and Physiological Predictors Determining the Maximal Static Apnea Diving Time of Male Freedivers

This study aimed to investigate what factors determine freedivers' maximal static apnea dive time. We correlated some physical/physiological factors with male freedivers’ maximum apnea diving duration. Thirty-six experienced male freedivers participated in this study. The divers participated in two days of the experiments. On the first day, apnea diving time, blood oxygen saturation (SpO2 ), heart rate (HR), blood pressure (BP), stress index, and blood parameters were measured before, during, and after the apnea diving in the pool. On the second day, body composition, lung capacity, resting and maximal oxygen consumption (VO2 max), and the Wingate anaerobic power were measured in the laboratory. The data were analyzed with Pearson’s Correlation using the SPSS 22 program. The correlation coefficient (R) of determination was set at 0.4, and the level of significance was set at p<0.05. There were positive correlations of diving experience, maximum SpO2 , and lung capacity with the maximum apnea time R>0.4, P<0.05). There were negative correlations of BMI, body fat percentage, body fat mass, minimum SpO2 , stress index, and total cholesterol with the maximum apnea diving time (R>-0.4, P<0.05). No correlations of age, height, weight, fat-free mass, skeletal muscle mass, HR, BP, blood glucose, betahydroxybutyrate, lactate, and hemoglobin levels with the maximum apnea diving time were observed (R<0.4, P>0.05). It is concluded that more experience in freediving, reduced body fat, extended SpO2 range, and increased lung capacity are the performance p

Effect of oxygen octahedral tilt on ferroelectric-antiferroelectric transition of PZT95/5 induced by hydrostatic pressure and electric field: A phenomenological thermodynamic analysis

Ceramic PZT95/5 lies near the boundary between the ferroelectric and antiferroelectric phases and undergoes complex domain switching and various phase transitions in response to temperature, pressure, and electric fields. This phenomenon often leads to unusual performances, making it challenging to characterize and control the electromechanical properties of the material. In particular, the phase transition from ferroelectric rhombohedral to antiferroelectric orthorhombic is caused by the combined effect of polarization switching and oxygen octahedral tilt. However, the underlying mechanism of their interaction is still unclear, resulting in a lack of thermodynamic models for ferroelectric-antiferroelectrics in multifield settings. In this study, a thermodynamic model was established by considering the combined effect of oxygen octahedral tilt, polarization, and stress, which can describe the polarity characteristics of phase transitions in PZT95/5 under multiple fields. This model comprehensively accounts for all phases of PZT95/5 and successfully simulates the experimental phase diagram of PZT95/5 under hydrostatic pressure. The tilt angle of the oxygen octahedra and the polarization were incorporated to reveal the special polarity microstructure of the intermediate phase between the ferroelectric and antiferroelectric phases and determine the effect of pressure on the incommensurate modulations. Exploring the application of antiferroelectric materials in smart devices via the pressure-induced transition of incommensurate modulation phases may become a new possibility.

Variability and drivers of carbonate chemistry at shellfish aquaculture sites in the Salish Sea, British Columbia

Abstract. Ocean acidification (OA) reduces seawater pH and calcium carbonate saturation states (Ω), which can have detrimental effects on calcifying organisms such as shellfish. Nearshore areas, where shellfish aquaculture typically operates, have limited data available to characterize variability in key ocean acidification parameters pH and Ω, as samples are costly to analyze and difficult to collect. This study collected samples from four nearshore locations at shellfish aquaculture sites on the Canadian Pacific coast from 2015–2018 and analyzed them for dissolved inorganic carbon (DIC) and total alkalinity (TA), enabling the calculation of pH and Ω for all seasons. The study evaluated the diel and seasonal variability in carbonate chemistry conditions at each location and estimated the contribution of drivers to seasonal and diel changes in pH and Ω. Nearshore locations experience a greater range of variability and seasonal and daily changes in pH and Ω than open waters. Biological uptake of DIC by phytoplankton is the major driver of seasonal and diel changes in pH and Ω at our nearshore sites. The study found that freshwater is not a key driver of diel variability, despite large changes over the day in some locations. We find that during summer at mid-depth (5–20 m), where it is cooler, pH, Ω, and oxygen conditions are still favourable for shellfish. These results suggest that if shellfish are hung lower in the water column, they may avoid high sea surface temperatures, without inducing OA and oxygen stress.

Mitochondrial perturbation in immune cells enhances cell-mediated innate immunity in Drosophila

BackgroundMitochondria participate in various cellular processes including energy metabolism, apoptosis, autophagy, production of reactive oxygen species, stress responses, inflammation and immunity. However, the role of mitochondrial metabolism in immune cells and tissues shaping the innate immune responses are not yet fully understood. We investigated the effects of tissue-specific mitochondrial perturbation on the immune responses at the organismal level. Genes for oxidative phosphorylation (OXPHOS) complexes cI-cV were knocked down in the fruit fly Drosophila melanogaster, targeting the two main immune tissues, the fat body and the immune cells (hemocytes).ResultsWhile OXPHOS perturbation in the fat body was detrimental, hemocyte-specific perturbation led to an enhanced immunocompetence. This was accompanied by the formation of melanized hemocyte aggregates (melanotic nodules), a sign of activation of cell-mediated innate immunity. Furthermore, the hemocyte-specific OXPHOS perturbation induced immune activation of hemocytes, resulting in an infection-like hemocyte profile and an enhanced immune response against parasitoid wasp infection. In addition, OXPHOS perturbation in hemocytes resulted in mitochondrial membrane depolarization and upregulation of genes associated with the mitochondrial unfolded protein response.ConclusionsOverall, we show that while the effects of mitochondrial perturbation on immune responses are highly tissue-specific, mild mitochondrial dysfunction can be beneficial in immune-challenged individuals and contributes to variation in infection outcomes among individuals.

Coupling field monitoring with crop growth modelling provides detailed insights on yield gaps at field level: A case study on ware potato production in the Netherlands

ContextYield gap analyses are useful to assess and benchmark the productivity of cropping systems. Often such analyses are performed at higher aggregation levels. As a result, these studies lack the detail to explain yield gaps at field level and hence make it difficult to translate findings into precise recommendations to farmers and extensionists. ObjectiveThis study provides a detailed approach for yield gap assessments at field level through coupling frequent field monitoring in farmers’ fields with crop growth modelling. We used ware potato production in the Netherlands as a case to study yield gaps at field level, as average productivity is high whilst yields are still highly variable among fields, and as ware potato is an important cash crop for farmers. MethodsOver two growing seasons, 96 ware potato fields were monitored throughout the growing season on a biweekly basis, taking measurements on soil, crop growth and yield. The crop growth model SWAP-WOFOST was used to simulate potential and water-limited potential yields. Various statistical methods were used to quantify yield gap explaining factors. ResultsThe average yield gap ranged from 20 to 31% depending on the year and soil type. Among fields, the yield gap ranged from 0 to 51%. On clayey soils, the yield gap was attributed mostly to oxygen stress. On sandy soils, the yield gap was determined mostly by drought stress in 2020, a relatively dry year, and by reducing factors (pests, diseases and poor agronomic practices) in 2021, an average year in terms of precipitation. The type of reducing factors differed per field. Furthermore, we found that earlier planting and later harvesting can increase yields, as Yp is radiation-limited. ConclusionsOverall, there is limited scope to narrow the yield gap as current ware potato production is already close to 80% of the potential yield, which is assumed to be approximately the maximum farmers can attain. However, yield and resource use efficiency gains are to be made for individual fields. Furthermore, we conclude that frequent field monitoring coupled with crop growth modelling is a powerful way to assess yield gap variability and to get detailed insight in the yield gap explaining factors at field level. SignificanceThis study showed that coupling frequent field monitoring with crop growth modelling allows to gain detailed insight in yield gap variability among fields. This method provides detailed information about yield gap explaining factors which can be used to improve yield and resource use efficiency at field level.

Amelioration of oxygen-induced retinopathy in neonatal mice with fetal growth restriction.

Introduction: With the aim of optimizing the balance of maintaining a safe oxygen saturation and reducing the risk of retinopathy of prematurity in human neonates with fetal growth restriction (FGR), the present study investigated the distinct effects of oxygen supplementation on the retinal neovasculature using a murine premature neonatal oxygen-induced retinopathy (OIR) model with or without fetal growth restriction. Methods: For comparison with normal birth-weight neonates, maternal low-protein diet-induced FGR neonates were subjected to fluctuating oxygen levels to generate oxygen-induced retinopathy. The retinal neovasculature was histologically evaluated, and comprehensive transcriptome analysis was conducted. Results: Compared to OIR neonates with normal birth weight, significant amelioration of the neovasculature, as indicated by decreases in the number of branch junctions, vascular distribution, maximal vascular radius and microaneurysm-like tufts, was observed in OIR mice with FGR. The results of retinal RNA-sequencing revealed downregulation of angiogenic factors that trigger pathological retinal neovascularization, such as the mitogen-activated protein kinase pathway and corresponding upstream signaling pathways in OIR mice with FGR. Conclusion: Our findings demonstrated that FGR neonates have a higher capacity for retinal oxygen stress, and the risk of OIR development is attenuated compared to that in mature neonates with normal birth weight.