Elevated Partial Pressure Of Oxygen Research Articles

Pulmonary oxygen toxicity breath markers after heliox diving to 81 metres.

Pulmonary oxygen toxicity (POT), an adverse reaction to an elevated partial pressure of oxygen in the lungs, can develop as a result of prolonged hyperbaric hyperoxic conditions. Initially starting with tracheal discomfort, it results in pulmonary symptoms and ultimately lung fibrosis. Previous studies identified several volatile organic compounds (VOCs) in exhaled breath indicative of POT after various wet and dry hyperbaric hypoxic exposures, predominantly in laboratory settings. This study examined VOCs after exposures to 81 metres of seawater by three navy divers during operational heliox diving. Univariate testing did not yield significant results. However, targeted multivariate analysis of POT-associated VOCs identified significant (P = 0.004) changes of dodecane, tetradecane, octane, methylcyclohexane, and butyl acetate during the 4 h post-dive sampling period. No airway symptoms or discomfort were reported. This study demonstrates that breath sampling can be performed in the field, and VOCs indicative of oxygen toxicity are exhaled without clinical symptoms of POT, strengthening the belief that POT develops on a subclinical-to-symptomatic spectrum. However, this study was performed during an actual diving operation and therefore various confounders were introduced, which were excluded in previous laboratory studies. Future studies could focus on optimising sampling protocols for field use to ensure uniformity and reproducibility, and on establishing dose-response relationships.

How storage circumstance alters the quality of seeds of Lallemantia iberica and Lallemantia royleana produced under maternal drought stress

Seed production underpins the agricultural industry and is impacted by the maternal environment during maturation. In addition, inappropriate post-harvest storage conditions can affect seed quality, by accelerating viability loss and reducing seed longevity. The objective of this research was to investigate the impact of storage conditions on the germination and physiological and biochemical processes of seeds of Lallemantia iberica and L. royleana under drought stress. Seeds were matured under maternal plant irrigation regimes of 30% (I30) and 60% (I60) of soil available water depletion and subjected to different storage conditions: control, natural aging (NA), controlled deterioration (CD), elevated partial pressure of oxygen (EPPO), and elevated partial pressure of nitrogen (EPPN). Seeds of both species matured under water deficit I60 had enhanced germination index, unsaturated and saturated fatty acid contents, total soluble sugar, sucrose and starch contents, and α- and β-amylase activities. This treatment also resulted in reduced seed electrical conductivity (EC), hydrogen peroxide (H2O2), and malondialdehyde (MDA) concentrations. The different seed storage conditions had negative effects on germination index, storage compounds, and fatty acids, with the smaller and greater changes under NA and EPPO aging, respectively. During the different aging conditions, it was noted that L. iberica seeds showed greater deterioration compared to L. royleana seeds. In conclusion, post-harvest conditions impact seed quality, with mild stress of the maternal environment increasing the seed longevity of both Lallemantia species.

Determining the effects of elevated partial pressure of oxygen on hypercapnia-induced cerebrovascular reactivity

Evaluation of cerebrovascular reactivity (CVR) to hypo- and hypercapnia is a valuable test for the assessment of vasodilatory reserve. While hypercapnia-induced CVR testing is usually performed at normoxia, mild hyperoxia may increase tolerability of hypercapnia by reducing the ventilatory distress. However, the effects of mild hyperoxia on CVR was unknown. We therefore recruited 21 patients with a range of steno-occlusive diseases and 12 healthy participants who underwent a standardized 13-minute step plus ramp CVR test with a carbon dioxide gas challenge at the subject’s resting end-tidal partial pressure of oxygen or at mild hyperoxia (PetO2 = 150 mmHg) depending on to which group they were assigned. In 11 patients, the second CVR test was at normoxia to examine test-retest differences. CVR was defined as % Δ Signal/ΔPetCO2. We found that there was no significant difference between CVR test results conducted at normoxia and at mild hyperoxia for participants in Groups 1 and 2 for the step and ramp portion. We also found no difference between test and retest CVR at normoxia for patients with cerebrovascular pathology (Group 3) for step and ramp portion. We concluded normoxic CVR is repeatable, and that mild hyperoxia does not affect CVR.

Identification of the rice Rc gene as a main regulator of seed survival under dry storage conditions.

Seed deterioration during storage results in poor germination, reduced vigour, and non-uniform seedling emergence. The aging rate depends on storage conditions and genetic factors. This study aims to identify these genetic factors determining the longevity of rice (Oryza sativa L.) seeds stored under experimental aging conditions mimicking long-term dry storage. Genetic variation for tolerance to aging was studied in 300 Indica rice accessions by storing dry seeds under an elevated partial pressure of oxygen (EPPO) condition. A genome-wide association analysis identified 11 unique genomic regions for all measured germination parameters after aging, differing from those previously identified in rice under humid experimental aging conditions. The significant single nucleotide polymorphism in the most prominent region was located within the Rc gene, encoding a basic helix-loop-helix transcription factor. Storage experiments using near-isogenic rice lines (SD7-1D (Rc) and SD7-1d (rc) with the same allelic variation confirmed the role of the wildtype Rc gene, providing stronger tolerance to dry EPPO aging. In the seed pericarp, a functional Rc gene results in accumulation of proanthocyanidins, an important sub-class of flavonoids having strong antioxidant activity, which may explain the variation in tolerance to dry EPPO aging.

Experimental rice seed aging under elevated oxygen pressure: Methodology and mechanism.

Seed aging during storage results in loss of vigor and germination ability due to the accumulation of damage by oxidation reactions. Experimental aging tests, for instance to study genetic variation, aim to mimic natural aging in a shorter timeframe. As the oxidation rate is increased by elevating the temperature, moisture, and oxygen levels, this study aimed to (1) investigate the effect of experimental rice seed aging by an elevated partial pressure of oxygen (EPPO), (2) elucidate the mechanism of dry-EPPO aging and (3) compare aging under dry-EPPO conditions to aging under traditional moist-controlled deterioration (CD) conditions and to long-term ambient storage. Dry seeds from 20 diverse rice accessions were experimentally aged under EPPO (200 times higher oxygen levels), at 50% relative humidity (RH), along with storage under high-pressure nitrogen gas and ambient conditions as controls. While no decline in germination was observed with ambient storage, there was significant aging of the rice seeds under EPPO storage, with considerable variation in the aging rate among the accessions, with an average decline toward 50% survival obtained after around 21 days in EPPO storage and total loss of germination after 56 days. Storage under high-pressure nitrogen gas resulted in a small but significant decline, by an average of 5% germination after 56 days. In a second experiment, seven rice seed lots were stored under EPPO as compared to a moist-CD test and two different long-term ambient storage conditions, i.e., conditioned warehouse seed storage (CWSS) and traditional rice seed storage (TRSS). Untargeted metabolomics (with identification of lipid and volatile compounds profiles) showed a relatively high increase in levels of oxidized lipids and related volatiles under all four storage conditions. These compounds had a high negative correlation with seed viability, indicating oxidation as a main deteriorating process during seed aging. Correlation analysis indicated that EPPO storage at 50% RH is more related to aging under TRSS at 60% and CD-aging at 75% ERH rather than CWSS at 40% ERH. In conclusion, aging rice seeds under EPPO conditions is a suitable experimental aging method for analyzing variation among seed lots or genotypes for longevity under storage.

Transcription Factor DOF4.1 Regulates Seed Longevity in Arabidopsis via Seed Permeability and Modulation of Seed Storage Protein Accumulation.

Seed longevity is modulated by multiple genetic factors in Arabidopsis thaliana. A previous genome-wide association study using the Elevated Partial Pressure of Oxygen (EPPO) aging assay pinpointed a genetic locus associated with this trait. Reverse genetics identified the transcription factor DOF4.1 as a novel seed longevity factor. dof4.1 loss-of-function plants generate seeds exhibiting higher germination after accelerated aging assays. DOF4.1 is expressed during seed development and RNAseq data show several putative factors that could contribute to the dof4.1 seed longevity phenotype. dof4.1 has reduced seed permeability and a higher levels of seed storage proteins mRNAs (cruciferins and napins) in developing seeds, as compared to wild-type seeds. It has been reported that mutant lines defective in cruciferins or napins present reduced seed longevity. The improved longevity of dof4.1 is totally lost in the quadruple mutant dof4.1 cra crb crc, but not in a dof4.1 line depleted of napins, suggesting a prominent role for cruciferins in this process. Moreover, a negative regulation of DOF4.1 expression by the transcription factor DOF1.8 is suggested by co-inoculation assays in Nicotiana benthamiana. Indeed, DOF1.8 expression anticorrelates with that of DOF4.1 during seed development. In summary, modulation of DOF4.1 levels during seed development contributes to regulate seed longevity.

The potential of alternative seed treatments to control anthracnose disease in white lupin

White lupin (Lupinus albus L.) is a promising crop to meet the rising global demand for plant-based protein. The seed-borne pathogen Colletotrichum lupini, however, threatens lupin cultivation worldwide. Seed dressings using synthetic fungicides were shown effective to reduce infection levels, but their negative environmental impact and exclusion from organic production calls for more sustainable solutions. In this study, a total of eleven different alternative seed treatments were tested in field trials in Switzerland between 2018 and 2021. Treatment types consisted of: hot water, steam, electron, long-term storage, elevated partial pressure of oxygen (EPPO), vinegar, plant extracts and biological control agents (BCAs). The BCAs were tested for potential antagonistic activity against C. lupini during white lupin infection under controlled conditions prior to field trials. Long-term storage and vinegar treatments successfully reduced disease incidence and increased yield to levels similar to those observed for certified seeds, without significantly affecting germination rate. Although promising, effectiveness of these treatments needs further validation. Four BCAs showed significant disease reductions under controlled conditions. Besides lowering disease severity, two BCAs also reduced C. lupini DNA in stem tissue. These reductions, however, were not observed in the field, highlighting the importance of field validations. The treatments identified in this study provide a solid basis for the development of sustainable and effective seed protection strategies in white lupin to control C. lupini successfully.

Hyperbaric Oxygen Therapy for Central Retinal Artery Occlusion: Patient Selection and Perspectives.

The central retinal artery occlusion (CRAO) is a rare ophthalmological emergency that can occur in the eye. CRAO can affect persons of any age, however it is most common in people over the age of 60. CRAO is associated with a number of risk factors, including giant cell arteritis, carotid artery atherosclerosis, cardiogenic emboli, hypertension, smoking, diabetes, and thromboembolic disease. The chance of each of these etiologies being present is assessed during the course of the investigation. Hyperbaric oxygen treatment (HBOT) is classified by the American Heart Association for CRAO at level IIb. In accordance with that, HBOT might be considered for the treatment of such a severe condition. HBOT can maintain retinal oxygenation during ischemic events by allowing oxygen to diffuse through choroidal capillaries that have been exposed to elevated partial pressures of oxygen. As a result, ischemia-related damage is reversed if applied within proper time frame. The amount of time that has passed prior to initiation of HBOT is considered to be the most critical factor in determining the best visual prognosis. According to the Undersea and Hyperbaric Medical Society, patients who are identified with CRAO after the onset of symptoms should be evaluated for HBOT within 24 hours. HBOT has the advantage of having a low risk profile, and it can be utilized to improve visual outcomes in proper patients.

Additional Treatment with Low-Molecular-Weight Heparin Provides a Better Patient Outcome for Neonatal Pulmonary Hemorrhage with Unfractionated Heparin Treatment

Pulmonary hemorrhage occurring in preterm newborns is a catastrophic event and is significantly associated with neonatal deaths. Low-weight-molecular heparin is a medical agent usually used as anticoagulants during pregnancy and has the advantages of good absorption, long half-life, and high bioavailability. This study evaluated the pulmonary function and coagulation function in neonates with pulmonary hemorrhage following intravenous drip of low-molecular-weight heparin and the effects of low-molecular-weight heparin on serum prealbumin and retinol-binding protein levels. A total of 96 neonates with pulmonary hemorrhage were included as study subjects and arranged into the control group and the observation group, 48 per group, based on intravenous drip of unfractionated heparin with or without low-molecular-weight heparin. The neonates receiving intravenous drip of unfractionated heparin and low-molecular-weight heparin exhibited elevated partial pressure of oxygen (PaO2) concomitant with declined partial pressure of carbon (PaCO2) compared to those receiving unfractionated heparin treatment alone. With regard to pulmonary function, neonates receiving combined treatment of unfractionated heparin and low-molecular-weight heparin displayed increased forced expiratory volume in the first second (FEV1), FEV1/forced expiratory vital capacity (FVC), and peak expiratory flow (PEF) ( P < 0.05 ) when comparable to neonates receiving unfractionated heparin treatment alone. As for coagulation function, neonates with pulmonary hemorrhage had decreased activated partial thromboplastin time (APTT), prothrombin time (PT), thromboplastin time (TT), and fibrinogen (FIB) after treatment. Expectedly, these decreases were more significantly in neonates undergoing unfractionated heparin coupled with low-molecular-weight heparin ( P < 0.05 ). The control group was given unfractionated heparin, and the observation group was given unfractionated heparin coupled with low-molecular-weight heparin. In addition to pulmonary function and coagulation function, it was also observed that neonates undergoing unfractionated heparin coupled with low-molecular-weight heparin exhibited higher serum levels of serum prealbumin and retinol-binding protein than those treated with unfractionated heparin alone. Finally, higher recovery rate and lower incidence rate of complications, such as pulmonary infection, intracranial hemorrhage, and respiratory distress, were found in the observation group than the control group ( P < 0.05 ). In conclusion, additional treatment with low-molecular-weight heparin could provide a better patient outcome for neonatal pulmonary hemorrhage with unfractionated heparin treatment, as it could notably improve pulmonary function and coagulation function and reduce the incidence of complications.

Endothelin receptor antagonist improves donor lung function in an ex vivo perfusion system

BackgroundA lung transplant is the last resort treatment for many patients with advanced lung disease. The majority of donated lungs come from donors following brain death (BD). The endothelin axis is upregulated in the blood and lung of the donor after BD resulting in systemic inflammation, lung damage and poor lung graft outcomes in the recipient. Tezosentan (endothelin receptor blocker) improves the pulmonary haemodynamic profile; however, it induces adverse effects on other organs at high doses. Application of ex vivo lung perfusion (EVLP) allows the development of organ-specific hormone resuscitation, to maximise and optimise the donor pool. Therefore, we investigate whether the combination of EVLP and tezosentan administration could improve the quality of donor lungs in a clinically relevant 6-h ovine model of brain stem death (BSD).MethodsAfter 6 h of BSD, lungs obtained from 12 sheep were divided into two groups, control and tezosentan-treated group, and cannulated for EVLP. The lungs were monitored for 6 h and lung perfusate and tissue samples were processed and analysed. Blood gas variables were measured in perfusate samples as well as total proteins and pro-inflammatory biomarkers, IL-6 and IL-8. Lung tissues were collected at the end of EVLP experiments for histology analysis and wet-dry weight ratio (a measure of oedema).ResultsOur results showed a significant improvement in gas exchange [elevated partial pressure of oxygen (P = 0.02) and reduced partial pressure of carbon dioxide (P = 0.03)] in tezosentan-treated lungs compared to controls. However, the lungs hematoxylin–eosin staining histology results showed minimum lung injuries and there was no difference between both control and tezosentan-treated lungs. Similarly, IL-6 and IL-8 levels in lung perfusate showed no difference between control and tezosentan-treated lungs throughout the EVLP. Histological and tissue analysis showed a non-significant reduction in wet/dry weight ratio in tezosentan-treated lung tissues (P = 0.09) when compared to control.ConclusionsThese data indicate that administration of tezosentan could improve pulmonary gas exchange during EVLP.

Evaluating the EPPO method for seed longevity analyses in Arabidopsis

Seed longevity (storability) is an important seed quality trait. High seed quality is important in agriculture, for the industry, and for safeguarding biodiversity as many species are stored as seeds in genebanks. To ensure ex-situ seed survival, seeds are mostly stored at low relative humidity and low temperature. Oxidation is the main cause of seed deterioration in these dry storage conditions. The molecular mechanisms underlying dry seed survival remain poorly understood. Research on seed longevity is hampered by the lack of an experimental ageing method that mimics dry ageing well. Here, we propose the Elevated Partial Pressure of Oxygen (EPPO) method as the best available method to mimic and accelerate dry seed ageing. We have tested seed germination in Arabidopsis thaliana after EPPO storage at two different relative humidity (RH) conditions and confirm the large effect of oxygen and the seed moisture content on ageing during dry storage. Comparative Quantitative trait locus (QTL) analysis shows that EPPO at 55 % RH mimics dry ageing better than the commonly used Artificial Ageing and Controlled Deterioration tests at higher moisture levels.

Alternative Oxidase (AOX) Senses Stress Levels to Coordinate Auxin-Induced Reprogramming From Seed Germination to Somatic Embryogenesis-A Role Relevant for Seed Vigor Prediction and Plant Robustness.

Somatic embryogenesis (SE) is the most striking and prominent example of plant plasticity upon severe stress. Inducing immature carrot seeds perform SE as substitute to germination by auxin treatment can be seen as switch between stress levels associated to morphophysiological plasticity. This experimental system is highly powerful to explore stress response factors that mediate the metabolic switch between cell and tissue identities. Developmental plasticity per se is an emerging trait for in vitro systems and crop improvement. It is supposed to underlie multi-stress tolerance. High plasticity can protect plants throughout life cycles against variable abiotic and biotic conditions. We provide proof of concepts for the existing hypothesis that alternative oxidase (AOX) can be relevant for developmental plasticity and be associated to yield stability. Our perspective on AOX as relevant coordinator of cell reprogramming is supported by real-time polymerase chain reaction (PCR) analyses and gross metabolism data from calorespirometry complemented by SHAM-inhibitor studies on primed, elevated partial pressure of oxygen (EPPO)–stressed, and endophyte-treated seeds. In silico studies on public experimental data from diverse species strengthen generality of our insights. Finally, we highlight ready-to-use concepts for plant selection and optimizing in vivo and in vitro propagation that do not require further details on molecular physiology and metabolism. This is demonstrated by applying our research & technology concepts to pea genotypes with differential yield performance in multilocation fields and chickpea types known for differential robustness in the field. By using these concepts and tools appropriately, also other marker candidates than AOX and complex genomics data can be efficiently validated for prebreeding and seed vigor prediction.

Altered amplitude of low-frequency fluctuation in basal ganglia correlates to pulmonary ventilation function in COPD patients: A resting-state fMRI study.

IntroductionPatients under chronic obstructive pulmonary disease (COPD) has been reported to be associated with a higher prevalence of cognitive impairment (CI). However, it is still largely unknown whether the aberrant resting‐state spontaneous neuronal activity pattern reflected by the amplitude of low‐frequency fluctuation (ALFF) analysis will be associated with the CI in COPD patients.MaterialsA total of 28 COPD patients and 26 healthy controls were enrolled in this study. Of all the subjects, structural and functional MRI data, spirometry tests performance and neuropsychological assessments of different cognitive domains were collected. Voxel‐based two‐sample t tests were used to detect brain regions showing differences in the ALFF value between COPD patients and healthy controls. An additional fMRI runs with supplementary oxygen delivery were employed to explore the impact of elevated partial pressure of oxygen (PaO2) or moderate hyperoxia on ALFF in COPD patients and healthy controls respectively.ResultsMore extensive white matter lesion was detected in COPD patients. COPD patients exhibit decreased ALFF value in bilateral basal ganglia areas and right thalamus, and aberrant ALFF value is correlated with PaO2 and pulmonary ventilation function (FEV1%pred). COPD patients performed worse in the Digit Span Test (reverse), Digit Symbol Substitution Test, Trail‐making test (A and B) than controls. After supplementary oxygen inhalation, the ALFF value of basal ganglia and right thalamus significantly increased in the controls, but not in the COPD patients.ConclusionsCOPD patients mainly exhibit impaired executive function but not long‐term memory in cognitive function assessment. Aberrant ALFF alteration in the deep brain may be directly related to lower PaO2 in COPD patients.

Commercial Divers’ Subjective Evaluation of Saturation

Commercial saturation diving involves divers living and working in an enclosed atmosphere with elevated partial pressure of oxygen (ppO2) for weeks. The divers must acclimatize to these conditions during compression, and for up to 28 days until decompression is completed. During decompression, the ppO2 and ambient pressure are gradually decreased; then the divers must acclimatize again to breathing normal air in atmospheric pressure when they arrive at surface. We investigated 51 saturation divers’ subjective evaluation of the saturation and post-decompression phase via questionnaires and individual interviews. The questions were about decompression headaches and fatigue; and time before recovering to a pre-saturation state. Twenty-two (44%) of the divers who responded declared having headaches; near surface (44%) or after surfacing (56%). 71% reported post-saturation fatigue after their last saturation, 82% of them described it as typical and systematic after each saturation. Recovery was reported to normally take from 1 to 10 days. The fatigue and headaches observed are compatible with divers’ acclimatization to the changes in ppO2 levels during saturation and decompression. They appear to be reversible post- decompression.

Delaying latency to hyperbaric oxygen-induced CNS oxygen toxicity seizures by combinations of exogenous ketone supplements.

Central nervous system oxygen toxicity (CNS‐OT) manifests as tonic‐clonic seizures and is a limitation of hyperbaric oxygen therapy (HBOT), as well as of recreational and technical diving associated with elevated partial pressure of oxygen. A previous study showed that ketone ester (1,3‐butanediol acetoacetate diester, KE) administration delayed latency to seizures (LS) in 3‐month‐old Sprague‐Dawley (SD) rats. This study explores the effect of exogenous ketone supplements in additional dosages and formulations on CNS‐OT seizures in 18 months old SD rats, an age group correlating to human middle age. Ketogenic agents were given orally 60 min prior to exposure to hyperbaric oxygen and included control (water), KE (10 g/kg), KE/2 (KE 5 g/kg + water 5 g/kg), KE + medium‐chain triglycerides (KE 5 g/kg + MCT 5 g/kg), and ketone salt (Na+/K+ β HB, KS) + MCT (KS 5 g/kg + MCT 5 g/kg). Rats were exposed to 100% oxygen at 5 atmospheres absolute (ATA). Upon seizure presentation (tonic‐clonic movements) experiments were immediately terminated and blood was tested for glucose and D‐beta‐hydroxybutyrate (D‐β HB) levels. While blood D‐β HB levels were significantly elevated post‐dive in all treatment groups, LS was significantly delayed only in KE (P = 0.0003), KE/2 (P = 0.023), and KE + MCT (P = 0.028) groups. In these groups, the severity of seizures appeared to be reduced, although these changes were significant only in KE‐treated animals (P = 0.015). Acetoacetate (AcAc) levels were also significantly elevated in KE‐treated animals. The LS in 18‐month‐old rats was delayed by 179% in KE, 219% in KE + MCT, and 55% in KE/2 groups, while only by 29% in KS + MCT. In conclusion, KE supplementation given alone and in combination with MCT elevated both β HB and AcAc, and delayed CNS‐OT seizures.

Hemoglobin and Erythropoietin After Commercial Saturation Diving.

Saturation divers are exposed to elevated partial pressure of oxygen (ppO2) in their hyperbaric work environment. Experimental studies indicate that oxygen transport is altered, and we have previously reported a drop in hematocrit and extensive downregulation of genes involved in blood oxygen transport capacity after decompression from professional saturation diving. Here we investigate the initial period of hematological adjustment back to normobaric air after professional saturation diving. Erythropoietin (EPO) and hemoglobin (Hb) were measured in blood from 13 divers at two time-points after saturation assignments lasting up to 4 weeks; first immediately after decompression and again 24 h later. Pre-dive levels defined baselines. The ppO2 varied from 40 kPa in the saturation chambers during storage, 50 to 80 kPa during bell excursions, and gradually reduced to 21 kPa during decompression to surface pressure. EPO was similar to baseline immediately after saturation diving (P = 0.4), and markedly increased within the next 24 h (99%, P < 0.0002). Hb levels remained slightly reduced at both time-points (4% immediately after; P = 0.02, 8% 24 h after; P < 0.001). The results imply that the hematological acclimatization back to normobaric air was ongoing, but not completed, during the first 24 h after professional saturation diving.

Seed dormancy release accelerated by elevated partial pressure of oxygen is associated with DOG loci.

Seed dormancy determines the timing of seed germination and may be released by dry storage, also referred to as after-ripening. Studies on dormancy-release mechanisms are often hampered by the long after-ripening requirements of seeds. After-ripening is thought to be mainly caused by oxidative processes during seed dry storage. These processes are also the main cause of seed ageing. Increasing partial oxygen pressure through the elevated partial pressure of oxygen (EPPO) system has been shown to mimic and accelerate dry seed ageing. In this study, we investigated whether the EPPO system may also release primary seed dormancy in Arabidopsis thaliana. EPPO mimics dry after-ripening at the genetic level, as quantitative trait locus (QTL) analysis after EPPO treatment identified the DELAY OF GERMINATION loci DOG1, DOG2, and DOG6 that were first described in a study using dry after-ripening to release seed dormancy. QTL analysis also showed that dormancy release by cold stratification (another common method to break seed dormancy) partly overlaps with release by after-ripening and EPPO treatment. We conclude that EPPO is an appropriate method to mimic and accelerate dormancy release and, as such, may have applications in both research and industry.

The Effect of Intermittent Hyperoxia on Stem Cell Mobilization

IntroductionModern medicine has made enormous progress in the past 150 years including the development of vaccines and pharmaceutical therapies. However, to date there is little progress in developing therapies that speed the healing of injured tissues. Hyperbaric oxygen therapy (HBOT) is a FDA approved therapy for non‐healing wounds consisting of daily intermittent doses of elevated partial pressure of oxygen (PO2) above 1520 torr. The hypothetical mechanism is its influence on mobilizing stem cells via cell signaling and gene transcription at effector tissues. Preclinical research showed a regimen of HBOT resulted in mobilization of stem cells and increased vasculogenesis in a wound healing model. Our study sought to determine if partial pressures of oxygen less than 760 torr would also mobilize stem cells.MethodsTwelve, 10‐week‐old Sprague Dawley rats were randomly divided into two groups. The treatment group was exposed to a hyperoxic environment with a PO2 = 319 torr. The control group was exposed to room air (PO2 = 159 torr). Treatments were performed 5 days per week for 2 hours daily for a total of 10 treatment days (20 hours). Animals were sacrificed and approximately 8 ml of venous blood was harvested from the inferior vena cava. Red blood cells were lysed and plasma was drawn off and frozen. Remaining cells were prepared for flow cytometry by exposing them to cell surface marker antibodies for CD34+and CD 133+. These cells were then analyzed on a BD LSRII flow cytometer using DIVA software. Analysis was completed using FlowJo software. Statistics were performed using an unpaired t‐test with a p&lt;.05 to indicate significance.ResultsAnimals treated with a PO2 = 319 torr showed an increase (p = 0.045) in mobilized CD133+/34 endothelial progenitor cells (EPC's), while no differences were seen in CD133−/34+ hematopoietic stem progenitor cells (HSPC's) when compared to the control group.DiscussionWe hypothesized that there would be an increase in the CD133+/34− EPC's and an increase in CD133−/34+ HSPC's. Although our hypothesis was correct regarding the EPC's we did not see an increase in HSPC's as expected.CD133+/34− EPC's are considered more primitive stem cells than the CD133−/34+ HSPC's. CD133+/34− EPC's are capable of differentiation into CD133−/34+ HSPC's as they progress along the oligopotent path to maturation. Future research should include a pathological condition to test for changes in stem cell populations and the effects of pathology on stem cell differentiation. Our data suggest that low doses of daily intermittent hyperoxia mobilize the population of CD133+/34− EPC's. These EPC's have been shown in vivo to increase vascular density in a skin graft model. Further study is needed to determine what amount of intermittent hyperoxia treatment results in the most efficacious treatment in an injury model (increased stem cell mobilization, vasculogenesis and functional recovery).Support or Funding InformationDOD Navy ‐ N00024‐17‐C‐4318This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Barley Seed Aging: Genetics behind the Dry Elevated Pressure of Oxygen Aging and Moist Controlled Deterioration.

Experimental seed aging approaches intend to mimic seed deterioration processes to achieve a storage interval reduction. Common methods apply higher seed moisture levels and temperatures. In contrast, the “elevated partial pressure of oxygen” (EPPO) approach treats dry seed stored at ambient temperatures with high oxygen pressure. To analyse the genetic background of seed longevity and the effects of seed aging under dry conditions, the EPPO approach was applied to the progeny of the Oregon Wolfe Barley (OWB) mapping population. In comparison to a non-treated control and a control high-pressure nitrogen treatment, EPPO stored seeds showed typical symptoms of aging with a significant reduction of normal seedlings, slower germination, and less total germination. Thereby, the parent Dom (“OWB-D”), carrying dominant alleles, is more sensitive to aging in comparison to the population mean and in most cases to the parent Rec (“OWB-R”), carrying recessive alleles. Quantitative trait locus (QTL) analyses using 2832 markers revealed 65 QTLs, including two major loci for seed vigor on 2H and 7H. QTLs for EPPO tolerance were detected on 3H, 4H, and 5H. An applied controlled deterioration (CD) treatment (aged at higher moisture level and temperature) revealed a tolerance QTL on 5H, indicating that the mechanism of seed deterioration differs in part between EPPO or CD conditions.

Effect of Hyperoxia on Central Nervous System Intercellular Communication Mediated by Tunneling Nanotubes

Oxygen toxicity occurs when exposure to elevated partial pressures of oxygen results in hyperoxia. Central nervous system oxygen toxicity (CNS‐OT) can culminate in seizures, and elucidating mechanisms of CNS‐OT will provide approaches for prevention, delay to onset or amelioration of hyperoxic damage. However, little is known of the pathophysiology of hyperoxia. A possible mediator is the tunneling nanotube (TnT). TnTs are thin, membranous connections mediating the transfer of intracellular materials, including proteins and organelles. We recently identified TnTs between normal brain and glioblastoma cells in mouse xenograft brain sections. When neurons or astrocytes are exposed to H2O2, stressed cells form TnTs and unidirectionally transfer materials, indicating that TnTs may be induced by stress as a defense mechanism. Therefore, we are evaluating the effect of oxygen tension on TnT formation and materials transfer and function in neurons and glia. These studies will reveal molecular changes in CNS cell connectivity. Preliminary data indicate that SK‐N‐SH cells grown in 85% oxygen produce more TnTs than cells grown in standard conditions. We also found increased expression of putative TnT markers, ezrin, cxn43, myoX and rhot1, in hyperoxic conditions. The anticonvulsant vigabatrin, which prevents hyperbaric oxygen‐induced seizures in rats, increases the number of TnTs per cell under norm‐ and hyperoxia, suggesting that vigabatrin may upregulate TnT production to facilitate the transfer of materials that protect against hyperoxia. Our studies will elucidate TnT formation and function and identify regulatory mechanisms governing TnT‐mediated behaviors following hyperoxia.