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The New Phytologist Jan 2024Leaf day respiration (R ) strongly influences carbon-use efficiencies of whole plants and the global terrestrial biosphere. It has long been thought that R is slower... (Review)
Review
Leaf day respiration (R ) strongly influences carbon-use efficiencies of whole plants and the global terrestrial biosphere. It has long been thought that R is slower than respiration in the dark at a given temperature, but measuring R by gas exchange remains a challenge because leaves in the light are also photosynthesizing. The Kok method and the Laisk method are widely used to estimate R . We highlight theoretical limitations of these popular methods, and recent progress toward their improvement by using additional information from chlorophyll fluorescence and by accounting for the photosynthetic reassimilation of respired CO . The latest evidence for daytime CO and energy release from the oxidative pentose phosphate pathway in chloroplasts appears to be important to understanding R .
Topics: Cell Respiration; Carbon Dioxide; Photosynthesis; Plant Leaves; Respiration
PubMed: 37858976
DOI: 10.1111/nph.19330 -
Environmental Microbiology Nov 2023Seasonal changes in light and physicochemical conditions have strong impacts on cyanobacteria, but how they affect community structure, metabolism, and biogeochemistry...
Seasonal changes in light and physicochemical conditions have strong impacts on cyanobacteria, but how they affect community structure, metabolism, and biogeochemistry of cyanobacterial mats remains unclear. Light may be particularly influential for cyanobacterial mats exposed to sulphide by altering the balance of oxygenic photosynthesis and sulphide-driven anoxygenic photosynthesis. We studied temporal shifts in irradiance, water chemistry, and community structure and function of microbial mats in the Middle Island Sinkhole (MIS), where anoxic and sulphate-rich groundwater provides habitat for cyanobacteria that conduct both oxygenic and anoxygenic photosynthesis. Seasonal changes in light and groundwater chemistry were accompanied by shifts in bacterial community composition, with a succession of dominant cyanobacteria from Phormidium to Planktothrix, and an increase in diatoms, sulphur-oxidizing bacteria, and sulphate-reducing bacteria from summer to autumn. Differential abundance of cyanobacterial light-harvesting proteins likely reflects a physiological response of cyanobacteria to light level. Beggiatoa sulphur oxidation proteins were more abundant in autumn. Correlated abundances of taxa through time suggest interactions between sulphur oxidizers and sulphate reducers, sulphate reducers and heterotrophs, and cyanobacteria and heterotrophs. These results support the conclusion that seasonal change, including light availability, has a strong influence on community composition and biogeochemical cycling of sulphur and O in cyanobacterial mats.
Topics: Proteome; Seasons; Cyanobacteria; Sulfides; Oxygen; Sulfur; Sulfates
PubMed: 37596970
DOI: 10.1111/1462-2920.16480 -
Annual Review of Physical Chemistry Jun 2024Oxygenic photosynthesis, the process that converts light energy into chemical energy, is traditionally associated with the absorption of visible light by chlorophyll... (Review)
Review
Oxygenic photosynthesis, the process that converts light energy into chemical energy, is traditionally associated with the absorption of visible light by chlorophyll molecules. However, recent studies have revealed a growing number of organisms capable of using far-red light (700-800 nm) to drive oxygenic photosynthesis. This phenomenon challenges the conventional understanding of the limits of this process. In this review, we briefly introduce the organisms that exhibit far-red photosynthesis and explore the different strategies they employ to harvest far-red light. We discuss the modifications of photosynthetic complexes and their impact on the delivery of excitation energy to photochemical centers and on overall photochemical efficiency. Finally, we examine the solutions employed to drive electron transport and water oxidation using relatively low-energy photons. The findings discussed here not only expand our knowledge of the remarkable adaptation capacities of photosynthetic organisms but also offer insights into the potential for enhancing light capture in crops.
Topics: Photosynthesis; Light; Oxygen; Electron Transport; Water; Oxidation-Reduction; Chlorophyll; Red Light
PubMed: 38382567
DOI: 10.1146/annurev-physchem-090722-125847 -
Trends in Plant Science Dec 2023Photorespiration is inevitable for oxygenic photosynthesis. It has fascinated researchers over decades because of its multicompartmental organization. Recently, Lin and...
Photorespiration is inevitable for oxygenic photosynthesis. It has fascinated researchers over decades because of its multicompartmental organization. Recently, Lin and Tsay identified a vacuole glycerate transporter contributing to photorespiratory metabolism under short-term nitrogen depletion. This key finding adds a fifth interacting subcellular compartment and extends the photorespiratory metabolic repair module.
Topics: Vacuoles; Photosynthesis; Membrane Transport Proteins; Oxygen; Nitrogen
PubMed: 37635005
DOI: 10.1016/j.tplants.2023.08.008 -
Eye (London, England) Apr 2024
Topics: Humans; Hyperbaric Oxygenation; Eye; Face; Oxygen
PubMed: 38052865
DOI: 10.1038/s41433-023-02840-1 -
Toxicological Sciences : An Official... Mar 2024Inflammatory bowel disease (IBD) is a chronic and debilitating disorder characterized by inflammation of the gastrointestinal tract. Despite extensive research, the... (Review)
Review
Inflammatory bowel disease (IBD) is a chronic and debilitating disorder characterized by inflammation of the gastrointestinal tract. Despite extensive research, the exact cause of IBD remains unknown, hampering the development of effective therapies. However, emerging evidence suggests that hypoxia, a condition resulting from inadequate oxygen supply, plays a crucial role in intestinal inflammation and tissue damage in IBD. Hypoxia-inducible factors (HIFs), transcription factors that regulate the cellular response to low oxygen levels, have gained attention for their involvement in modulating inflammatory processes and maintaining tissue homeostasis. The two most studied HIFs, HIF-1α and HIF-2α, have been implicated in the development and progression of IBD. Toxicological factors encompass a wide range of environmental and endogenous agents, including dietary components, microbial metabolites, and pollutants. These factors can profoundly influence the hypoxic microenvironment within the gut, thereby exacerbating the course of IBD and fostering the progression of colitis-associated colorectal cancer. This review explores the regulation of hypoxia signaling at the molecular, microenvironmental, and environmental levels, investigating the intricate interplay between toxicological factors and hypoxic signaling in the context of IBD, focusing on its most concerning outcomes: intestinal fibrosis and colorectal cancer.
Topics: Humans; Inflammatory Bowel Diseases; Inflammation; Hypoxia; Oxygen; Signal Transduction; Basic Helix-Loop-Helix Transcription Factors; Hypoxia-Inducible Factor 1, alpha Subunit; Cell Hypoxia
PubMed: 38200624
DOI: 10.1093/toxsci/kfae004 -
International Journal of Molecular... Nov 2023Mitochondrial dysfunction contributes to numerous chronic diseases, and mitochondria are targets for various toxins and xenobiotics. Therefore, the development of drugs... (Review)
Review
Mitochondrial dysfunction contributes to numerous chronic diseases, and mitochondria are targets for various toxins and xenobiotics. Therefore, the development of drugs or therapeutic strategies targeting mitochondria is an important task in modern medicine. It is well known that the primary, although not the sole, function of mitochondria is ATP generation, which is achieved by coupled respiration. However, a high membrane potential can lead to uncontrolled reactive oxygen species (ROS) production and associated dysfunction. For over 50 years, scientists have been studying various synthetic uncouplers, and for more than 30 years, uncoupling proteins that are responsible for uncoupled respiration in mitochondria. Additionally, the proteins of the mitochondrial alternative respiratory pathway exist in plant mitochondria, allowing noncoupled respiration, in which electron flow is not associated with membrane potential formation. Over the past two decades, advances in genetic engineering have facilitated the creation of various cellular and animal models that simulate the effects of uncoupled and noncoupled respiration in different tissues under various disease conditions. In this review, we summarize and discuss the findings obtained from these transgenic models. We focus on the advantages and limitations of transgenic organisms, the observed physiological and biochemical changes, and the therapeutic potential of uncoupled and noncoupled respiration.
Topics: Animals; Animals, Genetically Modified; Oxygen Consumption; Mitochondria; Cell Respiration; Metabolic Diseases; Respiration; Reactive Oxygen Species
PubMed: 38003681
DOI: 10.3390/ijms242216491 -
International Journal of Molecular... Jan 2024HBOT increases the proportion of dissolved oxygen in the blood, generating hyperoxia. This increased oxygen diffuses into the mitochondria, which consume the majority of... (Review)
Review
HBOT increases the proportion of dissolved oxygen in the blood, generating hyperoxia. This increased oxygen diffuses into the mitochondria, which consume the majority of inhaled oxygen and constitute the epicenter of HBOT effects. In this way, the oxygen entering the mitochondria can reverse tissue hypoxia, activating the electron transport chain to generate energy. Furthermore, intermittent HBOT is sensed by the cell as relative hypoxia, inducing cellular responses such as the activation of the HIF-1α pathway, which in turn, activates numerous cellular processes, including angiogenesis and inflammation, among others. These effects are harnessed for the treatment of various pathologies. This review summarizes the evidence indicating that the use of medium-pressure HBOT generates hyperoxia and activates cellular pathways capable of producing the mentioned effects. The possibility of using medium-pressure HBOT as a direct or adjunctive treatment in different pathologies may yield benefits, potentially leading to transformative therapeutic advancements in the future.
Topics: Humans; Hyperoxia; Hyperbaric Oxygenation; Oxygen; Hypoxia; Inflammation
PubMed: 38255851
DOI: 10.3390/ijms25020777 -
Nitric Oxide : Biology and Chemistry Sep 2023Several nitric oxide (NO) generating devices have been developed to deliver NO between 1 part per million (ppm) and 80 ppm. Although inhalation of high-dose NO may...
BACKGROUND
Several nitric oxide (NO) generating devices have been developed to deliver NO between 1 part per million (ppm) and 80 ppm. Although inhalation of high-dose NO may exert antimicrobial effects, the feasibility and safety of producing high-dose (more than 100 ppm) NO remains to be established. In the current study, we designed, developed, and tested three high-dose NO generating devices.
METHODS
We constructed three NO generating devices: a double spark plug NO generator, a high-pressure single spark plug NO generator, and a gliding arc NO generator. The NO and NO concentrations were measured at different gas flows and under various atmospheric pressures. The double spark plug NO generator was designed to deliver gas through an oxygenator and mixing with pure oxygen. The high-pressure and gliding arc NO generators were used to deliver gas through a ventilator into artificial lungs to mimic delivering high-dose NO in the clinical settings. The energy consumption was measured and compared among the three NO generators.
RESULTS
The double spark plug NO generator produced 200 ± 2 ppm (mean ± SD) of NO at gas flow of 8 L/min (or 320 ± 3 ppm at gas flow of 5 L/min) with electrode gap of 3 mm. The nitrogen dioxide (NO) levels were below 3.0 ± 0.1 ppm when mixing with various volumes of pure oxygen. The addition of a second generator increased the delivered NO from 80 (with one spark plug) to 200 ppm. With the high-pressure chamber, the NO concentration reached 407 ± 3 ppm with continuous air flow at 5 L/min when employing the 3 mm electrode gap under 2.0 atmospheric pressure (ATA). When compared to 1 ATA, NO production was increased 22% at 1.5 ATA and 34% at 2 ATA. The NO level was 180 ± 1 ppm when connecting the device to a ventilator with a constant inspiratory airflow of 15 L/min, and NO levels were below 1 (0.93 ± 0.02) ppm. The gliding arc NO generator produced up to 180 ± 4 ppm of NO when connecting the device to a ventilator, and the NO level was below 1 (0.91 ± 0.02) ppm in all testing conditions. The gliding arc device required more power (in watts) to generate the same concentrations of NO when compared to double spark plug or high-pressure NO generators.
CONCLUSIONS
Our results demonstrated that it is feasible to enhance NO production (more than 100 ppm) while maintaining NO level relatively low (less than 3 ppm) with the three recently developed NO generating devices. Future studies might include these novel designs to deliver high doses of inhaled NO as an antimicrobial used to treat upper and lower respiratory tract infections.
Topics: Nitric Oxide; Nitrogen Dioxide; Respiratory Therapy; Lung; Administration, Inhalation; Oxygen
PubMed: 37277062
DOI: 10.1016/j.niox.2023.05.007 -
Critical Reviews in Food Science and... 2024Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are polycyclic aromatic hydrocarbons (PAHs) functionalized with at least one carbonyl group and are generally thought... (Review)
Review
Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are polycyclic aromatic hydrocarbons (PAHs) functionalized with at least one carbonyl group and are generally thought to be more toxic than PAHs. In this review, the physical-chemical properties, toxicity, occurrence, and potential sources of OPAHs in food were comprehensively discussed. The toxicities of 1,2-naphthoquinone, 1,4-naphthoquinone, 6H-benzo[cd]pyren-6-one, benzo[a]anthracene-7,12-quinone and 9,10-phenanthrenequinone were prominent among the OPAHs. Both 1,4-naphthoquinone and 1,2-naphthoquinone exhibited strong genotoxicity, cytotoxicity, and developmental toxicity. 6H-benzo[cd]pyren-6-one and benzo[a]anthracene-7,12-quinone showed high genotoxicity and cardiovascular toxicity. Although 9,10-phenanthrenequinone showed no genotoxicity, it exhibited almost the strongest cytotoxicity. For the majority of foods, the concentrations of OPAHs and PAHs were on the same order of magnitude. OPAHs tend to be positively correlated with the corresponding PAH concentrations in oil and fried food, while for barbequed food and seafood, no obvious correlation was found. In addition, 9-fluorenone, 9,10-anthraquinone, benzanthrone and 1,2-acenaphthenequinone had high abundance in food. Environmental pollution, food composition, storage conditions, heating methods, and other treatments influence the accumulation of OPAHs in food. Furthermore, oxygen and water played an important role in the transformation from PAHs to OPAHs. In short, this review guides the evaluation and further reduction of OPAH-related health risks in food.
Topics: Polycyclic Aromatic Hydrocarbons; Humans; Food Contamination; Food Analysis; Animals; Oxygen
PubMed: 36384378
DOI: 10.1080/10408398.2022.2146652