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International Journal of Molecular... Dec 2020In eukaryotic algae, respiratory O uptake is enhanced after illumination, which is called light-enhanced respiration (LER). It is likely stimulated by an increase in...
In eukaryotic algae, respiratory O uptake is enhanced after illumination, which is called light-enhanced respiration (LER). It is likely stimulated by an increase in respiratory substrates produced during photosynthetic CO assimilation and function in keeping the metabolic and redox homeostasis in the light in eukaryotic cells, based on the interactions among the cytosol, chloroplasts, and mitochondria. Here, we first characterize LER in photosynthetic prokaryote cyanobacteria, in which respiration and photosynthesis share their metabolisms and electron transport chains in one cell. From the physiological analysis, the cyanobacterium sp. PCC 6803 performs LER, similar to eukaryotic algae, which shows a capacity comparable to the net photosynthetic O evolution rate. Although the respiratory and photosynthetic electron transports share the interchain, LER was uncoupled from photosynthetic electron transport. Mutant analyses demonstrated that LER is motivated by the substrates directly provided by photosynthetic CO assimilation, but not by glycogen. Further, the light-dependent activation of LER was observed even with exogenously added glucose, implying a regulatory mechanism for LER in addition to the substrate amounts. Finally, we discuss the physiological significance of the large capacity of LER in cyanobacteria and eukaryotic algae compared to those in plants that normally show less LER.
Topics: Cell Respiration; Cyanobacteria; Electron Transport; Light; Oxidation-Reduction; Oxygen; Photosynthesis
PubMed: 33396191
DOI: 10.3390/ijms22010342 -
Journal of the American Veterinary... Jul 2010To compare cardiac index (CI), oxygen delivery index (D(O(2))I), oxygen extraction ratio (O(2)ER), oxygen consumption index (V(O(2))I), and systemic vascular resistance...
OBJECTIVE
To compare cardiac index (CI), oxygen delivery index (D(O(2))I), oxygen extraction ratio (O(2)ER), oxygen consumption index (V(O(2))I), and systemic vascular resistance index (SVRI) in dogs with naturally occurring sepsis with published values for healthy dogs; compare those variables in dogs with sepsis that did or did not survive; and compare CI and D(O(2))I in dogs with sepsis with values in dogs with nonseptic systemic inflammatory response syndrome (nSIRS).
DESIGN
Cohort study.
ANIMALS
10 dogs with naturally occurring sepsis and 11 dogs with nSIRS.
PROCEDURES
Over 24 hours, CI, D(O(2))I, O(2)ER, V(O(2))I, and SVRI were measured 4 and 5 times in dogs with sepsis and with nSIRS, respectively. The mean values of each variable in each group were compared over time and between groups; data for dogs with sepsis that did or did not survive were also compared.
RESULTS
Mean D(O(2))I was significantly decreased, and mean CI, O(2)ER, V(O(2))I, and SVRI were not significantly different in dogs with sepsis, compared with published values for healthy dogs. Mean CI and D(O(2))I in dogs with sepsis were significantly greater than values in dogs with nSIRS. Among dogs with sepsis that did or did not survive, values of CI, D(O(2)I), O(2)ER, V(O(2))I, and SVRI did not differ significantly.
CONCLUSIONS AND CLINICAL RELEVANCE
Compared with values in healthy dogs, only D(O(2))I was significantly lower in dogs with sepsis. Values of CI and D(O(2))I were significantly higher in dogs with sepsis than in dogs with nSIRS, suggesting differing degrees of myocardial dysfunction between these groups.
Topics: Animals; Biological Transport; Dog Diseases; Dogs; Female; Male; Oxygen; Oxygen Consumption; Sepsis
PubMed: 20632789
DOI: 10.2460/javma.237.2.167 -
American Journal of Physiology. Renal... May 2015The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2 (-)) and their effects on medullary...
The goal of this study was to investigate the reciprocal interactions among oxygen (O2), nitric oxide (NO), and superoxide (O2 (-)) and their effects on medullary oxygenation and urinary output. To accomplish that goal, we developed a detailed mathematical model of solute transport in the renal medulla of the rat kidney. The model represents the radial organization of the renal tubules and vessels, which centers around the vascular bundles in the outer medulla and around clusters of collecting ducts in the inner medulla. Model simulations yield significant radial gradients in interstitial fluid oxygen tension (Po2) and NO and O2 (-) concentration in the OM and upper IM. In the deep inner medulla, interstitial fluid concentrations become much more homogeneous, as the radial organization of tubules and vessels is not distinguishable. The model further predicts that due to the nonlinear interactions among O2, NO, and O2 (-), the effects of NO and O2 (-) on sodium transport, osmolality, and medullary oxygenation cannot be gleaned by considering each solute's effect in isolation. An additional simulation suggests that a sufficiently large reduction in tubular transport efficiency may be the key contributing factor, more so than oxidative stress alone, to hypertension-induced medullary hypoxia. Moreover, model predictions suggest that urine Po2 could serve as a biomarker for medullary hypoxia and a predictor of the risk for hospital-acquired acute kidney injury.
Topics: Acute Kidney Injury; Animals; Biological Transport; Cell Hypoxia; Computer Simulation; Hypertension; Kidney Concentrating Ability; Kidney Medulla; Kidney Tubules; Models, Biological; Nitric Oxide; Nonlinear Dynamics; Oxidative Stress; Oxygen; Rats; Renal Circulation; Sodium; Superoxides
PubMed: 25651567
DOI: 10.1152/ajprenal.00600.2014 -
BMJ (Clinical Research Ed.) Nov 1998
Review
Topics: Biological Transport; Capillaries; Cell Hypoxia; Energy Metabolism; Humans; Oxygen Consumption
PubMed: 9812940
DOI: 10.1136/bmj.317.7169.1370 -
Advances in Experimental Medicine and... 2017Electron paramagnetic resonance (EPR) spin-label oximetry allows the oxygen permeability coefficient to be evaluated across homogeneous lipid bilayer membranes and, in... (Review)
Review
Electron paramagnetic resonance (EPR) spin-label oximetry allows the oxygen permeability coefficient to be evaluated across homogeneous lipid bilayer membranes and, in some cases, across coexisting membrane domains without their physical separation. The most pronounced effect on oxygen permeability is observed for cholesterol, which additionally induces the formation of membrane domains. In intact biological membranes, integral proteins induce the formation of boundary and trapped lipid domains with a low oxygen permeability. The effective oxygen permeability coefficient across the intact biological membrane is affected not only by the oxygen permeability coefficients evaluated for each lipid domain but also by the surface area occupied by these domains in the membrane. All these factors observed in fiber cell plasma membranes of clear human eye lenses are reviewed here.
Topics: Biological Transport; Cell Membrane; Cell Membrane Permeability; Electron Spin Resonance Spectroscopy; Humans; Lens, Crystalline; Lipid Bilayers; Membrane Lipids; Optic Nerve; Oxygen; Permeability
PubMed: 28685424
DOI: 10.1007/978-3-319-55231-6_5 -
American Journal of Physiology. Renal... Dec 2018The renal medulla is prone to hypoxia. Medullary hypoxia is postulated to be a leading cause of acute kidney injury, so there is considerable interest in predicting the...
The renal medulla is prone to hypoxia. Medullary hypoxia is postulated to be a leading cause of acute kidney injury, so there is considerable interest in predicting the oxygen tension in the medulla. Therefore we have developed a computational model for blood and oxygen transport within a physiologically normal rat renal medulla, using a multilevel modeling approach. For the top-level model we use the theory of porous media and advection-dispersion transport through a realistic three-dimensional representation of the medulla's gross anatomy to describe blood flow and oxygen transport throughout the renal medulla. For the lower-level models, we employ two-dimensional reaction-diffusion models describing the distribution of oxygen through tissue surrounding the vasculature. Steady-state model predictions at the two levels are satisfied simultaneously, through iteration between the levels. The computational model was validated by simulating eight sets of experimental data regarding renal oxygenation in rats (using 4 sets of control groups and 4 sets of treatment groups, described in 4 independent publications). Predicted medullary tissue oxygen tension or microvascular oxygen tension for control groups and for treatment groups that underwent moderate perturbation in hemodynamic and renal functions is within ±2 SE values observed experimentally. Diffusive shunting between descending and ascending vasa recta is predicted to be only 3% of the oxygen delivered. The validation tests confirm that the computational model is robust and capable of capturing the behavior of renal medullary oxygenation in both normal and early-stage pathological states in the rat.
Topics: Acute Kidney Injury; Animals; Biological Transport; Cell Hypoxia; Cellular Microenvironment; Computer Simulation; Diffusion; Kidney Medulla; Models, Biological; Oxygen; Rats; Renal Circulation; Reproducibility of Results
PubMed: 30256129
DOI: 10.1152/ajprenal.00363.2018 -
Biochimica Et Biophysica Acta.... May 2021Cytochrome bf (cytbf) lies at the heart of the light-dependent reactions of oxygenic photosynthesis, where it serves as a link between photosystem II (PSII) and... (Review)
Review
Cytochrome bf (cytbf) lies at the heart of the light-dependent reactions of oxygenic photosynthesis, where it serves as a link between photosystem II (PSII) and photosystem I (PSI) through the oxidation and reduction of the electron carriers plastoquinol (PQH) and plastocyanin (Pc). A mechanism of electron bifurcation, known as the Q-cycle, couples electron transfer to the generation of a transmembrane proton gradient for ATP synthesis. Cytbf catalyses the rate-limiting step in linear electron transfer (LET), is pivotal for cyclic electron transfer (CET) and plays a key role as a redox-sensing hub involved in the regulation of light-harvesting, electron transfer and photosynthetic gene expression. Together, these characteristics make cytbf a judicious target for genetic manipulation to enhance photosynthetic yield, a strategy which already shows promise. In this review we will outline the structure and function of cytbf with a particular focus on new insights provided by the recent high-resolution map of the complex from Spinach.
Topics: Cell Respiration; Cytochrome b6f Complex; Electron Transport; Electrons; Photosynthesis
PubMed: 33460588
DOI: 10.1016/j.bbabio.2021.148380 -
The Journal of Biological Chemistry Apr 2012The trace element copper is indispensable for all aerobic life forms. Its ability to cycle between two oxidation states, Cu(1+) and Cu(2+), has been harnessed by a wide... (Review)
Review
The trace element copper is indispensable for all aerobic life forms. Its ability to cycle between two oxidation states, Cu(1+) and Cu(2+), has been harnessed by a wide array of metalloenzymes that catalyze electron transfer reactions. The metabolic needs for copper are sustained by a complex series of transporters and carrier proteins that regulate its intracellular accumulation and distribution in both pathogenic microbes and their animal hosts. However, copper is also potentially toxic due in part to its ability to generate reactive oxygen species. Recent studies suggest that the macrophage phagosome accumulates copper during bacterial infection, which may constitute an important mechanism of killing. Bacterial countermeasures include the up-regulation of copper export and detoxification genes during infection, which studies suggest are important determinants of virulence. In this minireview, we summarize recent developments that suggest an emerging role for copper as an unexpected component in determining the outcome of host-pathogen interactions.
Topics: Adenosine Triphosphatases; Anti-Bacterial Agents; Bacteria; Biological Transport; Cation Transport Proteins; Copper; Copper-Transporting ATPases; Homeostasis; Host-Pathogen Interactions; Humans; Mycobacterium tuberculosis; Oxygen; Pseudomonas; Reactive Oxygen Species; Salmonella typhimurium; Trace Elements; Virulence
PubMed: 22389498
DOI: 10.1074/jbc.R111.316406 -
Cellular and Molecular Life Sciences :... Oct 2009Plants contain a large number of aquaporins with different selectivity. These channels generally conduct water, but some additionally conduct NH(3), CO(2) and/or... (Review)
Review
Plants contain a large number of aquaporins with different selectivity. These channels generally conduct water, but some additionally conduct NH(3), CO(2) and/or H(2)O(2). The experimental evidence and molecular basis for the transport of a given solute, the validation with molecular dynamics simulations and the physiological impact of the selectivity are reviewed here. The aromatic/arginine (ar/R) constriction is most important for solute selection, but the exact pore requirements for efficient conduction of small solutes remain difficult to predict. Yeast growth assays are valuable for screening substrate selectivity and are explicitly shown for hydrogen peroxide and methylamine, a transport analog of ammonia. Independent assays need to address the relevance of different substrates for each channel in its physiological context. This is emphasized by the fact that several plant NIP channels, which conduct several solutes, are specifically involved in the transport of metalloids, such as silicic acid, arsenite, or boric acid in planta.
Topics: Ammonia; Aquaporins; Biological Transport; Carbon Dioxide; Cell Membrane Permeability; Computer Simulation; Models, Molecular; Oxygen; Plant Proteins; Plants; Protein Structure, Tertiary; Protons; Signal Transduction; Urea; Water
PubMed: 19565186
DOI: 10.1007/s00018-009-0075-6 -
Artificial Organs Feb 2018Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart...
Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart or lung function during cardiopulmonary failure until organ recovery or replacement. Currently, the need for high levels of systemic anticoagulation and the risk for bleeding are main drawbacks of ECMO that can be addressed with a redesigned ECMO system. Our lab has developed an approach using microelectromechanical systems (MEMS) fabrication techniques to create novel gas exchange membranes consisting of a rigid silicon micropore membrane (SμM) support structure bonded to a thin film of gas-permeable polydimethylsiloxane (PDMS). This study details the fabrication process to create silicon membranes with highly uniform micropores that have a high level of pattern fidelity. The oxygen transport across these membranes was tested in a simple water-based bench-top set-up as well in a porcine in vivo model. It was determined that the mass transfer coefficient for the system using SµM-PDMS membranes was 3.03 ± 0.42 mL O min m cm Hg with pure water and 1.71 ± 1.03 mL O min m cm Hg with blood. An analytic model to predict gas transport was developed using data from the bench-top experiments and validated with in vivo testing. This was a proof of concept study showing adequate oxygen transport across a parallel plate SµM-PDMS membrane when used as a membrane oxygenator. This work establishes the tools and the equipoise to develop future generations of silicon micropore membrane oxygenators.
Topics: Animals; Diffusion; Dimethylpolysiloxanes; Equipment Design; Extracorporeal Membrane Oxygenation; Oxygen; Oxygenators, Membrane; Permeability; Porosity; Respiratory Insufficiency; Silicon; Swine
PubMed: 28800389
DOI: 10.1111/aor.12972