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Sample records for acid rtca cycle

  1. Prebiotic Metabolisms: Photo catalysis of the rTCA cycle by sphalerite colloids

    NASA Astrophysics Data System (ADS)

    Mangiante, D. M.; Bowen, B.; Northen, T.; Banfield, J. F.

    2010-12-01

    Explorations of mineral catalyzed reverse tricarboxylic acid (rTCA) cycle reactions provide a window into possible mechanisms for prebiotic metabolisms and the origins of life. The excitation of nano-scale semiconducting sphalerite minerals by ultra-violate light results in reducing electrons capable of catalyzing the reduction reactions present in the rTCA cycle. Current literature has utilized ion chromatography methods to characterize catalysis of two of the five redox active rTCA cycle compounds with high yield. This technique is unable to produce the untargeted analysis required to anticipate the myriad side reactions driven by excited photoelectrons and their ensuing radicals. By employing liquid chromatography coupled to mass spectrometry (LC-MS) we can examine the complete range of metabolites present across a reaction time series. The three dimensional LC-MS data set allows for the qualitative determination of individual metabolite features, while the comparison of intensities yields quantitative rates. These results allow us to describe the complete set of reactions resultant from a single rTCA cycle organic acid on a photo-activated sphalerite surface and provide a possible mechanism for how metabolic pathways could operate in enzyme free environments.

  2. Uncertainty of Prebiotic Scenarios: The Case of the Non-Enzymatic Reverse Tricarboxylic Acid Cycle

    NASA Astrophysics Data System (ADS)

    Zubarev, Dmitry Yu; Rappoport, Dmitrij; Aspuru-Guzik, Alán

    2015-01-01

    We consider the hypothesis of the primordial nature of the non-enzymatic reverse tricarboxylic acid (rTCA) cycle and describe a modeling approach to quantify the uncertainty of this hypothesis due to the combinatorial aspect of the constituent chemical transformations. Our results suggest that a) rTCA cycle belongs to a degenerate optimum of auto-catalytic cycles, and b) the set of targets for investigations of the origin of the common metabolic core should be significantly extended.

  3. Uncertainty of Prebiotic Scenarios: The Case of the Non-Enzymatic Reverse Tricarboxylic Acid Cycle

    NASA Astrophysics Data System (ADS)

    Zubarev, Dmitry; Rappoport, Dmitrij; Aspuru-Guzik, Alan

    2015-03-01

    We consider the much discussed hypothesis of the primordial nature of the non-enzymatic reverse tricarboxylic acid (rTCA) cycle and describe a modeling approach that quantifies the uncertainty of this hypothesis due to the combinatorial aspect of the constituent chemical transformations. Our results suggest that a) rTCA cycle belongs to a degenerate optimum of auto-catalytic cycles, and b) the set of targets for the investigations of the origin of the common metabolic core should be significantly extended. This work was supported by a grant from the Simons Foundation (SCOL 291937, Dmitry Zubarev).

  4. Prebiotic Metabolism: Production by Mineral Photoelectrochemistry of α-Ketocarboxylic Acids in the Reductive Tricarboxylic Acid Cycle

    NASA Astrophysics Data System (ADS)

    Guzman, Marcelo I.; Martin, Scot T.

    2009-11-01

    A reductive tricarboxylic acid (rTCA) cycle could have fixed carbon dioxide as bio chemically useful energy-storage molecules on early Earth. Nonenzymatic chemical pathways for some steps of the rTCA cycle, however, such as the production of the α-ketocarboxylic acids pyruvate and α-ketoglutarate, remain a challenging problem for the viability of the proposed prebiotic cycle. As a class of compounds, α-ketocarboxylic acids have high free energies of formation that disfavor their production. We report herein the production of pyruvate from lactate and of α-ketoglutarate from pyruvate in the millimolar concentration range as promoted by ZnS mineral photoelectrochemistry. Pyruvate is produced from the photooxidation of lactate with 70% yield and a quantum efficiency of 0.009 at 15°C across the wavelength range of 200-400 nm. The produced pyruvate undergoes photoreductive back reaction to lactate at a 30% yield and with a quantum efficiency of 0.0024. Pyruvate alternatively continues in photooxidative forward reaction to α-ketoglutarate with a 50% yield and a quantum efficiency of 0.0036. The remaining 20% of the carbon follows side reactions that produce isocitrate, glutarate, and succinate. Small amounts of acetate are also produced. The results of this study suggest that α-ketocarboxylic acids produced by mineral photoelectrochemistry could have participated in a viable enzyme-free cycle for carbon fixation in an environment where light, sulfide minerals, carbon dioxide, and other organic compounds interacted on prebiotic Earth.

  5. 75 FR 9017 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-26

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  6. 75 FR 52590 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  7. 76 FR 34124 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-10

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  8. 76 FR 11847 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-03

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  9. 75 FR 29811 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-27

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  10. 76 FR 58077 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-19

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  11. 76 FR 27743 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Program Management Committee meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of the RTCA Program Management Committee. DATES:...

  12. Oxaloacetate-to-malate conversion by mineral photoelectrochemistry: implications for the viability of the reductive tricarboxylic acid cycle in prebiotic chemistry

    NASA Astrophysics Data System (ADS)

    Guzman, Marcelo I.; Martin, Scot T.

    2008-10-01

    The carboxylic acids produced by the reductive tricarboxylic acid (rTCA) cycle are possibly a biosynthetic core of initial life, although several steps such as the reductive kinetics of oxaloacetate (OAA) to malate (MA) are problematic by conventional chemical routes. In this context, we studied the kinetics of this reaction as promoted by ZnS mineral photoelectrochemistry. The quantum efficiency φMA of MA production from the photoelectrochemical reduction of OAA followed φMA=0.13 [OAA] (2.1×10-3+[OAA])-1 and was independent of temperature (5 to 50°C). To evaluate the importance of this forward rate under a prebiotic scenario, we also studied the temperature-dependent rate of the backward thermal decarboxylation of OAA to pyruvate (PA), which followed an Arrhenius behavior as log (k-2)=11.74 4956/T, where k-2 is in units of s-1. These measured rates were employed in conjunction with the indirectly estimated carboxylation rate of PA to OAA to assess the possible importance of mineral photoelectrochemistry in the conversion of OAA to MA under several scenarios of prebiotic conditions on early Earth. As an example, our analysis shows that there is 90% efficiency with a forward velocity of 3 yr/cycle for the OAA→MA step of the rTCA cycle at 280 K. Efficiency and velocity both decrease for increasing temperature. These results suggest high viability for mineral photoelectrochemistry as an enzyme-free engine to drive the rTCA cycle through the early aeons of early Earth, at least for the investigated OAA→MA step.

  13. 76 FR 74842 - RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-01

    ... Federal Aviation Administration RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management Committee... Management Committee DATES: The meeting will be held December 13, 2011, from 8:30 a.m.-1:30 p.m....

  14. Tropospheric cycle of nitrous acid

    NASA Astrophysics Data System (ADS)

    Harrison, Roy M.; Peak, John D.; Collins, Gareth M.

    1996-06-01

    Measurements of the land surface exchange of nitrous acid over grass and sugar beet surfaces reveal both upward and downward fluxes with flux reversal occurring at an ambient concentration of nitrogen dioxide of about 10 ppb. This confirms earlier preliminary findings and strengthens the hypothesis that substantial production of nitrous acid can occur on land surfaces from reaction of nitrogen dioxide and water vapor. Detailed measurements of nitrous acid have been made in central urban, suburban, and rural environments. These measurements, in conjunction with a simple box model, indicate that the atmospheric concentrations of nitrous acid are explicable in terms of a small number of basic processes in which the most important are the surface production of nitrous acid from nitrogen dioxide, atmospheric production from the NO-OH reaction and loss of nitrous acid by photolysis and dry deposition. In the suburban atmosphere, concentrations of nitrous acid are strongly correlated with nitrogen dioxide. In the rural atmosphere a different behavior is seen, with much higher nitrous acid to nitrogen dioxide ratios occurring in more polluted air with nitrogen dioxide concentrations in excess of 10 ppb. At lower nitrogen dioxide concentrations, net deposition of nitrous acid at the ground leads to very low concentrations in advected air. The model study indicates that during daytime in the suburban atmosphere, production of HONO from the NO-OH reaction can compete with photolysis giving a HONO concentration of a few tenths of a part per billion. At the highest observed daytime concentrations of HONO, production of OH radical from its photolysis can proceed at a rate more than 10 times faster than from photolysis of ozone.

  15. 77 FR 2342 - Fifth Meeting: RTCA, Next Gen Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... TRANSPORTATION Federal Aviation Administration Fifth Meeting: RTCA, Next Gen Advisory Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA, NextGen... RTCA, NextGen Advisory Committee. DATES: The meeting will be held February 3, 2012, from 9:30...

  16. 75 FR 60495 - Eighteenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-30

    ... Federal Aviation Administration Eighteenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 203... RTCA Special Committee 203: Unmanned Aircraft Systems. DATES: The meeting will be held October...

  17. 75 FR 2925 - Sixteenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-19

    ... Federal Aviation Administration Sixteenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 203... RTCA Special Committee 203: Unmanned Aircraft Systems. DATES: The meeting will be held February...

  18. 77 FR 16890 - Eighteenth Meeting: RTCA Special Committee 213, Enhanced Flight Visions Systems/Synthetic Vision...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-22

    ... Federal Aviation Administration Eighteenth Meeting: RTCA Special Committee 213, Enhanced Flight Visions... of Transportation (DOT). ACTION: Notice of meeting RTCA Special Committee 213, Enhanced Flight... public of the eighteenth meeting of RTCA Special Committee 213, Enhanced Flight Visions...

  19. Tricarboxylic-acid-cycle intermediates and cycle endurance capacity.

    PubMed

    Brown, Amy C; Macrae, Holden S H; Turner, Nathan S

    2004-12-01

    The purpose of this study was to determine whether ingestion of a multinutrient supplement containing 3 tricarboxylic-acid-cycle intermediates (TCAIs; pyridoxine-alpha-ketoglutarate, malate, and succinate) and other substances potentially supporting the TCA cycle (such as aspartate and glutamate) would improve cyclists' time to exhaustion during a submaximal endurance-exercise test (approximately 70 % to 75 % VO2peak) and rate of recovery. Seven well-trained male cyclists (VO2max 67.4 2.1 mL x kg(-1) x in(-1), 28.6 +/- 2.4 y) participated in a randomized, double-blind crossover study for 7 wk. Each took either the treatment or a placebo 30 min before and after their normal training sessions for 3 wk and before submaximal exercise tests. There were no significant differences between the TCAI group (KI) and placebo group (P) in time to exhaustion during cycling (KI = 105 +/- 18, P = 113 +/- 11 min); respiratory-exchange ratio at 20-min intervals; blood lactate and plasma glucose before, after, and at 30-min intervals during exercise; perceived exertion at 20-min intervals during exercise; or time to fatigue after the 30-min recovery (KI = 16.1 +/- 3.2, P = 15 +/- 2 min). Taking a dietary sport supplement containing several TCAIs and supporting substances for 3 wk does not improve cycling performance at 75 % VO2peak or speed recovery from previously fatiguing exercise.

  20. Sulfuric acid-sulfur heat storage cycle

    DOEpatents

    Norman, John H.

    1983-12-20

    A method of storing heat is provided utilizing a chemical cycle which interconverts sulfuric acid and sulfur. The method can be used to levelize the energy obtained from intermittent heat sources, such as solar collectors. Dilute sulfuric acid is concentrated by evaporation of water, and the concentrated sulfuric acid is boiled and decomposed using intense heat from the heat source, forming sulfur dioxide and oxygen. The sulfur dioxide is reacted with water in a disproportionation reaction yielding dilute sulfuric acid, which is recycled, and elemental sulfur. The sulfur has substantial potential chemical energy and represents the storage of a significant portion of the energy obtained from the heat source. The sulfur is burned whenever required to release the stored energy. A particularly advantageous use of the heat storage method is in conjunction with a solar-powered facility which uses the Bunsen reaction in a water-splitting process. The energy storage method is used to levelize the availability of solar energy while some of the sulfur dioxide produced in the heat storage reactions is converted to sulfuric acid in the Bunsen reaction.

  1. Citric acid cycle intermediates in cardioprotection.

    PubMed

    Czibik, Gabor; Steeples, Violetta; Yavari, Arash; Ashrafian, Houman

    2014-10-01

    Over the last decade, there has been a concerted clinical effort to deliver on the laboratory promise that a variety of maneuvers can profoundly increase cardiac tolerance to ischemia and/or reduce additional damage consequent upon reperfusion. Here we will review the proximity of the metabolic approach to clinical practice. Specifically, we will focus on how the citric acid cycle is involved in cardioprotection. Inspired by cross-fertilization between fundamental cancer biology and cardiovascular medicine, a set of metabolic observations have identified novel metabolic pathways, easily manipulable in man, which can harness metabolism to robustly combat ischemia-reperfusion injury.

  2. 75 FR 14482 - Fifty-First Meeting: RTCA Special Committee 186: Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-25

    ... include: Specific Working Group Sessions Tuesday, April 13 RTCA--All Day, WG-1, SURF IA (Leaders), Garmin... RTCA--All Day, WG-1, SURF-IA (Leaders), Garmin Room. RTCA--All Day, WG-1, Wake Vortex, ARINC Room. RTCA..., WG-1, SURF IA (Leaders), Garmin Room. RTCA--All Day, WG-1, Wake Vortex, MacIntosh-NBAA Room &...

  3. 78 FR 14151 - Meeting: RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-04

    ... Federal Aviation Administration Meeting: RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management... Management Committee. DATES: The meeting will be held March 20, 2013, from 8:30 a.m.-1:30 p.m. ADDRESSES:...

  4. 77 FR 12905 - Meeting: RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-02

    ... Federal Aviation Administration Meeting: RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management... Program Management Committee. DATES: The meeting will be held March 21, 2012, from 8:30 a.m.-1:30...

  5. 78 FR 57673 - RTCA Program Management Committee; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... Federal Aviation Administration RTCA Program Management Committee; Meeting AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management... Management Committee. DATES: The meeting will be held October 8, 2013 from 8:30 a.m.-1:30 a.m. ADDRESSES:...

  6. 78 FR 43962 - Meeting: RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ... Federal Aviation Administration Meeting: RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management... Management Committee. DATES: The meeting will be held August 12, from 10:00 a.m.-2:00 p.m. ADDRESSES:...

  7. 78 FR 72747 - Meeting: RTCA Program Management Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-03

    ... Federal Aviation Administration Meeting: RTCA Program Management Committee AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Program Management... Management Committee. DATES: The meeting will be held December 18, from 8:30 a.m.-5:00 p.m. ADDRESSES:...

  8. The Pyruvate-Tricarboxylic Acid Cycle Node

    PubMed Central

    Bücker, René; Heroven, Ann Kathrin; Becker, Judith; Dersch, Petra; Wittmann, Christoph

    2014-01-01

    Despite our increasing knowledge of the specific pathogenicity factors in bacteria, the contribution of metabolic processes to virulence is largely unknown. Here, we elucidate a tight connection between pathogenicity and core metabolism in the enteric pathogen Yersinia pseudotuberculosis by integrated transcriptome and [13C]fluxome analysis of the wild type and virulence-regulator mutants. During aerobic growth on glucose, Y. pseudotuberculosis reveals an unusual flux distribution with a high level of secreted pyruvate. The absence of the transcriptional and post-transcriptional regulators RovA, CsrA, and Crp strongly perturbs the fluxes of carbon core metabolism at the level of pyruvate metabolism and the tricarboxylic acid (TCA) cycle, and these perturbations are accompanied by transcriptional changes in the corresponding enzymes. Knock-outs of regulators of this metabolic branch point and of its central enzyme, pyruvate kinase (ΔpykF), result in mutants with significantly reduced virulence in an oral mouse infection model. In summary, our work identifies the pyruvate-TCA cycle node as a focal point for controlling the host colonization and virulence of Yersinia. PMID:25164818

  9. Cell cycle nucleic acids, polypeptides and uses thereof

    DOEpatents

    Gordon-Kamm, William J.; Lowe, Keith S.; Larkins, Brian A.; Dilkes, Brian R.; Sun, Yuejin

    2007-08-14

    The invention provides isolated nucleic acids and their encoded proteins that are involved in cell cycle regulation. The invention further provides recombinant expression cassettes, host cells, transgenic plants, and antibody compositions. The present invention provides methods and compositions relating to altering cell cycle protein content, cell cycle progression, cell number and/or composition of plants.

  10. Citric acid cycle and role of its intermediates in metabolism.

    PubMed

    Akram, Muhammad

    2014-04-01

    The citric acid cycle is the final common oxidative pathway for carbohydrates, fats and amino acids. It is the most important metabolic pathway for the energy supply to the body. TCA is the most important central pathway connecting almost all the individual metabolic pathways. In this review article, introduction, regulation and energetics of TCA cycle have been discussed. The present study was carried out to review literature on TCA cycle.

  11. 78 FR 16757 - First Meeting: RTCA Tactical Operations Committee (TOC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration First Meeting: RTCA Tactical Operations Committee (TOC) AGENCY: Federal... Discussion Committee Operations FAA Taskings Discussion FAA Task Groups Discussion Anticipated Issues for...

  12. 78 FR 40264 - First Meeting: RTCA Tactical Operations Committee (TOC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-03

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration First Meeting: RTCA Tactical Operations Committee (TOC) AGENCY: Federal... approval: Terms of Reference--Structure, Scope, Leadership Anticipated Issues for TOC consideration...

  13. 78 FR 8684 - Fifteenth Meeting: RTCA Special Committee 217-Aeronautical Databases Joint with EUROCAE WG-44...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-06

    ... Federal Aviation Administration Fifteenth Meeting: RTCA Special Committee 217--Aeronautical Databases Joint with EUROCAE WG-44--Aeronautical Databases AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 217--Aeronautical...

  14. 78 FR 25134 - Sixteenth Meeting: RTCA Special Committee 217-Aeronautical Databases Joint With EUROCAE WG-44...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-29

    ... Federal Aviation Administration Sixteenth Meeting: RTCA Special Committee 217--Aeronautical Databases Joint With EUROCAE WG-44--Aeronautical Databases AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 217--Aeronautical...

  15. 78 FR 51809 - Seventeenth Meeting: RTCA Special Committee 217-Aeronautical Databases Joint With EUROCAE WG-44...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-21

    ... Federal Aviation Administration Seventeenth Meeting: RTCA Special Committee 217--Aeronautical Databases Joint With EUROCAE WG-44--Aeronautical Databases AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 217--Aeronautical...

  16. 77 FR 30046 - Ninth Meeting: RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite (Route) Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-21

    ... Satellite (Route) Services AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite... RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite (Route) Services. DATES: The...

  17. 77 FR 48584 - Tenth Meeting: RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite (Route) Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-14

    ... Satellite (Route) Services AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite... RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite (Route) Services. DATES: The...

  18. 78 FR 69928 - 35th Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-21

    ...-fifth meeting of the RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link... Federal Aviation Administration 35th Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link Services AGENCY: Federal Aviation Administration (FAA), U.S. Department...

  19. 78 FR 5242 - 32nd Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-24

    ...-second meeting of the RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link... Federal Aviation Administration 32nd Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link Services AGENCY: Federal Aviation Administration (FAA), U.S. Department...

  20. 78 FR 20167 - 33rd Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-03

    ...-first meeting of the RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link... Federal Aviation Administration 33rd Meeting: RTCA Special Committee 206, Aeronautical Information and Meteorological Data Link Services AGENCY: Federal Aviation Administration (FAA), U.S. Department...

  1. 75 FR 7305 - RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC) Revised Agenda...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-18

    ... Federal Aviation Administration RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC... RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC) revised agenda--rescheduled.../Industry Air Traffic Management Advisory Committee (ATMAC) revised agenda--rescheduled meeting. DATES:...

  2. 75 FR 52591 - Seventh Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... and Alternative Flight Deck Security Procedures AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 221 meeting: Aircraft Secondary Barriers and Alternative Flight... RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight Deck Security...

  3. 75 FR 55847 - Fourteenth Meeting: EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-14

    ... Federal Aviation Administration Fourteenth Meeting: EUROCAE WG-72: RTCA Special Committee 216...: Notice of EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security (Joint Meeting). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of EUROCAE WG-72: RTCA...

  4. 76 FR 50811 - Seventeenth Meeting: EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... Federal Aviation Administration Seventeenth Meeting: EUROCAE WG-72: RTCA Special Committee 216...: Notice of EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security (Joint Meeting). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of EUROCAE WG-72: RTCA...

  5. 76 FR 80447 - Eighth Meeting: RTCA Special Committee 219: Attitude and Heading Reference Systems (AHRS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-23

    ... Federal Aviation Administration Eighth Meeting: RTCA Special Committee 219: Attitude and Heading Reference...). ACTION: Notice of RTCA Special Committee 219: Attitude and Heading Reference Systems (AHRS). SUMMARY: The FAA is issuing this notice to advise the public of the eighth meeting of RTCA Special Committee...

  6. 76 FR 66350 - Eighteenth Meeting: RTCA Special Committee 205/EUROCAE WG-71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-26

    ... Federal Aviation Administration Eighteenth Meeting: RTCA Special Committee 205/EUROCAE WG-71: Software... Transportation (DOT). ACTION: Notice of RTCA Special Committee 205/EUROCAE WG-71 meeting: Software Considerations... RTCA Special Committee 205/EUROCAE WG-71: Software Considerations in Aeronautical Systems Agenda...

  7. 78 FR 20168 - Twenty Fourth Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-03

    ... Federal Aviation Administration Twenty Fourth Meeting: RTCA Special Committee 203, Unmanned Aircraft...: Meeting Notice of RTCA Special Committee 203, Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twenty third meeting of RTCA Special Committee 203, Unmanned...

  8. 77 FR 3029 - Twentieth Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-20

    ... Federal Aviation Administration Twentieth Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems... RTCA Special Committee 203, Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twentieth meeting of RTCA Special Committee 203, Unmanned Aircraft...

  9. 76 FR 24957 - Nineteenth Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-03

    ... Federal Aviation Administration Nineteenth Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 203 meeting... RTCA Special Committee 203: Unmanned Aircraft Systems. DATES: The meeting will be held May 17-19,...

  10. 75 FR 26321 - Seventeenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-11

    ... Federal Aviation Administration Seventeenth Plenary Meeting: RTCA Special Committee 203: Unmanned Aircraft Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 203... RTCA Special Committee 203: Unmanned Aircraft Systems. DATES: The meeting will be held June 8-10,...

  11. 77 FR 25781 - Twenty-First Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-01

    ... Federal Aviation Administration Twenty-First Meeting: RTCA Special Committee 203, Unmanned Aircraft...: Meeting Notice of RTCA Special Committee 203, Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twenty-first meeting of RTCA Special Committee 203, Unmanned...

  12. 77 FR 50207 - Twenty-Second Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-20

    ... Federal Aviation Administration Twenty-Second Meeting: RTCA Special Committee 203, Unmanned Aircraft...: Meeting notice of RTCA Special Committee 203, Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twenty-second meeting of RTCA Special Committee 203, Unmanned...

  13. 78 FR 6400 - Twenty Third Meeting: RTCA Special Committee 203, Unmanned Aircraft Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-30

    ... Federal Aviation Administration Twenty Third Meeting: RTCA Special Committee 203, Unmanned Aircraft...: Meeting Notice of RTCA Special Committee 203, Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twenty third meeting of RTCA Special Committee 203, Unmanned...

  14. 78 FR 8684 - Twelfth Meeting: RTCA Special Committee 222, Inmarsat AMS(R)S

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-06

    ... Federal Aviation Administration Twelfth Meeting: RTCA Special Committee 222, Inmarsat AMS(R)S AGENCY... RTCA Special Committee 222, Inmarsat AMS(R)S. SUMMARY: The FAA is issuing this notice to advise the public of the twelfth meeting of the RTCA Special Committee 222, Inmarsat AMS(R)S. DATES: The...

  15. 78 FR 5860 - Eighth Meeting: RTCA Next Gen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-28

    ... Federal Aviation Administration Eighth Meeting: RTCA Next Gen Advisory Committee (NAC) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA NextGen... meeting of the RTCA NextGen Advisory Committee (NAC). DATES: The meeting will be held February 7,...

  16. 76 FR 22162 - Third Meeting RTCA NextGen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-20

    ... Federal Aviation Administration Third Meeting RTCA NextGen Advisory Committee (NAC) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: RTCA NextGen Advisory Committee (NAC). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA NextGen Advisory Committee (NAC). DATES:...

  17. 76 FR 54526 - Fourth Meeting RTCA NextGen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-01

    ... Federal Aviation Administration Fourth Meeting RTCA NextGen Advisory Committee (NAC) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: RTCA NextGen Advisory Committee (NAC). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA NextGen Advisory Committee (NAC). DATES:...

  18. 78 FR 28940 - Ninth Meeting: RTCA Next Gen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-16

    ... Federal Aviation Administration Ninth Meeting: RTCA Next Gen Advisory Committee (NAC) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA NextGen... of the RTCA NextGen Advisory Committee (NAC). DATES: The meeting will be held June 4, 2013 from...

  19. 75 FR 1116 - RTCA Government/Industry Air Traffic Management Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-08

    ... Federal Aviation Administration RTCA Government/Industry Air Traffic Management Advisory Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Government/Industry Air Traffic... RTCA Government/Industry Air Traffic Management Advisory Committee. DATES: The meeting will be...

  20. 77 FR 56254 - 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-12

    ... Federal Aviation Administration 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held October 5,...

  1. 78 FR 57672 - 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... Federal Aviation Administration 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS) DATES: The meeting will be held October 7-11,...

  2. 78 FR 13396 - 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-27

    ... Federal Aviation Administration 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held March 12-15,...

  3. 76 FR 67019 - Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ... Federal Aviation Administration Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS... RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System...

  4. 77 FR 12106 - 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-28

    ... Federal Aviation Administration 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS... RTCA Special Committee 159, Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of the 88th meeting of RTCA Special Committee 159, Global Positioning System...

  5. 78 FR 33145 - Meeting: RTCA Special Committee 223, Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-03

    ... Federal Aviation Administration Meeting: RTCA Special Committee 223, Airport Surface Wireless...: Meeting Notice of RTCA Special Committee 223, Airport Surface Wireless Communications. SUMMARY: The FAA is issuing this notice to advise the public of the meeting of the RTCA Special Committee 223, Airport...

  6. 77 FR 2342 - Seventeenth Meeting: RTCA Special Committee 213, Enhanced Flight Vision/Synthetic Vision Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... Federal Aviation Administration Seventeenth Meeting: RTCA Special Committee 213, Enhanced Flight Vision... Transportation (DOT). ACTION: Notice of RTCA Special Committee 213, Enhanced Flight Vision/ Synthetic Vision... meeting of RTCA Special Committee 213, Enhanced Flight Vision/Synthetic Vision Systems (EFVS/SVS)....

  7. 78 FR 55774 - Twenty Fourth Meeting: RTCA Special Committee 213, Enhanced Flight Vision Systems/Synthetic...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-11

    ... TRANSPORTATION Federal Aviation Administration Twenty Fourth Meeting: RTCA Special Committee 213, Enhanced Flight.... Department of Transportation (DOT). ACTION: Meeting notice of RTCA Special Committee 213, Enhanced Flight... public of the twenty fourth meeting of the RTCA Special Committee 213, Enhanced Flight Vision...

  8. 78 FR 13395 - Meeting: RTCA Special Committee 223, Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-27

    ... Federal Aviation Administration Meeting: RTCA Special Committee 223, Airport Surface Wireless...: Meeting Notice of RTCA Special Committee 223, Airport Surface Wireless Communications SUMMARY: The FAA is issuing this notice to advise the public of the meeting of the RTCA Special Committee 223, Airport...

  9. 75 FR 66423 - Seventh Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-28

    ... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 223: Airport Surface Wireless... of RTCA Special Committee 223: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport...

  10. 75 FR 54421 - Sixth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-07

    ... Federal Aviation Administration Sixth Meeting: RTCA Special Committee 223: Airport Surface Wireless... of RTCA Special Committee 223: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport...

  11. 77 FR 37732 - Fourteenth Meeting: RTCA Special Committee 223, Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-22

    ... Federal Aviation Administration Fourteenth Meeting: RTCA Special Committee 223, Airport Surface Wireless...: Meeting Notice of RTCA Special Committee 223, Airport Surface Wireless Communications. SUMMARY: The FAA is issuing this notice to advise the public of the meeting of RTCA Special Committee 223, Airport...

  12. 77 FR 71028 - Twelfth Meeting: RTCA Special Committee 223, Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-28

    ... Federal Aviation Administration Twelfth Meeting: RTCA Special Committee 223, Airport Surface Wireless...: Meeting Notice of RTCA Special Committee 223, Airport Surface Wireless Communications. SUMMARY: The FAA is issuing this notice to advise the public of the meeting of the RTCA Special Committee 223, Airport...

  13. 76 FR 20436 - Ninth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-12

    ... Federal Aviation Administration Ninth Meeting: RTCA Special Committee 223: Airport Surface Wireless... of RTCA Special Committee 223: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport...

  14. 76 FR 6179 - Eighth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-03

    ... Federal Aviation Administration Eighth Meeting: RTCA Special Committee 223: Airport Surface Wireless... of RTCA Special Committee 223: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport...

  15. 76 FR 38740 - Tenth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... Federal Aviation Administration Tenth Meeting: RTCA Special Committee 223: Airport Surface Wireless... of RTCA Special Committee 223: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport...

  16. 78 FR 51810 - Twenty-Fourth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-21

    ... Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control... RTCA Special Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held on... TRANSPORTATION Federal Aviation Administration Twenty-Fourth Meeting: RTCA Special Committee 224,...

  17. 76 FR 67019 - Tenth Meeting: RTCA Special Committee 224, Airport Security Access Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ... Federal Aviation Administration Tenth Meeting: RTCA Special Committee 224, Airport Security Access Control... RTCA Special Committee 224, Airport Security Access Control. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224, Airport Security Access Control. DATES:...

  18. Metabolism: Part II. The Tricarboxylic Acid (TCA), Citric Acid, or Krebs Cycle.

    ERIC Educational Resources Information Center

    Bodner, George M.

    1986-01-01

    Differentiates the tricarboxylic acid (TCA) cycle (or Krebs cycle) from glycolysis, and describes the bridge between the two as being the conversion of pyruvate into acetyl coenzyme A. Discusses the eight steps in the TCA cycle, the results of isotopic labeling experiments, and the net effects of the TCA cycle. (TW)

  19. Sulfuric acid on Europa and the radiolytic sulfur cycle

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.; Johnson, R. E.; Anderson, M. S.

    1999-01-01

    A comparison of laboratory spectra with Galileo data indicates that hydrated sulfuric acid is present and is a major component of Europa's surface. In addition, this moon's visually dark surface material, which spatially correlates with the sulfuric acid concentration, is identified as radiolytically altered sulfur polymers. Radiolysis of the surface by magnetospheric plasma bombardment continuously cycles sulfur between three forms: sulfuric acid, sulfur dioxide, and sulfur polymers, with sulfuric acid being about 50 times as abundant as the other forms. Enhanced sulfuric acid concentrations are found in Europa's geologically young terrains, suggesting that low-temperature, liquid sulfuric acid may influence geological processes.

  20. Patterns of diversity of citric acid cycle enzymes.

    PubMed

    Weitzman, P D

    1987-01-01

    The citric acid cycle performs a dual role in cell metabolism, acting as a source of both 'energy' and biosynthetic starting materials. The widespread occurrence of the cycle throughout Nature is an excellent example of the unity of biochemistry, but closer examination reveals that there is considerable diversity in the citric acid cycle of different organisms with respect to metabolic role, molecular enzymology and mode of regulation. Two enzymes of the cycle--citrate synthase and succinate thiokinase--have been found to exhibit particularly striking patterns of diversity in structure and catalytic and regulatory function. Some of these patterns show a correlation with the taxonomic groupings of the organisms and with their physiological characteristics. Comparative enzyme studies have a contribution to make to an ultimate understanding of the cycle and its cellular operation, and there are substantial benefits to be gained from interactive studies on both prokaryotic and eukaryotic systems.

  1. Combined cycle phosphoric acid fuel cell electric power system

    SciTech Connect

    Mollot, D.J.; Micheli, P.L.

    1995-12-31

    By arranging two or more electric power generation cycles in series, combined cycle systems are able to produce electric power more efficiently than conventional single cycle plants. The high fuel to electricity conversion efficiency results in lower plant operating costs, better environmental performance, and in some cases even lower capital costs. Despite these advantages, combined cycle systems for the 1 - 10 megawatt (MW) industrial market are rare. This paper presents a low noise, low (oxides of nitrogen) NOx, combined cycle alternative for the small industrial user. By combining a commercially available phosphoric acid fuel cell (PAFC) with a low-temperature Rankine cycle (similar to those used in geothermal applications), electric conversion efficiencies between 45 and 47 percent are predicted. While the simple cycle PAFC is competitive on a cost of energy basis with gas turbines and diesel generators in the 1 to 2 MW market, the combined cycle PAFC is competitive, on a cost of energy basis, with simple cycle diesel generators in the 4 to 25 MW market. In addition, the efficiency and low-temperature operation of the combined cycle PAFC results in a significant reduction in carbon dioxide emissions with NO{sub x} concentration on the order of 1 parts per million (per weight) (ppmw).

  2. Citric acid cycle and the origin of MARS.

    PubMed

    Eswarappa, Sandeepa M; Fox, Paul L

    2013-05-01

    The vertebrate multiaminoacyl tRNA synthetase complex (MARS) is an assemblage of nine aminoacyl tRNA synthetases (ARSs) and three non-synthetase scaffold proteins, aminoacyl tRNA synthetase complex-interacting multifunctional protein (AIMP)1, AIMP2, and AIMP3. The evolutionary origin of the MARS is unclear, as is the significance of the inclusion of only nine of 20 tRNA synthetases. Eight of the nine amino acids corresponding to ARSs of the MARS are derived from two citric acid cycle intermediates, α-ketoglutatrate and oxaloacetate. We propose that the metabolic link with the citric acid cycle, the appearance of scaffolding proteins AIMP2 and AIMP3, and the subsequent disappearance of the glyoxylate cycle, together facilitated the origin of the MARS in a common ancestor of metazoans and choanoflagellates.

  3. 78 FR 63279 - Third Meeting: RTCA Tactical Operations Committee (TOC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-23

    ... Federal Aviation Administration Third Meeting: RTCA Tactical Operations Committee (TOC) AGENCY: Federal... Committee (TOC). The agenda will include the following: November 19, 2013 Opening of Meeting/Introduction of TOC Members Official Statement of Designated Federal Official Approval of July 23, 2013...

  4. Commercial Alloys for Sulfuric Acid Vaporization in Thermochemical Hydrogen Cycles

    SciTech Connect

    Thomas M. Lillo; Karen M. Delezene-Briggs

    2005-10-01

    Most thermochemical cycles being considered for producing hydrogen include a processing stream in which dilute sulfuric acid is concentrated, vaporized and then decomposed over a catalyst. The sulfuric acid vaporizer is exposed to highly aggressive conditions. Liquid sulfuric acid will be present at a concentration of >96 wt% (>90 mol %) H2SO4 and temperatures exceeding 400oC [Brown, et. al, 2003]. The system will also be pressurized, 0.7-3.5 MPa, to keep the sulfuric acid in the liquid state at this temperature and acid concentration. These conditions far exceed those found in the commercial sulfuric acid generation, regeneration and handling industries. Exotic materials, e.g. ceramics, precious metals, clad materials, etc., have been proposed for this application [Wong, et. al., 2005]. However, development time, costs, reliability, safety concerns and/or certification issues plague such solutions and should be considered as relatively long-term, optimum solutions. A more cost-effective (and relatively near-term) solution would be to use commercially-available metallic alloys to demonstrate the cycle and study process variables. However, the corrosion behavior of commercial alloys in sulfuric acid is rarely characterized above the natural boiling point of concentrated sulfuric acid (~250oC at 1 atm). Therefore a screening study was undertaken to evaluate the suitability of various commercial alloys for concentration and vaporization of high-temperature sulfuric acid. Initially alloys were subjected to static corrosion tests in concentrated sulfuric acid (~95-97% H2SO4) at temperatures and exposure times up to 200oC and 480 hours, respectively. Alloys with a corrosion rate of less than 5 mm/year were then subjected to static corrosion tests at a pressure of 1.4 MPa and temperatures up to 375oC. Exposure times were shorter due to safety concerns and ranged from as short as 5 hours up to 144 hours. The materials evaluated included nickel-, iron- and cobalt

  5. Sporulation of Tricarboxylic Acid Cycle Mutants of Bacillus subtilis

    PubMed Central

    Yousten, Allan A.; Hanson, Richard S.

    1972-01-01

    A mutant of Bacillus subtilis 168 lacking aconitase (EC 4.2.1.3) was found to be blocked at stage 0 or I of sporulation. Although adenosine triphosphate levels, which normally decrease in tricarboxylic acid cycle mutants at the completion of exponential growth, could be maintained at higher levels by feeding metabolizable carbon sources, this did not permit the cells to progress further into the sporulation sequence. When post-exponential-phase cells of mutants blocked in the first half of the tricarboxylic acid cycle were resuspended with an energy source in culture fluid from post-exponential-phase wild-type B. subtilis or Escherichia coli, good sporulation occurred. The spores produced retained the mutant genotype and were heat stable but lost refractility and heat stability several hours after their production. Images PMID:4110146

  6. 76 FR 70531 - Tenth Meeting: RTCA Special Committee 217/EUROCAE WG-44: Terrain and Airport Mapping Databases

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-14

    ... Federal Aviation Administration Tenth Meeting: RTCA Special Committee 217/EUROCAE WG-44: Terrain and... RTCA Special Committee 217/EUROCAE WG-44: Terrain and Airport Mapping Databases: For the tenth meeting... meeting of RTCA Special Committee 217/EUROCAE WG-44: Terrain and Airport Mapping Databases. The...

  7. 78 FR 16756 - Twenty-Second Meeting: RTCA Special Committee 213, Enhanced Flight Vision Systems/Synthetic...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... Federal Aviation Administration Twenty-Second Meeting: RTCA Special Committee 213, Enhanced Flight Vision... of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 213, Enhanced Flight Vision... of the twenty-second meeting of the RTCA Special Committee 213, Enhanced Flight Vision...

  8. Bioluminescence regenerative cycle (BRC) system for nucleic acid quantification assays

    NASA Astrophysics Data System (ADS)

    Hassibi, Arjang; Lee, Thomas H.; Davis, Ronald W.; Pourmand, Nader

    2003-07-01

    A new label-free methodology for nucleic acid quantification has been developed where the number of pyrophosphate molecules (PPi) released during polymerization of the target nucleic acid is counted and correlated to DNA copy number. The technique uses the enzymatic complex of ATP-sulfurylase and firefly luciferase to generate photons from PPi. An enzymatic unity gain positive feedback is also implemented to regenerate the photon generation process and compensate any decay in light intensity by self regulation. Due to this positive feedback, the total number of photons generated by the bioluminescence regenerative cycle (BRC) can potentially be orders of magnitude higher than typical chemiluminescent processes. A system level kinetic model that incorporates the effects of contaminations and detector noise was used to show that the photon generation process is in fact steady and also proportional to the nucleic acid quantity. Here we show that BRC is capable of detecting quantities of DNA as low as 1 amol (10-18 mole) in 40μlit aqueous solutions, and this enzymatic assay has a controllable dynamic range of 5 orders of magnitude. The sensitivity of this technology, due to the excess number of photons generated by the regenerative cycle, is not constrained by detector performance, but rather by possible PPi or ATP (adenosine triphosphate) contamination, or background bioluminescence of the enzymatic complex.

  9. Maintenance Carbon Cycle in Crassulacean Acid Metabolism Plant Leaves 1

    PubMed Central

    Kenyon, William H.; Severson, Ray F.; Black, Clanton C.

    1985-01-01

    The reciprocal relationship between diurnal changes in organic acid and storage carbohydrate was examined in the leaves of three Crassulacean acid metabolism plants. It was found that depletion of leaf hexoses at night was sufficient to account quantitatively for increase in malate in Ananas comosus but not in Sedum telephium or Kalanchoë daigremontiana. Fructose and to a lesser extent glucose underwent the largest changes. Glucose levels in S. telephium leaves oscillated diurnally but were not reciprocally related to malate fluctuations. Analysis of isolated protoplasts and vacuoles from leaves of A. comosus and S. telephium revealed that vacuoles contain a large percentage (>50%) of the protoplast glucose, fructose and malate, citrate, isocitrate, ascorbate and succinate. Sucrose, a major constituent of intact leaves, was not detectable or was at extremely low levels in protoplasts and vacuoles from both plants. In isolated vacuoles from both A. comosus and S. telephium, hexose levels decreased at night at the same time malate increased. Only in A. comosus, however, could hexose metabolism account for a significant amount of the nocturnal increase in malate. We conclude that, in A. comosus, soluble sugars are part of the daily maintenance carbon cycle and that the vacuole plays a dynamic role in the diurnal carbon assimilation cycle of this Crassulacean acid metabolism plant. PMID:16664005

  10. 76 FR 3931 - Second Meeting RTCA NextGen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-21

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Second Meeting RTCA NextGen Advisory Committee (NAC) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: RTCA NextGen Advisory Committee (NAC). SUMMARY: The FAA...

  11. 78 FR 43963 - Sixty-Second Meeting: RTCA Special Committee 135, Environmental Conditions and Test Procedures...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Sixty-Second Meeting: RTCA Special Committee 135, Environmental Conditions... public of the Sixty-Second meeting of the RTCA Special Committee 135, Environmental Conditions and...

  12. 78 FR 38093 - Seventh Meeting: RTCA Special Committee 226, Audio Systems and Equipment

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-25

    ... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 226, Audio Systems and Equipment... Notice of RTCA Special Committee 226, Audio Systems and Equipment. SUMMARY: The FAA is issuing this... Equipment ] DATES: The meeting will be held July 15-19, 2013 from 9:00 a.m.-5:00 p.m. ADDRESSES: The...

  13. 76 FR 50810 - Seventh Meeting: RTCA Special Committee 219: Attitude and Heading Reference System

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... Committee 219 meeting: Attitude and Heading Reference System. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 219: Attitude and Heading Reference System... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 219: Attitude and...

  14. 78 FR 7476 - Fifth Meeting: RTCA Special Committee 227, Standards of Navigation Performance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ... Federal Aviation Administration Fifth Meeting: RTCA Special Committee 227, Standards of Navigation...: Meeting Notice of RTCA Special Committee 227, Standards of Navigation Performance. SUMMARY: The FAA is... of Navigation Performance. DATES: The meeting will be held February 11-15, 2013 from 9:00 a.m. to...

  15. 78 FR 51809 - Seventh Meeting: RTCA Special Committee 227, Standards of Navigation Performance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-21

    ... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 227, Standards of Navigation...: Meeting Notice of RTCA Special Committee 227, Standards of Navigation Performance. SUMMARY: The FAA is..., Standards of Navigation Performance. DATES: The meeting will be held September 9-13, 2013 from 9:00 a.m.-...

  16. 77 FR 22835 - Second Meeting: RTCA Special Committee 227, Standards of Navigation Performance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-17

    ... Federal Aviation Administration Second Meeting: RTCA Special Committee 227, Standards of Navigation...: Notice of RTCA Special Committee 227, Standards of Navigation Performance. SUMMARY: The FAA is issuing... Navigation Performance. DATES: The meeting will be held May 7-11, 2012, from 9 a.m.-5 p.m. ADDRESSES:...

  17. 78 FR 16031 - Sixth Meeting: RTCA Special Committee 227, Standards of Navigation Performance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-13

    ... TRANSPORTATION Federal Aviation Administration Sixth Meeting: RTCA Special Committee 227, Standards of Navigation...: Meeting Notice of RTCA Special Committee 227, Standards of Navigation Performance. SUMMARY: The FAA is..., Standards of Navigation Performance. DATES: The meeting will be held April 8-17, 2013 from 9:00 a.m.-5:00...

  18. 77 FR 5615 - First Meeting: RTCA Special Committee 227, Standards of Navigation Performance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-03

    ... Federal Aviation Administration First Meeting: RTCA Special Committee 227, Standards of Navigation...: Notice of RTCA Special Committee 227, Standards of Navigation Performance. SUMMARY: The FAA is issuing... Navigation Performance ] DATES: The meeting will be held March 6-8, 2012, from 9 a.m.-5 p.m. ADDRESSES:...

  19. 77 FR 54648 - Seventh Meeting: RTCA NextGen Advisory Committee (NAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-05

    ... Federal Aviation Administration Seventh Meeting: RTCA NextGen Advisory Committee (NAC) AGENCY: Federal...Gen Advisory Committee (NAC). SUMMARY: The FAA is issuing this notice to advise the public of the seventh meeting of the RTCA NextGen Advisory Committee (NAC). DATES: The meeting will be held October...

  20. 76 FR 38742 - Eleventh Meeting: RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... Federal Aviation Administration Eleventh Meeting: RTCA Special Committee 220: Automatic Flight Guidance... Committee 220 Meeting: Automatic Flight Guidance and Control. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control...

  1. 75 FR 39091 - RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-07

    ... Federal Aviation Administration RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC... Traffic Management Advisory Committee (ATMAC). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC)....

  2. 75 FR 61552 - RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-05

    ... Federal Aviation Administration RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC... Traffic Management Advisory Committee (ATMAC) SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC) DATES:...

  3. 75 FR 27618 - RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-17

    ... Federal Aviation Administration RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC... Traffic Management Advisory Committee (ATMAC). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Government/Industry Air Traffic Management Advisory Committee (ATMAC)....

  4. 76 FR 33022 - Eighty-Sixth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-07

    ... Federal Aviation Administration Eighty-Sixth Meeting: RTCA Special Committee 159: Global Positioning... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The...

  5. 75 FR 28318 - Eighty-Second Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-20

    ... Federal Aviation Administration Eighty-Second Meeting: RTCA Special Committee 159: Global Positioning... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The...

  6. 75 FR 2581 - Eighty-First Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-15

    ... Federal Aviation Administration Eighty-First Meeting: RTCA Special Committee 159: Global Positioning... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The...

  7. 76 FR 27744 - Eighty-Fifth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ... Federal Aviation Administration Eighty-Fifth Meeting: RTCA Special Committee 159: Global Positioning... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The...

  8. 76 FR 22163 - Tenth Meeting: RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-20

    ... Federal Aviation Administration Tenth Meeting: RTCA Special Committee 220: Automatic Flight Guidance and... meeting: Automatic Flight Guidance and Control. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control. DATES:...

  9. 75 FR 28319 - Thirteenth Meeting: EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-20

    .... FOR FURTHER INFORMATION CONTACT: RTCA Secretariat, 1828 L Street, NW., Suite 805, Washington, DC 20036; telephone (202) 833-9339; fax (202) 833-9434; Web site http://www.rtca.org . SUPPLEMENTARY INFORMATION...:15 to 11:30: Discuss collaboration and associated topics with other organisations (Arinc, DSWG,...

  10. 75 FR 16901 - Thirteenth Meeting: EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-02

    .... FOR FURTHER INFORMATION CONTACT: RTCA Secretariat, 1828 L Street, NW., Suite 805, Washington, DC 20036; telephone (202) 833-9339; fax (202) 833-9434; Web site http://www.rtca.org . SUPPLEMENTARY INFORMATION...:15: Break. 11:15 to 11:30: Discuss collaboration and associated topics with other...

  11. 75 FR 49550 - Fifth Meeting: RTCA Special Committee 219: Attitude and Heading Reference System (AHRS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-13

    ... Federal Aviation Administration Fifth Meeting: RTCA Special Committee 219: Attitude and Heading Reference...: Notice of RTCA Special Committee 219: Attitude and Heading Reference System (AHRS). SUMMARY: The FAA is... Heading Reference System (AHRS). DATES: The meeting will be held September 14-16, 2010 from 9 a.m. to 5...

  12. 75 FR 61819 - First Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-06

    ... Federal Aviation Administration First Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  13. 75 FR 36471 - Seventh Meeting-RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-25

    ... Federal Aviation Administration Seventh Meeting--RTCA Special Committee 220: Automatic Flight Guidance and...: Automatic Flight Guidance and Control meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control. DATES: The...

  14. 75 FR 3959 - Fifth Meeting-RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-25

    ... Federal Aviation Administration Fifth Meeting--RTCA Special Committee 220: Automatic Flight Guidance and...: Automatic Flight Guidance and Control meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control. DATES: The...

  15. 76 FR 50809 - Eleventh Meeting: RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... Federal Aviation Administration Eleventh Meeting: RTCA Special Committee 220: Automatic Flight Guidance... Special Committee 220 meeting: Automatic Flight Guidance and Control. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance...

  16. 75 FR 59326 - Eighth Meeting-RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-27

    ... Federal Aviation Administration Eighth Meeting--RTCA Special Committee 220: Automatic Flight Guidance and...: Automatic Flight Guidance and Control meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control. DATES: The...

  17. 75 FR 15770 - Sixth Meeting-RTCA Special Committee 220: Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-30

    ... Federal Aviation Administration Sixth Meeting--RTCA Special Committee 220: Automatic Flight Guidance and...: Automatic Flight Guidance and Control meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control. DATES: The...

  18. 76 FR 15039 - RTCA Government/Industry NextGen Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-18

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration RTCA Government/Industry NextGen Advisory Committee AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Charter Renewal. SUMMARY: The FAA is...

  19. 77 FR 55894 - Thirteenth Meeting: RTCA Special Committee 223, Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-11

    ... Federal Aviation Administration Thirteenth Meeting: RTCA Special Committee 223, Airport Surface Wireless...: Meeting Notice of RTCA Special Committee 223, Airport Surface Wireless Communications. SUMMARY: The FAA is..., Airport Surface Wireless Communications. DATES: The meeting will be held October 2-3, 2012, from 9...

  20. 75 FR 30899 - Fourth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... Federal Aviation Administration Fourth Meeting: RTCA Special Committee 223: Airport Surface Wireless...: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport Surface Wireless Communications. DATES:...

  1. 75 FR 14483 - Third Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-25

    ... Federal Aviation Administration Third Meeting: RTCA Special Committee 223: Airport Surface Wireless...: Airport Surface Wireless Communications meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 223: Airport Surface Wireless Communications. DATES:...

  2. 75 FR 71790 - Second Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-24

    ... Federal Aviation Administration Second Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  3. 77 FR 64838 - Sixteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-23

    ... Federal Aviation Administration Sixteenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held November 15,...

  4. 76 FR 50811 - Eighth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... TRANSPORTATION Federal Aviation Administration Eighth Meeting: RTCA Special Committee 224: Airport Security... Committee 224 meeting: Airport Security Access Control Systems. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access Control...

  5. 78 FR 16757 - Twentieth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... Federal Aviation Administration Twentieth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held April 4, 2013 from...

  6. 76 FR 59481 - Ninth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-26

    ... TRANSPORTATION Federal Aviation Administration Ninth Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access Control...

  7. 77 FR 55894 - Fifteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-11

    ... Federal Aviation Administration Fifteenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems DATES: The meeting will be held September 27-28,...

  8. 77 FR 15448 - Twelfth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... Federal Aviation Administration Twelfth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Notice of meeting RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... 224, Airport Security Access Control Systems DATES: The meeting will be held April 5, 2012, from 10...

  9. 76 FR 9632 - Fifth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-18

    ... Federal Aviation Administration Fifth Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  10. 75 FR 80886 - Third Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-23

    ... Federal Aviation Administration Third Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  11. 76 FR 38742 - Seventh Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  12. 76 FR 16470 - Sixth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... Federal Aviation Administration Sixth Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  13. 78 FR 22025 - Twenty First Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-12

    ... Federal Aviation Administration Twenty First Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held April 9-10,...

  14. 78 FR 43963 - Twenty-Third Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ... Federal Aviation Administration Twenty-Third Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held on June 20,...

  15. 77 FR 25525 - Thirteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-30

    ... TRANSPORTATION Federal Aviation Administration Thirteenth Meeting: RTCA Special Committee 224, Airport Security... (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems... Committee 224, Airport Security Access Control Systems DATES: The meeting will be held May 30, 2012, from...

  16. 76 FR 3931 - Fourth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-21

    ... Federal Aviation Administration Fourth Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 Meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  17. 77 FR 71474 - Seventeenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-30

    ... Federal Aviation Administration Seventeenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held December 13,...

  18. 77 FR 2343 - Eleventh Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... Federal Aviation Administration Eleventh Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY: The FAA..., Airport Security Access Control Systems. DATES: The meeting will be held February 9, 2012, from 10...

  19. Phosphorus constrains accelerated nitrogen cycling in limed acidic forests

    NASA Astrophysics Data System (ADS)

    Deforest, J. L.; Shaw, A. N.; Kluber, L. A.; Burke, D. J.; Carrino-Kyker, S. R.; Smemo, K. A.

    2011-12-01

    Anthropogenic deposition can increase phosphorus (P) limitation by abiotic and biotic means. Soil acidification can remove P from available pools and nitrogen (N) deposition can increase the demand for P. We reason that chronic acidic deposition is promoting P limitation in acidic hardwood forests and thereby altering N cycling. The objectives of this study were to investigate the interactive influence of P availability and soil pH on N and P cycling and availability to determine if the response varies between two physiographic regions experiencing similar chronic acidic deposition. We addressed these objectives by experimentally manipulating soil pH, P, or both in strongly acidic glaciated and unglaciated hardwood forests in eastern Ohio, USA. Our results suggest complex interactions between P, soil pH, and the N cycle. Glaciated soils were found to be more N-saturated with nitrification rates 18 times greater than in unglaciated soils. Elevating pH, with or without added P, doubled nitrification rates in glaciated soils. For unglaciated soils, raising pH increased nitrification 10-fold, but increased nitrification only 5-fold in combination with P. This result suggests raising soil pH lowered the demand of soil N, or directly stimulated nitrifying activity, and that increasing P availability could limit N availability. To various degrees, readily available P was geochemically or biologically immobilized in all treatments, suggesting chronic P deficiency in these ecosystems. Phosphorus immobilization decreased as soil pH was elevated, but elevated P either had no effect (glaciated) or doubled P immobilization rates (unglaciated). These results suggest that raising soil pH reduces microbial P limitation for phosphate, whereas adding P appears to make phosphate scarcer. We suggest that P plays an important role in N transformations and cycling, but appears more important in unglaciated soils than in glaciated soils. Chronic soil acidification may have a greater

  20. Fatty acid biosynthesis during the life cycle of Debaryomyces etchellsii.

    PubMed

    Arous, Fatma; Mechichi, Tahar; Nasri, Moncef; Aggelis, George

    2016-07-01

    Fatty acid biosynthesis during the life cycle of the ascomycetous yeast Debaryomyces etchellsii cultivated on a non-fermentable substrate, i.e. glycerol, in nitrogen rich media (NRM) and nitrogen limited media (NLM) has been studied. Although considerable activities of key lipogenic enzymes, such as ATP citrate lyase (ACL) and malic enzyme (ME), were detected in vegetative cells during asexual proliferation (which occurred in the first growth stages in both NRM and NLM), lipid accumulation was restricted due to the high activities of NAD+-isocitrate dehydrogenase (NAD+-ICDH). A similar enzymatic profile has been found in ascii and free ascospores produced in NRM; thus lipid accumulation was low. On the contrary, very high activities of both ACL and ME and low activities of NAD+-ICDH were detected in ascii and free ascospores produced in NLM resulting in lipid accumulation. Neutral lipids (NL) were the predominant fraction of cellular lipids produced in vegetative cells and ascospores in both NRM and NLM. On the other hand, phospholipids (P) were the major polar lipids while glycolipids (G) were synthesized in low proportions. During transition from asexual to sexual phase, the percentage of NL increased with a significant decrease of P and, to a lesser extent, of G. High quantities of linoleic acid were found esterified in polar lipids, especially in P, during the vegetative stage of growth, while, with a few exceptions, during transition from asexual to sexual stage, linoleic acid concentration decreased markedly, mainly in P, while oleic acid concentration increased. PMID:27129978

  1. Autonomous Aircraft Operations using RTCA Guidelines for Airborne Conflict Management

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, Karthik; Wing, David J.; Barmore, Bryan E.; Barhydt, Richard; Palmer, Michael T.; Johnson, Edward J.; Ballin, Mark G.; Eischeid, Todd M.

    2003-01-01

    A human-in-the-loop experiment was performed at the NASA Langley Research Center to study the feasibility of DAG-TM autonomous aircraft operations in highly constrained airspace. The airspace was constrained by a pair of special-use airspace (SUA) regions on either side of the pilot's planned route. Traffic flow management (TFM) constraints were imposed as a required time of arrival and crossing altitude at an en route fix. Key guidelines from the RTCA Airborne Conflict Management (ACM) concept were applied to autonomous aircraft operations for this experiment. These concepts included the RTCA ACM definitions of distinct conflict detection and collision avoidance zones, and the use of a graded system of conflict alerts for the flight crew. Three studies were conducted in the course of the experiment. The first study investigated the effect of hazard proximity upon pilot ability to meet constraints and solve conflict situations. The second study investigated pilot use of the airborne tools when faced with an unexpected loss of separation (LOS). The third study explored pilot interactions in an over-constrained conflict situation, with and without priority rules dictating who should move first. Detailed results from these studies were presented at the 5th USA/Europe Air Traffic Management R&D Seminar (ATM2003). This overview paper focuses on the integration of the RTCA ACM concept into autonomous aircraft operations in highly constrained situations, and provides an overview of the results presented at the ATM2003 seminar. These results, together with previously reported studies, continue to support the feasibility of autonomous aircraft operations.

  2. Metabolic engineering in the biotechnological production of organic acids in the tricarboxylic acid cycle of microorganisms: Advances and prospects.

    PubMed

    Yin, Xian; Li, Jianghua; Shin, Hyun-Dong; Du, Guocheng; Liu, Long; Chen, Jian

    2015-11-01

    Organic acids, which are chemically synthesized, are also natural intermediates in the metabolic pathways of microorganisms, among which the tricarboxylic acid (TCA) cycle is the most crucial route existing in almost all living organisms. Organic acids in the TCA cycle include citric acid, α-ketoglutaric acid, succinic acid, fumaric acid, l-malic acid, and oxaloacetate, which are building-block chemicals with wide applications and huge markets. In this review, we summarize the synthesis pathways of these organic acids and review recent advances in metabolic engineering strategies that enhance organic acid production. We also propose further improvements for the production of organic acids with systems and synthetic biology-guided metabolic engineering strategies.

  3. Materials study supporting thermochemical hydrogen cycle sulfuric acid decomposer design

    NASA Astrophysics Data System (ADS)

    Peck, Michael S.

    Increasing global climate change has been driven by greenhouse gases emissions originating from the combustion of fossil fuels. Clean burning hydrogen has the potential to replace much of the fossil fuels used today reducing the amount of greenhouse gases released into the atmosphere. The sulfur iodine and hybrid sulfur thermochemical cycles coupled with high temperature heat from advanced nuclear reactors have shown promise for economical large-scale hydrogen fuel stock production. Both of these cycles employ a step to decompose sulfuric acid to sulfur dioxide. This decomposition step occurs at high temperatures in the range of 825°C to 926°C dependent on the catalysis used. Successful commercial implementation of these technologies is dependent upon the development of suitable materials for use in the highly corrosive environments created by the decomposition products. Boron treated diamond film was a potential candidate for use in decomposer process equipment based on earlier studies concluding good oxidation resistance at elevated temperatures. However, little information was available relating the interactions of diamond and diamond films with sulfuric acid at temperatures greater than 350°C. A laboratory scale sulfuric acid decomposer simulator was constructed at the Nuclear Science and Engineering Institute at the University of Missouri-Columbia. The simulator was capable of producing the temperatures and corrosive environments that process equipment would be exposed to for industrialization of the sulfur iodide or hybrid sulfur thermochemical cycles. A series of boron treated synthetic diamonds were tested in the simulator to determine corrosion resistances and suitability for use in thermochemical process equipment. These studies were performed at twenty four hour durations at temperatures between 600°C to 926°C. Other materials, including natural diamond, synthetic diamond treated with titanium, silicon carbide, quartz, aluminum nitride, and Inconel

  4. Crassulacean acid metabolism-cycling in Euphorbia milii

    PubMed Central

    Herrera, Ana

    2013-01-01

    Crassulacean acid metabolism (CAM) occurs in many Euphorbiaceae, particularly Euphorbia, a genus with C3 and C4 species as well. With the aim of contributing to our knowledge of the evolution of CAM in this genus, this study examined the possible occurrence of CAM in Euphorbia milii, a species with leaf succulence and drought tolerance suggestive of this carbon fixation pathway. Leaf anatomy consisted of a palisade parenchyma, a spongy parenchyma and a bundle sheath with chloroplasts, which indicates the possible functioning of C2 photosynthesis. No evidence of nocturnal CO2 fixation was found in plants of E. milii either watered or under drought; watered plants had a low nocturnal respiration rate (R). After 12 days without watering, the photosynthetic rate (PN) decreased 85 % and nocturnal R was nearly zero. Nocturnal H+ accumulation (ΔH+) in watered plants was 18 ± 2 (corresponding to malate) and 18 ± 4 (citrate) μmol H+ (g fresh mass)−1. Respiratory CO2 recycling through acid synthesis contributed to a night-time water saving of 2 and 86 % in watered plants and plants under drought, respectively. Carbon isotopic composition (δ13C) was −25.2 ± 0.7 ‰ in leaves and −24.7 ± 0.1 ‰ in stems. Evidence was found for the operation of weak CAM in E. milii, with statistically significant ΔH+, no nocturnal CO2 uptake and values of δ13C intermediate between C3 and constitutive CAM plants; ΔH+ was apparently attributable to both malate and citrate. The results suggest that daily malate accumulation results from recycling of part of the nocturnal respiratory CO2, which helps explain the occurrence of an intermediate value of leaf δ13C. Euphorbia milii can be considered as a CAM-cycling species. The significance of the operation of CAM-cycling in E. milii lies in water conservation, rather than carbon acquisition. The possible occurrence of C2 photosynthesis merits research. PMID:23596548

  5. 76 FR 66350 - Eighth Meeting: RTCA Special Committee 222 Inmarsat Aeronautical Mobile Satellite (Route) Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-26

    ... Satellite (Route) Services AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 222, Inmarsat Aeronautical Mobile Satellite (Route... Committee 222, Inmarsat Aeronautical Mobile Satellite (Route) Services for the Eighth Meeting. DATES:...

  6. 75 FR 65706 - Fifteenth Plenary Meeting, RTCA Special Committee 205/EUROCAE WG 71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-26

    ...: Software Considerations in Aeronautical Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 205/EUROCAE WG 71: ] Software Considerations in Aeronautical Systems... Committee 205/EUROCAE WG 71: Software Considerations in Aeronautical Systems. DATES: The meeting will...

  7. 78 FR 6401 - Seventy Fifth Meeting: RTCA Special Committee 147, Minimum Operational Performance Standards for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-30

    ... Operational Performance Standards for Traffic Alert and Collision Avoidance Systems Airborne Equipment AGENCY... RTCA Special Committee 147, Minimum Operational Performance Standards for Traffic Alert and Collision... Alert and Collision Avoidance Systems Airborne Equipment. DATES: The meeting will be held February...

  8. 76 FR 22163 - Ninth Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-20

    ... Alternative Flight Deck Security Procedures AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 221 meeting: Aircraft Secondary Barriers and Alternative Flight Deck... Special Committee 221: Aircraft Secondary Barriers and Alternative Flight Deck Security Procedures....

  9. 76 FR 38741 - Tenth Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... Alternative Flight Deck Security Procedures AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 221 meeting: Aircraft Secondary Barriers and Alternative Flight Deck... Special Committee 221: Aircraft Secondary Barriers and Alternative Flight Deck Security Procedures....

  10. 75 FR 80885 - Fifteenth Meeting: EUROCAE WG-72: RTCA Special Committee 216: Aeronautical Systems Security...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-23

    ... PMC/ICC action on SC 216 TOR. Publication Progress and Update. Subgroup and Action Item Reports. Plenary review of EUROCAE Council and RTCA PMC actions on ED-202 and SC-216 TOR. Continuation of...

  11. 75 FR 9016 - Fifth Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-26

    ... Alternative Flight Deck Security Procedures AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 221 meeting: Aircraft Secondary Barriers and Alternative Flight Deck... Special Committee 221: Aircraft Secondary Barriers and Alternative Flight Deck Security Procedures....

  12. The effect of propionic acid and valeric acid on the cell cycle in root meristems of Pisum sativum

    SciTech Connect

    Tramontano, W.A.; Yang, Shauyu; Delillo, A.R. )

    1990-01-01

    Propionic acid and valeric acid at 1mM reduced the mitotic index of root meristem cells of Pisum sativum to < 1% after 12 hr in aerated White's medium. This effect varied with different acid concentrations. After a 12 hr exposure to either acid, seedlings transferred to fresh medium without either acid, resumed their normal mitotic index after 12 hr, with a burst of mitosis 8 hr post-transfer. Exposure of root meristem cells to either acid also inhibited ({sup 3}H)-TdR incorporation. Neither acid significantly altered the distribution of meristematic cells in G1 and G2 after 12 hr. The incorporation of ({sup 3}H) - uridine was also unaltered by the addition of either acid. This information suggests that propionic acid and valeric acid, limit progression through the cell cycle by inhibiting DNA synthesis and arresting cells in G1 and G2. These results were consistent with previous data which utilized butyric acid.

  13. Salicylic acid antagonizes abscisic acid inhibition of shoot growth and cell cycle progression in rice

    NASA Astrophysics Data System (ADS)

    Meguro, Ayano; Sato, Yutaka

    2014-04-01

    We analysed effects of abscisic acid (ABA, a negative regulatory hormone), alone and in combination with positive or neutral hormones, including salicylic acid (SA), on rice growth and expression of cell cycle-related genes. ABA significantly inhibited shoot growth and induced expression of OsKRP4, OsKRP5, and OsKRP6. A yeast two-hybrid assay showed that OsKRP4, OsKRP5, and OsKRP6 interacted with OsCDKA;1 and/or OsCDKA;2. When SA was simultaneously supplied with ABA, the antagonistic effect of SA completely blocked ABA inhibition. SA also blocked ABA inhibition of DNA replication and thymidine incorporation in the shoot apical meristem. These results suggest that ABA arrests cell cycle progression by inducing expression of OsKRP4, OsKRP5, and OsKRP6, which inhibit the G1/S transition, and that SA antagonizes ABA by blocking expression of OsKRP genes.

  14. Photochemical synthesis of citric acid cycle intermediates based on titanium dioxide.

    PubMed

    Saladino, Raffaele; Brucato, John Robert; De Sio, Antonio; Botta, Giorgia; Pace, Emanuele; Gambicorti, Lisa

    2011-10-01

    The emergence of the citric acid cycle is one of the most remarkable occurrences with regard to understanding the origin and evolution of metabolic pathways. Although the chemical steps of the cycle are preserved intact throughout nature, diverse organisms make wide use of its chemistry, and in some cases organisms use only a selected portion of the cycle. However, the origins of this cycle would have arisen in the more primitive anaerobic organism or even back in the proto-metabolism, which likely arose spontaneously under favorable prebiotic chemical conditions. In this context, we report that UV irradiation of formamide in the presence of titanium dioxide afforded 6 of the 11 carboxylic acid intermediates of the reductive version of the citric acid cycle. Since this cycle is the central metabolic pathway of contemporary biology, this report highlights the role of photochemical processes in the origin of the metabolic apparatus.

  15. [Influence of chosen metals on the citric acid cycle].

    PubMed

    Rojczyk-Gołebiewska, Ewa; Kucharzewski, Marek

    2013-03-01

    Industrial activity growth influenced not only technological progress, but also had negative effects on human natural environment. It results among others in increased human exposition to heavy metals. In case of detoxication mechanisms disturbance in organism, heavy metals cumulate in tissues causing mutations and disrupting metabolism, including Krebs cycle. Recent studies have revealed that iron, zinc and manganese have especially strong influence on Krebs cycle. These elements act as cofactors or inhibitors regulating activity of particular enzymes of this cycle, which has a reflection in cellular energy production disturbances.

  16. 75 FR 29811 - 21st Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-27

    ... Federal Aviation Administration 21st Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and... Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 206: EUROCAE WG 76...

  17. 76 FR 11846 - 24th Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-03

    ... Federal Aviation Administration 24th Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and... Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 206: EUROCAE WG 76...

  18. 75 FR 55847 - 22nd Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-14

    ... Federal Aviation Administration 22nd Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and... Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 206: EUROCAE WG 76...

  19. 77 FR 29749 - Twelfth Meeting: RTCA Special Committee 217, Joint with EUROCAE WG-44, Terrain and Airport...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-18

    ..., Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 217, Joint with EUROCAE WG-44, Terrain and... meeting, RTCA Special Committee 217, Joint with EUROCAE WG-44, Terrain and Airport Mapping...

  20. 78 FR 69929 - Fifty-Ninth Meeting: RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-21

    ... Surveillance-Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast... RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast (ADS-B) DATES: The meeting...

  1. Closed cycle ion exchange method for regenerating acids, bases and salts

    DOEpatents

    Dreyfuss, Robert M.

    1976-01-01

    A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof are ions also produced as a by-product in the closed reaction cycle, and then regenerating the spent ion exchanger by contact with the by-product counter ions. The method is particularly applicable to closed cycle processes for the thermochemical production of hydrogen.

  2. Effects of intermediate metabolite carboxylic acids of TCA cycle on Microcystis with overproduction of phycocyanin.

    PubMed

    Bai, Shijie; Dai, Jingcheng; Xia, Ming; Ruan, Jing; Wei, Hehong; Yu, Dianzhen; Li, Ronghui; Jing, Hongmei; Tian, Chunyuan; Song, Lirong; Qiu, Dongru

    2015-04-01

    Toxic Microcystis species are the main bloom-forming cyanobacteria in freshwaters. It is imperative to develop efficient techniques to control these notorious harmful algal blooms (HABs). Here, we present a simple, efficient, and environmentally safe algicidal way to control Microcystis blooms, by using intermediate carboxylic acids from the tricarboxylic acid (TCA) cycle. The citric acid, alpha-ketoglutaric acid, succinic acid, fumaric acid, and malic acid all exhibited strong algicidal effects, and particularly succinic acid could cause the rapid lysis of Microcystis in a few hours. It is revealed that the Microcystis-lysing activity of succinic acid and other carboxylic acids was due to their strong acidic activity. Interestingly, the acid-lysed Microcystis cells released large amounts of phycocyanin, about 27-fold higher than those of the control. On the other hand, the transcription of mcyA and mcyD of the microcystin biosynthesis operon was not upregulated by addition of alpha-ketoglutaric acid and other carboxylic acids. Consider the environmental safety of intermediate carboxylic acids. We propose that administration of TCA cycle organic acids may not only provide an algicidal method with high efficiency and environmental safety but also serve as an applicable way to produce and extract phycocyanin from cyanobacterial biomass.

  3. Tricarboxylic Acid Cycle-Dependent Attenuation of Staphylococcus aureus In Vivo Virulence by Selective Inhibition of Amino Acid Transport▿

    PubMed Central

    Zhu, Yefei; Xiong, Yan Q.; Sadykov, Marat R.; Fey, Paul D.; Lei, Mei G.; Lee, Chia Y.; Bayer, Arnold S.; Somerville, Greg A.

    2009-01-01

    Staphylococci are the leading causes of endovascular infections worldwide. Commonly, these infections involve the formation of biofilms on the surface of biomaterials. Biofilms are a complex aggregation of bacteria commonly encapsulated by an adhesive exopolysaccharide matrix. In staphylococci, this exopolysaccharide matrix is composed of polysaccharide intercellular adhesin (PIA). PIA is synthesized when the tricarboxylic acid (TCA) cycle is repressed. The inverse correlation between PIA synthesis and TCA cycle activity led us to hypothesize that increasing TCA cycle activity would decrease PIA synthesis and biofilm formation and reduce virulence in a rabbit catheter-induced model of biofilm infection. TCA cycle activity can be induced by preventing staphylococci from exogenously acquiring a TCA cycle-derived amino acid necessary for growth. To determine if TCA cycle induction would decrease PIA synthesis in Staphylococcus aureus, the glutamine permease gene (glnP) was inactivated and TCA cycle activity, PIA accumulation, biofilm forming ability, and virulence in an experimental catheter-induced endovascular biofilm (endocarditis) model were determined. Inactivation of this major glutamine transporter increased TCA cycle activity, transiently decreased PIA synthesis, and significantly reduced in vivo virulence in the endocarditis model in terms of achievable bacterial densities in biofilm-associated cardiac vegetations, kidneys, and spleen. These data confirm the close linkage of TCA cycle activity and virulence factor production and establish that this metabolic linkage can be manipulated to alter infectious outcomes. PMID:19667045

  4. Stoichiometry of Reducing Equivalents and Splitting of Water in the Citric Acid Cycle.

    ERIC Educational Resources Information Center

    Madeira, Vitor M. C.

    1988-01-01

    Presents a solution to the problem of finding the source of extra reducing equivalents, and accomplishing the stoichiometry of glucose oxidation reactions. Discusses the citric acid cycle and glycolysis. (CW)

  5. Hydrogen Storage in the Carbon Dioxide - Formic Acid Cycle.

    PubMed

    Fink, Cornel; Montandon-Clerc, Mickael; Laurenczy, Gabor

    2015-01-01

    This year Mankind will release about 39 Gt carbon dioxide into the earth's atmosphere, where it acts as a greenhouse gas. The chemical transformation of carbon dioxide into useful products becomes increasingly important, as the CO(2) concentration in the atmosphere has reached 400 ppm. One approach to contribute to the decrease of this hazardous emission is to recycle CO(2), for example reducing it to formic acid. The hydrogenation of CO(2) can be achieved with a series of catalysts under basic and acidic conditions, in wide variety of solvents. To realize a hydrogen-based charge-discharge device ('hydrogen battery'), one also needs efficient catalysts for the reverse reaction, the dehydrogenation of formic acid. Despite of the fact that the overwhelming majority of these reactions are carried out using precious metals-based catalysts (mainly Ru), we review here developments for catalytic hydrogen evolution from formic acid with iron-based complexes. PMID:26842324

  6. Amino Acid Pools and Metabolism During the Cell Division Cycle of Arginine-Grown Candida utilis

    PubMed Central

    Nurse, P.; Wiemken, A.

    1974-01-01

    Synchronous cultures obtained by isopycnic density gradient centrifugation are used to investigate amino acid metabolism during the cell division cycle of the food yeast Candida utilis. Isotopic labeling experiments demonstrate that the rates of uptake and catabolism of arginine, the sole source of nitrogen, double abruptly during the first half of the cycle, while the cells undergo bud expansion. This is accompanied by a doubling in rate of amino acid biosynthesis, and an accumulation of amino acids. The accumulation probably occurs within the storage pools of the vacuoles. Amino acids derived from protein degradation contribute little to this accumulation. For the remainder of the cell cycle, during cell separation and until the next bud initiation, the rates of uptake and catabolism of arginine and amino acid biosynthesis remain constant. Despite the abrupt doubling in the rate of formation of amino acid pools, their rate of utilization for macromolecular synthesis increases steadily throughout the cycle. The significance of this temporal organization of nitrogen source uptake and amino acid metabolism during the cell division cycle is discussed. Images PMID:4591945

  7. New insights in nutritional management and amino acid supplementation in urea cycle disorders.

    PubMed

    Scaglia, Fernando

    2010-01-01

    Sodium phenylbutyrate is used in the pharmacological treatment of urea cycle disorders to create alternative pathways for nitrogen excretion. The primary metabolite, phenylacetate, conjugates glutamine in the liver and kidney to form phenylacetylglutamine that is readily excreted in the urine. Patients with urea cycle disorders taking sodium phenylbutyrate have a selective reduction in the plasma concentrations of branched chain amino acids despite adequate dietary protein intake. Moreover, this depletion is usually the harbinger of a metabolic crisis. Plasma branched chain amino acids and other essential amino acids were measured in control subjects, untreated ornithine transcarbamylase deficiency females, and treated patients with urea cycle disorders (ornithine transcarbamylase deficiency and argininosuccinate synthetase deficiency) in the absorptive state during the course of stable isotope studies. Branched chain amino acid levels were significantly lower in treated patients with urea cycle disorders when compared to untreated ornithine transcarbamylase deficiency females or control subjects. These results were replicated in control subjects who had low steady-state branched chain amino acid levels when treated with sodium phenylbutyrate. These studies suggested that alternative pathway therapy with sodium phenylbutyrate causes a substantial impact on the metabolism of branched chain amino acids in patients with urea cycle disorders, implying that better titration of protein restriction can be achieved with branched chain amino acid supplementation in these patients who are on alternative pathway therapy.

  8. Using Phospholipids and Stable Carbon Isotopes to Assess Microbial Community Structures and Carbon Cycle Pathways in Kamchatka Hot Springs

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Romanek, C. S.; Burgess, E. A.; Wiegel, J.; Mills, G.; Zhang, C. L.

    2006-12-01

    Phospholipid fatty acid (PLFA) and stable carbon isotopes were used to assess the microbial community structures in Kamchatka hot springs. Eighteen mats or surface sediments were collected from hot springs having temperatures of 31 to 91°C and pHs of 4.9 to 8.5. These samples were clearly separated into three groups according to the bacterial PLFA: 1) those dominated by terminally branched odd-numbered fatty acids, 2) those dominated by C18:1 and 3) those dominated by C20:1. With support from other minor PLFA components, group 2 may be used as biomarkers for Chloroflexales or other phototrophic bacteria and group 3 for Aquificales, respectively. Among the sampled hot springs, the Arkashin pool represents the simplest microbial structure with members of Aquificales being the dominant primary producers. On the other hand, the Zavarzin pool may represent the most heterogeneous pool that may include members of Chloroflexales and Aquificales as primary producers. Bacterial 16S rDNA clone libraries confirmed the presence of these microbial groups in the two pools. Results of stable carbon isotope fractionation between CO2 source, bulk biomass and total PLFA showed that primary producers in the Arkashin pool primarily used the reductive tricarboxylic acid (rTCA) cycle (e.g., members of Aquificales); whereas the Zavarzin pool may be a mixture of the 3-hydroxypropionate (3-HP) pathway (e.g. members of Chloroflexales) and the rTCA cycle. Bacterial contribution using the Calvin cycle was not significant and may be less important in Kamchatka hot springs.

  9. A Functional Tricarboxylic Acid Cycle Operates during Growth of Bordetella pertussis on Amino Acid Mixtures as Sole Carbon Substrates.

    PubMed

    Izac, Marie; Garnier, Dominique; Speck, Denis; Lindley, Nic D

    2015-01-01

    It has been claimed that citrate synthase, aconitase and isocitrate dehydrogenase activities are non-functional in Bordetella pertussis and that this might explain why this bacterium's growth is sometimes associated with accumulation of polyhydroxybutyrate (PHB) and/or free fatty acids. However, the sequenced genome includes the entire citric acid pathway genes. Furthermore, these genes were expressed and the corresponding enzyme activities detected at high levels for the pathway when grown on a defined medium imitating the amino acid content of complex media often used for growth of this pathogenic microorganism. In addition, no significant PHB or fatty acids could be detected. Analysis of the carbon balance and stoichiometric flux analysis based on specific rates of amino acid consumption, and estimated biomass requirements coherent with the observed growth rate, clearly indicate that a fully functional tricarboxylic acid cycle operates in contrast to previous reports.

  10. A Functional Tricarboxylic Acid Cycle Operates during Growth of Bordetella pertussis on Amino Acid Mixtures as Sole Carbon Substrates

    PubMed Central

    Garnier, Dominique; Speck, Denis

    2015-01-01

    It has been claimed that citrate synthase, aconitase and isocitrate dehydrogenase activities are non-functional in Bordetella pertussis and that this might explain why this bacterium’s growth is sometimes associated with accumulation of polyhydroxybutyrate (PHB) and/or free fatty acids. However, the sequenced genome includes the entire citric acid pathway genes. Furthermore, these genes were expressed and the corresponding enzyme activities detected at high levels for the pathway when grown on a defined medium imitating the amino acid content of complex media often used for growth of this pathogenic microorganism. In addition, no significant PHB or fatty acids could be detected. Analysis of the carbon balance and stoichiometric flux analysis based on specific rates of amino acid consumption, and estimated biomass requirements coherent with the observed growth rate, clearly indicate that a fully functional tricarboxylic acid cycle operates in contrast to previous reports. PMID:26684737

  11. Photoreduction fuels biogeochemical cycling of iron in Spain's acid rivers

    USGS Publications Warehouse

    Gammons, C.H.; Nimick, D.A.; Parker, S.R.; Snyder, D.M.; McCleskey, R.B.; Amils, R.; Poulson, S.R.

    2008-01-01

    A number of investigations have shown that photoreduction of Fe(III) causes midday accumulations of dissolved Fe(II) in rivers and lakes, leading to large diel (24-h) fluctuations in the concentration and speciation of total dissolved iron. Less well appreciated is the importance of photoreduction in providing chemical energy for bacteria to thrive in low pH waters. Diel variations in water chemistry from the highly acidic (pH 2.3 to 3.1) Ri??o Tinto, Ri??o Odiel, and Ri??o Agrio of southwestern Spain (Iberian Pyrite Belt) resulted in daytime increases in Fe(II) concentration of 15 to 66????M at four diel sampling locations. Dissolved Fe(II) concentrations increased with solar radiation, and one of the stream sites showed an antithetic relationship between dissolved Fe(II) and Fe(III) concentrations; both results are consistent with photoreduction. The diel data were used to estimate rates of microbially catalyzed Fe(II) oxidation (1 to 3??nmol L- 1 s- 1) and maximum rates of Fe(III) photoreduction (1.7 to 4.3??nmol L- 1 s- 1). Bioenergetic calculations indicate that the latter rates are sufficient to build up a population of Fe-oxidizing bacteria to the levels observed in the Ri??o Tinto in about 30??days. We conclude that photoreduction plays an important role in the bioenergetics of the bacterial communities of these acidic rivers, which have previously been shown to be dominated by autotrophic Fe(II)-oxidizers such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans. Given the possibility of the previous existence of acidic, Fe(III)-rich water on Mars, photoreduction may be an important process on other planets, a fact that could have implications to astrobiological research. ?? 2008 Elsevier B.V. All rights reserved.

  12. An alternative mechanism for guanidinoacetic acid to affect methylation cycle.

    PubMed

    Ostojic, Sergej M

    2014-12-01

    Guanidinoacetic acid (also known as glycocyamine; GAA) is an endogenous substance which occurs in humans and plays a central role in the biosynthesis of creatine. The formation of creatine from GAA consumes methyl groups, and increases production of homocysteine. GAA may have the potential to stimulate insulin secretion. Insulin reduces plasma homocysteine and raises methyl group supply. It is possible that the ability of GAA to trigger the insulin secretion modulates methyl group metabolism, and comparatively counterbalance for the direct effect of GAA on increased methylation demand. Possible insulinotropic effect of GAA may contribute to total in vivo methylation demand during biotransformation. PMID:25468046

  13. Structure-activity relationship between carboxylic acids and T cell cycle blockade.

    PubMed

    Gilbert, Kathleen M; DeLoose, Annick; Valentine, Jimmie L; Fifer, E Kim

    2006-04-01

    This study was designed to examine the potential structure-activity relationship between carboxylic acids, histone acetylation and T cell cycle blockade. Toward this goal a series of structural homologues of the short-chain carboxylic acid n-butyrate were studied for their ability to block the IL-2-stimulated proliferation of cloned CD4+ T cells. The carboxylic acids were also tested for their ability to inhibit histone deacetylation. In addition, Western blotting was used to examine the relative capacity of the carboxlic acids to upregulate the cyclin kinase-dependent inhibitor p21cip1 in T cells. As shown earlier n-butyrate effectively inhibited histone deacetylation. The increased acetylation induced by n-butyrate was associated with the upregulation of the cyclin-dependent kinase inhibitor p21cip1 and the cell cycle blockade of CD4+ T cells. Of the other carboxylic acids studied, the short chain acids, C3-C5, without branching were the best inhibitors of histone deacetylase. This inhibition correlated with increased expression of the cell cycle blocker p21cip1, and the associated suppression of CD4+ T cell proliferation. The branched-chain carboxylic acids tested were ineffective in all the assays. These results underline the relationship between the ability of a carboxylic acid to inhibit histone deacetylation, and their ability to block T cell proliferation, and suggests that branching inhibits these effects.

  14. Halogenated methanesulfonic acids: A new class of organic micropollutants in the water cycle.

    PubMed

    Zahn, Daniel; Frömel, Tobias; Knepper, Thomas P

    2016-09-15

    Mobile and persistent organic micropollutants may impact raw and drinking waters and are thus of concern for human health. To identify such possible substances of concern nineteen water samples from five European countries (France, Switzerland, The Netherlands, Spain and Germany) and different compartments of the water cycle (urban effluent, surface water, ground water and drinking water) were enriched with mixed-mode solid phase extraction. Hydrophilic interaction liquid chromatography - high resolution mass spectrometry non-target screening of these samples led to the detection and structural elucidation of seven novel organic micropollutants. One structure could already be confirmed by a reference standard (trifluoromethanesulfonic acid) and six were tentatively identified based on experimental evidence (chloromethanesulfonic acid, dichloromethanesulfonic acid, trichloromethanesulfonic acid, bromomethanesulfonic acid, dibromomethanesulfonic acid and bromochloromethanesulfonic acid). Approximated concentrations for these substances show that trifluoromethanesulfonic acid, a chemical registered under the European Union regulation REACH with a production volume of more than 100 t/a, is able to spread along the water cycle and may be present in concentrations up to the μg/L range. Chlorinated and brominated methanesulfonic acids were predominantly detected together which indicates a common source and first experimental evidence points towards water disinfection as a potential origin. Halogenated methanesulfonic acids were detected in drinking waters and thus may be new substances of concern. PMID:27267477

  15. Halogenated methanesulfonic acids: A new class of organic micropollutants in the water cycle.

    PubMed

    Zahn, Daniel; Frömel, Tobias; Knepper, Thomas P

    2016-09-15

    Mobile and persistent organic micropollutants may impact raw and drinking waters and are thus of concern for human health. To identify such possible substances of concern nineteen water samples from five European countries (France, Switzerland, The Netherlands, Spain and Germany) and different compartments of the water cycle (urban effluent, surface water, ground water and drinking water) were enriched with mixed-mode solid phase extraction. Hydrophilic interaction liquid chromatography - high resolution mass spectrometry non-target screening of these samples led to the detection and structural elucidation of seven novel organic micropollutants. One structure could already be confirmed by a reference standard (trifluoromethanesulfonic acid) and six were tentatively identified based on experimental evidence (chloromethanesulfonic acid, dichloromethanesulfonic acid, trichloromethanesulfonic acid, bromomethanesulfonic acid, dibromomethanesulfonic acid and bromochloromethanesulfonic acid). Approximated concentrations for these substances show that trifluoromethanesulfonic acid, a chemical registered under the European Union regulation REACH with a production volume of more than 100 t/a, is able to spread along the water cycle and may be present in concentrations up to the μg/L range. Chlorinated and brominated methanesulfonic acids were predominantly detected together which indicates a common source and first experimental evidence points towards water disinfection as a potential origin. Halogenated methanesulfonic acids were detected in drinking waters and thus may be new substances of concern.

  16. Activities of Tricarboxylic Acid Cycle Enzymes, Glyoxylate Cycle Enzymes, and Fructose Diphosphatase in Bakers' Yeast During Adaptation to Acetate Oxidation

    PubMed Central

    Gosling, J. P.; Duggan, P. F.

    1971-01-01

    Bakers' yeast oxidizes acetate at a high rate only after an adaptation period during which the capacity of the glyoxylate cycle is found to increase. There was apparently no necessity for the activity of acetyl-coenzyme A synthetase, the capacity of the tricarboxylic acid cycle, or the concentrations of the cytochromes to increase for this adaptation to occur. Elevation of fructose 1,6 diphosphatase occurred only when acetate oxidation was nearly maximal. Cycloheximide almost completely inhibited adaptation as well as increases in the activities of isocitrate lyase and aconitate hydratase, the only enzymes assayed. p-Fluorophenylalanine was partially effective and chloramphenicol did not inhibit at all. The presence of ammonium, which considerably delayed adaptation of the yeast to acetate oxidation, inhibited the increases in the activities of the glyoxylate cycle enzymes to different degrees, demonstrating noncoordinate control of these enzymes. Under the various conditions, the only enzyme activity increase consistently related to the rising oxygen uptake rate was that of isocitrate lyase which apparently limited the activity of the cycle. PMID:5557595

  17. The effects of climate change on the nitrogen cycle and acid deposition

    SciTech Connect

    Penner, J.E.; Walton, J.J. ); Graboske, B.C. )

    1990-09-01

    Increases in greenhouse gases are expected to lead to a number of changes to the atmosphere which may impact regional and global chemical cycles. With the increasing awareness of climate change and the possibility of global chemical changes to the atmosphere, it becomes important to ask whether these changes to global climate and chemical cycles might benefit or hinder control programs aimed at reducing acid deposition. In the following, we review several possible changes to climate that may be expected to impact the global cycle of reactive nitrogen. We then use our global model of the reactive nitrogen cycle to estimate the effects of several of the more important changes on the continental-scale deposition of nitric acid. 7 refs., 1 tab.

  18. 76 FR 79754 - Twelfth Meeting: RTCA Special Committee 220, Automatic Flight Guidance and Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-22

    ... first plenary meeting RTCA Paper No. 111-11/SC220-024 Presentation of FRAC comments WG 2 Presentation of FRAC comments WG 3 Break-out sessions for WG 2 and WG 3 to work on disposition of comments January 11, 2012 Continue Break-out sessions for WG 2 and WG 3 Continue disposition of comments January 12,...

  19. 77 FR 50543 - Third Meeting: RTCA Special Committee 227, Standards of Navigation Performance, (Joint With...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-21

    ... Performance, (Joint With EUROCAE WG-85) AGENCY: Federal Aviation Administration (FAA), U.S. Department of..., (Joint with EUROCAE WG-85). SUMMARY: The FAA is issuing this notice to advise the public of the third meeting of RTCA Special Committee 227, Standards of Navigation Performance, (Joint with EUROCAE...

  20. 78 FR 7850 - Sixty First Meeting: RTCA Special Committee 135, Environmental Conditions and Test Procedures for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... 135. The agenda will include the following: March 21, 2013 Chairmen's Opening Remarks, Introductions. Introduction of FAA Representative Approval of Summary from the Sixtieth Meeting (RTCA Paper No. 012-13/SC135..., Management Analyst, Business Operations Group, ANG-A12, Federal Aviation Administration. BILLING CODE...

  1. 76 FR 54527 - Fourth Meeting: RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-01

    ... and Battery Systems--Small and Medium Sizes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... and Medium Sizes. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems--Small and Medium Sizes....

  2. 76 FR 22161 - Second Meeting: RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-20

    ... and Battery Systems--Small and Medium Sizes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... and Medium Sizes. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems--Small and Medium Sizes....

  3. 76 FR 6180 - First Meeting: RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-03

    ... and Battery Systems--Small and Medium Sizes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... and Medium Sizes. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems--Small and Medium Sizes....

  4. 76 FR 38741 - Third Meeting: RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... and Battery Systems--Small and Medium Sizes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... and Medium Sizes. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 225: Rechargeable Lithium Batteries and Battery Systems--Small and Medium Sizes....

  5. 78 FR 69928 - First Meeting: RTCA Special Committee 228-Minimum Operational Performance Standards for Unmanned...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-21

    ... Standards for Unmanned Aircraft Systems AGENCY: Federal Aviation Administration (FAA), U.S. Department of... Unmanned Aircraft Systems. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 228--Minimum Operational Performance Standards for Unmanned Aircraft...

  6. 75 FR 44306 - Fifth Meeting: RTCA Special Committee 223: Airport Surface Wireless Communications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-28

    ..., Approve/ Review Meeting 4 Summary, RTCA Paper No. 099-10/SC223-009). Welcome from NASA Glenn Research Center Management: Dr. Gary Seng. Special Committee Leadership. Designated Federal Official (DFO): Mr...: The meeting will be held at the NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH...

  7. 75 FR 26320 - Fourteenth Plenary Meeting, RTCA Special Committee 205/EUROCAE WG 71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-11

    ...'Etoile, Technop le de Ch teau-Gombert, 38, rue Fr d ric Joliot-Curie, 13451 MARSEILLE Cedex 20. FOR...: Software Considerations in Aeronautical Systems AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 205/EUROCAE WG 71: Software Considerations in Aeronautical...

  8. 76 FR 50812 - Seventeenth Meeting: RTCA Special Committee 205/EUROCAE WG-71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... Federal Aviation Administration Seventeenth Meeting: RTCA Special Committee 205/EUROCAE WG-71: Software... Special Committee 205/EUROCAE WG-71 meeting: Software Considerations in Aeronautical Systems. SUMMARY: The...-71: Software Considerations in Aeronautical Systems Agenda for the 17th meeting. DATES: The...

  9. 78 FR 31627 - Twenty-Second Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-24

    ... Control Systems AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held on June 20,...

  10. 78 FR 7850 - Nineteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... Control Systems AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held February 21,...

  11. 76 FR 16469 - Sixteenth Meeting: RTCA Special Committee 205/EUROCAE WG-71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... Management (CNS/ATM) Systems. DO-xxx, Software Tool Qualification Considerations. DO-xxx, Formal Methods Supplement to DO-178C and DO-278A. Approve Entry into RTCA Final Review and Comment Process (FRAC). DO-xxx, Object-Oriented Technology Supplement to DO-178C and DO-278A. DO-xxx, Model-Based Development...

  12. 75 FR 67450 - Eighth Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-02

    ... and Alternative Flight Deck Security Procedures AGENCY: Federal Aviation Administration (FAA), DOT... Flight Deck Security Procedures. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight Deck...

  13. 78 FR 19355 - Announcement of Charter Renewal of the Radio Technical Commission for Aeronautics (RTCA), Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Announcement of Charter Renewal of the Radio Technical Commission for Aeronautics (RTCA), Inc. SUMMARY: The FAA is issuing this notice to advise the public of the charter...

  14. 75 FR 29810 - Sixth Meeting: RTCA Special Committee 221: Aircraft Secondary Barriers and Alternative Flight...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-27

    ... March 16-17, 2009, RTCA Paper No. 080-10/SC221-017 Leadership Comments Review of Threat Work Group--Status Report Review of Alternative Methods Work Group--Status Report Review of Installed Physical Secondary Barrier (IPSB) Work Group--Status Report Presentation/Discussion of SC-221 tentative...

  15. Effects of oxolinic acid on the sleep-wakefulness cycle of the rat

    PubMed Central

    D'Angelo, L.; Monti, J.M.

    1981-01-01

    1 A study was carried out in rats (prepared for chronic sleep recording) of the effects of oxolinic acid on the sleep-wakefulness cycle. 2 In addition, the actions of oxolinic acid on the sleep-wake cycle were assessed after pretreatment with drugs interfering with central catecholamine mechanisms or facilitating central γ-aminobutyric acid (GABA) activity. 3 Oxolinic acid (8-32 mg/kg) induced a significant and dose-related increase of waking EEG, while slow wave and REM sleep were decreased. 4 The effects of oxolinic acid on waking, slow wave and REM sleep were antagonized by α-methyl-p-tyrosine (50-100 mg/kg) which interferes with the synthesis of catecholamines. 5 FLA-63 (25 mg/kg) which is a specific inhibitor of noradrenaline synthesis, was effective in blocking oxolinic acid-related increase of waking and decrease of slow wave sleep. 6 Haloperidol (0.4-0.6 mg/kg) which blocks central dopamine and noradrenaline receptors, reversed oxolinic acid-induced actions on waking and slow wave sleep. Spiroperidol (2-4 mg/kg) which interferes with dopamine and 5-hydroxytryptamine mechanisms, only antagonized the effect of oxolinic acid on light slow wave sleep. REM sleep was further decreased by both neuroleptic agents. 7 γ-Hydroxybutyrate (25-50 mg/kg), which acts as a GABA agonist and amino-oxyacetic acid (20 mg/kg), which considerably increases central GABA levels, were ineffective in blocking oxolinic acid-related disruption of the sleep-wake cycle. 8 Our results suggest that the catecholamines are involved in the arousing effect of oxolinic acid. PMID:7317689

  16. Chopper-controlled discharge life cycling studies on lead-acid batteries

    NASA Technical Reports Server (NTRS)

    Kraml, J. J.; Ames, E. P.

    1982-01-01

    State-of-the-art 6 volt lead-acid golf car batteries were tested. A daily charge/discharge cycling to failure points under various chopper controlled pulsed dc and continuous current load conditions was undertaken. The cycle life and failure modes were investigated for depth of discharge, average current chopper frequency, and chopper duty cycle. It is shown that battery life is primarily and inversely related to depth of discharge and discharge current. Failure mode is characterized by a gradual capacity loss with consistent evidence of cell element aging.

  17. Results of chopper-controlled discharge life cycling studies on lead acid batteries

    NASA Technical Reports Server (NTRS)

    Ewashinka, J. G.; Sidik, S. M.

    1982-01-01

    A group of 108 state of the art nominally 6 volt lead acid batteries were tested in a program of one charge/discharge cycle per day for over two years or to ultimate battery failure. The primary objective was to determine battery cycle life as a function of depth of discharge (25 to 75 percent), chopper frequency (100 to 1000 Hz), duty cycle (25 to 87.5 percent), and average discharge current (20 to 260 A). The secondary objective was to determine the types of battery failure modes, if any, were due to the above parameters. The four parameters above were incorporated in a statistically designed test program.

  18. NHI-Acid Concentration Membranes -- Membrane Recommendations for the S-I Cycle

    SciTech Connect

    Frederick F Stewart

    2007-03-01

    Scope: The purpose of this draft report is to make recommendations concerning the applicability of specific membrane materials for acid concentration processes to the Sulfur-Iodine (S-I) thermochemical cycle integrated laboratory scale (ILS) demonstration. Introduction Acid concentration membrane processes have been studied for possible inclusion in the Sulfur-Iodine integrated laboratory scale (S-I ILS) demonstration. The need for this technology is driven by the chemical processes required for economical water splitting using the S-I cycle. Of the chemical processes inherent to the S-I cycle that have been identified as targets for deployment of membrane technology, three have been studied during the past three fiscal years as a part of the DOE Nuclear Hydrogen Initiative. First, the ability to concentrate hydriodic acid (HI) and iodine mixtures was sought as a method for aiding in the isolation of HI away from water and iodine. Isolated HI would then be delivered to the HI decomposition process for liberation of product hydrogen. Second, an extension of this technology to sulfuric acid was proposed to benefit sulfuric acid decomposition recycle. Third, decomposition of HI to form hydrogen is equilibrium limited. Removal of hydrogen, utilizing Le Chatelier’s principle, will increase to overall conversion and thus increasing the efficiency of the S-I cycle.

  19. [Effects of polyunsaturated fatty acids on Krebs cycle in the rat kidney in chronic phosphorus intoxication].

    PubMed

    Kulkybaev, G A; Merkusheva, N V

    1992-01-01

    The investigation of Krebs cycle state in kidney homogenates of August rats subjected to oral intoxication with oil solution of yellow phosphorus in a dose of 0.3 mg/kg, has shown that under conditions of balanced nutrition the activity of NAD-dependent isocitrate dehydrogenase, succinate dehydrogenase and accumulation of the substrate fund of the cycle decreased 3.5-fold as compared to the control. The addition of polyunsaturated fatty acids to the ration produced a positive effect on Krebs cycle state: dehydrogenase activity was not significantly changed, accumulation of Krebs cycle substrate was two-fold lower. However, this ration did not completely abolish the toxic action of yellow phosphorus on Krebs cycle.

  20. 76 FR 58078 - Thirteenth Meeting: RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-19

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  1. Thermochemical cycles

    NASA Technical Reports Server (NTRS)

    Funk, J. E.; Soliman, M. A.; Carty, R. H.; Conger, W. L.; Cox, K. E.; Lawson, D.

    1975-01-01

    The thermochemical production of hydrogen is described along with the HYDRGN computer program which attempts to rate the various thermochemical cycles. Specific thermochemical cycles discussed include: iron sulfur cycle; iron chloride cycle; and hybrid sulfuric acid cycle.

  2. Acetaminophen toxicity and 5-oxoproline (pyroglutamic acid): a tale of two cycles, one an ATP-depleting futile cycle and the other a useful cycle.

    PubMed

    Emmett, Michael

    2014-01-01

    The acquired form of 5-oxoproline (pyroglutamic acid) metabolic acidosis was first described in 1989 and its relationship to chronic acetaminophen ingestion was proposed the next year. Since then, this cause of chronic anion gap metabolic acidosis has been increasingly recognized. Many cases go unrecognized because an assay for 5-oxoproline is not widely available. Most cases occur in malnourished, chronically ill women with a history of chronic acetaminophen ingestion. Acetaminophen levels are very rarely in the toxic range; rather, they are usually therapeutic or low. The disorder generally resolves with cessation of acetaminophen and administration of intravenous fluids. Methionine or N-acetyl cysteine may accelerate resolution and methionine is protective in a rodent model. The disorder has been attributed to glutathione depletion and activation of a key enzyme in the γ-glutamyl cycle. However, the specific metabolic derangements that cause the 5-oxoproline accumulation remain unclear. An ATP-depleting futile 5-oxoproline cycle can explain the accumulation of 5-oxoproline after chronic acetaminophen ingestion. This cycle is activated by the depletion of both glutathione and cysteine. This explanation contributes to our understanding of acetaminophen-induced 5-oxoproline metabolic acidosis and the beneficial role of N-acetyl cysteine therapy. The ATP-depleting futile 5-oxoproline cycle may also play a role in the energy depletions that occur in other acetaminophen-related toxic syndromes.

  3. Glyoxylate cycle and metabolism of organic acids in the scutellum of barley seeds during germination.

    PubMed

    Ma, Zhenguo; Marsolais, Frédéric; Bernards, Mark A; Sumarah, Mark W; Bykova, Natalia V; Igamberdiev, Abir U

    2016-07-01

    During the developmental processes from dry seeds to seedling establishment, the glyoxylate cycle becomes active in the mobilization of stored oils in the scutellum of barley (Hordeum vulgare L.) seeds, as indicated by the activities of isocitrate lyase and malate synthase. The succinate produced is converted to carbohydrates via phosphoenolpyruvate carboxykinase and to amino acids via aminotransferases, while free organic acids may participate in acidifying the endosperm tissue, releasing stored starch into metabolism. The abundant organic acid in the scutellum was citrate, while malate concentration declined during the first three days of germination, and succinate concentration was low both in scutellum and endosperm. Malate was more abundant in endosperm tissue during the first three days of germination; before citrate became predominant, indicating that malate may be the main acid acidifying the endosperm. The operation of the glyoxylate cycle coincided with an increase in the ATP/ADP ratio, a buildup of H2O2 and changes in the redox state of ascorbate and glutathione. It is concluded that operation of the glyoxylate cycle in the scutellum of cereals may be important not only for conversion of fatty acids to carbohydrates, but also for the acidification of endosperm and amino acid synthesis. PMID:27181945

  4. Metabolic effects of intestinal absorption and enterohepatic cycling of bile acids

    PubMed Central

    Ferrebee, Courtney B.; Dawson, Paul A.

    2015-01-01

    The classical functions of bile acids include acting as detergents to facilitate the digestion and absorption of nutrients in the gut. In addition, bile acids also act as signaling molecules to regulate glucose homeostasis, lipid metabolism and energy expenditure. The signaling potential of bile acids in compartments such as the systemic circulation is regulated in part by an efficient enterohepatic circulation that functions to conserve and channel the pool of bile acids within the intestinal and hepatobiliary compartments. Changes in hepatobiliary and intestinal bile acid transport can alter the composition, size, and distribution of the bile acid pool. These alterations in turn can have significant effects on bile acid signaling and their downstream metabolic targets. This review discusses recent advances in our understanding of the inter-relationship between the enterohepatic cycling of bile acids and the metabolic consequences of signaling via bile acid-activated receptors, such as farnesoid X nuclear receptor (FXR) and the G-protein-coupled bile acid receptor (TGR5). PMID:26579438

  5. Effect of alternative pathway therapy on branched chain amino acid metabolism in urea cycle disorder patients.

    PubMed

    Scaglia, Fernando; Carter, Susan; O'Brien, William E; Lee, Brendan

    2004-04-01

    Urea cycle disorders (UCDs) are a group of inborn errors of hepatic metabolism caused by the loss of enzymatic activities that mediate the transfer of nitrogen from ammonia to urea. These disorders often result in life-threatening hyperammonemia and hyperglutaminemia. A combination of sodium phenylbutyrate and sodium phenylacetate/benzoate is used in the clinical management of children with urea cycle defects as a glutamine trap, diverting nitrogen from urea synthesis to alternatives routes of excretion. We have observed that patients treated with these compounds have selective branched chain amino acid (BCAA) deficiency despite adequate dietary protein intake. However, the direct effect of alternative therapy on the steady state levels of plasma branched chain amino acids has not been well characterized. We have measured steady state plasma branched chain and other essential non-branched chain amino acids in control subjects, untreated ornithine transcarbamylase deficiency females and treated null activity urea cycle disorder patients in the fed steady state during the course of stable isotope studies. Steady-state leucine levels were noted to be significantly lower in treated urea cycle disorder patients when compared to either untreated ornithine transcarbamylase deficiency females or control subjects (P<0.0001). This effect was reproduced in control subjects who had depressed leucine levels when treated with sodium phenylacetate/benzoate (P<0.0001). Our studies suggest that this therapeutic modality has a substantial impact on the metabolism of branched chain amino acids in urea cycle disorder patients. These findings suggest that better titration of protein restriction could be achieved with branched chain amino acid supplementation in patients with UCDs who are on alternative route therapy.

  6. Unsuspected task for an old team: succinate, fumarate and other Krebs cycle acids in metabolic remodeling.

    PubMed

    Bénit, Paule; Letouzé, Eric; Rak, Malgorzata; Aubry, Laetitia; Burnichon, Nelly; Favier, Judith; Gimenez-Roqueplo, Anne-Paule; Rustin, Pierre

    2014-08-01

    Seventy years from the formalization of the Krebs cycle as the central metabolic turntable sustaining the cell respiratory process, key functions of several of its intermediates, especially succinate and fumarate, have been recently uncovered. The presumably immutable organization of the cycle has been challenged by a number of observations, and the variable subcellular location of a number of its constitutive protein components is now well recognized, although yet unexplained. Nonetheless, the most striking observations have been made in the recent period while investigating human diseases, especially a set of specific cancers, revealing the crucial role of Krebs cycle intermediates as factors affecting genes methylation and thus cell remodeling. We review here the recent advances and persisting incognita about the role of Krebs cycle acids in diverse aspects of cellular life and human pathology.

  7. Lipotoxicity in steatohepatitis occurs despite an increase in tricarboxylic acid cycle activity.

    PubMed

    Patterson, Rainey E; Kalavalapalli, Srilaxmi; Williams, Caroline M; Nautiyal, Manisha; Mathew, Justin T; Martinez, Janie; Reinhard, Mary K; McDougall, Danielle J; Rocca, James R; Yost, Richard A; Cusi, Kenneth; Garrett, Timothy J; Sunny, Nishanth E

    2016-04-01

    The hepatic tricarboxylic acid (TCA) cycle is central to integrating macronutrient metabolism and is closely coupled to cellular respiration, free radical generation, and inflammation. Oxidative flux through the TCA cycle is induced during hepatic insulin resistance, in mice and humans with simple steatosis, reflecting early compensatory remodeling of mitochondrial energetics. We hypothesized that progressive severity of hepatic insulin resistance and the onset of nonalcoholic steatohepatitis (NASH) would impair oxidative flux through the hepatic TCA cycle. Mice (C57/BL6) were fed a high-trans-fat high-fructose diet (TFD) for 8 wk to induce simple steatosis and NASH by 24 wk. In vivo fasting hepatic mitochondrial fluxes were determined by(13)C-nuclear magnetic resonance (NMR)-based isotopomer analysis. Hepatic metabolic intermediates were quantified using mass spectrometry-based targeted metabolomics. Hepatic triglyceride accumulation and insulin resistance preceded alterations in mitochondrial metabolism, since TCA cycle fluxes remained normal during simple steatosis. However, mice with NASH had a twofold induction (P< 0.05) of mitochondrial fluxes (μmol/min) through the TCA cycle (2.6 ± 0.5 vs. 5.4 ± 0.6), anaplerosis (9.1 ± 1.2 vs. 16.9 ± 2.2), and pyruvate cycling (4.9 ± 1.0 vs. 11.1 ± 1.9) compared with their age-matched controls. Induction of the TCA cycle activity during NASH was concurrent with blunted ketogenesis and accumulation of hepatic diacylglycerols (DAGs), ceramides (Cer), and long-chain acylcarnitines, suggesting inefficient oxidation and disposal of excess free fatty acids (FFA). Sustained induction of mitochondrial TCA cycle failed to prevent accretion of "lipotoxic" metabolites in the liver and could hasten inflammation and the metabolic transition to NASH.

  8. Lipotoxicity in steatohepatitis occurs despite an increase in tricarboxylic acid cycle activity.

    PubMed

    Patterson, Rainey E; Kalavalapalli, Srilaxmi; Williams, Caroline M; Nautiyal, Manisha; Mathew, Justin T; Martinez, Janie; Reinhard, Mary K; McDougall, Danielle J; Rocca, James R; Yost, Richard A; Cusi, Kenneth; Garrett, Timothy J; Sunny, Nishanth E

    2016-04-01

    The hepatic tricarboxylic acid (TCA) cycle is central to integrating macronutrient metabolism and is closely coupled to cellular respiration, free radical generation, and inflammation. Oxidative flux through the TCA cycle is induced during hepatic insulin resistance, in mice and humans with simple steatosis, reflecting early compensatory remodeling of mitochondrial energetics. We hypothesized that progressive severity of hepatic insulin resistance and the onset of nonalcoholic steatohepatitis (NASH) would impair oxidative flux through the hepatic TCA cycle. Mice (C57/BL6) were fed a high-trans-fat high-fructose diet (TFD) for 8 wk to induce simple steatosis and NASH by 24 wk. In vivo fasting hepatic mitochondrial fluxes were determined by(13)C-nuclear magnetic resonance (NMR)-based isotopomer analysis. Hepatic metabolic intermediates were quantified using mass spectrometry-based targeted metabolomics. Hepatic triglyceride accumulation and insulin resistance preceded alterations in mitochondrial metabolism, since TCA cycle fluxes remained normal during simple steatosis. However, mice with NASH had a twofold induction (P< 0.05) of mitochondrial fluxes (μmol/min) through the TCA cycle (2.6 ± 0.5 vs. 5.4 ± 0.6), anaplerosis (9.1 ± 1.2 vs. 16.9 ± 2.2), and pyruvate cycling (4.9 ± 1.0 vs. 11.1 ± 1.9) compared with their age-matched controls. Induction of the TCA cycle activity during NASH was concurrent with blunted ketogenesis and accumulation of hepatic diacylglycerols (DAGs), ceramides (Cer), and long-chain acylcarnitines, suggesting inefficient oxidation and disposal of excess free fatty acids (FFA). Sustained induction of mitochondrial TCA cycle failed to prevent accretion of "lipotoxic" metabolites in the liver and could hasten inflammation and the metabolic transition to NASH. PMID:26814015

  9. Evolution and functional implications of the tricarboxylic acid cycle as revealed by phylogenetic analysis.

    PubMed

    Cavalcanti, João Henrique Frota; Esteves-Ferreira, Alberto A; Quinhones, Carla G S; Pereira-Lima, Italo A; Nunes-Nesi, Adriano; Fernie, Alisdair R; Araújo, Wagner L

    2014-10-01

    The tricarboxylic acid (TCA) cycle, a crucial component of respiratory metabolism, is composed of a set of eight enzymes present in the mitochondrial matrix. However, most of the TCA cycle enzymes are encoded in the nucleus in higher eukaryotes. In addition, evidence has accumulated demonstrating that nuclear genes were acquired from the mitochondrial genome during the course of evolution. For this reason, we here analyzed the evolutionary history of all TCA cycle enzymes in attempt to better understand the origin of these nuclear-encoded proteins. Our results indicate that prior to endosymbiotic events the TCA cycle seemed to operate only as isolated steps in both the host (eubacterial cell) and mitochondria (alphaproteobacteria). The origin of isoforms present in different cell compartments might be associated either with gene-transfer events which did not result in proper targeting of the protein to mitochondrion or with duplication events. Further in silico analyses allow us to suggest new insights into the possible roles of TCA cycle enzymes in different tissues. Finally, we performed coexpression analysis using mitochondrial TCA cycle genes revealing close connections among these genes most likely related to the higher efficiency of oxidative phosphorylation in this specialized organelle. Moreover, these analyses allowed us to identify further candidate genes which might be used for metabolic engineering purposes given the importance of the TCA cycle during development and/or stress situations.

  10. Evolution and Functional Implications of the Tricarboxylic Acid Cycle as Revealed by Phylogenetic Analysis

    PubMed Central

    Cavalcanti, João Henrique Frota; Esteves-Ferreira, Alberto A.; Quinhones, Carla G.S.; Pereira-Lima, Italo A.; Nunes-Nesi, Adriano; Fernie, Alisdair R.; Araújo, Wagner L.

    2014-01-01

    The tricarboxylic acid (TCA) cycle, a crucial component of respiratory metabolism, is composed of a set of eight enzymes present in the mitochondrial matrix. However, most of the TCA cycle enzymes are encoded in the nucleus in higher eukaryotes. In addition, evidence has accumulated demonstrating that nuclear genes were acquired from the mitochondrial genome during the course of evolution. For this reason, we here analyzed the evolutionary history of all TCA cycle enzymes in attempt to better understand the origin of these nuclear-encoded proteins. Our results indicate that prior to endosymbiotic events the TCA cycle seemed to operate only as isolated steps in both the host (eubacterial cell) and mitochondria (alphaproteobacteria). The origin of isoforms present in different cell compartments might be associated either with gene-transfer events which did not result in proper targeting of the protein to mitochondrion or with duplication events. Further in silico analyses allow us to suggest new insights into the possible roles of TCA cycle enzymes in different tissues. Finally, we performed coexpression analysis using mitochondrial TCA cycle genes revealing close connections among these genes most likely related to the higher efficiency of oxidative phosphorylation in this specialized organelle. Moreover, these analyses allowed us to identify further candidate genes which might be used for metabolic engineering purposes given the importance of the TCA cycle during development and/or stress situations. PMID:25274566

  11. Gas-aerosol cycling of ammonia and nitric acid in The Netherlands

    NASA Astrophysics Data System (ADS)

    Roelofs, Geert-Jan; Derksen, Jeroen

    2010-05-01

    Atmospheric ammonia and nitric acid are present over NW Europe in large abundance. Observations made during the IMPACT measurement campaign (May 2008, Cabauw, The Netherlands) show a pronounced diurnal cycle of aerosol ammonium and nitrate on relatively dry days. Simultaneously, AERONET data show a distinct diurnal cycle in aerosol optical thickness (AOT). We used a global aerosol-climate model (ECHAM5-HAM) and a detailed aerosol-cloud column model to help analyse the observations from this period. The study shows that the diurnal cycle in AOT is partly associated with particle number concentration, with distinct peaks in the morning and evening. More important is relative humidity (RH). RH maximizes in the night and early morning, decreases during the morning and increases again in the evening. The particle wet radius, and therefore AOT, changes accordingly. In addition, the RH variability also influences chemistry associated with ammonia and nitric acid (formation of ammonium nitrate, dissolution in aerosol water), resulting in the observed diurnal cycle of aerosol ammonium and nitrate. The additional aerosol matter increases the hygroscopicity of the particles, and this leads to further swelling by water vapor condensation and a further increase of AOT. During the day, as RH decreases and the particles shrink, aerosol ammonium and nitrate are again partly expelled to the gas phase. This behaviour contributes significantly to the observed diurnal cycle in AOT, and it illustrates the complexity of using AOT as a proxy for aerosol concentrations in aerosol climate studies in the case of heavily polluted areas.

  12. Temperature effects on sealed lead acid batteries and charging techniques to prolong cycle life.

    SciTech Connect

    Hutchinson, Ronda

    2004-06-01

    Sealed lead acid cells are used in many projects in Sandia National Laboratories Department 2660 Telemetry and Instrumentation systems. The importance of these cells in battery packs for powering electronics to remotely conduct tests is significant. Since many tests are carried out in flight or launched, temperature is a major factor. It is also important that the battery packs are properly charged so that the test is completed before the pack cannot supply sufficient power. Department 2665 conducted research and studies to determine the effects of temperature on cycle time as well as charging techniques to maximize cycle life and cycle times on sealed lead acid cells. The studies proved that both temperature and charging techniques are very important for battery life to support successful field testing and expensive flight and launched tests. This report demonstrates the effects of temperature on cycle time for SLA cells as well as proper charging techniques to get the most life and cycle time out of SLA cells in battery packs.

  13. C-Myc induced compensated cardiac hypertrophy increases free fatty acid utilization for the citric acid cycle.

    PubMed

    Olson, Aaron K; Ledee, Dolena; Iwamoto, Kate; Kajimoto, Masaki; O'Kelly Priddy, Colleen; Isern, Nancy; Portman, Michael A

    2013-02-01

    The protooncogene C-Myc (Myc) regulates cardiac hypertrophy. Myc promotes compensated cardiac function, suggesting that the operative mechanisms differ from those leading to heart failure. Myc regulation of substrate metabolism is a reasonable target, as Myc alters metabolism in other tissues. We hypothesize that Myc induced shifts in substrate utilization signal and promote compensated hypertrophy. We used cardiac specific Myc-inducible C57/BL6 male mice between 4-6 months old that develop hypertrophy with tamoxifen (tam) injections. Isolated working hearts and (13)Carbon ((13)C)-NMR were used to measure function and fractional contributions (Fc) to the citric acid cycle by using perfusate containing (13)C-labeled free fatty acids, acetoacetate, lactate, unlabeled glucose and insulin. Studies were performed at pre-hypertrophy (3-days tam, 3dMyc), established hypertrophy (7-days tam, 7dMyc) or vehicle control (Cont). Non-transgenic siblings (NTG) received 7-days tam or vehicle to assess drug effect. Hypertrophy was assessed by echocardiograms and heart weights. Western blots were performed on key metabolic enzymes. Hypertrophy occurred in 7dMyc only. Cardiac function did not differ between groups. Tam alone did not affect substrate contributions in NTG. Substrate utilization was not significantly altered in 3dMyc versus Cont. The free fatty acid FC was significantly greater in 7dMyc versus Cont with decreased unlabeled Fc, which is predominately exogenous glucose. Free fatty acid flux to the citric acid cycle increased while lactate flux was diminished in 7dMyc compared to Cont. Total protein levels of a panel of key metabolic enzymes were unchanged; however total protein O-GlcNAcylation was increased in 7dMyc. Substrate utilization changes for the citric acid cycle did not precede hypertrophy; therefore they are not the primary signal for cardiac growth in this model. Free fatty acid utilization and oxidation increase at established hypertrophy. Understanding the

  14. Novel flowering and fatty acid characters in rapid cycling Brassica napus L. resynthesized by protoplast fusion.

    PubMed

    Hansen, L N; Earle, E D

    1994-12-01

    Novel rapid cycling Brassica napus lines have been produced by protoplast fusion between rapid cycling B. oleracea and rapid cycling B. rapa. Fusion products were selected based on iodoacetate inactivation and regeneration ability. A total of 36 plants was recovered from 3 regenerating calli. All were confirmed as somatic hybrids by morphological features, flow cytometric estimation of nuclear DNA content, RAPD analysis and/or DNA hybridization. Plants from two of the calli contained chloroplasts from B. rapa, and plants from the third contained B. oleracea chloroplasts. Some plants flowered in vitro, but on average flowering was initiated 22 days after transfer to soil. Although seed set was fairly low after self pollination, more seeds were obtained from pollination of open flowers than from pollination of buds. Seeds of the somatic hybrid B. napus showed novel fatty acid compositions, different from the mean of the two parental lines. Flowering was monitored in plants grown from seeds of the somatic hybrids, rapid cycling B. napus (CrGC 5-1) and the two diploid parental genotypes. Progeny of the somatic hybrids flowered faster and were more vigorous than rapid cycling B. napus (CrGC 5-1). The improved lines contain chloroplasts from B. rapa, unlike rapid cycling B. napus (CrGC 5-1), which has B. oleracea chloroplasts. The somatic hybrid lines produced may be useful for genetic studies or further in vitro manipulations.

  15. Pull-in urea cycle for the production of fumaric acid in Escherichia coli.

    PubMed

    Zhang, Ting; Wang, Zening; Deng, Li; Tan, Tianwei; Wang, Fang; Yan, Yajun

    2015-06-01

    Fumaric acid (FA) is an important raw material in the chemical and pharmaceutical industries. In this work, Escherichia coli was metabolically engineered for the production of FA. The fumA, fumB, fumC, and frdABCD genes were deleted to cut off the downstream pathway of FA. In addition, the iclR and arcA genes were also deleted to activate the glyoxylate shunt and to reinforce the oxidative Krebs cycle. To increase the FA yield, this base strain was further engineered to be pulled in the urea cycle by overexpressing the native carAB, argI, and heterologous rocF genes. The metabolites and the proteins of the Krebs cycle and the urea cycle were analyzed to confirm that the induced urea cycle improved the FA accumulation. With the induced urea cycle, the resulting strain ABCDIA-RAC was able to produce 11.38 mmol/L of FA from 83.33 mmol/L of glucose in a flask culture during 24 h of incubation.

  16. Suppression of tricarboxylic acid cycle in Escherichia coli exposed to sub-MICs of aminoglycosides.

    PubMed Central

    Cavallero, A; Eftimiadi, C; Radin, L; Schito, G C

    1990-01-01

    The metabolic activity of Escherichia coli ATCC 25922 challenged with sub-MICs of aminoglycosides was analyzed with a batch calorimeter. High-performance and gas-liquid chromatographic techniques were utilized to evaluate the concentrations of metabolic reactants, intermediates, and end products. The data reported indicate that aminoglycosides inhibit or delay bacterial catabolism of carboxylic acids, with the following relative degrees of activity: amikacin greater than gentamicin greater than sisomicin greater than netilmicin greater than kanamycin. The decrease in total biomass production was proportional to the degree of tricarboxylic acid cycle inhibition. PMID:2183717

  17. On a hypothetical generational relationship between HCN and constituents of the reductive citric acid cycle.

    PubMed

    Eschenmoser, Albert

    2007-04-01

    Encouraged by observations made on the course of reactions the HCN-tetramer can undergo with acetaldehyde, I delineate a constitutional and potentially generational relationship between HCN and those constituents of the reductive citric acid cycle that are direct precursors of amino acids in contemporary metabolism. In this context, the robustness postulate of classical prebiotic chemistry is questioned, and, by an analysis of the (hypothetical) reaction-tree of a stepwise hydrolysis of the HCN-tetramer, it is shown how such a non-robust chemical reaction platform could harbor the potential for the emergence of autocatalytic cycles. It is concluded that the chemistry of HCN should be revisited by focussing on its non-robust parts in order to demonstrate its full potential as one of the possible roots of prebiotic self-organizing chemical processes.

  18. 75 FR 2924 - Thirteenth Plenary Meeting, RTCA Special Committee 205/EUROCAE WG 71: Software Considerations in...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-19

    ...: RTCA Secretariat, 1828 L Street, NW., Suite 805, Washington, DC 20036; telephone (202) 833-9339; fax... Personnel Reports (CAST, Unmanned Aircraft Systems, Security, WG-63/SAE S-18) 10:30 a.m.--Break 10:45 a.m...-Group Break Out Sessions 13:00 p.m.--CAST Meeting 14:30 p.m.--Break 14:45 p.m.--Plenary Session:...

  19. Effect on combined cycle efficiency of stack gas temperature constraints to avoid acid corrosion

    NASA Technical Reports Server (NTRS)

    Nainiger, J. J.

    1980-01-01

    To avoid condensation of sulfuric acid in the gas turbine exhaust when burning fuel oils contaning sulfur, the exhaust stack temperature and cold-end heat exchanger surfaces must be kept above the condensation temperature. Raising the exhaust stack temperature, however, results in lower combined cycle efficiency compared to that achievable by a combined cycle burning a sulfur-free fuel. The maximum difference in efficiency between the use of sulfur-free and fuels containing 0.8 percent sulfur is found to be less than one percentage point. The effect of using a ceramic thermal barrier coating (TBC) and a fuel containing sulfur is also evaluated. The combined-cycle efficiency gain using a TBC with a fuel containing sulfur compared to a sulfur-free fuel without TBC is 0.6 to 1.0 percentage points with air-cooled gas turbines and 1.6 to 1.8 percentage points with water-cooled gas turbines.

  20. Systems-level metabolic flux profiling elucidates a complete, bifurcated tricarboxylic acid cycle in Clostridium acetobutylicum.

    PubMed

    Amador-Noguez, Daniel; Feng, Xiao-Jiang; Fan, Jing; Roquet, Nathaniel; Rabitz, Herschel; Rabinowitz, Joshua D

    2010-09-01

    Obligatory anaerobic bacteria are major contributors to the overall metabolism of soil and the human gut. The metabolic pathways of these bacteria remain, however, poorly understood. Using isotope tracers, mass spectrometry, and quantitative flux modeling, here we directly map the metabolic pathways of Clostridium acetobutylicum, a soil bacterium whose major fermentation products include the biofuels butanol and hydrogen. While genome annotation suggests the absence of most tricarboxylic acid (TCA) cycle enzymes, our results demonstrate that this bacterium has a complete, albeit bifurcated, TCA cycle; oxaloacetate flows to succinate both through citrate/alpha-ketoglutarate and via malate/fumarate. Our investigations also yielded insights into the pathways utilized for glucose catabolism and amino acid biosynthesis and revealed that the organism's one-carbon metabolism is distinct from that of model microbes, involving reversible pyruvate decarboxylation and the use of pyruvate as the one-carbon donor for biosynthetic reactions. This study represents the first in vivo characterization of the TCA cycle and central metabolism of C. acetobutylicum. Our results establish a role for the full TCA cycle in an obligatory anaerobic organism and demonstrate the importance of complementing genome annotation with isotope tracer studies for determining the metabolic pathways of diverse microbes.

  1. An ATP and Oxalate Generating Variant Tricarboxylic Acid Cycle Counters Aluminum Toxicity in Pseudomonas fluorescens

    PubMed Central

    Singh, Ranji; Lemire, Joseph; Mailloux, Ryan J.; Chénier, Daniel; Hamel, Robert; Appanna, Vasu D.

    2009-01-01

    Although the tricarboxylic acid (TCA) cycle is essential in almost all aerobic organisms, its precise modulation and integration in global cellular metabolism is not fully understood. Here, we report on an alternative TCA cycle uniquely aimed at generating ATP and oxalate, two metabolites critical for the survival of Pseudomonas fluorescens. The upregulation of isocitrate lyase (ICL) and acylating glyoxylate dehydrogenase (AGODH) led to the enhanced synthesis of oxalate, a dicarboxylic acid involved in the immobilization of aluminum (Al). The increased activity of succinyl-CoA synthetase (SCS) and oxalate CoA-transferase (OCT) in the Al-stressed cells afforded an effective route to ATP synthesis from oxalyl-CoA via substrate level phosphorylation. This modified TCA cycle with diminished efficacy in NADH production and decreased CO2-evolving capacity, orchestrates the synthesis of oxalate, NADPH, and ATP, ingredients pivotal to the survival of P. fluorescens in an Al environment. The channeling of succinyl-CoA towards ATP formation may be an important function of the TCA cycle during anaerobiosis, Fe starvation and O2-limited conditions. PMID:19809498

  2. Hypertonic stress regulates amino acid transport and cell cycle proteins in chick embryo hepatocytes.

    PubMed

    Bruscalupi, Giovannella; Massimi, Mara; Spagnuolo, Silvana; Fiore, Anna Maria; Leoni, Silvia

    2012-02-01

    Hyperosmotic stress affects cell growth, decreasing cell volume and increasing the uptake of organic osmolytes. However, the sensitivity of embryonic cells to osmotic treatment remains to be established. We have analysed some aspects of cell-cycle control and amino-acid transport in hypertonic conditions during prenatal life. The effects of hyperosmotic stress on amino-acid uptake mediated by system A, (3)H-thymidine incorporation, and regulation of cell-cycle proteins were analysed in chick embryo hepatocytes. Hypertonic stress increased system A activity and caused cell-cycle delay. Effects on amino-acid transport involved p38 kinase activation and new carrier synthesis. Cyclin D1, cdk4 (cyclin-dependent kinase 4) and PCNA (proliferating-cell nuclear antigen) levels decreased, whereas cyclin E, p21 and p53 levels were unchanged. Incorporation of (3)H-leucine indicated decreased synthesis of cyclin D1. In contrast, analysis of mRNA by qRT-PCR (quantitative real-time PCR) showed a net increase of cyclin D1 transcripts, suggesting post-transcriptional regulation. The data show that chick embryo hepatocytes respond to hyperosmotic conditions by arresting cell growth to prevent DNA damage and increasing osmolyte uptake to regulate cell volume, indicating that the adaptive response to environmental stress exists during prenatal life.

  3. Sex-dependent activity of the spinal excitatory amino acid transporter: Role of estrous cycle.

    PubMed

    Sajjad, Jahangir; Felice, Valeria D; Golubeva, Anna V; Cryan, John F; O'Mahony, Siobhain M

    2016-10-01

    Females are more likely to experience visceral pain than males, yet mechanisms underlying this sex bias are not fully elucidated. Moreover, pain sensitivity can change throughout the menstrual cycle. Alterations in the glutamatergic system have been implicated in several pain-disorders; however, whether these are sex-dependent is unclear. Thus, we aimed to investigate sex differences in the spinal cord glutamate uptake and how it varies across the estrous cycle. The activity of the glutamate transporters, excitatory amino acid transporters (EAATs) was assessed using an ex vivo aspartate radioactive uptake assay in the lumbosacral spinal cord in Sprague-Dawley male and female rats. The gene expression of EAATs, glutamate receptor subunits NR1 and NR2B and the estrogen receptors ERα & ERβ in the spinal cord were also analyzed. EAAT activity was lower in females, particularly during the estrus phase, and this was the only cycle stage that was responsive to the pharmacological effects of the EAATs activator riluzole. Interestingly, EAAT1 mRNA expression was lower in high-estrogen and high-ERα states compared to diestrus in females. We conclude that the Spinal EAAT activity in females is different to that in males, and varies across the estrous cycle. Furthermore, the expression levels of estrogen receptors also showed a cycle-dependent pattern that may affect EAATs function and expression. PMID:27471194

  4. Regulation of leukocyte tricarboxylic acid cycle in drug-naïve Bipolar Disorder.

    PubMed

    de Sousa, Rafael T; Streck, Emilio L; Forlenza, Orestes V; Brunoni, Andre R; Zanetti, Marcus V; Ferreira, Gabriela K; Diniz, Breno S; Portela, Luis V; Carvalho, André F; Zarate, Carlos A; Gattaz, Wagner F; Machado-Vieira, Rodrigo

    2015-09-25

    Several lines of evidence suggest a role for mitochondrial dysfunction in the pathophysiology of bipolar disorder (BD). The tricarboxylic acid cycle (TCA cycle) is fundamental for mitochondrial energy production and produces substrates used in oxidative phosphorylation by the mitochondrial electron transport chain. The activity of the key TCA cycle enzymes citrate synthase, malate dehydrogenase, and succinate dehydrogenase has never been evaluated in BD. In the present study, these enzymes were assayed from leukocytes of drug-naïve BD patients in a major depressive episode (n=18) and compared to 24 age-matched healthy controls. Drug-naïve BD patients did not show differences in activities of citrate synthase (p=0.79), malate dehydrogenase (p=0.17), and succinate dehydrogenase (p=0.35) compared with healthy controls. No correlation between any TCA cycle enzyme activity and severity of depressive symptoms was observed. Overall, these data suggest that the activities of the TCA cycle enzymes are not altered in major depressive episodes of recent-onset BD, which may support the concept of illness staging and neuroprogression in BD. PMID:26297865

  5. Regulation of leukocyte tricarboxylic acid cycle in drug-naïve Bipolar Disorder.

    PubMed

    de Sousa, Rafael T; Streck, Emilio L; Forlenza, Orestes V; Brunoni, Andre R; Zanetti, Marcus V; Ferreira, Gabriela K; Diniz, Breno S; Portela, Luis V; Carvalho, André F; Zarate, Carlos A; Gattaz, Wagner F; Machado-Vieira, Rodrigo

    2015-09-25

    Several lines of evidence suggest a role for mitochondrial dysfunction in the pathophysiology of bipolar disorder (BD). The tricarboxylic acid cycle (TCA cycle) is fundamental for mitochondrial energy production and produces substrates used in oxidative phosphorylation by the mitochondrial electron transport chain. The activity of the key TCA cycle enzymes citrate synthase, malate dehydrogenase, and succinate dehydrogenase has never been evaluated in BD. In the present study, these enzymes were assayed from leukocytes of drug-naïve BD patients in a major depressive episode (n=18) and compared to 24 age-matched healthy controls. Drug-naïve BD patients did not show differences in activities of citrate synthase (p=0.79), malate dehydrogenase (p=0.17), and succinate dehydrogenase (p=0.35) compared with healthy controls. No correlation between any TCA cycle enzyme activity and severity of depressive symptoms was observed. Overall, these data suggest that the activities of the TCA cycle enzymes are not altered in major depressive episodes of recent-onset BD, which may support the concept of illness staging and neuroprogression in BD.

  6. High pressure sulfuric acid decomposition experiments for the sulfur-iodine thermochemical cycle.

    SciTech Connect

    Velasquez, Carlos E; Reay, Andrew R.; Andazola, James C.; Naranjo, Gerald E.; Gelbard, Fred

    2005-09-01

    A series of three pressurized sulfuric acid decomposition tests were performed to (1) obtain data on the fraction of sulfuric acid catalytically converted to sulfur dioxide, oxygen, and water as a function of temperature and pressure, (2) demonstrate real-time measurements of acid conversion for use as process control, (3) obtain multiple measurements of conversion as a function of temperature within a single experiment, and (4) assess rapid quenching to minimize corrosion of metallic components by undecomposed acid. All four of these objectives were successfully accomplished. This report documents the completion of the NHI milestone on high pressure H{sub 2}SO{sub 4} decomposition tests for the Sulfur-Iodine (SI) thermochemical cycle project. All heated sections of the apparatus, (i.e. the boiler, decomposer, and condenser) were fabricated from Hastelloy C276. A ceramic acid injection tube and a ceramic-sheathed thermocouple were used to minimize corrosion of hot liquid acid on the boiler surfaces. Negligible fracturing of the platinum on zirconia catalyst was observed in the high temperature decomposer. Temperature measurements at the exit of the decomposer and at the entry of the condenser indicated that the hot acid vapors were rapidly quenched from about 400 C to less than 20 C within a 14 cm length of the flow path. Real-time gas flow rate measurements of the decomposition products provided a direct measurement of acid conversion. Pressure in the apparatus was preset by a pressure-relief valve that worked well at controlling the system pressure. However, these valves sometimes underwent abrupt transitions that resulted in rapidly varying gas flow rates with concomitant variations in the acid conversion fraction.

  7. Acid-Tolerant Sulfate-Reducing Bacteria Play a Major Role in Iron Cycling in Acidic Iron Rich Sediments

    NASA Astrophysics Data System (ADS)

    Enright, K. A.; Moreau, J. W.

    2008-12-01

    Climate change drives drying and acidification of many rivers and lakes. Abundant sedimentary iron in these systems oxidizes chemically and biologically to form iron-ox(yhydrox)ide crusts and "hardpans". Given generally high sulfate concentrations, the mobilization and cycling of iron in these environments can be strongly influenced by bacterial sulfate reduction. Sulfate-reducing bacteria (SRB) induce reductive dissolution of oxidized iron phases by producing the reductant bisulfide as a metabolic product. These environmentally ubiquitous microbes also recycle much of the fixed carbon in sediment-hosted microbial mat communities. With prevalent drying, the buffering capacity for protons liberated from iron oxidation is exceeded, and the activity of sulfate-reducers is restricted to those species capable of tolerating low pH (and generally highly saline, i.e. sulfate-rich) conditions. These species will sustain the recycling of iron from more crystalline phases to more bioavailable species, as well as act as the only source of bisulfide for photosynthesizing microbial communities. The phylogeny and physiology of acid-tolerant SRB is therefore important to Fe, S and C cycling in iron-rich sedimentary environments, particularly those on a geochemical trajectory towards acidification. Previous studies have shown that these SRB species tend to be highly novel. We studied two distinct environments along a geochemical continuum towards acidification. In both settings, iron redox transformations exert a major, if not controlling, influence on reduction potential. An acidified, iron- rich tidal marsh receiving acid-mine drainage (San Francisco Bay, CA, USA) contained abundant textural evidence for reductive dissolution of Fe(III) in sediments with pH values varying from 2.4 - 3.8. From these sediments, full-length novel dsrAB gene sequences from acid-tolerant SRB were recovered, and sulfur isotope profiles reflected biological fractionation of sulfur under even the most

  8. Lead-acid battery with improved cycle life and increased efficiency for lead leveling application and electric road vehicles

    NASA Astrophysics Data System (ADS)

    Winsel, A.; Schulz, J.; Guetlich, K. F.

    1983-11-01

    Lifetime and efficiency of lead acid batteries are discussed. A gas lift pump was used to prevent acid stratification and to reduce the charging factor (down to 1.03 to 1.05). A re-expansion method was applied and an expander depot and a compound separation were built in. Cycle life is increased from 700 cycles to 1690 cycles. Efficiency is increased by energy and time saving due to the reduced charging factor and by the use of a recombination stopper and a charge indicator with remote control. It is suggested that the lead acid system is still one of the best possibilities for electric road vehicle applications.

  9. New low-antimony alloy for straps and cycling service in lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Prengaman, R. David

    Lead-antimony alloys used for the positive grids in lead-acid batteries for cycling service have generally used antimony contents of 4.5 wt.% and above. Tubular batteries for cycling service that impart high compression of the active material to the grid surface via gauntlet use alloys with antimony contents as low as 1.5 wt.%. These batteries are generally employed in less-severe cycling service. Value-regulated lead-acid (VRLA) batteries can give good cycling service without lead-antimony in the positive grid, but require a high tin content and high compression. The change in automotive battery positive grid alloys to lead-calcium-tin and the tin contents of VRLA positive grids and straps have dramatically increased the tin content of the recycled grid and strap lead in the USA, Europe, and Australia. The higher tin contents can contaminate the lead used for lead-antimony battery grids and generally must be removed to low levels to meet the specifications. This study describes a low-antimony alloy that contains a substantial amount of tin. The high tin content reduces the rate of corrosion of low-antimony positive grid alloys, improves conductivity, increases the bond between the grid and the active material, and cycles as well as the traditional 5-6 wt.% antimony alloys employed in conventional flat-plate batteries. The alloy is also used as a corrosion-resistant cast-on strap alloy for automotive batteries for high temperature service, as well as for posts, bushings, and connectors for all wet batteries.

  10. Modulation of fatty acid metabolism and tricarboxylic acid cycle to enhance the lipstatin production through medium engineering in Streptomyces toxytricini.

    PubMed

    Kumar, Punit; Dubey, Kashyap Kumar

    2016-08-01

    This work investigated the potential of medium engineering to obtain maximum biomass, non-conventional carbon sources for lipstatin production and modulation of tricarboxylic acid (TCA) cycle to promote lipstatin synthesis. It was found that 2:3 carbon and nitrogen ratio, produced maximum biomass of 7.9g/L in growth medium and 6.6g/L in pre-seed medium. Among the studied non-conventional carbon sources i.e., soya flour 40g/L and sesame oil 30mL/L were found producing 1109.37mg/L (1.24-fold of control) and 1196.75mg/L (1.34-fold of control) lipstatin respectively. Supplementation of TCA cycle intermediates revealed that NADH and succinic acid showed lipstatin production to 1132.99mg/L and 1171.10mg/L respectively. Experimental outcome was validated in 7L bioreactor and produced 2242.63mg/L lipstatin which was ∼14% higher than shake flask. PMID:26897471

  11. C-Myc Induced Compensated Cardiac Hypertrophy Increases Free Fatty Acid Utilization for the Citric Acid Cycle

    SciTech Connect

    Olson, Aaron; Ledee, Dolena; Iwamoto, Kate; Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Isern, Nancy G.; Portman, Michael A.

    2013-02-01

    The protooncogene C-Myc (Myc) regulates cardiac hypertrophy. Myc promotes compensated cardiac function, suggesting that the operative mechanisms differ from those leading to heart failure. Myc regulation of substrate metabolism is a reasonable target, as Myc alters metabolism in other tissues. We hypothesize that Myc-induced shifts in substrate utilization signal and promote compensated hypertrophy. We used cardiac specific Myc-inducible C57/BL6 male mice between 4-6 months old that develop hypertrophy with tamoxifen (tam). Isolated working hearts and 13Carbon (13C )-NMR were used to measure function and fractional contributions (Fc) to the citric acid cycle by using perfusate containing 13C-labeled free fatty acids, acetoacetate, lactate, unlabeled glucose and insulin. Studies were performed at pre-hypertrophy (3-days tam, 3dMyc), established hypertrophy (7-days tam, 7dMyc) or vehicle control (cont). Non-transgenic siblings (NTG) received 7-days tam or vehicle to assess drug effect. Hypertrophy was confirmed by echocardiograms and heart weights. Western blots were performed on key metabolic enzymes. Hypertrophy occurred in 7dMyc only. Cardiac function did not differ between groups. Tam alone did not affect substrate contribution in NTG. Substrate utilization was not significantly altered in 3dMyc versus cont. The free fatty acid FC was significantly greater in 7dMyc vs cont with decreased unlabeled Fc, which is predominately exogenous glucose. Free fatty acid flux to the citric acid cycle increased while lactate flux was diminished in 7dMyc compared to cont. Total protein levels of a panel of key metabolic enzymes were unchanged; however total protein O-GlcNAcylation was increased in 7dMyc. Substrate utilization changes did not precede hypertrophy; therefore they are not the primary signal for cardiac growth in this model. Free fatty acid utilization and oxidation increase at established hypertrophy. Understanding the mechanisms whereby this change maintained

  12. Sodium phenylbutyrate decreases plasma branched-chain amino acids in patients with urea cycle disorders.

    PubMed

    Burrage, Lindsay C; Jain, Mahim; Gandolfo, Laura; Lee, Brendan H; Nagamani, Sandesh C S

    2014-01-01

    Sodium phenylbutyrate (NaPBA) is a commonly used medication for the treatment of patients with urea cycle disorders (UCDs). Previous reports involving small numbers of patients with UCDs have shown that NaPBA treatment can result in lower plasma levels of the branched-chain amino acids (BCAA) but this has not been studied systematically. From a large cohort of patients (n=553) with UCDs enrolled in the Longitudinal Study of Urea Cycle Disorders, a collaborative multicenter study of the Urea Cycle Disorders Consortium, we evaluated whether treatment with NaPBA leads to a decrease in plasma BCAA levels. Our analysis shows that NaPBA use independently affects the plasma BCAA levels even after accounting for multiple confounding covariates. Moreover, NaPBA use increases the risk for BCAA deficiency. This effect of NaPBA seems specific to plasma BCAA levels, as levels of other essential amino acids are not altered by its use. Our study, in an unselected population of UCD subjects, is the largest to analyze the effects of NaPBA on BCAA metabolism and potentially has significant clinical implications. Our results indicate that plasma BCAA levels should to be monitored in patients treated with NaPBA since patients taking the medication are at increased risk for BCAA deficiency. On a broader scale, these findings could open avenues to explore NaPBA as a therapy in maple syrup urine disease and other common complex disorders with dysregulation of BCAA metabolism. PMID:25042691

  13. Thioredoxin, a master regulator of the tricarboxylic acid cycle in plant mitochondria.

    PubMed

    Daloso, Danilo M; Müller, Karolin; Obata, Toshihiro; Florian, Alexandra; Tohge, Takayuki; Bottcher, Alexandra; Riondet, Christophe; Bariat, Laetitia; Carrari, Fernando; Nunes-Nesi, Adriano; Buchanan, Bob B; Reichheld, Jean-Philippe; Araújo, Wagner L; Fernie, Alisdair R

    2015-03-17

    Plant mitochondria have a fully operational tricarboxylic acid (TCA) cycle that plays a central role in generating ATP and providing carbon skeletons for a range of biosynthetic processes in both heterotrophic and photosynthetic tissues. The cycle enzyme-encoding genes have been well characterized in terms of transcriptional and effector-mediated regulation and have also been subjected to reverse genetic analysis. However, despite this wealth of attention, a central question remains unanswered: "What regulates flux through this pathway in vivo?" Previous proteomic experiments with Arabidopsis discussed below have revealed that a number of mitochondrial enzymes, including members of the TCA cycle and affiliated pathways, harbor thioredoxin (TRX)-binding sites and are potentially redox-regulated. We have followed up on this possibility and found TRX to be a redox-sensitive mediator of TCA cycle flux. In this investigation, we first characterized, at the enzyme and metabolite levels, mutants of the mitochondrial TRX pathway in Arabidopsis: the NADP-TRX reductase a and b double mutant (ntra ntrb) and the mitochondrially located thioredoxin o1 (trxo1) mutant. These studies were followed by a comparative evaluation of the redistribution of isotopes when (13)C-glucose, (13)C-malate, or (13)C-pyruvate was provided as a substrate to leaves of mutant or WT plants. In a complementary approach, we evaluated the in vitro activities of a range of TCA cycle and associated enzymes under varying redox states. The combined dataset suggests that TRX may deactivate both mitochondrial succinate dehydrogenase and fumarase and activate the cytosolic ATP-citrate lyase in vivo, acting as a direct regulator of carbon flow through the TCA cycle and providing a mechanism for the coordination of cellular function.

  14. Thioredoxin, a master regulator of the tricarboxylic acid cycle in plant mitochondria

    PubMed Central

    Daloso, Danilo M.; Müller, Karolin; Obata, Toshihiro; Florian, Alexandra; Tohge, Takayuki; Bottcher, Alexandra; Riondet, Christophe; Bariat, Laetitia; Carrari, Fernando; Nunes-Nesi, Adriano; Buchanan, Bob B.; Reichheld, Jean-Philippe; Araújo, Wagner L.; Fernie, Alisdair R.

    2015-01-01

    Plant mitochondria have a fully operational tricarboxylic acid (TCA) cycle that plays a central role in generating ATP and providing carbon skeletons for a range of biosynthetic processes in both heterotrophic and photosynthetic tissues. The cycle enzyme-encoding genes have been well characterized in terms of transcriptional and effector-mediated regulation and have also been subjected to reverse genetic analysis. However, despite this wealth of attention, a central question remains unanswered: “What regulates flux through this pathway in vivo?” Previous proteomic experiments with Arabidopsis discussed below have revealed that a number of mitochondrial enzymes, including members of the TCA cycle and affiliated pathways, harbor thioredoxin (TRX)-binding sites and are potentially redox-regulated. We have followed up on this possibility and found TRX to be a redox-sensitive mediator of TCA cycle flux. In this investigation, we first characterized, at the enzyme and metabolite levels, mutants of the mitochondrial TRX pathway in Arabidopsis: the NADP-TRX reductase a and b double mutant (ntra ntrb) and the mitochondrially located thioredoxin o1 (trxo1) mutant. These studies were followed by a comparative evaluation of the redistribution of isotopes when 13C-glucose, 13C-malate, or 13C-pyruvate was provided as a substrate to leaves of mutant or WT plants. In a complementary approach, we evaluated the in vitro activities of a range of TCA cycle and associated enzymes under varying redox states. The combined dataset suggests that TRX may deactivate both mitochondrial succinate dehydrogenase and fumarase and activate the cytosolic ATP-citrate lyase in vivo, acting as a direct regulator of carbon flow through the TCA cycle and providing a mechanism for the coordination of cellular function. PMID:25646482

  15. Genetic and biochemical interactions involving tricarboxylic acid cycle (TCA) function using a collection of mutants defective in all TCA cycle genes.

    PubMed

    Przybyla-Zawislak, B; Gadde, D M; Ducharme, K; McCammon, M T

    1999-05-01

    The eight enzymes of the tricarboxylic acid (TCA) cycle are encoded by at least 15 different nuclear genes in Saccharomyces cerevisiae. We have constructed a set of yeast strains defective in these genes as part of a comprehensive analysis of the interactions among the TCA cycle proteins. The 15 major TCA cycle genes can be sorted into five phenotypic categories on the basis of their growth on nonfermentable carbon sources. We have previously reported a novel phenotype associated with mutants defective in the IDH2 gene encoding the Idh2p subunit of the NAD+-dependent isocitrate dehydrogenase (NAD-IDH). Null and nonsense idh2 mutants grow poorly on glycerol, but growth can be enhanced by extragenic mutations, termed glycerol suppressors, in the CIT1 gene encoding the TCA cycle citrate synthase and in other genes of oxidative metabolism. The TCA cycle mutant collection was utilized to search for other genes that can suppress idh2 mutants and to identify TCA cycle genes that display a similar suppressible growth phenotype on glycerol. Mutations in 7 TCA cycle genes were capable of functioning as suppressors for growth of idh2 mutants on glycerol. The only other TCA cycle gene to display the glycerol-suppressor-accumulation phenotype was IDH1, which encodes the companion Idh1p subunit of NAD-IDH. These results provide genetic evidence that NAD-IDH plays a unique role in TCA cycle function.

  16. Synthesis of cellulose by Acetobacter xylinum. VI. Growth on citric acid-cycle intermediates.

    PubMed

    GROMET-ELHANAN, Z; HESTRIN, S

    1963-02-01

    Gromet-Elhanan, Zippora (The Hebrew University, Jerusalem, Israel) and Shlomo Hestrin. Synthesis of cellulose by Acetobacter xylinum. VI. Growth on citric acid-cycle intermediates. J. Bacteriol. 85:284-292. 1963.-Acetobacter xylinum could be made to grow on ethanol, acetate, succinate, or l-malate. The growth was accompanied by formation of opaque leathery pellicles on the surface of the growth medium. These pellicles were identified as cellulose on the basis of their chemical properties, solubility behavior, and infrared absorption spectra. Washed-cell suspensions prepared from cultures grown on ethanol or the organic acids, in contrast to washed sugar-grown cells, were able to transform citric-cycle intermediates into cellulose. The variations in the substrate spectrum of cellulose synthesis between sugar-grown cells and organic acids-grown cells were found to be correlated with differences in the oxidative capacity of the cells. The significance of the findings that A. xylinum could be made to grow on ethanol on complex as well as synthetic media is discussed from the viewpoint of the whole pattern of Acetobacter classification.

  17. Cinnamic acid derivatives induce cell cycle arrest in carcinoma cell lines.

    PubMed

    Sova, Matej; Žižak, Željko; Stanković, Jelena A Antic; Prijatelj, Matevž; Turk, Samo; Juranić, Zorica D; Mlinarič-Raščan, Irena; Gobec, Stanislav

    2013-08-01

    Cinnamic acid derivatives can be found in plant material, and they possess a remarkable variety of biological effects. In the present study, we have investigated the cytotoxic effects of representative cinnamic acid esters and amides. The cytotoxicity was determined by MTT test on human cervix adenocarcinoma (HeLa), myelogenous leukemia (K562), malignant melanoma (Fem-x), and estrogen-receptor-positive breast cancer (MCF-7) cells, versus peripheral blood mononuclear cells (PBMCs) without or with the addition of the plant lectin phytohemaglutinin (PHA). The compounds tested showed significant cytotoxicity (IC50s between 42 and 166 µM) and furthermore selectivity of these cytotoxic effects on the malignant cell lines versus the PBMCs was also seen, especially when electron-withdrawing groups, such as a cyano group (compound 5), were present on the aromatic rings of the alcohol or amine parts of the cinnamic acid derivatives. The additional study on cell cycle phase distribution indicated that novel cinnamic acid derivatives inhibit cell growth by induction of cell death. Thus, cinnamic acids derivatives represent important lead compounds for further development of antineoplastic agents.

  18. Staphylococcus epidermidis Polysaccharide Intercellular Adhesin Production Significantly Increases during Tricarboxylic Acid Cycle Stress

    PubMed Central

    Vuong, Cuong; Kidder, Joshua B.; Jacobson, Erik R.; Otto, Michael; Proctor, Richard A.; Somerville, Greg A.

    2005-01-01

    Staphylococcal polysaccharide intercellular adhesin (PIA) is important for the development of a mature biofilm. PIA production is increased during growth in a nutrient-replete or iron-limited medium and under conditions of low oxygen availability. Additionally, stress-inducing stimuli such as heat, ethanol, and high concentrations of salt increase the production of PIA. These same environmental conditions are known to repress tricarboxylic acid (TCA) cycle activity, leading us to hypothesize that altering TCA cycle activity would affect PIA production. Culturing Staphylococcus epidermidis with a low concentration of the TCA cycle inhibitor fluorocitrate dramatically increased PIA production without impairing glucose catabolism, the growth rate, or the growth yields. These data lead us to speculate that one mechanism by which staphylococci perceive external environmental change is through alterations in TCA cycle activity leading to changes in the intracellular levels of biosynthetic intermediates, ATP, or the redox status of the cell. These changes in the metabolic status of the bacteria result in the attenuation or augmentation of PIA production. PMID:15838022

  19. Tricarboxylic acid cycle intermediate pool size: functional importance for oxidative metabolism in exercising human skeletal muscle.

    PubMed

    Bowtell, Joanna L; Marwood, Simon; Bruce, Mark; Constantin-Teodosiu, Dumitru; Greenhaff, Paul L

    2007-01-01

    The tricarboxylic acid (TCA) cycle is the major final common pathway for oxidation of carbohydrates, lipids and some amino acids, which produces reducing equivalents in the form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide that result in production of large amounts of adenosine triphosphate (ATP) via oxidative phosphorylation. Although regulated primarily by the products of ATP hydrolysis, in particular adenosine diphosphate, the rate of delivery of reducing equivalents to the electron transport chain is also a potential regulatory step of oxidative phosphorylation. The TCA cycle is responsible for the generation of approximately 67% of all reducing equivalents per molecule of glucose, hence factors that influence TCA cycle flux will be of critical importance for oxidative phosphorylation. TCA cycle flux is dependent upon the supply of acetyl units, activation of the three non-equilibrium reactions within the TCA cycle, and it has been suggested that an increase in the total concentration of the TCA cycle intermediates (TCAi) is also necessary to augment and maintain TCA cycle flux during exercise. This article reviews the evidence of the functional importance of the TCAi pool size for oxidative metabolism in exercising human skeletal muscle. In parallel with increased oxidative metabolism and TCA cycle flux during exercise, there is an exercise intensity-dependent 4- to 5-fold increase in the concentration of the TCAi. TCAi concentration reaches a peak after 10-15 minutes of exercise, and thereafter tends to decline. This seems to support the suggestion that the concentration of TCAi may be of functional importance for oxidative phosphorylation. However, researchers have been able to induce dissociations between TCAi pool size and oxidative energy provision using a variety of nutritional, pharmacological and exercise interventions. Brief periods of endurance training (5 days or 7 weeks) have been found to result in reduced TCAi pool

  20. Tricarboxylic acid cycle intermediate pool size: functional importance for oxidative metabolism in exercising human skeletal muscle.

    PubMed

    Bowtell, Joanna L; Marwood, Simon; Bruce, Mark; Constantin-Teodosiu, Dumitru; Greenhaff, Paul L

    2007-01-01

    The tricarboxylic acid (TCA) cycle is the major final common pathway for oxidation of carbohydrates, lipids and some amino acids, which produces reducing equivalents in the form of nicotinamide adenine dinucleotide and flavin adenine dinucleotide that result in production of large amounts of adenosine triphosphate (ATP) via oxidative phosphorylation. Although regulated primarily by the products of ATP hydrolysis, in particular adenosine diphosphate, the rate of delivery of reducing equivalents to the electron transport chain is also a potential regulatory step of oxidative phosphorylation. The TCA cycle is responsible for the generation of approximately 67% of all reducing equivalents per molecule of glucose, hence factors that influence TCA cycle flux will be of critical importance for oxidative phosphorylation. TCA cycle flux is dependent upon the supply of acetyl units, activation of the three non-equilibrium reactions within the TCA cycle, and it has been suggested that an increase in the total concentration of the TCA cycle intermediates (TCAi) is also necessary to augment and maintain TCA cycle flux during exercise. This article reviews the evidence of the functional importance of the TCAi pool size for oxidative metabolism in exercising human skeletal muscle. In parallel with increased oxidative metabolism and TCA cycle flux during exercise, there is an exercise intensity-dependent 4- to 5-fold increase in the concentration of the TCAi. TCAi concentration reaches a peak after 10-15 minutes of exercise, and thereafter tends to decline. This seems to support the suggestion that the concentration of TCAi may be of functional importance for oxidative phosphorylation. However, researchers have been able to induce dissociations between TCAi pool size and oxidative energy provision using a variety of nutritional, pharmacological and exercise interventions. Brief periods of endurance training (5 days or 7 weeks) have been found to result in reduced TCAi pool

  1. Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

    USGS Publications Warehouse

    Scott, D.T.; Runkel, R.L.; McKnight, Diane M.; Voelker, B.M.; Kimball, B.A.; Carraway, E.R.

    2003-01-01

    An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O 2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 ??M midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(III), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

  2. Correlation between citric acid and nitrate metabolisms during CAM cycle in the atmospheric bromeliad Tillandsia pohliana.

    PubMed

    Freschi, Luciano; Rodrigues, Maria Aurineide; Tiné, Marco Aurélio Silva; Mercier, Helenice

    2010-12-15

    Crassulacean acid metabolism (CAM) confers crucial adaptations for plants living under frequent environmental stresses. A wide metabolic plasticity can be found among CAM species regarding the type of storage carbohydrate, organic acid accumulated at night and decarboxylating system. Consequently, many aspects of the CAM pathway control are still elusive while the impact of this photosynthetic adaptation on nitrogen metabolism has remained largely unexplored. In this study, we investigated a possible link between the CAM cycle and the nitrogen assimilation in the atmospheric bromeliad Tillandsia pohliana by simultaneously characterizing the diel changes in key enzyme activities and metabolite levels of both organic acid and nitrate metabolisms. The results revealed that T. pohliana performed a typical CAM cycle in which phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase phosphorylation seemed to play a crucial role to avoid futile cycles of carboxylation and decarboxylation. Unlike all other bromeliads previously investigated, almost equimolar concentrations of malate and citrate were accumulated at night. Moreover, a marked nocturnal depletion in the starch reservoirs and an atypical pattern of nitrate reduction restricted to the nighttime were also observed. Since reduction and assimilation of nitrate requires a massive supply of reducing power and energy and considering that T. pohliana lives overexposed to the sunlight, we hypothesize that citrate decarboxylation might be an accessory mechanism to increase internal CO₂ concentration during the day while its biosynthesis could provide NADH and ATP for nocturnal assimilation of nitrate. Therefore, besides delivering photoprotection during the day, citrate might represent a key component connecting both CAM pathway and nitrogen metabolism in T. pohliana; a scenario that certainly deserves further study not only in this species but also in other CAM plants that nocturnally accumulate citrate.

  3. Analysis of the citric acid cycle intermediates using gas chromatography-mass spectrometry.

    PubMed

    Kombu, Rajan S; Brunengraber, Henri; Puchowicz, Michelle A

    2011-01-01

    Researchers view analysis of the citric acid cycle (CAC) intermediates as a metabolomic approach to identifying unexpected correlations between apparently related and unrelated pathways of metabolism. Relationships of the CAC intermediates, as measured by their concentrations and relative ratios, offer useful information to understanding interrelationships between the CAC and metabolic pathways under various physiological and pathological conditions. This chapter presents a relatively simple method that is sensitive for simultaneously measuring concentrations of CAC intermediates (relative and absolute) and other related intermediates of energy metabolism using gas chromatography-mass spectrometry.

  4. Corrosive Resistant Diamond Coatings for the Acid Based Thermo-Chemical Hydrogen Cycles

    SciTech Connect

    Mark A. Prelas

    2009-06-25

    This project was designed to test diamond, diamond-like and related materials in environments that are expected in thermochemical cycles. Our goals were to build a High Temperature Corrosion Resistance (HTCR) test stand and begin testing the corrosive properties of barious materials in a high temperature acidic environment in the first year. Overall, we planned to test 54 samples each of diamond and diamond-like films (of 1 cm x 1 cm area). In addition we use a corrosion acceleration method by treating the samples at a temperature much larger than the expected operating temperature. Half of the samples will be treated with boron using the FEDOA process.

  5. Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles

    SciTech Connect

    Daniel M. Ginosar; Lucia M. Petkovic; Anne W. Glenn; Kyle C. Burch

    2007-03-01

    The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

  6. DIBROMOACETIC ACID-INDUCED ELEVATIONS OF ESTRADIOL IN THE CYCLING AND OVARIECTOMOZED/ESTRADIOL-IMPLANTED FEMALE RAT

    EPA Science Inventory

    Goldman, JM and Murr, AS. Dibromoacetic Acid-induced Elevations of Estradiol in Both Cycling and Ovariectomized / Estradiol-implanted Female Rats

    ABSTRACT
    Haloacetic acids are one of the principal classes of disinfection by-products generated by the chlorination of mun...

  7. The Effect of Light on the Tricarboxylic Acid Cycle in Green Leaves

    PubMed Central

    Chapman, E. A.; Graham, D.

    1974-01-01

    Long term feeding of acetate-2-14C, 14CO2, citrate-1,5-14C, fumarate-2,3-14C, and succinate-2,3-14C to mung bean (Phaseolus aureus L. var. Mungo) leaves in the dark gave labeling predominantly in tricarboxylic acid cycle intermediates. Kinetics of the intermediates during dark/light/dark transitions showed a light-induced interchange of 14C between malate and aspartate, usually resulting in an accumulation of 14C in malate and a decrease of it in aspartate. 14C-Phosphoenolpyruvate also showed a marked decrease during illumination. Changes in other intermediates of the tricarboxylic acid cycle were relatively minor. The kinetic data have been analyzed using the Chance crossover theorem to locate control points during the dark/light/dark transitions. The major apparent control points are located at malate and isocitrate dehydrogenases, and less frequently at citrate synthase and fumarase. These findings are explained in terms of the light-induced changes in adenine nucleotides and nicotinamide adenine dinucleotides. PMID:16658810

  8. Biochar impacts soil microbial community composition and nitrogen cycling in an acidic soil planted with rape.

    PubMed

    Xu, Hui-Juan; Wang, Xiao-Hui; Li, Hu; Yao, Huai-Ying; Su, Jian-Qiang; Zhu, Yong-Guan

    2014-08-19

    Biochar has been suggested to improve acidic soils and to mitigate greenhouse gas emissions. However, little has been done on the role of biochar in ameliorating acidified soils induced by overuse of nitrogen fertilizers. In this study, we designed a pot trial with an acidic soil (pH 4.48) in a greenhouse to study the interconnections between microbial community, soil chemical property changes, and N2O emissions after biochar application. The results showed that biochar increased plant growth, soil pH, total carbon, total nitrogen, C/N ratio, and soil cation exchange capacity. The results of high-throughput sequencing showed that biochar application increased α-diversity significantly and changed the relative abundances of some microbes that are related with carbon and nitrogen cycling at the family level. Biochar amendment stimulated both nitrification and denitrification processes, while reducing N2O emissions overall. Results of redundancy analysis indicated biochar could shift the soil microbial community by changing soil chemical properties, which modulate N-cycling processes and soil N2O emissions. The significantly increased nosZ transcription suggests that biochar decreased soil N2O emissions by enhancing its further reduction to N2. PMID:25054835

  9. THE EFFECT OF ANOLYTE PRODUCT ACID CONCENTRATION ON HYBRID SULFUR CYCLE PERFORMANCE

    SciTech Connect

    Gorensek, M.; Summers, W.

    2010-03-24

    The Hybrid Sulfur (HyS) cycle (Fig. 1) is one of the simplest, all-fluids thermochemical cycles that has been devised for splitting water with a high-temperature nuclear or solar heat source. It was originally patented by Brecher and Wu in 1975 and extensively developed by Westinghouse in the late 1970s and early 1980s. As its name suggests, the only element used besides hydrogen and oxygen is sulfur, which is cycled between the +4 and +6 oxidation states. HyS comprises two steps. One is the thermochemical (>800 C) decomposition of sulfuric acid (H{sub 2}SO{sub 4}) to sulfur dioxide (SO{sub 2}), oxygen (O{sub 2}), and water. H{sub 2}SO{sub 4} = SO{sub 2} + 1/2 O{sub 2} + H{sub 2}O. The other is the SO{sub 2}-depolarized electrolysis of water to H{sub 2}SO{sub 4} and hydrogen (H{sub 2}), SO{sub 2} + 2 H{sub 2}O = H{sub 2}SO{sub 4} + H{sub 2}, E{sup o} = -0.156 V, explaining the 'hybrid' designation. These two steps taken together split water into H{sub 2} and O{sub 2} using heat and electricity. Researchers at the Savannah River National Laboratory (SRNL) and at the University of South Carolina (USC) have successfully demonstrated the use of proton exchange membrane (PEM) electrolyzers (Fig. 2) for the SO{sub 2}-depolarized electrolysis (sulfur oxidation) step, while Sandia National Laboratories (SNL) successfully demonstrated the high-temperature sulfuric acid decomposition (sulfur reduction) step using a bayonet-type reactor (Fig. 3). This latter work was performed as part of the Sulfur-Iodine (SI) cycle Integrated Laboratory Scale demonstration at General Atomics (GA). The combination of these two operations results in a simple process that will be more efficient and cost-effective for the massive production of hydrogen than alkaline electrolysis. Recent developments suggest that the use of PEMs other than Nafion will allow sulfuric acid to be produced at higher concentrations (>60 wt%), offering the possibility of net thermal efficiencies around 50% (HHV basis

  10. Abnormalities in the tricarboxylic Acid cycle in Huntington disease and in a Huntington disease mouse model.

    PubMed

    Naseri, Nima N; Xu, Hui; Bonica, Joseph; Vonsattel, Jean Paul G; Cortes, Etty P; Park, Larry C; Arjomand, Jamshid; Gibson, Gary E

    2015-06-01

    Glucose metabolism is reduced in the brains of patients with Huntington disease (HD). The mechanisms underlying this deficit, its link to the pathology of the disease, and the vulnerability of the striatum in HD remain unknown. Abnormalities in some of the key mitochondrial enzymes involved in glucose metabolism, including the pyruvate dehydrogenase complex (PDHC) and the tricarboxylic acid (TCA) cycle, may contribute to these deficits. Here, activities for these enzymes and select protein levels were measured in human postmortem cortex and in striatum and cortex of an HD mouse model (Q175); mRNA levels encoding for these enzymes were also measured in the Q175 mouse cortex. The activities of PDHC and nearly all of the TCA cycle enzymes were dramatically lower (-50% to 90%) in humans than in mice. The activity of succinate dehydrogenase increased with HD in human (35%) and mouse (23%) cortex. No other changes were detected in the human HD cortex or mouse striatum. In Q175 cortex, there were increased activities of PDHC (+12%) and aconitase (+32%). Increased mRNA levels for succinyl thiokinase (+88%) and isocitrate dehydrogenase (+64%) suggested an upregulation of the TCA cycle. These patterns of change differ from those reported in other diseases, which may offer unique metabolic therapeutic opportunities for HD patients.

  11. The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control

    SciTech Connect

    Yang, Yunfeng; McCue, Lee Ann; Parsons, Andrea B.; Feng, Sheng; Zhou, Jizhong

    2010-10-26

    It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. In this study, we showed that a fur deletion mutant of the γ-proteobacterium S. oneidensis could utilize TCA compounds. In addition, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and demonstrated its expression experimentally. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB. This work delineates an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other γ-proteobacteria.

  12. The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control

    SciTech Connect

    Yang, Yunfeng; McCue, Lee Ann; Parsons, Andrea; Feng, Sheng; Zhou, Jizhong

    2010-01-01

    Background: It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. It is unclear in the g-proteobacterium S. oneidensis whether TCA is also regulated by Fur and RyhB. Results: In the present study, we showed that a fur deletion mutant of S. oneidensis could utilize TCA compounds. Consistently, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and experimentally demonstrated the gene expression. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB. Conclusions: These cumulative results delineate an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other g-proteobacteria. This work represents a step forward for understanding the unique regulation in S. oneidensis.

  13. Evolution of the enzymes of the citric acid cycle and the glyoxylate cycle of higher plants. A case study of endosymbiotic gene transfer.

    PubMed

    Schnarrenberger, Claus; Martin, William

    2002-02-01

    The citric acid or tricarboxylic acid cycle is a central element of higher-plant carbon metabolism which provides, among other things, electrons for oxidative phosphorylation in the inner mitochondrial membrane, intermediates for amino-acid biosynthesis, and oxaloacetate for gluconeogenesis from succinate derived from fatty acids via the glyoxylate cycle in glyoxysomes. The tricarboxylic acid cycle is a typical mitochondrial pathway and is widespread among alpha-proteobacteria, the group of eubacteria as defined under rRNA systematics from which mitochondria arose. Most of the enzymes of the tricarboxylic acid cycle are encoded in the nucleus in higher eukaryotes, and several have been previously shown to branch with their homologues from alpha-proteobacteria, indicating that the eukaryotic nuclear genes were acquired from the mitochondrial genome during the course of evolution. Here, we investigate the individual evolutionary histories of all of the enzymes of the tricarboxylic acid cycle and the glyoxylate cycle using protein maximum likelihood phylogenies, focusing on the evolutionary origin of the nuclear-encoded proteins in higher plants. The results indicate that about half of the proteins involved in this eukaryotic pathway are most similar to their alpha-proteobacterial homologues, whereas the remainder are most similar to eubacterial, but not specifically alpha-proteobacterial, homologues. A consideration of (a) the process of lateral gene transfer among free-living prokaryotes and (b) the mechanistics of endosymbiotic (symbiont-to-host) gene transfer reveals that it is unrealistic to expect all nuclear genes that were acquired from the alpha-proteobacterial ancestor of mitochondria to branch specifically with their homologues encoded in the genomes of contemporary alpha-proteobacteria. Rather, even if molecular phylogenetics were to work perfectly (which it does not), then some nuclear-encoded proteins that were acquired from the alpha

  14. Evolution of the enzymes of the citric acid cycle and the glyoxylate cycle of higher plants. A case study of endosymbiotic gene transfer.

    PubMed

    Schnarrenberger, Claus; Martin, William

    2002-02-01

    The citric acid or tricarboxylic acid cycle is a central element of higher-plant carbon metabolism which provides, among other things, electrons for oxidative phosphorylation in the inner mitochondrial membrane, intermediates for amino-acid biosynthesis, and oxaloacetate for gluconeogenesis from succinate derived from fatty acids via the glyoxylate cycle in glyoxysomes. The tricarboxylic acid cycle is a typical mitochondrial pathway and is widespread among alpha-proteobacteria, the group of eubacteria as defined under rRNA systematics from which mitochondria arose. Most of the enzymes of the tricarboxylic acid cycle are encoded in the nucleus in higher eukaryotes, and several have been previously shown to branch with their homologues from alpha-proteobacteria, indicating that the eukaryotic nuclear genes were acquired from the mitochondrial genome during the course of evolution. Here, we investigate the individual evolutionary histories of all of the enzymes of the tricarboxylic acid cycle and the glyoxylate cycle using protein maximum likelihood phylogenies, focusing on the evolutionary origin of the nuclear-encoded proteins in higher plants. The results indicate that about half of the proteins involved in this eukaryotic pathway are most similar to their alpha-proteobacterial homologues, whereas the remainder are most similar to eubacterial, but not specifically alpha-proteobacterial, homologues. A consideration of (a) the process of lateral gene transfer among free-living prokaryotes and (b) the mechanistics of endosymbiotic (symbiont-to-host) gene transfer reveals that it is unrealistic to expect all nuclear genes that were acquired from the alpha-proteobacterial ancestor of mitochondria to branch specifically with their homologues encoded in the genomes of contemporary alpha-proteobacteria. Rather, even if molecular phylogenetics were to work perfectly (which it does not), then some nuclear-encoded proteins that were acquired from the alpha

  15. Novel Metabolic Abnormalities in the Tricarboxylic Acid Cycle in Peripheral Cells From Huntington's Disease Patients.

    PubMed

    Naseri, Nima N; Bonica, Joseph; Xu, Hui; Park, Larry C; Arjomand, Jamshid; Chen, Zhengming; Gibson, Gary E

    2016-01-01

    Metabolic dysfunction is well-documented in Huntington's disease (HD). However, the link between the mutant huntingtin (mHTT) gene and the pathology is unknown. The tricarboxylic acid (TCA) cycle is the main metabolic pathway for the production of NADH for conversion to ATP via the electron transport chain (ETC). The objective of this study was to test for differences in enzyme activities, mRNAs and protein levels related to the TCA cycle between lymphoblasts from healthy subjects and from patients with HD. The experiments utilize the advantages of lymphoblasts to reveal new insights about HD. The large quantity of homogeneous cell populations permits multiple dynamic measures to be made on exactly comparable tissues. The activities of nine enzymes related to the TCA cycle and the expression of twenty-nine mRNAs encoding for these enzymes and enzyme complexes were measured. Cells were studied under baseline conditions and during metabolic stress. The results support our recent findings that the activities of the pyruvate dehydrogenase complex (PDHC) and succinate dehydrogenase (SDH) are elevated in HD. The data also show a large unexpected depression in MDH activities. Furthermore, message levels for isocitrate dehydrogenase 1 (IDH1) were markedly increased in in HD lymphoblasts and were responsive to treatments. The use of lymphoblasts allowed us to clarify that the reported decrease in aconitase activity in HD autopsy brains is likely due to secondary hypoxic effects. These results demonstrate the mRNA and enzymes of the TCA cycle are critical therapeutic targets that have been understudied in HD. PMID:27611087

  16. Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles

    PubMed Central

    Coelho, Carla R. V.; Pernollet, Franck; van der Werf, Hayo M. G.

    2016-01-01

    A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets. PMID:27504959

  17. Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles.

    PubMed

    Coelho, Carla R V; Pernollet, Franck; van der Werf, Hayo M G

    2016-01-01

    A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets. PMID:27504959

  18. 75 FR 20423 - Tenth Meeting: RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-19

    ... Activities Briefing from SC-217/WG-44 (D-TAXI, Airport Data Base) Briefing from SC-186/WG-51 (CPDLC support... Air Traffic Data Communication Services AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data...

  19. 75 FR 30903 - Tenth Meeting: RTCA Special Committee 209: In Joint Session With EUROCAE WG 49: ATCRBS/Mode S...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... EUROCAE WG 49: ATCRBS/Mode S Transponder MOPS Maintenance AGENCY: Federal Aviation Administration (FAA... Transponder MOPS Maintenance. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 209: In Joint Session with EUROCAE WG-49 ATCRBS/Mode S Transponder...

  20. 75 FR 66828 - Eleventh Meeting: RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-29

    ... for Air Traffic Data Communication Services AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data Communication... Committee 214: Working Group 78: Standards for Air Traffic Data Communication Services. DATES: The...

  1. 78 FR 76888 - Twentieth Meeting: RTCA Special Committee 214/EUROCAE WG-78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-19

    ... INFORMATION: Pursuant to section 10(a) (2) of the Federal Advisory Committee Act (Pub. L. 92-463, 5 U.S.C... Federal Aviation Administration Twentieth Meeting: RTCA Special Committee 214/EUROCAE WG-78: Standards for Air Traffic Data Communication Services AGENCY: Federal Aviation Administration (FAA), U.S....

  2. 75 FR 44306 - Eleventh Meeting: Joint RTCA Special Committee 213: EUROCAE WG-79: Enhanced Flight Vision Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-28

    ... Federal Aviation Administration Eleventh Meeting: Joint RTCA Special Committee 213: EUROCAE WG- 79... September 21-23, 2010 from 8:30 a.m.--5 p.m. (0830-1700). ADDRESSES: The meeting will be held at the London... Systems/Synthetic Vision Systems (EFVS/SVS) meeting. The agenda will include: Tuesday, 21...

  3. 76 FR 17473 - Twelfth Meeting: RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-29

    ... for Air Traffic Data Communication Services AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 214: Working Group 78: Standards for Air Traffic Data Communication... Committee 214: Working Group 78: Standards for Air Traffic Data Communication Services. DATES: The...

  4. 76 FR 72241 - Fourteenth Meeting: RTCA Special Committee 214/EUROCAE WG-78: Standards for Air Traffic Data...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-22

    ... for Air Traffic Data Communication Services AGENCY: Federal Aviation Administration (FAA), U.S... Traffic Data Communication Services meeting. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 214/EUROCAE WG-78: Standards for Air Traffic...

  5. 75 FR 71183 - 23rd Meeting: RTCA Special Committee 206: EUROCAE WG 76 Plenary: AIS and MET Data Link Services

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-22

    ... Services and a revised Terms of Reference (TOR) for SC-206 has been approved by the RTCA Program Management Committee. A brief description of the document deliverables called out in the revised SC-206 TOR is provided... Architecture Recommendations are included in the TOR deliverables. The Concept of Use for AIS and MET Data...

  6. 76 FR 54527 - Ninth Meeting-RTCA Special Committee 217: Joint With EUROCAE WG-44 Terrain and Airport Mapping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-01

    ... Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 217: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases...: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases. DATES: The meeting will be...

  7. 75 FR 59327 - Seventh Meeting-RTCA Special Committee 217: Joint With EUROCAE WG-44 Terrain and Airport Mapping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-27

    ... Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 217: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases...: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases. DATES: The meeting will be held...

  8. 76 FR 27744 - Eighth Meeting-RTCA Special Committee 217: Joint With EUROCAE WG-44 Terrain and Airport Mapping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ... Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 217: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases...: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases. DATES: The meeting will be held June...

  9. 76 FR 6179 - Eighth Meeting-RTCA Special Committee 217: Joint With EUROCAE WG-44 Terrain and Airport Mapping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-03

    ...-44 Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 217: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases...: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases. DATES: The meeting will be held...

  10. 75 FR 10552 - Sixth Meeting-RTCA Special Committee 217: Joint With EUROCAE WG-44 Terrain and Airport Mapping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-08

    ... Terrain and Airport Mapping Databases AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 217: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases...: Joint with EUROCAE WG-44 Terrain and Airport Mapping Databases. DATES: The meeting will be held on...

  11. 75 FR 28852 - Ninth Meeting: Joint RTCA Special Committee 213: EUROCAE WG-79: Enhanced Flight Vision Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-24

    ... Flight Vision Systems/Synthetic Vision Systems (EFVS/SVS) AGENCY: Federal Aviation Administration (FAA.../Synthetic Vision Systems (EFVS/SVS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of Joint RTCA Special Committee 213: EUROCAE WG-79: Enhanced Flight Vision...

  12. 75 FR 71183 - Twelfth Meeting: Joint RTCA Special Committee 213: EUROCAE WG-79: Enhanced Flight Vision Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-22

    ...: Enhanced Flight Vision Systems/Synthetic Vision Systems (EFVS/SVS) AGENCY: Federal Aviation Administration... Flight Vision Systems/Synthetic Vision Systems (EFVS/SVS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of Joint RTCA Special Committee 213: EUROCAE WG-79: Enhanced Flight...

  13. 77 FR 12105 - 56th Meeting: RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-28

    ...--Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 186, Automatic Dependent Surveillance--Broadcast (ADS-B... 186, Automatic Dependent Surveillance--Broadcast (ADS-B) DATES: The meeting will be held March...

  14. 76 FR 3932 - Fifty-Third Meeting: RTCA Special Committee 186: Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-21

    ... Surveillance--Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 186: Automatic Dependent Surveillance--Broadcast (ADS-B) meeting. SUMMARY: The FAA is... Surveillance--Broadcast (ADS-B). DATES: The meeting will be held February 22-25, 2011 from 9 a.m. to 5...

  15. 78 FR 12136 - Fifty Eighth Meeting: RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-21

    ... Surveillance-Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 186, Automatic Dependent Surveillance-Broadcast... Surveillance and Broadcast Services (SBS) Program. Working Group Reports. Status of WG-4, Application...

  16. 76 FR 22160 - Fifty-Fourth Meeting: RTCA Special Committee 186: Automatic Dependent Surveillance-Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-20

    ... Surveillance--Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 186: Automatic Dependent Surveillance--Broadcast (ADS-B) meeting. SUMMARY: The FAA is... Surveillance--Broadcast (ADS-B). DATES: The meeting will be held May 3-5, 2011 from 9 a.m. to 5 p.m....

  17. 77 FR 46147 - 57th Meeting: RTCA Special Committee 186, Automatic Dependent Surveillance Broadcast (ADS-B)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-02

    ... Broadcast (ADS-B) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 186, Automatic Dependent Surveillance Broadcast (ADS-B... 186, Automatic Dependent Surveillance Broadcast (ADS-B) DATES: The meeting will be held August...

  18. Computational estimation of tricarboxylic acid cycle fluxes using noisy NMR data from cardiac biopsies

    PubMed Central

    2013-01-01

    Background The aerobic energy metabolism of cardiac muscle cells is of major importance for the contractile function of the heart. Because energy metabolism is very heterogeneously distributed in heart tissue, especially during coronary disease, a method to quantify metabolic fluxes in small tissue samples is desirable. Taking tissue biopsies after infusion of substrates labeled with stable carbon isotopes makes this possible in animal experiments. However, the appreciable noise level in NMR spectra of extracted tissue samples makes computational estimation of metabolic fluxes challenging and a good method to define confidence regions was not yet available. Results Here we present a computational analysis method for nuclear magnetic resonance (NMR) measurements of tricarboxylic acid (TCA) cycle metabolites. The method was validated using measurements on extracts of single tissue biopsies taken from porcine heart in vivo. Isotopic enrichment of glutamate was measured by NMR spectroscopy in tissue samples taken at a single time point after the timed infusion of 13C labeled substrates for the TCA cycle. The NMR intensities for glutamate were analyzed with a computational model describing carbon transitions in the TCA cycle and carbon exchange with amino acids. The model dynamics depended on five flux parameters, which were optimized to fit the NMR measurements. To determine confidence regions for the estimated fluxes, we used the Metropolis-Hastings algorithm for Markov chain Monte Carlo (MCMC) sampling to generate extensive ensembles of feasible flux combinations that describe the data within measurement precision limits. To validate our method, we compared myocardial oxygen consumption calculated from the TCA cycle flux with in vivo blood gas measurements for 38 hearts under several experimental conditions, e.g. during coronary artery narrowing. Conclusions Despite the appreciable NMR noise level, the oxygen consumption in the tissue samples, estimated from the NMR

  19. Advances in Acid Concentration Membrane Technology for the Sulfur-Iodine Thermochemical Cycle

    SciTech Connect

    Frederick F. Stewart; Christopher J. Orme

    2006-11-01

    One of the most promising cycles for the thermochemical generation of hydrogen is the Sulfur-Iodine (S-I) process, where aqueous HI is thermochemically decomposed into H2 and I2 at approximately 350 degrees Celsius. Regeneration of HI is accomplished by the Bunsen reaction (reaction of SO2, water, and iodine to generate H2SO4 and HI). Furthermore, SO2 is regenerated from the decomposition of H2SO4 at 850 degrees Celsius yielding the SO2 as well as O2. Thus, the cycle actually consists of two concurrent oxidation-reduction loops. As HI is regenerated, co-produced H2SO4 must be separated so that each may be decomposed. Current flowsheets employ a large amount (~83 mol% of the entire mixture) of elemental I2 to cause the HI and the H2SO4 to separate into two phases. To aid in the isolation of HI, which is directly decomposed into hydrogen, water and iodine must be removed. Separation of iodine is facilitated by removal of water. Sulfuric acid concentration is also required to facilitate feed recycling to the sulfuric acid decomposer. Decomposition of the sulfuric acid is an equilibrium limited process that leaves a substantial portion of the acid requiring recycle. Distillation of water from sulfuric acid involves significant corrosion issues at the liquid-vapor interface. Thus, it is desirable to concentrate the acid without boiling. Recent efforts at the INL have concentrated on applying pervaporation through Nafion-117, Nafion-112, and sulfonated poly(etheretherketone) (S-PEEK) membranes for the removal of water from HI/water and HI/Iodine/water feedstreams. In pervaporation, a feed is circulated at low pressure across the upstream side of the membrane, while a vacuum is applied downstream. Selected permeants sorb into the membrane, transport through it, and are vaporized from the backside. Thus, a concentration gradient is established, which provides the driving force for transport. In this work, membrane separations have been performed at temperatures as high as

  20. Microbial Fe cycling and mineralization in sediments of an acidic, hypersaline lake (Lake Tyrell, Victoria, Australia)

    NASA Astrophysics Data System (ADS)

    Roden, E. E.; Blöthe, M.; Shelobolina, E.

    2009-12-01

    Lake Tyrrell is a variably acidic, hypersaline, Fe-rich lake located in Victoria, Australia. Terrestrial acid saline lakes like Lake Tyrrell may be analogs for ancient Martian surface environments, as well as possible extant subsurface environments. To investigate the potential for microbial Fe cycling under acidic conditions and high salt concentration, we collected sediment core samples during three field trips between 2006 and 2008 from the southern, acidic edge of the lake. Materials from the cores were used for chemical and mineralogical analyses, as well as for molecular (16S rRNA genes) and culture-based microbiological studies. Near-surface (< 1 m depth) pore fluids contained low but detectable dissolved oxygen (ca. 50 uM), significant dissolved Fe(II) (ca. 500 uM), and nearly constant pH of around 4 - conditions conducive to enzymatic Fe(II) oxidation. High concentrations of Fe(III) oxides begin accumulate at a depth of ca. 10 cm, and may reflect the starting point for formation of massive iron concretions that are evident at and beneath the sediment surface. MPN analyses revealed low (10-100 cells/mL) but detectable populations of aerobic, halophilic Fe(II)-oxidizing organisms on the sediment surface and in the near-surface ground water. With culture-dependent methods at least three different halotolerant lithoautotrophic cultures growing on Fe(II), thiosulfate, or tetrathionate from different acidic sites were obtained. Analysis of 16S rRNA gene sequences revealed that these organisms are similar to previous described gamma proteobacteria Thiobacillus prosperus (95%), Halothiobacillus kellyi (99%), Salinisphaera shabanense (95%) and a Marinobacter species. (98%). 16S rRNA gene pyrosequencing data from two different sites with a pH range between 3 and 4.5 revealed a dominance of gamma proteobacteria. 16S rRNA gene pyrosequencing libraries from both cores were dominated by sequences related to the Ectothiorhodospiraceae family, which includes the taxa

  1. Electrochemical gating of tricarboxylic acid cycle in electricity-producing bacterial cells of Shewanella.

    PubMed

    Matsuda, Shoichi; Liu, Huan; Kouzuma, Atsushi; Watanabe, Kazuya; Hashimoto, Kazuhito; Nakanishi, Shuji

    2013-01-01

    Energy-conversion systems mediated by bacterial metabolism have recently attracted much attention, and therefore, demands for tuning of bacterial metabolism are increasing. It is widely recognized that intracellular redox atmosphere which is generally tuned by dissolved oxygen concentration or by appropriate selection of an electron acceptor for respiration is one of the important factors determining the bacterial metabolism. In general, electrochemical approaches are valuable for regulation of redox-active objects. However, the intracellular redox conditions are extremely difficult to control electrochemically because of the presence of insulative phospholipid bilayer membranes. In the present work, the limitation can be overcome by use of the bacterial genus Shewanella, which consists of species that are able to respire via cytochromes abundantly expressed in their outer-membrane with solid-state electron acceptors, including anodes. The electrochemical characterization and the gene expression analysis revealed that the activity of tricarboxylic acid (TCA) cycle in Shewanella cells can be reversibly gated simply by changing the anode potential. Importantly, our present results for Shewanella cells cultured in an electrochemical system under poised potential conditions showed the opposite relationship between the current and electron acceptor energy level, and indicate that this unique behavior originates from deactivation of the TCA cycle in the (over-)oxidative region. Our result obtained in this study is the first demonstration of the electrochemical gating of TCA cycle of living cells. And we believe that our findings will contribute to a deeper understanding of redox-dependent regulation systems in living cells, in which the intracellular redox atmosphere is a critical factor determining the regulation of various metabolic and genetic processes.

  2. The viability of a nonenzymatic reductive citric acid cycle - Kinetics and thermochemistry

    USGS Publications Warehouse

    Ross, D.S.

    2007-01-01

    The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate ??? pyruvate ??? oxaloacetate ??? malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite-magnetite-quartz and pyrrhotite-pyrite-magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life. ?? 2006 Springer Science + Business Media B.V.

  3. The Viability of a Nonenzymatic Reductive Citric Acid Cycle Kinetics and Thermochemistry

    NASA Astrophysics Data System (ADS)

    Ross, David S.

    2007-02-01

    The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate → pyruvate → oxaloacetate → malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite magnetite quartz and pyrrhotite pyrite magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life.

  4. Bioluminescence regenerative cycle (BRC) system: theoretical considerations for nucleic acid quantification assays.

    PubMed

    Hassibi, Arjang; Contag, Christopher; Vlad, Marcel O; Hafezi, Maryam; Lee, Thomas H; Davis, Ronald W; Pourmand, Nader

    2005-08-01

    A novel application of bioluminescence for nucleic acid quantification, the bioluminescence regenerative cycle (BRC), is described in theoretical terms and supported by preliminary experimental data. In the BRC system, pyrophosphate (PPi) molecules are released during biopolymerization and are counted and correlated to DNA copy number. The enzymes ATP-sulfurylase and firefly luciferase are employed to generate photons quantitatively from PPi. Enzymatic unity-gain positive feedback is implemented to amplify photon generation and to compensate for decay in light intensity by self-regulation. The cumulative total of photons can be orders of magnitude higher than in typical chemiluminescent processes. A system level theoretical model is developed, taking into account the kinetics of the regenerative cycle, contamination, and detector noise. Data and simulations show that the photon generation process achieves steady state for the time range of experimental measurements. Based on chain reaction theory, computations show that BRC is very sensitive to variations in the efficiencies of the chemical reactions involved and less sensitive to variations in the quantum yield of the process. We show that BRC can detect attomolar quantities of DNA (10(-18) mol), and that the useful dynamic range is five orders of magnitude. Sensitivity is not constrained by detector performance but rather by background bioluminescence caused by contamination by either PPi or ATP (adenosine triphosphate).

  5. The gamma-aminobutyric acid shunt contributes to closing the tricarboxylic acid cycle in Synechocystis sp PCC 6803

    SciTech Connect

    Xiong, W; Brune, D; Vermaas, WFJ

    2014-07-16

    A traditional 2-oxoglutarate dehydrogenase complex is missing in the cyanobacterial tricarboxylic acid cycle. To determine pathways that convert 2-oxoglutarate into succinate in the cyanobacterium Synechocystis sp. PCC 6803, a series of mutant strains, Delta sll1981, Delta slr0370, Delta slr1022 and combinations thereof, deficient in 2-oxoglutarate decarboxylase (Sll1981), succinate semialdehyde dehydrogenase (Slr0370), and/or in gamma-aminobutyrate metabolism (Slr1022) were constructed. Like in Pseudomonas aeruginosa, N-acetylornithine aminotransferase, encoded by slr1022, was shown to also function as gamma-aminobutyrate aminotransferase, catalysing gamma-aminobutyrate conversion to succinic semialdehyde. As succinic semialdehyde dehydrogenase converts succinic semialdehyde to succinate, an intact gamma-aminobutyrate shunt is present in Synechocystis. The Delta sll1981 strain, lacking 2-oxoglutarate decarboxylase, exhibited a succinate level that was 60% of that in wild type. However, the succinate level in the Delta slr1022 and Delta slr0370 strains and the Delta sll1981/Delta slr1022 and Delta sll1981/Delta slr0370 double mutants was reduced to 20-40% of that in wild type, suggesting that the gamma-aminobutyrate shunt has a larger impact on metabolite flux to succinate than the pathway via 2-oxoglutarate decarboxylase. C-13-stable isotope analysis indicated that the gamma-aminobutyrate shunt catalysed conversion of glutamate to succinate. Independent of the 2-oxoglutarate decarboxylase bypass, the gamma-aminobutyrate shunt is a major contributor to flux from 2-oxoglutarate and glutamate to succinate in Synechocystis sp. PCC 6803.

  6. Extending food deprivation reverses the short-term lipolytic response to fasting: role of the triacylglycerol/fatty acid cycle.

    PubMed

    Weber, Jean-Michel; Reidy, Shannon P

    2012-05-01

    The effects of short-term food deprivation on lipid metabolism are well documented, but little is known about prolonged fasting. This study monitored the kinetics of glycerol (rate of appearance, R(a) glycerol) and non-esterified fatty acids (R(a) NEFA) in fasting rabbits. Our goals were to determine whether lipolysis is stimulated beyond values seen for short-term fasting, and to characterize the roles of primary (intracellular) and secondary (with transit through the circulation) triacylglycerol/fatty acid cycling (TAG/FA cycling) in regulating fatty acid allocation to oxidation or re-esterification. R(a) glycerol (9.62±0.72 to 15.29±0.96 μmol kg(-1) min(-1)) and R(a) NEFA (18.05±2.55 to 31.25±1.93 μmol kg(-1) min(-1)) were stimulated during the first 2 days of fasting, but returned to baseline after 4 days. An initial increase in TAG/FA cycling was followed by a reduction below baseline after 6 days without food, with primary and secondary cycling contributing to these responses. We conclude that the classic activation of lipolysis caused by short-term fasting is abolished when food deprivation is prolonged. High rates of re-esterification may become impossible to sustain, and TAG/FA cycling could decrease to reduce its cost to 3% of total energy expenditure. Throughout prolonged fasting, fatty acid metabolism gradually shifts towards increased oxidation and reduced re-esterification. Survival is achieved by pressing fuel selection towards the fatty acid dominance of energy metabolism and by slowing substrate cycles to assist metabolic suppression. However, TAG/FA cycling remains active even after prolonged fasting, suggesting that re-esterification is a crucial mechanism that cannot be stopped without harmful consequences.

  7. Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0

    PubMed Central

    Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

    2016-01-01

    Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes. PMID:27212081

  8. Developments in absorptive glass mat separators for cycling applications and 36 V lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Toniazzo, V.; Lambert, U.

    The major markets for valve-regulated lead-acid (VRLA) batteries are undergoing a radical upheaval. In particular, the telecommunications industry requires more reliable power supplies, and the familiar 12 V electrical system in cars will probably be soon replaced by a 36/42 V system, or by other electrical systems if part of the automotive market is taken over by hybrid electrical vehicles (HEVs). In order to meet these new challenges and enable VRLA batteries to provide a satisfactory life in float and cycling applications in the telecommunication field, or in the high-rate-partial-state-of-charge service required by both 36/42 V automobiles and HEVs, the lead-acid battery industry has to improve substantially the quality of present VRLA batteries based on absorptive glass mat (AGM) technology. Therefore, manufacturing steps and cell components have to be optimized, especially AGM separators as these are key components for better production yields and battery performance. This paper shows how the optimal segregation of the coarse and fine fibres in an AGM separator structure can improve greatly the properties of the material. The superior capillarity, springiness and mechanical properties of the 100% glass Amerglass multilayer separator compared with commercial monolayer counterparts with the same specific surface-area is highlighted.

  9. Heteromeric amino acid transporters. In search of the molecular bases of transport cycle mechanisms.

    PubMed

    Palacín, Manuel; Errasti-Murugarren, Ekaitz; Rosell, Albert

    2016-06-15

    Heteromeric amino acid transporters (HATs) are relevant targets for structural studies. On the one hand, HATs are involved in inherited and acquired human pathologies. On the other hand, these molecules are the only known examples of solute transporters composed of two subunits (heavy and light) linked by a disulfide bridge. Unfortunately, structural knowledge of HATs is scarce and limited to the atomic structure of the ectodomain of a heavy subunit (human 4F2hc-ED) and distant prokaryotic homologues of the light subunits that share a LeuT-fold. Recent data on human 4F2hc/LAT2 at nanometer resolution revealed 4F2hc-ED positioned on top of the external loops of the light subunit LAT2. Improved resolution of the structure of HATs, combined with conformational studies, is essential to establish the structural bases for light subunit recognition and to evaluate the functional relevance of heavy and light subunit interactions for the amino acid transport cycle.

  10. Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0

    NASA Astrophysics Data System (ADS)

    Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

    2016-05-01

    Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes.

  11. Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0.

    PubMed

    Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

    2016-05-23

    Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes.

  12. Glutamate Utilization Couples Oxidative Stress Defense and the Tricarboxylic Acid Cycle in Francisella Phagosomal Escape

    PubMed Central

    Ramond, Elodie; Gesbert, Gael; Rigard, Mélanie; Dairou, Julien; Dupuis, Marion; Dubail, Iharilalao; Meibom, Karin; Henry, Thomas; Barel, Monique; Charbit, Alain

    2014-01-01

    Intracellular bacterial pathogens have developed a variety of strategies to avoid degradation by the host innate immune defense mechanisms triggered upon phagocytocis. Upon infection of mammalian host cells, the intracellular pathogen Francisella replicates exclusively in the cytosolic compartment. Hence, its ability to escape rapidly from the phagosomal compartment is critical for its pathogenicity. Here, we show for the first time that a glutamate transporter of Francisella (here designated GadC) is critical for oxidative stress defense in the phagosome, thus impairing intra-macrophage multiplication and virulence in the mouse model. The gadC mutant failed to efficiently neutralize the production of reactive oxygen species. Remarkably, virulence of the gadC mutant was partially restored in mice defective in NADPH oxidase activity. The data presented highlight links between glutamate uptake, oxidative stress defense, the tricarboxylic acid cycle and phagosomal escape. This is the first report establishing the role of an amino acid transporter in the early stage of the Francisella intracellular lifecycle. PMID:24453979

  13. Artificial Autopolyploidization Modifies the Tricarboxylic Acid Cycle and GABA Shunt in Arabidopsis thaliana Col-0.

    PubMed

    Vergara, Fredd; Kikuchi, Jun; Breuer, Christian

    2016-01-01

    Autopolyploidy is a process whereby the chromosome set is multiplied and it is a common phenomenon in angiosperms. Autopolyploidy is thought to be an important evolutionary force that has led to the formation of new plant species. Despite its relevance, the consequences of autopolyploidy in plant metabolism are poorly understood. This study compares the metabolic profiles of natural diploids and artificial autotetraploids of Arabidopsis thaliana Col-0. Different physiological parameters are compared between diploids and autotetraploids using nuclear magnetic resonance (NMR), elemental analysis (carbon:nitrogen balance) and quantitative real-time PCR (qRT-PCR). The main difference between diploid and autotetraploid A. thaliana Col-0 is observed in the concentration of metabolites related to the tricarboxylic acid cycle (TCA) and γ-amino butyric acid (GABA) shunt, as shown by multivariate statistical analysis of NMR spectra. qRT-PCR shows that genes related to the TCA and GABA shunt are also differentially expressed between diploids and autotetraploids following similar trends as their corresponding metabolites. Solid evidence is presented to demonstrate that autopolyploidy influences core plant metabolic processes. PMID:27212081

  14. A microbial arsenic cycle in sediments of an acidic mine impoundment: Herman Pit, Clear Lake, California

    USGS Publications Warehouse

    Blum, Jodi S.; McCann, Shelley; Bennett, S.; Miller, Laurence G.; Stolz, J. R.; Stoneburner, B.; Saltikov, C.; Oremland, Ronald S.

    2015-01-01

    The involvement of prokaryotes in the redox reactions of arsenic occurring between its +5 [arsenate; As(V)] and +3 [arsenite; As(III)] oxidation states has been well established. Most research to date has focused upon circum-neutral pH environments (e.g., freshwater or estuarine sediments) or arsenic-rich “extreme” environments like hot springs and soda lakes. In contrast, relatively little work has been conducted in acidic environments. With this in mind we conducted experiments with sediments taken from the Herman Pit, an acid mine drainage impoundment of a former mercury (cinnabar) mine. Due to the large adsorptive capacity of the abundant Fe(III)-rich minerals, we were unable to initially detect in solution either As(V) or As(III) added to the aqueous phase of live sediment slurries or autoclaved controls, although the former consumed added electron donors (i.e., lactate, acetate, hydrogen), while the latter did not. This prompted us to conduct further experiments with diluted slurries using the live materials from the first incubation as inoculum. In these experiments we observed reduction of As(V) to As(III) under anoxic conditions and reduction rates were enhanced by addition of electron donors. We also observed oxidation of As(III) to As(V) in oxic slurries as well as in anoxic slurries amended with nitrate. We noted an acid-tolerant trend for sediment slurries in the cases of As(III) oxidation (aerobic and anaerobic) as well as for anaerobic As(V) reduction. These observations indicate the presence of a viable microbial arsenic redox cycle in the sediments of this extreme environment, a result reinforced by the successful amplification of arsenic functional genes (aioA, and arrA) from these materials.

  15. Krebs cycle intermediates modulate thiobarbituric acid reactive species (TBARS) production in rat brain in vitro.

    PubMed

    Puntel, Robson L; Nogueira, Cristina W; Rocha, João B T

    2005-02-01

    The aim of this study was to investigate the effect of Krebs cycle intermediates on basal and quinolinic acid (QA)- or iron-induced TBARS production in brain membranes. Oxaloacetate, citrate, succinate and malate reduced significantly the basal and QA-induced TBARS production. The potency for basal TBARS inhibition was in the order (IC50 is given in parenthesis as mM) citrate (0.37) > oxaloacetate (1.33) = succinate (1.91) > > malate (12.74). alpha-Ketoglutarate caused an increase in TBARS production without modifying the QA-induced TBARS production. Cyanide (CN-) did not modify the basal or QA-induced TBARS production; however, CN- abolished the antioxidant effects of succinate. QA-induced TBARS production was enhanced by iron ions, and abolished by desferrioxamine (DFO). The intermediates used in this study, except for alpha-ketoglutarate, prevented iron-induced TBARS production. Oxaloacetate, citrate, alpha-ketoglutarate and malate, but no succinate and QA, exhibited significantly iron-chelating properties. Only alpha-ketoglutarate and oxaloacetate protected against hydrogen peroxide-induced deoxyribose degradation, while succinate and malate showed a modest effect against Fe2+/H2O2-induced deoxyribose degradation. Using heat-treated preparations citrate, malate and oxaloacetate protected against basal or QA-induced TBARS production, whereas alpha-ketoglutarate induced TBARS production. Succinate did not offer protection against basal or QA-induced TBARS production. These results suggest that oxaloacetate, malate, succinate, and citrate are effective antioxidants against basal and iron or QA-induced TBARS production, while alpha-ketoglutarate stimulates TBARS production. The mechanism through which Krebs cycle intermediates offer protection against TBARS production is distinct depending on the intermediate used. Thus, under pathological conditions such as ischemia, where citrate concentrations vary it can assume an important role as a modulator of oxidative

  16. Interplay between cell cycle and autophagy induced by boswellic acid analog

    PubMed Central

    Pathania, Anup S.; Guru, Santosh K.; Kumar, Suresh; Kumar, Ashok; Ahmad, Masroor; Bhushan, Shashi; Sharma, Parduman R.; Mahajan, Priya; Shah, Bhahwal A.; Sharma, Simmi; Nargotra, Amit; Vishwakarma, Ram; Korkaya, Hasan; Malik, Fayaz

    2016-01-01

    In this study, we investigated the role of autophagy induced by boswellic acid analog BA145 on cell cycle progression in pancreatic cancer cells. BA145 induced robust autophagy in pancreatic cancer cell line PANC-1 and exhibited cell proliferation inhibition by inducing cells to undergo G2/M arrest. Inhibition of G2/M progression was associated with decreased expression of cyclin A, cyclin B, cyclin E, cdc2, cdc25c and CDK-1. Pre-treatment of cells with autophagy inhibitors or silencing the expression of key autophagy genes abrogated BA145 induced G2/M arrest and downregulation of cell cycle regulatory proteins. It was further observed that BA145 induced autophagy by targeting mTOR kinase (IC50 1 μM), leading to reduced expression of p-mTOR, p-p70S6K (T389), p-4EBP (T37/46) and p-S6 (S240/244). Notably, inhibition of mTOR signalling by BA145 was followed by attendant activation of AKT and its membrane translocation. Inhibition of Akt through pharmacological inhibitors or siRNAs enhanced BA145 mediated autophagy, G2/M arrest and reduced expression of G2/M regulators. Further studies revealed that BA145 arbitrated inhibition of mTOR led to the activation of Akt through IGFR/PI3k/Akt feedback loop. Intervention in IGFR/PI3k/Akt loop further depreciated Akt phosphorylation and its membrane translocation that culminates in augmented autophagy with concomitant G2/M arrest and cell death. PMID:27680387

  17. High temperature abatement of acid gases from waste incineration. Part II: Comparative life cycle assessment study.

    PubMed

    Biganzoli, Laura; Racanella, Gaia; Marras, Roberto; Rigamonti, Lucia

    2015-01-01

    The performances of a new dolomitic sorbent, named Depurcal®MG, to be directly injected at high temperature in the combustion chamber of Waste-To-Energy (WTE) plants as a preliminary stage of deacidification, were experimentally tested during full-scale commercial operation. Results of the experimentations were promising, and have been extensively described in Biganzoli et al. (2014). This paper reports the Life Cycle Assessment (LCA) study performed to compare the traditional operation of the plants, based on the sole sodium bicarbonate feeding at low temperature, with the new one, where the dolomitic sorbent is injected at high temperature. In the latter the sodium bicarbonate is still used, but at lower rate because of the decreased load of acid gases entering the flue gas treatment line. The major goal of the LCA was to make sure that a burden shifting was not taking place somewhere in the life cycle stages, as it might be the case when a new material is used in substitution of another one. According to the comparative approach, only the processes which differ between the two operational modes were included in the system boundaries. They are the production of the two reactants and the treatment of the corresponding solid residues arising from the neutralisation of acid gases. The additional CO2 emission at the stack of the WTE plant due to the activation of the sodium bicarbonate was also included in the calculation. Data used in the modelling of the foreground system are primary, derived from the experimental tests described in Biganzoli et al. (2014) and from the dolomitic sorbent production plant. The results of the LCA show minor changes in the potential impacts between the two operational modes of the plants. These differences are for 8 impact categories in favour of the new operational mode based on the addition of the dolomitic sorbent, and for 7 impact categories in favour of the traditional operation. A final evaluation was conducted on the potential

  18. High temperature abatement of acid gases from waste incineration. Part II: Comparative life cycle assessment study.

    PubMed

    Biganzoli, Laura; Racanella, Gaia; Marras, Roberto; Rigamonti, Lucia

    2015-01-01

    The performances of a new dolomitic sorbent, named Depurcal®MG, to be directly injected at high temperature in the combustion chamber of Waste-To-Energy (WTE) plants as a preliminary stage of deacidification, were experimentally tested during full-scale commercial operation. Results of the experimentations were promising, and have been extensively described in Biganzoli et al. (2014). This paper reports the Life Cycle Assessment (LCA) study performed to compare the traditional operation of the plants, based on the sole sodium bicarbonate feeding at low temperature, with the new one, where the dolomitic sorbent is injected at high temperature. In the latter the sodium bicarbonate is still used, but at lower rate because of the decreased load of acid gases entering the flue gas treatment line. The major goal of the LCA was to make sure that a burden shifting was not taking place somewhere in the life cycle stages, as it might be the case when a new material is used in substitution of another one. According to the comparative approach, only the processes which differ between the two operational modes were included in the system boundaries. They are the production of the two reactants and the treatment of the corresponding solid residues arising from the neutralisation of acid gases. The additional CO2 emission at the stack of the WTE plant due to the activation of the sodium bicarbonate was also included in the calculation. Data used in the modelling of the foreground system are primary, derived from the experimental tests described in Biganzoli et al. (2014) and from the dolomitic sorbent production plant. The results of the LCA show minor changes in the potential impacts between the two operational modes of the plants. These differences are for 8 impact categories in favour of the new operational mode based on the addition of the dolomitic sorbent, and for 7 impact categories in favour of the traditional operation. A final evaluation was conducted on the potential

  19. Hydrogen Peroxide Cycling in Acidic Geothermal Environments and Potential Implications for Oxidative Stress

    NASA Astrophysics Data System (ADS)

    Mesle, M.; Beam, J.; Jay, Z.; Bodle, B.; Bogenschutz, E.; Inskeep, W.

    2014-12-01

    Hydrogen peroxide (H2O2) may be produced in natural waters via photochemical reactions between dissolved oxygen, organic carbon and light. Other reactive oxygen species (ROS) such as superoxide and hydroxyl radicals are potentially formed in environments with high concentrations of ferrous iron (Fe(II), ~10-100 μM) by reaction between H2O2 and Fe(II) (i.e., Fenton chemistry). Thermophilic archaea and bacteria inhabiting acidic iron-oxide mats have defense mechanisms against both extracellular and intracellular peroxide, such as peroxiredoxins (which can degrade H2O2) and against other ROS, such as superoxide dismutases. Biological cycling of H2O2 is not well understood in geothermal ecosystems, and geochemical measurements combined with molecular investigations will contribute to our understanding of microbial response to oxidative stress. We measured H2O2 and other dissolved compounds (Fe(II), Fe(III), H2S, O2), as well as photon flux, pH and temperature, over time in surface geothermal waters of several acidic springs in Norris Geyser Basin, Yellowstone National Park, WY (Beowulf Spring and One Hundred Spring Plain). Iron-oxide mats were sampled in Beowulf Spring for on-going analysis of metatranscriptomes and RT-qPCR assays of specific stress-response gene transcription (e.g., superoxide dismutases, peroxiredoxins, thioredoxins, and peroxidases). In situ analyses show that H2O2 concentrations are lowest in the source waters of sulfidic systems (ca. 1 μM), and increase by two-fold in oxygenated waters corresponding to Fe(III)-oxide mat formation (ca. 2 - 3 μM). Channel transects confirm increases in H2O2 as a function of oxygenation (distance). The temporal dynamics of H2O2, O2, Fe(II), and H2S in Beowulf geothermal waters were also measured during a diel cycle, and increases in H2O2 were observed during peak photon flux. These results suggest that photochemical reactions may contribute to changes in H2O2. We hypothesize that increases in H2O2 and O2

  20. Lead acid battery performance and cycle life increased through addition of discrete carbon nanotubes to both electrodes

    NASA Astrophysics Data System (ADS)

    Sugumaran, Nanjan; Everill, Paul; Swogger, Steven W.; Dubey, D. P.

    2015-04-01

    Contemporary applications are changing the failure mechanisms of lead acid batteries. Sulfation at the negative electrode, acid stratification, and dendrite formation now precede positive electrode failures such as grid corrosion and active material shedding. To attenuate these failures, carbon has been explored as a negative electrode additive to increase charge acceptance, eliminate sulfation, and extend cycle life. Frequently, however, carbon incorporation decreases paste density and hinders manufacturability. Discrete carbon nanotubes (dCNT), also known as Molecular Rebar®, are lead acid battery additives which can be stably incorporated into either electrode to increase charge acceptance and cycle life with no change to paste density and without impeding the manufacturing process. Here, full-scale automotive batteries containing dCNT in the negative electrode or both negative and positive electrodes are compared to control batteries. dCNT batteries show little change to Reserve Capacity, improved Cold Cranking, increased charge acceptance, and enhanced overall system efficiency. Life cycle tests show >60% increases when dCNT are incorporated into the negative electrode (HRPSoC/SBA) and up to 500% when incorporated into both electrodes (SBA), with water loss per cycle reduced >20%. Failure modes of cycled batteries are discussed and a hypothesis of dCNT action is introduced: the dCNT/Had Overcharge Reaction Mechanism.

  1. Glycerolipid/free fatty acid cycle and islet β-cell function in health, obesity and diabetes.

    PubMed

    Prentki, Marc; Madiraju, S R Murthy

    2012-04-28

    Pancreatic β-cells secrete insulin in response to fluctuations in blood fuel concentrations, in particular glucose and fatty acids. However, chronic fuel surfeit can overwhelm the metabolic, signaling and secretory capacity of the β-cell leading to its dysfunction and death - often referred to as glucolipotoxicity. In β-cells and many other cells, glucose and lipid metabolic pathways converge into a glycerolipid/free fatty acid (GL/FFA) cycle, which is driven by the substrates, glycerol-3-phosphate and fatty acyl-CoA, derived from glucose and fatty acids, respectively. Although the overall operation of GL/FFA cycle, consisting of lipolysis and lipogenesis, is "futile" in terms of energy expenditure, this metabolic cycle likely plays an indispensable role for various β-cell functions, in particular insulin secretion and excess fuel detoxification. In this review, we discuss the significance of GL/FFA cycle in the β-cell, its regulation and role in generating essential metabolic signals that participate in the lipid amplification arm of glucose stimulated insulin secretion and in β-cell growth. We propose the novel concept that the lipolytic segment of GL/FFA cycle is instrumental in producing signals for insulin secretion, whereas, the lipogenic segment generates signals relevant for β-cell survival/death and growth/proliferation.

  2. Radiolabeled acetate as a tracer of myocardial tricarboxylic acid cycle flux

    SciTech Connect

    Buxton, D.B.; Schwaiger, M.; Nguyen, A.; Phelps, M.E.; Schelbert, H.R.

    1988-09-01

    The kinetics of (1-14C)acetate oxidation in isolated perfused rat hearts have been determined over a range of perfusion conditions. Effluent measurements demonstrated that 14CO2 cleared biexponentially over 50 minutes after bolus injection of (1-14C)acetate into normoxic hearts perfused with 5 mM glucose and 10 mU/ml insulin. The clearance half-time (t1/2) for the predominant initial clearance phase was 3.1 +/- 0.5 minutes (n = 4). MVO2 was varied over a fourfold range by hypoxia and phenylephrine stimulation (t1/2, 7.2 +/- 1.2 and 2.2 +/- 0.2 minutes, respectively) and in the presence of alternate substrates (lactate, 2 mM; DL-3-hydroxybutyrate, 20 mM; and palmitate, 0.1 mM), which did not modify either tricarboxylic acid (TCA) cycle flux or acetate kinetics. A good correlation (r = 0.93) was observed between k, the rate constant for the initial phase of 14CO2 clearance, and TCA cycle flux, estimated from oxygen consumption. In contrast to results with (1-14C)acetate, lactate (2 mM) increased t1/2 for 14CO2 clearance from a bolus injection of (1-14C)palmitate from 3.0 +/- 0.4 minutes (n = 3) at control to 4.3 +/- 0.2 minutes (n = 3, p less than 0.01). Addition of acetate in nontracer amounts (0.5 or 5 mM) caused significant underestimation of TCA cycle flux when estimated with (1-14C)acetate. 14CO2 clearance accounted for 88-98% of total effluent 14C between 10 and 20 minutes after (1-14C)acetate bolus injection; rate constants for clearance of 14CO2 and total 14C clearance were very similar during this period, and these two rate constants did not differ significantly from each other under any conditions tested.

  3. DIBROMOACETIC ACID-INDUCED ELEVATIONS IN CIRCULATING ESTRADIOL: EFFECTS IN BOTH CYCLING AND OVARIECTOMIZED/STEROID-PRIMED FEMALE RATS

    EPA Science Inventory

    RTD-03-031
    Goldman, JM and Murr, AS. Dibromoacetic Acid-induced Elevations in Circulating Estradiol: Effects in Both Cycling and Ovariectomized/Steroid-primed Female Rats. Reproductive Toxicology (in press).

    Abstract

    Oral exposures to high concentrations of th...

  4. Triglyceride accumulation and fatty acid profile changes in Chlorella (Chlorophyta) during high pH-induced cell cycle inhibition

    SciTech Connect

    Guckert, J.B.; Cooksey, K.E. )

    1990-03-01

    Alkaline pH stress resulted in triglyceride (TG) accumulation in Chlorella CHLOR1 and was independent of medium nitrogen or carbon levels. Based on morphological observations, alkaline pH inhibited autospore release, thus increasing the time for cell cycle completion. Autospore release has been postulated to coincide with TG utilization within the microalgal cell division cycle. The alkaline pH stress affected lipid accumulation by inhibiting the cell division cycle prior to autospore release and, therefore, prior to TG utilization. Cells inhibited in this manner showed an increase in TG accumulation but a decrease in both membrane lipid classes (glycolipid and polar lipid). Unlike TG fatty acid profiles, membrane lipid fatty acid profiles were not stable during TG accumulation. The membrane profiles became similar to the TG, i.e. less unsaturated than in the membrane lipids of unstressed control cells.

  5. Translational regulation of mammalian and Drosophila citric acid cycle enzymes via iron-responsive elements.

    PubMed Central

    Gray, N K; Pantopoulos, K; Dandekar, T; Ackrell, B A; Hentze, M W

    1996-01-01

    The posttranscriptional control of iron uptake, storage, and utilization by iron-responsive elements (IREs) and iron regulatory proteins (IRPs) provides a molecular framework for the regulation of iron homeostasis in many animals. We have identified and characterized IREs in the mRNAs for two different mitochondrial citric acid cycle enzymes. Drosophila melanogaster IRP binds to an IRE in the 5' untranslated region of the mRNA encoding the iron-sulfur protein (Ip) subunit of succinate dehydrogenase (SDH). This interaction is developmentally regulated during Drosophila embryogenesis. In a cell-free translation system, recombinant IRP-1 imposes highly specific translational repression on a reporter mRNA bearing the SDH IRE, and the translation of SDH-Ip mRNA is iron regulated in D. melanogaster Schneider cells. In mammals, an IRE was identified in the 5' untranslated regions of mitochondrial aconitase mRNAs from two species. Recombinant IRP-1 represses aconitase synthesis with similar efficiency as ferritin IRE-controlled translation. The interaction between mammalian IRPs and the aconitase IRE is regulated by iron, nitric oxide, and oxidative stress (H2O2), indicating that these three signals can control the expression of mitochondrial aconitase mRNA. Our results identify a regulatory link between energy and iron metabolism in vertebrates and invertebrates, and suggest biological functions for the IRE/IRP regulatory system in addition to the maintenance of iron homeostasis. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8643505

  6. Tricarboxylic acid cycle and one-carbon metabolism pathways are important in Edwardsiella ictaluri virulence.

    PubMed

    Dahal, Neeti; Abdelhamed, Hossam; Lu, Jingjun; Karsi, Attila; Lawrence, Mark L

    2013-01-01

    Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of channel catfish (ESC). The disease causes considerable economic losses in the commercial catfish industry in the United States. Although antibiotics are used as feed additive, vaccination is a better alternative for prevention of the disease. Here we report the development and characterization of novel live attenuated E. ictaluri mutants. To accomplish this, several tricarboxylic acid cycle (sdhC, mdh, and frdA) and one-carbon metabolism genes (gcvP and glyA) were deleted in wild type E. ictaluri strain 93-146 by allelic exchange. Following bioluminescence tagging of the E. ictaluri ΔsdhC, Δmdh, ΔfrdA, ΔgcvP, and ΔglyA mutants, their dissemination, attenuation, and vaccine efficacy were determined in catfish fingerlings by in vivo imaging technology. Immunogenicity of each mutant was also determined in catfish fingerlings. Results indicated that all of the E. ictaluri mutants were attenuated significantly in catfish compared to the parent strain as evidenced by 2,265-fold average reduction in bioluminescence signal from all the mutants at 144 h post-infection. Catfish immunized with the E. ictaluri ΔsdhC, Δmdh, ΔfrdA, and ΔglyA mutants had 100% relative percent survival (RPS), while E. ictaluri ΔgcvP vaccinated catfish had 31.23% RPS after re-challenge with the wild type E. ictaluri.

  7. High temperature abatement of acid gases from waste incineration. Part II: Comparative life cycle assessment study

    SciTech Connect

    Biganzoli, Laura; Racanella, Gaia; Marras, Roberto; Rigamonti, Lucia

    2015-01-15

    Highlights: • Two scenarios of acid gases removal in WTE plants were compared in an LCA study. • A detailed inventory based on primary data has been reported for the production of the new dolomitic sorbent. • Results show that the comparison between the two scenarios does not show systematic differences. • The potential impacts are reduced only if there is an increase in the energy efficiency of the WTE plant. - Abstract: The performances of a new dolomitic sorbent, named Depurcal®MG, to be directly injected at high temperature in the combustion chamber of Waste-To-Energy (WTE) plants as a preliminary stage of deacidification, were experimentally tested during full-scale commercial operation. Results of the experimentations were promising, and have been extensively described in Biganzoli et al. (2014). This paper reports the Life Cycle Assessment (LCA) study performed to compare the traditional operation of the plants, based on the sole sodium bicarbonate feeding at low temperature, with the new one, where the dolomitic sorbent is injected at high temperature. In the latter the sodium bicarbonate is still used, but at lower rate because of the decreased load of acid gases entering the flue gas treatment line. The major goal of the LCA was to make sure that a burden shifting was not taking place somewhere in the life cycle stages, as it might be the case when a new material is used in substitution of another one. According to the comparative approach, only the processes which differ between the two operational modes were included in the system boundaries. They are the production of the two reactants and the treatment of the corresponding solid residues arising from the neutralisation of acid gases. The additional CO{sub 2} emission at the stack of the WTE plant due to the activation of the sodium bicarbonate was also included in the calculation. Data used in the modelling of the foreground system are primary, derived from the experimental tests described in

  8. Methylcitrate cycle defines the bactericidal essentiality of isocitrate lyase for survival of Mycobacterium tuberculosis on fatty acids

    PubMed Central

    Eoh, Hyungjin; Rhee, Kyu Y.

    2014-01-01

    Few mutations attenuate Mycobacterium tuberculosis (Mtb) more profoundly than deletion of its isocitrate lyases (ICLs). However, the basis for this attenuation remains incompletely defined. Mtb’s ICLs are catalytically bifunctional isocitrate and methylisocitrate lyases required for growth on even and odd chain fatty acids. Here, we report that Mtb’s ICLs are essential for survival on both acetate and propionate because of its methylisocitrate lyase (MCL) activity. Lack of MCL activity converts Mtb’s methylcitrate cycle into a “dead end” pathway that sequesters tricarboxylic acid (TCA) cycle intermediates into methylcitrate cycle intermediates, depletes gluconeogenic precursors, and results in defects of membrane potential and intrabacterial pH. Activation of an alternative vitamin B12-dependent pathway of propionate metabolism led to selective corrections of TCA cycle activity, membrane potential, and intrabacterial pH that specifically restored survival, but not growth, of ICL-deficient Mtb metabolizing acetate or propionate. These results thus resolve the biochemical basis of essentiality for Mtb’s ICLs and survival on fatty acids. PMID:24639517

  9. Phragmites australis response to Cu in terms of low molecular weight organic acids (LMWOAs) exudation: Influence of the physiological cycle

    NASA Astrophysics Data System (ADS)

    Rocha, A. Cristina S.; Almeida, C. Marisa R.; Basto, M. Clara P.; Vasconcelos, M. Teresa S. D.

    2014-06-01

    Plant roots have the ability to produce and secrete substances, such as aliphatic low molecular weight organic acids (ALMWOAs), into the rhizosphere for several purposes, including in response to metal contamination. Despite this, little is yet known about the exudation of such substances from marsh plants roots in response to metal exposure. This work aimed at assessing the influence of the physiological cycle of marsh plants on the exudation of ALMWOAs in response to Cu contamination. In vitro experiments were carried out with Phragmites australis specimens, collected in different seasons. Plant roots were exposed to freshwater contaminated with two different Cu concentrations (67 μg/L and 6.9 mg/L), being the ALMWOAs released by the roots measured. Significant differences (both qualitative and quantitative) were observed during the Phragmites australis life cycle. At growing stage, Cu stimulated the exudation of oxalic and formic acids but no significant stimulation was observed for citric acid. At developing stage, exposure to Cu caused inhibition of oxalic acid exudation whereas citric acid liberation was stimulated but only in the media spiked with the lowest Cu concentration tested. At the decaying stage, no significant variation on oxalic acid was observed, whereas the citric and formic acids release increased as a consequence of the plant exposure to Cu. The physiological cycle of Phragmites australis, and probably also of other marsh plants, is therefore an important feature conditioning plants response to Cu contamination, in terms of ALMWOAs exudation. Hence this aspect should be considered when conducting studies on rhizodeposition involving marsh plants exposed to metals and in the event of using marsh plants for phytoremediation purposes in contaminated estuarine areas.

  10. Which way does the citric acid cycle turn during hypoxia? The critical role of α-ketoglutarate dehydrogenase complex.

    PubMed

    Chinopoulos, Christos

    2013-08-01

    The citric acid cycle forms a major metabolic hub and as such it is involved in many disease states involving energetic imbalance. In spite of the fact that it is being branded as a "cycle", during hypoxia, when the electron transport chain does not oxidize reducing equivalents, segments of this metabolic pathway remain operational but exhibit opposing directionalities. This serves the purpose of harnessing high-energy phosphates through matrix substrate-level phosphorylation in the absence of oxidative phosphorylation. In this Mini-Review, these segments are appraised, pointing to the critical importance of the α-ketoglutarate dehydrogenase complex dictating their directionalities.

  11. Folic acid supplement use and menstrual cycle characteristics: a cross-sectional study of Danish pregnancy planners

    PubMed Central

    Cueto, Heidi T.; Riis, Anders H.; Hatch, Elizabeth E.; Wise, Lauren A.; Rothman, Kenneth J.; Sørensen, Henrik T.; Mikkelsen, Ellen M.

    2015-01-01

    Purpose To examine the association between folic acid (FA) supplementation obtained through either single FA tablets or multivitamins (MVs) and menstrual cycle characteristics among 5,386 women aged 18–40 years, enrolled in an Internet-based study of Danish women attempting pregnancy during 2007–2011. Methods In a cross-sectional study, we used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations of FA supplementation with menstrual cycle regularity, short (<27 days), long (30–33 days), and very long (≥34 days) cycle length, and duration and intensity of menstrual bleeding. Results Compared with non-use, FA supplementation was associated with reduced odds of short cycle length [OR=0.80, 95% CI: 0.68–0.94], and a trend towards increased odds of very long cycle length [OR=1.21, 95% CI: 0.87–1.68] compared with cycle length of 27–29 days. The inverse association with short cycle length was stronger among 18–30 year-old women [OR=0.68, 95% CI: 0.53–0.87], nulliparous women [OR=0.66, 95% CI: 0.52–0.84], and women who used both FA and MVs [OR=0.75, 95% CI: 0.60–0.95]. We found no clear association between FA supplementation and cycle regularity and duration and intensity of menstrual bleeding. Conclusion FA supplementation was inversely associated with short menstrual cycle length. This association was strongest among women aged 18–30 years, nulliparous women, and women who used both FA and MVs. PMID:26123570

  12. Contribution of the tricarboxylic acid (TCA) cycle and the glyoxylate shunt in Saccharomyces cerevisiae to succinic acid production during dough fermentation.

    PubMed

    Rezaei, Mohammad N; Aslankoohi, Elham; Verstrepen, Kevin J; Courtin, Christophe M

    2015-07-01

    Succinic acid produced by yeast during bread dough fermentation can significantly affect the rheological properties of the dough. By introducing mutations in the model S288C yeast strain, we show that the oxidative pathway of the TCA cycle and the glyoxylate shunt contribute significantly to succinic acid production during dough fermentation. More specifically, deletion of ACO1 and double deletion of ACO1 and ICL1 resulted in a 36 and 77% decrease in succinic acid levels in fermented dough, respectively. Similarly, double deletion of IDH1 and IDP1 decreased succinic acid production by 85%, while also affecting the fermentation rate. By contrast, double deletion of SDH1 and SDH2 resulted in a two-fold higher succinic acid accumulation compared to the wild-type. Deletion of fumarate reductase activity (FRD1 and OSM1) in the reductive pathway of the TCA cycle did not affect the fermentation rate and succinic acid production. The changes in the levels of succinic acid produced by mutants Δidh1Δidp1 (low level) and Δsdh1Δsdh2 (high level) in fermented dough only resulted in small pH differences, reflecting the buffering capacity of dough at a pH of around 5.1. Moreover, Rheofermentometer analysis using these mutants revealed no difference in maximum dough height and gas retention capacity with the dough prepared with S288C. The impact of the changed succinic acid profile on the organoleptic or antimicrobial properties of bread remains to be demonstrated.

  13. Contribution of the tricarboxylic acid (TCA) cycle and the glyoxylate shunt in Saccharomyces cerevisiae to succinic acid production during dough fermentation.

    PubMed

    Rezaei, Mohammad N; Aslankoohi, Elham; Verstrepen, Kevin J; Courtin, Christophe M

    2015-07-01

    Succinic acid produced by yeast during bread dough fermentation can significantly affect the rheological properties of the dough. By introducing mutations in the model S288C yeast strain, we show that the oxidative pathway of the TCA cycle and the glyoxylate shunt contribute significantly to succinic acid production during dough fermentation. More specifically, deletion of ACO1 and double deletion of ACO1 and ICL1 resulted in a 36 and 77% decrease in succinic acid levels in fermented dough, respectively. Similarly, double deletion of IDH1 and IDP1 decreased succinic acid production by 85%, while also affecting the fermentation rate. By contrast, double deletion of SDH1 and SDH2 resulted in a two-fold higher succinic acid accumulation compared to the wild-type. Deletion of fumarate reductase activity (FRD1 and OSM1) in the reductive pathway of the TCA cycle did not affect the fermentation rate and succinic acid production. The changes in the levels of succinic acid produced by mutants Δidh1Δidp1 (low level) and Δsdh1Δsdh2 (high level) in fermented dough only resulted in small pH differences, reflecting the buffering capacity of dough at a pH of around 5.1. Moreover, Rheofermentometer analysis using these mutants revealed no difference in maximum dough height and gas retention capacity with the dough prepared with S288C. The impact of the changed succinic acid profile on the organoleptic or antimicrobial properties of bread remains to be demonstrated. PMID:25828707

  14. Microbial ecology of a novel sulphur cycling consortia from AMD: implications for acid generation

    NASA Astrophysics Data System (ADS)

    Loiselle, L. M.; Norlund, K. L.; Hitchcock, A. P.; Warren, L. A.

    2009-05-01

    Recent work1 identified a novel microbial consortia consisting of two bacterial strains common to acid mine drainage (AMD) environments (autotrophic sulphur oxidizer Acidithiobacillus ferrooxidans and heterotrophic Acidiphilium spp.) in an environmental enrichment from a mine tailings lake. The two strains showed a specific spatial arrangement within an EPS macrostructure or "pod" allowing linked metabolic redox cycling of sulphur. Sulphur species characterisation of the pods using scanning transmission X-ray microscopy (STXM) indicated that autotrophic tetrathionate disproportionation by A. ferrooxidans producing colloidal elemental sulphur (S0) is coupled to heterotrophic S0 reduction by Acidiphilium spp. Geochemical modelling of the microbial sulphur reactions indicated that if they are widespread in AMD environments, then global AMD-driven CO2 liberation from mineral weathering have been overestimated by 40-90%1. Given the common co-occurrence of these two bacteria in AMD settings, the purpose of this study was to evaluate if these pods could be induced in the laboratory by pure strains and if so, whether their combined sulphur geochemistry mimicked the previous findings. Laboratory batch experiments assessed the development of pods with pure strain type cultures (A. ferrooxidans ATCC 19859 with mixotroph Acidiphilium acidophilum ATCC 738 or strict heterotroph Acp. cryptum ATCC 2158) using fluorescent in situ hybridization (FISH) imaging. The microbial sulphur geochemistry was characterized under autotrophic conditions identical to those used with the environmental AMD enrichment in which the pods were discovered. Results showed that the combined pure strain A. ferrooxidans and Acp. acidophilum form pods identical in structure to the AMD enrichment. To test the hypothesis that these pods form for mutual metabolic benefit, experiments were performed amending pure strain and AMD enrichment bacterial treatments with organic carbon and/or additional sulphur to

  15. Gluconeogenic carbon flow of tricarboxylic acid cycle intermediates is critical for Mycobacterium tuberculosis to establish and maintain infection.

    PubMed

    Marrero, Joeli; Rhee, Kyu Y; Schnappinger, Dirk; Pethe, Kevin; Ehrt, Sabine

    2010-05-25

    Metabolic adaptation to the host niche is a defining feature of the pathogenicity of Mycobacterium tuberculosis (Mtb). In vitro, Mtb is able to grow on a variety of carbon sources, but mounting evidence has implicated fatty acids as the major source of carbon and energy for Mtb during infection. When bacterial metabolism is primarily fueled by fatty acids, biosynthesis of sugars from intermediates of the tricarboxylic acid cycle is essential for growth. The role of gluconeogenesis in the pathogenesis of Mtb however remains unaddressed. Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes the first committed step of gluconeogenesis. We applied genetic analyses and (13)C carbon tracing to confirm that PEPCK is essential for growth of Mtb on fatty acids and catalyzes carbon flow from tricarboxylic acid cycle-derived metabolites to gluconeogenic intermediates. We further show that PEPCK is required for growth of Mtb in isolated bone marrow-derived murine macrophages and in mice. Importantly, Mtb lacking PEPCK not only failed to replicate in mouse lungs but also failed to survive, and PEPCK depletion during the chronic phase of infection resulted in mycobacterial clearance. Mtb thus relies on gluconeogenesis throughout the infection. PEPCK depletion also attenuated Mtb in IFNgamma-deficient mice, suggesting that this enzyme represents an attractive target for chemotherapy.

  16. Production of tartrates by cyanide-mediated dimerization of glyoxylate: a potential abiotic pathway to the citric acid cycle.

    PubMed

    Butch, Christopher; Cope, Elizabeth D; Pollet, Pamela; Gelbaum, Leslie; Krishnamurthy, Ramanarayanan; Liotta, Charles L

    2013-09-11

    An abiotic formation of meso- and DL-tartrates in 80% yield via the cyanide-catalyzed dimerization of glyoxylate under alkaline conditions is demonstrated. A detailed mechanism for this conversion is proposed, supported by NMR evidence and (13)C-labeled reactions. Simple dehydration of tartrates to oxaloacetate and an ensuing decarboxylation to form pyruvate are known processes that provide a ready feedstock for entry into the citric acid cycle. While glyoxylate and high hydroxide concentration are atypical in the prebiotic literature, there is evidence for natural, abiotic availability of each. It is proposed that this availability, coupled with the remarkable efficiency of tartrate production from glyoxylate, merits consideration of an alternative prebiotic pathway for providing constituents of the citric acid cycle.

  17. Production of Tartrates by Cyanide-Mediated Dimerization of Glyoxylate: A Potential Abiotic Pathway to the Citric Acid Cycle

    PubMed Central

    2013-01-01

    An abiotic formation of meso- and dl-tartrates in 80% yield via the cyanide-catalyzed dimerization of glyoxylate under alkaline conditions is demonstrated. A detailed mechanism for this conversion is proposed, supported by NMR evidence and 13C-labeled reactions. Simple dehydration of tartrates to oxaloacetate and an ensuing decarboxylation to form pyruvate are known processes that provide a ready feedstock for entry into the citric acid cycle. While glyoxylate and high hydroxide concentration are atypical in the prebiotic literature, there is evidence for natural, abiotic availability of each. It is proposed that this availability, coupled with the remarkable efficiency of tartrate production from glyoxylate, merits consideration of an alternative prebiotic pathway for providing constituents of the citric acid cycle. PMID:23914725

  18. Metabolism of glycerol, glucose, and lactate in the citric acid cycle prior to incorporation into hepatic acylglycerols.

    PubMed

    Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

    2013-05-17

    During hepatic lipogenesis, the glycerol backbone of acylglycerols originates from one of three sources: glucose, glycerol, or substrates passing through the citric acid cycle via glyceroneogenesis. The relative contribution of each substrate source to glycerol in rat liver acylglycerols was determined using (13)C-enriched substrates and NMR. Animals received a fixed mixture of glucose, glycerol, and lactate; one group received [U-(13)C6]glucose, another received [U-(13)C3]glycerol, and the third received [U-(13)C3]lactate. After 3 h, the livers were harvested to extract fats, and the glycerol moiety from hydrolyzed acylglycerols was analyzed by (13)C NMR. In either fed or fasted animals, glucose and glycerol provided the majority of the glycerol backbone carbons, whereas the contribution of lactate was small. In fed animals, glucose contributed >50% of the total newly synthesized glycerol backbone, and 35% of this contribution occurred after glucose had passed through the citric acid cycle. By comparison, the glycerol contribution was ~40%, and of this, 17% of the exogenous glycerol passed first through the cycle. In fasted animals, exogenous glycerol became the major contributor to acylglycerols. The contribution from exogenous lactate did increase in fasted animals, but its overall contribution remained small. The contributions of glucose and glycerol that had passed through the citric acid cycle first increased in fasted animals from 35 to 71% for glucose and from 17 to 24% for glycerol. Thus, a substantial fraction from both substrate sources passed through the cycle prior to incorporation into the glycerol moiety of acylglycerols in the liver.

  19. The role of the ω-3 fatty acid DHA in the human life cycle.

    PubMed

    Carlson, Sarah J; Fallon, Erica M; Kalish, Brian T; Gura, Kathleen M; Puder, Mark

    2013-01-01

    Dietary consumption of the essential fatty acids linoleic acid (LA; ω-6) and α-linolenic acid (ALA; ω-3) is necessary for human growth and development. In the past 150 years, the average Western diet has changed dramatically such that humans today consume a much higher proportion of ω-6 fatty acids relative to ω-3 fatty acids than ever before. The importance of ω-3 fatty acids in human development has been well established in fetal and neonatal development, with brain and retinal tissues highly dependent on ω-3 fatty acids, specifically docosahexaenoic acid (DHA) for membrane fluidity and signal transduction. In childhood, ω-3s have been shown to contribute to ongoing cognitive development and may be involved in metabolic programming of bone turnover and adipogenesis. ω-3s may also play important roles in adult neurophysiology and disease prevention.

  20. Metabolomic and mass isotopomer analysis of liver gluconeogenesis and citric acid cycle: II. Heterogeneity of metabolite labeling pattern.

    PubMed

    Yang, Lili; Kasumov, Takhar; Kombu, Rajan S; Zhu, Shu-Han; Cendrowski, Andrea V; David, France; Anderson, Vernon E; Kelleher, Joanne K; Brunengraber, Henri

    2008-08-01

    In this second of two companion articles, we compare the mass isotopomer distribution of metabolites of liver gluconeogenesis and citric acid cycle labeled from NaH(13)CO(3) or dimethyl [1,4-(13)C(2)]succinate. The mass isotopomer distribution of intermediates reveals the reversibility of the isocitrate dehydrogenase + aconitase reactions, even in the absence of a source of alpha-ketoglutarate. In addition, in many cases, a number of labeling incompatibilities were found as follows: (i) glucose versus triose phosphates and phosphoenolpyruvate; (ii) differences in the labeling ratios C-4/C-3 of glucose versus (glyceraldehyde 3-phosphate)/(dihydroxyacetone phosphate); and (iii) labeling of citric acid cycle intermediates in tissue versus effluent perfusate. Overall, our data show that gluconeogenic and citric acid cycle intermediates cannot be considered as sets of homogeneously labeled pools. This probably results from the zonation of hepatic metabolism and, in some cases, from differences in the labeling pattern of mitochondrial versus extramitochondrial metabolites. Our data have implications for the use of labeling patterns for the calculation of metabolic rates or fractional syntheses in liver, as well as for modeling liver intermediary metabolism.

  1. A new method for assembling metabolic networks, with application to the Krebs citric acid cycle.

    PubMed

    Mittenthal, J E; Clarke, B; Waddell, T G; Fawcett, G

    2001-02-01

    To understand why a molecular network has a particular connectivity one can generate an ensemble of alternative networks, all of which meet the same performance criteria as the real network. We have generated alternatives to the Krebs cycle, allowing group transfers and B(12)-mediated shifts that were excluded in previous work. Our algorithm does not use a reaction list, but determines the reactants and products in generic reactions. It generates networks in order of increasing number of reaction steps. We find that alternatives to the Krebs cycle are very likely to be cycles. Many of the alternatives produce toxic or unstable compounds and use group transfer reactions, which have unfavorable consequences. Although alternatives are better than the Krebs cycle in some respects, the Krebs cycle has the most favorable combination of traits.

  2. Quantifying Rates of Complete Microbial Iron Redox Cycling in Acidic Hot Springs

    NASA Astrophysics Data System (ADS)

    St Clair, B.; Pottenger, J. W.; Shock, E.

    2013-12-01

    concentrations of ferrous iron. Experimental design allowed us to measure biological and abiological rates independently. Results indicate a relatively consistent rate of biological iron oxidation between 20-100 ng Fe2+(gm wet sediment)-1 (second)-1 where oxide accumulations occur. Abiological oxidation rates increase significantly with increasing pH, and greatly limit soluble ferrous iron above a pH of 3.5 at high temperatures. Rates of biological iron reduction are typically comparable to oxidation, and can often double oxidation rates when supplemented with organic carbon. Abiological iron reduction rates are inconsequential when the pH is greater than 2, but increase sharply below this point. Results indicate that comparable rates of microbial oxidation and reduction are common in springs where biogenic iron oxide accumulates. It appears that the interplay of temperature, oxygen availability, and supply of organic carbon determines the extent and history of iron oxide accumulation. Taken together, our results show that complete microbial iron redox cycles are active in acidic hot springs wherever biogenic iron oxides accumulate.

  3. Amphipathic β2,2-Amino Acid Derivatives Suppress Infectivity and Disrupt the Intracellular Replication Cycle of Chlamydia pneumoniae

    PubMed Central

    Tiirola, Terttu M.; Strøm, Morten B.; Vuorela, Pia M.

    2016-01-01

    We demonstrate in the current work that small cationic antimicrobial β2,2-amino acid derivatives (Mw < 500 Da) are highly potent against Chlamydia pneumoniae at clinical relevant concentrations (< 5 μM, i.e. < 3.4 μg/mL). C. pneumoniae is an atypical respiratory pathogen associated with frequent treatment failures and persistent infections. This gram-negative bacterium has a biphasic life cycle as infectious elementary bodies and proliferating reticulate bodies, and efficient treatment is challenging because of its long and obligate intracellular replication cycle within specialized inclusion vacuoles. Chlamydicidal effect of the β2,2-amino acid derivatives in infected human epithelial cells was confirmed by transmission electron microscopy. Images of infected host cells treated with our lead derivative A2 revealed affected chlamydial inclusion vacuoles 24 hours post infection. Only remnants of elementary and reticulate bodies were detected at later time points. Neither the EM studies nor resazurin-based cell viability assays showed toxic effects on uninfected host cells or cell organelles after A2 treatment. Besides the effects on early intracellular inclusion vacuoles, the ability of these β2,2-amino acid derivatives to suppress Chlamydia pneumoniae infectivity upon treatment of elementary bodies suggested also a direct interaction with bacterial membranes. Synthetic β2,2-amino acid derivatives that target C. pneumoniae represent promising lead molecules for development of antimicrobial agents against this hard-to-treat intracellular pathogen. PMID:27280777

  4. Thiram and dimethyldithiocarbamic acid interconversion in Saccharomyces cerevisiae: a possible metabolic pathway under the control of the glutathione redox cycle.

    PubMed

    Elskens, M T; Penninckx, M J

    1997-07-01

    A rapid decrease of intracellular glutathione (GSH) was observed when exponentially growing cells of Saccharomyces cerevisiae were treated with sublethal concentrations of either dimethyldithiocarbamic acid or thiram [bis(dimethylthiocarbamoyl) disulfide]. The underlying mechanism of this effect possibly involves the intracellular oxidation of dimethyldithiocarbamate anions to thiram, which in turn oxidizes GSH. Overall, a linear relationship was found between thiram concentrations up to 21 microM and production of oxidized GSH (GSSG). Cytochrome c can serve as the final electron acceptor for dimethyldithiocarbamate reoxidation, and it was demonstrated in vitro that NADPH handles the final electron transfer from GSSG to the fungicide by glutathione reductase. These cycling reactions induce transient alterations in the intracellular redox state of several electron carriers and interfere with the respiration of the yeast. Thiram and dimethyldithiocarbamic acid also inactivate yeast glutathione reductase when the fungicide is present within the cells as the disulfide. Hence, whenever the GSH regeneration rate falls below its oxidation rate, the GSH:GSSG molar ratio drops from 45 to 1. Inhibition of glutathione reductase may be responsible for the saturation kinetics observed in rates of thiram elimination and uptake by the yeast. The data suggest also a leading role for the GSH redox cycle in the control of thiram and dimethyldithiocarbamic acid fungitoxicity. Possible pathways for the handling of thiram and dimethyldithiocarbamic acid by yeast are considered with respect to the physiological status, the GSH content, and the activity of glutathione reductase of the cells.

  5. Thiram and dimethyldithiocarbamic acid interconversion in Saccharomyces cerevisiae: a possible metabolic pathway under the control of the glutathione redox cycle.

    PubMed Central

    Elskens, M T; Penninckx, M J

    1997-01-01

    A rapid decrease of intracellular glutathione (GSH) was observed when exponentially growing cells of Saccharomyces cerevisiae were treated with sublethal concentrations of either dimethyldithiocarbamic acid or thiram [bis(dimethylthiocarbamoyl) disulfide]. The underlying mechanism of this effect possibly involves the intracellular oxidation of dimethyldithiocarbamate anions to thiram, which in turn oxidizes GSH. Overall, a linear relationship was found between thiram concentrations up to 21 microM and production of oxidized GSH (GSSG). Cytochrome c can serve as the final electron acceptor for dimethyldithiocarbamate reoxidation, and it was demonstrated in vitro that NADPH handles the final electron transfer from GSSG to the fungicide by glutathione reductase. These cycling reactions induce transient alterations in the intracellular redox state of several electron carriers and interfere with the respiration of the yeast. Thiram and dimethyldithiocarbamic acid also inactivate yeast glutathione reductase when the fungicide is present within the cells as the disulfide. Hence, whenever the GSH regeneration rate falls below its oxidation rate, the GSH:GSSG molar ratio drops from 45 to 1. Inhibition of glutathione reductase may be responsible for the saturation kinetics observed in rates of thiram elimination and uptake by the yeast. The data suggest also a leading role for the GSH redox cycle in the control of thiram and dimethyldithiocarbamic acid fungitoxicity. Possible pathways for the handling of thiram and dimethyldithiocarbamic acid by yeast are considered with respect to the physiological status, the GSH content, and the activity of glutathione reductase of the cells. PMID:9212433

  6. Annual cycle and spatial trends in fatty acid composition of suspended particulate organic matter across the Beaufort Sea shelf

    NASA Astrophysics Data System (ADS)

    Connelly, Tara L.; Businski, Tara N.; Deibel, Don; Parrish, Christopher C.; Trela, Piotr

    2016-11-01

    Fatty acid profiles of suspended particulate organic matter (POM) were determined over an annual cycle (September 2003 to August 2004) on the Beaufort Sea shelf, Canadian Arctic. Special emphasis was placed on the nutritional quality of the fatty acid pool available to zooplankton by examining spatial and temporal patterns in the proportions of total polyunsaturated fatty acids (PUFA) and the essential fatty acids 22:6n-3 (DHA) and 20:5n-3 (EPA). EPA and DHA were the two most abundant PUFA throughout the study period. A log-ratio multivariate (LRA) analysis revealed strong structure in fatty acid profiles related to season and depth. Dominant fatty acids accounting for the observed trend included 18:5n-3, 18:4n-3, 16:1n-7, 20:5n-3, 18:0 and 20:3n-3. We observed a shift in fatty acid profiles from summer to autumn (e.g., from 16:1n-7 and EPA to 18:5n-3 and 18:4n-3) that likely corresponded to a shift in the relative importance of diatoms versus dinoflagellates, prymnesiophytes and/or prasinophytes to the POM pool. Fatty acid composition during winter was dominated by more refractory saturated fatty acids. A surprising finding was the depth and seasonal trend of 20:3n-3, which was higher in winter, aligned with 18:0 in the LRA, but behaved differently than other n-3 PUFA. We interpret fatty acid profiles during summer to be predominantly driven by phytoplankton inputs, whereas fatty acid profiles in winter were dominated by fatty acids that were left over after consumption and/or were generated by heterotrophs. The highest diatom inputs (EPA, the diatom fatty acid marker), n-3/n-6 ratios, and C16 PUFA index were located in an upwelling region off Cape Bathurst. This study is the first annual time series of fatty acid profiles of POM in Arctic seas, expanding our knowledge of the composition of POM throughout the dark season.

  7. Analysis of trace inorganic anions in weak acid salts by single pump cycling-column-switching ion chromatography.

    PubMed

    Huang, Zhongping; Ni, Chengzhu; Zhu, Zhuyi; Pan, Zaifa; Wang, Lili; Zhu, Yan

    2015-05-01

    The application of ion chromatography with the single pump cycling-column-switching technique was described for the analysis of trace inorganic anions in weak acid salts within a single run. Due to the hydrogen ions provided by an anion suppressor electrolyzing water, weak acid anions could be transformed into weak acids, existing as molecules, after passing through the suppressor. Therefore, an anion suppressor and ion-exclusion column were adopted to achieve on-line matrix elimination of weak acid anions with high concentration for the analysis of trace inorganic anions in weak acid salts. A series of standard solutions consisting of target anions of various concentrations from 0.005 to 10 mg/L were analyzed, with correlation coefficients r ≥ 0.9990. The limits of detection were in the range of 0.67 to 1.51 μg/L, based on the signal-to-noise ratio of 3 and a 25 μL injection volume. Relative standard deviations for retention time, peak area, and peak height were all less than 2.01%. A spiking study was performed with satisfactory recoveries between 90.3 and 104.4% for all anions. The chromatographic system was successfully applied to the analysis of trace inorganic anions in five weak acid salts.

  8. Tandem dissolution of UO 3 in amide-based acidic ionic liquid and in situ electrodeposition of UO 2 with regeneration of the ionic liquid: a closed cycle

    DOE PAGES

    Wanigasekara, Eranda; Freiderich, John W.; Sun, Xiao-Guang; Meisner, Roberta A.; Luo, Huimin; Delmau, Lætitia H.; Dai, Sheng; Moyer, Bruce A.

    2016-05-19

    A closed cycle is demonstrated for the tandem dissolution and electroreduction of UO3 to UO2 with regeneration of the acidic ionic liquid. The dissolution is achieved by use of the acidic ionic liquid N,N-dimethylacetimidium bis(trifluoromethanesulfonimide) in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonimide) serving as the diluent. Bulk electrolysis performed at 1.0 V vs. Ag reference yields a dark brown-black uranium deposit (UO2) on the cathode. Anodic oxidation of water in the presence of dimethylacetamide regenerates the acidic ionic liquid. We have demonstrated the individual steps in the cycle together with a sequential dissolution, electroreduction, and regeneration cycle.

  9. Interconnection between tricarboxylic acid cycle and energy generation in microbial fuel cell performed by desulfuromonas acetoxidans IMV B-7384

    NASA Astrophysics Data System (ADS)

    Vasyliv, Oresta M.; Maslovska, Olga D.; Ferensovych, Yaroslav P.; Bilyy, Oleksandr I.; Hnatush, Svitlana O.

    2015-05-01

    Desulfuromonas acetoxidans IMV B-7384 is exoelectrogenic obligate anaerobic sulfur-reducing bacterium. Its one of the first described electrogenic bacterium that performs complete oxidation of an organic substrate with electron transfer directly to the electrode in microbial fuel cell (MFC). This bacterium is very promising for MFC development because of inexpensive cultivation medium, high survival rate and selective resistance to various heavy metal ions. The size of D. acetoxidans IMV B-7384 cells is comparatively small (0.4-0.8×1-2 μm) that is highly beneficial while application of porous anode material because of complete bacterial cover of an electrode area with further significant improvement of the effectiveness of its usage. The interconnection between functioning of reductive stage of tricarboxylic acid (TCA) cycle under anaerobic conditions, and MFC performance was established. Malic, pyruvic, fumaric and succinic acids in concentration 42 mM were separately added into the anode chamber of MFC as the redox agents. Application of malic acid caused the most stabile and the highest power generation in comparison with other investigated organic acids. Its maximum equaled 10.07±0.17mW/m2 on 136 hour of bacterial cultivation. Under addition of pyruvic, succinic and fumaric acids into the anode chamber of MFC the maximal power values equaled 5.80±0.25 mW/m2; 3.2±0.11 mW/m2, and 2.14±0.19 mW/m2 respectively on 40, 56 and 32 hour of bacterial cultivation. Hence the malic acid conversion via reductive stage of TCA cycle is shown to be the most efficient process in terms of electricity generation by D. acetoxidans IMV B-7384 in MFC under anaerobic conditions.

  10. Pseudolaric Acid B Induced Cell Cycle Arrest, Autophagy and Senescence in Murine Fibrosarcoma L929 Cell

    PubMed Central

    hua Yu, Jing; yu Liu, Chun; bin Zheng, Gui; Zhang, Li Ying; hui Yan, Ming; yan Zhang, Wen; ying Meng, Xian; fang Yu, Xiao

    2013-01-01

    Objective: PAB induced various cancer cell apoptosis, cell cycle arrest and senescence. But in cell line murine fibrosarcoma L929, PAB did not induce apoptosis, but autophagy, therefore it was thought by us as a good model to research the relationship of cell cycle arrest, autophagy and senescence bypass apoptosis. Methods: Inhibitory ratio was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis. Phase contrast microscopy visualized cell morphology. Hoechst 33258 staining for nuclear change, propidium iodode (PI) staining for cell cycle, monodansylcadaverine (MDC) staining for autophagy, and rodanmine 123 staining for mitochondrial membrane potential (MMP) were measured by fluorescence microscopy or flowcytometry. Apoptosis was determined by DNA ladder test. Protein kinase C (PKC) activity was detected by PKC assay kit. SA-β-galactosidase assay was used to detect senescence. Protein expression was examined by western blot. Results: PAB inhibited L929 cell growth in time-and dose-dependent manner. At 12 h, 80 μmol/L PAB induced obvious mitotic arrest; at 24 h, PAB began to induce autophagy; at 36 h, cell-treated with PAB slip into G1 cell cycle; and 3 d PAB induced senescence. In time sequence PAB induced firstly cell cycle arrest, then autophagy, then slippage into G1 phase, lastly senescence. Senescent cells had high level of autophagy, inhibiting autophagy led to apoptosis, and no senescence. PAB activated PKC activity to induce cell cycle arrest, autophagy and senescence, inhibiting PKC activity suppressed cell cycle arrest, autophagy and senescence. Conclusion: PAB induced cell cycle arrest, autophagy and senescence in murine fibrosarcoma L929 cell through PKC. PMID:23630435

  11. gamma-Linolenic acid blocks cell cycle progression by regulating phosphorylation of p27kip1 and p57kip2 and their interactions with other cycle regulators in cancer cells.

    PubMed

    Jiang, W G; Bryce, R P; Horrobin, D F; Mansel, R E

    1998-09-01

    gamma-Linolenic acid (gamma-LA), a n-6 essential fatty acid, has been previously shown to affect cell cycle and growth of cancer cells. This study examined the effects of gamma-LA on the cell cycle and cycle regulators in human colon cancer HT115 and breast cancer MCF7 cells. Brief treatment of cancer cells (<2 h) with gamma-LA resulted in a decrease in the phosphorylation of both cell cycle inhibitors, p27kip1 and p57kip2 as shown by immunoprecipitation and Western blotting. Protein levels of both inhibitors were increased following a prolonged culture of cells with the fatty acid. A co-precipitation study showed that in cells treated with gamma-LA there was an increase in the binding of these inhibitors with CDK4, CDC2, and cyclin E. Flow cytometry study indicated an inhibition of cell cycle progression by gamma-LA (G0/G1 -45.4%, S - 34.6%, G2+M - 20.0% in control, and 70.5%, 21.0%, and 8.5%, respectively, in gamma-LA treated cells). It is concluded that gamma-linolenic acid inhibits cell cycle progression in the cancer cell lines investigated, via its regulation of the phosphorylation and subsequent degradation of p27kip1 and p57kip2 and their interactions with other cycle regulators. PMID:9683802

  12. Omega-3 Polyunsaturated Fatty Acids Trigger Cell Cycle Arrest and Induce Apoptosis in Human Neuroblastoma LA-N-1 Cells.

    PubMed

    So, Wai Wing; Liu, Wai Nam; Leung, Kwok Nam

    2015-08-18

    Omega-3 (n-3) fatty acids are dietary long-chain fatty acids with an array of health benefits. Previous research has demonstrated the growth-inhibitory effect of n-3 fatty acids on different cancer cell lines in vitro, yet their anti-tumor effects and underlying action mechanisms on human neuroblastoma LA-N-1 cells have not yet been reported. In this study, we showed that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) exhibited time- and concentration-dependent anti-proliferative effect on the human neuroblastoma LA-N-1 cells, but had minimal cytotoxicity on the normal or non-tumorigenic cells, as measured by MTT reduction assay. Mechanistic studies indicated that DHA and EPA triggered G0/G1 cell cycle arrest in LA-N-1 cells, as detected by flow cytometry, which was accompanied by a decrease in the expression of CDK2 and cyclin E proteins. Moreover, DHA and EPA could also induce apoptosis in LA-N-1 cells as revealed by an increase in DNA fragmentation, phosphatidylserine externalization and mitochondrial membrane depolarization. Up-regulation of Bax, activated caspase-3 and caspase-9 proteins, and down-regulation of Bcl-XL protein, might account for the occurrence of apoptotic events. Collectively, our results suggest that the growth-inhibitory effect of DHA and EPA on LA-N-1 cells might be mediated, at least in part, via triggering of cell cycle arrest and apoptosis. Therefore, DHA and EPA are potential anti-cancer agents which might be used for the adjuvant therapy or combination therapy with the conventional anti-cancer drugs for the treatment of some forms of human neuroblastoma with minimal toxicity.

  13. Pt/TiO2 (Rutile) Catalysts for Sulfuric Acid Decomposition in Sulfur-Based Thermochemical Water-Splitting Cycles

    SciTech Connect

    L. M. Petkovic; D. M. Ginosar; H. W. Rollins; K. C. Burch; P. J. Pinhero; H. H. Farrell

    2008-04-01

    Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on platinum supported on titania (rutile) catalysts to investigate the causes of catalyst deactivation under sulfuric acid decomposition reaction conditions. Samples of 1 wt% Pt/TiO2 (rutile) catalysts were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different times on stream (TOS) between 0 and 548 h. Post-operation analyses of the spent catalyst samples showed that Pt oxidation and sintering occurred under reaction conditions and some Pt was lost by volatilization. Pt loss rate was higher at initial times but total loss appeared to be independent of the gaseous environment. Catalyst activity showed an initial decrease that lasted for about 66 h, followed by a slight recovery of activity between 66 and 102 h TOS, and a period of slower deactivation after 102 h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity and the activity profile suggested that a complex dynamical situation involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes affected catalyst activity in a non-monotonic way.

  14. Gluconeogenic carbon flow of tricarboxylic acid cycle intermediates is critical for Mycobacterium tuberculosis to establish and maintain infection

    PubMed Central

    Marrero, Joeli; Rhee, Kyu Y.; Schnappinger, Dirk; Pethe, Kevin; Ehrt, Sabine

    2010-01-01

    Metabolic adaptation to the host niche is a defining feature of the pathogenicity of Mycobacterium tuberculosis (Mtb). In vitro, Mtb is able to grow on a variety of carbon sources, but mounting evidence has implicated fatty acids as the major source of carbon and energy for Mtb during infection. When bacterial metabolism is primarily fueled by fatty acids, biosynthesis of sugars from intermediates of the tricarboxylic acid cycle is essential for growth. The role of gluconeogenesis in the pathogenesis of Mtb however remains unaddressed. Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes the first committed step of gluconeogenesis. We applied genetic analyses and 13C carbon tracing to confirm that PEPCK is essential for growth of Mtb on fatty acids and catalyzes carbon flow from tricarboxylic acid cycle–derived metabolites to gluconeogenic intermediates. We further show that PEPCK is required for growth of Mtb in isolated bone marrow–derived murine macrophages and in mice. Importantly, Mtb lacking PEPCK not only failed to replicate in mouse lungs but also failed to survive, and PEPCK depletion during the chronic phase of infection resulted in mycobacterial clearance. Mtb thus relies on gluconeogenesis throughout the infection. PEPCK depletion also attenuated Mtb in IFNγ-deficient mice, suggesting that this enzyme represents an attractive target for chemotherapy. PMID:20439709

  15. rre37 Overexpression Alters Gene Expression Related to the Tricarboxylic Acid Cycle and Pyruvate Metabolism in Synechocystis sp. PCC 6803

    PubMed Central

    Iijima, Hiroko; Watanabe, Atsuko; Takanobu, Junko; Hirai, Masami Yokota; Osanai, Takashi

    2014-01-01

    The tricarboxylic acid (TCA) cycle and pyruvate metabolism of cyanobacteria are unique and important from the perspectives of biology and biotechnology research. Rre37, a response regulator induced by nitrogen depletion, activates gene expression related to sugar catabolism. Our previous microarray analysis has suggested that Rre37 controls the transcription of genes involved in sugar catabolism, pyruvate metabolism, and the TCA cycle. In this study, quantitative real-time PCR was used to measure the transcript levels of 12 TCA cycle genes and 13 pyruvate metabolism genes. The transcripts of 6 genes (acnB, icd, ppc, pyk1, me, and pta) increased after 4 h of nitrogen depletion in the wild-type GT strain but the induction was abolished by rre37 overexpression. The repression of gene expression of fumC, ddh, and ackA caused by nitrogen depletion was abolished by rre37 overexpression. The expression of me was differently affected by rre37 overexpression, compared to the other 24 genes. These results indicate that Rre37 differently controls the genes of the TCA cycle and pyruvate metabolism, implying the key reaction of the primary in this unicellular cyanobacterium. PMID:25614900

  16. Inhibition of Pyruvate Dehydrogenase Kinase 2 Protects Against Hepatic Steatosis Through Modulation of Tricarboxylic Acid Cycle Anaplerosis and Ketogenesis.

    PubMed

    Go, Younghoon; Jeong, Ji Yun; Jeoung, Nam Ho; Jeon, Jae-Han; Park, Bo-Yoon; Kang, Hyeon-Ji; Ha, Chae-Myeong; Choi, Young-Keun; Lee, Sun Joo; Ham, Hye Jin; Kim, Byung-Gyu; Park, Keun-Gyu; Park, So Young; Lee, Chul-Ho; Choi, Cheol Soo; Park, Tae-Sik; Lee, W N Paul; Harris, Robert A; Lee, In-Kyu

    2016-10-01

    Hepatic steatosis is associated with increased insulin resistance and tricarboxylic acid (TCA) cycle flux, but decreased ketogenesis and pyruvate dehydrogenase complex (PDC) flux. This study examined whether hepatic PDC activation by inhibition of pyruvate dehydrogenase kinase 2 (PDK2) ameliorates these metabolic abnormalities. Wild-type mice fed a high-fat diet exhibited hepatic steatosis, insulin resistance, and increased levels of pyruvate, TCA cycle intermediates, and malonyl-CoA but reduced ketogenesis and PDC activity due to PDK2 induction. Hepatic PDC activation by PDK2 inhibition attenuated hepatic steatosis, improved hepatic insulin sensitivity, reduced hepatic glucose production, increased capacity for β-oxidation and ketogenesis, and decreased the capacity for lipogenesis. These results were attributed to altered enzymatic capacities and a reduction in TCA anaplerosis that limited the availability of oxaloacetate for the TCA cycle, which promoted ketogenesis. The current study reports that increasing hepatic PDC activity by inhibition of PDK2 ameliorates hepatic steatosis and insulin sensitivity by regulating TCA cycle anaplerosis and ketogenesis. The findings suggest PDK2 is a potential therapeutic target for nonalcoholic fatty liver disease.

  17. Metabolomics approach to assessing plasma 13- and 9-hydroxy-octadecadienoic acid and linoleic acid metabolite responses to 75-km cycling.

    PubMed

    Nieman, David C; Shanely, R Andrew; Luo, Beibei; Meaney, Mary Pat; Dew, Dustin A; Pappan, Kirk L

    2014-07-01

    Bioactive oxidized linoleic acid metabolites (OXLAMs) include 13- and 9-hydroxy-octadecadienoic acid (13-HODE + 9-HODE) and have been linked to oxidative stress, inflammation, and numerous pathological and physiological states. The purpose of this study was to measure changes in plasma 13-HODE + 9-HODE following a 75-km cycling bout and identify potential linkages to linoleate metabolism and established biomarkers of oxidative stress (F2-isoprostanes) and inflammation (cytokines) using a metabolomics approach. Trained male cyclists (N = 19, age 38.0 ± 1.6 yr, wattsmax 304 ± 10.5) engaged in a 75-km cycling time trial on their own bicycles using electromagnetically braked cycling ergometers (2.71 ± 0.07 h). Blood samples were collected preexercise, immediately post-, 1.5 h post-, and 21 h postexercise, and analyzed for plasma cytokines (IL-6, IL-8, IL-10, tumor necrosis factor-α, monocyte chemoattractant protein-1, granulocyte colony-stimulating factor), F2-isoprostanes, and shifts in metabolites using global metabolomics procedures with gas chromatography mass spectrometry (GC-MS) and liquid chromatography mass spectrometry (LC-MS). 13-HODE + 9-HODE increased 3.1-fold and 1.7-fold immediately post- and 1.5 h postexercise (both P < 0.001) and returned to preexercise levels by 21-h postexercise. Post-75-km cycling plasma levels of 13-HODE + 9-HODE were not significantly correlated with increases in plasma cytokines but were positively correlated with postexercise F2-isoprostanes (r = 0.75, P < 0.001), linoleate (r = 0.54, P = 0.016), arachidate (r = 0.77, P < 0.001), 12,13-dihydroxy-9Z-octadecenoate (12,13-DiHOME) (r = 0.60, P = 0.006), dihomo-linolenate (r = 0.57, P = 0.011), and adrenate (r = 0.56, P = 0.013). These findings indicate that prolonged and intensive exercise caused a transient, 3.1-fold increase in the stable linoleic acid oxidation product 13-HODE + 9-HODE and was related to increases in F2-isoprostanes, linoleate, and fatty acids in the linoleate

  18. Photosynthesis in Rhodospirillum rubrum. III. Metabolic Control of Reductive Pentose Phosphate and Tricarboxylic Acid Cycle Enzymes 1

    PubMed Central

    Anderson, Louise; Fuller, R. C.

    1967-01-01

    Enzymes of the reductive pentose phosphate cycle including ribulose-diphosphate carboxylase, ribulose-5-phosphate kinase, ribose-5-phosphate isomerase, aldolase, glyceraldehyde-3-phosphate dehydrogenase and alkaline fructose-1,6-diphos-phatase were shown to be present in autotrophically grown Rhodospirillum rubrum. Enzyme levels were measured in this organism grown photo- and dark heterotrophically as well. Several, but not all, of these enzymes appeared to be under metabolic control, mediated by exogenous carbon and nitrogen compounds. Light had no effect on the presence or levels of any of these enzymes in this photosynthetic bacterium. The enzymes of the tricarboxylic acid cycle and enolase were shown to be present in R. rubrum cultured aerobically, autotrophically, or photoheterotrophically, both in cultures evolving hydrogen and under conditions where hydrogen evolution is not observed. Light had no clearly demonstrable effect on the presence or levels of any of these enzymes. PMID:6042359

  19. ENERGY EFFICIENCY LIMITS FOR A RECUPERATIVE BAYONET SULFURIC ACID DECOMPOSITION REACTOR FOR SULFUR CYCLE THERMOCHEMICAL HYDROGEN PRODUCTION

    SciTech Connect

    Gorensek, M.; Edwards, T.

    2009-06-11

    A recuperative bayonet reactor design for the high-temperature sulfuric acid decomposition step in sulfur-based thermochemical hydrogen cycles was evaluated using pinch analysis in conjunction with statistical methods. The objective was to establish the minimum energy requirement. Taking hydrogen production via alkaline electrolysis with nuclear power as the benchmark, the acid decomposition step can consume no more than 450 kJ/mol SO{sub 2} for sulfur cycles to be competitive. The lowest value of the minimum heating target, 320.9 kJ/mol SO{sub 2}, was found at the highest pressure (90 bar) and peak process temperature (900 C) considered, and at a feed concentration of 42.5 mol% H{sub 2}SO{sub 4}. This should be low enough for a practical water-splitting process, even including the additional energy required to concentrate the acid feed. Lower temperatures consistently gave higher minimum heating targets. The lowest peak process temperature that could meet the 450-kJ/mol SO{sub 2} benchmark was 750 C. If the decomposition reactor were to be heated indirectly by an advanced gas-cooled reactor heat source (50 C temperature difference between primary and secondary coolants, 25 C minimum temperature difference between the secondary coolant and the process), then sulfur cycles using this concept could be competitive with alkaline electrolysis provided the primary heat source temperature is at least 825 C. The bayonet design will not be practical if the (primary heat source) reactor outlet temperature is below 825 C.

  20. Partial Life-Cycle and Acute Toxicity of Perfluoroalkyl Acids to Freshwater Mussels

    EPA Science Inventory

    Freshwater mussels are among the most sensitive aquatic organisms to many contaminants and have complex life-cycles that include several distinct life stages with unique contaminant exposure pathways. Standard acute (24–96 h) and chronic (28 d) toxicity tests with free larva (glo...

  1. Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae.

    PubMed

    van Rossum, Harmen M; Kozak, Barbara U; Niemeijer, Matthijs S; Duine, Hendrik J; Luttik, Marijke A H; Boer, Viktor M; Kötter, Peter; Daran, Jean-Marc G; van Maris, Antonius J A; Pronk, Jack T

    2016-05-01

    Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction.

  2. Alternative reactions at the interface of glycolysis and citric acid cycle in Saccharomyces cerevisiae.

    PubMed

    van Rossum, Harmen M; Kozak, Barbara U; Niemeijer, Matthijs S; Duine, Hendrik J; Luttik, Marijke A H; Boer, Viktor M; Kötter, Peter; Daran, Jean-Marc G; van Maris, Antonius J A; Pronk, Jack T

    2016-05-01

    Pyruvate and acetyl-coenzyme A, located at the interface between glycolysis and TCA cycle, are important intermediates in yeast metabolism and key precursors for industrially relevant products. Rational engineering of their supply requires knowledge of compensatory reactions that replace predominant pathways when these are inactivated. This study investigates effects of individual and combined mutations that inactivate the mitochondrial pyruvate-dehydrogenase (PDH) complex, extramitochondrial citrate synthase (Cit2) and mitochondrial CoA-transferase (Ach1) in Saccharomyces cerevisiae. Additionally, strains with a constitutively expressed carnitine shuttle were constructed and analyzed. A predominant role of the PDH complex in linking glycolysis and TCA cycle in glucose-grown batch cultures could be functionally replaced by the combined activity of the cytosolic PDH bypass and Cit2. Strongly impaired growth and a high incidence of respiratory deficiency in pda1Δ ach1Δ strains showed that synthesis of intramitochondrial acetyl-CoA as a metabolic precursor requires activity of either the PDH complex or Ach1. Constitutive overexpression of AGP2, HNM1, YAT2, YAT1, CRC1 and CAT2 enabled the carnitine shuttle to efficiently link glycolysis and TCA cycle in l-carnitine-supplemented, glucose-grown batch cultures. Strains in which all known reactions at the glycolysis-TCA cycle interface were inactivated still grew slowly on glucose, indicating additional flexibility at this key metabolic junction. PMID:26895788

  3. Recent new additives for electric vehicle lead-acid batteries for extending the cycle life and capacity

    SciTech Connect

    Kozawa, A.; Sato, A.; Fujita, K.; Brodd, D.

    1997-12-01

    An electrochemically prepared colloidal graphite was found to be an excellent additive for lead-acid batteries. The new additive extends the capacity and cycle life of new and old batteries and can regenerate old, almost dead, batteries. The colloidal graphite is stable in aqueous solution and the extremely fine particles are adsorbed mainly on the positive electrode. This additive has been given the name, {alpha}-Pholon. The amount required is very small: only 6% to 10% of volume of the {alpha}-Pholon solution (about 2% colloidal graphite in water solution). The beneficial effect of the new additive was demonstrated with motorcycle batteries and forklift batteries.

  4. Studies on the increase in serum concentrations of urea cycle amino acids among subjects exposed to cadmium

    SciTech Connect

    Nishino, H.; Shiroishi, K. ); Kagamimori, S.; Naruse, Y. ); Watanabe, M. )

    1988-05-01

    Itai-itai disease (I disease) is a combination of renal tubular damage and osteomalacia accompanied by osteoporosis among subjects exposed to cadmium (Cd). When the renal tubular damage progresses, the excretion of amino acids, especially, threonine, hydroxyproline, proline, citrulline, ornithine, arginine, etc. increase in urine. It was reported that the increase in urinary excretion of citrulline, arginine and ornithine may be associated with an inhibition of urea synthesis in the urea cycle. The authors have found that serum citrulline, arginine and ornithine also increased in I disease patients. In order to investigate the mechanism of the increase in these serum amino acids, comparative studies were performed using both healthy subjects and patients with renal disease as control groups.

  5. Redox cycles of vitamin E: Hydrolysis and ascorbic acid dependent reduction of 8a-(alkyldioxy)tocopherones

    SciTech Connect

    Liebler, D.C.; Kaysen, K.L.; Kennedy, T.A. )

    1989-12-12

    Oxidation of the biological antioxidant {alpha}-tocopherol (vitamin E; TH) by peroxyl radicals yields 8a-(alkyldioxy)tocopherones, which either may hydrolyze to {alpha}-tocopheryl quinone (TQ) or may be reduced by ascorbic acid to regenerate TH. To define the chemistry of this putative two-electron TH redox cycle, we studied the hydrolysis and reduction of 8a-((2,4-dimethyl-1-nitrilopent-2-yl)dioxyl)tocopherone (1) in acetonitrile/buffer mixtures and in phospholipid liposomes. TQ formation in acetonitrile/buffer mixtures, which was monitored spectrophotometrically, declined with increasing pH and could not be detected above pH 4. The rate of TQ formation from 1 first increased with time and then decreased in a first-order terminal phase. Rearrangement of 8a-hydroxy-{alpha}-tocopherone (2) to TQ displayed first-order kinetics identical with the terminal phase for TQ formation from 1. Both rate constants increased with decreasing pH. Hydrolysis of 1 in acetonitrile/H{sub 2}{sup 18}O yielded ({sup 18}O)TQ. These observations suggest that 1 loses the 8a-(alkyldioxy) moiety to produce the tocopherone cation (T{sup +}), which hydrolyzes to 2, the TQ-forming intermediate. Incubation of either 1 or 2 with ascorbic acid in acetonitrile/buffer yielded TH. Reduction of both 1 and 2 decreased with increasing pH. In phosphatidylcholine liposomes at pH 7, approximately 10% of the T{sup +} generated from 1 was reduced to TH by 5 mM ascorbic acid. The results collectively demonstrate that T{sup +} is the ascorbic acid reducible intermediate in a two-electron TH redox cycle, a process that probably would require biocatalysis to proceed in biological membranes.

  6. Identification of transport pathways for citric acid cycle intermediates in the human colon carcinoma cell line, Caco-2.

    PubMed

    Weerachayaphorn, Jittima; Pajor, Ana M

    2008-04-01

    Citric acid cycle intermediates are absorbed from the gastrointestinal tract through carrier-mediated mechanisms, although the transport pathways have not been clearly identified. This study examines the transport of citric acid cycle intermediates in the Caco-2 human colon carcinoma cell line, often used as a model of small intestine. Inulin was used as an extracellular volume marker instead of mannitol since the apparent volume measured with mannitol changed with time. The results show that Caco-2 cells contain at least three distinct transporters, including the Na+-dependent di- and tricarboxylate transporters, NaDC1 and NaCT, and one or more sodium-independent pathways, possibly involving organic anion transporters. Succinate transport is mediated mostly by Na+-dependent pathways, predominantly by NaDC1, but with some contribution by NaCT. RT-PCR and functional characteristics verified the expression of these transporters in Caco-2 cells. In contrast, citrate transport in Caco-2 cells occurs by a combination of Na+-independent pathways, possibly mediated by an organic anion transporter, and Na+-dependent mechanisms. The non-metabolizable dicarboxylate, methylsuccinate, is also transported by a combination of Na+-dependent and -independent pathways. In conclusion, we find that multiple pathways are involved in the transport of di- and tricarboxylates by Caco-2 cells. Since many of these pathways are not found in human intestine, this model may be best suited for studying Na+-dependent transport of succinate by NaDC1.

  7. Fatty acid and phospholipid syntheses are prerequisites for the cell cycle of Symbiodinium and their endosymbiosis within sea anemones.

    PubMed

    Wang, Li-Hsueh; Lee, Hsieh-He; Fang, Lee-Shing; Mayfield, Anderson B; Chen, Chii-Shiarng

    2013-01-01

    Lipids are a source of metabolic energy, as well as essential components of cellular membranes. Although they have been shown to be key players in the regulation of cell proliferation in various eukaryotes, including microalgae, their role in the cell cycle of cnidarian-dinoflagellate (genus Symbiodinium) endosymbioses remains to be elucidated. The present study examined the effects of a lipid synthesis inhibitor, cerulenin, on the cell cycle of both cultured Symbiodinium (clade B) and those engaged in an endosymbiotic association with the sea anemone Aiptasia pulchella. In the former, cerulenin exposure was found to inhibit free fatty acid (FFA) synthesis, as it does in other organisms. Additionally, while it also significantly inhibited the synthesis of phosphatidylethanolamine (PE), it did not affect the production of sterol ester (SE) or phosphatidylcholine (PC). Interestingly, cerulenin also significantly retarded cell division by arresting the cell cycles at the G0/G1 phase. Cerulenin-treated Symbiodinium were found to be taken up by anemone hosts at a significantly depressed quantity in comparison with control Symbiodinium. Furthermore, the uptake of cerulenin-treated Symbiodinium in host tentacles occurred much more slowly than in untreated controls. These results indicate that FFA and PE may play critical roles in the recognition, proliferation, and ultimately the success of endosymbiosis with anemones. PMID:24009685

  8. Fatty Acid and Phospholipid Syntheses Are Prerequisites for the Cell Cycle of Symbiodinium and Their Endosymbiosis within Sea Anemones

    PubMed Central

    Wang, Li-Hsueh; Lee, Hsieh-He; Fang, Lee-Shing; Mayfield, Anderson B.; Chen, Chii-Shiarng

    2013-01-01

    Lipids are a source of metabolic energy, as well as essential components of cellular membranes. Although they have been shown to be key players in the regulation of cell proliferation in various eukaryotes, including microalgae, their role in the cell cycle of cnidarian-dinoflagellate (genus Symbiodinium) endosymbioses remains to be elucidated. The present study examined the effects of a lipid synthesis inhibitor, cerulenin, on the cell cycle of both cultured Symbiodinium (clade B) and those engaged in an endosymbiotic association with the sea anemone Aiptasia pulchella. In the former, cerulenin exposure was found to inhibit free fatty acid (FFA) synthesis, as it does in other organisms. Additionally, while it also significantly inhibited the synthesis of phosphatidylethanolamine (PE), it did not affect the production of sterol ester (SE) or phosphatidylcholine (PC). Interestingly, cerulenin also significantly retarded cell division by arresting the cell cycles at the G0/G1 phase. Cerulenin-treated Symbiodinium were found to be taken up by anemone hosts at a significantly depressed quantity in comparison with control Symbiodinium. Furthermore, the uptake of cerulenin-treated Symbiodinium in host tentacles occurred much more slowly than in untreated controls. These results indicate that FFA and PE may play critical roles in the recognition, proliferation, and ultimately the success of endosymbiosis with anemones. PMID:24009685

  9. Diel cycles of arsenic speciation due to photooxidation in acid mine drainage from the Iberian Pyrite Belt (Sw Spain).

    PubMed

    Sarmiento, Aguasanta M; Oliveira, Vanessa; Gómez-Ariza, José Luis; Nieto, José Miguel; Sánchez-Rodas, Daniel

    2007-01-01

    Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems. PMID:16963107

  10. Polymorphisms in Genes of Tricarboxylic Acid Cycle Key Enzymes Are Associated with Early Recurrence of Hepatocellular Carcinoma.

    PubMed

    Wan, Shaogui; Wu, Yousheng; Zhou, Xingchun; Chen, Yibing; An, Jiaze; Yu, Xiaohe; Zhang, Huiqing; Yang, Hushan; Xing, Jinliang

    2015-01-01

    Alterations of activity and expression in tricarboxylic acid (TCA) cycle key enzymes have been indicated in several malignancies, including hepatocellular carcinoma (HCC). They play an important role in the progression of cancer. However, the impact of single nucleotide polymorphisms (SNPs) in genes encoding these key enzymes on the recurrence of HCC has not been investigated. In this study, we genotyped 17 SNPs in genes encoding TCA cycle key enzymes and analyzed their association with recurrence-free survival (RFS) in a cohort of 492 Chinese HCC patients by Cox proportional hazard model and survival tree analysis. We identified 7 SNPs in SDHC, SDHD, FH, and IDH2 genes to be significantly associated with the RFS of HCC patients. Moreover, all these SNPs were associated with the early recurrence (within 2 years after surgery) risk of diseases. Cumulative effect analysis showed that these SNPs exhibited a dose-dependent effect on the overall and early recurrence. Further stratified analysis suggested that number of risk genotypes modified the protective effect on HCC recurrence conferred by transcatheter arterial chemoembolization treatment. Finally, the survival tree analysis revealed that SNP rs10789859 in SDHD gene was the primary factor contributing to HCC recurrence in our population. To the best of our knowledge, we for the first time observed the association between SNPs in genes encoding TCA cycle key enzymes and HCC recurrence risk. Further observational and functional studies are needed to validate our findings and generalize its clinical usage. PMID:25894340

  11. USE OF THE COMPOSITION AND STABLE CARBONIISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (*13C) of individual microbial phospholipid fatty acids (PLFAs) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SOM) cy...

  12. Gluconeogenesis is associated with high rates of tricarboxylic acid and pyruvate cycling in fasting northern elephant seals.

    PubMed

    Champagne, Cory D; Houser, Dorian S; Fowler, Melinda A; Costa, Daniel P; Crocker, Daniel E

    2012-08-01

    Animals that endure prolonged periods of food deprivation preserve vital organ function by sparing protein from catabolism. Much of this protein sparing is achieved by reducing metabolic rate and suppressing gluconeogenesis while fasting. Northern elephant seals (Mirounga angustirostris) endure prolonged fasts of up to 3 mo at multiple life stages. During these fasts, elephant seals maintain high levels of activity and energy expenditure associated with breeding, reproduction, lactation, and development while maintaining rates of glucose production typical of a postabsorptive mammal. Therefore, we investigated how fasting elephant seals meet the requirements of glucose-dependent tissues while suppressing protein catabolism by measuring the contribution of glycogenolysis, glycerol, and phosphoenolpyruvate (PEP) to endogenous glucose production (EGP) during their natural 2-mo postweaning fast. Additionally, pathway flux rates associated with the tricarboxylic acid (TCA) cycle were measured specifically, flux through phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate cycling. The rate of glucose production decreased during the fast (F(1,13) = 5.7, P = 0.04) but remained similar to that of postabsorptive mammals. The fractional contributions of glycogen, glycerol, and PEP did not change with fasting; PEP was the primary gluconeogenic precursor and accounted for ∼95% of EGP. This large contribution of PEP to glucose production occurred without substantial protein loss. Fluxes through the TCA cycle, PEPCK, and pyruvate cycling were higher than reported in other species and were the most energetically costly component of hepatic carbohydrate metabolism. The active pyruvate recycling fluxes detected in elephant seals may serve to rectify gluconeogeneic PEP production during restricted anaplerotic inflow in these fasting-adapted animals.

  13. Novel Metabolic Abnormalities in the Tricarboxylic Acid Cycle in Peripheral Cells From Huntington’s Disease Patients

    PubMed Central

    Naseri, Nima N.; Bonica, Joseph; Xu, Hui; Park, Larry C.; Arjomand, Jamshid; Chen, Zhengming; Gibson, Gary E.

    2016-01-01

    Metabolic dysfunction is well-documented in Huntington’s disease (HD). However, the link between the mutant huntingtin (mHTT) gene and the pathology is unknown. The tricarboxylic acid (TCA) cycle is the main metabolic pathway for the production of NADH for conversion to ATP via the electron transport chain (ETC). The objective of this study was to test for differences in enzyme activities, mRNAs and protein levels related to the TCA cycle between lymphoblasts from healthy subjects and from patients with HD. The experiments utilize the advantages of lymphoblasts to reveal new insights about HD. The large quantity of homogeneous cell populations permits multiple dynamic measures to be made on exactly comparable tissues. The activities of nine enzymes related to the TCA cycle and the expression of twenty-nine mRNAs encoding for these enzymes and enzyme complexes were measured. Cells were studied under baseline conditions and during metabolic stress. The results support our recent findings that the activities of the pyruvate dehydrogenase complex (PDHC) and succinate dehydrogenase (SDH) are elevated in HD. The data also show a large unexpected depression in MDH activities. Furthermore, message levels for isocitrate dehydrogenase 1 (IDH1) were markedly increased in in HD lymphoblasts and were responsive to treatments. The use of lymphoblasts allowed us to clarify that the reported decrease in aconitase activity in HD autopsy brains is likely due to secondary hypoxic effects. These results demonstrate the mRNA and enzymes of the TCA cycle are critical therapeutic targets that have been understudied in HD. PMID:27611087

  14. Glutamate availability is important in intramuscular amino acid metabolism and TCA cycle intermediates but does not affect peak oxidative metabolism.

    PubMed

    Mourtzakis, M; Graham, T E; González-Alonso, J; Saltin, B

    2008-08-01

    Muscle glutamate is central to reactions producing 2-oxoglutarate, a tricarboxylic acid (TCA) cycle intermediate that essentially expands the TCA cycle intermediate pool during exercise. Paradoxically, muscle glutamate drops approximately 40-80% with the onset of exercise and 2-oxoglutarate declines in early exercise. To investigate the physiological relationship between glutamate, oxidative metabolism, and TCA cycle intermediates (i.e., fumarate, malate, 2-oxoglutarate), healthy subjects trained (T) the quadriceps of one thigh on the single-legged knee extensor ergometer (1 h/day at 70% maximum workload for 5 days/wk), while their contralateral quadriceps remained untrained (UT). After 5 wk of training, peak oxygen consumption (VO2peak) in the T thigh was greater than that in the UT thigh (P<0.05); VO2peak was not different between the T and UT thighs with glutamate infusion. Peak exercise under control conditions revealed a greater glutamate uptake in the T thigh compared with rest (7.3+/-3.7 vs. 1.0+/-0.1 micromol.min(-1).kg wet wt(-1), P<0.05) without increase in TCA cycle intermediates. In the UT thigh, peak exercise (vs. rest) induced an increase in fumarate (0.33+/-0.07 vs. 0.02+/-0.01 mmol/kg dry wt (dw), P<0.05) and malate (2.2+/-0.4 vs. 0.5+/-0.03 mmol/kg dw, P<0.05) and a decrease in 2-oxoglutarate (12.2+/-1.6 vs. 32.4+/-6.8 micromol/kg dw, P<0.05). Overall, glutamate infusion increased arterial glutamate (P<0.05) and maintained this increase. Glutamate infusion coincided with elevated fumarate and malate (P<0.05) and decreased 2-oxoglutarate (P<0.05) at peak exercise relative to rest in the T thigh; there were no further changes in the UT thigh. Although glutamate may have a role in the expansion of the TCA cycle, glutamate and TCA cycle intermediates do not directly affect VO2peak in either trained or untrained muscle.

  15. Effects of acid rain on mycorrhizal infection and N cycling in forest soils

    SciTech Connect

    Stroo, H.F.

    1986-01-01

    Increasing the acidity of simulated rain from pH 5.6 to 3.0 reduced the number of mycorrhizal roots on white pine seedlings by 20% after 16 weeks of exposure. Mycorrhizal infection of red oaks was 25% less at a rain pH of 3.5 than at pH 5.6. Simulated acid rain also caused increases in the N contents, net photosynthesis, and growth of seedlings, as well as decreases in root:shoot ratios and in the concentration of sucrose in the roots. To measure the effects of acid rain on N mineralization, nitrification, and total inorganic N, columns containing samples from the surface horizons of 12 forest soils were exposed to simulated rain at 3 times ambient deposition rates for 16 weeks. The effects on N mineralization varied between soils, with the greatest inhibitions being observed in soils with low organic matter contents. The apparent protection by organic matter was associated with an increase in short-term buffering capacity. The average amount of N mineralized after exposure was not significantly affected by rain pH. Similarly, nitrification was inhibited during exposure to simulated rain at pH 3.5, but was unaffected after exposure. Enrichments from an acid forest soil failed to show the presence of autotrophic nitrifiers, and the effects of temperature and selective inhibitors indicated that fungi were primarily responsible for nitrification in this soil. A fungus capable of heterotrophic nitrification at pH 4.0 was isolated and identified as Absidia cylindrospora Hagem.

  16. Tricarboxylic acid cycle-sustained oxidative phosphorylation in isolated myelin vesicles.

    PubMed

    Ravera, Silvia; Bartolucci, Martina; Calzia, Daniela; Aluigi, Maria Grazia; Ramoino, Paola; Morelli, Alessandro; Panfoli, Isabella

    2013-11-01

    The Central Nervous System (CNS) function was shown to be fueled exclusively by oxidative phosphorylation (OXPHOS). This is in line with the sensitivity of brain to hypoxia, but less with the scarcity of the mitochondria in CNS. Consistently with the ectopic expression of FoF1-ATP synthase and the electron transfer chain in myelin, we have reported data demonstrating that isolated myelin vesicles (IMV) conduct OXPHOS. It may suggest that myelin sheath could be a site for the whole aerobic degradation of glucose. In this paper, we assayed the functionality of glycolysis and of TCA cycle enzymes in IMV purified from bovine forebrain. We found the presence and activity of all of the glycolytic and TCA cycle enzymes, comparable to those in mitochondria-enriched fractions, in the same experimental conditions. IMV also contain consistent carbonic anhydrase activity. These data suggest that myelin may be a contributor in energy supply for the axon, performing an extra-mitochondrial aerobic OXPHOS. The vision of myelin as the site of aerobic metabolism may shed a new light on many demyelinating pathologies, that cause an a yet unresolved axonal degeneration and whose clinical onset coincides with myelin development completion.

  17. Lactic Acid Bacteria in Durum Wheat Flour Are Endophytic Components of the Plant during Its Entire Life Cycle

    PubMed Central

    Minervini, Fabio; Celano, Giuseppe; Lattanzi, Anna; Tedone, Luigi; De Mastro, Giuseppe; De Angelis, Maria

    2015-01-01

    This study aimed at assessing the dynamics of lactic acid bacteria and other Firmicutes associated with durum wheat organs and processed products. 16S rRNA gene-based high-throughput sequencing showed that Lactobacillus, Streptococcus, Enterococcus, and Lactococcus were the main epiphytic and endophytic genera among lactic acid bacteria. Bacillus, Exiguobacterium, Paenibacillus, and Staphylococcus completed the picture of the core genus microbiome. The relative abundance of each lactic acid bacterium genus was affected by cultivars, phenological stages, other Firmicutes genera, environmental temperature, and water activity (aw) of plant organs. Lactobacilli, showing the highest sensitivity to aw, markedly decreased during milk development (Odisseo) and physiological maturity (Saragolla). At these stages, Lactobacillus was mainly replaced by Streptococcus, Lactococcus, and Enterococcus. However, a key sourdough species, Lactobacillus plantarum, was associated with plant organs during the life cycle of Odisseo and Saragolla wheat. The composition of the sourdough microbiota and the overall quality of leavened baked goods are also determined throughout the phenological stages of wheat cultivation, with variations depending on environmental and agronomic factors. PMID:26187970

  18. Submolecular regulation of cell transformation by deuterium depleting water exchange reactions in the tricarboxylic acid substrate cycle.

    PubMed

    Boros, László G; D'Agostino, Dominic P; Katz, Howard E; Roth, Justine P; Meuillet, Emmanuelle J; Somlyai, Gábor

    2016-02-01

    The naturally occurring isotope of hydrogen ((1)H), deuterium ((2)H), could have an important biological role. Deuterium depleted water delays tumor progression in mice, dogs, cats and humans. Hydratase enzymes of the tricarboxylic acid (TCA) cycle control cell growth and deplete deuterium from redox cofactors, fatty acids and DNA, which undergo hydride ion and hydrogen atom transfer reactions. A model is proposed that emphasizes the terminal complex of mitochondrial electron transport chain reducing molecular oxygen to deuterium depleted water (DDW); this affects gluconeogenesis as well as fatty acid oxidation. In the former, the DDW is thought to diminish the deuteration of sugar-phosphates in the DNA backbone, helping to preserve stability of hydrogen bond networks, possibly protecting against aneuploidy and resisting strand breaks, occurring upon exposure to radiation and certain anticancer chemotherapeutics. DDW is proposed here to link cancer prevention and treatment using natural ketogenic diets, low deuterium drinking water, as well as DDW production as the mitochondrial downstream mechanism of targeted anti-cancer drugs such as Avastin and Glivec. The role of (2)H in biology is a potential missing link to the elusive cancer puzzle seemingly correlated with cancer epidemiology in western populations as a result of excessive (2)H loading from processed carbohydrate intake in place of natural fat consumption.

  19. Measurement of the water cycle in mixed ammonium acid sulfate particles

    NASA Astrophysics Data System (ADS)

    Spann, J. F.; Richardson, C. B.

    A single ammonium-hydrogen-sulfate particle is levitated in an evacuated quadrupole trap at room temperature and the temperature of an attached tube containing bulk water is slowly cycled introducing then removing water vapor. With increasing pressure the particle dissolves in stages, then grows as a solution droplet by water absorption. With decreasing pressure the droplet supersaturates, crystallizes, then dehydrates completely to return to its initial state. Particle mass, and thus composition, is measured continuously with an electrostatic balance. Twenty-six cycles were studied as solute composition ranged from ammonium bisulfate through letovicite to ammonium sulfate in roughly equal steps. Composition was changed in situ by reaction with ammonia at low partial pressure. With solute composition characterized by x = [NH 4]/[SO 4], deliquescence was found to occur at water activity aw = 0.394-0.029 ( x- 1) for 1 ⩽ x < 1.5 and aw = 0.710-0.023( x-1.5) for 1.5 ⩽ x < 2. Particle growth occurs at deliquescence and subsequently is in excellent agreement with that predicted in a model proposed by Tang for dissolution of a two-component mixed solute. Water activities of the solution droplets are measured up to aw = 0.9. The results are compared with those predicted by the Zdanovskii-Stokes-Robinson method of interpolation from binary data and with those obtained using the mixing rule of Meissner and Kusik. Particle crystallization from supersaturated solution is analyzed thermodynamically using measured water activities, the Gibbs-Duhem equation, and classical nucleation theory. The specific free energy barrier to crystallization, ΔG/ n, is found to increase from near zero to 0.04 eV as composition ranges from x = 1 to 2, where n is the number of formula units in the critical nucleus. New phase diagrams are presented and used to discuss the dynamics of mixed sulfate particles in the atmosphere.

  20. Pathways of acid mine drainage to Clear Lake: implications for mercury cycling.

    PubMed

    Shipp, William G; Zierenberg, Robert A

    2008-12-01

    Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (> or =197 mmol/L), aluminum (> or =52 mmol/L), and iron (> or =28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sulfide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg+2, making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 per thousand) and highly depleted isotope values for diagenetic pyrite (as low as -22.6 per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake

  1. Pathways of acid mine drainage to Clear Lake: implications for mercury cycling.

    PubMed

    Shipp, William G; Zierenberg, Robert A

    2008-12-01

    Pore fluids from Clear Lake sediments collected near the abandoned Sulphur Bank Mercury Mine have low pH (locally <4) and elevated sulfate (> or =197 mmol/L), aluminum (> or =52 mmol/L), and iron (> or =28 mmol/L) contents derived from oxidation of sulfide minerals at the mine site. Acid mine drainage (AMD) is entering Clear Lake by advective subsurface flow nearest the mine and by diffusion at greater distances. Oxygen and hydrogen isotope ratios, combined with pore fluid compositions, constrain the sources and pathways of contaminated fluids. Sediment cores taken nearest the mine have the highest concentrations of dissolved sulfate, aluminum, and iron, which are contributed by direct subsurface flow of AMD from sulfide-bearing waste rock. Sediment cores as far as 100 m west of the Clear Lake shoreline show the presence of AMD that originated in the acidic lake that occupies the abandoned Herman Pit at the mine site. High sulfate content in the AMD has the potential to promote the activity of sulfate-reducing bacteria in the organic-rich lake sediments, which leads to methylation of Hg+2, making it both more toxic and bioavailable. Quantitative depletion of pore water sulfate at depth and sulfur isotope values of diagenetic pyrite near 0 per thousand indicate that sulfate availability limits the extent of sulfate reduction in the lake sediments away from the mine. Profiles of pore water sulfate in the sediments near the mine show that excess sulfate is available to support the activity of sulfate-reducing bacteria near the mine site. Enriched isotope values of dissolved sulfate (as high as 17.1 per thousand) and highly depleted isotope values for diagenetic pyrite (as low as -22.6 per thousand) indicate active bacterial sulfate reduction in the AMD-contaminated sediments. Sulfate- and iron-rich acid mine drainage entering Clear Lake by shallow subsurface flow likely needs to be controlled in order to lower the environmental impacts of Hg in the Clear Lake

  2. Global transcription analysis of Krebs tricarboxylic acid cycle mutants reveals an alternating pattern of gene expression and effects on hypoxic and oxidative genes.

    PubMed

    McCammon, Mark T; Epstein, Charles B; Przybyla-Zawislak, Beata; McAlister-Henn, Lee; Butow, Ronald A

    2003-03-01

    To understand the many roles of the Krebs tricarboxylic acid (TCA) cycle in cell function, we used DNA microarrays to examine gene expression in response to TCA cycle dysfunction. mRNA was analyzed from yeast strains harboring defects in each of 15 genes that encode subunits of the eight TCA cycle enzymes. The expression of >400 genes changed at least threefold in response to TCA cycle dysfunction. Many genes displayed a common response to TCA cycle dysfunction indicative of a shift away from oxidative metabolism. Another set of genes displayed a pairwise, alternating pattern of expression in response to contiguous TCA cycle enzyme defects: expression was elevated in aconitase and isocitrate dehydrogenase mutants, diminished in alpha-ketoglutarate dehydrogenase and succinyl-CoA ligase mutants, elevated again in succinate dehydrogenase and fumarase mutants, and diminished again in malate dehydrogenase and citrate synthase mutants. This pattern correlated with previously defined TCA cycle growth-enhancing mutations and suggested a novel metabolic signaling pathway monitoring TCA cycle function. Expression of hypoxic/anaerobic genes was elevated in alpha-ketoglutarate dehydrogenase mutants, whereas expression of oxidative genes was diminished, consistent with a heme signaling defect caused by inadequate levels of the heme precursor, succinyl-CoA. These studies have revealed extensive responses to changes in TCA cycle function and have uncovered new and unexpected metabolic networks that are wired into the TCA cycle.

  3. Microbial contributions to coupled arsenic and sulfur cycling in the acid-sulfide hot spring Champagne Pool, New Zealand.

    PubMed

    Hug, Katrin; Maher, William A; Stott, Matthew B; Krikowa, Frank; Foster, Simon; Moreau, John W

    2014-01-01

    Acid-sulfide hot springs are analogs of early Earth geothermal systems where microbial metal(loid) resistance likely first evolved. Arsenic is a metalloid enriched in the acid-sulfide hot spring Champagne Pool (Waiotapu, New Zealand). Arsenic speciation in Champagne Pool follows reaction paths not yet fully understood with respect to biotic contributions and coupling to biogeochemical sulfur cycling. Here we present quantitative arsenic speciation from Champagne Pool, finding arsenite dominant in the pool, rim and outflow channel (55-75% total arsenic), and dithio- and trithioarsenates ubiquitously present as 18-25% total arsenic. In the outflow channel, dimethylmonothioarsenate comprised ≤9% total arsenic, while on the outflow terrace thioarsenates were present at 55% total arsenic. We also quantified sulfide, thiosulfate, sulfate and elemental sulfur, finding sulfide and sulfate as major species in the pool and outflow terrace, respectively. Elemental sulfur concentration reached a maximum at the terrace. Phylogenetic analysis of 16S rRNA genes from metagenomic sequencing revealed the dominance of Sulfurihydrogenibium at all sites and an increased archaeal population at the rim and outflow channel. Several phylotypes were found closely related to known sulfur- and sulfide-oxidizers, as well as sulfur- and sulfate-reducers. Bioinformatic analysis revealed genes underpinning sulfur redox transformations, consistent with sulfur speciation data, and illustrating a microbial role in sulfur-dependent transformation of arsenite to thioarsenate. Metagenomic analysis also revealed genes encoding for arsenate reductase at all sites, reflecting the ubiquity of thioarsenate and a need for microbial arsenate resistance despite anoxic conditions. Absence of the arsenite oxidase gene, aio, at all sites suggests prioritization of arsenite detoxification over coupling to energy conservation. Finally, detection of methyl arsenic in the outflow channel, in conjunction with

  4. Microbial contributions to coupled arsenic and sulfur cycling in the acid-sulfide hot spring Champagne Pool, New Zealand

    PubMed Central

    Hug, Katrin; Maher, William A.; Stott, Matthew B.; Krikowa, Frank; Foster, Simon; Moreau, John W.

    2014-01-01

    Acid-sulfide hot springs are analogs of early Earth geothermal systems where microbial metal(loid) resistance likely first evolved. Arsenic is a metalloid enriched in the acid-sulfide hot spring Champagne Pool (Waiotapu, New Zealand). Arsenic speciation in Champagne Pool follows reaction paths not yet fully understood with respect to biotic contributions and coupling to biogeochemical sulfur cycling. Here we present quantitative arsenic speciation from Champagne Pool, finding arsenite dominant in the pool, rim and outflow channel (55–75% total arsenic), and dithio- and trithioarsenates ubiquitously present as 18–25% total arsenic. In the outflow channel, dimethylmonothioarsenate comprised ≤9% total arsenic, while on the outflow terrace thioarsenates were present at 55% total arsenic. We also quantified sulfide, thiosulfate, sulfate and elemental sulfur, finding sulfide and sulfate as major species in the pool and outflow terrace, respectively. Elemental sulfur concentration reached a maximum at the terrace. Phylogenetic analysis of 16S rRNA genes from metagenomic sequencing revealed the dominance of Sulfurihydrogenibium at all sites and an increased archaeal population at the rim and outflow channel. Several phylotypes were found closely related to known sulfur- and sulfide-oxidizers, as well as sulfur- and sulfate-reducers. Bioinformatic analysis revealed genes underpinning sulfur redox transformations, consistent with sulfur speciation data, and illustrating a microbial role in sulfur-dependent transformation of arsenite to thioarsenate. Metagenomic analysis also revealed genes encoding for arsenate reductase at all sites, reflecting the ubiquity of thioarsenate and a need for microbial arsenate resistance despite anoxic conditions. Absence of the arsenite oxidase gene, aio, at all sites suggests prioritization of arsenite detoxification over coupling to energy conservation. Finally, detection of methyl arsenic in the outflow channel, in conjunction with

  5. Microbial contributions to coupled arsenic and sulfur cycling in the acid-sulfide hot spring Champagne Pool, New Zealand.

    PubMed

    Hug, Katrin; Maher, William A; Stott, Matthew B; Krikowa, Frank; Foster, Simon; Moreau, John W

    2014-01-01

    Acid-sulfide hot springs are analogs of early Earth geothermal systems where microbial metal(loid) resistance likely first evolved. Arsenic is a metalloid enriched in the acid-sulfide hot spring Champagne Pool (Waiotapu, New Zealand). Arsenic speciation in Champagne Pool follows reaction paths not yet fully understood with respect to biotic contributions and coupling to biogeochemical sulfur cycling. Here we present quantitative arsenic speciation from Champagne Pool, finding arsenite dominant in the pool, rim and outflow channel (55-75% total arsenic), and dithio- and trithioarsenates ubiquitously present as 18-25% total arsenic. In the outflow channel, dimethylmonothioarsenate comprised ≤9% total arsenic, while on the outflow terrace thioarsenates were present at 55% total arsenic. We also quantified sulfide, thiosulfate, sulfate and elemental sulfur, finding sulfide and sulfate as major species in the pool and outflow terrace, respectively. Elemental sulfur concentration reached a maximum at the terrace. Phylogenetic analysis of 16S rRNA genes from metagenomic sequencing revealed the dominance of Sulfurihydrogenibium at all sites and an increased archaeal population at the rim and outflow channel. Several phylotypes were found closely related to known sulfur- and sulfide-oxidizers, as well as sulfur- and sulfate-reducers. Bioinformatic analysis revealed genes underpinning sulfur redox transformations, consistent with sulfur speciation data, and illustrating a microbial role in sulfur-dependent transformation of arsenite to thioarsenate. Metagenomic analysis also revealed genes encoding for arsenate reductase at all sites, reflecting the ubiquity of thioarsenate and a need for microbial arsenate resistance despite anoxic conditions. Absence of the arsenite oxidase gene, aio, at all sites suggests prioritization of arsenite detoxification over coupling to energy conservation. Finally, detection of methyl arsenic in the outflow channel, in conjunction with

  6. L-Malate dehydrogenase activity in the reductive arm of the incomplete citric acid cycle of Nitrosomonas europaea.

    PubMed

    Deutch, Charles E

    2013-11-01

    The autotrophic nitrifying bacterium Nitrosomonas europaea does not synthesize 2-oxoglutarate (α-ketoglutarate) dehydrogenase under aerobic conditions and so has an incomplete citric acid cycle. L-malate (S-malate) dehydrogenase (MDH) from N. europaea was predicted to show similarity to the NADP(+)-dependent enzymes from chloroplasts and was separated from the NAD(+)-dependent proteins from most other bacteria or mitochondria. MDH activity in a soluble fraction from N. europaea ATCC 19718 was measured spectrophotometrically and exhibited simple Michaelis-Menten kinetics. In the reductive direction, activity with NADH increased from pH 6.0 to 8.5 but activity with NADPH was consistently lower and decreased with pH. At pH 7.0, the K m for oxaloacetate was 20 μM; the K m for NADH was 22 μM but that for NADPH was at least 10 times higher. In the oxidative direction, activity with NAD(+) increased with pH but there was very little activity with NADP(+). At pH 7.0, the K m for L-malate was 5 mM and the K m for NAD(+) was 24 μM. The reductive activity was quite insensitive to inhibition by L-malate but the oxidative activity was very sensitive to oxaloacetate. MDH activity was not strongly activated or inhibited by glycolytic or citric acid cycle metabolites, adenine nucleotides, NaCl concentrations, or most metal ions, but increased with temperature up to about 55 °C. The reductive activity was consistently 10-20 times higher than the oxidative activity. These results indicate that the L-malate dehydrogenase in N. europaea is similar to other NAD(+)-dependent MDHs (EC 1.1.1.37) but physiologically adapted for its role in a reductive biosynthetic sequence.

  7. IDH1 mutations alter citric acid cycle metabolism and increase dependence on oxidative mitochondrial metabolism.

    PubMed

    Grassian, Alexandra R; Parker, Seth J; Davidson, Shawn M; Divakaruni, Ajit S; Green, Courtney R; Zhang, Xiamei; Slocum, Kelly L; Pu, Minying; Lin, Fallon; Vickers, Chad; Joud-Caldwell, Carol; Chung, Franklin; Yin, Hong; Handly, Erika D; Straub, Christopher; Growney, Joseph D; Vander Heiden, Matthew G; Murphy, Anne N; Pagliarini, Raymond; Metallo, Christian M

    2014-06-15

    Oncogenic mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) occur in several types of cancer, but the metabolic consequences of these genetic changes are not fully understood. In this study, we performed (13)C metabolic flux analysis on a panel of isogenic cell lines containing heterozygous IDH1/2 mutations. We observed that under hypoxic conditions, IDH1-mutant cells exhibited increased oxidative tricarboxylic acid metabolism along with decreased reductive glutamine metabolism, but not IDH2-mutant cells. However, selective inhibition of mutant IDH1 enzyme function could not reverse the defect in reductive carboxylation activity. Furthermore, this metabolic reprogramming increased the sensitivity of IDH1-mutant cells to hypoxia or electron transport chain inhibition in vitro. Lastly, IDH1-mutant cells also grew poorly as subcutaneous xenografts within a hypoxic in vivo microenvironment. Together, our results suggest therapeutic opportunities to exploit the metabolic vulnerabilities specific to IDH1 mutation.

  8. Cycling of iron and trace metals in the sediments of acidic lakes

    SciTech Connect

    Gubala, C.P.

    1988-01-01

    This study focused on four lakes receiving acidic deposition located in the Adirondack Park, New York, U.S.A. The biogeochemistry of sediments and interstitial water along a depth transect in Big Moose, Lake was examined by chemical analysis of sediment and pore water. Solid phases of iron, manganese, aluminum, lead and zinc were quantified, using a sequential chemical extraction process. {sup 210}Pb dating, and equilibrium and diffusion transport modeling were used to assess the degree of post-depositional reprocessing of these metals. The sediment chemistry of Dart Lake, Lake Rondaxe and South Lake, were compared to the sediment processes observed in Big Moose Lake to assess inter-lake variability.

  9. Prolactin messenger ribonucleic acid levels, prolactin synthesis, and radioimmunoassayable prolactin during the estrous cycle in the Golden Syrian hamster

    SciTech Connect

    Massa, J.S. ); Blask, D.E. )

    1990-01-01

    The purpose of this study was to observe the molecular dynamics of pituitary prolactin (PRL) gene expression during the estrous cycle of the Golden Syrian hamster. PRL messenger ribonucleic acid (mRNA) levels, PRL synthesis were measured in the morning on each day of the cycle. We observed that all of these PRL indices declined or did not change from Day 2 to Day 3 of the cycle. From Day 3 to Day 4 however, PRL mRNA levels increased 33-38% and media {sup 3}H-PRL increased 32-42%, while there were no significant changes in pituitary {sup 3}H-PRL, or RIA-PRL in the media or pituitary. From Day 4 to Day 1 (estrus) there was reciprocal change in the levels of {sup 3}H-PRL in the pituitary vs. the media, with the former increasing 37-50% and the latter decreasing 25-32%. Pituitary RIA-PRL did also increased 45-64% from Day 4 to Day 1 while media RIA-PRL did not change. These data are consistent with the following hypothesis: On the morning of proestrus(Day 4) in the hamster, PRL mRNA levels are elevated compared to those on Day 3, signaling an increase in PRL synthesis. This newly synthesized PRL is shunted into a readily releasable pool on the morning of Day 4 (contributing to the afternoon surge of serum PRL), and into a preferentially stored pool by the morning of Day 1.

  10. Metformin and phenformin deplete tricarboxylic acid cycle and glycolytic intermediates during cell transformation and NTPs in cancer stem cells.

    PubMed

    Janzer, Andreas; German, Natalie J; Gonzalez-Herrera, Karina N; Asara, John M; Haigis, Marcia C; Struhl, Kevin

    2014-07-22

    Metformin, a first-line diabetes drug linked to cancer prevention in retrospective clinical analyses, inhibits cellular transformation and selectively kills breast cancer stem cells (CSCs). Although a few metabolic effects of metformin and the related biguanide phenformin have been investigated in established cancer cell lines, the global metabolic impact of biguanides during the process of neoplastic transformation and in CSCs is unknown. Here, we use LC/MS/MS metabolomics (>200 metabolites) to assess metabolic changes induced by metformin and phenformin in an Src-inducible model of cellular transformation and in mammosphere-derived breast CSCs. Although phenformin is the more potent biguanide in both systems, the metabolic profiles of these drugs are remarkably similar, although not identical. During the process of cellular transformation, biguanide treatment prevents the boost in glycolytic intermediates at a specific stage of the pathway and coordinately decreases tricarboxylic acid (TCA) cycle intermediates. In contrast, in breast CSCs, biguanides have a modest effect on glycolytic and TCA cycle intermediates, but they strongly deplete nucleotide triphosphates and may impede nucleotide synthesis. These metabolic profiles are consistent with the idea that biguanides inhibit mitochondrial complex 1, but they indicate that their metabolic effects differ depending on the stage of cellular transformation.

  11. Nitrogen cycling in s subarctic Alaskan watershed: the role of lichens and the potential effects of acid deposition

    SciTech Connect

    Gunther, A.J.

    1987-01-01

    It has been hypothesized that the loss of nitrogen-fixing lichens due to stress from air pollution could have adverse effects upon nitrogen availability, and thus primary productivity, in some ecosystems. There is general agreement, however, that the ecological role of these lichens has not been sufficiently well defined to determine whether they are keystone species. The objectives of this study were: (1) to examine the importance of nitrogen-fixing lichens to the nitrogen cycle in the drainage of Brooks Lake, Alaska, a nitrogen-limited nursery lake for the commercially important sockeye salmon (Oncorhychus nerka); and (2) to investigate the sensitivity of nitrogen fixation by lichens in this ecosystem to acid deposition. Biological nitrogen fixation was found to be the major source of new nitrogen to the Brooks Lake drainage. The rate of fixation is approximately 3 kg N/ha-yr, which compares to 0.3 kg N/ha-yr in precipitation and only 0.02 kg N/ha-yr in returning adult salmon. Cyanophillic lichens contribute about 0.21 kg N/ha-yr. The low levels of nitrogen in precipitation, combined with a lack of nitrogen-fixation activity in open lake waters, indicates that nitrogen in tributary streams is the major source of new nitrogen for Brooks Lake. The measurements of nitrogen inputs, along with estimates of other stocks and flows of nitrogen, were used to construct a steady-state box model of the nitrogen cycle in the drainage.

  12. Determination of sup 13 C labeling pattern of citric acid cycle intermediates by gas chromatography-mass spectrometry

    SciTech Connect

    Di Donato, L.; Montgomery, J.A.; Des Rosiers, C.; David, F.; Garneau, M.; Brunengraber, H. )

    1990-02-26

    Investigations of the regulation of the citric acid cycle require determination of labeling patterns of cycle intermediates. These were assayed to date, using infusion of: (i) ({sup 14}C)tracer followed by chemical degradation of intermediates and (ii) ({sup 13}C)tracer followed by NMR analysis of intermediates. The authors developed a strategy to analyze by GC-MS the ({sup 13}C) labeling pattern of {mu}mole samples of citrate (CIT), isocitrate (ICIT), 2-ketoglutarate (2-KG), glutamate (GLU) and glutamine (GLN). These are enzymatically or chemically converted to 2-KG, ICIT, 4-aminobutyrate (GABA) and 2-hydroxyglutarate (2-OHG). GC-MS analyses of TMS or TBDMS derivatives of these compounds yield the enrichment of each carbon. The authors confirmed the identity of each fragment using the spectra of (1-{sup 13}C), (5-{sup 13}C), (2,3,3,4,4-{sup 2}H{sub 5})glutamate and (1-{sup 13}C), (1,4-{sup 13}C)GABA.

  13. The pyruvate-tricarboxylic acid cycle node: a focal point of virulence control in the enteric pathogen Yersinia pseudotuberculosis.

    PubMed

    Bücker, René; Heroven, Ann Kathrin; Becker, Judith; Dersch, Petra; Wittmann, Christoph

    2014-10-24

    Despite our increasing knowledge of the specific pathogenicity factors in bacteria, the contribution of metabolic processes to virulence is largely unknown. Here, we elucidate a tight connection between pathogenicity and core metabolism in the enteric pathogen Yersinia pseudotuberculosis by integrated transcriptome and [(13)C]fluxome analysis of the wild type and virulence-regulator mutants. During aerobic growth on glucose, Y. pseudotuberculosis reveals an unusual flux distribution with a high level of secreted pyruvate. The absence of the transcriptional and post-transcriptional regulators RovA, CsrA, and Crp strongly perturbs the fluxes of carbon core metabolism at the level of pyruvate metabolism and the tricarboxylic acid (TCA) cycle, and these perturbations are accompanied by transcriptional changes in the corresponding enzymes. Knock-outs of regulators of this metabolic branch point and of its central enzyme, pyruvate kinase (ΔpykF), result in mutants with significantly reduced virulence in an oral mouse infection model. In summary, our work identifies the pyruvate-TCA cycle node as a focal point for controlling the host colonization and virulence of Yersinia.

  14. Tissue persistence and vaccine efficacy of tricarboxylic acid cycle and one-carbon metabolism mutant strains of Edwardsiella ictaluri.

    PubMed

    Dahal, Neeti; Abdelhamed, Hossam; Karsi, Attila; Lawrence, Mark L

    2014-06-30

    Edwardsiella ictaluri causes enteric septicemia in fish. Recently, we reported construction of E. ictaluri mutants with single and double gene deletions in tricarboxylic acid cycle (TCA) and one-carbon (C-1) metabolism. Here, we report the tissue persistence, virulence, and vaccine efficacy of TCA cycle (EiΔsdhC, EiΔfrdA, and EiΔmdh), C-1 metabolism (EiΔgcvP and EiΔglyA), and combination mutants (EiΔfrdAΔsdhC, EiΔgcvPΔsdhC, EiΔmdhΔsdhC, and EiΔgcvPΔglyA) in channel catfish. The tissue persistence study showed that EiΔsdhC, EiΔfrdA, EiΔfrdAΔsdhC, and EiΔgcvPΔsdhC were able to invade catfish and persist until 11 days post-infection. Vaccination of catfish fingerlings with all nine mutants provided significant (P<0.05) protection against subsequent challenge with the virulent parental strain. Vaccinated catfish fingerlings had 100% survival when subsequently challenged by immersion with wild-type E. ictaluri except for EiΔgcvPΔglyA and EiΔgcvP. Mutant EiΔgcvPΔsdhC was found to be very good at protecting catfish fry, as evidenced by 10-fold higher survival compared to non-vaccinated fish.

  15. Effect of multiple mutations in tricarboxylic acid cycle and one-carbon metabolism pathways on Edwardsiella ictaluri pathogenesis.

    PubMed

    Dahal, N; Abdelhamed, H; Lu, J; Karsi, A; Lawrence, M L

    2014-02-21

    Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of catfish (ESC). We have shown recently that tricarboxylic acid cycle (TCA) and one-carbon (C1) metabolism are involved in E. ictaluri pathogenesis. However, the effect of multiple mutations in these pathways is unknown. Here, we report four novel E. ictaluri mutants carrying double gene mutations in TCA cycle (EiΔmdhΔsdhC, EiΔfrdAΔsdhC), C1 metabolism (EiΔglyAΔgcvP), and both TCA and C1 metabolism pathways (EiΔgcvPΔsdhC). In-frame gene deletions were constructed by allelic exchange and mutants' virulence and vaccine efficacy were evaluated using in vivo bioluminescence imaging (BLI) as well as end point mortality counts in catfish fingerlings. Results indicated that all the double gene mutants were attenuated compared to wild-type (wt) E. ictaluri. There was a 1.39-fold average reduction in bioluminescence, and hence bacterial numbers, from all the mutants except for EiΔfrdAΔsdhC at 144 h post-infection. Vaccination with mutants was very effective in protecting channel catfish against subsequent infection with virulent E. ictaluri 93-146 strain. In particular, immersion vaccination resulted in complete protection. Our results provide further evidence on the importance of TCA and C1 metabolism pathways in bacterial pathogenesis.

  16. Fungi Contribute Critical but Spatially Varying Roles in Nitrogen and Carbon Cycling in Acid Mine Drainage

    PubMed Central

    Mosier, Annika C.; Miller, Christopher S.; Frischkorn, Kyle R.; Ohm, Robin A.; Li, Zhou; LaButti, Kurt; Lapidus, Alla; Lipzen, Anna; Chen, Cindy; Johnson, Jenifer; Lindquist, Erika A.; Pan, Chongle; Hettich, Robert L.; Grigoriev, Igor V.; Singer, Steven W.; Banfield, Jillian F.

    2016-01-01

    The ecosystem roles of fungi have been extensively studied by targeting one organism and/or biological process at a time, but the full metabolic potential of fungi has rarely been captured in an environmental context. We hypothesized that fungal genome sequences could be assembled directly from the environment using metagenomics and that transcriptomics and proteomics could simultaneously reveal metabolic differentiation across habitats. We reconstructed the near-complete 27 Mbp genome of a filamentous fungus, Acidomyces richmondensis, and evaluated transcript and protein expression in floating and streamer biofilms from an acid mine drainage (AMD) system. A. richmondensis transcripts involved in denitrification and in the degradation of complex carbon sources (including cellulose) were up-regulated in floating biofilms, whereas central carbon metabolism and stress-related transcripts were significantly up-regulated in streamer biofilms. These findings suggest that the biofilm niches are distinguished by distinct carbon and nitrogen resource utilization, oxygen availability, and environmental challenges. An isolated A. richmondensis strain from this environment was used to validate the metagenomics-derived genome and confirm nitrous oxide production at pH 1. Overall, our analyses defined mechanisms of fungal adaptation and identified a functional shift related to different roles in carbon and nitrogen turnover for the same species of fungi growing in closely located but distinct biofilm niches. PMID:26973616

  17. Fungi contribute critical but spatially varying roles in nitrogen and carbon cycling in acid mine drainage

    DOE PAGES

    Mosier, Annika C.; Miller, Christopher S.; Frischkorn, Kyle R.; Ohm, Robin A.; Li, Zhou; LaButti, Kurt; Lapidus, Alla; Lipzen, Anna; Chen, Cindy; Johnson, Jenifer; et al

    2016-03-03

    The ecosystem roles of fungi have been extensively studied by targeting one organism and/or biological process at a time, but the full metabolic potential of fungi has rarely been captured in an environmental context. We hypothesized that fungal genome sequences could be assembled directly from the environment using metagenomics and that transcriptomics and proteomics could simultaneously reveal metabolic differentiation across habitats. We reconstructed the near-complete 27 Mbp genome of a filamentous fungus, Acidomyces richmondensis, and evaluated transcript and protein expression in floating and streamer biofilms from an acid mine drainage (AMD) system. A. richmondensis transcripts involved in denitrification and inmore » the degradation of complex carbon sources (including cellulose) were up-regulated in floating biofilms, whereas central carbon metabolism and stress-related transcripts were significantly up-regulated in streamer biofilms. Finally, these findings suggest that the biofilm niches are distinguished by distinct carbon and nitrogen resource utilization, oxygen availability, and environmental challenges. An isolated A. richmondensis strain from this environment was used to validate the metagenomics-derived genome and confirm nitrous oxide production at pH 1. Overall, our analyses defined mechanisms of fungal adaptation and identified a functional shift related to different roles in carbon and nitrogen turnover for the same species of fungi growing in closely located but distinct biofilm niches.« less

  18. Measurement of (15)N enrichment of glutamine and urea cycle amino acids derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate using liquid chromatography-tandem quadrupole mass spectrometry.

    PubMed

    Nakamura, Hidehiro; Karakawa, Sachise; Watanabe, Akiko; Kawamata, Yasuko; Kuwahara, Tomomi; Shimbo, Kazutaka; Sakai, Ryosei

    2015-05-01

    6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) is an amino acid-specific derivatizing reagent that has been used for sensitive amino acid quantification by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). In this study, we aimed to evaluate the ability of this method to measure the isotopic enrichment of amino acids and to determine the positional (15)N enrichment of urea cycle amino acids (i.e., arginine, ornithine, and citrulline) and glutamine. The distribution of the M and M+1 isotopomers of each natural AQC-amino acid was nearly identical to the theoretical distribution. The standard deviation of the (M+1)/M ratio for each amino acid in repeated measurements was approximately 0.1%, and the ratios were stable regardless of the injected amounts. Linearity in the measurements of (15)N enrichment was confirmed by measuring a series of (15)N-labeled arginine standards. The positional (15)N enrichment of urea cycle amino acids and glutamine was estimated from the isotopic distribution of unique fragment ions generated at different collision energies. This method was able to identify their positional (15)N enrichment in the plasma of rats fed (15)N-labeled glutamine. These results suggest the utility of LC-MS/MS detection of AQC-amino acids for the measurement of isotopic enrichment in (15)N-labeled amino acids and indicate that this method is useful for the study of nitrogen metabolism in living organisms.

  19. Lewis acid promoted titanium alkylidene formation: off-cycle intermediates relevant to olefin trimerization catalysis.

    PubMed

    Sattler, Aaron; VanderVelde, David G; Labinger, Jay A; Bercaw, John E

    2014-07-30

    Two new precatalysts for ethylene and α-olefin trimerization, (FI)Ti(CH2SiMe3)2Me and (FI)Ti(CH2CMe3)2Me (FI = phenoxy-imine), have been synthesized and structurally characterized by X-ray diffraction. (FI)Ti(CH2SiMe3)2Me can be activated with 1 equiv of B(C6F5)3 at room temperature to give the solvent-separated ion pair [(FI)Ti(CH2SiMe3)2][MeB(C6F5)3], which catalytically trimerizes ethylene or 1-pentene to produce 1-hexene or C15 olefins, respectively. The neopentyl analogue (FI)Ti(CH2CMe3)2Me is unstable toward activation with B(C6F5)3 at room temperature, giving no discernible diamagnetic titanium complexes, but at -30 °C the following can be observed by NMR spectroscopy: (i) formation of the bis-neopentyl cation [(FI)Ti(CH2CMe3)2](+), (ii) α-elimination of neopentane to give the neopentylidene complex [(FI)Ti(═CHCMe3)](+), and (iii) subsequent conversion to the imido-olefin complex [(MeOAr2N═)Ti(OArHC═CHCMe3)](+) via an intramolecular metathesis reaction with the imine fragment of the (FI) ligand. If the reaction is carried out at low temperature in the presence of ethylene, catalytic production of 1-hexene is observed, in addition to the titanacyclobutane complex [(FI)Ti(CH(CMe3)CH2CH2)](+), resulting from addition of ethylene to the neopentylidene [(FI)Ti(═CHCMe3)](+). None of the complexes observed spectroscopically subsequent to [(FI)Ti(CH2CMe3)2](+) is an intermediate or precursor for ethylene trimerization, but notwithstanding these off-cycle pathways, [(FI)Ti(CH2CMe3)2](+) is a precatalyst that undergoes rapid initiation to generate a catalyst for trimerizing ethylene or 1-pentene.

  20. Trichloroacetic acid cycling in Sitka spruce saplings and effects on sapling health following long term exposure.

    PubMed

    Dickey, C A; Heal, K V; Stidson, R T; Koren, R; Schröder, P; Cape, J N; Heal, M R

    2004-07-01

    Trichloroacetic acid (TCA, CCl(3)COOH) has been associated with forest damage but the source of TCA to trees is poorly characterised. To investigate the routes and effects of TCA uptake in conifers, 120 Sitka spruce (Picea sitchensis (Bong.) Carr) saplings were exposed to control, 10 or 100 microg l(-1) solutions of TCA applied twice weekly to foliage only or soil only over two consecutive 5-month growing seasons. At the end of each growing season similar elevated TCA concentrations (approximate range 200-300 ng g(-1) dwt) were detected in both foliage and soil-dosed saplings exposed to 100 microg l(-1) TCA solutions showing that TCA uptake can occur from both exposure routes. Higher TCA concentrations in branchwood of foliage-dosed saplings suggest that atmospheric TCA in solution is taken up indirectly into conifer needles via branch and stemwood. TCA concentrations in needles declined slowly by only 25-30% over 6 months of winter without dosing. No effect of TCA exposure on sapling growth was measured during the experiment. However at the end of the first growing season needles of saplings exposed to 10 or 100 microg l(-1) foliage-applied TCA showed significantly more visible damage, higher activities of some detoxifying enzymes, lower protein contents and poorer water control than needles of saplings dosed with the same TCA concentrations to the soil. At the end of each growing season the combined TCA storage in needles, stemwood, branchwood and soil of each sapling was <6% of TCA applied. Even with an estimated half-life of tens of days for within-sapling elimination of TCA during the growing season, this indicates that TCA is eliminated rapidly before uptake or accumulates in another compartment. Although TCA stored in sapling needles accounted for only a small proportion of TCA stored in the sapling/soil system it appears to significantly affect some measures of sapling health.

  1. The complete targeted profile of the organic acid intermediates of the citric acid cycle using a single stable isotope dilution analysis, sodium borodeuteride reduction and selected ion monitoring GC/MS.

    PubMed

    Mamer, Orval; Gravel, Simon-Pierre; Choinière, Luc; Chénard, Valérie; St-Pierre, Julie; Avizonis, Daina

    2013-01-01

    The quantitative profiling of the organic acid intermediates of the citric acid cycle (CAC) presents a challenge due to the lack of commercially available internal standards for all of the organic acid intermediates. We developed an analytical method that enables the quantitation of all the organic acids in the CAC in a single stable isotope dilution GC/MS analysis with deuterium-labeled analogs used as internal standards. The unstable α-keto acids are rapidly reduced with sodium borodeuteride to the corresponding stable α-deutero-α-hydroxy acids and these, along with their unlabeled analogs and other CAC organic acid intermediates, are converted to their tert-butyldimethylsilyl derivatives. Selected ion monitoring is employed with electron ionization. We validated this method by treating an untransformed mouse mammary epithelial cell line with well-known mitochondrial toxins affecting the electron transport chain and ATP synthase, which resulted in profound perturbations of the concentration of CAC intermediates.

  2. Activation and repression of Epstein-Barr Virus and Kaposi's sarcoma-associated herpesvirus lytic cycles by short- and medium-chain fatty acids.

    PubMed

    Gorres, Kelly L; Daigle, Derek; Mohanram, Sudharshan; Miller, George

    2014-07-01

    The lytic cycles of Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are induced in cell culture by sodium butyrate (NaB), a short-chain fatty acid (SCFA) histone deacetylase (HDAC) inhibitor. Valproic acid (VPA), another SCFA and an HDAC inhibitor, induces the lytic cycle of KSHV but blocks EBV lytic reactivation. To explore the hypothesis that structural differences between NaB and VPA account for their functional effects on the two related viruses, we investigated the capacity of 16 structurally related short- and medium-chain fatty acids to promote or prevent lytic cycle reactivation. SCFAs differentially affected EBV and KSHV reactivation. KSHV was reactivated by all SCFAs that are HDAC inhibitors, including phenylbutyrate. However, several fatty acid HDAC inhibitors, such as isobutyrate and phenylbutyrate, did not reactivate EBV. Reactivation of KSHV lytic transcripts could not be blocked completely by any fatty acid tested. In contrast, several medium-chain fatty acids inhibited lytic activation of EBV. Fatty acids that blocked EBV reactivation were more lipophilic than those that activated EBV. VPA blocked activation of the BZLF1 promoter by NaB but did not block the transcriptional function of ZEBRA. VPA also blocked activation of the DNA damage response that accompanies EBV lytic cycle activation. Properties of SCFAs in addition to their effects on chromatin are likely to explain activation or repression of EBV. We concluded that fatty acids stimulate the two related human gammaherpesviruses to enter the lytic cycle through different pathways. Importance: Lytic reactivation of EBV and KSHV is needed for persistence of these viruses and plays a role in carcinogenesis. Our direct comparison highlights the mechanistic differences in lytic reactivation between related human oncogenic gammaherpesviruses. Our findings have therapeutic implications, as fatty acids are found in the diet and produced by the human microbiota. Small

  3. Mathematical modelling of the citric acid cycle for the analysis of glutamine isotopomers from cerebellar astrocytes incubated with [1(-13)C]glucose.

    PubMed

    Merle, M; Martin, M; Villégier, A; Canioni, P

    1996-08-01

    A mathematical model of the citric acid cycle devoted to the analysis of 13C-NMR data was developed for determining the relative flux of molecules through the anaplerotic versus oxidative pathways and the relative pyruvate carboxylase versus pyruvate dehydrogenase activities. Different variants of the model were considered depending on the reversibility of the conversion of fumarate into malate and oxaloacetate. The model also included the possibility of orientation-conserved transfer of the four-carbon citric acid cycle intermediates, leading to conversion of succinyl-CoA C1 into either malate C1 or C4. It was used to analyse NMR data from glutamine isotopomers produced by cerebellar astrocytes incubated with [1-13C]glucose. Partial cycling (39%) between oxaloacetate and fumarate was evident from the analysis. Application of the model to glutamate isotopomers from granule cells incubated with [1-13C]glucose [Martin, M.. Portais, J.C.. Labouesse. J., Canioni. P, & Merle, M. (1993) Eur. J. Biochem. 217, 617-625] indicated that total cycling of oxaloacetate into fumarate was, in this case, required to get the best fit. The results emphasized some important differences in carbon metabolism between cerebellar astrocytes and granule cells concerning the sources of carbon fuelling the citric acid cycle and the carbon fluxes on different pathways.

  4. The role of the cell cycle in the cellular uptake of folate-modified poly(l-amino acid) micelles in a cell population

    NASA Astrophysics Data System (ADS)

    Tang, Jihui; Liu, Ziwei; Ji, Fenqi; Li, Yao; Liu, Junjie; Song, Jian; Li, Jun; Zhou, Jianping

    2015-12-01

    Nanoparticles are widely recognized as a vehicle for tumor-targeted therapies. There are many factors that can influence the uptake of nanoparticles, such as the size of the nanoparticles, and/or their shape, elasticity, surface charge and even the cell cycle phase. However, the influence of the cell cycle on the active targeting of a drug delivery system has been unknown until now. In this study, we initially investigated the folate receptor α (FR-α) expression in different phases of HeLa cells by flow cytometric and immunocytochemical methods. The results obtained showed that FR-α expression was cell cycle-dependent, i.e. the S cells' folate receptor expression was the highest as the cell progressed through its cycle. Then, we used folate modified poly(l-amino acid) micelles (FA-PM) as an example to investigate the influence of the cell cycle on the active targeting drug delivery system. The results obtained indicated that the uptake of FA-PM by cells was influenced by the cell cycle phase, and the S cells took up the greatest number of folate conjugated nanoparticles. Our findings suggest that future studies on ligand-mediated active targeting preparations should consider the cell cycle, especially when this system is used for a cell cycle-specific drug.

  5. Mathematical models for determining metabolic fluxes through the citric acid and the glyoxylate cycles in Saccharomyces cerevisiae by 13C-NMR spectroscopy.

    PubMed

    Tran-Dinh, S; Bouet, F; Huynh, Q T; Herve, M

    1996-12-15

    We propose, first, a practical method for studying the isotopic transformation of glutamate or any other metabolite isotopomers in the citric acid and the glyoxylate cycles; second, two mathematical models, one for evaluating the flux through the citric acid cycle and the other for evaluating the flux through the latter coupled to the glyoxylate cycle in yeast. These models are based on the analysis of 13C-NMR spectra of glutamate obtained from Saccharomyces cerevisiae, NCYC strain, fed with 100% enriched [2-13C]acetate. The population of each glutamate isotopomer, the change in intensity of each multiplet component or the enrichment of any glutamate carbon is expressed by a specific analytical equation from which the flux in the citric acid and the glyoxylate cycles can be deduced. The aerobic metabolism of 100% [2-13C]acetate in acetate-grown S. cerevisiae cells was studied as a function of time using 13C-NMR. 1H-NMR and biochemical techniques. The C1 and C6 doublet and singlet of labeled trehalose increase continuously with time indicating that there is no isotopic transformation between trehalose isotopomers even though the corresponding formation rates are different. By contrast, the glutamate C4 singlet increases then decreases with time. The C4 doublet, which is lower than the singlet for t < 60 min, increases continuously and becomes higher than the singlet for t > 90 min. A similar observation was made for the C2 resonance singlet and doublet. In addition, the glutamate C2 multiplet consists of only seven instead of nine peaks as in random labeling. These results agree well with our models and demonstrate that, in the presence of acetate, anaplerotic carbon sources involved in the synthesis of acetyl-CoA are negligible in yeast. The flux in the citric acid cycle was deduced from a plot of the C4 area versus incubation time, while the flux within the glyoxylate cycle was determined from the relative intensity of the glutamate C4 doublet and singlet. The

  6. Antiproliferative Effect of Ascorbic Acid Is Associated with the Inhibition of Genes Necessary to Cell Cycle Progression

    PubMed Central

    Belin, Sophie; Kaya, Ferdinand; Duisit, Ghislaine; Giacometti, Sarah; Ciccolini, Joseph; Fontés, Michel

    2009-01-01

    Background Ascorbic acid (AA), or Vitamin C, is most well known as a nutritional supplement with antioxidant properties. Recently, we demonstrated that high concentrations of AA act on PMP22 gene expression and partially correct the Charcot-Marie-Tooth disease phenotype in a mouse model. This is due to the capacity of AA, but not other antioxidants, to down-modulate cAMP intracellular concentration by a competitive inhibition of the adenylate cyclase enzymatic activity. Because of the critical role of cAMP in intracellular signalling, we decided to explore the possibility that ascorbic acid could modulate the expression of other genes. Methods and Findings Using human pangenomic microarrays, we found that AA inhibited the expression of two categories of genes necessary for cell cycle progression, tRNA synthetases and translation initiation factor subunits. In in vitro assays, we demonstrated that AA induced the S-phase arrest of proliferative normal and tumor cells. Highest concentrations of AA leaded to necrotic cell death. However, quiescent cells were not susceptible to AA toxicity, suggesting the blockage of protein synthesis was mainly detrimental in metabolically-active cells. Using animal models, we found that high concentrations of AA inhibited tumor progression in nude mice grafted with HT29 cells (derived from human colon carcinoma). Consistently, expression of tRNA synthetases and ieF2 appeared to be specifically decreased in tumors upon AA treatment. Conclusions AA has an antiproliferative activity, at elevated concentration that could be obtained using IV injection. This activity has been observed in vitro as well in vivo and likely results from the inhibition of expression of genes involved in protein synthesis. Implications for a clinical use in anticancer therapies will be discussed. PMID:19197388

  7. Diel cycling of zinc in a stream impacted by acid rock drainage: Initial results from a new in situ Zn analyzer

    USGS Publications Warehouse

    Chapin, T.P.; Nimick, D.A.; Gammons, C.H.; Wanty, R.B.

    2007-01-01

    Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 ??g/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage. ?? Springer Science+Business Media B.V. 2006.

  8. Changes in lipid content and fatty acid composition along the reproductive cycle of the freshwater mussel Dreissena polymorpha: its modulation by clofibrate exposure.

    PubMed

    Lazzara, Raimondo; Fernandes, Denise; Faria, Melissa; López, Jordi F; Tauler, Romà; Porte, Cinta

    2012-08-15

    Total lipids and fatty acid profiles were determined along the reproductive cycle of the zebra mussel (Dreissena polymorpha). A total of 33 fatty acids with carbon atoms from 14 to 22 were identified: palmitic acid (16:0) was the most abundant fatty acid (13-24%) followed by docosahexaenoic acid (DHA; 22:6n-3), eicosapentaenoic acid (EPA; 20:5n-3) and palmitoleic acid (16:1n-7). Some individual fatty acids (16:0, 16:2n-4, 18:1n-7, 18:2n-6, 18:3n-4, 18:4n-3, 20:4n-3, 20:5n-3) were strongly related to reproductive events, while others having structural-type functions (18:0 and 22:6n-3) were rather stable during the study period. Multivariate analysis of the whole data set using the multivariate curve resolution alternating least squares method confirmed the strong relationship of fatty acid profiles with the reproductive cycle of zebra mussel. Additionally, the effects of the pharmaceutical clofibrate on lipid composition and fatty acid profiles were assessed following 7-day exposure of zebra mussels to a wide range of concentrations (20 ng/L to 2 mg/L). A significant reduction in total triglycerides (38%-48%) together with an increase in the amount of fatty acids per gram wet weight (1.5- to 2.2-fold) was observed in the exposed mussels. This work highlights the ability of clofibrate to induce changes on the lipidome of zebra mussels at concentrations as low as 200 ng/L. PMID:22728965

  9. Urinary loss of tricarboxylic acid cycle intermediates as revealed by metabolomics studies: an underlying mechanism to reduce lipid accretion by whey protein ingestion?

    PubMed

    Lillefosse, Haldis H; Clausen, Morten R; Yde, Christian C; Ditlev, Ditte B; Zhang, Xumin; Du, Zhen-Yu; Bertram, Hanne C; Madsen, Lise; Kristiansen, Karsten; Liaset, Bjørn

    2014-05-01

    Whey protein intake is associated with the modulation of energy metabolism and altered body composition both in human subjects and in animals, but the underlying mechanisms are not yet elucidated. We fed obesity-prone C57BL/6J mice high-fat diets with either casein (HF casein) or whey (HF whey) for 6 weeks. At equal energy intake and apparent fat and nitrogen digestibility, mice fed HF whey stored less energy as lipids, evident both as lower white adipose tissue mass and as reduced liver lipids, compared with HF-casein-fed mice. Explorative analyses of 48 h urine, both by (1)H NMR and LC-MS metabolomic platforms, demonstrated higher urinary excretion of tricarboxylic acid (TCA) cycle intermediates citric acid and succinic acid (identified by both platforms), and cis-aconitic acid and isocitric acid (identified by LC-MS platform) in the HF whey, relative to in the HF-casein-fed mice. Targeted LC-MS analyses revealed higher citric acid and cis-aconitic acid concentrations in fed state plasma, but not in liver of HF-whey-fed mice. We propose that enhanced urinary loss of TCA cycle metabolites drain available substrates for anabolic processes, such as lipogenesis, thereby leading to reduced lipid accretion in HF-whey-fed compared to HF-casein-fed mice.

  10. Acute Carnosine Administration Increases Respiratory Chain Complexes and Citric Acid Cycle Enzyme Activities in Cerebral Cortex of Young Rats.

    PubMed

    Macedo, Levy W; Cararo, José H; Maravai, Soliany G; Gonçalves, Cinara L; Oliveira, Giovanna M T; Kist, Luiza W; Guerra Martinez, Camila; Kurtenbach, Eleonora; Bogo, Maurício R; Hipkiss, Alan R; Streck, Emilio L; Schuck, Patrícia F; Ferreira, Gustavo C

    2016-10-01

    Carnosine (β-alanyl-L-histidine) is an imidazole dipeptide synthesized in excitable tissues of many animals, whose biochemical properties include carbonyl scavenger, anti-oxidant, bivalent metal ion chelator, proton buffer, and immunomodulating agent, although its precise physiological role(s) in skeletal muscle and brain tissues in vivo remain unclear. The aim of the present study was to investigate the in vivo effects of acute carnosine administration on various aspects of brain bioenergetics of young Wistar rats. The activity of mitochondrial enzymes in cerebral cortex was assessed using a spectrophotometer, and it was found that there was an increase in the activities of complexes I-III and II-III and succinate dehydrogenase in carnosine-treated rats, as compared to vehicle-treated animals. However, quantitative real-time RT-PCR (RT-qPCR) data on mRNA levels of mitochondrial biogenesis-related proteins (nuclear respiratory factor 1 (Nrf1), peroxisome proliferator-activated receptor-γ coactivator 1-α (Ppargc1α), and mitochondrial transcription factor A (Tfam)) were not altered significantly and therefore suggest that short-term carnosine administration does not affect mitochondrial biogenesis. It was in agreement with the finding that immunocontent of respiratory chain complexes was not altered in animals receiving carnosine. These observations indicate that acute carnosine administration increases the respiratory chain and citric acid cycle enzyme activities in cerebral cortex of young rats, substantiating, at least in part, a neuroprotector effect assigned to carnosine against oxidative-driven disorders. PMID:26476839

  11. Trace metal partitioning over a tidal cycle in an estuary affected by acid mine drainage (Tinto estuary, SW Spain).

    PubMed

    Hierro, A; Olías, M; Cánovas, C R; Martín, J E; Bolivar, J P

    2014-11-01

    The Tinto River estuary is highly polluted with the acid lixiviates from old sulphide mines. In this work the behaviour of dissolved and particulate trace metals under strong chemical gradients during a tidal cycle is studied. The pH values range from 4.4 with low tide to 6.9 with high tide. Precipitation of Fe and Al is intense during rising tides and As and Pb are almost exclusively found in the particulate matter (PM). Sorption processes are very important in controlling the mobility (and hence bioavailability) of some metals and particularly affect Cu below pH 6. Above pH~6 Cu is desorbed, probably by the formation of Cu(I)-chloride complexes. Although less pronounced than Cu, also Zn desorption above pH 6.5 seems to occur. Mn and Co are affected by sorption processes at pH higher than ca. 6. Cd behaves conservatively and Ni is slightly affected by sorption processes.

  12. Acute Carnosine Administration Increases Respiratory Chain Complexes and Citric Acid Cycle Enzyme Activities in Cerebral Cortex of Young Rats.

    PubMed

    Macedo, Levy W; Cararo, José H; Maravai, Soliany G; Gonçalves, Cinara L; Oliveira, Giovanna M T; Kist, Luiza W; Guerra Martinez, Camila; Kurtenbach, Eleonora; Bogo, Maurício R; Hipkiss, Alan R; Streck, Emilio L; Schuck, Patrícia F; Ferreira, Gustavo C

    2016-10-01

    Carnosine (β-alanyl-L-histidine) is an imidazole dipeptide synthesized in excitable tissues of many animals, whose biochemical properties include carbonyl scavenger, anti-oxidant, bivalent metal ion chelator, proton buffer, and immunomodulating agent, although its precise physiological role(s) in skeletal muscle and brain tissues in vivo remain unclear. The aim of the present study was to investigate the in vivo effects of acute carnosine administration on various aspects of brain bioenergetics of young Wistar rats. The activity of mitochondrial enzymes in cerebral cortex was assessed using a spectrophotometer, and it was found that there was an increase in the activities of complexes I-III and II-III and succinate dehydrogenase in carnosine-treated rats, as compared to vehicle-treated animals. However, quantitative real-time RT-PCR (RT-qPCR) data on mRNA levels of mitochondrial biogenesis-related proteins (nuclear respiratory factor 1 (Nrf1), peroxisome proliferator-activated receptor-γ coactivator 1-α (Ppargc1α), and mitochondrial transcription factor A (Tfam)) were not altered significantly and therefore suggest that short-term carnosine administration does not affect mitochondrial biogenesis. It was in agreement with the finding that immunocontent of respiratory chain complexes was not altered in animals receiving carnosine. These observations indicate that acute carnosine administration increases the respiratory chain and citric acid cycle enzyme activities in cerebral cortex of young rats, substantiating, at least in part, a neuroprotector effect assigned to carnosine against oxidative-driven disorders.

  13. Involvement of apoptotic cell death and cell cycle perturbation in retinoic acid-induced cleft palate in mice

    SciTech Connect

    Okano, Junko . E-mail: okajun@anat1.med.kyoto-u.ac.jp; Suzuki, Shigehiko; Shiota, Kohei

    2007-05-15

    Retinoic acid (RA), a metabolite of vitamin A, plays a key role in a variety of biological processes and is essential for normal embryonic development. On the other hand, exogenous RA could cause cleft palate in offspring when it is given to pregnant animals at either the early or late phases of palatogenesis, but the pathogenetic mechanism of cleft palate caused by excess RA remains not fully elucidated. The aim of the present study was to investigate the effects of excess of RA on early palatogenesis in mouse fetuses and analyze the teratogenic mechanism, especially at the stage prior to palatal shelf elevation. We gave all-trans RA (100 mg/kg) orally to E11.5 ICR pregnant mice and observed the changes occurring in the palatal shelves of their fetuses. It was found that apoptotic cell death increased not only in the epithelium of the palatal shelves but also in the tongue primordium, which might affect tongue withdrawal movement during palatogenesis and impair the horizontal elevation of palatal shelves. In addition, RA was found to prevent the G{sub 1}/S progression of palatal mesenchymal cells through upregulation of p21 {sup Cip1}, leading to Rb hypophospholylation. Thus, RA appears to cause G{sub 1} arrest in palatal mesenchymal cells in a similar manner as in various cancer and embryonic cells. It is likely that apoptotic cell death and cell cycle disruption are involved in cleft palate formation induced by RA.

  14. Acid deposition: effects on geochemical cycling and biological availability of trace elements. Report for September 1982-January 1985

    SciTech Connect

    Campbell, P.G.C.; Galloway, J.N.; Stokes, P.

    1985-01-01

    Acid deposition is caused by emissions of oxides of sulfur and nitrogen from such high temperature processes as fossil-fuel combustion and ore smelting. The emissions also contain elements present in the environment in trace amounts, for example, silver (Ag), arsenic (As), beryllium (Be), cadmium (Cd), cobalt (Co), copper (Cu), mercury (Hg), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), selenium (Se), tin (Sn), tellurium (Te), thallium (Th), Vanadium (V), and zinc (Zn). With the exception of mercury, these elements are not naturally present in the atmosphere owing to their characteristically low volatilities. The shift from natural to human control of deposition of trace elements significantly perturbs the biogeochemical cycles of these potentially toxic substances. This report addresses the following: Do elevated rates of their deposition cause changes in aquatic and terrestrial ecosystems. What are the interactions between their deposition and the concurrent acidification of ecosystems. The report focuses on elements generally classified as very toxic and relatively accessible in the environment, i.e. the 17 listed above plus aluminum (Al). A significant bibliography accompanies the report.

  15. Targeting triglyceride/fatty acid cycling in β-cells as a therapy for augmenting glucose-stimulated insulin secretion.

    PubMed

    Cantley, James; Biden, Trevor J

    2010-01-01

    Insulin secretion from pancreatic β-cells is triggered by signals arising from the metabolism of glucose and acting through separate initiation and amplification pathways. Despite decades of investigation, crucial details of this mechanism remain poorly understood, especially those relating to the amplifying pathway(s). Advances in this area are vital if we are to understand why insulin secretion fails in type 2 diabetes and to develop strategies to overcome this failure. Indeed, targeting the amplifying pathway(s) would constitute an attractive therapy for augmenting insulin secretion because it would closely link secretory responsiveness to the prevailing glycaemia. It is therefore noteworthy that the possibility of augmenting the amplification pathway(s) has recently been highlighted by studies investigating a metabolic cycle that links the breakdown of triacylglycerol (TAG), release of fatty acid (FA), and subsequent re-incorporation of that FA into TAG. This work reinvigorates and extends the long-standing idea that partitioning of endogenous lipid metabolism towards esterification products promotes the amplification phase of the secretory response. These conceptual advances, and their possible therapeutic application, will be discussed in the following article.

  16. The cellular and compartmental profile of mouse retinal glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and ~P transferring kinases

    PubMed Central

    Rueda, Elda M.; Johnson, Jerry E.; Giddabasappa, Anand; Swaroop, Anand; Brooks, Matthew J.; Sigel, Irena; Chaney, Shawnta Y.

    2016-01-01

    Purpose The homeostatic regulation of cellular ATP is achieved by the coordinated activity of ATP utilization, synthesis, and buffering. Glucose is the major substrate for ATP synthesis through glycolysis and oxidative phosphorylation (OXPHOS), whereas intermediary metabolism through the tricarboxylic acid (TCA) cycle utilizes non-glucose-derived monocarboxylates, amino acids, and alpha ketoacids to support mitochondrial ATP and GTP synthesis. Cellular ATP is buffered by specialized equilibrium-driven high-energy phosphate (~P) transferring kinases. Our goals were twofold: 1) to characterize the gene expression, protein expression, and activity of key synthesizing and regulating enzymes of energy metabolism in the whole mouse retina, retinal compartments, and/or cells and 2) to provide an integrative analysis of the results related to function. Methods mRNA expression data of energy-related genes were extracted from our whole retinal Affymetrix microarray data. Fixed-frozen retinas from adult C57BL/6N mice were used for immunohistochemistry, laser scanning confocal microscopy, and enzymatic histochemistry. The immunoreactivity levels of well-characterized antibodies, for all major retinal cells and their compartments, were obtained using our established semiquantitative confocal and imaging techniques. Quantitative cytochrome oxidase (COX) and lactate dehydrogenase (LDH) activity was determined histochemically. Results The Affymetrix data revealed varied gene expression patterns of the ATP synthesizing and regulating enzymes found in the muscle, liver, and brain. Confocal studies showed differential cellular and compartmental distribution of isozymes involved in glucose, glutamate, glutamine, lactate, and creatine metabolism. The pattern and intensity of the antibodies and of the COX and LDH activity showed the high capacity of photoreceptors for aerobic glycolysis and OXPHOS. Competition assays with pyruvate revealed that LDH-5 was localized in the photoreceptor

  17. Citric acid induces cell-cycle arrest and apoptosis of human immortalized keratinocyte cell line (HaCaT) via caspase- and mitochondrial-dependent signaling pathways.

    PubMed

    Ying, Tsung-Ho; Chen, Chia-Wei; Hsiao, Yu-Ping; Hung, Sung-Jen; Chung, Jing-Gung; Yang, Jen-Hung

    2013-10-01

    Citric acid is an alpha-hydroxyacid (AHA) widely used in cosmetic dermatology and skincare products. However, there is concern regarding its safety for the skin. In this study, we investigated the cytotoxic effects of citric acid on the human keratinocyte cell line HaCaT. HaCaT cells were treated with citric acid at 2.5-12.5 mM for different time periods. Cell-cycle arrest and apoptosis were investigated by 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining, flow cytometry, western blot and confocal microscopy. Citric acid not only inhibited proliferation of HaCaT cells in a dose-dependent manner, but also induced apoptosis and cell cycle-arrest at the G2/M phase (before 24 h) and S phase (after 24 h). Citric acid increased the level of Bcl-2-associated X protein (BAX) and reduced the levels of B-cell lymphoma-2 (BCL-2), B-cell lymphoma-extra large (BCL-XL) and activated caspase-9 and caspase-3, which subsequently induced apoptosis via caspase-dependent and caspase-independent pathways. Citric acid also activated death receptors and increased the levels of caspase-8, activated BH3 interacting-domain death agonist (BID) protein, Apoptosis-inducing factor (AIF), and Endonuclease G (EndoG). Therefore, citric acid induces apoptosis through the mitochondrial pathway in the human keratinocyte cell line HaCaT. The study results suggest that citric acid is cytotoxic to HaCaT cells via induction of apoptosis and cell-cycle arrest in vitro.

  18. Expression of genes encoding enzymes involved in the one carbon cycle in rat placenta is determined by maternal micronutrients (folic acid, vitamin B12) and omega-3 fatty acids.

    PubMed

    Khot, Vinita; Kale, Anvita; Joshi, Asmita; Chavan-Gautam, Preeti; Joshi, Sadhana

    2014-01-01

    We have reported that folic acid, vitamin B12, and omega-3 fatty acids are interlinked in the one carbon cycle and have implications for fetal programming. Our earlier studies demonstrate that an imbalance in maternal micronutrients influence long chain polyunsaturated fatty acid metabolism and global methylation in rat placenta. We hypothesize that these changes are mediated through micronutrient dependent regulation of enzymes in one carbon cycle. Pregnant dams were assigned to six dietary groups with varying folic acid and vitamin B12 levels. Vitamin B12 deficient groups were supplemented with omega-3 fatty acid. Placental mRNA levels of enzymes, levels of phospholipids, and glutathione were determined. Results suggest that maternal micronutrient imbalance (excess folic acid with vitamin B12 deficiency) leads to lower mRNA levels of methylene tetrahydrofolate reductase (MTHFR) and methionine synthase , but higher cystathionine b-synthase (CBS) and Phosphatidylethanolamine-N-methyltransferase (PEMT) as compared to control. Omega-3 supplementation normalized CBS and MTHFR mRNA levels. Increased placental phosphatidylethanolamine (PE), phosphatidylcholine (PC), in the same group was also observed. Our data suggests that adverse effects of a maternal micronutrient imbalanced diet may be due to differential regulation of key genes encoding enzymes in one carbon cycle and omega-3 supplementation may ameliorate most of these changes.

  19. In vitro evidence that D-serine disturbs the citric acid cycle through inhibition of citrate synthase activity in rat cerebral cortex.

    PubMed

    Zanatta, Angela; Schuck, Patrícia Fernanda; Viegas, Carolina Maso; Knebel, Lisiane Aurélio; Busanello, Estela Natacha Brandt; Moura, Alana Pimentel; Wajner, Moacir

    2009-11-17

    The present work investigated the in vitro effects of D-serine (D-Ser) on important parameters of energy metabolism in cerebral cortex of young rats. The parameters analyzed were CO(2) generation from glucose and acetate, glucose uptake and the activities of the respiratory chain complexes I-IV, of the citric acid cycle enzymes citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase and malate dehydrogenase and of creatine kinase and Na(+),K(+)-ATPase. Our results show that D-Ser significantly reduced CO(2) production from acetate, but not from glucose, reflecting an impairment of the citric acid cycle function. Furthermore, D-Ser did not affect glucose uptake. We also observed that the activity of the mitochondrial enzyme citrate synthase from mitochondrial preparations and purified citrate synthase was significantly inhibited by D-Ser, whereas the other activities of the citric acid cycle as well as the activities of complexes I-III, II-III, II and IV of the respiratory chain, creatine kinase and Na(+),K(+)-ATPase were not affected by this D-amino acid. We also found that L-serine did not affect citrate synthase activity from mitochondrial preparations and purified enzyme. The data indicate that D-Ser impairs the citric acid cycle activity via citrate synthase inhibition, therefore compromising energy metabolism production in cerebral cortex of young rats. Therefore, it is presumed that this mechanism may be involved at least in part in the neurological damage found in patients affected by disorders in which D-Ser metabolism is impaired, with altered cerebral concentrations of this D-amino acid.

  20. Activation of lytic cycle of Epstein-Barr virus by suberoylanilide hydroxamic acid leads to apoptosis and tumor growth suppression of nasopharyngeal carcinoma.

    PubMed

    Hui, K F; Ho, Dona N; Tsang, C M; Middeldorp, Jaap M; Tsao, George S W; Chiang, Alan K S

    2012-10-15

    Nasopharyngeal carcinoma (NPC) is strongly associated with Epstein-Barr virus (EBV). We reported that suberoylanilide hydroxamic acid (SAHA) induced EBV lytic cycle in EBV-positive gastric carcinoma cells and mediated enhanced cell death. However, expression of EBV lytic proteins was thought to exert antiapoptotic effect in EBV-infected cells. Here, we examined the in vitro and in vivo effects of SAHA on EBV lytic cycle induction in NPC cells and investigated the cellular consequences. Micromolar concentrations of SAHA significantly induced EBV lytic cycle in EBV-positive NPC cells. Increased apoptosis and proteolytic cleavage of poly(ADP-ribose) polymerase and caspase-3, -7 and -9 in EBV-positive versus EBV-negative NPC cells were observed. More than 85% of NPC cells expressing immediate-early (Zta), early (BMRF1) or late (gp350/220) lytic proteins coexpressed cleaved caspase-3. Tracking of expression of EBV lytic proteins and cleaved caspase-3 over time demonstrated that NPC cells proceeded to apoptosis following EBV lytic cycle induction. Inhibition of EBV DNA replication and late lytic protein expression by phosphonoformic acid did not impact on SAHA's induced cell death in NPC, indicating that early rather than late phase of EBV lytic cycle contributed to the apoptotic effect. In vivo effects of SAHA on EBV lytic cycle induction and tumor growth suppression were also observed in NPC xenografts in nude mice. Taken together, our data indicated that activation of lytic cycle from latent cycle of EBV by SAHA leads to apoptosis and tumor growth suppression of NPC thereby providing experimental evidence for virus-targeted therapy against EBV-positive cancer.

  1. The Effect of Limited Diffusion and Wet-Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids.

    PubMed

    Higgs, Paul G

    2016-06-08

    A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction.

  2. Reproductive cycle and seasonal variations in lipid content and fatty acid composition in gonad of the cockle Fulvia mutica in relation to temperature and food

    NASA Astrophysics Data System (ADS)

    Liu, Wenguang; Li, Qi; Kong, Lingfeng

    2013-09-01

    From March 2004 to February 2005, seasonal variations in lipid content and fatty acid composition of gonad of the cockle Fulvia mutica (Reeve) were studied on the eastern coast of China in relation to the reproductive cycle and environment conditions ( e.g., temperature and food availability). Histological analysis as well as lipid and fatty acid analyses were performed on neutral and polar lipids of the gonad. Results showed that gametogenesis occurred in winter and spring at the expense of lipids previously accumulated in summer and autumn, whereas spawning occurred in summer (20.4-24.6°C). The seasonal variation in lipid content was similar to that of the mean oocyte diameter. In both neutral and polar lipids, the 20:5n-3 and 22:6n-3 levels were relatively higher than saturated fatty acids, and polyunsaturated fatty acids were abundant, with series n-3 as the predominant component. Seasonal variations in the 20:5n-3 and 22:6n-3 levels and the principal n-3 fatty acids were clearly related to the reproductive cycle. The Σ(n-3) and Σ(n-6) values were relatively high during January-May, and the associated unsaturation index was significantly higher than that in other months. The results suggest that fatty acids play an important role in the gametogenesis of F. mutica.

  3. HCdc14A is involved in cell cycle regulation of human brain vascular endothelial cells following injury induced by high glucose, free fatty acids and hypoxia.

    PubMed

    Su, Jingjing; Zhou, Houguang; Tao, Yinghong; Guo, Zhuangli; Zhang, Shuo; Zhang, Yu; Huang, Yanyan; Tang, Yuping; Hu, Renming; Dong, Qiang

    2015-01-01

    Cell cycle processes play a vital role in vascular endothelial proliferation and dysfunction. Cell division cycle protein 14 (Cdc14) is an important cell cycle regulatory phosphatase. Previous studies in budding yeast demonstrated that Cdc14 could trigger the inactivation of mitotic cyclin-dependent kinases (Cdks), which are required for mitotic exit and cytokinesis. However, the exact function of human Cdc14 (hCdc14) in cell cycle regulation during vascular diseases is yet to be elucidated. There are two HCdc14 homologs: hCdc14A and hCdc14B. In the current study, we investigated the potential role of hCdc14A in high glucose-, free fatty acids (FFAs)-, and hypoxia-induced injury in cultured human brain vascular endothelial cells (HBVECs). Data revealed that high glucose, FFA, and hypoxia down-regulated hCdc14A expression remarkably, and also affected the expression of other cell cycle-related proteins such as cyclin B, cyclin D, cyclin E, and p53. Furthermore, the combined addition of the three stimuli largely blocked cell cycle progression, decreased cell proliferation, and increased apoptosis. We also determined that hCdc14A was localized mainly to centrosomes during interphase and spindles during mitosis using confocal microscopy, and that it could affect the expression of other cycle-related proteins. More importantly, the overexpression of hCdc14A accelerated cell cycle progression, enhanced cell proliferation, and promoted neoplastic transformation, whereas the knockdown of hCdc14A using small interfering RNA produced the opposite effects. Therefore, these findings provide novel evidence that hCdc14A might be involved in cell cycle regulation in cultured HBVECs during high glucose-, FFA-, and hypoxia-induced injury.

  4. Notch stimulates growth by direct regulation of genes involved in the control of glycolysis and the tricarboxylic acid cycle

    PubMed Central

    Slaninova, Vera; Krafcikova, Michaela; Perez-Gomez, Raquel; Steffal, Pavel; Trantirek, Lukas; Bray, Sarah J.

    2016-01-01

    Glycolytic shift is a characteristic feature of rapidly proliferating cells, such as cells during development and during immune response or cancer cells, as well as of stem cells. It results in increased glycolysis uncoupled from mitochondrial respiration, also known as the Warburg effect. Notch signalling is active in contexts where cells undergo glycolytic shift. We decided to test whether metabolic genes are direct transcriptional targets of Notch signalling and whether upregulation of metabolic genes can help Notch to induce tissue growth under physiological conditions and in conditions of Notch-induced hyperplasia. We show that genes mediating cellular metabolic changes towards the Warburg effect are direct transcriptional targets of Notch signalling. They include genes encoding proteins involved in glucose uptake, glycolysis, lactate to pyruvate conversion and repression of the tricarboxylic acid cycle. The direct transcriptional upregulation of metabolic genes is PI3K/Akt independent and occurs not only in cells with overactivated Notch but also in cells with endogenous levels of Notch signalling and in vivo. Even a short pulse of Notch activity is able to elicit long-lasting metabolic changes resembling the Warburg effect. Loss of Notch signalling in Drosophila wing discs as well as in human microvascular cells leads to downregulation of glycolytic genes. Notch-driven tissue overgrowth can be rescued by downregulation of genes for glucose metabolism. Notch activity is able to support growth of wing during nutrient-deprivation conditions, independent of the growth of the rest of the body. Notch is active in situations that involve metabolic reprogramming, and the direct regulation of metabolic genes may be a common mechanism that helps Notch to exert its effects in target tissues. PMID:26887408

  5. Application of citrate as a tricarboxylic acid (TCA) cycle intermediate, prevents diabetic-induced heart damages in mice

    PubMed Central

    Liang, Qianqian; Wang, Baoyu; Pang, Lingxia; Wang, Youpei; Zheng, Meiqin; Wang, Qing; Yan, Jingbin; Xu, Jinzhong

    2016-01-01

    Objective(s): Higher cellular reactive oxygen species (ROS) levels is important in reducing cellular energy charge (EC) by increasing the levels of key metabolic protein, and nitrosative modifications, and have been shown to damage the cardiac tissue of diabetic mice. However, the relation between energy production and heart function is unclear. Materials and Methods: Streptozotocin (STZ, 150 mg/kg body weight) was injected intraperitoneally once to mice that had been fasted overnight for induction of diabetes. After diabetic induction, mice received citrate (5 µg/kg) through intraperitoneal injection every other day for 5 weeks. The caspase-3, plasminogen activator inhibitor 1 (PAI1), protein kinase B (PKB), commonly known as AKT and phosphorylated-AKT (p-AKT) proteins were examined to elucidate inflammation and apoptosis in the heart. For histological analysis, heart samples were fixed with 10% formalin and stained with hematoxylin-eosin (HE) and Sirius red to assess pathological changes and fibrosis. The expression levels[AGA1] of marker proteins, tyrosine nitration, activity of ATP synthase and succinyl-CoA3-ketoacid coenzyme A transferase-1 (SCOT), and EC were measured. Results: Intraperitoneal injection of citrate significantly reduced caspase-3 and PAI-1 protein levels and increased p-AKT level on the 5th week; EC in the heart was found to be increased as well. Further, the expression level, activity, and tyrosine nitration of ATP synthase and SCOT were not affected after induction of diabetes. Conclusion: Results indicate that application of citrate, a tricarboxylic acid (TCA) cycle intermediate, might alleviate cardiac dysfunction by reducing cardiac inflammation, apoptosis, and increasing cardiac EC. PMID:27096063

  6. Cell cycle arrest evidence, parasiticidal and bactericidal properties induced by L-amino acid oxidase from Bothrops atrox snake venom.

    PubMed

    de Melo Alves Paiva, Raquel; de Freitas Figueiredo, Raquel; Antonucci, Gilmara Ausech; Paiva, Helder Henrique; de Lourdes Pires Bianchi, Maria; Rodrigues, Kelly C; Lucarini, Rodrigo; Caetano, Renato Cesar; Linhari Rodrigues Pietro, Rosemeire Cristina; Gomes Martins, Carlos Henrique; de Albuquerque, Sérgio; Sampaio, Suely Vilela

    2011-05-01

    The present article describes an l-amino acid oxidase from Bothrops atrox snake venom as with antiprotozoal activities in Trypanosoma cruzi and in different species of Leishmania (Leishmania braziliensis, Leishmania donovani and Leishmania major). Leishmanicidal effects were inhibited by catalase, suggesting that they are mediated by H(2)O(2) production. Leishmania spp. cause a spectrum of diseases, ranging from self-healing ulcers to disseminated and often fatal infections, depending on the species involved and the host's immune response. BatroxLAAO also displays bactericidal activity against both Gram-positive and Gram-negative bacteria. The apoptosis induced by BatroxLAAO on HL-60 cell lines and PBMC cells was determined by morphological cell evaluation using a mix of fluorescent dyes. As revealed by flow cytometry analysis, suppression of cell proliferation with BatroxLAAO was accompanied by the significant accumulation of cells in the G0/G1 phase boundary in HL-60 cells. BatroxLAAO at 25 μg/mL and 50 μg/mL blocked G0-G1 transition, resulting in G0/G1 phase cell cycle arrest, thereby delaying the progression of cells through S and G2/M phase in HL-60 cells. This was shown by an accentuated decrease in the proportion of cells in S phase, and the almost absence of G2/M phase cell population. BatroxLAAO is an interesting enzyme that provides a better understanding of the ophidian envenomation mechanism, and has biotechnological potential as a model for therapeutic agents. PMID:21300133

  7. Conformational Itinerary of Pseudomonas aeruginosa 1,6-Anhydro-N-acetylmuramic Acid Kinase during Its Catalytic Cycle*

    PubMed Central

    Bacik, John-Paul; Tavassoli, Marjan; Patel, Trushar R.; McKenna, Sean A.; Vocadlo, David J.; Khajehpour, Mazdak; Mark, Brian L.

    2014-01-01

    Anhydro-sugar kinases are unique from other sugar kinases in that they must cleave the 1,6-anhydro ring of their sugar substrate to phosphorylate it using ATP. Here we show that the peptidoglycan recycling enzyme 1,6-anhydro-N-acetylmuramic acid kinase (AnmK) from Pseudomonas aeruginosa undergoes large conformational changes during its catalytic cycle, with its two domains rotating apart by up to 32° around two hinge regions to expose an active site cleft into which the substrates 1,6-anhydroMurNAc and ATP can bind. X-ray structures of the open state bound to a nonhydrolyzable ATP analog (AMPPCP) and 1,6-anhydroMurNAc provide detailed insight into a ternary complex that forms preceding an operative Michaelis complex. Structural analysis of the hinge regions demonstrates a role for nucleotide binding and possible cross-talk between the bound ligands to modulate the opening and closing of AnmK. Although AnmK was found to exhibit similar binding affinities for ATP, ADP, and AMPPCP according to fluorescence spectroscopy, small angle x-ray scattering analyses revealed that AnmK adopts an open conformation in solution in the absence of ligand and that it remains in this open state after binding AMPPCP, as we had observed for our crystal structure of this complex. In contrast, the enzyme favored a closed conformation when bound to ADP in solution, consistent with a previous crystal structure of this complex. Together, our findings show that the open conformation of AnmK facilitates binding of both the sugar and nucleotide substrates and that large structural rearrangements must occur upon closure of the enzyme to correctly align the substrates and residues of the enzyme for catalysis. PMID:24362022

  8. Cell cycle arrest and apoptosis of melanoma cells by docosahexaenoic acid: association with decreased pRb phosphorylation.

    PubMed

    Albino, A P; Juan, G; Traganos, F; Reinhart, L; Connolly, J; Rose, D P; Darzynkiewicz, Z

    2000-08-01

    The incidence of cutaneous malignant melanoma is undergoing a dramatic increase in persons with light-color skin in all parts of the world. The prognosis for individuals with advanced disease is dismal due to the lack of effective treatment options. Thus, there is a need for new approaches to control tumor progression. Epidemiological, experimental, and mechanistic data implicate omega-6 polyunsaturated fatty acids (PUFAs) as stimulators and long-chain omega-3 PUFAs as inhibitors of development and progression of a range of human cancers, including melanoma. The aim of this study was to assess the mechanisms by which docosahexaenoic acid (DHA), an omega-3 PUFA, affects human melanoma cells. Exponentially growing melanoma cell lines were exposed in vitro to DHA and then assessed for (a) inhibition of cell growth; (b) expression of cyclins and cyclin-dependent kinase inhibitors in individual cells by flow cytometry and immunocytochemistry using specific monoclonal antibodies to cyclin D1, cyclin E, p21WAF1/CIP1, or p27(KIP1); and (c) expression of total pRb(T) independent of phosphorylation state and hypophosphorylated pRb(P-) in fixed cells by flow cytometry and immunocytochemistry using specific monoclonal antibodies to pRb(T) or pRb(P-), respectively. After treatment with increasing concentrations of DHA, cell growth in a majority of melanoma cell lines (7 of 12) was inhibited, whereas in 5 of 12 cell lines, cell growth was minimally affected. Two melanoma cell lines were examined in detail, one resistant (SK-Mel-29) and one sensitive (SK-Mel-110) to the inhibitory activity of DHA. SK-Mel-29 cells were unaffected by treatment with up to 2 microg/ml DHA whether grown in the absence or presence of 1% fetal bovine serum (FBS). No appreciable change was observed in cell growth, cell cycle distribution, the status of pRb phosphorylation, cyclin D1 expression, or the levels of the cyclin-dependent kinase inhibitors p21 and p27. In contrast, SK-Mel-110 cell growth was

  9. Assay of the human liver citric acid cycle probe phenylacetylglutamine and of phenylacetate in plasma by gas chromatography-mass spectrometry.

    PubMed

    Yang, D; Beylot, M; Agarwal, K C; Soloviev, M V; Brunengraber, H

    1993-07-01

    Phenylacetate, derived from phenylalanine, is converted in human and primate liver to phenylacetylglutamine. The latter has been used to assess the labeling pattern of liver citric acid cycle intermediates. We present gas chromatographic-mass spectrometric assays of phenylacetylglutamine, phenylacetate, and phenylalanine in biological fluids. The compounds are derivatized with dimethylformamide dimethyl acetal. Limits of detection are 0.1 nmol for phenylacetylglutamine and phenylacetate and 2 nmol for phenylalanine. Baseline plasma concentrations of phenylacetate and phenylacetylglutamine and 1 and 3 microM, respectively. The 24-h urinary excretions of phenylacetate and phenylacetylglutamine are about 4 mumol and 1 mmol, respectively. Ingestion of phenylalanine (in the form of aspartame) by a human is followed by sequential increases in phenylacetate and phenylacetylglutamine concentrations in plasma and urine. This assay opens the way to noninvasive probing of the 13C-labeling pattern of liver citric acid cycle intermediates in humans.

  10. Suppression of the allogeneic response by the anti-allergy drug N-(3,4-dimethoxycinnamonyl) anthranilic acid results from T-cell cycle arrest

    PubMed Central

    Zaher, Sarah S; Coe, David; Chai, Jian-Guo; Larkin, Daniel FP; George, Andrew JT

    2013-01-01

    Previously we have shown that indoleamine 2,3-dioxygenase (IDO) and the tryptophan metabolite, 3-hydroxykynurenine (3HK) can prolong corneal allograft survival. IDO modulates the immune response by depletion of the essential amino acid tryptophan by breakdown to kynurenines, which themselves act directly on T lymphocytes. The tryptophan metabolite analogue N-(3,4-dimethoxycinnamonyl) anthranilic acid (DAA, ‘Tranilast’) shares the anthranilic acid core with 3HK. Systemic administration of DAA to mice receiving a fully MHC-mismatched allograft of cornea or skin resulted in significant delay in rejection (median survival of controls 12 days, 13 days for cornea and skin grafts, respectively, and of treated mice 24 days (P < 0·0001) and 17 days (P < 0·03), respectively). We provide evidence that DAA-induced suppression of the allogeneic response, in contrast to that induced by tryptophan metabolites, was a result of cell cycle arrest rather than T-cell death. Cell cycle arrest was mediated by up-regulation of the cell cycle-specific inhibitors p21 and p15, and associated with a significant reduction in interleukin-2 production, allowing us to characterize a novel mechanism for DAA-induced T-cell anergy. Currently licensed as an anti-allergy drug, the oral bioavailability and safe therapeutic profile of DAA make it a candidate for the prevention of rejection of transplanted cornea and other tissues. PMID:23121382

  11. The effect of the menstrual cycle and of decompression stress on arachidonic acid-induced platelet aggregation and on intrinsic platelet thromboxane production in women compared with men.

    PubMed

    Markham, S M; Dubin, N H; Rock, J A

    1991-12-01

    Menstrual cycle variations in platelet aggregation and thromboxane production in association with sex steroids have been reported. External stimuli such as decompression sickness have been associated with clotting activity changes, specifically, increased platelet aggregation. Differences in response of platelets from women and men, when subjected to such a stress, have been observed. This study evaluated the ability of washed platelets from women in the proliferative and secretory phases of the menstrual cycle to aggregate in response to arachidonic acid and the aggregation difference between washed platelets from women and men in response to decompression stress and arachidonic acid. Additionally, platelet thromboxane production differences between the assessed platelet populations were compared. Our results indicate no difference in platelet aggregability between phases of the menstrual cycle. A significant aggregation difference between platelets from women and men was noted. Platelets from women were more sensitive to arachidonic acid aggregation. These differences were not affected by decompression stress. No difference in thromboxane B2 production was noted between the platelet populations evaluated.

  12. A simple mathematical model and practical approach for evaluating citric acid cycle fluxes in perfused rat hearts by 13C-NMR and 1H-NMR spectroscopy.

    PubMed

    Tran-Dinh, S; Hoerter, J A; Mateo, P; Bouet, F; Herve, M

    1997-04-15

    We propose a simple mathematical model and a practical approach for evaluating the flux constant and the absolute value of flux in the citric acid cycle in perfused organs by 13C-NMR and 1H-NMR spectroscopy. We demonstrate that 13C-NMR glutamate spectra are independent of the relative sizes of the mitochondrial and cytosolic compartments and the exchange rates of glutamates, unless there is a difference in 13C chemical shifts of glutamate carbons between the two compartments. Wistar rat hearts (five beating and four KCl-arrested hearts) were aerobically perfused with 100% enriched [2-(13)C]acetate and the kinetics of glutamate carbon labeling from perchloric acid extracts were studied at various perfusion times. Under our experimental conditions, the citric acid cycle flux constant, which represents the fraction of glutamate in exchange with the citric acid cycle per unit time, is about 0.350 +/- 0.003 min(-1) for beating hearts and 0.0741 +/- 0.004 min(-1) for KCl-arrested hearts. The absolute values of the citric acid flux for beating hearts and for KCl-arrested hearts are 1.06 +/- 0.06 micromol x min(-1) x mg(-1) and 0.21 +/- 0.02 micromol x min(-1) x g(-1), respectively. The fraction of unlabeled acetate determined from the proton signal of the methyl group is small and essentially the same in beating and arrested hearts (7.4 +/- 1.7% and 8.8 +/- 2.1%, respectively). Thus, the large difference in the Glu C2/C4 between beating and arrested hearts is not due to the important contribution from anaplerotic sources in arrested hearts but simply to a substantial difference in citric acid cycle fluxes. Our model fits the experimental data well, indicating a fast exchange between 2-oxoglutarate and glutamate in the mitochondria of rat hearts. Analysis of the flux constant, calculated from the half-time of glutamate C4 labeling given in the literature, allows for a comparison of the citric acid flux for various working conditions in different animal species.

  13. Compound specific amino acid δ15N in marine sediments: A new approach for studies of the marine nitrogen cycle

    NASA Astrophysics Data System (ADS)

    Batista, Fabian C.; Ravelo, A. Christina; Crusius, John; Casso, Michael A.; McCarthy, Matthew D.

    2014-10-01

    The nitrogen (N) isotopic composition (δ15N) of bulk sedimentary N (δ15Nbulk) is a common tool for studying past biogeochemical cycling in the paleoceanographic record. Empirical evidence suggests that natural fluctuations in the δ15N of surface nutrient N are reflected in the δ15N of exported planktonic biomass and in sedimentary δ15Nbulk. However, δ15Nbulk is an analysis of total combustible sedimentary N, and therefore also includes mixtures of N sources and/or selective removal or preservation of N-containing compounds. Compound-specific nitrogen isotope analyses of individual amino acids (δ15NAA) are novel measurements with the potential to decouple δ15N changes in nutrient N from trophic effects, two main processes that can influence δ15Nbulk records. As a proof of concept study to examine how δ15NAA can be applied in marine sedimentary systems, we compare the δ15NAA signatures of surface and sinking POM sources with shallow surface sediments from the Santa Barbara Basin, a sub-oxic depositional environmental that exhibits excellent preservation of sedimentary organic matter. Our results demonstrate that δ15NAA signatures of both planktonic biomass and sinking POM are well preserved in such surface sediments. However, we also observed an unexpected inverse correlation between δ15N value of phenylalanine (δ15NPhe; the best AA proxy for N isotopic value at the base of the food web) and calculated trophic position. We used a simple N isotope mass balance model to confirm that over long time scales, δ15NPhe values should in fact be directly dependent on shifts in ecosystem trophic position. While this result may appear incongruent with current applications of δ15NAA in food webs, it is consistent with expectations that paleoarchives will integrate N dynamics over much longer timescales. We therefore propose that for paleoceanographic applications, key δ15NAA parameters are ecosystem trophic position, which determines relative partitioning of 15N

  14. The Effect of Limited Diffusion and Wet-Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids.

    PubMed

    Higgs, Paul G

    2016-01-01

    A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction. PMID:27338479

  15. The Effect of Limited Diffusion and Wet–Dry Cycling on Reversible Polymerization Reactions: Implications for Prebiotic Synthesis of Nucleic Acids

    PubMed Central

    Higgs, Paul G.

    2016-01-01

    A long-standing problem for the origins of life is that polymerization of many biopolymers, including nucleic acids and peptides, is thermodynamically unfavourable in aqueous solution. If bond making and breaking is reversible, monomers and very short oligomers predominate. Recent experiments have shown that wetting and drying cycles can overcome this problem and drive the formation of longer polymers. In the dry phase, bond formation is favourable, but diffusion is restricted, and bonds only form between monomers that are initially close together. In the wet phase, some of the bonds are hydrolyzed. However, repositioning of the molecules allows new bonds to form in the next dry phase, leading to an increase in mean polymer length. Here, we consider a simple theoretical model that explains the effect of cycling. There is an equilibrium length distribution with a high mean length that could be achieved if diffusion occurred freely in the dry phase. This equilibrium is inaccessible without diffusion. A single dry cycle without diffusion leads to mean lengths much shorter than this. Repeated cycling leads to a significant increase in polymerization relative to a single cycle. In the most favourable case, cycling leads to the same equilibrium length distribution as would be achieved if free diffusion were possible in the dry phase. These results support the RNA World scenario by explaining a potential route to synthesis of long RNAs; however, they also imply that cycling would be beneficial to the synthesis of other kinds of polymers, including peptides, where bond formation involves a condensation reaction. PMID:27338479

  16. The puzzle of the Krebs citric acid cycle: assembling the pieces of chemically feasible reactions, and opportunism in the design of metabolic pathways during evolution.

    PubMed

    Meléndez-Hevia, E; Waddell, T G; Cascante, M

    1996-09-01

    The evolutionary origin of the Krebs citric acid cycle has been for a long time a model case in the understanding of the origin and evolution of metabolic pathways: How can the emergence of such a complex pathway be explained? A number of speculative studies have been carried out that have reached the conclusion that the Krebs cycle evolved from pathways for amino acid biosynthesis, but many important questions remain open: Why and how did the full pathway emerge from there? Are other alternative routes for the same purpose possible? Are they better or worse? Have they had any opportunity to be developed in cellular metabolism evolution? We have analyzed the Krebs cycle as a problem of chemical design to oxidize acetate yielding reduction equivalents to the respiratory chain to make ATP. Our analysis demonstrates that although there are several different chemical solutions to this problem, the design of this metabolic pathway as it occurs in living cells is the best chemical solution: It has the least possible number of steps and it also has the greatest ATP yielding. Study of the evolutionary possibilities of each one-taking the available material to build new pathways-demonstrates that the emergence of the Krebs cycle has been a typical case of opportunism in molecular evolution. Our analysis proves, therefore, that the role of opportunism in evolution has converted a problem of several possible chemical solutions into a single-solution problem, with the actual Krebs cycle demonstrated to be the best possible chemical design. Our results also allow us to derive the rules under which metabolic pathways emerged during the origin of life.

  17. Influence of tricarboxylic acid cycle intermediates and related metabolites on the biosynthesis of aflatoxin by resting cells of Aspergillus flavus.

    PubMed

    Shantha, T; Murthy, V S

    1981-11-01

    Resting cells of Aspergillus flavus synthesized aflatoxin from acetate as the sole carbon source after 36 h of incubation. Addition of pyruvate (5.5 mg/m) as cosubstrate to [1-14C]acetate and unlabeled acetate considerably reduced toxin production but increased the radioactivity on the tricarboxylic acid intermediates. This suggests that high tricarboxylic acid activity drastically affected toxin synthesis.

  18. Effects of valproic acid and pioglitazone on cell cycle progression and proliferation of T-cell acute lymphoblastic leukemia Jurkat cells

    PubMed Central

    Jazi, Marie Saghaeian; Mohammadi, Saeed; Yazdani, Yaghoub; Sedighi, Sima; Memarian, Ali; Aghaei, Mehrdad

    2016-01-01

    Objective(s): T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignant tumor. Administration of chemical compounds influencing apoptosis and T cell development has been discussed as promising novel therapeutic strategies. Valproic acid (VPA) as a recently emerged anti-neoplastic histone deacetylase (HDAC) inhibitor and pioglitazone (PGZ) as a high-affinity peroxisome proliferator-activated receptor-gamma (PPARγ) agonist have been shown to induce apoptosis and cell cycle arrest in different studies. Here, we aimed to investigate the underlying molecular mechanisms involved in anti-proliferative effects of these compounds on human Jurkat cells. Materials and Methods: Treated cells were evaluated for cell cycle progression and apoptosis using flowcytometry and MTT viability assay. Real-time RT-PCR was carried out to measure the alterations in key genes associated with cell death and cell cycle arrest. Results: Our findings illustrated that both VPA and PGZ can inhibit Jurkat E6.1 cells in vitro after 24 hr; however, PGZ 400 μM presents the most anti-proliferative effect. Interestingly, treated cells have been arrested in G2/M with deregulated cell division cycle 25A (Cdc25A) phosphatase and cyclin-dependent kinase inhibitor 1B (CDKN1B or p27) expression. Expression of cyclin D1 gene was inhibited when DNA synthesis entry was declined. Cell cycle deregulation in PGZ and VPA-exposed cells generated an increase in the proportion of aneuploid cell population, which has not reported before. Conclusion: These findings define that anti-proliferative effects of PGZ and VPA on Jurkat cell line are mediated by cell cycle deregulation. Thus, we suggest PGZ and VPA may relieve potential therapeutic application against apoptosis-resistant malignancies.

  19. Effect of sodium hypochlorite and peracetic acid on the surface roughness of acrylic resin polymerized by heated water for short and long cycles

    PubMed Central

    Sczepanski, Felipe; Sczepanski, Claudia Roberta Brunnquell; Berger, Sandrine Bittencourt; Consani, Rafael Leonardo Xediek; Gonini-Júnior, Alcides; Guiraldo, Ricardo Danil

    2014-01-01

    Objective: To evaluate the surface roughness of acrylic resin submitted to chemical disinfection via 1% sodium hypochlorite (NaClO) or 1% peracetic acid (C2H4O3). Materials and Methods: The disc-shaped resin specimens (30 mm diameter ×4 mm height) were polymerized by heated water using two cycles (short cycle: 1 h at 74°C and 30 min at 100°C; conventional long cycle: 9 h at 74°C). The release of substances by these specimens in water solution was also quantified. Specimens were fabricated, divided into four groups (n = 10) depending on the polymerization time and disinfectant. After polishing, the specimens were stored in distilled deionized water. Specimens were immersed in 1% NaClO or 1% C2H4O3 for 30 min, and then were immersed in distilled deionized water for 20 min. The release of C2H4O3 and NaClO was measured via visual colorimetric analysis. Roughness was measured before and after disinfection. Roughness data were subjected to two-way ANOVA and Tukey's test. Results: There was no interaction between polymerization time and disinfectant in influencing the average surface roughness (Ra, P = 0.957). Considering these factors independently, there were significant differences between short and conventional long cycles (P = 0.012), but no significant difference between the disinfectants hypochlorite and C2H4O3 (P = 0.366). Visual colorimetric analysis did not detect release of substances. Conclusion: It was concluded that there was the difference in surface roughness between short and conventional long cycles, and disinfection at acrylic resins polymerized by heated water using a short cycle modified the properties of roughness. PMID:25512737

  20. Effects of valproic acid and pioglitazone on cell cycle progression and proliferation of T-cell acute lymphoblastic leukemia Jurkat cells

    PubMed Central

    Jazi, Marie Saghaeian; Mohammadi, Saeed; Yazdani, Yaghoub; Sedighi, Sima; Memarian, Ali; Aghaei, Mehrdad

    2016-01-01

    Objective(s): T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignant tumor. Administration of chemical compounds influencing apoptosis and T cell development has been discussed as promising novel therapeutic strategies. Valproic acid (VPA) as a recently emerged anti-neoplastic histone deacetylase (HDAC) inhibitor and pioglitazone (PGZ) as a high-affinity peroxisome proliferator-activated receptor-gamma (PPARγ) agonist have been shown to induce apoptosis and cell cycle arrest in different studies. Here, we aimed to investigate the underlying molecular mechanisms involved in anti-proliferative effects of these compounds on human Jurkat cells. Materials and Methods: Treated cells were evaluated for cell cycle progression and apoptosis using flowcytometry and MTT viability assay. Real-time RT-PCR was carried out to measure the alterations in key genes associated with cell death and cell cycle arrest. Results: Our findings illustrated that both VPA and PGZ can inhibit Jurkat E6.1 cells in vitro after 24 hr; however, PGZ 400 μM presents the most anti-proliferative effect. Interestingly, treated cells have been arrested in G2/M with deregulated cell division cycle 25A (Cdc25A) phosphatase and cyclin-dependent kinase inhibitor 1B (CDKN1B or p27) expression. Expression of cyclin D1 gene was inhibited when DNA synthesis entry was declined. Cell cycle deregulation in PGZ and VPA-exposed cells generated an increase in the proportion of aneuploid cell population, which has not reported before. Conclusion: These findings define that anti-proliferative effects of PGZ and VPA on Jurkat cell line are mediated by cell cycle deregulation. Thus, we suggest PGZ and VPA may relieve potential therapeutic application against apoptosis-resistant malignancies. PMID:27635203

  1. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver.

    PubMed

    Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

    2016-09-01

    Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver.

  2. An Oral Load of [13C3]Glycerol and Blood NMR Analysis Detect Fatty Acid Esterification, Pentose Phosphate Pathway, and Glycerol Metabolism through the Tricarboxylic Acid Cycle in Human Liver.

    PubMed

    Jin, Eunsook S; Sherry, A Dean; Malloy, Craig R

    2016-09-01

    Drugs and other interventions for high impact hepatic diseases often target biochemical pathways such as gluconeogenesis, lipogenesis, or the metabolic response to oxidative stress. However, traditional liver function tests do not provide quantitative data about these pathways. In this study, we developed a simple method to evaluate these processes by NMR analysis of plasma metabolites. Healthy subjects ingested [U-(13)C3]glycerol, and blood was drawn at multiple times. Each subject completed three visits under differing nutritional states. High resolution (13)C NMR spectra of plasma triacylglycerols and glucose provided new insights into a number of hepatic processes including fatty acid esterification, the pentose phosphate pathway, and gluconeogenesis through the tricarboxylic acid cycle. Fasting stimulated pentose phosphate pathway activity and metabolism of [U-(13)C3]glycerol in the tricarboxylic acid cycle prior to gluconeogenesis or glyceroneogenesis. Fatty acid esterification was transient in the fasted state but continuous under fed conditions. We conclude that a simple NMR analysis of blood metabolites provides an important biomarker of pentose phosphate pathway activity, triacylglycerol synthesis, and flux through anaplerotic pathways in mitochondria of human liver. PMID:27432878

  3. Palladium alpha-lipoic acid complex formulation enhances activities of Krebs cycle dehydrogenases and respiratory complexes I-IV in the heart of aged rats.

    PubMed

    Sudheesh, N P; Ajith, T A; Janardhanan, K K; Krishnan, C V

    2009-08-01

    Age-related decline in the capacity to withstand stress, such as ischemia and reperfusion, results in congestive heart failure. Though the mechanisms underlying cardiac decay are not clear, age dependent somatic damages to mitochondrial DNA (mtDNA), loss of mitochondrial function, and a resultant increase in oxidative stress in heart muscle cells may be responsible for the increased risk for cardiovascular diseases. The effect of a safe nutritional supplement, POLY-MVA, containing the active ingredient palladium alpha-lipoic acid complex, was evaluated on the activities of the Krebs cycle enzymes such as isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase as well as mitochondrial complexes I, II, III, and IV in heart mitochondria of aged male albino rats of Wistar strain. Administration of 0.05 ml/kg of POLY-MVA (which is equivalent to 0.38 mg complexed alpha-lipoic acid/kg, p.o), once daily for 30 days, was significantly (p<0.05) effective to enhance the Krebs cycle dehydrogenases, and mitochondrial electron transport chain complexes. The unique electronic and redox properties of palladium alpha-lipoic acid complex appear to be a key to this physiological effectiveness. The results strongly suggest that this formulation might be effective to protect the aging associated risk of cardiovascular and neurodegenerative diseases.

  4. Metabolic bypass of the tricarboxylic acid cycle during lipid mobilization in germinating oilseeds. Regulation Of nad+-dependent isocitrate dehydrogenase versus fumarase

    PubMed

    Falk; Behal; Xiang; Oliver

    1998-06-01

    Biosynthesis of sucrose from triacylglycerol requires the bypass of the CO2-evolving reactions of the tricarboxylic acid (TCA) cycle. The regulation of the TCA cycle bypass during lipid mobilization was examined. Lipid mobilization in Brassica napus was initiated shortly after imbibition of the seed and proceeded until 2 d postimbibition, as measured by in vivo [1-14C]acetate feeding to whole seedlings. The activity of NAD+-isocitrate dehydrogenase (a decarboxylative enzyme) was not detected until 2 d postimbibition. RNA-blot analysis of B. napus seedlings demonstrated that the mRNA for NAD+-isocitrate dehydrogenase was present in dry seeds and that its level increased through the 4 d of the experiment. This suggested that NAD+-isocitrate dehydrogenase activity was regulated by posttranscriptional mechanisms during early seedling development but was controlled by mRNA level after the 2nd or 3rd d. The activity of fumarase (a component of the nonbypassed section of the TCA cycle) was low but detectable in B. napus seedlings at 12 h postimbibition, coincident with germination, and increased for the next 4 d. RNA-blot analysis suggested that fumarase activity was regulated primarily by the level of its mRNA during germination and early seedling development. It is concluded that posttranscriptional regulation of NAD+-isocitrate dehydrogenase activity is one mechanism of restricting carbon flux through the decarboxylative section of the TCA cycle during lipid mobilization in germinating oilseeds.

  5. Amino acid cycling in the Mississippi River Plume and effects from the passage of Hurricanes Isadore and Lili

    NASA Astrophysics Data System (ADS)

    Bianchi, Thomas S.; Grace, Bryan L.; Carman, Kevin R.; Maulana, Ivan

    2014-08-01

    We present data on the effects of Hurricanes Isadore and Lili on the spatial and temporal variations in concentrations of amino acids, and other bulk dissolved and particulate constituents in surface waters of the Mississippi River Plume (MRP) collected during 3 survey cruises (March 2002, October 2002, and April 2004). Abiotic factors (e.g., particle sorption and sediment resuspension) had the largest contribution in describing DAA and PAA dynamics in the MRP. The range of dissolved organic carbon (DOC) (88.61 to 699.90 μM) and particulate organic carbon (POC) (0.08 to 32.72 μM) values was slightly higher than the range observed for a broader region of the Louisiana shelf, but in general agreed with peak values at the mid-salinity range of the plume. The positive and negative correlations between acidic (e.g., aspartic acid and glutamic acid) and basic (e.g., histidine and arginine) DAA and salinity, respectively, in the MRP, were largely controlled by differential partitioning of amino acids with suspended sediments. Concentrations of β-alanine, γ-aminobutyric acid, and δ-aminovaleric acid were significantly higher during October 2002 compared to spring sampling events, due to resuspension of shelf sediments caused by the recent passage of Hurricane Isadore and the approach of Hurricane Lili, as it entered the Gulf of Mexico during our sampling.

  6. Enoyl-acyl carrier protein reductase (fabI) plays a determinant role in completing cycles of fatty acid elongation in Escherichia coli.

    PubMed

    Heath, R J; Rock, C O

    1995-11-01

    The role of enoyl-acyl carrier protein (ACP) reductase (E.C. 1.3.1.9), the product of the fabI gene, was investigated in the type II, dissociated, fatty acid synthase system of Escherichia coli. All of the proteins required to catalyze one cycle of fatty acid synthesis from acetyl-CoA plus malonyl-CoA to butyryl-ACP in vitro were purified. These proteins were malonyl-CoA:ACP transacylase (fabD), beta-ketoacyl-ACP synthase III (fabH), beta-ketoacyl-ACP reductase (fabG), beta-hydroxydecanoyl-ACP dehydrase (fabA), and enoyl-ACP reductase (fabI). Unlike the other enzymes in the cycle, FabA did not efficiently convert its substrate beta-hydroxybutyryl-ACP to crotonyl-ACP, but rather the equilibrium favored formation of beta-hydroxybutyryl-ACP over crotonyl-ACP by a ratio of 9:1. The amount of butyryl-ACP formed depended on the amount of FabI protein added to the assay. Extracts from fabI(Ts) mutants accumulated beta-hydroxybutyryl-ACP, and the addition of FabI protein to the fabI(Ts) extract restored both butyryl-ACP and long-chain acyl-ACP synthesis. FabI was verified to be the only enoyl-ACP reductase required for the synthesis of fatty acids by demonstrating that purified FabI was required for the elongation of both long-chain saturated and unsaturated fatty acids. These results were corroborated by analysis of the intracellular ACP pool composition in fabI(Ts) mutants that showed beta-hydroxybutyryl-ACP and crotonyl-ACP accumulated at the nonpermissive temperature in the same ratio found in the fabI(Ts) extracts and in the in vitro reconstruction experiments that lacked FabI. We conclude that FabI is the only enoyl-ACP reductase involved in fatty acid synthesis in E. coli and that the activity of this enzyme plays a determinant role in completing cycles of fatty acid biosynthesis.

  7. High cycling stability of anodes for lithium-ion batteries based on Fe3O4 nanoparticles and poly(acrylic acid) binder

    NASA Astrophysics Data System (ADS)

    Maroni, F.; Gabrielli, S.; Palmieri, A.; Marcantoni, E.; Croce, F.; Nobili, F.

    2016-11-01

    Fe3O4 nanoparticles synthesized by a base catalyzed method are tested as anode material for Li-ion batteries. The pristine nanoparticles are morphologically characterized showing an average size of 11 nm. Electrodes are prepared using high-molecular weight Poly (acrylic acid) as improved binder and ethanol as low cost and environmentally friendly solvent. The evaluation of electrochemical properties shows high specific capacity values of 857 mA hg-1 after 200 cycles at a specific current of 462 mAg-1, as well as an excellent rate capability with specific current values up to 18480 mAg-1. To the best of our knowledge, this is the first report of Fe3O4 nanoparticles cycling with PAA as binder.

  8. A CRADLE TO GATE LIFE CYCLE ANALYSIS OF THE BIOPOLYMER POLYLACTIC ACID: LOOKING BEYOND GLOBAL WARMING AND FOSSIL FUEL USE

    EPA Science Inventory

    Derived from corn, the biopolymer polylactic acid (PLA) has recently emerged in the marketplace and is advertised as a sustainable alternative to petroleum-based polymers. Research into the environmental implications of biobased production has focused primarily on global warming...

  9. Reversible effect of all-trans-retinoic acid on AML12 hepatocyte proliferation and cell cycle progression

    EPA Science Inventory

    The role of all-trans-retinoic acid (atRA) in the regulation of cellular proliferation and differentiation is well documented. Numerous studies have established the cancer preventive propertiesofatRAwhichfunctionstoregulate levels ofcellcycleproteinsessentialfortheGliS transition...

  10. Effects of continuous triiodothyronine infusion on the tricarboxylic acid cycle in the normal immature swine heart under extracorporeal membrane oxygenation in vivo

    PubMed Central

    Kajimoto, Masaki; O'Kelly Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy; Olson, Aaron K.

    2014-01-01

    Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO-induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age: 25–38 days) with ECMO received [2-13C]lactate, [2,4,6,8-13C4]octanoate (medium-chain fatty acid), and [U-13C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 min of each protocol. NMR analysis of left ventricular tissue determined the fractional contribution of these substrates to the tricarboxylic acid cycle. Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg·kg−1·h−1) during ECMO. Under both substrate loading conditions, T3 significantly increased the fractional contribution of lactate with a marginal increase in the fractional contribution of octanoate. Both T3 and high substrate provision increased the myocardial energy status, as indexed by phosphocreatine concentration/ATP concentration. In conclusion, T3 supplementation promoted lactate metabolism to the tricarboxylic acid cycle during ECMO, suggesting that T3 releases the inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve the resting energy state and facilitate weaning. PMID:24531815

  11. Effects of continuous triiodothyronine infusion on the tricarboxylic acid cycle in the normal immature swine heart under extracorporeal membrane oxygenation in vivo.

    PubMed

    Kajimoto, Masaki; Priddy, Colleen M O'Kelly; Ledee, Dolena R; Xu, Chun; Isern, Nancy; Olson, Aaron K; Portman, Michael A

    2014-04-15

    Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO-induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age: 25-38 days) with ECMO received [2-(13)C]lactate, [2,4,6,8-(13)C4]octanoate (medium-chain fatty acid), and [U-(13)C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 min of each protocol. NMR analysis of left ventricular tissue determined the fractional contribution of these substrates to the tricarboxylic acid cycle. Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg·kg(-1)·h(-1)) during ECMO. Under both substrate loading conditions, T3 significantly increased the fractional contribution of lactate with a marginal increase in the fractional contribution of octanoate. Both T3 and high substrate provision increased the myocardial energy status, as indexed by phosphocreatine concentration/ATP concentration. In conclusion, T3 supplementation promoted lactate metabolism to the tricarboxylic acid cycle during ECMO, suggesting that T3 releases the inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve the resting energy state and facilitate weaning.

  12. Comparison of Optimal Thermodynamic Models of the Tricarboxylic Acid Cycle from Heterotrophs, Cyanobacteria, and Green Sulfur Bacteria

    SciTech Connect

    Thomas, Dennis G.; Jaramillo Riveri, Sebastian I.; Baxter, Douglas J.; Cannon, William R.

    2014-12-15

    We have applied a new stochastic simulation approach to predict the metabolite levels, energy flow, and material flux in the different oxidative TCA cycles found in E. coli and Synechococcus sp. PCC 7002, and in the reductive TCA cycle typical of chemolithoautotrophs and phototrophic green sulfur bacteria such as Chlorobaculum tepidum. The simulation approach is based on equations of state and employs an assumption similar to that used in transition state theory. The ability to evaluate the thermodynamics of metabolic pathways allows one to understand the relationship between coupling of energy and material gradients in the environment and the selforganization of stable biological systems, and it is shown that each cycle operates in the direction expected due to its environmental niche. The simulations predict changes in metabolite levels and flux in response to changes in cofactor concentrations that would be hard to predict without an elaborate model based on the law of mass action. In fact, we show that a thermodynamically unfavorable reaction can still have flux in the forward direction when it is part of a reaction network. The ability to predict metabolite levels, energy flow and material flux should be significant for understanding the dynamics of natural systems and for understanding principles for engineering organisms for production of specialty chemicals, such as biofuels.

  13. Palmitic Acid-Induced Neuron Cell Cycle G2/M Arrest and Endoplasmic Reticular Stress through Protein Palmitoylation in SH-SY5Y Human Neuroblastoma Cells

    PubMed Central

    Hsiao, Yung-Hsuan; Lin, Ching-I; Liao, Hsiang; Chen, Yue-Hua; Lin, Shyh-Hsiang

    2014-01-01

    Obesity-related neurodegenerative diseases are associated with elevated saturated fatty acids (SFAs) in the brain. An increase in SFAs, especially palmitic acid (PA), triggers neuron cell apoptosis, causing cognitive function to deteriorate. In the present study, we focused on the specific mechanism by which PA triggers SH-SY5Y neuron cell apoptosis. We found that PA induces significant neuron cell cycle arrest in the G2/M phase in SH-SY5Y cells. Our data further showed that G2/M arrest is involved in elevation of endoplasmic reticular (ER) stress according to an increase in p-eukaryotic translation inhibition factor 2α, an ER stress marker. Chronic exposure to PA also accelerates beta-amyloid accumulation, a pathological characteristic of Alzheimer’s disease. Interestingly, SFA-induced ER stress, G2/M arrest and cell apoptosis were reversed by treatment with 2-bromopalmitate, a protein palmitoylation inhibitor. These findings suggest that protein palmitoylation plays a crucial role in SFA-induced neuron cell cycle G2/M arrest, ER stress and apoptosis; this provides a novel strategy for preventing SFA-induced neuron cell dysfunction. PMID:25402647

  14. Synthesis of polyhydroxyalkanoates from glucose that contain medium-chain-length monomers via the reversed fatty acid β-oxidation cycle in Escherichia coli.

    PubMed

    Zhuang, Qianqian; Wang, Qian; Liang, Quanfeng; Qi, Qingsheng

    2014-07-01

    Polyhydroxyalkanoates that contain the medium-chain-length monomers (mcl-PHAs) have a wide range of applications owing to their superior physical and mechanical properties. A challenge to synthesize such mcl-PHAs from unrelated and renewable sources is exploiting the efficient metabolic pathways that lead to the formation of precursor (R)-3-hydroxyacyl-CoA. Here, by engineering the reversed fatty acid β-oxidation cycle, we were able to synthesize mcl-PHAs in Escherichia coli directly from glucose. After deletion of the major thioesterases, the engineered E. coli produced 6.62wt% of cell dry weight mcl-PHA heteropolymers. Furthermore, when a low-substrate-specificity PHA synthase from Pseudomonas stutzeri 1317 was employed, recombinant E. coli synthesized 12.10wt% of cell dry weight scl-mcl PHA copolymers, of which 21.18mol% was 3-hydroxybutyrate and 78.82mol% was medium-chain-length monomers. The reversed fatty acid β-oxidation cycle offered an efficient metabolic pathway for mcl-PHA biosynthesis in E. coli and can be further optimized.

  15. Investigation of the Effects of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) on Apoptosis and Cell Cycle in a Zebrafish (Danio rerio) Liver Cell Line

    PubMed Central

    Cui, Yuan; Liu, Wei; Xie, Wenping; Yu, Wenlian; Wang, Cheng; Chen, Huiming

    2015-01-01

    This study aimed to explore the effects of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) on apoptosis and cell cycle in a zebrafish (Danio rerio) liver cell line (ZFL). Treatment groups included a control group, PFOA-IC50, PFOA-IC80, PFOS-IC50 and PFOS-IC80 groups. IC50 and IC80 concentrations were identified by cellular modeling and MTT assays. mRNA levels of p53, Bcl-2, Bax, Caspase-3 and NF-κB p65 were detected by qPCR. Cell apoptosis and cell cycle were detected by flow cytometry and the protein levels of p53, Bcl-2, Bax, Caspase-3 and NF-κB p65 were determined by western blotting. Both PFOA and PFOS inhibited the growth of zebrafish liver cells, and the inhibition rate of PFOS was higher than that of PFOA. Bcl-2 expression levels in the four groups were significantly higher than the control group and Bcl-2 increased significantly in the PFOA-IC80 group. However, the expression levels of Bax in the four treatment groups were higher than the control group. The percentage of cell apoptosis increased significantly with the treatment of PFOA and PFOS (p < 0.05). Cell cycle and cell proliferation were blocked in both the PFOA-IC80 and PFOS-IC80 groups, indicating that PFOA-IC80 and PFOS-IC50 enhanced apoptosis in ZFL cells. PMID:26690195

  16. A specialized citric acid cycle requiring succinyl-coenzyme A (CoA):acetate CoA-transferase (AarC) confers acetic acid resistance on the acidophile Acetobacter aceti.

    PubMed

    Mullins, Elwood A; Francois, Julie A; Kappock, T Joseph

    2008-07-01

    Microbes tailor macromolecules and metabolism to overcome specific environmental challenges. Acetic acid bacteria perform the aerobic oxidation of ethanol to acetic acid and are generally resistant to high levels of these two membrane-permeable poisons. The citric acid cycle (CAC) is linked to acetic acid resistance in Acetobacter aceti by several observations, among them the oxidation of acetate to CO2 by highly resistant acetic acid bacteria and the previously unexplained role of A. aceti citrate synthase (AarA) in acetic acid resistance at a low pH. Here we assign specific biochemical roles to the other components of the A. aceti strain 1023 aarABC region. AarC is succinyl-coenzyme A (CoA):acetate CoA-transferase, which replaces succinyl-CoA synthetase in a variant CAC. This new bypass appears to reduce metabolic demand for free CoA, reliance upon nucleotide pools, and the likely effect of variable cytoplasmic pH upon CAC flux. The putative aarB gene is reassigned to SixA, a known activator of CAC flux. Carbon overflow pathways are triggered in many bacteria during metabolic limitation, which typically leads to the production and diffusive loss of acetate. Since acetate overflow is not feasible for A. aceti, a CO(2) loss strategy that allows acetic acid removal without substrate-level (de)phosphorylation may instead be employed. All three aar genes, therefore, support flux through a complete but unorthodox CAC that is needed to lower cytoplasmic acetate levels.

  17. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

  18. [The function of mitochondrion, carnitine, coenzyme-A, fat acids, glucose, the Randle cycle and insulin: a lecture].

    PubMed

    Titov, V N

    2012-02-01

    In the function of feeding as biologic function of trophology, occurs the interchange of biologic reactions of exotrophy (postprandial hyperglycemia and hyperlipidemia) and periods of food absence (biologic reaction of endotrophy). The action of insulin is realized in the biologic reaction of exotrophy only. The phylogenetic late insulin manages the function of phylogenetic early mitochondrion in the biologic reaction of exotrophy. In the biologic reaction of exotrophy, the cells activatedly absorb glucose under effect of insulin through glucose carriers-4 and actively absorb fat acids in the form of nonpolar triglycerides in olein lipoproteins of very low density by force of receptor endocytosis. These mechanisms formed on late stages of phylogenesis in the becoming of biologic function of locomotion--the function of movement. In the biologic reaction of endotrophy the cells absorb passively glucose under effect of glycaemia in intercellular medium through glucose carriers and passively (on gradient of concentration) absorb the fat acids in polar form under passive diffusion through plasmatic membrane. These reactions are worked out on the early stages of phylogenesis in the becoming of biologic function of homeostasis. The syndrome of resistance to insulin is formed only in biologic reaction of exotrophy but the disorders can persist and during realization of biologic reaction of endotrophy. In the biologic reaction of exotrophy insulin "decides": a) glucose can be deposited only in a limited way and can be consumed (oxidized in mitochondrion) in the first instance: b) fat acids can be stored and kept to be used in biologic function of locomotion. In the biologic reaction of exotrophy insulin "endeavors" as fast and full as possible use glucose and preserve in vivo as much as possible of fat acids as a substratum for further realization of biologic function of locomotion. Insulin minimizes in cytosol the content of a) ketone bodies - metabolites of C4 butyric fat

  19. Tranexamic Acid

    MedlinePlus

    ... is used to treat heavy bleeding during the menstrual cycle (monthly periods) in women. Tranexamic acid is in ... tablets for more than 5 days in a menstrual cycle or take more than 6 tablets in a ...

  20. Impairment of glutamine/glutamate-γ-aminobutyric acid cycle in manganese toxicity in the central nervous system.

    PubMed

    Sidoryk-Wegrzynowicz, M

    2014-01-01

    Manganese (Mn) is an essential trace element that is required for maintaining the proper function and regulation of many biochemical and cellular reactions. Despite its essentiality, at excessive levels Mn is toxic to the central nervous system. The overdose accumulation of Mn in specific brain areas, such as the substantia nigra, the globus pallidus and the striatum, triggers neurotoxicity resulting in a neurological brain disorder, referred to as manganism. Manganese toxicity is associated with the disruption of glutamine (Gln)/glutamate (Glu) GABA cycle (GGC). The GGC represents a complex process, since Gln efflux from astrocytes must be met by its influx in neurons. Mn toxicity is associated with the disruption of both of these critical points in the cycle. In cultured astrocytes, pre-treatment with Mn inhibits the initial net uptake of Gln in a concentration-dependent manner. Manganese added directly to astrocytes induces deregulation in the expression of SNAT3, SNAT2, ASCT2 and LAT2 transporters and significantly decreases in Gln uptake mediated by the transporting Systems N and ASC, and a decrease in Gln efflux mediated by Systems N, ASC and L. Further, Mn disrupts Glu transporting systems leading to both a reduction in Glu uptake and elevation in extracellular Glu levels. Interestingly, there appear to be common signaling targets of Mn in GGC cycling in glial cells. Namely, the PKC signaling is affected by Mn in Gln and Glu transporters expression and function. Additionally, Mn was identified to deregulate glutamine synthetase (GS) expression and activity. Those evidences could triggers depletion of Gln synthesis/metabolism in glia cells and consequently diminish astrocytic-derived glutamine, while disruption of Glu removal/transport can mediate dyshomeostasis in neurotransmission of functioning neurons. Overdose and excessive Mn accumulations in astrocytes not only culminate in pathology, but also affect astrocytic protective properties and defect or

  1. Impairment of glutamine/glutamate-γ-aminobutyric acid cycle in manganese toxicity in the central nervous system.

    PubMed

    Sidoryk-Wegrzynowicz, M

    2014-01-01

    Manganese (Mn) is an essential trace element that is required for maintaining the proper function and regulation of many biochemical and cellular reactions. Despite its essentiality, at excessive levels Mn is toxic to the central nervous system. The overdose accumulation of Mn in specific brain areas, such as the substantia nigra, the globus pallidus and the striatum, triggers neurotoxicity resulting in a neurological brain disorder, referred to as manganism. Manganese toxicity is associated with the disruption of glutamine (Gln)/glutamate (Glu) GABA cycle (GGC). The GGC represents a complex process, since Gln efflux from astrocytes must be met by its influx in neurons. Mn toxicity is associated with the disruption of both of these critical points in the cycle. In cultured astrocytes, pre-treatment with Mn inhibits the initial net uptake of Gln in a concentration-dependent manner. Manganese added directly to astrocytes induces deregulation in the expression of SNAT3, SNAT2, ASCT2 and LAT2 transporters and significantly decreases in Gln uptake mediated by the transporting Systems N and ASC, and a decrease in Gln efflux mediated by Systems N, ASC and L. Further, Mn disrupts Glu transporting systems leading to both a reduction in Glu uptake and elevation in extracellular Glu levels. Interestingly, there appear to be common signaling targets of Mn in GGC cycling in glial cells. Namely, the PKC signaling is affected by Mn in Gln and Glu transporters expression and function. Additionally, Mn was identified to deregulate glutamine synthetase (GS) expression and activity. Those evidences could triggers depletion of Gln synthesis/metabolism in glia cells and consequently diminish astrocytic-derived glutamine, while disruption of Glu removal/transport can mediate dyshomeostasis in neurotransmission of functioning neurons. Overdose and excessive Mn accumulations in astrocytes not only culminate in pathology, but also affect astrocytic protective properties and defect or

  2. Changes in urinary amino acids excretion in relationship with muscle activity markers over a professional cycling stage race: in search of fatigue markers.

    PubMed

    Corsetti, Roberto; Barassi, Alessandra; Perego, Silvia; Sansoni, Veronica; Rossi, Alessandra; Damele, Clara Anna Linda; Melzi D'Eril, Gianlodovico; Banfi, Giuseppe; Lombardi, Giovanni

    2016-01-01

    The aim of this study was to identify the relationship between metabolic effort, muscular damage/activity indices, and urinary amino acids profile over the course of a strenuous prolonged endurance activity, as a cycling stage race is, in order to identify possible fatigue markers. Nine professional cyclists belonging to a single team, competing in the Giro d'Italia cycling stage race, were anthropometrically characterized and sampled for blood and urine the day before the race started, and on days 12 and 23 of the race. Diet was kept the same over the race, and power output and energy expenditure were recorded. Sera were assayed for muscle markers (lactate dehydrogenase, aspartate aminotransferase, and creatine kinase activities, and blood urea nitrogen), and creatinine, all corrected for plasma volume changes. Urines were profiled for amino acid concentrations, normalized on creatinine excretion. Renal function, in terms of glomerular filtration rate, was monitored by MDRD equation corrected on body surface area. Creatine kinase activity and blood urea were increased during the race as did serum creatinine while kidney function remained stable. Among the amino acids, taurine, glycine, cysteine, leucine, carnosine, 1-methyl histidine, and 3-methyl histidine showed a net decreased, while homocysteine was increased. Taurine and the dipeptide carnosine (β-alanyl-L-histidine) were significantly correlated with the muscle activity markers and the indices of effort. In conclusion, the metabolic profile is modified strikingly due to the effort. Urinary taurine and carnosine seem useful tools to evaluate the muscle damage and possibly the fatigue status on a long-term basis. PMID:26306846

  3. Changes in urinary amino acids excretion in relationship with muscle activity markers over a professional cycling stage race: in search of fatigue markers.

    PubMed

    Corsetti, Roberto; Barassi, Alessandra; Perego, Silvia; Sansoni, Veronica; Rossi, Alessandra; Damele, Clara Anna Linda; Melzi D'Eril, Gianlodovico; Banfi, Giuseppe; Lombardi, Giovanni

    2016-01-01

    The aim of this study was to identify the relationship between metabolic effort, muscular damage/activity indices, and urinary amino acids profile over the course of a strenuous prolonged endurance activity, as a cycling stage race is, in order to identify possible fatigue markers. Nine professional cyclists belonging to a single team, competing in the Giro d'Italia cycling stage race, were anthropometrically characterized and sampled for blood and urine the day before the race started, and on days 12 and 23 of the race. Diet was kept the same over the race, and power output and energy expenditure were recorded. Sera were assayed for muscle markers (lactate dehydrogenase, aspartate aminotransferase, and creatine kinase activities, and blood urea nitrogen), and creatinine, all corrected for plasma volume changes. Urines were profiled for amino acid concentrations, normalized on creatinine excretion. Renal function, in terms of glomerular filtration rate, was monitored by MDRD equation corrected on body surface area. Creatine kinase activity and blood urea were increased during the race as did serum creatinine while kidney function remained stable. Among the amino acids, taurine, glycine, cysteine, leucine, carnosine, 1-methyl histidine, and 3-methyl histidine showed a net decreased, while homocysteine was increased. Taurine and the dipeptide carnosine (β-alanyl-L-histidine) were significantly correlated with the muscle activity markers and the indices of effort. In conclusion, the metabolic profile is modified strikingly due to the effort. Urinary taurine and carnosine seem useful tools to evaluate the muscle damage and possibly the fatigue status on a long-term basis.

  4. Effect of cell cycle phase on the sensitivity of SAS cells to sonodynamic therapy using low-intensity ultrasound combined with 5-aminolevulinic acid in vitro.

    PubMed

    Li, Nan; Sun, Miao; Wang, Yao; Lv, Yanhong; Hu, Zheng; Cao, Wenwu; Zheng, Jinhua; Jiao, Xiaohui

    2015-08-01

    Sonodynamic therapy (SDT) with 5-aminolevulinic acid (5-ALA) can effectively inhibit various types of tumor in vitro and in vivo. However, the association between the efficacy of SDT and the phase of the cell cycle remains to be elucidated. 5-ALA may generate different quantities of sonosensitizer, protoporphyrin IX (PpIX), in different phases of the cell cycle, which may result in differences in sensitivity to 5-ALA-induced SDT. The present study aimed to investigate the effect of the cell cycle on the susceptibility of SAS cells to SDT following synchronization to different cell cycle phases. These results indicates that the rates of cell death and apoptosis of the SAS cells in the S and G2/M phases were significantly higher following SDT, compared with those in the G1-phase cells and unsynchronized cells, with a corresponding increase in PpIX in the S and G2/M cells. In addition, the expression of caspase-3 increased, while that of B-cell lymphoma (Bcl)-2 decreased markedly in theS and G2/M cells following SDT. Cyclin A was also expressed at higher levels in the S and G2/M cells, compared with the G1-phase cells. SDT also caused a significant upregulation of cyclin A in all phases of the cell cycle, however this was most marked in the S and G2/M cells. It was hypothesized that high expression levels of cyclin A in the S and G2/M cells may promote the induction of caspase-3 and reduce the induction of Bcl-2 by SDT and, therefore, enhance apoptosis. Taken together, these data demonstrated that cells in The S and G2/M phases generate more intracellular PpIX, have higher levels of cyclin A and are, therefore, more sensitive to SDT-induced cytotoxicity. These findings indicate the potential novel approach to preventing the onset of cancer by combining cell-cycle regulators with SDT. This sequential combination therapy may be a simple and cost-effective way of enhancing the effects of SDT in clinical settings.

  5. Development of an electrode for lead-acid batteries possessing a high electrochemical utilization factor and invariable cycling characteristics

    NASA Astrophysics Data System (ADS)

    Yolshina, L. A.; Kudyakov, V. Ya.; Zyryanov, V. G.

    Investigations have been carried out on the deposition of compact lead layers on the surfaces of various metallic substrates. It is shown that the lead coatings so obtained are non-uniform in thickness and feature high porosities. The lead-film electrode thus produced on the surface of a fine copper grid can be used as a positive electrode in the lead-acid battery.

  6. Abscisic Acid Participates in the Control of Cell Cycle Initiation Through Heme Homeostasis in the Unicellular Red Alga Cyanidioschyzon merolae.

    PubMed

    Kobayashi, Yuki; Ando, Hiroyuki; Hanaoka, Mitsumasa; Tanaka, Kan

    2016-05-01

    ABA is a phytohormone that is synthesized in response to abiotic stresses and other environmental changes, inducing various physiological responses. While ABA has been found in unicellular photosynthetic organisms, such as cyanobacteria and eukaryotic algae, its function in these organisms is poorly understood. Here, we found that ABA accumulated in the unicellular red alga Cyanidioschyzon merolae under conditions of salt stress and that the cell cycle G1/S transition was inhibited when ABA was added to the culture medium. A gene encoding heme-scavenging tryptophan-rich sensory protein-related protein (CmTSPO; CMS231C) was positively regulated by ABA, as in Arabidopsis, and CmTSPO bound heme in vitro. The intracellular content of total heme was increased by addition of ABA, but unfettered heme decreased, presumably due to scavenging by CmTSPO. The inhibition of DNA replication by ABA was negated by addition of heme to the culture medium. Thus, we propose a regulatory role for ABA and heme in algal cell cycle initiation. Finally, we found that a C. merolae mutant that is defective in ABA production was more susceptible to salt stress, indicating the importance of ABA to stress resistance in red algae. PMID:27044672

  7. Comamonas testosteroni uses a chemoreceptor for tricarboxylic acid cycle intermediates to trigger chemotactic responses towards aromatic compounds.

    PubMed

    Ni, Bin; Huang, Zhou; Fan, Zheng; Jiang, Cheng-Ying; Liu, Shuang-Jiang

    2013-11-01

    Bacterial chemotaxis towards aromatic compounds has been frequently observed; however, knowledge of how bacteria sense aromatic compounds is limited. Comamonas testosteroni CNB-1 is able to grow on a range of aromatic compounds. This study investigated the chemotactic responses of CNB-1 to 10 aromatic compounds. We constructed a chemoreceptor-free, non-chemotactic mutant, CNB-1Δ20, by disruption of all 19 putative methyl-accepting chemotaxis proteins (MCPs) and the atypical chemoreceptor in strain CNB-1. Individual complementation revealed that a putative MCP (tagged MCP2201) was involved in triggering chemotaxis towards all 10 aromatic compounds. The recombinant sensory domain of MCP2201 did not bind to 3- or 4-hydroxybenzoate, protocatechuate, catechol, benzoate, vanillate and gentisate, but bound oxaloacetate, citrate, cis-aconitate, isocitrate, α-ketoglutarate, succinate, fumarate and malate. The mutant CNB-1ΔpmdF that lost the ability to metabolize 4-hydroxybenzoate and protocatechuate also lost its chemotactic response to these compounds, suggesting that taxis towards aromatic compounds is metabolism-dependent. Based on the ligand profile, we proposed that MCP2201 triggers taxis towards aromatic compounds by sensing TCA cycle intermediates. Our hypothesis was further supported by the finding that introduction of the previously characterized pseudomonad chemoreceptor (McpS) for TCA cycle intermediates into CNB-1Δ20 likewise triggered chemotaxis towards aromatic compounds.

  8. Rhizosphere bacterial carbon turnover is higher in nucleic acids than membrane lipids: implications for understanding soil carbon cycling

    PubMed Central

    Malik, Ashish A.; Dannert, Helena; Griffiths, Robert I.; Thomson, Bruce C.; Gleixner, Gerd

    2015-01-01

    Using a pulse chase 13CO2 plant labeling experiment we compared the flow of plant carbon into macromolecular fractions of rhizosphere soil microorganisms. Time dependent 13C dilution patterns in microbial cellular fractions were used to calculate their turnover time. The turnover times of microbial biomolecules were found to vary: microbial RNA (19 h) and DNA (30 h) turned over fastest followed by chloroform fumigation extraction-derived soluble cell lysis products (14 days), while phospholipid fatty acids (PLFAs) had the slowest turnover (42 days). PLFA/NLFA 13C analyses suggest that both mutualistic arbuscular mycorrhizal and saprophytic fungi are dominant in initial plant carbon uptake. In contrast, high initial 13C enrichment in RNA hints at bacterial importance in initial C uptake due to the dominance of bacterial derived RNA in total extracts of soil RNA. To explain this discrepancy, we observed low renewal rate of bacterial lipids, which may therefore bias lipid fatty acid based interpretations of the role of bacteria in soil microbial food webs. Based on our findings, we question current assumptions regarding plant-microbe carbon flux and suggest that the rhizosphere bacterial contribution to plant assimilate uptake could be higher. This highlights the need for more detailed quantitative investigations with nucleic acid biomarkers to further validate these findings. PMID:25914679

  9. Acid rock drainage and rock weathering in Antarctica: important sources for iron cycling in the Southern Ocean.

    PubMed

    Dold, B; Gonzalez-Toril, E; Aguilera, A; Lopez-Pamo, E; Cisternas, M E; Bucchi, F; Amils, R

    2013-06-18

    Here we describe biogeochemical processes that lead to the generation of acid rock drainage (ARD) and rock weathering on the Antarctic landmass and describe why they are important sources of iron into the Antarctic Ocean. During three expeditions, 2009-2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2-4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe(2+)) and as superficial runoff (as Fe(3+)) into the sea, the latter with the formation of schwertmannite in the sea-ice. The formation of ARD in the Antarctic was catalyzed by acid mine drainage microorganisms found in cold climates, including Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 10(9) g DFe yr(-1) for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of magnitude as glacial or aeolian input to the Southern Ocean. Additionally, the two ARD sites alone liberate 0.026 and 0.057 × 10(9) g DFe yr(-1) as point sources to the sea. The increased iron input correlates with increased phytoplankton production close to the source. This might even be enhanced in the future by a global warming scenario, and could be a process counterbalancing global warming. PMID:23682976

  10. Acid rock drainage and rock weathering in Antarctica: important sources for iron cycling in the Southern Ocean.

    PubMed

    Dold, B; Gonzalez-Toril, E; Aguilera, A; Lopez-Pamo, E; Cisternas, M E; Bucchi, F; Amils, R

    2013-06-18

    Here we describe biogeochemical processes that lead to the generation of acid rock drainage (ARD) and rock weathering on the Antarctic landmass and describe why they are important sources of iron into the Antarctic Ocean. During three expeditions, 2009-2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2-4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe(2+)) and as superficial runoff (as Fe(3+)) into the sea, the latter with the formation of schwertmannite in the sea-ice. The formation of ARD in the Antarctic was catalyzed by acid mine drainage microorganisms found in cold climates, including Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 10(9) g DFe yr(-1) for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of magnitude as glacial or aeolian input to the Southern Ocean. Additionally, the two ARD sites alone liberate 0.026 and 0.057 × 10(9) g DFe yr(-1) as point sources to the sea. The increased iron input correlates with increased phytoplankton production close to the source. This might even be enhanced in the future by a global warming scenario, and could be a process counterbalancing global warming.

  11. Metal and acidity fluxes controlled by precipitation/dissolution cycles of sulfate salts in an anthropogenic mine aquifer

    NASA Astrophysics Data System (ADS)

    Cánovas, C. R.; Macías, F.; Pérez-López, R.

    2016-05-01

    Underground mine drainages are extremely difficult to study due to the lack of information about the flow path and source proximity in relation to the outflow adit. Geochemical processes controlling metals and acidity fluxes in a complex anthropogenic mine aquifer in SW Spain during the dry and rainy season were investigated by geochemical and statistical tools. High concentrations of acidity, sulfate, metals and metalloids (e.g. Fe, Cu, Zn, As, Cd, Ni, Co) were observed due to intense sulfide oxidation processes. The high residence time inside the anthropogenic aquifer, around 40 days, caused the release of significant quantities of metals linked to host rocks (e.g. Al, Ca, Ge, Li, Mg, REE). The most outstanding characteristic of the acid mine drainage (AMD) outflows is the existence of higher Fe/SO4 molar ratios than those theoretical of pyrite (0.50) during most of the monitored period, due to a fire which occurred in 1949 and remained active for decades. Permanent and temporal retention mechanisms of acidity and metals were observed in the galleries. Once released from sulfide oxidation, Pb and As are sorbed on Fe oxyhydroxysulfate or precipitated as low solubility minerals (i.e. anglesite) inside the galleries. The precipitation of evaporitic sulfate salts during the dry season and the subsequent re-dissolution after rainfall control the fluxes of acidity and main metals (i.e. Fe, Mg, Al) from this anthropogenic aquifer. Some elements, such as Cd, Cu, Ni, REE and Zn, are retained in highly soluble sulfate salts while other elements, such as Ge, Pb and Sc, have a lower response to washout processes due to its incorporation in less soluble sulfate salts. In this way, metal concentration during the washout processes would be controlled by the proportion and solubility of each type of evaporitic sulfate salt stored during the dry season. The recovery of metals of economic interest contained in the AMD could help to self-finance the remediation of these waters in

  12. Oxo-4-methylpentanoic acid directs the metabolism of GABA into the Krebs cycle in rat pancreatic islets.

    PubMed

    Hernández-Fisac, Inés; Fernández-Pascual, Sergio; Ortsäter, Henrik; Pizarro-Delgado, Javier; Martín del Río, Rafael; Bergsten, Peter; Tamarit-Rodriguez, Jorge

    2006-11-15

    OMP (oxo-4-methylpentanoic acid) stimulates by itself a biphasic secretion of insulin whereas L-leucine requires the presence of L-glutamine. L-Glutamine is predominantly converted into GABA (gamma-aminobutyric acid) in rat islets and L-leucine seems to promote its metabolism in the 'GABA shunt' [Fernández-Pascual, Mukala-Nsengu-Tshibangu, Martín del Río and Tamarit-Rodríguez (2004) Biochem. J. 379, 721-729]. In the present study, we have investigated how 10 mM OMP affects L-glutamine metabolism to uncover possible differences with L-leucine that might help to elucidate whether they share a common mechanism of stimulation of insulin secretion. In contrast with L-leucine, OMP alone stimulated a biphasic insulin secretion in rat perifused islets and decreased the islet content of GABA without modifying its extracellular release irrespective of the concentration of L-glutamine in the medium. GABA was transaminated to L-leucine whose intracellular concentration did not change because it was efficiently transported out of the islet cells. The L-[U-14C]-Glutamine (at 0.5 and 10.0 mM) conversion to 14CO2 was enhanced by 10 mM OMP within 30% and 70% respectively. Gabaculine (250 microM), a GABA transaminase inhibitor, suppressed OMP-induced oxygen consumption but not L-leucine- or glucose-stimulated respiration. It also suppressed the OMP-induced decrease in islet GABA content and the OMP-induced increase in insulin release. These results support the view that OMP promotes islet metabolism in the 'GABA shunt' generating 2-oxo-glutarate, in the branched-chain alpha-amino acid transaminase reaction, which would in turn trigger GABA deamination by GABA transaminase. OMP, but not L-leucine, suppressed islet semialdehyde succinic acid reductase activity and this might shift the metabolic flux of the 'GABA shunt' from gamma-hydroxybutyrate to succinic acid production.

  13. Metal and acidity fluxes controlled by precipitation/dissolution cycles of sulfate salts in an anthropogenic mine aquifer.

    PubMed

    Cánovas, C R; Macías, F; Pérez-López, R

    2016-05-01

    Underground mine drainages are extremely difficult to study due to the lack of information about the flow path and source proximity in relation to the outflow adit. Geochemical processes controlling metals and acidity fluxes in a complex anthropogenic mine aquifer in SW Spain during the dry and rainy season were investigated by geochemical and statistical tools. High concentrations of acidity, sulfate, metals and metalloids (e.g. Fe, Cu, Zn, As, Cd, Ni, Co) were observed due to intense sulfide oxidation processes. The high residence time inside the anthropogenic aquifer, around 40days, caused the release of significant quantities of metals linked to host rocks (e.g. Al, Ca, Ge, Li, Mg, REE). The most outstanding characteristic of the acid mine drainage (AMD) outflows is the existence of higher Fe/SO4 molar ratios than those theoretical of pyrite (0.50) during most of the monitored period, due to a fire which occurred in 1949 and remained active for decades. Permanent and temporal retention mechanisms of acidity and metals were observed in the galleries. Once released from sulfide oxidation, Pb and As are sorbed on Fe oxyhydroxysulfate or precipitated as low solubility minerals (i.e. anglesite) inside the galleries. The precipitation of evaporitic sulfate salts during the dry season and the subsequent re-dissolution after rainfall control the fluxes of acidity and main metals (i.e. Fe, Mg, Al) from this anthropogenic aquifer. Some elements, such as Cd, Cu, Ni, REE and Zn, are retained in highly soluble sulfate salts while other elements, such as Ge, Pb and Sc, have a lower response to washout processes due to its incorporation in less soluble sulfate salts. In this way, metal concentration during the washout processes would be controlled by the proportion and solubility of each type of evaporitic sulfate salt stored during the dry season. The recovery of metals of economic interest contained in the AMD could help to self-finance the remediation of these waters in

  14. Metal and acidity fluxes controlled by precipitation/dissolution cycles of sulfate salts in an anthropogenic mine aquifer.

    PubMed

    Cánovas, C R; Macías, F; Pérez-López, R

    2016-05-01

    Underground mine drainages are extremely difficult to study due to the lack of information about the flow path and source proximity in relation to the outflow adit. Geochemical processes controlling metals and acidity fluxes in a complex anthropogenic mine aquifer in SW Spain during the dry and rainy season were investigated by geochemical and statistical tools. High concentrations of acidity, sulfate, metals and metalloids (e.g. Fe, Cu, Zn, As, Cd, Ni, Co) were observed due to intense sulfide oxidation processes. The high residence time inside the anthropogenic aquifer, around 40days, caused the release of significant quantities of metals linked to host rocks (e.g. Al, Ca, Ge, Li, Mg, REE). The most outstanding characteristic of the acid mine drainage (AMD) outflows is the existence of higher Fe/SO4 molar ratios than those theoretical of pyrite (0.50) during most of the monitored period, due to a fire which occurred in 1949 and remained active for decades. Permanent and temporal retention mechanisms of acidity and metals were observed in the galleries. Once released from sulfide oxidation, Pb and As are sorbed on Fe oxyhydroxysulfate or precipitated as low solubility minerals (i.e. anglesite) inside the galleries. The precipitation of evaporitic sulfate salts during the dry season and the subsequent re-dissolution after rainfall control the fluxes of acidity and main metals (i.e. Fe, Mg, Al) from this anthropogenic aquifer. Some elements, such as Cd, Cu, Ni, REE and Zn, are retained in highly soluble sulfate salts while other elements, such as Ge, Pb and Sc, have a lower response to washout processes due to its incorporation in less soluble sulfate salts. In this way, metal concentration during the washout processes would be controlled by the proportion and solubility of each type of evaporitic sulfate salt stored during the dry season. The recovery of metals of economic interest contained in the AMD could help to self-finance the remediation of these waters in

  15. Enzymatic synthesis of L-lactic acid from carbon dioxide and ethanol with an inherent cofactor regeneration cycle.

    PubMed

    Tong, Xiaodong; El-Zahab, Bilal; Zhao, Xueyan; Liu, Youyan; Wang, Ping

    2011-02-01

    Efficient conversion of carbon dioxide is of great interests to today's endeavors in controlling greenhouse gas emission. A multienzyme catalytic system that uses carbon dioxide and ethanol to produce L-lactate was demonstrated in this work, thereby providing a novel reaction route to convert bio-based ethanol to an important building block for synthesis biodegradable polymers. The synthetic route has a unique internal cofactor regeneration cycle, eliminating the need of additional chemical or energy for cofactor regeneration. Lactate was successfully synthesized with 41% of ethanol converted in a batch reaction, while a turnover number of 2.2 day⁻¹ was reached for cofactor regeneration in a reaction with continuous feeding of ethanol. A kinetic model developed based on reaction kinetic parameters determined separately for each reaction step predicted well the reaction rates and yields of the multienzyme reaction system.

  16. Making fate and exposure models for freshwater ecotoxicity in life cycle assessment suitable for organic acids and bases.

    PubMed

    van Zelm, Rosalie; Stam, Gea; Huijbregts, Mark A J; van de Meent, Dik

    2013-01-01

    Freshwater fate and exposure factors were determined for organic acids and bases, making use of the knowledge on electrical interaction of ionizing chemicals and their sorption to particles. The fate factor represents the residence time in the environment whereas exposure factors equal the dissolved fraction of a chemical. Multimedia fate, exposure, and effect model USES-LCA was updated to take into account the influence of ionization, based upon the acid dissociation constant (pK(a)) of a chemical, and the environmental pH. Freshwater fate (FF) and exposure (XF) factors were determined for 415 acids and 496 bases emitted to freshwater, air, and soil. The relevance of taking account of the degree of ionization of chemicals was tested by determining the ratio (R) of the new vs. fate and exposure factors determined with USES-LCA suitable for neutral chemicals only. Our results show that the majority of freshwater fate and exposure factors of chemicals that are largely ionized in the environment are larger with the ionics model compared to the factors determined with the neutrals model version. R(FF) ranged from 2.4×10(-1) to 1.6×10(1) for freshwater emissions, from 1.2×10(-2) to 2.0×10(4) for soil emissions and from 5.8×10(-2) to 6.0×10(3) for air emissions, and R(XF) from 5.3×10(-1) to 2.2×10(1). Prediction of changed solid-water partitioning, implying a change in runoff and in removal via sedimentation, and prediction of negligible air-water partition coefficient, leading to negligible volatilization were the main contributors to the changes in freshwater fate factors.

  17. Laser confers less embryo exposure than acid tyrode for embryo biopsy in preimplantation genetic diagnosis cycles: a randomized study

    PubMed Central

    2011-01-01

    We compared two methods of zona pellucida drilling. 213 embryos were biopsied with acid Tyrode. Each biopsy took 3 minutes and the entire procedure ~29 minutes. 5% of blastomeres lysed, 49% of embryos became blastocyst and 36% of patients became pregnant. 229 embryos were biopsied with laser. Each biopsy took 30 seconds and the entire procedure ~7 minutes. 2.5% of blastomeres lysed, 50.6% of embryos became blastocyst and 47% of patients became pregnant. We can conclude that laser can be used for embryo biopsy. Reduction of embryo exposure and of removed blastomeres is associated with increased blastocysts available for transfer and a better clinical outcome. PMID:21527004

  18. Cerebral metabolic and circulatory effects of 1,1,1-trichloroethane, a neurotoxic industrial solvent. 2. Tissue concentrations of labile phosphates, glycolytic metabolites, citric acid cycle intermediates, amino acids, and cyclic nucleotides.

    PubMed

    Folbergrová, J; Hougaard, K; Westerberg, E; Siesjö, B K

    1984-01-01

    In order to obtain information on the mechanisms of neurotoxicity of 1,1,1-trichloroethane, rats maintained artificially ventilated on N2O:O2 (70:30) were exposed to a concentration of 1,1,1-trichloroethane of 8000 ppm, 43.7 mg L-1, that induces moderate ataxia in awake, spontaneously breathing animals. After 5 and 60 min of exposure, as well as after a 60-min recovery period following 60 min of exposure, the brain was frozen in situ and cortical tissue was assayed for phosphocreatine (PCr), + ATP, ADP, AMP, glycogen, glucose, pyruvate, lactate, citric acid cycle intermediates, associated amino acids, and cyclic nucleotides; in addition, purine nucleotides, nucleosides, and bases were assayed by HPLC techniques. Exposure of animals to 1,1,1-trichloroethane failed to alter blood glucose, lactate, and pyruvate concentrations. However, the solvent induced highly significant increases in tissue lactate and pyruvate concentrations that were also reflected in cisternal CSF. Associated with these changes were increases in all citric acid cycle intermediates except succinate, an increase in alanine concentration, and a rise in the glutamate/aspartate ratio. After 5 min, a small decrease in glycogen concentration also occurred. All these changes were reversed when the exposure was terminated. No changes were observed in tissue concentrations of purine nucleotides, nucleosides, and bases except for a small reduction of ATP concentration after 60 min of exposure, still noticeable after 60 min of recovery. Apart from a small reduction in cAMP concentration after 5 min of exposure, cyclic nucleotide concentrations did not change.

  19. Docosohaexanoic acid-supplemented PACA44 cell lines and over-activation of Krebs cycle: an integrated proteomic, metabolomic and interactomic overview.

    PubMed

    D'Alessandro, Angelo; D'Amici, Gian Maria; Timperio, Anna Maria; Merendino, Nicolò; Zolla, Lello

    2011-09-01

    Recent investigations have pointed out the ability of fatty acids, in particular of docosohaexanoic acid (DHA), to induce growth inhibition and apoptosis in the human PaCa-44 pancreatic cancer cell line through a series of mechanisms which has been hypothesized to mimic apoptosis. While preliminary evidences indicated the involvement of lipid-targeting oxidative stress in DHA-induced apoptotic processes, mainly through the alteration of the glutathione (GSH) homeostasis and oxidized-glutathione (GSSG) turn-over through their extra-cellular extrusion, no further molecular data have been hitherto accumulated. To this end, we hereby propose simultaneous protein-targeting and metabolite-oriented analyses, which have been integrated through the auxilium of in silico elaboration of those protein-protein interaction pathways and enrichment of biological/molecular functions. To determine the most suitable time window for the early onset of the DHA-triggered apoptosis phenomena we performed flow cytometry-based apoptotic assessment at 24, 48 and 72 h. Results indicated that the focus of apoptosis onset ranged from 48 to 72 h. From these analyses it emerges that the metabolism of control human PaCa-44 pancreatic cancer cell line mainly leans on glycolytic pathways, while it is promptly switched to Kreb's cycle activation (overexpression of Kreb's cycle enzymes in DHA-treated cells against controls) and modulation of the GSH homeostasis through an increased production of GSSG-reducing NADPH coenzyme via the shift of the glycolytic energy flux towards the pentose phosphate pathway. Interestingly, it also emerges a role for structural protein alteration in DHA-treated cells, which might be linked to cytoskeletal alterations occurring during apoptosis.

  20. The all-trans retinoic acid (atRA)-regulated gene Calmin (Clmn) regulates cell cycle exit and neurite outgrowth in murine neuroblastoma (Neuro2a) cells

    SciTech Connect

    Marzinke, Mark A.; Clagett-Dame, Margaret

    2012-01-01

    The vitamin A metabolite all-trans retinoic acid (atRA) functions in nervous system development and regulates cell proliferation and differentiation. Neuroblastoma cells (SH-SY5Y and Neuro2a or N2A) exposed to atRA undergo growth inhibition and neuronal differentiation, both of which are preceded by an increase in Clmn mRNA. Treatment of N2A cells with atRA produces a reduction in phosphohistone 3 immunostaining and BrdU incorporation, both indicators of a reduction in cell proliferation. These effects are nearly eliminated in atRA-treated shClmn knockdown cells. Loss of Clmn in the mouse N2A cell line also results in a significant reduction of atRA-mediated neurite outgrowth, a response that can be rescued by reintroduction of the Clmn sequence. In contrast, ectopic overexpression of Clmn produces an increase in the cyclin dependent kinase inhibitor, p21{sup Cip1}, a decrease in cyclin D1 protein and an increase in hypophosphorylated Rb, showing that Clmn participates in G{sub 1}/S arrest. Clmn overexpression alone is sufficient to inhibit N2A cell proliferation, whereas both Clmn and atRA must be present to induce neurite outgrowth. This study shows that the atRA-responsive gene Clmn promotes exit from the cell cycle, a requisite event for neuronal differentiation. -- Highlights: Black-Right-Pointing-Pointer Calmin is a retinoic acid-responsive gene. Black-Right-Pointing-Pointer Calmin promotes cell cycle exit in N2A cells. Black-Right-Pointing-Pointer Calmin overexpression increases p21Cip1 and decreases cyclin D1. Black-Right-Pointing-Pointer Calmin is required for RA-induced growth inhibition and neurite outgrowth.

  1. The seed's protein and oil content, fatty acid composition, and growing cycle length of a single genotype of chia (Salvia hispanica L.) as affected by environmental factors.

    PubMed

    Ayerza, Ricardo

    2009-01-01

    As a botanical source, variability in chia seed composition could be expected between growing locations, and between years within a location, due to genotype and environment effects as well genetic x environment's interactions. The objective of the present study was to determine the location effect on the growing cycle length, and seed's protein content, lipid content, and fatty acid profiles, of a single chia genotype. Seeds of chia genotype Tzotzol grown on eight sites in five different ecosystems were tested. One site was in Argentina, in the Semi-Arid Chaco ecosystem (T(5)); one was in Bolivia, in the Sub-Humid Chaco ecosystem (T(4)); and six in Ecuador, one in the Coastal Desert (T(3)), two on the Tropical Rain Forest (T(2)), and three in the Inter-Andean Dry Valley ecosystem (T(1)). Seeds from plants grown in T(4) and in T(3) contained significantly (P <0.05) more protein percentage than did seeds from the other three ecosystems. No significant (P <0.05) differences in protein content were found between T(3) and T(4), and between T(1), T(2), and T(5). Seeds from T(1) and T(5) ecosystems, with 33.5 and 32.2%, respectively, were the numerically highest oil content producers, but their results were only significantly (P <0.05) higher when compared with the T(2) seeds. Significant (P <0.05) differences in palmitic, stearic, oleic, linoleic and alpha-linolenic fatty acids between oils from seeds grown in different ecosystems were detected, however. Oil of seeds grown in the T(3) ecosystem had the palmitic, stearic and oleic fatty acids' highest contents. Palmitic and oleic fatty acid levels were significantly (P <0.05) higher when were compared to that of seeds grown in the T(1) ecosystem, and stearic when was compared to that of seeds grown in the T(5) ecosystem; omega-6 linoleic fatty acid content was significantly (P <0.05) lower in oils of seeds produced in T(1), and T(2) than in those produced in T(3), T(4), and T(5) ecosystems; omega-3 alpha-linolenic fatty

  2. Mercury cycling in boreal ecosystems: The long-term effect of acid rain constituents on peatland pore water methylmercury concentrations

    NASA Astrophysics Data System (ADS)

    Branfireun, Brian A.; Bishop, Kevin; Roulet, Nigel T.; Granberg, Gunnar; Nilsson, Mats

    Sulphate-reducing bacteria have been identified as primary methylators of mercury (Hg) in the laboratory and in field investigations. However, no studies have investigated the effect of long-term deposition of sulphate on methylmercury (MeHg) dynamics in peatlands, which are known to be significant sources of MeHg to downstream waters in the boreal forest zone. As an ancillary experiment to a larger project investigating the effects of acid rain constituents on peatland carbon dynamics, the influence of experimentally elevated Na2SO4 and/or NH4NO3 deposition on peat pore water MeHg concentrations was determined using a simple mesocosm experimental design. After three years, additions of S in amounts equivalent to the 1980s dry and wet deposition in Southern Sweden resulted in peat pore water MeHg concentrations up to six times above background levels. Elevated N loads had no effect on pore water MeHg concentrations.

  3. Interactive effects of acidity and aluminum exposure on the life cycle of the midge Chironomus riparius (Diptera)

    SciTech Connect

    Palawski, D.U.; Hunn, J.B.; Chester, D.N.; Wiedneyer, R.H. )

    1989-12-01

    The chronic toxicity of acidic pH and the toxicity of aluminum at pH 5.6 and pH 5.0 to the midge Chironomus riparius were determined in 30-day flow-through exposures. Larvae were exposed to water pHs of 7.2, 6.2, 5.8, 5.3, and 4.5; total aluminum concentrations were 14.6, 34.8, 61.4, 128.7, and 259.2 microgram/L at a water pH of 5.6 and to aluminum concentrations of 15.6, 32.5, 56.9, 111.4, and 235.2 microgram/L at a water pH of 5.0. The survival of midges was only 11% at pH 4.5 and 52.3% at pH 5.8. In soft water (12 mg/L as CaCO3) at pH 5.6, survival declined significantly at aluminum concentrations of 61 to 259 microgram/L, but significantly increased at 14.6 microgram/L. In soft water at pH 5.0, survival increased at concentrations of 14.6 to 111.4 microgram/L but decreased significantly at 235.2 microgram/L. At both pH 5.6 and pH 5.0, the toxicological response of midges to aluminum was thus bimodal, in that acid stress was slightly ameliorated by relatively low aluminum concentrations, but exacerbated by higher concentrations. 25 refs., 55 tabs.

  4. Effects of acidic deposition on nutrient uptake, nutrient cycling and growth processes of vegetation in the spruce-fir ecosystem

    SciTech Connect

    McLaughlin, S.B.; Garten, C.T.; Wullschleger, S.D.

    1996-10-16

    This report summarizes progress in three years of field research designed to evaluate biological and chemical indicators of the current and future health of the Southern Appalachian spruce-fir ecosystem. The emphasis of this research has been on the identification and understanding of mechanisms through which current levels of acidic deposition are impacting ecosystem processes. The identification of these principal mechanisms and key biological indicators of change was designed to improve our capabilities to detect, monitor, and assess the effects of air quality regulations and attendant future air quality changes on ecosystem response. Individual research tasks focused on the following research areas: (1) the significance of foliar uptake of atmospheric sources of nitrogen in relationship to plant utilization of N from available soil reserves; (2) linkages between atmospheric inputs to the soil surface, solution chemistry, and decomposition in the upper organic soil horizons; (3) effects of soil solution chemistry on uptake of cations and aluminum by fine roots; and (4) the effects of varying rates of calcium supply on carbon metabolism of Fraser fir and red spruce, and the relationship between calcium levels in wood cells and integrity of wood formed in bole and branches. Each of the individual tasks was designed to focus upon a mechanism or process that we consider critical to understanding chemical and biological linkages. These linkages will be important determinants in understanding the basis of past and potential future responses of the high elevation Southern Appalachian Forest to acidic deposition and other co-occurring environmental stresses. This report contains (1) background and rationale for the research undertaken in 1992-94; (2) a summary of principal research findings; (3) publications from this research; and (4) characterization of data sets produced by this research which will be the basis of future research, analyses and/or publications.

  5. An efficient proton-coupled electron-transfer process during oxidation of ferulic acid by horseradish peroxidase: coming full cycle.

    PubMed

    Derat, Etienne; Shaik, Sason

    2006-10-25

    Quantum mechanics/molecular mechanics calculations were utilized to study the process of oxidation of a native substrate (ferulic acid) by the active species of horseradish peroxidase (Dunford, H. B. Heme Peroxidases; Wiley-VCH: New York, 1999), Compound I and Compound II, and the manner by which the enzyme returns to its resting state. The results match experimental findings and reveal additional novel features. The calculations demonstrate that both oxidation processes are initiated by a proton-coupled electron-transfer (PCET) step, in which the active species of the enzyme participate only as electron-transfer partners, while the entire proton-transfer event is being relayed from the substrate to and from the His42 residue by a water molecule (W402). The reason for the observed (Henriksen, A; Smith, A. T.; Gajhede, M. J. Biol. Chem. 1999, 274, 35005-35011) similar reactivities of Compound I and Compound II toward ferulic acid is that the reactive isomer of Compound II is the, hitherto unobserved, Por(*)(+)Fe(III)OH isomer that resembles Compound I. The PCET mechanism reveals that His42 and W402 are crucial moieties and they determine the function of the HRP enzyme and account for its ability to perform substrate oxidation (Poulos, T. L. Peroxidases and Cytochrome P450. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000; Vol. 4, pp 189). In view of the results, the possibility of manipulating substrate oxidation by magnetic fields is an intriguing possibility. PMID:17044722

  6. SdhE-dependent formation of a functional Acetobacter pasteurianus succinate dehydrogenase in Gluconobacter oxydans--a first step toward a complete tricarboxylic acid cycle.

    PubMed

    Kiefler, Ines; Bringer, Stephanie; Bott, Michael

    2015-11-01

    The obligatory aerobic α-proteobacterium Gluconobacter oxydans 621H possesses an unusual metabolism in which the majority of the carbohydrate substrates are incompletely oxidized in the periplasm and only a small fraction is metabolized in the cytoplasm. The cytoplasmic oxidation capabilities are limited due to an incomplete tricarboxylic acid (TCA) cycle caused by the lack of succinate dehydrogenase (Sdh) and succinyl-CoA synthetase. As a first step to test the consequences of a functional TCA cycle for growth, metabolism, and bioenergetics of G. oxydans, we attempted to establish a heterologous Sdh in this species. Expression of Acetobacter pasteurianus sdhCDAB in G. oxydans did not yield an active succinate dehydrogenase. Co-expression of a putative sdhE gene from A. pasteurianus, which was assumed to encode an assembly factor for covalent attachment of flavin adenine dinucleotide (FAD) to SdhA, stimulated Sdh activity up to 400-fold to 4.0 ± 0.4 U (mg membrane protein)(‒1). The succinate/oxygen reductase activity of membranes was 0.68 ± 0.04 U (mg membrane protein)(‒1), indicating the formation of functional Sdh complex capable of transferring electrons from succinate to ubiquinone. A. pasteurianus SdhE could be functionally replaced by SdhE from the γ-proteobacterium Serratia sp. According to these results, the accessory protein SdhE was necessary and sufficient for heterologous synthesis of an active A. pasteurianus Sdh in G. oxydans. Studies with the Sdh-positive G. oxydans strain provided evidence for a limited functionality of the TCA cycle despite the absence of succinyl-CoA synthetase.

  7. Environmental analysis of plastic production processes: comparing petroleum-based polypropylene and polyethylene with biologically-based poly-beta-hydroxybutyric acid using life cycle analysis.

    PubMed

    Harding, K G; Dennis, J S; von Blottnitz, H; Harrison, S T L

    2007-05-31

    Polymers based on olefins have wide commercial applicability. However, they are made from non-renewable resources and are characterised by difficulty in disposal where recycle and re-use is not feasible. Poly-beta-hydroxybutyric acid (PHB) provides one example of a polymer made from renewable resources. Before motivating its widespread use, the advantages of a renewable polymer must be weighed against the environmental aspects of its production. Previous studies relating the environmental impacts of petroleum-based and bio-plastics have centred on the impact categories of global warming and fossil fuel depletion. Cradle-to-grave studies report equivalent or reduced global warming impacts, in comparison to equivalent polyolefin processes. This stems from a perceived CO(2) neutral status of the renewable resource. Indeed, no previous work has reported the results of a life cycle assessment (LCA) giving the environmental impacts in all major categories. This study investigates a cradle-to-gate LCA of PHB production taking into account net CO(2) generation and all major impact categories. It compares the findings with similar studies of polypropylene (PP) and polyethylene (PE). It is found that, in all of the life cycle categories, PHB is superior to PP. Energy requirements are slightly lower than previously observed and significantly lower than those for polyolefin production. PE impacts are lower than PHB values in acidification and eutrophication.

  8. Environmental analysis of plastic production processes: comparing petroleum-based polypropylene and polyethylene with biologically-based poly-beta-hydroxybutyric acid using life cycle analysis.

    PubMed

    Harding, K G; Dennis, J S; von Blottnitz, H; Harrison, S T L

    2007-05-31

    Polymers based on olefins have wide commercial applicability. However, they are made from non-renewable resources and are characterised by difficulty in disposal where recycle and re-use is not feasible. Poly-beta-hydroxybutyric acid (PHB) provides one example of a polymer made from renewable resources. Before motivating its widespread use, the advantages of a renewable polymer must be weighed against the environmental aspects of its production. Previous studies relating the environmental impacts of petroleum-based and bio-plastics have centred on the impact categories of global warming and fossil fuel depletion. Cradle-to-grave studies report equivalent or reduced global warming impacts, in comparison to equivalent polyolefin processes. This stems from a perceived CO(2) neutral status of the renewable resource. Indeed, no previous work has reported the results of a life cycle assessment (LCA) giving the environmental impacts in all major categories. This study investigates a cradle-to-gate LCA of PHB production taking into account net CO(2) generation and all major impact categories. It compares the findings with similar studies of polypropylene (PP) and polyethylene (PE). It is found that, in all of the life cycle categories, PHB is superior to PP. Energy requirements are slightly lower than previously observed and significantly lower than those for polyolefin production. PE impacts are lower than PHB values in acidification and eutrophication. PMID:17400318

  9. Pomegranate Juice Metabolites, Ellagic Acid and Urolithin A, Synergistically Inhibit Androgen-Independent Prostate Cancer Cell Growth via Distinct Effects on Cell Cycle Control and Apoptosis

    PubMed Central

    Vicinanza, Roberto; Henning, Susanne M.; Heber, David

    2013-01-01

    Ellagitannins (ETs) from pomegranate juice (PJ) are bioactive polyphenols with chemopreventive potential against prostate cancer (PCa). ETs are not absorbed intact but are partially hydrolyzed in the gut to ellagic acid (EA). Colonic microflora can convert EA to urolithin A (UA), and EA and UA enter the circulation after PJ consumption. Here, we studied the effects of EA and UA on cell proliferation, cell cycle, and apoptosis in DU-145 and PC-3 androgen-independent PCa cells and whether combinations of EA and UA affected cell proliferation. EA demonstrated greater dose-dependent antiproliferative effects in both cell lines compared to UA. EA induced cell cycle arrest in S phase associated with decreased cyclin B1 and cyclin D1 levels. UA induced a G2/M arrest and increased cyclin B1 and cdc2 phosphorylation at tyrosine-15, suggesting inactivation of the cyclin B1/cdc2 kinase complex. EA induced apoptosis in both cell lines, while UA had a less pronounced proapoptotic effect only in DU-145. Cotreatment with low concentrations of EA and UA dramatically decreased cell proliferation, exhibiting synergism in PC-3 cells evaluated by isobolographic analysis and combination index. These data provide information on pomegranate metabolites for the prevention of PCa recurrence, supporting the role of gut flora-derived metabolites for cancer prevention. PMID:23710216

  10. SILAC-based proteomic analysis reveals that salidroside antagonizes cobalt chloride-induced hypoxic effects by restoring the tricarboxylic acid cycle in cardiomyocytes.

    PubMed

    Xu, Zhong-Wei; Chen, Xi; Jin, Xiao-Han; Meng, Xiang-Yan; Zhou, Xin; Fan, Feng-Xu; Mao, Shi-Yun; Wang, Yue; Zhang, Wen-Cheng; Shan, Na-Na; Li, Yu-Ming; Xu, Rui-Cheng

    2016-01-01

    Hypoxic status alters the energy metabolism and induces cell injury in cardiomyocytes, and it further triggers the occurrence and development of cardiovascular diseases. Our previous studies have shown that salidroside (SAL) exhibits anti-hypoxic activity. However, the mechanisms remain obscure. In the present study, we successfully screened 92 different expression proteins in CoCl2-induced hypoxic conditions, 106 different expression proteins in the SAL-mediated anti-hypoxic group were compared with the hypoxic group using quantitative proteomics strategy, respectively. We confirmed that SAL showed a positive protective function involving the acetyl-CoA metabolic, tricarboxylic acid (TCA) cycle using bioinformatics analysis. We also demonstrated that SAL plays a critical role in restoring the TCA cycle and in protecting cardiomyocytes from oxidative injury via up-regulation expressions of PDHE1-B, ACO2, SUCLG1, SUCLG2 and down-regulation of MDH2. SAL also inhibited H9c2 cell apoptosis by inhibiting the activation of pro-apoptotic molecules caspase 3 and caspase 9 as well as activation of the anti-apoptotic molecular Bcl-2. Additionally, SAL also improved mitochondrial membrane potential (ΔΨm), reduced reactive oxygen species (ROS) and intercellular Ca(2+) concentration ([Ca(2+)]i) accumulation and inhibited the excessive consumption of ATP in H9c2 cells. PMID:26435418

  11. SILAC-based proteomic analysis reveals that salidroside antagonizes cobalt chloride-induced hypoxic effects by restoring the tricarboxylic acid cycle in cardiomyocytes.

    PubMed

    Xu, Zhong-Wei; Chen, Xi; Jin, Xiao-Han; Meng, Xiang-Yan; Zhou, Xin; Fan, Feng-Xu; Mao, Shi-Yun; Wang, Yue; Zhang, Wen-Cheng; Shan, Na-Na; Li, Yu-Ming; Xu, Rui-Cheng

    2016-01-01

    Hypoxic status alters the energy metabolism and induces cell injury in cardiomyocytes, and it further triggers the occurrence and development of cardiovascular diseases. Our previous studies have shown that salidroside (SAL) exhibits anti-hypoxic activity. However, the mechanisms remain obscure. In the present study, we successfully screened 92 different expression proteins in CoCl2-induced hypoxic conditions, 106 different expression proteins in the SAL-mediated anti-hypoxic group were compared with the hypoxic group using quantitative proteomics strategy, respectively. We confirmed that SAL showed a positive protective function involving the acetyl-CoA metabolic, tricarboxylic acid (TCA) cycle using bioinformatics analysis. We also demonstrated that SAL plays a critical role in restoring the TCA cycle and in protecting cardiomyocytes from oxidative injury via up-regulation expressions of PDHE1-B, ACO2, SUCLG1, SUCLG2 and down-regulation of MDH2. SAL also inhibited H9c2 cell apoptosis by inhibiting the activation of pro-apoptotic molecules caspase 3 and caspase 9 as well as activation of the anti-apoptotic molecular Bcl-2. Additionally, SAL also improved mitochondrial membrane potential (ΔΨm), reduced reactive oxygen species (ROS) and intercellular Ca(2+) concentration ([Ca(2+)]i) accumulation and inhibited the excessive consumption of ATP in H9c2 cells.

  12. Catalytic therapy of cancer by ascorbic acid involves redox cycling of exogenous/endogenous copper ions and generation of reactive oxygen species.

    PubMed

    Hadi, S M; Ullah, M F; Shamim, U; Bhatt, S H; Azmi, A S

    2010-01-01

    Catalytic therapy is a cancer treatment modality based on the generation of reactive oxygen species (ROS) through administration of ascorbate/medicinal herbal extracts and copper. It is known that antioxidants such as ascorbate also exhibit prooxidant activity in the presence of transition metals such as copper. Based on our work and that in the literature, in this review we propose a mechanism for the cytotoxic action of ascorbate against cancer cells. It involves redox cycling of exogenous/endogenous copper ions and the consequent generation of ROS leading to oxidative DNA breakage. Using human peripheral lymphocytes and the Comet assay, we have shown that ascorbic acid is able to cause oxidative breakage in cellular DNA. Such DNA degradation is inhibited by neocuproine (a Cu(I) sequestering agent) and scavengers of ROS indicating that the cellular DNA breakage involves the generation of Cu(I) and formation of ROS. Similar results are also obtained with plant polyphenol antioxidants that are important constituents of medicinal herbal extracts. Copper is an essential component of chromatin and can take part in redox reactions. It is well established that tissue, cellular and serum copper levels are considerably elevated in various malignancies. Therefore, cancer cells may be more subject to electron transfer between copper ions and ascorbate/plant polyphenols to generate ROS. In this review we cite evidence to indicate that in catalytic therapy cytotoxic action against cancer cells involves redox cycling of exogenous/endogenous copper ions.

  13. From CO2 to cell: energetic expense of creating biomass using the Calvin-Benson-Bassham and reductive citric acid cycles based on genome data.

    PubMed

    Mangiapia, Mary; Scott, Kathleen

    2016-04-01

    The factors driving the dominance of the Calvin-Benson-Bassham cycle (CBB) or reductive citric acid cycle (rCAC) in autotrophic microorganisms in different habitats are debated. Based on costs for synthesizing a few metabolic intermediates, it has been suggested that the CBB poses a disadvantage due to higher metabolic cost. The purpose of this study was to extend this estimate of cost from metabolite synthesis to biomass synthesis. For 12 gammaproteobacteria (CBB) and five epsilonproteobacteria (rCAC), the amount of ATP to synthesize a gram of biomass from CO2 was calculated from genome sequences via metabolic maps. The eleven central carbon metabolites needed to synthesize biomass were all less expensive to synthesize via the rCAC (66%-89% of the ATP needed to synthesize them via CBB). Differences in cell compositions did result in differing demands for metabolites among the organisms, but the differences in cost to synthesize biomass were small among organisms that used a particular pathway (e.g. rCAC), compared to the difference between pathways (rCAC versus CBB). The rCAC autotrophs averaged 0.195 moles ATP per g biomass, while their CBB counterparts averaged 0.238. This is the first in silico estimate of the relative expense of both pathways to generate biomass.

  14. New betulinic acid derivatives induce potent and selective antiproliferative activity through cell cycle arrest at the S phase and caspase dependent apoptosis in human cancer cells.

    PubMed

    Santos, Rita C; Salvador, Jorge A R; Cortés, Roldán; Pachón, Gisela; Marín, Silvia; Cascante, Marta

    2011-06-01

    New semisynthetic derivatives of betulinic acid (BA) RS01, RS02 and RS03 with 18-45 times improved cytotoxic activity against HepG2 cells, were tested for their ability to induce apoptosis and cell cycle arrest in HepG2, HeLa and Jurkat cells. All the compounds induced significant increase in the population at the S phase more effectively than BA. RS01, RS02 and RS03 were also found to be potent inducers of apoptosis with RS01 being markedly more potent than BA, suggesting that the introduction of the imidazolyl moiety is crucial for enhancing the induction of apoptosis and the cell cycle arrest. The mechanism of apoptosis induction has been studied in HepG2 cells and found to be mediated by activation of the postmitochondrial caspases-9 and -3 cascade and possibly by mitochondrial amplification loop involving caspase-8. These facts were corroborated by detection of mitochondrial cytochrome c release and DNA fragmentation. Because RS01, RS02 and RS03 exhibited significant improved antitumor activity with respect to BA, they may be promising new agents for the treatment of cancer. In particular, RS01 is the most promising compound with an IC(50) value 45 times lower than BA on HepG2 cells and 61 times lower than the one found for the non-tumoral Chang liver cells.

  15. Non-growing Rhodopseudomonas palustris increases the hydrogen gas yield from acetate by shifting from the glyoxylate shunt to the tricarboxylic acid cycle.

    PubMed

    McKinlay, James B; Oda, Yasuhiro; Rühl, Martin; Posto, Amanda L; Sauer, Uwe; Harwood, Caroline S

    2014-01-24

    When starved for nitrogen, non-growing cells of the photosynthetic bacterium Rhodopseudomonas palustris continue to metabolize acetate and produce H2, an important industrial chemical and potential biofuel. The enzyme nitrogenase catalyzes H2 formation. The highest H2 yields are obtained when cells are deprived of N2 and thus use available electrons to synthesize H2 as the exclusive product of nitrogenase. To understand how R. palustris responds metabolically to increase H2 yields when it is starved for N2, and thus not growing, we tracked changes in biomass composition and global transcript levels. In addition to a 3.5-fold higher H2 yield by non-growing cells we also observed an accumulation of polyhydroxybutyrate to over 30% of the dry cell weight. The transcriptome of R. palustris showed down-regulation of biosynthetic processes and up-regulation of nitrogen scavenging mechanisms in response to N2 starvation but gene expression changes did not point to metabolic activities that could generate the reductant necessary to explain the high H2 yield. We therefore tracked (13)C-labeled acetate through central metabolic pathways. We found that non-growing cells shifted their metabolism to use the tricarboxylic acid cycle to metabolize acetate in contrast to growing cells, which used the glyoxylate cycle exclusively. This shift enabled cells to more fully oxidize acetate, providing the necessary reducing power to explain the high H2 yield.

  16. Non-growing Rhodopseudomonas palustris Increases the Hydrogen Gas Yield from Acetate by Shifting from the Glyoxylate Shunt to the Tricarboxylic Acid Cycle*

    PubMed Central

    McKinlay, James B.; Oda, Yasuhiro; Rühl, Martin; Posto, Amanda L.; Sauer, Uwe; Harwood, Caroline S.

    2014-01-01

    When starved for nitrogen, non-growing cells of the photosynthetic bacterium Rhodopseudomonas palustris continue to metabolize acetate and produce H2, an important industrial chemical and potential biofuel. The enzyme nitrogenase catalyzes H2 formation. The highest H2 yields are obtained when cells are deprived of N2 and thus use available electrons to synthesize H2 as the exclusive product of nitrogenase. To understand how R. palustris responds metabolically to increase H2 yields when it is starved for N2, and thus not growing, we tracked changes in biomass composition and global transcript levels. In addition to a 3.5-fold higher H2 yield by non-growing cells we also observed an accumulation of polyhydroxybutyrate to over 30% of the dry cell weight. The transcriptome of R. palustris showed down-regulation of biosynthetic processes and up-regulation of nitrogen scavenging mechanisms in response to N2 starvation but gene expression changes did not point to metabolic activities that could generate the reductant necessary to explain the high H2 yield. We therefore tracked 13C-labeled acetate through central metabolic pathways. We found that non-growing cells shifted their metabolism to use the tricarboxylic acid cycle to metabolize acetate in contrast to growing cells, which used the glyoxylate cycle exclusively. This shift enabled cells to more fully oxidize acetate, providing the necessary reducing power to explain the high H2 yield. PMID:24302724

  17. Anaplerotic Accumulation of Tricarboxylic Acid Cycle Intermediates as Well as Changes in Other Key Metabolites During Heterotopic Ossification

    PubMed Central

    Davis, Eleanor L.; Salisbury, Elizabeth A.; Olmsted‐Davis, Elizabeth

    2015-01-01

    ABSTRACT Heterotopic ossification (HO) is the de novo formation of bone that occurs in soft tissue, through recruitment, expansion, and differentiation of multiple cells types including transient brown adipocytes, osteoblasts, chondrocytes, mast cells, and platelets to name a few. Much evidence is accumulating that suggests changes in metabolism may be required to accomplish this bone formation. Recent work using a mouse model of heterotopic bone formation reliant on delivery of adenovirus‐transduced cells expressing low levels of BMP2 showed the immediate expansion of a unique brown adipocyte‐like cell. These cells are undergoing robust uncoupled oxidative phosphorylation to a level such that oxygen in the microenvironment is dramatically lowered creating areas of hypoxia. It is unclear how these oxygen changes ultimately affect metabolism and bone formation. To identify the processes and changes occurring over the course of bone formation, HO was established in the mice, and tissues isolated at early and late times were subjected to a global metabolomic screen. Results show that there are significant changes in both glucose levels, as well as TCA cycle intermediates. Additionally, metabolites necessary for oxidation of stored lipids were also found to be significantly elevated. The complete results of this screen are presented here, and provide a unique picture of the metabolic changes occurring during heterotopic bone formation. J. Cell. Biochem. 117: 1044–1053, 2016. © 2015 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc. PMID:26627193

  18. Metabolic engineering of Aspergillus oryzae NRRL 3488 for increased production of L-malic acid.

    PubMed

    Brown, Stephen H; Bashkirova, Lena; Berka, Randy; Chandler, Tyler; Doty, Tammy; McCall, Keith; McCulloch, Michael; McFarland, Sarah; Thompson, Sheryl; Yaver, Debbie; Berry, Alan

    2013-10-01

    Malic acid, a petroleum-derived C4-dicarboxylic acid that is used in the food and beverage industries, is also produced by a number of microorganisms that follow a variety of metabolic routes. Several members of the genus Aspergillus utilize a two-step cytosolic pathway from pyruvate to malate known as the reductive tricarboxylic acid (rTCA) pathway. This simple and efficient pathway has a maximum theoretical yield of 2 mol malate/mol glucose when the starting pyruvate originates from glycolysis. Production of malic acid by Aspergillus oryzae NRRL 3488 was first improved by overexpression of a native C4-dicarboxylate transporter, leading to a greater than twofold increase in the rate of malate production. Overexpression of the native cytosolic alleles of pyruvate carboxylase and malate dehydrogenase, comprising the rTCA pathway, in conjunction with the transporter resulted in an additional 27 % increase in malate production rate. A strain overexpressing all three genes achieved a malate titer of 154 g/L in 164 h, corresponding to a production rate of 0.94 g/L/h, with an associated yield on glucose of 1.38 mol/mol (69 % of the theoretical maximum). This rate of malate production is the highest reported for any microbial system.

  19. High night temperature strongly impacts TCA cycle, amino acid and polyamine biosynthetic pathways in rice in a sensitivity-dependent manner.

    PubMed

    Glaubitz, Ulrike; Erban, Alexander; Kopka, Joachim; Hincha, Dirk K; Zuther, Ellen

    2015-10-01

    Global climate change combined with asymmetric warming can have detrimental effects on the yield of crop plants such as rice (Oryza sativa L.). Little is known about metabolic responses of rice to high night temperature (HNT) conditions. Twelve cultivars with different HNT sensitivity were used to investigate metabolic changes in the vegetative stage under HNT compared to control conditions. Central metabolism, especially TCA cycle and amino acid biosynthesis, were strongly affected particularly in sensitive cultivars. Levels of several metabolites were correlated with HNT sensitivity. Furthermore, pool sizes of some metabolites negatively correlated with HNT sensitivity under control conditions, indicating metabolic pre-adaptation in tolerant cultivars. The polyamines putrescine, spermidine and spermine showed increased abundance in sensitive cultivars under HNT conditions. Correlations between the content of polyamines and 75 other metabolites indicated metabolic shifts from correlations with sugar-phosphates and 1-kestose under control to correlations with sugars and amino and organic acids under HNT conditions. Increased expression levels of ADC2 and ODC1, genes encoding enzymes catalysing the first committed steps of putrescine biosynthesis, were restricted to sensitive cultivars under HNT. Additionally, transcript levels of eight polyamine biosynthesis genes were correlated with HNT sensitivity. Responses to HNT in the vegetative stage result in distinct differences between differently responding cultivars with a dysregulation of central metabolism and an increase of polyamine biosynthesis restricted to sensitive cultivars under HNT conditions and a pre-adaptation of tolerant cultivars already under control conditions with higher levels of potentially protective compatible solutes. PMID:26208642

  20. High night temperature strongly impacts TCA cycle, amino acid and polyamine biosynthetic pathways in rice in a sensitivity-dependent manner.

    PubMed

    Glaubitz, Ulrike; Erban, Alexander; Kopka, Joachim; Hincha, Dirk K; Zuther, Ellen

    2015-10-01

    Global climate change combined with asymmetric warming can have detrimental effects on the yield of crop plants such as rice (Oryza sativa L.). Little is known about metabolic responses of rice to high night temperature (HNT) conditions. Twelve cultivars with different HNT sensitivity were used to investigate metabolic changes in the vegetative stage under HNT compared to control conditions. Central metabolism, especially TCA cycle and amino acid biosynthesis, were strongly affected particularly in sensitive cultivars. Levels of several metabolites were correlated with HNT sensitivity. Furthermore, pool sizes of some metabolites negatively correlated with HNT sensitivity under control conditions, indicating metabolic pre-adaptation in tolerant cultivars. The polyamines putrescine, spermidine and spermine showed increased abundance in sensitive cultivars under HNT conditions. Correlations between the content of polyamines and 75 other metabolites indicated metabolic shifts from correlations with sugar-phosphates and 1-kestose under control to correlations with sugars and amino and organic acids under HNT conditions. Increased expression levels of ADC2 and ODC1, genes encoding enzymes catalysing the first committed steps of putrescine biosynthesis, were restricted to sensitive cultivars under HNT. Additionally, transcript levels of eight polyamine biosynthesis genes were correlated with HNT sensitivity. Responses to HNT in the vegetative stage result in distinct differences between differently responding cultivars with a dysregulation of central metabolism and an increase of polyamine biosynthesis restricted to sensitive cultivars under HNT conditions and a pre-adaptation of tolerant cultivars already under control conditions with higher levels of potentially protective compatible solutes.

  1. Deoxycholic acid and selenium metabolite methylselenol exert common and distinct effects on cell cycle, apoptosis, and MAP kinase pathway in HCT116 human colon cancer cells.

    PubMed

    Zeng, Huawei; Botnen, James H; Briske-Anderson, Mary

    2010-01-01

    The cell growth inhibition induced by bile acid deoxycholic acid (DCA) may cause compensatory hyperproliferation of colonic epithelial cells and consequently increase colon cancer risk. On the other hand, there is increasing evidence for the efficacy of certain forms of selenium (Se) as anticancer nutrients. Methylselenol has been hypothesized to be a critical Se metabolite for anticancer activity in vivo. In this study, we demonstrated that both DCA (75-300 micromol/l) and submicromolar methylselenol inhibited colon cancer cell proliferation by up to 64% and 63%, respectively. In addition, DCA and methylselenol each increased colon cancer cell apoptosis rate by up to twofold. Cell cycle analyses revealed that DCA induced an increase in only the G1 fraction with a concomitant drop in G2 and S-phase; in contrast, methylselenol led to an increase in the G1 and G2 fractions with a concomitant drop only in the S-phase. Although both DCA and methylselenol significantly promoted apoptosis and inhibited cell growth, examination of mitogen-activated protein kinase (MAPK) pathway activation showed that DCA, but not methylselenol, induced SAPK/JNK1/2, p38 MAPK, ERK1/2 activation. Thus, our data provide, for the first time, the molecular basis for opposite effects of methylselenol and DCA on colon tumorigenesis.

  2. Determination of carbon-reduction-cycle intermediates in leaves of Arbutus unedo L. suffering depressions in photosynthesis after application of abscisic acid or exposure to dry air.

    PubMed

    Loske, D; Raschke, K

    1988-02-01

    Gas exchange and contents of photosynthetic intermediates of leaves of Arbutus unedo L. were determined with the aim of recognizing the mechanisms of inhibition that were responsible for the "midday depression" of photosynthesis following exposure to dry air, and the decline in photosynthetic capacity following application of abscisic acid (ABA). Rapidly killed (<0.1 s) leaf samples were taken when gas analysis showed reduced CO2 assimilation. Determination of the contents of 3-phosphoglyceric acid (PGA), ribulose 1,5-bisphosphate (RuBP), triose phosphates, fructose 1,6-bisphosphate and hexose phosphates in the samples showed that significant variation occurred only in the level of PGA. As a result, the ratio PGA/RuBP decreased with increasing inhibition of photosynthesis, particularly when application of ABA had been the cause. A comparison of metabolite patterns did not bring out qualitative differences that would have indicated that effects of ABA and of dry air had been caused by separate mechanisms. Depression of photosynthesis occurred in the presence of sufficient RuBP which indicated that the carboxylation reaction of the carbon-reduction-cycle was inhibited after application of ABA or exposure to dry air. PMID:24226409

  3. Modulation of docetaxel-induced apoptosis and cell cycle arrest by all- trans retinoic acid in prostate cancer cells

    PubMed Central

    Nehmé, A; Varadarajan, P; Sellakumar, G; Gerhold, M; Niedner, H; Zhang, Q; Lin, X; Christen, R D

    2001-01-01

    We report that all- trans retinoic acid (ATRA) enhanced the toxicity of docetaxel against DU145 and LNCaP prostate cancer cells, and that the nature of the interaction between ATRA and docetaxel was highly synergistic. Docetaxel-induced apoptotic cell death was associated with phosphorylation and hence inactivation of Bcl-2. ATRA enhanced docetaxel-induced apoptosis and combined treatment with ATRA and docetaxel resulted in down-regulation of Bcl-2. Docetaxel caused phosphorylation and hence inactivation of cdc2 kinase result ing in G2/M arrest. ATRA inhibited docetaxel-induced phosphorylation of cdc2 resulting in activation of cdc2 kinase and partial reversal of the G2/M arrest. ATRA also inhibited docetaxel-induced activation of MAPK indicating that the effects of docetaxel and ATRA on cdc2 phosphorylation are dependent on MAPK. We conclude that ATRA synergistically enhances docetaxel toxicity by down-regulating Bcl-2 expression and partially reverses the docetaxel-induced G2/M arrest by inhibiting docetaxel-induced cdc2 phosphorylation in a pathway that is dependent on MAPK. © 2001 Cancer Research Campaign http://www.bjcancer.com PMID:11384110

  4. Reducing persistent organic pollutants while maintaining long chain omega-3 fatty acid in farmed Atlantic salmon using decontaminated fish oils for an entire production cycle.

    PubMed

    Berntssen, M H G; Olsvik, P A; Torstensen, B E; Julshamn, K; Midtun, T; Goksøyr, A; Johansen, J; Sigholt, T; Joerum, N; Jakobsen, J-V; Lundebye, A-K; Lock, E-J

    2010-09-01

    Oily fish are an important source of health promoting nutrients such as the very long chain marine omega-3 (VLC-n3) fatty acids and simultaneously a source of potentially hazardous contaminants. Fish oils that are used in fish feed are the main source for both contaminants and VLC-n3. Decontamination techniques have recently been developed to effectively remove persistent organic contaminants from fish oils. The aim of the present study was to assess the level of potentially hazardous contaminants and the health beneficial fatty acids in Atlantic salmon reared on novel decontaminated feeds. Atlantic salmon were fed for 18 months (an entire seawater production cycle) on diets based on decontaminated or non-treated (control) fish oils until market size (approximately 5 kg). The level of known notorious persistent organic pollutants (POPs, i.e. dioxins, dioxin-like polychlorinated biphenyls (DL-PCBs), non dioxin-like PCBs, poly brominated diphenyl ethers (PBDE), and organochlorine pesticides), as well as fatty acid composition were analysed in fish oils, the two diets, and Atlantic salmon fillet. The oil decontamination process was a two-step procedure using active carbon and short path distillation. The fillet levels of POPs in market size fish were reduced by 68-85% while the concentration of very long chain omega-3 fatty acids was reduced by 4-7%. No differences in biomarkers of dioxin-like component exposures, such as hepatic gene expression of CYP1A or AhR2B, CYP1A protein expression and 7-ethoxyresorufin O-deethylase (EROD) activity, were observed between salmon raised on normal or decontaminated feeds, thus indicating that the difference in POPs levels were of no biological significance to the fish. Atlantic salmon reared on decontaminated feeds had sum polychlorinated dibenzodioxins/furans (PCDD/Fs) and DL-PCB concentrations that were comparable with terrestrial food products such as beef, while the level of marine omega-3 fatty acids remained as high as for

  5. Observations of Sub-3 nm Particles and Sulfuric acid Concentrations during Aerosol Life Cycle Intensive Observation Period 2011 in Long Island, New York

    NASA Astrophysics Data System (ADS)

    Yu, H.; Kanawade, V. P.; You, Y.; Hallar, A. G.; Mccubbin, I. B.; Chirokova, G.; Sedlacek, A. J.; Springston, S. R.; Wang, J.; Kuang, C.; Lee, Y.; McGraw, R. L.; Mikkila, J.; Lee, S.

    2012-12-01

    Atmospheric new particle formation (NPF) is an important source of aerosol particles. But the NPF processes are not well understood, in part because of our limited understanding of the formation of atmospheric sub-3 nm size aerosols and the limited number of simultaneous observations of particle size distributions and the aerosol nucleation precursors. During Aerosol Life Cycle Intensive Observation Period (July-August 2011) in Long Island, New York, we deployed a particle size magnifier (Airmodus A09) running at different working fluid saturation ratios and a TSI CPC3776 to extract the information of sub-3 nm particles formation. A scanning mobility particle spectrometer (SMPS), a chemical ionization mass spectrometer (CIMS), and a number of atmospheric trace gas analyzers were used to simultaneously measure aerosol size distributions, sulfuric acid, and other possible aerosol precursors, respectively. Our observation results show that sub-3 nm particles existed during both NPF and non-NPF events, indicating the formation of sub-3nm particle didn't always lead to NPF characterized by typical banana shaped aerosol size distributions measured by SMPS. However, sub-3 nm particles were much higher during NPF events. Sub-3 nm particles were well-correlated with sulfuric acid showing the same diurnal variations and noontime peaks, especially for NPF days. These results are consistent with laboratory studies showing that formation of sub-3 nm particles is very sensitive to sulfuric acid (than amines and ammonia) [Yu et al. GRL 2012]. HYSPLIT back trajectory analysis indicates that air masses from Great Lakes, containing more SO2, VOCs and secondary organics, may contribute to growth of sub-3 nm particles and NPF.

  6. Effects of Continuous Triiodothyronine Infusion on Citric Acid Cycle in the Normal Immature Swine Heart under Extracorporeal Membrane Oxygenation in vivo

    SciTech Connect

    Kajimoto, Masaki; O'Kelly-Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Isern, Nancy G.; Olson, Aaron; Portman, Michael A.

    2014-02-13

    Extracorporeal membrane oxygenation (ECMO) is frequently used in infants with postoperative cardiopulmonary failure. ECMO also suppresses circulating triiodothyronine (T3) levels and modifies myocardial metabolism. We assessed the hypothesis that T3 supplementation reverses ECMO induced metabolic abnormalities in the immature heart. Twenty-two male Yorkshire pigs (age 25-38 days) with ECMO were received [2-13C]lactate, [2,4,6,8-13C]octanoate (medium chain fatty acid) and [U-13C]long-chain fatty acids as metabolic tracers either systemically (totally physiological intracoronary concentration) or directly into the coronary artery (high substrate concentration) for the last 60 minutes of each protocol. Nuclear magnetic resonance (NMR) analysis of left ventricular tissue determined the fractional contribution (Fc) of these substrates to the citric acid cycle (CAC). Fifty percent of the pigs in each group received intravenous T3 supplement (bolus at 0.6 μg/kg and then continuous infusion at 0.2 μg/kg/hour) during ECMO. Under both substrate loading conditions T3 significantly increased lactate-Fc with a marginal increase in octanoate-Fc. Both T3 and high substrate provision increased myocardial energy status indexed by [Phosphocreatine]/[ATP]. In conclusion, T3 supplementation promoted lactate metabolism to the CAC during ECMO suggesting that T3 releases inhibition of pyruvate dehydrogenase. Manipulation of substrate utilization by T3 may be used therapeutically during ECMO to improve resting energy state and facilitate weaning.

  7. The acid and alkalinity budgets of weathering in the Andes-Amazon system: Insights into the erosional control of global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Torres, Mark A.; West, A. Joshua; Clark, Kathryn E.; Paris, Guillaume; Bouchez, Julien; Ponton, Camilo; Feakins, Sarah J.; Galy, Valier; Adkins, Jess F.

    2016-09-01

    The correlation between chemical weathering fluxes and denudation rates suggests that tectonic activity can force variations in atmospheric pCO2 by modulating weathering fluxes. However, the effect of weathering on pCO2 is not solely determined by the total mass flux. Instead, the effect of weathering on pCO2 also depends upon the balance between 1) alkalinity generation by carbonate and silicate mineral dissolution and 2) sulfuric acid generation by the oxidation of sulfide minerals. In this study, we explore how the balance between acid and alkalinity generation varies with tectonic uplift to better understand the links between tectonics and the long-term carbon cycle. To trace weathering reactions across the transition from the Peruvian Andes to the Amazonian foreland basin, we measured a suite of elemental concentrations (Na, K, Ca, Mg, Sr, Si, Li, SO4, and Cl) and isotopic ratios (87Sr/86Sr and δ34S) on both dissolved and solid phase samples. Using an inverse model, we quantitatively link systematic changes in solute geochemistry with elevation to downstream declines in sulfuric acid weathering as well as the proportion of cations sourced from silicates. With a new carbonate-system framework, we show that weathering in the Andes Mountains is a CO2 source whereas foreland weathering is a CO2 sink. These results are consistent with the theoretical expectation that the ratio of sulfide oxidation to silicate weathering increases with increasing erosion. Altogether, our results suggest that the effect of tectonically-enhanced weathering on atmospheric pCO2 is strongly modulated by sulfide mineral oxidation.

  8. Okadaic acid overcomes the blocked cell cycle caused by depleting Cdc2-related kinases in Trypanosoma brucei

    SciTech Connect

    Li Ziyin; Tu Xiaoming; Wang, Ching C. . E-mail: ccwang@cgl.ucsf.edu

    2006-11-01

    Mitosis and cytokinesis are highly coordinated in eukaryotic cells. But procyclic-form Trypanosoma brucei under G1 or mitotic arrest is still capable of dividing, resulting in anucleate daughter cells (zoids). Okadaic acid (OKA), an inhibitor of protein phosphatases PP1 and PP2A, is known to inhibit kinetoplast replication and cell division yielding multinucleate cells with single kinetoplasts. However, when OKA was applied to cells arrested in G1 or G2/M phase via RNAi knockdown of specific cdc2-related kinases (CRKs), DNA synthesis and nuclear division were resumed without kinetoplast replication or cell division, resulting in multinucleate cells as in the wild type. Cells arrested in G2/M via depleting the mitotic cyclin CycB2 or an aurora B kinase homologue TbAUK1 were, however, not released by OKA treatment. The phenomenon is thus similar to the OKA activation of Cdc2 in Xenopus oocyte by inhibiting PP2A [Maton, et al., Differential regulation of Cdc2 and Aurora-A in Xenopus oocytes: a crucial role of phosphatase 2A. J. Cell Sci. 118 (2005) 2485-2494]. A simultaneous knockdown of the seven PP1s or the PP2A catalytic subunit in T. brucei by RNA interference did not, however, result in multinucleate cells. This could be explained by assuming a negative regulation, either directly or indirectly, of CRK by an OKA-sensitive phosphatase, which could be a PP2A as in the Xenopus oocyte and a positive regulation of kinetoplast replication by an OKA-susceptible protein(s). Test of a PP2A-specific inhibitor, fostriecin, on cells arrested in G2/M via CRK depletion or a knockdown of the PP2A catalytic subunit from the CRK-depleted cells both showed a partial lift of the G2/M block without forming multinucleate cells. These observations support the abovementioned assumption and suggest the presence of a novel OKA-sensitive protein(s) regulating kinetoplast replication that still remains to be identified.

  9. Enhanced succinic acid production in Aspergillus saccharolyticus by heterologous expression of fumarate reductase from Trypanosoma brucei.

    PubMed

    Yang, Lei; Lübeck, Mette; Ahring, Birgitte K; Lübeck, Peter S

    2016-02-01

    Aspergillus saccharolyticus exhibits great potential as a cell factory for industrial production of dicarboxylic acids. In the analysis of the organic acid profile, A. saccharolyticus was cultivated in an acid production medium using two different pH conditions. The specific activities of the enzymes, pyruvate carboxylase (PYC), malate dehydrogenase (MDH), and fumarase (FUM), involved in the reductive tricarboxylic acid (rTCA) branch, were examined and compared in cells harvested from the acid production medium and a complete medium. The results showed that ambient pH had a significant impact on the pattern and the amount of organic acids produced by A. saccharolyticus. The wild-type strain produced higher amount of malic acid and succinic acid in the pH buffered condition (pH 6.5) compared with the pH non-buffered condition. The enzyme assays showed that the rTCA branch was active in the acid production medium as well as the complete medium, but the measured enzyme activities were different depending on the media. Furthermore, a soluble NADH-dependent fumarate reductase gene (frd) from Trypanosoma brucei was inserted and expressed in A. saccharolyticus. The expression of the frd gene led to an enhanced production of succinic acid in frd transformants compared with the wild-type in both pH buffered and pH non-buffered conditions with highest amount produced in the pH buffered condition (16.2 ± 0.5 g/L). This study demonstrates the feasibility of increasing succinic acid production through the cytosolic reductive pathway by genetic engineering in A. saccharolyticus.

  10. The impact of acid mine drainage on the methylmercury cycling at the sediment-water interface in Aha Reservoir, Guizhou, China.

    PubMed

    He, Tianrong; Zhu, Yuzhen; Yin, Deliang; Luo, Guangjun; An, Yanlin; Yan, HaiYu; Qian, Xiaoli

    2015-04-01

    The methylmercury (MeHg) cycling at water-sediment interface in an acid mine drainage (AMD)-polluted reservoir (Aha Reservoir) and a reference site (Hongfeng Reservoir) were investigated and compared. Both reservoirs are seasonal anoxic and alkaline. The concentrations of sulfate, sulfide, iron, and manganese in Aha Reservoir were enriched compared to the reference levels in Hongfeng reservoir due to the AMD input. It was found that the MeHg accumulation layer in Aha Reservoir transitioned from the top sediment layer in winter to the water-sediment interface in spring and then to the overlying water above sediment in summer. It supported the assumption that spring methylation activity may start in sediments and migrate into the water column with seasonal variation. The weaker methylation in sediment during spring and summer was caused by the excessive sulfide (∼15-20 μM) that reduced the bioavailability of mercury, while sulfate reduction potential was in the optimal range for the methylation in the overlying water. This led to a transport flux of MeHg from water to sediment in spring and summer. In contrast, such inversion of MeHg accumulation layer did not occur in Hongfeng Reservoir. The sulfate reduction potential was in the optimal range for the methylation in top sediment, and dissolved MeHg was positively related to sulfide in pore water of Hongfeng Reservoir (r = 0.67, p < 0.001). This result suggested that accumulation of MeHg in lake water and cycling of MeHg at sediment-water interface associate with some sensitive environmental factors, such as sulfur.

  11. Combined Sulfur K-edge XANES Spectroscopy and Stable Isotope Analysis of Fulvic Acids and Groundwater Sulfate Identify Sulfur Cycling in a Karstic Catchment Area

    SciTech Connect

    Einsiedl,F.; Schafer, T.; Northrup, P.

    2007-01-01

    Chemical and isotope analyses on groundwater sulfate, atmospheric deposition sulfate and fulvic acids (FAs) associated sulfur were used to determine the S cycling in a karstic catchment area of the Franconian Alb, Southern Germany. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy provided information on the oxidation state and the mechanism of the incorporation of sulfur in FAs. During base flow {delta}{sup 34}S values of groundwater sulfate were slightly depleted to those of recent atmospheric sulfate deposition with mean amount-weighted {delta}{sup 34}S values of around + 3{per_thousand}. The {delta}{sup 18}O values of groundwater sulfate shifted to lower values compared to those of atmospheric deposition and indicated steadiness from base flow to peak flow. The reduced sulfur species (S{sub -1}/thiol; S{sub 0}/thiophene, disulfide, S{sub +2}2/sulfoxide) of soil FAs averaged around 49% of the total sulfur and {delta}{sup 34}S value in FAs was found to be 0.5{per_thousand}. The formation of polysulfides and thiols in FAs in concert with a decreasing isotope value of {delta}{sup 34}S in FAs with respect to those of atmospheric deposition sulfate suggests oxidation of H{sub 2}S, enriched in the {sup 32}S isotope, with organic material. The depletion of {delta}{sup 18}O-SO{sub 4}{sup 2-} by several per mil in groundwater sulfate with respect to those of atmospheric deposition is, therefore, consistent with the hypothesis that SO{sub 4}{sup 2-} has been cycled through the organic S pool as well as that groundwater sulfate is formed by oxidation of H{sub 2}S with organic matter in the mineral soil of the catchment area.

  12. Mutational Analysis of Deinococcus radiodurans Bacteriophytochrome Reveals Key Amino Acids Necessary for the Photochromicity and Proton Exchange Cycle of Phytochromes*S⃞

    PubMed Central

    Wagner, Jeremiah R.; Zhang, Junrui; von Stetten, David; Günther, Mina; Murgida, Daniel H.; Mroginski, Maria Andrea; Walker, Joseph M.; Forest, Katrina T.; Hildebrandt, Peter; Vierstra, Richard D.

    2008-01-01

    The ability of phytochromes (Phy) to act as photointerconvertible light switches in plants and microorganisms depends on key interactions between the bilin chromophore and the apoprotein that promote bilin attachment and photointerconversion between the spectrally distinct red light-absorbing Pr conformer and far red light-absorbing Pfr conformer. Using structurally guided site-directed mutagenesis combined with several spectroscopic methods, we examined the roles of conserved amino acids within the bilin-binding domain of Deinococcus radiodurans bacteriophytochrome with respect to chromophore ligation and Pr/Pfr photoconversion. Incorporation of biliverdin IXα (BV), its structure in the Pr state, and its ability to photoisomerize to the first photocycle intermediate are insensitive to most single mutations, implying that these properties are robust with respect to small structural/electrostatic alterations in the binding pocket. In contrast, photoconversion to Pfr is highly sensitive to the chromophore environment. Many of the variants form spectrally bleached Meta-type intermediates in red light that do not relax to Pfr. Particularly important are Asp-207 and His-260, which are invariant within the Phy superfamily and participate in a unique hydrogen bond matrix involving the A, B, and C pyrrole ring nitrogens of BV and their associated pyrrole water. Resonance Raman spectroscopy demonstrates that substitutions of these residues disrupt the Pr to Pfr protonation cycle of BV with the chromophore locked in a deprotonated Meta-Rc-like photoconversion intermediate after red light irradiation. Collectively, the data show that a number of contacts contribute to the unique photochromicity of Phy-type photoreceptors. These include residues that fix the bilin in the pocket, coordinate the pyrrole water, and possibly promote the proton exchange cycle during photoconversion. PMID:18192276

  13. Compartmentation of acetyl CoA studied by analysis of tricarboxylic acid cycle acids and 3-hydroxybutyrate in bile of rats given [2,2,2-2H3]ethanol.

    PubMed Central

    Norsten, C; Cronholm, T

    1990-01-01

    Acetate, 3-hydroxybutyrate, pyruvate, lactate, citrate, 2-oxoglutarate, succinate, fumarate and malate were analysed in rat bile by gas chromatography and gas chromatography/mass spectrometry of their O-melthyloxime-t-butyldimethylsilyl derivatives. The concentration of acetate increased to about 1.8 mmol/l after administration of [2,2,2-2H3]ethanol. Acetate was formed from ethanol to an extent of about 82% and retained all of the 2H at C-2, whereas 15% of the 2H had been lost in the tricarboxylic acid cycle intermediates and 24% in 3-hydroxybutyrate. Thus the exchange of 2H for 1H takes place after formation of acetyl CoA. For citrate and 3-hydroxybutyrate, 41% and 11% respectively was formed from [2,2,2-2H3]ethanol. These results indicate that different pools of acetyl CoA are used for the synthesis of ketone bodies and citrate, with the latter being derived from ethanol to a much larger extent. Smaller fractions of 2-oxoglutarate (16%) and succinate (5%) were derived from [2,2,2--2H3]ethanol, indicating significant contributions from amino acids. PMID:2405844

  14. Inhibition of phosphotidylinositol-3 kinase pathway by a novel naphthol derivative of betulinic acid induces cell cycle arrest and apoptosis in cancer cells of different origin

    PubMed Central

    Majeed, R; Hamid, A; Sangwan, P L; Chinthakindi, P K; Koul, S; Rayees, S; Singh, G; Mondhe, D M; Mintoo, M J; Singh, S K; Rath, S K; Saxena, A K

    2014-01-01

    Betulinic acid (BA) is a pentacyclic triterpenoid natural product reported to inhibit cell growth in a variety of cancers. However, the further clinical development of BA got hampered because of poor solubility and pharmacological properties. Interestingly, this molecule offer several hotspots for structural modifications in order to address its associated issues. In our endeavor, we selected C-3 position for the desirable chemical modification in order to improve its cytotoxic and pharmacological potential and prepared a library of different triazoline derivatives of BA. Among them, we previously reported the identification of a potential molecule, that is, 3{1N(5-hydroxy-naphth-1yl)-1H-1,2,3-triazol-4yl}methyloxy betulinic acid (HBA) with significant inhibition of cancer cell growth and their properties. In the present study, we have shown for the first time that HBA decreased the expression of phosphotidylinositol-3 kinase (PI3K) p110α and p85α and caused significant downregulation of pAKT and of NFκB using human leukemia and breast cancer cells as in vitro models. Further it was revealed that PI3K inhibition by HBA induced cell cycle arrest via effects on different cell cycle regulatory proteins that include CDKis cyclins and pGSK3β. Also, this target-specific inhibition was associated with mitochondrial apoptosis as was reflected by the increased expression of mitochondrial bax, downregulated bcl2 and decreased mitochondrial levels of cytochrome c, together with reactive oxygen species generation and decline in mitochondrial membrane potential. The apoptotic effectors such as caspase 8, caspase 9 and caspase 3 were found to be upregulated besides DNA repair-associated enzyme, that is, PARP cleavage caused cancer cell death. Pharmacodynamic evaluation revealed that both HBA and BA were safe upto the dose of 2000 mg/kg body weight and with acceptable pharmacodynamic parameters. The in vitro data corroborated with in vivo anticancer activity wherein Ehrlich

  15. Mode of action and resistance studies unveil new roles for tropodithietic acid as an anticancer agent and the γ-glutamyl cycle as a proton sink.

    PubMed

    Wilson, Maxwell Z; Wang, Rurun; Gitai, Zemer; Seyedsayamdost, Mohammad R

    2016-02-01

    While we have come to appreciate the architectural complexity of microbially synthesized secondary metabolites, far less attention has been paid to linking their structural features with possible modes of action. This is certainly the case with tropodithietic acid (TDA), a broad-spectrum antibiotic generated by marine bacteria that engage in dynamic symbioses with microscopic algae. TDA promotes algal health by killing unwanted marine pathogens; however, its mode of action (MoA) and significance for the survival of an algal-bacterial miniecosystem remains unknown. Using cytological profiling, we herein determine the MoA of TDA and surprisingly find that it acts by a mechanism similar to polyether antibiotics, which are structurally highly divergent. We show that like polyether drugs, TDA collapses the proton motive force by a proton antiport mechanism, in which extracellular protons are exchanged for cytoplasmic cations. The α-carboxy-tropone substructure is ideal for this purpose as the proton can be carried on the carboxyl group, whereas the basicity of the tropylium ion facilitates cation export. Based on similarities to polyether anticancer agents we have further examined TDA's cytotoxicity and find it to exhibit potent, broad-spectrum anticancer activities. These results highlight the power of MoA-profiling technologies in repurposing old drugs for new targets. In addition, we identify an operon that confers TDA resistance to the producing marine bacteria. Bioinformatic and biochemical analyses of these genes lead to a previously unknown metabolic link between TDA/acid resistance and the γ-glutamyl cycle. The implications of this resistance mechanism in the context of the algal-bacterial symbiosis are discussed. PMID:26802120

  16. Triiodothyronine increases myocardial function and pyruvate entry into the citric acid cycle after reperfusion in a model of infant cardiopulmonary bypass.

    PubMed

    Olson, Aaron K; Bouchard, Bertrand; Ning, Xue-Han; Isern, Nancy; Rosiers, Christine Des; Portman, Michael A

    2012-03-01

    Triiodothyronine (T3) supplementation improves clinical outcomes in infants after cardiac surgery using cardiopulmonary bypass by unknown mechanisms. We utilized a translational model of infant cardiopulmonary bypass to test the hypothesis that T3 modulates pyruvate entry into the citric acid cycle (CAC), thereby providing the energy support for improved cardiac function after ischemia-reperfusion (I/R). Neonatal piglets received intracoronary [2-(13)Carbon((13)C)]pyruvate for 40 min (8 mM) during control aerobic conditions (control) or immediately after reperfusion (I/R) from global hypothermic ischemia. A third group (I/R-Tr) received T3 (1.2 μg/kg) during reperfusion. We assessed absolute CAC intermediate levels and flux parameters into the CAC through oxidative pyruvate decarboxylation (PDC) and anaplerotic carboxylation (PC) using [2-(13)C]pyruvate and isotopomer analysis by gas and liquid chromatography-mass spectrometry and (13)C-nuclear magnetic resonance spectroscopy. When compared with I/R, T3 (group I/R-Tr) increased cardiac power and oxygen consumption after I/R while elevating flux of both PDC and PC (∼4-fold). Although neither I/R nor I/R-Tr modified absolute CAC levels, T3 inhibited I/R-induced reductions in their molar percent enrichment. Furthermore, (13)C-labeling of CAC intermediates suggests that T3 may decrease entry of unlabeled carbons at the level of oxaloacetate through anaplerosis or exchange reaction with asparate. T3 markedly enhances PC and PDC fluxes, thereby providing potential substrate for elevated cardiac function after reperfusion. This T3-induced increase in pyruvate fluxes occurs with preservation of the CAC intermediate pool. Our labeling data raise the possibility that T3 reduces reliance on amino acids for anaplerosis after reperfusion.

  17. Microbial Iron Cycling in Acidic Geothermal Springs of Yellowstone National Park: Integrating Molecular Surveys, Geochemical Processes, and Isolation of Novel Fe-Active Microorganisms

    PubMed Central

    Kozubal, Mark A.; Macur, Richard E.; Jay, Zackary J.; Beam, Jacob P.; Malfatti, Stephanie A.; Tringe, Susannah G.; Kocar, Benjamin D.; Borch, Thomas; Inskeep, William P.

    2012-01-01

    Geochemical, molecular, and physiological analyses of microbial isolates were combined to study the geomicrobiology of acidic iron oxide mats in Yellowstone National Park. Nineteen sampling locations from 11 geothermal springs were studied ranging in temperature from 53 to 88°C and pH 2.4 to 3.6. All iron oxide mats exhibited high diversity of crenarchaeal sequences from the Sulfolobales, Thermoproteales, and Desulfurococcales. The predominant Sulfolobales sequences were highly similar to Metallosphaera yellowstonensis str. MK1, previously isolated from one of these sites. Other groups of archaea were consistently associated with different types of iron oxide mats, including undescribed members of the phyla Thaumarchaeota and Euryarchaeota. Bacterial sequences were dominated by relatives of Hydrogenobaculum spp. above 65–70°C, but increased in diversity below 60°C. Cultivation of relevant iron-oxidizing and iron-reducing microbial isolates included Sulfolobus str. MK3, Sulfobacillus str. MK2, Acidicaldus str. MK6, and a new candidate genus in the Sulfolobales referred to as Sulfolobales str. MK5. Strains MK3 and MK5 are capable of oxidizing ferrous iron autotrophically, while strain MK2 oxidizes iron mixotrophically. Similar rates of iron oxidation were measured for M. yellowstonensis str. MK1 and Sulfolobales str. MK5. Biomineralized phases of ferric iron varied among cultures and field sites, and included ferric oxyhydroxides, K-jarosite, goethite, hematite, and scorodite depending on geochemical conditions. Strains MK5 and MK6 are capable of reducing ferric iron under anaerobic conditions with complex carbon sources. The combination of geochemical and molecular data as well as physiological observations of isolates suggests that the community structure of acidic Fe mats is linked with Fe cycling across temperatures ranging from 53 to 88°C. PMID:22470372

  18. Microbial iron cycling in acidic geothermal springs of yellowstone national park: integrating molecular surveys, geochemical processes, and isolation of novel fe-active microorganisms.

    PubMed

    Kozubal, Mark A; Macur, Richard E; Jay, Zackary J; Beam, Jacob P; Malfatti, Stephanie A; Tringe, Susannah G; Kocar, Benjamin D; Borch, Thomas; Inskeep, William P

    2012-01-01

    Geochemical, molecular, and physiological analyses of microbial isolates were combined to study the geomicrobiology of acidic iron oxide mats in Yellowstone National Park. Nineteen sampling locations from 11 geothermal springs were studied ranging in temperature from 53 to 88°C and pH 2.4 to 3.6. All iron oxide mats exhibited high diversity of crenarchaeal sequences from the Sulfolobales, Thermoproteales, and Desulfurococcales. The predominant Sulfolobales sequences were highly similar to Metallosphaera yellowstonensis str. MK1, previously isolated from one of these sites. Other groups of archaea were consistently associated with different types of iron oxide mats, including undescribed members of the phyla Thaumarchaeota and Euryarchaeota. Bacterial sequences were dominated by relatives of Hydrogenobaculum spp. above 65-70°C, but increased in diversity below 60°C. Cultivation of relevant iron-oxidizing and iron-reducing microbial isolates included Sulfolobus str. MK3, Sulfobacillus str. MK2, Acidicaldus str. MK6, and a new candidate genus in the Sulfolobales referred to as Sulfolobales str. MK5. Strains MK3 and MK5 are capable of oxidizing ferrous iron autotrophically, while strain MK2 oxidizes iron mixotrophically. Similar rates of iron oxidation were measured for M. yellowstonensis str. MK1 and Sulfolobales str. MK5. Biomineralized phases of ferric iron varied among cultures and field sites, and included ferric oxyhydroxides, K-jarosite, goethite, hematite, and scorodite depending on geochemical conditions. Strains MK5 and MK6 are capable of reducing ferric iron under anaerobic conditions with complex carbon sources. The combination of geochemical and molecular data as well as physiological observations of isolates suggests that the community structure of acidic Fe mats is linked with Fe cycling across temperatures ranging from 53 to 88°C.

  19. Mode of action and resistance studies unveil new roles for tropodithietic acid as an anticancer agent and the γ-glutamyl cycle as a proton sink

    PubMed Central

    Wilson, Maxwell Z.; Wang, Rurun; Gitai, Zemer; Seyedsayamdost, Mohammad R.

    2016-01-01

    While we have come to appreciate the architectural complexity of microbially synthesized secondary metabolites, far less attention has been paid to linking their structural features with possible modes of action. This is certainly the case with tropodithietic acid (TDA), a broad-spectrum antibiotic generated by marine bacteria that engage in dynamic symbioses with microscopic algae. TDA promotes algal health by killing unwanted marine pathogens; however, its mode of action (MoA) and significance for the survival of an algal–bacterial miniecosystem remains unknown. Using cytological profiling, we herein determine the MoA of TDA and surprisingly find that it acts by a mechanism similar to polyether antibiotics, which are structurally highly divergent. We show that like polyether drugs, TDA collapses the proton motive force by a proton antiport mechanism, in which extracellular protons are exchanged for cytoplasmic cations. The α-carboxy-tropone substructure is ideal for this purpose as the proton can be carried on the carboxyl group, whereas the basicity of the tropylium ion facilitates cation export. Based on similarities to polyether anticancer agents we have further examined TDA’s cytotoxicity and find it to exhibit potent, broad-spectrum anticancer activities. These results highlight the power of MoA-profiling technologies in repurposing old drugs for new targets. In addition, we identify an operon that confers TDA resistance to the producing marine bacteria. Bioinformatic and biochemical analyses of these genes lead to a previously unknown metabolic link between TDA/acid resistance and the γ-glutamyl cycle. The implications of this resistance mechanism in the context of the algal-bacterial symbiosis are discussed. PMID:26802120

  20. TRIIODOTHYRONINE INCREASES MYOCARDIAL FUNCTION AND PYRUVATE ENTRY INTO THE CITRIC ACID CYCLE AFTER REPERFUSION IN A MODEL OF INFANT CARDIOPULMONARY BYPASS

    SciTech Connect

    Olson, Aaron; Bouchard, Bertrand; Ning, Xue-Han; Isern, Nancy G.; Des Rosiers, Christine; Portman, Michael A.

    2012-03-01

    We utilized a translational model of infant CPB to test the hypothesis that T3 modulates pyruvate entry into the citric acid cycle (CAC) thereby providing the energy support for improved cardiac function after ischemia-reperfusion. Methods and Results: Neonatal piglets received intracoronary [2-13Carbon(13C)]-pyruvate for 40 minutes (8 mM) during control aerobic conditions (Cont) or immediately after reperfusion (IR) from global hypothermic ischemia. A third group (IR-Tr) received T3 (1.2 ug/kg) during reperfusion. We assessed absolute CAC intermediate levels (aCAC) and flux parameters into the CAC through oxidative pyruvate decarboxylation (PDC ) and anaplerotic carboxylation (PC; ) using 13C-labeled pyruvate and isotopomer analysis by gas and liquid chromatography-mass spectrometry and 13C NMR. Neither IR nor IR-Tr modified aCAC. However, compared to IR, T3 (group IR-Tr) increased cardiac power and oxygen consumption after CPB while elevating both PDC and PC (~ four-fold). T3 inhibited IR induced reductions in CAC intermediate molar percent enrichment (MPE) and oxaloacetate(citrate)/malate MPE ratio; an index of aspartate entry into the CAC. Conclusions: T3 markedly enhances PC and PDC thereby providing substrate for elevated cardiac function and work after reperfusion. The increases in pyruvate flux occur with preservation of the CAC intermediate pool. Additionally, T3 inhibition of reductions in CAC intermediate MPEs indicates that T3 reduces the reliance on amino acids (AA) for anaplerosis after reperfusion. Thus, AA should be more available for other functions such as protein synthesis.