scholarly journals Effect of fluorophenylalanine on indole-3-acetic acid oxidation in Avena coleoptiles

2014 ◽  
Vol 61 (3-4) ◽  
pp. 389-397
Author(s):  
Andrew B. Maksymowych ◽  
Joseph A.J. Orkwiszewski
Keyword(s):  
Maximum Velocity ◽  
Acid Oxidation ◽  
Michaelis Constant ◽  
Phenolic Metabolism ◽  
Treatment Groups ◽  
Wide Range ◽  
Amino Acid Analog ◽  
Activity Temperature ◽  
Coleoptile Elongation ◽  
Indole 3 Acetic Acid

Effects of the amino acid analog D,L-p-fluorophenylalanine on auxin oxidizing activity from <i>Avena saliva</i> cv. Clintford have been examined. Incubation of etiolated <i>Avena</i> coleoptile apices with D,L-p-fluorophenylalanine, previously reported to promote elongation and depress phenolic metabolism, lowers auxin oxidizing activity. Temperature and pH profiles demonstrated that depression of oxidizing activity by D,L-p-fluorophenylalanine occurs over a relatively wide range. Incubation of coleoptiles in media containing L-phenylalanine alone or L-phenylalanine combined with D,L-p-fluorophenylalanine result in oxidizing activities which are, respectively, slightly higher than or restored to control levels. Thus, dark incubation of coleoptiles with D,L-p-fluorophenylalanine results in auxin oxidizing activity which differs from that of control and other treatment groups. Oxidizing activity from D,L-p-fluorophenylalanine pretreated coleoptiles has a Michaelis constant (70 µM) and a maximum velocity (0.200) which are consistently lower than the control constants. These findings provide further clarification of the effects of D,L-p-fluorophenylalanine, on coleoptile elongation and auxin oxidizing activity in etiolated <i>Avena</i> coleoptiles.

Investigation on a Type of Flow Control to Weaken Unsteady Separated Flows by Unsteady Excitation in Axial Flow Compressors

2004 ◽  
Author(s):  
Xin-Qian Zheng ◽  
Xiao-Bo Zhou ◽  
Sheng Zhou
Keyword(s):  
Wide Spectrum ◽  
Excitation Frequency ◽  
Axial Flow ◽  
Maximum Velocity ◽  
Excitation Amplitude ◽  
High Order Scheme ◽  
Wide Range ◽  
Optimal Excitation ◽  
Suction And Blowing ◽  
Axial Flow Compressors

By solving unsteady Reynolds-averaged 2-D N-S equations discretized by a high-order scheme, the results showed that the disordered unsteady separated flow could be effectively controlled by periodic suction and blowing in a wide range of incidence, resulting in enhancement of time-averaged aerodynamic performances. The effects of unsteady excitation frequency, amplitude and excitation location were investigated in detail. The effective excitation frequency spans a wide spectrum and there is an optimal excitation frequency that is nearly equal to the Characteristic frequency of vortex shedding. Excitation amplitude exhibits a threshold value (nearly 10% in term of the ratio of maximum velocity of periodic suction and blowing to the velocity of free flow) and an optimal value (nearly 35%). The optimal excitation location is just upstream of the separation point. We also explored feasible unsteady actuators by utilizing upstream wake for constraining unsteady separation in axial flow compressors.

Minimum intracellular PO2 for maximum cytochrome turnover in red muscle in situ

1987 ◽  
Vol 252 (5) ◽  
pp. H906-H915 ◽  
Author(s):  
T. E. Gayeski ◽  
R. J. Connett ◽  
C. R. Honig
Keyword(s):  
Energy Demand ◽  
Concentration Ratio ◽  
Probability Distributions ◽  
Michaelis Constant ◽  
Cytochrome Aa3 ◽  
Wide Range ◽  
Red Muscle

Probability distributions of myoglobin (Mb) saturation and intracellular PO2 were determined with subcellular spatial resolution in dog gracilis muscles during steady-state twitch contraction at 5-100% of maximal rate of O2 consumption (VO2). Calculations (Clark, A., and P. A.A. Clark. Biophys. J. 48: 931-938, 1985) and measurements (Gayeski, T. E. J., and C. R. Honig. Adv. Exp. Med. Biol. 200: 487-494, 1986) indicate that the PO2 in equilibrium with Mb is virtually identical to the PO2 at cytochrome aa3. Median intracellular PO2 and PO2 in the lower tails of probability distributions were poorly correlated with VO2. The variability of cell PO2 was greatly diminished when median PO2 was less than the PO2 for half saturation of MB, since Mb acts as a PO2 buffer. The lower tails of PO2 distributions contained almost no anoxic loci even when median PO2 was less than 1 Torr. VO2 was well correlated with the concentration ratio of phosphocreatine to free creatine (PCr/Crf) over a wide range of PO2. PO2 greater than or equal to 0.5 Torr supported maximal VO2 and energy demand. We conclude that 1) the mechanism of action of cytochrome aa3 is the same in red muscle in vivo as in mitochondria in vitro, and 2) an upper bound on the apparent Michaelis constant for maximal VO2 of red muscle is approximately 0.06 Torr.

scholarly journals Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

2019 ◽  
Vol 49 (3) ◽  
pp. 827-849 ◽  
Author(s):  
Eunok Yim ◽  
Alexandre Stegner ◽  
Paul Billant
Keyword(s):  
Turbulent Viscosity ◽  
Maximum Velocity ◽  
Stability Limit ◽  
Velocity Profiles ◽  
Instability Criterion ◽  
Marginal Stability ◽  
Vertical Wavelength ◽  
Centrifugal Instability ◽  
Wide Range ◽  
Anticyclonic Eddies

AbstractWe investigate the linear stability of intense baroclinic anticyclones, with a particular focus on the centrifugal (inertial) instability. Various vertical and radial velocity profiles are studied. The vertical profiles are such that the velocity is maximum at the surface. These profiles correspond to oceanic eddies such as submesoscale mixed-layer eddies or intense mesoscale eddies in the upper thermocline. The results show that the main characteristics of the centrifugal instability (growth rate, vertical wavelength) depend weakly on the baroclinic structure of the anticyclone. The dominant azimuthal wavenumber is for small Burger number (Bu) and for higher Bu, where Bu is the square root of the ratio of the deformation radius over the characteristic eddy radius where the velocity is maximum. The marginal stability limits of the centrifugal instability for the different velocity profiles collapse approximately on a single curve in the parameter space (Ro, Bu), where is the Rossby number, with being the maximum velocity. By means of an asymptotic analysis for short vertical wavelength, an explicit prediction for the marginal stability limit is derived for a wide range of velocity profiles. We then suggest to use, for most of oceanic anticyclones, the instability criterion valid for a Gaussian eddy: where is the Ekman number, H is the eddy depth, and ν is the turbulent viscosity at the ocean surface. Some baroclinic anticyclones can remain stable even if they have a core region of negative absolute vorticity provided that they are small enough. This formula explains the few observations of intense anticyclonic eddies having a negative core vorticity around .

Mechanisms of potassium transfer across the dually perfused rat placenta

1993 ◽  
Vol 265 (2) ◽  
pp. R341-R347 ◽  
Author(s):  
T. Mohammed ◽  
J. Stulc ◽  
J. D. Glazier ◽  
R. D. Boyd ◽  
C. P. Sibley
Keyword(s):  
Diffusion Coefficient ◽  
Maximum Velocity ◽  
T Test ◽  
Michaelis Constant ◽  
Diffusion Limited ◽  
51Cr Edta ◽  
The Asymmetry ◽  
Paired T Test

The purpose of this study was to directly investigate the mechanisms of K+ transfer across the rat placenta, which was isolated and perfused through both its maternal and fetal circulations. Unidirectional maternofetal (Kmf) and fetomaternal (Kfm) clearances for 42K, 51Cr-labeled EDTA (used as a diffusion-limited paracellular marker), and 3H2O (used as a flow-limited marker) were respectively 232 +/- 36, 12 +/- 4, and 1,020 +/- 260 (mf) and 96 +/- 26, 18 +/- 6, and 737 +/- 176 (fm) microliters.min-1 x g placenta-1. Calculated K+ fluxes were asymmetric, being 0.75 +/- 0.12 and 0.41 +/- 0.12 mumol.min-1 x g placenta-1 for maternofetal and fetomaternal, respectively (mean +/- SE, n = 6; P < 0.01, paired t test). Although Kmf for 3H2O was 28% higher than Kfm, this could not completely account for the asymmetry in K+ fluxes. Kmf for 42K was 12-70 times higher than that for 51Cr-EDTA (presumed to be a paracellular marker), although its diffusion coefficient is only 2.5 times higher. An apparent Michaelis constant (Km) of 11.0 +/- 2.4 mM and maximum velocity (Vmax) of 3.8 +/- 0.33 mumol.min-1 x g placenta-1 was calculated by Michaelis-Menten analysis of the transcellular component of maternofetal flux (Jmf) for K+. Ouabain or barium (1 mM in maternal and fetal perfusate) reduced Kmf for 42K from 250 +/- 38 to 76 +/- 13 microliters.min-1 x g placenta-1 (n = 4; P < 0.01) and from 358 +/- 31 to 106 +/- 18 microliters.min-1 x g placenta-1 (n = 5; P < 0.001). Neither drug had any effect on Kmf for 51Cr-EDTA or 3H2O.(ABSTRACT TRUNCATED AT 250 WORDS)

Copper transport and kinetics in cultured C6 rat glioma cells

1995 ◽  
Vol 269 (4) ◽  
pp. C892-C898 ◽  
Author(s):  
Y. Qian ◽  
E. Tiffany-Castiglioni ◽  
E. D. Harris
Keyword(s):  
Membrane Fraction ◽  
Glioma Cells ◽  
Maximum Velocity ◽  
C6 Cells ◽  
Michaelis Constant ◽  
Rat Glioma ◽  
Saturation Kinetics ◽  
Efflux Mechanism ◽  
Import And Export ◽  
P Type

C6 rat glioma cells accumulate and efflux 67Cu. Both processes showed saturation kinetics with increasing 67Cu concentration. The Michaelis constant (Km) for uptake was 0.63 +/- 0.14 microM; maximum velocity (Vmax) was 3.29 +/- 0.57 pmol Cu.mg protein-1.min-1. The Km for efflux was 0.15 +/- 0.06 microM; Vmax was 1.08 +/- 0.71 pmol Cu.mg protein-1.min-1. p-Chloromercuribenzoate (p-CMB) totally blocked 67Cu efflux but had no effect on Km or Vmax of uptake. Total 67Cu in the cell after 50 min was partitioned equally between particulate and soluble fractions. p-CMB-treated cells accumulated more 67Cu, but < 10% was bound to the particulate (membrane) fraction. Pb also increased 67Cu accumulation without affecting Km and Vmax of 67Cu uptake. These data suggest that carriers for import and export of Cu in C6 cells are distinct or operate in two different cellular environments. Efflux is a sulfhydryl-dependent process subject to inhibition by Pb. The data are consistent with a P-type ATPase in the efflux of Cu from cells and the potential for Pb to inhibit the efflux mechanism.

scholarly journals Determining Ideal Balance Among Branched-Chain Amino Acids (BCAA) as a Proof of Concept Study in Healthy Children

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 1068-1068
Author(s):  
Haneen Saleemani ◽  
Rajavel Elango ◽  
Gabriella Horvath ◽  
Sylvia Stockler
Keyword(s):  
Protein Synthesis ◽  
Future Research ◽  
Acid Oxidation ◽  
P Value ◽  
Healthy Children ◽  
Proof Of Concept ◽  
Body Protein ◽  
Wide Range ◽  
Medical Foods ◽  
Total Body

Abstract Objectives Medical foods for children with in-born errors of metabolism (propionic academia, PROP) are formulated with imbalanced mixture of the BCAA (high leucine, to minimal or no valine and isoleucine), and therefore their use is controversial. The objective of the current study was to determine an ideal BCAA ratio at which total body protein synthesis is optimized in healthy children using the indicator amino acid oxidation (IAAO) method. Methods The study design was based on the oxidation of the stable isotope L-[1–,13C] phenylalanine to ,13CO2 to compare protein synthesis among seven different BCAA ratios. Leucine intake was gradually reduced from current high doses in medical foods; isoleucine and valine were kept constant. This study was done as a proof of concept in healthy children, to allow characterization of the metabolic responses to wide range of leucine test intakes, to help design narrow BCAA ratio range to test in children with PROP. Results A total of 8 healthy children were studied, completing 42 study days. ANOVA showed significant differences in F13CO2 with different BCAA ratios; P value &lt;0.001. A BCAA ratio of (leucine: Isoleucine: Valine = 1:0:0) was associated with the highest F13CO2 compared to other ratios (p value &lt;0.001), indicating low total body protein synthesis. By reducing leucine intake, with BCAA ratio between (1: 0.26: 0.28 to 1:0.35:0.4) protein synthesis was optimized. Conclusions Using the IAAO method in healthy children, we tested for the first time the effect of different BCAA ratios on protein synthesis. Results from this study confirmed that the BCAA ratio of (leucine: Isoleucine: Valine = 1:0:0), which is similar to the ratio in medical foods, limited total body protein synthesis. Furthermore, a balanced BCAA ratio that optimized protein synthesis was found to be between (1: 0.26: 0.28) and (1: 0.35:0.4). Thus, we propose reformulating the BCAA mixture in medical foods, by reducing leucine content by 50%. Future research in children with PROP with our proposed BCAA ratio is necessary to confirm improved patient growth outcomes. Funding Sources Faculty of Applied Medical Sciences, Department of Clinical Nutrition, King Abdulaziz University and BC Children's Hospital Research Institute.

scholarly journals Indole-3-Acetic Acid Oxidation and Crocin Bleaching by Horseradish Peroxidase

1988 ◽  
Vol 86 (4) ◽  
pp. 1310-1314 ◽  
Author(s):  
Wolfgang F. Osswald ◽  
Wolfgang Schütz ◽  
Erich F. Elstner
Keyword(s):  
Acetic Acid ◽  
Horseradish Peroxidase ◽  
Acid Oxidation ◽  
Indole 3 Acetic Acid

THE PENTOSE PHOSPHATE METABOLIC PATHWAY IN THE HUMAN ERYTHROCYTE: II. THE TRANSKETOLASE AND TRANSALDOLASE ACTIVITY OF THE HUMAN ERYTHROCYTE

1961 ◽  
Vol 39 (3) ◽  
pp. 533-543 ◽  
Author(s):  
Y. S. Brownstone ◽  
O. F. Denstedt
Keyword(s):  
Human Erythrocyte ◽  
Soluble Fraction ◽  
Pentose Phosphate ◽  
Ion Concentration ◽  
Thiamine Pyrophosphate ◽  
Magnesium Ions ◽  
Michaelis Constant ◽  
Hydrogen Ion Concentration ◽  
Wide Range ◽  
Human Red Cells

Transketolase, in the human erythrocyte, is confined to the soluble fraction of the cell. The activation energy for the formation of sedoheptulose-7-phosphate (S-7-P) from pentose phosphate was found to be 11,500 calories and the rate of formation of S-7-P to be directly proportional to the concentration of the enzyme. The Michaelis constant, with ribose-5-phosphate (R-5-P) as the added substrate, was found to be 6 × 10−3 M. The activity of the enzyme is close to the maximum over a wide range of hydrogen ion concentration (pH 7.1 to 8.3) with only a gradual decrease beyond these limits. The transketolase, in the dialyzed stroma-free hemolyzate, is active without the addition of magnesium ions or thiamine pyrophosphate. It is unaffected by sulphydryl-binding inhibitors and by EDTA and oxythiamine pyrophosphate.Transaldolase activity also has been demonstrated in the hemolyzate of human red cells. The rate of the production of hexose phosphate from sedoheptulose-7-phosphate was found to be of the order of 40 μmoles/g Hb/hour. The activity of the enzyme is close to the maximum between pH 7.18 and 7.75.

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