Effect of Ethylene on the Respiratory Response of Isolated Sweet Potato Mitochondria

1978 ◽  
Vol 5 (3) ◽  
pp. 239 ◽  
Author(s):  
GP Arron ◽  
DA Day ◽  
SD Grover ◽  
GG Laties
Keyword(s):  
Low Temperature ◽  
Sweet Potato ◽  
Redox State ◽  
Plant Hormone ◽  
Plant Tissues ◽  
Respiratory Response ◽  
Apparent Effect ◽  
Uptake Rates ◽  
Stimulation Of

The plant hormone ethylene had no apparent effect on the redox state of the respiratory chain components of sweet potato mitochondria during oxidation of succinate. Low temperature e.p.r. spectra of sweet potato mitochondria, in various respiratory states, were not altered by the presence of ethylene. Oxygen uptake rates and ADP/O ratios of sweet potato mitochondria oxidising malate or succinate were also not affected by ethylene. The role of ethylene in the stimulation of respiration in plant tissues is discussed.

Cardiac responses to induced lactate oxidation: NMR analysis of metabolic equilibria

1995 ◽  
Vol 269 (1) ◽  
pp. H160-H168 ◽  
Author(s):  
E. D. Lewandowski ◽  
L. A. Damico ◽  
L. T. White ◽  
X. Yu
Keyword(s):  
Nmr Spectra ◽  
Redox State ◽  
31P Nmr ◽  
Dry Weight ◽  
Lactate Oxidation ◽  
Cardiac Responses ◽  
Oxidative Metabolites ◽  
Proportional Increase ◽  
Stimulation Of

The role of lactate as a source of pyruvate oxidation in supporting cardiac work, energetics, and formation of oxidative metabolites was examined in normal myocardium. 13C- and 31P-nuclear magnetic resonance (NMR) spectra were acquired from isolated rabbit hearts supplied 2.5 mM [3-13C]lactate or [3-13C]pyruvate with or without stimulation of pyruvate dehydrogenase (PDH) by dichloroacetate (DCA). Similar workloads determined by rate-pressure products were noted with pyruvate (21,700 +/- 2,400; mean +/- SE) and lactate (18,970 +/- 1,510). Oxygen consumption was similar in all four groups with means between 19.0 and 22.2 mumol.min-1.g dry weight-1 (SE = 1.6-2.0) as was the ratio of phosphocreatine to ATP with means between 1.8 and 2.1 (SE = 0.1-0.6). Intracellular pH, determined from 31P-NMR spectra, was essentially the same with pyruvate (7.06 +/- 0.02) and lactate (7.05 +/- 0.04). 13C enrichment of glutamate was higher with lactate (92%) than with pyruvate (70%). Pyruvate plus DCA induced no change in glutamate content at 9-10 mumol/g, but 13C enrichment increased to 83%, while lactate plus DCA maintained enrichment at 90%. Levels of alpha-ketoglutarate were lower with lactate (1.81 mumol/g) than with pyruvate (2.36 mumol/g). Lactate plus DCA elevated glutamate by 60% with a proportional increase in alpha-ketoglutarate. Thus the balance between glutamate and alpha-ketoglutarate was affected by substrate supply only and not by PDH activation. The results suggest that the equilibrium between alpha-ketoglutarate and glutamate is sensitive to cytosolic redox state, an important consideration for 13C-NMR analyses that rely on glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)

Low temperature effects on grapevine photosynthesis: the role of inorganic phosphate

2004 ◽  
Vol 31 (8) ◽  
pp. 789 ◽  
Author(s):  
Luke Hendrickson ◽  
Wah Soon Chow ◽  
Robert T. Furbank
Keyword(s):  
Low Temperature ◽  
Carbon Assimilation ◽  
O2 Evolution ◽  
Vitis Vinifera L ◽  
Regulatory Processes ◽  
Photosynthetic O2 Evolution ◽  
Grapevine Leaves ◽  
Sugar Levels ◽  
Stimulation Of

The photosynthetic response of grapevine leaves (Vitis vinifera L. cv. Riesling) to low temperature was studied to determine the role of end-product limitation and orthophosphate (Pi) recycling to the chloroplast under these conditions. As reported previously, the response of photosynthesis in air to stomatal conductance declined at temperatures below 15°C, suggesting that at low temperatures inhibition of photosynthesis in grapevine has a strong non-stomatal component. Stimulation of carbon assimilation at ambient CO2 by reducing O2 from 21 to 2 kPa, O2 declined to zero below 15°C, a phenomenon often associated with a restriction in photosynthesis due to end-product-synthesis limitation. This stimulation could be restored by feeding Pi. Photosynthesis in leaf disks at both high and low irradiances in non-photorespiratory conditions (1% CO2) was highly sensitive to reductions in temperature. Below 15°C, feeding Pi caused a large stimulation of photosynthetic O2 evolution. Metabolite measurements indicated that despite a decline in Rubisco carbamylation state, ribulose 1,5-bisphosphate (RuBP) levels dropped at low temperature and the ratio of 3-phosphoglycerate (3-PGA) to triose phosphate (TP) remained largely unchanged. These results suggest that grapevine-leaf photosynthesis is severely restricted at low temperature by non-stomatal mechanisms. The return of Pi to the chloroplast plays an important role in this limitation but a coordinated set of regulatory processes maintain a homeostasis of phosphorylated sugar levels.

Effect of sleep on CO2 stimulation of breathing in acute and chronic hypoxia

1960 ◽  
Vol 15 (6) ◽  
pp. 1135-1138 ◽  
Author(s):  
Donal J. Reed ◽  
Ralph H. Kellogg
Keyword(s):  
Sea Level ◽  
Adult Male ◽  
Chronic Hypoxia ◽  
Minute Volume ◽  
Respiratory Response ◽  
Apparent Effect ◽  
Respiratory Minute Volume ◽  
Stimulation Of

The effect of sleep on the respiratory response to graded increases in CO2 was studied in four adult male, sea-level residents during hypoxia at sea level, during 23 days at 14,250 ft. and after return to sea level. One subject was also studied at sea level breathing CO2 mixtures with alternating high and low O2. Hypoxia had no apparent effect on the change in respiratory response to CO2 associated with sleep under any of the conditions studied, but it shifted the curve relating respiratory minute volume to alveolar CO2 tension about 1 mm Hg to the left awake and during sleep. It was concluded that sleep and hypoxia act independently rather than interacting in their effect on the respiratory response to CO2. Submitted on June 6, 1960

ROLE OF THE ROOT IN THE TRANSLOCATION OF PRODUCTS OF PHOTOSYNTHESIS IN SUGAR BEET, SOYBEAN, AND PUMPKIN

1967 ◽  
Vol 45 (10) ◽  
pp. 1811-1822 ◽  
Author(s):  
H. Winter ◽  
D. C. Mortimer
Keyword(s):  
Sugar Beet ◽  
Root Function ◽  
Glyceric Acid ◽  
Apparent Velocity ◽  
Beet Root ◽  
Demineralized Water ◽  
Uptake Rates ◽  
Sugar Beet Root ◽  
Stimulation Of

The influence of root function on the export of 14C-labelled products from leaves of sugar beet, soybean, and pumpkin plants was examined with reference to the concept of a circulatory mechanism for translocation. When roots were placed on demineralized water for periods up to 10 days, oxygen uptake rates were reduced. In sugar beet, this was accompanied by an apparent stimulation of about 21% in the quantity of labelled sugar exported from the leaf. In soybean and pumpkin the quantity of export was not altered, but the distribution of exported 14C in the plant was modified to favor a decrease in the proportion recovered from the young parts and an increase in that from the stem and root. The absence of nutrient in the root medium did not result in any significant changes in the pattern of slow metabolism of the sugar translocated to the roots of sugar beet or soybean. In the pumpkin, the proportion of radioactivity recovered in the amino acids was lower, and glyceric acid accumulated in the fed leaf. When portions of the sugar beet root were excised 30 min before assimilation of 14CO2 by a leaf, the quantity of labelled sucrose exported during a 30-min interval was reduced to about 25% of normal, but the apparent velocity of translocation was not altered and the reduction in quantity could be eliminated by extending the time allowed for export. These results led to the conclusion that the root does not exert a controlling influence on translocation, but that it can contribute to the efficiency of the process.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

Redox State in Atrial Fibrillation Pathogenesis and Relevant Therapeutic Approaches

2019 ◽  
Vol 26 (5) ◽  
pp. 765-779 ◽  
Author(s):  
Alexios S. Antonopoulos ◽  
Athina Goliopoulou ◽  
Evangelos Oikonomou ◽  
Sotiris Tsalamandris ◽  
Georgios-Angelos Papamikroulis ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Clinical Studies ◽  
Redox State ◽  
Redox Balance ◽  
Therapeutic Approaches ◽  
Critical Determinant ◽  
Electrophysiological Properties ◽  
Antioxidant Agents ◽  
Clinical Benefits

Background: Myocardial redox state is a critical determinant of atrial biology, regulating cardiomyocyte apoptosis, ion channel function, and cardiac hypertrophy/fibrosis and function. Nevertheless, it remains unclear whether the targeting of atrial redox state is a rational therapeutic strategy for atrial fibrillation prevention. Objective: To review the role of atrial redox state and anti-oxidant therapies in atrial fibrillation. Method: Published literature in Medline was searched for experimental and clinical evidence linking myocardial redox state with atrial fibrillation pathogenesis as well as studies looking into the role of redoxtargeting therapies in the prevention of atrial fibrillation. Results: Data from animal models have shown that altered myocardial nitroso-redox balance and NADPH oxidases activity are causally involved in the pathogenesis of atrial fibrillation. Similarly experimental animal data supports that increased reactive oxygen / nitrogen species formation in the atrial tissue is associated with altered electrophysiological properties of atrial myocytes and electrical remodeling, favoring atrial fibrillation development. In humans, randomized clinical studies using redox-related therapeutic approaches (e.g. statins or antioxidant agents) have not documented any benefits in the prevention of atrial fibrillation development (mainly post-operative atrial fibrillation risk). Conclusion: Despite strong experimental and translational data supporting the role of atrial redox state in atrial fibrillation pathogenesis, such mechanistic evidence has not been translated to clinical benefits in atrial fibrillation risk in randomized clinical studies using redox-related therapies.

scholarly journals Biogeochemical Controls on the Redox Evolution of Earth’s Oceans and Atmosphere

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 191-196 ◽  
Author(s):  
Christopher T. Reinhard ◽  
Noah J. Planavsky
Keyword(s):  
Redox State ◽  
Modeling Tools ◽  
Evolutionary Trajectory ◽  
Geochemical Tracers ◽  
Atmosphere System ◽  
Ocean Atmosphere ◽  
Dramatic Shift ◽  
Redox Evolution

The redox state of Earth’s atmosphere has undergone a dramatic shift over geologic time from reducing to strongly oxidizing, and this shift has been coupled with changes in ocean redox structure and the size and activity of Earth’s biosphere. Delineating this evolutionary trajectory remains a major problem in Earth system science. Significant insights have emerged through the application of redox-sensitive geochemical systems. Existing and emerging biogeochemical modeling tools are pushing the limits of the quantitative constraints on ocean–atmosphere redox that can be extracted from geochemical tracers. This work is honing our understanding of the central role of Earth’s biosphere in shaping the long-term redox evolution of the ocean–atmosphere system.

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