Effects of 5-hydroxytryptamine on carbohydrate metabolism in Hymenolepis diminuta (Cestoda)

1983 ◽  
Vol 61 (2) ◽  
pp. 137-143 ◽  
Author(s):  
M. S. Rahman ◽  
D. F. Mettrick ◽  
R. B. Podesta
Keyword(s):  
Carbohydrate Metabolism ◽  
Gas Phase ◽  
Specific Activity ◽  
Energy Charge ◽  
Hymenolepis Diminuta ◽  
Total Carbon ◽  
Adenylate Energy Charge ◽  
Acetate Excretion ◽  
Carbon Transfer ◽  
Adenine Nucleotide Pool

Under in vitro anaerobic and aerobic incubations the presence of 5-hydroxytryptamine (5-HT) resulted in an accelerated rate of carbon transfer through the carbohydrate metabolic pathways of Hymenolepis diminuta resulting in an increase in worm tissue total carbon pools. Under aerobic incubation, levels of phosphoglycerates, phosphoenolpyruvate (PEP), and pyruvate were significantly increased over the corresponding levels under anaerobic incubation. Excreted end products of carbohydrate metabolism also differed significantly depending on the gas phase and the presence of 5-HT. Under atmospheric (21%) oxygen concentrations excreted levels of lactate, succinate, and acetate were all significantly elevated; under a 95% O2–5% CO2 gas phase only lactate excretion was increased, and under a 95% N2–5% CO2 gas phase only succinate and acetate excretion increased. The presence of oxygen reduced acetate excretion by up to 55% and under the 95% O2–5% CO2 gas phase succinate excretion was reduced 48%. Irrespective of gas phase or the presence of 5-HT, adenine nucleotide pool sizes and the adenylate energy charge remained constant. The addition of 5-HT had no significant effect in increasing the specific activity of phosphofructokinase (PFK). In the presence of ATP the addition of cAMP increased PFK activity by up to 48%; AMP enhanced the enzyme activity by up to 69%, irrespective of the presence or absence of 5-HT. These results are discussed in terms of the effects of 5-HT, gas phase, and nucleotide pools on the motility, metabolism, and control of H. diminuta, and of other parasites which respond to 5-HT.

scholarly journals Labeling of the releasable adenine nucleotides of washed human platelets

Blood ◽  
1977 ◽  
Vol 49 (1) ◽  
pp. 89-99 ◽  
Author(s):  
HJ Reimers ◽  
MA Packham ◽  
JF Mustard
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Human Platelets ◽  
Transport Processes ◽  
Adenylate Energy Charge ◽  
Prolonged Incubation ◽  
Atp Pool ◽  
Adenine Nucleotide Pool

Abstract In rabbit platelets, the metabolically active ATP pool equilibrates with the releasable ATP pool within 1 day. The studies showing this have now been extended to human platelets. Human platelets labeled with 14C-adenosine or 14C-adenine were incubated for up to 10 hr in vitro at 37 degrees C. After 10 hr, about 12% of the total platelet 14C-ATP and 14C-ADP had become releasable with thrombin (4.2 units/ml). Lysis of platelets did not occur, since less than 1% of the platelet-bound 51Cr from platelets labeled with this radioisotope appeared in the ambient fluid upon thrombin treatment. The 14C-ATP/14C-ADP ratio of the released adenine nucleotides (7.6) was similar to the 14C-ATP/14C-ADP ratio of the nonreleasable adenine nucleotides (7.1) 2 hr after the labeling with 14C-adenosine. However, upon prolonged incubation (10 hr) in vitro, the 14C-ATP/14C-ADP ratio of the releasable adenine nucleotides decreased to 2.7. The adenylate energy charge and the 14C- ATP/14C-ADP ratio of the metabolic adenine nucleotide pool did not change significantly during the time of observation. The 14C-ATP content of the platelets decreased by less than 1% hr of incubation at 37 degrees C. These observations are interpreted to mean that the 14C is transferred from the metabolically active, nonreleasable adenine nucleotide pool of human platelets into the releasable adenine nucleotide pool as ATP and is partially hydrolyzed there to yield ADP. The transfer of ATP across the storage organelle membrane of platelets may be similar to transport processes in the chromaffin cells of the adrenal medulla and may represent a general phenomenon in cells that possess storage organelles containing adenine nucleotides.

Octopus mantle citrate synthase

1976 ◽  
Vol 54 (6) ◽  
pp. 886-891 ◽  
Author(s):  
J. H. A. Fields ◽  
H. Guderley ◽  
K. B. Storey ◽  
P. W. Hochachka
Keyword(s):  
Citrate Synthase ◽  
Specific Activity ◽  
Energy Charge ◽  
Krebs Cycle ◽  
Fold Increase ◽  
Adenylate Energy Charge ◽  
Michaelis Constant ◽  
Acetyl Coa ◽  
Muscle Work ◽  
Krebs Cycle Intermediates

Citrate synthase (EC 4.1.3.7) in mantle muscle of the octopus, Octopus cyanea, occurs in relatively low specific activity and is largely independent of pH between 7.5 and 9.0. Catalytic activity is regulated by the adenylate energy charge and by at least two Krebs cycle intermediates, α-ketoglutarate and citrate. Of the adenylates, ATP is by far the most potent inhibitor, at near-physiological concentrations (4 mM), causing almost a 20-fold increase in the Michaelis constant for acetyl-CoA. Citrate and α-ketoglutarate, on the other hand, are competitive with respect to oxaloacetate, rather than acetyl-CoA, and bring about large increases in the Michaelis constant for oxaloacetate. The regulatory properties of citrate synthase allow a curtailment of carbon flow into the Krebs cycle during periods of burst muscle work, when mantle anaerobic glycolysis is strongly activated.

Contracture of isolated rat heart cells on anaerobic to aerobic transition

1982 ◽  
Vol 242 (6) ◽  
pp. H1022-H1030 ◽  
Author(s):  
C. Hohl ◽  
A. Ansel ◽  
R. Altschuld ◽  
G. P. Brierley
Keyword(s):  
Rat Heart ◽  
Adenine Nucleotide ◽  
Energy Charge ◽  
Creatine Phosphate ◽  
Isolated Rat Heart ◽  
Heart Cells ◽  
Adenylate Energy Charge ◽  
Adult Rat ◽  
Oxygen Paradox ◽  
Adenine Nucleotide Pool

Adult rat heart myocytes prepared by collagenase perfusion show a progressive loss of adenylate energy charge and total adenine nucleotide as a function of time of anaerobic incubation in the absence of glucose. Re-aeration of the rod-shaped anaerobic cells produces a population of viable rounded cells in hypercontracture. The round cells show extensive morphological dislocations but remain metabolically competent in that they 1) restore adenosine 5'-triphosphate levels to the extent permitted by the depleted adenine nucleotide pool: 2) reestablish a low Na+-K+ ratio; and 3) restore creatine phosphate to 73% of control. The hypercontracture on re-aeration of anaerobic myocytes closely resembles an analogous contracture of heart cells in situ produced when hypoxic perfused hearts are reoxygenated, the so-called "oxygen paradox." Both processes are eliminated by inclusion of glucose during the anaerobic phase and by inhibitors of respiration and uncouplers of oxidative phosphorylation added before reoxygenation. Mitochondria in the hypercontracted myocytes retain high acceptor control ratios. Contracture on re-aeration occurs to nearly the same extent in the presence of either mM Ca2+ or 0.1 mM EGTA. Contracture appears related to dislocations in intracellular Ca metabolism that result from the declining energy charge and depleted nucleotide pool produced during anoxic incubation.

scholarly journals Labeling of the releasable adenine nucleotides of washed human platelets

Blood ◽  
1977 ◽  
Vol 49 (1) ◽  
pp. 89-99 ◽  
Author(s):  
HJ Reimers ◽  
MA Packham ◽  
JF Mustard
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Human Platelets ◽  
Transport Processes ◽  
Adenylate Energy Charge ◽  
Prolonged Incubation ◽  
Atp Pool ◽  
Adenine Nucleotide Pool

In rabbit platelets, the metabolically active ATP pool equilibrates with the releasable ATP pool within 1 day. The studies showing this have now been extended to human platelets. Human platelets labeled with 14C-adenosine or 14C-adenine were incubated for up to 10 hr in vitro at 37 degrees C. After 10 hr, about 12% of the total platelet 14C-ATP and 14C-ADP had become releasable with thrombin (4.2 units/ml). Lysis of platelets did not occur, since less than 1% of the platelet-bound 51Cr from platelets labeled with this radioisotope appeared in the ambient fluid upon thrombin treatment. The 14C-ATP/14C-ADP ratio of the released adenine nucleotides (7.6) was similar to the 14C-ATP/14C-ADP ratio of the nonreleasable adenine nucleotides (7.1) 2 hr after the labeling with 14C-adenosine. However, upon prolonged incubation (10 hr) in vitro, the 14C-ATP/14C-ADP ratio of the releasable adenine nucleotides decreased to 2.7. The adenylate energy charge and the 14C- ATP/14C-ADP ratio of the metabolic adenine nucleotide pool did not change significantly during the time of observation. The 14C-ATP content of the platelets decreased by less than 1% hr of incubation at 37 degrees C. These observations are interpreted to mean that the 14C is transferred from the metabolically active, nonreleasable adenine nucleotide pool of human platelets into the releasable adenine nucleotide pool as ATP and is partially hydrolyzed there to yield ADP. The transfer of ATP across the storage organelle membrane of platelets may be similar to transport processes in the chromaffin cells of the adrenal medulla and may represent a general phenomenon in cells that possess storage organelles containing adenine nucleotides.

Effects of Glyoxylate on Adenine Nucletodies and Aggregation of Human Platelets

1975 ◽  
Author(s):  
H. Holmsen ◽  
C. A. Setkowsky ◽  
H. J. Day
Keyword(s):  
Adenine Nucleotide ◽  
Energy Charge ◽  
Krebs Cycle ◽  
Lactate Production ◽  
Human Platelets ◽  
Adenylate Energy Charge ◽  
Atp Levels ◽  
Extracellular Glucose ◽  
Adenine Nucleotide Pool ◽  
Na Uptake

Glyoxylate (G) reduces the ATP/ADP ratio and the adenine nucleotide pool in Ascites tumor cells, probably through inhibition of Krebs cycle and accumulation of citrate (JBC 246, 1607 1971). Incubation of human platelets in plasma or after gelfiltration with G reduced the level of metabolic ATP with a corresponding accumulation of hypoxanthine within the first 10 min after which no changes took place. The decrease in ATP levels is noticeable above 15 mM and is maximal (60–75% decrease) at 45 mM G. Oligomycin, antimycin A (AA), pyruvate, succinate, aspartate or glutamate did not alter the effect of G; 2-deoxyglucose (2-DG) and absence of extracellular glucose enhanced the G-induced reduction in ATP levels. Lactate production was not altered by 45 mM G. The same degree of ATP reduction was observed in the absence and presence of extracellular Na indicating that G did not cause depletion of the adenine nucleotide pool by activating the Na-dependent platelet AMP deaminase through increased Na uptake. The adenylate energy charge (AEC) remained constant (0.89–0.93) despite the large fall in the ATP levels. Primary and secondary platelet aggregation also remained unaffected by G-induced reduction of the ATP levels. Incubation with 2-DG plus AA reduced both ATP levels and AEC, with complete abolishment of secondary and primary aggregation at AEC lower than 0.85 and 0.80, respectively. Although the mechanism whereby G reduces the levels of metabolic ATP remains obscure, these experiments demonstrate clearly that the platelets’ ability to undergo primary and secondary aggregation does not correlate with the level of metabolic ATP, but may correlate with AEC.(Supported by NIH Grant HL 14217–05.)

Hepatic preconditioning preserves energy metabolism during sustained ischemia

2000 ◽  
Vol 279 (1) ◽  
pp. G163-G171 ◽  
Author(s):  
C. Peralta ◽  
R. Bartrons ◽  
L. Riera ◽  
A. Manzano ◽  
C. Xaus ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
High Energy ◽  
Energetic Cost ◽  
Main Role ◽  
Adenylate Energy Charge ◽  
Glycogen Depletion ◽  
Adenine Nucleotide Pool

We evaluated the possibility that ischemic preconditioning could modify hepatic energy metabolism during ischemia. Accordingly, high-energy nucleotides and their degradation products, glycogen and glycolytic intermediates and regulatory metabolites, were compared between preconditioned and nonpreconditioned livers. Preconditioning preserved to a greater extent ATP, adenine nucleotide pool, and adenylate energy charge; the accumulation of adenine nucleosides and bases was much lower in preconditioned livers, thus reflecting slower adenine nucleotide degradation. These effects were associated with a decrease in glycogen depletion and reduced accumulation of hexose 6-phosphates and lactate. 6-Phosphofructo-2-kinase decreased in both groups, reducing the availability of fructose-2,6-bisphosphate. Preconditioning sustained metabolite concentration at higher levels although this was not correlated with an increased glycolytic rate, suggesting that adenine nucleotides and cAMP may play the main role in the modulation of glycolytic pathway. Preconditioning attenuated the rise in cAMP and limited the accumulation of hexose 6-phosphates and lactate, probably by reducing glycogen depletion. Our results suggest the induction of metabolic arrest and/or associated metabolic downregulation as energetic cost-saving mechanisms that could be induced by preconditioning.

Sign in / Sign up

Export Citation Format

Share Document