Transmural bioenergetic responses of normal myocardium to high workstates

1995 ◽  
Vol 268 (5) ◽  
pp. H1891-H1905 ◽  
Author(s):  
J. Zhang ◽  
D. J. Duncker ◽  
Y. Xu ◽  
Y. Zhang ◽  
G. Path ◽  
...  
Keyword(s):  
Blood Flow ◽  
Outer Layer ◽  
Energy Production ◽  
Canine Model ◽  
High Energy ◽  
Resonance Spectroscopy ◽  
Subepicardial Layer ◽  
Lactate Uptake ◽  
Inorganic Phosphates ◽  
Inotropic Stimulation

The response of myocardial high-energy and inorganic phosphates (HEP and Pi, respectively) and associated changes in myocardial blood flow, lactate uptake, and O2 consumption (MVo2) rates were examined in an open-chest canine model during progressively increasing workloads achieved by catecholamine infusion. HEP and Pi levels (measured with transmurally localized 31P-nuclear magnetic resonance spectroscopy) were unaffected by moderate increases in the level of energy expenditure but were significantly altered by high workloads, especially in the subepicardium. The MVo2 and HEP data from three different protocols that utilized pharmacological augmentation of blood flow demonstrated that the maximal rate of myocardial energy production during inotropic stimulation was dictated by perfusion limitation. This limitation was more severe in the subepicardial layer at the high workloads despite equivalent or even higher increases in blood flow to this layer, reflecting a preferential enhancement of demand in the outer layer by catecholamines. In contrast, under basal conditions, existence of a marginal perfusion limitation was evident in the inner but not in the outer layer.

scholarly journals Tirilazad Pretreatment Improves Early Cerebral Metabolic and Blood Flow Recovery from Hyperglycemic Ischemia

1995 ◽  
Vol 15 (1) ◽  
pp. 88-96 ◽  
Author(s):  
Yuichi Maruki ◽  
Raymond C. Koehler ◽  
Jeffrey R. Kirsch ◽  
Kathleen K. Blizzard ◽  
Richard J. Traystman
Keyword(s):  
Lipid Peroxidation ◽  
Blood Flow ◽  
Intracranial Pressure ◽  
Intracellular Ph ◽  
High Energy ◽  
Vehicle Group ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Early Reperfusion ◽  
Tirilazad Mesylate

Acidosis may augment cerebral ischemic injury by promoting lipid peroxidation. We tested the hypothesis that when acidosis is augmented by hyperglycemia, pretreatment with the 21-aminosteroid tirilazad mesylate (U74006F), a potent inhibitor of lipid peroxidation in vitro, improves early cerebral metabolic recovery. In a randomized, blinded study, anesthetized dogs received either tirilazad mesylate (1 mg/kg plus 0.2 mg/kg/h; n = 8) or vehicle (n = 8). Hyperglycemia (400–500 mg/dl) was produced prior to 30 min of global incomplete cerebral ischemia. Intracellular pH and high energy phosphates were measured by phosphorus magnetic resonance spectroscopy. During ischemia, microsphere-determined CBF decreased to 8 ± 4 ml min−1 100 g−1 and intracellular pH decreased to 5.6 ± 0.2 in both groups. During the first 20 min of reperfusion, ATP partially recovered in the vehicle group to 57 ± 21% of baseline, but then declined progressively in association with elevated intracranial pressure. By 30 min, ATP recovery was greater in the tirilazad group (77 ± 35 vs. 36 ± 19%), although postischemic hyperemia was similar. By 45 min, the tirilazad group had a higher intracellular pH (6.5 ± 0.5 vs. 5.9 ± 0.6) and a lower intracranial pressure (18 ± 6 vs. 52 ± 24 mm Hg). By 180 min, blood flow and ATP were undetectable in seven of eight vehicle-treated dogs, whereas ATP was >67% and pH was >6.7 in six of eight tirilazad-treated dogs. Thus, tirilazad acts during early reperfusion to prevent secondary metabolic decay associated with severe acidotic ischemia. If tirilazad acts by inhibiting lipid peroxidation, then these data are consistent with extreme acidosis limiting recovery by a mechanism involving lipid peroxidation.

Regional blood flow and skeletal muscle energy status in endotoxemic rats

1987 ◽  
Vol 252 (5) ◽  
pp. E581-E587 ◽  
Author(s):  
M. M. Jepson ◽  
M. Cox ◽  
P. C. Bates ◽  
N. J. Rothwell ◽  
M. J. Stock ◽  
...  
Keyword(s):  
Blood Flow ◽  
Protein Synthesis ◽  
Regional Blood Flow ◽  
High Energy ◽  
Whole Body ◽  
Sublethal Dose ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Energy Status ◽  
Brown Adipose

Endotoxins induce muscle wasting in part as a result of depressed protein synthesis. To investigate whether these changes reflect impaired energy transduction, blood flow, O2 extraction, and high-energy phosphates in muscle and whole-body O2 consumption (VO2) have been measured. VO2 was measured for 6h after an initial sublethal dose of endotoxin (Escherichia coli lipopolysaccharide 0.3 mg/100 g body wt sc) or saline and during 6h after a second dose 24 h later. In fed or fasted rats, VO2 was either increased or better maintained after endotoxin. In anesthetized fed rats 3-4 after the second dose of endotoxin VO2 was increased, and this was accompanied by increased blood flow to liver (hepatic arterial supply), kidney, and perirenal brown adipose tissue and a 57 and 64% decrease in flow to back and hindlimb muscle, respectively, with no change in any other organ. Hindlimb arteriovenous O2 was unchanged, indicating markedly decreased aerobic metabolism in muscle, and the contribution of the hindlimb to whole-body VO2 decreased by 46%. Adenosine 5'-triphosphate levels in muscle were unchanged in endotoxin-treated rats, and this was confirmed by topical nuclear magnetic resonance spectroscopy, which also showed muscle pH to be unchanged. These results show that although there is decreased blood flow and aerobic oxidation in muscle, adenosine 5'-triphosphate availability does not appear to be compromised so that the endotoxin-induced muscle catabolism and decreased protein synthesis must reflex some other mechanism.

Hyperglycemia during Hypothermic Canine Cardiopulmonary Bypass Increases Cerebral Lactate 

1995 ◽  
Vol 82 (2) ◽  
pp. 512-520 ◽  
Author(s):  
Alan E. Feerick ◽  
William E. Johnston ◽  
Larry W. Jenkins ◽  
Cheng Y. Lin ◽  
Jonathan H. Mackay ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Cerebral Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Energy Charge ◽  
Canine Model ◽  
High Energy ◽  
Serum Glucose ◽  
High Energy Phosphates ◽  
Lactate Levels

Background Hyperglycemia frequently occurs during cardiopulmonary bypass (CPB), although its direct effects on cerebral perfusion and metabolism are not known. Using a canine model of hypothermic CPB, we tested whether hyperglycemia alters cerebral blood flow and metabolism and cerebral energy charge. Methods Twenty anesthetized dogs were randomized into hyperglycemic (n = 10) and normoglycemic (n = 10) groups. The hyperglycemic group received an infusion of D50W, and the normoglycemic animals received an equal volume of 0.9% NaCl. Both groups underwent 120 min of hypothermic (28 degrees C) CPB using membrane oxygenators, followed by rewarming and termination of CPB. Cerebral blood flow (radioactive microspheres) and the cerebral metabolic rate for oxygen were measured intermittently during the experiment and brain tissue metabolites were obtained after bypass. Results Before CPB, the glucose-treated animals had higher serum glucose levels (534 +/- 12 mg/dL; mean +/- SE) than controls (103 +/- 4 mg/dL; P < 0.05), and this difference was maintained throughout the study. Cerebral blood flow and metabolism did not differ between groups at any time during the experiment. Sagittal sinus pressure was comparable between groups throughout CPB. Tissue high-energy phosphates and water contents were similar after CPB, although cerebral lactate levels were greater in hyperglycemic (37.2 +/- 5.7 mumol/g) than normoglycemic animals (19.7 +/- 3.7 mumol/g; P < 0.05). After CPB, pH values of cerebrospinal fluid for normoglycemic (7.33 +/- 0.01) and hyperglycemic (7.34 +/- 0.01) groups were similar. Conclusions Hyperglycemia during CPB significantly increases cerebral lactate levels without adversely affecting cerebral blood flow and metabolism, cerebrospinal fluid pH, or cerebral energy charge.

Myocardial oxygenation and high-energy phosphate levels during graded coronary hypoperfusion

2001 ◽  
Vol 280 (1) ◽  
pp. H318-H326 ◽  
Author(s):  
Jianyi Zhang ◽  
Kamil Ugurbil ◽  
Arthur H. L. From ◽  
Robert J. Bache
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
High Energy ◽  
Coronary Perfusion Pressure ◽  
Resonance Spectroscopy ◽  
Coronary Perfusion ◽  
High Energy Phosphate ◽  
Total Occlusion ◽  
Highly Correlated

This study was performed to determine the myocyte Po 2 required to sustain normal high-energy phosphate (HEP) levels in the in vivo heart. In 10 normal dogs, myocyte Po 2 values were calculated from the myocardial deoxymyoglobin resonance (Mb-δ) intensity determined with 1H-NMR spectroscopy during sequential flow reductions produced by a hydraulic occluder that decreased coronary perfusion pressure to ∼60, 50, and 40 mmHg and, finally, during total occlusion. Myocardial blood flow was measured with microspheres, and HEP levels were determined with 31P magnetic resonance spectroscopy. During control conditions, Mb-δ was undetectable. Myocardial blood flow was 1.11 ± 0.06 ml · min−1 · g−1 during basal conditions and decreased with sequential graded occlusions to 0.78 ± 0.05, 0.58 ± 0.03, and 0.38 ± 0.04 ml · min−1 · g−1, respectively; blood flow during total occlusion was 0.07 ± 0.02 ml · min−1 · g−1. Reductions of blood flow caused progressive increases of Mb-δ, which were associated with decreases of phosphocreatine (PCr), ATP, and the PCr-to-ATP ratio, as well as progressive increases of the Pi-to-PCr ratio. There was a strong linear correlation between normalized blood flow and Mb-δ ( R 2 = 0.89, P < 0.01). Reductions of HEP and Po 2 were also highly correlated (although nonlinearly); with the assumption that myoglobin was 90% saturated with O2 during basal conditions and 5% saturated during total coronary occlusion, the intracellular Po 2 values for 20% reductions of PCr and ATP were ∼4.4 and ∼0.9 mmHg, respectively. The data indicate that O2 availability plays an increasing role in regulation of oxidative phosphorylation when mean intracellular Po 2 values fall below 5 mmHg in the in vivo heart.

Myocardial oxygenation and high-energy phosphate levels during KATP channel blockade

2003 ◽  
Vol 285 (4) ◽  
pp. H1420-H1427 ◽  
Author(s):  
Jianyi Zhang ◽  
Arthur H. L. From ◽  
Kamil Ugurbil ◽  
Robert J. Bache
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
High Energy ◽  
Arterial Stenosis ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Channel Blockade ◽  
High Energy Phosphate ◽  
Similar Reduction ◽  
Myocardial Oxygenation

Inhibition of ATP-sensitive K+ (KATP) channel activity has previously been demonstrated to result in coronary vasoconstriction with decreased myocardial blood flow and loss of phosphocreatine (PCr). This study was performed to determine whether the high-energy phosphate abnormality during KATP channel blockade can be ascribed to oxygen insufficiency. Myocardial blood flow and oxygen extraction were measured in open-chest dogs during KATP channel blockade with intracoronary glibenclamide, whereas high-energy phosphates were examined with 31P magnetic resonance spectroscopy (MRS), and myocardial deoxymyoglobin (Mb-δ) was determined with 1H MRS. Glibenclamide resulted in a 20 ± 8% decrease of myocardial blood flow that was associated with a loss of phosphocreatine (PCr) and accumulation of inorganic phosphate. Mb-δ was undetectable during basal conditions but increased to 58 ± 5% of total myoglobin during glibenclamide administration. This degree of myoglobin desaturation during glibenclamide was far greater than we previously observed during a similar reduction of blood flow produced by a coronary stenosis (22% of myoglobin deoxygenated during stenosis). The findings suggest that reduction of coronary blood flow with an arterial stenosis was associated with a decrease of myocardial energy demands and that this response to hypoperfusion was inhibited by KATP channel blockade.

Myocardial energy metabolism and morphology in a canine model of sepsis

1994 ◽  
Vol 266 (2) ◽  
pp. H757-H768 ◽  
Author(s):  
M. A. Solomon ◽  
R. Correa ◽  
H. R. Alexander ◽  
L. A. Koev ◽  
J. P. Cobb ◽  
...  
Keyword(s):  
Free Energy ◽  
Energy Metabolism ◽  
Canine Model ◽  
High Energy ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Resonance Spectroscopy ◽  
Myocardial Depression ◽  
Ventricular Ejection Fraction ◽  
Myocardial Energy Metabolism

The mechanism responsible for sepsis-induced myocardial depression is not known. To determine if sepsis-induced myocardial depression is caused by inadequate free energy available for work, we studied myocardial energy metabolism in a canine model of sepsis. Escherichia coli-infected (n = 18) or sterile (n = 16) fibrin clots were implanted intraperitoneally into beagles. Myocardial function and structure was assessed using radionuclide ventriculograms, echocardiograms, and light and electron microscopy. The adequacy of energy metabolism was evaluated by comparing catecholamine-induced work increases [myocardial O2 consumption (MVO2) and rate pressure product (RPP)] with a simultaneously obtained estimate of intracellular free energy [phosphocreatine-to-adenosine triphosphate ratio (PCr:ATP)] determined by 31P-magnetic resonance spectroscopy. When compared with control animals, septic animals had a decrease in left ventricular ejection fraction (EF, P < 0.0001) on day 1 and fractional shortening (FS, P < 0.0003) on day 2 after clot implantation. On day 2, neither septic nor control animals had statistically significant decreases in PCr:ATP, despite catecholamine-induced increases in MVO2 and RPP (mean maximal increases in septic animals 135 +/- 31 and 51 +/- 10%, respectively). Light and electron microscopic findings showed that hearts of septic animals, compared with control animals, had a greater degree of morphological abnormalities. Thus, in a canine model of sepsis with alterations in myocyte ultrastructure and documented myocardial depression (decreased EF and FS), intracellular free energy levels (PCr:ATP) were maintained despite catecholamine-induced increases in myocardial work (increased MVO2 and RPP), suggesting high-energy synthetic capabilities are not limiting cardiac function.

Assessing desalination as a sustainable alternative using a multiple criteria decision support model

2008 ◽  
Vol 3 (3) ◽  
Author(s):  
M. B. Fernandes ◽  
M. C. Almeida ◽  
A. G. Henriques
Keyword(s):  
Decision Support ◽  
Energy Production ◽  
Fossil Fuels ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
High Energy ◽  
Economic Benefits ◽  
Multiple Criteria ◽  
Water Production ◽  
Decision Support Model

Desalination technologies provide an alternative for potable water production, having significant potential for application where fresh water scarcity exists. Potential benefits have to be balanced with other factors, such as high costs, high energy consumption, and significant environmental impacts, for the understanding of real risks and gains of desalination within the context of integrated water resources management. Multiple factors can be considered when analysing the viability of a desalination project but often a limited approach is used. The complexity in the analysis lies in finding the alternatives that obey to multiple objectives (e.g. reduced environmental impact, social acceptance, less cost associated). In this paper, development of a methodology based on multiple criteria decision support system for the evaluation and ranking the potential of desalination technologies is described and applied to a Portuguese case study. Relevant factors to the selection of desalination technologies were identified using SWOT analysis and the MACBETH (Measuring Attractiveness by a Categorical Based Evaluation Technique) approach was applied. Technical alternatives considered include reverse osmosis and multi-effect desalination (MED), together with energy production by fossil fuels or solar energy. Production of water by conventional approaches was also considered. Results, for non-economic benefits, show higher score for MED solar but, in the cost-benefit analysis, conventional methods of water production have higher ranking since costs of renewable energies are not yet competitive. However, even if not preferred in economic terms, desalination is ranked significantly above the conventional approaches for non-economic criteria.

Blood flow and high-energy phosphates in microregions of left ventricular subendocardium

1981 ◽  
Vol 240 (5) ◽  
pp. H804-H810 ◽  
Author(s):  
H. D. Kleinert ◽  
H. R. Weiss
Keyword(s):  
Blood Flow ◽  
Linear Relationship ◽  
Tissue Perfusion ◽  
High Energy ◽  
Left Ventricular ◽  
Significant Loss ◽  
Tissue Blood Flow ◽  
High Energy Phosphates ◽  
Tissue Samples ◽  
Heterogeneous Distribution

Blood flow and high-energy phosphate (HEP) content were determined simultaneously in multiple microregions of left ventricular subendocardium in 29 normal anesthetized open-chest rabbits by use of a new micromethod to determine whether a direct linear relationship existed between these parameters. Tissue samples weighed 1-2 mg. ATP and creatine phosphate (CP) content were quantitated in quick-frozen hearts by fluorometry at sites where tissue perfusion was measured by H2 clearance by use of bare-tipped platinum electrodes. A series of validation studies were conducted to ensure that 1) no significant damage to the tissue surrounding the electrode occurred during the period of experimentation and 2) no significant loss of biochemical constituents had occurred due to labile processes during freezing or storage of the tissue. Blood flow, ATP, and CP values averaged 79.1 +/- 24.1 (SD) ml.min-1.100 g-1, 4.9 +/- 1.3 mumol/g tissue, and 8.0 +/- 3.0 mumol/g tissue, respectively, and are similar to those reported in studies using larger tissue samples. Correlation between the heterogeneous distribution of tissue perfusion and HEP revealed no direct linear relationship between these parameters in the normal unstressed rabbit subendocardium.

Magnetic resonance spectroscopy of high-energy phosphates and lactate immediately after coronary artery bypass surgery

Perfusion ◽  
1998 ◽  
Vol 13 (5) ◽  
pp. 328-333 ◽  
Author(s):  
D NF Harris ◽  
J A Wilson ◽  
S D Taylor-Robinson ◽  
K M Taylor
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Cerebral Ischaemia ◽  
Artery Bypass ◽  
High Energy ◽  
Jugular Bulb ◽  
Resonance Spectroscopy ◽  
High Energy Phosphates ◽  
Intracellular Acidosis ◽  
High Incidence

Hypothermic cardiopulmonary bypass (CPB) is associated with a high incidence of neuropsychological defects, marked cerebral swelling immediately after surgery and jugular bulb desaturation during rewarming. This suggests cerebral ischaemia may occur, but evidence is indirect. We studied four patients with 31P magnetic resonance spectroscopy (MRS) and four with 1H MRS before and immediately after coronary surgery. There was no visible lactate in 1H MR spectra. In 31P MR spectra, the ratio of phosphocreatine to adenosine triphosphate was maintained (before: 2.13 ± 0.86 vs after: 2.57 ± 1.31; mean ± 1 SD) and there was no intracellular acidosis (intracellular pH: 7.1 ± 0.04 vs 7.16 ± 0.08), while phosphocreatine/inorganic phosphate was increased immediately after the operation (2.92 ± 0.37 vs 6.39 ± 2.67, p = 0.03). This suggests rebound replacement of energy stores following recovery from temporary cerebral ischaemia during CPB: intra-operative studies would be needed to test this hypothesis further.

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