Mechanical and metabolic response of the perfused isolated fish heart to anoxia and acidosis

1980 ◽  
Vol 58 (5) ◽  
pp. 886-889 ◽  
Author(s):  
Jeffrey D. Turner ◽  
William R. Driedzic
Keyword(s):  
Mechanical Performance ◽  
Contractile Response ◽  
Metabolic Response ◽  
Mechanical Function ◽  
Hypercapnic Acidosis ◽  
Fish Heart ◽  
Sea Raven ◽  
Pressure Development ◽  
Mean Pressure ◽  
Contractile Failure

Sea raven (Hemitriperus americanus) and ocean pout (Macrozoarces americanus) hearts were excised and perfused in an isolated system. The contractile response of hearts perfused with buffer equilibrated with 100% O2, 100% N2, or 99% O2: 1% CO2 was monitored and work was calculated from mean pressure development times cardiac output. Hearts subjected to either anoxia or hypercapnic acidosis could not sustain mechanical performance as well as hearts perfused with buffer equilibrated with 100% O2. The decrease in mechanical function was not due to an unavailability of ATP. Alternatively it is suggested that contractile failure is related to a decrease in intracellular pH.

Alterations in myocardial lipid metabolism during lactation in the rat

1998 ◽  
Vol 275 (2) ◽  
pp. E265-E271 ◽  
Author(s):  
Xin Wang ◽  
David G. Hole ◽  
Teresa H. M. Da Costa ◽  
Rhys D. Evans
Keyword(s):  
Fatty Acid ◽  
Mechanical Performance ◽  
Marked Decrease ◽  
Low Density Lipoproteins ◽  
Nonesterified Fatty Acid ◽  
Low Density ◽  
Mechanical Function ◽  
Lipoprotein Lipase Activity ◽  
Very Low Density Lipoproteins ◽  
Lactating Mammary Gland

Metabolism of nonesterified fatty acid (palmitate, 1.1 mM) and triacylglycerol (TAG; triolein, 0.4 mM in the form of both rat chylomicrons and very low density lipoproteins) was studied in isolated perfused working hearts from fed nulliparous, lactating, and weaned rats. Hearts from virgin rats oxidized palmitate readily, but optimal cardiac mechanical performance occurred during perfusion with chylomicrons. In hearts from lactating dams, there was a significant increase in palmitate oxidation and a marked decrease in TAG oxidation from both chylomicrons and very low density lipoproteins compared with hearts from nulliparous animals. There was a concomitant decrease in lipoprotein lipase activity in hearts from lactating animals, and TAG in the absence of palmitate could not support optimal cardiac mechanical function. After litter removal, the changes in fatty acid and TAG metabolism observed in lactation returned to nulliparous values within 96 h. These results suggest that, during lactation, both exogenous and endogenous TAGs are directed away from heart and toward the lactating mammary gland; the heart, therefore, has to rely to a greater extent on nonesterified fatty acid for energy provision under these conditions.

Aerobic and anaerobic contributions to energy metabolism in perfused isolated sea raven (Hemitripterus americanus) hearts

1983 ◽  
Vol 61 (8) ◽  
pp. 1880-1883 ◽  
Author(s):  
William R. Driedzic ◽  
Donna L. Scott ◽  
Anthony P. Farrell
Keyword(s):  
Anaerobic Metabolism ◽  
Lactate Production ◽  
Fish Heart ◽  
Atp Production ◽  
Isolated Hearts ◽  
Relative Contribution ◽  
Sea Raven ◽  
Hemitripterus Americanus ◽  
Aerobic And Anaerobic ◽  
Experimental Preparation

The relative contribution of aerobic and anaerobic metabolism to ATP production was assessed in sea raven (Hemitripterus americanus) hearts. The problem was approached by measuring the rates of oxygen consumption and lactate production by perfused isolated hearts performing mechanical work. In the experimental preparation aerobic metabolism could account for essentially all of the ATP synthesized; as such, the organization of metabolism in this fish heart appears similar to reptilian and mammalian hearts under conditions of adequate oxygen availability.

scholarly journals Cardiac performance in the in situ perfused fish heart during extracellular acidosis: interactive effects of adrenaline

1983 ◽  
Vol 107 (1) ◽  
pp. 415-429 ◽  
Author(s):  
A. P. Farrell ◽  
K. R. MacLeod ◽  
W. R. Driedzic ◽  
S. Wood
Keyword(s):  
Stroke Volume ◽  
Cardiac Performance ◽  
Interactive Effects ◽  
Perfused Heart ◽  
Fish Heart ◽  
Extracellular Acidosis ◽  
Sea Raven ◽  
Filling Time ◽  
Inotropic Responses

The physiological integrity of the in situ perfused heart of the ocean pout was established by its ability to maintain cardiac output (Q) over a range of work loads, and by the dependence of Q upon the filling pressure of the heart. Similar observations have been reported previously for the in situ perfused heart of the sea raven. Physiological levels of extracellular acidosis (pH 7.6/1% CO2 and pH 7.4/2% CO2) significantly depressed cardiac performance in sea raven and ocean pout hearts in situ. Negative chronotropic and inotropic responses were observed. Adrenaline (AD; 10(−7) M) under control conditions (pH 7.9/0.5% CO2) produced a sustained tachycardia. The tachycardia reduced filling time of the ventricle and stroke volume was compromised because of the constant preload to the heart. Consequently, AD produced only an initial, transient increase in stroke volume and Q. Thereafter, stroke volume was reduced in proportion with the increase in heart rate, and Q remained unchanged. The combined challenge of extracellular acidosis and AD demonstrated interactive effects between AD and acidosis in situ. Q and power output were maintained in both species at both levels of extracellular acidosis during the combined challenge. Thus AD alone can maintain (but not improve upon) basal Q during extracellular acidosis. The effects of extracellular acidosis, circulating catecholamines and venous return pressure to the heart are discussed in relation to the regulation of Q following exhaustive exercise.

Propionyl-L-carnitine-mediated improvement in contractile function of rat hearts oxidizing acetoacetate

1995 ◽  
Vol 268 (1) ◽  
pp. H441-H447 ◽  
Author(s):  
R. R. Russell ◽  
J. I. Mommessin ◽  
H. Taegtmeyer
Keyword(s):  
Citric Acid ◽  
Citric Acid Cycle ◽  
Mechanical Performance ◽  
Ketone Bodies ◽  
Contractile Function ◽  
Sustained Improvement ◽  
Acid Cycle ◽  
Rat Hearts ◽  
Beta Hydroxybutyrate ◽  
Contractile Failure

Prior evidence has suggested that propionyl-L-carnitine improves function in ischemic hearts by providing carnitine for dissipation of acyl-CoA derivatives and propionate for enrichment of the citric acid cycle. Because contractile failure in hearts oxidizing ketone bodies is due to sequestration of free coenzyme A, which can be reversed by the addition of anaplerotic substrates that enrich the citric acid cycle, experiments were performed to determine whether the addition of propionyl-L-carnitine (2 mM) can improve performance in working rat hearts utilizing acetoacetate (7.5 mM). Whereas the addition of propionyl-L-carnitine to acetoacetate resulted in a sustained improvement in the work output of the heart, the addition of propionate (2 mM) or L-carnitine (2 mM) alone to acetoacetate had negligible effects on contractile function. Propionyl-L-carnitine increased the uptake of acetoacetate by 130%, whereas beta-hydroxybutyrate release was minimal and unchanged compared with other groups. These observations show that rates of acetoacetate oxidation are increased commensurate with increased contractile function. Tissue metabolite data indicate that the utilization of propionyl-L-carnitine did not lead to accumulation of citric acid cycle intermediates in the span from citrate to 2-oxoglutarate but to an increase in the tissue content of malate. The results show that addition of propionyl-L-carnitine in hearts oxidizing acetoacetate results in improved mechanical performance that is comparable to the mechanical performance of hearts perfused with glucose as the only substrate. This improvement is most likely conferred by anaplerosis, as suggested by enhanced rates of acetoacetate utilization and citric acid flux.

scholarly journals Bottom-Pressure Development Due to an Abrupt Slope Reduction at Stepped Spillways

Water ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 41
Author(s):  
Mohammad J. Ostad Mirza Tehrani ◽  
Jorge Matos ◽  
Michael Pfister ◽  
Anton J. Schleiss
Keyword(s):  
Large Scale ◽  
Pressure Head ◽  
Bottom Pressure ◽  
Local Pressure ◽  
Stepped Spillways ◽  
Pressure Distributions ◽  
Pressure Development ◽  
Mean Pressure ◽  
The Mean ◽  
Horizontal Step

Fluctuating bottom-pressures on stepped chutes are relevant for the spillway design. An abrupt slope reduction causes a local alteration of the bottom-pressure development. Little information is available regarding the air–water flow properties near an abrupt slope reduction on stepped chutes, particularly on the local pressure evolution. Nevertheless, the option of providing a chute slope reduction may be of interest in spillway layout. The experiments presented herein include pressure distributions on both vertical and horizontal step faces, subsequent to an abrupt slope reduction on stepped chutes. A relatively large-scale physical model including abrupt slope reductions from 50° to 18.6° and from 50° to 30° was used, operated with skimming flow. The data indicate a substantial influence of the tested slope reductions on the bottom-pressure development. In the vicinity of the slope reduction, the mean pressure head near the edge of the horizontal step face reached 0.4 to 0.6 times the velocity head upstream of the slope reduction, for critical flow depths normalized by the step height ranging between 2.6 and 4.6.

scholarly journals Regional electrical activation and mechanical function in the partially ischemic left ventricle of dogs

1996 ◽  
Vol 271 (6) ◽  
pp. H2411-H2420 ◽  
Author(s):  
T. Delhaas ◽  
T. Arts ◽  
F. W. Prinzen ◽  
R. S. Reneman
Keyword(s):  
Left Ventricle ◽  
Mechanical Performance ◽  
Anterior Wall ◽  
Left Ventricular ◽  
Electrical Activation ◽  
Mechanical Function ◽  
Partial Occlusion ◽  
External Work ◽  
Ischemic Area ◽  
Ejection Phase

During normoxia, asynchronous electrical activation of the left ventricle significantly affects regional mechanical performance. Regional fiber strain and external work during the ejection phase are found to be lower in early-activated than in late-activated regions. Because electrical activation is known to be delayed during ischemia, the present study was designed to investigate the influence of this electrical asynchrony on regional fiber strain, if any, during moderate and severe myocardial ischemia. Regional electrical activation time (t(ea)) and fiber strain during the ejection phase (ef,e) were measured in the epicardial layers of the left ventricular anterior wall during normoxia and after 15 min of total occlusion (n = 5) or 30, 60, 120, and 180 min of partial occlusion of the left anterior interventricular coronary artery (LAICA; n = 11). Myocardial blood flow (MBF) was assessed with radioactive microspheres. Blood gases, pH, and lactate and Pi contents were determined in arterial, local venous, and coronary sinus blood. During normoxia, t(ea) and ef,e were similar in various epicardial regions of the left ventricular anterior wall. During total LAICA occlusion, in the ischemic area, subepicardial MBF decreased from 0.86 +/- 0.36 (SD) to 0.18 +/- 0.09 ml.g-1.min-1 and subepicardial ef,e decreased from -0.11 +/- 0.02 to -0.01 +/- 0.01, whereas the delay in t(ea) between the normoxic basal-lateral and ischemic apical-medial areas increased slightly but significantly from 1.9 +/- 8.0 to 7.5 +/- 8.0 ms. After a 180-min partial occlusion of the LAICA, in the ischemic area, subepicardial MBF decreased from 0.62 +/- 0.17 to 0.49 +/- 0.18 ml.g-1.min-1 and ef,e decreased from -0.08 +/- 0.01 to -0.03 +/- 0.01. No significant change in the difference in t(ea) between the normoxic and ischemic areas could be detected (5.1 +/- 4.8 and 5.2 +/- 5.8 ms in the control situation and after 180-min partial occlusion, respectively). These findings indicate that in the ischemic epicardium 1) mechanical function is more affected than electrical impulse conduction and 2) delayed activation, if any, is accompanied by decreased instead of increased fiber strain, as found in the normoxic left ventricle.

Obstructive jaundice blunts myocardial contractile response to isoprenaline in the dog: a clue to the susceptibility of jaundiced patients to shock?

1985 ◽  
Vol 69 (6) ◽  
pp. 647-653 ◽  
Author(s):  
O. Binah ◽  
A. Bomzon ◽  
L. M. Blendis ◽  
D. Mordohovich ◽  
O. S. Better
Keyword(s):  
Bile Duct ◽  
Obstructive Jaundice ◽  
Mechanical Performance ◽  
Contractile Response ◽  
Bile Duct Ligation ◽  
Force Frequency ◽  
Contractile Responses ◽  
Duct Ligation ◽  
The Face ◽  
Myocardial Contractile

1. Patients with obstructive jaundice are susceptible to postoperative shock. To clarify the mechanism of this phenomenon, we compared the contractile response to isoprenaline of isolated ventricular preparations from three groups of dogs: (a) dogs with chronic bile-duct ligation (CBDL), (b) dogs with choledochocaval anastomosis (CDCA) and (c) sham-operated dogs (SO). 2. Isolated ventricular muscles from CBDL and CDCA dogs showed a depressed contractile response to isoprenaline as compared with SO dogs. Mechanical performance was spared in the CBDL and CDCA dogs. 3. There were no differences in the contractile responses of SO and CBDL dogs, either to ouabain or to changes in the rates of stimulation (force-frequency relationships). These data demonstrate that, in the dog, obstructive jaundice and/or cholaemia are associated with blunted contractile response to β-adrenoreceptor stimulation in the face of intact basic mechanical performance. 4. Similar inotropic refractoriness to β-adrenoreceptor stimulation could contribute to the susceptibility to postoperative shock in patients with obstructive jaundice.

Substrate dependence of myocardial response to hypoxia in the presence of theophylline

1983 ◽  
Vol 245 (2) ◽  
pp. H363-H367
Author(s):  
T. R. Snow ◽  
T. Caspar
Keyword(s):  
Mechanical Performance ◽  
Pyridine Nucleotide ◽  
Significant Loss ◽  
Papillary Muscles ◽  
Mechanical Function ◽  
Dynamic Relation ◽  
Oxidation Reduction ◽  
Hypoxic Episode ◽  
Substrate Dependence ◽  
The Impact

The experiments reported here were designed to determine whether stimulating glycogenolysis with theophylline affects the ability of isolated rabbit papillary muscles to sustain and recover from a transient hypoxic episode (15 min). Different substrates [glucose (Glc), pyruvate (Pyr), and butyrate (BA)] were used to either support the glycogen levels or permit their depletion. To evaluate the metabolic consequences, the dynamic relation (coupling coefficient) between the oxidation-reduction level of the intramitochondrial pyridine nucleotide NADH and the mechanical power was determined using a microfluorometer. In the absence of theophylline, the presence of Glc was associated with a smaller decrease in developed tension (tau) during the hypoxic period (Glc 53 +/- 5%) when compared with the nonglycolytic substrates (Pyr 33 +/- 5% or BA 31 +/- 6%). The extent of the recovery was not dependent on the available substrate. The addition of theophylline was accompanied by a substrate-dependent increase in tau: Glc 153 +/- 9%, Pyr 134 +/- 9%, and BA 116 +/- 7%. Theophylline increased the impact of the hypoxic episode on mechanical performance: Glc 17 +/- 4%, Pyr 4 +/- 4%, and BA 6 +/- 5%. With Glc, recovery was comparable to control. For the nonglycolytic substrates, recovery of mechanical function was depressed (Pyr 69 +/- 7%, BA 71 +/- 6%), and there was a significant loss of metabolic sensitivity. These data show that the inotropic response to theophylline is in part determined by the available substrate; theophylline exacerbates the impact of a hypoxic episode, and this effect may be due to the metabolic consequences of its presence.

scholarly journals The Effects of Inlet Box Aerodynamics on the Mechanical Performance of a Variable Pitch in Motion Fan

2012 ◽  
Vol 2012 ◽  
pp. 1-10
Author(s):  
A. G. Sheard
Keyword(s):  
Mechanical Performance ◽  
Operating Regime ◽  
Control Flow ◽  
Blade Angle ◽  
Variable Pitch ◽  
Root Cause ◽  
Bearing Failures ◽  
Pressure Development ◽  
Inlet Box ◽  
Development Capability

This paper describes research involving an in-service failure of a “variable pitch in motion” fan’s blade bearing. Variable pitch in motion fans rotate at a constant speed, with the changing blade angle varying the load. A pitch-change mechanism facilitates the change in blade angle. A blade bearing supports each blade enabling it to rotate. The author observed that as the fan aerodynamic stage loading progressively increased, so did the rate of blade-bearing wear. The reported research addressed two separate, but linked, needs. First, the ongoing need to increase fan pressure development capability required an increase in fan loading. This increase was within the context of an erosive operating regime which systematically reduced fan pressure development capability. The second need was to identify the root cause of blade-bearing failures. The author addressed the linked needs using a computational analysis, improving the rotor inflow aerodynamic characteristics through an analysis of the inlet box and design of inlet guide vanes to control flow nonuniformities at the fan inlet. The results of the improvement facilitated both an increase in fan-pressure-developing capability and identification of the root cause of the blade-bearing failures.

Regional intramuscular pressure development and fatigue in the canine gastrocnemius muscle in situ

1997 ◽  
Vol 83 (6) ◽  
pp. 1867-1876 ◽  
Author(s):  
Bill T. Ameredes ◽  
Mark A. Provenzano
Keyword(s):  
Gastrocnemius Muscle ◽  
Mechanical Performance ◽  
Muscle Tension ◽  
Central Zone ◽  
Intramuscular Pressure ◽  
Plantaris Muscle ◽  
Pressure Development ◽  
Zone Ii ◽  
Whole Muscle

Ameredes, Bill T., and Mark A. Provenzano. Regional intramuscular pressure development and fatigue in the canine gastrocnemius muscle in situ. J. Appl. Physiol. 83(6): 1867–1876, 1997.—Intramuscular pressure (PIM) was measured simultaneously in zones of the medial head of the gastrocnemius-plantaris muscle group (zone I, popliteal origin; zone II, central; zone III, near calcaneus tendon) to determine regional muscle mechanics during isometric tetanic contractions. Peak PIM averages were 586, 1,676, and 993 mmHg deep in zones I, II, and III and 170, 371, and 351 mmHg superficially in zones I, II, and III, respectively. During fatigue, loss of PIM across zones was greatest in zone III (−81%) and least in zone I (−60%) when whole muscle tension loss was −49%. Recovery of PIM was greatest in zone III and least in zone II, achieving 86% and 67% of initial PIM, respectively, when tension recovered to 89%. These data demonstrate that 1) regional mechanical performance can be measured as PIM within a whole muscle, 2) PIM is nonuniform within the canine gastrocnemius-plantaris muscle, being greatest in the deep central zone, and 3) fatigue and recovery of PIM are dissimilar across regions. These differences suggest distinct local effects that integrate to determine whole muscle mechanical capacity during and after intense exercise.

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