Adaptation speed of cardiac mitochondrial oxygen consumption decreases with higher heart rate

1993 ◽  
Vol 265 (6) ◽  
pp. H1893-H1898 ◽  
Author(s):  
M. H. Eijgelshoven ◽  
J. B. Hak ◽  
J. H. Van Beek ◽  
N. Westerhof
Keyword(s):  
Skeletal Muscle ◽  
Heart Rate ◽  
Oxygen Consumption ◽  
Response Time ◽  
Metabolic Demand ◽  
Average Delay ◽  
Mitochondrial Oxygen Consumption ◽  
Atp Production ◽  
Mean Response Time ◽  
The Mean

The purpose of the present study was to determine whether the mean response time of cardiac mitochondrial oxygen consumption after a step in metabolic demand is constant in heart muscle, as has already been found for skeletal muscle. The mean response time reflects the average delay between the change in ATP hydrolysis due to a heart rate step and mitochondrial ATP production. Isolated rabbit hearts with a water-filled balloon in the left ventricle were perfused according to Langendorff with a constant flow of Tyrode solution at 28 degrees C. The mean response time increased significantly from 7.6 s for a step in heart rate from 60 to 70 min-1 to 12.1 s for a step from 60 to 120 min-1. The mean response times for heart rate steps downward from 120 min-1 were all approximately 12 s, but for the step from 120 to 140 min-1 the response time was 16.8 s. These results demonstrate that the mean response time of cardiac mitochondrial oxygen consumption in most cases increases with heart rate. These findings are in contrast to those obtained in skeletal muscle, where the response time at which ATP synthesis adapts to a change in work load is constant.

Response time of cardiac mitochondrial oxygen consumption to heart rate steps

1991 ◽  
Vol 260 (2) ◽  
pp. H613-H625 ◽  
Author(s):  
J. H. Van Beek ◽  
N. Westerhof
Keyword(s):  
Heart Rate ◽  
Response Time ◽  
Time Course ◽  
Mean Transit Time ◽  
Impulse Response Function ◽  
Heart Tissue ◽  
Experimental Information ◽  
O2 Consumption ◽  
Mean Response Time ◽  
The Mean

We investigated the time course of cardiac mitochondrial O2 consumption following steps in heart rate in 16 isolated rabbit hearts perfused with Tyrode solution. The time course was characterized by the mean response time, i.e., the first statistical moment (mean time) of the impulse response function. Like the mean transit time for an indicator, it provides an important characteristic of the response time course. The venous O2 content transients during steps in heart rate were measured and corrected for O2 diffusion and vascular transport using a mathematical model with experimental information derived from O2 washout following steps in arterial O2 concentration or perfusion flow. We deduce from these washout experiments that the effective O2 solubility in heart tissue is 86 +/- 13% (mean +/- SE) of solubility in water. The measured venous mean response time following a step in heart rate at 37 degrees C was 17.6 +/- 1.1 s. The mean response time of cardiac mitochondrial O2 consumption to changes in heart rate after correction for O2 transport was 7.7 +/- 0.7 s.

Mitochondrial dehydrogenase activity affects adaptation of cardiac oxygen consumption to demand

1993 ◽  
Vol 264 (2) ◽  
pp. H448-H453 ◽  
Author(s):  
J. B. Hak ◽  
J. H. Van Beek ◽  
M. H. Eijgelshoven ◽  
N. Westerhof
Keyword(s):  
Oxygen Consumption ◽  
Response Time ◽  
Dehydrogenase Activity ◽  
Calcium Uptake ◽  
High Energy ◽  
Mitochondrial Calcium ◽  
High Energy Phosphates ◽  
Mean Response Time ◽  
The Mean ◽  
Mitochondrial Calcium Uptake

The effect of regulation of mitochondrial dehydrogenase activities on the mean response time of mitochondrial oxygen consumption, which characterizes the delay between changes in ATP hydrolysis and changes in oxygen consumption, was investigated in isolated rabbit hearts and perfused with Tyrode solution at 28 degrees C. Perfusion with ruthenium red (RR) blocks mitochondrial calcium uptake and thus decreases mitochondrial dehydrogenase activities. Perfusion with pyruvate increases pyruvate dehydrogenase activity. The mean response time was 11.8 +/- 0.7 s (means +/- SE) during control, 12.2 +/- 1.2 s during perfusion with 0.9 microgram/ml RR, and 20.7 +/- 3.4 s during perfusion with 2.1 micrograms/ml RR. Blockade with 0.9 microgram/ml RR, which is presumably partial, did not slow the response, suggesting that mitochondrial calcium uptake may not be rate limiting. Strong blockade of mitochondrial calcium uptake increases the mean response time, presumably due to decreased calcium activation of the mitochondrial dehydrogenases. Perfusion with pyruvate significantly decreased the mean response time to 10.0 +/- 1.4 s compared with 11.9 +/- 0.7 s during perfusion with glucose. This decrease with pyruvate is not compatible with a shift to regulation by high-energy phosphates but may reflect increased mitochondrial oxidative capacity caused by increased NADH levels.

Dynamics of myocardial lactate efflux after a step in heart rate in isolated rabbit hearts

1993 ◽  
Vol 265 (6) ◽  
pp. H2081-H2085 ◽  
Author(s):  
J. B. Hak ◽  
J. H. van Beek ◽  
M. H. van Wijhe ◽  
N. Westerhof
Keyword(s):  
Heart Rate ◽  
Response Time ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Atp Synthesis ◽  
Dry Weight ◽  
Rabbit Heart ◽  
Metabolic Demand ◽  
Mean Response Time

We investigated whether a glycolytic burst contributes to the initial adaptation of ATP synthesis to increased cardiac metabolic demand. Six isolated rabbit hearts were perfused with glucose-containing Tyrode solution at 28 degrees C. In venous and arterial samples the lactate concentration was determined with a sensitive enzymatic cycling method. After the heart rate was doubled from 60 to 120 beats/min, lactate efflux increased from 0.23 +/- 0.10 (SE) to 0.45 +/- 0.12 mumol.min-1.g-1 dry weight with a mean response time of 21.3 s but without an overshoot. The transport time for lactate is longer than 15.7 s, suggesting that lactate production adapts with a mean response time of less than 6 s. Because no overshoot in lactate efflux was found, it is unlikely that a glycolytic burst after a step in heart rate contributes to the fast adaptation of ATP synthesis to demand in the isolated rabbit heart, although it might be possible that a change in cytosolic lactate production is not reflected in an increase in lactate efflux. Extrapolation of the results of this study to the in vivo situation should be done with caution.

scholarly journals Development of Perceptual Inhibition in Adolescents—a Critical Period?

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 457
Author(s):  
Isabel María Introzzi ◽  
María Marta Richard’s ◽  
Yesica Aydmune ◽  
Eliana Vanesa Zamora ◽  
Florencia Stelzer ◽  
...  
Keyword(s):  
Response Time ◽  
Executive Functions ◽  
Critical Period ◽  
Search Task ◽  
Probability Distributions ◽  
Linear Trajectory ◽  
Gaussian Functions ◽  
Mean Response Time ◽  
The Mean ◽  
One Year

Recent studies suggest that the developmental curves in adolescence, related to the development of executive functions, could be fitted to a non-linear trajectory of development with progressions and retrogressions. Therefore, the present study proposes to analyze the pattern of development in Perceptual Inhibition (PI), considering all stages of adolescence (early, middle, and late) in intervals of one year. To this aim, we worked with a sample of 275 participants between 10 and 25 years, who performed a joint visual and search task (to measure PI). We have fitted ex-Gaussian functions to the probability distributions of the mean response time across the sample and performed a covariance analysis (ANCOVA). The results showed that the 10- to 13-year-old groups performed similarly in the task and differ from the 14- to 19-year-old participants. We found significant differences between the older group and all the rest of the groups. We discuss the important changes that can be observed in relation to the nonlinear trajectory of development that would show the PI during adolescence.

scholarly journals Low Levels of Lipopolysaccharide Modulate Mitochondrial Oxygen Consumption in Skeletal Muscle

Metabolism ◽  
2015 ◽  
Vol 64 (3) ◽  
pp. 416-427 ◽  
Author(s):  
Madlyn I. Frisard ◽  
Yaru Wu ◽  
Ryan P. McMillan ◽  
Kevin A. Voelker ◽  
Kristin A. Wahlberg ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Mitochondrial Oxygen Consumption ◽  
Low Levels

scholarly journals Mechanical Ventilation Preserves Diaphragm Mitochondrial Function in a Rat Sepsis Model

2020 ◽  
Author(s):  
Pierre Eyenga ◽  
Damien Roussel ◽  
Benjamin Rey ◽  
Patrice Ndille ◽  
Loic Teulier ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Oxygen Consumption ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Oxidase Activity ◽  
Ros Generation ◽  
Mitochondrial Oxygen Consumption ◽  
Atp Production ◽  
Mitochondrial Ros ◽  
Mda Content

Abstract Background: To describe the effect of mechanical ventilation on diaphragm mitochondrial oxygen consumption, ATP production, reactive oxygen species (ROS) generation, and cytochrome-c oxidase activity and content, and their relationship to diaphragm strength in an experimental model of sepsis.Methods: A cecal ligation and puncture (CLP) protocol was performed in 12 rats while 12 controls underwent sham-operation. Half of the rats in each group were paralyzed and mechanically ventilated. We performed blood gas analysis and lactic acid assays 6 hours after surgery. Afterwards, we measured diaphragm strength and mitochondrial oxygen consumption, ATP and ROS generation, and cytochrome-c oxidase activity. We also measured malondialdehyde (MDA) content as an index of lipid peroxidation, and mRNA expression of the pro-inflammatory interleukin-1β (IL-1β) in diaphragms.Results: CLP rats showed severe hypotension, metabolic acidosis, and upregulation of diaphragm IL-1β mRNA expression. Compared to sham controls, spontaneously breathing CLP rats showed lower diaphragm force and increased susceptibility to fatigue, along with depressed mitochondrial oxygen consumption and ATP production and cytochrome-c oxidase activity. These rats also showed increased mitochondrial ROS generation and MDA content. Mechanical ventilation markedly restored mitochondrial oxygen consumption and ATP production in CLP rats; lowered mitochondrial ROS production by the complex 3; and preserved cytochrome-c oxidase activity.Conclusion: In an experimental model of sepsis, early initiation of mechanical ventilation restores diaphragm mitochondrial function.

Making the Grade: An Exploration of Incline Running on a Bodyweight-Supportive Treadmill

2020 ◽  
pp. 1-5
Author(s):  
Megan Wagner ◽  
Kevin D. Dames
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Repeated Measures ◽  
Perceived Exertion ◽  
Rating Of Perceived Exertion ◽  
Treadmill Running ◽  
Metabolic Effects ◽  
Metabolic Demand ◽  
Experimental Conditions ◽  
Cross Sectional

Context: Bodyweight-supporting treadmills are popular rehabilitation tools for athletes recovering from impact-related injuries because they reduce ground reaction forces during running. However, the overall metabolic demand of a given running speed is also reduced, meaning athletes who return to competition after using such a device in rehabilitation may not be as fit as they had been prior to their injury. Objective: To explore the metabolic effects of adding incline during bodyweight-supported treadmill running. Design: Cross-sectional. Setting: Research laboratory. Participants: Fourteen apparently healthy, recreational runners (6 females and 8 males; 21 [3] y, 1.71 [0.08] m, 63.11 [6.86] kg). Interventions: The participants performed steady-state running trials on a bodyweight-supporting treadmill at 8.5 mph. The control condition was no incline and no bodyweight support. All experimental conditions were at 30% bodyweight support. The participants began the sequence of experimental conditions at 0% incline; this increased to 1%, and from there on, 2% incline increases were introduced until a 15% grade was reached. Repeated-measures analysis of variance was used to compare all bodyweight-support conditions against the control condition. Main Outcome Measures: Oxygen consumption, heart rate, and rating of perceived exertion. Results: Level running with 30% bodyweight support reduced oxygen consumption by 21.6% (P < .001) and heart rate by 12.0% (P < .001) compared with the control. Each 2% increase in incline with bodyweight support increased oxygen consumption by 6.4% and heart rate by 3.2% on average. A 7% incline elicited similar physiological measures as the unsupported, level condition. However, the perceived intensity of this incline with bodyweight support was greater than the unsupported condition (P < .001). Conclusions: Athletes can maintain training intensity while running on a bodyweight-supporting treadmill by introducing incline. Rehabilitation programs should rely on quantitative rather than qualitative data to drive exercise prescription in this modality.

Study of Industrial Model for Five-Input, Five-Stage Queueing Network

2016 ◽  
pp. 300-339
Author(s):  
Jitendra Kumar ◽  
Vikas Shinde
Keyword(s):  
Response Time ◽  
Textile Industry ◽  
Optimal Path ◽  
Queueing Network ◽  
Numerical Illustration ◽  
Mean Response Time ◽  
Final Destination ◽  
Optimal Capacity ◽  
Mean Waiting Time ◽  
The Mean

In this paper, we have developed an industrial model for textile industry with five-input, five-stage queueing network, wherein system receives orders from clients that are waiting to be served. The aim of this paper is to compute the optimal path that will provide the least response time for delivery of items to the final destination, through the five stages under queueing network. The mean number of items that can be delivered is minimum response time constitute the optimal capacity of the network. The last node in each stage of the network can be executed in the least possible response time. Various performance indices were carried out such as mean number of item in the system, mean number of item in queue, mean response time, mean waiting time. We have established the equivalent queueing network to analyze the various performance measures with numerical illustration and graph.

scholarly journals Individual Differences in Cerebral Blood Flow in Area 17 Predict the Time to Evaluate Visualized Letters

1996 ◽  
Vol 8 (1) ◽  
pp. 78-82 ◽  
Author(s):  
Stephen M. Kosslyn ◽  
William L. Thompson ◽  
Irene J. Kim ◽  
Scott L. Rauch ◽  
Nathaniel M. Alpert
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Individual Differences ◽  
Response Time ◽  
Parietal Lobe ◽  
Regions Of Interest ◽  
Area 17 ◽  
Mean Response Time ◽  
Shape Characteristic ◽  
The Mean

Sixteen subjects closed their eyes and visualized uppercase letters of the alphabet at two sizes, as small as possible or as large as possible while remaining “visible.” Subjects evaluated a shape characteristic of each letter (e.g., whether it has any curved lines), and responded as quickly as possible. Cerebral blood flow was normalized to the same value for each subject, and relative blood flow was computed for a set of regions of interest. The mean response time for each subject in the task was regressed onto the blood flow values. Blood flow in area 17 was negatively correlated with response time (r = -0.65), as was blood flow in area 19 (r = -0.66), whereas blood flow in the inferior parietal lobe was positively correlated with response time (r = 0.54). The first two effects persisted even when variance due to the other correlations was removed. These findings suggest that individual differences in the activation of specific brain loci are directly related to performance of tasks that rely on processing in those loci.

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