scholarly journals Model analysis of the relationship between intracellular Po2 and energy demand in skeletal muscle

2012 ◽  
Vol 303 (11) ◽  
pp. R1110-R1126 ◽  
Author(s):  
Jessica Spires ◽  
L. Bruce Gladden ◽  
Bruno Grassi ◽  
Gerald M. Saidel ◽  
Nicola Lai
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Contraction ◽  
Energy Demand ◽  
Experimental Studies ◽  
Experimental Conditions ◽  
Permeability Surface ◽  
The Relationship ◽  
And Diffusion ◽  
Main Factor

On the basis of experimental studies, the intracellular O2 (iPo2)-work rate (WR) relationship in skeletal muscle is not unique. One study found that iPo2 reached a plateau at 60% of maximal WR, while another found that iPo2 decreased linearly at higher WR, inferring capillary permeability-surface area ( PS) and blood-tissue O2 gradient, respectively, as alternative dominant factors for determining O2 diffusion changes during exercise. This relationship is affected by several factors, including O2 delivery and oxidative and glycolytic capacities of the muscle. In this study, these factors are examined using a mechanistic, mathematical model to analyze experimental data from contracting skeletal muscle and predict the effects of muscle contraction on O2 transport, glycogenolysis, and iPo2. The model describes convection, O2 diffusion, and cellular metabolism, including anaerobic glycogenolysis. Consequently, the model simulates iPo2 in response to muscle contraction under a variety of experimental conditions. The model was validated by comparison of simulations of O2 uptake with corresponding experimental responses of electrically stimulated canine muscle under different O2 content, blood flow, and contraction intensities. The model allows hypothetical variation of PS, glycogenolytic capacity, and blood flow and predictions of the distinctive effects of these factors on the iPo2-contraction intensity relationship in canine muscle. Although PS is the main factor regulating O2 diffusion rate, model simulations indicate that PS and O2 gradient have essential roles, depending on the specific conditions. Furthermore, the model predicts that different convection and diffusion patterns and metabolic factors may be responsible for different iPo2-WR relationships in humans.

scholarly journals Regulation of oxidative phosphorylation in different muscles and various experimental conditions

2003 ◽  
Vol 375 (3) ◽  
pp. 799-804 ◽  
Author(s):  
Bernard KORZENIEWSKI
Keyword(s):  
Skeletal Muscle ◽  
Oxidative Phosphorylation ◽  
Muscle Contraction ◽  
Mitochondrial Protein ◽  
Experimental Studies ◽  
Kinetic Properties ◽  
Protonmotive Force ◽  
Experimental Conditions ◽  
Parallel Activation ◽  
Stimulation Of

It has been shown previously that direct stimulation of oxidative-phosphorylation complexes in parallel with the stimulation of ATP usage is able to explain the stability of intermediate metabolite (ATP/ADP, phosphocreatine/creatine, NADH/NAD+, protonmotive force) concentrations accompanied by a large increase in oxygen consumption and ATP turnover during transition from rest to intensive exercise in skeletal muscle. It has been also postulated that intensification of parallel activation in the ATP supply–demand system is one of the mechanisms of training-induced adaptation of oxidative phosphorylation in skeletal muscle. In the present paper, it is demonstrated, using the computer model of oxidative phosphorylation in intact skeletal muscle developed previously, that the direct activation of oxidative phosphorylation during muscle contraction can account for the following kinetic properties of oxidative phosphorylation in skeletal muscle encountered in different experimental studies: (i) increase in the respiration rate per mg of mitochondrial protein at a given ADP concentration as a result of muscle training and decrease in this parameter in hypothyroidism; (ii) asymmetry (different half-transition time, t1/2) in phosphocreatine concentration time course between on-transient (rest→work transition) and off-transient (recovery after exercise); (iii) overshoot in phosphocreatine concentration during recovery after exercise; (iv) variability in the kinetic properties of oxidative phosphorylation in different kinds of muscle under different experimental conditions. No other postulated mechanism is able to explain all these phenomena at the same time and therefore the present paper strongly supports the idea of the parallel activation of ATP usage and different oxidative-phosphorylation complexes during muscle contraction.

scholarly journals Direct Measurements of the Permeability Surface Area for Insulin and Glucose in Human Skeletal Muscle

2003 ◽  
Vol 88 (10) ◽  
pp. 4559-4564 ◽  
Author(s):  
Soffia Gudbjörnsdóttir ◽  
Mikaela Sjöstrand ◽  
Lena Strindberg ◽  
John Wahren ◽  
Peter Lönnroth
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Glucose Tolerance ◽  
Plasma Insulin ◽  
Glucose Tolerance Test ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Oral Glucose Tolerance ◽  
Permeability Surface ◽  
One Step

Abstract To elucidate mechanisms regulating capillary transport of insulin and glucose, we directly calculated the permeability surface (PS) area product for glucose and insulin in muscle. Intramuscular microdialysis in combination with the forearm model and blood flow measurements was performed in healthy males, studied during an oral glucose tolerance test or during a one-step or two-step euglycemic hyperinsulinemic clamp. PS for glucose increased significantly from 0.29 ± 0.1 to 0.64 ± 0.2 ml/min·100 g after oral glucose tolerance test, and glucose uptake increased from 1.2 ± 0.4 to 2.6 ± 0.6 μmol/min·100 g (P < 0.05). During one-step hyperinsulinemic clamp (plasma insulin, 1.962 pmol/liter), PS for glucose increased from 0.2 ± 0.1 to 2.3 ± 0.9 ml/min·100 g (P < 0.05), and glucose uptake increased from 0.6 ± 0.2 to 5.0 ± 1.4 μmol/min·100 g (P < 0.05). During the two-step clamp (plasma insulin, 1380 ± 408 and 3846 ± 348 pmol/liter), the arterial-interstitial difference and PS for insulin were constant. The PS for glucose tended to increase (P = not significant), whereas skeletal muscle blood flow increased from 4.4 ± 0.7 to 6.2 ± 0.8 ml/min·100 ml (P < 0.05). The present data show that PS for glucose is markedly increased by oral glucose, whereas a further vasodilation exerted by high insulin concentrations may not be physiologically relevant for capillary delivery of either glucose or insulin in resting muscle.

Relation of blood flow to VO2, PO2, and PCO2 in dog gastrocnemius muscle

1988 ◽  
Vol 255 (5) ◽  
pp. H1004-H1010 ◽  
Author(s):  
D. E. Mohrman ◽  
R. R. Regal
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Gastrocnemius Muscle ◽  
Muscle Blood Flow ◽  
Carbon Dioxide Tension ◽  
Experimental Conditions ◽  
Muscle Oxygen ◽  
Muscle Oxygen Consumption ◽  
Relationship Of ◽  
The Relationship

We pump-perfused gastrocnemius-plantaris muscle preparations at constant pressure to study the relationship of muscle blood flow (Q) to muscle oxygen consumption (VO2), venous oxygen tension (PVO2), and venous carbon dioxide tension (PVCO2) during steady-state exercise at different rates. Tests were performed under four experimental conditions produced by altering the perfusate blood-gas status with a membrane lung. The consistency of the relationship of Q to other variables was evaluated by statistical analysis of fitted curves. Not one of the above listed variables had the same relationship with Q in all four of the experimental conditions we tested. However, we did find that a consistent relationship existed among Q, PVO2, and PVCO2 in our data. That relationship is well described by the equation (Q-23).[PVO2 - (0.5.PVCO2) - 3] = 105 (when Q is expressed in ml.100 g-1.min-1 and PVO2 and PVCO2 in mmHg). One interpretation of this result is that both PO2 and PCO2 are important variables in the control of blood flow in skeletal muscle the combined influence of which could account for nearly all of the hyperemia response to steady-state muscle exercise.

Conditions for dipyridamole potentiation of skeletal muscle active hyperemia

1986 ◽  
Vol 250 (1) ◽  
pp. H62-H67 ◽  
Author(s):  
R. E. Klabunde
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Contraction ◽  
Recovery Time ◽  
Free Flow ◽  
Isometric Contractions ◽  
Vascular Conductance ◽  
Arterial Infusion ◽  
Maximal Tension

The effects of dipyridamole on active hyperemia were evaluated in dog gracilis muscles undergoing sustained isometric contractions. Muscles were stimulated to contract for 5, 15, 25, and 50 s at 20% maximal tension (20% Tmax) or for 10 s at 100% Tmax during intra-arterial infusion of either saline or dipyridamole (1 microM). In two separate groups of dogs, muscles were stimulated to contract under free-flow or restricted-flow (ischemic) conditions. In the later group, blood flow was reduced to 50% of precontraction level during the period of contraction. Dipyridamole increased resting vascular conductance by about 45%; however, it did not affect the change in vascular conductance resulting from muscle contraction. The recovery time for active hyperemia following free-flow contractions at 20% Tmax was not altered by dipyridamole. However, dipyridamole increased the recovery time following 50 s of restricted-flow contraction (20% Tmax) and 10 s of 100% Tmax contractions by 46 and 169%, respectively. These results suggest that adenosine contributes to active hyperemia following sustained ischemic contractions at 20% Tmax and contractions at 100% Tmax but not from contractions at 20% Tmax where blood flow is allowed to increase freely.

scholarly journals Distinguishing the effects of convective and diffusive O2 delivery on V̇o2 on-kinetics in skeletal muscle contracting at moderate intensity

2013 ◽  
Vol 305 (5) ◽  
pp. R512-R521 ◽  
Author(s):  
Jessica Spires ◽  
L. Bruce Gladden ◽  
Bruno Grassi ◽  
Matthew L. Goodwin ◽  
Gerald M. Saidel ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Energy Demand ◽  
Experimental Studies ◽  
Moderate Intensity ◽  
Oxygen Utilization ◽  
Muscle Oxygen ◽  
Mean Response Time ◽  
Convective Oxygen Delivery ◽  
Dynamics Simulations ◽  
O2 Delivery

With current techniques, experimental measurements alone cannot characterize the effects of oxygen blood-tissue diffusion on muscle oxygen uptake (V̇o2) kinetics in contracting skeletal muscle. To complement experimental studies, a computational model is used to quantitatively distinguish the contributions of convective oxygen delivery, diffusion into cells, and oxygen utilization to V̇o2 kinetics. The model is validated using previously published experimental V̇o2 kinetics in response to slowed blood flow (Q) on-kinetics in canine muscle (τQ = 20 s, 46 s, and 64 s) [Goodwin ML, Hernández A, Lai N, Cabrera ME, Gladden LB. J Appl Physiol. 112:9–19, 2012]. Distinctive effects of permeability-surface area or diffusive conductance ( PS) and Q on V̇o2 kinetics are investigated. Model simulations quantify the relationship between PS and Q, as well as the effects of diffusion associated with PS and Q dynamics on the mean response time of V̇o2. The model indicates that PS and Q are linearly related and that PS increases more with Q when convective delivery is limited by slower Q dynamics. Simulations predict that neither oxygen convective nor diffusive delivery are limiting V̇o2 kinetics in the isolated canine gastrocnemius preparation under normal spontaneous conditions during transitions from rest to moderate (submaximal) energy demand, although both operate close to the tipping point.

scholarly journals Relationship between Isometric Muscle Force and Fractal Dimension of Surface Electromyogram

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Matteo Beretta-Piccoli ◽  
Gennaro Boccia ◽  
Tessa Ponti ◽  
Ron Clijsen ◽  
Marco Barbero ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Muscle Contraction ◽  
Biceps Brachii ◽  
Isometric Force ◽  
Voluntary Contraction ◽  
Experimental Conditions ◽  
Surface Electromyogram ◽  
Mean Frequency ◽  
Muscle Contraction Intensity ◽  
The Relationship

The relationship between fractal dimension of the surface electromyogram (sEMG) and the intensity of muscle contraction is still controversial in simulated and experimental conditions. To support the use of fractal analysis to investigate myoelectric fatigue, it is crucial to establish the interdependence between fractal dimension and muscle contraction intensity. We analyzed the behavior of fractal dimension, conduction velocity, mean frequency, and average rectified value in twenty-eight volunteers at nine levels of isometric force. sEMG was obtained using bidimensional arrays in the biceps brachii muscle. The values of fractal dimension and mean frequency increased with force unless a plateau was reached at 30% maximal voluntary contraction. Overall, our findings suggest that, above a certain level of force, the use of fractal dimension to evaluate the myoelectric manifestations of fatigue may be considered, regardless of muscle contraction intensity.

scholarly journals The Effectiveness of Mating Induction on Men’s Financial Risk-Taking: Relationship Experience Matters

2022 ◽  
Vol 12 ◽  
Author(s):  
Tingting Liu ◽  
Zhuanzhuan Wang ◽  
Anrun Zhu ◽  
Xi Zhang ◽  
Cai Xing
Keyword(s):  
Risk Taking ◽  
Romantic Relationship ◽  
Financial Risk ◽  
Experimental Studies ◽  
Financial Industry ◽  
Experimental Conditions ◽  
Significant Interaction Effect ◽  
And Control ◽  
The Relationship ◽  
Risk Taking Behaviors

Substantial evidence from experimental studies has shown that mating motivation increases men’s financial risk-taking behaviors. The present study proposed a new moderator, men’s past relationship experience, for this well-accepted link between mating motivation and financial risk-taking tendency. Heterosexual young men were randomly assigned to the mating condition and control condition, and they completed a set of financial risk-taking tasks and reported their past relationship experience. A significant main effect of mating motivation and a significant interaction effect between experimental conditions (mating group and control group) and relationship experience emerged, suggesting that mating motivation increased financial risk-taking tendency only among men who have never been committed in a romantic relationship, rather than those who have had such experience. This moderating effect was replicated in two experiments. The present study contributed to the understanding of individual differences in the relationship between mating motivation and male financial risk-taking. The present findings also have important implications for financial industry and gambling companies to better target clients and advertise their high-risk products.

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