The Fenn Effect: A Fundamental Mystery in Muscle

2017 ◽  
pp. 139-153
Author(s):  
Haruo Sugi
Keyword(s):  
Fenn Effect

scholarly journals Muscle Energetics and the Fenn Effect

1972 ◽  
Vol 12 (5) ◽  
pp. 512-527 ◽  
Author(s):  
Philip W. Brandt ◽  
Morton Orentlicher
Keyword(s):  
Muscle Energetics ◽  
Fenn Effect

The off rate of Ca2+ from troponin C is regulated by force-generating cross bridges in skeletal muscle

2002 ◽  
Vol 92 (6) ◽  
pp. 2409-2418 ◽  
Author(s):  
Ying Wang ◽  
W. Glenn L. Kerrick
Keyword(s):  
Skeletal Muscle ◽  
Troponin C ◽  
Transient Increase ◽  
Skinned Fibers ◽  
Mouse Skeletal Muscle ◽  
Actomyosin Atpase ◽  
Intact Muscle ◽  
Intracellular Ca ◽  
Cross Bridges ◽  
Fenn Effect

The effects of dissociation of force-generating cross bridges on intracellular Ca2+, pCa-force, and pCa-ATPase relationships were investigated in mouse skeletal muscle. Mechanical length perturbations were used to dissociate force-generating cross bridges in either intact or skinned fibers. In intact muscle, an impulse stretch or release, a continuous length vibration, a nonoverlap stretch, or an unloaded shortening during a twitch caused a transient increase in intracellular Ca2+ compared with that in isometric controls and resulted in deactivation of the muscle. In skinned fibers, sinusoidal length vibrations shifted pCa-force and pCa-actomyosin ATPase rate relationships to higher Ca2+ concentrations and caused actomyosin ATPase rate to decrease at submaximal Ca2+ and increase at maximal Ca2+ activation. These results suggest that dissociation of force-generating cross bridges during a twitch causes the off rate of Ca2+ from troponin C to increase (a decrease in the Ca2+ affinity of troponin C), thus decreasing the Ca2+ sensitivity and resulting in the deactivation of the muscle. The results also suggest that the Fenn effect only exists at maximal but not submaximal force-activating Ca2+ concentrations.

Effect of initial length on relations between oxygen uptake and load in dog muscle

1976 ◽  
Vol 230 (4) ◽  
pp. 1008-1012 ◽  
Author(s):  
WN Stainsby ◽  
JK Barclay
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
The Other ◽  
Mammalian Skeletal Muscle ◽  
Initial Length ◽  
Muscle Preparation ◽  
Optimal Length ◽  
Muscle Energetics ◽  
Isotonic Contractions ◽  
Fenn Effect

Oxygen uptake for brief tetanic contractions was calculated from measurements of blood flow and blood arteriovenous oxygen content differences. Each muscle preparation was pretested under isometric conditions to establish optimal length, Lo. After this one group of preparations performed afterload isotonic contractions at several loads with initial length, Li, less than Lo. The other groups of preparations performed similar contractions with Li greater than Lo. When Li was less than Lo, oxygen uptake for the highest load was always greater than oxygen uptake at the lowest load whereas intermediate loads were usually higher than both extremes. However, when Li was greater than Lo, oxygen uptake at the highest load was always less than oxygen uptake at the lowest load; again the intermediate loads were usually higher than both extremes. The data confirm and extend similar effects of initial length on heat production for contractions by amphibian muscles (7). It seems likely that the differences in initial lengths may account for the fact that the Fenn effect has not previously been observed in studies of mammalian skeletal muscle energetics.

scholarly journals Muscle force, work and cost: a novel technique to revisit the Fenn effect

2015 ◽  
Vol 218 (13) ◽  
pp. 2075-2082 ◽  
Author(s):  
J. O. Ortega ◽  
S. L. Lindstedt ◽  
F. E. Nelson ◽  
S. A. Jubrias ◽  
M. J. Kushmerick ◽  
...  
Keyword(s):  
Muscle Force ◽  
Novel Technique ◽  
Fenn Effect

scholarly journals Mechanical control of the rising phase of contraction of frog skeletal and cardiac muscle.

1977 ◽  
Vol 70 (6) ◽  
pp. 697-705 ◽  
Author(s):  
E Bozler
Keyword(s):  
Isometric Contraction ◽  
Time Course ◽  
Contractile Activity ◽  
Muscle Length ◽  
Isometric Contractions ◽  
Activation Process ◽  
Control Activity ◽  
Isotonic Contraction ◽  
Fenn Effect ◽  
Isotonic Shortening

The effect of shortening on contractile activity was studied in experiments in which shortening during the rising phase of an isotonic contraction was suddenly stopped. At the same muscle length and the same time after stimulation the rise in tension was much faster, if preceded by shortening, than during an isometric contraction, demonstrating an increase in contractile activity. In this experiment the rate of tension rise determined in various phases of contraction was proportional to the rate of isotonic shortening at the same time after stimulation. Therefore, the time course of the isotonic rising phase could be derived from the tension rise after shortening. The rate of isotonic shortening was found to be unrelated to the tension generated at various lengths and to correspond closely to the activation process induced by shortening. The length response explains differences between isotonic and isometric contractions with regard to energy release (Fenn effect) and time relations. These results extend previous work which showed that shortening during later phases of a twitch prolongs, while lengthening abbreviates contraction. Thus the length responses, which have been called shortening activation and lengthening deactivation, control activity throughout an isotonic twitch.

scholarly journals Energetics of Contraction in Phasic and Tonic Skeletal Muscles of the Chicken

1973 ◽  
Vol 62 (3) ◽  
pp. 303-323 ◽  
Author(s):  
Jack A. Rall ◽  
B. A. Schottelius
Keyword(s):  
Latissimus Dorsi ◽  
Skeletal Muscles ◽  
Energy Liberation ◽  
Isometric Contractions ◽  
Base Line ◽  
Tension Development ◽  
Tension Time ◽  
Activation Heat ◽  
Initial Heat ◽  
Fenn Effect

Comparative energetics of chicken latissimus dorsi muscles, tonic anterior (ALD) and phasic posterior (PLD), were investigated by measuring initial heat production. Heat components were analyzed in terms of the equation: E = A + W + αF(Δ¯L) + f(P, t) As the muscles were stretched by increments, heat produced in isometric twitches and tetani decreased in a linear fashion. Two processes are involved: one tension independent, the activation heat, or A; and the other tension dependent, Wi + αF(Δ¯L) + f(P, t). In twitches, A, per unit tension, is equivalent in the PLD and ALD. Tension-dependent heat, per unit tension, is greater in the PLD due to Wi; but tension-time-related heat, f(P, t), per unit tension, is similar in both muscles. In tetanic contractions, differences in A and f(P, t), per unit tension, are attributed to the greater Vmax in the PLD. The differences in the energetics of isometric contractions in the PLD and ALD, therefore, can be explained by inherent differences in tension development, compliance, and myosin and reticular ATPase activities. Data from isotonic twitches were quantified by means of the equivalent tension technique. Both muscles exhibited an extra heat associated with shortening, αF(Δ¯L). In the PLD, the ratio αF/Pot is greater; it is load independent and ½ the value of a/Po in both muscles. Enthalpy efficiency, We + Wi/E, is comparable in both muscles. A Fenn effect is observed only when isotonic energy liberation is compared to a decreasing isometric energy expenditure base line.

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