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Titolo:
DETACHMENT OF LOW-FORCE BRIDGES CONTRIBUTES TO THE RAPID TENSION TRANSIENTS OF SKINNED RABBIT SKELETAL-MUSCLE FIBERS
Autore:
SEOW CY; SHROFF SG; FORD LE;
Indirizzi:
INDIANA UNIV,KRANNERT INST CARDIOL,1111 W 10 ST INDIANAPOLIS IN 46220 INDIANA UNIV,KRANNERT INST CARDIOL INDIANAPOLIS IN 46220
Titolo Testata:
Journal of physiology
fascicolo: 1, volume: 501, anno: 1997,
pagine: 149 - 164
SICI:
0022-3751(1997)501:1<149:DOLBCT>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
2,3-BUTANEDIONE MONOXIME; FROG-MUSCLE; CONTRACTILE ACTIVATION; CROSS-BRIDGES; BUTANEDIONE MONOXIME; IONIC-STRENGTH; CARDIAC-MUSCLE; FAST-TWITCH; FIBERS; CROSSBRIDGES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
43
Recensione:
Indirizzi per estratti:
Citazione:
C.Y. Seow et al., "DETACHMENT OF LOW-FORCE BRIDGES CONTRIBUTES TO THE RAPID TENSION TRANSIENTS OF SKINNED RABBIT SKELETAL-MUSCLE FIBERS", Journal of physiology, 501(1), 1997, pp. 149-164

Abstract

1. To probe the cross-bridge cycle and to learn more about the cardioplegic agent BDM (2,3-butanedione monoxime), its effects on the force-velocity properties and tension transients of skinned rabbit muscle fibres were studied at 1-2 degrees C and pH 7.0. 2. Three millimolar BDMdecreased isometric force by 50%, velocity by 29%, maximum power by 73%, and stiffness by 25%, so that the relative stiffness (stiffness/force ratio) increased by 50% compared with reference conditions in the absence of BDM. 3. Tension transients obtained under the reference condition (0 BDM) could be represented by three components whose instantaneous stiffness accounted for the initial (Phase 1) force deviation and whose exponential recoveries caused the rapid, partial (Phase 2) force recovery following the step. The fastest component had non-linear extension-force properties that accounted for about half the isometric stiffness and it recovered fully. The two slower components had linearextension-force properties that together accounted for the other halfof the sarcomere stiffness. These components recovered only partiallyfollowing the step, producing the intermediate (T-2) level which the force approached during Phase 2. 4. Matching the force transients obtained under test conditions (3 mM BDM) required three alterations: (1) reducing the amplitude of the two slower components by 50%, in proportion to isometric force, (2) adding a, non-relaxing component and (3) decreasing the amplitude of the rapidly recovering component by 12.5% so that its relative amplitude (amplitude/isometric force) was increased by 75%. The non-recovering component and the increase in relative amplitude of the rapid component were responsible for the increase in relative stiffness of the fibres produced by BDM. The rapidly recoveringcomponent had the same time constant and step-size-dependent recoveryrates as the fastest of the three monoexponential components isolatedfrom the tension transient response under the reference condition. BDM therefore appeared to augment the fastest component of the tension transient under the reference condition. 5. The results suggest that BDM detains cross-bridges in low-force, attached states. Since these bridges are attached, they contribute to sarcomere stiffness. Since they are detained, relaxation or reversal of their immediate responses is probably due to bridge detachment rather than to their undergoing the power stroke. The observation that a portion of the test response matched the fastest component of the reference response when the amplitude of the fastest component was increased suggests that a part of the normal rapid, transient tension recovery following a release step is due to detachment of low-force bridges moved to negative-force positions by the step.

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Documento generato il 25/11/20 alle ore 18:36:52