title: Possible Cause of Nonlinear Tension Rise in Activated Muscle Fiber during Stretching.
abstract: Tension in contracting muscle fiber under conditions of ramp stretching rapidly increases, but after reaching a critical stretch Pcsharply decreases. To find out the cause of these changes in muscle fiber tension, we stopped stretching before and after reaching Pcand left the fiber stretched for 50 msec. After rapid tension drop, the transient tension rise not accompanied by fiber stiffness increase was observed only in fibers heated to 25°C and stretched to Pc. Under other experimental conditions, this growth was absent. We suppose that stretch of the fiber to Pcinduces transition of stereo-specifically attached myosin heads to pre-power stroke state and when the stretching is stopped, they make their step on actin and generate force. When the tension reaches Pc, all stereospecifically attached myosin heads turn out to be non-stereospecifically, or weakly attached to actin, and are unable to make the force-generating step.
authors.affiliation: Institute of Immunology and Physiology, Ural Division of the Russian Academy of Sciences, Ekaterinburg, Russia. cherepashkin2@yandex.ru.
authors.forename: P V
authors.initials: PV
authors.lastname: Kochubei
authors.affiliation: Institute of Immunology and Physiology, Ural Division of the Russian Academy of Sciences, Ekaterinburg, Russia.
authors.forename: S Yu
authors.initials: SY
authors.lastname: Bershitsky
mesh_terms: D000199:Actins / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D003470:Culture Media / Q000737:chemistry; D004548:Elasticity; D007537:Isometric Contraction / Q000502:physiology*; D008954:Models, Biological; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D052580:Muscle Stretching Exercises; D009218:Myosins / Q000502:physiology*; D011817:Rabbits; D046509:Tissue Culture Techniques
chemical_list: D000199:Actins; D003470:Culture Media; D009218:Myosins
keywords: actin-myosin interaction; eccentric contraction; muscle fiber; stiffness; tension