Biomaterial Database

Stable maintenance heat rate and contractile properties of different single muscle fibres from Xenopus laevis at 20 degrees C. 1987

G Elzinga, and J Lännergren, and G J Stienen

Laboratory for Physiology, Free University, Amsterdam, The Netherlands.

1. Different types of fibres were isolated from the iliofibularis muscle of Xenopus laevis. Resting length was adjusted to obtain a sarcomere length of 2.3 microns as judged by laser diffraction. Heat production was measured during tetanic contractions lasting 0.3-2 s at 20 degrees C. From twenty fibres the force-velocity relationship was determined as well. 2. After correcting the records for heat loss, and taking the relevant heat capacities into account, stable maintenance heat rate was determined by fitting the corrected heat records from 0.35 s after the onset of contraction onwards by a straight line. The value obtained was then normalized on the dry weight of the fibre. The force-velocity relationships were fitted according to Hill's equation, yielding values for a and Vmax (Hill, 1938). 3. Stable maintenance heat rate (hb) depended on fibre type and ranged from 0.05 to 0.86 W g-1 dry wt. Isometric tetanic force per cross-sectional area (P0) varied between 190 and 427 kN m-2. Therefore the variations in hb were not proportional to the variations in P0. 4. The maximum velocity of shortening (Vmax) differed considerably from fibre to fibre (4.6-10.3 lengths s-1). Between Vmax and hb a non-linear relationship was found. The curvature of this relationship was such that its slope (delta hb/delta Vmax) increased with Vmax. 5. A proportional relationship was found between the rate of force redevelopment, following a period of rapid shortening, and hb. 6. Maximum power output during loaded shortening as derived from the force-velocity (P-V) relationships was on average 2.2 times higher than hb. 7. The curvature of the force-velocity relationship, as reflected by the value of a/P0, varied between fibres from 0.18 to 0.53. A larger value of a/P0 i.e. a less curved relationship, corresponded with a larger value of hb. 8. Since hb reflects the rate at which ATP is hydrolysed during contraction, the results suggest that the maximum velocity of shortening and the in vivo actomyosin ATPase under isometric conditions are non-linearly related. This would imply that these two variables are not dominated by the same rate-limiting step of the cross-bridge cycle.

UI	MeSH Term	Description	Entries
D007537	Isometric Contraction	Muscular contractions characterized by increase in tension without change in length.	Contraction, Isometric,Contractions, Isometric,Isometric Contractions
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D001833	Body Temperature Regulation	The processes of heating and cooling that an organism uses to control its temperature.	Heat Loss,Thermoregulation,Regulation, Body Temperature,Temperature Regulation, Body,Body Temperature Regulations,Heat Losses,Loss, Heat,Losses, Heat,Regulations, Body Temperature,Temperature Regulations, Body,Thermoregulations
D005260	Female		Females
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001696	Biomechanical Phenomena	The properties, processes, and behavior of biological systems under the action of mechanical forces.	Biomechanics,Kinematics,Biomechanic Phenomena,Mechanobiological Phenomena,Biomechanic,Biomechanic Phenomenas,Phenomena, Biomechanic,Phenomena, Biomechanical,Phenomena, Mechanobiological,Phenomenas, Biomechanic
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D013997	Time Factors	Elements of limited time intervals, contributing to particular results or situations.	Time Series,Factor, Time,Time Factor
D014982	Xenopus laevis	The commonest and widest ranging species of the clawed "frog" (Xenopus) in Africa. This species is used extensively in research. There is now a significant population in California derived from escaped laboratory animals.	Platanna,X. laevis,Platannas,X. laevi