QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by JOHNSTON, I. A. Articles by GLEESON, T. T. Search for Related Content PubMed Articles by JOHNSTON, I. A. Articles by GLEESON, T. T.

Journal of Experimental Biology 113,123-132 (1984)
Published by Company of Biologists 1984

Thermal Dependence of Contractile Properties of Red and White Fibres Isolated From the Iliofibularis Muscle of the Desert Iguana (Dipsosaurus Dorsalis)

IAN A. JOHNSTON ¹ and TODD T. GLEESON ²

¹ Department of Physiology, University of St Andrews St Andrews, Fife KY16 9TS, Scotland, U.K.
² Department of Physiology, University of St Andrews St Andrews, Fife KY16 9TS, Scotland, U.K.; Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado 80309, U.S.A.

Single fibres were isolated from the ‘red’ and ‘white’ portions of the iliofibularis muscle from the desert iguana (Dipsosaurus dorsalis). Muscle fibres were chemically skinned with the non-ionic detergent Brij. 58.

Maximal Ca²⁺-activated tensions at 40°C were 32.3±1.5 Ncm^-2 for red and 33.0±2.1 Ncm^-2 for white muscle fibres (mean±S.E. mean). Unloaded contraction velocities (V_max) were determined by the ‘slack-test’ method. Average values for V_max at 40°C were 7.1±0.4 and 16.1±1.1 muscle length s^-1 (L₀ s^-1) for red and white fibres respectively. The red portion of the iliofibularis contained fibres with V_max values between 1.1 and 12.9 L₀ s^-1. Around 18% of the red fibre population had maximum contraction velocities less than 4.0L₀s^-1. These slower fibres were principally located in the region closest to the femur in situ. They probably correspond to the multiply-innervated ‘tonic type’ fibres that can be identified histochemically.

Q₁₀ values for V_max over the range 5-15°C were higher for red (4.2) than white (2.3) muscle fibres. Above 25-30°C Q₁₀ values for V_max were in the range 1.3-1.9 for both fibre types. Maximum Ca²⁺-activated tensions were largely independent of temperature between 20 and 45°C. Dipsosaurus is maximally active in the field at 35-42°C, which corresponds to a zone of relative thermal independence of muscle contractile properties and locomotory performance.

Key words: Reptiles, contractile properties, skeletal muscle, temperature, Dipsosaurus dorsalis

Accepted on April 2, 1984

This article has been cited by other articles:

				K. E. Bonine, T. T. Gleeson, and T. Garland Jr Muscle fiber-type variation in lizards (Squamata) and phylogenetic reconstruction of hypothesized ancestral states J. Exp. Biol., December 1, 2005; 208(23): 4529 - 4547. [Abstract] [Full Text] [PDF]

				F. E. Nelson and B. C. Jayne The effects of speed on the in vivo activity and length of a limb muscle during the locomotion of the iguanian lizard Dipsosaurus dorsalis J. Exp. Biol., March 12, 2002; 204(20): 3507 - 3522. [Abstract] [Full Text] [PDF]