title: Mechanical properties of intact single fibres from wild-type  and MLC/mIgf-1 transgenic mouse muscle.
abstract: The effects of overexpression of the local form of insulin like growth factor-1 (mIgf-1) on skeletal muscle were investigated by comparing the mechanical properties of single intact fibres from the flexor digitorum brevis of wild-type (WT) and (MLC/mIgf-1) transgenic mice (TG)at 21-24 degrees C. Isolated single fibres were clean enough to measure accurately the sarcomere length. The parameters investigated were: tetanic absolute and specific force, the force-velocity relationship, and the sarcomere length-tension relationship. In addition, we investigated the properties of the "static stiffness", a non-crossbridge Ca(2+)-dependent increase of fibre stiffness previously found in frog muscle. Both average cross-sectional area and tetanic force almost doubled in TG fibres, so that specific force was the same in both preparation: 312 +/- 20 and 344 +/- 34 kN m(-2) in WT and TG fibres, respectively. None of the relative force-velocity parameters was altered by Igf-1 overexpression, however, V(max) (8-10 l(0) s(-1)) was greater than previously reported in whole muscles. The sarcomere length-tension relationship was the same in TG and WT fibres showing the classical shape with a plateau region between 2.28 and 2.52 microm and a linear descending limb. The static stiffness was present in both WT and TG fibres and showed similar characteristics to that of frog skeletal muscle. In contrast to the other parameters, static stiffness in TG fibres was about 24% smaller than in WT fibres suggesting a possible effect of Igf-1 overexpression on its mechanism.
authors.affiliation: Dipartimento di Scienze Fisiologiche and Istituto Interuniversitario di Miologia, Università degli Studi di Firenze, Florence, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Colombini
authors.forename: Giulia
authors.initials: G
authors.lastname: Benelli
authors.forename: Marta
authors.initials: M
authors.lastname: Nocella
authors.forename: Antonio
authors.initials: A
authors.lastname: Musarò
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cecchi
authors.forename: M Angela
authors.initials: MA
authors.lastname: Bagni
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D020013:Calcium Signaling / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D053580:Muscle Strength / Q000502:physiology; D009129:Muscle Tonus / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D012518:Sarcomeres / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D007334:Insulin-Like Growth Factor I