Correlation of electrophysiological,histochemical, and mechanical properties in fibres of the coxa rotator muscle of the locust,Locusta migratoria |
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Authors: | Antje R Müller H Wolf S Galler W Rathmayer |
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Institution: | (1) Fakultät für Biologie, Universität Konstanz, Postfach 5560, W-7750 Konstanz, Fed. Rep. Germany;(2) Present address: Institut für Zoologie, Universität Salzburg, A-5020 Salzburg, Österreich |
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Abstract: | Summary The fibre composition of the anterior coxa rotator muscle of the locust middle leg (M92) was examined. The muscle is composed of 90–100 fibres. Muscle fibres were characterized with regard to innervation pattern, electrophysiological properties, and morphological parameters. Activity and isoenzyme composition of myofibrillar ATPase, succinic acid dehydrogenase (SDH) activity and glycogen content were examined employing histochemical techniques. Shortening velocity and the dependence of tension on intracellular Ca2+ were determined in skinned fibre experiments. A close match was observed between the innervation pattern of the muscle fibres and their histochemical and physiological properties. The combination of all parameters examined allowed an accurate classification of the muscle fibres into three types. Within a given type, broad variability of some properties was observed (SDH activity, Ca2+ sensitivity) while others assumed distinct values (innervation pattern, shortening velocity). The comprehensive characterization of muscle fibre properties permits a functional interpretation of fibre heterogeneity with regard to muscle performance. Fibres with the same innervation pattern may be recruited specifically, according to their electric properties and Ca2+ sensitivities. The resulting specific recruitment of fibres with different mechanical responses should allow a subtle control of muscular force, with regard to force amplitude, temporal characteristics of contraction, and metabolic cost.Abbreviations CI1
common inhibitory neurone one
- ejp
ijp excitatory, inhibitory junctional potential
- EGTA
ethylene glycol-bis -aminoethyl ether] N,N,N ,N -tetraacetic acid
- mATPase
myofibrillar adenosinetriphosphatase
- MOPSO
3-N-morpholino]-2-hydroxypropanesulfonic acid
- M92
anterior rotator muscle of the coxa
- n
Hill coefficient
- pCa50
pCa corresponding to half-maximal tension
- P0
maximal isometric tension
- SDH
succinic acid dehydrogenase
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V
max
maximal shortening velocity |
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Keywords: | Skinned muscle fibres Neuromuscular properties Histochemistry Mechanical properties Locusta migratoria |
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