|
|
|
|
|
|
|
|
|||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
Journal of Cell Science, Vol 10, 419-441, Copyright © 1972 by Company of Biologists
Submitted on August 2, 1971
1 Departments of Physiology and Zoology, The University, Glasgow, W.2, Scotland
Insect muscle fibres can be classed as either phasic or tonic according to their response to potassium depolarization. The phasic fibres contract only transiently during prolonged potassium depolarization, whereas the tonic fibres give a sustained contracture.
The extensor tibiae muscle in the metathoracic leg of the locust contains both tonic (T/et) and phasic (P/et) fibres; the electrical, mechanical and ultrastructural properties of these fibres have been compared with those of phasic fibres from the retractor unguis muscle (P/ru) in the same leg. A broad correlation has been established between the mechanical response and the amount of sarcoplasmic reticulum (SR) in the fibres.
At maximal body length the rise time to peak twitch tension for the T/et fibres was found to be 790±60 ms, for the P/et fibres 59±2.5 ms and for the P/ru fibres, 30±1.1 ms. The half-decay times for the isometric twitch contractions were 2950±88 ms for the T/et fibres, 119±4.2 ms for the P/et, and 35±2.3 ms for the P/ru. The P/et and P/ru gave brief isometric contractures during potassium depolarization; under the same treatment the T/et fibres remained contracted throughout the treatment period.
The major structural differences between the 3 types lies in the SR. Expressed as percentages of total fibre volume, the SR represents in the T/et 1.1%, in the P/et 6.8%, and in the P/ru 19%. The surface area of the SR, in terms of µm2/µm3 of fibre volume is 1.0±0.1 in the T/et, 2.9±0.2 in the P/et and 11.9±1.0 in the P/ru. Microtubules, often associated with elements of the SR, are sparsely distributed amongst the contractile elements in the T/et fibres. All 3 muscle types have a well developed T-system which forms dyadic associations with the SR. Larger-diameter Z-invaginations which conduct tracheoles into the muscles also give rise to ‘longitudinal T-tubules’, particularly in the T/et fibres. Dyads arise by association of cisternae of the SR: (i) with T-tubules sensu strictu, (ii) with Z-invaginations and T-tubule-like extensions from them, and (iii) directly with the plasma membrane at the surface of the fibre.
Submitted on August 2, 1971
This article has been cited by other articles:
|
|
 |
|
  W. M. Kier and F. H. Schachat Muscle specialization in the squid motor system J. Exp. Biol., January 15, 2008; 211(2): 164 - 169. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. M. Kier and N. A. Curtin Fast muscle in squid (Loligo pealei): contractile properties of a specialized muscle fibre type J. Exp. Biol., July 1, 2002; 205(13): 1907 - 1916. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Burrows and H. Wolf Jumping and kicking in the false stick insect Prosarthria teretrirostris: kinematics and motor control J. Exp. Biol., June 1, 2002; 205(11): 1519 - 1530. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P T O'Donnell, V L Collier, K Mogami, and S I Bernstein Ultrastructural and molecular analyses of homozygous-viable Drosophila melanogaster muscle mutants indicate there is a complex pattern of myosin heavy-chain isoform distribution. Genes & Dev., August 1, 1989; 3(8): 1233 - 1246. [Abstract] [PDF]
|
|
